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Sample records for sinterable ceramic product

  1. Solidification of HLLW into sintered ceramics

    International Nuclear Information System (INIS)

    O-Oka, K.; Ohta, T.; Masuda, S.; Tsunoda, N.

    1979-01-01

    Simulated HLLW from the PNC reprocessing plant at Tokai was solidified into sintered ceramics by normal sintering or hot-pressing with addition of some oxides. Among various ceramic products obtained so far, the most preferable was nepheline-type sintered solids formed with addition of SiO 2 and Al 2 O 3 to the simulated waste calcine. The solid shows advantageous properties in leach rate and mechanical strength, which suggest that the ceramic solids were prepared with additions of ZrO 2 or MnO 2 , and some of them showed good characteristics

  2. Microwave sintering of ceramic materials

    Science.gov (United States)

    Karayannis, V. G.

    2016-11-01

    In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

  3. Boric oxide or boric acid sintering aid for sintering ceramics

    International Nuclear Information System (INIS)

    Lawler, H.A.

    1979-01-01

    The invention described relates to the use of liquid sintering aid in processes involving sintering of ceramic materials to produce dense, hard articles having industrial uses. Although the invention is specifically discussed in regard to compositions containing silicon carbide as the ceramic material, other sinterable carbides, for example, titanium carbide, may be utilized as the ceramic material. A liquid sintering aid for densifying ceramic material is selected from solutions of H 3 BO 3 , B 2 O 3 and mixtures of these solutions. In sintering ceramic articles, e.g. silicon carbide, a shaped green body is formed from a particulate ceramic material and a resin binder, and the green body is baked at a temperature of 500 to 1000 0 C to form a porous body. The liquid sintering aid of B 2 O 3 and/or H 3 BO 3 is then dispersed through the porous body and the treated body is sintered at a temperature of 1900 to 2200 0 C to produce the sintered ceramic article. (U.K.)

  4. Low temperature sintering of fluorapatite glass-ceramics

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A.

    2014-01-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disc-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. PMID:24252652

  5. Pressureless sintering of whisker-toughened ceramic composites

    Science.gov (United States)

    Tiegs, T.N.

    1993-05-04

    A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

  6. Low temperature sintering of fluorapatite glass-ceramics.

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Development and sintering of alumina based mixed oxide ceramic products for sensor applications in petroleum industries

    Energy Technology Data Exchange (ETDEWEB)

    Yadava, Y.P.; Muniz, L.B.; Aguiar, L.A.R.; Sanguinetti Ferreira, R.A. [Departamento de Engenharia Mecanica, Universidade Federal de Pernambuco, CEP 50741-530, Recife-PE (Brazil); Albino Aguiar, J. [Departamento de Fisica, Universidade Federal de Pernambuco, CEP 50670-901 Recife-PE (Brazil)

    2005-07-01

    In petroleum production, different types of sensors are required to monitor temperature, pressure, leakage of inflammable gases, etc. These sensors work in very hostile environmental conditions and frequently suffer from abrasion and corrosion problems. Presently perovskite oxide based ceramic materials are increasingly being used for such purposes, due to their highly inert behavior in hostile environment. In the present work, we have developed and characterized alumina based complex perovskite oxide ceramics, Ba{sub 2}AlSnO{sub 5.5}. These ceramics were prepared by solid state reaction process and produced in the form of circular discs by uniaxial pressure compaction technique. Green ceramic bodies were sintered at different sintering temperatures (1200 to 1500 deg. C) in air atmosphere. Structural and microstructural characteristics of sintered Ba{sub 2}AlMO{sub 5.5} were studied by XRD and SEM techniques. Mechanical properties were tested by Vickers microhardness tests. Ceramics sintered in the temperature range 1300 deg. C 1400 deg. C presented best results in terms of microstructural characteristics and mechanical performance. (authors)

  8. Method of sintering ceramic materials

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

  9. Flash sintering of ceramic materials

    Science.gov (United States)

    Dancer, C. E. J.

    2016-10-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

  10. Sintered ceramics having controlled density and porosity

    International Nuclear Information System (INIS)

    Brassfield, H.C.; DeHollander, W.R.; Nivas, Y.

    1980-01-01

    A new method was developed for sintering ceramic uranium dioxide powders, in which ammonium oxalate is admixed with the powder prior to being pressed into a cylindrical green body, so that the end-point density of the final nuclear-reactor fuel product can be controlled. When the green body is heated, the ammonium oxalate decomposes and leaves discrete porosity in the sintered body, which corresponds to the ammonium oxalate regions in the green body. Thus the end-point density of the sintered body is a function of the amount of ammonium oxalate added. The final density of the sintered product is about 90-97% of the theoretical. The addition of ammonium oxalate also allows control of the pore size and distribution throughout the fuel. The process leaves substantially no impurities in the sintered strucuture. (DN)

  11. Solidification of high level liquid waste (HLLW) into ceramics by sintering process

    International Nuclear Information System (INIS)

    Masuda, Sumio; Oguino, Naohiko; Tsunoda, Naomi; O-oka, Kazuo; Ohta, Takao.

    1979-01-01

    One of the alternatives to vitrified solid which is acceptable and well characterized for storing radioactive HLLW with desirable long-term stability is ceramics. On the other hand, the solidification process of highly radioactive wastes should be simple and suitable for continuous production. On the above described basis, the authors have made preliminary study on the production of sintered ceramics by the addition of several oxides to HLLW. The simulated waste and additive oxides were pressed in a mold to make the preforms of 50 mm diameter and 10 to 15 mm thick. The preforms were then normally sintered at temperature from 1000 to 1400 deg C for 2 to 4 hours. The characterization of the sintered solids revealed the following facts. (1) X-ray diffraction analysis showed that the expected crystals were formed by normal-sintering as well as by hot-pressing. (2) The bulk density of the ceramics by normal-sintering was around 90 to 95% of the assumed theoretical values. (3) The leach-rate of the solids was affected by the bulk density. (4) Other properties of the solids, such as thermal expansion or thermal conductivity, are dominantly determined by those of main crystals in the solids. Sintering process is generally simple and productive as far as normal sintering is concerned. However, hot-pressing is an intermittent and time consuming process. From this fact, the authors intended to adopt the normal sintering process for the ceramic solidification of high level liquid wastes. (Wakatsuki, Y.)

  12. Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Roman-Manso, B.; Pablos, A. de; Belmonte, M.; Osendi, M. I.; Miranzo, P.

    2014-04-01

    Concentrated ceramic inks based on (SiC) powders, with different amounts of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique. The densification of the as-produced 3D structures, previously heat treated in air at 600 degree centigrade for the organics burn-out, is achieved with a Spark Plasma Sintering (SPS) furnace. The effects of the amount of sintering additives (7 - 20 wt. %) and the size of the SiC powders (50 nm and 0.5 {mu}m) on the processing of the inks, microstructure, hardness and elastic modulus of the sintered scaffolds, are studied. The use of nano-sized (SiC) powders significantly restricts the attainable maximum solids volume fraction of the ink (0.32 compared to 0.44 of the submicron-sized powders-based ink), involving a much larger porosity of the green ceramic bodies. Furthermore, reduced amounts of additives improve the mechanical properties of the ceramic skeleton; particularly, the stiffness. The grain size and specific surface area of the starting powders, the ink solids content, green porosity, amount of sintering additives and SPS temperatures are the main parameters to be taken into account for the production of these SiC cellular ceramics. (Author)

  13. Novel sintered ceramic materials incorporated with EAF carbon steel slag

    Science.gov (United States)

    Karayannis, V.; Ntampegliotis, K.; Lamprakopoulos, S.; Papapolymerou, G.; Spiliotis, X.

    2017-01-01

    In the present research, novel sintered clay-based ceramic materials containing electric arc furnace carbon steel slag (EAFC) as a useful admixture were developed and characterized. The environmentally safe management of steel industry waste by-products and their valorization as secondary resources into value-added materials towards circular economy have attracted much attention in the last years. EAF Carbon steel slag in particular, is generated during the manufacture of carbon steel. It is a solid residue mainly composed of rich-in- Fe, Ca and Si compounds. The experimental results show that the beneficial incorporation of lower percentages of EAFC up to 6%wt. into ceramics sintered at 950 °C is attained without significant variations in sintering behavior and physico-mechanical properties. Further heating up to 1100 °C strongly enhances the densification of the ceramic microstructures, thus reducing the porosity and strengthening their mechanical performance. On the other side, in terms of thermal insulation behavior as well as energy consumption savings and production cost alleviation, the optimum sintering temperature appears to be 950 °C.

  14. Magnetic Glass Ceramics by Sintering of Borosilicate Glass and Inorganic Waste

    OpenAIRE

    Ponsot, In?s M. M. M.; Pontikes, Yiannis; Baldi, Giovanni; Chinnam, Rama K.; Detsch, Rainer; Boccaccini, Aldo R.; Bernardo, Enrico

    2014-01-01

    Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based on two iron-rich slags, coming from non-ferrous metallurgy and recycled borosilicate glass. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low te...

  15. SnO2*CoO ceramic obtained by microwave sintering

    International Nuclear Information System (INIS)

    Bordignon, M.A.N; Moura, F.; Zaghete, M.A.; Varela, J.A.; Perazolli, L.

    2009-01-01

    This work consists in the sintering study of CoO doped SnO 2 using microwave sintering oven and silicon carbide as a susceptor. The powders were obtained by dry oxides mixture and conformed in cylindrical shapes with 6mmx8mm and green density to 60%. Then the compacts were sintering up to 1.050 deg C, using heating rate of 50 deg C/min and isotherm up to 30min. The densities obtained were above 95% for both techniques. It was observed that occurred a temperature reducing of 400 deg C and time reducing of 210min to obtain the same densities, when was used the microwave oven without the phenomena of thermal runaway. So the sintered compacts were accomplished using DRX and SEM. It was made the electrical characterization (current x voltage) and it was found to have great potential in the production of dense ceramic-based SnO 2 with low resistivity to obtain electro-ceramic devices. (author)

  16. Method and apparatus for radio frequency ceramic sintering

    Science.gov (United States)

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  17. Sintering characteristics of nano-ceramic coatings

    NARCIS (Netherlands)

    de Hosson, J.T.M.; Popma, R.

    2003-01-01

    This paper concentrates on sintering characteristics of nano-sized ceramic SiO2 particles. The sintering process is studied as a function of temperature using a conventional furnace and using a laser beam. The underlying idea is to combine the nanoceramic sol-gel concept with inkjet technology and

  18. Techniques for ceramic sintering using microwave energy

    International Nuclear Information System (INIS)

    Kimrey, H.D.; Janney, M.A.; Becher, P.F.

    1987-01-01

    The use of microwave energy for ceramic sintering offers exciting new possibilities for materials processing. Based on experience gathered in microwave processing associated with the heating of fusion plasmas, we have developed hardware and methods for uniformly heating ceramic parts of large volume and irregular shape to temperatures in excess of 1600 0 C, in vacuum or pressurized atmosphere. Microwave processing at 28 GHz yields enhanced densification rates with a corresponding reduction in sintering temperatures. 6 refs

  19. Laser sintering of ceramics of Y2O3 pure e doped

    International Nuclear Information System (INIS)

    Oliveira, T.C. de; Goncalves, R.S.; Silva, R.S. da

    2012-01-01

    The Yttria (Y 2 O 3 ) is one of the most promising materials for refractory and optical applications due mainly to its high corrosion resistance, wide range of optical transmission and high melting point. However, due to its high melting point, ceramic bodies to obtain high density Y 2 O 3 high temperatures and require special sintering. Recently it has been proposed in the literature a new method of sintering in which a CO 2 laser, in continuous mode, is employed as the primary source of heat during sintering. Irradiation with laser light produces heating surface at elevated temperatures in a time interval of a few seconds, allowing to obtain dense ceramic bodies at elevated temperatures and with different properties from those sintered by conventional methods. In this paper, Y 2 O 3 powders of pure and doped with Mn, Ca and Zn were synthesized by the polymeric precursors and after calcination at 600 ° C/4h showed single phase. For the production and characterization of the samples used techniques DTA / TG, XRD Dilatometry, SEM and Radioluminescence. The sintered ceramics had a high relative density and strong dependence on the dopant used, which accelerate the densification process. Measures Radioluminescence showed characteristic peaks of Y 2 O 3 and dependence on the dopant used. (author)

  20. The pressureless sintering and mechanical properties of AlON ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, N., E-mail: zhangning5832@163.com [Key Lab. of Advanced Materials and Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China); Liang, B.; Wang, X.Y.; Kan, H.M.; Zhu, K.W. [Key Lab. of Advanced Materials and Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China); Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China)

    2011-07-25

    Highlights: {yields} A one-step pressureless sintering process was proposed, which is simple and viable. {yields} Cheap and easily available {alpha}-Al{sub 2}O{sub 3} and aluminum powders were chosen as raw materials substituting for expensive AlN ultrafine powders. {yields} The sintering temperature of AlON ceramic was reduced by 50 deg. C and the flexural strength was enhanced by 29.4%. - Abstract: Aluminum oxynitride (AlON) ceramic was synthesized by one-step pressureless sintering technology using low cost and easily available {alpha}-Al{sub 2}O{sub 3} and aluminum powders as raw materials. The sintering temperature was reduced because aluminum powders were nitridized into high activity AlN under the flowing nitrogen atmosphere. The curves of thermal analysis, microstructure and atomic distribution were investigated. The influence of sintering temperatures on phase composition, sintering densification and flexural strength was also explored. The experimental results showed that {alpha}-Al{sub 2}O{sub 3} and aluminum powders were acceptable substitutes for more expensive AlN ultrafine powders. Under the optimum sintering process at 1750 deg. C for 2 h, the sintered density and flexural strength of AlON ceramic were higher, 3.62 g/cm{sup 3} and 321 MPa, respectively. The sintering temperature was decreased by 50 deg. C because newly formed high activity AlN in situ reacted with Al{sub 2}O{sub 3} into Al{sub 23}O{sub 27}N{sub 5}, enhancing flexural strength by 29.4%. However, the sintering temperature could not be too high because grain growth and displacement of oxygen atoms from AlON ceramics by nitrogen atoms caused a decline in sintering densification and flexural strength.

  1. Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

    International Nuclear Information System (INIS)

    Aloisi, Mirko; Karamanov, Alexander; Taglieri, Giuliana; Ferrante, Fabiola; Pelino, Mario

    2006-01-01

    A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 deg. C/min, increased by about 20% and 30%, respectively

  2. Highly textured KNN-based piezoelectric ceramics by conventional sintering

    International Nuclear Information System (INIS)

    Zapata, Angelica Maria Mazuera; Silva Junior, Paulo Sergio da; Zambrano, Michel Venet

    2016-01-01

    Full text: Texturing in ferroelectric ceramics has played an important role in the enhancement of their piezoelectric properties. Common methods for ceramic texturing are hot pressing and template grain ground; nevertheless, the needed facilities to apply hot pressing and the processing of single crystal make the texture of ceramics expensive and very difficult. In this study, a novel method was investigated to obtain highly textured lead-free ceramics. A (K 0.5 Na 0.5 ) 0.97 Li 0. 0 3 Nb 0.8 Ta 0. 2 matrix (KNLNT), with CuO excess was sintered between 1070 and 1110 °C following a solid state reaction procedure. The CuO excess promotes liquid phase formation and a partial melting of the material. XRD patterns showed the intensity of (100) family peaks became much stronger with the increasing of sintering temperature and CuO. In addition, Lotgering factor was calculated and exhibited a texture degree between 40 % and 70 % for sintered samples having 13 and 16 wt. % CuO, respectively. These, highly textured ceramics, with adequate cut, can be used as substitutes single crystals for texturing of KNN-based lead-free ceramics. (author)

  3. Microstructure evolution during pressureless sintering of bulk oxide ceramics

    Directory of Open Access Journals (Sweden)

    Karel Maca

    2009-06-01

    Full Text Available The author’s experience concerning the infl uence of the choice of different pressureless heating schedules on the fi nal microstructure of oxide ceramic materials is summarized in the paper. Alumina, ceria, strontium titanate, as well as tetragonal (3 mol% Y2O3 and cubic (8 mol% Y2O3 zirconia were cold isostatically pressed or injection moulded and pressureless sintered with different heating schedules – namely with Constant-Rate of Heating with different dwell temperatures (CRH, with Rate-Controlled Sintering (RCS and with Two-Step Sintering (TSS. It was examined whether some of these three sintering schedules, with the same fi nal density achieved, can lead to a decrease of the grain size of sintered ceramics. The results showed that only TSS (and only for selected materials brought significant decrease of the grain size.

  4. Sintering behavior of LZSA glass-ceramics

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2009-06-01

    Full Text Available The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3 shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter. Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.

  5. Lanthanide (Nd, Gd) compounds with garnet and monazite structures. Powders synthesis by “wet” chemistry to sintering ceramics by Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Potanina, Ekaterina, E-mail: ekaterina.potanina@list.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Golovkina, Ludmila, E-mail: golovkina_lyudmila@mail.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Orlova, Albina, E-mail: albina.orlova@inbox.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Nokhrin, Aleksey, E-mail: nokhrin@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation); Boldin, Maksim, E-mail: boldin@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation); Sakharov, Nikita, E-mail: nvsaharov@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation)

    2016-05-15

    Complex oxide Y{sub 2.5}Nd{sub 0.5}Al{sub 5}O{sub 12} with garnet structure and phosphates NdPO{sub 4} and GdPO{sub 4} with monazite structure were obtained by using precipitation methods. Ceramics Y{sub 2.5}Nd{sub 0.5}Al{sub 5}O{sub 12} and NdPO{sub 4} were processed by Spark Plasma Sintering (SPS). Relative density more 98%, sintering time did not exceed 8 min, sintering temperature 1330–1390 °C. Leaching rates of elements from ceramics were 10{sup −6}–10{sup −7} g/(cm{sup 2} d). The process of ceramics sintering has two-stage character: the first step of sintering-compaction process is related to the plastic flow of the material, the second step–to the process of grain boundary diffusion and grain growth. - Highlights: • Powders were obtained by precipitation (sol–gel) method. • Ceramics were sintering by Spark Plasma Sintering method (ρ{sub rel} > 98%); shrinkage time does not exceed 8 min. • The process of ceramics sintering has two-stage character.

  6. Alumina-zirconium ceramics synthesis by selective laser sintering/melting

    International Nuclear Information System (INIS)

    Shishkovsky, I.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

    2007-01-01

    In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al 2 O 3 . By applying finely dispersed Y 2 O 3 powder inclusions, the type of the ceramic structure is significantly changed

  7. The effect of spark plasma sintering on lithium disilicate glass-ceramics.

    Science.gov (United States)

    Al Mansour, Fatima; Karpukhina, Natalia; Grasso, Salvatore; Wilson, Rory M; Reece, Mike J; Cattell, Michael J

    2015-10-01

    To evaluate the effects of spark plasma sintering (SPS) on the microstructure of lithium disilicate glass-ceramics. IPS e.max CAD glass-ceramic samples were processed using spark plasma sintering (SPS) and conventionally sintered (CS) as a comparison. Specimens were sintered at varying temperatures (T1: 840°C, T2: 820°C, T3: 800°C), heating rates (HR1: 150°C/min, HR2: 300°C/min, HR3: 500°C/min) and pressures (P1: 15MPa, P2: 50MPa, P3: 70MPa). IPS e.max Press glass powder samples were densified at 750 and 800°C (50 or 200MPa pressure). Samples were characterized using XRD, HTXRD, and SEM and quantitative image analysis. There was a significant increase in median crystal size (MCS) between the CS and the SPS T1 groups. A statistical difference (p>0.05) in MCS between SPS T1 and SPS T2 groups was observed. The SPS HR3 sample produced a smaller MCS than the CS, SPS HR1 and HR2 groups (pglass samples resulted in fine fibrils or graduated lithium disilicate crystals. The effects of SPS were used to refine the microstructure of IPS e.max CAD lithium disilicate glass-ceramics. Densification by SPS of IPS e.max Press glass resulted in textured and fine nano-crystalline microstructures. SPS generated glass-ceramic microstructures may have unique properties and could be useful in the production of CAD/CAM materials for dentistry. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Sintering and annealing effects on undoped yttria transparent ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Letue, Laetitia; Petit, Johan, E-mail: johan.petit@onera.fr; Ritti, Marie-Hélène; Lalanne, Sylvie; Landais, Stéphane

    2017-06-15

    Transparent yttrium oxide (Y{sub 2}O{sub 3}) ceramics were processed by several densifications steps without any doping species. The green bodies were obtained by the aqueous way and sintered at high temperature under vacuum and then under high pressure. We studied the effects of different sintering cycles and air annealing at different steps of the process on the density and the grain growth. We also focused on the reaction between yttria ceramics and BN-coated graphite crucible which occurs during HIP. We noted that a low heating rate and two annealing steps are necessary to improve our samples’ transparency. - Highlights: • The quality of transparent ceramics is compared with the tested process parameters. • Air annealing is critical when using a carbon environment in the process. • Intra-granular pores, and so the final transparency, are directly linked to the sintering heating rates.

  9. Magnetic Glass Ceramics by Sintering of Borosilicate Glass and Inorganic Waste

    Directory of Open Access Journals (Sweden)

    Inès M. M. M. Ponsot

    2014-07-01

    Full Text Available Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based on two iron-rich slags, coming from non-ferrous metallurgy and recycled borosilicate glass. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1000 °C, whereas glass/slag interactions resulted in the formation of magnetite crystals, providing ferrimagnetism. Such behavior could be exploited for applying the obtained glass ceramics as induction heating plates, according to preliminary tests (showing the rapid heating of selected samples, even above 200 °C. The chemical durability and safety of the obtained glass ceramics were assessed by both leaching tests and cytotoxicity tests.

  10. Preparation and electromagnetic properties of low-temperature sintered ferroelectric-ferrite composite ceramics

    International Nuclear Information System (INIS)

    Yue Zhenxing; Chen Shaofeng; Qi Xiwei; Gui Zhilun; Li Longtu

    2004-01-01

    For the purpose of multilayer chip EMI filters, the new ferroelectric-ferrite composite ceramics were prepared by mixing PMZNT relaxor ferroelectric powder with composition of 0.85Pb(Mg 1/3 Nb 2/3 )O 3 -0.1Pb(Ni 1/3 Nb 2/3 )O 3 -0.05PbTiO 3 and NiCuZn ferrite powder with composition of (Ni 0.20 Cu 0.20 Zn 0.60 )O(Fe 2 O 3 ) 0.97 at low sintering temperatures. A small amount of Bi 2 O 3 was added to low sintering temperature. Consequently, the dense composite ceramics were obtained at relative low sintering temperatures, which were lower than 940 deg. C. The X-ray diffractometer (XRD) identifications showed that the sintered ceramics retained the presence of distinct ferroelectric and ferrite phases. The sintering studies and scanning electron microscope (SEM) observations revealed that the co-existed two phases affect the sintering behavior and grain growth of components. The electromagnetic properties, such as dielectric constant and initial permeability, change continuously between those of two components. Thus, the low-temperature sintered ferroelectric-ferrite composite ceramics with tunable electromagnetic properties were prepared by adjusting the relative content of two components. These materials can be used for multilayer chip EMI filters with various properties

  11. Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite

    International Nuclear Information System (INIS)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin

    2015-01-01

    Highlights: • Glass ceramic composite is prepared from oil shale fly ash and MSWI bottom ash. • A novel method for the production of glass ceramic composite is presented. • It provides simple route and lower energy consumption in terms of recycling waste. • The vitrified slag can promote the sintering densification process of glass ceramic. • The performances of products decrease with the increase of oil shale fly ash content. - Abstract: Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2 h) showed the properties of density of 1.92 ± 0.05 g/cm 3 , weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced

  12. Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin, E-mail: leeam@dlut.edu.cn

    2015-04-15

    Highlights: • Glass ceramic composite is prepared from oil shale fly ash and MSWI bottom ash. • A novel method for the production of glass ceramic composite is presented. • It provides simple route and lower energy consumption in terms of recycling waste. • The vitrified slag can promote the sintering densification process of glass ceramic. • The performances of products decrease with the increase of oil shale fly ash content. - Abstract: Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2 h) showed the properties of density of 1.92 ± 0.05 g/cm{sup 3}, weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced

  13. Sintered bentonite ceramics for the immobilization of cesium- and strontium-bearing radioactive waste

    Science.gov (United States)

    Ortega, Luis Humberto

    The Advanced Fuel Cycle Initiative (AFCI) is a Department of Energy (DOE) program, that has been investigating technologies to improve fuel cycle sustainability and proliferation resistance. One of the program's goals is to reduce the amount of radioactive waste requiring repository disposal. Cesium and strontium are two primary heat sources during the first 300 years of spent nuclear fuel's decay, specifically isotopes Cs-137 and Sr-90. Removal of these isotopes from spent nuclear fuel will reduce the activity of the bulk spent fuel, reducing the heat given off by the waste. Once the cesium and strontium are separated from the bulk of the spent nuclear fuel, the isotopes must be immobilized. This study is focused on a method to immobilize a cesium- and strontium-bearing radioactive liquid waste stream. While there are various schemes to remove these isotopes from spent fuel, this study has focused on a nitric acid based liquid waste. The waste liquid was mixed with the bentonite, dried then sintered. To be effective sintering temperatures from 1100 to 1200°C were required, and waste concentrations must be at least 25 wt%. The product is a leach resistant ceramic solid with the waste elements embedded within alumino-silicates and a silicon rich phase. The cesium is primarily incorporated into pollucite and the strontium into a monoclinic feldspar. The simulated waste was prepared from nitrate salts of stable ions. These ions were limited to cesium, strontium, barium and rubidium. Barium and rubidium will be co-extracted during separation due to similar chemical properties to cesium and strontium. The waste liquid was added to the bentonite clay incrementally with drying steps between each addition. The dry powder was pressed and then sintered at various temperatures. The maximum loading tested is 32 wt. percent waste, which refers to 13.9 wt. percent cesium, 12.2 wt. percent barium, 4.1 wt. percent strontium, and 2.0 wt. percent rubidium. Lower loadings of waste

  14. The effects of sintering behavior on piezoelectric properties of porous PZT ceramics for hydrophone application

    International Nuclear Information System (INIS)

    Zeng Tao; Dong Xianlin; Chen Heng; Wang Yonglin

    2006-01-01

    Porous lead zirconate titanate (PZT) ceramics were fabricated by adding polymethyl methacrylate (PMMA) and the effects of sintering behavior on their microstructure and piezoelectric properties were investigated. The porosity of PZT ceramics decreased with an increase in the sintering temperature at a fixed PMMA addition. The dielectric constant (ε), longitudinal piezoelectric coefficient (d 33 ) and hydrostatic figures of merit (d h g h ) of 34% porous PZT ceramics increased with an increase in sintering temperature from 1050 to 1300 deg. C. When sintered at 1300 deg. C, longitudinal piezoelectric coefficient of 34% porous PZT ceramic was very close to that of 95% dense PZT ceramics, while the hydrostatic figures of merit of 34% porous PZT ceramics is about fifteen times more than that of 95% dense PZT ceramics. Compared with PZT-polymer composites, the dielectric constant of 34% porous PZT sintered at 1300 deg. C is much higher, which can be more efficient to resist the interference in receiving sensitivities caused by loading effect of the cable

  15. Influence of feldspar containing lithium in the sintering of triaxial ceramics

    International Nuclear Information System (INIS)

    Oliveira, Camila Felippe de; Strecker, Kurt

    2011-01-01

    In this work, the properties of a ceramic material based on a triaxial mass composed of clay, quartz and 15 to 30% feldspar, albite or spodumene, has been investigated. Specimen were prepared by uniaxial pressing under 28.5MPa and sintering at temperatures of 1000, 1100 and 1200 deg C, for 1h. The samples were characterized by their linear shrinkage, apparent porosity, apparent density and flexural strength, as well as analysis of the microstructure. The best results were obtained for samples prepared with 30% spodumene and sintered at 1200 deg C, with a shrinkage of 6.4%, density of 2.01g/cm 3 , porosity of 14.3% and flexural strength of 13.4MPa, while samples prepared with albite exhibited shrinkage of 5.8%, density of 1.9g/cm 3 , porosity of 18.9% and strength of 9.8MPa. Therefore, by the substitution of albite by spodumene in the ceramic triaxial mass, lower sintering temperatures may be employed, thus reducing production costs by the lesser energy consumption. (author)(

  16. Sintering mechanism of blast furnace slag-kaolin ceramics

    International Nuclear Information System (INIS)

    Mostafa, Nasser Y.; Shaltout, Abdallah A.; Abdel-Aal, Mohamed S.; El-maghraby, A.

    2010-01-01

    A general ceramics processing scheme by cold uniaxial pressing and conventional sintering process have been used to prepare ceramics from mixtures of blast furnace slag (BFS) and kaolin (10%, 30% and 50% kaolin). The properties of the ceramics were studied by measuring linear shrinkage, bulk density, apparent porosity and mechanical properties of samples heated at temperatures from 800 o C to 1100 o C. The formed crystalline phases were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). Slag melt formed at relatively low temperatures (800-900 o C) modified the sintering process to liquid phase sintering mechanism. Combination of BFS with 10% kaolin gave the highest mechanical properties, densification and shrinkage at relatively low firing temperatures. The crystalline phases were identified as gehlenite (Ca 2 Al 2 SiO 7 ) in both BFS and BFS with 10% kaolin samples. Anorthite (CaAl 2 Si 2 O 8 ) phase increased with increasing kaolin contents. In the case of kaolin-rich mixtures (30% and 50% kaolin), increased expansion took place during firing at temperatures in the range 800-1000 o C. This effect could be attributed to the entrapment of released gases.

  17. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    Science.gov (United States)

    Gephart, Sean

    materials. While FAST sintered materials showed higher average values, in general they also showed consistently larger variation in the scattered data and consequently larger standard deviation for the resulting material properties. In addition, dynamic impact testing (V50 test) was conducted on the resulting materials and it was determined that there was no discernable correlation between observed mechanical properties of the ceramic materials and the resulting dynamic testing. Another study was conducted on the sintering of SiC and carbon fiber reinforced SiC ceramic matrix composites (CMC) using FAST. There has been much interest recently in fabricating high strength, low porosity SiC CMC.s for high temperature structural applications, but the current methods of production, namely chemical vapor infiltration (CVI), melt infiltration (MI), and polymer infiltration and pyrolysis (PIP), are considered time consuming and involve material related shortcomings associated with their respective methodologies. In this study, SiC CMC.s were produced using the 25 ton laboratory unit with a target sample size of 40 mm diameter and 3 mm thickness, as well as on the larger 250 ton industrial FAST system targeting a sample size of 101.6 x 101.6 x 3 mm3 to investigate issues associated with scaling. Several sintering conditions were explored including: pressure of 35-65 MPa, temperature of 1700-1900°C, and heating rates between 50-400°C/min. The SiC fibers used in this study were coated using chemical vapor deposition (CVD) with boron nitride (BN) and pyrolytic carbon to act as a barrier layer and preserve the integrity of the fibers during sintering. Then the barrier coating was coated by an outer layer of SiC to enhance the bonding between the fibers and the SiC matrix. Microstructures of the sintered samples were examined by FE-SEM. Mechanical properties including flexural strength-deflection and stress-strain were characterized using 4-point bend testing. Tensile testing was

  18. Production and study of the behavior of ceramic sintering SR2ALWO5,5 to application on the oil industry

    International Nuclear Information System (INIS)

    Lima, M.M.; Ferreira, R.A. Sanguinetti; Yadava, Y.P.

    2011-01-01

    The complex perovskita ceramics based on tungsten are highly inert corrosive environments. For this reason, this type of ceramic is used in the manufacture of parts and components for the oil industry where the hostile environment is constant problem. We are working in manufacturing temperature sensors encased in ceramic to petroleum industry. Produce ceramic Sr 2 AlWO 5,5 thermo-mechanical process using a ball mill and subsequently heat treatment temperature of 1200°C for 24 hours. Studied the sintering behavior in the temperature range from 1200 to 1350 °C. In this process, the ceramic powder had a high homogeneity in terms of size and distribution of particles, which facilitates sintering at low temperature and shorter time. Structure and microstructure of calcined ceramic was analyzed by X-ray diffraction and scanning electron microscopy and presented at the congress. (author)

  19. Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

    Science.gov (United States)

    Varghese, Jobin; Vahera, Timo; Ohsato, Hitoshi; Iwata, Makoto; Jantunen, Heli

    2017-10-01

    In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications.

  20. [Characterization of alumina adobe and sintered body of GI-infiltrated ceramic].

    Science.gov (United States)

    Wang, H; Chao, Y; Liao, Y; Liang, X; Zhu, Z; Gao, W

    2001-06-01

    This study was conducted to elucidate the mechanism of formation of porous structure by investigating the porosity of the alumina adobe and sintered body of GI-II Infiltrate Ceramic, and its role in strengthening and toughening this kind of ceramic composite. The alumina powder size-mass distribution was obtained by BI-XDC powder size analysis device; the open pore parameters of alumina adobe and sintered body were analyzed using the mercury pressure method. Their fracture surfaces were observed under scanning electronic microscope. Fine powder had two main size groups of 0.09-0.1 micron and 0.2-0.5 micron, respectively, and coarse powder, with size between 1.5 to 4.5 microns, occupied the majority of powder mass. Alumina adobe's pores became larger after sintering. The median pore radii of adobe and sintered body were 0.2531 micron and 0.3081 micron, respectively; the average pore radii changed from 0.0956 micron to 0.1102 micron. Under scanning electronic microscope, fine alumina powders were fused partially together and their surfaces were blunted, but coarse powders did not show such phenomena. The alumina size distribution contributes to the formation of porous structure of alumina sintered body. This porous structure is not only the shape skeleton but also the mechanical skeleton of GI-II Infiltrated Ceramic. It plays an important role in raising the mechanical properties of this kind of ceramic composite.

  1. Conventional and two step sintering of PZT-PCN ceramics

    Science.gov (United States)

    Keshavarzi, Mostafa; Rahmani, Hooman; Nemati, Ali; Hashemi, Mahdieh

    2018-02-01

    In this study, PZT-PCN ceramic was made via sol-gel seeding method and effects of conventional sintering (CS) as well as two-step sintering (TSS) were investigated on microstructure, phase formation, density, dielectric and piezoelectric properties. First, high quality powder was achieved by seeding method in which the mixture of Co3O4 and Nb2O5 powder was added to the prepared PZT sol to form PZT-PCN gel. After drying and calcination, pyrochlore free PZT-PCN powder was synthesized. Second, CS and TSS were applied to achieve dense ceramic. The optimum temperature used for 2 h of conventional sintering was obtained at 1150 °C; finally, undesired ZrO2 phase formed in CS procedure was removed successfully with TSS procedure and dielectric and piezoelectric properties were improved compared to the CS procedure. The best electrical properties obtained for the sample sintered by TSS in the initial temperature of T 1 = 1200 °C and secondary temperature of T 2 = 1000 °C for 12 h.

  2. An investigation in texturing high Tc superconducting ceramics by creep sintering

    International Nuclear Information System (INIS)

    Regnier, P.; Deschanels, X.; Maurice, F.; Schmirgeld, L.; Aguillon, C.; Senoussi, S.; Mac Carthy, M.; Tatlock, G.J.

    1991-01-01

    We study in detail the possibility of high-T c superconducting ceramics texturing by high pressing them during sintering. We show texture variations as a function of the applied load, of the deformation, of the temperature, and of the sintering stage length, of the rate of variation of temperature, of the material nature in contact with ceramic and of the original powder quality. We present results obtained by optical microscopy, electronic microscopy, X-rays, and local chemical analysis

  3. Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

    Science.gov (United States)

    Singh, M.

    2011-01-01

    During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

  4. Two-step sintering of ultrafine-grained barium cerate proton conducting ceramics

    International Nuclear Information System (INIS)

    Wang, Siwei; Zhang, Lei; Zhang, Lingling; Brinkman, Kyle; Chen, Fanglin

    2013-01-01

    Ultra-fine grained dense BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) ceramics have been successfully prepared via a two-step sintering method. Co-precipitation method has been adopted to prepare nano-sized BZCYYb precursors with an average particle size of 30 nm. By controlling the sintering profile, an average grain size of 184 nm was obtained for dense BZCYYb ceramics via the two-step sintering method, compared to 445 nm for the conventional sintered samples. The two-step sintered BZCYYb samples showed less impurity and an enhanced electrical conductivity compared with the conventional sintered ones. Further, the two-step sintering method was applied to fabricate anode supported solid oxide fuel cells (SOFCs) using BZCYYb as the electrolyte, resulting in dense ultrafine-grained electrolyte membranes and porous anode substrates with fine particles. Due to the reduced ohmic as well as polarization resistances, the maximum power output of the cells fabricated from the two-step sintering method reached 349 mW m −2 at 700 °C, significantly improved from 172 mW cm −2 for the conventional sintered cells, suggesting that two-step sintering method is very promising for optimizing the microstructure and thus enhancing the electrochemical performances for barium cerate based proton-conducting SOFCs.

  5. Fractal corrections of BaTiO3-ceramic sintering parameters

    Directory of Open Access Journals (Sweden)

    Mitić V.V.

    2014-01-01

    Full Text Available Morphology of ceramics grains and pores as well as Brownian character of particle dynamics inside ceramics specimen contributes to better understanding of the sintering process. BaTiO3-ceramics, studied in this paper, has light fractal form and it is emanated in three aspects. First, the surface of grains, even in starting green body as well as distribution of grains shows fractal behavior. Second, existence of pores and their distribution follow the rules of fractal geometry. Third, movement of particles inside viscous flow underlies the rule of Brownian motion, which is essentially a fractal category. These three elements, each in its domain influence sintering dynamics, and can be described by dimensionless quantitative factors, αs αp and αm, being normalized to the interval [0,1]. Following sintering process, the associate formulae of Frenkel, Scherer and Mackenzie-Shuttleworth are shown from the angle of view of ceramics fractal dimension changing that approaches to 3. Also, it is shown that the energy balance is not violated after applying fractal correction to quasi equilibrium of the energy emanating from surface area reduction ES and energy adopted by viscous flow Ef .[Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

  6. Predicting sintering deformation of ceramic film constrained by rigid substrate using anisotropic constitutive law

    International Nuclear Information System (INIS)

    Li Fan; Pan Jingzhe; Guillon, Olivier; Cocks, Alan

    2010-01-01

    Sintering of ceramic films on a solid substrate is an important technology for fabricating a range of products, including solid oxide fuel cells, micro-electronic PZT films and protective coatings. There is clear evidence that the constrained sintering process is anisotropic in nature. This paper presents a study of the constrained sintering deformation using an anisotropic constitutive law. The state of the material is described using the sintering strains rather than the relative density. In the limiting case of free sintering, the constitutive law reduces to a conventional isotropic constitutive law. The anisotropic constitutive law is used to calculate sintering deformation of a constrained film bonded to a rigid substrate and the compressive stress required in a sinter-forging experiment to achieve zero lateral shrinkage. The results are compared with experimental data in the literature. It is shown that the anisotropic constitutive law can capture the behaviour of the materials observed in the sintering experiments.

  7. On the Mechanism of Microwave Flash Sintering of Ceramics

    Directory of Open Access Journals (Sweden)

    Yury V. Bykov

    2016-08-01

    Full Text Available The results of a study of ultra-rapid (flash sintering of oxide ceramic materials under microwave heating with high absorbed power per unit volume of material (10–500 W/cm3 are presented. Ceramic samples of various compositions—Al2O3; Y2O3; MgAl2O4; and Yb(LaO2O3—were sintered using a 24 GHz gyrotron system to a density above 0.98–0.99 of the theoretical value in 0.5–5 min without isothermal hold. An analysis of the experimental data (microwave power; heating and cooling rates along with microstructure characterization provided an insight into the mechanism of flash sintering. Flash sintering occurs when the processing conditions—including the temperature of the sample; the properties of thermal insulation; and the intensity of microwave radiation—facilitate the development of thermal runaway due to an Arrhenius-type dependency of the material’s effective conductivity on temperature. The proper control over the thermal runaway effect is provided by fast regulation of the microwave power. The elevated concentration of defects and impurities in the boundary regions of the grains leads to localized preferential absorption of microwave radiation and results in grain boundary softening/pre-melting. The rapid densification of the granular medium with a reduced viscosity of the grain boundary phase occurs via rotation and sliding of the grains which accommodate their shape due to fast diffusion mass transport through the (quasi-liquid phase. The same mechanism based on a thermal runaway under volumetric heating can be relevant for the effect of flash sintering of various oxide ceramics under a dc/ac voltage applied to the sample.

  8. Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

    Directory of Open Access Journals (Sweden)

    Román-Manso, B.

    2014-04-01

    Full Text Available Concentrated ceramic inks based on β-SiC powders, with different amounts of Y2O3 and Al2O3 as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique. The densifi cation of the as-produced 3D structures, previously heat treated in air at 600 ºC for the organics burn-out, is achieved with a Spark Plasma Sintering (SPS furnace. The effects of the amount of sintering additives (7 - 20 wt. % and the size of the SiC powders (50 nm and 0.5 μm on the processing of the inks, microstructure, hardness and elastic modulus of the sintered scaffolds, are studied. The use of nano-sized β-SiC powders significantly restricts the attainable maximum solids volume fraction of the ink (0.32 compared to 0.44 of the submicron-sized powders-based ink, involving a much larger porosity of the green ceramic bodies. Furthermore, reduced amounts of additives improve the mechanical properties of the ceramic skeleton; particularly, the stiffness. The grain size and specific surface area of the starting powders, the ink solids content, green porosity, amount of sintering additives and SPS temperatures are the main parameters to be taken into account for the production of these SiC cellular ceramics.Se han fabricado andamiajes de carburo de silicio (SiC usando la técnica de “Robocasting”, a partir de tintas cerámicas conteniendo β-SiC y distintas cantidades de Y2O3 and Al2O3, como aditivos de sinterización. La densificación de las estructuras tridimensionales, previamente calcinadas a 600 ºC para eliminar los aditivos orgánicos, se realizó en un horno de “Spark Plasma Sintering” (SPS. Se analizó el efecto de la cantidad de aditivos de sinterización (7-20 % en peso y del tamaño de partícula inicial del polvo de SiC (50 nm y 0.5 μm en el procesado de las tintas, en la microestructura, la dureza y el módulo elástico de las estructuras sinterizadas. El uso de polvo

  9. Dielectric Properties of Sol-Gel Derived Barium Strontium Titanate and Microwave Sintering of Ceramics

    Science.gov (United States)

    Selmi, Fathi A.

    This thesis consists of two areas of research: (1) sol-gel processing of Ba_{rm 1-x}Sr_{rm x} TiO_3 ceramics and their dielectric properties measurement; and (2) microwave versus conventional sintering of ceramics such as Al_2 O_3, Ba_{ rm 1-x}Sr_{rm x}TiO_3, Sb-doped SnO _2 and YBa_2Cu _3O_7. Sol-gel powders of BaTiO_3, SrTiO_3, and their solid solutions were synthesized by the hydrolysis of titanium isopropoxide and Ba and Sr methoxyethoxides. The loss tangent and dielectric constant of both sol-gel and conventionally prepared and sintered Ba_{rm 1-x}Sr _{rm x}TiO _3 ceramics were investigated at high frequencies. The sol-gel prepared ceramics showed higher dielectric constant and lower loss compared to those prepared conventionally. Ba _{rm 1-x}Sr _{rm x}TiO_3 ceramics were tunable with applied bias, indicating the potential use of this material for phase shifter applications. Porous Ba_{0.65}Sr _{0.35}TiO_3 was also investigated to lower the dielectric constant. Microwave sintering of alpha -Al_2O_3 and SrTiO_3 was investigated using an ordinary kitchen microwave oven (2.45 GHz; 600 Watts). The use of microwaves with good insulation of alpha -Al_2O_3 and SrTiO_3 samples resulted in their rapid sintering with good final densities of 96 and 98% of the theoretical density, respectively. A comparison of grain size for conventionally and microwave sintered SrTiO_3 samples did not show a noticeable difference. However, the grain size of microwave sintered alpha-Al_2O _3 was found to be larger than that of conventionally sintered sample. These results show that rapid sintering of ceramics can be achieved by using microwave radiation. The sintering behavior of coprecipitated Sb-doped SnO_2 was investigated using microwave power absorption. With microwave power, samples were sintered at 1450^circC for 20 minutes and showed a density as high as 99.9% of theoretical. However, samples fired in a conventional electric furnace at the same temperature for 4 hours showed only

  10. Highly transparent Tb3Al5O12 magneto-optical ceramics sintered from co-precipitated powders with sintering aids

    Science.gov (United States)

    Dai, Jiawei; Pan, Yubai; Xie, Tengfei; Kou, Huamin; Li, Jiang

    2018-04-01

    Highly transparent terbium aluminum garnet (Tb3Al5O12, TAG) magneto-optical ceramics were fabricated from co-precipitated nanopowders with tetraethoxysilane (TEOS) as sintering aid by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The ball milled TAG powder shows better dispersity than the as-synthesized powder, and its average particle size is about 80 nm. For the ceramic sample pre-sintered at 1720 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the in-line transmittance exceeds 76% in the region of 400-1580nm (except the absorption band), reaching a maximum value of 81.8% at the wavelength of 1390 nm. The microstructure of the TAG ceramic is homogeneous and its average grain size is approximately 19.7 μm. The Verdet constant of the sample is calculated to be -182.7 rad·T-1·m-1 at room temperature.

  11. Reaction sintering of ceramic-metal composites

    International Nuclear Information System (INIS)

    Botta Filho, W.J.; Rodrigues, J.A.; Tomasi, R.; Pandolfelli, V.C.; Passos, J.F.S.S.; Folgueras, M.V.

    1990-01-01

    Reaction sintering experiments have been carried out in the system Al 2 O 3 -ZrAl 2 -Nb 2 O 5 with the objective of producing ceramic-metal composites of improved toughness. The sintering treatments have been done in the temperature range of 700 0 C to 1400 0 C under different conditions of vacuum and in air and argon atmospheres. The treated samples have been analysed by X-ray diffraction and analytical electron microscopy. The results are discussed in function of the degree of reaction, the development of microstructure and the densification. These results have shown that although an exchange reaction can occur to produce a composite, the control of the reaction to obtain a dense microstructure has not been possible yet. (author) [pt

  12. [Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

    Science.gov (United States)

    Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

    2017-04-01

    This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
.

  13. Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

    International Nuclear Information System (INIS)

    Wang, Y.P.; Zhou, L.; Zhang, M.F.; Chen, X.Y.; Liu, J.-M.; Liu, Z.G.

    2004-01-01

    Single-phased ferroelectromagnet BiFeO 3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 deg. C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm 2 , 4.0 μC/cm 2 , and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe 2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials

  14. Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite.

    Science.gov (United States)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin

    2015-04-01

    Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2h) showed the properties of density of 1.92 ± 0.05 g/cm(3), weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. FDTD simulation of microwave sintering of ceramics in multimode cavities

    Energy Technology Data Exchange (ETDEWEB)

    Iskander, M.F.; Smith, R.L.; Andrade, A.O.M.; Walsh, L.M. (Univ. of Utah, Salt Lake City, UT (United States). Dept. of Electrical Engineering); Kimrey, H. Jr. (Oak Ridge National Lab., TN (United States))

    1994-05-01

    At present, various aspects of the sintering process such as preparation of sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide an improved understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process. In this paper, the authors utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a ceramic loading plate placed at the base of the cavity. The FDTD simulation thus provides realistic representation of a typical sintering experiment. Aspects that have been successfully simulated include the effects of various types of insulation, the role of SiC rods on the uniformity of the resulting microwave fields, and the possible shielding effects that may result from excessive use of SiC. These results as well as others showing the electromagnetic fields and power-deposition patterns in multiple ceramic samples are presented.

  16. Transparent Lu 2 O 3 :Eu ceramics by sinter and HIP optimization

    Science.gov (United States)

    Seeley, Z. M.; Kuntz, J. D.; Cherepy, N. J.; Payne, S. A.

    2011-09-01

    Evolution of porosity and microstructure was observed during densification of lutetium oxide ceramics doped with europium (Lu 2O 3:Eu) fabricated via vacuum sintering and hot isostatic pressing (HIP'ing). Nano-scale starting powder was uniaxially pressed and sintered under high vacuum at temperatures between 1575 and 1850 °C to obtain densities ranging between 94% and 99%, respectively. Sintered compacts were then subjected to 200 MPa argon gas at 1850 °C to reach full density. Vacuum sintering above 1650 °C led to rapid grain growth prior to densification, rendering the pores immobile. Sintering between 1600 and 1650 °C resulted in closed porosity yet a fine grain size to allow the pores to remain mobile during the subsequent HIP'ing step, resulting in a fully-dense highly transparent ceramic without the need for subsequent air anneal. Light yield performance was measured and Lu 2O 3:Eu showed ˜4 times higher light yield than commercially used scintillating glass indicating that this material has the potential to improve the performance of high energy radiography devices.

  17. Effects of AlN on the densification and mechanical properties of pressureless-sintered SiC ceramics

    Directory of Open Access Journals (Sweden)

    Qisong Li

    2016-02-01

    Full Text Available In the present work, SiC ceramics was fabricated with AlN using B4C and C as sintering aids by a solid-state pressureless-sintered method. The effects of AlN contents on the densification, mechanical properties, phase compositions, and microstructure evolutions of as-obtained SiC ceramics were thoroughly investigated. AlN was found to promote further densification of the SiC ceramics due to its evaporation over 1800 °C, transportation, and solidification in the pores resulted from SiC grain coarsening. The highest relative density of 99.65% was achieved for SiC sample with 15.0 wt% AlN by the pressureless-sintered method at 2130 °C for 1 h in Ar atmosphere. Furthermore, the fracture mechanism for SiC ceramics containing AlN tended to transfer from single transgranular fracture mode to both transgranular fracture and intergranular fracture modes when the sample with 30.0 wt% AlN sintered at 1900 °C for 1 h in Ar. Also, SiC ceramics with 30.0 wt% AlN exhibited the highest fracture toughness of 5.23 MPa m1/2 when sintered at 1900 °C.

  18. Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-Wei [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science & Engineering

    2018-02-02

    Solid oxide fuel cells and solid oxide electrolysis cells rely on solid electrolytes in which a large ionic current dominates. This project was initiated to investigate microstructural changes in such devices under electrochemical forces, because nominally insignificant processes may couple to the large ionic current to yield non-equilibrium phenomena that alter the microstructure. Our studies had focused on yttria-stabilized cubic zirconia (YSZ) widely used in these devices. The experiments have revealed enhanced grain growth at higher temperatures, pore and gas bubble migration at all temperatures, and the latter also lead to enhanced sintering of highly porous ceramics into fully dense ceramics at unprecedentedly low temperatures. These results have shed light on kinetic processes that fall completely outside the realm of classical ceramic processing. Other fast-oxygen oxide ceramics closely related to, and often used in conjunction with zirconia ceramics, have also be investigated, as are closely related scientific problems in zirconia ceramics. These include crystal structures, defects, diffusion kinetics, oxygen potentials, low temperature sintering, flash sintering, and coarsening theory, and all have resulted in greater clarity in scientific understanding. The knowledge is leveraged to provide new insight to electrode kinetics and near-electrode mixed conductivity and to new materials. In the following areas, our research has resulted in completely new knowledge that defines the state-of-the-art of the field. (a) Electrical current driven non-equilibrium phenomena, (b) Enhanced grain growth under electrochemically reducing conditions, (c) Development of oxygen potential polarization in electrically loaded electrolyte, (d) Low temperature sintering and grain growth, and (e) Structure, defects and cation kinetics of fluorite-structured oxides. Our research has also contributed to synthesis of new energy-relevant electrochemical materials and new understanding

  19. Study of ceramics sintering under high pressures

    International Nuclear Information System (INIS)

    Kunrath Neto, A.O.

    1990-01-01

    A systematic study was made on high pressure sintering of ceramics in order to obtain materials with controlled microstructure, which are not accessible by conventional methods. Some aspects with particular interest were: to achieve very low porosity, with fine grains; to produce dispersed metastable and denser phases which can act as toughening agents; the study of new possibilities for toughening enhancement. (author)

  20. Nd:YAG transparent ceramics fabricated by direct cold isostatic pressing and vacuum sintering

    Science.gov (United States)

    Ge, Lin; Li, Jiang; Zhou, Zhiwei; Liu, Binglong; Xie, Tengfei; Liu, Jing; Kou, Huamin; Shi, Yun; Pan, Yubai; Guo, Jingkun

    2015-12-01

    The sintering behavior of neodymium doped yttrium aluminum garnet (Nd:YAG) ceramics was investigated on the basis of densification trajectory, microstructure evolution and transmittance. Nd:YAG ceramics with in-line transmittance of 83.9% at 1064 nm and 82.5% at 400 nm were obtained by direct cold isostatic pressing (CIP) at 250 MPa and solid-state reactive sintering at 1790 °C for 30 h under vacuum. Compared with the porosity and the average pore diameter of the sample from uniaxial dry-pressing followed by CIP, those from direct CIP are much smaller. The samples pressed at 250 MPa were sintered from 1500 °C to 1750 °C for 0.5-20 h to study their sintering behavior. At the temperature higher than 1500 °C, pure YAG phase is formed, followed by the densification and grain growth process. The relative density and the grain size increase with the increase of sintering time and temperature, and the sintering behavior is more sensitive to temperature than holding time. The mechanism controlling densification and grain growth at sintering temperature of 1550 °C is grain boundary diffusion.

  1. UTILIZATION OF BASALT FIBERS AS A RAW MATERIAL FOR CLAY CERAMIC PRODUCTION

    Directory of Open Access Journals (Sweden)

    Supawan Vichaphund

    2016-03-01

    Full Text Available This research aimed to investigate the possibility of utilization basalt fibers as a raw material for ceramic production. Both quartz and feldspar were replaced partially or entirely by basalt fiber in the range of 10-25 wt%. The mixture of ceramic powders and basalt fibers were uniaxially pressed and sintered at temperatures between 1000 and 1200°C for 1 h. The substitution of basalt fibers in ceramic compositions demonstrated the positive effect on the physical and mechanical properties. The addition of basalt fibers in an appropriate amount enhance the densification and reduce sintering temperature of clay-based ceramics (CB-0 from 1200 to 1150°C. The highest density and strength were 2.40 g/cm³ and 116 MPa, respectively, when replacing feldspar and quartz with basalt up to 20 wt% (CB-20 and sintering at 1150°C.

  2. Sinter recrystalization and properties evaluation of glass-ceramic from waste glass bottle and magnesite for extended application

    Directory of Open Access Journals (Sweden)

    As'mau Ibrahim Gebi

    2016-12-01

    Full Text Available In a bid to address environmental challenges associated with the management of waste Coca cola glass bottle, this study set out to develop glass ceramic materials using waste coca cola glass bottles and magnesite from Sakatsimta in Adamawa state. A reagent grade chrome (coloring agent were used to modify the composition of the coca cola glass bottle;  X-ray fluorescence(XRF, X-ray diffraction (XRD and Thermo gravimetric analysis (TGA were used to characterize raw materials, four batches GC-1= Coca cola glass frit +1%Cr2O3, GC-2=97% Coca cola glass frit+ 2% magnesite+1%Cr2O3, GC-3=95% Coca cola glass frit+ 4%magnesite+1%Cr2O3, GC-4=93%Coca cola glass frit+ 6%magnesite+ 1%Cr2O3 were formulated and prepared. Thermal Gradient Analysis (TGA results were used as a guide in selection of three temperatures (7000C, 7500C and 8000C used for the study, three particle sizes -106+75, -75+53, -53µm and 2 hr sintering time were also used, the sinter crystallization route of glass ceramic production was adopted. The samples were characterized by X-ray diffraction (XRD and Scanning Electron Microscope (SEM, the density, porosity, hardness and flexural strength of the resulting glass ceramics were also measured. The resulting glass ceramic materials composed mainly of wollastonite, diopside and anorthite phases depending on composition as indicated by XRD and SEM, the density of the samples increased with increasing sintering temperature and decreasing particle size. The porosity is minimal and it decreases with increasing sintering temperature and decreasing particle size. The obtained glass ceramic materials possess appreciable hardness and flexural strength with GC-3 and GC-4 having the best combination of both properties.

  3. Development of nano-structured silicon carbide ceramics: from synthesis of the powder to sintered ceramics

    International Nuclear Information System (INIS)

    Reau, A.

    2008-12-01

    The materials used inside future nuclear reactors will be subjected to very high temperature and neutrons flux. Silicon carbide, in the form of SiC f /SiC nano-structured composite is potentially interesting for this type of application. It is again necessary to verify the contribution of nano-structure on the behaviour of this material under irradiation. To verify the feasibility and determine the properties of the matrix, it was envisaged to produce it by powder metallurgy from SiC nanoparticles. The objective is to obtain a fully dense nano-structured SiC ceramic without additives. For that, a parametric study of the phases of synthesis and agglomeration was carried out, the objective of which is to determine the active mechanisms and the influence of the key parameters. Thus, studying the nano-powder synthesis by laser pyrolysis allowed to produce, with high production rates, homogeneous batches of SiC nanoparticles whose size can be adjusted between 15 and 90 nm. These powders have been densified by an innovating method: Spark Plasma Sintering (SPS). The study and the optimization of the key parameters allowed the densification of silicon carbide ceramic without sintering aids while preserving the nano-structure of material. The thermal and mechanical properties of final materials were studied in order to determine the influence of the microstructure on their properties. (author)

  4. Lower sintering temperature of nanostructured dense ceramics compacted from dry nanopowders using powerful ultrasonic action

    Science.gov (United States)

    Khasanov, O.; Reichel, U.; Dvilis, E.; Khasanov, A.

    2011-10-01

    Nanostructured high dense zirconia ceramics have been sintered from dry nanopowders compacted by uniaxial pressing with simultaneous powerful ultrasonic action (PUA). Powerful ultrasound with frequency of 21 kHz was supplied from ultrasonic generator to the mold, which was the ultrasonic wave-guide. Previously the mold was filled by non-agglomerated zirconia nanopowder having average particle size of 40 nm. Any binders or plasticizers were excluded at nanopowder processing. Compaction pressure was 240 MPa, power of ultrasonic generator at PUA was 1 kW and 3 kW. The fully dense zirconia ceramics has been sintered at 1345°C and high-dense ceramics with a density of 99.1%, the most grains of which had the sizes Dgr <= 200 nm, has been sintered at low sintering temperature (1325°C). Applied approach prevents essential grain growth owing to uniform packing of nanoparticles under vibrating PU-action at pressing, which provides the friction forces control during dry nanopowder compaction without contaminating binders or plasticizers.

  5. Ceramic-intermetallic composites produced by mechanical alloying and spark plasma sintering

    CERN Document Server

    Cabanas-Moreno, J G; Martínez-Sanchez, R; Delgado-Gutierrez, O; Palacios-Gomez, J; Umemoto, M

    1998-01-01

    Nano-and microcomposites of intermetallic (Co/sub 3/Ti, AlCo/sub 2 /Ti) and ceramic (TiN, Ti(C, N), Al/sub 2/O/sub 3/) phases have been produced by spark plasma sintering (SPS) of powders resulting from mechanical alloying of Al-Co-Ti elemental powder mixtures. The mechanically alloyed powders consisted of mixtures of nanocrystalline and amorphous phases which, on sintering, transformed into complex microstructures of the intermetallic and ceramic phases. For Al contents lower than about 30 at% in the original powder mixtures, the use of SPS led to porosities of 1-2% in the sintered compacts and hardness values as high as ~1700 kg/mm/sup 2/; in these cases, the composite matrix was TiN and Ti(C, N), with the Al/sub 2/O/sub 3/ phase found as finely dispersed particles in the matrix and the Co /sub 3/Ti and AlCo/sub 2/Ti phases as interdispersed grains. (19 refs).

  6. Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2017-06-01

    Full Text Available Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering. Poly (vinyl alcohol (PVA was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.

  7. Production of coloured glass-ceramics from incinerator ash using thermal plasma technology.

    Science.gov (United States)

    Cheng, T W; Huang, M Z; Tzeng, C C; Cheng, K B; Ueng, T H

    2007-08-01

    Incineration is a major treatment process for municipal solid waste in Taiwan. It is estimated that over 1.5 Mt of incinerator ash are produced annually. This study proposes using thermal plasma technology to treat incinerator ash. Sintered glass-ceramics were produced using quenched vitrified slag with colouring agents added. The experimental results showed that the major crystalline phases developed in the sintered glass-ceramics were gehlenite and wollastonite, but many other secondary phases also appeared depending on the colouring agents added. The physical/mechanical properties, chemical resistance and toxicity characteristic leaching procedure of the coloured glass-ceramics were satisfactory. The glass-ceramic products obtained from incinerator ash treated with thermal plasma technology have great potential for building applications.

  8. Microwave-assisted sintering of non-stoichiometric strontium bismuth niobate ceramic: Structural and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Rajveer [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India); Department of Physics, Atmaram Sanatan Dharma College, University of Delhi, Dhaula Kuan, New Delhi 110021 (India); Luthra, Vandna [Department of Physics, Gargi College, University of Delhi, Siri Fort Road, New Delhi 110049 (India); Tandon, R.P., E-mail: ram_tandon@hotmail.com [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India)

    2016-11-01

    In recent years the microwave sintering has been utilized for the synthesis of materials in enhancement of the properties. In this paper strontium bismuth niobate (Sr{sub 0.8}Bi{sub 2.2}Nb{sub 2}O{sub 9}:SBN) bulk ceramic has been synthesized by microwave reactive sintering and conventional heating techniques. A relative density of 99.6% has been achieved for microwave sintered SBN, which is higher than that of (98.81%) conventionally sintered SBN. The phase formation of SBN synthesized by both processes has been confirmed by X-ray diffraction (XRD). The surface morphology of SBN was observed by scanning electron microscopy (SEM). The microstructure was found to be more uniform in case of SBN sintered by microwave sintering. The dielectric properties of SBN were studied as a function of frequency in the temperature range of 30–500 °C. Both the samples synthesized by two different processes were found to follow Curie–Weiss law above the transition temperature. The Curie temperature was found to be higher for microwave sintered SBN. The dielectric constant and the transition temperature were observed to be higher for SBN ceramic synthesized by microwave sintering technique. The ac and dc activation energy values were also found to be higher for microwave sintered SBN as compared to conventional sintering technique.

  9. Preparation and piezoelectric properties of (K0.5Na0.5)NbO3 lead-free piezoelectric ceramics with pressure-less sintering

    International Nuclear Information System (INIS)

    Du Hongliang; Li Zhimin; Tang Fusheng; Qu Shaobo; Pei Zhibin; Zhou Wancheng

    2006-01-01

    Lead-free piezoelectric ceramics (K 0.5 Na 0.5 )NbO 3 (abbreviated as KNN) with the relative density of 97.6% have been synthesized by press-less sintering owing to the careful control of processing conditions. The phase structure of KNN ceramics with different sintering temperature and heating rate was analyzed. Results show that the pure perovskite phase with orthorhombic symmetry is in all ceramics specimens. The effect of heating rate and sintering temperature on microstructure and piezoelectric properties of KNN ceramics was investigated. The densification behavior and piezoelectric properties of KNN ceramics were enhanced by improving heating rate and sintering temperature. Pure KNN ceramics sintered at 1120 deg. C with heating rate of 5 deg. C/min showed optimized densification and piezoelectric properties (ρ = 4.4 g/cm 3 , d 33 = 120 pC/N -1 , k p = 0.40 and T c = 400 deg. C). The results show that KNN is a promising candidate for lead-free piezoelectric ceramics

  10. Effect of CASP glass doping on sintering and dielectric properties of SBN ceramics

    International Nuclear Information System (INIS)

    Chen Guohua; Qi Bing

    2009-01-01

    16CaO-29Al 2 O 3 -34SiO 2 -13PbO-4B 2 O 3 -2ZnO-2P 2 O 5 (CASP) glass doped-Sr 0.5 Ba 0.5 Nb 2 O 6 (SBN50) ceramics have been synthesized by solid-state ceramic route. The effects of CASP glass on the firing, microstructure and dielectric characterization of SBN50 ceramics are investigated. The densities of the ceramic samples firstly increase and then slightly decrease with increasing CASP glass content. The appropriate amount of doping glass is 2%. The SBN50 ceramics doped with CASP glass can be sintered at a relatively low temperature, 1200 deg. C. X-ray diffraction analysis shows the single phase (tetragonal tungsten bronze type structure) is preserved for all the samples. The diffuse character of the ceramic system increases and the dielectric constant at phase transition temperature (T c ) markedly decreases as CASP glass content increases. Interestingly, the CASP glass addition drastically alters the microstructure of the sintered ceramics. The isotropic grains in the pure SBN50 ceramics transform to rod like grains after the addition of CASP glass. The grain size of SBN phase is found to obviously increase with increase in CASP glass doping level

  11. Effect of sintering process parameters on the properties of 3Y-PSZ ceramics

    International Nuclear Information System (INIS)

    Chu, H L; Chen, R S; Wang, C L; Hwang, W S; Lee, H E; Sie, Y Y; Wang, M C

    2013-01-01

    The effect of sintering process parameters on the properties of 3 mol% yttria partially stability zirconia (3Y-PSZ) ceramics has been investigated. The relative density of the sintered pellet rapidly increases from 70.5 to 93.6% with rose temperature from 1473 to 1573 K. In addition, the relative density only slightly increases from 94.9 to 96.6 %, when rose sintered temperature from 1573 to 1773 K. This result shows that no significant influence on the densification behavior when sintering at 1573 to 1773 K for 2 h. The Vickers hardness and toughness also increase with the sintered temperature

  12. Translucence in dental prosthesis based on zirconia ceramics: effect of the sintering parameters

    International Nuclear Information System (INIS)

    Santos, C.

    2011-01-01

    In this work the translucence of Zirconia dental ceramics was evaluated as function of sintering conditions (temperature and isothermal holding time). Samples with 15x15x1mm, were sintered at 1450 to 1600 deg C, with holding of 2h or 4h. Sintered samples were characterized by relative density, crystalline phases and microstructural aspects. Full density was obtained in samples sintered at 1530 and 1600 deg C, which presented higher grain sizes. Na increasing of translucence was observed in samples sintered at 1530 and 1600, correlating these properties with increasing of density and grain size of the samples. (author)

  13. Sintering and densification; new techniques: sinter forging

    International Nuclear Information System (INIS)

    Winnubst, A.J.A.

    1998-01-01

    In this chapter pressure assisted sintering methods will be described. Attention will mainly be paid to sinter forging as a die-wall free uniaxial pressure sintering technique, where large creep strains are possible. Sinter forging is an effective tool to reduce sintering temperature and time and to obtain a nearly theoretically dense ceramic. In this way grain size in tetragonal zirconia ceramics can be reduced down to 100 nm. Another important phenomenon is the reduction of the number density and size of cracks and flaws resulting in higher strength and improved reliability, which is of utmost importance for engineering ceramics. The creep deformation during sinter forging causes a rearrangement of the grains resulting in a reduction of interatomic spaces between grains, while grain boundary (glassy) phases can be removed. The toughness and in some cases the wear resistance is enhanced after sinter forging as a result of the grain-boundary-morphology improvement. (orig.)

  14. Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material.

    Science.gov (United States)

    Li, Weiyan; Sun, Jian

    2018-05-10

    BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. RESULTS Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. CONCLUSIONS PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin.

  15. Spark plasma sintering and microwave electromagnetic properties of MnFe{sub 2}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Penchal Reddy, M., E-mail: drlpenchal@gmail.com [Center for Advanced Materials, Qatar University, Doha 2713 (Qatar); Mohamed, A.M.A. [Center for Advanced Materials, Qatar University, Doha 2713 (Qatar); Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, Suez 4372 (Egypt); Venkata Ramana, M. [Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China); Zhou, X.B.; Huang, Q. [Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Ningbo 315201 (China)

    2015-12-01

    MnFe{sub 2}O{sub 4} ferrite powder was synthesized by a facile one-pot hydrothermal route and then consolidated into dense nanostructured compacts by the spark plasma sintering (SPS) technique. The effect of sintering temperature, on densification, morphology, magnetic and microwave absorption properties was examined. Spark plasma sintering resulted in uniform microstructure, as well as maximum relative density of 98%. The magnetic analysis indicated that the MnFe{sub 2}O{sub 4} ferrite nanoparticles showed ferrimagnetic behavior. Moreover, the dielectric loss and magnetic loss properties of MnFe{sub 2}O{sub 4} ferrite nanoparticles were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy. It is believed that such spark plasma sintered ceramic material will be applied widely in microwave absorbing area. - Highlights: • Successful synthesis of dense MnFe{sub 2}O{sub 4} ceramics using spark plasma sintering. • Lower temperature and shorter sintering time, compared to conventional methods. • Optimal sintering condition was achieved. • The magnetic properties of the sintered samples are sensitive to the density and microstructure.

  16. Phase Transformation of Andalusite-Mullite and Its Roles in the Microstructure and Sinterability of Refractory Ceramic

    Science.gov (United States)

    Li, Bowen; He, Mengsheng; Wang, Huaguang

    2017-07-01

    Andalusite has been realized as a special mineral for the production of refractory ceramics due to its unique property to automatically decompose into mullite and silica during heating at high temperature. The phase transformation from andalusite to mullite plays a critical role for the effective applications of andalusite. This study investigated the microstructural characteristics and sinterability of andalusite powder during high-temperature decomposition. The andalusite powder was bonded with kaolin and prepared as a cylinder green body at 20 MPa; it was then fired at 1423 K to 1723 K (1150 °C to 1450 °C). The microstructures and mechanical strengths of the sintered ceramics were studied by the compressive test, X-ray diffraction, and scanning electron microscopy. The results showed that newly born mullite appeared as rodlike microcrystals and dispersed around the initial andalusite. At 1423 K (1150 °C), the mullitization of andalusite was started, but the complete mullitization was not found until firing at 1723 K (1450 °C). The compressive strength of the ceramics increased from 93.7 to 294.6 MPa while increasing the fire temperature from 1423 K to 1723 K (1150 °C to 1450 °C). Meanwhile, the bulk density of the ceramics was only slightly changed from 2.15 to 2.19 g/cm3.

  17. Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy

    International Nuclear Information System (INIS)

    Florio, Daniel Zanetti de

    1998-01-01

    ZrO 2 :8 mol %Y 2 O 3 solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO 2 produced at a Pilot Plant at IPEN and 99.9% pure Y 2 O 3 of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

  18. Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues

    International Nuclear Information System (INIS)

    Roether, J.A.; Daniel, D.J.; Amutha Rani, D.; Deegan, D.E.; Cheeseman, C.R.; Boccaccini, A.R.

    2010-01-01

    Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 deg. C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 deg. C. This produced a glass-ceramic with high density (∼2.58 g/cm 3 ), minimum water absorption (∼2%) and relatively high mechanical strength (∼81 ± 4 MPa). Thermal shock testing showed that 950 deg. C sintered samples could withstand a 700 deg. C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste.

  19. Studies of ZrO2-Y2O3 ceramics properties sintered in conventional and microwave oven

    International Nuclear Information System (INIS)

    Gelfuso, M.V.; Capistrano, D.; Thomazini, D.; Grzebielucka, E.C.; Chinelatto, A.L.; Chinelatto, A.S.A.

    2009-01-01

    The ceramic materials processing with nano grain size has developed materials with new properties or improves some of its existing properties. To obtain ceramics with nano grain size, besides that to obtaining nanometric powders, a major goal is to keep the grains size after sintering. Contributing in this line of research, this study aimed to sinter zirconia-Yttria powders through two processes: conventional and microwave sintering. Zirconia stabilized with Yttria powders were obtained by chemical route based on Pechini method. Cylindrical samples were sintered between 1300 to 1500 deg C between 10 and 40 minutes. The samples were characterized by Xray diffraction, Scanning Electron Microscopy and apparent density. It was observed that the final microstructure is influenced by both methods of sintering as the curve of firing used. (author)

  20. Enhanced proton conductivity of yttrium-doped barium zirconate with sinterability in protonic ceramic fuel cells

    International Nuclear Information System (INIS)

    Park, Ka-Young; Seo, Yongho; Kim, Ki Buem; Song, Sun-Ju; Park, Byoungnam; Park, Jun-Young

    2015-01-01

    Highlights: • Report effects of ceramic processing methods on the electrical conductivity of BZY. • Present effects of sintering aids on the conductivity and density of BZY. • CuO is the most effective sintering aid for the BZY. • Polymer gelation is the most effective method in terms of conductivity of BZY. • Grain boundary conductivity of the polymer gelation BZY is higher than others. - Abstract: In this study, we report the effects of various ceramic processing methods with different sintering aids on the relative density, crystallinity, microstructure, and electrical conductivity of proton conducting BaZr 0.85 Y 0.15 O 3−δ (BZY) pellets in details. First, the BZY ceramic pellets are fabricated by the solid-state reactive sintering by adding diverse sintering aids including CuO, NiO, ZnO, SnO, MgO, and Al 2 O 3 . Among these, CuO is found to be the most effective sintering aid in terms of the sintering temperature and total conductivity. However, transition metals as sintering aids have detrimental effects on the electrical conductivity of the BZY electrolytes. Second, the BZY electrolytes have been synthesized by four different methods: the solid-state, combustion, hydrothermal, and polymer gelation methods. The BZY pellets synthesized by the polymer gelation method exhibit dense microstructure with a high relative density of 95.3%. Moreover, the electrical conductivity of the BZY pellets synthesized by the polymer gelation method is higher than those prepared by the solid-state methods under the same test conditions: 1.28 × 10 −2 S cm −1 (by the polymer gelation method) vs. 0.53 × 10 −2 S cm −1 by the solid-state method at 600 °C in wet 5% H 2 in Ar

  1. Microwave Sintering of Ceramic Materials for Industrial Application Final Report CRADA No. TC-1116-95

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tandon, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Callis, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-10-19

    The goal of this project was to develop the commercial capability in the US to sinter alumina oxide ceramic parts for the semiconductor manufacturing equipment industry. We planned to use the millimeter microwave (30 GHz) sintering system first developed by IAP in Russia.

  2. Bioactive Glass-Ceramic Foam Scaffolds from ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Science.gov (United States)

    Molino, Giulia; Vitale Brovarone, Chiara

    2018-01-01

    Highly porous bioactive glass-ceramic scaffolds were effectively fabricated by an inorganic gel casting technique, based on alkali activation and gelification, followed by viscous flow sintering. Glass powders, already known to yield a bioactive sintered glass-ceramic (CEL2) were dispersed in an alkaline solution, with partial dissolution of glass powders. The obtained glass suspensions underwent progressive hardening, by curing at low temperature (40 °C), owing to the formation of a C–S–H (calcium silicate hydrate) gel. As successful direct foaming was achieved by vigorous mechanical stirring of gelified suspensions, comprising also a surfactant. The developed cellular structures were later heat-treated at 900–1000 °C, to form CEL2 glass-ceramic foams, featuring an abundant total porosity (from 60% to 80%) and well-interconnected macro- and micro-sized cells. The developed foams possessed a compressive strength from 2.5 to 5 MPa, which is in the range of human trabecular bone strength. Therefore, CEL2 glass-ceramics can be proposed for bone substitutions. PMID:29495498

  3. Bioactive Glass-Ceramic Foam Scaffolds from ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Directory of Open Access Journals (Sweden)

    Hamada Elsayed

    2018-02-01

    Full Text Available Highly porous bioactive glass-ceramic scaffolds were effectively fabricated by an inorganic gel casting technique, based on alkali activation and gelification, followed by viscous flow sintering. Glass powders, already known to yield a bioactive sintered glass-ceramic (CEL2 were dispersed in an alkaline solution, with partial dissolution of glass powders. The obtained glass suspensions underwent progressive hardening, by curing at low temperature (40 °C, owing to the formation of a C–S–H (calcium silicate hydrate gel. As successful direct foaming was achieved by vigorous mechanical stirring of gelified suspensions, comprising also a surfactant. The developed cellular structures were later heat-treated at 900–1000 °C, to form CEL2 glass-ceramic foams, featuring an abundant total porosity (from 60% to 80% and well-interconnected macro- and micro-sized cells. The developed foams possessed a compressive strength from 2.5 to 5 MPa, which is in the range of human trabecular bone strength. Therefore, CEL2 glass-ceramics can be proposed for bone substitutions.

  4. Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O3 lead-free ceramics

    International Nuclear Information System (INIS)

    Chen, Xiaoming; Ruan, Xuezheng; Zhao, Kunyun; He, Xueqing; Zeng, Jiangtao; Li, Yongsheng; Zheng, Liaoying; Park, Chul Hong; Li, Guorong

    2015-01-01

    Highlights: • Li-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d 33 (512 pC/N) and a planar electromechanical coupling factor k p (0.49), which have the characteristics of soft Pb(Zr,Ti)O 3 (PZT) piezoceramic, on the other hand, the mechanical quality factor Q m is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature

  5. Barium titanate nanometric polycrystalline ceramics fired by spark plasma sintering.

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Ryukhtin, Vasyl; Cinert, Jakub; Lukáč, František

    2016-01-01

    Roč. 42, č. 14 (2016), s. 15989-15993 ISSN 0272-8842 R&D Projects: GA ČR GB14-36566G; GA MŠk LM2015056 Institutional support: RVO:61389021 ; RVO:61389005 Keywords : BaTiO3 * Spark plasma sintering * Electrical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; JH - Ceramics, Fire-Resistant Materials and Glass (UJF-V) Impact factor: 2.986, year: 2016 http://www.sciencedirect.com/science/article/pii/S0272884216311695

  6. COMPACTION OF LITHIUM-SILICATE CERAMICS USING SPARK PLASMA SINTERING

    Directory of Open Access Journals (Sweden)

    Tomas Frantisek Kubatik

    2016-12-01

    Full Text Available This paper deals with the compaction of ceramics based on lithium-silicate by spark plasma sintering (SPS. The initial powder was prepared by calcination in a resistance furnace at a temperature of 1300 °C with the ratio of Li/Si = 1. Compacting by SPS was carried out at temperatures of 800 - 1000 °C with a maximum pressure of 80 MPa. Samples with open porosity of less than 1 % were prepared at the temperature of 1000 °C. According to the quantitative Rietveld refinement of x-ray diffraction data, the dominant phases in all samples were Li₂Si₂O₅ and Li₂SiO₃, together representing over 80 wt. % of the sintered material.

  7. Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues

    Energy Technology Data Exchange (ETDEWEB)

    Roether, J.A.; Daniel, D.J. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Amutha Rani, D. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Deegan, D.E. [Tetronics Ltd., Swindon, Wiltshire SN3 4DE (United Kingdom); Cheeseman, C.R., E-mail: c.cheeseman@imperial.ac.uk [Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Boccaccini, A.R., E-mail: a.boccaccini@imperial.ac.uk [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom)

    2010-01-15

    Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 deg. C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 deg. C. This produced a glass-ceramic with high density ({approx}2.58 g/cm{sup 3}), minimum water absorption ({approx}2%) and relatively high mechanical strength ({approx}81 {+-} 4 MPa). Thermal shock testing showed that 950 deg. C sintered samples could withstand a 700 deg. C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste.

  8. X-ray powder diffraction analysis of liquid-phase-sintered silicon carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, A.L.; Sanchez-Bajo, F. [Universidad de Extremadura, Badajoz (Spain). Dept. de Electronica e Ingenieria Electromecanica; Cumbrera, F.L. [Universidad de Extremadura, Badajoz (Spain). Dept. de Fisica

    2002-07-01

    In an attempt to gain a comprehensive understanding of the microstructural evolution in liquid-phase-sintered silicon carbide ceramics, the effect of the starting {beta}-SiC powder has been studied. Pellets of two different {beta}-SiC starting powders were sintered with simultaneous additions of Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} at 1950 C for 1 hour in flowing argon atmosphere. Here we have used X-ray diffraction to obtain the relative abundance of the resulting SiC polytypes after sintering. The significant influence of the defects concentration on the {beta} to {alpha} transformation rate has been determined using the Rietveld method. (orig.)

  9. Preparation and Microstructure of Porous ZrB2 Ceramics Using Reactive Spark Plasma Sintering Method

    Institute of Scientific and Technical Information of China (English)

    YUAN Huiping; LI Junguo; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    Zirconium oxide (ZrO2) and boron carbide (B4C) were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering (RSPS). The reactions between ZrO2 and B4C which produce ZrB2 and gas (such as CO and B2O3) result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB2-SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB2-based ceramics.

  10. Effect of Nb doping on sintering and dielectric properties of PZT ceramics

    Directory of Open Access Journals (Sweden)

    Ali Mirzaei

    2016-09-01

    Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

  11. Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiaoming [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Ruan, Xuezheng; Zhao, Kunyun [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); He, Xueqing [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Zeng, Jiangtao, E-mail: zjt@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Li, Yongsheng [School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zheng, Liaoying [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Park, Chul Hong [Department of Physics Education, Pusan National University, Pusan 609735 (Korea, Republic of); Li, Guorong [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-05-25

    Highlights: • Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d{sub 33} (512 pC/N) and a planar electromechanical coupling factor k{sub p} (0.49), which have the characteristics of soft Pb(Zr,Ti)O{sub 3} (PZT) piezoceramic, on the other hand, the mechanical quality factor Q{sub m} is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature.

  12. Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

    Science.gov (United States)

    Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

    2018-05-01

    Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

  13. Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

    Science.gov (United States)

    Chen, Chang-hong; Feng, Ke-qin; Zhou, Yu; Zhou, Hong-ling

    2017-08-01

    Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060°C) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060°C. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000°C.

  14. Utilisation of different types of coal fly ash in the production of ceramic tiles

    OpenAIRE

    KocKal, N. U.

    2012-01-01

    The influence of varying proportions of different types of fly ash (used in place of feldspar) and different sintering temperatures on the sintered properties of ceramic tile bodies was evaluated. The results indicated that sintering ceramic tiles with a high fly ash content at a high temperature caused a decrease in the properties because of bloating. The ceramic samples containing a higher amount of fly ash that were sintered at low temperature exhibited lower water absorption, larger shrin...

  15. Spark Plasma Sintering of Dielectric Ceramics Zr0.8Sn0.2TiO4

    Czech Academy of Sciences Publication Activity Database

    Ctibor, P.; Kubatík, Tomáš František; Sedláček, J.; Kotlan, Jiří

    2016-01-01

    Roč. 22, č. 3 (2016), s. 435-439 ISSN 1392-1320 Institutional support: RVO:61389021 Keywords : titanates * dielectric ceramics * spark plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.393, year: 2016 http://www.matsc.ktu.lt/index.php/MatSc/article/view/8767

  16. Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

    Energy Technology Data Exchange (ETDEWEB)

    Zaiou, S.; Harabi, A.; Harabi, E.; Guechi, A.; Karboua, N.; Benhassine, M.-T.; Zouai, S.; Guerfa, F., E-mail: Zaiou_21@yahoo.fr, E-mail: harabi52@gmail.com, E-mail: semouni84@gmail.com, E-mail: guechia@yahoo.fr, E-mail: kanour17@yahoo.fr, E-mail: mtb25dz@gmail.com, E-mail: zouaisouheila@yahoo.fr, E-mail: guerfatiha@gmail.com [Ceramics Lab., Faculty of Exact Science, Physics Department, Mentouri University of Constantine (Algeria)

    2016-10-15

    In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO{sub 3} is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm{sup 3} ). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. (author)

  17. Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

    Directory of Open Access Journals (Sweden)

    S. Zaiou

    Full Text Available Abstract In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type and 20 wt% calcium oxide extracted from CaCO3 is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm3. Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy.

  18. Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

    International Nuclear Information System (INIS)

    Zaiou, S.; Harabi, A.; Harabi, E.; Guechi, A.; Karboua, N.; Benhassine, M.-T.; Zouai, S.; Guerfa, F.

    2016-01-01

    In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO 3 is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm 3 ). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. (author)

  19. Luminescence properties of the Mg co–doped Ce:SrHfO_3 ceramics prepared by the Spark Plasma Sintering Method

    International Nuclear Information System (INIS)

    Chiba, Hiroyuki; Kurosawa, Shunsuke; Harata, Koichi; Murakami, Rikito; Yamaji, Akihiro; Ohashi, Yuji; Pejchal, Jan; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira

    2016-01-01

    1300 or 1400 °C pre–sintered Al/Ce/Mg:SrHfO_3 and Al/Ce:SrHfO_3 ceramics were prepared by the Spark Plasma Sintering (SPS) in order to search for a new scintillation material with a high–effective atomic number(Z_e_f_f) and good light output. The SrHfO_3 has a high Z_e_f_f of 60, and high gamma–ray detection efficiency is expected. Meanwhile it has a high melting point of over 2500 °C, and single crystal is hard to be grown. On the other hand, high melting materials can be prepared as ceramics, and the SPS method is a simple process to fabricate the ceramics within a few hours. Thus, we prepared the samples using the SPS method, and their optical and scintillation properties were investigated. We found that Al/Ce/Mg:SrHfO_3 and Al/Ce:SrHfO_3 ceramics had an emission wavelength at around 400 nm originating from 5d–4f transition of Ce"3"+. Moreover, Al/Ce/Mg:SrHfO_3 pre-sintered at a temperature of 1400 °C had a light output of approximately 5,000 ph/MeV. In this paper, the light output of Mg-co-doped samples was improved compared with the Mg-free ones. The light output also depends on the pre-sintering temperature. - Highlights: • Luminescence Properties of Al/Ce/Mg:SrHfO_3 ceramics scintillator was investigated. • These ceramics were prepared by the Spark Plasma Sintering Method. • Light output of the Al/Ce/Mg:SrHfO_3 ceramics was approximately 5,000 ph/MeV.

  20. SnO{sub 2}{sup *}CoO ceramic obtained by microwave sintering; Ceramicas de SnO{sub 2} {sup *}CoO obtidas por sinterizacao microondas

    Energy Technology Data Exchange (ETDEWEB)

    Bordignon, M.A.N; Moura, F.; Zaghete, M.A.; Varela, J.A.; Perazolli, L. [Universidade Estadual Paulista (UNESP), Araraquara, SP (Brazil). Chemistry Institute. Dept. de Biochemistry and Technological Chemistryl

    2009-07-01

    This work consists in the sintering study of CoO doped SnO{sub 2} using microwave sintering oven and silicon carbide as a susceptor. The powders were obtained by dry oxides mixture and conformed in cylindrical shapes with 6mmx8mm and green density to 60%. Then the compacts were sintering up to 1.050 deg C, using heating rate of 50 deg C/min and isotherm up to 30min. The densities obtained were above 95% for both techniques. It was observed that occurred a temperature reducing of 400 deg C and time reducing of 210min to obtain the same densities, when was used the microwave oven without the phenomena of thermal runaway. So the sintered compacts were accomplished using DRX and SEM. It was made the electrical characterization (current x voltage) and it was found to have great potential in the production of dense ceramic-based SnO{sub 2} with low resistivity to obtain electro-ceramic devices. (author)

  1. Glass-ceramic coating material for the CO2 laser based sintering of thin films as caries and erosion protection.

    Science.gov (United States)

    Bilandžić, Marin Dean; Wollgarten, Susanne; Stollenwerk, Jochen; Poprawe, Reinhart; Esteves-Oliveira, Marcella; Fischer, Horst

    2017-09-01

    The established method of fissure-sealing using polymeric coating materials exhibits limitations on the long-term. Here, we present a novel technique with the potential to protect susceptible teeth against caries and erosion. We hypothesized that a tailored glass-ceramic material could be sprayed onto enamel-like substrates to create superior adhesion properties after sintering by a CO 2 laser beam. A powdered dental glass-ceramic material from the system SiO 2 -Na 2 O-K 2 O-CaO-Al 2 O 3 -MgO was adjusted with individual properties suitable for a spray coating process. The material was characterized using X-ray fluorescence analysis (XRF), heating microscopy, dilatometry, scanning electron microscopy (SEM), grain size analysis, biaxial flexural strength measurements, fourier transform infrared spectroscopy (FTIR), and gas pycnometry. Three different groups of samples (each n=10) where prepared: Group A, powder pressed glass-ceramic coating material; Group B, sintered hydroxyapatite specimens; and Group C, enamel specimens (prepared from bovine teeth). Group B and C where spray coated with glass-ceramic powder. All specimens were heat treated using a CO 2 laser beam process. Cross-sections of the laser-sintered specimens were analyzed using laser scanning microscopy (LSM), energy dispersive X-ray analysis (EDX), and SEM. The developed glass-ceramic material (grain size d50=13.1mm, coefficient of thermal expansion (CTE)=13.310 -6 /K) could be spray coated on all tested substrates (mean thickness=160μm). FTIR analysis confirmed an absorption of the laser energy up to 95%. The powdered glass-ceramic material was successfully densely sintered in all sample groups. The coating interface investigation by SEM and EDX proved atomic diffusion and adhesion of the glass-ceramic material to hydroxyapatite and to dental enamel. A glass-ceramic material with suitable absorption properties was successfully sprayed and laser-sintered in thin films on hydroxyapatite as well as on

  2. Study of pore closure during pressure-less sintering of advanced oxide ceramics

    Czech Academy of Sciences Publication Activity Database

    Spusta, T.; Svoboda, Jiří; Maca, K.

    2016-01-01

    Roč. 115, AUG (2016), s. 347-353 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : Ceramic material * Sintering * Porosity * Modelling * Hot isostatic pressing Subject RIV: BJ - Thermodynamics Impact factor: 5.301, year: 2016

  3. Low-temperature sintering and microwave dielectric properties of Al2TeO6–TeO2 ceramics

    International Nuclear Information System (INIS)

    Kagomiya, Isao; Kodama, Yuichiro; Shimizu, Yukihiro; Kakimoto, Ken-ichi; Ohsato, Hitoshi; Miyauchi, Yasuharu

    2015-01-01

    Highlights: • This is the first study of dielectric properties of Al 2 TeO 6 –TeO 2 sintered at 900 °C. • The sintering at 900 °C contributed to densification, but it causes TeO 2 evaporation. • The annealing at 750 °C was effective for the further densification. • The both ε r and Q · f in the Al 2 TeO 6 –TeO 2 were improved with the annealing. - Abstract: We propose Al 2 TeO 6 –TeO 2 ceramics as a candidate for use as low-temperature co-fired ceramics (LTCC). We investigated microwave dielectric properties and low-temperature sintering conditions for Al 2 TeO 6 –TeO 2 ceramics. The calcined Al 2 TeO 6 powders were sintered at 900 °C for 2–10 h with 30–50 wt% additive TeO 2 . X-ray powder diffraction patterns showed that the sintered samples were Al 2 TeO 6 –TeO 2 composite with no other phase. The apparent density was improved with the additive TeO 2 content of up to 45 wt%. The dielectric constant (ε r ) increased by adding TeO 2 content from 35 to 45 wt%, although the quality factor (Q · f) decreased. During sintering at 900 °C, the ε r of the Al 2 TeO 6 –TeO 2 decreased slightly, whereas the Q · f increased gradually. The observed microstructures showed that the longer sintering time makes fewer pores in Al 2 TeO 6 –TeO 2 ceramics. Sintering at 900 °C for a long time contributes to densification, but it simultaneously causes TeO 2 evaporation. To prevent TeO 2 evaporation, we investigated the effects of annealing at 750 °C after sintering at 900 °C. Apparent densities or ε r for the annealed samples were higher than those of the non-annealed samples. The Q · f improved with increasing annealing duration time, suggesting that sintering proceeded well during annealing with slower TeO 2 evaporation at 750 °C. The results show that annealing at 750 °C is effective to facilitate sintering and to control TeO 2 evaporation

  4. Spark-plasma sintering of ZrB2 ultra-high-temperature ceramics

    OpenAIRE

    Zamora Rodríguez, Víctor

    2013-01-01

    This work was performed in the context of the research line entitled Processing and Sintering of Advanced Ceramic Materials in the Grupo Especializado de Materiales of the University of Extremadura, and was supported by the Ministerio de Ciencia y Tecnología (Government of Spain) and FEDER funds under the Grant Nº MAT 2007-61609.

  5. Thermal Conductivity and High-Frequency Dielectric Properties of Pressureless Sintered SiC-AlN Multiphase Ceramics

    Directory of Open Access Journals (Sweden)

    Jialin Gu

    2018-06-01

    Full Text Available SiC-AlN multiphase ceramics with 10 wt. %Y2O3-BaO-SiO2 additives were fabricated by pressureless sintering in a nitrogen atmosphere. The effects of SiC contents and sintering temperatures on the sinterability, microstructure, thermal conductivity and high-frequency dielectric properties were characterized. In addition to 6H-SiC and AlN, the samples also contained Y3Al5O12 and Y4Al2O9. SiC-AlN ceramics sintered with 50 wt. % SiC at 2173 K exhibited the best thermal diffusivity and thermal conductivity (26.21 mm2·s−1 and 61.02 W·m−1·K−1, respectively. The dielectric constant and dielectric loss of the sample sintered with 50 wt. % SiC and 2123 K were 33–37 and 0.4–0.5 at 12.4–18 GHz. The dielectric constant and dielectric loss of the samples decreased as the frequency of electromagnetic waves increased from 12.4–18 GHz. The dielectric thermal conductivity properties of the SiC-AlN samples are discussed.

  6. Photoacoustic spectroscopy investigation of sintered zinc-tin-oxide ceramics

    Directory of Open Access Journals (Sweden)

    Ivetić Tamara B.

    2007-01-01

    Full Text Available In this paper the changes that occurred in differently activated ZnO-SnO2 and sintered samples were investigated using photoacoustic spectroscopy. ZnO and SnO2 powders, mixed in the molar ratio 2:1, were mechanically activated in a planetary ball mill for 10-160 min. The mixtures were pres­sed and isothermally sintered at 1300°C for two hours. X-ray diffraction analysis of the obtained sintered samples was performed in order to investigate changes of the phase composition and confirmed only the presence of a pure zinc stannate (Zn2SnO4 phase in all the sintered samples as a result of the solid state reaction and reaction sintering between the starting ZnO and SnO2 powders. The microstructure of the sintered sam­ples was examined by scanning electron microscopy and showed that mechanical activation leads to the formation of a structure with reduced particle size which accelerates spinel formation. Grain growth of the spinel phase slows down the densification process and together with the agglomerates formed during mechanical activation causes the appearance of a porous microstructure. The photoacoustic (PA phase and amplitude spectra of the sintered samples were recorded as a function of the chopped frequency of the laser beam used (red laser with a power of 25 mW, λ=632 nm in a thermal-transmission detection configuration. PA experimental data were analyzed using the Rosenzweig-Gersho thermal-piston model, which enabled determination of the thermal diffusivity, ZT (m2s-1, diffusion coefficient of the minority free carriers D (m2s-1 and the optical absorption coefficient (m-1. The detected differences of the measured thermal-electrical properties of the obtained Zn2SnO4 ceramics indicate changes in the material induced by the different preparation procedure of the starting powders before the sintering process.

  7. Compaction of lithium-silicate ceramics using spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Kubatík, Tomáš František; Lukáč, František; Mušálek, Radek; Brožek, Vlastimil; Stehlíková, K.; Chráska, Tomáš

    2017-01-01

    Roč. 61, č. 1 (2017), s. 40-44 ISSN 0862-5468 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Li2Si2O5 * Li2SiO3 * Spark plasma sintering (SPS) * Quantitative Rietveld refinement * X-ray diffraction (XRD) Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 0.439, year: 2016 http://www.ceramics-silikaty.cz/index.php?page=cs_detail_doi&id=789

  8. Investigations of dielectric enhancement in (Ta2O5)1-x(TiO2)x ceramics prepared by laser-sintering technique

    International Nuclear Information System (INIS)

    Ji, L.F.; Jiang, Y.J.

    2007-01-01

    The maximum dielectric permittivity of Ti-doped Ta 2 O 5 ceramics may reach 450 by a laser-sintering technique. The aim of this study is to investigate the mechanisms of the dielectric enhancement based on the unique structural and morphological properties of the laser-sintered ceramics. The reason for the dielectric enhancement is due to the crystal structure distortion in the high-temperature phase, the oriented grain growth taking place in a direction deviating from [001] in the laser-sintered ceramics. The concurrent nature of quenching effects, a sharp temperature gradient and mass transfer in liquid phase originated from laser high energy irradiation with strict directivity leads to the structural and morphological properties. (orig.)

  9. Microwave sintering of cordierite ceramic precursors obtained by starch direct consolidation

    International Nuclear Information System (INIS)

    Sandoval, M.L.; Talou, M.H.; Camerucci, M.A.; Universidad Nacional de Mar Del Plata; Souto, P.M. de; Kiminami, R.H.G.A.

    2009-01-01

    Microwave sintering of cordierite disk precursors (mixture of kaolin, talc and alumina) with potato starch was studied. Green disks were obtained by thermal consolidation of stable aqueous suspensions of the ceramic powders (29.6 % vol.) with potato starch (11.5 % vol.) at 75 and 85 deg C, 4h; drying (50 deg C,12h) and calcination (650 deg C, 2h). The reaction-sintering by microwave heating (power: 2.45 GHz; heating rate: 50 deg C/min) at different temperatures (1250-1330 deg C) and dwell times (10-20 min) was carried out. For comparative purposes, the reaction-sintering by conventional heating was analyzed (1330 deg C, 4h a 3 deg C/min). The evolution of the phases as a function of temperature and time was studied by XRD analysis. The developed microstructures (dense or porous) were characterized by density and porosity measurements, and SEM. The obtained results were analyzed in relation to the characteristics of starch behavior in aqueous suspension at temperature and the employed consolidation and sintering conditions. (author)

  10. Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

    Science.gov (United States)

    Zhong, Zhi-Min; Goldsby, Jon C.

    2005-01-01

    Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the

  11. Effect of sintering temperatures on titanium matrix composites reinforced by ceramic particles

    Energy Technology Data Exchange (ETDEWEB)

    Romero, F.; Amigo, V.; Busquets, D.; Klyatskina, E. [Mechanical and Materials Engineering Department. Polytechnical University of Valencia, Valencia (Spain)

    2005-07-01

    Titanium and titanium composites have a potential use in aerospace and biotechnology industries, and nowadays in others like sports and fashion ones. In this work composite materials, based on titanium matrix reinforced with ceramic particles, have been developed. PM route is used to obtain compact and sintered samples. TiN and TiAl powders, are milled with Ti powder in different volumetric percentages in a ball mill. These mixtures are pressed in a uniaxial press and sintered in a vacuum furnace at different temperatures between 1180 to 1220 deg. C. Porosity of samples is analysed, before and after the sintering process, by Archimedes technique and by image analysis. Mechanical properties and the reinforcement particles influence in the titanium matrix are studied by flexion test in green and sintered states, and by hardness and microhardness tests. Complimentarily, a microstructural analysis is carried out by optical and electron microscopy, and the reactivity between the reinforce particles and titanium matrix are studied. (authors)

  12. Effect of surface treatments on the bond strength between resin cement and differently sintered zirconium-oxide ceramics.

    Science.gov (United States)

    Yenisey, Murat; Dede, Doğu Ömür; Rona, Nergiz

    2016-01-01

    This study investigated the effects of surface treatments on bond strength between resin cement and differently sintered zirconium-oxide ceramics. 220 zirconium-oxide ceramic (Ceramill ZI) specimens were prepared, sintered in two different period (Short=Ss, Long=Ls) and divided into ten treatment groups as: GC, no treatment; GSil, silanized (ESPE-Sil); GSilPen, silane flame treatment (Silano-Pen); GSb, sandblasted; GSbSil, sandblasted+silanized; GSbCoSil, sandblasted+silica coated (CoJet)+silanized; GSbRoSil, sandblasted+silica coated (Rocatech-Plus)+silanized; GSbDSil, sandblasted+diamond particle abraded (Micron MDA)+silanized; GSbSilPen, sandblasted+silane flame treatment+silanized; GSbLSil, sandblasted+Er:Yag (Asclepion-MCL30) laser treated+silanized. The composite resin (Filtek Z-250) cylinders were cemented to the treated ceramic surfaces with a resin cement (Panavia F2.0). Shear bond strength test was performed after specimens were stored in water for 24h and thermo-cycled for 6000 cycles (5-55 °C). Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tamhane's multiple comparison test (α=0.05). According to the ANOVA, sintering time, surface treatments and their interaction were statistically significant (pzirconium-oxide ceramics. Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  13. [Influence of compaction pressure and pre-sintering temperature on the machinability of zirconia ceramic].

    Science.gov (United States)

    Huang, Huil; Li, Jing; Zhang, Fuqiang; Sun, Jing; Gao, Lian

    2011-10-01

    In order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic. 3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. Pre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality. The best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.

  14. Liquid Film Capillary Mechanism for Densification of Ceramic Powders during Flash Sintering

    Directory of Open Access Journals (Sweden)

    Rachman Chaim

    2016-04-01

    Full Text Available Recently, local melting of the particle surfaces confirmed the formation of spark and plasma during spark plasma sintering, which explains the rapid densification mechanism via liquid. A model for rapid densification of flash sintered ceramics by liquid film capillary was presented, where liquid film forms by local melting at the particle contacts, due to Joule heating followed by thermal runaway. Local densification is by particle rearrangement led by spreading of the liquid, due to local attractive capillary forces. Electrowetting may assist this process. The asymmetric nature of the powder compact represents an invasive percolating system.

  15. Effect of B2O3 and P2O5 on fluorosilicic mica glass-ceramic sintering process

    Directory of Open Access Journals (Sweden)

    Wu S.

    2010-01-01

    Full Text Available To study the effect of B2O3 and P2O5 on fluorosilicic mica glass-ceramic sintering process, six sets of K2O-MgO-SiO2-F glasses were prepared by using B2O3 and P2O5 as sintering aid, respectively. Green bodies of the glass powder were formed by gel casting and sintered at 800, 850, 900, 950, 1000oC for 6 hours, resectively. The sintering and crystallization behavior were studied by thermal shrinkage , X-ray diffraction and SEM. The results showed that the shrinkage rate of the glass with 2wt% B2O3 and P2O5 was highest, while the rate of the glass with 5wt% P2O5 was lowest. An additional crystal other than fluorosilicic mica was precipitated in the glass ceramics generated by sintering of glass powder. The present results confirmed that the glass powder of pure K2O-MgO-SiO2-Fsystem had poor sinterability, while glass powder with minor addition of P2O5 and/or B2O3 showed good sinterability. This result was also verified by SEM.

  16. Effects of B{sub 2}O{sub 3} content and sintering temperature on crystallization and microstructure of CBS glass–ceramic coatings

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Wang, Shubin, E-mail: shubinwang@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials and Engneering, Beihang University, Beijing 100191 (China); Liu, Jianggao; Feng, Mengjie; Yang, Xinwang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-11-30

    Graphical abstract: (a) TEM photogram of CG3 sintered at 800 °C, crystals are obvious; (b) the XRD patterns of CG3 glass samples sintered at various temperatures; (c) SEM photogram of CG3 sintered at 800 °C; (d) Kissinger, Augis–Bennett and Ozawa kinetics plots of CG3 glass samples. - Highlights: • Combining sol–gel method with direct sintering method to reduce the temperature of coatings formation. • Characterizing CaO–SiO{sub 2}–B{sub 2}O{sub 3} glass–ceramic coatings on porous substrates. • Surface crystallization of CBS glass–ceramic coatings: nucleation and kinetics. • Activation energies for crystal growth in CBS glass–ceramics with different contents of B{sub 2}O{sub 3}. - Abstract: Borosilicate glass–ceramics precursors with varying compositional ratios in the CaO–SiO{sub 2}–B{sub 2}O{sub 3} (CBS) system were synthesized by sol–gel method. The precursors were calcined at 1200 °C for 2 h to form glass powders. The glass–ceramics were prepared by overlaying glass slurries on the substrates before sintering at different temperatures. The as-prepared glasses and glass–ceramics were characterized by differential scanning calorimetry and X-ray diffraction. The crystallization activation energies (E{sub c}) were calculated using the Kissinger method from DSC results. The morphology and crystallization behavior of the glass–ceramics were monitored by scanning electron microscopy. Both glass transition and crystallization temperatures decreased, however, the metastable zone increased. The E{sub c} values of CBS glasses and glass–ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B{sub 2}O{sub 3} content, whereas that of the calcined G3 glass was 104.9 kJ/mol. Finally, the coatings were prepared at a low temperature (700 °C). The crystals that grew on the surface of multilayer coatings demonstrated heterogeneous surface nucleation and crystallization after heat-treatment from 700 °C to 850 °C for 4 h.

  17. Study on Microstructures and Mechanical Properties of Foam Titanium Carbide Ceramics Fabricated by Reaction Sintering Process

    Science.gov (United States)

    Ma, Yana; Bao, Chonggao; Chen, Jie; Song, Suocheng; Han, Longhao

    2018-05-01

    Foam titanium carbide (TiC) ceramics with a three-dimensional network structure were fabricated by the reaction sintering process, in which polyurethane foam was taken as the template, and TiO2 and phenolic resin were used as the reactants. Phase, microstructures and fracture morphologies of foam TiC ceramics were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that when the mass ratios of phenolic resin and TiO2 (F/T) are (0.8-1.2): 1, foam TiC ceramics with pure TiC phase can be formed. As the F/T ratios increase, crystal lattice parameters of fabricated foam TiC ceramics become bigger. When the value of F/T decreases from 1.2 to 0.8, grain size of TiC grows larger and microstructures get denser; meanwhile, the compressive strength increases from 0.10 to 1.05 MPa. Additionally, either raising the sintering temperatures or extending holding time can facilitate the completion of the reaction process and increase the compressive strength.

  18. Comparison of Reactive and Non-Reactive Spark Plasma Sintering Routes for the Fabrication of Monolithic and Composite Ultra High Temperature Ceramics (UHTC Materials

    Directory of Open Access Journals (Sweden)

    Roberto Orrù

    2013-04-01

    Full Text Available A wider utilization of ultra high temperature ceramics (UHTC materials strongly depends on the availability of efficient techniques for their fabrication as dense bodies. Based on recent results reported in the literature, it is possible to state that Spark Plasma Sintering (SPS technology offers a useful contribution in this direction. Along these lines, the use of two different SPS-based processing routes for the preparation of massive UHTCs is examined in this work. One method, the so-called reactive SPS (R-SPS, consists of the synthesis and densification of the material in a single step. Alternatively, the ceramic powders are first synthesized by Self-propagating High-temperature Synthesis (SHS and then sintered by SPS. The obtained results evidenced that R-SPS method is preferable for the preparation of dense monolithic products, while the sintering of SHS powders requires relatively milder conditions when considering binary composites. The different kinetic mechanisms involved during R-SPS of the monolithic and composite systems, i.e., combustion-like or gradual solid-diffusion, respectively, provides a possible explanation. An important role is also played by the SHS process, particularly for the preparation of composite powders, since stronger interfaces are established between the ceramic constituents formed in situ, thus favoring diffusion processes during the subsequent SPS step.

  19. Sintering study in vertical fixed bed reactor for synthetic aggregate production

    International Nuclear Information System (INIS)

    Quaresma, D.S.; Neves, A.S.S.; Melo, A.O.; Pereira, L.F.S.; Bezerra, P.T.S.; Macedo, E.N.; Souza, J.A.S.

    2017-01-01

    The synthetic aggregates are being employed in civil construction for the reduction of mineral extraction activities. Within this context, the recycling of industrial waste is the basis of the majority of processes to reduce the exploitation of mineral resources. In this work the sintering in a vertical fixed bed reactor for synthetic aggregate production using 20% pellets and 80% charcoal was studied. The pellets were prepared from a mixture containing clay, charcoal and fly ash. Two experiments varying the speed of air sucking were carried out. The material produced was analyzed by X-ray diffraction, scanning electron microscopy, measures of their ceramic properties, and particle size analysis. The results showed that the solid-state reactions, during the sintering process, were efficient and the produced material was classified as coarse lightweight aggregate. The process is interesting for the sintering of aggregates, and can be controlled by composition, particle size, temperature gradient and gaseous flow. (author)

  20. Microstructure and thermoelectric properties of β-FeSi2 ceramics fabricated by hot-pressing and spark plasma sintering

    International Nuclear Information System (INIS)

    Qu Xiurong; Lue Shuchen; Hu Jianmin; Meng Qingyu

    2011-01-01

    Highlights: → With increasing hot-pressing (HP) temperature, the thermoelectric figure of merit of β-FeSi 2 ceramics is improved slightly. → The grain size of the sample sintered by the spark plasma sintering (SPS) process is smaller than that by the HP process. → The SPS sample shows excellent thermoelectric performance attributed to low thermal conductivity. - Abstract: The microstructure and thermoelectric properties of β-FeSi 2 ceramics by hot pressing (HP) and spark plasma sintering (SPS) are investigated. With increasing hot-pressing temperature, the density, electronic conductivity and thermal conductivity of the samples increase significantly, the thermoelectric figure of merit is improved slightly. The microstructure study indicates that the sizes of the β-FeSi 2 and ε-FeSi phases in the sample sintered by the SPS process are smaller than that by the HP process. The SPS sample shows excellent thermoelectric performance due to the low thermal conductivity.

  1. Reaction-sintered porous mineral-based mullite ceramic membrane supports made from recycled materials.

    Science.gov (United States)

    Dong, Yingchao; Zhou, Jian-Er; Lin, Bin; Wang, Yongqing; Wang, Songlin; Miao, Lifeng; Lang, Ying; Liu, Xingqin; Meng, Guangyao

    2009-12-15

    Bulk porous mullite supports for ceramic membranes were prepared directly using a mixture of industrial waste fly ash and bauxite by dry-pressing, followed by sintering between 1200 and 1550 degrees C. The effects of sintering temperature on the phase composition and shrinkage percent of porous mullite were studied. The XRD results indicate that secondary mullitization reaction took place above 1200 degrees C, and completed at 1450 degrees C. During sintering, the mixture samples first shrunk, then expanded abnormally between 1326 and 1477 degrees C, and finally shrunk again above 1477 degrees C. This unique volume self-expansion is ascribed to the secondary mullitization reaction between bauxite and fly ash. More especially, the micro-structural variations induced by this self-expansion sintering were verified by SEM, porosity, pore size distribution and nitrogen gas permeation flux. During self-expansion sintering, with increasing temperature, an abnormal increase in both open porosity and pore size is observed, which also results in the increase of nitrogen gas flux. The mineral-based mullite supports with increased open porosity were obtained. Furthermore, the sintered porous mullite membrane supports were characterized in terms of thermal expansion co-efficient and mechanical strength.

  2. The harmful effects of sintering aids in Pr:LuAG optical ceramic scintillator

    Czech Academy of Sciences Publication Activity Database

    Shen, Y.; Shi, Y.; Feng, X.; Pan, Y.; Li, J.; Zeng, J.-Y.; Nikl, Martin; Krasnikov, A.; Vedda, A.; Moretti, F.

    2012-01-01

    Roč. 95, č. 7 (2012), s. 2130-2132 ISSN 0002-7820 R&D Projects: GA MŠk LH12185 Institutional research plan: CEZ:AV0Z10100521 Keywords : scintillator * optical ceramics * sintering aids * luminescence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.107, year: 2012

  3. Physics and Technology of Transparent Ceramic Armor: Sintered Al2O3 vs Cubic Materials

    National Research Council Canada - National Science Library

    Krell, Andreas; Hutzler, Thomas; Klimke, Jens

    2006-01-01

    Sintered sub-micrometer alumina (alpha-Al2O3) is the hardest transparent armor. However, its trigonal structure gives rise to a strong thickness effect that makes thicker components translucent. Cubic ceramics (no birefringence...

  4. Influence of sintering temperature in red ceramic with addition of mill scale

    International Nuclear Information System (INIS)

    Arnt, A.B.C.; Rocha, M.R.; Bernardin, A.M.; Meller, J.G.

    2010-01-01

    This study aimed to evaluate the influence of sintering temperature in a red ceramic body with the addition of mill scale. This residue consists of oxides of iron had to replace the function of pigments used in ceramic materials. After chemical characterization, by X-ray diffraction, X-ray fluorescence and scanning electron microscopy, this residue was added at a rate of 5% in commercial ceramic past. The formulations were subjected to different burn temperatures of around 950 deg C, 1000 deg C and 1200 deg C. The formulations were evaluated for physical loss to fire, linear firing shrinkage, water absorption and flexural strength by 3 and intensity of tone. The results indicate that the different firing temperatures influence the strength and stability of tone in the formulations tested. (author)

  5. LOW-TEMPERATURE SINTERED (ZnMg2SiO4 MICROWAVE CERAMICS WITH TiO2 ADDITION AND CALCIUM BOROSILICATE GLASS

    Directory of Open Access Journals (Sweden)

    BO LI

    2011-03-01

    Full Text Available The low-temperature sintered (ZnMg2SiO–TiO2 microwave ceramic using CaO–B2O3–SiO2 (CBS as a sintering aid has been developed. Microwave properties of (Zn1-xMgx2SiO4 base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO2 additives on the crystal phases, microstructures and microwave characteristics of (ZnMg2SiO4 (ZMS ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMS–TiO2 ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO2. Proper amount of TiO2 could tune the large negative temperature coefficient of resonant frequency (tf of ZMS system to a near zero value. (Zn0.8Mg0.22SiO4 codoped with 10 wt.% TiO2 and 3 wt.% CBS sintered at 950°C exhibits the dense microstructure and excellent microwave properties: εr = 9.5, Q·f = 16 600 GHz and tf = −9.6 ppm/°C.

  6. Sintering Theory and Practice

    Science.gov (United States)

    German, Randall M.

    1996-01-01

    Although sintering is an essential process in the manufacture of ceramics and certain metals, as well as several other industrial operations, until now, no single book has treated both the background theory and the practical application of this complex and often delicate procedure. In Sintering Theory and Practice, leading researcher and materials engineer Randall M. German presents a comprehensive treatment of this subject that will be of great use to manufacturers and scientists alike. This practical guide to sintering considers the fact that while the bonding process improves strength and other engineering properties of the compacted material, inappropriate methods of control may lead to cracking, distortion, and other defects. It provides a working knowledge of sintering, and shows how to avoid problems while accounting for variables such as particle size, maximum temperature, time at that temperature, and other problems that may cause changes in processing. The book describes the fundamental atomic events that govern the transformation from particles to solid, covers all forms of the sintering process, and provides a summary of many actual production cycles. Building from the ground up, it begins with definitions and progresses to measurement techniques, easing the transition, especially for students, into advanced topics such as single-phase solid-state sintering, microstructure changes, the complications of mixed particles, and pressure-assisted sintering. German draws on some six thousand references to provide a coherent and lucid treatment of the subject, making scientific principles and practical applications accessible to both students and professionals. In the process, he also points out and avoids the pitfalls found in various competing theories, concepts, and mathematical disputes within the field. A unique opportunity to discover what sintering is all about--both in theory and in practice What is sintering? We see the end product of this thermal

  7. Cellular ceramics made from porcelain tile polishing wastes: influence of sintering time

    International Nuclear Information System (INIS)

    Guimaraes, A.F.; Zanelatto, C.C.; Uggioni, E.; Bernardin, A.M.

    2009-01-01

    This paper deals with the physical, microstructural and mechanical characterization of cellular ceramics made from porcelain polishing wastes, which were expanded by the bubble formation technique during the sintering process. The microstructure, linear expansion, bulk density (mercury immersion) and mechanical behavior (compressive strength) were determined to characterize the glass foam obtained. Moreover, the porcellaneous residue was characterized by chemical and phase analyses, particle size (laser diffraction) and thermal behavior. As a result, the higher the soaking time during heat treatment at 1200 deg C the lower the density obtained for the cellular ceramic due to CO 2 expansion, and lower the mechanical strength of the samples. The microstructure shows spherical cells and completely closed pores, resulting in a cheap way to obtain low density material with adequate mechanical strength, avoiding the disposal of wastes from the ceramic industry. (author)

  8. Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3–Al2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Denghao Li

    2014-06-01

    Full Text Available CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior, microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from 1250 °C to 1050 °C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3 ceramic sintered at 1100 °C presented good microwave dielectric properties of εr=7.27, Q×f=16,850 GHz and τf=−39.53 ppm/°C, which is much better than those of pure CaSiO3 ceramic sintered at 1340 oC (Q×f=13,109 GHz. The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.

  9. Process-generated nanoparticles from ceramic tile sintering: Emissions, exposure and environmental release.

    Science.gov (United States)

    Fonseca, A S; Maragkidou, A; Viana, M; Querol, X; Hämeri, K; de Francisco, I; Estepa, C; Borrell, C; Lennikov, V; de la Fuente, G F

    2016-09-15

    The ceramic industry is an industrial sector in need of significant process changes, which may benefit from innovative technologies such as laser sintering of ceramic tiles. Such innovations result in a considerable research gap within exposure assessment studies for process-generated ultrafine and nanoparticles. This study addresses this issue aiming to characterise particle formation, release mechanisms and their impact on personal exposure during a tile sintering activity in an industrial-scale pilot plant, as a follow-up of a previous study in a laboratory-scale plant. In addition, possible particle transformations in the exhaust system, the potential for particle release to the outdoor environment, and the effectiveness of the filtration system were also assessed. For this purpose, a tiered measurement strategy was conducted. The main findings evidence that nanoparticle emission patterns were strongly linked to temperature and tile chemical composition, and mainly independent of the laser treatment. Also, new particle formation (from gaseous precursors) events were detected, with nanoparticles efficiency of the filtration system was successfully tested and evidenced a >87% efficiency in particle number concentrations removal. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Production of ceramics from coal fly ash

    Directory of Open Access Journals (Sweden)

    Angjusheva Biljana

    2012-01-01

    Full Text Available Dense ceramics are produced from fly ash from REK Bitola, Republic of Macedonia. Four types of fly ash from electro filters and one from the collected zone with particles < 0.063 mm were the subject of this research. Consolidation was achieved by pressing (P= 133 MPa and sintering (950, 1000, 1050 and 11000C and heating rates of 3 and 100/min. Densification was realized by liquid phase sintering and solid state reaction where diopside [Ca(Mg,Al(Si,Al2O6] was formed. Ceramics with optimal properties (porosity 2.96±0.5%, bending strength - 47.01±2 MPa, compressive strength - 170 ±5 MPa was produced at 1100ºC using the heating rate of 10ºC/min.

  11. TiC含量和烧结工艺对AlN-TiC复相陶瓷烧结性能的影响%Effect of TiC Content and Sintering Process on Sintering Properties of AIN-SiC Composite Ceramics

    Institute of Scientific and Technical Information of China (English)

    程卫华

    2012-01-01

    Taking A1N and TiC as raw materials, the A1N-TiC composite ceramics were prepared by hot pressing sintering process, and the effects of TiC content and sintering process on sintering properties of A1N-SiC composite ceramics were studied. The results show that the composite ceramics didnlt generate new phase and consisted of A1N and TiC phases during sintering. The compact composite ceramics could be prepared after sintering at 1 900 ℃ for 1 h, the relative density reached more than 99%and the TiC content had no effect on sintering properties of the composite ceramics.%以A1N和TiC粉为原料,采用热压烧结工艺制备AlN-TiC复相陶瓷,研究了TiC含量、烧结工艺对复相陶瓷烧结性能的影响。结果表明:在烧结过程中复相陶瓷没有新相生成,由AlN和TiC两相组成;在1900℃下烧结1h后,可以制备出致密的A1N-TiC复相陶瓷,其相对密度达到了99%以上,TiC的加入量对复相陶瓷的烧结性能无影响。

  12. Effects of surrounding powder in sintering process on the properties of Sb and Mn- doped barium-strontium titanate PTCR ceramics

    Directory of Open Access Journals (Sweden)

    Pornsuda Bomlai

    2006-05-01

    Full Text Available In this research, the effects of surrounding powder used during sintering of Sb and Mn doped bariumstrontium titanate (BST ceramics were studied. The ceramic samples were prepared by a conventional mixed-oxide method and placed on different powders during sintering. Phase formation, microstructure and PTCR behavior of the samples were then observed. Microstructures and PTCR behavior varied with the type of surrounding powder, whereas the crystal structure did not change. The surrounding powder has more effects on the shape of the grain than on the size. The grain size of samples was in the range of 5-20 μm. The most uniform grain size and the highest increase of the ratio of ρmax/ρRT were found to be about 106 for samples which had been sintered on Sb-doped BST powder. This value was an order of magnitude greater than for samples sintered on a powder of the equivalent composition to that of the sample pellet.

  13. Sintering and crystallization behavior of CaMgSi2O6-NaFeSi2O6 based glass-ceramics

    International Nuclear Information System (INIS)

    Goel, Ashutosh; Kansal, Ishu; Ferrari, Anna Maria; Pascual, Maria J.; Barbieri, Luisa; Bondioli, Federica; Lancellotti, Isabella; Ribeiro, Manuel J.; Ferreira, Jose M. F.

    2009-01-01

    We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi 2 O 6 -10 mol % NaFeSi 2 O 6 . The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850-950 deg. C in both air and N 2 atmosphere. X-ray diffraction studies adjoined with the Rietveld-reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with diopside as the primary crystalline phase were obtained where the amount of diopside varied with the heating conditions.

  14. Effect of the sintering method on microstructure and thermal and mechanical properties of zirconium oxophosphate ceramics Zr2O(PO4)2

    Science.gov (United States)

    Bregiroux, Damien; Cedelle, Julie; Ranc, Isabelle; Barreteau, Céline; Mata Osoro, Gustavo; Wallez, Gilles

    2017-12-01

    Due to an ultra-low thermal expansion, Zr2O(PO4)2 could find many applications as a thermal shock resistant material. To this end, ceramic processing is a key step in order to reach best properties. In this work, Zr2O(PO4)2 was sintered by conventional sintering and by the spark plasma sintering technique (SPS) with and without additive. Samples made by conventional sintering with ZnO as sintering aid have a maximum relative density of around 92%. Microstructure is composed of large grains and microcracks can be observed. When doped with 5 wt. % of MgO, samples can be densified by SPS up to 99.6% of the relative density and the grain size maintained between 0.5 and 1.5 μm. Thermal conductivity and Vickers microhardness were investigated as a function of the microstructure. Best values were obtained for the ceramic doped with 5 wt.% MgO and sintered by SPS, thanks to a fine microstructure and a small amount of residual microcracks.

  15. Microwave sintering of zirconia toughened alumina at 28GHz

    International Nuclear Information System (INIS)

    Samandi, M.; Ji, H.; Miyake, S.

    1998-01-01

    Microwave radiation from a 10 kW, CW gyrotron operating at 28 GHz was employed to sinter 10% zirconia toughened alumina (ZTA) ceramic samples. It has been established that the use of millimetre wave radiation circumvents the difficulties encountered during the sintering of ceramics, i e. formation of hot spot, by radiation at industrially permissible frequency of 2.45GHz. Further, careful density measurement and microstructural characterisation of mm- wave and conventionally sintered samples by XRD, SEM and TEM has unequivocally demonstrated the effectiveness of mm-wave radiation for obtaining high density ceramics at lower sintering temperatures. Copyright (1998) Australasian Ceramic Society

  16. Effects of sintering processes on mechanical properties and microstructure of TiB2–TiC + 8 wt% nano-Ni composite ceramic cutting tool material

    International Nuclear Information System (INIS)

    Zou Bin; Huang Chuanzhen; Song Jinpeng; Liu Ziye; Liu Lin; Zhao Yan

    2012-01-01

    Highlights: ► TiB 2 –TiC + 8 wt% nano-Ni ceramic tool material was sintered by six processes. ► The properties of material depended mainly on the holding stages and duration. ► SP1 process was involved with the multiple holding stages and longer duration. ► SP1 process led to many pores, and coarsening and brittle rupture of grains. ► Tool material sintered by SP6 process exhibited the optimum mechanical properties. - Abstract: TiB 2 –TiC composite powder was prepared by ball-milled with ethanol and vacuum dry, and TiB 2 –TiC + 8 wt% nano-Ni composite ceramic cutting tool material was sintered using vacuum hot-pressed sintering technique by six processes which included the different holding stages and times. The effects of sintering processes on the mechanical properties and microstructure were investigated. The polished surface and fracture surface of TiB 2 –TiC + 8 wt% nano-Ni ceramics sintered by the different sintering processes were observed by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy-dispersive spectrometry (EDS), and the relationships between mechanical properties and microstructure were discussed. The mechanical properties and microstructure depended mainly on the total holding time and the different holding stages. The longer holding time and multiple holding stages led to coarsening of TiB 2 and TiC grains, formation of pores and the brittle rupture of grains, which deteriorated the mechanical properties of TiB 2 –TiC + 8 wt% nano-Ni ceramic. TiB 2 –TiC + 8 wt% nano-Ni composite ceramic cutting tool material sintered by SP6 process exhibited the optimum resultant mechanical properties because of its finer microstructure and higher relative density, and its flexural strength, fracture toughness and hardness were 916.8 MPa, 7.80 MPa m 1/2 and 22.54 GPa, respectively.

  17. Evaluation of growth of calcium phosphate ceramics on sintered Ti-Ca-P composites

    Energy Technology Data Exchange (ETDEWEB)

    Karanjai, Malobika [Centre for Nano Materials, International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O, Hyderabad - 500 005, Andhra Pradesh (India)], E-mail: malobika_k@rediffmail.com; Sundaresan, Ranganathan [Centre for Nano Materials, International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O, Hyderabad - 500 005, Andhra Pradesh (India); Mohan, Tallapragada Raja Rama; Kashyap, Bhagwati Prasad [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai - 400 076, Maharashtra (India)

    2008-12-01

    Sintered Ti-Ca-P composites having in situ formed calcium phosphate phases developed by powder metallurgy processing were soaked for 28 days in simulated body fluid (SBF) with a pH of 7.4 at 37 deg. C and evaluated for the growth of calcium phosphate ceramics onto its surface. The composites were taken out once every 7 days and characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) for evaluating the Ca-P growth. Based on the change in chemistry of the SBF and phase contents, a model has been proposed for mechanism of growth of calcium phosphate compounds on sintered Ti-Ca-P composites immersed in SBF.

  18. Two-stage sintering of Al2O3 with polysiloxane

    International Nuclear Information System (INIS)

    Godoy, A.L.E.; Bressiani, A.H.A.

    2014-01-01

    The final stage of sintering involves grain growth which often is not desirable in the microstructure of structural ceramics and cutting tools. The ceramics derived from inorganic polymers allow the production of thermo mechanical materials due to their hardness and especially their excellent structural stability under aggressive environment. The aim of this study is to investigate the effect of two steps sintering process on density, microstructure and hardness of ceramics derived from the mixture alumina-polysiloxane (PMS). Alumina was ball-milled for 12, 24 and 48 hours. The alumina powder mean particle size was characterized by laser diffraction. It was added 10% wt of PMS. Pellets were prepared by die pressing and sintering at 1650°C/10min and 1550°C/1h. The sintered materials were characterized by evaluation of apparent density by helium picnometry, X-ray diffraction, scanning electron microscopy and Vickers indentation analysis for hardness determination. The specimens are composed by mullite and the best results were obtained with the addition of alumina milled for 48 hours. (author)

  19. Characterization of humidity-controlling porous ceramics produced from coal fly ash and waste catalyst by co-sintering

    Science.gov (United States)

    Lin, Kae-Long; Ma, Chih-Ming; Lo, Kang-Wei; Cheng, Ta-Wui

    2018-04-01

    In this study, the following operating conditions were applied to develop humidity-controlling porous ceramic (HCPC) products: sintering temperatures of 800-1000 °C and percentages of coal fly ash in waste catalyst of 0%-40%. The HCPC samples then underwent a flexural strength test, to determine their quality according to the Chinese National Standards (CNS 3298). Their microstructures, crystal structures, and pore volume were determined in terms of equilibrium moisture content, water vapor adsorption/desorption, and hygroscopic sorption properties over 48 h. Nitrogen adsorption/desorption isotherms showed a hydrophobic behavior (type H3 isotherm). The water vapor adsorption/desorption and hygroscopic sorption properties satisfied the JIS A1470 intensity specification for building materials (>29 g/m2). At sintering temperatures of 950-1000 °C, HCPC samples for coal fly ash containing 20%-30% waste catalyst met the JIS A1470 intensity specifications for building materials (<29 g/m2).

  20. Effects of varied porosity on the physic-mechanical properties of sintered ceramic from Ifon clay

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE

    2017-12-01

    Full Text Available The effects of saw dust admixture on the physic-mechanical properties of sintered clay bonded carbonized palm kernel shell ceramic was investigated. Composite mixtures of powdered carbonized palm kernel shell and clay from Ifon deposit were produced using equal amount of clay and carbonized palm kernel shell. These were then mixed with varied amount of saw dust (0%, 5% and 10% in a ball mill for 6 hours. From this standard sample specimens were produced using uniaxial compression after mixing each mixture with 10% moisture of clay contents. The compressed samples were sintered at 9500C and soaked for one hour. The sintered samples were characterized for various physic-mechanical properties using state of the art equipment’s. The fired samples were also characterized using ultra-high-resolution field emission scanning electron microscope (UHR-FEGSEM equipped with energy dispersive spectroscopy (EDX. It was observed that the apparent porosity and water absorption of the clay bonded carbonized palm kernel shell ceramic increased with increased amount of saw dust admixture, cold crushing strength, Young’ modulus of elasticity and absorbed energy of the sample reduced with increased amount of saw dust admixture. It was concluded that the sample with 0% saw dust admixture is judged to possess optimum physic-mechanical properties.

  1. Micromolding for ceramic microneedle arrays

    NARCIS (Netherlands)

    van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; Lüttge, Regina

    2011-01-01

    The fabrication process of ceramic microneedle arrays (MNAs) is presented. This includes the manufacturing of an SU-8/Si-master, its double replication resulting in a PDMS mold for production by micromolding and ceramic sintering. The robustness of the replicated structures was tested by means of

  2. Sintered cobalt-rare earth intermetallic product

    International Nuclear Information System (INIS)

    Benz, M.C.

    1975-01-01

    A process is described for preparing novel sintered cobalt--rare earth intermetallic products which can be magnetized to form permanent magnets having stable improved magnetic properties. A cobalt--rare earth metal alloy is formed having a composition which at sintering temperature falls outside the composition covered by the single Co 5 R intermetallic phase on the rare earth richer side. The alloy contains a major amount of the Co 5 R intermetallic phase and a second solid CoR phase which is richer in rare earth metal content than the Co 5 R phase. The specific cobalt and rare earth metal content of the alloy is substantially the same as that desired in the sintered product. The alloy, in particulate form, is pressed into compacts and sintered to the desired density. The sintered product is comprised of a major amount of the Co 5 R solid intermetallic phase and up to about 35 percent of the product of the second solid CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase

  3. Oxide ceramics

    International Nuclear Information System (INIS)

    Ryshkewitch, E.; Richerson, D.W.

    1985-01-01

    The book explores single-phase ceramic oxide systems from the standpoint of physical chemistry and technology. This second edition also focuses on advances in technology since publication of the original edition. These include improvements in raw materials and forming and sintering techniques, and the major role that oxide ceramics have had in development of advanced products and processes. The text is divided into five major sections: general fundamentals of oxide ceramics, advances in aluminum oxide technology, advances in zirconia technology, and advances in beryllium oxide technology

  4. Pressureless sintering and gas flux properties of porous ceramic membranes for gas applications

    Directory of Open Access Journals (Sweden)

    David O. Obada

    Full Text Available The preparation and characterization of kaolin based ceramic membranes using styrofoam (STY and sawdust (SD as pore formers have been prepared by mechano-chemical synthesis using pressureless sintering technique with porogen content between (0–20 wt% by die pressing. Pellets were fired at 1150 °C and soaking time of 4 h. The membranes cast as circular disks were subjected to characterization studies to evaluate the effect of the sintering temperature and pore former content on porosity, density, water absorption and mechanical strength. Obtained membranes show effective porosity with maximum at about 43 and 47% respectively for membranes formulated with styrofoam and sawdust porogens but with a slightly low mechanical strength that does not exceed 19 MPa. The resultant ceramic bodies show a fine porous structure which is mainly caused by the volatilization of the porogens. The fabricated membrane exhibited high N2 gas flux, hence, these membranes can be considered as efficient for potential application for gas separation by reason of the results shown in the gas flux tests. Keywords: Porosity, Pore formers, Kaolin, Physico-mechanical properties, Gas separation, Gas flux

  5. Neodymium ion diffusion during sintering of Nd : YAG transparent ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hollingsworth, Joel P; Kuntz, Joshua D; Soules, Thomas F [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550 (United States)

    2009-03-07

    Using an electron microprobe, we measured and characterized the Nd{sup 3+} ion diffusion across a boundary between Nd doped and undoped ceramic yttrium aluminium garnet (YAG) for different temperature ramps and hold times and temperatures. The results show significant Nd ion diffusion on the order of micrometres to tens of micrometres depending on the time and temperature of sintering. The data fit well a model including bulk diffusion, grain boundary diffusion and grain growth. Grain boundary diffusion dominates and grain growth limits grain boundary diffusion by reducing the total cross-sectional area of grain boundaries. (fast track communication)

  6. Development of ceramics based fuel, Phase I, Kinetics of UO2 sintering by vibration compacting of UO2 powder (Introductory report)

    International Nuclear Information System (INIS)

    Ristic, M.M.

    1962-10-01

    After completing the Phase I of the task related to development of ceramics nuclear fuel the following reports are presented: Kinetics of UO 2 sintering; Vibrational compacting and sintering of UO 2 ; Characterisation of of UO 2 powder by DDK and TGA methods; Separation of UO 2 powder

  7. Effect of microwave-assisted sintering on dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Suman, E-mail: sumanranigju@gmail.com; Ahlawat, Neetu; Punia, R.; Kundu, R. S. [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hissar 125001, Haryana (India); Ahlawat, N. [Matu Ram Institute of Engineering and Management, Rohtak (India)

    2016-05-23

    In this present work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It was observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.

  8. Elaboration of new ceramic composites containing glass fibre production wastes

    International Nuclear Information System (INIS)

    Rozenstrauha, I.; Sosins, G.; Krage, L.; Sedmale, G.; Vaiciukyniene, D.

    2013-01-01

    Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50 % of organic matter as well as waste glass from aluminium borosilicate glass fibre with relatively high softening temperature (> 600 degree centigrade). In order to elaborate different new ceramic products (porous or dense composites) the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia) with illite content in clay fraction up to 80-90 % was used as a matrix. The raw materials were investigated by differential-thermal (DTA) and XRD analysis. Ternary compositions were prepared from mixtures of 15 - 35 wt % of sludge, 20 wt % of waste glass and 45 - 65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 degree centigrade in different treatment conditions. Materials produced in temperature range 1090 - 1100 degree centigrade with the most optimal properties - porosity 38 - 52 %, water absorption 39 -47 % and bulk density 1.35 - 1.67 g/cm 3 were selected for production of porous ceramics and materials showing porosity 0.35 - 1.1 %, water absorption 0.7 - 2.6 % and bulk density 2.1 - 2.3 g/cm 3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM). By X-ray diffraction analysis (XRD) the quartz, diopside and anorthite crystalline phases were detected. (Author)

  9. Processing of pure titanium containing titanium-based reinforcing ceramics additives using spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Mondiu Olayinka DUROWOJU

    2017-06-01

    Full Text Available The densification behaviour, microstructural changes and hardness characteristics during spark plasma sintering of CP-Ti reinforced with TiC, TiN, TiCN and TiB2 were investigated. Commercially pure Ti powders were dry mixed with varied amounts (2.5 and 5 wt. % of the ceramic additives using a T2F Turbula mixer for 5 h and at a speed of 49 rpm. The blended composite powders were then sintered using spark plasma sintering system (model HHPD-25 from FCT Germany at a heating rate of 100oC min-1, dwell time of 5 min and sintering temperature of 950ºC. The sintering of CP-Ti was used as a base study to select the proper spark plasma sintering temperature for full density. Densification was monitored through analysis of the recorded punch displacement and the measured density of the sintered samples using Archimedes method. High densities ranging from 97.8% for 5% TiB2 addition to 99.6% for 5% TiCN addition were achieved at a relatively low temperature of 950°C. Microstructural analyses show a uniform distribution of the additives and finer structure showing their inhibitive effect on grain growth. An improved hardness was observed in all the cases with highest values obtained with TiCN as a result of the combined effect of TiC and TiN. A change in the fracture mode from trans granular to intergranular was also observed.

  10. Density determination of sintered ceramic nuclear fuel materials

    International Nuclear Information System (INIS)

    Landspersky, H.; Medek, J.

    1980-01-01

    The feasibility was tested of using solids for pycnometric determination of the density of uranium dioxide-based sintered ceramic fuel materials manufactured by the sol-gel method in the shape of spherical particles of 0.7 to 1.0 mm in size and of particles smaller than 200 μm. For fine particles, this is the only usable method of determining their density which is a very important parameter of the fine fraction when it is employed for the manufacture of fuel elements by vibration compacting. The method consists in compacting a mixture of pycnometric material and dispersed particles of uranium dioxide, determining the size and weight of the compact, and in calculating the density of the material measured from the weight of the oxide sample in the mixture. (author)

  11. Treatment of copper industry waste and production of sintered glass-ceramic.

    Science.gov (United States)

    Coruh, Semra; Ergun, Osman Nuri; Cheng, Ta-Wui

    2006-06-01

    Copper waste is iron-rich hazardous waste containing heavy metals such as Cu, Zn, Co, Pb. The results of leaching tests show that the concentration of these elements exceeds the Turkish and EPA regulatory limits. Consequently, this waste cannot be disposed of in its present form and therefore requires treatment to stabilize it or make it inert prior to disposal. Vitrification was selected as the technology for the treatment of the toxic waste under investigation. During the vitrification process significant amounts of the toxic organic and inorganic chemical compounds could be destroyed, and at the same time, the metal species are immobilized as they become an integral part of the glass matrix. The copper flotation waste samples used in this research were obtained from the Black Sea Copper Works of Samsun, Turkey. The samples were vitrified after being mixed with other inorganic waste and materials. The copper flotation waste and their glass-ceramic products were characterized by X-ray analysis (XRD), scanning electron microscopy and by the toxicity characteristic leaching procedure test. The products showed very good chemical durability. The glass-ceramics fabricated at 850 degrees C/2 h have a large application potential especially as construction and building materials.

  12. Utilization of Electric Arc Furnace Dust as raw material for the production of ceramic and concrete building products.

    Science.gov (United States)

    Sikalidis, Constantine; Mitrakas, Manassis

    2006-01-01

    The up to 20 wt% addition of the Electric Arc Furnace Dust (EAFD) hazardous waste on the properties of extruded clay-based ceramic building products fired at various temperatures (850 to 1050 degrees C), as well as of dolomite-concrete products was investigated. Chemical, mineralogical and particle size distribution analyses were performed in order to characterize the used EAFD. The results showed that the ceramic specimens prepared had water absorption, firing shrinkage, apparent density, mechanical strength, colour and leaching behaviour within accepted limits. Addition of 7.5 to 15 wt% EAFD presented improved properties, while 20 wt% seems to be the upper limit. Dolomite-concrete specimens were prepared by vibration and press-forming of mixtures containing cement, sand, dolomite, EAFD and water. Modulus of rupture values were significantly increased by the addition of EAFD. The leaching tests showed stabilization of all toxic metals within the sintered ceramic structure, while the leaching behaviour of lead in dolomite-concrete products needs further detailed study.

  13. Post-treatment of Plasma-Sprayed Amorphous Ceramic Coatings by Spark Plasma Sintering

    Science.gov (United States)

    Chraska, T.; Pala, Z.; Mušálek, R.; Medřický, J.; Vilémová, M.

    2015-04-01

    Alumina-zirconia ceramic material has been plasma sprayed using a water-stabilized plasma torch to produce free standing coatings. The as-sprayed coatings have very low porosity and are mostly amorphous. The amorphous material crystallizes at temperatures above 900 °C. A spark plasma sintering apparatus has been used to heat the as-sprayed samples to temperatures above 900 °C to induce crystallization, while at the same time, a uniaxial pressure of 80 MPa has been applied to their surface. After such post-treatment, the ceramic samples are crystalline and have very low open porosity. The post-treated material exhibits high hardness and significantly increased flexural strength. The post-treated samples have a microstructure that is best described as nanocomposite with the very small crystallites embedded in an amorphous matrix.

  14. Influences of donor dopants on the properties of PZT-PMS-PZN piezoelectric ceramics sintered at low temperatures

    International Nuclear Information System (INIS)

    Yoon, Seokjin; Choi, Jiwon; Choi, Jooyoung; Wan, Dandan; Li, Qian; Yang, Ying

    2010-01-01

    0.90Pb(Zr 0.48 Ti 0.52 )O 3 -0.05Pb(Mn 1/3 Sb 2/3 )O 3 -0.05Pb(Zn 1/3 Nb 2/3 )O 3 quaternary piezoelectric ceramics with CuO added were synthesized by using a conventional method at low sintering temperatures. CuO additive, 1.0 wt%, significantly improves the sinterability of 0.90PZT-0.05PMS-0.05PZN ceramics, lowering the sintering temperature to 900 .deg. C and showing moderate electrical properties: d 33 = 306 pC/N, Q m = 997, k p = 53.6%, tanδ = 0.50%, and ε T 33 = 1351. To obtain more optimal piezoelectric properties, we selected Bi 2 O 3 and Nb 2 O 5 as donor dopants to introduce a softening effect. The crystal structure, micro-morphology and electrical properties were studied in terms of the Bi 2 O 3 and the Nb 2 O 5 contents. Our study demonstrates that Bi 2 O 3 is very effective in improving the piezoelectric properties, causing a significant enhancement in d 33 and k p values. Particularly, 0.75-wt%-Bi 2 O 3 -added 0.90PZT-0.05PMS-0.05PZN + 1.0 wt% CuO ceramics show excellent electrical properties: d 33 = 363 pC/N, Q m = 851, k p = 59.3%, tanδ = 0.38%, and ε T 33 = 1596. On the other hand, the effect of Nb 2 O 5 on the piezoelectric properties is very complicated, 0.50 wt% Nb 2 O 5 doped 0.90PZT-0.05PMS-0.05PZN + 1.0 wt% CuO ceramics have a remarkable improvement in k p value and maintain good electrical properties: d 33 = 300 pC/N, Q m = 971, k p = 58.4%, tanδ = 0.36%, and ε T 33 = 1332.

  15. Methodological approach of load sintering of ceramics (superconductor, alumina, alumina-aluminium nitride-magnesia system)

    International Nuclear Information System (INIS)

    Roy, J.F.

    1993-05-01

    Sintering parameters knowledge of ceramic powders by improvements of a high temperature pressing (computer piloting and data acquiring) allow a better control of fabrication and of the desired properties (mechanical, electro-magnetic...). By using experiences plan, maximum of informations are obtained with a minimum of experimental tests. This is applied to the sintering of three compounds; for YBaCuO, the superconductive phase is obtained at 450 deg and without post heat treatment; for Al 2 O 3 , mechanical properties and a partial microstructure controls are obtained; for the Al 2 O 3 -AlN-MgO system, an optimization of the mechanical properties is obtained. (A.B.). 63 refs., figs., tabs

  16. Production of pure sintered alumina

    International Nuclear Information System (INIS)

    Rocha, J.C. da; Huebner, H.W.

    1982-01-01

    With the aim of optimizing the sintering parameters, the strength of a large number of alumina samples was determined which were produced under widely varying sintering conditions and with different amounts of MgO content. The strength as a function of sintering time or temperature was found to go through a maximum. With increasing time, this maximum is shifted to lower temperatures, and with decreasing temperature to longer times. Data pairs of sintering times and temperatures which yeld the strength maximum were determined. The value of the strength at the maximum remains unchanged. The strength is high (= 400 MN/m 2 , at a grain size of 3 um and a porosity of 2 per cent) and comparable to foreign aluminas produced for commercial purposes, or even higher. The increase in the sintering time from 1 h to 16 h permits a reduction of the sintering temperature from 1600 to 1450 0 C without losing strength. The practical importance of this fact for a production of sintered alumina on a large scale is emphasized. (Author) [pt

  17. Influence of sintering temperature on microstructures and energy-storage properties of barium strontium titanate glass-ceramics prepared by sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jia; Zhang, Yong; Song, Xiaozhen; Zhang, Qian; Yang, Dongliang; Chen, Yongzhou [Beijing Key Laboratory of Fine Ceramics, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China)

    2015-12-15

    The sol-gel processing, microstructures, dielectric properties and energy-storage properties of barium strontium titanate glass-ceramics over the sintering temperature range of 1000-1150 C were studied. Through the X-ray diffraction result, it is revealed that the crystallinity increases as the sintering temperature increased from 1000 to 1080 C and has reached a steady-state regime above 1100 C. Scanning electron microscopy images showed that with the increase of sintering temperature, the crystal size increased. Dielectric measurements revealed that the increase in the sintering temperature resulted in a significant increase in the dielectric constant, a strong sharpness of the temperature-dependent dielectric response and a pronounced decrease of the temperature of the dielectric maximum. The correlation between charge spreading behavior and activation energies of crystal and glass was discussed by the employment of the impedance spectroscopy studies. As a result of polarization-electric field hysteresis loops, both the charged and discharged densities increased with increasing sintering temperature. And the maximum value of energy storage efficiency was found to occur at 1130 C. Finally, the dependence of released energy and power densities calculated from the discharged current-time (I-t) curves on the sintering temperature was studied. The relationship between the energy storage properties and microstructure was correlated. Polarization-electric field hysteresis loops for the BST glass-ceramics sintered at different temperatures. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Recycling of the reduction sludge of manganese in the production of ceramics

    International Nuclear Information System (INIS)

    Castro, C.G.; Araujo, F.G.S.; Kruger, F.L.

    2011-01-01

    To study the use of manganese reduction residues, from the electric arc furnaces for the production of manganese ferro-alloys, as raw materials for construction bricks, different ceramic compositions were formulated with contents of 0, 2.5, 5 and 10wt% of waste addition to the clay used commercially, and sintered at different temperatures, 850, 950 and 1050°C. After firing, the ceramic samples were studied by optical microscopy, scanning electron microscopy (SEM), x-ray diffraction and by spectrophotometry. Their mechanical properties were evaluated by flexural strength, apparent porosity and specific mass, water absorption, linear shrinkage and loss on ignition. With the help of technics and experiment planning programs, the effects of the variables: temperature, composition and interaction between them over the results were discussed. This work proved that the addition of manganese reduction sludge to the clay, for the production of ceramic construction bricks, is highly feasible, from a technical standpoint. (author)

  19. Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic

    International Nuclear Information System (INIS)

    Reau, A.

    2008-01-01

    Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC f /SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC f /SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

  20. LSA glass-ceramic tiles made by powder pressing

    International Nuclear Information System (INIS)

    Figueira, F.C.; Bertan, F.M.; Riella, H.G.; Uggioni, E.; Bernardin, A.M.

    2009-01-01

    A low cost alternative for the production of glass-ceramic materials is the pressing of the matrix glass powders and its consolidation simultaneously with crystallization in a single stage of sintering. The main objective of this work was to obtain LSA glass ceramics with low thermal expansion, processed by pressing and sintering a ceramic frit powder. The raw materials were homogenized and melted (1480 deg C, 80min), and the melt was poured in water. The glass was chemically (XRF and AAS) and thermally (DTA, 10 deg C/min, air) characterized, and then ground (60min and 120min). The ground powders were characterized (laser diffraction) and compressed (35MPa and 45MPa), thus forming four systems. The compacts were dried (150 deg C, 24h) and sintered (1175 deg C and 1185 deg C, 10 deg C/min). Finally, the glass-ceramics were characterized by microstructural analysis (SEM and XRD), mechanical behavior (σbending) and thermal analysis (α). The best results for thermal expansion were those for the glass-ceramics processed with smaller particle size and greater compaction pressure. (author)

  1. Method of forming a ceramic to ceramic joint

    Science.gov (United States)

    Cutler, Raymond Ashton; Hutchings, Kent Neal; Kleinlein, Brian Paul; Carolan, Michael Francis

    2010-04-13

    A method of joining at least two sintered bodies to form a composite structure, includes: providing a joint material between joining surfaces of first and second sintered bodies; applying pressure from 1 kP to less than 5 MPa to provide an assembly; heating the assembly to a conforming temperature sufficient to allow the joint material to conform to the joining surfaces; and further heating the assembly to a joining temperature below a minimum sintering temperature of the first and second sintered bodies. The joint material includes organic component(s) and ceramic particles. The ceramic particles constitute 40-75 vol. % of the joint material, and include at least one element of the first and/or second sintered bodies. Composite structures produced by the method are also disclosed.

  2. Discrimination symbol applying method for sintered nuclear fuel product

    International Nuclear Information System (INIS)

    Ishizaki, Jin

    1998-01-01

    The present invention provides a symbol applying method for applying discrimination information such as an enrichment degree on the end face of a sintered nuclear product. Namely, discrimination symbols of information of powders are applied by a sintering aid to the end face of a molded member formed by molding nuclear fuel powders under pressure. Then, the molded product is sintered. The sintering aid comprises aluminum oxide, a mixture of aluminum oxide and silicon dioxide, aluminum hydride or aluminum stearate alone or in admixture. As an applying means of the sintering aid, discrimination symbols of information of powders are drawn by an isostearic acid on the end face of the molded product, and the sintering aid is sprayed thereto, or the sintering aid is applied directly, or the sintering aid is suspended in isostearic acid, and the suspension is applied with a brush. As a result, visible discrimination information can be applied to the sintered member easily. (N.H.)

  3. Corrosion behaviors of ceramics against liquid sodium. Sodium corrosion characteristics of sintering additives

    International Nuclear Information System (INIS)

    Tachi, Yoshiaki; Kano, Shigeki; Hirakawa, Yasushi; Yoshida, Eiichi

    1998-01-01

    It has been progressed as the Frontier Materials Research to research and develop ceramics to apply for several components of fast breeder reactor using liquid sodium as coolant instead of metallic materials. Grain boundary of ceramics has peculiar properties compared with matrix because most of ceramics are produced by hardening and firing their raw powders. Some previous researchers indicated that ceramics were mainly corroded at grain boundaries by liquid sodium, and ceramics could not be used under corrosive environment. Thus, it is the most important for the usage of ceramics in liquid sodium to improve corrosion resistance of grain boundaries. In order to develop the advanced ceramics having good sodium corrosion resistance among fine ceramics, which have recently been progressed in quality and characteristics remarkably, sodium corrosion behaviors of typical sintering additives such as MgO, Y 2 O 3 and AlN etc. have been examined and evaluated. As a result, the followings have been clarified and some useful knowledge about developing advanced ceramics having good corrosion resistance against liquid sodium has been obtained. (1) Sodium corrosion behavior of MgO depended on Si content. Samples containing large amount of Si were corroded severely by liquid sodium, whereas others with low Si contents showed good corrosion resistance. (2) Both Y 2 O 3 and AlN, which contained little Si, showed good sodium corrosion resistance. (3) MgO, Y 2 O 3 and AlN are thought to be corroded by liquid sodium, if they contain some SiO 2 . Therefore, in order to improve sodium corrosion resistance, it is very important for these ceramics to prevent the contamination of matrix with SiO 2 through purity control of their raw powders. (author)

  4. Clinical acceptability of metal-ceramic fixed partial dental prosthesis fabricated with direct metal laser sintering technique-5 year follow-up.

    Science.gov (United States)

    Prabhu, Radhakrishnan; Prabhu, Geetha; Baskaran, Eswaran; Arumugam, Eswaran M

    2016-01-01

    In recent years, direct metal laser sintered (DMLS) metal-ceramic-based fixed partial denture prostheses have been used as an alternative to conventional metal-ceramic fixed partial denture prostheses. However, clinical studies for evaluating their long-term clinical survivability and acceptability are limited. The aim of this study was to assess the efficacy of metal-ceramic fixed dental prosthesis fabricated with DMLS technique, and its clinical acceptance on long-term clinical use. The study group consisted of 45 patients who were restored with posterior three-unit fixed partial denture prosthesis made using direct laser sintered metal-ceramic restorations. Patient recall and clinical examination of the restorations were done after 6months and every 12 months thereafter for the period of 60 months. Clinical examination for evaluation of longevity of restorations was done using modified Ryge criteria which included chipping of the veneered ceramic, connector failure occurring in the fixed partial denture prosthesis, discoloration at the marginal areas of the veneered ceramic, and marginal adaptation of the metal and ceramic of the fixed denture prosthesis. Periapical status was assessed using periodical radiographs during the study period. Survival analysis was made using the Kaplan-Meier method. None of the patients had failure of the connector of the fixed partial denture prostheses during the study period. Two exhibited biological changes which included periapical changes and proximal caries adjacent to the abutments. DMLS metal-ceramic fixed partial denture prosthesis had a survival rate of 95.5% and yielded promising results during the 5-year clinical study.

  5. Research on sintering behavior and microwave dielectric property of (Mg0.95Ca0.05)TiO3 ceramics for cross coupling filter

    Science.gov (United States)

    Luo, Chunya; Ma, Zhichao; Hu, Laisheng; Hu, Mingzhe; Huang, Xiaomin

    2015-12-01

    The microwave dielectric properties of 0.95%MgTiO3-0.05%CaTiO3 (abbreviated as 95MCT hereafter) ceramics have been studied for application in dielectric cross coupling filters. ZnO and Nb2O5 were selected as liquid sintering aids to lower the sintering temperature and enhance the Qf value of 95MCT and simultaneously we varied the mole ratio of ZnO : Nb2O5 to tune the microwave dielectric properties of 95MCT. When the ZnO : Nb2O5 mole ratio was 1.5 and the co-doping content was 0.25 wt.%, the optimal sintering temperature of 95MCT ceramic could be lowered from 1400∘C to 1320∘C and the Qf value could be improved by about 7.7%. The optimal microwave dielectric properties obtained under this condition were Qf = 72730 GHz (6.8 GHz), ɛr = 20.29 and τf = -6.84ppm/∘C, which demonstrated great potential usage in ceramic industry. High values of Qf ceramic were used to design the dielectric cross coupling filter. The dielectric filter measured at 2.35 GHz exhibited a 6.7% bandwidth (insert loss > -3 dB) of center frequency.

  6. STRUCTURAL AND DIELECTRIC STUDIES ON Sr0.5-3y/2LayBa0.5Nb2O6 CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

    Directory of Open Access Journals (Sweden)

    Zahariman S. R.

    2013-12-01

    Full Text Available Sr0.5Ba0.5Nb2O6 (SBN50 ceramic doped with different concentration of Lanthanum, La according to stoichiometric formulation of Sr0.5-3y/2LayBa0.5Nb2O6 (LSBN with y = 0.01, 0.03, 0.05 and 0.07 prepared using traditional ceramic method at the calcination temperature of 1200°C and sintered at 1300°C at varied sintering time. The effects of the sintering time and La3+ substitution on the morphological, compositional, structural and electrical properties of the LSBN is presented using scanning electronic microscopy (SEM, energy dispersive spectroscopy (EDS, X-ray diffraction (XRD and dielectric analysis. The XRD spectra confirm the presence of TTB structure in the ceramics. The Curie temperature (Tc of the ceramic identified from the dielectric studies performed in the temperature range of 28°C to 300°C. The temperature dependent dielectric exhibits broad peaks indicating a diffuse phase transition and relaxor behavior of the ceramic. The measured density of the samples is proportional to the sintering time and inversely proportional to the amount of the La3+ substitution. The solubility limit of La3+ ions in the SBN solid solution is at y ~ 0.05. This observation is also supported by the dielectric results where the dielectric properties of the ceramic deteriorate for y > 0.05 La substitution.

  7. XPS Analysis of Ni and Oxygen in Single-Sintered SrTiO3 Multifunction Ceramic

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    XPS analyses have been performed to investigate the chemical conditions of Ni and oxygen on grain surfaces in single-sintered SrTiO3 capacitor-varistor ceramic doped with Nb2O5 and NiO. It is ascertained that Ni is in form of Ni2+ ions, which substitute for Ti4+ ions on grain surfaces during the oxidizing annealing. Moreover, it is confirmed that three kinds of chemically adsorbed oxygen such as O2-, O- and O~ are formed on grain surfaces. It is proposed that these behaviors contribute greatly to the generation of multiple types of grain boundary acceptor states in the ceramic.

  8. An investigation into texturing of high-Tc superconducting ceramics by creep-sintering

    International Nuclear Information System (INIS)

    Regnier, P.; Le Hazif, R.; Chaffron, L.

    1989-01-01

    The possibility of preparing highly textured samples of YBa 2 Cu 3 O 7-x high-Tc ceramics by creep-sintering under an uniaxial stress was investigated in detail. It is shown that the quality of the texture is sharply dependant on: the applied load, the temperature of the sintering dwell, the rate at which this dwell is reached, the exact instant at which the load is applied and the nature of the material in contact with the sample. It is also shown that further annealing without applied stress enhances the texture and considerably increases the grain size. Deformation, which was systematically recorded, occurs within a few minutes after the load is applied and exhibits a stress dependance typical of a viscous flow. Systematic examination by polarized light microscopy has indicated that the texture was homogeneous throughout the whole thickness of all the prepared samples. The resistivity versus temperature curves show that the transition is very sharp and well above 77 K

  9. Effect of silica fiber on the mechanical and chemical behavior of alumina-based ceramic core material

    OpenAIRE

    Weiguo Jiang; Kaiwen Li; Jiuhan Xiao; Langhong Lou

    2017-01-01

    In order to improve the chemical leachability, the alumina-based ceramic core material with the silica fiber was injected and sintered at 1100 °C/4 h, 1200 °C/4 h, 1300 °C/4 h and 1400 °C/4 h, respectively. The micrographs of ceramic core materials at sintered and leached state were characterized by scanning electron microscopy (SEM). The phase composition of ceramic core material after sintering and the leaching product after leaching were detected by X-ray diffraction (XRD). The porosity, r...

  10. Master Sintering Surface: A practical approach to its construction and utilization for Spark Plasma Sintering prediction

    Directory of Open Access Journals (Sweden)

    Pouchly V.

    2012-01-01

    Full Text Available The sintering is a complex thermally activated process, thus any prediction of sintering behaviour is very welcome not only for industrial purposes. Presented paper shows the possibility of densification prediction based on concept of Master Sintering Surface (MSS for pressure assisted Spark Plasma Sintering (SPS. User friendly software for evaluation of the MSS is presented. The concept was used for densification prediction of alumina ceramics sintered by SPS.

  11. Bonding of TRIP-Steel/Al2O3-(3Y-TZP Composites and (3Y-TZP Ceramic by a Spark Plasma Sintering (SPS Apparatus

    Directory of Open Access Journals (Sweden)

    Aslan Miriyev

    2016-07-01

    Full Text Available A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening.

  12. Investigation on the effect of sintering temperature on kaolin hollow fibre membrane for dye filtration.

    Science.gov (United States)

    Mohtor, Nur Hamizah; Othman, Mohd Hafiz Dzarfan; Ismail, Ahmad Fauzi; Rahman, Mukhlis A; Jaafar, Juhana; Hashim, Nur Awanis

    2017-07-01

    Despite its extraordinary price, ceramic membrane can still be able to surpass polymeric membrane in the applications that require high temperature and pressure conditions, as well as harsh chemical environment. In order to alleviate the high cost of ceramic material that still becomes one of the major factors that contributes to the high production cost of ceramic membrane, various attempts have been made to use low cost ceramic materials as alternatives to well-known expensive ceramic materials such as alumina, silica, and zirconia in the fabrication of ceramic membrane. Thus, local Malaysian kaolin has been chosen as the ceramic material in this study for the preparation of kaolin hollow fibre membrane since it is inexpensive and naturally abundant in Malaysia. Due to the fact that the sintering process plays a prominent role in obtaining the desired morphology, properties, and performances of prepared ceramic membrane, the aim of this work was to study the effect of different sintering temperatures applied (ranging from 1200 to 1500 °C) in the preparation of kaolin hollow fibre membrane via dry/wet phase inversion-based spinning technique and sintering process. The morphology and properties of membrane were then characterised by SEM, AFM, FTIR, XRD, and three-point bending test, while the performances of membrane were investigated by conducting water permeation and Reactive Black 5 (RB5) dye rejection tests. From the experimental results obtained, the sintering temperature of 1400 °C could be selected as the optimum sintering temperature in preparing the kaolin hollow fibre membrane with the dense sponge-like structure of separation layer that resulted in the good mechanical strength of 70 MPa with the appreciable water permeation of 75 L/h m 2  bar and RB5 rejection of 68%.

  13. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, Na)NbO₃ and (Ba, Na)(Ti, Nb)O₃ Based Ceramics Prepared by Different Sintering Routes.

    Science.gov (United States)

    Eiras, José A; Gerbasi, Rosimeire B Z; Rosso, Jaciele M; Silva, Daniel M; Cótica, Luiz F; Santos, Ivair A; Souza, Camila A; Lente, Manuel H

    2016-03-08

    Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO₃, such as (K, Na)NbO₃ (KNN) and (Ba, Na)(Ti, Nb)O₃ (BTNN) families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS) and high-energy ball milling (HEBM), following heat treatments (calcining and sintering), in oxidative (O₂) atmosphere have been used to prepare single phase highly densified KNN ("pure" and Cu 2+ or Li 1+ doped), with theoretical densities ρ th > 97% and BTNN ceramics (ρ th - 90%), respectively. Using BTTN ceramics with a P 4 mm perovskite-like structure, we showed that by increasing the NaNbO₃ content, the ferroelectric properties change from having a relaxor effect to an almost "normal" ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients ( k 15 , g 15 and d 15 ) improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu 2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects.

  14. Verification of the Skorohod-Olevsky Viscous Sintering (SOVS) Model

    Energy Technology Data Exchange (ETDEWEB)

    Lester, Brian T. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-11-16

    Sintering refers to a manufacturing process through which mechanically pressed bodies of ceramic (and sometimes metal) powders are heated to drive densification thereby removing the inherit porosity of green bodies. As the body densifies through the sintering process, the ensuing material flow leads to macroscopic deformations of the specimen and as such the final configuration differs form the initial. Therefore, as with any manufacturing step, there is substantial interest in understanding and being able to model the sintering process to predict deformation and residual stress. Efforts in this regard have been pursued for face seals, gear wheels, and consumer products like wash-basins. To understand the sintering process, a variety of modeling approaches have been pursued at different scales.

  15. Development of porous ceramics by lycopodium using uniaxial pressing and sintering

    Directory of Open Access Journals (Sweden)

    Rita Serzane

    2010-12-01

    Full Text Available In this work microporous hydroxyapatite (HAp ceramics were fabricated using lycopodium as a porosifier. The samples were produced by uniaxial pressing and then heating at high temperatures, 1100°C and 1200°C, to burn-out porogens and sintering. The obtained samples had porosity over the variable range of 12 to 45% with different pore size ranging from 0.2 to 25 µm. Chemical and physical characterization was determined by scanning electron microscopy (SEM, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and bending strength measurements. The bending strength of the prepared samples was in the range of 1.97–21.81 MPa.

  16. Sintered cobalt-rare earth intermetallic product

    International Nuclear Information System (INIS)

    Benz, M.G.

    1975-01-01

    This patent describes a sintered product having substantially stable permanent magnet properties in air at room temperature. It comprises compacted particulate cobalt--rare earth alloy consisting essentially of a Co 5 R intermetallic phase and a CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase, where R is a rare earth metal. The Co 5 R intermetallic phase is present in an amount of at least 65 percent by weight of the sintered product and the CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase is present in a positive amount having a value ranging up to about 35 percent by weight of the product. The sintered product has a density of at least 87 percent and has pores which are substantially noninterconnecting and wherein the component grains have an average size less than 30 microns

  17. Investigation of the sinterability of ZrO_2 (Y_2O3_)-bioglass dental ceramics by dilatometry

    International Nuclear Information System (INIS)

    Bicalho, Luiz de Araujo; Barboza, Miguel Ribeiro Justino; Santos, Claudinei dos; Habibe, Alexandre Fernandes; Magnago, Roberto de Oliveira

    2013-01-01

    The objective of this work is to study by dilatometry, the liquid phase sintering of ZrO_2 ceramics using bioglass as sintering additive. Y_2 O_3 - stabilized ZrO_2 powders were mixed with 3, 5 and 10 wt% of bioglass with the composition based on 3CaOP_2 O_5 -MgO-SiO_2 system. Specimens were prepared by cold uniaxial pressing under 80MPa and the green relative density was determined. The sintering behavior was studied by measuring the linear shrinkage of samples in a dilatometer in relation to the temperature. The heating and cooling rates used in this study were 10 deg C/min and the maximum sintering temperatures was 1300 deg C with a 120 min isothermal holding time. The results of the shrinkage and shrinkage rates in regard of the sintering temperature and time were related to the amount of bioglass added. The sintered samples were characterized by X-ray diffraction analysis and their relative density. SEM micrographs indicates similar microstructure, and an increase of bioglass content leads to increasing of monoclinic ZrO_2 phase content. The dilatometry results indicate a reduction of the temperature where a maximum shrinkage rate occurs, as function of bioglass increasing. Furthermore, the use of liquid phase reduces the maximum sintering temperature of 1447 deg C to 1250-1280 deg C. (author)

  18. Sintering and electrical properties of titania- and zirconia-containing In2O3-SnO2 (ITO) ceramics

    International Nuclear Information System (INIS)

    Nadaud, N.; Nanot, M.; Bock, P.

    1994-01-01

    The deposition rate and film quality of In 2 O 3 -SnO 2 (ITO) transparent electrodes processed by sputtering are improved when using dense sputtering targets. Unfortunately, ITO ceramics do not sinter easily. It is shown that addition of TiO 2 ( 2 was also investigated

  19. Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

    Science.gov (United States)

    Kumar, Manoj; Yadav, K. L.

    2007-12-01

    Single-phase BiFe1-xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1-xMnxO3 system. An enhancement in magnetization was observed for BiFe1-xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23μC /cm2 under the applied field of 42kV/cm and remanent polarization of 3.99μC/cm2 for x =0.3 ceramic.

  20. Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

    Science.gov (United States)

    Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

    2017-07-01

    The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

  1. The First Static and Dynamic Analysis of 3-D Printed Sintered Ceramics for Body Armor Applications

    Science.gov (United States)

    2016-09-01

    hardness , and fracture strength) and semi-infinite penetration performance of 3-D printed sintered alumina. These results are compared with traditionally...parameters (including density, hardness , and fracture strength), semi-infinite penetration performance, and the fracture profile following impact of 3...of advanced ceramics differs mostly in terms of the initial green part formation when compared with a traditional manufacturing process. The

  2. Lower sintering temperature of nanostructured dense ceramics compacted from dry nanopowders using powerful ultrasonic action

    OpenAIRE

    Khasanov, O.; Reichel, U.; Dvilis, E.; Khasanov, A.

    2011-01-01

    Nanostructured high dense zirconia ceramics have been sintered from dry nanopowders compacted by uniaxial pressing with simultaneous powerful ultrasonic action (PUA). Powerful ultrasound with frequency of 21 kHz was supplied from ultrasonic generator to the mold, which was the ultrasonic wave-guide. Previously the mold was filled by non-agglomerated zirconia nanopowder having average particle size of 40 nm. Any binders or plasticizers were excluded at nanopowder processing. Compaction pressur...

  3. Coupling in-situ X-ray micro- and nano-tomography and discrete element method for investigating high temperature sintering of metal and ceramic powders

    Directory of Open Access Journals (Sweden)

    Yan Zilin

    2017-01-01

    Full Text Available The behaviour of various powder systems during high temperature sintering has been investigated by coupling X-ray microtomography and discrete element method (DEM. Both methods are particularly relevant to analyse particle interactions and porosity changes occurring during sintering. Two examples are presented. The first one deals with a copper powder including artificially created pores which sintering has been observed in situ at the European synchrotron and simulated by DEM. 3D images with a resolution of 1.5 μm have been taken at various times of the sintering cycle. The comparison of the real displacement of particle centers with the displacement derived from the mean field assumption demonstrates significant particle rearrangement in some regions of the sample. Although DEM simulation showed less rearrangement, it has been able to accurately predict the densification kinetics. The second example concerns multilayer ceramic capacitors (MLCCs composed of hundreds of alternated metal electrode and ceramic dielectric layers. The observation of Ni-based MLCCs by synchrotron nanotomography at Argon National Laboratory with a spatial resolution between 10 and 50 nm allowed understanding the origin of heterogeneities formed in Ni layers during sintering. DEM simulations confirmed this analysis and provided clues for reducing these defects.

  4. Effects of talc and clay addition on pressureless sintering of porous ...

    Indian Academy of Sciences (India)

    Porous Si3N4 ceramics were successfully synthesized using cheaper talc and clay as sintering additives by pressureless sintering technology and the microstructure and mechanical properties of the ceramics were also investigated. The results indicated that the ceramics consisted of elongated -Si3N4 and small Si2N2O ...

  5. Sintering of composite

    International Nuclear Information System (INIS)

    Bordia, R.K.; Scherer, G.W.

    1988-01-01

    Several constitutive laws have been used in the literature to predict the response of sintering bodies under external and internal stress fields. These analyses are based on the assumptions of linear and isotropic behavior. The authors provide a critical examination of these equations and show that some of the available constitutive laws predict a negative Poisson's ratio. These laws have been used to analyze sintering of ceramic matrix composites with rigid inclusions and predict large values of the internal stresses and significant retardation of the densification of composites. Since a negative value of Poisson's ratio has never been observed in sinter - forging experiments, the authors conclude that either the stresses are small (as predicted by the constitutive laws with positive Poisson's ratio) or the basic assumption of linearity and isotropy used in all the analyses is incorrect. Finally, the authors discuss some phenomena that could be important in understanding the densification of ceramic matrix composites

  6. Microstructural analysis of ceramic masses with waste kaolin addition for the red ceramic production

    International Nuclear Information System (INIS)

    Vida, Talita Almeida; Fagury Neto, Elias; Rabelo, Adriano Alves

    2010-01-01

    Incorporating reject industrial ceramic mixtures has proved viable in the reduction of environmental liabilities. In this study, we sought to study the potential use of ceramic formulations with the addition of tailings from the production of kaolin clay to the region of the city of Maraba-PA. Formulations were obtained with two clays of this region with the addition of up to 60% by weight of kaolin waste. The microstructural analyses were carried out from the preparation of specimens that were sintered at 1000 and 1200 °C with level 3 hours. The samples prepared were used to observe the microstructure by optical microscope, to determine the constituents of each formulation after burning. And later analysis was performed X-rays diffraction, to quantify the phases present. It was observed that increasing the content of the mixture of kaolin clay caused the reaction of kaolinite forming the primary mullite from 1000 ° C. For a firing temperature around 1200 ° C showed the presence of mullite even the addition of 20% kaolin, noting also the presence of secondary kaolinite. (author)

  7. LOW TEMPERATURE SINTERING OF ALUMINA BIOCERAMIC UNDER NORMAL PRESSURE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superfine alumina powder with high purity (mean particle size is less than 0. 35μm) were used as main starting material for sintering alumina ceramic. A multiple additive MgO-ZrO2 (Y2O3) was homogeneously added into the batch by the chemical coprecipitation method. Sintering of alumina bioceramic at low tempera ture (<1600C) was achieved resulting in a dense and high strength alumina ceramic with the bending strength up to 382 MPa and an improved fracture toughness. Mechanism that the multiple additives promote the sintering of alumina ceramic is discussed on the base of XRD and SEM analysis.

  8. Final flotation waste kinetics of sintering at different heating regimes

    Directory of Open Access Journals (Sweden)

    Cocić Mira

    2016-01-01

    Full Text Available In the copper extraction, especially during the process of flotation enrichment and the pyrometallurgical processing, the waste materials that represent huge polluters of environment are being generated. In order to examine the application of Final flotation waste (FFW in the manufacturing of new materials from the glass-ceramic group phase and mineral composition were examined as well as thermal properties. FFW kinetics of sintering has been tested at different dyamics (1°C/min, 29°C/min and 43°C/min, in order to find the optimum conditions for sintering with a minimum amount of energy and time consumption. The samples were examined using: X-ray diffraction, X-ray fluorescence analysis, SEM (Scanning Electron Microscopy and thermal microscopy. The best results for the production of glass ceramic materials were obtained during the sintering at heating regime of 29°C/min. [Projekat Ministarstva nauke Republike Srbije, br. 176010

  9. Microstructure and fracture analysis of fully ceramic microencapsulated fuel

    International Nuclear Information System (INIS)

    Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J.; Lee, S. J.

    2015-01-01

    Nuclear fuel enhancing the accident tolerance is satisfied two parts. First, the performance has to be retained compared to the existing UO 2 nuclear fuel and zircaloy cladding system under the normal operation condition. Second, under the severe accident condition, the high temperature structural integrity has to be kept and the generation rate of hydrogen has to be reduced largely. FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix compared to the current commercial UO 2 fuel system. SiC ceramic has excellent properties for fuel application. SiC ceramic has low neutron absorption cross-section, excellent irradiation resistivity and high thermal conductivity. Additionally, the relative thermal conductivity of the SiC ceramic as compared to UO 2 is quite good, reducing operational release of fission products form the fuel. TRISO coating layer which is deposited on UO 2 kernel is consists of PyC/SiC/PyC trialyer and buffer PyC layer. SiC matrix composite with TRISO particle was fabricated by hot pressing. 3 to 20 wt.% of sintering additives were added to investigate reaction between sintering additives and outer PyC layer of TRISO coating layer. The relative densities of all specimens show above 92%. The reaction between sintering additives and PyC is observed in most TRISO particles, the thickness of reactants shows about ten micrometers. The thermal shock resistance of SiC matrix composite was investigated

  10. Utilisation of different types of coal fly ash in the production of ceramic tiles

    Directory of Open Access Journals (Sweden)

    Kockal, N. U.

    2012-10-01

    Full Text Available The influence of varying proportions of different types of fly ash (used in place of feldspar and different sintering temperatures on the sintered properties of ceramic tile bodies was evaluated. The results indicated that sintering ceramic tiles with a high fly ash content at a high temperature caused a decrease in the properties because of bloating. The ceramic samples containing a higher amount of fly ash that were sintered at low temperature exhibited lower water absorption, larger shrinkage and strength because of the densification observed also in microstructural investigation.

    Se ha evaluado la influencia de la proporción de diferentes tipos de cenizas volantes (en lugar de feldespato y diferentes temperaturas de sinterización en las propiedades de soportes cerámicos. Los resultados indicaron que las composiciones con un alto contenido de cenizas volantes provocaron una disminución en las propiedades de las piczas cocidas a alta temperatura como consecuencia del hinchamiento. Las composiciones con una mayor cantidad de cenizas sinterizadas a baja temperatura mostraron una menor absorción de agua, mayor contracción y resistencia mecánica debido a la densificación como también se observó en la investigación microestructural.

  11. Eco-technological process of glass-ceramic production from galvanic sludge and aluminium slag

    Directory of Open Access Journals (Sweden)

    Stanisavljević M.

    2010-01-01

    Full Text Available Methods of purification of waste water which are most commonly used in the Republic of Serbia belong to the type of conventional systems for purification such as chemical oxidation and reduction, neutralization, sedimentation, coagulation, and flocculation. Consequently, these methods generate waste sludge which, unless adequately stabilized, represents hazardous matter. The aluminium slag generated by melting or diecasting aluminium and its alloys is also hazardous matter. In this sense, this paper establishes ecological risk of galvanic waste sludge and aluminium slag and then describes the process of stabilization of these waste materials by means of transformation into a glass-ceramic structure through sintering. The obtained product was analyzed with Fourier Transform Infrared Spectroscopy (FT-IR and X-ray diffraction (XRD. The object of the paper is the eco-technological process of producing glass-ceramics from galvanic sludge and aluminium slag. The aim of the paper is to incorporate toxic metals from galvanic sludge and aluminium slag into the glass-ceramic product, in the form of solid solutions.

  12. Fabrication and scintillation properties of highly transparent Pr:LuAG ceramics using Sc,La-based isovalent sintering aids

    Czech Academy of Sciences Publication Activity Database

    Shen, Y.; Feng, X.; Babin, Vladimir; Nikl, Martin; Vedda, A.; Moretti, F.; Dell'Orto, E.; Pan, Y.; Li, J.; Zeng, Y.

    2013-01-01

    Roč. 39, č. 5 (2013), s. 5985-5990 ISSN 0272-8842 R&D Projects: GA MŠk LH12185; GA AV ČR KAN300100802 Institutional support: RVO:68378271 Keywords : Pr:LuAG transparent ceramics * isovalent sintering aids * scintillation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.086, year: 2013

  13. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, NaNbO3 and (Ba, Na(Ti, NbO3 Based Ceramics Prepared by Different Sintering Routes

    Directory of Open Access Journals (Sweden)

    José A. Eiras

    2016-03-01

    Full Text Available Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO3, such as (K, NaNbO3 (KNN and (Ba, Na(Ti, NbO3 (BTNN families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS and high-energy ball milling (HEBM, following heat treatments (calcining and sintering, in oxidative (O2 atmosphere have been used to prepare single phase highly densified KNN (“pure” and Cu2+ or Li1+ doped, with theoretical densities ρth > 97% and BTNN ceramics (ρth - 90%, respectively. Using BTTN ceramics with a P4mm perovskite-like structure, we showed that by increasing the NaNbO3 content, the ferroelectric properties change from having a relaxor effect to an almost “normal” ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients (k15, g15 and d15 improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects.

  14. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, Na)NbO3 and (Ba, Na)(Ti, Nb)O3 Based Ceramics Prepared by Different Sintering Routes

    Science.gov (United States)

    Eiras, José A.; Gerbasi, Rosimeire B. Z.; Rosso, Jaciele M.; Silva, Daniel M.; Cótica, Luiz F.; Santos, Ivair A.; Souza, Camila A.; Lente, Manuel H.

    2016-01-01

    Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO3, such as (K, Na)NbO3 (KNN) and (Ba, Na)(Ti, Nb)O3 (BTNN) families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS) and high-energy ball milling (HEBM), following heat treatments (calcining and sintering), in oxidative (O2) atmosphere have been used to prepare single phase highly densified KNN (“pure” and Cu2+ or Li1+ doped), with theoretical densities ρth > 97% and BTNN ceramics (ρth ~ 90%), respectively. Using BTTN ceramics with a P4mm perovskite-like structure, we showed that by increasing the NaNbO3 content, the ferroelectric properties change from having a relaxor effect to an almost “normal” ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients (k15, g15 and d15) improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects. PMID:28773304

  15. UO2 fuel pellets fabrication via Spark Plasma Sintering using non-standard molybdenum die

    Science.gov (United States)

    Papynov, E. K.; Shichalin, O. O.; Mironenko, A. Yu; Tananaev, I. G.; Avramenko, V. A.; Sergienko, V. I.

    2018-02-01

    The article investigates spark plasma sintering (SPS) of commercial uranium dioxide (UO2) powder of ceramic origin into highly dense fuel pellets using non-standard die instead of usual graphite die. An alternative and formerly unknown method has been suggested to fabricate UO2 fuel pellets by SPS for excluding of typical problems related to undesirable carbon diffusion. Influence of SPS parameters on chemical composition and quality of UO2 pellets has been studied. Also main advantages and drawbacks have been revealed for SPS consolidation of UO2 in non-standard molybdenum die. The method is very promising due to high quality of the final product (density 97.5-98.4% from theoretical, absence of carbon traces, mean grain size below 3 μm) and mild sintering conditions (temperature 1100 ºC, pressure 141.5 MPa, sintering time 25 min). The results are interesting for development and probable application of SPS in large-scale production of nuclear ceramic fuel.

  16. `Joint Research and Development of Industrial Technology,` an international research collaboration for fiscal 1997. Research and development for practical application of low-temperature sinterable, highly heat-radiating materials for ceramics; 1997 nendo kokusai kenkyu kyoryoku jigyo `sangyo kiban gijutsu kyodo kenkyu kaihatsu`. Teion shoketsu kohonetsusei ceramics kiban zairyo no jitsuyoka gijutsu no kenkyu kaihatsu seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    A highly heat-conducting AlN ceramic substrate is developed for the cooling of semiconductor integrated circuit devices and power controlling semiconductor devices. In the development of a low-temperature sinterable ceramic texture, a sintering assistant is selected. In this process various assistants are tested for the effect of their presence on the occurrence of AlN oxidation and on the magnitude of standard energy for aluminate compound formation. The volatility at high temperatures of the components of the assistants are also examined. The sintering assistant developed for this project (mixture of Y2O3, CaO, LaB6, and WO3) is used in the sintering of an AlN material powder developed by The Dow Chemical Co., and then it is demonstrated that highly heat-conducting AlN substrates are mass-produced by continuous sintering at 1600degC in a nitrogen atmosphere, the product having a relative density of 100%, average heat conductivity of 154W/mK, bend resisting strength of 440MPa, and a fracture toughness value of 3.8MPam{sup 1/2}. 6 refs., 92 figs., 10 tabs.

  17. Microstructural and electrical properties of cordierite-based ceramics obtained after two-step sintering technique

    Directory of Open Access Journals (Sweden)

    Obradović Nina

    2016-01-01

    Full Text Available Cordierite-based ceramic materials are attracting much interest for their various applications in industry, for manufacturing multilayer circuit boards, catalytic converters, filters, thermal insulation, kiln furniture, components of portable electronic devices, etc. In order to reduce production costs and modify cordierite-based materials, mechanical activation can be used. In this study, microstructural and electrical properties of mechanically activated MgO-Al2O3-SiO2 system have been analyzed. The mixtures of MgO-Al2O3-SiO2 powders were mechanically activated in a planetary ball mill for the time periods from 0 to 160 min. Morphological investigations have been performed on the obtained powders. The effects of activation and two-step sintering process on microstructure were investigated by scanning electron microscopy (SEM. Electrical measurements showed variations of the dielectric constant (εr and loss tangent (tan δ as a function of time of mechanical treatment.

  18. Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

    Directory of Open Access Journals (Sweden)

    Karima Amer Almasri

    Full Text Available The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3 based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM, Fourier transforms infrared reflection spectroscopy (FTIR, and X-ray diffraction (XRD. The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature. Keywords: Soda lime silica glass, Wollastonite, Sintering, Structural properties, Optical properties

  19. Effects of sintering temperature on the density and porosity

    African Journals Online (AJOL)

    2013-03-01

    bonding) between the salt beads at all the temperatures in which sintering was performed. .... and the sintering of some covalent solids and low- stability ceramics. The entire sintering process is gen- erally considered to occur in ...

  20. Significantly enhanced piezoelectricity in low-temperature sintered Aurivillius-type ceramics with ultrahigh Curie temperature of 800 °C

    International Nuclear Information System (INIS)

    Cai, Kai; Huang, Chengcheng; Guo, Dong

    2017-01-01

    We report an Aurivillius-type piezoelectric ceramic (Ca 1−2x (LiCe) x Bi 4 Ti 3.99 Zn 0.01 O 15 ) that has an ultrahigh Curie temperature (T c ) around 800 °C and a significantly enhanced piezoelectric coefficient (d 33 ), comparable to that of textured ceramics fabricated using the complicated templating method. Surprisingly, the highest d 33 of 26 pC/N was achieved at an unexpectedly low sintering temperature (T s ) of only 920 °C (∼200 °C lower than usual) despite the non-ideal density. Study of different synthesized samples indicates that a relatively low T s is crucial for suppressing Bi evaporation and abnormal grain growth, which are indispensable for high resistivity and effective poling due to decreased carrier density and restricted anisotropic conduction. Because the layered structure is sensitive to lattice defects, controlled Bi loss is considered to be crucial for maintaining structural order and spontaneous polarization. This low-T s system is very promising for practical applications due to its high piezoelectricity, low cost and high reproducibility. Contrary to our usual understanding, the results reveal that a delicate balance of density, Bi loss and grain morphology achieved by adjusting the sintering temperature is crucial for the enhancing performance in Aurivillius-type high- T c ceramics. (paper)

  1. Application of the final flotation waste for obtaining the glass-ceramic materials

    Directory of Open Access Journals (Sweden)

    Cocić Mira

    2017-01-01

    Full Text Available This work describes the investigation of the final flotation waste (FFW, originating from the RTB Bor Company (Serbia, as the main component for the production of glass-ceramic materials. The glass-ceramics was synthesized by the sintering of FFW, mixtures of FFW with basalt (10%, 20%, and 40%, and mixtures of FFW with tuff (20% and 40%. The sintering was conducted at the different temperatures and with the different time duration in order to find the optimal composition and conditions for crystallization. The increase of temperature, from 1100 to 1480°C, and sintering time, from 4 to 6h resulted in a higher content of hematite crystal in the obtained glass-ceramic (up to 44%. The glass-ceramics sintered from pure FFW (1080°C/36h has good mechanical properties, such as high propagation speed (4500 m/s and hardness (10800 MPa, as well as very good thermal stability. The glass-ceramics obtained from mixtures shows weaker mechanical properties compared to that obtained from pure FFW. The mixtures of FFW with tuff have a significantly lower bulk density compared to other obtained glass-ceramics. Our results indicate that FFW can be applied as a basis for obtaining the construction materials. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176010: Composition, genesis, application, and contribution to the environmental sustainability

  2. Liquid phase sintered superconducting cermet

    International Nuclear Information System (INIS)

    Ray, S.P.

    1990-01-01

    This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

  3. Characteristics of products generated by selective sintering and stereolithography rapid prototyping processes

    Science.gov (United States)

    Cariapa, Vikram

    1993-01-01

    The trend in the modern global economy towards free market policies has motivated companies to use rapid prototyping technologies to not only reduce product development cycle time but also to maintain their competitive edge. A rapid prototyping technology is one which combines computer aided design with computer controlled tracking of focussed high energy source (eg. lasers, heat) on modern ceramic powders, metallic powders, plastics or photosensitive liquid resins in order to produce prototypes or models. At present, except for the process of shape melting, most rapid prototyping processes generate products that are only dimensionally similar to those of the desired end product. There is an urgent need, therefore, to enhance the understanding of the characteristics of these processes in order to realize their potential for production. Currently, the commercial market is dominated by four rapid prototyping processes, namely selective laser sintering, stereolithography, fused deposition modelling and laminated object manufacturing. This phase of the research has focussed on the selective laser sintering and stereolithography rapid prototyping processes. A theoretical model for these processes is under development. Different rapid prototyping sites supplied test specimens (based on ASTM 638-84, Type I) that have been measured and tested to provide a data base on surface finish, dimensional variation and ultimate tensile strength. Further plans call for developing and verifying the theoretical models by carefully designed experiments. This will be a joint effort between NASA and other prototyping centers to generate a larger database, thus encouraging more widespread usage by product designers.

  4. Properties and Clinical Application of Three Types of Dental Glass-Ceramics and Ceramics for CAD-CAM Technologies

    Science.gov (United States)

    Ritzberger, Christian; Apel, Elke; Höland, Wolfram; Peschke, Arnd; Rheinberger, Volker M.

    2010-01-01

    The main properties (mechanical, thermal and chemical) and clinical application for dental restoration are demonstrated for three types of glass-ceramics and sintered polycrystalline ceramic produced by Ivoclar Vivadent AG. Two types of glass-ceramics are derived from the leucite-type and the lithium disilicate-type. The third type of dental materials represents a ZrO2 ceramic. CAD/CAM technology is a procedure to manufacture dental ceramic restoration. Leucite-type glass-ceramics demonstrate high translucency, preferable optical/mechanical properties and an application as dental inlays, onlays and crowns. Based on an improvement of the mechanical parameters, specially the strength and toughness, the lithium disilicate glass-ceramics are used as crowns; applying a procedure to machine an intermediate product and producing the final glass-ceramic by an additional heat treatment. Small dental bridges of lithium disilicate glass-ceramic were fabricated using a molding technology. ZrO2 ceramics show high toughness and strength and were veneered with fluoroapatite glass-ceramic. Machining is possible with a porous intermediate product.

  5. Microstructure, crystal structure and electrical properties of Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics obtained at different sintering conditions

    International Nuclear Information System (INIS)

    Bodak, O.; Akselrud, L.; Demchenko, P.; Kotur, B.; Mrooz, O.; Hadzaman, I.; Shpotyuk, O.; Aldinger, F.; Seifert, H.; Volkov, S.; Pekhnyo, V.

    2002-01-01

    Details of the formation of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics under different sintering conditions have been studied by optical microscopy, scanning electron microscopy (SEM), electron probe and energy dispersive spectroscopy (EDX) microanalyses, X-ray diffraction (XRD) and electrical resistivity measurements. Microstructure studies of samples sintered at 1170 deg. C for 1 h indicated the presence of a secondary phase besides the main spinel phase with modified composition. XRD measurements showed that the spinel phase exhibits a tetragonally distorted spinel structure (space group I4 1 /amd, a=5.9410(5) A, c=8.4196(15) A). The secondary phase (solid solution based on NiO) crystallizes with the NaCl-type structure (space group Fm3-bar m, a=4.1872(3) A). The content of the secondary phase in ceramics is 10.61 mass%. For NiMn 2 O 4 ceramics, prepared under the same sintering conditions, the decomposition with Ni 1-x Mn x O solid solution (NaCl-type structure) and spinel phase formation have been observed. The tetragonal modification of the spinel phase for NiMn 2 O 4 ceramics is more preferable (space group I4 1 /amd, a=5.9764(5) A, c=8.4201(8) A). The distribution of atoms in the structure has been proposed for both ceramics. According to XRD results the Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramic samples, sintered at 920 deg. C for 8 h (program 1), at 920 deg. C for 8 h and at 750 deg. C for 24 h (program 2), at 920 deg. C for 8 h, at 1200 deg. C for 1 h and at 920 deg. C for 24 h (program 3) and at 920 deg. C for 8 h, at 1200 deg. C for 1 h, at 920 deg. C for 24 h and at 750 deg. C for 48 h (program 4), contain a single phase with the cubic spinel structure (space group Fd3-bar m). Small residuals of the secondary phase for the ceramics, prepared via programs 3 and 4, have been observed by SEM investigations. The structure transformations of the spinel phase for Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics sintered at 1170 deg. C are attributed to a Jahn

  6. Microwave sintering of nano size powder β-TCP bioceramics

    Directory of Open Access Journals (Sweden)

    Mirhadi B.

    2014-01-01

    Full Text Available A nano sized beta tricalcium phosphate (β-TCP powder was conventional sintered (CS and microwave sintered (MW, in order to obtain dense β-TCP ceramics. In this work the effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on tricalcium phosphate (TCP was investigated by SEM (scanning electron microscopyand XRD(X-ray diffraction and then compared with conventional sintered samples. Nano-size β-TCP powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and diammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of submicrometre β-TCP powder in situ. The β-TCP samples microwave (MW sintered for 15 min at 1100°C, with average grain size of 3μm, showed better densification, higher density and certainly higher hardness than samples conventionally sintered for 2 h at the same temperature. By comparing sintered and MW sintered β-TCP samples, it was concluded that MW sintered β-TCP samples have superior mechanical properties.

  7. Influences of spark plasma sintering temperature on the microstructures and thermoelectric properties of (Sr0.95Gd0.05)TiO3 ceramics

    Science.gov (United States)

    Li, Liang-Liang; Qin, Xiao-Ying; Liu, Yong-Fei; Liu, Quan-Zhen

    2015-06-01

    (Sr0.95Gd0.05)TiO3 (SGTO) ceramics are successfully prepared via spark plasma sintering (SPS) respectively at 1548, 1648, and 1748 K by using submicron-sized SGTO powders synthesized from a sol-gel method. The densities, microstructures, and thermoelectric properties of the SGTO ceramics are studied. Though the Seebeck coefficient shows no obvious difference in the case that SPS temperatures range from 1548 K to 1648 K, the electrical conductivity and the thermal conductivity increase remarkably due to the increase in grain size and density. The sample has a density higher than 98% theoretical density as the sintering temperature increases up to 1648 K and shows average grain sizes increasing from ˜ 0.7 μm to 7 μm until 1748 K. As a result, the maximum of the dimensionless figure of merit of ˜ 0.24 is achieved at ˜ 1000 K for the samples sintered at 1648 K and 1748 K, which was ˜ 71% larger than that (0.14 at ˜ 1000 K) for the sample sintered at 1548 K due to the enhancement of the power factor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174292, 51101150, and 11374306).

  8. Transparent La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} ceramics obtained by combustion method and vacuum sintering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhengjuan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhou, Guohong, E-mail: sic_zhough@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Qin, Xianpeng; Yang, Yan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Guangjun [SCHOTT Glass Technologies (Suzhou) Co. Ltd., Suzhou 215009 (China); Menke, Yvonne [Schott AG, Corporate Research and Technology Development, Hattenbergstrasse 10, 55122 Mainz (Germany); Wang, Shiwei, E-mail: swwang51@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2014-02-05

    Highlights: • Combustion method and vacuum sintering were used to fabricate La{sub 2-x}Gd{sub x}Zr{sub 2}O{sub 7}. • The lattice parameters decreased with the increase of Gd{sup 3+} concent(x). • The absorption edge of the transmittance curves shifted to UV region from 0.4-2.0. • All the ceramics have high n (2.08), making them candidate for optical lens. • With the increase of x, the effective atomic number and density increased. -- Abstract: Transparent La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} (x = 0–2.0) ceramics were prepared via vacuum sintering from nanometric powders synthesized by a simple combustion method. The changes of phase composition, morphology and in-line transmittance of the resulting ceramics with Gd{sup 3+} content’s variation were investigated. With the increase of Gd{sup 3+} content, the samples keep the pyrochlore structure, but the X-ray diffraction peaks of the powders and ceramics shift to higher angle as the lattice parameters become smaller. All the ceramics are transparent with high in-line transmittance and high refractive index (2.08 @ 632.8 nm, x = 0.4–1.6). These results indicate that La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} ceramics might be used as optical lens. Moreover, with the increase of Gd{sup 3+} content, the effective atomic number and density of the ceramics increase, therefore making them promising host candidates for scintillators.

  9. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  10. Emerging Ceramic-based Materials for Dentistry

    Science.gov (United States)

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  11. Pressure sintering and creep deformation: a joint modeling approach

    International Nuclear Information System (INIS)

    Notis, M.R.

    1979-10-01

    Work related to microchemical and microstructural aspects of the joint modeling of pressure sintering and creep in ceramic oxides is reported. Quantitative techniques for the microchemical analysis of ceramic oxides and for the examination of impurity segregation effects in polycrystalline ceramic materials were developed. This has included fundamental absorption corrections for the oxygen anion species as a function of foil thickness. The evolution in microstructure during the transition from intermediate stage to final stage densification during hot pressing of cobalt oxide and preliminary studies with doped oxides were studied. This work shows promise in using time-integrated microstructural effects to elucidate the role of impurities in the sintering of ceramic materials

  12. Effects of sintering process, pH and temperature on chemical durability of Ce{sub 0.5}Pr{sub 0.5}PO{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jiyan; Teng, Yuancheng, E-mail: tyc239@163.com; Huang, Yi; Wu, Lang; Zhang, Kuibao; Zhao, Xiaofeng

    2015-10-15

    The Ce{sub 0.5}Pr{sub 0.5}PO{sub 4} ceramics with high relative density of 99% and small average grain size of 0.15 μm were prepared by hot-pressing at 1150 °C for 2 h. The effects of sintering process, pH values and temperature on the chemical durability of the ceramics were investigated. The results show that normalized elemental leaching rates of Pr (LR{sub Pr}) and Ce (LR{sub Ce}) of the hot-pressed ceramics are slightly lower than that of the ceramics sintered at 1500 °C for 4 h by normal pressure. The LR{sub Pr} and LR{sub Ce} reach the highest values (∼10{sup −3} g m{sup −2} d{sup −1}) when pH = 3, while the LR{sub Pr} and LR{sub Ce} have the lowest values (∼10{sup −7} g m{sup −2} d{sup −1}) when pH = 7. The surface of the ceramic in pH = 3 leachate appears serious corrosion with plenty of pores. The precipitation of low-soluble was formed on sample surface during leaching tests at pH = 9 and 11. - Highlights: • The Ce{sub 0.5}Pr{sub 0.5}PO{sub 4} ceramics with high relative density of 99% and small average grain size of 0.15 µm were prepared by hot-pressing at 1150 ºC for 2 h. • The normalized elemental leaching rates of Pr (LR{sub Pr}) and Ce (LR{sub Ce}) of the hot-pressed ceramics are slightly lower than that of the ceramics sintered at 1500 ºC for 4 h by normal pressure. • The LR{sub Pr} and LR{sub Ce} reach the highest values (∼10{sup −3} g m{sup −2} d{sup −1}) when pH = 3, while the LR{sub Pr} and LR{sub Ce} have the lowest values (∼10{sup −7} g m{sup −2} d{sup −1}) when pH = 7.

  13. Development of nano-structured silicon carbide ceramics: from synthesis of the powder to sintered ceramics; Elaboration de ceramiques nanostructurees en carbure de silicium: de la synthese de la poudre a la ceramique frittee

    Energy Technology Data Exchange (ETDEWEB)

    Reau, A.

    2008-12-15

    The materials used inside future nuclear reactors will be subjected to very high temperature and neutrons flux. Silicon carbide, in the form of SiC{sub f}/SiC nano-structured composite is potentially interesting for this type of application. It is again necessary to verify the contribution of nano-structure on the behaviour of this material under irradiation. To verify the feasibility and determine the properties of the matrix, it was envisaged to produce it by powder metallurgy from SiC nanoparticles. The objective is to obtain a fully dense nano-structured SiC ceramic without additives. For that, a parametric study of the phases of synthesis and agglomeration was carried out, the objective of which is to determine the active mechanisms and the influence of the key parameters. Thus, studying the nano-powder synthesis by laser pyrolysis allowed to produce, with high production rates, homogeneous batches of SiC nanoparticles whose size can be adjusted between 15 and 90 nm. These powders have been densified by an innovating method: Spark Plasma Sintering (SPS). The study and the optimization of the key parameters allowed the densification of silicon carbide ceramic without sintering aids while preserving the nano-structure of material. The thermal and mechanical properties of final materials were studied in order to determine the influence of the microstructure on their properties. (author)

  14. Development of a mixed-conductive ceramic membrane for syngas production

    International Nuclear Information System (INIS)

    Etchegoyen, G.

    2005-10-01

    Natural gas conversion into syngas (H 2 +CO) is very attractive for hydrogen and clean fuel production via GTL technology by providing an alternative to oil products and reducing greenhouse gas emission. Syngas production, using a mixed ionic-electronic conducting ceramic membrane, is thought to be particularly promising. The purpose of this PhD thesis was to develop this type of membrane. Mixed-conducting oxide was synthesized, characterized and then, shaped via tape casting and co-sintered in order to obtain multilayer membranes with controlled architectures and microstructures. Oxygen permeation fluxes were measured with a specific device to evaluate membrane performances. As a result, the optimisation of architecture and microstructure made it possible to increase oxygen permeation flux by a factor 30. Additional researches were focused on the oxide composition in order to achieve higher dimensional stability. (author)

  15. Current state of the Uranium dioxide sintering theory

    International Nuclear Information System (INIS)

    Baranov, V.; Devyatko, Y.; Tenishev, A.; Khlunov, A.; Khomyakov, O.

    2011-01-01

    The basic approaches to the description of the ceramics sintering phenomenon are considered. It is established that diffusive sintering models incorrectly describe an intermediate stage of this process. The physical model of sintering, considering the substance plastic flow of pressing under the influence of internal stress forces and capillary forces, as the basic mechanism defining the shrinkage of sintering oxide nuclear fuel, is offered. (authors)

  16. Fabrication of Nd:YAG transparent ceramics with both TEOS and MgO additives

    International Nuclear Information System (INIS)

    Yang Hao; Qin Xianpeng; Zhang Jian; Wang Shiwei; Ma Jan; Wang Lixi; Zhang Qitu

    2011-01-01

    Research highlights: → It is well known that the use of TEOS as sintering aid is required to reach fully dense and transparent Nd:YAG ceramics. However, it is difficult to produce high quality transparent Nd:YAG ceramics only using TEOS as sintering aid. In this present work, high quality transparent Nd:YAG ceramic was fabricated using both TEOS and MgO as sintering aids. There have been few reports that both TEOS and MgO were co-added as sintering aids in YAG or Nd:YAG transparent ceramics to date. The transmittance of Nd:YAG ceramic is 83.8% at 1064 nm. The effect of MgO on the optical properties of transparent ceramics was also studied. - Abstract: Neodymium doped YAG transparent ceramics were fabricated by vacuum reactive sintering method using commercial α-Al 2 O 3 , Y 2 O 3 and Nd 2 O 3 powders as the starting materials with both tetraethyl orthosilicate (TEOS) and MgO as sintering aids. The morphologies and microstructure of the powders and Nd:YAG transparent ceramics were investigated. Fully dense Nd:YAG ceramics with average grain size of ∼10 μm were obtained by vacuum sintering at 1780 deg. C for 8 h. No pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 83.8% at 1064 nm.

  17. Emerging ceramic-based materials for dentistry.

    Science.gov (United States)

    Denry, I; Kelly, J R

    2014-12-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. © International & American Associations for Dental Research.

  18. Sintering kinetics and mass transport in ceramic engobes; Cinetica de sinterizacion y transporte de masa en engobes ceramicos por el metodo Pechini

    Energy Technology Data Exchange (ETDEWEB)

    Dal Bo, M.; Boschi, A. O.; Hotza, D.

    2013-10-01

    This work is concerned to study the sintering rate and mass transport mechanism in ceramic engobes. Specimens of engobes were prepared from a determined formulation by slip casting. Sintering was carried in two steps: (i) at constant heating rate of 7.5 degree centigrade/min and (ii) with an isothermal treatment, during 120 min. According to the dilatometric curves obtained with the engobe sintering during isothermal treatment, the dominant sintering mechanism and the rate of reactions, between the 775 and 975 degree centigrade, were determined. The results showed that between 775 and 800 degree centigrade, the sintering rate can be described by ln[d({Delta}L/L{sub 0})/dt] = -5.64 + 1.77.E10{sup -}3T. At higher temperatures, from 850 to 975 degree centigrade, this rate can be expressed by ln[d({Delta}L/L{sub 0})/ dt] = -30.73 + 3.E10{sup -}2T. The dominant transport mass mechanisms were the grain rearrangement, solution-precipitation and grain boundaries reaction. (Author)

  19. Production and processing of spinel semi-porous sintered blocks to CAD-CAM with lanthanum-glass infiltration for dental applications

    International Nuclear Information System (INIS)

    Lourenco, A.A.C.; Ogasawara, T.; Costa Neto, C.A.; Santos, F.V.C.

    2009-01-01

    The objective of this research was to obtain direct synthesis and sintering spinel by using powder mixing method for CAD-CAM ceramics manufacturing. Powders of alumina and magnesia (71.8 wt% Al2O3 and 28.2 wt% MgO) were mixed with 5 wt% of PVA and PEG binders and homogenized using ball mill (12h), then deagglomerated and submitted to uniaxial pressing into discs and plates (54 to 221.96 MPa), followed by isostatic pressing (186.03 MPa) and sintering at 1500 deg C(GrI) , 1600 C(GrII) and 1700 deg C(GrIII). Characterizations: XRD, density and four-point flexural strength and (for GrIII) elasticity modulus and Vickers microhardness. Lanthanum-glass was infiltrated into samples from all three Groups. Conclusions: (1) Plenty success for the pediatrician method; (2) Maximum density achieved for GrIII, best mechanical strength for GrII (compared to that of commercial product ), this last one being the most indicated for In-Ceram manufacturing via CAD-CAM route; (3) The flexural strength of GrI might be improved a lot after Lanthanum-glass infiltration. (author)

  20. Cordierite obtaining by reactive sintering of kaolin, tal and transition alumina; Obtencao de ceramicas a base de mulita-cordieta via sinterizacao reativa de caulim, talco e alumina

    Energy Technology Data Exchange (ETDEWEB)

    Almeida Filho, Humberto Dias de; Sales, Lindemberg Felismino; Goncalves, Joao de Freitas; Macedo, Daniel Araujo de [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Departamento de Engenharia de Materiais

    2016-07-01

    Cordierite and mullite are important applications in the manufacture of ceramic products with high resistance to thermal shock. The present work aimed to obtaining ceramics based on cordierite (2MgO.2Al2O3.5SiO2) and mullite (3Al2O3.2SiO2) via reactive sintering of one formulation containing kaolin ceramics, talc and alumina. Uniaxially pressed tablet to 125 MPa were sintered between 1100 and 1400 ° C for 1 h. The sintering temperature effect in the phase composition was evaluated by X-ray diffraction. The morphological characterization was performed by scanning electron microscopy. Samples sintered at 1300 ° C had 10 wt% of spinel (MgAl2O4) as secondary and apparent phase density 2.56 g / cm3. (author)

  1. A method for the densification of ceramic layers, especially ceramic layers within solid oxide cell (SOC) technology, and products obtained by the method

    DEFF Research Database (Denmark)

    2013-01-01

    A ceramic layer, especially for use in solid oxide cell (SOC) technology, is densified in a method comprising (a) providing a multilayer system by depositing the porous ceramic layer, which is to be densified, onto the selected system of ceramic layers on a support, (b) pre-sintering the resulting......(s) in the porous layer surface and (e) performing a thermal treatment at a temperature T2, where T2 > ?1, to obtain densification of and grain growth in the porous layer formed in step (b). The method makes it possible to obtain dense ceramic layers at temperatures, which are compatible with the other materials...... present in a ceramic multilayer system....

  2. Effects of the co-addition of LiSbO3-LiTaO3 on the densification of (Na1/2K1/2)NbO3 lead free ceramics by atmosphere sintering

    International Nuclear Information System (INIS)

    Jiang Na; Fang Bijun; Wu Jian; Du Qingbo

    2011-01-01

    Research highlights: → This manuscript shows a synthesis method that can easily obtain excellent lead-free samples, which is valuable for industrial production. → Pure phase perovskite 0.94(Na 1/2 K 1/2 )NbO 3 -0.03LiSbO 3 -0.03LiTaO 3 (0.94NKN-0.03LS-0.03LT) lead-free piezoelectric ceramics with high relative density, being 94.73%, and excellent integral electrical properties, piezoelectric constant d 33 being 228 pC/N, were prepared by atmosphere sintering method. Which can be attributed to the co-doping of LiSbO 3 -LiTaO 3 . - Abstract: Pure phase perovskite 0.94(Na 1/2 K 1/2 )NbO 3 -0.03LiSbO 3 -0.03LiTaO 3 (0.94NKN-0.03LS-0.03LT) lead-free piezoelectric ceramics were prepared by the conventional solid-state reaction method. Due to the co-addition of LiSbO 3 -LiTaO 3 , the 0.94NKN-0.03LS-0.03LT ceramics prepared by atmosphere sintering at 1040 deg. C exhibit high relative density, being 94.73%, and rather homogenous microstructure. X-ray diffraction (XRD) measurement confirmed that the sintered ceramics exhibit pure tetragonal perovskite structure. The 0.94NKN-0.03LS-0.03LT ceramics exhibit excellent integral electrical properties, in which the value of piezoelectric constant d 33 is 228 pC/N, the electromechanical coupling factors K p and K t are 0.220 and 0.230, respectively, the mechanical quality factor Q m is 32.19, and the remnant polarization P r is 23.06 μC/cm 2 . Such excellent electrical properties are considered as correlating with the high relative density of the synthesized ceramics induced by the co-doping of LiSbO 3 -LiTaO 3 .

  3. Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering

    International Nuclear Information System (INIS)

    Magnant, J.; Pailler, R.; Le Petitcorps, Y.; Maille, L.; Guette, A.; Marthe, J.

    2013-01-01

    Fabrication of multidirectional continuous carbon and silicon carbide fiber reinforced ceramic matrix composites (CMC) by a new short time hybrid process was studied. This process is based, first, on the deposition of fiber interphase and coating by chemical vapor infiltration, next, on the introduction of silicon nitride powders into the fibrous preform by slurry impregnation and, finally, on the densification of the composite by liquid phase spark plasma sintering (LP-SPS). The homogeneous introduction of the ceramic charges into the multidirectional fiber pre-forms was realized by slurry impregnation from highly concentrated and well-dispersed aqueous colloid suspensions. The chemical degradation of the carbon fibers during the fabrication was prevented by adapting the sintering pressure cycle. The composites manufactured are dense. Microstructural analyses were conducted to explain the mechanical properties achieved. One main important result of this study is that LP-SPS can be used in some hybrid processes to densify fiber reinforced CMC. (authors)

  4. Thermophysical Properties of High-Frequency Induction Heat Sintered Graphene Nanoplatelets/Alumina Ceramic Functional Nanocomposites

    Science.gov (United States)

    Ahmad, Iftikhar; Subhani, Tayyab; Wang, Nannan; Zhu, Yanqiu

    2018-05-01

    This paper concerns the thermophysical properties of high-frequency induction heat (HFIH) sintered alumina ceramic nanocomposites containing various graphene nanoplatelets (GNP) concentrations. The GNP/alumina nanocomposites demonstrated high densities, fine-grained microstructures, highest fracture toughness and hardness values of 5.7 MPa m1/2 and 18.4 GPa, which found 72 and 8%, superior to the benchmarked monolithic alumina, respectively. We determine the role of GNP in tuning the microstructure and inducing toughening mechanisms in the nanocomposites. The sintered monolithic alumina exhibited thermal conductivity value of 24.8 W/mK; however, steady drops of 2, 15 and 19% were recorded after adding respective GNP contents of 0.25, 0.5 and 1.0 wt.% in the nanocomposites. In addition, a dwindling trend in thermal conductions with increasing temperatures was recorded for all sintered samples. Simulation of experimental results with proven theoretical thermal models showed the dominant role of GNP dispersions, microstructural porosity, elastic modulus and grain size in controlling the thermal transport properties of the GNP/alumina nanocomposites. Thermogravimetric analysis showed that the nanocomposite with up to 0.5 mass% of GNP is thermally stable at the temperatures greater than 875 °C. The GNP/alumina nanocomposites owning a distinctive combination of mechanical and thermal properties are promising contenders for the specific components of the aerospace engine and electronic devices having contact with elevated temperatures.

  5. Textured Na x CoO2 Ceramics Sintered from Hydrothermal Platelet Nanocrystals: Growth Mechanism and Transport Properties

    Science.gov (United States)

    Zhang, Wei; Liu, Pengcheng; Wang, Yifeng; Zhu, Kongjun; Tai, Guoan; Liu, Jinsong; Wang, Jing; Yan, Kang; Zhang, Jianhui

    2018-05-01

    Nanostructuring is an effective approach to improve thermoelectric (TE) performance, which is caused by the interface and quantum effects on electron and phonon transport. For a typical layered structure such as sodium cobalt (NCO), a highly textured ceramic with nanostructure is beneficial for the carrier transport properties due to the strong anisotropy. In this paper, we established a textured NCO ceramic with highly oriented single crystals in nanoscale. The Na0.6CoO2 platelet crystals were prepared by a one-step hydrothermal method. The growth mechanism was revealed to involve dissolution-recrystallization and exchange reactions. NCO TE ceramics fabricated by a press-aided spark plasma sintering method showed a high degree of texturing, with the platelet crystals basically lying along the in-plane direction perpendicular to the press direction. TE properties of the textured NCO ceramics showed a strong anisotropic behavior. The in-plane electrical conductivity was considerably larger than the out-of-plane data because of fewer grain boundaries and interfaces that existed in the in-plane direction. Moreover, the in-plane Seebeck coefficient was higher because of the anisotropic electronic nature of NCO. Although the in-plane thermal conductivity was high, a prior ZT value was enabled for these NCO ceramics along this direction because of the dominant electrical transport. This finding provides a new approach to prepare highly oriented ceramics.

  6. Effects of La{sub 2}O{sub 3}-doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Hong Wei; Chang, Chun Rui [College of Science, North China University of Science and Technology, Hebei Province (China); Li, Yuan Liang [Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, North China University of Science and Technology, Hebei Province (China); Yan, Chun Liang [Analysis and Testing Center, North China University of Science and Technology, Hebei Province (China)

    2016-03-15

    Using BaCO{sub 3}, SrCO{sub 3} and TiO{sub 2}, et al as crude materials, La{sub 2}O{sub 3} as dopant, Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) Ceramics of perovskite structure were prepared by solid state reaction method. We investigated the effects of La{sub 2}O{sub 3} -doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics. The experiment results show that: The amount of La{sub 2}O{sub 3} can increase the dielectric constant of the sample, with the doping amount increasing, the dielectric constant increases. The sintering temperature has also significant impact on the dielectric properties. The dielectric constant of the sample reaches its highest point at 1280 °C. (author)

  7. Model for the evaluation and prediction of production rate of sinter ...

    African Journals Online (AJOL)

    A model has been derived for evaluation and prediction of production rate of sinter machine operating on vertical mode. The quadratic model expressed as: P = 0.4395 V – 0.0526 V2 + 0.54, showed that the production rate of the sinter machine was dependent on the vertical sintering height. The maximum deviation of the ...

  8. A comparative approach to synthesis and sintering of alumina/yttria nanocomposite powders using different precipitants

    Energy Technology Data Exchange (ETDEWEB)

    Kafili, G. [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Movahedi, B., E-mail: b.movahedi@ast.ui.ac.ir [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Milani, M. [Faculty of Advanced Materials and Renewable Energy Research Center, Tehran (Iran, Islamic Republic of)

    2016-11-01

    Alumina/yttria nanocomposite powder as an yttrium aluminum garnet (YAG) precursor was synthesized via partial wet route using urea and ammonium hydrogen carbonate (AHC) as precipitants, respectively. The products were characterized using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The use of urea produced very tiny spherical Y-compounds with chemical composition of Y{sub 2}(CO{sub 3}){sub 3}·nH{sub 2}O, which were attracted to the surface of alumina nanoparticles and consequently, a core-shell structure was obtained. The use of ammonium hydrogen carbonate produced sheets of Y-compounds with chemical composition of Y(OH)CO{sub 3} covering the alumina nanoparticles. A fine-grained YAG ceramic (about 500 nm), presenting a non-negligible transparency (45% RIT at IR range) was obtained by the spark plasma sintering (SPS) of alumina-yttria nanocomposite synthesized in the urea system. This amount of transmission was obtained by only the sintering of the powder specimen without any colloidal forming process before sintering or adding any sintering aids or dopant elements. However, by spark plasma sintering of alumina-yttria nanocomposite powder synthesized in AHC system, an opaque YAG ceramic with an average grain size of 1.2 μm was obtained. - Highlights: • Urea proved to be an appropriate precipitant for obtaining a core-shell alumina/yttria nanocomposite. • Alumina/yttria nanocomposite powders with more appropriate morphology and highly sinterability. • A fine-grained YAG ceramic was obtained by SPS of alumina-yttria nanocomposite.

  9. Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

    International Nuclear Information System (INIS)

    Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

    2017-01-01

    Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al_2O_3 and Y_2O_3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

  10. Compressive deformation of liquid phase-sintered porous silicon carbide ceramics

    Directory of Open Access Journals (Sweden)

    Taro Shimonosono

    2014-12-01

    Full Text Available Porous silicon carbide ceramics were fabricated by liquid phase sintering with 1 wt% Al2O3–1 wt% Y2O3 additives during hot-pressing at 1400–1900 °C. The longitudinal strain at compressive fracture increased at a higher porosity and was larger than the lateral strain. The compressive Young's modulus and the strain at fracture depended on the measured direction, and increased with the decreased specific surface area due to the formation of grain boundary. However, the compressive strength and the fracture energy were not sensitive to the measured direction. The compressive strength of a porous SiC compact increased with increasing grain boundary area. According to the theoretical modeling of the strength–grain boundary area relation, it is interpreted that the grain boundary of a porous SiC compact is fractured by shear deformation rather than by compressive deformation.

  11. Bifunctional behavior of Er3+ ions as the sintering additive and the fluorescent agent in Er3+ single doped γ-AlON transparent ceramics

    International Nuclear Information System (INIS)

    Wang, Ying; Xie, Xiumin; Qi, Jianqi; Wang, Shanshan; Wei, Nian; Lu, Zhongwen; Chen, Xingtao; Lu, Tiecheng

    2016-01-01

    We report on the sintering promoting and fluorescent activator roles of Er 3+ in AlON:Er 3+ transparent ceramics prepared by pressureless sintering with Er 2 O 3 and AlON powder. There shows that the transparency of samples varied with the content of Er 2 O 3 additive. The AlON:Er 3+ ceramics showed upconversion luminescence peaking at 546 nm, 662 nm and 840 nm under the 980 nm excitation due to transition of 4 S 3/2 / 2 H 11/2 → 4 I 15/2 , 4 F 9/2 → 4 I 15/2 and 4 S 3/2 / 2 H 11/2 → 4 I 13/2 of Er 3+ ions, respectively. The infrared spectra exhibited strong emission at 1534 nm corresponds to 4 I 13/2 → 4 I 15/2 transition. The mechanism of the IR and visible emission bands in AlON:Er 3+ ceramics are discussed, which suggest it should be attractive for lighting and display devices applications.

  12. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  13. Building ceramics with improved thermal insulation parameters

    Directory of Open Access Journals (Sweden)

    Rzepa Karol

    2016-01-01

    Full Text Available One of the most important performance characteristics of masonry units is their high thermal insulation. There are many different ways to improve this parameter, however the most popular methods in case of ceramic masonry units are: addition of pore-creating raw materials and application of proper hole pattern. This study was an attempt to improve thermal insulation of ceramics by applying thermal insulation additives. Perlite dust created as a subgrain from expansion of perlite rock was used. Perlite subgrain is not very popular among consumers, that’s why it’s subjected to granulation to obtain coarse grain. The authors presented concept of direct application of perlite dust for the production of building ceramics with improved thermal insulation. Fineness of this additive is asset for molding of ceramic materials from plastic masses. Based on the results it was found that about 70% perlite by volume can be added to obtain material with a coefficient of heat conductivity of 0,37 W/mK. Higher content of this additive in ceramic mass causes deterioration of its rheological properties. Mass loses its plasticity, it tears up and formed green bodies are susceptible to deformation. During sintering perlite takes an active part in compaction process. Higher sintering dynamics is caused by: high content of alkali oxides in perlite and glass nature of perlite. Alkali oxides generate creation of liquid phase which intensifies mass compaction processes. Active role of perlite in sintering process causes good connection of its grains with clay groundwork which is important factor for mechanical parameters of ceramic materials. It was also noted that addition of perlite above 40% by volume of mass effectively neutralized negative effect of efflorescence in ceramic materials.

  14. Temperature variation in metal ceramic technology analyzed using time domain optical coherence tomography

    Science.gov (United States)

    Sinescu, Cosmin; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

    2014-01-01

    The quality of dental prostheses is essential in providing good quality medical services. The metal ceramic technology applied in dentistry implies ceramic sintering inside the dental oven. Every ceramic material requires a special sintering chart which is recommended by the producer. For a regular dental technician it is very difficult to evaluate if the temperature inside the oven remains the same as it is programmed on the sintering chart. Also, maintaining the calibration in time is an issue for the practitioners. Metal ceramic crowns develop a very accurate pattern for the ceramic layers depending on the temperature variation inside the oven where they are processed. Different patterns were identified in the present study for the samples processed with a variation in temperature of +30 °C to +50 °C, respectively - 30 0°C to -50 °C. The OCT imagistic evaluations performed for the normal samples present a uniform spread of the ceramic granulation inside the ceramic materials. For the samples sintered at a higher temperature an alternation between white and darker areas between the enamel and opaque layers appear. For the samples sintered at a lower temperature a decrease in the ceramic granulation from the enamel towards the opaque layer is concluded. The TD-OCT methods can therefore be used efficiently for the detection of the temperature variation due to the ceramic sintering inside the ceramic oven.

  15. Microstructural evolution during the synthesis of bulk components from nanocrystalline ceramic powder, part II: microstructure and properties

    International Nuclear Information System (INIS)

    Ajaal, T. T.; Metak, A. M.

    2004-01-01

    Part I of this review, published in 5 /4th of Al-Nawah magazine, was devoted to the synthetic techniques used in the production processes of a bulk components of nanocrystalline materials. In this part, the microstructural evolution and its effect on the materials properties will be detailed. Minimizing grain growth and maximizing densification during the sintering stage of the ultrafine particles as well as the homogeneous densification in pressureless sintering, grain growth and rapid rate pressureless sintering will be discussed. Ceramics are well known for their high strength at elevated temperatures, as well as the extreme brittleness that prevents their application in many critical components. However, researchers have found that brittleness can be overcome by reducing particle sizes to nanometer levels. These fine grain structures are believed to provide improved ductility the individual grains can slide over one another without causing cracks. In addition, nanophase ceramics are more easily formed than their conventional counterparts, and easier to machine without cracking or breaking. Shrinkage during sintering is also greatly reduced in nanophase ceramics, and they can be sintered at lower temperatures than conventional ceramics. As a result, nanophase ceramics have the potential to deliver an ideal combination of ductility and high-temperature strength, allowing increased efficiency in applications ranging from automobile engines to jet aircraft. This part of the review covers the microstructural evolution during the synthetic process of nanocrystalline ceramic materials and its effects on the materials properties.(author)

  16. Fabrication of crystal-oriented barium-bismuth titanate ceramics in high magnetic field and subsequent reaction sintering

    International Nuclear Information System (INIS)

    Tanaka, Satoshi; Tomita, Yusuke; Furushima, Ryoichi; Uematsu, Keizo; Shimizu, Hiroyuki; Doshida, Yutaka

    2009-01-01

    High magnetic field was applied to fabricate novel lead-free piezoelectric ceramics with a textured structure. A compact of crystallographically oriented grains was prepared by dry forming in a high magnetic field from a mixed slurry of bismuth titanate and barium titanate powders. Bismuth titanate particles with a size of about 1 μ m were used as the host material. In the forming process, the slurry was poured into a mold and set in a magnetic field of 10 T until completely dried. Bismuth titanate particles were highly oriented in the slurry under the magnetic field. The dried powder compact consisted of highly oriented bismuth titanate particles and randomly oriented barium titanate particles. Barium bismuth titanate ceramics with a- and b-axis orientations were successfully produced from the dried compact by sintering at temperatures above 1100 deg. C.

  17. Tough hybrid ceramic-based material with high strength

    International Nuclear Information System (INIS)

    Guo, Shuqi; Kagawa, Yutaka; Nishimura, Toshiyuki

    2012-01-01

    This study describes a tough and strong hybrid ceramic material consisting of platelet-like zirconium compounds and metal. A mixture of boron carbide and excess zirconium powder was heated to 1900 °C using a liquid-phase reaction sintering technique to produce a platelet-like ZrB 2 -based hybrid ceramic bonded by a thin zirconium layer. The platelet-like ZrB 2 grains were randomly present in the as-sintered hybrid ceramic. Relative to non-hybrid ceramics, the fracture toughness and flexural strength of the hybrid ceramic increased by approximately 2-fold.

  18. Microwave processing of a dental ceramic used in computer-aided design/computer-aided manufacturing.

    Science.gov (United States)

    Pendola, Martin; Saha, Subrata

    2015-01-01

    Because of their favorable mechanical properties and natural esthetics, ceramics are widely used in restorative dentistry. The conventional ceramic sintering process required for their use is usually slow, however, and the equipment has an elevated energy consumption. Sintering processes that use microwaves have several advantages compared to regular sintering: shorter processing times, lower energy consumption, and the capacity for volumetric heating. The objective of this study was to test the mechanical properties of a dental ceramic used in computer-aided design/computer-aided manufacturing (CAD/CAM) after the specimens were processed with microwave hybrid sintering. Density, hardness, and bending strength were measured. When ceramic specimens were sintered with microwaves, the processing times were reduced and protocols were simplified. Hardness was improved almost 20% compared to regular sintering, and flexural strength measurements suggested that specimens were approximately 50% stronger than specimens sintered in a conventional system. Microwave hybrid sintering may preserve or improve the mechanical properties of dental ceramics designed for CAD/CAM processing systems, reducing processing and waiting times.

  19. Spinel formation for stabilizing simulated nickel-laden sludge with aluminum-rich ceramic precursors.

    Science.gov (United States)

    Shih, Kaimin; White, Tim; Leckie, James O

    2006-08-15

    The feasibility of stabilizing nickel-laden sludge from commonly available Al-rich ceramic precursors was investigated and accomplished with high nickel incorporation efficiency. To simulate the process, nickel oxide was mixed alternatively with gamma-alumina, corundum, kaolinite, and mullite and was sintered from 800 to 1480 degrees C. The nickel aluminate spinel (NiAl2O4) was confirmed as the stabilization phase for nickel and crystallized with efficiencies greater than 90% for all precursors above 1250 degrees C and 3-h sintering. The nickel-incorporation reaction pathways with these precursors were identified, and the microstructure and spinel yield were investigated as a function of sintering temperature with fixed sintering time. This study has demonstrated a promising process for forming nickel spinel to stabilize nickel-laden sludge from a wide range of inexpensive ceramic precursors, which may provide an avenue for economically blending waste metal sludges via the building industry processes to reduce the environmental hazards of toxic metals. The correlation of product textures and nickel incorporation efficiencies through selection of different precursors also provides the option of tailoring property-specific products.

  20. Phase evolution and dielectric properties of MgTi2O5 ceramic sintered with lithium borosilicate glass

    International Nuclear Information System (INIS)

    Shin, Hyunho; Shin, Hee-Kyun; Jung, Hyun Suk; Cho, Seo-Yong; Hong, Kug Sun

    2005-01-01

    Phase evolution, densification, and dielectric properties of MgTi 2 O 5 dielectric ceramic, sintered with lithium borosilicate (LBS) glass, were studied. Reaction between LBS glass and MgTi 2 O 5 was significant in forming secondary phases such as TiO 2 and (Mg,Ti) 2 (BO 3 )O. The glass addition was not necessarily deleterious to the dielectric properties due to the formation of TiO 2 : permittivity increased and temperature coefficient of resonance frequency could be tuned to zero with the addition of LBS glass, although the inevitable glass-induced decrease of quality factor was not retarded by the formation of TiO 2 . The sintered specimen with 10 wt% LBS fired at 950 deg. C for 2 h showed permittivity of 19.3, quality factor of 6800 GHz, and τ f of -16 ppm/ deg. C

  1. Temperature variations in sintering ovens for metal ceramic dental prostheses: non-destructive assessment using OCT

    Science.gov (United States)

    Sinescu, C.; Bradu, A.; Duma, V.-F.; Topala, F. I.; Negrutiu, M. L.; Podoleanu, A. G.

    2018-02-01

    We present a recent investigation regarding the use of optical coherence tomography (OCT) in the monitoring of the calibration loss of sintering ovens for the manufacturing of metal ceramic dental prostheses. Differences in the temperatures of such ovens with regard to their specifications lead to stress and even cracks in the prostheses material, therefore to the failure of the dental treatment. Evaluation methods of the ovens calibration consist nowadays of firing supplemental samples; this is subjective, expensive, and time consuming. Using an in-house developed swept source (SS) OCT system, we have demonstrated that a quantitative assessment of the internal structure of the prostheses, therefore of the temperature settings of the ovens can be made. Using en-face OCT images acquired at similar depths inside the samples, the differences in reflectivity allow for the evaluation of the differences in granulation (i.e., in number and size of ceramic grains) of the prostheses material. Fifty samples, divided in five groups, each sintered at different temperatures (lower, higher, or equal to the prescribed one) have been analyzed. The consequences of the temperature variations with regard to the one prescribed were determined. Rules-of-thumb were extracted to monitor objectively, using only OCT images of currently manufactured samples, the settings of the oven. The method proposed allows for avoiding producing prostheses with defects. While such rules-of-thumb achieve a qualitative assessment, an insight in our on-going work on the quantitative assessment of such losses of calibration on dental ovens using OCT is also made.

  2. Reactive Spark Plasma Sintering and Mechanical Properties of Zirconium Diboride–Titanium Diboride Ultrahigh Temperature Ceramic Solid Solutions

    Directory of Open Access Journals (Sweden)

    Karthiselva N. S.

    2016-09-01

    Full Text Available Ultrahigh temperature ceramics (UHTCs such as diborides of zirconium, hafnium tantalum and their composites are considered to be the candidate materials for thermal protection systems of hypersonic vehicles due to their exceptional combination of physical, chemical and mechanical properties. A composite of ZrB2-TiB2 is expected to have better properties. In this study, an attempt has been made to fabricate ZrB2-TiB2 ceramics using mechanically activated elemental powders followed by reactive spark plasma sintering (RSPS at 1400 °C. Microstructure and phase analysis was carried out using X-ray diffractometer (XRD and electron microscopy to understand microstructure evolution. Fracture toughness and hardness were evaluated using indentation methods. Nanoindentation was used to measure elastic modulus. Compressive strength of the composites has been reported.

  3. Structural properties and neutron irradiation effects of ceramics

    International Nuclear Information System (INIS)

    Yano, Toyohiko

    1994-01-01

    In high temperature gas-cooled reactors and nuclear fusion reactors being developed at present, various ceramics are to be used in the environment of neutron irradiation for undertaking important functions. The change of the characteristics of those materials by neutron irradiation must be exactly forecast, but it has been known that the response of the materials is different respectively. The production method of ceramics and the resulted structures of ceramics which control their characteristics are explained. The features of covalent bond and ionic bond, the synthesis of powder and the phase change by heating, sintering and sintering agent, and grain boundary phase are described. The smelling of ceramics by neutron irradiation is caused by the formation of the clusters of Frenkel defects and minute spot defects. Its restoration by annealing is explained. The defects remaining in materials after irradiation are the physical defects by flipping atoms cut due to the collision with high energy particles and the chemical defects by nuclear transformation. Some physical defects can be restored, but chemical defects are never restored. The mechanical properties of ceramics and the effect of irradiation on them, and the thermal properties of ceramics and the effect of irradiation on them are reported. (K.I.)

  4. Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

    Science.gov (United States)

    Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

    2014-01-01

    The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

  5. Influence of Sintering Temperature on Pore Structure and Electrical properties of Technologically Modified MgO-Al2O3 Ceramics

    Directory of Open Access Journals (Sweden)

    Halyna Klym

    2015-03-01

    Full Text Available Technologically modified spinel ceramics are prepared from Al2O3 and 4MgCO3×Mg(OH2×5H2O powders at 1200, 1300 and 1400 oC. The influence of sintering temperature on porous structure and exploitation properties of obtained humidity-sensitive MgO-Al2O3 ceramics are studied. It is shown that increasing of preparing temperature from 1200 to 1400 oC result in transformation of pore size distribution in ceramics from tri- to bi-modal including the open macro- and mesopores with sizes from tem to hundreds nm and nanopores until to a few nm. The studied ceramic elements with electrical resistances ~ 10-2-102 MОhm are high humidity sensitive in the region of 30-95 % with minimal hysteresis in adsorption-desorption cycles. It is established that increasing of humidity sensitivity in ceramics are related to achievement near to optimum pore size distribution and quantity of pores in the all regions. Prolonged degradation transformation in ceramics at higher temperature and relative humidity result in lose sensitivity up to 40-50 %.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5189

  6. Hexagonal OsB2: Sintering, microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Xie, Zhilin; Lugovy, Mykola; Orlovskaya, Nina; Graule, Thomas; Kuebler, Jakob; Mueller, Martin; Gao, Huili; Radovic, Miladin; Cullen, David A.

    2015-01-01

    Highlights: • ReB 2 -type hexagonal OsB 2 powder has been densified by spark plasma sintering. • The sintered OsB 2 contains ∼80 wt.% hexagonal and ∼20 wt.% orthorhombic phases. • The average grain size of the sintered OsB 2 sample was 0.56 ± 0.26 μm. • H = 31 ± 9 GPa and E = 574 ± 112 GPa measured by nanoindentation. - Abstract: The metastable high pressure ReB 2 -type hexagonal OsB 2 bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB 2 were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB 2 bulk ceramics

  7. Characterization of microstructure of Si3N4 whisker reinforced glass ceramic

    International Nuclear Information System (INIS)

    Han, Byoung Sung; Choi, Shung Shaon

    1993-01-01

    Glass ceramics, especially fiber-reinforced composite ceramics, have attracted a great deal of attention in improving the reliability of ceramic components because of the improvement in various mechanical properties. Through hot-pressing and sintering, 225 cordierite was transformed with glass ceramic and mullite phase. Particularly glass glain size increased with the increasing of the sintering temperature and the heat treatment enhance the toughness and hardness of materials. Like the increased sintering temperature, the roughness increased with increasing whisker vol.%. In case of whisker-rinforced glass ceramic, the fracture surface of samples has been associated with a whisker orientation of samples. (Author)

  8. Quartz crystal reinforced quartz glass by spark plasma sintering

    International Nuclear Information System (INIS)

    Torikai, D.; Barazani, B.; Ono, E.; Santos, M.F.M.; Suzuki, C.K.

    2011-01-01

    The Spark Plasma Sintering presents fast processing time when compared to conventional sintering techniques. This allows to control the grain growth during sintering as well as the diffusion rate of a multi-material compounds, and make possible obtainment of functionally graded materials and nanostructured compounds. Powders of high purity silica glass and crystalline silica were sintered in a SPS equipment at temperatures around 1350° C, i.e., above the softening temperature of silica glass and below the melting temperature of quartz crystal. As a result, glass ceramics with pure silica glass matrix reinforced with crystalline alpha-quartz grains were fabricated at almost any desired range of composition, as well as controlled size of the crystalline reinforcement. X-ray diffraction and density measurements showed the possibility to manufacture a well controlled density and crystallinity glass-ceramic materials. (author)

  9. Nano-ceramics and its molding technologies

    International Nuclear Information System (INIS)

    Liu Jian; Xu Yunshu

    2007-01-01

    Nano-ceramics and its related knowledge were introduced. Fabrication of nano-ceramic powder, as well as the molding and sintering technologies of nano-ceramics were reviewed. Features of the present molding technologies were analyzed. The applications of nano-ceramics were prospected. (authors)

  10. Instrumentation for studying binder burnout in an immobilized plutonium ceramic wasteform

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, M; Pugh, D; Herman, C

    2000-04-21

    The Plutonium Immobilization Program produces a ceramic wasteform that utilizes organic binders. Several techniques and instruments were developed to study binder burnout on full size ceramic samples in a production environment. This approach provides a method for developing process parameters on production scale to optimize throughput, product quality, offgas behavior, and plant emissions. These instruments allow for offgas analysis, large-scale TGA, product quality observation, and thermal modeling. Using these tools, results from lab-scale techniques such as laser dilametry studies and traditional TGA/DTA analysis can be integrated. Often, the sintering step of a ceramification process is the limiting process step that controls the production throughput. Therefore, optimization of sintering behavior is important for overall process success. Furthermore, the capabilities of this instrumentation allows better understanding of plant emissions of key gases: volatile organic compounds (VOCs), volatile inorganics including some halide compounds, NO{sub x}, SO{sub x}, carbon dioxide, and carbon monoxide.

  11. Effect of rigid inclusions on sintering

    International Nuclear Information System (INIS)

    Rahaman, M.N.; De Jonghe, L.C.

    1988-01-01

    The predictions of recent theoretical studies on the effect of inert, rigid inclusions on the sintering of ceramic powder matrices are examined and compared with experimental data. The densification of glass matrix composites with inclusion volume fractions of ≤0.15 can be adequately explained by Scherer's theory for viscous sintering with rigid inclusions. Inclusions cause a vast reduction in the densification rates of polycrystalline matrix composites even at low inclusion volume fractions. Models put forward to explain the sintering of polycrystalline matrix composites are discussed

  12. Rapid processing of ferrite ceramics with promising magneto-dielectric characteristics

    Directory of Open Access Journals (Sweden)

    Zhuohao Xiao

    2017-12-01

    Full Text Available Ferrite ceramics, Ni0.88Zn0.07Co0.05Fe1.98O4, with the addition of 4wt.% Bi2O3 as sintering aid, were fabricated by using a simple one-step processing without involving the step of calcination. X-ray diffraction (XRD results indicated that single phase ferrite ceramics can be achieved after sintering at 1000∘C for 2h. The samples demonstrated relative densities in the range of 97–99%. Desired magneto-dielectric properties have been approached by adjusting the sintering temperature and sintering time duration. This technique is believed to be applicable to other ceramic materials.

  13. Pressureless sintering behavior of injection molded alumina ceramics

    Directory of Open Access Journals (Sweden)

    Liu W.

    2014-01-01

    Full Text Available The pressureless sintering behaviors of two widely used submicron alumina (MgOdoped and undoped with different solid loadings produced by injection molding have been studied systematically. Regardless of the sinterability of different powders depending on their inherent properties, solid loading plays a critical role on the sintering behavior of injection molded alumina, which greatly determines the densification and grain size, and leads to its full densification at low temperatures. As compared to the MgO-doped alumina powder, the undoped specimens exhibit a higher sinterability for its smaller particle size and larger surface area. While full densification could be achieved for MgO-doped powders with only a lower solid loading, due to the fact that MgO addition can reduce the detrimental effect of the large pore space on the pore-boundary separation.

  14. Thermo-mechanical properties of mullite/zirconia reinforced alumina ceramic composites

    International Nuclear Information System (INIS)

    Wahsh, M.M.S.; Khattab, R.M.; Awaad, M.

    2012-01-01

    Highlights: ► Alumina–mullite–zirconia ceramic composites were prepared from alumina and zircon. ► Constant amount of magnesia was added as a sintering aid. ► Mechanical properties were enhanced with increasing of zircon up to 30.52 mass%. ► All of ceramic composites were achieved excellent thermal shock resistance. -- Abstract: Alumina–mullite–zirconia ceramic composites were prepared by reaction bonding of alumina and zircon mixtures after firing at different temperatures 1300°, 1400° and 1500 °C. Constant amount of magnesia was added as a sintering aid. The technological parameters of the sintered ceramic composites, i.e. the mechanical properties and densification parameter as well as thermal shock resistance, have been investigated. The phase compositions and microstructure of the sintered ceramic composites were detected by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results indicated that alumina–mullite–zirconia ceramic composites fired at 1500 °C for 2 h were achieved a good densification parameters and mechanical properties as well as excellent thermal shock resistance. In addition, these ceramic composites were showed enhancement in Vickers’ microhardness and fracture toughness values.

  15. Two step sintering of zirconia-escandia-ceria

    International Nuclear Information System (INIS)

    Grosso, R.L.; Muccillo, E.N.S.

    2011-01-01

    Recent reports show that the ceramic system based on zirconia-scandia-ceria is a good candidate to act as solid electrolyte in solid oxide fuel cells operating at intermediate temperatures (600-800 °C). In this work, commercial ZrO_2 containing 10 mol% scandium oxide and 1 mol% cerium oxide was sintered by the two stage method. This technique was proposed to in order to obtain ceramic materials with high density along with fine grain sizes, because it avoids the grain growth occurring in the last stage of sintering. A number of experimental conditions were fully exploited by varying the dwell temperature (T_2) and the dwell time. The peak temperature (T_1) was chosen from linear shrinkage results. High (>98%) density values were obtained using this method. The medium grain size was evaluated for selected sintered samples. X-ray diffraction patterns reveal a secondary (rhombohedral) phase in sintered samples. The intensity of the secondary phase is a function of T_1 being small for relatively higher peak temperatures. (author)

  16. Lutetium oxide-based transparent ceramic scintillators

    Science.gov (United States)

    Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

    2016-01-19

    In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

  17. Sintering temperature and impedance analysis of Mn{sub 0.9}Co{sub 1.2}Ni{sub 0.27}Mg{sub 0.15}Al{sub 0.03}Fe{sub 0.45}O{sub 4} NTC ceramic prepared by W/O microemulsion method

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Junbo [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Qing, E-mail: zhaoq@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); Gao, Bo [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); Chang, Aimin, E-mail: changam@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); Zhang, Bo; Zhao, Pengjun; Ma, Renjun [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2014-12-25

    Highlights: • The ceramics are mainly in spinel phase and cubic cobalt oxide phase. • A perfect sintering temperature of 1450 °C for the Mn–Co–Ni–Mg–Al–Fe–O was proposed. • The NTC characteristic of the ceramics derive from grain boundary resistance R{sub gb}. - Abstract: The Mn{sub 0.9}Co{sub 1.2}Ni{sub 0.27}Mg{sub 0.5}Al{sub 0.03}Fe{sub 0.45}O{sub 4} negative temperature coefficient (NTC) ceramics derived from nano-particles were sintered at 1380 °C, 1450 °C and 1560 °C, respectively. X-ray diffraction (XRD) result showed that the ceramics sintered at 1380 °C and 1450 °C were mainly in the cubic spinel structure except for a little of tetragonal spinel, and that sintered at 1560 °C was consisted of cubic spinel and cubic cobalt oxide phase. Scanning electron microscopy (SEM) image indicated that the grain size of the ceramic increased sharply when the sintering temperature increased from 1380 °C to 1450 °C, and it changed little when the temperature further increased to 1560 °C, while the porosity was enlarged seriously. Thus a perfect sintering temperature of 1450 °C was proposed. Impedance analysis revealed that the grain resistance R{sub g} showed positive temperature coefficient thermistor characteristic, while the grain boundary resistance R{sub gb} possessed negative temperature coefficient characteristic. Because the grain boundary resistance R{sub gb} was two orders of magnitude larger than the grain resistance R{sub g}, the material thus showed negative temperature coefficient thermistor characteristic.

  18. Characterisation of the sintering behaviour of Waelz slag from electric arc furnace (EAF) dust recycling for use in the clay ceramics industry.

    Science.gov (United States)

    Quijorna, N; de Pedro, M; Romero, M; Andrés, A

    2014-01-01

    Waelz slag is an industrial by-product from the recovery of electric arc furnace (EAF) dust which is mainly sent to landfills. Despite the different chemical and mineralogical compositions of Waelz slag compared to traditional clays, previous experiments have demonstrated its potential use as a clay substitute in ceramic processes. Indeed, clayey products containing Waelz slag could improve mechanical and environmental performance, fixing most of the metallic species and moreover decreasing the release of some potential pollutants during firing. However, a deeper understanding of the complex phase transformations during its thermal treatment and the connection of this behaviour with the end properties is desirable in order to explain the role that is played by the Waelz slag and its potential contribution to the ceramic process. For this purpose, in the present study, the chemical, mineralogical, thermal and environmental behaviour of both (i) unfired powdered samples, and (ii) pressed specimen of Waelz slag fired up to different temperatures within the typical range of clay based ceramic production, has been studied. The effect of the heating temperature on the end properties of the fired samples has been assessed. In general, an increase of the firing temperature promotes sintering and densification of the products and decreases the open porosity and water absorption which also contributes to the fixation of heavy metals. On the contrary, an increase in the leaching of Pb, Cr and Mo from the fired specimens is observed. This can be attributed to the creation of Fe and Ca molybdates and chromates that are weakly retained in the alkali matrix. On the other side, at temperature above 950 °C a weight gain related to the emission of evolved gases is observed. In conclusion, the firing temperature of the ceramic process is a key parameter that affects not only the technical properties but also strongly affects the leaching behaviour and the process emissions

  19. Problems and possibilities of development of boron nitride ceramics

    International Nuclear Information System (INIS)

    Rusanova, L.N.; Romashin, A.G.; Kulikova, G.I.; Golubeva, O.P.

    1988-01-01

    The modern state of developments in the field of technology of ceramics produced from boron nitride is analyzed. Substantial difficulties in production of pure ceramics from hexagonal and wurtzite-like boron nitride are stated as related to the structure peculiarities and inhomogeneity of chemical bonds in elementary crystal cells of various modifications. Advantages and disadvantages of familiar technological procedures in production of boron nitride ceramics are compared. A new technology is suggested, which is based on the use of electroorganic compounds for hardening and protection of porous high-purity boron-nitride die from oxidation, and as high-efficient sintered elements for treatment of powders of various structures and further pyrolisis. The method is called thermal molecular lacing (TML). Properties of ceramics produced by the TML method are compared with characteristics of well-known brands of boron nitride ceramics

  20. Method of manufacturing gadolinium oxide-incorporated nuclear fuel sintering products

    International Nuclear Information System (INIS)

    Komono, Akira; Seki, Makoto; Omori, Sadayuki.

    1987-01-01

    Purpose: To manufacture nuclear fuel sintering products excellent in burning property and mechanical property. Constitution: In the manufacturing step for nuclear fuel sintering products, specific metal oxides are added for promoting the growth of crystal grains in the sintering. Those metal oxides melted at a temperature lower than the sintering temperature of a mixture of nuclear fuel oxide powder and oxide power, or those metal oxides causing eutectic reaction are used as the metal oxide. Particularly, those compounds having oxygen atom - metal atom ratio (O/M) of not less than 2 are preferably used. As such metal oxides usable herein transition metal oxides, e.g., Nb 2 O 5 , TiO 2 , MoO 3 and WO 3 are preferred, with Nb 2 O 3 and TiO 2 being preferred particularly. (Seki, T.)

  1. Microstructure, crystal structure and electrical properties of Cu{sub 0.1}Ni{sub 0.8}Co{sub 0.2}Mn{sub 1.9}O{sub 4} ceramics obtained at different sintering conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bodak, O.; Akselrud, L.; Demchenko, P.; Kotur, B.; Mrooz, O.; Hadzaman, I.; Shpotyuk, O.; Aldinger, F.; Seifert, H.; Volkov, S.; Pekhnyo, V

    2002-12-16

    Details of the formation of Cu{sub 0.1}Ni{sub 0.8}Co{sub 0.2}Mn{sub 1.9}O{sub 4} ceramics under different sintering conditions have been studied by optical microscopy, scanning electron microscopy (SEM), electron probe and energy dispersive spectroscopy (EDX) microanalyses, X-ray diffraction (XRD) and electrical resistivity measurements. Microstructure studies of samples sintered at 1170 deg. C for 1 h indicated the presence of a secondary phase besides the main spinel phase with modified composition. XRD measurements showed that the spinel phase exhibits a tetragonally distorted spinel structure (space group I4{sub 1}/amd, a=5.9410(5) A, c=8.4196(15) A). The secondary phase (solid solution based on NiO) crystallizes with the NaCl-type structure (space group Fm3-bar m, a=4.1872(3) A). The content of the secondary phase in ceramics is 10.61 mass%. For NiMn{sub 2}O{sub 4} ceramics, prepared under the same sintering conditions, the decomposition with Ni{sub 1-x}Mn{sub x}O solid solution (NaCl-type structure) and spinel phase formation have been observed. The tetragonal modification of the spinel phase for NiMn{sub 2}O{sub 4} ceramics is more preferable (space group I4{sub 1}/amd, a=5.9764(5) A, c=8.4201(8) A). The distribution of atoms in the structure has been proposed for both ceramics. According to XRD results the Cu{sub 0.1}Ni{sub 0.8}Co{sub 0.2}Mn{sub 1.9}O{sub 4} ceramic samples, sintered at 920 deg. C for 8 h (program 1), at 920 deg. C for 8 h and at 750 deg. C for 24 h (program 2), at 920 deg. C for 8 h, at 1200 deg. C for 1 h and at 920 deg. C for 24 h (program 3) and at 920 deg. C for 8 h, at 1200 deg. C for 1 h, at 920 deg. C for 24 h and at 750 deg. C for 48 h (program 4), contain a single phase with the cubic spinel structure (space group Fd3-bar m). Small residuals of the secondary phase for the ceramics, prepared via programs 3 and 4, have been observed by SEM investigations. The structure transformations of the spinel phase for Cu{sub 0.1}Ni{sub 0.8}Co

  2. Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy; Estudos de sinterizacao e de envelhecimento termico de ceramicas de zirconia - itria por espectroscopia de impedancia

    Energy Technology Data Exchange (ETDEWEB)

    Florio, Daniel Zanetti de

    1998-07-01

    ZrO{sub 2}:8 mol %Y{sub 2}O{sub 3} solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO{sub 2} produced at a Pilot Plant at IPEN and 99.9% pure Y{sub 2}O{sub 3} of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

  3. Investigation of vitreous and crystalline ceramic materials for immobilization of alpha-contaminated residues

    International Nuclear Information System (INIS)

    Palmer, C.R.; Mellinger, G.B.; Rusin, J.M.

    1981-01-01

    Experimental investigations of two alternatives for immobilizing dispersible solid wastes contaminated with alpha-emitting radionuclides are reviewed. Borosilicate glasses and sintered silicate ceramics are being studied for such wastes, and results so far indicate both may offer attractive alternatives to waste generators. Waste oxide solubilities, de-vitrification behaviour and effects of residual carbon are examined for glasses incorporating incinerator ash and hydrated ferric oxide sludge. Glasses will accommodate these wastes at loadings of 30-60 wt% while maintaining good performance characteristics. A brief comparative evaluation of cold-pressed and sintered ceramics is also described. The effects on process and product properties of the choice of additives, waste loading and sintering temperature were determined. This approach also appears to promise economic waste loadings while achieving relatively durable waste forms. (author)

  4. Simulation of the d.c. critical current in superconducting sintered ceramics

    International Nuclear Information System (INIS)

    Riedinger, R.; Habig, P.; Hlil, E.K.; Arnaud, M.; Boulesteix, C.

    1990-01-01

    The new superconducting high-T c sintered ceramics can be described in some case as a lattice of interconnected rods, in other cases as a more or less random packing of parallelepiped crystallites; their size is about a few microns. The d.c. critical current at zero voltage of such a material is not related to the critical current of the bulk material, but to its granular structure. Indeed, the critical current between two adjacent cells is governed by the critical current of the weak link between them; this link behaves within some limits as a Josephson junction, the critical current of which is known. For our present problem, the system can be modeled as a lattice of Josephson junctions. We present here results for the d.c. critical current at zero voltage of lattices of identical Josephson junctions in two dimensions. The influence of the finiteness of size of the sample is examined. The relationship with normal conductivity simulations and percolation is discussed

  5. Thermal Conductivity Measurement and Analysis of Fully Ceramic Microencapsulated fuel

    International Nuclear Information System (INIS)

    Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J.; Lee, S. J.

    2015-01-01

    FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix in comparison with the current commercial UO2 fuel system of LWR. In addition to a safety enhancement of FCM fuel, thermal conductivity of SiC ceramic matrix is better than that of UO2 fuel. Because the centerline temperature of FCM fuel is lower than that of the current UO2 fuel due to the difference of thermal conductivity of fuel, an operational release of fission products from the fuel can be reduced. SiC ceramic has attracted for nuclear fuel application due to its high thermal conductivity properties with good radiation tolerant properties, a low neutron absorption cross-section and a high corrosion resistance. Thermal conductivity of ceramic matrix composite depends on the thermal conductivity of each component and the morphology of reinforcement materials such as fibers and particles. There are many results about thermal conductivity of fiber-reinforced composite like as SiCf/SiC composite. Thermal conductivity of SiC ceramics and FCM pellets with the volume fraction of TRISO particles were measured and analyzed by analytical models. Polycrystalline SiC ceramics and FCM pellets with TRISO particles were fabricated by hot press sintering with sintering additives. Thermal conductivity of the FCM pellets with TRISO particles of 0 vol.%, 10 vol.%, 20 vol.%, 30 vol.% and 40 vol.% show 68.4, 52.3, 46.8, 43.0 and 34.5 W/mK, respectively. As the volume fraction of TRISO particles increased, the measured thermal conductivity values closely followed the prediction of Maxwell's equation

  6. Glass-ceramics with multibarrier structure obtained from industrial waste

    Energy Technology Data Exchange (ETDEWEB)

    Berzina, L.; Cimdins, R.; Rozenstrauha, I. [Riga Tech. Univ. (Latvia). Fac. of Chem. Technol.; Bossert, J. [Technisches Inst.: Materialwissenschaft, Friedrich-Schiller-Univ., Jena (Germany); Kravtchenko, I. [Inst. for Problems of Material Science, Kiev (Ukraine)

    1997-12-31

    Recycling problem for various kind of waste is solved by processing the waste to ecological depositable products with multibarrier structure. In order to form a multibarrier structure the ecologically incompatible substances may be diluted and chemically bound until their recycling products gain a structure like natural mineral or glass (I. barrier). After that, remineralized materials are converted into a new product by melting or powder technology using an ecological compatible type of waste as a matrix phase (II. barrier). Waste which are treated this way could be applied to produce ceramic building materials and goods such as floor tiles, stone pavement and casting products. Industrial waste from the metallurgical factory in Latvia ``Liepajas metalurgs`` are metallurgical slag, filter dust, etching waste and sewage used in technologies. The main constituents of chemical compositions of these waste are: Fe, Ca, Si, Mg, Al, Mn etc. In some types of waste a small amount of ecologically risky elements such as Cr, Ni, Zr, Sn and Pb can occur. The combination of metallurgical waste with peat ashes from Riga thermal power station, oil shale ashes or glass waste under controlled sintering procedure gives bulk materials with surface or/and bulkcrystallization. The structure of glass-ceramics built this way may prevent the migration of ecologically risky elements into environment due to corrosion or friction. Physical-chemical properties and thermal behaviour (DTA, dilatometry, melting) of waste define the range of sintering for production of glass-ceramics (powder technology) and decorative glass-ceramic materials (melting and powder technology). (orig.) 5 refs.

  7. Hexagonal OsB{sub 2}: Sintering, microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Zhilin [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Lugovy, Mykola [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Institute for Problems of Materials Science, 3 Krzhizhanivskii Str., Kyiv 03142 (Ukraine); Orlovskaya, Nina, E-mail: Nina.Orlovskaya@ucf.edu [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Graule, Thomas; Kuebler, Jakob [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, CH-8600 Dubendorf (Switzerland); Mueller, Martin [Laboratory of Mechanical Metallurgy, EPFL, CH-1015 Lausanne (Switzerland); Gao, Huili [Department of Mechanical Engineering, Texas A& M University, College Station, TX 77843 (United States); Radovic, Miladin [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Cullen, David A. [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2015-06-15

    Highlights: • ReB{sub 2}-type hexagonal OsB{sub 2} powder has been densified by spark plasma sintering. • The sintered OsB{sub 2} contains ∼80 wt.% hexagonal and ∼20 wt.% orthorhombic phases. • The average grain size of the sintered OsB{sub 2} sample was 0.56 ± 0.26 μm. • H = 31 ± 9 GPa and E = 574 ± 112 GPa measured by nanoindentation. - Abstract: The metastable high pressure ReB{sub 2}-type hexagonal OsB{sub 2} bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB{sub 2} were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB{sub 2} bulk ceramics.

  8. Effect of sintering condition on the microstructure and electrical properties of lead-free (Na0.5K0.5NbO3 - Bi0.5(Na0.83K0.170.5TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Wang Chun Huy

    2017-01-01

    Full Text Available In this work, the piezoelectric ceramic system of the (1-x(Na0.5K0.5NbO3 - xBi(Na0.83K0.17TiO3 with composition close to the morphotropic phase boundary is studied. (Na0.5K0.5NbO3 with 0∼5 mole% Bi(Na0.83K0.17TiO3 has been prepared following the conventional mixed oxide process. The effect of sintering time on the properties of 0.97(Na0.5K0.5NbO3-0.03Bi(Na0.83K0.17TiO3 ceramics is discussed. For 0.97(Na0.5K0.5NbO3-0.03Bi(Na0.83K0.17TiO3 ceramics, the electromechanical coupling coefficients of the thickness mode kt and the piezoelectric constant d33 reach 0.46 and 155 p/CN, respectively, at the sintering of 1100 °C for 3 h. Dielectric and piezoelectric properties have maximum values at the sintering temperature of 1100 °C for 5 h. For 0.97(Na0.5K0.5NbO3 -0.03Bi(Na0.83K0.17TiO3 ceramics, the electromechanical coupling coefficients of the thickness mode kt and the piezoelectric constant d33 reach 0.56 and 190, respectively, at the sintering of 1100 °C for 5 h. The effect of prolonging the sintering time to the 0.97(Na0.5K0.5NbO3-0.03Bi(Na0.83K0.17TiO3 system is a helpful method on ceramic processing to improve densification and properties.

  9. Laser Surface Treatment of Sintered Alumina

    Science.gov (United States)

    Hagemann, R.; Noelke, C.; Kaierle, S.; Wesling, V.

    Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed.

  10. Influence of B2O3 content on sintering behaviour and dielectric properties of La2O3-B2O3-CaO/Al2O3 glass-ceramic composites for LTCC applications

    Science.gov (United States)

    Wang, F. L.; Zhang, Y. W.; Chen, X. Y.; Mao, H. J.; Zhang, W. J.

    2018-01-01

    La2O3-B2O3-CaO glasses with different B2O3 content were synthesized by melting method to produce glass/ceramic composites in this work. XRD and DSC results revealed that the diminution of B2O3 content was beneficial to increase the crystallization tendency of glass and improve the quality of crystalline phase, while decreasing the effect of glass during sintering process as sintering aids. The choice of glass/ceramic mass ratio was also influenced by the B2O3 content of glass. Dense samples sintered at 875 ºC showed good dielectric properties which meet the requirement of LTCC applications: moderate dielectric constant (7.8-9.4) and low dielectric loss (2.0×10-3).

  11. FY 1998 report on the R and D of the industrial science technology. R and D of synergy ceramics; 1998 nendo sangyo kagaku gijutsu kenkyu kaihatsu seika hokokusho. Synergy ceramics no kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Hazardous ingredients in gases exhausted from diesel, refuse treatment facilities, etc. are becoming the problem. The development is expected of porous ceramic films which have functions of separation/purification at high temperature. By making good use of the technology to synthesize ceramic films with uniform through pores of several ten nm order and the technology to form 1D through pores of several ten - 100{mu} m order, the development of the following technologies were made and are in sight: enhancement of functions of gas separation/purification, function of catalyst-carrying to be given, porous film formation/base material fabrication. For the commercialization of high performance structure use ceramic parts, required is innovation of the production method by which the production cost is reduced without damaging the characteristics. Technologies were used of micro-fine raw materials, rapid sintering, texture assessment, analysis, etc., and study was made of cost reduction in high performance ceramic parts. For energy conservation by reducing the sintering temperature, the following were trially conducted: mechanical ironing, use of low grade raw material, use of superplastic reformation and forging, etc. (NEDO)

  12. An experimental investigation of the thermal/fluid properties of the nitrate to ammonia and ceramic (NAC) product slurry

    International Nuclear Information System (INIS)

    Muguercia, I.; Lagos, L.; Yang, G.; Li, W.; Ebadian, M.A.; Mattus, A.J.; Lee, D.D.; Walker, J.W.; Hunt, R.D.

    1994-01-01

    Recently, a new immobilization technique for LLW, the Nitrate to Ammonia and Ceramic (NAC) process, has been developed. Instead of mixing the liquid waste form directly with the cement to make concrete blocks, the NAC process eliminates the nitrate from the LLW by converting it to ammonia gas. Aluminum particles are used as a reductant to complete this conversion. The final product of the NAC process is gibbsite, which can be further sintered to a ceramic waste form. Experimental tests are conducted to measure the apparent viscosity, the pressure drop, and the heat transfer coefficient of the pipe flow of the Nitrate to Ammonia and Ceramic (NAC) process product slurry. The tests indicate that the NAC product slurry exhibits a typical pseudoplastic fluid behavior. The pressure drop in the pipe flow is a function of the Reynolds number and the slurry temperature. The results also indicate that at a low slurry temperature, the slurry is uniformly heated peripherally. At a high slurry temperature, however, the slurry may be thermally stratified. In a straight pipe, the Nusselt number is reduced as the slurry temperature increases

  13. Werkstoffwoche 98. Vol. 7. Symposium 9: Ceramics. Symposium 14: Simulation of ceramics

    International Nuclear Information System (INIS)

    Heinrich, J.; Ziegler, G.; Hermel, W.; Riedel, H.

    1999-01-01

    The leading subject of this proceedings volume is ceramic materials, with papers on the following subject clusters: Processing (infiltration, sintering, forming) - Physics and chemistry of ceramics (functional ceramics, SiC, ceramic precursors, microstructural properties) - Novel concepts (composites, damage induced by oxidation and mechanical stress, performance until damage under mechanical and thermal stress, layers, nanocomposites). 28 of the conference papers have been prepared for individual retrieval from the ENERGY database. (orig./CB) [de

  14. Production of nuclear ceramic fuel for nuclear power plants at 'Ulba metallurgical plant' OSC

    International Nuclear Information System (INIS)

    Khadeev, V.G.

    2000-01-01

    The paper describes the flow-sheet of production of uranium dioxide powders and nuclear ceramic fuel pellets of them existing at the facility. 'UMP' OSC applies ADU extraction process of UO2 powders production. An indisputable success of the process is the possibility of use of the wide range of raw materials. Uranium hexafluoride, uranium oxides, uranium metal, uranium tetrafluoride, uranyl salts, uranium ore concentrates, all possible types of uranium-containing materials the processing of which by routine methods is difficult (ashes, scraps, etc.) are used as the raw materials. In addition, a reprocessed nuclear fuel can be used for fuel production. The quality of uranium dioxide powder produced does not depend on the type of uranium raw material used. High selectivity of extraction refining makes possible to obtain material with rather low impurities content that meets practically all specifications for uranium dioxide known to us. Ceramic and process features of uranium dioxide powders, namely, specific surface, bulk density, grain size and sinterability make possible to produce nuclear ceramic fuel with specified features. Quality of uranium dioxide powders produced by 'UMP' OSC was highly rated by General Electric company that is one of the leading companies from fuel manufactures in the USA market . It has certified 'UMP' OSC as its supplier. Currently, our company makes great efforts on establishing production of uranium dioxide powders with natural isotopes content for production of fuel for CANDU reactors. Trial lots of such powders are under tests at some companies manufacturing fuel for this type reactors in Canada, USA and Corea

  15. Dense cermets containing fine grained ceramics and their manufacture

    International Nuclear Information System (INIS)

    King, H.L.

    1986-01-01

    This patent describes a method of producing a ceramic-metal composite (cermet) containing boride-oxide ceramic having components of a first metal boride and a second metal oxide, which ceramic is in mixture in the cermet with elemental metal of the second metal, wherein the cermet is produced by sintering a reaction mixture of the first metal oxide, boron oxide and the elemental second metal. The improvement consists of: combining for the reaction mixture; A. (a) first metal oxide; (b) boron oxide; (c) ceramic component in very finely divided form; and (d) elemental second metal in very finely divided form and in an amount of at least a 100 percent molar excess beyond that amount stoichiometrically required to produce the second metal oxide during sintering; and B. sintering the reaction mixture in inert gas atmosphere

  16. Mineralogy and microstructure of sintered lignite coal fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Marina Ilic; Christopher Cheeseman; Christopher Sollars; Jonathan Knight [Faculty of Technology and Metallurgy, Belgrade (Yugoslavia)

    2003-02-01

    Lignite coal fly ash from the 'Nikola Tesla' power plant in Yugoslavia has been characterised, milled, compacted and sintered to form monolithic ceramic materials. The effect of firing at temperatures between 1130 and 1190{sup o}C on the density, water accessible porosity, mineralogy and microstructure of sintered samples is reported. This class C fly ash has an initial average particle size of 82 {mu}m and contains siliceous glass together with the crystalline phases quartz, anorthite, gehlenite, hematite and mullite. Milling the ash to an average particle size of 5.6 m, compacting and firing at 1170{sup o}C for 1 h produces materials with densities similar to clay-based ceramics that exhibit low water absorption. Sintering reduces the amount of glass, quartz, gehlenite and anhydrite, but increases formation of anorthite, mullite, hematite and cristobalite. SEM confirms the formation of a dense ceramic at 1170{sup o}C and indicates that pyroplastic effects cause pore formation and bloating at 1190{sup o}C. 23 refs., 6 figs., 2 tabs.

  17. Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

    Science.gov (United States)

    Osorio, Raquel; Monticelli, Francesca; Osorio, Estrella; Toledano, Manuel

    2012-01-01

    Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pre-treated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups. Key words:CAD/CAM ceramic, alumina, zirconia, resin cement, surface pre-treatment, sandblasting, silica-coating, chemical aging, bond degradation, microtensile bond strength. PMID:22322517

  18. Transparent ceramic photo-optical semiconductor high power switches

    Science.gov (United States)

    Werne, Roger W.; Sullivan, James S.; Landingham, Richard L.

    2016-01-19

    A photoconductive semiconductor switch according to one embodiment includes a structure of sintered nanoparticles of a high band gap material exhibiting a lower electrical resistance when excited by light relative to an electrical resistance thereof when not exposed to the light. A method according to one embodiment includes creating a mixture comprising particles, at least one dopant, and at least one solvent; adding the mixture to a mold; forming a green structure in the mold; and sintering the green structure to form a transparent ceramic. Additional system, methods and products are also presented.

  19. Dilatometric study of anisotropic sintering of alumina/zirconia laminates with controlled fracture behaviour

    Czech Academy of Sciences Publication Activity Database

    Maca, K.; Pouchlý, V.; Drdlík, D.; Hadraba, Hynek; Chlup, Zdeněk

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4287-4295 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GA15-06390S; GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Alumina/zirconia laminate * Crack deflection * Master sintering curve * Sintering shrinkage Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass OBOR OECD: Ceramic s Impact factor: 3.411, year: 2016

  20. LSA glass-ceramic tiles made by powder pressing; Obtencao de placas vitroceramicas do sistema LSA utilizando a prensagem de pos

    Energy Technology Data Exchange (ETDEWEB)

    Figueira, F.C.; Bertan, F.M. [Colorminas Colorificio e Mineracao, Icara, SC (Brazil); Riella, H.G. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Programa de Pos-Graduaco em Engenharia Quimica; Uggioni, E. [Universidade do Extremo Sul Catarinense (UFSC), Florianopolis, SC (Brazil). Curso de Engenharia de Materiais; Bernardin, A.M., E-mail: amb@unesc.ne [Servico Nacional de Aprendizagem Industrial (SENAI), Tijucas, SC (Brazil). Dept. de Tecnologia em Ceramica

    2009-07-01

    A low cost alternative for the production of glass-ceramic materials is the pressing of the matrix glass powders and its consolidation simultaneously with crystallization in a single stage of sintering. The main objective of this work was to obtain LSA glass ceramics with low thermal expansion, processed by pressing and sintering a ceramic frit powder. The raw materials were homogenized and melted (1480 deg C, 80min), and the melt was poured in water. The glass was chemically (XRF and AAS) and thermally (DTA, 10 deg C/min, air) characterized, and then ground (60min and 120min). The ground powders were characterized (laser diffraction) and compressed (35MPa and 45MPa), thus forming four systems. The compacts were dried (150 deg C, 24h) and sintered (1175 deg C and 1185 deg C, 10 deg C/min). Finally, the glass-ceramics were characterized by microstructural analysis (SEM and XRD), mechanical behavior ({sigma}bending) and thermal analysis ({alpha}). The best results for thermal expansion were those for the glass-ceramics processed with smaller particle size and greater compaction pressure. (author)

  1. Superconductive ceramics obtained with sol gel method

    International Nuclear Information System (INIS)

    Arcangeli, A.; Mosci, A.; Nardi, A.; Vatteroni, R.; Zondini, C.

    1988-01-01

    Several sol gel routes have been considered, studied and developed to produce large quantities of granulates which can be processed to obtain ceramics having good superconducting characteristics. In the considered process a mixture of commercial nitrates is atomized, at room temperature, in a solution 1:1 of Primene JMT and Benzene and a pale blue gel of the starting elements is suddently formed. The granulates obtained are free flowing, very reactive and well suited for pressing. For their intrinsic characteristics they could be very good precursors for the production of large quantities of superconductive ceramics in different forms. The precipitated gel is dried, calcinated, pressed in the form of cylindrical pellets which are sintered up to 960 degrees C. No griding or different thermal treatments are needed. The sintered material has low electric resistence, shows a clear Meissner effect and has a transition temperature of between 91 and 95 K

  2. New ceramics incorporated with industrial by-products as pore formers for sorption of toxic chromium from aqueous media

    Science.gov (United States)

    Domopoulou, Artemi

    2015-04-01

    The incorporation of secondary resources including various industrial wastes as pore-forming agents into clayey raw material mixtures for the development of tailored porous ceramic microstructures is currently of increasing interest. In the present research, sintered ceramic compacts were developed incorporated with industrial solid by-products as pore formers, and then used as new sorbents for chromium removal from aqueous media. The microstructures obtained were characterized through X-ray diffraction (XRD) analysis as well as scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). Sorption potential of chromium from synthetic solutions on the porous ceramics was studied by static adsorption experiments as a function of the pore-former percentage in the ceramic matrix as well as the initial heavy metal (chromium) concentration, solution pH and temperature. Kinetic studies were conducted and adsorption isotherms of chromium were determined using the Langmuir equation. Preliminary experimental results concerning the adsorption characteristics of chromium on the ceramic materials produced appear encouraging for their possible beneficial use as new sorbents for the removal of toxic chromium from aqueous media. Keywords: sorbents, ceramics, industrial solid by-products, pore-former, chromium. Acknowledgements: This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program ARCHIMEDES III: Investing in knowledge society through the European Social Fund.

  3. Fabrication of Li_2TiO_3 pebbles by a selective laser sintering process

    International Nuclear Information System (INIS)

    Zhou, Qilai; Gao, Yue; Liu, Kai; Xue, Lihong; Yan, Youwei

    2015-01-01

    Highlights: • Selective laser sintering (SLS) is employed to fabricate ceramic pebbles. • Quantities and diameter of the pebbles could be easily controlled by adjusting the model of pebbles. • All the pebbles could be prepared at a time within several minutes. • The Li_2TiO_3 pebbles sintered at 1100 °C show a notable crush load of 43 N. - Abstract: Lithium titanate, Li_2TiO_3, is an important tritium breeding material for deuterium (D)–tritium (T) fusion reactor. In test blanket module (TBM) design of China, Li_2TiO_3 is considered as one candidate material of tritium breeders. In this study, selective laser sintering (SLS) technology was introduced to fabricate Li_2TiO_3 ceramic pebbles. This fabrication process is computer assisted and has a high level of flexibility. Li_2TiO_3 powder with a particle size of 1–3 μm was used as the raw material, whilst epoxy resin E06 was adopted as a binder. Green Li_2TiO_3 pebbles with certain strengths were successfully prepared via SLS. Density of the green pebbles was subsequently increased by cold isostatic pressing (CIP) process. Li_2TiO_3 pebbles with a diameter of about 2 mm were obtained after high temperature sintering. Density of the pebbles reaches 80% of theoretical density (TD) with a comparable crush load of 43 N. This computer assisted approach provides a new efficient route for the production of Li_2TiO_3 ceramic pebbles.

  4. Effect of ZrO2 on the sintering behavior, strength and high-frequency dielectric properties of electrical ceramic porcelain insulator

    Science.gov (United States)

    Singh Mehta, Niraj; Sahu, Praveen Kumar; Ershad, Md; Saxena, Vipul; Pyare, Ram; Ranjan Majhi, Manas

    2018-01-01

    In the present study, the effect of ZrO2 on the sintering, strength and dielectric behavior of electrical ceramic porcelain insulator with substituting alumina content by zirconia (in weight percentage from 0% to 30%) is investigated. The different composition of samples containing different zirconia (ZrO2) contents of 0, 10, 20, and 30 wt% are prepared using the uniaxial pressure technique applying 160 MPa pressure. Further, the prepared samples are also analyzed for sintering temperatures (1350 °C), and effects are observed on mechanical and electric properties of porcelain insulator. Different characterizations such as Dilatometer, x-ray diffraction, scanning electron microscopy and differential thermal analysis/thermo gravimetric analysis were used to evaluate the thermal, phase detection, micro structural and weight loss changes by increasing concentration of ZrO2 on base porcelain composition. At 1350 °C, for the composition having 20 wt% ZrO2 with 10 wt% alumina, the maximum density was observed 2.81 g cm-3 with a porosity of 2.23%. The highest tensile strength of 41 ± 3 MPa is observed for the same sample composition. The minimum value of thermal expansion coefficient is found to be in the range of 10-6 for the sample with 30 wt% ZrO2 content sintered at 1350 °C compared to other prepared samples. Similarly, the highest dielectric value (5.1-4.4) having dielectric loss (0.08-0.12) is achieved for the sample with 30 wt% ZrO2 content sintered at 1350 °C in the frequency range of 4-20 GHz at room temperature. According to the mechanical properties, the composition having 20 wt% ZrO2 on base ceramic porcelain composition has enormous potential to serve as a high strength refractory material. For dielectric properties, the composition having 30 wt% ZrO2 is more suitable for the electrical application.

  5. Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics.

    Science.gov (United States)

    Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

    2015-09-01

    This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey's multiple comparisons post-hoc test (α=0.05). The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (Pceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia.

  6. Studies of ZrO{sub 2}-Y{sub 2}O{sub 3} ceramics properties sintered in conventional and microwave oven; Estudos das propriedades de ceramicas de ZrO{sub 2}-Y{sub 2}O{sub 3} sinterizadas em forno convencional de microondas

    Energy Technology Data Exchange (ETDEWEB)

    Gelfuso, M V; Capistrano, D; Thomazini, D [Universidade de Fortaleza (UNIFOR), CE (Brazil); Grzebielucka, E C; Chinelatto, A L; Chinelatto, A S.A. [Universidade Estadual de Ponta Grossa (DEMa/UFPG), PR (Brazil). Dept. de Engenharia de Materiais

    2009-07-01

    The ceramic materials processing with nano grain size has developed materials with new properties or improves some of its existing properties. To obtain ceramics with nano grain size, besides that to obtaining nanometric powders, a major goal is to keep the grains size after sintering. Contributing in this line of research, this study aimed to sinter zirconia-Yttria powders through two processes: conventional and microwave sintering. Zirconia stabilized with Yttria powders were obtained by chemical route based on Pechini method. Cylindrical samples were sintered between 1300 to 1500 deg C between 10 and 40 minutes. The samples were characterized by Xray diffraction, Scanning Electron Microscopy and apparent density. It was observed that the final microstructure is influenced by both methods of sintering as the curve of firing used. (author)

  7. Coating of ceramic powders by chemical vapor deposition techniques (CVD)

    International Nuclear Information System (INIS)

    Haubner, R.; Lux, B.

    1997-01-01

    New ceramic materials with selected advanced properties can be designed by coating of ceramic powders prior to sintering. By variation of the core and coating material a large number of various powders and ceramic materials can be produced. Powders which react with the binder phase during sintering can be coated with stable materials. Thermal expansion of the ceramic materials can be adjusted by varying the coating thickness (ratio core/layer). Electrical and wear resistant properties can be optimized for electrical contacts. A fluidized bed reactor will be designed which allow the deposition of various coatings on ceramic powders. (author)

  8. Mechanical behavior of alumina and alumina-feldspar based ceramics in an acetic acid (4%) environment

    International Nuclear Information System (INIS)

    Stumpf, Aisha S.G.; Bergmann, Carlos P.; Vicenzi, Juliane; Fetter, Rebecca; Mundstock, Karina S.

    2009-01-01

    This study investigates the mechanical properties of alumina-feldspar based ceramics when exposed to an aggressive environment (acetic acid 4%). Alumina ceramics containing different concentrations of feldspar (0%, 1%, 5%, 10%, or 40%) were sintered at either 1300, 1600, or 1700 o C. Flaws (of width 0%, 30%, or 50%) were introduced into the specimens using a saw. Half of these ceramic bodies were exposed to acetic acid. Their flexural strength, K IC , and porosity were measured and the fractured samples were evaluated using scanning electronic- and optical microscopy. It was found that in the ceramic bodies sintered at 1600 o C, feldspar content up to 10% improved flexural strength and K IC, and reduced porosities. Generally, it was found that acetic acid had a weakening effect on the flexural strength of samples sintered at 1700 o C but a beneficial effect on K IC of ceramics sintered at 1600 o C. It was concluded that alumina-based ceramics with feldspar content up to 10% and sintered at higher temperatures would perform better in an aggressive environment similar to oral cavity.

  9. Flexural resistance of Cerec CAD/CAM system ceramic blocks. Part 2: Outsourcing materials.

    Science.gov (United States)

    Sedda, Maurizio; Vichi, Alessandro; Del Siena, Francesco; Louca, Chris; Ferrari, Marco

    2014-02-01

    To test different Cerec CAD/CAM system ceramic blocks, comparing mean flexural strength (sigma), Weibull modulus (m), and Weibull characteristic strength (sigma0) in an ISO standardized set-up. Following the recent ISO Standard (ISO 6872:2008), 11 types of ceramic blocks were tested: IPS e.max CAD MO, IPS e.max CAD LT and IPS e.max CAD HT (lithium disilicate glass-ceramic); In-Ceram SPINELL, In-Ceram Alumina and In-Ceram Zirconia (glass-infiltrated materials); inCoris AL and In-Ceram AL (densely sintered alumina); In-Ceram YZ, IPS e.max Zir-CAD and inCoris ZI (densely sintered zirconia). Specimens were cut out from ceramic blocks, finished, crystallized/infiltrated/sintered, polished, and tested in a three-point bending test apparatus. Flexural strength, Weibull characteristic strength, and Weibull modulus were obtained. A statistically significant difference was found (P ceramic (sigma = 272.6 +/- 376.8 MPa, m = 6.2 +/- 11.3, sigma0 = 294.0 +/- 394.1 MPa) and densely sintered alumina (sigma = 441.8 +/- 541.6 MPa, m = 11.9 +/- 19.0, sigma0 = 454.2 +/- 565.2 MPa). No statistically significant difference was found (P = 0.254) in glass infiltrated materials (sigma = 376.9 +/- 405.5 MPa, m = 7.5 +/- 11.5, sigma0 = 393.7 +/- 427.0 MPa). No statistically significant difference was found (P = 0.160) in densely sintered zirconia (sigma = 1,060.8 +/- 1,227.8 MPa, m = 5.8 +/- 7.4, sigma0 = 1,002.4 +/- 1,171.0 MPa). Not all the materials tested fulfilled the requirements for the clinical indications recommended by the manufacturer.

  10. Research and development of the industrial basic technologies of the next generation, 'composite materials (fine ceramics)'. Evaluation of the first phase research and development; Jisedai sangyo kiban gijutsu kenkyu kaihatsu 'fine ceramics'. Daiikki kenkyu kaihatsu hyoka

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1984-03-30

    The results of the first phase research and development project for developing fine ceramics as the basic technologies of the next generation are evaluated. The R and D themes are selected to develop fine ceramics of high strength, corrosion resistance, precision and wear resistance, noting their excellent characteristics. Development of the basic techniques for these materials is of high significance, and highly rated. The efforts in the first-phase R and D project are aimed at development of silicon nitride and silicon carbide for synthesis of the stock materials; explosive forming/treating the stock powders; forming, sintering and processing/joining; evaluation of the characteristics; non-destructive testing methods; designs; and evaluation of the parts, among others, as the elementary techniques for production, evaluation and application of the fine ceramic materials. The technical targets of improving functions have been achieved, or bright prospects have been obtained therefor in development of the techniques for synthesis of the stock materials, forming/sintering and processing/joining. The silica reduction for stock synthesis, basic techniques for molding/sintering, and rheological considerations for the molding/sintering techniques represent the techniques of the next generation, because they break through the limitations of the conventional techniques. (NEDO)

  11. [Effect of repeated sintering and variations in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers].

    Science.gov (United States)

    Cui, Huang; Jia, Yu; Shaofeng, Meng; Biyun, Gao

    2017-08-01

    Objective The aim of this study is to evaluate the effect of repeated sintering and variation in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers. Methods A total of 24 computer aided design and computer aided manufacturing (CAD/CAM) veneers was fabricated using the IPS e.max-CAD LS2 and then randomly divided into four groups (S0, S1, S2, S3; n=6). Each group was sintered 0, 1, 2, 3 times individually according to the manufacturer's recommendation. The color parameters (L, C, H, a, b values) of all the specimens were measured by a Vita easyshade dental colorimeter. The results were statistically analyzed using the SAS 9.1.3 software for MANOVA and LSD. Subsequently, the microstructures of the intersecting surfaces of the specimens were observed by scanning electron microscopy (SEM). Results After repeated sintering, the L value significantly decreased (P<0.05). For the C and b values, statistical differences were observed among the groups except between S2 and S3. SEM results showed that the interlocking microstructures of rod-shaped Li₂Si₂O₅ crystals became more compact when the number of sintering times was increased. Conclusion Repeated sintering exhibited significant influence on the color of the IPS e.max-CAD LS2 veneers.

  12. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: Multiple-unit FDPs.

    Science.gov (United States)

    Pjetursson, Bjarni Elvar; Sailer, Irena; Makarov, Nikolay Alexandrovich; Zwahlen, Marcel; Thoma, Daniel Stefan

    2015-06-01

    To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported fixed dental prostheses (FDPs) and to describe the incidence of biological, technical and esthetic complications. Medline (PubMed), Embase and Cochrane Central Register of Controlled Trials (CENTRAL) searches (2006-2013) were performed for clinical studies focusing on tooth-supported FDPs with a mean follow-up of at least 3 years. This was complemented by an additional hand search and the inclusion of 10 studies from a previous systematic review [1]. Survival and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions. Forty studies reporting on 1796 metal-ceramic and 1110 all-ceramic FDPs fulfilled the inclusion criteria. Meta-analysis of the included studies indicated an estimated 5-year survival rate of metal-ceramic FDPs of 94.4% (95% CI: 91.2-96.5%). The estimated survival rate of reinforced glass ceramic FDPs was 89.1% (95% CI: 80.4-94.0%), the survival rate of glass-infiltrated alumina FDPs was 86.2% (95% CI: 69.3-94.2%) and the survival rate of densely sintered zirconia FDPs was 90.4% (95% CI: 84.8-94.0%) in 5 years of function. Even though the survival rate of all-ceramic FDPs was lower than for metal-ceramic FDPs, the differences did not reach statistical significance except for the glass-infiltrated alumina FDPs (p=0.05). A significantly higher incidence of caries in abutment teeth was observed for densely sintered zirconia FDPs compared to metal-ceramic FDPs. Significantly more framework fractures were reported for reinforced glass ceramic FDPs (8.0%) and glass-infiltrated alumina FDPs (12.9%) compared to metal-ceramic FDPs (0.6%) and densely sintered zirconia FDPs (1.9%) in 5 years in function. However, the incidence of ceramic fractures and loss of retention was significantly (p=0.018 and 0.028 respectively) higher for densely sintered zirconia FDPs compared to all other types of FDPs. Survival rates of all

  13. Effect of ZnO Nanoparticles on the Sintering Behavior and Physical Properties of Bi0.5(Na0.8K0.2)0.5TiO3 Lead-Free Ceramics

    Science.gov (United States)

    Vuong, Le Dai; Truong-Tho, Nguyen

    2017-11-01

    Sintered Bi0.5(Na0.8K0.2)0.5TiO3 + x wt.% ZnO nanoparticle (BNKT- xZnOn) ceramics have been fabricated by conventional annealing with the aid of ultrasound waves for preliminary milling. Because of the presence of the liquid Bi2O3-ZnO phase at the eutectic point of 738°C, the sintering temperature decreased from 1150°C to 1000°C, and the morphology phase boundary of BNKT- xZnOn ceramics can be clarified by two separated peaks at (002)T and (200)T of 2 θ in the x-ray diffraction (XRD) patterns. The improvement of ferroelectric properties has been obtained for BNZT-0.2 wt.% ZnOn ceramics by the increase of remanent polarization up to 20.4 μC/cm2 and a decrease of electric coercive field down to 14.2 kV/cm. The piezoelectric parameters of the ceramic included a piezoelectric charge constant of d 31 = 78 pC/N; electromechanical coupling factors k p = 0.31 and k t = 0.34, larger than the values of 42 pC/N, 0.12 and 0.13, respectively, were obtained for the BNKT ceramics.

  14. Homogeneity of Gd-based garnet transparent ceramic scintillators for gamma spectroscopy

    Science.gov (United States)

    Seeley, Z. M.; Cherepy, N. J.; Payne, S. A.

    2013-09-01

    Transparent polycrystalline ceramic scintillators based on the composition Gd1.49Y1.49Ce0.02Ga2.2Al2.8O12 are being developed for gamma spectroscopy detectors. Scintillator light yield and energy resolution depend on the details of various processing steps, including powder calcination, green body formation, and sintering atmosphere. We have found that gallium sublimation during vacuum sintering creates compositional gradients in the ceramic and can degrade the energy resolution. While sintering in oxygen produces ceramics with uniform composition and little afterglow, light yields are reduced, compared to vacuum sintering. By controlling the atmosphere during the various process steps, we were able to minimize the gallium sublimation, resulting in a more homogeneous composition and improved gamma spectroscopy performance.

  15. Powder densification maps in Selective Laser Sintering

    International Nuclear Information System (INIS)

    Bourell, D.; Wohlert, M.; Harlan, N.; Beaman, J.; Das, S.

    2002-01-01

    Selective Laser Sintering (SLS) is a manufacturing process in which a part is produced without the need for part-specific tooling. It competes effectively with other manufacturing processes when part geometry is complex and the production run is not large. Traditionally, this was limited to prototype production, although tooling applications are now appearing. This paper describes several applications of powder densification maps to advance solutions in direct SLS of metallic and ceramic powders. Time-dependent plasticity issues arise in pre-processing of powder to make it suitable for SLS and in post-processing of SLS parts to obtain desired density. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  16. Wear Behavior of Cold Pressed and Sintered Al2O3/TiC/CaF2Al2O3/TiC Laminated Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    Xuefeng YANG; Jian CHENG; Peilong SONG; Shouren WANG; Liying YANG; Yanjun WANG; Ken MAO

    2013-01-01

    A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance,such as low friction coefficient and low wear rate.Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure.Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear.Al2O3/TiC ceramic was also cold pressed and sintered for comparison.Friction analysis of the two ceramics was then conducted via a wear-and-tear machine.Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum,respectively.Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite.Under the friction load,the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits.This process formed a smooth,self-lubricating film,which led to better anti-wear properties.Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

  17. Concentrated solar energy used for sintering magnesium titanates for electronic applications

    Science.gov (United States)

    Apostol, Irina; Rodríguez, Jose; Cañadas, Inmaculada; Galindo, Jose; Mendez, Senen Lanceros; de Abreu Martins, Pedro Libȃnio; Cunha, Luis; Saravanan, Kandasamy Venkata

    2018-04-01

    Solar energy is an important renewable source of energy with many advantages: it is unlimited, clean and free. The main objective of this work was to sinter magnesium titanate ceramics in a solar furnace using concentrated solar energy, which is a novel and original process. The direct conversion of solar power into high temperature makes this process simple, feasible and ecologically viable/environmentally sustainable. We performed the solar sintering experiments at Plataforma Solar de Almeria-CIEMAT, Spain. This process takes place in a vertical axis solar furnace (SF5-5 kW) hosting a mobile flat mirror heliostat, a fixed parabolic mirror concentrator, an attenuator and a test table the concentrator focus. We sintered (MgO)0.63(TiO2)0.37, (MgO)0.49(TiO2)0.51, (MgO)0.50(TiO2)0.50 ceramics samples in air at about 1100 °C for a duration of 16 min, 1 h, 2 h and 3 h in the solar furnace. The MgO/TiO2 ratio and the dwell time was varied in order to obtain phase pure MgTiO3 ceramic. We obtained a pure MgTiO3 geikielite phase by solar sintering of (MgO)0.63(TiO2)0.37 samples at 1100 °C (16 min-3 h). Samples of (MgO)0.63(TiO2)0.37, solar sintered at 1100 °C for 3 h, resulted in well-sintered, non-porous samples with good density (3.46 g/cm3). The sintered samples were analyzed by XRD for phase determination. The grain and surface morphology was observed using SEM. Electrical measurements were carried out on solar sintered samples. The effect of processing parameters on microstructure and dielectric properties were investigated and is presented.

  18. Sintering effect on material properties of electrochemical reactors used for removal of nitrogen oxides and soot particles emitted from diesel engines

    DEFF Research Database (Denmark)

    He, Zeming; Andersen, Kjeld Bøhm; Keel, Li

    2010-01-01

    In the present work, 12-layered electrochemical reactors (comprising five cells) with a novel configuration including supporting layer lanthanum strontium manganate (LSM)-yttria stabilised zirconia (YSZ), electrode layer LSM-gadolinia-doped cerium oxide (CGO) and electrolyte layer CGO were...... fabricated via the processes of slurry preparation, tape casting and lamination and sintering. The parameters of porosity, pore size, pore size distribution, shrinkage, flow rate of the sintered reactors and the electrical conductivities of the supporting layer and the electrode in the sintered reactors were...... characterised. The effect of sintering temperature on microstructures and properties of the sintered samples was discussed, and 1,250 °C was determined as the appropriate sintering temperature for reactor production based on the performance requirements for applications. Using the present ceramic processing...

  19. Microwave combustion and sintering without isostatic pressure

    International Nuclear Information System (INIS)

    Ebadian, M.A.

    1998-01-01

    In recent years interest has grown rapidly in the application of microwave energy to the processing of ceramics, composites, polymers, and other materials. Advances in the understanding of microwave/materials interactions will facilitate the production of new ceramic materials with superior mechanical properties. One application of particular interest is the use of microwave energy for the mobilization of uranium for subsequent redeposition. Phase III (FY98) will focus on the microwave assisted chemical vapor infiltration tests for mobilization and redeposition of radioactive species in the mixed sludge waste. Uranium hexachloride and uranium (IV) borohydride are volatile compounds for which the chemical vapor infiltration procedure might be developed for the separation of uranium. Microwave heating characterized by an inverse temperature profile within a preformed ceramic matrix will be utilized for CVI using a carrier gas. Matrix deposition is expected to commence from the inside of the sample where the highest temperature is present. The preform matrix materials, which include aluminosilicate based ceramics and silicon carbide based ceramics, are all amenable to extreme volume reduction, densification, and vitrification. Important parameters of microwave sintering such as frequency, power requirement, soaking temperature, and holding time will be investigated to optimize process conditions for the volatilization of uranyl species using a reactive carrier gas in a microwave chamber

  20. Sintering study in vertical fixed bed reactor for synthetic aggregate production; Estudo da sinterizacao em reator vertical de leito fixo para producao de agregado sintetico

    Energy Technology Data Exchange (ETDEWEB)

    Quaresma, D.S.; Neves, A.S.S.; Melo, A.O.; Pereira, L.F.S.; Bezerra, P.T.S.; Macedo, E.N.; Souza, J.A.S., E-mail: danysq@gmail.com [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Faculdade de Engenharia Quimica

    2017-04-15

    The synthetic aggregates are being employed in civil construction for the reduction of mineral extraction activities. Within this context, the recycling of industrial waste is the basis of the majority of processes to reduce the exploitation of mineral resources. In this work the sintering in a vertical fixed bed reactor for synthetic aggregate production using 20% pellets and 80% charcoal was studied. The pellets were prepared from a mixture containing clay, charcoal and fly ash. Two experiments varying the speed of air sucking were carried out. The material produced was analyzed by X-ray diffraction, scanning electron microscopy, measures of their ceramic properties, and particle size analysis. The results showed that the solid-state reactions, during the sintering process, were efficient and the produced material was classified as coarse lightweight aggregate. The process is interesting for the sintering of aggregates, and can be controlled by composition, particle size, temperature gradient and gaseous flow. (author)

  1. Fabrication of unglazed ceramic tile using dense structured sago waste and clay composite

    International Nuclear Information System (INIS)

    Aripin; S Tani; S Mitsudo; T Saito; T Idehara

    2010-01-01

    In Indonesia, the sago processing industry generates every year huge amount of sago waste, and converting this waste into a useful material is possible. In the present study, physical properties of dense structured sago waste and clay composite were investigated in order to study the feasibility of reuse this sample as raw material in the producing of ceramics. Firstly, the chemical composition of ash (obtained from the sago waste) and clay was characterized. The prepared sample was sintered at the temperature range from 800 to 1,200 °C using electric furnace. The density, linear shrinkage and water absorption of the sintered sample were determined by using the Archimedes' method. The experimental result indicated that the density of the sintered sample increased with increasing sintering temperature up to 1100°C and then slightly decreased afterward. The water absorption of the products decreased with an increase in sintering temperature. In the sintered sample at 1,100 °C, the water absorption decreased rapidly and water adsorption of less than 1 % was achieved. This water absorption was less than 5 % which was needed for unglazed floor tile. The result of water adsorption suggest that it is possible to use this sample as a raw material for producing the ceramic floor tile. (author)

  2. Modeling sintering of multilayers under influence of gravity

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Olevsky, Eugene; Tadesse Molla, Tesfaye

    2013-01-01

    , which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod-Olevsky viscous sintering framework, the classical...... laminate theory and the elastic-viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant. © 2012 The American Ceramic Society....

  3. Method of manufacture of single phase ceramic superconductors

    Science.gov (United States)

    Singh, Jitrenda P.; Poeppel, Roger B.; Goretta, Kenneth C.; Chen, Nan

    1995-01-01

    A ceramic superconductor is produced by close control of oxygen partial pressure during sintering of the material. The resulting microstructure of YBa.sub.2 Cu.sub.3 O.sub.x indicates that sintering kinetics are enhanced at reduced p(O.sub.2) and that because of second phase precipitates, grain growth is prevented. The density of specimens sintered at 910.degree. C. increased from 79 to 94% theoretical when p(O.sub.2) was decreased from 0.1 to 0.0001 MPa. The increase in density with decrease in p(O.sub.2) derives from enhanced sintering kinetics, due to increased defect concentration and decreased activation energy of the rate-controlling species undergoing diffusion. Sintering at 910.degree. C resulted in a fine-grain microstructure, with an average grain size of about 4 .mu.m. Post sintering annealing in a region of stability for the desired phase converts the second phases and limits grain growth. The method of pinning grain boundaries by small scale decompositive products and then annealing to convert its product to the desired phase can be used for other complex asides. Such a microstructure results in reduced microcracking, strengths as high as 230 MPa and high critical current density capacity.

  4. Boron Carbide: Stabilization of Highly-Loaded Aqueous Suspensions, Pressureless Sintering, and Room Temperature Injection Molding

    Science.gov (United States)

    Diaz-Cano, Andres

    Boron carbide (B4C) is the third hardest material after diamond and cubic boron nitride. It's unique combination of properties makes B4C a highly valuable material. With hardness values around 35 MPa, a high melting point, 2450°C, density of 2.52 g/cm3, and high chemical inertness, boron carbide is used in severe wear components, like cutting tools and sandblasting nozzles, nuclear reactors' control rots, and finally and most common application, armor. Production of complex-shaped ceramic component is complex and represents many challenges. Present research presents a new and novel approach to produce complex-shaped B4C components. Proposed approach allows forming to be done at room temperatures and under very low forming pressures. Additives and binder concentrations are kept as low as possible, around 5Vol%, while ceramics loadings are maximized above 50Vol%. Given that proposed approach uses water as the main solvent, pieces drying is simple and environmentally safe. Optimized formulation allows rheological properties to be tailored and adjust to multiple processing approaches, including, injection molding, casting, and additive manufacturing. Boron carbide samples then were pressureless sintered. Due to the high covalent character of boron carbide, multiples sintering aids and techniques have been proposed in order to achieve high levels of densification. However, is not possible to define a clear sintering methodology based on literature. Thus, present research developed a comprehensive study on the effect of multiple sintering aids on the densification of boron carbide when pressureless sintered. Relative densities above 90% were achieved with values above 30MPa in hardness. Current research allows extending the uses and application of boron carbide, and other ceramic systems, by providing a new approach to produce complex-shaped components with competitive properties.

  5. Preparation and Characterization of TiB2-(Supra-Nano-Dual-Phase High-Entropy Alloy Cermet by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Shulei Zhang

    2018-01-01

    Full Text Available This paper introduces the preparation method and characterization results of TiB2 ceramics with CoCrFeNiAl high-entropy alloy (HEA as a sintering aid by Spark Plasma Sintering (SPS. Good wettability between HEA and TiB2 was proved by the sessile drop method, indicating promising prospects for this composite. The sintering results showed that the addition of HEA could dramatically promote the sinterability of TiB2. TiB2-5 wt. % HEA dense ceramics prepared at the optimal temperature of 1650 °C showed fine morphology without formation of brittle phases. The liquid phase in the ceramics was highly consistent with the so-called “supra-nano-dual-phase materials (SNDPM”, with near-ideal strength. This study represents the first time that a ceramic-SNDPM composite has been fabricated since the invention of such structures.

  6. Preparation of novel ceramics with high CaO content from steel slag

    International Nuclear Information System (INIS)

    Zhao, Lihua; Li, Yu; Zhou, Yuanyuan; Cang, Daqiang

    2014-01-01

    Highlights: • Efficiently utilize such solid waste with high CaO content. • A novel ceramics was put forward by traditional ceramic process. • The novel ceramics attained high strength. • Sintering mechanisms of the novel ceramics were discussed. - Abstract: Steel slag, an industrial waste discharged from steelmaking process, cannot be extensively used in traditional aluminosilicate based ceramics manufacturing for its high content of calcium oxide. In order to efficiently utilize such solid waste, a method of preparing ceramics with high CaO content was put forward. In this paper, steel slag in combination with quartz, talcum, clay and feldspar was converted to a novel ceramic by traditional ceramic process. The sintering mechanism, microstructure and performances were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) techniques, combined experimenting of linear shrinkage, water absorption and flexural strength. The results revealed that all crystal phases in the novel ceramic were pyroxene group minerals, including diopsite ferrian, augite and diopsite. Almost all raw materials including quartz joined the reaction and transformed into pyroxene or glass phase in the sintering process, and different kinds of clays and feldspars had no impact on the final crystal phases. Flexural strength of the ceramic containing 40 wt.% steel slag in raw materials can reach 143 MPa at sintering temperature of 1210 °C and its corresponding water absorption, weight loss, linear shrinkage were 0.02%, 8.8%, 6.0% respectively. Pyroxene group minerals in ceramics would contribute to the excellent physical and mechanical properties

  7. Effect of the application of surface treatments before and after sintering on the flexural strength, phase transformation and surface topography of zirconia.

    Science.gov (United States)

    Kurtulmus-Yilmaz, Sevcan; Aktore, Huseyin

    2018-05-01

    To evaluate the effects of airborne-particle abrasion (APA) and Er,Cr:YSGG laser irradiation on 4-point-flexural strength, phase transformation and morphologic changes of zirconia ceramics treated at pre-sintered or post-sintered stage. Three hundred and forty-two bar shaped zirconia specimens were milled with different sizes according to the flexural strength test (n = 10), X-ray diffraction (XRD) (n = 4) and field emission scanning electron microscope (FE-SEM) (n = 4) analyses. For each test protocol, specimens were divided into 4 main groups whether the surface treatments applied before or after sintering and whether the specimens received heat treatment or not as pre-sintered, post-sintered no-heat and post-sintered heat-treated groups, and a group was served as control. Main groups were further divided into 6 equal subgroups according to surface treatment method applied (2 W-, 3 W-, 4 W-, 5 W-, 6 W-laser irradiations and APA). Surface treatments were applied to pre-sintered groups before sintering and to post-sintered groups after sintering. Post-sintered heat-treated groups were subjected to veneer ceramic firing simulation after surface treatments. Flexural strength and flexural modulus values were statistically analysed and monoclinic phase content was calculated. Weibull analysis was used to evaluate strength reliability and fractographic analysis was conducted. Highest flexural strength values were detected at post-sintered no-heat APA and 4W-laser groups (P SEM images pre-sintered groups. Application of surface treatments at pre-sintered stage may be detrimental for zirconia ceramics in terms of flexural strength. Treating the surface of zirconia ceramic before sintering process is not recommended due to significant decrease in flexural strength values. 2 W-4 W Er,Cr:YSGG laser irradiations can be regarded as alternative surface treatment methods when zirconia restoration would be subjected to veneer ceramic firing procedures

  8. Improvement of conditions for ceramics sintering on the base of lead zirconate-titanate

    International Nuclear Information System (INIS)

    Glinchuk, M.D.; Kim, P.V.; Bykov, I.P.; Lyashchenko, A.B.

    1989-01-01

    Lead zirconate-titanate powders of different graininess are studied for their phase composition. The finest grains of the powder consist of lead zirconate-titanate with the rhombohedral structure. Grains of 3-5 μm size are a mixture of lead zirconate-titanate and lead titanate, the latter exceeding 50% (by weight) causes the effect of anomalous expansion in the process of sintering. Control of the technological parameters of the synthesis permits producing powder with favourable correlation of the above phases and grain sizes. Sintering of such a powder induces no effect of the anomalous expansion with an increased density of the product attained

  9. Densification of silicon and zirconium carbides by a new process: spark plasma sintering; Densification des carbures de silicium et de zirconium par un procede innovant: le spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Guillard, F

    2006-12-15

    Materials research for suitable utilization in 4. generation nuclear plants needs new ways to densify testing components. Two carbides, silicon and zirconium carbide seems to be the most suitable choice due to their mechanical, thermal and neutron-transparency properties against next nuclear plant specifications. Nevertheless one main difficulty remains, which is densifying them even at high temperature. Spark Plasma Sintering a new metal-, ceramic- and composite-sintering process has been used to densify both SiC and ZrC. Understanding bases of mass transport mechanisms in SPS have been studied. Composites and interfaces have been processed and analyzed. This manuscript reports original results on SiC and ZrC ceramics sintered with commercial powder started, without additives. (author)

  10. Fabrication and testing of ceramic UO{sub 2} fuel - I-III. Part II, Fabrication of sintered pressed samples UO{sub 2} (Final report); Izrada i ispitivanje keramickog goriva na bazi UO{sub 2}- I-III, II Deo - Dobijanje sinterovanih ispresaka UO{sub 2} (zavrsni izvestaj)

    Energy Technology Data Exchange (ETDEWEB)

    Novakovic, M; Ristic, M M [Institute of Nuclear Sciences Boris Kidric, Laboratorija za termotehniku reaktora, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    Procedure for fabrication of sintered ceramic UO{sub 2} pellets was developed in the Department of reactor materials. The tasks described in this report deal with design and construction of laboratory equipment for treatment of ceramic materials, and fabrication of UO{sub 2} pellets. The procedure was based on cold pressing of appropriately prepared powder and sintering of the of thus obtained pressed samples.

  11. Effect of calcium fluoride on sintering behaviour of SiO2-CaO-Na2O-MgO glass-ceramic system

    Directory of Open Access Journals (Sweden)

    Bahman Mirhadi

    2012-09-01

    Full Text Available The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM system containing calcium fluoride (CaF2 have been investigated by differential thermal analysis (DTA, X-ray diffraction (XRD and scanning electron microscopy (SEM. The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 °C.

  12. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

    Full Text Available Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.

  13. Ceramic Laser Materials

    Science.gov (United States)

    Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

    2012-01-01

    Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

  14. Wettability of zirconium diboride ceramics by Ag, Cu and their alloys with Zr

    International Nuclear Information System (INIS)

    Muolo, M.L.; Ferrera, E.; Novakovic, R.; Passerone, A.

    2003-01-01

    Sintered ZrB 2 ceramics, pure and with 4 wt.% Ni as sintering aid, have been tested in contact with liquid Ag, Cu, Ag-Cu and Ag-Cu-Zr. ''Pure'' ZrB 2 ceramics are wetted by Ag-Zr alloys, and ZrB 2 /Ni ceramics also by pure Cu. The wetting behaviour is briefly discussed in terms of existing wetting theories

  15. High temperature resistant cermet and ceramic compositions

    Science.gov (United States)

    Phillips, W. M. (Inventor)

    1978-01-01

    Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

  16. Processing of porous zirconia ceramics by direct consolidation with starch

    International Nuclear Information System (INIS)

    Garrido, Liliana B; Albano, Maria P

    2008-01-01

    Porous ceramics are used especially for those environments with high temperatures, heavy wear and in a corrosive medium. Zirconium-based materials are useful for such applications as sensors, filters, support for catalytic reactions, porous components for sofc and in biomedical applications. A conventional method for producing porous ceramics consists of the addition and later decomposition by calcination (pyrolisis) of different organic materials that act as pore formers. Several wet processing possibilities have been developed. Among these is a technique of direct consolidation with starch. This process begins with the preparation of an aqueous suspension of the ceramic with the dispersants needed to stabilize it, to which the starch is added. After casting in a waterproof mold, the suspension thermally hardens into the desired shape. The dry compacts undergo the sintering cycle to obtain pieces almost in their final form. This study aims to optimize the processing of porous zirconium ceramics using starch as a pore and binder forming agent. Zirconium with 3% yttrium molar stabilized in tetragonal phase was used. The aqueous suspensions (52-55% vol) of the zirconium-starch mixtures with different compositions were stabilized with a commercial solution of ammonium polyacrylate as a dispersant and were hardened in plastic molds at 90 o C for 30 min. The influence of added volume of starch on the physical characteristics of the pieces in green state was established while maintaining the temperature, the gelling time and the conditions of constant drying. The sintering was carried out at 1000-1500 o C-2h. The characteristics of the sintered product were evaluated by measuring density, volumetric contraction, intrusion of Hg and the evolution of the crystalline phases by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microstructural properties of ceramic (pore volume, the relation between open and closed porosity, size distribution, morphology of

  17. Production of mullite-zirconia ceramics composites by 'In situ' reaction

    International Nuclear Information System (INIS)

    Melo, F.C.L. de; Cairo, C.A.A.; Piorino Neto, F.; Devezas, T.C.

    1987-01-01

    Mullita-zirconia ceramic composites were produced by 'In situ' reaction of alumina and brazilian zircon. The ideal curve of thermal treatment (reaction + sinterization) was determined for the obtention of composites of maximum mechanical resistence. The retained fraction of tetragonal fase was evaluated by X-ray difraction and correlated with the values of mechanical resistence obtained by different treatment curves. The performance of the developed composites under corrosion and thermal shock was evaluated by glass casting. (Author) [pt

  18. Powder addition assessment of manganese residue ceramic matrix coating

    International Nuclear Information System (INIS)

    Conceicao, A.C.R. da; Santos, O.C.; Leao, M.A.

    2016-01-01

    The use of recycled materials in the composition of new products follows the production's worldwide trending, meeting new technological requirements and environmental concerns. This work aims to utilize the residue of manganese dust on ceramic mass for the production of ceramic coating. The raw materials were characterized by both x-ray fluorescence and diffraction. The powder residue added to clay in the percentage of 0%, 5%, 10% and 15% (measured in weight) was compressed by a uniaxial pressing of 30MPa and the sintering temperatures were 900°, 1000° and 1100°. The samples were analysed in relation to flexural strength, bulk density, water absorption and linear shrinkage. The microstructural variation was also analysed by x-ray diffraction and electron microscopy. The results showed that there is a viability for the production of porcelain ceramic coating (A3 and A4 formulations) and stoneware (A2 formulation) according to the specification of technical standards. author)

  19. Initial results of a high-power microwave sintering experiment at ORNL

    International Nuclear Information System (INIS)

    Kimrey, H.D.; White, T.L.; Bigelow, T.S.; Becher, P.F.

    1986-01-01

    Experiments have recently begun at Oak Ridge National Laboratory to develop microwave sintering techniques suitable for large ceramic parts. Microwave sintering offers the advantages of faster heating rates, more uniform heating, and greater energy efficiency than conventional sintering techniques. We are using 28-GHz, 200-kW cw gyrotrons as the heating source. An untuned cavity is used as the applicator to eliminate geometry sensitivity in coupling efficiency

  20. Prediction of thermal fatigue life of ceramics

    International Nuclear Information System (INIS)

    Kamiya, N.; Kamigaito, O.

    1979-01-01

    On the assumption that the thermal fatigue life of ceramics is determined mainly by the duration over which a crack reaches a small critical length, a prediction of the life was made by application of fracture mechanics to ceramics based on subcritical crack growth. Approximated formulae were derived. Experimental examination showed that the formulae proved to be valid for glass, sintered mullite under moderate shock severity, and zirconia. Data given by other authors also prove their validity. The deviation of the life from the formulae for sintered mullite under a thermal shock of extremely low severty, suggests that a certain mechanism, for example strengthening, is needed to understand the life of the sintered mullite. (author)

  1. Remedial processing of oil shale fly ash (OSFA) and its value-added conversion into glass-ceramics.

    Science.gov (United States)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin

    2015-12-01

    Recently, various solid wastes such as sewage sludge, coal fly ash and slag have been recycled into various products such as sintered bricks, ceramics and cement concrete. Application of these recycling approaches is much better and greener than conventional landfills since it can solve the problems of storage of industrial wastes and reduce exploration of natural resources for construction materials to protect the environment. Therefore, in this study, an attempt was made to recycle oil shale fly ash (OSFA), a by-product obtained from the extracting of shale oil in the oil shale industry, into a value-added glass-ceramic material via melting and sintering method. The influence of basicity (CaO/SiO2 ratio) by adding calcium oxide on the performance of glass-ceramics was studied in terms of phase transformation, mechanical properties, chemical resistances and heavy metals leaching tests. Crystallization kinetics results showed that the increase of basicity reduced the activation energies of crystallization but did not change the crystallization mechanism. When increasing the basicity from 0.2 to 0.5, the densification of sintering body was enhanced due to the promotion of viscous flow of glass powders, and therefore the compression strength and bending strength of glass-ceramics were increased. Heavy metals leaching results indicated that the produced OSFA-based glass-ceramics could be taken as non-hazardous materials. The maximum mechanical properties of compression strength of 186 ± 3 MPa, bending strength of 78 ± 6 MPa, good chemical resistances and low heavy metals leaching concentrations showed that it could be used as a substitute material for construction applications. The proposed approach will be one of the potential sustainable solutions in reducing the storage of oil shale fly ash as well as converting it into a value-added product. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Development of microstructure during sintering and aluminium exposure of titanium diboride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Gunnar

    1997-12-31

    In the production of aluminium, much less energy need be consumed if an inert, wetted cathode is present in the electrolysis cell. Titanium diboride, TiB{sub 2}, is easily wetted and does not readily dissolve in liquid aluminium, but it degrades, probably because aluminium penetrates into it during electrolysis. This degradation is linked to impurities present in the TiB{sub 2} after sintering. This thesis studies the sintering process and how aluminium penetrates into the material. High-purity, high-density TiB{sub 2} compacts were made by hot pressing at 50 MPa in an argon atmosphere at 1790-1960 {sup o}C. Samples were made with different impurity additions. These samples were exposed to liquid aluminium at 980 {sup o}C for 24 hours. All samples were penetrated, but the amount and appearance depended on the sintering aid used. Unlike the other samples, pure TiB{sub 2} was easily penetrated by metallic aluminium because of the open porosity and microcracks of this material. Grain boundary penetration was common among the samples. Differences in penetration behaviour between grain boundaries are probably due to differences in grain boundary energy. But no relation to segregants or boundary misorientation was found. The orientation of grain boundary planes and de-wetting of thin films upon cooling may explain the observed microstructure development. The samples sintered with Ti addition suffered extensive penetration despite their high densities. The grain boundaries of these samples became faceted and contained thicker films of metallic aluminium, presumably because of increased solubility due to iron segregations. All secondary phases present in the grain junctions after sintering, except from the B{sub 4}C phase, reacted with the penetrated aluminium. This did not cause swelling and cracking, as has been suggested by other authors. 101 refs., 48 figs., 7 tabs.

  3. The energy consumption in the ceramic tile industry in Brazil

    International Nuclear Information System (INIS)

    Ciacco, Eduardo F.S.; Rocha, Jose R.; Coutinho, Aparecido R.

    2017-01-01

    The ceramic industry occupies a prominent place in the Brazilian industrial context, representing about 1.0% in the GDP composition. On the other hand, it represent about 1.9% of all energy consumed in the country, and 5.8% of the energy consumed in the Brazilian industrial sector in 2014. Regarding the power consumption by the ceramic industry, most is derived from renewable sources (firewood), followed by use of fossil fuels, mainly natural gas (NG). This study was conducted to quantify the energy consumption in the production of ceramic tiles (CT), by means of experimental data obtained directly in the industry and at every step of the manufacturing process. The step of firing and sintering has the highest energy consumption, with approximately 56% of the total energy consumed. In sequence, have the atomization steps with 30% and the drying with 14%, of total energy consumption in the production of ceramic tiles, arising from the use of NG. In addition, it showed that the production of ceramic tiles by wet process has energy consumption four times the dry production process, due to the atomization step.

  4. Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

    Science.gov (United States)

    Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

    2016-01-01

    The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

  5. Permittivity and performance of dielectric pads with sintered ceramic beads in MRI: early experiments and simulations at 3 T.

    Science.gov (United States)

    Luo, Wei; Lanagan, Michael T; Sica, Christopher T; Ryu, Yeunchul; Oh, Sukhoon; Ketterman, Matthew; Yang, Qing X; Collins, Christopher M

    2013-07-01

    Passive dielectric materials have been used to improve aspects of MRI by affecting the distribution of radiofrequency electromagnetic fields. Recently, interest in such materials has increased with the number of high-field MRI sites. Here, we introduce a new material composed of sintered high-permittivity ceramic beads in deuterated water. This arrangement maintains the ability to create flexible pads for conforming to individual subjects. The properties of the material are measured and the performance of the material is compared to previously used materials in both simulation and experiment at 3 T. Results show that both permittivity of the beads and effect on signal-to-noise ratio and required transmit power in MRI are greater than those of materials consisting of ceramic powder in water. Importantly, use of beads results in both higher permittivity and lower conductivity than use of powder. Copyright © 2012 Wiley Periodicals, Inc.

  6. Recycling of the reduction sludge of manganese in the production of ceramics; Reciclagem da lama de reducao de manganes na producao de ceramicas vermelhas

    Energy Technology Data Exchange (ETDEWEB)

    Castro, C.G.; Araujo, F.G.S., E-mail: camilac46@gmail.com [Universidade Federal de Ouro Preto (REDEMAT/UFOP), MG (Brazil); Kruger, F.L. [Fundacao Gorceix (DEPEC), Ouro Preto, MG (Brazil). Departamento de Pesquisa e de Educacao Continuada; Jannotti Junior, N. [Vale Manganes, Ouro Preto, MG (Brazil)

    2011-07-01

    To study the use of manganese reduction residues, from the electric arc furnaces for the production of manganese ferro-alloys, as raw materials for construction bricks, different ceramic compositions were formulated with contents of 0, 2.5, 5 and 10wt% of waste addition to the clay used commercially, and sintered at different temperatures, 850, 950 and 1050°C. After firing, the ceramic samples were studied by optical microscopy, scanning electron microscopy (SEM), x-ray diffraction and by spectrophotometry. Their mechanical properties were evaluated by flexural strength, apparent porosity and specific mass, water absorption, linear shrinkage and loss on ignition. With the help of technics and experiment planning programs, the effects of the variables: temperature, composition and interaction between them over the results were discussed. This work proved that the addition of manganese reduction sludge to the clay, for the production of ceramic construction bricks, is highly feasible, from a technical standpoint. (author)

  7. Densification of silicon and zirconium carbides by a new process: spark plasma sintering

    International Nuclear Information System (INIS)

    Guillard, F.

    2006-12-01

    Materials research for suitable utilization in 4. generation nuclear plants needs new ways to densify testing components. Two carbides, silicon and zirconium carbide seems to be the most suitable choice due to their mechanical, thermal and neutron-transparency properties against next nuclear plant specifications. Nevertheless one main difficulty remains, which is densifying them even at high temperature. Spark Plasma Sintering a new metal-, ceramic- and composite-sintering process has been used to densify both SiC and ZrC. Understanding bases of mass transport mechanisms in SPS have been studied. Composites and interfaces have been processed and analyzed. This manuscript reports original results on SiC and ZrC ceramics sintered with commercial powder started, without additives. (author)

  8. Glass-ceramics: Their production from wastes - a review

    Energy Technology Data Exchange (ETDEWEB)

    Rawlings, R.D.; Wu, J.P.; Boccaccini, A.R. [University of London, London (United Kingdom). Imperial College of Science & Technology, Dept. of Medicine

    2006-02-15

    Glass-ceramics are polycrystalline materials of fine microstructure that are produced by the controlled crystallisation (devitrification) of a glass. Numerous silicate based wastes, such as coal combustion ash, slag from steel production, fly ash and filter dusts from waste incinerators, mud from metal hydrometallurgy, different types of sludge as well as glass cullet or mixtures of them have been considered for the production of glass-ceramics. Developments of glass-ceramics from waste using different processing methods are described comprehensively in this review, covering R&D work carried out worldwide in the last 40 years. Properties and applications of the different glass-ceramics produced are discussed. The review reveals that considerable knowledge and expertise has been accumulated on the process of transformation of silicate waste into useful glass-ceramic products. These glass-ceramics are attractive as building materials for usage as construction and architectural components or for other specialised technical applications requiring a combination of suitable thermo-mechanical properties. Previous attempts to commercialise glass-ceramics from waste and to scale-up production for industrial exploitation are also discussed.

  9. Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring

    Directory of Open Access Journals (Sweden)

    V.A. Izhevskyi

    2000-10-01

    Full Text Available Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of alpha- and beta-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. % were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from beta-SiC to alpha-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.

  10. Effect of bioglass additions on the sintering of Y-TZP bioceramics

    Energy Technology Data Exchange (ETDEWEB)

    Habibe, A.F.; Maeda, L.D.; Souza, R.C.; Barboza, M.J.R.; Daguano, J.K.M.F. [USP-EEL, Universidade de Sao Paulo, Escola de Engenharia de Lorena, Polo Urbo-Industrial, Gleba AI6, s/n, P.O. Box 116, CEP 12600-970, Lorena-SP (Brazil); Rogero, S.O. [IPEN/CNEN-SP, Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes, 2242, Sao Paulo-SP, CEP 05508-900 (Brazil); Santos, C., E-mail: claudinei@demar.eel.usp.br [USP-EEL, Universidade de Sao Paulo, Escola de Engenharia de Lorena, Polo Urbo-Industrial, Gleba AI6, s/n, P.O. Box 116, CEP 12600-970, Lorena-SP (Brazil)

    2009-08-01

    The objective of this work was to evaluate the influence of bioglass additions on the sintering and mechanical properties of yttria-stabilized zirconia ceramics, Y-TZP. Samples containing different bioglass additions, varying between 0 and 30 wt.%, were cold uniaxial pressed at 80 MPa and sintered in air at 1200 deg. C or 1300 deg. C for 120 min. Sintered samples were characterized by X-ray Diffractometry and Scanning Electron Microscopy. Hardness and fracture toughness were determined using Vickers indentation method. As a preliminary biological evaluation, in vitro cytotoxicity tests by Neutral Red Uptake method (using mouse connective tissue cells, NCTC clone L929 from ATCC bank) were realized to determine the cytotoxicity level of ZrO{sub 2}-bioglass ceramics. The increasing of bioglass amount leads to the decreasing of relative density due to martensitic (tetragonal-monoclinic) transformation during cooling of the sintered samples. Y-TZP samples sintered at 1300 deg. C containing 5 wt.% of bioglass presented the best results, with high relative density, hardness and fracture toughness of 11.3 GPa and 6.1 MPa m{sup 1/2}, respectively. Furthermore, the un-cytotoxic behavior was observed in all sintering conditions and bioglass amounts used in this study.

  11. PRODUCTION OF PROTOTYPE PARTS USING DIRECT METAL LASER SINTERING TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    Josef Sedlak

    2015-08-01

    Full Text Available Unconventional methods of modern materials preparation include additive technologies which involve the sintering of powders of different chemical composition, granularity, physical, chemical and other utility properties. The technology called Rapid Prototyping, which uses different technological principles of producing components, belongs to this type of material preparation. The Rapid Prototyping technology facilities use photopolymers, thermoplastics, specially treated paper or metal powders. The advantage is the direct production of metal parts from input data and the fact that there is no need for the production of special tools (moulds, press tools, etc.. Unused powder from sintering technologies is re-used for production 98% of the time, which means that the process is economical, as well as ecological.The present paper discusses the technology of Direct Metal Laser Sintering (DMLS, which falls into the group of additive technologies of Rapid Prototyping (RP. The major objective is a detailed description of DMLS, pointing out the benefits it offers and its application in practice. The practical part describes the production and provides an economic comparison of several prototype parts that were designed for testing in the automotive industry.

  12. Sintering of uranium dioxide obtained by continuous precipitation of AUC

    International Nuclear Information System (INIS)

    Amaya, C.D.; Sterba, M.E.; Russo, D.O.

    1993-01-01

    The Nuclear Materials Division in Bariloche Atomic Center evaluates the ceramic behaviour of UO 2 powders obtained from continuously precipitated and reduced AUC (Ammonium Uranyl Tri Carbonate). An analysis is made of powder characteristics (particle morphology and size distribution and specific area) on behaviour of UO 2 during sintering (compaction, sintering, pore and grain microstructure, etc.). 1 ref

  13. Industrial ceramics - Properties, forming and applications

    International Nuclear Information System (INIS)

    Fantozzi, Gilbert; Niepce, Jean-Claude; Bonnefont, Guillaume; Alary, J.A.; Allard, B.; Ayral, A.; Bassat, J.M.; Elissalde, C.; Maglione, M.; Beauvy, M.; Bertrand, G.; Bignon, A.; Billieres, D.; Blanc, J.J.; Blumenfeld, P.; Bonnet, J.P.; Bougoin, M.; Bourgeon, M.; Boussuge, M.; Thorel, A.; Bruzek, C.E.; Cambier, F.; Carrerot, H.; Casabonne, J.M.; Chaix, J.M.; Chevalier, J.; Chopinet, M.H.; Couque, H.; Courtois, C.; Leriche, A.; Dhaler, D.; Denape, J.; Euzen, P.; Ganne, J.P.; Gauffinet, S.; Girard, A.; Gonon, M.; Guizard, C.; Hampshire, S.; Joulin, J.P.; Julbe, A.; Ferrato, M.; Fontaine, M.L.; Lebourgeois, R.; Lopez, J.; Maquet, M.; Marinel, S.; Marrony, M.; Martin, J.F.; Mougin, J.; Pailler, R.; Pate, M.; Petitpas, E.; Pijolat, C.; Pires-Franco, P.; Poirier, C.; Poirier, J.; Pourcel, F.; Potier, A.; Tulliani, J.M.; Viricelle, J.P.; Beauger, A.

    2013-01-01

    After a general introduction to ceramics (definition, general properties, elaboration, applications, market data), this book address conventional ceramics (elaboration, material types), thermo-structural ceramics (oxide based ceramics, non-oxide ceramics, fields of application, functional coatings), refractory ceramics, long fibre and ceramic matrix composites, carbonaceous materials, ceramics used for filtration, catalysis and the environment, ceramics for biomedical applications, ceramics for electronics and electrical engineering (for capacitors, magnetic, piezoelectric, dielectric ceramics, ceramics for hyper-frequency resonators), electrochemical ceramics, transparent ceramics (forming and sintering), glasses, mineral binders. The last chapter addresses ceramics used in the nuclear energy sector: in nuclear fuels and fissile material, absorbing ceramics and shields, in the management of nuclear wastes, new ceramics for reactors under construction or for future nuclear energy

  14. Microwave sintering of cordierite ceramic precursors obtained by starch direct consolidation; Sinterizacion por microondas de precursores ceramicos de cordierita obtenidos por consolidacion directa con almidon

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval, M.L.; Talou, M.H.; Camerucci, M.A., E-mail: andcamer@fi.mdp.edu.a [Consejo Nacional de Investigaciones Cientificas e Tecnicas (INTEMA-CONICET-UNMdP), Mar del Plata (Argentina). Inst. de Investigaciones en Ciencia y Tecnologia de Materiales. Lab. de Materiales Estructurales; Universidad Nacional de Mar Del Plata (UNMdP) (Argentina). Fac. de Ingenieria; Souto, P.M. de; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (DEMa/UFScar), SP (Brazil). Dept. de Engenharia de Materiais

    2009-07-01

    Microwave sintering of cordierite disk precursors (mixture of kaolin, talc and alumina) with potato starch was studied. Green disks were obtained by thermal consolidation of stable aqueous suspensions of the ceramic powders (29.6 % vol.) with potato starch (11.5 % vol.) at 75 and 85 deg C, 4h; drying (50 deg C,12h) and calcination (650 deg C, 2h). The reaction-sintering by microwave heating (power: 2.45 GHz; heating rate: 50 deg C/min) at different temperatures (1250-1330 deg C) and dwell times (10-20 min) was carried out. For comparative purposes, the reaction-sintering by conventional heating was analyzed (1330 deg C, 4h a 3 deg C/min). The evolution of the phases as a function of temperature and time was studied by XRD analysis. The developed microstructures (dense or porous) were characterized by density and porosity measurements, and SEM. The obtained results were analyzed in relation to the characteristics of starch behavior in aqueous suspension at temperature and the employed consolidation and sintering conditions. (author)

  15. Scratch resistance of SiO2 and SiO2 - ZrO2 sol-gel coatings on glass-ceramic obtained by sintering

    International Nuclear Information System (INIS)

    Soares, V. O.; Soares, P.; Peitl, O.; Zanotto, E. D.; Duran, A.; Castro, Y.

    2013-01-01

    The sol-gel process is widely used to obtain coatings on glass-ceramic substrates in order to improve the scratch and abrasion resistance, also providing a bright and homogeneous appearance of a glaze avoiding expensive final polishing treatments. This paper describes the preparation of silica and silica / zirconia coatings by sol-gel method on Li 2 O-Al 2 O3-SiO 2 (LAS) glassceramic substrates produced by sintering. The coatings were deposited by dip-coating on LAS substrates and characterized by optical microscopy and spectral ellipsometry. On the other hand, hardness and elastic modulus, coefficient of friction and abrasion and scratch resistance of the coatings were determined and compared with the substrate properties. Coatings deposited on LAS glass-ceramic confere the substrate a bright and homogeneous aspect, similar to a glaze, improving the appearance and avoiding the final polishing. However these coatings do not increase the scratch resistance of the substrate only equaling the properties of the glass-ceramic. (Author)

  16. An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

    Science.gov (United States)

    Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

    2013-05-01

    The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

  17. Preparation of Biomorphic TiO2 Ceramics from Rattan Templates

    Directory of Open Access Journals (Sweden)

    Liangcun Qian

    2015-05-01

    Full Text Available In this work, biomorphic ceramics were produced from various rattan templates, and sol infiltration was used with vacuum/positive pressure technology. Finally, the samples were sintered to form TiO2 ceramics with a rattan microstructure. Through X-ray diffraction (XRD, thermogravimetric (TG data, dimensional variation analysis, and scanning electron microscopy (SEM images of biomorphic ceramics, the results of this experiment showed that the times of sol-gel infiltration were decreased due to use of the vacuum/positive pressure technology. In order to further supply the TiO2 content and fill the pyrolysis gaps in the charcoal/TiO2 composites sintered at 800 °C, it was necessary to repeat the sol-gel process. In the transverse section, ceramics for the rattan templates without the rattan edge, more perfect biomorphic features were achieved. Conversely, deformations occurred along the transverse section of the ceramics for the templates made with the rattan edge. Meanwhile, the fracture phenomenon took place along the ceramic axial section. The main reason for deformation and fracture was that the anisotropic structure of the template was stressed during the sintering process. Furthermore, the micrometer-sized pores were found in the ceramics along the axial section because of the removal of the charcoal templates.

  18. [Effect of compaction pressure on the properties of dental machinable zirconia ceramic].

    Science.gov (United States)

    Huang, Hui; Wei, Bin; Zhang, Fu-qiang; Sun, Jing; Gao, Lian

    2010-10-01

    To investigate the effect of compaction pressure on the linear shrinkage, sintering property and machinability of the dental zirconia ceramic. The nano-size zirconia powder was compacted at different isostatic pressure and sintered at different temperature. The linear shrinkage of sintered body was measured and the relative density was tested using the Archimedes method. The cylindrical surface of pre-sintering blanks was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. The sintering behaviour depended on the compaction pressure. Increasing compaction pressure led to higher sintering rate and lower sintering temperature. Increasing compaction pressure also led to decreasing linear shrinkage of the sintered bodies, from 24.54% of 50 MPa to 20.9% of 400 MPa. Compaction pressure showed only a weak influence on machinability of zirconia blanks, but the higher compaction pressure resulted in the poor surface quality. The better sintering property and machinability of dental zirconia ceramic is found for 200-300 MPa compaction pressure.

  19. Study of nano-metric silicon carbide powder sintering. Application to fibers processing

    International Nuclear Information System (INIS)

    Malinge, A.

    2011-01-01

    Silicon carbide ceramic matrix composites (SiCf/SiCm) are of interest for high temperature applications in aerospace or nuclear components for their relatively high thermal conductivity and low activation under neutron irradiation. While most of silicon carbide fibers are obtained through the pyrolysis of a poly-carbo-silane precursor, sintering of silicon carbide nano-powders seems to be a promising route to explore. For this reason, pressureless sintering of SiC has been studied. Following the identification of appropriate sintering aids for the densification, optimization of the microstructure has been achieved through (i) the analysis of the influence of operating parameters and (ii) the control of the SiC β a SiC α phase transition. Green fibers have been obtained by two different processes involving the extrusion of SiC powder dispersion in polymer solution or the coagulation of a water-soluble polymer containing ceramic particles. Sintering of these green fibers led to fibers of around fifty microns in diameter. (author) [fr

  20. Sintering behavior of porous wall tile bodies during fast single-firing process

    Directory of Open Access Journals (Sweden)

    Sidnei José Gomes Sousa

    2005-06-01

    Full Text Available In ceramic wall tile processing, fast single-firing cycles have been widely used. In this investigation a fast single-firing porous wall tile mixture was prepared using raw materials from the North Fluminense region.Specimens were obtained by uniaxial pressing and sintered in air at various temperatures (1080 - 1200 °C using a fast-firing cycle (60 minutes. Evolution of the microstructure was followed by XRD and SEM. The results revealed that the main phases formed during the sintering step are anorthite, gehlenite and hematite. It appears that the sintering process is characterized by the presence of a small amount of a liquid phase below 1140 °C. As a result, the microstructure of the ceramic bodies showed a network of small dense zones interconnected with a porous phase. In addition, the strength of the material below 1140 °C appeared to be related to the type and quantity of crystalline phases in the sintered bodies.

  1. Critical issues and future directions in sintering science

    International Nuclear Information System (INIS)

    Brook, R.J.; Tuan, W.H.; Xue, L.A.

    1988-01-01

    The quality of available powders and the emphasis on direct microstructural observation have continued to improve the value of sintering studies for the processing of ceramics. Future concerns will relate to mechanisms for the correction of microstructural inhomogeneity so that pressureless processing of composites can be reliably achieved and to more systematic exploitation of dopants (sintering additives). These themes are illustrated using examples from the processing of alumina composites and doped barium titanate compositions

  2. Effect of molar ratios of MgO/Al{sub 2}O{sub 3} on the sintering behavior and thermal shock resistance of MgOAl{sub 2}O{sub 3}SiO{sub 2} composite ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Dong, E-mail: 1078155409@qq.com [School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Luo, Xudong, E-mail: luoxudongs@aliyun.com [School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhang, Guodong [School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Xie, Zhipeng [Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-01-01

    In order to determine the relationship between the property of MgOAl{sub 2}O{sub 3}SiO{sub 2} composite ceramics and molar ratios of MgO/Al{sub 2}O{sub 3}, especially the sintering behavior and thermal shock resistance, the MgOAl{sub 2}O{sub 3}SiO{sub 2} composite ceramics were fabricated with micro-size MgO, Al{sub 2}O{sub 3} powder and nano-size SiO{sub 2} as main raw materials. The sample was characterized by phase analysis, densification and thermal shock times. Moreover, field emission scanning electron microscope was also conducted to study microstructure of the samples before and after thermal shock. Effect of different molar ratios of MgO/Al{sub 2}O{sub 3} on the sintering behavior and thermal shock resistance of composite ceramics were investigated. The results showed that the sample possess better sintering behavior and thermal shock resistance with the molar ratio of MgO/Al{sub 2}O{sub 3} equal to 2/1. Grains of periclase and spinel were directly bonded together, resulting in a dense and compact microstructure, and the bulk density of obtained sample reached 3.4 g/cm{sup 3}. The microstructure of sample after thermal shock revealed that the crack propagation path was deflected and bifurcated, the main-crack propagation was restricted and more fracture energy was consumed, the thermal shock resistance of composite ceramics was greatly improved. - Highlights: • Effect of MgO/Al{sub 2}O{sub 3} on the composite ceramic was firstly researched with 1 mol% SiO{sub 2}. • Microcracks for a short distance by interlinking can eliminate the crack propagation. • The composite ceramic have optimal synthetic property with MgO/Al{sub 2}O{sub 3} was 2/1.

  3. Sintering of cermets on the base of corundum and molybdenum

    International Nuclear Information System (INIS)

    Fedotov, A.V.

    1987-01-01

    Liquid-phase sintering of cermets has been studied to develop rational technology allowing to produce a dense material at lower temperatures. Molybdenum of the MPCh mark with the specific surface ranged from 1900 to 4000 cm 2 /g and the corundum powder of the VK-94-1 mark with the specific surface of 6000 cm 2 /g containing upto 10% of the glass-phase have been used as initial materials. It is shown that application of the VK-94-1 ceramics powder for molybdenum content cermets allows to decrease the temperature of dense material production (∼ upto 100 deg C). To produce dense materials, it is necessary to restrict the initial porosity of compaction and to correspond it to the sintering conditions. The increase of molybdenum dispersion allows to produce material with the more homogeneous structure, higher density and strength. Molybdenum presence decreases recrystallization of corundum crystals and causes structure production resistant to high-temperature heating

  4. Development of Advanced Ceramic Manufacturing Technology; FINAL

    International Nuclear Information System (INIS)

    Pujari, V.K.

    2001-01-01

    Advanced structural ceramics are enabling materials for new transportation engine systems that have the potential for significantly reducing energy consumption and pollution in automobiles and heavy vehicles. Ceramic component reliability and performance have been demonstrated in previous U.S. DOE initiatives, but high manufacturing cost was recognized as a major barrier to commercialization. Norton Advanced Ceramics (NAC), a division of Saint-Gobain Industrial Ceramics, Inc. (SGIC), was selected to perform a major Advanced Ceramics Manufacturing Technology (ACMT) Program. The overall objectives of NAC's program were to design, develop, and demonstrate advanced manufacturing technology for the production of ceramic exhaust valves for diesel engines. The specific objectives were (1) to reduce the manufacturing cost by an order of magnitude, (2) to develop and demonstrate process capability and reproducibility, and (3) to validate ceramic valve performance, durability, and reliability. I n order to achieve these objectives, NAC, a leading U.S. advanced ceramics component manufacturer, assembled a multidisciplinary, vertically integrated team. This team included: a major diesel engine builder, Detroit Diesel Corporation (DDC); a corporate ceramics research division, SGIC's Northboro R and D Center; intelligent processing system developers, BDM Federal/MATSYS; a furnace equipment company, Centorr/Vacuum Industries; a sintering expert, Wittmer Consultants; a production OEM, Deco-Grand; a wheel manufacturer and grinding operation developer, Norton Company's Higgins Grinding Technology Center (HGTC); a ceramic machine shop, Chand Kare Technical Ceramics; and a manufacturing cost consultant, IBIS Associates. The program was divided into four major tasks: Component Design and Specification, Component Manufacturing Technology Development, Inspection and Testing, and Process Demonstration

  5. Camber Evolution and Stress Development of Porous Ceramic Bilayers During Co-Firing

    DEFF Research Database (Denmark)

    Ni, De Wei; Esposito, Vincenzo; Schmidt, Cristine Grings

    2013-01-01

    sintering mismatch stress in co-fired CGO-LSM/CGO bilayer laminates was significantly lower than general sintering stresses expected for free sintering conditions. As a result, no co-firing defects were observed in the bilayer laminates, illustrating an acceptable sintering compatibility of the ceramic...

  6. High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

    Science.gov (United States)

    Exner, H.; Streek, A.

    2015-03-01

    Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

  7. Influence of sintering temperature on the characteristics of a-alumina filtration tubes

    International Nuclear Information System (INIS)

    Zarina Abdul Wahid; Rafindde Ramli; Andanastuti Muchtar; Abd Wahab Mohammad

    2005-01-01

    The emerging technology of ceramic membrane filters has created a lot of impact on the materials development and separation industries. Ceramic membrane filters have been used in many separation industry applications particularly in food, dairy, beverages, biotechnology, pharmaceutical and waste treatment industries. This is due to the fact that ceramics are inert and durable and can withstand high temperatures as well as extreme chemical conditions. They also have favourable mechanical properties and lower fouling rates. In this study, ceramic filtration tubes having dimensions of 10 mm outer diameter, 6 mm inner diameter and 880 mm long were prepared from a-alumina using the extrusion technique. The effects of sintering temperature on the pore size, microstructure and porosity of the alumina tube were investigated. The optimum sintering temperature was determined based on the performance of the tubes with regards to porosity, pore size and microstructure. The alumina tubes were sintered at six different temperatures i.e. 1250 degree C, 1300 degree C, 1350 degree C, 1400 degree C, 1450 degree C and 1500 degree C. The porous structures of the alumina tubes were studied using Scanning Electron Microscope (SEM) whereas a Mercury Porosimeter was used to determine the porosity and pore size distribution. (Author)

  8. Fractographical characterization of hot pressed and pressureless sintered AlN-doped ZrB{sub 2}–SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, Zohre [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Nayebi, Behzad [School of Materials and Metallurgy Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Young Researchers and Elite Club, Khorramabad Branch, Islamic Azad University, Khorramabad (Iran, Islamic Republic of); Shahedi Asl, Mehdi [Department of Mechanical Engineering, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Ghassemi Kakroudi, Mahdi, E-mail: mg_kakroudi@tabrizu.ac.ir [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2015-12-15

    In this paper, ZrB{sub 2}–SiC composites doped with 0–5 wt.% AlN were prepared by a low pressure hot pressing as well as a pressureless sintering methods at 1900 °C for 2 h. The influence of aluminum nitride addition on the sinterability and microstructure development of such ceramic composites was studied by a fractographical approach. The results revealed that only 1 wt.% AlN can aid the densification process of the hot pressed ceramic composite via the liquid phase sintering mechanism due to the formation of nano-scale metakaolinite spinel layers. In the pressureless sintering method, adding more AlN can increase the formation of gaseous products which raised the amount of porosities in the final microstructure. The formation of nano-graphite phase in the hot pressing process, the formation of Al{sub 2}OC in the pressureless sintering process, and the formation of BN in the both processes were disclosed by X-ray diffraction, SEM and TEM analyses. - Highlights: • The effect of AlN addition on densification of ZrB{sub 2}–SiC composites was studied. • AlN promotes the densification in hot pressed samples by liquid phase formation. • A fully dense composite was obtained by adding 1 wt.% AlN in hot pressing process. • In pressureless sintering, more AlN content intensifies the formation of porosities.

  9. Fiscal 1997 achievement report. Research and development of synergy ceramics; 1997 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Research and development is conducted on two subjects, that is, 1) hyper organized structure control technology and 2) structural element control technology. In addition, joint research and development is conducted on the creation of new materials by hyper organized structure controlling, hyper organized structure controlling for ceramics by a structurization reaction process, designing of precursors to ceramics, and the hyper organized structure control for ceramics by nanostructure process control. The joint research and development endeavors further deal with re-entrusted projects which involve researches on sintered structure control by powdery particulate structure control; dynamic process of synergy ceramics; oxynitride liquids, glasses, and glass-ceramics; and multifunctional ceramic laminates for engineering applications. Under subject 1), researches are made on the development of precursors into ceramics by utilizing chemical reactions of organic metal compounds, and analyses are conducted into the effects, exerted by the molecular structures of precursors and the conditions of a reaction for their development into ceramics, on the microstructures and various properties of the ceramics to be composed. Under subject 2), high strength, great hardness, and high resistance to wear are realized by allowing the precipitation of nano-particulates in crystals of a fine and very compact sintered body of alumina. (NEDO)

  10. Yb:Y2O3 transparent ceramics processed with hot isostatic pressing

    Science.gov (United States)

    Wang, Jun; Ma, Jie; Zhang, Jian; Liu, Peng; Luo, Dewei; Yin, Danlei; Tang, Dingyuan; Kong, Ling Bing

    2017-09-01

    Highly transparent 5 at.% Yb:Y2O3 ceramics were fabricated by using a combination method of vacuum sintering and hot isostatic pressing (HIP). Co-precipitated Yb:Y2O3 powders, with 1 at.% ZrO2 as the sintering aid, were used as the starting material. The Yb:Y2O3 ceramics, vacuum sintered at 1700 °C for 2 h and HIPed at 1775 °C for 4 h, exhibited small grain size of 1.9 μm and highly dense microstructure. In-line optical transmittance of the ceramics reached 83.4% and 78.9% at 2000 and 600 nm, respectively. As the ceramic slab was pumped by a fiber-coupled laser diode at about 940 nm, a maximum output power of 0.77 W at 1076 nm was achieved, with a corresponding slope efficiency of 10.6%.

  11. New materials through a variety of sintering methods

    Science.gov (United States)

    Jaworska, L.; Cyboroń, J.; Cygan, S.; Laszkiewicz-Łukasik, J.; Podsiadło, M.; Novak, P.; Holovenko, Y.

    2018-03-01

    New sintering techniques make it possible to obtain materials with special properties that are impossible to obtain by conventional sintering techniques. This issue is especially important for ceramic materials for application under extreme conditions. Following the tendency to limit critical materials in manufacturing processes, the use of W, Si, B, Co, Cr should be limited, also. One of the cheapest and widely available materials is aluminum oxide, which shows differences in phase composition, grain size, hardness, strain and fracture toughness of the same type of powder, sintered via various methods. In this paper the alumina was sintered using the conventional free sintering process, microwave sintering, Spark Plasma Sintering (SPS), high pressure-high temperature method (HP-HT) and High Pressure Spark Plasma Sintering (HP SPS). Phase composition analysis, by X-ray diffraction of the alumina materials sintered using various methods, was carried out. For the conventional sintering method, compacts are composed of α-Al2O3 and θ-Al2O3. For compacts sintered using SPS, microwave and HP-HT methods, χ-Al2O3 and γ-Al2O3 phases were additionally present. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. On the basis of images from scanning electron microscope quantitative analysis was performed to determine the degree of grain growth of alumina after sintering.

  12. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

    International Nuclear Information System (INIS)

    Duarte, Daniel Gomes

    2009-01-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

  13. Laser sintering of doped strontium aluminate via modified sol-gel for use as a ceramic pigment

    International Nuclear Information System (INIS)

    Soares, F.M. dos S.; Valerio, M.E.G.

    2017-01-01

    Powder of Dy"3"+ co-doped SrAl_2O_4 :Eu"3"+ was produced via proteic sol-gel method, a modified sol-gel route which allows the formation of oxides at lower temperatures than other methods. CO_2 laser sintering was used as a method for heat treatment, effective in reducing trivalent europium ions in doped samples. Thermal analysis of the precursors, performed by TG and DTA, revealed that the crystallization of SrAl_2O_4 phase occurred at approximately 1060 °C. X-ray diffraction showed that the samples, before and after sintering, had monoclinic and hexagonal phases formation. DLS technique revealed the presence of nanosized and micrometric particles, and particle agglomerates, confirmed by SEM images. Micrographs of the fracture surface of a sintered pellet revealed a high degree of densification caused by heat treatment. Photoluminescence measurements showed that the samples after synthesis and before heat treatment with laser had reddish emission, composed of characteristic narrow emission lines from Eu"3"+ and more intense emission when the samples were excited at 265 nm. The laser treatment promoted the reduction of Eu"3"+ to Eu"2"+ and this effect was confirmed by the presence of a wide emission band in the green region of the spectrum with a maximum emission obtained after excitation at 350 nm. The luminescent decay time of the thermally treated sample was approximately 100 min. Via XRF measurements of acquired frit and DTA and TG of the frit, pigment and mixtures of both, it was noticed good compatibility in terms of thermal processes, that indicated that the pigment has a potential to be used in ceramic tiles. (author)

  14. CeO2-stabilized tetragonal ZrO2 polycrystals (Ce-TZP ceramics)

    International Nuclear Information System (INIS)

    Andrade Nono, M.C. de.

    1990-12-01

    This work presents the development and the characterization of CeO 2 -stabilized tetragonal ZrO 2 polycrystals (Ce-TZP ceramics), since it is considered candidate material for applications as structural high performance ceramics. Sintered ceramics were fabricated from mixtures of powders containing different CeO 2 content prepared by conventional and nonconventional techniques. These powders and their resultant sintered ceramics were specified by chemical and physical characterization, compactation state and mechanical properties. The chemical characteristics were determined by chemical analysis and the physical characteristics were evaluated by phase content, particle and agglomerate size and aspect, and powder porosity. (author)

  15. Effects of SiC and MgO on aluminabased ceramic foams filters

    Directory of Open Access Journals (Sweden)

    CAO Da-li

    2007-11-01

    Full Text Available Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phases after 1 hour sintering at 1 500 consist of alumina, silicon carbide, spinel and mullite.

  16. Microwave dielectric properties of low-fired Li_2TiO_3–MgO ceramics for LTCC applications

    International Nuclear Information System (INIS)

    Ma, Jian-Li; Fu, Zhi-Fen; Liu, Peng; Wang, Bing; Li, Yang

    2016-01-01

    Graphical abstract: This figure gives the Q × f and τ_f of Li_2TiO_3–MgO ceramics sintered at various temperatures with different LiF contents. Addition of LiF enhanced the sinterability and optimized the microwave dielectric properties of Li_2TiO_3–MgO ceramics. The excellent microwave dielectric properties (ε_r = 15.8, Q × f = 64,500 GHz, and τ_f = −0.2 ppm/°C) of Li_2TiO_3–MgO ceramics sintered at 850 °C illustrated that LiF is a simple effective sintering aids for Li_2TiO_3–MgO ceramics. Such sample was compatible with Ag electrodes, suitable for the low-temperature co-fired ceramics (LTCC) applications. - Highlights: • Temperature stability of Li_2TiO_3 ceramics were improved by doping MgO. • The low-fired Li_2TiO_3–MgO ceramics are fabricated. • LiF liquid phase reduced sintering temperature of Li_2TiO_3–MgO ceramics to 850 °C. • The low-fired Li_2TiO_3–MgO ceramics possess well microwave dielectric properties. • The sample was compatible with Ag electrodes and suitable for LTCC applications. - Abstract: We fabricated the low-fired Li_2TiO_3–MgO ceramics doped with LiF by a conventional solid-state route, and investigated systematically their sintering characteristics, microstructures and microwave dielectric properties. The results showed that temperature stability of Li_2TiO_3 ceramics were improved by doping MgO. Well microwave dielectric properties for Li_2TiO_3–13 wt%MgO (LTM) ceramics with ε_r = 16.4, Q × f = 87,500 GHz, and τ_f = −1.2 ppm/°C were obtained at 1325 °C. Furthermore, addition of LiF enhanced the sinterability and optimized the microwave dielectric properties of LTM ceramics. A typically sample of LTM-4 wt%LiF ceramics with optimum dielectric properties (ε_r = 15.8, Q × f = 64,500 GHz, and τ_f = −0.2 ppm/°C) were achieved at 850 °C for 4 h. Such sample was compatible with Ag electrodes, suitable for the low-temperature co-fired ceramics (LTCC) applications.

  17. The production of sinterable UO2 from AUC

    International Nuclear Information System (INIS)

    Chang, I.S.; Do, J.B.; Choi, Y.D.; Park, M.H.; Yun, H.H.; Kim, E.H.; Kim, Y.W.

    1982-01-01

    Fluidization, feeding and discharging, and mixing of fine particles (-up to 40μ in diameter) in fluidized bed reactor has been examined. The degree of conversion has been estimated using the kinetic data differential scanning colorimetry(DSC) and thermogravimetic analysis (TGA) of ammonium uranyl carbonate (AUC) and residence time distribution data. Satisfactory operation is obtained with a sintered ceramic distributor and filters. The reactor equilvalent to approximately 1.1-1.3 stages. Thermal analysis of AUC in hydrogen atmosphere shows that the decomposition of AUC to UO 3 at 200degC is followed by reduction of UO 3 to UO 2 in two steps in the range between 400degC and 500degC and the complete conversion to UO 2 takes two minutes at 550degC. The overall conversion of above 99.5% in the fluidized bed reactor is estimated with 40 minutes of a mean particle residence time at 600degC. (Author)

  18. Dynamic Fracture Toughness of TaC/CNTs/SiC CMCs Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Qiaoyun Xie

    2015-01-01

    Full Text Available This study focuses on the fracture toughness of TaC and carbon nanotubes (CNTs reinforced SiC ceramic matrix composites (CMCs, prepared by spark plasma sintering (SPS technique. A high densification of 98.4% was achieved under the sintering parameter of 133°C/min, 1800°C, and 90 MPa pressure. Vickers indentation was employed to measure the indentation toughness on the polished surface of ceramic samples, SEM was applied to directly observe the crack propagation after indentation, and split Hopkinson pressure bar (SHPB was developed to determine the dynamic fracture toughness within the ceramic samples subjected to an impact in a three-point bending configuration.

  19. Superplastically foaming method to make closed pores inclusive porous ceramics

    International Nuclear Information System (INIS)

    Kishimoto, Akira; Hayashi, Hidetaka

    2011-01-01

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  20. Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique

    Directory of Open Access Journals (Sweden)

    Chmielewski Marcin

    2017-01-01

    Full Text Available The presented paper investigates the relationship between the microstructure and thermal properties of copper-silicon carbide composites obtained through hot pressing (HP and spark plasma sintering (SPS techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal-ceramic boundary. It is the product of silicon dissolving process in copper occurring at an elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

  1. Ceramic Hosts for Fission Products Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Peter C Kong

    2010-07-01

    Natural spinel, perovskite and zirconolite rank among the most leach resistant of mineral forms. They also have a strong affinity for a large number of other elements and including actinides. Specimens of natural perovskite and zirconolite were radioisotope dated and found to have survived at least 2 billion years of natural process while still remain their loading of uranium and thorium . Developers of the Synroc waste form recognized and exploited the capability of these minerals to securely immobilize TRU elements in high-level waste . However, the Synroc process requires a relatively uniform input and hot pressing equipment to produce the waste form. It is desirable to develop alternative approaches to fabricate these durable waste forms to immobilize the radioactive elements. One approach is using a high temperature process to synthesize these mineral host phases to incorporate the fission products in their crystalline structures. These mineral assemblages with immobilized fission products are then isolated in a durable high temperature glass for periods measured on a geologic time scale. This is a long term research concept and will begin with the laboratory synthesis of the pure spinel (MgAl2O4), perovskite (CaTiO3) and zirconolite (CaZrTi2O7) from their constituent oxides. High temperature furnace and/or thermal plasma will be used for the synthesis of these ceramic host phases. Nonradioactive strontium oxide will be doped into these ceramic phases to investigate the development of substitutional phases such as Mg1-xSrxAl2O4, Ca1-xSrxTiO3 and Ca1-xSrxZrTi2O7. X-ray diffraction will be used to establish the crystalline structures of the pure ceramic hosts and the substitution phases. Scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) will be performed for product morphology and fission product surrogates distribution in the crystalline hosts. The range of strontium doping is planned to reach the full substitution of the divalent

  2. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  3. Production of porous sintered materials using wastes of manufacturing engineering in self-propagating high-temperature synthesis

    Directory of Open Access Journals (Sweden)

    Y. S. Povstyana

    2016-06-01

    Full Text Available The increasing amount of wastes produced by the manufacturing engineering, as well as their physical and mechanical properties and restorability provide a search for sphere of their application. The actual problem of modern science is the utilization of wastes and using them in further production that will minimize their harmful impact on the environment and reduce the cost of expensive raw materials. Wastes are ideally suitable for the manufacture of porous permeable materials (filters. Powder metallurgy allows obtaining products with controlled filtration, physical and mechanical properties. Such materials are good filters for regeneration of technical liquids, oils, cooling fluids, sewage etc. The article analyzes the methods and technologies for the manufacture of porous ceramic materials and a new technology for their manufacture, which is based on use of mill scale and natural mineral – saponite as the main components. Compression technology provides products at low pressures and sintering by passing high-temperature synthesis. The proposed technology is characterized by low cost and good physical and mechanical properties of the product that gives a reason to use them for filtering and regeneration of technical liquids.

  4. Sintering of magnesia: effect of additives

    Indian Academy of Sciences (India)

    Effect of different additives, namely Cr2O3, Fe2O3 and TiO2, up to 2 wt% was studied on the sinter- ing and .... mental distribution of the components is shown in figure 7. It shows ... Chiang Y M, Birniand D and Kingery W 1996 Physical ceram-.

  5. Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of humidity sensors. PMID:27916913

  6. Effect of heat treatment on the optical properties of perovskite BaZr0.5Ce0.3Y0.2O3-δ ceramic prepared by spark plasma sintering

    Science.gov (United States)

    Xing, Bohang; Cheng, Zhi; Wang, Cao; Zhao, Zhe

    2017-09-01

    The effect of heat treatment on the in-line transmittance of BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) ceramics prepared by spark plasma sintering method was investigated. The loss of Ba in transparent BZCY532 ceramics is the key reason for the loss of transmittance during the annealing process. This problem can be effectively alleviated by using a powder bed of BZCY532. Heat treatment atmospheres, wet air and dry air, were also found to be critical for obtaining high quality transparent ceramics. A highly transparent BZCY532 ceramic with the in-line transmittance (Tin) of 71.4% at 2000 nm can be obtained by using SPS method followed by an annealing in powder bed at 1500 °C in wet air.

  7. Bioactive glass-reinforced bioceramic ink writing scaffolds: sintering, microstructure and mechanical behavior.

    Science.gov (United States)

    Shao, Huifeng; Yang, Xianyan; He, Yong; Fu, Jianzhong; Liu, Limin; Ma, Liang; Zhang, Lei; Yang, Guojing; Gao, Changyou; Gou, Zhongru

    2015-09-10

    The densification of pore struts in bioceramic scaffolds is important for structure stability and strength reliability. An advantage of ceramic ink writing is the precise control over the microstructure and macroarchitecture. However, the use of organic binder in such ink writing process would heavily affect the densification of ceramic struts and sacrifice the mechanical strength of porous scaffolds after sintering. This study presents a low-melt-point bioactive glass (BG)-assisted sintering strategy to overcome the main limitations of direct ink writing (extrusion-based three-dimensional printing) and to produce high-strength calcium silicate (CSi) bioceramic scaffolds. The 1% BG-added CSi (CSi-BG1) scaffolds with rectangular pore morphology sintered at 1080 °C have a very small BG content, readily induce apatite formation, and show appreciable linear shrinkage (∼21%), which is consistent with the composite scaffolds with less or more BG contents sintered at either the same or a higher temperature. These CSi-BG1 scaffolds also possess a high elastic modulus (∼350 MPa) and appreciable compressive strength (∼48 MPa), and show significant strength enhancement after exposure to simulated body fluid-a performance markedly superior to those of pure CSi scaffolds. Particularly, the honeycomb-pore CSi-BG1 scaffolds show markedly higher compressive strength (∼88 MPa) than the scaffolds with rectangular, parallelogram, and Archimedean chord pore structures. It is suggested that this approach can potentially facilitate the translation of ceramic ink writing and BG-assisted sintering of bioceramic scaffold technologies to the in situ bone repair.

  8. Fiscal 1998 intellectual infrastructure project utilizing civil sector functions. Research and development project on prompt-effect type intellectual infrastructure creation (Research and development concerning relations between sintered body textural structure and material characteristics in fine ceramics); 1998 nendo minkan no kino wo katsuyoshita chiteki kiban jigyo seika hokokusho. Sokkogata chiteki kiban sosei kenkyu kaihatsu jigyo (fine ceramics no shoketsutai soshiki kozo to zairyo tokusei tono kankei ni kansuru kenkyu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Research and development was carried out involving fine ceramic sintered body textural structure evaluation methods for the development of process technologies for achieving higher quality and lower cost. Studies centered about a method for evaluating coarse pores and coarse grains in sintered bodies, relations between sintered body fracture strength and textural structure, and the standardization of evaluation methods. As the result, an evaluation method for observing pore structures in a sintered body flake specimen under an optical microscope and another for observing coarse grains under a polarization microscope were proposed. As for the effect of coarse defects on the fracture strength of ceramics, it was demonstrated experimentally and theoretically that coarse defects several tens of micrometers in size greatly affected the fracture strength. In the study of methods for sintered body grain size evaluation, findings were obtained about the processing of the specimen surface. (NEDO)

  9. The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

    International Nuclear Information System (INIS)

    Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V.

    2015-01-01

    In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

  10. The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

    Energy Technology Data Exchange (ETDEWEB)

    Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V. [NAS of Ukraine, Donetsk (Ukraine). Donetsk Inst. for Physics and Engineering

    2015-07-01

    In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

  11. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  12. Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

    Science.gov (United States)

    Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

    2017-11-01

    The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

  13. Effect of sintering temperature on the densification of B4C pellets

    International Nuclear Information System (INIS)

    Gomide, R.G.; Durazzo, M.; Riella, H.G.

    1990-01-01

    Boron is largely used in several types of nuclear reactors control and safety systems. In the majority of these applications sintered boron carbide pellets are used. Near stoichiometric B 4 C hardly densifies during pressureless sintering. As a starting point of an overall program to produce > 70% TD B 4 C pellets pressing parameters have been studied for further study of the influence of sintering temperature in the densification of this ceramic material. Dilatometric analyses show that sintering starts at 1760 0 C for the F 1200 ESK - type boron carbide powders. Moreover, the sintering experiments show that up to 92% TD pellets can be obtained. (author) [pt

  14. Phase structure and piezoelectric properties of Li-modified NKLN lead-free piezoelectric ceramics

    International Nuclear Information System (INIS)

    Kim, Sin-Woong; Lee, Sung-Chan; Kim, Min-Soo; Jeong, Soon-Jong; Kim, In-Sung; Song, Jae-Sung

    2012-01-01

    Through the low-temperature sintering method, a sintered body with excellent characteristics was produced in an eco-friendly niobate-based piezoelectric ceramic, whose application was low in expectation due to poor sinterability. Li 2 CO 3 was added in excess to (Na 0.49 K 0.45 Li 0.06 )NbO 3 , and ceramics were manufactured using a commercial sintering method. Then, the sinterability and the piezoelectric properties of the specimens containing varying amounts of Li 2 CO 3 were investigated. The microstructure demonstrated the typical abnormal grain growth tendencies with the addition of Li 2 CO 3 , and this was explained through changes in the critical driving force in the interface reaction-controlled nucleation and growth theory. When the specimen had been sintered at 1000 .deg. C for 4 hours in air after the addition of 1.5 mol% Li 2 CO 3 , the sintered body showed outstanding characteristics with a piezoelectric coefficient of 180 pC/N, an electromechanical coupling coefficient of 0.32, and a dielectric constant of 975. These results showed that eco-friendly niobate-based ceramics, whose use in applications was expected to be difficult in spite of their excellent properties, could be used to produce piezoelectric materials with outstanding properties through a commercial low-temperature sintering method using additives.

  15. Phase structure and piezoelectric properties of Li-modified NKLN lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sin-Woong; Lee, Sung-Chan; Kim, Min-Soo; Jeong, Soon-Jong; Kim, In-Sung; Song, Jae-Sung [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

    2012-09-15

    Through the low-temperature sintering method, a sintered body with excellent characteristics was produced in an eco-friendly niobate-based piezoelectric ceramic, whose application was low in expectation due to poor sinterability. Li{sub 2}CO{sub 3} was added in excess to (Na{sub 0.49}K{sub 0.45}Li{sub 0.06})NbO{sub 3}, and ceramics were manufactured using a commercial sintering method. Then, the sinterability and the piezoelectric properties of the specimens containing varying amounts of Li{sub 2}CO{sub 3} were investigated. The microstructure demonstrated the typical abnormal grain growth tendencies with the addition of Li{sub 2}CO{sub 3}, and this was explained through changes in the critical driving force in the interface reaction-controlled nucleation and growth theory. When the specimen had been sintered at 1000 .deg. C for 4 hours in air after the addition of 1.5 mol% Li{sub 2}CO{sub 3}, the sintered body showed outstanding characteristics with a piezoelectric coefficient of 180 pC/N, an electromechanical coupling coefficient of 0.32, and a dielectric constant of 975. These results showed that eco-friendly niobate-based ceramics, whose use in applications was expected to be difficult in spite of their excellent properties, could be used to produce piezoelectric materials with outstanding properties through a commercial low-temperature sintering method using additives.

  16. Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

    Science.gov (United States)

    Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

    2017-04-17

    LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

  17. The role of ceramic materials in the production of hydrogen with simultaneous CO{sub 2} capture

    Energy Technology Data Exchange (ETDEWEB)

    Barros, B.S. [Universidade Federal de Pernambuco (UFPE), PE (Brazil)

    2016-07-01

    Full text: Hydrogen is considered one of the most promising alternatives to fossil fuels. However, it is mainly obtained from syngas resulting from natural gas steam reforming (SMR), producing a significant amount of carbon dioxide as a side product. Carbon dioxide emission (CO2) is a major contributor to global warming, and one-third of those emissions come from fuel combustion for power generation. A new interesting process has been described to control CO2 emission: the reforming optimized by CO2 sorption, which associates conventional methane reforming and in situ capture of CO2 via absorption in a solid oxide. Furthermore, this strategy can increase the H2 production and concentrate CO2 for the eventual use as chemicals or energy vectors. Alkaline and alkaline-earth ceramics have been proposed for CO2 capture through adsorption and chemisorption processes. These materials can be classified into two large groups: dense and porous ceramics. Dense ceramics mainly trap CO2 chemically: the CO2 is chemisorbed. Among these ceramics, CaO is the most studied one. CaO-based materials have been highlighted as the solid sorbents in the capture of CO2 because of their favorable thermodynamic and chemical properties. The main problem with CaO is the strong decrease in the sorption capacity after multiple carbonation–calcination cycles. This talk will cover some strategies to improve this sorption capacity, such as the deposition of calcium oxide on an inert support, Ca12Al14O33 (mayenite). This oxide has no sorption properties but presents a large surface area, and provides stable network inhibiting deactivation of CaO by sintering. (author)

  18. PHASE EVOLUTION AND MICROWAVE DIELECTRIC PROPERTIES OF (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) CERAMICS WITH ULTRA-LOW SINTERING TEMPERATURES

    Science.gov (United States)

    Zhou, Di; Guo, Jing; Yao, Xi; Pang, Li-Xia; Qi, Ze-Ming; Shao, Tao

    2012-11-01

    The (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) ceramics were prepared via the solid state reaction method. The sintering temperature decreased almost linearly from 755°C for (Li0.5Bi0.5)WO4 to 560°C for (Li0.5Bi0.5)MoO4. When the x≤0.3, a wolframite solid solution can be formed. For x = 0.4 and x = 0.6 compositions, both the wolframite and scheelite phases can be formed from the X-ray diffraction analysis, while two different kinds of grains can be revealed from the scanning electron microscopy and energy-dispersive X-ray spectrometer results. High performance of microwave dielectric properties were obtained in the (Li0.5Bi0.5)(W0.6Mo0.4)O4 ceramic sintered at 620°C with a relative permittivity of 31.5, a Qf value of 8500 GHz (at 8.2 GHz), and a temperature coefficient value of +20 ppm/°C. Complex dielectric spectra of pure (Li0.5Bi0.5)WO4 ceramic gained from the infrared spectra were extrapolated down to microwave range, and they were in good agreement with the measured values. The (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) ceramics might be promising for low temperature co-fired ceramic technology.

  19. Method and device for the dry preparation of ceramic uranium dioxide nuclear fuel wastes

    International Nuclear Information System (INIS)

    Pirk, H.; Roepenack, H.; Goeldner, U.

    1977-01-01

    Reprocessing of waste, resulting from the production of ceramic sintered bodies from uranium dioxide for use as nuclear fuel, in a dry process into very finely dispersed pure U 3 O 8 powder may be improved by applying vibrating screening during oxidation. An appropriate device is described. (UWI) [de

  20. Bioactive Glass-Ceramic Scaffolds from Novel ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Science.gov (United States)

    Elsayed, Hamada; Rincón Romero, Acacio; Ferroni, Letizia; Gardin, Chiara; Zavan, Barbara; Bernardo, Enrico

    2017-01-01

    Highly porous wollastonite-diopside glass-ceramics have been successfully obtained by a new gel-casting technique. The gelation of an aqueous slurry of glass powders was not achieved according to the polymerization of an organic monomer, but as the result of alkali activation. The alkali activation of a Ca-Mg silicate glass (with a composition close to 50 mol % wollastonite—50 mol % diopside, with minor amounts of Na2O and P2O5) allowed for the obtainment of well-dispersed concentrated suspensions, undergoing progressive hardening by curing at low temperature (40 °C), owing to the formation of a C–S–H (calcium silicate hydrate) gel. An extensive direct foaming was achieved by vigorous mechanical stirring of partially gelified suspensions, comprising also a surfactant. The open-celled structure resulting from mechanical foaming could be ‘frozen’ by the subsequent sintering treatment, at 900–1000 °C, causing substantial crystallization. A total porosity exceeding 80%, comprising both well-interconnected macro-pores and micro-pores on cell walls, was accompanied by an excellent compressive strength, even above 5 MPa. PMID:28772531

  1. Fabrication and properties of yttria, ceria doped zirconia-aluminia ceramic composites

    International Nuclear Information System (INIS)

    Lyubushkin, R.A.; Ivanov, O.N.; Chuev, V.P.; Buzov, A.A.

    2011-01-01

    At present, zirconia-based ceramics are gaining popularity in dentistry, particularly in fixed prosthodontics. clinically, it is important that ceramic restorations reproduce the translucency and color of natural teeth. Zirconia based ceramics is a high performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. Y 2 O 3 -stabilized tetragonal zirconia polycrystalline (YTZ/Al 2 O 3 ) and CeO 2 -stabilized tetragonal zirconia polycrystalline (CZA) ceramics with high-performance were prepared for dental application by use the wet chemical route, consolidated by cold isostatic pressing, and two-step sintering method. Physical and mechanical properties test results show that the bending strength, fracture toughness, and the density of full sintered ceramics suggest that the material is relatively suitable for dental restoration.

  2. Production technology of an electrolyte for Na/S batteries

    Science.gov (United States)

    Heimke, G.; Mayer, H.; Reckziegel, A.

    1982-05-01

    The trend to develop a cheap electrochemical electric battery and the development of the Na/S system are discussed. The main element in this type of battery is the beta Al2O3 solid electrolyte. Characteristics for this material of first importance are: specific surface, density of green and of sintered material, absence of cracks, gas permeability, resistance to flexion, purity, electrical conductivity, crystal structure and dimensions. Influence of production method on all these characteristics were investigated, e.g., method of compacting powder, tunnel kiln sintering versus static chamber furnace sintering, sintering inside a container or not, and type of kiln material when sintering in a container. In the stationary chamber furnace, beta alumina ceramics were produced with a density of 3.2 g/cm3, a mechanical strength higher than 160 MPa, and an electrical conductivity of about 0.125 Ohm-1cm-1 at 300 C. The best kiln material proved to be MgO and MgAl2O3.MgO ceramics.

  3. Ceramic component with reinforced protection against radiations

    International Nuclear Information System (INIS)

    Dubuisson, J.; Laville, H.; Le Gal, P.

    1986-01-01

    Ceramic components hardened against radiations are claimed (for example capacitors or ceramic substrates for semiconductors). They are prepared with a sintered ceramic containing a high proportion of heavy atoms (for instance barium titanate and a bismuth salt) provided with a glass layer containing a high proportion of light atoms. The two materials are joined by vitrification producing a diffusion zone at the interface [fr

  4. Influence of the amount containing spodumene or albite on the sintering of a triaxial ceramic

    International Nuclear Information System (INIS)

    Oliveira, Camila Felippe de; Strecker, Kurt

    2012-01-01

    In this study, we investigated the properties of porcelain stoneware, made with albite or spodumene. The amount of the feldspar in the compositions ranged from 15 to 30% by weight. Specimens were pressed and sintered at 1000, 1100, 1200 and 1280 °C with an isotherm of 1 hour at the maximum temperature. The samples were characterized by analysis of the fracture surface using scanning electron microscopy and the vitrification curves, showing both the linear shrinkage and porosity in relation to the sintering temperature. The best results were obtained for samples containing 30% spodumene sintered at 1280 °C, with a linear shrinkage of 9.97% and porosity of 13.28%, while the corresponding results of samples containing 30% albite were 10.13% and 12.17%, respectively. It is concluded that the use of spodumene in the production of porcelain stoneware is viable, resulting in comparable properties. (author)

  5. Measurements for the production of aluminium oxide ceramics with defined microstructure parameters by using colloidal-chemical processings

    International Nuclear Information System (INIS)

    Baer, D.; Foerthmann, R.; Naoumidis, A.; Nickel, H.

    1992-04-01

    The aim of this work is to verify the influences of the different single procedure steps on the microstructure of sintered alumina and to get a correlation between the product characteristics and the characteristic data. The powder production was carried out by using the sol-gel-process followed by freeze-drying of the gel. From the boehmit-powder porous and inhomogen microstructure of the sintered pellets was obtained. The unfavourable morphology of the hydroxide-powder could be eliminated by pre-calcination followed by powder-milling. Because of the wet-milling after the pre-calcination the powder was doped with α-Al 2 O 3 , caused by the abrasion of the milling-mug and -balls, and therefore the calcinating temperature could be reduced to 1050deg C. Two charges of the colloidal-chemical produced powder and four commercial powders with different characteristics with regard to the purity or doping and particle-size and -distribution were compared with themselves. These powders were cold-isostatically pressed and sintered under different conditions. It could be shown that the influence of the impurities on the microstructure is higher than the influence of the grain size distribution. Impurities lead to a discontinous grain size distribution and intracristalline pores in sintered bodies, even using powders with a small grain size distribution. Measurements on the slip casted samples yielded for all powders different relationships between the viscosity and the pH. There was no visible influence of different pH-values on the microstructure (pH always measured at the minimum of the viscosity). Here the influence of the purity and the grain size distribution on the microstructure was less pronounced compared with the isostatically pressed ceramics. (orig.) [de

  6. Influence of sintering temperature in red ceramic with addition of mill scale; Influencia da temperatura de sinterizacao em ceramica vermelha com adicao de carepa/residuo de laminacao

    Energy Technology Data Exchange (ETDEWEB)

    Arnt, A.B.C.; Rocha, M.R.; Bernardin, A.M.; Meller, J.G., E-mail: anb@unesc.ne [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Engenharia de Materiais. Lab. de Fenomenos de Superficies e Tratamentos Termicos

    2010-07-01

    This study aimed to evaluate the influence of sintering temperature in a red ceramic body with the addition of mill scale. This residue consists of oxides of iron had to replace the function of pigments used in ceramic materials. After chemical characterization, by X-ray diffraction, X-ray fluorescence and scanning electron microscopy, this residue was added at a rate of 5% in commercial ceramic past. The formulations were subjected to different burn temperatures of around 950 deg C, 1000 deg C and 1200 deg C. The formulations were evaluated for physical loss to fire, linear firing shrinkage, water absorption and flexural strength by 3 and intensity of tone. The results indicate that the different firing temperatures influence the strength and stability of tone in the formulations tested. (author)

  7. Investigation of control conditions of uranium dioxide pellets sinterability through microspheres

    International Nuclear Information System (INIS)

    Assis, Gino de.

    1996-01-01

    Promotion or inhibition of ceramic powders sinterability, the decisive question in ceramic processing is approached in this dissertation. Each high density microsphere has been considered as a solid inclusion in a low density microspheres matrix, generating big pores. Such pores make it difficult for the pellets density due the fact that they are difficult to be eliminated. A master mixture, allowing the pellet densification in the projected range has been reached. Batches of microspheres have been observed sometimes with high apparent density and sometimes with low apparent density. This apparent density variation was attributed to changing the oxygen partial pressure during calcination under air atmosphere. It is evident that the control of the apparent density of the microspheres needs a further research in order to adjust the sinterability of the microspheres on the desired level.It was demonstrated that the produced microspheres do not have impurities levels that can promote its sinterability or avoid their use in nuclear area

  8. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N, E-mail: swada@yamanashi.ac.jp [Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510 (Japan)

    2011-10-29

    Porous potassium niobate (KNbO{sub 3}, KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  9. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    International Nuclear Information System (INIS)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N

    2011-01-01

    Porous potassium niobate (KNbO 3 , KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  10. Fracture mechanics of ceramics. Vol. 8. Microstructure, methods, design, and fatigue

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.H.; Lange, F.F.

    1986-01-01

    This paper presents information on the following topics: fracture mechanics and microstructures; non-lubricated sliding wear of Al 2 O 3 , PSZ and SiC; mixed-mode fracture of ceramics; some fracture properties of alumina-containing electrical porcelains; transformation toughening in the Al 2 O 3 -Cr 2 O 3 /ZrO 2 -HfO 2 system; strength toughness relationships for transformation toughened ceramics; tensile strength and notch sensitivity of Mg-PSZ; fracture mechanisms in lead zirconate titanate ceramics; loading-unloading techniques for determining fracture parameters of brittle materials utilizing four-point bend, chevron-notched specimens; application of the potential drop technique to the fracture mechanics of ceramics; ceramics-to-metal bonding from a fracture mechanics perspective; observed changes in fracture strength following laser irradiation and ion beam mixing of Ni overlayers on sintered alpha-SiC; crack growth in single-crystal silicon; a fracture mechanics and non-destructive evaluation investigation of the subcritical-fracture process in rock; slow crack growth in sintered silicon nitride; uniaxial tensile fatigue testing of sintered silicon carbide under cyclic temperature change; and effect of surface corrosion on glass fracture

  11. Morphological analysis and modelling of sintering and of sintered materials

    International Nuclear Information System (INIS)

    Jernot, Jean-Paul

    1982-01-01

    This research thesis addresses the study of solid phase sintering of metallic powders, and aims at describing as precisely as possible the different involved matter transport mechanisms, first by using a thermodynamic approach to sintering. Sintering diagrams are also used to determine prevailing mechanisms. The microstructure of sintered materials has been studied by using image quantitative analysis, thus by using a morphological approach to sintering. Morphological parameters allow, on the one hand, the evolution of powders during sintering to be followed, and, on the other hand, sintered products to be correctly characterised. Moreover, the author reports the study of the evolution of some physical properties of sintered materials with respect to their microstructure parameters. This leads to the development of a modelling of the behaviour of these materials [fr

  12. Manufacturing of Porous Ceramic Preforms Based on Halloysite Nanotubes (Hnts

    Directory of Open Access Journals (Sweden)

    Kujawa M.

    2016-06-01

    Full Text Available The aim of this study was to determine the influence of manufacturing conditions on the structure and properties of porous halloysite preforms, which during pressure infiltration were soaked with a liquid alloy to obtain a metal matrix composite reinforced by ceramic, and also to find innovative possibilities for the application of mineral nanotubes obtained from halloysite. The method of manufacturing porous ceramic preforms (based on halloysite nanotubes as semi-finished products that are applicable to modern infiltrated metal matrix composites was shown. The ceramic preforms were manufactured by sintering of halloysite nanotubes (HNT, Natural Nano Company (USA, with the addition of pores and canals forming agent in the form of carbon fibres (Sigrafil C10 M250 UNS SGL Group, the Carbon Company. The resulting porous ceramic skeletons, suggest innovative application capabilities mineral nanotubes obtained from halloysite.

  13. Study on Metal Microfilter Coated with Ceramics by Using Plasma Thermal Spray Method

    International Nuclear Information System (INIS)

    Song, In Gyu; Shin, Hyun Myung; Choi, Hae Woon; Lee, Young Min

    2011-01-01

    This research was performed on a microfilter made of a hybrid material (ceramic + metal) that was coated with ceramics on the metal-filter surface by using the thermal spray method. The ceramic powders used were Al 2 O 3 +40TiO 2 powder with a particle size of 20 μm and Al 2 O 3 (98%+)powder with a particle size of 45 μm. The metal filters were filter-grade 20 μm, 30 μm, and 50 μm sintered metal powder filters (SIKA-R 20 IS, 30 IS, 50 IS: Sinter Metals Filters) and filter-grade 75 μm sintered mesh filter with five layers. Ceramic-coated filters that were coated using the thermal spray method had a great influence on powder material, particle size, and coating thickness. However, these filters showed a fine performance when used as micro-filters

  14. Study on Metal Microfilter Coated with Ceramics by Using Plasma Thermal Spray Method

    Energy Technology Data Exchange (ETDEWEB)

    Song, In Gyu; Shin, Hyun Myung; Choi, Hae Woon [Keimyung University, Daegu (Korea, Republic of); Lee, Young Min [Korea Polytechincs VI, Daegu (Korea, Republic of)

    2011-09-15

    This research was performed on a microfilter made of a hybrid material (ceramic + metal) that was coated with ceramics on the metal-filter surface by using the thermal spray method. The ceramic powders used were Al{sub 2}O{sub 3}+40TiO{sub 2} powder with a particle size of 20 {mu}m and Al{sub 2}O{sub 3} (98%+)powder with a particle size of 45 {mu}m. The metal filters were filter-grade 20 {mu}m, 30 {mu}m, and 50 {mu}m sintered metal powder filters (SIKA-R 20 IS, 30 IS, 50 IS: Sinter Metals Filters) and filter-grade 75 {mu}m sintered mesh filter with five layers. Ceramic-coated filters that were coated using the thermal spray method had a great influence on powder material, particle size, and coating thickness. However, these filters showed a fine performance when used as micro-filters.

  15. The effects of composition and sintering temperature on the silica foam fabricated by slurry method

    International Nuclear Information System (INIS)

    Baharom, Syazwani; Ahmad, Sufizar; Taib, Hariati; Muda, Rizamarhaiza

    2016-01-01

    Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO_2) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO_2 were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO_2 that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO_2 ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO_2 ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO_2 ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm"3 up to 0.75 g/cm"3, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

  16. Pressure-assisted sintering of high purity barium titanate

    NARCIS (Netherlands)

    van den Cruijsem, S.; Varst, van der P.G.T.; With, de G.; Bortzmeyer, D.; Boussuge, M.; Chartier, Th.; Hausonne, J.M.; Mocellin, A.; Rousset, A.; Thevenot, F.

    1997-01-01

    The dielectric behaviour of High Purity Barium titanate (HPB) ceramics is strongly dependent on the grain size and porosity. For applications, control of grain size and porosity is required. Pressure-assisted sintering techniques at relatively low temperatures meet these requirements. In this study,

  17. Near net shape, low cost ceramic valves for advanced engine applications

    Energy Technology Data Exchange (ETDEWEB)

    Pidria, M.; Merlone, E.; Parussa, F. [Fiat Research Centre, Orbassano (Italy); Handelsman, J.; Gorodnev, A. [Ceracom Materials Ltd., Yavneh (Israel)

    2003-07-01

    Future gasoline and diesel engines with electro-hydraulic or electro-mechanical valve control systems require the development of lighter valves to achieve the best results in terms of increased performances, lower fuel consumption and overall efficiency. Ceramic materials can adequately satisfy the required mechanical and thermal properties, nevertheless they still lack as far as manufacturing costs are concerned. Objective of the work was the development of a low-cost forming and sintering process, to produce near-net shape ceramic valves thus requiring very low finishing operations and significantly minimizing material waste. Between available technical ceramic materials, silicon nitride has been chosen to replace conventional steels and Ni-based alloys for the exhaust valves application. The work was then devoted to (i) the selection of the best starting materials composition, taking into account the requirements of a cost effective and high volume production, (ii) the development of an innovative pressure-injection molding process to produce near-net shape parts via a thermosetting feedstock and (iii) the optimization of a proper pressure-less sintering route to obtain cost-competitive, real scale components with adequate final density and mechanical properties. (orig.)

  18. Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

    Energy Technology Data Exchange (ETDEWEB)

    Lisenker, Ilya; Stoldt, Conrad R., E-mail: stoldt@colorado.edu [Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO (United States)

    2016-03-31

    The effect of high-frequency (HF) electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP) ion conducting ceramic was investigated. LAGP with the nominal composition Li{sub 1.5}Al{sub 0.5}Ge{sub 1.5}(PO{sub 4}){sub 3} was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy to compare conventionally and field-sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 h of sintering were minor with measured sintering strains of 31 vs. 26% with and without field, respectively. Ionic conductivity of the sintered pellets was evaluated, and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  19. Microstructure Evolution and Mechanical Properties Improvement in Liquid-Phase-Sintered Hydroxyapatite by Laser Sintering

    Directory of Open Access Journals (Sweden)

    Songlin Duan

    2015-03-01

    Full Text Available CaO-Al2O3-SiO2 (CAS as a liquid phase was introduced into hydroxyapatite (HAp to prepare bone scaffolds. The effects of the CAS content (1, 2, 3, 4 and 5 wt% on microstructure and mechanical properties of HAp ceramics were investigated. The optimal compression strength, fracture toughness and Vickers hardness reached 22.22 MPa, 1.68 MPa·m1/2 and 4.47 GPa when 3 wt% CAS was added, which were increased by 105%, 63% and 11% compared with those of HAp ceramics without CAS, respectively. The improvement of the mechanical properties was attributed to the improved densification, which was caused by the solid particle to rearrange during liquid phase sintering. Moreover, simulated body fluid (SBF study indicated the HAp ceramics could maintain the mechanical properties and form a bone-like apatite layer when they were immersed in SBF. Cell culture was used to evaluate biocompatibility of the HAp ceramics. The results demonstrated MG-63 cells adhered and spread well.

  20. Development of a mixed-conductive ceramic membrane for syngas production; Developpement d'une membrane ceramique conductrice mixte pour la production de gaz de synthese

    Energy Technology Data Exchange (ETDEWEB)

    Etchegoyen, G

    2005-10-15

    Natural gas conversion into syngas (H{sub 2}+CO) is very attractive for hydrogen and clean fuel production via GTL technology by providing an alternative to oil products and reducing greenhouse gas emission. Syngas production, using a mixed ionic-electronic conducting ceramic membrane, is thought to be particularly promising. The purpose of this PhD thesis was to develop this type of membrane. Mixed-conducting oxide was synthesized, characterized and then, shaped via tape casting and co-sintered in order to obtain multilayer membranes with controlled architectures and microstructures. Oxygen permeation fluxes were measured with a specific device to evaluate membrane performances. As a result, the optimisation of architecture and microstructure made it possible to increase oxygen permeation flux by a factor 30. Additional researches were focused on the oxide composition in order to achieve higher dimensional stability. (author)

  1. A low-temperature process for the denitration of Hanford single-shell tank, nitrate-based waste utilizing the nitrate to ammonia and ceramic (NAC) or nitrate to ammonia and glass (NAG) process: Phase 2 report

    International Nuclear Information System (INIS)

    Mattus, A.J.; Walker, J.F. Jr.; Youngblood, E.L.; Farr, L.L.; Lee, D.D.; Dillow, T.A.; Tiegs, T.N.

    1994-12-01

    Continuing benchtop studies using Hanford single-shell tank (SST) simulants and actual Oak Ridge National Laboratory (ORNL) low-level waste (LLW), employing a new denitration process for converting nitrate to ammonia and ceramic (NAC), have conclusively shown that between 85 and 99% of the nitrate can be readily converted to gaseous ammonia. In this process, aluminum powders can be used to convert alkaline, nitrate-based supernate to ammonia and an aluminum oxide-sodium aluminate-based solid. The process may be able to use contaminated aluminum scrap metal from DOE sites to effect the conversion. The final, nitrate-free ceramic product can be pressed and sintered like other ceramics or silica and/or fluxing agents can be added to form a glassy ceramic or a flowable glass product. Based upon the starting volumes of 6.2 and 3.1 M sodium nitrate solution, volume reductions of 50 to 70% were obtained for the waste form produced. Sintered pellets produced from supernate from Melton Valley Storage Tanks (MVSTs) have been leached in accordance with the 16.1 leach test for the radioelements 85 Sr and 137 Cs. Despite lengthy counting times, 85 Sr could not be detected in the leachates. 137 Cs was only slightly above background and corresponded to a leach index of 12.2 to 13.7 after 8 months of leaching. Leach testing of unsintered and sintered reactor product spiked with hazardous metals proved that both sintered and unsintered product passed the Toxicity Characteristic Leaching Procedure (TCLP) test. Design of the equipment and flowsheet for a pilot demonstration-scale system to prove the nitrate destruction portion of the NAC process and product formation is under way

  2. Ceramic design methodology and the AGT-101

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, G.L.; Carruthers, W.D.; Evershed, R.J.; Kidwell, J.R.

    1985-03-01

    The Garrett/Ford Advanced Gas Turbine (AGT101) technology project has made significant progress in the areas of ceramic component design, analysis, and test evaluation using an iterative approach. Design stress limits are being defined for state-of-the-art fine ceramics with good correlation between analytical predictions and empirical results. Recent tests in both rigs and engines are demonstrating the feasibility of high temperature/strength ceramic materials in the gas turbine environment. Component transient stress fields are being defined providing the data base for lower stress/longer life component design. Thermally induced transient stresses to 220 MPa (32 ksi) in reaction bonded silicon nitride (RBSN), 310 Mpa (45 ksi) in sintered alpha silicon carbide (SASC), and 345 MPa (50 ksi) in sintered silicon nitride (SSN) have been successfully demonstrated in AGT101 component screening and qualification test rigs.

  3. Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

    Science.gov (United States)

    Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

    2017-11-25

    The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

  4. Liquid phase sintered ceramic bone scaffolds by combined laser and furnace.

    Science.gov (United States)

    Feng, Pei; Deng, Youwen; Duan, Songlin; Gao, Chengde; Shuai, Cijun; Peng, Shuping

    2014-08-21

    Fabrication of mechanically competent bioactive scaffolds is a great challenge in bone tissue engineering. In this paper, β-tricalcium phosphate (β-TCP) scaffolds were successfully fabricated by selective laser sintering combined with furnace sintering. Bioglass 45S5 was introduced in the process as liquid phase in order to improve the mechanical and biological properties. The results showed that sintering of β-TCP with the bioglass revealed some features of liquid phase sintering. The optimum amount of 45S5 was 5 wt %. At this point, the scaffolds were densified without defects. The fracture toughness, compressive strength and stiffness were 1.67 MPam1/2, 21.32 MPa and 264.32 MPa, respectively. Bone like apatite layer was formed and the stimulation for apatite formation was increased with increase in 45S5 content after soaking in simulated body fluid, which indicated that 45S5 could improve the bioactivity. Furthermore, MG-63 cells adhered and spread well, and proliferated with increase in the culture time.

  5. Shape distortion and thermo-mechanical properties of dense SOFC components from green tape to sintered body

    DEFF Research Database (Denmark)

    Teocoli, Francesca; Esposito, Vincenzo; Ni, De Wei

    stresses, which develop a camber in the final sintered body. To analyze the phenomena, shrinkage of SOFC components single layers and camber development of bi-layers were measured in-situ by optical dilatometry. In addition, a thoughtful investigation of the viscoelastic properties of individual layers......Sintering of ceramic materials is a critical process, especially when the components are shaped as multilayer. Microstructural changes and stresses take place in ceramics as single layer from the green stage to the densification stage, leading to shape distortion, delamination and cracks...

  6. CONSTRUCTION MATERIALS FROM WASTE PRODUCTS

    Directory of Open Access Journals (Sweden)

    Тахира Далиевна Сидикова

    2016-02-01

    Full Text Available We have studied the physical and chemical processes occurring during the thermal treatment of ceramic masses on the basis of compositions of natural raw materials and waste processing facilities. The study of structures of ceramic samples species has shown different types of crystalline phases.The results have shown that the waste of Kaytashsky tungsten-molybdenum ores (KVMR may be used as the main raw material to develop new compositions for ceramic materials. The optimal compositions of ceramic tiles for the masses and technological parameters of obtaining sintered materials based on the compositions of kaolin fireclay KVMR have been developed.It has been found that the use of the waste of Kaytashskoy tungsten-molybdenum ore (KVMR in the composition of the ceramic material will expand the raw material base of ceramic production, reduce the roasting temperature and the cost of ceramic materials and products.

  7. Development of ceramics based fuel, Phase I, Kinetics of UO{sub 2} sintering by vibration compacting of UO{sub 2} powder (Introductory report); Razvoj goriva na bazi keramike, I faza, Kinetika sinterovanja UO{sub 2} vibraciono kompaktiranje praha UO{sub 2} (Uvodni izvestaj)

    Energy Technology Data Exchange (ETDEWEB)

    Ristic, M M [Institute of Nuclear Sciences Vinca, Laboratorija za reaktorske materijale, Beograd (Serbia and Montenegro)

    1962-10-15

    After completing the Phase I of the task related to development of ceramics nuclear fuel the following reports are presented: Kinetics of UO{sub 2} sintering; Vibrational compacting and sintering of UO{sub 2}; Characterisation of of UO{sub 2} powder by DDK and TGA methods; Separation of UO{sub 2} powder.

  8. Physical properties of inorganic PMW-PNN-PZT ceramics

    Science.gov (United States)

    Sin, Sang-Hoon; Yoo, Ju-hyun; Kim, Yong-Jin; Baek, Sam-ki; Ha, Jun-Soo; No, Chung-Han; Song, Hyun-Seon; Shin, Dong-Chan

    2015-07-01

    In this work, inorganic Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)x(Zr0.5Ti0.5)0.97-xO3 (x = 0.02 ∼ 0.12) composition ceramics were fabricated by the conventional solid state reaction method. And then their micro structure and ferroelectric properties were investigated according to the amount of PNN substitution. Small amounts of Li2CO3 and CaCO3 were used in order to decrease the sintering temperature of the ceramics. The 0.10 mol PNN-substituted PMW-PNN- PZT ceramics sintered at 920°C showed the excellent physical properties of piezoelectric constant (d33), electromechanical coupling factor (kp), mechanical quality coefficient (Qm), and dielectric constant of 566 pC/N, 0.61, 73, and 2183, respectively.

  9. Sol-gel synthesis and characterization of fine-grained ceramics in the alumina-titania system

    Energy Technology Data Exchange (ETDEWEB)

    Otterstein, E. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany)], E-mail: otterstein@physik1.uni-rostock.de; Karapetyan, G. [Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock (Germany); Nicula, R. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany); Stir, M. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany); National Institute for Materials Physics, 105b Atomistilor Strasse, P.O.B. MG7, 077125 Bucharest-Magurele (Romania); Schick, C. [Institute of Physics, University of Rostock, Universitaetsplatz 3, 18051 Rostock (Germany); Burkel, E. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany)

    2008-02-05

    Fine-grained ceramics of the Al{sub 2}O{sub 3}-TiO{sub 2} system were synthesised by reactive sintering of sol-gel precursors (Al- and Ti-alkoxides). The thermal behaviour of the as-prepared xerogels was examined by thermal analysis and X-ray powder diffraction. Preliminary results concerning powder consolidation into bulk ceramic parts using spark plasma sintering (SPS) are discussed.

  10. Production and Characterization of Glass-Ceramic Materials for Potential Use in Dental Applications: Thermal and Mechanical Properties, Microstructure, and In Vitro Bioactivity

    Directory of Open Access Journals (Sweden)

    Francesco Baino

    2017-12-01

    Full Text Available Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness, and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution.

  11. (Na, K)NbO3-Based Ceramics for Self-Powered Energy Harvesting Applications.

    Science.gov (United States)

    Kim, Jinhwan; Koh, Jung-Hyuk

    2015-03-01

    Self-powered energy harvesting technologies have been intensively investigated by employ- ing Pb-free piezoelectric materials. One such Pb-free piezoelectric material, the ceramic 0.97(Na0.5K0.5)NbO3-0.03(Bi0.5Na0.5)TiO3, was prepared by employing the conventional mixed oxide method. 0.97(Na0.5K0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics were prepared and the effect of sintering temperature on the microstructure, piezoelectric and ferroelectric properties were system- atically investigated for energy harvesting applications. The crystal structure of 0.97(Na0.5K0.5)NbO3- 0.03(Bi0.5Na0.5) TiO3 Pb-free piezoelectric ceramics, sintered at temperatures between 1080 °C and 1160 °C, was examined by X-ray diffraction analysis. The dielectric properties of 0.97(Na0.5K0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics were measured from 1 kHz to 1 MHz for the various sintering temperatures. We expect that optimization of sintering parameters can improve the piezoelectric and ferroelectric properties of 0.97 (Na0.5K0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics for energy harvesting.

  12. Application of the coal-mining waste in building ceramics production

    Directory of Open Access Journals (Sweden)

    Vaysman Yakov Iosifovich

    Full Text Available In the process of construction ceramics production a substantial quantity of non-renewable natural resources - clays - are used. One of the ways of science development in building materials production is investigation of the possibility of regular materials production using technogenic waste. Application of coal-mining waste (technogenic raw material in charge composition for production of ceramic products provides rational use of fuel, contributes to implementation of resource saving technologies on construction materials production enterprises. Though science development on revealing new raw material sources should be conducted with account for safety, reliability, technical, ecological and economical sides of the problem, which is especially current. The article deals with the problem of coal-mining waste usage in building ceramics production instead of fresh primary component (clay, fluxes, thinning agents and combustible additives. The interdependence between the density and shrinkage of the ceramic products and the amount and quality of coal-mining waste in its composition was established. The optimal proportion of coal-mining waste and clay in building ceramics production was estimated.

  13. Study parameters process for production of red glazed ceramic plates with waste of stones

    International Nuclear Information System (INIS)

    Santos, J.C.; Taguchi, S.P.; Silva, A.C.

    2014-01-01

    The volume of fine waste's solid dimension stone industry has required a destination appropriate for them due to environmental and economic issues. The main goal of this work was to study the produce plates of glazed pottery with dimension stone waste. For analyzing the crystal structure, the test was conducted X-ray and X-ray fluorescence to determine the chemical composition of clay and the waste. Particle size was analysed too. Ceramic duo type (120x30x10mm) were sintered at 1280° C for 15 and 60 minutes. Characterized the samples for water absorption. The glaze had a strong anchorage in the ceramic base, but the high melting temperature caused cracks in the ceramic base, increasing the water absorption values. Thus, flux was added, based on the phase diagram Na_2O: CaO: SiO_2, which reduced the melting temperature of the glaze to 980 °C, enabling to produce the ceramic at 1100°C for 30 minutes, more uniform surface and best technological properties. (author)

  14. The effects of composition and sintering temperature on the silica foam fabricated by slurry method

    Energy Technology Data Exchange (ETDEWEB)

    Baharom, Syazwani, E-mail: hd140001@siswa.uthm.edu.my; Ahmad, Sufizar, E-mail: sufizar@uthm.edu.my; Taib, Hariati, E-mail: hariati@uthm.edu.my; Muda, Rizamarhaiza, E-mail: hd130013@siswa.uthm.edu.my [Department of Material and Design Engineering, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

    2016-07-19

    Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO{sub 2}) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO{sub 2} were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO{sub 2} that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO{sub 2} ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO{sub 2} ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO{sub 2} ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm{sup 3} up to 0.75 g/cm{sup 3}, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

  15. Ceramic UO2 powder production at Cameco Corporation

    International Nuclear Information System (INIS)

    Kwong, A.K.; Kuchurean, S.M.

    1997-01-01

    This presentation covers the various aspects of ceramic grade uranium dioxide (UO 2 ) powder production at Cameco Corporation and its use as fuel and blanket fuel for heavy-water and light-water reactors, respectively. In addition, it discusses the significant production variables that affect production and product quality. It also provides an insight into how various support groups such as Quality Assurance, Analytical Services, and Technology Development fit into the quality cycle and contribute to a successful operation. The ability of Cameco to identify, measure and control the physical and chemical properties of ceramic grade UO 2 has resulted in the production of uniform quality powder. This has meant that 100% of Cameco's ceramic grade UO 2 powder produced since mid-1989 has been accepted by the fuel manufacturers. (author)

  16. FDTD simulation of microwave sintering in large (500/4000 liter) multimode cavities

    Energy Technology Data Exchange (ETDEWEB)

    Subirats, M.; Iskander, M.F.; White, M.J. [Univ. of Utah, Salt Lake City, UT (United States). Electrical Engineering Dept.; Kiggans, J. [Oak Ridge National Lab., TN (United States)

    1996-12-31

    To help develop large-scale microwave-sintering processes and to explore the feasibility of the commercial utilization of this technology, the authors used the recently developed multi-grid 3D Finite-Difference Time-Domain (FDTD) code and the 3D Finite-Difference Heat-Transfer (FDHT) code to determine the electromagnetic (EM) fields, the microwave power deposition, and temperature-distribution patterns in layers of samples processed in large-scale multimode microwave cavities. This paper presents results obtained from the simulation of realistic sintering experiments carried out in both 500 and 4,000 liter furnaces operating at 2.45 GHz. The ceramic ware being sintered is placed inside a cubical crucible box made of rectangular plates of various ceramic materials with various electrical and thermal properties. The crucible box can accommodate up to 5 layers of ceramic samples with 16 to 20 cup-like samples per layer. Simulation results provided guidelines regarding selection of crucible-box materials, crucible-box geometry, number of layers, shelf material between layers, and the fraction volume of the load vs. that of the furnace. Results from the FDTD and FDHT simulations will be presented and various tradeoffs involved in designing an effective microwave-processing system will be compared graphically.

  17. Structural Ceramic Nanocomposites: A Review of Properties and Powders’ Synthesis Methods

    Science.gov (United States)

    Palmero, Paola

    2015-01-01

    Ceramic nanocomposites are attracting growing interest, thanks to new processing methods enabling these materials to go from the research laboratory scale to the commercial level. Today, many different types of nanocomposite structures are proposed in the literature; however, to fully exploit their exceptional properties, a deep understanding of the materials’ behavior across length scales is necessary. In fact, knowing how the nanoscale structure influences the bulk properties enables the design of increasingly performing composite materials. A further key point is the ability of tailoring the desired nanostructured features in the sintered composites, a challenging issue requiring a careful control of all stages of manufacturing, from powder synthesis to sintering. This review is divided into four parts. In the first, classification and general issues of nanostructured ceramics are reported. The second provides basic structure–property relations, highlighting the grain-size dependence of the materials properties. The third describes the role of nanocrystalline second-phases on the mechanical properties of ordinary grain sized ceramics. Finally, the fourth part revises the mainly used synthesis routes to produce nanocomposite ceramic powders, underlining when possible the critical role of the synthesis method on the control of microstructure and properties of the sintered ceramics. PMID:28347029

  18. Bioactivity and mineralization of hydroxyapatite with bioglass as sintering aid and bioceramics with Na3Ca6(PO4)5 and Ca5(PO4)2SiO4 in a silicate matrix

    International Nuclear Information System (INIS)

    Demirkiran, Hande; Mohandas, Arunesh; Dohi, Motokazi; Fuentes, Alonso; Nguyen, Kytai; Aswath, Pranesh

    2010-01-01

    Hydroxyapatite and Bioglass-45S5 were sintered together creating new ceramic compositions that yielded increased apatite deposition and osteoblast differentiation and proliferation in vitro compared to hydroxyapatite. The sintered products characterized by X-ray diffraction, revealed hydroxyapatite as the main phase when small quantities (1, 2.5 and 5 wt.%) of bioglass was added. Bioglass behaved as a sintering aid with β-TCP (Ca 3 (PO 4 ) 2 ) being the minor phase. The amount of β-TCP increased with the amount of bioglass added. In compositions with larger additions of bioglass (10 and 25 wt.%), new phases with compositions of calcium phosphate silicate (Ca 5 (PO 4 ) 2 SiO 4 ) and sodium calcium phosphate (Na 3 Ca 6 (PO 4 ) 5 ) were formed respectively within amorphous silicate matrices. In vitro cell culture studies of the ceramic compositions were examined using bone marrow stromal cell (BMSC). Cell proliferation and differentiation of bone marrow stromal cells into osteoblasts were determined by Pico Green DNA assays and alkaline phosphatase (ALP) activity, respectively. All hydroxyapatite-bioglass co-sintered ceramics exhibited larger cell proliferation compared to pure hydroxyapatite samples. After 6 days in cell culture, the ceramic with Ca 5 (PO 4 ) 3 SiO 4 in a silicate matrix formed by reacting hydroxyapatite with 10 wt.% bioglass exhibited the maximum proliferation of the BMSC's. The ALP activity was found to be largest in the ceramic with Na 3 Ca 6 (PO 4 ) 5 embedded in a silicate matrix synthesized by reacting hydroxyapatite with 25 wt.% bioglass.

  19. Sintering of YBaCu0, implications of the phase diagram

    International Nuclear Information System (INIS)

    Gervais, M.; Douy, A.; Dubois, B.; Coutures, J.P.; Odier, P.

    1989-01-01

    The motivations of this experimental work are to underline the implications between the phases diagram constitution and the sintering of YBaCu0 superconductors. This preliminary work is focussed on the solid → liquid transformations of this system, in the vicinity of the (123) phase. Two transformations are observed at 915 and 935 0 C depending of the composition of the compound. They both have an important role on the sintering process and the chemical homogeneity of the ceramic. No such transformations seems to occur in the domain (123)-(211)-BaCu0 2 , the sintered sample has therefore a better chemical homogeneity [fr

  20. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Saurabh [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Goel, Ashutosh [Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8065 (United States); Correia, Ana Filipa [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Pascual, Maria J. [Instituto de Cerámica y Vidrio (CSIC), Kelsen 5, Campus de Cantoblanco, 28049 Madrid (Spain); Lee, Hye-Young; Kim, Hae-Won [Institute of Tissue Regeneration Engineering (ITREN) & College of Dentistry, Dankook University, Cheonan 330714 (Korea, Republic of); Department of Nanobiomedical Science & BK21 PLUS NBM Global Research Centre for Regenerative Medicine, Dankook University, Cheonan 330714 (Korea, Republic of); Ferreira, José M.F., E-mail: jmf@ua.pt [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal)

    2015-08-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO–(19.24 − x) MgO–x ZnO–5.61 P{sub 2}O{sub 5}–38.49 SiO{sub 2}–0.59 CaF{sub 2} (x = 2–10) have been synthesised by melt–quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1 h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content > 4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO. - Highlights: • The addition of zinc to glasses decreased T{sub g} and promoted crystallisation. • Zinc enhanced the sintering ability and increased mechanical strength by 36%. • The apatite formation ability decreased with increasing Zn contents. • Zinc stimulated mesenchymal stem cell proliferation in a dose dependent manner.

  1. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics

    International Nuclear Information System (INIS)

    Kapoor, Saurabh; Goel, Ashutosh; Correia, Ana Filipa; Pascual, Maria J.; Lee, Hye-Young; Kim, Hae-Won; Ferreira, José M.F.

    2015-01-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO–(19.24 − x) MgO–x ZnO–5.61 P 2 O 5 –38.49 SiO 2 –0.59 CaF 2 (x = 2–10) have been synthesised by melt–quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1 h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content > 4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO. - Highlights: • The addition of zinc to glasses decreased T g and promoted crystallisation. • Zinc enhanced the sintering ability and increased mechanical strength by 36%. • The apatite formation ability decreased with increasing Zn contents. • Zinc stimulated mesenchymal stem cell proliferation in a dose dependent manner

  2. Liquid Phase Sintered Ceramic Bone Scaffolds by Combined Laser and Furnace

    Directory of Open Access Journals (Sweden)

    Pei Feng

    2014-08-01

    Full Text Available Fabrication of mechanically competent bioactive scaffolds is a great challenge in bone tissue engineering. In this paper, β-tricalcium phosphate (β-TCP scaffolds were successfully fabricated by selective laser sintering combined with furnace sintering. Bioglass 45S5 was introduced in the process as liquid phase in order to improve the mechanical and biological properties. The results showed that sintering of β-TCP with the bioglass revealed some features of liquid phase sintering. The optimum amount of 45S5 was 5 wt %. At this point, the scaffolds were densified without defects. The fracture toughness, compressive strength and stiffness were 1.67 MPam1/2, 21.32 MPa and 264.32 MPa, respectively. Bone like apatite layer was formed and the stimulation for apatite formation was increased with increase in 45S5 content after soaking in simulated body fluid, which indicated that 45S5 could improve the bioactivity. Furthermore, MG-63 cells adhered and spread well, and proliferated with increase in the culture time.

  3. Study on 95 alumina ceramic metallizing and glazing technique

    International Nuclear Information System (INIS)

    Zhou Qun; Wang Wei

    2007-12-01

    Electric heater is a component of pressurizer in NPP. So the connector of heater must suit for special requirement with high reliability. It need join 95% alumina ceramic and special metal together. Traditional technique is to glazing ceramic at first, then sintering metal powder on ceramic. It result in melting glaze when metallizing at high temperature. The research on high temperature glaze hasn't got ideal result. In another way, the experiments prove low temperature metallizing couldn't get enough strength. Base on present conditions, a new technique is introduced. It is first metallizing then glazing. It can not only provide high strength with high temperature metallizing , but also avoid melting glaze at high temperature. Compared with other ways, the experiments prove it is feasible. The test data can satisfy requirement. This research has been put into production. (authors)

  4. Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

    Directory of Open Access Journals (Sweden)

    Changzhou Yu

    2017-02-01

    Full Text Available Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P. titanium in a graphite furnace backfilled with argon and studied the effects of common contaminants (C, O, N on sintering densification of titanium. It is found that on the surface of the as-sintered titanium, a severely contaminated porous scale was formed and identified as titanium oxycarbonitride. Despite the porous surface, the sintered density in the sample interiors increased with increasing sintering temperature and holding time. Tensile specimens cut from different positions within a large sintered cylinder reveal different tensile properties, strongly dependent on the impurity level mainly carbon and oxygen. Depending on where the specimen is taken from the sintered compact, ultimate tensile strength varied from 300 to 580 MPa. An average tensile elongation of 5% to 7% was observed. Largely depending on the interstitial contents, the fracture modes from typical brittle intergranular fracture to typical ductile fracture.

  5. Recycling of mill scale in sintering process

    Directory of Open Access Journals (Sweden)

    El-Hussiny N.A.

    2011-01-01

    Full Text Available This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

  6. 77 FR 51046 - Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same; Notice...

    Science.gov (United States)

    2012-08-23

    ... INTERNATIONAL TRADE COMMISSION [Docket No. 2908] Certain Sintered Rare Earth Magnets, Methods of... Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same, DN 2908; the..., methods of making same and products [[Page 51047

  7. Incorporation of Pr into LuAG ceramics

    Science.gov (United States)

    Marchewka, M. R.; Chapman, M. G.; Qian, H.; Jacobsohn, L. G.

    2017-06-01

    An investigation of the effects of Pr in (Lu1-xPrx)3Al5O12 (LuAG:Pr) ceramics was carried out by means of x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), and attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR) measurements coupled with luminescence measurements. It was found that the Pr concentration that maximizes luminescence emission depends on the thermal processing conditions. While the calcined LuAG:Pr powder showed maximum luminescence emission for Pr concentrations between 0.18 and 0.33 at.%, maximum emission of ceramic bodies sintered at 1500 °C for 20 h was obtained with Pr concentrations between 0.018 and 0.18 at.%. Further, for short sintering times up to about 3 h, luminescence emission intensity is maximum for Pr concentrations around 0.33 at.%. Longer sintering times lead to the formation of PrAlO3 as a secondary phase, concomitant with a reduction of the intensity of luminescence emission.

  8. Cellular ceramics made from porcelain tile polishing wastes: influence of sintering time; Ceramicas cellulares obtidas a partir de residuo de polimento de porcelanato: influencia do tempo de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, A.F.; Zanelatto, C.C.; Uggioni, E. [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Dept. de Engenharia de Materiais; Bernardin, A.M., E-mail: amb@unesc.ne [Servico Nacional de Aprendizagem Industrial, Tijucas, SC (Brazil). Tecnologia em Ceramica

    2009-07-01

    This paper deals with the physical, microstructural and mechanical characterization of cellular ceramics made from porcelain polishing wastes, which were expanded by the bubble formation technique during the sintering process. The microstructure, linear expansion, bulk density (mercury immersion) and mechanical behavior (compressive strength) were determined to characterize the glass foam obtained. Moreover, the porcellaneous residue was characterized by chemical and phase analyses, particle size (laser diffraction) and thermal behavior. As a result, the higher the soaking time during heat treatment at 1200 deg C the lower the density obtained for the cellular ceramic due to CO{sub 2} expansion, and lower the mechanical strength of the samples. The microstructure shows spherical cells and completely closed pores, resulting in a cheap way to obtain low density material with adequate mechanical strength, avoiding the disposal of wastes from the ceramic industry. (author)

  9. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    Science.gov (United States)

    Wananuruksawong, R.; Jinawath, S.; Padipatvuthikul, P.; Wasanapiarnpong, T.

    2011-10-01

    Silicon nitride (Si3N4) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si3N4 ceramic as a dental core material. The white Si3N4 was prepared by pressureless sintering at relative low sintering temperature of 1650 °C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si3N4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si3N4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (tube furnace between 1000-1200°C. The veneered specimens fired at 1100°C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98×10-6 °C-1, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  10. Properties of millimetre wave sintered and oxygenated YBa2Cu3Ox bulk material

    International Nuclear Information System (INIS)

    Hunyar, C.

    1999-12-01

    High temperature superconductors are ceramic materials whose properties strongly depend on the techniques used for their production. The successful use of microwaves for the sintering of other oxidic ceramics suggests the examination of the advantages and disadvantages of that production technique for superconductors. For this purpose pellets of commercially available YBa 2 Cu 3 O x powder from the Solvay company were pressed and sintered by millimetre wave heating (30 GHz, generated in a gyrotron). In various experiments the sintering temperatures were varied between 920 C and 990 C, and the holding times between 15 min and 240 min. The densities of the pellets were measured by the Archimedes method and the material structure was examined with an optical microscope. A strong densification from 86 to 93% of theoretical density could be observed within 30 min at a holding temperature of 960 C. With sintering temperatures above 960 C no significant increase in density occurred. At 950 C, only minor grain growth could be observed, which increased up to 960 C temperature. At higher temperatures a mixture of small grains and crystallites of about 150 μm size established itself. CuO already present in the original powder started to melt along the grain boundaries where it acts as a limiting factor for grain growth. With millimetre wave sintering the same material densities could be achieved in less than one third of the time needed for conventional sintering processes. In addition the effects of millimetre wave heating on the oxygen diffusion in YBCO were investigated with several pairs of identical samples. The pairs were deoxygenated and subsequently oxygenated in an atmosphere of pure O 2 in a conventional tube furnace and by millimetre wave heating respectively. To compare the oxygen concentration of the samples, their specific surface resistance at room temperature, which correlates with the oxygen content, was measured in a cylindrical copper resonator with

  11. Hydrostatic pressing effect on some properties of Al2O3 and Sc2O3 base ceramics

    International Nuclear Information System (INIS)

    Artemova, K.K.; Rudenko, L.A.; Maslova, G.Ya.; Levkovich, N.A.; Orlova, L.A.

    1981-01-01

    Found is the effect of hydrostatic pressing pressure on some physico-mechanical properties of the ceramic on the Al 2 O 3 and Se 2 O 3 base. Mathematical models, describing dependences of the strength of materials made of Al 2 O 3 and Sc 2 O 3 on sintering conditions and on hydrostatic pressing pressure, are plotted. Production regimes on the Al 2 O 3 and Sc 2 O 3 base ceramics with improved properties are optimized [ru

  12. Comparison of thermal analysis, micro structural and compositional of archaeological indigenous ceramic (Caninhas site of Canas - SP) with actual clay/ceramic of region

    International Nuclear Information System (INIS)

    Nakano, F.P.; Taguchi, S.P.; Matos, C.C.; Ribeiro, R.B.

    2009-01-01

    The ceramic material found at the archaeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archaeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archaeological ceramics were identified by the illite, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archaeological application. (author)

  13. Densification and mechanical properties of sintered Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Paneto, Flavio Jose; Pereira, Joaquim Lopes; Oliveira, Jean de Lima; Jesus Filho, Edson de; Silva, Leandro Anselmo da; Cabral, Ricardo de Freitas; Santos, Claudinei dos [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Lima, Eduardo de Sousa [Institutlo Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil)

    2014-06-15

    In this work, Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} ceramic composites were developed with different proportions of Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12}, which were mixed and compacted at different pressures of 40MPa to 100MPa, being consequently sintered at 1600 deg C-2h. The sintered samples were characterized by X-ray diffraction presenting α-Al{sub 2}O{sub 3} and Y{sub 3}Al{sub 5}O{sub 12} as crystalline phases. Samples with relative densities ranging from 78 to 80% and 87 to 91% were obtained depending on the composition and the compaction pressure used. The hardness values obtained were of 1010 to 1080HV and 370- 470HV, for mixes Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} having the composition with levels of 20 and 36.5wt.%, respectively. (author)

  14. Synthesis and dielectric characterization of Ba0.6Sr0.4TiO3 ferroelectric ceramics

    International Nuclear Information System (INIS)

    Nedelcu, L.; Ioachim, A.; Toacsan, M.; Banciu, M.G.; Pasuk, I.; Berbecaru, C.; Alexandru, H.V.

    2011-01-01

    Ferroelectric ceramics Ba 0.6 Sr 0.4 TiO 3 (BST 40) were prepared, by solid-state reaction in the temperature range 1210-1450 deg. C. Maximum values of the ceramic densities were around 94% of their theoretical value. X-ray diffraction techniques (XRD) and scanning electron spectroscopy (SEM) were used to analyze the structure and the surface morphology of ceramics. Rounded, well defined or abnormal granular growth was observed in the SEM images, vs. sintering conditions and purity of the raw materials. In all samples, BST 40 ceramic is the major phase, but there are also present small amounts of secondary phases, as revealed in XRD diffraction patterns. Permittivity and dielectric loss measurements were performed in the temperature range - 150 to + 150 deg. C, and 150 Hz-5 MHz frequency values. Permittivity values rising from 1200 to 12,500, with increasing sintering temperatures, were recorded. Narrow and well defined transition peaks were noticed at higher sintering temperatures. Curie temperature was around 2 deg. C, for samples with the mentioned composition. Permittivity and losses vs. frequency show different behavior whether BST ceramics are in polar or non-polar state and with the distance toward phase transition. Microwave measurements performed at room temperature have shown lower values of permittivity, compared with similar data at low frequency, and dielectric losses lower than 1% at 0.7 GHz. The sintering conditions (temperatures, sintering time, etc.) and purity of the raw materials lead to important changes of transition temperatures in the polymorphic diagram, which we have built-for the other Ba1-xSrxTiO3 compositions (x = 0.25-0.90) sintered at 1260 deg. C for 2 h.

  15. Spark plasma sintering of α-Si3N4 ceramics with Al2O3 and Y2O3 as additives and its morphology transformation

    International Nuclear Information System (INIS)

    Ceja-Cardenas, L.; Lemus-Ruiz, J.; Jaramillo-Vigueras, D.; Torre, S.D. de la

    2010-01-01

    The spark plasma sintering SPS technique has been used to densify pure α-Si 3 N 4 commercial powder, having Y 2 O 3 and Al 2 O 3 additions; from 0, 2.5 and 5.0 wt% to 0, 1.5 and 3 wt%, respectively. Such powder admixtures were previously spray-dried at 160 o C in such a way that powder was thoroughly homogenized. Set sintering treatment included: 0-20 min holding time and 38 MPa axial load, sintering temperature of 1500 o C and heating rate of 300 o C/min. The maximum relative density developed on studied specimens ranged from 99.4 to 99.8% and could only be attained once the β-phase nucleated from the α-silicon nitride matrix. Obtained Si 3 N 4 composites combine both α- and β-phases. The later phase becomes evident trough the rod-like geometry, which forms throughout the presence of a liquid face. The largest hardness value developed (1588 Hv (20kgf) ) on studied ceramics (3M-series - 3 min) matched close to the corresponding counterpart found in literature (1600 Hv), the former developed in much shorter sintering times. Using X-ray diffraction XRD and scanning electron microscope SEM analyses, the two major phases of Si 3 N 4 were identified in the resultant microstructures. The morphology evolution of Si 3 N 4 particles as occurred upon SPS-sintering is analyzed.

  16. Application of automotive paint sludge in the production of white ceramic

    International Nuclear Information System (INIS)

    Praxedes, P.B.; Ponte, H.A.; Mymrine, V.

    2016-01-01

    Full text: Paint wastes of an automotive industry were evaluated in terms of their chemical and mineralogical characteristics in order to analyse its potential use as a reinforcing agent in white ceramic. Both kaolin and sludge paint were analysed using the techniques of XRF, XRD, SEM, EDS. In order to understand the behaviour of the sludge during firing, TGA and DTA analysis were done. Samples containing kaolin and 0, 1, 2, 4 and 8 (wt.%) sludge paint were prepared. The ceramics were compacted at 10MPa and sintered at 1000 °C, 1200 °C, 1250 °C and 1300 °C. Water absorption, linear shrinkage and flexural strength were the mechanical properties evaluated in the samples. The experimental results showed that the samples with lagers amounts of sludge performed better or similar to the samples that only contained kaolin. The insertion of 8 (wt.%) of sludge in the specimen increased flexural strength in 63%. (author)

  17. Production of nano-crystalline zirconia powders and fabrication of high strength ultra-fine-grained ceramics

    International Nuclear Information System (INIS)

    Rajendran, S.

    1993-01-01

    Hydrous zirconia containing 2 and 2.5 mol% Y 2 O 3 was prepared by a hydroxide co-precipitation method and portions were dispersed in ethanol before drying(P2), milled in ethanol after drying (P3) or after calcination at 550 deg C (P4) or milled in iso-propanal after calcination at 1000 deg C (P5). The crystallisation behaviour and sintering characteristics of the materials were investigated. The calcined as dried powder (P1) has strongly bonded hard aggregates and the material reached a density of only about 80% of theoretical after sintering at 1500 deg C. Powder characteristics and the sinterability of the alcohol treated materials depended on the conditions of processing and heat treatment. The sinter-activity of the powders decreased from P2 to P5. Powder P3 was composed of relatively weakly bonded crystallites and could be sintered at 1400 deg C, while the powders P4 and P5 contained hard agglomerates and required a sintering temperature of 1450 and 1550 deg C respectively to achieve similar density. Powder (P2) had zirconium alkoxide species on the particle surface which decomposed at about 300 deg C. The calcined powder had very weak agglomerates composed of fine, uniform zirconia crystals and/or aggregates and sintered to high density at 1150 deg C. The final ceramic had a very uniform microstructure with an average grain size of about 150nm and exhibited fracture strength as high as 1700 MPa. A detailed account of the formation of aggregates of strongly bonded crystallites during calcination of hydrous zirconia, influence of alcohol in producing soft agglomerates and the sintering characteristics of the powders is reported. 46 refs., 2 tabs., 15 figs

  18. Preparation and Characteristics of Porous Ceramics by a foaming Technology at Low Temperature

    Science.gov (United States)

    Zhang, H. Q.; Wang, S. P.; Wen, J.; Wu, N.; Xu, S. H.

    2017-12-01

    Recycling and converting coal gangue and red mud into porous ceramics with good performance is a feasible disposal route. In this present work, porous foam ceramics was prepared using coal gangue and red mud as main raw materials at low sintering temperature, The amount of coal gangue and red mud were up to 70 wt%. To regulate the forming and sintering performance of the product, quartz sands and clay material were added to the formula. The green body was formed by a foaming technology using aluminum powders as foaming agents at room temperature. After foamed, the specimens were dried at 60-80 °C, and then calcined at 1060°C. Effects of concentration of NaOH and amount of aluminum powders on the phase, mechanical properties and microstructure were investigated here. Such study is expected to provide a new utilization route of the coal gangue and red mud, and brings both intensive environmental and economic benefits.

  19. Fabrication and characterisation of ceramics via low-cost DLP 3D printing

    International Nuclear Information System (INIS)

    Varghesea, G.; Moral, M.; Castro-García, M.; López-López, J.J.; Marín-Rueda, J.R.; Yagüe-Alcaraz, V.; Hernández-Afonso, L.; Ruiz-Morales, J.C.; Canales-Vázquez, J.

    2018-01-01

    Astereolithography-based additive manufacturing technique has been used for the fabrication of advanced ceramics. A customised 3D printer using a Digital Light Processing (DLP) projector as UV source has been built to fabricate green bodies from photosensitive resins loaded with 25–60wt% of alumina, 3- and 8-YSZ. The 3D-printed bodies were then sintered in the 1200–1500°C and exhibited thermal stability. As expected, higher ceramic loadings rendered objects with higher density for a given sintering temperature. The limit of solid loading in the resin is approximately 60% and beyond those contents, the extra ceramic appears as powder loosely adhered to the sintered objects. Photogrammetry was used to evaluate the accuracy of the 3D printing process and highlighted a marked deviation between the CAD model and the resulting object, particularly in the top part of the specimens, possibly due to the use of volatile solvents which cause changes in the photoresins used. Nevertheless, that problem may be overcome by thermostatising the printer vat and/or using solvents with higher boiling point. The results obtained suggest the potential application of low cost DLP 3D printing techniques to process ceramics for a number of applications including ceramic fuel cells, piezoelectrics, dental applications, etc. [es

  20. X-ray shielding behaviour of kaolin derived mullite-barites ceramic

    Science.gov (United States)

    Ripin, A.; Mohamed, F.; Choo, T. F.; Yusof, M. R.; Hashim, S.; Ghoshal, S. K.

    2018-03-01

    Mullite-barite ceramic (MBC) is an emergent material for effective shielding of redundant ionizing radiation exposure. The composition dependent mechanical, thermal, and microstructure properties of MBC that makes MBC a high performing novel radiation shielding candidate remained unexplored. This paper examines the possibility of exploiting Malaysian kaolin (AKIM-35) and barite (BaSO4) derived ceramic (MBC) system for X-ray shielding operation. Using conventional pressing and sintering method six ceramic samples are prepared by mixing AKIM-35 with barite at varying contents (0, 10, 20, 30, 40 and 50 wt%). Synthesized pressed mixtures are calcined at 400 °C for 30 min and then sintered to 1300 °C for 120 min at a heating rate of 10 °C/min. Sintered samples are characterized via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), lead equivalent (LE), uniformity and dose reduction analyses. XRD pattern of prepared ceramics revealed the presence of monoclinic barium alumino-silicate (BAS) and orthorhombic mullite as major shielding phases together with other minor phase of barite and hexagonal quartz (SiO2) structures. Furthermore, FESEM images of ceramics (between 0 and 30 wt%) displayed the existence of compacted monoclinic plate of BAS and acicular mullite morphology (ceramics at 40 and 50 wt%). Radiation tests displayed the capacity of ceramics (at 0 and 10 wt%) to shield the X-ray radiation emanated at tube potential range of 50-120 kV. The highest radiation attenuation is ascertained at 70 kV where the dose is reduced remarkably between 99.11% and 97.42%. Ceramics at 0 and 10 wt% demonstrated the highest lead (Pb) equivalent thickness (LE) of 0.44 mm and 0.34 mm, respectively. It is established that such MBC may contribute towards the development of shielding material against ionizing radiation in diagnostic radiology (X-ray) dose range.

  1. Preparation of textured Bi3TiNbO9 ceramics

    International Nuclear Information System (INIS)

    Zhou Zhiyong; Cheng Baozhu; Li Yuchen; Dong Xianlin

    2007-01-01

    Single phase of textured Bi 3 TiNbO 9 (BTNO) ceramics were prepared by a two-step sintering method: synthesizing seed-crystal platelets by molten-salt method with oxide mixture as precursor and then sintering the platelets via hot-pressing method. Molten-salt-synthesized fine BTNO plate-like crystallines (∼400 nm) had an orientation degree of 0.42. After hot-pressed under different conditions, textured BTNO ceramics with different orientation degree were obtained and the orientation degree of textured BTNO ceramics increased with the applied pressure as well as the sintering temperature. X-ray diffraction (XRD) patterns of textured BTNO revealed that the face perpendicular to the hot-pressing axis (-perpendicular ) exhibits stronger (0 0 l) diffraction peaks, while the face parallel to the hot-pressing axis (-parallel ) shows stronger (0 2 0)/(2 0 0) and weaker (0 0 l) diffraction peaks, which also can be apparently observed from SEM images. Highly oriented BTNO with a degree of 0.78 was obtained under an applied pressure of 60 MPa at 1050 deg. C

  2. Method of preparing porous, rigid ceramic separators for an electrochemical cell. [Patent application

    Science.gov (United States)

    Bandyopadhyay, G.; Dusek, J.T.

    Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200/sup 0/C for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide, and magnesium-aluminium oxide have advantageously been used to form separators by this method.

  3. Modified PZT ceramics as a material that can be used in micromechatronics

    Science.gov (United States)

    Zachariasz, Radosław; Bochenek, Dariusz

    2015-11-01

    Results on investigations of the PZT type ceramics with the following chemical composition: Pb0.94Sr0.06(Zr0.50 Ti0.50)0.99 Cr0.01O3 (PSZTC) which belongs to a group of multicomponent ceramic materials obtained on basis of the PZT type solid solution, are presented in this work. Ceramics PSZTC was obtained by a free sintering method under the following conditions: Tsint = 1250 °C and tsint = 2 h. Ceramic compacts of specimens for the sintering process were made from the ceramic mass consisting of a mixture of the synthesized PSZTC powder and 3% polyvinyl alcohol while wet. The PSZTC ceramic specimens were subjected to poling by two methods: low temperature and high temperature. On the basis of the examinations made it has been found that the ceramics obtained belongs to ferroelectric-hard materials and that is why it may be used to build resonators, filters and ultrasonic transducers. Contribution to the Topical Issue "Materials for Dielectric Applications" edited by Maciej Jaroszewski and Sabu Thomas.

  4. Analysis of the properties of silicon nitride based ceramic (Si_3N_4) cutting tool using different addictive

    International Nuclear Information System (INIS)

    Pereira, Joaquim Lopes; Souza, Jose Vitor Candido de; Raymundo, Emerson Augusto; Silva, Oliverio Macedo Moreira

    2013-01-01

    The constant search for new materials is part of the scientific and technological development of the industries. Ceramic been presenting important developments in terms of scientific and technological development, highlighting the predominance of covalent ceramics, which has important applications where abrasion resistance and hardness are required. Between covalent materials, several research papers in search of property improvements and cost reduction. However the production of ceramics of silicon nitride (Si_3N_4) with a reduced cost is possible only if used methods and different additives. The aim of this work is the development of compositions based on silicon nitride (Si_3N_4) using different additives such as Y_2O_3, CeO_2, Al_2O_3 , and CTR_2O_3 in varying amounts. For the development of ceramics, the mixtures were homogenized, dried, compacted and sintered using the sintering process of 1850°C for 1 hour, with a heating rate of 25°C/min. The characterizations were performed as a function of relative density by Archimedes method, the mass loss measured before and after sintering, phase analysis by X-ray diffraction, microstructure by scanning electron microscopy (SEM), and hardness and fracture toughness indentation method. The results showed relative density 97-98, Vickers hardness 17-19 GPa, fracture toughness from 5.6 to 6.8 MPa.m"1"/"2. The different phases were obtained depending on the types of additives used. The obtained results are promising for tribological applications. (author)

  5. Addition of niobia in alumina and its effects at its sintered microstructure

    International Nuclear Information System (INIS)

    Gomes, L.B.; Lima, M.M.O.; Pereira, A.S.; Bergmann, C.P.

    2016-01-01

    In this work, niobia was used as sintering additive of alumina in concentrations of 0.15, 0.5, 2 and 4 wt%. Homogenized powders was uniaxially pressed (200MPa) forming ceramic pellets with 10 mm diameter. The green bodies were sintered at 1400, 1500 and 1600°C for 60 minutes using a heating rate of 2,5°C.min -1 . After sintering, the specimens were polished using diamond paste with different particle sizes. The specimen's microstructure was analyzed by Scanning Electron Microscopy (SEM) and crystalline phases were determined by X-ray Diffraction (XRD). Results indicate that when niobia and alumina react they form AlNbO4 by liquid phase sintering. This phase is located among alumina grain. It was also verified that niobia addition promotes grain growth, acting as sintering agent, and this effect grows as niobia content and sintering temperature increase. (author)

  6. Preparation and sintering of Zr(C,N,O) phases

    International Nuclear Information System (INIS)

    Tamborenea, S.; Mazzoni, A.D.; Aglietti, E.F.

    2003-01-01

    The Zr(C,O,N) compounds form a great mono-phase zone belonging to the pseudoternary ZrO-ZrN-ZrC system.Theses phases have cubic crystalline structure with a o parameter depending on the C, O 2 and N 2 content.These phases have many potential applications in the manufacture of ceramic pieces utilizable as electronic conductors.The Zr (C,O,N) phases can be obtained from ZrO 2 by carbonitriding reactions: that is carbothermal reduction and simultaneous nitriding.In this work a series of experiences of carbonitriding of zirconia under different conditions (temperatures between 1400 and 1600degC, times of 120 min, carbon content between 20 and 40%) in order to obtain suitable powders to be sintered.The XRD analysis shows the Zr(C,O,N) as the main products and β -ZrON as the only secondary product in proportions depending on the obtaining conditions.The variables employed were the C content and the reaction temperature.The Zr(C,O,N) content varies between 40 and 90% and tends to increase with the temperature and the carbon content whereas the β -ZrON phase varies between the 40 and 10 % decreasing its proportion with temperature and the carbon content.The oxidation resistance of these phases was studied by DTA-TG tests in air.Results show complete oxidation reaction at ∼500degC in air.The sintering of these materials was made on disks obtained by pressing of powders of Zr(C,N,O) contents higher than 90%.Sintering was performed in nitrogen atmosphere and temperatures between 1450 and 1620degC.Disks were characterized by pycnometry and Hg volumeter.The densities obtained were between 5 and 6,6g/cm 3 with a tendency to increase with the Zr(C,N,O) phase content, the temperature and the sintering time.Sintered disks were characterized by dilatometry in N 2

  7. Numerical study of the grain growth and the thermal properties of ceramics

    International Nuclear Information System (INIS)

    Shahtahmasebi, N.; Shariaty ghleno, A.M.; Hosaini, M.

    2000-04-01

    The physical properties of ceramics strongly depends on the grain size, which itself depends on the sintering process. In this work we propose a model for sintering based on the gross features known experimental and the preform numerical study

  8. Furnace for the continuous sintering of pellets of ceramic nuclear fuel material

    International Nuclear Information System (INIS)

    Heyraud, J.

    1977-01-01

    The furnace comprises a hearth for the longitudinal displacement of pellet containers, means for injecting gas at both ends of the furnace, for sucking gas between preheating and sintering zones and for condensing the binder, means for displacing the containers from an introduction lock-chamber to an extraction lock-chamber, a conveyor belt which passes through a glove box and provides a leak-tight connection between the lock-chambers. A station for loading containers with pellet sub-containers prior to sintering and a station for unloading the pellet sub-containers after sintering are juxtaposed within the glove box. 3 claims, 1 drawing figure

  9. Clinical marginal and internal adaptation of CAD/CAM milling, laser sintering, and cast metal ceramic crowns.

    Science.gov (United States)

    Tamac, Ece; Toksavul, Suna; Toman, Muhittin

    2014-10-01

    Metal ceramic crowns are widely used in clinical practice, but comparisons of the clinical adaptation of restorations made with different processing techniques are lacking. The purpose of this study was to compare the clinical marginal and internal adaptation of metal ceramic crowns fabricated with 3 different techniques: computer-aided design and computer-aided manufacturing (CAD/CAM) milling (CCM), direct metal laser sintering (DMLS), and traditional casting (TC). Twenty CCM, 20 DMLS, and 20 TC metal ceramic crowns were fabricated for 42 patients. Before luting the crowns, silicone replicas were obtained to measure marginal gap and internal adaptation that was evaluated at 3 regions: axial wall, axio-occlusal angle, and occlusal surface. Measurements were made with a reflected light binocular stereomicroscope at 20× magnification and analyzed with 1-way analysis of variance (ANOVA) and the Bonferroni post hoc test (α=.05). The mean marginal gap values were 86.64 μm for CCM, 96.23 μm for DMLS, and 75.92 μm for TC. The means at the axial wall region were 117.5 μm for the CCM group, 139.02 μm for the DMLS group, and 121.38 μm for the TC group. One-way ANOVA revealed no statistically significant differences among the groups for measurements at the marginal gap (P=.082) and the axial wall region (P=.114). The means at the axio-occlusal region were 142.1 μm for CCM, 188.12 μm for DMLS, and 140.63 μm for TC, and those at the occlusal surface region were 265.73 μm for CCM, 290.39 μm for DMLS, and 201.09 μm for TC. The mean values of group DMLS were significantly higher at the axio-occlusal region and the occlusal surface region than those of other groups (Pmetal ceramic crowns performed similarly in terms of clinical marginal and axial wall adaptation. The cement film thickness at the occlusal region and axio-occlusal region were higher for DMLS crowns. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc

  10. Production of sintered alumina from powder; optimization of the sinterized parameters for the maximum mechanical resistence

    International Nuclear Information System (INIS)

    Rocha, J.C. da.

    1981-02-01

    Pure, sinterized alumina and the optimization of the parameters of sinterization in order to obtain the highest mechanical resistence are discussed. Test materials are sinterized from a fine powder of pure alumina (Al 2 O 3 ), α phase, at different temperatures and times, in air. The microstructures are analysed concerning porosity and grain size. Depending on the temperature or the time of sinterization, there is a maximum for the mechanical resistence. (A.R.H.) [pt

  11. The production of sinterable uranium dioxide from ammonium diuranate

    International Nuclear Information System (INIS)

    Fane, A.G.; Le Page, A.H.

    1975-02-01

    The development of a 0.13 m diameter pulsed fluidised bed reactor for the continuous production of sinterable uranium dioxide from ammonium diuranate is described. Calcination-reduction at 670 to 680 0 C produced powders with surface areas of 4 to 6 m 2 g -1 giving pellet densities in excess of 10.6 g cm -3 . Sinterability was relatively insensitive to changes in operating conditions, provided the availability of hydrogen was adequate, for gas flow rates in the range 0.95 to 1.4 l S -1 , pulse frequencies of 0.5 and 0.75 Hz and mean residence times of the solids from 0.6 to 1.4 hours. Sinterability was shown to be improved either by use of higher input concentrations, or by use of a secondary flow of hydrogen (about 5 per cent of input) fed into the powder collection system and flowing countercurrent to the UO 2 product. The maximum throughput of 17 kg UO 2 h -1 (0.6 hours mean residence time) required only 120 per cent of the stoichiometric requirement at an input concentration of 50 vol.per cent with secondary hydrogen flow. Results are given for studies of the kinetics of reduction of calcined ammonia diuranate in hydrogen and the residence time distribution of solids in a pulsed fluidised bed. Estimates based on these data suggested that the overall conversion of ammonium diuranate to uranium dioxide in the continuously operated pulsed fluidised bed reactor was in excess of 99 per cent. Continuous stabilisation of the UO 2 product was demonstrated at 12 kg h -1 or UO 2 , in a 0.15 m diameter glass stabiliser, using 10 vol.per cent air in nitrogen and a temperature of about 50 0 C. (author)

  12. Composite elements with superconducting ceramic materials and preparation process

    International Nuclear Information System (INIS)

    Drifford, M.; Lambard, J.

    1990-01-01

    Supraconducting ceramic powder is introduced in a ductile metal with an open porosity, then the tube is sealed at both ends and necked to form a composite element which is sintered and the ceramic becomes superconductive by gaseous diffusion. Then the composite element can be placed into a gasproof cladding [fr

  13. Fabrication of lead-free piezoelectric Li2CO3-added (Ba,Ca)(Ti,Sn)O3 ceramics under controlled low oxygen partial pressure and their properties

    Science.gov (United States)

    Noritake, Kouta; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

    2018-02-01

    Reduction-resistant lead-free (Ba,Ca)(Ti,Sn)O3 piezoceramics with high piezoelectric constants were fabricated by optimizing the amount of Li2CO3 added. Oxygen partial pressure was controlled during the sintering of (Ba,Ca)(Ti,Sn)O3 ceramics in a reducing atmosphere using H2-CO2 gas. Enhanced grain growth and a high-polarization state after poling treatment were achieved by adding Li2CO3. Optimizing the amount of Li2CO3 added to (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics sintered under a low oxygen partial pressure resulted in improved piezoelectric properties while maintaining the high sintered density. The prepared Li2CO3-added ceramic samples had homogeneous microstructures with a uniform dispersion of each major constituent element. However, the residual Li content in the 3 mol % Li2CO3-added (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics after sintering was less than 0.3 mol %. Sintered bodies of this ceramic prepared in a CO2 (1.5%)-H2 (0.3%)/Ar reducing atmosphere (PO2 = 10-8 atm at 1350 °C), exhibited sufficient electrical resistivity and a piezoelectric constant (d 33) exceeding 500 pC/N. The piezoelectric properties of this nonreducible ceramic were comparable or superior to those of the same ceramic sintered in air.

  14. Microwave processing for ceramic materials in microsystem technology

    International Nuclear Information System (INIS)

    Rhee, S.

    2002-11-01

    In this study, the applicability of microwaves for sintering of monolithic ceramics and ceramic microcomponents was investigated. Experiments with 2.45 GHz and 30 GHz microwaves were conducted and contrasted to conventional thermal processing. The advantages and disadvantages of microwave processing were then assessed. Nanoscale zirconia and sub-micron lead-zirconate-titanate electroceramics were selected for the evaluation. (orig.)

  15. Tetragonal zirconia ceramics in Zr O2-Ce O2 system (Ce-TZP): preparation, characterization and mechanical properties

    International Nuclear Information System (INIS)

    Andrade Nono, M.C. de.

    1992-01-01

    This paper describes and discusses the results achieved in a study about Ce-TZP ceramics prepared from conventional powder mixtures of Zr O 2 and Ce O 2 (with composition in the range of 8 to 16 mol% Ce O 2 ). Physical and chemical characteristics were related with the powder compaction behavior and with the sintering state. The sintered ceramics showed a level of high porosity (≅ 4%), mainly due to the fairly adequate powder characteristics and compaction. The crystalline phases were analysed from X-rays diffraction data and showed that these ceramics can present tetragonal-to-monoclinic stress induced transformation. The bending strength, fracture toughness and Vickers hardness results were influenced by Ce O 2 content microstructure and sintering temperature. These Ce-TZP ceramics showed mechanical strength results comparable to those published in the international literature. (author)

  16. Effect of polymorphism of Al2O3 on the sintering and microstructure of transparent MgAl2O4 ceramics

    Science.gov (United States)

    Han, Dan; Zhang, Jian; Liu, Peng; Wang, Shiwei

    2017-09-01

    Transparent MgAl2O4 ceramics were fabricated by reactive sintering in air followed by hot isostatic press treatment using commercial Al2O3 powder (γ-Al2O3 or α-Al2O3) and MgO powder as raw materials. The densification rate, microstructure and optical properties of the ceramics were investigated. Densification temperature of the sample from γ-Al2O3/MgO was lower than that from α-Al2O3/MgO. However, in-line transmission (2 mm thick) of the sample from α-Al2O3/MgO at the wavelength of 600 nm and 1100 nm were respectively 77.7% and 84.3%, higher than those (66.7%, 81.4%) of the sample from γ-Al2O3/MgO. SEM observation revealed that the sample from α-Al2O3/MgO exhibited a homogeneous and pore-free microstructure, while, the sample from γ-Al2O3/MgO showed an apparent bimodal microstructure containing pores.

  17. Bioactivity analysis of the Ta (V doped SiO2–CaO–Na2O–P2O5 ceramics prepared by solid state sintering method

    Directory of Open Access Journals (Sweden)

    Rehana Zia

    2016-02-01

    Full Text Available The main objective of the study was to control the degradation rate of material at a higher degradation rate improving the chemical stability of the material. Ta is known to have good chemical resistance, biocompatibility and show no adverse biological response. In the present study, SiO2–Na2O–CaO–P2O5 bioceramics with different Ta2O5 contents was prepared by solid state sintering method at 1000 °C. The as-sintered ceramics were subjected to immersion studies in stimulated body fluid (SBF for 21 days under static condition and characterized by XRD, FTIR, SEM, and AAS. The findings of the research indicate that the addition of Ta2O5 controlled degradability, and all samples showed sufficient bioactivity.

  18. Mechanical performance of a biocompatible biocide soda-lime glass-ceramic.

    Science.gov (United States)

    López-Esteban, S; Bartolomé, J F; Dí Az, L A; Esteban-Tejeda, L; Prado, C; López-Piriz, R; Torrecillas, R; Moya, J S

    2014-06-01

    A biocompatible soda-lime glass-ceramic in the SiO2-Na2O-Al2O3-CaO-B2O3 system containing combeite and nepheline as crystalline phases, has been obtained at 750°C by two different routes: (i) pressureless sintering and (ii) Spark Plasma Sintering. The SPS glass-ceramic showed a bending strength, Weibull modulus, and toughness similar values to the cortical human bone. This material had a fatigue limit slightly superior to cortical bone and at least two times higher than commercial dental glass-ceramics and dentine. The in vitro studies indicate that soda-lime glass-ceramic is fully biocompatible. The in vivo studies in beagle jaws showed that implanted SPS rods presented no inflammatory changes in soft tissues surrounding implants in any of the 10 different cases after four months implantation. The radiological analysis indicates no signs of osseointegration lack around implants. Moreover, the biocide activity of SPS glass-ceramic versus Escherichia coli, was found to be >4log indicating that it prevents implant infections. Because of this, the SPS new glass-ceramic is particularly promising for dental applications (inlay, crowns, etc). Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Consolidation & Factors Influencing Sintering Process in Polymer Powder Based Additive Manufacturing

    Science.gov (United States)

    Sagar, M. B.; Elangovan, K.

    2017-08-01

    Additive Manufacturing (AM) is two decade old technology; where parts are build layer manufacturing method directly from a CAD template. Over the years, AM techniques changes the future way of part fabrication with enhanced intricacy and custom-made features are aimed. Commercially polymers, metals, ceramic and metal-polymer composites are in practice where polymers enhanced the expectations in AM and are considered as a kind of next industrial revolution. Growing trend in polymer application motivated to study their feasibility and properties. Laser sintering, Heat sintering and Inhibition sintering are the most successful AM techniques for polymers but having least application. The presentation gives up selective sintering of powder polymers and listed commercially available polymer materials. Important significant factors for effective processing and analytical approaches to access them are discussed.

  20. Development of import subtituting technologies for increasing productivity of sintering machines and strength of agglomerates

    Directory of Open Access Journals (Sweden)

    В. Л. Трушко

    2016-11-01

    Full Text Available A problem of industrial fluxed agglomerates self-destruction in the process of cooling after sintering has been examined. It has been revealed that the main reason of strength degradation is polymorphism of dicalcium silicate Ca2SiO4 (or short designation С2S: β-Ca2SiO4 ® γ-Ca2SiO4. Ways for increasing the  agglomerate  strength by physical and crystal-chemical stabilization of the high temperature modification of C2S have been proposed and tested. Physical stabilization of C2S agglomerate is increased with its structure reinforcement due to thickening of walls between large pores that is achieved by increasing height of the sintered layer through improvement of its gas permeability. The task is addressed by substituting the previously used import sintering ore with the  polydisperse ore from the Yakovlevo field, which improves the charge  pelletizing by 3-4 times and helps to bring the  height of the sintered layer and the strength of the domestic agglomerate up to the international best practice standards, while eliminating a need to purchase import high-vacuum   exhausters. In practice crystal-chemical stabilization of C2S within iron-ore  agglomerate is ensured by adding an  opti- mal multicomponent additive in the form of the    waste product  generated in production  of alumina  from bauxites, i.e. the red mud, to the initial sinter charge. Thus mechanical strength of agglomerates and pellets is increased by 5-10 % and their hot strength improves by 20-40 %. The productivity of sintering machines and blast furnaces improves by 5-10 %. Specific coke consumption reduces by 2-2.5 %. In production of iron-ore pellets red mud is substituting the import  bentonite.

  1. Elaboration of new ceramic composites containing glass fibre production wastes

    Directory of Open Access Journals (Sweden)

    Rozenstrauha, I.

    2013-04-01

    Full Text Available Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50% of organic matter as well as waste glass from aluminiumborosilicate glass fibre with relatively high softening temperature (> 600 ºC. In order to elaborate different new ceramic products (porous or dense composites the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia with illite content in clay fraction up to 80-90% was used as a matrix. The raw materials were investigated by differential-thermal (DTA and XRD analysis. Ternary compositions were prepared from mixtures of 15–35 wt % of sludge, 20 wt % of waste glass and 45–65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 ºC in different treatment conditions. Materials produced in temperature range 1090–1100 ºC with the most optimal properties - porosity 38-52%, water absorption 39–47% and bulk density 1.35–1.67 g/cm3 were selected for production of porous ceramics and materials showing porosity 0.35–1.1%, water absorption 0.7–2.6 % and bulk density 2.1–2.3 g/cm3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM. By X-ray diffraction analysis (XRD the quartz, diopside and anorthite crystalline phases were detected.Durante la obtención de ciertas fibras de vidrio se generan dos subproductos o residuos principalmente: Lodo de arcilla montmorillonítica capaz de adsorber el 50 % de materia orgánica y un vidrio silicato alumínico con temperatura de reblandecimiento relativamente alta (> 600 ºC. Con el fin de elaborar nuevos

  2. Silicate bonded ceramics of laterites

    International Nuclear Information System (INIS)

    Wagh, A.S.; Douse, V.

    1989-05-01

    Sodium silicate is vacuum impregnated in bauxite waste (red mud) at room temperature to develop ceramics of mechanical properties comparable to the sintered ceramics. For a concentration up to 10% the fracture toughness increases from 0.12 MNm -3/2 to 0.9 MNm -3/2 , and the compressive strength from 7 MNm -2 to 30 MNm -2 . The mechanical properties do not deteriorate, when soaked in water for an entire week. The viscosity and the concentration of the silicate solution are crucial, both for the success of the fabrication and the economics of the process. Similar successful results have been obtained for bauxite and lime stone, even though the latter has poor weathering properties. With scanning electron microscopy and energy dispersive analysis, an attempt is made to identify the crystals formed in the composite, which are responsible for the strength. The process is an economic alternative to the sintered ceramics in the construction industry in the tropical countries, rich in lateritic soils and poor in energy. Also the process has all the potential for further development in arid regions abundant in limestone. (author). 6 refs, 20 figs, 3 tabs

  3. Influence of Y2O3 Addition on Crystallization, Thermal, Mechanical, and Electrical Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramic for Ceramic Ball Grid Array Package

    Science.gov (United States)

    Li, Bo; Li, Wei; Zheng, Jingguo

    2018-01-01

    Y2O3 addition has a significant influence on the crystallization, thermal, mechanical, and electrical properties of BaO -Al2O3 -B2O3 -SiO2 (BABS) glass-ceramics. Semi-quantitative calculation based on x-ray diffraction demonstrated that with increasing Y2O3 content, both the crystallinity and the phase content of cristobalite gradually decreased. It is effective for the additive Y2O3 to inhibit the formation of cristobalite phase with a large coefficient of thermal expansion value. The flexural strength and the Young's modulus, thus, are remarkably increased from 140 MPa to 200 MPa and 56.5 GPa to 63.7 GPa, respectively. Also, the sintering kinetics of BABS glass-ceramics with various Y2O3 were investigated using the isothermal sintering shrinkage curve at different sintering temperatures. The sintering activation energy Q sharply decreased from 99.8 kJ/mol to 81.5 kJ/mol when 0.2% Y2O3 was added, which indicated that a small amount of Y2O3 could effectively promote the sintering procedure of BABS glass-ceramics.

  4. Effects of PbO-B2O3 Glass Doping on the Sintering Temperature and Piezoelectric Properties of 0.35Pb (Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 Ceramics

    Science.gov (United States)

    Yi, Jinqiao; Shen, Meng; Liu, Sisi; Jiang, Shenglin

    2015-12-01

    0.35Pb(Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 (PNN-PZT) ceramics doped with 0.5PbO-0.5B2O3 glass have been synthesized by the conventional solid-state sintering technique. The effects of 0.5PbO-0.5B2O3 glass on the sintering temperature and piezoelectric properties of PNN-PZT ceramics were studied. The results indicated that the sintering temperature of PNN-PZT was significantly reduced due to the incorporation of 0.5PbO-0.5B2O3 glass dopant. When the content of 0.5PbO-0.5B2O3 glass was 0.5 wt.%, the sintering temperature of PNN-PZT was observed to reduce from above 1200°C to 920°C while the samples maintained high density (7.91 g/cm3), excellent piezoelectric constant ( d 33 = 479 pC/N), large electromechanical coupling coefficient ( K p = 0.55), and relatively low electromechanical quality factor ( Q m = 79). Moreover, large dielectric constant ( ɛ 33 T / ɛ 0 = 2904) and low dielectric loss (tan δ = 0.0166) were obtained in this work.

  5. Sintering and microstructure of ice: a review

    International Nuclear Information System (INIS)

    Blackford, Jane R

    2007-01-01

    Sintering of ice is driven by the thermodynamic requirement to decrease surface energy. The structural morphology of ice in nature has many forms-from snowflakes to glaciers. These forms and their evolution depend critically on the balance between the thermodynamic and kinetic factors involved. Ice is a crystalline material so scientific understanding and approaches from more conventional materials can be applied to ice. The early models of solid state ice sintering are based on power law models originally developed in metallurgy. For pressure sintering of ice, these are based on work on hot isostatic pressing of metals and ceramics. Recent advances in recognizing the grain boundary groove geometry between sintering ice particles require models that use new approaches in materials science. The newer models of sintering in materials science are beginning to incorporate more realistic processing conditions and microstructural complexity, and so there is much to be gained from applying these to ice in the future. The vapour pressure of ice is high, which causes it to sublime readily. The main mechanism for isothermal sintering of ice particles is by vapour diffusion; however other transport mechanisms certainly contribute. Plastic deformation with power law creep combined with recrystallization become important mechanisms in sintering with external pressure. Modern experimental techniques, low temperature scanning electron microscopy and x-ray tomography, are providing new insights into the evolution of microstructures in ice. Sintering in the presence of a small volume fraction of the liquid phase causes much higher bond growth rates. This may be important in natural snow which contains impurities that form a liquid phase. Knowledge of ice microstructure and sintering is beneficial in understanding mechanical behaviour in ice friction and the stability of snow slopes prone to avalanches. (topical review)

  6. Use of the extraction residue of emeralds in a formulation mass of ceramic tiles

    International Nuclear Information System (INIS)

    Cavalcante, R. F.; Nascimento, R.M.; Paskocimas, C.A.; Dutra, R.P.S.

    2012-01-01

    Companies involved in mining and beneficiation of emerald represent an important area of industrial development in Brazil, with a significant contribution to world production of this ore. As a result, large volumes of waste generated and emerald are constantly abandoned in the environment, contributing negatively to their preservation. On the other hand the interest in the use of mining waste as an additive in production of ceramic materials has grown among researchers in recent years. The ceramic industry is constantly seeking to expand the market for the sector and trying to improve product quality and increase the variety of applications. The technology of obtaining ceramic coating that uses waste from mining is still a largely unexplored market. Thus, the purpose of this study was to characterize the waste generated from mining emerald as well as to evaluate its potential use as raw material for production melting of ceramic tiles. Ceramic mixtures were prepared from raw materials characterized by X-ray fluorescence and X-ray diffraction. Five compositions were prepared using the waste codes of emeralds from 0%, 10%, 20%, 30% and 40%. Samples were prepared by pressing, sintered at 1000, 1100 and 1200 deg C and characterized to establish their mineralogical composition, water absorption, linear shrinkage and modulus of rupture. The results showed that the residue of emeralds studied can be embedded in the mass of ceramic tiles up to 20% in replacement of feldspar without compromising the end product properties. (author)

  7. Production of continuous piezoelectric ceramic fibers for smart materials and active control devices

    Science.gov (United States)

    French, Jonathan D.; Weitz, Gregory E.; Luke, John E.; Cass, Richard B.; Jadidian, Bahram; Bhargava, Parag; Safari, Ahmad

    1997-05-01

    Advanced Cerametrics Inc. has conceived of and developed the Viscous-Suspension-Spinning Process (VSSP) to produce continuous fine filaments of nearly any powdered ceramic materials. VSSP lead zirconate titanate (PZT) fiber tows with 100 and 790 filaments have been spun in continuous lengths exceeding 1700 meters. Sintered PZT filaments typically are 10 - 25 microns in diameter and have moderate flexibility. Prior to carrier burnout and sintering, VSSP PZT fibers can be formed into 2D and 3D shapes using conventional textile and composite forming processes. While the extension of PZT is on the order of 20 microns per linear inch, a woven, wound or braided structure can contain very long lengths of PZT fiber and generate comparatively large output strokes from relatively small volumes. These structures are intended for applications such as bipolar actuators for fiber optic assembly and repair, vibration and noise damping for aircraft, rotorcraft, automobiles and home applications, vibration generators and ultrasonic transducers for medical and industrial imaging. Fiber and component cost savings over current technologies, such as the `dice-and-fill' method for transducer production, and the range of unique structures possible with continuous VSSP PZT fiber are discussed. Recent results have yielded 1-3 type composites (25 vol% PZT) with d33 equals 340 pC/N, K equals 470, and g33 equals 80 mV/N, kt equals 0.54, kp equals 0.19, dh equals 50.1pC/N and gh equals 13 mV/N.

  8. Ceramic UO2 powder production at Cameco Corporation

    International Nuclear Information System (INIS)

    Mulligan, J.J.

    2005-01-01

    This paper describes the various aspects of ceramic grade UO 2 powder production at Cameco Corporation's Port Hope conversion facility. It discusses the significant safety systems, production processes and plant monitoring and control systems. It also provides an insight into how various support groups such as Quality Assurance, Analytical Services, and Technology Development contribute to the consistent production of high quality UO 2 powder. The ability of Cameco to identify, measure and control the physical and chemical properties of ceramic grade UO 2 has resulted in the production of uniform quality powder that has consistently met customer requirements. (author)

  9. Fabrication and characterisation of ceramics via low-cost DLP 3D printing

    Directory of Open Access Journals (Sweden)

    Giftymol Varghese

    2018-01-01

    Full Text Available A stereolithography-based additive manufacturing technique has been used for the fabrication of advanced ceramics. A customised 3D printer using a Digital Light Processing (DLP projector as UV source has been built to fabricate green bodies from photosensitive resins loaded with 25–60 wt% of alumina, 3- and 8-YSZ. The 3D-printed bodies were then sintered in the 1200–1500 °C and exhibited thermal stability. As expected, higher ceramic loadings rendered objects with higher density for a given sintering temperature. The limit of solid loading in the resin is approximately 60% and beyond those contents, the extra ceramic appears as powder loosely adhered to the sintered objects. Photogrammetry was used to evaluate the accuracy of the 3D printing process and highlighted a marked deviation between the CAD model and the resulting object, particularly in the top part of the specimens, possibly due to the use of volatile solvents which cause changes in the photoresins used. Nevertheless, that problem may be overcome by thermostatising the printer vat and/or using solvents with higher boiling point. The results obtained suggest the potential application of low cost DLP 3D printing techniques to process ceramics for a number of applications including ceramic fuel cells, piezoelectrics, dental applications, etc.

  10. Microstructural, compositional and mechanical properties of the archaeological indigenous ceramics of Caninhas, Sao Paulo,Brazil

    International Nuclear Information System (INIS)

    Nakano, F.P.; Taguchi, S.P.; Ribeiro, R.B.; Rosa, S.J.L.; Bornal, W.G.; Queiroz, C.M.

    2009-01-01

    Archaeological ceramics contain infinity of data about social and cultural indigenous site Caninhas/SP. The ceramics present a gradient of color (ochre to dark gray), when from the surface to the center of the piece, indicating compositional variability caused by inefficient sintering carried out by indigenous peoples. It was analyzed the composition phases by X-rays diffraction (XRD) and mapping by EDS, identifying the illite, quartz and lutecite phases (ochre region) and illite, quartz, hydrated alumina and lutecite phases (dark gray region). The results of EDS confirmed the stages identified by X-rays diffraction and suggesting the presence of roots and scrap of ceramics sintered in the composition of indigenous ceramics, when compared by optical microscope and scanning electron microscope. Vickers hardness identified as fragile and heterogeneous are archaeological ceramics, reaching approximately 203 HV in the grains of silica and 16 HV in the ceramic matrix. (author)

  11. Laser Sintering Technology and Balling Phenomenon.

    Science.gov (United States)

    Oyar, Perihan

    2018-02-01

    The aim of this review was to evaluate the balling phenomenon which occurs typically in Selective Laser Sintering (SLS). The balling phenomenon is a typical SLS defect, and observed in laser sintered powder, significantly reduces the quality of SLS, and hinders the further development of SLS Technology. Electronic database searches were performed using Google Scholar. The keywords "laser sintering, selective laser sintering, direct metal laser melting, and balling phenomenon" were searched in title/abstract of publications, limited to December 31, 2016. The inclusion criteria were SLS, balling phenomenon, some alloys (such as Cr-Co, iron, stainless steel, and Cu-based alloys) mechanical properties, microstructure and bond strength between metal-ceramic crown, laboratory studies, full text, and in English language. A total of 100 articles were found the initial search and yielded a total of 50 studies, 30 of which did not fulfill the inclusion criteria and were therefore excluded. In addition, 20 studies were found by screening the reference list of all included publications. Finally, 40 studies were selected for this review. The method in question is regulated by powder material characteristics and the conditions of laser processing. The procedure of formation, affecting factors, and the mechanism of the balling effect are very complex.

  12. Clay Ceramic Filter for Water Treatment

    Directory of Open Access Journals (Sweden)

    Zereffa Enyew Amare

    2017-05-01

    Full Text Available Ceramic water filters were prepared from different proportions of kaolin and soft wood and sintered at 900 °C, 950 °C, and 1000 °C. The flow rate, conductivity, pH of filtered water and removal efficiency (microbial, water hardness agent’s, nitrite and turbidity were analysed. The ceramic filter with 15 % saw dust, 80 % clay and 5 % grog that was fired at temperature of 950 °C or 1000 °C showed the best removal efficiency. Statistical ANOVA tests showed a significant difference between ceramic filters with various compositions in their removal efficiencies.

  13. Reactive spark plasma synthesis of CaZrTi2O7 zirconolite ceramics for plutonium disposition

    Science.gov (United States)

    Sun, Shi-Kuan; Stennett, Martin C.; Corkhill, Claire L.; Hyatt, Neil C.

    2018-03-01

    Near single phase zirconolite ceramics, prototypically CaZrTi2O7, were fabricated by reactive spark plasma sintering (RSPS), from commercially available CaTiO3, ZrO2 and TiO2 reagents, after processing at 1200 °C for only 1 h. Ceramics were of theoretical density and formed with a controlled mean grain size of 1.9 ± 0.6 μm. The reducing conditions of RSPS afforded the presence of paramagnetic Ti3+, as demonstrated by EPR spectroscopy. Overall, this study demonstrates the potential for RSPS to be a disruptive technology for disposition of surplus separated plutonium stockpiles in ceramic wasteforms, given its inherent advantage of near net shape products and rapid throughput.

  14. Fatigue properties and impedance analysis of potassium sodium niobate-strontium titanate transparent ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhiyong; Fan, Huiqing; Lei, Shenhui; Wang, Ju; Tian, Hailin [Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Xi' an (China)

    2016-10-15

    Highly transparent ferroelectric ceramics based on 0.9K{sub 0.5}Na{sub 0.5}NbO{sub 3}-0.1SrTiO{sub 3} were prepared using a pressure-less solid-state sintering method without using hot isostatic pressing and spark plasma sintering. An independence electromechanical response of bipolar switching cycles (S{sub 33} only degraded 3.2 % up to 10{sup 7} cycles) was presented in this transparent ceramics, which indicated an extremely stable property under electric field. From impedance spectroscopy and X-ray photoelectron spectroscopy analyses, it was concluded that such optical transparency and fatigue-resistant behaviors were mainly attributed to the lower density of oxygen vacancies in the ceramics. (orig.)

  15. Flame-sintered ceramic exoelectron dosimeter samples

    International Nuclear Information System (INIS)

    Petel, M.; Holzapfel, G.

    1979-01-01

    New techniques for the preparation of integrating solid state dosimeters, particularly exoelectron dosimeters, have been initiated. The procedure consists in melting the powdered dosimeter materials in a hot, fast gas stream and depositing the ceramic layer. The gas stream is generated either through a chemical flame or by an electrical arc plasma. Results will be reported on the system Al 2 O 3 /stainless steel as a first step to a usable exoelectron dosimeter

  16. [Fractographic analysis of clinically failed anterior all ceramic crowns].

    Science.gov (United States)

    DU, Qian; Zhou, Min-bo; Zhang, Xin-ping; Zhao, Ke

    2012-04-01

    To identify the site of crack initiation and propagation path of clinically failed all ceramic crowns by fractographic analysis. Three clinically failed anterior IPS Empress II crowns and two anterior In-Ceram alumina crowns were retrieved. Fracture surfaces were examined using both optical stereo and scanning electron microscopy. Fractographic theory and fracture mechanics principles were applied to disclose the damage characteristics and fracture mode. All the crowns failed by cohesive failure within the veneer on the labial surface. Critical crack originated at the incisal contact area and propagated gingivally. Porosity was found within the veneer because of slurry preparation and the sintering of veneer powder. Cohesive failure within the veneer is the main failure mode of all ceramic crown. Veneer becomes vulnerable when flaws are present. To reduce the chances of chipping, multi-point occlusal contacts are recommended, and layering and sintering technique of veneering layer should also be improved.

  17. Synthesis and characterization of nickel oxide doped barium strontium titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, M. [Dept. of Electrical Engineering, Bengal Institute of Technology Kolkata (India); Mukherjee, S. [Dept. of Metallurgical Engineering, Jadavpur University, Kolkata (India); Maitra, S. [Govt. College of Engg. and Ceramic Technology, Kolkata (India)

    2012-01-15

    Barium strontium titanate (BST) ceramics (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} were synthesized by solid state sintering using barium carbonate, strontium carbonate and rutile as the precursor materials. The samples were doped with nickel oxide in different proportions. Different phases present in the sintered samples were determined from X-ray diffraction investigation and the distribution of different phases in the microstructure was assessed from scanning electron microscopy study. It was observed that the dielectric properties of BST were modified significantly with nickel oxide doping. These ceramics held promise for applications in tuned circuits. (author)

  18. Ceramic material with porosity for adsorption in spilling of petroleum; Material ceramico com alta porosidade para adsorcao em derrame de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Maria Celeste Ribeiro; Mothe, Cheila G. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Escola de Quimica; Duailibi Filho, Jamil [Instituto Nacional de Tecnologia (INT), Rio de Janeiro, RJ (Brazil)

    2004-07-01

    In the present work the ceramic blocks with high porosity were placed into a tank, where simulated oil spill with petroleum and water by the Guanabara Bay. From a mixture of caulinitic clays from the Rio de Janeiro State and pore forming agent, conforming by extrusion followed by drying and sintering between 900 deg C and 1100 deg C porous ceramic blocks were processed. The adsorption process was monitored by thermal analysis in samples before and after sintering, ceramic after adsorption and petroleum. The TG/DTG curves of the samples, before sintering, showed a mass loss around 10%. At 400 deg C, suggests that the mass loss was caused by the dehydroxylation of caulinitic, samples after sintering did not show mass loss at all, ceramic with petroleum adsorption showed at 100 deg C water loss between 150 deg C and 470 deg C, suggesting oil's decomposition and the second one showed oil adsorption about 22%. The preliminary results seem to be a useful tool since it showed the composition's influence on the adsorption's properties. Many works have studied the oil adsorption with caulinitic clays particles but did not use porous ceramic. (author)

  19. A CO2 laser based system for the production of nanoscaled powders

    International Nuclear Information System (INIS)

    Kurland, H.-D.; Schindler, K.; Staupendahl, G.; Oestreich, Ch.; Loogk, M.; Mueller, E.

    2002-01-01

    Nowadays the world-wide industrial competition is increasingly determined by the use of new materials which allow optimised and in part totally new qualities of products or the production of more compact components. Thereby the importance of ultrafine ceramic powders with grain sizes of only a few nanometers rises rapidly. These powders show some interesting physical and chemical features which result from the extremely small dimensions of their particles, for example very high specific surfaces, high surface energy or special behaviour in the phase transformation. Their thermodynamic and kinetic (short diffusion lengths) parameters are mirrored in high sintering activities and hence relatively low sintering temperatures as well as very special properties of the sintered materials, especially the possibility of super plasticity. Nanoscaled powders also have a broad potential for the production of thin layers for example in the electronics industry or as part of composite materials with components of lower thermal stability. At present different technologies for the manufacturing of nanoscaled powders are intensively used and developed. In this paper a technique for the production of ceramic nanopowders by evaporation of solid starting materials with CO 2 laser radiation is presented

  20. Research of ceramic matrix for a safe immobilization of radioactive sludge waste

    Science.gov (United States)

    Dorofeeva, Ludmila; Orekhov, Dmitry

    2018-03-01

    The research and improvement of the existing method for radioactive waste hardening by fixation in a ceramic matrix was carried out. For the samples covered with the sodium silicate and tested after the storage on the air the speed of a radionuclides leaching was determined. The properties of a clay ceramics and the optimum conditions of sintering were defined. The experimental data about the influence of a temperature mode sintering, water quantities, sludge and additives in the samples on their mechanical durability and a water resistance were obtained. The comparative analysis of the conducted research is aimed at improvement of the existing method of the hardening radioactive waste by inclusion in a ceramic matrix and reveals the advantages of the received results over analogs.

  1. Effects of talc and clay addition on pressureless sintering of porous ...

    Indian Academy of Sciences (India)

    Administrator

    costs as well as decreasing the sintering temperature are required ... In the glass ceramics, the talc and clay was widely used as a flux to decrease ... nitrogen–gas pressure of 0⋅3 MPa. .... rate-controlling for high diffusion velocity and diffusion.

  2. Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

    Science.gov (United States)

    Leenakul, Wilaiwan; Tunkasiri, Tawee; Tongsiri, Natee; Pengpat, Kamonpan; Ruangsuriya, Jetsada

    2016-04-01

    45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. TECHNOLOGY OF PRODUCTION OF CERAMIC TILES BASED ON DOLERITE AND FUSIBLE CLAY

    Directory of Open Access Journals (Sweden)

    Pleshko Marianna Viktorovna

    2018-02-01

    Full Text Available The paper presents a completely new composition of the ceramic mass for production of ceramic tiles for interior lining of walls, on the basis of fusible clay. The optimal compositions of jade engobe and glossy glaze, the most suitable for this composition, are determined. A new technological scheme is developed for production of ceramic tiles for interior lining based on dolerite and fusible clay. The curve of firing, which is the most suitable for charge masses and decorative coating compositions being used, has been constructed. Subject: ceramic mass for the production of ceramic facing tiles. Ceramic tiles are the most popular building material in Russia. The most promising technology for its production from the standpoint of technical and economic efficiency is the technology of rapid single firing, which is rarely used at the plants of our country. In this regard, the development and implementation of new effective compositions of ceramic masses and decorative coatings that are the most compatible with the specifics of rapid single firing technology, based on new unconventional raw materials, are very relevant and promising. Research objectives: development of technological parameters, compositions of ceramic masses and decorative coatings of ceramic tiles for the internal wall lining that provide an increase in tiles production efficiency using the technology of rapid single firing through the use of non-traditional plagioclase-pyroxene raw materials: dolerites, loam and technogenic raw materials. Materials and methods: technological, numerical and experimental studies were conducted. To select the optimal composition of the ceramic mass, the method of mathematical planning was used, namely the simplex-centroid design of Scheffe. To identify the scientific foundations of the energy-efficient production technology being developed, differential thermal and X-ray phase, optical, electron microscopic and dilatometric studies were applied

  4. Possibilities of special cements in ceramic applications

    International Nuclear Information System (INIS)

    Capmas, A.; Bier, T.A.

    1993-01-01

    About 25 years ago, the only way to have confinement material for high temperature applications was to prepare a ceramic by sintering or fusion at high temperature. A new technology came, with the production of Low Cement Castables. This new product was obtained by a careful choice of the granulometry of the aggregates, an optimization of the defloculation of fine particles, including the cement (Calcium Aluminate Cement) and the addition of silica fume. Silica fume brought two improvements: a) a fluidifying effect, due partly to the low sensitivity of viscosity to pH, and partly to the geometric effect of the nicely spherical particle, b) a chemical effect, brought by the reaction of silica and Calcium Aluminate Cement to give a coherent zeolithic structure, through which water could escape during the first firing. From a ceramist point of view, it is interesting to understand how this components, nearly colloidal system mixed in water can be heated up to ceramization without any noticeable change in mechanical characteristics and shrinkage. From a more practical point of view, it is also interesting to realize that some characteristics, usually attributed only to ceramics, also apply with low cement castables technology: high compressive strength, flexural strength, corrosion resistance, abrasion resistance, impact resistance. (orig.)

  5. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; Zanetti De Florio, Daniel

    2017-01-01

    Gadolinium, yttrium and samarium-doped barium cerate (BCGd, BCY and BCSm, respectively) polycrystalline green pellets were submitted to electric field-assisted pressureless sintering experiments isothermally in the temperature range 800-1200oC under 100-200 V cm-1 electric fields, limiting to 1-5...

  6. Fabrication and studies of microstructure and mechanical properties of Ba2MgNbO5,5 ceramics for application in the petroleum industry

    International Nuclear Information System (INIS)

    Oliveira, J.C. da S.; Ferreira, R.A.S.; Yadava, Y.P.

    2011-01-01

    The present work aims at the elaboration of a ceramic complex perovskite ceramic components for temperature sensors for oil wells, as well as the study of microstructural characteristics and mechanical properties of ceramics Ba 2 MgNbO 5,5 . The manufacture of pottery Ba 2 MgNbO 5,5 was performed using a thermo-mechanical and solid-state sintering. The pellets of compressed green were calcined for 24 hours at a temperature of 1200°C and then crushed with the help of a set pistil / agate mortar. The resulting powder was compacted and new pellets were sintered at a temperature of 1250°C. Basic studies of stability of ceramics sintered in the environment of crude oil, from onshore wells and the sea, the state of Sergipe in northeastern Brazil. The test results showed that the ceramic is inert to crude oil and can be used to produce ceramic components for the oil industry. (author)

  7. Studies on development of new functional natural materials from agricultural products - Technology developments for ceramic powders and materials from rice phytoliths

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dae Kap; Kim, Yong Ik [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Yoon, Nang Kyu; Seong, Seo Yong [Myongseong Ceramics Com., Taejon (Korea, Republic of); Ryu, Sang Eun [Bae Jae Univ., Taejon (Korea, Republic of); Lee, Jae Chun [Myungji Univ., Seoul (Korea, Republic of)

    1995-08-01

    Based on an estimation of annual rice production of 5.2 million tons, rice husks by-production reaches to 1.17 million tons per year in Korea. Distinguished to other corns, rice contains a lot of Si; 10-20% by weight in rice husks calculated as silica. The aim of this research project is to develop technologies for ceramic powders and materials utilizing the silica in rice husks called phytoliths. In this first year research, researches of the following subjects were performed; material properties of rice husks, milling of rice husks, acid treatments, oxidations at low and high temperatures, sintering and crystalization of amorphous silica, low temperature carburization, formation of silicon carbide whiskers, and brick lightening method using milled rice husks. 11 tabs., 49 figs., 75 refs. (Author).

  8. FABRICATION AND MECHANICAL PROPERTIES OF Na0.5Bi0.5TiO3–BaTiO3 LEAD-FREE PIEZOELECTRIC CERAMICS

    Directory of Open Access Journals (Sweden)

    PAN YUSONG

    2014-03-01

    Full Text Available Piezoelectric ceramics with 0.94Na0.5Bi0.5TO3–0.06BaTiO3 compositions were fabricated by solid state mixed oxide method and sintered at different temperatures varying from 1050°C to 1150°C to obtain dense ceramics. Phase analysis using X-ray diffraction showed tetragonal perovskite structure of Na0.5Bi0.5TO3 with no BaTiO3 peak detected. The SEM observation revealed that the crystal grain size of the piezoelectric ceramics is on the nano-size dimensions under all the sintering temperature. The study on the compressive mechanical characteristics showed that the compressive strength of the 0.94Na0.5Bi0.5TO3–0.06BaTiO3 piezoelectric ceramics increases with the rise of sintering temperature and sintering time. The change behavior of the compressive strength with the rise of cold pressure presents increasing firstly and then decreases.

  9. Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic; Elaboration de ceramiques nanostructurees en carbure de silicium (SiC): de la synthese de poudre a la ceramique frittee

    Energy Technology Data Exchange (ETDEWEB)

    Reau, A. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMA), 91 - Gif-sur-Yvette (France)

    2008-07-01

    Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC{sub f}/SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC{sub f}/SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

  10. Structure and multiferroic properties of barium hexaferrite ceramics

    International Nuclear Information System (INIS)

    Tan, Guolong; Chen, Xiuna

    2013-01-01

    Simultaneous occurrence of large ferroelectricity and strong ferromagnetism have been observed in barium hexaferrite ceramics. Barium hexaferrite (BaFe 12 O 19 ) powders with hexagonal crystal structure were successfully synthesized in a polymer precursor method using barium acetate and ferric acetylacetonate as the precursors. The powders were pressed into pellets which were sintered into ceramics at 1200 °C and 1300 °C for 1 h. The structure and morphology of the ceramics were examined using X-ray diffraction and field emission scanning electron microscopy. Large spontaneous polarization was observed in the BaFe 12 O 19 ceramics at room temperature, revealing a clear ferroelectric hysteresis loop. The maximum remanent polarization of the BaFe 12 O 19 ceramic was estimated approximately 11.8 μC cm −2 . The FeO 6 octahedron in its perovskite-like hexagonal unit cell and the shift of Fe 3+ off the center of octahedron are suggested to be the origin of the polarization in BaFe 12 O 19 . The BaFe 12 O 19 ceramics also showed strong ferromagnetism at room temperature. - Graphical abstract: Ferroelectric hysteresis loops of BaFe 12 O 19 ceramics measured at a frequency of 120 Hz, which shows that the ceramics sintered at 1200 °C is ferroelectric with P r ∼11.8 μC/cm 2 . Highlights: ► Large ferroelectricity and strong ferromagnetism were observed in barium hexaferrite ceramics. ► The maximum remanent polarization of the BaFe 12 O 19 ceramic was estimated to be 11.8 μC cm −2 . ► The FeO 6 octahedron and off-center shift of Fe 3+ are suggested to be the origin of the polarization.

  11. Sinterability and microstructure evolution during sintering of ferrous powder mixtures

    Directory of Open Access Journals (Sweden)

    Kétner Bendo Demétrio

    2013-01-01

    Full Text Available The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%, in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

  12. Effects of process variables on the properties of YBa2Cu3O(7-x) ceramics formed by investment casting

    Science.gov (United States)

    Hooker, M. W.; Taylor, T. D.; Leigh, H. D.; Wise, S. A.; Buckley, J. D.; Vasquez, P.; Buck, G. M.; Hicks, L. P.

    1993-01-01

    An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa2Cu3O7 ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g., particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.

  13. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; de Florio, D. Z.

    2017-01-01

    Gadolinium, yttrium and samarium-doped barium cerate pressed pellets were submitted to flash sintering experiments isothermally in the temperature range 800-1300oC under 200 V cm-1 electric field. The pellets were positioned inside a dilatometer furnace with Pt-Ir electrodes connected either to a...

  14. Fabrication of fully ceramic microencapsulated fuel by hot pressing

    International Nuclear Information System (INIS)

    Lee, H. G.; Kim, D. J; Park, J. Y.; Kim, W. J.; Lee, S. J

    2014-01-01

    Fully ceramic microencapsulated(FCM) nuclear fuel is one of the recently suggested concept to enhance stability nuclear fuel itself. The requirements to increase the accident tolerance of nuclear fuel are mainly two parts: First, the performance has to be maintained compared to the existing UO 2 nuclear fuel and zircaloy cladding system under the normal operation condition. Second, under the severe accident condition, the high temperature structural integrity has to be kept and the generation rate of hydrogen has to be decrease largely. FCM nuclear fuel consists of tristructural isotropic(TRISO) fuel particle and SiC matrix. The relative thermal conductivity of the SiC matrix as compared to UO 2 is quite good, yielding as-irradiated fuel centerline temperature compared to high temperature for the existing fuel leading to reduced stored energy in the core and reduced operational release of fission products from the fuel. Generally SiC ceramics are fabricated via liquid phase sintering due to strong covalent bonding property and low self-diffusivity coefficient. Hot pressing is very effective method to conduct sintering of SiC powder including different second phase. In this study, SiC-matrix composite including TRISO particles were sintered by hot pressing with Al 2 O 3 -Y 2 O 3 additive system. Various sintering condition were investigated to obtain high relative density above 95%. The internal distribution of TRISO particles within SiC-matrix composite was observed by x-ray radiograph. From the analysis of the cross-section of SiC-matrix composite, the fracture of TRISO particles was investigated. In order to uniform distribution of TRISO particle embedded in the SiC matrix, SiC powder overcoating is considered. SiC matrix composite including TRISO was fabricated by hot pressing. FCM pallets with full density were obtained with Al 2 O 3 -Y 2 O 3 additive system. From the microstructure image, the effect of the sintering additive contents and sintering mechanism

  15. Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

    International Nuclear Information System (INIS)

    Freitas, C.T. de.

    1980-06-01

    The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO 2 gels and UO 2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO 2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author) [pt

  16. Processing of non-oxide ceramics from sol-gel methods

    Science.gov (United States)

    Landingham, Richard; Reibold, Robert A.; Satcher, Joe

    2014-12-12

    A general procedure applied to a variety of sol-gel precursors and solvent systems for preparing and controlling homogeneous dispersions of very small particles within each other. Fine homogenous dispersions processed at elevated temperatures and controlled atmospheres make a ceramic powder to be consolidated into a component by standard commercial means: sinter, hot press, hot isostatic pressing (HIP), hot/cold extrusion, spark plasma sinter (SPS), etc.

  17. The Integration Method of Ceramic Arts in the Product Design

    Science.gov (United States)

    Shuxin, Wang

    2018-03-01

    As one of the four ancient civilization countries, the firing technology of ceramic invented by China has made a great contribution to the progress and development of human society. In modern life, even the development of technology still needs the ceramics, there are large number of artists who take the ceramics as carrier active in the field of contemporary art. The ceramics can be seen everywhere in our daily life, this paper mainly discusses the integration means of ceramic art in the product design.

  18. Determination of suitability of natural Polish resources for production of ceramic proppants applied in gas exploration from European shale formations

    Science.gov (United States)

    Szymanska, Joanna; Mizera, Jaroslaw

    2017-04-01

    Poland is one of few European countries undertaking innovative research towards effective exploration of hydrocarbons form shale deposits. With regard for strict geological conditions, which occur during hydraulic fracturing, it is required to apply ceramic proppants enhancing extraction of shale gas. Ceramic proppants are granules (16/30 - 70/120 Mesh) classified as propping agents. These granules located in the newly created fissures (due to injected high pressure fluid) in the shale rock, act as a prop, what enables gas flow up the well. It occurs if the proppants can resist high stress of the closing fractures. Commonly applied proppants are quartz sands used only for shallow reservoirs and fissile shales (in the USA). Whereas, the ceramic granules are proper for extraction of gas on the high depths at hard geomechanical conditions (in Europe) to increase output even by 30 - 50%. In comparison to other propping materials, this kind of proppants predominate with mechanical strength, smoother surface, lower solubility in acids and also high stability in water. Such parameters can be available through proper raw materials selection to further proppants production. The Polish ceramic proppants are produced from natural resources as kaolin, bauxite and white clay mixed with water and binders. Afterwards, the slurries are subjected to granulation in a mechanical granulator and sintered at high temperatures (1200 - 1550°C). Taking into consideration presence of geomechanical barriers, that prevent fracture propagation beyond shale formations, it is crucial to determine quality of applied natural deposits. Next step is to optimize the proppants production and select the best kind of granules, what was the aim of this research. Utility of the raw materials was estimated on basis of their particle size distribution, bulk density, specific surface area (BET) and thermal analysis (thermogravimetry). Morphology and shape were determined by Scanning Electron Microscopy (SEM

  19. Glass phase expelling during liquid phase sintering of YSZ

    International Nuclear Information System (INIS)

    Souza, Milton Ferreira de; Souza, Dulcina Pinatti Ferreira de

    1998-01-01

    Expelling of the liquid phase during sintering of Zr O 2 -6.5 mol % Y 2 O 3 - 0.5 mol % Pr 2 O 3 ceramic was observed as a result of grain coarsening. ZrO 2 - 7.0 mol % Y 2 O 3 samples, without Pr 2 O 3 addition, do not show this effect under the same sintering conditions. The expelling process is caused by surface tension forces and attracting van der Waals forces between the grains, coupled with the existence of two glass phases on the grain boundaries. The amount of expelled glass phase increases with grain growth, but saturates above 16 μm average grain size. (author)

  20. Spark Plasma Sintering and Densification Mechanisms of Antimony-Doped Tin Oxide Nanoceramics

    Directory of Open Access Journals (Sweden)

    Junyan Wu

    2013-01-01

    Full Text Available Densification of antimony-doped tin oxide (ATO ceramics without sintering aids is very difficult, due to the volatilization of SnO2, formation of deleterious phases above 1000°C, and poor sintering ability of ATO particles. In this paper, monodispersed ATO nanoparticles were synthesized via sol-gel method, and then ATO nanoceramics with high density were prepared by spark plasma sintering (SPS technology using the as-synthesized ATO nanoparticles without the addition of sintering aids. The effect of Sb doping content on the densification was investigated, and the densification mechanisms were explored. The results suggest that ATO nanoparticles derived from sol-gel method show good crystallinity with a crystal size of 5–20 nm and Sb is incorporated into the SnO2 crystal structure. When the SPS sintering temperature is 1000°C and the Sb doping content is 5 at.%, the density of ATO nanoceramics reaches a maximum value of 99.2%. Densification mechanisms are explored in detail.