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Sample records for sintered zirconium-oxide ceramics

  1. Ultrasonic characterization of ceramic joints. [Zirconium Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, W.A. Jr.; McClung, R.W.

    1987-01-01

    We describe the development of ultrasonic techniques for the characterization of cermic joints, including the ability to determine which face of a 50-..mu..m-thick layer of braze filler metal is unbonded, thus providing information about the integreity of the ceramic-filler metal bond. We also describe the development of a rapid technique using Lamb waves to probe the bond between alumina coupons in flexature-strength specimens, which geometry makes conventional ultrasonic evaluation of the bond difficult. Also described are techniques for the detection of cracking under sessile drops on alumina disks and the determination of the extent and profile of cracks produced in the bond of flexture-strength specimens subjected to three-point bending. 3 refs., 13 figs.

  2. Effects of Dental Adhesive Cement and Surface Treatment on Bond Strength and Leakage of Zirconium Oxide Ceramics

    National Research Council Canada - National Science Library

    TSUKAKOSHI, Makoto; SHINYA, Akikazu; GOMI, Harunori; LASSILA, Lippo V.J; VALLITTU, Pekka K; SHINYA, Akiyoshi

    2008-01-01

    To evaluate the interactive influence of adhesive materials and surface treatments on bond strength of zirconium oxide ceramics, six types of adhesive resin cements (RelyX ARC (RA), Super-Bond C & B (SB), Linkmax (LM...

  3. Effect of Surface Treatments on Leakage of Zirconium Oxide Ceramics

    Directory of Open Access Journals (Sweden)

    Göknil Alkan Demetoğlu

    2016-08-01

    Full Text Available Objective: The aim of this pilot study was to compare the effects of pretreatments on leakage of zirconia ceramics. Materials and Methods: The speciments divided into 6 groups that were subsequently treated as follows: group 1, no treatment (control; group 2, the ceramic surfaces were airborne-particle abraded with 110 μm aluminum-oxide (Al2O3 particles; group 3, after abrasion of the surfaces with 110 μm Al2O3 particles, silica coating using 30 μm (Al2O3 particles modified by silica (rocatec system and application of the silane coupling agent (espe-sil; group 4, ceramic surfaces irritated with neodymium-doped yttrium aluminium garnet (Nd:YAG laser [fidelis plus 3 foton (Ljubljana, Slovenia] at 20 hz, 100 mj, 2 w, 100 μs; group 5, ceramic surfaces irritated with Nd:YAG laser at fidelis plus 3 fotona (Ljubljana, Slovenia at 20 hz, 100 mj, 2 w, 100 μs; group 6; application of a zirconia primer (z-prime plus bisco, IL, USA agent. And all ceramics tested for leakage. Results: For marginal leakage, score 0 was found in all groups. Conclusion: No significant differences were found in marginal leakage under all conditions.

  4. Bond strength of selected composite resin-cements to zirconium-oxide ceramic

    Science.gov (United States)

    Fons-Font, Antonio; Amigó-Borrás, Vicente; Granell-Ruiz, María; Busquets-Mataix, David; Panadero, Rubén A.; Solá-Ruiz, Maria F.

    2013-01-01

    Objectives: The aim of this study was to evaluate bond strengths of zirconium-oxide (zirconia) ceramic and a selection of different composite resin cements. Study Design: 130 Lava TM cylinders were fabricated. The cylinders were sandblasted with 80 µm aluminium oxide or silica coated with CoJet Sand. Silane, and bonding agent and/or Clearfil Ceramic Primer were applied. One hundred thirty composite cement cylinders, comprising two dual-polymerizing (Variolink II and Panavia F) and two autopolymerizing (Rely X and Multilink) resins were bonded to the ceramic samples. A shear test was conducted, followed by an optical microscopy study to identify the location and type of failure, an electron microscopy study (SEM and TEM) and statistical analysis using the Kruskal-Wallis test for more than two independent samples and Mann-Whitney for two independent samples. Given the large number of combinations, Bonferroni correction was applied (α=0.001). Results: Dual-polymerizing cements provided better adhesion values (11.7 MPa) than the autopolymerizing (7.47 MPa) (p-value M-WAdhesive failure (separation of cement and ceramic) was produced at a lesser force than cohesive failure (fracture of cement) (p-value M-Wcement and the ceramic. Key words:Shear bond strength, silica coating, surface treatment, zirconia ceramics, phosphate monomer. PMID:22926485

  5. An In Vivo Evaluation of the Fit of Zirconium-Oxide Based, Ceramic Single Crowns with Vertical and Horizontal Finish Line Preparations.

    Science.gov (United States)

    Vigolo, Paolo; Mutinelli, Sabrina; Biscaro, Leonello; Stellini, Edoardo

    2015-12-01

    Different types of tooth preparations influence the marginal precision of zirconium-oxide based ceramic single crowns. In this in vivo study, the marginal fits of zirconium-oxide based ceramic single crowns with vertical and horizontal finish lines were compared. Forty-six teeth were chosen in eight patients indicated for extraction for implant placement. CAD/CAM technology was used for the production of 46 zirconium-oxide-based ceramic single crowns: 23 teeth were prepared with vertical finishing lines, 23 with horizontal finishing lines. One operator accomplished all clinical procedures. The zirconia crowns were cemented with glass ionomer cement. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at 50× magnification. On conclusion of microscopic assessment, ESEM evaluation was completed on all specimens. The comparison of the gap between the two types of preparation was performed with a nonparametric test (two-sample Wilcoxon rank-sum test) with a level of significance fixed at p crowns with vertical and horizontal finish line preparations were not different. © 2015 by the American College of Prosthodontists.

  6. ZIRCONIUM OXIDE NANOSTRUCTURES PREPARED BY ANODIC OXIDATION

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Y. Y.; Bhuiyan, M.S.; Paranthaman, M. P.

    2008-01-01

    Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic fi lms can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide fi lm to fl ake off. Further studies are needed to defi ne the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

  7. Translucency and Strength of High Translucency Monolithic Zirconium Oxide Materials

    Science.gov (United States)

    2016-05-17

    the most esthetic full veneer restorative material in dentistry for many years. In the mid-1900’s, dental materials researchers began marketing and...OBSOLETE 48. DATE Page 3 of 3 Pages Translucency and Strength of High-Translucency Monolithic Zirconium-Oxide Materials Abstract Dental materials...one common problem has involved an increase in the fracture rate of the veneered zirconium oxide compared to metal-ceramic crowns potentially caused

  8. Nondestructive evaluation of sintered ceramics

    Science.gov (United States)

    Baaklini, George Y.; Klima, Stanley J.; Sanders, William A.

    1988-01-01

    Radiography and several acoustic and thermoacoustic microscopy techniques are investigated for application to structural ceramics for advanced heat engines. A comparison is made of the results obtained from the use of scanning acoustic microscopy (SAM), scanning laser acoustic microscopy (SLAM), and thermoacoustic microscopy (TAM). These techniques are evaluated on research samples of green and sintered monolithic silicon nitrides and silicon carbides in the form of modulus-of-rupture (MOR) bars containing deliberately introduced flaws. Strengths and limitations of the techniques are described, with the emphasis being on statistics of detectability of flaws that constitute potential fracture origins. Further, it is shown that radiographic evaluation and guidance helped develop uniform high-density Si3N4 MOR bars with improved four-point flexural strength (875, 544, and 462 MPa at room temperature, 1200 C, 1370 C, respectively) and reduced scatter in bend strength.

  9. Sintering characteristics of nano-ceramic coatings

    NARCIS (Netherlands)

    De Hosson, JTM; 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

  10. Sintering behavior of nano-ceramic coatings

    NARCIS (Netherlands)

    De Hosson, JTM; Popma, R; Hooijmans, J; Komarneni, S; Parker, JC; Hahn, H

    2000-01-01

    This paper concentrates on the densification of sol gel derived thin nano-ceramic coatings by laser radiation and by furnace treatment. Deposition of the film is done by means of spin coating of Zirconia. The sintering of the layer is observed using a number of different measuring techniques.

  11. Plasma Synthesis and Sintering of Advanced Ceramics

    Science.gov (United States)

    1990-09-15

    glow discharge, corona discharge, RF or microwave discharge, etc.) and the electron concentration in the plasma are important. The efficiency of... corona discharge, and the low pressure capacitively or inductively coupled RF discharge. It is probable that a low pressure microwave discharge would also...Rhodes, "Agglomerate and Particle Size Effects on Sintering Yttria- Stabilized Zirconia ", J. Am. Ceram. Soc., 64 [1] 19-22 (1981). 4. T. S. Yeh and M

  12. 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.

  13. Effects of zirconium oxide on the sintering of SrCe{sub 1−x}Zr{sub x}O{sub 3−δ} (0.0 ≦ x ≦ 0.5)

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Kai-Ti, E-mail: kady0525@hotmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Jang, Jason Shian-Ching, E-mail: jscjang@ncu.edu.tw [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Department of Mechanical Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Ren, Yu-Jing; Tsai, Pei-Hua [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Li, Chuan; Tseng, Chung-Jen [Department of Mechanical Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Lin, Jing-Chie [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan, ROC (China); Hsi, Chi-Shiung [Department of Materials Science and Engineering, National United University, Miaoli 36003, Taiwan, ROC (China); Hung, I-Ming [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Taoyuan 32003, Taiwan, ROC (China)

    2014-12-05

    Graphical abstract: SEM cross-sectional microstructures of (a) the HTM with multilayer-supported structure sintered at 1550 °C for 4 h; the sequence of distinct layer is SrCeO{sub 3}, SrCe{sub 0.6}Zr{sub 0.4}O{sub 3-δ}, and SrZrO{sub 3} from the middle to the outer surface. (b) Enlaged image from circle A in Fig. 7(a). (c) Enlarged image from circle B in Fig. 7(a). - Highlights: • The sinterability of SrCe{sub 1-x}Zr{sub x}O{sub 3-δ} (0.0 ≦ x ≦ 0.5) oxides decreased with increasing Zr contents. • The porosities of sintered SrCe{sub 1-x}Zr{sub x}O{sub 3-δ}(0.0 ≦ x ≦ 0.5) oxides increased with increasing Zr contents. • SrCe{sub 0.6}Zr{sub 0.4}O{sub 3-δ} ceramics sintered at 1500 °C has the largest porosity in the SrCe{sub 1-x}Zr{sub x}O{sub 3-δ}(0.0 ≦ x ≦ 0.5) ceramics system. • A flat HTM with porous supporting layers was fabricated by constrained sintering. - Abstract: SrCe{sub 1−x}Zr{sub x}O{sub 3−δ} (0.0 ≦ x ≦ 0.5) proton-conducting oxides had been successfully prepared using a solid state reaction method. In this study, the relationships between the Zr contents and microstructures, shrinkages, and sintering of these SrCe{sub 1−x}Zr{sub x}O{sub 3−δ} (0.0 ≦ x ≦ 0.5) were systemically studied by using X-ray Diffraction, Scanning Electron Microscopy, and Thermal dilatometer analysis (TDA). The XRD results showed that no second phase could be found from the 1500 °C sintered SrCe{sub 1−x}Zr{sub x}O{sub 3−δ}. The SEMs shows that the porosities of sintered SrCe{sub 1−x}Zr{sub x}O{sub 3−δ} increased with increasing the Zr contents. The largest porosity about 27.53% could be obtained at the SrCe{sub 0.6}Zr{sub 0.4}O{sub 3−δ} ceramics sintered at 1500 °C for 2 h in the SrCe{sub 1−x}Zr{sub x}O{sub 3−δ} ceramics. According to the sintering behaviour and properties characterizations, a flat HTM with porous supporting layers of SrCe{sub 0.6}Zr{sub 0.4}O{sub 3−δ} and SrZrO{sub 3} was fabricated by constrained

  14. Evaluation of zirconium-oxide-based ceramic single-unit posterior fixed dental prostheses (FDPs) generated with two CAD/CAM systems compared to porcelain-fused-to-metal single-unit posterior FDPs: a 5-year clinical prospective study.

    Science.gov (United States)

    Vigolo, Paolo; Mutinelli, Sabrina

    2012-06-01

    The purpose of this prospective clinical study was to determine the success rate of single-unit posterior fixed dental prostheses (FDPs) with zirconia copings generated with two CAD/CAM systems, compared to porcelain-fused-to-metal (PFM) single-unit posterior FDPs after 5 years of function. From 2005 to 2006, 60 patients who needed a single-unit FDP on a first molar in the mandibular jaw (left or right) in a private office setting were included in this study. The 60 first mandibular molars were randomly divided into three groups (n = 20): in the control group (group C), 20 PFM FDPs were included. In the other two groups CAD/CAM technology was used for the fabrication of the zirconium-oxide copings: 20 single-unit posterior FDPs with zirconia copings were generated with the Procera system (group P, Nobel Biocare); 20 single-unit posterior FDPs with zirconia copings were generated with the Lava system (group L, 3M ESPE). For the ANOVA follow-up data, the clinical life table method was applied. The statistical analysis was performed using two nonparametric tests, the log-rank test for k-groups and the Fisher exact test. No statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) evaluated together and metal-ceramic posterior single FDPs was found at 5 years of function; however, clinical data showed that technical problems, such as extended fracture of the veneering ceramic, tended to occur more frequently in the zirconia-ceramic FDP groups. The difference in the frequency of failure was statistically significant only in the comparison of groups C and P. Even if no statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) considered together and metal-ceramic posterior single FDPs was found at 5 years of function, clinical data showed that the two zirconia-ceramic FDP groups tended to have more frequent clinical problems: for this reason all the clinical and

  15. Translucency and Strength of High-Translucency Monolithic Zirconium-Oxide Materials

    Science.gov (United States)

    2016-05-12

    dental manufacturers and laboratories have been marketing high- translucency monolithic zirconia restorative materials with claims of good esthetics ...restorations to combine the esthetics of all-ceramic restorations with the strength properties of zirconia. The purpose of this study was to evaluate...the translucency and strength of new highly translucent monolithic zirconia ceramic materials. Four monolithic zirconium-oxide materials marketed as

  16. 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.

  17. 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.

  18. Spark plasma sintering and spark plasma joining of refractory ceramics

    Science.gov (United States)

    Hoefer, Jeffrey Andrew

    Consolidation of refractory ceramics such as boron carbide (B4C) and silicon carbide (SiC) by conventional sintering techniques (pressure-less sintering, hot pressing, hot isostatic pressing etc.) can prove challenging due to the high temperatures required for sintering. Typically sintering additives are used in order to decrease sintering temperature, but at the sacrifice of purity. Typically B4C requires sintering temperatures above 2000°C without the use of additives, while SiC is generally considered not sinterable without additives, and requires temperatures above 2000°C even with additives. Spark Plasma Sintering (SPS) has emerged as a technology that can reduce the sintering temperature considerably compared to more conventional techniques. The simultaneous application of pressure, heat, and current can reduce sintering temperatures without the use of sintering aids to 1600°C and 2000°C for boron carbide and silicon carbide respectively. One shortcoming of SPS, however, is the difficulty in producing complex shapes. Therefore, for carbide materials such as B4C and SiC, which are difficult to machine, the ability to produce complex shapes is worthy of investigation. One means of creating complex shapes is by joining simple shapes. Joining of monolithic ceramics, in particular SiC, has been achieved, however in all cases an intermediate joining material is used (Ti foil, Silica Powder etc.). Joining of materials using SPS, or as it is called, Spark Plasma Joining, can eliminate the need for an intermediate joining material, producing a high purity and high strength joint. This study investigates SPS of 3 different B4C Powders, as well as SPS joining of simple shape monolithic SiC. Sintering parameters such as temperature, pressure, time, and heating rate are all considered. Influence of sintering parameters on density, grain size, mechanical strength, and joint quality is investigated in detail.

  19. 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.

  20. Hydrothermal-Assisted Cold Sintering Process: A New Guidance for Low-Temperature Ceramic Sintering.

    Science.gov (United States)

    Guo, Hanzheng; Guo, Jing; Baker, Amanda; Randall, Clive A

    2016-08-17

    Sintering is a thermal treatment process that is generally applied to achieve dense bulk solids from particulate materials below the melting temperature. Conventional sintering of polycrystalline ceramics is prevalently performed at quite high temperatures, normally up to 1000 to 1200 °C for most ceramic materials, typically 50% to 75% of the melting temperatures. Here we present a new sintering route to achieve dense ceramics at extraordinarily low temperatures. This method is basically modified from the cold sintering process (CSP) we developed very recently by specifically incorporating the hydrothermal precursor solutions into the particles. BaTiO3 nano polycrystalline ceramics are exemplified for demonstration due to their technological importance and normally high processing temperature under conventional sintering routes. The presented technique could also be extended to a much broader range of material systems than previously demonstrated via a hydrothermal synthesis using water or volatile solutions. Such a methodology is of significant importance, because it provides a chemical roadmap for cost-effective inorganic processing that can enable broad practical applications.

  1. Precipitation synthesis and sintering of lanthanum doped yttria transparent ceramics

    Science.gov (United States)

    Huang, Yihua; Jiang, Dongliang; Zhang, Jingxian; Lin, Qingling

    2009-08-01

    Co-precipitation method was used to prepare lanthanum doped yttria nanopowder. After calcinations at 1000 °C, lanthanum ion entered into the yttria lattice. Effect of lanthanum oxide as an equal valent additive on the sintering of yttria was investigated. The addition of lanthanum ions was found to be effective for promoting the densification process during sintering, and make it easier for the ceramic to be transparency at moderate 1700 °C in vacuum. After sintering at 1500 and 1700 °C for 4 h in vacuum, translucent and transparent poly-crystalline ceramics with uniform lanthanum distribution was obtained, respectively. The grain size (75 ± 13 μm) of 7% lanthanum doped yttria sintered at 1700 °C was about 10 times bigger than that sintered at 1500 °C (7.6 ± 1.9 μm). The refractive indices of lanthanum ion doped sample were higher than undoped sample in vis-UV light range. The in-line transmittance of 2 mm thick samples sintered at 1700 °C reached 74% at 800 nm (89.7% of theoretical transmittance) wavelength.

  2. Preparation of translucent YAG:Ce ceramics by reaction sintering

    Science.gov (United States)

    Michalik, D.; Sopicka-Lizer, M.; Pawlik, T.; Chrapoński, J.

    2012-05-01

    The paper presents preparation of YAG precursor powders mixture with ability for the reaction sintering at lower temperature. The powder mixture was mechanochemically processed and characterized for the specific surface area and crystallinity (XRD). Sintering experiments were performed on the batched powders, mechanochemically processed powders and as-synthesised YAG powders. XRD measurements and SEM/TEM studies were applied for characterization of the phase composition and development of YAG ceramics. Transmittance of the resultant ceramics was measured. It has been shown that YAG structure formed at 200 °C lower temperature in comparison to the reference specimen and contamination by the side phases (YAM, YAP) was limited. The best translucency was achieved for the reaction sintering of the mechanochemically processed powders.

  3. Translucency and strength of high-translucency monolithic zirconium oxide materials.

    Science.gov (United States)

    Church, Todd D; Jessup, Jeffrey P; Guillory, Villa L; Vandewalle, Kraig S

    2017-01-01

    The purpose of this study was to evaluate the translucency and strength of highly translucent monolithic zirconia ceramic materials recently introduced to the market. Four monolithic zirconium oxide materials promoted as having high translucency (BruxZir Shaded 16, BruxZir HT, Lava Plus, and inCoris TZI C) were compared to a high-translucency, lithium disilicate monolithic glass-ceramic material (IPS e.max CAD HT). To evaluate translucency, the materials were sectioned into 0.5-, 1.0-, 1.5-, and 2.0-mm-thick specimens; all were sintered and polished. Translucency parameters were calculated with a spectrophotometer. To evaluate flexural strength and modulus, the ceramic materials were sectioned to create beams and fractured in a universal testing machine. The lithium disilicate had significantly greater translucency than the zirconia materials at each thickness. In general, the translucencies of the zirconia materials were similar at each thickness. However, at the manufacturers' recommended minimal thicknesses, 0.5-mm specimens of BruxZir Shaded 16, inCoris TZI C, and Lava Plus were more translucent than the 1.0-mm-thick specimens of IPS e.max CAD HT. Translucency significantly decreased for each material at each increase in thickness. The flexural strengths of the zirconia materials were similar to each other and significantly greater than that of IPS e.max CAD HT. Flexural moduli were more variable. Of the zirconia materials, BruxZir Shaded 16 had an overall better combination of translucency, strength, and modulus.

  4. 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.

  5. 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.

  6. Sintering behavior in zirconium phosphate bonded silicon nitride porous ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen Fei [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Shen Qiang [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)], E-mail: sqqf@263.net; Schoenung, Julie M. [Department of Chemical Engineering and Materials Science, University of California Davis, CA 95616 (United States); Zhang Lianmeng [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2008-12-15

    A new method for preparing high bending strength porous silicon nitride ceramics with controlled porosity has been developed by using a pressureless sintering technique with zirconium phosphate (ZrP{sub 2}O{sub 7}) as a binder phase. The sintering behavior in these porous ceramics is investigated in this study by using XRD, SEM, and HRTEM analysis. The results show that the sintering process can be divided into two stages: one is at temperatures below 250 deg. C, during which ZrO{sub 2} can react completely with H{sub 3}PO{sub 4} to form ZrP{sub 2}O{sub 7}, and a ZrP{sub 2}O{sub 7} bonded Si{sub 3}N{sub 4} porous structure is formed; the other is at temperatures above 250 deg. C, at which solid state sintering of the ZrP{sub 2}O{sub 7} dominates and a continuous open porosity network is obtained. The effect of the ZrP{sub 2}O{sub 7} binder content on sintering behavior, porosity and mechanical properties is also investigated.

  7. Environmentally Friendly Zirconium Oxide Pretreatment

    Science.gov (United States)

    2013-05-01

    treatment with heat and alkaline solution drives condensation, and consequently, leads to film cracking. Each of the two post-treated films peeled from...the fluorozirconate salts are used in abrasives , aluminum production, ceramics, glass manufacturing, and in the preparation of fluxes. However, the

  8. 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.

  9. Clinical Outcomes of Zirconium-Oxide Posts: Up-to-Date Systematic Review.

    Science.gov (United States)

    Al-Thobity, Ahmad M

    2016-06-01

    The aim of this systematic review was to investigate the clinical outcomes of the use of zirconium-oxide posts in the past 20 years. The addressed question was: Do zirconium-oxide posts maintain the long-term survival rate of endodontically treated teeth? A database search was made of articles from January 1995 to December 2014; it included combinations of the following keywords: "zirconia," "zirconium oxide," "dowel/dowels," "post/posts," and "post and core." Exclusion criteria included review articles, experimental studies, case reports, commentaries, and articles published in a language other than English. Articles were reviewed by the titles, followed by the abstracts, and, finally, the full text of the selected studies. Four studies were included after filtering the selected studies according to the inclusion and exclusion criteria. In one study, the prefabricated zirconia posts with indirect glass-ceramic cores had significantly higher failure rates than other posts with direct composite cores. In two studies, no failure of the cemented posts was observed throughout the follow-up period. Due to the limited number of clinical studies, it can be concluded that the long-term success rate of prefabricated zirconium-oxide posts is unclear.

  10. 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 Impact factor: 0.439, year: 2016 http://www. ceramics -silikaty.cz/index.php?page=cs_detail_doi&id=789

  11. Fabrication and characterization of spark plasma sintered Ce:LuAG ceramic for scintillation application

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. Arun; Senthilselvan, J., E-mail: jsselvan@hotmail.com [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai–600 025, Tamil Nadu (India)

    2016-05-23

    Rare earth Cerium doped Lutetium Aluminum Garnet (Ce:LuAG) ceramics are widely used as phosphor material in medical imaging and high-energy physics. Due to its technological importance, an attempt has been made to fabricate Ce:LuAG ceramics by using spark plasma sintering (SPS) technique. XRD patterns of SPS sintered Ce:LuAG ceramics reveals a mixed LuAG and CeO{sub 2} (antisite defect) phases. The microstructures of SPS sintered Ce:LuAG ceramics shows limited densification, inappropriate compaction of particles and existence of residual pores, voids between the grain boundaries affects the transparency of Ce:LuAG ceramics. Relative density and hardness of post sintered Ce:LuAG ceramic is also determined. The effect of Ce{sup 3+} doping concentration and sintering temperature on optical luminescence behavior of Ce:LuAG ceramic is presented.

  12. Effect of mechanical cycling on the flexural strength of densely sintered ceramics

    NARCIS (Netherlands)

    Itinoche, Koiti Marco; Ozcan, Mudu; Bottino, Marco Antonio; Oyafuso, Denise

    2006-01-01

    Objectives. The aim of this study was to evaluate the effect of mechanical cycling on the biaxial flexural strength of two densely sintered ceramic materials. Methods. Disc shaped zirconia (In-Ceram Zirconia) and high alumina (Procera AllCeram) ceramic specimens (diameter: 15 min and thickness: 1.2

  13. Modeling the mechanical behavior of ceramic and heterophase structures manufactured using selective laser sintering and spark plasma sintering

    Science.gov (United States)

    Skripnyak, Vladimir A.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.; Vaganova, Irina K.

    A model for predicting mechanical properties of ultra-high temperature ceramics and composites manufactured by selective laser sintering (SLS) and spark plasma sintering (SPS) under shock loading is presented. The model takes into account the porous structure, the specific volume and average sizes of phases, and the temperature of sintering. Residual stresses in ceramic composites reinforced with particles of refractory borides, carbides and nitrides after SLS or SPS were calculated. It is shown that the spall strength of diboride-zirconium matrix composites can be increased by the decreasing of porosity and the introduction of inclusions of specially selected refractory strengthening phases.

  14. Diffusion of insoluble carbon in zirconium oxides

    CERN Document Server

    Vykhodets, V B; Koester, U; Kondrat'ev, V V; Kesarev, A G; Hulsen, C; Kurennykh, T E

    2011-01-01

    The diffusion coefficient of insoluble carbon in zirconium oxides has been obtained for the temperature range of 900-1000A degrees C. There are no published data on the diffusion of insoluble impurities; these data are of current interest for the diffusion theory and nuclear technologies. Tracer atoms 13C have been introduced into oxides by means of ion implantation and the kinetics of their emission from the samples in the process of annealing in air has been analyzed. The measurements have been performed using the methods of nuclear microanalysis and X-ray photoelectron spectroscopy. The diffusion activation energy is 2.7 eV and the carbon diffusion coefficient is about six orders of magnitude smaller than that for oxygen self-diffusion in the same systems. This result indicates the strong anomaly of the diffusion properties of carbon in oxides. As a result, zirconium oxides cannot be used in some nuclear technologies, in particular, as a material of sources for accelerators of short-lived carbon isotopes.

  15. Effects of sintering atmosphere controlled using carbon pellet on translucency of AlN ceramics

    Science.gov (United States)

    Honma, T.; Kamitamari, M.; Kuroki, Y.; Okamoto, T.; Takata, M.

    2011-05-01

    Translucent AlN ceramics were sintered with a carbon pellet in order to control the CO gas surrounding the sample during sintering. The total transmittance of the ceramics increased by sintering with the carbon pellet because of the decrease of light scattering. One of causes of the light scattering was the presence of calcium aluminates at grain boundaries. The light scattering can be controlled by the CO gas using the carbon pellet.

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

    Science.gov (United States)

    Gephart, Sean

    The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques. This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering. The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4 x 4 x 0.315 inches3 (101.6 x 101.6 x 8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered

  17. A role of electrons in zirconium oxidation

    Directory of Open Access Journals (Sweden)

    Alekseev Pavel N.

    2017-01-01

    Full Text Available Growing the oxide scale on the zirconium cladding of fuel elements in pressured-water reactors (PWR is caused by the current of oxygen anions off the waterside to the metal through the layer of zirconia and by the strictly equal inverse electronic current. This process periodically speeds up the corrosion of the zirconium cladding in the aqueous coolant due to the breakaway of the dense part of oxide scale when its thickness reaches 2 mkm. It is shown that the electronic resistivity of zirconia is not limiting the zirconium oxidation at working temperatures. For gaining this limitation, a metal of lesser valence than zirconium has to be added to this oxide scale up to 15%. Then, oxygen vacancies arise in the complex zirconia, increase its band-gap, and thus, sharply decrease the electronic conductivity and form the solid oxide electrolyte whose growth is inhibited in contact with water at working temperatures of PWR.

  18. [Influence on microstructure of dental zirconia ceramics prepared by two-step sintering].

    Science.gov (United States)

    Jian, Chao; Li, Ning; Wu, Zhikai; Teng, Jing; Yan, Jiazhen

    2013-10-01

    To investigate the microstructure of dental zirconia ceramics prepared by two-step sintering. Nanostructured zirconia powder was dry compacted, cold isostatic pressed, and pre-sintered. The pre-sintered discs were cut processed into samples. Conventional sintering, single-step sintering, and two-step sintering were carried out, and density and grain size of the samples were measured. Afterward, T1 and/or T2 of two-step sintering ranges were measured. Effects on microstructure of different routes, which consisted of two-step sintering and conventional sintering were discussed. The influence of T1 and/or T2 on density and grain size were analyzed as well. The range of T1 was between 1450 degrees C and 1550 degrees C, and the range of T2 was between 1250 degrees C and 1350 degrees C. Compared with conventional sintering, finer microstructure of higher density and smaller grain could be obtained by two-step sintering. Grain growth was dependent on T1, whereas density was not much related with T1. However, density was dependent on T2, and grain size was minimally influenced. Two-step sintering could ensure a sintering body with high density and small grain, which is good for optimizing the microstructure of dental zirconia ceramics.

  19. 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.

  20. Coloration and thermoluminescence of translucent AlN ceramics sintered with Ca3Al2O6 as sintering additive

    Science.gov (United States)

    Honma, T.; Kuroki, Y.; Okamoto, T.; Takata, M.; Kanechika, Y.; Azuma, M.; Taniguchi, H.

    2011-03-01

    Coloration of translucent AlN ceramics sintered with Ca3Al2O6 as a sintering additive occurs by exposure to ultraviolet light. The trap related to this coloration was investigated by thermoluminescence (TL) measurements. With increasing oxygen content, the TL intensity increased, reflecting an increase in the trap concentration in the samples. The thermal activation energy of the trap also decreased with decreasing defect density. The trap is considered to be an oxygen-induced defect.

  1. Activated sintering of ceramics on the basis of Al[2]O[3

    OpenAIRE

    Matrenin, Sergey Veniaminovich; Ovechkin, Boris Borisovich; Zenin, Boris Sergeevich; Tayukin, R. V.

    2015-01-01

    Ceramic sintering on the basis of Al2O3 activated by nanopowder additives Al[2]O[3] and Al has been studied. The given paper shows that adding nanopowder Al[2]O[3] in the amount of up to 20 wt. % into the coarse powder [alpha]-Al[2]O[3] activates the sintering process and, as a result, leads to the increase in density and microhardness of sintered alumina ceramics. The study has revealed a significant effect of alumina ceramic density growth which is due to introducing the submicron powder Ti...

  2. Activated sintering of ceramics on the basis of AI2O3

    Science.gov (United States)

    Matrenin, S. V.; Ovechkin, B. B.; Zenin, B. S.; Tayukin, R. V.

    2015-10-01

    Ceramic sintering on the basis of Al2O3 activated by nanopowder additives Al2O3 and Al has been studied. The given paper shows that adding nanopowder Al2O3 in the amount of up to 20 wt. % into the coarse powder α-Al2O3 activates the sintering process and, as a result, leads to the increase in density and microhardness of sintered alumina ceramics. The study has revealed a significant effect of alumina ceramic density growth which is due to introducing the submicron powder TiO2 to the initial blends composition.

  3. Synergistic Sintering of Lignite Fly Ash and Steelmaking Residues towards Sustainable Compacted Ceramics

    Directory of Open Access Journals (Sweden)

    V. G. Karayannis

    2017-01-01

    Full Text Available The development of value-added ceramic materials deriving only from industrial by-products is particularly interesting from technological, economic, and environmental point of views. In this work, the synergistic sintering of ternary and binary mixtures of fly ash, steelmaking electric arc furnace dust, and ladle furnace slag for the synthesis of compacted ceramics is reported. The sintered specimens’ microstructure and mineralogical composition were characterized by SEM-EDS and XRD, respectively. Moreover, the shrinkage, apparent density, water absorption, and Vickers microhardness (HV were investigated at different sintering temperatures and raw material compositions. The characterization of the sintered compacts revealed the successful consolidation of the ceramic microstructures. According to the experimental findings, the ceramics obtained from fly ash/steel dust mixtures exhibited enhanced properties compared to the other mixtures tested. Moreover, the processing temperature affected the final properties of the produced ceramics. Specifically, a 407% HV increase for EAFD and a 2221% increase for the FA-EAFD mixture were recorded, by increasing the sintering temperature from 1050 to 1150°C. Likewise, a 972% shrinkage increase for EAFD and a 577% shrinkage increase for the FA-EAFD mixture were recorded, by increasing the sintering temperature from 1050 to 1150°C. The research results aim at shedding more light on the development of sustainable sintered ceramics from secondary industrial resources towards circular economy.

  4. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Li Fan [Department of Engineering, University of Leicester, Leicester, LE1 7RH (United Kingdom); Pan Jingzhe, E-mail: jp165@le.ac.uk [Department of Engineering, University of Leicester, Leicester, LE1 7RH (United Kingdom); Guillon, Olivier [Institute of Materials Science, Technische Universitaet Darmstadt, D-64287 Darmstadt (Germany); Cocks, Alan [Department of Engineering Science, University of Oxford, Oxford OX1 3PJ (United Kingdom)

    2010-10-15

    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.

  6. Synthesis of highly sinterable Yb: SrF2 nanopowders for transparent ceramics

    Science.gov (United States)

    Li, Weiwei; Huang, Haijun; Mei, Bingchu; Song, Jinghong

    2018-01-01

    In this paper, ytterbium doped strontium fluoride (Yb: SrF2) nanoparticles were synthesized by direct precipitation method. High-speed centrifugation was used to separate high sintering activity of nanopowders from powders with hard aggregated and large size. Using powders at different parts of the centrifugal tube as starting powders, Yb: SrF2 transparent ceramics was fabricated by hot pressed (HP) method for the first time. Effects of morphology and particle size on the sinterability of Yb: SrF2 nanopowders were investigated. The transmittance reached 77% at the wavelength of 1200 nm and pores stilled remained in the ceramics. The spectroscopic and thermal properties of Yb: SrF2 transparent ceramics were also investigated. This paper provides an effective way to obtain well dispersed and high sinterability nanoparticles for SrF2 ceramics sintering.

  7. Technical characterization of sintered glass-ceramics derived from glass fibers recovered by pyrolysis

    OpenAIRE

    Martín, María Isabel; López Gómez, Félix Antonio; Alguacil,Francisco José; Romero, Maximina

    2015-01-01

    Sintered wollastonite-plagioclase glass-ceramics were prepared through crystallization of a parent glass generated by vitrification of pyrolysis residual glass fibers that had been pyrolytically recovered from waste composite materials. A vitrifiable mixture consisting of 95 wt.% glass fiber and 5 wt.% Na2O was melted at 1450ºC to obtain a glass frit. The glass-ceramic materials were produced by a sinter-crystallization process from the powdered glass frit. The effect of firing temperature on...

  8. 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.

  9. Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

    Science.gov (United States)

    Wan, Wei; Huang, Chun-e.; Yang, Jian; Zeng, Jinzhen; Qiu, Tai

    2014-07-01

    Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N' N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10-6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10-3 (at 1 MHz).

  10. Effect of additive composition on mechanical properties of pressureless sintered silicon carbide ceramics sintered with alumina, aluminum nitride and yttria

    Science.gov (United States)

    Eom, Jung-Hye; Seo, Yu-Kwang; Kim, Young-Wook; Lee, Seoung-Jae

    2015-05-01

    Silicon carbide (SiC) ceramics were pressureless sintered with 3 vol% Al2O3-Y2O3-AlN additives with the AlN/(Al2O3+AlN) molar ratios of 0-0.75 at 1850-2000 °C for 1 hr and the effects of additive composition (i.e., changes in the AlN/(Al2O3+AlN) molar ratio while maintaining constant Y2O3 content) on the mechanical properties of the pressureless-sintered SiC ceramics were investigated. Self-reinforced microstructures consisting of relatively large platelet SiC grains and relatively small equiaxed grains have been obtained in all specimens when sintered at 1900 °C for 1 h in an argon atmosphere. The achievement of self-reinforced microstructures under such mild conditions (holding for 1 hr at 1900 °C) is caused by the beneficial effects of additive composition and the acceleration of the β→α phase transformation of SiC by seeding, i.e., the addition of 1 vol% α-SiC into β-SiC. The typical flexural strength and fracture toughness of the pressureless-sintered SiC ceramics with an AlN/(Al2O3+AlN) mole ratio of 0.5 were 433 MPa and 6.6 MPa·m1/2 at room temperature, respectively.

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

    OpenAIRE

    Inès M. M. M. Ponsot; Yiannis Pontikes; Giovanni Baldi; Rama K. Chinnam; Rainer Detsch; Aldo R. Boccaccini; Enrico Bernardo

    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...

  12. Monitoring of temperature profiles and surface morphologies during laser sintering of alumina ceramics

    Directory of Open Access Journals (Sweden)

    Bin Qian

    2014-06-01

    Full Text Available Additive manufacturing of alumina by laser is a delicate process and small changes of processing parameters might cause less controlled and understood consequences. The real-time monitoring of temperature profiles, spectrum profiles and surface morphologies were evaluated in off-axial set-up for controlling the laser sintering of alumina ceramics. The real-time spectrometer and pyrometer were used for rapid monitoring of the thermal stability during the laser sintering process. An active illumination imaging system successfully recorded the high temperature melt pool and surrounding area simultaneously. The captured images also showed how the defects form and progress during the laser sintering process. All of these real-time monitoring methods have shown a great potential for on-line quality control during laser sintering of ceramics.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-Wei

    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

  14. Sintering stress and microstructure in ceramic powder compacts

    Energy Technology Data Exchange (ETDEWEB)

    Chu, May-Ying (Lawrence Berkeley Lab., CA (USA) California Univ., Berkeley, CA (USA). Dept. of Materials Science and Mineral Engineering)

    1990-08-01

    The behavior of the sintering stress and microstructure during sintering is studied under various thermal and physical conditions. Specifically, the study includes sintering under isothermal or constant heating rate conditions; and altering the starting compact structure by pre-coarsening to increase the particle size, or by compaction to increase the starting density. Loading dilatometry is used to measure the ratio of the densification strain rate to the creep strain rate and the continuous shrinkage history of the systems. The data show that the ratio of the densification to the creep strain rate is remarkably constant within a wide temperature range for densification, from the earliest stages of densification to at least the onset of the final stage. As a consequence, the sintering stress, which is proportional to the strain rate ratio, is nearly independent of sintered density or of temperature. Analysis leads to a simple method for determining the simultaneous densification strain rate over the creep strain rate ratio. A rigorous densification strain rate equation is derived for a model system. The constant sintering stress allows progress on formulating a sintering equation to predict the densification behavior of powder compacts. Analysis of dilatometry data from compacts sintered at various heating rates, and of numerical computations, indicate the need to include separate coarsening processes with different activation energies. The same model is used to describe the differences in pore spacing evolution between pre-coarsened and as-received systems.

  15. [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.

  16. Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

    Science.gov (United States)

    Barnes, M. W.; Tucker, D. S.; Hone, L.; Cook, S.

    2017-01-01

    Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

  17. The effect of sintering temperature on the structure and properties of corundum/mullite ceramics

    Directory of Open Access Journals (Sweden)

    Yu-Ming T.

    2015-01-01

    Full Text Available In this work, samples are prepared by adding secondary raw bauxite and some suitable amount pure silica. After dry pressing molding, using solid phase sintering method sinter them at 1380ºC,1410ºC,1440ºC,1410ºC,1500ºC,1530ºC, respectively. A performance of the material is characterized by using SEM and XRD, such as microscopic morphology, phase composition and the compressive strength, etc. Combining results of experiments, explore the mechanism of sintering temperature on the properties of ceramic materials.

  18. Characterization of Green-Emitting Translucent Zinc Oxide Ceramics Prepared Via Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Mei [University of California; DeVito, David M [ORNL; Howe, Jane Y [ORNL; Yang, Xiaocheng [West Virginia University; Giles, Nancy C. [Air Force Institute of Technology; Neal, John S [ORNL; Munir, Zuhair [University of California

    2011-01-01

    Translucent, green-emitting zinc oxide (ZnO) bodies, 19 mm in diameter and 0.72 mm in thickness, have been prepared via spark plasma sintering method. The consolidation of ZnO powders was investigated over the temperature range of 550-1050 C and the pressure range of 55-530 MPa. Samples sintered at temperatures >850 C and pressures of {approx}120 MPa were translucent and had densities of {approx}100%. Samples sintered at 950 C and 130 MPa showed a higher maximum transmittance than the samples sintered at higher or lower temperatures or pressures, with an excellent in-line transmission of 70% in the IR region around 2330 nm. The dense ZnO ceramics exhibited a strong green emission and a weak ultraviolet emission, and the relative intensity of the green emission increased with increasing sintering temperature.

  19. Hybrid processing and anisotropic sintering shrinkage in textured ZnO ceramics

    Science.gov (United States)

    Keskinbora, Kahraman; Suzuki, Tohru S.; Ozgur Ozer, I.; Sakka, Yoshio; Suvaci, Ender

    2010-12-01

    We have studied the combined effects of the templated grain growth and magnetic alignment processes on sintering, anisotropic sintering shrinkage, microstructure development and texture in ZnO ceramics. Suspensions of 0-10 vol % ZnO template particles were slip cast in a 12 T rotating magnetic field. Sintering and texture characteristics were investigated via thermomechanical analysis and electron backscatter diffraction, respectively. Sintering as well as texture characteristics depend on template concentration. For the studied ZnO system, there is a critical template concentration (2 vol % in this study) above which densification is limited by the templates owing to constrained sintering. Below this limit, the densification is enhanced and the anisotropic shrinkage is reduced, which is attributed to densifying characteristics of the templates.

  20. Study on high temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics

    Directory of Open Access Journals (Sweden)

    Bai P.

    2009-01-01

    Full Text Available High temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics were studied. The effects of the sintering temperature and the sintering time on the relative density, strength and fracture toughness of Al2O3/ZrO2/TiC ceramics were investigated. The results showed that the sintering temperature and sintering time had a great effect on the relative density and the mechanical properties of Al2O3/ZrO2/TiC ceramics. The mechanical strength increased from 120MPa to 360MPa and KIC increased from 3.7 J/m2 to 6.9 J/m2 when the sintering temperature increased from 1400ºC to 1600ºC, however, the mechanical strength decreased rapidly from 370MPa to 330MPa and KIC decreased from 6.9 J/m2 to 6.1 J/m2 when the sintering time increased from 30min to 90min. Furthermore, the addition of TiC and ZrO2 in the Al2O3 matrix significantly improved mechanical strength and fracture toughness of the Al2O3 matrix ceramics.

  1. 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.

  2. Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

    Directory of Open Access Journals (Sweden)

    J. Marchi

    2001-10-01

    Full Text Available Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polished/etched samples was carried out with help of scanning electron microscopy. Silicon carbide ceramics with more than 90% of the theoretical density were obtained by pressureless sintering if a suitable proportion of the additives is used.

  3. [Determination of linear sintering shrinkage rate of slip-casting infiltrated ceramic].

    Science.gov (United States)

    Meng, Y; Cao, Y; Liao, Y

    1998-05-01

    This study tested the linear sintering shrinkage (SS) rate of ceramic infiltrated with different glasses (Vita In-ceram, G I-I La, G I-II La, G I-II Ce), the results showed that the linear SS rate was 0.08%-0.32%, which occurred mainly in the firing stage of alumina (P 0.05). It suggests that the effects of glass infiltration on the dimensional stability of GI glasses were comparable with that of Vita In-ceram.

  4. Near-Net-Shape Processing of Sintered Fibrous Ceramics Achieved

    Science.gov (United States)

    Angel, Paul W.

    2000-01-01

    A variety of sintered fibrous ceramic (SFC) materials have been developed over the last 50 years as thermal barrier materials for reentry applications. SFC materials typically exhibit very low thermal conductivities combined with low densities and good thermal stability up to 2500 F. These materials have flown successfully on the space shuttle orbiters since the 1960's. More recently, the McDonnell Douglas Corporation successfully used SFC tiles as a heat shield on the underside of its DC X test vehicle. For both of these applications, tiles are machined from blocks of a specific type of SFC called an alumina-enhanced thermal barrier (AETB). The sizes of these blocks have been limited by the manufacturing process. In addition, as much as 80 to 90 percent of the material can be lost during the machining of tiles with significant amounts of curvature. To address these problems, the NASA Glenn Research Center at Lewis Field entered a cooperative contract with the Boeing Company to develop a vacuum-assisted forming process that can produce large (approximately 4 square feet), severely contoured panels of AETB while saving costs in comparison to the conventional cast-and-machine billet process. For shuttle use, AETB is slurry cast, drained, and fired to form square billets conforming to the shape of the filtration box. The billets are then cut into tiles of the appropriate size for thermally protecting the space shuttle. Processing techniques have limited the maximum size of AETB billets to 21.5 square inches by 6.5-in. thick, but the space shuttles use discrete heat shield tiles no more than 8 to 12 square inches. However, in other applications, large, complex shapes are needed, and the tiling approach is undesirable. For such applications, vacuum-assisted forming can produce large parts with complex shapes while reducing machining waste and eliminating cemented joints between bonded billets. Because it allows contoured shapes to be formed, material utilization is

  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

    -5 A the electric current pulse amplitude. The sintering experiments were carried out in ambient atmosphere with the pellets positioned inside a vertical dilatometer furnace with Pt-Ir electrodes connected either to a power supply for applying the electric field or to an impedance analyzer for collecting [-Z''(ω) x......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...... of the electrical conductivity of flash sintered specimens. Joule heating is assumed to be the primary effect of the electric current pulse through the specimens. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively...

  6. Clinical outcome of metal-ceramic crowns fabricated with laser-sintering technology.

    Science.gov (United States)

    Abou Tara, Milia; Eschbach, Stephanie; Bohlsen, Frank; Kern, Matthias

    2011-01-01

    This study evaluated the clinical outcome of posterior single-unit metal-ceramic crowns fabricated using computer-aided design/computer-assisted manufacture laser-sintering technology. Sixty restorations were placed in 39 patients and cemented with glass-ionomer cement. Follow-ups were performed annually. During a mean observation period of 47 months, one restoration was regarded a dropout, one crown failed (biologic failure), and one debonded. One abutment tooth had to be treated endodontically, and three teeth were treated because of caries. No further technical complications, eg, veneering ceramic chipping, occurred during the observation period. The results suggest that the clinical outcome of posterior single-unit metal-ceramic crowns fabricated using laser-sintering technology is promising.

  7. The Effect of Dopants on Sintering and Microstructure of Lead-free KNN Ceramics

    Directory of Open Access Journals (Sweden)

    Ilze SMELTERE

    2011-03-01

    Full Text Available Lead-free potassium sodium niobate (K0.5Na0.5NbO3 (KNN has been prepared via conventional ceramic processing method. The influence of 0.5 wt% - 1.5 wt% MnO2 and WO3 addition on the sintering, crystallographic structure, microstructure and dielectric properties of KNN has been investigated. Optimal sintering temperatures of KNN ceramics were observed to be in the narrow interval: 1090 °C - 1110 °C for MnO2 doped KNN; 1150 °C - 1170 °C for pure KNN and doped with WO3. XRD patterns showed that all the samples have single perovskite structure with monoclinic structure. Microstructure of ceramics was changed greatly by using dopants.http://dx.doi.org/10.5755/j01.ms.17.1.251

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

    Science.gov (United States)

    Ponsot, Inès M M M; Pontikes, Yiannis; Baldi, Giovanni; Chinnam, Rama K; Detsch, Rainer; Boccaccini, Aldo R; Bernardo, Enrico

    2014-07-31

    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.

  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. Joint Test Protocol: Environmentally Friendly Zirconium Oxide Pretreatment Demonstration

    Science.gov (United States)

    2013-12-01

    This change in pH results in the precipitation and subsequent bonding of zirconium oxide and additives to the surface of the substrate. The...that will be exposed to a corrosive environment known to cause stress-corrosion cracking, such as sodium hydroxide for carbon steel or chloride ions...Substrate descriptions and test specimen codes. Specimen Code Alloy Name Composition M1 AA2024-T3 (bare) 4.5% copper, 1.5% magnesium 0.6

  11. Standard specification for nuclear-grade zirconium oxide powder

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This specification defines the physical and chemical requirements for zirconium oxide powder intended for fabrication into shapes, either entirely or partially of zirconia, for use in a nuclear reactor core. 1.2 The material described herein shall be particulate in nature. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

  12. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; de Florio, D. Z.

    2017-01-01

    substantial improvement of the electrical conductivity. Joule heating is assumed to be the primary effect for sintering. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively, as the reasons for the decrease...

  13. X-Ray Diffraction Phase Analyses for Granulated and Sintered Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Suminar Pratapa

    2007-11-01

    Full Text Available One basic problematic aspect in x-ray diffraction phase analysis is microabsorption effect which may arise from the size of the crystallite phases. Complication of the problem may intensify in sintered ceramic materials where milling of the samples is not simple. We report the Rietveld x-ray diffraction phase analysis of MgO-α-Al2O3 powder mixtures with phase content ratio of 1:1 by weight and MgO-Y2O3 sintered ceramic composites with Y2O3 contents of 10%, 20% and 30% by weight. The mixtures were pre-sintered at 1000°C for 2 hours and then milled while the composites were sintered at 1550°C for 3 hours. The phase composition analysis was done using Rietica, a non-commercial Rietveld method-based software. Relative and absolute phase compositions were examined and results showed that there was a significant amount of phase composition bias resulted from the examination. For the powder mixture, milling can reduce microabsorption effect and hence the calculation bias. For the ceramic composite where milling is almost impossible, additional of Y2O3 caused smaller crystallite size of MgO, so that composition bias is smaller in composites with higher Y2O3 content. A mathematical model is proposed to provide more acceptable phase composition results.

  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. Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

    OpenAIRE

    MARCHI, J.; J.C. Bressiani; Bressiani,A. H. A.

    2001-01-01

    Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polis...

  16. Influence of Li-B-Si Additions on the Sintering and Microwave Dielectric Properties of Ba-Nd-Ti Ceramics

    Science.gov (United States)

    Li, Enzhu; Duan, Shuxin; Sun, Shumeng; Li, Hao; Mi, Yuean; Zhou, Xiaohua; Zhang, Shuren

    2013-12-01

    Li2O-B2O3-SiO2 (LBS) synthesized via a solid-state reaction process was chosen as a novel sintering aid for tungsten-bronze-type Ba4Nd9.3Ti18O54 (BNT) ceramic. The effects of LBS additions on the sintering behaviors, microstructures, and microwave dielectric properties of the BNT ceramic have been investigated, indicating that LBS addition obviously lowered the sintering temperature of the BNT ceramic without damaging its microwave dielectric properties. BNT ceramic doped with 3 wt.% and 4 wt.% LBS addition could be well sintered at 975°C and 950°C for 3 h and had excellent properties: ɛ r = 65.99, Q × f = 4943 GHz ( f = 4.4 GHz), τ f = 19 ppm/°C, and ɛ r = 64.56, Q × f = 4929 GHz ( f = 4.3 GHz), τ f = 11 ppm/°C, respectively.

  17. 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.

  18. 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

  19. Indirect selective laser sintering of apatite-wollostonite glass-ceramic.

    Science.gov (United States)

    Xiao, K; Dalgarno, K W; Wood, D J; Goodridge, R D; Ohtsuki, C

    2008-10-01

    This paper develops an indirect selective laser sintering (SLS) processing route for apatite-wollastonite (A-W) glass-ceramic, and shows that the processing route, which can create porous three-dimensional products suitable for bone implants or scaffolds, does not affect the excellent mechanical and biological properties of the glass-ceramic. 'Green parts' with fine integrity and well-defined shape have been produced from glass particles of single-size range or mixed-size ranges with acrylic binder in various ratios by weight. A subsequent heat treatment process has been developed to optimize the crystallization process, and an infiltration process has been explored to enhance mechanical strength. Three-point bending test results show flexural strengths of up to 102 MPa, dependent on porosity, and simulated body fluid (SBF) tests show that the laser sintered porous A-W has comparable biological properties to that of conventionally produced A-W.

  20. Elaboration of translucent ZnO ceramics by spark plasma sintering under low temperature

    Science.gov (United States)

    Lin, Debao; Fan, Lingcong; Shi, Ying; Xie, Jianjun; Lei, Fang; Ren, Dudi

    2017-09-01

    ZnO is considered to be a potential ultrafast scintillator. In this work, nanosized ZnO powders were synthesized via thermal decomposition of precursors prepared by indirect-precipitation method from zinc nitrate and urea in aqueous solutions. The resultant single phased ZnO powder calcined at 600 °C for 2 h had a primary grain size of 66.0 nm with good dispersity showing excellent sinterability. Translucent ZnO ceramic with a relative density of 99.2% was fabricated successfully by spark plasma sintering at 850 °C for 10 min under the pressure of 80 MPa. The obtained ZnO ceramic exhibited fully dense and homogenous microstructure with average grain size of ∼1 μm, leading to an in-line optical transmission of 11.8% at a wavelength of 950 nm.

  1. 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)

  2. Synthesis, characterization and sintering behaviour of indialite ceramic from fly ash.

    Science.gov (United States)

    Yao, Zhitong; Tan, Shengheng; Xia, Meisheng; Ye, Ying; Li, Jinhui

    2011-10-01

    Indialite ceramic was prepared using fly ash and magnesium carbonate powder as precursors. The effects of sintering aids LiOH · H2O and TiO2 on its crystallization and morphology evolution were studied as well. X-ray diffraction results indicated that the formation of indialite was achieved by solid-state sintering reactions at 1200 °C for 4 h. With increasing amounts of LiOH · H2O, the viscosity decreased and β-spodumene, spinel phases started to develop at the expense of indialite. Scanning electron microscopy observations revealed that the surface of the sintered samples became smoother with higher porosity losses and grain size reduction. As the TiO2 contents increased from 4 to 10%, dauphine-twinned quartz and rutile were formed by simultaneously consuming indialite. In this process, the viscosity showed no significant changes.

  3. 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.

  4. Effects of Laser Treatment on the Bond Strength of Differently Sintered Zirconia Ceramics.

    Science.gov (United States)

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

    2016-07-01

    The purpose of this study was to investigate the effects of carbon dioxide (CO2) and Erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiations on the shear bond strength (SBS) of differently sintered zirconia ceramics to resin cement. Eighty zirconia specimens were prepared, sintered in two different periods (short = Ss, long = Ls), and divided into four treatment groups (n = 10 each). These groups were (a) untreated (control), (b) Er:YAG laser irradiated with 6 W power for 5 sec, (c) CO2 laser with 2 W power for 10 sec, (d) CO2 laser with 4 W power for 10 sec. Scanning electron microscope (SEM) images were recorded for each of the eight groups. Eighty composite resin discs (3 × 3 mm) were fabricated and cemented with an adhesive resin cement to ceramic specimens. The SBS test was performed after specimens were stored in water for 24 h by an universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed with two way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test (α = 0.05). According to the ANOVA, the sintering time, surface treatments and their interaction were statistically significant (p laser-irradiated groups were significantly higher than the control groups, there was no statistically significant difference among them (p > 0.05). Variation in sintering time from 2.5 to 5.0 h may have influenced the SBS of Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Although CO2 and Er:YAG laser irradiation techniques may increase the SBS values of both tested zirconia ceramics, they are recommended for clinicians as an alternative pretreatment method.

  5. Influence of Bi2O3 on sintering and crystallization of cordierite ceramics

    Directory of Open Access Journals (Sweden)

    Đorđević N.

    2005-01-01

    Full Text Available The influence of Bi2O3 on the process of cordierite ceramics preparation, 2MgO-2Al2O3-5SiO2 (MAS was investigated. The following binary systems were used for the presented research: MgO/Bi2O3 (sintered at 820ºC and 1100ºC, Al2O3/Bi2O3 and SiO2/Bi2O3 (sintered at 1100ºC. The composition of these systems consisted of 80% of oxide and 20% Bi2O3. The effects of sintering, composition and morphology were investigated by X-ray diffraction, scanning electron microscopy and EDS analysis. It has been found that Bi2O3, besides a liquid phase, forms intermediary unstable compounds with MgO and Al2O3. MAS ceramics were sintered with 10% Bi2O3 at 1000ºC, 1100ºC and 1200ºC. .

  6. [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.
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  7. Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues.

    Science.gov (United States)

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

    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 degrees 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 degrees C. This produced a glass-ceramic with high density (approximately 2.58 g/cm(3)), minimum water absorption (approximately 2%) and relatively high mechanical strength (approximately 81+/-4 MPa). Thermal shock testing showed that 950 degrees C sintered samples could withstand a 700 degrees 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. 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

  9. Reactive sintering of ceramic lithium ion electrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Badding, Michael Edward; Dutta, Indrajit; Iyer, Sriram Rangarajan; Kent, Brian Alan; Lonnroth, Nadja Teresia

    2017-06-06

    Disclosed herein are methods for making a solid lithium ion electrolyte membrane, the methods comprising combining a first reactant chosen from amorphous, glassy, or low melting temperature solid reactants with a second reactant chosen from refractory oxides to form a mixture; heating the mixture to a first temperature to form a homogenized composite, wherein the first temperature is between a glass transition temperature of the first reactant and a crystallization onset temperature of the mixture; milling the homogenized composite to form homogenized particles; casting the homogenized particles to form a green body; and sintering the green body at a second temperature to form a solid membrane. Solid lithium ion electrolyte membranes manufactured according to these methods are also disclosed herein.

  10. Investigation of mechanical properties based on grain growth and microstructure evolution of alumina ceramics during two step sintering process

    Science.gov (United States)

    Khan, U. A.; Hussain, A.; Shah, M.; Shuaib, M.; Qayyum, F.

    2016-08-01

    Alumina ceramics having small grain size and high density yield good mechanical properties, which are required in most mechanical applications. Two Step Sintering (TSS) is used to develop dense alumina ceramics. In this research work the effect of sintering temperatures on microstructure and density of the alumina specimens developed by using TSS has been investigated. It has been observed that TSS is more efficient in controlling grain growth and increasing the density as compared to One Step Sintering (OSS) of alumina. Scanning electron micrographs of sintered alumina specimens have been compared. It has been observed that TSS proves to be a better technique for increasing density and controlling grain growth of alumina ceramics than OSS. More relative density, hardness, fracture toughness and small grain size was achieved by using TSS over OSS technique.

  11. 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.

  12. Plasma dynamic synthesis of ultradispersed zinc oxide and sintering ceramics on its basis by SPS method

    Science.gov (United States)

    Shanenkova, Yu; Sivkov, A.; Ivashutenko, A.; Shanenkov, I.; Firsov, K.

    2017-05-01

    Zinc oxide is a well-known semiconductor material having good electrical, optical and catalytic properties. It can be used in different areas from cosmetics to drug delivery and biosensors. The synthesis of nanosized zinc oxide is an urgent task for obtaining ZnO-based ceramics with enhanced physical properties. This work shows the possibility to implement the plasma dynamic synthesis of zinc oxide in one short-term process (less than 1 ms) using an electrodischarge zinc-containing plasma jet, flowing into oxygen atmosphere. It allows synthesizing a mono-crystalline powder with particle size distribution from tens to hundred nanometers. The synthesized powdered product is investigated using by X-Ray diffractometry (XRD), scanning electron microscopy and high-resolution transmission electron microscopy. According to XRD, the obtained product consists of hexagonal zinc oxide with lattice parameters a = b = 3.24982 Å, c = 5.20661 Å that is clearly confirmed by microscopy data. This powder was used to produce a bulk ceramics sample on its basis by spark plasma sintering. The influence of sintering parameters on the structure of the resulting sample was studied. The optimal parameters were found which allows obtaining the more dense ceramics with a better microstructure. It was also found that the absence of exposure time after reaching the working temperature and pressure allows decreasing the porosity of ceramics.

  13. 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).

  14. 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.

  15. Sintering kinetic of Bi4Ti3O12 based ceramics

    Directory of Open Access Journals (Sweden)

    Villegas, M.

    2006-06-01

    Full Text Available The shrinkage behaviour in based-Bi4Ti3O12 ceramics has been studied by constant heating rate experiments (CHR. Undoped and WO3 doped BIT ceramics were prepared by two different ways: mixed oxide method and hidroxide-based coprecipitation method. Analyses of the initial and intermediate sintering stages were evaluated using different Coble’s based models. Sintering behaviour is modified by both, the dopant and the processing method. Powders obtained by the mixed oxide method sintered through a solid state mechanism, while coprecipitated powders sintered with the presence of a small amount of a transitory liquid phase.Se ha estudiado el comportamiento durante la sinterización de cerámicas basadas en Bi4Ti3O12 (BIT. Muestras sin dopar y dopadas con WO3 fueron preparadas por dos rutas diferentes: vía convencional por mezcla de óxidos y vía química por el método de coprecipitación de hidróxidos. Las variaciones en la contracción de las muestras se siguieron mediante ensayos de dilatometría. Para determinar los parámetros cinéticos se utilizaron diferentes modelos teóricos basados en los de Coble para los estados inicial e intermedio de la sinterización. Tanto el método de procesamiento como la cantidad de dopante modifican el comportamiento durante la sinterización de estas cerámicas. La sinterización de las muestras obtenidas por vía convencional se produce en estado sólido mientras que en aquellas obtenidas por vía química la sinterización se produce en presencia de una pequeña cantidad de fase líquida.

  16. Effect of Sintering Temperature on the Microstructure and Mechanical Properties of Low-Cost Light-Weight Proppant Ceramics

    Science.gov (United States)

    Wang, K. Y.; Wang, H. J.; Zhou, Y.; Wu, Y. Q.; Li, G. M.; Tian, Y. M.

    2017-09-01

    In this paper, the low-cost light-weight proppant ceramics were prepared with the solid wastes of coal gangue as the raw materials, and the effect of sintering temperature on the apparent porosity, bulk density, bending strength, microstructure and phase composition were investigated. The results showed that the ceramics, sintered at 1350°C, has the best performance with the bending strength of 85MPa, bulk density of 2.7 g/cm3 and apparent porosity of 18%. These properties of ceramics were very close to that of the bauxite-sintered, and thus the gangue were very probably selected for the preparation of proppants that involved in the exploitation of coalbed methane.

  17. Fabrication of Ce3+ doped Gd3Ga3Al2O12 ceramics by reactive sintering method

    Science.gov (United States)

    Ye, Yong; Liu, Peng; Yan, Dongyue; Xu, Xiaodong; Zhang, Jian

    2017-09-01

    Ce3+ doped Gd3Ga3Al2O12 (Ce:GGAG) ceramics were fabricated by solid state reactive sintering method in this study. The ceramics were pre-sintered in normal muffle furnace in air at various temperature range from 1410 °C to 1550 °C for 10 h and post-treated by hot isostatic press at 1400 °C/2 h in 200 MPa Ar. The phase and microstructure evolution of Ce: GGAG samples during the densification process were investigated by X-ray diffraction and scanning electron microscope. Pure GGAG phase appeared with the temperature increased to 1200 °C. The fully dense and translucent GGAG ceramics were fabricated by pre-sintering at 1450 °C and followed by HIP treatment.

  18. Sinterable Ceramic Powders from Laser Heated Gas Phase Reactions and Rapidly Solidified Ceramic Materials.

    Science.gov (United States)

    1984-07-01

    Gattuso, T. R., Meunier, M., Adler, D., and Haggerty, J. S., "IR Laser- Induced Deposition of Silicon Thin Films ", to be published in the Proceedings of...and Thin Films by Laser Induced Gas Phase Reactions", presented at the Nineteenth University Conference on Ceramic Science, Emergent Process Methods... Silicon Carbonitrides from Monomeric Organosilicon Precursors". To be presented at the 1983 Annual Meeting of the American Ceramic Society, April 1983

  19. Investigation into the Properties of Sintered Ceramics from Dysna Clay and Non-Plastics Additives

    Directory of Open Access Journals (Sweden)

    Jolanta Pranckevičienė

    2011-04-01

    Full Text Available Recycling mineral wool spinning waste represents a rather serious problem. The results of the present research show that the suggested sintering ceramics out of low melting illite clay and mineral wool spinning waste is a promising way for solving the problem of mineral wool waste utilization. The conducted research into the properties of this compound has shown that by introducing 20% of waste into low melting clay allows producing ceramic materials possessing the following parameters: value of absorption is equal to 2,2%, density – 2169 kg/m3.The data of dilatometric investigation have demonstrated that adding 20 % of MVCF component leads to reducing length from 2,8% to 1,4% at the temperature of 1070 ºC. Article in Lithuanian

  20. Influence of the powder preparation on the sintering of Yb-doped Sc 2O 3 transparent ceramics

    Science.gov (United States)

    Bravo, A. C.; Longuet, L.; Autissier, D.; Baumard, J. F.; Vissie, P.; Longuet, J. L.

    2009-03-01

    We report the preparation and the sintering of high quality Yb:Sc 2O 3 powders with the ultimate intent to make transparent Yb:Sc 2O 3 ceramics for laser applications. The aim of the study is to compare two routes of powder preparation and observe the influence of the powder processing on the sintering of Yb-doped Sc 2O 3 ceramics. The powders were prepared (i) either from commercial oxides by a classical ceramic way (solid state reaction process) (ii) or by a wet chemical route. In that case, a carbonate precursor was synthesized by a coprecipitation method from a mixed solution of scandium and ytterbium nitrates using aqueous ammonium hydrogen carbonate as a precipitating agent. The Yb:Sc 2O 3 powder was obtained after heat treatment of the carbonate precursor at 700 °C. The powders prepared by these two methods were characterized by BET measurements, XRD and SEM and their sintering behaviour was investigated by dilatometry. The effects of a grinding step and of the addition of a sintering aid addition (TEOS) were investigated. The microstructures of the vacuum sintered materials were observed by scanning electron microscopy. Electron probe microanalysis allowed to characterize the repartition of the dopant Yb 3+ in the Sc 2O 3 matrix. Translucent ceramics with densities close to 99% were obtained in the best conditions.

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

    Science.gov (United States)

    Obada, David O.; Dodoo-Arhin, David; Dauda, Muhammad; Anafi, Fatai O.; Ahmed, Abdulkarim S.; Ajayi, Olusegun A.

    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.

  2. Investigations on the defect chemistry and the sintering of barium titanate ceramics by oxygen coulometry

    Science.gov (United States)

    Langhammer, Hans Theo; Song, Quan Ming; Felgner, Karl-Heinz; Abicht, Hans-Peter

    2002-02-01

    The application of the oxygen coulometry method on the investigation of the defect chemistry and the sintering process of donor- and acceptor-doped barium titanate ceramics is described. The measuring principle is based on two identical solid electrolyte circonia cells with two electrode pairs both for measuring of the oxygen partial pressure and for oxygen pumping. Three different oxygen exchange processes of the samples could be detected. (1) The oxygen exchange due to the change of the equilibrium temperature at a fixed oxygen partial pressure, which is caused by the change of the concentration of oxygen vacancies. (2) The oxygen exchange which is related to the valence change of Mn Ti during the change of the ambient atmosphere. The data are consistent with the assumption that manganese occurs as Mn 3+ at an oxygen partial pressure of 2.4 Pa and a temperature of about 1400 °C. (3) During the sintering of donor-doped barium titanate ceramics, oxygen expelling processes were detected which are related to the incorporation of the donor into the lattice. In the case of a doping level of 0.5 mol% La, the estimated amount of expelled oxygen is less than expected for exclusive electronic donor compensation.

  3. EFFECT OF SINTERING TEMPERATURE ON MICROSTRUCTURE AND IN-VITRO BEHAVIOR OF BIOACTIVE GLASS-CERAMICS

    Directory of Open Access Journals (Sweden)

    Hashmi M. U.

    2013-12-01

    Full Text Available In this work, powders of the composition (CaO 46- SiO2 34- P2O5 14.5- MgO 4- CaF2 1- MgF2 0.5 (wt. % were thoroughly mixed and melted in a muffle furnace. The melt was quenched in water to form glass. Three glass-ceramics were prepared by sintering glass samples at three different temperatures 850, 900 and 950°C according to the exothermal peaks of DTA. The DTA peaks correspond to the bioactive crystalline phases hydroxyapatite (HA and wollastonite as confirmed by the XRD data. Study of diameter-shrinkage co-efficient and bulk-density of samples revealed higher densification rate for the range 900 - 950°C than that for the range 850 - 900°C.SEM and optical microscope results illustrated a tendency towards closely packed structure and increasing grain size with the increase of sintering temperature. The samples were immersed in SBF for 30 days at room temperature for in-vitro evaluation.EDS analysis, showing the presence of carbon (C along with calcium (Ca and phosphorus (P suggests the formation of hydroxycarbonate-apatite (HCA phase that indicates the bioactivity of the material which increases with the increase of sintering temperature.

  4. Biological evaluation of an apatite-mullite glass-ceramic produced via selective laser sintering.

    Science.gov (United States)

    Goodridge, Ruth D; Wood, David J; Ohtsuki, Chikara; Dalgarno, Kenneth W

    2007-03-01

    The biological performance of a porous apatite-mullite glass-ceramic, manufactured via a selective laser sintering (SLS) method, was evaluated to determine its potential as a bone replacement material. Direct contact and extract assays were used to assess the cytotoxicity of the material. A pilot animal study, implanting the material into rabbit tibiae for 4 weeks, was also carried out to assess in vivo bioactivity. The material produced by SLS did not show any acute cytotoxic effects by either contact or extract methods. There was no evidence of an apatite layer forming on the surface of the material when soaked in SBF for 30 days, suggesting that the material was unlikely to exhibit bioactive behaviour in vivo. It is hypothesized that the material was unable to form an apatite layer in SBF due to the fact that this glass-ceramic was highly crystalline and the fluorapatite crystal phase was relatively stable in SBF, as were the two aluminosilicate crystal phases. There was thus no release of calcium and phosphorus and no formation of silanol groups to trigger apatite deposition from solution within the test time period. Following implantation in rabbit tibiae for 4 weeks, bone was seen to have grown into the porous structure of the laser-sintered parts, and appeared to be very close to, or directly contacting, the material surface. This result may reflect the local environment in vivo compared to that artificially found with the in vitro SBF test and, furthermore, confirms previous in vivo data on these glass-ceramics.

  5. Low-Temperature Sintering of AlN Ceramics by Sm2O3-Y2O3-CaO Sintering Additives Formed via Decomposition of Nitrate Solutions

    Science.gov (United States)

    Zhan, Jun; Cao, Ye; Zhang, Hao; Guo, Jun; Zhang, Jianhua; Geng, Chunlei; Shi, Changdong; Cui, Song; Tang, Wenming

    2017-01-01

    The Sm, Y and Ca anhydrous nitrates were mixed with the AlN powder in ethanol and then decomposed into the Sm2O3-Y2O3-CaO sintering additives via calcining. Low-temperature sintering of the AlN ceramics was carried out at temperature range from 1675 to 1750 °C. Effects of the composition and adding amount of the sintering additives on the phases, microstructures and properties of the AlN ceramics were investigated. During sintering the AlN ceramics, main secondary phases of CaYAl3O7 and CaSmAl3O7 form. The relative density, bending strength and thermal conductivity of the AlN ceramics increase with the increase in the rare-earth oxides in them. The thermal conductivity of the sintered AlN ceramics is also greatly affected by the distribution of the secondary phases. As sintered at 1750 °C, the AlN ceramics by adding the sintering additives of 2 wt.% Sm2O3, 2 wt.% Y2O3 and 1 wt.% CaO formed via decomposition of their nitrates is fully dense and have the optimal bending strength and thermal conductivity of 402.1 MPa and 153.7 W/(m K), respectively.

  6. Ceramic Sintering

    Science.gov (United States)

    1974-10-01

    Plessy Co. of Frenchtown, N.J. The vendor’s analysis showed it to be 91% alpha Si^ and the rest beta . The impurity content, as determined... Cristobalite . This was also the crystalline form of the oxide on the powder on which the samples lay. Figure 5 showj oxidation data obtained at 1550oC

  7. 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

  8. Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering.

    Science.gov (United States)

    Bae, Eun-Jeong; Kim, Ji-Hwan; Kim, Woong-Chul; Kim, Hae-Young

    2014-08-01

    The purpose of this study was to compare the fracture strength of the metal and the bond strength in metal-ceramic restorations produced by selective laser sintering (SLS) and by conventional casting (CAST). Non-precious alloy (StarLoy C, DeguDent, Hanau, Germany) was used in CAST group and metal powder (SP2, EOS GmbH, Munich, Germany) in SLS group. Metal specimens in the form of sheets (25.0 × 3.0 × 0.5 mm) were produced in accordance with ISO 9693:1999 standards (n=30). To measure the bond strength, ceramic was fired on a metal specimen and then three-point bending test was performed. In addition, the metal fracture strength was measured by continuing the application of the load. The values were statistically analyzed by performing independent t-tests (α=.05). The mean bond strength of the SLS group (50.60 MPa) was higher than that of the CAST group (46.29 MPa), but there was no statistically significant difference. The metal fracture strength of the SLS group (1087.2 MPa) was lower than that of the CAST group (2399.1 MPa), and this difference was statistically significant. In conclusion the balling phenomenon and the gap formation of the SLS process may increase the metal-ceramic bond strength.

  9. Influence of tooth resilience in correlation to the fracture strength of four-unit zirconium-oxide bridges constructed with the LAVA® -CAD/CAM-System

    OpenAIRE

    Kunth, Axel

    2010-01-01

    The objective of this in-vitro-study was to analyse the influence of tooth resilience in correlation to the fracture strength of tooth-tooth, tooth-implant and purely implant stored four-unit zirconium-oxide bridges constructed with the LAVA® -CAD/CAM-System. The 80 dies were embedded in Paladur Clear® (Heraeus Kulzer); whereby a defined mobility of the dies was reached using heat shrink tubing (3M, type HSR) which was wrapped around the dental roots. 40 full-ceramic bridges of the same d...

  10. Combining Esthetic Layering and Lithium Disilicate Sintering Technique on Zirconia Frameworks: A Veneering Option to Prevent Ceramic Chipping.

    Science.gov (United States)

    Saeidi Pour, Reza; Edelhoff, Daniel; Rafael, Caroline Freitas; Prandtner, Otto; Frei, Stefan; Maziero Volpato, Claudia Angela; Liebermann, Anja

    Major and minor chipping of veneering porcelain are two of the most frequent complications in all-ceramic restorations with zirconia frameworks. In cases of major chipping, replacement of the affected restoration may be necessary. High-strength lithium disilicate ceramic offers new options to serve as veneering material in a sintering technique or as repair material for chipping in combination with the adhesive technique. The purpose of three case presentations here was to describe the use of lithium disilicate ceramic on zirconia frameworks for reliable and esthetic veneering in the posterior region and to repair extended chipping in conventional veneering materials.

  11. Glass-ceramic coating material for the CO2laser 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

  12. 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.

  13. 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.

  14. Microstructure and luminescent properties of Ce:Lu2SiO5 ceramic scintillator by spark plasma sintering

    Science.gov (United States)

    Xie, Jianjun; Shi, Ying; Fan, Lincong; Xu, Zhibin

    2013-02-01

    Spark plasma sintering (SPS) processing was employed to fabricate cerium (Ce3+) ions doped lutetium silicate (Lu2SiO5) translucent scintillation ceramics. Polycrystalline Ce:Lu2SiO5 ceramic bulks were densified from as-prepared powder by spark plasma sintering at 1350 °C for 5 min under pressure of 50 MPa. Translucent monolithic Ce:Lu2SiO5 ceramic specimen was obtained with excellent luminescent characteristics after being annealed in air at 1000 °C for 15 h. Under 360 nm UV excitation, a broad emission peak centered at about 425 nm was detected for Ce:Lu2SiO5 ceramic. The luminescence intensity of annealed ceramic sample (doped by 0.5 mol% Ce3+) was 3 times greater than that of BGO single crystal under X-ray excitation. The decay constant under γ-ray excitation of Cs-137 radioactive source was measured to 44.36 ns. The good luminescent characteristics made Ce:Lu2SiO5 polycrystalline ceramics a promising scintillator candidate with high performance for radiation detection in future.

  15. Tough yttria-stabilized zirconia ceramic by low-temperature spark plasma sintering of long-term stored nanopowders.

    Science.gov (United States)

    Bezdorozhev, Oleksii; Borodianska, Hanna; Sakka, Yoshio; Vasylkiv, Oleg

    2011-09-01

    Weakly agglomerated 1.75 and 3 mol% yttria stabilized zirconia nanopowders were used in this study after six years of storage in vacuum-processed plastic containers. The proper storage conditions of the Y-TZP nanopowders avoided the hard agglomeration. Untreated and bead-milled nanopowders were used to obtain dense ceramics by slip casting and subsequent low-temperature sintering. Fully dense nanostructured 1.75Y-TZP and 3Y-YZP ceramics with and without doping of 1 wt% Al2O3 were produced by an optimized spark plasma sintering (SPS) technique at the temperatures of 1050-1150 degrees C at a pressure of 100 MPa. The SPS has revealed the clear advantage of consolidation of the weakly agglomerated nanopowders without preliminary deagglomeration. The Vickers hardness of both the low-temperature and spark plasma sintered samples was found to lie in the range of 10.98-13.71 GPa. A maximum fracture toughness of 15.7 MPa m(1/2) (average 14.23 MPa m(1/2)) was achieved by SPS of the 1.75Y-TZP ceramic doped with 1 wt% Al2O3 whereas the toughness of the 3Y-TZP ceramics with and without alumina doping was found to vary between 3.55 and 5.5 MPa m(1/2).

  16. 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.

  17. The effect of sintering temperature on electrical characteristics of Fe2TiO5/Nb2O5 ceramics for NTC thermistor

    Science.gov (United States)

    Wiendartun, Risdiana, Fitrilawati, Siregar, R. E.

    2016-02-01

    A study on the fabrication of Iron Titanium Oxide (Fe2TiO5) ceramics for negative temperature coefficient (NTC) thermistors has been carried out, in order to know the effect of sintering temperature on the electrical characteristic of 1.0 % mole Nb2O5 doped Fe2TiO5 ceramics.These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and Nb2O5 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1000 °C, 1100 °C and 1200 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD spectra showed that the crystal structure of all ceramics of Fe2TiO5 made at various sintering temperatures are orthorhombic. The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical resistances data that was measured at temperature 30-300 °C, it is found that the value of thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT) decreases with respect to the increasing of sintering temperature. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 6394-6959 K). This can be applied as temperature sensor, and will fulfill the market requirement.

  18. Comparison of the optical properties of pre-colored dental monolithic zirconia ceramics sintered in a conventional furnace versus a microwave oven.

    Science.gov (United States)

    Kim, Hee-Kyung; Kim, Sung-Hun

    2017-10-01

    The purpose of this study was to compare the optical properties of pre-colored dental monolithic zirconia ceramics of various thicknesses sintered in a microwave and those in a conventional furnace. A2-shade of pre-colored monolithic zirconia ceramic specimens (22.0 mm × 22.0 mm) in 3 thickness groups of 0.5, 1.0, and 1.5 mm were divided into 2 subgroups according to the sintering methods (n=9): microwave and conventional sintering. A spectrophotometer was used to obtain CIELab color coordinates, and translucency parameters and CIEDE2000 color differences (ΔE00) were measured. The relative amount of monoclinic phase (Xm) was estimated with x-ray diffraction. The surface topography was analyzed by atomic force microscope and scanning electron microscope. Statistical analyses were conducted with two-way ANOVA (α=.05). There were small interaction effects on CIE L*, a*, and TP between sintering method and thickness (Pmicrowave sintering regardless of thickness. Color differences between two sintering methods ranged from 0.52 to 0.96 ΔE00 units. The Xm values ranged from 7.03% to 9.89% for conventional sintering, and from 7.31% to 9.17% for microwave sintering. The microwave-sintered specimen demonstrated a smoother surface and a more uniform grain structure compared to the conventionally-sintered specimen. With reduced processing time, microwave-sintered pre-colored dental monolithic zirconia ceramics can exhibit similar color perception and translucency to those by conventional sintering.

  19. 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.

  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. Study of the microstructure and the hardness of PZT piezoelectric ceramics types I and III used in electro acoustic transducers; Estudo da microestrutura e da microdureza das ceramicas piezoeletricas tipos PZT I e III utilizadas em transdutores eletroacusticos

    Energy Technology Data Exchange (ETDEWEB)

    Cabral, Ricardo de Freitas; Itaboray, Lucas Mendes; Santos, Anna Paula de Oliveira [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil)

    2015-12-15

    The field of electronic processing of the ceramic piezoelectric type imported powdered led to the production of ceramics with 97% of theoretical density, homogeneous microstructure with great potential for applications in piezoelectric devices such as electro acoustic transducers. However, the production of electronic ceramics National piezoelectric type is not yet able to have as raw material zirconate titanate Lead (PZT) 100% made in Brazil. Thus, this is used for supply of domestic production, the zirconium oxide. In this work, both post PZT types I and III, imported, were uniaxially pressed at 70 MPa and sintered at 1200 and 1250 deg C for 3 hours. Hardness measurements were performed by micro indentation, X-ray diffraction analysis and Scanning Electron Microscopy. The hardness of PZT I was 393 HV. (author)

  2. Simulation of temperature distribution for large sized ceramic substrates in vertical type sintering furnace; Tategata denkiro shosei deno ogata seramikkusu kiban no ondo bunpu shumyureshon

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, M.; Ami, N.; Hirasawa, S. [Hitachi, Ltd., Tokyo (Japan)

    2000-01-01

    The temperature distribution in large sized ceramic substrates at 1600 degree C sintered by vertical type furnace was simulated by using a model of heat conduction and radiation heat transfer. The temperature distribution at the center of each ceramic substrate is larger than that in each ceramic substrate at steady state in the case of 3 substrates were fired. The temperature distribution becomes narrow by using a high thermal conductivity material setter or inserting heat insulating material between the bottom setter and the furnace floor. The temperature distribution in each ceramic substrate is closely related to the distance between the surface of the ceramic substrate and the bottom of the upper setter. (author)

  3. Sintering in Laser Sintering

    Science.gov (United States)

    Bourell, David L.

    2016-03-01

    Laser sintering is a popular additive manufacturing technology, particularly for service parts. Invented by C. Deckard in the mid-1980s, the approach of using a laser to densify a powder bed selectively has been extensively researched and has been applied to metals, ceramics, polymers and composites. In the traditional powder-metallurgical sense, sintering involves solid-state atomic transport resulting in neck formation and eventual densification in a powder mass. The use of the term "sintering" as a descriptive term for the powder-bed additive manufacturing process has been problematical to the technical community, because the predominant densification mechanism has been shown for most applications to be melting and reflow. The term has perpetuated as a name for the additive manufacturing process, at least for polymers. The technical term "sintering" is accurately associated with laser sintering insofar as powder pre-processing and part post-processing are concerned. It may also be used to describe formation of "part cake". This paper describes the circumstances surrounding the coining of the term, "laser sintering" and provides some examples of how sintering is used in pre- and post-processing.

  4. Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics

    Directory of Open Access Journals (Sweden)

    Mendes A.M.

    2017-02-01

    Full Text Available In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ commercial ceramics has been studied using the central composite design (CCD method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr atoms coordinated to seven oxygen (O atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics.

  5. Effects of B2O3 content and sintering temperature on crystallization and microstructure of CBS glass-ceramic coatings

    Science.gov (United States)

    Li, Pengyang; Wang, Shubin; Liu, Jianggao; Feng, Mengjie; Yang, Xinwang

    2015-11-01

    Borosilicate glass-ceramics precursors with varying compositional ratios in the CaO-SiO2-B2O3 (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 (Ec) 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 Ec values of CBS glasses and glass-ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B2O3 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.

  6. Phase Composition and Microstructure of Hot-Pressing Sintered Ti2AlN Metal-Ceramic Bulk Material

    Directory of Open Access Journals (Sweden)

    LIANG Suying

    2017-06-01

    Full Text Available Ti2AlN metal-ceramic bulk material was fabricated by hot-pressing sintering (HPS using TiN, Ti and Al powder in a stoichiometric ratio of 1:1:1.03 after mechanical mixing. XRD, SEM and TEM were employed to investigate the phase composition and microstructures of the products. The results show that the high purity Ti2AlN can be obtained by HPS at 1300 ℃ for 2.5 h. The sintered Ti2AlN presented a hexagonal system layered structure with an anisotropy. Twins are found in the Ti2AlN. There were a few nano-scale TiN particles in the products.

  7. 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.

  8. Effects of the sintering conditions of dental zirconia ceramics on the grain size and translucency.

    Science.gov (United States)

    Kim, Mi-Jin; Ahn, Jin-Soo; Kim, Ji-Hwan; Kim, Hae-Young; Kim, Woong-Chul

    2013-05-01

    This study aimed to identify the effects of the sintering conditions of dental zirconia on the grain size and translucency. Ten specimens of each of two commercial brands of zirconia (Lava and KaVo) were made and sintered under five different conditions. Microwave sintering (MS) and conventional sintering (CS) methods were used to fabricate zirconia specimens. The dwelling time was 20 minutes for MS and 20 minutes, 2, 10, and 40 hours for CS. The density and the grain size of the sintered zirconia blocks were measured. Total transmission measurements were taken using a spectrophotometer. Two-way analysis of variance model was used for the analysis and performed at a type-one error rate of 0.05. There was no significant difference in density between brands and sintering conditions. The mean grain size increased according to sintering conditions as follows: MS-20 min, CS-20 min, CS-2 hr, CS-10 hr, and CS-40 hr for both brands. The mean grain size ranged from 347-1,512 nm for Lava and 373-1,481 nm for KaVo. The mean light transmittance values of Lava and KaVo were 28.39-34.48% and 28.09-30.50%, respectively. Different sintering conditions resulted in differences in grain size and light transmittance. To obtain more translucent dental zirconia restorations, shorter sintering times should be considered.

  9. Effect of sintering temperature on mechanical behaviour and bioactivity of sol-gel synthesized bioglass-ceramics using rice husk ash as a silica source

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, J.P., E-mail: jyotiprakash_nitrkl@rediffmail.com [Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Bera, J., E-mail: bera@rediffmail.com [Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India)

    2010-11-01

    Bioglass-ceramics with SiO{sub 2}-Na{sub 2}O-CaO composition was prepared by sol-gel method using rice husk ash as a silica source. Material was sintered at different temperatures ranging from 900 to 1050 deg. C for 2 h. Phase-formation behaviour, densification characteristics, and mechanical strength of glass-ceramics were investigated. The material sintered at 1000 deg. C showed a good mechanical strength. Mechanical properties were correlated with microstructural features. Both in vitro bioactivity and biodegradability of sintered material were investigated by incubating in simulated body fluid and Tris buffer solution, respectively. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to investigate the surface deposition during body fluid incubation. Both bioactivity and degradability decreased with increase in sintering temperature.

  10. Effect of sintering temperature on mechanical behaviour and bioactivity of sol-gel synthesized bioglass-ceramics using rice husk ash as a silica source

    Science.gov (United States)

    Nayak, J. P.; Bera, J.

    2010-11-01

    Bioglass-ceramics with SiO2-Na2O-CaO composition was prepared by sol-gel method using rice husk ash as a silica source. Material was sintered at different temperatures ranging from 900 to 1050 °C for 2 h. Phase-formation behaviour, densification characteristics, and mechanical strength of glass-ceramics were investigated. The material sintered at 1000 °C showed a good mechanical strength. Mechanical properties were correlated with microstructural features. Both in vitro bioactivity and biodegradability of sintered material were investigated by incubating in simulated body fluid and Tris buffer solution, respectively. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to investigate the surface deposition during body fluid incubation. Both bioactivity and degradability decreased with increase in sintering temperature.

  11. An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system

    DEFF Research Database (Denmark)

    Pallesen, U.; Dijken van, J.W.V.

    2000-01-01

    The purpose of this study was to evaluate Cerec CAD/CAM inlays processed of two industrially made machinable ceramics during an 8-yr follow-up period. Each of 16 patients received two similar ceramic inlays. Half the number of the inlays were made of a feldspathic (Vita Mark II) and the other...... be concluded that the CAD/CAM inlays processed of the two ceramics functioned well during the 8-yr follow-up period....

  12. 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.

  13. 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.

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

    Directory of Open Access Journals (Sweden)

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

    2009-01-01

    Full Text Available 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 ° C.

  15. 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.

  16. Sintering of transparent Yb-doped Lu{sub 2}O{sub 3} ceramics using nanopowder produced by laser ablation method

    Energy Technology Data Exchange (ETDEWEB)

    Kijko, V.S. [Ural Federal University named after the first President of Russia B.N. Yeltsin, Mira St. 19, Ekaterinburg 620002 (Russian Federation); Maksimov, R.N., E-mail: romanmaksimov@e1.ru [Ural Federal University named after the first President of Russia B.N. Yeltsin, Mira St. 19, Ekaterinburg 620002 (Russian Federation); Institute of Electrophysics UB RAS, Amundsen St.106, Ekaterinburg 620016 (Russian Federation); Shitov, V.A. [Institute of Electrophysics UB RAS, Amundsen St.106, Ekaterinburg 620016 (Russian Federation); Demakov, S.L.; Yurovskikh, A.S. [Ural Federal University named after the first President of Russia B.N. Yeltsin, Mira St. 19, Ekaterinburg 620002 (Russian Federation)

    2015-09-15

    Highlights: • Yb:Lu{sub 2}O{sub 3} nanoparticles synthesized by laser ablation method were investigated. • Transparent Yb:Lu{sub 2}O{sub 3} ceramics were fabricated via vacuum and spark plasma sintering. • Highest transmittance was 79.3% at 1080 nm for vacuum sintered Yb:Lu{sub 2}O{sub 3} sample. - Abstract: Transparent Yb-doped Lu{sub 2}O{sub 3} ceramic samples were fabricated via conventional vacuum and spark plasma sintering. Nanoparticles synthesized by laser ablation method were used as starting material. The morphology and phase evolution of the nanopowder were studied by transmission electron microscopy, simultaneous thermal analysis and X-ray diffraction. The obtained nanoparticles exhibited the monoclinic phase and were fully converted into the main cubic phase after calcination at 1100 °C for 1 h. Conventional vacuum sintering of Yb:Lu{sub 2}O{sub 3} powder compact at 1780 °C for 20 h resulted in a fully-dense ceramics with an average grain size of 1.6 μm and optical transmittance of 79.3% at 1080 nm. Spark plasma sintering of the calcined Yb:Lu{sub 2}O{sub 3} nanoparticles at 1450 °C and 15 kN for 40 min led to a 0.2 μm-grained ceramics exhibiting an optical transmittance of 75.6% at 1080 nm.

  17. In vitro evaluation of the bond strength between various ceramics and cobalt-chromium alloy fabricated by selective laser sintering.

    Science.gov (United States)

    Bae, Eun-Jeong; Kim, Hae-Young; Kim, Woong-Chul; Kim, Ji-Hwan

    2015-08-01

    This study aimed to present the clinical applicability of restorations fabricated by a new method, by comparing the bond strength of between ceramic powder with different coefficient of thermal expansion and alloys fabricated by Selective laser sintering (SLS). Fifty Co-Cr alloy specimens (25.0 × 3.0 × 0.5 mm) were prepared by SLS and fired with the ceramic (8.0 × 3.0 × 0.5 mm) (ISO 9693:1999). For comparison, ceramics with different coefficient of thermal expansion were used. The bond strength was measured by three-point bending testing and surfaces were observed with FE-SEM. Results were analyzed with a one-way ANOVA (α=.05). The mean values of Duceram Kiss (61.18 ± 6.86 MPa), Vita VM13 (60.30 ± 7.14 MPa), Ceramco 3 (58.87 ± 5.33 MPa), Noritake EX-3 (55.86 ± 7.53 MPa), and Vintage MP (55.15 ± 7.53 MPa) were found. No significant difference was observed between the bond strengths of the various metal-ceramics. The surfaces of the specimens possessed minute gaps between the additive manufactured layers. All the five powders have bond strengths higher than the required 25 MPa minimum (ISO 9693); therefore, various powders can be applied to metal structures fabricated by SLS.

  18. Fabrication of Yb:Sc2O3 laser ceramics by vacuum sintering co-precipitated nano-powders

    Science.gov (United States)

    Liu, Qiang; Dai, Zhengfa; Hreniak, Dariusz; Li, Shanshan; Liu, Wenbin; Wang, Wei; Luo, Wei; Li, Chaoyu; Dai, Jiawei; Chen, Haohong; Kou, Huamin; Shi, Yun; Pan, Yubai; Li, Jiang

    2017-10-01

    Ytterbium doped scandium oxide (Yb:Sc2O3) nano-powders were synthesized by a co-precipitation method. Ammonium hydrogen carbonate (NH4HCO3) and ammonia sulfate ((NH4)2SO4) were used in the precipitation process as the precipitant and dispersing agent, respectively. Structural properties and morphology of the precursor and nano-powders were investigated by BET, XRD, and SEM measurements. Ultra-fine and low agglomerated 5 at%Yb:Sc2O3 powders with the average particle size of 86 nm were obtained after calcination of the precipitate at 1100 °C for 5 h, that was found to be the optimal temperature for preparation of 5 at%Sc2O3 powders for further sintering. 5 at%Yb:Sc2O3 transparent ceramics with in-line transmittance of 73.9% at 1100 nm and average grain size of 182 μm were fabricated by vacuum sintering of the optimal powder at 1850 °C for 10 h. The microstructure, the spectroscopic properties and the gain characteristics of obtained 5 at%Yb:Sc2O3 ceramics were also studied and discussed.

  19. Effect of silicon content on the sintering and biological behaviour of Ca10(PO4)(6-x)(SiO4)x(OH)(2-x) ceramics.

    Science.gov (United States)

    Palard, Mickaël; Combes, Julien; Champion, Eric; Foucaud, Sylvie; Rattner, Aline; Bernache-Assollant, Didier

    2009-05-01

    Silicated hydroxyapatite powders (Ca10(PO4)(6-x)(SiO4)x(OH)(2-x); Si(x)HA) were synthesized using a wet precipitation method. The sintering of Si(x)HA ceramics with 0 cells. The proliferation of cells on the surface of the ceramics increased up to 5 days of culture, indicating that the materials were biocompatible. However, the silicon content did not influence the cell proliferation.

  20. Translucent Nano Mullite Based Composite Ceramic Fabricated by Spark Plasma Sintering

    National Research Council Canada - National Science Library

    IMAI, Takahito; NAITOH, Yusuke; YAMAMOTO, Takeshi; OHYANAGI, Manshi

    2006-01-01

      Dense translucent mullite-amorphous composite was fabricated from the metakaoline powder by spark plasma sintering, which was synthesized from halloysite powder mined in Algeria by annealing process...

  1. Sintering behavior of Y2O3 doped Bi2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Alizadeh M.

    2007-01-01

    Full Text Available Influence of sintering temperature and soaking time on densification of Bi2O3 samples doped with 25%mol Y2O3 was investigated by shrinkage and relative density measurements. Samples were sintered in air at different temperatures in the range of 800 to 1000°C for 24 hr. The results showed that samples sintered at 950°C have the maximum relative density. Several samples were sintered at 950°C for duration of 0 to 36 hr in order to evaluate the effect of soaking time on densification of samples. It was found that the samples were sintered at 950°C for 36hr had higher relative density than others did for smaller time duration X-ray diffraction (XRD analyses detected δ -Bi2O3 as the sole stable phase in all samples. Scanning Electron Microscopy (SEM investigation of fractured surface of the samples showed that porosities decrease by increasing of sintering temperature and grow by further increasing of temperature.

  2. Spark plasma sintering of MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite thermistor ceramics and a comparison investigation with conventional sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bo; Zhao, Qing [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Chang, Aimin, E-mail: changam@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Wu, Yiquan, E-mail: wuy@alfred.edu [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, NY 14802 (United States); Li, Hongyi [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Product Quality Supervision and Inspection Institute of Xinjiang Uygur Autonomous Region, Urumqi 830013 (China)

    2016-08-05

    The microstructure and negative temperature coefficient (NTC) electrical properties of the MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite ceramics prepared by spark plasma sintering (SPS) were investigated. The effects of SPS and conventional sintering (CS) on electrical properties and high temperature aging characteristics of 0.6MgAl{sub 2}O{sub 4}–0.4LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} ceramics were comparatively studied. X-ray diffraction (XRD) results showed both SPS- and CS-sintered ceramics were indexed to be cubic spinel MgAl{sub 2}O{sub 4} phase and orthorhombic perovskite LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} phase isomorphic to LaCrO{sub 3}. Microstructural study reveled that SPS-sintered specimens had a higher relative density more than 96%. The electrical properties of the SPS-sintered NTC thermistors could be adjusted by changing MgAl{sub 2}O{sub 4} content and sintering temperature. The SPS-sintered samples possessed a higher resistivity than that from conventionally sintered ceramics. The reasons for the increase of resistivity in the SPS-sintered samples, and the aging mechanism of the thermistor ceramics were investigated through applying the defect chemistry theory. - Highlights: • MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite ceramics have been successfully fabricated by SPS. • Comparison investigation has been performed on the SPS- and CS-sintered ceramics. • The NTC electrical properties of these composite ceramics have been investigated. • The aging mechanism of the thermistor ceramics has been investigated.

  3. Sinterability study of ceramic bodies made from a mixture of mineral coal bottom ash and soda-lime glass cullet.

    Science.gov (United States)

    Villanova, Daniela L; Bergmann, Carlos P

    2007-02-01

    The aim of this study was to investigate the sinterability to improve the technical properties of ceramic bodies made from coal bottom ash and soda-lime glass cullet. Different mixtures of bottom ash and glass cullet were formulated. The amount of bottom ash was 100, 70, 50 and 30 wt.%. The particle size distribution was the same for all formulations. The mixture containing 50 wt.% bottom ash also had its particle size distribution changed. Samples were formed by dry pressing and then fired at 950, 1050 and 1150 degrees C. Samples were evaluated for linear shrinkage, water absorption, flexural mechanical resistance, scanning electronic microscopy, pyroplastic deformation and thermodilatometric analysis. The higher firing temperature led to a decrease in water absorption and increased linear shrinkage, mechanical resistance and pyroplastic deformation. This effect was also observed for addition of glass up to 50 wt.%. The effect of smaller particles of bottom ash was more significant for linear shrinkage and mechanical resistance of ceramic bodies fired at 1150 degrees C. The use of a finer powder contributed to increase these properties. The influence of finer particles on water absorption and mechanical resistance of ceramic bodies fired at 950 and 1050 degrees C was not significant.

  4. Processing of an apatite-mullite glass-ceramic and an hydroxyapatite/phosphate glass composite by selective laser sintering.

    Science.gov (United States)

    Lorrison, J C; Dalgarno, K W; Wood, D J

    2005-08-01

    The work presented details the results of an investigation into the feasibility of using Selective Laser Sintering (SLS) to directly produce customised bioceramic implants. The materials used were bioactive in nature and included a glass-ceramic and a combination of hydroxyapatite and phosphate glass. The glass-ceramic was selected from the range of apatite-mullite materials in the SiO2.Al2O3.CaO.CaF2.P2O5 series, due to their potentially suitable biological and mechanical properties. The hydroxyapatite and phosphate glass combination was chosen to allow an alternative production approach to be investigated. The viability of using both these materials with the SLS process was assessed and the process route and resulting material properties characterised using a variety of techniques including Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results obtained indicate that it was possible to produce multiple layer components from both materials using the SLS process. The glass-ceramic materials could only be processed at very low scan speeds and powers, yielding relatively brittle components. It was though possible to produce parts from the hydroxyapatite and phosphate glass combination across a much wider range of parameters, producing parts which had a greater potential for possible implant production.

  5. The Influence of Sintering Method on Kaolin-Based Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene as Binder

    Science.gov (United States)

    Romisuhani, A.; AlBakri, M. M.; Kamarudin, H.; Andrei, S. V.

    2017-11-01

    The influence of sintering method on kaolin-based geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene as binder were studied. Geopolymer were formed at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. 12 M of sodium hydroxide solution were mixed with sodium silicate at a ratio of 0.24 to form alkaline activator. Powder metallurgy technique were used in order to produce kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene. The samples were heated at temperature of 1200 °C with two different sintering method which are conventional method and two-step sintering method. The strength and density were tested.

  6. Synthesis of lead-free piezoelectric powders by ultrasonic-assisted hydrothermal method and properties of sintered (K0.48Na0.52)NBO3 ceramics.

    Science.gov (United States)

    Isobe, Gaku; Maeda, Takafumi; Bornmann, Peter; Hemsel, Tobias; Morita, Takeshi

    2014-02-01

    (K,Na)NbO3 ceramics have attracted much attention as lead-free piezoelectric materials with high piezoelectric properties. High-quality (K,Na)NbO3 ceramics can be sintered using KNbO3 and NaNbO3 powders synthesized by a hydrothermal method. In this study, to enhance the quality factor of the ceramics, high-power ultrasonic irradiation was employed during the hydrothermal method, which led to a reduction in the particle size of the resultant powders.

  7. Rapid Sintering of Silica Xerogel Ceramic Derived from Sago Waste Ash Using Sub-millimeter Wave Heating with a 300 GHz CW Gyrotron

    Science.gov (United States)

    Aripin, Haji; Mitsudo, Seitaro; Sudiana, I. Nyoman; Tani, Shinji; Sako, Katsuhide; Fujii, Yutaka; Saito, Teruo; Idehara, Toshitaka; Sabchevski, Sliven

    2011-06-01

    In this paper, we present and discuss experimental results from a microwave sintering of a silica-glass ceramic, produced from a silica xerogel extracted from a sago waste ash. As a radiation source for the microwave heating a sub-millimeter wave gyrotron (Gyrotron FU CW I) with an output frequency of 300 GHz has been used. The powders of silica xerogel have been dry pressed and then sintered at temperatures ranging from 300°C to 1500°C. The influence of the sintering temperature on the technological properties such as porosity and bulk density was studied in detail. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy have been used in order to study the structure of the produced silica glass-ceramics. It has been found that the silica xerogel crystallizes at a temperature of 800°C, which is about 200°C lower than the one observed in the conventional process. The silica xerogel samples sintered by their irradiation with a sub-millimeter wave at 900°C for 18 minutes are fully crystallized into a silica glass-ceramic with a density of about 2.2 g/cm3 and cristobalite as a major crystalline phase. The results obtained in this study allow one to conclude that the microwave sintering with sub-millimeter waves is an appropriate technological process for production of silica glass-ceramics from a silica xerogel and is characterized with such advantages as shorter times of the thermal cycle, lower sintering temperatures and higher quality of the final product.

  8. Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P2O5-SiO2-MgO system

    Directory of Open Access Journals (Sweden)

    A. W. Huang

    2015-06-01

    Full Text Available Alumina-based ceramics, Al2O3, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al2O3 is processed by solid-state sintering at a temperature of about 1600 oC, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al2O3 ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P2O5-SiO2-MgO glass. Powder mixtures of 90 wt.% Al2O3 and 10 wt.% bioglass were milled, compacted and sintered at 1200 oC to 1450 oC. Comparatively, monolithic Al2O3 samples were sintered at 1600 oC/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 oC/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m1/2. XRD analysis indicate alumina (αAl2O3, whitlockite (3CaO.P2O5 and diopsite [3(Ca,MgO.P2O5], as crystalline phases. Comparatively, monolithic sintered Al2O3 samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m1/2 of hardness and fracture toughness respectively.

  9. Thermal stability and field assisted sintering of cerium-doped YSZ ceramic nanoparticles obtained via a hydrothermal process

    Directory of Open Access Journals (Sweden)

    Dragut Dumitru V.

    2017-01-01

    Full Text Available Owing to its extraordinary range of properties, yttria-doped zirconia holds a unique place among the ceramic oxide systems. To improve the properties for some specific custom design applications, co-doping with other rare earth oxides such as ceria is needed. The aim of this paper is to identify the correlations between the phase composition evolution with increasing thermal treatment temperature in order to establish the thermal stability in connection with the ceria content and how does it influence the yttria-stabilised zirconia microstructure. The ZrO2–3Y2O3–nCeO2 (n = 3, 6 and 9 wt.% samples were obtained by a hydrothermal process and submitted to a thermal treatment up to 1600 °C. Intensive characterization was performed via X-ray powder diffraction and EDX analysis. It was found that up to 400 °C, a monophasic structure was formed. At higher temperatures tetragonal zirconia is formed as a major phase with the presence of secondary monoclinic and cubic phases, depending on the Ce content and thermal treatment temperature. Sintered compacts with densities up to 99.5% from the theoretical density were obtained starting from the 6%CeO2–3%Y2O3–ZrO2-nanostructured powders using a special field-assisted (FAST sintering process. With increasing CeO2 content to 9% only, tetragonal zirconia with 6–9 nm crystallite sizes is formed during the FAST sintering process.

  10. Influence of Sintering Temperature on the Microstructure and Property of Low-cost Ceramic Proppants Prepared by Adding Purple Sands

    Science.gov (United States)

    Ma, H. Q.; Tian, Y. M.; Li, G. M.; Wang, K. Y.; Zhou, Y.; Bai, P. B.

    2017-09-01

    High-strength corundum-mullite based ceramic proppants have been fabricated from 2nd bauxite (62.3wt%Al2O3) and purple sands, which were used as main raw materials by solid sintering method, combined with the additive of feldspar and pyrolusite powder. The phase analysis was studied by X-ray diffraction (XRD) and the morphology of specimen was observed by the scanning electron microscopy (SEM). The result showed that the additive of feldspar was beneficial to the formation of internal liquid phase of sample with the sintering temperature increasing, which reduced the pores and promoted the densification of sample. Meanwhile the proper liquid phase resulted in the growth of mullite and promoted the close integration of mullite and corundum, forming the network structure of needle-like mullite. Ultimately the proppants exhibited the optimal performance at 1450 °C with bulk density of 1.59 g/cm3, apparent density of 3.11 g/cm3 and the lowest breakage ratio of 3.76% under 52 MPa pressure.

  11. Fabrication and luminescent properties of La2O2S:Eu3+ translucent ceramic by pressureless reaction sintering

    Science.gov (United States)

    Lian, Jingbao; Wang, Bingxin; Liang, Ping; Liu, Feng; Wang, Xuejiao

    2014-04-01

    La2O2S:Eu3+ translucent ceramic (LOS:Eu) was fabricated by pressureless reaction sintering method. It is found that the (La, Eu)2(OH)4SO4ṡ2H2O precursor is synthesized by co-precipitation using commercially available La(NO3)3, Eu(NO3)3, (NH4)2SO4 and NH3ṡH2O as the starting materials. And this precursor can be converted into pure La2O2SO4:Eu3+ phosphor by calcination at 800 °C for 1 h in air, which is composed of a few small needle agglomerated particles. Then the La2O2SO4:Eu3+ phosphor compact can be sintered into the LOS:Eu at 1500 °C for 2 h in the hybrid atmosphere of flowing hydrogen and argon. Under 387 nm UV light excitation, the LOS:Eu reveals a red light emission at 628 nm as the most prominent peak, which corresponds to the 5D0 → 7F2 transition of Eu3+ ions.

  12. Influences of composition of starting powders and sintering temperature on the pore size distribution of porous corundum-mullite ceramics

    Directory of Open Access Journals (Sweden)

    Shujing Li

    2005-01-01

    Full Text Available Porous corundum-mullite ceramics were prepared by an in-situ decomposition pore-forming technique. Starting powders were mixtures of milled Al(OH3 and microsilica and were formed into oblong samples with a length of 100mm and a square cross-section with edge size of 20mm. The samples were heated at 1300°C, 1400°C, 1500°C or 1600°C for 3h in air atmosphere, respectively. Apparent porosity was detected by Archimedes’ Principle with water as a medium. Pore size distribution and the volume percentage of micropores were measured by mercury intrusion porosimetry. The results show that the pore morphology parameters in the samples depend on four factors: particle size distribution of starting powders, decomposition of Al(OH3, the expansion caused by mullite and sintering. The optimum mode which has a higher apparent porosity up to 42.3%, well-distributed pores and more microsize pores up to 16.3% is sample No.3 and the most apposite sintering temperature of this sample is 1500°C.

  13. 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.

  14. 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.

  15. Sintered gahnite–cordierite glass-ceramic based on raw materials ...

    Indian Academy of Sciences (India)

    ... the development crystalline phases through the heating and sintering process between 1000 and 1340°C. The microstructure of crystallized samples at 1340°C showed the appearance of dominant euhedral octahedral crystals of gahnite and hexagonal cordierite, in the low micro-scale, disseminated in the glassy matrix.

  16. 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.

  17. 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.

  18. 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)

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

    Science.gov (United States)

    Yan, Zilin; Martin, Christophe L.; Bouvard, Didier; Jauffrès, David; Lhuissier, Pierre; Salvo, Luc; Olmos, Luis; Villanova, Julie; Guillon, Olivier

    2017-06-01

    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.

  20. 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.

  1. CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior.

    Science.gov (United States)

    Zucuni, C P; Guilardi, L F; Fraga, S; May, L G; Pereira, G K R; Valandro, L F

    2017-07-01

    This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Obtaining solid electrolytes based on zirconium oxide; Obtencao de eletrolitos solidos baseados em oxido de zirconio

    Energy Technology Data Exchange (ETDEWEB)

    Cajas, P.C.; Munoz, R.; Silva, C.R.M da, E-mail: patolacajas@gmail.com [Universidade de Brasilia (UnB), Brasilia, DF (Brazil)

    2014-07-01

    Ceramic materials based on zirconia were synthesized by the controlled precipitation method, ZrO{sub 2}: 3% molY{sub 2}O{sub 3}: η mol% Y{sub 2}O{sub 3} (η = 3,4,5), using commercial zirconia, TZ-3YB-E, and a concentrate of mixed rare earth oxides. The powder samples were thermally treated at 600 ° C (2h) to remove unwanted carbonates formed in the synthesis process, and then subjected to milling using attrition mill and finally compacted by uniaxial pressing and sintered at 1500 ° C (2h). The densities were analyzed by the Archimedes method, obtaining results higher than 96% of theoretical. Using XRD and Rietveld refinements, the phases present in the samples were known qualitatively and quantitatively, observing a mixture of the cubic and tetragonal phases. An improvement in the conductivity in the samples co-doped with complex impedance spectroscopy was determined.

  3. Effect of Co3O4 doping and sintering temperature on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

    Science.gov (United States)

    Ghazali, Mohd Sabri Mohd; Abdullah, Wan Rafizah Wan; Zakaria, Azmi; Zulkifli, Muhamad Azman; Zaid, Mohd Hafiz Mohd; Rizwan, Zahid

    2017-09-01

    It is necessary to investigate the electronic states of ceramic based ZnO vasristor and effect of doped impurities at different concentration. Band gap (Eg) of the ceramic (99-x) mol% ZnO+0.5 mol% Bi2O3+0.5 mol% TiO2+ xCo3O4 where x = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples were prepared via solid-state route and sintered at the sintering temperature at 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of Co3O4, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.368 ± 0.002 and 2.352 ± 0.001 eV at 0.8 mol% Co3O4 for 45 and 90 min sintering time; respectively. XRD analysis indicates that two main phases existed at all concentrations which are ZnO and secondary phases, Bi12TiO20, Zn2Ti3O8, ZnCo2O4 and Co3Ti3O. Relative density decreases with the addition of Co3O4 compared to that of undoped at all doping level. When Co3O4 is added in the ceramics, relative density increases with the increase of doping level at both 45 and 90 min sintering time. The variation of sintering temperatures and XRD findings of steepness factor are correlated with the UV-Vis spectrophotometer results of based ZnO varistor doped with Co3O4 due to the growth of interface states.

  4. Fracture behavior of metal-ceramic fixed dental prostheses with frameworks from cast or a newly developed sintered cobalt-chromium alloy.

    Science.gov (United States)

    Krug, Klaus-Peter; Knauber, Andreas W; Nothdurft, Frank P

    2015-03-01

    The aim of this study was to investigate the fracture behavior of metal-ceramic bridges with frameworks from cobalt-chromium-molybdenum (CoCrMo), which are manufactured using conventional casting or a new computer-aided design/computer-aided manufacturing (CAD/CAM) milling and sintering technique. A total of 32 metal-ceramic fixed dental prostheses (FDPs), which are based on a nonprecious metal framework, was produced using a conventional casting process (n = 16) or a new CAD/CAM milling and sintering process (n = 16). Eight unveneered frameworks were manufactured using each of the techniques. After thermal and mechanical aging of half of the restorations, all samples were subjected to a static loading test in a universal testing machine, in which acoustic emission monitoring was performed. Three different critical forces were revealed: the fracture force (F max), the force at the first reduction in force (F decr1), and the force at the critical acoustic event (F acoust1). With the exception of the veneered restorations with cast or sintered metal frameworks without artificial aging, which presented a statistically significant but slightly different F max, no statistically significant differences between cast and CAD/CAM sintered and milled FDPs were detected. Thermal and mechanical loading did not significantly affect the resulting forces. Cast and CAD/CAM milled and sintered metal-ceramic bridges were determined to be comparable with respect to the fracture behavior. FDPs based on CAD/CAM milled and sintered frameworks may be an applicable and less technique-sensitive alternative to frameworks that are based on conventionally cast frameworks.

  5. Complexity of the relationships between the sintering-temperature-dependent grain size, airborne-particle abrasion, ageing and strength of 3Y-TZP ceramics.

    Science.gov (United States)

    Cotič, Jasna; Jevnikar, Peter; Kocjan, Andraž; Kosmač, Tomaž

    2016-04-01

    This study was designed to explore the complex relationships between the sintering-temperature-dependent grain size, airborne-particle abrasion, ageing and strength of 3Y-TZP ceramics. Biomedical grade 3Y-TZP powder was used to fabricate 180 discs. Half of them were sintered at 1400°C for 2h and half at 1500°C for 2h. A total of 18 groups of 10 were formed and subjected to the fully crossed experimental protocol of airborne-particle abrasion with Al2O3 at 2.5bar (no abrasion, 50μm, 110μm) and accelerated ageing at 134°C (no ageing, 12h, 48h). The relative amount of monoclinic phase was determined with XRD. The biaxial flexural strength was measured and statistically analyzed using the three-way ANOVA followed by predetermined contrasts and Tukey's HSD test (α=0.05). The low-temperature-sintered, fine-grained ceramic exhibited an excellent ageing resistance, while the high-temperature-sintered, coarse-grained ceramic experienced a higher surface strengthening and a substantially improved ageing resistance with respect to the airborne-particle abrasion. The overall performance of this material was superior. Our results show that the sintering temperature has a minor effect on the flexural strength, but it plays a crucial role in the surface strengthening and the ageing behaviour of 3Y-TZP dental ceramics. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. Translucence in dental prosthesis based on zirconia ceramics: effect of the sintering parameters; Translucidez em proteses dentarias a base de zirconia estabilizada com itria: efeito dos parametros de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Santos, C., E-mail: claudinei@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Costa, L.; Habibe, R.H.; Souza, J.V.C.; Habibe, C.H. [Centro Universitario de Volta Redonda (MeMAT/UNIFOA), RJ (Brazil). Pro-Reitoria de Pesquisa e Extensao; Silva, O.M.M. [Centro Tecnico Aeroespacial (CTA/IAE/AMR), Sao Jose dos Campos, SP (Brazil)

    2011-07-01

    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)

  7. Indirect selective laser sintering of an apatite-mullite glass-ceramic for potential use in bone replacement applications.

    Science.gov (United States)

    Goodridge, R D; Dalgarno, K W; Wood, D J

    2006-01-01

    The feasibility of using indirect selective laser sintering (SLS) to produce parts from glass-ceramic materials for bone replacement applications has been investigated. A castable glass based on the system SiO2 x Al2O3 x P2O5 x CaO x CaF2 that crystallizes to a glass-ceramic with apatite and mullite phases was produced, blended with an acrylic binder, and processed by SLS. Green parts with good structural integrity were produced using a wide range of processing conditions, allowing both monolayer and multilayer components to be constructed. Following SLS the parts were post-processed to remove the binder and to crystallize fully the material, evolving the apatite and mullite phases. The parts were heated to 1200 degrees C using a number of different time-temperature profiles, following which the processed material was analysed by differential thermal analysis, X-ray diffraction, and scanning electron microscopy, and tested for flexural strength. An increase in strength was achieved by infiltrating the brown parts with a resorbable phosphate glass, although this altered the crystal phases present in the material.

  8. 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.

  9. Reliability and failure modes of implant-supported zirconium-oxide fixed dental prostheses related to veneering techniques

    Science.gov (United States)

    Baldassarri, Marta; Zhang, Yu; Thompson, Van P.; Rekow, Elizabeth D.; Stappert, Christian F. J.

    2011-01-01

    Summary Objectives To compare fatigue failure modes and reliability of hand-veneered and over-pressed implant-supported three-unit zirconium-oxide fixed-dental-prostheses(FDPs). Methods Sixty-four custom-made zirconium-oxide abutments (n=32/group) and thirty-two zirconium-oxide FDP-frameworks were CAD/CAM manufactured. Frameworks were veneered with hand-built up or over-pressed porcelain (n=16/group). Step-stress-accelerated-life-testing (SSALT) was performed in water applying a distributed contact load at the buccal cusp-pontic-area. Post failure examinations were carried out using optical (polarized-reflected-light) and scanning electron microscopy (SEM) to visualize crack propagation and failure modes. Reliability was compared using cumulative-damage step-stress analysis (Alta-7-Pro, Reliasoft). Results Crack propagation was observed in the veneering porcelain during fatigue. The majority of zirconium-oxide FDPs demonstrated porcelain chipping as the dominant failure mode. Nevertheless, fracture of the zirconium-oxide frameworks was also observed. Over-pressed FDPs failed earlier at a mean failure load of 696 ± 149 N relative to hand-veneered at 882 ± 61 N (profile I). Weibull-stress-number of cycles-unreliability-curves were generated. The reliability (2-sided at 90% confidence bounds) for a 400N load at 100K cycles indicated values of 0.84 (0.98-0.24) for the hand-veneered FDPs and 0.50 (0.82-0.09) for their over-pressed counterparts. Conclusions Both zirconium-oxide FDP systems were resistant under accelerated-life-time-testing. Over-pressed specimens were more susceptible to fatigue loading with earlier veneer chipping. PMID:21557985

  10. Hydration characteristics of zirconium oxide replaced Portland cement for use as a root-end filling material.

    Science.gov (United States)

    Camilleri, J; Cutajar, A; Mallia, B

    2011-08-01

    Zirconium oxide can be added to dental materials rendering them sufficiently radiopaque. It can thus be used to replace the bismuth oxide in mineral trioxide aggregate (MTA). Replacement of Portland cement with 30% zirconium oxide mixed at a water/cement ratio of 0.3 resulted in a material with adequate physical properties. This study aimed at investigating the microstructure, pH and leaching in physiological solution of Portland cement replaced zirconium oxide at either water-powder or water-cement ratios of 0.3 for use as a root-end filling material. The hydration characteristics of the materials which exhibited optimal behavior were evaluated. Portland cement replaced by zirconium oxide in varying amounts ranging from 0 to 50% in increments of 10 was prepared and divided into two sets. One set was prepared at a constant water/cement ratio while the other set at a constant water/powder ratio of 0.3. Portland cement and MTA were used as controls. The materials were analyzed under the scanning electron microscope (SEM) and the hydration products were determined. X-ray energy dispersive analysis (EDX) was used to analyze the elemental composition of the hydration products. The pH and the amount of leachate in Hank's balanced salt solution (HBSS) were evaluated. A material that had optimal properties that satisfied set criteria and could replace MTA was selected. The microstructure of the prototype material and Portland cement used as a control was assessed after 30 days using SEM and atomic ratio diagrams of Al/Ca versus Si/Ca and S/Ca versus Al/Ca were plotted. The hydration products of Portland cement replaced with 30% zirconium oxide mixed at water/cement ratio of 0.3 were calcium silicate hydrate, calcium hydroxide and minimal amounts of ettringite and monosulphate. The calcium hydroxide leached in HBSS solution resulted in an increase in the pH value. The zirconium oxide acted as inert filler and exhibited no reaction with the hydration by-products of Portland

  11. Development of optical ceramic materials for infrared applications by optimizing sintering conditions

    Science.gov (United States)

    Isogai, Masafumi; Sano, Masahiko

    2017-05-01

    The authors developed production process of polycrystalline Zinc Sulfide (ZnS) materials which have been widely applied to windows and domes for infrared sensor systems. Commercially available ZnS powders of ca. 5 um particle sizes were used as a starting material and Spark Plasma Sintering method (SPS) was applied to the powders for firing process. It was found that the densification of the sintered materials was inhibited by outgassing from ZnS powders during the sintering process (ca. 400 Celsius). Thermal desorption spectroscopy analyses revealed the components of outgassing, such as hydrogen sulfide, sulfur oxide and organic molecules. Based on these analyses, the optimum conditions on heating rate and starting temperature of uniaxial pressurization were investigated to remove the outgassing. The polycrystalline ZnS materials fired under the optimized SPS conditions have such characteristics as better transmittance than 65 % and good uniformity in both 3 - 5 um and 8 - 12 um wavelength regions. These results show the importance of removing outgassing from starting materials.

  12. Removal of methylene blue and rhodamine B from water by zirconium oxide/graphene

    Directory of Open Access Journals (Sweden)

    Sumita Rani

    2016-04-01

    Full Text Available Methylene blue (MB and rhodamine B dyes (RB were degraded from water using zirconium oxide (ZrO2 and zirconium oxide/graphene composites (ZrO2/GR as photocatalyst. The photocatalytic efficiency was calculated from absorption spectra obtained using UV–visible spectroscopy. It has been observed that photodegradation time as well as photocatalytic efficiency increase with the concentration of catalyst up to a certain limit after which effect was reversed. The degradation was studied as a function of pH also. It was found that photocatalytic efficiency was more in alkaline medium than acidic medium. Degradation of RB takes place at higher value of pH as compared to MB. The degradation time for MB was 1 h using ZrO2 which get reduced to 32 min using ZrO2/GR composite and for RB it reduced to 40 min (using ZrO2/GR from 80 min (ZrO2.

  13. Synthesis and characterization of mesoporous and nano-crystalline phosphate zirconium oxides

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Enriquez, J.M., E-mail: jmanuelher@hotmail.co [Instituto Tecnologico de Cd. Madero, Division de Estudios de Posgrado e Investigacion, Juventino Rosas y Jesus Urueta S/N, Col. Los Mangos, 89440 Cd. Madero, Tam. (Mexico); Cortez Lajas, L.A.; Garcia Alamilla, R.; Castillo Mares, A.; Sandoval Robles, G. [Instituto Tecnologico de Cd. Madero, Division de Estudios de Posgrado e Investigacion, Juventino Rosas y Jesus Urueta S/N, Col. Los Mangos, 89440 Cd. Madero, Tam. (Mexico); Garcia Serrano, L.A. [Instituto Politecnico Nacional, Escuela Superior de Ingenieria Textil, Av. Instituto Politecnico Nacional s/n, Edificio 8, Col. Linda Vista, Delegacion Gustavo A. Madero, 07738 Mexico, D.F. (Mexico)

    2009-08-26

    In this work the preparation and characterization of the materials such as zirconia (ZrO{sub 2}) and zirconia promoted with phosphate ion (ZrO{sub 2}-PO{sub 4}{sup 3-}) is presented. Pure zirconium hydroxide [Zr(OH){sub 4}] was synthesized by the sol-gel method using precursors such as zirconium n-butoxide and 1-butanol maintaining a pH 8 during the synthesis. Zr(OH){sub 4} was impregnated with 15 wt.% of the acid agent. Both were calcined in a dynamic air atmosphere for 3 h at 400, 500 and 600 deg. C. The supports were characterized by thermal analysis, X-ray diffraction, nitrogen physisorption as well as infrared spectroscopy. The results showed a positive effect on the physicochemical properties of the catalytic supports after Zr(OH){sub 4} impregnation with the dopping agent (H{sub 3}PO{sub 4}). Phosphate zirconium oxides remained thermically stable after calcination. It was observed that the dopping agent remained firmly attached to the zirconium oxide surface, inhibiting the particle growth and delaying the syntherization of the material and the apparition of the monoclinic phase, obtaining mesoporous and nano-crystalline materials (crystallite size 1.0-6.5 nm) with high surface areas (210-329 m{sup 2}/g) and tetragonal structure defined for the calcination temperature of 600 deg. C.

  14. Low-Temperature Sintering and Microwave Dielectric Properties of Zn2SiO4 Ceramic Added with Crystalline Zinc Borate

    Science.gov (United States)

    Chaware, Varsha; Deshmukh, Ravindra; Sarode, Chetan; Gokhale, Suresh; Phatak, Girish

    2015-07-01

    The physical and dielectric properties of composites of known microwave materials, Zn2SiO4 and Zn3B2O6, prepared by solid-state reaction, were investigated with the purpose of developing a low-loss dielectric material for low-temperature co-fired ceramic applications. An off-stoichiometric phase of Zn2SiO4 with extra SiO2 was used to avoid the occurrence of unreacted ZnO. During sintering, zinc borate was found to partially react with residual SiO2 to form Zn2SiO4. The residual zinc borate was converted to a boron-rich glassy phase which helped to reduce the sintering temperature of the composite. Good relative sintering density (>90%) at temperatures below the melting temperature of zinc borate is indicative of a sintering mechanism of diffusion-based mass transfer. Composites containing 15 wt.% zinc borate, 2.5 wt.% lithium carbonate and 20 wt.% zinc borate in zinc silicate had dielectric constants of 6.8 and 6.1, quality factors (Q×f) of 48,800 and 94,300 GHz when sintered at 900°C and 950°C, respectively. These quality factor results are close to the best values reported for zinc silicate at these sintering temperatures.

  15. On the Densification Behavior of (0.2, 0.5, and 1 Wt Pct) CNT-YSZ Ceramic Composites Processed via Spark Plasma Sintering

    Science.gov (United States)

    Karanam, Abhinav; Bichler, Lukas; Fong, Randy

    2015-08-01

    Yttria-Stabilized Zirconia (YSZ) is a promising thermal insulating ceramic for high temperature applications due to its stability and chemical inertness. As was demonstrated with other technical ceramics ( e.g., Alumina), addition of Single-Wall Carbon Nanotubes (CNTs) to a ceramic matrix may significantly enhance its mechanical properties. In this work, 8 mol pct YSZ with 0.2, 0.5, and 1 wt pct CNT composites were fabricated via the spark plasma sintering process. The densification, Vicker's microhardness, specific gravity, and microstructure evolution of the composites were investigated. The results suggest that the addition of CNTs to YSZ hindered densification and grain growth during SPS processing leading to inhomogeneous grain size distribution. However, the CNTs had a profound impact on the hardness of the composite ceramics, with an increase from 697 HV (YSZ) to 1195 HV (1 wt pctCNT-YSZ).

  16. Sintered gahnite–cordierite glass-ceramic based on raw materials ...

    Indian Academy of Sciences (India)

    Abstract. Glass-ceramic based on Zn-containing cordierite was prepared from kaolin, silica'sand and commer- cial ZnO. The addition of AlF3, MgF2 and CaF2 was performed as nucleation catalysts. Dark brown glasses were obtained from the glass batches. The transformation and crystallization temperatures were in the ...

  17. Ceramic scaffolds produced by computer-assisted 3D printing and sintering: characterization and biocompatibility investigations.

    NARCIS (Netherlands)

    Warnke, P.H.; Seitz, H.; Warnke, F.; Becker, S.T.; Sivananthan, S.; Sherry, E.; Liu, Q.; Wiltfang, J.; Douglas, T.E.L.

    2010-01-01

    Hydroxyapatite (HAP) and tricalcium phosphate (TCP) are two very common ceramic materials for bone replacement. However, in general HAP and TCP scaffolds are not tailored to the exact dimensions of the defect site and are mainly used as granules or beads. Some scaffolds are available as ordinary

  18. Improvement of strength of carbon nanotube-dispersed Si3N4 ceramics by bead milling and adding lower-temperature sintering aids

    Directory of Open Access Journals (Sweden)

    Mitsuaki Matsuoka

    2014-09-01

    Full Text Available Studies on the dispersion of carbon nanotubes (CNTs in silicon nitride (Si3N4 ceramics to provide the latter with electrical conductivity have been carried out in recent years. The density and the strength of Si3N4 ceramics were degraded, however, because the CNTs prevented Si3N4 from densifying. The CNTs disappeared after firing at high temperatures owing to the reaction between CNTs and Si3N4 or SiO2, or both Si3N4 and SiO2. In order to improve the density and suppress the reaction, sintering aids for lower-temperature densification of Si3N4 are needed. In this study, we added HfO2 as a sintering aid to a Si3N4–Y2O3–Al2O3–AlN–TiO2 system to fabricate CNT-dispersed Si3N4 ceramics at lower temperatures. Furthermore, bead milling was applied to disperse the CNTs homogeneously. Agglomerates of CNTs were pulverized by bead milling without obvious changes in morphology to eliminate larger fracture origins in CNT-dispersed ceramics. As a result of both the addition of HfO2 and bead milling, we successfully fabricated dense CNT-dispersed Si3N4 ceramics with high strength and electrical conductivity.

  19. 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)

  20. Anomalous behavior of linear resistivity arising in intergrain ordering process of weak-sintered ceramic system YBa 2Cu 4O 8

    Science.gov (United States)

    Hagiwara, M.; Fujii, A.; Hayashi, T.; Shima, T.; Deguchi, H.

    2011-11-01

    Faint electric resistivity behavior is searched experimentally near and below intergrain ordering temperature of weakly sintered ceramic YBa2Cu4O8 (Y124). For this purpose, a new method to detect linear and nonlinear resistivity sensitively by combination of pulse delta method and numerical Fourier-transformation has been designed. Making use of the experimental system for several weak sintered Y124 samples, it is revealed that linear resistivity just above the intergrain ordering point first drops toward zero steeply with decreasing temperature, and then turns abruptly upward to forms faint maximum at lower temperature. Such a novel behavior of 'revival of resistivity' is confirmed to be reproducible, and considered to be an essential frustration effect for d-wave type grain system with irregular or inhomogeneous ceramic structure.

  1. [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 (Pveneers.

  2. 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.

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

    Science.gov (United States)

    Almasri, Karima Amer; Sidek, Hj. Ab Aziz; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd

    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.

  4. 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.

  5. Anomalous behavior of linear resistivity in the vanishing process along the intergrain ordering of weak-sintered ceramic superconductor YBa2Cu4O8

    Science.gov (United States)

    Hagiwara, M.; Fujii, A.; Shima, T.; Deguchi, H.; Shoho, T.; Koyama, K.

    2011-09-01

    Intergrain ordering nature of weak-sintered ceramic of YBa2Cu4O8 (Y124) is studied experimentally by ultra precise electric resistivity observation together with magnetic measurements for linear and nonlinear susceptibilities. For this purpose, a new method to detect pure linear resistivity down to the order of 1 nΩm has been developed with the help of combination technique of pulse delta method and FFT treatment. Making use of this experimental system for several weak-sintered Y124 samples, it has been revealed that linear resistivity first drops toward zero steeply with decreasing temperature, and then turns abruptly upward to forms faint maximum at lower temperature. Such peaking of electric resistivity has been found to occur below the intergrain ordering temperature that was estimated by the magnetic behavior. This newfound phenomenon, to say 'revival of resistivity', is being regarded as general nature for the weak-sintered ceramics, and considered to be an intrinsic frustration effect for actual d-wave type ceramics of irregular network structure.

  6. Oxidation Characterization of Hafnium-Based Ceramics Fabricated by Hot Pressing and Electric Field-Assisted Sintering

    Science.gov (United States)

    Gasch, Matt; Johnson, Sylvia; Marschall, Jochen

    2010-01-01

    Ceramic borides, such as hafnium diboride (HfB2) and zirconium diboride (ZrB2), are members of a family of materials with extremely high melting temperatures referred to as Ultra High Temperature Ceramics (UHTCs). UHTCs constitute a class of promising materials for use in high temperature applications, such as sharp leading edges on future-generation hypersonic flight vehicles, because of their high melting points. The controlled development of microstructure has become important to the processing of UHTCs, with the prospect of improving their mechanical and thermal properties. The improved oxidation resistance of HfB2 has also become important if this material is to be successfully used at temperatures above 2000 C. Furthermore, the use of UHTCs on the leading edges of vehicles traveling at hypersonic speeds will mean exposure to a mixed oxidation environment comprised of both molecular and atomic oxygen. The current study has investigated the high-temperature oxidation behavior of HfB2-based materials in a pure O2 environment, as well as in environments containing different levels of dissociated oxygen (O/O2). Materials were processed by two techniques: conventional hot pressing (HP) and electric field-assisted sintering (FAS). Their oxidation behavior was evaluated in both a tube furnace at 1250 C for 3 hours and in a simulated re-entry environment in the Advanced Heating Facility (AHF) arcjet at NASA Ames Research Center, during a 10-minute exposure to a cold wall heat flux of 250W/sq cm and stagnation pressure of 0.1-0.2 atm. The microstructure of the different materials was characterized before and after oxidation using scanning electron microscopy (SEM).

  7. Functional properties of Sm{sub 2}NiMnO{sub 6} multiferroic ceramics prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gheorghiu, Felicia, E-mail: felicia.gheorghiu@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); RAMTECH Centre, Interdisciplinary Research Department-Field Science, “Al. I. Cuza” Univ., Blvd. Carol I, Nr. 11, 700506 Iasi (Romania); Curecheriu, Lavinia [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Lisiecki, Isabelle [CNRS, Univ Paris 06, UMR 7070, LM2N, bât. F, B.P. 52, 4 place Jussieu, Paris F-75231, Cedex 05 (France); Beaunier, Patricia [UPMC, Univ Paris 06, UMR 7197, LRS, Le Raphaël, 3 rue Galilée, 94200 Ivry (France); Feraru, Simona; Palamaru, Mircea N. [Faculty of Chemistry, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Musteata, Valentina [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41A, 700487 Iasi (Romania); Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 700050 Iasi (Romania); Mitoseriu, Liliana, E-mail: lmtsr@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania)

    2015-11-15

    In the present work, it was reported for the first time the new synthesis of Sm{sub 2}NiMnO{sub 6} double perovskite oxides by sol–gel auto-combustion method. The Rietveld analysis of the X-ray ceramics diffraction pattern recorded at room temperature for Sm{sub 2}NiMnO{sub 6} ceramics sintered at 1000 °C/5 min from powders obtained at 700 °C/7 h confirm the formation of the double perovskite with a monoclinic structure and the space group P2{sub 1}/n. The HRTEM analysis shows clear lattice fringes that confirm a high crystallinity level of the material corresponding to the monoclinic structure. The non-linear dielectric character was checked for the first time in Sm{sub 2}NiMnO{sub 6} double perovskite and the results reveals a strong nonlinearity and a small hysteretic behaviour. The present structural, magnetic and dielectric data make the Sm{sub 2}NiMnO{sub 6} system due to its multiferroic character a promising candidate to different modern electronic devices applications. - Highlights: • The Sm{sub 2}NiMnO{sub 6} double perovskite were prepared by sol–gel auto-combustion method. • The Rietveld and HRTEM analysis confirm a double perovskite monoclinic structure. • The non-linear character reveals a strong nonlinearity. • The magnetic transitions indicate a change in the spin ordering. • The Sm{sub 2}NiMnO{sub 6} system is a promising multiferroic candidate to modern applications.

  8. A discrete nonlinear mass transfer equation with applications in solid-state sintering of ceramic materials

    Science.gov (United States)

    Hristopulos, D. T.; Leonidakis, L.; Tsetsekou, A.

    2006-03-01

    The evolution of grain structures in materials is a complex and multiscale process that determines the material's final properties [1]. Understanding the dynamics of grain growth is a key factor for controlling this process. We propose a phenomenological approach, based on a nonlinear, discrete mass transfer equation for the evolution of an arbitrary initial grain size distribution. Transition rates for mass transfer across grains are assumed to follow the Arrhenius law, but the activation energy depends on the degree of amorphization of each grain. We argue that the magnitude of the activation energy controls the final (sintered) grain size distribution, and we verify this prediction by numerical simulation of mass transfer in a one-dimensional grain aggregate.

  9. 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)

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

    Science.gov (United States)

    2016-09-01

    While typical US body armor tends to use higher-performance ceramics (such as boron carbide), this program examined 8-mm-thick alumina as the initial...cost- effective material for evaluation of the depth of penetration (DOP). Additionally, 6- and 8-mm-thick alumina were used to develop a deeper...baseline curve (Fig. 12). A linear regression of the reference data yielded the following equation: DOP = 0.1959 × Vx-ray – 84.406. (1) The square of the

  11. Pyroelectric response in crystalline hafnium zirconium oxide (Hf1-xZrxO2) thin films

    Science.gov (United States)

    Smith, S. W.; Kitahara, A. R.; Rodriguez, M. A.; Henry, M. D.; Brumbach, M. T.; Ihlefeld, J. F.

    2017-02-01

    Pyroelectric coefficients were measured for 20 nm thick crystalline hafnium zirconium oxide (Hf1-xZrxO2) thin films across a composition range of 0 ≤ x ≤ 1. Pyroelectric currents were collected near room temperature under zero applied bias and a sinusoidal oscillating temperature profile to separate the influence of non-pyroelectric currents. The pyroelectric coefficient was observed to correlate with zirconium content, increased orthorhombic/tetragonal phase content, and maximum polarization response. The largest measured absolute value was 48 μCm-2 K-1 for a composition with x = 0.64, while no pyroelectric response was measured for compositions which displayed no remanent polarization (x = 0, 0.91, and 1).

  12. Chemical solution deposited lanthanum zirconium oxide thin films: Synthesis and chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H.S., E-mail: sean.chen@cantab.net [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Kumar, R.V.; Glowacki, B.A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2010-07-01

    Pyrochlore lanthanum zirconium oxide (LZO) thin films textured along <4 0 0> are synthesized using lanthanum acetate hydrate, zirconium propoxide, propionic acid, acetic acid glacial, and methanol as precursors. The materials growth and chemistry are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA). The formation of inkjet printed LZO films on Ni-5%W tape is found to be based on the decomposition of the LZO precursor solution. In the annealing process, Zr metal-oxides bonds are first eliminated between 150 and 250 deg. C, while carboxylates from precursors remain in LZO after the annealing carried out at 900 {sup o}C for an hour. Annealed LZO films have dense and smooth structure that are composed of nanoparticles sizing 10-15 nm and some pinholes sizing 25-35 nm accounted for less than 0.1% of the area are observed.

  13. 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.

  14. 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)

  15. 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)

  16. Development of a dielectric ceramic based on diatomite-titania. Part one: powder preparation and sintering study

    Directory of Open Access Journals (Sweden)

    Tavares Elcio Correia de Souza

    1997-01-01

    Full Text Available This work presents powder preparation and sintering experiments of a mixture diatomite-titania. X-ray diffraction, DTA, TGA as well as chemical and microstructural analyses were made. The sintering process was investigated as a function of sintering temperature and time, mass variation, linear shrinkage and activation energy. The results show that sintering of diatomite-titania could be described by a viscous flow mechanism.

  17. Sinterização de cerâmicas em microondas. Parte III: Sinterização de zircônia, mulita e alumina Microwave sintering of ceramics. Part III: Sintering of zirconia, mullite and alumina

    Directory of Open Access Journals (Sweden)

    R. R. Menezes

    2007-09-01

    Full Text Available O aquecimento utilizando microondas possui muitas vantagens com relação aos métodos convencionais de aquecimento, como redução no tempo de processamento, economia de energia e melhora na uniformidade microestrutural dos corpos cerâmicos. Assim esse trabalho tem por objetivo a utilização da sinterização híbrida com microondas na queima rápida de materiais cerâmicos. Foram utilizados materiais que requerem altas temperaturas para densificação. Foram sinterizados materiais que apresentam bruscas e acentuadas mudanças nas suas propriedades dielétricas com a elevação da temperatura, zircônia, e materiais com baixas perdas dielétricas na temperatura ambiente, que apresentam dificuldades de aquecimento com microondas em baixas temperaturas, alumina e mulita. Foi utilizando material susceptor como agente auxiliar de aquecimento. Com base nos resultados obtidos pode-se concluir que o sistema de sinterização híbrida desenvolvido pode ser utilizado com sucesso na sinterização rápida e uniforme dos materiais estudados, sendo possível a sinterização de zircônia em ciclos de 20 min, mulita em ciclos de 16 min e alumina em ciclos de 40 min.Thermal processing by microwaves offers several advantages over conventional heating methods, such as shorter processing times, energy savings and improved microstructural homogeneity of ceramic bodies. Thus, this work focused on the fast hybrid microwave sintering of ceramic materials that require high sintering temperatures for densification. The materials studied here were zirconia, which displays abrupt and severe increases in dielectric loss with rising temperature, and alumina and mullite, which show low dielectric losses at ambient temperature and are difficult to microwave at low temperatures. A susceptor was used as an auxiliary heating agent. The results indicate that the sintering system developed here can be used efficiently for the rapid, homogeneous sintering of all the ceramics

  18. 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.

  19. 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

  20. Influence of feldspar containing lithium in the sintering of triaxial ceramics; Sinterizacao de uma massa ceramica triaxial com feldspato contendo litio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Camila Felippe de; Strecker, Kurt, E-mail: camilaufsj@yahoo.com.br [Universidade Federal de Sao Joao del-Rei (UFSJ), MG (Brazil)

    2011-07-01

    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{sup 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{sup 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)(.

  1. Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-dimensional replica techniques.

    Science.gov (United States)

    Kim, Ki-Baek; Kim, Jae-Hong; Kim, Woong-Chul; Kim, Hae-Young; Kim, Ji-Hwan

    2013-05-01

    One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (α=.05). In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

  2. 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)

  3. The Novel Design of Zirconium Oxide-Based Screw-Retained Restorations, Maximizing Exposure of Zirconia to Soft Peri-implant Tissues: Clinical Report After 3 Years of Follow-up.

    Science.gov (United States)

    Linkevicius, Tomas

    Current use of zirconium oxide (ZrO₂)-based screw-retained restorations does not guarantee maximum contact of soft peri-implant tissues with ZrO₂, because veneering porcelain usually covers the major subgingival part of the restoration. Ceramics preclude direct interaction between zirconia and soft tissue cells, thus reducing biocompatibility and benefit to the patient. The four case reports discussed in this article describe the new design modality of the ZrO₂ screw-retained restorations, in which zirconia is exposed to the tissues and no veneering porcelain is located below the gingival margin. The article also shows the impact of this treatment on soft peri-implant tissues after 3 years of follow-up. Soft tissue recession, vestibular contour, bleeding on probing, and probing depth were evaluated.

  4. 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.

  5. Two-photon polymerization of 3-D zirconium oxide hybrid scaffolds for long-term stem cell growth.

    Science.gov (United States)

    Skoog, Shelby A; Nguyen, Alexander K; Kumar, Girish; Zheng, Jiwen; Goering, Peter L; Koroleva, Anastasia; Chichkov, Boris N; Narayan, Roger J

    2014-06-01

    Two-photon polymerization is a technique that involves simultaneous absorption of two photons from a femtosecond laser for selective polymerization of a photosensitive material. In this study, two-photon polymerization was used for layer-by-layer fabrication of 3-D scaffolds composed of an inorganic-organic zirconium oxide hybrid material. Four types of scaffold microarchitectures were created, which exhibit layers of parallel line features at various orientations as well as pores between the line features. Long-term cell culture studies involving human bone marrow stromal cells were conducted using these 3-D scaffolds. Cellular adhesion and proliferation were demonstrated on all of the scaffold types; tissuelike structure was shown to span the pores. This study indicates that two-photon polymerization may be used to create microstructured scaffolds out of an inorganic-organic zirconium oxide hybrid material for use in 3-D tissue culture systems.

  6. Mullite (3Al2O3·2SiO2 ceramics obtained by reaction sintering of rice husk ash and alumina, phase evolution, sintering and microstructure

    Directory of Open Access Journals (Sweden)

    M.F. Serra

    2016-03-01

    Partial densification was achieved (30% and highly converted materials were obtained. The developed microstructure consisted in a dense ceramic matrix with homogenous interconnected porosity, with a narrow pore size distribution below 20 μm. The developed material gives enough information for designing mullite ceramics materials with either porous or dense microstructures with structural, insulating or filtering applications employing RHA as silica source and calcined alumina as the only other raw material.

  7. Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds

    Directory of Open Access Journals (Sweden)

    Nor Monica Ahmad

    2016-06-01

    Full Text Available A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB, polyethylene glycol (PEG, and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE. Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM, Electrochemical Impedance Spectroscopy (EIS, and Cyclic voltamogram (CV. The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075–10 µM and 10–55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.

  8. Low-Temperature Sintering Behavior and Dielectric Properties of Li2O-Nb2O5-TiO2 Ceramics with Li-B-Si-O Glass

    Science.gov (United States)

    Li, Enzhu; Zhang, Peng; Mi, Yuean; Wang, Jing; Yuan, Ying; Zhou, Xiaohua

    2015-11-01

    This paper reports an investigation of the low-temperature sintering behaviors, microstructures, and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 (LNT) ceramics fired with addition of different amounts of Li2O-B2O3-SiO2 (LBS) glass. The results suggest that addition of LBS glass can effectively reduce the sintering temperature of LNT ceramic from 1100°C to 900°C without detriment of its microwave dielectric properties. However, addition of excess LBS glass leads to rapid grain growth and therefore decreases the density and microwave dielectric properties of the LNT ceramic. Optimized specimens with 1.0 wt.% LBS glass sintered at 900°C possessed excellent microwave dielectric properties of ɛ r ≈ 66.17, Q × f ≈ 5170 GHz ( f = 4.32 GHz), and τ f ≈ 19.2 ppm/°C.

  9. Electrical and dielectric properties of ZnO and CeO{sub 2} doped ZrTi{sub 2}O{sub 6} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    George, Aneesh; Thomas, Jijimon K.; John, Annamma [Department of Physics, Mar Ivanios College, Thiruvananthapuram 695015 (India); Solomon, Sam, E-mail: samdmrl@yahoo.com [Department of Physics, Mar Ivanios College, Thiruvananthapuram 695015, India and Department of Physics, St. John' s College, Anchal, Kollam 691306 (India)

    2014-01-28

    Zirconium oxide (ZrO{sub 2}) and titanium dioxide (TiO{sub 2}) are the important catalyst supports, since it has acidic and basic properties. The intermediate phase zirconium titanate ZrTi{sub 2}O{sub 6}, which is a solid solution with Zr:Ti ratio 1:2 has outstanding dielectric properties. The effects of doping of ZnO and CeO{sub 2} on the dielectric and electrical properties of ZrTi{sub 2}O{sub 6} ceramic are investigated. On adding 0.5 wt% ZnO, the dielectric constant is increased but, on adding CeO{sub 2}, the dielectric constant is decreased. The bulk density of pure sample sintered at 1530 °C is 91% of theoretical density while that of the doped samples sintered at 1450 °C is more than 94% of theoretical density. Scanning electron micrographs reveal that the samples are well sintered with minimum porosity. The semicircle behavior in the Cole-Cole plots at room temperature reveals that the samples are good ionic conductor. The induced impedance is reduced for doped samples and this can be used as a material for electrolyte in Solid Oxide Fuel Cell.

  10. Mechanical and Thermal Properties of Epoxy Composites Containing Zirconium Oxide Impregnated Halloysite Nanotubes

    Directory of Open Access Journals (Sweden)

    Moon il Kim

    2017-12-01

    Full Text Available Liquid epoxy resins have received much attention from both academia and the chemical industry as eco-friendly volatile organic compound (VOC-free alternatives for applications in coatings and adhesives, especially in those used in households. Epoxy resins show high chemical resistance and high creep resistance. However, due to their brittleness and lack of thermal stability, additional fillers are needed for improving the mechanical and thermal properties. Halloysite nanotubes (HNTs are naturally abundant, inexpensive, and eco-friendly clay minerals that are known to improve the mechanical and thermal properties of epoxy composites after suitable surface modification. Zirconium is well known for its high resistance to heat and wear. In this work, zirconium oxide-impregnated HNTs (Zr/HNTs were added to epoxy resins to obtain epoxy composites with improved mechanical and thermal properties. Zr/HNTs were characterized by field-emission transmission electron microscopy, transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Changes in the thermal properties of the epoxy composites were characterized by thermo mechanical analysis and differential scanning calorimetry. Furthermore, flexural properties of the composites were analyzed using a universal testing machine.

  11. High-κ Lanthanum Zirconium Oxide Thin Film Dielectrics from Aqueous Solution Precursors.

    Science.gov (United States)

    Woods, Keenan N; Chiang, Tsung-Han; Plassmeyer, Paul N; Kast, Matthew G; Lygo, Alexander C; Grealish, Aidan K; Boettcher, Shannon W; Page, Catherine J

    2017-03-29

    Metal oxide thin films are critical components in modern electronic applications. In particular, high-κ dielectrics are of interest for reducing power consumption in metal-insulator-semiconductor (MIS) field-effect transistors. Although thin-film materials are typically produced via vacuum-based methods, solution deposition offers a scalable and cost-efficient alternative. We report an all-inorganic aqueous solution route to amorphous lanthanum zirconium oxide (La 2 Zr 2 O 7 , LZO) dielectric thin films. LZO films were spin-cast from aqueous solutions of metal nitrates and annealed at temperatures between 300 and 600 °C to produce dense, defect-free, and smooth films with subnanometer roughness. Dielectric constants of 12.2-16.4 and loss tangents MIS devices utilizing LZO as the dielectric layer (1 kHz). Leakage currents <10 -7 A cm -2 at 4 MV cm -1 were measured for samples annealed at 600 °C. The excellent surface morphology, high dielectric constants, and low leakage current densities makes these LZO dielectrics promising candidates for thin-film transistor devices.

  12. Thermoluminescence of zirconium oxide nanostructured to mammography X-ray beams

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, L.L. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, 11500 Mexico D.F. (Mexico); Rivera, T., E-mail: trivera@ipn.mx [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, 11500 Mexico D.F. (Mexico); Roman, J. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, 11500 Mexico D.F. (Mexico); Azorin, J. [Universidad Autonoma Metropolitana-Iztapalapa. Av. San Rafael Atlixco 187, 09340 Mexico D.F. (Mexico); Gaona, E. [Universidad Autonoma Metropolitana-Xochimilco. Calz. Del Hueso 1100, 04960 Mexico D.F. (Mexico)

    2012-07-15

    In the present work thermoluminescent (TL) response of zirconium oxide (ZrO{sub 2}) nanostructured induced by mammography X-ray radiation was investigated. Measurements were made of the response per unit air kerma of ZrO{sub 2} with mammography equipment parameters (semiautomatic exposure control, 24 kVp and 108 mAs). The calibration curves were obtained by simultaneously irradiating ZrO{sub 2} samples and ion chamber. Samples of ZrO{sub 2} showed a linear response as a function of entrance skin air kerma. The observed results in TL properties suggest that ZrO{sub 2} nanostructured could be considered as an effective material for X-ray beams dosimetry if appropriate calibration procedures are performed. - Highlights: Black-Right-Pointing-Pointer X-ray low energy thermoluminescent of ZrO{sub 2} dosimeter is developed. Black-Right-Pointing-Pointer Air kerma measurements were made by thermoluminescent dosimeter ZrO{sub 2} using mammography equipment parameters. Black-Right-Pointing-Pointer Entrance surface skin doses were made using thermoluminescent dosimeter of ZrO{sub 2} to X-ray beam quality control.

  13. The influence of small stoichiometric deviations in the properties dielectric of barium titanate ceramics laser sintering; A influencia de pequenos desvios estequiometricos nas propriedades eletricas de ceramicas de titanato de bario sinterizadas a laser

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcelo Souza da; Silva, Ronaldo Santos da, E-mail: ssiilva990@hotmmail.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SP (Brazil). Departameneto de Fisica. Grupo de Materiais Ceramicos Avancados

    2012-07-01

    It has recently been investigated the influence of the laser sintering on the electrical properties of the ceramic bodies. This work is dedicated to studying how a small deviation stoichiometric barium and / or titanium may interfere with the dielectric properties of ceramics based on barium titanate (BaTiO3) when they are sintered by laser. Ceramics based on doped barium titanate lanthanum (Ba{sub 0,998}La{sub 0,002}Ti{sub 1-n}O{sub 3}) were produced and laser sintering. The crystalline phase was verified by X-ray diffraction, information on the microstructure of the sintered samples laser were obtained with the aid of the technique of electron microscopy (SEM) and, the impedance spectroscopy technique was used to characterize the dielectric material. The preliminary results obtained show ceramic bodies with a density of 93% and with good homogeneity of the microstructure. The high values of dielectric permittivity of the ceramics were observed for samples with a deviation where the stoichiometric ratio [Ba]/[Ti] <1. (author)

  14. Low temperature sintering and microwave dielectric properties of BaZn2Ti4O11 ceramics with Li2O-B2O3-SiO2 glass

    Science.gov (United States)

    Duan, S. X.; Li, E. Z.; Chen, Y. W.; Tang, B.; Yuan, Y.; Zhang, S. R.

    2017-02-01

    The effects of Li2O-B2O3-SiO2 glass (LBS) on the sintering behavior, phase evolution, microstructure and microwave dielectric properties of the BaZn2Ti4O11 ceramic were studied in detail. The results show that LBS significantly lowers the sintering temperature of the BaZn2Ti4O11 ceramic from 1200 °C to 850 °C. Small amount of LBS promotes the sintering process of the BaZn2Ti4O11 ceramic and obtains excellent microwave dielectric properties. However, excessive LBS addition leads to the change of phase and growth of abnormal grain, destroying the compact microstructure and deteriorating the microwave dielectric properties of the BaZn2Ti4O11 ceramic. BaZn2Ti4O11 ceramic with 4∼6 wt.% LBS can be well sintered at 850 °C and shows excellent microwave dielectric properties: ɛr = 22.95∼24.92, Q×f = 27181∼31301 GHz.

  15. Sinterização de cerâmicas em microondas. Parte I: aspectos fundamentais Microwave sintering of ceramics. Part I: fundamental aspects

    Directory of Open Access Journals (Sweden)

    R. R. Menezes

    2007-03-01

    Full Text Available O processamento de materiais baseado no aquecimento por meio de energia de microondas vem ganhado a cada dia mais destaque e importância em várias aplicações industriais, em virtude de uma série de vantagens em potenciais frente aos métodos convencionais de aquecimento. Na sinterização de materiais cerâmicos o uso de microondas permite redução no tempo de processamento, economia de energia e melhora na uniformidade microestrutural dos corpos cerâmicos. Como conseqüência das vantagens frente às técnicas de aquecimentos convencionais, a sinterização usando microondas vem sendo estudada por vários grupos de pesquisa em todo o mundo. Entretanto, os benefícios do uso das microondas só são obtidos quando a sinterização é realizada com o controle e entendimento científico de uma série de parâmetros e aspectos envolvidos no processo. Assim, esse trabalho tem por objetivo abordar aspectos científicos fundamentais do processo de sinterização de cerâmicas usando microondas, enfocando particularmente a interação matéria/microondas, aspectos peculiares do processo e a técnica de sinterização híbrida.Processing of materials based on heating by microwave energy has gained increasing importance in many industrial applications due to its potential advantages over conventional heating methods. In the sintering of ceramic materials, the use of microwave energy decreases the processing time, saves energy and improves the microstructural homogeneity of ceramic bodies. These advantages have motivated various research groups around the world to study microwave sintering. However, the benefits deriving from the use of microwaves depend on the control and scientific understanding of the parameters and aspects of the process. This paper offers a review of the fundamental scientific aspects of microwave sintering of ceramics, focusing on the interaction between materials and microwaves and highlighting particular points of the hybrid

  16. THE POLARIZING EFFECTS IN SINTERED KAOLIN

    African Journals Online (AJOL)

    compacted and sintered density of the ceramic have been studied, and a density — pressure relationship for before- and after-sintering conditions obtained. INTRODUCTION. Ceramics have been known to mankind for thousands of years, and have been used in construction materials. In many applications, ceramics have.

  17. The influence of co-sintering Bi2O3 on Yb0.2Ce0.8O2-δ ceramic SOFC

    Science.gov (United States)

    Budiana, B.; Suasmoro, S.

    2017-01-01

    Ceramic Yb-doped CeO2 were prepared through two ways. First, sintering of mixed 20 mol % Yb2O3 and 80 mol % CeO2 at 1350 °C for 20 h and second sintering of mixed 96 mol % calcined Yb-doped CeO2 with 4 mol % Bi2O3 as a co-sintering agent at 1100 °C for 8h. Phase identification revealed that for the first sample was a cubic phase (a=5,3939Å) while the second sample showed three phases, CeO2 (cubic a=5,4254Å), YbxCe1-xO2-δ (cubic a=5,3980Å) and Bi5Yb3O12 (cubic a=10,5343Å). Cole-cole plot of impedance revealed 3 semicircles as marked of grain, grain boundary and electrode responses for B1 while for B2 showed two semicircles as marked of grain, grain boundary+electrode responses. Plot of log (σt) versus 1/T for both samples possed 2 activation energy regime, for the Sample B1 at T>650 °C Ea grain =1,01±0,04 eV and T650 °C, Ea grain =0,99±0,03 eV and T<650 °C Ea grain=0,70±0,09 eV.

  18. Effects of B{sub 2}O{sub 3} addition on sintering behavior and microwave dielectric properties of ixiolite-structure ZnTiNb{sub 2}O{sub 8} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Haitao, E-mail: msse_wuht@ujn.edu.cn; Mei, Quanjing; Xing, Chunfang; Bi, Jinxin

    2016-09-15

    The effects of B{sub 2}O{sub 3} additives on the sintering behavior, microstructure and microwave dielectric properties of ixiolite-structure ZnTiNb{sub 2}O{sub 8} ceramics prepared by conventional solid-state route were investigated. The B{sub 2}O{sub 3} additives, acting as a sintering aid, can effectively decrease the sintering temperature of ZnTiNb{sub 2}O{sub 8} ceramics to 1050 °C, due to the formation of liquid phase. Little second phase from XRD results was observed throughout the entire experiments. The variations in the dielectric constant (ε{sub r}) and quality factor (Q·f) of the ixiolite-structure ZnTiNb{sub 2}O{sub 8} ceramics were studied systematically depending on the adopting of B{sub 2}O{sub 3} and the sintering temperatures. With the increase of the B{sub 2}O{sub 3} addition, ε{sub r} and Q·f decreased and the temperature coefficient of resonant frequency (τ{sub f}) slightly fluctuated around −20 ppm/°C. The optimal microwave dielectric properties with high ε{sub r} ∼35.04, Q·f ∼50,100 GHz, and a near-zero τ{sub f} ∼−20.21 ppm/°C were obtained at 1 wt%-B{sub 2}O{sub 3}-doped samples sintered at 1050 °C. The relatively low sintering temperature and high dielectric properties in microwave range would make ZnTiNb{sub 2}O{sub 8} ceramics promising for application in electronics. - Highlights: • B{sub 2}O{sub 3} was doped to reduce the sintering temperature of ZnTiNb{sub 2}O{sub 8} ceramics. • The τ{sub f} values of ZnTiNb{sub 2}O{sub 8} ceramics were in range of −10.21 to −32.2 ppm/°C. • The 1 wt% B{sub 2}O{sub 3}-doped ZnTiNb{sub 2}O{sub 8} ceramics were sintered at 1050 °C. • The optimal microwave dielectric properties were ε{sub r} ∼35.04 and Q·ƒ ∼50,100 GHz.

  19. Shear bond strength of veneering ceramic to zirconia core after different surface treatments.

    Science.gov (United States)

    Kirmali, Omer; Akin, Hakan; Ozdemir, Ali Kemal

    2013-06-01

    The aim of this study was to evaluate the effect of different surface treatments: sandblasting, liners, and different laser irradiations on shear bond strength (SBS) of pre-sintered zirconia to veneer ceramic. The SBS between veneering porcelain and zirconium oxide (ZrO2) substructure was weak. Various surface treatment methods have been suggested for zirconia to obtain high bond strength to veneering porcelain. There is no study that evaluated the bond strength between veneering porcelain and the different surface treatments on pre-sintered ZrO2 substructure. Two hundred specimens with 7 mm diameter and 3 mm height pre-sintered zirconia blocks were fabricated. Specimens were randomly divided into 10 groups (n=20) according to surface treatments applied. Group C, untreated (Control); Group E, erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiated; Group N, neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiated; Group SB, sandblasted; Group L, liner applied; Group NL, Nd:YAG laser irradiated+liner applied; Group EL, Er:YAG laser irradiated+liner applied; Group SN, sandblasted+Nd:YAG laser irradiated; Group SE, sandblasted+Er:YAG laser irradiated; and Group SL, sandblasted+liner applied. The disks were then veneered with veneering porcelain. Before the experiment, specimens were steeped in 37°C distilled water for 24 h. All specimens were thermocycled for 5000 cycles between 5°C and 55°C with a 30 sec dwell time. Shear bond strength test was performed at a crosshead speed of 1 mm/min. The fractured specimens were examined under a stereomicroscope to evaluate the fracture pattern. Surface treatments significantly changing the topography of the yttrium-stabilized tetragonal zirconia (Y-TZP) ceramic according to scanning electron microscopic (SEM) images. The highest mean bond strength value was obtained in Group SE, and the lowest bond strength value was observed in NL group. Bond strength values of the other groups were similar to each other. This

  20. Influence of Cr2O3 additive and sintering temperature on the structural characteristics and piezoelectric properties of Bi4Ti2.95W0.05O12.05 Aurivillius ceramics

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2016-12-01

    Full Text Available In this paper, Cr2O3 (0–0.4 wt% as an additive was added into Bi4Ti2.95W0.05O12.05 (BITW for preparing a kind of W/Cr co-doped BIT (BITW-yCr Aurivillius ceramics, both W6+ and Cr3+ are considered to substitute Ti4+ in the [TiO6] octahedron of BIT. Besides the orthorhombic Bi4Ti3O12 as the major phase, BITW-yCr ceramics also contain the cubic Bi2Ti2O7 as the second phase which was formed due to the doping effect of WO3, but its formation could be depressed by the addition of less Cr2O3. Additionally, the cell parameters of BITW ceramics are also changed by the incorporation of Cr2O3, as the distortion degree of the orthorhombic structure (a/b increases firstly and then decreases with its addtional amount (y. On the other hand, the grain growth of BITW-yCr ceramics is mainly controlled by the sintering process, there a higher sintering temperature results in a larger grain size. In comparison to BIT ceramics, BITW-yCr ceramics with less Cr-addition (y=0–0.2 require a higher sintering temperature to attain the best dense state, moreover, as y increases, the sintering temperature to gain the highest piezoelectric activity also increases. Finally, BITW-0.2Cr which was sintered at 1150 °C exhibits a higher piezoelectric activity than the others, which could be attributed to its larger orthorhombic distortion and larger grain size, its ideal piezoelectric constant (d33=28 pC/N provides it with great applying potentiality.

  1. 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.

  2. Multifunctional zirconium oxide doped chitosan based hybrid nanocomposites as bone tissue engineering materials.

    Science.gov (United States)

    Bhowmick, Arundhati; Jana, Piyali; Pramanik, Nilkamal; Mitra, Tapas; Banerjee, Sovan Lal; Gnanamani, Arumugam; Das, Manas; Kundu, Patit Paban

    2016-10-20

    This paper reports the development of multifunctional zirconium oxide (ZrO2) doped nancomposites having chitosan (CTS), organically modified montmorillonite (OMMT) and nano-hydroxyapatite (HAP). Formation of these nanocomposites was confirmed by various characterization techniques such as Fourier transform infrared spectroscopy and powder X-ray diffraction. Scanning electron microscopy images revealed uniform distribution of OMMT and nano-HAP-ZrO2 into CTS matrix. Powder XRD study and TEM study revealed that OMMT has partially exfoliated into the polymer matrix. Enhanced mechanical properties in comparison to the reported literature were obtained after the addition of ZrO2 nanoparticle into the nanocomposites. In rheological measurements, CMZH I-III exhibited greater storage modulus (G') than loss modulus (G″). TGA results showed that these nanocomposites are thermally more stable compare to pure CTS film. Strong antibacterial zone of inhibition and the lowest minimum inhibition concentration (MIC) value of these nanocomposites against bacterial strains proved that these materials have the ability to prevent bacterial infection in orthopedic implants. Compatibility of these nanocomposites with pH and blood of human body was established. It was observed from the swelling study that the swelling percentage was increased with decreasing the hydrophobic OMMT content. Human osteoblastic MG-63 cell proliferations were observed on the nanocomposites and cytocompatibility of these nanocomposites was also established. Moreover, addition of 5wt% OMMT and 5wt% nano-HAP-ZrO2 into 90wt% CTS matrix provides maximum tensile strength, storage modulus, aqueous swelling and cytocompatibility along with strong antibacterial effect, pH and erythrocyte compatibility. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Laser sintering of ceramics of Y{sub 2}O{sub 3} pure e doped; Sinterizacao a laser de ceramicas de Y{sub 2}O{sub 3} pura e dopada

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, T.C. de; Goncalves, R.S.; Silva, R.S. da, E-mail: tiagocordeirotc@yahoo.com.br [Universidade Federal de Sergipe (UFS), SE (Brazil). Departamento de Fisica

    2012-07-01

    The Yttria (Y{sub 2}O{sub 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{sub 2}O{sub 3} high temperatures and require special sintering. Recently it has been proposed in the literature a new method of sintering in which a CO{sub 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{sub 2}O{sub 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{sub 2}O{sub 3} and dependence on the dopant used. (author)

  4. Evaluating the effect of increasing ceramic content on the mechanical properties, material microstructure and degradation of selective laser sintered polycaprolactone/β-tricalcium phosphate materials.

    Science.gov (United States)

    Doyle, Heather; Lohfeld, Stefan; McHugh, Peter

    2015-08-01

    Orthopaedic scaffold materials were fabricated from polycaprolactone (PCL) and composite PCL-β-tricalcium phosphate (PCL/β-TCP) powders using selective laser sintering (SLS). Incorporating β-TCP particles is desirable to promote osteogenesis. The effects of increasing β-TCP content on the material's mechanical properties and microstructure were evaluated. The wt% of β-TCP and PCL particle sizes were found to influence material microstructure and mechanical properties, with increasing ceramic content causing a small but significant increase in stiffness but significant reductions in strength. Degradation of materials was achieved using accelerated ageing methods. The influence of β-TCP content on degradation at 7 weeks was evaluated through changes in mechanical properties and microstructure, and the ceramic particles were found to reduce elastic modulus and increase strength. The results of this study highlight the influence of ceramic content on mechanical properties and degradation behaviour of PCL/β-TCP SLS materials, and indicate that these changes must be considered in the design of scaffolds for critical-sized defects. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

  5. Phase-Pure of BiFeO3 Ceramic Based on Citric Acid - Assisted Gel by Sintering Time Variation

    Science.gov (United States)

    Suastiyanti, Dwita; Ismojo

    2017-07-01

    Bismuth ferrite powder (BiFeO3/BFO) with high purity was synthesized by sol-gel process. It was used Bi5O(OH)9(NO3)4 and Fe(NO3)3.9H2O as main compound sources. Citric acid (C6H8O7) was used as fuell. As multiferroic material, BFO promises important technological applications in several devices like data strorage, spinotronics, sensor, actuator devices etc. This research would know the optimum process condition of sol-gel process to produce BFO powder by varying of sintering time. The novelty of this research is how to produce BFO in single phase by simple method. It was used calcination condition at 160°C for 4 hours and sintering condition at 600°C with varying of sintering time of 4, 6 and 8 hours. Thermogravimetric Analysis/Differential Thermal Analysis (TGA/DTA), X Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to characterize the powder. Loss of mass and heat flow were seen at TGA/DTA test at 160°C approximately (used as reference of calcination temperature). BFO powder sintered at for 8 hours has no secondary phase, meanwhile for another sintering time (4 and 6 hours) it has Bi2O3 as secondary phase. It is also show at SEM observation result that powder with sintering time of 8 hours has finer grain than of 4 and 6 hours sintering at the same temperature. The grains of BFO powder has heterogenous in size, shape and still agglomerated.

  6. Preliminary study of cyclic thermal shock resistance of plasma-sprayed zirconium oxide turbine outer air seal shrouds

    Science.gov (United States)

    Bill, R. C.; Wisander, D. W.

    1977-01-01

    Several experimental concepts representing potential high pressure turbine seal material systems were subjected to cyclic thermal shock exposures similar to those that might be encountered under severe engine start-up and shut-down sequences. All of the experimental concepts consisted of plasma-sprayed yttria stabilized ZrO2 on the high temperature side of the blade tip seal shroud. Between the ZrO2 and a cooled, dense metal backing, various intermediate layer concepts intended to mitigate thermal stresses were incorporated. Performance was judged on the basis of the number of thermal shock cycles required to cause loss of seal material through spallation. The most effective approach was to include a low modulus, sintered metal pad between the ZrO2 and the metallic backing. It was also found that reducing the density of the ZrO2 layer significantly improved the performance of specimens with plasma-sprayed metal/ceramic composite intermediate layers.

  7. Role of sintering time, crystalline phases and symmetry in the piezoelectric properties of lead-free KNN-modified ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Marcos, F., E-mail: frmarcos@icv.csic.es [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Marchet, P.; Merle-Mejean, T. [SPCTS, UMR 6638 CNRS, Universite de Limoges, 123, Av. A. Thomas, 87060 Limoges (France); Fernandez, J.F. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain)

    2010-09-01

    Lead-free KNN-modified piezoceramics of the system (Li,Na,K)(Nb,Ta,Sb)O{sub 3} were prepared by conventional solid-state sintering. The X-ray diffraction patterns revealed a perovskite phase, together with some minor secondary phase, which was assigned to K{sub 3}LiNb{sub 6}O{sub 17}, tetragonal tungsten-bronze (TTB). A structural evolution toward a pure tetragonal structure with the increasing sintering time was observed, associated with the decrease of TTB phase. A correlation between higher tetragonality and higher piezoelectric response was clearly evidenced. Contrary to the case of the LiTaO{sub 3} modified KNN, very large abnormal grains with TTB structure were not detected. As a consequence, the simultaneous modification by tantalum and antimony seems to induce during sintering a different behaviour from the one of LiTaO{sub 3} modified KNN.

  8. Modified Lanthanum Zirconium Oxide buffer layers for low-cost, high performance YBCO coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Parans Paranthaman, M., E-mail: paranthamanm@ornl.go [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Sathyamurthy, S.; Li, Xiaoping [American Superconductor Corporation, Devens, MA 01434 (United States); Specht, E.D.; Wee, S.H.; Cantoni, C.; Goyal, A. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Rupich, M.W. [American Superconductor Corporation, Devens, MA 01434 (United States)

    2010-03-01

    The pyrochlore Lanthanum Zirconium Oxide, La{sub 2}Zr{sub 2}O{sub 7} (LZO), has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO{sub 2} cap/YSZ barrier/Y{sub 2}O{sub 3} seed on Ni-5%W metal tape. The main focus of this research is to ascertain whether: (i) we can further improve the barrier properties of LZO; (ii) we can modify the LZO cation ratio and still achieve a high level of performance; and (iii) it is possible to reduce the number of buffer layers. We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La{sub 2}O{sub 3}-ZrO{sub 2} system. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of La{sub x}Zr{sub 1-x}O{sub y} (x = 0.2-0.6) on standard Y{sub 2}O{sub 3} buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase with only (0 0 1) texture can be achieved in a broad compositional range of x = 0.2-0.6 in La{sub x}Zr{sub 1-x}O{sub y}. Both CeO{sub 2} cap layers and MOD-YBCO films were grown epitaxially on these modified LZO barriers. High critical currents per unit width, I{sub c} of 274-292 A/cm at 77 K and self-field were achieved for MOD-YBCO films grown on La{sub x}Zr{sub 1-x}O{sub y} (x 0.4-0.6) films. These results indicate that LZO films can be grown with a broad compositional range and still support high performance YBCO coated conductors. In addition, epitaxial MOD La{sub x}Zr{sub 1-x}O{sub y} (x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 mum thick YBCO films grown on a single MOD-LZO buffered Ni-3W substrates using pulsed laser deposition show a critical current density, J{sub c}, of 0.55 MA/cm{sup 2} (I{sub c} of 169 A/cm) at 77 K and 0.01 T. This work holds promise for a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  9. Solution Processed Lanthanum Zirconium Oxide as a Primary Barrier Layer for High Ic Coated Conductors

    Energy Technology Data Exchange (ETDEWEB)

    Sathyamurthy, Srivatsan [ORNL; Paranthaman, Mariappan Parans [ORNL; Heatherly Jr, Lee [ORNL; Martin, Patrick M [ORNL; Specht, Eliot D [ORNL; Goyal, Amit [ORNL; Kodenkandath, Thomas [American Superconductor Corporation, Westborough, MA; Li, Xiaoping [American Superconductor Corporation, Westborough, MA; Rupich, Marty [American Superconductor Corporation, Westborough, MA

    2006-01-01

    High-quality lanthanum zirconium oxide (La{sub 2}Zr{sub 2}O{sub 7} or LZO) films have been deposited and processed on Ni-W substrates using a sol-gel processing approach. It has been demonstrated that crack-free coatings with thicknesses up to 100 nm can be processed in a single step, while thicker coatings (200-225 nm) were processed using a multiple coating and annealing process. Using simulated metalorganic deposition (MOD)-YBa{sub 2}Cu{sub 3}O{sub 7-:{angstrom}} (YBCO) processing conditions, the barrier properties of the sol-gel LZO coating with a thickness of 120 nm were found to be comparable to that of the standard 3-layer buffer stack deposited using physical vapor deposition. Secondary ion mass spectroscopy depth profile analysis of LZO films annealed in oxygen-18 shows that LZO effectively stops the diffusion of Ni within the first 80-100 nm. Using MOD processes, a CeO{sub 2} cap layer and superconducting YBCO layer were deposited on sol-gel LZO/Ni-W. For the first time, using such an all-solution conductor architecture, a critical current (I{sub c}) of 140 A/cm with a corresponding critical current density (J{sub c}) of 1.75 MA/cm{sup 2} has been demonstrated. Using a very thin Y{sub 2}O{sub 3} seed layer ({approx}10 nm) deposited by electron beam evaporation; improved texture quality in the LZO layers has been demonstrated. The performance of the LZO deposited on these samples was evaluated using a sputtered CeO{sub 2} cap layer and MOD YBCO layer. Critical currents of up to 255 A/cm (3.2 MA/cm{sup 2}) with 0.8-{micro}m-thick YBCO films have been demonstrated, comparable to the performance of films grown using physical vapor deposited yttria stabilized zirconia as a barrier layer. Similar experiments using an MOD-CeO{sub 2} cap layer and MOD-YBCO layer yielded critical currents of 200 A/cm (2.5 MA/cm{sup 2}) with 0.8-{micro}m-thick YBCO films.

  10. Modified Lanthanum Zirconium Oxide Buffer for Low-Cost, High Performance YBCO Coated Conductors

    Energy Technology Data Exchange (ETDEWEB)

    Paranthaman, Mariappan Parans [ORNL; Sathyamurthy, Srivatsan [ORNL; Li, Xiaoping [American Superconductor Corporation, Westborough, MA; Specht, Eliot D [ORNL; Wee, Sung Hun [ORNL; Cantoni, Claudia [ORNL; Goyal, Amit [ORNL; Rupich, M. W. [American Superconductor Corporation, Westborough, MA

    2010-01-01

    Lanthanum Zirconium Oxide, La2Zr2O7 (LZO) has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed/Ni-5W. The main focus of this research is to see (i) whether we can improve further the barrier properties of LZO; (ii) can we widen the LZO composition and still achieve the high performance?; and (iii) is it possible to reduce the number of buffer layers? We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La2O3-ZrO2 system. Using metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of LaxZr1-xOy (x = 0.2-0.6) on standard Y2O3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase without the (111) texture can be achieved in a wider compositional window of x = 0.2-0.6 in LaxZr1-xOy. Both CeO2 cap layers and MOD-YBCO films were grown 2 epitaxially on these modified LZO barriers. Transport property measurements indicate that we can achieve a higher critical current, Ic of 274-292 A/cm at 77 K and self-field on MOD-YBCO films grown on LaxZr1-xOy (x = 0.4-0.6) films. These results indicate that LZO films can be grown with a wider compositional window and still achieve high performance YBCO coated conductors. In addition, epitaxial MOD LaxZr1-xOy (x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 m thick YBCO films with a Jc of 0.55 MA/cm2 at 77 K and 0.01 T were grown on a single MOD LZO buffered Ni-3W substrate using pulsed laser deposition. This work promises a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  11. Analysis of zirconium and nickel based alloys and zirconium oxides by relative and internal monostandard neutron activation analysis methods

    Energy Technology Data Exchange (ETDEWEB)

    Shinde, Amol D.; Acharya, Raghunath; Reddy, Annareddy V. R. [Bhabha Atomic Research Centre, Mumbai (India)

    2017-04-15

    The chemical characterization of metallic alloys and oxides is conventionally carried out by wet chemical analytical methods and/or instrumental methods. Instrumental neutron activation analysis (INAA) is capable of analyzing samples nondestructively. As a part of a chemical quality control exercise, Zircaloys 2 and 4, nimonic alloy, and zirconium oxide samples were analyzed by two INAA methods. The samples of alloys and oxides were also analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and direct current Arc OES methods, respectively, for quality assurance purposes. The samples are important in various fields including nuclear technology. Samples were neutron irradiated using nuclear reactors, and the radioactive assay was carried out using high-resolution gamma-ray spectrometry. Major to trace mass fractions were determined using both relative and internal monostandard (IM) NAA methods as well as OES methods. In the case of alloys, compositional analyses as well as concentrations of some trace elements were determined, whereas in the case of zirconium oxides, six trace elements were determined. For method validation, British Chemical Standard (BCS)-certified reference material 310/1 (a nimonic alloy) was analyzed using both relative INAA and IM-NAA methods. The results showed that IM-NAA and relative INAA methods can be used for nondestructive chemical quality control of alloys and oxide samples.

  12. 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.

  13. Comparative evaluation of electrical conductivity of hydroxyapatite ceramics densified through ramp and hold, spark plasma and post sinter Hot Isostatic Pressing routes.

    Science.gov (United States)

    Buchi Suresh, M; Biswas, P; Mahender, V; Johnson, Roy

    2017-01-01

    Hydroxyapatite ceramics synthesized through sonochemical route were processed and densified through ramp & hold (R&H) and Spark Plasma Sintering (SPS) routes. The effect of processing route on the relative density and electrical conductivity were studied. Further, the samples were Hot Isostatically Pressed (HIP) under argon pressure at elevated temperature to further densify the sample. All these samples processed under different conditions were characterized by X-ray diffraction, Scanning Electron Microscopy and AC Conductivity. The samples have exhibited hydroxyapatite phase; however, microstructures exhibited distinctly different grain morphologies and grain sizes. AC impedance spectroscopic measurement was carried out on hydroxyapatite samples processed through different routes and the corresponding spectra were analyzed by the analogy to equivalent circuit involving resistors and capacitors. SPS sintered sample after HIPing has exhibited the highest conductivity. This can be attributed to the higher density in combination with finer grain sizes. Activation energy based on Arrhenius equation is calculated and the prominent conduction mechanism is proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Phase and Microstructural Correlation of Spark Plasma Sintered HfB2-ZrB2 Based Ultra-High Temperature Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Ambreen Nisar

    2017-07-01

    Full Text Available The refractory diborides (HfB2 and ZrB2 are considered as promising ultra-high temperature ceramic (UHTCs where low damage tolerance limits their application for the thermal protection system in re-entry vehicles. In this regard, SiC and CNT have been synergistically added as the sintering aids and toughening agents in the spark plasma sintered (SPS HfB2-ZrB2 system. Herein, a novel equimolar composition of HfB2 and ZrB2 has shown to form a solid-solution which then allows compositional tailoring of mechanical properties (such as hardness, elastic modulus, and fracture toughness. The hardness of the processed composite is higher than the individual phase hardness up to 1.5 times, insinuating the synergy of SiC and CNT reinforcement in HfB2-ZrB2 composites. The enhanced fracture toughness of CNT reinforced composite (up to a 196% increment surpassing that of the parent materials (ZrB2/HfB2-SiC is attributed to the synergy of solid solution formation and enhanced densification (~99.5%. In addition, the reduction in the analytically quantified interfacial residual tensile stress with SiC and CNT reinforcements contribute to the enhancement in the fracture toughness of HfB2-ZrB2-SiC-CNT composites, mandatory for aerospace applications.

  15. 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)

  16. Low temperature sintering and microwave dielectric properties of MnZrNb{sub 2}O{sub 8} ceramics with H{sub 3}BO{sub 3} addition

    Energy Technology Data Exchange (ETDEWEB)

    Bi, J.X.; Xing, C.F.; Yang, C.H.; Wu, H.T., E-mail: mse_wuht@ujn.edu.cn; Jiang, X.S.

    2016-08-15

    The effects of H{sub 3}BO{sub 3} additions on sintering characteristic, phase composition, microstructure and microwave dielectric properties of MnZrNb{sub 2}O{sub 8} ceramics were investigated. The MnZrNb{sub 2}O{sub 8} ceramics were prepared by the solid-state method. The phase composition, microstructure and elemental composition of the ceramics were studied using X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive Analysis. Only a single-phase MnZrNb{sub 2}O{sub 8} was formed in MnZrNb{sub 2}O{sub 8} ceramics with H{sub 3}BO{sub 3} addition. A small amount of H{sub 3}BO{sub 3} successfully reduced the sintering temperature of MnZrNb{sub 2}O{sub 8} ceramics from 1250 to 1200 °C without much degradation of the microwave dielectric properties. In addition, the τ{sub f} values were shifted to positive direction with the increase of H{sub 3}BO{sub 3} contents. Typically, the MnZrNb{sub 2}O{sub 8} ceramic with 1 wt% H{sub 3}BO{sub 3} sintered at 1250 °C for 4 h exhibited excellent microwave dielectric properties with ε{sub r} = 25.80, Q·f = 28,419 GHz and τ{sub f} = −8.4 ppm/°C. - Highlights: • Addition of H{sub 3}BO{sub 3} reduced the sintering temperature of MnZrNb{sub 2}O{sub 8} ceramics. • The τ{sub f} values were shifted to positive direction with the H{sub 3}BO{sub 3} addition. • The MnZrNb{sub 2}O{sub 8} ceramic with 1 wt% H{sub 3}BO{sub 3} was obtained sintered at 1250 °C for 4 h. • The microwave properties were ε{sub r} = 25.80, Q·f = 28,419 GHz and τ{sub f} = −8.4 ppm/°C.

  17. 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.

  18. Effect of Co{sub 3}O{sub 4} content on sintering and microstructure of 4% mol yttria stabilized zirconia ceramics; Efeito do teor de Co{sub 3}O{sub 4} na sinterizacao e microestrutura de ceramicas de zirconia 4% mol de itria

    Energy Technology Data Exchange (ETDEWEB)

    Grilo, J.P.F.; Neto, P.P.B.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M., E-mail: grilo.jpf@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2011-07-01

    In attempt to reduce the sintering temperature of yttria stabilized zirconia (4% mol, 4YSZ), Co{sub 3}O{sub 4} powders obtained by polymeric precursor method were used as sintering aids. Commercial 4YSZ powder and Co{sub 3}O{sub 4} calcined at 800 deg C for 2 h were characterized by XRD and SEM. Sintering behaviour of ceramics as a function of Co{sub 3}O{sub 4} content (between 0.5 and 4 wt.%) was investigated by dilatometry. Based on dilatometric analysis, ceramics were sintered between 1200 and 1400 deg C for 2 h in air and then characterized using different techniques. XRD results exhibit the attainment of monophasic Co{sub 3}O{sub 4} and the most part of tetragonal zirconia in the sintered ceramics. (author)

  19. 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.

  20. Layer-by-layer deposition of zirconium oxide films from aqueous solutions for friction reduction in silicon-based microelectromechanical system devices

    Energy Technology Data Exchange (ETDEWEB)

    Liu Junfu [Zyvex Corporation, 1321 N. Plano Road, Richardson, TX 75081 (United States)]. E-mail: j.f.liu@unh.edu; Nistorica, Corina [Zyvex Corporation, 1321 N. Plano Road, Richardson, TX 75081 (United States); Gory, Igor [Zyvex Corporation, 1321 N. Plano Road, Richardson, TX 75081 (United States); Skidmore, George [Zyvex Corporation, 1321 N. Plano Road, Richardson, TX 75081 (United States); Mantiziba, Fadziso M. [Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75083 (United States); Gnade, Bruce E. [Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75083 (United States)

    2005-12-01

    This work reports layer-by-layer deposition of zirconium oxide on a Si surface from aqueous solutions using the successive ionic layer adsorption and reaction technique. The process consists of repeated cycles of adsorption of zirconium precursors, water rinse, and hydrolysis. The film composition was determined by X-ray photoelectron spectroscopy. The film thickness was determined by Rutherford backscattering spectrometry, by measuring the Zr atom concentration. The average deposition rate from a 0.1 M Zr(SO{sub 4}){sub 2} solution on a SiO{sub 2}/Si surface is 0.62 nm per cycle. Increasing the acidity of the zirconium precursor solution inhibits the deposition of the zirconium oxide film. Atomic force microscopy shows that the zirconium oxide film consists of nanoparticles of 10-50 nm in the lateral dimension. The surface roughness increased with increasing number of deposition cycles. Friction measurements made with a microelectromechanical system device reveal a reduction of 45% in the friction coefficient of zirconium oxide-coated surfaces vs. uncoated surfaces in air.

  1. 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.

  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. 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.

  4. 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.

  5. 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.)

  6. Effect of Zirconium Oxide Nanofiller and Dibutyl Phthalate Plasticizer on Ionic Conductivity and Optical Properties of Solid Polymer Electrolyte

    Directory of Open Access Journals (Sweden)

    Siti Mariah Mohd Yasin

    2014-01-01

    Full Text Available New solid polymer electrolytes (SPE based on poly(ethylene oxide (PEO doped with lithium trifluoromethanesulfonate (LiCF3SO3, dibutyl phthalate (DBP plasticizer, and zirconium oxide (ZrO2 nanoparticles were prepared by solution-casting technique. The conductivity was enhanced by addition of dibutyl phthalate (DBP plasticizer and ZrO2 nanofiller with maximum conductivity (1.38×10-4 Scm-1. The absorption edge and band gap values showed decreases upon addition of LiSO3CF3, DBP, and ZrO2 due to the formation of localized states in the SPE and the degree of disorder in the films increased.

  7. Zirconium oxide-coated sand based batch and column adsorptive removal of arsenic from water: Isotherm, kinetic and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    Saif Ali Chaudhry

    2017-06-01

    Full Text Available This paper reports zirconium oxide-coated sand preparation, characterization by SEM, EDX, XRD, FT-IR and thermoanalytical techniques, and use as an adsorbent for the removal of most toxic form of arsenic, As(III, from aqueous solution in both batch and column methods. Batch experimental parameters such as contact time, concentration, dose of adsorbent, pH of As(III solution and temperature were optimized. The adsorption data was fitted to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms at 303, 308 and 313 K. The maximum Langmuir monolayer adsorption capacity was found to be 136.98 μg/g at 313 K. Values of ΔH°, ΔG° and ΔS° were found to be −12.90, −8.74 to –8.28 and 0.014 kJ/mol, suggesting exothermic and spontaneous adsorption process with slight increase in entropy. The adsorption process followed pseudo-second order kinetics and was controlled by film diffusion step. The column studies showed that when flow rate was increased from 3.0 to 5.0 mL/min, the arsenic adsorption capacity of ZrOCS increased from 33.104 to 42.231 μg/g and breakthrough, and exhaustion times got reduced reduced. The results indicated that zirconium oxide-coated sand (ZrOCS is an excellent adsorbent for the removal of As(III from water.

  8. 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)

  9. Effect of LiF as Sintering Agent on the Densification and Phase Formation in Al2O3-4 Wt Pct Nb2O5 Ceramic Compound

    Science.gov (United States)

    Santos, J. L.; Marçal, R. L. S. B.; Jesus, P. R. R.; Gomes, A. V.; Lima, E. P.; Monteiro, S. N.; de Campos, J. B.; Louro, L. H. L.

    2017-10-01

    Different amounts of LiF were added to an Al2O3-4 pct Nb2O5 basic ceramic, as sintering agent. Improved new ceramics were obtained with LiF concentrations varying from 0.25 to 1.50 wt pct and three sintering temperatures of 1573 K, 1623 K, and 1673 K (1300 °C, 1350 °C, and 1400 °C). The addition of 0.5 wt pct LiF yielded the highest densification, 94 pct of the theoretical density, in association with a sintering temperature of 1673 K (1400 °C). Based on X-ray diffraction (XRD), this improvement was due not only to the presence of transformed phases, more precisely Nb3O7F, but also to the absence of LiAl5O8. The preferential interaction of LiF with Nb2O5, instead of Al2O3, contributed to increase the alumina sintering ability by liquid phase formation. Scanning electron microscopy (SEM) results revealed well-connected grains and isolated pores, whereas the chemical composition analysis by energy dispersive energy (EDX) indicated a preferential interaction of fluorine with niobium, in agreement with the results of XRD. It was also observed from thermal analysis that the polyethylene glycol binder burnout temperature increased for all LiF concentrations. This may be related to the formation of hydrogen bridge bonds.

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

    OpenAIRE

    As'mau Ibrahim Gebi; Shehu Aliyu Yaro; Malik Abdulwahab; mamuda rayyan dodo

    2016-01-01

    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 G...

  11. Thermoelectric sintered glass-ceramics with a Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} phase

    Energy Technology Data Exchange (ETDEWEB)

    Lingner, Julian [Johannes Gutenberg-Universitaet Mainz, Institut fuer Physik, Mainz (Germany); SCHOTT AG, Material Development, Mainz (Germany); Funahashi, Ryoji; Combe, Emmanuel [National Institute of Advanced Industrial Science and Technology, Osaka (Japan); Letz, Martin [SCHOTT AG, Material Development, Mainz (Germany); Jakob, Gerhard [Johannes Gutenberg-Universitaet Mainz, Institut fuer Physik, Mainz (Germany)

    2015-07-15

    Glass-ceramic materials containing Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} crystals with plate-like structures are prepared by a melting process and a subsequent sintering step after manual quenching. The chemical starting compositions of the samples are Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub x} (BSC222), Bi{sub 1.8}Sr{sub 2}Co{sub 2}O{sub x} (Bi1.8) and Bi{sub 2}Sr{sub 2}Co{sub 1.7}O{sub x} (Co1.7). All three samples are p-type conductors. The electric properties of Seebeck coefficient S and electrical resistivity ρ show only a slight dependence on chemical composition. The Seebeck values increase with increasing temperature, and at T = 873 K, they reach S = 180, 176 and 167 μV/K, respectively. The electrical resistivity slightly decreases with temperature for two samples and increases for the Co1.7 sample. The thermal conductivity for all measured samples at this temperature is around κ = 0.8 W/(m K). The figure of merit ZT increases with temperature for all samples. The materials reach a ZT value of 0.03 at T = 873 K. (orig.)

  12. 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., E-mail: virginia@unifor.b [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)

  13. Laser sintering and dielectric characterization of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics; Sinterizacao a laser e caracterizacao dieletrica de ceramicas de CaCu{sub 3}Ti{sub 4}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Jesus, L.M.; Barbosa, L.B.; Silva, R.S. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Fisica. Grupo de Materiais Ceramicos Avancados

    2012-07-01

    Calcium and copper titanate (CaCu{sub 3}Ti{sub 4}O{sub 12} - CCTO) has been prepared by several researchers mainly through conventional ceramic processing. However, other synthesis methods have been tested in the last years. In this work, we have studied the CCTO synthesis by a route based on the Pechini method and its sintering using a new method, in which a CO{sub 2} laser is used as the main heating source. Besides, the dielectric properties of CCTO ceramics were investigated in order to verify the influence of this sintering process on the ceramic properties. The laser sintered ceramics presented high relative density (95 ± 1%), with homogeneous microstructure and single crystalline phase and dielectric constant changing from ∼ 1100 to 2100 (with dielectric loss of ∼ 0.05), when measured at 1 kHz and at room temperature. (author)

  14. Investigation of nano-structured Zirconium oxide film on Ti6Al4V substrate to improve tribological properties prepared by PIII&D

    Energy Technology Data Exchange (ETDEWEB)

    Saleem, Sehrish [Department of Physics, Government College University, Lahore 54000 (Pakistan); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Ahmad, R., E-mail: ahriaz@gcu.edu.pk [Department of Physics, Government College University, Lahore 54000 (Pakistan); Centre for Advanced Studies in Physics (CASP), Government College University, Lahore 54000 (Pakistan); Ayub, R. [Centre for Advanced Studies in Physics (CASP), Government College University, Lahore 54000 (Pakistan); Ikhlaq, Uzma [Department of Physics, Government College University, Lahore 54000 (Pakistan); Jin, Weihong; Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

    2017-02-01

    Highlights: • ZrO{sub 2} film was deposited on Ti6Al4V alloy using the plasma immersion ion implantation and deposition at various bias voltage. • The deposited film was characterized by XPS, AFM, Ellipometry, Nano-indentation and Pin-on disk machine. • A dense zirconium oxide film with the maximum thickness 108 nm was formed at maximum applied voltage. • The hardness and wear resistance of film is much higher as compared to the substrate. - Abstract: Plasma immersion ion implantation and deposition (PIII&D) is the most attractive and efficient technique used in the medical field to tailor materials for biomedical applications. In the present study zirconium oxide nano-structured thin films were deposited on surface of Ti6Al4V alloy for bias voltages of 15, 20 and 25 kV. The chemical composition, surface roughness and thickness of deposited films were characterized by the x-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and ellipsometry respectively. The XPS results confirm the formation of a dense zirconium oxide film of the treated specimens. AFM results exhibit a smooth film with maximum roughness of about 8.4 nm is formed. The thickness of the film is increased with the increase in bias voltages and is maximum at 25 kV. The effect of bias voltages on wear characteristics was further investigated by pin-on-disk test. It is observed that the friction coefficient is reduced, whereas wear resistance is enhanced and it is found to be maximum at 25 kV compared to the other bias voltages. Nanohardness is improved up to twice compared to untreated specimen at the maximum bias voltage. Therefore, it is concluded that deposition of zirconium oxide using the PIII&D is produced a dense layer on the substrate surface, which can be used as a promising candidate for the improved tribological properties of Ti6Al4V.

  15. A sensitive determination of terbutaline in pharmaceuticals and urine samples using a composite electrode based on zirconium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Aysegul Kutluay; Teker, Tugce; Duzmen, Sehriban; Aslanoglu, Mehmet, E-mail: maslanoglu@harran.edu.tr

    2016-10-01

    An accurate and precise determination of terbutaline has been carried out using a glassy carbon electrode (GCE) modified with a composite of multi-walled carbon nanotubes (MWCNTs) and nanoparticles of zirconium oxide (ZrO{sub 2}NPs). Energy dispersive X-ray and scanning electron microscopic techniques were utilized for the characterization of the composite layer. Terbutaline exhibited a broad oxidation peak at 770 mV on a GCE. However, MWCNTs/GCE presented an electrocatalytic effect toward the oxidation of terbutaline with a better anodic peak at 660 mV. Furthermore, the electrochemical behavior of terbutaline has greatly been improved at a GCE modified with a composite of MWCNTs and nanoparticles of ZrO{sub 2}. The ZrO{sub 2}NPs/MWCNTs/GCE exhibited a sharp anodic wave at 645 mV with a large enhancement of the current response for terbutaline. Square wave voltammetry (SWV) was performed for the determination of terbutaline at ZrO{sub 2}NPs/MWCNTs/GCE. A linear plot was obtained for the current responses of terbutaline against concentrations in the range of 10–160 nM yielding a detection limit of 2.25 nM (based on 3S{sub b}/m). Improved voltammetric behavior, long-time stability and good reproducibility were obtained for terbutaline at the proposed electrode. A mean recovery of 101.2% with an RSD% of 1.9 was obtained for the analysis of the drug formulation. The accurate and precise quantification of terbutaline makes the ZrO{sub 2}NPs/MWCNTs/GCE system of great interest for monitoring its therapeutic use. - Graphical abstract: A sensitive determination of terbutaline in pharmaceuticals and urine samples using a composite electrode based on zirconium oxide nanoparticles. Display Omitted - Highlights: • A composite electrode was prepared using nanoparticles of ZrO{sub 2} and MWCNTs. • The ZrO{sub 2}NPs/MWCNTs/GCE has greatly improved the voltammetry of terbutaline • The proposed electrode enabled a detection limit of 2.25 nM. • The proposed electrode

  16. Investigation of nano-structured Zirconium oxide film on Ti6Al4V substrate to improve tribological properties prepared by PIII&D

    Science.gov (United States)

    Saleem, Sehrish; Ahmad, R.; Ayub, R.; Ikhlaq, Uzma; Jin, Weihong; Chu, Paul K.

    2017-02-01

    Plasma immersion ion implantation and deposition (PIII&D) is the most attractive and efficient technique used in the medical field to tailor materials for biomedical applications. In the present study zirconium oxide nano-structured thin films were deposited on surface of Ti6Al4V alloy for bias voltages of 15, 20 and 25 kV. The chemical composition, surface roughness and thickness of deposited films were characterized by the x-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and ellipsometry respectively. The XPS results confirm the formation of a dense zirconium oxide film of the treated specimens. AFM results exhibit a smooth film with maximum roughness of about 8.4 nm is formed. The thickness of the film is increased with the increase in bias voltages and is maximum at 25 kV. The effect of bias voltages on wear characteristics was further investigated by pin-on-disk test. It is observed that the friction coefficient is reduced, whereas wear resistance is enhanced and it is found to be maximum at 25 kV compared to the other bias voltages. Nanohardness is improved up to twice compared to untreated specimen at the maximum bias voltage. Therefore, it is concluded that deposition of zirconium oxide using the PIII&D is produced a dense layer on the substrate surface, which can be used as a promising candidate for the improved tribological properties of Ti6Al4V.

  17. PREPARATION OF Al₂O₃-CaAl₁₂O₁₉-ZrO₂ COMPOSITE CERAMIC MATERIAL BY THE HYDRATION AND SINTERING OF Ca₇ZrAl₆O₁₈-REACTIVE ALUMINA MIXTURE

    Directory of Open Access Journals (Sweden)

    Dominika Madej

    2016-03-01

    Full Text Available Ceramic material of composition belonging to the Al₂O₃-CaAl₁₂O₁₉-ZrO₂ compatibility field was obtained as a result of hydration and sintering of the mixture of Al₂O₃ and Ca₇ZrAl₆O₁₈ powders. The hydrated Al₂O₃- Ca₇ZrAl₆O₁₈ mixture products were studied by XRD, DTA-TG-EGA and FT-IR after 14 days of curing and hydration at 50°C. C₃AH₆, Al(OH₃ and CaZrO₃ compounds were formed upon hydration. CaZrO₃ and the lime-rich calcium aluminates formed as transient phases during hydration and dehydration processes were converted to CA6 and ZrO₂ in the presence of an excess of Al₂O₃ during sintering at 1500°C. The Al₂O₃-based dense refractory composite material was investigated by XRD, FT-IR, SEM-EDS and mercury porosimetry. The sintered ceramic microstructure consists of a homogeneous distribution of zirconia grains in an alumina matrix reinforced with the calcium hexaaluminate phase. The presence of Al₂O₃, CaAl₁₂O₁₉ and ZrO₂ in the synthesized material was confirmed by XRD and FT-IR techniques. By applying the mercury intrusion porosimetry technique, the heterogeneous pore size distribution of the refractory composite material was determined.

  18. Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing

    Directory of Open Access Journals (Sweden)

    Qifeng Lu

    2015-07-01

    Full Text Available A powerful characterization technique, pulse capacitance-voltage (CV technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111 substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD. The results indicated that: (1 more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrOx; (2 the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N2 ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 1012 cm−2 for as-deposited sample to 4.55 × 1012 cm−2 for the 800 °C annealed one. In addition, the leakage current density increase from about 10−6 A/cm2 at Vg = +0.5 V for the as-deposited sample to 10−3 A/cm2 at Vg = +0.5 V for the 900 °C annealed one.

  19. Chemical characterization and bioactivity of epoxy resin and Portland cement-based sealers with niobium and zirconium oxide radiopacifiers.

    Science.gov (United States)

    Viapiana, Raqueli; Guerreiro-Tanomaru, Juliane Maria; Hungaro-Duarte, Marco Antonio; Tanomaru-Filho, Mário; Camilleri, Josette

    2014-09-01

    The purpose of this study was to characterize and to evaluate the bioactivity potential of experimental root canal sealers (ES) based on Portland cement, epoxy resin with nano- and micro-particles of niobium or zirconium oxide used as radiopacifiers in comparison to AH Plus and MTA Fillapex. Specimens of the sealers (10 mm in diameter×1 mm thick) were prepared and the radiopacity was evaluated according to ISO 6876 (2012) specifications. Characterization of the sealers was performed under the scanning electron microscope (SEM) immediately after setting and after immersion for 28 days in Hank's balanced salt solution (HBSS). In addition X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were also performed. The pH and calcium ion release were measured after 1, 7, 14, 21 and 28 days after completion of seating using a digital pH meter and an atomic absorption spectrophotometer, respectively. The experimental sealers exhibited an average radiopacity of 2.5 mm thickness of aluminum, which was similar to MTA Fillapex (P>0.05) and inferior to AH Plus (Pepoxy resin and radiopacifier exhibited a degree of bioactivity although no evidence of cement hydration was demonstrated on material characterization. The radiopacifier particle size had limited effect on the sealer microstructure and chemical properties. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Synthesis of amorphous zirconium oxide with luminescent characteristics; Sintesis de oxido de circonio amorfo con caracteristicas luminiscentes

    Energy Technology Data Exchange (ETDEWEB)

    Barrera S, M.; Chavez G, M.; Soto E, A.M.; Velasquez O, C.; Garcia S, M.A.; Olvera T, L.; Rivera M, T. [UAM-I, 09340 Mexico D.F. (Mexico)

    2004-07-01

    It was prepared zirconium oxide, ZrO{sub 2}, by means of hydrolysis-condensation reactions (sol-gel method), using zirconium propoxide, Zr(C{sub 3}H{sub 7}O){sub 4}, as precursor and nitric acid, HNO{sub 3}, as catalyst of the hydrolysis reaction. In this synthesis it was used a molar ratio water-alkoxide, r=n{sub H2O}/n{sub Zr}(C{sub 3}H{sub 7}0){sub 4}, high, similar to 200, so that the hydrolysis happens quickly and the nucleation and growth are completed in very little time. The solid was characterized with Ftir spectrophotometry, Differential thermal analysis (Dta), Thermal gravimetric analysis (T G), X-ray diffraction of powders, Scanning electron microscopy (Sem) and X-ray Dispersion energy (EDX). The ZrO{sub 2} obtained by this way is amorphous even to 300 C and it consists of big aggregates. The amorphous ZrO{sub 2}, presents thermoluminescent behavior, after it was irradiated with UV radiation and beta particles of {sup 90}Sr/{sup 90}Y and it was thermally stimulated. (Author)

  1. Concentration and immobilization of 137Cs from liquid radioactive waste using sorbents based on hydrated titanium and zirconium oxides

    Science.gov (United States)

    Voronina, A. V.; Noskova, A. Y.; Gritskevich, E. Y.; Mashkovtsev, M. A.; Semenishchev, V. S.

    2017-09-01

    The possibility of use of sorbents based on hydrated titanium and zirconium oxides (T-3A, T-35, NPF-HTD) for concentration and immobilization of 137Cs from liquid radioactive waste of various chemical composition (fresh water, seawater, solutions containing NaNO3, ammonium acetate, EDTA) was evaluated. It was shown that the NPF-HTD and T-35 sorbents separate 137Cs from fresh water and seawater with distribution coefficients as high as 6.2.104 and 6.1.104, 4.0.105 and 1.6.105 L kg-1 respectively; in 1 M ammonium acetate these values were 2.0.103 and 1.0.103 L kg-1. The NPF-HTD sorbent showed the highest selectivity for cesium in NaNO3 solution: cesium distribution coefficients in 1M NaNO3 was 1.4.106 L kg-1. All studied sorbents are suitable for deactivation of solutions containing EDTA. Cesium distribution coefficients were around 102-103 L kg-1 depending on EDTA concentration. Chemical stability of the sorbents was also studied. It was shown that 137Cs leaching rate from all sorbents meet the requirements for matrix materials.

  2. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Raphael Pilo

    2016-03-01

    Full Text Available The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC or Self Adhesive Resin Cement (SARC. Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa were significantly higher than those for SARC (2.28 ± 0.58 MPa. The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  3. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate.

    Science.gov (United States)

    Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

    2016-03-25

    The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  4. Synthesis of hydrous zirconium oxide-impregnated chitosan beads and their application for removal of fluoride and lead

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Dong-Wan [Department of Environment and Energy, Sejong University, Seoul 143-747 (Korea, Republic of); Jeon, Byong-Hun, E-mail: bhjeon@hanyang.ac.kr [Department of Natural Resources and Environmental Engineering, Hanyang University, 222 6 Wangsimni-ro, Seongdong-gu, Seoul, 133-791 (Korea, Republic of); Jeong, Yoojin [Department of Environment and Energy, Sejong University, Seoul 143-747 (Korea, Republic of); Nam, In-Hyun [Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon (Korea, Republic of); Choi, Ui-Kyu [Mine reclamation corporation, Coal Center, 2 Segye-ro, Wonju, Gangwon-do, 16464 (Korea, Republic of); Kumar, Rahul [Department of Natural Resources and Environmental Engineering, Hanyang University, 222 6 Wangsimni-ro, Seongdong-gu, Seoul, 133-791 (Korea, Republic of); Song, Hocheol, E-mail: hcsong@sejong.ac.kr [Department of Environment and Energy, Sejong University, Seoul 143-747 (Korea, Republic of)

    2016-05-30

    A composite adsorbent capable of simultaneous removal of both cationic and anionic contaminants from aqueous solutions was developed by impregnating hydrous zirconium oxide (HZO) into chitosan beads (CB). The optimal mass ratio of chitosan to HZO was 2:2. The composite adsorbent (HZOCB) had the rugged surface (52.74 m{sup 2} g{sup −1}) with irregular cracks caused by HZO inclusion and amine functional groups. The rate of Pb{sup 2+} adsorption by HZOCB was relatively rapid. Most of Pb{sup 2+} (89%) was adsorbed within 2.5 h. A binary sorbate system was noticeably favorable for F{sup −} adsorption as compared to single sorbate system. Adsorption of F{sup −} and Pb{sup 2+} followed pseudo-second order kinetics. The maximum sorption capacities obtained from Langmuir isotherm model were 22.1 and 222.2 mg g{sup −1}, respectively. The study demonstrates that the developed composite could be a potential adsorbent for the simultaneous remediation of F{sup −} and Pb{sup 2+} contamination in water.

  5. Bond Strength of Resin Cements to Zirconia Ceramic Using Adhesive Primers.

    Science.gov (United States)

    Stefani, Ariovaldo; Brito, Rui Barbosa; Kina, Sidney; Andrade, Oswaldo Scopin; Ambrosano, Gláucia Maria Bovi; Carvalho, Andreia Assis; Giannini, Marcelo

    2016-07-01

    To evaluate the influence of adhesive primers on the microshear bond strength of resin cements to zirconia ceramic. Fifty zirconia plates (12 mm × 5 mm × 1.5 mm thick) of a commercially available zirconium oxide ceramic (ZirCad) were sintered, sandblasted with aluminum oxide particles, and cleaned ultrasonically before bonding. The plates were randomly divided into five groups of 10. Three resin cements were selected (RelyX ARC, Multilink Automix, Clearfil SA Cement self-adhesive resin cement), along with two primers (Metal-Zirconia Primer, Alloy Primer) and one control group. The primers and resin cements were used according to manufacturers' recommendations. The control group comprised the conventional resin cement (RelyX ARC) without adhesive primer. Test cylinders (0.75 mm diameter × 1 mm high) were formed on zirconia surfaces by filling cylindrical Tygon tube molds with resin cement. The specimens were stored in distilled water for 24 hours at 37°C, then tested for shear strength on a Shimadzu EZ Test testing machine at 0.5 mm/min. Bond strength data were analyzed statistically by two-way ANOVA and Dunnett's test (5%). The bond strength means in MPa (± s.d.) were: RelyX ARC: 28.1 (6.6); Multilink Automix: 37.6 (4.5); Multilink Automix + Metal-Zirconia Primer: 55.7 (4.0); Clearfil SA Cement: 46.2 (3.3); and Clearfil SA Cement + Alloy Primer: 47.0 (4.1). Metal-Zirconia Primer increased the bond strength of Multilink Automix resin cement to zirconia, but no effect was observed for Alloy Primer using Clearfil SA Cement. RelyX ARC showed the lowest bond strength to zirconia. © 2015 by the American College of Prosthodontists.

  6. Bactericidal activity and silver release of porous ceramic candle filter prepared by sintering silica with silver nanoparticles/zeolite for water disinfection

    Science.gov (United States)

    Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Thanh Nguyen, Duc; Hien Nguyen, Quoc

    2014-09-01

    Porous ceramic candle filters (PCCF) were prepared by sintering silica from rice husk with silver nanoparticles (AgNPs)/zeolite A at about 1050 °C to create bactericidal PCCF/AgNPs for water disinfection. The silver content in PCCF/AgNPs was of 300-350 mg kg-1 determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and the average pore size of PCCF/AgNPs was of 50-70 Å measured by Brunauer-Emmett-Teller (BET) method. The bactericidal activity and silver release of PCCF/AgNPs have been investigated by flow test with water flow rate of 5 L h-1 and initial inoculation of E. coli in inlet water of 106 CFU/100 mL. The volume of filtrated water was collected up to 500 L. Results showed that the contamination of E. coli in filtrated water was <1 CFU/100 mL and the content of silver released from PCCF/AgNPs into filtrated water was <1 μg L-1, it is low, far under the WHO guideline of 100 μg L-1 at maximum for drinking water. Based on the content of silver in PCCF/AgNPs and in filtrated water, it was estimated that one PCCF/AgNPs could be used to filtrate of ˜100 m3 water. Thus, as-prepared PCCF/AgNPs releases low content of silver into water and shows effectively bactericidal activity that is promising to apply as point-of-use water treatment technology for drinking water disinfection.

  7. Sinterização ultra-rápida de materiais cerâmicos usando radiação laser Ultra-fast laser sintering of ceramic materials

    Directory of Open Access Journals (Sweden)

    Z. S. Macedo

    2000-12-01

    Full Text Available Nessa comunicação apresentamos nossos primeiros resultados de sinterização ultra-rápida em materiais cerâmicos óxidos usando a radiação de um laser de CO2 como fonte de aquecimento. Os compostos Bi4Ti3O12 (BIT e Bi4Ge3O12 (BGO foram sintetizados via reação do estado sólido, conformados em corpos cerâmicos cilíndricos de 12 mm de diâmetro e 2 mm de espessura e, posteriormente, levados ao laser para o processo de sinterização. A análise dos pós reagidos, efetuada por difratometria de raios X, confirmou a presença de fase cristalina única em cada um dos sistemas investigados. A potência máxima do laser necessária para a sinterização apresentou forte dependência com a estratégia usada na irradiação. A análise da microestrutura, realizada por microscopia eletrônica de varredura (MEV, revelou um alto grau de eficiência do processo desenvolvido. Em alguns casos, pudemos verificar que a sinterização ocorreu a uma profundidade de até 1 mm, apontando para a viabilidade de obtenção de corpos cerâmicos sinterizados como um todo.In this communication we present our first results on ultra-fast laser sintering of oxide ceramics employing a CO2 laser as the heating source. The Bi4Ti3O12 (BIT and Bi4Ge3O12 (BGO compounds were synthesized following a solid state route in air atmosphere. Cylindrical ceramic bodies with 12 mm in diameter and 2 mm in thickness were shaped and sintered under laser irradiation. The X-ray diffraction of the calcined powders confirmed the presence of single phase in each of the investigated systems. The maximum laser power required to the sintering process showed to have a strong dependency on the strategy used for irradiation. The microstructure analysis of the samples, performed by scanning electron microscopy (SEM, revealed the high efficiency of the process. In some cases we could verify that the sintering occurred until a depth of 1mm, indicating the feasibility of obtaining the ceramic bodies

  8. Efeito da adição de polímero precursor cerâmico na sinterização de alumina Effect of the addition of ceramic polymeric precursor on alumina sintering

    Directory of Open Access Journals (Sweden)

    A. L. E Godoy

    2010-03-01

    Full Text Available Foram estudados os efeitos da adição de polímero precursor na sinterização, microestrutura e dureza da alumina. O polímero inorgânico polifenilmetilvinilhidrogenosilsesquioxano (PPS foi utilizado como aditivo em cerâmicas de alumina sinterizadas a 1650 ºC. Os materiais sinterizados foram caracterizados por dilatometria, determinando-se a densidade aparente por picnometria de hélio, pela análise de carbono total, por difração de raios X, por microscopia eletrônica de varredura, espectrometria de energia dispersiva de raios X e por análise de indentação Vickers para determinação de dureza e tenacidade a fratura. Foram obtidas fases heterogêneas de Si2Al4O4N4 nas amostras com PPS. Dentre as amostras analisadas, a que contém 5% de PPS apresentou dureza e tenacidade à fratura superiores à da alumina pura. A preparação de compósitos cerâmicos com pequenas quantidades de polímero precursor mostrou-se um processo adequado para cerâmicas à base de alumina, sendo uma rota simples de conformação com grande potencial para a obtenção de peças com geometria complexa.The effects of the addition of precursor polymer on sintering, microstructure and hardness of alumina ceramics were studied. The linear shrinkage of cold-pressed specimens was studied by dilatometry. Polyphenylmethylvinylhidrogensilsesquioxane (PPS polymer sintering aid was used for alumina based ceramics sintered at 1650 ºC. The sintered materials were characterized by determination of apparent density by helium picnometry, by evaluation of total carbon content, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, and by Vickers indentation analysis for determining hardness and fracture toughness. Heterogeneous Si2Al4O4 phases were obtained in specimens with PPS. The specimens with 5% of PPS presented hardness and toughness greater than the obtained for pure alumina. The preparation of ceramic composites using small amounts of

  9. Lightweight high performance ceramic material

    Science.gov (United States)

    Nunn, Stephen D [Knoxville, TN

    2008-09-02

    A sintered ceramic composition includes at least 50 wt. % boron carbide and at least 0.01 wt. % of at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb, and Lu, the sintered ceramic composition being characterized by a density of at least 90% of theoretical density.

  10. Differential Effects of Surface-Functionalized Zirconium Oxide Nanoparticles on Alveolar Macrophages, Rat Lung, and a Mouse Allergy Model.

    Science.gov (United States)

    Vennemann, Antje; Alessandrini, Francesca; Wiemann, Martin

    2017-09-19

    Nanoparticles (NPs) may affect the lung via their chemical composition on the surface. Here, we compared the bioactivity of zirconium oxide (ZrO₂) NPs coated with either aminopropilsilane (APTS), tetraoxidecanoic acid (TODS), polyethyleneglycol (PGA), or acrylic acid (Acryl). Supernatants from NPs-treated cultured alveolar macrophages (NR8383) tested for lactate dehydrogenase, glucuronidase, tumor necrosis factor α, and H₂O₂ formation revealed dose-dependent effects, with only gradual differences among particles whose gravitational settling and cellular uptake were similar. We selected TODS- and Acryl-coated NPs for intratracheal administration into the rat lung. Darkfield and hyperspectral microscopy combined with immunocytochemistry showed that both NPs qualities accumulate mainly within the alveolar macrophage compartment, although minute amounts also occurred in neutrophilic granulocytes. Dose-dependent signs of inflammation were found in the broncho-alveolar lavage fluid on day 3 but no longer on day 21 post-application of ≥1.2 mg per lung; again only minor differences occurred between TODS- and Acryl-coated NPs. In contrast, the response of allergic mice was overall higher compared to control mice and dependent on the surface modification. Increases in eosinophils, lymphocytes and macrophages were highest following ZrO₂-PGA administration, followed by ZrO₂-Acryl, ZrO₂-TODS, and ZrO₂-APTS. We conclude that surface functionalization of ZrO₂ NPs has minor effects on the inflammatory lung response of rats and mice, but is most relevant for an allergic mouse model. Allergic individuals may therefore be more susceptible to exposure to NPs with specific surface modifications.

  11. A sensitive determination of terbutaline in pharmaceuticals and urine samples using a composite electrode based on zirconium oxide nanoparticles.

    Science.gov (United States)

    Baytak, Aysegul Kutluay; Teker, Tugce; Duzmen, Sehriban; Aslanoglu, Mehmet

    2016-10-01

    An accurate and precise determination of terbutaline has been carried out using a glassy carbon electrode (GCE) modified with a composite of multi-walled carbon nanotubes (MWCNTs) and nanoparticles of zirconium oxide (ZrO2NPs). Energy dispersive X-ray and scanning electron microscopic techniques were utilized for the characterization of the composite layer. Terbutaline exhibited a broad oxidation peak at 770mV on a GCE. However, MWCNTs/GCE presented an electrocatalytic effect toward the oxidation of terbutaline with a better anodic peak at 660mV. Furthermore, the electrochemical behavior of terbutaline has greatly been improved at a GCE modified with a composite of MWCNTs and nanoparticles of ZrO2. The ZrO2NPs/MWCNTs/GCE exhibited a sharp anodic wave at 645mV with a large enhancement of the current response for terbutaline. Square wave voltammetry (SWV) was performed for the determination of terbutaline at ZrO2NPs/MWCNTs/GCE. A linear plot was obtained for the current responses of terbutaline against concentrations in the range of 10-160nM yielding a detection limit of 2.25nM (based on 3Sb/m). Improved voltammetric behavior, long-time stability and good reproducibility were obtained for terbutaline at the proposed electrode. A mean recovery of 101.2% with an RSD% of 1.9 was obtained for the analysis of the drug formulation. The accurate and precise quantification of terbutaline makes the ZrO2NPs/MWCNTs/GCE system of great interest for monitoring its therapeutic use. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. As(III) and As(V) adsorption on nanocomposite of hydrated zirconium oxide coated carbon nanotubes.

    Science.gov (United States)

    Liu, Dengchao; Deng, Shubo; Maimaiti, Ayiguli; Wang, Bin; Huang, Jun; Wang, Yujue; Yu, Gang

    2018-02-01

    Novel hydrated zirconium oxide (ZrO(OH)2) coated carbon nanotubes (CNTs) were prepared via a filtration-steam hydrolysis method, and were used to remove As(III) and As(V) from drinking water. This adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The ZrO(OH)2 coated on the surface of CNTs was amorphous, and the coating thickness was in the range of 1-8 nm. The ZrO(OH)2/CNTs nanocomposite showed high adsorption for both As(III) and As(V) with the maximum adsorption capacities of 78.2 and 124.6 mg/g, respectively, according to the Langmuir fitting. The adsorption capacities of ZrO(OH)2/CNTs at the equilibrium concentration of 10 μg/L were 2.0 mg/g for As(III) and 7.2 mg/g for As(V) at pH 7, much higher than those of ZrO(OH)2 nanoparticles. Meanwhile, the adsorption rates of As(III) and As(V) on the ZrO(OH)2/CNTs were higher than the ZrO(OH)2 nanoparticles. The spent adsorbent can be regenerated by re-coating ZrO(OH)2 as the preparation method, and the adsorbed amounts of As(III) and As(V) on the ZrO(OH)2/CNTs changed little within six cycles. This ZrO(OH)2/CNTs nanocomposite shows a promising application potential for the removal of As(III) and As(V) from drinking water. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. On the microstructural and magnetic properties of fine-grained CoFe{sub 2}O{sub 4} ceramics produced by combining polyol process and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gaudisson, T.; Artus, M. [Laboratoire ITODYS, Université Paris-Diderot, Sorbonne Paris Cité, CNRS-UMR-7086, 7205 Paris (France); Acevedo, U. [Departamento MMC, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 Ciudad de México (Mexico); Herbst, F.; Nowak, S. [Laboratoire ITODYS, Université Paris-Diderot, Sorbonne Paris Cité, CNRS-UMR-7086, 7205 Paris (France); Valenzuela, R. [Departamento MMC, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 Ciudad de México (Mexico); Ammar, S., E-mail: ammarmer@univ-paris-diderot.fr [Laboratoire ITODYS, Université Paris-Diderot, Sorbonne Paris Cité, CNRS-UMR-7086, 7205 Paris (France)

    2014-12-15

    Starting from polyol-made CoFe{sub 2}O{sub 4} ferrite nanoparticles of different aggregation states, high-density fine-grained ceramics were produced using Spark Plasma Sintering technique at 600 and 500 °C, under vacuum and applying a uniaxial pressure of more than 80 MPa. The grain growth of thus produced ceramics appears to be proportional to the temperature plateau and inversely proportional to the aggregation state of the initial powders. Average grain sizes ranging between about 50 and 350 nm were obtained. In all the cases, magnetic measurements evidenced a ferrimagnetic behavior at room temperature with non-zero coercivity, while their starting powders exhibited superparamagnetic features. - Highlights: • CoFe{sub 2}O{sub 4} nanoparticles of different aggregation states were produced in polyol. • Dense and fine-grained CoFe{sub 2}O{sub 4} ceramics were produced by SPS starting from these nanoparticles. • The CoFe{sub 2}O{sub 4} grain growth during SPS appears to be mainly driven by diffusion mechanism. • The ceramics are ferrimagnetic at 300 K while their starting powders are superparamagnetic.

  14. 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 sintering and microstructural developments of the chemically pure magnesia using the pressureless sintering technique between ... Department of Ceramic Engineering, National Institute of Technology, Rourkela 769008, India ...

  15. Spark plasma sintering of Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x} monolithic ceramics obtained by mechanically induced self-sustaining reaction

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, Amparo, E-mail: aborrell@upvnet.upv.es [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Salvador, Maria Dolores [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garcia-Rocha, Victoria [ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Fernandez, Adolfo [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Chicardi, Ernesto; Gotor, Francisco J. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Calle Americo Vespucio 49, 41092 Sevilla (Spain)

    2012-05-01

    Nanometer-sized titanium-niobium carbonitride powders (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with different Ti/Nb atomic ratios were obtained by a mechanically induced self-sustaining reaction, and sintered by spark plasma sintering technique at 1500 Degree-Sign C for 1 min in a vacuum atmosphere. Mechanical properties such as hardness and Young's modulus were determined by nanoindentation technique and friction and wear coefficients assessed by ball-on-disk testing using alumina ball in dry sliding conditions. The fracture surface and wear tracks of samples were examined by scanning electron microscopy. Results showed that it is possible to obtain dense monolithic ceramics from the solid solution (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti{sub 0.3}Nb{sub 0.7}C{sub 0.5}N{sub 0.5} ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa.

  16. Ceramics for thermonuclear fusion. II Synthesis and sintering of lithium metasilicate. Materiales ceramicos fertiles en fusion termonuclear. II Sintesis y sinterizacion de metasilicato de litio

    Energy Technology Data Exchange (ETDEWEB)

    La Iglesia, A.; Romero, M.P. (Universidad Complutense de Madrid (Spain) Facultad de Ciencias Geologicas)

    1990-01-01

    The synthesis and sintering of lithium metasilicate, a possible candidate as fuel in nuclear fusion has been studied. This synthesis has been carried out by solid state reaction between lithium carbonate and silicon oxide. As was demonstrated by X-ray diffraction the formation takes place by a consecutive reaction. The thermogravimetric analysis has shown the influence of the silica particle size and crystallinity on the reaction giving rise to activation energy values of 51,6 kJ/mol for silica gel with high specific surface and 272,0 kJ/mol for silica glass with low specific surface. The sintering study shows it is necessary to use lithium metasilicate from high specific surface silica and carrying out the sintering between 800{sup 0} and 900{sup 0}C for obtaining sintered densities between 75-85% of theoretical density. (Author)

  17. Synthesis of polymer/zirconium hydroxide core-shell microspheres and the hollow porous zirconium oxide microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Dianbin; Yan, Enwei; Yu, Jinhui; Zhang, Wei; Liu, Bin [Key Laboratory of Functional Polymer Materials, the Ministry of Education, Institute of Polymer Chemistry, Nankai University, Tianjin 300071 (China); Yang, Xinlin, E-mail: xlyang88@nankai.edu.cn [Key Laboratory of Functional Polymer Materials, the Ministry of Education, Institute of Polymer Chemistry, Nankai University, Tianjin 300071 (China)

    2012-10-15

    Narrow-disperse poly(N,N Prime -methylenebisacryamide-co-methacrylic acid)/zirconium hydroxide (P(MBA-co-MAA)/Zr(OH){sub 4}) core-shell composite microspheres were synthesized by the controlled sol-gel hydrolysis of inorganic zirconium n-butoxide (Zr(OBu){sub 4}) precursor in ethanol and acetonitrile mixed solvent with P(MBA-co-MAA) microspheres as templates. The thickness of the outer inorganic Zr(OH){sub 4} shell-layer was well-controlled via altering the mass ratio of Zr(OBu){sub 4} to P(MBA-co-MAA) core particles as well as the water used for the hydrolysis. The corresponding hollow porous zirconium oxide (ZrO{sub 2}) microspheres were obtained after the selective removal of P(MBA-co-MAA) core via the calcination of P(MBA-co-MAA)/Zr(OH){sub 4} core-shell microspheres under 550 Degree-Sign C for 4 h in air. The structure and morphology of the resultant core-shell microspheres and the hollow porous ZrO{sub 2} microspheres were characterized by transmission electron microscopy (TEM), STEM together with EDX spectrum, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, micromeritic analyzer, and thermogravimetric (TGA) analysis. -- Graphical abstract: Monodisperse P(MBA-co-MAA)/(ZrOH){sub 4} core-shell microspheres with amorphous zirconium hydroxide shell-layer were prepared by the controlled hydrolysis of Zr(OBu){sub 4} in acetonitrile/ethanol (4/1, V/V) mixed solvent. The mechanism of the encapsulation of zirconium hydroxide shell-layer over P(MBA-co-MAA) templates were performed via the efficient hydrogen-bonding interaction between the carboxylic acid groups as well as the amide groups on the surface of P(MBA-co-MAA) templates and the hydroxyl groups of the zirconium hydroxide molecules during the controlled hydrolysis. Highlights: Black-Right-Pointing-Pointer Synthesis of P(MBA-co-MAA)/Zr(OH){sub 4} core-shell composite microspheres. Black-Right-Pointing-Pointer Controlled thickness of Zr(OH){sub 4} shell-layer via altering loadings

  18. Influence of Li2CO3 and V2O5 combined additions on the sintering and dielectric properties of Ca0.5Sr0.5TiO3 ceramics prepared from powders synthesized by sol-gel method

    Directory of Open Access Journals (Sweden)

    Nouara Lamrani

    2014-06-01

    Full Text Available In this work, we have studied the influence of lithium carbonate (Li2CO3 associated with the vanadium oxide (V2O5 on sintering and dielectrics properties of Ca0.5Sr0.5TiO3 ceramic materials obtained from nanopowder synthesized by sol-gel method. The nanopowder was obtained by controlled mixing of titanium butoxide dissolved in butanol-2 and acetic acid with a saturated aqueous solution of calcium acetate and strontium carbonate and subsequent drying of the formed gel at 80 °C and calcination at 1100 °C. The synthesized nanopowder was mixed with different amount of additives, and then uniaxally pressed and sintered in air atmosphere at temperature determined by dilatomertic measurements. The pure Ca0.5Sr0.5TiO3 sample obtained by this process required a sintering temperature around 1500 °C. The addition of Li2CO3 combined with V2O5 improved sinterability and caused a shift of dilatimeric shrinkage curve to much lower temperatures. Thus, dense ceramics (98% of theoretical density were obtained at sintering temperature ≤ 1300 °C. The effect of adding Li2CO3-V2O5 on the structure of ceramics and the dielectric properties is discussed and show that type I dielectric properties (linear variation of the permittivity are conserved, but with an increase of dielectric loss.

  19. Sinter forging of zirconia toughened alumina

    NARCIS (Netherlands)

    He, Y.; Winnubst, Aloysius J.A.; Verweij, H.; Burggraaf, Anthonie; Burggraaf, A.J.

    1994-01-01

    Sinter forging experiments have been carried out on powder compacts of zirconia toughened alumina (ZTA) Ceramics Alumina-15 wt% zirconia was prepared by a gel precipitation method and calcined at temperatures of 900 or 1100°C. Full densification of ZTA ceramics was obtained within 15 min at 1400°C

  20. Fabrication and electro-optic properties of 0.9Pb[(Mg,Zn)1/3Nb2/3]O3-0.1PbTiO3 transparent ceramics by a conventional sintering technique

    Science.gov (United States)

    Fujii, Ichiro; Nakashima, Saki; Wada, Takahiro

    2017-10-01

    0.9Pb[(Mg1- x Zn x )1/3Nb2/3]O3-0.1PbTiO3 (x = 0-0.4) ceramics were fabricated by a conventional sintering technique. The ceramics became transparent at x = 0, 0.1, and 0.2, and the transmittances were 47, 43, and 53% at an infrared wavelength of 1310 nm, respectively. Birefringence of the transparent ceramics was quadratically increased as a function of electric field, with some deviations observed beyond certain electric fields at x = 0 and 0.2. An effective quadratic electro-optic (EO) coefficient was calculated with a half-wave electric field, and it was 6.30, 25.5, and 13.8 × 10-16 m2/V2 at x = 0, 0.1, and 0.2, respectively. The large EO effect at x = 0.1 was associated with the composition where a transition from a relaxor state to a ferroelectric state occurred. Microstructure, density, refractive index, and dielectric and ferroelectric properties were also investigated.

  1. 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 ...

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

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Porous Si3N4 ceramics were successfully synthesized using cheaper talc and clay as sintering addi- tives 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 β-Si3N4 and ...

  3. Influence of the amount containing spodumene or albite on the sintering of a triaxial ceramic; Comparacao da sinterizacao de uma massa ceramica triaxial contendo albita ou espodumenio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Camila Felippe de; Strecker, Kurt, E-mail: camilaufsj@yahoo.com.br [Universidade Federal de Sao Joao del-Rei (UFSJ), MG (Brazil)

    2012-07-01

    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)

  4. 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

  5. Plasma-sprayed dual density ceramic turbine seal system

    Science.gov (United States)

    Clingman, D. L.; Schechter, B.; Cross, K. R.; Cavanagh, J. R.

    1979-01-01

    Dual density, plasma sprayed ceramic coating systems were investigated for possible application as abradable turbine tip seal systems in small gas turbine engines. Abradability, erosion resistance, internal leakage, and microstructural characterization were investigated for polyester and cenosphere filled zirconium oxide composites. Results indicate the polyester system is more abradable but displays significantly less erosion resistance than the cenosphere system. It is also stated that the absence of significant blade tip damage during abradability testing of both systems suggests additional effort may result in a more nearly optimum balance of abradability and erosion resistance.

  6. Investigation of the sinterability of ZrO{sub 2} (Y{sub 2}O3{sub )}-bioglass dental ceramics by dilatometry; Estudo da sinterabilidade de ceramicas dentarias de ZrO{sub 2} (Y{sub 2}O3{sub )}-biovidro usando dilatometria

    Energy Technology Data Exchange (ETDEWEB)

    Bicalho, Luiz de Araujo; Barboza, Miguel Ribeiro Justino [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Strecker, Kurt [Universidade Federal de Sao Joao del Rei (UFSJ), MG (Brazil); Santos, Claudinei dos; Habibe, Alexandre Fernandes; Magnago, Roberto de Oliveira [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil)

    2013-06-15

    The objective of this work is to study by dilatometry, the liquid phase sintering of ZrO{sub 2} ceramics using bioglass as sintering additive. Y{sub 2} O{sub 3} - stabilized ZrO{sub 2} powders were mixed with 3, 5 and 10 wt% of bioglass with the composition based on 3CaOP{sub 2} O{sub 5} -MgO-SiO{sub 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{sub 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)

  7. Laser sintering of doped strontium aluminate via modified sol-gel for use as a ceramic pigment; Sinterizacao a laser do aluminato de estroncio dopado via sol-gel modificado para aplicacao como pigmento ceramico

    Energy Technology Data Exchange (ETDEWEB)

    Soares, F.M. dos S.; Valerio, M.E.G. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil)

    2017-01-15

    Powder of Dy{sup 3+} co-doped SrAl{sub 2}O{sub 4} :Eu{sup 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{sub 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{sub 2}O{sub 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{sup 3+} and more intense emission when the samples were excited at 265 nm. The laser treatment promoted the reduction of Eu{sup 3+} to Eu{sup 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)

  8. 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.

  9. Selection of optimal sintering temperature of K0.5Na0.5NbO3 ceramics for electromechanical applications

    Directory of Open Access Journals (Sweden)

    Gaurav Vats

    2014-03-01

    Full Text Available This paper has considered the selection of the optimal processing parameter (sintering temperature leading to best possible properties of K0.5Na0.5NbO3 (KNN for electromechanical applications. Vital piezoelectric properties for such applications include the piezoelectric coupling coefficient (kp, piezoelectric coefficient (d31, Curie temperature (Tc, remanent polarization (Pr, coercive field (Ec, density (ρ, elastic compliance (S11E and S12E and dielectric loss (tan δ. The weights and priority of these physical properties for KNN are calculated using the modified digital logic (MDL method. The priority order of these properties used for the selection of optimal processing parameters is as d31>tan δ>S11E=S12E>Tc=Pr>ρ>kp>Ec. The weights obtained using MDL are further incorporated with analytic hierarchy process (AHP and VlseKriterijumska Optimisacija I Kompromisno Resenje (VIKOR in order to determine the optimal sintering temperature for KNN. Both methods suggest that 1080 °C and 1120 °C are the most and least desirable sintering temperatures, respectively. Finally, sensitivity analysis is performed for the robustness of our results and prediction of most influential parameter in terms of sensitivity. tan δ is found to be the most sensitive property for alteration in the present ranking.

  10. Si3N4 ceramic cutting tool sintered with CeO2 and Al2O3 additives with AlCrN coating

    Directory of Open Access Journals (Sweden)

    José Vitor Candido Souza

    2011-12-01

    Full Text Available Ceramic cutting tools are showing a growing market perspective in terms of application on machining operations due to their high hardness, wear resistance, and machining without a cutting fluid, therefore are good candidates for cast iron and Nickel superalloys machining. The objective of the present paper was the development of Si3N4 based ceramic cutting insert, characterization of its physical and mechanical properties, and subsequent coating with AlCrN using a PVD method. The characterization of the coating was made using an optical profiler, XRD, AFM and microhardness tester. The results showed that the tool presented a fracture toughness of 6.43 MPa.m½ and hardness of 16 GPa. The hardness reached 31 GPa after coating. The machining tests showed a decrease on workpiece roughness when machining with coated insert, in comparison with the uncoated cutting tool. Probably this fact is related to hardness, roughness and topography of AlCrN.

  11. Luminescence properties of the Mg co-doped Ce:SrHfO.sub.3./sub. ceramics prepared by the Spark Plasma Sintering Method

    Czech Academy of Sciences Publication Activity Database

    Chiba, H.; Kurosawa, S.; Harata, K.; Murakami, R.; Yamaji, A.; Ohashi, Y.; Pejchal, Jan; Kamada, K.; Yokota, Y.; Yoshikawa, A.

    2016-01-01

    Roč. 90, Jul (2016), s. 287-291 ISSN 1350-4487. [International Conference on Luminescent Detectors and Transformers of Ionizing Radiation (LUMDETR). Tartu (Estonsko), 20.09.2015-25.09.2015] R&D Projects: GA MŠk(CZ) LH14266 Institutional support: RVO:68378271 Keywords : ceramics scintillator * high effective atomic number material Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.442, year: 2016

  12. Preparation and characterization of sugar cane bagasse fiber modified with nanoparticles of zirconium oxide; Preparacao e caracterizacao de fibras de bagaco de cana modificadas com nanoparticulas de oxido de zirconio

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, K.C.C. de; Mulinari, D.R.; Voorwald, H.C.J.; Cioffi, M.O.H., E-mail: kcccarvalho@hotmail.com.b [UNESP, Guaratingueta, SP (Brazil). Fac. de Engenharia. Dept. de Materiais e Tecnologia(FEG)

    2010-07-01

    The sugar cane bagasse fiber are renewable materials and have great application potential when used as reinforcement in a polymer matrix to give rise to composite materials and as supports for adsorption of heavy metals. This paper therefore describes the preparation and characterization of bleached and hydrated zirconium oxide modified sugar cane bagasse fiber by conventional precipitation method. Through the technique of electron microscopy we observed the presence of oxide nanoparticles on the fiber surface, proving the efficiency of the conventional precipitation method. With the X-ray diffraction analysis it was determined a decrease of 6.2% in the crystallinity index of modified fibers when compared to the bleached fibers showing the deposition of amorphous zirconium oxide on the fiber surface. (author)

  13. Evaluation of the Three-year Experience with All-ceramic Crowns with Polycrystalline Ceramic Cores

    Directory of Open Access Journals (Sweden)

    Lenka Vavřičková

    2013-01-01

    Full Text Available The objective of the study was to evaluate the clinical outcomes of all-ceramic crowns three years after placement of the restoration in the oral cavity. The aim of the present clinical study were surveyed the Procera®, Cercon® and LAVA™ systems. In total, 121 crowns were followed in 33 patients (7 men and 26 women with an average age of 53.5 years. The eighty crowns were placed in anterior and forty one crowns in posterior teeth. The crowns were fabricated in two dental laboratories and delivered in two private dental practices. The clinical trial was conducted according to American Dental Association guidelines. The patients were requested to provide their consent to the regular clinical examination including radiographic and photographic records.  A total of 102 crowns were made of zirconium oxide ceramic cores – 58 Cercon®; 43 LAVA™, while 19 crowns were made of aluminum oxide cores Procera®. The veneering ceramic LAVA™ Ceram was used. The success rate was analyzed using Kaplan-Meier statistics and, in our case, the overall three-year success rate reached 96.7%.  All-ceramic crowns with polycrystalline ceramic cores have low susceptibility to fracture, in this study just 3.3%.

  14. Spark Plasma Sintered AlN-BN Composites and Its Thermal Conductivity

    NARCIS (Netherlands)

    Zhao Haiyang, [No Value; Wang Weimin, [No Value; Wang Hao, [No Value; Fu Zhengyi, [No Value

    2008-01-01

    A series of samples of hexagonal boron nitride-aluminum nitride ceramic composites with different amounts of CaF(2) as sintering aid were prepared by spark plasma sintered at 1700-1850 degrees C for 5 min. The addition of CaF(2) effectively lowered the sintering temperature and promoted the

  15. The Study of Microwave and Electric Hybrid Sintering Process of AZO Target

    Directory of Open Access Journals (Sweden)

    Ling-yun Han

    2016-01-01

    Full Text Available We simulated the microwave sintering of ZnO by 3D modelling. A large-size Al-doped ZnO (AZO green ceramic compact was prepared by slurry casting. Through studying the microwave and electric hybrid sintering of the green compact, a relative density of up to 98.1% could be obtained by starting microwave heating at 1200°C and increasing the power 20 min later to 4 kW for an AZO ceramic target measuring 120 × 240 × 12 mm. The resistivity of AZO targets sintered with microwave assistance was investigated. The energy consumption of sintering could be greatly reduced by this heating method. Until now, few studies have been reported on the microwave and electric hybrid sintering of large-size AZO ceramic targets. This research can aid in developing sintering technology for large-size high-quality oxide ceramic targets.

  16. 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

  17. Novel nanostructure zinc zirconate, zinc oxide or zirconium oxide pastes coated on fluorine doped tin oxide thin film as photoelectrochemical working electrodes for dye-sensitized solar cell.

    Science.gov (United States)

    Hossein Habibi, Mohammad; Askari, Elham; Habibi, Mehdi; Zendehdel, Mahmoud

    2013-03-01

    Zinc zirconate (ZnZrO(3)) (ZZ), zinc oxide (ZnO) (ZO) and zirconium oxide (ZrO(2)) (ZRO) nano-particles were synthesized by simple sol-gel method. ZZ, ZO and ZRO nano-particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectrum (DRS). Nanoporous ZZ, ZO and ZRO thin films were prepared doctor blade technique on the fluorine-doped tin oxide (FTO) and used as working electrodes in dye sensitized solar cells (DSSC). Their photovoltaic behavior were compared with standard using D35 dye and an electrolyte containing [Co(bpy)(3)](PF(6))(2), [Co(pby)(3)](PF(6))(3), LiClO(4), and 4-tert-butylpyridine (TBP). The properties of DSSC have been studied by measuring their short-circuit photocurrent density (Jsc), open-circuit voltage (VOC) and fill factor (ff). The application of ZnZrO(3) as working electrode produces a significant improvement in the fill factor (ff) of the dye-sensitized solar cells (ff=56%) compared to ZnO working electrode (ff=40%) under the same condition. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Photocatalytic activity against azo dye and cytotoxicity on MCF-7 cell lines of zirconium oxide nanoparticle mediated using leaves of Lagerstroemia speciosa.

    Science.gov (United States)

    Sai Saraswathi, V; Santhakumar, K

    2017-04-01

    Metal oxide nanoparticles are gaining interest in recent years. The present paper explains about the green synthesis of zirconium oxide nanoparticles (ZrO NPs) mediated from the leaves of Lagerstroemia speciosa. The prepared ZrO NPs were characterized by UV-vis spectroscopy, FT-IR, X-ray diffraction analysis (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Thermogravimetric Analysis (TGA). The photocatalytic activity of ZrO NPs was studied for azo dye by exposing to sunlight. The azo dye was degraded up to 94.58%. Also the ZrO NPs were studied for in vitro cytotoxicity activity against breast cancer cell lines-MCF-7 and evaluated by MTT assay. The cell morphological changes were recorded by light microscope. The cells viability was seen at 500μg/mL when compared against control. Hence the research highlights, that the method was simple, eco-friendly towards environment by phytoremediation activity of the azo dye and cytotoxicity activity against MCF-7 cell lines. Hence the present paper may help to further explore the metal nanoparticle for its potential applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Application of poly(dimethylsiloxane) fiber sol-gel coated onto NiTi alloy electrodeposited with zirconium oxide for the determination of organochlorine pesticides in herbal infusions.

    Science.gov (United States)

    Budziak, Dilma; Martendal, Edmar; Carasek, Eduardo

    2008-08-01

    A PDMS fiber sol-gel coated onto an NiTi alloy previously electrodeposited with zirconium oxide (named NiTi-ZrO(2)-PDMS) was applied to the determination of organochlorine pesticides (OCPs) in infusions of peppermint (Mentha piperita L.), lemon grass (Cymbopogon citratus Stapf), chamomile (Matricaria recutita L.), lemon balm (Melissa officinalis L.), and anise seeds (Pimpinella anisum L.). Salting-out effect, extraction time, and extraction temperature were optimized firstly by means of a full-factorial design and then using a Doehlert matrix. No salt addition and 50 min of extraction at 70 degrees C were the optimum conditions. Satisfactory LODs in the range of 2-17 ng/L, as well as good correlation coefficients (at least 0.9981) in the linear range studied, were obtained. Calibration was successfully applied using an infusion of M. recutita L. and recovery tests were performed to ensure the accuracy of the method, with values in the range of 77-120%. Comparison of the NiTi-ZrO(2)-PDMS with commercially available PDMS fibers showed that the proposed fiber has an extraction efficiency comparable to that of PDMS 30 microm for the compounds evaluated, demonstrating its potential applicability.

  20. 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.

  1. Diffusion of silver during sintering in high permittivity COG dielectrics

    NARCIS (Netherlands)

    Mikkenie, R.; Groen, W.A.; Drift, R. van der

    2010-01-01

    To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to

  2. Microstructural and continuum evolution modeling of sintering.

    Energy Technology Data Exchange (ETDEWEB)

    Braginsky, Michael V.; Olevsky, Eugene A. (San Diego State University, San Diego, CA); Johnson, D. Lynn (Northwest University, Evanston, IL); Tikare, Veena; Garino, Terry J.; Arguello, Jose Guadalupe, Jr.

    2003-12-01

    All ceramics and powder metals, including the ceramics components that Sandia uses in critical weapons components such as PZT voltage bars and current stacks, multi-layer ceramic MET's, ahmindmolybdenum & alumina cermets, and ZnO varistors, are manufactured by sintering. Sintering is a critical, possibly the most important, processing step during manufacturing of ceramics. The microstructural evolution, the macroscopic shrinkage, and shape distortions during sintering will control the engineering performance of the resulting ceramic component. Yet, modeling and prediction of sintering behavior is in its infancy, lagging far behind the other manufacturing models, such as powder synthesis and powder compaction models, and behind models that predict engineering properties and reliability. In this project, we developed a model that was capable of simulating microstructural evolution during sintering, providing constitutive equations for macroscale simulation of shrinkage and distortion during sintering. And we developed macroscale sintering simulation capability in JAS3D. The mesoscale model can simulate microstructural evolution in a complex powder compact of hundreds or even thousands of particles of arbitrary shape and size by 1. curvature-driven grain growth, 2. pore migration and coalescence by surface diffusion, 3. vacancy formation, grain boundary diffusion and annihilation. This model was validated by comparing predictions of the simulation to analytical predictions for simple geometries. The model was then used to simulate sintering in complex powder compacts. Sintering stress and materials viscous module were obtained from the simulations. These constitutive equations were then used by macroscopic simulations for simulating shrinkage and shape changes in FEM simulations. The continuum theory of sintering embodied in the constitutive description of Skorohod and Olevsky was combined with results from microstructure evolution simulations to model shrinkage

  3. Tailored Ceramics for Laser Applications

    Energy Technology Data Exchange (ETDEWEB)

    Hollingsworth, Joel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2007-12-10

    Transparent ceramics match or exceed the performance of single-crystal materials in laser applications, with a more-robust fabrication process. Controlling the distribution of optical dopants in transparent ceramics would allow qualitative improvements in amplifier slab design by allowing gain and loss to be varied within the material. My work aims to achieve a controlled pattern or gradient of dopant prior to sintering, in order to produce tailored ceramics.

  4. DC-magnetron sputtering of ZnO:Al films on (00.1)Al{sub 2}O{sub 3} substrates from slip-casting sintered ceramic targets

    Energy Technology Data Exchange (ETDEWEB)

    Miccoli, I., E-mail: ilio.miccoli@unisalento.it [Photovoltaics R and D Lab, Alfa Impianti S.r.l., Via Baden Powell, I-73044 Galatone, Lecce (Italy); Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, I-73100 Lecce (Italy); Spampinato, R.; Marzo, F. [Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, I-73100 Lecce (Italy); Prete, P. [Istituto per la Microelettronica e Microsistemi del CNR, Unità di Lecce, Via Monteroni, I-73100 Lecce (Italy); Lovergine, N. [Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, I-73100 Lecce (Italy)

    2014-09-15

    Highlights: • ZnO:Al was DC-sputtered on sapphire >350 °C by slip-casting sintered AZO target. • Films are highly (00.1)-oriented, smooth and transparent in the NIR–visible range. • Films growth rate decreases with temperature, while their grain size increases. • A high temperature reduction for sticking coefficients of impinging species is proved. • We prove that Thornton model does not apply to high-temperature DC-sputtered ZnO. - Abstract: High (>350 °C) temperature DC-sputtering deposition of ZnO:Al thin films onto single-crystal (00.1) oriented Al{sub 2}O{sub 3} (sapphire) substrates is reported, using a ultrahigh-density, low-resistivity and low-cost composite ceramic target produced by slip-casting (pressureless) sintering of ZnO–Al{sub 2}O{sub 3} (AZO) powders. The original combination of high-angle θ–2θ (Bragg–Brentano geometry) X-ray diffraction with low angle θ–2θ X-ray reflectivity (XRR) techniques allows us to define the AZO target composition and investigate the structural properties and surface/interface roughness of as-sputtered ZnO:Al films; besides, the growth dynamics of ZnO:Al is unambiguously determined. The target turned out composed of the sole wurtzite ZnO and spinel ZnAl{sub 2}O{sub 4} phases. X-ray diffraction analyses revealed highly (00.1)-oriented (epitaxial) ZnO:Al films, the material mean crystallite size being in the 13–20 nm range and increasing with temperature between 350 °C and 450 °C, while the film growth rate (determined via XRR measurements) decreases appreciably. XRR spectra also allowed to determine rms surface roughness <1 nm for present films and showed ZnO:Al density changes by only a few percent between 350 °C and 450 °C. The latter result disproves the often-adopted Thornton model for the description of the sputter-grown ZnO films and instead points out toward a reduction of the sticking coefficients of impinging species, as the main origin of film growth rate and grain size dependence

  5. Sintering of polydisperse viscous droplets

    Science.gov (United States)

    Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Dingwell, Donald B.

    2017-03-01

    Sintering—or coalescence—of compacts of viscous droplets is driven by the interfacial tension between the droplets and the interstitial gas phase. The process, which occurs in a range of industrial and natural settings, such as the manufacture of ceramics and the welding of volcanic ash, causes the compact to densify, to become stronger, and to become less permeable. We investigate the role of droplet polydispersivity in sintering dynamics by conducting experiments in which populations of glass spheres with different size distributions are heated to temperatures above the glass transition interval. We quantify the progress of sintering by tracking changes in porosity with time. The sintering dynamics is modeled by treating the system as a random distribution of interstitial gas bubbles shrinking under the action of interfacial tension only. We identify the scaling between the polydispersivity of the initial droplets and the dynamics of bulk densification. The framework that we develop allows the sintering dynamics of arbitrary polydisperse populations of droplets to be predicted if the initial droplet (or particle) size distribution is known.

  6. The effect of ceramic thickness and number of firings on the color of two all-ceramic systems.

    Science.gov (United States)

    Ozturk, Ozge; Uludag, Bulent; Usumez, Aslihan; Sahin, Volkan; Celik, Gozde

    2008-08-01

    All-ceramic restorations have been advocated for superior esthetics, and various materials have been used to improve ceramic core strength, but there is a lack of information on how color is affected by different core substructures and fabrication procedures. The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of lithium disilicate glass-ceramic (IPS e.max Press) and zirconium-oxide (DC-Zirkon) all-ceramic systems. Thirty disc-shaped specimens, 4 mm in diameter with a 1-mm core thickness, and 0.5-, 1-, or 1.5-mm dentin ceramic thicknesses, were made from each of 2 ceramic systems (n=10). Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade), and data were expressed in CIELAB system coordinates. Repeated measures ANOVA was used to analyze the data (number of firings, ceramic composition, and ceramic thickness) for significant differences. The Tukey HSD test and paired 2-tailed tests were used to perform multiple comparisons (alpha=.05). L*a*b* values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (PL*a*b* values between the number of firings and ceramic composition (PL*a*b* color data as the number of firings increased, which resulted in perceptual color changes in L*a*b* color parameters.

  7. Synthesis and Characterization of Microwave Sintered Silica Xerogel Produced from Rice Husk Ash

    Science.gov (United States)

    Sudiana, I. N.; Mitsudo, S.; Nishiwaki, T.; Susilowati, P. E.; Lestari, L.; Firihu, M. Z.; Aripin, H.

    2016-08-01

    Silica xerogel ceramic produced from rice husk ash (RHA) taken from South East Sulawesi Indonesia has been successfully sintered by using a millimeter waves (MMW) heating system with a 28 GHz gyrotron as radiation source. The ceramic was also sintered by using an electric furnace where served as a comparison. Densification, microstructural, and morphological characterization of the silica were then investigated by using an Archimedes densification measurement method device, a X-ray diffraction (XRD) and a Scanning Electron Microscopy (SEM), respectively. Effect of microwave energy on the properties of silica xerogel ceramic were evaluated and discussed and compared to conventionally sintered results. The notably different densification and microstructure of sintered samples after sintering were found. The results suggest that microwave radiation provides a microwave effect during sintering.

  8. 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.

  9. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    Science.gov (United States)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  10. Glass ceramic toughened with tetragonal zirconia

    Science.gov (United States)

    Keefer, Keith D.; Michalske, Terry A.

    1986-01-01

    A phase transformation-toughened glass ceramic and a process for making it are disclosed. A mixture of particulate network-forming oxide, network-modifying oxide, and zirconium oxide is heated to yield a homogeneous melt, and this melt is then heat-treated to precipitate an appreciable quantity of tetragonal zirconia, which is retained at ambient temperature to form a phase transformation-toughened glass ceramic. Nucleating agents and stabilizing agents may be added to the mixture to facilitate processing and improve the ceramic's properties. Preferably, the mixture is first melted at a temperature from 1200.degree. to 1700.degree. C. and is then heat-treated at a temperature within the range of 800.degree. to 1200.degree. C. in order to precipitate tetragonal ZrO.sub.2. The composition, as well as the length and temperature of the heat-treatment, must be carefully controlled to prevent solution of the precipitated tetragonal zirconia and subsequent conversion to the monoclinic phase.

  11. Comprehensive profiling of ribonucleosides modification by affinity zirconium oxide-silica composite monolithic column online solid-phase microextraction - Mass spectrometry analysis.

    Science.gov (United States)

    Jiang, Han-Peng; Chu, Jie-Mei; Lan, Meng-Dan; Liu, Ping; Yang, Na; Zheng, Fang; Yuan, Bi-Feng; Feng, Yu-Qi

    2016-09-02

    More than 140 modified ribonucleosides have been identified in RNA. Determination of endogenous modified ribonucleosides in biological fluids may serve as non-invasive disease diagnostic strategy. However, detection of the modified ribonucleosides in biological fluids is challenging, especially for the low abundant modified ribonucleosides due to the serious matrix interferences of biological fluids. Here, we developed a facile preparation strategy and successfully synthesized zirconium oxide-silica (ZrO2/SiO2) composite capillary monolithic column that exhibited excellent performance for the selective enrichment of cis-diol-containing compounds. Compared with the boronate-based affinity monolith, the ZrO2/SiO2 monolith showed ∼2 orders of magnitude higher extraction capacity and can be used under physiological pH (pH 6.5-7.5). Using the prepared ZrO2/SiO2 composite monolith as the trapping column and reversed-phase C18 column as the analytical column, we further established an online solid-phase microextraction (SPME) in combination with liquid chromatography-mass spectrometry (online SPME-LC-MS/MS) analysis for the comprehensive profiling of ribonucleosides modification in human urine. Our results showed that 68 cis-diol-containing ribosylated compounds were identified in human urine, which is, to the best of our knowledge, the highest numbers of cis-diol-containing compounds were determined in a single analysis. It is worth noting that four modified ribonucleosides were discovered in the human urine for the first time. In addition, the quantification results from the pooled urine samples showed that compared to healthy controls, the contents of sixteen ribose conjugates in the urine of gastric cancer, eleven in esophagus cancer and seven in lymphoma increased more than two folds. Among these ribose conjugates, four ribose conjugates increased more than two folds in both gastric cancer and esophagus cancer; three ribose conjugates increased more than two

  12. Irradiation effects of the zirconium oxidation and the uranium diffusion in zirconia; Effets d'irradiation sur l'oxydation du zirconium et la diffusion de l'uranium dans la zircone

    Energy Technology Data Exchange (ETDEWEB)

    Bererd, N

    2003-07-01

    The context of this study is the direct storage of spent fuel assemblies after operation in reactor. In order to obtain data on the capacities of the can as the uranium diffusion barrier, a fundamental study has been carried out for modelling the internal cladding surface under and without irradiation. The behaviour of zirconium in reactor conditions has at first been studied. A thin uranium target enriched with fissile isotope has been put on a zirconium sample, the set being irradiated by a thermal neutrons flux leading to the fission of the deposited uranium. The energetic history of the formed fission products has revealed two steps: 1)the zirconium oxidation and 2)the diffusion of uranium in the zirconia formed at 480 degrees C. A diffusion coefficient under irradiation has been measured. Its value is 10{sup -15} cm{sup 2}.s{sup -1}. In order to be able to reveal clearly the effect of the irradiation by the fission products on the zirconium oxidation, measurements of thermal oxidation and under {sup 129}Xe irradiation have been carried out. They have shown that the oxidation is strongly accelerated by the irradiation and that the temperature is negligible until 480 degrees C. On the other hand, the thermal diffusion of the uranium in zirconium and in zirconia has been studied by coupling ion implantation and Rutherford backscattering spectroscopy. This study shows that the uranium diffuses in zirconium and is trapped in zirconia in a UO{sub 3} shape. (O.M.)

  13. Analysis of the deconvolution of the thermoluminescent curve of the zirconium oxide doped with graphite; Analisis de la deconvolucion de la curva termoluminiscente del oxido de zirconio dopado con grafito

    Energy Technology Data Exchange (ETDEWEB)

    Salas C, P. [IMP, 07000 Mexico D.F. (Mexico); Estrada G, R. [Depto. de Fisica y Matematicas, UIA, Unidad Stanta Fe, 01000 Mexico D.F. (Mexico); Gonzalez M, P.R.; Mendoza A, D. [ININ, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2003-07-01

    In this work, we present a mathematical analysis of the behavior of the thermoluminescent curve (Tl) induced by gamma radiation in samples made of zirconium oxide doped with different amounts of graphite. In accordance with the results gamma radiation induces a Tl curve with two maximum of emission localized in the temperatures at 139 and 250 C, the area under the curve is increasing as a function of the time of exposition to the radiation. The analysis of curve deconvolution, in accordance with the theory which indicates that this behavior must be obey a Boltzmann distribution, we found that each one of them has a different growth velocity as the time of exposition increase. In the same way, we observed that after the irradiation was suspended each one of the maximum decrease with different velocity. The behaviour observed in the samples is very interesting because the zirconium oxide has attracted the interest of many research groups, this material has demonstrated to have many applications in thermoluminescent dosimetry and it can be used in the quantification of radiation. (Author)

  14. Influence of M{sub g}O SIO{sub 2} in sintering behavior of Al{sub 2}TiO{sub 5} ceramics; Influencia de M{sub g}O e SiO{sub 2} nas caracteristicas de ceramicas a base de Al{sub 2}TiO{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Guedes-Silva, C.C.; Zaninelli, G.; Genova, L.A., E-mail: cecilia.guedes@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Carvalho, F.M.S. [Universidade de Sao Paulo (IGC/USP), SP (Brazil). Instituto de Geociencias

    2012-07-01

    Aluminum titanate based ceramics (Al{sub 2}TiO{sub 5}) are very appreciated by exhibiting high thermal shock resistance owing to their low thermal conductivity, low Young's modulus and low coefficient of thermal expansion. However, it is very difficult to obtain dense components of Al{sub 2}TiO{sub 5} due to anisotropy of thermal expansion and susceptibility to phase dissociation in temperature range between 1000 and 1300 deg C. In this paper, the effect of SiO{sub 2} and MgO additions are evaluated considering densification, microstructure and thermal expansion coefficient of aluminum titanate ceramics. Samples with different contents of additives and sintered at 1600 deg C for 1 h were analyzed by X ray powder diffraction, scanning electron microscopy and dilatometry. The results showed that the sintered materials are formed by equiaxial grains of Al{sub 2}TiO{sub 5} with residual content of Al{sub 2}O{sub 3}. Moreover, these additives changed the grains size distribution, the coefficient of thermal expansion and the densification of materials. (author)

  15. Master sintering curves for UO{sub 2} and UO{sub 2}–SiC composite processed by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhichao [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Subhash, Ghatu, E-mail: subhash@ufl.edu [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Tulenko, James S. [Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2014-11-15

    Highlights: • Constructed master sintering curves for spark plasma sintering (SPS) of nuclear fuels. • Characterized sinterability of UO{sub 2} and UO{sub 2}–SiC powder compacts during SPS. • Determined activation energies for sintering of UO{sub 2} and UO{sub 2}–SiC composites by SPS. - Abstract: Master sintering curve (MSC) theory has been applied successfully to UO{sub 2} and UO{sub 2}–SiC composite ceramics processed using spark plasma sintering (SPS). By applying the constant heating rate method, where the powder compact was heated at a constant rate to a specified maximum temperature and then cooled naturally, the apparent activation energies for sintering have been determined to be 140 kJ/mol for UO{sub 2} and 420 kJ/mol for UO{sub 2}–SiC composite. The ability of the derived MSCs to control and predict final density in the sintered compact was demonstrated by additional experimental runs using the isothermal heating method, in which the powder is held for a specified time at the maximum sintering temperature. It is shown that the master sintering curve is an effective tool to characterize the densification and sinterability behavior of a given nuclear powder compact during spark plasma sintering. The reason for significantly lower activation energy in SPS processed UO{sub 2} pellets compared to conventional sintering has been rationalized on the basis of field activation in SPS process.

  16. Microwave Sintering of Electroless Ni Plated WC Powders

    OpenAIRE

    EROL, Ayhan; YONETKEN, Ahmet

    2010-01-01

    Nickel matrix reinforced with WC has been manufactured by microwave sintering at various temperatures. A uniform nickel layer on WC powders was deposited prior to sintering using electroless plating technique, allowing close surface contact than can be achieved using conventional methods such as mechanical alloying. The reactivity between WC powders to form compounds is controlled through Ni layer existing on the starting powders. A composite consisting of quaternary additions, a ceramic phas...

  17. Prospective Comparison of a Metal-Free Ceramic Total Knee Arthroplasty with an Identical Metal System.

    Science.gov (United States)

    Trieb, Klemens; Ullmann, David; Metzinger, Katharina; Kramar, Reinhard; Mauerer, Andreas; Hofstätter, Stefan; Fiala, Rainer

    2018-02-01

    The aim of this open-label, prospective, short-term study was to carry out an initial comparison of a completely metal-free ceramic with a geometrically identical metallic arthroplasty over a 1-year follow-up period. This study investigates a completely metal-free system using a composite matrix material containing aluminum oxide (Al 2 O 3 , BPK-S Integration, Peter Brehm GmbH, Weisendorf, Germany) or zirconium oxide (ZrO 2 , BPK-S Integration Ceramic, Biolox Delta-CeramTec GmbH, Plochingen, Germany). Eighty patients (40 in each group) received either a completely metal-free ceramic system (matrix of aluminum and zirconium oxide) or an anatomically identical metallic knee system made of a cobalt-chromium alloy. Clinical assessment was performed preoperatively, and during follow-up at 3 and 12 months, using the Knee Society Score, Oxford Knee Score, and EQ-5D-VAS. For radiological evaluation, standard preoperative and postoperative standardized radiographs were taken at the given follow-up visits. The postoperative clinical scores improved significantly at the 3- and 12-month follow-ups, but did not differ statistically between the two groups. The radiologically evaluated mean postoperative mechanical and anatomical axes showed proper alignment within both groups at all times. No revision surgery had to be performed, and no complications or loosening were recorded whatsoever. To our knowledge, this is the first study comparing a total ceramic metal-free knee system with a geometrically identical metallic TKA (total knee arthroplasty). Longer follow-ups will be required to demonstrate the overall efficiency of this TKR and perhaps to expand its medical indication. Georg Thieme Verlag KG Stuttgart · New York.

  18. Comparative Study of Shear Bond Strength of Three Veneering Ceramics to a Zirconia Core

    Directory of Open Access Journals (Sweden)

    Aalaei Sh

    2016-03-01

    Full Text Available Statement of Problem: Fracture of veneering porcelain has been described as the most frequent reason for the failure of zirconia-based fixed restorations. Objectives: The purpose of this study was to evaluate and compare the shear bond strength of a zirconium oxide core material to three commercial veneering ceramics. Materials and Methods: Three types of veneering ceramics were selected including IPS -emax Ceram, Vita VM9, and Cerabien. Thirty block specimens of zirconia core material were prepared in 4×4×9 mm dimensions. Three groups were created and the veneering ceramic was added to each of 10 blocks. Shear bond test was conducted with universal testing machine. Data were analyzed using one-way ANOVA (p = 0.05. Results: Mean shear bond strength values and standard deviations were 26.03 MPa (6.32, 23.85 MPa (4.01, and 19.16 MPa (3.72 for Vita VM9, IPS emax Ceram, and Cerabien, respectively. Cerabien ceramic showed more failure as compared to the other ceramics. However, there was no significant difference among the three veneering groups. Conclusions: Within the limitation of this study, it can be concluded that shear bond strength between zirconia core and three veneering ceramics was not significantly different.

  19. Fabrication of sinterable silicon nitride by injection molding

    Science.gov (United States)

    Quackenbush, C. L.; French, K.; Neil, J. T.

    1982-01-01

    Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

  20. Process for Making a Ceramic Composition for Immobilization of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Ebbinghaus, Bartley B.; Van Konynenburg, Richard A.; Vance, Eric R.; Stewart, Martin W.; Walls, Philip A.; Brummond, William Allen; Armantrout, Guy A.; Curtis, Paul G.; Hobson, Beverly F.; Farmer, Joseph; Herman, Connie Cicero; Herman, David Thomas

    1999-06-22

    Disclosed is a process for making a ceramic composition for the immobilization of actinides, particularly uranium and plutonium. The ceramic is a titanate material comprising pyrochlore, brannerite and rutile. The process comprises oxidizing the actinides, milling the oxides to a powder, blending them with ceramic precursors, cold pressing the blend and sintering the pressed material.

  1. Advanced Ceramic Technology for Space Applications at NASA MSFC

    Science.gov (United States)

    Alim, Mohammad A.

    2003-01-01

    The ceramic processing technology using conventional methods is applied to the making of the state-of-the-art ceramics known as smart ceramics or intelligent ceramics or electroceramics. The sol-gel and wet chemical processing routes are excluded in this investigation considering economic aspect and proportionate benefit of the resulting product. The use of ceramic ingredients in making coatings or devices employing vacuum coating unit is also excluded in this investigation. Based on the present information it is anticipated that the conventional processing methods provide identical performing ceramics when compared to that processed by the chemical routes. This is possible when sintering temperature, heating and cooling ramps, peak temperature (sintering temperature), soak-time (hold-time), etc. are considered as variable parameters. In addition, optional calcination step prior to the sintering operation remains as a vital variable parameter. These variable parameters constitute a sintering profile to obtain a sintered product. Also it is possible to obtain identical products for more than one sintering profile attributing to the calcination step in conjunction with the variables of the sintering profile. Overall, the state-of-the-art ceramic technology is evaluated for potential thermal and electrical insulation coatings, microelectronics and integrated circuits, discrete and integrated devices, etc. applications in the space program.

  2. ceramics by differential scanning calorimetry

    Indian Academy of Sciences (India)

    Administrator

    YbxGd2–xZr2O7 (x = 0, 1, 2) ceramics were pressureless-sintered using ceramic powders acquired by chemical-coprecipitation and calcination methods. Heat capacities of YbxGd2–xZr2O7 were measured with a heat flux-type differential scanning calorimetry in the temperature range of 298–1200 K. At 298 K, the heat.

  3. Activation of consolidation processes of alumina ceramics

    Science.gov (United States)

    Matrenin, S. V.; Zenin, B. S.; Tayukin, R. V.

    2016-02-01

    The methods for activating sintering ceramics based on Al2O3 by mechanical activation in the planetary mill, by adding in the mixture of nanopowders (NP) Al, Al2O3, and submicron powder TiO2, and by applying the technology of spark plasma sintering (SPS) are developed. It has been shown that adding the nanopowder up to 20 wt. % Al2O3 in a coarse powder α-Al2O3 activates the sintering process resulting in increased density and hardness of the sintered alumina ceramics. Substantial effect of increasing density of alumina ceramics due to adding the submicron powder TiO2 in the compound of initial powder mixtures has been established.

  4. Supported microporous ceramic membranes

    Science.gov (United States)

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  5. DC resistivity of alumina and zirconia sintered with TiC

    Indian Academy of Sciences (India)

    Pure alumina and zirconia powders were sintered separately with increasing amount of TiC up to ∼ 65 vol.%, as a conducting second phase with an aim to prepare conducting structural ceramics which can be precisely machined by EDM technique. TiC did not help in sintering the parent phase but it decreased the d.c. ...

  6. Microstructure and Electrical Properties of AZO/Graphene Nanosheets Fabricated by Spark Plasma Sintering

    OpenAIRE

    Yang, Shuang; Chen, Fei; Shen, Qiang; Enrique J. Lavernia; Zhang, Lianmeng

    2016-01-01

    In this study we report on the sintering behavior, microstructure and electrical properties of Al-doped ZnO ceramics containing 0?0.2 wt. % graphene sheets (AZO-GNSs) and processed using spark plasma sintering (SPS). Our results show that the addition of

  7. Influence of Europium Doping on Various Electrical Properties of Low-Temperature Sintered 0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu Lead-Free Ceramics

    Science.gov (United States)

    Tian, Yongshang; Li, Shuiyun; Sun, Shulin; Gong, Yansheng; Li, Tiantian; Yu, Yongshang; Jing, Qiangshan

    2018-01-01

    0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu (BCT-BZT-Cu- xEu; x = 0-0.90%) lead-free ceramics were sintered at 1220°C with as-synthesized nanoparticles by a modified Pechini method. The structural characteristics and electrical properties of the ceramics that were influenced by varying europium-doping were investigated. All the ceramics featured high densification (relative density: ˜ 96%). X-ray powder diffraction results indicated the samples possessed pure orthorhombic phase. The maximum relative permittivity ( ɛ r, 10869) was found at x around 0.30%. Europium ions could dope on different substitution sites in the ABO3 lattice, which evidently influenced electrical properties with various volumes of oxygen vacancy. Moreover, the formation mechanisms of oxygen vacancy and defect electron complexes were stated. The piezoelectric properties were impacted by defect electron complexes, internal stress, ionic electronegativity, etc. The optimal electrical properties, i.e., d 33 = 384 pC/N, Q m = 92, and k p = 0.36, were detected at x = 0.45%.

  8. Scratch resistance of SiO{sub 2} and SiO{sub 2} - ZrO{sub 2} sol-gel coatings on glass-ceramic obtained by sintering; Resistencia al desgaste de recubrimientos sol-gel de SiO{sub 2} y SiO{sub 2} - ZrO{sub 2} sobre materiales vitroceramicos obtenidos por sinterizacion

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-10-01

    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{sub 2}O-Al{sub 2}O3-SiO{sub 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)

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang Hao [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Qin Xianpeng [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Zhang Jian, E-mail: jianzhang@ntu.edu.sg [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang Shiwei [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Ma Jan [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang Lixi [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China); Zhang Qitu, E-mail: njzqt@126.com [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China)

    2011-04-28

    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 {alpha}-Al{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and Nd{sub 2}O{sub 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 {approx}10 {mu}m 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.

  10. Sintering and Electrical Characterization of La and Nb Co‐doped SrTiO3 Electrode Materials for Solid Oxide Cell Applications

    DEFF Research Database (Denmark)

    Sudireddy, Bhaskar Reddy; Agersted, Karsten

    2014-01-01

    Single‐phase lanthanum and niobium co‐doped strontium titanate (Sr1–3x/2LaxTi0.9Nb0.1O3; x = 0–0.02) ceramics were prepared. Dilatometry in reducing atmosphere showed an increase in the sintering rate and sintered density with an increase in La amount. Microscopy of fractured surfaces of sintered...

  11. Manufacturing tailored property ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Ewsuk, K.G. [Sandia National Labs., Albuquerque, NM (United States). Ceramic Processing Science Dept.; Harrison, L.W. [E.I. du Pont de Nemours and Co., Inc., Wilmington, DE (United States). Central Research and Development Dept.

    1994-11-14

    Composite materials are desirable for many advanced engineering applications where the properties of a single phase material cannot meet all of the service requirements; however, existing process technology has limited the development and commercialization of composites. Lack of reproducible sintering to high density is one of the major obstacles to commercializing ceramic composites. Final-stage, non-reactive liquid phase sintering (NLPS) theory provides metrics for sinterability that can be used as guidelines to design and manufacture dense ceramic-filled-glass (CFG) composites. Additionally, within the constraints defined by the NLPS theory, sum-property models can be used to predict CFG composite properties, and to design composites with properties tailored to specific applications. By integrating composite process models with composite property models, processable, application-tailored CFG composites for microelectronics packaging have been designed and fabricated.

  12. Sinterability of powders of parent glass ceramic belonging to the LZSA system treated by ion exchange; Sinterabilidade de pos de precursor vitroceramico do sistema LZSA tratados por troca ionica

    Energy Technology Data Exchange (ETDEWEB)

    Montedo, Oscar Rubem Klegues [Unidade Academica de Ciencias, Engenharias e Tecnologia, Universidade do Extremo Sul Catarinense (UNESC), Criciuma - SC (Brazil); Ronsani, Patricia; Oliveira, Antonio Pedro Novaes de [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Florianopolis - SC (Brazil)

    2012-07-01

    . Ion exchange method was employed by means of surface modification of the glass powders of LZSA (Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}-Al{sub 2}O{sub 3}) system submitted to a 70wt% NaNO{sub 3}/30wt% NaSO{sub 4} bath salt followed by a heat treatment. Chemical analysis by X-ray fluorescence was used to evaluate the efficiency of ion exchange, while optical dilatometry was employed to evaluate sintering of compacts. Evaluation of the structure of sintered bodies was made by scanning electron microscopy. Substitution of Li{sup +} ions by Na{sup +} ions on the surface of powders during heat treatments of 450 and 600 deg C for 2-10 h promoted an increase in densification of the sintered bodies. (author)

  13. Modeling sintering of multilayers under influence of gravity

    DEFF Research Database (Denmark)

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

    2013-01-01

    There is a tendency for multiple functional ceramic layers used in various applications to have increasing surface areas and decreasing thicknesses. Sintering samples with such geometry is challenging, as differential shrinkage of the layers causes undesired distortions. In this work, a model, wh...

  14. Method of making an air electrode material having controlled sinterability

    Science.gov (United States)

    Vasilow, Theodore R.; Kuo, Lewis J. H.; Ruka, Roswell J.

    1994-01-01

    A tubular, porous ceramic electrode structure (3) is made from the sintered admixture of doped lanthanum manganite and an additive containing cerium where a solid electrolyte (4), substantially surrounds the air electrode, and a porous outer fuel electrode (7) substantially surrounds the electrolyte, to form a fuel cell (1).

  15. Laser Sintered Calcium Phosphate Bone

    National Research Council Canada - National Science Library

    Vail, Neil

    1999-01-01

    ...) technology selective laser sintering (SLS). BME has successfully implemented a pilot facility to fabricate calcium phosphate implants using anatomical data coupled with the selective laser sintering process...

  16. Combined macro-meso scale modeling of sintering. Part II, Mesoscale simulations

    Energy Technology Data Exchange (ETDEWEB)

    TIKARE,VEENA; OLEVSKY,EUGENE A.; BRAGINSKY,MICHAEL V.

    2000-05-23

    A mesoscale kinetic Monte Carlo model is presented to simulate microstructural evolution during sintering of 2D complex microstructures which evolves by grain growth, pore migration and densification. No assumptions about the geometry of the evolving microstructure are made. The results of these simulations are used to generate sintering stress and normalize viscous bulk modulus for use in continuum level simulation of sintering. The advantage of these simulations is that they can be used to generate more accurate parameters as various assumptions regarding geometry and transport mechanism are made. The previous companion paper used the results from the mesoscale simulations to simulate shrinkage and warpage in sintering of bilayer ceramics.

  17. 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.

  18. Laser Sintering Technology and Balling Phenomenon.

    Science.gov (United States)

    Oyar, Perihan

    2017-10-13

    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.

  19. Aggregate Morphology Evolution by Sintering: Number & Diameter of Primary Particles.

    Science.gov (United States)

    Eggersdorfer, Max L; Kadau, Dirk; Herrmann, Hans J; Pratsinis, Sotiris E

    2012-04-01

    The structure of fractal-like agglomerates (physically-bonded) and aggregates (chemically- or sinter-bonded) is important in aerosol synthesis of nanoparticles, and in monitoring combustion emissions and atmospheric particles. It influences also particle mobility, scattering, and eventually performance of nanocomposites, suspensions and devices made with such particles. Here, aggregate sintering by viscous flow of amorphous materials (silica, polymers) and grain boundary diffusion of crystalline ceramics (titania, alumina) or metals (Ni, Fe, Ag etc.) is investigated. A scaling law is found between average aggregate projected area and equivalent number of constituent primary particles during sintering: from fractal-like agglomerates to aggregates and eventually compact particles (e.g. spheres). This is essentially a relation independent of time, material properties and sintering mechanisms. It is used to estimate the equivalent primary particle diameter and number in aggregates. The evolution of aggregate morphology or structure is quantified by the effective fractal dimension (Df ) and mass-mobility exponent (Dfm ) and the corresponding prefactors. The Dfm increases monotonically during sintering converging to 3 for a compact particle. Therefore Dfm and its prefactor could be used to gauge the degree or extent of sintering of agglomerates made by a known collision mechanism. This analysis is exemplified by comparison to experiments of silver nanoparticle aggregates sintered at different temperatures in an electric tube furnace.

  20. 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...

  1. Densification and dielectric properties of SrO–Al2O3–B2O3 ceramic ...

    Indian Academy of Sciences (India)

    The addition of B2O3 and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600°C with optimum density (∼ 4 g/cm3) as compared with pure alumina powders recycled from Al dross (3.55 g/cm3 sintered at ... Ceramic Department, National Research Centre, 12622 Dokki, Cairo, Egypt ...

  2. Effects of flux concentrations and sintering temperature on dental porcelain

    Science.gov (United States)

    Ghose, Polash; Gafur, Md. Abdul; Das, Sujan Kumar; Ranjan Chakraborty, Shyamal; Mohsin, Md.; Deb, Arun Kumar; Rakibul Qadir, Md.

    2014-02-01

    In this study, samples of dental porcelain bodies have been made by using the materials collected from selected deposits employing different mixing proportions of clay, quartz and feldspar. Dental porcelain ceramics have been successfully fabricated by using the sintering technique together with some Na2CO3 additive. The dental porcelain powder has been pressed into pellets at first and subsequently sintered at 700, 800, 900, 1000 and 1100 °C for 2 h. The physical and mechanical properties of the prepared samples have been investigated. The sintering behavior of the fired samples has been evaluated by bulk density, linear shrinkage, water absorption and apparent porosity measurements. This study includes the evaluation of the Vickers's microhardness by microhardness tester. Phase analysis and microstructural study have been performed by XRD and optical microscope respectively. Optical properties have been investigated using UV-visible spectroscopy. Influence of firing conditions on leucite formation, densification and microstructural development of the sintered samples has been investigated. It has been found that the choice of sintering temperature is one of the key factors in controlling leucite crystallization in dental porcelain ceramics. It has also been found that the flux concentration of material and the effect of temperature on preparation of dental porcelain contribute to the firing shrinkage and hardness, which has been found to increase with the increase of treatment temperature.

  3. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    Ceramic carbon composites were fabricated by colloidal processing using glucose as soluble carbon source.Glucose is converted into conducting carbon at high temperature treatment. Ceramic carbon composites were sintered inflowing argon at 1400◦C showing resistor behaviour even at low carbon content (1 wt%).

  4. Deposition of Crystalline Hydroxyapatite Nanoparticles on Y-TZP Ceramic: A Potential Solution to Enhance Bonding Characteristics of Y-TZP Ceramics

    Directory of Open Access Journals (Sweden)

    Abbas Azari

    2017-08-01

    Full Text Available Objectives: Many advantages have been attributed to dental zirconia ceramics in terms of mechanical and physical properties; however, the bonding ability of this material to dental structure and/or veneering ceramics has always been a matter of concern. On the other hand, hydroxyapatite (HA shows excellent biocompatibility and good bonding ability to tooth structure, with mechanically unstable and brittle characteristics, that make it clinically unacceptable for use in high stress bearing areas. The main purpose of this study was to introduce two simple yet practical methods to deposit the crystalline HA nanoparticles on zirconia ceramics. Materials and Methods: zirconia blocks were treated with HA via two different deposition methods namely thermal coating and air abrasion. Specimens were analyzed by scanning electron microscopy, energy dispersive spectroscopy (EDS and X-ray diffraction (XRD.Results: In both groups, the deposition techniques used were successfully accomplished, while the substrate showed no structural change. However, thermal coating group showed a uniform deposition of crystalline HA but in air abrasion method, there were dispersed thin islands of HA.Conclusions: Thermal coating method has the potential to significantly alter the surface characteristics of zirconia. The simple yet practical nature of the proposed method may be able to shift the bonding paradigm of dental zirconia ceramics. This latter subject needs to be addressed in future investigations.Keywords: Zirconium Oxide; Hydroxyapatites; Dental Bonding; Microscopy, Electron, Scanning; X-Ray Diffraction; Spectrometry, X-Ray Emission

  5. Ceramics as biomaterials for dental restoration.

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Watzke, Ronny; Peschke, Arnd; Kappert, Heinrich

    2008-11-01

    Sintered ceramics and glass-ceramics are widely used as biomaterials for dental restoration, especially as dental inlays, onlays, veneers, crowns or bridges. Biomaterials were developed either to veneer metal frameworks or to produce metal-free dental restorations. Different types of glass-ceramics and ceramics are available and necessary today to fulfill customers' needs (patients, dentists and dental technicians) regarding the properties of the biomaterials and the processing of the products. All of these different types of biomaterials already cover the entire range of indications of dental restorations. Today, patients are increasingly interested in metal-free restoration. Glass-ceramics are particularly suitable for fabricating inlays, crowns and small bridges, as these materials achieve very strong, esthetic results. High-strength ceramics are preferred in situations where the material is exposed to high masticatory forces.

  6. Liquid phase sintered SiC ceramics from starting materials of different grade Cerâmicas à base de SiC sinterizadas via fase líquida a partir de matérias-primas de diferentes purezas

    Directory of Open Access Journals (Sweden)

    V. A. Izhevskyi

    2004-09-01

    Full Text Available Possibility of high performance ceramics manufactured from commercial SiC powder of technical grade has been shown. Sintering behavior and microstructure formation under conditions of liquid phase sintering (LPS with oxynitride sintering aids (AlN-Y2O3 of three SiC-based compositions have been investigated. Two of the compositions were based on Alcoa 1000 SiC powder of technical grade, and the third one, which was used as a reference, was based on H.C. Starck UF-15 fine grade commercial powder. Milling process used for Alcoa 1000 SiC powder granulometry improvement has been investigated in detail, while chemical treatment of milled SiC powders has been used for pick-up impurities removal. Dilatometric experiments showed that SiC powder of technical grade after appropriate treatment exhibits sinterability comparable with the fine grade SiC. Microstructural investigations performed on sintered samples showed that the final microstructure of the Alcoa 1000 SiC based materials was practically identical with the H.C. Starck SiC based reference ones. Preliminary investigations of hardness and fracture toughness were carried out revealing excellent results for the materials produced from cheaper, nationally produced starting powder.Neste trabalho é apresentada a possibilidade de obtenção de cerâmicas de SiC de alto desempenho a partir de matéria-prima comercial de grau técnico. Foi realizado o estudo de sinterização via fase líquida e desenvolvimento microestrutural de três composições à base de SiC tendo como aditivos de sinterização AlN e Y2O3 . Duas destas composições são à base de SiC-1000 da Alcoa, grau técnico, e a terceira, utilizada como referência, à base do UF-15 da H.C. Starck - Alemanha, pó comercial de granulometria fina. O processo de moagem do pó SiC-1000 da Alcoa foi acompanhado por medidas de distribuição granulométrica e posterior ataque químico, para remoção de impurezas. Os pós de grau técnico, ap

  7. Effects of sintering temperatures on microstructure and wear resistance of iron-silica composite

    Science.gov (United States)

    Amir, Adibah; Mamat, Othman

    2015-07-01

    Ceramic particle reinforced into metal base matrix composite has been reported to produce higher strength and wear resistance than its alloys because the ceramic phases can strongly resist abrasion. In this study the iron matrix was reinforced with two compositions of 20 and 25 wt. % fine silica particles. The compacts were produced by using powder metallurgy fabrication technique and sintered at three sintering temperatures: 1000, 1100 and 1200°C. Effects of various sintering temperatures on microstructures and the composite's wear resistance were evaluated via optical and SEM microscopy. Both compositions were also subjected to ball-on-disk wear test. The results showed the reinforcement weight fraction of 20 wt.% of silica and sintering temperature at 1100°C exhibited better result, in all aspects. It possessed higher mechanical properties, it's microstructure revealed most intact reinforcing region and it displayed higher wear resistance during wear test.

  8. Solid state synthesis and sintering of monazite-type ceramics: application to minor actinides conditioning; Synthese par voie solide et frittage de ceramiques a structure monazite. Application au conditionnement des actinides mineurs

    Energy Technology Data Exchange (ETDEWEB)

    Bregiroux, D

    2005-11-15

    In the framework of the French law of 1991 concerning the nuclear waste management, several studies are undertaken to develop specific crystalline conditioning matrices. Monazite, a rare earth (TR{sup 3+}) orthophosphate with a general formula TR{sup 3+}PO{sub 4}, is a natural mineral containing significant amount of thorium and uranium. Monazite has been proposed as a host matrix for the minor actinides (Np, Am and Cm) specific conditioning, thanks to its high resistance to self irradiation and its low solubility. Its is now of prime importance to check the conservation of these properties on synthesized materials, which implies to master all the stages of the elaboration process, from the powder synthesis to the sintering of controlled microstructure pellets. This work can be divided into two main parts: The first part deals with the synthesis by high temperature solid state route of TR{sup 3+}PO{sub 4} powders (with TR{sup 3+} = La{sup 3+} to Gd{sup 3+}, Pu{sup 3+} and Am{sup 3+}). The chemical reactions occurring during the firing of starting reagents are described in the case of monazite with only one or several cations. From these results, a protocol of synthesis is described. The incorporation of tetravalent cations (Ce{sup 4+}, U{sup 4+}, Pu{sup 4+}) in the monazite structure was also studied. The second part of the present work deals with the elaboration of controlled density and microstructure monazite pellets and their related mechanical and thermal properties. The study of crushing and sintering is presented. For the first time, experimental results are confronted with theoretical models in order to deduce the densification and grain growth mechanisms. By the comprehension of the various physicochemical phenomena occurring during the various stages of the monazite pellets elaboration process (powder synthesis, crushing, sintering...), this work allowed the development of a protocol of elaboration of controlled microstructure monazite TR{sup 3+}PO{sub 4

  9. SinterHab

    Science.gov (United States)

    Rousek, Tomáš; Eriksson, Katarina; Doule, Ondřej

    2012-05-01

    This project describes a design study for a core module on a Lunar South Pole outpost, constructed by 3D printing technology with the use of in-situ resources and equipped with a bio-regenerative life support system. The module would be a hybrid of deployable (CLASS II) and in-situ built (CLASS III) structures. It would combine deployable membrane structures and pre-integrated rigid elements with a sintered regolith shell for enhanced radiation and micrometeorite shielding. The closed loop ecological system would support a sustainable presence on the Moon with particular focus on research activities. The core module accommodates from four to eight people, and provides laboratories as a test bed for development of new lunar technologies directly in the environment where they will be used. SinterHab also includes an experimental garden for development of new bio-regenerative life support system elements. The project explores these various concepts from an architectural point-of-view particularly, as they constitute the building, construction and interior elements. The construction method for SinterHab is based on 3D printing by sintering of the lunar regolith. Sinterator robotics 3D printing technology proposed by NASA JPL enables construction of future generations of large lunar settlements with little imported material and the use of solar energy. The regolith is processed, placed and sintered by the Sinterator robotics system which combines the NASA ATHLETE and the Chariot remotely controlled rovers. Microwave sintering creates a rigid structure in the form of walls, vaults and other architectural elements. The interior is coated with a layer of inflatable membranes inspired by the TransHab project. The life-support system is mainly bio-regenerative and several parts of the system are intrinsically multifunctional and serve more than one purpose. The plants for food production are also an efficient part of atmosphere revitalization and water treatment. Moreover

  10. Sintering behavior and microwave dielectric properties of a new ...

    Indian Academy of Sciences (India)

    63

    Sintering behavior and microwave dielectric properties of a new complex perovskite: (1–x)(Sr0.3Ca0.427Nd0.182)TiO3-xSmAlO3 ceramics. JING JING QU1, FEI LIU2,*, XING WEI1, CHANG LAI YUAN3, XIAN PEI. HUANG3. 1Department of Information Engineering, Guilin University of Aerospace. Technology, Guilin 541004 ...

  11. Sintering behaviour and microwave dielectric properties of a new ...

    Indian Academy of Sciences (India)

    X-ray diffraction patterns illustrated that solid solutions with the orthorhombic perovskite were shown to be formed in the ranges of 0.05 ≤ x ≤ 0.4 . Moreover, the dielectric constant ( ϵ r ) of sintered ceramics had a quasi-linear decrease with the increase in SmAlO 3 content. A certain amount of Sm and Al substitution for A- ...

  12. Microwave Sintering and Its Application on Cemented Carbides

    OpenAIRE

    Rumman Md Raihanuzzaman; Lee Chang Chuan; Zonghan Xie; Reza Ghomashchi

    2015-01-01

    Cemented carbides, owing to their excellent mechanical properties, have been of immense interest in the field of hard materials for the past few decades. A number of processing techniques have been developed to obtain high quality carbide tools, with a wide range of grain size depending on the application and requirements. Microwave sintering is one of the heating processes, which has been used to prepare a wide range of materials including ceramics. A deep understanding ...

  13. 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.

  14. Fuel electrode containing pre-sintered nickel/zirconia for a solid oxide fuel cell

    Science.gov (United States)

    Ruka, Roswell J.; Vora, Shailesh D.

    2001-01-01

    A fuel cell structure (2) is provided, having a pre-sintered nickel-zirconia fuel electrode (6) and an air electrode (4), with a ceramic electrolyte (5) disposed between the electrodes, where the pre-sintered fuel electrode (6) contains particles selected from the group consisting of nickel oxide, cobalt and cerium dioxide particles and mixtures thereof, and titanium dioxide particles, within a matrix of yttria-stabilized zirconia and spaced-apart filamentary nickel strings having a chain structure, and where the fuel electrode can be sintered to provide an active solid oxide fuel cell.

  15. Effect of ultrashort pulsed laser on bond strength of Y-TZP zirconia ceramic to tooth surfaces.

    Science.gov (United States)

    Unal, Server Mutluay; Nigiz, Remzi; Polat, Zelal Seyfioglu; Usumez, Aslıhan

    2015-01-01

    There is limited knowledge about the effects of ultrashort pulsed laser on zirconia ceramic surfaces. The aim of this study was to evaluate the effects of ytterbium (Yb)-doped fiber laser and other surface treatment methods -namely, sandblasting with 110 µm aluminum oxide or 30 µm silica-coated alumina on shear bond strength (SBS) of zirconia to tooth surface. A total of 128 zirconium oxide disks were made by using CAD-CAM technology. Disk surfaces were sandblasted with Al2O3 particles or silica-coated alumina or irradiated with Yb-doped fiber based nanosecond pulsed laser at 85W output power at 25 kHz. Disks were luted to dentin using two different resin cement. SBS of each specimen was measured. Results were statistically analyzed using two-way analysis of variance (ANOVA) and Bonferroni and Dunnett tests (plaser regardless of the resin cement used.

  16. 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.

  17. 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.

  18. 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.

  19. Influence of granule characteristics on fabrication of translucent alumina ceramics with high strength and reliability

    National Research Council Canada - National Science Library

    TANAKA, Satoshi; GOI, Shota; KATO, Zenji

    2016-01-01

      Translucent alumina ceramics with high strength and reliability were fabricated through dry pressing of industry-grade granules and subsequent vacuum-sintering prior to hot isostatic pressing (HIP...

  20. Synthesis and Sintering of ZnO Nanopowders

    Directory of Open Access Journals (Sweden)

    Anne Aimable

    2017-05-01

    Full Text Available Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders’ nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv50~60 nm, easily redispersable by using a continuous Segmented Flow Tubular Reactor (SFTR, which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a “scale-out” concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 °C and 1100 °C, and Spark Plasma Sintering (SPS at 900 °C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 °C, while also limiting the grain growth, thus leading to a nanostructured material.

  1. Study of hydroxyapatite behaviour during sintering of 316L steel

    Directory of Open Access Journals (Sweden)

    A. Szewczyk-Nykiel

    2010-07-01

    Full Text Available 316L stainless steel – hydroxyapatite composite biomaterials with different hydroxyapatite weight fraction in the composite wereinvestigated. Hydroxyapatite (HAp – Ca10(PO46(OH2 is well known biomaterial. HAp reveals excellent chemical and biological affinitywith bony tissues. On the other hand hydroxyapatite shows low mechanical properties. The combination of very good biocompatibility of hydroxyapatite and high mechanical properties of stainless steel seems to be a good solution. In presented research natural originhydroxyapatite and 316L austenitic stainless steel were used. In this work, metal-ceramics composites were fabricated by the powdermetallurgy technology (involving pressing and sintering process. Sintering was carried out at 1250oC in hydrogen atmosphere. Thedensity, porosity and hardness were investigated. Metallographic microscope and SEM were carried out in order to investigate themicrostructure. The horizontal NETZSCH DIL 402E dilatometer was used to evaluate the dimensional changes and phenomena occurringduring sintering. The research displayed that physical properties of sintered 316L-HAp composites decrease with increase ofhydroxyapatite content. Microstructure of investigated composites consists of austenitic and probably inclusions of hydroxyapatite andheterogeneous eutectic occurring on the grain boundaries. It was shown that amount of hydroxyapatite in the powder mixtures influencethe dimensional changes occurring during sintering.

  2. PENGARUH SUHU SINTERING TERHADAP SIFAT MEKANIK KERAMIK BERBAHAN LEMPUNG DAN ABU SEKAM PADI

    Directory of Open Access Journals (Sweden)

    sadang Husain

    2016-02-01

    Full Text Available Abstract.  Study about the influence of sintering temperature on mechanical properties of ceramics has been done using clay and rice husk ash. Limitation of mechanical properties tested is the comppressive strength. This is done in order to determine the effect of variation of sintering temperature to compressive strength of ceramic with clay and rice husk ash. In addition, the calculation of fuel density and shrinkage also performed in this study. Variation in the composition of clay and rice husk ash is made to see the maximum composition of these materials. The result shows that the density of the ceramic material on the composition of  clay and rice husk ash volume 100: 0, 90:10, 80:20, 70:30, 60:40, and 50:50 are 2.14; 2.01; 1.98; 1.88; 1.84; and 1.78 g / cm3 respectively. Shrinkage of ceramic material has ranges between 3.4% -11.4%. The value of maximum compressive strength of clay and rice husk ash ceramic at 7000C, 8000C, and 9000C sintering temperature are 115.58; 115.58, and 128.42 kg / cm3. This value conforms the standard if used for bricks. The greater the sintering temperature, the higher the compressive strength of the ceramic. The best composition of clay and rice husk ash is 70:30. This ceramic can be used as building material, especially in the swampy area because it has a lighter weight.   Keywords: Ceramics, Clay, Rich husk ash, comppressive strength

  3. The Effect of MnO2 Content and Sintering Atmosphere on The Electrical Properties of Iron Titanium Oxide NTC Thermistors using Yarosite

    Science.gov (United States)

    Wiendartun; Gustaman Syarif, Dani

    2017-02-01

    The effect of MnO2 content and sintering atmosphere on the characteristics of Fe2TiO5 ceramics for Negative Thermal Coefficient (NTC) thermistors by using Fe2O3 derived from yarosite has been studied. The ceramics were produced by pressing a homogeneous mixture of Fe2O3, TiO2 and MnO2 (0-2.0 w/o) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1100-1200°C for 3 hours in air, O2 and N2 gas. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 30°C to 200°C. Microstructure and structural analyses were also carried out by using an scanning electron microscope (SEM) and x-ray diffraction (XRD). The XRD data showed that the pellets crystallize in orthorhombic. The presence of second phase could not be identified from the XRD analyses. The SEM images showed that the grain size of pellet ceramics increase with increasing of MnO2 addition, and the grains size of the ceramic sintered in oxygen gas is smaller than sintered in nitrogen gas. Electrical data showed that the value of room temperature resistance (RRT) tend to decrease with respect to the increasing of MnO2 addition and the pellet ceramics sintered in oxygen gas had the largest thermistor constant (B), activation energy (Ea), sensitivity (α) and room temperature resistance (RRT), compared to the sintered in nitrogen gas. From the electrical characteristics data, it was known that the electrical characteristics of the Fe2TiO5 pellet ceramics followed the NTC characteristic. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 2207-7145K). This can be applied as temperature sensor, and will fulfill the market requirement.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon-Geun, E-mail: hglee@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Kim, Daejong [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Lee, Seung Jae [KEPCO Nuclear Fuel, 242, Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Park, Ji Yeon; Kim, Weon-Ju [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of)

    2017-01-15

    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{sub 2}O{sub 3} and Y{sub 2}O{sub 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.

  5. Liquid Phase Sintering

    Science.gov (United States)

    2004-01-01

    Industry spends billions of dollars each year on machine tools to manufacture products out of metal. This includes tools for cutting every kind of metal part from engine blocks to Shuttle main engine components. Cutting tool tips often break because of weak spots or defects in their composition. Based on a new concept called defect trapping, space offers a novel environment to study defect formation in molten metal materials as they solidify. After the return of these materials from space, researchers can evaluate the source of the defect and seek ways to eliminate them in products prepared on Earth. A widely used process for cutting tip manufacturing is liquid phase sintering. Compared to Earth-sintered samples which slump due to buoyancy induced by gravity, space samples are uniformly shaped and defects remain where they are formed. By studying metals sintered in space the US tool industry can potentially enhance its worldwide competitiveness. The Consortium for Materials Development in Space along with Wyle Labs, Teledyne Advanced Materials, and McDornell Douglas have conducted experiments in space.

  6. Electrical properties and sensing ability of novel piezoelectric ceramic fibers with Pt core

    Science.gov (United States)

    Du, Jianzhou; Qiu, Jinhao; Zhu, Kongjun; Ji, Hongli; Zhao, Huayun

    2012-04-01

    The traditional sintering method was used to sinter the pure and Fe2O3 doped 0.55Pb(Ni0.33Nb0.67)O3-0.45Pb(Zr0.3Ti0.7)O3 (abbreviate as PNN-PZT and PFNN-PZT, respectively) ceramics. The addition of Fe2O3 significantly improved the microstructure and electrical properties. Compared with pure PNN-PZT ceramics, higher dielectric and piezoelectric properties of d31~-390 pC/N, ɛ r ~6298 were obtained for the PFNN-PZT sample sintered at 1175°C for 2 h. Hence, the PFNN-PZT ceramics sample was selected to fabricate piezoelectric ceramic fibers with Pt core (PFC). Both the green fibers and bulk ceramics were sintered at 1150-1225°C for 2 h in a closed crucible, respectively. The effect of sintering temperature on the microstructure and electrical properties of the PFNN-PZT fibers was investigated. The optimal piezoelectric properties are obtained for the sample sintered at 1175°C for 2 h. The relative dielectric constant and piezoelectric constant show peak values of ɛ r~3683, d31~-197.4 pC/N, respectively. The PFC is a new type piezoelectric device, which can be used for sensors or actuators. The results of sensing experiment show that the piezoelectric ceramic fiber with Pt core has high sensitivity for the Lamb waves.

  7. Fabrication of translucent boron nitride dispersed polycrystalline silicon nitride ceramics

    Science.gov (United States)

    Joshi, B.; Fu, Z.; Niihara, K.; Lee, S. W.

    2011-03-01

    Optical transparency was achieved at infrared region and overall translucent silicon nitride was fabricated using hot press sintering (HPS). The increase in h-BN content decreased the optical transparency. Microstructral observations shows that the optical, mechanical and tribological properties of BN dispersed polycrystalline Si3N4 ceramics were affected by the density, α:β-phase ratio and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of α-Si3N4, AlN, MgO and h-BN at 1850°C. The composite contained from 0.25 to 2 mass % BN powder with sintering aids (9% AlN + 3% MgO). Maximum transmittance of 57% was achieved for 0.25 mass % BN doped Si3N4 ceramics. Fracture toughness was increased and wear volume and friction coefficient were decreased with increase in BN content.

  8. Development of ceramic coatings and application of their infrared radiation

    OpenAIRE

    RAKHIMOV RUSTAM KHAKIMOVICH; SAIDOV MUHTAR SAFARBAEVICH

    2016-01-01

    Smelting and sintering of the initial ceramics were performed at the Big Solar Furnace with thermal power of 1000 kW at 2500-2700°С. As the base of some ceramics CaMgSi2О6 or Al2O3 + CaZrO3 were used. The spectrum of the infrared radiation of ceramic coatings changed in depending on the introduced dopant oxides. The ceramics exhibit pulse or pulse pair infrared (IR) radiation which could be photoluminescence or thermal radiation. The attempt is made to explain pulse radiation supposing the po...

  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 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. Second report on sintering diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Swinkels, F.B.; Ashby, M.F.

    1980-04-01

    Sintering-mechanism diagrams are diagrams with axes of neck-size or density, and temperature, which identify the fields of dominance of each of the several mechanisms which contribute to sintering, and show the rate or extent of sintering that all the mechanisms, acting together, produce. The present paper incorporates certain new ideas about sintering into the diagrams: the coupling of boundary diffusion and surface diffusion; new criteria for the stages of sintering; and an approximate treatment of particle rearrangement. Diagrams showing how both the neck size and the density of compacts of wires and of spheres change with time and temperature are developed. Their use is illustrated by an analysis of a large body of sintering data for both wires and spheres of Ag, Cu, Ni, Fe, W, NaCl and Stainless Steel.

  11. 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.

  12. Anisotropy in shrinkage during sintering

    Directory of Open Access Journals (Sweden)

    Zavaliangos A.

    2006-01-01

    Full Text Available While significant progress in modeling of sintering has been accomplished since the original paper by Frenkel "Viscous flow of crystalline bodies under action of surface tension", there are still several issues that remain open. One of them is anisotropy during sintering. In this paper we present some recent developments that improve our understanding of sintering anisotropy based on simulations of a two- dimensional array of particles. A number of possible sources of anisotropy are examined and evaluated. .

  13. Sintering trials of analogues of americium oxides for radioisotope power systems

    Science.gov (United States)

    Watkinson, E. J.; Ambrosi, R. M.; Kramer, D. P.; Williams, H. R.; Reece, M. J.; Chen, K.; Sarsfield, M. J.; Barklay, C. D.; Fenwick, H.; Weston, D. P.; Stephenson, K.

    2017-08-01

    European Space Agency radioisotope power systems will use americium oxide as the heat source in pellet or disc form. The oxide form is yet to be decided. Sintering trials with CeO2 and Nd2O3 as analogues for AmO2 and Am2O3 were conducted. Spark plasma sintering (SPS) and cold-press-and-sinter methods were compared. Different sintering parameters and particle characteristics were investigated with commercial and synthesised powders. The synthesised powders contained lath-shaped particles, and batches with different particle sizes and specific surface areas were made and sintered. This is the first study in the public literature to report the sintering of lath-shaped CeO2. The targeted density range of 85-90% was met using both techniques. No ball-milling was required. Cold-pressing-and-sintering CeO2 produced intact discs. Large cracking was prevalent in the SPS discs. Some powders pressed more successfully than others. Powder morphology had a significant effect on the result but it was not possible to fully quantify the effects in this study. The cold-pressed-and-sintered CeO2 discs had comparable Vickers hardness values to a nuclear ceramic (UO2). The hardness values were greater than the spark plasma sintered CeO2 sample. Efforts to SPS near-net shaped pellets using CeO2 and Nd2O3 are reported. A follow on investigation was conducted to assess how the 85-90% T.D. target could be achieved. The aspect ratio impacts the sintering parameters and behaviour. The Vickers hardness of Nd2O3 is reported for the first time and compared to the results of sintered CeO2.

  14. Sintering of HDH Ti Powder

    Directory of Open Access Journals (Sweden)

    Kováčik Jaroslav

    2014-12-01

    Full Text Available Titanium powders prepared by hydro-dehydration process (HDH powder were pressure less sintered in vacuum oven at different temperatures, time and green density. The sintering properties of powders of two particle sizes - 30 and 150 microns were investigated. The usual powder metallurgical (PM results were observed, i.e., decreasing final porosity with increasing sintering temperature and time at constant heating rate. Higher green density leading to higher final density for both powder sizes was also observed. The obtained results will be used as comparative material for future sintering experiments of Ti based composites.

  15. 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.

  16. Slip-casting alumina ceramics for crown and bridge restorations.

    Science.gov (United States)

    Pröbster, L; Diehl, J

    1992-01-01

    The In-Ceram technique uses alumina ceramics and glass in a two-step firing procedure to create a high-strength core material for single-tooth restorations as well as small fixed partial dentures. Fine-grain alumina particles are sintered to form a porous substructure, which is infiltrated with molten glass. The combination of these two processes gives the material its outstanding properties. The sintering process is almost without shrinkage, providing an excellent fit, while the glass infiltration leaves practically no porosities, resulting in high strength.

  17. Characterization of ceramic powders used in the inCeram systems to fixed dental Prosthesis

    Directory of Open Access Journals (Sweden)

    Alexandra Almeida Diego

    2007-03-01

    Full Text Available InCeram (Vita Zahnfabrik- Germany is known as a high strength ceramic being used for core crowns and for fixed partial denture frameworks. InCeram system consists of slip-casting technique which is used for to build the framework, which is then pre-sintered obtaining an open-pore microstructure. The material gains its strength by infiltration of the lanthanum glass into the porous microstructure. In this work, commercial alumina (Al2O3, alumina-zirconia (Al2O3-ZrO2 and glasses lanthanum oxide-rich powders, used in InCeram system, were characterized, using x ray diffraction, dilatometry and scanning electron microscopy. The characteristics of these powders were related aiming to consider their substitution for new ceramic materials.

  18. Reactive Spark Plasma Sintering: Successes and Challenges of Nanomaterial Synthesis

    Directory of Open Access Journals (Sweden)

    Dina V. Dudina

    2013-01-01

    Full Text Available Spark plasma sintering (SPS, initially developed as an advanced sintering technique for consolidating nanopowders into nanostructured bulk materials, has been recently looked at in much broader perspective and gained a strong reputation of a versatile method of solid state processing of metals, ceramics, and composites. The powders in the SPS-dies experience the action of pulsed electric current and uniaxial pressure; they are heated at very high rates unachievable in furnace heating and sintered within shorter times and at lower temperatures than in conventional methods. The principle of SPS and convenient design of the facilities make it attractive for conducting solid state synthesis. In this paper, based on our own results and the literature data, we analyze the microstructure formation of the products of chemical reactions occurring in the SPS in an attempt to formulate the requirements to the microstructure parameters of reactant mixtures and SPS conditions that should be fulfilled in order to produce a nanostructured material. We present successful syntheses of nanostructured ceramics and metal matrix composite with nanosized reinforcements in terms of microstructure stability and attractive properties of the materials and discuss the challenges of making a dense nanostructured material when reaction and densification do not coincide during the SPS. In the final part of the paper, we provide an outlook on the further uses of reactive SPS in the synthesis of nanostructured materials.

  19. Investigations of the influence of the mode of fixation and aging on the fracture resistance of Cercon-crowns

    OpenAIRE

    Glävke, Rico

    2012-01-01

    The aim of this thesis was an investigation of the breaking resistance of Cercon all-ceramic crowns, which were fixed to natural teeth using various materials. 60 molars were prepared according to preparation guidelines and moulded for this purpose. These moulds were cast in plaster and wax caps were modelled on the stumps. These wax caps were transferred into zirconium oxide caps using the scanning and milling unit Cercon brain and the sintering furnace Cercon heat. A veneer of these framewo...

  20. 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)

  1. 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)

  2. Comparison of the bond strength of laser-sintered and cast base metal dental alloys to porcelain.

    Science.gov (United States)

    Akova, Tolga; Ucar, Yurdanur; Tukay, Alper; Balkaya, Mehmet Cudi; Brantley, William A

    2008-10-01

    The purpose of this study was to compare shear bond strengths of cast Ni-Cr and Co-Cr alloys and the laser-sintered Co-Cr alloy to dental porcelain. Dental porcelain was applied on two cast and one laser-sintered base metal alloy. Ten specimens were prepared for each group for bond strength comparison. ANOVA followed by Tukey HSD multiple comparison test (alpha=0.05) was used for statistical analysis. Fractured specimens were observed with a stereomicroscope to classify the type of failure after shear bond testing. While the mean shear bond strength was highest for the cast Ni-Cr metal-ceramic specimens (81.6+/-14.6 MPa), the bond strength was not significantly different (P>0.05) from that for the cast Co-Cr metal-ceramic specimens (72.9+/-14.3 MPa) and the laser-sintered Co-Cr metal-ceramic specimens (67.0+/-14.9 MPa). All metal-ceramic specimens prepared from cast Ni-Cr and Co-Cr alloys exhibit a mixed mode of cohesive and adhesive failure, whereas five of the metal-ceramic specimens prepared from the laser-sintered Co-Cr alloy exhibited the mixed failure mode and five specimens exhibited adhesive failure in the porcelain. The new laser-sintering technique for Co-Cr alloy appears promising for dental applications, but additional studies of properties of the laser-sintered alloy and fit of castings prepared by this new technique are needed before its acceptance into dental laboratory practice. Laser sintering of Co-Cr alloy seems to be an alternative technique to conventional casting of dental alloys for porcelain fused to metal restorations.

  3. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  4. 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.

  5. Microstructure and properties of gravity sintered 316l stainless steel powder with nickel boride addition

    Directory of Open Access Journals (Sweden)

    Božić Dušan

    2016-01-01

    Full Text Available The present work demonstrates a procedure for synthesis of stainless steel powder by gravity sintering method. As an additive to the basic powder, NiB powder was added in the amount of 0.2 - 1.0 wt.%. Gravity sintering was done in vacuum, at the temperatures of 1100°C-1250°C, in the course of 3 - 60 min, using ceramic mould. Structural characterization was conducted by XRD, and microstructural analysis by optical and scanning electron microscope (SEM. Mechanical properties were investigated by tensile tests with steel rings. Density and permeability were determined by standard techniques for porous samples. Gravity sintered stainless steel with NiB addition had more superior mechanical and physico-chemical properties compared to stainless steel obtained by standard powder metallurgy procedures - pressing and sintering. [Projekat Ministarstva nauke Republike Srbije, br. 172005

  6. 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.

  7. 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.

  8. 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.

  9. A combined SEM, CV and EIS study of multi-layered porous ceramic reactors for flue gas purification

    DEFF Research Database (Denmark)

    He, Zeming; Andersen, Kjeld Bøhm; Nygaard, Frederik Berg

    2013-01-01

    The effect of sintering temperature of 12-layered porous ceramic reactors (comprising 5 cells) was studied using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The difference in microstructures of the reactors was evaluated by SEM...

  10. Ceramic films produced by a gel-dipping process

    Energy Technology Data Exchange (ETDEWEB)

    Santacruz, I.; Ferrari, B.; Nieto, M.I.; Moreno, R. [Instituto de Ceramica y Vidrio, CSIC, Camino de Valdelatas s/n, E-28049 Madrid (Spain)

    2003-09-01

    A novel method for manufacturing self-supporting ceramic films is based on the use of aqueous suspensions containing low concentrations of a biopolymer (carrageenan) and the formation of the film by immersion of a graphite substrate into the ceramic suspension heated at 60 C. A film is obtained by dipping after cooling at RT; burning out graphite during sintering leaves homogeneous, dense, and self-supported films (see Figure for an SEM image). (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  11. NDE for heat engine ceramics

    Science.gov (United States)

    Klima, S. J.

    1984-01-01

    Radiographic, ultrasonic, and scanning laser acoustic microscopy (SLAM) techniques were used to characterize silicon nitride and silicon carbide MOR bars in various stages of fabrication. Conventional and microfocus x-ray techniques were found capable of detecting minute high density inclusions in as-received powders, green compacts, and fully densified specimens. Significant density gradients in sintered bars were observed by radiography, ultrasonic velocity, and SLAM. Ultrasonic attenuation was found sensitive to microstructural variations due to grain and void morphology and distribution. SLAM was also capable of detecting voids, inclusions, and cracks in finished test bars. It was determined that thermoacoustic microscopy techniques have promise for application to green and densified ceramics.

  12. Fabrication of transparent ceramics using nanoparticles

    Science.gov (United States)

    Cherepy, Nerine J; Tillotson, Thomas M; Kuntz, Joshua D; Payne, Stephen A

    2012-09-18

    A method of fabrication of a transparent ceramic using nanoparticles synthesized via organic acid complexation-combustion includes providing metal salts, dissolving said metal salts to produce an aqueous salt solution, adding an organic chelating agent to produce a complexed-metal sol, heating said complexed-metal sol to produce a gel, drying said gel to produce a powder, combusting said powder to produce nano-particles, calcining said nano-particles to produce oxide nano-particles, forming said oxide nano-particles into a green body, and sintering said green body to produce the transparent ceramic.

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

    Directory of Open Access Journals (Sweden)

    Hossein Bagheri

    2016-05-01

    Full Text Available Objectives: 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.Materials and Methods: 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.Results: 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 (P<0.05. Sandblasting significantly increased the BFS for the zirconia (P<0.05, but the BFS was significantly decreased after laser irradiation (P<0.05.    Conclusions: The BFS of the machinable ceramics 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. 

  14. 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.

  15. Solution combustion synthesis: Effect of calcination and sintering temperature on structural, dielectric and ferroelectric properties of five layer Aurivillius oxides

    Science.gov (United States)

    Dubey, Shivangi; Subohi, Oroosa; Kurchania, Rajnish

    2017-09-01

    The effect of calcination temperature on phase formation and sintering temperature on structural, dielectric, electrical and ferroelectric properties of Ba2Bi4Ti5O18 (BBT), Pb2Bi4Ti5O18 (PBT) and Sr2Bi4Ti5O18 (SBT) ceramics prepared by solution combustion route using glycine as a fuel are investigated in this paper. Calcination temperature was optimized at 650 °C for BBT and 750 °C for SBT and PBT, at which these compounds showed pure phase formation. It was observed that density and grain size of the sintered pellets increases with increasing sintering temperature. The dielectric constant was found to be dependent on grain size and density. Transition temperature, activation energy and remnant polarization were found to increase with an increase in sintering temperature. Porosity and conductivity decreases with an increase in the sintering temperature. Thus improving the dielectric, electrical and ferroelectric properties of five layered Aurivillius oxides.

  16. 3D Mapping Of Density And Crack Propagation Through Sintering Of Catalysis Tablets By X-Ray Tomography

    DEFF Research Database (Denmark)

    Jacobsen, Hjalte Sylvest; Puig-Molina, A.; Dalskov, N.

    2016-01-01

    For hydrogen production, by steam reforming, porous ceramics are broadly used as catalyst support, due to their stability and ease in shaping. Catalyst supports in the form of tablets are conventionally produced by powder pressing and subsequent sintering. However, if the process is not done...... properly, cracks may arise and propagate during the sintering of the tablets. This can lead to weak sintered tablets that get rejected in the quality control. For this work, crack-containing samples of rejected tabletized support were provided. The formation, growth and closure of internal cracks during...... sintering of the rejected tabletized support material are studied by 3D X-ray tomography. This is a powerful technique, which due to its nondestructive nature is suitable to study the development of internal cracks in the tablets during sintering. Cracks could be identified in the green tablet (before...

  17. 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.

  18. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    Science.gov (United States)

    Wada, S.; Mase, Y.; Shimizu, S.; Maeda, K.; Fujii, I.; Nakashima, K.; Pulpan, P.; Miyajima, N.

    2011-10-01

    Porous potassium niobate (KNbO3, 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.

  19. Complex oxide with negative thermal expansion for producing ceramic matrix composites with invar effect

    Science.gov (United States)

    Dedova, Elena S.; Pertushina, Mariya U.; Kondratenko, Anton I.; Gorev, Mikhail V.; Kulkov, Sergei N.

    2016-11-01

    The article investigates the phase composition of (Al2O3-20 wt % ZrO2)-ZrW2O8 ceramic composites obtained by cold-pressing and sintering processes. Using X-ray analysis it has been shown that composites mainly have monoclinic modification of zirconium dioxide and orthorhombic phase of aluminum oxide. After adding zirconium tungstate the phase composition of sintered ceramics changes, followed by the formation of tungsten-aluminates spinel such as Alx(WOy)z. It has been shown that thermal expansion coefficient of material decreases approximatly by 30%, as compared with initial ceramics.

  20. [Ceramic posts].

    Science.gov (United States)

    Mainjot, Amélie; Legros, Caroline; Vanheusden, Alain

    2006-01-01

    As a result of ceramics and all-ceram technologies development esthetic inlay core and abutments flooded the market. Their tooth-colored appearance enhances restoration biomimetism principally on the marginal gingiva area. This article reviews indications and types of cores designed for natural teeth and implants.

  1. Models of current sintering

    Directory of Open Access Journals (Sweden)

    Angst Sebastian

    2017-01-01

    Full Text Available Densification of (semi-conducting particle agglomerates with the help of an electrical current is much faster and more energy efficient than traditional thermal sintering or powder compression. Therefore, this method becomes more and more common among experimentalists, engineers, and in industry. The mechanisms at work at the particle scale are highly complex because of the mutual feedback between current and pore structure. This paper extends previous modelling approaches in order to study mixtures of particles of two different materials. In addition to the delivery of Joule heat throughout the sample, especially in current bottlenecks, thermoelectric effects must be taken into account. They lead to segregation or spatial correlations in the particle arrangement. Various model extensions are possible and will be discussed.

  2. 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.

  3. Viscoelastic properties, gelation behavior and percolation theory model for the temperature induced forming (TIF) ceramic slurries

    Science.gov (United States)

    Yang, Yunpeng

    Controlled ceramic processing is required to produce ceramic parts with few strength-limiting defects and the economic forming of near net shape components. Temperature induced forming (TIF) is a novel ceramic forming process that uses colloidal processing to form ceramic green bodies by physical gelation. The dissertation research shows that TIF alumina suspensions (>40vol%) can be successfully fabricated by using 0.4wt% of ammonium citrate powder and ceramic parts have been successfully fabricated by direct casting using the TIF alumina suspensions, which has a relative density of ˜65%. The sintered sample at 1550°C for 2h is translucent and has a uniform grain size.

  4. Structural properties of a bone-ceramic composite as a promising material in spinal surgery

    Energy Technology Data Exchange (ETDEWEB)

    Kirilova, I. A., E-mail: IKirilova@mail.ru; Sadovoy, M. A.; Podorozhnaya, V. T., E-mail: VPodorognaya@niito.ru; Taranov, O. S. [Novosibirsk Research Institute of Traumatology and Orthopedics n.a. Ya.L. Tsivyan, Novosibirsk (Russian Federation); Klinkov, S. V.; Kosarev, V. F. [Christianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk (Russian Federation); Shatskaya, S. S. [Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Novosibirsk (Russian Federation)

    2015-11-17

    The paper describes the results of in vitro tests of composite bone-ceramic implants and procedures for modifying implant surfaces to enhance osteogenesis. Analysis of CBCI ESs demonstrated that they have a porous structure with the mean longitudinal pore size of 70 µm and the mean transverse pore size of 46 µm; surface pores are open, while inner pores are closed. Elemental analysis of the CBCI surface demonstrates that CBCIs are composed of aluminum and zirconium oxides and contain HA inclusions. Profilometry of the CBCI ES surface revealed the following deviations: the maximum deviation of the profile in the sample center is 15 µm and 16 µm on the periphery, while the arithmetical mean and mean square deviations of the profile are 2.65 and 3.4 µm, respectively. In addition, CBCI biodegradation products were pre-examined; a 0.9% NaCl solution was used as a comparison group. Potentially toxic and tissue accumulated elements, such as cadmium, cobalt, mercury, and lead, are present only in trace amounts and have no statistically significant differences with the comparison group, which precludes their potential toxic effects on the macroorganism. Ceramic-based CBCI may be effective and useful in medicine for restoration of the anatomic integrity and functions of the bone tissue.

  5. Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

    Science.gov (United States)

    Kwon, Taek-Ka; Pak, Hyun-Soon; Han, Jung-Suk; Lee, Jai-Bong; Kim, Sung-Hun

    2013-01-01

    PURPOSE All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS The mean fracture strengths were as follows: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (Pveneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain. PMID:23755332

  6. Engineering Ceramic Nanophosphors for Optical Applications

    Science.gov (United States)

    2009-06-11

    pellets and films on sintering − Optical blackening from residual free carbon • To overcome drawbacks of metal organic precursors − Fluorinating...Riman, JB Brown, KR Mikeska, J. Appl. Phys. 93:2946 (2003). Heavy Metal Fluoride Glass Formation • ZBLA and ZBLAN have better fiber drawing ability than...Riman, E Snitzer, J Amer. Ceram. Soc., 76:3147 (1993). Sol-Gel Precursor Selection • Metal organic precursors cause undersirable properties − “Foam

  7. Preparation and spectroscopic characterization of Lu 2O 3:Eu 3+ nanopowders and ceramics

    Science.gov (United States)

    Wang, Zhifang; Zhang, Weiping; Lin, Lin; You, Baogui; Fu, Yibing; Yin, Min

    2008-06-01

    Nanocrystalline Lu2O3 doping with different Eu3+ concentrations was prepared by co-precipitation method. The crystal structure and morphology were analyzed by means of XRD and HRTEM. The resultant powders were sintered into translucent ceramics in vacuum and then in nitrogen without any additive. The surface morphology of the unpolished sintered specimens was characterized using SEM. The excitation and emission spectra of Lu2O3:Eu3+ powders and ceramics were measured at room temperature by using synchrotron radiation as the light source. Pronounced changes of the spectroscopic properties with increasing Eu3+ content were observed and the reasons were studied. The fluorescent lifetimes of nanopowders shortened obviously with increasing Eu content, but no such effect was observed for the sintered ceramics. Luminescence of ceramics samples decays faster than the corresponding nanopowders.

  8. Needs assessment for nondestructive testing and materials characterization for improved reliability in structural ceramics for heat engines

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.; McClung, R.W.; Janney, M.A.; Hanusiak, W.M.

    1987-08-01

    A needs assessment was performed for nondestructive testing and materials characterization to achieve improved reliability in ceramic materials for heat engine applications. Raw materials, green state bodies, and sintered ceramics were considered. The overall approach taken to improve reliability of structural ceramics requires key inspections throughout the fabrication flowsheet, including raw materials, greed state, and dense parts. The applications of nondestructive inspection and characterization techniques to ceramic powders and other raw materials, green ceramics, and sintered ceramics are discussed. The current state of inspection technology is reviewed for all identified attributes and stages of a generalized flowsheet for advanced structural ceramics, and research and development requirements are identified and listed in priority order. 164 refs., 3 figs.

  9. From micro to nano: properties and potential applications of micro- and nano-filled polymer ceramic composites in microsystem technology.

    Science.gov (United States)

    Hanemann, T; Boehm, J; Henzi, P; Honnef, K; Litfin, K; Ritzhaupt-Kleissl, E; Hausselt, J

    2004-08-01

    In microsystem technology, four important material classes are established either for the generation or the replication of microstructured surfaces: silicon, polymers, metals and ceramics. Composite materials consisting of a polymer matrix and ceramic fillers show improved thermomechanical properties in comparison to polymers and can be introduced as a new additional material class. The substitution of micro-sized ceramic fillers by nano-sized ceramics in composites has a strong influence on the composite's physical properties: the reduction of ceramic particle size down to the nanometre scale results in an improved sinter activity owing to the large surface area. The fabrication of dense ceramics is simplified and can be used for a rapid prototyping of microstructured ceramic parts. The addition of nano-sized ceramics with particle sizes of composites with modified refractive indices for use in polymer waveguides. The influence of the ceramic particle size, the ceramic content and different dispersion methods on the composite's physical properties are discussed.

  10. Microstructural optimization of solid-state sintered silicon carbide

    Science.gov (United States)

    Vargas-Gonzalez, Lionel R.

    Silicon carbide armor, manufactured through solid-state sintering, liquid-phase sintering, and hot-pressing, is being used by the United States Armed Forces for personal and vehicle protection. There is a lack of consensus, however, on which process results in the best-performing ballistic armor. Previous studies have shown that hot-pressed ceramics processed with secondary oxide and/or rare earth oxides, which exhibit high fracture toughness, perform well in handling and under ballistic impact. This high toughness is due to the intergranular nature of the fracture, creating a tortuous path for cracks and facilitating crack deflection and bridging. However, it has also been shown that higher-hardness sintered SiC materials might perform similarly or better to hot-pressed armor, in spite of the large fracture toughness deficit, if the microstructure (density, grain size, purity) of these materials are improved. In this work, the development of theoretically-dense, clean grain boundary, high hardness solid-state sintered silicon carbide (SiC) armor was pursued. Boron carbide and graphite (added as phenolic resin to ensure the carbon is finely dispersed throughout the microstructure) were used as the sintering aids. SiC batches between 0.25--4.00 wt.% carbon were mixed and spray dried. Cylindrical pellets were pressed at 13.7 MPa, cold-isostatically pressed (CIP) at 344 MPa, sintered under varying sintering soaking temperatures and heating rates, and varying post hot-isostatic pressing (HIP) parameters. Carbon additive amounts between 2.0--2.5 wt.% (based on the resin source), a 0.36 wt.% B4C addition, and a 2050°C sintering soak yielded parts with high sintering densities (˜95.5--96.5%) and a fine, equiaxed microstructure (d50 = 2.525 mum). A slow ramp rate (10°C/min) prevented any occurrence of abnormal grain growth. Post-HIPing at 1900°C removed the remaining closed porosity to yield a theoretically-dense part (3.175 g/cm3, according to rule of mixtures). These

  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. Mesoscale Thermodynamically motivated Statistical Mechanics based Kinetic Model for Sintering monoliths

    Science.gov (United States)

    Mohan, Nisha

    Modeling the evolution of microstructure during sintering is a persistent challenge in ceramics science, although needed as the microstructure impacts properties of an engineered material. Bridging the gap between microscopic and continuum models, kinetic Monte Carlo (kMC) methods provide a stochastic approach towards sintering and microstructure evolution. These kMC models work at the mesoscale, with length and time-scales between those of atomistic and continuum approaches. We develop a sintering/compacting model for the two-phase sintering of boron nitride ceramics and allotropes alike. Our formulation includes mechanisms for phase transformation between h-BN and c-BN and takes into account thermodynamics of pressure and temperature on interaction energies and mechanism rates. In addition to replicating the micro-structure evolution observed in experiments, it also captures the phase diagram of Boron Nitride materials. Results have been analyzed in terms of phase diagrams and crystal growth. It also serves with insights to guide the choice of additives and conditions for the sintering process.While detailed time and spatial resolutions are lost in any MC, the progression of stochastic events still captures plausible local energy minima and long-time temporal developments. DARPA.

  13. 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.

  14. 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.

  15. Investigation of TaC–TaB2 ceramic composites

    Indian Academy of Sciences (India)

    their composites [2]. Optimization of sintering conditions and microstructural parameters led to the following mechan- ical property: flexural strength ranging from 670 to 900 MPa for TaC-based ceramics [14]. In this work, the densification, microstructure, mechanical properties of TaC–TaB2 compos- ites were investigated.

  16. 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

  17. Effects of surface-finishing protocols on the roughness, color change, and translucency of different ceramic systems.

    Science.gov (United States)

    Akar, Gülcan Coşkun; Pekkan, Gürel; Çal, Ebru; Eskitaşçıoğlu, Gürcan; Özcan, Mutlu

    2014-08-01

    Surface-finishing protocols have a mechanical impact on ceramic surfaces that could eventually affect surface topography and light scattering. An optimum protocol is needed to avoid damaging the optical properties of ceramics. The purpose of this study was to determine the effects of different surface-finishing protocols on the surface roughness, color change, and translucency of ceramic and metal ceramic restorations. Standardized disk-shaped specimens (1.5 × 10 mm, n=128) were fabricated from 3 different ceramic core materials (aluminum oxide [Al2O3]-AL, zirconium oxide [ZrO2]-ZR, lithium disilicate [Li2Si2O5]-LIT), veneered (V) with dentin ceramics (n=32 per group), and placed in the following groups: ALV, ZRV, and LITV. The metal ceramic group acted as the control (n=32). Four different surface-finishing methods were tested. Airborne-particle abrasion with 50 μm Al2O3, polishing with adjustment kit, polishing with adjustment kit plus diamond polishing paste, and autoglazing (n=8 subgroup) were applied on the veneering ceramics. The specimens were analyzed with a profilometer for surface roughness, and color change and translucency were measured with a clinical spectrophotometer. Statistical analyses were performed with 1-way ANOVA and the Tukey honest significant difference tests (α=.05). Specimens treated with the airborne particle abrasion method showed significantly higher mean profilometer for surface roughness values in all groups (P.05). With the diamond polishing paste method, lower surface roughness values were achieved in the ZRV and metal ceramic groups acted as the control groups. Different surface-finishing methods affected the color change of the ceramic systems, except for ZRV. Surface-finishing protocols significantly affected the translucency values of the ALV, LITV, and metal ceramic groups (P<.05). No single surface-finishing protocol can be recommended to obtain the smoothest surface and the least color change without affecting

  18. Laser ceramics with rare-earth-doped anisotropic materials.

    Science.gov (United States)

    Akiyama, Jun; Sato, Yoichi; Taira, Takunori

    2010-11-01

    The fabrication of laser-grade anisotropic ceramics by a conventional sintering process is not possible owing to optical scattering at randomly oriented grain boundaries. In this Letter, we report the first (to our knowledge) realization of transparent anisotropic ceramics by using a new crystal orientation process based on large magnetic anisotropy induced by 4f electrons. By slip casting in a 1.4 T magnetic field and subsequent heat treatments, we could successfully fabricate laser-grade calcium fluorapatite ceramics with a loss coefficient of 1.5 cm(-1).

  19. Sintering of bi-layered porous structures: Stress development and shape evolution

    DEFF Research Database (Denmark)

    Ni, De Wei; Esposito, Vincenzo; Ramousse, Severine

    viscosity of layers was determined as a function of temperature and density using a vertical sintering approach. The distortion in the bi-layer configurations was experimentally recorded and compared with the analytical calculations. The sintering mismatch stress was calculated from both the camber......Ce0.9Gd0.1O1.95 (CGO) and (La, Sr)MnO3 (LSM) are electro-ceramics materials with high potential for several electrochemical applications such as solid Oxide Fuel Cell (SOFC), gas separation membranes, and flue gas purification application. In the latter case, these materials are shaped as thick...

  20. Investigation of Nanostructure Formation of Alumina by Magnetic Pulse Compression and Subsequent Spark Plasma Sintering

    Science.gov (United States)

    Kovaleva, I. V.; Zholnin, A. G.; Grigoryev, E. G.; Olevsky, E. A.

    Comparative analysis of the structure and properties of samples prepared from alumina nanopowder using conventional or magnetic pulse compression (MPC), and the subsequent spark plasma sintering (SPS) was performed. In sintered corundum first identified the presence of areas with bimodal structure and the regularities of their formation. It was concluded that one of the most promising technologies for creating nanostructured ceramics is the application of the MPC and the SPS. Alumina submicron structure was obtained with a grain size of about 200-300 nm. The relative density of these samples determined by hydrostatic method was 95-96% of the theoretical.

  1. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

    This is a comprehensive book applying especially to junior and senior engineering students pursuing Materials Science/ Engineering, Ceramic Engineering and Mechanical Engineering degrees. It is also a reference book for other disciplines such as Chemical Engineering, Biomedical Engineering, Nuclear Engineering and Environmental Engineering. Important properties of most engineering ceramics are given in detailed tables. Many current and possible applications of engineering ceramics are described, which can be used as a guide for materials selection and for potential future research. While covering all relevant information regarding raw materials, processing properties, characterization and applications of engineering ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  2. Transparent ceramic scintillators for gamma-ray spectroscopy and radiography

    Energy Technology Data Exchange (ETDEWEB)

    Cherepy, Nerine

    2010-01-01

    Transparent ceramics have become available in useful sizes for a variety of applications within the past 15 years thanks to improved understanding of sintering phenomena on the nanoscale.1,2 While traditional ceramics may comprise single or multiple crystalline and amorphous mineral phases and are typically translucent or opaque to light, modern optically transparent ceramics are fully dense monoliths of micron-scale (or smaller) crystallites, in most cases formed from pure-phase cubic crystal structures. Fabrication of transparent ceramics begins with high-purity ceramic nanopowders, which are consolidated into a ‘green body’ by pressing or casting. The green body is sintered to near-full density, and the residual porosity is removed by processing the samples in a pressure vessel with high-pressure argon gas (hot isostatic pressing). A few commercial transparent ceramics are Lumicera lenses (a barium-based oxide made by Murata Mfg.), laser gain media—Nd:YAG (neodymium-doped yttrium aluminum garnet) is available from Konoshima—and transparent armor (aluminum oxynitride and spinel are available from Surmet and other vendors). As the manufacturing processes for transparent ceramics become better understood, industrial optical uses for these transparent materials with excellent mechanical robustness are likely to expand.

  3. 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)

  4. Effect of calcium phosphate addition on sintering of El-Oued sand quartz raw materials

    Directory of Open Access Journals (Sweden)

    L. Foughali

    2014-12-01

    Full Text Available This work addresses the development of an eventual low cost ceramic insulating or microfiltration membrane supports from inexpensive raw materials such Eloued quartz sand (EQS and calcium phosphate (CP using uniaxially dry compaction method. The prepared samples were sintered at different temperatures ranging between 1200 and 1550 ºC. Subsequently, the effects of sintering temperature and amount of CP on samples proprieties were investigated. It is observed that X-ray diffracion measurements confirmed that EQS was transformed into cristobalite and tridymite phases when both sintering temperature and holding time were increased. This transformation is favored with increasing amount of CP, it is observed also formation of CaSiO3 and Ca(Fe(AlPO4. The SEM images of the samples sintered at different temperatures illustrate that silica grains, CP grains, intergranular phase contents (Si, Ca, P, and O and an important open porosity depend on the sintering temperature. The porosity ratio changes in the range between 37% and 34% according to sintering temperature and to CP content; these values are in good agreement with SEM images. The thermal expansion behavior shows a weak expansion in the range of temperature between 600 and 1000 ºC which is situated between 1.27% and 1.33% (variation of 0.05% at 400 ºC.

  5. 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.

  6. Injection Molding of Sinterable Silicon-Base, Nonoxide Ceramics.

    Science.gov (United States)

    1978-12-01

    XRD) analysis techniques were used on a mixture of alpha- Si3N4, beta -Si3N4 , Si20N2, Si, SiO 2 (alpha- cristobalite ), and SiC. After invest- igation of...apparently always leads to the hexagonal beta -Si3 N4 structure, or to the beta solid solution with the same structure and slightly larger lattice...parameters. The stoichiometry of the beta solid solution is stated to be Si6-xAIXOXN 8 -x; that is, it lies along the join between Si3 N4 and (A12 03 .AIN

  7. Sinterable Ceramic Powders from Laser-Heated Gases.

    Science.gov (United States)

    1988-02-01

    Reactions 25 3. Crystal Structure of Silicon Powders Produced from Laser-Heated Silane 37 IV . Post Synthesis Processing 1. Wetting and Dispersion of Silicon...Society, Session IV , High Temperature Materials Synthesis, Honolulu, Hawaii, Oct. 18-23, 1987 p87-05 IAS S! SIZM CAauiC POWDES: Sy XDS, c ZMUISTICS...ether. carboxylic acid. and aldehyde clases : water is also included.Acrigto William and Goodman.’ a single crystalline sili- The single-crstalline

  8. Ceramic technology for advanced heat engines project

    Energy Technology Data Exchange (ETDEWEB)

    1990-09-01

    The Ceramic Technology for Advanced Heat Engines Project was developed by the Department of Energy's Office of Transportation Systems in Conservation and Renewable Energy. This project was developed to meet the ceramic technology requirements of the OTT's automotive technology programs. This project is managed by ORNL and is closely coordinated with complementary ceramics tasks funded by other DOE offices, NASA, DoD, and industry. Research is discussed under the following topics; Turbomilling of SiC Whiskers; microwave sintering of silicon nitride; and milling characterization; processing of monolithics; silicon nitride matrix; oxide matrix; silicate matrix; thermal and wear coatings; joining; design; contact interfaces; time-dependent behavior; environmental effects; fracture mechanics; nondestructive evaluation; and technology transfer. References, figures, and tables are included with each topic.

  9. Fatigue strength testing of LTCC and alumina ceramics bonds

    Science.gov (United States)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  10. Microstructure and Electrical Properties of AZO/Graphene Nanosheets Fabricated by Spark Plasma Sintering.

    Science.gov (United States)

    Yang, Shuang; Chen, Fei; Shen, Qiang; Lavernia, Enrique J; Zhang, Lianmeng

    2016-07-29

    In this study we report on the sintering behavior, microstructure and electrical properties of Al-doped ZnO ceramics containing 0-0.2 wt. % graphene sheets (AZO-GNSs) and processed using spark plasma sintering (SPS). Our results show that the addition of <0.25 wt. % GNSs enhances both the relative density and the electrical resistivity of AZO ceramics. In terms of the microstructure, the GNSs are distributed at grain boundaries. In addition, the GNSs are also present between ZnO and secondary phases (e.g., ZnAl₂O₄) and likely contribute to the measured enhancement of Hall mobility (up to 105.1 cm²·V(-1)·s(-1)) in these AZO ceramics. The minimum resistivity of the AZO-GNS composite ceramics is 3.1 × 10(-4) Ω·cm which compares favorably to the value of AZO ceramics which typically have a resistivity of 1.7 × 10(-3) Ω·cm.

  11. Investigation of ceramics based on Cu-Sn powder obtained by plasma dynamic method

    Science.gov (United States)

    Shanenkova, Yu; Sivkov, A.; Ivashutenko, A.; Tsimmerman, A.

    2017-05-01

    Composites based on copper matrix are of a great interest in various applications. Copper-tin alloys are intensively investigated due to their thermal and chemical stability in combination with good mechanical properties. This work shows the possibility to obtain Cu-Sn ceramics by spark plasma sintering using nanoscale powders consisting of copper and tin, synthesized by plasma dynamic method. This method is implemented by using a coaxial magnetoplasma accelerator with copper electrodes and adding the solid precursor (tin) in the accelerator before carrying out the synthesis process. The synthesized Cu-Sn powders were investigated by X-Ray diffractometry and transmission electron microscopy. It was determined that the final material consists of phase Cu41Sn11. Using this product, the bulk ceramics samples were obtained by spark plasma sintering at different temperatures (150 °C, 250 °C and 500 °C). The changes in microstructure of copper-tin ceramics in dependence on the sintering temperature were also studied. After analyzing all ceramics samples by X-Ray diffractometry and scanning electron microscopy methods, it was found that the optimal temperature for sintering Cu-Sn ceramics, which was made of the powder synthesized by a plasma dynamic method, was equal to 250 °C at pressure 60 MPa. At these conditions, the ceramics sample had the lowest porosity with the smallest grain size.

  12. Selective laser sintering of cermet mixtures Ti and B4C

    Science.gov (United States)

    Filippov, A. A.; Fomin, V. M.; Malikov, A. G.; Orishich, A. M.

    2016-10-01

    The work is dedicated to the creation of a new heterogeneous ceramic-composite materials based on boron carbide and titanium, using a laser, in order to further layer-growing 3D products from these materials. The paper discussed two methods for obtaining ceramic-composite material: laser sintering of boron carbide powder and a metal-melting the powder mixture. We study the microstructure of the samples at various energy process modes. An attempt was made to justify the applicability of the regime used for the cultivation of layered products.

  13. Effective Utilization of Semicharcoal in Sintering

    Science.gov (United States)

    Wang, Zhe; Zhang, Jian-liang; Meng, Fan-yi; Wang, Run-bo

    The influence of semicharcoal substitution for coke breeze on sintering performance was investigated by pot-grate sintering test. At a fixed fuel ratio, sinter productivity and strength decreased with the substitution increasing from 0 to 100% due to better combustibility. To enhance the utilization efficiency of 100% semicharcoal, sintering parameters (moisture and suction pressure) was adjusted. With the moisture increasing, sinter performance of 100% semicharcoal increased because of the suppression of semicharcoal incomplete combustion. As the moisture further increasing to 9.0%, sinter quality gave rise to a decrease trend. The results also showed that the increase of suction pressure was benefit for the increase of heat transfer rate, leading to the improvement of heat utilization energy. Measures to enhance magnetite oxidation during sintering are discussed based on current understanding of the fundamentals that control the sintering process.

  14. 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.

  15. 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.

  16. 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.

  17. Sintering kinetics of MgCO3-TiO2 systems

    Directory of Open Access Journals (Sweden)

    Petrović V.

    2006-01-01

    Full Text Available Ceramic materials have been in use in many different areas of human well-being for a very long time. The most common way of obtaining this material is using the process of sintering. During mechanical activation inorganic materials are ground when the grain size reduced. The crystal structure distorts and also changes, leading some systems to a chemical reaction and formation of a new compound. In this work we explain the influence of mechanical activation on sintering kinetics in MgCO3-TiO2 systems. We noticed a temperature drop and time reduction needed for MgTiO3 sintering when the duration of mechanical activation was longer.

  18. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

    Science.gov (United States)

    Kolte, Jayant; Salame, Paresh H.; Daryapurkar, A. S.; Gopalan, P.

    2015-09-01

    In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ¯ ≈ 10 n m ). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ˜1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher's power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (˜180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS) we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC) leading to high dielectric constant in microwave sintered BFO.

  19. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3, synthesized by microwave sintering

    Directory of Open Access Journals (Sweden)

    Jayant Kolte

    2015-09-01

    Full Text Available In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ̄   ≈ 10   n m . Microwave sintering resulted in reducing the sintering time substantially (by 1h, and has resulted in submicron sized grains and high resistivity ∼1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher’s power law behavior, suggesting correlated barrier hopping (CBH mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (∼180 °C indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC leading to high dielectric constant in microwave sintered BFO.

  20. Dislocation generation during early stage sintering.

    Science.gov (United States)

    Sheehan, J. E.; Lenel, F. V.; Ansell, G. S.

    1973-01-01

    Discussion of the effects of capillarity-induced stresses on dislocations during early stage sintering. A special version of Hirth's (1963) theoretical calculation procedures modified to describe dislocation nucleation on planes meeting the sintering body's neck surface obliquely is shown to predict plastic flow at stress levels know to exist between micron size metal particles in the early stages of sintering.

  1. Measuring Elastic Modulus of Sintered Metal

    Science.gov (United States)

    Fedors, R. F.; Eastman, A. F.

    1983-01-01

    Technique minimizes effect of substrate on thin sintered coating. Uniaxial tension test yields approximate value for elastic modulus of sintered material on thin substrate. Electrode composed of central perforated nickel plated steel sheet about 4 mils (0.1mm) thick, coated on each face by porous sintered nickel about 8 mils (0.2mm) thick.

  2. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    A mesoscale numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element method for calculating stresses. The sintering behavior of a sample constrained by a rigid substrate...

  3. 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

  4. 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.

  5. Effects of porosity and crystallinity of glass ceramics on the in vivo bioactive response

    Energy Technology Data Exchange (ETDEWEB)

    Xin Renlong [School of Materials Science and Engineering, Chongqing University, Chongqing (China); Zhang Qiyi; Leng Yang [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Hong Kong (China); Chen Jiyong [Engineering Research Center in Biomaterials, Sichuan University, Chengdu (China)], E-mail: rlxin@cqu.edu.cn

    2008-12-15

    Two types of glass ceramics with different porosities and crystallinities were produced by sintering 45S5 Bioglass (registered) particulates. The in vivo bioactive response of the glass ceramics was evaluated by implanting them in rabbit muscle sites. After six weeks implantation, silicon-rich networks were observed on both types of ceramics, but the number of networks was much larger in the poorly crystallized dense ceramics than in the well crystallized porous ones. This indicated that the crystallization of glass ceramics retarded the formation of networks on surfaces. Apatite precipitation was found in pore areas of the porous ceramics, but not on the dense ones, suggesting that porosity was necessary for glass ceramics to induce apatite precipitation in a rabbit model. (communication)

  6. Topography, microhardness, and precision of fit on ready-made zirconia abutment before/after sintering process.

    Science.gov (United States)

    Kanno, Taro; Milleding, Percy; Wennerberg, Ann

    2007-09-01

    Sintering porcelain on a ceramic abutment may change the microstructure and result in aging processes that influence the mechanical properties, internal strain, and the three-dimensional form of the abutment, thus causing a possible misfit between the abutment and the fixture. The aim was to investigate topography, microhardness, and precision of fit on yttrium-stabilized zirconia (Y-TZP) abutments before/after the sintering process. Ten Y-TZP abutment samples were ground to a shape used in the clinical situation and divided at random into two groups: before/after sintering. After the surface roughness was measured on all abutments, the abutments were connected to fixture replicas, embedded in resin, and cut in the longitudinal axis. Both sides of the cut samples were measured with respect to microhardness and minimum distance between fixture and abutment surface. t-Test, one-way analysis of variance, and Bonferroni multiple comparisons were used to investigate statistical significant differences. The surface roughness (S(a) and S(dr)) after sintering was significantly higher than before sintering. The total average values of microhardness after sintering were statistically lower than before sintering with a difference of 2%. The total distance between abutment/fixture before/after sintering demonstrated no statistically significant difference. Contact between abutment/fixture was most common at the top area of the fixture. A slight decrease of microhardness and contamination of porcelain particles immediately below the veneered part were found on the Y-TZP abutment after sintering. The sintering process did not affect the precision of fit.

  7. 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.

  8. Influence of Stony Rocks Additives on Strengthening of Aluminosilicate Ceramics from Fusible Clays

    OpenAIRE

    Govorova, L.P.; Vakalova, T.V.; Shvagrukova, E.V.; Zagaynova, L.A.

    2015-01-01

    The paper presents the results of the research, connected with the granulometric and mineralogical compositions of fusible clay raw materials of Krasnoyarsk region - argillic and loose clay varieties. The influence of granitoid and diabase rocks stony additives on the sinterability and strength characteristics of the ceramic materials based on fusible clays is evaluated. It is found that the introduction of sintering additives into the loose fusible clay leads to the significant increase of s...

  9. SUPPORTED DENSE CERAMIC MEMBRANES FOR OXYGEN SEPARATION

    Energy Technology Data Exchange (ETDEWEB)

    Timothy L. Ward

    2002-07-01

    Mixed-conducting ceramics have the ability to conduct oxygen with perfect selectivity at elevated temperatures, making them extremely attractive as membrane materials for oxygen separation and membrane reactor applications. While the conductivity of these materials can be quite high at elevated temperatures (typically 800-1000 C), much higher oxygen fluxes, or, alternatively, equivalent fluxes at lower temperatures, could be provided by supported thin or thick film membrane layers. Based on that motivation, the objective of this project was to explore the use of ultrafine aerosol-derived powder of a mixed-conducting ceramic material for fabrication of supported thick-film dense membranes. The project focused on the mixed-conducting ceramic composition SrCo{sub 0.5}FeO{sub x} (SCFO) because of the desirable permeability and stability of that material, as reported in the literature. Appropriate conditions to produce the submicron SrCo{sub 0.5}FeO{sub x} powder using aerosol pyrolysis were determined. Porous supports of the same composition were produced by partial sintering of a commercially obtained powder that possessed significantly larger particle size than the aerosol-derived powder. The effects of sintering conditions (temperature, atmosphere) on the porosity and microstructure of the porous discs were studied, and a standard support fabrication procedure was adopted. Subsequently, a variety of paste and slurry formulations were explored utilizing the aerosol-derived SCFO powder. These formulations were applied to the porous SCFO support by a doctor blade or spin coating procedure. Sintering of the supported membrane layer was then conducted, and additional layers were deposited and sintered in some cases. The primary characterization methods were X-ray diffraction and scanning electron microscopy, and room-temperature nitrogen permeation was used to assess defect status of the membranes.We found that non-aqueous paste/slurry formulations incorporating

  10. MECHANICAL TESTING OF SINTERED MATERIALS

    Directory of Open Access Journals (Sweden)

    Cristina IONICI

    2011-07-01

    Full Text Available Alloying elements have an important affect upon the mechanical properties of the Sintered Materials.Compression tests show that the cupper based material obtains high results in cryogenic environments.Testsreveal the weak resistance of materials that contain 0,8% C, due to a poor classification and a inhomogenousmetallographycal structure.

  11. The effect of forming stresses on the sintering of ultra-fine Ce0.9Gd0.1O2-δ powders

    DEFF Research Database (Denmark)

    Glasscock, Julie; Esposito, Vincenzo; Foghmoes, Søren Preben Vagn

    2013-01-01

    The effect of particle and pore arrangement on sintering and densification of ultra-fine (∼130nm) Ce0.9Gd0.1O2-δ powder was evaluated. The common understanding that higher initial density of a ceramic network leads to a higher sintered density is not valid for fine powders, which have extremely...... good sinterability when there is a favourable particle packing. The effect of the applied stresses during forming (which produce different particle packing arrangements) was investigated by forging green bodies by different shaping techniques, including casting, and cold isostatic pressing. Samples...

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

    Directory of Open Access Journals (Sweden)

    Weiguo Jiang

    2017-12-01

    Full Text Available 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, room temperature bend strength, creep property at elevated temperature and the leaching rate in aqueous caustic solution were studied. The experimental results show that the ceramic core material with silica fiber obtain a fair balance between mechanical and chemical properties at sintering of 1300 °C/4 h. Specifically, the leach rate of ceramic core material with silica fiber is increased apparently. High leaching surface and weak adhesive strength between agglomerated alumina particles are the reasons that responsible for the ceramic core material with silica fiber be leaching fast than that of the ceramic core material without fiber.

  13. Ceramic Seal.

    Energy Technology Data Exchange (ETDEWEB)

    Smartt, Heidi A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Romero, Juan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Custer, Joyce Olsen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hymel, Ross W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Krementz, Dan [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Gobin, Derek [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Harpring, Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Martinez-Rodriguez, Michael [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Varble, Don [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); DiMaio, Jeff [Tetramer Technologies, Pendleton, SC (United States); Hudson, Stephen [Tetramer Technologies, Pendleton, SC (United States)

    2016-11-01

    Containment/Surveillance (C/S) measures are critical to any verification regime in order to maintain Continuity of Knowledge (CoK). The Ceramic Seal project is research into the next generation technologies to advance C/S, in particular improving security and efficiency. The Ceramic Seal is a small form factor loop seal with improved tamper-indication including a frangible seal body, tamper planes, external coatings, and electronic monitoring of the seal body integrity. It improves efficiency through a self-securing wire and in-situ verification with a handheld reader. Sandia National Laboratories (SNL) and Savannah River National Laboratory (SRNL), under sponsorship from the U.S. National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), have previously designed and have now fabricated and tested Ceramic Seals. Tests have occurred at both SNL and SRNL, with different types of tests occurring at each facility. This interim report will describe the Ceramic Seal prototype, the design and development of a handheld standalone reader and an interface to a data acquisition system, fabrication of the seals, and results of initial testing.

  14. ceramic pigment

    Indian Academy of Sciences (India)

    In contrast, the relatively poor blue colour obtained by dispersing Co2SiO4 into ceramic glazes is mainly attributed to the evolution of Co2+ initially in octahedral coordination of olivine structure to tetrahedral coordination of glassy phase. On the other hand, regarding the growing concern on. Co costs and environmental ...

  15. Influence of Indium-Tin Oxide Additive on the Sintering Process and Conductivity of Na3Zr2Si2PO12 Solid Electrolyte

    Science.gov (United States)

    Chen, Dan; Luo, Fa; Gao, Lu; Zhou, Wancheng; Zhu, Dongmei

    2017-11-01

    Because of the poor sintering ability and low phase purity limit in the application of a Na3Zr2Si2PO12 solid electrolyte, it is important to find an effective way to obtain a pure and dense Na3Zr2Si2PO12 ceramic at reduced temperature. In this study, high conductive indium-tin oxide (ITO) was innovatively used as the sintering additive to improve the purity and density of the Na3Zr2Si2PO12 ceramic. The influence of ITO additive on density, phase, microstructure and conductivity of the Na3Zr2Si2PO12 ceramic was investigated. Archimedes method, x-ray diffraction, scanning electron microcopy and complex impedance spectroscopy were used as experimental techniques to evaluate the effect of the additive. The results show that the ITO sintering additive increases not only the purity and density but also the conductivity of the Na3Zr2Si2PO12 ceramic. The Na3Zr2Si2PO12 ceramic with 3 wt.% ITO additive sintered at 1150°C for 4 h possesses a high density of 3.15 g/cm3 and good conductivity of (3.95 ± 0.12) × 10-4 S/cm.

  16. Development of high-thermal-conductivity silicon nitride ceramics

    Directory of Open Access Journals (Sweden)

    You Zhou

    2015-09-01

    Full Text Available Silicon nitride (Si3N4 with high thermal conductivity has emerged as one of the most promising substrate materials for the next-generation power devices. This paper gives an overview on recent developments in preparing high-thermal-conductivity Si3N4 by a sintering of reaction-bonded silicon nitride (SRBSN method. Due to the reduction of lattice oxygen content, the SRBSN ceramics could attain substantially higher thermal conductivities than the Si3N4 ceramics prepared by the conventional gas-pressure sintering of silicon nitride (SSN method. Thermal conductivity could further be improved through increasing the β/α phase ratio during nitridation and enhancing grain growth during post-sintering. Studies on fracture resistance behaviors of the SRBSN ceramics revealed that they possessed high fracture toughness and exhibited obvious R-curve behaviors. Using the SRBSN method, a Si3N4 with a record-high thermal conductivity of 177 Wm−1K−1 and a fracture toughness of 11.2 MPa m1/2 was developed. Studies on the influences of two typical metallic impurity elements, Fe and Al, on thermal conductivities of the SRBSN ceramics revealed that the tolerable content limits for the two impurities were different. While 1 wt% of impurity Fe hardly degraded thermal conductivity, only 0.01 wt% of Al caused large decrease in thermal conductivity.

  17. Laser all-ceramic crown removal-a laboratory proof-of-principle study-phase 2 crown debonding time.

    Science.gov (United States)

    Rechmann, Peter; Buu, Natalie C H; Rechmann, Beate M T; Finzen, Frederick C

    2014-10-01

    The removal of all-ceramic crowns is a time consuming procedure in the dental office. Little research has been done in alternative removal techniques for all-ceramic crowns. The objective of the second phase of this proof-of-principle laboratory pilot study was to evaluate whether Ivoclar Vivadent all-ceramic crowns can be efficiently removed from natural teeth without damage to the underlying tooth structure using an Erbium laser. The ceramic materials used were IPS E.max CAD Lithium-disilicate (LS2 ) (E.max CAD) and IPS E.max ZirCAD Zirconium-oxide (ZrO2 ) (ZirCAD) (Ivoclar, Vivadent, Liechtenstein). Molars, either as stand-alone teeth or placed in an artificial row of teeth, were prepared to receive all-ceramic crowns. Copings and full contour crowns with either featheredge or regular margins were produced. The all-ceramic crowns were bonded to the teeth with Ivoclar Multilink Automix. The time for Er:YAG laser debonding of each crown was then measured. The Er:YAG (LiteTouch, Syneron, Yokneam, Israel) was used with an 1,100 µm diameter fiber tip with energies up to 600 mJ per pulse (wavelength 2,940 nm, 10 Hz repetition rate, pulse duration 100 µs at 126 mJ/pulse, and 400 µs at 590 mJ/pulse). The irradiation was applied at a distance of 10 mm from the crown surface following a defined pattern. Air-water spray was applied to the crowns at a rate of 67 ml/minute. All of the all-ceramic crowns were successfully debonded with the laser. On average, an all-ceramic E.max CAD crown was debonded in 190 ± 92 seconds (average ± SD). The debonding time for ZirCAD featheredge crowns was 226 ± 105 seconds and for ZirCAD crowns with regular margins it was 312 ± 102 seconds. No crowns fractured and no damage to the underlying dentin was detected. The bonding cement deteriorated due to the Er:YAG irradiation. Additionally, no carbonization at the dentin/cement interface was observed. Er:YAG laser energy can successfully be used

  18. Valorisation of ilmenite mud waste in the manufacture of commercial ceramic

    OpenAIRE

    Contreras Llanes, Manuel; Martín, M. I.; Gázquez González, Manuel Jesús; Romero, M.; Bolívar Raya, Juan Pedro

    2014-01-01

    This paper reports the results of a study focused on the production of ceramic tiles from ilmenite mud (MUD), a waste generated by the industry devoted to the TiO2 pigment production. Ceramic tiles were produced from mixtures of a commercial red stoneware mixture (RSM) with different concentrations of mud (3, 5, 7, 10, 30 and 50 wt.%). The samples were sintered to simulate a fast-firing process. The sintering behaviour of the fired samples was evaluated according to ISO methodologies by linea...

  19. Bioactive glasses and glass-ceramics.

    Science.gov (United States)

    Rawlings, R D

    1993-01-01

    Bioactive materials are designed to induce a specific biological activity; in most cases the desired biological activity is one that will give strong bonding to bone. A range of materials has been assessed as being capable of bonding to bone, but this paper is solely concerned with bioactive glasses and glass-ceramics. Firstly, the structure and processing of glasses and glass-ceramics are described, as a basic knowledge is essential for the understanding of the development and properties of the bioactive materials. The effect of composition and structure on the bioactivity is then discussed, and it will be shown that bioactivity is associated with the formation of an apatite layer on the surface of the implant. A survey of mechanical performance demonstrates that the structure and mechanical properties of glass-ceramics depend upon whether the processing involves casting or sintering and that the strength and toughness of glass-ceramics are superior to those of glasses. Attempts to further improve the mechanical performance by the use of non-monolithic components, i.e. bioactive coatings on metal substrates and glass and glass-ceramic matrix composites, are also reviewed and are shown to have varying degrees of success. Finally, some miscellaneous applications, namely bioactive bone cements and bone fillers, are briefly covered.

  20. Sintering of SiC ceramics, via liquid phase, with Al{sub 2}O{sub 3}-Yb{sub 2}O{sub 3} additives; Sinterizacao de ceramicas de SiC, via fase liquida, com aditivos de Al{sub 2}O{sub 3}-Yb{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Atilio, I.; Oliveira, M.R.; Garcia, G.C.R.; Ribeiro, S., E-mail: isabelaatilio@hotmail.com [Universidade de Sao Paulo (USP/EEL), Lorena, SP (Brazil). Escola de Engenharia. Dept. de Engenharia de Materiais

    2012-07-01

    The objective of this work was to study the sintering of SiC, through liquid phase, using the additive system Al{sub 2}O{sub 3} and Yb{sub 2}O{sub 3} for the first time. The samples were sintered at temperatures of 1900, 1950 and 2000 deg C for 60 minutes. The melting point of the system was determined according to DIN 51730. It has been found the ability of wetting of SiC in the system. The densification results were: 86,36% at 1900 deg C, 88,25% at 1950 deg C and 82,09% at 2000 deg C. The average linear shrinkage was approximately 17%. There was a conversion of β-SiC in α-SiC at all temperatures and sintering phase formation Yb{sub 3}Al{sub 5}O{sub 12}. The melting temperature was 1850 deg C for de system, consistent with the value in the phase diagram, and the wetting angle of 20 deg. The system (Yb{sub 2}O{sub 3}-Al{sub 2}O{sub 3}) is promising to make liquid phase sintering of SiC, for presenting a good result of wettability. (author)

  1. 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.

  2. Structural design and experimental analysis of a selective laser sintering system with nano-hydroxyapatite powder.

    Science.gov (United States)

    Shuai, Cijun; Gao, Chengde; Nie, Yi; Hu, Huanglong; Qu, Hongyi; Peng, Shuping

    2010-08-01

    Hydroxyapatite (HA) is a ceramic transposition material which has been widely used for artificial bone. However, its applications are limited to a small implantation for non-bearing bone repair due to its high brittleness, low strength and poor mechanical properties. Thus, nanotechnology has been employed to improve the mechanical properties (torsion modulus, tensile strength and fatigue resistance, etc.) of HA for bone implantation. In this study, we developed a selective laser sintering system for fabrication of artificial bone with nano-HA powder. The key characteristics of this novel system is the laser with fast heating and fast cooling properties, which efficiently prevents the nanosize particles from forming micron size ones in the process of the sintering. The microstructure of the sintered nano-HA scaffolds produced in this system was investigated under Scanning Electron Microscopy (SEM). We showed that the size of nano particles were increased with the prolonged sintering time. Moreover, they are more in shape of granules instead of the original shape of needle. We suggest that the nano HA scaffolds which meet the requirements for the mechanical and biological properties of bone can be obtained by optimizing the sintering time.

  3. Silica containing highly porous alumina ceramic

    Science.gov (United States)

    Svinka, R.; Svinka, V.; Zake, I.

    2011-04-01

    Porous alumina ceramic were produced by slip casting of aqueous alumina slurry with added small amount of metallic aluminium powder. Pores form in result of chemical reaction of aluminum with water by hydrogen gas evolution reaction and solidification of suspension. Porosity of such materials sintered at a temperature of 1600 - 1750°C varies from 60 to 90%. Pore size distribution and mechanical strength of these materials depend largely on the grain size of used raw materials. The major part of pores in the materials produced without additive of silica are larger than 10 ±m, but with 5 - 10 wt.% additive of silica in the raw mix pore size decreases considerably. The sintering shrinkage decreases to 2.5%. Coefficient of thermal expansion equally decreases from 8.9-10-6 K-1 to 7.1 10-6 K-1 and classification temperature increases to 1600°C, while deformation at high temperature decreases considerably.

  4. Correlation between structural, electrical and magnetic properties of GdMnO{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Samantaray, S. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, D.K. [Department of Physics, Institute of Technical Education and Research, S ‘O’ A University, Bhubaneswar 751030, Odisha (India); Pradhan, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, P.; Sekhar, B.R. [Institue of Physics, Sachivalaya Marg, Bhubaneswar, Odisha (India); Behera, Debdhyan [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha (India); Rout, P.P.; Das, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Sahu, D.R. [School of Physics, University of the Witwatersrand, Johannesburg (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India)

    2013-08-15

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO{sub 3} (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO{sub 3}. Room temperature dielectric constant (ε{sub r}) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO{sub 3} at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO{sub 3} sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO{sub 3}. • Possibility of room temperature application of GdMnO{sub 3} as multifunctional material.

  5. 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.

  6. 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.

  7. 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.

  8. Sintered wire cesium dispenser photocathode

    Science.gov (United States)

    Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

    2014-03-04

    A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

  9. Melting and Sintering of Ashes

    DEFF Research Database (Denmark)

    Hansen, Lone Aslaug

    1997-01-01

    The thesis contains an experimental study of the fusion and sintering of ashes collected during straw and coal/straw co-firing.A laboratory technique for quantitative determination of ash fusion has been developed based on Simultaneous Thermal Analysis (STA). By means of this method the fraction...... of melt in the investigated ashes has been determined as a function of temperature. Ash fusion results have been correlated to the chemical and mineralogical composition of the ashes, to results from a standard ash fusion test and to results from sintering experiments. Furthermore, the ash fusion results...... have been employed in a simple model for prediction of ash deposit formation, the results of which have been compared to ash deposition formation rates measured at the respective boilers.The ash fusion results were found to directly reflect the ash compositional data:a) Fly ashes and deposits from...

  10. Impact of sintering temperature on the structural, electrical, and optical properties of doped ZnO nanoparticle-based discs

    Science.gov (United States)

    Sendi, Rabab Khalid; Mahmud, Shahrom

    2012-11-01

    In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to make high-density ZnO discs doped with Bi2O3 and Mn2O3 via the conventional ceramic processing method. Different sintering temperatures were found to have significant impacts on the ZnO discs, especially on enhancing grain growth even at a low sintering temperature of only 980 °C. The strong solid-state reaction during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles that promoted a strong surface reaction even at low sintering temperatures. Moreover, the sintering process also improved the grain crystallinity, as shown in the lowering of the intrinsic compressive stress based on the X-ray diffraction lattice constant and full-wave half-maximum data. The sintering temperatures also significantly influenced the electrical properties of the doped ZnO discs with a marked drop in the breakdown voltage from 330 V (sample at 980 °C) to 80 V (sample at 1380 °C). The resistivity also experienced a dramatic drop from 304.4 kΩ cm (sample at 980 °C) to 98.86 kΩ cm (sample at 1380 °C). The observed shift in the energy band-gap from a higher to a lower value may be attributed to the conversion of compressive stress to tensile stress with increasing sintering temperature. The Raman spectra indicate that the sintering temperatures and dopants in the discs had significant effects on the E2(high) phonon mode and ZnO crystal structures. Therefore, the sintering process can be used as a new technique for controlling the breakdown voltage of doped ZnO discs made from ZnO nanoparticles with improved structural and optical properties.

  11. Vacuum-sintered body of a novel apatite for artificial bone

    Science.gov (United States)

    Tamura, Kenichi; Fujita, Tatsushi; Morisaki, Yuriko

    2013-12-01

    We produced regenerative artificial bone material and bone parts using vacuum-sintered bodies of a novel apatite called "Titanium medical apatite (TMA®)" for biomedical applications. TMA was formed by chemically connecting a Ti oxide molecule with the reactive [Ca10(PO4)6] group of Hydroxyapatite (HAp). The TMA powders were kneaded with distilled water, and solid cylinders of compacted TMA were made by compression molding at 10 MPa using a stainless-steel vessel. The TMA compacts were dried and then sintered in vacuum (about 10-3 Pa) or in air using a resistance heating furnace in the temperature range 1073-1773 K. TMA compacts were sintered at temperatures greater than 1073 K, thus resulting in recrystallization. The TMA compact bodies sintered in the range 1273-1773 K were converted into mixtures composed of three crystalline materials: α-TCP (tricalcium phosphate), β-TCP, and Perovskite-CaTiO3. The Perovskite crystals were stable and hard. In vacuum-sintering, the Perovskite crystals were transformed into fibers (approximately 1 µm in diameter × 8 µm in length), and the fiber distribution was uniform in various directions. We refer to the TMA vacuum-sintered bodies as a "reinforced composite material with Perovskite crystal fibers." However, in atmospheric sintering, the Perovskite crystals were of various sizes and were irregularly distributed as a result of the effect of oxygen. After sintering temperature at 1573 K, the following results were obtained: the obtained TMA vacuum-sintered bodies (1) were white, (2) had a density of approximately 2300 kg/m3 (corresponding to that of a compact bone or a tooth), and had a thermal conductivity of approximately 31.3 W/(m·K) (corresponding to those of metal or ceramic implants). Further, it was possible to cut the TMA bodies into various forms with a cutting machine. An implant made of TMA and inserted into a rabbit jaw bone was covered by new bone tissues after just one month because of the high

  12. Enhanced sintering ability of biphasic calcium phosphate by polymers used for bone scaffold fabrication.

    Science.gov (United States)

    Gao, Chengde; Yang, Bo; Hu, Huanlong; Liu, Jinglin; Shuai, Cijun; Peng, Shuping

    2013-10-01

    Biphasic calcium phosphate (BCP), which is composed of hydroxyapatite [HAP, Ca10(PO4)6(OH)2] and β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2], is usually difficult to densify into a solid state with selective laser sintering (SLS) due to the short sintering time. In this study, the sintering ability of BCP ceramics was significantly improved by adding a small amount of polymers, by which a liquid phase was introduced during the sintering process. The effects of the polymer content, laser power and HAP/β-TCP ratios on the microstructure, chemical composition and mechanical properties of the BCP scaffolds were investigated. The results showed that the BCP scaffolds became increasingly more compact with the increase of the poly(l-lactic acid) (PLLA) content (0-1 wt.%) and laser power (6-10 W). The fracture toughness and micro-hardness of the sintered scaffolds were also improved. Moreover, PLLA could be gradually decomposed in the late sintering stages and eliminated from the final BCP scaffolds if the PLLA content was below a certain value (approximately 1 wt.% in this case). The added PLLA could not be completely eliminated when its content was further increased to 1.5 wt.% or higher because an unexpected carbon phase was detected in the sintered scaffolds. Furthermore, many pores were observed due to the removal of PLLA. Micro-cracks and micro-pores occurred when the laser power was too high (12 W). These defects resulted in a deterioration of the mechanical properties. The hardness and fracture toughness reached maximum values of 490.3±10 HV and 1.72±0.10 MPa m(1/2), respectively, with a PLLA content of approximately 1 wt.% and laser power of approximately 10 W. Poly(l-lactic-co-glycolic acid) (PLGA) showed similar effects on the sintering process of BCP ceramics. Rectangular, porous BCP scaffolds were fabricated based on the optimum values of the polymer content and laser power. This work may provide an experimental basis for improving the mechanical

  13. Sol-gel synthesis of carbon based materials reinforced ultra high temperature ceramic composites

    OpenAIRE

    Wang, Xiaojing

    2017-01-01

    This Ph.D. research is based on the development of novel sol-gel techniques for synthesis of nanostructured ultra high temperature ceramics (UHTCs) and subsequent spark plasma sintering (SPS) for densifying the UHTC composites. The liquid nature of the sol-gel process offers advantages such as high purity and ability for mixing and infiltration, and thus it can overcome some shortcomings of the conventional power processing of ceramics. SPS delivers microstructures with good density and fine ...

  14. In situ-growth of silica nanowires in ceramic carbon composites

    OpenAIRE

    Rahul Kumar; Parag Bhargava

    2017-01-01

    An understanding of the processing and microstructure of ceramic–carbon composites is critical to development of these composites for applications needing electrically conducting, thermal shock resistant ceramic materials. In the present study green compacts of carbon ceramic composites were prepared either by slurry processing or dry powder blending of one or more of the three — clay, glass, alumina and carbon black or graphite. The dried green compacts were sintered at 1400 °C in flowing ar...

  15. Study of ceramics having high heat impact resistance by applying the gradient composition technique; Keisha sosei shuho wo oyoshita kotainetsu shogekisei ceramics ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    When symmetrical gradient compositions like ceramics/metal/ceramics are adopted, composites having a large compressive residual stress in the surface ceramics layer can be fabricated. For the symmetrical gradient composition materials, such as Al2O3/TiC/Ni/TiC/Al2O3, it was clarified from the preliminary studies that their toughness was enhanced in 50 to 300%, their hardness in 10 to 20%, and their bending strength in 200 to 300% compared with the usual sintered alumina. In this study, such symmetrical gradient composition structures were designed and fabricated, to intend to enhance the ceramics in the surface layer. For the sintering process, the nitriding reaction heat of Si was utilized in the high pressure nitrogen gas, and the SHS/HIP method was applied, by which inhomogeneous materials with different sintering temperatures in individual parts can be sintered. The heat impact resistant properties of materials fabricated by this process were experimentally evaluated, and the thermal stress analysis was conducted to clarify the improvement mechanism of their heat impact resistant properties. Fundamental data were obtained, as to the development of super high temperature materials, which can be used stably even under the severe conditions. 13 refs., 36 figs., 10 tabs.

  16. Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-11-01

    Full Text Available 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 <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors.

  17. 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 sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors. PMID:27916913

  18. 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

    2016-11-30

    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 sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors.

  19. Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi2O3-TiO2 Ceramics

    Directory of Open Access Journals (Sweden)

    Reza Zamiri

    2011-02-01

    Full Text Available The optical band-gap energy (Eg is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. Eg of the ceramic ZnO + xBi2O3 + xTiO2, where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. Eg was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature.

  20. Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi2O3-TiO2 Ceramics

    Science.gov (United States)

    Ghazali, Mohd Sabri Mohd; Zakaria, Azmi; Rizwan, Zahid; Kamari, Halimah Mohamed; Hashim, Mansor; Zaid, Mohd Hafiz Mohd; Zamiri, Reza

    2011-01-01

    The optical band-gap energy (Eg) is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. Eg of the ceramic ZnO + xBi2O3 + xTiO2, where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. Eg was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature. PMID:21673903

  1. Strengthening and Strength Uniformity of Structural Ceramics

    Science.gov (United States)

    1984-04-01

    OT I -.’ 1 𔃻i ’ " . CS852A/snvv" - .WIJ " o Vo.t ’ Rockwell Intemational Scince Center * SC5295.3AR As detailed In Appendix II, the stresses...compositions (e.g., multilayered capacitors), and sintered powder/fiber composites by pointing a direction to minimize sin- tering stresses and eliminating...mate- ceramics with low thermal expansion, low alas- rials for current adiabatic diesel designs is tic modulus, high strength and high thermal in direct

  2. Fabrication of porous silicon nitride ceramics using binder jetting technology

    Science.gov (United States)

    Rabinskiy, L.; Ripetsky, A.; Sitnikov, S.; Solyaev, Y.; Kahramanov, R.

    2016-07-01

    This paper presents the results of the binder jetting technology application for the processing of the Si3N4-based ceramics. The difference of the developed technology from analogues used for additive manufacturing of silicon nitride ceramics is a method of the separate deposition of the mineral powder and binder without direct injection of suspensions/slurries. It is assumed that such approach allows reducing the technology complexity and simplifying the process of the feedstock preparation, including the simplification of the composite materials production. The binders based on methyl ester of acrylic acid with polyurethane and modified starch were studied. At this stage of the investigations, the technology of green body's fabrication is implemented using a standard HP cartridge mounted on the robotic arm. For the coordinated operation of the cartridge and robot the specially developed software was used. Obtained green bodies of silicon powder were used to produce the ceramic samples via reaction sintering. The results of study of ceramics samples microstructure and composition are presented. Sintered ceramics are characterized by fibrous α-Si3N4 structure and porosity up to 70%.

  3. High efficiency tantalum-based ceramic composite structures

    Science.gov (United States)

    Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor); DiFiore, Robert R. (Inventor); Katvala, Victor W. (Inventor)

    2010-01-01

    Tantalum-based ceramics are suitable for use in thermal protection systems. These composite structures have high efficiency surfaces (low catalytic efficiency and high emittance), thereby reducing heat flux to a spacecraft during planetary re-entry. These ceramics contain tantalum disilicide, molybdenum disilicide and borosilicate glass. The components are milled, along with a processing aid, then applied to a surface of a porous substrate, such as a fibrous silica or carbon substrate. Following application, the coating is then sintered on the substrate. The composite structure is substantially impervious to hot gas penetration and capable of surviving high heat fluxes at temperatures approaching 3000.degree. F. and above.

  4. Development of the microstructure of the silicon nitride based ceramics

    Directory of Open Access Journals (Sweden)

    Bressiani J.C.

    1999-01-01

    Full Text Available Basic regularities of silicon nitride based materials microstructure formation and development in interrelation with processing conditions, type of sintering additives, and starting powders properties are discussed. Models of abnormal or exaggerated grain growth are critically reassessed. Results of several model experiments conducted in order to determine the most important factors directing the microstructure formation processes in RE-fluxed Si3N4 ceramics are reviewed. Existing data on the mechanisms governing the microstructure development of Si3N4-based ceramics are analyzed and several principles of microstructure tailoring are formulated.

  5. Effect of nanostructure on osteoinduction of porous biphasic calcium phosphate ceramics.

    Science.gov (United States)

    Li, Bo; Liao, Xiaoling; Zheng, Li; Zhu, Xiangdong; Wang, Zhe; Fan, Hongsong; Zhang, Xingdong

    2012-10-01

    In order to evaluate the effect of the nanostructure of calcium phosphate ceramics on osteoinductive potential, porous biphasic calcium phosphate (BCP) ceramics with a nano- or submicron structure were prepared via microwave sintering and compared to conventional BCP ceramics. The selective protein adsorption of bovine serum albumin and lysozyme (LSZ) and the osteogenic differentiation of human mesenchymal stem cells in vitro was investigated. Porous BCP nanoceramics showed higher ability to adsorb proteins, especially low molecular weight protein of LSZ, than conventional BCP ceramics, and the BCP nanoceramics promoted bone sialoprotein expression more than conventional BCP did. Further in vivo study to investigate ectopic bone formation and bone repair efficiency proved the highly osteoinductive potential of nanostructured BCP ceramics. The results suggest that nanostructured BCP ceramics have the potential to become a new generation of bioceramics for bone tissue engineering grafts. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Metal particles in a ceramic matrix--scanning electron microscopy and transmission electron microscopy characterization.

    Science.gov (United States)

    Konopka, K

    2006-09-01

    This paper is concerned with ceramic matrix (Al(2)O(3)) composites with introduced metal particles (Ni, Fe). The composites were obtained via sintering of powders under very high pressure (2.5 GPa). Scanning electron microscopy and transmission electron microscopy were chosen as the tools for the identification and description of the shape, size and distribution of the metal particles. The Al(2)O(3)-Ni composite contained agglomerates of the Ni particles surrounded by ceramic grains and nanometre-size Ni particles located inside the ceramic grains and at the ceramic grain boundaries. In the Al(2)O(3)-Fe composite, the Fe particles were mostly surrounded by ceramic grains. Moreover, holes left by the Fe particles were found. The high pressure used in the fabrication of the composites changed the shape of the metal and ceramic powder grains via plastic deformation.

  7. Hydrothermal ceramic for porcelain-fused-to-metal crowns: an initial experience report from clinical practice.

    Science.gov (United States)

    Mattmüller, A; Wassmann, J; Biffar, R

    1996-08-01

    The development of hydrothermal ceramics was an important requirement for fusing hydrolysis-resistant ceramics to precious metal alloys with low melting interval. Clinical findings since 1992 confirm the wide range of application of these metal-ceramic restorations in dentistry. Initial problems concerning temperature regulation of the ceramic ovens were rectified by checking and adjusting them for lower sintering temperatures. The golden yellow color is only one advantage of the ceramic-veneered alloy. Other advantages include its nonporous, smooth surface, translucence, and suitability for use in all types of dental restorations and reconstructions. Hydrothermal ceramic veneers thus can help to substantially reduce the number of different alloys used in a patient's mouth.

  8. Microstructure characterization of porous microalloyed aluminium-silicate ceramics

    Directory of Open Access Journals (Sweden)

    Purenović Jelena

    2011-01-01

    Full Text Available Kaolinite and bentonite clay powders mixed with active additives, based on Mg(NO32 and Al(NO32, sintered at high temperatures produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus. Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. The ceramics samples were characterized by scanning electron microscopy (SEM, energy dispersive spectrometer (EDS, X-ray diffraction analysis (XRD and IR spectroscopy analysis, prior and after treatment in “synthetic water”, i.e. in aqueous solution of arsenic-salt. Grain size distribution for untreated and treated samples was done with software SemAfore 4. It has shown great variety in size distribution of grains from clay powders to sintered samples.

  9. Characteristics of vacuum sintered stainless steels

    OpenAIRE

    Z. Brytan; L.A. Dobrzański; M. Actis Grande; M. Rosso

    2009-01-01

    Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless s...

  10. Fit of all-ceramic posterior fixed partial denture frameworks in vitro.

    Science.gov (United States)

    Bindl, Andreas; Mörmann, Werner H

    2007-12-01

    The objective of this study was to evaluate, by scanning electron microscopy, the marginal and internal fit of all-ceramic three-unit fixed partial denture (FPD) frames fabricated by computer-assisted design/computer-aided machining (CAD/CAM) and CAM techniques using blocks of infiltration ceramic, high-strength yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia sinter ceramic, high-strength dense sintered Y-TZP zirconia ceramic, and glass ceramic. Slip-cast infiltration ceramic was used as a traditional control. The cementation interface widths of the FPD frame copings on butt (A) shoulders of Cerec In-Ceram zirconia (A1, 53 +/- 17 microm) were smaller than those of slip-cast In-Ceram zirconia (A6, 113 +/- 25 microm). Cerec Y-TZP zirconia (A2, 53 +/- 9 pm) and DCS Y-TZP zirconia (A4, 32 +/- 6 microm) interfaces were both significantly smaller than those of Cercon Y-TZP zirconia (A5, 120 +/- 6 microm). Internally, A2 (103 +/- 14) interfaces were smaller than A4 interfaces (144 +/- 15 microm). On chamfer shoulders (B), Cerec Y-TZP zirconia (B1, 71 +/- 5 microm) interfaces were smaller than Cercon interfaces (B2, 129 +/- 38 microm); internally, B1 (80 +/- 11 microm) interfaces were smaller than B2 interfaces (130 +/- 12 microm). CAD/CAM produced better marginal and internal accuracy of fit compared to slip casting and CAM techniques.

  11. Processing and characterization of alumina–mullite ceramics

    Directory of Open Access Journals (Sweden)

    Chaouki Sadik

    2014-12-01

    Full Text Available Processing of mullite and alumina based refractory ceramic by unidirectional dry pressing, from two mixtures that include silica sand, pure alumina (PA and recycled alumina (RA is described. The samples were sintered up to 1600 °C to study the refractory properties. The fired properties of materials (firing shrinkage, water absorption, density, flexural strength, refractoriness, and SEM microstructure were evaluated. Promising refractories materials based on mullite and alumina were obtained.

  12. Laser-driven synthesis of SiC ceramic powders

    Energy Technology Data Exchange (ETDEWEB)

    Curcio, F.; Ghiglione, G.; Musci, M.; Nannetti, C.

    1989-01-01

    Ultrafine silicon carbide ceramic powders were produced by irradiating silane and acethylene mixtures with a CW carbon dioxide laser. The process and powder characteristics were studied against the most important experimental parameters. Sintering tests were done in order to evaluate the performance of the laser produced powders: densifications up to 99% of the theoretical value were achieved and metallographic analyses evidenced the superior quality of the best obtained specimens.

  13. (La2O3) glass–ceramic composites

    Indian Academy of Sciences (India)

    2017-07-26

    Jul 26, 2017 ... and 6.9 MPa m1/2, respectively. For the glass–ceramic Si3N4 composites with glass frit GY#, the flexural strength, Vick- ers hardness, elastic modulus and fracture toughness reach a maximum of 648 MPa, 13.9 GPa, 216 GPa and 6.4 MPa m1/2, respectively. The physical properties of the sintered compos-.

  14. Monolithic ceramics

    Science.gov (United States)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  15. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    SBLTi), samples were calcined by solid-state reaction and densified using the microwave sintering and conventional sintering techniques. Their structural, morphological and mechanical properties were investigated. The microwave sintered ...

  16. FT-IR characterization of articulated ceramic bricks with wastes from ceramic industries.

    Science.gov (United States)

    Nirmala, G; Viruthagiri, G

    2014-05-21

    The 30 ceramic test samples with the kaolinitic clay and ceramic rejects (in the as-received state and sintered at temperatures 900-1200°C) were investigated through spectral studies in order to elucidate the possibility of recycling the wastes from the government ceramic industry of Vriddhachalam, Tamilnadu state, South India. A detailed attribution of all the spectroscopic frequencies in the spectra recorded in the 4000-400cm(-1) region was attempted and their assignment to different minerals was accomplished. X-ray diffraction analysis was performed to demonstrate the reliability of IR attributions. The indication of well-ordered kaolinite is by the band at 1115cm(-1) in the raw samples which tends to shift towards 1095cm(-1) in all the fired samples. The peaks at 563cm(-1) and 795cm(-1) can be assigned to anorthite and dickite respectively. The presence of quartz and anorthite is confirmed both by XRD and FTIR. The microstructural observations were done through the SEM images which visualized the vitrification of the fired bricks at higher temperatures. The refractory properties of the samples found through the XRF analysis are also appreciable. The present work suggests that the incorporation of the rejects into the clay mixture will be a valid route for the ceramic industries to reduce the costs of the ceramic process. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

    Science.gov (United States)

    Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

    2015-01-01

    The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

  18. Fabrication of translucent boron nitride dispersed polycrystalline silicon nitride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, B [Department of Metallurgy and Material Engineering, Sunmoon University (Korea, Republic of); Fu, Z [State Key Lab of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology (China); Niihara, K [Nagaoka University of Technology, Nagaoka (Japan); Lee, S W, E-mail: joshibhupen@gmail.com [Department of Environment Engineering, Sunmoon University, Asan (Korea, Republic of)

    2011-03-15

    Optical transparency was achieved at infrared region and overall translucent silicon nitride was fabricated using hot press sintering (HPS). The increase in h-BN content decreased the optical transparency. Microstructral observations shows that the optical, mechanical and tribological properties of BN dispersed polycrystalline Si{sub 3}N{sub 4} ceramics were affected by the density, {alpha}:{beta}-phase ratio and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of {alpha}-Si{sub 3}N{sub 4}, AlN, MgO and h-BN at 1850 deg. C. The composite contained from 0.25 to 2 mass % BN powder with sintering aids (9% AlN + 3% MgO). Maximum transmittance of 57% was achieved for 0.25 mass % BN doped Si{sub 3}N{sub 4} ceramics. Fracture toughness was increased and wear volume and friction coefficient were decreased with increase in BN content.

  19. High-temperature-pressure polymerized resin-infiltrated ceramic networks.

    Science.gov (United States)

    Nguyen, J F; Ruse, D; Phan, A C; Sadoun, M J

    2014-01-01

    The aim of this study was to produce composite blocks (CB) for CAD/CAM applications by high-temperature-pressure (HT/HP) polymerization of resin-infiltrated glass-ceramic networks. The effect of network sintering and the absence/presence of initiator was investigated. Mechanical properties were determined and compared with those of Paradigm MZ100 (3M ESPE) blocks and HT/HP polymerized experimental "classic" CB, in which the filler had been incorporated by conventional mixing. The networks were made from glass-ceramic powder (VITA Zahnfabrik) formed by slip casting and were either sintered or not. They were silanized, infiltrated by urethane dimethacrylate, with or without initiator, and polymerized under HT/HP (300 MPa, 180°C) to obtain resin-infiltrated glass-ceramic network (RIGCN) CB. HT/HP polymerized CB were also made from an experimental "classic" composite. Flexural strength (σf), fracture toughness (KIC), and Vickers hardness were determined and analyzed by one- or two-way analysis of variance (ANOVA), Scheffé multiple-means comparisons (α = 0.05), and Weibull statistics (for σf). Fractured surfaces were characterized with scanning electron microscopy. The mechanical properties of RIGCN CB were significantly higher. Sintering induced significant increases in σf and hardness, while the initiator significantly decreased hardness. The results suggested that RIGCN and HT/HP polymerization could be used to obtain CB with superior mechanical properties, suitable for CAD/CAM applications.

  20. Microwave assisted sintering of gadolinium doped barium cerate electrolyte for intermediate temperature solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arumugam Senthil, E-mail: senthu.ramp@gmail.com [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Balaji, Ramamoorthy [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Jayakumar, Srinivasalu [Department of Physics, PSG Institute of Technology and Applied Research, Coimbatore, 641 062, Tamilnadu (India); Pradeep, Chandran [Department of Physics, Indian Institute of Technology, Madras, 600 036, Tamilnadu (India)

    2016-10-01

    In Solid Oxide Fuel Cell (SOFC), electrolyte plays a vital role to increase the energy conversion efficiency. The main hurdle of such electrolyte in fuel cell is its higher operating temperature (1000 °C) which results in design limitation and higher fabrication cost. In order to reduce the operating temperature of SOFC, a suitable electrolyte has been prepared through co-precipitation method followed by microwave sintering of solid ceramic. The calcination temperature for the as-prepared powder was identified using Differential Scanning Calorimetry. The crystal structure of the sample was found to exhibit its orthorhombic perovskite structure. The particle size was determined using High-Resolution Transmission Electron Microscope with uniform in shape and size, match with XRD results and confirmed from structural analysis. Thus, the sample prepared via co-precipitation method and the solid ceramic sintered through microwave can be a promising electrolyte for fuel cells operated at intermediate temperature. - Highlights: • To synthesis the composite electrolyte by chemical method and sinter using microwave. • To reduce the operating temperature of electrolyte for high ionic conductivity in SOFC's. • To study the phase purity and to develop nanocomposite at reduced temperature.