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Sample records for sintered powder samples

  1. Sinterable powders

    International Nuclear Information System (INIS)

    Zanghi, J.S.; Kasprzyk, M.R.

    1979-01-01

    A description is given of sinterable powders and methods of producing sintered products using such powders. The powders consist of (a) a particulate ceramic material, e.g. SiC, having specified particle size and surface area; (b) a carbon source material, e.g. sugar or a phenol-formaldehyde resin; and (c) a residue from a solution of H 3 BO 3 , B 2 O 3 , or mixtures of these as sintering aid. (U.K.)

  2. Strain-enhanced sintering of iron powders

    Energy Technology Data Exchange (ETDEWEB)

    Amador, D.R.; Torralba, J.M. [Universidad Carlos III de Madrid, Departamento de Ciencias de Materiales e Ingenieria Metalurgica, Leganes, Madrid (Spain); Monge, M.A.; Pareja, R. [Universidad Carlos III de Madrid, Departamento de Fisica, Madrid (Spain)

    2005-02-01

    Sintering of ball-milled and un-milled Fe powders has been investigated using dilatometry, X-ray, density, and positron annihilation techniques. A considerable sintering enhancement is found in milled powders showing apparent activation energies that range between 0.44 and 0.80 eV/at. The positron annihilation results, combined with the evolution of the shrinkage rate with sintering temperature, indicate generation of lattice defects during the sintering process of milled and un-milled powders. The sintering enhancement is attributed to pipe diffusion along the core of moving dislocations in the presence of the vacancy excess produced by plastic deformation. Positron annihilation results do not reveal the presence of sintering-induced defects in un-milled powders sintered above 1200 K, the apparent activation energy being in good agreement with that for grain-boundary diffusion in {gamma}-Fe. (orig.)

  3. Sintering of titanium alloy by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Cosme, C.R.M. [Universidade de Brasilia (UnB), DF (Brazil); Henriques, V.A.R.; Cairo, C.A.A.; Taddei, E.B. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    Full text: Titanium alloys are suitable for biomaterial applications, considering its biocompatibility and low elastic modulus compared to steel. Bone resorption in this case can be reduced by load sharing between the implant and natural bone.Starting powders were obtained by hydride method, carried out under positive hydrogen pressure at 500 deg C for titanium and 800 deg C for Nb, Zr and Ta powders. After reaching the nominal temperature, the material was held for 3h, with subsequent cooling to room temperature and milling of the friable hydride. Samples were produce by mixing of initial metallic powders followed by and cold isostatic pressing. Subsequent densification by sintering was performed at temperature range between 900 and 1700 deg C. Characterization was carried out with scanning electron microscopy, X-ray diffractometry and microhardness measurements. Microstructural examinations revealed higher amount of &⧣946;-phase for higher sintering temperature and dissolution of Ta and NB particles. In vitro tests revealed low cytotoxicity of sintered samples. (author)

  4. Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

    Directory of Open Access Journals (Sweden)

    Changzhou Yu

    2017-02-01

    Full Text Available Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P. titanium in a graphite furnace backfilled with argon and studied the effects of common contaminants (C, O, N on sintering densification of titanium. It is found that on the surface of the as-sintered titanium, a severely contaminated porous scale was formed and identified as titanium oxycarbonitride. Despite the porous surface, the sintered density in the sample interiors increased with increasing sintering temperature and holding time. Tensile specimens cut from different positions within a large sintered cylinder reveal different tensile properties, strongly dependent on the impurity level mainly carbon and oxygen. Depending on where the specimen is taken from the sintered compact, ultimate tensile strength varied from 300 to 580 MPa. An average tensile elongation of 5% to 7% was observed. Largely depending on the interstitial contents, the fracture modes from typical brittle intergranular fracture to typical ductile fracture.

  5. Low temperature spark plasma sintering of YIG powders

    International Nuclear Information System (INIS)

    Fernandez-Garcia, L.; Suarez, M.; Menendez, J.L.

    2010-01-01

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 o C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 o C leads to dense samples with minimal formation of YFeO 3 , opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  6. Low temperature spark plasma sintering of YIG powders

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Garcia, L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Suarez, M., E-mail: m.suarez@cinn.e [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-07-16

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 {sup o}C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 {sup o}C leads to dense samples with minimal formation of YFeO{sub 3}, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  7. Data on the densification during sintering of binder jet printed samples made from water- and gas-atomized alloy 625 powders

    Directory of Open Access Journals (Sweden)

    Amir Mostafaei

    2017-02-01

    Full Text Available Binder jet printing (BJP is a metal additive manufacturing method that manufactures parts with complex geometry by depositing powder layer-by-layer, selectively joining particles in each layer with a polymeric binder and finally curing the binder. After the printing process, the parts still in the powder bed must be sintered to achieve full densification (A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016; A. Mostafaei, E. Stevens, E. Hughes, S. Biery, C. Hilla, M. Chmielus, 2016; A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016 [1–3]. The collected data presents the characterization of the as-received gas- and water-atomized alloy 625 powders, BJP processing parameters and density of the sintered samples. The effect of sintering temperatures on the microstructure and the relative density of binder jet printed parts made from differently atomized nickel-based superalloy 625 powders are briefly compared in this paper. Detailed data can be found in the original published papers by authors in (A. Mostafaei, J. Toman, E.L. Stevens, E.T. Hughes, Y.L. Krimer, M. Chmielus, 2017 [4].

  8. Powder densification maps in Selective Laser Sintering

    International Nuclear Information System (INIS)

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

    2002-01-01

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

  9. Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

    OpenAIRE

    Changzhou Yu; Peng Cao; Mark Ian Jones

    2017-01-01

    Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P.) titanium in a graphite furnace backfilled with argon and stu...

  10. Evaluation of Sintering Behavior of Premix Al-Zn-Mg-Cu Alloy Powder

    Directory of Open Access Journals (Sweden)

    Haris Rudianto

    2015-01-01

    Full Text Available Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. Formation of liquid phase seems to support achieving high sintering density. Optimum mechanical properties also were obtained under those conditions. T6 heat treatment was done to improve the mechanical properties by formation of precipitation strengthening, and MgZn2 appears to be dominant strengthening precipitate. X-ray diffraction, optical microscopy, and SEM-EDS were used to characterize powder, and sintered and heat treated samples.

  11. Impact strength of sintered astaloy CrM powders

    International Nuclear Information System (INIS)

    Kazior, J.; Ploszczak, J.; Nykiel, M.; Pieczonka, T.

    2003-01-01

    In this paper results of a series of impact tests on sintered Astaloy CrM powders alloys modified by boron are presented and discussed. Boron in different forms, i.e. as elemental boron powder, boron carbide B 4 C powder or mixture of boron and carbon elemental powders, was used in different weight percentage to activate sintering of Astaloy CrM powder and to increase hardenability, with aim of increasing impact strength in view of structural applications. (author)

  12. Polymer powders for selective laser sintering (SLS)

    Science.gov (United States)

    Schmid, Manfred; Amado, Antonio; Wegener, Konrad

    2015-05-01

    Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers. The commonly applied SLS powder to date is polyamide 12 (PA 12). PA 12 or ccompounds of PA 12 (dry blends) are approximately 90 % of complete industrial consumption. The remaining small quantity is distributed on polyamide 11 (PA11) and some other `exotic' polymers (TPU, PEBA, P(E)EK). Industry is awaiting commodity polymers like polypropylene (PP) or polyethylene (PE) crucial to open new market segments. But several approaches launching those polymers failed. But what are the reasons for the difficulties in developing new SLS powders? The contribution is to answer this and highlights the combination of intrinsic and extrinsic polymer properties necessary to generate a polymer powder promising for SLS application. Particle shape, powder distribution, thermal, rheological and optical requirements must be considered and only a particularly controlled property combination leads to successful SLS implementation. Thermal behavior, particle shape and -distribution is discussed in detail, although the other properties can't be disregarded for providing new commercially successful SLS powder finally.

  13. Production of sintered alumina from powder; optimization of the sinterized parameters for the maximum mechanical resistence

    International Nuclear Information System (INIS)

    Rocha, J.C. da.

    1981-02-01

    Pure, sinterized alumina and the optimization of the parameters of sinterization in order to obtain the highest mechanical resistence are discussed. Test materials are sinterized from a fine powder of pure alumina (Al 2 O 3 ), α phase, at different temperatures and times, in air. The microstructures are analysed concerning porosity and grain size. Depending on the temperature or the time of sinterization, there is a maximum for the mechanical resistence. (A.R.H.) [pt

  14. Consolidation of copper and aluminium powders by spark plasma sintering

    Science.gov (United States)

    Saiprasad, M.; Atchayakumar, R.; Thiruppathi, K.; Raghuraman, S.

    2016-09-01

    Processing in the powder metallurgy route has emerged as an economical process for the production of near net shaped components with a wide range of desired mechanical properties suitable for various applications of industrial needs. This research work was conducted with an objective of studying the improvisation of density and hardness of Copper-Aluminium alloy prepared by spark plasma sintering. Cu-Al alloy with a composition of 95% copper and 5% aluminium was prepared by SPS process. SPS is a low voltage, DC pulse current activated, pressure-assisted sintering, which enables sintering at lower temperatures and shorter durations. The combination offered by Cu-Al alloy of high strength and high corrosion resistance results their applications under a wide variety of conditions. The density and hardness of the prepared sample were measured by conducting appropriate tests. Apparently, the values of hardness and density of the specimen prepared by SPS seemed to be better than that of conventional sintering. The experimental procedure, testing methodologies and analysis are presented.

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

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    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

  16. Field assisted hot pressing of sintering Inconel 718 MIM samples

    Science.gov (United States)

    Dugauguez, Olivier; Torralba, Jose Manuel; Barriere, Thierry; Gelin, Jean-Claude

    2016-10-01

    In this investigation on samples obtained by Metal Injection Molding (MIM), the conventional way of sintering in a furnace will be compared to Field Assisted Hot pressing (FAHP) sintering. The difficulty of this method is to be able to control the shrinkage of the sample and so its shape. It has yet not been investigated with a super alloy powder and so, the effects of a high sintering rate. By accelerating the sintering kinetics, the thermal behavior may be modified. Hence, the behavior of the Inconel 718 sintered by FAHP has been investigated. The sintered samples were all injected from a feedstock composed of a fine particle Inconel powder and a binder principally composed of Cellulose Acetate Butyrate CAB and Poly-Ethylene Glycol PEG. The effects of the two methods on the microstructure and the mechanical properties are then compared. There was no difference in distribution of pores between the conventional sintering and the FAHP sintering but a finer grain size showed better hardness.

  17. Powder injection molding of Stellite 6 powder: Sintering, microstructural and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Gülsoy, H. Özkan [Marmara University, Technology Faculty, Metall. and Mater. Eng., 34722 Istanbul (Turkey); Özgün, Özgür, E-mail: oozgun@bingol.edu.tr [Bingol University, Faculty of Engineering and Architecture, Mechanical Eng. Dep., 12000 Bingol (Turkey); Bilketay, Sezer [Marmara University, Technology Faculty, Metall. and Mater. Eng., 34722 Istanbul (Turkey)

    2016-01-10

    The purpose of this study was to produce Co-based Stellite 6 superalloy components by using the method of Powder Injection Molding (PIM) and to characterize the microstructural and mechanical properties of the produced components. The experimental studies were started through the formation of feedstock by mixing Stellite 6 powder with a multicomponent binder system. Prepared feedstock was formed by utilizing powder injection molding technique. Then the molded samples were subjected to the solvent and thermal debinding processes. Different sintering cycles were applied to the raw components for the purpose of determining the optimum sintering conditions. The densities of the sintered components were determined in accordance with the Archimedes' principle. The microstructural characterization was performed through scanning electron microscope (SEM) analysis, energy dispersive spectrometry (EDS) analyses, and X-ray diffraction (XRD) analysis. Hardness measurement and tensile test were conducted in order to determine the mechanical properties. The results illustrated that the injection molded Stellite 6 components were composed of fine and equiaxed grains, plenty of carbide precipitates exhibiting homogenous distribution throughout the microstructure formed at the grain boundaries and thus the mechanical properties were considerably high.

  18. Powder injection molding of Stellite 6 powder: Sintering, microstructural and mechanical properties

    International Nuclear Information System (INIS)

    Gülsoy, H. Özkan; Özgün, Özgür; Bilketay, Sezer

    2016-01-01

    The purpose of this study was to produce Co-based Stellite 6 superalloy components by using the method of Powder Injection Molding (PIM) and to characterize the microstructural and mechanical properties of the produced components. The experimental studies were started through the formation of feedstock by mixing Stellite 6 powder with a multicomponent binder system. Prepared feedstock was formed by utilizing powder injection molding technique. Then the molded samples were subjected to the solvent and thermal debinding processes. Different sintering cycles were applied to the raw components for the purpose of determining the optimum sintering conditions. The densities of the sintered components were determined in accordance with the Archimedes' principle. The microstructural characterization was performed through scanning electron microscope (SEM) analysis, energy dispersive spectrometry (EDS) analyses, and X-ray diffraction (XRD) analysis. Hardness measurement and tensile test were conducted in order to determine the mechanical properties. The results illustrated that the injection molded Stellite 6 components were composed of fine and equiaxed grains, plenty of carbide precipitates exhibiting homogenous distribution throughout the microstructure formed at the grain boundaries and thus the mechanical properties were considerably high.

  19. Characterization and Sintering of Armstrong Process Titanium Powder

    Science.gov (United States)

    Xu, Xiaoyan; Nash, Philip; Mangabhai, Damien

    2017-04-01

    Titanium and titanium alloys have a high strength to weight ratio and good corrosion resistance but also need longer time and have a higher cost on machining. Powder metallurgy offers a viable approach to produce near net-shape complex components with little or no machining. The Armstrong titanium powders are produced by direct reduction of TiCl4 vapor with liquid sodium, a process which has a relatively low cost. This paper presents a systematic research on powder characterization, mechanical properties, and sintering behavior and of Armstrong process powder metallurgy, and also discusses the sodium issue, and the advantages and disadvantages of Armstrong process powders.

  20. Powder metallurgy: Solid and liquid phase sintering of copper

    Science.gov (United States)

    Sheldon, Rex; Weiser, Martin W.

    1993-01-01

    Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

  1. Spark plasma sintering of commercial and development titanium alloy powders

    OpenAIRE

    Weston, N.S.; Derguti, F.; Tudball, A.; Jackson, M.

    2015-01-01

    Emerging lower cost titanium metal powder produced via an electrolytic method has been fully consolidated using spark plasma sintering (SPS) generating microstructures comparable to those observed in Ti–6Al–4V PM product. This is the first time powder from an alternative titanium extraction method has been processed via SPS and it is benchmarked with commercial alloys (CP–Ti, Ti–6Al–4V, and Ti–5Al–5V–5Mo–3Cr). The effect of powder feedstock size, morphology, and alloy chemistry on the consoli...

  2. Influence of spark plasma sintering conditions on the sintering and functional properties of an ultra-fine grained 316L stainless steel obtained from ball-milled powder

    Energy Technology Data Exchange (ETDEWEB)

    Keller, C., E-mail: clement.keller@insa-rouen.fr [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Tabalaiev, K.; Marnier, G. [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Noudem, J. [Laboratoire de Cristallographie des Matériaux, CNRS-UMR 6508, Université de Caen, ENSICAEN, 7 bd du Maréchal Juin, 14050 Caen (France); Sauvage, X. [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Hug, E. [Laboratoire de Cristallographie des Matériaux, CNRS-UMR 6508, Université de Caen, ENSICAEN, 7 bd du Maréchal Juin, 14050 Caen (France)

    2016-05-17

    In this work, 316L samples with submicrometric grain size were sintered by spark plasma sintering. To this aim, 316L powder was first ball-milled with different conditions to obtain nanostructured powder. The process control agent quantity and milling time were varied to check their influence on the crystallite size of milled powder. Samples were then sintered by spark plasma sintering using different sets of sintering parameters (temperature, dwell time and pressure). For each sample, grain size and density were systematically measured in order to investigate the influence of the sintering process on these two key microstructure parameters. Results show that suitable ball-milling and subsequent sintering can be employed to obtain austenitic stainless steel samples with grain sizes in the nanometer range with porosity lower than 3%. However, ball-milling and subsequent sintering enhance chromium carbides formation at the sample surface in addition to intragranular and intergranular oxides in the sample as revealed by X-ray diffraction and transmission electron microscopy. It has been shown that using Boron nitride together with graphite foils to protect the mold from powder welding prevent such carbide formation. For mechanical properties, results show that the grain size refinement strongly increases the hardness of the samples without deviation from Hall-Petch relationship despite the oxides formation. For corrosion resistance, grain sizes lower than a few micrometers involve a strong decrease in the pitting potential and a strong increase in passivation current. As a consequence, spark plasma sintering can be considered as a promising tool for ultra-fine grained austenitic stainless steel.

  3. Method for preparing a sinterable uranium dioxide powder

    International Nuclear Information System (INIS)

    Thornton, T.A.; Holaday, V.D. Jr.

    1985-01-01

    This invention provides an improved method for preparing a sinterable uranium dioxide powder for the preparation of nuclear fuel, using microwave radiation in a microwave induction furnace. The starting compound may be uranyl nitrate hexahydrate, ammonium diuranate or ammonium uranyl carbonate. The starting compound is heated in a microwave induction furnace for a period of time sufficient for compound decomposition. The decomposed compound is heated in a microwave induction furnace in a reducing atmosphere for a period of time sufficient to reduce the decomposed compound to uranium dioxide powder

  4. Influence of various manufacturing parameters on some characteristics of UO2 powders and their sintering behaviour

    International Nuclear Information System (INIS)

    Mintz, M.H.; Vaknin, Sh.; Kremener, A.; Hadari, Z.

    1977-02-01

    Various parameters in the process of manufacturing uranium dioxide are examined and their influence on the characteristics and sintering behaviour of the powders obtained established. In addition some correlations between the powder aggregates microstructure and their adhesion properties and sintering behaviour are indicated. Shrinkage during the sintering process is also discussed

  5. An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2015-04-01

    Full Text Available This study investigates phase transformation and mechanical properties of porous NiTi alloys using two different powder compacts (i.e., Ni/Ti and Ni/TiH2 by a conventional press-and-sinter means. The compacted powder mixtures were sintered in vacuum at a final temperature of 1373 K. The phase evolution was performed by in situ neutron diffraction upon sintering and cooling. The predominant phase identified in all the produced porous NiTi alloys after being sintered at 1373 K is B2 NiTi phase with the presence of other minor phases. It is found that dehydrogenation of TiH2 significantly affects the sintering behavior and resultant microstructure. In comparison to the Ni/Ti compact, dehydrogenation occurring in the Ni/TiH2 compact leads to less densification, yet higher chemical homogenization, after high temperature sintering but not in the case of low temperature sintering. Moreover, there is a direct evidence of the eutectoid decomposition of NiTi at ca. 847 and 823 K for Ni/Ti and Ni/TiH2, respectively, during furnace cooling. The static and cyclic stress-strain behaviors of the porous NiTi alloys made from the Ni/Ti and Ni/TiH2 compacts were also investigated. As compared with the Ni/Ti sintered samples, the samplessintered from the Ni/TiH2 compact exhibited a much higher porosity, a higher close-to-total porosity, a larger pore size and lower tensile and compressive fracture strength.

  6. In situ observation and neutron diffraction of NiTi powder sintering

    International Nuclear Information System (INIS)

    Chen, Gang; Liss, Klaus-Dieter; Cao, Peng

    2014-01-01

    This study investigated NiTi powder sintering behaviour from elemental powder mixtures of Ni/Ti and Ni/TiH 2 using in situ neutron diffraction and in situ scanning electron microscopy. The sintered porous alloys have open porosities ranging from 2.7% to 36.0%. In comparison to the Ni/Ti compact, dehydrogenation occurring in the Ni/TiH 2 compact leads to less densification yet higher chemical homogenization only after high-temperature sintering. For the first time, direct evidence of the eutectoid phase transformation of NiTi at 620 °C is reported by in situ neutron diffraction. A comparative study of cyclic stress–strain behaviours of the porous NiTi alloys made from Ni/Ti and Ni/TiH 2 compacts indicate that the samples sintered from the Ni/TiH 2 compact exhibited a much higher porosity, larger pore size, lower fracture strength, lower close-to-overall porosity ratio and lower Young’s modulus. Instead of enhanced densification by the use of TiH 2 as reported in the literature, this study shows an adverse effect of TiH 2 on powder densification in NiTi

  7. Structural comparison of sintering products made of "TiC + Ti" composite powders and "Ti + C" powder mixtures

    Science.gov (United States)

    Krinitcyn, Maksim G.; Pribytkov, Gennadii A.; Korosteleva, Elena N.; Firsina, Irina A.; Baranovskii, Anton V.

    2017-12-01

    In this study, powder composite materials comprised of TiC and Ti with different ratios are processed by sintering of Ti and C powder mixtures and self-propagating high-temperature synthesis (SHS) in "Ti+C" system followed by sintering. The microstructure and porosity of obtained composites are investigated and discussed. The dependence of porosity on sintering time is explained theoretically. Optimal regimes that enable to obtain the most homogeneous structure with the least porosity are described.

  8. Sintering of B{sub 4}C powder obtained by a modified carbo-thermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, R.M.; Kazumi, M.H.; Goncalves, D.P.; Melo, F.C.L. [Centro Tecnico Aeroespacial (CTA) - Instituto de Aeronautica e Espaco, Praca Marechal Eduardo Gomes, 50 Campus do CTA - Vila das Acacias, 12228-904 Sao Jose dos Campos-SP (Brazil)

    2005-07-01

    Boron carbide is one of the hardest materials and a highly refractory material that is of great interest for structural, electronic and nuclear applications. B{sub 4}C is commercially manufactured by the carbo-thermal reduction of a mixture of boron oxide (B{sub 2}O{sub 3}) in an batch electric arc furnace process. However the carbo-thermal reaction on the stoichiometric starting composition results an excess carbon residue because of the boron loss in the form of B{sub 2}O{sub 2}. Thus, a modified carbo-thermal reaction is applied with an excess B{sub 2}O{sub 3} to compensate the loss and to obtain stoichiometric powders. The aim of this work is to study the sinterability of this powder with the lower carbon residue acting as sintering additive. Pressureless sintering in the temperatures of 1900 deg. C/30 min and 2100 deg. C/30 min in argon atmosphere were applied. The synthesized powders were analysed by XRD and SEM. Density of 94% of theoretical density was achieved for sample prepared with the powder obtained with 50% B{sub 2}O{sub 3} excess synthesized at 1700 deg. C/15 min. (authors)

  9. Nano or micro grained alumina powder? A choose before sintering

    Directory of Open Access Journals (Sweden)

    Román, R.

    2008-12-01

    Full Text Available Two different wet routes have been used to synthesize alumina powders in order to compare the characteristics of the final product and its behaviour during sintering. The Homogeneous Precipitation (HP gives rise to nanoparticulated powders of about 2 nm. However, such particles quickly aggregate and grow with calcination temperature. The Polymerized Organic-Inorganic Synthesis (POI produces homogeneous particle size powders (about 1 micron after resin charring. The characterization of the powder surface is the basis of an efficient process control. Particle characterization parameters (morphology, crystallinity and degree of aggregation are characterized by different techniques, such as DTA/TG, IR, XRD, SEM and TEM, and compared between these synthesis methods. The results show the evolution from the amorphous to the corundum alumina phase for both processes and their ability for sintering, as well discuses the beneficial of nanoparticles obtained by HP during sintering.

    Se han utilizado dos diferentes síntesis por vía húmeda para la preparación de polvos de alúmina con el fin de comparar las características de los productos finales y su comportamiento durante la sinterización. La Precipitación Homogénea (HP da lugar a polvos nanoparticulados de unos 2nm. Se observa sin embargo, como estas partículas se agregan rápidamente y crecen con la temperatura de calcinación. La Síntesis por Polimerización Orgánica-Inorgánica (POI produce polvos de tamaño de partícula homogéneo (en torno a 1 micra después de la descomposión de la resina. La caracterización de la superficie de los polvos es la base de un control eficiente del proceso. Los parámetros de caracterización de las partículas obtenidas (morfología, cristalinidad y grado de agregación se obtienen por diferentes técnicas como DTA/TG, IR, XRD, SEM y TEM, y se comparan entre estos métodos de síntesis. Los resultados muestran la evolución desde el amorfo a la fase

  10. Developing Characterization Procedures for Qualifying both Novel Selective Laser Sintering Polymer Powders and Recycled Powders

    Energy Technology Data Exchange (ETDEWEB)

    Bajric, Sendin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-12

    Selective laser sintering (SLS) is an additive technique which is showing great promise over conventional manufacturing techniques. SLS requires certain key material properties for a polymer powder to be successfully processed into an end-use part, and therefore limited selection of materials are available. Furthermore, there has been evidence of a powder’s quality deteriorating following each SLS processing cycle. The current investigation serves to build a path forward in identifying new SLS powder materials by developing characterization procedures for identifying key material properties as well as for detecting changes in a powder’s quality. Thermogravimetric analyses, differential scanning calorimetry, and bulk density measurements were investigated.

  11. Bulk nanocrystalline Al85Ni10La5 alloy fabricated by spark plasma sintering of atomized amorphous powders

    International Nuclear Information System (INIS)

    Sasaki, T.T.; Hono, K.; Vierke, J.; Wollgarten, M.; Banhart, J.

    2008-01-01

    Amorphous Al 85 Ni 10 La 5 powders were consolidated to cylindrical samples by spark plasma sintering (SPS), and their microstructures and mechanical properties were investigated. When the powders were consolidated below the crystallization temperature, an amorphous phase was retained in the consolidated sample. Sintering above the crystallization temperature caused full crystallization. The Vickers hardness of the amorphous-containing sample was about 350 HV in the as-sintered state and increased up to 450 HV by a subsequent heat treatment just below the crystallization temperature. The highest hardness was achieved in a nanocrystalline microstructure. Compression tests revealed the brittle nature of the consolidated samples although the fracture and yield strength was higher than 1 GPa. The brittleness is due to the low relative density of the amorphous-containing samples and the presence of a large amount of intermetallic compounds in the fully crystallized sample

  12. Microstructural analysis of sinterized aluminum powder obtained by the high energy milling of beverage cans

    International Nuclear Information System (INIS)

    Souza, Jose Raelson Pereira de; Peres, Mauricio Mhirdaui

    2016-01-01

    The objective is the study of the effect of high energy milling on the sintering of aluminum from beverage cans. The selected aluminum cans were cut and subjected to high energy milling under a common atmosphere (in the air). In milling, three grams of aluminum was used to maintain the ratio of 10/1 between the mass of the beads and the material. The milling time was varied in 1h, 1.5h and 2h, keeping the other variables constant. The particle size distribution was measured by laser granulometry, for further compaction and sintering at a temperature of 600 ° C for 2 h. The samples were characterized by scanning electron microscopy (SEM). The granulometric analysis of the powders found that higher milling times produced finer particles. Powders with granulometry of less than 45 μm were obtained at 1 h, 1.5 h and 2 h times. The times of 1.5h and 2h promoted finer particles with better distribution of size. The SEM analyzes showed little variation in the shape of the particles as a function of the variation of the grinding times, presenting irregularities in the platelet geometry. The sintering time and temperature were effective in the densification of the powder particles, which were influenced by the average particle size

  13. Master sintering curves of two different alumina powder compacts

    Directory of Open Access Journals (Sweden)

    Vaclav Pouchly

    2009-12-01

    Full Text Available Concept of Master Sintering Curve is a strong tool for optimizing sintering schedule. The sintering behaviour can be predicted, and sintering activation energy can be calculated with the help of few dilatometric measurements. In this paper an automatic procedure was used to calculate Master Sintering Curves of two different alumina compacts. The sintering activation energies were determined as 640 kJ/mol for alumina with particle size of 240 nm, respective 770 kJ/mol for alumina with particle size of 110 nm. The possibility to predict sintering behaviour with the help of Master Sintering Curve was verified.

  14. Effect of Sintering Atmosphere and Solution Treatment on Density, Microstructure and Tensile Properties of Duplex Stainless Steels Developed from Pre-alloyed Powders

    Science.gov (United States)

    Murali, Arun Prasad; Mahendran, Sudhahar; Ramajayam, Mariappan; Ganesan, Dharmalingam; Chinnaraj, Raj Kumar

    2017-10-01

    In this research, Powder Metallurgy (P/M) of Duplex Stainless Steels (DSS) of different compositions were prepared through pre-alloyed powders and elemental powders with and without addition of copper. The powder mix was developed by pot mill for 12 h to obtain the homogeneous mixture of pre-alloyed powder with elemental compositions. Cylindrical green compacts with the dimensions of 30 mm diameter and 12 mm height were compacted through universal testing machine at a pressure level of 560 ± 10 MPa. These green compacts were sintered at 1350 °C for 2 h in hydrogen and argon atmospheres. Some of the sintered stainless steel preforms were solution treated at 1050 °C followed by water quenching. The sintered as well as solution treated samples were analysed by metallography examination, Scanning Electron Microscopy and evaluation of mechanical properties. Ferrite content of sintered and solution treated DSS were measured by Fischer Ferritoscope. It is inferred that the hydrogen sintered DSS depicted better density (94% theoretical density) and tensile strength (695 MPa) than the argon sintered steels. Similarly the microstructure of solution treated DSS revealed existence of more volume of ferrite grains than its sintered condition. Solution treated hydrogen sintered DSS A (50 wt% 316L + 50 wt% 430L) exhibited higher tensile strength of 716 MPa and elongation of 17%, which are 10-13% increment than the sintered stainless steels.

  15. Material Evaluation and Process Optimization of CNT-Coated Polymer Powders for Selective Laser Sintering

    Directory of Open Access Journals (Sweden)

    Shangqin Yuan

    2016-10-01

    Full Text Available Multi-walled carbon nanotubes (CNTs as nano-reinforcements were introduced to facilitate the laser sintering process and enhance the thermal and mechanical properties of polymeric composites. A dual experimental-theoretical method was proposed to evaluate the processability and predict the process parameters of newly developed CNT-coated polyamide 12 (CNTs/PA12 powders. The thermal conductivity, melt viscosity, phase transition and temperature-dependent density and heat capacity of PA12 and CNTs/PA12 powders were characterized for material evaluation. The composite powders exhibited improved heat conduction and heat absorption compared with virgin polymer powders, and the stable sintering range of composite powders was extended and found to be favourable for the sintering process. The microstructures of sintered composites revealed that the CNTs remained at the powder boundaries and formed network architectures, which instantaneously induced the significant enhancements in tensile strength, elongation at break and toughness without sacrificing tensile modulus.

  16. Production of NdFeB powders by HDDR from sintered magnets

    International Nuclear Information System (INIS)

    Janasi, S.R.; Rodrigues, D.; Landgraf, F.J.G.; Campos, M.F. de

    2010-01-01

    The production of NdFeB powders by the HDDR process from metallic alloys has been widely investigated. Different HD and DR conditions have been used to induce anisotropy and to improve the intrinsic coercivity of the obtained powders. The purpose of this study is to apply the HDDR process in the reprocessing of NdFeB sintered magnet scraps. There were investigated different processing conditions as temperature and time of desorption and recombination (DR). The results of X ray diffraction show the formation of the magnetic phase Nd 2 Fe 14 B in all the investigated conditions. Magnetic measurements by vibrating sample magnetometer indicate that powders with intrinsic coercivity up to 790 kA/m were obtained. (author)

  17. An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

    OpenAIRE

    Chen, Gang; Liss, Klaus-Dieter; Cao, Peng

    2015-01-01

    This study investigates phase transformation and mechanical properties of porous NiTi alloys using two different powder compacts (i.e., Ni/Ti and Ni/TiH2) by a conventional press-and-sinter means. The compacted powder mixtures were sintered in vacuum at a final temperature of 1373 K. The phase evolution was performed by in situ neutron diffraction upon sintering and cooling. The predominant phase identified in all the produced porous NiTi alloys after being sintered at 1373 K is B2 NiTi phase...

  18. Validation of DEM modeling of sintering using an in situ X-ray microtomography analysis of the sintering of NaCl powder

    Science.gov (United States)

    Martin, Sylvain; Navarro, Sebastián; Palancher, Hervé; Bonnin, Anne; Léchelle, Jacques; Guessasma, Mohamed; Fortin, Jérôme; Saleh, Khashayar

    2016-11-01

    This paper aims to validate the discrete element method (DEM) model of sintering. In situ X-ray microtomography experiments have been carried out at the ESRF to follow the sintering of NaCl powder, the properties of which are close to the DEM model assumptions. DEM simulations are then run using an improved implicit method. The comparison between experiment and simulation shows the capability of DEM to predict the behavior of the sample on both particle and packing scale. The main advantages and limits of this approach are finally discussed based on these results and those of previous studies.

  19. Effects of Admixed Titanium on Densification of 316L Stainless Steel Powder during Sintering

    Directory of Open Access Journals (Sweden)

    Aslam Muhammad

    2014-07-01

    Full Text Available Effects of admixed titanium on powder water atomized (PWA and powder gas atomized (PGA 316L stainless steel (SS have been investigated in terms of densification. PGA and PWA powders, having different shapes and sizes, were cold pressed and sintered in argon atmosphere at 1300°C. The admixed titanium compacts of PGA and PWA have shown significant effect on densification through formation of intermetallic compound and reducing porosity during sintering process. PWA, having particle size 8 μm, blended with 1wt% titanium has exhibited higher sintered density and shrinkage as compared to gas atomized powder compacts. Improved densification of titanium blended PGA and PWA 316L SS at sintering temperature 1300°C is probably due to enhanced diffusion kinetics resulting from stresses induced by concentration gradient in powder compacts.

  20. Densification and volumetric change during supersolidus liquid phase sintering of prealloyed brass Cu28Zn powder: Modeling and optimization

    Directory of Open Access Journals (Sweden)

    Mohammadzadeh A.

    2014-01-01

    Full Text Available An investigation has been made to use response surface methodology and central composite rotatable design for modeling and optimizing the effect of sintering variables on densification of prealloyed Cu28Zn brass powder during supersolidus liquid phase sintering. The mathematical equations were derived to predict sintered density, densification parameter, porosity percentage and volumetric change of samples using second order regression analysis. As well as the adequacy of models was evaluated by analysis of variance technique at 95% confidence level. Finally, the influence and interaction of sintering variables, on achieving any desired properties was demonstrated graphically in contour and three dimensional plots. In order to better analyze the samples, microstructure evaluation was carried out. It was concluded that response surface methodology based on central composite rotatable design, is an economical way to obtain arbitrary information with performing the fewest number of experiments in a short period of time.

  1. The role of the native oxide shell on the microwave sintering of copper metal powder compacts

    International Nuclear Information System (INIS)

    Mahmoud, Morsi M.; Link, Guido; Thumm, Manfred

    2015-01-01

    Highlights: • Thin oxide native layer had a critical role on microwave sintering of copper. • Explain why microwaves interact with copper powder differently than its bulk. • Abnormal expansion in copper is due to the plastic deformation and crack formation. • In-situ setup gives important insight about the microwave sintering of metals. • Microwave sintering is a promising candidate technology in powder metallurgy. - Abstract: Successful microwave sintering of several metal powders had been reported by many researchers with remarkable improvements in the materials properties and/or in the overall process. However, the concept behind microwave heating of metal powders has not been fully understood till now, as it is well known that bulk metals reflect microwaves. The progress of microwave sintering of copper metal powder compacts was investigated via combining both in-situ electrical resistivity and dilatometry measurements that give important information about microstructural changes with respect to the inter-particle electrical contacts during sintering. The sintering behavior of copper metal powders was depending on the type of the gas used, particle size, the initial green density, the soaking sintering time and the thin oxide layer on the particles surfaces. The thin copper oxide native layer (ceramics) that thermodynamically formed on the particles surfaces under normal handling and ambient environmental conditions had a very critical and important role in the microwave absorption and interaction, the sintering behavior and the microstructural changes. This finding could help to have a fundamental understanding of why MW’s interact with copper metal powder in a different way than its bulk at room temperature, i.e. why a given metal powder could be heated using microwaves while its bulk reflects it

  2. In situ Investigation of Titanium Powder Microwave Sintering by Synchrotron Radiation Computed Tomography

    Directory of Open Access Journals (Sweden)

    Yu Xiao

    2016-01-01

    Full Text Available In this study, synchrotron radiation computed tomography was applied to investigate the mechanisms of titanium powder microwave sintering in situ. On the basis of reconstructed images, we observed that the sintering described in this study differs from conventional sintering in terms of particle smoothing, rounding, and short-term growth. Contacted particles were also isolated. The kinetic curves of sintering neck growth and particle surface area were obtained and compared with those of other microwave-sintered metals to examine the interaction mechanisms between mass and microwave fields. Results show that sintering neck growth accelerated from the intermediate period; however, this finding is inconsistent with that of aluminum powder microwave sintering described in previous work. The free surface areas of the particles were also quantitatively analyzed. In addition to the eddy current loss in metal particles, other heating mechanisms, including dielectric loss, interfacial polarization effect, and local plasma-activated sintering, contributed to sintering neck growth. Thermal and non-thermal effects possibly accelerated the sintering neck growth of titanium. This study provides a useful reference of further research on interaction mechanisms between mass and microwave fields during microwave sintering.

  3. Influence of sintering temperature on the phases and photoelectric characteristics of BiOCl/ZnO composite powders

    Science.gov (United States)

    Chen, Song; Zhu, De-gui

    2017-12-01

    Zinc oxide is a typical functional oxide that has been widely researched for various industry applications due to its peculiar physical characteristics. However, to achieve its potential in promising applications, much work has been diligently performed to improve the physical properties of ZnO. In this work, an aqueous suspension route was used to prepare BiOCl/ZnO composite powders, and sintering processes were applied to investigate the influence of sintering temperature on the phase evolutions, microstructures, and photoelectric characteristics of BiOCl/ZnO composite powders. The results indicated that the photoelectric properties mainly depend on the relevant content of BiOCl in the composite powders and the sintering temperature. The photoelectric measurements in K2SO4 solutions show that the photoelectric properties of the samples with the appropriate BiOCl content (0.3mol% and 2.0mol%) are better than those of ZnO and commercial TiO2 (P25) powders, but the photoelectric measurements in NaOH solutions indicate that the photoelectric characteristics of the as-sintered samples are only better than those of P25.

  4. Sintered Nickel Powder Wicks for Flat Vertical Heat Pipes

    Directory of Open Access Journals (Sweden)

    Geir Hansen

    2015-03-01

    Full Text Available The fabrication and performance of wicks for flat heat pipe applications produced by sintering a filamentary nickel powder has been investigated. Tape casting was used as an intermediate step in the wick production process. Thermogravimetric analysis was used to study the burn-off of the organic binder used and to study the oxidation and reduction processes of the nickel. The wicks produced were flat, rectangular and intended for liquid transport in the upwards vertical direction. Rate-of-rise experiments using heptane were used to test the flow characteristics of the wicks. The wick porosities were measured using isopropanol. The heat transfer limitation constituted by the vapour static pressure and the capillary pressure was discussed. The influence on wick performance by using pore former in the manufacturing was studied. When Pcap/Psat > 1, the use of a pore former to increase the wick permeability will always improve the wick performance. When Pcap/Psat < 1, it was shown that if the effective pore radius and the permeability increase with an equal percentage the overall influence on the wick capacity is negative. A criterion for a successful pore former introduction is proposed and the concept of a pore former evaluation plot is presented.

  5. Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering

    Science.gov (United States)

    Tünçay, Mehmet Masum; Nguyen, Lucie; Hendrickx, Philippe; Brochu, Mathieu

    2016-10-01

    Spark plasma sintering (SPS) is a powder metallurgy process that sinters powder materials within a short time by simultaneous application of electrical current and pressure. SPS differs from other conventional powder metallurgy processes by its heating mechanism, which is Joule heating of the sample within a graphite die. This study investigates the consolidation of aluminum powder by SPS. Different pressures were used and particle bonding evaluated by means of fracture surface analysis. Electrical resistance, obtained from online monitoring of the variation of voltage and current during the process, showed an enhanced descent at 0.3 T m, and the area under this drop was associated with ductility: the greater the area, the higher the ductility. This temperature corresponds to a significant increase in the hardness ratio of the oxide layer to aluminum, where breakdown of the oxide layer becomes easier, permitting enhanced metallurgical bonding between the powder particles.

  6. Effect of sintering conditions on the microstructural and mechanical characteristics of porous magnesium materials prepared by powder metallurgy.

    Science.gov (United States)

    Čapek, Jaroslav; Vojtěch, Dalibor

    2014-02-01

    There has recently been an increased demand for porous magnesium materials in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such materials. Many works have dealt with the preparation of porous magnesium; however, the effect of sintering conditions on material properties has rarely been investigated. In this work, we investigated porous magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of porous magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of porous magnesium. © 2013.

  7. Sintering and Microstructures of SUS 316L Powder Produced by 3D Printing Process

    Directory of Open Access Journals (Sweden)

    Kim W.J.

    2017-06-01

    Full Text Available Selective laser sintering (SLS is a type of laminating sintering technique, using CO2 laser with (metal, polymer, and ceramic powders. In this result, the flake SUS 316L was used to achieve a high porous product, and compare to spherical type. After SLS, the porosity of flake-type sample with 34% was quite higher than that of the spherical-type one that had only 11%. The surface roughness of the flake SLS sample were also investigated in both inner and surface parts. The results show that the deviation of the roughness of the surface part is about 64.40μm, while that of the internal one was about 117.65μm, which presents the containing of high porosity in the uneven surfaces. With the process using spherical powder, the sample was quite dense, however, some initial particles still remained as a result of less energy received at the beneath of the processing layer.

  8. Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

    Directory of Open Access Journals (Sweden)

    Michalski B.

    2013-01-01

    Full Text Available In this study the SPS method was applied for low RE content (8,5% at. and high RE content (13,5 % at. MQ powders. The powders were sintered in a wide range of temperature, for 5 min., under pressure of 35 MPa. The low RE content grade, densified reluctantly and gained the density close to the theoretical value only for 850 °C. The coercivity decreased gradually with increasing sintering temperature. On the other hand, the densification of the higher RE content grade powder occurred much easier and the coercivity, close to the theoretical value, was achieved already at 650 °C. The coercivity of this material also decreased with increasing sintering temperature. Microstructural studies revealed that the SPS sintering process leads to partial decomposition of the Nd2Fe14B phase. The proportion of the RE-rich and iron phases increases parallel to the increasing sintering temperature. On the basis of the current results one can conclude that fabrication of high density MQ powders based magnets by the SPS method is possible, however the powders having higher RE content should be used for this purpose and the sintering temperature as low as possible, related to density, should be kept.

  9. Structure and Properties of VT6 Alloy Obtained by Layered Selective Sintering of a Powder

    Science.gov (United States)

    Teresov, A. D.; Ivanov, Yu. F.; Petrikova, E. A.; Koval, N. N.

    2017-12-01

    This paper is focused on a clarification and analysis of the regularities of formation of the structure and properties of samples of the titanium-based alloy VT6, obtained by methods of conventional metallurgy and formed by layered selective electron-beam sintering in vacuum (using the Arcam A2X (3D printer) system (Arcam, Sweden)) of VT6 titanium powder with particle size 40-100 μm. Additional modification of the samples was realized by irradiating the surface with an intense pulsed electron beam (15 keV, 45 J/cm2, 200 μs, 10 pulses, 0.3 s-1, 3.5·10-2 Pa). It is shown that the action of a pulsed electron beam on the surface of samples formed by layered selective electron-beam sintering leads to a significant reduction in the porosity of the surface layer of the material and formation in the surface layer of a polycrystalline structure (grain size 15-60 μm) with a substructure in the form of crystallization cells (cell size 0.5-1.2 μm). Electron-beam processing of samples prepared by methods of conventional metallurgy for the indicated electron-beam parameters leads to the formation in the surface layer of a polycrystalline structure (grain size 50-800 μm) with a laminar intragrain substructure. Mechanical tests, performed by stretching flat samples, showed that the highest combination of mechanical strength and plasticity is possessed by samples obtained by layered selective electron-beam sintering with subsequent irradiation by an intense pulsed electron beam.

  10. Fabrication of TiNi powder by mechanical alloying and shape memory characteristics of the sintered alloy

    International Nuclear Information System (INIS)

    Terayama, Akira; Kyogoku, Hideki; Komatsu, Shinichiro; Sakamura, Masaru

    2006-01-01

    This paper presents the fabrication condition of TiNi alloy powder by mechanical alloying and shape memory characteristics of the sintered alloy. The effect of mechanical alloying condition on the characteristics of mechanically alloyed powder (MA powder) was investigated. Also, the difference in sintering behavior between the MA powder and the elementally mixed powders by V-blender and the shape memory characteristics of the sintered alloys were also examined. The MA powder was fabricated by milling using a planetary ball mill in a rotational speed between 200 and 500 min -1 for various milling times in an atmosphere of Ar gas. These two of powders prepared in different processes were sintered using a pulse-current pressure sintering equipment at various sintering temperatures. The powder agglomerated and its particle size became larger with an increase in milling time. The mixture of Ti and Ni powders changed into an amorphous state by processing for 3.6 ks over 300 min -1 . The sintered alloy of the MA powder showed more uniform phase of TiNi than that of the elementally mixed powders sintered in a same manner, however, the former showed a lower density than the latter due to a larger particle size of the MA powder of before-sintering. It was found from the measurement of the transformation temperature of the sintered alloy of the MA powder using DSC that the alloy has shape memory characteristics, and the transformation temperatures of the alloy are higher than those of the alloy of the elementally mixed powders due to waste of Ni powder. (author)

  11. The evaluation of microstructure and mechanical properties of sintered sub-micron WC-Co powders

    International Nuclear Information System (INIS)

    Nor Izan Izura; Mohd Asri Selamat; Noraizham Mohamad Diah; Talib Ria Jaafar

    2007-01-01

    A cemented tungsten carbide (WC-Co) is widely used for a variety of machining, cutting, drilling and other applications. The properties of this tungsten heavy alloy are sensitive to processing and degraded by residual porosity. The sequence of high end powder metallurgy process include mixing, compacting and followed by multi-atmosphere sintering of green compact were analyzed. The sub micron (<1.0 μm) and less than 10.0 μm of WC powders are sintered with a metal binder 6% Co to provide pore-free part. The powder compacts were sintered at temperatures cycle in the range of 1200 degree Celsius-1550 degree Celsius in nitrogen-based sintering atmosphere. To date, however there have been few reported studies in the literature that the best sintering was carried out via liquid phase sintering in vacuum at approximately 1500 degree Celsius. from this study we found that in order to attain high mechanical properties, a fine grain size of powder is necessary. Therefore, the attention of this work is to develop and produce wear resistant component with better properties or comparable to the commercial ones. (author)

  12. Enery Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications

    Energy Technology Data Exchange (ETDEWEB)

    Thomas Zwitter; Phillip Nash; Xiaoyan Xu; Chadwick Johnson

    2011-03-31

    This is the final technical report for the Department of Energy NETL project NT01931 Energy Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications. Titanium has been identified as one of the key materials with the required strength that can reduce the weight of automotive components and thereby reduce fuel consumption. Working with newly developed sources of titanium powder, Webster-Hoff will develop the processing technology to manufacture low cost vehicle components using the single press/single sinter techniques developed for iron based powder metallurgy today. Working with an automotive or truck manufacturer, Webster-Hoff will demonstrate the feasibility of manufacturing a press and sinter titanium component for a vehicle application. The project objective is two-fold, to develop the technology for manufacturing press and sinter titanium components, and to demonstrate the feasibility of producing a titanium component for a vehicle application. The lowest cost method for converting metal powder into a net shape part is the Powder Metallurgy Press and Sinter Process. The method involves compaction of the metal powder in a tool (usually a die and punches, upper and lower) at a high pressure (up to 60 TSI or 827 MPa) to form a green compact with the net shape of the final component. The powder in the green compact is held together by the compression bonds between the powder particles. The sinter process then converts the green compact to a metallurgically bonded net shape part through the process of solid state diffusion. The goal of this project is to expand the understanding and application of press and sinter technology to Titanium Powder applications, developing techniques to manufacture net shape Titanium components via the press and sinter process. In addition, working with a vehicle manufacturer, demonstrate the feasibility of producing a titanium component for a vehicle. This is not a research program, but rather a

  13. Improved critical current densities in bulk FeSe superconductor using ball milled powders and high temperature sintering

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, M.; Furutani, K.; Murakami, M. [Graduate School of Science and Engineering, Superconducting Materials Laboratory, Shibaura Institute of Technology, Tokyo (Japan); Kumar, Dinesh; Rao, M.S. Ramachandra [Department of Physics, Nano Functional Materials Technology Centre and Materials Science Research Centre, Indian Institute of Technology Madras, Chennai (India); Koblischka, M.R. [Institute of Experimental Physics, Saarland University, Saarbruecken (Germany)

    2016-12-15

    The present study is investigating the effect of high temperature sintering combined with ball milled powders for the preparation of FeSe material via solid state sintering technique. The commercial powders of Fe (99.9% purity) and Se (99.9% purity) were mixed in a nominal ratio Fe:Se = 1:1 and thoroughly ground and ball-milled in a glove box during 6 h. Then, the powder mixture was pressed into pellets of 5 mm in diameter and 2 mm thickness using an uniaxial pressure of 100 MPa. The samples were sealed in quartz tubes and sintered at 600 C for 24 h. Then, the pellets were again thoroughly ground and ball-milled in the glove box and pressed into pellets, and the final sintering was performed at two different temperatures, namely at 900 C for 24 h and at 950 C for 24 h. X-ray diffraction results confirmed that both samples showed mainly of the β-FeSe with tetragonal structure. The temperature dependence of magnetization (M-T) curves revealed a sharp superconducting transition T{sub c,} {sub onset} = 8.16 K for the sample sintered at 900 C. Further, scanning electron microscopy observations proved that samples sintered at 900 C show a platelike grain structure with high density. As a result, improved irreversibility fields around 5 T and the critical current density (J{sub c}) values of 6252 A cm{sup -2} at 5 K and self-field are obtained. Furthermore, the normalized volume pinning force versus the reduced field plots indicated a peak position at 0.4 for the sample sintered at 900 C. Improved flux pinning and the high J{sub c} values are attributed to the textured microstructure of the material, produced by a combination of high temperature sintering and ball milling. (copyright 2016 The Authors. Phys. Status Solidi A published by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Effects of forming temperature and sintering rate to the final properties of FeCuAl powder compacts formed through uniaxial die compaction process

    Science.gov (United States)

    Rahman, M. M.; Ismail, M. A.; Sopyan, I.; Rahman, H. Y.

    2018-01-01

    This paper presents the outcomes of an experimental investigation on the effects of forming temperature and sintering schedule to the final characteristics of FeCuAl powder mass formed at different temperature and sintered at different schedule. A lab-scale uni-axial die compaction rig was designed and fabricated which enabled the compaction of powder mass at room temperature as well as elevated temperature. Iron (Fe) powder ASC 100.29 was mechanically mixed with other elemental powders, namely copper (Cu), and aluminum (Al) for 60 minutes and compacted at three different temperature, i.e., 30°C, 150°C, and 200°C by applying 425 MPa of simultaneous downward and upward axial loading to generate green compacts. The as-pressed samples were inspected visually and the defect-free green compacts were subsequently sintered in an argon gas fired furnace at 800°C for 60 min at three different heating/cooling rates, i.e., 5, 10, and 15°C/min, respectively. The sintered samples were then characterised for their physical, electrical, and mechanical properties. The microstructures of the sintered samples were also analysed. The results revealed that a forming temperature of 150°C and a sintering rate of 10°C/min could produce a product with better characteristics.

  15. 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.

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

    Science.gov (United States)

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

    2018-04-01

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

  17. Study of the suitability of a commercial hydroxyapatite powder to obtain sintered compacts for medical applications

    Science.gov (United States)

    Palacio, C.; Jaramillo, D.; Correa, S.; Arroyave, M.

    2017-06-01

    Hydroxyapatite (HA) is a material widely used by the medical community due to its Ca/P ratio is comparable to the Ca/P ratio of bones and teeth, which promotes osteoinduction and osteoconduction processes when in contact with bone tissue, either as volume piece or coating. This work focuses on studying the quality of the commercial HA powder MKnano-#MKN-HXAP-S12 µm, after processing, to obtain sintered compact discs with suitable physical and chemical characteristics for implants applications. The HA powder was processed through calcination, grinding, pressing and sintering to evaluate the effect of such as procedures in the compacts dics quality. The raw powder was characterized by laser diffraction, SEM, XRF, XRD, TGA and DSC while the characteristics of the obtained compact discs were determined by dilatometry and XRD to identify the sintering temperature range, constituent phases, the amorphous content and the crystallinity degree, parameters that allow determining their suitability for implants applications. Although, it was not possible to obtain sintered compacts with the suitable chemical composition and without fractures, this work allowed to identify the parameters that determine the suitability of a HA powder to obtain sintered compacts for medical applications, as well as the characterization protocol that allows the evaluation of such parameters.

  18. 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

    formed with techniques that apply low levels of stress had a particle arrangement which significantly enhanced sintering at low temperature, compared to those prepared by high stress techniques. The sample geometry, heat treatment for organic removal and the initial density of the green body had......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...

  19. Influence of Grain Growth Inhibitors and Powder Size on the Properties of Ultrafine and Nanostructured Cemented Carbides Sintered in Hydrogen

    Directory of Open Access Journals (Sweden)

    Tamara Aleksandrov Fabijanić

    2016-08-01

    Full Text Available The influence of grain growth inhibitors and powder size on the microstructure and mechanical properties of ultrafine and nanostructured cemented carbides was researched. Three different WC powders, with an addition of different type and content of grain growth inhibitors GGIs, VC and Cr3C2 and with dBET grain sizes in the range from 95 to 150 nm were selected as starting powders. Four different mixtures with 6 and 9 wt. % Co were prepared. The consolidated samples are characterized by different microstructural and mechanical properties with respect to the characteristics of starting powders. Increased sintering temperatures led to microstructural irregularities in the form of a discontinuous WC growth, carbide agglomerates and abnormal grain growth as a consequence of coalescence via grain boundary elimination. The addition of 0.45% Cr3C2 contributed to microstructure homogeneity, reduced discontinuous and continuous grain growth, and increased Vickers hardness by approximately 70 HV and fracture toughness by approximately 0.15 MN/m3/2. The reduction of the starting powder to a real nanosize of 95 nm resulted in lower densities, and significant hardness increase, with a simultaneously small increase in fracture toughness. The consolidation of real nanopowders (dBET < 100 nm solely by conventional sintering in hydrogen without isostatic pressing is not preferred.

  20. 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.

  1. Effect of agglomerate strength on sintered density for yttria powders containing agglomerates of monosize spheres

    International Nuclear Information System (INIS)

    Ciftcioglu, M.; Akine, M.; Burkhart, L.

    1987-01-01

    The effect of agglomerate strength on sintered density was determined for several yttria powders made by intentionally agglomerating 0.1-μm, monodisperse yttriuim hydrocarbonate precursor spheres and calcining separate portions of the precursor at different temperatures to vary the strength of the intraaglomeate bonds. In this way, the effects of differences in particle morphology and other characteristics among the powders were minimized and the effect of agglomerate strength could be seen more clearly

  2. The Promotion of Liquid Phase Sintering of Boron-Containing Powder Metallurgy Steels by Adding Nickel

    Directory of Open Access Journals (Sweden)

    Wu Ming-Wei

    2015-01-01

    Full Text Available Boron is a feasible alloying element for liquid phase sintering (LPS of powder metallurgy (PM steels. This study investigated the effect of nickel (Ni, which is widely used in PM steels, on the liquid phase sintering of boron-containing PM steels. The results showed that the addition of 1.8wt% Ni does not apparently modify the LPS mechanism of boron-containing PM steels. However, adding 1.8wt% Ni slightly improves the LPS densification from 0.60 g/cm3 to 0.65 g/cm3, though the green density is reduced. Thermodynamic simulation demonstrated that the presence of Ni lowers the temperature region of liquid formation, resulting in enhanced LPS densification. Moreover, original graphite powders remains in the steels sintered at 1200 ºC. These graphite powders mostly dissolve into the base iron powder when the sintering temperature is increased from 1200 ºC to 1250 ºC.

  3. Some aspects of barreling in sintered plain carbon steel powder metallurgy preforms during cold upsetting

    Directory of Open Access Journals (Sweden)

    Sumesh Narayan

    2012-04-01

    Full Text Available The present research establishes a relationship of bulged diameter with densification and hydrostatic stress in forming of sintered iron (Fe powder metallurgy preforms cold upset under two different frictional conditions, namely, nil/no and graphite lubricant condition. Sintered plain carbon steel cylindrical preforms with carbon (C contents of 0, 0.35, 0.75 and 1.1% with constant initial theoretical density of 84% and aspect ratio of 0.4 and 0.6 were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 minutes at 1200 °C. Each sintered preform was cold upset under two different frictional constraints. It is seen that the degree of bulging reduces with reducing frictional constraints at the die contact surface. Further, it is found that the bulging ratio changed as a function of relative density and hydrostatic stress, respectively, according to the power law equations.

  4. 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.

  5. 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.

  6. Production of a Powder Metallurgical Hot Work Tool Steel with Harmonic Structure by Mechanical Milling and Spark Plasma Sintering

    Science.gov (United States)

    Deirmina, Faraz; Pellizzari, Massimo; Federici, Matteo

    2017-04-01

    Commercial AISI-H13 gas atomized powders (AT) were mechanically milled (MM) to refine both the particle size and the microstructure. Different volume fractions of coarser grained (CG) AT powders were mixed with the ultra-fine grained (UFG) MM and consolidated by spark plasma sintering to obtain bulks showing a harmonic structure ( i.e. a 3D interconnected network of UFG areas surrounding the CG atomized particles). The low sintering temperature, 1373.15 K (1100 °C) and the short sintering time (30 minutes) made it possible to obtain near full density samples while preserving the refined microstructure induced by MM. A combination of high hardness and significantly improved fracture toughness is achieved by the samples containing 50 to 80 vol pct MM, essentially showing harmonic structure. The design allows to easily achieve specific application oriented properties by varying the MM volume fraction in the initial mixture. Hardness is governed by the fine-grained MM matrix and improved toughening is due to (1) deviatory effect of AT particles and (2) energy dissipation as a result of the decohesion in MM regions or AT and MM interface.

  7. 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.

  8. Investigation of the sintering kinetics of lead powders. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Higgins, P.K.; Munir, Z.A.

    1977-08-01

    An analysis of the parameters involved in the sintering of lead powders under vacuum has been made. Sintering was accomplished at temperatures between 250/sup 0/ and 280/sup 0/C. Evaluation of surface area reduction data results in values of the mechanism exponent N between 5.3 and 6.7. Lack of shrinkage and the low vapor pressure of lead at the experimental temperatures lead to the conclusion that surface diffusion is the rate-controlling sintering mechanism. However, comparison of the experimentally measured activation energy, 170 kJ/mol (40.7 Kcal/mol), to that reported in the literature for surface self-diffusion of lead showed a significant discrepancy. Effects of pore isolation and surface oxide layers are proposed as possible explanations for this discrepancy as well as the deviation in the N values from those obtained theoretically. An attempt to isolate the effect of the oxide layer was made by sintering lead in a hydrogen atmosphere. Under these conditions, sintering is accompanied by shrinkage, thus indicating the presence of bulk-transport process. A mechanism exponent corresponding to viscous flow sintering was obtained. Furthermore, the calculated activation energy for this process was in good agreement with that reported for creep in lead.

  9. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    OpenAIRE

    Gerda Vaitkūnaitė; Vladislav Markovič; Olegas Černašėjus

    2015-01-01

    The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS) method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treat...

  10. Flame-sintered ceramic exoelectron dosimeter samples

    International Nuclear Information System (INIS)

    Petel, M.; Holzapfel, G.

    1979-01-01

    New techniques for the preparation of integrating solid state dosimeters, particularly exoelectron dosimeters, have been initiated. The procedure consists in melting the powdered dosimeter materials in a hot, fast gas stream and depositing the ceramic layer. The gas stream is generated either through a chemical flame or by an electrical arc plasma. Results will be reported on the system Al 2 O 3 /stainless steel as a first step to a usable exoelectron dosimeter

  11. Formation of peripheral porosity regions around urania in zirconia-urania mixed oxide powder compact sintering

    International Nuclear Information System (INIS)

    Das, P.; Choudhury, R.

    1992-01-01

    Sintering studies of zirconia-urania mixed oxide powder compacts (in stages of 5% urania up to a maximum of 20% addition) were carried out at temperatures between 1000-1400deg C for various soaking periods. The formation of a peripheral porosity region around comparatively coarser urania particle was a characteristic feature in this mixed oxide sintered compact. At even a higher sintering temperature (1800deg C), where extensive solid solution formation takes place, this porosity region demarcates the solutionized particles from the host zirconia apparently acting as a discontinuity in the system. Relative shrinkage difference between the dissimilar particles probably contributes to the porosity regions around the minor second phase at a lower temperature while at higher temperature generation of 'Kirkendall porosity' may be responsible for such an effect. (orig.)

  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. Study of nano-metric silicon carbide powder sintering. Application to fibers processing

    International Nuclear Information System (INIS)

    Malinge, A.

    2011-01-01

    Silicon carbide ceramic matrix composites (SiCf/SiCm) are of interest for high temperature applications in aerospace or nuclear components for their relatively high thermal conductivity and low activation under neutron irradiation. While most of silicon carbide fibers are obtained through the pyrolysis of a poly-carbo-silane precursor, sintering of silicon carbide nano-powders seems to be a promising route to explore. For this reason, pressureless sintering of SiC has been studied. Following the identification of appropriate sintering aids for the densification, optimization of the microstructure has been achieved through (i) the analysis of the influence of operating parameters and (ii) the control of the SiC β a SiC α phase transition. Green fibers have been obtained by two different processes involving the extrusion of SiC powder dispersion in polymer solution or the coagulation of a water-soluble polymer containing ceramic particles. Sintering of these green fibers led to fibers of around fifty microns in diameter. (author) [fr

  14. Spark plasma sintering of hydrothermally derived ultrafine Ca doped lanthanum chromite powders

    Directory of Open Access Journals (Sweden)

    Rendón-Angeles, J. C.

    2006-08-01

    Full Text Available Lanthanum chromite nano-particles, with a composition of La0.9Ca0.1CrO3 and La0.8Ca0.2CrO3, were produced by 1 h of hydrothermal reaction at 400 and 425°C respectively. The sintering of the powders was conducted using a spark plasma apparatus over the temperature range 1300-1550ºC for 1 min with a constant loading pressure of 45 MPa. Additional sintering experiments using conventional firing were carried out for comparison. Fully densified (98 % r.d. lanthanum chromite pellets with fine equiaxial grains 2.3 μm in size were obtained using the SPS (spark plasma sintering method. In contrast, a maximum relative density of 97 % was produced using La0.8Ca0.2CrO3 sintered conventionally at 1400ºC for 300 min, and the average grain size of the resulting sintered sample was 6 μm.

    Partículas ultrafinas de cromita de lantano, con una composición de La0.9Ca0.1CrO3 y La0.8Ca0.2CrO3, se obtuvieron después de 1 hora de síntesis hidrotermal a las temperaturas de 400 y 425°C respectivamente. Los compuestos obtenidos, con un tamaño de partícula de ~ 200 nm, se caracterizaron utilizando las técnicas de DRX, MEB y MET. La sinterización de estos polvos se efectuó en un equipo de chispa de plasma en el rango de temperatura de 1300-1500°C durante 1 min, y a una presión de compactación de 45 MPa. Ambos polvos también se sinterizaron siguiendo un tratamiento térmico convencional, en aire, con el propósito de comparar ambos métodos de sinterización. Las muestras de cromita de lantano sinterizadas por plasma presentaban una densidad relativa del 98 % (/t; y una microestructura monofásica con granos equaxiales con un tamaño medio de grano menor de 2.3 μm. En contraste, la composición La0.8Ca0.2CrO3, sinterizada a 1400°C/300 min, por métodos convencionales alcanzó una densidad relativa máxima del 97 % y su microestructura estaba formada por una sola fase con un tamaño medio de grano de 6 μm.

  15. Prediction of heating rate controlled viscous flow activation energy during spark plasma sintering of amorphous alloy powders

    Science.gov (United States)

    Paul, Tanaji; Harimkar, Sandip P.

    2017-07-01

    The viscous flow behavior of Fe-based amorphous alloy powder during isochronal spark plasma sintering was analyzed under the integrated theoretical background of the Arrhenius and directional structural relaxation models. A relationship between viscous flow activation energy and heating rate was derived. An extension of the pertinent analysis to Ti-based amorphous alloys confirmed the broad applicability of such a relationship for predicting the activation energy for sintering below the glass transition temperature (T g) of the amorphous alloy powders.

  16. Peculiarities of compaction during sintering of high-disperse tungsten powder porous bodies depending on heat treatment

    International Nuclear Information System (INIS)

    Vermenko, L.A.; Get'man, O.I.; Rakitin, S.P.; Skorokhod, V.V.

    1981-01-01

    A fall in the activity of tungsten powder obtained by reduction at a final temperature of 950 deg C and annealed before pressing at 1700 deg C and above is shown to be due to a decrease in the inner porosity of the particles, their contraction and rounding-off rather than to their enlargement in the maximum value of porous channel contractions in a pressed part ans its behaviour during sintering. A preliminary heat treatment of tungsten powders obtained by reduction at a final temperature of 700 deg C, has a non-monotonic effect on their activity in sintering. Formation of a new porous structure is found responsible for the behaviour of a porous body in sintering for tungsten powders during short-term (tau 30 s) shrinkage- free sintering of pressed parts, namely: an increase in the maximum values of porous channel contractions. A correction is established between volume shrinkage and the maximum value of contractions in enhanced capillaries [ru

  17. Characterization of an aluminum-filled polyamide powder for applications in selective laser sintering

    International Nuclear Information System (INIS)

    Mazzoli, Alida; Moriconi, Giacomo; Pauri, Marco Giuseppe

    2007-01-01

    Solid free-form fabrication (SFF) techniques use layer-based manufacturing to create physical objects directly from computer-generated models. Using an additive approach to manufacture shapes, SFF systems join liquid, powder or sheet materials. Selective laser sintering (SLS) is a SFF technique by which parts are built layer-by-layer offering the key advantage of the direct manufacturing of functional parts. In SLS, a laser beam is traced over the surface of a tightly compacted powder made of thermoplastic material. In this paper is characterized a new aluminum-filled polyamide powder developed for applications in SLS. This material is promising for many applications that require a metallic look of the part, good finishing properties, high stiffness and higher part quality

  18. Low-field vortex pinning model for undoped sintered MgB2 powders

    International Nuclear Information System (INIS)

    Agassi, Y D

    2011-01-01

    Sintered MgB 2 powders constitute a porous ensemble of irregularly shaped agglomerates of tightly packed grains. The low-field critical current density in such powders was experimentally observed to scale with the inverse of the average agglomerate size. Motivated by this observation we consider a flux pinning model which accounts for the MgB 2 powder porosity by focusing on a single finite-size agglomerate size. According to the model the observed critical current density dependence on the agglomerate size reflects the outward pull exerted on a vortex that is pinned in proximity to the agglomerate edges. The calculated critical current density replicates the observed scaling within agglomerate-size bounds. Implications of the model are discussed.

  19. Disk shaped radiation sources fabricated by compression and formation of sinter powder

    International Nuclear Information System (INIS)

    Kawano, Takao

    2008-01-01

    Sinters are deposits found at the bottom of hot springs, some of which contain naturally occurring radioisotopes of the uranium and thorium series. A disk-shaped radiation source was developed by compressing sinter powder. Ten disk-shaped radiation sources were fabricated by this method and their weight, thickness, mass density, and radioactivity were determined. The results indicated that special skills or techniques are not required for production of a radiation source with this method, and the production method is robust. Thus, the method is suitable for the simultaneous fabrication of multiple uniform radiation sources. To evaluate the ability of this fabrication method to produce sinter radiation sources applicable to courses involving radiation protection or similar investigations, the dependence of the radiation count rate on distance, shielding thickness, and shielding materials was examined using a conventional GM survey meter. The results showed that the sinter radiation source is suitable to comprehend characteristics of radiation and principle of radiation protection related to distance and shielding. (author)

  20. Magnetic properties of Pr-Fe-B sintered magnets produced from hydride powder and from partially and totally desorbed hydride power

    International Nuclear Information System (INIS)

    Faria, R.N.; Williams, A.J.; Abell, J.S.; Harris, I.R.

    1996-01-01

    The effect of a post-sintering heat treatment on the magnetic properties of Pr-Fe-B based magnets has been studied. For particular processing conditions, annealing the Pr 16 Fe 76 B 8 magnets at 1000 deg C resulted in an increase in an increase in iHc from 14.9 to around 17.5 kOe. The magnetic properties, before and after annealing, of magnets prepared from this standard HD powder were compared with those of samples prepared from partially and totally desorbed HD powder. Sintered magnets prepared from the hydrided powder exhibit a superior intrinsic coercivity compared to that of magnets prepared from the totally desorbed powder. However, the remanence and energy product of the latter are significantly higher. The squareness factor (0.93) has been improved considerably and good overall magnetic properties (Br∼11.7 kG, (BH) max ∼35.2 MGOe and iHc∼15.2 kOe) have been achieved for the sintered magnet prepared from partially desorbed powder. (author)

  1. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    Directory of Open Access Journals (Sweden)

    Gerda Vaitkūnaitė

    2015-03-01

    Full Text Available The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treated and untreated areas of the material has been made.

  2. Sintering behaviour and microstructure of 3Y-TZP + 8 mol% CuO nano-powder composite

    NARCIS (Netherlands)

    Ran, S.; Winnubst, Aloysius J.A.; Koster, H.; de Veen, P.J.; Blank, David H.A.

    2007-01-01

    Nanocrystalline 3Y-TZP and copper-oxide powders were prepared by co-precipitation of metal chlorides and copper oxalate complexation– precipitation, respectively.Asignificant enhancement in sintering activity of 3Y-TZP nano-powders, without presence of liquid phase,was achieved by addition of 8 mol%

  3. Analysis of reactions during sintering of CuO-doped 3Y-TZP nano-powder composites

    NARCIS (Netherlands)

    Winnubst, Aloysius J.A.; Ran, S.; Speets, E.A.; Blank, David H.A.

    2009-01-01

    3Y-TZP (yttria-doped tetragonal zirconia) and CuO nano powders were prepared by co-precipitation and copper oxalate complexation–precipitation techniques, respectively. During sintering of powder compacts (8 mol% CuO-doped 3Y-TZP) of this two-phase system several solid-state reactions clearly

  4. Sintered FeCuRe Alloys Produced from Commercially Available Powders

    Directory of Open Access Journals (Sweden)

    Borowiecka-Jamrozek J.

    2017-09-01

    Full Text Available This paper discusses the mechanical properties of materials fabricated from commercially available powders designed for use as a metal matrix of diamond-impregnated composites. The powders with the catalogue numbers CSA and CSA800 produced in China were tested under laboratory conditions. The specimens were fabricated in a graphite mould using hot pressing. The materials were analysed for density, porosity, hardness and static tensile strength. A scanning electron microscope (SEM was employed to observe the microstructure and fracture surfaces of the specimens. The experimental data was used to determine how the chemical composition of the powders and the process parameters affected the microstructure and properties of the materials. The properties of the sintered materials produced from the Chinese powders were compared with the properties reported for specimens fabricated from cobalt powder (Co SMS. Even though the hot pressed CSA and CSA800 powders had inferior mechanical properties to their cobalt analogue, they seem well-suited for general-purpose diamond-impregnated tools with less demanding applications.

  5. Nanoclay/Polymer Composite Powders for Use in Laser Sintering Applications: Effects of Nanoclay Plasma Treatment

    Science.gov (United States)

    Almansoori, Alaa; Majewski, Candice; Rodenburg, Cornelia

    2017-11-01

    Plasma-etched nanoclay-reinforced Polyamide 12 (PA12) powder is prepared with its intended use in selective laser sintering (LS) applications. To replicate the LS process we present a downward heat sintering (DHS) process, carried out in a hot press, to fabricate tensile test specimens from the composite powders. The DHS parameters are optimized through hot stage microscopy, which reveal that the etched clay (EC)-based PA12 (EC/PA12) nanocomposite powder melts at a temperature 2°C higher than that of neat PA12, and 1-3°C lower than that of the nonetched clay-based nanocompsite (NEC/PA12 composite). We show that these temperature differences are critical to successful LS. The distribution of EC and NEC onto PA12 is investigated by scanning electron microscopy (SEM). SEM images show clearly that the plasma treatment prevents the micron-scale aggregation of the nanoclay, resulting in an improved elastic modulus of EC/PA12 when compared with neat PA12 and NEC/PA12. Moreover, the reduction in elongation at break for EC/PA12 is less pronounced than for NEC/PA12.

  6. Fabrication of silicon nitride nanoceramics—Powder preparation and sintering: A review

    Directory of Open Access Journals (Sweden)

    Toshiyuki Nishimura et al

    2007-01-01

    Full Text Available Fine-grained silicon nitride ceramics were investigated mainly for their high-strain-rate plasticity. The preparation and densification of fine silicon nitride powder were reviewed. Commercial sub-micrometer powder was used as raw powder in the "as-received" state and then used after being ground and undergoing classification operation. Chemical vapor deposition and plasma processes were used for fabricating nanopowder because a further reduction in grain size caused by grinding had limitations. More recently, nanopowder has also been obtained by high-energy milling. This process in principle is the same as conventional planetary milling. For densification, primarily hot pressing was performed, although a similar process known as spark plasma sintering (SPS has also recently been used. One of the advantages of SPS is its high heating rate. The high heating rate is advantageous because it reduces sintering time, achieving densification without grain growth. We prepared silicon nitride nanopowder by high-energy milling and then obtained nanoceramics by densifying the nanopowder by SPS.

  7. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Hola, Marketa [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Otruba, Vitezslav [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Kanicky, Viktor [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic)]. E-mail: viktork@chemi.muni.cz

    2006-05-15

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm{sup 3}) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between {+-} 3% and {+-} 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed

  8. Impact of iron powder pressing temperature on high-temperature corrosion of the obtained sinters

    Directory of Open Access Journals (Sweden)

    A. Jaroń

    2010-07-01

    Full Text Available The work presents the results of kinetic studies of the high-temperature oxidation process of metallic iron sinters obtained by a hotpressing method in an anaerobic atmosphere. The conducted studies for a model arrangement (iron allow to determine the effect of conditions for obtaining metallic pressed materials on the course of a high-temperature corrosion process. What is more, iron oxide sinters characterized by an expanded surface disclosed by a morphological analysis of the resulting scales may be used as catalyst carriers or as input material for obtaining porous iron by reduction. Sinters intended for research were obtained in a device for one-axial hot-pressing of samples at a pressure of 8 MPa within the temperature range 600 – 900oC in vacuum. The research into the kinetics of metallic sinters oxidation was carried out in the standard apparatus for high-temperature thermogravimetric studies using a continuous method with automatic recording of measurement within the temperature range 500 – 700oC in synthetic air atmosphere. The dependence of oxidation kinetics of metallic sinters on a pressing temperature was determined. Morphology as well as the chemical and phase composition of the tested samples were described using the SEM/EDX and XRD methods.

  9. Nuclear energy - Uranium dioxide powder and sintered pellets - Determination of oxygen/uranium atomic ratio by the amperometric method. 2. ed.

    International Nuclear Information System (INIS)

    2007-01-01

    This International Standard specifies an analytical method for the determination of the oxygen/uranium atomic ratio in uranium dioxide powder and sintered pellets. The method is applicable to reactor grade samples of hyper-stoichiometric uranium dioxide powder and pellets. The presence of reducing agents or residual organic additives invalidates the procedure. The test sample is dissolved in orthophosphoric acid, which does not oxidize the uranium(IV) from UO 2 molecules. Thus, the uranium(VI) that is present in the dissolved solution is from UO 3 and/or U 3 O 8 molecules only, and is proportional to the excess oxygen in these molecules. The uranium(VI) content of the solution is determined by titration with a previously standardized solution of ammonium iron(II) sulfate hexahydrate in orthophosphoric acid. The end-point of the titration is determined amperometrically using a pair of polarized platinum electrodes. The oxygen/uranium ratio is calculated from the uranium(VI) content. A portion, weighing about 1 g, of the test sample is dissolved in orthophosphoric acid. The dissolution is performed in an atmosphere of nitrogen or carbon dioxide when sintered material is being analysed. When highly sintered material is being analysed, the dissolution is performed at a higher temperature in purified phosphoric acid from which the water has been partly removed. The cooled solution is titrated with an orthophosphoric acid solution of ammonium iron(II) sulfate, which has previously been standardized against potassium dichromate. The end-point of the titration is detected by the sudden increase of current between a pair of polarized platinum electrodes on the addition of an excess of ammonium iron(II) sulfate solution. The paper provides information about scope, principle, reactions, reagents, apparatus, preparation of test sample, procedure (uranium dioxide powder, sintered pellets of uranium dioxide, highly sintered pellets of uranium dioxide and determination

  10. [Determination of major expansion properties of refractory die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Chao, Y; Kuang, X; Liao, Y; Wang, H

    1999-02-01

    To determinate major expansion properties of refractory die material. The setting expansion ratio of refractory die material for slip casting core of sintered titanium powder at room temperature was performed, as well as thermal expansion ratio from room temperature to 800 degrees C. The maximum setting expansion ratio in 2 hours reached 0.3407%; The final setting expansion ratio in 24 hours was 0.3117%; The mean thermal expansion coefficient was mainly in range of 8 x 10(-6)-11 x 10(-6)/degree C; The expansion property seemed very stable after sintering repeatedly and the small shrinkage after sintering could be compensated with the die spacer and setting expansion. The expansion properties of the refractory die material that we synthesized can fulfil the application requirements of slip casting core of sintered titanium powder.

  11. Processing of Polysulfone to Free Flowing Powder by Mechanical Milling and Spray Drying Techniques for Use in Selective Laser Sintering

    Directory of Open Access Journals (Sweden)

    Nicolas Mys

    2016-04-01

    Full Text Available Polysulfone (PSU has been processed into powder form by ball milling, rotor milling, and spray drying technique in an attempt to produce new materials for Selective Laser Sintering purposes. Both rotor milling and spray drying were adept to make spherical particles that can be used for this aim. Processing PSU pellets by rotor milling in a three-step process resulted in particles of 51.8 μm mean diameter, whereas spray drying could only manage a mean diameter of 26.1 μm. The resulting powders were characterized using Differential Scanning Calorimetry (DSC, Gel Permeation Chromatography (GPC and X-ray Diffraction measurements (XRD. DSC measurements revealed an influence of all processing techniques on the thermal behavior of the material. Glass transitions remained unaffected by spray drying and rotor milling, yet a clear shift was observed for ball milling, along with a large endothermic peak in the high temperature region. This was ascribed to the imparting of an orientation into the polymer chains due to the processing method and was confirmed by XRD measurements. Of all processed powder samples, the ball milled sample was unable to dissolve for GPC measurements, suggesting degradation by chain scission and subsequent crosslinking. Spray drying and rotor milling did not cause significant degradation.

  12. Nuclear energy - Determination of chlorine and fluorine in uranium dioxide powder and sintered pellets

    International Nuclear Information System (INIS)

    2008-01-01

    This International Standard describes a method for determining the chlorine and fluorine concentrations in uranium dioxide and in sintered fuel pellets by pyrohydrolysis of samples, followed either by liquid ion-exchange chromatography or by selective electrode measurement of chlorine and fluorine ions. Many ion-exchange chromatography systems and ion-selective electrode measurement systems are available

  13. Feasibility of Plasma Treated Clay in Clay/Polymer Nanocomposites Powders for use Laser Sintering (LS)

    Science.gov (United States)

    Almansoori, Alaa; Seabright, Ryan; Majewski, C.; Rodenburg, C.

    2017-05-01

    The addition of small quantities of nano-clay to nylon is known to improve mechanical properties of the resulting nano-composite. However, achieving a uniform dispersion and distribution of the clay within the base polymer can prove difficult. A demonstration of the fabrication and characterization of plasma-treated organoclay/Nylon12 nanocomposite was carried out with the aim of achieving better dispersion of clay platelets on the Nylon12 particle surface. Air-plasma etching was used to enhance the compatibility between clays and polymers to ensure a uniform clay dispersion in composite powders. Downward heat sintering (DHS) in a hot press is used to process neat and composite powders into tensile and XRD specimens. Morphological studies using Low Voltage Scanning Electron Microscopy (LV-SEM) were undertaken to characterize the fracture surfaces and clay dispersion in powders and final composite specimens. Thermogravimetric analysis (TGA) testing performed that the etched clay (EC) is more stable than the nonetched clay (NEC), even at higher temperatures. The influence of the clay ratio and the clay plasma treatment process on the mechanical properties of the nanocomposites was studied by tensile testing. The composite fabricated from (3% EC/N12) powder showed ~19 % improvement in elastic modulus while the composite made from (3% NEC/N12) powder was improved by only 14%). Most notably however is that the variation between tests is strongly reduced when etch clay is used in the composite. We attribute this to a more uniform distribution and better dispersion of the plasma treated clay within polymer powders and ultimately the composite.

  14. Very large mode area ytterbium fiber amplifier with aluminum-doped pump cladding made by powder sinter technology

    International Nuclear Information System (INIS)

    He, Wenbin; Leich, Martin; Grimm, Stephan; Kobelke, Jens; Zhu, Yuan; Bartelt, Hartmut; Jäger, Matthias

    2015-01-01

    We demonstrate amplification experiments using a very large mode area Yb-doped double-clad fiber with 100 µm aluminum-cer codoped core and 440 µm pump cladding realized by high aluminum codoping. The material for core and pump cladding was fabricated by reactive powder sinter technology. A high numerical aperture (NA) of the pump cladding with NA = 0.21 and a low one of the core with NA = 0.084 could be realized. Using a 0.55 m short fiber sample as the main amplifier in a three-stage ns pulsed fiber master oscillator power amplifier system we achieved 3 ns, 2 mJ output pulses with 360 kW peak power limited by the available pump power. Stimulated Raman scattering effects and amplified spontaneous emission were successfully suppressed. (letter)

  15. Homogeneity characterisation of (U,Gd)O2 sintered pellets by X-ray diffraction powder analysis applying Rietveld method

    International Nuclear Information System (INIS)

    Leyva, Ana G.; Vega, Daniel R.; Trimarco, Veronica G.; Marchi, Daniel E.

    1999-01-01

    The (U,Gd)O 2 sintered pellets are fabricated by different methods. The homogeneity characterisation of Gd content seems to be necessary as a production control to qualify the process and the final product. The micrographic technique is the most common method used to analyse the homogeneity of these samples, this method requires time and expertise to obtain good results. In this paper, we propose an analysis of the X-ray diffraction powder patterns through the Rietveld method, in which the differences between the experimental data and the calculated from a crystalline structure model proposed are evaluated. This result allows to determine the cell parameters, that can be correlated with the Gd concentration, and the existence of other phases with different Gd ratio. (author)

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

    International Nuclear Information System (INIS)

    Ristic, M.M.

    1962-10-01

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

  17. A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

    Science.gov (United States)

    Farid Seyed Shirazi, Seyed; Gharehkhani, Samira; Mehrali, Mehdi; Yarmand, Hooman; Metselaar, Hendrik Simon Cornelis; Adib Kadri, Nahrizul; Azuan Abu Osman, Noor

    2015-06-01

    Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.

  18. A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing.

    Science.gov (United States)

    Shirazi, Seyed Farid Seyed; Gharehkhani, Samira; Mehrali, Mehdi; Yarmand, Hooman; Metselaar, Hendrik Simon Cornelis; Adib Kadri, Nahrizul; Osman, Noor Azuan Abu

    2015-06-01

    Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.

  19. Anisotropic powder from sintered NdFeB magnets by the HDDR processing route

    Energy Technology Data Exchange (ETDEWEB)

    Sheridan, R.S.; Sillitoe, R.; Zakotnik, M.; Harris, I.R. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Williams, A.J., E-mail: a.j.williams@bham.ac.uk [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2012-01-15

    Sintered NdFeB-based scrap magnets were recovered and processed using the HD and HDDR routes. The effects of varying the HDDR processing temperature were investigated (over the range 835-930 deg. C). The disproportion was carried out with a pressure ramp to a maximum of 1000 mbar hydrogen pressure with a 1 h hold time at each step and the optimum recombination conditions were set at 100 mbar with a 20 min hold time. Anisotropic NdFeB powder was produced in all cases with the best magnetic properties achieved at a processing temperature of 880 deg. C, producing powder with a remanence of 1.10({+-}0.02) T and an intrinsic coercivity of 800 ({+-}16) kA m{sup -1} and giving a (BH){sub max} of 129({+-}2.5) kJ m{sup -3}. - Highlights: > Production of anisotropic permanent magnet powder from scrap NdFeB magnets by HDDR. > Reaction pressure increases with increasing processing temperature. > Best magnetic properties achieved by processing at 880 deg. C.

  20. Anisotropic powder from sintered NdFeB magnets by the HDDR processing route

    International Nuclear Information System (INIS)

    Sheridan, R.S.; Sillitoe, R.; Zakotnik, M.; Harris, I.R.; Williams, A.J.

    2012-01-01

    Sintered NdFeB-based scrap magnets were recovered and processed using the HD and HDDR routes. The effects of varying the HDDR processing temperature were investigated (over the range 835-930 deg. C). The disproportion was carried out with a pressure ramp to a maximum of 1000 mbar hydrogen pressure with a 1 h hold time at each step and the optimum recombination conditions were set at 100 mbar with a 20 min hold time. Anisotropic NdFeB powder was produced in all cases with the best magnetic properties achieved at a processing temperature of 880 deg. C, producing powder with a remanence of 1.10(±0.02) T and an intrinsic coercivity of 800 (±16) kA m -1 and giving a (BH) max of 129(±2.5) kJ m -3 . - Highlights: → Production of anisotropic permanent magnet powder from scrap NdFeB magnets by HDDR. → Reaction pressure increases with increasing processing temperature. → Best magnetic properties achieved by processing at 880 deg. C.

  1. The influence of density of pressed iron powder samples on the quality of boride layers

    Directory of Open Access Journals (Sweden)

    Ivanov S.

    2003-01-01

    Full Text Available In this work the influence of the density of pressed iron powder on the quality of boride layers has been analysed. Examinations were performed on pressed samples of iron powder. The used granulation was 50-100, 100-150 and 150-200 mm. The samples were pressed under pressure of 200, 400, 600, 800 and 1000 MPa. Boroning was performed in a solid mixture based on boron-carbide, and was in principle the same for all samples. The obtained boride layers varied in depth and quality (porosity, the contact with metal. It has been observed that simultaneously with boroning sintering also occurred, and this fact offers a wide application possibility in the chemical-thermal treatment for sintered materials.

  2. Forming of titanium and titanium alloy miniature-cylinders by electrical-field activated powder sintering and forming

    Directory of Open Access Journals (Sweden)

    Zulkipli Muhammad

    2015-01-01

    Full Text Available As demands on miniature products increase significantly, a rapid process and production system for high-throughput, highly flexible and cost-efficient volume production of miniaturised components made from a wide range of materials is needed. A novel and electrical-field-activated sintering and forming process shows the potential to produce solid parts from powder material without any binder. Using titanium (Ti and titanium alloy (90Ti10Sn powder material, several processing parameters have been investigated, such as pressure, heating rate, heating temperature and holding time, which helped to contribute to the optimum result. In this study, using graphite dies, graphite punches and tungsten carbide punches, solid samples were produced, having a cylinder shape of Ø4.00 mm × 4.00 mm. Several properties of the solid Ti and 90Ti10Sn samples, such as density, hardness and the microstructures, were examined, and these showed that good results have been obtained.

  3. Ceramic powders of CaZrO3. Preparation and sintering

    International Nuclear Information System (INIS)

    Tamborenea, S.; Coronel, A.; Mazzoni, A.D.; Aglietti, E.F.

    2003-01-01

    Calcium zirconate (CaZrO 3 ) is a compound belonging to the perovskite family of the A 2+ B 4+ O 3 6- type with orthorhombic crystalline structure (distorted perovskite).CaZrO 3 is used in the manufacture of sensors of oxygen, humidity, hydrogen and hydrocarbides.Additionally, it is also being studied for the manufacture of thermistors.The calcium zirconate preparation by solid state reaction from stoichiometric mixtures of CaCO 3 and ZrO 2 is studied.The formation reaction was followed by thermal analysis techniques (DTA-TG-DTG) and X-ray diffraction (XRD).The different behaviour of the mixtures was studied according to the milling type employed.It could be observed a shift of some peaks, mainly of TG (gravimetry) with a tendency to a temperature decrease.These changes are mainly influenced by the amorphization effects on the carbonate and by the mixing caused by the milling type used.The powder (CaZrO 3 ) was isostatically pressed obtaining then green densities of 50% of the theoretical one.Sintering was made in air between 1300 and 1600degC at times between 0 and 240.Densities reached were between 90 and 95% increasing with the temperature and the sintering time

  4. Small-angle neutron scattering investigations on sintering behavior in the powder compacts of ceria (CeO2)

    International Nuclear Information System (INIS)

    Bedekar, Vinila; Patra, A.K.; Sen, D.; Mazumder, S.; Tyagi, A.K.

    2008-01-01

    Nano-crystalline ceria powders have been synthesized by gel combustion process. The effect of sintering temperature on the pore morphology of the powder compacts has been investigated by small-angle neutron scattering (SANS) in the accessible scattering wave vector 'q' range of 0.003-0.17 nm -1 of a double crystal based instrument. The scattering profiles do not follow normal 'q -4 ' power law at higher q-values. The X-ray diffraction and light scattering results indicate that the ceria nano-powders are in the form of porous agglomerates. The porosity of the sintered compacts has been attributed to inter-agglomerate, inter-aggregate and intra-aggregate pores. Scattering profiles have been modeled by using a tri-modal size distribution of pores

  5. Sintering of Synroc D

    International Nuclear Information System (INIS)

    Robinson, G.

    1982-01-01

    Sintering has been investigated as a method for the mineralization and densification of high-level nuclear defense waste powder. Studies have been conducted on Synroc D composite powder LS04. Optimal densification has been found to be highly dependent on the characteristics of the starting material. Powder subjected to milling, which was believed to reduce the level of agglomeration and possibly particle size, was found to densify better than powder not subjected to this milling. Densities of greater than 95% of theoretical could be achieved for samples sintered at 1150 to 1200 0 C. Mineralogy was found to be as expected for Synroc D for samples sintered in a CO 2 /CO atmosphere where the Fe +2 /Fe +3 ratio was maintained at 1.0 to 5.75. In a more oxidizing, pure CO 2 atmosphere a new phase, not previously identified in Synroc D, was found

  6. Production of NdFeB powders by HDDR from sintered magnets; Obtencao de pos de NdFeB por HDDR a partir de imas sinterizados

    Energy Technology Data Exchange (ETDEWEB)

    Janasi, S.R.; Rodrigues, D.; Landgraf, F.J.G. [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil). Lab. de Metalurgia e Materiais Ceramicos; Silva, B.F.A. da; Takiishi, H [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Campos, M.F. de [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil)

    2010-07-01

    The production of NdFeB powders by the HDDR process from metallic alloys has been widely investigated. Different HD and DR conditions have been used to induce anisotropy and to improve the intrinsic coercivity of the obtained powders. The purpose of this study is to apply the HDDR process in the reprocessing of NdFeB sintered magnet scraps. There were investigated different processing conditions as temperature and time of desorption and recombination (DR). The results of X ray diffraction show the formation of the magnetic phase Nd{sub 2}Fe{sub 14}B in all the investigated conditions. Magnetic measurements by vibrating sample magnetometer indicate that powders with intrinsic coercivity up to 790 kA/m were obtained. (author)

  7. Sintering of B4C by pressureless liquid phase sintering

    International Nuclear Information System (INIS)

    Rocha, Rosa Maria da; Melo, Francisco Cristovao Lourenco de

    2009-01-01

    The effect of three different sintering additive systems on densification of boron carbide powder was investigated. The sintering additives were Al 2 O 3 :Y 2 O 3 , AlN:Y 2 O 3 and BN:Y 2 O 3 compositions. Powder mixtures were prepared with 10 vol% of sintering aids following conventional powder technology processes. Samples were sintered by pressureless sintering at 2050 deg C/30min in argon atmosphere. Sintered samples were compared to a sintered B 4 C without sintering additive. Samples were characterized by XRD to analyze the crystalline phases after sintering and SEM to observe the microstructure and the second phase distribution. YB 4 and YB 2 C 2 were identified in all samples, indicating a reaction between Y 2 O 3 , B 4 C and B 2 O 3 present at the B 4 C particle surface. The best densification result was achieved with Al 2 O 3 :Y 2 O 3 additive system, showing 92.0 % of theoretical density, low porosity and 15.2 % of linear shrinkage. But this sample showed the highest weight loss. (author)

  8. Development of AUC-based process at BARC for production of free-flowing and sinterable UO2 powder

    International Nuclear Information System (INIS)

    Keni, V.S.; Ghosh, S.K.; Ganguly, C.; Majumdar, S.

    1994-01-01

    Ammonium uranium carbonate (AUC) process has been developed and industrially used in Germany for preparation of free-flowing and sinterable UO 2 powder for fabrication of UO 2 fuel pellets for light water reactors (LWR). Efforts are underway at Bhabha Atomic Research Centre (BARC) for developing AUC-based process which would yield free-flowing UO 2 powder suitable for direct pelletisation and sintering to very high density (> 96% T.D.) UO 2 fuel pellets for pressurised heavy water reactors (PHWRs) in India. The first phase of this work has been completed jointly by Chemical Engineering Division (ChED) and Radiometallurgy Division (RMD) in batches of 1.5 kg. It was possible to fabricate UO 2 pellets of density 93-95% T.D. on a reproducible basis. At ChED, process parameters have been optimised for fabrication of AUC with suitable physical properties in batches of 1.5 kg (U), starting with nuclear pure uranyl nitrate solution. At RMD calcination parameters of AUC was optimised in batches of 500 g for obtaining free-flowing UO 2 powder, suitable for direct pelletisation and sintering. The pelletisation and sintering have been carried out at Radiometallurgy Division in batches of 1-1.5 kg. The maximum achievable density of UO 2 pellets has been in the range of 95.5-96% T.D. (author). 11 refs

  9. Production of dispersed nanometer sized YAG powders from alkoxide, nitrate and chloride precursors and spark plasma sintering to transparency

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, M., E-mail: m.suarez@cinn.e [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fernandez, A. [Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L.; Torrecillas, R. [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-03-18

    Yttrium aluminum garnet (YAG) was synthesized from different starting materials, i.e., alkoxide, nitrate and chloride precursors. The conversion steps from the precursors to crystalline YAG were studied by Raman spectroscopy. Dispersed YAG powders were formed at a relatively low temperature, around 800 {sup o}C by the chlorides route, whereas alkoxide precursors needed firing over 900 {sup o}C and nitrates even over 1100 {sup o}C. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 {sup o}C with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  10. Production of dispersed nanometer sized YAG powders from alkoxide, nitrate and chloride precursors and spark plasma sintering to transparency

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Torrecillas, R.

    2010-01-01

    Yttrium aluminum garnet (YAG) was synthesized from different starting materials, i.e., alkoxide, nitrate and chloride precursors. The conversion steps from the precursors to crystalline YAG were studied by Raman spectroscopy. Dispersed YAG powders were formed at a relatively low temperature, around 800 o C by the chlorides route, whereas alkoxide precursors needed firing over 900 o C and nitrates even over 1100 o C. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 o C with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  11. Powder-metallurgy preparation of NiTi shape-memory alloy using mechanical alloying and spark-plasma sintering.

    Czech Academy of Sciences Publication Activity Database

    Novák, P.; Moravec, H.; Vojtěch, V.; Knaislová, A.; Školáková, A.; Kubatík, Tomáš František; Kopeček, Jaromír

    2017-01-01

    Roč. 51, č. 1 (2017), s. 141-144 ISSN 1580-2949 R&D Projects: GA ČR(CZ) GA14-03044S Institutional support: RVO:61389021 ; RVO:68378271 Keywords : mechanical alloying * spark plasma sintering * NiTi * shape memory alloy Subject RIV: JG - Metallurgy; JG - Metallurgy (FZU-D) OBOR OECD: Materials engineering ; Materials engineering (FZU-D) Impact factor: 0.436, year: 2016 https://www.researchgate.net/publication/313900224_Powder-metallurgy_preparation_of_NiTi_shape-memory_alloy_using_mechanical_alloying_and_spark-plasma_sintering

  12. Magnetic and structural properties of spark plasma sintered nanocrystalline NdFeB-powders

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2015-10-15

    Near-stoichiometric NdFeB melt-spun ribbons have been subjected to spark plasma sintering varying the process temperature T{sub SPS} and pressure p{sub SPS} between 600 and 800 °C and 50–300 MPa, respectively. Produced bulk magnets were analyzed regarding microstructure and magnetic properties. For all samples the intrinsic coercivity H{sub c,J} gradually decreases with increasing sintering temperature and pressure, while residual induction B{sub r} increases simultaneously with sample density. Densities close to the theoretical limit were achieved for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. With increasing T{sub SPS} precipitations of Nd-rich and Fe-rich phases have been observed as a result of a decomposition of the hard magnetic Nd{sub 2}Fe{sub 14}B phase. Under optimum sintering conditions of p{sub SPS}=300 MPa and T{sub SPS}=650 °C high-density bulk magnets with H{sub c,J}=652 kA/m, B{sub r}=0.86 T and (BH){sub max}=106 kJ/m{sup 3} have been produced. - Highlights: • Consolidation close to the theoretical density for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. • Highest (BH){sub max} of 106 kJ/m{sup 3} for p{sub SPS}=300 MPa and T{sub SPS}=650 °C with 98% theo. • H{sub c,J} gradually decreases with increasing T{sub SPS}, while B{sub r} increases simultaneously with. • With increasing T{sub SPS}, Nd- and Fe-rich precipitations are observed. • Reduction in t{sub SPS} is economic but does not increase (BH){sub max} significantly.

  13. Properties of sintered Al2O3-Cr composites depending on the method of preparation of the powder mixture

    Directory of Open Access Journals (Sweden)

    Chmielewski M.

    2006-01-01

    Full Text Available Continuous progress in modern science and industry depends on the availability of new effective devices and materials. New generation materials should be characterized by a specified combination of properties which sometimes exclude one another. Al2O3-Cr composites belong to this group of materials. This study is concerned with the effect of the method of preparation of the starting powders upon the properties of sintered Al2O3-Cr composites. The composites were produced using powder mixtures with various volumetric shares of the starting powders (from 25 to 75vol.%. The mixtures were prepared by conventional mechanical mixing in a ball-mill or by mechanical alloying in a high-energy mill of the attritor type. It has been found that with mechanically alloyed powders the Al2O3-Cr composites have better bending strength, hardness and frictional wear resistance.

  14. HRTEM and Nanoindentation Studies of Bulk WC Nanocrystalline Materials Prepared by Spark Plasma Sintering of Ball-Milled Powders

    Science.gov (United States)

    Sherif El-Eskandarany, M.; Al-Hazza, Abdulsalam; Al-Hajji, L. A.

    2017-01-01

    In the present work, mechanical milling technique using a high-energy ball mill was employed for preparing of nanoscaled WC grains powders with an average grain size of 7 nm in diameters of WC. The present study demonstrates a successful consolidation process achieved at 1250 °C for sintering of ball-milled WC powders into full dense bulk buttons (above 99.6%), using SPS technique. The as-consolidated WC bulk nanocrystalline buttons revealed high hardness value ( 24 GPa) with low elastic modulus ( 332 GPa). Moreover, they possessed a high fracture toughness (15 MPa m1/2) that has never been reported for pure WC.

  15. Irradiation creep of nano-powder sintered silicon carbide at low neutron fluences

    International Nuclear Information System (INIS)

    Koyanagi, T.; Shimoda, K.; Kondo, S.; Hinoki, T.; Ozawa, K.; Katoh, Y.

    2014-01-01

    The irradiation creep behavior of nano-powder sintered silicon carbide was investigated using the bend stress relaxation method under neutron irradiation up to 1.9 dpa. The creep deformation was observed at all temperatures ranging from 380 to 1180°C mainly from the irradiation creep but with the increasing contributions from the thermal creep at higher temperatures. The apparent stress exponent of the irradiation creep slightly exceeded unity, and instantaneous creep coefficient at 380 to 790°C was estimated to be ∼1 × 10 -5 [MPa -1 dpa -1 ] at ∼0.1 dpa and 1 × 10 -7 to 1 × 10 -6 [MPa -1 dpa -1 ] at ∼1 dpa. The irradiation creep strain appeared greater than that for the high purity SiC. Microstructural observation and data analysis indicated that the grain-boundary sliding associated with the secondary phases contributes to the irradiation creep at 380–790°C to 0.01–0.11 dpa. (author)

  16. Sintering, microstructure and properties of WC-AISI304 powder composites

    Energy Technology Data Exchange (ETDEWEB)

    Marques, B.J. [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal); Fernandes, C.M., E-mail: cmfernandes@ua.pt [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal); ISEC, Mechanical Department, Engineering Institute of Coimbra, Rua Pedro Nunes, 3030-199 Coimbra (Portugal); Senos, A.M.R. [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal)

    2013-06-15

    Highlights: ► Total replacement of Co binder by stainless steel AISI 304 in WC based composites. ► Processing conditions for WC–stainless steel composites. ► Mechanical behavior and oxidation resistance of WC–stainless steel composites. -- Abstract: Tungsten carbide–stainless steel (AISI 304) based composites were successfully prepared by powder metallurgy routes using vacuum sintering at a maximum temperature of 1500 °C. The effects of the binder amount (between 6 and 15 wt.%) on the phase composition, microstructure and mechanical properties, namely hardness and fracture toughness, were investigated. Appreciable amount of (M,W){sub 6}C up to 12 wt.% was detected, especially for the higher SS contents. However, a good compromise between toughness and hardness was observed. Besides that, improved oxidation resistance was noticed in WC–SS based composites compared with WC–Co composites. The results are discussed having in mind the correlation between chemical composition, phase composition, microstructure and mechanical behavior.

  17. Synthesis, microstructure and mechanical properties of Ti3SiC2-TiC composites pulse discharge sintered from Ti/Si/TiC powder mixture

    International Nuclear Information System (INIS)

    Tian Wubian; Sun Zhengming; Hashimoto, Hitoshi; Du Yulei

    2009-01-01

    Ti 3 SiC 2 -TiC composites with the volume fractions of TiC from 0 to 90% were fabricated by pulse discharge sintering (PDS) technique using Ti-Si-TiC as starting powders in the sintering temperature range of 1250-1400 deg. C. Phase content and microstructure of the synthesized samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The samples sintered at 1400 deg. C are almost fully dense for all compositions with relative density higher than 98%. The phase distribution in the synthesized samples is non-uniform. The Vickers hardness increases almost linearly with the volume fraction of TiC up to a value of 20.1 ± 1.4 GPa at 90 vol.% TiC. The flexural strength increases with the volume fraction of TiC to a maximum value of 655 ± 10 MPa at 50 vol.% TiC. The relationship between microstructure and mechanical properties is discussed.

  18. Improved HDDR processing route for production of anisotropic powder from sintered NdFeB type magnets

    Energy Technology Data Exchange (ETDEWEB)

    Sheridan, R.S.; Williams, A.J.; Harris, I.R.; Walton, A., E-mail: a.walton@bham.ac.uk

    2014-01-15

    The hydrogenation disproportionation desorption recombination (HDDR) process has been investigated as a possible means of producing bonded magnets from used NdFeB-type sintered magnets with compositions, Nd{sub 13.4}Dy{sub 0.8}Al{sub 0.7}Nb{sub 0.3}Fe{sub 78.5}B{sub 6.3} and Nd{sub 12.5}Dy{sub 1.8}Al{sub 0.9}Nb{sub 0.6}Co{sub 5.0}Fe{sub 72.8}B{sub 6.4} (atomic%). It has been shown that by increasing the processing temperature, an increase in the equilibrium pressure for disproportionation and in the overall reaction time was observed. The magnetic properties of the lower Dy content magnet were affected significantly by the change in processing temperature with a peak in properties observed at 880 °C producing magnetic powder with a remanence of 1.08 (±0.02) T, a coercivity of 840 (±17) kA m{sup −1}, and a maximum energy product of 175 (±2.5) kJ m{sup −3}. Further work on magnets with a significantly higher Dy content has shown that simultaneous processing of sintered magnets with varying compositions can be achieved by increasing the hydrogen pressure, however a range of magnetic properties are produced depending on the initial compositions of the samples in the input feed. - Highlights: • Reduced oxidation during the HDDR processing in this work compared to the previous paper resulted in a powder with a higher coercivity. • Increasing the hydrogen pressure for disproportionation allowed for Dy, Co rich NdFeB compositions to be processed. • Mixed compositions (which will be typical from “real scrap”) can be processed simultaneously in the same equipment. • Mixed feeds produced lower magnetic properties due to overprocessing of the low Dy content compositions.

  19. Low temperature synthesis and sintering behaviour of Gd-doped ceria nanosized powders: comparison between two synthesis procedures

    Directory of Open Access Journals (Sweden)

    Tartaj, J.

    2009-04-01

    Full Text Available Two different routes of synthesis of Ce0.9Gd0.1O1.95 (CGO nanopowders are presented; the ethylene glycol-metal nitrate polymerized complex solution method and the precipitation technique using ammonia as the precipitant agent. The powders characteristics were examined by X-ray diffraction (XRD, transmission electron microscopy (TEM, Brunauer-Emmett-Teller (BET surface area and simultaneous thermogravimetric and differential thermal analysis (TG/DTA. Scanning electron microscopy (SEM observations were used to determine the agglomeration degree of the powders, and the uniformity of the green compacts. The Hg-porosimetry results were used to investigate the pore size. The densification process was studied by constant heating rate dilatometry and isothermal sintering at different temperatures. Microstructural development of each sample at different sintering temperatures and times was followed by SEM.

    Se presentan dos diferentes rutas de síntesis de nanopolvos de Ce0.9Gd0.1O1.95 (CGO: precipitación de hidróxidos, a partir de soluciones de nitratos utilizando amonia como agente precipitante y formación de complejos polimerizados etilene-glicol nitratos metálicos. Las características de los polvos se determinaron por DRX, microscopía de transmisión (TEM, superficie específica por Brunauer-Emmett-Teller (BET, y ensayos de ATD/ATG. El grado de aglomeración de los nanopolvos y la uniformidad de los compactos en verde se ha observado por Microscopía electrónica de barrido, (SEM. El tamaño de poro de los compactos en verde se ha medido mediante porosimetría de Hg. El comportamiento a la sinterización se ha evaluado por dilatometría a velocidad de calentamiento constante y por sinterización isoterma a diferentes temperaturas. La evolución microestructural se ha seguido por SEM.

  20. Selective Laser Sintering And Melting Of Pristine Titanium And Titanium Ti6Al4V Alloy Powders And Selection Of Chemical Environment For Etching Of Such Materials

    Directory of Open Access Journals (Sweden)

    Dobrzański L.A.

    2015-09-01

    Full Text Available The aim of the investigations described in this article is to present a selective laser sintering and melting technology to fabricate metallic scaffolds made of pristine titanium and titanium Ti6Al4V alloy powders. Titanium scaffolds with different properties and structure were manufactured with this technique using appropriate conditions, notably laser power and laser beam size. The purpose of such elements is to replace the missing pieces of bones, mainly cranial and facial bones in the implantation treatment process. All the samples for the investigations were designed in CAD/CAM (3D MARCARM ENGINEERING AutoFab (Software for Manufacturing Applications software suitably integrated with an SLS/SLM system. Cube-shaped test samples dimensioned 10×10×10 mm were designed for the investigations using a hexagon-shaped base cell. The so designed 3D models were transferred to the machine software and the actual rapid manufacturing process was commenced. The samples produced according to the laser sintering technology were subjected to chemical processing consisting of etching the scaffolds’ surface in different chemical mediums. Etching was carried out to remove the loosely bound powder from the surface of scaffolds, which might detach from their surface during implantation treatment and travel elsewhere in an organism. The scaffolds created were subjected to micro- and spectroscopic examinations

  1. Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Selective Laser Melting of Powder Produced by Granulation-Sintering-Deoxygenation Method

    Science.gov (United States)

    Sun, Pei; Fang, Z. Zak; Zhang, Ying; Xia, Yang

    2017-12-01

    Commercial spherical Ti powders for additive manufacturing applications are produced today by melt-atomization methods at relatively high costs. A meltless production method, called granulation-sintering-deoxygenation (GSD), was developed recently to produce spherical Ti alloy powder at a significantly reduced cost. In this new process, fine hydrogenated Ti particles are agglomerated to form spherical granules, which are then sintered to dense spherical particles. After sintering, the solid fully dense spherical Ti alloy particles are deoxygenated using novel low-temperature deoxygenation processes with either Mg or Ca. This technical communication presents results of 3D printing using GSD powder and the selective laser melting (SLM) technique. The results showed that tensile properties of parts fabricated from spherical GSD Ti-6Al-4V powder by SLM are comparable with typical mill-annealed Ti-6Al-4V. The characteristics of 3D printed Ti-6Al-4V from GSD powder are also compared with that of commercial materials.

  2. A methodology to investigate the intrinsic effect of the pulsed electric current during the spark plasma sintering of electrically conductive powders

    Directory of Open Access Journals (Sweden)

    Antonio Mario Locci, Alberto Cincotti, Sara Todde, Roberto Orrù and Giacomo Cao

    2010-01-01

    Full Text Available A novel methodology is proposed for investigating the effect of the pulsed electric current during the spark plasma sintering (SPS of electrically conductive powders without potential misinterpretation of experimental results. First, ensemble configurations (geometry, size and material of the powder sample, die, plunger and spacers are identified where the electric current is forced to flow only through either the sample or the die, so that the sample is heated either through the Joule effect or by thermal conduction, respectively. These ensemble configurations are selected using a recently proposed mathematical model of an SPS apparatus, which, once suitably modified, makes it possible to carry out detailed electrical and thermal analysis. Next, SPS experiments are conducted using the ensemble configurations theoretically identified. Using aluminum powders as a case study, we find that the temporal profiles of sample shrinkage, which indicate densification behavior, as well as the final density of the sample are clearly different when the electric current flows only through the sample or through the die containing it, whereas the temperature cycle and mechanical load are the same in both cases.

  3. Fabrication of Al2O3–20 vol.% Al nanocomposite powders using high energy milling and their sinterability

    International Nuclear Information System (INIS)

    Zawrah, M.F.; Abdel-kader, H.; Elbaly, N.E.

    2012-01-01

    Highlights: ► Al 2 O 3 /Al nanocomposite powders were prepared via high energy ball milling. After 20 h milling, the size of Al 2 O 3 –20 vol.% Al nanocomposite particles was in the range of 23–29 nm. A uniform distribution of nanosized Al reinforcement throughout the Al 2 O 3 matrix, coating the particles was successfully obtained. ► There was no any sign of phase changes during the milling. A competition between the cold welding mechanism and the fracturing mechanism were found during milling and finally the above two mechanisms reached an equilibrium. ► The highest value of relative density was obtained for the sintered bodies at 1500 °C. ► The harness of the sintered composite was decreased while the fracture toughness was improved after addition Al into alumina. -- Abstract: In this study, alumina-based matrix nanocomposite powders reinforced with Al particles were fabricated and investigated. The sinterability of the prepared nanocomposite powder at different firing temperature was also conducted. Their mechanical properties in terms of hardness and toughness were tested. Alumina and aluminum powder mixtures were milled in a planetary ball mill for various times up to 30 h in order to produce Al 2 O 3 –20% Al nanocomposite. The phase composition, morphological and microstructural changes during mechanical milling of the nanocomposite particles were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) techniques, respectively. The crystallite size and internal strain were evaluated by XRD patterns using Scherrer methods. A uniform distribution of the Al reinforcement in the Al 2 O 3 matrix was successfully obtained after milling the powders. The results revealed that there was no any sign of phase changes during the milling. The crystal size decreased with the prolongation of milling times, while the internal strain increased. A simple model is presented to illustrate the mechanical

  4. Improved compaction of ZnO nano-powder triggered by the presence of acetate and its effect on sintering

    International Nuclear Information System (INIS)

    Dargatz, Benjamin; Gonzalez-Julian, Jesus; Guillon, Olivier

    2015-01-01

    The retention of nanocrystallinity in dense ceramic materials is still a challenge, even with the application of external pressure during sintering. The compaction behavior of high purity and acetate enriched zinc oxide (ZnO) nano-powders was investigated. It was found that acetate in combination with water plays a key role during the compaction into green bodies at moderate temperatures. Application of constant pressure resulted in a homogeneous green body with superior packing density (86% of theoretical value) at moderate temperature (85 °C) in the presence of water. In contrast, no improvement in density could be achieved if pure ZnO powder was used. This compaction behavior offers superior packing of the particles, resulting in a high relative density of the consolidated compact with negligible coarsening. Dissolution accompanying creep diffusion based matter transport is suggested to strongly support reorientation of ZnO particles towards densities beyond the theoretical limit for packing of ideal monosized spheres. Finally, the sintering trajectory reveals that grain growth is retarded compared to conventional processing up to 90% of theoretical density. Moreover, nearly no radial shrinkage was observed after sinter-forging for bodies performed with this advanced processing method. (paper)

  5. Nano-composite powders Ag-SnO2 prepared by reactive milling sintering and microstructural evolution

    International Nuclear Information System (INIS)

    Lorrain, Nathalie

    2000-01-01

    This work aims at controlling the synthesis and the sintering of nano-composite powders Ag-SnO 2 in order to obtain a dense and nano-structured material for electrical contact as a substitute of the toxic compound Ag - CdO. The powder is prepared by reactive milling from silver oxide (Ag 2 O) and silver bronze (Ag 3 Sn) powders. This process leads to a fine dispersion of silver and tin oxide nanometer sized particles. We first studied the mechanisms of reaction promoted by milling in vacuum and in air. A two-stage oxidation of tin in Ag 3 Sn occurs: during forced contact with Ag 2 O, tin oxidises in SnO, then in SnO 2 . In air, gaseous oxygen also participates to the oxidation of tin in SnO 2 but the reaction is slower because of the formation of silver carbonates from a reaction of Ag 2 O with CO 2 .Then the sintering behaviour of the nano-composite powder as a function of the compacting pressure and of the heating rate has been studied. We show: (i) a diffusion of pure silver towards porosity and free surfaces (exo-diffusion) which destroys the nano-structure and (ii) a severe de-densification. We show that the origin of these phenomena is due to carbonates on to the Ag 2 O starting powder, which are incorporated, in the milled Ag-SnO 2 powder in course of milling; during sintering, decomposition gases generate internal stresses. Low stresses lead to a diffusional creep with exo-diffusion whereas high stresses induce an intensive de-densification by local plastic deformation but no exo-diffusion. A modelling shows that exo-diffusion is limited by heating very quickly a strongly compacted powder that contains a high quantity of carbonates. The experimental results confirm the predictions of the model. Finally, we propose solutions allowing a full densification and a process for decreasing the tin oxide concentration. (author) [fr

  6. Effect Of DyMn Alloy-Powder Addition On Microstructure And Magnetic Properties Of NdFeB Sintered Magnets

    Directory of Open Access Journals (Sweden)

    Lee M.-W.

    2015-06-01

    Full Text Available Micostructural change and corresponding effect on coercivity of a NdFeB sintered magnet mixed with small amount of DyMn powder was investigated. In the sintered magnet mixed with the DyMn alloy-powder Dy-rich shell was formed at outer layer of the main grains, while Mn was mostly concentrated at Nd-rich triple junction phase (TJP, lowering melting temperature of the Nd-rich phase that eventually improved the microstructural characteristics of the gain boundary phase. The coercivity of a magnet increased more than 3.5 kOe by the mixing of the DyMn alloy-powder.

  7. Sintering by SPS of ultrafine TiCxN1-x powders obtained using mechanically induced self sustaining reaction

    International Nuclear Information System (INIS)

    Borrell, A.; Fernandez, A.; Torrecillas, R.; Cordoba, J. M.; Aviles, M. A.; Gotor, F. J.

    2010-01-01

    In this work high purity and nanometer character titanium carbonitride TiC x N 1 -x powders were obtained by mechanically induced self sustaining reaction (MSR) in a high-energy planetary ball mill, from a mixture of titanium with graphite or carbon nano fiber (CNFs) in a nitrogen atmosphere. A promising method for developing these materials is the coupling of the MSR with SPS sintering technique. The product is sintered at 1400 degree centigrade and 1700 degree centigrade, obtaining a completely dense monolithic ceramic (>99% t.d). In this work, the influence of SPS treatment and carbon precursor on material microstructures was studied and the main mechanical properties of the end material were evaluated. (Author) 21 refs.

  8. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Directory of Open Access Journals (Sweden)

    Zorica Branković

    2016-12-01

    Full Text Available Bismuth ferrite, BiFeO3 (BFO, powder was synthesized by hydrothermal method from Bi(NO33·5 H2O and Fe(NO33·9 H2O as precursors. The synthesized powder was further sintered using spark plasma sintering (SPS. The sintering conditions were optimized in order to achieve high density, minimal amount of secondary phases and improved ferroelectric and magnetic properties. The optimal structure and properties were achieved after spark plasma sintering at 630 °C for 20 min, under uniaxial pressure of 90 MPa. The composition, microstructure, ferroelectric and magnetic properties of the SPS samples were characterized and compared to those of conventionally sintered ceramics obtained from the same powder. Although the samples sintered using conventional method showed slightly lower amount of secondary phases, the spark plasma sintered samples exhibited favourable microstructure and better ferroelectric properties.

  9. [Determination of normal temperature properties of refractory die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Kuang, X; Liao, Y; Chao, Y; Wang, H

    1999-05-01

    The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the normal temperature properties of the refractory die material compatible with slip casting core. to mix the die material at five different ratios (8/1, 7.5/1, 7/1, 6.5/1, and 6/1) and measure their solidification time with self-manufactured Vicker's needle; to prepare five cylindrical specimens (phi 10 x 15 mm) in different drying time for determining their compressive strength, and then to let another five specimens fire at 1000 degrees C four times for measuring the residual compressive strength at room temperature. The setting time was 16.25 minutes (7.5/1), and the lower the powder-liquid ratio, the longer the setting time. The normal compressive strength was 25.32 MPa (drying 24 hours), while the longer the drying time, the higher the compressive strength achieved (P die material meet the demand of slip casting core of sintered powder.

  10. Coercivity enhancement in (Ce,Nd)-Fe-B sintered magnets prepared by adding NdH{sub x} powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Le-le [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Li, Zhu-bai, E-mail: lzbgj@163.com [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Ma, Qiang; Li, Yong-feng; Zhao, Qian [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Zhang, Xue-feng, E-mail: xuefeng056@163.com [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); School of Science, Inner Mongolia University of Science and Technology, Baotou 014010 (China)

    2017-08-01

    (Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdH{sub x} powders in Ce{sub 9}Nd{sub 4.5}Fe{sub 80}B{sub 6.5} powders. The coercivity is rather low in Ce{sub 9}Nd{sub 4.5}Fe{sub 80}B{sub 6.5} magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd){sub 2}Fe{sub 14}B. The investigation of scanning electron microscope shows that the addition of NdH{sub x} powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdH{sub x} powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdH{sub x} powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product.

  11. The possibility of the boronizing process on the pressed samples of iron powder

    Directory of Open Access Journals (Sweden)

    Požega Emina D.

    2009-01-01

    Full Text Available The paper presents results of the experimental investigation of the boronizing process on nonsintering iron powder samples (NC100.24, Höganäs, Sweden. Experiments are planned within the limits of applicability of simultaneous sintering at chemical-thermal treatment process (boronizing. The simlex plan of 15 experimental points was used for the experiment, while a polynomial function of fourth degree was employed in the modeling of a mixture composition based on the volume changes, porosity and the depth layer changes. Boronizing was carried out in mixture with born carbide by addition of ammonium bifluoride, ammonium chloride and boron potassium fluoride as activators, by proportion definited plan.

  12. Spark plasma sintering of cBN(core/SiO2(shell powder prepared by rotary chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Jianfeng Zhang

    2014-09-01

    Full Text Available SiO2 nanolayer coated cubic boron nitride (cBN, cBN(core/SiO2(shell powder, was prepared by rotary chemical vapor deposition. The cBN/SiO2 powder was densified by spark plasma sintering at 1873 K for 0.3 ks. The hexagonal boron nitride (hBN phase was not observed in the cBN–SiO2 composites, indicating that the SiO2 nanolayer depressed the phase transformation from cBN to hBN. The relative density of cBN–SiO2 increased with increasing SiO2 content (CSiO2. The highest hardness of the cBN–SiO2 composite was 17.5 GPa at CSiO2=38 wt% and a load of 0.98 N.

  13. Impact of Fe powder sintering and soldering in production of porous heating surface on flow boiling heat transfer in minichannels

    Science.gov (United States)

    Depczyński, Wojciech; Piasecki, Artur; Piasecka, Magdalena; Strąk, Kinga

    2017-10-01

    This paper focuses on identification of the impact of porous heated surface on flow boiling heat transfer in a rectangular minichannel. The heated element for Fluorinert FC-72 was a thin plate made of Haynes-230. Infrared thermography was used to determine changes in the temperature on its outer smooth side. The porous surface in contact with the fluid in the minichannel was produced in two processes: sintering or soldering of Fe powder to the plate. The results were presented as relationships between the heat transfer coefficient and the distance from the minichannel inlet and as boiling curves. Results obtained for using a smooth heated plate at the saturated boiling region were also presented to compare. In the subcooled boiling region, at a higher heat flux, the heat transfer coefficient was slightly higher for the surface prepared via soldering. In the saturated boiling region, the local heat transfer coefficients obtained for the smooth plate surface were slightly higher than those achieved from the sintered plate surface. The porous structures formed have low thermal conductivity. This may induce noticeable thermal resistance at the diffusion bridges of the sintered structures, in particular within the saturated boiling region.

  14. Sintering of zirconia in high-pressure

    International Nuclear Information System (INIS)

    Kunrath, A.O.; Strohaecker, T.R.; Pereira, A.S.; Jornada, J.A.H. da; Piermarini, G.J.

    1989-01-01

    A systematic study about the sintering of zirconia hyperfines powders in high-pressure is presented. The differents conditions effect of sintering in microstructure and in hardness and tenacity properties of zirconia samples with a very fine grain is also studied. (C.G.C.) [pt

  15. EMF measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions

    Science.gov (United States)

    Shishkovskiy, I.; Sherbakov, V.; Morozov, Yu.

    2007-06-01

    Rapid prototyping (RP) and manufacturing (M) is a novel layer-by-layer fabrication technique which has become increasingly popular due to its inherent flexibility for the manufacture of simple and complex 3D parts. Early we had been shown opportunity of selective laser sintering (SLS) of different type powder systems (intermetallics, ceramics, ferrites, high-temperature superconductors), traditional use for self-propagated high-temperature synthesis (SHS). The non-thermal heating affect of an external electromagnetic field during SHS is related to the specific system under study due to differences in movement of defects and ions at the 'plasma-like' molten combustion wave front. We have developed and refined the testing scheme for electro-thermal phenomena studies which can directly influence on the SHS combustion wave front. This work studies electromotive force (EMF) measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions (Ni-Ti, Ni-Al). Analysis using an analog-digital-analog computer converter allowed some control of the laser movement and hence some control of the exothermal reaction - in so doing it provided near optimum conditions for forming layered 3D articles. Comparative results of structural-phase transformation during laser control SHS in reaction-capable compositions are presented.

  16. Influence of high sintering pressure on the microhardness and wear resistance of diamond powder and silicon carbide-based composites

    Directory of Open Access Journals (Sweden)

    Osipov Oleksandr Sergueevitch

    2004-01-01

    Full Text Available The work reported on here involved the development of several samples of "diamond-SiC" composite produced under sintering pressures of up to 9.0 GPa at temperatures of up to 1973 7K. The average size of the diamond micropowder crystals used was 40/28 µm. The sintering process was carried out in a 2500-ton hydraulic press equipped with an anvil-type high-pressure device having a toroidal work surface and a central concavity diameter of 20 mm. The microhardness and wear resistance of the samples were found to be dependent on the sintering pressure. The experimental results indicated that the maximum microhardness and minimum wear resistance coefficients of each compact were attained when the pressure applied during sintering exceeded 6.5 GPa. Based on the established values of pressure, this study served to identify the types of devices applicable for the manufacture of composite material inserts for a variety of rock drilling applications.

  17. Influence of nitrogen and air atmosphere during thermal treatment on micro and nano sized powders and sintered TiO2 specimens

    Directory of Open Access Journals (Sweden)

    Labus N.

    2014-01-01

    Full Text Available The influence of air and nitrogen atmosphere during heating on TiO2 nano and micro sized powders as well as sintered polycrystalline specimens was analyzed. Sintering of TiO2 nano and micro powders in air atmosphere was monitored in a dilatometer. Non compacted nano and micro powders were analyzed separately in air and nitrogen atmospheres during heating using thermo gravimetric (TG and differential thermal analysis (DTA. The anatase to rutile phase transition temperature interval is influenced by the powder particle size and atmosphere change. At lower temperatures for nano TiO2 powder a second order phase transition was detected by both thermal techniques. Polycrystalline specimens obtained by sintering from nano powders were reheated in the dilatometer in nitrogen and air atmosphere, and their shrinkage is found to be different. Powder particle size influence, as well as the air and nitrogen atmosphere influence was discussed. [Projekat Ministarstva nauke Republike Srbije, br. OI172057 i br. III45014

  18. Powder metallurgy preparation of Al-Cu-Fe quasicrystals using mechanical alloying and Spark Plasma Sintering

    Czech Academy of Sciences Publication Activity Database

    Novák, P.; Kubatík, Tomáš František; Vystrčil, J.; Hendrych, R.; Kříž, J.; Mlynár, J.; Vojtěch, D.

    2014-01-01

    Roč. 52, September (2014), s. 131-137 ISSN 0966-9795 Institutional support: RVO:61389021 Keywords : Nanostructure intermetallics * Ternary alloys systems * Mechanical alloying and milling * Sintering * Diffraction Subject RIV: JG - Metallurgy Impact factor: 2.131, year: 2014 http://www.sciencedirect.com/science/article/pii/S0966979514001198#

  19. Influence of spark plasma sintering and baghdadite powder on mechanical properties of hydroxyapatite

    NARCIS (Netherlands)

    Khandan, A.; Karamian, E.; Mehdikhani-Nahrkhalaji, M.; Mirmohammadi, H.; Farzadi, A.; Ozada, N.; Heidarshenas, B.; Zamani, K.

    2015-01-01

    Since hydroxyapatite-based materials have similar composition and crystallinity as natural calcified tissues, can be used for bone/tissue engineering. In the present study a novel nanocomposite based on bioceramics such as Natural Hydroxyapatite (NHA) and Baghdadite (BAG), was sintered by spark

  20. XRD analysis and microstructure of milled and sintered V, W, C, and Co powders

    CSIR Research Space (South Africa)

    Bolokang, AS

    2011-01-01

    Full Text Available )C solid solution, a rhombohedral V2O3 and new t-type (Cr23C6) carbide were formed after sintering. The possible formation mechanisms behind detected phases are discussed. It is evident that complete MA process depends strongly on the starting compositions...

  1. Sintering of powders obtained by mechanical alloying of Cu-1.2 Al w%, Cu-2.3 Ti w% and Cu-2.7 V w%

    International Nuclear Information System (INIS)

    Rivas, C; Sepulveda, A; Zuniga, A; Donoso, E; Palma, R

    2008-01-01

    This work studies the effect of compacting pressure, temperature and sintering time on density and microstructure after sintering mechanically alloyed powders of Cu-1.2 Al w%, Cu- 2.3 Ti w% and Cu-2.7 V w%. The alloys were manufactured from elementary powders of Cu, Ti, Al and V, by reactive milling. The powders were compacted and sintered under reducer atmosphere. For each alloy, the final density and resulting microstructure of 8 different compacting and sintering conditions were studied, where the following parameters were considered: (1) Compacting pressure (200 MPa and 400 MPa), (2) Sintering temperature (850 o C and 950 o C), (3) Sintering time (1h and 4h). Adjustments were made using lineal regression to describe the effect of the variation of pressure, temperature and time on the density of the materials obtained, and the morphology of the residual porosity was described by observation under an optic microscope. The final maximum density obtained was, in ascending order: Cu-V, 66% of the theoretical density, TD; Cu-Ti, 65% TD and Cu-Al, 77% TD. The reactive milling process produced flake-shaped particles, hardened by deformation, which made the alloys have a final density that was much less than the sintered pure copper (density 87% TD). This is because the hardened powder resists deformation during compacting, which creates less points of contact between particles, slows down sintering, and yields a lower density. The alloying element influenced the size of the particle obtained during the milling, which is attributed to the different milling mediums (toluene for Ti and V, methanol for Al) and to the different hardness of each ceramic when forming in the copper during milling. The bigger the particle size, the greater the green density, the lesser the densification, and the greater the final density, in accordance with the theory. For the three alloys, the increased compacting pressure gives greater green density, greater densification and a final greater

  2. On a discrepancy in modulus of elasticity as determined from separate resonance frequencies of a bar sintered from copper-coated iron powder

    Czech Academy of Sciences Publication Activity Database

    Kupková, M.; Kupka, M.; Strobl, S.; Černý, Martin; Khabiti, G.; Gierl, C.

    2007-01-01

    Roč. 57, č. 7 (2007), s. 639-642 ISSN 1359-6462 Institutional research plan: CEZ:AV0Z30460519 Keywords : copper-coated iron powder * sintering * mechanical properties testing Subject RIV: JG - Metallurgy Impact factor: 2.481, year: 2007

  3. Spray Drying as a Processing Technique for Syndiotactic Polystyrene to Powder Form for Part Manufacturing Through Selective Laser Sintering

    Science.gov (United States)

    Mys, N.; Verberckmoes, A.; Cardon, L.

    2017-03-01

    Selective laser sintering (SLS) is a rapidly expanding field of the three-dimensional printing concept. One stumbling block in the evolution of the technique is the limited range of materials available for processing with SLS making the application window small. This article aims at identifying syndiotactic polystyrene (sPS) as a promising material. sPS pellets were processed into powder form with a lab-scale spray dryer with vibrating nozzle. This technique is the focus of this scope as it almost eliminates the agglomeration phenomenon often encountered with the use of solution-based processing techniques. Microspheres obtained were characterized in shape and size by scanning electron microscopy and evaluation of the particle size distribution. The effect the processing technique imparts on the intrinsic properties of the material was examined by differential scanning calorimetry analysis.

  4. Analysis of natural milk and milk powder samples by NAA

    International Nuclear Information System (INIS)

    Al-Jobori, S.M.; Itawi, R.K.; Saad, A.; Shihab, K.M.; Jalil, M.; Farhan, S.S.

    1990-01-01

    As a part of the Iraqi Food Analysis Programme the concentration of Na, Mg, P, Cl, K, Ca, Zn, Se, Br, Rb and I in natural milk collected from different regions of Iraq, and in milk powder samples was determined by NAA technique. It was found that except for the elements I, Rb and Br the concentration of the elements was approximately identical in both natural milk and milk powders. (author) 4 refs.; 3 figs.; 5 tabs

  5. Analysis of natural milk and milk powder samples by NAA

    International Nuclear Information System (INIS)

    Al-Jobori, S. M.; Itawi, R. K.; Saad, A; Shihab, K. M.; Jalil, M.; Farhan, S. S.

    1993-01-01

    As a part of the Iraqi food analysis program (IFAP) the concentration of Na, Mg, P, Cl, K, Ca, Zn, Se, Br, Rb, and I in natural milk collected from different regions of Iraq, and in milk powder samples have been determined by using the NAA techniques. It was found that except for the elements I, Rb, and Br the concentrations of the elements was approximately identical in both the natural milk and milk powder. (author)

  6. A study on improvement of UO2 powder production process for high sintered density

    International Nuclear Information System (INIS)

    Park, Jin Hoh; Hwang, Sung Tae; Jun, Kwan Sik; Choi, Yoon Dong; Choi, Jong Hyun; Lee, Kyoo Il; Kim, Tae Joon; Jung, Kyung Chae; Kim, Kwang Lak; Kwon, Sang Woon; Kim, Byung Hoh; Hong, Soon Bok

    1995-01-01

    Various conversion processes were reviewed from the viewpoint of manufacturing cost, product quality and liquid waste. The MDD process was selected a suitable target process for the good quality of UO 2 powder and the recycling availability of nitric acid. The MDD process consists of two steps, double salt preparation [(NH 4 ) 2 UO 2 (NO 3 ) 4 ] from uranyl nitrate solution and thermal decomposition/reduction to UO 2 powder. The reaction mechanism and properties for the intermediates were analyzed to define the proposed operational conditions of the process. The conceptual process was proposed and experimental facility was designed and installed. 12 figs, 7 tabs, 7 refs. (Author)

  7. PHOTOEMISSION METHOD OF TEMPERATURE MEASURING IN THE PROCESS OF SPARK PLASMA SINTERING POWDERS OF REFRACTORY METALS

    Directory of Open Access Journals (Sweden)

    D. V. Minko

    2012-01-01

    Full Text Available Construction and algorithm of the photoemission pyrometer based on a photomultiplier are outlined; the calibration procedure is set out. The application of the photoemission method in a rapidly changing temperature is showed. It is proved that during spark plasma sintering the maximal temperature is 5500– 7500 °C, while the speed of temperature increase to its maximum ~108–109 °C/s, and the rate of decrease to 2000–4000 °C may be 106–107 °C/sec. It is recommended to use photoemission method when developing technological conditions, adjustment and control of technological processes using modern high-energy equipment (plasma, laser, cathode-ray tube to produce new materials, coatings and products for mechanical engineering, electronic industry and medicine.

  8. A study on improvement of UO{sub 2} powder production process for high sintered density

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Hoh; Hwang, Sung Tae; Jun, Kwan Sik; Choi, Yoon Dong; Choi, Jong Hyun; Lee, Kyoo Il; Kim, Tae Joon; Jung, Kyung Chae; Kim, Kwang Lak; Kwon, Sang Woon; Kim, Byung Hoh; Hong, Soon Bok [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-01-01

    Various conversion processes were reviewed from the viewpoint of manufacturing cost, product quality and liquid waste. The MDD process was selected a suitable target process for the good quality of UO{sub 2} powder and the recycling availability of nitric acid. The MDD process consists of two steps, double salt preparation [(NH{sub 4}){sub 2}UO{sub 2}(NO{sub 3}){sub 4}] from uranyl nitrate solution and thermal decomposition/reduction to UO{sub 2} powder. The reaction mechanism and properties for the intermediates were analyzed to define the proposed operational conditions of the process. The conceptual process was proposed and experimental facility was designed and installed. 12 figs, 7 tabs, 7 refs. (Author).

  9. Comparison between powder and slices diffraction methods in teeth samples

    Energy Technology Data Exchange (ETDEWEB)

    Colaco, Marcos V.; Barroso, Regina C. [Universidade do Estado do Rio de Janeiro (IF/UERJ), RJ (Brazil). Inst. de Fisica. Dept. de Fisica Aplicada; Porto, Isabel M. [Universidade Estadual de Campinas (FOP/UNICAMP), Piracicaba, SP (Brazil). Fac. de Odontologia. Dept. de Morfologia; Gerlach, Raquel F. [Universidade de Sao Paulo (FORP/USP), Rieirao Preto, SP (Brazil). Fac. de Odontologia. Dept. de Morfologia, Estomatologia e Fisiologia; Costa, Fanny N. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (LIN/COPPE/UFRJ), RJ (Brazil). Lab. de Instrumentacao Nuclear

    2011-07-01

    Propose different methods to obtain crystallographic information about biological materials are important since powder method is a nondestructive method. Slices are an approximation of what would be an in vivo analysis. Effects of samples preparation cause differences in scattering profiles compared with powder method. The main inorganic component of bones and teeth is a calcium phosphate mineral whose structure closely resembles hydroxyapatite (HAp). The hexagonal symmetry, however, seems to work well with the powder diffraction data, and the crystal structure of HAp is usually described in space group P63/m. Were analyzed ten third molar teeth. Five teeth were separated in enamel, detin and circumpulpal detin powder and five in slices. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the National Synchrotron Light Laboratory - LNLS, Campinas, Brazil. The LNLS synchrotron light source is composed of a 1.37 GeV electron storage ring, delivering approximately 4x10{sup -1}0 photons/s at 8 keV. A double-crystal Si(111) pre-monochromator, upstream of the beamline, was used to select a small energy bandwidth at 11 keV . Scattering signatures were obtained at intervals of 0.04 deg for angles from 24 deg to 52 deg. The human enamel experimental crystallite size obtained in this work were 30(3)nm (112 reflection) and 30(3)nm (300 reflection). These values were obtained from measurements of powdered enamel. When comparing the slice obtained 58(8)nm (112 reflection) and 37(7)nm (300 reflection) enamel diffraction patterns with those generated by the powder specimens, a few differences emerge. This work shows differences between powder and slices methods, separating characteristics of sample of the method's influence. (author)

  10. Comparison between powder and slices diffraction methods in teeth samples

    International Nuclear Information System (INIS)

    Colaco, Marcos V.; Barroso, Regina C.; Porto, Isabel M.; Gerlach, Raquel F.; Costa, Fanny N.

    2011-01-01

    Propose different methods to obtain crystallographic information about biological materials are important since powder method is a nondestructive method. Slices are an approximation of what would be an in vivo analysis. Effects of samples preparation cause differences in scattering profiles compared with powder method. The main inorganic component of bones and teeth is a calcium phosphate mineral whose structure closely resembles hydroxyapatite (HAp). The hexagonal symmetry, however, seems to work well with the powder diffraction data, and the crystal structure of HAp is usually described in space group P63/m. Were analyzed ten third molar teeth. Five teeth were separated in enamel, detin and circumpulpal detin powder and five in slices. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the National Synchrotron Light Laboratory - LNLS, Campinas, Brazil. The LNLS synchrotron light source is composed of a 1.37 GeV electron storage ring, delivering approximately 4x10 -1 0 photons/s at 8 keV. A double-crystal Si(111) pre-monochromator, upstream of the beamline, was used to select a small energy bandwidth at 11 keV . Scattering signatures were obtained at intervals of 0.04 deg for angles from 24 deg to 52 deg. The human enamel experimental crystallite size obtained in this work were 30(3)nm (112 reflection) and 30(3)nm (300 reflection). These values were obtained from measurements of powdered enamel. When comparing the slice obtained 58(8)nm (112 reflection) and 37(7)nm (300 reflection) enamel diffraction patterns with those generated by the powder specimens, a few differences emerge. This work shows differences between powder and slices methods, separating characteristics of sample of the method's influence. (author)

  11. Hot deformed anisotropic nanocrystalline NdFeB based magnets prepared from spark plasma sintered melt spun powders

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Y.H.; Huang, Y.L. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Liu, Z.W., E-mail: zwliu@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zeng, D.C. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Ma, S.C.; Zhong, Z.C. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

    2013-09-01

    Highlights: • Microstructure evolution and its influence on the magnetic properties were investigated. • The increase of stray field and weakening of domain-wall pinning effects were the main reasons of the decrease of the coercivity with increasing the compression ratio. • The influences of non-uniform plastic deformation on the microstructure and magnetic properties were investigated. • Magnetic properties and temperature coefficient of coercivity are indeed very promising without heavy rare earth elements. -- Abstract: Anisotropic magnets were prepared by spark plasma sintering (SPS) followed by hot deformation (HD) using melt-spun powders as the starting material. Good magnetic properties with the remanence J{sub r} > 1.32 T and maximum of energy product (BH){sub max} > 303 kJ/m{sup 3} have been obtained. The microstructure evolution during HD and its influence on the magnetic properties were investigated. The fine grain zone and coarse grain zone formed in the SPS showed different deformation behaviors. The microstructure also had an important effect on the temperature coefficients of coercivity. A strong domain-wall pinning model was valid to interpret the coercivity mechanism of the HDed magnets. The increase of stray field and weakening of domain-wall pinning effects were the main reasons of the decrease of the coercivity with increasing the compression ratio. The influences of non-uniform plastic deformation on the microstructure and magnetic properties were investigated. The polarization characteristics of HDed magnets were demonstrated. It was found out that the HDed magnets had better corrosion resistance than the counterpart sintered magnet.

  12. New experimental procedure for measuring volume magnetostriction on powder samples

    International Nuclear Information System (INIS)

    Rivero, G.; Multigner, M.; Valdes, J.; Crespo, P.; Martinez, A.; Hernando, A.

    2005-01-01

    Conventional techniques used for volume magnetostriction measurements, as strain gauge or cantilever method, are very useful for ribbons or thin films but cannot be applied when the samples are in powder form. To overcome this problem a new experimental procedure has been developed. In this work, the experimental set-up is described, together with the results obtained in amorphous FeCuZr powders, which exhibit a strong dependence of the magnetization on the strength of the applied magnetic field. The magnetostriction measurements presented in this work point out that this dependence is related to a magnetovolume effect

  13. [Determination of high temperature compressive strength and refractory degree of die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Kuang, X; Liao, Y; Chao, Y; Meng, Y

    1999-05-01

    The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the high temperature properties of the refractory die material compatible with slip casting core. To prepare three cylindrical specimens (phi 10 x 15 mm) and determine their compressive strength at 1000 degrees C: to make four specimens in flat-topped cone for determining the practical refractory degree by decreasing the pressing temperatures in a sequence of 1420, 1400, 1350 and 1100 degrees C. The compressive strength of this material was 17.8 MPa at 1000 degrees C. Its practical refractory degree was higher than 1100 degrees C. The high temperature properties of the refractory die material that we developed meet the demand of slip casting core of sintered powder.

  14. A sample holder for in-house X-ray powder diffraction studies of protein powders

    DEFF Research Database (Denmark)

    Frankær, Christian Grundahl; Harris, Pernille; Ståhl, Kenny

    2011-01-01

    A sample holder for handling samples of protein for in-house X-ray powder diffraction (XRPD) analysis has been made and tested on lysozyme. The use of an integrated pinhole reduced the background, and good signal-to-noise ratios were obtained from only 7 l of sample, corresponding to approximately...... 2-3 mg of dry protein. The sample holder is further adaptable to X-ray absorption spectroscopy (XAS) measurements. Both XRPD and XAS at the Zn K-edge were tested with hexameric Zn insulin....

  15. Studying hardness, workability and minimum bending radius in selectively laser-sintered Ti–6Al–4V alloy samples

    Science.gov (United States)

    Galkina, N. V.; Nosova, Y. A.; Balyakin, A. V.

    2018-03-01

    This research is relevant as it tries to improve the mechanical and service performance of the Ti–6Al–4V titanium alloy obtained by selective laser sintering. For that purpose, sintered samples were annealed at 750 and 850°C for an hour. Sintered and annealed samples were tested for hardness, workability and microstructure. It was found that incomplete annealing of selectively laser-sintered Ti–6Al–4V samples results in an insignificant reduction in hardness and ductility. Sintered and incompletely annealed samples had a hardness of 32..33 HRC, which is lower than the value of annealed parts specified in standards. Complete annealing at temperature 850°C reduces the hardness to 25 HRC and ductility by 15...20%. Incomplete annealing lowers the ductility factor from 0.08 to 0.06. Complete annealing lowers that value to 0.025. Complete annealing probably results in the embrittlement of sintered samples, perhaps due to their oxidation and hydrogenation in the air. Optical metallography showed lateral fractures in both sintered and annealed samples, which might be the reason why they had lower hardness and ductility.

  16. Preparation and Sintering Behaviour of Alumina Powder by Ammonia Precipitation Method

    Directory of Open Access Journals (Sweden)

    Wang Liuyan

    2017-01-01

    Full Text Available In this paper, alumina precursor was prepared by the ammonia precipitation method which used Al (NO3 3 9H2O as aluminum source and NH4OH as a precipitator, adding a small amount of PEG4000 as the surface active agent. Finally γ-Al2O3 was obtained at 900° for 2h. The stable alumina crystal form of α-Al2O3 was got at 1100° for 2h. The influence of precipitation agent on the precursor was studied by means of TG / DTA and Tem, XRD etc. The effects of the synthesis temperature and time on the phase composition and morphology of the alumina powder were also analysed.

  17. A thermal conductivity cell for small powdered samples.

    Science.gov (United States)

    Cremers, C. J.

    1971-01-01

    A thermal conductivity cell is described for making measurements of the thermal conductivity and thermal diffusivity of small samples of powdered dielectric materials. The principle used is that of the line heat source. A novel way is described for applying this method so that much smaller samples than normal may be tested. This size requirement is necessary for investigations involving limited samples as does the Lunar Science Program. The method is checked by measuring the conductivity of standard samples and comparing the results with those found in the literature.

  18. Investigation of the Sintering Process Using Non-Contact Electromagnetic Acoustic Transducers

    Energy Technology Data Exchange (ETDEWEB)

    James C. Foley; David K. Rehbein; Daniel J. Barnard

    2001-05-30

    In-situ characterizations of green state part density and sintering state have long been desired in the powder metal community. Recent advances in non-contact electromagnetic acoustic transducer (EMAT) technology have enabled in-situ monitoring of acoustic amplitude and velocity as sintering proceeds. Samples were made from elemental powders of Al (99.99%), Al (99.7%), Ag, (99.99%), Cu (99.99%) and Fe (99.9%). The powders were pressed in a uniaxial die and examined with acoustic waves for changes in velocity and amplitude during sintering for the samples containing Al, Ag, and Cu. The changes in acoustic properties were correlated with sample microstructures and mechanical properties. Evolution of a series of reverberating echoes during sintering is shown to provide information on the state of sintering, and changes in sintering kinetics as well as having the potential for detection of interior flaws.

  19. Influence of Molecular Weight Average, Degree of Crystallinity, and Viscosity of Different Polyamide PA12 Powder Grades on the Microstructures of Laser Sintered Part

    Directory of Open Access Journals (Sweden)

    Yusoff WAY

    2015-01-01

    Full Text Available Laser Sintering (LS allows functional parts to be produced in a wide range of powdered materials using a dedicated machine, and is thus gaining popularity within the field of rapid prototyping. It offers the user the ability to optimise part design in order to meet customer requirements with few manufacturing restrictions. A problem with LS is that sometimes the surface of the parts produced displays a texture similar to that of the skin of an orange (the so-called “orange peel” texture. The main aim of this research is to develop a methodology of controlling the input material properties of PA12 powder that will ensure consistent and good quality of the fabricated parts. Melt Flow Rate (MFR and Gel permeation chromatography (GPC were employed to measure the flow viscosity and molecular weight distributions of Polyamide PA12 powder grades. The experimental results proved that recycle PA12 powder with higher melt viscosity polymer has a higher entanglement with a longer molecule chain causes a higher resistance to flow which cause poor and rough surface finished on laser sintered part.

  20. Sintering of nonstoichiometric UO2

    International Nuclear Information System (INIS)

    Susnik, D.; Holc, J.

    1983-01-01

    Activated sintering of UO 2 pellets at 1100 deg C is described. In CO 2 atmosphere is UO 2 is nonstoichiometric and pellets from active UO 2 powders sinter at 900 deg C to high density. At 1100 deg C the final sintered density is practically achieved at heating on sintering temperature. After reduction and cooling in H 2 atmosphere which is followed sintering in CO 2 the structure is identical to the structured UO 2 pellets sintered at high temperature in H 2 . Density of activated sintered UO 2 pellets is stable, even after additional sintering at 1800 deg C. (author)

  1. Phase transformation of NiTi alloys during vacuum sintering

    Science.gov (United States)

    Wang, Jun; Hu, Kuang

    2017-05-01

    The aim of this study is to ascertain the Phase transformation of NiTi alloys during vacuum sintering. NiTi shape memory alloys (SMA) of atomic ratio 1:1 were prepared through press forming and vacuum sintering with the mixture of Ni and Ti powders. Different samples were prepared by changing the sintering time and the sintering temperature. Phase and porosity of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that in the process of sintering NiTi2 and Ni3Ti phases are formed firstly and then transform into NiTi phase. The quantity of NiTi2 and Ni3Ti phases gradually decreased but not eliminate completely with increase of sintering time. The porosity of specimen sintering at 900°C decreases slightly with increase of sintering time. With increase of sintering time the porosity of specimen sintering at 1050°C decreased firstly and then increased because of generation rich titanium liquid in the process of sintering.

  2. Structural behavior and microstructural hard metal sintered at 1350 deg C from the powder of nanometer WC with 10 wt% Co

    Energy Technology Data Exchange (ETDEWEB)

    Batista, A.C.; Perpetuo, G.J.; Leocadio, R.R.V., E-mail: adrianocorrea77@gmail.com [Rede Tematica de Engenharia de Materiais (REDEMAT), Ouro Preto, Minas Gerais (Brazil); Oliveira, H.C.P. de [Instituto Superior Tecnico (IST), Lisboa (Portugal). Departamento de Materiais

    2014-07-01

    The hard metal (WC-10%Co), processed via powder metallurgy, using powder of nanometer WC, were characterized from the point of view to the microstructural and structural techniques, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) for mapping and punctual. To analyze the behavior of hard metal after the sintering process performed in resistive furnace at 1350°C for 1 hour under vacuum of 10-2 mbar, the analysis identified the formation of WC grains, the pore distribution and behavior and evolution of the phases WC and Co, generating phases η (Co{sub 3}W{sub 3}C and Co{sub 6}W{sub 6}C). (author)

  3. Sample Handling System for in-situ Powder X-ray Diffraction Instruments., Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation is a Powder Handling System (PHS) that will deliver powdered samples to in situ planetary XRD instruments and provide unique means of...

  4. Synthesis of (Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 powder and sintered ferrites by high energy ball-milling process

    International Nuclear Information System (INIS)

    Shi, X.L.; Yang, H.; Shao, G.Q.; Duan, X.L.; Xiong, Z.; Sun, P.; Wang, T.G.

    2007-01-01

    (Mg 0.476 Mn 0.448 Zn 0.007 )(Fe 1.997 Ti 0.002 )O 4 nanocrystalline powder prepared by high energy ball-milling process were consolidated by microwave and conventional sintering processes. Phases, microstructure and magnetic properties of the ferrites prepared by different processes were investigated. The (Mg 0.476 Mn 0.448 Zn 0.007 )(Fe 1.997 Ti 0.002 )O 4 nanocrystalline powder could be prepared by high energy ball-milling process of raw Fe 3 O 4 , MnO 2 , ZnO, TiO 2 and MgO powders. Prefired and microwave sintered ferrites could achieve the maximum density (4.86 g/cm -3 ), the average grain size (15 μm) was larger than that (10 μm) prepared by prefired and conventionally sintered ferrites with pure ferrite phase, and the saturation magnetization (66.77 emu/g) was lower than that of prefired and conventionally sintered ferrites (88.25 emu/g), the remanent magnetization (0.7367 emu/g) was higher than that of prefired and conventionally sintered ferrites (0.0731 emu/g). Although the microwave sintering process could increase the density of ferrites, the saturation magnetization of ferrites was decreased and the remanent magnetization of ferrites was also increased

  5. Processing and Properties of Distaloy Sa Sintered Alloys with Boron and Carbon

    Directory of Open Access Journals (Sweden)

    Karwan-Baczewska J.

    2015-04-01

    Full Text Available Prealloyed iron-based powders, manufactured in Höganäs Company, are used in the automotive parts industry. The properties and life time of such sintered parts depend, first of all, on their chemical composition, the production method of the prealloyed powder as well as on the technology of their consolidation and sintering. One of simpler and conventional methods aimed at increasing the density in sintered products is the process of activated sintering, performed, for example, by adding boron as elementary boron powder. Under this research project obtained were novel sintered materials, based on prealloyed and diffusion bonded powder, type: Distaloy SA, with the following chemical composition: Fe-1.75% Ni-1.5%Cu- 0.5%Mo with carbon (0.55%; 0.75% and boron (0.2%, 0.4% and 0.6%. Distaloy SA samples alloyed with carbon and boron were manufactured by mixing powders in a Turbula mixer, then compressed using a hydraulic press under a pressure of 600 MPa and sintered in a tube furnace at 1473 K, for a 60 minute time, in the hydrogen atmosphere. After the sintering process, there were performed density and porosity measurements as well as hardness tests and mechanical properties were carried out, too. Eventually, analyzed was the effect of boron upon density, hardness and mechanical properties of novel sintered construction parts made from Distaloy SA powder.

  6. Novel iron oxide-silica coreshell powders compacted by using pulsed electric current sintering: optical and magnetic properties

    Czech Academy of Sciences Publication Activity Database

    Mahmed, N.; Heczko, Oleg; Maki, R.; Söderberg, O.; Haimi, E.; Hannula, S.-P.

    2012-01-01

    Roč. 32, č. 11 (2012), s. 2981-2988 ISSN 0955-2219 Institutional research plan: CEZ:AV0Z10100520 Keywords : sintering * SiO 2 * ferrites * grain growth * transparent Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.360, year: 2012 http://www.sciencedirect.com/science/article/pii/S0955221912001240

  7. Morphological analysis and modelling of sintering and of sintered materials

    International Nuclear Information System (INIS)

    Jernot, Jean-Paul

    1982-01-01

    This research thesis addresses the study of solid phase sintering of metallic powders, and aims at describing as precisely as possible the different involved matter transport mechanisms, first by using a thermodynamic approach to sintering. Sintering diagrams are also used to determine prevailing mechanisms. The microstructure of sintered materials has been studied by using image quantitative analysis, thus by using a morphological approach to sintering. Morphological parameters allow, on the one hand, the evolution of powders during sintering to be followed, and, on the other hand, sintered products to be correctly characterised. Moreover, the author reports the study of the evolution of some physical properties of sintered materials with respect to their microstructure parameters. This leads to the development of a modelling of the behaviour of these materials [fr

  8. Sintering behaviour and mechanical properties of Cr3C2–NiCr ...

    Indian Academy of Sciences (India)

    the densification were remarkably promoted by the liquid phase formation at 1350. ◦. C. The densities as high as 97% of the theoretical density have been achieved by liquid phase sintering through the solution–reprecipitation and grain. Figure 1. XRD pattern of powder mixture and cermet samples sintered at four.

  9. Porous copper template from partially spark plasma-sintered Cu–Zn ...

    Indian Academy of Sciences (India)

    Administrator

    Dezincification and pore formation are conducted on sintered 0∙5 mm thick 12 mm diameter disc samples. The size, distribution and nature of pores in porous templates of Cu are then investigated using optical microscopy and SEM–EDS analysis. Keywords. Metal; corrosion; porous structure; sintering; powder metallurgy. 1.

  10. [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.

  11. Synthesis, Sintering, and Electrical Properties of BaCe0.9−xZrxY0.1O3−δ

    DEFF Research Database (Denmark)

    Ricote, S.; Caboche, G.; Estournes, C.

    2008-01-01

    BaCe0.9-xZrxY0.1O3-delta powders were synthesized by a solid-state reaction. Different contents of cerium and zirconium were studied. Pellets were sintered using either conventional sintering in air at 1700 degrees C or the Spark Plasma Sintering (SPS) technique. The density of the samples sinter......, and reproduction in any medium, provided the original work is properly cited....

  12. Self-Consolidation Mechanism Of Porous Ti-6Al-4V Implant Prototypes Produced By Electro-Discharge-Sintering Of Spherical Ti-6Al-4V Powders

    Directory of Open Access Journals (Sweden)

    Lee W.H.

    2015-06-01

    Full Text Available Electro-Discharge-Sintering (EDS was employed to fabricate Ti-6Al-4V porous implant prototypes from atomized powders (100 – 150 μm, that were subjected to discharges of 0.75 to 2.0 kJ/0.7g-powder from 150, 300, and 450 μF capacitors. Both fully porous and porous-surfaced Ti-6Al-4V compacts with various solid core sizes were self-consolidated in less than 86 – 155 μsec. It is known that EDS can simultaneously produce the pinch pressure to squeeze and deform powder particles and the heat to weld them together. The formation of a solid core in these prototypes depends on the amounts of both the pinch pressure and heat generated during a discharge. The size of the solid core and the thickness of the porous layer can be successfully controlled by manipulating the discharge conditions such as input energy and capacitance.

  13. Solid-state sintering of tungsten heavy alloys

    International Nuclear Information System (INIS)

    Gurwell, W.E.

    1994-10-01

    Solid-state sintering is a technologically important step in the fabrication of tungsten heavy alloys. This work addresses practical variables affecting the sinterability: powder particle size, powder mixing, and sintering temperature and time. Compositions containing 1 to 10 micrometer (μM) tungsten (W) powders can be fully densified at temperatures near the matrix solidus. Blending with an intensifier bar provided good dispersion of elemental powders and good as-sintered mechanical properties under adequate sintering conditions. Additional ball milling increases powder bulk density which primarily benefits mold and die filling. Although fine, 1 μm W powder blends have high sinterability, higher as-sintered ductilities are reached in shorter sintering times with coarser, 5 μm W powder blends; 10μm W powder blends promise the highest as-sintered ductilities due to their coarse microstructural W

  14. Effect of Sintering Time on Superconducting Wire Bi-Pb-Sr-Ca-Cu-O With Dopant MgO Sheated Ag Using Powder in Tube Method

    Directory of Open Access Journals (Sweden)

    Hariyati Lubis

    2018-01-01

    , A., (2008, Production of YBCO Superconductor Sample by Powder-In-Tube Method (PITM; and Effect of Cd and Ga Doping on the System, University, Department of Physics, Malatya-Turkey Sharma, D., Kumar, R., Awana, V.P.S. 2013. DC and AC Susceptibility Study of Sol-Gel Synthesized Bi2Sr2CaCu2O8+x Superconductor. Ceramic International. 39:1143-1152

  15. Evaluation of the influence of the Ca/P ratio on the values of crystallinity and growth of crystals during sintering of hydroxyapatite powders'; Avaliacao da influencia da razao Ca/P nos valores de cristalinidade e crescimento de cristais durante a sinterizacao de pos de hidroxiapatita

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo, A.G.S.; Araujo Junior, A.G.; Strecker, K., E-mail: adrianogalvao26@yahoo.com.br [Universidade Federal de Sao Joao del-Rei (UFSJ), MG (Brazil)

    2014-07-01

    Samples of hydroxyapatite (HAp) were synthesized by co-precipitation of solution with the precursors ions. At the end of synthesis samples with different reasons of calcium and phosphor were obtained and sintered in different temperature. The X-ray diffraction show that stoichiometry of the powders influenced in the sintering process. The samples with low calcium concentration (Ca/P=1,47) presented others peaks different those of stoichiometry hydroxyapatite. Phases of tricalcium phosphate (TCP (Ca{sub 3}(PO{sub 4}){sub 2})) were observed and the intensity of peaks increased with the increase of the sintering temperature due the decomposition of HAp in others calcium phosphates. The diffraction patterns of the samples with high calcium concentration (Ca/P=1,73) presented some peaks of lower intensity associated with Ca(OH){sub 2} and CaO. The crystals of material with Ca/P = 1,47 decreased their size and the values of crystallinity with the increased of temperature and the start of decomposition these powders. The hydroxyapatite with Ca/P=1,73 increased their size and crystallinity values with the increase of temperature. (author)

  16. Scanning pattern angle effect on the resulting properties of selective laser sintered monolayers of Cu-Sn-Ni powder

    Science.gov (United States)

    Sabelle, Matías; Walczak, Magdalena; Ramos-Grez, Jorge

    2018-01-01

    Laser-based layer manufacturing of metals, also known as additive manufacturing, is a growing research field of academic and industrial interest. However, in the associated laser-driven processes (i.e. selective laser sintering (SLS) or melting (SLM)), optimization of some parameters has not been fully explored. This research aims at determining how the angle of laser scanning pattern (i.e. build orientation) in SLS affects the mechanical properties and structure of an individual Cu-Sn-Ni alloy metallic layer sintered in the process. Experiments consist in varying the angle of the scanning pattern (0°, 30°, 45° 60° and 90° relative to the transverse dimension of the piece), at constant scanning speed and laser beam power, producing specimens of different thicknesses. A noticeable effect of the scan angle on the mechanical strength and degree of densification of the sintered specimens is found. Thickness of the resulting monolayer correlates negatively with increasing scan angle, whereas relative density correlates positively. A minimum porosity and maximum UTS are found at the angle of 60°. It is concluded that angle of the scanning pattern angle plays a significant role in SLS of metallic monolayers.

  17. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    ... involves compaction of polymeric powder under pressure and sintering of the preforms at temperature above its melting point. In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering temperatures and strength development.

  18. Application of the microcalorimetry to the study of annealing and recrystallization phenomena during the sintering of metallic powders

    International Nuclear Information System (INIS)

    Cytermann, R.; Mazadier, M.; Auguin, B.; Defresne, A.; Gilles, P.

    1975-01-01

    Nickel powders compressed isostatically at pressures between 1 and 13 kbars were studied. The tests were all carried out under a current of hydrogen after vacuum degassing and at the same temperature increase rate. Cold-hardening of the powders was shown by the broadening of the X-ray diffraction lines. Microcalorimetry confirmed the separation of the compacting process into two stages: rearrangement with local deformation and bulk plastic deformation [fr

  19. Sintering and electrical properties of strontium-doped lanthanum manganite

    Energy Technology Data Exchange (ETDEWEB)

    Tarrago, Diego Pereira; Sousa, Vania Caldas de [Universidade Federal do Rio Grande do Sul (LABIOMAT/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Biomateriais], Email: dptarrago@gmail.com; Moreno Buriel, Berta; Chinarro Martini, Eva; Jurado Egea, Jose Ramon [Consejo Superior de Investigaciones Cientificas (ICV/CSIC), Madrid (Spain). Inst. de Ceramica y Vidrio; Malfatti, Celia de Fraga [Universidade Federal do Rio Grande do Sul (LAPEC/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Pesquisa em Corrosao

    2010-07-01

    Lanthanum strontium manganites (LSM) are potential materials for cathode applications in solid oxide fuel cells (SOFC) due to their good catalytic activity, chemical stability and compatibility with electrolyte materials in high temperatures. The sinterability of single phase La{sub 1-x}Sr{sub x}Mn{sub O3} (x=0.18) perovskite powders and the electrical properties of the resulting samples are analyzed in this study. Using a heating microscope, the powders were pressed and sintered at different pressures and temperatures, resulting in an open porosity of 33.36% when compacted at 125 MPa and sintered at 1200 degree C. Top and cross-section s canning electron microscopy (SEM) micrographs revealed interconnected pores in the sintered body and, hence, a suitable microstructure for the application. The activation energy for conductance was 0.04 eV and the tested LSM bulk started to exhibit adequate electrical properties at about 500 degree C. (author)

  20. Zone refining of sintered, microwave-derived YBCO superconductors

    International Nuclear Information System (INIS)

    Warrier, K.G.K.; Varma, H.K.; Mani, T.V.; Damodaran, A.D.; Balachandran, U.

    1993-07-01

    Post-sintering treatments such as zone melting under thermal gradient has been conducted on sintered YBCO tape cast films. YBCO precursor powder was derived through decomposition of a mixture of nitrates of cations in a microwave oven for ∼4 min. The resulting powder was characterized and made into thin sheets by tape casting and then sintered at 945 C for 5 h. The sintered tapes were subjected to repeated zone refining operations at relatively high speeds of ∼30 mm/h. A microstructure having uniformly oriented grains in the a-b plane throughout the bulk of the sample was obtained by three repeated zone refining operations. Details of precursor preparation, microwave processing and its advantages, zone refining conditions, and microstructural features are presented in this paper

  1. Sintering of nano crystalline o silicon carbide doping with

    Indian Academy of Sciences (India)

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by ...

  2. Analysis and modeling of sintering of Sr-hexaferrite produced by PIM technology

    Directory of Open Access Journals (Sweden)

    Zlatkov B.S.

    2011-01-01

    Full Text Available The powder injection moulding (PIM technology is lately becoming more and more significant due to complex design possibilities and good repeatability. This technology requires optimization of all steps starting with material and binder, injection, debinding and sintering parameters. Sintering is one of the key links in this technology. The powder injection moulding process is specific as during feedstock injection powder particles mixed into the binder do not come into mechanical contact. Shrinkage during sintering of PIM samples is high. In this work we have analyzed and modeled the sintering process of isotropic PIM samples of Sr-hexaferrite. The Master Sintering Curve (MSC principle has been applied to analyze sintering of two types of PIM Sr-hexaferrite samples with completely removed binder and only the extraction step of the debinding procedure (thermal debinding proceeding simultaneously with sintering. Influence of the heating rate on resulting sample microstructures has also been analyzed. Influence of the sintering time and temperature was analyzed using three different phenomenological equations.

  3. Validation of a realistic powder sample using data from DMC at PSI

    DEFF Research Database (Denmark)

    Willendrup, Peter Kjær; Filges, U.; Keller, L.

    2006-01-01

    We present results of a virtual experiment, carried out by means of a McStas simulation of the powder diffractometer DMC at PSI, using the new powder sample component PowderN. This powder component takes tabulated crystallographic input to define realistic powder lines. The simulated output data...... from the virtual experiment on the compound Na2Ca3Al2F14 are compared to real measurement data from the DMC instrument. The agreement is very good with respect to peak positions, widths, background intensity and relative peak intensities. This work represents an important step towards reliable virtual...... experiments and also act as a validation of the PowderN sample component in McStas....

  4. Numerical simulation of electric field assisted sintering

    Science.gov (United States)

    McWilliams, Brandon A.

    A fully coupled thermal-electric-sintering finite element model was developed and implemented to explore electric field assisted sintering techniques (FAST). FAST is a single step processing operation for producing bulk materials from powders, in which the powder is heated by the application of electric current under pressure. This process differs from other powder processing techniques such as hot isostatic pressing (HIP) and traditional press and sinter operations where the powder or compact is heated externally, in that the powder is heated directly as a result of internal Joule heating (for conductive powders) and/or by direct conduction from the die and punches. The overall result is much more efficient heating which allows heating rates of >1000°C/min to be achieved which is desirable for sintering bulk nanocrystalline and other novel high performance materials. Previous modeling efforts on FAST have only considered the thermal-electric aspect of the problem and have neglected densification. In addition to the introduction of a sintering model, a detailed thermal-electric study of process parameters was carried out in order to identify key system variables and quantify their effect on the overall system response and subsequent thermal history of a consolidated sample. This analysis was compared to empirical data from a parallel experimental study and shown to satisfactorily predict the observed trends. This model was then integrated with a phenomenologically based sintering model to capture the densification of the sample. This fully coupled model was used to predict densification kinetics under FAST like conditions and examine the evolution of material properties as the sample transitions from a loose powder to a fully dense compact and the resulting effect on the electrical and thermal fields within the compact. This model was also used to explore the effect of non-uniform thermal, electrical, stress and density fields on the final geometry and local

  5. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  6. Structure and electrical properties of Mn-modified Pb((Zn1/3Nb2/3)0.20 (Zr0.50Ti0.50)0.80)O3 ceramics sintered in a protective powder atmosphere

    International Nuclear Information System (INIS)

    Hou, Y.D.; Cui, B.; Zhu, M.K.; Wang, H.; Wang, B.; Yan, H.; Tian, C.S.

    2004-01-01

    The effects of PbO atmosphere on structure and electrical properties of Mn-modified Pb((Zn 1/3 Nb 2/3 ) 0.20 (Zr 0.50 Ti 0.50 ) 0.80 )O 3 ceramics were investigated. Specimens were prepared with and without a PbZrO 3 protective ambient, by columbite two-stage process in a temperature region from 1050 to 1200 deg. C. The results indicated that PbZrO 3 powder is favored to the liquid-state sintering process of specimens in PbO vapor pressure equilibrium. The specimens sintered with PbZrO 3 powder showed the homogenous and intergranular microstructure; whereas, the specimens sintered without PbZrO 3 powder demonstrated the inhomogenous and transgranular microstructure. Without protective PbZrO 3 powder, the flow of PbO from the compact to the exterior resulted in the formation of amorphous phase in grain boundaries, which deteriorated the electric properties seriously. By the use of PbO protective atmosphere, the excellent piezoelectric and dielectric properties (Q m = 1160, tan δ = 0.004, K p =0.54) were obtained at 1100 deg. C for 2 h

  7. Synthesis, Sintering, and Electrical Properties of BaCe0.9−xZrxY0.1O3−δ

    Directory of Open Access Journals (Sweden)

    S. Ricote

    2008-01-01

    Full Text Available BaCe0.9−xZrxY0.1O3−δ powders were synthesized by a solid-state reaction. Different contents of cerium and zirconium were studied. Pellets were sintered using either conventional sintering in air at 1700∘C or the Spark Plasma Sintering (SPS technique. The density of the samples sintered by SPS is much higher than by conventional sintering. Higher values of ionic conductivity were obtained for the SPS sample.

  8. PRODUCTION OF WELDMENTS FROM SINTERED TITANIUM ALLOYS

    Directory of Open Access Journals (Sweden)

    A. YE. Kapustyan

    2014-04-01

    Full Text Available Purpose. Limited application of details from powder titanium alloys is connected with the difficulties in obtaining of long-length blanks, details of complex shape and large size. We can solve these problems by applying the welding production technology. For this it is necessary to conduct a research of the structure and mechanical properties of welded joints of sintered titanium alloys produced by flash welding. Methodology. Titanium industrial powders, type PT5-1 were used as original substance. Forming of blanks, whose chemical composition corresponded to BT1-0 alloy, was carried out using the powder metallurgy method. Compounds were obtained by flash welding without preheating. Microstructural investigations and mechanical tests were carried out. To compare the results investigations of BT1-0 cast alloy were conducted. Findings. Samples of welded joints of sintered titanium blanks from VT1-0 alloy using the flash butt welding method were obtained. During welding the microstructure of basic metal consisting of grains of an a-phase, with sizes 40...70 mkm, is transformed for the seam weld and HAZ into the lamellar structure of an a-phase. The remaining pores in seam weld were practically absent; in the HAZ their size was up to 2 mkm, with 30 mkm in the basic metal. Attainable level of mechanical properties of the welded joint in sintered titanium alloys is comparable to the basic metal. Originality. Structure qualitative changes and attainable property complex of compounds of sintered titanium alloys, formed as a result of flash butt welding were found out. Practical value. The principal possibility of high-quality compounds obtaining of sintered titanium alloys by flash welding is shown. This gives a basis for wider application of sintered titanium alloys due to long-length blanks production that are correspond to deformable strand semi finished product.

  9. Powder Handling Device for X-ray Diffraction Analysis with Minimal Sample Preparation, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This project consists in developing a Vibrating Powder Handling System for planetary X-Ray Diffraction instruments. The principle of this novel sample handling...

  10. Miniature Sample Collection and Delivery System using Gas-Entrained Powder Transport Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a miniature system for acquisition and delivery of solid samples to landed planetary instruments. This system would entrain powder produced by...

  11. The investigation of the microstructure and mechanical properties of ordered alominide-iron (boron) nanostructures produced by mechanical alloying and sintering

    Science.gov (United States)

    Izadi, S.; Akbari, Gh.; Janghorban, K.; Ghaffari, M.

    In this study, mechanical alloying (MA) of Fe-50Al, Fe-49.5Al-1B, and Fe-47.5Al-5B (at.%) alloy powders and mechanical properties of sintered products of the as-milled powders were investigated. X-ray diffraction (XRD) results showed the addition of B caused more crystallite refinement compared to the B-free powders. To consider the sintering and ordering behaviors of the parts produced from cold compaction of the powders milled for 80 h, sintering was conducted at various temperatures. It was found that the sintering temperature has no meaningful effect on the long-range order parameter. The transformation of the disordered solid solution developed by MA to ordered Fe-Al- (B) intermetallics was a consequence of sintering. Also, the nano-scale structure of the samples was retained even after sintering. The microhardness of pore-free zones of the nanostructured specimens decreased by increasing the sintering temperature. Moreover, the sintering temperature has no effect on the compressive yield stress. However, the fracture strain increased by increasing the sintering temperature. The samples containing 1 at.% B showed more strain to fracture compared with the B-free and 5 at.% B samples.

  12. Effect of diffusing TbF3 powder on magnetic properties and microstructure transformation of sintered Nd-Fe-Cu-B magnets

    Science.gov (United States)

    Yang, Xiao; Guo, Shuai; Ding, Guangfei; Cao, Xuejing; Zeng, Jiling; Song, Jie; Lee, Don; Yan, Aru

    2017-12-01

    The coercivity of sintered Nd-Fe-Cu-B magnets is markedly enhanced from 12.57 to 21.70 kOe while the remanence decreases from 13.80 to 13.49 kGs by grain boundary diffusion of TbF3 powder for 2 h. Microstructure analysis suggests that, during the diffusion process, F diffuses into the magnets easily and forms a new F-rich phase. The enrichment of F in grain boundary near the surface leads to the Cu movement into the interior and the Cu reduction in the surface of magnets. Diffusion of Tb leads to an increase of local total rare earth elements content. Under the combined effect of Cu reduction and increase of local total rare earth elements content, grain growth area is formed and further diffusion is suppressed. That excessive Tb diffuses into matrix phase leads to a decrease in remanence. When the grain growth area is removed, the deterioration of remanence recovers to 13.80 kGs without any reduction of coercivity.

  13. Models of current sintering

    Science.gov (United States)

    Angst, Sebastian; Engelke, Lukas; Winterer, Markus; Wolf, Dietrich E.

    2017-06-01

    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.

  14. The effects of composition, temperature and sample size on the sintering of chem-prep high field varistors.

    Energy Technology Data Exchange (ETDEWEB)

    Garino, Terry J.

    2007-09-01

    The sintering behavior of Sandia chem-prep high field varistor materials was studied using techniques including in situ shrinkage measurements, optical and scanning electron microscopy and x-ray diffraction. A thorough literature review of phase behavior, sintering and microstructure in Bi{sub 2}O{sub 3}-ZnO varistor systems is included. The effects of Bi{sub 2}O{sub 3} content (from 0.25 to 0.56 mol%) and of sodium doping level (0 to 600 ppm) on the isothermal densification kinetics was determined between 650 and 825 C. At {ge} 750 C samples with {ge}0.41 mol% Bi{sub 2}O{sub 3} have very similar densification kinetics, whereas samples with {le}0.33 mol% begin to densify only after a period of hours at low temperatures. The effect of the sodium content was greatest at {approx}700 C for standard 0.56 mol% Bi{sub 2}O{sub 3} and was greater in samples with 0.30 mol% Bi{sub 2}O{sub 3} than for those with 0.56 mol%. Sintering experiments on samples of differing size and shape found that densification decreases and mass loss increases with increasing surface area to volume ratio. However, these two effects have different causes: the enhancement in densification as samples increase in size appears to be caused by a low oxygen internal atmosphere that develops whereas the mass loss is due to the evaporation of bismuth oxide. In situ XRD experiments showed that the bismuth is initially present as an oxycarbonate that transforms to metastable {beta}-Bi{sub 2}O{sub 3} by 400 C. At {approx}650 C, coincident with the onset of densification, the cubic binary phase, Bi{sub 38}ZnO{sub 58} forms and remains stable to >800 C, indicating that a eutectic liquid does not form during normal varistor sintering ({approx}730 C). Finally, the formation and morphology of bismuth oxide phase regions that form on the varistors surfaces during slow cooling were studied.

  15. Effects of sintering temperature on electrical properties of sheep enamel hydroxyapatite

    Science.gov (United States)

    Dumludag, F.; Gunduz, O.; Kılıc, O.; Kılıc, B.; Ekren, N.; Kalkandelen, C.; Oktar, F. N.

    2017-12-01

    Bioceramics, especially calcium phosphate based bioceramics, whose examples are hydroxyapatite, and calcium phosphate powders have been widely used in the biomedical engineering applications. Hydroxyapatite (HA) is one of the most promising biomaterials, which are derived from natural sources, chemical method, animal like dental enamel and corals. The influence of sintering temperature on the electrical properties (i.e. DC conductivity, AC conductivity) of samples of sintered sheep enamel (SSSE) was studied in air and in vacuum ambient at room temperature. The sheep enamel were sintered at varying temperatures between 1000°C and 1300°C. DC conductivity results revealed that while dc conductivity of the SSSE decreases with increasing the sintering temperature in air ambient the values increased with increasing the sintering temperature in vacuum ambient. AC conductivity measurements were performed in the frequency range of 40 Hz - 105 Hz. The results showed that ac conductivity values decrease with increasing the sintering temperature.

  16. Borax as flux on sintering of iron Ancor Steel 1000® under glow discharge

    Science.gov (United States)

    Ariza Suarez, H. G.; Sarmiento Santos, A.; Ortiz Otálora, C. A.

    2016-02-01

    This work studies the flux effect of borax (di sodium tetraborate decahydrate) on sintering of iron Ancor Steel 1000® in abnormal glow discharge. The incidence of the percentage by weight of borax and the sintering temperature in the process were observed. Samples of powder metallurgical iron were prepared with proportions of 0.50%, 2.0%, 4.0% and 6.0% by weight of borax using the procedures of powder metallurgy. The samples were sintered at 800 and 1100°C for 30min, by glow discharge at low pressure in a reducing atmosphere composed of 20% H2+80% Ar. The samples in compact green-state were analyzed by TGA-DSC to determine the fusion process and mass loss during sintering. The analysis of microhardness and density, shows that at a sintering temperature of 800°C the sample density decreases and the sample microhardness increases with respect to sintered samples without borax. Sintered samples were analysed by DRX showing the absence of precipitates.

  17. Process for microwave sintering boron carbide

    Science.gov (United States)

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  18. Nickel and Copper-Free Sintered Structural Steels Containing Mn, Cr, Si, and Mo Developed for High Performance Applications

    Directory of Open Access Journals (Sweden)

    Cias A.

    2017-03-01

    Full Text Available In an attempt to study the sinterability of potential high-strength nickel-free sintered structural steels containing Mn, Cr, Si and Mo compacts were prepared based on sponge and water atomised iron powders and on Astaloy prealloyed powders. To these were admixed ferromanganese, ferroslicon, and graphite. The samples were sintered at temperatures 1120 and 1250°C in laboratory tube furnaces in hydrogen, hydrogen-nitrogen atmospheres with dew points better than -60°C or in nitrogen in a semiclosed container in a local microatmosphere. After sintering the samples were slowly cooled or sinterhardened. Generally resultant microstructures were inhomogeneous, consisted of pearlite/ bainite/martensite, but were characterised by an absence of oxide networks. Sintering studies performed over a range of compositions have shown that superior strength, ranging beyond 900 MPa, along with reasonable tensile elongation, can be achieved with these new steels.

  19. Gas-pressurized dispersive powder flow tester for low volume sample characterization.

    Science.gov (United States)

    Majid, Ainnur Marlyana Abd; Wong, Tin Wui

    2013-05-01

    The conventional powder flow testers require sample volumes larger than 40g and are met with experimental hiccups due to powder cohesion. This study designed a gas-pressurized dispersive powder flow tester where a high velocity air is used to disaggregate powder (9g) and eliminate its cohesion. The pressurized gas entrained solid particles leaving an orifice where the distance, surface area, width and weight of particle dispersion thereafter are determined as flow index. The flow indices of seven lactose grades with varying size, size distribution, shape, morphology, bulk and tapped densities characteristics were examined. They were compared against Hausner ratio and Carr's index parameters of the same powder mass. Both distance and surface area attributes of particle dispersion had significant negative correlations with Hausner ratio and Carr's index values of lactose. The distance, surface area and ease of particle dispersion varied proportionately with circular equivalent, surface weighted mean and volume weighted mean diameters of lactose, and inversely related to their specific surface area and elongation characteristics. Unlike insensitive Hausner ratio and Carr's index, an increase in elongation property of lactose particles was detectable through reduced powder weight loss from gas-pressurized dispersion as a result of susceptible particle blockage at orifice. The gas-pressurized dispersive tester is a useful alternative flowability measurement device for low volume and cohesive powder. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

    International Nuclear Information System (INIS)

    Liu, Junliang; Zeng, Yanwei; Zhang, Xingkai; Zhang, Ming

    2015-01-01

    Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%

  1. Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Junliang, E-mail: liujunliang@yzu.edu.cn [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zeng, Yanwei [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Zhang, Xingkai [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zhang, Ming [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Testing Center of Yangzhou University, Yangzhou 225002 (China)

    2015-05-15

    Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%.

  2. A Transient Liquid Phase Sintering Bonding Process Using Nickel-Tin Mixed Powder for the New Generation of High-Temperature Power Devices

    Science.gov (United States)

    Feng, Hongliang; Huang, Jihua; Yang, Jian; Zhou, Shaokun; Zhang, Rong; Chen, Shuhai

    2017-07-01

    A transient liquid phase sintering (TLPS) bonding process, Ni-Sn TLPS bonding was developed for the new generation of power semiconductor packaging. A model Ni/Ni-Sn/Ni sandwiched structure was assembled by using 30Ni-70Sn mixed powder as the reactive system. The results show that the bonding layer is composed of Ni3Sn4 and residual fine Ni particles with a small amount of Ni3Sn2 at 340°C for 240 min, which has a heat-resistant temperature higher than 790°C. The microstructural evolution and thermal characteristic of the bonding layer for various times at 300°C and 340°C were also studied, respectively. This reveals that, after isothermally holding for 240 min at 300°C and for 180 min at 340°C, Sn has been completely transformed into Ni-Sn intermetallic compounds (IMCs) and the bonding layer is mainly composed of Ni3Sn4 and residual Ni particles. The analysis result for the mechanical properties of the joint shows that the hardness of the bonding layer at 340°C for 240 min is uniform and that the average value reaches 3.66 GPa, which is close to that of the Ni3Sn4 block material. The shear test shows that, as the holding time increases from 60 min to 180 min at 340°C, because of the existence of Sn, the disparity of shear strength between room temperature and 350°C is large. But when the holding time is 180 min or longer, Sn has been completely transformed into Ni-Sn IMCs. Their performances are very similar whether at room temperature or 350°C.

  3. Analysis of early-stage sintering mechanisms of mechanically activated BaTiO3

    Directory of Open Access Journals (Sweden)

    Nikolić M.V.

    2006-01-01

    Full Text Available Barium-titanate powder was mechanically activated in a planetary-ball mill for 60 and 120 minutes. Non-isothermal sintering of non-activated and activated powder samples was investigated using a dilatometer in the temperature interval from room to 1380oC with three different heating rates (10, 20 and 30oC/min. Early-stage sintering mechanisms for all three types of samples were analyzed, showing significant differences between the non-activated and mechanically activated samples.

  4. Production and characterization of sintered ceramics from paper mill sludge and glass cullet.

    Science.gov (United States)

    Asquini, L; Furlani, E; Bruckner, S; Maschio, S

    2008-03-01

    Three different types of paper mill sludge were first incinerated and then attrition milled separately or mixed with glass cullet in varying proportions to obtain powders of different compositions. These powders were then dried, sieved, uniaxially pressed into samples and air sintered. Fired samples were characterized by density, water absorption, shrinkage on firing, strength, hardness and fracture toughness measurements; SEM and X-ray diffractions were also carried out to investigate microstructure and phase composition. Some sintered samples displayed fairly good physical and mechanical properties as a consequence of their low residual porosity and fine microstructure.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-01

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

  6. Production of high-strength Al85Y8Ni5Co2 bulk alloy by spark plasma sintering

    International Nuclear Information System (INIS)

    Surreddi, K B; Scudino, S; Sakaliyska, M; Eckert, J; Srivastava, V C; Uhlenwinkel, V; Kim, J S

    2010-01-01

    Highly dense bulk samples were produced by spark plasma sintering (SPS) through combined devitrification and consolidation of partially amorphous Al 85 Y 8 Ni 5 Co 2 gas atomized powders. The microstructure of the consolidated samples shows a mixed structure containing crystalline, ultrafine-grained and amorphous/nanocrystalline particles. The sintered sample exhibits a remarkable high strength of about 1050 MPa combined with 3.7 % fracture strain.

  7. Powdered alcohol: Awareness and likelihood of use among a sample of college students.

    Science.gov (United States)

    Vail-Smith, Karen; Chaney, Beth H; Martin, Ryan J; Don Chaney, J

    2016-01-01

    In March 2015, the Alcohol and Tobacco Tax and Trade Bureau approved the sale of Palcohol, the first powdered alcohol product to be marketed and sold in the U.S. Powdered alcohol is freeze-dried, and one individual-serving size packet added to 6 ounces of liquid is equivalent to a standard drink. This study assessed awareness of powered alcohol and likelihood to use and/or misuse powdered alcohol among college students. Surveys were administered to a convenience sample of 1,841 undergraduate students. Only 16.4% of respondents had heard of powdered alcohol. After being provided a brief description of powdered alcohol, 23% indicated that they would use the product if available, and of those, 62.1% also indicated likelihood of misusing the product (eg, snorting it, mixing it with alcohol). Caucasian students (OR = 1.5) and hazardous drinkers (based on AUDIT-C scores; OR = 4.7) were significantly more likely to indicate likelihood of use. Hazardous drinkers were also six times more likely to indicate likelihood to misuse the product. These findings can inform upstream prevention efforts in states debating bans on powdered alcohol. In states where powdered alcohol will soon be available, alcohol education initiatives should be updated to include information on the potential risks of use and be targeted to those populations most likely to misuse. This is the first peer-reviewed study to assess the awareness of and likelihood to use and/or misuse powdered alcohol, a potentially emerging form of alcohol. © American Academy of Addiction Psychiatry.

  8. Two steps sintering alumina doped with niobia; Sinterizacao em duas etapas de alumina aditivada com niobia

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, L.B.; Hatzfeld, J.; Heck, M.; Pokorny, A.; Bergmann, C.P., E-mail: lucas.gomes@ufrgs.br [Universidade Federal do Rio Grande do Sul (LACER/UFRGS) Porto Alegre, RS (Brazil). Laboratorio de Materiais Ceramicos

    2014-07-01

    In this work, high surface area commercial alumina was doped with niobia and sintered in two steps in order to obtain dense materials with lower processing temperatures. The powders were milled and uniaxially pressed (200 MPa). The first step of sintering took place at 1100°C for 3, 6, 9 and 12 hours, followed by the second step at 1350°C for 3 hours. The relative density, porosity and water absorption of the samples were determined by the Archimedes method. The crystalline phases were analyzed by X-ray Diffraction (XRD) and the morphology of the samples after sintering, evaluated by Scanning Electron Microscopy (SEM). The results indicate that the use of niobia combined with the two steps sintering promotes an increase in the density of the material, even at lower sintering temperatures. (author)

  9. Improvement of mechanical properties by additive assisted laser sintering of PEEK

    International Nuclear Information System (INIS)

    Kroh, M.; Bonten, C.; Eyerer, P.

    2014-01-01

    The additive assisted laser sintering was recently developed at IKT: A carbon black (CB) additive is used to adjust the polymer's laser absorption behavior with the aim to improve the interconnection of sintered powder layers. In this paper a parameter study, Polyetheretherketone (PEEK) samples were prepared with different contents of carbon black and were laser sintered with varying thermal treatment. The samples were mechanically tested and investigated by optical light and transmission electron microscopy. An influence on the morphology at the border areas of particles and intersections of laser sintered layers was found. Depending on the viscosity of the raw material and CB content, different shapes of lamellae were observed. These (trans-) crystalline or polymorph structures, respectively, influence the thermal and mechanical behavior of the virgin PEEK. Moreover, the thermal treatment during the sintering process caused an improvement of mechanical properties like tensile strength and elongation at break

  10. 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.)

  11. Phase characterisation in spark plasma sintered TiPt alloy

    CSIR Research Space (South Africa)

    Chikosha, S

    2011-12-01

    Full Text Available The conclusions drawn from this presentation are that Spark Plasma Sintering (SPS) of equiatomic BE TiPt powder produces fully sintered specimens, with incomplete homogenisation. There is a need for improved furnace atmosphere control so...

  12. Discrimination symbol applying method for sintered nuclear fuel product

    International Nuclear Information System (INIS)

    Ishizaki, Jin

    1998-01-01

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

  13. Preparation and Characterization of Sintered Microporous Polymeric Filters

    Directory of Open Access Journals (Sweden)

    Meysam Salari

    2017-09-01

    Full Text Available Nowadays filtration process is increasingly used in various areas such as water purification, food industries, filtering the air dust and other separation applications. In this work, the HDPE microporous filters have been fabricated at different pressure and time conditions via sintering process and then were characterized by different techniques. It can be expected that microstructure and mechanical properties of the samples could be controlled by changing the fabrication parameters like temperature, pressure, time of the process and also by changing the properties of the resin such as powder shape, particle size and rheological properties. In the first step, by using DSC, MFI, rheology test and optical microscope, the most suitable polymeric powder for sintering process was chosen. The sintering temperature was fixed in the vicinity of melting temperature of the used HDPE powder, based on DSC result. In order to evaluate mechanical properties and porosity of the samples, the results obtained from the shear punch test, acetone drop permeability, gas permeability, transition optical microscopy and SEM, have been used; then the effect of pressure and time parameters on the characteristics of the product has been studied. Finally, it was concluded that it is possible to make microporous filters with suitable mechanical properties, using sintering process at controlled pressure and temperature conditions.It can be seen that by increasing time and pressure, on the one hand the mechanical properties of the products increase, and on the other hand, their porosity and the gas permeability of the vents decrease.

  14. Sintering analysis of 8YSZ electrolyte correlated to the electrical performance

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Cristiane Abrantes da; Furtado, Jose Geraldo de Melo [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Miranda, Paulo Emilio Valadao de, E-mail: pmiranda@labh2.coppe.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Departmento de Engenharia Metalurgica e de Materiais

    2010-07-01

    The understanding of the mechanisms associated with densification and sintering of yttria stabilized zirconia (YSZ), a main solid oxide fuel cell electrolyte, enables the improvement of its microstructure. The present work that has the objective to study the sintering and densification processes of polycrystalline nanostructured 8% mol YSZ (8YSZ), correlating the microstructural development with the electrical performance of the material. The sintering behaviors of nanocrystalline 8YSZ powders obtained by two different chemical synthesis techniques (glycine-nitrate combustion process and Pechini method) were studied based on sintering dilatometer method. X-ray diffraction and scanning electron microscopy were used in the microstructural characterization. Full-densified 8YSZ (98.8%) were obtained and it was found that the samples obtained by the Pechini's method showed a higher densification degree in the final stage of sintering and resulted in ceramics with higher final relative density and better electrical behavior. (author)

  15. Rapid detection of whey in milk powder samples by spectrophotometric and multivariate calibration.

    Science.gov (United States)

    de Carvalho, Bruna Mara Aparecida; de Carvalho, Lorendane Millena; dos Reis Coimbra, Jane Sélia; Minim, Luis Antônio; de Souza Barcellos, Edilton; da Silva Júnior, Willer Ferreira; Detmann, Edenio; de Carvalho, Gleidson Giordano Pinto

    2015-05-01

    A rapid method for the detection and quantification of the adulteration of milk powder by the addition of whey was assessed by measuring glycomacropeptide protein using mid-infrared spectroscopy (MIR). Fluid milk samples were dried and then spiked with different concentrations of GMP and whey. Calibration models were developed using multivariate techniques, from spectral data. For the principal component analysis and discriminant analysis, excellent percentages of correct classification were achieved in accordance with the increase in the proportion of whey samples. For partial least squares regression analysis, the correlation coefficient (r) and root mean square error of prediction (RMSEP) in the best model were 0.9885 and 1.17, respectively. The rapid analysis, low cost monitoring and high throughput number of samples tested per unit time indicate that MIR spectroscopy may hold potential as a rapid and reliable method for detecting milk powder frauds using cheese whey. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Profile of yttrium segregation in BaCe0,9Y0,1O3-δ as function of sintering temperature

    International Nuclear Information System (INIS)

    Hosken, C.M.; Souza, D.P.F. de

    2010-01-01

    Researches on solid oxide fuel cells indicate barium cerate perovskite as a very attractive material for using as electrolyte due to its high protonic conductivity. The objective of this work is investigate the yttrium segregation during sintering of BaCe 0,9 Y 0,1 O 3-δ doped with Zn O as a sintering aid. The powders were prepared by citrate process. Powders were isostatic pressed into pellets and sintered in air at 1200, 1275, 1325 and 1400 deg C. The samples were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy. Secondary phase containing Yttrium and Cerium was detected as sintering temperature increased. Increase of the lattice parameter and activation energy for electrical conductivity were also detected on samples sintered at 1400 deg C. (author)

  17. Influence of starting powder milling on magnetic properties of Mn-Zn ferrite

    OpenAIRE

    Miodrag M. Milutinov; Maria Vesna Nikolić; Snežana G. Luković; Nelu Blaž; Nebojša Labus; Obrad S. Aleksić; Ljiljana D. Živanov

    2017-01-01

    In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200°C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss den...

  18. THERMAL AND ELECTRIC FIELDS AT SPARK PLASMA SINTERING OF THERMOELECTRIC MATERIALS

    Directory of Open Access Journals (Sweden)

    L. P. Bulat

    2014-09-01

    Full Text Available Problem statement. Improvement of thermoelectric figure of merit is connected with the usage of nanostructured thermoelectric materials fabricated from powders by the spark plasma sintering (SPS method. Preservation of powder nanostructure during sintering is possible at optimum temperature modes of thermoelectrics fabrication. The choice of these modes becomes complicated because of anisotropic properties of semiconductor thermoelectric materials. The decision of the given problem by sintering process simulation demands the competent approach to the problem formulation, a correct specification of thermoelectric properties, the properties of materials forming working installation, and also corrects boundary conditions. The paper deals with the efficient model for sintering of thermoelectrics. Methods. Sintering process of the bismuth telluride thermoelectric material by means of SPS-511S installation is considered. Temperature dependences of electric and thermal conductivities of bismuth telluride, and also temperature dependences of installation elements materials are taken into account. It is shown that temperature distribution in the sample can be defined within the limits of a stationary problem. The simulation is carried out in the software product Comsol Multiphysics. Boundary conditions include convective heat exchange and also radiation under Stefan-Boltzmann law. Results. Computer simulation of electric and thermal processes at spark plasma sintering is carried out. Temperature and electric potential distributions in a sample are obtained at the sintering conditions. Determinative role of graphite compression mould in formation of the temperature field in samples is shown. The influence of geometrical sizes of a graphite compression mould on sintering conditions of nanostructured thermoelectrics is analyzed. Practical importance. The optimum sizes of a cylindrical compression mould for fabrication of volume homogeneous samples based on

  19. Thermally stimulated current spectra of binder resin powders for copiers: Correction for thermal shrinkage of the sample powder compactions

    Science.gov (United States)

    Ikezakt, K.; Murata, Y.

    2008-12-01

    Thermally stimulated current (TSC) spectra observed under open- circuit condition for styrene- acrylic binder resin powder compactions for toners are corrected for their thermal shrinkage during TSC observation. For this binder resin, extrinsic current from motion of powder compactions with charges due to their thermal shrinkage was found to be much more effective than the sensitivity coefficient of a TSC measuring apparatus used. Particle size dependence of charge retention power of the resin powders was also examined by using this correction method and found that it decreased with decreasing their particle size.

  20. [Preparation of sub-standard samples and XRF analytical method of powder non-metallic minerals].

    Science.gov (United States)

    Kong, Qin; Chen, Lei; Wang, Ling

    2012-05-01

    In order to solve the problem that standard samples of non-metallic minerals are not satisfactory in practical work by X-ray fluorescence spectrometer (XRF) analysis with pressed powder pellet, a method was studied how to make sub-standard samples according to standard samples of non-metallic minerals and to determine how they can adapt to analysis of mineral powder samples, taking the K-feldspar ore in Ebian-Wudu, Sichuan as an example. Based on the characteristic analysis of K-feldspar ore and the standard samples by X-ray diffraction (XRD) and chemical methods, combined with the principle of the same or similar between the sub-standard samples and unknown samples, the experiment developed the method of preparation of sub-standard samples: both of the two samples above mentioned should have the same kind of minerals and the similar chemical components, adapt mineral processing, and benefit making working curve. Under the optimum experimental conditions, a method for determination of SiO2, Al2O3, Fe2O3, TiO2, CaO, MgO, K2O and Na2O of K-feldspar ore by XRF was established. Thedetermination results are in good agreement with classical chemical methods, which indicates that this method was accurate.

  1. EFFECT OF FLUORINE AND CHLORINE IONS ON THE REACTION SINTERING OF MECHANICALLY ACTIVATED ZIRCON-ALUMINA MIXTURE

    Directory of Open Access Journals (Sweden)

    R. Zamani Foroshani

    2015-09-01

    Full Text Available The aim of this work was to study the effect of fluorine and chlorine ions on the formation of mullite during the reaction sintering of mechanically activated zircon-alumina powder mixture. The results showed that mechanical activation of zirconalumina powder mixture for 20 h led to grain refinement and partial amorphization. In the presence of fluorine and chlorine ions, complete formation of mullite in the mechanically activated sample occurred after 2 h of reaction sintering at 1300oC and 1400oC, respectively. In the sample lacking fluorine and chlorine ions, mullitization was not completed even after 2 h of reaction sintering at 1400oC. It was concluded that presence of fluorine and chlorine ions enhance the dissociation of zircon and formation of mullite during the reaction sintering of mechanically activated zircon-alumina mixture.

  2. Foaming Glass Using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    Foam glass is a high added value product which contributes to waste recycling and energy efficiency through heat insulation. The foaming can be initiated by a chemical or physical process. Chemical foaming with aid of a foaming agent is the dominant industrial process. Physical foaming has two...... variations. One way is by saturation of glass melts with gas. The other involves sintering of powdered glass under a high gas pressure resulting in glass pellets with high pressure bubbles entrapped. Reheating the glass pellets above the glass transition temperature under ambient pressure allows the bubbles...... to expand. After heat-treatment foam glass can be obtained with porosities of 80–90 %. In this study we conduct physical foaming of cathode ray tube (CRT) panel glass by sintering under high pressure (5-25 MPa) using helium, nitrogen, or argon at 640 °C (~108 Pa s). Reheating a sample in a heating...

  3. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

  4. A variable-temperature sample container for low-temperature neutron powder diffraction

    International Nuclear Information System (INIS)

    Arzi, E.; Sandor, E.

    1983-01-01

    A variable-temperature sample container was developed for the neutron powder diffraction study of crystal structures and phase transitions in soldified gases. It consists of two coaxial tubes made of boron-free fused silica and fitted with heating coils and thermocouples. The exchange space between the tubes is filled with low-pressure helium gas controlled by two fine needle valves. Used in conjunction with a centre-stick-type liquid-helium cryostat and a proportional temperature controller, it maintains a powder sample of about 8 cm 3 volume at a constant temperature anywhere in the 4.2 to 77.4 K temperature range. Its stability is not worse than +-0.15 K and the liquid-helium consumption is about 1 litre a day above 17 K, increasing up to 6 litres a day at lower temperatures. It can also be used for the preparation of fine-grained powder samples directly from the gas phase. (Auth.)

  5. Physico-chemical characterisation of some samples of fresh milk and milk powder

    Directory of Open Access Journals (Sweden)

    Soceanu Alina

    2015-12-01

    Full Text Available Milk consumption is important in the diet of all age groups because it provides important nutrients that are essential for humans. Children are the largest consumers of milk, thus, it’s very important that milk is free of toxic compounds that can be harmful for humans. Aim of the study was to determine the physico-chemical characteristics of some samples of milk powder for different stage of baby growing and for some samples of fresh milk: raw cow’s milk, milk trade and UHT type. The following physico-chemical properties: density, pH, acidity, the presence of acetone, enzymes, antiseptics, dry substance, the ash, total fat, saponification and peroxide index, total nitrogen and protein content were determined. Comparing the values of acidity for analyzed samples it can be concluded that the powder milk acidity value is much lower than the fresh milk. The presence of antiseptics and acetone was not identified, and amylase and peroxidase were found only in raw cow's milk. The highest protein content was found for milk powder (27.22%.

  6. Extension of the master sintering curve for constant heating rate modeling

    Science.gov (United States)

    McCoy, Tammy Michelle

    density of the pellets based on the green density and the theoretical density of each of the compositions. The Master Sintering Curve (MSC) model is then utilized to generate data that can be utilized to predict the final density of the respective powder over a range of heating rates. The Elton Master Sintering Curve Extension (EMSCE) is developed to extend the functionality of the MSC tool. The parameters generated from the original MSC are used in tandem with the solution to the closed integral, theta ≡ 1cTo T1Texp -QRT dT, over a set range of temperatures. The EMSCE is used to generate a set of sintering curves having both constant heating rate and isothermal hold portions. The EMSCE extends the usefulness of the MSC by allowing this generation of a complete sintering schedule rather than just being able to predict the final relative density of a given material. The EMSCE is verified by generating a set of curves having both constant heating rate and an isothermal hold for the heat-treatment. The modeled curves are verified experimentally and a comparison of the model and experimental results are given for a selected composition. Porosity within the final product can hinder the product from sintering to full density. It is shown that some of the compositions studied did not sinter to full density because of the presence of large porosity that could not be eliminated in a reasonable amount of time. A statistical analysis of the volume fraction of porosity is completed to show the significance of the presence in the final product. The reason this is relevant to the MSC is that the model does not take into account the presence of porosity and assumes that the samples sinter to full density. When this does not happen, the model actually under-predicts the final density of the material.

  7. Effect of sintering temperature on magnetization and Mössbauer parameters of cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Grish, E-mail: grishphysics@gmail.com [Department of Physics, DSB Campus Kumaun University, Nainital 263002, Uttarakhand (India); Srivastava, R.C. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India); Reddy, V.R. [UGC-DAE CSR, Khandwa Road, DAVV Campus, Indore 452017, Madhya Pradesh (India); Agrawal, H.M. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India)

    2017-04-01

    Nanoparticles of cobalt ferrite of different particle size were prepared using sol-gel method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy techniques were employed for characterization of nanoparticles for structural and magnetic properties. The particle size and saturation magnetization increase with the increase of sintering temperature. The saturation magnetization increases from 53 to 85 emu/g as the sintering temperature increases from 300 to 900 °C. The remanence increases while the coercivity decreases slightly with the increase of sintering temperature. Mössbauer spectra show the ferrimagnetic nature of all the samples and the cation distribution strictly depends on the sintering temperature. The stoichiometry of the cobalt ferrite formed was estimated to be (Co{sup 2+}{sub x}Fe{sup 3+}{sub 1−x})[Co{sup 2+}{sub 1−x}Fe{sup 3+}{sub 1+x}]O{sub 4}, based on our Mössbauer analysis. The inverse spinel structure gradually transforms towards the normal spinel structure as the sintering temperature increases. - Highlights: • After 500 °C sintering the cobalt ferrite shows complete crystallization. • An inversion sintering temperature between 900 °C and 1200 °C is proposed where the Fe{sup +3} again starts migration from B site to A site. • Sintering temperature is one of the prime factors which effect the magnetization and cation distribution between two sites A and B.

  8. Phosphorus containing sintered alloys (review)

    International Nuclear Information System (INIS)

    Muchnik, S.V.

    1984-01-01

    Phosphorus additives are considered for their effect on the properties of sintered alloys of different applications: structural, antifriction, friction, magnetic, hard, superhard, heavy etc. Data are presented on compositions and properties of phosphorus-containing materials produced by the powder metallurgy method. Phosphorus is shown to be an effective activator of sintering in some cases. When its concentration in the material is optimal it imparts the material such properties as strength, viscosity, hardness, wear resistance. Problems concerning powder metallurgy of amorphous phosphorus-containing alloys are reported

  9. EFFECT OF THE Si POWDER ADDITIONS ON THE PROPERTIES OF SiC COMPOSITES

    Directory of Open Access Journals (Sweden)

    GUOGANG XU

    2012-09-01

    Full Text Available By means of transient plastic phase process, the SiC silicon carbide kiln furniture materials were produced through adding Si powder to SiC materials. At the condition of the same additions of SiO2 powder, the effect of the Si powder additions on properties of silicon carbide materials after sintered at 1450°C for 3 h in air atmosphere was studied by means of SEM and other analysis methods. The results showed that silicon powder contributes to both sintering by liquid state and plastic phase combination to improve the strength of samples. When the Si powder additions is lower than 3.5 %, the density and strength of samples increase and porosity decrease with increasing Si powder additions. However when the Si powder additions is higher than 3.5 %, the density and strength of samples decrease and porosity increase with increasing Si powder additions. With increasing of Si additions, the residual strength of sample after thermal shocked increased and linear change rate decreased, and get to boundary value when Si additions is 4.5 %. The results also indicated that at the same sintering temperature, the sample with 3.5 % silicon powder has maximum strength.

  10. Safety consideration when handling metal powders

    CSIR Research Space (South Africa)

    Benson, JM

    2012-03-01

    Full Text Available Metal powder compaction offers unique advantages in the manufacture of net-shape components using techniques such as laser sintering, conventional press and sintering, metal injection moulding, direct rolling, direct forging, and hot isostatic...

  11. Spectrochemical analysis of powdered biological samples using transversely excited atmospheric carbon dioxide laser plasma excitation

    Science.gov (United States)

    Zivkovic, Sanja; Momcilovic, Milos; Staicu, Angela; Mutic, Jelena; Trtica, Milan; Savovic, Jelena

    2017-02-01

    The aim of this study was to develop a simple laser induced breakdown spectroscopy (LIBS) method for quantitative elemental analysis of powdered biological materials based on laboratory prepared calibration samples. The analysis was done using ungated single pulse LIBS in ambient air at atmospheric pressure. Transversely-Excited Atmospheric pressure (TEA) CO2 laser was used as an energy source for plasma generation on samples. The material used for the analysis was a blue-green alga Spirulina, widely used in food and pharmaceutical industries and also in a few biotechnological applications. To demonstrate the analytical potential of this particular LIBS system the obtained spectra were compared to the spectra obtained using a commercial LIBS system based on pulsed Nd:YAG laser. A single sample of known concentration was used to estimate detection limits for Ba, Ca, Fe, Mg, Mn, Si and Sr and compare detection power of these two LIBS systems. TEA CO2 laser based LIBS was also applied for quantitative analysis of the elements in powder Spirulina samples. Analytical curves for Ba, Fe, Mg, Mn and Sr were constructed using laboratory produced matrix-matched calibration samples. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique for elemental quantification, and reasonably well agreement between ICP and LIBS data was obtained. Results confirm that, in respect to its sensitivity and precision, TEA CO2 laser based LIBS can be successfully applied for quantitative analysis of macro and micro-elements in algal samples. The fact that nearly all classes of materials can be prepared as powders implies that the proposed method could be easily extended to a quantitative analysis of different kinds of materials, organic, biological or inorganic.

  12. Influence of green compaction on the sintering behaviour of SiC-TiC-TiB{sub 2} composites

    Energy Technology Data Exchange (ETDEWEB)

    Waesche, R.; Yarim, R.; Nicolaides, D. [Federal Inst. for Materials Research and Testing (BAM), Berlin (Germany)

    2004-07-01

    The influence of different processing parameters like powder milling time and die pressure during manufacturing of SiC-TiC-TiB{sub 2} particulate composites has been investigated. The results show that at least a pressure of 90 MPa is necessary for obtaining fully dense samples. The degree of densification is dependent on the compaction process. At low green densities only the powder agglomerates are able to sinter. With increasing compaction pressure the contact area between the agglomerates increases also leading to increasing sintering densities up to fully dense samples. (orig.)

  13. Modeling Macroscopic Shape Distortions during Sintering of Multi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye

    Ceramic multi-layered composites are being used as components in various technologies ranging from electronics to energy conversion devices. Thus, different architectures of multi-layers involving ceramic materials are often required to be produced by powder processing, followed by sintering...... the camber development during co-firing. The effect of extrinsic factors (e.g. gravity, thickness ratio and friction) on the shape evolution of bi-layers during co-firing has been studied using the developed model and experiments. Furthermore, a new analytical model describing stresses during sintering...... of tubular bi-layer structures has been developed by using the direct correspondence between elasticity and linear viscous problems. The finite element model developed in this study and sintering experiments of tubular bi-layer sample have been used to verify and validate the developed analytical model...

  14. Borax as a lubricant in powder metallurgy

    Directory of Open Access Journals (Sweden)

    Héctor Geovanny Ariza-Suarez

    2014-12-01

    were compacted at 700 MPa in a uniaxial press of 15 tons. DSC-TGA analysis of the mixture with borax was realized. The specimens were sintered in a plasma reactor at 1000 for 30 minutes, with a combined atmosphere of hydrogen and argon. Microhardness and density of the sintered samples was haracterized. XRD analysis was realized to detect possible compounds formation by interaction of borax. This paper shows that borax can be used as a lubricant in powder metallurgy.

  15. Electro sinter forging of titanium disks

    DEFF Research Database (Denmark)

    Cannella, Emanuele; Nielsen, Chris Valentin; Bay, Niels Oluf

    Electro sinter forging (ESF) is a new sintering process based on the principle of electrical Joule heating. In the present work, middle frequency direct current (MFDC) was flowing through the powder compact, which was under mechanical pressure. The main parameters are the high electrical current,...

  16. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    Abstract. Ultra high molecular weight polyethylene (UHMWPE) is a high performance polymer having low coefficient of friction, good abrasion resistance, good chemical ... In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering ...

  17. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural respon...

  18. Phase and microstructural characterization of Mo–Si–B multiphase intermetallic alloys produced by pressureless sintering

    International Nuclear Information System (INIS)

    Taleghani, P.R.; Bakhshi, S.R.; Borhani, G.H.; Erfanmanesh, M.

    2014-01-01

    Highlights: • Active and ultra-fine Mo–Si–B powders were produced by mechanical alloying. • The phases of MoSi 2 and MoB were obtained by sintering Mo–57Si–10B at 1400 °C for 2 h. • Composite based on MoB/MoSi 2 was obtained by sintering Mo–47Si–23B at 1300 °C for 3 h. • High content of MoB in the composite based on MoB/MoSi 2 increased density. • High hardness of the composite based on MoB/MoSi 2 is related to MoB matrix. -- Abstract: In this study Mo–47Si–23B and Mo–57Si–10B powders (at.%) was milled for 20 h in attritor ball mill with a rotational speed of 365 rpm and the ball/powder mass ratio 20/1. After degassing of As-mechanically alloyed powders at 450 °C, the powders were pressed into cylindrical samples with 25 mm diameter under 600 MPa pressure. The samples were sintered by using of a tube resistance furnace under Ar atmosphere. Phase and microstructure characteristic of mechanically alloyed powders and sintered samples, were investigated by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. Also hardness test was performed. Homogeneous distribution of active and ultra-fine powders were obtained after milling for 20 h. Mo–57Si–10B alloy with MoB and MoSi 2 dominant phases was produced by sintering at 1400 °C for 2 h. Dominant phases similar to Mo–57Si–10B alloy sintered at 1400 °C for 2 h could be synthesized in Mo–47Si–23B alloy after sintering at 1300 °C for 3 h, but volume fraction of MoB phase was different. The Mo–47Si–23B alloy contained a higher phase fraction of MoB compound as compared to Mo–57Si–10B alloy. Very high density in Mo–47Si–23B alloys was obtained, due to the presence of high volume fraction of MoB phase. Formation heat of MoB acted as a positive potential to increase driving force of sintering and consequently bulk density. Finally, a uniform and fine distribution of MoSi 2 particles in MoB continuous matrix in the microstructure of Mo-47Si

  19. Raman and dielectric studies of GdMnO3 bulk ceramics synthesized from nano powders

    Science.gov (United States)

    Samantaray, S.; Mishra, D. K.; Roul, B. K.

    2017-05-01

    Nanocrystalline GdMnO3 (GMO) powders has been synthesized by a simple chemical route i. e. pyrophoric reaction technique and then sintered in the form of bulk pellet at 850°C for 24 hours by adopting slow step sintering schedule. It is observed that by reducing the particles size, chemical route enhances the mixing process as well as decreasing the sintering temperature to get single phase material system in compared to the polycrystalline sample prepared directly from the micron sized commercial powder. Raman spectroscopic studies confirm that the sample is in single phase without any detectable impurity. Frequency dependent dielectric properties i.e., dielectric constant (K) and dielectric loss (tanδ) of GMO ceramics sintered at 850°C for 24 hours were studied at room temperature. The sample showed high K value (˜2736) in the frequency of 100 Hz at room temperature.

  20. Microstructure and microanalysis studies of copper-nickel-tin alloys obtained by conventional powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, Waldemar A.; Carrio, Juan A.G.; Masson, T.J.; Vitor, E.; Abreu, C.D.; Marques, I.M., E-mail: fisica.cch@mackenzie.br [Universidade Presbiteriana Mackenzie (CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades; Silva, L.C.E. da, E-mail: jgcarrio@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    The aim of this paper was to analyze the microstructural development in samples of Cu-Ni-Sn alloys (weight %) obtained by powder metallurgy (P/M). The powders were mixed for 1/2 hour. After this, they were pressed, in a cold uniaxial pressing (1000 kPa). In the next step the specimens were sintered at temperatures varying from 650 up to 780 deg C under vacuum. Secondly, the samples were homogenized at 500 deg C for several special times. The alloys were characterized by optical microscopy, electrical conductivity and Vickers hardness. X-rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples. (author)

  1. Plasma sintering of ferritic steel reinforced with niobium carbide prepared by high energy milling; Sinterizacao a plasma de aco ferritico reforcado com carbeto de niobio preparado por moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Silva Junior, J.F. da; Almeida, E.O.; Gomes, U.U.; Alves Junior, C.; Messias, A.P. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil). Lab. de Materiais Ceramicos e Metais Especiais; Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil). Lab. de Processamento de Materiais por Plasma

    2010-07-01

    Plasma is an ionized gas where ions are accelerated from anode to cathode surface, where the sample is placed. There are a lot of collisions on cathode surface by ions heating and sintering the sample. High energy milling (HEM) is often used to produce composite particles to be used on powder metallurgy. These particles can exhibit fine particles and high phase dispersion. This present work aim to study ferritic steels reinforced with 3%NbC prepared by HEM and sintered on plasma furnace. Ferritic steel and NbC powders were milled during 5 hours and characterized by SEM, XRD and laser scattering. Then, these composite powders were compacted in a cylindrical steel die and then sintered in a plasma furnace. Vickers microhardness tests and SEM and XRD analysis were performed on sintered samples. (author)

  2. Fabrication and study of double sintered TiNi-based porous alloys

    Science.gov (United States)

    Sergey, Anikeev; Valentina, Hodorenko; Timofey, Chekalkin; Victor, Gunther; Ji-hoon, Kang; Ji-soon, Kim

    2017-05-01

    Double-sintered porous TiNi-based alloys were fabricated and their structural characteristics and physico-mechanical properties were investigated. A fabrication technology of powder mixtures is elaborated in this article. Sintering conditions were chosen experimentally to ensure good structure and properties. The porous alloys were synthesized by solid-state double diffusion sintering (DDS) of Ti-Ni powder and prepare to obtain dense, crack-free, and homogeneous samples. The Ti-Ni compound sintered at various temperatures was investigated by scanning electron microscopy. Phase composition of the sintered alloys was determined by x-ray diffraction. Analysis of the data confirmed the morphology and structural parameters. Mechanical and physical properties of the sintered alloys were evaluated. DDS at 1250 °C was found to be optimal to produce porous samples with a porosity of 56% and mean pore size of 90 μm. Pore size distribution was unimodal within the narrow range of values. The alloys present enhanced strength and ductility, owing to both the homogeneity of the macrostructure and relative elasticity of the bulk, which is hardened by the Ni-rich precipitates. These results suggest the possibility to manufacture porous TiNi-based alloys for application as a new class of dental implants.

  3. Microstructural evaluation of the NbC-20Ni cemented carbides during sintering

    International Nuclear Information System (INIS)

    Rodrigues, D.; Cannizza, E.

    2016-01-01

    Full text: Fine carbides in a metallic matrix (binder) form the microstructure of the cemented carbides. Grain size and binder content are the main variables to adjust hardness and toughness. These products are produced by Powder Metallurgy, and traditional route involves mixing carbides with binder by high energy milling, pressing and sintering. During sintering, a liquid phase promotes densification, and a final relative density higher than 99% is expected. Sintering is carried out at high temperatures, and dissolution of the carbides changes the chemical composition of the binder. To control grain growth of the main carbide, which reduces hardness, small quantities of secondary carbides are used. These additives limit dissolution and precipitation of the main carbides reducing the final grain size. This paper focused the structural and chemical evolution during sintering using NbC-20Ni cermets. Mixtures of very fine NbC carbides and carbonyl Ni powders were produce by intense milling. These mixtures were pressed using uniaxial pressures from 50 to 200MPa. Shrinkage was evaluated using dilatometric measurements under an atmosphere of dynamic argon. Samples were also sintered under vacuum in high temperature industrial furnace. The sintered samples were characterized in terms of density hardness, toughness and microstructure. DRX was the main tool used to evaluate the structural evolution of the binder. In situ chemical analysis helped to understand the dissolution mechanisms. (author)

  4. Microstructural evaluation of the NbC-20Ni cemented carbides during sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, D. [BRATS Sintered Filters and Metallic Powders, Cajamar, SP (Brazil); Cannizza, E. [EHT Cannizza Consultoria Em Engenharia Ltda, Sao Paulo, SP (Brazil)

    2016-07-01

    Full text: Fine carbides in a metallic matrix (binder) form the microstructure of the cemented carbides. Grain size and binder content are the main variables to adjust hardness and toughness. These products are produced by Powder Metallurgy, and traditional route involves mixing carbides with binder by high energy milling, pressing and sintering. During sintering, a liquid phase promotes densification, and a final relative density higher than 99% is expected. Sintering is carried out at high temperatures, and dissolution of the carbides changes the chemical composition of the binder. To control grain growth of the main carbide, which reduces hardness, small quantities of secondary carbides are used. These additives limit dissolution and precipitation of the main carbides reducing the final grain size. This paper focused the structural and chemical evolution during sintering using NbC-20Ni cermets. Mixtures of very fine NbC carbides and carbonyl Ni powders were produce by intense milling. These mixtures were pressed using uniaxial pressures from 50 to 200MPa. Shrinkage was evaluated using dilatometric measurements under an atmosphere of dynamic argon. Samples were also sintered under vacuum in high temperature industrial furnace. The sintered samples were characterized in terms of density hardness, toughness and microstructure. DRX was the main tool used to evaluate the structural evolution of the binder. In situ chemical analysis helped to understand the dissolution mechanisms. (author)

  5. Study of radioactivity levels in detergent powders samples by gamma spectroscopy

    Directory of Open Access Journals (Sweden)

    Ali A. Abojassim

    2014-10-01

    Full Text Available This study focuses on the evaluation of the natural radioactivity levels in ten samples of the detergent powders that available in Iraqi markets. We have determined the specific activities of uranium, thorium and potassium using gamma spectroscopy and calculation of radiation hazard indices. The results of the activities of radionuclides (238U, 232Th, 40K for detergent powders samples, are found that the 238U specific activities were varied from (11.489 ± 2.089 Bq/kg to (36.062 ± 2.478 Bq/kg, while the 232th specific activities were varied from (1.411 ± 0.609 Bq/kg to (9.272 ± 1.642 Bq/kg and 40K were varied from (8.189 ± 2.339 Bq/kg to (91.888 ± 4.164 Bq/kg. These values are always lower than those of raw materials, what is explained by the conservation of radioactive material throughout the manufacturing process. The radium equivalent activity Raeq, the external hazard index Hex and the internal hazard index Hin dose due to natural radioactivity estimated below the regulatory standard recommended which are (370 Bq/kg, 1 and 1 according to OECD 1979 and ICRP 2000, allows us to show that Detergent powders samples products are not contaminated by radioactivity, are healthy and do not have harmful radiological impact on the consumer.

  6. EFFECT OF SINTERING PROFILES ON THE PROPERTIES AND AGEING RESISTANCE OF Y-TZP CERAMIC

    Directory of Open Access Journals (Sweden)

    C.Y. Tan

    2011-12-01

    Full Text Available A commercially available Y-TZP ceramic powder was fabricated under four different sintering profiles in order to investigate the effects of conventional single-stage sintering (SSS with dwell times of 1 min and 2 h, respectively, compared with two-stage sintering (TSS, on the physical and mechanical properties of Y-TZP. Sintering was performed up to 1400oC at a ramp rate of 10oC/min. It was revealed that samples sintered via TSS yielded better properties than the SSS samples sintered at 1400oC using a dwell time of 2 h. In the hydrothermal ageing test, TSS samples did not undergo low-temperature degradation via the tetragonal to monoclinic phase transformation. Nevertheless, it was found by XRD analysis that Y-TZP ceramics sintered by the SSS method using a short dwell time of 1 min were effective in maintaining tetragonal phase stability after 50 h of exposure to superheated steam conditions.

  7. Model approach to estimate the probability of accepting a lot of heterogeneously contaminated powdered food using different sampling strategies.

    Science.gov (United States)

    Valero, Antonio; Pasquali, Frédérique; De Cesare, Alessandra; Manfreda, Gerardo

    2014-08-01

    Current sampling plans assume a random distribution of microorganisms in food. However, food-borne pathogens are estimated to be heterogeneously distributed in powdered foods. This spatial distribution together with very low level of contaminations raises concern of the efficiency of current sampling plans for the detection of food-borne pathogens like Cronobacter and Salmonella in powdered foods such as powdered infant formula or powdered eggs. An alternative approach based on a Poisson distribution of the contaminated part of the lot (Habraken approach) was used in order to evaluate the probability of falsely accepting a contaminated lot of powdered food when different sampling strategies were simulated considering variables such as lot size, sample size, microbial concentration in the contaminated part of the lot and proportion of contaminated lot. The simulated results suggest that a sample size of 100g or more corresponds to the lower number of samples to be tested in comparison with sample sizes of 10 or 1g. Moreover, the number of samples to be tested greatly decrease if the microbial concentration is 1CFU/g instead of 0.1CFU/g or if the proportion of contamination is 0.05 instead of 0.01. Mean contaminations higher than 1CFU/g or proportions higher than 0.05 did not impact on the number of samples. The Habraken approach represents a useful tool for risk management in order to design a fit-for-purpose sampling plan for the detection of low levels of food-borne pathogens in heterogeneously contaminated powdered food. However, it must be outlined that although effective in detecting pathogens, these sampling plans are difficult to be applied since the huge number of samples that needs to be tested. Sampling does not seem an effective measure to control pathogens in powdered food. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. 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)

  9. Development of a Sinter/HIP process for the superalloy Udimet 700 with investigations of the influence of the sinteratmosphere

    International Nuclear Information System (INIS)

    Wenning, L.

    1991-03-01

    The oxidation free treatment of reactive metalpowders like the nickel base alloy Udimet 700 demands sufficient oxygen free sinteratmospheres in nowadays sinter-HIP plants are not reachable. The reported work deals with the development of a sinter-HIP process which enables a sufficient low partial pressure of oxygen by scavenging the Udimet 700 powder packings with argon during vacuum sintering. By this the sinter hindering oxidation is avoided. Intensive investigations of the sinteratmosphere with a mass spectrometer and a zirconium oxide probe verify the reduction of the oxygen content of the residual gas atmosphere reached with different processes. In a second part the applicability of the scavenging gas process during the capsule free sinter-HIP treatment of metall injection moulded (MIM) samples is shown. (orig.) [de

  10. Comparative sinterability of combustion synthesized and commercial titanium carbides

    International Nuclear Information System (INIS)

    Manley, B.W.

    1984-11-01

    The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 0 C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables

  11. Evaluation of Rock Powdering Methods to Obtain Fine-grained Samples for CHEMIN, a Combined XRD/XRF Instrument

    Science.gov (United States)

    Chipera, S. J.; Vaniman, D. T.; Bish, D. L.; Sarrazin, P.; Feldman, S.; Blake, D. F.; Bearman, G.; Bar-Cohen, Y.

    2004-01-01

    A miniature XRD/XRF (X-ray diffraction / X-ray fluorescence) instrument, CHEMIN, is currently being developed for definitive mineralogic analysis of soils and rocks on Mars. One of the technical issues that must be addressed to enable remote XRD analysis is how best to obtain a representative sample powder for analysis. For powder XRD analyses, it is beneficial to have a fine-grained sample to reduce preferred orientation effects and to provide a statistically significant number of crystallites to the X-ray beam. Although a two-dimensional detector as used in the CHEMIN instrument will produce good results even with poorly prepared powder, the quality of the data will improve and the time required for data collection will be reduced if the sample is fine-grained and randomly oriented. A variety of methods have been proposed for XRD sample preparation. Chipera et al. presented grain size distributions and XRD results from powders generated with an Ultrasonic/Sonic Driller/Corer (USDC) currently being developed at JPL. The USDC was shown to be an effective instrument for sampling rock to produce powder suitable for XRD. In this paper, we compare powder prepared using the USDC with powder obtained with a miniaturized rock crusher developed at JPL and with powder obtained with a rotary tungsten carbide bit to powders obtained from a laboratory bench-scale Retsch mill (provides benchmark mineralogical data). These comparisons will allow assessment of the suitability of these methods for analysis by an XRD/XRF instrument such as CHEMIN.

  12. A study of pressureless microwave sintering, microwave-assisted hot press sintering and conventional hot pressing on properties of aluminium/alumina nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Abedinzadeh, Reza; Safavi, Seyed Mohsen; Karimzadeh, Fathallah [Isfahan University, Isfahan (Iran, Islamic Republic of)

    2016-05-15

    Bulk Al/4wt-%Al{sub 2}O{sub 3} nanocomposites were prepared by consolidating nanocomposite powders using pressureless microwave sintering, microwave-assisted hot press sintering and conventional hot pressing techniques. Microstructural observations revealed that the microwave-assisted hot press sintering at different sintering temperatures of 400.deg.C and 500.deg.C resulted in more densification and smaller grain size for Al/Al{sub 2}O{sub 3} nanocomposite as compared with the conventional hot pressing. Moreover, the application of pressure in microwave sintering process led to more densification and grain growth. Mechanical properties resulting from microhardness and nanoindentation tests were also compared between three-method processed samples. It was found that the microwave-assisted hot-pressed sample exhibited higher hardness and elastic modulus in comparison with microwave-sintered and conventional hot-pressed samples. The improvement in the mechanical properties can be ascribed to lower porosity of microwave-assisted hot-pressed sample.

  13. Measurement of radioactive lines in powdered milk samples in Londrina (Parana State, Brazil) region

    International Nuclear Information System (INIS)

    Melquiades, Fabio Luiz

    2000-01-01

    This work deals with the measurement of radioactive lines in powdered milk, with high resolution gamma spectrometry, using a HPGe detector with relative efficiency of 10%, coupled to the electronic nuclear chain and a multichannel card of 8192 channels. Some tests were realized before beginning the measurements. The first of them was to define the shield to be used, making several measured with different shields according to the available materials, opting finally for a shield composed of bricks of lead (10 cm thickness), plates of iron (4nm thickness) and of aluminum (2 mm thickness). Four different geometries for the samples recipients were tested, and the Marinelli beaker of 2,1 liters totally filled was the one which supplied the best peak/background ratio. A statistical inference was also realized to determine the sampling that represents each one of the lots of milk to be measured, resulting in a number of 6 samples, for a confidence level of 95%. Two different kinds of powdered milk produced at Londrina were analyzed, Integral Powdered Milk Cativa and Integral Powdered Milk Polly. The samples were properly put in the Marinelli beaker of 2,1 L, sealed and kept for 40 days to reach the secular equilibrium. The counting time for each measurement was two days. It was possible to identify the radionuclides 40 K, 137 Cs and 232 Th (from 208 Tl), whose activities were calculated according to the International Atomic Energy Agency norms (IAEA, 1989). The detector efficiency was measured using calibrated samples, prepared with the certified reference materials IAEA-326 and IAEA-375. Corrections for self-absorption were accomplished, based on measures of samples with different densities. The results obtained for the powdered milk Cativa were: 464± 12 Bq/kg for 40 K, 3,46 ± 1,05 and 0,46 ± 1,05 and 0,46 ± 0,16 Bq/kg for the minimum detectable activities of 137 Cs and 232 Th, respectively. For the milk Polly, the results were: 452±10 Bq/kg for 40 K, 3,19 ± 0

  14. Fabrication and Spark Plasma Sintering of Magnetic alpha-Fe/MgO Nanocomposite by Mechanical Alloying.

    Science.gov (United States)

    Lee, Chung-Hyo

    2016-02-01

    Solid-state reduction has occurred during mechanical alloying of a mixture of Fe2O3 and Mg powders at room temperature. It is found that magnetic nanocomposite in which MgO is dispersed in alpha-Fe matrix with nano-sized grains is obtained by mechanical alloying of Fe2O3 with Mg for 30 min. Consolidation of the ball-milled powders was performed in a spark plasma sintering (SPS) machine up to 800-1000 degrees C. X-ray diffraction result shows that the average grain size of alpha-Fe in a-Fe/MgO nanocomposite sintered at 800 degrees C is in the range of 110 nm. It can be also seen that the coercivity of SPS sample sintered at 800 degrees C is still high value of 88 Oe, suggesting that the grain growth of magnetic alpha-Fe phase during SPS process tends to be suppressed.

  15. Consolidation of W–Ta composites: Hot isostatic pressing and spark and pulse plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dias, M., E-mail: marta.dias@itn.pt [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Guerreiro, F. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); Galatanu, A. [National Institute of Materials Physics, Atomistilor 105 bis Bucharest-Magurele, 077125 Ilfov (Romania); Rosiński, M. [Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw (Poland); Monge, M.A.; Munoz, A. [Departamento de Física, Univerdidad Carlos III de Madrid, Avd. de la Universidad 30, 28911 Madrid (Spain); Alves, E. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Carvalho, P.A. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2015-10-15

    Highlights: • Consolidation of W–Ta composites using three techniques: HIP, SPS and PPS. • Comparison of consolidation methods in terms of W–Ta interdiffusion and densification. • Microstructure analysis in terms of oxides formation. - Abstract: Composites consisting of tantalum fiber/powder dispersed in a nanostructured W matrix have been consolidated by spark and pulse plasma sintering as well as by hot isostatic pressing. The microstructural observations revealed that the tungsten–tantalum fiber composites consolidated by hot isostatic pressing and pulse plasma sintering presented a continuous layer of Ta{sub 2}O{sub 5} phase at the W/Ta interfaces, while the samples consolidated by spark plasma sintering evidenced a Ta + Ta{sub 2}O{sub 5} eutectic mixture due to the higher temperature of this consolidation process. Similar results have been obtained for the tungsten–tantalum powder composites. A (W, Ta) solid solution was detected around the prior nanostructured W particles in tungsten–tantalum powder composites consolidated by spark and pulse plasma sintering. Higher densifications were obtained for composites consolidated by hot isostatic pressing and pulse plasma sintering.

  16. Reactive Sintering of Bimodal WC-Co Hardmetals

    OpenAIRE

    Marek Tarraste; Kristjan Juhani; Jüri Pirso; Mart Viljus

    2015-01-01

    Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal har...

  17. Sintered ceramics having controlled density and porosity

    International Nuclear Information System (INIS)

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

    1980-01-01

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

  18. Aluminum powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  19. X-ray diffraction studies on crystallite size evolution of CoFe2O4 nanoparticles prepared using mechanical alloying and sintering

    International Nuclear Information System (INIS)

    Waje, Samaila Bawa; Hashim, Mansor; Yusoff, Wan Daud Wan; Abbas, Zulkifly

    2010-01-01

    Nanosized cobalt ferrite spinel particles have been prepared by using mechanically alloyed nanoparticles. The effects of various preparation parameters on the crystallite size of cobalt ferrite which includes milling time; ball-to powder weight ratio (BPR) and sintering temperature, were studied using X-ray diffractometer (XRD). Scherrer's equation was used to study the crystallite size evolution of the as-prepared materials. The results of the as-milled sample revealed that both milling time and BPR plays a role in determining the crystallite size of the milled powder. However, where sintering is involved, the sintering temperature results in grain growth, and thus plays a dominant role in determining the final crystallite size of the samples sintered at higher temperature (above 900 deg. C). From the vibrating-sample magnetometer (VSM) measurement it was observed that the coercivity of the as-milled samples without sintering is almost negligible, which is a type characteristic of superparamagnetic material. However, for the sintered samples, the saturation increases while coercivity decreases with increases sintering temperature.

  20. Calibration sampling paradox in near infrared spectroscopy: a case study of multi-component powder blend.

    Science.gov (United States)

    Karande, A D; Liew, C V; Heng, P W S

    2010-08-16

    The objective of this study was to illustrate the sampling paradox resulting from the different strategies of spectral acquisition while preparing and implementing the calibration models for prediction of blend components in multi-component cohesive blends. A D-optimal mixture design was used to create 24 blending runs of the formulation consisting of chlorpheniramine maleate, lactose, microcrystalline cellulose and magnesium stearate. Three strategies: (a) laboratory mixing and static spectral acquisition, (b) IBC mixing and static spectral acquisition and (c) IBC mixing and dynamic spectral acquisition were investigated for obtaining the most relevant and representative calibration samples. An optical head comprising a sapphire window mounted on the lid of the IBC was used for static and dynamic NIR spectral acquisition of the powder blends. For laboratory mixed samples, powders were blended for fixed period of 30 min and later on scanned for NIR spectra. For IBC mixed blends, the spectral acquisition was carried out in-line for 2 min and stopped for static spectral acquisition. The same cycle was repeated for the next 28 min. Partial least square (PLS) calibration models for each component were built and ranked according to their calibration statistics. Optimal calibration models were selected from each strategy for each component and used for in-line prediction of blend components of three independent test runs. Although excellent statistics were obtained for the PLS models from the three strategies, significant discrepancies were observed during prediction of the independent blends in real time. Models built using IBC mixed blends and dynamic spectral acquisition resulted in the most accurate predictions for all the blend components, whereas models prepared using static spectral acquisition (laboratory mixed and IBC) showed erroneous prediction results. The prediction performance differences between the models obtained using the different strategies could be

  1. Microwave Sintering of Bi2Te3- and PbTe-Based Alloys: Structure and Thermoelectric Properties

    Science.gov (United States)

    Arreguin-Zavala, J.; Vasilevskiy, D.; Turenne, S.; Masut, R. A.

    2013-07-01

    Microwave sintering is well known as an expeditious process in applications involving ceramics and biomaterials. For powders in the nanometer range, rapid microwave heating could reduce material exposure to elevated temperatures, thus preserving nanostructures in the resulting materials. To investigate the potential of this technique for thermoelectric (TE) materials, we have prepared samples of bismuth-telluride- and lead-telluride-based alloys from powders, for both materials, having sizes of partially agglomerated particles distributed from 0.15 μm to 7 μm. Sintering of the cold-pressed powders was carried out in a microwave furnace for 900 s at temperatures in the range of 583 K to 623 K for bismuth telluride and 793 K to 813 K for lead telluride specimens. For optimized sintering times and temperatures, the samples obtained showed relative densities of almost 95%. Scanning electron microscopy shows some residual porosity and a reduction of grain size, up to a factor of 5 for PbTe, compared with optimized hot-extruded specimens. For bismuth telluride samples, the TE performance in the range of 300 K to 460 K is poor, which is attributed to the arbitrary texture obtained from cold pressing of a highly anisotropic alloy prior to its sintering. In contrast, PbTe exhibits isotropic properties, hence deficiency of texturing is not expected to have a negative impact on its TE properties. Harman measurements show a value of ZT = 0.42 at 617 K for PbTe p-type sintered samples, which is comparable to hot-extruded alloys from similar powders. The present work demonstrates that microwave sintering is a promising alternative to other powder consolidation techniques for polycrystalline materials exhibiting isotropic TE properties.

  2. Mechanical properties of the samples produced by volume powder cladding of stainless steel using a continuous fiber laser

    International Nuclear Information System (INIS)

    Bykovskiy, D P; Petrovskiy, V N; Mironov, V D; Osintsev, A V; Ochkov, K Yu

    2016-01-01

    Samples for tensile tests were manufactured by using one of the additive technologies - direct laser material deposition. Investigations were carried out at the facility Huffman HC-205 equipped with a fiber laser with a power up to 3.5 kW. Various strategies of layering metallic powder of stainless steel 316L were considered to optimize the modes of constructing the samples. We measured the stress-strain state of the produced samples by the method of digital image correlation. It is found that the nominal tensile strength of the samples produced by the direct growing using laser powder of 316L steel is of high level - 767 MPa. (paper)

  3. Effects of ball milling and sintering on alumina and alumina-boron compounds

    Science.gov (United States)

    Cross, Thomas

    Alumina has a wide variety of applications, but the processing of alumina based materials can be costly. Mechanically milling alumina has been shown to enhance the sintering properties while decreasing the sintering temperature. Additions of boron have also proven to increase sintering properties of alumina. These two processes, mechanical milling and boron additions, will be combined to test the sintering properties and determine if they are improved upon even further compared to the individual processes. Multiple samples of pure alumina, 0.2 weight percent boron, and 1.0 weight percent boron are batched and processed in a ball mill for different time intervals. These samples are then characterized to observe the structure and properties of the samples after milling but before sintering. Pellets are dry pressed from the milled powders, sintered at 1200°C for one to 10 hours, and characterized to determine the impact of processing. X-ray diffractometry (XRD) was used on each sample to determine crystallite size and lattice parameters at different stages throughout the experiment. XRD was also used to identify any samples with an aluminum borate phase. Scanning electron microscopy (SEM) was used to observe the powder and pellet morphology and to measure bulk chemical composition. Samples were sputter coated with an Au-Pd coating observed in the SEM to characterize the topography as a function of variables such as milling time, boron composition, and sintering time. Additionally, porosity and change in diameter were measured to track the sintering process. Milling sample for longer periods of time would be unnecessary due to the crystallite size leveling off between 10 and 12 hours of milling time. Samples of alumina with 0.2 weight percent boron prove to have very little effect on the sintering properties. At 1.0 weight percent boron, there are changes in diffraction patterns and topography after being sintered for one hour. The porosities of all of the sintered

  4. Hydrogen Decrepitation Press-Less Process recycling of NdFeB sintered magnets

    Science.gov (United States)

    Xia, Manlong; Abrahamsen, Asger B.; Bahl, Christian R. H.; Veluri, Badrinath; Søegaard, Allan I.; Bøjsøe, Poul

    2017-11-01

    A Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling method for recycling of anisotropic NdFeB magnets is demonstrated. The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered in a graphite mold. Coercivities up to 534 kA/m were obtained in porous samples based on powder size d 100 μm. The coercivity reached Hci = 957 kA/m being 86% of the original N48M material without addition of rare earth elements.

  5. Structural and electrical properties of copper-nickel-aluminum alloys obtained by conventional powder metallurgy method

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, Waldemar A.; Carrio, Juan A.G.; Silveira, C.R. da; Pertile, H.K.S., E-mail: fisica.cch@mackenzie.br [Universidade Presbiteriana Mackenzie (UPM/CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades. Dept. de Fisica; Silva, L.C.E. da; Buso, S.J., E-mail: jgcarrio@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    This work looked for to search out systematically, in scale of laboratory, copper-nickel-aluminum alloys (Cu-Ni-Al) with conventional powder metallurgy processing, in view of the maintenance of the electric and mechanical properties with the intention of getting electric connectors of high performance or high mechanical damping. After cold uniaxial pressing (1000 kPa), sintering (780 deg C) and convenient homogenization treatments (500 deg C for different times) under vacuum (powder metallurgy), the obtained Cu-Ni-Al alloys were characterized by optical microscopy, electrical conductivity, Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, hardness, macrostructures and microstructures of the samples. (author)

  6. Structural and electrical properties of copper-nickel-aluminum alloys obtained by conventional powder metallurgy method

    International Nuclear Information System (INIS)

    Monteiro, Waldemar A.; Carrio, Juan A.G.; Silveira, C.R. da; Pertile, H.K.S.

    2009-01-01

    This work looked for to search out systematically, in scale of laboratory, copper-nickel-aluminum alloys (Cu-Ni-Al) with conventional powder metallurgy processing, in view of the maintenance of the electric and mechanical properties with the intention of getting electric connectors of high performance or high mechanical damping. After cold uniaxial pressing (1000 kPa), sintering (780 deg C) and convenient homogenization treatments (500 deg C for different times) under vacuum (powder metallurgy), the obtained Cu-Ni-Al alloys were characterized by optical microscopy, electrical conductivity, Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, hardness, macrostructures and microstructures of the samples. (author)

  7. The fracture strength of cryomilled 99.7 Al nanopowders consolidated by high frequency induction sintering

    International Nuclear Information System (INIS)

    El-Danaf, Ehab A; Almajid, Abdulhakim A; Soliman, Mahmoud S; Baig, Muneer

    2014-01-01

    Mechanical Attrition of metallic powders induces severe plastic deformation and consequently reduces the average grain size. Powders of 99.7 Al (45μm particle size), cryomilled for 7 hrs having a crystal size of ∼ 20 nm, were consolidated by high frequency induction sintering under a constant pressure of 50 MPa and at two temperatures of 500 and 550 °C for two sintering dwell times of 1 and 3 minutes at a constant heating rate of 400 °C/min. The bright field TEM image and X-ray line broadening technique, for the cryomilled powders, were used to measure-the crystallite size. Simple compression at an initial strain rate of 10 −4 s −1 was conducted at room temperature, 373 and 473 K, and the yield strength was documented and correlated with the sintering parameters. The as-received 99.7 Al powders-consolidated using one of the sintering parameters was used as a reference material to compare the mechanical properties. Hardness, density and crystal size of the consolidated sample, that gave the highest yield and fracture strength, were measured

  8. Production of a low young modulus titanium alloy by powder metallurgy

    Directory of Open Access Journals (Sweden)

    Dalcy Roberto dos Santos

    2005-12-01

    Full Text Available Titanium alloys have several advantages over ferrous and non-ferrous metallic materials, such as high strengthto-weight ratio and excellent corrosion resistance. A blended elemental titanium powder metallurgy process has been developed to offer low cost commercial products. The process employs hydride-dehydride (HDH powders as raw material. In this work, results of the Ti-35Nb alloy sintering are presented. This alloy due to its lower modulus of elasticity and high biocompatibility is a promising candidate for aerospace and medical use. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by isochronal sintering between 900 up to 1600 °C, in vacuum. Sintering behavior was studied by means of microscopy and density. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Samples sintered at high temperatures display a fine plate-like alpha structure and intergranular beta. A few remaining pores are still found and density above 90% for specimens sintered in temperatures over 1500 °C is reached.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  10. 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.

  11. Effect of sintering temperature on physical properties & hardness of CoCrMo alloys fabricated by metal injection moulding process

    Science.gov (United States)

    Ridhwan Abdullah, Ahmad; Aidah Nabihah Dandang, Nur; Zalikha Khalil, Nur; Harun, Wan Sharuzi Wan

    2017-10-01

    Metal Injection Moulding (MIM) process is one of the Powder Metallurgy manufacturing techniques utilised to produce Cobalt Chromium Molybdenum (CoCrMo) compacts. The objective of this study is to determine physical properties and hardness of CoCrMo alloy compact sintered at three different sintering temperature at the similar soaking time. At the beginning, sample were fabricated by using Injection Moulding machine. Cobalt Chrome Molybdenum (CoCrMo) metal powder was selected for this study. A morphological study was conducted using optical microscope (OM) and micro-Vickers hardness testing. From the result obtained, it shows upward trend either on the hardness or physical properties of the samples. CoCrMo sintered compact become harder and volume of pores on surface become less due to the increase on sintering temperature. However, effect of increasing sintering temperature shows significant shrinkage of the sample, beginning losses in dimensional accuracy. It is discovered that a little change in sintering temperature gives significant impact on the microstructure, physical, mechanical of the alloy.

  12. Utilization of dilatometer for characterization of UO2 powders

    International Nuclear Information System (INIS)

    Bhattacharjee, S.; Broczkowski, M.E.; Kryst, K.; Ioffe, M.S.; Murchie, M.P.

    2010-01-01

    Particle size and specific surface area measurements are conventional characterization techniques for ceramic powders to predict sintering behaviour. Dilatometry is one of the most popular techniques in ceramics to study the sintering characteristics for optimization of firing processes. Uranium dioxide (UO 2 ) powders from different sources were characterized by conventional techniques and these characteristics were correlated with sintering behaviour, as measured with a dilatometer. The suitability of dilatometry to correlate the sintering characteristics of UO 2 powder with variations in the O/U ratio, particle size and green density was discussed. Explanations of features in the sintering profiles for UO 2 powders have been presented. (author)

  13. Effects of sintering atmosphere and initial particle size on sintering of gadolinia-doped ceria

    International Nuclear Information System (INIS)

    Batista, Rafael Morgado

    2014-01-01

    The effects of the sintering atmosphere and initial particle size on the sintering of ceria containing 10 mol% gadolinia (GdO 1.5 ) were systematically investigated. The main physical parameter was the specific surface area of the initial powders. Nanometric powders with three different specific surface areas were utilized, 210 m 2 /g, 36,2 m 2 /g e 7,4 m 2 /g. The influence on the densification, and micro structural evolution were evaluated. The starting sintering temperature was verified to decrease with increasing on the specific surface area of raw powders. The densification was accelerated for the materials with smaller particle size. Sintering paths for crystallite growth were obtained. Master sintering curves for gadolinium-doped ceria were constructed for all initial powders. A computational program was developed for this purpose. The results for apparent activation energy showed noticeable dependence with specific surface area. In this work, the apparent activation energy for densification increased with the initial particle size of powders. The evolution of the particle size distributions on non isothermal sintering was investigated by WPPM method. It was verified that the grain growth controlling mechanism on gadolinia doped ceria is the pore drag for initial stage and beginning of intermediate stage. The effects of the sintering atmosphere on the stoichiometry deviation of ceria, densification, microstructure evolution, and electrical conductivity were analyzed. Inert, oxidizing, and reducing atmospheres were utilized on this work. Deviations on ceria stoichiometry were verified on the bulk materials. The deviation verified was dependent of the specific surface area and sintering atmosphere. Higher reduction potential atmospheres increase Ce 3+ bulk concentration after sintering. Accelerated grain growth and lower electrical conductivities were verified when reduction reactions are significantly present on sintering. (author)

  14. Preparation of Ni-Ti shape memory alloy by spark plasma sintering method

    Czech Academy of Sciences Publication Activity Database

    Salvetr, P.; Kubatík, Tomáš František; Novák, P.

    2016-01-01

    Roč. 16, č. 4 (2016), s. 804-808 ISSN 1213-2489 Institutional support: RVO:61389021 Keywords : Ni-Ti alloy * Powder metallurgy * Reactive sintering * Spark plasma sintering Subject RIV: JK - Corrosion ; Surface Treatment of Materials

  15. Analysis of the Magnetocaloric Effect in Powder Samples Obtained by Ball Milling

    Science.gov (United States)

    Blázquez, J. S.; Ipus, J. J.; Moreno-Ramírez, L. M.; Borrego, J. M.; Lozano-Pérez, S.; Franco, V.; Conde, C. F.; Conde, A.

    2015-06-01

    Since the discovery of the giant magnetocaloric effect (MCE) close to room temperature in FeRh and particularly in Gd5Si2Ge2 compounds, the study of this phenomenon has experienced an exponential growth. Among the different techniques used to produce magnetocaloric materials, ball milling has been shown as a very versatile one and presents several advantages over other preparation techniques ( e.g., easy scale-up to industrial production). Although a general decrease of the peak value of the magnetic entropy change is observed for milled samples, it can be compensated by the large broadening of the MCE peak, leading to an increase of the refrigeration capacity. In this short review, several aspects inherent to powder samples affecting MCE will be discussed, such as the relevant effect of the demagnetizing field, the possible multiphase character, and the presence of Curie temperature distributions. In mechanically alloyed samples, the two latter factors are typically affected by the degree of integration of the different starting constituents.

  16. Sintering behavior and mechanical properties of a metal injection molded Ti–Nb binary alloy as biomaterial

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Dapeng, E-mail: dpzhao@hotmail.com [College of Biology, Hunan University, 410082 Changsha (China); Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany); Chang, Keke [RWTH Aachen University, Materials Chemistry, D-52056 Aachen (Germany); Ebel, Thomas [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany); Nie, Hemin [College of Biology, Hunan University, 410082 Changsha (China); Willumeit, Regine; Pyczak, Florian [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany)

    2015-08-15

    Highlights: • The sintering of the MIM Ti–Nb alloy consists of three steps. • The Nb particles act as diffusion barriers during sintering. • The TiC{sub x} only precipitate in the cooling step during sintering. • The TiC{sub x} hardly influence the sintering process of MIM Ti–Nb alloy. • The MIM Ti–Nb alloy exhibits high strength, low Young’s modulus but poor ductility. - Abstract: Sintering behavior, microstructure and mechanical properties of a Ti–16Nb alloy processed by metal injection molding (MIM) technology using elemental powders were investigated in this work by optical microscopy, X-ray diffraction (XRD), dilatometer, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). It was found that from 700 °C to 1500 °C the homogenization and densification process of MIM Ti–16Nb alloy consisted of three steps, i.e., Ti-diffusion-controlled step, Ti–Nb-diffusion step and matrix-diffusion step. Titanium carbide formation was observed in the samples sintered at 1300 °C and 1500 °C, but not in the ones sintered at 900 °C and 1100 °C. The MIM Ti–16Nb specimens sintered at 1500 °C exhibited a good combination of high tensile strength and low Young’s modulus. However, the titanium carbide particles led to poor ductility.

  17. Liquid Phase Sintering of (Ti,Zr)C with WC-Co.

    Science.gov (United States)

    Ma, Taoran; Borrajo-Pelaez, Rafael; Hedström, Peter; Blomqvist, Andreas; Borgh, Ida; Norgren, Susanne; Odqvist, Joakim

    2017-01-11

    (Ti,Zr)C powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,Zr)C, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,Zr)C phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ₁) or Zr (γ₂). The γ₂ phase grains have a core-shell structure with a (Ti,Zr)C core following the full sintering cycle. The major differences observed in (Ti,Zr)C with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ₁, and γ₂) is about 10% smaller in WC-(Ti,Zr)C-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

  18. Liquid Phase Sintering of (Ti,ZrC with WC-Co

    Directory of Open Access Journals (Sweden)

    Taoran Ma

    2017-01-01

    Full Text Available (Ti,ZrC powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,ZrC, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,ZrC phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ1 or Zr (γ2. The γ2 phase grains have a core-shell structure with a (Ti,ZrC core following the full sintering cycle. The major differences observed in (Ti,ZrC with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ1, and γ2 is about 10% smaller in WC-(Ti,ZrC-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

  19. Boundary structure modification and magnetic properties of Nd-Fe-B sintered magnets by co-doping with Dy{sub 2}O{sub 3}/S powders

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Fang [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Leichen [School of Engineering Technology, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Ping [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, Xuzhe [School of Engineering Technology, Purdue University, West Lafayette, Indiana 47907 (United States); Sui, Yanli [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Zhimeng, E-mail: guozhimengustb@163.com [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Gao, Xuexu [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-05-01

    In this paper, the effect of Dy{sub 2}O{sub 3}/S co-doping on the magnetic properties and microstructure was studied in Nd-Fe-B sintered magnets. With S co-doping, the coercivity increased due to grain boundary modification and Dy selective introduction. Continuous grain boundary phases were formed in the co-doped magnets with smaller grain size. The average grain size after a doping of 0.2 wt% S is 7.25 µm, which is approximately 2.37 µm smaller than that of the S-free sintered magnets(9.62 µm). The coercivity of the Dy{sub 2}O{sub 3}/0.2 wt% S co-doped magnets could be increased from 20.9 to 22.8 kOe with changing the remanence and the maximum magnetic energy product slightly. S precipitates in the Nd-rich phases were hexagonal Nd{sub 2}O{sub 2}S phase. Dy avoided the Nd{sub 2}O{sub 2}S phase in the triple junction region, resulting in more available Dy atoms diffusing into the Nd{sub 2}Fe{sub 14}B phase grains to enhance the anisotropy field. Dy-saving was achieved by forming Nd{sub 2}O{sub 2}S phase in the Dy{sub 2}O{sub 3}/S co-doped magnets. - Highlights: • The average grain size of Dy{sub 2}O{sub 3}/S co-doped magnets is 2.37 μm smaller than that of Dy{sub 2}O{sub 3} doped magnets. • The Dy atoms avoid the Nd{sub 2}O{sub 2}S phases and more of them become available to diffuse into the Nd{sub 2}Fe{sub 14}B phases. • The coercivity reaches maximum when S content is 0.2 wt%, 9% higher than the 20.9 kOe coercivity of the S-free magnets.

  20. Characterization of TiC-FeCrMn Cermets Produced by Powder Metallurgy Method

    Directory of Open Access Journals (Sweden)

    Märt Kolnes

    2015-09-01

    Full Text Available TiC-NiMo cermets combine relatively low density with high hardness. Because nickel is known as a toxin and allergen and allergy to nickel is a phenomenon which has assumed growing importance in recent years there has been a flurry of activity to find alternatives to the nickel binder in cermets. It is also the global research and technical development trend in the powder metallurgy cermets industry. In present research TiC-based cermets with FeCrMn binder system were fabricated. Three different sintering conditions were used (vacuum sintering, sinter/HIP and sintering under low Ar pressure. Because of high vapor pressure of manganese different sintering conditions and technologies were investigated to depress the Mn-loss during sintering. Chemical composition of TiC-FeCrMn cermets after different sintering conditions were analyzed by energy-dispersive X-ray spectroscopy (EDS and mechanical properties – hardness and fracture toughness were evaluated on the samples. Results of research showed that Ni-free TiC-based CrMn-steels bonded cermets compare unfavorably with cermets bonded with CrNi austenitic steels in terms of fracture toughness and corrosion resistance. Noticeable Mn-loss during vacuum sintering can be avoided when sintering under low Ar gas pressure.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7364

  1. Effect of nitrogen on the preparation (powder synthesis - sintering) and on the dielectric properties of 'MgAlON' spinel solid solutions

    International Nuclear Information System (INIS)

    Morey, O.

    2000-01-01

    The aim of this work is to show the effect of nitrogen on the synthesis, the sintering and the dielectric behaviour of 'MgAlON' spinel solid solutions. 'MgAlON' solid solutions (1.1 ≤ N ≤ 4.2 %) have been prepared by solid state reactions between Al 2 O 3 , MgO and AlN at high temperature (1450 degrees Celsius) under nitrogen atmosphere and characterized by granulometric analysis, Brunauer-Emmet-Teller (BET) surface area analysis, X-ray diffraction, scanning electron microscopy, Al 27 NMR, FTIR spectroscopy and thermoluminescence. Point defects have been revealed. They are in particular due to the nitrogen amount incorporated into the structure. The O/N substitution in the anionic lattice induces a delay to the densification when the nitrogen composition increases. The dielectric properties of these materials have been studied by two methods. The first one has a macroscopic character and is destructive. It allows to know the breakdown voltage and to calculate the dielectric rigidity of the material. The second one ('SEMM': 'Scanning Electron Microscopy Mirror') has a microscopic character and is nondestructive. Its principle is based on the charge injection with an electric beam. It gives the yield of charge trapping of the material. The good behaviour of these materials to the charge injection has been correlated to the oxygen vacancies in increasing amount with the nitrogen composition. (O.M.)

  2. Application of Box-Behnken Design and Response Surface Methodology for Surface Roughness Prediction Model of CP-Ti Powder Metallurgy Components Through WEDM

    Science.gov (United States)

    Das, Arunangsu; Sarkar, Susenjit; Karanjai, Malobika; Sutradhar, Goutam

    2018-04-01

    The present work was undertaken to investigate and characterize the machining parameters (such as surface roughness, etc.) of uni-axially pressed commercially pure titanium sintered powder metallurgy components. Powder was uni-axially pressed at designated pressure of 840 MPa to form cylindrical samples and the green compacts were sintered at 0.001 mbar for about 4 h with sintering temperature varying from 1350 to 1450 °C. The influence of the sintering temperature, pulse-on and pulse-off time at wire-EDM on the surface roughness of the preforms has been investigated thoroughly. Experiments were conducted under different machining parameters in a CNC operated wire-cut EDM. The surface roughness of the machined surface was measured and critically analysed. The optimum surface roughness was achieved under the conditions of 6 μs pulse-on time, 9 μs pulse-off time and at sintering temperature of 1450 °C.

  3. Application of Box-Behnken Design and Response Surface Methodology for Surface Roughness Prediction Model of CP-Ti Powder Metallurgy Components Through WEDM

    Science.gov (United States)

    Das, Arunangsu; Sarkar, Susenjit; Karanjai, Malobika; Sutradhar, Goutam

    2017-06-01

    The present work was undertaken to investigate and characterize the machining parameters (such as surface roughness, etc.) of uni-axially pressed commercially pure titanium sintered powder metallurgy components. Powder was uni-axially pressed at designated pressure of 840 MPa to form cylindrical samples and the green compacts were sintered at 0.001 mbar for about 4 h with sintering temperature varying from 1350 to 1450 °C. The influence of the sintering temperature, pulse-on and pulse-off time at wire-EDM on the surface roughness of the preforms has been investigated thoroughly. Experiments were conducted under different machining parameters in a CNC operated wire-cut EDM. The surface roughness of the machined surface was measured and critically analysed. The optimum surface roughness was achieved under the conditions of 6 μs pulse-on time, 9 μs pulse-off time and at sintering temperature of 1450 °C.

  4. Potential use of only Yb2O3 in producing dense Si3N4 ceramics with high thermal conductivity by gas pressure sintering

    OpenAIRE

    Zhu, Xinwen; Zhou, You; Hirao, Kiyoshi; Ishigaki, Takamasa; Sakka, Yoshio

    2010-01-01

    Yb2O3 is an efficient sintering additive for enhancing not only thermal conductivity but also the high-temperature mechanical properties of Si3N4 ceramics. Here we report the fabrication of dense Si3N4 ceramics with high thermal conductivity by the gas pressure sintering of α-Si3N4 powder compacts, using only Yb2O3 as an additive, at 1900 °C under a nitrogen pressure of 1 MPa. The effects of Yb2O3 content, sample packing condition and sintering time on the densification, microstructure and th...

  5. Effect of sintering temperature on structural and electrical properties of gadolinium doped ceria (Ce0.9Gd0.1O1.95)

    DEFF Research Database (Denmark)

    Jadhav, L. D.; Pawar, S. H.; Chourashiya, M. G.

    2007-01-01

    Gadolinium doped ceria oxide is one of the promising materials as an electrolyte for IT-SOFCs. Ce0.9Gd0.1O1.95 (GDC10) powder was prepared by solid state reaction and sintered at 1473 K, 1573 K, 1673 K and 1773 K All samples were studied using X-ray diffraction, scanning electron micrograph and d.......c. conductivity measurement. The crystallinity and surface morphology of the samples improved with sintering temperature. Further, the electrical conductivity measurement indicated that the conduction mechanism is mainly ionic. The conductivity of samples sintered at 1673 K and 1773 K at 800°C are of the order...

  6. High-level radioactive waste fixation in sintered vitreous matrix

    International Nuclear Information System (INIS)

    Russo, D.O.; Messi de Bernasconi, N.; Audero, M.A.

    1987-01-01

    The safe storage of high-level wastes from fuel elements reprocessing includes, as a first step, the fixation of the same in materials having a good resistance to the leaching in aqueous medium, such as borosilicate glass. As an alternative to the usual method of the molten glasses, a procedure for the sintering of a powdered glass and waste mixture at lower temperatures (600-700 deg C) has been developed, which minimizes the volatilization of active compounds during the process. Two glasses matrices of different composition and characteristics were used, to which the simulated wastes were added in the ratio of a 10% in weight of oxides. Two sintering techniques were employed 1: cold pressing and further sintering; 2: hot pressing and sintering under pressure. The densities were measured, the microstructure of the samples was analyzed and leaching essays were made in distilled water. The pellet's microstructure was observed by means of optical microscopy, by reflection in polished samples and by transparency in thin slices. The presence of crystalline compounds was analyzed by means of x rays and electron microprobe. The results have shown the convenience to continue with hot pressing essays, because a denser product with a higher resistance to the leaching is thus obtained. (M.E.L.) [es

  7. Profile of yttrium segregation in BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} as function of sintering temperature; Perfil da segregacao do itrio em BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} em funcao da temperatura de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Hosken, C.M.; Souza, D.P.F. de, E-mail: camila.hosken@gmail.co [Universidade Federal de Sao Carlos (LAPCEC/UFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais. Lab. de Preparacao e Caracterizacao Eletrica em Ceramicas

    2010-07-01

    Researches on solid oxide fuel cells indicate barium cerate perovskite as a very attractive material for using as electrolyte due to its high protonic conductivity. The objective of this work is investigate the yttrium segregation during sintering of BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} doped with Zn O as a sintering aid. The powders were prepared by citrate process. Powders were isostatic pressed into pellets and sintered in air at 1200, 1275, 1325 and 1400 deg C. The samples were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy. Secondary phase containing Yttrium and Cerium was detected as sintering temperature increased. Increase of the lattice parameter and activation energy for electrical conductivity were also detected on samples sintered at 1400 deg C. (author)

  8. Microstructure and Magnetic Properties of NdFeB Sintered Magnets Diffusion-Treated with Cu/Al Mixed Dyco Alloy-Powder

    Directory of Open Access Journals (Sweden)

    Lee M.-W.

    2017-06-01

    Full Text Available We investigated the microstructural and magnetic property changes of DyCo, Cu + DyCo, and Al + DyCo diffusion-treated NdFeB sintered magnets. The coercivity of all diffusion treated magnet was increased at 880ºC of 1st post annealing(PA, by 6.1 kOe in Cu and 7.0 kOe in Al mixed DyCo coated magnets, whereas this increment was found to be relatively low (3.9 kOe in the magnet coated with DyCo only. The diffusivity and diffusion depth of Dy were increased in those magnets which were treated with Cu or Al mixed DyCo, mainly due to comparatively easy diffusion path provided by Cu and Al because of their solubility with Ndrich grain boundary phase. The formation of Cu/Al-rich grain boundary phase might have enhanced the diffusivity of Dy-atoms. Moreover, relatively a large number of Dy atoms reached into the magnet and mostly segregated at the interface of Nd2Fe14B and grain boundary phases covering Nd2Fe14B grains so that the core-shell type structures were developed. The formation of highly anisotropic (Nd, Dy2Fe14B phase layer, which acted as the shell in the core-shell type structure so as to prevent the reverse domain movement, was the cause of enhancing the coercivity of diffusion treated NdFeB magnets. Segregation of cobalt in Nd-rich TJP followed by the formation of Co-rich phase was beneficial for the coercivity enhancement, resulting in the stabilization of the metastable c-Nd2O3 phase.

  9. Effect of Alloying Type and Lean Sintering Atmosphere on the Performance of PM Components

    Science.gov (United States)

    Sundaram, M. Vattur; Shvab, R.; Millot, S.; Hryha, E.; Nyborg, L.

    2017-12-01

    In order to be cost effective and to meet increasing performance demands, powder metallurgy steel components require continuous improvement in terms of materials and process development. This study demonstrates the feasibility of manufacturing structural components using two different alloys systems, i.e. lean Cr-prealloyed and diffusion bonded water atomised powders with different processing conditions. The components were sintered at two different temperatures, i.e. 1120 and 1250 °C for 30 minutes in three different atmospheres: vacuum, N2- 10%H2 atmosphere as well as lean N2-5%H2-0.5%CO-(0.1-0.4)%CH4 sintering atmosphere. Components after sintering were further processed by either low pressure carburizing, sinterhardening or case hardening. All trials were performed in the industrial furnaces to simulate the actual production of the components. Microstructure, fractography, apparent and micro hardness analyses were performed close to the surface and in the middle of the sample to characterize the degree of sintering (temperature and atmosphere) and the effect of heat treatment. In all cases, components possess mostly martensitic microstructure with a few bainitic regions. The fracture surface shows well developed sinter necks. Inter- and trans-granular ductile and cleavage fracture modes are dominant and their fraction is determined by the alloy and processing route.

  10. Automated analysis of carbon in powdered geological and environmental samples by Raman spectroscopy.

    Science.gov (United States)

    Sparkes, Robert; Hovius, Niels; Galy, Albert; Kumar, R Vasant; Liu, James T

    2013-07-01

    Raman spectroscopy can be used to assess the structure of naturally occurring carbonaceous materials (CM), which exist in a wide range of crystal structures. The sources of these geological and environmental materials include rocks, soils, river sediments, and marine sediment cores, all of which can contain carbonaceous material ranging from highly crystalline graphite to amorphous-like organic compounds. In order to fully characterize a geological sample and its intrinsic heterogeneity, several spectra must be collected and analyzed in a precise and repeatable manner. Here, we describe a suitable processing and analysis technique. We show that short-period ball-mill grinding does not introduce structural changes to semi-graphitized material and allows for easy collection of Raman spectra from the resulting powder. Two automated peak-fitting procedures are defined that allow for rapid processing of large datasets. For very disordered CM, Lorentzian profiles are fitted to five characteristic peaks, for highly graphitized material, three Voigt profiles are fitted. Peak area ratios and peak width measurements are used to classify each spectrum and allow easy comparison between samples. By applying this technique to samples collected in Taiwan after Typhoon Morakot, sources of carbon to offshore sediments have been identified. Carbon eroded from different areas of Taiwan can be seen mixed and deposited in the offshore flood sediments, and both graphite and amorphous-like carbon have been recycled from terrestrial to marine deposits. The practicality of this application illustrates the potential for this technique to be deployed to sediment-sourcing problems in a wide range of geological settings.

  11. Effect of sintering temperature on microstructure and compressive strength of B4C-AlSi eutectic alloy

    International Nuclear Information System (INIS)

    Liu Jinyun; Zha Wusheng; Liu Gaihua; Lan Jun; Feng Quanhe; Zou Congpei

    2008-01-01

    The block neutron absorber of B 4 C based on Al-Si eutectic alloy has been prepared by powder-metallurgy method. The effects of sinter temperature on microstructure, compressive strength, and ductility of sintered billets have been investigated. It has been shown that the sintering temperature decides sensitively the compressive strength and ductility of sintered billets. Sintered under 550, 555, 560, and 565 degree C, the billet shows different states, such as sub-sintered, best-sintered, over-sintered, and molten. Sintered under 550 degree C, the powder have not been metallurgically combined with each other. Beyond 560 degree C, the billets are molten. The 555 degree C is the best sintering temperature, under which the powder have been partly melted and the metallurgical combination has been occurred, then the billets have a better ductility. (authors)

  12. The observation of resistivity change on the ultrasonic treated Fe-Cr ODS sinter alloy under magnetic field influence

    Science.gov (United States)

    Silalahi, Marzuki; Purwanto, Setyo; Mujamilah; Dimyati, Arbi

    2018-03-01

    About the observation of resistivity change on the ultrasonic treated Fe-Cr ODS sinter alloy under magnetic field influence. This paper reported about the observation of the resistivity change in the ultrasonic pre-treated Fe-Cr ODS sinter alloy under the influence of magnetic field at the Center for Science and Technology of Advanced Material, Nuclear Energy Agency of Indonesia. Fe-Cr ODS alloy were sinthesized by vacuum sintering of Fe- and Cr-powder dispersed Y2O3. However, before sintering the powder mixture was subjected to the irradiation process by ultrasonic for 50 hours at 20 kHz and then isostatic pressed up to 50.91 MPa to form a coin of 10 mm in diameter. LCR meassurement revealed the decreasing of resistivity about 3 times by increasing of applied magnetic field from 0 to 70 mT. In addition, VSM meassurement was performed on both as powder material and as sintered sample. The results showed increasing the magnetization with increasing magnetic field and the curve exhibits almost exact symmetry S-form with small hysterese indicating fast changing magnetization and demagnetization capability without energy loss. This opens strong speculations about the existence of magnetoresistant property of the material which is important for many application in field of sensors or electro magnetic valves.

  13. Preparation of superconducting powders by freeze-drying

    International Nuclear Information System (INIS)

    Johnson, S.M.; Gusman, M.I.; Rowcliffe, D.J.; Geballe, T.H.; Sun, J.Z.

    1987-01-01

    A method of preparing superconducting powders by freeze-drying is described. Powders produced by this method are homogeneous, have high purities, and are very reactive. Materials sintered from these powders have densities up to 89% of the theoretical density, and exhibit very sharp resistivity drops and large Meissner effects. The microstructure of the materials is very sensitive to the sintering temperature

  14. Comparative Study of Structural, Electrical, and Magnetic Behaviour of Ni-Cu-Zn Nanoferrites Sintered by Microwave and Conventional Techniques

    Directory of Open Access Journals (Sweden)

    Biju Thangjam

    2017-01-01

    Full Text Available Ni0.8-xCuxZn0.2Fe2O4 spinel type ferrite nanoparticles have been synthesized by citrate precursor method. These nanoparticles were then given heat treatment using microwave and conventional sintering techniques. Various characterizations using X-ray powder diffraction (XRD, scanning electron microscope (SEM, LCR meter, and B-H loop tracer were carried out on the sintered specimens. The XRD spectra of these ferrites confirmed the formation of spinel structure. The average crystallite size calculated using Scherrer’s formula was found to be in the nanometer range, its value varying from 33 nm to 39 nm. Microwave sintered samples exhibited superior electrical and magnetic behaviour over their conventionally sintered counterparts. Feasibility of low temperature synthesis and promising properties will render these ferrites suitable for multilayer chip inductor applications.

  15. Characterization of sintered samples of La/Sr/Cu/O by X-ray diffraction, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS)

    International Nuclear Information System (INIS)

    Gonzalez, C.O. de; Polla, Griselda; Manghi, Estela

    1987-01-01

    Samples of La/Sr/Cu/O were sinterized by solid state reaction starting from a nominal composition of La 1 .8, Sr 0 .2, CuO 4 . They presented superconductive properties with T c = 40.9 K (onset) and δ T c = 17 K. Two phases were observed by X-ray diffraction and the more abundant was the tetragonal phase. The mean grain size was 1-5 μm. The X-ray photoelectron spectroscopy measurements were carried out using Mg kα (1486.6 eV) as incident radiation. Sample temperature was varied between -180 deg C and 420 deg C, approximately. The temperature variation produces a change in the atomic concentration of the surface components. Deconvolutions of the O 1s peaks show three components with binding energies (B.E.). The decomposition of Cu 2p 3 /2 peaks presents two components corresponding to Cu + and Cu 2+ . (Author) [es

  16. Enhanced Sintering of TiNi Shape Memory Foams under Mg Vapor Atmosphere

    Science.gov (United States)

    Aydoğmuş, Tarik; Bor, Şakir

    2012-12-01

    TiNi alloy foams are promising candidates for biomaterials to be used as artificial orthopedic implant materials for bone replacement applications in biomedical sector. However, certain problems exist in their processing routes, such as formation of unwanted secondary intermetallic phases leading to brittleness and deterioration of shape memory and superelasticity characteristics; and the contamination during processing resulting in oxides and carbonitrides which affect mechanical properties negatively. Moreover, the eutectic reaction present in Ti-Ni binary system at 1391 K (1118 °C) prevents employment of higher sintering temperatures (and higher mechanical properties) even when equiatomic prealloyed powders are used because of Ni enrichment of TiNi matrix as a result of oxidation. It is essential to prevent oxidation of TiNi powders during processing for high-temperature (>1391 K i.e., 1118 °C) sintering practices. In the current study, magnesium powders were used as space holder material to produce TiNi foams with the porosities in the range of 40 to 65 pct. It has been found that magnesium prevents secondary phase formation and contamination. It also prevents liquid phase formation while enabling employment of higher sintering temperatures by two-step sintering processing: holding the sample at 1373 K (1100 °C) for 30 minutes, and subsequently sintering at temperatures higher than the eutectic temperature, 1391 K (1118 °C). By this procedure, magnesium may allow sintering up to temperatures close to the melting point of TiNi. TiNi foams produced with porosities in the range of 40 to 55 pct were found to be acceptable as implant materials in the light of their favorable mechanical properties.

  17. Sintering and electrical properties of Ce{sub 1−x}Bi{sub x}O{sub 2−δ} solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Prekajski, M., E-mail: prekajski@vinca.rs [Vinca Institute of Nuclear Science, Material Science Laboratory, University of Belgrade, PO Box 522, Belgrade (Serbia); Stojmenović, M. [Vinca Institute of Nuclear Science, Material Science Laboratory, University of Belgrade, PO Box 522, Belgrade (Serbia); Radojković, A.; Branković, G. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1a, 11030 Belgrade (Serbia); Oraon, H.; Subasri, R. [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500 005 (India); Matović, B. [Vinca Institute of Nuclear Science, Material Science Laboratory, University of Belgrade, PO Box 522, Belgrade (Serbia)

    2014-12-25

    Highlights: • Ce{sub 1−x}Bi{sub x}O{sub 2−δ} (x = 0.1–0.5) powders were conventional and microwave sintered. • Conventional sintering requires much higher temperatures for densification. • The highest ionic conductivity was obtained for the Ce{sub 0.80}Bi{sub 0.20}O{sub 2−δ} sample. - Abstract: Solid solution Ce{sub 1−x}Bi{sub x}O{sub 2−δ} nanopowders with the composition of x = 0.1–0.5 were synthesized by using Self Propagating Room Temperature procedure (SPRT). The results obtained by XRPD show that synthesized samples were single-phase solid solution at room temperature. Powders were densified by using Conventional (CS) and Microwave (MS) Sintering techniques at different temperatures, in an air atmosphere for 1 h. Scanning electron microscopy (SEM) and complex impedance method measurements were carried out on sintered samples. Maximum achieved density was for sample with Ce{sub 0.80}Bi{sub 0.20}O{sub 2−δ} composition for both applied sintering techniques. The highest conductivity was obtained for the ceramic composition Ce{sub 0.80}Bi{sub 0.20}O{sub 2−δ} sintered by microwave technique at 700 °C.

  18. 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.

  19. Characterization of Uranium Oxide and Ln-bearing Uranium Oxide during Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Henderson, J.B. [Netzsch Instruments, Inc., Estes Park, CO (United States); Byler, D.D.; Stanek, C.R.; Dunwoody, J.T.; Luther, E.P.; Volz, H.M.; Vogel, S.C.; McClellan, K.J. [Los Alamos National Laboratory, Los Alamos, NM (United States)

    2009-06-15

    In support of the transmutation fuel development as part of the effort to close the fuel cycle, research has been carried out to gain an in-depth understanding of the evolution of material properties during sintering as well as the properties of post-sintered oxide fuels. Of course the effects of material and test parameters such as starting powder O/M, green density, particle size distribution, heating rate and atmosphere on the densification of oxide and mixed oxide fuels have been widely studied, sometimes with conflicting results. However, the evolution of thermophysical properties such as specific heat and thermal conductivity during densification is not well known. Further, the effects of lanthanides on densification as well as on other thermodynamic and transport properties during sintering have not been widely studied. The purpose of this work was to characterize the effects of key material and test parameters on the thermophysical properties during sintering (both surface and volume transport) and on post-sintered UO{sub 2+x} and UO{sub 2+x} + lanthanide samples. Mixtures of UO{sub 2+x} and lanthanide component powder as well as pre-synthesized solid solutions have been studied. In addition to the standard bulk characterization methods such as dilatometry (thermal expansion / densification), laser flash (thermal diffusivity / thermal conductivity), differential scanning calorimetry (specific heat and transformation energetics) and thermogravimetric analysis (mass change), we have employed ancillary techniques such as neutron scattering, laboratory X-ray diffraction and scanning electron microscopy to help evaluate phases, lattice parameters and microstructure during sintering. The experimental data from the methods mentioned above have been cross-correlated to help explain the physics which govern the sintering process as well as those which govern the development of the thermophysical properties of these materials. The results of this work will be

  20. New materials through a variety of sintering methods

    Science.gov (United States)

    Jaworska, L.; Cyboroń, J.; Cygan, S.; Laszkiewicz-Łukasik, J.; Podsiadło, M.; Novak, P.; Holovenko, Y.

    2018-03-01

    New sintering techniques make it possible to obtain materials with special properties that are impossible to obtain by conventional sintering techniques. This issue is especially important for ceramic materials for application under extreme conditions. Following the tendency to limit critical materials in manufacturing processes, the use of W, Si, B, Co, Cr should be limited, also. One of the cheapest and widely available materials is aluminum oxide, which shows differences in phase composition, grain size, hardness, strain and fracture toughness of the same type of powder, sintered via various methods. In this paper the alumina was sintered using the conventional free sintering process, microwave sintering, Spark Plasma Sintering (SPS), high pressure-high temperature method (HP-HT) and High Pressure Spark Plasma Sintering (HP SPS). Phase composition analysis, by X-ray diffraction of the alumina materials sintered using various methods, was carried out. For the conventional sintering method, compacts are composed of α-Al2O3 and θ-Al2O3. For compacts sintered using SPS, microwave and HP-HT methods, χ-Al2O3 and γ-Al2O3 phases were additionally present. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. On the basis of images from scanning electron microscope quantitative analysis was performed to determine the degree of grain growth of alumina after sintering.

  1. Sintering equation: determination of its coefficients by experiments - using multiple regression

    International Nuclear Information System (INIS)

    Windelberg, D.

    1999-01-01

    Sintering is a method for volume-compression (or volume-contraction) of powdered or grained material applying high temperature (less than the melting point of the material). Maekipirtti tried to find an equation which describes the process of sintering by its main parameters sintering time, sintering temperature and volume contracting. Such equation is called a sintering equation. It also contains some coefficients which characterise the behaviour of the material during the process of sintering. These coefficients have to be determined by experiments. Here we show that some linear regressions will produce wrong coefficients, but multiple regression results in an useful sintering equation. (orig.)

  2. Production of pure sintered alumina

    International Nuclear Information System (INIS)

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

    1982-01-01

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

  3. Study on selective laser sintering of glass fiber reinforced polystyrene

    Science.gov (United States)

    Yang, Laixia; Wang, Bo; Zhou, Wenming

    2017-12-01

    In order to improve the bending strength of Polystyrene (PS) sintered parts by selective laser sintering, Polystyrene/glass fiber (PS/GF) composite powders were prepared by mechanical mixing method. The size distribution of PS/GF composite powders was characterized by laser particle size analyzer. The optimum ratio of GF was determined by proportioning sintering experiments. The influence of process parameters on the bending strength of PS and PS/GF sintered parts was studied by orthogonal test. The result indicates that the particle size of PS/GF composite powder is mainly distributed in 24.88 μm~139.8 μm. When the content of GF is 10%, it has better strengthen effect. Finally, the article used the optimum parameter of the two materials to sinter prototype, it is found that the PS/GF prototype has the advantages of good accuracy and high strength.

  4. Comparison of SPS Processing Behavior between As Atomized and Cryomilled Aluminum Alloy 5083 Powder

    Science.gov (United States)

    Kellogg, Frank; McWilliams, Brandon; Sietins, Jennifer; Giri, Anit; Cho, Kyu

    2017-11-01

    Aluminum 5083 powder, both as atomized and cryomilled, was consolidated via spark plasma sintering (SPS). This study quantified and compared the effects of heating an aluminum alloy powder directly through Joule heating vs indirectly through thermal conduction from the die during SPS processing. When consolidated under the same processing conditions, the cryomilled powders showed faster heating rates and densification than the as atomized powder. It was also possible to process the cryomilled powder in a non-conductive die but not the as atomized powder. This could be ascribed to an improvement in electrical conductivity of the powder due to the break up and redistribution of surface oxides after cryomilling. The changes in behavior as a result of cryomilling and/or changing die material led to samples with different fracture morphologies and increased hardness values.

  5. Characterization investigations during mechanical alloying and sintering of Ni-W solid solution alloys dispersed with WC and Y{sub 2}O{sub 3} particles

    Energy Technology Data Exchange (ETDEWEB)

    Genc, Aziz, E-mail: agenc@itu.edu.t [Particulate Materials Laboratories, Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak, 34469 Istanbul (Turkey); Luetfi Ovecoglu, M. [Particulate Materials Laboratories, Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak, 34469 Istanbul (Turkey)

    2010-10-15

    Research highlights: {yields} Characterization investigations on the Ni-W solid solution alloys fabricated via mechanical alloying and the evolution of the properties of the powders with increasing MA durations. {yields} Reinforcement of the selected Ni-W powders with WC and Y{sub 2}O{sub 3} particles and further MA together for 12 h. {yields} There is no reported literature on the development and characterization of Ni-W solid solution alloys matrix composites fabricated via MA. {yields} Sintering of the developed composites and the characterization investigations of the sintered samples. {yields} Identification of new 'pomegranate-like' structures in the bulk of the samples. - Abstract: Blended elemental Ni-30 wt.% W powders were mechanically alloyed (MA'd) for 1 h, 3 h, 6 h, 12 h, 24 h, 36 h and 48 h in a Spex mixer/mill at room temperature in order to investigate the effects of MA duration on the solubility of W in Ni and the grain size, hardness and particle size. Microstructural and phase characterizations of the MA'd powders were carried out using X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). On the basis of achieved saturation on the solid solubility, hardness and particle size, the Ni-30 wt.% W powders MA'd for 48 h were chosen as the matrix which was reinforced with different amounts of WC and/or with 1 wt.% Y{sub 2}O{sub 3} particles. The reinforced powders were further MA'd for 12 h. The MA'd powders were sintered at 1300 {sup o}C for 1 h under Ar and H{sub 2} gas flowing conditions. Microstructural characterizations of the sintered samples were conducted via XRD and SEM. Sintered densities were measured by using the Archimedes' method. Vickers microhardness tests were performed on both MA'd powders and the sintered samples. Sliding wear experiments were done in order to investigate wear behaviors of the sintered samples.

  6. Formation and properties of two-phase bulk metallic glasses by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Xie Guoqiang, E-mail: xiegq@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, Akihisa [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2011-06-15

    Research highlights: > Two-phase bulk metallic glasses with high strength and good soft magnetic properties as well as satisfying large-size requirements were produced by spark plasma sintering. > Effects of sintering temperature on thermal stability, microstructure, mechanical and magnetic properties were investigated. > Densified samples were obtained by the spark plasma sintering at above 773 K. - Abstract: Using a mixture of the gas-atomized Ni{sub 52.5}Nb{sub 10}Zr{sub 15}Ti{sub 15}Pt{sub 7.5} and Fe{sub 73}Si{sub 7}B{sub 17}Nb{sub 3} glassy alloy powders, we produced the two-phase bulk metallic glass (BMG) with high strength and good soft magnetic properties as well as satisfying large-size requirements by the spark plasma sintering (SPS) process. Two kinds of glassy particulates were homogeneously dispersed each other. With an increase in sintering temperature, density of the produced samples increased, and densified samples were obtained by the SPS process at above 773 K. Good bonding state among the Ni- and Fe-based glassy particulates was achieved.

  7. Defects and microstructure of a hydrothermally derived (Bi1/2K1/2TiO3 powder

    Directory of Open Access Journals (Sweden)

    Manabu Hagiwara

    2017-03-01

    Full Text Available Fine powders of bismuth potassium titanate (Bi1/2K1/2TiO3 (BKT synthesized by hydrothermal reactions have been reported to have good sinterability and high chemical stability against long-time sintering. In this study, detailed chemical and structural characterizations were performed on a hydrothermal BKT powder sample to identify the origin of such properties. The results of X-ray diffraction, infrared transmittance, and diffuse reflectance measurements revealed that the hydrothermal BKT particle contained high concentrations of lattice hydroxyl group and Bi vacancy, whereas the observation by transmission electron microscope showed that its surface was covered with numerous Bi2O3 nanoparticles to achieve the overall stoichiometric cation ratio of BKT. We found that the unique composite nanostructure of the hydrothermal BKT powder led to a large suppression of Bi evaporation during high-temperature sintering, thereby contributing to its superior chemical stability.

  8. A novel specimen-preparing method using epoxy resin as binding material for LIBS analysis of powder samples.

    Science.gov (United States)

    Shi, Linli; Lin, Qingyu; Duan, Yixiang

    2015-11-01

    In view of the inevitable preprocessing of powder samples for LIBS detection, epoxy resin glue was investigated for the first time as a binder of powder samples due to its superior property of improved performance in laser induced breakdown spectroscopy (LIBS) technique as a quantitative analytical tool. For comparative studies of the epoxy resin and traditional polyethylene (PE) pellets in soil, sample detection, the signal intensities of Fe (I) at 404.58 nm, Ca (I) at 443.57 nm, and Cr (I) at 453.52 nm, were studied and subsequently, the calibration curves for these elements were constructed using the standard samples with variable concentrations. The signal intensities of epoxy resin samples were, on average, about 2 times greater than those obtained with the traditional PE pellet samples. Meanwhile, the resin samples showed better R square values of 0.981, 0.985 and 0.979 for curves of Fe (I) 404.58 nm, Ca (I) 443.57 nm, and Cr (I) 453.52 nm, compared to the 0.974, 0.950 and 0.934, of the PE pellet samples. Furthermore, the former represented lower limits of detection (LOD) for Fe, Ca and Cr. These experimental results indicated that this proposed novel method based on epoxy resin can attach samples of properties of high homogeneity, cohesiveness, smoothness and hardness, which are conducive to system stability, testing accuracy and signal enhancement. This method can make LIBS more practical in powder sample analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Evaluation of press-and-sinter parameters for tantalum pentoxide by the diametral compression test

    International Nuclear Information System (INIS)

    Livne, Z.; Fields, R.J.; Agulyansky, A.

    1997-01-01

    Submicron Ta 2 O 5 powder was consolidated by cold pressing using pressures between 24 MPa and 240 MPa followed by sintering at temperatures in the range 1300 degrees C to 1500 degrees C. The resulting disks were fractured in diametral compression tests (DCT) to determine the tensile strength. The strength, mode of fracture, and fracture surface were subsequently used to identify potential processing routes for high density, fine grained Ta 2 O 5 for the use as sputtering targets. Besides the conventional single or triple cleft fracture, two other modes of failure were observed in the diametrical compression test: delamination due to stratification flaws introduced by high pressure pre-pressing before sintering, and fragmentation caused by slow microcrack growth in the presence of phase transformation stresses arising in samples sintered above the transformation temperature of 1360 degrees C

  10. Sintering behavior, microstructure and mechanical properties of vacuum sintered SiC/spinel nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guoqiang, E-mail: lguoqi1@lsu.edu [Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803 (United States); Department of Mechanical Engineering, Southern University, Baton Rouge, LA 70813 (United States); Tavangarian, Fariborz [Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803 (United States)

    2014-12-05

    Highlights: • Bulk SiC/spinel nanocomposite was synthesized from talc, aluminum and graphite powders. • Sintering behavior and mechanical properties of SiC/spinel nanocomposite was studied. • The obtained bulk SiC/spinel nanocomposite had a mean crystallite size of about 34 nm. - Abstract: A mixture of SiC and spinel (MgAl{sub 2}O{sub 4}) nanopowder was prepared through the ball milling of talc, aluminum and graphite powder. The powder was uniaxially pressed into the form of pellets and the prepared specimens were annealed at various temperatures for different holding times. The prepared samples were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), nanoindentation test, cold crushing strength (CCS) test and Archimedes principle test. The obtained results showed that the hardness, CCS and bulk density did not follow the same trend at different temperatures due to the interaction among various parameters. The detailed investigation of microstructure, phase changes and experimental conditions revealed the mechanisms behind these behaviors. The best sample obtained after annealing at 1200 °C for 1 h in vacuum had the mean hardness of 1.6 GPa and the mean CCS of 118 MPa.

  11. Granulation of fine powder

    Science.gov (United States)

    Chen, Ching-Fong

    2016-08-09

    A mixture of fine powder including thorium oxide was converted to granulated powder by forming a first-green-body and heat treating the first-green-body at a high temperature to strengthen the first-green-body followed by granulation by crushing or milling the heat-treated first-green-body. The granulated powder was achieved by screening through a combination of sieves to achieve the desired granule size distribution. The granulated powder relies on the thermal bonding to maintain its shape and structure. The granulated powder contains no organic binder and can be stored in a radioactive or other extreme environment. The granulated powder was pressed and sintered to form a dense compact with a higher density and more uniform pore size distribution.

  12. Structure and hardness of a hard metal alloy prepared with a WC powder synthesized at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Costa, F.A. da [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)], E-mail: francineac@yahoo.com; Medeiros, F.F.P. de [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Silva, A.G.P. da [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Gomes, U.U. [Departamento de Fisica Teorica e Experimental, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Filgueira, M. [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Souza, C.P. de [Laboratorio de Termodinamica e Reatores, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)

    2008-06-25

    The structure and hardness of a WC-10 wt% Co alloy prepared with an experimental WC powder are compared with those of another alloy of the same composition produced under the same conditions and prepared with a commercial WC powder. The experimental WC powder was synthesized by a gas-solid reaction between APT and methane at low temperature and the commercial WC powder was conventionally produced by a solid-solid reaction between tungsten and carbon black. WC-10 wt% Co alloys with the two powders were prepared under the same conditions of milling and sintering. The structure of the sample prepared with the experimental WC powder is homogeneous and coarse grained. The structure of the sample prepared with the commercial powder is heterogeneous. Furthermore the size and shape of the WC grains are significantly different.

  13. Determination of flavor enhancers in milk powder by one-step sample preparation and two-dimensional liquid chromatography.

    Science.gov (United States)

    Ma, Jing; Zhang, Bing; Wang, Yunan; Hou, Xiaofang; He, Langchong

    2014-04-01

    Maltol, ethyl maltol, vanillin, and ethyl vanillin are important food additives as flavor enhancers. To quantify the four additives in milk powder, a novel 2D liquid chromatographic (2DLC) method was developed in this article. In such a 2DLC system, the target fractions eluted from the first dimensional column (C4) are stored onto the trapping column (C8) for subsequent analysis; after that, they were switched into the second dimensional column (C18) by a two-position six-port switching valve. A one-step sample preparation method was used prior to 2DLC chromatographic analysis, which was easy and convenient. After optimization of all experimental parameters, the new method was validated in terms of linearity, LODs, and LOQs, intra- and interday precision, and accuracy. A conventional single-dimensional liquid chromatographic method was also proposed in this work for comparison. In order to evaluate the applicability of the new 2DLC method, five brands of commercial milk powder samples (n = 8) were analyzed. Vanillin and ethyl vanillin were detected in two samples, respectively. It is showed that the 2DLC method is effective in quality control programs of milk powder products. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Sintering and densification; new techniques: sinter forging

    International Nuclear Information System (INIS)

    Winnubst, A.J.A.

    1998-01-01

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

  15. Nanocrystalline NdFeB magnet prepared by mechanically activated disproportionation and desorption-recombination in-situ sintering

    International Nuclear Information System (INIS)

    Xiaoya, Liu; Yuping, Li; Lianxi, Hu

    2013-01-01

    The process of mechanically activated disproportionation and desorption-recombination in-situ sintering was proposed to synthesize highly densified nanocrystalline NdFeB magnet, and its validity was demonstrated by experimental investigation with the use of a Nd 16 Fe 76 B 8 (atomic ratio) alloy. Firstly, the as-cast alloy was disproportionated by mechanical milling in hydrogen, with the starting micron-sized Nd 2 Fe 14 B phase decomposed into an intimate mixture of nano-structured NdH 2.7 , Fe 2 B and α-Fe phases. The as-disproportionated alloy powders were compacted by cold pressing and then subjected to desorption-recombination in-situ sintering. The microstructure of both the as-disproportionated and the subsequently sintered samples was characterized by X-ray diffraction and electron transmission microscopy, respectively. The magnetic properties of the sintered samples were measured by using vibrating sample magnetometer. The results showed that, by vacuum sintering, not only was the powder compact consolidated, but also the as-disproportionated microstucture transformed into nanocrystalline Nd 2 Fe 14 B phase via the well-known desorption-recombination reaction, thus giving rise to nanocrystalline NdFeB magnet. In the present study, the optimal sintering parameters were found to be 780 °C×30 min. In this case, the coercivity, the remanence, and maximum energy product of the magnet sample achieved 0.8 T, 635.3 kA/m, and 106.3 kJ/m 3 , respectively. - Highlights: ► Nano-structured disproportionated NdFeB alloy powders by mechanical milling in hydrogen. ► Highly densified green magnet compact by cold pressing of as-disproportionated NdFeB alloy powders. ► Nanocrystalline NdFeB magnets by desorption-recombination in-situ sintering under vacuum. ► Magnetic properties significantly improved by relative density enhancement and nanocrystallization of Nd 2 Fe 14 B phase. ► The effects of sintering parameters on magnetic properties and the underlying

  16. Nanocrystalline NdFeB magnet prepared by mechanically activated disproportionation and desorption-recombination in-situ sintering

    Energy Technology Data Exchange (ETDEWEB)

    Xiaoya, Liu; Yuping, Li [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Lianxi, Hu, E-mail: hulx@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2013-03-15

    The process of mechanically activated disproportionation and desorption-recombination in-situ sintering was proposed to synthesize highly densified nanocrystalline NdFeB magnet, and its validity was demonstrated by experimental investigation with the use of a Nd{sub 16}Fe{sub 76}B{sub 8} (atomic ratio) alloy. Firstly, the as-cast alloy was disproportionated by mechanical milling in hydrogen, with the starting micron-sized Nd{sub 2}Fe{sub 14}B phase decomposed into an intimate mixture of nano-structured NdH{sub 2.7}, Fe{sub 2}B and {alpha}-Fe phases. The as-disproportionated alloy powders were compacted by cold pressing and then subjected to desorption-recombination in-situ sintering. The microstructure of both the as-disproportionated and the subsequently sintered samples was characterized by X-ray diffraction and electron transmission microscopy, respectively. The magnetic properties of the sintered samples were measured by using vibrating sample magnetometer. The results showed that, by vacuum sintering, not only was the powder compact consolidated, but also the as-disproportionated microstucture transformed into nanocrystalline Nd{sub 2}Fe{sub 14}B phase via the well-known desorption-recombination reaction, thus giving rise to nanocrystalline NdFeB magnet. In the present study, the optimal sintering parameters were found to be 780 Degree-Sign C Multiplication-Sign 30 min. In this case, the coercivity, the remanence, and maximum energy product of the magnet sample achieved 0.8 T, 635.3 kA/m, and 106.3 kJ/m{sup 3}, respectively. - Highlights: Black-Right-Pointing-Pointer Nano-structured disproportionated NdFeB alloy powders by mechanical milling in hydrogen. Black-Right-Pointing-Pointer Highly densified green magnet compact by cold pressing of as-disproportionated NdFeB alloy powders. Black-Right-Pointing-Pointer Nanocrystalline NdFeB magnets by desorption-recombination in-situ sintering under vacuum. Black-Right-Pointing-Pointer Magnetic properties significantly

  17. Fabrication of Mg2Si thermoelectric materials by mechanical alloying and spark-plasma sintering process.

    Science.gov (United States)

    Lee, Chung-Hyo; Lee, Seong-Hee; Chun, Sung-Yong; Lee, Sang-Jin

    2006-11-01

    A mixture of pure Mg and Si powders with an atomic ratio 2:1 has been subjected to mechanical alloying (MA) at room temperature to prepare the Mg2Si thermoelectric material. Mg2Si intermetallic compound with a grain size of 50 nm can be obtained by MA of Mg66.7Si33.3 powders for 60 hours and subsequently annealed at 620 degrees C. Consolidation of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800-900 degrees C under 50 MPa. The shrinkage of consolidated samples during SPS was significant at about 250 degrees and 620 degrees C. X-ray diffraction data shows that the SPS compact from 60 h MA powders consolidated up to 800 degrees C consists of only nanocrystalline Mg2Si compound with a grain size of 100 nm.

  18. Method of manufacturing sintered nuclear fuel

    International Nuclear Information System (INIS)

    Watarumi, Kazutoshi.

    1984-01-01

    Purpose: To obtain composite pellets with an improved strength. Method: A core mainly composed of fuel materials is previously prepared, embedded into the central portion of a pellet, silted therearound with cladding material, and then pressmolded and sintered. For instance, a rugby-ball like core body with the maximum outer diameter of 6 mm and the height of 6 mm is made by compressive molding with uranium dioxide powder, then coating material comprising the same powder incorporated with 0.1 % by weight of SiC fibers is filled around the core body, which is molded into a composite pellet by means of pressing and then sintered at 1600 0 C, to obtain a sintered pellet of 93.5 % theoretical density. As the result of the compression test for the pellet, it showed a strength greater by 15 % than that of the similar mono-layer pellet. (Kamimura, M.)

  19. Neutron powder diffraction of small-volume samples at high pressure using compact opposed-anvil cells and focused beam

    International Nuclear Information System (INIS)

    Okuchi, T; Sasaki, S; Ohno, Y; Abe, J; Osakabe, T; Hattori, T; Sano-Furukawa, A; Utsumi, W; Arima, H; Harjo, S; Ito, T; Aizawa, K; Komatsu, K; Kagi, H

    2012-01-01

    Neutron powder diffraction techniques of small-volume samples at high pressure using compact opposed-anvil cells were developed at J-PARC pulsed neutron source. For this purpose we apply a few types of super-hard materials as opposed anvils with culet diameters between 3 to 5 mm. Generated pressures with these anvils were up to 9 GPa for 2 to 4 mm 3 and up to 14 GPa for 0.7 mm 3 sample volumes, which not only depends on the anvil geometry and material but even more depends on the metallic gasket geometry and material. A representative anvil geometry with 4 mm in culet diameter, along with TiZr 'null alloy' metallic gasket containing varying sample volumes, were then applied to time-of-flight neutron powder diffraction experiments, where methane hydrate of 4 mm 3 volume and lead of 0.7 mm 3 volume were separately measured and their signal-to-background ratios were evaluated. A neutron-focusing optics was used to concentrate the neutron beam into these small-volume samples to increase the intensity of diffraction. Although spurious diffraction peaks from the anvils were prominent, more than seven diffraction peaks are clearly observed from both of the samples. In spite of the smaller sample capacity than previous standard high-pressure apparatus for neutron, it is concluded that the opposed-anvil cells will become alternative apparatuses for neutron scattering at strong pulsed neutron sources where sufficient neutron intensity was granted.

  20. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Administrator

    Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for conventional sintered (8–10 and 135–155 GPa) samples. Keywords. Microwave sintering; La-substituted SBTi ceramics; mechanical properties. 1. Introduction. In recent years, bismuth layer-structured ferroelectrics.

  1. Structure and strength of aluminum with sub-micrometer/micrometer grain size prepared by spark plasma sintering

    DEFF Research Database (Denmark)

    Le, G.M.; Godfrey, A.; Hansen, Niels

    2013-01-01

    A spark plasma sintering (SPS) technique has been applied to prepare fully dense Al samples from Al powder. By applying a sintering temperature of 600°C and a loading pressure of 50MPa, fully recrystallized samples of nearly 100% density with average grain sizes of 5.2μm, 1.3μm and 0.8μm have been...... successfully prepared using a sintering time of less than 30min and without the need for a nitrogen atmosphere. A similarity between the grain size and powder particle size is found, which suggests a potential application of the SPS technique to prepare samples with a variety of grain sizes by tailoring...... the initial powder particle size. The SPS samples show higher strength than Al samples with an identical grain size prepared using thermo-mechanical processing, and a better strength-ductility combination, with the 1.3μm grain size sample showing a yield strength (σ0.2%) of 140MPa and a uniform elongation...

  2. A study of Al-Mo powder processing as a possible way to corrosion resistent aluminum-alloys

    Directory of Open Access Journals (Sweden)

    Wilson Corrêa Rodrigues

    2009-06-01

    Full Text Available Elementary Al and Mo powder mixtures have been processed by high energy ball milling up to milling times of 100 hours. The shift of the pitting potential and the X ray analysis of green milled samples showed that part of the Mo has formed a supersaturated solid solution of Mo in Al. Elementary Mo powder, however, was still present after 100 hours of milling. Sintering led to the formation of the intermetallic Al12Mo phase.

  3. Role of Cu During Sintering of Fe0.96Cu0.04 Nanoparticles

    Science.gov (United States)

    Sivaprahasam, D.; Sriramamurthy, A. M.; Bysakh, S.; Sundararajan, G.; Chattopadhyay, K.

    2018-01-01

    Nanoparticle agglomerates of passivated Fe (n-Fe) and Fe0.96Cu0.04 (n-Fe0.96Cu0.04), synthesized through the levitational gas condensation (LGC) process, were compacted and sintered using the conventional powder metallurgy method. The n-Fe0.96Cu0.04 agglomerates produced lower green density than n-Fe, and when compacted under pressure beyond 200 MPa, they underwent lateral cracking during ejection attributed to the presence of a passive oxide layer. Sintering under dynamic hydrogen atmosphere can produce a higher density of compact in n-Fe0.96Cu0.04 in comparison to n-Fe. Both the results of dilatometry and thermogravimetric (TG) measurements of the samples under flowing hydrogen revealed enhancement of the sintering process as soon as the reduction of oxide layers could be accomplished. The shrinkage rate of n-Fe0.96Cu0.04 reached a value three times higher than n-Fe at a low temperature of 723 K (450 °C) during heating. This enhanced shrinkage rate was the manifestation of accumulation of Cu at the surface of the particles. The formation of a thin-surface melted layer enriched with copper during heating to isothermal holding facilitated as a medium of transport for diffusion of the elements. The compacts produced by sintering at 773 K (500 °C), with relative density 82 pct, were found to be unstable and oxidized instantly when exposed to ambient atmosphere. The stable compacts of density more than 92 pct with 300- to 450-nm grain size could only be produced when sintering was carried out at 973 K (700 °C) and beyond. The 0.22 wt pct residual oxygen obtained in the sintered compact is similar to what is used for conventional ferrous powder metallurgy products.

  4. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0.39 m (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0.5 wt% together ...

  5. Preparation, Characterization and application of Alumina Powder Produced by advanced Preparation Techniques

    International Nuclear Information System (INIS)

    Khalil, T.; Abou El Nour, F.; Bossert, J.; Ashor, A.H.

    2000-01-01

    Aluminum oxide powders were prepared by advanced chemical techniques. The morphology of the produced powders were examined using scanning electron microscopy (SEM). Surface characteristics of the powders were measured through nitrogen gas adsorption and application of the BET equation at 77 K, through the use of nitrogen gas adsorption at liquid nitrogen temperature and application of the Brunauer-Emett-Teller (BET) equation. The total surface area, total pore volume and pore radius of the powders were calculated through the construction of the plots relating the amount of nitrogen gas adsorbed V 1 and the thickness of the adsorbed layer t(V 1 -t plots). The thermal behaviour of the powders were studied with the help of differential thermal analysis (DTA) and thermogravimetry (TG). Due to the presence of some changes in the DTA base lines, possibly as a result of phase transformations, X-ray diffraction was applied to identify these phases. The sintering behaviour of the compact powders after isostatic pressing was evaluated using dilatometry. The sintering temperature of the studied samples were also determined using heating microscopy. The effect of changing sintering temperature and of applying different isostatic pressures on the density and porosity of the compacts was investigated

  6. 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.

  7. Effect of Bottom Ash and Fly Ash as a Susceptor Material on The Properties of Aluminium Based Composites Prepared by Microwave Sintering

    Directory of Open Access Journals (Sweden)

    Wan Muhammad Wan Nur Azrina Binti

    2017-01-01

    Full Text Available The use of aluminium as a single material in automotive applications is not suitable without a mixture with reinforcement materials that can support the properties at high temperature. In this study, aluminium based composite were prepared with weight percentage of SiC reinforcement, varying from 5 to 20 wt%. Aluminium powder and reinforcement materials were mixed using ball milling machine with speed of 100 rpm for 2 hours. The powder mixture were then compressed at pressure 4 tonnes with 5 minutes holding time. The compact samples were sintered using microwave sintering technique. Microwave sintering techniques in this study using two different types of susceptor materials that are bottom ash and fly ash. Sintered aluminium based composites using bottom ash susceptor material involving the sintering temperature of 526 °C for 30 minutes whereas for the samples sintered using fly ash susceptor material, involving a temperature of 523 °C for 15 minutes. From the result, the sintered samples using fly ash susceptor material, showed higher density with a value of 2.1933 g/cm3 compared to bottom ash 2.0002 g/cm3 and having the higher hardness value 72.1315 HV compared to bottom ash 50.0511HV. The using of fly ash could affect the heating rate during the sintering process which could influence the properties of aluminium based composites. In conclusion, the type of susceptor could affect the physical and mechanical properties of aluminum-based composite reinforced with silicon carbide.

  8. 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

  9. Sintering, microstructural and dilatometric studies of combustion synthesized Synroc phases

    International Nuclear Information System (INIS)

    Muthuraman, M.; Patil, K.C.; Senbagaraman, S.; Umarji, A.M.

    1996-01-01

    Sintering, microstructure, and linear thermal expansion properties of Synroc-B and constituent phases, viz. perovskite CaTiO 3 , zirconolite ZrTi 2 O 7 , hollandite (ideal formula BaAl2Ti 6 O 16 ) have been investigated. Synroc-B powder when pelletized and sintered at 1250 C for 2 h achieved >95% theoretical density. Sintered Synroc-B has a linear thermal expansion coefficient α of 8.72 x 10 -6 K -1 and Vicker's microhardness 9.88 GPa. The linear thermal expansion curves did not show any hysteresis indicating the absence of microcracking in the sintered bodies

  10. Effect of sintering temperatures on the in vitro bioactivity, molecular structure and mechanical properties of titanium/carbonated hydroxyapatite nanobiocomposites

    Science.gov (United States)

    Youness, Rasha A.; Taha, Mohammed A.; Ibrahim, Medhat A.

    2017-12-01

    Titanium-containing carbonated hydroxyapatite (Ti-CHA) nanocomposite powders, with different CHA contents, have been prepared using high-energy ball milling method. The effect of sintering temperatures, 900, 1100 and 1300 °C on molecular structure and microstructure of these samples were examined by XRD; Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Furthermore, their mechanical properties including hardness, longitudinal modulus, Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by ultrasonic non-destructive technique. Moreover, bioactivity of sintered samples at different firing temperatures was assessed by immersing them in simulated body fluid at 37 ± 0.5 °C for 7 days and then, analyzed by FTIR spectroscopy. The results pointed out that increasing sintering temperature up to 1100 °C caused significant increases in densities and mechanical properties of these nanocomposite samples. However, further increase of firing temperature to 1300 °C was responsible for complete CHA decomposition and the resultant α-tricalcium (α-TCP) phase greatly affected these properties. On the contrary, better bioactivity was observed for sintered samples at 900 °C only. However, increase of sintering temperature of these samples up to 1300 °C led to severe decrease in their bioactivity due to the formation of highly soluble α-TCP phase.

  11. Preliminary investigation of liquid phase sintering in ferrous systems

    International Nuclear Information System (INIS)

    Klein, J.

    1975-04-01

    Liquid phase sintering was utilized to achieve, by a simple compaction and sintering procedure involving short times and moderate temperatures, a virtually full dense high carbon Fe:C alloy and high boron Fe:B alloy. Parameters such as powder characteristics and mixing, compacting pressure, heating program and the liquid phase fraction were found to influence the sintered density. The response of the Fe:C alloy to a heat treatment is reported along with preliminary experiments in the iron base ternary system Fe:W:C. Residual porosities observed in microstructures of certain liquid phase sintered compacts were accounted for by a proposed capillary flow of the liquid phase and a local densification competing against an overall densification. Some general recommendations are made for liquid phase sintering of powder aggregates. 15 fig., 7 tables

  12. Demonstration Exercise of a Validated Sample Collection Method for Powders Suspected of Being Biological Agents in Georgia 2006

    International Nuclear Information System (INIS)

    Marsh, B.

    2007-01-01

    August 7, 2006 the state of Georgia conducted a collaborative sampling exercise between the Georgia National Guard 4th Civil Support Team Weapons of Mass Destruction (CST-WMD) and the Georgia Department of Human Resources Division of Public Health demonstrating a recently validated bulk powder sampling method. The exercise was hosted at the Federal Law Enforcement Training Center (FLETC) at Glynn County, Georgia and involved the participation of the Georgia Emergency Management Agency (GEMA), Georgia National Guard, Georgia Public Health Laboratories, the Federal Bureau of Investigation Atlanta Office, Georgia Coastal Health District, and the Glynn County Fire Department. The purpose of the exercise was to demonstrate a recently validated national sampling standard developed by the American Standards and Test Measures (ASTM) International; ASTM E2458 S tandard Practice for Bulk Sample Collection and Swab Sample Collection of Visible Powders Suspected of Being Biological Agents from Nonporous Surfaces . The intent of the exercise was not to endorse the sampling method, but to develop a model for exercising new sampling methods in the context of existing standard operating procedures (SOPs) while strengthening operational relationships between response teams and analytical laboratories. The exercise required a sampling team to respond real-time to an incident cross state involving a clandestine bio-terrorism production lab found within a recreational vehicle (RV). Sample targets consisted of non-viable gamma irradiated B. anthracis Sterne spores prepared by Dugway Proving Ground. Various spore concentration levels were collected by the ASTM method, followed by on- and off-scene analysis utilizing the Center for Disease Control (CDC) Laboratory Response Network (LRN) and National Guard Bureau (NGB) CST mobile Analytical Laboratory Suite (ALS) protocols. Analytical results were compared and detailed surveys of participant evaluation comments were examined. I will

  13. The influence of Si on the microstructure and sintering behavior of ultrafine WC

    Science.gov (United States)

    Nanda Kumar, A. K.; Watabe, Masaaki; Kurokawa, Kazuya

    2012-11-01

    The microstructure of sintered nanoscale tungsten carbide powders with 1 wt % Si addition was found to be populated by an abnormally large number of elongated grains. Interrupted sintering experiments were conducted to clarify the origins of the excessive abnormal grain growth seen in the microstructure. It was observed that rapid coarsening occurred at high temperatures owing to the formation of a liquid phase. However, the grain shape evolution during this coarsening period was found to be a consequence of excessive stacking faults and micro twins on the basal planes probably generated by reaction of WC with Si. Analyses of the microstructures and the isothermal and non isothermal coarsening behaviors suggested that the platelet morphology evolved by defect-assisted nucleation and growth on faceted grains. Based on experimental evidence from samples interrupted at low temperatures and crystal growth theories, we discuss the possible mechanisms that eventually led to the rampant platelet-type morphology. Further, the influence of such rapid grain growth on the shrinkage rate during sintering is also discussed. In comparison with the cyclic coarsening-densification process of sintering in pure nanoscale WC, the addition of Si leads to only two distinct sintering stages: either densification dominated or coarsening dominated. Concurrent densification and coarsening cannot be sustained particularly in the presence of a liquid phase that significantly enhances coarsening.

  14. Effect of post-sintering treatment on properties of Bi-based high Tc superconductors

    International Nuclear Information System (INIS)

    Nagai, Masayuki; Kozuka, Akira; Morishita, Ken; Nishino, Tadashi; Hattori, Takeo; Takata, Masasuke

    1989-01-01

    A new method to obtain the pure 110K phase in the system Bi-Sr-Ca-Cu-O was examined employing post-sintering treatment. The mixture of Bi 2 O 3 , SrCO 3 , CaCO 3 and CuO with the basic composition of Bi/Sr/Ca/Cu=2/2/1/2 was calcined. The resulting powder was soaked in ethanol containing copper acetate and calcium acetate, the amounts of which were determined to give the composition of Bi/Sr/Ca/Cu=2/2/2/3 after sintering. The resistivity was measured by the d.c. four probe method in a cryostat. The current level was maintained at 50 mA and the voltage drop was determined by averaging the values in the forward and reverse directions. The zero T c ranged from 65 to 69K for the samples after sintering, while that ranged from 69 to 71K for those with post-sintering treatment. The effect of the treatment was not drastic but significant. Modified post-sintering treatment is being examined and the results are reported in the symposium

  15. Analysis of wear in organic and sintered friction materials used in small wind energy converters

    Directory of Open Access Journals (Sweden)

    Jorge Alberto Lewis Esswein Junior

    2008-09-01

    Full Text Available Wind energy converters of small size used in isolated units to generate electrical energy must present low maintenance cost to such facilities economically viable. The aspect to be analyzed in cost reduction is the brake system, since in isolated systems the use of brake is more frequent reducing the brake pads life time. This study aims at analyzing the wear behavior of some materials used in brake pads. An organic material was analyzed comparing it with a commercial brake pad, and the sintered material was developed and tested. The materials behaviors were evaluated in both wear and friction coefficient. The sintered samples were made by powder metallurgy. The composition was compacted at 550 MPa and sintered in a furnace with controlled atmosphere to avoid oxidation. Despite the different compositions of the two types of materials, they presented a very similar wear; however, the sintered material presented a higher friction coefficient. An adjustment in the braking system of the wind generator might be proposed to use the sintered brake pad, due to its higher friction coefficient. Consequently, the braking action becomes lower, reducing the wear rate of the material.

  16. Laser sintering of ceramics of Y2O3 pure e doped

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  17. Comparison of four commercial DNA extraction kits for the recovery of Bacillus spp. spore DNA from spiked powder samples.

    Science.gov (United States)

    Mölsä, Markos; Kalin-Mänttäri, Laura; Tonteri, Elina; Hemmilä, Heidi; Nikkari, Simo

    2016-09-01

    Bacillus spp. include human pathogens such as Bacillus anthracis, the causative agent of anthrax and a biothreat agent. Bacillus spp. form spores that are physically highly resistant and may remain active over sample handling. We tested four commercial DNA extraction kits (QIAamp DNA Mini Kit, RTP Pathogen Kit, ZR Fungal/Bacterial DNA MiniPrep, and genesig Easy DNA/RNA Extraction kit) for sample inactivation and DNA recovery from two powders (icing sugar and potato flour) spiked with Bacillus thuringiensis spores. The DNA was analysed using a B. thuringiensis-specific real-time PCR assay. The detection limit was 3×10(1)CFU of spiked B. thuringiensis spores with the QIAamp DNA Mini, RTP Pathogen, and genesig Easy DNA/RNA Extraction kits, and 3×10(3)CFU with the ZR Fungal/Bacterial DNA MiniPrep kit. The results showed that manual extraction kits are effective and safe for fast and easy DNA extraction from powder samples even in field conditions. Adding a DNA filtration step to the extraction protocol ensures the removal of Bacillus spp. spores from DNA samples without affecting sensitivity. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. 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.

  19. Experimental sintering of ash at conduit conditions and implications for the longevity of tuffisites

    Science.gov (United States)

    Gardner, James E.; Wadsworth, Fabian B.; Llewellin, Edward W.; Watkins, James M.; Coumans, Jason P.

    2018-03-01

    Escape of gas from magma in the conduit plays a crucial role in mitigating explosivity. Tuffisite veins—ash-filled cracks that form in and around volcanic conduits—represent important gas escape pathways. Sintering of the ash infill decreases its porosity, eventually forming dense glass that is impermeable to gas. We present an experimental investigation of surface tension-driven sintering and associated densification of rhyolitic ash under shallow conduit conditions. Suites of isothermal (700-800 °C) and isobaric H2O pressure (20 and 40 MPa) experiments were run for durations of 5-90 min. Obsidian powders with two different size distributions were used: 1-1600 μm (mean size = 89 μm), and 63-400 μm (mean size = 185 μm). All samples evolved similarly through four textural phases: phase 1—loose and cohesion-less particles; phase 2—particles sintered at contacts and surrounded by fully connected tortuous pore space of up to 40% porosity; phase 3—continuous matrix of partially coalesced particles that contain both isolated spherical vesicles and connected networks of larger, contorted vesicles; phase 4—dense glass with 2-5% fully isolated vesicles that are mainly spherical. Textures evolve faster at higher temperature and higher H2O pressure. Coarse samples sinter more slowly and contain fewer, larger vesicles when fully sintered. We quantify the sintering progress by measuring porosity as a function of experimental run-time, and find an excellent collapse of data when run-time is normalized by the sintering timescale {λ}_s=η \\overline{R}/σ , where η is melt viscosity, \\overline{R} is mean particle radius, and σ is melt-gas surface tension. Because timescales of diffusive H2O equilibration are generally fast compared to those of sintering, the relevant melt viscosity is calculated from the solubility H2O content at experimental temperature and pressure. We use our results to develop a framework for estimating ash sintering rates under shallow

  20. Yttrium oxide transparent ceramics by low-temperature microwave sintering

    International Nuclear Information System (INIS)

    Luo, Junming; Zhong, Zhenchen; Xu, Jilin

    2012-01-01

    Graphical abstract: The figure shows the SEM photos of the surfaces of the Y 2 O 3 transparent ceramic samples obtained by microwave sintering and vacuum sintering. It is clearly demonstrated that the grain distribution of the vacuum sintering sample is not uniform with the smallest and the largest particle size at about 2 μm and 15 μm respectively, while the grain distribution of microwave sintering sample is uniform with the average diameter at about 2–4 μm (the smallest reported so far) and with no abnormal growth-up or coarsening phenomenon. We have further found out that the smaller the grain size, the higher the mechanical and optical properties. Display Omitted Highlights: ► The microwave sintering temperature of the sample is lower compared with vacuum. ► The microwave sintering time of the sample is shorter compared with vacuum. ► The mechanical properties of the microwave sintering sample is improved greatly. ► The Y 2 O 3 grain of microwave sintering sample is the smallest reported so far. -- Abstract: Yttrium oxide (Y 2 O 3 ) transparent ceramics samples have been successfully fabricated by microwave sintering processing at relatively low temperatures. In comparison with the vacuum sintering processing, Y 2 O 3 transparent ceramics can be obtained by microwave sintering at lower sintering temperature and shorter sintering time, and they possess higher transmittances and mechanical properties. The technologies of low-temperature microwave sintering and the relationships of the microstructures and properties of the specified samples have been investigated in detail. We have found out that the low-temperature microwave sintering technique has its obvious advantages over the conventional methods in manufacturing yttrium oxide transparent ceramics.

  1. Alloying Behavior and Properties of FeSiBAlNiCo x High Entropy Alloys Fabricated by Mechanical Alloying and Spark Plasma Sintering

    Science.gov (United States)

    Wang, Wen; Li, Boyu; Zhai, Sicheng; Xu, Juan; Niu, Zuozhe; Xu, Jing; Wang, Yan

    2018-02-01

    In this paper, FeSiBAlNiCo x (x = 0.2, 0.8) high-entropy alloy (HEA) powders were fabricated by mechanical alloying process, and the powders milled for 140 h were sintered by spark plasma sintering (SPS) technique. The microstructures and properties of as-milled powders and as-sintered samples were investigated. The results reveal that the final milling products (140 h) of both sample powders present the fully amorphous structure. The increased Co contents obviously enhance the glass forming ability and thermal stability of amorphous HEA powders, which are reflected by the shorter formation time of fully amorphous phase and the higher onset crystallization temperature, respectively. According to coercivity, the as-milled FeSiBAlNiCo x (x = 0.2, 0.8) powders (140 h) are the semi-hard magnetic materials. FeSiBAlNiCo0.8 HEA powders possess the highest saturation magnetization and largest remanence ratio. The SPS-ed products of both bulk HEAs are composed of body-centered cubic solid solution, and FeSi and FeB intermetallic phases. They possess the high relative density above 97% and excellent microhardness exceeding 1150 HV. The as-sintered bulks undergo the remarkable increase in saturation magnetization compared with the as-milled state. The SPS-ed FeSiBAlNiCo0.8 HEA exhibits the soft magnetic properties. The electrochemical corrosion test is carried out in 3.5% NaCl solution. The SPS-ed FeSiBAlNiCo0.2 HEA reveals the better passivity with low passive current density, and the higher pitting resistance with wide passive region.

  2. 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.

  3. Bimodal metal micro-nanopowders for powder injection molding

    Science.gov (United States)

    Pervikov, Aleksandr; Rodkevich, Nikolay; Glazkova, Elena; Lerner, Marat

    2017-12-01

    The paper studies a bimodal metal powder composition designed to prepare feedstock for powder injection molding, as well as microstructure and porosity of sintered pats. Two kinds of metal powder compositions are used, in particular, a mixture of micro- and nanopowders and a bimodal powder prepared with dispersion of steel wire. The feedstock is prepared by mixing a bimodal metal powder composition with acetylacetone and paraffin wax. The microstructure of the debound parts is observed by scanning electron microscopy. The sintered parts are characterized by density measurements and metallographic analysis. The technique of the metal powder composition proves to affect the characteristics of sintered parts. Nanoparticles are shown in the interstitial spaces among the microparticles upon mixing micro- and nanopowders, but the regular distribution of nanoparticles on the surface of microparticles is observed in the bimodal powder providing the reduction of the porosity of sintered parts and increasing the density to the proper density of steel.

  4. Compaction of Ti–6Al–4V powder using high velocity compaction technique

    International Nuclear Information System (INIS)

    Khan, Dil Faraz; Yin, Haiqing; Li, He; Qu, Xuanhui; Khan, Matiullah; Ali, Shujaat; Iqbal, M. Zubair

    2013-01-01

    Highlights: • We compacted Ti–6Al–4V powder by HVC technique. • As impact force rises up, the green density of the compacts increases gradually. • At impact force 1.857 kN relative sintered density of the compacts reaches 99.88%. • Spring back of the green compact’s decreases gradually with increasing impact force. • Mechanical properties of the samples increases with increasing impact force. - Abstract: High velocity compaction technique was applied to the compaction of pre-alloyed, hydride–dehydride Ti–6Al–4V powder. The powder was pressed in single stroke with a compaction speed of 7.10–8.70 ms −1 . When the speed was 8.70 ms −1 , the relative density of the compacts reaches up to 85.89% with a green density of 3.831 g cm −3 . The green samples were sintered at 1300 °C in Ar-gas atmosphere. Scanning electron microscope (SEM) was used to examine the surface of the sintered samples. Density and mechanical properties such as Vickers micro hardness and bending strength of the powder samples were investigated. Experimental results indicated that with the increase in impact force, the density and mechanical properties of the compacts increased. The sintered compacts exhibited a maximum relative density of 99.88% with a sintered density of 4.415 g cm −3 , hardness of 364–483 HV and the bending strength in the range of 103–126.78 MPa. The springback of the compacts decreased with increasing impact force

  5. Structural and superconducting properties of PIT processed sintered MgB{sub 2}/Fe wires

    Energy Technology Data Exchange (ETDEWEB)

    Balamurugan, S.; Nakamura, T.; Osamura, K.; Muta, I.; Hoshino, T

    2004-10-01

    In this paper, we report the structural and superconducting properties of MgB{sub 2}/Fe wires that are produced by different sintering conditions. Good quality MgB{sub 2}/Fe wires are fabricated by the powder-in-tube (PIT) method using commercially available MgB{sub 2} powder at ambient pressure. In order to check the annealing effect, the different pieces of the as-rolled wires are sintered at 1323 K for 0.30-1.20 ks. XRD data confirms that they are hexagonal MgB{sub 2} structure. All the sintered samples show higher T{sub c} values in the range of 38.2-38.4 K with high J{sub c} than the as-rolled sample. No significant change in T{sub c} is seen among the annealed samples. On the other hand, the annealed samples show significant change in the J{sub c} values as well as in micro-structural features due to variable sintering time. On annealing at 1323 K for 0.60 ks, we obtain the best quality sample with a J{sub c} of 372 A/mm{sup 2} at 33.1 K in self-field with a maximum T{sub c} of 38.4 K. Among the annealed samples, 1.20 ks sample shows lower J{sub c}. Longer annealing time reduced J{sub c}, indicating a possible interfacial reaction between the Fe sheath and the MgB{sub 2} core.

  6. [Ultra-Fine Pressed Powder Pellet Sample Preparation XRF Determination of Multi-Elements and Carbon Dioxide in Carbonate].

    Science.gov (United States)

    Li, Xiao-li; An, Shu-qing; Xu, Tie-min; Liu, Yi-bo; Zhang, Li-juan; Zeng, Jiang-ping; Wang, Na

    2015-06-01

    The main analysis error of pressed powder pellet of carbonate comes from particle-size effect and mineral effect. So in the article in order to eliminate the particle-size effect, the ultrafine pressed powder pellet sample preparation is used to the determination of multi-elements and carbon-dioxide in carbonate. To prepare the ultrafine powder the FRITSCH planetary Micro Mill machine and tungsten carbide media is utilized. To conquer the conglomeration during the process of grinding, the wet grinding is preferred. The surface morphology of the pellet is more smooth and neat, the Compton scatter effect is reduced with the decrease in particle size. The intensity of the spectral line is varied with the change of the particle size, generally the intensity of the spectral line is increased with the decrease in the particle size. But when the particle size of more than one component of the material is decreased, the intensity of the spectral line may increase for S, Si, Mg, or decrease for Ca, Al, Ti, K, which depend on the respective mass absorption coefficient . The change of the composition of the phase with milling is also researched. The incident depth of respective element is given from theoretical calculation. When the sample is grounded to the particle size of less than the penetration depth of all the analyte, the effect of the particle size on the intensity of the spectral line is much reduced. In the experiment, when grounded the sample to less than 8 μm(d95), the particle-size effect is much eliminated, with the correction method of theoretical α coefficient and the empirical coefficient, 14 major, minor and trace element in the carbonate can be determined accurately. And the precision of the method is much improved with RSD < 2%, except Na2O. Carbon is ultra-light element, the fluorescence yield is low and the interference is serious. With the manual multi-layer crystal PX4, coarse collimator, empirical correction, X-ray spectrometer can be used to

  7. 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)

  8. Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase

    Energy Technology Data Exchange (ETDEWEB)

    Michael Bakas; Henry Chu

    2009-01-01

    Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

  9. Sintering of nanopowders of ZrO{sub 2} (Y{sub 2}O{sub 3}): Effect of compaction pressure on densification; Sinterizacao de pos nanoparticulados de ZrO{sub 2} (Y{sub 2}O{sub 3}): efeito da pressao de compactacao na densificacao

    Energy Technology Data Exchange (ETDEWEB)

    Palmeira, Alexandre Alvarenga; Magnago, Roberto de Oliveira; Pereira, Glayce Cassaro [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Bondioli, Marcelo Jose; Strecker, Kurt [Universidade Federal Sao Joao Del-Rey (UFSJ), MG (Brazil); Santos, Claudinei dos [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)

    2014-06-15

    In this work studied the powders (nano) sintered of ZrO{sub 2} (Y{sub 2}O{sub 3}) by dilatometry. Was identified the effect of compaction pressure variation in the final results of densification of materials. Powders were compacted at different compaction pressures. The compacts were subjected to temperatures of 1250°C to 1400°C with sintering levels ranging from 0 to 8 hours. Samples were characterized by X-ray diffraction and relative density using Archimedes method. The results were compared with powders (micro) of similar composition in order to compare the effect of particle size on densification parameters. The samples were further subjected to microstructural characterization in order to identify the average grain size of the sintering under each condition used in both materials. (author)

  10. Thermodynamics and mechanisms of sintering

    International Nuclear Information System (INIS)

    Pask, J.A.

    1978-10-01

    A phenomenological overview and exploration of the thermodynamic and geometric factors play a role in the process of densification of model compact systems consisting of crystalline spheres of uniform size in regular and irregular packing that form grain boundaries at every contact point. A further assumption is the presence of isotropic surface and grain boundary energies. Although such systems are unrealistic in comparison with normal powder compacts, their potential sintering behavior can be analyzed and provided with a limiting set of behavior conditions which can be looked upon as one boundary condition. This approach is logically realistic since it is easier to understand and provide a basis for understanding the more complex real powder systems

  11. Powder Handling Device for X-ray Diffraction Analysis with Minimal Sample Preparation, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This project consists of developing a Vibrating Sample Holder (VSH) for planetary X-Ray Diffraction (XRD) instruments. The principle of this novel sample handling...

  12. The Structure and Properties of the Samples Produced by Selective Laser Melting of 410L Steel-based Metal Powder

    Science.gov (United States)

    Deev, Artem; Kuznetsov, Pavel; Zhukov, Anton; Bobyr, Vitaliy

    Additive technologies, which obtained the wide spreading in the last decade, allow producing items of any shape from metal materials practically without additional mechanical treatment. This approach based on the layer by layer melting of powder material accordingly to the premade 3D-CAD model, provides the geometrical accuracy which mostly depends on the size of the used material. In the present study, as material a 410 L steel powder was chosen, for which the basic dependencies between the selective laser melting (SLM) parameters and the mechanical properties were determined. Trial batches of standard samples for uniaxial tension and impact strength tests (according to the ASTM A370 and ASTM E8 M standards) were produced. It was shown that in the as build (after SLM) the fracture appeared to be brittle with the impact strength 3-5 J/cm2. The carried out heat treatment of quenching-tempering cycle and subsequent tests provide the viscous fracture and evaluation of impact strength up to 20-30 J/cm2. Presumably, this is due to a refinement of the grain structure and the inner stresses reduction of the samples, which also acknowledges the execution EBSD analysis, which points to the presence of quenched and tempered martensite. The presence of high inner stresses can be attributed to two α-γ-α transformations that were revealed by dilatometry investigation. In the range of cooling or heating rates from 1 to 500 °C/s temperatures of phase transformation are shifted.

  13. APPLICATION OF HEATING MICROSCOPY ON SINTERING AND MELTING BEHAVIOUR OF NATURAL SANDS OF ARCHAEOLOGICAL INTEREST

    Directory of Open Access Journals (Sweden)

    Montanari F.

    2013-09-01

    Full Text Available In antiquity, beach sand was one of the main raw materials for glass-making and for the production of other vitreous materials, like Egyptian blue and faience. During the 1st century AD, glass and pigments manufacturing industry was active along the Gulf of Naples, Italy, where we sampled four littoral sands. Samples were analyzed with different techniques: chemical analysis was performed by means of X-Ray Fluorescence (XRF and mineralogical analyses with X-Ray Powder Diffraction (XRPD and Raman Spectroscopy. The complete sintering to melting thermal behaviour of the four sands was studied by heating microscopy or hot-stage microscope (HSM equipped with an high resolution camera capable to collect sample profile during heating. The effect of the grain size on the sintering curves, which were automatically elaborated by specimen profile transformation, was also investigated. Finally, some deductions about the granulometry effect and the presence of alkaline and alkaline-earth oxides on sintering and melting behaviour were drawn. All the four sands were found suitable for highly sintered manufacts rather than glasses, to reach complete amorphous materials the addition of fluxes was necessary.

  14. ELASTO-PLASTIC DEFORMATION OF COMPOSITE POWDERS WITH LAYERED CARBON AND CARBIDE-FORMING ELEMENT COATING

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevsky

    2012-01-01

    Full Text Available Coating structure formation under magnetron spraying of titanium and carbon cathodes and combined cathodes, namely cobalt (EP 131 – nickel, tungsten – carbon have been investigated under conditions of carbide separate synthesis within the temperature range of 650–1200 °C. Usage of cobalt and nickel particles as matrix material leads to their rapid thermal expansion under heating during sintering process in the dilatometer. Subsequent plastic deformation of sintered samples provides obtaining a composite powder material that is a composite with framing structure of cobalt, titanium and tungsten carbides in the coatings.

  15. Powder technology

    International Nuclear Information System (INIS)

    Agueda, Horacio

    1989-01-01

    Powder technology is experiencing nowadays a great development and has broad application in different fields: nuclear energy, medicine, new energy sources, industrial and home artifacts, etc. Ceramic materials are of daily use as tableware and also in the building industry (bricks, tiles, etc.). However, in machine construction its utilization is not so common. The same happens with metals: powder metallurgy is employed less than traditional metal forming techniques. Both cases deal with powder technology and the forming techniques as far as the final consolidation through sintering processes are very similar. There are many different methods and techniques in the forming stage: cold-pressing, slip casting, injection molding, extrusion molding, isostatic pressing, hot-pressing (which involves also the final consolidation step), etc. This variety allows to obtain almost any desired form no matter how complex it could be. Some applications are very specific as in the case of UO 2 pellets (used as nuclear fuels) but with the same technique and other materials, it is possible to manufacture a great number of different products. This work shows the characteristics and behaviour of two magnetic ceramic materials (ferrites) fabricated in the laboratory of the Applied Research Division of the Bariloche Atomic Center for different purposes. Other materials and products made with the same method are also mentioned. Likewise, densities and shrinkage obtained by different methods of forming (cold-pressing, injection molding, slip casting and extrusion molding) using high-purity alumina (99.5% Al 2 O 3 ). Finally, different applications of such methods are given. (Author) [es

  16. Evaluation of microstructure and phase relations in a powder processed Ti-44Al-12Nb alloy

    International Nuclear Information System (INIS)

    Kumar, S.G.; Reddy, R.G.; Wu, J.; Holthus, J.

    1995-01-01

    Titanium aluminides based on the ordered face-centered tetragonal γTiAl phase possess attractive properties, such as low density, high melting point, good elevated temperature strength, modulus retention, and oxidation resistance, making these alloys potential high-temperature structural materials. These alloys can be processed by both ingot metallurgy and powder metallurgy routes. In the present study, three variations of the powder metallurgy route were studied to process a Ti-44Al-12Nb (at.%) alloy: (a) cold pressing followed by reaction sintering (CP process); (b) cold pressing, vacuum hot pressing, and then sintering (HP process); and (c) arc melting, hydride-dehydride process to make the alloy powder, cold isostatic pressing, and then sintering (AM process). Microstructural and phase relations were studied by x-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). The phases identified were Ti 3 Al and TiAl; an additional Nb 2 Al phase was observed in the HP sample. The microstructures of CP and HP processed samples are porous and chemically inhomogeneous whereas the AM processed sample revealed fine equiaxed microstructure. This refinement of the microstructure is attributed to the fine, homogeneous powder produced by the hydride-dehydride process and the high compaction pressures

  17. Low density, variation in sintered density and high nitrogen in uranium dioxide

    International Nuclear Information System (INIS)

    Balakrishna, Palanki; Murty, B.N.; Anuradha, M.; Nageshwara Rao, P.; Jayaraj, R.N.; Ganguly, C.

    2000-01-01

    Low sintered density and density variation in sintered UO 2 were found to have been caused by non uniformity in the granule feed characteristics to the compacting press. The nitrogen impurity content of sintered UO 2 was found to be sintering furnace related and associated with low sintered density pellets. The problems of low density, variation in sintered density and high nitrogen could be solved by the replacement of the prevailing four punch precompaction by a single punch process; by the introduction of a vibro-sieve for the separation of fine particles from the press feed granules; by innovation in the powder feed shoe design for simultaneous and uniform dispensing of powder in all the die holes; by increasing the final compaction pressure and by modifying the gas flows and preheat temperature in the sintering furnace. (author)

  18. Use of an Ultrasonic/Sonic Driller/Corer to Obtain Sample Powder for CHEMIN, a Combined XRD/XRF Instrument

    Science.gov (United States)

    Chipera, S. J.; Bish, D. L.; Vaniman, D. T.; Sherrit, S.; Bar-Cohen, Y.; Sarrazin, P.; Blake, D. F.

    2003-01-01

    A miniature CHEMIN XRD/XRF (X-Ray Diffraction/X-Ray Fluourescence) instrument is currently being developed for definitive mineralogic analysis of soils and rocks on Mars. One of the technical issues that must be addressed in order to enable XRD analysis on an extraterrestrial body is how best to obtain a representative sample powder for analysis. For XRD powder diffraction analyses, it is beneficial to have a fine-grained sample to reduce preferred orientation effects and to provide a statistically significant number of crystallites to the X-ray beam. Although a 2-dimensional detector as used in the CHEMIN instrument will produce good results with poorly prepared powders, the quality of the data will improve if the sample is fine-grained and randomly oriented. An Ultrasonic/Sonic Driller/Corer (USDC) currently being developed at JPL is an effective mechanism of sampling rock to produce cores and powdered cuttings. It requires low axial load (XRF spectrometer such as CHEMIN, powders obtained from the JPL ultrasonic drill were analyzed and the results were compared to carefully prepared powders obtained using a laboratory bench scale Retsch mill.

  19. Amperometric detection of Sudan I in red chili powder samples using Ag nanoparticles decorated graphene oxide modified glassy carbon electrode.

    Science.gov (United States)

    Prabakaran, E; Pandian, K

    2015-01-01

    A simple and sensitive electrochemical method was developed to determine the concentration of Sudan I in chili powder based on silver nanoparticles decorated graphene oxide modified glassy carbon electrode (AgNPs@GO/GCE). The voltammetry behaviour of Sudan I on modified GCE was investigated in phosphate buffer medium (PBS) with various pH ranges and the electron transfer properties were studied. It is found that the AgNPs@GO/GCE can catalyse the reduction of azo group, -N=N- followed by electrochemical oxidation of (-)OH group present in Sudan I dye molecule. Quantitative detection of Sudan I present in food products was carried out by amperometry method in which reduction potential was fixed at -0.77 V vs. Ag/AgCl. The amperometry method showed an excellent performance with a sensitivity of 6.83 μA mM(-1) and a detection limit of 11.4 × 10(-7)ML(-1). A linear calibration graph was constructed in the ranging 3.90 × 10(-6) to 3.19 × 10(-5)ML(-1). The method was successfully applied for the determination of Sudan I in red chili powder samples. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Effect of milling parameters on sinterability, mechanical and electrical properties of Cu-4 wt.% ZrO{sub 2} nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Taha, Mohammed A., E-mail: mtahanrc@gmail.com [Solid-State Physics Department, National Research Centre, El-Buhooth St., 12622, Dokki, Cairo (Egypt); Nassar, Amira H. [Solid-State Physics Department, National Research Centre, El-Buhooth St., 12622, Dokki, Cairo (Egypt); Zawrah, M.F. [Ceramics Department, National Research Centre, El-Buhooth St., 12622, Dokki, Cairo (Egypt)

    2016-09-15

    Mechanical alloying was used to produce Cu matrix nanocomposite reinforced by 4 wt.% ZrO{sub 2} nanoparticles with different milling time up to 16 h and ball-to-powder ratios (BPRs) up to 40:1. The milled nanocomposite powders were investigated by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). To study the sinterability, the milled powders were cold pressed and sintered at 800 °C for 1 h in argon atmosphere. In order to investigate the relative density and microstructures of the sintered nanocomposites, scanning electron microscopy (SEM) as well as energy dispersive spectrometer (EDS) were employed. The electrical and mechanical properties of the sintered nanocomposites were also examined. The results revealed that a uniform distribution of ZrO{sub 2} reinforcement in Cu matrix was successfully obtained and the agglomeration, crystal and particle sizes were decreased after either milling times and/or BPRs. The results also pointed out that the relative density, microhardness, compressive strength and electrical conductivity of the sintered nanocomposite samples were increased with the increasing of milling time and/or BPRs while apparent porosity was decreased. The maximum values of microhardness, compressive strength and electrical conductivity were 872 MPa, 304 MPa and 45.9% IACS, respectively for the milled sample for 16 h and BRP 40:1. - Highlights: • Cu-4 wt.% ZrO{sub 2} nanoparticles with different parameter by mechanical alloying. • The increased milling times and/or BPRs led to a decrease in the particle size. • Microhardness is increased with increasing ball-to-powder weight ratios. • Compressive strength is increased with increasing milling time. • Electrical conductivity of the samples was increasing with increase milling time.

  1. Method for analysing radium in powder samples and its application to uranium prospecting

    International Nuclear Information System (INIS)

    Gong Xinxi; Hu Minzhi.

    1987-01-01

    The decayed daughter of Rn released from the power sample (soil) in a sealed bottle were collected on a piece of copper and the radium in the sample can be measured by counting α-particles with an Alphameter for uranium prospection, thus it is called the radium method. This method has many advantages, such as high sensitivity (the lowest limit of detection for radium sample per gram is 2.7 x 10 -15 g), high efficiency, low cost and easy to use. On the basis of measuring more than 700 samples taken along 20 sections in 8 deposits, the results show that the radium method is better than γ-measurement and equal to 210 Po method for the capability to descover anomalies. The author also summarizes the anomaly intensities of radium method, 210 Po method and γ-measurement respectively at the surface with deep blind ores, with or without surficial mineralization, and the figures of their profiles and the variation of Ra/ 210 Po ratios. According to the above-mentioned distinguishing features, the uranium mineralization located in deep and/or shallow parts can be distinguishd. The combined application of radium, 210 Po and γ-measurement methods may be regarded as one of the important methods used for anomaly assessment. Based on the experiments of the radium measurements with 771 stream sediments samples in an area of 100 km 2 , it is demonstrated that the radium mehtod can be used in the stages of uranium reconnaissance and prospecting

  2. Measurement of agglomerate strength distributions in agglomerated powders

    International Nuclear Information System (INIS)

    Ciftcioglu, M.; Aking, M.; Burkhart, L.

    1986-01-01

    Strength distributions of particle agglomerates in six different yttria powders were measured using a calibrated ultrasonic sound field. The density of sintered pellets was directly related to the agglomerate strength of each powder. No systematic relation to the sintered density was observed for bulk densities or pressure-density compaction data for the loose powders, or for pore size distributions or green densities for the pressed compacts

  3. Foam glass obtained through high-pressure sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    2018-01-01

    are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic......Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (106.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use...... a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N2) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies...

  4. Effect of powder sample granularity on fluorescent intensity and on thermal parameters in x-ray diffraction Rietveld analysis

    International Nuclear Information System (INIS)

    Sparks, C.J.; Specht, E.D.; Ice, G.E.; Kumar, R.; Zschack, P.; Shiraishi, T.; Hisatsune, K.

    1991-01-01

    The effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu 50 Au 44 Ni 6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity. A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30 degrees 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce >5 μm particles and high packing densities

  5. Properties of millimetre wave sintered and oxygenated YBa2Cu3Ox bulk material

    International Nuclear Information System (INIS)

    Hunyar, C.

    1999-12-01

    High temperature superconductors are ceramic materials whose properties strongly depend on the techniques used for their production. The successful use of microwaves for the sintering of other oxidic ceramics suggests the examination of the advantages and disadvantages of that production technique for superconductors. For this purpose pellets of commercially available YBa 2 Cu 3 O x powder from the Solvay company were pressed and sintered by millimetre wave heating (30 GHz, generated in a gyrotron). In various experiments the sintering temperatures were varied between 920 C and 990 C, and the holding times between 15 min and 240 min. The densities of the pellets were measured by the Archimedes method and the material structure was examined with an optical microscope. A strong densification from 86 to 93% of theoretical density could be observed within 30 min at a holding temperature of 960 C. With sintering temperatures above 960 C no significant increase in density occurred. At 950 C, only minor grain growth could be observed, which increased up to 960 C temperature. At higher temperatures a mixture of small grains and crystallites of about 150 μm size established itself. CuO already present in the original powder started to melt along the grain boundaries where it acts as a limiting factor for grain growth. With millimetre wave sintering the same material densities could be achieved in less than one third of the time needed for conventional sintering processes. In addition the effects of millimetre wave heating on the oxygen diffusion in YBCO were investigated with several pairs of identical samples. The pairs were deoxygenated and subsequently oxygenated in an atmosphere of pure O 2 in a conventional tube furnace and by millimetre wave heating respectively. To compare the oxygen concentration of the samples, their specific surface resistance at room temperature, which correlates with the oxygen content, was measured in a cylindrical copper resonator with

  6. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

    Full Text Available The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions and different atmospheres (i.e., defect chemistry on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT.

  7. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Science.gov (United States)

    Malič, Barbara; Koruza, Jurij; Hreščak, Jitka; Bernard, Janez; Wang, Ke; Fisher, John G.; Benčan, Andreja

    2015-01-01

    The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). PMID:28793702

  8. Orientation distribution in Bi2Te3-based compound prepared by spark plasma sintering

    International Nuclear Information System (INIS)

    Kim, K.T.; Kim, Y.H.; Lim, C.H.; Cho, D.C.; Lee, Y.S.; Lee, C.H.

    2005-01-01

    P-type Bi 0.5 Sb 1.5 Te 3 compounds doped with 3wt.% Te were fabricated by spark plasma sintering after mixing large powders(P L ) and small powders(P S ). We could obtained the highest figure of merit(Z C ) of 2.89 x 10 -3 /K in sintered compound mixed to P L :P S =80:20. This resulted from the increase of orientation by large powders(P S ) and the reduce of pores by small powders. The figure of merit(Z C ) of the sintered compound using only small powders(P S ) showed lower value of 2.67 x 10 -3 /K compared with that of sintered compound mixed to P L :P S =80:20 due to the increase of electrical resistivity. (orig.)

  9. 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.

  10. Laser Sintering Technology and Balling Phenomenon.

    Science.gov (United States)

    Oyar, Perihan

    2018-02-01

    The aim of this review was to evaluate the balling phenomenon which occurs typically in Selective Laser Sintering (SLS). The balling phenomenon is a typical SLS defect, and observed in laser sintered powder, significantly reduces the quality of SLS, and hinders the further development of SLS Technology. Electronic database searches were performed using Google Scholar. The keywords "laser sintering, selective laser sintering, direct metal laser melting, and balling phenomenon" were searched in title/abstract of publications, limited to December 31, 2016. The inclusion criteria were SLS, balling phenomenon, some alloys (such as Cr-Co, iron, stainless steel, and Cu-based alloys) mechanical properties, microstructure and bond strength between metal-ceramic crown, laboratory studies, full text, and in English language. A total of 100 articles were found the initial search and yielded a total of 50 studies, 30 of which did not fulfill the inclusion criteria and were therefore excluded. In addition, 20 studies were found by screening the reference list of all included publications. Finally, 40 studies were selected for this review. The method in question is regulated by powder material characteristics and the conditions of laser processing. The procedure of formation, affecting factors, and the mechanism of the balling effect are very complex.

  11. 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.

  12. Effect Of Compaction Pressure And Sintering Temperature On The Liquid Phase Sintering Behavior Of Al-Cu-Zn Alloy

    Directory of Open Access Journals (Sweden)

    Lee S.H.

    2015-06-01

    Full Text Available The liquid phase sintering characteristics of Al-Cu-Zn alloy were investigated with respect to various powder metallurgy processing conditions. Powders of each alloying elements were blended to form Al-6Cu-5Zn composition and compacted with pressures of 200, 400, and 600 MPa. The sintering process was performed at various temperatures of 410, 560, and 615°C in N2 gas atmosphere. Density and micro-Vickers hardness measurements were conducted at different processing stages, and transverse rupture strength of sintered materials was examined for each condition, respectively. The microstructure was characterized using optical microscope and scanning electron microscopy. The effect of Zn addition on the liquid phase sintering behavior during P/M process of the Al-Cu-Zn alloy was also discussed in detail.

  13. Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.

    Science.gov (United States)

    Nouri, A; Hodgson, P D; Wen, C E

    2010-04-01

    The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

  14. Corrosion Properties of Sintered and Wrought Stainless Seel

    DEFF Research Database (Denmark)

    Mathiesen, Troels; Maahn, Ernst Emanuel

    1997-01-01

    The corrosion properties of a range of stainless steels produced by powder metallurgy (PM) are compared with wrought AISI304 and AISI316 Steel. Characterisation of the passivation properties in 0.5M H2SO4 and pittingresistance in 0.3% chloride solution by polarisation show properties...... of the sintered PM150 that are comparable or better than those of wrought 316 steel depending on the applied sintering technique....

  15. Intense pulsed light sintering of copper nanoink for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hak-Sung; Dhage, Sanjay R.; Shim, Dong-Eun [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); Hahn, H.T. [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); University of California, Material Science and Engineering Department, California NanoSystems Institute, Los Angeles, CA (United States)

    2009-12-15

    An intense pulsed light (IPL) from a xenon flash lamp was used to sinter copper nanoink printed on low-temperature polymer substrates at room temperature in ambient condition. The IPL can sinter the copper nanoink without damaging the polymer substrates in extremely short time (2 ms). The microstructure of the sintered copper film was investigated using X-ray powder diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray micro tomography, and atomic force microscopy (AFM). The sintered copper film has a grainy structure with neck-like junctions. The resulting resistivity was 5{mu}{omega} cm of electrical resistivity which is only 3 times as high as that of bulk copper. The IPL sintering technique allows copper nanoparticles to be used in inkjet printing on low-temperature substrates such as polymers in ambient conditions. (orig.)

  16. Sysnthesis of powders by freeze-drying

    International Nuclear Information System (INIS)

    Johnson, S.M.; Gusman, M.I.; Hildenbrand, D.L.

    1988-01-01

    The freeze-drying method of synthesizing powders of the superconducting oxide YBa 2 Cu 3 O 7 - δ is described. This process produces homogeneous, submicron powders of high purity. The effects of salt selection, solution concentration and pH on the process are described. Some evaluation of the sintering behavior and the effects on critical current density are included

  17. Fabrication and properties of YBa2Cu3O7- x ceramics at different sintering temperatures

    Science.gov (United States)

    Prayoonphokkharat, Poom; Jiansirisomboon, Sukanda; Watcharapasorn, Anucha

    2013-07-01

    The influence of sintering temperatures on the fabrication of YBCO ceramics under normal air atmosphere was investigated in this study. YBCO ceramics were prepared by mixing starting compounds of Y2O3, BaCO3 and CuO powders, which were calcined at 850°C for 12 h. The powder was pelletized and sintered at different temperatures, from 930°C-1050°C, for 12 h. Phase identification was carried out by x-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study microstructure and chemical composition. In addition, density, Vickers hardness properties, the change of resistance and dielectric properties with temperature above T c were investigated. It was found that, at 950°C-1000°C, high-purity YBCO ceramic could be obtained. Outside this temperature range, either impurity phases were present or melting occurred. SEM images showed that grain size, which ranged from 1.5-2.5 µm, and hardness were related to density and liquid phase present in the sample. Furthermore, the sintering temperature affected oxygen content which, in turn, determined the conductive or semi-conductive behavior observed by electrical property measurement.

  18. Composites of amorphous and nanocrystalline Zr–Cu–Al–Nb bulk materials synthesized by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Drescher, P., E-mail: philipp.drescher@uni-rostock.de [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Witte, K. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Yang, B. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Steuer, R.; Kessler, O. [Chair of Materials Science, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Burkel, E. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Schick, C. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Seitz, H. [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany)

    2016-05-15

    The fabrication of Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} bulk metallic glass composite samples by spark plasma sintering (SPS) process has been successfully realized. The unique characteristics of bulk metallic glasses could lead to the possibility of future applications as new structural and functional materials. The densification of an amorphous Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} powder was realized in a systematic study changing the sintering temperature in the SPS process leading to stable composites characteristic of amorphous and nanocrystalline structures. X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis, transmission electron microscopy (TEM) as well as hardness tests were applied to determine the structural and mechanical properties of the sintered materials. A stable amorphous bulk metallic glass based on Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} with a low fraction of crystallites could be fabricated applying a nominal sintering temperature of 400 °C. Higher sintering temperatures lead to composites with high fractions of nanocrystalline material with porosities below 0.5%.

  19. Synthesis of Cu-CNTs nanocomposites via double pressing double sintering method

    Directory of Open Access Journals (Sweden)

    Marjan Darabi

    2018-01-01

    Full Text Available In this research, copper (Cu-carbon nanotubes (CNTs nanocomposites were synthesized with different weight percentages of CNTs by double pressing double sintering (DPDS method as well as conventional sintering method. A planetary ball mill was used to disperse CNTs in Cu matrix. The milled powders were first cold pressed to 450 MPa in a uniaxial stainless-steel die with cylindrical compacts (diameter: 12 mm and height: 5 mm. The effect of CNTs content and the DPDS method on the properties of the nanocomposites were investigated. The microstructure and phase analysis of Cu-CNTs nanocomposite samples were studied by FESEM and X-Ray Diffraction. The electrical conductivity of nanocomposites was measured and compared to both sintering methods. Mechanical properties of Cu-CNTs nanocomposites were characterized using bending strength and micro-hardness measurements. Enhancements of about 32% in bending strength, 31.6% in hardness and 19.5% in electrical conductivity of Cu-1 wt.% CNTs nanocomposite synthesized by DPDS method were observed as compared to Cu-1 wt.% CNTs nanocomposites fabricated under the similar condition by a conventional sintering process.

  20. Manufacturing of metal supported BSCF membranes by spark plasma sintering

    OpenAIRE

    Laptev, Alexander; Bram, Martin; Zivcec, Maria; Baumann, Stefan; Jarligo, Maria Ophelia; Sebold, Doris; Pfaff, Ewald; Broeckmann, Christoph

    2013-01-01

    Spark plasma sintering (SPS), also known as field assisted sintering technique (FAST), is a relatively new method for rapid consolidation of metallic or ceramic powders. In the present work, its suitability for the manufacturing of metal supported Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) based membrane by co-sintering of functional ceramic BSCF layer and porous metallic support has been investigated. The BSCF based membranes are highly attractive for oxygen separation from air due to mixed ionic and e...

  1. Cleanable sintered metal filters in hot off-gas systems

    International Nuclear Information System (INIS)

    Schurr, G.A.

    1981-01-01

    Filters with sintered metal elements, arranged as tube bundles with backflush air cleaning, are the equivalent of bag filters for high-temperature, harsh environments. They are virtually the only alternative for high-temperature off-gas systems where a renewable, highly efficient particle trap is required. Tests were conducted which show that the sintered metal elements installed in a filter system provide effective powder collection in high-temperature atmospheres over thousands of cleaning cycles. Such a sintered metal filter system is now installed on the experimental defense waste calciner at the Savannah River Laboratory. The experimental results included in this paper were used as the basis for its design

  2. Influence of sintering parameters in the ferroelectric properties os strontium bismuth tantalate samples obtained by oxide mixture; Estudo da influencia dos parametros de sinterizacao nas propriedades ferroeletricas de amostras de tantalato de bismuto - estroncio obtidas por mistura de oxidos

    Energy Technology Data Exchange (ETDEWEB)

    Souza, R.R. de; Pereira, A.S.; Sousa, V.C., E-mail: ricson.souza@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Egea, J.R.J. [Instituto de Ceramica y Vidrio (ICV/CSIC), Madrid (Spain)

    2012-07-01

    The family of compounds layered-type perovskite, know as Aurivilius presents great alternative not only by the absence of lead in the composition, but because the polarization retention, replacing PZT in FeRAM devices. The strontium bismuth tantalate (SrBi{sub 2}Ta{sub 2}O{sub 9}) or SBT is ferroelectric material that has attracted considerable interest, since it has high fatigue resistance, supporting high hysteresis loops, with the change in polarization.Checking polarization and depolarization currents stimulated by temperature it is possible to obtain, for example, information about the nature of charges and about the activation energy for the process of dielectric relaxation. For analysis of ferroelectric properties of this compound, it is essential to obtain specimens with a relative density around 95%. Thus, it is important the optimization of the sintering process in order to obtain a ceramic body with a high densification. The influence of sintering parameters to obtain SrBi{sub 2}Ta{sub 2}O{sub 9} in the polarization properties and in the microstructure of sintered samples was investigated by thermostimulated currents and electronic microscopy, respectively. Results show that variation of these parameters may cause changes in the ferroelectric properties of the material. (author)

  3. 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.

  4. Comminution of B4C powders with a high-energy mill operated in air in dry or wet conditions and its effect on their spark-plasma sinterability

    DEFF Research Database (Denmark)

    Ortiz, Angel L.; Sánchez-Bajo, Florentino; Leal, Victor Manuel Candelario

    2017-01-01

    to the nanoscale. While this is accompanied by oxidation and aggregation, these are not serious drawbacks. Wet shaker milling in methanol (i.e., conventional ball-milling) resulted only in a moderate B4C particle refinement with greater contamination by the milling tools, which limits its usefulness. It was also......-plasma sintering confirmed this recommendation, and also showed the usefulness of dry shaker milling to obtain refined B4C microstructures for structural applications....

  5. Effect of compacting pressure, powder degassing and thermobaric treatment on densification and properties of nanocrystalline titanium nitride

    Directory of Open Access Journals (Sweden)

    Andrei V. Kapylou

    2009-09-01

    Full Text Available The effects of compacting pressure, powder degassing and high pressure sintering temperature and time on the densification and properties of nanocrystalline titanium nitride have been investigated. For this reason, TiN powder with a mean particle size of 55 nm was pressed in the range of compacting pressure from 0.2 to 1.0 GPa and sintered under static pressure of 3.5 GPa in the temperature range of 900–1600°C for 45–120 s. Some of green bodies were degassed in vacuum before sintering. It was shown that samples compacted in the pressure range of 0.2–0.6 GPa have the highest density after the thermobaric treatment. The maximum density (about 97.3 %TD was obtained with degassed samples. Microhardness and microstructure investigations have shown that recrystallization of the TiN nanopowder begins at the sintering temperatures of 1100–1200°C and sintering time less than one minute. The maximum microhardness obtained was 23.2±1.0 GPa and themaximum Young modulus was 370 GPa.

  6. Effect of {alpha}-Si{sub 3}N{sub 4} Addition on Sintering of {alpha}-Sialon Powder via Carbonthermal Reduction Nitridation of Boron-rich Slag-based Mixture

    Energy Technology Data Exchange (ETDEWEB)

    Wu Junbin; Jiang Tao; Xue Xiangxin, E-mail: komsae@163.com [School of Materials and Metallurgy, Northeastern University, Shenyang (China)

    2011-10-29

    With boron-rich slag, silica fume, bauxite chalmette, carbon black and {alpha}-Si{sub 3}N{sub 4} as starting materials, {alpha}-Sialon powders were prepared by carbothermal reduction-nitridation(CRN). Different contents of {alpha}-Si{sub 3}N{sub 4} addition were added to investigate the {alpha}-Sialon formation as a function of {alpha}-Si{sub 3}N{sub 4} addition from boron rich slag based mixture fired at 1480 deg. C for 8 h under N{sub 2} flowing of 0.4 L/min. Phase assembly, microstructure of reaction products were determined by X-ray Diffraction and Scanning Electron Microscope. The results showed that the main phases of the samples were a-Sialon, h-BN, AlN and small quantity of SiC. With the increasing amount of the {alpha}-Si{sub 3}N{sub 4} addition, the h-BN content remained in a constant and AlN content was running down steadily, while the {alpha}-Sialon content increased gradually. The aspect ratio and the amount of elongated {alpha}-Sialon grains could be tailored by using different amounts of the {alpha}-Si{sub 3}N{sub 4} addition.

  7. Effect of sintering on crystallization and structural properties of soda lime silica glass

    Directory of Open Access Journals (Sweden)

    Zaid Mohd Hafiz Mohd

    2017-01-01

    Full Text Available The effect of sintering temperatures on crystallization and structural of the soda lime silica (SLS glass was reported. Elemental weight composition of the SLS glass powder was identified through Energy dispersive X-ray fluorescence (EDXRF analysis while the thermal behavior of the glass was determined using Differential thermal analysis (DTA technique. Archimedes’ method and direct geometric measurement were respectively used to determine bulk density and linear shrinkage of the glass samples. Crystallisation behavior of the samples was investigated by X-ray diffraction (XRD analysis and chemical bonds present in the samples were measured using Fourier Transform Infrared (FTIR spectroscopy. Results showed an increase in the density and linear shrinkage of the samples as a function of the sintering temperature. The XRD analysis revealed the formation of α-quartz (SiO2 and a minor amount of devitrite phases in the samples and these were further verified through the detection of chemical bonds by FTIR after sintering at 800ºC. The properties of the glass-ceramics can be explained on the basis of crystal chemistry which indicated that the alkali ions formed as carriers in the random network structure and can be recommended for the manufacture of glass fiber or toughened glass-ceramic insulators.

  8. Preparation and Characterization of Mg1-xB2 Bulk Samples and Cu/Nb Sheathed Wires with Low Grade Amorphous Boron Powder

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Alexiou, Aikaterini; Rubesova, Katerina

    2014-01-01

    MgB2 bulk and wire samples were prepared using cheap, low grade amorphous boron powders. Based on chemical analysis performed on the starting reagents, three nominal stoichiometries were studied. It was found that the structural and superconducting properties of the bulk samples were not affected...... by the composition, but that residual Mg was left in the wires for the nominal MgB2 composition. In contrast, slightly Mg-deficient compositions were free from residual Mg and exhibited higher critical current densities. The MgB2 phase formation kinetics was not influenced by the variations in the nominal powder...

  9. TiO2 doped UO2 fuels sintered by spark plasma sintering

    Science.gov (United States)

    Yao, Tiankai; Scott, Spencer M.; Xin, Guoqing; Lian, Jie

    2016-02-01

    UO2 fuels doped with oxide additives Cr2O3 and TiO2 display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO2-doped UO2 fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The grain size can reach 80 μm by sintering at 1700 °C for 20 min, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric fuel pellets upon SPS process. Thermal-mechanical properties of the sintered doped fuel pellets including thermal conductivity and hardness are measured and compared with undoped fuel pellets. The enlarged grain size (80 μm) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grained UO2 fuel pellets to improve fuel performance.

  10. Dosimetric and thermoluminescent characteristics of sintered samples based on Li{sub 2}OAl{sub 2}O{sub 3}nSiO{sub 2} systems

    Energy Technology Data Exchange (ETDEWEB)

    Cogollo P, R.; Salcedo Q, J. [Universidad de Cordoba, Materials and Applied Physics Group, Carrera 6 No. 76-103, Monteria, Cordoba (Colombia); Gutierrez F, O., E-mail: rafaelcogollo@correo.unicordoba.edu.co [Metropolitan Technological Institute, Alquimia Group, Calle 54 No. 30-01, Medellin (Colombia)

    2013-10-01

    This work describes the thermoluminescent (Tl) characteristics of lithium aluminosilicates, Li{sub 2}OAl{sub 2}O{sub 3}nSiO{sub 2}, for its possible use as Tl dosimeter for low doses. The sinterized tablets of Li{sub 2}OAl{sub 2}O{sub 3}nSiO{sub 2} were characterized by means of X-ray diffraction (XRD), and irradiated at different doses using a Theratron 780 C-{sup 60}Co unit in air at room temperature. The Rasheedy's technique was used for the kinetic trap parameters determination. The XRD results show a mixture of two phases of 64% {beta}-spodumene and 36% {beta}-eucryptite in the sinterized tablets. Tl analysis indicates that in these systems, recombination processes prevail, and that these systems can be used successfully as Tl dosimeters for therapeutic dose ranges. (Author)

  11. Effects of Milling Atmosphere and Increasing Sintering Temperature on the Magnetic Properties of Nanocrystalline Ni0.36Zn0.64Fe2O4

    Directory of Open Access Journals (Sweden)

    Abdollah Hajalilou

    2015-01-01

    Full Text Available Nanocrystalline Ni0.36Zn0.64Fe2O4 was synthesized by milling a powder mixture of Zn, NiO, and Fe2O3 in a high-energy ball mill for 30 h under three different atmospheres of air, argon, and oxygen. After sintering the 30 h milled samples at 500°C, the XRD patterns suggested the formation of a single phase of Ni-Zn ferrite. The XRD results indicated the average crystallite sizes to be 15, 14, and 16 nm, respectively, for the 30 h milled samples in air, argon, and oxygen atmospheres sintered at 500°C. From the FeSEM micrographs, the average grain sizes of the mentioned samples were 83, 75, and 105 nm, respectively, which grew to 284, 243, and 302 nm after sintering to 900°C. A density of all the samples increased while a porosity decreased by elevating sintering temperature. The parallel evolution of changes in magnetic properties, due to microstructural variations with changes in the milling atmosphere and sintering temperature in the rage of 500–900°C with 100°C increments, is also studied in this work.

  12. Development of a Master Sintering Curve for Al-Mg Alloy

    Directory of Open Access Journals (Sweden)

    Yong-Shin Lee

    2016-01-01

    Full Text Available A new master sintering curve (MSC is proposed for Al-Mg alloy in order to effectively design the pressure-assisted sintering process. In this work, hot pressing experiments of Al-Mg alloy powders are performed. The changes of relative density during hot pressing are measured for the various heating rates of 5°C/min, 10°C/min, and 20°C/min at the fixed pressure of 50 MPa. A work of sintering, designated as Θ, is introduced and defined as Θ(t,T=∫0t1/Texp-Q/RTdt. A work of sintering, Θ, could be interpreted as a measure for the amount of sintering work. The MSC in this work defines the relation between the apparent density and a work of sintering, Θ. Since the measurement of an apparent activation energy, Q, is very difficult, the correct value of Q is obtained numerically using a mean residual square method. Then, the master sintering curves for sintering of Al-Mg alloy powders are proposed for the sintering temperatures of 400°C and 500°C through scaling procedures. It is expected that the master sintering curves proposed in this work could help an engineer to design pressure-assisted sintering process for Al-Mg alloy.

  13. The Influence of Sintering Temperature toward Density and Strength of Plastic-Ruber Composite

    Directory of Open Access Journals (Sweden)

    Heru Sukanto

    2012-11-01

    Full Text Available The research investigates the effect of sintering temperature on density and mechanical properties of HDPE-rubbercomposite which was produced by pressured sintering methodThe materials that were used are HDPE plastic waste of oilbottle and unused tire. These materials were powdered via mechanical grinding manually. The powder size of -20 mesh wasselected as a raw material for specimen. Producing the specimens involved powder technology. Pressured sintering processwas commited for 5 minutes under pressure load of 1 MPa. The sintering temperature was variated along 110 to 140oC byincreasing 10oC incrementally. Specimen testing involved density, bending strength and izot impact strength. All of testingwas conducted on ASTM standard testing.The result reveals that increasing sintering temperature will grow up the density,bending strength and impact strength of specimen up to 10%, 12% and 72% respectively. The extreme increasing ofspecimen properties occurs at the temperature range of 120 to 130oC..

  14. 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...

  15. A method for sintering

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides a method for sintering, comprising in the following order the steps of: providing a body in the green state or in the pre-sintered state on a support; providing a load on at least one spacer on the support such that the load is located above said body in the green...

  16. The Influence of Milling and Spark Plasma Sintering on the Microstructure and Properties of the Al7075 Alloy

    Directory of Open Access Journals (Sweden)

    Orsolya Molnárová

    2018-04-01

    Full Text Available The compact samples of an Al7075 alloy were prepared by a combination of gas atomization, high energy milling, and spark plasma sintering. The predominantly cellular morphology observed in gas atomized powder particles was completely changed by mechanical milling. The continuous-like intermetallic phases present along intercellular boundaries were destroyed; nevertheless, a small amount of Mg(Zn,Cu,Al2 phase was observed also in the milled powder. Milling resulted in a severe plastic deformation of the material and led to a reduction of grain size from several µm into the nanocrystalline region. The combination of these microstructural characteristics resulted in abnormally high microhardness values exceeding 300 HV. Consolidation through spark plasma sintering (SPS resulted in bulk samples with negligible porosity. The heat exposition during SPS led to precipitation of intermetallic phases from the non-equilibrium microstructure of both gas atomized and milled powders. SPS of the milled powder resulted in a recrystallization of the severely deformed structure. An ultra-fine grained structure (grain size close to 500 nm with grains divided primarily by high-angle boundaries was formed. A simultaneous release of stored deformation energy and an increase in the grain size caused a drop of microhardness to values close to 150 HV. This value was retained even after annealing at 425 °C.

  17. A new method to fabricate Fe-TiC composite using conventional sintering and steam hammer

    OpenAIRE

    LAHOUEL, Ali; BOUDEBANE, Saïd; IOST, Alain; MONTAGNE, Alex

    2017-01-01

    International audience; The aim of this research paper is to fabricate a Fe-TiC composite by a novel and simple manufacturing method. The latter is based on two cumulative processes; a conventional sintering (transient liquid phase sintering) and a hot forging with steam hammer respectively. The blinder phase of the studied simples is varied from carbon steel to high alloy steel using alloying additive powders. The obtained outcomes showed that after the sintering process, the relative densit...

  18. Microstructure and mechanical properties of a new group of nanocrystalline medical-grade stainless steels prepared by powder metallurgy

    International Nuclear Information System (INIS)

    Javanbakht, M.; Hadianfard, M.J.; Salahinejad, E.

    2015-01-01

    Highlights: • This paper focuses on the structure and mechanical properties of PM alloys. • A eutectic Mn–Si alloy sintering aid was successfully used. • Mechanical properties were improved by adding the sintering aid. - Abstract: This paper focuses on the structure and mechanical properties of powder metallurgy stainless steels (Fe–Cr–Mn–Mo–Si–N–C) developed for biomedical applications. The samples were prepared by mechanical alloying and subsequent liquid-phase sintering with a eutectic Mn–Si alloy additive. By changing the sintering aid content, the pore configuration, compressive strengths, and impact properties of the samples were assessed. The Rietveld X-ray diffraction analysis showed after sintering at 1050 °C for 60 min followed by water-quenching, a nanocrystalline austenitic structure was formed in the material. According to the mechanical experiments, by increasing the additive content from 0 wt% to 6 wt%, sintering densification, yield stress, compression strength, and absorbed impact energy were improved, where spoiling occurred when adding 8 wt% additive. Also, as realized from the impact fracture surface features, despite the presence of some unmelted additive particles, the role of the pore elimination in toughness prevailed over that of these particles

  19. 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.

  20. Synthesis and Spark Plasma Sintering of Soft Magnetic Composite in a Fe₂O₃–Al System by Mechanical Alloying.

    Science.gov (United States)

    Lee, Chung-Hyo

    2017-04-01

    We have applied mechanical alloying (MA) to produce soft magnetic composite material using a mixture of elemental Fe₂O₃–Al powders. An optimal milling and sintering conditions to obtain soft magnetic α-Fe/Al₂O₃ composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimeter and vibrating sample magnetometer measurements. It is found that the average grain sizes of α-Fe in α-Fe/Al₂O₃ composite ball-milled for 5 hours is estimated to be in the range of 50 nm. The saturation magnetization of ball-milled powders showed a maximum value of 88 emu/g after 30 min. of MA and reaches to 77 emu/g after 5 h of MA. The magnetic hardening due to the reduction of the α-Fe grain size with ball milling was also observed. Densification of the ball-milled powders was performed in the spark plasma sintering (SPS) machine at 1000 °C and 1100 °C. FE-SEM observation shows that the average grain size of α-Fe in α-Fe/Al₂O₃ composite sintered at 1000 °C is in the range of 100 nm, which is nearly same value estimated from the so-called Hall plot. It can be also seen that the coercivity of SPS sample sintered at 1000 °C is still high value of 92 Oe, suggesting that the grain growth of magnetic α-Fe phase during SPS process tends to be suppressed.

  1. Finite element modeling and numerical simulation of sintered tungsten components under hydrogen atmosphere

    Science.gov (United States)

    Mamen, B.; Song, J.; Barriere, T.; Gelin, J.-C.

    2013-05-01

    Powder injection molding (PIM) is a suitable technology for manufacturing of complex shapes with tungsten powders and has a great potential in many applications. Sintering is one of the most important steps in Powder Injection Molding process. The sintering behaviour of tungsten injection moulded components, under pure hydrogen atmosphere at temperature up to 1700°C using fine 0.4μm and coarse powders 7.0 μm, is investigated by means of the beam bending and dilatometric tests in the Setaram{copyright, serif} analyser. To simulate the shrinkage and shape distortion of tungsten injection moulded components during the sintering process using finite element methods, viscoplastic constitutive law is implemented in ABAQUS software as user subroutine UMAT and incorporated with the identified parameters. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows good agreement between the two.

  2. 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. ...

  3. Mechanistic evaluation of the effect of sintering on Compritol 888 ATO matrices

    DEFF Research Database (Denmark)

    Rao, Monica; Ranpise, Anuradha; Borate, Sameer

    2009-01-01

    transform infrared spectroscopy results did not show any drug-wax interaction due to sintering. Differential scanning calorimetric and powder X-ray diffraction studies ruled out the occurrence of solid solution and polymorphic changes of the drug. Drug release from the wax tablets with or without sintering...... was best described by the Higuchi equation....

  4. Thermoelectric properties of SiC/C composites from wood charcoal by pulse current sintering

    NARCIS (Netherlands)

    Fujisawa, M; Hata, T; Bronsveld, P; Castro, [No Value; Tanaka, F; Kikuchi, H; Imamura, Y

    2005-01-01

    SiC/C composites were investigated by sintering a mix of wood charcoal and SiO2 powder (32-45 mu m) at 1400, 1600 and 1800 degrees C under N-2 atmosphere with a pulse current sintering method. Thermoelectric properties of SiC/C composites were investigated by measuring the Seebeck coefficient and

  5. The effect of particle size distributions on the microstructural evolution during sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

    2013-01-01

    Microstructural evolution and sintering behavior of powder compacts composed of spherical particles with different particle size distributions (PSDs) were simulated using a kinetic Monte Carlo model of solid state sintering. Compacts of monosized particles, normal PSDs with fixed mean particle ra...

  6. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Unknown

    the use of sintering aids. In the meantime, Prochazka. (1975) reported that with addition of boron and carbon to submicron size β-SiC, sintering of silicon carbide to near theoretical density was achieved. He proposed that during the firing of pure submicron powders of covalently bonded solids, densification is prevented by a ...

  7. DC resistivity of alumina and zirconia sintered with TiC

    Indian Academy of Sciences (India)

    Unknown

    Abstract. 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 ...

  8. 3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields

    Directory of Open Access Journals (Sweden)

    Dan Kang

    2014-01-01

    Full Text Available In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  9. Effects of sintering process on wear and mechanical behavior properties of titanium carbide/hexagonal boron nitrid/steel 316L base nanocomposites

    Science.gov (United States)

    Sadooghi, Ali; Payganeh, Gholamhassan

    2018-02-01

    Powder metallurgy process is one of the approaches to manufacture nanocomposite samples, in which the product quality depends upon the pressure, temperature, and sintering time. In this manuscript, steel is selected as the base material together with 2% carbon-based reinforcing TiC particles, and 2% hBN particles as the self-lubricant material. The powders were mixed for 5 h in high ball milling, and compacted with two pressures of 350 and 450 MPa, sintered in the furnace for 2 and 4 h, and sintering temperatures of 1350 and 1450 °C were utilized. SEM, XRD, and EDX tests are performed to identify the nanocomposite structure, and DTA tests are carried out to specify the temperature graph of the material. Finally, hardness, wear, and bending tests are done to find the corresponding mechanical properties of the samples. As a result, the optimum process parameters, including pressure, temperature and sintering duration is achieved. Results show that adding the reinforcing particles into a steel matrix increase the hardness, as well as flexural strength of the nanocomposite product. Also, coefficient of friction shows a decreases.

  10. Hybrid Powder - Single Crystal X-Ray Diffraction Instrument for Planetary Mineralogical Analysis of Unprepared Samples, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a planetary exploration XRD/XRF instrument based on a hybrid diffraction approach that complements powder XRD analysis, similar to that of the...

  11. Rapid identification of Bacillus anthracis spores in suspicious powder samples by using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).

    Science.gov (United States)

    Dybwad, Marius; van der Laaken, Anton L; Blatny, Janet Martha; Paauw, Armand

    2013-09-01

    Rapid and reliable identification of Bacillus anthracis spores in suspicious powders is important to mitigate the safety risks and economic burdens associated with such incidents. The aim of this study was to develop and validate a rapid and reliable laboratory-based matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis method for identifying B. anthracis spores in suspicious powder samples. A reference library containing 22 different Bacillus sp. strains or hoax materials was constructed and coupled with a novel classification algorithm and standardized processing protocol for various powder samples. The method's limit of B. anthracis detection was determined to be 2.5 × 10(6) spores, equivalent to a 55-μg sample size of the crudest B. anthracis-containing powder discovered during the 2001 Amerithrax incidents. The end-to-end analysis method was able to successfully discriminate among samples containing B. anthracis spores, closely related Bacillus sp. spores, and commonly encountered hoax materials. No false-positive or -negative classifications of B. anthracis spores were observed, even when the analysis method was challenged with a wide range of other bacterial agents. The robustness of the method was demonstrated by analyzing samples (i) at an external facility using a different MALDI-TOF MS instrument, (ii) using an untrained operator, and (iii) using mixtures of Bacillus sp. spores and hoax materials. Taken together, the observed performance of the analysis method developed demonstrates its potential applicability as a rapid, specific, sensitive, robust, and cost-effective laboratory-based analysis tool for resolving incidents involving suspicious powders in less than 30 min.

  12. Ultra-fast microwave sintering of PZT/FCO particulate composites prepared by ultrasonic mixing; Sinterizacao ultrarrapida por micro-ondas de compositos particulados PZT/FCO preparados por mistura em ultrassom

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, C.P.; Zabotto, F.L.; Garcia, D.; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2017-07-15

    Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3} (PZT) and Fe{sub 2}CoO{sub 4} (FCO) powders were synthesized separately by the Pechini method and then ultrasonically mixed in molar proportions of 80/20 and 50/50 of PZT/FCO. The resulting composites were pressed and subjected to conventional and ultrafast microwave-assisted sintering. The structure and microstructure of the sintered samples were analyzed, respectively, by X-ray diffraction and scanning electron microscopy. The dielectric constant as a function of temperature, electrical resistivity and magnetoelectric coupling coefficient were measured. The results indicated that the ultrasonic mixing method applied to PZT and FCO was fast and efficient, and that sintering resulted in globally connected (0-3) particulate composites and uniform distribution of the ferromagnetic phase (FCO) grains in the ferroelectric matrix (PZT). The structural analysis indicated that microwave sintering changed the arrangement (1-3) of the material's local connectivity, which was attributed to the intensification of diffusion processes that occur in this type of sintering, particularly in nanometric systems. The high values of resistivity indicated that although both sintering methods preserved the integrity of the two phases, microwave sintering was more efficient, ensuring the magnetoelectric behavior of all the composites under study. The values of H{sub max} field were dependent on the ferrite phase concentration and sintering; 80/20 1.4 and 1.9 kOe, and 50/50 3.5 and 3.0 kOe in the samples sintered by microwave and conventionally, consistent with the literature, which confirmed the integrity of the constituent phases PZT and FCO. (author)

  13. Evaluation of aluminosilicate glass sintering during differential scanning calorimetry

    International Nuclear Information System (INIS)

    Souza, Juliana Pereira de

    2015-01-01

    In this work a difference in the baseline in differential scanning calorimetry analyses, observed in a work where aluminosilicate glasses microspheres containing Ho were studied for application in selective internal radiotherapy as hepatocellular carcinoma treatment, was studied. The glasses with nominal composition 53,7 SiO 2 .10,5 Al 2 O 3 . 35,8 MgO in %mol were produced from traditional melting. The first obtained were milled and sieved in the range of 45 a 63 μm. The material was used to produce glass microspheres by the gravitational fall method. The glass powder and the microspheres were characterized by X ray fluorescence spectrometry, laser diffraction, X ray diffraction, differential scanning calorimetry, differential thermal analysis, thermogravimetry, mass spectrometry, and scanning electron microscopy. After the thermal analyses, pellets were formed in the crucibles and were analyzed by scanning electron microscopy, X ray diffraction, and He pycnometry. The difference in the baseline was associated to the viscous flow sintering process and happens because of the decrease in the detected heat flow due to the sample shrinkage. Other events as concurrent crystallization with the sintering process were also studied. (author)

  14. 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.

  15. Enhanced infrared transmittance properties in ultrafine MgAl2O4 nanoparticles synthesised by a single step combustion method, followed by hybrid microwave sintering

    Science.gov (United States)

    Mathew, C. T.; Vidya, S.; Koshy, Jacob; Solomon, Sam; Thomas, Jijimon K.

    2015-09-01

    Infrared transparent ceramics found to have potential applications as infrared windows and domes in strategic defence and space missions. Synthesis of ultrafine nanostructured MgAl2O4 ceramics by a modified single step auto-igniting combustion technique, followed by sintering of the sample by resistive and resistive-microwave hybrid heating to high density and their excellent infrared transmission characteristics are presented in this paper. Structural characterisations of MgAl2O4 nanoparticles reveal that the as prepared powder is phase pure, with average crystallite size ∼15 nm and possess a cubic structure. Optical band gap calculated using the Kubelka-Munk method is 5.75 eV. The thermal stability of the nanopowder at elevated temperatures has been studied using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). Hybrid heating yield a substantial reduction in sintering temperature and soaking time relative to the conventional resistive heating, and the samples achieved >99% density by microwave-resistive hybrid heating. Scanning electron micrograph (SEM) showed that the pellets are well sintered. The pellet sintered by hybrid heating showed a better transmittance of ∼79% in the UV-Visible region and ∼82% in the mid IR region compared to pellet sintered by resistive heating which has ∼68% in the UV-Visible region and ∼66% in the mid IR region. The results confirm the effective use of nanocrystalline powders from modified combustion synthesis as starting material for the development of high quality IR transparent windows and domes. In addition the microwave hybrid sintering technique employed in the present study also contributes to the results of better transmittance characteristics in highly densified MgAl2O4 ceramic pellets.

  16. Microwave synthesis and sintering characteristics of CaCu 3 Ti 4 O 12

    Indian Academy of Sciences (India)

    CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2.45 GHz, 1.1 kW. The optimum calcination temperature using microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were sintered to 94% density at 1000°C/60 min.

  17. Influence of the raw-material characteristics on mullite-zirconia composites obtained by reactions sintering

    International Nuclear Information System (INIS)

    Emiliano, J.V.; Segadaes, A.M.B.C.

    1989-01-01

    A number of authors have shown that there are some difficulties in preparing mullite-zirconia composites with good thermomechanical properties through reaction-sintering of Al 2 O 3 and ZrSiO 4 powders. The present work was aimed at investigating the effect of the characteristics of the alumina powders on the reaction-sintering behaviour, microstructural development and final properties of the composites prepared by conventional processes. The results obtained showed that the use of high purity reactive powders, supposed to yield enhanced properties can be overshadowed when conventional techniques of powder processing are used, as these give rise to microstructural inhomogeneities [pt

  18. Fabrication and Characterization of Thermoelectric Fe2VAl Alloy Powders by Mechanical Alloying.

    Science.gov (United States)

    Lee, Chung-Hyo

    2015-01-01

    A mixture of elemental Fe50V25Al25 powders has been subjected to mechanical alloying (MA) at room temperature to prepare the Heusler Fe2VAl thermoelectric alloy. Fe2VAI alloy with a grain size of 90 nm can be obtained by MA of Fe50V25Al25 powders for 60 h and subsequently annealed at 700 degrees C. Consolidation of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 900-1000 degrees C under 60 MPa. The shrinkage of consolidated samples during SPS was significant at about 400 degrees C. X-ray diffraction data shows that the SPS compact from 60 h MA powders consolidated up to 900 degrees C consists of only nanocrystalline Fe2VAl alloy with a grain size of 200 nm.

  19. Low temperature fabrication of magnesium phosphate cement scaffolds by 3D powder printing.

    Science.gov (United States)

    Klammert, Uwe; Vorndran, Elke; Reuther, Tobias; Müller, Frank A; Zorn, Katharina; Gbureck, Uwe

    2010-11-01

    Synthetic bone replacement materials are of great interest because they offer certain advantages compared with organic bone grafts. Biodegradability and preoperative manufacturing of patient specific implants are further desirable features in various clinical situations. Both can be realised by 3D powder printing. In this study, we introduce powder-printed magnesium ammonium phosphate (struvite) structures, accompanied by a neutral setting reaction by printing farringtonite (Mg(3)(PO(4))(2)) powder with ammonium phosphate solution as binder. Suitable powders were obtained after sintering at 1100°C for 5 h following 20-40 min dry grinding in a ball mill. Depending on the post-treatment of the samples, compressive strengths were found to be in the range 2-7 MPa. Cytocompatibility was demonstrated in vitro using the human osteoblastic cell line MG63.

  20. Improvement of mechanical strength of sintered Mo alloyed steel by optimization of sintering and cold-forging processes with densification

    Science.gov (United States)

    Kamakoshi, Y.; Shohji, I.; Inoue, Y.; Fukuda, S.

    2017-10-01

    Powder metallurgy (P/M) materials have been expected to be spread in automotive industry. Generally, since sintered materials using P/M ones contain many pores and voids, mechanical properties of them are inferior to those of conventional wrought materials. To improve mechanical properties of the sintered materials, densification is effective. The aim of this study is to improve mechanical strength of sintered Mo-alloyed steel by optimizing conditions in sintering and cold-forging processes. Mo-alloyed steel powder was compacted. Then, pre-sintering (PS) using a vacuum sintering furnace was conducted. Subsequently, coldforging (CF) by a backward extrusion method was conducted to the pre-sintered specimen. Moreover, the cold-forged specimen was heat treated by carburizing, tempering and quenching (CQT). Afterwards, mechanical properties were investigated. As a result, it was found that the density of the PS specimen is required to be more than 7.4 Mg/m3 to strengthen the specimen by heat treatment after CF. Furthermore, density and the microstructure of the PS specimen are most important factors to make the high density and strength material by CF. At the CF load of 1200 kN, the maximum density ratio reached approximately 99% by the use of the PS specimen with proper density and microstructure. At the CF load of 900 kN, although density ratio was high like more than 97.8%, transverse rupture strength decreased sharply. Since densification caused high shear stress and stress concentration in the surface layer, microcracks occurred by the damages of inter-particle sintered connection of the surface layer. On the contrary, in case of the CF load of 1200 kN, ultra-densification of the surface layer occurred by a sufficient plastic flow. Such sufficient compressed specimens regenerated the sintered connections by high temperature heat treatment and thus the high strength densified material was obtained. These processes can be applicable to near net shape manufacturing

  1. Sintering of beryllium oxide

    International Nuclear Information System (INIS)

    Caillat, R.; Pointud, R.

    1955-01-01

    This study had for origin to find a process permitting to manufacture bricks of beryllium oxide of pure nuclear grade, with a density as elevated as possible and with standardized shape. The sintering under load was the technique kept for the manufacture of the bricks. Because of the important toxicity of the beryllium oxide, the general features for the preliminary study of the sintering, have been determined while using alumina. The obtained results will be able to act as general indication for ulterior studies with sintering under load. (M.B.) [fr

  2. Preliminary study of sintering of metallic niobium processed for mechanical milling; Estudo preliminar da sinterizacao de niobio metalico processado por moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Tamura, H.M.; Vurobi Junior, S.; Cintho, O.M., E-mail: lenatamura@interponta.com.b [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil); Sandim, H.R.Z.; Leite, G.S. [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia

    2010-07-01

    In present study was preliminary study of mechanical milling influence on preparing of metallic niobium powder for sintering. Sample of metallic niobium in powder passing in sieve no. 635 mesh was processed by mechanical milling in SPEX mill for 8 hours using power grinding of 7:1 and a nitrogen atmosphere. The powder was annealed at different temperatures, 900 deg C, 1000 deg C, 1100 deg C and 1200 deg C for 1 hour in an atmosphere of hydrogen and argon to study their crystallization, which then were formed into blank for analysis of the curves compressibility. These samples were also subjected to x-ray diffraction in that their data were compared between the annealing temperatures. We also evaluate the compressibility curves of niobium samples with and without grinding these samples were subjected to x-ray diffraction and fluorescence. (author)

  3. Effect of sintering temperature on structural and electrical properties ...

    Indian Academy of Sciences (India)

    TECS

    vity measurement. The crystallinity and surface morphology of the samples improved with sintering tempera- ture. Further, the electrical conductivity measurement indicated that the conduction mechanism is mainly ionic. The conductivity of samples sintered at 1673 K and 1773 K at 800°C are of the order of 0⋅1 S-cm. –1.

  4. Sintered soft magnetic materials. Properties and applications

    Science.gov (United States)

    Bas, J. A.; Calero, J. A.; Dougan, M. J.

    2003-01-01

    A comparison is presented of the characteristics and production requirements of a variety of materials used to produce sintered soft magnetic parts. These include pure iron, phosphorous-iron, silicon-iron, nickel-iron, and cobalt-iron, together with new coated materials based on encapsulated iron powders. In these bonded materials an organic and/or inorganic insulator is used to coat the metallic powder particles giving a magnetic composite. The suitability of the different materials for use in both direct and alternating current applications is reviewed, and examples are provided of their application in both the automotive and other sectors. The results of a comparative study of motors using stators and rotors based on both conventional laminated materials and the insulated iron powders are presented, in which the new materials show advantages of reduced hysteresis losses at high frequencies, and isotropy of magnetic properties. Nevertheless, the applications of these materials in electrical motors requires the modification of existing designs.

  5. 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.

  6. Fabrication of 200 mm Diameter Sintering Body of Skutterudite Thermoelectric Material by Spark Plasma Sintering

    Science.gov (United States)

    Tomida, T.; Sumiyoshi, A.; Nie, G.; Ochi, T.; Suzuki, S.; Kikuchi, M.; Mukaiyama, K.; Guo, J. Q.

    2017-05-01

    Filled skutterudite is a promising material for thermoelectric power generation because its ZT value is relatively high. However, mass production of high-performance thermoelectric materials remains a challenge. This study focused on the sintering process of thermoelectric materials. Large-diameter n-type (Yb or La, Ca, Al, Ga, In)0.8(Co, Fe)4Sb12 skutterudite sintering bodies with a small thickness were successfully produced by the spark plasma sintering (SPS) method. When direct current flows through the thermoelectric sintering body during the SPS pulse, the Peltier effect causes a temperature difference within the sintering body. To eliminate the Peltier effect, an electrical insulating material was inserted between the punch (electrode) and the sintering body. In this way, an n-type La-filled skutterudite sample with a diameter of 200 mm, thickness of 21 mm, and weight of 5 kg was successfully produced. The thermoelectric properties and microstructures of the sample were almost the same throughout the whole sintering body, and the dimensionless figure of merit reached 1.0 at 773 K.

  7. Net shape fabrication of stainless-steel micro machine components from metallic powder

    International Nuclear Information System (INIS)

    Imbaby, M; Jiang, K; Chang, I

    2008-01-01

    A fabrication process of the net shape 316-L stainless-steel micro machine components is reported. The fabrication process combines softlithography and powder metallurgy to produce microcomponents of complex geometries of high quality. The process starts with softlithography by producing ultra thick SU-8 master moulds and their negative replicas of polydimethylsiloxane (PDMS). Then stainless-steel slurry is prepared by mixing super fine 316-L steel powder and binder to fill the PDMS moulds. The two binders used in the experiments were Duramax D-3005 and a mixture of B1000 and B1007. The PDMS micro moulds are filled with the metallic slurries and green parts are obtained from de-moulding, before going through de-binding and sintering in forming gas atmosphere. The fabrication steps were repeatedly tested. The resultant micro parts show high quality shape retention which is attributed to the quality of the SU-8 master moulds. The hardness property of the sintered microcomponents was tested with a micro indenter and a 200 g load was applied. The Vickers hardness of the sintered components was found to be about 255, which was higher than 225 of annealed 316L stainless steel and the two binders make little difference on the hardness of the sintered samples

  8. Development of Cu-Be bronzes through powder metallurgy

    International Nuclear Information System (INIS)

    Abbas, M.

    2012-01-01

    Copper and copper alloys are the major group of commercial alloy. One of the important copper bronzes is Copper beryllium. This is unique among all engineering alloys. Copper beryllium alloy possesses the highest strength in all the copper base alloys. Development of copper beryllium alloy with powder metallurgy is challenging problem due to toxicity of beryllium dust. Purpose of this project to find out parameters by which copper beryllium with all unique properties should obtained. For this purpose efforts are put on development of alternative to copper beryllium system like copper-tin and copper-aluminum by powder metallurgy route. Different time of milling with uniaxial pressure of about 200 MPa and different sintering temperature according to phase diagram of alloy, with different soaking time is tried. Problems may occur like decrease in density after sintering, breaking of samples by Rockwell A, B and C indenters arid by hammering. Cold iso-static pressing at 300 MPa and sintering at above 900 degree C is used to develop copper beryllium alloy. As quenched samples are heat treated at 260 degree C, 315 degree C and 370 degree C with different soaking time of 30, 90 and 180 minutes to find out optimum time and temperature parameters. . It is observed that at aging at 260 degree C for 180 minutes, aging at 315 degree C for 180 minutes and aging at 370 degree C for 30 minutes produce optimum result. By observing these pellets by SEM, precipitates appeared in peak-aged alloy and bigger precipitates in over-aged alloy. Copper beryllium alloy developed through powder metallurgy has better prospects than other copper bronzes. (author)

  9. Sintering Behavior, Microstructure, and Mechanical Properties: A Comparison among Pressureless Sintered Ultra-Refractory Carbides

    Directory of Open Access Journals (Sweden)

    Laura Silvestroni

    2010-01-01

    Full Text Available Nearly fully dense carbides of zirconium, hafnium, and tantalum were obtained by pressureless sintering at 1950°C with the addition of 5–20 vol% of MoSi2. Increasing the amount of sintering aid, the final density increased too, thanks to the formation of small amounts of liquid phase constituted by M-Mo-Si-O-C, where M is either Zr, Hf, or Ta. The matrices of the composites obtained with the standard procedure showed faceted squared grains; when an ultrasonication step was introduced in the powder treatment, the grains were more rounded and no exaggerated grains growth occurred. Other secondary phases observed in the microstructure were SiC and mixed silicides of the transition metals. Among the three carbides prepared by pressurless sintering, TaC-based composites had the highest mechanical properties at room temperature (strength 590 MPa, Young's modulus 480 GPa, toughness 3.8 MPa·m1/2. HfC-based materials showed the highest sinterability (in terms of final density versus amount of sintering aid and the highest high-temperature strength (300 MPa at 1500  °C.

  10. Powder metallurgical processing and metal purity: A case for ...

    Indian Academy of Sciences (India)

    The paper reviews the role of sintered tantalum as volumetric efficient electrical capacitor. Powder characteristics and sintering aspects are discussed. The role of impurities in influencing the electrical properties has been described. Today's driving force behind the Ta market is the use of surface mounted versions known as ...

  11. Analysis of Laser Sintering Technology

    Directory of Open Access Journals (Sweden)

    Vladislav Markovič

    2014-02-01

    Full Text Available The new, high-tech development and customization is one ofthe most important factors in promoting the country‘s economicgrowth indicators. The economic downturn in the industryrequires technology and equipment using a minimumof raw materials and providing maximum performance. Thisstatement perfectly describes the innovative, forward-looking,cost-effective laser powder sintering (SLS technology. Here,thanks to the latest engineering achievements, product surfacesare modified and improved, they gain new characteristics. SLSis viable in automobile, engineering, construction, aerospace,aircraft, printing, medical and other areas.In order to create a product which meets the standards andtechnical documentation it is necessary to use and ensure highquality of raw materials, high-end equipment, qualified personnel,the working environment with proper climatic conditions, ergonomics,etc. But all of these, the quality of the product becomesthe decisive indicators meaningless if know how to properly selectthe laser processing operation. Scanning speed, beam power,pulse frequency, protective gases, powder layer thickness – allof them are the physical and mechanical characteristics of thechange in a small range changes the quality of the product of thefuture, the field of application and performance characteristics.

  12. Reactive Sintering of Bimodal WC-Co Hardmetals

    Directory of Open Access Journals (Sweden)

    Marek Tarraste

    2015-09-01

    Full Text Available Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal hardmetal has perspective for demanding wear applications for its increased combined hardness and toughness. Compared to coarse material there is only slight decrease in fracture toughness (K1c is 14.7 for coarse grained and 14.4 for bimodal, hardness is increased from 1290 to 1350 HV units.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7511

  13. Simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by slurry-sampling graphite furnace AAS.

    Science.gov (United States)

    Minami, Hirotsugu; Yada, Masako; Yoshida, Tomomi; Zhang, Qiangbin; Inoue, Sadanobu; Atsuya, Ikuo

    2004-03-01

    A fast and accurate analytical method was established for the simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by graphite furnace atomic absorption spectrometry using a slurry sampling technique and a Hitachi Model Z-9000 atomic absorption spectrometer. The slurry samples were prepared by the ultrasonication of silicon carbide or silicon nitride powders with 0.1 M nitric acid. Calibration curves were prepared by using a mixed standard solution containing aluminum, calcium, iron and 0.1 M nitric acid. The analytical results of the proposed method for aluminum, calcium and iron in silicon carbide and silicon nitride reference materials were in good agreement with the reference values. The detection limits for aluminum, calcium and iron were 0.6 microg/g, 0.15 microg/g and 2.5 microg/g, respectively, in solid samples, when 200 mg of powdered samples were suspended in 20 ml of 0.1 M nitric acid and a 10 microl portion of the slurry sample was then measured. The relative standard deviation of the determination of aluminum, calcium and iron was 5 - 33%.

  14. Effect of sintering temperature and heating mode on consolidation of ...

    Indian Academy of Sciences (India)

    sintering of various Al-based composites. Microwave heat- ing of metallic powders (Al–Cu–Fe) to single phase was first reported by Vauchera et al (2008). To the best of our know- ... insulation also consisted of graphite coated SiC rods. Tem- perature ... Figure 3 compares thermal profile for 7775 aluminum alloy compacts ...

  15. Effect of sintering on controlled release profile of diltiazem ...

    African Journals Online (AJOL)

    The study was designed to formulate and evaluate diltiazem hydrochloride wax matrix tablets for controlled release using sintering technique. Granules of diltiazem hydrochloride-wax were prepared by melt granulation technique. This was formed by triturating the drug powder with a melted carnauba wax (drug: wax ratio, ...

  16. Quartz crystal reinforced quartz glass by spark plasma sintering

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  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. Tailoring the thermal conductivity of the powder bed in Electron Beam Melting (EBM) Additive Manufacturing.

    Science.gov (United States)

    Smith, C J; Tammas-Williams, S; Hernandez-Nava, E; Todd, I

    2017-09-05

    Metallic powder bed additive manufacturing is capable of producing complex, functional parts by repeatedly depositing thin layers of powder particles atop of each other whilst selectively melting the corresponding part cross-section into each layer. A weakness with this approach arises when melting overhanging features, which have no prior melted material directly beneath them. This is due to the lower thermal conductivity of the powder relative to solid material, which as a result leads to an accumulation of heat and thus distortion. The Electron Beam Melting (EBM) process alleviates this to some extent as the powder must first be sintered (by the beam itself) before it is melted, which results in the added benefit of increasing the thermal conductivity. This study thus sought to investigate to what extent the thermal conductivity of local regions in a titanium Ti-6Al-4V powder bed could be varied by imparting more energy from the beam. Thermal diffusivity and density measurements were taken of the resulting sintered samples, which ranged from being loosely to very well consolidated. It was found that the calculated thermal conductivity at two temperatures, 40 and 730 °C, was more than doubled over the range of input energies explored.

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

    International Nuclear Information System (INIS)

    Haubner, R.; Lux, B.

    1997-01-01

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

  20. Preparation of Cu and Fly Ash Composite by Powder Metallurgy Technique

    International Nuclear Information System (INIS)

    Chew, P. Y.; Lim, P. S.; Ng, M. C.; Zahi, S.; You, A. H.

    2011-01-01

    Cu and Fly Ash (FA) mixtures with different weight percentages were prepared. Pellets of the mixture powder were produced with the dimension of 17.7 mm in diameter and 10-15 mm in height. These different composites were compacted at a constant pressure of 280 MPa. One of the selected weight percentages was then compacted to form into pellet and sintered at different temperatures which were at 900, 950 and 1000 deg. C respectively for 2 hours. Density of green pellet was measured before sintered in furnace. After sintering, all the pellets with different temperatures were re-weighed and sintered density were calculated. The densification of the green and sintered pellets was required to be measured as one of the parameter in selection of the best material properties. Porosity of the pellet shall not be ignored in order to analyze the close-packed particles stacking in the pellet. SEM micrograph had been captured to observe the presence of pores and agglomeration of particles in the sample produced.

  1. Embrittling Components in Sintered Steels: Comparison of Phosphorus and Boron

    Science.gov (United States)

    Danninger, Herbert; Vassileva, Vassilka; Gierl-Mayer, Christian

    2017-12-01

    In ferrous powder metallurgy, both boron and phosphorus have been known to be sintering activators for a long time. However, the use has been widely different: while P is a standard additive to sintered iron and steels, boron has been frequently studied, but its use in practice is very limited. Both additives are also known to be potentially embrittling, though in a different way. In the present study the differences between the effects of both elements are shown: while P activates sintering up to a certain threshold, in part by stabilizing ferrite, in part by forming a transient liquid phase, boron is the classical additive enhancing persistent liquid phase, being virtually insoluble in the iron matrix. The consequence is that sintered steels can tolerate quite a proportion of phosphorus, depending on composition and sintering process; boron however is strongly embrittling in particular in combination with carbon, which requires establishing a precisely defined content that enhances sintering but is not yet embrittling. The fracture mode of embrittled materials is also different: while with Fe-P the classical intergranular fracture is observed, with boron a much more rugged fracture surface appears, indicating some failure through the eutectic interparticle network but mostly transgranular cleavage. If carbon is added, in both cases transgranular cleavage dominates even in the severely embrittled specimens, indicating that no more the grain boundaries and sintering necks are the weakest links in the systems.

  2. Pressing-sintering process of UO2 pellet of controllable microstructure

    International Nuclear Information System (INIS)

    Wu Zhiming; Peng Qingshan

    1999-11-01

    The authors present the pressability and sinterability of two different matrix UO 2 powders from Ammonium Diuranate (ADU) process and the improvements by adding different quantities of additives. A focal point is made in the effect of the additives on the density, thermal stability and microstructure of UO 2 pellet. It is indicated by the results that a UO 2 pellet being of proper density, good thermal stability and better microstructure can be produced using of high sinterable UO 2 powder ex ADU, adding a certain quantity of pore former through calculation under conditions of high green density and high sintering temperature

  3. The influence of sintering on the dispersion of carbon nanotubes in ceramic matrix composites

    Science.gov (United States)

    Tapasztó, Orsolya; Lemmel, Hartmut; Markó, Márton; Balázsi, Katalin; Balázsi, Csaba; Tapasztó, Levente

    2014-10-01

    Optimizing the dispersion of carbon nanostructures in ceramic matrix composites is a fundamental technological challenge. So far most efforts have been focused on improving the dispersion of nanostructures during the powder phase processing, due to the limited information and control on their possible redistribution during the sintering. Here, we address this issue by comparing multi-walled carbon nanotubes reinforced Si3N4 composites prepared from the same starting powder dispersion but sintered using two different techniques. We employ ultra-small angle neutron scattering measurements to gain reliable information on the dispersion of nanostructures allowing a direct comparison of their redistribution during the sintering.

  4. The electric conductivity of some forms of sintered synthetic zeolites

    International Nuclear Information System (INIS)

    Susic, M.; Petrovic, V.; Ristic, M.; Petranovic, N.

    1978-01-01

    Some forms of synthetic zeolites were sintered and their electric conductivity was measured. The conductivity was observed in correlation with the conductivity of non-sintered pressed samples. Also the change in microstructural constituents in the course of the process of sintering was observed with an optical microscope. It has been found that there is a considerable change in conductivity due to sintering as well as a change in the activation energy for conduction. Also the porosity is noticeably changed. A marked affect of the nature of counter ions on the electric conductivity is shown

  5. 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.

  6. Low temperature sintering of fluorapatite glass-ceramics

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A.

    2014-01-01

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

  7. [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.

  8. 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)

  9. Micro-powder injection moulding of tungsten; Prozessentwicklung fuer das Mikro-Pulverspritzgiessen von Wolfram

    Energy Technology Data Exchange (ETDEWEB)

    Zeep, B.

    2007-12-15

    For He-cooled Divertors as integral components of future fusion power plants, about 300000 complex shaped tungsten components are to be fabricated. Tungsten is the favoured material because of its excellent properties (high melting point, high hardness, high sputtering resistance, high thermal conductivity). However, the material's properties cause major problems for large scale production of complex shaped components. Due to the resistance of tungsten to mechanical machining, new fabrication technologies have to be developed. Powder injection moulding as a well established shaping technology for a large scale production of complex or even micro structured parts might be a suitable method to produce tungsten components for fusion applications but is not yet commercially available. The present thesis is dealing with the development of a powder injection moulding process for micro structured tungsten components. To develop a suitable feedstock, the powder particle properties, the binder formulation and the solid load were optimised. To meet the requirements for a replication of micro patterned cavities, a special target was to define the smallest powder particle size applicable for micro-powder injection moulding. To investigate the injection moulding performance of the developed feedstocks, experiments were successfully carried out applying diverse cavities with structural details in micro dimension. For debinding of the green bodies, a combination of solvent debinding and thermal debinding has been adopted for injection moulded tungsten components. To develop a suitable debinding strategy, a variation of the solvent debinding time, the heating rate and the binder formulation was performed. For investigating the thermal consolidation behaviour of tungsten components, sinter experiments were carried out applying tungsten powders suitable for micro-powder injection moulding. First mechanical tests of the sintered samples showed promising material properties such

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

    Science.gov (United States)

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

    2017-09-01

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

  11. Síntese de pós nanométricos e sinterização de cerâmicas de Ba1-xCa xTiO3 a baixas temperaturas Low temperature synthesis and sintering of Ba1-xCa xTiO3 nanometric powders

    Directory of Open Access Journals (Sweden)

    R. S. Silva

    2006-09-01

    Full Text Available Pós nanométricos de titanato de bário e cálcio (Ba1-xCa xTiO3: x = 0,05/0,10/0,15/0,23 mol% foram sintetizados a temperaturas relativamente baixas (800 °C por meio do método de precursores poliméricos modificado. Corpos cerâmicos foram obtidos com alta densidade relativa (> 97% e microestrutura com tamanho de grãos homogêneos, a temperatura e tempo de sinterização relativamente baixos (1275 °C/1 h. Observamos também que o tamanho de cristalitos no pó calcinado e o tamanho médio de grãos nos corpos cerâmicos sinterizados diminuem com o aumento da concentração de Ca.Barium calcium titanate nanopowders (Ba1-xCa xTiO3: x = 0.05, 0.10, 0.15 and 0.23 mol% have been synthesized at relative low temperature ( 800 ºC through the modified polymeric precursor method. High relative density ceramics (> 97% and microstructure with homogeneous grain size were obtained at relative low temperature and time of sintering (1275 °C/1 h. It was also observed that the crystallite size of the calcined powder and the average grain size of the sintered ceramics decrease with the increase of the calcium concentration.

  12. Tribological behaviour and statistical experimental design of sintered iron-copper based composites

    Science.gov (United States)

    Popescu, Ileana Nicoleta; Ghiţă, Constantin; Bratu, Vasile; Palacios Navarro, Guillermo

    2013-11-01

    The sintered iron-copper based composites for automotive brake pads have a complex composite composition and should have good physical, mechanical and tribological characteristics. In this paper, we obtained frictional composites by Powder Metallurgy (P/M) technique and we have characterized them by microstructural and tribological point of view. The morphology of raw powders was determined by SEM and the surfaces of obtained sintered friction materials were analyzed by ESEM, EDS elemental and compo-images analyses. One lot of samples were tested on a "pin-on-disc" type wear machine under dry sliding conditions, at applied load between 3.5 and 11.5 × 10-1 MPa and 12.5 and 16.9 m/s relative speed in braking point at constant temperature. The other lot of samples were tested on an inertial test stand according to a methodology simulating the real conditions of dry friction, at a contact pressure of 2.5-3 MPa, at 300-1200 rpm. The most important characteristics required for sintered friction materials are high and stable friction coefficient during breaking and also, for high durability in service, must have: low wear, high corrosion resistance, high thermal conductivity, mechanical resistance and thermal stability at elevated temperature. Because of the tribological characteristics importance (wear rate and friction coefficient) of sintered iron-copper based composites, we predicted the tribological behaviour through statistical analysis. For the first lot of samples, the response variables Yi (represented by the wear rate and friction coefficient) have been correlated with x1 and x2 (the code value of applied load and relative speed in braking points, respectively) using a linear factorial design approach. We obtained brake friction materials with improved wear resistance characteristics and high and stable friction coefficients. It has been shown, through experimental data and obtained linear regression equations, that the sintered composites wear rate increases

  13. Bonding evolution with sintering temperature in low alloyed steels with chromium

    Directory of Open Access Journals (Sweden)

    Fuentes-Pacheco L.

    2009-01-01

    Full Text Available At present, high performance PM steels for automotive applications follow a processing route that comprises die compaction of water-atomized powder, followed by sintering and secondary treatments, and finishing operations. This study examines Cr-alloyed sintered steels with two level of alloying. In chromium-alloyed steels, the surface oxide on the powder is of critical importance for developing the bonding between the particles during sintering. Reduction of this oxide depends mainly on three factors: temperature, dew point of the atmosphere, and carbothermic reduction provided by the added graphite. The transformation of the initial surface oxide evolves sequence as temperature increases during sintering, depending on the oxide composition. Carbothermic reduction is supposed to be the controlling mechanism, even when sintering in hydrogen-containing atmospheres. The effect of carbothermic reduction can be monitored by investigating the behavior of the specimens under tensile testing, and studying the resultant fracture surfaces.

  14. Ti-Nb-Sn-hydroxyapatite composites synthesized by mechanical alloying and high frequency induction heated sintering.

    Science.gov (United States)

    Wang, Xiaopeng; Chen, Yuyong; Xu, LiJuan; Xiao, Shulong; Kong, Fantao; Woo, Kee Do

    2011-11-01

    A β-type Ti-based composite, Ti-35Nb-2.5Sn-15-hydroxyapatite (HA), has been synthesized by mechanical alloying and powder metallurgy. The effects of milling time on microstructure, mechanical properties and biocompatibility of the sintered composites were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), microhardness tests, compression tests and cells culture. The results revealed when milling time increased, the homogeneity and relative density of the sintered composite increased, but the finished sintering temperature decreased. The compression Young's modulus of sintered composite from 12 h milled powders was about 22 GPa and its compression strength was 877 MPa. The cell culture results indicated cell viability for these sintered composites was very good. These results revealed the Ti-35Nb-2.5Sn-15HA composite could be useful for medical implants. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Production of Al2O3–SiC nano-composites by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Mansour Razavi

    2017-07-01

    Full Text Available In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600 °C for 10 min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5 h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329 MPa, respectively, in Al2O3–20 wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale.

  16. Fusibility and sintering characteristics of ash

    International Nuclear Information System (INIS)

    Ots, A. A.

    2012-01-01

    The temperature characteristics of ash fusibility are studied for a wide range of bituminous and brown coals, lignites, and shales with ratios R B/A of their alkaline and acid components between 0.03 and 4. Acritical value of R B/A is found at which the fusion temperatures are minimal. The sintering properties of the ashes are determined by measuring the force required to fracture a cylindrical sample. It is found that the strength of the samples increases sharply at certain temperatures. The alkali metal content of the ashes has a strong effect on their sintering characteristics.

  17. Effects of sintering atmosphere and temperature on structural and magnetic properties of Ni-Cu-Zn ferrite nano-particles: Magnetic enhancement by a reducing atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Gholizadeh, Ahmad, E-mail: gholizadeh@du.ac.ir; Jafari, Elahe, E-mail: ah_gh1359@yahoo.com

    2017-01-15

    In this work, effects of sintering atmosphere and temperature on structural and magnetic properties of Ni{sub 0.3}Cu{sub 0.2}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles prepared by citrate precursor method have been studied. The structural characterization of the samples by X-ray powder diffraction and FT-IR spectroscopy is evidence for formation of a cubic structure with no presence of impurity phase. Calculated values of crystallite size and unit cell parameter show an increase with sintering temperature under different atmospheres. Variation of saturation magnetization with sintering temperature and atmosphere can be attributed to change of three factors: magnetic core size, inversion parameter and the change of Fe{sup 3+}-ion concentration due to the presence of Fe{sup 4+} and Fe{sup 2+} ions. The saturation magnetization gradually grows with sintering temperature due to increase of magnetic core size and a maximum 63 emu/g was achieved at 600 °C under carbon monoxide-ambient atmosphere. - Highlights: • Different sintering atmosphere and temperature cause substantial differences in Ni{sub 0.3}Cu{sub 0.2}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles. • The saturation magnetization gradually grows. • A maximum 63 emu/g was achieved at 600 °C under a reducing atmosphere.

  18. Spark plasma sintered Sm(2)Co(17)-FeCo nanocomposite permanent magnets synthesized by high energy ball milling.

    Science.gov (United States)

    Sreenivasulu, G; Gopalan, R; Chandrasekaran, V; Markandeyulu, G; Suresh, K G; Murty, B S

    2008-08-20

    Nanocomposite Sm(2)Co(17)-5 wt% FeCo magnets were synthesized by high energy ball milling followed by consolidation into bulk shape by the spark plasma sintering technique. The evolution of magnetic properties was systematically investigated in milled powders as well as in spark plasma sintered samples. A high energy product of 10.2 MGOe and the other magnetic properties of M(s) = 107 emu g(-1), M(r) = 59 emu g(-1), M(r)/M(s) = 0.55 and H(c) = 6.4 kOe were achieved in a 5 h milled and spark plasma sintered Sm(2)Co(17)-5 wt% FeCo nanocomposite magnet. The spark plasma sintering was carried out at 700 °C for 5 min with a pressure of 70 MPa. The nanocomposite showed a higher Curie temperature of 955 °C for the Sm(2)Co(17) phase in comparison to its bulk Curie temperature for the Sm(2)Co(17) phase (920 °C). This higher Curie temperature can improve the performance of the magnet at higher temperatures.

  19. Formation of porous wollastonite-based ceramics after sintering with yeast as the pore-forming agent

    Directory of Open Access Journals (Sweden)

    Obradović Nina

    2017-01-01

    Full Text Available In this paper, synthesis of porous wollastonite-based ceramics was reported. Ceramic precursor, methylhydrocyclosiloxane, together with micro-sized CaCO3, was used as starting material. After 20 min of ultrasound treatment, and calcination at 250 oC for 30 min, yeast as a pore-forming agent was added to the as-obtained powders. Sintering regime was set up based on the results obtained by differential thermal analysis. Prepared mixture was pressed into pallets and sintered at 900 oC for 1 h. After the sintering regime, porous wollastonite-based ceramics was obtained. The phase composition of the sintered samples as well as microstructures was analyzed by X-ray diffraction method and SEM. In a batch test, the influence of pH, contact time and initial ion concentration on adsorption efficiency of As+5, Cr+6, and phosphate ions on synthesized wollastonite-based ceramics were studied. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber-Morris model that predicted intra-particle diffusion as a rate-controlling step of overall process. High adsorption capacities 39.97, 21.87, and 15.29 mgg-1 were obtained for As+5, Cr+6, and phosphate ions, respectively.

  20. Dehydrogenation and Sintering of TiH2: An In Situ Study

    Science.gov (United States)

    Chen, Gang; Liss, Klaus D.; Auchterlonie, Graeme; Tang, Huiping; Cao, Peng

    2017-06-01

    This first-ever study investigated dehydrogenation and microstructural evolution of TiH2 during sintering under vacuum using in situ neutron diffraction, in situ transmission electron microscopy, and ex situ neutron tomography. The densification behavior, microstructure, hydrogen concentration, and in situ phase transformation were reported. The shrinkage, weight loss percentage, and densification of the TiH2 powder compact monotonically increase with sintering temperature, while the open porosity behaves differently; porosity first increases at the initial sintering stage and then decreases during further sintering. The in situ phase transformation observations reveal that dehydrogenation starts from the outer area of either a particle or a powder compact and progressively carries forward into the interior of the particle or the compact. A shrinking core model was proposed to elucidate the dehydrogenation process for a single particle and a powder compact.

  1. Li3-xMxN (M = Co, Ni) synthesized by Spark Plasma Sintering for hydrogen storage

    International Nuclear Information System (INIS)

    Zhang Junxian; Cerny, Radovan; Villeroy, Benjamin; Godart, Claude; Chandra, Dhanesh; Latroche, Michel

    2011-01-01

    Research highlights: → Anion substitution in light hydrides (amides) is realized experimentally. → The compounds have been synthesized by in-situ Spark plasma Sintering. → The structural characterization has been done by synchrotron powder diffraction. - Abstract: Lithium nitride has recently emerged as a promising material for hydrogen storage. The hydrogen storage capacity reaches 10.2 wt% H by the formation of compounds, such as imides, amides, and others. Hydrogenation of lithium nitride is highly exothermic, and thus desorbing hydrogen from these compounds requires high temperature and cannot be used for reversible hydrogen storage. Ab initio calculations predict that partial substitution of Li by transition metals like Cu or Ni can reduce the reaction enthalpy between amide and imide. In this work, we present the synthesis of the ternary system Li 3-x M x N (M = Co or Ni) by Spark Plasma Sintering (SPS). The samples are hydrogenated at 255 deg. C by solid gas reaction. The sample crystal structures have been analyzed by synchrotron X-ray powder diffraction using a high resolution powder diffractometer. The structural models for Co and Ni-substituted Li 3 N have been confirmed. The effect of the substitution on the phase formation upon hydrogenation has been investigated at various metal and hydrogen concentration. Different behaviors are observed depending on the nature of M.

  2. Spark Plasma Sintering of a Gas Atomized Al7075 Alloy: Microstructure and Properties

    Directory of Open Access Journals (Sweden)

    Orsolya Molnárová

    2016-12-01

    Full Text Available The powder of an Al7075 alloy was prepared by gas atomization. A combination of cellular, columnar, and equiaxed dendritic-like morphology was observed in individual powder particles with continuous layers of intermetallic phases along boundaries. The cells are separated predominantly by high-angle boundaries, the areas with dendritic-like morphology usually have a similar crystallographic orientation. Spark plasma sintering resulted in a fully dense material with a microstructure similar to that of the powder material. The continuous layers of intermetallic phases are replaced by individual particles located along internal boundaries, coarse particles are formed at the surface of original powder particles. Microhardness measurements revealed both artificial and natural ageing behavior similar to that observed in ingot metallurgy material. The minimum microhardness of 81 HV, observed in the sample annealed at 300 °C, reflects the presence of coarse particles. The peak microhardness of 160 HV was observed in the sample annealed at 500 °C and then aged at room temperature. Compression tests confirmed high strength combined with sufficient plasticity. Annealing even at 500 °C does not significantly influence the distribution of grain sizes—about 45% of the area is occupied by grains with the size below 10 µm.

  3. Microstructure and properties of sintered mullite developed from ...

    Indian Academy of Sciences (India)

    Dense mullite aggregates with 72% Al2O3 have been synthesized by reaction sintering of two varieties of Indian bauxite and silica sol. The bauxites used are of inferior grade with different levels of accessory impurities such as Fe2O3, TiO2, CaO. The phase and microstructure development of sintered samples were ...

  4. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    NiZnCu hexagonal ferrite (abbreviated as ZT/NZC) composite samples were prepared successfully by using restricted shrinkage sintering process (RSS) (Liu et al 2009a, b). But the electromagnetic performance degra- dation of co-sintered layer ...

  5. Comparison of Residual Stresses in Inconel 718 Simple Parts Made by Electron Beam Melting and Direct Laser Metal Sintering

    Science.gov (United States)

    Sochalski-Kolbus, L. M.; Payzant, E. A.; Cornwell, P. A.; Watkins, T. R.; Babu, S. S.; Dehoff, R. R.; Lorenz, M.; Ovchinnikova, O.; Duty, C.

    2015-03-01

    Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting (EBM) and the other with direct laser metal sintering. Spatially indexed stress-free cubes were obtained by electrical discharge machining (EDM) equivalent prisms of similar shape. The (311) interplanar spacings from the EDM sectioned sample were compared to the interplanar spacings calculated to fulfill stress and moment balance. We have shown that applying stress and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. In addition, our work has shown that residual stresses in electron beam melted parts are much smaller than that of direct laser metal sintered parts most likely due to the powder preheating step in the EBM process.

  6. Assessment of powder blend uniformity: Comparison of real-time NIR blend monitoring with stratified sampling in combination with HPLC and at-line NIR Chemical Imaging.

    Science.gov (United States)

    Bakri, Barbara; Weimer, Marco; Hauck, Gerrit; Reich, Gabriele

    2015-11-01

    Scope of the study was (1) to develop a lean quantitative calibration for real-time near-infrared (NIR) blend monitoring, which meets the requirements in early development of pharmaceutical products and (2) to compare the prediction performance of this approach with the results obtained from stratified sampling using a sample thief in combination with off-line high pressure liquid chromatography (HPLC) and at-line near-infrared chemical imaging (NIRCI). Tablets were manufactured from powder blends and analyzed with NIRCI and HPLC to verify the real-time results. The model formulation contained 25% w/w naproxen as a cohesive active pharmaceutical ingredient (API), microcrystalline cellulose and croscarmellose sodium as cohesive excipients and free-flowing mannitol. Five in-line NIR calibration approaches, all using the spectra from the end of the blending process as reference for PLS modeling, were compared in terms of selectivity, precision, prediction accuracy and robustness. High selectivity could be achieved with a "reduced" approach i.e. API and time saving approach (35% reduction of API amount) based on six concentration levels of the API with three levels realized by three independent powder blends and the additional levels obtained by simply increasing the API concentration in these blends. Accuracy and robustness were further improved by combining this calibration set with a second independent data set comprising different excipient concentrations and reflecting different environmental conditions. The combined calibration model was used to monitor the blending process of independent batches. For this model formulation the target concentration of the API could be achieved within 3 min indicating a short blending time. The in-line NIR approach was verified by stratified sampling HPLC and NIRCI results. All three methods revealed comparable results regarding blend end point determination. Differences in both mean API concentration and RSD values could be

  7. Method of making bonded or sintered permanent magnets

    Science.gov (United States)

    McCallum, R. William; Dennis, Kevin W.; Lograsso, Barbara K.; Anderson, Iver E.

    1993-08-31

    An isotropic permanent magnet is made by mixing a thermally responsive, low viscosity binder and atomized rare earth-transition metal (e.g., iron) alloy powder having a carbon-bearing (e.g., graphite) layer thereon that facilitates wetting and bonding of the powder particles by the binder. Prior to mixing with the binder, the atomized alloy powder may be sized or classified to provide a particular particle size fraction having a grain size within a given relatively narrow range. A selected particle size fraction is mixed with the binder and the mixture is molded to a desired complex magnet shape. A molded isotropic permanent magnet is thereby formed. A sintered isotropic permanent magnet can be formed by removing the binder from the molded mixture and thereafter sintering to full density.

  8. Microstructural and electrical investigation of Cu-Ni-Cr alloys obtained by powder metallurgy method

    Energy Technology Data Exchange (ETDEWEB)

    Carrio, Juan A.G.; Carvalhal, M.A.; Ayabe, L.M.; Monteiro, W.A., E-mail: jgcarrio@mackenzie.br [Universidade Presbiteriana Mackenzie (UPM/CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades. Dept. de Fisica; Silva, L.C.E. da; Silva Junior, R.V., E-mail: fisica.cch@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    The aim of this work, using the powder metallurgy process, is to synthesize metallic alloys with high mechanical strength and high electric conductivity, after melting optimizing and thermal treatments. The Cu-Ni-Cr (wt%) alloys are characterized in their mechanical and electrical properties as well as the obtained microstructure. Through the process of powder metallurgy, contacts and structural parts can be obtained. The alloys elements are added to copper with the intention to improve their strength, ductility and thermal stability, without causing considerable damages in their form, electrical and thermal conductivity, and corrosion resistance. The metallic powders were mixed for a suitable time and then they were pressed in a cold uniaxial pressing (1000 kPa). Afterwards, the specimens were sintered in temperatures varying from 700 up to 800 deg C under vacuum. At last, the samples were homogenized at 550 deg C under vacuum, for special times. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples. The alloys were characterized by optical microscopy, X-rays powder diffraction, electrical conductivity and Vickers hardness. (author)

  9. Enhanced method of magnetic powder alignment for production of PLP Nd-Fe-B magnets

    Energy Technology Data Exchange (ETDEWEB)

    Popov, A.G. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation); Golovnia, O.A., E-mail: golovnya@imp.uran.ru [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation); Protasov, A.V. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation)

    2017-04-15

    It is demonstrated how the high degree of powder alignment in PLP magnets can be achieved by loading the powder into a container placed in a magnetic field of moderate strength. The strip-cast alloy with a composition of 30.00 Nd, 1.95 Dy, 66.42 Fe, 0.99 B, 0.54 Co, 0.1 Ga (wt%) was subjected to hydrogen decrepitation and then milled in a vibratory mill in toluene to an average particle size of 2.9 µm determined by the FSSS method. The powder was compacted in the magnetic field of 0.2 – 1.2 T to the filling density 2.6 – 3.2×10{sup 3} kg/m{sup 3}. It is shown that loading the powder into a container placed in a magnetic field enhances the degree of powder alignment in sintered Nd-Fe-B magnets produced from non-pressed powder. At the filling density less than 3.2×10{sup 3} kg/m{sup 3}, the density of magnets is high but insufficient, because of the formation of magnetostatic chains of particles, which impedes the powder compaction. The simulation by the discrete-element method qualitatively proves that the magnetostatic interaction of the chains of particles that are formed in the course of loading in the magnetic field stimulates a decrease in the density of the sintered magnets and its non-uniform distribution over the sample. As a result of the optimization of the parameters of the alignment and compaction of the powder loaded in a magnetic field, PLP magnets with B{sub r} ≥1.34 T, H{sub c} ≥950 kA/m, (BH){sub max} ≥340 kJ/m{sup 3}, and the degree of alignment exceeding 96% were produced. - Highlights: • The pressless process (PLP) in magnet production is studied. • A new method of the loading of powder in an applied DC magnetic field is suggested. • The method allows achieving higher degree of alignment in moderate magnetic field. • Density of sintered magnets is studied experimentally and via DEM simulation. • Low density is caused by the formation of magnetostatic chains of powder particles.

  10. Computer Modeling of Direct Metal Laser Sintering

    Science.gov (United States)

    Cross, Matthew

    2014-01-01

    A computational approach to modeling direct metal laser sintering (DMLS) additive manufacturing process is presented. The primary application of the model is for determining the temperature history of parts fabricated using DMLS to evaluate residual stresses found in finished pieces and to assess manufacturing process strategies to reduce part slumping. The model utilizes MSC SINDA as a heat transfer solver with imbedded FORTRAN computer code to direct laser motion, apply laser heating as a boundary condition, and simulate the addition of metal powder layers during part fabrication. Model results are compared to available data collected during in situ DMLS part manufacture.

  11. Selective laser sintering in biomedical engineering.

    Science.gov (United States)

    Mazzoli, Alida

    2013-03-01

    Selective laser sintering (SLS) is a solid freeform fabrication technique, developed by Carl Deckard for his master's thesis at the University of Texas, patented in 1989. SLS manufacturing is a technique that produces physical models through a selective solidification of a variety of fine powders. SLS technology is getting a great amount of attention in the clinical field. In this paper the characteristics features of SLS and the materials that have been developed for are reviewed together with a discussion on the principles of the above-mentioned manufacturing technique. The applications of SLS in tissue engineering, and at-large in the biomedical field, are reviewed and discussed.

  12. SEM hot stage sintering of UO2

    International Nuclear Information System (INIS)

    Miller, D.J.

    1976-06-01

    The sintering of hyperstoichiometric uranium dioxide powder compacts, in the hot stage of a scanning electron microscope, was continuously monitored using 16 mm time lapse movies. From alumina microspheres placed on the surface of the compacts, shrinkage measurements were obtained. Converting shrinkage measurements into densification profiles indicates that a maximum densification rate is reached at a critical density, independent of the constant heating rates. At temperatures above 1350 0 C, the movement of the reference microspheres made shrinkage measurements impossible. It is believed the evolution of UO 3 gas from hyperstoichiometric UO 2 is the cause of this limitation

  13. Effects of lower cobalt binder concentrations in sintering of tungsten carbide

    International Nuclear Information System (INIS)

    Li Tao; Li Qingfa; Fuh, J.Y.H.; Yu, P.C.; Wu, C.C.

    2006-01-01

    Cemented tungsten carbides have received much attention because of their superior characteristics. Traditional cemented tungsten carbides usually contain 3-30 wt% binder phase. In this paper, WC with low Co concentration less than 3 wt% is studied using traditional powder metallurgy. The binder phase has tremendous effect on sinterability of WC. High sinterability and high hardness can be achieved for the WC (0.7 μm) with 0.5 wt% Co. Abnormal grain growth (AGG) is often observed in sintering WC with small amount of Co. It seems that AGG is affected by the concentration of Co and a range of Co concentrations may exist for the large amount of AGG. To control the grain size, VC is added to inhibit the grain growth of WC. It is observed that the hardness is affected by the amount of addition of VC. Controlling the ratio of C/W less than unity at low Co concentrations will result in the production of W 2 C phase. The hardness of WC-Co is affected by the amount of W 2 C phase in the sample and W 2 C is stable during the normal cooling process

  14. Factors governing microstructure development of Cr2O3-doped UO2 during sintering

    International Nuclear Information System (INIS)

    Bourgeois, L.; Dehaudt, Ph.; Lemaignan, C.; Hammou, A.

    2001-01-01

    Sintering and grain growth of compacted uranium dioxide powder pellets doped with Cr 2 O 3 were investigated at constant heating rates ranging from 75 to 500 K h -1 . The influence of parameters such as the oxygen potential of the sintering atmosphere and pellet green density on the final microstructure was studied. Dilatometric analysis and monitoring of microstructural development revealed a phenomenon of abnormal grain growth promoting densification. The existence of a eutectic between Cr and Cr 2 O 3 is also discussed. Grain growth does not appear to be widely affected by small differences in residual porosity, which is a function of green density, so that it is possible to propose a solubility limit for Cr 2 O 3 in stoichiometric UO 2 at 1700 deg. C. Examination of microstructural changes during annealing, with or without pore formers, showed the existence of limiting grain sizes for doped samples above the solubility limit. Lastly, experimental sintering conditions need to be checked in order to obtain reproducible results [fr

  15. Study of the sintering process and the formation of a (Th, U) O2 solid solution

    International Nuclear Information System (INIS)

    Tomasi, Roberto

    1979-01-01

    The effect of some variables in the (Th, U) O 2 sintering process and solid solution formation was studied. ThO 2 , U 3 O 8 and UO 2 powder were prepared. The ThO 2 powders were obtained by calcination of thorium at 500 and 750 deg C; the U 3 O 8 powders were derived from the calcination of ADU at 660 and 750 deg C; the UO 2 powder were prepared from ADU and from ATCU. The different characteristics of these materials were determined by measurements of surface area, by scanning electron microscopy, tap density tests, X-ray diffractometry and by measurements of the O/U ratios. The oxide mixtures were chosen in order to produce a final composition with 10 w/o of UO 2 . A mixture of thorium oxalate and ADU was also prepared by calcining these salts in air at 700 deg C, in order to obtain certain amount of solid solution prior to sintering. The sintering operations were developed in an argon atmosphere at temperatures between 1400 and 1700 deg C, during interval varying from 1 to 4 hours. The effect of the mixture characteristics on the sintering process and solid solution formation were studied considering the results of densification, microstructure development and X-ray diffractometry. The ThO 2 powder characteristics have a main effect on the mixtures compactability and sinterability, the higher calcining temperatures increasing the green density, but decreasing the final density of the sintered pellets. In the sintering of mixtures containing U 3 O 3 , this oxide is reduced to UO 2 and it is possible to obtain pellets with density and microstructures similar to those produced from mixtures containing UO 2 . But if oxygen in excess is present during sintering, the process is affected, occurring exaggerated grain growth. The densification results were related to the Coble's kinetics equation for second stage of sintering, valid for bulk diffusion, grain boundary acting as vacancy sinks. The sintering activation energy is independent from the powder starting

  16. Production of titanium alloys for advanced aerospace systems by powder metallurgy

    Directory of Open Access Journals (Sweden)

    Vinicius André Rodrigues Henriques

    2005-12-01

    Full Text Available Titanium alloys parts are ideally suited for advanced aerospace systems because of their unique combination of high specific strength at both room temperature and moderately elevated temperature, in addition to excellent corrosion resistance. Despite these features, use of titanium alloys in engines and airframes is limited by cost. The alloys processing by powder metallurgy eases the obtainment of parts with complex geometry. In this work, results of the Ti-6Al-4V and Ti-13Nb-13Zr alloys production are presented. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900 up to 1500 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure from the elements dissolution with low interstitial pick-up.

  17. Titanium nitride deposition in titanium implant alloys produced by powder metallurgy

    International Nuclear Information System (INIS)

    Henriques, V.A.R.; Cairo, C.A.A.; Faria, J.; Lemos, T.G.; Galvani, E.T.

    2009-01-01

    Titanium nitride (TiN) is an extremely hard material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve wear resistance. Electron Beam Physical Vapor Deposition (EB-PVD) is a form of deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work are presented results of TiN deposition in targets and substrates of Ti (C.P.) and Ti- 13 Nb- 13 Zr obtained by powder metallurgy. Samples were produced by mixing of hydride metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900°C up to 1400 °C, in vacuum. The deposition was carried out under nitrogen atmosphere. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure, with ideal characteristics for an adequate deposition and adherence. The film layer presented a continuous structure with 15μm. (author)

  18. Addition of niobia in alumina and its effects at its sintered microstructure

    International Nuclear Information System (INIS)

    Gomes, L.B.; Lima, M.M.O.; Pereira, A.S.; Bergmann, C.P.

    2016-01-01

    In this work, niobia was used as sintering additive of alumina in concentrations of 0.15, 0.5, 2 and 4 wt%. Homogenized powders was uniaxially pressed (200MPa) forming ceramic pellets with 10 mm diameter. The green bodies were sintered at 1400, 1500 and 1600°C for 60 minutes using a heating rate of 2,5°C.min -1 . After sintering, the specimens were polished using diamond paste with different particle sizes. The specimen's microstructure was analyzed by Scanning Electron Microscopy (SEM) and crystalline phases were determined by X-ray Diffraction (XRD). Results indicate that when niobia and alumina react they form AlNbO4 by liquid phase sintering. This phase is located among alumina grain. It was also verified that niobia addition promotes grain growth, acting as sintering agent, and this effect grows as niobia content and sintering temperature increase. (author)

  19. Hydrogen Decrepitation Press-Less Process Recycling of NdFeB sintered magnets

    DEFF Research Database (Denmark)

    Xia, Manlong; Abrahamsen, Asger Bech; Bahl, Christian

    2017-01-01

    A Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling method for recycling of anisotropic NdFeB magnets is demonstrated. The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered...

  20. An investigation on microwave sintering of Fe, Fe–Cu and Fe–Cu–C ...

    Indian Academy of Sciences (India)

    The powder characteristics of metallic powders play a key role during sintering. Densification and mechanical properties were also influenced by it. The current study examines the effect of heating mode on densification, microstructure, phase compositions and properties of Fe, Fe–2Cu and Fe–2Cu–0.8C systems.

  1. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Science.gov (United States)

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  2. Heavy metal content and element analysis of infant formula and milk powder samples purchased on the Tanzanian market: International branded versus black market products.

    Science.gov (United States)

    Sager, M; McCulloch, C R; Schoder, D

    2018-07-30

    Milk powder is a food for malnourished African children and for healthy infants of women with HIV/AIDS. High demand and low purchasing power has resulted in a huge informal, black market in Sub-Saharan Africa. Forty-three milk powder batches were analyzed for 43 chemical elements using ICP-MS One sample (2.3%) was contaminated at a lead concentration of 240 µg/kg dry weight exceeding the European threshold (130 µg/kg dry weight). Macroelement contents revealed a trend decreasing in concentration through skimmed, full cream products to infant formulae. Concentration ranges by dry weight differed in respect of uncertainty intervals of  ±10%. Median Ca, K and P concentrations declined from 11.14 g/kg to 3.21 g/kg, 14.11 g/kg to 4.95 g/kg and 9.12 g/kg to 2.75 g/kg dry mass, respectively. Milk powder samples obtained from the Tanzanian black market were comparable in respect of nutritional and chemical content to international branded full cream products. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. 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

  4. Application of fine-grained coke breeze fractions in the process of iron ore sintering

    Directory of Open Access Journals (Sweden)

    M. Niesler

    2014-01-01

    Full Text Available The testing cycle, described in the paper, included fine-grained coke breeze granulation tests and iron concentrate sintering tests with the use of selected granulate samples. The use of granulated coke breeze in the sintering process results in a higher process efficiency, shorter sintering duration and fuel saving.

  5. 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

  6. Evaluation of a fluid versus a powder pepsin formulation to detect Trichinella spiralis larvae in meat samples by a digestion technique

    DEFF Research Database (Denmark)

    Maddox-Hyttel, Charlotte; Nockler, K.; Pozio, E.

    2007-01-01

    the digestion fluid and the amount of debris remaining after digestion. For the ring trial, at each laboratory 20 blinded replicate 100-g samples of pork meat containing a known number of encapsulated T. spiralis larvae (0 to 30) were digested by the magnetic stirrer method using either the standard pepsin......Pepsin powder constitutes a health risk, potentially causing severe allergic reactions to those handling the chemical. A fluid pepsin formulation was produced and tested, first in a preliminary study and then in a ring trial encompassing four European National Reference Laboratories (NRLs......). The purpose of each trial was to ascertain and compare the action of pepsin powder with that of the pepsin fluid for digesting meat and liberating encapsulated Trichinella spiralis larvae for subsequent counting. The quality of digestion was furthermore evaluated by assessing the visibility through...

  7. Evaluation of a fluid versus a powder pepsin formulation to detect Trichinella spiralis larvae in meat samples by a digestion technique

    DEFF Research Database (Denmark)

    Maddox-Hyttel, Charlotte; Nockler, K.; Pozio, E.

    2007-01-01

    Pepsin powder constitutes a health risk, potentially causing severe allergic reactions to those handling the chemical. A fluid pepsin formulation was produced and tested, first in a preliminary study and then in a ring trial encompassing four European National Reference Laboratories (NRLs......). The purpose of each trial was to ascertain and compare the action of pepsin powder with that of the pepsin fluid for digesting meat and liberating encapsulated Trichinella spiralis larvae for subsequent counting. The quality of digestion was furthermore evaluated by assessing the visibility through...... the digestion fluid and the amount of debris remaining after digestion. For the ring trial, at each laboratory 20 blinded replicate 100-g samples of pork meat containing a known number of encapsulated T. spiralis larvae (0 to 30) were digested by the magnetic stirrer method using either the standard pepsin...

  8. Magnetic flux motion in (PrxY1−xBa2Cu3O7−δ polycrystal samples sintered in Ar and O2 atmospheres

    Directory of Open Access Journals (Sweden)

    S. Favre

    2016-09-01

    Full Text Available We present a comparative study of the magnetic flux motion in ceramic pellets made of (PrxY1−xBa2Cu3O7−δ as a function of their composition and morphology. Samples produced in Ar or O2 atmosphere present noticeable differences in their magnetic response that we explain in terms of their structural parameters. The material’s parameters that most influence the flux dynamics are morphology and oxygen content, that change dramatically with the sintering atmosphere. Moderate changes are also observed as a function of the Pr content. Magnetic pinning efficiency is discussed in terms of intergranular couplings and effective activation energies, estimated from AC-susceptibility and magnetoresistance measurements.

  9. Outside Mainstream Electronic Databases: Review of Studies Conducted in the USSR and Post-Soviet Countries on Electric Current-Assisted Consolidation of Powder Materials

    Directory of Open Access Journals (Sweden)

    Eugene G. Grigoryev

    2013-09-01

    Full Text Available This paper reviews research articles published in the former USSR and post-soviet countries on the consolidation of powder materials using electric current that passes through the powder sample and/or a conductive die-punch set-up. Having been published in Russian, many of the reviewed papers are not included in the mainstream electronic databases of the scientific articles and thus are not known to the scientific community. The present review is aimed at filling this information gap. In the paper, the electric current-assisted sintering techniques based on high- and low-voltage approaches are presented. The main results of the theoretical modeling of the processes of electromagnetic field-assisted consolidation of powder materials are discussed. Sintering experiments and related equipment are described and the major experimental results are analyzed. Sintering conditions required to achieve the desired properties of the sintered materials are provided for selected material systems. Tooling materials used in the electric current-assisted consolidation set-ups are also described.

  10. Obtaining of PA 6/Ni ferrite composites. Structural characterization by XRD of the ferrites powders and composites

    International Nuclear Information System (INIS)

    Bezerra, Daniella C.; Gouveia, Taciana R. de; Leite, Amanda M.D.; Costa, Ana Cristina F.M.; Araujo, Edcleide M.

    2009-01-01

    In general, the ferrites are absorbers of electromagnetic radiation and have the versatility to be manufactured with different geometries, or be used in the form of polycrystalline ferrites (sintered sample), or composites of ferrite (in addition of the powder appropriate matrix). The nylon 6, in turn, belongs to a class of polymers, attractive for applications in engineering due to the combination of properties such as dimensional stability, good resistance to impact without notch and excellent chemical resistance. The objective of this study was to characterize structurally the Ni ferrite powders and nylon 6/ Ni ferrite composites obtained by X-ray diffraction (DRX). The Ni ferrite powders were mixed with a polymer matrix of nylon 6 in internal mixer Haake Blucher at a temperature of 240 deg C and 60 rpm, at concentrations of 10 and 30 wt.% of Ni ferrite powders. For both concentrations we observed the characteristic diffraction peaks of ferrite and nylon 6. (author)

  11. Integrated analysis of oxide nuclear fuel sintering

    International Nuclear Information System (INIS)

    Baranov, V.; Kuzmin, R.; Tenishev, A.; Timoshin, I.; Khlunov, A.; Ivanov, A.; Petrov, I.

    2011-01-01

    Dilatometric and thermal-gravimetric investigations have been carried out for the sintering process of oxide nuclear fuel in gaseous Ar - 8% H 2 atmosphere at temperatures up to 1600 0 C. The pressed compacts were fabricated under real production conditions of the OAO MSZ with application of two different technologies, so called 'dry' and 'wet' technologies. Effects of the grain size growth after the heating to different temperatures were observed. In order to investigate the effects produced by rate of heating on properties of sintered fuel pellets, the heating rates were varied from 1 to 8 0 C per minute. Time of isothermal overexposure at maximal temperature (1600 0 C) was about 8 hours. Real production conditions were imitated. The results showed that the sintering process of the fuel pellets produced by two technologies differs. The samples sintered under different heating rates were studied with application of scanning electronic microscopy analysis for determination of mean grain size. A simulation of heating profile for industrial furnaces was performed to reduce the beam cycles and estimate the effects of variation of the isothermal overexposure temperatures. Based on this data, an optimization of the sintering conditions was performed in operations terms of OAO MSZ. (authors)

  12. Effects of helium and deuterium irradiation on SPS sintered W–Ta composites at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mateus, R., E-mail: rmateus@ipfn.ist.utl.pt [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Dias, M. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Lopes, J. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); ISEL, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa (Portugal); Rocha, J.; Catarino, N.; Franco, N. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Livramento, V. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); and others

    2013-11-15

    Energetic He{sup +} and D{sup +} ions were implanted into different W–Ta composites in order to investigate their stability under helium and deuterium irradiation. The results were compared with morphological and chemical modifications arising from exposure of pure W and Ta. Special attention was given to tantalum hydride (Ta{sub 2}H) formation due to its implications for tritium inventory. Three W–Ta composites with 10 and 20 at.% Ta were prepared from elemental W powder and Ta fibre or powder through low-energy ball milling in argon atmosphere. Spark plasma sintering (SPS) was used as the consolidation process in the temperature range from 1473 to 1873 K. The results obtained from pure elemental samples and composites are similar. However, Ta{sub 2}H is easily formed in pure Ta by using a pre-implantation stage of He{sup +}, whereas in W–Ta composites the same reaction is clearly reduced, and it can be inhibited by controlling the sintering temperature.

  13. Study of properties of chemically modified samples of halloysite mineral with X-ray fluorescence and X-ray powder diffraction methods

    Science.gov (United States)

    Banaś, D.; Kubala-Kukuś, A.; Braziewicz, J.; Majewska, U.; Pajek, M.; Wudarczyk-Moćko, J.; Czech, K.; Garnuszek, M.; Słomkiewicz, P.; Szczepanik, B.

    2013-12-01

    Elemental and chemical composition of raw and activated samples of halloysite mineral using wavelength dispersive X-ray fluorescence (WDXRF), total reflection X-ray fluorescence (TXRF) and X-ray powder diffraction (XRPD) methods were determined. As the result, it has been shown that application of the complementary X-ray spectrometry techniques allows very precise observation of changes in composition of halloysite mineral samples caused by its chemical modifications. Sample preparation procedure and usability of the research methods applied are described in details. Procedure of activation of raw halloysite mineral samples by etching them in sulfuric acid of various concentrations has been described and discussed. The ability of the samples to adsorb lead from intentionally contaminated water was tested and confirmed.

  14. Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

    Science.gov (United States)

    Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.

    1975-01-01

    Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

  15. Comparison of properties in silicon nitrides sintered with oxide and organometallic additives

    International Nuclear Information System (INIS)

    Luxem, W.; Saruhan, B.

    1994-01-01

    An homogeneous introduction of sintering additives to silicon nitride powder compacts is of great importance in the fabrication of high strength silicon nitride ceramics. Inhomogenities and impurities brought into the compacts with addition of sintering additives may influence the microstructure and phase development and subsequently degrade the mechanical properties and reliability of silicon nitride ceramics. Sintering additives in the system of Sm 2 O 3 + Al 2 O 3 as metaloxides and nitrates are introduced to two different kinds of α-silicon nitride powder. Thereby, a more homogeneous distribution of additives through an intimate mixing is aimed. Advantages of this type of processing of silicon nitride powders against conventional method are discussed. The contribution of powder characteristics in determination of these factors are displayed. (orig.)

  16. Spark plasma sintering of pure and doped tungsten as plasma facing material

    Science.gov (United States)

    Autissier, E.; Richou, M.; Minier, L.; Naimi, F.; Pintsuk, G.; Bernard, F.

    2014-04-01

    In the current water cooled divertor concept, tungsten is an armour material and CuCrZr is a structural material. In this work, a fabrication route via a powder metallurgy process such as spark plasma sintering is proposed to fully control the microstructure of W and W composites. The effect of chemical composition (additives) and the powder grain size was investigated. To reduce the sintering temperature, W powders doped with a nano-oxide dispersion of Y2O3 are used. Consequently, the sintering temperature for W-oxide dispersed strengthened (1800 °C) is lower than for pure W powder. Edge localized mode tests were performed on pure W and compared to other preparation techniques and showed promising results.

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

    Science.gov (United States)

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

    2015-06-01

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

  18. High hardness BaCb-(BxOy/BN) composites with 3D mesh-like fine grain-boundary structure by reactive spark plasma sintering.

    Science.gov (United States)

    Vasylkiv, Oleg; Borodianska, Hanna; Badica, Petre; Grasso, Salvatore; Sakka, Yoshio; Tok, Alfred; Su, Liap Tat; Bosman, Michael; Ma, Jan

    2012-02-01

    Boron carbide B4C powders were subject to reactive spark plasma sintering (also known as field assisted sintering, pulsed current sintering or plasma assisted sintering) under nitrogen atmosphere. For an optimum hexagonal BN (h-BN) content estimated from X-ray diffraction measurements at approximately 0.4 wt%, the as-prepared BaCb-(BxOy/BN) ceramic shows values of Berkovich and Vickers hardness of 56.7 +/- 3.1 GPa and 39.3 +/- 7.6 GPa, respectively. These values are higher than for the vacuum SPS processed B4C pristine sample and the h-BN -mechanically-added samples. XRD and electronic microscopy data suggest that in the samples produced by reactive SPS in N2 atmosphere, and containing an estimated amount of 0.3-1.5% h-BN, the crystallite size of the boron carbide grains is decreasing with the increasing amount of N2, while for the newly formed lamellar h-BN the crystallite size is almost constant (approximately 30-50 nm). BN is located at the grain boundaries between the boron carbide grains and it is wrapped and intercalated by a thin layer of boron oxide. BxOy/BN forms a fine and continuous 3D mesh-like structure that is a possible reason for good mechanical properties.

  19. Titanium dental copings prepared by a powder metallurgy method: a preliminary report.

    Science.gov (United States)

    Eriksson, Mikael; Andersson, Matts; Carlström, Elis

    2004-01-01

    The purpose of this study was to determine if the Procera pressed-powder method can be used to fabricate titanium copings. Commercially pure titanium powder was used to prepare the copings. The powder was pressed onto an enlarged tooth preparation die of aluminum using cold isostatic pressing. The outer shape of the coping was formed using a Procera milling machine, and the copings were vacuum sintered. Titanium copings could be prepared using this method. The density of the sintered copings reached 97% to 99%+ of theoretic density, and the copings showed ductile behavior after sintering. Enlarging the tooth preparation die to compensate for the sintering shrinkage could optimize the final size of the copings. Ductile and dense titanium dental copings can be produced with powder-metal processing using cold isostatic pressing, followed by milling and sintering to final shape. The forming technique has, if properly optimized, a potential of becoming a more cost-efficient production method than spark erosion.

  20. Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, J.C., E-mail: jpereira@uc.edu.ve [Instituto de Tecnología de Materiales, Universidad Politécnica de Valencia, Camino de vera s/n, Valencia, España (Spain); Centro de Investigaciones en Mecánica, Facultad de Ingeniería, Universidad de Carabobo (Venezuela, Bolivarian Republic of); Zambrano, J.C. [Centro de Investigaciones en Mecánica, Facultad de Ingeniería, Universidad de Carabobo (Venezuela, Bolivarian Republic of); Afonso, C.R.M. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos (UFSCar), São Carlos, SP (Brazil); Amigó, V. [Instituto de Tecnología de Materiales, Universidad Politécnica de Valencia, Camino de vera s/n, Valencia, España (Spain)

    2015-03-15

    Nickel-based superalloys such as NiCoCrAlY are widely used in high-temperature applications, such as gas turbine components in the energy and aerospace industries, due to their strength, high elastic modulus, and high-temperature oxidation resistance. However, the processing of these alloys is complex and costly, and the alloys are currently used as a bond coat in thermal barrier coatings. In this work, the effect of cold press and sintering processing parameters on the microstructure and mechanical properties of NiCoCrAlY alloy were studied using the powder metallurgy route as a new way to obtain NiCoCrAlYTa samples from a gas atomized prealloyed powder feedstock. High mechanical strength and adequate densification up to 98% were achieved. The most suitable compaction pressure and sintering temperature were determined for NiCoCrAlYTa alloy through microstructure characterization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy microanalysis (EDS) were performed to confirm the expected γ-Ni matrix and β-NiAl phase distribution. Additionally, the results demonstrated the unexpected presence of carbides and Ni–Y-rich zones in the microstructure due to the powder metallurgy processing parameters used. Thus, microhardness, nanoindentation and uniaxial compression tests were conducted to correlate the microstructure of the alloy samples with their mechanical properties under the different studied conditions. The results show that the compaction pressure did not significantly affect the mechanical properties of the alloy samples. In this work, the compaction pressures of 400, 700 and 1000 MPa were used. The sintering temperature of 1200 °C for NiCoCrAlYTa alloy was preferred; above this temperature, the improvement in mechanical properties is not significant due to grain coarsening, whereas a lower temperature produces a decrease in mechanical properties due to high porosity and