Sintered nuclear fuel and method of preparing same

International Nuclear Information System (INIS)

Abate-Daga, G.; Amato, I.

1975-01-01

A description is given of a method of preparing a nuclear fuel containing a consumable nuclear poison uniformly distributed therein in the form of coated micro-spheres of between 10 and 2,000 microns diameter, consisting in preparing sintered micro-spheres of the consumable poison, covering those micro-spheres with a protective coating and incorporating the coated micro-spheres into uranium dioxide powder, followed by sintering

Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

International Nuclear Information System (INIS)

Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

High purity W and W-0.9La 2 O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 o C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

Sinterability and microstructure evolution during sintering of ferrous powder mixtures

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Kétner Bendo Demétrio

2013-01-01

Full Text Available The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%, in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

Scaffolds of PDLLA/bioglass 58S produced via selective laser sintering

Energy Technology Data Exchange (ETDEWEB)

Pereira, Rafaela do Vale; Salmoria, Gean Vitor; Moura, Marcela Oliveira Caldeira de; Aragones, Aguedo; Fredel, Marcio Celso, E-mail: rafaelavpereira@gmail.com [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

2014-08-15

Scaffolds of PDLLA were produced to be implemented in maxillofacial surgeries inducing bone repair and regeneration. To prepare these scaffolds, bioglass (BG58S) was synthesized by sol-gel method, in order to be applied as osteoconductive dispersed particles in PDLLA matrix. Once presenting greater facility on parts fabrication, this polymeric matrix enables complex geometries production besides presenting compatible degradation rate for scaffold absorption and bone regeneration. Scaffolds production was performed by selective laser sintering in order to obtain tailored-made parts. FTIR and XRD analyses were carried out to observe the composition and evaluate the presence of crystallized phases in bioglass, obtaining Wollastonite. SEM was used to observe the BG particle distribution in PDLLA matrix and flexural test was performed to evaluate the composite mechanical properties. Results showed that was possible to obtain pieces using SLS method and with addition of 10%wt BG to polymeric matrix, flexural modulus and strength increased regarding to pure polymer. (author)

Mechanical characteristics of microwave sintered silicon carbide

Indian Academy of Sciences (India)

In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

Flash sintering of ceramic materials

Science.gov (United States)

Dancer, C. E. J.

2016-10-01

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

Synthesis of Cu-CNTs nanocomposites via double pressing double sintering method

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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.

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

Residual stress in TI6AL4V objects produced by direct metal laser sintering

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Van Zyl, Ian

2016-12-01

Full Text Available Direct Metal Laser Sintering produces 3D objects using a layer-by- layer method in which powder is deposited in thin layers. Laser beam scans over the powder fusing powder particles as well as the previous layer. High-concentration of laser energy input leads to high thermal gradients which induce residual stress within the as- built parts. Ti6Al4V (ELI samples have been manufactured by EOSINT M280 system at prescribed by EOS process-parameters. Residual stresses were measured by XRD method. Microstructure, values and directions of principal stresses inTi6Al4V DMLS samples were analysed.

Removable partial denture alloys processed by laser-sintering technique.

Science.gov (United States)

Alageel, Omar; Abdallah, Mohamed-Nur; Alsheghri, Ammar; Song, Jun; Caron, Eric; Tamimi, Faleh

2018-04-01

Removable partial dentures (RPDs) are traditionally made using a casting technique. New additive manufacturing processes based on laser sintering has been developed for quick fabrication of RPDs metal frameworks at low cost. The objective of this study was to characterize the mechanical, physical, and biocompatibility properties of RPD cobalt-chromium (Co-Cr) alloys produced by two laser-sintering systems and compare them to those prepared using traditional casting methods. The laser-sintered Co-Cr alloys were processed by the selective laser-sintering method (SLS) and the direct metal laser-sintering (DMLS) method using the Phenix system (L-1) and EOS system (L-2), respectively. L-1 and L-2 techniques were 8 and 3.5 times more precise than the casting (CC) technique (p laser-sintered and cast alloys were biocompatible. In conclusion, laser-sintered alloys are more precise and present better mechanical and fatigue properties than cast alloys for RPDs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1174-1185, 2018. © 2017 Wiley Periodicals, Inc.

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.)

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

Microstructural and Mechanical Properties of Porous 60NiTi Prepared by Conventional Press-and-sinter Method

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Khanlari Khashayar

2017-01-01

Full Text Available An intermetallic nickel-titanium alloy, 60NiTi, comprised of approximately 60 wt.% Ni and 40 wt.% Ti, contains a broad combination of physical and mechanical properties such as high hardness, low elastic modulus, resistance to aqueous corrosion and good biocompatibility. These unique combinations make this alloy an attractive candidate for medical components such as implants and prosthesis, where biocompatible materials with high hardness and low stiffness are typically used. The conventional press-and-sinter method which represents the least complex, most flexible and economic powder metallurgy method was used to produce porous 60NiTi parts suitable for biomedical applications. The effect of sintering holding time on the microstructure and mechanical properties is investigated. The structure of the as sintered parts is quite porous which is beneficial based on the medical point of view. The ultimate compressive strength of the samples is higher than that of the compact human bone and can, therefore, meet the strength demand of implants for general bone replacement applications.

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.

Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

International Nuclear Information System (INIS)

Watanabe, Yoshimi; Shibuya, Masafumi; Sato, Hisashi

2013-01-01

The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

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.)

Sintering of Kernel UO2 for High Temperature Reactor Fuel

International Nuclear Information System (INIS)

Sukarsono; Dwi-Heru-Sucahyo; Hidayati; Evi-Hertiviana; Bambang-Sugeng

2000-01-01

Sintering investigation of UO 2 gel has been done. The gel was preparedthrough two ways. The first, gel was produced using PVA as additive agent.The second gel was produced using HMTA and Urea as additive agent. From thepreparation of gel, the PVA method better than the urea - HMTA method,because was not necessary the cold temperature for sol preparation and alsowas not necessary the hot temperature for gelation process. After nextprocessing, the sintered gel of gel through PVA, also better than HMTAprocess. (author)

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

The Influence of Sintering Temperature of Reactive Sintered (Ti, MoC-Ni Cermets

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Marek Jõeleht

2015-09-01

Full Text Available Titanium-molybdenum carbide nickel cermets ((Ti, MoC-Ni were produced using high energy milling and reactive sintering process. Compared to conventional TiC-NiMo cermet sintering the parameters for reactive sintered cermets vary since additional processes are present such as carbide synthesis. Therefore, it is essential to acquire information about the suitable sintering regime for reactive sintered cermets. One of the key parameters is the final sintering temperature when the liquid binder Ni forms the final matrix and vacancies inside the material are removed. The influence of the final sintering temperature is analyzed by scanning electron microscopy. Mechanical properties of the material are characterized by transverse rupture strength, hardness and fracture toughness.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7179

SINTERING EFFECTS ON THE DENSIFICATION OF NANOCRYSTALLINE HYDROXYAPATITE

Directory of Open Access Journals (Sweden)

M. Amiriyan

2011-06-01

Full Text Available The effects of sintering profiles on the densification behaviour of synthesized nanocrystalline hydroxyapatite (HA powder were investigated in terms of phase stability and mechanical properties. A wet chemical precipitation method was successfully employed to synthesize a high purity and single phase HA powder. Green HA compacts were prepared and subjected to sintering in air atmosphere over a temperature range of 700° C to 1300° C. In this study two different holding times were compared, i.e. 1 minute versus the standard 120 minutes. The results revealed that the 1 minute holding time sintering profile was indeed effective in producing a HA body with high density of 98% theoretical when sintered at 1200° C. High mechanical properties such as fracture toughness of 1.41 MPa.m1/2 and hardness of 9.5 GPa were also measured for HA samples sintered under this profile. Additionally, XRD analysis indicated that decomposition of the HA phase during sintering at high temperatures was suppressed.

A method for preparing a sintered glass powder for manufacturing microspheres

International Nuclear Information System (INIS)

Budrick, R.G.; King, F.T.; Nolen, R.L. Jr.; Solomon, D.E.

1975-01-01

The invention relates to the manufacture of sintered glass-powder. It relates to a method comprising the step of forming a vitreous gel so that it contains an occluded substance adapted to expand when heated, said gel being subsequently dried, then crushed and sorted prior to being washed and dried again. Application to the manufacture of sintered glass-powder for forming microspheres adapted to contain a thermonuclear fuel [fr

Effect of wrapped Zn plate on the densification of Al-MWCNTs composites produced by cold pressing and liquid phase sintering

Energy Technology Data Exchange (ETDEWEB)

Joo, M.R. [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Choi, H.J. [School of Advanced Materials Engineering, Kookmin University, Seoul 136-702 (Korea, Republic of); Shin, S.E. [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Bae, D.H., E-mail: donghyun@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

2016-09-30

To produce highly dense and cost-effective Al-multi-walled carbon nanotube (Al-MWCNT) composites, the composite powders are wrapped by a Zn plate and then cold-pressed. The green compacts are then sintered at 550 °C, which shows ~99%density after sintering for 24 h. During sintering, Zn atoms fill the voids at the powder boundaries by capillary action and are then dissolved into the Al matrix because of the high solubility of Zn in Al, thus assisting densification of the composite powder. The Al/Zn-based composites containing 4 vol% MWCNTs show compressive yield strength (~380 MPa) and high work hardening capacity.

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.

Microstructures and mechanical properties of 9Cr oxide dispersion strengthened steel produced by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Xie, Rui [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); School of Metallurgy, Northeastern University, Shenyang 110819 (China); Lu, Zheng, E-mail: luz@atm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Lu, Chenyang; Li, Zhengyuan [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Ding, Xueyong [School of Metallurgy, Northeastern University, Shenyang 110819 (China); Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China)

2017-02-15

Highlights: • A 9Cr-ODS steel was produced by mechanical alloying and spark plasma sintering. • Bimodal grain size distribution was observed. • Formation mechanism of bimodal grain size distribution was discussed. • The size and number density of nanoscale particles were obtained by SAXS and HRTEM. • The contribution of nano-sized particles to yield strength is dominating. - Abstract: 9Cr oxide dispersion strengthened (ODS) steel was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The nano-sized particles, grain size distribution and mechanical properties of 9Cr-ODS steel sintered at 950 °C were studied by synchrotron radiation small angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), electron backscatter diffraction (EBSD) and tensile experiment. The results showed that bimodal grain size distribution in the matrix is observed, which is attributed to the heterogeneous recrystallization process during the SPS. High-density nano-sized Y{sub 2}Ti{sub 2}O{sub 7} and some large oxides of Cr{sub 2}Mn(Ti)O{sub 4} are formed in 9Cr-ODS steel. The number density and average size of Y{sub 2}Ti{sub 2}O{sub 7} obtained from SAXS are 4.72 × 10{sup 22}/m{sup 3} and 4.4 nm, respectively. The yield strengths of 9Cr-ODS steel fabricated by SPS are compared with the typical 9Cr-ODS steel produced by HIP.

Structural characterization of biomedical Co–Cr–Mo components produced by direct metal laser sintering

International Nuclear Information System (INIS)

Barucca, G.; Santecchia, E.; Majni, G.; Girardin, E.; Bassoli, E.; Denti, L.; Gatto, A.; Iuliano, L.; Moskalewicz, T.; Mengucci, P.

2015-01-01

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co–Cr–Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin ε (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The ε-lamellae grown on the {111} γ planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields. - Highlights: • Samples of a Co–Cr–Mo biomedical alloy were produced by direct metal laser sintering. • Hardness values unexpectedly high were attributed to a peculiar microstructure. • Fine lamellae of the ε-phase alternated to the γ-phase were observed for the first time. • A nucleation and growth model for the observed microstructure is proposed

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

International Nuclear Information System (INIS)

Baharom, Syazwani; Ahmad, Sufizar; Taib, Hariati; Muda, Rizamarhaiza

2016-01-01

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO_2) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO_2 were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO_2 that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO_2 ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO_2 ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO_2 ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm"3 up to 0.75 g/cm"3, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

Sintering method for nuclear fuel pellet

International Nuclear Information System (INIS)

Omuta, Hirofumi; Nakabayashi, Shigetoshi.

1997-01-01

When sintering a compressed nuclear fuel powder in an atmosphere of a mixed gas comprising hydrogen and nitrogen, steams are added to the mixed gas to suppress the nitrogen content in sintered nuclear fuel pellets. In addition, the content of nitrogen impurities in the nuclear fuel pellets can be controlled by controlling the amount of steams to be added to the mixed gas, namely, by controlling the dew point as an index thereof. If the addition amount of steams to the mixed gas is determined by controlling the dew point as an index, the content of nitrogen impurities in the sintered nuclear fuel pellets can be controlled reliably to a specified value of 0.0075% or less. If ammonolyzed gas is used as the mixed gas, a more economical mixed gas can be obtained than in the case of forming mixed gas by mixing the hydrogen gas and the nitrogen gas. (N.H.)

77 FR 51046 - Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same; Notice...

Science.gov (United States)

2012-08-23

... INTERNATIONAL TRADE COMMISSION [Docket No. 2908] Certain Sintered Rare Earth Magnets, Methods of... Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same, DN 2908; the..., methods of making same and products [[Page 51047

Granulation of coke breeze fine for using in the sintering process

Directory of Open Access Journals (Sweden)

Mohamed F.M.

2010-01-01

Full Text Available Coke breeze is the main fuel used in the sintering process. The value of -3+1 mm. represents the most favorable particle size for coke breeze in the sintering process. About 20% of total coke fines (-0.5 mm are produced during different steps of preparation. Introducing these fines during the sintering process proves to be very harmful for different operating parameters. Thus ,this study aims at investigating the production of granules resulting from these fines using molasses as organic binder and its application in sintering of an iron ore. The results showed that the granules having the highest mechanical properties were obtained with 14.5 wt % molasses addition. The sintering experiments were performed by using coke breeze in different shapes (-3+1 mm in size, coke breeze without sieving and coke breeze granules -3+1 mm. The reduction experiments, microscopic structure and X-ray analysis for the produced sinter were carried out. The results revealed that, all sinter properties (such as shatter test, productivity of sinter machine and blast furnace, reduction time and chemical composition for produced sinter by using coke breeze with size -3+1 mm and coke breeze granules were almost the same. The iron ore sinter which was produced by using coke breeze without sieving yielded low productivity for both sinter machine and blast furnace. Furthermore, using coke breeze without sieving in sintering of an iron ore decreases the vertical velocity of sinter machine and increases the reduction time.

Defectoscopy of direct laser sintered metals by low transmission ultrasonic frequencies

Directory of Open Access Journals (Sweden)

Ebersold Zoran

2012-01-01

Full Text Available This paper focuses on the improvement of ultrasonic defectoscopy used for machine elements produced by direct laser metal sintering. The direct laser metal sintering process introduces the mixed metal powder and performs its subsequent laser consolidation in a single production step. Mechanical elements manufactured by laser sintering often contain many hollow cells due to weight reduction. The popular pulse echo defectoscopy method employing very high frequencies of several GHz is not successful on these samples. The aim of this paper is to present quadraphonic transmission ultrasound defectoscopy which uses low range frequencies of few tens of kHz. Therefore, the advantage of this method is that it enables defectoscopy for honeycombed materials manufactured by direct laser sintering. This paper presents the results of testing performed on AlSi12 sample. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057

Superior sinterability of nano-crystalline gadolinium doped ceria powders synthesized by co-precipitation method

International Nuclear Information System (INIS)

Hari Prasad, D.; Kim, H.-R.; Park, J.-S.; Son, J.-W.; Kim, B.-K.; Lee, H.-W.; Lee, J.-H.

2010-01-01

Reduced sintering temperature of doped ceria can greatly simplify the fabrication process of solid oxide fuel cells (SOFCs) by utilizing the co-firing of all cell components with a single step. In the present study, nano-crystalline gadolinium doped ceria (GDC) powders of high sinterability at lower sintering temperature has been synthesized by co-precipitation at room temperature. The successful synthesis of nano-crystalline GDC was confirmed by XRD, TEM and Raman spectroscopy analysis. Dilatometry studies showed that GDC prepared by this method can be fully densified (97% relative density) at a sintering temperature of 950 o C which is fairly lower than ever before. It has also been found that the sintered samples have a higher ionic conductivity of 1.64 x 10 -2 S cm -1 at 600 o C which is suitable for the intermediate temperature SOFC application.

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.)

Structural characterization of biomedical Co–Cr–Mo components produced by direct metal laser sintering

Energy Technology Data Exchange (ETDEWEB)

Barucca, G., E-mail: g.barucca@univpm.it [SIMAU, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); Santecchia, E.; Majni, G. [SIMAU, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); Girardin, E. [DISCO, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); Bassoli, E.; Denti, L.; Gatto, A. [DIMeC, University of Modena and Reggio Emilia, via Vignolese 905/B, Modena 41125 (Italy); Iuliano, L. [DISPEA, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy); Moskalewicz, T. [Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków (Poland); Mengucci, P. [SIMAU, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy)

2015-03-01

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co–Cr–Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin ε (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The ε-lamellae grown on the {111}{sub γ} planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields. - Highlights: • Samples of a Co–Cr–Mo biomedical alloy were produced by direct metal laser sintering. • Hardness values unexpectedly high were attributed to a peculiar microstructure. • Fine lamellae of the ε-phase alternated to the γ-phase were observed for the first time. • A nucleation and growth model for the observed microstructure is proposed.

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

Energy Technology Data Exchange (ETDEWEB)

Baharom, Syazwani, E-mail: hd140001@siswa.uthm.edu.my; Ahmad, Sufizar, E-mail: sufizar@uthm.edu.my; Taib, Hariati, E-mail: hariati@uthm.edu.my; Muda, Rizamarhaiza, E-mail: hd130013@siswa.uthm.edu.my [Department of Material and Design Engineering, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

2016-07-19

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO{sub 2}) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO{sub 2} were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO{sub 2} that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO{sub 2} ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO{sub 2} ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO{sub 2} ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm{sup 3} up to 0.75 g/cm{sup 3}, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

Influence of sintering temperature on mechanical properties of spark plasma sintered pre-alloyed Ti-6Al-4 V powder

Energy Technology Data Exchange (ETDEWEB)

Muthuchamy, A.; Patel, Paridh; Rajadurai, M. [VIT Univ., Vellore, Tamil Nadu (India); Chaurisiya, Jitendar K. [NIT, Suratkal (India); Annamalai, A. Raja [VIT Univ., Vellore, Tamil Nadu (India). Centre for Innovative Manufacturing Research

2018-04-01

Spark plasma sintering provides faster heating that can create fully, or near fully, dense samples without significant grain growth. In this study, pre-alloyed Ti-6Al-4 V powder compact samples produced through field assisted sintering in a spark plasma sintering machine are compared as a function of consolidation temperature. The effect of sintering temperature on the densification mechanism, microstructural evolution and mechanical properties of spark plasma sintered Ti-6Al-4 V alloy compacts was investigated in detail. The compact, sintered at 1100 C, exhibited near net density, highest hardness and strength as compared to the other compacts processed at a temperature lower than 1100 C.

Microstructures and mechanical properties of Fe-28Al-5Cr/TiC composites produced by hot-pressing sintering

International Nuclear Information System (INIS)

Zhang Xinghua; Yang Jun; Ma Jiqiang; Bi Qinling; Cheng Jun; Liang Yongmin; Liu Weimin

2011-01-01

Highlights: → The near fully dense Fe-28Al-5Cr/TiC composites are produced by hot-pressing sintering. → All the materials exhibit high compressive and bending strength. → Compressive strength increases but bending strength and ductility diminish with rising TiC amount in the composites. → Wear resistance significantly increases with rising TiC amount. - Abstract: The mechanical properties and microstructures of Fe-28Al-5Cr based composites reinforced with 15, 25, 35, 50 wt.% TiC ceramic particle, produced by hot-pressing sintering method, were investigated. The relative density of all the composites was up to 99%. The distribution of TiC was uniform in the composites. Results of XRD analysis showed that the composites were composed of TiC and disorder Fe 3 Al phases. All the materials exhibited very high strength of 1200-2000 MPa. The hardness and compressive strength of the composites increased obviously but compressive strain decreased gradually except 50% composite with increasing TiC content. The bending strength and deflection of the composites decreased significantly with increasing TiC content. The bending fracture surfaces of all the materials were examined using scanning electron microscopy (SEM). The fracture mode transformed gradually from tough dimple fracture mode to brittle cleavage facets crack mode with the increase of TiC content. Wear resistance of the Fe-28Al-5Cr alloy was also significantly improved by addition of TiC.

Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

International Nuclear Information System (INIS)

Wang, G.P.; Liu, W.Q.; Huang, Y.L.; Ma, S.C.; Zhong, Z.C.

2014-01-01

Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively

Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Wang, G.P., E-mail: wgp@jxnu.edu.cn [College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022 (China); Liu, W.Q. [Key Laboratory of Advanced Functional Materials Science and Engineering, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Huang, Y.L.; Ma, S.C.; Zhong, Z.C. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

2014-01-15

Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively.

Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

Energy Technology Data Exchange (ETDEWEB)

Antonov, E N; Krotova, L I; Minaev, N V; Minaeva, S A; Mironov, A V; Popov, V K [Institute on Laser and Information Technologies of the Russian Academy of Sciencies, Troitsk, Moscow (Russian Federation); Bagratashvili, V N [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2015-11-30

We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 – 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering. (interaction of laser radiation with matter. laser plasma)

Stable solidification of cesium with an allophane additive by a pressing/sintering method

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaoxia [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240 (China); Wu, Yan, E-mail: wu_yan@sjtu.edu.cn [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240 (China); Wei, Yuezhou [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240 (China); College of Resources and Metallurgy, Guangxi University, Nanning, 530004 (China); Mimura, Hitoshi; Matsukura, Minoru [UNION SHOWA K.K., 1-8-40Kounan Minato-ku, Tokyo, 108-0075 (Japan)

2017-03-15

Pyrolysis of AMP/SiO{sub 2} adsorbed Cs (AMP-Cs/SiO{sub 2}) occurred at > 400 °C sintering temperature, and Cs immobilisation decreased from 100% to 40% after sintering at 1200 °C. To safely dispose radioactive Cs, allophane was immobilized with AMP-Cs/SiO{sub 2} to prepare a stable form by using a pressing/sintering method. The structure of AMP-Cs/SiO{sub 2} collapsed, and cesium aluminosilicate formed more easily under conditions of higher sintering temperature (>800 °C) or increasing mixing ratio of allophane (mass ratio = 1:3 AMP-Cs/SiO{sub 2}-allophane). The decomposition products of AMP-Cs/SiO{sub 2} were Cs{sub 2}O, MoO{sub 3} and P{sub 2}O{sub 5} at 1200 °C. Cs{sub 2}O volatilisation was depressed by allophane addition, and a stable immobilisation phase of Cs{sub 4}Al{sub 4}Si{sub 20}O{sub 48} formed. An immobilisation ratio of Cs of approximately 100% was maintained. The leachability of Cs for AMP-Cs/SiO{sub 2}-allophane (1:3, 1200 °C) in distilled water at 25 °C and 90 °C for 15 days was estimated as 0.174% and 1.55%, respectively. - Highlights: • A pressing/sintering method was used to solidify AMP-Cs/SiO{sub 2}-allophane. • The volatility of Cs{sub 2}O could be effectively restrained by allophane. • Cs{sub 4}Al{sub 4}Si{sub 20}O{sub 48} was formed for stable solidification of Cs. • The leachability of Cs from sintered AMP-Cs/SiO{sub 2}-allophane was relatively low.

Science of sintering

International Nuclear Information System (INIS)

Kuczynski, G.

1977-01-01

Although the methods of integration of materials by sintering, have been used since the early history of humanity, the actual understanding of the process involved came only in the last three decades. As in the most human endeavors, the art preceded theory. The comprehension of the elementary processes occuring during sintering comes from the studies of model system. Although the elementary processes occuring during sintering are today quite well understood, the problem of shrinkage of a powder compact which was at the origin of Sintering Science is still far from solved. This is due to the complexity of the internal geometry of the compacts. The recent attempts to apply statistics to this problem, seem to offer some promise

Metallurgical and Mechanical Evaluation of 4340 Steel Produced by Direct Metal Laser Sintering

Science.gov (United States)

Jelis, Elias; Clemente, Matthew; Kerwien, Stacey; Ravindra, Nuggehalli M.; Hespos, Michael R.

2015-03-01

Direct metal laser sintering (DMLS) was used to produce high-strength low-alloy 4340 steel specimens. Mechanical and metallurgical analyses were performed on the specimens to determine the samples with the highest strengths and the least porosity. The optimal process parameters were thus defined based on the corresponding experimental conditions. Additionally, the effects of fabricating specimens with both virgin and recycled powders were studied. Scanning electron microscopy and electron-dispersive spectroscopy were performed on both types of powders to determine the starting morphology and composition. The initial tensile results are promising, suggesting that DMLS can produce specimens equal in strength to wrought materials. However, there is evidence of cracking on several of the heat-treated tensile specimens that is unexplained. Several theories point to disturbances in the build chamber environment that went undetected while the specimens were being fabricated.

Compactibility of Al/Al2O3 Isotropic Composite with Variation of Holding Time Sintering.

Directory of Open Access Journals (Sweden)

Eddy S Siradj

2008-11-01

Full Text Available The requirement of component with structural ability, light weight and also strength is increasing base on Metal Matrix Composites (MMCs by aluminum as matrix (AMCs. A structural ability is connected to composites compactibility which is depend on quality of interfacial bounding. Powder metallurgy is one of method to produce composite with powder mixing, compacting and sintering. Volume fractions reinforced and sintering time can influence composites compactibility. Volume fractions reinforced variable can produce different reinforcement effect. Beside that, on sintering enables the formation of new phase during sintering time. In this research, Al/Al2O3 isotropic composites are made with aluminum as matrix and alumina (Al2O3 as reinforced. Volume fraction reinforced used 10%. 20%. 30% and 40%. Sintering temperature and compaction pressure are each 600oC and 15 kN. The tests that applied are compression and metallographic test. The result that obtained is optimum compactibility of Al/Al2O3 composite reached at holding time 2 hour. During sintering, new phase can occur that is aluminum oxides (alumina, with unstable properties. The best volume fraction reinforced and holding time sintering are 40% and 2 hours.

Pressureless sintering of whisker-toughened ceramic composites

Science.gov (United States)

Tiegs, T.N.

1993-05-04

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

A finite difference model of the iron ore sinter process

OpenAIRE

Muller, J.; de Vries, T.L.; Dippenaar, B.A.; Vreugdenburg, J.C.

2015-01-01

Iron ore fines are agglomerated to produce sinter, which is an important feed material for blast furnaces worldwide. A model of the iron ore sintering process has been developed with the objective of being representative of the sinter pot test, the standard laboratory process in which the behaviour of specific sinter feed mixtures is evaluated. The model aims to predict sinter quality, including chemical quality and physical strength, as well as key sinter process performance parameters such ...

Porous alumina scaffold produced by sol-gel combined polymeric sponge method

Science.gov (United States)

Hasmaliza, M.; Fazliah, M. N.; Shafinaz, R. J.

2012-09-01

Sol gel is a novel method used to produce high purity alumina with nanometric scale. In this study, three-dimensional porous alumina scaffold was produced using sol-gel polymeric sponge method. Briefly, sol gel alumina was prepared by evaporation and polymeric sponge cut to designated sizes were immersed in the sol gel followed by sintering at 1250 and 1550°C. In order to study the cell interaction, the porous alumina scaffold was sterilized using autoclave prior to Human Mesenchymal Stem Cells (HMSCs) seeding on the scaffold and the cell proliferation was assessed by alamarBlue® assay. SEM results showed that during the 21 day period, HMSCs were able to attach on the scaffold surface and the interconnecting pores while maintaining its proliferation. These findings suggested the potential use of the porous alumina produced as a scaffold for implantation procedure.

The relationship between the addition method of the Ni-activator and the sinterability for the Ni-doped W-powder compact

International Nuclear Information System (INIS)

Moon, I.H.; Kim, J.S.

1984-01-01

The relationship between the nickel size added to tungsten powder and the sinterability was investigated for the Ni-doped W-powder compact. The Ni-added W-powder compact with various particle size ratios of W to Ni were prepared by mechanical mixing as well as by salt solution and reduction method. In the latter method the size of reduced Ni-particle could be controlled by drying rate of salt solution. The smaller the size of nickel particles added to W was, the activatedly sintered W-powder compact has shown higher sinterability in the initial stage of sintering. The dependence of sinterability on the size of Ni-activator could be partly explained by some physical characteristics of Ni-activator at sintering temperature. (Auth.)

Effects of thermal treatments on microstructure and mechanical properties of a Co-Cr-Mo-W biomedical alloy produced by laser sintering.

Science.gov (United States)

Mengucci, P; Barucca, G; Gatto, A; Bassoli, E; Denti, L; Fiori, F; Girardin, E; Bastianoni, P; Rutkowski, B; Czyrska-Filemonowicz, A

2016-07-01

Direct Metal Laser Sintering (DMLS) technology based on a layer by layer production process was used to produce a Co-Cr-Mo-W alloy specifically developed for biomedical applications. The alloy mechanical response and microstructure were investigated in the as-sintered state and after post-production thermal treatments. Roughness and hardness measurements, and tensile and flexural tests were performed to study the mechanical response of the alloy while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) techniques and microanalysis (EDX) were used to investigate the microstructure in different conditions. Results showed an intricate network of ε-Co (hcp) lamellae in the γ-Co (fcc) matrix responsible of the high UTS and hardness values in the as-sintered state. Thermal treatments increase volume fraction of the ε-Co (hcp) martensite but slightly modify the average size of the lamellar structure. Nevertheless, thermal treatments are capable of producing a sensible increase in UTS and hardness and a strong reduction in ductility. These latter effects were mainly attributed to the massive precipitation of an hcp Co3(Mo,W)2Si phase and the contemporary formation of Si-rich inclusions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Single-phase highly densified SrBi{sub 2}Ta{sub 2}O{sub 9} compacts produced by high-pressure sintering

Energy Technology Data Exchange (ETDEWEB)

Pereira, Altair Soria; Souza, Ricson Rocha de; Sousa, Vania Caldas de, E-mail: altair@if.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil)

2016-07-01

Full text: The development of high-performance lead-free piezoelectric ceramics is an important scientific and technological challenge, as environmental and health issues have imposed restrictions to the use of lead zirconate titanates, the most employed material in ferroelectric devices [1]. Strontium bismuth tantalate (SBT),SrBi{sub 2}Ta{sub 2}O{sub 9}, is an interesting alternative ferroelectric material as its polarization can be modified at low voltages and it shows limited polarization switching fatigue. However, the production of highly densified single-phase bulk SBT by conventional sintering procedures is strongly compromised by stoichiometric changes due to bismuth loss. In this work, high-pressure sintering has been exploited as an alternative procedure to obtain SBT highly-densified single-phase compacts. Using toroidal-type high-pressure chambers, samples were produced by reaction sintering of BiTaO{sub 4} and SrCO{sub 3} powders, mixed in the stoichiometric ratio corresponding to SrBi{sub 2}Ta{sub 2}O{sub 9}, at pressures of 2.5 GPa and 7.7 GPa, and temperatures up to 1250°C, during 10 min. X-ray diffraction and scanning electron microscopy associated to energy-dispersive X-ray spectroscopy were used to follow the phase composition and the microstructure evolution as a function of the processing conditions. A single-phase SBT compact, with a relative density of 93% and a homogeneous microstructure, was produced by sintering at 2.5 GPa/900°C [2]. References: [1] K. Panda, J. Mater. Sci. 44, 5049-5062 (2009). [2] Ricson R.Souza, Rejane K. Kirchner, Jose R. Jurado, Altair S. Pereira, Vania C. Sousa. Journal of Solid State Chemistry 233, 259-268 (2016). (author)

Synthesis of highly sinterable YAG nanopowders by a modified co-precipitation method

International Nuclear Information System (INIS)

Chen, Zhi-Hui; Yang, Yun; Hu, Zhang-Gui; Li, Jiang-Tao; He, Shu-Li

2007-01-01

A hydrate precursor of yttrium aluminum garnet (YAG) was synthesized by a modified co-precipitation method, in which n-butanol was employed as a low-cost recyclable dehydration solvent. A mixed solution of ethanol and ammonia were used as precipitant. Pure YAG phase appeared after the as-prepared precursors being calcined at 850 o C for 2 h. The nanocrystalline YAG particles calcined at 1100 o C were well dispersed with average diameter of about 40 nm, which can be densified to transparency under vacuum sintering at 1700 o C for 5 h with TEOS as sintering additive

Study of ceramics sintering under high pressures

International Nuclear Information System (INIS)

Kunrath Neto, A.O.

1990-01-01

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

Evaluation of thermal properties of sintered beryllium oxide produced from Indian beryl ore

International Nuclear Information System (INIS)

Nair, Sathi R.; Ghanwat, S.J.; Patro, P.K.; Syambabu, M.; Mawal, N.E.; Mahata, T.; Sinha, P.K.

2014-01-01

Beryllium oxide (BeO) ceramics possess many interesting properties such as good thermal conductivity, high electrical resistivity, high chemical and thermal stability, low dielectric constant, low dielectric loss and low neutron absorption coefficient. These properties lead to its wide use in vacuum electronics technology, nuclear technology, microelectronics and photoelectron technology. The above properties depend on the purity of the material as well as density and microstructure of the sintered body. For high temperature application thermal conductivity and thermal expansion are two important parameters. In the present study, high purity fine BeO powder has been prepared by beryllate route starting with crude beryllium hydroxide. The powder has been sintered at 1550℃ and sintered samples have been evaluated for its thermal properties

Weldability Characteristics of Sintered Hot-Forged AISI 4135 Steel Produced through P/M Route by Using Pulsed Current Gas Tungsten Arc Welding

Science.gov (United States)

Joseph, Joby; Muthukumaran, S.; Pandey, K. S.

2016-01-01

Present investigation is an attempt to study the weldability characteristics of sintered hot-forged plates of AISI 4135 steel produced through powder metallurgy (P/M) route using matching filler materials of ER80S B2. Compacts of homogeneously blended elemental powders corresponding to the above steel were prepared on a universal testing machine (UTM) by taking pre-weighed powder blend with a suitable die, punch and bottom insert assembly. Indigenously developed ceramic coating was applied on the entire surface of the compacts in order to protect them from oxidation during sintering. Sintered preforms were hot forged to flat, approximately rectangular plates, welded by pulsed current gas tungsten arc welding (PCGTAW) processes with aforementioned filler materials. Microstructural, tensile and hardness evaluations revealed that PCGTAW process with low heat input could produce weldments of good quality with almost nil defects. It was established that PCGTAW joints possess improved tensile properties compared to the base metal and it was mainly attributed to lower heat input, resulting in finer fusion zone grains and higher fusion zone hardness. Thus, the present investigation opens a new and demanding field in research.

The usability of ark clam shell (Anadara granosa) as calcium precursor to produce hydroxyapatite nanoparticle via wet chemical precipitate method in various sintering temperature.

Science.gov (United States)

Khiri, Mohammad Zulhasif Ahmad; Matori, Khamirul Amin; Zainuddin, Norhazlin; Abdullah, Che Azurahanim Che; Alassan, Zarifah Nadakkavil; Baharuddin, Nur Fadilah; Zaid, Mohd Hafiz Mohd

2016-01-01

This paper reported the uses of ark clam shell calcium precursor in order to form hydroxyapatite (HA) via the wet chemical precipitation method. The main objective of this research is to acquire better understanding regarding the effect of sintering temperature in the fabrication of HA. Throughout experiment, the ratio of Ca:P were constantly controlled, between 1.67 and 2.00. The formation of HA at these ratio was confirmed by means of energy-dispersive X-ray spectroscopy analysis. In addition, the effect of sintering temperature on the formation of HA was observed using X-ray diffraction analysis, while the structural and morphology was determined by means of field emission scanning electron microscopy. The formation of HA nanoparticle was recorded (~35-69 nm) in the form of as-synthesize HA powder. The bonding compound appeared in the formation of HA was carried out using Fourier transform infrared spectroscopy such as biomaterials that are expected to find potential applications in orthopedic and biomedical industries .

Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

Directory of Open Access Journals (Sweden)

Nguyen Thi Hoang Oanh

2017-03-01

Full Text Available This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C nanocomposites with different volume fractions (10% and 20% of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS at 900 and 1000 °C producing bulk materials with relative densities of 95–97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD, scanning electron microscopy (SEM, and high resolution transmission electron microscopy (HRTEM. XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC sintered at 900 °C show TiC nanoparticles about 10–30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 °C, more TiC precipitates from Cu–TiH2–C than those of Cu–Ti–C composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu–TiH2–C and Cu–Ti–C nanocomposites sintered at 1000 °C are 314 and 306 HV, respectively.

Method of manufacturing gadolinium oxide-incorporated nuclear fuel sintering products

International Nuclear Information System (INIS)

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

1987-01-01

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

Properties and sinterability of wet and dry attrition-milled OREOXed powder

International Nuclear Information System (INIS)

Lee, J. W.; Kim, J. H.; Kim, W. K.; Park, K. I.; Lee, J. W.

2001-01-01

The powder properties and sinterability were investigated with the powder prepared by wet and dry attrition milling of OREOX-treated powder. The OREOX-treated powder was prepared from the simulated spent fuel. Powder having less than 1 μm of average particle size could be obtained by dry milling, but not be obtained by wet milling. Thus, specific surface area of dry milled powder was higher than that of wet milled powder. With increasing of milling time, dry milled powder formed dense agglomerate while wet milled powder showed loose agglomerate. The pellets with higher than 95% T.D. of sintered density and larger than 7 μm of grain size were made with the milled powder regardless of milling method. The milling time in wet milling has greatly improved the sinterability. The pellets produced with dry milled powder have higher sintered density and larger grain size

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.

2018-04-01

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.

Sintering behaviour of CeO2-Gd2O3 powders prepared by the oxalate coprecipitation method

International Nuclear Information System (INIS)

Duran, P.; Jurado, J.R.; Moure, C.

1993-01-01

The powder and compact characteristics as well as the sintering behaviour of two CeO 2 -Gd 2 O 3 compositions prepared by the oxalate coprecipitation method are studied as a function of the powder particle size and the pore-size distribution in the powder compacts. Shrinkage was measured at a constant heating rate and the results are compared with those obtained by isothermal sintering experiments. Grain growth and microstructural development on sintered samples were studied. (orig.)

Spark plasma sintering and porosity studies of uranium nitride

Energy Technology Data Exchange (ETDEWEB)

Johnson, Kyle D., E-mail: kylej@kth.se; Wallenius, Janne; Jolkkonen, Mikael; Claisse, Antoine

2016-05-15

In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD – corresponding to an absolute density of 14.25 g/cm{sup 3} out of a theoretical density of 14.28 g/cm{sup 3} – have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density. - Highlights: • UN pellets are fabricated over a wide array of densities using the SPS method. • The sintereing parameters necessary to produce pellets over a wide array of density space are charted. • Pellets of extremely high density (99.9% of TD, absolute density of 14.25 g/cm{sup 3}) are fabricated. • Full-closure of the porosity in this material is obtained at around 2.5% of total porosity.

Effect of particle size distribution on sintering of tungsten

International Nuclear Information System (INIS)

Patterson, B.R.; Griffin, J.A.

1984-01-01

To date, very little is known about the effect of the nature of the particle size distribution on sintering. It is reasonable that there should be an effect of size distribution, and theory and prior experimental work examining the effects of variations in bimodal and continuous distributions have shown marked effects on sintering. Most importantly, even with constant mean particle size, variations in distribution width, or standard deviation, have been shown to produce marked variations in microstructure and sintering rate. In the latter work, in which spherical copper powders were blended to produce lognormal distributions of constant geometric mean particle size by weight frequency, blends with larger values of geometric standard deviation, 1nσ, sintered more rapidly. The goals of the present study were to examine in more detail the effects of variations in the width of lognormal particle size distributions of tungsten powder and determine the effects of 1nσ on the microstructural evolution during sintering

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

Microstructure and Mechanical Properties of Highly Alloyed FeCrMoVC Steel Fabricated by Spark Plasma Sintering

Science.gov (United States)

Oh, Seung-Jin; Jun, Joong-Hwan; Lee, Min-Ha; Shon, In-Jin; Lee, Seok-Jae

2018-05-01

In this study, we successfully fabricated highly alloyed FeCrMoVC specimens within 2 min by using the spark plasma sintering (SPS) method. The densities of the sintered specimens were almost identical to their theoretical values. Fine (Mo, V)-rich carbides with lamellar structure were precipitated along the grain boundaries of the as-sintered specimen, whereas relatively large carbides were formed additionally in the transgranular region during the tempering treatment. Compared with the specimen produced by a conventional casting method, the FeCrMoVC specimens from SPS showed smaller grain size with finer carbides and higher hardness values.

Functionally graded Nylon-11/silica nanocomposites produced by selective laser sintering

International Nuclear Information System (INIS)

Chung, Haseung; Das, Suman

2008-01-01

Selective laser sintering (SLS), a layered manufacturing-based freeform fabrication approach was explored for constructing three-dimensional structures in functionally graded polymer nanocomposites. Here, we report on the processing and properties of functionally graded polymer nanocomposites of Nylon-11 filled with 0-10% by volume of 15 nm fumed silica nanoparticles. SLS processing parameters for the different compositions were developed by design of experiments (DOE). The densities and micro/nanostructures of the nanocomposites were examined by optical microscopy and transmission electron microscopy (TEM). The tensile and compressive properties for each composition were then tested. These properties exhibit a nonlinear variation as a function of filler volume fraction. Finally, two component designs exhibiting a one-dimensional polymer nanocomposite material gradient were fabricated. The results indicate that particulate-filled functionally graded polymer nanocomposites exhibiting a one-dimensional composition gradient can be successfully processed by SLS to produce three-dimensional components with spatially varying mechanical properties

Preparation of Nd–Fe–B sintered magnets from HDDR-processed powder

Energy Technology Data Exchange (ETDEWEB)

Takagi, Kenta, E-mail: k-takagi@aist.go.jp [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Akada, Misaho [Magnetic Materials R& D Center, Research Associations of Magnetic Materials for High-Efficiency Motors (MagHEM), Nagoya 463-8560 (Japan); Soda, Rikio; Ozaki, Kimihiro [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan)

2015-11-01

The electric-current sintering technique was used to fully densify hydrogenation–disproportionation–desorption–recombination (HDDR)-processed Nd–Fe–B powder at temperatures below the grain growth temperature in order to produce high-coercive bulk magnets. However, the sintered magnets exhibited anomalous coercivity reduction that depended on sintered density. Reheating examination of the sintered magnets revealed that the reduced coercivity was increased in proportion to the heating temperature, resulting in complete recovery of coercivity. As a result, the combination of electric-current sintering and post-annealing produced sintered magnets with a coercivity of 15 kOe. Scanning and transmission electron microscopy revealed no evidence that associated the anomalous coercivity reduction and recovery with grain boundary morphology. On the other hand, various HDDR powders with different particle sizes were sintered, and finer powders yielded lower coercivity after sintering, implying that the anomalous coercivity reduction was associated with particle surface oxides of the raw powder. - Highlights: • We conduct a sintering of HDDR-processed Nd–Fe–B powder without coercivity reduction. • Rapid current sintering allows densification of this powder without grain growth. • However, the sintered magnets show an anomalous coercivity reduction phenomenon. • It is found that post-annealing completely recovers the reduced coercivity. • The anomalous coercivity reduction would be due to surface oxide of the raw powder.

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

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)

Comparison of Ti(C,N)-based cermets processed by hot-pressing sintering and conventional pressureless sintering

International Nuclear Information System (INIS)

Xu, Qingzhong; Ai, Xing; Zhao, Jun; Qin, Weizhen; Wang, Yintao; Gong, Feng

2015-01-01

Highlights: • The HP sintered Ti(C,N)-based cermets exhibit high hardness with fine grain size. • The PLS sintered cermets possess high mechanical properties with low porosity. • The applied pressure can rearrange particles and contribute to grain refinement. • The heating rate can greatly affect the solid and liquid phase sintering of cermets. - Abstract: A suitable sintering method is important to obtain the Ti(C,N)-based cermets with superior properties. In this paper, Ti(C,N)-based cermets were fabricated by hot-pressing sintering (HP) and conventional pressureless sintering (PLS) technology, respectively, to investigate the influence of different sintering methods on the microstructure and mechanical properties of cermets materials. The microstructure, fracture morphology, indention cracks and phase composition were observed and detected using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The transverse rupture strength (TRS), Vickers hardness (HV) and fracture toughness (K IC ) were also measured. The results reveal that all of the Ti(C,N)-based cermets exhibit core–rim microstructures with black cores, white cores and grey rims embedded into metal binder phases. The grain size of the samples fabricated by HP is much finer and the structure is more compact than those fabricated by PLS, while there exist pores in the HP sintered samples. The sintering process has no influence on the phase composition of cermets, but affects the phase content and crystallinity. The samples fabricated by PLS present higher transverse rupture strength, fracture toughness and density than samples fabricated by HP. However, the HP sintered samples possess a higher hardness

Microstructure and properties of sintered silicon carbides fabricated by different methods

International Nuclear Information System (INIS)

Maruyama, Tadashi; Kitamura, Hideya; Iseki, Takayoshi

1986-01-01

Studies were made of effects of fabrication methods on the properties and microstructure of sintered silicon carbides. The specimens used in this investigation were three kinds of commercially available SiC bodies which were fabricated by reaction bonding, pressureless sintering and hot-pressing. The hot-pressed SiC contained a small amount of BeO. Measurements were carried out on density, the polytype by X-ray diffraction method and 4-point bend strength. Microstructural observation was also carried out using an optical microscope, a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The results of density measurement showed that the open porosities of three specimens were negligibly small and that the density of the hot pressed SiC had nearly the theoretical density. The measurement of 4-point bend strength indicated that the reaction bonded SiC had the highest value and the hot-pressed SiC the lowest. The analysis of the polytype indicated that all the specimens consisted mainly of α-SiC of 6 H type. In the reaction bonded SiC, about 11 % of 3 C type (β-SiC) and 9 % of free Si were recognized. The average grain diameter and fracture mode of each specimen were determined from observation with an optical microscope and SEM. In the hot-pressed SiC, the fracture occurred mainly at grain boundaries, whereas it occurred mostly in grains in the reaction bonded and pressureless sintered SiC. A lot of stacking faults were observed in all the specimens with a TEM. In addition, small closed pores were often recognized in the pressureless sintered SiC. In the hot-pressed SiC, a contrast originated from strain field within grains was observed, and dislocations near grain boundaries were a characteristic feature of this material. Small short partial dislocations accompanied by stacking fault were often observed in the reaction bonded SiC. (author)

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...

Hexagonal OsB2: Sintering, microstructure and mechanical properties

International Nuclear Information System (INIS)

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

2015-01-01

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

Method of producing spherical lithium aluminate particles

International Nuclear Information System (INIS)

Yang, L.; Medico, R.R.; Baugh, W.A.

1983-01-01

Spherical particles of lithium aluminate are formed by initially producing aluminium hydroxide spheroids, and immersing the spheroids in a lithium ion-containing solution to infuse lithium ions into the spheroids. The lithium-infused spheroids are rinsed to remove excess lithium ion from the surface, and the rinsed spheroids are soaked for a period of time in a liquid medium, dried and sintered to form lithium aluminate spherical particles. (author)

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)

Process for obtaining sintered conglomerates with a high density of rare earth oxides and actinides

International Nuclear Information System (INIS)

Pasto, A.E.

1974-01-01

The invention concerns a method to produce agglomerates of actinide and rare earth oxides possessing a cubic-monoclinic transformation in order to obtain high densities close to the theoretical density, and the articles produced by the method. The process is based on the use of a rare earth or actinide oxide, in particular Eu 2 O 3 , with a cubic-monoclinic phase transformation, the oxide being sintered by hot compression at a temperature 50 deg C to 100 deg C above the transformation temperature. The sintered agglomerates obtained can have a purity of at least 99.9% and a density of practically 100%. These agglomerates are suitable in particular for the formation of nuclear reactor control rods [fr

Optimization of thorium oxalate precipitation conditions relative to thorium oxide sinterability

International Nuclear Information System (INIS)

White, G.D.; Bray, L.A.; Hart, P.E.

1980-01-01

The effect of thorium oxalate precipitation conditions on derived oxide sinterability was investigated with the objective of producing ThO 2 powder that could be sintered to high density without premilling. Precipitation conditions examined were temperature, digestion time and agitation method which were employed in a two-level factorial experimental design to delineate their effects. The two levels for each of the factors, respectively, were 10 0 C and 70 0 C, 15 min and 360 min, and mechanical stirrer and a homogenizer that imparted both mechanical and ultrasonic agitation. The ThO 2 derived from each of the precipitation trials was characterized with respect to morphology, surface area, and crystallite size as well as sinterability. Only precipitation temperature had a significant effect upon all the properties of the derived oxide powders

Assessment of polyphase sintered iron-cobalt-iron boride cermets

International Nuclear Information System (INIS)

Nowacki, J.; Pieczonka, T.

2004-01-01

Sintering of iron, cobalt and boron powders has been analysed. As a result iron-iron boride, Fe-Fe 2 B and iron/cobalt boride with a slight admixture of molybdenum, Fe - Co - (FeMoCo) 2 B cermets have been produced. Iron was introduced to the mixture as the Astalloy Mo Hoeganaes grade powder. Elemental amorphous boron powder was used, and formation of borides occurred both during heating and isothermal sintering periods causing dimensional changes of the sintered body. Dilatometry was chosen to control basic phenomena taking place during multiphase sintering of investigated systems. The microstructure and phase constituents of sintered compacts were controlled as well. The cermets produced were substituted to: metallographic tests, X-ray analysis, measurements of hardness and of microhardness, and of wear in the process of sliding dry friction. Cermets are made up of two phases; hard grains of iron - cobalt boride, (FeCo) 2 B (1800 HV) constituting the reinforcement and a relatively soft and plastic eutectic mixture Fe 2 B - Co (400-500 HV) constituting the matrix. (author)

Sintering-alkaline processing of borosilicate ores of Tajikistan

International Nuclear Information System (INIS)

Nazarov, F.A.

2018-01-01

The aim of the work is to study the processes of decomposition of boron-containing ore by sintering with NaOH, finding the optimal parameters of the decomposition process, studying the kinetics of processes and developing the technological foundations for ore processing. The processes of borosilicate ore processing were studied by sintering with NaOH. Possible mechanisms of chemical reactions of the process of sintering-alkaline decomposition of boron-containing ore are established, the results of which are substantiated by physicochemical methods of analysis. A principal technological scheme for processing of borosilicate ores by a sintering-alkaline method has been developed. In the first chapter, data on alkaline and caking processes for processing boron-containing and aluminium comprising raw materials are available in the literature. Based on this, the directions of our own research are outlined. The second chapter is devoted to the study of the chemical and mineralogical compositions of borosilicate ores and their concentrates with the help of X-ray phase and chemical analysis methods, the stoichiometric calculation of the formation of aluminum, iron, and boron salts has been carried out, and a thermodynamic analysis of the processes of sintering borosilicate ores with alkali has been considered. The third chapter presents the results of a study of sintering-alkaline method of processing of initial borosilicate ore of the Ak-Arkhar Deposit and its concentrate without calcination and after calcination. The kinetics of sintering of borosilicate ores with sodium hydroxide was studied. The optimal conditions of borosilicate ore sintering before and after the preliminary calcination with alkali were determined. Optimal parameters of the sintering process have been found: sintering temperature 800-8500 deg C, duration of the process - 60 minutes, mass ratio of NaOH to raw materials 2: 1. The conditions for sintering of borosilicate concentrate with alkali have been

Mechanical characteristics of microwave sintered silicon carbide

Indian Academy of Sciences (India)

Unknown

sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered .... product, could be due to oxidation of SiC, e.g. 50% weight gain of a green SiC sample ... because, the charging current is 90° advanced in phase, ideally, with respect to the ...

Study on the Characteristics of Walnut Shell/Co-PES/Co-PA Powder Produced by Selective Laser Sintering

Directory of Open Access Journals (Sweden)

Yueqiang Yu

2018-05-01

Full Text Available Agricultural and forestry wastes are used as materials for selective laser sintering (SLS to alleviate resource shortage, reduce the pollution of the environment, lower the cost of materials, and improve the accuracy of parts produced by SLS. However, the mechanical properties of wood–plastic parts are poor, and thus they cannot be applied widely. In order to improve the mechanical properties of wood–plastic parts, a new type of walnut shell polymer composite (WSPC was prepared by a polymer mixing method and was used to produce parts via SLS. Additionally, the dimensional accuracy, morphologies, density, and mechanical properties of the WSPC parts were studied. The results showed that the addition of a small amount of copolyamide (Co-PA powder could effectively improve the mechanical properties and decrease the density of the WSPC parts. By increasing the amount of Co-PA powder and decreasing that of copolyester (Co-PES powder, the mechanical properties first increased, then decreased, and finally increased again; in addition, the density first decreased then increased. By increasing the preheating temperature, the mechanical properties and density of the WSPC parts were enhanced.

Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

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Ilya eLisenker

2016-03-01

Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

Fabrication And Properties Of Silver Based Multiwall Carbon Nanotube Composite Prepared By Spark Plasma Sintering Method

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Lis M.

2015-06-01

Full Text Available The paper presents results of investigations of the obtained nanocomposite materials based on silver with addition of multiwall carbon nanotubes. The powder of carbon nanotubes content from 0.1 to 3 wt. % was produced by application of powder metallurgy methods, through mixing and high-energetic milling, and also chemical methods. Modification of carbon nanotubes included electroless deposition of silver particles on the carbon nanotube active surfaces and chemical reduction with strong reducing agent – sodium borohydride (NaBH4. The obtained powder mixtures were consolidated by SPS – Spark Plasma Sintering method. The formed composites were subjected to tests of relative density, electrical conductivity and electro-erosion properties. Detailed examinations of the structure with application of X-ray microanalysis, with consideration of carbon nanotubes distribution, were also carried out. The effect of manufacturing methods on properties of the obtained composites was observed.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-05-15

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

Report on in-situ studies of flash sintering of uranium dioxide

Energy Technology Data Exchange (ETDEWEB)

Raftery, Alicia Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-01-24

Flash sintering is a novel type of field assisted sintering that uses an electric field and current to provide densification of materials on very short time scales. The potential for field assisted sintering techniques to be used in producing nuclear fuel is gaining recognition due to the potential economic benefits and improvements in material properties. The flash sintering behavior has so far been linked to applied and material parameters, but the underlying mechanisms active during flash sintering have yet to be identified. This report summarizes the efforts to investigate flash sintering of uranium dioxide using dilatometer studies at Los Alamos National Laboratory and two separate sets of in-situ studies at Brookhaven National Laboratory’s NSLS-II XPD-1 beamline. The purpose of the dilatometer studies was to understand individual parameter (applied and material) effects on the flash behavior and the purpose of the in-situ studies was to better understand the mechanisms active during flash sintering. As far as applied parameters, it was found that stoichiometry, or oxygen-to-metal ratio, has a significant effect on the flash behavior (time to flash and speed of flash). Composite systems were found to have degraded sintering behavior relative to pure UO₂. The critical field studies are complete for UO_2.00 and will be analyzed against an existing model for comparison. The in-situ studies showed that the strength of the field and current are directly related to the sample temperature, with temperature-driven phase changes occurring at high values. The existence of an ‘incubation time’ has been questioned, due to a continuous change in lattice parameter values from the moment that the field is applied. Some results from the in-situ experiments, which should provide evidence regarding ion migration, are still being analyzed. Some preliminary conclusions can be made from these results with regard to using field assisted sintering to

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

Laser sintering of copper nanoparticles

International Nuclear Information System (INIS)

Zenou, Michael; Saar, Amir; Ermak, Oleg; Kotler, Zvi

2014-01-01

Copper nanoparticle (NP) inks serve as an attractive potential replacement to silver NP inks in functional printing applications. However their tendency to rapidly oxidize has so far limited their wider use. In this work we have studied the conditions for laser sintering of Cu-NP inks in ambient conditions while avoiding oxidation. We have determined the regime for stable, low-resistivity copper (< ×3 bulk resistivity value) generation in terms of laser irradiance and exposure duration and have indicated the limits on fast processing. The role of pre-drying conditions on sintering outcome has also been studied. A method, based on spectral reflectivity measurements, was used for non-contact monitoring of the sintering process evolution. It also indicates preferred spectral regions for sintering. Finally, we illustrated how selective laser sintering can generate high-quality, fine line (<5 µm wide) and dense copper circuits. (paper)

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-06-15

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

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)

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 response...... to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number...

Monitoring Sintering Burn-Through Point Using Infrared Thermography

Directory of Open Access Journals (Sweden)

Francisco G. Bulnes

2013-08-01

Full Text Available Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burnthrough point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Study of effect of sintering time on the 2223 phase growth Bi-Pb-Sr-Ca-Cu-O superconductor by Rietveld method

International Nuclear Information System (INIS)

Parikin; Prasuad, W; Gunawan

1996-01-01

It has been reported that the sintering time is as important for the preparation of superconductor as the sintering temperature and method. This paper reports on the finding of the optimum sintering time in the preparation of the 2223 phase bismuth (Bi) superconductor. The samples were synthesized with nominal composition 1.84 : 0.34 : 1.91 : 2.03 : 3.06 from raw materials by solid state reaction and sintered at 860 o C for five days. The resintering were done three times, i.e. 24, 48 and 96 hours. The Rietveld analysis shows that the 2223 phase grows continuously as a function of the sintering time. The highest percentage of the 2223 phase (80.64%) were obtained at 96 hours sintering time. The result suggests that the 2223 phase can be obtained effectively by sintering with sufficiently long time

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Energy Technology Data Exchange (ETDEWEB)

Lisenker, Ilya; Stoldt, Conrad R., E-mail: stoldt@colorado.edu [Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO (United States)

2016-03-31

The effect of high-frequency (HF) electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP) ion conducting ceramic was investigated. LAGP with the nominal composition Li{sub 1.5}Al{sub 0.5}Ge{sub 1.5}(PO{sub 4}){sub 3} was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy to compare conventionally and field-sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 h of sintering were minor with measured sintering strains of 31 vs. 26% with and without field, respectively. Ionic conductivity of the sintered pellets was evaluated, and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

A Review of Metal Injection Molding- Process, Optimization, Defects and Microwave Sintering on WC-Co Cemented Carbide

Science.gov (United States)

Shahbudin, S. N. A.; Othman, M. H.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

2017-08-01

This article is about a review of optimization of metal injection molding and microwave sintering process on tungsten cemented carbide produce by metal injection molding process. In this study, the process parameters for the metal injection molding were optimized using Taguchi method. Taguchi methods have been used widely in engineering analysis to optimize the performance characteristics through the setting of design parameters. Microwave sintering is a process generally being used in powder metallurgy over the conventional method. It has typical characteristics such as accelerated heating rate, shortened processing cycle, high energy efficiency, fine and homogeneous microstructure, and enhanced mechanical performance, which is beneficial to prepare nanostructured cemented carbides in metal injection molding. Besides that, with an advanced and promising technology, metal injection molding has proven that can produce cemented carbides. Cemented tungsten carbide hard metal has been used widely in various applications due to its desirable combination of mechanical, physical, and chemical properties. Moreover, areas of study include common defects in metal injection molding and application of microwave sintering itself has been discussed in this paper.

A new integrated evaluation method of heavy metals pollution control during melting and sintering of MSWI fly ash.

Science.gov (United States)

Li, Rundong; Li, Yanlong; Yang, Tianhua; Wang, Lei; Wang, Weiyun

2015-05-30

Evaluations of technologies for heavy metal control mainly examine the residual and leaching rates of a single heavy metal, such that developed evaluation method have no coordination or uniqueness and are therefore unsuitable for hazard control effect evaluation. An overall pollution toxicity index (OPTI) was established in this paper, based on the developed index, an integrated evaluation method of heavy metal pollution control was established. Application of this method in the melting and sintering of fly ash revealed the following results: The integrated control efficiency of the melting process was higher in all instances than that of the sintering process. The lowest integrated control efficiency of melting was 56.2%, and the highest integrated control efficiency of sintering was 46.6%. Using the same technology, higher integrated control efficiency conditions were all achieved with lower temperatures and shorter times. This study demonstrated the unification and consistency of this method. Copyright © 2015 Elsevier B.V. All rights reserved.

Non-pressurized sintered silicon carbide with titanium carbide reinforcement

International Nuclear Information System (INIS)

Adler, J.

1992-01-01

A non-pressurized compression of SiC-TiC composite materials can be achieved via liquid phase sintering by the application of oxidic additives. Materials with TiC proportions up to 40% by volume of TiC and densities of 97 to 98% TD were produced at sintering temperatures around 1875 C. With SiC sintered in the liquid phase an increase of toughness at fracture of 80% compared with conventionally non-pressurized sintered SiC was achieved with B/C additive. No further increase could be achieved by the addition of TiC particles. However, the oxidation resistance at 1200 C was worsened. (orig.) [de

Microporous Ti implant compact coated with hydroxyapatite produced by electro-discharge-sintering and electrostatic-spray-deposition.

Science.gov (United States)

Jo, Y J; Kim, Y H; Jo, Y H; Seong, J G; Chang, S Y; Van Tyne, C J; Lee, W H

2014-11-01

A single pulse of 1.5 kJ/0.7 g of atomized spherical Ti powder from 300 μF capacitor was applied to produce the porous-surfaced Ti implant compact by electro-discharge-sintering (EDS). A solid core surrounded by porous layer was self-consolidated by a discharge in the middle of the compact in 122 μsec. Average pore size, porosity, and compressive yield strength of EDS Ti compact were estimated to be about 68.2 μm, 25.5%, and 266.4 MPa, respectively. Coatings with hydroxyapatite (HAp) on the Ti compact were conducted by electrostatic-spray-deposition (ESD) method. As-deposited HAp coating was in the form of porous structure and consisted of HAp particles which were uniformly distributed on the Ti porous structure. By heat-treatment at 700 degrees C, HAp particles were agglomerated each other and melted to form a highly smooth and homogeneous HAp thin film consisted of equiaxed nano-scaled grains. Porous-surfaced Ti implant compacts coated with highly crystalline apatite phase were successfully obtained by using the EDS and ESD techniques.

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.

Laser sintering of metal powders on top of sintered layers under multiple-line laser scanning

International Nuclear Information System (INIS)

Xiao Bin; Zhang Yuwen

2007-01-01

A three-dimensional numerical model for multiple-line sintering of loose powders on top of multiple sintered layers under the irradiation of a moving Gaussian laser beam is carried out. The overlaps between vertically deposited layers and adjacent lines which strengthen bonding are taken into account. The energy equation is formulated using the temperature transforming model and solved by the finite volume method. The effects of the number of the existing sintered layers, porosity and initial temperature coupled with the optimal combination laser intensity and scanning velocity are presented. The results show that the liquid pool moves slightly towards the negative scanning direction and the shape of the liquid pool becomes shallower with higher scanning velocity. A higher laser intensity is needed to achieve the required overlaps when the number of the existing sintered layers increases. Increasing porosity or initial temperature enhances the sintering process and thus less intensity is needed for the overlap requirement

Microstructure and mechanical behavior of ODS and non-ODS Fe–14Cr model alloys produced by spark plasma sintering

International Nuclear Information System (INIS)

Auger, M.A.; Castro, V. de; Leguey, T.; Muñoz, A.; Pareja, R.

2013-01-01

In this work the spark plasma sintering (SPS) technique has been explored as an alternative consolidation route for producing ultra-fine grained Fe–14Cr model alloys containing a dispersion of oxide nanoparticles. Elemental powders of Fe and Cr, and nanosized Y 2 O 3 powder have been mechanically alloyed in a planetary ball mill and rapidly sintered in a spark plasma furnace. Two alloys, with nominal compositions Fe–14%Cr and Fe–14%Cr–0.3%Y 2 O 3 (wt.%), have been fabricated and their microstructure and mechanical properties investigated. The results have been compared with those obtained for other powder metallurgy processed alloys of the same composition but consolidated by hot isostatic pressing. The SPS technique under the present conditions has produced Fe–14Cr materials that apparently exhibit different microstructures yielding inferior mechanical properties than the counterpart material consolidated by hot isostatic pressing. Although the presence of a dispersion of Y-rich particles is evident, the oxide dispersion strengthened (ODS) Fe–14Cr alloy consolidated by SPS exhibits poor tensile properties. The extensive decoration of the powder particle surfaces with Cr-rich precipitates and the residual porosity appear to be responsible for the impaired properties of this ODS alloy consolidated by SPS

Microstructure and mechanical behavior of ODS and non-ODS Fe–14Cr model alloys produced by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Auger, M.A.; Castro, V. de [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Leguey, T., E-mail: leguey@fis.uc3m.es [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Muñoz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain)

2013-05-15

In this work the spark plasma sintering (SPS) technique has been explored as an alternative consolidation route for producing ultra-fine grained Fe–14Cr model alloys containing a dispersion of oxide nanoparticles. Elemental powders of Fe and Cr, and nanosized Y{sub 2}O{sub 3} powder have been mechanically alloyed in a planetary ball mill and rapidly sintered in a spark plasma furnace. Two alloys, with nominal compositions Fe–14%Cr and Fe–14%Cr–0.3%Y{sub 2}O{sub 3} (wt.%), have been fabricated and their microstructure and mechanical properties investigated. The results have been compared with those obtained for other powder metallurgy processed alloys of the same composition but consolidated by hot isostatic pressing. The SPS technique under the present conditions has produced Fe–14Cr materials that apparently exhibit different microstructures yielding inferior mechanical properties than the counterpart material consolidated by hot isostatic pressing. Although the presence of a dispersion of Y-rich particles is evident, the oxide dispersion strengthened (ODS) Fe–14Cr alloy consolidated by SPS exhibits poor tensile properties. The extensive decoration of the powder particle surfaces with Cr-rich precipitates and the residual porosity appear to be responsible for the impaired properties of this ODS alloy consolidated by SPS.

Reaction sintering of ceramic-metal composites

International Nuclear Information System (INIS)

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

1990-01-01

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

Properties of Mo-alloyed sintered manganese steels

International Nuclear Information System (INIS)

Romanski, A.; Cias, A.

1998-01-01

Sintered alloy steels are needed for mostly PM structural parts. Powder metallurgy techniques provide a means of fabricating high quality steel parts with tailored mechanical properties. It is now possible to produce sintered steel parts with properties equal to an even superior to those of parts made by more traditional routes. Challenges arise both with the material selection and component fabrication. This work outlines the processing for high performance structural application. (author)

Determination of optimum thermal debinding and sintering process parameters using Taguchi Method

CSIR Research Space (South Africa)

Seerane, M

2015-07-01

Full Text Available powder and a wax-based binder. The binder’s backbone component is a low density polyethylene (LDPE). Careful selection of thermal debinding parameters was guided by thermo- gravimetric analysis (TGA) results. The Taguchi method was used to determine... International Light Metals Technology Conference (LMT 2015), Port Elizabeth, South Africa, July 27-29 Determination of Optimum Process for Thermal Debinding and Sintering using Taguchi Method SEERANE Mandya,*, CHIKWANDA Hildab, MACHAKA Ronaldc CSIR...

Influence of sintering atmospheres on the aluminium sintering characteristics

International Nuclear Information System (INIS)

Mintzer, S.; Bermudez Belkys, S.

1993-01-01

This paper describes the aluminium powder (Al) cool compacted (at 95% from theoretical density) which was sintered at 903 K during 4 hours at different atmospheres; oxidizing (air), inert Argon (Ar), Nitrogen (N) and high vacuum. The results obtained show: a) porosity measurements; greater porosity when sintering in Ar and air. b) Metallographic and Scanning observations: many fine pores (< 1 μm) and pore lines distributed at random, at air sintering and greater pores distributed preferentially near the surface, in Ar and N atmospheres. c) Dimensional changes: tendency to contraction of the samples at N and vacuum sintering and expansion in Ar or air. d) Mechanical properties: greater strength and fluence stresses at air and N sintering. The analysis of the results is performed considering sintering modes in presence of an oxide layer and dropped inert gases. (Author)

Microstructure and properties of multiphase sintered cermets Fe-Fe2B

International Nuclear Information System (INIS)

Nowacki, J.; Klimek, L.

1998-01-01

The process of multiphase sintering of iron in the vacuum has been analysed. As a result of the process iron-iron boride cermets have been produced. Fe-Fe 2 B cermets were obtained as a result of sintering of the Fe and B pure elements in the vacuum. Attemps at sintering in the solid phase and with the participation of the liquid phase, the Fe-Fe 2 B eutectic, have been made. Metallographic qualitative and quantitative studies, X-ray structural qualitative and qauantitative analysis allowed to determine the structure of Fe 2 B cermets, as well as a description of the kinetics of quantitative changes in phase proportions in the course of sintering. It has been found that their structure varies widely depending on sintering parameters and the composition of the sinters. Measurements of the Fe-Fe 2 B cermets hardness and measurements on wear during dry friction by the pin-on-disc method have shown distinct advantages of the cermets as a modern constructional materials. The hardness of Fe-Fe 2 B cermets, depending on their chemical composition and sintering parameters, ranges widely from 150 to 1500 HV, and their resistance to wear is comparable to that of diffusively boronized steels. FeFe 2 B cermets are a composite material in which iron boride, Fe 2 B, with a hardness of about 1800 HV plays the role of the reinforcement,while iron-iron boride, Fe-Fe 2 B, with a hardness of about 500 HV plays the role of matrix. The eutectic in the spaces between iron boride grains is composed of boron solid solution plates in iron with a hardness of arround 250 HV, and iron boride, Fe 2 B, plates with a hardness of approximaly 1800 HV. The combination of such different materials, a hard reinforcement and a relatively plastic matrix produces favourable properties of the cermet thus produced high hardness (1500 HV) constant over whole cross section of the material, resistance of abrasive wear and acceptable ductility. The properties mentioned above, resulting from the cermet

Master sintering curve: A practical approach to its construction

Directory of Open Access Journals (Sweden)

Pouchly V.

2010-01-01

Full Text Available The concept of a Master Sintering Curve (MSC is a strong tool for optimizing the sintering process. However, constructing the MSC from sintering data involves complicated and time-consuming calculations. A practical method for the construction of a MSC is presented in the paper. With the help of a few dilatometric sintering experiments the newly developed software calculates the MSC and finds the optimal activation energy of a given material. The software, which also enables sintering prediction, was verified by sintering tetragonal and cubic zirconia, and alumina of two different particle sizes.

Rapid prototyping: een veelbelovende methode

NARCIS (Netherlands)

Haverman, T.M.; Karagozoglu, K.H.; Prins, H.; Schulten, E.A.J.M.; Forouzanfar, T.

2013-01-01

Rapid prototyping is a method which makes it possible to produce a three-dimensional model based on two-dimensional imaging. Various rapid prototyping methods are available for modelling, such as stereolithography, selective laser sintering, direct laser metal sintering, two-photon polymerization,

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

Reaction sintering of two-dimensional silicon carbide fiber-reinforced silicon carbide composite by sheet stacking method

International Nuclear Information System (INIS)

Yoshida, Katsumi; Mukai, Hideki; Imai, Masamitsu; Hashimoto, Kazuaki; Toda, Yoshitomo; Hyuga, Hideki; Kondo, Naoki; Kita, Hideki; Yano, Toyohiko

2007-01-01

Two-dimensionally plain woven SiC fiber-reinforced SiC composite has been developed by reaction sintering using a sheet stacking method in order to further increase mechanical and thermal properties of the composite and to obtain flexibility of manufacturing process of 2D woven SiC/SiC composites which can be applied to the fabrication of larger parts. In addition, sinterability and mechanical properties of the composite were investigated. In this study, relative density of the composites was about 90-93% and a dense composite could be obtained by reaction sintering using the sheet stacking method. The bulk density and maximum bending strength of SiC/SiC composite with a C/SiC weight ratio of 0.6 were higher than that of the composite with C/SiC ratios of 0.5 or 0.7. The values were 2.9 g/cm 3 and 200 MPa, respectively. However, the composites obtained in this study fractured in almost brittle manner due to the lower fiber volume fraction

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.

Microstructural Analysis of Sintered Gradient Materials Based on Distaloy SE Powder

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Zarębski K.

2016-06-01

Full Text Available The study describes the microstructural analysis of cylindrically-shaped functionally graded products sintered from iron powder with scheduled graded structure on the cross-section running from the core to the surface layer of the sinter. Different types of structure were produced using Distaloy SE powder in two compositions - one without the addition of carbon, and another with 0.6wt% C. Two methods were used to fill the die cavity and shape the products. The first method involving a two-step compaction of individual layers. The second method using an original technique of die filling enabled the formation of transition zone between the outer layer and the core still at the stage of product shaping. As part of microstructural analysis, structural constituents were identified and voids morphology was examined. Studies covered the effect of the type of the applied method on properties of the graded zone obtained in the manufactured products

Application of the Taguchi Method for Optimizing the Process Parameters of Producing Lightweight Aggregates by Incorporating Tile Grinding Sludge with Reservoir Sediments.

Science.gov (United States)

Chen, How-Ji; Chang, Sheng-Nan; Tang, Chao-Wei

2017-11-10

This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L 16 (4⁵) was adopted, which consisted of five controllable four-level factors (i.e., sludge content, preheat temperature, preheat time, sintering temperature, and sintering time). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the particle density, water absorption, bloating ratio, and loss on ignition of the produced LWA. Overall, the produced aggregates had particle densities ranging from 0.43 to 2.1 g/cm³ and water absorption ranging from 0.6% to 13.4%. These values are comparable to the requirements for ordinary and high-performance LWAs. The results indicated that it is considerably feasible to produce high-performance LWA by incorporating tile grinding sludge with reservoir sediments.

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.

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

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Pieczonka T.

2017-06-01

Full Text Available Aluminium oxide layer on aluminium particles cannot be avoided. However, to make the metal-metal contacts possible, this sintering barrier has to be overcome in some way, necessarily to form sintering necks and their development. It is postulated that the disruption of alumina layer under sintering conditions may originate physically and chemically. Additionally, to sinter successfully non alloyed aluminium powder in nitrogen, the operation of both types mechanism is required. It is to be noted that metallic aluminium surface has to be available to initiate reactions between aluminium and the sintering atmosphere, i.e. mechanical disruption of alumina film precedes the chemical reactions, and only then chemically induced mechanisms may develop. Dilatometry, gravimetric and differential thermal analyses, and microstructure investigations were used to study the sintering response of aluminium at 620°C in nitrogen, which is the only sintering atmosphere producing shrinkage.

Compaction and sintering of nickel powder used encapsulation of irradiation targets

Energy Technology Data Exchange (ETDEWEB)

Miyano, Rosana S.L.; Guimaraes, Raquel R.F.L.; Rossi, Jesualdo L., E-mail: rosatac@gmail.com, E-mail: raquel.lucchesi@icloud.com, E-mail: jelrossi@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais; Wendhausen, Paulo A.P.; Evangelista, Leandro L., E-mail: paulo.wendhausen@ufsc.br, E-mail: leandro.materiais@gmail.com [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Laboratorio de Materiais

2015-07-01

The objective of this study was to develop an alternative way to produce targets for irradiation containing uranium, for the pair of {sup 99}Mo production {sup 99m}Tc radionuclide. These targets were obtained by powder metallurgy, the compact serving as means for encapsulation a uranium cylinder to be irradiated. The targets were compacted in an axial hydraulic press applying different pressures up to 800 MPa. The sintering temperature was 600 °C in hydrogen atmosphere and it was used two sintering cycles, one for 4 h and the for 4 h plus 8 h time. The nickel powder was of high purity, that in order to provide the sealing of the fissile content within the compacted. The bulk density of compacted was evaluated by the method geometric. The porosity was measured by mercury porosimetry technique. The microstructure was investigated by optical microscopy. The results obtained with sintering powders involving confirm the feasibility of achieving a casing for uranium targets. (author)

Compaction and sintering of nickel powder used encapsulation of irradiation targets

International Nuclear Information System (INIS)

Miyano, Rosana S.L.; Guimaraes, Raquel R.F.L.; Rossi, Jesualdo L.; Wendhausen, Paulo A.P.; Evangelista, Leandro L.

2015-01-01

The objective of this study was to develop an alternative way to produce targets for irradiation containing uranium, for the pair of 99 Mo production 99m Tc radionuclide. These targets were obtained by powder metallurgy, the compact serving as means for encapsulation a uranium cylinder to be irradiated. The targets were compacted in an axial hydraulic press applying different pressures up to 800 MPa. The sintering temperature was 600 °C in hydrogen atmosphere and it was used two sintering cycles, one for 4 h and the for 4 h plus 8 h time. The nickel powder was of high purity, that in order to provide the sealing of the fissile content within the compacted. The bulk density of compacted was evaluated by the method geometric. The porosity was measured by mercury porosimetry technique. The microstructure was investigated by optical microscopy. The results obtained with sintering powders involving confirm the feasibility of achieving a casing for uranium targets. (author)

Pressureless sintering behavior of injection molded alumina ceramics

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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.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

Science.gov (United States)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

Characterization of x-ray diffraction and electron spin resonance: Effects of sintering time and temperature on bovine hydroxyapatite

International Nuclear Information System (INIS)

Kusrini, Eny; Sontang, Muhammad

2012-01-01

The physical and chemical properties of a hydroxyapatite produced by the sintering of bovine bone were investigated by powder x-ray diffraction (PXRD), electron spin resonance (ESR), energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and differential thermal analysis (DTA). A bovine bone powder was sintered at different temperatures ranging from 500 to 1400 °C. The influences of post-irradiation storage on the radiation ESR response of the bovine bone powder before and after sintering were also studied. The results indicate that the sintered bovine bone powder contained hydroxyapatite. Diffraction patterns were sharp and clear based on the (211), (300), and (202) reflections corresponding to bovine hydroxyapatite (BHA), which confirmed the phase purity and high crystalline grade of the BHA produced. The PXRD profile of BHA was dependent on sintering temperatures and times. The molecular formula of BHA was determined by Rietveld analysis showed a similar structure and composition to calcium hydroxyapatite in hexagonal P6 3 /m space group a=b=9.435 Å and c=6.895 Å. ESR data showed that the sintering process can decrease the number of free radicals in BHA; it also revealed that the number of free radicals is constant during long storage periods (75 days). The sintering technique described in this study may be used to extract hydroxyapatite from biowaste bovine bone, leading to its application as a bone filler. - Highlights: ► Natural hydroxyapatite was produced from the bio-wasting bovine bones by sintering method. ► PXRD profile of BHA is dependent on the different temperatures and times in sintering process. ► ESR data is useful to study the typical of free radicals formed in the samples after irradiation. ► Stability and physicochemical properties of BHA is dependent on the different storage times. ► Technique is able to be used to find the natural hydroxyapatite applicable for bone filler.

An investigation of the tribological and nano-scratch behaviors of Fe–Ni–Cr alloy sintered by direct metal laser sintering

International Nuclear Information System (INIS)

Amanov, Auezhan; Sasaki, Shinya; Cho, In-Sik; Suzuki, Yusuke; Kim, Hae-Jin; Kim, Dae-Eun

2013-01-01

Highlights: ► Fe–Ni–Cr alloy was sintered by direct metal laser sintering. ► HFUP technique was able to produce a hardened surface layer. ► HFUP-treated specimen showed better tribological and scratch properties. - Abstract: In this work, the friction and wear behavior of Fe–Ni–Cr alloy specimens processed by direct metal laser sintering (DMLS) method was investigated by using a ball-on-disk reciprocating tribotester sliding against a hardened steel ball under dry sliding conditions. After DMLS, the specimens were further treated by hot isostatic pressing (HIP) in order to reduce the porosity and to increase the density. Subsequently, one of the specimens was subjected to high-frequency ultrasonic peening (HFUP) with the aim to enhance the tribological properties. The microstructural characterization was conducted using a scanning electron microscope (SEM) and an atomic force microscope (AFM). In addition, nano-scratch tests were carried out on the specimens using a nano-scratch testing (NST) system. The friction and nano-scratch tests results showed that the HFUP-treated specimen led to a reduction in friction coefficient and wear rate, and an increase in resistance to scratch compared to that of the HFUP-free specimen, which may be attributed to the increase in hardness and the formation of corrugated structure

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

Effect of sintering temperature on the densification of B4C pellets

International Nuclear Information System (INIS)

Gomide, R.G.; Durazzo, M.; Riella, H.G.

1990-01-01

Boron is largely used in several types of nuclear reactors control and safety systems. In the majority of these applications sintered boron carbide pellets are used. Near stoichiometric B 4 C hardly densifies during pressureless sintering. As a starting point of an overall program to produce > 70% TD B 4 C pellets pressing parameters have been studied for further study of the influence of sintering temperature in the densification of this ceramic material. Dilatometric analyses show that sintering starts at 1760 0 C for the F 1200 ESK - type boron carbide powders. Moreover, the sintering experiments show that up to 92% TD pellets can be obtained. (author) [pt

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)

Two steps sintering alumina doped with niobia

International Nuclear Information System (INIS)

Gomes, L.B.; Hatzfeld, J.; Heck, M.; Pokorny, A.; Bergmann, C.P.

2014-01-01

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)

Structural characterization of biomedical Co-Cr-Mo components produced by direct metal laser sintering.

Science.gov (United States)

Barucca, G; Santecchia, E; Majni, G; Girardin, E; Bassoli, E; Denti, L; Gatto, A; Iuliano, L; Moskalewicz, T; Mengucci, P

2015-03-01

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co-Cr-Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin ε (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The ε-lamellae grown on the {111}γ planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields. Copyright © 2014 Elsevier B.V. All rights reserved.

Sintering by infiltration of loose mixture of powders, a method for metal matrix composite elaboration

International Nuclear Information System (INIS)

Constantinescu, V.; Orban, R.; Colan, H.

1993-01-01

Starting from the observation that Sintering by Infiltration of Loose Mixture of Powders confers large possibilities for both complex shaped and of large dimensions Particulate Reinforced Metal Matrix Composite components elaboration, its mechanism comparative with those of the classical melt infiltration was investigated. Appropriate measures in order to prevent an excessive hydrostatic flow of the melt and, consequently, reinforcement particle dispersion, as well as to promote wetting in both infiltration and liquid phase sintering stages of the process were established as necessary. Some experimental results in the method application to the fusion tungsten carbide and diamond reinforced metal matrix composite elaboration are, also, presented. (orig.)

High performance sinter-HIP for hard metals

International Nuclear Information System (INIS)

Hongxia Chen; Deming Zhang; Yang Li; Jingping Chen

2001-01-01

The horizontal sinter-HIP equipment with great charge capacity and high performance, developed and manufactured by Central Iron and Steel Research Institute(CISRI), is mainly used for sintering and condensation of hard metals. This equipment is characterized by large hot zone, high heating speed, good temperature uniformity and fast cooling system. The equipment can provide uniform hot zone with temperature difference less than 6 o C at 1500-1600 o C and 6-10 MPa by controlling temperature, pressure and circulation of gas precisely. Using large scale horizontal sinter-HIP equipment to produce hard matals have many advantages such as stable quality, high efficiency of production, high rate of finished products and low production cost, so this equipment is a good choice for manufacturer of hard metals. (author)

Sintering Theory and Practice

Science.gov (United States)

German, Randall M.

1996-01-01

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

On the sintering kinetics in UO2

International Nuclear Information System (INIS)

Marajofsky, A.

1998-01-01

The fabrication process of UO 2 pellets from powders involve pressing and a sintering anneal at high temperature (1650 deg. C to 1750 deg. C) during two or more hours in a hydrogen atmosphere. An alternative method is the oxidative sintering, made at lower temperature (1000 deg. C to 1300 deg. C) in a CO 2 or CO/CO 2 atmosphere. The sintering phenomena consist in the densification of the material by a thermal treatment below the fusion point. For a compact made by pressing a powder, sintering is the process of annulation of the porosity present in the compact or pellet. Several theories describe the sintering phenomena dividing it in three stages, initial, intermediate and final: in all of them the densification is a continuous growing function of time. Nevertheless it has been experimentally reported that a reduction of the density occurs in the third step of the sintering. The phenomena has been called solarization. Solarization has been attributed to the effect of the evolved gases from additives or to the CO 2 atmosphere in oxidative sintering. Thus, it is convenient to distinguish between solarization in oxidative or reducing conditions. Reducing solarization is a consequence of the tendency towards equilibrium of intergranular pores. In oxidative sintering it occurs in the reducing anneal after the sintering and is due to the change in the lattice parameter. This work shows examples of both types of solarization and qualitative interpretation of this phenomena. Both situations show the need of strict control of the sintering and powder production conditions. (author)

Vacuum-sintered body of a novel apatite for artificial bone

Science.gov (United States)

Tamura, Kenichi; Fujita, Tatsushi; Morisaki, Yuriko

2013-12-01

We produced regenerative artificial bone material and bone parts using vacuum-sintered bodies of a novel apatite called "Titanium medical apatite (TMA®)" for biomedical applications. TMA was formed by chemically connecting a Ti oxide molecule with the reactive [Ca10(PO4)6] group of Hydroxyapatite (HAp). The TMA powders were kneaded with distilled water, and solid cylinders of compacted TMA were made by compression molding at 10 MPa using a stainless-steel vessel. The TMA compacts were dried and then sintered in vacuum (about 10-3 Pa) or in air using a resistance heating furnace in the temperature range 1073-1773 K. TMA compacts were sintered at temperatures greater than 1073 K, thus resulting in recrystallization. The TMA compact bodies sintered in the range 1273-1773 K were converted into mixtures composed of three crystalline materials: α-TCP (tricalcium phosphate), β-TCP, and Perovskite-CaTiO3. The Perovskite crystals were stable and hard. In vacuum-sintering, the Perovskite crystals were transformed into fibers (approximately 1 µm in diameter × 8 µm in length), and the fiber distribution was uniform in various directions. We refer to the TMA vacuum-sintered bodies as a "reinforced composite material with Perovskite crystal fibers." However, in atmospheric sintering, the Perovskite crystals were of various sizes and were irregularly distributed as a result of the effect of oxygen. After sintering temperature at 1573 K, the following results were obtained: the obtained TMA vacuum-sintered bodies (1) were white, (2) had a density of approximately 2300 kg/m3 (corresponding to that of a compact bone or a tooth), and had a thermal conductivity of approximately 31.3 W/(m·K) (corresponding to those of metal or ceramic implants). Further, it was possible to cut the TMA bodies into various forms with a cutting machine. An implant made of TMA and inserted into a rabbit jaw bone was covered by new bone tissues after just one month because of the high

Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

International Nuclear Information System (INIS)

Freitas, C.T. de.

1980-06-01

The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO 2 gels and UO 2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO 2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author) [pt

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

Science.gov (United States)

Suastiyanti, Dwita; Ismojo

2017-07-01

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

Properties, structure and machnining capabilities sintered corundum abrasives

Directory of Open Access Journals (Sweden)

Cz.J. Niżankowski

2010-07-01

Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

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

Influence of Various Process Parameters on the Density of Sintered Aluminium Alloys

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Mateusz Laska

2012-01-01

Full Text Available This paper presents the results of density measurements carried out on Alumix sintered parts. ECKA Alumix aluminium powders were used because of their wide application in the powder metallurgy industry. The compacts were produced using a wide range of compaction pressures for three different chemical compositions. The compacts were then sintered under a pure dry nitrogen atmosphere at three different temperatures. The heating and cooling rates were the same throughout the entire test. The results showed that the green density increases with compaction pressure, but that sintered density is independent of green density (compaction pressure for each sintering temperature.

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)

A preparation method and effects of Al–Cr coating on NdFeB sintered magnets

International Nuclear Information System (INIS)

Zheng, Jingwu; Lin, Min; Xia, Qingping

2012-01-01

A 50 μm Al–Cr coating on NdFeB sintered magnets was prepared through dipping in solution, shaking dry and heating at 300 °C. The morphology and composition of the Al–Cr coating were investigated with scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The corrosion resistance of NdFeB sintered magnets with and without the Al–Cr coating was analyzed by normal salt spray, polarization curves and electrochemical impedance spectroscopy. The magnetic properties were measured with a hysteresis loop tracer. The results show that the Al–Cr coating forms an overlapping structure and Al flakes lie nearly parallel to the substrate, which improves the anticorrosion and increases normal salt spray test from 10 to 100 h. The corrosion potential of NdFeB sintered magnets with and without the Al–Cr coating moves positively from −0.67 to −0.48 V, which is in accordance with Nyquist and Bode plots. The Al–Cr coating has little influence on the magnetic properties of the NdFeB sintered magnets. - Highlights: ► The Al–Cr coating can be prepared by dipping in solution, shaking dry and heating. ► The coating morphology shows to be an intense overlapping structure. ► The barrier effect combines with passivation and cathodic protection. ► The anticorrosion abilities improve while magnetic properties change little. ► Compared with other surface treatments, this method is convenient and low cost.

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)

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

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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.

Properties of Bulk Sintered Silver As a Function of Porosity

Energy Technology Data Exchange (ETDEWEB)

Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

2012-06-01

This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

Corrosion of Ti6Al4V pins produced by direct metal laser sintering

Energy Technology Data Exchange (ETDEWEB)

Damborenea, J.J. de, E-mail: jdambo@cenim.csic.es [Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avenida Gregorio del Amo, 8, E-28040 Madrid (Spain); Arenas, M.A. [Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avenida Gregorio del Amo, 8, E-28040 Madrid (Spain); Larosa, Maria Aparecida; Jardini, André Luiz [National Institute of Biofabrication (INCT-BIOFABRIS), State of University of Campinas (UNICAMP), Campinas (Brazil); School of Chemical Engineering, State of University of Campinas (UNICAMP), Campinas (Brazil); Carvalho Zavaglia, Cecília Amélia de [National Institute of Biofabrication (INCT-BIOFABRIS), State of University of Campinas (UNICAMP), Campinas (Brazil); Faculty of Mechanical Engineering, State of University of Campinas (UNICAMP), Campinas (Brazil); Conde, A. [Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avenida Gregorio del Amo, 8, E-28040 Madrid (Spain)

2017-01-30

Highlights: • Pins of Ti6Al4V have been produced by DMLS technique. • Corrosion behavior of pins is similar to Ti6Al4V commercial Kirschner wires. • Formation of voluminous white oxide can appear at potentials higher than 2.4 V. • Defects originated during processing may cause this unusual behavior. - Abstract: Direct Metal Laser Sintering (DMLS) technique allows the manufacturing a wide variety of medical devices for any type of prosthetic surgery (HIP, dental, cranial, maxillofacial) as well as for internal fixation devices (K-Wires or Steinmann Pins). There are a large number of research studies on DMLS, including microstructural characterization, mechanical properties and those based on production quality assurance but the influence of porosity in the corrosion behavior of these materials not been sufficiently considered. In the present paper, surgical pins of Ti6Al4V have been produced by DMLS. After testing in a phosphate buffered saline solution, the surface of the titanium alloy appeared locally covered by a voluminous white oxide. This unexpected behavior was presumably due to the existence of internal defects in the pins as result of the manufacturing process. The importance of these defects—that might act as crevice nucleation sites- has been revealed by electrochemical techniques and confirmed by computed tomography.

Corrosion of Ti6Al4V pins produced by direct metal laser sintering

International Nuclear Information System (INIS)

Damborenea, J.J. de; Arenas, M.A.; Larosa, Maria Aparecida; Jardini, André Luiz; Carvalho Zavaglia, Cecília Amélia de; Conde, A.

2017-01-01

Highlights: • Pins of Ti6Al4V have been produced by DMLS technique. • Corrosion behavior of pins is similar to Ti6Al4V commercial Kirschner wires. • Formation of voluminous white oxide can appear at potentials higher than 2.4 V. • Defects originated during processing may cause this unusual behavior. - Abstract: Direct Metal Laser Sintering (DMLS) technique allows the manufacturing a wide variety of medical devices for any type of prosthetic surgery (HIP, dental, cranial, maxillofacial) as well as for internal fixation devices (K-Wires or Steinmann Pins). There are a large number of research studies on DMLS, including microstructural characterization, mechanical properties and those based on production quality assurance but the influence of porosity in the corrosion behavior of these materials not been sufficiently considered. In the present paper, surgical pins of Ti6Al4V have been produced by DMLS. After testing in a phosphate buffered saline solution, the surface of the titanium alloy appeared locally covered by a voluminous white oxide. This unexpected behavior was presumably due to the existence of internal defects in the pins as result of the manufacturing process. The importance of these defects—that might act as crevice nucleation sites- has been revealed by electrochemical techniques and confirmed by computed tomography.

PRODUCTION OF PROTOTYPE PARTS USING DIRECT METAL LASER SINTERING TECHNOLOGY

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Josef Sedlak

2015-08-01

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

Corrosion of Ti6Al4V pins produced by direct metal laser sintering

Science.gov (United States)

de Damborenea, J. J.; Arenas, M. A.; Larosa, Maria Aparecida; Jardini, André Luiz; de Carvalho Zavaglia, Cecília Amélia; Conde, A.

2017-01-01

Direct Metal Laser Sintering (DMLS) technique allows the manufacturing a wide variety of medical devices for any type of prosthetic surgery (HIP, dental, cranial, maxillofacial) as well as for internal fixation devices (K-Wires or Steinmann Pins). There are a large number of research studies on DMLS, including microstructural characterization, mechanical properties and those based on production quality assurance but the influence of porosity in the corrosion behavior of these materials not been sufficiently considered. In the present paper, surgical pins of Ti6Al4V have been produced by DMLS. After testing in a phosphate buffered saline solution, the surface of the titanium alloy appeared locally covered by a voluminous white oxide. This unexpected behavior was presumably due to the existence of internal defects in the pins as result of the manufacturing process. The importance of these defects-that might act as crevice nucleation sites- has been revealed by electrochemical techniques and confirmed by computed tomography.

Microwave sintering of nano size powder β-TCP bioceramics

Directory of Open Access Journals (Sweden)

Mirhadi B.

2014-01-01

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

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)

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.

Ferritic oxide dispersion strengthened alloys by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Allahar, Kerry N., E-mail: KerryAllahar@boisestate.edu [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Burns, Jatuporn [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Jaques, Brian [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Wu, Y.Q. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Charit, Indrajit [Department of Chemical and Materials Engineering, University of Idaho, McClure Hall Room 405D, Moscow, ID 83844 (United States); Cole, James [Idaho National Laboratory, Idaho Falls, ID 83401 (United States); Butt, Darryl P. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States)

2013-11-15

Spark plasma sintering (SPS) was used to consolidate a Fe–16Cr–3Al (wt.%) powder that was mechanically alloyed with Y{sub 2}O{sub 3} and Ti powders to produce 0.5 Y{sub 2}O{sub 3} and 0.5 Y{sub 2}O{sub 3}–1Ti powders. The effects of mechanical alloying and sintering conditions on the microstructure, relative density and hardness of the sintered oxide dispersion strengthened (ODS) alloys are presented. Scanning electron microscopy indicated a mixed fine-grain and coarse-grain microstructure that was attributed to recrystallization and grain growth during sintering. Analysis of the transmission electron microscopy (TEM) and atom probe tomography (APT) data identified Y–O and Y–O–Ti nanoclusters. Elemental ratios of these nanoclusters were consistent with that observed in hot-extruded ODS alloys. The influence of Ti was to refine the grains as well as the nanoclusters with there being greater number density and smaller sizes of the Y–O–Ti nanoclusters as compared to the Y–O nanoclusters. This resulted in the Ti-containing samples being harder than the Ti-free alloys. The hardness of the alloys with the Y–O–Ti nanoclusters was insensitive to sintering time while smaller hardness values were associated with longer sintering times for the alloys with the Y–O nanoclusters. Pressures greater than 80 MPa are recommended for improved densification as higher sintering temperatures and longer sintering times at 80 MPa did not improve the relative density beyond 97.5%.

Two step sintering of zirconia-escandia-ceria

International Nuclear Information System (INIS)

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

2011-01-01

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

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.

Hydrothermal Cold Sintering

Science.gov (United States)

Kang, Xiaoyu

Solid state sintering transforms particle compact to a physically robust and dense polycrystalline monolith driven by reduction of surface energy and curvature. Since bulk diffusion is required for neck formation and pore elimination, sintering temperature about 2/3 of melting point is needed. It thus places limitations for materials synthesis and integration, and contributes to significant energy consumption in ceramic processing. Furthermore, since surface transport requires lower temperature than bulk processes, grain growth is often rapid and can be undesired for physical properties. For these reasons, several techniques have been developed including Liquid Phase Sintering (LPS), Hot Pressing (HP) and Field Assisted Sintering Technique (FAST), which introduce either viscous melt, external pressure or electric field to speed up densification rates at lower temperature. However, because of their inherent reliability on bulk diffusion, temperatures required are often too high for integrating polymers and non-noble metals. Reduction of sintering temperature below 400 °C would require a different densification mechanism that is based on surface transport with external forces to drive volume shrinkage. Densification method combining uniaxial pressure and solution under hydrothermal condition was first demonstrated by Kanahara's group at Kochi University in 1986 and was brought to our attention by the work of Kahari, etc, from University of Oulu on densification of Li2MoO 4 in 2015. This relatively new process showed promising ultra-low densification temperature below 300 °C, however little was known about its fundamental mechanism and scope of applications, which became the main focus of this dissertation. In this work, a uniaxial hydraulic press, a standard stainless steel 1/2 inch diameter die with heating band were utilized in densifying metal oxides. Applied pressure and sintering temperature were between 100 MPa and 700 MPa and from room temperature to 300 �

A preparation method and effects of Al-Cr coating on NdFeB sintered magnets

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jingwu [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China); Lin, Min, E-mail: linm@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering Chinese Academy of Science, 519 Road Zhuangshi, District Zhenghai, Ningbo 315201, People' s Republic of China (China); Xia, Qingping [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)

2012-11-15

A 50 {mu}m Al-Cr coating on NdFeB sintered magnets was prepared through dipping in solution, shaking dry and heating at 300 Degree-Sign C. The morphology and composition of the Al-Cr coating were investigated with scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The corrosion resistance of NdFeB sintered magnets with and without the Al-Cr coating was analyzed by normal salt spray, polarization curves and electrochemical impedance spectroscopy. The magnetic properties were measured with a hysteresis loop tracer. The results show that the Al-Cr coating forms an overlapping structure and Al flakes lie nearly parallel to the substrate, which improves the anticorrosion and increases normal salt spray test from 10 to 100 h. The corrosion potential of NdFeB sintered magnets with and without the Al-Cr coating moves positively from -0.67 to -0.48 V, which is in accordance with Nyquist and Bode plots. The Al-Cr coating has little influence on the magnetic properties of the NdFeB sintered magnets. - Highlights: Black-Right-Pointing-Pointer The Al-Cr coating can be prepared by dipping in solution, shaking dry and heating. Black-Right-Pointing-Pointer The coating morphology shows to be an intense overlapping structure. Black-Right-Pointing-Pointer The barrier effect combines with passivation and cathodic protection. Black-Right-Pointing-Pointer The anticorrosion abilities improve while magnetic properties change little. Black-Right-Pointing-Pointer Compared with other surface treatments, this method is convenient and low cost.

Sintering diagrams of UO2

International Nuclear Information System (INIS)

Mohan, A.; Soni, N.C.; Moorthy, V.K.

1979-01-01

Ashby's method (see Acta Met., vol. 22, p. 275, 1974) of constructing sintering diagrams has been modified to obtain contribution diagrams directly from the computer. The interplay of sintering variables and mechanisms are studied and the factors that affect the participation of mechanisms in UO 2 are determined. By studying the physical properties, it emerges that the order of inaccuracies is small in most cases and do not affect the diagrams. On the other hand, even a 10% error in activation energies, which is quite plausible, would make a significant difference to the diagram. The main criticism of Ashby's approach is that the numerous properties and equations used, communicate their inaccuracies to the diagrams and make them unreliable. The present study has considerably reduced the number of factors that need to be refined to make the sintering diagrams more meaningful. (Auth.)

Effect of recycling blast furnace flue dust as pellets on the sintering performance

Directory of Open Access Journals (Sweden)

El-Hussiny N.A.

2010-01-01

Full Text Available The Egyptian Iron and Steel Company generates a great amount of blast furnace flue dust. The recovery of metals and carbon from this flue dust becomes a very important demand due to the increase of the price of coke breeze and the decrease of the primary source of metals. At the same time, it make the environment more safe by decreasing pollution. Introducing these dust fines in the sintering process proves to be very harmful for different operating parameters. Thus, this study aims at investigating the production of pellets resulting from these fines, using molasses as organic binder and its application in sintering of iron ore. The sintering experiments were performed using flue dust as pellets as a substitute of coke breeze. The results revealed that, sintering properties such as inter strength increases with using the flue dust pellets, while productivity of both the sinter machine and sinter machine at blast furnace yard decreases. Also the vertical velocity of the sinter machine and the weight loss during the reduction of produced the sinter by hydrogen decrease.

Peculiarities of formation and sintering of fine dispersed molybdenum powders

International Nuclear Information System (INIS)

Kalamazov, R.U.; Pak, V.I.; Tsvetkov, Yu.V.; Lem, I.N.

1989-01-01

Pressing of fine dispersed Mo powders sintering of compacts in H 2 and vacuum is studied. It is shown that powder preannealing at 600 deg C in H 2 for 2 hours is necessary for formation of dense sintered compacts. Qualitatively choice of pressing conditions is possible when using electron-positron annihilation method. Peculiarities of compacting and sintering of fine- and coarse-dispersed powder mixtures are considered. The obtained results are discussed from the view point of sintering recrystallization mechanism

Full densification of inkjet-printed copper conductive tracks on a flexible substrate utilizing a hydrogen plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Kwon, Young-Tae [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Lee, Young-In [Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811 (Korea, Republic of); Kim, Seil [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Lee, Kun-Jae [Department of Energy Engineering, Dankook University, Cheonan 31116 (Korea, Republic of); Choa, Yong-Ho, E-mail: choa15@hanyang.ac.kr [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of)

2017-02-28

Highlights: • Hydrogen thermally- and plasma- treatments are applied to reduce and sinter the inkjet-printed copper patterns at low temperature. • Plasma sintered Cu patterns have fully densified microstructure with the resistivity of 3.23 μW cm. • Cu conductive track with dense microstructure remains its electrical resistivity after 1 month. • Thermal sintered Cu patterns show a relatively poor microstructure and high resistivity. - Abstract: Low temperature sintering techniques are crucial in developing flexible printed electronics. In this work, we demonstrate a novel hydrogen plasma sintering method that achieves a full reduction and densification of inkjet-printed patterns using a copper complex ion ink. After inkjet printing on polyethylene terephthalate (PET) substrates, both hydrogen plasma and conventional hydrogen thermal treatment were employed to compare the resulting microstructures, electrical properties and anti-oxidation behavior. The plasma treated pattern shows a fully densified microstructure with a resistivity of 3.23 μΩ cm, while the thermally treated pattern shows a relatively poor microstructure and high resistivity. In addition, the hydrogen plasma-treated copper pattern retains its electrical resistivity for one month without any significant decrease. This novel hydrogen plasma sintering technique could be used to produce conductive patterns with excellent electrical properties, allowing for highly reliable flexible printed electronics.

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Uranium dioxide. Sintering test

International Nuclear Information System (INIS)

Anon.

Description of a sintering method and of the equipment devoted to uranium dioxide powder caracterization and comparison between different samples. Determination of the curve giving specific volume versus pressure and micrographic examination of a pellet at medium pressure [fr

Shrinkage calibration method for μPIM manufactured parts

DEFF Research Database (Denmark)

Quagliotti, Danilo; Tosello, Guido; Salaga, J.

2016-01-01

Five green and five sintered parts of a micro mechanical component, produced by micro powder injection moulding, were measured using an optical coordinate measuring machine. The aim was to establish a method for quality assurance of the final produced parts. Initially, the so called “green” parts...... were compared with the sintered parts (final products) calculating the percentage of shrinkage after sintering. Successively, the expanded uncertainty of the measured dimensions were evaluated for each single part as well as for the overall parts. Finally, the estimated uncertainty for the shrinkage...... was evaluated propagating the expanded uncertainty previously stated and considering green and sintered parts correlated. Results showed that the proposed method can be effective instating tolerances if it is assumed that the variability on the dimensions induced by the shrinkage equals the propagated expanded...

The study of Ashby-type sintering diagrams for uranium dioxide

International Nuclear Information System (INIS)

Georgeoni, P.

1980-01-01

Computer modelling of binary and ternary Ashby-type sintering diagrams for stoechiometric and hyperstoechiometric uranium dioxide (in the range O/U = 2, 0-2, 10). Material data and mass transfer equations, selected from the literature, were used. Sintering isochronous curves were calculated and traced as well. Improvement of a modern dilatometric method by reading and processing experimental curves on a computer and by determining for them a criterion of proximity to the theoretical model equation. It was possible: to develop a reliable method of determination for the dominant mechanism, diffusion coefficient and real process activation energy; to draw up the real sintering diagram; to understand the quantitative and qualitative changes occuring during the actual sintering process of UO 2 , concerning massing and modification of pore shape; to recommend the technological parameters of the thermal regime concerning the elimination of lubricant and binder additives in order to obtain high quality sintered tablets. (author)

Standard test methods for analysis of sintered gadolinium oxide-uranium dioxide pellets

CERN Document Server

American Society for Testing and Materials. Philadelphia

2006-01-01

1.1 These test methods cover procedures for the analysis of sintered gadolinium oxide-uranium dioxide pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Section Carbon (Total) by Direct CombustionThermal Conductivity Method C1408 Test Method for Carbon (Total) in Uranium Oxide Powders and Pellets By Direct Combustion-Infrared Detection Method Chlorine and Fluorine by Pyrohydrolysis Ion-Selective Electrode Method C1502 Test Method for Determination of Total Chlorine and Fluorine in Uranium Dioxide and Gadolinium Oxide Gadolinia Content by Energy-Dispersive X-Ray Spectrometry C1456 Test Method for Determination of Uranium or Gadolinium, or Both, in Gadolinium Oxide-Uranium Oxide Pellets or by X-Ray Fluorescence (XRF) Hydrogen by Inert Gas Fusion C1457 Test Method for Determination of Total Hydrogen Content of Uranium Oxide Powders and Pellets by Carrier Gas Extraction Isotopic Uranium Composition by Multiple-Filament Surface-Ioni...

A study on some properties of sintered stainless steel powder compacts with sintering conditions

International Nuclear Information System (INIS)

Lee, Bang Sik; Kim, Kwan Hyu; Lee, Doh Jae; Choi, Dap Chun

1986-01-01

Sintered specimens for the mechanical and corrosion tests were prepared from 316L, 410L and 434L stainless steel powder compacts with green densities in the range of 6.2∼7.0g/cm 3 . The experimental variables studied were green density, sintering atmosphere, temperature and time, type of lubricant used and cooling rate after sintering operation. Mechanical properties of green compacts and sintered specimens were evaluated. The corrosion tests were performed by potentiodynamic anodic polarization technique. Mechanical properties were very sensitive to the sintering atmosphere; sintering in dissociated ammonia resulted in the strengthing but embrittlement of sintered 316L, 410L and 434L strainless steel powder compacts. Their corrosion resistance was also decreased. The tensile strength was increased with increases in sintering time and temperature while the decreases in the yield strength were observed. The tensile properties of green compacts were shown to closely related to the green density. Addition of 1% acrawax as a lubricant was appeared to be most effective for the improvement of green strength. (Author)

Coarsening-densification transition temperature in sintering of uranium dioxide

International Nuclear Information System (INIS)

Balakrishna, Palanki; Narasimha Murty, B.; Chakraborthy, K.P.; Jayaraj, R.N.; Ganguly, C.

2001-01-01

The concept of coarsening-densification transition temperature (CDTT) has been proposed to explain the experimental observations of the study of sintering undoped uranium dioxide and niobia-doped uranium dioxide powder compacts in argon atmosphere in a laboratory tubular furnace. The general method for deducing CDTT for a given material under the prevailing conditions of sintering and the likely variables that influence the CDTT are described. Though the present work is specific in nature for uranium dioxide sintering in argon atmosphere, the concept of CDTT is fairly general and must be applicable to sintering of any material and has immense potential to offer advantages in designing and/or optimizing the profile of a sintering furnace, in the diagnosis of the fault in the process conditions of sintering, and so on. The problems of viewing the effect of heating rate only in terms of densification are brought out in the light of observing the undesirable phenomena of coring and bloating and causes were identified and remedial measures suggested

Fabrication and testing of the sintered ceramic UO2 fuel - I - III, Part III - testing of sintered uranium dioxide properties dependent on the fabrication procedure

International Nuclear Information System (INIS)

Novakovic, M.; Ristic, M.M.

1961-12-01

The objective of this task was testing the influence of some parameters on the properties of sintered UO 2 . The influence of parameters tested were as follows: adhesives; pressure in the pressing procedure; temperature of sintering of the UO 2 powder. Other parameters were chosen according to the theoretical study. Sintering was done in argon atmosphere. Characterization of the UO 2 powder was performed meaning determining the needed chemical, physical and physico-chemical properties. Some new methods were developed within this task: SET method for measuring the specific surfaces, DTA, TGA, high-temperature torsion

Mechanisms of sintering

International Nuclear Information System (INIS)

Mohan, Ashok; Soni, N.C.; Moorthy, V.K.

1980-01-01

The basic mechanisms by which the material moves during sintering have not only held a strange fascination but are also very important in determining the properties of the end product. Kuczynski's exponent method has been subsequently refined by several schools to make it increasingly reliable. There is now a fairly good understanding of mechanisms in some of the materials. However in others the issue is complicated by their basic nature. The problems of ambiguity in criterion and that of more than one mechanism being simultaneously operative have been tackled with dexterity by Ashby for drawing sintering mechanism diagrams. The method has been modified to give Relative Contribution Diagrams (RCD). These yield additional information and have been used for analysis. The main criticism against this is that it uses a very large number of rate equations and material properties, which can communicate their inaccuracies to the diagram. A case study of UO 2 was undertaken and it has been shown quantitatively that inaccuracies in a smaller number of properties only affect the diagrams to any significant extent. (auth.)

Apparatus and method for direct measurement of coal ash sintering and fusion properties at elevated temperatures and pressures

Science.gov (United States)

Khan, M. Rashid

1990-01-01

A high-pressure microdilatometer is provided for measuring the sintering and fusion properties of various coal ashes under the influence of elevated pressures and temperatures in various atmospheres. Electrical resistivity measurements across a sample of coal ash provide a measurement of the onset of the sintering and fusion of the ash particulates while the contraction of the sample during sintering is measured with a linear variable displacement transducer for detecting the initiation of sintering. These measurements of sintering in coal ash at different pressures provide a mechanism by which deleterious problems due to the sintering and fusion of ash in various combustion systems can be minimized or obviated.

All-photonic drying and sintering process via flash white light combined with deep-UV and near-infrared irradiation for highly conductive copper nano-ink

Science.gov (United States)

Hwang, Hyun-Jun; Oh, Kyung-Hwan; Kim, Hak-Sung

2016-01-01

We developed an ultra-high speed photonic sintering method involving flash white light (FWL) combined with near infrared (NIR) and deep UV light irradiation to produce highly conductive copper nano-ink film. Flash white light irradiation energy and the power of NIR/deep UV were optimized to obtain high conductivity Cu films. Several microscopic and spectroscopic characterization techniques such as scanning electron microscopy (SEM), a x-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize the Cu nano-films. Optimally sintered Cu nano-ink films produced using a deep UV-assisted flash white light sintering technique had the lowest resistivity (7.62 μΩ·cm), which was only 4.5-fold higher than that of bulk Cu film (1.68 μΩ•cm). PMID:26806215

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

Directory of Open Access Journals (Sweden)

Yan Zilin

2017-01-01

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

Microstructural stability of spark-plasma-sintered Wf/W composite with zirconia interface coating under high-heat-flux hydrogen beam irradiation

Directory of Open Access Journals (Sweden)

M. Avello de Lama

2017-12-01

In this paper, the durability and chemical stability of Wf/W composite specimens under cyclic heat-flux loads up to 20 MW/m² (surface temperature: 1260 °C was investigated using hydrogen neutral beam. The bulk material was fabricated by means of spark-plasma-sintering (SPS method using fine tungsten powder and a stack of tungsten wire meshes as reinforcement where the surface of the wire was coated with zirconia thin film to produce an engineered interface. The impact of plasma beam irradiation on microstructure was examined for two kinds of specimens produced at different sintering temperatures, 1400 °C and 1700 °C. Results of microscopic (SEM and chemical (EDX analysis are presented comparing the microstructure and element distribution maps obtained before and after heat flux loading. Effects of different sintering temperatures on damage behaviour are discussed. The present composite materials are shown to be applicable as plasma-facing material for high-heat-flux components.

Visible luminescence peculiar to sintered silica nanoparticles: Spectral and decay properties

Energy Technology Data Exchange (ETDEWEB)

Vaccaro, L. [Dipartimento di Fisica e Chimica, Università di Palermo, Via Archirafi 36, I-90123 Palermo (Italy); Cannas, M., E-mail: marco.cannas@unipa.it [Dipartimento di Fisica e Chimica, Università di Palermo, Via Archirafi 36, I-90123 Palermo (Italy); Cangialosi, C. [Dipartimento di Fisica e Chimica, Università di Palermo, Via Archirafi 36, I-90123 Palermo (Italy); Laboratoire H. Curien, UMR CNRS 5516, Université St-Etienne, St-Etienne F-42000 (France); Spallino, L.; Gelardi, F.M. [Dipartimento di Fisica e Chimica, Università di Palermo, Via Archirafi 36, I-90123 Palermo (Italy)

2015-10-15

We report that the sintering at 1000 °C of silica nanoparticles (an average diameter of 14 nm) produces a transparent sample that exhibits a bright visible emission under UV excitation. The use of time resolved luminescence spectroscopy and a tunable laser source allows us to single out three contributions centered at 1.96 eV, 2.41 eV and 3.43 eV. The excitation spectra of these emissions evidence bell shaped bands consistent with transitions between localized defects’ states. For each emission we study the intensity and the lifetime in the temperature range from 300 K down to 10 K, thus evidencing the competition between radiative and non-radiative processes in the optical cycle of luminescent centers. The comparison with the luminescence properties of silica, both nanoparticles and bulk, points out that the observed emissions are peculiar to the sintered silica network. - Highlights: • Solid-phase sintering at 1000 °C of silica nanoparticles produces a transparent sample. • Sintered silica nanoparticles emit a bright luminescence under UV excitation. • Three emissions, centered around 2.0 V, 2.4 eV and 3.4 eV, are distinguished on the basis of the excitation and decay properties. • The observed excitation/emission bands originate from localized defect states peculiar to the sintered silica network. • The luminescence efficiency decreases with temperature due to the activation of non-radiative channels.

Kinetics of UO2 sintering

International Nuclear Information System (INIS)

Ristic, M.M.

1962-01-01

Detailed conclusions related to the UO 2 sintering can be drawn from investigating the kinetics of the sintering process. This report gives an thorough analysis of the the data concerned with sintering available in the literature taking into account the Jander and Arrhenius laws. This analysis completes the study of influence of the O/U ratio and the atmosphere on the sintering. Results presented are fundamentals of future theoretical and experimental work related to characterisation of the UO 2 sintering process

Sintering study in vertical fixed bed reactor for synthetic aggregate production

International Nuclear Information System (INIS)

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

2017-01-01

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

Production of sintered porous metal fluoride pellets

Science.gov (United States)

Anderson, L.W.; Stephenson, M.J.

1973-12-25

Porous pellets characterized by a moderately reactive crust and a softer core of higher reactivity are produced by forming agglomerates containing a metal fluoride powder and a selected amount ofwater. The metal fluoride is selected to be sinterable and essentially non-reactive with gaseous fluorinating agents. The agglomerates are contacted with a gaseous fluorinating agent under controlled conditions whereby the heat generated by localized reaction of the agent and water is limited to values effccting bonding by localized sintering. Porous pellets composed of cryolite (Na/sub 3/AlF/sub 6/) can be used to selectively remove trace quantities of niobium pentafluoride from a feed gas consisting predominantly of uranium hexafluoride. (Official Gazette)

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.

The Effects of Solid Phase Additives on Sintering Properties of Alumina Bioceramic

Institute of Scientific and Technical Information of China (English)

WANG Xin-yu; LI Shi-pu; HE Jian-hua; JIANG Xin; LI Jian-hua

2003-01-01

In order to reduce the sintering temperature and improve the preparing conditions of alumina bioceramics,the Mg-Zr-Y composite solid phase additives were added into high purity Al2O3 micro-powder by chemical coprecipitation method.The powder was shaped under 200MPa cold isostatic pressure,and then the biscuits were sintered at 1600℃ under normal pressure.The sintered alumina materials were tested and the sintering mechanism was discussed.The results show that physical properties of the material were improved comparatively.The Mg-Zr-Y composite solid additives could promote the sintering of alumina bioceramics and the mechanism is solid phase sintering.

Contribution to the modelling of solid state sintering

International Nuclear Information System (INIS)

Martin, Sylvain

2014-01-01

This thesis deals with the simulation of the sintering of nuclear fuel on a pellet scale. The goal is to develop numerical tools which can contribute to a better understanding of the physical phenomena involved in the sintering process. Hence, a multi scale approach is proposed. First of all, a Discrete Element model is introduced. It aims at modeling the motion of particles on a Representative Elementary Volume scale using an original Discrete Element Method. The latter is a Non Smooth Method called Contact Dynamics. Recently, there have been numerous papers about the simulation of sintering using Discrete Element Method. As far as we know, all these papers use smooth methods. Different studies show that the results match well experimental data. However, some limits come from the fact that smooth methods use an explicit scheme which needs very small time steps. In order to obtain an acceptable time step, the mass of particles have to be dramatically increased. The Non Smooth Contact Dynamics uses an implicit scheme, thus time steps can be much larger without scaling up the mass of particles. The comparison between smooth and non smooth approaches shows that our method leads to a more realistic representation of rearrangement. An experimental validation using synchrotron X-Ray microtomography is then presented, followed by a parametric study on the sintering of bimodal powders that aims at showing the capacity of this model. The second part presents a mechanical model on the sub-Granular scale, using a Finite Element method. This targets a better understanding of the behavior of two grains in contact. The model is currently being developed but the first results already show that some parameters like the shape of the surface of the neck are very sensitive. In the future, the Non smooth Contact Dynamics model of sintering may be improved using the results obtained by the sub-Granular scale mechanical model. (author) [fr

Full densification of inkjet-printed copper conductive tracks on a flexible substrate utilizing a hydrogen plasma sintering

Science.gov (United States)

Kwon, Young-Tae; Lee, Young-In; Kim, Seil; Lee, Kun-Jae; Choa, Yong-Ho

2017-02-01

Low temperature sintering techniques are crucial in developing flexible printed electronics. In this work, we demonstrate a novel hydrogen plasma sintering method that achieves a full reduction and densification of inkjet-printed patterns using a copper complex ion ink. After inkjet printing on polyethylene terephthalate (PET) substrates, both hydrogen plasma and conventional hydrogen thermal treatment were employed to compare the resulting microstructures, electrical properties and anti-oxidation behavior. The plasma treated pattern shows a fully densified microstructure with a resistivity of 3.23 μΩ cm, while the thermally treated pattern shows a relatively poor microstructure and high resistivity. In addition, the hydrogen plasma-treated copper pattern retains its electrical resistivity for one month without any significant decrease. This novel hydrogen plasma sintering technique could be used to produce conductive patterns with excellent electrical properties, allowing for highly reliable flexible printed electronics.

[Rapid prototyping: a very promising method].

Science.gov (United States)

Haverman, T M; Karagozoglu, K H; Prins, H-J; Schulten, E A J M; Forouzanfar, T

2013-03-01

Rapid prototyping is a method which makes it possible to produce a three-dimensional model based on two-dimensional imaging. Various rapid prototyping methods are available for modelling, such as stereolithography, selective laser sintering, direct laser metal sintering, two-photon polymerization, laminated object manufacturing, three-dimensional printing, three-dimensional plotting, polyjet inkjet technology,fused deposition modelling, vacuum casting and milling. The various methods currently being used in the biomedical sector differ in production, materials and properties of the three-dimensional model which is produced. Rapid prototyping is mainly usedforpreoperative planning, simulation, education, and research into and development of bioengineering possibilities.

The preparation of sintered NdFeB magnet with high-coercivity and high temperature-stability

Energy Technology Data Exchange (ETDEWEB)

Yan, G H; Chen, R J; Ding, Y; Guo, S; Lee, Don; Yan, A R, E-mail: yangh@nimte.ac.cn [Zhejiang province Key Laboratory of Magnetic Materials and Application Technology, Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201 (China)

2011-01-01

The NdFeB magnets with high intrinsic coercivity have been produced by using the conventional powder metallurgy method (including SC, HD and JM) of sintered NdFeB magnets. The effects of grain boundary phases on the microstructure and magnetic properties of as-sintered and annealed magnets have been tried to investigate. Also the Curie temperature of the magnets was studied. By adopting suitable component ratio of some heavy rare-earth atoms and some micro-quantity additives, we have prepared high-coercivity sintered NdFeB magnets with magnetic properties of {sub j}H{sub c}=36.3kOe, B{sub r}=11.7kGs and (BH){sub max}=34.0MGOe. The temperature coefficient of residual magnetic flux of the magnets (between 20 and 200 deg. C) is -0.113%/deg. C, while the temperature coefficient of intrinsic coercivity -0.355%/deg. C. The Curie temperature of the magnets is about 342 deg. C.

The preparation of sintered NdFeB magnet with high-coercivity and high temperature-stability

International Nuclear Information System (INIS)

Yan, G H; Chen, R J; Ding, Y; Guo, S; Lee, Don; Yan, A R

2011-01-01

The NdFeB magnets with high intrinsic coercivity have been produced by using the conventional powder metallurgy method (including SC, HD and JM) of sintered NdFeB magnets. The effects of grain boundary phases on the microstructure and magnetic properties of as-sintered and annealed magnets have been tried to investigate. Also the Curie temperature of the magnets was studied. By adopting suitable component ratio of some heavy rare-earth atoms and some micro-quantity additives, we have prepared high-coercivity sintered NdFeB magnets with magnetic properties of j H c =36.3kOe, B r =11.7kGs and (BH) max =34.0MGOe. The temperature coefficient of residual magnetic flux of the magnets (between 20 and 200 deg. C) is -0.113%/deg. C, while the temperature coefficient of intrinsic coercivity -0.355%/deg. C. The Curie temperature of the magnets is about 342 deg. C.

Laser-Induced Reductive Sintering of Nickel Oxide Nanoparticles under Ambient Conditions

KAUST Repository

Paeng, Dongwoo; Lee, Daeho; Yeo, Junyeob; Yoo, Jae-Hyuck; Allen, Frances I.; Kim, Eunpa; So, Hongyun; Park, Hee K.; Minor, Andrew M.; Grigoropoulos, Costas P.

2015-01-01

© 2015 American Chemical Society. This work is concerned with the kinetics of laser-induced reductive sintering of nonstoichiometric crystalline nickel oxide (NiO) nanoparticles (NPs) under ambient conditions. The mechanism of photophysical reductive sintering upon irradiation using a 514.5 nm continuous-wave (CW) laser on NiO NP thin films has been studied through modulating the laser power density and illumination time. Protons produced due to high-temperature decomposition of the solvent present in the NiO NP ink, oxygen vacancies in the NiO NPs, and electronic excitation in the NiO NPs by laser irradiation all affect the early stage of the reductive sintering process. Once NiO NPs are reduced by laser irradiation to Ni, they begin to coalesce, forming a conducting material. In situ optical and electrical measurements during the reductive sintering process take advantage of the distinct differences between the oxide and the metallic phases to monitor the transient evolution of the process. We observe four regimes: oxidation, reduction, sintering, and reoxidation. A characteristic time scale is assigned to each regime.

Laser-Induced Reductive Sintering of Nickel Oxide Nanoparticles under Ambient Conditions

KAUST Repository

Paeng, Dongwoo

2015-03-19

© 2015 American Chemical Society. This work is concerned with the kinetics of laser-induced reductive sintering of nonstoichiometric crystalline nickel oxide (NiO) nanoparticles (NPs) under ambient conditions. The mechanism of photophysical reductive sintering upon irradiation using a 514.5 nm continuous-wave (CW) laser on NiO NP thin films has been studied through modulating the laser power density and illumination time. Protons produced due to high-temperature decomposition of the solvent present in the NiO NP ink, oxygen vacancies in the NiO NPs, and electronic excitation in the NiO NPs by laser irradiation all affect the early stage of the reductive sintering process. Once NiO NPs are reduced by laser irradiation to Ni, they begin to coalesce, forming a conducting material. In situ optical and electrical measurements during the reductive sintering process take advantage of the distinct differences between the oxide and the metallic phases to monitor the transient evolution of the process. We observe four regimes: oxidation, reduction, sintering, and reoxidation. A characteristic time scale is assigned to each regime.

Characteristics Of The Porous Body Sintered By Nano-Sized Fe-Cr-Al Alloy Powder

Directory of Open Access Journals (Sweden)

Lee Su-In

2015-06-01

Full Text Available Porous metal with uniform honeycomb structure was successfully produced by sintering using Fe-Cr-Al nano powder, which was prepared by the pulsed wire evaporation (PWE in ethanol. Its process consisted of the several steps; 1 coating on the surface of polyurethane sponge with the liquid droplets generated from the ethanol-based slurry where the Fe-Cr-Al nano powders were uniformly dispersed, 2 heat treatment of debinding to remove the polyurethane sponge and 3 sintering of the porous green body formed by Fe-Cr-Al nano powders. The strut thickness of porous Fe-Cr-Al was increased by the increase of spraying times in ESP step. Also, The shrinkages and the oxidation resistance of the sintered porous body was increased with increase of sintering temperature. The optimal sintering temperature was shown to 1450°C in views to maximize the oxidation resistance and sinterability.

Microstructure and properties of TiC-high manganese steel cermet prepared by different sintering processes

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhi; Lin, Tao, E-mail: lintao@ustb.edu.cn; He, Xinbo; Shao, Huiping; Zheng, Jianshu; Qu, Xuanhui

2015-11-25

In the paper, the TiC −50 wt.% high manganese steel cermet was made with different sintering processes including vacuum sintering, hot pressing, microwave sintering and spark plasma sintering (SPS). The microstructure, porosity and fracture morphology of the samples were analyzed with scanning electron microscopy (SEM). Phase analysis was carried out using X-ray diffraction (XRD). The density, hardness, transverse rupture strength (TRS) and wear resistance were investigated for the effect of the sintering processes. The results showed that the core–shell structure was not clearly observed for the TiC particles in microstructures and the high manganese steel matrix is BCC structure. Hot pressing, microwave sintering and SPS are useful processes for densification of the cermet. Nearly full density and higher hardness can be reached by these three processes at a lower sintering temperature and in a shorter sintering time. However, higher TRS can be reached by means of alloying completely in a longer sintering time, for example vacuum sintering. Pre-sintering in a long sintering time at a lower sintering temperature is also useful for improving the TRS. Finally, vacuum sintering is an effective process for producing this composite with the lowest cost in the mass production. - Highlights: • TiC-high manganese steel cermets were prepared by four sintering processes. • The core–shell structure was not clearly observed for the TiC particles in microstructures. • Th high manganese steel matrix is BCC structure instead of FCC structure. • Pre-sintering before microwave sintering is also useful for improving the TRS. • Vacuum sintering can be effective way for prepare this cermet in mass production.

Method of making highly sinterable lanthanum chromite powder

Science.gov (United States)

Richards, Von L.; Singhal, Subhash C.

1992-01-01

A highly sinterable powder consisting essentially of LaCrO.sub.3, containing from 5 weight % to 20 weight % of a chromite of dopant Ca, Sr, Co, Ba, or Mg and a coating of a chromate of dopant Ca, Sr, Co, Ba, or Mg; is made by (1) forming a solution of La, Cr, and dopant; (2) heating their solutions; (3) forming a combined solution having a desired ratio of La, Cr, and dopant and heating to reduce solvent; (4) forming a foamed mass under vacuum; (5) burning off organic components and forming a charred material; (6) grinding the charred material; (7) heating the char at from 590.degree. C. to 950 C. in inert gas containing up to 50,000 ppm O.sub.2 to provide high specific surface area particles; (8) adding that material to a mixture of a nitrate of Cr and dopant to form a slurry; (9) grinding the particles in the slurry; (10) freeze or spray drying the slurry to provide a coating of nitrates on the particles; and (11) heating the coated particles to convert the nitrate coating to a chromate coating and provide a highly sinterable material having a high specific surface area of over 7 m.sup.2 /g.

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

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

Directory of Open Access Journals (Sweden)

Pouchly V.

2012-01-01

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

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.

Finite element modeling of camber evolution during sintering of bi-layers

DEFF Research Database (Denmark)

Tadesse Molla, Tesfaye; Ni, De Wei; Bulatova, Regina

2014-01-01

The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber...... developments during sintering of bilayers composed of La0.85Sr0.15MnO3 and Ce0.9Gd0.1O1.95 tapes. Free shrinkage kinetics of both tapes were used to estimate the parameters necessary for the finite element models. Systematic investigations of the factors affecting the kinetics of distortions such as gravity...... and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence...

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.

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

Institute of Scientific and Technical Information of China (English)

YUAN Huiping; LI Junguo; SHEN Qiang; ZHANG Lianmeng

2015-01-01

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

An Investigation of Sintering Parameters on Titanium Powder for Electron Beam Melting Processing Optimization.

Science.gov (United States)

Drescher, Philipp; Sarhan, Mohamed; Seitz, Hermann

2016-12-01

Selective electron beam melting (SEBM) is a relatively new additive manufacturing technology for metallic materials. Specific to this technology is the sintering of the metal powder prior to the melting process. The sintering process has disadvantages for post-processing. The post-processing of parts produced by SEBM typically involves the removal of semi-sintered powder through the use of a powder blasting system. Furthermore, the sintering of large areas before melting decreases productivity. Current investigations are aimed at improving the sintering process in order to achieve better productivity, geometric accuracy, and resolution. In this study, the focus lies on the modification of the sintering process. In order to investigate and improve the sintering process, highly porous titanium test specimens with various scan speeds were built. The aim of this study was to decrease build time with comparable mechanical properties of the components and to remove the residual powder more easily after a build. By only sintering the area in which the melt pool for the components is created, an average productivity improvement of approx. 20% was achieved. Tensile tests were carried out, and the measured mechanical properties show comparatively or slightly improved values compared with the reference.

[Study on preparation and physicochemical properties of surface modified sintered bone].

Science.gov (United States)

Li, Jingfeng; Zheng, Qixin; Guo, Xiaodong

2012-06-01

The aim of this study is to investigate a new method for preparing a biomimetic bone material-surface modified sintered bovine cancellous bone, and to improve its bioactivity as a tissue engineering bone. The prepared sintered bovine cancellous bones with the same size were randomly divided into two groups, immersing in 1 and 1. 5 times simulated body fluid (SBF), respectively. The three time periods of soak time were 7, 14, and 21 days. After sintered bone was dried, the surface morphology of sintered bone and surface mineralization composition were observed under scanning electron microscopy (SEM). By comparing the effect of surface modification of sintered bone materials, we chose the most ideal material and studied its pore size, the rate of the porosity, the compress and bend intensity. And then the material and the sintered bone material without surface modification were compared. The study indicated that sintered bone material immersed in SBF (1.5 times) for 14 days showed the best effect of surface modification, retaining the original physico-chemical properties of sintered bone.

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

Characterization of plasma nitrided layers produced on sintered iron

Directory of Open Access Journals (Sweden)

Marcos Alves Fontes

2014-07-01

Full Text Available Plasma nitriding is a thermo-physical-chemical treatment process, which promotes surface hardening, caused by interstitial diffusion of atomic nitrogen into metallic alloys. In this work, this process was employed in the surface modification of a sintered ferrous alloy. Scanning electron microscopy (SEM, X-ray diffraction (XRD analyses, and wear and microhardness tests were performed on the samples submitted to ferrox treatment and plasma nitriding carried out under different conditions of time and temperature. The results showed that the nitride layer thickness is higher for all nitrided samples than for ferrox treated samples, and this layer thickness increases with nitriding time and temperature, and temperature is a more significant variable. The XRD analysis showed that the nitrided layer, for all samples, near the surface consists in a mixture of γ′-Fe4N and ɛ-Fe3N phases. Both wear resistance and microhardness increase with nitriding time and temperature, and temperature influences both the characteristics the most.

Method of forming a ceramic to ceramic joint

Science.gov (United States)

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

2010-04-13

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

A study for preparation of Ti-Fe coating by high temperature sintering method

International Nuclear Information System (INIS)

Hu Yonghai

1995-03-01

A new technology for preparation of Ti-Fe alloy coating on the steel substrate was investigated by high temperature sintering method. The pulp of titanium hydride powder was coated on the cleaned steel substrate, then heated in vacuum for desorption of hydrogen and sintered at high temperature in argon atmosphere for forming Ti-Fe alloy coating. The electron probe analysis shows a strong coherent diffusion layer formed between the elements of titanium and iron. X-ray diffraction analysis indicates that the coating consists of α-Ti, TiFe and TiFe 2 three phases. The wear resistance of the coating is twice as large as that of grey cast iron and the hardness determined can reach 7300∼7800 N/mm 2 . The coating is almost porous free. The corrosion potential increases with the time and the corrosion resistance is near to that of pure titanium. The working life of ridge-type diaphragm valve coated by Ti-Fe alloy for carbonization tower of alkali factories is five times higher than that of valve made of grey cast iron. Therefore, this new technology can be widely used in metallurgical, chemical and nuclear industries. (9 figs., 10 tabs.)

Techniques for ceramic sintering using microwave energy

International Nuclear Information System (INIS)

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

1987-01-01

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

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.

Kinetics of sintering of uranium dioxide

International Nuclear Information System (INIS)

Soni, N.C.; Moorthy, V.K.

1978-01-01

The kinetics of sintering of UO 2 powders derived from ADU route and calcined at different temperatures was studied. The activation energy for sintering was found to depend on the calcination temperature, the density chosen and the sintering temperature range. The motive force for sintering is the excess free energy in the particle system. This exists in the powder compact in the form of surface energy and the excess lattice energy due to defects. The defects which can be eliminated at the operating temperature are responsible for the mobility and hence sintering. This concept of the motive force for sintering has been used to explain the difference in the activation energies observed in the present study. This would also explain phenomena such as attainment of limiting density, presence of optimum sintering temperature and the influence of calcination treatments on the sintering behaviour of powders. (author)

Conventional and two step sintering of PZT-PCN ceramics

Science.gov (United States)

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

2018-02-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Thermal Properties of Silver Nanoparticle Sintering Bonding Paste for High-Power LED Packaging

Directory of Open Access Journals (Sweden)

Ping Zhang

2016-01-01

Full Text Available This paper describes the preparation of low-temperature sintered nanosilver paste with inverse microemulsion method with Span-80/Triton X-100 as the mixed-surfactant and analyzes the influence of different sintering parameters (temperature, pressure on the shear properties of low-temperature sintering of nanosilver. Experimental results show that the shear strength of the low-temperature sintering of nanosilver increases as the temperature and pressure increase. But there are many pores and relative fewer cracks on the sintering layer after low-temperature sintered. The test thermal resistance of low-temperature sintered nanosilver paste is 0.795 K/W which is greater than SAC305 weld layer with a T3ster thermal analyzer. The adhesive performance and the heat dispersion of low-temperature sintered nanosilver paste need to be further researched and improved.

Effect of sintering time on the performance of turmeric dye-sensitized solar cells

Science.gov (United States)

Basuki, Hidajat, R. Lullus Lambang G.; Suyitno, Kristiawan, Budi; Rachmanto, Rendy Adhi

2017-01-01

This study reports the effect of sintering time on the performance of the dye-sensitized solar cells with turmeric dyes as sensitizers. Sintering TiO2 semiconductors were conducted at a temperature of 450°C for 30, 50, 90, 120, 150, and 180 minutes. The natural dye was extracted from dried turmeric powders with ethanol solvent. The results show that size of grains and the opening area of TiO2 semiconductor depended on the sintering time. The improvement of the properties of TiO2 semiconductor allowed more turmeric dyes were adsorbed by the semiconductors and then improved the performance of solar cells. The sintering time of 150 minutes produced large grains with an average diameter of 68.87 nm, and a porosity area of 26.51% caused the performance of DSSCs was the highest among other sintering time. The Voc, Jsc, and efficiency of DSSCs with turmeric-based natural dyes 0.64 V, 0.47 mA/cm2, and 0.2%, respectively.

Unidirectional infiltration method to produce crown for dental prosthesis application

International Nuclear Information System (INIS)

Pontes, F.H.D.; Taguchi, S.P.; Machado, J.P.B.; Santos, C.

2009-01-01

Alumina ceramics have been used in dental prosthesis because it is inert, presents higher corrosion and shear resistance when compared to metals, excellent aesthetic, and mechanical resistance. In this work it was produced an infrastructure material for applications in dental crowns, obtained by glass infiltration in alumina preform. Various oxides, among that, rare-earth oxide produced by Xenotime, were melted at 1450 deg C and heat treatment at 700 deg C to obtain the glass (REglass). The alumina was pre-sintered at 1100 deg C cut and machined to predetermine format (unidirectional indirect infiltration) and finally conducted to infiltration test. The alumina was characterized by porosity (Hg-porosity and density) and microstructure (SEM). The glass wettability in alumina was determined as function of temperature, and the contact angle presented a low value (θ<90 deg), showing that glass can be infiltrated spontaneously in alumina. The infiltration test was conducted at glass melting temperature, during 30, 60, 180, 360 minutes. After infiltration, the samples were cut in longitudinal section, ground and polished, and analyzed by XRD (crystalline phases), SEM (microstructure) and EDS (composition).The REglass presents higher infiltration height when compared to current processes (direct infiltration), and homogeneous microstructure, showing that it is a promising method used by prosthetics and dentists. (author)

Unidirectional infiltration method to produce crown for dental prosthesis application

Energy Technology Data Exchange (ETDEWEB)

Pontes, F.H.D.; Taguchi, S.P. [Universidade de Sao Paulo (EEL/DEMAR/USP), Lorena, SP (Brazil). Escola de Engenharia; Borges Junior, L.A. [Centro Universitario de Volta Redonda, RJ (Brazil); Machado, J.P.B. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Santos, C. [ProtMat Materiais Avancados, Guaratingueta, SP (Brazil)

2009-07-01

Alumina ceramics have been used in dental prosthesis because it is inert, presents higher corrosion and shear resistance when compared to metals, excellent aesthetic, and mechanical resistance. In this work it was produced an infrastructure material for applications in dental crowns, obtained by glass infiltration in alumina preform. Various oxides, among that, rare-earth oxide produced by Xenotime, were melted at 1450 deg C and heat treatment at 700 deg C to obtain the glass (REglass). The alumina was pre-sintered at 1100 deg C cut and machined to predetermine format (unidirectional indirect infiltration) and finally conducted to infiltration test. The alumina was characterized by porosity (Hg-porosity and density) and microstructure (SEM). The glass wettability in alumina was determined as function of temperature, and the contact angle presented a low value (θ<90 deg), showing that glass can be infiltrated spontaneously in alumina. The infiltration test was conducted at glass melting temperature, during 30, 60, 180, 360 minutes. After infiltration, the samples were cut in longitudinal section, ground and polished, and analyzed by XRD (crystalline phases), SEM (microstructure) and EDS (composition).The REglass presents higher infiltration height when compared to current processes (direct infiltration), and homogeneous microstructure, showing that it is a promising method used by prosthetics and dentists. (author)

Deformation behavior of sintered nanocrystalline silver layers

International Nuclear Information System (INIS)

Zabihzadeh, S.; Van Petegem, S.; Duarte, L.I.; Mokso, R.; Cervellino, A.; Van Swygenhoven, H.

2015-01-01

The microstructure of porous silver layers produced under different low temperature pressure-assisted sintering conditions is characterized and linked with the mechanical behavior studied in situ during X-ray diffraction. Peak profile analysis reveals important strain recovery and hardening mechanism during cyclic deformation. The competition between both mechanisms is discussed in terms of porosity and grain size

An Investigation of Sintering Parameters on Titanium Powder for Electron Beam Melting Processing Optimization

Directory of Open Access Journals (Sweden)

Philipp Drescher

2016-12-01

Full Text Available Selective electron beam melting (SEBM is a relatively new additive manufacturing technology for metallic materials. Specific to this technology is the sintering of the metal powder prior to the melting process. The sintering process has disadvantages for post-processing. The post-processing of parts produced by SEBM typically involves the removal of semi-sintered powder through the use of a powder blasting system. Furthermore, the sintering of large areas before melting decreases productivity. Current investigations are aimed at improving the sintering process in order to achieve better productivity, geometric accuracy, and resolution. In this study, the focus lies on the modification of the sintering process. In order to investigate and improve the sintering process, highly porous titanium test specimens with various scan speeds were built. The aim of this study was to decrease build time with comparable mechanical properties of the components and to remove the residual powder more easily after a build. By only sintering the area in which the melt pool for the components is created, an average productivity improvement of approx. 20% was achieved. Tensile tests were carried out, and the measured mechanical properties show comparatively or slightly improved values compared with the reference.

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-08-01

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

Spark Plasma Sintering and Densification Mechanisms of Antimony-Doped Tin Oxide Nanoceramics

Directory of Open Access Journals (Sweden)

Junyan Wu

2013-01-01

Full Text Available Densification of antimony-doped tin oxide (ATO ceramics without sintering aids is very difficult, due to the volatilization of SnO2, formation of deleterious phases above 1000°C, and poor sintering ability of ATO particles. In this paper, monodispersed ATO nanoparticles were synthesized via sol-gel method, and then ATO nanoceramics with high density were prepared by spark plasma sintering (SPS technology using the as-synthesized ATO nanoparticles without the addition of sintering aids. The effect of Sb doping content on the densification was investigated, and the densification mechanisms were explored. The results suggest that ATO nanoparticles derived from sol-gel method show good crystallinity with a crystal size of 5–20 nm and Sb is incorporated into the SnO2 crystal structure. When the SPS sintering temperature is 1000°C and the Sb doping content is 5 at.%, the density of ATO nanoceramics reaches a maximum value of 99.2%. Densification mechanisms are explored in detail.

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.

Sintering of cermets on the base of corundum and molybdenum

International Nuclear Information System (INIS)

Fedotov, A.V.

1987-01-01

Liquid-phase sintering of cermets has been studied to develop rational technology allowing to produce a dense material at lower temperatures. Molybdenum of the MPCh mark with the specific surface ranged from 1900 to 4000 cm 2 /g and the corundum powder of the VK-94-1 mark with the specific surface of 6000 cm 2 /g containing upto 10% of the glass-phase have been used as initial materials. It is shown that application of the VK-94-1 ceramics powder for molybdenum content cermets allows to decrease the temperature of dense material production (∼ upto 100 deg C). To produce dense materials, it is necessary to restrict the initial porosity of compaction and to correspond it to the sintering conditions. The increase of molybdenum dispersion allows to produce material with the more homogeneous structure, higher density and strength. Molybdenum presence decreases recrystallization of corundum crystals and causes structure production resistant to high-temperature heating

EFFECT OF DIFFERENT COMPACTION PRESSURE AND DIFFERENT SINTERING ROUTE ON K0.5NA0.5NBO₃ PHYSICAL AND DIELECTRIC PROPERTIES

Directory of Open Access Journals (Sweden)

Nor Fatin Khairah Bahanurddin

2016-07-01

Full Text Available Alkaline niobate known as K0.5Na0.5NbO3 (KNN, a lead-free piezoelectric ceramic was synthesized via a solid state reaction method. The samples were compacted at different pressures (100, 200, 300 and 400 MPa and sintered using two different techniques (conventional furnace and hot isostatic pressing (HIP. The effect of compaction pressure and sintering technique on physical and dielectric properties was studied. The optimum compaction pressure (300 MPa and sintering via HIP (at 1080 °C for 30 min increased the density and grain size ( range 30 - 300 nm and improved its dielectric properties. Therefore, the combination of suitable compaction pressure and sintering technique has produced larger grain size and higher density of KNN which resulted in outstanding dielectric properties. At room temperature, excellent values of ε r (5517.35 and tan δ (0.954, recorded at 1 MHz were measured for the KNN300HIP sample with highest density (4.4885 g/cm³.

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

Structural and dielectric properties of barium strontium titanate produced by high temperature hydrothermal method

International Nuclear Information System (INIS)

Razak, K.A.; Asadov, A.; Yoo, J.; Haemmerle, E.; Gao, W.

2008-01-01

The preparation procedure, structural and dielectric properties of hydrothermally derived Ba x Sr 1-x TiO 3 (BST) were studied. BST with initial Ba compositions of 75, 80, 85 and 90 mol.% were prepared by a high temperature hydrothermal synthesis. The obtained powders were pressed into pellet, cold isostatically pressed and sintered at 1200 deg. C for 3 hours. The phase compositions and lattice parameters of the as prepared powders and sintered samples were analysed using X-ray diffractometry. A fitting software was used to analyse the XRD spectra to separate different phases. It was found that BST powder produced by the high temperature hydrothermal possessed a two-phase structure. This structure became more homogeneous during sintering due to interdiffusion but a small amount of minor phase can still be traced. Samples underwent an abnormal grain growth, whereby some grains grow faster than the other due to the presence of two-phase structure. The grain size increased with increasing Ba amount. Dielectric constant and polarisation increased with increasing Ba content but it was also affected by the electronic state and grain size of the compositions

Identification of Material Parameters for the Simulation of Acoustic Absorption of Fouled Sintered Fiber Felts

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Nicolas Lippitz

2016-08-01

Full Text Available As a reaction to the increasing noise pollution, caused by the expansion of airports close to residential areas, porous trailing edges are investigated to reduce the aeroacoustic noise produced by flow around the airframe. Besides mechanical and acoustical investigations of porous materials, the fouling behavior of promising materials is an important aspect to estimate the performance in long-term use. For this study, two sintered fiber felts were selected for a long-term fouling experiment where the development of the flow resistivity and accumulation of dirt was observed. Based on 3D structural characterizations obtained from X-ray tomography of the initial materials, acoustic models (Biot and Johnson–Champoux–Allard in the frame of the transfer matrix method were applied to the sintered fiber felts. Flow resistivity measurements and the measurements of the absorption coefficient in an impedance tube are the basis for a fouling model for sintered fiber felts. The contribution will conclude with recommendations concerning the modeling of pollution processes of porous materials.

Production and corrosion resistance of NdFeBZr magnets with an improved response to thermal variations during sintering

International Nuclear Information System (INIS)

Yu, L.Q.; Zhong, X.L.; Zhang, Y.P.; Yan, Y.G.; Zhen, Y.H.; Zakotnik, M.

2011-01-01

This study describes an attempt to produce NdFeB magnets that are insensitive to the sintering temperature. It was found that addition of Zr to NdFeB magnets significantly augmented the thermal stability of this magnetic material during sintering at high temperature even at industrial scale. The best sintered magnets were produced by jet-milling the powder (to achieve an average 3.4 μm particle size), and then aligned, pressed and sintered under argon at 1100 o C for 3 h followed by appropriate heat treatment. The magnetic properties of the resulting magnets were: (BH) m =403.8 kJ m -3 (±4.7 kJ m -3 ), B r =1430 mT (±9 mT) and i H c =907 kA m -1 (±12 kA m -1 ). Large grain growth, in excess of 100 μm in the Zr-free magnets, was observed during sintering at 1100 o C. This did not occur in the presence of Zr. These observations imply that the sensitivity of this class of magnets to high sintering temperatures is greatly reduced by Zr addition. Corrosion resistance of NdFeB was therefore significantly improved by the addition of small amounts of Zr. - Research highlights: →This study describes an attempt to produce NdFeB magnets that are insensitive to the sintering temperature. → It was found that addition of Zr to NdFeB magnets significantly augmented the thermal stability of this magnetic material during sintering at high temperature; even at industrial scale. → The magnetic properties of the resulting magnets were: (BH) m =403.8 kJ m -3 (±4.7 kJ m -3 ), B r =1430 mT (±9 mT) and i H c =907 kA m -1 (±12 kA m -1 ).

An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

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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.

Microwave sintering of hydroxyapatite-based composites

International Nuclear Information System (INIS)

Fang, Y.; Roy, D.M.; Cheng, J.; Roy, R.; Agrawal, D.K.

1993-01-01

Composites of hydroxyapatite/partially stabilized zirconia (HAp/PSZ) and hydroxyapatite/silicon carbide whiskers (HAp/SiC) were sintered at 1100-1200 degrees C by microwave at 2.45 GHz. Characterization of the sintered composites was carried out by density, microstructure, phase composition, and fracture toughness measurements. The results show that although not yet fully densified, a much higher sintered density in the HAp/PSZ composite was achieved by microwave sintering than by conventional sintering at the same temperature. A relative density of 93% was achieved by 20 min. microwave processing at 1200 degrees C. Comparatively, 2 h conventional sintering of the same material at 1200 degrees C led to only 75.5% relative density. K IC of this microwave sintered HAp/PSZ of 93% density was found to be 3.88 MPa√m, which is 250% of the value for pure HAp of the same density. A further increase in K IC could be expected if full or nearly full densification was achieved. Sintering of PSZ particles in the HAp/PSZ composite was also observed in the microwave processed sample. Microwave sintering of HAp/SiC was not successful in the current study due to the oxidation of SiC in air at high temperature. 8 refs., 4 figs., 1 tab

Tensile Properties Characterization of AlSi10Mg Parts Produced by Direct Metal Laser Sintering via Nested Effects Modeling.

Science.gov (United States)

Palumbo, Biagio; Del Re, Francesco; Martorelli, Massimo; Lanzotti, Antonio; Corrado, Pasquale

2017-02-08

A statistical approach for the characterization of Additive Manufacturing (AM) processes is presented in this paper. Design of Experiments (DOE) and ANalysis of VAriance (ANOVA), both based on Nested Effects Modeling (NEM) technique, are adopted to assess the effect of different laser exposure strategies on physical and mechanical properties of AlSi10Mg parts produced by Direct Metal Laser Sintering (DMLS). Due to the wide industrial interest in AM technologies in many different fields, it is extremely important to ensure high parts performances and productivity. For this aim, the present paper focuses on the evaluation of tensile properties of specimens built with different laser exposure strategies. Two optimal laser parameters settings, in terms of both process quality (part performances) and productivity (part build rate), are identified.

Inversion defects in MgAl2O4 elaborated by pressureless sintering, pressureless sintering plus hot isostatic pressing, and spark plasma sintering

International Nuclear Information System (INIS)

Mussi, A.; Granger, G. Bernard; Addad, A.; Benameur, N.; Beclin, F.; Bataille, A.

2009-01-01

The distribution of inversion defects of Al was investigated in dense magnesium-aluminate spinel elaborated by pressureless sintering, pressureless sintering plus hot isostatic pressing, and spark plasma sintering. This study was conducted by energy electron loss spectroscopy analyses and more particularly by energy loss near edge structure investigations of the Al-L 2,3 edge. Several aspects are discussed with the purpose of understanding why charged defects dispersal reveals a special configuration.

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.

Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

Energy Technology Data Exchange (ETDEWEB)

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

2014-04-01

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

Analysis of the sintering stresses and shape distortion produced in co-firing of CGO-LSM/CGO bi-layer porous structures

DEFF Research Database (Denmark)

Ni, De Wei; Esposito, Vincenzo; Schmidt, Cristine Grings

such as cracks, de-lamination and shape distortion can result as a consequence of sintering mismatch stresses caused by the strain rate difference between layers. This work seeks to understand the underlying mechanisms that occur during the co-firing of porous CGO-LSM/CGO bi-layer laminates, by evaluating...... the sintering mismatch stress and distortion development through modeling and experiments....

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

Sintering with a chemical reaction as applied to uranium monocarbide

International Nuclear Information System (INIS)

Accary, A.; Caillat, R.

1960-01-01

The present paper provides a survey of different investigations whose aim was the preparation and fabrication of uranium monocarbide for nuclear use. If a chemical reaction takes place in the sample during the sintering operation, it may be expected that the atom rearrangements involved in this reaction should favour the sintering process and thereby lower the temperature needed to yield a body of a given density. With this hypothesis in mind, the following methods have been studied: - Sintering of U-C mixtures; - Sintering of UO 2 -C mixtures; - Hot pressing of U-C mixtures; - Extrusion of U-C mixtures. To generalize our result, it could be said that a chemical reaction does not lead to high densification, if one depends on a simple contact between discrete particles. On the contrary, a chemical reaction can help sintering if, as our hot pressing experiments shows, the densification can be achieved prior to the reaction. (author) [fr

LOW TEMPERATURE SINTERING OF ALUMINA BIOCERAMIC UNDER NORMAL PRESSURE

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

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

Strain rate dependency of laser sintered polyamide 12

Directory of Open Access Journals (Sweden)

Cook J.E.T.

2015-01-01

Full Text Available Parts processed by Additive Manufacturing can now be found across a wide range of applications, such as those in the aerospace and automotive industry in which the mechanical response must be optimised. Many of these applications are subjected to high rate or impact loading, yet it is believed that there is no prior research on the strain rate dependence in these materials. This research investigates the effect of strain rate and laser energy density on laser sintered polyamide 12. In the study presented here, parts produced using four different laser sintered energy densities were exposed to uniaxial compression tests at strain rates ranging from 10−3 to 10+3 s−1 at room temperature, and the dependence on these parameters is presented.

Coal fly ash utilization: Low temperature sintering of wall tiles

International Nuclear Information System (INIS)

Chandra, Navin; Sharma, Priya; Pashkov, G.L.; Voskresenskaya, E.N.; Amritphale, S.S.; Baghel, Narendra S.

2008-01-01

We present here a study of the sintering of fly ash and its mixture with low alkali pyrophyllite in the presence of sodium hexa meta phosphate (SHMP), a complex activator of sintering, for the purpose of wall tile manufacturing. The sintering of fly ash with SHMP in the temperature range 925-1050 deg. C produces tiles with low impact strength; however, the incremental addition of low alkali pyrophyllite improves impact strength. The impact strength of composites with ≥40% (w/w) pyrophyllite in the fly ash-pyrophyllite mix satisfies the acceptable limit (19.6 J/m) set by the Indian Standards Institute for wall tiles. Increasing the pyrophyllite content results in an increase in the apparent density of tiles, while shrinkage and water absorption decrease. The strength of fly ash tiles is attributed to the formation of a silicophosphate phase; in pyrophyllite rich tiles, it is attributed to the formation of a tridymite-structured T-AlPO 4 phase. Scanning electron micrographs show that the reinforcing rod shaped T-AlPO 4 crystals become more prominent as the pyrophyllite content increases in the sintered tiles

A novel method for producing magnesium based hydrogen storage alloys

International Nuclear Information System (INIS)

Walton, A.; Matthews, J.; Barlow, R.; Almamouri, M.M.; Speight, J.D.; Harris, I.R.

2003-01-01

Conventional melt casting techniques for producing Mg 2 Ni often result in no stoichiometric compositions due to the excess Mg which is added to the melt in order to counterbalance sublimation during processing. In this work a vapour phase process known as Low Pressure Pack Sublimation (LPPS) has been used to coat Ni substrates with Mg at 460-600 o C producing layers of single phase Mg 2 Ni. Ni substrates coated to date include powder, foils and wire. Using Ni-Fe substrates it has also been demonstrated that Fe can be distributed through the Mg 2 Ni alloy layer which could have a beneficial effect on the hydrogen storage characteristics. The alloy layers formed have been characterised by XRD and SEM equipped with EDX analysis. Hydrogen storage properties have been evaluated using an Intelligent Gravimetric Analyser (IGA). LPPS avoids most of the sintering of powder particles during processing which is observed in other vapour phase techniques while producing a stoichiometric composition of Mg 2 Ni. It is also a simple, low cost technique for producing these alloys. (author)

Recycling of mill scale in sintering process

Directory of Open Access Journals (Sweden)

El-Hussiny N.A.

2011-01-01

Full Text Available This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

Effect of Organic Binders on The Quality of Manganese Ore Sinter Fines Briquettes

International Nuclear Information System (INIS)

Mohamed, F. M.; Ahmed, Y.M.Z.; Shalabi, M. E. H.

2004-01-01

Sinai Manganese Company imports the manganese ore sinter from abroad for ferromanganese alloy production. Large quantities of manganese ore sinter fines are produced in this process. These fines must be agglomerated to a suitable size in order to be reused for charging the electric arc furnace. The aim of this work is studying the briquetting ability of these fines using organic binders such as starch and bitumen. The results showed that, the suitable briquettes were produced with the addition of 5 % of starch and 20% H 2 O under pressure 3 ton/cm 2 or 8 % bitumen under pressure 4 ton/cm 2 and 3 days curing time

Plasma sintering of ferritic steel reinforced with niobium carbide prepared by high energy milling

International Nuclear Information System (INIS)

Silva Junior, J.F. da; Almeida, E.O.; Gomes, U.U.; Alves Junior, C.; Messias, A.P.; Universidade Federal do Rio Grande do Norte

2010-01-01

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)

Effect of cryogenic milling on Al7075 prepared by spark plasma sintering method.

Czech Academy of Sciences Publication Activity Database

Lukáč, František; Chráska, Tomáš; Molnárová, O.; Málek, P.; Cinert, Jakub

2017-01-01

Roč. 32, S1 (2017), S221-S224 ISSN 0885-7156. [European Powder Diffraction Conference (EPDIC) /15./. Bari, 12.06.2016-15.06.2016] R&D Projects: GA ČR(CZ) GA15-15609S Institutional support: RVO:61389021 Keywords : Intermetallic precipitates * cryogenic milling * powder metallurgy * ultrafine-grained materials * Al7075 alloy Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 0.674, year: 2016 https://www.cambridge.org/core/journals/powder-diffraction/ article /effect-of-cryogenic-milling-on-al7075-prepared-by-spark-plasma-sintering-method/17E9F722BAFD428BA7310194FEE551C6

Improvement of mechanical properties of zirconia-toughened alumina by sinter forging

NARCIS (Netherlands)

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

1994-01-01

ZTA powder with a composition of 85 wt% alumina/15 wt% zirconia was prepared by a gel precipitation method. Sinter forging was performed with this powder to enhance the mechanical properties of ZTA materials. The influence of processing flaws on mechanical properties of sinter forged materials and

Phase identification and morphology study of hematite (Fe2O3) with sintering time varitions

Science.gov (United States)

Yazirin, Cepi; Puspitasari, Poppy; Sasongko, Muhammad Ilman Nur; Tsamroh, Dewi Izzatus; Risdanareni, Puput

2017-09-01

Iron oxide has been the interest of many studies due to its applications in various scientific and industrial fields including in environment, corrosion, soil science, and exhaust emissions. Iron oxide (Fe2O3) has potential applications in catalytic reactions in electronic devices such as semiconductors, paint formulations, and lithium rechargeable batteries. Fe2O3 can be synthesized through the process of stirring, decomposition of organic iron, sol-gel, combustion, and evaporating solvents. Most of the methods used involve several steps and take a long time. The aim of this research was to investigate the phase and morphology characterization of iron oxide (Fe2O3) powder with solvent ethylene glycol after being sintered for 1 hour, 2 hours and 3 hours. The characterization tools utilized were XRD, SEM-EDX, and FTIR. The results of XRD analysis showed that the Fe2O3 sintered for 1 hour had the smallest crystallite size with a diameter of 21.05 nm. In the XRD test, the beam of X-ray was shot directly at the grain being tested. The results of SEM analysis showed thatthe Fe2O3 sintered for 1 hour produced the best result due to its crystallite size of 12.36 nm and hada shape of homogeneous nanosphere; the duration of sintering indeed had a great influence on the grain size of iron oxide (Fe2O3). In addition, the results of the elemental composition analysis indicate that the longer the sintering process, the higher the concentration of O but the lower the Fe.

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

Sinterability of mixtures of UO2 of different morphological features

International Nuclear Information System (INIS)

Villegas de Maroto, Marina; Celora de Lavagnino, Julia; Marajofsky, Adolfo; Leyva, A.G.

1981-01-01

The reprocessing of scrap in the production of UO2 pellets, is important from an economical view-point of the fuel cycle. The recovery method by means of a humid process, tested for UO2 scrap, includes the dissolution of the pellets in a nitric media at boiling point, the precipitation of ammonium diuranates (ADU) and its conversion into UO2 at 600 deg C. The microestructural results and the sintering density of the pellets produced in these tests are compared. It is shown that, although the addition of said UO2 powders impaires the performance of the original mixture produced by the factory, the results thus obtained are, nevertheless, within specifications. This facts show that the mixture would then be able for production. (M.E.L.) [es

Effects of Sintering and Extrusion on the Microstructures and Mechanical Properties of a SiC/Al-Cu Composite

Science.gov (United States)

Sun, Chao; Shen, Rujuan; Song, Min

2012-03-01

This article studied the effects of sintering and extrusion on the microstructures and mechanical properties of SiC particle reinforced Al-Cu alloy composite produced by powder metallurgy method. It has been shown that both extrusion and increasing sintering temperature can significantly improve the strength and plasticity of the composite. The extrusion and increase of the sintering temperature can break up the oxide coating on the matrix powder surfaces, decrease the number of pores, accelerate the elements' diffusion and increase the density and particle interfacial bonding strength, thus significantly improve the mechanical properties of the composite. The strength and hardness of the composite increase and the elongation decreases with increasing the aging time at under-aged stage, while the strength and hardness start to decrease and the elongation starts to increase with increasing the aging time at over-aged stage due to the formation and growth of the secondary strengthening precipitates in the Al-Cu matrix.

Sintering studies on iron-carbon-copper compacts

Directory of Open Access Journals (Sweden)

Perianayagam Philomen-D-Anand Raj

2016-01-01

Full Text Available Sintered Iron-Carbon-Copper parts are among the most widely used powder metallurgy product in automobile. In this paper, studies have been carried out to find out the sintering characteristics of iron-carbon-copper compacts when sintered in nitrogen atmosphere. The effects of various processing parameters on the sintering characteristics were studied. The various processing parameters considered were compaction pressure, green density and sintering temperature. The sintering characteristics determined were sintered density, porosity, dimensional change, micro hardness and radial crush strength. The results obtained have been discussed on the basis of micro structural observations. The characteristics of SEM fractography were also used to determine the mechanism of fracture. The fracture energy is strongly dependent on density of the compact.

Changes of Fe matrix lattice constant during liquid phase sintering of Fe-Cu-C compacts by x-ray diffraction techniques

International Nuclear Information System (INIS)

Mazli Mustapha; Abdul Kadir Masrom; Mohammad, M.; Meh, B.; Zawati Harun

2002-01-01

The dissolution of graphite and copper during sintering of PM steels prepared from iron, copper and graphite powder mixes were studied using X-Ray Diffraction method. This paper present the investigation carried out to study the changes of iron's lattice constant during liquid phase sintering of the compacts. The electrical conductivity measurement method was also used for determining the extent of carbon and copper dissolution and its influence on the formation of sintered compacts. In the experiment, the Fe-Cu-C powders were compacted into a pellets using hand press machine and were then sintered in a 5% H 2 + 95% N 2 gas atmosphere at different sintering temperature in the range of 400 degree C and 1200 degree C. The effect of sintering parameters on the mechanical properties of the sintered compacts was studied to find a correlation between mechanical behaviour, microstructure, and the resistivity in order to develop nondestructive testing method. It was observed that measurement of Fe matrix lattice constant and electrical conductivity of sintered compacts could be a viable method in studying all stages of sintering process. (Author)

Production of three-dimensional structures of PHB using selective laser sintering

International Nuclear Information System (INIS)

Pereira, Tatiana F.; Costa, Marysilvia F.; Thire, Rossana M.S.M.; Oliveira, Marcelo F.; Maia, Izaque A.; Silva, Jorge V.L.

2011-01-01

Selective Laser Sintering (SLS) is a technology of layer-by-layer fabrication of three-dimensional physical models directly from their computational design. The poly(3-hydroxybutyrate) (PHB) is a microbial, biodegradable and semicrystalline polyester. The objective of this work was to produce PHB parts, evaluating the reuse of material in the production of the new parts. Images of SEM of part surface showed the formation of neck that indicates sintering between PHB particles during processing. Analysis of NMR and DSC of the reused polymer showed no changes in the chemical structure and thermal properties of PHB. The parts produced from virgin and reused PHB showed no significant difference in their thermal properties. This could suggest that the reuse of raw material did not influence the process reproducibility. (author)

Nuclear fuel pellet sintering boat unloading apparatus and method

International Nuclear Information System (INIS)

Huggins, T.B.; Widener, W.H.; Klapper, K.K.

1990-01-01

This patent describes a method for unloading nuclear fuel pellets from a sintering boat having an open top. It comprises: pivoting a transfer housing loaded with the boat filled with nuclear fuel pellets about a generally horizontal axis from an upright position remote from a pellet deposit surface to an inverted position adjacent to the deposit surface to move the boat from an upright to inverted orientation with the pellets retained within the boat by a latched lid in a closed condition on the housing; unlatching the lid of the housing as the housing reaches its inverted position but engaging the unlatched lid with the deposit surface to retain it in its closed condition; and reverse pivoting the housing from its inverted position back toward its upright position to permit the unlatched lid to pivot from the closed condition to an opened condition thereby allowing pellets to slide out of the open top of the inverted boat and down the opened lid of the housing to the deposit site

Tensile Properties Characterization of AlSi10Mg Parts Produced by Direct Metal Laser Sintering via Nested Effects Modeling

Directory of Open Access Journals (Sweden)

Biagio Palumbo

2017-02-01

Full Text Available A statistical approach for the characterization of Additive Manufacturing (AM processes is presented in this paper. Design of Experiments (DOE and ANalysis of VAriance (ANOVA, both based on Nested Effects Modeling (NEM technique, are adopted to assess the effect of different laser exposure strategies on physical and mechanical properties of AlSi10Mg parts produced by Direct Metal Laser Sintering (DMLS. Due to the wide industrial interest in AM technologies in many different fields, it is extremely important to ensure high parts performances and productivity. For this aim, the present paper focuses on the evaluation of tensile properties of specimens built with different laser exposure strategies. Two optimal laser parameters settings, in terms of both process quality (part performances and productivity (part build rate, are identified.

Immobilization of high level nuclear wastes in sintered glasses. Devitrification evaluation produced with different thermal treatments

International Nuclear Information System (INIS)

Messi de Bernasconi, N.B.; Russo, D.O.; Bevilacqua, M.E.; Sterba, M.E.; Heredia, A.D.; Audero, M.A.

1990-01-01

This work describes immobilization of high level nuclear wastes in sintered glass, as alternative way to melting glass. Different chemical compositions of borosilicate glass with simulate waste were utilized and satisfactory results were obtained at laboratory scale. As another contribution to the materials studies by X ray powder diffraction analysis, the devitrification produced with different thermal treatments, was evaluated. The effect of the thermal history on the behaviour of fission products containing glasses has been studied by several working groups in the field of high level waste fixation. When the glass is cooled through the temperature range from 800 deg C down to less than 400 deg C (these temperatures are approximates) nucleation and crystal growth can take place. The rate of crystallization will be maximum near the transformation point but through this rate may be low at lower temperatures, devitrification can still occur over long periods of time, depending on the glass composition. It was verified that there can be an appreciable increase in leaching in some waste glass compositions owing to the presence of crystalline phases. On the other hand, other compositions show very little change in leachability and the devitrified product is often preferable as there is less tendency to cracking, particularly in massive blocks of glass. A borosilicate glass, named SG7, which was developed specially in the KfK for the hot pressing of HLW with glass frit was studied. It presents a much enhanced chemical durability than borosolicate glass developed for the melting process. The crystallization behaviour of SG7 glass products was investigated in our own experiments by annealing sintered samples up to 3000 h at temperatures between 675 and 825 deg C. The samples had contained simulated waste with noble metals, since these might act as foreign nuclei for crystallization. Results on the extent of devitrification and time- temperature- transformation curves are

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)

Al2O3-TiC Composite Prepared by Spark Plasma Sintering Process: Evaluation of Mechanical and Tribological Properties

Science.gov (United States)

Kumar, Rohit; Chaubey, A. K.; Bathula, Sivaiah; Prashanth, K. G.; Dhar, Ajay

2018-03-01

Al2O3-10TiC composites were synthesized by spark plasma sintering (SPS) process. Microstructural and mechanical properties of the composite reveal homogeneous distribution of the fine TiC particles in the matrix. The samples were produced with different sintering temperature, and it shows that the hardness and density gradually increases with increasing sintering temperature. Abrasion wear test result reveals that the composite sintered at 1500 °C shows high abrasion resistance (wt. loss 0.016 g) and the lowest abrasion resistance was observed for the composite sample sintered at 1100 °C (wt. loss 1.459 g). The profilometry surface roughness study shows that sample sintered at 1100 °C shows maximum roughness ( R a = 6.53 µm) compared to the sample sintered at 1500 °C ( R a = 0.66 µm) corroborating the abrasion wear test results.

Effect of the sintering temperature and time on phase assemblage and electrical conductivity of zirconia-scandia-ceria

International Nuclear Information System (INIS)

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

2012-01-01

ZrO 2 -based solid electrolytes have been extensively studied over the last decades for application in solid oxide fuel cells (SOFCs). Zirconia containing scandia and ceria solid electrolyte is a potential candidate in SOFCs operating at intermediate temperatures (600 - 800 deg C). In this work, commercial ZrO 2 containing 10 mol% Sc 2 O 3 and 1 mol% CeO 2 was sintered by the conventional and two-step methods. Several sintering conditions were evaluated by varying the temperature as well as the residence time. High values of sintered density (> 98%) were obtained. A careful selection of the sintering conditions is necessary in order to obtain a single cubic phase, as revealed by X-ray diffraction results. The grain growth can be controlled in specimens sintered by the two-step method. The electrical conductivity show similar behavior for the grain component independent on the sintering method. (author)

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.

Adjustment of Part Properties for an Elastomeric Laser Sintering Material

Science.gov (United States)

Wegner, A.; Ünlü, T.

2018-03-01

Laser sintering of polymers is gaining more and more importance within the field of small series productions. Polyamide 12 is predominantly used, although a variety of other materials are also available for the laser sintering process. For example, elastomeric, rubberlike materials offer very different part property profiles. Those make the production of flexible parts like, e.g., sealings, flexible tubes or shoe soles possible because they offer high part ductility and low hardness. At the chair for manufacturing technology, a new elastomeric laser sintering material has been developed and then commercialized by a spin-off from university. The aim of the presented study was the analysis of the new material's properties. Proof was found that Shore hardness can be modified by varying the parameter settings. Therefore, the correlation between process parameters, energy input, Shore hardness and other part properties like mechanical properties were analyzed. Based on these results, suitable parameter settings were established which lead to the possibility of producing parts with different Shore hardnesses.

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.

Mineralogy and microstructure of sintered lignite coal fly ash

Energy Technology Data Exchange (ETDEWEB)

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

2003-02-01

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

The influence of sintering temperature on microstructure and mechanical properties of Ni-Al intermetallics fabricated by SPS

Energy Technology Data Exchange (ETDEWEB)

Thömmes, A., E-mail: thoemmes.alexander@gmail.com; Shevtsova, L. I., E-mail: edeliya2010@mail.ru; Laptev, I. S., E-mail: ilya-laptev-nstu@mail.ru; Mul, D. O., E-mail: ddariol@yandex.ru [Novosibirsk State Technical University, Novosibirsk, 630073 (Russian Federation); Mali, V. I., E-mail: vmali@mail.ru; Anisimov, A. G., E-mail: anis@hydro.nsc.ru [Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, 630090 (Russian Federation)

2015-10-27

In the present study PN85Yu15 was used as elemental powder to produce a sintered compound with Ni3Al as main phase. The Spark Plasma Sintering (SPS) technique is used to compact the powders. The powder was sintered in a temperature range between 1000°C and 1150°C to observe the influence of the sintering temperature on the microstructure and the mechanical properties. The microstructure was observed with optical microscope (OM), the phase composition was characterized by X-ray diffraction (XRD) technique. Density and microhardness were observed and compared the values with the results of other researchers. The compressive-, density- and microhardness tests show as clear result that with increasing the sintering temperature nearly all properties become better and also the microstructure studies show that porous places become less.

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

Science.gov (United States)

Gephart, Sean

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

Grain growth in uranium nitride prepared by spark plasma sintering

Science.gov (United States)

Johnson, Kyle D.; Lopes, Denise Adorno

2018-05-01

Uranium mononitride (UN) has long been considered a potential high density, high performance fuel candidate for light water reactor (LWR) and fast reactor (FR) applications. However, deployability of this fuel has been limited by the notable resistance to sintering and subsequent difficulty in producing a desirable microstructure, the high costs associated with 15N enrichment, as well as the known proclivity to oxidation and interaction with steam. In this study, the stimulation of grain growth in UN pellets sintered using SPS has been investigated. The results reveal that by using SPS and controlling temperature, time, and holding pressure, grain growth can be stimulated and controlled to produce a material featuring both a desired porosity and grain size, at least within the range of interest for nuclear fuel candidates. Grain sizes up to 31 μm were obtained using temperatures of 1650 °C and hold times of 15 min. Evaluation by EBSD reveal grain rotation and coalescence as the dominant mechanism in grain growth, which is suppressed by the application of higher external pressure. Moreover, complete closure of the porosity of the material was observed at relative densities of 96% TD, resulting in a material with sufficient porosity to accommodate LWR burnup. These results indicate that a method exists for the economic fabrication of an 15N-bearing uranium mononitride fuel with favorable microstructural characteristics compatible with use in a light water-cooled nuclear reactor.

Fracture Toughness and Micro-Strain of Y-TZP Nanoceramics at Different Sintering Temperature

Directory of Open Access Journals (Sweden)

Rabiha S. Yaseen

2017-11-01

Full Text Available The objective of this research is to study the effect of sintering temperature on the mechanical properties and micro-strain of yttria tetragonal zirconia polycrystalls (Y-TZP nanostructure.   Where green disk formed by uniaxially press, sintered at (1500 – 1550 – 1600⁰C in air for 2hr then polished to mirror shape for fracture toughness and micro-hardness measurement by Vickers indenter at (60 kg to 100gm loads. Atomic force microscopy (AFM technique was use to measure the change in grain size and shape of the samples, X-ray diffraction (XRD evaluated to identify the phases and to measure the micro-strain of the samples.          The Results show that increasing sintering temperature will increase the grain size with increasing the average of micro-strain. Tetragonal  phase is the prevailing phase with small amount of cubic phase and the amount of monoclinic phase was under detection limite after sintering but there is increas in lattice dimension according to micro-strain calculation and grinding process produce micro-strain. With increasing the sintering temperature micro-hardness and fracture toughness will increas.

Study on the characteristics and sinterability of DUPIC powder by using simulated fuel

International Nuclear Information System (INIS)

Lee, Jae-Won; Lee, Jung-Won; Kim, Jong-Ho; Yim, Sung-Paal; Lee, Young-Woo; Yang, Myung-Seung

2002-01-01

The sinterability of the OREOX (oxidation and reduction of oxide fuels) powder was investigated in terms of the number of the OREOX cycles and milling time using simulated spent fuel of an equivalent burnup of 35,000 MWD/MTU. Wet milled powder was prepared and sintered to compare the morphology and sinterability with the dry milled powder. Powders having a medium particle size of less than 1μm were obtained by dry milling of OREOX powders regardless of the number of cycles. The specific surface area of the simulated DUPIC powder was governed by the number of OREOX cycles rather than by milling time. The sound pellets with a sintered density of higher than 95% TD and average grain size of larger than 8μm were obtained with the dry milled powder after 1 cycle of OREOX treatment. The powders prepared by dry milling for a short time and wet milling for a long time after 3 cycles of OREOX treatment also produced pellets with a sintered density of higher than 95% TD and average grain size of larger than 8μm. (author)

Study of high-coercivity sintered NdFeB magnets

International Nuclear Information System (INIS)

Bai, G.; Gao, R.W.; Sun, Y.; Han, G.B.; Wang, B.

2007-01-01

Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of j H c =25.6 kOe, B r =13.2 kG and (BH) max =39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 deg. C) is -0.53% deg. C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors

Producing transparent PLZT ceramics using different synthesis method

International Nuclear Information System (INIS)

Dambekalne, M.; Antonova, M.; Livinsh, M.; Kalvane, A.; Plonska, M.; Garbarz-Glos, B.

2004-01-01

Full text: Ceramic samples of Pb 1-x La x (Zr 0.65 Ti 0.35 )O 3 (x 8, 9, 10) were prepared from powders being sintered by two methods: 1) peroxohydroxopolimer (PHP), where as precursors were used solutions of inorganic salts TiCl 4 , ZrOCl 4 ·8H 2 O, Pb(NO 3 ) 2 , La(NO 3 ) 3 ·6H 2 O); 2) sol-gel, using as precursors solutions of metal organic salts Pb(COOCH 3 ) 2 ·3H 2 O, La(COOCH 3 ) 3 ·1.5H 2 O, Zr(OCH 2 CH 2 CH 3 ) 4 , Ti(OCH 2 CH 2 CH 3 ) 4 . The thermal regimes for both powders were similar: synthesis at 600 0 C for 2 - 4h, obtaining amorphous nanopowder. Ceramic samples were produced by hot pressing at 1100 - 1200 0 C for 2 - 6h and pressure of 20Mpa.Optical transmittance of ceramic samples from PHP derived powders was higher than that from sol- gel derived. The transparency of poled plates with thickness of 0.3mm (wavelength λ = 630nm) was 67 - 69% and 56 - 59%, respectively. It can be explained by lack of technical support for sol-gel processing in atmosphere of neutral gas, as metal organic precursors are extremely sensitive to moisture of air. X-ray and DTA studies were used for powders. Dielectrics, ferroelectric and optical properties as well as studies of icrostructure were carried out for ceramic samples. The grain size of ceramics produced from PHP powders is 3- 4μ, for sol-gel ceramics less than 1μ

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

Characterization of novel W alloys produced by HIP

Energy Technology Data Exchange (ETDEWEB)

Monge, M.A.; Auger, M.A.; Leguey, T.; Pareja, R. [Universidad Carlos 3, Dept. de Fisica, Madrid (Spain); Bolzoni, L.; Gordo, E. [Universidad Carlos 3, Dept. de Ciencias de Materiales, Madrid (Spain)

2007-07-01

Full text of publication follows: Tungsten is considered as a candidate material for plasma-facing components (PFCs) in a future fusion power reactor because of its refractory characteristics, low tritium retention and low sputtering yielding. However, its use in PFCs requires the development of a tungsten material that, in addition to these properties, maintains good mechanical properties after a prolonged exposure at high temperatures. Sintering would be the most suitable method to produce tungsten materials for these applications if their recrystallization temperature is high enough and the grain growth is restrained. Usual sintering conditions for tungsten requires very high temperatures that induces a coarse grained structure in the sintered material, and a low recrystallization temperature in the hot worked material. This causes the failure of its mechanical properties. The combined addition of a sintering activator, which lowers the sintering temperature and favors the densification, and an insoluble oxide that produces a dispersion strengthening and grain growth inhibition, may result in a tungsten material with improved mechanical characteristics. Cu, Ni and Fe are the most used activators to produce tungsten heavy alloys but they may be no recommendable for PFCs. The present work assesses the possibility of using jointly Ti as sintering activator and Y{sub 2}O{sub 3} particles as strengthening dispersoids in tungsten. Pure tungsten and tungsten alloys having 0.5 wt % Y{sub 2}O{sub 3}, x wt % Ti and 0.5 wt % Y{sub 2}O{sub 3}+ x wt % Ti have been prepared by powder metallurgy; 0{<=}x{<=}4%. Elemental powders were blended or ball milled, canned, out-gassed and finally consolidated by a two-stage HIP process under a pressure of 200 MPa. The first stage was performed at 1523 K for 2 h, and after un-canning, the second HIP at 1973 K for 30 min. It is found that Ti addition favors the densification attaining a fully dense material, while pure W and W-0.5Y{sub 2

Studies on the sintering of copper powder compacts

International Nuclear Information System (INIS)

Elmasry, M.A.A.; Abadir, M.F.; Mahdy, A.N.; Elkinawy, W.S.

1995-01-01

Solid state sintering behavior of cylindrical compacts, (1 cm diameter and 1 cm height), made of copper powder was studied within a range of compacting pressure of 75 up to 300 MPa, sintering temperature of 600 up to to 900 degree C, and sintering time of 5 up to 60 min in a reducing atmosphere composed of H2 and N 2 gases with a volumetric ratio 3:1. The green and the sintered densities were found to to increase with the compacting pressure. Higher sintering temperature, and time favour increased sintered density. probable mechanisms during the initial stage of sintering were disclosed. It was found that low pressures cause dilation of closed pores, and vice versa. At low pressures and temperatures the surface diffusion mechanism is favoured, While high temperatures favour lattice diffusion mechanism. at high pressures, the lattice diffusion mechanism is suppressed while surface diffusion predominates. Density and hence shrinkage were also found to increase with the increase of sintering time, While its rate increases with the increase of sintering temperature. the influence of sintering conditions on the hardness of the compacts was studied. An increase in hardness, When higher compacting pressures and higher sintering temperatures were adopted, has bee obtained. 11 figs

Large-scale roll-to-roll photonic sintering of flexo printed silver nanoparticle electrodes

DEFF Research Database (Denmark)

Hösel, Markus; Krebs, Frederik C

2012-01-01

In this report we employ static and roll-to-roll (R2R) photonic sintering processes on flexo printed silver nanoparticle-based electrode structures with a heat-sensitive 60 mm thin barrier foil as a substrate. We use large area electrode structures to visualize the increased optical footprint...... as the nanoparticles are already sintered. The advantage of single exposure is the ability to produce higher R2R processing speeds without overlapping, which is shown in the form of theoretical calculations....

Interpretation of Frenkel’s theory of sintering considering evolution of activated pores: III. Determination of equilibrium sintering time

Directory of Open Access Journals (Sweden)

Yu C.L.

2015-01-01

Full Text Available In this article, the Frenkel’s theory of liquid-phase sintering was interpreted regarding pores as the activated volume. The mathematical model established by Nikolić et al. was used to infer the equilibrium sintering time at varied sintering temperatures during the isothermal sintering of codierite glass by Giess et al. Through the calculation, the equilibrium time at 800ºC, 820ºC, 840ºC and 860ºC is inferred to be 7014.42mins, 1569.65mins, 368.92mins and 114.61mins, respectively. The equilibrium time decreases as the temperature increases. And the theoretical value is in good accordance with the experimental results. Thus, the model established by Nikolić et al. can be applied successfully to predict the equilibrium sintering time of the cordierite glass at varied temperatures during isothermal sintering.

Electrical sintering of silver nanoparticle ink studied by in-situ TEM probing.

Directory of Open Access Journals (Sweden)

Magnus Hummelgård

Full Text Available Metallic nanoparticle inks are used for printed electronics, but to reach acceptable conductivity the structures need to be sintered, usually using a furnace. Recently, sintering by direct resistive heating has been demonstrated. For a microscopic understanding of this Joule heating sintering method, we studied the entire process in real time inside a transmission electron microscope equipped with a movable electrical probe. We found an onset of Joule heating induced sintering and coalescence of nanoparticles at power levels of 0.1-10 mW/μm³. In addition, a carbonization of the organic shells that stabilize the nanoparticles were found, with a conductivity of 4 10⁵ Sm⁻¹.

Investigation of rye straw ash sintering characteristics and the effect of additives

International Nuclear Information System (INIS)

Wang, Liang; Skreiberg, Øyvind; Becidan, Michael; Li, Hailong

2016-01-01

Highlights: • Rye straw ash has a high sintering tendency at elevated temperatures. • Addition of additive increases melting temperature of the rye straw ash. • Kaolin addition leads to formation of silicates binding K in the ash. • Calcite and Ca-sludge promotes formation of silicates and phosphates in the ash. • Calcite addition restrains attaching and accumulation of rye straw ash melts. - Abstract: The understanding of ash sintering during combustion of agricultural residues is far from complete, because of the high heterogeneity of the content and composition of ash forming matters and the complex transformation of them. In order to make agricultural residues competitive fuels on the energy market, further research efforts are needed to investigate agricultural residues’ ash sintering behavior and propose relevant anti-sintering measures. The aim of this work was to investigate the ash characteristics of rye straw and effects of additives. Three additives were studied regarding their abilities to prevent and abate rye straw ash sintering. Standard ash fusion characterization and laboratory-scale sintering tests were performed on ashes from mixtures of rye straw and additives produced at 550 °C. Ash residues from sintering tests at higher temperatures were analyzed using a combination of X-ray diffraction (XRD) and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM–EDX). High sintering and melting tendency of the rye straw ash at elevated temperatures was observed. Severe sintering of the rye straw ash was attributed to the formation and fusion of low temperature K–silicates and K–phosphates with high K/Ca ratios. Among the three additives, calcite served the best one to mitigate sintering of the rye straw ash. Ca from the calcite promoted formation of high temperature silicates and calcium rich K–phosphates. In addition, calcite may hinder aggregating of ash melts and further formation of large ash slag. Therefore

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

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.

Determination of Sintered (Th,U)O2 Pellet at the Grain Growth Step

International Nuclear Information System (INIS)

Indrati-Y, Tundjung; Pristi-Hartati, Murdani; Ari-Handayani; Ginting, Aslina Br

2000-01-01

The determination of sintered (Th,U)O 2 pellet at the grain growth stephave been done by dilatometer and Scanning Electron Microscope (SEM). Thecalculation method based on the densification curve and quantitativemetallurgy. The green pellet be produced by single action compaction. Itspellet was heated on the dilatometer with heating rate 11 o C/minute and inthe argon atmosphere, 2 liters/hour. The activation energy at thedensification step can be calculated by densification curve only, but theactivation energy at the grain growth step can be calculated by densificationcurve or quantitative metallurgy. The capability of the dilatometer can beoperated until 1200 o C, so the densification curve based on the experiencecan be used to calculate activation energy at the densification step, 4.492kcal/mole. The activation energy at the grain growth step, which is 25.277kcal/mole, can be predicted by trial and error on n value. That activationenergy is almost the same with activation energy that based on thequantitative metallurgy method 25.042 kcal/mole. All of the activation energyfor the (Th,U)O 2 pellet sintering process is 29.769 kcal/mole. (author)

Heat processing of gels into sintered uranium dioxide modelled by thermal analysis. I

International Nuclear Information System (INIS)

Landspersky, H.; Urbanek, V.

1979-01-01

Thermoanalytical methods were used for investigating the processes of air drying and calcination of gels prepared by internal gelation of uranyl nitrate, urea and urotropine solutions at 90 degC. The gels were dried in air at room temperature, at 220 degC in a controlled atmosphere or by azeotropic distillation with CCl 4 . The course of thermal decomposition of the gel depends not only on the drying method used but also on the medium in which the drying process takes place. If the drying is carried out so as to produce a macroporous structure after the elimination of most of the water, ammonia and possibly other gelation by-products and non-reacted gelating agents, the resulting gels can be further processed by calcination, reduction and sintering, thus obtaining compact undamaged spheres of sintered uranium dioxide. Dilatometric analysis generated of uranium trioxide gels showed that the transformation of UO 3 to U 3 O 8 generated another intermediate thermal decomposition product showing a change in dimensions at temperatures of about 520 degC and a change in colour. This phenomenon is analogous to the decomposition of UO 3 prepared by thermal decomposition of α-UO 3 .2H 2 O involving a change in weight producing the UOsub(3-x) compound or a phase transformation with a change in colour; the structural conversion cannot be identified by X-ray structural analysis. (author)

Simulated UO{sub 2} fuel containing CsI by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Wangle, T. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, Praha 1, 115 19 (Czech Republic); Tyrpekl, V. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Cologna, M., E-mail: marco.cologna@ec.europa.eu [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Somers, J. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany)

2015-11-15

Herein, an innovative preparation procedure has been deployed enabling, for the first time, the incorporation of volatile fission product simulant into highly dense nuclear fuel pellets. Highly volatile fission products were embedded in a dense UO{sub 2} matrix in the form of CsI by simply mixing starting materials and consolidation in a Spark Plasma Sintering step at 1000 °C with a 5 min dwell time. CsI particles were evenly distributed throughout the pellet and were located at the grain boundaries. The sintering rate is dependent on the O/U ratio of the powder. Addition of CsI also acts as a sintering aid, reducing the temperature of maximum densification. - Highlights: • A new method was developed to incorporation of volatile fission products simulants into dense nuclear fuel pellets. • CsI doped UO{sub 2} pellets were synthetized for the first time, by Spark Plasma Sintering. • The sintering rate in Spark Plasma Sintering is dependent on the O/U ratio of UO{sub 2+x}.

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.

Sintering of solution-based nano-particles by a UV laser pulse train

Science.gov (United States)

Zhang, Jie; Li, Ming; Morimoto, Kiyoshi

2011-03-01

Sintering of palladium (Pd) and silicon (Si) nano-particles (NPs) by a 266nm laser pulse train on ink-printed films was investigated. Organic Pd-ink, and organic Si-ink were used as precursors. A high repetition rate DPSS laser (up to 300 kHz, 25ns, 266nm, Coherent AVIA series), which produces a ns pulse train with 3.3 μs -33.3 μs interval of pulse-topulse, was used as the heating source. Highly electrically conductive Pd (Resistivity=~150μΩ.cm) thin film on PET substrate and semi-conductive Si (Resistivity=~23kΩ.cm) thin film on glass substrate were successfully obtained with this laser pulse train sintering process. The sintered films were characterized by AFM, SEM, TEM and Raman spectroscopy, respectively. The pulse train heating process was also numerically simulated.

HAp physical investigation - the effect of sintering temperature

International Nuclear Information System (INIS)

Mohd Reusmaazran Yusof; Idris Besar; Rusnah Mustaffa; Cik Rohaida Che Hak

2004-01-01

The paper presents the effect of sintering temperature on the physical properties of porous hydroxyapatite (HAp). In this study, the HAp was prepared using polymeric sponge techniques with different binder concentration. The sintering process was carried out in air for temperature ranging from 1200 degree C to 1600 degree C. Different physical properties namely density and porosity were observed at different sintering temperatures. The HAp prepared with higher PVP binder showed a slightly decreased in apparent density with increasing sintering temperature, while those HAp prepared with lower PVP showed a slightly increase in apparent density with increasing sintering temperature. The total porosity was found to be approximately constant in the whole sintering temperature range. However, closed porosity decreases with increasing sintering temperature for HAp prepared by lower binder concentration. On the other hand, the HAp prepared by higher binder concentration HAp showed increasing closed porosity with increasing sintering temperature. Other features such as the influence of sintering temperatures on grain and strut also be presented in this paper. (Author)

Preparation and characterization of sintered Mo-Re alloys

International Nuclear Information System (INIS)

Morito, F.

1993-01-01

By the method of powder metallurgy, we have tried to fabricate Mo-Re alloys, which were electron beam weldable. Severe quality control was carried out during the whole fabrication process focused to reducing oxygen contamination. It is inevitable that the starting raw powders of Mo and Re were both high purity with 99.99 mass% up. Moreover, high vacuum sintering was performed before final sintering with high-purity hydrogen gas. As a result, we obtained electron beam weldable Mo-Re alloys, the total oxygen content of which was about 10 mass ppm or less, respectively. Several specimens were melted by electron beam welding (EBW) method. It was found that EBW gives an easy and effective survey to examine the weldability and the quality of the materials. Fracture surfaces examined by AES exhibited very low content of oxygen, carbon and nitrogen or that less than detectability limit. In conclusion, we have succeeded to obtain defect-free welds of sintered Mo-Re alloys. Furthermore it was found that Mo-Re alloys showed excellent potentialities not only in mechanical properties at low temperature but also in the respects of microstructure. (orig.)

Vacuum Pressureless Sintering of Ti-6Al-4V Alloy with Full Densification and Forged-Like Mechanical Properties

Science.gov (United States)

Zhang, Ce; Lu, Boxin; Wang, Haiying; Guo, Zhimeng; Paley, Vladislav; Volinsky, Alex A.

2018-01-01

Ti-6Al-4V ingots with a nearly 100% density, fine and homogeneous basket-weave microstructure, and better comprehensive mechanical properties (UTS = 935 MPa, Y.S. = 865 MPa, El. = 15.8%), have been manufactured by vacuum pressureless sintering of blended elemental powders. Coarse TiH2 powder, Al powder (2, 20 μm), V powder, and Al-V master alloy powder were used as raw materials to produce different powder mixtures ( D 50 = 10 μm). Then, the compacts made by cold isostatic pressing were consolidated by different sintering curves. A detailed investigation of different as-sintered samples revealed that a higher density can be obtained by generating transient molten Al in the sintering process. Coarse Al powder and a rapid heating rate under the melting point of Al contribute to molten Al formation. The presence of temporary liquid phase changes the sintering mechanism, accelerating the sintering neck formation, improving sinterability of the powder mixtures. Density of 99.5% was achieved at 1150 °C, which is markedly lower than the sintering temperatures reported for conventional blended elemental powder metallurgy routes. In addition, low interstitial content, especially for oxygen (0.17 wt.%), is obtained by strict process control.

Engineering properties of sintered waste sludge as lightweight aggregate in a densified concrete mixture

Institute of Scientific and Technical Information of China (English)

彭予柱

2009-01-01

The global trend towards carbon reduction,energy conservation,and sustainable use of resources has led to an increased focus on the use of waste sludge in construction.We used waste sludge from a reservoir to produce high-strength sintered lightweight aggregate,and then used the densified mixture design algorithm to create high-performance concrete from the sintered aggregate with only small amounts of mixing water and cement.Ultrasonic,electrical resistance and concrete strength efficiency tests were perfo...

Optimization of Sintering Time and Holding Time for 3D Printing of Fe-Based Metallic Glasses

Directory of Open Access Journals (Sweden)

Wenzheng Wu

2018-06-01

Full Text Available Fe-based metallic glasses are amorphous alloys with high strength, high hardness, and excellent corrosion resistance; however, the immaturity of processing methods has prevented their wide application in industrial production. Fe-based metallic glass parts were manufactured employing pneumatic injection additive manufacturing in this study. An evenly dispersed and stable Fe-based metallic glass powder slurry with a solids content of 50% was prepared firstly. Then the Fe-based metallic glass parts were printed. The printed parts were dried, debinded, and sintered for strengthening. The deformations of the printed parts and sintered parts relative to the original model were then analyzed by a 3D scanning reconstruction method. The slightly average bulging and sunken deformation of the printed parts and sintered parts confirmed the good printing accuracy of the pneumatic injection manufacture system. The effects of the sintering temperature and holding time on the properties of the sintered parts were studied. For a sintering temperature of 580 °C and holding time of 1 h, the surface quality of the sintered parts was better. The sintering of 3D-printed Fe-based metallic glass parts was preliminarily realized in this study, and the feasibility of preparing Fe-based metallic glass using pneumatic injection additive manufacture was verified.

Study of high-coercivity sintered NdFeB magnets

Energy Technology Data Exchange (ETDEWEB)

Bai, G. [School of Physics and Microelectronics, Shandong University, Jinan, 250100 (China); Department of Mathematics and Physics, Xi' an Institute of Technology, Xi' an, 710032 (China); Gao, R.W. [School of Physics and Microelectronics, Shandong University, Jinan, 250100 (China)]. E-mail: gaorwbox@sdu.edu.cn; Sun, Y. [School of Physics and Microelectronics, Shandong University, Jinan, 250100 (China); Han, G.B. [School of Physics and Microelectronics, Shandong University, Jinan, 250100 (China); Wang, B. [School of Physics and Microelectronics, Shandong University, Jinan, 250100 (China); Baotou Rare Earth Research Institute, Batou 014030 (China)

2007-01-15

Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of {sub j} H {sub c}=25.6 kOe, B {sub r}=13.2 kG and (BH){sub max}=39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 deg. C) is -0.53% deg. C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors.

Investigation of control conditions of uranium dioxide pellets sinterability through microspheres

International Nuclear Information System (INIS)

Assis, Gino de.

1996-01-01

Promotion or inhibition of ceramic powders sinterability, the decisive question in ceramic processing is approached in this dissertation. Each high density microsphere has been considered as a solid inclusion in a low density microspheres matrix, generating big pores. Such pores make it difficult for the pellets density due the fact that they are difficult to be eliminated. A master mixture, allowing the pellet densification in the projected range has been reached. Batches of microspheres have been observed sometimes with high apparent density and sometimes with low apparent density. This apparent density variation was attributed to changing the oxygen partial pressure during calcination under air atmosphere. It is evident that the control of the apparent density of the microspheres needs a further research in order to adjust the sinterability of the microspheres on the desired level.It was demonstrated that the produced microspheres do not have impurities levels that can promote its sinterability or avoid their use in nuclear area

The influence of green microstructure and sintering parameters on precipitation process during copper-nickel-zinc ferrites sintering

International Nuclear Information System (INIS)

Barba, A.; Clausell, C.; Jarque, J. C.; Monzo, M.

2014-01-01

Microstructural changes that occur during heat treatment of copper-nickel-zinc ferrites have been studied. The process of precipitation of the two types of crystals that occur during the sintering process has been analyzed. It is found that this process depends on dry relative density of the press specimens and on the following sintering parameters: sintering temperature, sintering time and cooling rate of the thermal cycle. Crystal precipitates characterization have been done by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These techniques have allowed to determine the nature of these crystals, which in this case correspond to zinc and copper oxides. It has been used two chemical reactions to explain the bulk precipitation and subsequent re-dissolution of these crystal precipitates during sintering. (Author)

Basic study of Eu.sup.2+./sup.-doped garnet ceramic scintillator produced by spark plasma sintering

Czech Academy of Sciences Publication Activity Database

Sugiyama, K.; Yanagida, T.; Fujimoto, Y.; Yokota, Y.; Ito, A.; Nikl, Martin; Goto, T.; Yoshikawa, A.

2012-01-01

Roč. 35, č. 2 (2012), s. 222-226 ISSN 0925-3467 R&D Projects: GA MŠk LH12150 Institutional research plan: CEZ:AV0Z10100521 Keywords : Eu 2+ 5d–4f transition * scintillator * spark plasma sintering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.918, year: 2012

Sintering of composite

International Nuclear Information System (INIS)

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

1988-01-01

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

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

International Nuclear Information System (INIS)

Florio, Daniel Zanetti de

1998-01-01

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

Efficient Radiation Shielding Through Direct Metal Laser Sintering

Data.gov (United States)

National Aeronautics and Space Administration — We have developed a method for efficient component-level radiation shielding that can be printed by direct metal laser sintering (DMLS) from files generated by the...

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.

METHOD FOR PRODUCING CEMENTED CARBIDE ARTICLES

Science.gov (United States)

Onstott, E.I.; Cremer, G.D.

1959-07-14

A method is described for making molded materials of intricate shape where the materials consist of mixtures of one or more hard metal carbides or oxides and matrix metals or binder metals thereof. In one embodiment of the invention 90% of finely comminuted tungsten carbide powder together with finely comminuted cobalt bonding agent is incorporated at 60 deg C into a slurry with methyl alcohol containing 1.5% paraffin, 3% camphor, 3.5% naphthalene, and 1.8% toluene. The compact is formed by the steps of placing the slurry in a mold at least one surface of which is porous to the fluid organic system, compacting the slurry, removing a portion of the mold from contact with the formed object and heating the formed object to remove the remaining organic matter and to sinter the compact.

Reduction of surface erosion caused by helium blistering in sintered beryllium and sintered aluminum powder

International Nuclear Information System (INIS)

Das, S.K.; Kaminsky, M.

1976-01-01

Studies have been conducted to find materials with microstructures which minimize the formation of blisters. A promising class of materials appears to be sintered metal powder with small average grain sizes and low atomic number Z. Studies of the surface erosion of sintered aluminum powder (SAP 895) and of aluminum held at 400 0 C due to blistering by 100 keV helium ions have been conducted and the results are compared to those obtained earlier for room temperature irradiation. A significant reduction of the erosion rate in SAP 895 in comparison to annealed aluminum and SAP 930 is observed. In addition results on the blistering of sintered beryllium powder (type I) irradiated at room temperature and 600 0 C by 100 keV helium ions are given. These results will be compared with those reported recently for vacuum cast beryllium foil and a foil of sintered beryllium powder (type II) which was fabricated differently, than type I. For room temperature irradiation only a few blisters could be observed in sintered beryllium powder type I and type II and they are smaller in size and in number than in vacuum cast beryllium. For irradiation at 600 0 C large scale exfoliation of blisters was observed for vacuum cast beryllium but much less exfoliation was seen for sintered beryllium powder, type I, and type II. The results show a reduction in erosion rate cast beryllium, for both room temperature and 600 0 C

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

Science.gov (United States)

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

2018-04-01

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Science of sintering and its future

International Nuclear Information System (INIS)

Ristic, M.M.

1975-01-01

Some new books published by M.Yu. Baljshin, V.A. Ivensen, V.V. Skorohod and others are characterized by the wish to give a complete approach to the problems of sintering theory. Bearing just this in mind while writing the book ''An Essay on the Generalization of Sintering Theory'' (G.V.Samsonov, M.M. Ristic with the collaborators) an idea was born: to ask the most eminent scientists in this field to present their own opinions on the theme ''The Science of Sintering and Modern Views on its Future''. There were formed 18 questions, given in the appendix to be answered. The received answers were presented in 10 chapters of this book. The fourth part of the book consists of papers of eminent scientists engaged in the field of sintering science (some of which were published here for the first time). This material is published in the book with the consent of the authors and these original contributions provide a more profound knowledge of sintering. The initial idea, that the book should have a monograph character and in which the answers would serve as some data on the latest notions of the science of sintering, was somewhat changed since the original opinions of individual scientists are given in the book and these, are sometimes very contradictory. This, in fact, gives the book a special charm because the unsolved problems in the science of sintering are most evidently stressed in this way

Factors Affecting the Sintering of UO2 Pellets

International Nuclear Information System (INIS)

El-Hakim, E.; Afifi, Y.K.

1999-01-01

Sintering of UO 2 pellets is affected by many parameters such as; UO 2 powder parameters, the conditions followed for preparing the green UO 2 pellets and the sintering scheme(heating and cooling rate, soaking time and temperature). The aim of this work is to study the effect of some these parameters on the characteristics of the sintered UO 2 pellets were qualified according to the technical specifications of Candu fuel. Pressed green pellets at different pressing force (15 to 50 k N) were sintered at 1650 ±20 degree for two hours to study the effect of pressing force on the sintered pellets characteristics; visual inspection, pellet dimensions, density and shrinkage ratio. Compacted green pellets at a pressing force of 48 k N were sintered at different sintering temperature (1600± 20 degree, 1650 ±20 degree, 1700± 20 degree) for two hours to study the effect of sintering temperature on the sintered pellets characteristics. The effect of the heating rate (200,300 and 400 degree per hour) on the sintered pellets characteristics was also investigated. It was found that the pressing force used to compact the green pellets had an effect on the density of the sintered pellets. Pellets pressed at 15 k N have a density of 10.3 g/cm 3 while, those pressed at 50 k N have a density of 10.6 g/cm 3. It was observed that increasing the heating rate to 400 degree /h lead to cracked pellets

Sintering systems for recycling plant fly ash and bottom ash from incineration plant. Production of artificial aggregate and permeable block by sintering method. Toshi gomi shokyakubai hibai no saishigenka gijutsu. Nenshoho ni yoru jinko kotsuzai to tosuisei block no seizo

Energy Technology Data Exchange (ETDEWEB)

Okamura, T.; Masuno, K.; Kaneko, M. (Ebara Corp., Tokyo (Japan))

1994-07-20

With the background that making the incineration residue of municipal waste nonpollutant or recycling the residue have been an urgent problem, Japan's first incineration ash recycle experiment pilot plant was built in the Nanbu Waste Incineration Plant of Funabashi City in 1993. In this paper, the outline of the one-year plant operation has been introduced. This plant consists of an artificial aggregate production line and a permeable block production line. In the former line, the incineration or fly ash is combined with plasticizer (clay) and then added by moisture. After the mixed material is extruded and pelletized, the pellets are sintered in a rotary kiln to be artificial aggregate. The sintering temperature is 1200[degree]C at a maximum and throughput of the raw materials is 130 kg/h. The evaporated and dispersed salt or low boiling point heavy metals are mixed in the flue gas and collected with bug filters. To produce the permeable block, the following processes are executed: the artificial aggregate is crushed and combined with powdered glass, a binder. The resulting material, after press-molded, is sintered at the temperature of up to 1050[degree]C. The test results showed that the products and plant waste represent satisfactorily acceptable level. 9 figs., 5 tabs.

Effects of sintering atmosphere and initial particle size on sintering of gadolinia-doped ceria; Efeitos da atmosfera de sinterizacao e do tamanho de particula na sinterizacao da ceria-gadolinia

Energy Technology Data Exchange (ETDEWEB)

Batista, Rafael Morgado

2014-07-01

The effects of the sintering atmosphere and initial particle size on the sintering of ceria containing 10 mol% gadolinia (GdO{sub 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{sup 2}/g, 36,2 m{sup 2}/g e 7,4 m{sup 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{sup 3+} bulk concentration after sintering. Accelerated grain growth and lower electrical conductivities were verified when reduction reactions are significantly present on sintering. (author)

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Modeling of sintering of functionally gradated materials

International Nuclear Information System (INIS)

Gasik, M.; Zhang, B.

2001-01-01

The functionally gradated materials (FGMs) are distinguished from isotropic materials by gradients of composition, phase distribution, porosity, and related properties. For FGMs made by powder metallurgy, sintering control is one of the most important factors. In this study sintering process of FGMs is modeled and simulated with a computer. A new modeling approach was used to formulate equation systems and the model for sintering of gradated hard metals, coupled with heat transfer and grain growth. A FEM module was developed to simulate FGM sintering in conventional, microwave and hybrid conditions, to calculate density, stress and temperature distribution. Behavior of gradated WC-Co hardmetal plate and cone specimens was simulated for various conditions, such as mean particle size, green density distribution and cobalt gradation parameter. The results show that the deformation behavior and stress history of graded powder compacts during heating, sintering and cooling could be predicted for optimization of sintering process. (author)

Beta Ti-45Nb and Ti-50Nb alloys produced by powder metallurgy for aerospace application

Energy Technology Data Exchange (ETDEWEB)

Martins, G.V.; Trava-Airoldi, V.J.; Machado, J.P.B., E-mail: givmartins@yahoo.com.br, E-mail: vladimir@las.inpe.br, E-mail: joaopaulo@las.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Silva, C.R.M., E-mail: cosmeroberto@gmail.com [Universidade de Brasilia (UnB), Brasilia, DF (Brazil); Nunes, C.A., E-mail: cnunes@demar.eel.usp.br [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Polo Urbo Industrial; Borges Junior, L.A., E-mail: borges.jr@itelefonica.com.br [Centro Universitario de Volta Redond (UNIFOA), Volta Redonda, RJ (Brazil)

2009-07-01

Beta titanium alloys parts are used on advanced aerospace systems because of their high strength to weight ratio and excellent corrosion resistance. Production of powder metallurgy titanium alloys components may lead to a substantial reduction in the cost, compared to those produced by conventional cast and wrought processes, because additional working operations and material waste can be avoided. In this work, beta Ti-45Nb and Ti- 50Nb were produced by the blended elemental technique, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering. Sintered samples were characterized for phase composition by XRD, microstructure by SEM, hardness by Vickers indentation, specific mass by the Archimedes method and elastic modulus by resonance ultrasound. The sintered samples presented only the beta phase, higher hardness and lower elastic modulus when compared to Ti6Al4V alloy and experimental specific mass value near theoretical specific mass. These characteristics are adequate for application on several aerospace parts. (author)

Beta Ti-45Nb and Ti-50Nb alloys produced by powder metallurgy for aerospace application

International Nuclear Information System (INIS)

Martins, G.V.; Trava-Airoldi, V.J.; Machado, J.P.B.; Silva, C.R.M.; Nunes, C.A.

2009-01-01

Beta titanium alloys parts are used on advanced aerospace systems because of their high strength to weight ratio and excellent corrosion resistance. Production of powder metallurgy titanium alloys components may lead to a substantial reduction in the cost, compared to those produced by conventional cast and wrought processes, because additional working operations and material waste can be avoided. In this work, beta Ti-45Nb and Ti- 50Nb were produced by the blended elemental technique, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering. Sintered samples were characterized for phase composition by XRD, microstructure by SEM, hardness by Vickers indentation, specific mass by the Archimedes method and elastic modulus by resonance ultrasound. The sintered samples presented only the beta phase, higher hardness and lower elastic modulus when compared to Ti6Al4V alloy and experimental specific mass value near theoretical specific mass. These characteristics are adequate for application on several aerospace parts. (author)

Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

International Nuclear Information System (INIS)

Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

2004-01-01

The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out

Development of synthetic graphite resistive elements for sintering furnace

International Nuclear Information System (INIS)

Otani, C.; Rezende, Mirabel C.; Polidoro, H.A.; Otani, S.

1987-01-01

The synthetic graphites have been produced using lignin coke, natural graphite and phenolic resin. The bulk density, porosity, flexural strength and eletrical resistivity measurements have been performed on specimens at about 2400 0 C. The performance of these materials, as heating elements, was evaluated in a sintering furnace prototype. This paper reports the fabrication process and the experimental results. (Author) [pt

Hot impact densification (HID) - a new method of producing ceramic nuclear fuel pellets with tight dimensional tolerances

International Nuclear Information System (INIS)

Hrovat, M.; Rachor, L.; Muehling, G.; Vollath, D.; Zimmermann, H.

1984-01-01

The hot impact densification (HID) is a new powerful method for producing ceramic fuel pellets for nuclear reactors. Green ceramic bodies are directly processed to pellets by high speed shaping in the plastic temperature region of ceramic material. Opposed to the well established press sintering procedure it can be heated, densified, and cooled by orders of magnitude faster. Therefore, at high throughputs, small equipment dimensions become possible. The fuel pellets produced meet all requirements, particular the dimensional tolerances achieved are very closed, consequently circular grinding is omitted. Furthermore, the relatively high temperature level of the impact pressing favors the mixed crystal formation of uranium and plutonium oxide. This improves the solubility of the fuel in nitric acid, an essential point at reprocessing. A prototype facility is designed so that automatic fabrication in continuous operation will be possible. The target working cycle for a fuel pellet is in the range of some seconds. (orig.)

Guideline tests on the corrosion of sintered uranium oxide by lead and sodium about 450 deg. C

International Nuclear Information System (INIS)

Portnoff, A.; Pointud, R.

1958-05-01

Within the frame of the investigation of behaviour of a fuel element (such as UO 2 ) under irradiation, the authors report the study of the physical-chemical action of the coolant at different temperatures on the body to be irradiated. Thus, sintered uranium oxide has been submitted to corrosion by lead and by sodium during 250 hours at temperatures between 400 and 500 C. The physical characteristics of the UO 2 powder and of different sintered UO 2 pellets produced from this powder under different sintering processes are indicated, as well as the results of a spectrographic analysis of the sintered UO 2 . Corrosion devices, treatments and obtained results are reported for corrosion by lead and by sodium. In the latter case, extraction processes are discussed (using butyl alcohol, or melting in vaseline oil)

Liquid phase sintered superconducting cermet

International Nuclear Information System (INIS)

Ray, S.P.

1990-01-01

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

Some Non-Destructive Testing Methods Applicable to Sintered Materials; Quelques Methodes d'Essais Non Destructifs Applicables aux Materiaux Frittes; Nekotorye metody nedestruktivnykh ispytanii, primenimye k spechennym materialam; Algunos Metodos de Ensayo No Destructivo Aplicables a los Materiales Sinterizados

Energy Technology Data Exchange (ETDEWEB)

Labusca, Elena; Mirion, I.; Andreescu, N.; Alecu, M.; Biscoveanu, I. [Institut de Physique Atomique, Bucarest (Romania)

1965-10-15

Bearing in mind the specific granular structure of sintered materials produced from powders, whose compaction process is linked with the sintering treatment, we have experimented with methods of checking the degree of sintering and certain other properties. The non-destructive methods used include: (1) Examination of the crystalline structure of solid sinters, using metallography and electron microscopy. These methods show the homogeneity of the structure, the grain size and orientation, the presence of various flaws such as inclusions and pores, and the actual course of the sintering process, including crystal formation, grain growth, etc. In certain cases the microscopic examination can be combined with micro-hardness tests. This examination of the microcrystalline structure is one of the principal methods of checking the quality of sintered materials, and is irreplaceable by any other method. (2) The degree of compaction, which is the main factor in determining the quality of sintered materials, can also be checked by measuring certain properties such as electrical and thermal conductivity in relation to density, since for sintered materials conductivity is directly proportional to the degree of sintering. We have also tested and found satisfactory a method for checking porosity, and have obtained interesting experimental data, especially on free porosity, which is susceptible to gaseous inclusions. The paper gives experimental data on the application of these methods to certain sintered materials of importance in nuclear technology. (author) [French] En tenant compte de la structure specifique granulaire des materiaux frittes, elabores a partir de poudres, pour lesquels le proces de consolidation evolue en fonction du traitement de frittage, on a experimente des methodes de controle du degre de frittage et de quelques proprietes. Parmi les methodes non destructives utilisees, les auteurs citent les suivantes: 1. Examen de la structure cristalline des corps

Glucoamylase biosynthesis by cells of Aspergillus niger C sub 58-III immobilized in sintered glass and pumice stones

Energy Technology Data Exchange (ETDEWEB)

Fiedurek, J.; Lobarzewski, J. (Uniwersytet Marii Curie-Sklodowskiej, Lublin (Poland). Inst. Mikrobiologii i Biochemii)

1990-09-01

A simple method of A. niger C{sub 58-III} cell immobilization is described. This strain produces extracellular glucoamylase. According to the proposed method A. niger spores were first immobilized by adsorption in sintered glass Rasching rings (RR) or pumice stones (PS). Growing out from spores, A. niger cells produced extracellular glucoamylase. This technique facilitates the culture growth in a filamentous spongy structure of the supports with a continuous accumulation of biomass. After every 24 h it was possible to obtain culture liquid rich in glucoamylase. This procedure can be repeated 30 times using the same sample of immobilized A. niger culture without any loss of glucoamylase activity in the liquid medium. In a 96 h period immobilized A. niger cells produced 300 units . ml{sup -1} whereas a shake culture of this fungus produced only 186 units . ml{sup -1}. (orig.).

Maps of Fe-Al phases formation kinetics parameters during isothermal sintering

Energy Technology Data Exchange (ETDEWEB)

Pochec, Ewelina, E-mail: epochec@wat.edu.pl [Department of Advanced Materials and Technology, Military University of Technology (Poland); Jozwiak, Stanislaw; Karczewski, Krzysztof; Bojar, Zbigniew [Department of Advanced Materials and Technology, Military University of Technology (Poland)

2012-10-10

Highlights: Black-Right-Pointing-Pointer The sintering temperature and compaction pressure have a strong influence on the sinters structure. Black-Right-Pointing-Pointer The measurements confirmed the presence of the high-aluminium phases from Fe-Al equilibrium system in tested sinters. Black-Right-Pointing-Pointer The kinetics of Fe-Al phase formation can be described by Johnson-Mehl-Avrami modelling. - Abstract: The influence of technological parameters (compaction pressure and sintering temperature) on Fe-Al phase formation was investigated. The kinetics of phase transformation preceding and during an SHS reaction was studied in isothermal conditions by DSC using the JMA (Johnson-Mehl-Avrami) model. This model allowed us to determine basic kinetic parameters, including the Avrami exponent, which characterises the rate and manner of particular phase nucleation. The activation energy (E{sub a}) of particular phase formation was determined by the Kissinger method. XRD analysis and SEM observations of sintered material showed that not only Fe{sub 2}Al{sub 5} phase and low-aluminium solid solution in iron but also aluminium-rich FeAl{sub 2} and FeAl{sub 3} phases are formed during the sintering of an FeAl50 elementary powder mixture in isothermal conditions with an SHS reaction. The above conclusions were confirmed by iron-based solid solution lattice parameter studies and microhardness measurements.

Effect of slurries density on the properties of ceramic foam produced via polymer replication method

International Nuclear Information System (INIS)

Mohd Al Amin Muhammad Nor; Lee Chain Hong; Hazizan Md Akil; Zainal Ariffin Ahmad

2007-01-01

Ceramic foams are a class of high porosity materials that are used or being considered for a wide range of technological applications. Ceramic foam was produce by polymer replication method. In this process, commercial polymeric sponge was use as template, dipping with ceramic particles slurry, drying and then sintered to yield a replica of the original foams. The study was focus on the fabrication of different density of ceramic foams by varying the density of ceramic slurries (1.1876, 1.2687, 1.3653 and 1.5295 g/cm?3). Properties of ceramic foam produced such as density was characterized accordingly to ASTM C 271-94 and porosity were characterized using Archimedes methods. Compressive and bending strength was performed accordingly to ASTM C1161-94 and C773-88 (1999), respectively. The morphological study was performed using Scanning Electron Microscopy (SEM) and EDX. Density of ceramic foams produced was about 0.5588 and 1.1852 g/cm 3 , where as porosity was around 26.28 and 70.59 %. Compressive and bending strength was increase from strength also increases from 2.60 to 23.07 MPa and 1.20 to 11.10 MPa, respectively, with increasing of slurries density from 1.1876 to 1.3653 g/cm 3 . The SEM micrographs show that the cells structure become denser as the slurries density increased. EDX proved that the ceramic used is porcelain. As conclusion, increasing in slurries density produced ceramic foams with good mechanical properties such as compressive and bending strength and denser body. (Author)

Two-dimensional simulation of sintering process

International Nuclear Information System (INIS)

Vasconcelos, Vanderley de; Pinto, Lucio Carlos Martins; Vasconcelos, Wander L.

1996-01-01

The results of two-dimensional simulations are directly applied to systems in which one of the dimensions is much smaller than the others, and to sections of three dimensional models. Moreover, these simulations are the first step of the analysis of more complex three-dimensional systems. In this work, two basic features of the sintering process are studied: the types of particle size distributions related to the powder production processes and the evolution of geometric parameters of the resultant microstructures during the solid-state sintering. Random packing of equal spheres is considered in the sintering simulation. The packing algorithm does not take into account the interactive forces between the particles. The used sintering algorithm causes the densification of the particle set. (author)

Three-dimensional simulation of viscous-flow agglomerate sintering.

Science.gov (United States)

Kirchhof, M J; Schmid, H -J; Peukert, W

2009-08-01

The viscous-flow sintering of different agglomerate particle morphologies is studied by three-dimensional computer simulations based on the concept of fractional volume of fluid. For a fundamental understanding of particle sintering characteristics, the neck growth kinetics in agglomerate chains and in doublets consisting of differently sized primary particles is investigated. Results show that different sintering contacts in agglomerates even during the first stages are not completely independent from each other, even though differences are small. The neck growth kinetics of differently sized primary particles is determined by the smaller one up to a size difference by a factor of approximately 2, whereas for larger size differences, the kinetics becomes faster. In particular, the agglomerate sintering kinetics is investigated for particle chains of different lengths and for different particle morphologies each having ten primary particles and nine initial sintering contacts. For agglomerate chains, the kinetics approximately can be normalized by using the radius of the fully coalesced sphere. In general, different agglomerate morphologies show equal kinetics during the first sintering stages, whereas during advanced stages, compact morphologies show significantly faster sintering progress than more open morphologies. Hence, the overall kinetics cannot be described by simply using constant morphology correction factors such as fractal dimension or mean coordination number which are used in common sintering models. However, for the first stages of viscous-flow agglomerate sintering, which are the most important for many particle processes, a sintering equation is presented. Although we use agglomerates consisting of spherical primary particles, our methodology can be applied to other aggregate geometries as well.

Current state of the Uranium dioxide sintering theory

International Nuclear Information System (INIS)

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

2011-01-01

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

Microstructure and properties of multiphase sintered cermets Fe-Fe{sub 2}B; Mikrostruktura i wlasnosci spiekanych reakcyjnie cermetali Fe-Fe{sub 2}B

Energy Technology Data Exchange (ETDEWEB)

Nowacki, J. [Wydzial Inzynierii Materialowej, Politechnika Szczecinska, Szczecin (Poland); Klimek, L. [Instytut Inzynierii Materialowej i Technik Bezwiorowych, Politechnika Lodzka, Lodz (Poland)

1998-12-31

The process of multiphase sintering of iron in the vacuum has been analysed. As a result of the process iron-iron boride cermets have been produced. Fe-Fe{sub 2}B cermets were obtained as a result of sintering of the Fe and B pure elements in the vacuum. Attemps at sintering in the solid phase and with the participation of the liquid phase, the Fe-Fe{sub 2}B eutectic, have been made. Metallographic qualitative and quantitative studies, X-ray structural qualitative and qauantitative analysis allowed to determine the structure of Fe{sub 2}B cermets, as well as a description of the kinetics of quantitative changes in phase proportions in the course of sintering. It has been found that their structure varies widely depending on sintering parameters and the composition of the sinters. Measurements of the Fe-Fe{sub 2}B cermets hardness and measurements on wear during dry friction by the pin-on-disc method have shown distinct advantages of the cermets as a modern constructional materials. The hardness of Fe-Fe{sub 2}B cermets, depending on their chemical composition and sintering parameters, ranges widely from 150 to 1500 HV, and their resistance to wear is comparable to that of diffusively boronized steels. FeFe{sub 2}B cermets are a composite material in which iron boride, Fe{sub 2}B, with a hardness of about 1800 HV plays the role of the reinforcement,while iron-iron boride, Fe-Fe{sub 2}B, with a hardness of about 500 HV plays the role of matrix. The eutectic in the spaces between iron boride grains is composed of boron solid solution plates in iron with a hardness of arround 250 HV, and iron boride, Fe{sub 2}B, plates with a hardness of approximaly 1800 HV. The combination of such different materials, a hard reinforcement and a relatively plastic matrix produces favourable properties of the cermet thus produced high hardness (1500 HV) constant over whole cross section of the material, resistance of abrasive wear and acceptable ductility. The properties mentioned above

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

Science.gov (United States)

Ortega, Luis Humberto

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

Sintering and microstructure of ice: a review

International Nuclear Information System (INIS)

Blackford, Jane R

2007-01-01

Sintering of ice is driven by the thermodynamic requirement to decrease surface energy. The structural morphology of ice in nature has many forms-from snowflakes to glaciers. These forms and their evolution depend critically on the balance between the thermodynamic and kinetic factors involved. Ice is a crystalline material so scientific understanding and approaches from more conventional materials can be applied to ice. The early models of solid state ice sintering are based on power law models originally developed in metallurgy. For pressure sintering of ice, these are based on work on hot isostatic pressing of metals and ceramics. Recent advances in recognizing the grain boundary groove geometry between sintering ice particles require models that use new approaches in materials science. The newer models of sintering in materials science are beginning to incorporate more realistic processing conditions and microstructural complexity, and so there is much to be gained from applying these to ice in the future. The vapour pressure of ice is high, which causes it to sublime readily. The main mechanism for isothermal sintering of ice particles is by vapour diffusion; however other transport mechanisms certainly contribute. Plastic deformation with power law creep combined with recrystallization become important mechanisms in sintering with external pressure. Modern experimental techniques, low temperature scanning electron microscopy and x-ray tomography, are providing new insights into the evolution of microstructures in ice. Sintering in the presence of a small volume fraction of the liquid phase causes much higher bond growth rates. This may be important in natural snow which contains impurities that form a liquid phase. Knowledge of ice microstructure and sintering is beneficial in understanding mechanical behaviour in ice friction and the stability of snow slopes prone to avalanches. (topical review)

The Effects of Post-Sintering Treatments on Microstructure and Mechanical Properties of Mn-Mo Steel

Science.gov (United States)

Fiał, Ch.

2017-12-01

The effect of heat treatment on density, hardness, microstructure and tensile properties of Fe-0.85Mo-1.3Mn-0.6C sintered steel were investigated. Pre-alloyed Astaloy 85Mo, ferromanganese and UF4 graphite powders were mixed for 60 minutes in a Turbula mixer and then pressed in single-action die at 660MPa to produce green compacts (according to PN EN ISO 2740).The compacts were sintered in a specially designed semi-closed container at 1120 or 1250°C for 60 minutes in N2. The chemical composition of the sintering atmosphere was modified by adding getter and/or activator into the container. Two different types of heat treatment in nitrogen were carried out: sinteraustempering at 525°C for 60 minutes; and sinterhardening with additional tempering at 200°C for 60 minutes. The slightly better combination of strength and plasticity of steel for both sintering temperatures were achieved after sinterhardening+tempering variant. Average values of 0.2% offset yield stress, ultimate tensile strength and elongation after sintering in 1250°C, were 415MPa, 700MPa, and 2.0%, respectively.

Sintered cobalt-rare earth intermetallic product

International Nuclear Information System (INIS)

Benz, M.C.

1975-01-01

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

Highly textured KNN-based piezoelectric ceramics by conventional sintering

International Nuclear Information System (INIS)

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

2016-01-01

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

Peridynamic Theory as a New Paradigm for Multiscale Modeling of Sintering

Energy Technology Data Exchange (ETDEWEB)

Silling, Stewart A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Abdeljawad, Fadi [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ford, Kurtis Ross [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-09-01

Sintering is a component fabrication process in which powder is compacted by pressing or some other means and then held at elevated temperature for a period of hours. The powder grains bond with each other, leading to the formation of a solid component with much lower porosity, and therefore higher density and higher strength, than the original powder compact. In this project, we investigated a new way of computationally modeling sintering at the length scale of grains. The model uses a high-fidelity, three-dimensional representation with a few hundred nodes per grain. The numerical model solves the peridynamic equations, in which nonlocal forces allow representation of the attraction, adhesion, and mass diffusion between grains. The deformation of the grains is represented through a viscoelastic material model. The project successfully demonstrated the use of this method to reproduce experimentally observed features of material behavior in sintering, including densification, the evolution of microstructure, and the occurrence of random defects in the sintered solid.

Sintered-to-size FBR fuel

International Nuclear Information System (INIS)

Rasmussen, D.E.; Schaus, P.S.

1984-04-01

Fabrication of sintered-to-size PuO 2 -UO 2 fuel pellets was completed for testing of proposed FBR product specifications. Approximately 6000 pellets were fabricated to two nominal diameters and two densities by cold pressing and sintering to size. Process control and correlation between test and production batches are discussed

Comparative microstructural and corrosion development of VCrNiCoFeCu equiatomic multicomponent alloy produced by induction melting and spark plasma sintering

Science.gov (United States)

Fazakas, É.; Heczel, A.; Molnár, D.; Varga, B.; Zadorozhnyy, V.; Vida, Á.

2018-03-01

The present study focuses on the corrosion behavior of a single-phase FCC high entropy alloy (VCrNiCoFeCu) casted by two different methods: induction melting and spark plasma sintering. The corrosion resistance has been evaluated using immersion tests in 3.5% NaCl solution, the potentiodynamic polarization measurements and the results are compared how is dependent the corrosion rate as a function of the production methods. Our results show that induction melted sample is stable in salty environment. On the other hand, based on the changes of polarization curves, there must be an evolution of oxide films on the SPSed sample until reaching the stable oxide layer.

The microwave effects on the properties of alumina at high frequencies of microwave sintering

International Nuclear Information System (INIS)

Sudiana, I. Nyoman; Ngkoimani, La Ode; Usman, Ida; Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke; Aripin, H.

2016-01-01

Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

The microwave effects on the properties of alumina at high frequencies of microwave sintering

Energy Technology Data Exchange (ETDEWEB)

Sudiana, I. Nyoman, E-mail: sudiana75@yahoo.com; Ngkoimani, La Ode; Usman, Ida [Department of Physics, Faculty of Mathematic and Natural Science, Halu Oleo University, Kampus Bumi Tridharma Anduonohu, Kendari 93232 (Indonesia); Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke [Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui-shi 910-8507 (Japan); Aripin, H. [Center for Material Processing and Renewable Energy, Faculty of Learning Teacher and Education Science, Siliwangi University, Jl. Siliwangi 24 Tasikmalaya 46115, West Java (Indonesia)

2016-03-11

Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

Sintering of micro-trusses created by extrusion-3D-printing of lunar regolith inks

Science.gov (United States)

Taylor, Shannon L.; Jakus, Adam E.; Koube, Katie D.; Ibeh, Amaka J.; Geisendorfer, Nicholas R.; Shah, Ramille N.; Dunand, David C.

2018-02-01

The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1-2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.

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.

Sintering of a class F fly ash

Energy Technology Data Exchange (ETDEWEB)

Joseph J. Biernacki; Anil K. Vazrala; H. Wayne Leimer [Tennessee Technological University, Cookeville, TN (United States). Department of Chemical Engineering

2008-05-15

The sinterability of a class F fly ash was investigated as a function of processing conditions including sintering temperature (1050-1200{sup o}C) and sintering time (0-90 min). Density, shrinkage, splitting tensile strength, water absorption and residual loss on ignition (RLOI) were evaluated as measures of sintering efficiency. Scanning electron microscopy (SEM), X-ray microanalysis and X-ray diffraction was used to examine microstructure and phase development due to processing. The results show that premature densification can inhibit complete carbon removal and that carbon combustion is influenced by both internal and external mass transfer conditions. 18 refs., 10 figs., 1 tab.

Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

Directory of Open Access Journals (Sweden)

Huibin Zhang

2017-02-01

Full Text Available Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2, silicon (Si and graphite (C elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD and scanning electron microscope (SEM. Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process.

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

International Nuclear Information System (INIS)

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

1989-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-12-01

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

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 ...

The quantitative characterization of sintering of urania powders

International Nuclear Information System (INIS)

Das, P.; Kulkarni, U.D.

1981-01-01

This paper presents a unified approach towards characterization of the sintering behaviour of UO 2 powders in terms of their extrinsic properties. Empirical equations connecting the sintering index with various powder parameters have been set up. The influence of various powder parameters, either individually or as dimensionless/dimensional groups, on the sintering behaviour has been studied. The relative importance of these factors has also been analysed. A good polynomial fit has been obtained for variation of sintering index with some of the powder parameters and dimensionless/dimensional groups. The equations are expected to provide a good basis for assessing the sinterability of UO 2 powders. (Auth.)

The effect of sintering temperature on the 3Y-TZP co-doped with equimolar addition of the yttria and niobia

International Nuclear Information System (INIS)

Fonseca, Flavia Baccaro; Dorat, Daniele Ramos; Melo, Francisco Cristovao Lourenco de; Piorino Neto, Francisco; Reis, Danieli Aparecida

2010-01-01

The aim of this work is to identify the better sintering temperature to densify zirconia co-doped with yttria and niobia and to verify the existence of the stable tetragonal phase (t´) under applied stress at room temperature to be applied as a TBC material. Four compositions with equimolar addition of yttria and niobia in the 3Y-TZP were produced, 13.0 %, 14.5 %, 16.0 % and 17.5 %. The mixtures were prepared in high energy ball milling for 10 minutes and the samples prepared on uniaxial and isostatic pressing. The selected sintering temperatures were 1500 deg C, 1550 deg C, 1600 deg C and 1650 deg C, for 1 hour. Analysis of conventional and high resolution X-Ray Diffraction and measures of specific mass by Archimedes method were performed. Through measures of the specific mass, the best sintering temperature was 1550 deg C, with relative specific mass above 95 %. The x-ray diffraction analysis indicate a probable existence of t´ in all samples. (author)

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

International Nuclear Information System (INIS)

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

2009-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2002-07-01

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

CuFeO2 formation using fused deposition modeling 3D printing and sintering technique

Science.gov (United States)

Salea, A.; Dasaesamoh, A.; Prathumwan, R.; Kongkaew, T.; Subannajui, K.

2017-09-01

CuFeO2 is a metal oxide mineral material which is called delafossite. It can potentially be used as a chemical catalyst, and gas sensing material. There are methods to fabricate CuFeO2 such as chemical synthesis, sintering, sputtering, and chemical vapor deposition. In our work, CuFeO2 is prepared by Fused Deposition Modeling (FDM) 3D printing. The composite filament which composed of Cu and Fe elements is printed in three dimensions, and then sintered and annealed at high temperature to obtain CuFeO2. Suitable polymer blend and maximum percent volume of metal powder are studied. When percent volume of metal powder is increased, melt flow rate of polymer blend is also increased. The most suitable printing condition is reported and the properties of CuFeO2 are observed by Scanning Electron Microscopy, and Dynamic Scanning Calorimeter, X-ray diffraction. As a new method to produce semiconductor, this technique has a potential to allow any scientist or students to design and print a catalyst or sensing material by the most conventional 3D printing machine which is commonly used around the world.

Effect of Sintering Temperature on the Properties of Aluminium-Aluminium Oxide Composite Materials

Directory of Open Access Journals (Sweden)

Dewan Muhammad Nuruzzaman

2016-12-01

Full Text Available In this study, aluminium-aluminium oxide (Al-Al2O3 metal matrix composites of different weight percentage reinforcements of aluminium oxide were processed at different sintering temperatures. In order to prepare these composite specimens, conventional powder metallurgy (PM method was used. Three types specimens of different compositions such as 95%Al+5%Al2O3, 90%Al+10%Al2O3 and 85%Al+15%Al2O3 were prepared under 20 Ton compaction load. Then, all the specimens were sintered in a furnace at two different temperatures 550oC and 580oC. In each sintering process, two different heating cycles were used. After the sintering process, it was observed that undistorted flat specimens were successfully prepared for all the compositions. The effects of sintering temperature and weight fraction of aluminium oxide particulates on the density, hardness and microstructure of Al-Al2O3 composites were observed. It was found that density and hardness of the composite specimens were significantly influenced by sintering temperature and percentage aluminium oxide reinforcement. Furthermore, optical microscopy revealed that almost uniform distribution of aluminium oxide reinforcement within the aluminium matrix was achieved.

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-01-15

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

Effect of rigid inclusions on sintering

International Nuclear Information System (INIS)

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

1988-01-01

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

Characterization of Al–Al4C3 nanocomposites produced by mechanical milling

International Nuclear Information System (INIS)

Santos-Beltrán, A.; Goytia-Reyes, R.; Morales-Rodriguez, H.; Gallegos-Orozco, V.; Santos-Beltrán, M.; Baldenebro-Lopez, F.; Martínez-Sánchez, R.

2015-01-01

In this work, a mixture of Al–C–Al 4 C 3 nanopowder previously synthesized by mechanical milling and subsequent thermal treatment was used to reinforce the Al matrix. The nanocomposites were fabricated via high-energy ball milling and subsequent sintering process for different periods of time at 550 °C. Hardness and compression tests were performed to evaluate the mechanical properties of the nanocomposites in the as-milled and sintered conditions. According to the results the reinforcement located in the grain boundaries is responsible for the brittle behavior observed in the nanocomposites during the compression test. The combined effect of sintering and precipitation mechanisms produced an evident increase of the strength of the Al matrix at a relatively short sintering time. By using the Rietveld method the crystallite size and microstrain measurements were determined and correlated with the microhardness values. For the proper characterization of the nanoparticles present in the Al matrix, atomic force microscopy and high resolution electron microscopy were used. - Highlights: • Nanostructured Al 4 C 3 reinforcement was fabricated via mechanical milling and heat treatment. • We found a significant increase of the mechanical properties at short sintering times. • The formation of Al 4 C 3 with during sintering time restricted the excessive growth of the crystallite. • Al 4 C 3 located in the grain boundaries causes brittle fracture observed in compression tests. • There is a correlation between, crystallite size and microstrain values with microhardness

Densification and grain growth during sintering of porous Ce0.9Gd0.1O1.95tape cast layers: A comprehensive study on heuristic methods

DEFF Research Database (Denmark)

Ni, De Wei; Schmidt, Cristine Grings; Teocoli, Francesca

2013-01-01

The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine the domin...... and grain boundary mobility in the porous body was estimated around 10−18–10−16m3N−1s−1 at the investigated temperature range.© 2013 Elsevier Ltd. All rights reserved.......The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine...... the dominant sintering mechanisms and kinetics, both in isothermal and at constant heating rate (iso-rate) conditions. Densification of porous CGO10 tape is thermally activated with typical activation energy which was estimated around 440–470 kJ mol−1. Grain growth showed similar thermal activation energy...

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

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.

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

Extension of the master sintering curve for constant heating rate modeling

Science.gov (United States)

McCoy, Tammy Michelle

The purpose of this work is to extend the functionality of the Master Sintering Curve (MSC) such that it can be used as a practical tool for predicting sintering schemes that combine both a constant heating rate and an isothermal hold. Rather than just being able to predict a final density for the object of interest, the extension to the MSC will actually be able to model a sintering run from start to finish. Because the Johnson model does not incorporate this capability, the work presented is an extension of what has already been shown in literature to be a valuable resource in many sintering situations. A predicted sintering curve that incorporates a combination of constant heating rate and an isothermal hold is more indicative of what is found in real-life sintering operations. This research offers the possibility of predicting the sintering schedule for a material, thereby having advanced information about the extent of sintering, the time schedule for sintering, and the sintering temperature with a high degree of accuracy and repeatability. The research conducted in this thesis focuses on the development of a working model for predicting the sintering schedules of several stabilized zirconia powders having the compositions YSZ (HSY8), 10Sc1CeSZ, 10Sc1YSZ, and 11ScSZ1A. The compositions of the four powders are first verified using x-ray diffraction (XRD) and the particle size and surface area are verified using a particle size analyzer and BET analysis, respectively. The sintering studies were conducted on powder compacts using a double pushrod dilatometer. Density measurements are obtained both geometrically and using the Archimedes method. Each of the four powders is pressed into ¼" diameter pellets using a manual press with no additives, such as a binder or lubricant. Using a double push-rod dilatometer, shrinkage data for the pellets is obtained over several different heating rates. The shrinkage data is then converted to reflect the change in relative

Design of sintering-stable heterogeneous catalysts

DEFF Research Database (Denmark)

Gallas-Hulin, Agata

One of the major issues in the use of metal nanoparticles in heterogeneous catalysis is sintering. Sintering occurs at elevated temperatures because of increased mobility of nanoparticles, leading to their agglomeration and, as a consequence, to the deactivation of the catalyst. It is an emerging...... problem especially for the noble metals-based catalysis. These metals being expensive and scarce, it is worth developing catalyst systems which preserve their activity over time. Encapsulation of nanoparticles inside zeolites is one of the ways to prevent sintering. Entrapment of nanoparticles inside...

Solidification of HLLW into sintered ceramics

International Nuclear Information System (INIS)

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

1979-01-01

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

Low Temperature Two-Steps Sintering (LTTSS) - an innovative method for consolidating porous UO2 pellets

International Nuclear Information System (INIS)

Sanjay Kumar, D.; Ananthasivan, K.; Senapati, Abhiram; Venkata Krishnan, R.

2015-01-01

Metallic uranium and its alloys are an important fuel for fast reactors. Presently, metallic uranium is being prepared using expensive fluoro-metallothermic process. Recent reports suggest that metal oxide could be reduced to metal using a novel electrochemical de-oxidation method and this could serve as attractive alternate for expensive metallothermic process. In view of which, a research program is being pursued in our Centre to develop an optimum process parameter for the scaled up preparation of metallic uranium efficiently. One of the important process parameter is the size, nature and distribution of porosity in the urania pellet. Essentially the ceramic form of the urania should encompass interconnected porosity that would allow percolation of melts into the UO 2 . However, the matrix density of the pellet should be high to ensure that it possesses good handling strength and is electrically conducting. Hence preparation of high dense porous UO 2 pellets was required. In this study, we report the preparation of porous UO 2 pellets possessing a very high matrix density by using the citrate gel-combustion method. The 'as-prepared' powders were consolidated at various compaction pressures as such and these pellets were sintered in 8 mol %Ar+H 2 gas with a flow rate of 250 mL/min at 1073 K for 30 min followed by soaking at 1473 K for 4 h with heating rate of 5 K min -1 in a molybdenum furnace. X-ray diffraction studies revealed that these pellets contained UO 2 . The morphological analysis sintered pellets was carried out by using Scanning Electron Microscope (M/s. Philips model XL 30, Netherlands). All these pellets were gold coated

Experimental investigations on the synthesis of W–Cu nanocomposite through spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Elsayed, Ayman, E-mail: aymanhamada@cmrdi.sci.eg [Central Metallurgical R& D Institute, Department of Powder Technology, P.O. Box 87, Helwan, Cairo 11421 (Egypt); Li, Wei [San Diego State University, College of Engineering, Department of Mechanical Engineering, 5500 Campanile Drive, San Diego, CA 92128-1326 (United States); El Kady, Omayma A. [Central Metallurgical R& D Institute, Department of Powder Technology, P.O. Box 87, Helwan, Cairo 11421 (Egypt); Daoush, Walid M. [Helwan University, Faculty of Industrial Education, Department of Production Technology, Cairo (Egypt); Olevsky, Eugene A.; German, Randall M. [San Diego State University, College of Engineering, Department of Mechanical Engineering, 5500 Campanile Drive, San Diego, CA 92128-1326 (United States)

2015-08-05

Highlights: • Tungsten–copper composites have been synthesized using SPS of nano powders. • Various preparation methods, namely mixing, milling and coating have been used. • Conventional compaction and sintering has also been used for comparison. • The composites by SPS have shown finer microstructure and better hardness. • Mixing has proven best preparation method with best physical/mechanical properties. - Abstract: Elemental powders of nanosized tungsten and chemically deposited nanosized copper were used for preparing tungsten/copper composites, which are used as electric contact components. A composite of 70 wt.%W/30 wt.%Cu (52 vol%W/48 vol%Cu) composition was prepared by three powder metallurgy techniques. Elemental mixing, mechanical milling and electroless Cu coating on tungsten particles were used for the synthesis. The obtained powder blends underwent consolidation by rapid hot pressing using the spark plasma sintering (SPS) route at 950 °C under vacuum and by conventional vacuum pressureless sintering for comparison. The elemental powders and the sintered composites were investigated by optical microscopy and SEM. Electrical conductivity, hardness, transverse rupture strength, and wear properties were measured. Results show that the synthesis of the composite by the investigated route yields good performance. Samples prepared by SPS have shown better mechanical properties than those prepared by compaction and sintering due to their fine microstructure.

Evaluation of sintering effects on SiC-incorporated UO2 kernels under Ar and Ar–4%H2 environments

International Nuclear Information System (INIS)

Silva, Chinthaka M.; Lindemer, Terrence B.; Hunt, Rodney D.; Collins, Jack L.; Terrani, Kurt A.; Snead, Lance L.

2013-01-01

Silicon carbide (SiC) is suggested as an oxygen getter in UO 2 kernels used for tristructural isotropic (TRISO) particle fuels and to prevent kernel migration during irradiation. Scanning electron microscopy and X-ray diffractometry analyses performed on sintered kernels verified that an internal gelation process can be used to incorporate SiC in UO 2 fuel kernels. Even though the presence of UC in either argon (Ar) or Ar–4%H 2 sintered samples suggested a lowering of the SiC up to 3.5–1.4 mol%, respectively, the presence of other silicon-related chemical phases indicates the preservation of silicon in the kernels during sintering process. UC formation was presumed to occur by two reactions. The first was by the reaction of SiC with its protective SiO 2 oxide layer on SiC grains to produce volatile SiO and free carbon that subsequently reacted with UO 2 to form UC. The second process was direct UO 2 reaction with SiC grains to form SiO, CO, and UC. A slightly higher density and UC content were observed in the sample sintered in Ar–4%H 2 , but both atmospheres produced kernels with ∼95% of theoretical density. It is suggested that incorporating CO in the sintering gas could prevent UC formation and preserve the initial SiC content

Metallurgical structure modification of UO{sub 2} pellet during sintering - experience at NFC, Hyderabad, India

Energy Technology Data Exchange (ETDEWEB)

Santra, N.; Sinha, T.K.; Singh, A.K.; Sairam, S.; Sheela, S.; Saibaba, N., E-mail: santra@nfc.gov.in [Nuclear Fuel Complex, Dept. of Atomic Energy, Hyderabad (India)

2013-07-01

Nuclear Fuel Complex (NFC), Department of Atomic Energy (DAE) produces UO{sub 2} fuel pellets by powder compaction, high temperature sintering followed by centreless wet grinding method from the stabilized UO{sub 2} powder generated through ADU-route. Enhancement of fuel burn up of the Indian PHWRs becomes very important in order to effectively utilize the fuel to the maximum extent inside the reactor. Burn up is mainly limited by increased fission gas release from the fuel during reactor operation. Without introducing much change in the design, rate of release of fission gas can be reduced through enlargement of UO{sub 2} grain size. In Powder Metallurgical (PM) route of fuel fabrication, trials were taken by doping various oxide powder additives like TiO{sub 2}, Al{sub 2}O{sub 3}, SiO{sub 2}, Nb{sub 2}O{sub 5} and Cr{sub 2}O{sub 3}. The dopant normally goes into the solid solution of parent matrix during sintering at 1700 {sup o}C and thus enhance the rate of diffusion. Aliovalant dopant can alter the defect chemistry of the parent material either by creating vacancy or interstitial. It is apparently understood that the combination of above mechanisms are responsible for structural modification of UO{sub 2}. Hence selection of dopant remains largely empirical. It has been observed at NFC Hyderabad that the Cr{sub 2}O{sub 3} is the most suitable for achieving average UO{sub 2} grain size of about 70 micron and 98%TD of the sintered pellet. The paper discusses about the various experimental trials, sintered densities, metallographic examination, effect of different quantities, analysis and result obtained thereof. (author)

Bioactive glass-reinforced bioceramic ink writing scaffolds: sintering, microstructure and mechanical behavior.

Science.gov (United States)

Shao, Huifeng; Yang, Xianyan; He, Yong; Fu, Jianzhong; Liu, Limin; Ma, Liang; Zhang, Lei; Yang, Guojing; Gao, Changyou; Gou, Zhongru

2015-09-10

The densification of pore struts in bioceramic scaffolds is important for structure stability and strength reliability. An advantage of ceramic ink writing is the precise control over the microstructure and macroarchitecture. However, the use of organic binder in such ink writing process would heavily affect the densification of ceramic struts and sacrifice the mechanical strength of porous scaffolds after sintering. This study presents a low-melt-point bioactive glass (BG)-assisted sintering strategy to overcome the main limitations of direct ink writing (extrusion-based three-dimensional printing) and to produce high-strength calcium silicate (CSi) bioceramic scaffolds. The 1% BG-added CSi (CSi-BG1) scaffolds with rectangular pore morphology sintered at 1080 °C have a very small BG content, readily induce apatite formation, and show appreciable linear shrinkage (∼21%), which is consistent with the composite scaffolds with less or more BG contents sintered at either the same or a higher temperature. These CSi-BG1 scaffolds also possess a high elastic modulus (∼350 MPa) and appreciable compressive strength (∼48 MPa), and show significant strength enhancement after exposure to simulated body fluid-a performance markedly superior to those of pure CSi scaffolds. Particularly, the honeycomb-pore CSi-BG1 scaffolds show markedly higher compressive strength (∼88 MPa) than the scaffolds with rectangular, parallelogram, and Archimedean chord pore structures. It is suggested that this approach can potentially facilitate the translation of ceramic ink writing and BG-assisted sintering of bioceramic scaffold technologies to the in situ bone repair.

Laser sintering of doped strontium aluminate via modified sol-gel for use as a ceramic pigment

International Nuclear Information System (INIS)

Soares, F.M. dos S.; Valerio, M.E.G.

2017-01-01

Powder of Dy"3"+ co-doped SrAl_2O_4 :Eu"3"+ was produced via proteic sol-gel method, a modified sol-gel route which allows the formation of oxides at lower temperatures than other methods. CO_2 laser sintering was used as a method for heat treatment, effective in reducing trivalent europium ions in doped samples. Thermal analysis of the precursors, performed by TG and DTA, revealed that the crystallization of SrAl_2O_4 phase occurred at approximately 1060 °C. X-ray diffraction showed that the samples, before and after sintering, had monoclinic and hexagonal phases formation. DLS technique revealed the presence of nanosized and micrometric particles, and particle agglomerates, confirmed by SEM images. Micrographs of the fracture surface of a sintered pellet revealed a high degree of densification caused by heat treatment. Photoluminescence measurements showed that the samples after synthesis and before heat treatment with laser had reddish emission, composed of characteristic narrow emission lines from Eu"3"+ and more intense emission when the samples were excited at 265 nm. The laser treatment promoted the reduction of Eu"3"+ to Eu"2"+ and this effect was confirmed by the presence of a wide emission band in the green region of the spectrum with a maximum emission obtained after excitation at 350 nm. The luminescent decay time of the thermally treated sample was approximately 100 min. Via XRF measurements of acquired frit and DTA and TG of the frit, pigment and mixtures of both, it was noticed good compatibility in terms of thermal processes, that indicated that the pigment has a potential to be used in ceramic tiles. (author)

Development of 2024 AA-Yttrium composites by Spark Plasma Sintering

Science.gov (United States)

Vidyasagar, CH S.; Karunakar, D. B.

2018-04-01

The method of fabrication of MMNCs is quite a challenge, which includes advanced processing techniques like Spark Plasma Sintering (SPS), etc. The objective of the present work is to fabricate aluminium based MMNCs with the addition of small amounts of yttrium using Spark Plasma Sintering and to evaluate their mechanical and microstructure properties. Samples of 2024 AA with yttrium ranging from 0.1% to 0.5 wt% are fabricated by Spark Plasma Sintering (SPS). Hardness of the samples is determined using Vickers hardness testing machine. The metallurgical characterization of the samples is evaluated by Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FE-SEM). Unreinforced 2024 AA sample is also fabricated as a benchmark to compare its properties with those of the composite developed. It is found that the yttrium addition increases the above mentioned properties by altering the precipitation kinetics and intermetallic formation to some extent and then decreases gradually when yttrium wt% increases beyond 0.3 wt%. High density (˂ 99.75) is achieved in the samples and highest hardness achieved is 114 Hv, fabricated by spark plasma sintering and uniform distribution of yttrium is observed.

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

Science.gov (United States)

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

2017-12-01

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

Design and Fabrication of an Experimental Microheater Array Powder Sintering Printer

Science.gov (United States)

Holt, Nicholas; Zhou, Wenchao

2018-03-01

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. For MAPS to work effectively, a microscale air gap needs to be maintained between the heater array and the conductive ink. In this article, we present an experimental MAPS printer with air gap control for printing conductive circuits. First, we discuss design aspects necessary to implement MAPS. An analysis is performed to validate that the design can maintain the desired air gap between the microheaters and the sintering layer, which consists of a silver nanoparticle ink. The printer is tested by printing conductive lines on a flexible plastic substrate with silver nanoparticle ink. Results show MAPS performs on par with or better than the existing fabrication methods for printed electronics in terms of both the print quality (conductivity of the printed line) and print speed, which shows MAPS' great promise as a competitive new method for digital production of printed electronics.

High-Pressure Spark Plasma Sintering (HP SPS): A Promising and Reliable Method for Preparing Ti-Al-Si Alloys.

Science.gov (United States)

Knaislová, Anna; Novák, Pavel; Cygan, Sławomir; Jaworska, Lucyna; Cabibbo, Marcello

2017-04-27

Ti-Al-Si alloys are prospective material for high-temperature applications. Due to low density, good mechanical properties, and oxidation resistance, these intermetallic alloys can be used in the aerospace and automobile industries. Ti-Al-Si alloys were prepared by powder metallurgy using reactive sintering, milling, and spark plasma sintering. One of the novel SPS techniques is high-pressure spark plasma sintering (HP SPS), which was tested in this work and applied to a Ti-10Al-20Si intermetallic alloy using a pressure of 6 GPa and temperatures ranging from 1318 K (1045 °C) to 1597 K (1324 °C). The low-porosity consolidated samples consist of Ti₅Si₃ silicides in an aluminide (TiAl) matrix. The hardness varied between 720 and 892 HV 5.

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-01

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Effect of different sintering aids on thermo-mechanical properties and oxidation of SiC fibers - Reinforced ZrB{sub 2} composites

Energy Technology Data Exchange (ETDEWEB)

Sciti, D., E-mail: diletta.sciti@istec.cnr.it [ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council, Via Granarolo 64, I-48018 Faenza (Italy); Silvestroni, L. [ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council, Via Granarolo 64, I-48018 Faenza (Italy); Saccone, G.; Alfano, D. [CIRA, Italian Aerospace Research Center, 81043 Capua (Italy)

2013-01-15

Reinforced zirconium diboride composites containing 15 vol% of Hi Nicalon SiC chopped fibers were hot pressed with addition of various sintering additives, Si{sub 3}N{sub 4}, ZrSi{sub 2} or MoSi{sub 2}. Depending on the sintering aid, different densification temperatures were set in the range 1650-1750 Degree-Sign C. Temperature and additive strongly influenced the matrix/fiber interface, which in turn had a strong impact on the mechanical properties and the oxidation behavior at 1650 Degree-Sign C. Even the workability, performed either by conventional machining or electro discharge machining, varied depending on the sintering additive and the secondary phases formed in the system. The system containing Si{sub 3}N{sub 4} turned out to have the highest mechanical properties, but intermediate oxidation resistance; the composite containing ZrSi{sub 2} had the lowest sintering temperature, but displayed the worst oxidation resistance, and finally the composite containing MoSi{sub 2} showed intermediate mechanical properties, but the highest oxidation resistance and lowest degree of damage upon machining. Preliminary measurements of thermal shock resistance by the water quenching method were also carried out. -- Highlights: Black-Right-Pointing-Pointer We produced SiC fibers reinforced ZrB{sub 2} using different sintering aids. Black-Right-Pointing-Pointer The sintering additives affected properties, oxidation and machinability. Black-Right-Pointing-Pointer The system containing Si{sub 3}N{sub 4} had the highest mechanical properties. Black-Right-Pointing-Pointer The composite containing MoSi{sub 2} had the highest oxidation resistance. Black-Right-Pointing-Pointer ZrB{sub 2}-SiC fibers have higher thermal shock resistance than ZrB{sub 2}-SiC particles.

Methods of producing transportation fuel

Science.gov (United States)

Nair, Vijay [Katy, TX; Roes, Augustinus Wilhelmus Maria [Houston, TX; Cherrillo, Ralph Anthony [Houston, TX; Bauldreay, Joanna M [Chester, GB

2011-12-27

Systems, methods, and heaters for treating a subsurface formation are described herein. At least one method for producing transportation fuel is described herein. The method for producing transportation fuel may include providing formation fluid having a boiling range distribution between -5.degree. C. and 350.degree. C. from a subsurface in situ heat treatment process to a subsurface treatment facility. A liquid stream may be separated from the formation fluid. The separated liquid stream may be hydrotreated and then distilled to produce a distilled stream having a boiling range distribution between 150.degree. C. and 350.degree. C. The distilled liquid stream may be combined with one or more additives to produce transportation fuel.

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

Science.gov (United States)

Diaz-Cano, Andres

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

Anisotropy of the ferromagnetic L10 phase in the Mn-Al-C alloys induced by high-pressure spark plasma sintering

Science.gov (United States)

Tyrman, Muriel; Ahmim, Smail; Pasko, Alexandre; Etgens, Victor; Mazaleyrat, Frédéric; Quetel-Weben, Simon; Perrière, Loïc; Guillot, Ivan

2018-05-01

The metastable τ-phase of MnAl equi-atomic compound belongs to a family of ferromagnetic alloys with L10 crystal structure. Stabilization of the phase by adding 2 at. % using manganese carbide (Mn23C6) enhances the magnetization in relation with the increase in lattice volume. It is thus a promising candidate for rare-earth-free permanent magnets. Coercivity of Mn-Al-C alloys being still weak, there is an interest to see to which extend sintering/transformation of the ɛ-phase by Spark Plasma Sintering (SPS) can increase the coercivity and the anisotropy. The structural and the magnetic properties were studied for samples sintered at 550 °C under uniaxial pressure of 100, 200, 300 and 400 MPa. Coercivity, remanence and anistotropy appears with the sintering pressure. The high pressure applied while sintering produces preferential orientation of the flake-shaped grains which influences the remanence.

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.

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.

Study of Thermal Fatigue Resistance of a Composite Coating Made by a Vacuum Fusion Sintering Method

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Thermal fatigue behavior of a Ni-base alloy chromium carbide composite coating made by a vacuum fusion sintering method are discussed. Results show that thermal fatigue behavior is associated with cyclic upper temperature and coating thickness. As the thickness of the coating decreases, the thermal fatigue resistance increases. The thermal fatigue resistance cuts down with the thermal cyclic upper temperature rising. The crack growth rate decreases with the increase in cyclic number until crack arrests. Thermal fatigue failure was not found along the interface of the coating/matrix. The tract of thermal fatigue crack cracks along the interfaces of phases.

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

Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability

International Nuclear Information System (INIS)

Bianco, Alessandra; Cacciotti, Ilaria; Lombardi, Mariangela; Montanaro, Laura

2009-01-01

Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. This paper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO 3 ) 2 .4H 2 O and (b) titration of Ca(OH) 2 . The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. Samples were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N 2 adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m 2 /g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO 3 ) 2 .4H 2 O decomposed around 1000 deg. C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH) 2 were thermally stable up to 1200 deg. C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 deg. C Si-substituted hydroxyapatites derived from Ca(OH) 2

A method of producing hydroxymethyfurfural

DEFF Research Database (Denmark)

2011-01-01

The present invention relates to a method of producing 5-hydroxymethylfurfural by dehydration of fructose and/or glucose and/or mannose.......The present invention relates to a method of producing 5-hydroxymethylfurfural by dehydration of fructose and/or glucose and/or mannose....

Densification of LSGM electrolytes using activated microwave sintering

Science.gov (United States)

Kesapragada, S. V.; Bhaduri, S. B.; Bhaduri, S.; Singh, P.

Lanthanum gallate doped with alkaline rare earths (LSGM) powders were densified using an activated microwave sintering process for developing a dense stable electrolyte layer for applications in intermediate temperature-solid oxide fuel cells (IT-SOFCs). Due to heat generation in situ, the process of sintering gets activated with faster kinetics compared to a conventional sintering process. The effect of various microwave process parameters on the microstructure and phase formation was studied. The sintered pellets were characterized using scanning electron microscopy-energy dispersive analysis (SEM-EDAX), and X-ray diffraction (XRD). The density of LSGM pellets microwave sintered at 1350 °C for 20 min is greater than 95% theoretical density with a fine grained microstructure (˜2-3 μm) and without the presence of other phase(s).

The sintering behavior of close-packed spheres

DEFF Research Database (Denmark)

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

2012-01-01

The sintering behavior of close-packed spheres is investigated using a numerical model. The investigated systems are the body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed spheres (hcp). The sintering behavior is found to be ideal, with no grain growth until full dens...... density is reached for all systems. During sintering, the grains change shape from spherical to tetrakaidecahedron, similar to the geometry analyzed by Coble [R.L. Coble, J. Appl. Phys. 32 (1961) 787]....

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-25

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

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)

Influence of metallic additives on manganese ferrites sintering

Science.gov (United States)

Shevelev, S. A.; Luchnikov, P. A.; Yarullina, A. R.

2018-01-01

Influence of cuprum nanopowder additive received by electric explosion on the process of manganese ferrites MgFe2O4 consolidating at thermal sintering was researched by dilatometry method. Cuprum nanopowder at a rate of 5 mass % was added into the original commercial-grade powder of manganese ferrite MgFe2O4. Powder mixture was numerously blended with screening for better blending before pressing. Powder compacts were formed by cold one-axle static pressing. It was proved that introduction of cuprum additive caused shrinkage increase at final heating stage. There was abnormal compact enlarging at sintering in the air at isothermal stage; the specified process was not observed in vacuum. This difference can be explained by changes in conditions of gaseous discharge from volume of pores.

Effects of sintering temperature on the density and porosity

African Journals Online (AJOL)

2013-03-01

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

Sintering characteristics of nano-ceramic coatings

NARCIS (Netherlands)

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

2003-01-01

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

Clean recycle and utilization of hazardous iron-bearing waste in iron ore sintering process.

Science.gov (United States)

Gan, Min; Ji, Zhiyun; Fan, Xiaohui; Chen, Xuling; Zhou, Yang; Wang, Guojing; Tian, Ye; Jiang, Tao

2018-04-18

Applying recycled iron-bearing waste materials (RIM) into iron ore sintering process is the general disposal approach worldwide, while its use is still a thorny problem. Results showed that adding RIM increased contents of hazardous elements (K, Na, Pb, Zn, and Cl) in sinter product, and also enhanced emission concentration of PM 2.5 in flue gas; increasing reaction temperature, and contents of CaO & coke breeze in raw mixtures improved hazardous elements removal. Based on these features, a novel method through granulating natural iron ores and RIM separately and distributing granulated RIM in bottom sintering layers was proposed for clean RIM cycle. When recycling 5% RIM, granulating RIM separately with higher contents of CaO and coke breeze removed hazardous elements effectively, the contents of which in sinter were reduced to comparable level of the case without RIM. Moreover, distributing RIM in bottom sintering layer reached intensive release of hazardous elements and PM 2.5 during sintering, which reduced the flue gas volume needing purification by about 2/3. Through activated carbon purification, about 60% of PM 2.5 comprised high contents of hazardous elements was removed. Novel technique eliminated the negative impact of RIM and has the prospect to reach clean recycle in sinter-making plants. Copyright © 2018. Published by Elsevier B.V.

A new UO2 sintering technology for the recycling of defective fuel pellets

International Nuclear Information System (INIS)

Song, K. W.; Kim, K. S.; Jeong, Y. H.

1998-01-01

A new UO 2 sintering technology to recycle defective UO 2 pellets has been developed. The defective UO 2 pellets were oxidized in an air to produce U 3 O 8 powder, and the U 3 O 8 powder was mixed with fresh AUC-UO 2 powder in the range of 10 to 100 wt%. Nb 2 O 5 and TiO 2 are added to the mixed powder. The mixed powder was pressed and sintered at 1680 deg C for 4 hours in hydrogen. The density of UO 2 pellets without sintering agents decreased linearly with the U 3 O 8 content at the rate of 0.2 %TD per 1 wt% U 3 O 8 , and the density was below 93.5 %TD at the U 3 O 8 contents above 10 wt%. However, the mixed UO 2 and U 3 O 8 powder containing Nb 2 O 5 (≥0.3 wt%) and TiO 2 (≥0.1 wt%) yielded a sintered density above 94 %TD in all ranges of U 3 O 8 contents. It was found that higher mixing ratios of U 3 O 8 to UO 2 powder did not affect the grain size of UO 2 pellets under the addition of Nb 2 O 5 , but decreased the grain size of UO 2 pellets under the addition of TiO 2 . The doped UO 2 pellets have grain sizes larger than 20 μm, and have small density gain after re-sintering test, owing to large pores. Therefore, the sintering agents such as Nb 2 O 5 and TiO 2 can make highly densified UO 2 pellets from the powder comprising a large amount of U 3 O 8 powder

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.

The effects of applied current on one-dimensional interdiffusion between copper and nickel in spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Rudinsky, S.; Gauvin, R.; Brochu, M., E-mail: mathieu.brochu@mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec H3A 0C5 (Canada)

2014-10-21

Spark plasma sintering (SPS) is a powder metallurgy technique that employs the use of fast sintering kinetics to produce final consolidated components in a matter of minutes. In order to use blended powders in SPS to obtain fully alloyed parts, diffusion during sintering must be understood. An investigation into the effects of current on the diffusion of copper and nickel was performed using SPS. Bulk specimens were used to generate diffusion couples in SPS in alternating orientations with respect to the direction of the current. Control samples were produced using a horizontal insertion vacuum furnace. Experiments were performed at temperatures between 850°C and 1000°C for 3 h. Concentration profiles were obtained by the use of both energy-dispersive spectroscopy and a Monte Carlo simulated correction curve. Diffusion coefficients and activation energies were calculated for samples produced by SPS and annealing without current. It was shown that, at temperatures near 0.9 T{sub m}, the application of current in SPS inhibits diffusion between copper and nickel due to the re-orientation of electrons caused by the loss of ferromagnetism in nickel. Activation energy for diffusion is, however, decreased due to the temperature gradients arising from the difference in resistivity between the two species.

Influence of extrusion parameters on sic distribution and properties of AA6061/SiC composites produced by kobo method

Energy Technology Data Exchange (ETDEWEB)

WoĨniak, Jarosáaw; Kostecki, Marek; Broniszewski, Kamil; Olszyna, Andrzej [Faculty of Material Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Bochniak, Wáodzimierz [Faculty of Non-Ferrous Metals, AGH University of Science and Technology, Cracow (Poland)

2013-07-01

The influence of extrusion parameters on reinforcements distribution and properties of AA6061+x% vol. SiC p (x=0; 2.5; 5; 7.5; 10) composites was discussed in this paper The averages size of AA6061 and SiC particles were 10.6 μ m and 0.42 μ m, respectively. The composites were consolidated via powder metallurgy processing (without the sintering) and extruded by KoBo method. The microstructure was examined on each steps of production. High values of density for all produced composites were achieved. Additionally, hardness and Young’s modulus were investigated. The best reinforcement distribution and mechanical properties were obtained for composites extruded with the highest extrusion ratio. Key words: aluminum alloy, extrusion, aged hardening, metal matrix composites, microstructure.

The influence of dislocation defects on the sintering kinetics of ferrite powders

International Nuclear Information System (INIS)

Fadeeva, I.V.; Portnoi, K.V.; Oleinikov, N.N.; Tretyakov, D.Yu.

1976-01-01

In the presented paper are given the results of the X-ray investigations of non-equilibrium defects in powders of nickel-zinc ferrites. The block size, the crystal lattice microdistortions and stacking faults of two types were determined by the method of Fourier's analysis of diffraction line profiles. The influence of similar defects on sintering of ferrite powders was shown. The kinetics data on densification processes occurring during sintering of active powders can adequately be described in terms of the equations which describe reactions in the solid phase, where the interaction limit is on the border of the phases with different geomtery of the border. The correlation between the behaviour of compacts and dislocation defects in powders during sintering is established

Immobilization of Uranium Silicides in Sintered Glass

International Nuclear Information System (INIS)

Mateos, P.; Russo, D.O.; Heredia, A.D.; Sanfilippo, M.

2003-01-01

High activity nuclear spent fuels vitrification by fusion is a well known technology which has industrial scale in France, England, Japan, EEUU. Borosilicates glasses are used in this process.Sintered glasses are an alternative to the immobilization task in which there is also a wide experience around the world.The available technics are: cold pressing and sintering , hot-pressing and hot isostatic pressing.This work compares Borosilicates and Iron silicates sintered glasses behaviour when different ammounts of nuclear simulated waste is added

Influence of sintering temperature on screen printed Cu2ZnSnS4 (CZTS) films

International Nuclear Information System (INIS)

Wang Yu; Huang Yanhua; Lee, Alex Y.S.; Wang Chiou Fu; Gong Hao

2012-01-01

Highlights: ► The influences of sintering temperature on structure and properties of screen printed Cu 2 ZnSnS 4 (CZTS) were investigated. ► It was found that the direct optical band gap increased with increasing the sintering temperature. ► The screen printed CZTS film after sintering at 450 °C had a high photosensitivity (G i − G d )/G d of 14%. ► The hexagonal CuS phase aggregated after sintering at 500 °C and higher temperature. - Abstract: Screen printing is a useful and simple method for coating layers of several solar materials, but care must be taken in preparing stoichiometric CZTS film due to its instability at a high processing temperature and a small chemical potential domain. This paper reports screen printing prepared CZTS films and the influence of sintering temperature on CZTS properties. The thermostability, structural, electronic and optical properties are studied. The direct optical band gap energies of the films vary from 1.39 to 1.60 eV, while the resistivities change from 830 to 6 Ω cm after sintering at different temperatures up to 550 °C. A high photosensitivity of 14% is achieved for the sample sintered at 450 °C. The phenomena observed are also discussed.

Synergistic effect of carbon nanotube as sintering aid and toughening agent in spark plasma sintered molybdenum disilicide-hafnium carbide composite

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, Biswajyoti; Asiq Rahman, O.S.; Sribalaji, M [Materials Science and Engineering, Indian Institute of Technology Patna, Bihta Kanpa Road, Bihta, Patna, Bihar 801103 (India); Bakshi, Srinivasa Rao [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Keshri, Anup Kumar, E-mail: anup@iitp.ac.in [Materials Science and Engineering, Indian Institute of Technology Patna, Bihta Kanpa Road, Bihta, Patna, Bihar 801103 (India)

2016-12-15

Hafnium carbide (HfC) along with sintering aids was consolidated at a relatively lower temperature i.e. 1600 °C (i.e. T=~0.41 T{sub m}) under a uniaxial load of 50 MPa by spark plasma sintering. Two different sintering aids such as molybdenum disilicide (MoSi{sub 2}) and carbon nanotube (CNT) were added to enhance the densification and lower the extent of grain growth in the sintered pellets. Density of the sintered pellet increased from 96.0±0.8% in HfC +5 wt% MoSi{sub 2} (HM) to 99.0±0.5% with the addition of 2 wt% CNT in HfC+5 wt% MoSi{sub 2} (HMC) at sintering temperature of 1600 °C. Further, the extent of grain growth drastically reduced from 204% in HM to 50% in HMC. Analysis of linear shrinkage during densification revealed that CNT addition increased densification rate and decreased the time required to reach the density of 99.0±0.5% at 1600 °C. Increased densification and lower degree of grain growth could be due to the synergistic effect offered by the CNT, which are as follows: (i) Lubrication effect of CNT, (ii) Lower activation energy for grain boundary diffusion (iii) Reduction in liquid phase sintering temperature and (iv) Grain boundary pinning. Fracture toughness of the sintered HM and HMC composite was obtained using indentation technique. By the addition of 2 wt% CNT in HM, drastic increase of 91% in fracture toughness was seen. This significant improvement in fracture toughness was due to the enhanced densification and relatively lower grain size of HMC. Also crack bridging, crack deflection, crack arrest, CNT and graphene sheet pull-out and swording played major role in toughening of HMC pellet.

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

International Nuclear Information System (INIS)

Reau, A.

2008-12-01

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

Subcritical CO{sub 2} sintering of microspheres of different polymeric materials to fabricate scaffolds for tissue engineering

Energy Technology Data Exchange (ETDEWEB)

Bhamidipati, Manjari; Sridharan, BanuPriya [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Scurto, Aaron M. [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS (United States); Detamore, Michael S., E-mail: detamore@ku.edu [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS (United States)

2013-12-01

The aim of this study was to use CO{sub 2} at sub-critical pressures as a tool to sinter 3D, macroporous, microsphere-based scaffolds for bone and cartilage tissue engineering. Porous scaffolds composed of ∼ 200 μm microspheres of either poly(lactic-co-glycolic acid) (PLGA) or polycaprolactone (PCL) were prepared using dense phase CO{sub 2} sintering, which were seeded with rat bone marrow mesenchymal stromal cells (rBMSCs), and exposed to either osteogenic (PLGA, PCL) or chondrogenic (PLGA) conditions for 6 weeks. Under osteogenic conditions, the PLGA constructs produced over an order of magnitude more calcium than the PCL constructs, whereas the PCL constructs had far superior mechanical and structural integrity (125 times stiffer than PLGA constructs) at week 6, along with twice the cell content of the PLGA constructs. Chondrogenic cell performance was limited in PLGA constructs, perhaps as a result of the polymer degradation rate being too high. The current study represents the first long-term culture of CO{sub 2}-sintered microsphere-based scaffolds, and has established important thermodynamic differences in sintering between the selected formulations of PLGA and PCL, with the former requiring adjustment of pressure only, and the latter requiring the adjustment of both pressure and temperature. Based on more straightforward sintering conditions and more favorable cell performance, PLGA may be the material of choice for microspheres in a CO{sub 2} sintering application, although a different PLGA formulation with the encapsulation of growth factors, extracellular matrix-derived nanoparticles, and/or buffers in the microspheres may be advantageous for achieving a more superior cell performance than observed here. - Highlights: • The first long-term culture of CO{sub 2}-sintered microsphere-based scaffolds. • Established important thermodynamic differences between sintering PLGA and PCL. • PCL sintering with CO{sub 2} required manipulation of both

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

Energy Technology Data Exchange (ETDEWEB)

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

2005-07-01

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

Synthesis of dense yttrium-stabilised hafnia pellets for nuclear applications by spark plasma sintering

International Nuclear Information System (INIS)

Tyrpekl, Vaclav; Holzhäuser, Michael; Hein, Herwin; Vigier, Jean-Francois; Somers, Joseph; Svora, Petr

2014-01-01

Graphical abstract: Densification of HfO 2 –Y 2 O 3 micro-beads by Spark Plasma Sintering High density pellets with homogenous distribution of Hf and Y serve as neutron absorbers. - Abstract: Dense yttrium–stabilised hafnia pellets (91.35 wt.% HfO 2 and 8.65 wt.% Y 2 O 3 ) were prepared by spark plasma sintering consolidation of micro-beads synthesised by the “external gelation” sol–gel technique. This technique allows a preparation of HfO 2 –Y 2 O 3 beads with homogenous yttria–hafnia solid solution. A sintering time of 5 min at 1600 °C was sufficient to produce high density pellets (over 90% of the theoretical density) with significant reproducibility. The pellets have been machined in a lathe to the correct dimensions for use as neutron absorbers in an experimental test irradiation in the High Flux Reactor (HFR) in Petten, Holland, in order to investigate the safety of americium based nuclear fuels

Spark Plasma Co-Sintering of Mechanically Milled Tool Steel and High Speed Steel Powders.

Science.gov (United States)

Pellizzari, Massimo; Fedrizzi, Anna; Zadra, Mario

2016-06-16

Hot work tool steel (AISI H13) and high speed steel (AISI M3:2) powders were successfully co-sintered to produce hybrid tool steels that have properties and microstructures that can be modulated for specific applications. To promote co-sintering, which is made difficult by the various densification kinetics of the two steels, the particle sizes and structures were refined by mechanical milling (MM). Near full density samples (>99.5%) showing very fine and homogeneous microstructure were obtained using spark plasma sintering (SPS). The density of the blends (20, 40, 60, 80 wt % H13) was in agreement with the linear rule of mixtures. Their hardness showed a positive deviation, which could be ascribed to the strengthening effect of the secondary particles altering the stress distribution during indentation. A toughening of the M3:2-rich blends could be explained in view of the crack deviation and crack arrest exerted by the H13 particles.

Spark Plasma Co-Sintering of Mechanically Milled Tool Steel and High Speed Steel Powders

Directory of Open Access Journals (Sweden)

Massimo Pellizzari

2016-06-01

Full Text Available Hot work tool steel (AISI H13 and high speed steel (AISI M3:2 powders were successfully co-sintered to produce hybrid tool steels that have properties and microstructures that can be modulated for specific applications. To promote co-sintering, which is made difficult by the various densification kinetics of the two steels, the particle sizes and structures were refined by mechanical milling (MM. Near full density samples (>99.5% showing very fine and homogeneous microstructure were obtained using spark plasma sintering (SPS. The density of the blends (20, 40, 60, 80 wt % H13 was in agreement with the linear rule of mixtures. Their hardness showed a positive deviation, which could be ascribed to the strengthening effect of the secondary particles altering the stress distribution during indentation. A toughening of the M3:2-rich blends could be explained in view of the crack deviation and crack arrest exerted by the H13 particles.

Ash chemistry and sintering, verification of the mechanisms

Energy Technology Data Exchange (ETDEWEB)

Hupa, M; Skrifvars, B J; Backman, R; Lauren, T; Uusikartano, T; Malm, H; Stenstroem, P; Vesterkvist, M [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

1997-10-01

In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). During 1996 the work has focused on identifying bed agglomeration mechanisms and analysing bed agglomerates in both full scale and lab scale FB reactors, as well as comparing how well the compression strength based sintering test can predict bed agglomeration in an FB furnace. (orig.)

Study on factors affecting sintering density of Gd2O3-UO2 pellets

International Nuclear Information System (INIS)

Zhu Shuming; Zou Congpei; Yang Jing; Yang Youqing; Mei Xiaohui

1996-02-01

The sintered density of Gd 2 O 3 -UO 2 burnable poison fuel pellets is an important quality index and is one of main QC items. Therefore, the efforts were made to investigate the factors affecting the sintered density of Gd 2 O 3 -UO 2 , that is, the influences of pre-treatment of Gd 2 O 3 powder, additives, mixing methods and time, sintering atmosphere, sintering temperature and time on the final density of Gd 2 O 3 UO 2 pellets contained 0, 3%, 7% and 10% (mass percentage) Gd 2 O 3 . The results show: the pre-treatment is useful for improving the distribution of Gd 2 O 3 ; the additive of ammonium oxalate will effectively adjust the density of pellets; 1750 degree C is the suitable sintering temperature. The proper process parameters have been obtained, and the Gd 2 O 3 -UO 2 pellets prepared for in-pile irradiation test meet the design requirements for the density (93.5%∼96.5% of T.D.), homogeneity, microstructure, etc. (8 refs., 3 figs., 8 tabs.)

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.

Rapid laser sintering of metal nano-particles inks.

Science.gov (United States)

Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

2016-09-23

Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

Application of spark plasma sintering for fabricating Nd-Fe-B composite

Science.gov (United States)

Sivkov, A. A.; Ivashutenko, A. S.; Lomakina, A. A.

2015-10-01

Constant magnets are applied in such fields as electric equipment and electric generators with fixed rotor. Rare earth metal neodymium is well known as promising material. Production of magnets by sintering three elements (neodymium, iron and boron) is one the most promising methods. But there are difficulties in choosing the right temperature for sintering and further processing. Structure and properties of the product, consisted of rare earth metals, was analyzed. X-ray analysis of the resulting product and the finished constant magnet was performed. Vickers microhardness was obtained.

Phase characterisation in spark plasma sintered TiPt alloy

CSIR Research Space (South Africa)

Chikosha, S

2011-12-01

Full Text Available stream_source_info chikosha_2011.pdf.txt stream_content_type text/plain stream_size 4354 Content-Encoding UTF-8 stream_name chikosha_2011.pdf.txt Content-Type text/plain; charset=UTF-8 PHASE CHARACTERISATION IN SPARK... to form “necks”  Radiant Joule heat and pressure drives “neck” growth and material transfer © CSIR 2006 www.csir.co.za Page 6 Objective  Produce TiPt alloy compacts by Spark plasma sintering (SPS) of equiatomic...

Multiphysics modeling of selective laser sintering/melting

Science.gov (United States)

Ganeriwala, Rishi Kumar

A significant percentage of total global employment is due to the manufacturing industry. However, manufacturing also accounts for nearly 20% of total energy usage in the United States according to the EIA. In fact, manufacturing accounted for 90% of industrial energy consumption and 84% of industry carbon dioxide emissions in 2002. Clearly, advances in manufacturing technology and efficiency are necessary to curb emissions and help society as a whole. Additive manufacturing (AM) refers to a relatively recent group of manufacturing technologies whereby one can 3D print parts, which has the potential to significantly reduce waste, reconfigure the supply chain, and generally disrupt the whole manufacturing industry. Selective laser sintering/melting (SLS/SLM) is one type of AM technology with the distinct advantage of being able to 3D print metals and rapidly produce net shape parts with complicated geometries. In SLS/SLM parts are built up layer-by-layer out of powder particles, which are selectively sintered/melted via a laser. However, in order to produce defect-free parts of sufficient strength, the process parameters (laser power, scan speed, layer thickness, powder size, etc.) must be carefully optimized. Obviously, these process parameters will vary depending on material, part geometry, and desired final part characteristics. Running experiments to optimize these parameters is costly, energy intensive, and extremely material specific. Thus a computational model of this process would be highly valuable. In this work a three dimensional, reduced order, coupled discrete element - finite difference model is presented for simulating the deposition and subsequent laser heating of a layer of powder particles sitting on top of a substrate. Validation is provided and parameter studies are conducted showing the ability of this model to help determine appropriate process parameters and an optimal powder size distribution for a given material. Next, thermal stresses upon

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

Constrained sintering of an air-plasma-sprayed thermal barrier coating

International Nuclear Information System (INIS)

Cocks, A.C.F.; Fleck, N.A.

2010-01-01

A micromechanical model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon a thick superalloy substrate. The coating comprises random splats with intervening penny-shaped cracks. The crack faces make contact at asperities, which progressively sinter in-service by interfacial diffusion, accommodated by bulk creep. Diffusion is driven by the reduction in interfacial energy at the developing contacts and by the local asperity contact stress. At elevated operating temperature, both sintering and creep strains accumulate within the plane of the coating. The sensitivities of sintering rate and microstructure evolution rate to the kinetic parameters and thermodynamic driving forces are explored. It is demonstrated that the sintering response is governed by three independent timescales, as dictated by the material and geometric properties of the coating. Finally, the role of substrate constraint is assessed by comparing the rate of constrained sintering with that for free sintering.

Sol-gel synthesis of lithium metatitanate as tritium breeding material under different sintering conditions

Science.gov (United States)

Lu, Wei; Wang, Jing; Pu, Wenjing; Li, Kaiping; Ma, Shubing; Wang, Weihua

2018-04-01

Lithium metatitanate (Li2TiO3) is a promising tritium breeding material candidate for solid blanket of D-T fusion reactors, due to its high mechanical strength, chemical stability, and tritium release rate. In this paper, Li2TiO3 powder with homogeneous crystal structure is synthesized by sol-gel method. The chemical reactions in gel thermal cracking and sintering process are studied by thermo gravimetric/differential scanning calorimetry (TG-DSC). The relationship between the sintering condition and the particle/grain size is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results show that below 673 K the gel precursor is completely decomposed and Li2TiO3 phase initially forms. The LiTiO2 by-product formed under the reductive atmosphere in muffle furnace, could be oxidized continually to Li2TiO3 at higher sintering temperature (≥1273 K) for longer sintering time (≥10 h). Both grain and particle sizes rely on a linear growth with the increase of sintering time at 1273 K. Over 1473 K, significant agglomerations exist among particles. The optimal sintering condition is selected as 1273 K for 10 h, for the purer Li2TiO3 phase (>99%), smaller grain and particle size.

The pressureless sintering and mechanical properties of AlON ceramic

Energy Technology Data Exchange (ETDEWEB)

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

2011-07-25

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

Spark plasma sintering of tungsten-yttrium oxide composites from chemically synthesized nanopowders and microstructural characterization

International Nuclear Information System (INIS)

Yar, M.A.; Wahlberg, Sverker; Bergqvist, Hans; Salem, H.G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

Nano-crystalline W-1%Y 2 O 3 (wt.%) powder was produced by a modified solution chemical reaction of ammonium paratungstate (APT) and yttrium nitrate. The precursor powder was found to consist of particles of bimodal morphology i.e. large APT-like particles up to 20 μm and rectangular yttrium containing ultrafine plates. After thermal processing tungsten crystals were evolved from W-O-Y plate like particles. spark plasma sintering (SPS) was used to consolidate the powder at 1100 and 1200 deg. C for different holding times in order to optimize the sintering conditions to yield high density but with reduced grain growth. Dispersion of yttrium oxide enhanced the sinterability of W powder with respect to lanthanum oxide. W-1%Y 2 O 3 composites with sub-micron grain size showed improved density and mechanical properties as compared to W-La 2 O 3 composites. Sample sintered in two steps showed improved density, due to longer holding time at lower temperature (900 deg. C) and less grain growth due to shorter holding time at higher temperature i.e. 1 min at 1100 deg. C.

Production of Al2O3–SiC nano-composites by spark plasma sintering

International Nuclear Information System (INIS)

Mansour Razavi; Ali Reza Farajipour; Mohammad Zakeri; Mohammad Reza Rahimipour; Ali Reza Firouzbakht

2017-01-01

In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600°C for 10min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5h. 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 2329MPa, respectively, in Al2O3–20wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale. [es

Recrystallization and embrittlement of sintered tungsten

International Nuclear Information System (INIS)

Bega, N.D.; Babak, A.V.; Uskov, E.I.

1982-01-01

The recrystallization of sintered tungsten with a cellular structure of deformation is studied as related to its embrittlement. It is stated that in case of preliminary recrystallization the sintered tungsten crack resistance does not depend on the testing temperature. The tungsten crack resistance is shown to lower with an increase of the structure tendency to primary recrystallization [ru

Influence of Sintering Temperature on Hardness and Wear Properties of TiN Nano Reinforced SAF 2205

Science.gov (United States)

Oke, S. R.; Ige, O. O.; E Falodun, O.; Obadele, B. A.; Mphalele, M. R.; Olubambi, P. A.

2017-12-01

Conventional duplex stainless steel degrade in wear and mechanical properties at high temperature. Attempts have been made by researchers to solve this problems leading to the dispersion of second phase particles into duplex matrix. Powder metallurgy methods have been used to fabricate dispersion strengthened steels with a challenge of obtaining fully dense composite and grain growth. This could be resolved by appropriate selection of sintering parameters especially temperature. In this research, spark plasma sintering was utilized to fabricate nanostructured duplex stainless steel grade SAF 2205 with 5 wt.% nano TiN addition at different temperatures ranging from 1000 °C to 1200 °C. The effect of sintering temperature on the microstructure, density, hardness and wear of the samples was investigated. The results showed that the densities and grain sizes of the sintered nanocomposites increased with increasing the sintering temperature. The microstructures reveal ferrite and austenite grains with fine precipitates within the ferrite grains. The study of the hardness and wear behaviors, of the samples indicated that the optimum properties were obtained for the sintering temperature of 1150 °C.

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.

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.

Microstructure and phase analysis of Zirconia-ODS (Oxide Dispersion Strengthen) alloy sintered by APS with milling time variation

Science.gov (United States)

Sugeng, Bambang; Bandriyana, B.; Sugeng, Bambang; Salam, Rohmad; Sumariyo; Sujatno, Agus; Dimyati, Arbi

2018-03-01

Investigation on the relationship between the process conditions of milling time and the microstructure on the synthesis of the zirconia-ODS steel alloy has been performed. The elemental composition of the alloy was determined on 20 wt% Cr and zirconia dispersoid of 0.50 wt%. The synthesis was carried out by powder metallurgy method with milling time of 3, 5 and 7 hours, static compression of 20 Ton and sintering process for 4 minutes using the APS (Arc Plasma Sintering) equipment. SEM-EDX and XRD test was carried out to characterize the phase and morphology of the alloy and the effect to the mechanical properties was evaluated by the Vickers Hardness testing. The synthesis produced sample of ODS steel with good dense and very little porous with the Fe-Cr phase that clearly observed in the XRD peak pattern. In addition milling time increased the homogeneously of Fe-Cr phase formulation, enhanced the grain refinement of the structure and increase the hardness of the alloy.

[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.

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

Science.gov (United States)

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

2018-01-01

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

Methods of producing cesium-131

Science.gov (United States)

Meikrantz, David H; Snyder, John R

2012-09-18

Methods of producing cesium-131. The method comprises dissolving at least one non-irradiated barium source in water or a nitric acid solution to produce a barium target solution. The barium target solution is irradiated with neutron radiation to produce cesium-131, which is removed from the barium target solution. The cesium-131 is complexed with a calixarene compound to separate the cesium-131 from the barium target solution. A liquid:liquid extraction device or extraction column is used to separate the cesium-131 from the barium target solution.

Ash chemistry and sintering, verification of the mechanisms

Energy Technology Data Exchange (ETDEWEB)

Hupa, M.; Skrifvars, B.J. [Aabo Akademi, Turku (Finland)

1996-12-01

In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). In one part of study the melting behavior was calculated for ten biomass ashes and compared with lab measurements of sintering tendencies. The comparison showed that the T{sub 15} temperatures, i.e. those temperatures at which the ashes contained 15 % molten phase, correlated fairly well with the temperature at which the sintering measurements detected sintering. This suggests that partial melting can be predicted fairly accurate for some ashes already with the today existing thermodynamic calculation routines. In some cases, however the melting calculations did not correlate with the detected sintering temperatures. In a second part detailed measurements on ash behavior was conducted both in a semi full scale CFB and a lab scale FBC. Ashes and deposits were collected and analyzed in several different ways. These analyses show that the ash chemistry shifts radically when the fuel is shifted. Fuels with silicate based ashes behaved totally different than those with an oxide or salt based ash. The chemistry was also affected by fuel blending. The ultimate goal has been to be able to predict the ash thermal behavior during biomass thermal conversion, using the fuel and ash elemental analyses and a few operational key parameters as the only input data. This goal has not yet today been achieved. (author)

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

Preparation of Ti3Al intermetallic compound by spark plasma sintering

Science.gov (United States)

Ito, Tsutomu; Fukui, Takahiro

2018-04-01

Sintered compacts of single phase Ti3Al intermetallic compound, which have excellent potential as refractory materials, were prepared by spark plasma sintering (SPS). A raw powder of Ti3Al intermetallic compound with an average powder diameter of 176 ± 56 μm was used in this study; this large powder diameter is disadvantageous for sintering because of the small surface area. The samples were prepared at sintering temperatures (Ts) of 1088, 1203, and 1323 K, sintering stresses (σs) of 16, 32, and 48 MPa, and a sintering time (ts) of 10 min. The calculated relative densities based on the apparent density of Ti3Al provided by the supplier were approximately 100% under all sintering conditions. From the experimental results, it was evident that SPS is an effective technique for dense sintering of Ti3Al intermetallic compounds in a short time interval. In this report, the sintering characteristics of Ti3Al intermetallic compacts are briefly discussed and compared with those of pure titanium compacts.