Reduction of Sintering Temperature of Porous Tungsten Skeleton Used for Production of W-Cu Composites by Ultra High Compaction Pressure of Tungsten Powder

2011 ◽  
Vol 264-265 ◽  
pp. 807-812 ◽  
Author(s):  
A. Ghaderi Hamidi ◽  
H. Arabi ◽  
Saeed Rastegari
Keyword(s):  
Sintering Temperature ◽  
Tungsten Powder ◽  
Compaction Pressure ◽  
Green Density ◽  
Optimum Structure ◽  
Cold Isostatic Press ◽  
Copper Melt ◽  
Method Of Production ◽  
Lower Temperature ◽  
Structural Heterogeneities

Production of tungsten-copper composites includes compaction and sintering of tungsten powder, then infiltration of copper melt within the tungsten skeleton. Sintering of tungsten compacts usually requires a temperature range of 1800 to 2200°C. This means, this process not only needs advanced heating equipments and high expenses but also may cause formation of defects such as structural heterogeneities, cracks and distortions. In this research the required sintering temperature was reduced to 1500°C by increasing compaction pressure. Also the relation between compaction pressure applied through a cold isostatic press (CIP), and green density of the compacted tungsten powder was established. In addition, the effect of various pressures on densification of tungsten compacts during sintering at moderate temperature, i.e. 1500°C was studied, and the optimum structure for infiltration was chosen. Then by infiltrating Cu melt into the optimized W-skeleton, composites of W-Cu having a density of 17.2 gr/cm3 were produced. This method of production provides an innovative technique for obtaining a desired density of infiltrable skeleton, sinterable at a lower temperature than the temperatures used for the conventionally packed W-compacts without introducing structural inhomogeneities during sintering. Study of some characteristics of the optimized composite produced by the above technique satisfied the requirements for production of W-Cu composites having all the specifications given for these types of composites produced at higher temperatures than 1500°C.

Research on the Manufacture of some Tungsten-Copper Composite after Vacuum Sintering

2011 ◽  
Vol 672 ◽  
pp. 311-314
Author(s):  
Cristina Ileana Pascu ◽  
Alexandru Stanimir ◽  
Ioan Vida-Simiti
Keyword(s):  
Sintering Temperature ◽  
Tungsten Powder ◽  
Compaction Pressure ◽  
Great Power ◽  
Densification Process ◽  
Vacuum Sintering ◽  
Infiltration Temperature ◽  
High Tension ◽  
Copper Composite ◽  
Electrical Apparatus

The paper presents the results of the experimental research carried out in order to obtain pseudoalloys WNiCu used in electrical industry, for the electrical apparatus of high tension and great power. As a result it was compulsory to study the parameters that influence the densification process and the sintered properties, depending on the grain-size distribution of tungsten powder, compaction pressure and sintering temperature in vacuum. Therefore, it has been studied the influence of these parameters on the density, hardness and microstructures changes for the composites with 78%W-2%Ni-20%Cu, (% wt). The better results were obtained for the value of 1350 0C for the copper infiltration temperature.

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

10.14311/1604 ◽  
2012 ◽  
Vol 52 (4) ◽  
Author(s):  
Mateusz Laska ◽  
Jan Kazior
Keyword(s):  
Sintered Density ◽  
Sintering Temperature ◽  
Compaction Pressure ◽  
Nitrogen Atmosphere ◽  
Chemical Compositions ◽  
Green Density ◽  
Heating And Cooling ◽  
Wide Range ◽  
Different Temperatures ◽  
Metallurgy Industry

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.

scholarly journals Transport and Dielectric Properties of Mechanosynthesized La2/3Cu3Ti4O12 Ceramics

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 313
Author(s):  
Mohamad M. Ahmad ◽  
Hicham Mahfoz Kotb ◽  
Celin Joseph ◽  
Shalendra Kumar ◽  
Adil Alshoaibi
Keyword(s):  
Dielectric Constant ◽  
Sintering Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Boundary Conductivity ◽  
X Ray ◽  
Giant Dielectric ◽  
Mechanochemical Milling ◽  
Giant Dielectric Constant ◽  
Lower Temperature

La2/3Cu3Ti4O12 (LCTO) powder has been synthesized by the mechanochemical milling technique. The pelletized powder was conventionally sintered for 10 h at a temperature range of 975–1025 °C, which is a lower temperature process compared to the standard solid-state reaction. X-ray diffraction analysis revealed a cubic phase for the current LCTO ceramics. The grain size of the sintered ceramics was found to increase from 1.5 ± 0.5 to 2.3 ± 0.5 μm with an increase in sintering temperature from 975 to 1025 °C. The impedance results show that the grain conductivity is more than three orders of magnitude larger than the grain boundary conductivity for LCTO ceramics. All the samples showed a giant dielectric constant (1.7 × 103–3.4 × 103) and dielectric loss (0.09–0.17) at 300 K and 10 kHz. The giant dielectric constant of the current samples was attributed to the effect of internal barrier layer capacitances due to their electrically inhomogeneous structure.

Cu/GDC Cermet Anodes by Sintering via Surface Modification with MgO Sol

2007 ◽  
Vol 544-545 ◽  
pp. 953-956
Author(s):  
Kyoung Ran Han ◽  
Youn Ji Jeong ◽  
Chang Sam Kim ◽  
Hai Won Lee
Keyword(s):  
Surface Modification ◽  
Copper Oxide ◽  
Composite Powder ◽  
Sintering Temperature ◽  
Electronic Conductivity ◽  
Molten Copper ◽  
Uniform Microstructure ◽  
Fabrication Procedure ◽  
Lower Temperature ◽  
Oxide Melts

CuO/GDC composite powder with 50 wt% of CuO was prepared by surface modification of ~60 nm GDC powder with Cu precursors. Since copper oxide melts at lower temperature than GDC sintering temperature, fabrication procedure was modified by inducing infiltration of molten copper oxide via capillary force and then followed by heat treatment at ~1000. Surface modification was carried out with a MgO sol to suppress agglomeration of GDC. Such prepared Cu/GDC cermets showed uniform microstructure and excellent electronic conductivity of ~8500 S/cm for the Cu/GDC cermet and ~10200 S/cm for the modified one at 800.

Densification of Sr-Mg Doped SiAlONs with GPS and SPS

2007 ◽  
Vol 554 ◽  
pp. 95-100 ◽  
Author(s):  
S. Kurama ◽  
Mathias Herrmann
Keyword(s):  
Mechanical Properties ◽  
Sintering Temperature ◽  
Phase 1 ◽  
Densification Process ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Lower Temperature ◽  
The Stability ◽  
Thermal Stability Of ◽  
Mg Doped

At temperature above 1200°C, the thermal stability of α-SiAlON phases has been debated since 1992; however, it has been discussed if any α-SiAlON phase can be formed in Ce, La, Eu and Sr-doped SiAlON systems. In our previous studies it was shown that the use of Mg-Ce and Mg-Sr elements as dopants SiAlON compositions, in which all elements just have very low or no stability in the α-SiAlON structure, would promote the stability of Mg-Ce elements in the α- SiAlON phase [1, 2]. However, in Mg-Sr systems, it was obtained that Mg2+ is predominantly incorporated in α-SiAlON structure whereas Sr2+ mainly remains in the grain boundaries [2]. In this study, by applying spark plasma sintering (SPS) (at 1400-1700°C) and post-sintering thermal heat treatment (at 1500°C for 5 hrs and 1700°C for 2hrs) Mg or Mg-Sr doped SiAlON (50:50 mole ratios) ceramics were prepared. The results were compared with GPS sintered samples data. The effect of sintering temperature on densification process, phase transformation, microstructure and mechanical properties of samples were investigated. The results showed that by using SPS, Sr-Mg doped samples can be sintered at lower temperature (at 1600°C) than at GPS (at 1800°C) and it has no Sr-doped grain boundary phases.

Microstructure Changes of Beta Alumina Sintering at Lower Temperature

2013 ◽  
Vol 456 ◽  
pp. 517-520
Author(s):  
Hua Li ◽  
Jia Chun Lu ◽  
Guang Yu Cheng ◽  
Yang Ni Zhu ◽  
Xin Biao Jiang
Keyword(s):  
Sintering Temperature ◽  
Precursor Powder ◽  
Phase Content ◽  
Microstructure Changes ◽  
Powder Particles ◽  
Lower Temperature ◽  
Beta Alumina

Changes in the microstructure and phase content of beta alumina near the lowest possible β-Al2O3 to β-Al2O3 transform temperature were investigated through varying sintering temperature. Obvious microstructure varieties were observed in stabilized β/β alumina specimens following extended sintering treatments. The results show that there is a slightly lower temperature of 1150°C for nanometer precursor powder particles to transform into grains and for β-Al2O3 to convert into β-Al2O3.

Sintering of Vitrified Bond CBN Grinding Tool

2007 ◽  
Vol 280-283 ◽  
pp. 1391-1394 ◽  
Author(s):  
Zhi Hong Li ◽  
Yong Hong Zhang ◽  
Y.M. Zhu ◽  
Zheng Fang Yang
Keyword(s):  
High Speed ◽  
High Performance ◽  
High Efficiency ◽  
Sintering Temperature ◽  
Cubic Boron Nitride ◽  
Heating Process ◽  
Initial Oxidation ◽  
Grinding Tool ◽  
Vitrified Bond ◽  
Lower Temperature

Cubic boron nitride(CBN) is a superhard materials with many advantages and many uses. Vitrified bond CBN grinding tool is a promising abrasive tool of high performance used for high speed, high efficiency, high precision grinding with lower grinding cost and less environment pollution. Sintering of vitrified bond CBN grinding tool was investigated in this paper. The results showed that practical sintering temperature of this tool was much lower than the initial oxidation temperature of CBN particle measured by comprehensive thermal analysis. The upper limit of sintering temperature should be determined by taking account of the thermal analyzing results, heating process of CBN and its change in strength and structure. Within the sintering temperature range of the vitrified bond, relatively higher sintering temperature was beneficial to the strength of bond bridge and the holding strength between bond and CBN abrasive particles. CBN tool sintered at relatively lower temperature tended to fracture through the bond bridge, while the one sintered at higher temperature tended to fracture along the boundary between CBN abrasive grain and vitrified bond.

HIGH POTENTIAL GRADIENT OF ZnO VARISTORS PREPARED BY Y2O3-DOPING AND LOW-TEMPERATURE SINTERING

2009 ◽  
Vol 23 (25) ◽  
pp. 3013-3022 ◽  
Author(s):  
LEI KE ◽  
DONG-MEI JIANG ◽  
CHUN-XIA WANG ◽  
XUE-MING MA
Keyword(s):  
Low Temperature ◽  
Sintering Temperature ◽  
Early Period ◽  
Potential Gradient ◽  
High Energy ◽  
High Potential ◽  
Low Temperature Sintering ◽  
Experimental Conditions ◽  
Zno Varistors ◽  
Lower Temperature

A high potential gradient of ZnO varistors were fabricated by Y 2 O 3-doping and low-temperature sintering. The value of the potential gradient increased to 2460.5 V/mm with the Y 2 O 3 content of 0.08 mol% and the sintering temperature of 800°C. The effects of Y 2 O 3-doping and sintering temperature on the electrical properties of ZnO varistors were investigated. Under the given experimental conditions, additive Y 2 O 3 exists in the form of Y 2 O 3 phase after sintering at 800°C. High-energy ball-milling in the early period of the experiment induced the grain refinement and realized the sintering formation at the lower temperature of 800°C. Both Y 2 O 3-doping and low-temperature sintering restrained the ZnO grain growth and increased the potential gradient.

Preparation of BaTiO3 by Sol-Gel-Processing

1988 ◽  
Vol 121 ◽  
Author(s):  
G. G. Tomandl ◽  
H. Rösch ◽  
A. Stiegelschmitt
Keyword(s):  
Sintering Temperature ◽  
Sol Gel ◽  
Milling Process ◽  
Special Treatment ◽  
Green Density ◽  
Barium Acetate ◽  
Calcium And Magnesium ◽  
Titanium Ethoxide ◽  
Future Work ◽  
Gel Processing

ABSTRACTBarium acetate, titanium ethoxide, and the acetates of calcium and magnesium and zirconium-n-propoxide as additives, were dissolved in an acetic acid methanol mixture. By adding water, this sol was converted to a gel.Extended investigations of the calcination result in a crystalline barium tita-nate without other titanate phases, with a very small amount of carbonate and a negligible contents of free carbon. Aggregates could not be destroyed totally by the milling process. Therefore, the green density of the green bodies reaches only 60 to 65 %. Thus, a minimum sintering temperature of 1200° C was necessary to obtain a density of at least 95 %. In future work, a special treatment to destroy the aggregates must be developed to lower the sintering temperature.

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