Retainer-Dependent Wear of Silicon Nitride Bearings at High Temperatures

1994 ◽  
Vol 116 (3) ◽  
pp. 463-469
Author(s):  
Y. Mutoh ◽  
K. Tanaka ◽  
M. Uenohara
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Wear Rate ◽  
High Temperatures ◽  
Carbon Composite ◽  
The Self ◽  
Soft Or ◽  
Bearing Life ◽  
Sintered Alloys

Several retainer materials for high-temperature silicon nitride bearings to be used in air were examined with a high-temperature rolling three-ball tester. The “soft” or “self-lubricating” retainer materials (metal-bonded MoS2-WS2 alloys, a carbon-carbon composite and graphite) tended to yield longer bearing life, lower silicon nitride wear rate and lower traction coefficients than the hard retainers (Fe-based sintered alloys, chromia and silicon nitride). The main problem in the use of the self-lubricating retainer materials was their rapid wear by tribo-oxidation at high temperatures.

Study on the High-Heat Tribological Characteristics of Lubricating Wear-Resisting Coating Prepared by Supersonic Plasma Spraying

2011 ◽  
Vol 80-81 ◽  
pp. 661-666
Author(s):  
Yun Cai Zhao ◽  
Jia Jia Mao ◽  
Chun Ming Deng ◽  
Wem You Ma
Keyword(s):  
High Temperature ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Plasma Spraying ◽  
High Heat ◽  
The Self ◽  
Tribological Characteristics ◽  
Wear Properties ◽  
Abrasive Resistance ◽  
Supersonic Plasma

This paper is about the study of the KF301/WS2composite lubrication wear-resisting coatings prepared by supersonic plasma spraying. Basing on the research of the tribological characteristics, it has been discussed the self-lubricity and the failure mechanism showed by composite lubrication coatings under high-temperature conditions. Research shows that the wear rate of the coatings increased with the increase of the temperature. At 300°C, the wear rate is 1.02×10-4mg/m; At 750°C, the wear rate is 2.61×10-4mg/m. With the increase of temperature, friction coefficient of the coatings shows gradually increasing. When the temperature falls below 600°C, friction coefficient keeps around 0.08; At 750°C, the friction coefficient is 0.12. Temperature has great effect on the friction and wear properties ofthe self-lubricating wear-resisting coatings, mainly manifests in two aspects: first, with the increase of the temperature, under the common influence of thermal stress and frictional contact stress, it promotes the WS2solid lubricant film cracking, breakage, shedding process, and lubrication and abrasive resistance reduces; on the other hand, the WS2occurs chemical reaction under high temperature, generating lubricity phase of NiWO4, CrS, and lubricity phases are well supplied, lubricating film has an effect of continuous lubrication on the rubbing surface, So the coating shows low-friction, and it also represents that the KF-301/ WS2self-lubricating composite coating has good lubrication and abrasive resistance under high temperature．

Pip Processing, Microstructure and Properties of Si34N Fiber and Al2O3 Fiber Reinforced Silicon Nitride

1994 ◽  
Vol 365 ◽  
Author(s):  
Stuart T. Schwab ◽  
Richard A. Page ◽  
David L. Davidson ◽  
Renee C. Graef
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Carbon Composite ◽  
Organic Polymer ◽  
High Temperature Strength ◽  
Fiber Reinforced ◽  
Southwest Research Institute ◽  
Structural Applications ◽  
Al2o3 Fiber ◽  
Manufacturing Techniques

ABSTRACTPolymer infiltration/pyrolysis (PIP) processing has the potential to become an affordable means of manufacturing continuous fiber-reinforced ceramic-matrix components. The PIP method is very similar to the well-known polymer-matrix and carbon-carbon composite manufacturing techniques, the major difference being the use of a preceramic polymer in place of the organic polymer or carbon precursor. To date, the majority of research in the field of preceramic polymers has centered on precursors to silicon carbide (SiC). The Southwest Research Institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si3N4) because its high-temperature strength, resistance to oxidation, and other properties make it an attractive candidate for many advanced high-temperature structural applications. PIP Si3N4 composites with NICALON SiC fiber reinforcement have exhibited good fracture toughness (KIC ∼ 16MPa·m1/ 2). We report here processing, microstructure and preliminary mechanical properties of two new PIP Si3N4 composites. One is reinforced with Tonen Si3N4 fiber (plain weave) while the other is reinforced with ALMAX Al2O3 fiber (8 Harness satin weave).

The self-propagation high-temperature synthesis of ultrafine high purity tungsten powder from scheelite

1996 ◽  
Vol 11 (7) ◽  
pp. 1825-1830 ◽  
Author(s):  
J. C. Jung ◽  
S. G. Ko ◽  
C. W. Won ◽  
S. S. Cho ◽  
B. S. Chun
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
High Purity ◽  
Tungsten Powder ◽  
The Self ◽  
Molar Ratio ◽  
Temperature Synthesis ◽  
Complete Reduction ◽  
High Temperature Synthesis ◽  
Hcl Solution

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of CaO · WO3 and Mg. The complete reduction of CaO · WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/CaO · WO3 of 3: 1. The MgO and CaO in the product were leached with an HCl solution. The product tungsten had a purity of 99.980% which was higher than that of the reactants. The high purity results because the nontungsten reactants and products are volatilized by the high temperatures generated during the rapid exothermic SHS reaction and are dissolved during HCl leaching of the product.

Temperature-Dependent Coefficient of Thermal Expansion of Silicon Nitride Films Used in Microelectromechanical Systems

1999 ◽  
Vol 605 ◽  
Author(s):  
Melissa Bargmann ◽  
Amy Kumpel ◽  
Haruna Tada ◽  
Patricia Nieva ◽  
Paul Zavracky ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Silicon Nitride ◽  
Cantilever Beam ◽  
High Temperatures ◽  
Microelectromechanical Systems ◽  
Coefficient Of Thermal Expansion ◽  
Temperature Dependent ◽  
Temperature Property ◽  
Silicon Nitride Films

AbstractMicroelectromechanical systems (MEMS) have potential application in high temperature environments such as in thermal processing of microelectronics. The MEMS designs require an accurate knowledge of the temperature dependent thermomechanical properties of the materials. Techniques used at room temperature often cannot be used for high-temperature property measurements. MEMS test structures have been developed in conjunction with a novel imaging apparatus designed to measure either the modulus of elasticity or thermal expansion coefficient of thin films at high temperatures. The MEMS test structure is the common bi-layered cantilever beam which undergoes thermally induced deflection at high temperatures. An individual cantilever beam on the order of 100 νm long can be viewed up to approximately 800°C. With image analysis, the curvature of the beam can be determined; and then the difference in coefficient of thermal expansion between the two layers can be determined using numerical modeling. The results of studying silicon nitride films on silicon oxide are presented for a range of temperatures.

Magnesium reduction of WO3 in a self-propagating high-temperature synthesis (SHS) process

1995 ◽  
Vol 10 (4) ◽  
pp. 795-797 ◽  
Author(s):  
Seog Gueon Ko ◽  
Chang Whan Won ◽  
Byong Sun Chun ◽  
H.Y. Sohn
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
High Purity ◽  
Exothermic Reaction ◽  
The Self ◽  
Molar Ratio ◽  
Temperature Synthesis ◽  
Complete Reduction ◽  
High Temperature Synthesis ◽  
Hcl Solution

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of WO3 and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO3 of 3. The product tungsten had a purity of 99.980% which was higher than that of the reactant WO3. This is because the impurities were either volatilized at the high temperatures generated during the rapid exothermic reaction or dissolved into the HCl solution during leaching.

Decoupled electrolytes towards enhanced energy and high temperature performance of thermally regenerative ammonia batteries

2020 ◽  
Vol 8 (25) ◽  
pp. 12351-12360 ◽  
Author(s):  
Weiguang Wang ◽  
Gequn Shu ◽  
Xiuping Zhu ◽  
Hua Tian
Keyword(s):  
Power Generation ◽  
High Temperature ◽  
Energy Density ◽  
High Temperatures ◽  
The Self ◽  
Temperature Performance

An electrolyte decoupling strategy is proposed for ammonia batteries to restrain the self-discharge and enhance energy density as well as power generation at high temperatures.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

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