Tribological Properties and Thermal Conductivity of Si3 N4 / Si3N4-BN Alternate Layered Composites

2006 ◽  
Vol 317-318 ◽  
pp. 363-368
Author(s):  
T. Hirao ◽  
Kiyoshi Hirao ◽  
Yukihiko Yamauchi
Keyword(s):  
Thermal Conductivity ◽  
Friction Coefficient ◽  
Tribological Properties ◽  
Hot Pressing ◽  
Layered Composite ◽  
Test Method ◽  
Ring Test ◽  
Layered Composites ◽  
Si3n4 Layer ◽  
Thermal Conductivities

Alternate layered composites of Si3N4 layers and layers of Si3N4 with 20 vol% of hBN (Si3N4-BN layers) were fabricated and their tribological properties and thermal conductivities were evaluated. The layered composites were fabricated by alternate stacking of a monolithic Si3N4 layer and a Si3N4-BN layer in the form of a green sheet, followed by hot-pressing or annealing. For comparison, Si3N4 and Si3N4 with 10% hBN were fabricated by hot-pressing powder mixtures. Tribological properties were evaluated on the side plane of the composites by a block-on-ring test method under a dry sliding condition and thermal conductivities were evaluated. The layered composites were found to have lower friction coefficients and higher wear resistance than to simple composites. Moreover, for the layered composite with an aligned β-Si3N4, the friction coefficient on the plane composed of faceted hexagonal grains was lower. The layered composite with an aligned β-Si3N4 in the Si3N4 layer, fabricated by annealing for 72 h indicated both a low friction coefficient (0.28) and high thermal conductivity (130 W/mK).

Effect of ultrasonic melt treatment on the tribological behavior of 7075 aluminum alloy

2020 ◽  
Vol 62 (12) ◽  
pp. 1243-1250
Author(s):  
Fahri Vatansever ◽  
Alpay Tamer Erturk ◽  
Erol Feyzullahoglu
Keyword(s):  
Surface Roughness ◽  
Aluminum Alloy ◽  
Tribological Properties ◽  
Lower Surface ◽  
Test Method ◽  
Ring Test ◽  
7075 Aluminum Alloy ◽  
Melt Treatment ◽  
Ultrasonic Melt Treatment ◽  
Worn Surfaces

Abstract In this study, the tribological properties of 7075 aluminum alloy produced by ultrasonic melt treatment (UST) are investigated. Tribological properties of untreated and ultrasonically treated samples under dry and lubricated sliding conditions were analyzed experimentally by the block on ring test method. Worn surfaces of untreated and ultrasonically treated samples were scanned by 3D optical profilometer and analyzed to search out wear characteristics in the material. Furthermore, microstructural examinations were conducted to investigate the beneficial effects of UST on the microstructural properties of the alloy using optical and scanning electron microscopy. According to the results obtained, UST refines the α-Al phase of the alloy and disperses precipitates to grain boundaries more uniformly. Also, hardness and density of the alloy increased through the effect of UST. Due to these favorable effects, the wear resistance of the alloy increased and the worn surfaces of the ultrasonically treated samples exhibited lower surface roughness according to 3D surface roughness measurements.

Fabrication, Structure and Properties of Aluminum-Aluminide Layered Composites

1996 ◽  
Vol 434 ◽  
Author(s):  
D. E. Alman
Keyword(s):  
Layered Structure ◽  
Hot Pressing ◽  
Tensile Tests ◽  
Layered Composite ◽  
Structure And Properties ◽  
Layered Composites ◽  
Heat Treated

AbstractThe fabrication of aluminum-aluminide layered composites by reactive bonding of elemental Al and Ni foils was investigated. It was observed that after hot-pressing, thin Ni foils were converted to NiAl. The as-processed Al-NiAl layered structure could be heat-treated to produce an equilibrium Al-Al3Ni layered composite. Tensile tests revealed that composites could be produced that failed in a “tough” manner and were stronger and stiffer than aluminum.

Observation of Thermophysical and Tribological Properties of CNT Reinforced Si3N4

2009 ◽  
Vol 409 ◽  
pp. 354-357 ◽  
Author(s):  
Orsolya Koszor ◽  
Andre Lindemann ◽  
François Davin ◽  
Csaba Balázsi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Silicon Nitride ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Tribological Properties ◽  
Reference Sample ◽  
Si3n4 Ceramic ◽  
Pronounced Difference

Thermophysical and tribological measurements have been performed on carbon nanotube added silicon nitride composites. Higher thermal conductivity values were observed in the case of the sample with CNT than for the reference sample. As was observed from tribological measurements, nanocomposite Si3N4 without carbon nanotubes shows a higher friction coefficient than carbon nanotube - Si3N4. The results of wear study indicate that the Si3N4 ball (used as static partner) was more damaged with MWCNTs addition nanocomposite than with pure Si3N4 ceramic. A pronounced difference was observed in the wear rate: there was a much higher wear for carbon nanotube - Si3N4 than for Si3N4 without MWCNTs.

scholarly journals Graphene as a nanofiller for enhancing the tribological properties and thermal conductivity of base grease

RSC Advances ◽  
2019 ◽  
Vol 9 (72) ◽  
pp. 42481-42488
Author(s):  
Hui Fu ◽  
Guoping Yan ◽  
Meng Li ◽  
Hao Wang ◽  
Yapeng Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Friction Coefficient ◽  
Tribological Properties ◽  
Friction Surface ◽  
Base Grease

The addition of graphene-reinforced grease to the mechanical friction surface can effectively reduce the friction coefficient and accelerate heat transportation.

Determination of the transverse shear stress in layered composites

2020 ◽  
Vol 86 (2) ◽  
pp. 44-53
Author(s):  
Yu. I. Dudarkov ◽  
M. V. Limonin
Keyword(s):  
Shear Stress ◽  
Transverse Shear ◽  
Composite Beam ◽  
Layered Composite ◽  
Equivalent Model ◽  
Shear Stresses ◽  
Transverse Shear Stress ◽  
Layered Composites ◽  
Laminate Composites ◽  
Transverse Shear Stresses

An engineering approach to estimation of the transverse shear stresses in layered composites is developed. The technique is based on the well-known D. I. Zhuravsky equation for shear stresses in an isotropic beam upon transverse bending. In general, application of this equation to a composite beam is incorrect due to the heterogeneity of the composite structure. According to the proposed method, at the first stage of its implementation, a transition to the equivalent model of a homogeneous beam is made, for which the Zhuravsky formula is valid. The transition is carried out by changing the shape of the cross section of the beam, provided that the bending stiffness and generalized elastic modulus remain the same. The calculated shear stresses in the equivalent beam are then converted to the stress values in the original composite beam from the equilibrium condition. The main equations and definitions of the method as well as the analytical equation for estimation of the transverse shear stress in a composite beam are presented. The method is verified by comparing the analytical solution and the results of the numerical solution of the problem by finite element method (FEM). It is shown that laminate stacking sequence has a significant impact both on the character and on the value of the transverse shear stress distribution. The limits of the applicability of the developed technique attributed to the conditions of the validity of the hypothesis of straight normal are considered. It is noted that under this hypothesis the shear stresses do not depend on the layer shear modulus, which explains the absence of this parameter in the obtained equation. The classical theory of laminate composites is based on the similar assumptions, which gives ground to use this equation for an approximate estimation of the transverse shear stresses in in a layered composite package.

Experimental study on the effect of surface texture on tribological properties of nanodiamond films under water lubrication

2021 ◽  
pp. 135065012110334
Author(s):  
Ying Yan ◽  
Xuelin Lei ◽  
Yun He
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Tribological Properties ◽  
Surface Texture ◽  
Diamond Film ◽  
Diamond Films ◽  
Nanocrystalline Diamond ◽  
Water Contact ◽  
Texture Density ◽  
Short Run

The effect of nanoscale surface texture on the frictional and wear performances of nanocrystalline diamond films under water-lubricating conditions were comparatively investigated using a reciprocating ball-on-flat tribometer. Although the untreated nanocrystalline diamond film shows a stable frictional state with an average friction coefficient of 0.26, the subsequent textured films show a beneficial effect on rapidly reducing the friction coefficient, which decreased to a stable value of 0.1. Furthermore, compared with the nanocrystalline diamond coating, the textured films showed a large decreasing rate of the corresponding ball wear rate from 4.16 × 10−3 to 1.15 × 10−3 mm3/N/m. This is due to the fact that the hydrodynamic fluid film composed of water and debris can provide a good lubrication environment, so the entire friction process has reached the state of fluid lubrication. Meanwhile, the surface texture can greatly improve the hydrophilicity of the diamond films, and as the texture density increases, the water contact angle decreases from 94.75° of the nanocrystalline diamond film to 78.5° of the textured films. The proper textured diamond film (NCD90) exhibits superior tribological properties among all tested diamond films, such as short run-in period, low coefficient of friction, and wear rate.

scholarly journals Preparation and Properties of Layered SiC-Graphene Composites for EDM

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2916
Author(s):  
Ondrej Hanzel ◽  
Zoltán Lenčéš ◽  
Peter Tatarko ◽  
Richard Sedlák ◽  
Ivo Dlouhý ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Surface Layer ◽  
Positive Influence ◽  
Layered Composite ◽  
Layered Composites ◽  
Good Adhesion ◽  
Electric Discharge Machining ◽  
Layer Sequence ◽  
The Individual ◽  
Scratch Tests

Three and five-layered silicon carbide-based composites containing 0, 5, and 15 wt.% of graphene nanoplatelets (GNPs) were prepared with the aim to obtain a sufficiently high electrical conductivity in the surface layer suitable for electric discharge machining (EDM). The layer sequence in the asymmetric three-layered composites was SiC/SiC-5GNPs/SiC-15GNPs, while in the symmetric five-layered composite, the order of layers was SiC-15GNPs/SiC-5GNPs/SiC/SiC-5GNPs/SiC-15GNPs. The layered samples were prepared by rapid hot-pressing (RHP) applying various pressures, and it was shown that for the preparation of dense 3- or 5-layered SiC/GNPs composites, at least 30 MPa of the applied load was required during sintering. The electrical conductivity of 3-layered and 5-layered composites increased significantly with increasing sintering pressure when measured on the SiC surface layer containing 15 wt.% of GNPs. The increasing GNPs content had a positive influence on the electrical conductivity of individual layers, while their instrumented hardness and elastic modulus decreased. The scratch tests confirmed that the materials consisted of well-defined layers with straight interfaces without any delamination, which suggests good adhesion between the individual layers.

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