SiC In Water Research Articles

A two-stage approach to Ni-P-SiC coatings and their friction against SiC in water

Inspired by the low friction of self-mated SiC in water, a two-stage technique is proposed to deposit Ni-P-SiC coating with a high particle content to achieve low friction against SiC in water. The process comprises the electrophoretic deposition of SiC particles layer on a mild steel substrate followed by the electroless plating of NiP coating. The effects of SiC content on the surface appearance, phase structure and cohesive strength were studied. Much attention was paid on the friction behavior of the coatings in water. Experiment results show that compared with the traditional electroless plating method, the two-stage technique can enhance the implanted SiC particle content effectively. Notable, with the increasing of SiC content, the friction coefficient decreases correspondingly and the lowest friction coefficient of 0.015 can be achieved for the Ni-P-SiC coatings with the highest SiC particle content. The major surface degradation mode is abrasive wear during running-in then tribochemical wear dominates at the low friction stage.

Effect of double network hydrogel film thickness on the run-in tribological properties of a friction system using DN gel

This study aims to investigate the potential of double network hydrogel (DN gel) in a low friction mechanical system. In this study, the effect of the thickness of DN gel films on the friction property are clarified. An indentation test, contact pressure measurement, and series of friction tests in water using three different thickness (1.5, 3, 6 mm) of DN gel film and a SiC disc were carried out.Friction of DN gel film sliding against SiC in water can be classified into two types as “Friction region I: friction remains substantially unchanged during the test” and “Friction region II: friction decreases due to run-in”. Friction region transition can be related to the Hersey number region, which consists of viscosity of lubricant, sliding speed and apparent contact pressure. Hersey number larger than 1.5 × 10−10 is a necessary condition for friction region II where different lubrication regimes can be found.1.5 and 6 mm thick DN gel films have exhibit super low friction (μ < 0.01) under a wide range of friction conditions as friction region II, and especially 1.5 mm thick DN gel film, super low friction is achieved by twice run-in phenomena.

Platinum-catalyzed hydrolysis etching of SiC in water: A density functional theory study

A comprehensive study of the physicochemical interactions and the reaction mechanism of SiC etching with water by Pt catalysts can reveal key details about the surface treatment and catalytic phenomena at interfaces. Therefore, density functional theory simulations were performed to study the kinetics of Pt-assisted water dissociation and breaking of a Si–C bond compared to the HF-assisted mechanism. These calculations carefully considered the elastic and chemical interaction energies at the Pt–SiC interface, activation barriers of Si–C bond dissociation, and the catalytic role of Pt. It was found that the Pt-catalyzed etching of SiC in water is initiated via hydrolysis reactions that break the topmost Si–C bonds. The activation barrier strongly depends on the elastic and chemical interactions. However, chemical interactions are a dominant factor and mainly contribute to the lowering of the activation barrier, resulting in an increased rate of reaction.

Comparisons of Tribological Properties of Ti(C,N)/SiC in Water and Seawater

Ti(C,N)-based cermets offer good high temperature strength, perfect chemical stability, excellent wear resistance, and relatively better machinability. In the present work, the tribological behaviors of Ti(C,N)/SiC sliding pairs lubricated in water and seawater were evaluated using a ball-on-disk tribometer. The experimental results show that a relatively low friction coefficient (about 0.025) can be obtained when lubricated with artificial seawater at the sliding speed of 200 mm/s, while the friction coefficient is about 0.2 in purified water. The wear surface profiles and the lubricants collected after running-in process for the high and low friction conditions were compared. In addition, the effects of salt molar concentration of the lubricant on the Ti(C,N)/SiC friction properties were investigated. It was found that the smooth and flat surface is the premise to gain the low friction. At the same time, the proper concentration of silica colloid, which is affected by the salt ions, is also an essential one. Moreover, the high sliding speed (200 mm/s) is beneficial to achieve low friction.

Preparation of high solid loading, low viscosity ZrB2–SiC aqueous suspensions using PEI as dispersant

PEI was used as dispersant for ZrB2 and SiC powders in water. The dispersion behavior of ZrB2 and SiC in water was studied by zeta potential measurements, particle size distribution measurements and interparticle interaction calculations. Well-dispersed ZrB2 and SiC aqueous suspensions were obtained using 0.6wt% PEI at pH 6. The rheological behavior of ZrB2–SiC aqueous suspensions was also investigated. Finally, a high solid loading (52vol%), low viscosity (980mPas at 100s−1) ZrB2–SiC aqueous suspension was successfully prepared.

Nanofluid as a coolant for electronic devices (cooling of electronic devices)

Nanofluids are the suspension of ultrafine solid nanoparticles in a base fluid. Nanofluids are expected to be a promising coolant candidate for thermal management system of next generation high heat dissipation electronic systems. Nanofluids are used with different volume fractions. A minichannel heat sink with a 20 × 20 cm bottom is analyzed for SiC-water nanofluid and TiO2-water nanofluid turbulent flow as coolants through hydraulic diameters. The results showed that enhancement in thermal conductivity by dispersed SiC in water at 4% volume fraction was 12.44% and by dispersed TiO2 in water was 9.99% for the same volume fraction. It was found that by using SiC-water nanofluid as a coolant instead of water, an improvement of approximately 7.25%–12.43% could be achieved and by using TiO2-water 7.63%–12.77%. The maximum pumping power by using SiC-water nanofluid at 2 m/s and 4% vol. was 0.28 W and at 6 m/s and 4% volume equal to 5.39 W. By using TiO2-water nanofluid at 2 m/s and 4% vol. it was found to be 0.29 W and 5.64 W at 6 m/s with the same volume of 4%.

154 水中における炭化ケイ素の摩擦摩耗特性に及ぼす温度変化の影響(機素潤滑設計I,一般講演)

154 水中における炭化ケイ素の摩擦摩耗特性に及ぼす温度変化の影響(機素潤滑設計I,一般講演)

Running-in effect on the load-carrying capacity of a water-lubricated SiC thrust bearing

It is known the friction of self-mated SiC in water strongly depends on the roughness of their contact surfaces, and a proper running-in process is the way to obtain low friction by smoothing the contact surfaces of SiC with tribochemical wear. In this paper, the running-in process of surface-contacted SiC (thrust-bearing-type contact) in water is studied experimentally. It is found the maximum running-in load has a large influence on the load-carrying capacity, which is measured as the critical load for the transition from hydrodynamic to mixed lubrication in this research. A multi-step loading running-in method is proposed to increase the load-carrying capacity of SiC thrust bearings working in water. Finally, the running-in process of a laser textured SiC surface is studied, the effect of the pore area ratio on the roughness of the run-in surface is reported, and the mechanism of the effect of micropores is discussed.

Friction and wear properties of CNx/SiC in water lubrication

Amorphous carbon nitride coatings (a-CN x ) were deposited on SiC disk by ion beam assisted deposition (IBAD). The tribological behavior of a-CN x coating sliding against SiC ball in water was investigated and compared with that of SiC/SiC system at room temperature. The influences of testing conditions on friction coefficient and specific wear rate of both kinds of tribopairs were studied. The worn surfaces on disks were observed by scanning electron microscope (SEM). The results indicate that the running-in period of a-CN x /SiC was shorter than that of SiC/SiC system in water. At a sliding velocity of 120 mm/s, the mean steady-state friction coefficients of SiC/SiC (0.096) was higher than that of a-CN x /SiC (0.05), while at 160 mm/s, lower friction coefficient (0.01) was obtained for SiC/SiC in water. With an increment of normal load, the mean steady-state friction coefficients after running-in first decreased, reaching a minimum value, and then increased. For self-mated SiC, the specific wear rate of SiC ball was a little higher than that of SiC disk, while for a-CN x /SiC, the specific wear rate of SiC ball were 10 times smaller than that of a-CN x coating. Furthermore, the specific wear rate of SiC ball sliding against a-CN x coating was reduced by a factor up to 100~1000 in comparison to that against SiC in water. The wear mechanism of SiC/SiC system in water is related to micro-fracture of ceramic and instability of tribochemical reaction layer. Conversely, wear mechanism for a-CN x /SiC is related to formation and transfer of easy-shear friction layer.

A study on surface polishing of SiC with a tribochemical reaction mechanism

This work investigates the surface polishing of silicon carbide SiC using the tribochemical reaction mechanism. Different metal discs – cast iron, AISI 304 stainless steel, S45C medium carbon steel plated chromium, brass and copper – are used to polish SiC in water and kerosene, respectively. The experimental results show that ferrous metal discs can effectively polish SiC in water. Also, no surface damage or scratches on the polished surface of SiC are observed by this method. The polishing debris was analyzed by electron spectroscopy for chemical analysis. The analyzed results indicate that the polishing surface of SiC is removed tribochemically with the aid of catalytic effect of iron oxide. Moreover, in this process the maximum material removal rate is about 0.06 μm/h.

Bulk Homogeneous Uniaxial Stress Arising from Surface Damage of Crystalline Silicon and Germanium

Abrasion of two opposing surfaces of either crystalline Si or Ge produces a compressive, homogeneous, uniaxial stress extending throughout the bulk perpendicular to the surfaces. This is concluded by analyzing the splittings, intensities, and polarizations of the sharp Lyman absorption lines of bulk shallow impurities in the abraded materials. This effect so far has been observed for samples of thickness, t, from 0.4 to 5 mm for Si ground with water slurries of SiC or alumina with optical faces coplanar with {100} and {111} planes while {100}, {110}, {111}, and {112} planes of Ge have been abraded with SiC in water and examined over the range 0.8 ≤ t ≤ 3.0 mm. For both materials, the internal stress is found to be inversely proportional to t. Controlled etching indicates the damaged layers producing the bulk stress to be &lt; 0.5 μm thick.

The Lubrication Effect of Micro-Pits on Parallel Sliding Faces of SiC in Water

Silicon carbide is regarded as a promising material for sliding bearings and mechanical seals working in water. In order to improve its load carrying capacity (or anti-seizure ability) in water, micro-pits were formed on one of the contact surfaces by ion reaction etching. The effect of micro-pits on the critical load for the transition from EHL to mixed lubrication was studied experimentally in the cases of bearing type contact (with relatively rich water supply) and seal type contact (with relatively poor water supply). In order to understand the mechanisms of the lubrication effect of micro-pits, the experimental results obtained from bearing type contact and seal type contact were compared, and a theoretical analysis was carried out. Presented at the 57th Annual Meeting Houston, Texas May 19–23, 2002

Excimer laser assisted chemical machining of SiC ceramic

A highly effective method of machining ceramic has been newly developed using a krypton fluoride (KrF) excimer laser with a 248 nm wavelength. The laser was irradiated on SiC in water to form a soft hydrous oxide layer by photochemical reaction. The softened layer was then cut with a diamond tool to form a mirror surface finish. The optimum conditions were found for both high machining rate and better surface integrity of SiC.

Laser Processing of Cast Iron for Enhanced Erosion Resistance

The surfaces of nodular and gray cast iron specimens have been modified by CO2 laser processing for enhanced hardness and erosion resistance. Control of the near-surface microstructure was achieved primarily by controlling resolidification of the laser melted layer through variations in laser beam/target interaction time and beam power density. Typical interaction times and power densities used in this study were 5 msec and 500 kW/cm2. Analysis of the laser melted surface showed a dramatic increase in hardness and a greatly refined microstructure. Depending on the processing parameters, two basic kinds of microstructure can be produced in the laser hardened layer—a feathery microstructure with a very high hardness (up to 1245 HV) and a dendritic microstructure with a metastable, fully austenitic matrix and a lower hardness (600 to 800 HV). Erosion testing was done in a rotating paddle device using slurries of SiO2 or SiC in water. Weight loss and crater profile measurements were used to evaluate the erosion characteristics of the various microstructures. Both ductile and gray cast iron showed marked improvement in erosion resistance after laser processing.