Papers by Author: Zhong Xiang Hu

Abstract: Pb/Ni multilayer coatings, with either Pb or Ni as the top layer, were brush plated on ANSI 304 stainless steel to improve its performance as bipolar plates in polymer electrolyte membrane fuel cells (PEMFC). Surface morphology and cross-sectional microstructure of the coatings were characterized with scanning electron microscope (SEM) and optical microscope, respectively. The corrosion resistance of brush plated coatings in a simulated PEMFC environment was investigated using both three-electrode method and immersion of 300 h. Coating surfaces after the immersion were characterized with energy dispersive X-ray spectrometer (EDS). The results show that the multilayer coatings were smooth, dense, and small in grain size with clear layered structure. In the simulated PEMFC environment, the corrosion of multilayer coatings was mainly uniform corrosion. Coatings with different top layers exhibit different corrosion behaviors. Ni layer was corroded preferentially as the anode while the Pb layer was protected.

Abstract: Brush plated of Cu/Ni multilayer coating from a single sulfate electrolyte was prepared. The influence of applied voltage on the composition of the deposit and deposition rate was investigated to optimize the plating parameters. Wear tests were carried out in ball-on-plate geometry unlubricated. Wear scar morphology was observed using scanning electron microscopy and optical microscopy. It was found that the brush plated multilayer coating was highly dense and free from porosity. The multilayer coating showed less wear than Ni coating brush plated from the same solution. The increase in the wear resistance of the multilayer coating was attributed to lubricating effect of the transform film formed by Cu wear particles.

Abstract: Grinding wheel passivation is an inevitable phenomenon during grinding process. It has important guiding significance for the formulation of grinding technique to unveil the passivation rule and generation mechanism. Taking grinding efficiency as evaluation indicator, the passivation curve of grinding wheel during full passivation period under the constant-force grinding condition is established through experiments in this dissertation, which is divided into three stages according to passivation speeds and passivation patters, i.e. early passivation stage, stable passivation stage and sharp passivation stage. Of which, the passivation speed is the slowest but with the highest grinding efficiency in early passivation stage. The change of passivation curve with the time is a process from concave to convex, which is totally different from the wearing process of grinding wheel in this stage. With combination of experiment conditions and wearing characteristics of grinding wheel, the passivation rule and its generation reasons are discussed deeply. Furthermore the exponential function y = abx is adopted to make fitting for passivation curve based on the scatter plot of stable passivation stage and regression equation is derived through the fitting result of origin thus to testify the correctness of the inference.

Abstract: The compressing piston and cylinder of refrigerating compressor frequently come into failures as anti-wearability for metal material is weak. Engineering ceramics is appreciated by designers thanks to its excellent performances. However, it is difficult to machining material because of high hardness. The FEA modules for displacement and stress distributions of compressing piston and cylinder under declared running conditions are established based on the theories of elasto-plasticity and aerodynamics, which reveal the optimal precision conjugation clearance dependence of pressure distributions regularity between friction couple. Based on the FEA analytical results, the feasibility of replacing metal material with Si3N4 ceramics in the friction couple manufacture is researched. Special clamps have been designed to guarantee the superficial quality as mirror surface and tolerances of form and position, technological procedures are programmed, and with satisfactory machining effect.

Abstract: Based on retrieval for domestic and international literatures about the grinding fluids special for ceramic machining use, this paper put forward a method to enhance the engineering ceramic grinding machining efficiency using the organic grinding fluid added with the long chain alcohol The experiment, performed on the constant force cutter, greatly increased the ceramic grinding efficiency by 2.4 times through the comparative experiment for several normal grinding fluids as well as by adding additives. In addition, this paper conducted the matter structural analysis for the liquid-solid interface using the Raman Spectrum technology and preliminarily discussed the mechanism of this grinding fluid.

Abstract: This paper carries out grinding efficiency experiments on various formulas composed of long carbon chain alcohol and halogenated hydrocarbons with the first principle of grinding fluid as main evaluating index and finds via infrared spectrum testing that the conjugating ways of lubricating films between alcohol-type grinding fluid and ceramics is based on chemical adsorption or hydrogen bonding adsorption and generates alkoxy silane or polyalkoxy silane with perfect anti-friction action under the condition of grinding high temperature. With adding of halogenated hydrocarbons, it can further make grinding fluid with perfect extreme pressure property and improves grinding efficiency. Furthermore, this dissertation firstly introduces heat capacity as analysis means and discusses the influential factors on the removal rate of ceramics materials when using abovementioned grinding fluid. It is shown from the result that the material removal rate when silicon nitride ceramics grinding will increase with the augmentation of heat capacity.