Advanced Materials Research Vol. 619

Abstract: grind-hardening test was performed on 42CrMo steel in the paper. Microstructure of the hardened layer was observed and the wear-resistance of hardened specimens was done too. The results showed that microstructure of the fully hardened layer was mainly composed by lath martensite; microhardness of the hardened layer was above 700HV and the abrasive wear and the adhesive wear properties of hardened layer were 2~9 times than that of the base.

Abstract: In order to improve the strength and wear-resistance of agricultural diesel engine crankshaft, the grinding-hardening experiment of crankshaft material 42CrMo steel was carried out on MM7132 surface grinder. Microstructure of the specimens was observed with SSX-550 scanning electron microscope (SEM) and the abrasion experiment was carried out on ML -100 abrasive wear testing machine. The results showed that the maximum mircrohardness of 42CrMo steel after grind hardening was 850HV and the maximum depth of grind hardening layer was 1.25mm. The hardened layer was fully occupied by lath martensite; a little of martensite and much tempered sorbite appeared in the transitional region. The wear-resistance of the specimens after grind hardening was improved by three times.

Abstract: Gas emission quantity has been affected by several natural factors and development of technology, which is a nonlinear and high-dimension problem. By using least square support vector machine (LSSVM), gas emission quantity in mined- out working face has been calculated, and then it has been compared and analyzed with measurement. Besides, gas emission quantity in pre-mining has been predicted. The results indicate that the higher the prediction accuracy of LSSVM is, the stronger the generalization is.

Abstract: The explosion suppression fire extinguisher is an important component part of fire extinguishing and explosion suppression system of special equipment. Because of particularity and specificity of the place where it is used, the explosion suppression fire extinguisher’s body itself is commonly called the special gas cylinder. The material for special gas cylinder selected and used in the earliest design is mainly the ordinary steel gas cylinders such as the carbon structural steel gas cylinder. Because of the following characteristics: being rich in their resources, the prices are low and the process is simple, they can meet the requirements for the use in many kinds of places, and up to now, there are still used widely. But with the continuous development of special equipment in the fields of land, seas and oceans, aviation and aerospace and so on, the single material for the ordinary steel gas cylinder is unable to meet the special requirements of some special equipment. Therefore, it is necessary to research and manufacture new materials whose performance is different from the performance of steel gas cylinder and replace steel gas cylinder with the new materials, in order to meet the different demand in every field. With the continuous development of materials science of our country, some new materials and new technologies are researched and applied continuously. To design the rational manufacturing process by analyzing and researching the performance and technology of these new materials can meet the new requirements of new type of special equipment for explosion suppression fire extinguisher and improve the protective ability of special equipment.

Abstract: Coal seam mehtane deposit at depth has been paid attention to. With the theory of coal structure, techniques of isothermal high-pressure adsorption and the method of Soxhlet solvent extraction, the behaviors of methane adsorbed by coal sample and its residuals were studied. At the condition of the isothermal and high methane pressure, the results of adsorption experiment show that when the methane pressure is continuously increased, the capability of methane absorbed by Pingdingshan fat coal sample gradually increases, reach to a maximum, then decrease, this phenomenon do not accord with the Langmuir’s model, but the capability of methane absorbed by Jiaozuo anthracite sample and Pingdingshan fat coal’s residuals with tetrahydrofuran gradually increase to a fixed value, and is not changed any longer. Solvent extraction of coal indicate that low molecular weight compounds contained in coal have three modes of occurrence, including free, absorbent and co-soluble mode. We can infer to conclusion: (1) low molecular weight compounds contained in coal affect greatly on the behaviors of methane adsorbed by coal at isothermal high-pressure condition, (2) low molecular weight compounds contained in fat coal is high in content, and the free mode of them are forced to remove and displace the potential space of methane molecule occupancy, the capability of methane absorbed by coal is reduced at condition of methane pressure above certain value. And it is concluded that at fat coal rank, methane content gradually increases, reach to a maximum, then decrease, but at rank of the anthracite, it gradually increases to a fixed value, and is not changed any longer with the increase of buried deepness and confining pressure in coal seam.

Abstract: The diamond thin films was deposited by hot filament CVD method in the Cemented Carbide (YG6) substrate. The surface morphology and quality of the diamond film coating was detected by scanning electron microscopy and Raman spectrometer. The internal stress of the diamond thin films and Cemented Carbide substrate, exerted by load, was calculated by the method of finite element numerical analysis. The analysis result shows that the internal stress of the film is tensile stress. The maximum appear in the blade and the tip place, the stress distribution more evenly in the middle area of the film. The stress is a zonal distribution and reduced gradually from the matrix surface to bottom in the Cemented Carbide, the results of the finite element analysis can provide the reference for the other methods to determin the diamond film stress and improve the stress between the membrane and substrate.

Abstract: In this paper, GaAs PHEMT samples are prepared by the method of molecular beam epitaxy (MBE), The optimal parameters are determined by studying the impact of the barrier layer thickness, spacer layer thickness, Al composition of the barrier layer and the spacer layer , the channel thickness and channel In composition on Ns and μn.

Abstract: In order to investigate the pore characteristics of the different destroyed-types of coals and its effects of coal and gas outburst, this article studyed the low temperature nitrogen adsorption curve, specific surface area, pore volume and its distribution with the method of low-temperature nitrogen adsorption, also studed their changes with the different destroyed-type of coals, and the influences of pore shape and distribution for coal and gas outburst. The results showed that three different destroyed-types of coals have loops, the pore shapes of the coals mainly open-shaped, maybe also contain the flask-shaped. The raw coal has more open-shaped pores, fragmentated coal contains a large number of micropore, the crushed coal richs micropore and mesopore. The crushed coal in the large aperture of the medium relative pressure range mainly has open-shaped pore, then in maller pore size range of low relative pressure mainly has closed pore. With the increasing of destroyed-degree, the porosity increased, the anti-destruction capability reduced, the coal is more easily broken, then the risk of outburst is greater.