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2016 Vol. 26, No. 01
Published: 2016-02-10
1
The development and key technological improvement of synthetic diamond in China
LUO Xi-yu，， XU Yan-jun，， LIU Yi-bo，
DOI: 10.13228/j.boyuan.issn1006-6543.20150071
Synthetic diamond was started in 1963 in China. The evolution data of its output and quality were presented. The output has been successively at the top of the world from 2000 until 2013 and quality has attained the advanced world level. A quality evaluation method revealing the intrinsic quality was also presented， which is the first chemical evaluation method for the absolute content determination of oxygen， nitrogen and other impurity in diamond. The content comparative analysis of representative diamond at home and abroad was made by this way. The testing results are very approached to each other. The achievement in the field of synthetic diamond in China should owe to three major technological improvements： large-sized cubic hinge press， high quality cemented carbide anvil and industrialization of powder catalyst and indirect heating. Technological characteristics and development of the three aspects were elaborated.
2016 Vol. 26 (01): 1-13 [
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Study on oxidation behavior of SiC particles
LI Min，WANG Ai-qin，，XIE Jing-pei，SUN Ya-li
DOI: 10.13228/j.boyuan.issn1006-6543.20150030
The changes of microstructure and elements in SiC particles before and after oxidation were studied； the oxidation weight gain trend and influencing factors were also presented. The results show that， oxidation reaction makes the morphology of SiC particles changed greatly， which has passivation effect on the SiC particles， and makes SiC particles lose sharp edges， tending to be smoother. SiO2 forms on SiC particles surface after oxidation. During the early oxidation stage， the weight of SiC increases with the increasing oxidation temperature and oxidation time， the oxidation rate is mainly controlled by the interfacial chemical reaction rate. During later oxidation stage， the weight of the SiC increases slowly， and the oxidation rate is controlled by the diffusion rate of O2 and CO in the surface oxide film. A simple estimation formula for oxide thickness of SiC particles was proposed.
2016 Vol. 26 (01): 14-19 [
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Research on rheology of feedstock for Ni- Al2O3 powder injection molding
FU Jie，SHANG Feng，，LI Hua-qiang，QIAO Bin，，CAO Zhen-wei，SUN Wei
DOI: 10.13228/j.boyuan.issn1006-6543.20150037
Ni-Al2O3 feedstock with 55% (volume percent) powder loading and diverse content of Ni was prepared in mixing module of HAAKE PolyLab QC torque rheometer. The formulation of binder is 60%PW＋35%LDPE＋5%SA (mass percent). The viscosity of feedstock was measured at MLW-400 capillary rheometer at 130 ℃， 140 ℃， 150 ℃. The value of power law exponent and flow activation energy was calculated through curvefit and regress of MATLAB. The results show that content of Ni has little influence on power law exponent of feedstock， which indicates the formulation of binder is appropriate and feedstock is homogeneous. However， the sensitivity of feedstock for temperature increases with the Ni content increasing. The experimental results provide reference to preparation of Ni-Al2O3 composites using powder injection molding and laid foundation on research of Ni content on properties of Al2O3 ceramic.
2016 Vol. 26 (01): 20-23 [
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24
The preparation of submicron tungstic oxide powder by reduction-oxidation method
WANG Ting
DOI: 10.13228/j.boyuan.issn1006-6543.20150039
Submicron tungsten oxide powder was prepared by reduction-oxidation method. Scanning electron microscope was used to observe the powder morphology， and the particle size distribution was analyzed through laser particle size analyzer. The results show that submicron tungstic oxide powder can be obtained by controlling the reduction-oxidation temperature and holding time.
2016 Vol. 26 (01): 24-27 [
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Study on the preparation of AlN dispersion strengthened 2024 aluminum alloy by in situ synthesis
CAO Hui-qin，GUO Zhi-meng，YE An-ping，LUO Ji
DOI: 10.13228/j.boyuan.issn1006-6543.20150100
Nanoscaled aluminum nitride (AlN) dispersion strengthened 2024 aluminum alloys were prepared using a novel approach in which compacts of Al-Mg-Cu were partially nitrided in flowing nitrogen gas atmosphere. The compacts were subsequently consolidated through sintering and hot extrusion. The microstructure and mechanical properties of the material were preliminarily investigated. Transmission electron microscope and X-ray diffraction pattern reveal that AlN particles form during nitridation of the Al-Mg-Cu compacts. The material exhibits excellent mechanical properties after hot extrusion and heat treatment. The ultimate tensile and yield strength of the extruded samples containing 7.95% (volume percent) AlN with T6 heat treatment are 665 MPa and 553 MPa， respectively.
2016 Vol. 26 (01): 28-31 [
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Effects of CeO2 on the Si precipitation mechanism of SiCp/Al-Si composite
WANG Rong-qi，XIE Jing-pei，WU Wen-jie，WANG Ai-qin
DOI: 10.13228/j.boyuan.issn1006-6543.20150029
SiCp/Al-Si composite with CeO2 addition was fabricated by powder metallurgy. The effect of CeO2 content on microstructure of the composite was investigated. The effects of CeO2 on the Si precipitation mechanism during sintering was also discussed. The results show that CeO2 can effectively refine the average size of precipitated silicon and increase its quantity. The optimum mass percent of CeO2 is 0.6%. Higher or lower CeO2 content will reduce the refining effects. As the heterogeneous nucleation substrate of precipitated silicon， CeO2 can improve the silicon nucleation rate， thus refine the precipitated silicon size and increase its precipitation quantity.
2016 Vol. 26 (01): 32-35 [
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36
Study on sintering process of hastelloy C-276 fiber felt
XU Pei-min，YANG Yan-an，ZHANG Xiao-qing，GUO Liang，HOU Li-qiang
DOI: 10.13228/j.boyuan.issn1006-6543.20150034
Hastelloy C-276 fiber made by bundle-drawing was employed as raw material， and then the fiber felt blank was prepared through shearing fiber， preparing mesh by wet method and superposing mesh. According to orthogonal experiments， the hastelloy C-276 fiber felt samples were prepared by vacuum pressure sintering. The effect of sintering temperature， holding time and pressure on the loss rate of bubble point pressure was studied. The results show that sintering temperature is the most significant factor influencing the loss rate of bubble point pressure. The optimum sintering process for hastelloy C-276 fiber felt is sintering temperature of 1 150 ℃， holding time of 4.5 hours and pressure of 0.8 kPa.
2016 Vol. 26 (01): 36-38 [
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39
Microstructure and properties of Cu-15%Cr2AlC composite prepared by cold-pressing and sintering
SUN Lin，LIU Jin-yun，GUO Yang，JIN Ying-Rong，LU Yun
DOI: 10.13228/j.boyuan.issn1006-6543.20150035
With homemade high purity Cr2AlC ceramic powder as raw material， the Cu-15%Cr2AlC (mass percent) composite material was prepared by cold-pressing and sintering. The effect of pressing pressure， sintering temperature and sintering time on the resistivity， thermal conductivity， friction coefficient， fracture mode and microstructure of the composite was studied. Results show that resistivity and friction coefficient of the composite decrease， and thermal conductivity of the composite increases with the increasing of the pressing pressure and sintering temperature. The resistivity decreases， the friction coefficient decreases firstly and then increases， and the thermal conductivity increases firstly and then decreases with sintering time increasing. The fracture mode of the composite is brittle fracture. With the increasing of sintering temperature and sintering time， solid solution strengthening occurs between Cr2AlC and Cu， which causing lattice constant distortion of Cr2AlC.
2016 Vol. 26 (01): 39-45 [
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Effect of Al2O3 content on friction and wear properties of copper-based powder metallurgy friction materials
WANG Tian-guo，LIANG Qi-chao，QIN Qun
DOI: 10.13228/j.boyuan.issn1006-6543.20150064
The effect of Al2O3 content on friction and wear properties of copper matrix composite prepared by powder metallurgy method was investigated. The results demonstrate that the effects of Al2O3 on the friction and wear performance of the materials are closely related to the friction speed. With increasing of Al2O3 content， hardness and friction coefficient of Cu-based friction materials increase， density decreases and the wear extent decreases firstly and then increases subsequently. When Al2O3 content is 9% (mass percent)， friction coefficient of the material is high and stable， wear rate is the lowest. The friction surface displays a rough morphology with a number of wide scars when the material does not contain Al2O3. The scars decrease and even disappear with increase of Al2O3 content. The dispersed Al2O3 particles can strengthen the surface hardness of the material， causing the wear rate decreasing.
2016 Vol. 26 (01): 46-50 [
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51
Study on the properties of wollastonite fiber -molybdenum disulfide filled polytetrafluoroethylene composites
XU En-en，FAN Hui-li，GUO Zhi-meng，Zhang Le-mei
DOI: 10.13228/j.boyuan.issn1006-6543.20150090
Polytetrafluoroethylene (PTFE) composites filled with wollastonite fiber (WF) and molybdenum?disulfide (MoS2) were prepared through powder metallurgy. The influence of WF content on the tensile strength， hardness， friction and wear properties of the WF- MoS2/PTFE composites were investigated. The friction surface was observed by scanning electron microscope (SEM). The results show that the hardness increases， and the elongation at break reduces about 70% than pure PTFE by filling with the WF and MoS2. Tensile strength of the composite decreases gradually when mass percent of WF is more than 7%. The friction coefficient of the composite increases rapidly and the wear loss further decreases with addition of WF. The investigation of SEM indicates that WF on the friction surface gives priority to the load， the friction between PTFE matrix and dual surface is reduced， thus the wear loss is decreased. MoS2 particles are easy to wear， and its fragment has lubrication effect. PTFE filling with 18% MoS2 and 7% WF (mass percent) has a relative lower friction coefficient and wear loss.
2016 Vol. 26 (01): 51-55 [
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The influence factors analysis of metal catalyst to the activity of Fenton reagent
ZHOU Hong-xing
DOI: 10.13228/j.boyuan.issn1006-6543.20150031
Based on the analysis of Fenton oxidation mechanism， the influence of metal catalyst Fe2+/Fe3+ on activity of?Fenton reagent was studied. The results show that， Fe2+ and Fe3+ both have?catalytic effect on the activity of?Fenton reagent， and Fe2+ has more catalysis than Fe3+. The removal rate of wastewater COD in coking phenol reaches 90.2% (mass percent) with the H2O2 dosage of 12 mmol/L，?reaction temperature of 25 ℃， reaction time of 25 min， and the molar ratio of [Fe2+]/[H2O2] is 1∶10. The activity of Fe2+ and Fe3+ increases with synergistic effect of light， especially ultraviolet ray. The enhancement tendency of Fe3+ is significantly higher than that of Fe2+.
2016 Vol. 26 (01): 56-59 [
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Research progress in preparation methods of TiN hard films
WANG Hong-tao, LI Hong
DOI: 10.13228/j.boyuan.issn1006-6543.20150014
Abstract: TiN hard film has been widely used for its many excellent properties in recent years. Several new preparation methods of TiN were introduced. The preparation mechanism and technological characteristics were also analyzed. Moreover, the development trend of the preparation methods for the TiN hard film was pointed out.
2016 Vol. 26 (01): 60-63 [
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Research development on the phase generation of multi-principal element high-entropy alloys
LI Wen-hu，AI Tao-tao
DOI: 10.13228/j.boyuan.issn1006-6543.20150033
Multi-principal element high-entropy alloy is a new multi alloy which based on the design idea of “multiple high tangle degree”， with high strength， high hardness， good corrosion resistance， high wear resistance and good high temperature thermal stability， etc. The definition and phase generation theory were presented. In addition， the progress in the field of high-entropy alloy in recent years was also summarized.
2016 Vol. 26 (01): 64-67 [
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Problems of production of powder metallurgy DCT automobile synchronizer gear hub and its solutions
GU Wen-jin
DOI: 10.13228/j.boyuan.issn1006-6543.20150093
The powder metallurgy (PM) automobile synchronizer gear hub is starting the trend of replacing steel hub for it can meet the requirements of energy conservation， environmental protection and sustainable development. With the rapid development of automobile industry and the continuous increase proportion of powder metallurgy parts in automobile parts， the PM synchronizer gear hub has more and more market demand， where the synchronizer gear hub gradually transforms from 5 MT to 6 MT， from MT to AMT and DCT. The change of product structure and the higher and higher requirements of technology lead to some technical difficulties in the practical manufacturing， which have restricted the improvement of its quality and producing efficiency. The solutions were proposed to solve the technical difficulties in the practical manufacturing.
2016 Vol. 26 (01): 68-71 [
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