环形电镀金刚石线锯研究

环形电镀金刚石线锯是将金刚石磨粒固着于环形钢丝基体上的一种切割工具。使用自制的环形电镀金刚石线锯进行多晶硅的切割试验,阐述了钢丝基体材料的选择,焊接方法,环形电镀金刚石线锯的制作工艺。采用切割工艺参数为:锯丝线速度20～40 m/s,工件进给速度2～10 mm/min,锯丝张紧力60～100 N。试验表明:硅片表面平整光滑,表面粗糙度Ra达到0.328～0.562μm,体现出环形金刚石线锯切割的良好特性。     

含硼聚晶金刚石复合片(B-PDC)的研究

利用国产六面顶压机,在高温高压的条件下,采用黏结剂Co熔渗催化方法合成含硼聚晶金刚石复合片。对加入不同体积分数的含硼金刚石合成的样品进行性能测试,最后对样品的性能测试结果进行讨论分析,并对聚晶金刚石层微观结构做了扫描电镜观察和XRD物相分析。结果表明:样品的抗冲击韧性和耐热性比普通金刚石复合片有显著提高,当添加含硼金刚石微粉体积分数为2a%～3a%时综合性能最好。     

超高频微区感应钎焊中加热温度的影响因素

提出了超高频微区感应钎焊工艺方法.重点分析了导磁体材料、线圈结构以及感应器与工件之间的间隙三个因素对感应加热温度的影响规律,并通过试验研究获得了微区感应钎焊的最佳工艺参数.采用优化的工艺参数进行微区感应钎焊金刚石磨粒试验.结果表明,钎料熔融区域宽度可控制在3 mm以内,钎料对金刚石磨粒浸润良好.扫描电镜(SEM)和X射线能谱仪(EDS)测试结果显示,金刚石与钎料界面附近的C和Cr两种元素存在相互扩散.     

Carbon doped α-Al2O3 coatings grown by chemical vapor deposition

Alumina (Al₂O₃) coatings deposited by chemical vapor deposition (CVD) with different modifications and dopants are widely applied as wear resistant coatings on cemented carbide cutting tools. The aim of this work was to investigate the influence of CH₄ addition on the deposition of α-Al₂O₃ by low-pressure chemical vapor deposition (LPCVD). The coatings were deposited at 1005 °C on a TiN–TiCN base layer using a precursor gas mixture of AlCl₃, CH₄, CO₂, HCl, H₂S, and H₂. Coating characterization was conducted by scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), glancing angle X-ray diffraction (GAXRD), nanoindentation and tribological ball-on-disk tests against Al₂O₃ balls. Additionally, the ball-on-disk wear tracks were investigated by Raman spectroscopy.     

Composition profiles and adhesion evaluation of conductive diamond coatings on dielectric ceramics

Sintered silicon nitride (Si₃N₄) ceramic substrates were investigated as dielectric substrates for the growth of metal-like boron-doped nanocrystalline diamond (NCD) and microcrystalline diamond coatings via the Hot Filament Chemical Vapor Deposition (HFCVD) technique. The structural, electrical and chemical properties of both the ceramic substrates and the diamond coatings may potentiate their applicability in particular in harsh environments and highly demanding situations. Boron doping was achieved via a boron oxide solution in ethanol dragged into the reaction chamber with argon. The coatings were characterized by scanning electron microscopy, UV μ-Raman scattering, X-ray diffraction, time-of-flight secondary ion mass spectroscopy, Brale indentation for adhesion evaluation and two-point contact probe for resistivity measurements. The HFCVD technique led to a maximal growth rate of about 1 μm/h. Several metal-like boron doped diamond coatings were obtained. It was found that at lower substrate temperature, lower system pressure and higher methane concentration, the resistivity of the conducting NCD coatings is about 3 orders of magnitude higher when compared with samples obtained with higher substrate temperature, higher system pressure and lower methane concentration. Nevertheless, for every metal-like boron-doped coating the use of the Si₃N₄ ceramic substrate guaranteed a superior adhesion level.     

Linear antenna microwave plasma CVD deposition of diamond films over large areas

Diamond thin films were grown by linear antenna microwave plasma CVD process over large areas (up to 20 × 10 cm²) from a hydrogen based gas mixture. The influence of the gas composition (H₂, CH₄, CO₂) and total gas pressure (0.1 and 2 mbar) on the film growth is presented. For CH₄/H₂ gas mixtures, the surface crystal size does not show dependence on the methane concentration and total pressure and remains below 50 nm as observed by SEM. Adding CO₂ (up to 10%) significantly improves the growth rate. However, still no significant change of morphology is observed on films grown at 2 mbar. The crucial improvement of the diamond film purity (as detected by Raman spectroscopy) and crystal size is found for deposition at 0.1 mbar. In this case, crystals are as large as 500 nm and the growth rate increases up to 38 nm/h.     

Compressive behavior of MWCNT/epoxy composite mats

Mats of vertically-aligned multiwall carbon nanotubes were grown in an thermal CVD reactor with simultaneous feed of the catalyst and carbon precursors. Mats were soaked into epoxy resin solutions without any prior chemical modification and then cured to produce composite plates of z-axis nano-reinforcement. Direct observations of the epoxy–CNT interactions at the nanoscale revealed that epoxy interacted naturally with the MWCNTs without affecting their physical characteristics, alignment, or the mat’s morphology. The compressive behavior of the pristine and composite mats was consistent with mechanical predictions accounting for an elastic regime followed by elastic instability and compaction. Strong evidence of reinforcement in the MWCNT/epoxy composites was indicated by increased strength, stiffness and toughness values with respect to the as-grown mats and pure polymer. The elastic instability strain of the composites was of the order of 0.4.     

Interfacial reactions and wetting in Al–Mg/oxide ceramic interpenetrating composites made by a pressureless infiltration technique

The present paper considers the microstructures of Al–Mg/oxide ceramic interpenetrating composites made by a pressureless infiltration technique. The composites were produced using an Al–10 wt.% Mg alloy with two oxide ceramic foams, spinel (MgAl₂O₄) and mullite (Al₆Si₂O₁₃), at 915 °C in a flowing N₂ atmosphere. Full infiltration of the aluminium alloy into the ceramic preform has been achieved with good bonding between the metal and ceramic phases. The composites were characterised by a range of techniques and compared with those for alumina from the literature. It has been found that the metal–ceramic interface of the composite consisted of an oxide layer near the ceramic phase and a nitride layer from Mg₃N₂ to AlN near the metal phase. The improvement of Al wetting and adhesion on the oxide ceramics by the addition of Mg and in the presence of N₂ was studied by a sessile drop technique to clarify which compound that formed at the interface contributed to the spontaneous infiltration.     

工业设计产业区域竞争优势比较研究

运用波特钻石模型理论确定影响设计产业竞争优势的关键因素,开发量表并设计问卷,完成珠三角和长三角设计产业竞争优势比较研究。分析显示:两地制造业和国际设计需求相对不足,设计企业经营管理和竞争策略颇为类似,政府设计促进政策实效不佳;但长三角在设计师薪酬、产业配套和发展机遇方面优于珠三角,其产业整体竞争力亦强于珠三角。