Fe3O4-10-HCPT及Fe3O4-HCPT@SiO2核壳纳米粒子的制备

为有效控制磁性四氧化三铁纳米粒子在水介质中的分散,防止其聚集.通过控制Na Cl溶液的物质的量浓度,对比研究磁性四氧化三铁纳米粒子在超声前和超声后在盐中的分散情况.实验结果表明,磁性四氧化三铁纳米粒子在0.4 mol/L的氯化钠中分散性最好,聚集度较小;进一步为了制备粒径均匀的复合磁性纳米载药粒子,通过调节10-羟基喜树碱溶液的p H,将10-羟基喜树碱和磁性纳米粒子制备成复合纳米粒子,并将其用二氧化硅包覆制备了复合载药纳米粒子,其复合纳米粒子的粒径大约为120 nm,结果显示通过该方法成功制备了理想的磁性纳米载药粒子.     

超重型切削过程硬质合金刀具高温力学特性

超重型切削过程中,刀具的高温失效是硬质合金刀具破损的主要形式之一。首先,通过理论分析、切削仿真及数学模型进行切削热产生过程分析,并研究切削温度对硬质合金刀具变形抗力的影响;然后,进行切削温度及材料高温硬度测量实验,实验结果验证模型有效,硬质合金和工件材料试块的硬度在1000℃时分别下降了28%和60%左右;最后,从刀具几何结构优化设计和复合涂层技术两方面提出超重型切削专用硬质合金刀具抗高温性能的提效措施,在5组切削参数下进行刀具寿命对比实验,优化设计的XF8刀具寿命是YT15刀具的2~5倍。研究结果可以为重型高效切削刀具技术的研究及推广提供借鉴。     

Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons

The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.     

光电探测器薄膜生长条件及机理分析

将苝四甲酸二酐（3,4,9,10-perlenetetracrboxylic dianhydride,PTCDA）真空蒸发到无机半导体p-Si衬底上,研制的p-Si/PTCDA异质结光电探测器,对光照非常敏感,是一种响应度很高的宽带光电子元器件。讨论分析了不同的衬底制备条件制备p-Si/PTCDA异质结薄膜的情况,实验结果表明,制备过程中细微的环境变化,显著影响了器件质量,通过分析成膜质量与器件内部微观机制、能带结构、载流子输运之间的关系,确定制备异质结有机薄膜的硅晶面选择,以及衬底的温度最佳的选择范围。     

10kV配电线路杆塔接地装置冲击特性研究

分析10kV配电线路杆塔接地装置的冲击接地电阻特性对于提高配网的供电可靠性起着十分重要的作用。本文采用了考虑土壤火花放电的时域传输线优化模型计算接地装置计算分段导体的电气参数,并建立PSCAD仿真土壤火花效应的等效计算模型：通过对10kV配电线路的水平一垂直型和方格放射型两种常见的接地装置在经过雷电流时．冲击电阻随土壤电阻率,雷电流幅值以及接地装置埋深大小变化的关系,提出在10kV配电线路中根据地质条件、雷电参数和技术经济要求选择合适的接地装置。     

钎焊温度对SiC/YG8接头微观组织的影响

在保温时间为5min、钎焊温度为940~990℃条件下,采用CuMnNi钎料钎焊SiC陶瓷与YG8硬质合金.利用金相显微镜、扫描电镜和能谱仪对接头的微观组织进行分析,研究钎焊温度对接头微观组织的影响.结果表明:在靠近SiC一侧生成一层带状反应层,主要由Cu基固溶体、硅化物、碳和碳化物组成;焊缝主要由基底Cu基固溶体以及Mn、Si、Co、Cu、Ni元素形成的化合物组成.随着钎焊温度的增加,焊缝的宽度减少,焊缝中心的Cu基固溶体基底减少,而化合物相增多.     

高温-超压-高CO2背景下致密砂岩储层成岩作用特征——以莺歌海盆地LD10区新近系梅山组-黄流组为例

利用薄片鉴定、扫描电镜、阴极发光及碳氧同位素分析等手段,对莺歌海盆地LD10区新近系梅山组-黄流组高温-超压-高CO₂背景下的储层成岩作用特征及其对孔隙的影响进行了系统研究。研究结果表明: ①莺歌海盆地LD10区新近系梅山组-黄流组储层发育重力流沉积,岩性以中-细粒长石岩屑石英砂岩为主,储层物性以特低-低孔、特低渗特征为主。②压实、胶结和溶蚀作用是研究区主要的成岩作用类型。超压对黏土矿物的转化及石英次生加大具有明显抑制作用,并在一定程度上保护了原生孔隙。富含CO₂的高温流体不仅造成了黏土矿物的异常转化,同时促进了溶蚀作用发生,增加了次生孔隙。③研究区黄二段储层的成岩演化序列为: 菱铁矿胶结→石英次生加大→绿泥石胶结→长石淋滤溶蚀→高岭石形成→早期方解石胶结→早期白云石胶结→长石溶蚀→方解石溶蚀→伊利石大量生成→晚期铁方解石、铁白云石形成。④总体上,压实作用使孔隙度减少了45.30%～62.93%,胶结作用使孔隙度减少了1.65%～35.01%,溶蚀作用使孔隙度增加了0.72%～8.00%。其中,黄流组中下部砂岩储层受到了超压保护和CO₂溶蚀作用的双重影响,物性较好,钻井过程中应考虑高CO₂风险。     

Phase evolution,crystal structure,and microwave dielectric properties of gillespite-type ceramics

A gillespite-structured MCuSi₄O₁₀ (M = Ba_1-xSr_x, Sr_1-xCa_x) ceramics with tetrahedral structure (P4/ncc) were prepared by solid-state reaction method. X-ray diffraction and thermogravimetry with differential scanning calorimetry (TG-DSC) were employed to study the phase synthesis process of BaCuSi₄O₁₀. Pure BaCuSi₄O₁₀ phase was obtained at 1075°C and decomposed into BaSiO₃, BaCuSi₂O₆, and SiO₂ when calcined at 1200°C. The relationships between the crystal structure and microwave dielectric properties of MCuSi₄O₁₀ ceramics were revealed based on the Rietveld refinement and P-V-L complex chemical bond theory. The dielectric constant (ε_r) decreased linearly with decreasing total bond susceptibility and ionic polarizability. Quality factor (Q × f) was closely dependent on bond strength and lattice energy. The temperature coefficient of resonant frequency (τ_f) was controlled by the stability of [CuO₄]⁶⁻ plane in MCuSi₄O₁₀. Optimum microwave dielectric properties were obtained for SrCuSi₄O₁₀ when sintered at 1100°C for 3 hours with a ε_r of 5.59, a Q × f value of 82 252 GHz, and a τ_f of −41.34 ppm/°C. Thus, SrCuSi₄O₁₀ is a good candidate for millimeter-wave devices.     

Trans-10 18:1 in ruminant meats: A review

Trans (t) fatty acids (TFA) from partially hydrogenated vegetable oils (i.e., industrial trans) have been phased out of foods in many countries due to their promotion of cardiovascular disease. This leaves ruminant-derived foods as the main source of TFA. Unlike industrial TFA where catalytic hydrogenation yields a broad distribution of isomers, ruminant TFA are enzymatically derived and can result in enrichment of specific isomers. Comparisons between industrial and ruminant TFA have often exonerated ruminant TFA due to their lack or at times positive effects on health. At extremes, however, ruminant-sourced foods can have either high levels of t10- or t11-18:1, and when considering enriched sources, t10-18:1 has properties similar to industrial TFA, whereas t11-18:1 can be converted to an isomer of conjugated linoleic acid (cis(c)9,t11-conjugated linoleic acid), both of which have potential positive health effects. Increased t10-18:1 in meat-producing ruminants has not been associated with negative effects on live animal production or meat quality. As such, reducing t10-18:1 has not been of immediate concern to ruminant meat producers, as there have been no economic consequences for its enrichment; nevertheless at high levels, it can compromise the nutritional quality of beef and lamb. In anticipation that regulations regarding TFA may focus more on t10-18:1 in beef and lamb, the present review will cover its production, analysis, biological effects, strategies for manipulation, and regulatory policy.     

Mechanism and prediction of failure of diamond films deposited on various substrates by HFCVD

Diamond films were deposited on the WC-Co cemented carbide and Si3N4 ceramic cutting tool substrates by hot-filament-assisted chemical vapour deposition. The adherence property of diamond films was estimated using the critical load (Pcr) in the indentation test. The adhesive strength of diamond films is related to the intermediate layer between the film and the substrate. Poor adhesion of diamond films to polished cemented carbide substrate is owing to the formation of graphite phase in the interface. The adhesion of diamond films deposited on acid etched cemented carbide substrate is improved, and the peeling-off of the films often happens in the loosen layer of WC particles where the cobalt element is nearly removed. The diamond films' adhesion to cemented carbide substrate whose surface layer is decarbonizated is strengthened dramatically because WC phase forms by reaction between the deposited carbon and tungsten in the surface layer of substrates during the deposition of diamond, which results in chemical combination in the film-substrate interface. The adhesion of diamond films to silicon nitride substrate is the firmest due to the formation of chemical combination of the SiC intermediate layer in the interfaces. In the piston-turning application, the diamond-coated Si3N4 ceramic and the cemented carbide cutting tools usually fail in the form of collapsing of edge and cracking or flaking respectively. They have no built-up edge(BUE) as long as coating is intact.As it wears through, BUE develops and the cutting force on it increases 1 - 3 times than that prior to failure. This can predict the failure of diamond-coated cutting tools.