知识·权力和学术自由

本文对学术自由的合法性依据 ,即“对真理的追求”进行了质疑 ,指出知识还具有权力性特征 ,正是这一特征造成了学术自由与外部权威的紧张关系。学术史就是知识和权力交织、纽结的历史。在学术自由已为各国法律普遍认可之后 ,学术自由的理论和实践层面依然存在着诸多悬而未决的疑难。     

粉末注射成形耐热不锈钢的工艺研究

以元素混合粉为原料,研究了耐热不锈钢的注射成形工艺.重点讨论了烧结温度、时间及气氛对耐热不锈钢致密度、力学性能及微观组织的影响,获得的最佳工艺为烧结温度1375℃,时间60 min,真空气氛.在此条件下制备了致密度98.12%、抗拉强度510 MPa、铁素体组织的PIM耐热不锈钢.     

MICROSTRUCTURE AND PROPERTIES OF C-Cu NANOSTRUCTURE THIN FILM

Nanostructured C-Cu thin films were deposited by reactive sputtering method and co-sputtering method. The relationships between microstructures, properties, and depo-sition parameters were studied and the results obtained from TEM, AFM, and XPS.indicate that the thin films are nanostructural, and have good in-depth uniformity. Theselected area electron diffraction (SAED) found that the nanosize Cu particles havethe fcc structure and the others are amorphous carbon or nanocrystallized graphiticcarbon. The peak positions of the Cu and C in XPS indicate them to be at the ele-mental state. In the IR transmission spectrum, diamond two-phonon absorption andgraphite Raman peaks were observed, which suggests microcrystal diamond particlesand graphite components exist in the C-Cu film. The higher electrical resistivity wasobtained.     

Nd：NaR（WO4）2晶体光谱性能研究（R=Bi，Y）

采用提拉法生长出了掺钕钨酸铋钠（分子式Nd：NaBi（WO4）2，简称Nd：NBW）和掺钕钨酸钇钠（分子式Nd：NaY（WO4）2，简称Nd：NYW）晶体。通过TG-DTA分析得到Nd：NBW的熔点为936．2℃，Nd：NYW的熔点为1209．07℃。由吸收光谱可以看出，Nd：NBW在802nm有较强的吸收峰，Nd：NYW在804nm，752nm，586nm附近有较强、较宽的吸收峰，二者均适合于LD泵浦；并计算了晶体中Nd^＋3＋的吸收截面积。通过比较Nd：NBW和Nd：NYW的红外光谱和拉曼光谱结果，认为二者结构基本相同，为四方晶系、白钨矿结构、141/a空间群。     

Electric and mechanical performances of Bi0.5Sb1.5Te3 prepared by spark plasma sintering

Thermoelectric (TE) materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi2Te3 and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering (SPS) on electric performance of Bi0.5Sb1.5Te3 thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800, the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature (from 300 to 500 ℃) and pressure(from 30 to 60 MPa), and the density and mechanical strength of Bi0.5Sb1.5Te3 thermoelectric material increase, too.     

Understanding the Influence of Copper Nanoparticles on Thermal Characteristics and Microstructural Development of a Tin-Silver Solder

This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification (after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5 °C, while addition of 1.0 wt.% copper nanoparticles lowered the solidification temperature to 217.5 °C, which is close to the melting point of the ternary eutectic Sn-Ag-Cu solder alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and precipitate as the Cu₆Sn₅, which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu₆Sn_5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle surrounded by the Cu₆Sn₅ intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness.     

二辊轧机轧辊堆焊新技术应用

介绍了二辊粗轧机轧辊利用堆焊新技术开展堆焊修复试验与应用，并介绍了堆焊材料的选择、堆焊工艺以及取得的良好效果。     

钼塑性变形抗力数学模型的研究

在Gleeble-1500热模拟试验机上,对钼板进行塑性变形抗力的研究。通过不同的变形温度、应变速率和应变对变形抗力的影响,分析了钼的高温变形特征,并对钼板进行塑性变形抗力的研究,进而采用非线性回归方法建立了钼板的变形抗力模型。通过理论计算与实测值进行对比,证明此模型有较好的线性拟合性。     

A study on the wear behavior of hardened medium carbon steel

It is well known that the mechanical properties such as strength and hardness of structural steel are usually enhanced by the martensite-phase transformation method. In many industrial applications, hardness has always been used as an index to reflect the wear-resistance performance. As a result, steel is quenched to a large extent in order to increase the hardness and wear-resistance performance. In general, from the wear mechanism, no exact relationship between the hardness and wear resistance of materials can be formulated. Also there are few conclusive studies on the effects of running procedures on wear-resistance performance. Therefore, the friction behavior of S45C carbon steel with and without a quenching process was evaluated by a rotating tribometer under various test conditions. The experimental results show that the running conditions cause a great influence on the wear-resistance performance of the materials. Under low speed and light apparent pressure conditions, the quenched specimens have high wear-resistance performance. Contrarily, at high speed and heavy loading, the wear-resistance performance of hardened specimens decreases due to tempering effects at the rubbing surface when the contact temperature becomes increased. Therefore, this causes more severe wear to the hardened specimens than to the unhardened specimens.     

添加剂硫对Ni-Mn-Co粉末触媒合成金刚石的影响

本研究考察了高温高压条件下添加剂硫对Ni-Mn-Co粉末触媒合成金刚石的影响，并在此基础上，考察了含硫金刚石的机械性能。研究表明：硫对Ni70Mn25Co5粉末触媒合成金刚石的成核有明显的抑制作用，随着硫含量的增加，成核呈减少趋势；添加剂硫影响晶体的颜色和晶形，随添加剂含量的增加，晶体的颜色呈加深趋势，硫的添加使晶体的表面出现孔洞缺陷，当硫含量较低时，孔洞缺陷多分布在（100）晶面上，当硫含量较高时，（111）晶面上也出现孔洞，致使晶体的完整性受到制约；添加剂硫影响金刚石的机械性能，随着添加剂硫含量的增加，含硫金刚石的冷冲击强度（TI）和热冲击强度（TTI）呈明显的下降趋势。