Preparation and characterization of 3-mercaptopropyl trimethoxysilane self-assembled monolayers

Silane coupling regent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared on the single-crystal silicon substrate to form 2-dimensional self-assembled monolayers (SAMs). The growth behavior of SAMs formed from 3-MPTS was investigated using atomic force microscopy (AFM), contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy (XPS). The formation behavior of MPTS SAMs was investigated by a series of AFM images and the roughness of MPTS SAMs on silicon sub-strates with the assembling time from 1 min to 24 h. The water contact angle measurements indicated the growth behavior of MPTS that correlated with the AFM measurements at different immersion times, too. The chemical states of the typical elements in the MPTS SAMs were analyzed using X-ray photoelectron spectroscopy. The results show that MPTS is self-assembled on the substrate.     

Microstructure and tribological properties of laser clad Ni-Ag/Tic composite coating

Ni-Ag/TiC composite coating was prepared on the 45 steel substrates by means of laser cladding. Microstructure and wear properties of composite coatings were analyzed using optical microscopy, field emission scanning electron microscopy and wear machine. The experimental results show that defects, such as cracks and pores, do not occur in the laser-cladded Ni-Ag/TiC composite coating and 45 steel substrate, and they present good metallurgical bonding between them. Compared with Ni/TiC composite coating, micro- hardness values of the two coatings do not present evident differences. The wear experiment result shows that Ni-Ag/TiC composite coated with Ag possesses low friction coefficient and good wear resistance compared with Ni/TiC composite coating.     

Friction properties of OTS SAMs and silicon surface under water lubrication

The friction and wear properties of silicon surface covered with octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) were investigated by a UMT-2 microtribometer with and without water as lubricant, and then compared with that of bare silicon surface. Dry friction measurement results show that OTS SAMs have a very low friction coefficient compared to bare silicon surface under lower sliding velocity and normal contact load. However, heavy wear occurs on OTS SAMs under higher contact stress and sliding velocity. Under water lubrication, OTS SAMs can prevent wear obviously and meanwhile present low coefficient of friction even under high velocities. The improved frictional and anti-wear property on OTS SAMs surface is attributed to the hydrophobic property of OTS and hydrodynamic effect of water. Furthermore, a wear critical phase diagram for OTS SAMs with and without water was proposed, which indicates that OTS SAMs working under water lubrication owns a wider range of available load and velocity to reduce friction and prevent wear. Funded by the National Natural Science Foundation of China (Nos. 50575123, 50275071, 50545035) and National Basic Research Program of China (“973” Program) (No. 2003CB716205)     

CFRP主缆与索夹间摩擦学性能试验研究

为研究悬索桥碳纤维增强复合材料(carbon fiber reinforced plastics,CFRP)主缆在索夹处的摩擦学性能,分析主缆与索夹间的摩擦接触特征,引用摩擦因数相关计算公式,分别进行平直接触及实桥接触下的当量摩擦因数试验.结果表明,CFRP主缆与索夹间的摩擦因数约为0.36,能满足抗滑移安全性能设计要求;径向挤压应力小于14.6 MPa时,CFRP丝与索夹的摩擦学性能比较稳定,径向挤压应力大于14.6 MPa时,摩擦因数有减小趋势;两种接触条件下,摩擦因数能较好吻合;理论计算偏于设计安全,适用于CFRP主缆与索夹间摩擦因数的计算.     

Gr/Al-0.7Si-1.2Mg复合材料制备及摩擦性能研究

采用二次热压法制备Gr质量分数为10%~25%的Gr/Al-0.7Si-1.2Mg复合材料,研究了制备工艺对组织结构及其摩擦磨损性能的影响.结果表明,采用较快速率升温的热压法可有效防止石墨铝复合材料制备过程的有害界面反应,得到组织均匀且致密的石墨铝基复合材料.Gr/Al-0.7Si-1.2Mg复合材料的摩擦系数随载荷的增大而降低,在较大载荷时,可形成完整的石墨润滑膜,不同石墨含量的复合材料的磨擦系数趋于一致,达到0.17.石墨含量高的复合材料容易形成润滑层,所以摩擦系数在较低载荷下就能达到最小值.复合材料相对密度对磨损率的影响较大,接近理论密度的复合材料在本研究试验条件下能保持较低的磨损率,最低可达到0.5×10-3~2.1×10-3mm3/m.     

聚醚系非离子表面活性剂结构与性能关系的研究

系统地研究了聚醚系非离子表面活性剂中的疏水基结构、分子量和环氧乙烷与环氧丙烷的比例等对聚醚性能的影响．结果表明：聚醚的疏水基结构对其性能有较大的影响，酯醚具有较好的平滑性，酚醚的润湿性和抱合性较好，醇醚的乳化性和胺醚的水溶性较好；疏水基碳链增长或支碳链数增多，均可有效地降低聚醚水溶液的表面张力，改善其润湿性能，增强纤维的抱合性；聚醚醚链结构中的环氧乙烷和环氧丙烷（EO／PO）比例增加，纤维与金属之间的动摩擦系数增大，平滑性降低，而纤维与纤维之间的静、动摩擦系数的比值明显增大，抱合性增强；而聚醚相对分子质量的增大可明显提高其耐磨性，改善纤维抱合性，     

相关系数与Copula函数相关性比较研究

对传统的几种相关性测度指标进行对比分析,并探讨了Copula函数在相关分析中的应用。结果表明,Copula函数是相关性测度的＂归一＂指标,且能提供更丰富的相关信息,在相关分析中具有独特的优势。     

数值模拟分析摩擦与拉深件壁厚变化的关系

分析了摩擦在拉深成形中的作用;讨论了存在摩擦的情况下,数值模拟时摩擦模型和屈服准则的选择：研究了摩擦系数与拉深件最大壁厚变薄率的内在关系。结果表明,摩擦系数与拉深件最大壁厚变薄率之间存在线性增长的关系。     

脉冲真空电弧离子镀沉积类金刚石薄膜的结构和力学性能研究

利用脉冲真空电孤离子镀技术在3Cr13不锈钢上制备了类金刚石(DLC)薄膜．通过Raman光谱分析了膜的结构特征，采用摩擦磨损试验机测试了薄膜在不同载荷下的摩擦系数，运用划痕仪研究了膜基的结合强度．结果表明：所镀制的薄膜具有典型类金刚石结构特征，膜中ID／IG为1．33；摩擦系数随着载荷的增大而减小，载荷为5N，转速120r／min时的摩擦系数为0．02；Ti过渡层的引入显著地提高了膜基结合力．     

化学生物絮凝与化学絮凝工艺的比较研究

通过分析研究两种工艺的污泥产量和污泥沉降性能,对化学生物絮凝与化学絮凝工艺进行了比较研究,探讨了化学生物絮凝强化一级处理工艺的特点。结果表明:化学生物絮凝工艺对较低浓度污水的处理效果要优于化学絮凝工艺。化学生物絮凝工艺对CODC r的平均去除率比化学絮凝工艺要高4.7%,对浊度的平均去除率高1.0%,对TP的平均去除率高5.5%。     

浅析齿轮齿间摩擦力及其对轮齿齿廓的影响

本分析了齿轮齿间摩擦力的变化规律及其主、从动轮上摩擦力的方向．由于摩擦力的影响，高速齿轮机构和软齿面齿轮长期运行后，轮齿的齿廓不再保持渐开线的形状。     

制动盘（鼓）研究现状与发展趋势

对制动盘（鼓）的国内外研究现状作了较全面的综述,从制动盘（鼓）的材料、制动盘（鼓）与摩擦片的接触、制动过程中摩擦表面的温度等多方面进行了探讨,提出了能够适应高速制动中的摩擦高温,并具备环保与节能特征的摩擦制动盘（鼓）是研究与发的必然趋势。     

小麦摩擦与拉伸性能

为解决小麦收获机械中存在的损失、损伤、含杂率高、断裂及粘附问题,对小麦进行摩擦和拉伸试验。以"济麦20号"为试验对象,含水率36.16%为试验边界条件,采用PM-8188谷物水分测试仪测试含水率、机械式静摩擦试验台测试静摩擦因数、QT-1186电子试验机测试拉伸特性。结果表明:橡胶材料与小麦各部分的静摩擦因数较大,仿生拨禾机构和仿生脱粒机构采用橡胶材料能够增加静摩擦力;小麦各部分的抗拉能力从下向上逐渐减小,采用水平旋转揉搓脱粒工艺、仿生切割摘穗部件能够提高脱净率、降低含杂率、减少额外功耗。     

挤压铸造ZA27合金的力学性能及摩擦磨损性能

研究了挤压铸造对ZA27合金力学性能的影响,挤压铸造可以显著地提高ZA27合金的常温力学性能和高温力学性能.随着比压的增加,其综合力学性能提高.比压为750 MPa时,与金属型重力铸造合金相比,抗拉强度提高了约19.2%,硬度提高了约25.5%,伸长率增加了12.3%.采用MM-W1立式万能摩擦磨损试验机研究了比压对ZA27合金的摩擦磨损性能的影响,结果表明,在转速为200 r/min,载荷为100 N,摩擦副为45钢,20号机油润滑条件下,挤压比压为750 MPa时,合金的摩擦磨损性能较好.     

A Comparative Study on the Pozzolanic Activity between Nano-SiO2 and Silica Fume

The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bond and bending streugths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca（OH）2 and nano-SiO2, the reaction rate of Ca（ OH）2 with nano- SiO2 and the velocity of C-S-H gel formation from Ca （ OH）2 with nano-SiO2 showed marked increases over those of Ca（ OH）2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% .NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca（ OH）2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.     

AAO模板上碳纳米棒定向膜的制备及摩擦性能分析

在多孔阳极氧化铝（AAO）模板上的有序纳米孔中电化学沉积过渡金属Co作为催化剂，通过催化化学气相沉积（CCVD）法制备出有序、均匀的非晶态碳纳米棒定向膜。采用扫描电子显微镜（SEM）、能谱仪（EDS）及激光Raman光谱等方法分析了非晶态碳纳米棒定向膜的微观结构和形貌，并讨论了其摩擦因数与载荷及速度的关系。实验结果表明，非晶态碳纳米棒定向膜具有较小的摩擦因数，并且随着载荷的增加而减小，随速度的增加而先减小后增大，当滑动速度为0.18 m/s时摩擦因数最小。     

东西方科学传统和思维方式比较

古代中国与古希腊分别代表着东西方早期科学文化发展的先进水平，但由于认知世界的视角不同，知识的兴趣中心的差异，导致了东西方形成了不同的哲学传统，科学传统，并形成了特点各异的思维方式。这种差异性对东西方近现代科学技术发展的影响是不可低估的，甚至至今仍然产生着微妙作用。因此，对东西方科学传统和思维方式进行比较研究，不仅具有理论价值，同时也具有现实意义。     

短流程等温淬火初始温度对组织及性能的影响

为了研究短流程等温淬火的初始温度对铸件组织和性能的影响,采用消失模铸造工艺制备铸件.当铸件分别冷却到1 173和1 223 K初始温度时,放入50%KNO₃+50%NaNO₂淬火介质进行等温处理,然后空冷至室温.结果表明,铸件中出现了珠光体,ADI-1223和ADI-1173的硬度分别为381和366 HV.当载荷为10 N时,ADI-1223的摩擦系数为0. 289,磨损体积为71. 3×10^-5 mm³;ADI-1173的摩擦系数为0. 273,磨损体积为83. 7×10^-5 mm³.当载荷为12 N时,ADI-1223的摩擦系数为0. 242,磨损体积为114. 1×10^-5 mm³; ADI-1173的摩擦系数为0. 213,磨损体积为136. 5×10^-5 mm³.因此,ADI-1223的硬度高于ADI-1173,摩擦系数大于ADI-1173,磨损量小于ADI...     

中美数据库法律保护的比较研究

本文在全面把握网络环境下中美两国数据库法律保护的最新动态基础上,分析、比较和 研究了两国之间数据库法律保护的差距,提出了加强我国数据库法律保护的对策。