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941.
942.
《Journal of Macromolecular Science: Physics》2013,52(2):459-470
Abstract Melting and crystallization behavior of poly(ethylene oxide) (PEO) with different molecular weight was investigated by modulated‐temperature differential scanning calorimetry (MT‐DSC)—step‐scan alternating DSC. It was found that by separating the reversing and nonreversing components of the (total) heat flow, PEO 10000, which exhibits the highest degree of crystallinity, shows the smallest nonreversing signal during crystallization. This effect can be attributed to the favorable structural features associated with spacial alignment. On the other hand, the crystallization process of PEO with molecular weight of 3400 is hindered by a relatively high content of end groups that may cause defects in the crystal lattice. For PEO 35000, low segmental mobility and chain entanglements lower the rate of crystallization. The area of the reversing component of PEO melting for different molecular weight fractions confirms that for PEO 10000, recrystallization is less intensive than for both the lower and higher molecular weight analogues. 相似文献
943.
Nathan A. Stump Jerry B. Burns Sheng Dai Gleb Mamantov Jack P. Young Joseph R. Peterson 《光谱学快报》2013,46(6):1073-1083
The temperature dependence of the features which arise from the 7F0,1 → 5D3 absorption transitions in EuOCl as seen by diffuse-reflectance spectroscopy has been investigated. The transitions shift linearly to higher energy with increasing temperature. The ratio of the intensities of the transitions arising from the 7F0 state to those arising from the 7F1 state also appears to be a linear function of temperature. 相似文献
944.
夸克胶子等离子体中的次带头阶得拜屏蔽质量 总被引：1，自引：0，他引：1
采用实时有限温度下的QCD,考虑到胶子的衰减率计算了QGP中次领头阶得拜屏蔽质量的贡献,克服了通常计算中的红外发散的困难,且不必引入非微扰的磁屏蔽质量作红外截断.指出了所得结果的正定性和规范无关性并与格点模拟的结果进行了比较. 相似文献
945.
不同温度条件下,采用原子层沉积(ALD)技术在单晶硅基底表面制备了Al2O3薄膜.利用原子力显微镜观察了Al2O3薄膜的表面形貌和粗糙度,利用纳米压痕仪测定了薄膜的硬度,并通过UMT-2型往复摩擦磨损试验机(球-盘接触方式)考察了制备温度、载荷和对偶球对Al2O3薄膜的摩擦学性能的影响.结果表明:不同温度条件下制备得到的Al2O3薄膜的粗糙度不同;制备温度为100和200℃的Al2O3薄膜的摩擦性能较优;在所用载荷范围内,摩擦系数存在最低值;与不同对偶球对摩时,由于对偶球硬度不同,Al2O3薄膜呈现不同的摩擦磨损现象. 相似文献
946.
947.
高温磨损中合金组成体的作用及其相互依赖 总被引：7，自引：2，他引：5
作者用其自制的高温磨损试验机考察了不同含碳量的Fe-Cr及Fe-Cr-Mn合金的高温耐磨性。通过数据分析及磨损面和亚表层之结构和组织的观察,论述了共晶碳化物及金属基体在高温磨损条件下对材料耐磨性的贡献和相互依赖性。作者指出,高硬度共晶碳化物在高温磨损过程中能够发挥一定的抵抗磨料的作用而使合金的耐磨性提高;基体组织在高温时的塑性变形是影响合金高温耐磨性的一个重要因素,它直接影响共晶碳化物发挥抵抗磨料作用的程度;Fe-Cr-Mn合金中由于Mn的加入改善了基体组织的性能,使其硬度和高温耐磨性均比Fe-Cr合金的高。 相似文献
948.
Ningning HU;Xiuheng ZHANG;Peng CHEN;Songquan WANG;Tianchi CHEN 《摩擦学学报》2023,43(12):1434-1444
In response to the problem of sudden failure in the high-temperature lubrication performance of lubricating oil, in order to achieve continuous lubrication of lubricating materials within a certain temperature range, a study on the design method of adaptive lubrication additives for sudden changes in operating conditions is carried out. This study prepared a series of silver pyrazole methyl pyridine complexes with the same lubrication mechanism but different physicochemical properties that decompose and release silver particles at high temperatures. A lubricating oil additive ratio strategy suitable for real-time lubrication was designed. The friction and wear resistance of composite lubricating oil additives containing silver complexes were studied using a four ball friction and wear tester. The research results showed that compared with lubricating oil additives containing only a single complex, The formulated lubricating oil has better stability and can continuously decompose and transport silver particles at different temperatures, ensuring continuous low friction of the contact surface over a wide temperature range, with better self-healing ability and lubrication performance. Through various characterization methods to analyze the wear mechanism of the experimental results, it was found that under the influence of the layered structure of complex 1 and the small size effect of complex 2, the negative impact of complex 3 on the wear of the contact surface during the friction process can be effectively suppressed. Therefore, there is a good synergistic effect of wear resistance between complex 3 and complexes 1, 2. However, compared to lubricants containing only a single complex 1, 2, the expected lubrication effect between complexes 1 and 2 did not occur due to the influence of van der Waals forces. Based on the thermogravimetric analysis results of a series of silver containing complexes, the formula equation of silver containing series complexes was derived by fitting the relationship curve between the friction coefficient and temperature of composite lubricant additives, and the empirical formula was modified by Matlab. It was found that the appropriate ratio and addition amount were the key factors affecting the anti-wear and antifriction performance of lubricant additives. The optimal ratio of composite lubricant additives was determined to be 1.0:1.0:0.5, We have mastered the decomposition efficiency of the complex in lubricating oil after being proportioned during the continuous heating process, further proving that the silver release efficiency of the proportioned lubricating oil increases, making it more suitable as a backup lubricating oil additive under sudden operating conditions. The research results can provide data support and theoretical guidance for the subsequent design of lubricating effect control methods of lubricant release materials. 相似文献
949.
Haichao LI;Fenghua SU;Yanjun CHEN;Songsheng LIN;Zhujun LI 《摩擦学学报》2023,43(4):385-396
Silicon doped hydrogen-free diamond-like carbon (Si-DLC) films were prepared using a superimposed high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) deposition system with anode layer ion source assistance. The composition, microstructure, and tribological properties of Si-DLC films doped with different Si content at elevated temperature (25~500 ℃) were systematically investigated. Raman and XPS were used to analyze the influence of Si doping amount on microstructure, chemical composition and tribological properties of the films before and after high temperature friction. The results showed that Si-DLC film displayed a typical amorphous structure. The proportion of sp3-C/sp2-C in the films gradually increased with the increase of Si dopant. Si atoms in Si-DLC films mainly combined with C and O atoms to form C-Si-C and C-Si-O bonds. The formation of Si-C bonds contributed to the reduction of the internal stress and the improvement of the film-substrate adhesion. At room temperature, Si-DLC coating had a low friction coefficient due to the formation of transfer film. At high temperature, the formation of Si-C bonds was propitious to improve the high temperature stability of Si-DLC film. In addition, the partial oxidation of Si-C bonds to Si-O-C bonds in the friction region enables the film to had both low friction and low wear at high temperature. 相似文献
950.
为研究不同服役温度下高湿度暖湿气流对车轮材料黏着与损伤的影响,为列车轮轨的安全可靠服役提供理论参考.本文作者利用轮轨滚动接触磨损/疲劳试验机模拟宽温环境(-55～60℃)下,着重考察间歇暖湿气流对高速轮轨界面黏着与车轮表面损伤的响应行为.结果表明：同种暖湿气流(RH 99%)作用下,环境温度对轮轨滚动接触界面的黏着与损伤存在显著影响;在低温环境下,轮轨间的黏着系数会瞬时大幅度下跌,而高温环境下反而出现轻微上升的现象.在低温工况下暖湿气流诱导下的车轮损伤(如塑性变形和表面疲劳裂纹等)明显高于高温环境,磨损机制由低温环境下的疲劳磨损和磨粒磨损为主逐渐转变为高温环境下的氧化磨损、黏着磨损和疲劳磨损.因此,为进一步保障高寒地区列车通过隧道等湿热环境时的安全可靠运行,暖湿气流诱导列车轮轨低黏着状态的行为须予以关注和引起重视. 相似文献