Glidants and Lubricant Properties of Several Types of Talcs

Abstract

Glidant and lubricant efficiencies of a number of different types of talcs were evaluated. The in vitro properties of tablets lubricated with talcs were compared to those lubricated with magnesium stearate. Talc lubricated tablets showed superior in vitro properties compared to magnesium stearate lubricated tablets. Different sources of talcs showed significant differences in glidant and lubricant efficiencies.     

The Tabletting Properties of Dika Fat Lubricant

The lubricant property of dika fat, a solid vegetable oil extracted from the kernels of Irvingiaqabonensis var gabonensis and var excelsia was investigated. An instrumented tablet machine (ITM) was used to evaluate the effect of dika fat on the unit ejection force (EJF/A) of a model direct compression formulation. Dika fat, at equivalent concentration levels, performed better than magnesium stearate, stearic acid and a hydrogenated vegetable oil STEROTEX, in reducing EJF/A of tablets compressed from the model direct compression formulation. Dika fat imparted no adverse effect on the hardness, disintegration and dissolution of directly compressed hydrochlorothiazide tablets prepared in this study.     

The Tabletting Properties of Dika Fat Lubricant

Abstract

The lubricant property of dika fat, a solid vegetable oil extracted from the kernels of Irvingiaqabonensis var gabonensis and var excelsia was investigated. An instrumented tablet machine (ITM) was used to evaluate the effect of dika fat on the unit ejection force (EJF/A) of a model direct compression formulation. Dika fat, at equivalent concentration levels, performed better than magnesium stearate, stearic acid and a hydrogenated vegetable oil STEROTEX, in reducing EJF/A of tablets compressed from the model direct compression formulation. Dika fat imparted no adverse effect on the hardness, disintegration and dissolution of directly compressed hydrochlorothiazide tablets prepared in this study.     

石墨烯改性润滑油的悬浮分散特性和摩擦学性能

用分光光度法定量评定润滑油中石墨烯的浓度,根据石墨烯的浓度(0.0125~0.075 mg/mL)与润滑油吸光度之间的正相关特性考察了石墨烯的初始浓度、超声处理时间以及表面活性剂掺量等因素对石墨烯改性润滑油悬浮分散特性的影响和最佳工艺参数范围,并将优化出的分散性良好、长期稳定悬浮的石墨烯改性润滑油用于摩擦学性能测试。结果表明,适当的超声分散和表面改性可提高石墨烯改性润滑油的分散悬浮效果。石墨烯浓度为0.025 mg/mL时石墨烯改性润滑油的摩擦系数降低74.78%,磨斑尺寸减小了28.33%。     

CO2跨临界循环系统混合物热物性预研究

CO2跨临界循环在太阳能热泵或热泵热水器等逆循环方面的应用是未来发展趋势之一,文章对CO2和PAG润滑油的混合物热物性进行了研究.选用润滑油热物性关联式对PAG润滑油的热物性进行了计算,根据已知实验数据对一些关联式进行了修正.采用热力学状态方程模型计算了CO2在PAG润滑油中的溶解度,并对CO2/PAG混合物的热物性进行了计算.     

WC／C固体润滑涂层的滑动摩擦磨损性能研究

在CETR UMT-2摩擦磨损试验机上用Si3N4陶瓷球和纯钛(TA2)球作为对磨副,对物理气相沉积(PVD)方法制备的WC/C固体润滑涂层进行了球一盘式的滑动摩擦磨损实验.利用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱(EDX)对磨损表面进行了微观分析,探讨了WC/C涂层的摩擦磨损机理.结果表明:滑动速度对WC/C涂层的摩擦特性影响很大,较小的滑动速度有利于在两种对磨副的磨痕表面形成致密连续的转移膜.Si<,3>N<,4>球作为对磨副时,WC/C涂层的损伤主要表现为剥层及氧化磨损;纯钛球作为对磨副时,涂层损伤表现为轻微的磨粒磨损和氧化磨损,WC/C涂层拥有良好的抗钛粘着性能.     

纳米铜润滑油添加剂的制备及其摩擦学性能

为了研究纳米铜粉的制备与其摩擦学性能,利用高能球磨机采用干湿磨相结合的方法制备了纳米铜粉,再将其加入500SN齿轮油中制成润滑油添加剂,用透射电镜(TEM)及万能磨擦磨损试验机研究了纳米铜粉的微观形貌及其润滑油添加剂的摩擦学性能。结果表明:纳米铜粉粒径为10～40 nm,在修饰剂中分散较好,颗粒表面有明显包覆层;纳米铜润滑油添加剂可提高基础油的减摩抗磨性能;纳米铜粉含量0.05%的纳米铜润滑油样的摩擦学性能最好且摩擦系数最低;低载荷下纳米铜润滑油样的摩擦学性能优于高载荷下的。     

纳米偏硼酸钙/还原石墨烯润滑添加剂的制备及摩擦学性能

为了研究表面改性纳米偏硼酸钙/还原石墨烯润滑添加剂的合成方法,以偏硼酸钙、还原石墨烯为原料,油酸为修饰剂,利用等离子体辅助球磨制备纳米偏硼酸钙/还原石墨烯复合粉体,并测试其摩擦学性能.采用扫描电镜、透射电镜、X射线衍射仪和红外光谱仪对纳米偏硼酸钙/还原石墨烯复合粉体进行形貌观察;采用形状测量激光显微镜、扫描电镜对摩擦副表面进行测试;采用MOAⅡ油液分析光谱仪对摩擦油样进行检测.结果表明:在钢球机械研磨和等离子体热效应的耦合作用下,等离子体辅助球磨10 h的偏硼酸钙与还原石墨烯继续球磨10 h后,被细化为10 nm左右的颗粒状,并均匀地负载于还原石墨烯上.等离子体快速加热使得偏硼酸钙粉体表面发生热爆,部分偏硼酸钙飞溅在还原石墨烯上,并随即被其包裹为球状复合结构.等离子体辅助球磨10 h为偏硼酸钙表面引入羧基基团,并在后续球磨中与还原石墨烯表面的羟基发生酯化反应,原位完成油酸对偏硼酸钙和还原石墨烯的表面改性,使得纳米偏硼酸钙/还原石墨烯复合粉体在5W-40型机油中具有良好的分散性.在摩擦过程中,比表面积大的还原石墨烯不断吸附在摩擦表面,同时被还原石墨烯包裹为球状的纳米偏硼酸钙粒子,使摩擦副表面产生多活动中心的滚动摩擦,从而有效改进复合油的减摩抗磨性能.     

新型固体润滑剂──氟化石墨的制备与性能的研究

通过电解熔盐KF·ZHF制取氟气,再将氟气与石墨在500℃时进行反应,从而制备了氟化石墨新材料．其密度值为2．53g／cm³、电阻率为3.1×10³Ω·cm,颜色为灰白色,在波数1219、1350cm^－1附近有F-C共价键红外光谱吸收峰．对氟化石墨、石墨、二硫化钼进行摩擦因数测试,结果表明：氟化石墨摩擦因数最小．还讨论了氟化石墨的一些特殊性能和工艺条件．     

几种粉尘层反应动力学参数的研究

研究了两种烟煤和玉米淀粉、石权子粉粉尘层的反应动力学参数。实验是采用热重分析方法在氧浓度分别为0、2％、8％、20％、50％和100％及层流条件下进行的．并用气相色谱在不同的温度范田内对粉样的气相成分进行了分析，依据实验结果求出上述4种粉尘的氧化、热解动力学参数并对粉尘层氧化某些机理作了描述。     

纳米坡缕石润滑油添加剂对灰铸铁HT200摩擦磨损性能的影响

制备坡缕石纳米粒子添加到150N基础油的润滑油体系,在MMU-10G摩擦磨损试验机上分别对该纳米粒子润滑油体系和纯150N基础油,在混合润滑条件下的铸铁HT200试样对摩时的摩擦磨损性能进行研究,并用SEM和金相显微镜对磨损表面进行观察和分析,借助EDX测定试样表面成分的变化,探讨摩擦磨损性能变化的机理。结果表明:自制备的用KH550硅烷偶联剂球磨修饰的坡缕石纳米粒子在基础油中分散性良好,在该润滑剂润滑条件下对摩的试样表面生成了自修复膜层,其磨损量明显减小,失重量下降约25.2%,平均摩擦系数下降约32.3%。     

Asymptotic Properties of Several Estimators of Weibull Parameters

In this paper several estimators for the scale and the shape parameters of the Weibull law are obtained by postulating a stochastic model aimed at studying the aging process of certain inexpensive industrial products. These estimators are consistent and asymptotically multi-normal.     

Experimental Study on the Rheological Properties of MF Lubricant Based on the Herschel-Bulkley Model

Journal of Superconductivity and Novel Magnetism - As an effective method to improve the load capacity of the oil-film bearing, a kind of nano-scale magnetic fluid (MF) by taking silicon oil as...     

基于量子逻辑的几类有穷自动机之间的关系

根据初始状态和终止状态是否为分明的,非确定型量子有穷自动机可分为四类,确定型量子有穷自动机可分为三类.本文详细讨论了四类非确定型量子有穷自动机之间的关系以及三类确定型量子有穷自动机之间的关系,并且利用新的构造方法,证明了初态为分明的确定型量子有穷自动机与终态为分明的确定型量子有穷自动机是等价的.这些结论为实际应用中计算模型的合理选取提供了理论依据.     

Cu／C复合润滑剂的摩擦学性能

将纳米Cu和纳米金刚石复配成Cu／C复合添加剂,对Cu／C复合添加剂在500SN基础油中的减摩抗磨性能进行了研究。结果表明：Cu／C复合试油能明显改善500SN基础油的摩擦学性能,当纳米Cu的添加量为4％,纳米C的添加量为2％时,Cu／C复合试油的减摩效果最好,同500SN空白试油相比,摩擦系数可降低94．8％;当纳米Cu的添加量为3％,纳米C的添加量为4％时,Cu／C复合试油的抗磨效果最好,同500SN空白试油相比,磨损量减少108．6％。     

关于金属纳米材料力学性能的几个问题

金属纳米材料具有独特的力争陛能,如高强度、超高延展性和理想弹塑性等。本文通过对几种纳米金属材料的力学性能的阐述,讨论了它们的强度、应变硬化、超塑性、理想弹塑性等相关的力学性能。并简要地指出了影响其力学性质的主要因素。     

Influence of the Physicochemical Variability of Magnesium Stearate on Its Lubricant Properties: Possible Solutions

The variability of the physicochemical properties of 13 commercial batches of magnesium stearate (from three vendors) were determined using various physicochemical tests. Differences observed were related to the crystal lattice and the hydration state of the samples as well as the impurities contained in their matrices. A formulation model containing 2% of magnesium stearate was used to determine the lubricant properties of 6 of the 13 magnesium stearate lots received. The tablet press used was a Stoks® Single Station Instrumented F Press. The different lubricant properties observed were related to the particle size of the magnesium stearate lot used. The influence of the crystalline structure on the lubricant properties of magnesium stearate was also shown whereas the influence of the adsorbed water did not appear to determine process capabilities. Two possible solutions were evaluated to reduce the lubricant property differences among the lots tested. By decreasing the particle size of a lot of magnesium stearate, it has been possible to significantly improve its lubricant properties. Magnesium stearate in association with talc also presented an improvement of its lubricant properties.     

Influence of the Physicochemical Variability of Magnesium Stearate on Its Lubricant Properties: Possible Solutions

Abstract

The variability of the physicochemical properties of 13 commercial batches of magnesium stearate (from three vendors) were determined using various physicochemical tests. Differences observed were related to the crystal lattice and the hydration state of the samples as well as the impurities contained in their matrices. A formulation model containing 2% of magnesium stearate was used to determine the lubricant properties of 6 of the 13 magnesium stearate lots received. The tablet press used was a Stoks® Single Station Instrumented F Press. The different lubricant properties observed were related to the particle size of the magnesium stearate lot used. The influence of the crystalline structure on the lubricant properties of magnesium stearate was also shown whereas the influence of the adsorbed water did not appear to determine process capabilities. Two possible solutions were evaluated to reduce the lubricant property differences among the lots tested. By decreasing the particle size of a lot of magnesium stearate, it has been possible to significantly improve its lubricant properties. Magnesium stearate in association with talc also presented an improvement of its lubricant properties.     

Turning of Brasses Using Minimum Quantity of Lubricant (MQL) and Flooded Lubricant Conditions

A lot of effort is being carried out to reduce the use of lubricants in metal machining operations from the viewpoint of cost, ecology and human health issues. Minimal quantity lubrication (MQL) is now an established alternative to conventional flood lubricant system. This paper reports on the experimental work carried out during turning of brasses with different amounts of MQL. Turning with flood lubrication was also performed and a comparison is made. The various parameters studied include the feed, cutting power, specific cutting power, and surface roughness. The results of the study suggest that with proper selection of the MQL system, results similar to flood lubricant condition can be achieved.     

两种Ni-Zn铁氧体复合材料的烧结性能和射频磁性能*

用sol-gel法获得了两种铁氧体复合材料：以镁橄榄石为基体的Ni-Zn铁氧体复合材料和以MAS为基体的Ni-Zn铁氧体复合材料。比较了这两种复合材料的结晶性能和烧结性能。两种复合材料在射频区（100MHz-1GHz)的磁性能优于纯Ni-Zn铁氧体，这种优于纯Ni-Zn铁氧体的磁性能与复合材料的显微结构密切相关：复合材料中Ni-Zn尖晶石晶粒的尺寸较一般纯Ni-Zn铁氧体晶粒尺寸小一个数量级，晶粒间的磁相互作用较纯铁氧体晶粒间弱。