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1. chinaXiv:202003.00082 [pdf]

Measuring colloidal forces between clay microparticles with optical tweezers

赵宇; 武京治; 胡良博; 蒋宇
Subjects: Geosciences >> Geology

The interaction forces between clay micro-particles play an important role in the macroscopic strength behavior of clayey soils. Optical tweezers were used in the present study to explore the interaction between clay micro- particles. This technology uses a highly focused laser beam to manipulate small objects and can also be used as a force transducer for the measurement of forces on the order of pico-Newtons (pN). Polystyrene beads were first used to measure the surface interactions between polystyrene beads and clay particles for accurate calibration of the system because of their perfectly spherical shape and optical homogeneity, and were successful in obtaining force mea- surements within the range of 20 pN. Subsequently the interactive force was measured when a small clay particle was moved along the surface of a large clay particle. The force measured varies as the interaction of clay surfaces may evolve along their relative motion, leading to force measurements up to 40 ∼ 80 pN. The present study shows a promising potential of optical tweezers in exploring the complex micro-scale phenomena in clay minerals.

submitted time 2020-03-26 Hits188Downloads81 Comment 0

2. chinaXiv:201703.01078 [pdf]

N掺杂对V-Al-C涂层微观结构、力学及摩擦性能的影响

王鑫; 王振玉; 冯再新; 柯培玲; 汪爱英
Subjects: Materials Science >> Materials Science (General)

采用磁控溅射技术在硅片(100)和高速钢上制备V-Al-C和V-Al-C-N涂层,利用XRD,XPS,SEM,纳米压痕仪和摩擦磨损试验机 对比分析了涂层的相结构、化学组成、表面形貌、断面结构、力学性能以及不同介质中(大气、去离子水和海水)涂层的摩擦学性能。结果表明:V-Al-C涂层呈柱状晶结构生长,晶粒粗大;N的引入阻碍V-Al-C涂层的柱状晶结构生长,结构致密化,晶粒尺寸减小,形成非晶碳包裹纳米晶的纳米复合结构,使硬度从(14±0.48)GPa增加到(24.5±0.8)GPa,韧性得到相应提高(H/E>0.1)。摩擦试验结果显示:大气干摩擦条件下,V-Al-C涂层摩擦系数为0.70,引入N后V-Al-C-N摩擦系数降为0.42,这主要是由于V-Al-C-N涂层在摩擦过程中生成了具有润滑效果的V2O5,在非晶碳与V2O5耦合润滑作用下,涂层摩擦系数降低了40%;对于同一涂层,在去离子水和海水环境下的摩擦系数较大气干摩擦条件下降低,主要原因为:前者吸附的水分子可形成边界润滑作用。进一步研究表明:海水环境摩擦时,海水中Mg2+、Ca2+生成Mg(OH)2、CaCO3,均可提供进一步润滑效果,摩擦系数最低。在以上三种环境摩擦过程中,30min后V-Al-C涂层均因严重的磨粒磨损已磨穿而失效,且在腐蚀和磨损的协同作用下,海水环境中的磨损率最高。使用N掺杂制备的V-Al-C-N涂层均显示出良好的抗磨损性能,在干摩擦时磨损率为3.0×10-16m3/Nm,在海水中为1.4×10 15m3/Nm。

submitted time 2017-03-31 From cooperative journals:《金属学报》 Hits894Downloads374 Comment 0

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