Friction Modifier Behaviour in Lubricated MEMS Devices

Low viscosity fluids could provide reliable lubrication for certain microelectromechanical system’s (MEMS) applications where high-sliding speeds and/or high sliding distances occur. However, while the use of low viscosity fluids leads to reduced hydrodynamic friction, high boundary friction can be a significant issue at low entrainment speeds. This article describes a series of tests of low viscosity fluids, blended with a friction modifier additive so as to provide a combination of both low hydrodynamic and low boundary friction at MEMS scales. The low viscosity fluids tested were hexadecane, low viscosity silicone oil, toluene and water. With the exception of water, the addition of the organic friction modifier octadecylamine to all these lubricating fluids produced a significant reduction in boundary friction. For a MEMS contact lubricated with silicone oil for instance, boundary friction was reduced from 0.5 to close to 0.05. The presence of the amine dissolved in the toluene had the effect of reducing boundary friction from 0.75 to 0.55; this was further reduced to 0.25 after the specimens had been immersed in the toluene-additive blend for 48 h. A water-soluble additive, diethylamine, was added to de-ionized water, at 0.1% by weight concentration. Although an initial reduction in boundary friction was observed (0.45–0.25), under these conditions the rapid onset of severe wear negated these effects. It is suggested that corrosion of silicon by water, followed by abrasion, is the cause of this accelerated wear.     

Aniline- and N,N-dimethylformamide-assisted processing route for graphite nanoplates: intercalation and exfoliation pathway

Aniline-intercalated graphite nanoplates (AGNPs) were synthesized directly from graphite via an intercalation and exfoliation pathway using aniline as the intercalating agent and N,N-dimethylformamide (DMF) as the exfoliating agent. Thus, the obtained AGNPs were dispersible in various organic solvents like ethanol, isopropanol, chloroform, and benzene. This process is convenient, readily scalable and eco-friendly. We found that π-π interactions and the charge transfer complex formation between aniline and graphite nanoplates (GNPs) are responsible for the dispersion of AGNPs in organic solvents. The formation of AGNPs was confirmed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), X-ray photoelectron (XPS), Raman and UV-Visible spectroscopic measurements.     

切割速度对硅片翘曲的影响

根据线切割机的工作原理,结合12英寸(1英寸=2.54 cm)单晶直径大、SiC磨削路线长和磨削发热量大的特点,制定了包括线速度、耗线量、砂浆温度、砂浆流量及各部分温度的工艺参数。根据单位时间内钢线的切割面积相等的理论设计了对称变化的切割速度曲线,又根据砂浆磨削能力的影响设计了非对称变化的切割速度曲线。用两种切割速度变化曲线进行了对比实验,根据实验结果确定在实际切割中必须考虑砂浆磨削能力的影响从而必须采用非对称的切割速度变化曲线。分析了影响线切割机加工质量的因素,并且给出了提高线切割机加工质量的改善方向。     

Elastic analysis of a half-plane with multiple inclusions using volume integral equation method

A volume integral equation method (VIEM) is used to calculate the elastostatic field in an isotropic elastic half-plane containing circular inclusions subject to remote loading parallel to the traction-free boundary. The material of the inclusions may be either isotropic or anisotropic and they are assumed to be distributed in square or hexagonal array. A detailed analysis of the stress field at the interface between the matrix and one of the inclusions is carried out for different distances between the inclusion and the surface of the half-plane. The results of the calculations are compared with available results. The VIEM is shown to be very accurate and effective for investigating the local stresses in the presence of multiple inclusions. The method can be applied to multiple inclusions of arbitrary geometry and elastic properties embedded in extended isotropic elastic media.     

Preparation of water-dispersible graphene by facile surface modification of graphite oxide

Water-dispersible graphene was prepared by reacting graphite oxide and 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS). X-ray diffraction study showed that the basal reflection (002) peak of graphite oxide was absent in the ANS-functionalized graphene (ANS-G), indicating crystal layer delamination. Ultraviolet-visible spectral data were recorded to assess the solubility of the ANS-G in water. Fourier transform infrared spectral analysis suggested the attachment of ANS molecules to the surface of graphene. Raman and x-ray photoelectron spectroscopy revealed that oxygen functionality in the graphite oxide had been removed during reduction. Atomic force microscopy found that the thickness of ANS-G in water was about 1.8 nm, much higher than that of single layer graphene. Thermal stability measurements also indicated successful removal of oxygen functionality from the graphite oxide and the attachment of thermally unstable ANS to the graphene surfaces. The electrical conductivity of ANS-G, determined by a four-point probe, was 145 S m(-1) at room temperature.     

Fabrication of three-dimensional autocloned photonic crystal on sapphire substrate

We applied the laser interference lithography method to form a patterned sapphire substrate (PSS). A three-dimensional photonic crystal was formed by autocloning the PSS with alternate Ta2O5/SiO2 coatings. A high total integrated reflectance (TIR) band was obtained around the 410 to 470?nm wavelength range that matched the emission spectrum of the gallium nitride (GaN) light-emitting diode (LED) for application in manipulating the light extraction of the sapphire-based GaN LED.     

Reparable key distribution protocols for Internet environments

A new concept of reparable key distribution protocol is introduced in this paper. The merit of a reparable protocol is in that once all compromised keys have been replaced by secure keys, the protocol is secure. We show that the key distribution protocol of Lu et al. (1989), for Internet is not reparable. A reparable one is proposed instead