Formation of nanocrystalline microstructure in arc ion plated CrN films

Applying negative bias voltages caused significant microstructure changes in arc ion plated CrN films. Nanocrystalline microstructures were obtained by adjusting the negative bias voltage. Structural characterizations of the films were carried out using X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HR-TEM). The results indicated that increasing ion bombardment by applying negative bias voltages resulted in the formation of defects in the CrN films, inducing microstructure evolution from micro-columnar to nanocrystalline. The microhardness and residual stresses of the films were also affected. Based on the experimental results, the evolution mechanisms of the film microstructure and properties were discussed by considering ion bombardment effects.     

不同负载条件下Al/Cu双层复合材料的界面特征(英文)

研究叠轧过程压下量对轧制Al/Cu双层板界面微观组织及力学性能的影响。采用透射电镜观察压下量为30%~65%时Al/Cu双层的界面微观组织。针对不同的界面组织,分别采用三点弯曲试验和剥离试验测试Al/Cu双层板的弯曲强度和连接强度。讨论了界面冶金接量对其连接强度的影响。结果表明,叠轧时随着压下量减小,Al/Cu双层板的弯曲强度、连接强度均降低,这主要与材料界面组织密切相关。三点弯曲试验也验证了这一点。     

Optimization of Extrusion Rice Bran Stabilization Process

Effects of processing variables, production rate, number of die openings and initial moisture content on the discharge temperature and power input during rice bran extrusion with an autogenous single-screw extruder were analyzed. At extrusion temperatures above 128°C, all lipase activity in the bran was lost regardless of moisture content of the bran fed. Net specific energy input (NSE) varied with changes in die opening and moisture contents and total power efficiency was increased with increasing production rate without change in NSE value. Percolation rate through the extruded bran bed was increased to nine times over that of raw bran; the extraction time to reach 1% residual oil in extruded bran was reduced to 10 min from 100 min for the raw bran.     

Lubrication properties of silver-palladium alloy prepared by ion plating method for high temperature stud bolt

As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.     

Effects of Cr interlayer on mechanical and tribological properties of Cr-Al-Si-N nanocomposite coating

Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ～50 N is observed for the coating containing Cr interlayer of 60 nm as compared ～ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.     

Formation of nanocrystalline microstructure in arc ion plated CrN films

Applying negative bias voltages caused significant microstructure changes in arc ion plated CrN films. Nanocrystalline microstructures were obtained by adjusting the negative bias voltage. Structural characterizations of the films were carried out using X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HR-TEM). The results indicated that increasing ion bombardment by applying negative bias voltages resulted in the formation of defects in the CrN films, inducing microstructure evolution from micro-columnar to nanocrystalline. The microhardness and residual stresses of the films were also affected. Based on the experimental results, the evolution mechanisms of the film microstructure and properties were discussed by considering ion bombardment effects.     

Distribution of electric field for carbon nanotube assembly: Experiments (II)

The distribution effect of electric field on the alignment and attachment of carbon nanotubes (CNTs) were investigated. The experimental results were compared with the simulation results according to three different shaped electrodes. In previous simulation, the round shaped electrodes were expected to be more effective for aligning and attaching a single CNT between two electrodes than conical or rectangular shaped electrodes. To verify the simulation results, three different shaped electrodes were introduced and a single multi-walled carbon nanotube (MWNT) was attached. The optimal conditions for aligning and attaching MWNTs such as the frequency, applied voltage and concentration of MWNTs solution were investigated. Through repeated experiments, frequency of 100 kHz-10 MHz, applied voltage of 0.3-1.3 V_rms/μm, concentration of 5 μg/mL in MWNTs solution were obtained as a possible condition range to attach MWNTs. Under these conditions, the yield of MWNTs attachment between two electrodes was up to 70%. In previous simulation, furthermore, it was verified that the size of the stable or quasi-stable region made CNTs aligned and attached on different shaped electrodes from the comparison of the experimental and simulation results. Most single MWNT attachment was accomplished on the round shaped electrodes.     

Structure of Ferroelectric (Ba,Sr)TiO3 Thin Films for Tunable Microwave Devices

Ferroelectric (Ba,Sr)TiO₃ films have been deposited on (001) MgO single crystals by a pulsed laser deposition with oxygen background while heating the substrates. Deposited BST films exhibit epitaxial growth along (001), which are confirmed by x-ray diffraction measurement. Structure of (Ba,Sr)TiO₃ along in-plane and surface normal direction have been investigated and found to have a tetragonal distortion depend on the deposition conditions, such as oxygen pressure. Lattice parameter decreases with increasing oxygen pressure, and tetragonallity (c/a) changes from 1.005 to 0.997 as oxygen pressure increase. Interestingly, energy gap measured by FTIR decreases with decreasing oxygen pressure until it reach a certain oxygen pressure, then increases again with increasing oxygen pressure. Furthermore, microwave properties of devices measured by a HP 8510C vector network analyzer from 0.045–20 GHz suggest that the least distorted films exhibit a larger dielectric constant changes with dc bias field.     

模糊可靠性计算的一种方法

通常可以将模糊可靠性问题转化为常规可靠性问题来计算机械零件的模糊可靠性。由于模糊可靠性问题的复杂性 ,一般不会得到计算模糊可靠性的解析式 ,这时可以将其展开成级数的形式 ,得到模糊可靠性计算的级数表达式 ,或者得到转换的常规可靠性的级数表达式 ,然后再用仿真法估计机械零件的模糊可靠性。采取本文的方法 ,可以减少可靠性分析的计算量 ,在一些特殊的情况下 ,计算量会大大地减少。