Study of compatibility of polymethylsiloxane liquid PMS-10 with structural materials

The influence of structural materials on the principal electrophysical characteristics (relative permittivity, loss tangent, volume electric resistivity, and electric strength) of polymethylsiloxane liquid PMS-10 is considered in the paper.     

Enhancement of the electrical strength of liquid dielectrics saturated with elegas due to excessive gas pressure at environmental temperatures up to 100 °C

The results of investigations of the influence of high temperatures and pressure on the electrical strength of polymethylsioxane liquid PMS-20 and castor oil saturated with elegas have been presented. It has been experimentally determined that the compensation of the temperature decrease of the electrical strength of the examined liquids may be attained due to an increase of the excessive elegas pressure.     

Comparative parameters of the electrorheological effect in suspensions of nanosized barium titanyl acetates and titanyl oxalates in PMS-20 silicon oil

The regularities of the effect of intensities of dc and ac electric fields (50 Hz frequency) on dielectric and electrorheological parameters of electrorheological fluids based on PMS-20 silicon oil with nanosized fillers, barium titanyl acetate and titanyl oxalate, are revealed.     

The effect of nitrogen pressure on cathodic arc deposited NbN thin films

NbN thin films were deposited on non-standard grade high speed steel (HSS) (79.90 wt.% Fe, 0.71 wt.% C, 6.09 wt.% W, 4.52 wt.% Mo, 3.95 wt.% Cr, 1.82 wt.% Co, 1.75 wt.% V and a hardness of 65 HRC) using cathodic arc deposition at 0.125, 0.5, 1.0 and 1.5 Pa nitrogen pressures (P_N2), with a bias voltage of − 150 V. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Nanoindentation and Rockwell C analysis were used to characterize the thin films in order to identify the NbN phases and to investigate the influence of P_N2 on mechanical properties. Hexagonal β-Nb₂N, ε-NbN and δ′-NbN_0.95 are identified in XRD analysis. Hardness values derived by nanoindentation technique are 20 GPa for β-Nb₂N, ε-NbN and 40 GPa for δ'-NbN_0.95. Due to the complexity of phase system special attention was focused on identification of NbN phases by deconvolating the XRD peaks especially at 0.5 Pa in which both ε-NbN and β-Nb₂N were found. Rockwell C analysis revealed that the film adhesion is found to be poor at lower P_N2, due to the brittle nature of β-Nb₂N.     

The treatment influence on the electric strength and conductivity of fibroin

The influence of thermal treatment and liquid nitrogen treatment of cocoons on the electric properties of natural silk fibroin has been studied. It is found that, at the cocoon treatment by liquid nitrogen, the ratio of the amorphous and crystalline parts of the fibroin is preserved and the concentration of submicrocracks in them changes to a lesser extent than at treatment by heated air and a UHF field. The increase of the degree of crystallinity in the polymers leads to a certain increase of their breakdown voltage.     

The effect of phosphorus and nitrogen co-doped on the synthesis of diamond at high pressure and high temperature

The synthesis of phosphorus and nitrogen co-doped diamond is investigated in the NiMnCo–C system by adding P₃N₅ or carbonyl iron powders mixed with phosphorus powders under high pressure and high temperature. Experimental results show that the color distribution in diamond crystals with low concentration of P₃N₅ additive is not uniform. The color becomes deep green with the increase of P₃N₅ additive. The optical images and FTIR spectra reveal that the nitrogen atoms are more easily incorporated via {111} than {100} in the same conditions. In addition, the result of FTIR spectra of synthesized diamond indicates that the hydrogen atoms in the form of sp³–CH₂– are more likely to enter the diamond lattice in the P/N co-doped system, compared with the single N-doped system. The absorption peak at 3107 cm^− 1 attributed to vibration of H-related point defects (sp²–CHCH–) is observed in diamonds, which is often found in natural diamonds. The Raman shifting to lower frequency and FWHM value becoming wider are due to the doping of phosphorus atoms.     

新型串联囊式蓄能器对油源压力脉动影响的试验研究

本文对目前各处压力滤波器进行了分析,指出它们存在的缺陷,并开发设计出一种新型串联囊式蓄能器。理论及试验证实它对油源压力脉动衰减幅度大,衰减频带度,是一种性能良好的脉动衰减器。     

Effects of nitrogen on the passivity of Fe-20Cr alloy

Influences of nitrogen on the passivity of Fe-20Cr-(0, 1.1)N alloys were examined by in situ electrochemical techniques. Nitrogen was incorporated in the form of (Fe, Cr)-nitrides in the passive film, and Cr was enriched in the film of the alloy with nitrogen. Photocurrent analysis demonstrated that the structure of passive film formed on Fe-20Cr-1.1N alloy is Cr-substituted γ-Fe₂O₃ with (Fe, Cr)-nitrides. Mott-Schottky analysis revealed that the film formed on Fe-20Cr-1.1N contained higher Cr⁶⁺ and lower Cr³⁺ vacancy concentrations compared with that on Fe-20Cr alloy. All of these results were associated with the enhanced protectiveness of the film on Fe-20Cr-1.1N.     

氟尿嘧啶外涂与干扰素注射联合液氮冷冻治疗多发性跖疣的疗效及对患者免疫功能的影响

目的:探讨氟尿嘧啶外涂与干扰素注射联合液氮冷冻治疗多发性跖疣的疗效及对患者免疫功能的影响。方法:将78例多发性跖疣患者分为两组,每组39例。对照组采用液氮冷冻联合氟尿嘧啶外涂。观察组在对照组基础上,给予注射干扰素。观察两组皮损变化情况。对比两组治疗前后T淋巴细胞水平变化。采用DLQL法评估患者生存质量变化。 结果: 观察组的疗效显著优于对照组,差异有统计学意义（Z=2.312,P<0.05）;观察组治疗后CD3、CD4、CD4/CD8显著升高（P<0.05）;治疗后,观察组的CD3、CD4、CD4/CD8显著高于对照组,差异有统计学意义（P<0.05）;观察组治疗后皮损评分、DLQL评分显著降低（P<0.05）;治疗后,观察组的皮损评分、DLQL评分显著低于对照组,差异有统计学意义（P<0.05）。结论:氟尿嘧啶外涂与干扰素注射联合液氮冷冻治疗多发性跖疣的疗效确切,能显著提高患者免疫功能。     

TiC-Al2O3陶瓷裂纹治愈及强度的研究

500MPa,是未经热处理试样平均抗弯强度的2.5倍;1000℃时平均抗弯强度为352MPa,1200℃时平均抗弯强度为259MPa.XRD衍射分析表明,热处理使TiC-Al2O3陶瓷中的TiC发生氧化反应,生成TiO2填充裂纹是材料愈合和抗弯强度提高的主要原因;治愈温度超过800℃后,锐钛矿TiO2转变为金红石TiO2时产生裂纹,降低了材料的强度.     

考虑包辛格效应的高强钢U型件冲压回弹规律分析

回弹问题限制高强钢的广泛使用。数值模拟预测高强钢回弹的精度很大程度上取决于所应用的材料模型是否能对材料的包辛格效应准确描述。本研究旨在将力学解析方法、数值模拟技术、响应面分析法综合应用于高强度薄钢板U型件冲压回弹的预测中。基于考虑包辛格效应的材料模型实现高精度模拟预测回弹,随后利用理论解析方法结合有限元模拟与响应面法分析压边力、摩擦系数、模具圆角半径对回弹的影响规律。结果表明,摩擦系数较小时,板料的回弹程度随压边力的增大而减小;而摩擦系数较大时,板料的回弹程度随压边力的增大而增大。选择合适的模具圆角半径可以显著减小零件的回弹量。     

Effect of rolling conditions on the recrystallization and strength of nickel under stress at high temperatures

Metal Science and Heat Treatment -     

Effect of electric field strength on the electroluminescence spectra of a blue-emitting device

The electroluminescence spectrum of a triple-layer blue-emitting device based on 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPCP) is affected by electric field strength (EFS). At higher EFS, the device shows emission of 460 nm which arises from the light-emitting layer TPCP; at lower EFS, electrons are blocked in the electron transport layer 8-hydroxyquinoline aluminium (ALQ) and the device emits light at 517 nm of ALQ; at medium EFS, electrons are gradually injected from the ALQ layer into the TPCP layer resulting in a widely banded emission composed of both TPCP and ALQ and this emission peak shifts from initial 517 nm to final 460 nm when the drive voltage is slowly increased. This phenomenon is interpreted as evidence for electron tunneling injection into the TPCP layer.     

Influences of temperature and electric field on the bending strength of lead zirconate titanate ceramics

The present work studies the effects of temperature and a d.c. electric field on the bending strength of PZT-841 ceramics using three-point bending measurement. In the temperature range from 30°C to the Curie point T_c (≈272°C), the bending strength as a function of temperature exhibits a valley shape and the valley floors at a temperature around 225°C, revealing a 25% reduction in comparison with the bending strength at room temperature. Meanwhile, elastic compliance and damping factor exhibit peaks, respectively, at 225°C and 220°C, implying a strong correlation between bending strength and compliance. A positive or negative electric field larger than 3 kV/cm reduces the bending strength of PZT-841 ceramics significantly. For example, the bending strength under a positive field of 20 kV/cm is only one half of that without application of any electric field. The electric field is able to fracture mechanically sustained samples. Under a constant load of 70 MPa, the mean value of the critical electric field at fracture is 11.0 kV/cm. A 90°-domain wall kinetic model is herein proposed to understand the observed phenomena.     

The effect of tin and nitrogen on liquid phase sintering of Al–Cu–Mg–Si alloys

Alloys of Al–3.8Cu–1Mg, Al–3.8Cu–1Mg–0.7Si, Al–3.8Cu–1Mg–0.1Sn and Al–3.8Cu–1Mg–0.7Si–0.1Sn were made using elemental powders and conventional press-and-sinter powder metallurgy techniques. The sintering of these alloys was studied at 590 °C under atmospheres of nitrogen or argon using a horizontally aligned, push-rod dilatometer. Sintered samples were characterized using scanning electron microscopy and positron annihilation lifetime spectroscopy. Under argon, shrinkage occurs in a single stage and the shrinkage rate decays monotonically over time. Sintering shrinkage under nitrogen occurs in three distinct stages and the rate increases over time. Tin decreases shrinkage under argon but activates shrinkage under nitrogen. Positron spectroscopy indicates that the presence of tin does not alter the vacancy concentration in the sintered alloys, suggesting that tin does not bind preferentially to vacancies in the aluminum matrix in these AlCuMgSi alloys. Rather, it appears that tin may limit the formation of aluminum nitride on specific surfaces.     

含液相固体压力作用下的耦合变形行为研究

以耦合变形的凝固工艺为背景,基于ABAQUS提供的流体单元模拟了含液相固体在压力作用下的耦合变形行为.液相被视为粘性不可压材料,将液固界面划分成离散的流体单元,代表液相区对固体外壳的等静压作用.为了对比研究,文章还对实圆柱体、不含液相的圆柱壳体压缩变形进行了数值模拟.对不同情况下,压缩结束时材料内部的等效塑性应变分布规律、液固相耦合变形时液相区的等静压随耦合变形的变化规律,以及变形过程中载荷随压缩量的变化情况进行了系统研究.结果表明,实圆柱体内空腔存在与否对载荷及材料的塑性流动有显著影响,而圆柱空腔内存在液体与否对压缩量小于30%时的载荷变化影响不大.