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81.
《Ceramics International》2019,45(12):15015-15024
Constant- and varied-depth nanoscratching tests of GGG single crystal were carried out at different scratching velocities. The morphologies of the scratched grooves and chips were analysed using scanning electron microscope. The experimental results indicated that higher scratching velocity led to shallower penetration depth, shallower residual depth, and larger continuous chips. Increasing the scratching velocity could effectively improve the plasticity and reduce the brittle-to-ductile transition depth of GGG single crystal. Based on the contact stress and contact area between the analysed sample and Berkovich indenter, a model for predicting the penetration depth was developed, which took into account the strain rate effect and elastic recovery of materials. The model was verified using constant- and varied-depth nanoscratching tests, and the predicted and experimental results were in good agreement. Subsurface damage underneath the ductile surface was characterised using transmission electron microscope. The TEM results demonstrated that higher scratching velocity led to the slipping planes appearing in more directions, which prevented the generation of long slipping plane and reduced the depth of the damage layers. The plastic deformation of GGG at the scratching velocity of 100 μm/s was dominated by poly-crystalline nanocrystallites and amorphous phases, and was similar to that at the low scratching velocity. This study provided a fundamental understanding of the strain-rate dependence of surface/subsurface deformation mechanisms of GGG during ultra-precision machining. 相似文献
82.
Xiaoyan Dong Xu Li Hongyun Chen Congcong Sun Junpeng Shi Feihong Pang Xiuli Chen Huanfu Zhou 《Ceramics International》2021,47(5):6077-6083
High-performance capacitors, which possess a high energy storage density, large power density and fast charge/discharge rate, are in high demand in pulsed power systems. Although several studies have been conducted to obtain excellent energy storage performances, the scientific and feasible guidance is lacking on how to quickly and efficiently find a material system with high recoverable energy storage density (Wrec), large energy storage efficiency (η), and excellent thermal stability. Herein, a strategy is proposed to concurrently regulate the temperature corresponding to the maximum dielectric constant (Tm) to around room temperature and enhance the relaxor characteristic. To our satisfaction, excellent energy storage performances with a high Wrec of 3.05 J/cm3, large η of 95%, and wide temperature stability (20–180 °C) were achieved in 0.85BaTiO3-0.15Bi(Mg05Sn0.5)O3 (0.15BMS) ceramics. In addition, these ceramics also exhibited a large discharge energy density (Wdis = 0.74 J/cm3) and fast discharge time (t0.9 = 105 ns) over a broad temperature range (20–180 °C), which confirms their significant application potential in the high-temperature field. These results indicate that this work can provide an effective guideline approach to attain high-performance capacitors for application in pulsed power capacitors. 相似文献
83.
The charge generation mechanism of organic heterojunction (OHJ) consisted of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) and different hole transporting materials (HTMs) are studied systematically by current-voltage (I–V) and capacitance-voltage measurements. The analysis of I–V characteristics of the devices based on OHJs at forward and reverse voltages by comparing the thickness of HTM layers finds that a forward and reverse symmetrical I–V curve is observed at thin HTM layers and the forward current becomes larger than the reverse current with the increase of HTM thickness, fully illustrating the effectiveness of OHJ charge generation. Moreover, the I–V characteristics at different temperatures indicate that the efficient charge generation is originated from electron tunneling rather than diffusion. And the C–V and capacitance-frequency (C–F)characteristics further illustrate the highly efficient charge generation ability of OHJs so that the charge density is as high as 4.5 × 1017 cm−3, guaranteeing the high conductivity of OHJs, which is very beneficial to developing highly efficient OLEDs using OHJs as charge injector and generator. 相似文献
84.
《Ceramics International》2022,48(20):29601-29613
Sliding wear behaviors of atmospheric plasma-sprayed Yttria Stabilized Zirconia (YSZ) coating mated with four metallic or ceramic counterparts (Si3N4, Al2O3, GCr15 and ZrO2) were investigated. It has been found that YSZ coatings in contact with Si3N4 and GCr15 show better tribological performances than the other cases, which is due to the formation of the tribolayer mainly consisting of Si3N4 and Fe2O3 respectively on the worn surfaces. In the case of YSZ coating-Al2O3 and YSZ coating-ZrO2 tribopairs, the wear debris are more irregular and larger in size, resulting in severe abrasive wear and brittle fracture of debris particles. In particular, the specific wear rate of YSZ coating sliding against GCr15 is negative due to the significant material transfer of the tribo-oxide layer, while that of YSZ coating sliding against ZrO2 is the highest. Amorphization of the wear particles appears in the four cases due to the repeated mechanical action. It has been demonstrated that the wear of YSZ coating deteriorates with the increased flash temperature between the contact surfaces during rubbing process. 相似文献
85.
86.
建筑工程质量安全是施工企业管理的底线和红线。结合中铁建设集团有限公司近些年在质量管理方面的心得和经验,从施工企业的制度建设、标准化建设、管控手段、人员素质提升、创优创誉等方面,探讨建筑施工企业的质量管理。 相似文献
87.
J. Vanerek A. Benesova P. Rovnanik R. Drochytka 《Journal of Adhesion Science and Technology》2014,28(14-15):1405-1417
This article describes the evaluation of the durability of joints composed of wood adherends with a bonded layer of fibre-reinforced polymer (FRP) fabric. Carbon and glass fibres in an epoxy matrix were studied. The main purpose of FRP usage with timber in the construction industry is generally to improve the stiffness/strength of reinforced members without any influence on their service-life or any environmental impact. From the perspective of the timber reinforcement process, optimal dimensional stability during moisture changes in wood should be one of the most important criteria for such joints. Therefore, FRP/wood joints were evaluated with regard to the influence of real external environmental conditions on the bondline over a period of 40?months. During exposure to these conditions, specimen failures and defects were continuously visually evaluated. The decisive factor in this evaluation was bond integrity, verified by the tensile shear strength of the FRP/wood joint. After the experimental study, it was noted that the first 20?months have a significant effect on bondline failure occurrences, which involve decreases in tensile shear strength. In the next 20?months, the FRP/wood bondlines resist other severe hygrothermal stresses without significant strength decreases. An additional observed parameter was the percentage of wood failure in the bonded area of single lap joints, which characterises the mode of failure of the bonded joint. To determine the influence of ageing on adhesive due to ultraviolet radiation and varying temperature, infrared absorption spectroscopy analysis was performed to reveal changes in the macromolecular structure of the epoxy adhesive. Findings showed that UV radiation had a significant influence on the degradation of the adhesive structure. 相似文献
88.
矿山基建采准工作面布置,直接影响到基建工程量、投资费用和施工时间;而基建采准工作面位置的选择与设计布置又是一个系统工程,需考虑各种因素和条件,如山势地形、矿体规模、矿区地质,矿石储量、开采规模等等。以焦作千业水泥有限责任公司5000t/d熟料线的谷堆后矿区为例,详细介绍了该矿的储量、地形、矿体、夹层、上部覆盖层等总体概况;在此基础上重点介绍了该矿山基建采准工作面的设计布置情况,包括考虑因素、设计方案和建成后的生产情况。 相似文献
89.
90.