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采用真空阴极电弧沉积技术在TC11钛合金基体上沉积约10μm厚的Ti/Ti N/Zr/Zr N多层膜,通过对比镀膜前后试样的屈服强度、抗拉强度、疲劳强度、疲劳寿命,以及断口形貌,研究沉积Ti/Ti N/Zr/Zr N多层膜对基体疲劳性能的影响,探讨疲劳断裂机理。结果表明:多层膜对TC11钛合金基体材料的屈服强度和抗拉强度影响不大,但由于膜层硬而脆而降低了基体材料的收缩率和延伸率;多层膜提高基体材料的疲劳极限;低应力下,裂纹源在多层膜表面萌生,并向内部扩展,在多层结构的膜层界面处受到阻碍,发生偏转,从而提高基体疲劳寿命;高应力下,膜层容易破裂,裂纹源增多,降低基体疲劳寿命;应力水平在520 MPa到650 MPa范围内,疲劳寿命增量从+40.82%降到-36.88%。 相似文献
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以短切碳纤维毡和环氧树脂为原材料制成复合材料,考察了该材料在单向拉伸载荷下的力阻响应。实验结果表明,该材料具有正力阻效应(拉应变引起材料的电阻增大)。其中,单层碳纤维毡/环氧树脂复合材料的力阻灵敏度可达13.9,但在加载过程中其电阻表现出逐渐衰减趋势;多层碳纤维毡/环氧树脂复合材料的力阻性能更为稳定,但随着层数的增加灵敏度逐渐降低,5层复合材料的力阻灵敏度下降到5.7。多层复合材料的立体导电网络是其稳定性提升和灵敏度下降的主要原因。将碳纤维毡/环氧树脂多层复合材料敷设在梁结构表面形成智能表层,利用其力阻性能实现了梁结构在循环载荷下的变形监测以及在单调载荷作用下损伤监测。 相似文献
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不同碳源对LiFePO4/C复合材料性能的影响 总被引:4,自引:0,他引:4
采用机械液相活化法与高温固相法相结合制备了锂离子电池正极材料LiFePO4和LiFePO4/C.考察了蔗糖、柠檬酸、葡萄糖、酒石酸等不同碳源对材料性能的影响,并采用XRD、 SEM和恒电流充放电测试等方法对材料的结构、表面形貌及电化学性能进行了研究,利用Raman光谱和TEM分析材料中碳的存在状态.结果表明,得到的样品结构均为橄榄石型,碳源的加入能有效地减小材料的颗粒尺寸,并且材料的电导率比纯LiFePO4的电导率提高了5个数量级.LiFePO4/C样品的表面包覆层均为非晶碳,以柠檬酸为碳源合成的LiFePO4/C材料,具有较小的颗粒尺寸,均匀多孔的表面碳包覆层和最佳的电化学性能.在0.1C下第3次的放电比容量达141.0mAh/g,循环10次后容量无衰减. 相似文献
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以钼粉、过氧化氢(30%)、苹果酸、硫脲为原料,通过连续的水热法-热分解碳包覆,制备出了分级结构的C@MoS_2@C纳米带,并通过X射线衍射、扫描透射及电化学性能表征方法对该纳米复合材料的形貌结构、组成成分及锂电性能进行测试。研究结果表明,通过该连续的水热法-热分解碳包覆,以碳包覆的三氧化钼纳米带为模板,制备出分级结构的C@MoS_2纳米带复合材料,其MoS_2纳米片均匀的负载在碳层表面,通过再一次简单的热分解碳包覆,实现了在MoS_2表面均匀覆盖一层无定形碳,得到了三层分级结构的C@MoS_2@C纳米带复合材料。通过这种形貌结构的筑造,极大提高了其作为锂电负极材料的导电性、结构稳定性,该材料作为锂电负极材料在0.2 A/g的恒流充放电下循环100次后放电比容量达到1025.5m Ah/g,在1.0 A/g的大电流充放电循环中放电比容量仍然达到820 m Ah/g。 相似文献
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大部分能源必须转化为电能才能为人类所利用,而在电能的传输和分配过程中,开关起着决定性作用。电触头是开关的核心组件,其质量和性能直接关系到终端设备工作的稳定性和安全性。长期以来,传统Ag/CdO复合电触头材料的毒性问题无法得到有效解决,而现有无Cd电触头材料(Ag/SnO2、Ag/ZnO、Ag/C、Ag/Ni等)仍存在诸多问题。因此,开发新型环保高性能电触头增强相材料是低压开关用电触头发展的迫切需求和必然趋势。近年来,MAX相作为一种新型层状陶瓷材料,兼具金属的导电、导热、易加工和陶瓷的耐高温、耐腐蚀、稳定性好等双重特性,完全契合电触头增强相材料的性能要求,在银基复合电触头中展示出较强的开发和应用潜力。在已报道的MAX相家族中,Ti2SnC的导电性最为优异,增强银基复合材料后对其在服役过程中保持低接触电阻和温升十分有利。因此,本工作选择Ti2SnC作为Ag基增强相材料,研究制备工艺对复合材料结构和性能的影响。首先,本工作基于粉末冶金工艺在不同烧结温度下制备了Ag/10%Ti2SnC(质量分数)(Ag/... 相似文献
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通过真空驱动自组装法及蒸汽处理得到结构疏松的硅/碳纳米管/石墨烯自支撑负极材料(Si/CNTs/GP)。纳米硅颗粒(50 nm)为活性物质, 均匀分布在石墨烯片层结构中间; 石墨烯作为碳基体, 通过自组装构筑形成二维导电网络; 碳纳米管(CNTs)具有超高导电性和良好的力学强度, 它通过吸附作用均匀分布在石墨烯基体上形成导电的支撑网络结构。经过蒸汽处理后, 石墨烯层间距明显增大, 层与层之间不再是紧密堆叠的结构, 而是形成一种疏松、褶皱、内部空隙丰富的片层结构。Si/CNTs/GP负极材料中丰富的内部空穴和贯穿孔洞, 提供了材料很高的比表面积, 能有效提高电解液对材料的浸润性, 极大缩短了离子传输距离。同时这些内部空穴也有效缓冲硅充放电时的体积膨胀, 提高了材料的结构稳定性和电化学性能。该负极材料在4 A/g的大电流密度下容量维持在600 mAh/g, 表现出良好的大电流循环稳定性能。 相似文献
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Z.Y. Nuru C.J. Arendse T.F.G. Muller M. Maaza 《Materials Science and Engineering: B》2012,177(14):1194-1199
We report on the microstructure and optical properties of AlxOy–Pt–AlxOy interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of AlxOy. The top and bottom AlxOy layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of AlxOy. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the AlxOy–Pt–AlxOy interference-type multilayer stack for use in high temperature solar-thermal applications. 相似文献
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A high-pressure technique was adopted to obtain perovskite-type . A new perovskite was characterized to have a cubic symmetry with ; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement. 相似文献
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The preparation conditions of the high TC ceramic superconductor Ba(Pb,Bi)O3 is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition. 相似文献
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Spectrally selective AlxOy/Pt/AlxOy multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both AlxOy layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of AlxOy/Pt/AlxOy multilayer absorber indicated the AlxOy layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively. 相似文献
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S. Nomura J. Kuwata S.J. Jang L.E. Cross R.E. Newnham 《Materials Research Bulletin》1979,14(6):769-774
The electrostriction in crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP2 above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q11 = 1.6·10?2m4/C2, Q12 = ?0.86·10?2m4/C2, and Q44 = 0.85·10?2m4/C2. 相似文献
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The monoclinic-to-tetragonal structure transition of oxides V1?xMox02 with has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with to be semiconducting, while a metallic behavior was observed in the region . 相似文献
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A. Rogalski 《Thin solid films》1980,67(1):179-186
heterojunctions with a long wavelength spectral cutoff (λc ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with RoA equal to 170 Ω cm2 and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given. 相似文献
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SixCyHz films have been prepared at 200°C by reactive plasma deposition from SiH4 and CH4 diluted in helium in a tubular reactor. These films have a ratio s (equal to ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH4-CH4-He plasma have been performed and the results are related to the composition of the deposited layers. 相似文献
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