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1.
用热压成型法制备了纳米Si3N4填充的聚四氟乙烯(PTFE)复合材料,研究了纳米Si3N4质量分数、表面处理对PTFE复合材料力学和摩擦磨损性能的影响,用扫描电子显微镜(SEM)对拉伸断口形貌进行观察,分析了复合材料增强机制.结果表明:未处理纳米Si3N4能提高复合材料的硬度和耐磨性,但拉伸强度和冲击强度有所降低;表面处理纳米Si3N4后,PTFE复合材料的拉伸强度、冲击强度、减摩性能有所提高.拉伸断口的微观分析表明,表面处理Si3N4在PTFE基体中有较好的分散性,与PTFE基体界面结合较好. 相似文献
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《机械工程材料》2016,(10)
对铸态镍铝青铜(NAB)进行了920℃正火和675℃退火热处理,研究了不同状态NAB的显微组织和拉伸性能;采用直流电压降(DCPD)法测试了其疲劳裂纹扩展速率,观察了裂纹扩展路径及疲劳断口形貌。结果表明:退火态与铸态试样的显微组织均由基体α相、残余β相以及三种Ni-Fe-Al金属间化合物相(κⅡ,κⅢ,κⅣ)组成,而正火态试样组织则由较多的残余β相以及均匀分布的κⅣ相组成,其强度更高但塑性明显降低;铸态试样的疲劳裂纹扩展速率最快,正火态试样的最慢;铸态和退火态试样中的疲劳裂纹在κ相相界处扩展,断裂方式主要为脆性解理断裂,而正火态试样的疲劳裂纹主要穿过α相扩展,断口出现了疲劳辉纹,且其疲劳裂纹扩展路径最为曲折。 相似文献
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以平均粒径约80μm的纯Nb和纯Si粉末为原料,采用500W、750W、1 000W和1 500W功率的激光束为热源,通过双通道同轴送粉激光熔化沉积(Laser melting deposition,LMD)技术制备了四种Nb-16Si二元合金。利用扫描电子显微镜(Scanning electron microscope,SEM)、X射线能量色散谱仪(Energy dispersive spectrometer,EDS)以及X射线衍射仪(X-raydiffraction,XRD)等手段分析了沉积态合金的宏微观组织演变与维氏硬度。结果表明,随LMD激光功率由500W增至1 500W,沉积试样表面形貌逐渐趋于光滑,相对密度由91.1%增至98.5%。激光功率对沉积态Nb-16Si合金相组成无明显影响,在高能激光束的作用下,纯Nb粉末与纯Si粉末发生原位反应,直接合成了室温亚稳态的Nb3Si相和NbSS(Niobium solid solution,NbSS)相。激光功率强烈影响Nb-16Si合金的显微组织形貌,随激光功率的增加,合金中先共晶NbSS相由枝晶状逐渐转变为细小等轴状,其平均尺寸... 相似文献
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制备了12%Mg_2Si/A356-1.2%Fe(质量分数,下同)富铁再生铝基复合材料,研究了振动频率(100,150,200Hz)和变质剂锰铬质量比(0∶1,3∶7,1∶1,7∶3,1∶0)对其铸态组织和性能的影响,并对比分析了固溶+时效态复合材料和A356-0.5%Fe再生铝合金的组织和抗拉强度。结果表明:机械振动有助于细化未变质复合材料中的共晶Si相、Mg_2Si相和富铁相,促进其均匀分布,从而提高复合材料的室温抗拉强度;锰铬变质后的富铁相由针状变为鱼骨状、颗粒状或汉字状,当锰铬质量比为1∶1时,室温抗拉强度最大,为125 MPa;在振动频率200Hz、锰铬质量比1∶1条件下,固溶+时效态复合材料中形成了六角晶型α-Fe(Al_8Fe_2Si)相,而A356-0.5Fe再生铝合金中形成了单斜晶型β-Fe(Al_5FeSi)相,复合材料的室温和200,300℃高温抗拉强度均高于A356-0.5%Fe再生铝合金的。 相似文献
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采用热分析仪、光学显微镜等研究了3104铝合金的铸态和不同工艺均匀化退火后的显微组织,为其制定了合理的均匀化退火工艺,利用扫描电镜及其附件确定了合金均匀化退火后组织中主要化合物的形貌及类型。结果表明:3104铝合金合适的均匀化退火工艺为590℃保温12 h;均匀化退火后,因合金成分的差异,形成了形貌各异、类型不同的金属间化合物,主要有(FeMn)Al6、MnAl6、(Al、Fe、Mn、Si)四元相、Mg2Si相、(Al、Mn、Si)三元相、Al8Mg5、(Al、Mn、Mg、Fe)四元相等。 相似文献
8.
采用喷射沉积法制备15%(体积分数)4.5 m SiCp/Al-20Si复合材料及其基体合金,研究该组材料的微观组织、力学性能、高周疲劳性能以及疲劳断口形貌。结果表明:SiC颗粒的加入有利于提高材料的力学性能;复合材料及其基体的高调疲劳寿命随应力幅值的减小而增加,在相同应力幅值下,复合材料的疲劳寿命远远高于基体合金。疲劳裂纹从大颗粒的初晶Si的断裂以及Si相脱离处形核,并开始扩展。对于复合材料而言,SiC颗粒尺寸较小,不容易发生断裂,在形核过程中,当裂纹遇到SiC颗粒时,裂纹或者避开增强体,或者受阻于SiC颗粒,只能在基体合金中扩展,从而扩大了疲劳形核区的面积,提高了材料的疲劳寿命。Si颗粒的脱离、Si相的断裂以及SiC颗粒与基体界面的脱粘是复合材料疲劳断裂失效的主要机制。 相似文献
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以环氧树脂为基体,以经退火的Fe73.5Cu1Nb3Si13.5B9非晶粉体为增强材料,制备了树脂基复合材料。研究了非晶粉体退火条件、纳米晶粉体含量及去应力退火条件对树脂基磁性复合材料的起始磁导率μi的影响。结果表明,以经550℃×0.5h退火的Fe73.5Cu1Nb3Si13.5B9纳米晶粉体为组元的树脂基复合材料的起始磁导率μi最大,为2.528;随着纳米晶粉体含量的增加,树脂基复合材料的起始磁导率μi增大;去应力退火可以提高树脂基复合材料的起始磁导率μi。 相似文献
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A. A. Bloshkin 《Optoelectronics, Instrumentation and Data Processing》2014,50(3):252-259
Results of mathematical simulation of the hole spectrum and optical absorption in Si/Ge x Si1?x /Si quantum wells formed on virtual Ge y Si1?y substrates are presented. It is shown that the presence of elastic strains in such a system can significantly change the position of absorption lines in GeSi heterostructures. Selecting the quantum well and virtual substrate compositions can change the intersublevel absorption wavelength in the range from 6 to 12 µm for light polarized in the quantum well plane. When tensile strain is applied, the change in the hole transition intensity under the influence of the light polarized in the quantum well plane reaches a factor of 1.8. Compressive strain changes the intersubband transition intensity by a factor of 1.45. 相似文献
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Atomic force microscopy (AFM) has been used for tribological studies of Si surfaces covered by oxide layers of various kinds: chemical oxides prepared by the SC1 (NH4OH/H2O2/H2O) and the SC2 (HCl/H2O2/H2O) treatments and a thermal oxide. In the case of the SC1 chemical oxide, the oxide layer was scratched and the underlying Si substrate was ploughed by the Si3N4 AFM tip. On the other hand, no wear of the sample was noted on the other surfaces: the AFM often produced elevated patterns in the shape of the scanned area, which were no longer visible after HF etching. By annealing the SC1-treated surface in N2 gas at above 200 degrees C for 30 min, the oxide layer could not be scratched any more. By soaking the thermal oxide in KOH, the oxide layer was then scratched. It is concluded that the presence of OH bases is the necessary condition for the nano-scratching of the oxide layers. 相似文献
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Field evaporation studies of crystalline <100> Si were performed in a three-dimensional atom-probe, which utilized a local electrode geometry. Several distinct phenomena were observed. Si field evaporation rates showed: (1) no measurable dependence on temperature below 110K, (2) an exponential dependence on evaporation rate as a function of temperature above 110K, and (3) no dependence on substrate doping (i.e., electrical conductivity) as high as 10 Omega cm in the temperature range of 40-150K. Two distinct evaporation modes were observed. The first was associated with approximately 1at% H+ in the mass spectrum. Negligible amounts of H were detected in the mass spectra of the second mode. When the pulse fraction (pf) was increased from 5% to 30%, the presence of H+ in the mass spectra, i.e. operation in the first mode, was associated with a degradation in mass resolution by as much as 80% for the 10 Omega cm Si samples. Conversely, no loss in mass resolution was detected for the approximately 0.001 Omega cm samples over the pf range studied. 相似文献
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Using a pin-on-disk tribometer, dry friction and wear properties at different temperatures were investigated for reaction-sintered silicon carbide Si/SiC and its composites with nickel Si/SiC-Ni. The friction and wear properties of the composites are improved by the addition of nickel. The analysis on the worn surfaces and sub-surfaces by SEM suggest that shallow grooves are the main wear feature at 15°C. At 600°C, surface cracking and fracture is the predominating wear mechanism for Si/SiC, and the formation of flake pits on the surface due to crack propagation at subsurface is the main wear mechanism for Si/SiC-Ni. Finally the relationships between wear resistance and mechanical properties are discussed. 相似文献
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介绍了通过使用原子力显微镜,在H钝化Si(100)的表面局部阳极氧化反应的表面氧化图案上刻写的纳米级Si结构加工。这种氧化图形可被用作Si的可选择性蚀刻工艺的掩膜。带有临界特性的小到30nm的边门Si场效应晶体管也通过这种方法加工。 相似文献
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Tribological properties of Si/Si contacts were measured on a microscale by using an atomic force/friction force microscope. Friction forces and pull-off forces between a Si tip and a polished surface of a Si(100) wafer were studied as a function of applied normal load and relative humidity of the surrounding air. The results show that pull-off forces and friction coefficients increased and were strongly influenced by capillary forces with increasing humidity. Tribological interactions during 20 passes of overlapping sliding contact at 50% relative humidity and very small loads of 70 nN were confined to the layer of adsorbates and chemical reactions, without measurable solid damage on the Si(100) wafer. 相似文献
17.
The core structure of a Lomer dislocation in SiGe/Si system has been revealed at atomic level. This is attained by applying the image deconvolution technique in combination with dynamical diffraction effect correction to the high-resolution image taken with a 200 kV field-emission gun high-resolution electron microscope. The Lomer dislocation has a Hornstra-like core. The contrast of the image simulated on the basis of derived atomic configuration is in agreement with that of the experimental image. 相似文献
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Miki Nakano Koji Miyake Atsushi Korenaga Shinya Sasaki Yasuhisa Ando 《Tribology Letters》2009,35(2):133-139
The tribological properties of patterned surfaces were investigated under lubricated conditions. Micropatterns were fabricated
on a Si surface using a combination of photolithography and plasma etching. NiFe film with a 150 nm thickness was then deposited
on the patterned Si surface. We prepared four kinds of patterned surfaces: dimple, grating, bump, and mesh patterns. The dimensions
of the patterns were: size 30–40 μm, pitch 120 μm, and depth 10–12 μm. Friction tests were carried out using a pin-on-plate
tribometer. The pin specimen was made of cast iron and had a flat end. The normal load was varied from 9.8 to 98 mN, and the
average sliding speed from 1.0 to 5.0 mm s−1. Slideway lubricating oils or a gear oil were used as the lubricant, and the ISO viscosity grades of these oils were VG32,
VG68, and VG320. The results showed that the friction coefficients of the two reverse patterns showed very similar tendencies
and that circular patterns had a lower friction coefficient than did the rectangular patterns at a high bearing characteristic
number. The surface geometry of the Si surface did not affect the friction coefficients at a low bearing characteristic number. 相似文献
19.
N. BIBIĆ V. MILINOVIĆ M. MILOSAVLJEVIĆ F. SCHREMPEL M. ŠILJEGOVIĆ K.P. LIEB 《Journal of microscopy》2008,232(3):539-541
Ion beam mixing of Fe/Si bilayers, induced by 100 keV 40Arions at room temperature was investigated. Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for structural characterization. The main focus of this study was on the influence of the substrate structure on interface mixing. The influence of the substrate structure is due to the two classes of irradiated bilayers, Fe thin films deposited on crystalline or pre‐amorphized Si substrates. An about 76% higher efficiency of atomic transport across the pre‐amorphized Fe/a‐Si interface as compared to that of Fe/c‐Si bilayers was observed. 相似文献
20.
A. P. Krasnov A. V. Naumkin M. O. Panova A. Yu. Pereyaslavtsev N. S. Gavryushenko V. G. Bulgakov G. A. Yudin T. A. Kovaleva 《Journal of Friction and Wear》2017,38(4):259-264
The friction of an ultrathin coating (~5 nm) formed as a result of the modifier segregation towards the surface of modified epoxy polymer in the form of multiple short chains of Si, F modifier has been investigated in a range of loads from 0.1000 to 0.0005 N. During the investigation of the reverse friction of ceramic (Al2O3) ball on the coating, the sharp decrease in coefficient of friction at a load of less than 0.002 N has been shown, which is probably caused by the change in the mechanism of friction during the transition of friction to the zone of a self-lubricating coating. Under these conditions, the difference between the static coefficient of friction (stop effect) and dynamic coefficient of friction increases. 相似文献