STRENGTH ANALYSIS OF CLAMPING IN MICRO/NANO SCALE EXPERIMENTS

Two kinds of clamping in micro/nano scale experiments are investigated in this paper, one based on electron-beam-induced deposition, and the other on the van der Waals interaction. The clamping strength and mechanism are analyzed both theoretically and experimentally. The influence of relative humidity on the micro/nano clamping and the method of electrostatic clamping are discussed. The clamping strength and performance of different clamping methods are compared considering the size and material of the clamped objects, and the application environments.

Interfacial Shear Strength Measurements of SiC Fiber-Reinforced Titanium Composites

A continuous loading push-out test technique was used to measure the interfacial shear strength of SiC fiber reinforced Ti matrix composites. The interfacial shear strength of samples as-fabricated and after heat exposed at 700 and 800℃ for 50 h was successfully determined. It has been found that the interfacial shear strength of the specimen exposed at 700℃ was higher than that of as-prepared and exposed samples at 800℃. The shear strength of the as-prepared samples was about 112.45 MPa, and increased to about 153.77 MPa after heat-treating at 700℃ for 50 h, but decreased to 133.11 MPa after treating at 800℃ for 50 h. Scanning electron microscope （SEM） was used to investigate the interfacial morphology of the samples. The brittle phase was the main products of interface for samples exposed at 800℃, and the interface was easily peeled off.

Interfacial Microstructure of Al-Sn-Pb Alloy/Steel During Liquid-Solid Bonding Rolling

Studies were conducted on the interfacial microstructure of a steel/liquid aluminium and its evolution during the bonding rolling process. The effects of wetting time and deformation on the diffusion layer and on the bonding strength were examined. By means of electron microscopy and electron probe analysis, it was found that the diffusion layer is mainly composed of FeAI3. For a steel temperature of 250℃ and an aluminium temperature of 850 ~C, the diffusion layer was formed within 3 s, and the shear strength of the samples increased after 8 to 14 s. Although the interface was not damaged, it was deformed notably. For an aluminium temperature of 750℃ and a wetting time of 11 to 17 s, the shear strength of the interface remained high, but the interface was obviously broken during rolling, leading to reduced bonding strength.

Effect of Relative Reduction on Property of Steel-Mushy Cu-Graphite Composite

The rolling treatment of steel-mushy QTi3.5-3.5 graphite composite was conducted under different relative reduction at room temperature. The effect of room-temperature rolling on interracial mechanical property of steel-mushy QTi3.5-3.5 graphite composite was studied and the relationship between interracial shear strength and relative reduction was established. The results show that, for steel-mushy QTi3.5-3.5 graphite composite, which consists of 1.2 mm-thick 08AI steel plate and 2.8 mm-thick QTi3.5-3.5 graphite layer, there is a nonlinear relationship between interracial shear strength and relative reduction in graphite layer. When relative reduction is smaller than 1.1%,interracial shear strength increases with increasing the relative reduction. When relative reduction is larger than 1.1%, interracial shear strength decreases with increasing the relative reduction. When relative reduction is 1.1%,the largest interracial shear strength of 145.2 MPa can be obtained.

Influence of Pressing Time on Steel-copper-graphite Bonding

The bonding of steel plate with QTi3.5-3.5 graphite slurry was studied by using pressing bonding technique. The influence of pressing time on the interracial mechanical property of bonding plate was researched. The results show that： under the conditions of 620℃ preheating temperature of steel plate, 530℃ preheating temperature of dies, 46% solid fraction of QTi3.5-3.5 graphite slurry and 50 MPa pressure, there exists a nonlinear relationship between pressing time and interracial shear strength. The interracial shear strength of bonding plate increases with increasing pressing time and reaches a largest value about 127 MPa when pressing time is longer than 120 s. At the interface with the best mechanical property, there exists a continuous Fe-Cu inter-diffusion zone and a metallurgical bonding.

Lithiation-enhanced charge transfer and sliding strength at the silicon-graphene interface:A first-principles study

The application of silicon as ultrahigh capacity electrodes in lithiumion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a result of its large volumetric change during lithiation and delithiation. Graphene coating is one feasible technique to mitigate the mechanical degradation of Si anode and improve its conductivity. In this paper, first-principles calculations are performed to study the atomic structure, charge transfer and sliding strength of the interface between lithiated silicon and graphene. Our results show that Li atoms segre- gate at the （lithiated） Si-graphene interface preferentially, donating electrons to graphene and enhancing the interfacial sliding resistance. Moreover, the interfacial cohesion and sliding strength can be further enhanced by introducing single-vacancy defects into graphene. These findings provide insights that can guide the design of stable and efficient anodes of silicon/graphene hybrids for energy storage applications.

EFFECTS OF DIFFERENT FUNCTIONALIZATION SCHEMES ON THE INTERFACIAL STRENGTH OF CARBON NANOTUBE POLYETHYLENE COMPOSITE

The mechanical performance of carbon nanotube （CNT） reinforced polymer com- posites is primarily controlled by the dispersive capacity and interracial shear strength of CNTs in polymer matrices. CNT functionalizations will improve dispersion and strengthen interracial bonding of CNTs in matrices. To understand the effects of different functionalization schemes on the interracial strength of CNT-polymer composites, pullout of the covalent, noncovalent, and mixed functionalized single-walled carbon nanotube （SWCNT） from polyethylene （PE） matrix was simulated by using molecular dynamics, respectively. The results show that the SWCNT-PE interracial shear strength is significantly improved by SWCNT functionalizations, particularly by mixed functionalization.

Joining of C_f/SiBCN composite with two Ni-based brazing fillers and interfacial reactions

G/SiBCN ceramic composite was joined using Ni-19Cr-10Si （BNi5） and Ni-33Cr-24Pd-3.5Si-0.5B filler alloys at 1170 ℃ for 10 min. Two kinds of Ni-based filler alloys exhibited good wettability on the CdSiBCN com- posite, with a contact angle of 13° and 4°, respectively, The microstructures of the brazed joints were investigated by electron-probe microanalysis （EPMA）, and three-point bend test was conducted for the joints at room temperature. When being brazed with BNi5 filler alloy, no evident reaction layer was ob- served at the surface of the joined composite, and the joint microstructure was characterized by Ni2Si matrix with scatteringly distributing mixture compounds of Cr23C6, Ni2Si and CrB. While Ni-Cr-Pd（Si,B） brazing alloy was used, a Cr23C6 reaction layer with a thickness of 11 μm was formed at the surface of the base composite. In the central part of the brazed joint, the phases were composed of Ni（Cr, Si） solid solution and complex compounds including Pd2Si, （Ni,Pd）2Si and Ni-B. The strength of Cf/SiBCN joint brazed with BNi5 filler alloy was 62.9 MPa at room temperature, whereas that with Ni-Cr-Pd（Si,B） filler alloy was at the same level.