Applied Mechanics and Materials Vol. 302

Abstract: In this thesis, elastic properties of three BCN superhard materials with different structures are computed by using CASTEP software developed according to the first principles which are based on density functional theory (DFT) and plane wave method. CA-PZ of local density approximation (LDA) and PBE of generalized gradient approximation (GGA) are adopted to describe the exchange-correlation effect between electrons. The results are compared with other findings and c-BN data. Through analysis, it is found that the spatial anisotropy do exist in the Young's modulus of single crystals all three BCN compounds.

Abstract: The influence of light radiation with different wavelengths (546, 380, 365 nm) on the coatings of oxidized graphite and its intercalated compound with ammonium dodecahydrododecaborate (NH4)2B12H12 was studied. The transmission and absorption spectra of the coatings were measured before and after irradiation. It was shown that the optical density of the coatings increased because of carbon release (blackening), which was especially strong during UV irradiation. Under the same conditions (wavelength, power, time), the change in the optical density was much larger for the intercalated compound than for oxidized graphite. This can be explained by the presence of the anion B12H12 2- in the former. It is not appropriate to refer to graphite oxide or reduced graphite oxide simply as graphene since their properties are substantially different.

Abstract: TiO2/graphene oxide (TiO2/GO) nanocomposites were prepared by the sol-gel method using tetrabutyl titanate and graphite oxide as the main raw materials. The microstructure of TiO2/GO nanocomposites was analyzed by X-ray diffraction and transmission electron microscopy. The results showed that graphene oxide was uniformly covered with sphere-like anatase TiO2 nanoparticles, which had a diameter of about 10 nm. Reactive brilliant red X-3B (X-3B) was used as model pollutant to study the photocatalytic activity of the composites. The effect of key factors on X-3B degradation was investigated. The results indicated that the photocatalytic activity of TiO2/GO nanocomposites was higher than that of pure TiO2 and the mixture of TiO2 and graphite oxide under the same conditions, and the nanocomposites had the best photocatalytic activity, when the content of graphene oxide was 100 mg. Moreover, it was found that the rate of photocatalytic degradation decreased with the increase of the initial dye concentration, and the optimum amount of nanocomposites was 0.8g/L when the initial concentration of X-3B solution was 100 mg/L, and the degradation rate could reach 96% after 60 min irradiation.

Abstract: Anisotropic conductive film (ACF), is a lead-free and fine-pitch interconnect materials that is commonly used in liquid crystal display (LCD) manufacturing to make and maintain the electrical and mechanical connections from the driver IC to the substrate. A key issue in the ACF technology is the packaging yield or failure probability, and performance of ACF’s material formula composition. This paper utilizes the V-shaped curve method to analyze the failure probability of composite ACF packages with a smart composition or a functional formula. In the proposed model, the probability of opening failures is modeled using a Poisson function, modified to take into account the average conception on the effective conductive area between opposing pads. Meanwhile, the probability estimation of bridging failures is based on the Box-Strip-Brick model between the neighboring pad pairs in the array. The results show the derived probability formulation can involve the probability conceptions of the composite ACF into a complete evaluation computation.

Abstract: The potential of near-infrared spectroscopy (NIRS) was investigated for its ability to rapidly discriminate the various brands of fermented Cordyceps mycelium powder. Relationship between mycelium powder varieties and the absorbance spectra was well established with the spectra region of 12500-4000 cm-1. Spectra preprocessing was performed using 1st derivative. Principal component analysis (PCA) was adopted for the clustering analysis and re-expressing of the hyper spectral data, and then, the obtained principal components (PCs) were used as the input of back-propagation artificial neural network (BPANN) to build PCA-BPANN model for the variety discrimination. The unknown samples in prediction set were precisely identified with the correlation coefficient R of 0.9959 and root-mean-square error of prediction (RMSEP) of 0.1007, which suggests that the NIR spectroscopy, if coupled with appropriate pattern recognition method, is very promising for rapid and nondestructive discrimination of fermented Cordyceps mycelium powder.

Abstract: We generated supercontinuum by utilizing photonic crystal fibers with randomly distributed air holes in the cladding and successfully applied it to optical frequency metrology. Ultra-broad spectra covering a range from the UV to the near infrared were obtained by launching 80 fs Ti: sapphire laser pulses into nonperiodic photonic crystal fibers. In the meanwhile, the experimental results revealed that the distribution of the output spectrum depended on the polarization state of the seeding pulses. Besides, taking advantage of this supercontinuum, we also acquired the clear beat signals by using a new scheme in optical frequency metrology.

Abstract: Nonlinear oscillations of a simply supported functionally graded materials (FGM) rectangular plate under one-to-one internal resonance are investigated in this paper. The FGM rectangular thin plate is subjected to the transversal and in-plane excitations. Material properties are assumed to be temperature-dependent. Based on the Galerkin’s method, a two-degree-of-freedom nonlinear system with quadratic and cubic nonlinearities governing equations of motions for the FGM rectangular thin plate is derived. The averaged equations are obtained by the method of multiple scales. Numerical simulations illustrate that there exist nonlinear oscillations for the FGM rectangular thin plate.

Abstract: A series of nanofiltration membranes with high flux at low operating pressure were prepared by dynamic self-assembly of poly (styrenesulfonic acid sodium salt) (PSS), poly (4-styrenesulfonic acid-co-maleic acid) sodium salt (PSS-co-MA) and poly (allylamine hydrochloride) (PAH) on the modified polyacrylonitrile (PAN) membrane. Fourier transform infrared spectroscopy (FTIR-ATR) testified that the polyelectrolyte could successfully deposit on the surface of the modified polyacrylonitrile ultrafiltration membrane. The effects of substrates, assemble bilayer number and the capping PAH solution concentration, operating pressure and CuCl2 concentration on CuCl2 removal were investigated. The [PAH/PSS] 1 PAH/PSS-co-MA/PAHc NF membrane composed of only 2.5 bi-layers displayed 88.9% CuCl2 rejection and the permeate flux was 25.1 L/ m2.h when the operating pressure was 0.2 MPa. The CuCl2 rejection was still above 86.3% when the operation pressure increased to 0.8 MPa, meanwhile, the permeate flux increased greatly to 85.8 L/ m2.h.

Abstract: In the present work, the finite element analysis was employed to study the distribution and level of thermal residual stress generated in matrix reinforced with SO2 nanoparticles. Using Cohesive Element as the bonding of the interface between fiber and matrix, three–dimensional finite element models of periodic cells were established. The results of the models with and without nanoparticles were compared. The residual thermal stressdue to the mismatch of the thermal expansion coefficients between matrix and fibers, especially theshear stress in the interface, decreased with nanoparticles, which could explain the reinforcing mechanism of nanoparticles. Our numerical study can be of great significance in designing new composites with high performance

Abstract: this paper, the adhesive wear characterization of MoS2, PTFE and mixture of MoS2 and PTFE films coated on stainless steel substrate, i.e. SUS440C, have been studied. The films were deposited by dry spray techniquecommercially available domestically. The films properties which are surface hardness, film thickness, surface roughness and adhesion strength were investigated. The thickness and the surface hardness of the films were approx. 7, 6.8 and 6.2 µm and 0.1,0,8 and 0.4GPa for MoS2, PTFE and the mixture of MoS2 and PTFE, respectively.The surface roughness of MoS2, PTFEwerefound to be similar with the value of Ra of approx. 0.302-0.303 µm. The mixture of MoS2 and PTFE showed smoother surface with the surface roughness (Ra) of approx.0.260µm. The PTFE film has shown better adhesion strength with higher critical load for first failure and full delamination. However, the failure pattern observed suggested lower severity of surface damage.Theresults fromtribologicaltests between the coated SUS440C ball and the SUS304 discshowedstrong effect of the coating on adhesive wear behavior of the contacting systems.For MoS2coated surface, the coatingsurface peeled offgraduallyuntil the surface ofthe substrate was revealed. Whereas, the PTFEcoated surface had delaminated immediately once in contact resulting in plate liked wear debris.The mixture ofMoS2 andPTFE haslower thefriction coefficient compared to the individual coating. Thewearbehavior found on the mixture of MoS2 and PTFE coated surface had similar characteristic to those found on surfacecoatingwithMoS2. It also showed lower wear occurrences with better appearance due to tearing wearat the edges of the worn suggesting better load capacity of the mixed film than the individual PTFE coating.