Advanced Materials Research Vols. 535-537

Abstract: Chitosan (CTS) and Ag-loading nano-SiO2 (SLS) are excellent antibacterial materials. However, when used alone, these monocomponent antibacterial agents are sometimes far from meeting requirements in special conditions. In this study, crosslinked chitosan-coated Ag-loading nano-SiO2 composites (CCTS-SLS) were synthesized by adsorption crosslinking reaction. Then Escherichia coil (ATCC 8099) was taken as the experimental bacteria for antibacterial tests. The experimental results indicate that the mass ratio of SLS to chitosan had the greatest influences on the value of MIC (minimal inhibitory concentration) for CCTS-SLS composite. However, the heating temperature had a weak influence on the antibacterial performance of CCTS-SLS composite.

Abstract: MnO2 doped Bi0.5(Na0.82K0.18)0.5TiO3/P(VDF-TrFE) 0-3 composites with high pyroelectric coefficient were prepared for different volume fractions of MnO2 doped Bi0.5(Na0.82K0.18)0.5TiO3 ceramic powder in P(VDF-TrFE) copolymer matrix. The dielectric constant, dielectric loss and the piezoelectric coefficient increased as MnO2 doped Bi0.5(Na0.82K0.18)0.5TiO3 ceramic volume fraction increased. The pyroelectric coefficient and figure of merit of Bi0.5(Na0.82K0.18)0.5TiO3/P(VDF-TrFE) with different MnO2 amount and 0.8mol% MnO2 doped Bi0.5(Na0.82K0.18)0.5TiO3/P(VDF-TrFE) as a function of ceramic volume fraction were studied respectively. The results indicated that 0.8mol% MnO2 doped Bi0.5(Na0.82K0.18)0.5TiO3/P(VDF-TrFE) in 20vol% ceramic volume fraction show the best pyroelectric properties with pyroelectric coefficient p= 7.8×10-5C/m2K and figure of merit FD=11.4×10-6Pa-0.5.

Abstract: Field emission property of Ga-doped carbon nanotube (CNT) film has been studied and compared with those of un-doped, N-doped as well as B and N co-doped CNT films. It is found that the Ga-doped CNT film exhibits superior field emission property to the other films. The turn-on field for Ga-doped CNT film is well below 1.0 V/μm, lower than those for un-doped (2.22 V/μm), N-doped (1.1 V/μm), B and N co-doped (4.4 V/μm) CNT films. Its current density reaches 5000 μA/cm² at 2.6 V/μm which is well above those for un-doped (1400 μA/cm²), N-doped (3000 μA/cm²) as well as B and N co-doped (2) CNT films at applied electric field of 5.7 V/μm. First principles calculations were carried out to obtain the binding energy and electronic nature altering of a CNT by Ga doping. It is shown that Ga-doped CNT (8,0) alters from semiconductor to intrinsic metal and a binding energy of 2.7527 eV is obtained. The field emission property can not simply be explained by the defect concentration, but can be understood by significant altering in the local density of states near the Fermi level introduced by dopants.

Abstract: Thermogravimetry (TG) analysis was employed to investigate the effects of antioxidants on the temperature response of PEG200 at 5% and 10% weight loss respectively, and to compare the TG profiles of cutting fluid 010 with that of PEG200 adulterated with antioxidants. Thermal aging method was utilized to survey the electrical conductivity, pH value and relative viscosity of PEG600 stock solution. Meanwhile, effects of 13 antioxidants on the anti-thermal oxidation activity of PEG600 was studied and the properties of the antioxidant-modified PEG were compared with that stipulated by the trade standard of silicon wafer cutting fluid in terms of electrical conductivity, pH value and relative viscosity. The results showed that addition of antioxidants such as 626, 1098, B900 and p-hydroxyanisole increased the temperature of PEG200 at weight loss significantly. A large disparity was displayed between the thermal gravity curves of cutting fluid 010 and that of antioxidants-containing PEG200. Electrical conductivities for all 13 PEG600 samples with anti-oxidants after thermal aging excel that of the manufacture’s standard. All antioxidant-modified PEG600 samples, except that containing DLTP and 626, satisfy the criteria of pH value by the manufacture’s standard. The viscosity of PEG600 changed little after adding antioxidants 1010 and B225, which revealed that these two antioxidants posses certain property of inhibiting polymerization of PEG600.

Abstract: This paper presents an experiment investigation on the effects on the surface quality and strength of a model in FDM, of critical factors including stratification parameters, build orientation, brace structure, auxiliary brace, and defects in STL files. With experiments using MEM-300, the conclusions can be drawn that, no matter what the number of interval is, greater filling line width always easily lead to poor surface quality, and that when the demands on surface quality and strength conflict one another, the demands on the both must first be balanced to obtain the better economical processing program.

Abstract: Using atomizing Cu-Ni-Sn-Pb powder as the matrix alloy and adding 2wt% graphite as solid lubricant phase, a Cu-based self-lubricating composite reinforced with SiC ( with 0wt%, 1wt% and 2wt%14µm SiC) was prepared under the optimized powder metallurgy sintering condition. The structure and properties of the samples were analyzed using a scanning electron microscopy, X-ray diffraction, a tensile tester, a hardness tester, and a friction tester. The results indicate that the prepared sample of 1wt%14µm SiC, when sintered at 910°C for 4 hours, possessed a perfect composite structure in alloy strengthening, graphite lubrication and SiC particle reinforcing. The main phases consisted of α-solid solution of copper, CuNi2Sn, Pb, graphite, and SiC. The wear loss was 12.6mg and the friction coefficient was 0.26. SiC particles reinforcement was optimized using fine grain to enhance the anti-wear and self-lubricating properties of the alloy matrix.

Abstract: An in-situ synthesis process combining an infiltration casting with a following heating treatment was applied to fabricate special titanium carbide (TiC) particles-reinforced iron matrix surface gradient composites in this article. The microstructure and wear-resistance of the titanium carbide particle reinforced iron matrix surface gradient composites were researched by using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and abrasive wear testing. The results showed that two materials had been reacted completely between the titanium plate and gray cast iron, and the titanium carbide particles distributed in the matrix with the thickness of 266.7 μm reaction layer. The average size of titanium carbide between titanium plate and iron matrix was about 1-2μm. Under the same condition, the wear mechanism of titanium carbide particles-reinforced iron matrix surface gradient composites appeared as: micro-ploughing, micro-cutting and broken titanium carbide.

Abstract: With the increased market demand of W-Cu composite materials, the research of ultrafine W-Cu composite powder is gradually in-depth, and some achievements have been made. This article describes some ultrafine W-Cu composite powder preparation methods in recent years, such as the mechanical alloying, oxide co-reduction, mechanical thermal chemical method, homogeneous precipitation method, spray drying, sol-gel method, etc. We simply analyzed the advantages and disadvantages of each method.

Abstract: Natural fractures controlled by the palaeotectonic stress field and artificial fractures controlled by the current stress field totally determined the distribution of the seepage system in super low permeability reservoir. Synthetically evaluation of the influence of fractures on oilfield development and the research on regularity of natural fractures distribution and the effect of stress field on the fractures are made in this paper, which is of important theoretical and practical significance in improving the development effect in super low permeability reservoir.