Advanced Materials Research Vols. 311-313

Abstract: Two kind of polyimide/silica nanocomposites which were recorded poly(amic acid)/ silica(PAA/SiO₂) and SiO₂ in poly(amic acid) ammonium salt(PAS/SiO₂) respectively, have been prepared for different methods. The size of SiO₂ in PAA/SiO₂ and PAS/SiO₂ are measured by Particle size analysis and the average particle size are 377nm and 53.7nm. Transmission electron microscopy(TEM) images of PAS/ SiO₂ confirm that the size of particles are ranged from 40 to 80nm. The stuctures of samples have been characterized by FT-IR spectra. The thermal stability of PAA/SiO₂ and PAS/SiO₂ are studied by thermogravimetric analysis (TGA) and the thermal behaviors were investigated by differential scanning calorimetry (DSC) in this paper. It is shown that PAA/SiO₂ have slightly better thermal properties than that of PAS/SiO₂. The results obtained from Instron universal strength tester present the water-solube PAS/SiO₂ own the excellent mechanical prperties as same as PAA/SiO₂.

Abstract: In order to investigate the effect and sintering behavior of microwave on TiB₂/Cu composite powder compacts, Cu-5vol%TiB₂ and Cu-10vol%TiB₂ composites were prepared by microwave sintering. The X-Ray Diffraction (XRD) results show that no new crystal phase appears during the sintering process. SEM results illustrate that TiB₂ particles evenly distribute over the composites, but the bad wettability between the Cu and TiB₂ results in the interface of the composites not ideal. The density of Cu-5vol%TiB₂ sintered sample is higher than that of Cu-10vol%TiB₂, but the microhardness is lower. Scanning electron microscope (SEM) analysis of the free-packed powder shows that the microwave sintering of Cu-TiB₂ composites starts from the branch side of Cu powders, and then as the sintering continuing, the composites gradually realize the densification through atomic surface diffusion and bulk diffusion. At the same time, liquid phase sintering occurs in the experimental conditions.

Abstract: Ceramic-lined steel pipes were made by adding nano-SiO₂, Na₂B₄O₇ additives into (Al-Fe₂O₃) combustion system on the basic of using centrifugal-SHS. The effect of nano-SiO₂ on the density and corrosion-resistance of ceramic-lined steel pipes were studied with the condition of adding 4% Na₂B₄O₇. The density was tested by Archimedes principle and the corrosion resistance was tested by weight-loss method. It is shown that the best density of composite steel pipes is got by adding 6% nano-SiO₂ and the best corrosion-resistance is got by adding 4% nano-SiO₂.

Abstract: Sulfate attack of cementitious materials is closely related to the essential properties of cementitious materials and erosive environments. Therefore, the foundation of service life prediction model becomes very difficult and complicated. In this paper, the temperature and concentration of an erosive solution were taken into account in lab accelerating test, the service life prediction model of sulfate attack based on equivalent time and damage variable was founded by using Arrhenius equation, the concept of maturity, Fick’s law and the theory of damage mechanics. Dynamic elastic modulus value change, and/or mass change, and/or compressive or flexural strength change, et al. can be used as damage variable to show the evolving process of sulfate attack in concrete in this prediction model, and certain changed rate was considered as the damage critical value in concrete in terms of the standard or references or test results. To estimate the possible service life of concrete structures in sulfate attacking condition by lab accelerating test according to this prediction model, it will be benefit to guide the selection of raw materials and design of durability in concrete.

Abstract: OMMT was compounded by MMT and 1% (v/v) acetic acid dissolved chitosan via solution intercalate method, and then prepared the composites with epoxy resin. The change about spacing of montmorillonite was tested by XRD, and the molecular structure of OMMT was tested by Fourier infrared spectrum. The tensile strength and impact strength of epoxy resin composites were also tested. The result showed that the spacing of montmorillonite first increased then decreased along with the increasing mass fraction of chitosan. The maximum value (d₀₀₁=1.983 nm) appeared when mass fraction of chitosan was 30%. And tensile strength and impact strength were improved by 86.8 and 51.2% respectively.

Abstract: In recent years, wood of greatly value are decreasing continuously. However, the percentage of low-grade wood or fast-growing species are increasing. The utilization of fast-growing species is one of the significant themes of investigation in wood industry. Fast-growing poplar (southern type poplar) which have been planted successfully and grown over a wide area in China are well known as famous fast-growing species of the most important commercial trees and industrial timber. In this paper, the distributions of plantation resources and methods of industrial utilization of fast-growing poplar in China were analyzed, respectively. High-valued wood products made of fast-growing poplar will be an inevitable trend in wood industry, including wood-based panel, engineered wood, solid wood door, curved laminated veneer lumber, and wood floor, in the 21st century. In this paper, varieties of poplar products inclued poplar composites board, poplar floor, poplar technological door, curved laminated veneer poplar molding components and poplar scientific wood were introduced. On the basis of research and application, the author emphatically analyzed multi-layer wood floorings made of fast-growing poplar veneer and MDF, curved furniture components made of poplar veneer, sofa frame maed from poplar composites board.

Abstract: The iron-based composite ceramic powder Fe-WC is produced by ball milling with synthetic tungsten mine and graphite. The process is accomplished through mechanical activation and reductive diffusion of the reactant powders during the milling process. The products are analyzed by means of XRD, DTA and EPMA. The results approved that the reaction does not carry through completely when the milling time is less than 8h. However, the composite powder of Fe and WC is gained by annealing from powders milled under 180V of the milling machine. The apparent activation energy of the reductive reaction is gradually decreased with the extending of milling time by mechanical activation.

Abstract: To estimate the disbond defects of the carbon fiber composite materials with honeycomb sandwich structure applied in the aerospace, active infrared thermographic NDT (non-destructive testing) is researched. The specimen with known disbond defects is detected by an active infrared thermography system. The specimen is stimulated by a pulse heating source. Based on the thermal wave propagation theory, the surface temperature of the specimen contained defects will differ from the surrounding sound area because of their different thermal-physical properties. The surface temperature is monitored using infrared camera and analyzed by a computer in the time domain. The experiment results show that the active infrared thermographic NDT is rapid, effective and intuitive for detecting the disbond defects in composite materials with honeycomb sandwich structure.

Abstract: The antibacterial PET (polyethylene terephthalate) masterbatch was extruded from twin screw extruder, using silver and zinc-loading Nano-SiO2 antibacterial agent (SLSZ) as the functional material. The content of SLSZ and extruding techniques were investigated. The dispersion and compatibility of antibacterial agent in antibacterial PET masterbatch were further characterized using Scanning Electron Microscopy and Transmission Electron Microscopy. The antibacterial performances and adsorption process of the antibacterial PET masterbatch against Escherichia coli (E. coli) were tested using alive-bacteria-counting method. The experimental results indicate that when the content of SLSZ was 30 wt. %, the antibacterial agent with an average diameter of 150nm showed excellent dispersion and compatibility in antibacterial PET masterbatch, and had excellent antibacterial performances. The adsorption process of antibacterial PET masterbatch against E. coli was controlled by Coulomb force between them. As the amount of the antibacterial PET masterbatch increased, the adsorbing rate and capacity were increased.

Abstract: CdS/ZnS core-shell structure was synthesized with reverse microemulsions in the system of cetyl trimethyl ammonium bromide (CTAB)/ C₅H₁₂O/ C₆H₁₄/H₂O and precipitator mixed thioacetamide (TAA )and ethylenediamine (EDA), which was coated on the surface of Al particles. The characteristics of the composite particles were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM )and Fourier transform infrared (FTIR). Emissivity of composite material in 8~14 µm waveband was 0.2574. The results showed composite material had lower infrared emissivity when PH value was between10 and 11, mol ratio of Zn/Cd was 0.3, and the reaction temperature was 70°C.