Advanced Materials Research Vols. 233-235

Abstract: B₄C ceramics were obtained using hot-pressing method. The effect of different sintering temperatures on the microstructures and mechanical properties of B₄C ceramics were investigated. Oxidation resistances were studied over the range 600-850°C. The experimental results showed that the relative density, bending strength and fracture toughness all increased first and then decreased with increasing the sintering temperature. The Vickers-hardness increased as the sintering temperature increasing. When the sintering temperature was 1950°C, the B₄C ceramics showed the optimized properties. The values of its relative density, Vickers-hardness, bending strength and fracture toughness were 99.1%, 34.0 GPa, 524.6 MPa and 6.56 MPa·m^1/2, respectively.

Abstract: Based on pressure swing adsorption, Proportion Pressure Swing Adsorption (PPSA), a new enrichment method with high safety, was suggested to enrich the low concentration coal bed gas. A mixture of active carbon (CA) and carbon molecular sieve (CMS) was employed as adsorbent in the process of PPSA. The methane and oxygen in coal bed gas were adsorbed simultaneously. The experimental study was carried out in order to verify the feasibility of this method. The equilibrium adsorption characteristic of CA and CMS were tested. The results showed that both concentrations of CH₄ and O₂ in desorption gas could be controlled well and would not exceed the explosion limit in enrichment process by adjusting the mass ratio of CMS5/AC1. Therefore, the new method, PPSA, can guarantee the safety in enrichment of coal bed methane.

Abstract: In order to study the occurrence regularity of early-age plastic shrinkage cracking, a series of indoor and outdoor experiments have been done in this paper. The synthesized discriminant index which is used to discriminate the situation that whether the early-age plastic shrinkage cracking happens or not has been put forward in this paper. It includes the index of unit volume accumulated evaporation besides the index of evaporation rate. Meanwhile, using Bayes Discriminant Method, based on the former indexes, the critical figure which is in connection with given environment conditions has been obtained and it can be used to detect whether early-age plastic shrinkage cracking happens or not by plotting the sense data which comes from the check specimen. The precision of prediction results that whether early-age plastic shrinkage cracking happens or not has been raised substantially by using this kind of discrimination method. The theory and method are useful for engineering application.

Abstract: Hairball-like bismuth trisulphide microcrystallines has been successfully prepared via one step solvothermal process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The morphologies of the Bi₂S₃ microcrystallines were influenced by reaction time, temperature, the mole ratio of the reactants and concentration of starting materials, and the growth process has been proposed. The electrochemical behavior of Bi₂S₃ was investigated using the cyclic voltammetry.

Abstract: An atomistic simulation of the structural properties of the new ternary A₄Rh₁₃Si₉ and A₄Ir₁₃Si₉ compounds, where A is Th, U, has been carried out using interatomic pair potentials based on the lattice inversion method. The calculated lattice parameters are corresponding to the experimental results. The phase stability of the intermetallics A₄Rh₁₃Si₉ and A₄Ir₁₃Si₉ is tested by high temperature disturbance under the control of the pair potentials. Moreover, the phonon densities of states, specific heat and vibrational entropy related to dynamic phenomena are evaluated for the first time. The method utilized in the present investigation offers a rather easy and direct way to study the structural and vibrational properties of A₄Rh₁₃Si₉ and A₄Ir₁₃Si₉.

Abstract: Due to similar publication in another journal the authors have withdrawn the paper.

Abstract: In this article, through the measurements on neat cement paste strength and heat of hydration at the early stage and using several analytical methods including XRD and SEM, effect of large amount of fly ash on the hydration process and cement's hardening mechanism of portland cement was studied when water to binder ratio is 0.35 and fly ash content is between 20% and 50%.The research outcomes find that the pozzolanic activities of fly ash are not good at the early stage.The more the content of fly ash was, the bigger the effect on strength would be.

Abstract: An atomistic simulation is presented on the phase stability and lattice parameters of the new actinide intermetallic compounds A₃Ni₅Al₁₉ (A = Th, U). Calculations are based on a series of interatomic pair potentials related to the actinides and transition metals, which are obtained by lattice inversion method. Calculated lattice constants are found to agree with a report in the literature. It is noted that, the total and partial phonon densities of states are first evaluated for the A₃Ni₅Al₁₉ (A = Th, U) compounds. The analysis for the inverted potentials explains qualitatively the contributions of different atoms to the vibrational modes.

Abstract: Chemically functionalized muliti-walled carbon nanotubes (MWCNTs)/vinyl ester resin (VE) nanocomposites were prepared. MWCNTs were first treated by H₂SO₄/HNO₃ acid mixture, and then carboxylated MWCNTs were grafted of methacrylic acid glycidyl ester (GMA). Raman microscopy and Fourier transform infrared spectroscopy (FT-IR) analyses proved the effectivenss of acid-treatment and chemical functionalization. Furthermore, chemical functionalization did not greatly disrupt carbon nanotubes structure and Transmission electron microscopy (TEM) showed that there was a GMA thin layer on the MWCNTs surface, which contributes to the homogenous dispersion of MWCNTs in vinyl ester resin matrix and the CNTs-VE interfacial interaction. Thus the nanocomposites containing MWCNT-GMA possess larger storage modulus values as well as higher glass transition temperatures (Tg).

Abstract: Microcapsules were prepared by in situ polymerization of melamine-formaldehyde resin to form shell over oxygen resin droplets. Stirring rate, temperature, pH value as well as mass ratio of shell and core are the main parameters affecting the stability of microcapsules. High stirring rate leads to small size of microcapsules. The temperature influences the speed of the reaction and the morphology. The pH value decides whether the condensation reaction can take place. The size of microcapsules is about 15-61um.