Journal of Wuhan University of Technology-Mater. Sci. Ed.

Structure and mechanical properties of Calcium silicate hydrate (C-S-H) at a molecular level act as “DNA” of cement-based construction materials. In order to understand loading resistance capability of C-S-H gel, research on molecular dynamics (MD) was carried out to simulate the uniaxial tension test on C-S-H model along x, y, and z directions. Due to the structure and dynamic differences of the layered structure, the C-S-H model demonstrates heterogeneous mechanical behavior. On an XY plane, the cohesive force can reach 4 GPa which is mainly provided by the Ca-O and Si-O ionic-covalent bonds. The good plasticity of calcium silicate sheet is attributed to the silicate branch structure formation and the recovery role of interlayer calcium atoms. However, in z direction, C-S-H layers connected by the unstable H-bonds network, have the weakest tensile strength 2.2 GPa. This results in the brittle failure mode in z direction. The relatively low tensile strength and poor plasticity in z direction provides molecular insights into the tensile weakness of cement materials at macro-level.

The crystallization kinetics of Li2O-Al2O3-GeO2-P2O5 (LAGP) glass fabricated via the conventional melt-quenching method was studied by differential scanning calorimetry (DSC) under nonisothermal condition at different heating rates. The activation energy of glass transition Eg is 634.4 kJ/mol, indicating that LAGP glass is easy to crystallize at an elevated temperature. The activation energy of crystallization E c and Avrami index n obtained from Matusita’s model are 442.01 kJ/mol and 1.7, respectively. The value of n reveals that bulk crystallization predominates slightly over surface crystallization during crystallization process. LAGP glass-ceramics after different heat treatments have the same crystalline phases determined as major phase LiGe2(PO4)3, with AlPO4 and GeO2 as their impurity phases.

A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 °. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.

The dynamic observations of bainitic transformation in a Fe-C-Mn-Si superbainite steel were conducted on a high temperature laser scanning confocal microscope. It is indicated that the mutual intersection of bainite sheaves often occurs during growth of bainite ferrite, resulting in an interlocked bainite microstructure. Moreover, bainite transformation is promoted by higher austenization temperature and the longer and finer bainite platelets are obtained. Further, The average growth rate of bainite after austenization at 1 100 ° is calculated as 5.8 µm·s−1. In situ observation investigation makes it possible to identify bainite transformation in real time during isothermal holding.

CdS thin films were deposited by ILGAR(ion lay gas reaction) method. The effect of annealing temperature under N2 atmosphere on the structural, chemical, topographical development and optical and electrical properties of CdS thin films was investigated by XRD, SEM, XPS, UV-VIS and two-probe technique. It is found that the cubicphase of as-deposited CdS film transforms to hexagonal phase with a perfected orientation along (002) plane at 300 °C. The band gap decreases with increasing annealing temperature until 300 °C, which is consistent with the grain growth. The fall of dark and light resistivitiy is obvious with increasing annealing temperature, corresponding to the continuous grain growth and deviation of stoichiometry at higher temperature. The smooth and uniform surface of as-deposited films becomes rougher through thermal treatment, which is related to grain growth and sublimation of CdS at a higher annealing temperature.

The electronic structure, cohesive energy and interfacial energy of ferrite (100)/NbC (100) and TiC (100)/NbC (100) interfaces have been investigated by the first-principles calculation. Moreover, the heterogeneous nuclei mechanism of NbC particle was also analyzed. The results showed that the stacking sequences have a great influence on the cohesive energy and equilibrium interfacial separation of the above-mentioned interfaces. Compared with C-terminated interfaces, the cohesive energy of Nb-terminated ones is lower while the equilibrium interface distance is larger. Among the two C-terminated interface structures, the interfacial energy between the NbC and ferrite is 4.54 J/m2, which is larger than that of NbC/TiC interface (1.80 J/m2). Therefore, NbC particles prefer heterogeneous nucleation on TiC particles surface rather than the ferrite matrix, which agrees well with the experimental result.

A novel pH-sensitive complex was prepared by using oxidized konjac glucomannan and 4-aminosalicylic acid (4-ASA) through glutaraldehyde as a cross-linking agent. The product was characterized by FTIR and 13C NMR spectra, and the thermogravimetric analysis was also studied. The drug release studies in vitro showed that the amount of 4-ASA released from the complex was about 4%, 56% and 17% after 12 h at pH 1.2, 6.8 and 7.4, respectively. The data demonstrate that the rate of the drug release of the complex can be more effectively controlled by pH value. The results showed that the novel pH-sensitive complex could be potentially useful for colon-targeting drug delivery system.

The segregation of thermal diffusion salt bath chromizing process was analyzed. The experimental chromizing ingredients were prepared by the four groups A, B, C, and D. In order to study the segregation status of this case, the cooling molten salt in the crucible was removed by drilling from the heart core of molten salt. The core of molten salt was analyzed by X-ray fluorescence spectroscopy and XRD. Through the analysis, we can conclude that the Cr element deposited in the bottom was 4.51 times than the top. Chloride added to the molten salt will reduce segregation. Meantime we proposed some measures to overcome the segregation problem.

Hydrogen is a promising fuel for it is clean, highly abundant and non-toxic, but on-board storage of hydrogen is still a challenge. So it is imperative to have an efficient method of hydrogen storage. The mesoporous MCM-48 especially the nickel-containing MCM-48 has great potential in hydrogen storage. MCM- 48 was prepared by hydrothermal synthesis. Then electroless plating technology was used to deposit Ni on the surface of MCM-48 under ultrasonic environment. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption-desorption were employed to investigate the pore structure properties. The results showed that all the samples had Ia3d cubic structure and pore channels were highly ordered. Hydrogen adsorption studies showed that the MCM-48 after nickel plating adsorbed nearly twice the amount of hydrogen than pure MCM-48 at 2.0 MPa, 263 K. So we believe that a small amount of Ni can improve the capacity of hydrogen adsorption of MCM-48 efficiently.

A low-cost rout for modification the polyacrylontrile(PAN) precursor fibers was developed. The approach involved pretreatment PAN precursor fibers with UV irradiation for various periods of time before the fibers were stabilized. The effect of UV irradiation on the chemical structure, orientation factor, density, crystallite size and morphology of the fibers in the process of stabilization was characterized by use of fourier transform infrared spectroscopy(FTIR), float-sink procedure, X-ray diffraction(XRD), scanning electron microscope(SEM), respectively. The results showed that UV irradiation could increase the density of the fibers in stabilization process. FTIR analysis indicated that the cyclization of nitrile groups was initiated at room temperature by UV irradiation. The transformation of C≡N groups to C=N ones was accelerated in the process of stabilization. The orientation factor of irradiated fibers was also increased. The crystallite size was decreased at first and increased later, and the better irradiation time of UV was 3 min according to the XRD test. SEM analysis indicated that irradiation could decrease the internal and surface defects of the stabilized fibers treated at 300 °C.