Formation Processes of β-C2S by the Decomposition of Hydrothermally Prepared C-S-H with Ca(OH)2

A mixture of CaO and silicic acid prepared with a Ca/Si ratio of 2.0 was hydrothermally synthesized at 80° to 200°C, and the thermal decomposition behavior of the products (C-S-H with Ca(OH)₂) was analyzed using XRD, ²⁹Si MAS NMR, and the trimethylsililation method (TMS). It was found that the main silicate anion structure of C-S-H was a mixture of a dimer and a single-chain polymer (larger than Si₅O₁₆) and that polymerization advanced with an increase of the synthesizing temperature. On heating, the products decomposed to form β-C₂S. It was found that the decomposition was gradual and that the-higher the temperature of hydrothermal synthesis, the lower was the temperature of the decomposition into β-C₂S. Although the decomposition proceeded to form a monomer (β-C₂S) from the polymer and dimer, this dimer was resistant to heat and did not decompose unless heated to above 400°C.     

Color and Vanadium Valency in V-Doped ZrO2

The distribution and chemical states of vanadium in V-doped ZrO₂ were studied to clarify the origin of the color of vanadium-zirconium yellow pigment in comparison with vanadium-tin yellow pigment. ESCA data and measurements of lattice constants of V-doped ZrO₂ revealed that vanadium was dissolved mainly as V⁴⁺ substituting for Zr in ZrO₂ lattice, and its solubility limit was 0.5 wt% as V₂O₅. It was found that the yellow color of vanadium-zirconium yellow was produced predominantly by the dissolved vanadium and that the contribution of vanadium oxide on ZrO₂ grains to the yellow color was about 1/30 of that of the dissolved vanadium when compared on the basis of equimolar quantity of vanadium. Most of the undissolved vanadium oxide was in an amorphous or a poorly crystallized state.     

Effects of ageing on bainitic and thermally induced martensitic transformations in ductile Cu–Al–Mn-based shape memory alloys

The effects of ageing at 473–573 K on the hardness, microstructure and thermoelastic martensitic transformation in Cu–Al–Mn-based shape memory alloys were investigated. It was found that hardness was dramatically increased by ageing due to the formation of fine bainitic plates and that the volume fraction of the bainite phase with ageing time can be described by the Austin–Rickett equation. The martensitic transformation temperatures decreased with the formation of bainite plates, mainly due to the composition change of the β-matrix. Moreover, the growth of thermally induced martensite plates was disturbed by the existence of bainite plates. Consequently, the transformation intervals (M_s–M_f and A_f–A_s) and transformation hystereses (A_f–M_s and A_s–M_f) increased with the progress of bainitic transformation.     

Effect of treatment of activated carbon fiber cloth electrodes with cold plasma upon performance of electric double-layer capacitors

Charge/discharge behavior of electric double-layer capacitors composed of activated carbon fiber cloth (ACFC) electrodes and an organic electrolyte was investigated. The modification of the ACFC electrodes was performed using cold plasma generated in argon-oxygen atmosphere. The effect of the cold plasma treatment of the ACPC electrodes on the capacitor performance was discussed on the basis of the physical and chemical properties of the ACFC surface such as pore radius distribution and surface atom concentration.     

Controlling and monitoring interfacial reactions in composites of azidosilane modified glass filled polyethylene

Model composites of spherical glass particles dispersed in a matrix of high density polyethylene were prepared with controlled variations in the interfacial structure. Dynamic-mechanical measurements of the composites in the melt state were recorded. The physical properties are found to relate to the morphology, bonding, reactivity, and other characteristics of the interfacial region which can be controlled by the applied chemistry. The interfacial reactions can be monitored in-sity by dynamic-mechanical analysis and differential scanning calorimetry.     

Characterization and corrosion protection properties of polypyrrole / montmorillonite electropolymerized onto aluminium alloy 1100

Films of Polypyrrole/Montmorillonite (PPy/MT) clays were electropolymerized potentiostatically on aluminium alloy 1100, using sodium dodecylbenzenesulfonate (SDBS) as a dopant. Two clay species were used: Na⁺-Montmorillonite (MT-Na) and modified-Montmorillonite (MT-M). The characterization of the PPy/MT films performed by XRD and TEM shows that the exfoliation method employed, as well the electrochemical polymerization method used in this work, allow nanocomposite materials to be obtained. The PPy/MT films were found to have less electrical conductivity than pure PPy. The corrosion protection of aluminium alloy 1100 covering PPy/MT was evaluated by electrochemical techniques in 0.05 mol L⁻¹ NaCl medium. The electrochemical parameters derived from the polarization curves, together with the EIS data, revealed that the corrosion resistance of PPy/clay coatings depends on the type and concentration of Montmorillonite employed. The best performance in the corrosion protection of the aluminum was achieved with PPy/MT films containing 1% of clay.     

Kinetic arrest behavior in martensitic transformation of NiCoMnSn metamagnetic shape memory alloy

High-field magnetic measurements were carried out in order to investigate behaviors of field-induced reverse martensitic transformation and kinetic arrest of NiCoMnSn metamagnetic shape memory alloy. In the thermomagnetization curves, it was confirmed that the reverse martensitic transformation temperature decreases 67 K by applying magnetic field of 5 T, while in the magnetic field cooling process under 5 T, martensitic transformation does not occur down to low temperatures. Equilibrium magnetic field, defined from the critical magnetic fields of the metamagnetic evidence in the magnetization curves, exhibits almost constant below about 100 K, suggesting that the entropy change becomes zero, which is considered to cause kinetic arrest behavior.     

EXPERIMENTAL STUDIES ON A NOVEL CHEMICAL HEAT PUMP DRYER USING A GAS-SOLID REACTION

The authors have been studying Chemical Heat Pumps (CHP) from the viewpoints of energy saving and environmental impact. The CHP can store thermal energy in the form of chemical energy by an endothermic reaction, and release it at various temperature levels during heat demand periods by exo/endothermic reactions. The authors have proposed in an earlier study a novel chemical heat pump (CHP) system for environmentally-friendly effective utilization of thermal energy in drying as a chemical heat pump dryer (CHPD). In this exploratory study, we test the effectiveness of operating the proposed CHPDs experimentally. Basic experiments on the CHPDs such as hot dry air production for convective drying are performed on lab-scale CHPD apparatuses using gas-solid reactions in calcium oxide/calcium hydroxide reactant beds. The proposed CHPDs are found to produce hot air by CHP operation for drying. The temperature levels of the produced hot air and the reaction rates/conversions are as good as in the case of hot water supply system using basically same CHP operation. The cold heat for air dehumidification is also found to be generated/recovered by the same CHPD system. The generated heat amounts can be increased by changing the operating conditions although the heat recovery must be enhanced for practical application of CHPDs.     

Numerical simulation on the dynamics of photoinduced cooperative phenomena in molecular crystals

We develop a new simulation method to study the dynamics of initial nucleation processes of photoinduced structural change of molecular crystals. In order to describe the nonadiabatic transition in each molecule, we employ a model of localized electrons coupled with a fully quantized phonon mode, and the time-dependent Schrödinger equation for the model is numerically solved. By applying a mean-field approximation in solving the Schrödinger equation, the calculation method is quite efficient on parallel computing systems. We show that coherently driven molecular distortion plays an important role in the successive conversion of electronic states which leads to photoinduced cooperative phenomena.