Bone-like apatite layer formation on the new resin-modified glass-ionomer cement

In this study, the apatite-forming ability of the new resin-modified glass-ionomer cement was evaluated by soaking the cement in the simulated body fluid. The Fourier Transform Infrared (FTIR) spectrometer and X-Ray Diffraction (XRD) patterns of the soaked cement pointed to the creation of poorly crystalline carbonated apatite. It was found that the releasing of calcium ions from the soaked cement will dominate the undesirable effect of polyacrylic acid on apatite formation. Consequently, the ionic activity products (IAPs) of the apatite in the surrounding medium increased which accelerated apatite nucleation induced by the presence of the Si–OH and COOH groups. Accordingly, the apatite nuclei started to form via primary heterogeneous nucleation and continued by secondary nucleation. Therefore, nucleation and growth occurs as in the layer-by-layer mode so that finite numbers of monolayers are produced. Subsequent formation of film occurs by formation of discrete nuclei (layer-plus-island or SK growth).     

Meso-scale deformation and damage in thermally bonded nonwovens

Thermal bonding is the fastest and the cheapest technique for manufacturing nonwovens. Understanding mechanical behaviour of these materials, especially related to damage, can aid in design of products containing nonwoven parts. A finite element (FE) model incorporating mechanical properties related to damage such as maximum stress and strain at failure of fabric’s fibres would be a powerful design and optimisation tool. In this study, polypropylene-based thermally bonded nonwovens manufactured at optimal processing conditions were used as a model system. A damage behaviour of the nonwoven fabric is governed by its single-fibre properties, which are obtained by conducting tensile tests over a wide range of strain rates. The fibres for the tests were extracted from the nonwoven fabric in a way that a single bond point was attached at both ends of each fibre. Additionally, similar tests were performed on unprocessed fibres, which form the nonwoven. Those experiments not only provided insight into damage mechanisms of fibres in thermally bonded nonwovens but also demonstrated a significant drop in magnitudes of failure stress and respective strain in fibres due to the bonding process. A novel technique was introduced in this study to develop damage criteria based on the deformation and fracture behaviour of a single fibre in a thermally bonded nonwoven fabric. The damage behaviour of a fibrous network within the thermally bonded fabric was simulated with a FE model consisting of a number of fibres attached to two neighbouring bond points. Additionally, various arrangements of fibres’ orientation and material properties were implemented in the model to analyse the respective effects.     

Ultrafast Thermal Plasma Preparation of Solid Si Films with Potential Application in Photovoltaic Cells: A Parametric Study

An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm²/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as Mo. After solvent evaporation, the resulting porous layer is exposed to the flame tale of inductively coupled RF plasma to sinter and melt the surface particles and to prepare a solid film of silicon. It is shown that by controlling the flow dynamics and heat transfer around the substrate, and managing the kinetic parameters (i.e., exposure time, substrate transport speed, and reaction kinetics) in the reactor, we can produce solid crystalline Si films with the potential applications in photovoltaic cells industry. The results indicate that the optimum formation conditions with a film thickness of 250-700 μm is when the exposure time in the plasma is in the range of 5-12.5 s for a 100 × 50 mm large layer. By combining the Fourier’s law of conduction with the experimental measurements, we obtained an effective heat diffusivity and developed a model to obtain heat diffusion in the porous layer exposed to the plasma. The model further predicts the minimum and maximum exposure time for the substrate in the plasma flame as a function of material properties, the porous layer thickness and of the imposed heat flux.     

Optimal Allocation of Water Reuse Using Modified TODIM-GP Approach with Considering the Leopold Matrix Outputs

Allocation of water use is one of the most important challenges of water resources management that needs to evaluate water reuse options, especially in areas with limited water resources, arid climate, increasing water demand due to population growth. In this study, the modified TODIM method (Multi-Criteria Decision-Making in Portuguese with considering the risk preferences of decision makers) that can be used with goal programming (GP) by considering Leopold matrix outputs in order to preform Environmental Impact Assessment (EIA). The present study is aimed at optimally allocate water reuse to multiple stakeholders in Najafabad, Isfahan, Iran. The results showed that the numerical model developed with an integration of optimization and quantitative evaluation can be considered as a useful tool to develop feasible guidelines for adapting the requirements of different stakeholders for optimized allocation of recycled water.