A New Paradigm for Materials Discovery: Heuristics‐Assisted Combinatorial Chemistry Involving Parameterization of Material Novelty

The combinatorial chemistry (combi‐chem) of inorganic functional materials has not yet led to the discovery of commercially interesting materials, in contrast to the many successful discoveries of heterogeneous catalysts leading to commercialization. Novel materials for practical use are likely hidden in the multicompositional search space that contains an infinite number of possible stoichiometries, as well as a large number of well‐known materials. To discover new, inorganic luminescent materials (phosphors) from the SrO‐CaO‐BaO‐La₂O₃‐Y₂O₃‐Si₃N₄‐Eu₂O₃ search space, heuristics optimization strategies, such as the non‐dominated‐sorting genetic algorithm (NSGA) and particle swarm optimization (PSO) are coupled with high‐throughput experimentation (HTE) in such a manner that the experimental evaluation of fitness functions for the NSGA and PSO is accomplished by the HTE. The proposed strategy also involves the parameterization of the material novelty to avoid systematically a futile convergence on well‐known, already‐established materials. Although the process starts with random compositions, we finally converge on a novel, single‐phase, yellow‐green‐emitting luminescent material, La_4–xCa_xSi₁₂O_3+xN_18?x:Eu²⁺, that has strong potential for practical use in white light‐emitting diodes (WLEDs).     

High‐performance heat‐sink composites incorporating micron‐sized inorganic fillers and Sn/In metal particles

A novel thermal‐barrier composite system was developed by incorporating fusible metal particles in the epoxy matrix system. Using the latent heat of melting, the Sn/In metal particles having melting temperature at 125°C were imbedded in the polymer matrix to suppress the thermal shock and transient temperature variation. The high‐density metal particles were successfully dispersed in the polymer matrix without sinking by incorporating inorganic particles of aluminum nitride (AlN) and boron nitride (BN), which desirably facilitated the heat dissipation to give a high thermal conductivity at around 10 W/m‐K. Under the repeated melting and cooling cycles, the spherical shape of metal particles and the latent heat of melting were retained demonstrating the reversible thermal‐barrier capability of the developed composite system. Under the constant‐heating conditions, it was validated that the temperature rise was delayed by the endothermic melting of Sn/In particles. The developed composite system could find various applications since it could minimize damages caused by the repeated thermal fatigue and/or accidental thermal shock. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Emulsion properties of pork myofibrillar protein in combination with microbial transglutaminase and calcium alginate under various pH conditions

In this study, the effects of microbial transglutaminase (MTG) and calcium alginate (CA) systems in combination with soybean oil on the emulsion properties of porcine myofibrillar protein (MP) were evaluated under various pH conditions. MTG was shown to improve emulsifying capacity and creaming stability, which increased with increasing pH values up to 6.5. The CA did not influence emulsifying capacity, but it improved the creaming stability of the MP-stabilized emulsions. Both MTG and CA enhanced the rheological properties, but their effects on the physical characteristics of the protein evidenced an opposite trend in relation to pH, i.e., the MTG system improved both the emulsion and gelling properties with increasing pH, whereas the CA system was effective when the pH was lowered. By combining the two MP gelling systems, a stable and pH-insensible emulsion could be produced.     

Effects of microbial transglutaminase and sodium alginate on cold-set gelation of porcine myofibrillar protein with various salt levels

The effects of microbial transglutaminase (TG) and sodium alginate (SA) systems on cold-set gelation of myofibrillar protein (MP) at various salt levels were investigated. The gelation kinetics data showed that both TG and SA had optimal but different salt levels to form an acceptable cold-set MP gel. Although their gelling characteristics were altered with different salt levels, the combination of TG and SA showed a rapid cold-set MP gel formation, regardless of salt levels. The effect of TG and SA on gel strength was reversed by increasing the salt level, while the cold-set MP gel strength of the TG and SA combination was not affected by salt levels. Furthermore, the SA system contributed to improved water-binding ability and cold-set MP gel formation, while the TG system enhanced the gel strength of the MP after cooking at low-salt levels. In addition, TG's effects on gel strength of MP increased at higher salt levels, the SA system prevented the moisture loss induced by the TG reaction. There was no evidence of any interaction between SA and MP in the thermogram and gel electrophoresis data. Results from this study suggested that a system combining TG with SA had the potential advantage of improving the water-binding ability and producing cold-set MP gelation at an even lower salt level than TG alone.     

Electromagnetic wave shielding effectiveness of Fe73.5Si13.5B9Nb3Cu1 powder/epoxy composites

Magnetic powders composed of Fe_73.5Si_13.5B₉Nb₃Cu₁ were prepared using a ball milling technique, and selected powders were annealed at 823 K in a vacuum. Scanning electron microscopy observations determined the shapes of the powders to be of a flake type. To test the electromagnetic wave absorption properties, Fe_73.5Si_13.5B₉Nb₃Cu₁ and epoxy composites were fabricated using an electron beam curing technique with powder/epoxy ratios of 20/80, 30/70, 40/60, and 50/50 by weight. The complex permeability and permittivity of the composites were measured using a network analyzer (0.5–8 GHz), and were used to calculate the refection losses as a function of the composite thickness and frequency. The band width of a reflection loss below ?20 dB was 700 MHz from 4.23 GHz to 4.93 GHz at 3.8 mm thickness, attributed to the composite containing 50 wt% of powder. For the composite containing 50 wt% of annealed powder, the minimum reflection loss was observed near 8 GHz at 2.8 mm thickness.     

Ternary Poly(styrene‐co‐acrylonitrile)/Poly(vinyl chloride) Blend Composites with Multi‐Walled Carbon Nanotubes and Enhanced Physical Characteristics

We report a ternary system of poly(styrene‐co‐acrylonitrile) (SAN), poly(vinyl chloride) (PVC), and multi‐walled carbon nanotube (MWCNT) composites prepared by both a solution blending method and the SOAM. The MWCNT content in the composites was optimized by both TGA and mechanical characterization of binary mixtures of SAN/MWCNT and PVC/MWCNT composites. The dispersion of MWCNTs in the miscible SAN/PVC blends was characterized by FT‐Raman spectroscopy, FE‐SEM, and FE‐TEM. The distribution of MWCNTs in the SAN/PVC blends was examined in terms of their wetting coefficients and minimization of the interfacial energy. Composites prepared using the SOAM method showed superior physical properties to the SAN/PVC blends and SAN/PVC/MWCNT composites prepared using the solution blending method.

     

Electron‐beam‐radiation‐induced grafting of acrylonitrile onto polypropylene fibers: Influence of the synthesis conditions

Electron‐beam‐radiation‐induced grafting of acrylonitrile onto polypropylene fibers was investigated with a pre‐irradiation method. Grafting conditions such as the solvents, additives, monomer concentration, radiation dose, and temperature were varied, and the effects on the degree of grafting were studied. The nature of the reaction medium and additives had a considerable influence on the degree of grafting. The dilution of acrylonitrile with N,N‐dimethylformamide significantly enhanced the degree of grafting in comparison with other solvents. The addition of sulfuric acid to the reaction mixture led to an increase in the degree of grafting and an acceleration of the rate of grafting. The order of dependence of the rate of grafting on the pre‐irradiation dose and monomer concentration was found to be 1.31 and 1.21, respectively, in the presence of sulfuric acid. The activation energy for grafting was calculated to be 21.9 kJ/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Lipase-Catalyzed Synthesis of Saccharide–Fatty Acid Esters Using Suspensions of Saccharide Crystals in Solvent-Free Media

Saccharide–fatty acid esters, important biobased and biodegradable emulsifiers in foods, cosmetics, and pharmaceuticals, were produced with high yields and productivity via immobilized Rhizomucor miehei lipase-catalyzed esterification in solvent-free systems at 65 °C. Preliminary experiments demonstrated high rates of reaction occurred in the presence of acetone near or above its boiling point, due to the formation of 10–200 μm suspensions of saccharide particles. Subsequently, a two-step process was developed to produce a solvent-free supersaturated solution of 1.5–2.0 wt% saccharide that remained stable for ≥10–12 h. The solvent-free suspensions were used in a bioreactor system at 65 °C, consisting of a reservoir open to the atmosphere that contained molecular sieves, a peristaltic pump, and a packed bed bioreactor, operated under continuous recirculation. At 10 h intervals, suspensions were re-formed by treating the substrate/product mixture with additional acyl acceptor and applying strong agitation. Using this system and approach, a product mixture containing 88% fructose oleate was formed, of which 92% was monoester, within 6 days. This equates to a productivity of 0.2 mmol h⁻¹ g⁻¹, which is similar to values reported for synthesis in the presence of solvent.     

Atmospheric Gas-Aerosol Equilibrium II. Analysis of Common Approximations and Activity Coefficient Calculation Methods

The gas-aerosol equilibrium model, SCAPE, presented in Part I is used to evaluate the sensitivity of thermodynamic calculations of aerosol composition to common approximations and the choice of activity coefficient estimation method. The treatment of weak electrolytes, associated ammonia, NH₃(aq), and bisulfate ion, HSO₄ ^?, is analyzed. Comparisons of the three multi-component activity coefficient estimation methods are carried out with a variety of data. On the basis of the sensitivity analysis results, recommendations are provided for treating these electrolytes and for selecting an activity coefficient estimation method in atmospheric gas-aerosol equilibrium calculations. The two gas-aerosol equilibrium models, SCAPE and AIM, are compared. Remaining questions in gas-aerosol equilibrium are highlighted.