The on demand generation of hydrogen from Co-Ni bimetallic nano catalyst prepared by dual use of hydrogel: As template and as reactor

We report the preparation of metal nanoparticles in various formulations inside p(2-acrylamido-2-methyl-1-propansulfonic acid; p(AMPS)) hydrogels and their utilization as a catalyst in hydrolysis of NaBH₄. The swollen, flexible p(AMPS) network was used for metal ion loading and reduction in situ for the preparation of Co:Ni nanoparticles as bimetallic clusters in various formulation, and Co and Ni bimetallic catalysts as Co + Co, Co + Ni, Ni + Co and Ni + Ni. In addition to utilization of hydrogels as support materials, the p(AMPS)-metal nanoparticle system was used as catalyst to generate hydrogen in the hydrolysis of NaBH₄ with very high yield. Various parameters for the hydrolysis reaction were determined and the activation parameters were calculated. For the first time, inclusion of ferrite magnetic particles to control hydrogen generation on demand by using an externally applied magnetic field to remove the hydrogel-catalyst system from the hydrolysis medium is reported.     

Controllable hydrogen generation by use smart hydrogel reactor containing Ru nano catalyst and magnetic iron nanoparticles

In this study, p(AMPS) hydrogels are synthesized from 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) via a photo polymerization technique. The hydrogels are used as template for metal nanoparticles and magnetic ferrite nanoparticles, and also as a catalysis vessel in the generation of hydrogen from the hydrolysis of NaBH₄. Approximately 5 nm Ru (0) and 20-30 nm magnetic ferrite particles are generated in situ inside this p(AMPS) hydrogel network and then used as a catalysis medium in hydrogen production by hydrolysis of sodium boron hydride in a basic medium. With an applied external magnetic field, the hydrogel reactor, containing Ru and ferrite magnetic particles, can be removed from the catalysis medium; providing on-demand generation of hydrogen. The effect of various parameters such as the initial concentration of NaBH₄, the amount of catalyst and temperature on the hydrolysis reaction is evaluated. The activation energy for hydrogen production by Ru (0) nanoparticles is found to be 27.5 kJ mol⁻¹; while the activation enthalpy is 30.4 kJ mol⁻¹. The hydrogen generation rate in presence of 5 wt% NaOH and 50 mg p(AMPS)-Ru catalyst is 8.2 L H₂ min⁻¹ g Ru.     

Computation of Instantaneous Fuel Consumption for the Determination of Combustion Efficiency with Special Reference to Coal Briquette Size

This study comprises of the computation of instantaneous fuel consumptions as a straight means for the interpretation of combustion-related characteristics of coal. The model relies on the determination of the extent of combustion by the calculated fuel combustion amounts at specific instants in order to examine the oxidation behavior and possible influences governed by any variable of interest. In this context, coal briquettes prepared by varying dimensions with and without a volume constraint were evaluated and instantaneous fuel consumptions corresponding to the determined instants were computed for comparison rather than introducing the model with a single experiment. Thus, the influences imposed by the enlargement of the briquette volume as well as by the variations in the compactness of briquettes on the effectiveness and efficiency of combustion reactions were dealt. The applicability of the model was checked by the trends revealed from the view of reaction kinetics in terms of activation energies. At the end of the study, the results deduced on the grounds of instantaneous fuel consumption values were seen to have been in full confirmation by those related to reaction kinetics, showing the applicability of the model in reflecting the particular cases during a combustion reaction.     

Influence of α-Al2O3 addition on sintering and grain growth behaviour of 8 mol% Y2O3-stabilised cubic zirconia (c-ZrO2)

The effect of α-Al₂O₃ addition on sintering and grain growth behaviour of high purity 8 mol% yttria-stabilised cubic zirconia (c-ZrO₂) was investigated. For these purposes, 1 wt.% α-Al₂O₃ was selected as a dopant in c-ZrO₂. The slip-cast specimens were sintered at different temperatures between 1150 and 1400 °C. It was seen that doped c-ZrO₂ had a faster sintering rate and lower sintering temperature than undoped c-ZrO₂. In particular, doped c-ZrO₂ achieved a density of 95% of its theoretical value at 1275 °C, while undoped c-ZrO₂ reached the same value at 1325 °C. The different sinterability of doped c-ZrO₂ and undoped c-ZrO₂ can be attributed to their different behaviour of grain growth. For grain growth measurements, the specimens sintered at 1400 °C were annealed at 1400, 1500 and 1600 °C for 10, 30 and 66 h. It was seen that grain growth rate could be controlled by the deliberate addition of 1 wt.% grain boundary phase of α-Al₂O₃. A grain growth exponent of 2 and activation energy for grain growth of 298 kJ/mol were obtained for undoped c-ZrO₂. The α-Al₂O₃ containing specimens had a grain growth exponent of 3 and activation energy of 361 kJ/mol. The slow grain growth in doped c-ZrO₂ is attributed to solute ions segregation in grain boundary region. The addition of the grain boundary phase results in limiting matter transfer along the grain boundary resulting in slower grain growth.     

Activated carbon from paulownia wood: Yields of chemical activation stages

Paulownia wood was used as a raw material in the preparation of activated carbon by chemical activation with phosphoric acid. The conversion of wood into activated carbon consists of sample preparation, impregnation, carbonization, and finishing. Mass changes associated with the impregnation, filtration, carbonization, and washing processes were measured, and the yields of these processes were calculated and analyzed. The effects of final carbonization temperature (300–600°C) and impregnation ratio (1–4) on the yields of chemical activation stages were investigated. Experimental results show that the final carbonization temperature and impregnation ratio have a significant effect on the yield of these stages.     

Adsorptive polyHIPE composites based on biosorbent immobilized nanoclay: Effects of immobilization techniques

Styrene/divinyl benzene‐based macroporous polyHIPE composites were prepared from water‐in‐oil (w/o) high internal phase emulsion (HIPE) templates by using both organo‐modified montmorillonite (MMT) and a nonionic surfactant. For this purpose, Spirulina (Sp) microalgae was immobilized onto Na‐MMT clay by using two different modification techniques. They are based on conventional adsorption in solution (SOL) and novel cryoscopic expansion (C‐XP) assisted adsorption. Highly porous nanocomposites were prepared by using different percentages of modified nanoclays (SpSOLM/SpXPM) with a constant internal phase volume of 80%. The emulsion stability, morphology, and dye adsorption capacities were discussed by paying attention to nanoclay immobilization techniques, clay loading degree and surfactant concentration. The critical amount of nonionic surfactant for formation of the stable neat HIPE template was found to be only 5 vol% with respect to volume of organic phase. However, this amount was further reduced to much less value (2 vol%) with Sp immobilized nanoclays via help of cooperative interactions of Sp and MMT nanoclay. The C‐XP assisted modification of clay led to nanocomposites with 580% higher adsorption capacity for cationic dye. This remarkable benefit was obtained with even 0.5% clay loading and only 2% surfactant concentration. POLYM. ENG. SCI., 58:1229–1240, 2018. © 2017 Society of Plastics Engineers     

Synthesis and characterization of pyrrole and thiophene functional polystyrenes via “click chemistry”

Novel side-chain pyrrole or thiophene functional polystyrenes (PS-Py and PS-Th) were synthesized by using ‘‘click chemistry’’ strategy. First, approximately 40% of chloro groups of poly(styrene-co-chloromethylstyrene) P(S-co-CMS), prepared by nitroxide mediated radical polymerization (NMRP), were converted to azido groups by using NaN₃ in N,N-dimethylformamide. Propargyl pyrrole was prepared by etherification of 4-(1H-pyrrol-1-yl)phenol prepared by Clauson-Kaas reaction using propargylbromide. Propargyl thiophene was synthesized by heterogeneous esterification reaction between 3-thiophenecarboxylic acid and propargylbromide. Finally, azido-functionalized polystyrene was coupled to these propargyl functional heterocyclics with high efficiency by click chemistry. The intermediates at various stages and final polymers were characterized by spectral analysis and cyclic voltammetry.     

Microstructural development of interface layers between co-sintered alumina and spinel compacts

Tests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500 °C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40 μm length and 5 μm width was observed after 16 h at 1500 °C. Growth rate of the columnar spinel grains from parent spinel towards alumina follows parabolic kinetics, controlled by a mixed process of O²⁻ ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth.     

CuO as a sintering additive for (Bi1/2Na1/2)TiO3-BaTiO3-(K0.5Na0.5)NbO3 lead-free piezoceramics

CuO as a sintering additive was utilized to explore a low-temperature sintering of 0.92(Bi_1/2Na_1/2)TiO₃-0.06BaTiO₃-0.02(K_0.5Na_0.5)NbO₃ lead-free piezoceramic which has shown a promise for actuator applications due to its large strain. The sintering temperature guaranteeing the relative density of greater than 98% is drastically decreased with CuO addition, and saturates at a temperature as low as ∼930 °C when the addition level exceeds ca. 1 mol.%. Two distinguished features induced by the addition of CuO were noted. Firstly, the initially existing two-phase mixture gradually evolves into a rhombohedral single phase with an extremely small non-cubic distortion. Secondly, a liquid phase induced by the addition of CuO causes an abnormal grain growth, which can be attributed to the grain boundary reentrant edge mechanism. Based on these two observations, it is concluded that the added CuO not only forms a liquid phase but also diffuses into the lattice. In the meantime, temperature dependent permittivity measurements both on unpoled and poled samples suggest that the phase stability of the system is greatly influenced by the addition of CuO. Polarization and strain hysteresis measurements relate the changes in the phase stability closely to the stabilization of ferroelectric order, as exemplified by a significant increase in both the remanent strain and polarization values. Electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the stabilization of ferroelectric order originates from a significant amount of Cu²⁺ diffusing into the lattice on B-site. There, it acts as an acceptor and forms a defect dipole in association with a charge balancing oxygen vacancy.     

Extrusion of poly(ether imide) foams using pressurized CO2: Effects of imposition of supercritical conditions and nanosilica modifiers

Foams of an engineering plastic, poly(ether imide), were extruded using a single screw extruder employing pressurized CO₂ as the blowing agent. The porosity, pore size distributions, and the density of the foams were especially affected by the pressure drop, the pressure loss rate, and temperature at the die. Significant increases in porosity and pore size and corresponding decreases in density were observed when the pressure imposed on CO₂ became greater than the critical pressure values of CO₂ (i.e., the temperature was always greater than the critical temperature of the CO₂ in the extruder and the die). The viscoelastic material functions of the extruded foams depended especially on the density of the foam, with the elastic modulus increasing with density. The incorporation of nanosilica particles in the 0.08–0.6% by weight range increased only the density of the foam and did not provide any benefits in controlling of the nucleation rate and the pore size distribution, presumably due to their poor dispersibility and agglomerated state in the single screw extruder. POLYM. ENG. SCI., 54:2064–2074, 2014. © 2013 Society of Plastics Engineers