Super absorbent,light, and highly flame retardant cellulose‐based aerogel crosslinked with citric acid

Light (0.089–0.12 g cm^?3), superabsorbent (84–99 g water/1 g aerogel), and highly flame retardant non‐crosslinked cellulose aerogel (CA) and crosslinked cellulose aerogel (CL‐CA) have been successfully produced from pruning waste of blueberry tree. The prepared aerogels with three dimensional porous structure have a remarkably thermal stability and flame retardant performance, which totally burned after 136–200 s. Besides, CA and CL‐CA have an important Brunauer–Emmet–Teller surface area, which are 348 and 275 m² g^?1, respectively. The concepts of this study are simple and bio‐wastes are easily available and sustainable at low cost, and therefore, the current process is appropriate for industrial scale production and has a significant potential in the future of green materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45315.     

Effect of talc on the properties of polypropylene/ethylene/propylene/diene terpolymer blends

In the present study, the effect of talc content on the mechanical, thermal, and microstructural properties of the isotactic polypropylene (i‐PP) and elastomeric ethylene/propylene/diene terpolymer (EPDM) blends were investigated. In the experimental study, five different talc concentrations, 3, 6, 9, 12, and 15 wt %, were added to i‐PP/EPDM (88/12) blends to produce ternary composites. The mechanical properties such as yield and tensile strengths, elongation at break, elasticity modulus, izod impact strength for notch tip radius of 1 mm, and hardness with and without heat treatments and thermal properties, such as melt flow index (MFI), of the ternary composites have been investigated. The annealing heat treatment was carried out at 100°C for holding time of 75 h. From the tensile test results, an increased trend for the yield and tensile strengths and elasticity modulus was seen for lower talc contents, while elongation at break showed a sharp decrease with the addition of talc. In the case of MFI, talc addition decreased the MFI of i‐PP/EPDM blends. It was concluded that, taking into consideration, mechanical properties and annealing heat treatment, heat treatment has much more effect on higher yield and tensile strengths, elongation at break, elasticity modulus, impact strength, and hardness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3033–3039, 2006     

Structure and Dielectric Properties of Pb(Sc2/3W1/3)O3–Pb(Zr/Ti)O3 Relaxors

The structure and dielectric properties of (1− x )Pb(Sc_2/3W_1/3)O₃–( x )Pb(Zr/Ti)O₃ ceramics have been investigated over a full substitution range. All compositions with x < 0.5 adopt a cubic perovskite structure; however, for x ≤ 0.25 a doubled cell results from a 1:1 ordered distribution of the B-site cations. The structural order in Pb(Sc_2/3W_1/3)O₃ (PSW) can be described by a random-site model with one cation site occupied by Sc³⁺ and the other by a random distribution of (Sc_1/3³⁺W_2/3⁶⁺). The ordering is destabilized in solid solutions of PSW with PbZrO₃ (PSW–PZ), but stabilized by PbTiO₃ in the (1− x )PSW–( x )PT system. The changes in order are accompanied by alterations in the dielectric response of the two systems. For PSW–PZ the temperature of the permittivity maximum ( T _ɛ,max) increases linearly with x ; however, for PSW–PT T _ɛ,max decreases in the ordered region (up to x = 0.25) and then increases rapidly as the order is lost. Similar effects were produced by modifying the degree of order of (0.75)PSW–(0.25)PT; when the order parameter was reduced from ∼1.0 to ∼0.65, T _ɛ,max increased by more than 60°C.     

An empirical model for kinetics of boron removal from boron-containing wastewaters by ion exchange in a batch reactor

In this study, it was investigated boron removal from boron containing wastewaters prepared synthetically. The experiments in which Amberlite IRA 743, boron specific resin was used was carried out in a batch reactor. The ratio of resin/boron solution, boron concentration, stirring speed and temperature were selected as experimental parameters. The obtained experimental results showed that percent of boron removal increased with increasing ratio of resin/boron solution and with decreasing boron concentration in the solution. Stirring speed and temperature had not significant effects on the percent of total boron removal, but they increased the starting boron removal rate. As a result, it was seen that about 99 % of boron in the wastewater could be removed at optimum conditions. On the other hand, the process kinetics were predicted by using heterogeneous fluid-solid reaction models. It was seen statistically that the kinetics of this process agreed the pseudo- second order model, as follows: X_Bl(1−X_B) = 11,241.5[OH][C]^−1.76[S/L]^2.17exp(−19,57l.2/RT)t^1.24     

Shrinkage cracking of lightweight concrete made with cold-bonded fly ash aggregates

Shrinkage cracking performance of lightweight concrete (LWC) has been investigated experimentally on ring-type specimens. LWCs with and without silica fume were produced at water-cementitious material ratios (w/cm) of 0.32 to 0.55 with cold-bonded fly ash coarse aggregates and natural sand. Coarse aggregate volume ratios were 30%, 45%, and 60% of the total aggregate volume in the mixtures. A total of 12 lightweight aggregate concrete mixtures was cast and tested for compressive strength, static elastic modulus, split-tensile strength, free shrinkage, weight loss, creep, and restrained shrinkage. It was found that the crack opening on ring specimens was wider than 2 mm for all concretes. Free shrinkage, weight loss, and maximum crack width increased, while compressive and split-tensile strengths, static elastic modulus, and specific creep decreased with increasing coarse aggregate content. The use of silica fume improved the mechanical properties but negatively affected the shrinkage performance of LWCs. Shrinkage cracking performance of LWCs was significantly poorer than normal weight concrete (NWC).     

Electro-optical properties,decomposition pathways and the hydrostatic pressure-dependent behaviours of a double-cation hydrogen storage material of $$\hbox {Al}_{3}\hbox {Li}_{4}(\hbox {BH}_{4})_{13}$$

Electro-optical properties, the decomposition pathways and the pressure-dependent behaviours of \(\hbox {Al}_{3}\hbox {Li}_{4}(\hbox {BH}_{4})_{13}\) have been investigated using a first-principle plane-wave pseudopotential method. \(\hbox {Al}_{3}\hbox {Li}_{4}(\hbox {BH}_{4})_{13}\) is a kind of double-cation borohydride, consisting of distorted tetrahedral anions \([\hbox {Al}(\hbox {BH}_{4})_{4}]^{-}\) and cations \([\hbox {Li}_{4}(\hbox {BH}_{4})]^{3+}\), which obeys the stability criteria of decomposition reactions. Herein, two possible decomposition reactions of the compound are proposed, which release 18 hydrogen molecules (about 12.03 wt%) in the first reaction and 24 hydrogen molecules (about 16.04 wt%) in the second reaction. On increasing the pressure on the structure, the lattice parameter, the volume of unit cell, the quasiparticle band gap and also enthalpy of the system decrease nearly monotonically; therefore, the acceptor levels gradually get filled and the Fermi level shifts upward. Results of computational investigations of the structural, electronic and thermodynamic parameters and their pressure-dependent behaviours indicate that \(\hbox {Al}_{3}\hbox {Li}_{4}(\hbox {BH}_{4})_{13}\) has intriguing properties. Therefore, it would be a very promising material for hydrogen storage technology.     

An arbitrary Lagrangian‐Eulerian framework with exact mass conservation for the numerical simulation of 2D rising bubble problem

An arbitrary Lagrangian‐Eulerian framework, which combines the advantages of both Lagrangian and Eulerian methods, is presented to solve incompressible multiphase flow problems. The incompressible Navier‐Stokes equations are discretized using the side‐centered unstructured finite volume method, where the velocity vector components are defined at the midpoint of each cell face, while the pressure term is defined at element centroids. The pressure field is treated to be discontinuous across the interface with the discontinuous treatment of density and viscosity. The surface tension term at the interface is treated as a force tangent to the interface and computed with several different approaches including the use of Legendre polynomials. In addition, the several different discretizations of interface kinematic boundary conditions are investigated. For the application of the interface kinematic boundary condition, a special attention is given to satisfy both local and global discrete geometric conservation law to conserve the total mass of both species at machine precision. The mesh vertices are deformed by solving the linear elasticity equations due to the normal displacement of interface. The resulting algebraic equations are solved in a fully coupled manner, and a one‐level restricted additive Schwarz preconditioner with a block‐incomplete factorization within each partitioned subdomain is used for the resulting fully coupled system. The method is validated by simulating the classical benchmark problem of a single rising bubble in a viscous fluid due to buoyancy. The results of numerical simulations are found out to be in an excellent agreement with the earlier results in the literature. The mass of the bubble is conserved, and discontinuous pressure field is obtained to avoid errors due to the incompressibility condition in the vicinity of the interface, where the density and viscosity jumps occur.     

Conductance-capacitance and voltage behavior of 1% Os-doped YMnO3/p-Si contacts under varying frequencies

The admittance characterizations of the ferroelectric Perovskite Materials 1% Osmium (Os)-doped YMnO₃ and p-Si contacts were conducted by capacitance–voltage (C–V) and conductance–voltage (G–V) curves at various frequencies. In measurements performed in this study, it was seen that the device behaves like a metal/oxide layer/semiconductor (MOS) or a metal/insulator layer/semiconductor (MIS) capacitor, just because of the ferroelectric thin film at the metal/Si substrate interface. Therefore, an accumulation region (saturation region) formed in the forward bias C–V and G–V curves at each frequency. The accumulation region series resistance value R_sc was determined from the C–V and G–V curves. The R_sc value ranged from 652 Ω at 20 kHz to 56 Ω at 1000 kHz. Furthermore, the series resistance R_s versus V curves with frequency as a parameter were plotted from the C–V and G–V data. A peak appeared around 0.0 V in the R_s vs V curve at each frequency. The peak position of the R_s shifted towards positive voltages from approximately ? 0.2 V at 20 kHz to about 0.10 V at 1000 kHz. The peak position in the corrected conductance vs voltage curves shifted towards positive voltages from approximately 0.0 V at 20 kHz to about 0.20 V at 1000 kHz. It was seen that the series resistance effect caused the highest error in the capacitance occurs in accumulation and in some part of the depletion region at C–V and G–V results depending on frequency. So to conclude, it is not possible to disregard the series resistance everytime. Therefore, the series resistance must be measured and must be considered at the measured admittance.

     

Polypyrrole doped graphene nanocomposites as advanced positive electrodes for vanadium redox flow battery

Obtaining high catalytic activity and cycling stability of electrodes play a crucial role in vanadium redox flow batteries (VRFBs). However, some limitations, such as cost and required multiple synthesis procedures force us as an alternative solution; polypyrrole–sulfur-doped graphenes (PPy–SGs) are synthesized with a user-friendly electrochemical method and applied as a positive electrode for VRFB for the first time in the literature. Polypyrrole and sulfur-doped graphenes are formed on the graphite electrodes simultaneously in a 0.001 M pyrrole and 1.0 M H₂SO₄ solution at room temperature by a single-step cyclic voltammetry (CV) process. The electrode surface modification parameters such as the amount of S-doping, defect, and functionality rate of polymers and graphene are controlled by changing the cycle numbers at the scanned in a specific potential range. FTIR, Raman, XPS, SEM, and CV methods show the formation of PPy and sulfur-doped graphene layers on graphite electrode surfaces. The effects of PPy–SGs were investigated in VRFB for VO⁺²/VO₂⁺ redox reactions. The electrochemical measurements of the PPy–SGs are carried out by CV and electrochemical impedance spectroscopy (EIS) analysis. According to CV results, PPy–SG20 demonstrates the best performance as a positive electrode material of the VRFB. This can be attributed to the significant improvement in the electrochemical kinetics by polypyrrole decorating graphene and enhancing active sites.

     

Microwave treatment and fluorine addition on Co-B catalyst to improve the hydrogen production rate

In this paper, microwave heating treatment process and fluorine addition over Co-B-F catalyst was applied to produce hydrogen via the hydrolysis of NaBH₄. The effects of microwave heating treatment time, microwave heating treatment power, microwave inert gases and temperature on the catalyst were studied. X-ray absorption spectrometer, scanning electron microscopy coupled to energy-dispersive spectroscopy, nitrogen adsorption analyzer and infrared spectrometer were performed for the chemical characterization of the catalysts. It was found that Co-B-F and microwave-treated Co-B-F catalysts exhibited excellent catalytic activity to produce hydrogen. The rates of the maximum hydrogen production for untreated and microwave-treated Co-B-F catalysts are 1868 and 3400?mL/g/min, respectively.