Enhancement of physical and optical performances of polycarbonate‐based diffusers for direct‐lit LED backlight unit by incorporation of nanoclay platelets

Using twin‐extrusion compounding followed by compression molding processes, polycarbonate/clay nanocomposite optical diffusers with highly intercalated and exfoliated nanostructure could be prepared for application in direct‐lit LED backlight unit. The incorporation of nanoclay platelets with an appropriate level of content substantially improved thermal resistance, as well as thermo‐mechanical, and mechanical flexural properties. The optical property of luminance uniformity with respect to both location and viewing angle was also enhanced by the load of nanoclay platelets along with silicone bead, probably due to efficient scattering and diffusion action of the nanoclay. However, excess loading of nanoclay had insignificant effect on the improvement of properties for the nanocomposite diffusers. In addition, the presence of nanoclay platelets in the PC matrix effectively suppressed the moisture absorption rate, suggesting the feasibility of avoiding the warpage phenomena of the optical diffuser during use. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42973.     

PtCu alloy nanotube arrays supported on carbon fiber cloth as flexible anodes for direct methanol fuel cell

The rapid development of flexible and portable electrochemical energy devices has promoted the demand for flexible and lightweight electrocatalysts. Here we report flexible high performance electrocatalysts based on PtCu alloy nanotube arrays on carbon fiber cloth (CFC) (PtCu ANTAs/CFC) for direct methanol fuel cell (DMFC). Compared with Pt NTAs/CFC and commercial Pt/C, the PtCu ANTAs/CFC electrocatalysts exhibit significantly improved electrocatalytic activity and durability. Furthermore, the PtCu ANTAs/CFC electrocatalysts show excellent flexibility and they can keep almost constant electrocatalytic performance under the different distorted states, such as normal, bending and twisting states. The improved performance of the flexible PtCu ANTAs/CFC electrocatalysts can be ascribed to unique ANTAs, synergistic effect between Pt and Cu, and porous structure of CFC. This work shows the significant progress of high‐performance Pt‐based flexible anodes for DMFCs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 975–983, 2016     

ZrB2–SiC–G Composite Prepared by Spark Plasma Sintering of In‐Situ Synthesized ZrB2–SiC–C Composite Powders

To avoid introduction of milling media during ball‐milling process and ensure uniform distribution of SiC and graphite in ZrB₂ matrix, ultrafine ZrB₂–SiC–C composite powders were in‐situ synthesized using inorganic–organic hybrid precursors of Zr(OPr)₄, Si(OC₂H₅)₄, H₃BO₃, and excessive C₆H₁₄O₆ as source of zirconium, silicon, boron, and carbon, respectively. To inhabit grain growth, the ZrB₂–SiC–C composite powders were densified by spark plasma sintering (SPS) at 1950°C for 10 min with the heating rate of 100°C/min. The precursor powders were investigated by thermogravimetric analysis–differential scanning calorimetry and Fourier transform infrared spectroscopy. The ceramic powders were analyzed by X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The lamellar substance was found and determined as graphite nanosheet by scanning electron microscopy, Raman spectrum, and X‐ray diffraction. The SiC grains and graphite nanosheets distributed in ZrB₂ matrix uniformly and the grain sizes of ZrB₂ and SiC were about 5 μm and 2 μm, respectively. The carbon converted into graphite nanosheets under high temperature during the process of SPS. The presence of graphite nanosheets alters the load‐displacement curves in the fracture process of ZrB₂–SiC–G composite. A novel way was explored to prepare ZrB₂–SiC–G composite by SPS of in‐situ synthesized ZrB₂–SiC–C composite powders.     

Effect of Excess Magnesia on the Preparation of Cordierite Based on Waste Foundry Sand

Waste foundry sand collected from lost foam casting industry is a solid waste that contains ZrSiO₄. For the purpose of re‐utilization, it is adopted to synthesize cordierite with the addition of MgO powders and fused silica by direct sintering, meanwhile the effect of various MgO mole ratios on the sintering behaviors is investigated using XRD, SEM, and mercury porosimetry. The lowest temperature corresponding to the formation of cordierite is 1150°C, and the increase of MgO mole ratio does not reduce the temperature for cordierite crystallization but increase the microhardness and thermal expansion coefficients.     

Prediction of Solubility Properties from Transfer Energies for Acidic Phosphorus-Containing Rare-Earth Extractants Using Implicit Solvation Model

The differences of thermodynamics energies from the pure phase to a solution were used to predict the solubility properties of acidic phosphorus–containing rare-earth extractants. Four solvents, namely tributylphosphate, n-dodecane, toluene, and n-octanol were used. The thermodynamic cycle of the implicit solvation model and the structure model with short carbon chains were used. The relationship obtained by simulation of the solubility properties and extractant structures agreed qualitatively with reported experimental results. These results provide guidance for the design of new efficient extractants.     

Attrition of Victorian brown coal during drying in a fluidized bed

Analyzing the attrition of Victorian brown coal during air and steam fluidized bed drying, the change in particle size distribution over a range of initial moisture contents (60% to 0%) and residence times (0 to 60 minutes) was determined. Dried at a temperature of 130°C with a fluidization velocity 0.55 m/s and an initial particle size of 0.5–1.2 mm, both fluidization mediums show a shift in the particle size distribution between three and four minutes of fluidization, with a decrease in mean particle size from 665 µm to around 560 µm. Using differential scanning calorimetry (DSC), the change in particle size has been attributed to the transition between bulk and non-freezable water (approximately 55% moisture loss) and can be linked to the removal of adhesion water, but not to fluidization effects. This is proved through the comparison of air fluidized bed drying, steam fluidized bed drying, and fixed bed drying—the fixed bed drying is being used to determine the particle size distribution as a function of drying. The results show the three drying methods produce similar particle size distributions, indicating that both fluidization and fluidization medium have no impact upon the particle size distribution at short residence times around ten minutes. The cumulative particle size distribution for air and steam fluidized bed dried coal has been modeled using the equation P_d = A₂ + (A₁ ? A₂)/(1 + (d/x₀)^p), with the resultant equations predicting the effects of moisture content on the particle size distribution. Analyzing the effect of longer residence times of 30 and 60 minutes, the particle size distribution for steam fluidized bed dried coal remains the same, while air fluidized bed dried coal has a greater proportion of smaller particles.     

A Precursor Approach to Electrospun Polyaniline Nanofibers for Gas Sensors

Polyaniline (PANI) has served as one of the most promising conducting materials in a variety of fields including sensors, actuators, and electrodes. Fabrication of 1D PANI fibers using electrospinning methods has gained a significant amount of attention. Due to the extremely poor solubility of PANI in common organic solvents, fabrication of electrospun PANI fiber has been carried out either by using corrosive solvents such as H₂SO₄ or by electrospinning in the presence of other matrix polymers. Herein, a new approach to the fabrication of PANI fibers using tert‐butyloxycarbonyl‐protected PANI (t‐Boc PANI) as the conducting polymer precursor is reported. The t‐Boc PANI is soluble in common organic solvents (e.g., chloroform and tetrahydrofuran), and electrospinning of t‐Boc PANI in those solvents affords nano/micrometer‐sized t‐Boc PANI fibers. Treatment of the electrospun t‐Boc PANI fibers with HCl results in the removal of the acid labile t‐Boc group and the generation of conducting (≈20 S cm^?1) PANI fibers. The HCl‐doped PANI fibers are successfully used in the detection of gaseous ammonia with a detection limit of 10 ppm.

     

Microstructure and mechanical properties of additive manufactured steel-Al structure materials with nickel gradient layers

The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing(AM) was investigated in this work based on the cold metal transfer welding.The results show that the microstructure gradually changed from the steel side to the aluminum side.The microstructure in the steel layer consisted of vermiform like 8ferrite and austenite structure,while in the aluminum layer the microstructure was constituted by α-Al grains and typical reticulate distributive Al-Si eutectic structure.Besides,a 7 μm thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer.The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa,the rupture morphology showed a brittle fracture characteristic.     

Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.