Fabrication of Aluminum Oxynitride (γ‐AlON) Transparent Ceramics with Modified Gelcasting

Transparent aluminum oxynitride (AlON) ceramics have been prepared through aqueous gelcasting forming technique starting from the raw materials of single phase AlON powders. The powder was specially treated for anti‐hydrolysis in ethanol before the shaping technique. The surface‐treated AlON powders could then be dispersed in an aqueous‐organic solution to prepare stable slurries containing 35 vol% solids loading. The obtained stable slurries were subsequently casted, calcined, and pressureless sintered at 1950°C for 8 h in nitrogen atmosphere. High transparent AlON ceramics with an average grain size of 112 μm and the in‐line transmittance of 81% at wavelength 1100 nm have been obtained.     

Rapid Bonding of Ti3SiC2 and Ti3AlC2 by Pulsed Electrical Current Heating

Inspired by pressure resistance welding of metallic materials, herein we describe how two MAX phases—Ti₃SiC₂ and Ti₃AlC₂—were successfully joined by a rapid electric current heating method in a pulsed electric current sintering furnace. No welding agent was employed and the total processing time was less than 6 min. When the bulk temperature of the joint couple exceeded 1070°C, good joints, with shear strength above 50 MPa, were achieved in both homo‐ and heterojunction joints.     

Steam reforming of ethanol over skeletal Ni‐based catalysts: A temperature programmed desorption and kinetic study

An investigation on reaction scheme and kinetics for ethanol steam reforming on skeletal nickel catalysts is described. Catalytic activity of skeletal nickel catalyst for low‐temperature steam reforming has been studied in detail, and the reasons for its high reactivity for H₂ production are attained by probe reactions. Higher activity of water gas shift reaction and methanation contributes to the low CO selectivity. Cu and Pt addition can promote WGSR and suppress methanation, and, thus, improve H₂ production. A reaction scheme on skeletal nickel catalyst has been proposed through temperature programmed reaction spectroscopy experiments. An Eley‐Rideal model is put forward for kinetic studies, which contains three surface reactions: ethanol decomposition, water gas shift reaction, and methane steam reforming reaction. The kinetics was studied at 300–400°C using a randomized algorithms method and a least‐squares method to solve the differential equations and fit the experimental data; the goodness of fit obtained with this model is above 0.95. The activation energies for the ethanol decomposition, methane steam reforming, and water gas shift reaction are 187.7 kJ/mol, 138.5 kJ/mol and 52.8 kJ/mol, respectively. Thus, ethanol decomposition was determined to be the rate determining reaction of ethanol steam reforming on skeletal nickel catalysts. © 2013 American Institute of Chemical Engineers AIChE J 60: 635–644, 2014     

Mixture semisupervised principal component regression model and soft sensor application

Traditionally, data‐based soft sensors are constructed upon the labeled historical dataset which contains equal numbers of input and output data samples. While it is easy to obtain input variables such as temperature, pressure, and flow rate in the chemical process, the output variables, which correspond to quality/key property variables, are much more difficult to obtain. Therefore, we may only have a small number of output data samples, and have much more input data samples. In this article, a mixture form of the semisupervised probabilistic principal component regression model is proposed for soft sensor application, which can efficiently incorporate the unlabeled data information from different operation modes. Compared to the total supervised method, both modeling efficiency and soft sensing performance are improved with the inclusion of additional unlabeled data samples. Two case studies are provided to evaluate the feasibility and efficiency of the new method. © 2013 American Institute of Chemical Engineers AIChE J 60: 533–545, 2014     

Synthesis and Luminescence Properties of Blue‐Emitting Phosphor Eu2+‐Doped Zinc Fluoro‐Phosphate Zn2[PO4]F

Eu²⁺‐doped zinc fluoro‐phosphate Zn₂[PO₄]F was synthesized by the conventional high‐temperature solid‐state reaction. The phase formation was confirmed by X‐ray powder diffraction measurements and the structure refinement. The photoluminescence excitation and emission spectra, and the decay curves were measured. The natures of the Eu²⁺ emission in inorganic hosts, e.g., the emission and excitation properties, the chromaticity coordinates, the Stokes shifts, the absolute quantum efficiency, and the luminescence thermal stability were reported. Under the excitation of near‐UV light, Eu²⁺‐doped Zn₂[PO₄]F presents a narrow blue‐emitting band centered at 423 nm. The thermal stability of the blue luminescence was evaluated by the luminescence intensities as a function of temperature. The phosphor shows an excellent thermal stability on temperature quenching effects.     

Ca2+‐Doped LaCrO3: A Novel Energy‐Saving Material with High Infrared Emissivity

The present study describes the successful synthesis of a Ca²⁺‐doped LaCrO₃ ceramic with high infrared (IR) emissivity, which is important for high‐temperature applications for significant energy saving. It is demonstrated that 20 mol% Ca²⁺‐doped LaCrO₃, i.e., La_0.8Ca_0.2CrO₃, exhibited an IR emissivity as high as 0.95 in the spectral region of 3–5 μm, which was 33.8% higher than that of LaCrO₃. By using La_0.8Ca_0.2CrO₃ as IR radiation agent in surface coating of heating unit, the radiative heat transfer could be enhanced significantly. The mechanism of the high IR emissivity of La_0.8Ca_0.2CrO₃ was attributed to the following aspects: Ca²⁺ doping introduced an impurity energy level of Cr⁴⁺ into LaCrO₃ and increased the hole carrier concentration, enhancing both impurity absorption and hole carrier absorption in the IR region; moreover, the doping caused lattice distortion enhanced the lattice vibration absorption. This novel high IR emissivity ceramic shows a promising future in high‐temperature applications for the purpose of energy‐saving.     

The Competitive and Combining Effects of Grain Boundary and Fe/Mo Antisite Defects on the Low‐Field Magnetoresistance in Sr2FeMoO6

Sr₂FeMoO₆ ceramics with different Fe/Mo antisite defect (ASD) concentrations and grain‐boundary (GB) properties were prepared. The competitive and combining effects of GB and Fe/Mo ASD on the transport and magnetoresistance were discussed. The GB properties, that is, intergrain coupling strength, positively related with resistivity value, is extremely sensitive to the total flux of reducing gas, in general, lower total gas flux leads to larger resistivity, thus stronger intergrain coupling strength, and then the contributions of GB effect to low‐field magnetoresistance (LFMR) increase appreciably regardless of the amount of ASD. In detail, when ASD concentration is less than 26%, LFMR is dominantly controlled by the GB effect. However, the suppressed ASD effect on LFMR behavior comes to play when the ASD content is larger than or equal to 26%, where the GB and ASD effects contribute together to the LFMR.     

Typoselectivity of Crude Geobacillus sp. T1 Lipase Fused with a Cellulose-Binding Domain and Its Use in the Synthesis of Structured Lipids

Typoselectivity of crude CBD-T1 lipase (Geobacillus sp. T1 lipase fused with a cellulose binding domain) was investigated. Multi-competitive reaction mixtures including a set of n-chain fatty acids (C8:0, C10:0, C12:0, C14:0, C18:1 n-9, C18:2 n-6 and C18:3 n-3) and tripalmitin-enriched triacylglycerols were studied in hexane. The crude CBD-T1 lipase discriminated strongly against C18:1 n-9 [competitive factor (α) = 0.23] and showed the highest preference for C8:0 (α = 1). Utilizing the catalytic properties of crude CBD-T1 lipase, acidolysis of soybean oil with C8:0 was selected as a model reaction to investigate the ability of the lipase to produce MLM-type (medium-long-medium) structured lipids. Several reaction parameters (added water amount, reaction temperature, substrate molar ratio and reaction time) examined for incorporating C8:0 into soybean oil, the optimum conditions were: 1:3 (soybean oil/C8:0) of molar ratio, 3 mL of hexane, 50 °C of temperature, 48 h of reaction time, 20 % of crude CBD-T1 lipase (w/w total substrates), and 7.5 % of water (w/w enzyme). Under these conditions, the incorporation of C8:0 was 29.6 mol%. The results suggest that crude CBD-T1 lipase, which showed different fatty acid specificity profiles, is a potential biocatalyst for the modification of fats and oils.     

Molten Salt Synthesis of Bismuth Ferrite Nano‐ and Microcrystals and their Structural Characterization

Bismuth ferrite nano‐ and microcrystals were prepared by a facile molten salt technique in two kinds of molten‐salt‐based systems (NaCl–KCl and NaCl–Na₂SO₄). In the NaCl–KCl salt system, a systematic study indicating the effects of process parameters (e.g., calcination temperature, holding time as well as the molten salt ratios) on the bismuth ferrite formation mechanism and structural characteristics is reported. The results show that almost pure phase BiFeO₃ powders with minimum impurity phase of Bi₂Fe₄O₉ were synthesized at temperatures of 700°C–800°C, whereas high calcination temperature (e.g., 900°C) resulted in the formation of almost pure phase Bi₂Fe₄O₉ powders. The prolonged holding time increased the particle size via the Ostwald ripening mechanism; however, there was little effect on the particle morphology. Similar phenomenon occurred as increasing the molten salt ratios. In the NaCl–Na₂SO₄ salt systems, it is found that low NP‐9 (nonylphenyl ether, NP‐9) surfactant content (0–5 mL) led to the formation of almost pure phase BiFeO₃ powders, whereas high NP‐9 surfactant content (e.g., 20 mL) resulted in pure phase Bi₂Fe₄O₉ powders. The average particle size of the BiFeO₃ powders was decreased as increasing the NP‐9 surfactant content, whereas their morphologies did not change significantly. Because of the simplicity and versatility of the approach used, it is expected that this methodology can be generalized to the large‐scale preparation of other important transitional metal oxides with controllable sizes and shapes.     

Structure and Photoluminescence of A Blue‐Green‐Emitting Phosphor for Near‐UV White LEDs

A series of phosphors Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce³⁺ and a characteristic emission at 544 nm of Tb³⁺. The emission can be tuned from blue to green by altering the relative ratio of Ce³⁺ to Tb³⁺ in the composition. The energy‐transfer mechanism from Ce³⁺ to Tb³⁺ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca₁₂Al₁₄O₃₂F₂ host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.