Analysis of the use of voltammetric results as a steady state approximation to evaluate kinetic parameters of the hydrogen evolution reaction

The use of the voltammetric response j^vol(η) of a potentiodynamic sweep at a slow scan rate vs in place of a steady state polarization curve j^ss(η) for the determination of the kinetic parameters of the hydrogen evolution reaction is analyzed. It is proposed to consider jvol(η,vs)≅jss(η) when the condition 0.99≤jvol(η,vs)/jss(η)≤1.01 is verified in the overpotentials range η ≤ −0.05 V. It has been also established a simple relationship between the maximum admissible scan rate and the equilibrium polarization resistance R_p. Finally, the application of this criterion on different electrodes is described and discussed.     

Synthesis,photoluminescence properties and energy transfer behavior of color-tunable fluorapatite phosphor Sr9Gd(PO4)5(SiO4)F2:Tb3+/Sm3+

Tb³⁺-Sm³⁺ co-doped Sr₉Gd(PO₄)₅(SiO₄)F₂ (SGPSF) phosphors were prepared through a solid-state reaction, and their luminescence properties as well as energy transfer mechanism have been investigated in detail. The SGPSF:Tb³⁺, Sm³⁺ phosphors system could be efficiently excited at wavelengths ranging from 200 to 500 nm, which is well matched with the spectra of near ultraviolet chips. The emission of SGPSF:Tb³⁺, Sm³⁺ phosphor covers the entire visible region with sharp peaks in the blue, green, and red regions. The emission color of SGPSF:Tb³⁺, Sm³⁺ could be adjusted from green (0.275, 0.378) to red (0.519, 0.295) by controlling the doping content of Sm³⁺/Tb³⁺.     

Facile Synthesis of 3‐Halobenzo‐heterocyclic‐2‐carbonyl Compounds via in situ Halogenation‐Oxidation

A facile method to synthesize 3‐halobenzo‐heterocyclic‐2‐carbonyl compounds is described. Mechanistic studies suggested that a halo‐cyclization process, which generated the unstable spiro‐acetal transition state and readily convertible to the corresponding carbonyl compound might be involved. Diverse 3‐halobenzo‐heterocyclic‐2‐carbonyl compounds could be synthesized with up to 95 % yield in mild conditions with inexpensive starting materials.

     

Photoluminescence properties of Eu-doped WO3-Eu2(WO4)3 composites and single-phase Eu2(WO4)3 powders

The development of highly stable and efficient oxide-based red phosphors is urgently required for next-generation lighting devices. Herein, we report the micro/crystal structures and luminescent properties of single-phase Eu₂(WO₄)₃ and Eu³⁺-doped WO₃-Eu₂(WO₄)₃ composite phosphors prepared by a one-step conventional solid-state reaction method in air atmosphere. As increasing Eu contents in the mixtures of WO₃ and Eu₂O₃, the intensities of the X-ray diffraction peaks of Eu₂(WO₄)₃ increased while that of WO₃ decreased. The photoluminescence intensity of the synthesized phosphors increased with increase in the Eu content when calcined at 900 °C, while it degraded at a higher temperature. Red-emitting single-phase Eu₂(WO₄)₃ powders were successfully obtained when the WO₃ and Eu₂O₃ powders were calcined in the ratio of 3:1. The intensity of the red emission spectra of the Eu₂(WO₄)₃ phosphor was higher than those of the 6, 12, and 24 at.% Eu-added WO₃ composites at excitation wavelengths of 394 and 465 nm. On the other hand, the intensity of emission from the single-phase phosphor was lower than that of the Eu-doped WO₃-Eu₂(WO₄)₃ composites under excitation of UV light at 254 nm. Thus, we propose two prospective phosphors for application as red phosphors at various wavelengths.     

Compositional design,structure stability,and microwave dielectric properties in Ca3MgBGe3O12 (B = Zr,Sn) garnet ceramics with tetravalent cations on B-site

Two garnet-structured Ca₃MgBGe₃O₁₂ (B = Zr, Sn) ceramics with tetravalent cations at B-site were prepared by conventional solid state reaction. The crystal structure, microstructure evolution, and microwave dielectric performance were investigated using X-ray powder diffraction, Rietveld refinement, scanning electron microscopy, Raman spectroscopy, and infrared spectroscopy techniques. Dense Ca₃MgZrGe₃O₁₂ and Ca₃MgSnGe₃O₁₂ ceramics were obtained at sintering temperatures of 1420 and 1400 °C, respectively. The dielectric constant, unloaded quality factor, and temperature coefficient of resonance frequency of Ca₃MgZrGe₃O₁₂ were 10.80 ± 0.2; 79,600 ± 1000 GHz (f = 12.61 GHz); and ?66.8 ± 1 ppm/°C, respectively, and the corresponding values for Ca₃MgSnGe₃O₁₂ were 9.68 ± 0.2; 83,400 ± 1000 GHz (f = 14.19 GHz); and ?57.9 ± 1 ppm/°C, respectively. The dielectric performances of the two ceramics were compared by analyzing the ionic polarizability, packing fraction, and bond valence. The intrinsic dielectric properties were predicted by fitting the infrared reflectivity spectra.     

Conversion of Canola Meal into a High-Protein Feed Additive via Solid-State Fungal Incubation Process

The study goal was to determine the optimal fungal culture to reduce glucosinolates (GLS), fiber, and residual sugars while increasing the protein content and nutritional value of canola meal. Solid‐state incubation conditions were used to enhance filamentous growth of the fungi. Flask trials were performed using 50 % moisture content hexane‐extracted (HE) or cold‐pressed (CP) canola meal with incubation for 168 h at 30 °C. Incubation on HE canola meal Trichoderma reesei (NRRL‐3653) achieved the greatest increase in protein content (23 %), while having the lowest residual levels of sugar (8 % w/w) and GLS (0.4 μM/g). Incubation on CP canola meal Trichoderma reesei (NRRL‐3653), A. pullulans (NRRL‐58522), and A. pullulans (NRRL‐Y‐2311‐1) resulted in the greatest improvement in protein content (22.9, 16.9 and 15.4 %, respectively), while reducing total GLS content from 60.6 to 1.0, 3.2 and 10.7 μM/g, respectively. HE and CP canola meal GLS levels were reduced to 65.5 and 50.7 % by thermal treatments while solid‐state microbial conversion further reduced GLS up to 99 and 98 %, respectively. Fiber levels increased due to the concentration effect of removing oligosaccharides and GLS.     

三元乙丙/氯磺化聚乙烯共混胶相容性研究

本文主要研究了三元乙丙橡胶(EPDM)/氯磺化聚乙烯(CSM)共混胶性能,通过添加增容剂氯化聚乙烯(CPE)和乙烯-醋酸乙烯酯(EVM)、交联助剂甲基丙烯酸锌(ZDMA)和三(甲基丙烯酸)三羟甲基丙烷酯(TMPTMA)来改善EPDM/CSM共混胶的相容性,对比分析EPDM/CSM共混胶的物性、动态力学性能和微观相态。结果表明,随着CSM用量的增加,CSM/EPDM共混胶拉伸强度明显下降,EPDM与CSM相容性不良;加入CPE、EVM、ZDMA、TMPTMA后,共混胶拉伸强度、撕裂强度都增加,硬度也都不同程度增大,加入ZDMA的共混胶拉伸强度提高最大;加入CPE、EVM、ZDMA、TMPTMA后,EPDM 与CSM共混胶的相容性稍有改善,共混胶阻尼曲线中间的“平台区”都有所下降;ZDMA改善EPDM/CSM共混胶相容性要比其它组分好。     

用SRK状态方程计算二氧化碳在N-甲基二乙醇胺水溶液中的溶解度

本文对二氧化碳在Ｎ－甲基二乙醇胺水溶液中的溶解度数据进行了收集和评估,并用ＳＲＫ状态方程对文献数据进行了关联计算。结果表明本模型对二氧化碳溶解度的计算精度与实验的测定精度相当。可用于过程的模拟计算。