Ketonization of fatty methyl esters over Sn−Ce−Rh−O catalyst

A mixture of methyl esters of fatty acids obtained by transterification of nonerucic rape oil was ketonized. The starting material, diluted with methanol, was converted at atmospheric pressure over a catalyst that contained Sn, Ce, and Rh oxides in a molar ratio of 90:9:1. At a temperature of 385°C ketones were obtained with a total yield of 63% at the 96% conversion of starting material. The reported experiments prove that catalysts other than iron that are active in ketonization of primary alcohols can be successfully used in ketonization of esters of fatty acids. The kind of diluent used plays a crucial role in the conversion.     

热处理对锌−镍−磷−纳米二氧化硅复合电镀层性能的影响

先采用由110 g/L ZnCl_2、100 g/L NiCl_2·6H_2O、80 g/L CH_3COONH_4、40 g/L CH_3COONa、5～10g/L NaH_2PO_2·H_2O、180 g/L KCl、0.04～0.08 g/L十二烷基硫酸钠和4～6 g/L纳米SiO_2 (平均粒径7～40 nm)组成的镀液,在pH为4～5、温度为45℃和电流密度为1.5 A/dm2的条件下电镀20 min得到厚度为30～40μm的Zn-Ni-P-纳米SiO_2复合镀层。然后在氮气保护和不同温度(200、300、400和500℃)下热处理2 h。研究了热处理温度对复合镀层微观结构、显微硬度和耐蚀性的影响。结果表明,经300℃热处理的Zn-Ni-纳米SiO_2复合镀层的综合性能较好,显微硬度为198 HV,耐蚀性最好。     

Iron-Catalyzed C−C Bond Formation via Chelation-Assisted C−H Activation

This review provides a brief overview of iron-catalyzed C−C bond forming reactions via heteroatom-assisted C−H bond activation, which have been extensively developed in the last decade. Three major types of reactions are discussed, namely, (1) C−H activation/C−C coupling using organometallic reagents under oxidative conditions, (2) C−H activation/C−C coupling using organic electrophiles under redox-neutral conditions, and (3) C−H activation/C−C coupling using unsaturated hydrocarbons under redox-neutral or oxidative conditions.     

Preparation and ionic conduction of CaZr1−xScxO3−α ceramics

A series of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) perovskite oxide ceramics were successfully fabricated at 1400 °C for 10 h and then further sintered at 1650 °C for 10 h via a solid-state reaction sintering process. Conductivities of the ceramics were measured under the atmosphere that contains 1% H₂/Ar and 5.63 kPa H₂O/Ar by the electrochemical impedance spectra technique. It was found that the conductivities of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) ceramics increased with the increase of the measuring temperature, and the conductivity achieved its maximum value of 2.03×10⁻⁵–6.5×10⁻³ S cm⁻¹ when the doping amount of Sc (x) was 0.10. Additionally, element doping can increase the conductivities and decrease the conductivity activation energies of CaZr_1−xSc_xO_3−α ceramics. The results of transport number measurement indicated that the CaZr_0.9Sc_0.1O_3−α is almost a pure protonic conductor at 500–750 °C, while it is a mixed protonic-oxygen ionic-electronic conductor at 750–1300 °C.     

Whole-body utilization of n−3 PUFA in n−6 PUFA-deficient rats

We evaluated the utilization of α-linolenic acid (18∶3n−3) in growing rats consuming a diet deficient in n−6 PUFA. After 90 d, whole-body 18∶3n−3 accumulation was 55% lower, total n−3 PUFA accumulation was 21% lower, and 18∶3n−3 disappearance was 14% higher in n−6 PUFA-deficient rats. Part of the reduction of whole-body 18∶3n−3 in n−6 PUFA-deficient rats was due to the 25% increase in net conversion of 18∶3n−3 to long-chain n−3 PUFA. Despite adequate 18∶3n−3 intake, n−6 PUFA deficiency decreased the accumulation of 18∶3n−3 and total n−3 PUFA.     

镍−钨−碳化硅复合电镀层结合强度的影响因素

在Cr5钢表面电沉积制备了Ni-W-SiC复合镀层.通过单因素试验研究了基体的表面粗糙度,预镀层的种类和厚度,复合镀时的阴极电流密度,以及复合镀层厚度对其结合强度的影响,采用扫描电镜和能谱仪分析了拉伸试验后不同试样基体一侧的微观形貌和元素组成.结果表明,当基体表面粗糙度(Ra)为4μm,预镀1μm厚的纯Ni层后在电流密...     

Lamellar-interpenetrated Al−Si−Mg/Al2O3−ZrO2 composites prepared by freeze casting and pressureless infiltration

Using freeze casting and pressureless infiltration methods, we prepared lamellar Al−Si−Mg/Al₂O₃−ZrO₂ composites with initial ceramic loading of 30 vol% and different Al₂O₃:ZrO₂ weight ratios (Al₂O₃:ZrO₂=1:9, 3:7, 5:5, 7:3 and 9:1). The resultant composites inherited the lamellar structure of the Al₂O₃−ZrO₂ scaffolds, and the thickness of both metal and ceramic layers showed a trend of first increase and then decrease with increasing Al₂O₃ content. During pressureless infiltration, multiple chemical reactions took place between ZrO₂ and the Al−12Si−10Mg alloy and the main reaction products were (Al_1−m, Si_m)₃Zr, Al₂O₃ and ZrSi₂ phases. The degree of the reaction depended on the ZrO₂ content in the ceramic composition. In general, the compressive strength of the composites decreased with increasing Al₂O₃ content, but three-point bending strength showed a first decrease and then increase. When Al₂O₃:ZrO₂=1:9, the compressive and bending strength of the composites reached about 997±60 MPa and 426±10 MPa, respectively. A simple model was proposed to illustrate the fracture mode and toughening mechanism of the composites.     

不同组合配位剂对化学镀镍−钨−磷合金的影响

以柠檬酸钠为主要配位剂,乳酸、甘氨酸、硫酸铵分别为辅助配位剂,在硬铝上二次浸锌后化学镀Ni-W-P合金。基础镀液和工艺条件为:NiSO₄·6H₂O 20 g/L,Na₂WO₄·2H₂O 20 g/L,NaH₂PO₂·H₂O 30 g/L,CH₃COONa·3H₂O 20 g/L,硫脲2 mg/L,pH 8.0,温度85℃,时间1 h。研究了不同配位剂组合对化学镀Ni-W-P合金沉积速率及镀层显微硬度和孔隙率的影响。结果表明,使用30 g/L柠檬酸钠+10 mL/L乳酸时,所得镀层的孔隙率最低,为0.63个/cm²;使用30 g/L柠檬酸钠+10 g/L甘氨酸时,镀层的显微硬度较单一使用柠檬酸钠时有所提高;使用30 g/L柠檬酸钠+25 g/L硫酸铵时,沉积速率最高,为14.69 mg/(cm²·h),镀层的显微硬度高达786.9 HV。     

New Trends and Future Opportunities in the Enzymatic Formation of C−C,C−N,and C−O bonds

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature's catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021 , 1, 1–21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021 , 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C−C, C−N and C−O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis.     

超声波功率对电沉积钴−镍−钨合金性能的影响

以纯铜为基体,在100 kHz频率的超声波辅助下电沉积Co-Ni-W合金镀层。镀液组成和工艺条件为:CoSO_4·7H_2O 0.6 mol/L,NiSO_4·6H_2O 0.2 mol/L,Na_2WO_4·2H_2O 0.18 mol/L,H_3BO_3 0.2 mol/L,Na_2SO_4·10H_2O 0.05mol/L,Na_3C_6H_5O_7·2H_2O 0.4 mol/L,pH 6.0,温度(40±2)℃,电流密度0.6 A/dm2,超声波功率0～750 W,时间15 min。研究了超声波功率对电沉积过程及合金镀层表面形貌、元素组成、相结构、显微硬度和耐蚀性的影响。结果表明:超声波辅助可削弱电沉积过程中浓差极化的影响,强化液相传质,促进反应界面的电子转移。超声波功率高于150W时,Co-Ni-W合金镀层的W原子分数显著提升。超声波功率为300～600W时,镀层平整、致密,呈纳米晶结构。超声波功率≥600W时,镀层趋于非晶态结构。超声波功率为450～600W时,Co-Ni-W合金镀层具有较高的显微硬度和良好的耐蚀性。     

Electrodeposition of Fe−Ni−Co alloys part I: Direct current deposition

Effects of hydrodynamic conditions, current density and solution temperature on the d.c. electrodeposition of Fe–Ni–Co alloys have been investigated with stationary planar and rotating cylindrical electrodes. The deposition rate of Fe showed mass transfer effects at cathodic potentials –1.35 V/sce. Deposition of Ni appeared to be kinetically controlled; deposition of Co appeared to be under kinetic control at potentials –1.35 V/sce but under mixed control at –1.65 V. Current efficiency of the codeposition process increased with increasing current density and decreased with increasing rotation rate. Higher solution temperatures and rotation rates extended the applied current density range where smooth, adherent, and metallic-looking deposits could be obtained. An increase in solution temperatures also decreased anomalous codeposition of Fe–Ni–Co. Calculations based on the Hessami-Tobias model provide qualitative agreement with dependence of experimental electrodeposition on applied current density, hydrodynamics and temperature.     

Cloud point extraction of 2,4−dichlorophenol from aqueous samples employing β−cyclodextrin

In this study, β?cyclodextrin (β?CD) was used to enhance the extraction of 2,4?dichlorophenol (2,4?DCP) from the aqueous sample in cloud point extraction (CPE) using spectrophotometric method. Several parameters have been investigated with and without the presence of β?CD modifier, such as pH, equilibration temperature, analyte concentration, and water content in the CPE and CPE?βCD systems, respectively. Equilibrium data are described by the Langmuir isotherm in both CPE systems with and without β?CD modifier. The thermodynamic parameters (positive values of ΔH° and ΔS°, negative values of ΔG°) indicate that the solubilization of 2,4?DCP in a polyethylene glycol silicone surfactant (DC193C) is endothermic, entropy gained, and spontaneous in both systems. In the CPE?βCD system, the results show that the β?CD modifier is capable of enhancing the extraction of 2,4?DCP pollutant from aqueous samples.     

Perovskite forming ceramics of the system SrxLa1−x TiIVx+yCoIIyCoIII1−x−2yO3 for NTC thermistor applications

The paper reports the preparation, structure and electrical properties of oxide ceramic semiconductors based on the series Sr_xLa_1−x Ti^IV_x+yCo^II_yCo^III_1−x−2yO₃ with perovskite type stucture: 0<x<1, 0<y<(1−x)/2. The study starts from LaCoO₃ which is highly conductive yielding metallic condutivity above 330°C. The upset trigonal distortion of LaCoO₃ is reduced when Sr^II/Ti^IV is substituted for La^III/Co^III corresponding to increasing values of x and also when 2 Co^III are introduced for Ti^IV/Co^II into the lattice corresponding to increasing values of y. At high values of x and y othorhombic distortion occurs. At the same time, the interaction between the Co^III atoms of LaCoO₃ is increasingly interrupted providing increasing values of the the resistivity value ρ_25°C and of the B_25/100°C value deduced from measurements at 25 and 100°C according to ρ(T )=ρ_25°C e^B/T. The range of variation of x an y makes possible to prepare ceramics with desired electrical properties within the limits of ρ_25°C=1.1 Ωcm, B=1910 K and ρ_25°C=1 bis 8×10⁶ Ωcm at B-values up to 6500 K. Dependent on composition, NTC ceramics for thermistor or insurance applications are accessible. Thermistors do not show aging even at higher temperature, e.g. at 500°C, provided the single phase state is achieved as a result of mixed oxide preparation and sintering. Hence, high temperature thermistor applications are also made possible. The semiconductor behavior can be understood using the conventional polaron state hopping model.     

脉冲电沉积制备低锡铜−锌−锡三元仿金合金

在304不锈钢表面脉冲电镀低锡Cu-Zn-Sn仿金合金,镀液组成为:CuSO4·5H2O 0.18 mol/L,ZnSO4·7H2O 0.06 mol/L,Na2SnO3·3H2O 0.05 mol/L,Na3C6H5O7·2H2O 22.66 g/L,Na2CO325 g/L,羟基乙叉二膦酸(HEDP)100 mL/L.研究了电镀时间、脉冲频率、脉冲占空比和平均电流密度对Cu-Zn-Sn合金镀层色泽、表面形貌和组成的影响,得到脉冲电镀的最佳工艺条件为:电镀时间66 s,脉冲频率4 kHz,占空比40％,平均电流密度3.5 A/dm2.在最优条件下所得合金镀层呈金黄色,Cu、Zn、Sn的质量分数分别为88.03％、11.69％和0.28％,表面形貌和元素比例均优于直流镀层,但二者的相结构相同.     

Optical modulation and magnetic transition in PbTi1−xPdxO3−δ ferroelectric thin films

The PbTi_1−xPd_xO_3−δ (xPTPO) thin films prepared by chemical solution deposition have been investigated by means of structural characterizations, optical and magnetic measurements. X-ray diffraction patterns show that all the films have a pseudotetragonal perovskite structure, but also exhibit a lattice dilatation behavior and increased internal strain as the x increases. A possible mechanism for strain-induced structural evolution is discussed. Raman scattering further corroborates this change in average structure, where the characteristic variation of phonon modes, indirectly reveal the incorporation of Pd²⁺ ions into host lattice. Transmittance spectra analysis indicates that Pd doping has a key effect on the energy band structure. The optical bandgap of xPTPO films decreases significantly with increasing Pd content, expressed by (3.5–9.0x) eV (0≤x≤0.09). Also, magnetic switching driven by doping has been confirmed in the films, which is attributed to the competition between ferromagnetic and paramagnetic/antiferromagnetic components.     

Bonding phase formation in eco-friendly periclase−spinel−Al bricks used in RH degassing process

Mere unburnt periclase–spinel–Al bricks have been accepted by steel mills in the chromium-free campaign of the lining materials for Ruhrstahl ?Heraeus (RH) degassers, in terms of comparable/optimistic performance to traditional material, low carbon emission due to unburnt manufacturing process and chromium-free material for eco-friendly steel-making process. Investigations are made on the used periclase–spinel–Al bricks for the thermal evolution of their components and the formation of novel phase and bonding structure. Under the working atmosphere of RH degasser, metallic Al particles got molten above its melting point, leaving Al rim around their circumference, and AlN formed in the gaseous state dispersing into overall matrix of periclase–spinel–Al bricks with rising temperature. AlN formed and Mg reduced in their gaseous state germinated MgAlON whisker initially in the original space of metallic Al particles, and MgAlON whisker grew further all over the matrix. A whisker-interwoven network has been full of the matrix behind the hot face and toward the cold face of the used bricks, which is a completely novel type of bond and distinguished from traditional ceramic one. The whisker-interwoven network is somewhat like the stripe graphite containing microstructure of magnesia–carbon brick, which results in low wettability and high flexibility. The superior performance of periclase–spinel–Al bricks is attributed to such a bonding structure of whisker-interwoven network, which could reduce slag penetration and facilitate thermomechanical stress resistance.     

Synthesis,characterization and catalytic properties of La2−x Sr x NiO4−δ

Various compositionsx in the catalyst system La_2–x Sr _x NiO_4– have been prepared by conventional techniques and characterized by X-ray powder diffraction, electron microscopy and BET surface measurements. The catalytic properties of these catalysts have been tested in the propylene oxidation reaction. The catalytic activity can be correlated with the oxygen content and with the strontium substitution.     

Electrochemical performance and chemical stability of proton-conducting BaZr0.8−xCexY0.2O3−δ electrolytes

Protonic ceramic fuel cells (PCFCs) using BaZr_0.8−xCe_xY_0.2O_3−δ (BZCY) as electrolyte materials have attracted widespread attention because of their high performance at reduced temperature. However, there are few systematic studies on both the performance and stability of BZCY materials. In this paper, we report our work on the electrochemical performance and chemical stability of BaZr_0.8−xCe_xY_0.2O_3−δ (x = 0, 0.1, 0.3, 0.5, and 0.7) series. The results show that electronic hole conductivity decreases with increasing Ce⁴⁺ content, especially at high temperature. In addition, H₂ atmosphere reduces the conductive activation energy of BZCY. On the contrary, air atmosphere causes serious electronic leakage. These effects are also reflected in the operation of PCFCs, that is, the higher the Ce⁴⁺ content, the higher the open-circuit voltage and output power density. However, low Ce⁴⁺ content may stabilize the materials in CO₂ atmosphere. At 700°C, an anode-supported PCFC based on BaZr_0.1Ce_0.7Y_0.2O_3−δ electrolyte, using humid H₂ fuel, gives a peak power density of 1.0 W cm⁻². At 600°C, BaZr_0.8Y_0.2O_3−δ and BaZr_0.7Ce_0.1Y_0.2O_3−δ show a good stability in CO₂-containing atmosphere.