Microstructure evolution and corrosion behavior of Fe-Al-based intermetallic aluminide coatings under acidic condition

Two Fe-Al-based intermetallic aluminide coatings were fabricated on 430-SS (Fe-Cr) and 304-SS (Fe-Cr-Ni) substrates by pressure-assisted solid diffusion bonding with coating on pure Fe as control. The microstructure and intermetallic phases of the coatings were characterized by SEM, EDS and EBSD. A network of Cr₂Al₁₃ with matrix of Fe₄Al₁₃ was formed by inter-diffusing of Al with the substrates. The corrosion behavior of intermetallic coatings was investigated in 0.5 mol/L HCl solution by mass-loss, OCP, Tafel plot and EIS. It was found that corrosion resistance was greatly enhanced by dozens of times after the addition of Cr and Ni compared with that on pure Fe. The presence of cracks in the coating on 430-SS provided a pathway for corrosion media to penetrate to the substrate and accelerated the corrosion rate. Moreover, the corrosion product was analyzed by XRD, demonstrating that the addition of Cr and Ni facilitated the formation of more corrosion resistant phases, and therefore improved corrosion resistance.     

Co-substitution of zirconium and neodymium on hyperfine interactions and AC susceptibility of SrFe_(12)O_(19) nanohexaferrites

This study presents the influence of Zn and Nd co-substitution on structure,morphology,AC susceptibility and ZFC-FC magnetizations of Sr nanohexaferrites(NHFs),SrFe_(12-x)(Zn,Nd)_xO_(19)(0.0≤x≤1.0),which was produced by sol-gel approach.XRD powder patterns,scanning electron microscopy(SEM) and high-resolution transmission electron spectroscopy(HR-TEM) approve the synthesis of Sr M-type hexaferrite.Mossbauer spectra show that Zn~(2+)ions occupy 2 b and 4f_1 sites while Nd~(3+)ions locate at 2 a,4f_2 and 12 k sites.The magnetic properties of the produced Sr-NHFs were investigated also by ZFC-FC magnetizations and AC susceptibility.According to the M_(FC)-M_(ZFC) results(between 2 and 400 K),no blocking temperature was detected which indicates the ferromagnetic(FM) behavior of NHFs.At lower temperatures,a super-spin glass like behavior is discerned.The AC susceptibility indicates that the magnetic interactions are improved due to the inclusion of low content(x=0.1) of Nd~(3+)and Zn~(2+)ions into the Sr-NHFs.However,with further increasing the Nd~(3+)and Zn~(2+)contents(x=0.9),the magnetic interactions are weakened.     

Synthesis,structure and unprecedented self-assembly strategy of two six-membered Zn–organic macrocycles

Two novel cyclohexane-like metallamacrocycles [ZnCH₃COO(L)]₆·solvent (1) and [Zn(HNO₃)(L)]₆·solvent (2) (HL = 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine) have been synthesized under hydrothermal conditions and characterized by IR spectra, single crystal X-ray diffraction, PXRD analysis, thermogravimetric analysis. The X-ray single crystal diffraction indicates that the self-assembly of the metallamacrocycle generates a fused-ring network that is further assembled into a 3D structure with 1D suprachannels. In particular, a designed self-assembly strategy has been applied to achieving six-membered Zn–organic metallamacrocycles unprecedentedly.     

Corrosion inhibition of mild steel using Novel Bis Schiff’s Bases as corrosion inhibitors: Electrochemical and Surface measurement

Purpose: The aim of the present investigation is to evaluate the corrosion inhibiting properties of four novel synthesize compounds namely N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-nitrobenzylidene)benzene-1,4-diamine) SB-I, N¹,N^1′-(1,4-phenylene)bis(N⁴-benzylidenebenzene-1,4-diamine) SB-II, N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-methylbenzylidene)benzene-1,4-diamine) SB-III, N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-methoxybenzylidene)benzene-1,4-diamine) SB-IV for mild steel in 1 M HCl. Corrosion inhibitors find wide application in industries during pickling of steel, descaling and oil well acidization. Inhibitors have attracted great attention due to cost effectiveness and simplicity of the methods. Method: Different experimental techniques such as weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to evaluate the corrosion inhibition performance of SBs for mild steel in acid solution. After the corrosion experiments, the surface morphology of metal surface in the absence and presence of SBs were studied by scanning electron microscopy (SEM) and Atomic force microscopy (AFM). Findings: The corrosion inhibition efficiency of SBs for mild steel are 71.42% (SB-I), 89.52 (SB-II), 92.85 (SB-III), 96.19 (SB-IV). Tafel polarization revealed that all the SBs behaved as mixed-type inhibitor but predominantly of cathodic type. The inhibition actions of these Schiff base molecules blocked the electrode surface by means of adsorption of the inhibitor molecule on metal surface, obeying the Langmuir adsorption isotherm. SEM/AFM studies of the metal surfaces confirm the protection of metal surface in presence of inhibitor as compared to the damaged surface in blank acid solution.     

On the role of aggregation effects in the performance of perylene-diimide based solar cells

A model bulk-heterojunction of a perylene diimide (PDI) monomeric derivative is studied for interrogating the role of PDI aggregates in the photocurrent generation efficiency (η_PC) of PDI-based organic photovoltaic (OPV) devices. Blend films of the PDI derivative and the poly(indenofluorene) (PIF) polymer annealed between room temperature and 220 °C, are used as the photoactive layers for the fabrication of OPVs. The positive effect of thermal annealing is assigned to the evolution of PDI aggregates in the amorphous PIF matrix. Annealing increases the electron mobility by three orders of magnitude. In contrast, owned to the thermally inert PIF matrix used, hole mobility increases only by a factor of six. High resolution cross-sectional scanning electron microscopy suggests that η_PC in PDI-based OPVs is not limited by the PDI aggregates but by their improper alignment. In situ Raman spectra and density functional theory calculations identify a marker for monitoring the strength of π–π stacking interactions between PDI monomers. It s further demonstrated that the electron-collecting electrode of the PIF:PDI devices dictates their performance. The use of Al is found to impede charge extraction and this is attributed to an unidentified product of the reaction between PDI and Al that leads to the formation of an electron-blocking layer. Device performance rectifies when a Ca/Al electrode is used and the power conversion efficiency is increased by a factor of four.     

Preparation of in situ grown silicon carbide nanofibers radially onto carbon fibers and their effects on the microstructure and flexural properties of carbon/carbon composites

Silicon carbide nanofibers (SiCNFs) used as the second reinforcements of carbon/carbon composites were grown radially on the carbon fiber surface. The microstructure of SiCNFs and their effects on the microstructure and flexural properties of C/C composites were investigated. Results show that there are many defects such as twin crystals and stacking faults in SiCNFs which were grown by catalytic chemical vapor deposition. During the same process, the skin region of carbon fiber has changed. Several SiC layers are formed and the arrangement of the graphite layers around SiC layers is more orderly. In the next chemical vapor infiltration, due to the induction of SiCNFs, the middle textural pyrocarbon were formed firstly and then is the high textural pyrocarbon. The existence of SiCNFs also contributes to the three-phase interface between pyrocarbon, SiCNFs and carbon fibers, resulting in a good bond between carbon fiber and matrix. Those structural changes lead the better flexural properties of SiCNF–C/C composites compared with C/C composites.     

Interface measurement technique for liquid film flowing inside small grooves by laser induced fluorescence

During the recent past, an optical investigation method of liquid films flowing within grooves of small dimensions, was developed by our research team. This non-intrusive method, based on the visualization of a transverse flow section, uses the laser induced fluorescence and image processing techniques in order to characterize the geometry of the liquid–gas interface. This article proposes to describe the principle and the practical application of this method and to present its possibilities through a certain number of applications carried out within our laboratory on isothermal flows and two-phase flows running in small grooves.     

4-苯基氨基硫脲在盐酸介质中对Q235钢的缓蚀性能

目的研究4-苯基氨基硫脲(4-PTC)对Q235钢在1mol/L HCl中的缓蚀作用。方法采用异硫氰酸苯酯和水合肼为原料,合成4-PTC。采用熔点分析、核磁共振氢谱和红外光谱等方法确定合成物质为目标产物4-苯基氨基硫脲。采用静态失重法、电化学极化曲线法、电化学阻抗谱法和扫描电子显微镜法,分析研究4-PTC的缓蚀性能。结果静态失重实验表明,当4-PTC浓度增加到1.0 mmol/L时,缓蚀效率达到85.9%,在Q235钢表面吸附符合Langmuir吸附等温式,形成单分子吸附层。计算得到吉布斯自由能为?35.60 k J/mol,说明缓蚀剂分子在Q235钢表面吸附同时存在物理吸附和化学吸附过程。动电位极化曲线表明,该缓蚀剂是以阴极型为主的混合型缓蚀剂,当4-PTC浓度增加到1.0 mmol/L时,缓蚀效率达到83.6%。电化学阻抗谱表明,随4-PTC浓度的增加,电荷转移电阻值增大,双电层电容值减小,金属腐蚀速率降低,缓蚀作用增强。当4-PTC浓度增加到1.0 mmol/L时,缓蚀效率达到84.7%。扫描电子显微镜表明,缓蚀剂分子能有效保护金属表面,抑制腐蚀。结论在盐酸介质中,4-PTC对Q235钢具有优良的缓蚀性能。     

葡萄果渣酵素的发酵工艺优化及其理化特性

以果酒及果醋酿造过程中废弃的葡萄果渣、糖蜜为原料,利用酵母菌、乳酸菌、醋酸菌多菌种共酵过程中物质间的转化与利用从而得到营养价值更高的酵素保健饮品。在确定基本超声条件（超声频率40 kHz、超声功率50 W、超声温度30 ℃）的前提下,考察活菌接种量、初始pH值、糖添加量、超声时间对超氧化物歧化酶活力及活菌数的影响;并探究因素间交互作用的影响,利用响应面法设计4因素3水平试验,对葡萄果渣酵素发酵工艺进行优化,优化后得到初始pH 5.0、糖添加量8%、活菌接种量12%、超声时间60 min,并将该条件用于5 L罐的工艺放大,对补料方式进行改进,发酵终点时pH值为3.5,可滴定酸度为2.89%,总酚质量浓度为5.5 mg/mL。检测得到功能性成分如原花青素质量浓度为3.78 mg/mL,SOD活力达到988 U/mL。采用总抗氧化能力试剂盒测定得到该酵素对2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)阳离子自由基清除能力（以Trolox当量计）为（44.5±2.5）μg/g。经检测,该葡萄果渣酵素含有丰富的酒石酸、苹果酸、琥珀酸、柠檬酸,发酵过程中散发葡萄特有的醇、酚、萜类香气,葡萄果渣酵素香气独特且绵密。得到的葡萄果渣酵素上清液色泽透明亮丽,香气绵柔,口感、滋味评价均较高。     

机械蒸汽再压缩系统的流程模拟及性能研究

为使得整个机械蒸汽再压缩(MVR)蒸发系统的稳定性、节能性更好,借助Aspen Plus软件学习版,根据MVR运行原理,构建了MVR性能分析模型,并通过改变MVR节点的参数,模拟研究了蒸发量、补充新鲜蒸汽量与进料温度、蒸发压强的关系;蒸发量、沸点与进料浓度(NaCl质量分数)、蒸发压强的关系;蒸发器换热量、COP与蒸发压强、压缩机压力升的关系。通过分析模拟结果得出:适当减小压缩比,可以提高蒸发系统的COP;原料液应该加热到沸点后,再进入蒸发器中进行换热;从节能效果看,MVR蒸发系统更适合在低温低压下运行;在蒸发前,应对浓度较大的原料液进行适当的稀释。