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Effect of extrusion temperature on microstructure and mechanical properties of a low-alloying and ultra-high strength Mg-Zn-Ca-Mn matrix composite containing trace TiC nanoparticles

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Journal of Magnesium and Alloys 2020年第3期8卷 676-691页

作者： k.B.Nie Z.H.Zhu k.k.Deng J.g.Han College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024PR China Sharvci key laboratory of advanced magnesium-based materials Taiyuan University of TechnologyTaiyuan 030024PR China

Mechanical properties of microalloying Mg-2.2Zn-1.8Ca-0.5Mn(wt%)matrix composites reinforced by 0.5 wt%TiC nanoparticles before and after extrusion were investigated based on the detailed microstructural analysis.A uniform distribution of TiC nanoparticles was realized in the nanocomposite by the method of ultrasonic-assisted semisolid *** morphology of eutectic Ca2Mg6Zn3 phases changed from plate-like in the free TiC nanoparticles region to lamellar in the dense TiC nanoparticles region for the as-cast *** the grain structure and precipitates were obviously refined as the extrusion temperature decreased from 350 to 270℃.The nanocomposite exhibited excellent tensile yield strength(352-428 MPa)which was governed by the extrusion *** grain refinement strengthening with the contribution ratio of^80%to this strength increment was much higher relative to thermal expansion effect,Orowan strengthening and dislocation *** recrystallized grain structure with a substantial of ne precipitates appeared in the nanocomposite extruded at 270℃.The refined grain structure was not only due to dynamic recrystallization,but also the synergistic pinning effect of nano-TiCp,precipitated MgZn2 and α-Mn *** tensile toughness value of nanocomposite after extrusion improved with increasing the extrusion *** micro-cracks formed along the remnant coarse Ca2Mg6Zn3 led to the structural failure during tension.

关键词： Magnesium matrix nanocomposite Microstructure Mechanical properties:Strengthening mechanism Extrusion

Photolysis studies on HCOOH and HCOO^- in presence of TiO_2 photocatalyst as suspension in aqueous medium

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Journal of Natural gas Chemistry 2009年第1期18卷 50-54页

作者： g. R. Dey k. N. R. Nair k. k. Pushpa Radiation and Photochemistry Division Bhabha Atomic Research Centre Trombay Mumbai 400 085 India

Photolysis studies on formic acid （HCOOH） and formate ion （HCOO-） in presence of TiO2, a photocatalyst, as suspension in water were carried out separately using 350 nm ultraviolet light. The products, such as H2, CO, CO2 and CH4, generated during the experiments were monitored with varying the ambient, light exposure time, and the concentration of HCOOH/HCOO-. The yields of CO in all these systems increased with light exposure time. In aerated systems, CO yields were higher in contrast to the deoxygenated （Ar-purged） systems under identical conditions. It is proposed apparently that the formation of CO is taking place during the chemical reduction of in-situ generated CO2, a photo-mineralized product of HCOOH/HCOO-, but not through the direct photodecomposition or photodehydration （CO＋H2O） of solute molecules. The rates of CO formation during 1.3 M HCOOH photolysis in presence of TiO2 photocatalyst were evaluated to be 0.21 and 0.13 μl/min in aerated and Ar-purged systems, respectively. As compared with HCOOH systems, the CO yields are lower when 0.2 M HCOONa was exposed to light under identical conditions. The CO growth rates were evaluated to be 0.07 and 0.046 μl/min^-1 for aerated and deoxygenated HCOONa systems, respectively; moreover, the trend is quite similar to that of the HCOOH system. Under these conditions, the emission of H2 was also observed, and its yield was significantly higher in Ar-purged system as compared with the CO yields. However, in aerated system, the yields of these products were just opposite. The formation of low yield of methane was observed during photolysis of HCOOH/HCOO ions. In CO2 ambient, the yields of CO and H2 varied drastically with time.

关键词： formic acid formate ion photolysis TiO2

Multiple sclerosis drug repurposing for neuroregeneration

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Neural Regeneration Research 2024年第3期19卷 507-508页

作者： Peter göttle Michael Dietrich Patrick küry Department of Neurology Medical FacultyHeinrich-Heine UniversityDüsseldorfGermany

Multiple sclerosis(MS)is an autoimmune disorder of the central nervous system(CNS)and is primarily characterized by immune cell infiltration leading to relapses followed by remission phases and a disease course turning progressive over time with neurodegenerative processes taking over(Amin and Hersh,2023).Of note,beyond relapse-associated worsening early in disease progression independent of relapse activity may arise independently of relapse activity and can occur in all ***-mediated damage of myelin sheaths and the subsequent loss of mature oligodendrocytes are resulting in impaired axonal integrity,neurodegeneration and accounts for irreversible neuronal damage(kuhlmann et al.,2023).The current landscape of available disease-modifying therapies comprises mainly immunomodulatory drugs that effectively diminish relapses and slow down progression at the onset form of the disease,namely relapsing MS(RMS).In this regard,a number of drugs have been approved as disease-modifying therapies for MS by US Food and Drug Administration and European Medicines Agencies(Box 1).

关键词： drugs impaired irreversible

CFD Simulation of a Hydrogen/Argon Plasma Jet Reactor for Coal Pyrolysis

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Chemical Research in Chinese Universities 2004年第4期20卷 446-451页

作者： CHEN H. g. XIE k. C. Taiyuan University of Technology Taiyuan University of Technology Taiyuan 030024 P. R. China City University London EC1V 0HB UKand Taiyuan 030024 P. R. China

A Computational Fluid Dynamics(CFD) model was formulated for DC arc hydrogen/argon plasma jet reactors used in the process of the thermal H_2/Ar plasma pyrolysis of coal to acetylene. In this model, fluid flow, convective heat transfer and conjugate heat conductivity are considered simultaneously. The error caused by estimating the inner-wall temperature of a reactor is avoided. The thermodynamic and transport properties of the hydrogen/argon mixture plasma system, which are usually expressed by a set of discrete data, are fitted into expressions that can be easily implemented in the program. The effects of the turbulence are modeled by two standard k-εequations. The temperature field and velocity field in the plasma jet reactor were calculated by employing SIMPLEST algorithm. The knowledge and insight obtained are useful for the design improvement and scale-up of plasma reactors.

关键词： Plasma Reactor Computational fluid dynamics Coal pyrolysis

First principles study of structural, electronic, elastic and magnetic properties of cerium and praseodymium hydrogen system REH_x(RE:Ce, Pr and x=2, 3)

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Journal of Rare Earths 2015年第3期33卷 289-303页

作者： g.Sudha Priyanga R.Rajeswarapalanichamy k.Iyakutti Department of Physics N.M.S.S.V.N College Madurai Tamilnadu-625019 India Department of Physics and Nanotechnology SRM University Chennai Tamilnadu-603203. India

The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REH x（RE=Ce, Pr and x=2, 3） were investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At zero pressure all the hydrides were stable in the ferromagnetic state. The calculated lattice parameters were in good agreement with the experimental results. The bulk modulus decreased with the increase in the hydrogen content for these hydrides. The electronic structure revealed that di-hydrides were metallic whereas trihydrides were half metallic at zero pressure. A pressure-induced structural phase transition from cubic to hexagonal phase was predicted in these hydrides. The computed elastic constants indicated that these hydrides were mechanically stable at zero pressure. The calculated Debye temperature values were in good agreement with experimental and other theoretical results. A half metallic to metallic transition was also observed in REH3 under high pressure. Ferromagnetism was quenched in these hydrides at high pressures.

关键词： ab-initio calculations electronic structure structural phase transition magnetic properties elastic properties rare earths

Microwave assisted synthesis, spectroscopic, thermal, and antifungal studies of some lanthanide(Ⅲ) complexes with a heterocyclic bishydrazone

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Journal of Rare Earths 2008年第1期26卷 16-21页

作者： k. Mohanan B. Sindhu kumari g. Rijulal Department of Chemistry University of Kerala

A bishydrazone formed by the condensation of isatinmonohydrazone and salicylaldehyde reacted with lanthanide（Ⅲ） chloride to form complexes of the type [Ln（HISA）2Cl3], where, Ln=La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, or gd（Ⅲ） and HISA= [（2-hydroxybenzaldehyde）-3-isatin]bishydrazone. Both reactions were carried out under microwave conditions. The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, UV visible, infrared, far infrared, and proton NMR spectral data. The ligand acted as neutral tridentate, coordinating through the carbonyl oxygen, azomethine nitrogen, and phenolic oxygen without deprotonation. The ligand and lanthanum（Ⅲ） complex were subjected to X-ray diffraction studies. The X-ray diffraction pattern of ligand exhibited its crystalline nature and that of the lanthanum（Ⅲ） complex indicated its amorphous character. The thermal decomposition behaviour of the complex, [La（HISA）2Cl3], was examined in the temperature range of 40-800 ℃ using Tg, DTg, and DTA. The ligand and the metal complexes were screened for their antifungal activities.

关键词： microwave synthesis bishydrazones lanthanum(Ⅲ) complex thermal decomposition antifungal activity rare earths

A gradient Model for Young's Modulus and Surface Electrode Resistance of Ionic Polymer-Metai Composite

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Acta Mechanica Solida Sinica 2019年第6期32卷 754-766页

作者： H.g.Liu k.Xiong M.Wang Faculty of Civil Engineering and Mechanics Jiangsu UniversityZhenjiang 212013China State key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronauticsf Nanjing 210016China

A new model is proposed to estimate Young's modulus and surface electrode resistance of the ionic polymer-metai composite(IPMC)with a gradient distribution of micros true *** entire IPMC electrode is divided into two parts,i.e.,the porous metal electrode and the gradient polymer-metai composite electrode,according to the geometrie properties of the electroless plated metal *** validity and accuracy of the model are justified by comparing with the experimental observations of IPMC *** differences between model predictions and experimental data of Young's modulus and surface resistance of IPMC samples are+6.8%and-5.5%,respectively,indicating a reasonably good agreement.

关键词： Ionic polymer-metai composite gradient electrode model Young's modulus Resistance

Current self-limitation in a transverse nanosecond discharge with a slotted cathode

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Plasma Science and Technology 2017年第3期19卷 69-74页

作者： N A ASHURBEkOV k O IMINOV O A POPOV g S SHAkHSINOV Dagestan State University Faculty of Physics 43a Gadjieva Street Makhachkala 367002 Russia Moscow Power Engineering Institute Krasnokazal'mennaya 14 Moscow 111250 Russia

A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy （few kV） ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed.

关键词： nanosecond discharge electron beams upper current limitation slotted cathode

Effect of Aging Time and Temperature on Mechanical Properties and Microstructural Evolution of 2205 Ferritic-Austenitic Stainless Steel

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Journal of Materials Science & Technology 2009年第5期25卷 597-602页

作者： H.keshmiri A.Momeni k.Dehghani g.R.Ebrahimi g.Heidari Esfarayen Steel Complex Department of Mining and Metallurgy Amir Kabir University of Technology Tarbiat Moalem University of Sabzevar

Duplex stainless steels （DSS） with ferritic-austenitic microstructures offer good combination of resistance to pitting corrosion and high strength that are not concomitantly attainable using conventional single phase austenitic or ferritic stainless steels, The DSS used in this investigation was 2205 alloy having a stable microstructure consisting of about 45% ferrite and 55% austenite at ambient temperature. In order to investigate aging behavior of this steel and the influences on mechanical properties, different aging treatments were conducted at temperatures of 350-950℃ for various aging time of 15, 30, 60 and 180 min. The aged specimens were subjected to impact testing and hardness measurements. Finally, the changes in microstructure due to aging were studied by optical and scanning electron microscopy. The results showed that aging at temperatures lower than 550℃ for different time had negligible effects on mechanical properties. Besides, no considerable changes in term of precipitation of harmful intermetallic particles were observed in microstructure below this temperature. However, a critical temperature range, 550-650 ℃, was introduced here. Aging in this range led to a significant decrease in toughness and notable increase in hardness. The formation of intermetallic phases such as CT was recognized as the major reason for the observed changes.

关键词： Duplex stainless steel Aging Toughness Sigma phase