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MODELING OF STATIC RECRySTALLIzATION KINETICS OF Nb-BEARING STEELS

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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 271-278页

作者： L.Q. Ma z.y. liu S.H. Jiao X.Q. yuan D. Wu The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110004 China Institute of Research and Development Baosteel Co. Ltd Shanghai 201900 China

By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （Qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of Qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.

关键词： Nb-bearing steel static recrystallization Tp (start temperature of strain-induced precipitation) activation energy

PREPARATION AND PROPERTIES OF Ni-Cr AND Fe-Cr-Al FILMS By VACUUM EVAPORATION

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Acta Metallurgica Sinica(English Letters) 2003年第4期16卷 283-288页

作者： X.W. Shi, z.y. liu, B.C. zeng and CM. LiInstitute of Materials Science & Technology, College of Mechanical Engineering, South China University of Technology, Guangzhou 510640, China Inst. of Mat. Sci. and Technol. Coll. of Mech. Eng. South China Univ. of Technol. Guangzhou 510640 China

Ni-Cr and Fe-Cr-Al films deposited on the Al2O3 substrate are studied by a method of vacuum evaporation in this paper. Influence of resistance value on density and evaporation parameters of the films reveals that the resistance of films and the adhesion of films to substrates are determined by the evaporation time and the substrate temperate under the condition of the maximum vacuity of 6.2×10-4 Pa, respectively.

关键词： vacuum evaporation resistance of film vacuity

PREPARATION AND CHARACTERIzATION OF POLy-CRySTALLINE SILICON THIN FILM

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Acta Metallurgica Sinica(English Letters) 2003年第4期16卷 309-312页

作者： y.F. Hu, H. Shen, z.y. liu and L.S.WenCollege of Mechanical Engineering, South China University of Technology, Guangzhou 510640, ChinaGuangzhou Institute of Energy Conversion, The Chinese Academy of Sciences, Guangzhou 510070, China Coll. of Mech. Eng. South China Univ. of Technol. Guangzhou 510640 China Guangzhou Inst. of Energy Conversion Chinese Acad. of Sci. Guangzhou 510070 China

Poly-crystalline silicon thin film has big potential of reducing the cost of solar cells. In this paper the preparation of thin film is introduced, and then the morphology of poly-crystalline thin film, is discussed. On the film we developed poly-crystalline silicon thin film solar cells with efficiency up to 6.05% without anti-reflection coating.

关键词： poly-crystalline silicon thin film RTCVD (rapid thermal chem- ical vapor deposition) SSP (silicon sheet from powder)

EFFECT OF RARE EARTH ON VANADIzATION PROCESS IN BORAX BATH

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Acta Metallurgica Sinica(English Letters) 1999年第5期12卷 968-973页

作者： X.K. Tao, X.Cong, R.S. Peng, J.liu and z.y. liu Tianjin Institute of Technology, Tianjin 300191, China

This paper investigates the effect of rare earth elements on the kinetic process, microstructure and mechanical properties of vanadization in borax bath. The results show that addition of rare earth elements to vanadizing agent has obvious catalytic effect on the rate of vanadization, which has been enchanced by 30%. The wear and corrosion resistance of vanadium carbide layer were prompted by the addition of rare earth to the agent. Through increasing vanadium potential of the agent, activating the surface of workpieces and decreasing the activation energy of diffusion of carbon, rare earth elements accelerate the rate of vanadization process.

关键词： rare earth elements vanadization in borax bath activation energy of diffusion

OBSERVATION ON DEFECTS IN POLyCRySTALLINE SILICON THIN FILMS

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 295-299页

作者： y.F. Hu1), H. Shen2), L. Wang3), z.C. Liang3), z.y. liu1) and L.S. Wen1) 1) College of Mechanical Engineering, South China University of Technology, Guan gzhou 510640, China 2) The School of Physics and Engineering, zhongshan University, Guangzhou 510275 , China 3) Guangzhou Institute of Energy Conversion, The Chinese Academy of Sciences, G uangzhou 510640, China College of Mechanical Engineering South China University of Technology Guangzhou 510640 China School of Physics and Engineering Zhongshan University Guangzhou 510275 China Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 510640 China

Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemica l vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer. Intra-granular defects such as stacking faults, twins and microstructure defects were investigated on thin fil ms by scan electron microscopy (SEM) technique.

关键词： poly-Si thin film intra-granular defects surface cross-section

LOW CyCLE FATIGUE BEHAVIOR OF Az91HP ALLOy IN AS HIGHP RESSURE DIE CASTING

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Acta Metallurgica Sinica(English Letters) 2000年第4期13卷 961-966页

作者： liu, z. Xu, y.y. Wang, z.G. Wang, y. liu, z.y. Inst of Metal Research Chinese Acad of Sciences Shenyang China

Fully reversed total strain-controlled low-cycle fatigue tests were conducted at room temperature in air to study the fatigue behavior of Az91HP magnesium alloy in as high pressure die casting and subsequently heat treatment. All the specimens in different heat histories exhibit cyclic strain hardening in different degrees. It is difficult to distinguish the fatigue behavior of the die casting specimens from that of the solution aging specimens. The solution treated specimens show longer fatigue life at high strain amplitude and shorter fatigue life at low strain amplitude than the die casting and solution aging specimens though they have the lowest yield strength with higher strain hardening. Fatigue fracture surfaces for strain amplitude larger than 0.005 show very similar to those found by monotonic tensile tests. The SEM examination reveals that the regions of fatigue crack growth and final fracture can be characterized by quasi-cleavage mechanisms, but some shallow dimples, slip bands and secondary cracks are found on the fracture surface in the fracture crack growth areas.

关键词： Cracks Die casting Fatigue of materials Heat treatment

High Strain Rate Superplasticity in a Micro-grained Al-Mg-Sc Alloy with Predominant High Angle Grain Boundaries

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Journal of Materials Science & Technology 2012年第11期28卷 1025-1030页

作者： F. C. liu z.y. Ma F. C. zhang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China State Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004China

Friction stir processing （FSP） was applied to extruded AI-Mg-Sc alloy to produce fine-grained microstructure with a grain size of 2.2μm. Electron backscatter diffraction （EBSD） result showed that the grain boundary misorientation distribution was very close to a random grain assembly for randomly oriented cubes. Super- plastic investigations in the temperature range of 425-500 ℃ and strain rate range of 1x100^-2-1x10 s^-1 showed that a maximum elongation of 1500% was achieved at 475 ℃ and a high strain rate of 1x100^-2-1x10 s^-1. The FSP AI-Mg-Sc exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. The origin for enhanced superplas- tic deformation kinetics in the FSP alloy can be attributed to its high fraction of high angle grain boundaries （HAGBs）. The analyses of the superplastic data and scanning electron microscopy （SEM） examinations on the surfaces of deformed specimens indicated that grain boundary sliding is the main superplastic deformation mechanism for the FSP AI-Mg-Sc alloy.

关键词： Superplasticity Friction stir processing Aluminum Microstructure Friction stir welding

STRUCTURE IMPROVEMENT AND TEMPERATURE FIELD SIMULATION OF PREPARING NANOPOWDER By EVAPORATION-CONDENSATION METHOD

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 178-182页

作者： J.S. Bao y. yin T.G. liu z.y. yang School of Mechanical and Electrical Engineering China University of Mining and Technology Xuzhou221116 China

A new apparatus, with a segregable conical water cooling condenser, which is heated by an electric arc using the evaporation-condensation method to prepare carbon-coated nanopowder, has been developed by the authors. Numerical simulation of the temperature field is done by the ANSyS software, and temperature in the reaction vessel is measured with the help of an experiment, to verify the simulation result. Influence of the temperature field in the reaction vessel, on the process of preparing nanopowder is then discussed simply. It is shown that the segregable conical water cooling condenser and carbon-coated surface process can be used to prepare steady carbon-coated metal nanopowder, at a lower cost and higher yield rate than the traditional structure. Simulation of the temperature field in the apparatus shows that the arc heating method can form a temperature field in the apparatus, which is quite favorable for nanopowder formation. Experiments show that the rational parameters using this apparatus, with the arc heating method to prepare carbon-coated nanopowder are electricity 60-100 A and arc length 5-8 mm.

关键词： Evaporation-condensation method Electric arc heating Temperature field Condenser structure

Advances in the treatment of autism spectrum disorder:Wharton jelly mesenchymal stem cell transplantation

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World Journal of Methodology 2025年第1期15卷 72-79页

作者： Serdar Kabatas ErdinçCivelek Eyüp Can Savrunlu Umut Karaaslan Özlem yıldız Erdal Karaöz Department of Neurosurgery University of Health Sciences TurkeyGaziosmanpaşa Training and Research HospitalIstanbul 34255Türkiye Department of Pediatric Allergy-Immunology Institute of Health Sciences Marmara UniversityIstanbul 34865Türkiye Center for Stem Cell&Gene Therapy Research and Practice University of Health Sciences TurkeyIstanbul 34255Türkiye Department of Child and Adolescent Psychiatry University of Health SciencesGaziosmanpaşa Training and Research HospitalIstanbul 34255Türkiye Department of Child and Adolescent Psychiatry Kocaeli University Faculty of MedicineKocaeli 41001Türkiye Center for Regenerative Medicine and Stem Cell Research&Manufacturing Liv HospitalIstanbul 34340Türkiye Department of Histology and Embryology Istinye UniversityFaculty of MedicineIstanbul 34010Türkiye Center for Stem Cell and Tissue Engineering Research and Practice Istinye UniversityIstanbul 34340Türkiye

BACKGROUND Autism spectrum disorder(ASD)is a complex neurodevelopmental disorder with multifaceted *** recent studies,neuroinflammation and immune dysregulation have come to the forefront in its *** are studies suggesting that stem cell therapy may be effective in the treatment of *** To evolve the landscape of ASD treatment,focusing on the potential benefits and safety of stem cell *** A detailed case report is presented,displaying the positive outcomes observed in a child who underwent intrathecal and intravenous Wharton’s jelly-derived mesenchymal stem cells(WJ-MSCs)transplantation combined with *** The study demonstrates a significant improvement in the child’s functional outcomes(Childhood Autism Rating Scale,Denver 2 Developmental Screening Test),especially in language and gross motor *** serious side effects were encountered during the 2-year *** The findings support the safety and effectiveness of WJ-MSC transplantation in managing ASD.

关键词： Autism spectrum disorder Neurorehabilitation Stem cell transplantation Wharton jelly mesenchymal stem cells Inflammation