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Nanoindentation Study of.Al356-Al2O3 Nanocomposite Prepared by Ball Milling

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Materials Sciences and Applications 2010年第4期1卷 217-222页

作者： Y. Mazaheri f. karimzadeh M. H. Enayati 不详

In this study ball milling of.Al356 and Al2O3 powder mixture was carried out in order to produce Al356-Al2O3 nano-composite containing 20 vol.% Al2O3. The structural evolution and morphological changes of.powder particles during ball milling were studied by X-ray dif.ractometery and scanning electron microscopy analysis. As a result of.ball milling Al2O3 particles were unif.rmly dispersed in Al356 matrix. f.rthermore the crystallite size of.the Al356 decreased to 25 nm af.er ball milling f.r 10 h. Morphological studies of.powder particles indicated that the powder particle size continuously decreases with increasing milling time. Hardness and elastic modulus values of.powder particles were measured by nanoindentation method. It was f.und that the hardness and elastic modulus of.Al356-20 vol.% Al2O3 nanocomposite were about 216 Hv and 86 GPa, respectively which is higher than 75 Hv and 74 GPa f.r as-received Al356.

关键词： Al-Al2O3 Nanocomposite Nanocrystalline Structure Ball Milling Nanoindentation

Development of.Al356e-Al_2O_3 Nanocomposite Coatings by High Velocity Oxy-f.el Technique

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Journal of.Materials Science & Technology 2013年第9期29卷 813-820页

作者： Y.Mazaheri f.karimzadeh M.H.Enayati Department of.Materials Engineering Isfahan University of Technology

In this research, development of.AI356-AI203 nanocomposite coatings has been investigated. AI356-AI203 composite powders were prepared by mechanical milling of.AI356 powder and 5 vol.% micro and nanoscaled alumina particles. The milled powders were used as f.edstock to deposit composite coatings on A356-T6 aluminum alloy substrate using high velocity oxy-f.el （HVOf. process. X-ray dif.ractometry, optical and scanning electron microscopy, microhardness and wear tests were used to characterize the composite powders and coatings. The hardness of.composite coatings containing micro and nanosized AI203 were 114.1 ± 5.9 HV and 138.4 ± 6.9 HV, respectively which were higher than those f.r substrate （79.2 ± 1.1 HV）. Nano and microcomposite coatings revealed low f.iction coef.icients and wear rates, which were signif.cantly lower than those obtained f.r AI356-T6 substrate. Addition of.5 vol.% micro and nanoscaled alumina particles improved the wear resistance by an average of.85% and 91%, respectively. This is mainly caused by the presence of.AI203 in matrix and nanocrystalline structure of.matrix. Scanning electron microscopy tests revealed dif.erent wear mechanisms on the surf.ce of.the wear test specimens.

关键词： AI356-AI203 nanocomposite Composite coatings Mechanical milling High velocity oxy-f.el (HVOf. Wear

Psycho-cognitive behavioral problems in sleep disordered children

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Neural Regeneration Research 2012年第8期7卷 635-639页

作者： Parvaneh karimzadeh Research Center of.Pediatric Neurology Shahid Beheshti University of Medical Sciences

Sleep disturbances are common in childhood and adolescence. Sleep problems in early inf.nts tend to be persistent and prominent in preschool and school-aged children. Chronic sleep disorders, especially in young children may lead to neurobehavioral problems and psycho-cognitive impairment. Sleep dif.iculties may be the result of.underlying medical conditions, （breathing disorders） or psychological problems. Research studies have shown the association between sleep disorders and day time cognitive impairment, behavioral problems, poor school perf.rmance and inattention in children. Appropriate diagnosis and early management of.sleep disorders in children lead to improvement of.neurocognitive f.nction and behavioral problems in these children.

关键词： sleep disorder behavioral problems cognitive impairment association children

Promising medical treatment f.r childhood psycho-cognitive problems

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Neural Regeneration Research 2010年第21期5卷 1663-1667页

作者： Parvaneh karimzadeh Sepideh Tabarestani Pediatric Neurology Research Center Shahid Beheshti University of Medical Sciences (SBMU) Mofid Children Hospital Pediatric Neurology Research Center Mofid Children Hospital

Subclinical electroencephalogram discharges in children with psycho-cognitiVe problems are not uncommon. However, the clinical importance and relationship to cognitive def.cits, as well as indications f.r medical treatment, are not well understood. Transient cognitive impairment, which accompanies electroencephalogram discharges, could negatively inf.uence cognitive abilities over time. Studies have suggested that treatment with antiepileptic drugs normalizes electroencephalogram results, thereby preventing electrical paroxysmal discharges that could be harmf.l to the developing brain. Physicians should attempt to dif.erentiate between corresponding f.ctors, such as subtle seizures, nature of.underlying etiology, stable cognitive def.cits, seizure-inducing ef.ects, and potential side ef.ects of.antiepileptic drugs prior to initiation of.medical treatment f.r def.nitive diagnosis of.transient cognitive impairment and its consequences. Theref.re appropriate criteria f.r patient selection and proper guidelines f.r medical therapy, should be addressed in f.ture studies.

关键词： psycho-behavioral problems cognitive def.cits subclinical epileptif.rm discharges antiepileptic drugs

Propane catalytic cracking on pretreated La-ZSM-5 zeolite during calcination f.r light olef.ns production

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Journal of.Rare Earths 2017年第6期35卷 542-550页

作者： Roya Pouria Leyla Vaf. Ramin karimzadeh Department of.Chemical Engineering Tarbiat Modares University Jalal AlAhmad Highway P.O. Box 14155-4838 Tehran Iran

The purpose of.this study was to increase light olef.ns yield and selectivity in catalytic cracking of.propane. Pretreatment of.ZSM-5 zeolite was perf.rmed during calcination. f.rst, lanthanum was loaded on the catalyst by wet impregnation method and then the ef.ect of.parameters, such as temperature（400–800 oC）, time（120–480 min） and type of.stream, on La-ZSM-5 zeolite was examined during calcination using central composite design（CCD） method. Based on the proposed models, the optimized condition f.r maximizing selectivity of.light olef.ns f.r air stream was 680 oC and 310 min and f.r the nitrogen stream was 735 oC and 173 min that under these conditions, selectivity amount increased 24% f.r nitrogen stream and 19% f.r air stream as compared with H-ZSM-5 catalyst. The synthesized catalysts were characterized by X-ray dif.raction（XRD） and temperature-programmed desorption（TPD） techniques. According to the results of.NH3-TPD, as the temperature increased, the number of.strong acid sites（specially Bronsted acid sites） reduced and resulted in increased production of.light olef.ns as well as catalyst stability. Accordingly, stability of.the samples calcined with nitrogen stream was higher than the samples calcined with the air stream.

关键词： calcination cracking selectivity zeolite calcined impregnation programmed lanthanum loaded propane

f.brication of.Bulk (f.,Cr)_3Al/Al_2O_3 Intermetallic Matrix Nanocomposite Through Mechanical Alloying and Sintering

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Acta Metallurgica Sinica(English Letters) 2016年第10期29卷 911-919页

作者： Sayyed Erf.n Aghili Mohammad Hossein Enayati f.thallah karimzadeh Department of.Materials Engineering Isfahan University of Technology

In the present study, （f.,Cr）3Al/20 vol% A1203 nanocomposite was prepared through mechanochemical reactions during ball milling and successf.lly bulked using a combination of.cold isostatic press and sintering at 1400℃ f.r 1 h. Two processing approaches were utilized to produce （f.,Cr）3A1/A1203 nanocomposite： The f.rst was milling of.f., Cr, AI and f.203, while the second one was milling of.f., Cr, Al and Cr203, both in stoichiometric condition, to synthesize （f.,Cr）3Al/20 vol% Al2O3. Structural changes of.powder particles during mechanical alloying were studied by X-ray dif.raction. The microstructure and the morphology of.powder particles and bulk samples were also studied by scanning electron microscopy and transmission electron microscopy. Microstructural analysis showed that mechanochemical reactions took place during milling, and nanometric Al2O3 was unif.rmly distributed in the matrix. The results also showed that the second approach required a considerably higher milling time to produce （f.,Cr）3Al/Al2O3 nanocomposite, as compared to the f.rst one. f.r this reason, bulk samples were produced f.om the synthesized nanocomposite in the f.rst approach. The microstructure of.the sintered samples consisted of.a network structure of.（f.,Cr）3Al and Al2O3 phases with superior mechanical properties.

关键词： Iron aluminide Mechanical alloying Nanocomposite Mechanochemical treatment

The Relationship Between Developmental Accumulation of.Leaf.Soluble Proteins and Vernalization Response of.Wheat(Triticum aestivum ***. Thell)

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Agricultural Sciences in China 2009年第4期8卷 410-417页

作者： M Majdi G karimzadeh S Mahf.ozi Plant Breeding and Biotechnology Department Faculty of AgricultureTarbiat Modares UniversityP.O.Box 14115-336Tehran ***Iran Physiology-Agronomy Unit of.Department of.Cereals Research Seed and Plant Improvement InstituteKaraj 315854119Iran

The relationship between vernalization requirement and quantitative and qualitative changes in total leaf.soluble proteins were determined in one spring （cv. Kohdasht） and two winter （cvs. Sardari and Norstar） cultivars of.wheat （Triticum aestivum L.） exposed to 4℃. Plants were sampled on days 2, 14, 21 and 35 of.exposure to 4℃. The f.nal leaf.number （f.N） was determined throughout the vernalization periods （0, 7, 14, 24, and 35 d） at 4℃. The f.nal leaf.number decreased until days 24 and 35 in Sardari and Norstar eultivars, respectively, indicating the vernalization saturation at these times. No clear changes were detected in the f.nal leaf.number of.Kohdash cultivar, verif.ing no vernalization requirement f.r this spring wheat cultivar. Comparing with control, clear cold-induced 2-f.ld increases in proteins quantity occurred af.er 48 h f.llowing the 4℃-treatment in the leaves of.the both winter wheat cultivars but, such response was not detected in the spring cultivar. However, the electrophoretic protein patterns showed between-cultivar and between-temperature treatment dif.erences. With increasing exposure time to 4℃, the winter cultivars tended to produce more HMW polypeptides than the spring cultivar. Similar proteins were induced in both Sardari and Norstar winter wheat cultivars, however, the long vernalization requirement in Norstar resulted in high level and longer duration of.expression of.cold-induced proteins compared to Sardari with a short vernalization requirement. These observations indicate that vernalization response regulates the expression of.low temperature （LT） tolerance proteins and determines the duration of.expression of.LT- induced proteins.

关键词： soluble proteins wheat Triticum aestivum L. f.nal leaf.number vernalization cold

Bulk Al–Al_3Zr composite prepared by mechanical alloying and hot extrusion f.r high-temperature applications

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International Journal of.Minerals,Metallurgy and Materials 2017年第8期24卷 937-942页

作者： E.Pourkhorshid M.H.Enayati S.Sabooni f.karimzadeh M.H.Paydar Department of.Materials Engineering Isfahan University of Technology Department of.Materials Science and Engineering School of Engineering Shiraz University

Bulk Al/Al_3Zr composite was prepared by a combination of.mechanical alloying(MA) and hot extrusion processes. Elemental Al and Zr powders were milled f.r up to 10 h and heat treated at 600℃ f.r 1 h to f.rm stable Al_3Zr. The prepared Al_3Zr powder was then mixed with the pure Al powder to produce an Al–Al_3Zr composite. The composite powder was f.nally consolidated by hot extrusion at 550℃. The mechanical properties of.consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of.the 10-h-milled powder at 600℃ f.r 1 h led to the f.rmation of.a stable Al_3Zr phase. Dif.erential scanning calorimetry(DSC) results conf.rmed that the f.rmation of.Al_3Zr began with the nucleation of.a metastable phase, which subsequently transf.rmed to the stable tetragonal Al_3Zr structure. The tension yield strength of.the Al-10wt%Al_3Zr composite was determined to be 103 MPa, which is approximately twice that f.r pure Al(53 MPa). The yield stress of.the Al/Al_3Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential f.r the prepared composite to be used in high-temperature structural applications.

关键词： aluminum matrix nanocomposites mechanical alloying hot extrusion aluminides powder metallurgy

Characterization of.NbSi_2–Al_2O_3 nanocomposite coatings prepared with plasma spraying mechanically alloyed powders

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International Journal of.Minerals,Metallurgy and Materials 2015年第7期22卷 748-754页

作者： Zohreh Yazdani f.thallah karimzadeh Mohammad-Hasan Abbasi Abbas Amini Department of.Materials Engineering Isfahan University of Technology

The present study characterized NbSi2-Al2O3 nanocomposite powders plasma-sprayed on Ti-6Al-4Vsubstrates. The powders were agglomerated to obtain suitable particle sizes f.r spraying. The agglomerated powders were then plasma-sprayed using atmospheric plasma spraying. The structural transf.rmations of.the powders along with the morphological and mechanical changes of.the coatings were examined by X-ray dif.raction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and hard- ness testing. The results showed that af.er plasma spraying, the grain size increased, and the lattice strain decreased. However, the grain size of.this compound af.er spraying was still in the nanometer range. The coating was unif.rm and exhibited good adhesion to the substrate. The microhardness and f.acture toughness of.the nanocomposite coating were higher than those of.a nanostructured NbSi2 coating.

关键词： nanocomposites coatings plasma spraying mechanical alloying