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Bulk Al–Al_3Zr composite prepared by mechanical alloying and hot extrusion for 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 for up to 10 h and heat treated at 600℃ for 1 h to form 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 finally 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℃ for 1 h led to the formation of a stable Al_3Zr phase. Differential scanning calorimetry(DSC) results confirmed that the formation of Al_3Zr began with the nucleation of a metastable phase, which subsequently transformed 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 for 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 for the prepared composite to be used in high-temperature structural applications.

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

Thermal stability evaluation of nanostructured Al6061 alloy produced by cryorolling

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Transactions of Nonferrous Metals Society of China 2017年第4期27卷 754-762页

作者： M.ABBASI-BAHARANCHI f.karimzadeh M.H.ENAYATI Department of Materials Engineering Isfahan University of Technology Isfahan 84156-83111 Iran

Grain growth of nanostructured Al6061produced by cryorolling and aging process was investigated during isothermalheat treatment in100?500°C temperature *** electron microscopy(TEM)observations demonstrate that aftercryorolling and aging at130°C for30h,the microstructure contains61nm grains with dispersed50?150nm precipitates and0.248%lattice *** addition,an increase in tensile strength up to362MPa because of formation of fine strengtheningprecipitation and nano-sized grains was *** stability investigation within100?500°C temperature range showedrelease of lattice strain,dissolution of precipitates and grain *** to the X-ray diffraction(XRD)analysis,Mg2Siprecipitates disappeared after annealing at temperatures higher than300°*** to the results,due to the limited grain growthup to200°C,there would be little decrease in mechanical properties,but within300?500°C range,the grain growth,dissolution ofstrengthening precipitates and decrease in mechanical properties are *** activation energies for grain growth werecalculated to be203.3kJ/mol for annealing at100?200°C and166.34kJ/mol for annealing at300?500°*** effect ofprecipitation dissolution on Al lattice parameter,displacement of Al6061(111)XRD peak and Portevin?LeChatelier(PLC)effect onstress?strain curves is also discussed.

关键词： mechanical characterization X-ray diffraction aluminium alloy bulk deformation grain growth grain refinement

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 infants 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 difficulties 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 performance and inattention in children. Appropriate diagnosis and early management of sleep disorders in children lead to improvement of neurocognitive function and behavioral problems in these children.

关键词： sleep disorder behavioral problems cognitive impairment association children

Promising medical treatment for 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 deficits, as well as indications for medical treatment, are not well understood. Transient cognitive impairment, which accompanies electroencephalogram discharges, could negatively influence cognitive abilities over time. Studies have suggested that treatment with antiepileptic drugs normalizes electroencephalogram results, thereby preventing electrical paroxysmal discharges that could be harmful to the developing brain. Physicians should attempt to differentiate between corresponding factors, such as subtle seizures, nature of underlying etiology, stable cognitive deficits, seizure-inducing effects, and potential side effects of antiepileptic drugs prior to initiation of medical treatment for definitive diagnosis of transient cognitive impairment and its consequences. Therefore appropriate criteria for patient selection and proper guidelines for medical therapy, should be addressed in future studies.

关键词： psycho-behavioral problems cognitive deficits subclinical epileptiform discharges antiepileptic drugs

Thermodynamic Aspects of Nanostructured CoAl Intermetallic Compound during Mechanical Alloying

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Journal of Materials Science & Technology 2011年第7期27卷 601-606页

作者： S.N. Hosseini T. Mousavi f. karimzadeh M.H. Enayati Department of Materials Engineering Nanotechnology and Advanced Materials Institute Isfahan University of Technology84156-83111 Iran

The nanostructured CoAl intermetallic compound was produced by mechanical alloying （MA） of the Co50Al50 elemental powder mixture in a planetary high energy ball mill. The ordered B2-CoAl structure with the grain size of about 6 nm was formed via a gradual reaction after 10 h of MA. A thermodynamic analysis of the process was also done. The results showed that the intermetallic compound of CoAl had the minimum Gibbs free energy compared to solid solution and amorphous states indicating the initial MA product was the most stable phase in the Co-Al system which was changed to a partially disordered structure with a steady long-range order of 0.82 at further milling. This amount of disordering caused the enthalpy of final product to show an increase of about 5.1 kJ·mol-1. Calculation of enthalpy related to the triple defect formation revealed that the enthalpy required for Al anti-sites formation was about 3 times greater than that for Co anti-sites formation.

关键词： Intermetallics CoAl Nanostructured materials Mechanical alloying Thermodynamics

Propane catalytic cracking on pretreated La-ZSM-5 zeolite during calcination for light olefins production

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

作者： Roya Pouria Leyla Vafi 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 olefins yield and selectivity in catalytic cracking of propane. Pretreatment of ZSM-5 zeolite was performed during calcination. first, lanthanum was loaded on the catalyst by wet impregnation method and then the effect 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 for maximizing selectivity of light olefins for air stream was 680 oC and 310 min and for the nitrogen stream was 735 oC and 173 min that under these conditions, selectivity amount increased 24% for nitrogen stream and 19% for air stream as compared with H-ZSM-5 catalyst. The synthesized catalysts were characterized by X-ray diffraction（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 olefins 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

fabrication of Bulk (fe,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 Erfan Aghili Mohammad Hossein Enayati fathallah karimzadeh Department of Materials Engineering Isfahan University of Technology

In the present study, （fe,Cr）3Al/20 vol% A1203 nanocomposite was prepared through mechanochemical reactions during ball milling and successfully bulked using a combination of cold isostatic press and sintering at 1400℃ for 1 h. Two processing approaches were utilized to produce （fe,Cr）3A1/A1203 nanocomposite： The first was milling of fe, Cr, AI and fe203, while the second one was milling of fe, Cr, Al and Cr203, both in stoichiometric condition, to synthesize （fe,Cr）3Al/20 vol% Al2O3. Structural changes of powder particles during mechanical alloying were studied by X-ray diffraction. 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 uniformly distributed in the matrix. The results also showed that the second approach required a considerably higher milling time to produce （fe,Cr）3Al/Al2O3 nanocomposite, as compared to the first one. for this reason, bulk samples were produced from the synthesized nanocomposite in the first approach. The microstructure of the sintered samples consisted of a network structure of （fe,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 Mahfoozi 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 final leaf number （fLN） was determined throughout the vernalization periods （0, 7, 14, 24, and 35 d） at 4℃. The final 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 final leaf number of Kohdash cultivar, verifying no vernalization requirement for this spring wheat cultivar. Comparing with control, clear cold-induced 2-fold increases in proteins quantity occurred after 48 h following 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 differences. 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. final leaf number vernalization cold

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 fathallah 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 for spraying. The agglomerated powders were then plasma-sprayed using atmospheric plasma spraying. The structural transformations of the powders along with the morphological and mechanical changes of the coatings were examined by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and hard- ness testing. The results showed that after plasma spraying, the grain size increased, and the lattice strain decreased. However, the grain size of this compound after spraying was still in the nanometer range. The coating was uniform and exhibited good adhesion to the substrate. The microhardness and fracture toughness of the nanocomposite coating were higher than those of a nanostructured NbSi2 coating.

关键词： nanocomposites coatings plasma spraying mechanical alloying