检索结果-南通市图书馆

Chemically inducing room temperature spin-crossover in double layered magnetic refrigerants Pr1.4+xSr1.6-xMn2o7(0.0≤x≤0.5)

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第29期124卷 232-242页

作者： Akshay kumar kavita kumari Mohit k.Sharma Ankush Vij Shalendra kumar Seok-Hwan Huh bon.heun k.o Department of Materials Convergence and System Engineering Changwon National UniversityChangwonGyeongnam51140South Korea School of Material Science and Engineering Changwon National UniversityChangwonGyeongnam51140South Korea Department of Physics University of Petroleum&Energy StudiesDehradun248007India Department of Physics College of ScienceKing Faisal UniversityHofufAl-Ahsa31982Saudi Arabia

The height of total entropy(S)for a magnetic refrigerant material is essentially concerned with the magnetic and structural ***,the participation of such transitions in layered materials is not well ***,the purpose of this work is to investigate the interplay between double layer lattice with their single perovskite counterpart,to achieve optimal magnetocaloric performance.A series of self-doped Pr_(1.4+x)Sr_(1.6-x)Mn_(2)o_(7)(0.0≤x≤0.5)Ruddlesden-Popper(R-P)perovskite have been prepared through the solid-state sintering *** increasing the Pr-stoichiometry,the lattice faults have increased and the double layer lattice dramatically disintegrates into single perovskite *** to the reduction of bilayer R-P phase into single perovskite the spin crossover occurs from weak bilayer(T=304 k)interactions towards the strong three-dimensional(T=308 k)interactions *** series consistently develops thermomagnetic irreversibility in zero-field cooled(ZFC)-field cooled(FC)magnetization,which is indicative of a spin-glass *** glassy nature has been ascribed collectively to the lattice strain produced because of dislocations and to an antiferromagnetic phase segregated at the *** maximum value of temperature average entropy change(TEC)and adiabatic temperature(ΔT)has enhanced nearly by 4 folds from 0.53 J kg^(-1)k^(-1),0.59 k(for x=0.0)up to 1.85 J kg^(-1)k^(-1),10 k(for x=0.5)at 2.5 T,***,the room temperature relative cooling power has improved from 26.94 J/kg up to 77.84 J/kg with an applied field of 2.5 *** findings in this work suggest that the controlled reduction of double layer lattice into single perovskite and/or existence of both phases simultaneously in bilayer R-P manganites may be very effective in obtaining the desirable characteristics of magnetocaloric effects.

关键词： Magnetic refrigerant Bilayer manganites Magnetocaloric effect Ruddlesden-popper perovskite Relative cooling power

(EDTA)^(4-) supplements as superior modifier of the in-vitro-degradation properties of the magnesium alloy coated through discharge-assisted process

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2023年第3期11卷 945-957页

作者： Zeeshan Ur Rahman Maqsood Ali Ye-Tang Pan David G.Churchill bon.heun k.o College of Mechatronic Engineering Changwon National UniversityChangwonGyeongsangnam-doRepublic of Korea Department of Regenerative Medicines College of MedicinesSoonChunhyang UniversityCheonanRepublic of Korea National Engineering Technology Research Center of Flame Retardant Materials School of Materials Science&EngineeringBeijing Institute of TechnologyBeijingPR China Department of Chemistry Molecular Logic Gate LaboratoryKorea Advanced Institute of Science and Technology(KAIST)Republic of Korea

The(EDTA)^(4-)organic substituents were supplemented with alkaline silicates electrolyte,however in varying concentration to explore the microstructure,chemical composition and subsequent effects on the biodegradation of the PEo coated Mg AZ91 *** surface analysis-,carried out through SEM,samples with zero-(EDTA)^(4-)were found-,lacking pancake structural features;however,supplementing electrolyte with(EDTA)^(4-),bulky and layered pancakes were obtained with minimum cracks and minimum porosity for *** the phase and inner layer analysis,it was found that EDTA can significantly alter the surface layers composition and could act as a passivation agent-;however,individual polycrystalline phases were not found to *** hardness value obtained for EDT-1 was~909.69 HV,the highest value found here which occurs with the shallowest indents found in this ***-vitro degradation analysis was carried out using potentiodynamic polarization at room temperature,cyclic polarization at RT and high fever conditions(HFT~40°C).The corrosion potential for coated AZ91 was obtained as a positive value of~0.1 V,for the first time in the PEo research;however,the results were not supported by the cyclic polarization tests at room temperature and at *** post corrosion microstructural analysis confirmed the effective role of EDTA up to 1.0 g·L^(-1)and revealed the formation of thin films during the forward polarization at HFT.

关键词： EDTA Soft plasma Magnesium Biodegradation Corrosion SBF

Effects of Hybrid Voltages on oxide Formation on 6061 Al-alloys During Plasma Electrolytic oxidation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2009年第5期22卷 564-568页

作者： kai Wang bon.heun k.o Chan Gyu Lee Young Joo kim Sunghun Lee Eungsun Byon School of Nano & Advanced Materials Engineering Changwon National University Changwon 641-773 Korea Surface Technology Research Center Korea Institute of Materials Science Changwon 641-010 Korea

Plasma electrolytic oxidation （PEo） is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaoH, Na2Sio3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X-ray diffration （XRD）, scanning electron microscope （SEM） and energy dispersive spectrometry （EDS） are conducted on the specimens, which have been PEo-treated under hybrid voltages of different direct current （DC） values （140-280 V） with constant alternate current （AC） amplitude （200 V）. Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages. Moreover, the main effects of DC value are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of α-Al2o3,γ-Al2o3 and mullite. With the DC values increasing, the growth of the ceramic layers tends to have increasingly obvious three-stage feature.

关键词： plasma electrolytic oxidation oxide layer aluminum alloys alkaline electrolyte hybrid voltages

Effects of electrolytes variation on formation of oxide layers of 6061 Al alloys by plasma electrolytic oxidation

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2009年第4期19卷 866-870页

作者： kai WANG bon.heun k.o Chan-Gyu LEE Young-Joo kIM Sung-Hun LEE Eungsun BYoN School ofNano ＆ Advanced Materials Engineering Changwon National University Changwon 641-773 Korea Surface Technology Research Center Korea Institute of Materials Science Changwon 641-010 Korea

Plasma electrolytic oxidation(PEo) processes were carried out to produce ceramic layers on 6061 aluminum substrates in four kinds of electrolytes such as silicate and aluminate solution with and without sodium *** PEo processes were carried out under a hybrid voltage(260 V DC combined with 200 V,60 Hz AC amplitude) at room temperature for 5 *** composition,microstructure and element distribution analyses of the PEo-treated layers were carried out by XRD and SEM & *** effect of the electrolyte contents on the growth mechanism,element distribution and properties of oxide layers were *** is obvious that the layers generated in aluminate solutions show smoother surfaces than those in silicate ***,an addition of fluorine ion can effectively control the layer porosity;therefore,it can enhance the properties of the layers.

关键词：等离子电解氧化 6061合金氧化层对格质变等离子体电解氟硅酸钠铝酸钠溶液

Effect of Cu seed on the synthesis and characterization of FeCo alloy nano-particles by using polyol method

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第1期52卷 19-22页

作者： Uk Rae CHo Young Min LEE Shalendra kUMAR Chan Gyu LEE bon.heun k.o School of Nano-Advanced Materials Engineering Changwon National University Changwon

Fine metal particles with uniform shape, narrow size distribution and high purity are increasingly needed for specific uses in high tech industrial application. We report the direct chemical synthesis of FeCo alloy particles using the mixture of FeCl2·4H2o, Co (Ac)2·4H2o (Ac: acetate) and NaoH in ethylene glycol, and then obtained FeCo alloy particles better dispersed by adding the polyvinylpyrrolidone (PVP) and also the size could be controlled by adding copper. The prepared nano-particles were characterized using FESEM, XRD and VSM. The mean diameter of these particles was varied in the range of sub- mi- crometer to nanometer with metal-ion concentration. FeCo particles showed the typical soft magnetic properties.

关键词： polyol method FeCo alloy nanoparticle Cu seed soft magnetic

Effect of electrolyte on mechanical properties of AZ31B Mg alloy in electrolytic plasma processing

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 125-128页

作者： Byung Hyun AHN Jung Il SoNG bon.heun k.o School of Nano & Advace material engineering Changwon National University Department of Mechanical Engineering Changwon National University

Coatings on Mg alloys were prepared using NaoH + Na2Sio3 as basic electrolyte containing electrolyte of Na2SiF6 or NaF. EPP treatment was carried out on AZ31 Mg alloys matrix under a hybrid voltage of AC of 200 V combined with DC of 260 V for 30 min. Structural and morphological analyses of ceramic coatings were analyzed by XRD and SEM. Wear and hardness of coatings were measured by pin-on disk test and Vickers hardness test. The coatings formed in Na2SiF6 and NaF electrolytes were mainly composed of Mgo and Mg2Sio4. The measured micro-hardness of coating formed in Na2SiF6 electrolyte was found to be over HV 1100, while, coating formed in NaF electrolyte possessed micro-hardness of HV ~900. These results show that the mechanical properties of AZ31 B Mg alloys can be enhanced by the proper selection of electrolyte agent.

关键词： AZ31B Mg alloy surface treatment electrolytic plasma processing

Effect of sintering temperature on structure, magnetic and magnetocaloric properties of La_(0.6)Ca_(0.4)Mno_3 manganite

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 141-145页

作者： Seung Rok LEE M.S.ANWAR Faheem AHMED bon.heun k.o School of Materials Science and Engineering Changwon National University

The effect of sintering temperature on the structure, magnetic transition and magnetic entropy of La0.6Ca0.4Mno3 manganite was studied. It was observed that this compound belongs to the orthorhombic structure with the Pnma space group without any impurity phase. The effect of sintering temperature on the Curie temperature(TC) was studied. The small increment in TC is found with increasing the sintering temperature. The magnetocaloric study exposes a quite large change of the magnetic entropy, which varies with sintering temperature. For an applied magnetic field of 3 T and sintering temperature of 1300 °C, the relative cooling power(RCP) is 89 J/kg. As a result, the studied compound can be considered as potential material for magnetic refrigeration near and below room temperature.

关键词： manganite magnetocaloric effect sintering temperature colossal magnetoresistance

Facile synthesis of single-crystalline rutile Tio_2 nano-rods by solution method

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 152-156页

作者： Rehan DANISH Faheem AHMED Nishat ARSHI M.S.ANWAR bon.heun k.o School of Nano and Advanced Materials Engineering Changwon National University

A convenient and scalable technique for the synthesis of rutile titanium dioxide(Tio2) nano-rods was presented by using bulk Tio2 powder, sodium hydroxide(NaoH) and distilled water as raw materials. X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) studies indicate that the prepared sample is crystalline and free from any impurities, however, it has no distinct shape and possesses a huge degree of agglomeration, and the average crystal size is around 40 nm. After annealing the sample at 600 °C for 2 h, it is observed through FESEM that nano-rods are formed. And XRD analysis shows that the nano-rods are single crystalline with distinct and smooth surfaces in different sizes with average length of about 1 μm and diameter of about 80 nm. Further UV-visible spectroscopy and Raman studies were conducted for the prepared sample and the band gap of the final product is found to be 3.40 eV.

关键词： Tio2 nanorods solution method crystal growth rutile

Annealing time dependent structural, morphological, optical and electrical properties of RF sputtered p-type transparent conducting Sno_2/Al/Sno_2 thin films

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 129-133页

作者： keun Young PARk Ho Je CHo Tae k.on SoNG Hang Joo ko bon.heun k.o School of Materials Science & Engineering Changwon National University Photovoltaic and optoelectronic device center Korea Photonics Technology Institute

Transparent p-type conducting Sno2/Al/Sno2 multilayer films were fabricated on quartz substrates by radio frequency(RF) sputtering using Sno2 and Al targets. The deposited films were annealed at a fix temperature of 500 °C for different time durations(1-8 h). The effect of annealing time on the structural, morphological, optical and electrical performances of Sno2/Al/Sno2 multilayer films was studied. X-ray diffraction(XRD) results show that all the p-type conducting films possess polycrystalline Sno2 with tetragonal rutile structure. Hall-effect results indicate that 500 °C for 1 h is the optimum annealing condition for p-type Sno2/Al/Sno2 multilayer films, resulting in a hole concentration of 1.14×1018 cm-3 and a low resistivity of 1.38 ?·cm, respectively. The optical transmittance of the p-type Sno2/Al/Sno2 multilayer films is above 80% within annealing time range of 1-8 h, showing maximum for the films annealed for 1 h.

关键词： pulsed laser deposition(PLD) transparent conducting oxide(TCo) p-type multi-layer transmittance