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Surface effects on static bending of nanowires based on non-local elasticity theory

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Progress in Natural Science:Materials International 2015年第5期25卷 520-524页

作者： Quan Wu alex.a.volinsky Lijie Qiao Yanjing Su Corrosion and Protection Center Key Laboratory for Environmental Fracture (MOE) University of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

The surface elasticity and non-local elasticity effects on the elastic behavior of statically bent nanowires are investigated in the present investigation. Explicit solutions are presented to evaluate the surface stress and non-local elasticity effects with various boundary *** with the classical Euler beam, a nanowire with surface stress and/or non-local elasticity can be either stiffer or less stiff, depending on the boundary conditions. The concept of surface non-local elasticity was proposed and its physical interpretation discussed to explain the combined effect of surface elasticity and non-local elasticity. The effect of the nanowire size on its elastic bending behavior was investigated. The results obtained herein are helpful to characterize mechanical properties of nanowires and aid nanowire-based devices design.

关键词： Surface effect Non-local elasticity Nanowires Size effect Euler–Bernoulli beam

Fabrication and characterization of anodic oxide nanotubes on TiNb alloys

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Rare Metals 2016年第2期35卷 140-148页

作者： Ming Jin Xin Lu Yi Qiao Lu-Ning Wang alex.a.volinsky School of Materials Science and Engineering University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

Titanium and its alloys have been extensively used as implant materials owing to their high specific strength, good biocompatibility and excellent corrosion resistance. Oxide nanotubular array layer can be formed on Ti alloy surface by electrochemical anodization treatment. In this work, the morphology of nanotubes formed on Ti-Nb alloys（Nb content of 5 wt%, 10 wt%, 20 wt%, 30 wt% and40 wt%） was investigated using an electrolyte containing ethylene glycol and NH_4 F. Oxide layers consisting of highly ordered nanotubes with a range of diameters（approximately40-55 nm for the inner diameter and 100-120 nm for the outer diameter） and lengths（approximately 10-20 lm） can be formed on alloys in the Ti-x Nb system, independent on the Nb content. The nanotubes formed on the Ti-Nb alloy surface were transformed from the anatase to rutile structure of titanium oxide. The oxide nanotubular surface is highly hydrophilic compared with the intact Ti Nb foil. The surface wettability varies with the nanotube diameter. As the nanotube diameter increases while the nanotube layer thickness remains constant, the capillary wetting of the nanotube surface decreases and the surface becomes less *** changes the nanotubular surface wettability further and establishes less hydrophilic surface conditions due to the removal of hydroxyl groups and residue fluoridecontaining species. It is believed that the surface wettability is changed due to the decreasing content of hydroxyl groups in ambient atmosphere. This work can provide guidelines for improving structural and environmental conditions responsible for changing surface wettability of Ti Nb surfaces for biomedical applications.

关键词： Ti-Nb alloy Anodization Nanotubes Wettability Implants

Spheroidization of molybdenum powder by radio frequency thermal plasma

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International Journal of Minerals,Metallurgy and Materials 2015年第11期22卷 1212-1218页

作者： Xiao-ping Liu Kuai-she Wang Ping Hu Qiang Chen alex.a.volinsky School of Metallurgical Engineering Xi'an University of Architecture & Technology Metallurgical Engineering Research Center of Shaanxi Province State Technical Center Jinduicheng Molybdenum Co.Ltd Department of Mechanical Engineering University of South Florida

To control the morphology and particle size of dense spherical molybdenum powder prepared by radio frequency（RF） plasma from irregular molybdenum powder as a precursor, plasma process parameters were optimized in this paper. The effects of the carrier gas flow rate and molybdenum powder feeding rate on the shape and size of the final products were studied. The molybdenum powder morphology was examined using high-resolution scanning electron microscopy. The powder phases were analyzed by X-ray diffraction. The tap density and apparent density of the molybdenum powder were investigated using a Hall flow meter and a Scott volumeter. The optimal process parameters for the spherical molybdenum powder preparation are 50 g/min powder feeding rate and 0.6 m^3/h carrier gas rate. In addition, pure spherical molybdenum powder can be obtained from irregular powder, and the tap density is enhanced after plasma processing. The average size is reduced from 72 to 62 μm, and the tap density is increased from 2.7 to 6.2 g/cm^3. Therefore, RF plasma is a promising method for the preparation of high-density and high-purity spherical powders.

关键词： powder materials molybdenum radio frequency plasma spheroidization processing parameters

Initial formation of corrosion products on pure zinc in simulated body fluid

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Journal of Materials Science & Technology 2018年第12期34卷 2271-2282页

作者： Lijun Liu Yao Meng Chaofang Dong Yu Yan alex.a.volinsky Lu-Ning Wang State Key Laboratory for Advanced Metals and Materials School of Materials Science and EngineeringUniversity of Science and Technology Beijing Institute for Advanced Materials and Technology University of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

Zinc was recently suggested to be a potential candidate material for degradable coronary artery *** corrosion behavior of pure zinc exposed to r-SBF up to 336 h was investigated by electrochemical measurements and immersion tests. The morphology and chemical composites of the corrosion products were investigated by scanning electron microscope, grazing-incidence X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer. The results demonstrate that the initial corrosion products on the pure zinc mainly consist of zinc oxide/hydroxide and zinc/calcium phosphate compounds. The pure Zn encounters uniform corrosion with an estimated corrosion rate of 0.02-0.07 mmy;during the immersion, which suggests the suitability of pure Zn for biomedical applications.

关键词： Zinc Stent Corrosion Simulated body fluid

Microstructure and Hardness of Laser Shocked Ultra-fine-grained Aluminum

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Journal of Materials Science & Technology 2011年第9期27卷 793-796页

作者： Tiantian He Yi Xiong Zhiqiang Guo Lingfeng Zhang Fengzhang Ren alex.a.volinsky School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471003 China State Key Laboratory of Metastable Mater-ials Science and Technology Yanshan University Qinhuangdao 066004 China Department of Mechanical Engineering University of South Florida Tampa FL 33620 USA

Ultra-fine-grained commercial purity aluminum was produced by severe cold rolling, annealing and then strain- ing at ultra-high rate by a single pass laser shock. Resulted microstructure was investigated by transmission electron microscopy. Microhardness of annealed 0.6μm ultra-fine grained aluminum increased by 67% from 24 to 40 HV. Many 0.3 μm sub-grains appeared at the shock wave center after a single pass laser shock, while high density dislocation networks were observed in some grains at the shock wave edges. Accordingly, microhardness at the impact center increased by 37.5% from 40 to 55 HV. From the impact center to the edge, microhardness decreased by 22% from 55 to 45 HV.

关键词： Ultra-fine grains Commercial purity aluminum Laser processing Microstructure Hardness

Recycle of valuable products from oily cold rolling mill sludge

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International Journal of Minerals,Metallurgy and Materials 2013年第10期20卷 941-946页

作者： Bo Liu Shen-gen Zhang Jian-jun Tian De-an Pan Yang Liu alex.a.volinsky Institute for Advanced Materials and Technology University of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

Oily cold rolling mill （CRM） sludge contains lots of iron and alloying elements along with plenty of hazardous organic components, which makes it as an attractive secondary source and an environmental contaminant at the same time. The compound methods of ＂vacuum distillation ＋ oxidizing roasting＂ and ＂vacuum distillation ＋ hydrogen reduction＂ were employed for the recycle of oily cold rolling mill sludge. First, the sludge was dynamically vacuum distilled in a rotating furnace at 50 r/rain and 600℃ for 3 h, which removed almost hazardous organic components, obtaining 89.2wt% ferrous resultant. Then, high purity ferric oxide powders （99.2wt%） and reduced iron powders （98.9wt%） were obtained when the distillation residues were oxidized and reduced, respectively. The distillation oil can be used for fuel or chemical feedstock, and the distillation gases can be collected and reused as a fuel.

关键词： cold rolling mills sludge recycling distillation oxidation hydrogen reduction

Treatment method of hazardous pickling sludge by reusing as glass–ceramics nucleation agent

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Rare Metals 2016年第3期35卷 269-274页

作者： Jian Yang Shen-Gen Zhang De-An Pan Bo Liu Chun-Li Wu alex.a.volinsky Institute for Advanced Materials and Technology University of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

Heavy metal containing pickling sludge（PS） is one of the by-products of the stainless-steel-making industry,which has been considered hazardous due to contained chromium and *** methods of PS disposing are landfill and cement *** research is aimed at disposing PS by solidification/stabilization and reusing it as a nucleation agent of glass–*** crystallization behavior and the properties of a glass in the CaO–MgO–SiO2–Al2O3 system were studied by considering PS as the nucleation *** results confirm that introducing 14 wt% PS as the nucleation agent of glass–ceramics can decrease crystallization temperature by 110.8 °C,refine the grain size by forming isometric crystals with size of 2 lm,enhance Vickers hardness by 2690 MPa and decrease water absorption from（1.21 ± 0.10） wt% to（0.04 ± 0.01） wt%.Therefore,it is reasonable to conclude that PS can be utilized as a nucleation agent to improve the crystallization and mechanical properties of the glass–*** testing results of US EPA toxicity characteristic leaching procedure（TCLP）confirm the safety of this reusing method.

关键词： Glass–ceramics Pickling sludge Nucleation agent Heavy metal stabilization

Review of the fatigue behavior of hard coating–ductile substrate systems

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International Journal of Minerals,Metallurgy and Materials 2021年第1期28卷 46-55页

作者： Yan-yun Bai Jin Gao Tao Guo Ke-wei Gao alex.a.volinsky Xiao-lu Pang School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Department of Mechanical Engineering University of South FloridaTampaFL 33620USA Beijing Advanced Innovation Center for Materials Genome Engineering University of Science and Technology BeijingBeijing 100083China

With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is ***, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate *** also present different opinions on whether coatings can improve or reduce the fatigue life of *** this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.

关键词： fatigue hard coating residual stress fracture toughness film thickness

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

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Journal of Iron and Steel Research International 2016年第3期23卷 220-224页

作者： Shen-gen ZHANG Jian YANG Bo LIU De-an PAN Chun-li WU alex.a.volinsky Institute for Advanced Materials and Technology School of Materials Science and EngineeringUniversity of Science and Technology Beijing Department of Mechanical Engineering University of South Florida

One-step crystallization is one of the most energy conserving methods for glass-ceramics ***,only a few kinetics studies focused on the glass-ceramics prepared by the one-step *** onestep crystallization kinetic parameters were studied using differential scanning *** activation energy（Ea）and the Avrami parameter（n）were calculated as 152.79kJ·mol-1 and 4.39,*** parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent *** properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering *** crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

关键词： glass-ceramics one-step crystallization crystallization kinetics continuous nucleation