Preparation and Antibacterial Activity of Three-component NiFe204@PANI@Ag Nanocomposite

A new three-component and magnetically responsive NiFe2O4@PANI@Ag nanocomposite has been fabricated by coating of nickel ferrite, NiFe2O4, nanoparticles with polyaniline （PANI） and subsequent immobilization of silver nanoparticles onto the surface of polyaniline shell. The as-prepared nanocomposite has been characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, and vibrating sample magnetometer （VSM）. The saturation magnetization of the NiFe2O4 core decreases dramatically after coating with polyaniline and silver nanoparticles, however, the nanocomposite NiFe2O4@PANI@Ag can be still separated from solution media through magnetic decantation. The antibacterial activity of the synthesized nanocomposite was studied and compared with those of naked NiFe2O4, NiFe2O4@PANI and some standard antibacterial drugs.     

Synthesis,Surface Characterization and Photocatalytic Activity of TiO2 Supported on Almond Shell Activated Carbon

Three types of photocatalysts were synthesized by metal organic chemical vapor deposition and impregnation methods using the almond shell activated carbon as support. These photocatalysts denoted by （TiO2/ASAC （V）, TiO2/ASAC （11） and TiO2/ASAC （12）） were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, diffuse reflectance spectroscopy （DRS） and nitrogen adsorption-desorption isotherms. SEM observation shows that TiO2 was deposited on activated carbon surface. XRD results confirm that TiO2 existed in a mixture of anatase and rutile phases. The DRS spectra show the characteristic absorption edge of TiO2 at approximate 380 nm corresponding to the optical band gap of 3.26 eV. Besides, FTIR spectrum indicated the presence of （Ti-O） groups. The specific surface area of photocatalysts decreased drastically in comparison with the original activated carbon. The catalysts were very efficient for the photodegradation of total organic carbon （TOC） from industrial phosphoric acid solution under UV irradiation. The kinetics of photocatalytic TOC degradation was found to follow a pseudo- first-order model. The prepared TiO2/ASAC showed high photoactivity for the photodegradation of TOC in the following order： TiO2/ASAC （V） 〉 TiO2/ASAC （11） 〉 TiO2/ASAC （12） 〉 ASAC 〉 TiO2 （P25）.     

Surfactant Assisted Dispersion and Adhesion Behavior of Carbon Nanotubes on Cu-Zr and Cu-Zr-Al Amorphous Powders

Carbon nanotubes （CNTs） were dispersed in gas atomized Cu47.5Zr47.5Al5 （CZA） and CusoZrso （CZ） amorphous powders, in an effort to elucidate the mechanisms of adhesion of CNTs onto amorphous metallic powders. CNTs were homogenously dispersed in water using a zwitterionic （ZW） surfactant. Then CZA and CZ powders were submersed in the ZW-CNTsuspensions with varying amounts of dwell time in an ultrasonic bath. The ZW-CNT- metal powder suspensions were dried, and CNT-metal composite powders were obtained after decomposition of the surfactant by calcination. Zeta potential measurements on ZW-CNT-metal powder suspensions and scanning electron microscopy investigation into the CNT-metal composite powders both indicated an ideal dwell time, for a specific alloy composition, of metallic powders in ZW-CNT suspension to achieve optimal adhesion of CNTs onto amorphous metallic powder surfaces. The results are rationalized on the basis of hydrolysis of metal ions into suspension creating a net positive charge on the metallic powder surfaces, and the interaction between the charged powder surfaces and the charged hydrophilic head groups of ZW, which has the other end attached to CNTs.     

Tensile Strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum Matrix Composites Fabricated by Powder Metallurgy Combined with Friction Stir Processing

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube(CNT) reinforced Al(CNT/AI) and 6061 Al(CNT/6061AI) composites.Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061 AI composites.Mg and Si elements tended to segregate at CNT—Al interfaces in the CNT/6061 AI composite during artificial aging treatment.The tensile properties of both the Al and 6061 Al were increased by CNT incorporation.The electrical conductivity of CNT/AI was decreased by CNT addition,while CNT/6061 AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.     

Microstructure Evolution and Tensile Properties of Ti3Al/Ni-based Superalloy Welded Joint

In the present work,the dissimilar joining of a Ti_3AI-based alloy to a Ni-based superalloy was attempted by gas tungsten arc(GTA) welding technology.Sound joints were successfully achieved by using a Cu—Ni alloy as filler material.According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti_3AI interface were verified as follows:Ti_2AINb phase dissolved with Cu and Ni;AI(Cu,Ni)_2Ti,(Cu,Ni)_2Ti and(Nb,Ti) solid solution;Cu-rich phase and a complex multi-element phase.The In718/weld interface is characterized by solid solutions of Ni,Cu,Cr,Fe and Nb.The average tensile strength of the as-welded joints at room temperature is 1 63 MPa,and after a post—weld heat treatment it is increased slightly to 177 MPa.The fracture occurred at the surfacial layer of the joined Ti_3AI base alloy,indicating that the Ti_2AINb layer dissolved with Cu and Ni is the weak link of the Ti_3AI/ln71 8 joint.     

Effects of Y on the Microstructure,Mechanical and Bio-corrosion Properties of Mg-Zn-Ca Bulk Metallic Glass

The micro-alloying effects of Y on the microstructure, mechanical properties, and bio-corrosion behavior of Mg69-xZn27Ca4Yx（x= 0, 1, 2 at.%） alloys were investigated through X-ray diffraction, compressive tests,electrochemical treatments, and immersion tests. The Mg69Zn27Ca4 alloy was found to be absolutely amorphous, and its glass-forming ability decreased with the addition of Y. The Mg68Zn27Ca4Y1 alloy exhibited an ultrahigh compressive strength above 1010 MPa as well as high capacity for plastic strain above 3.1%.Electrochemical and immersion tests revealed that these Y-doped MgeZ neC a alloys had good bio-corrosion resistance in simulated body fluid（SBF） at 37℃. The results of the cytotoxicity test showed high cell viabilities for these alloys, which means good bio-compatibility.     

A Facile Synthetic Approach to Reduced Graphene Oxide-Fe3O4 Composite as High Performance Anode for Lithium-ion Batteries

Reduced graphene oxide-Fe3O4（rGO—Fe3O4） composite has been prepared via a facile and effective hydrothermal method by synthesizing Fe3O4 nanospheres on the planes of reduced graphene oxide（rGO）.Characterizations suggest the successful attachment of Fe3O4 nanospheres to rGO sheets.The rGO—Fe3O4composite（66.7 wt%of Fe3O4 in the composite） exhibits a stable capacity of 668 mAh g-1 without noticeable fading for up to 200 cycles in the voltage range of 0.001—3.0 V,and the superior performance of rGO-Fe3O4 is clearly established by comparison of the results with those from bare Fe3O4 nanospheres（capacity declined to 117 mAh g-1 only at the 200 th cycle）.The excellent electrochemical performance of rGO—Fe3O4 composite can be attributed to the fact that the uniform dispersion of the Fe3O4 nanospheres growing on the rGO sheets avoids aggregation during Li uptake-release cycling,which is desired for cycle stability.Meanwhile,the rGO sheets afford not only elastic buffer to alleviate the volume variations of Fe3O4nanospheres,but also good ionic and electronic transport medium in the electrode.     

Synthesis and Characterization of a Novel Silver-Substituted Calcium Phosphate Cement

Antibacterial materials play an important role in clinical application,and silver has been known to exhibit strong cytotoxicity towards a broad range of micro-organisms.In this work,the amorphous calcium phosphate with silver substitution(Ag-ACP) was synthesized by chemical precipitation method,and the valence of silver in ACP was adjusted by temperature.The processed Ag-ACP was combined with slightly acidic compounds to form new calcium phosphate cement(CPC).Our results indicate that the valence of silver in CPC was adjusted successfully by chemical precipitation method and heat treatment.X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) results demonstrated that silver ion in CPC-1 and CPC-2 existed in Ag3PO4;after heat treatment of 460 ℃,silver became more stable in CPC-3 and CPC-4.Silver in CPC-1 and CPC-2exhibited better releasing property.After heat treatment at 460 ℃,the amount of silver ion released from CPC decreased significantly.Besides,the antibacterial ability of Ag-CPC was adjusted by changing the valence of silver in Ag-CPC.Depending on the low valence of silver and good silver release,CPC-1 and CPC-2exhibited better antibacterial activity.We believe that this study will motivate the development and applications of antibacterial CPC in bone tissue regeneration.     

Microstructure and Mechanical Properties in Dissimilar Butt Friction Stir Welding of Severely Plastic Deformed Aluminum AA 1050 and Commercially Pure Copper Sheets

In this study,AA 1050 aluminum alloy and commercially pure copper in annealed and severely plastic deformed conditions were used.The technique used for imposing the severe strain to the sheets was constrained groove pressing（CGP） process.The annealed and severely plastic deformed sheets were subjected to friction stir welding（FSW） at different rotation and traverse speeds.Cu was placed in advancing side.Constant offset of approximately 1 mm was used toward Al side for all welds.A range of welding parameters which can lead to acceptable welds with appropriate mechanical properties was found.For the FSWed CGPed samples,it was observed that the welding heat input caused grain growth and decrease in hardness value at Al side of the stir zone.It was found that,generally the weakest parts of weld joints of annealed and CGPed samples were Al base metal and stir zone,respectively.Further investigations showed that several forms of intermetallic compounds were produced.     

Density Functional Theory Study on the Oxidation of Hydrosilylated Silicon Nanocrystals

As a leading surface modification approach,hydrosilylation enables freestanding silicon nanocrystals(Si NCs) to be well dispersed in a desired medium.Although hydrosilylation-induced organic layers at the NC surface may somehow retard the oxidation of Si NCs,oxidation eventually occurs to Si NCs after relatively long time exposure to air.We now investigated the oxidation of hydrosilylated Si NCs in the frame work of density functional theory(DFT).Three oxygen configurations that may be introduced by the oxidation of a Si NC are considered.It is found that a hydrosilylated Si NC is less prone to oxidation than a fully H-passivated Si NC in the point of view of thermodynamics.At the ground state,backbond oxygen(BBO) and hydroxyl(OH) hardly change the gap between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of a hydrosilylated Si NC.At the excited state,the decrease in the HOMO-LUMO gap induced by the introduction of doubly bonded oxygen(DBO) is more significant than that induced by the introduction of BBO or OH.We have correlated the changes in the optical absorption(emission) of a hydrosilylated Si NC after oxidation to those of the HOMO—LUMO gap at the ground state(excited state).     

Dry Sliding Tribological Properties of a Dendrite-reinforced Zr-based Bulk Metallic Glass Matrix Composite

In-situ dendrite-reinforced metallic glass matrix （MGM） composites with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 were prepared with a vacuum arc melter by the copper mold suction casting. Effect of different normal loads and sliding velocities on the tribological properties of MGM composites was studied. The results showed that the friction coefficient and wear rate of composites initially descended with increasing the normal load and reached a minimum of 0.339 and 1.826 × 10^-4 mm^3/（N m） at 10 N, respectively, then ascended. Similarly, the friction coefficient and wear rate of composites initially decreased with the increase in the sliding velocity and reached a minimum of 0.330 and 2.389 × 10^-4 mm^3/（N m） at 0.4 m/s and 0.3 m/s, respectively, then raised. The wear mechanism of composites was mainly adhesive wear accompanied by abrasive wear at lower normal load and sliding velocity. However, the wear mechanism of composites was abrasive wear and adhesive wear as well as delamination at higher normal load and sliding velocity due to the nucleation and propagation of surface and subsurface cracks during the wear process. The flake-like and particle-like wear debris was the dominant shapes of debris observed.     

Comparative Study of the Structure and Properties of Ti-O-based Nanowire Films Prepared by Anodization and Chemical Oxidation Methods

Net-like titanium oxide or H-titanate nanowire films were grown on Ti substrates in 2 mol/L NaOH solutions at 80 ℃ via anodization method or chemical oxidation followed by proton-exchange. The microstructure, thermal stability and photoelectrochemical property of two types of films were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and photocurrent measurement. It is found that the anodic film mainly consists of a 500-nm-thick nenowire layer whereas the film formed by chemical oxidization is made up of two layers： a nanowire layer （nearly 1 tim in thickness） and an underlying non- nanowire layer （at least 1 μm in thickness）. In both two cases, the as-formed nanowires are partly crystallized. Thermal stability investigation reveals that the net-like structure of the anodic nanowire film almost keeps unchanged at a temperature less than 400℃ but is totally destroyed when being calcinated at 600 ℃. In contrast, the nanowire layer formed by chemical method is stable even after being calcinated at 600 ℃. Our results also show that the uncalcinated or calcinated anodic films are much more photoactive than the corresponding films prepared by chemical oxidization. The difference in photoelectrochemical property of two types of films is discussed based on their microstructures.     

Structural,Optical,Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol

Biological entities and inorganic materials have been in constant touch with each other ever since inception of life on earth.This method has lots of merits such as not requiring complex procedures,template supporting etc.In this work,Aloe vera plant mediated synthesis of tetragonal zirconia nanoparticles has been performed and thermogravimetric and differential thermal analysis（TG/DTA）,X-ray diffraction（XRD）,scanning electron microscopy（SEM） with energy dispersive X-ray spectroscopy（EDX）,atomic force microscopy（AFM）,ultraviolet—visible（UV—VIS） technique and Fourier transform infrared spectroscopy（FTIR） have been provided for characterizing the nanoparticles.Formation of homogeneously distributed spherical zirconia nanoparticles of 50—100 nm in size is predicted.The antimicrobial and antifungal properties are also investigated for synthesis of zirconia nanoparticles and the treated cotton by agar diffusion method against Staphylococcus aureus and Escherichia coli bacterial pathogens and fungal strains Candida albicans and Aspergillus niger,respectively.     

Effect of Post Cryorolling Treatments on Microstructural and Mechanical Behaviour of Ultrafine Grained Al-Mg-Si Alloy

To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material （UFG）, AI 6061 alloy was subjected to cryorolling followed by warm rolling （CR ＋ WR） and compared with cryorolling followed by short annealing （CR ＋ SA） at the same temperature. Transmission electron microscopy （TEM） was used to characterize the microstructural features of the processed material. The mechanical properties were investigated through Vickers hardness testing and tensile testing at room temperature. TEM, X-ray diffraction （XRD） and differential scanning calorimetry （DSC） were used to investigate the precipitation evolution in UFG material. Results indicated that the alloy subjected to CR ＋ WR has shown improved mechanical properties （114 HV, ultimate tensile strength （UTS）： 350 MPa） as compared to that in the case of CR ＋ SA （105 HV, UTS： 285 MPa）. The size of the precipitates observed in CR ＋ WR sample after peak ageing treatment is finer than that of peak aged CR ＋ SA sample. The UTS of peak aged CR ＋ WR sample （UTS： 390 MPa） was found to be higher than that of peak aged CR ＋ SA sample （UTS： 355 MPa）, without decrease in ductility.     

Effects of Annealing Temperature on Cu-Doped ZnO Nanosheets

The synthesis of Cu-doped ZnO nanosheets at room temperature was reported in our previous paper. The effects of annealing temperature on Cu-doped ZnO nanosheets were studied in this paper. Cu-doped ZnO nanosheets were annealed at 200-500℃ in air. The annealed specimens were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The results show that Cu concentration in Cu-doped ZnO nanosheets reduced with increasing annealing temperature. When annealing temperature was lower than Zn melting point （410℃）, the morphologies of the Cu-doped ZnO nanosheets remained nearly the same as that before annealing. However, when the annealing temperature was over Zn melting point, Cu-doped ZnO nanosheets changed to nanowires, wormlike nanosheets or did not change. The change of Cu concentration in Cu-doped ZnO nanosheets is explained by oxidation thermodynamics. A physical model is suggested to explain the morphology changes of Cu-doped ZnO nanosheets, based on the existence of Cu-rich layer beneath Cu-doped ZnO nanosheets.     

Influence of Sputtered NanocrystaUine Coating on Oxidation and Hot Corrosion of a Nickel-based Superalloy M951

The isothermal and cyclic oxidation behaviors in air and hot corrosion behaviors in Na2SO4 ＋ 25 wt% K2SO4 salt of M951 cast superalloy and a sputtered nanocrystalline coating of the same material were studied. Scanning electron microscopy, energy dispersive X-ray spectroscope, X-ray diffraction, and transmission electron microscopy were employed to examine the morphologies and phase composition of the M951 alloy and nanocrystalline coating before and after oxidation and hot corrosion. The as-sputtered nanocrystalline layer has a homogeneous y phase structure of very fine grain size （30-200 nm） with the preferential growth texture of （111） parallel to the interface. Adherent AI203 rich oxide scale formed on the cast M951 alloy and its sputtered coating after isothermal oxidation at 900 and 1000 ℃. However, when being isothermal oxidized at 1100℃ and cyclic oxidized at 1000 ℃, the oxide scale formed on the cast alloy was a mixture of NiO, NiAl2O4, Al2O3 and Nb205 and spalled seriously, while that formed on the sputtered coating mainly consisted of Al2O3 and was very adherent. Nanocrystallization promoted rapid formation of Al2O3 scale during the early stage of oxidation and enhanced the adhesion of the oxide scale, thus improved the oxidation resistance of the substrate alloy. Serious corrosion occurred for the cast alloy. The sputtered nanocrystalline coating apparently improved the hot corrosion resistance of the cast alloy in the mixed sulfate by the formation of a continuous Al2O3 and Cr2O3 mixed oxide layer on the surface of the coating, and the pre- oxidation treatment of the coating led to an even better effect.     

Effect of Hot Isostatic Pressing Conditions and Cooling Rate on Microstructure and Properties of Ti-6Al-4V Alloy from Atomized Powder

The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.     

Waterborne Epoxy Nanocoatings Modified by Nanoemulsions and Nanoparticles

Electrically conductive coatings are required for static charge dissipation in power ground network. In the present investigation electrically conductive nanocoatings were prepared by the incorporation of graphite, nano-SiO2 concentrate, acrylic nanoemulsion and fluorocarbon emulsion onto the waterborne epoxy polymer. The nanosize distribution of nano-SiO2 concentrate and nanoemulsion was characterized with laser diffraction analyzer and scanning electron microscopy （SEM）. From the results of SEM image, the graphite particles were well distributed in conductive coating. The corrosion resistance and thermal stability of nanocoatings were comparatively studied by SEM and thermogravimetry （TG）. The corrosion-inhibiting properties of the conductive nanocoatings were investigated by salt immersion test. The measurements of contact angle, bonding strength and heat-freeze charge demonstrated that 1.5-2.0 wt% nanoparticles improve the resistance to pollution, adherence and resistance to heat-freeze charge of conductive nanocoatings. The measured results of surface electric resistance of nanocoatings demonstrated that a small amount of nano- SiO2 particles could enhance the conductivity in the corrosive environment.     

Microstructure and Properties of 3.5 vol.% TiBw/Ti6Al4V Composite Tubes Fabricated by Hot-hydrostatic Extrusion

Tubes of 3.5 vol,% TiB whiskers reinforced Ti6Al4V matrix composites （TiBw/Ti6Al4V） were successfully fabricated by a two-step hot-hydrostatic extrusion process： （3 extrusion at 1100 ℃ and subsequent near-β extrusion at 950℃. The dimensions of tubes were about 7 mm in diameter and 2 mm in thickness. A refined basket-weave structure in Ti6Al4V matrix was achieved at ambient temperature after the extrusion process. Besides, the original network structure formed by TiB whiskers synthesized was broken, while the TiB whiskers were preferentially aligned in the extruding direction. Meanwhile, a fibrous texture was evolved finally, resulting from partial dynamic recrystallization during the β extrusion and the involvement of α phase during the near-β extrusion. The tensile and compressive tests results showed that both the strength and ductility of the tubes were significantly improved. In particular, the tubes exhibited good mechanical properties at elevated temperatures.     

Heat-induced Internal Strain Relaxation and its Effect on the Microstructure of Polyacrylonitrile-based Carbon Fiber

The transformation of the internal strain and its effect on the microstructure of polyacrylonitrile-based carbon fiber during the high-temperature graphitization were investigated. The internal compressive strain within the carbon turbostratic structure was confirmed through a careful analysis by wide-angle X-ray diffraction and Raman spectroscopy. Heat-induced strain/stress relaxation along the fiber axis was observed and was found to have a profound effect on the structure of both the crystallites and microvoids. The results indicated that, the relaxation of residual strain changed the graphite layers from a wrinkled and distorted morphology to a straight and smooth one, and consequently led the crystallites to stack closely and orderly with increasing stack height. The strain relaxation also changed the morphology of crystallites and microvoids, resulting in an anisotropic growth for the latters.