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.     

Effects of Al2O3 Nano-additive on Performance of Micro-arc Oxidation Coatings Formed on AZ91D Mg Alloy

Ceramic coatings were prepared on AZ91 D Mg alloy by micro-arc oxidation （MAO） in aluminate electrolytes, with Al2O3 nano-additive suspending at different concentrations. Effects of nano-additive concentration on the structure, phase composition, hardness and anti-corrosion property of the MAO coatings were analyzed by scanning electron microscopy, X-ray diffraction, micro-hardness test and electrochemical method, respectively. The results revealed that Al2O3 nano-particles were mostly incorporated into ceramic coating chemically, transferred into MgAl2O4, rather than being trapped mechanically during MAO process. With the increase of Al2O3 concentration, the voltage-time response, content of MgAl2O4, hardness and anti-corrosion property increased. However, when the concentration varied from 10 g/L to 15 g/L, these behaviors and properties changed only a little. This result indicated that, after the concentration of Al2O3 nano-additive reaching 10 g/L, the incorporation of Al2O3 nano-particles turned into a saturation state, due to the complex process during MAO treatment. Therefore, 10 g/L might be a proper concentration for MAO coating to incorporate Al2O3 nano-particles,     

Highly Improved Gaseous Hydrogen Storage Characteristics of the Nanocrystalline and Amorphous Nd-Cu-added Mg2Ni-type Alloys by Melt Spinning

The nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of （Mg24Ni10Cu2）loo-xNdx （x = 0-20） were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy inspections reveal that, by varying the spinning rate and the Nd content, different microstructures could be obtained by melt spinning. Particularly, the as-spun Nd-free alloy holds an entire nanocrystalline structure but the as-spun Nd-added alloy has a nanocrystalline and amorphous structure, which implies that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Also, the degree of the amorphization in the as-spun Nd-added alloys clearly increases with increasing the spinning rate and the Nd content. The H-storage capacity and the hydrogenation kinetics of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and the phase composition of the alloys. Specially, enhancing the spinning rate from 0 （the as-cast was defined as the spinning rate of 0 m/s） to 40 m/s makes the hydrogen absorption saturation ratio （R5a） （a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity） increase from 35.2% to 90.3% and the hydrogen desorption ratio （R10d） （a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity） rise from 12.7% to 44.9% for the （x = 5） alloy. And the growing of the Nd content from 0 to 20 gives rise to the R5a and R10d values rising from 85.7% to 94.5% and from 36.7% to 54.8% for the as-spun （30 m/s） alloys, respectively.     

Different Diffusion Behavior of Cu and Ni Undergoing Liquidesolid Electromigration

The diffusion behavior of Cu and Ni atoms undergoing liquidesolid electromigration（L-S EM） was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 103A/cm2 at 250℃. The flowing direction of electrons significantly influences the cross-solder interaction of Cu and Ni atoms, i.e., under downwind diffusion, both Cu and Ni atoms can diffuse to the opposite interfaces; while under upwind diffusion,Cu atoms but not Ni atoms can diffuse to the opposite interface. When electrons flow from the Cu to the Ni, only Cu atoms diffuse to the opposite anode Ni interface, resulting in the transformation of interfacial intermetallic compound（IMC） from Ni3Sn4into（Cu,Ni）6Sn5and further into [（Cu,Ni）6Sn5t Cu6Sn5], while no Ni atoms diffuse to the opposite cathode Cu interface and thus the interfacial Cu6Sn5 remained.When electrons flow from the Ni to the Cu, both Cu and Ni atoms diffuse to the opposite interfaces,resulting in the interfacial IMC transformation from initial Cu6Sn5into（Cu,Ni）6Sn5and further into[（Cu,Ni）6Sn5t（Ni,Cu）3Sn4] at the anode Cu interface while that from initial Ni3Sn4into（Cu,Ni）6Sn5and further into（Ni,Cu）3Sn4at the cathode Ni interface. It is more damaging with electrons flowing from the Cu to the Ni than the other way.     

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.     

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).     

Effect of Alumina Dispersion on Microstructural and Nanomechanical Properties of Pulse Electrodeposited Nickel-Alumina Composite Coatings

Nickel-gamma alumina（Ni—γAI2O3） composite coatings were synthesized by pulsed electrodeposition technique with different concentrations of alumina（0,10,20 and 50 g/L） in Watt’s bath.Both ultrasonic vibration and magnetic-stirring were utilized to disperse Al2O3 and to achieve its optimum loading.Microstructure shows that agglomerates occur at higher loadings,but 10 g/L Al2O3 addition in bath has shown uniform dispersion of alumina with improved mechanical properties such as hardness,Young’s modulus and yield strength by 40%,46%and 35%,respectively,when compared to that of pure Ni coating.Further,elasto-plastic indentation mechanics has shown that strength at 29%strain is enhanced to 110.5 GPa for 10 g/L Al2O3electrophoretically deposited Ni—yAI2O3 coating when compared to that of electrodeposited Ni（81.8 GPa）.     

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.     

Fabrication and Characterization of Electrodeposited Ni-SiC-h/BN Composite Coatings

Ni—SiC—h/BN composite materials were prepared by electrodeposition technique with the dispersion of SiC（10 g/L） and h/BN nanosheets（10 g/L） in a nickel sulfamate electrolytic bath.Different ratio of sodium dodecyl sulfate（SDS） and cetyltrymethyl ammonium bromide（CTAB） surfactants were used to evaluate the effect of surfactants on the properties of the electrodeposited composite coatings.The coating samples were characterized by scanning electron microscopy,X-ray diffraction,Vickers microhardness test,scratch and tribology tests.The results revealed that the co-deposition of nanoparticles was significantly influenced by surfactants during electrodeposition process.Pyramidal or polyhedral nickel crystallites were observed at higher ratio of SDS/CTAB while smaller oval grains with refined surface morphologies were obtained at lower ratio of SDS/CTAB surfactants.In addition,wt%of particles co-deposition was increased,and Vickers microhardness,wear and coefficient of friction of the electrodeposited composite coatings were improved at increased CTAB and decreased SDS contents in the electrolyte during electrodeposition process.     

Influences of Reaction Parameters and Ce Contents on Structure and Properties of Nano-scale Ce-HA Powders

Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this study.The crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were studied.The results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce contents.With the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually decrease.The reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical composition.The obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.     

Ionic Potential： A General Material Criterion for the Selection of Highly Efficient Arsenic Adsorbents

Arsenic is a highly toxic element and its contamination in water bodies is a worldwide problem. Arsenic adsorption with metal oxides/hydroxides-based adsorbents is an effective approach to remove arsenic species from water for the health of both human beings and the environment. However, no material criterion had been proposed for the selection of potential candidates. Equally puzzling is the fact that no clear explanation was available on the poor arsenic adsorption performance of some commonly used adsorbents, such as active carbon or silica. Furthermore, in-depth examination was also not available for the dramatically different competing adsorption effects of various anions on the arsenic adsorption. Through the arsenic adsorption mechanism study on these highly efficient arsenic adsorbents, we found that ionic potential could be used as a general material criterion for the selection of highly efficient arsenic adsorbents and such a criterion could help us to understand the above questions on arsenic adsorbents. This material criterion could be further applied to the selection of highly efficient adsorbents based on ligand exchange between their surface hydroxyl groups and adsorbates in general, which may be used for the prediction of novel adsorbents for the removal of various contaminations in water.     

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.     

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.     

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）.     

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.     

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.     

In Vitro Comparative Effect of Three Novel Borate Bioglasses on the Behaviors of Osteoblastic MC3T3-E1 Cells

Most related investigations focused on the effects of borate glass on cell proliferation/biocompatibility in vitro or bone repair in vivo; however, very few researches were carried out on other cell behaviors. Three novel borate bioglasses were designed as scaffolds for bone regeneration in this wok. Comparative effects of three bioglasses on the behaviors of osteoblastic MC3T3-E1 cells were evaluated. Excellent cytocompatibility of these novel borate bioglasses were approved in this work. Meanwhile, the promotion on cell proliferation, protein secretion and migration with minor cell apoptosis were also discussed in details, which contributed to the potential clinical application as a new biomaterial for orthopedics.     

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.     

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.     

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.