bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Microstructure Characterizations of Novel C/C-Zr(Hf)B2-Zr(Hf)C-SiC Composites
Authors: Li Jie Wen , Wei Xi , Zhang Wei Gang , Ge Min
Published: April 2014

A series of novel C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were prepared by chemical vapor infiltration (CVI) of pyrolytic carbon and polymeric impregnation and pyrolysis (PIP) with hybrid polymeric precursors of SiC (polycarbosilane), Zr (Hf)C and Zr (Hf)B2 in carbon fiber preforms. The formed ultra-high temperature ceramics (UHTCs) matrix of SiC-ZrC-ZrB2 and SiC-HfC-HfB2 were designed to improve the oxidation resistance of carbon/carbon composite at very high temperatures above 2000°C. The pyrolysis process of Zr (Hf)C and Zr (Hf)B2 polymeric precursors was investigated, and the results showed that the hybrid precursors could be successfully transformed into Zr (Hf)C and Zr (Hf)B2 ceramic particles with the sizes of nanometer with temperatures above 1500°C. Furthermore, the multiscale structure of C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were also characterized , showing that the carbon fibers were covered by pyrolytic carbon, and the continuous ceramic matrix was well dispersed, formed by Zr (Hf)C and Zr (Hf)B2 nanoparticles distributing homogeneously in the continuous SiC matrix. This homogeneous dispersion of composite ceramics of Zr (Hf)C and Zr (Hf)B2 with SiC plays excellent protection of C/C composites from oxidation at high temperature via formation of stable oxides coatings.
Catalytic Mechanism of Dioctyldilauryltin on the Dealcoholized RTV-2 Silicone Rubber
Authors: Shi Lu Lu , Zheng Jing Wu , Ying Yao , Jiang Li Qiang , Che Sheng Lei , Qiao Liang
Published: April 2014

Using dioctyldilauryltin as the catalyst, a series of RTV-2 silicone rubbers were prepared by applying tetraethoxysilane (TEOS) to hydroxyl terminated polydimethylsiloxane (HPDMS) matrix. The effect of the catalyst contents on the curing time of the silicone rubber was studied by SEM and FTIR methods. The results showed that the curing time decreased obviously with the increase of the catalyst contents and the rise of the temperatures. The mechanism was proposed here and revealed that when the catalyst transferring in the liquid silicone rubber meets Si-O-R of TEOS and Si-OH of HPDMS, it stopped and promoted the dealcoholization condensation reaction, which made the molecular chains of the silicone rubber crosslink. Therefore, under the action of catalyst, the vulcanization time of the RTV-2 silicone rubber is controlled by the velocity of condensation reaction itself and the diffusion of the catalyst in the liquid silicone rubber. The latter has the larger effect on the complete curing time.
Theoretical Thermodynamic Analysis and Phase Analysis of AZ91D/Flyash Composites
Authors: Chu Hong Chao , Yu Si Rong , Wang Cui Xiang , Lou Qi
Published: April 2014

The thermodynamic calculation is valuable for judging the feasibility of a reaction. In the present paper, the enthalpy change (∆HR), entropy change (∆SR) and Gibbs free energy change (∆GR) among various components in AZ91D Mg alloy-Cenosphere composites (FAC/AZ91D) were calculated. Through the calculation, we obtained the relationships between the Gibbs free energy changes and temperatures. The difficulty degree of every potential reaction could be directly reflected by the correlation curve between the temperature and the Gibbs free energy change. The analysis result provided the theoretical basis for the reaction temperature and the solution treatment temperature of the FAC/AZ91D system. At the same time, the analysis based on the minimum principle of the reaction free energy revealed the final components (MgO, Mg2Si and MgAl2O4), which was partially similar to the result of XRD analysis (MgO, Mg2Si and Mg17Al12).
Preparation of Al2O3 Based Nano-Micro Composite Gradient Self-Lubricating Ceramic Tool Materials
Authors: Yi Ming Dong , Xu Chong Hai , Chen Zhao Qiang , Wu Guang Yong
Published: April 2014

Aiming at the low mechanical property of existing self-lubricating ceramic cutting tool material, a new Al2O3 based nanomicro composite gradient self-lubricating ceramic tool material was developed by applying the design concept of nanomicro composite. The self-lubricating ceramics was composed of ceramic matrix and self-lubricating component, and was prepared by hot pressing technology at a hot-pressing temperature of 1650°C, pressure of 30MPa, and duration of 15min. The model of gradient ceramic tool material is symmetrical composition distribution, and the compositional distribution n and layer number are 1.8 and 7, respectively. The result shows that the interfaces between layers are bonded well and no cracks or defects can be observed. Compare with the homogeneous material, the flexural strength, hardness and fracture toughness of Al2O3 based graded material increase by 74%, 5.2% and 3.9%, respectively.
Distribution of WC Particle in Cast Steel and its Effect on Abrasion Resistance
Authors: Han Yang , Zhang Ai Ling , Yang Lin , Deng Li Qiang , Han Ya Ling
Published: April 2014

Aiming at the problem of short service life of abrasion resistance materials, the addition of ceramic particle like WC is used to improve abrasion properties of the cutting pick body. One kind of wear-resistant alloy has been prepared through mixing WC and other metal powder together and consolidating at high temperature in order to solve the segregation phenomenon of WC phase caused by its high density. After casting, the segregation phenomenon has almost faded away. Abrasion test results show that the abrasion property of the casting samples, which are added with wear-resistant ingredient and treated by different heat treatment processes, is better than that of the conventional cutting picks. Distribution of WC phase in cast steel was examined by SEM with EDS and FESEM. The result shows that WC exists in both steel matrix and cast inclusions evenly. Due to the excellent wet ability between WC and molten steel, the WC particle is covered by steel matrix firmly enough to avoid the flaking off during the abrasion process. At the same time, the WC particle itself has good wearing properties. It is the most important reason for the reinforcement of abrasion resistance of cast steel.
Microstructure and Properties of Tungsten Copper Composite Material
Authors: Guo Ting Biao , Zhao Jun Yuan , Ding Yu Tian
Published: April 2014

The copper-tungsten system in the liquid and solid phase is completely immiscible. In this paper, the powder solid-phase sintering method was used to prepare the copper-tungsten composites of different compositions (CuxWy, x=63, 78, 84, 87, 90, 91, y=37, 22, 16, 13, 10, 9 (x+y=100)). By XRD and SEM analysis of the sample microstructure, the trend of the ratio of the conductivity, density and hardness of the samples with different ratio were determined. The results show that with the increasing tungsten content, the conductivity of the copper-tungsten composite increases, whereas the amplitude reduces. The actual density of the sample is smaller than its theoretical density. The more the tungsten content is, the smaller its hardness value.
Freestanding FeCrAl-Y2O3 Amorphous/Crystalline Composite Coating Fabricated by Electron-Beam Physical Vapor Deposition
Authors: Lin Xiu , Song Guang Ping , Gou Hua Song , Zhao Yi Jie , Chen Yang , Sun Yue , Zhao Shu Yuan , He Xiao Dong
Published: April 2014

Freestanding FeCrAl-Y2O3 amorphous/crystalline composite coating with a thickness of about 200μm has been produced from electron-beam physical vapor deposition of FeCrAl and yttria materials with a substrate temperature of 500 oC around. The microstructure was composed of columnar grains near the substrate side and an amorphous top layer. Local crystallization occurred during room temperature preservation. It is inferred that the crystallization activation energy of the material is very low.
Mechanical Property of Fecral-Y2O3 Foil Fabricated by EBPVD
Authors: Lin Xiu , Song Guang Ping , Gou Hua Song , Zhao Yi Jie , Chen Yang , Sun Yue , Zhao Shu Yuan , He Xiao Dong
Published: April 2014

As a rapid deposition method, Electron Beam Physical Vapor Deposition (EBPVD) permits the fast fabrication of self-standing thick coatings with thickness in the range from several micrometers to hundreds of micrometers. In this paper, we present a new way to fabricate ferritic ODS alloy foil. By this method, 1.2 wt.% of yttria was successfully added to the ferritic base material. The base alloys are mainly composed of bcc structured Fe (Cr,Al) solid solution. The steady state creep rate of ferritic ODS is almost two magnitudes lower than that of FeCrAl alloy. Further thermo-mechanical treatment is expected to improve strength and ductility of both ODS and non-ODS material.
A New Cutting Wire Prepared by Copper-Diamond Composite Electroplating
Authors: Wang Zhao Yang , Zheng Jing Wu , Cai Wei , Qiao Liang , Ying Yao , Jiang Li Qiang , Che Sheng Lei
Published: April 2014

iamond cutting wire, as a new one, could overcome the defects of traditional cutting wire and would have a wide potential application. Electroplating diamond wire was prepared by composite electroplating in this article. The influence of cathodic current density, the diamond content in the electrolyte and other process conditions on the amount of diamond in the composite coating was checked by EDTA titration analysis. Effects of the diamond content in the electrolyte on electrochemical process of copper-diamond composite electro-deposition were investigated by measuring electrochemical polarization curves. With increasing the cathode current density and the diamond content in the electrolyte, the amount of diamond in the composite increased firstly, and reached a maximum, then decreased. The cathode current decreased with the increase of diamond content in the electrolyte. Copper-diamond composite plating process could be explained by Guglielmi two-step adsorption mechanism. The influence of plating parameters on the deposition behaviors of copper–diamond composite coating layers is ascribe to the change of diamond adsorption state on the cathode surface. After heat treatment, the largest wire tensile force is 159.7 N and the tensile strength reaches to 2258.8 MP.
Finite Element Analysis of the Effect of Particle Shape on the Thermal Conductivity in Diamond/Cu Composites
Authors: Guo Hong , Han Yuan Yuan , Zhang Xi Min , Yin Fa Zhang , Fan Ye Ming , Wang Peng Peng
Published: April 2014

The effect of diamond shape on the thermal conductivity of diamond/Cu composites was studied by combine finite element method with the tests. The finite element result show that the thermal conductivity of the hexoctahedron diamond/Cu composites and the square diamond/Cu composites is 819 W/m·K and 1013 W/m·K respectively. And the testing results indicate that the thermal conductivity of the single hexoctahedron diamond/Cu composites and the hexoctahedron mixed with the square diamond/Cu composites is 659W/m·K and 720 W/m·K respectively. The testing results consist with the finite element calculation. Under the same circumstances, more {100} faces can bring in less overall thermal resistance in the composites thus improve the thermal conductivity of the composites. The results show that using square diamond particles helps to improve the thermal conductivity of diamond/Cu composites.
Microstructure and Tensile Properties of As-Cast Mg-5Sn-4Cu Alloy
Authors: Wang Xu Dong , Lu Zheng , Feng Zhao Hui , Zhang Xian Feng , Ma Zhi Feng , Sun Gang
Published: April 2014

The microstructure and tensile properties of permanent-mould cast Mg-5wt%Sn-4wt%Cu alloy was investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and tensile test in this paper. The result indicated that the microstructures of the as-cast samples consist of 30-40 μm size primary solidification phase, primary dendrite Mg2(Cu,Sn) which is a network-like interdendritic eutectic intermetallic compounds along grain boundaries and particle like Mg2(Sn,Cu) phases. The Mg-5Sn-4Cu alloy exhibit maximum ultimate tensile strength and yield strength, and the values are 142 MPa and 91 MPa at room temperature. This improved mechanical property is mainly ascribed to the formation of network-like secondary phases of primary dendrite Mg2(Cu,Sn).
Effect of Ce Addition on the Ignition-Proof Properties and Surface Tension of AZ91D-2.5Ca(Wt.%) Magnesium Alloy
Authors: Qin Lin , Ding Jian , Fang Zheng , Zhao Wei Min
Published: April 2014

In order to develop ignition-proof magnesium alloys, the effect of alloying element Ce on the ignition-proof properties and surface tension of AZ91D-2.5Ca alloy were investigated. The results show that the addition of Ce can significantly raise the ignition temperature and change the structure of surface oxide film as well as the surface tension. When the Ce content increases to 1.2%, the ignition point reaches 1371K. Upon the addition of Ce, the oxide film of AZ91D-2.5Ca melt changes to fine and close structure from the porous structure before the Ce addition. The composite oxide film mainly composed of MgO, Al2O3, CaO and Ce2O3. The surface tension of AZ91D-2.5Ca decrease with the increasing Ce content, as the active-element Ce enriched at the melt surface.
Deformation Behavior of ZK60 Magnesium Alloy at Elevated Temperature
Authors: Wang Chun Yan , Qi Hai Qun , Wu Kun , Zheng Ming Yi
Published: April 2014

The high temperature compressive tests of squeeze casting ZK60 magnesium alloy in the testing temperature range of 523-723K and strain rate range of 0.001-10s-1 were performed on Gleeble-1500D thermal simulator testing machine. Optical microscopy was performed to elaborate on the dynamic recrystallization (DRX) grain growth. TEM observation indicated that the mechanical twinning, dislocation slip, and dynamic recrystallization are the materials typical deformation features. Variations of flow behavior with deformation temperature as well as strain rate were analyzed. Analysis of the flowing deformation behavior and microstructure observations indicated that the flow localization was observed at lower testing temperature and higher strain rates. Dynamic recrystallization occurred at higher testing temperature and moderate strain rates, which improved the ductility of the material. The results indicated that at the testing temperatures lower than 573K and strain rates higher than 1s-1, the material exhibited flow instability manifesting as bands of flow localizations. These temperatures and strain rates should be avoided in processing the material. Dynamic recrystallization occurs in the temperature range 573-723K and the strain rate range 0.001-0.1s-1. The number of dynamic recrystallization grains is less at lower temperature and higher strain rate than higher temperature and lower strain rate. The dynamic recrystallization is inadequate at 573-623K while the dynamic recrystallization grain growth has been observed in the temperature range of 673-723K. Therefore it may be considered that the optimum processing parameters for hot working of squeeze casting ZK60 magnesium alloy are 648K and 0.001-0.01s-1, at which fine dynamic recrystallization microstructure can be obtained.
Preparation and Characterization of TPU Toughened PLA Elastic Fibers
Authors: Wang Shi Chao , Xiang Heng Xue , Wen Xiao Shuang , Zhou Zhe , Zhu Mei Fang
Published: April 2014

Poly (lactic acid) (PLA) elastic fibers were prepared by melt spinning using Thermoplastic polyurethane (TPU) as a toughing agent and PLA-g-MA(Maleic anhydride) as a compatibilizer. Thermal properties and thermal stability of PLA/TPU composites, as well as the cross section morphology and mechanical properties of fibers were studied in the present investigation. DSC results showed that PLA was immiscible with TPU. In addition, the incorporation of TPU decreased the melting enthalpy of PLA/TPU composites. TG results indicated that the initial degradation temperatures of composites were also decreased by the appearance of TPU, and it decreased by 9°Cwhen TPU content was up to 20wt%. FESEM results confirmed that strong interactions were existed between PLA and TPU phases, which were benefit for the improvement of PLA/TPU fibers’ mechanical properties. Results of tensile testing demonstrated that TPU could improve the toughness of fibers effectively and the elongation-at-break of fibers increased from 2.2% of PLA to 203.9% of PLA/TPU.
Polyaniline Grafted Amino-Functionalized Graphene Nanocomposite with Excellent Electrochemical Performance for Supercapacitor Electrode Materials
Authors: Liu Yu , Su Xin Yan , Guang Shan Yi , Xu Hong Yao
Published: April 2014

The amino-functionalized graphene/polyaniline nanocomposites (AGNS/PANI) were fabricated through in-situ chemical oxidative polymerization of aniline in the presence of amino-functionalized graphene sheets (AGNS). FTIR, UV-vis spectroscopy analyses revealed that aminophenyl groups covalently bound to the basal plane of graphene via a diazonium addition, and the polyaniline chains grafted to graphene sheets. The FE-SEM images show that PANI nanorods aligned vertically on the surface of graphene. The AGNS/PANI nanocomposite exhibits excellent electrochemical performance for supercapacitor electrode materials.
Preparation and Biological Characterization of Electrospun Aligned Poly(butylene carbonate) Nano-Fibers
Authors: Shao Mei Ling , Yang Qing , He Jing , Hsiao Benjamin S.
Published: April 2014

A novel biomaterial poly (butylene carbonate) (PBC) was used to fabricate aligned nanofibresby electrospinning with a high-speed transfer roller as the receiving device. The morphology of the fibers was evaluated by scanning electron microscopy (SEM). To expand the application of the biomaterial, cold plasma treatment and induced grafting technology were applied to improve its hydrophilicity and biocompatibility. The properties of the fibers, pretreated withhelium and following grafting with gelatin,were evaluated with X-ray photoelectron spectroscopy. The cytotoxicity of the materials to Schwann cells (RSC96) was investigated. Results indicated that aligned nanofibers can be received at high rotation speed.After plasma pretreatment, the activity of the surface was improved significantly and the grafting reaction was successful. SEM observations showed that cells can grow on the fibersurface along the direction of fiberorientation after seeding with RSC96 for 3 and 5 days. Modification of the nanofibersurface with gelatin significantly increased RSC96 attachment and proliferation.
Fabrication and Properties of Porous Scaffolds of PLA-PEG Biocomposite for Bone Tissue Engineering
Authors: Wang Ning , Zang Yong Ju , Ren Gui Zhi , Wu Qi Lin
Published: April 2014

Porous scaffolds of polylactic acid-polyethylene glycol block copolymers (PLA-PEG) biocomposite were fabricated by solvent casting-particulate leaching method using sodium chloride as the porogen. With the aim of evaluating the influence of porosity on mechanical properties and biocompatibility, three specimens of scaffolds which have different porosity (around 50%, 60%, 70%) were fabricated. Murine fibroblast grew cells (L929) were seeded into PLA-PEG porous biocomposite scaffolds. The tetrazolium salt 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium Bromide (MTT), scanning electron microscopy and confocal microscopy were carried out to characterize cell proliferation and morphology. The composite scaffolds with the porosity of 50% possessed better mechanical properties. All scaffolds support attachment, spreading and proliferation of L929, and the biocompatibility of scaffolds could be improved by increasing the porosity. The fabricated PLA-PEG porous biocomposite scaffolds with good mechanical properties and biocompatibility might be used in bone tissue engineering.
Morphology Control of Polyimide Fibers by Phase Separation under Different Coagulation Bath Conditions
Authors: Dong Jie , Yin Chao Qing , Lu Hong Xu , Zhang Zi Xin , Zhang Qing Hua
Published: April 2014

In order to investigate the effects of the coagulation bath temperature and composition on the formation of polyimide fiber in wet spinning, theoretical ternary phase diagrams of water/NMP/PI system at two coagulation bath temperatures was investigated based on the extended Flory-Huggins theory. The cloud-points data of the system for more dilute PI terpolymer solutions were determined by cloud point titration, and the cloud point data for more concentrated PI terpolymer solutions were calculated by Boom's linearized cloud point curve correlation. The obtained diagrams showed that if the titration process constructed at a higher temperature, the meta-stable two-phase region in the ternary phase diagram increases, which is beneficial for the de-mixing of the filament via nucleation and growth mechanisms, resulting in a homogenous dense structure for PI fiber.
Design of ACF Microwave Absorbing Composites with Triangle Patches and Circular Aperture Elements
Authors: Zang Yong Ju , Zhuang Ao , Ou Xiang Hui , Geng Qi Xin , Chen Qi Ping , Wu Qi Lin
Published: April 2014

The combination element frequency selective surface (FSS) with regular triangle patches and circular aperture elements in activated carbon fiber (ACF) felts were designed. The effects of the structure parameters and periodic arrangement of regular triangle patches on ACF felt composites were investigated. As the regular triangle patches were embedded into circular apertures, the combination element ACF felt screen (ACFFS) composites presented fluctuant absorbing characteristics and showed double-band frequency response characteristic including band pass and band stop. When the regular triangle edge length (L) increased, the effective absorption frequency (the reflection loss below-10 dB) shifted to low frequency, and the effective bandwidth increased without reducing the maximum absorption value. When the regular triangle patches (L = 30 mm) were in staggered rows, the effective absorption frequency drifted by 3.1 GHz, and the effective bandwidth was enhanced from 4.3 GHz to 11.0 GHz. Although the regular triangle patches are not central symmetry, it is proved that the absorption properties can be improved obviously by both horizontal polarization and vertical polarization.
Cellulose Nanofiber-Supported Polyaniline Nanocomposite Conductive Film and its Conductive Properties
Authors: Xiang Cao , Chen Shi Yan , Lu Chuan , Ge Yan , Wang Hua Ping
Published: April 2014

As a conducting polymer, polyaniline (PANI) have found wide applications including electrode material, sensors and supercapacitors, which is attributed to a combination of the advantages for both organic semiconductors and nanomaterials. This article concentrates on the preparation of bacteria cellulose-polyaniline (BC/PANI) conducting nanocomposite films via in situ polymerization of anailine onto bacteria cellulose (BC) scaffold. A series of nanocomposites were prepared with different anailine concentration, doping acid concentration and molar ratio of monomer and oxidant. The as-prepared conducting nanocomposites were characterized by conductivity measurement, scanning electronic microscope (SEM), fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyser (TGA), etc, to find out the best preparation conditions. The results indicated that PANI coated on the surface of nanofibers of bacterial cellulose, the nanoconductive path formed and the conductivity of the film ranged from 2.0×10-8to 0.24 S·cm-1. In addition, the method of combining organic and inorganic acids can solve the de-doped problem caused by using traditional inorganic small molecule acid, such as HCl.
Glutaraldehyde-Cross-Linked Poly(acrylic acid-co-acrylamide)/Poly(vinyl alcohol) Superabsorbent Membranes
Authors: Wang Man Yi , Wang Yan Ping , Yu Yan Ting , Wang Yi Min , Ni Jian Hua
Published: April 2014

The superabsorbent membranes were prepared with acrylic acid (AA) and acrylamide (AM) as the monomers, poly (vinyl alcohol) (PVA) as toughening components, potassium persulfate (KPS) as the initiator agent, and glutaraldehyde (GA) as cross-linker by means of aqueous solution polymerization. Their structures were analyzed by FTIR spectroscopy. The effects of synthesis and heat-treatment conditions on water absorbency of superabsorbent membranes were investigated. Their water absorbency with different pH was studied as well. The results showed that the superabsorbent membranes exhibited intelligently pH-responsiveness.
Preparation and Characterization of Polyacrylonitrile Membranes with High Strength via Thermally Induced Phase Separation Process
Authors: Liu Chun Yi , He Chun Ju
Published: April 2014

Polyacrylonitrile (PAN) membranes were prepared via thermally induced phase separation (TIPS) process using polyethylene glycol (PEG) as plasticizing agent and polyvinyl pyrrolidone (PVP) as porogen, which presented high strength, i.e. 6MPa. A systematic study was carried out to investigate the effect of PVP content, PAN concentration and cooling conditions on the pore shape, pore size, water flux and mechanical properties of the membranes, which were characterized by scanning electron microscope, filtration measurement and tensile test. PAN membranes with uniformly distributed pores were fabricated by adjusting the mixed diluent composition. Results of filtration confirm that water flux of PAN membranes mainly depends on the pore structure. Moreover, while PVP content is increased, water flux first increases and then declines, and tensile strength and elongation at break first declines and then increases. In conclusion, the successful application of TIPS provides a new route to the structure modulation and performance enhancement of PAN membranes.
Application of Orthogonal Design on Optimization of Spinning Conditions for BTDA-TDI/MDI Ternary Copolyimide Fiber
Authors: Guo Bing Hua , Ren Yu Dong , Chen Lei , Yu Jun Rong , Zhu Jing , Hu Zu Ming
Published: April 2014

A polyimide fiber derived from benzophenone-3,3’,4,4’-tetracarboxylic acid dianhydride (BTDA), toluene diisocyanate (TDI) and 4,4’-methylenebis (phenyl isocyanate) (MDI) has been prepared by wet spinning. The chemical structure of the synthetic polyimide was characterized by Fourier transform infrared (FTIR) spectrometry. Also, field emission scanning electron microscope (FESEM) was used to observe the surface and cross-section morphologies of the resulting fibers. In addition, the obtained fibers possessed good thermal and thermo-oxidative stabilities with the initial degradation temperatures in air and nitrogen 499°C and 527°C, respectively. In order to obtain the optimized processing conditions, orthogonal design was applied. An optimal parameter combination was determined which leaded to maximum of tensile strength . As evidenced by variance analysis, the tensile strength of resultant fibers was influenced by negative draw ratio of spinneret remarkably making it the significant factor.
Synthesis of Allyl Functionalized Telechelic PVP by Reversible Addition-Fragmentation Chain Transfer (RAFT) Polymerization
Authors: Li Song Tao , Li Dan , He Chun Ju
Published: April 2014

Telechelic polymers have been explored widely because they are precursors for preparing multi-block copolymers, grafted polymers, star polymers, and polymer networks [1-2]. A variety of telechelic polymers with terminals like hydroxy, carboxylic, epoxy groups and carbon–carbon double bond have been prepared by controlled radical polymerization (CRP) techniques including nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT)[3-5].The CRP techniques can not only control the molecular weight but also can be carried out in the presence of many functional groups from monomers, initiators, or chain transfer agents (CTA).
Effect of Additive on the Performance of PVDF Membrane via Non-Solvent Induced Phase Separation
Authors: Cao Xiao Hui , Qiu Ming , Qin Ai Wen , He Chun Ju , Wang Hai Feng
Published: April 2014

Poly (vinylidene fluoride) membranes were prepared from the ternary mixture of PVDF/ 1, 2 - propylene glycol/dimethylacetamidevianon-solvent induced phase separation (NIPS). The effect of the addition of the 1, 2 - propylene glycol content, the Coagulation Bath Temperature and the concentration of PVDF on the performance and structure of the PVDF membranes was studied in the present investigation.The results showed that with increasing polymer concentration, the mechanical strength increased,and the structure of membrane changed from finger-like macro-voids structureto sponge-like structure.It was found that water flux, breaking elongation and tensile strength of the membrane increased with increasing 1, 2 - propylene glycol content, when the content reached 41wt.%, the water flux reaches a maximum.The morphology of PVDF can be improved by the addition of 1, 2 - propylene glycol, which was changed from finger-like structure to sponge-like structure. And the dense skin layer of PVDF membranes became thicker with increasing 1, 2 – propyleneglycol. The tensile strength decreasedfrom 3.3 to 2.1MPa, breaking elongation decreased from 315% to 280% andthe pure water flux increased from 91 to 909 L·m-2·h-1. as the coagulation bath temperature (CBT) decreased from 30°C to 5°C.With this condition, the sponge-like hollow fiber membrane hassuccessfully spun.
Fabrication of Polyvinylpyrrolidone/Boehmite Nanofibers by Electrospinning
Authors: Wang Zhi Jie , Gong Jing Hua , Yang Shu Guang , Ma Jing Hong , Xu Jian
Published: April 2014

Polyvinylpyrrolidone (PVP)/boehmite nanocomposites fibers were successfully prepared by electrospinning using boehmite sol containing PVP as the spinning solution. Several techniques, including Fourier transform infrared (FT-IR), thermal gravimetric analyzer (TGA) and field emission scanning electron microscopy (FE-SEM) were used to characterize their ingredients, thermal properties and morphology. The results showed that PVP concentration exhibited significant effect on the PVP/boehmite nanofibers morphology. With increasing PVP concentration, the morphology changed from beaded, beaded fiber to uniform fiber. These PVP/boehmite nanofibers can be used as good candidates for continuously preparing uniform and compact alumina nanofibers.
Influences of Carbon and Nitrogen Content on the Precipitation of 18Cr18Mn Steel
Authors: Li Jing Yuan , Fang Fei , Wang Yi De , Li Bo , Zhang Xiang Jun
Published: April 2014

The effect of carbon and nitrogen contents on microstructure and the mechanism of precipitation of 18Cr18Mn steels at as-cast and aging treatment state were investigated by thermodynamics calculation, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that the increase in carbon and nitrogen contents promotes the precipitation of carbides and nitrides, respectively, inhibiting σ phase precipitation during solidification process. The rod-like σ phases present in 18Cr18Mn0.44N as-cast steel with 0.025%C. The coarse lamellar structure Cr23C6 phases with a space width of 0.34μm exist in 18Cr18Mn0.44N as-cast steel with 0.16%C. However, Cr23C6 and σ phase disappear in the interior of the grains and a small amount of nitrides exist only in grain boundaries of 18Cr18Mn0.72N0.020C as-cast steel. The precipitation of Cr23C6 and σ phases are greatly inhibited in high nitrogen austenitic stainless steels at 800°C aging treatment. Additionally, Cr2N, the main precipitation phase, nucleates at austenitic grain boundary and grows towards inner grains with a lamellar morphology. Moreover, the quantity of Cr2N increases and incubation time of it decreases as nitrogen or carbon content increasing.
Study on Pack Rolling and Annealing Process for Ultra-Fined Grain Austenite Stainless Steel
Authors: Chen Yu Lai , Huang Jing , Fang Fei
Published: April 2014

In this study, ultra-fined grain austenite stainless steel was obtained by pack rolling and subsequent annealing. The microstructure and defect were analyzed by using scanning electronic microscopy (SEM) and X-ray diffraction (XRD), etc. Thus the influence of the rolling reduction, the annealing temperature and the annealing time on the microstructure of 304 austenite stainless steel was accomplished. The results indicate that with the pack rolling reduction increased, the grains were elongated more obviously along the rolling direction. There were numerous dislocations and twinning within the grains. Moreover, there is amount of strain induced martensite with the rolling. The grains were remarkable refined after annealing, in which the microstructure was reversed and recrystallized, and the strain induced the martensite transferred to austenite. The average grain size decreased to 0.5μm with the sample of the 75% rolling reduction after annealing at 800°C for 30 minutes. In addition, the mechanism of the pack rolling on the grain size reduction was analyzed.
Microstructure and Mechanical Properties of Cold-Rolled Mg-6Al-1Zn Alloy Strip Treated by Electropulsing Treatment
Authors: Jiang Yan Bin , Guan Lei , Tang Guo Yi
Published: April 2014

The effect of electropulsing treatment (EPT) on the microstructure and mechanical properties of the cold-rolled Mg-6Al-1Zn alloy strip was investigated. It is found that EPT accelerated the recrystallization behaviour of the cold-rolled Mg-6Al-1Zn alloy strip at a relatively low temperature within a short time of 14 seconds. When the temperature of EPT was 423 K, recovery of Mg matrix happened and few β-Mg17Al12 phaseprecipitated in the Mg matrix. With increasing the temperature to 463 K, recrystallization occurred, accompanying dissolution of β-Mg17Al12 phase. When the temperature was increased to 483 K, complete recrystallization took place and obtained fine microstructure of quasi-single-phase recrystallized grains. The elongation to failurewas increased from the 6.3 % of the rolled strip to 23.5 %, while the tensile strength was decreased from 368 MPa to 300 MPa. Further increasing the temperature of EPT, the apparent grain growth occurred and both the tensile strength and elongation to failure reduced. A mechanism for rapid recrystallization process during EPT was discussed.
Preparation of 1D or 3D Nano ZnO Crystals in High-Viscosity Solvent
Authors: Gu Peng Fei , Wang Xu Dong , Wang Xiang Ke , Liu Qing Long , Meng Hui Min
Published: April 2014

1D or 3D nanoZnO crystals were prepared in diethylene glycol (DEG) via solvothermal process without surfactants at 160oC. Zinc acetate dihydrate was elected as zinc source, while water, sodium hydroxide, or ammonia solution was respectively as assistant agents. The morphologies of the products were characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). With a certain content of water or sodium hydroxide, 1D ZnO nanorods were gained, having diameters of 20-90 nm and lengths of 0.04-1.8μm. With a certain content of ammonia solution, 3D shiitake-like ZnO hierarchical structures were gained. The pileus of shiitake structure composes of nanorods with diameters of 35-40 nm, while the stipe composes of one hexagonal rod with diameters of 250-350nm, or many hexagonal rods with diameters of 100-200nm. The morphology and size could be regulated by changing the amount of water, NaOH, or ammonia solution. Solvothermal process in high-viscosity solvent may provide a facile method for preparing nanomaterials.
Hydrodynamic Lubrication during Non-Sinusoidal Oscillation for a Continuous Casting Mould
Authors: Yang Jie , Meng Xiang Ning , Zhu Miao Yong
Published: April 2014

A hydrodynamic lubrication model of a flux channel was established for a continuous casting mould with non-sinusoidal oscillation. A new experimental apparatus was developed simultaneously for analysing the lubrication mechanism. A mixed oil, which was simulated mould flux, was poured and infiltrated into the channel, and the flux consumption was determined in the process of oscillation. Based on the combination of analytical calculation and cold model experiment, the flux channel is divided into two parts to clarify the behaviours of flux infiltration and shell deformation. The results show that oscillation marks and surface cracks are formed at the bottom of the meniscus during the negative and positive strip time respectively. Meanwhile, the liquid flux is periodically infiltrated into the channel by negative pressure below the meniscus because the cyclic movement of the shell lags behind the mould oscillation. The casting performances were improved by increasing the non-sinusoidal oscillation factor.
Electron Beam Additive Manufacturing and its Applications in Aerospace Field
Authors: Li Min Xue , Qu Wen Qing
Published: April 2014

The concept of additive manufacturing is put forward on the basis of the nowadays research hotspot-3D print. This paper focuses on the main branch technology of additive manufacturing, i.e., electron beam melting (EBM) in high energy beam rapid manufacturing area, enumerating the advantages of EBM compared with laser rapid prototyping and introducing its process principle as well as its research status. The application situation of EBM in aerospace especially it’s utility in aircraft engine and industrialization of industrial aspects was also introduced, and its development prospect in the future was forecasted.
Magnetic and Mössbauer Studies on Mixed-Metal Cyano-Bridged Compounds GunM1.5-n[Fe(CN)6]·xH2O(M=Ni, Gu)
Authors: Lin Qing , Dong Xin Long , He Yun , Xu Jian Mei , Wang Rui Jun
Published: April 2014

Mixed-metal cyano-bridged compounds GunM1.5-n[Fe (CN)6]·xH2O(M=Ni, Gu) have been prepared by co-precipitation. The magnetic results show that the compound Cu0.75Ni0.75[Fe (CN)6]·xH2O is ferromagnetic, undergoes a paramagnetic to the ferromagnetic transition temperature at 21.77 K. The paramagnetic curie temperature θ, residual magnetization Mr, and coercive field Hcare different from bimetallic Prussian Blue analogues Ni3[Fe (CN)6]2·xH2O and Cu3[Fe (CN)6]2· xH2O. As to Cu3[Fe (CN)6]2·xH2O, the magnetic susceptibilities follow the Curie-Weiss law and the Weiss paramagnetic Curie temperature is 19.1 K. The Mossbauer spectrum at room temperature reveals a doublet with the isomer shift parameter (-0.03 mm/s) and quadrupole splitting (QS= 1.09 mm/s). As the sample was cooled down to 16K, the magnetic splitting phenomenon was detected in the compound.
Microstructure Evolution of Laser Direct Deposited Ti-5Al-2Sn-2Zr-4Mo-4Cr Titanium Alloy
Authors: Wang Yu Dai , Jiang Shuai , Sun Fan , Li Huai Xue , Sun Mei
Published: April 2014

In the present study, Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy was fabricated by laser direct deposition technology. Microstructure of the laser deposited Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy was characterized by optical microscopy (OM) and scanning electron microscopy (SEM). The laser deposited alloy has two types of periodic banded feature induced by the different stages of the thermal cycles during the laser deposition process. Moreover, microstructure evolves from the bottom to top of the laser deposited sample, and the mechanism of which is demonstrated.
Preparation of MAO Ceramic Coating on Ti-6Al-4V Alloy Surface
Authors: Yu Si Rong , Yao Qiang , Chu Hong Chao
Published: April 2014

Micro-arc oxidation (MAO) technology was applied for preparing ceramic coating on Ti alloy. The ceramic coating was characterized using X-ray diffraction, surface roughness meter, eddy current thickness meter, and confocal microscopy. The effects of the current density, the duty cycle and the oxidation time on the thickness and roughness of the ceramic coating were examined. The polarization curves of Ti alloy surface were measured before and after MAO treatment using electrochemical workstation. The results show that the phases of the ceramic coating mainly consist of Ti element, rutile and anatase. With the increase of the current density, the duty cycle and the oxidation time, both thickness and roughness of the ceramic coating increase. After MAO treatment, the corrosion current of Ti alloy decreases, the corrosion potential increases, and the corrosion resistance is improved.
Properties of TiAl/TiAlN/TiAlCN Films Deposited by Arc Ion Plating on GCr15 Rings
Authors: Yang Li Jun , Zhang Ze Hui , Dang Xin An , Li Lin
Published: April 2014

Ring is one of the major textile spinning machine consumable part, it has an important influence on yarn quality and cost. Ring of domestic cotton spinning enterprises generally has poor hardness, bad accuracy, not durable and difficult to guarantee the quality of the yarn, foreign ring has excellent performance, but it is too expensive, so it is difficult to widely used in China[1]. Vacuum arc ion plating technology has a wide range of applications in the aerospace, automobile, mold, tool, electronics and other fields [2-3]. TiN film which is prepared by arc ion plating technology has been widely used because of the TiN film has poor oxidation resistance and wear resistance at high temperatures, so the ternary films are developed on TiN film, such as TiAlN [4], TiCN etc. Traveller circle in the ring on the slide to produce large amounts of heat, it makes the ring surface temperature reach 400°C. When higher than 400°C, the TiCN film failure, therefore, ring should not be plated on the TiCN films. While TiAlN film oxidation temperature reaches 800°C. In HSS twist drill, depositing of TiAlN film can improve the service life more than four times [5]. Studies [6-8] have found that using pulsed laser deposition and chemical vapor deposition technique to prepare TiAlCN film, its wear resistance, high temperature stability is better. Pulsed laser deposition is mainly used in laboratory research. It is difficult to deposit a large area uniform film. Chemical vapor deposition of deposition rate is less than the arc ion plating, and produces lots of waste gas, leading to the environment is polluted. Arc ion plating technology can deposit the uniform films of large area with high deposition rate and deposition with no environmental pollution, therefore, this study, by means of vacuum arc ion plating technology to prepare high-precision, long-life and low-cost domestic cotton spinning ring. In order to obtain the best film process parameters, the performance of film is investigated at different bias and arc current.
Laser Ablation Resistance Behavior of Organosilicone Composite Coating on Various Substrates
Authors: Li Jing , Guan Zhen Wei , Zhang Yu Zhong , Wang Yan , Wang Zhi Yong
Published: April 2014

In modern combat, laser weapons are widely used due to their high precision, velocity and heat detriment. Hence, it is of great importance to fabricate protective coating on the surface of core components, i.e. gasoline tank and aerofoil. In this study, an organosilicone composite coating was prepared on steel and aluminum substrates through a simple spray process to resist laser ablation destroy. This composite coating consists of organic resin base and inorganic functional fillings, which were made up of glass powder with high melting point materials such as SiO2, BN and ZrO2etc. Laser ablation resistance behavior was studied by means of oxyacetylene torch and laser irradiation. Results demonstrate that the coating presents excellent heat resistant behavior under 3000°C. Moreover, after impulse laser attack up to 105W/cm2, both substrates remain unhurt. As a result, this organosilicone composite coating can be used for anti-laser application in various fields.
SHS Reactive Arc Spray - A New Method to Prepare Multiphase Ceramic Coatings
Authors: Liu Hong Wei , Zhu Sheng , Yin Feng Liang
Published: April 2014

Ti (C,N)-TiB2-Al2O3 multiphase ceramic coatings were in-situ synthesized on a steel substrate by SHS reactive arc spray technique. The composition and microstructure of the coatings were characterized by X ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The results showed that multiphase ceramic coatings, composed of TiB2, TiB, TiC0.3N0.7, TiN, Al2O3 and AlN, can be prepared with the reactive cored wires by SHS reactive arc spray. The coatings exhibit the typical layer microstructure, with discrete second phases distributed in the continuous base phase. The bonding strength between the coating and substrate is 18.9MPa. The micro-hardness and elastic modulus of the coatings are 4.91GPa and 461.4GPa, respectively. The abrasion resistance is 3 times more than that of the substrate.
Multiple Helium Atoms Diffusion in Tungsten: A Molecular Dynamic Simulation
Authors: Tao Peng , Shu Xiao Lin
Published: April 2014

The diffusion process of multiple He atoms in W is simulated by a molecular dynamics (MD) method with the W-H-He analytic bond-order potential. The diffusivities of different number of helium (He) atoms in W are determined by the mean squared displacement (MSD) method at different temperatures. The diffusivity-temperature (D-T) relationship is fitted to the Arrhenius equation to obtain the pre-factor and the diffusion barrier. Under the temperature of 1200K He atoms diffuse together, and above 1200K they separate from each other. When the number of He atoms is greater than three, all He atoms oscillate at the tetrahedral interstitial site (TIS) instead of diffusing under 400K. In the temperature range of 400-1200K, the diffusion barriers of He atoms, the number of which is from two to five, are 0.098, 0.170, 0.125 and 0.112eV, respectively. Contrasting with one He atom (0.058eV), the higher diffusion barriers reflect a greater difficulty in diffusion of multiple He atoms in W. In addition, when the number of He atoms is over five, vacancies are formed in W, and He atoms occupy the vacancies.
Prediction Model of Pressure Distribution under Floating Strips
Authors: Hou Shuai , Liu Yu Jia , Hua Fuan , Wang Xin Yue , Wang Zhao Dong , Li Jian Guo , Li Jia Dong , Li Yong , Wang Guo Dong
Published: April 2014

The accuracy prediction of the strip's upper pressure and lower pressure is very important to the accuracy control of air flotation oven, therefore the aluminum can get high surface quality and improving the product quality. And the pressure prediction is very important factor in air flotation oven. In this paper, pso-lssvm pressure prediction model was established. The experiment was carried out in an experimental air flotation oven and pressure data was collected, then the pso-lssvm model was trained based on the training data. The pso-lssvm pressure model' result was compared with the experimental value. The experimental result shows that the pso-lssvm model can get higher accuracy and is suited to predict pressure distribution.
Prediction of the Hardness of Cu-3Ti-1Cr Alloy Using Least Square Support Vector Machines
Authors: Fang San Feng , Wang Ming Pu
Published: April 2014

A new model based on least square support vector machines (LSSVM) and capable of forecasting the hardness of Cu-3Ti-1Cr alloy has been proposed. Data mining and artificial intelligence techniques were used to examine the forecasting capability of the model. In order to improve predictive accuracy and generalization ability of LSSVM model, leave-one-out-cross-validation (LOOCV) technique was adopted to determine the optimal hyper-parameters of LSSVM automatically. The forecasting performance of the LSSVM model and the partial least squares (PLS) regression integrated with radial basis function (RBF-PLS) has been compared with the experimental values. The result demonstrates that the LSSVM model is superior to the conventional RBF-PLS model in predicting the hardness of Cu-3Ti-1Cr alloy and of better generalization performance than the RBF-PLS model. The present calculated results are consistent with the experimental values. We would expect the proposed LSSVM model as a powerful tool to forecast the variation of the hardness of copper alloys with prior cold work, aging temperature and aging time.