The influences of Y content on the crystal structure, hydrogen storage thermodynamics and kinetics, and pulverization resistance of La_1-xY_xNi_4.8Mn_0.2 (x=0.6, 0.7, 0.8) alloys were investigated systematically. The results show that all the alloys have CaCu₅ type hexagonal structure; with increasing Y content, the lattice parameter a, crystal volume V decreased, while the lattice parameter c kept almost unchanged, and c/a increased linearly. With the increase of Y content, the absorption/desorption plateau pressures increased dramatically; however, the hydrogen storage capacity decreased; the slopes of hydrogen absorption/desorption plateau declined, and the hysteresis increased lightly; A similar variation trend was presented between the hysteresis and FWHM (the full width at half maximum) of (111) XRD patterns with increasing Y content; the pulverization resistance improved. When Y content x=0.8, the alloy showed good performance both in the hydrogen absorption and desorption.

ABSTRACT A mixture of concentrated HNO₃/H₂SO₄ was used to modify the multi-walled carbon nano-tubes (CNTs) and the multi-walled carbon nano-tubes (CNTs)/natural rubber(NR) composites were prepared. The influence of the structure of CNTs on the mechanical properties, dynamic properties, payne-effect, the dynamic heat generation and tanδ of multi-walled carbon nano-tubes (CNTs)/natural rubber(NR) composites were investigated. The results show that after acid treatment the free functional groups, atoms of hydrogen and oxygen functional groups formed on the surface of CNTs, the interactions between large diameter CNTs and the rubber matrix such as physical absorption, hydrogen bonding and chemical bonding were improved; and with increase of diameter of CNTs in the nanocomposite, the characteristic values of temperature dropped, the tensile strength exhibited an upward trend, and the payne-effects of filler-filler decreased obviously. Temperature and tanδ rising trend were consistent. With the increase of the amounts of CNTs filled to the composite, inter-aggregate distance of CNTs was decrease and easy to form CNTs aggregating, leding to the payne-effect increased.

ABSTRACT Laser modification was conducted to build micro-structure textures on the warship steel surface. Nano-SiO₂ powders were dispersed in a low surface energy fluoropolymers to form a polymer-based nanocomposites, and coated on the textured surfaces to build the micro-nano bionic structure for the super- hydrophobic surface. The micrograph and elements were investigated by optical microscope, scanning electron microscopy and X-ray photoelectron spectroscopy. The contact angles and roll angles were measured. The results show that the surfaces of the micro-nano structure have bigger contact angle than that of those with a single micron or nano-structure surfaces. The contact angles increase with increasing SiO₂ concentration. When the concentration of SiO₂ is 0.167 mol/L, the contact angle is as high as 168.2°. Single micron and nano-structured surface accords with the Wenzel model. Even if the surface is placed vertically, the droplet does not roll. The surfaces of the micro-nano structure satisfy the Cassie model, and possess large contact angle and small roll angle. The roll angle decreases with increasing SiO₂ concentration. When the concentration of SiO₂ is 0.167 mol/L, the roll angle is only 0.29°.

ABSTRACT Deionized water and 3.5%NaCl were used to simulate the gentle and harsh corrosion environments respectively in this work. The atmospheric corrosion behavior of weathering steel in different corrosion orders was compared by alternative corrosion tests. The results of SEM and EIS of the rusted samples revealed that there was no compact rust layer formed in only gentle or harsh corrosion environment, while a compact rust layer formed after alternative corrosion in gentle and harsh environments. Corrosion mass gain results show that when corrosion started in the harsh environment followed by in the gentle environment, the formation of a compact rust layer needed less time than that in the opposite corrosion order.

ABSTRACT Quasi-static and dynamic tensile mechanical behaviour of ultra-high strength cold rolled dual phase steel DP1000 at room temperature and wide strain rates (0.0001-2250 s^-1) with electronic universal testing machine CMT4105 and split Hopkinson tensile bar (SHTB) apparatus were investigated. The results show that DP1000 steel is a sensitive material to strain rate, and the strength increases with the increase of strain rate; Johnson-Cook model can represent, to some extent, deformational behaviour for DP1000 steel at high strain rates, but owing to strain rate sensitivity, the goodness of fit is poor at high strain rate. The polynomial of strain rate effect was modified based on Johnson-Cook model, and the modified dynamic constitutive model can make a satisfied prediction to the plastic flow stress of DP1000 steel at high strain rates, and the average coefficient of determination can be improved from 0.9434 to 0.9850.

ABSTRACTS Quartz fibre/nano-hydroxyapatite/polyamide 66 (QF/n-HA/PA66) composite biomaterial was prepared by extrusion method in this study. The composition and morphology of the composite were characterized by FT-IR, XPS, XRD and SEM. The mechanical strength was tested by universal material testing machine and the cytotoxicity was evaluated using L929 cell line. The results showed that QF was uniformly dispersed in n-HA/PA66, with the hydrogen bond formed between QF and PA66. The mechanical strength of QF/n-HA/PA66 composite biomaterial was improved with the increase of the quartz fibre content. When the QF content (mass fraction) increased to 38%, the composite’ tensile strength, compressive strength and flexural strength reach 81 MPa, 190 MPa and 195 MPa respectively, higher than those of human cortical bone. The load bearing on the n-HA/PA66 composite matrix transferred to QF fibre, and the load bearing rapidly diffused in all directions because of stress transmission along the axial direction of the QF fibre. While this stress transmission had an efficacy of load disperse in some extent, thus enhanced the capability of the composites adapting to loadings, and the mechanical strength of QF/n-HA/PA66 remarkably increased. After 3 days of culture with the L929 cell line, no negative effects of the composite on cell viability were observed, demonstrating that the composite had no cytoxicity.

ABSTRACT The friction and wear properties of sintered Cu-based powder metallurgy(P/M) brake linings constituted with electrolytic copper powder, dispersion strengthening copper powder and Fe-Co-Cu alloy powder as matrix, respectively, were reported. The results show that the dispersive oxide and metallic elements influence the composition, thickness and hardness of friction film. Thus, the coefficient of friction (CF) of specimens is influenced. Specimens with dispersion strengthening Al₂O₃-Cu matrix display stable coefficient of friction and higher wear than other specimens. The absence of mechanical hybrid deformation layer in specimen of Fe-Co-Cu matrix lead to the friction occurred between the oxide film and the mating plate, which provides well wear resistance.

ABSTRACT The feasibility of replacing high activation element Co by low activation element Ti in reduced activated 9Cr3W steel was investigated in this paper. JMatPro phase diagram calculations were used as a theoretical guidance for preparing and heat treatment of experimental steels. The microstructure and mechanical properties of experimental steels were investigated by OM and SEM observation, tensile and creep tests. The results show that Ti and Co both can improve the creep properties of base steel 9Cr3W. The δ ferrite caused by Ti addition can be resolved into the matrix by choosing proper heat treatment parameters. 1%Co in reduced activation 9Cr3W steel can be replaced by 0.03%Ti.

ABSTRACT Polyurethane (PU)/AlBronze composite coatings were prepared by using flaky Al and bronze powders and PU as composite pigments and adhesives, respectively. The microstructure and infrared emissivity of the coatings were systematically investigated by scanning electron microscopy, infrared emissometer and theoretical simulation. The results show that PU/AlBronze composite coatings have similar one-dimensional photonic structural characteristics. The infrared emissivity of PU/AlBronze composite coatings with composite metal pigments is as low as 0.186 at the pigments content of 40%, and it is significantly lower than that of PU/Al and PU/Bronze composite coatings with single metal pigments. The reasons for this phenomenon are: (1) the reflection spectra of one-dimensional photonic structure in PU/AlBronze composite coatings have multiple reflection peaks; (2) comparing to PU/Bronze composite coatings with high density metal pigments, PU/AlBronze composite coatings have lower thickness of surface resin layer, reducing the emissivity increment of the coatings significantly.

Ni+CrAlYSiN composite coatings were prepared on K417 by vacuum arc evaporation from a NiCrAlYSi target in Ar/N₂ mixture. Characterization of the coatings was carried out using SEM, EDX and TEM. The results show that the composite coatings mainly consist of nanocrystalline γ-Ni, fcc-AlN and fcc-CrN. Increase of the bias from -100 V to -300 V leads to a decrease of the grain size, the number and size of droplets. With increasing bias voltage, the content of N decreased, Ni increased, and the contents of Cr and Al initially increased and then decreased; the deposition rate decreased. With increaseing the nitrogen flow rate, the content of N increased and those of Ni, Cr and Al decreased; while the deposition rate initially increased and then decreased. Comparing to the NiCrAlYSi coating, the Ni+CrAlYSiN coating with a maximum hardness about 9.80 GPa improved about 60% in hardness and 30% in wear resistance.

ABSTRACT I (50%Pb-50%Sn) and Ⅱ(35%Pb-60%Sn-5%Zn) solder alloys were selected as a medium layer, and the solder alloys were plated by hot dipping. Both hot-dipped steel and lead were welded by transient liquid phase diffusion bonding-TLP, and the lead/steel laminated composites were obtained. The interface morphology and phase of samples were observed by SEM and XRD. Physical and chemical properties were tested by electrochemical workstation and four-probe techniques. The results show that the interface of lead/steel laminated composite is good. Comparing with conventional lead anode, the electrode potential of layered composite anodes which prepared by optimized parameters decreased 120 mV and 180 mV, respectively. The catalytic activity of the samples was significantly improved; The resistivity of composites decreased 28%—40%.

ABSTRACT A type of medium carbon high boron iron-base alloy was designed, and the microstructure and property before and after quenching were investigated. The results show that the microstructure of the as-cast medium carbon high boron iron-base alloy consists of pearlite (P), martensite (M) and borocarbide. The volume fraction of borocarbide, which was mainly composed of M₂₃(B, C)₆, M(B, C), M₃(B, C) and M₂(B, C), was 31.3%. After quenched at the temperature of 950, 1000, 1050 and 1100 ℃, the matrix microstructure changed into martensite with a small amount of residual austenite content of 3.5%, 4.0%, 4.6% and 5.4% respectively. There was no change on borocarbide type, but the network pattern of borocarbide was broken because of partial dissolution. The volume fraction of borocarbide after quenching at the four temperatures were 30.6%, 29.1%, 27.3% and 26.4% respectively; With raising of quenching temperature, the amount of solid-solution alloy elements in matrix increased, and the borocarbide reduced gradually, therefore the separation effect to the matrix was reduced. The hardness and impact toughness of the alloy after quenching were significantly enhanced. After quenching at 950-1100 ℃, the hardness increased firstly and then decreased with quenching temperature, while the impact toughness consistently raised.

ABSTRACT The influence of strain rate on the hot ductility of Cr17Mn6Ni4Cu2N has been investigated by hot tensile tests. Results show that: in slab shell, the microstructure is dendrite ferrite distributing in austenite, and reduction of area (RA) decreases as strain rate increasing from 0.1 to 10 s^-1, the positions of cracks nucleus are changed from δ ferrite dendrites to austenite grain boundary; in slab core, the microstructure is ferrite distributing on austenite grain boundary, and RA increases with strain rate, the positions of cracks nucleus are changed from grain boundary ferrite to the co-existence of grain boundary ferrite and austenite grain boundary. As the materials deform at higher strain rate, the strength can be improved both in austenite and ferrite, which will transfer the cracks nucleating positions from ferrite to austenite grain boundary. In shell the higher strain rate strengthens the stress concentration of austenite grain boundary, leading to the decrease of ductility; in core, the higher strain rate decreases the stress concentration of ferrite, resulting in the increase of ductility.

ABSTRACT Using Fe₄₈Cr₁₆Mo₁₅C₁₇B₄ alloy rods as electrode materials, Fe-based amorphous coatings were prepared on the 1Cr18Ni9Ti stainless steel surface by electro-spark deposition technique. The microstructures of the coatings were characterized by XRD. The surface and cross section morphologies of the coatings were observed by SEM. The microhardness, wear resistance and electrochemical polarization curves of the coatings were measured. The results show that the coatings are amorphous, dense and metallurgically bonded to the matrix, and the microhardness is 1129 kg/mm². Compared to the stainless steel matrix, the coatings have much better wear properties and more excellent corrosion resistance in 1 mol/L HCl aqueous solution.

ABSTRACT Thermoelectric material β-FeSi₂ was prepared by the technology of combustion synthesis-heat treatment in this paper, silicon-iron intermetallic phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy, and the effects of different contents of Mn and Cu on the synthesis of β-FeSi₂ were investigated. The results show that only heat treatment transform α-Fe₂Si₅ into β-FeSi₂; addition of appropriate amount of Mn and Cu can increase β phase yield in product after heat treatment, but separate doping Mn or Cu can not eliminate α phase. When 1.0%Mn and 0.6%Cu meanwhile is added, β phase reach the highest peak, and α-Fe₂Si₅ completely transform into β-FeSi₂; heat treatment can largely refine crystal particle obtained by self-propagating high-temperature synthesis.

ABSTRACT The complex of β-cyclodextrin (β-CD) and oleic acid was prepared as a kind of lubricant additive. The effects of testing load, friction time and additive content on tribological performance were investigated using four ball testing methods, and the lubrication mechanism of the complex was analyzed. The results showed that the friction coefficient of lubricant of complex continuously reduced with the increasing of time under the load of 196 N, 294 N and 392 N. The anti-wear property of complex was better than that of β-CD and oleic acid for different additive content. When the content was 0.9%, lubricant of complex had the best friction-reducing ability. The host β-CD molecules of complex were decomposed and guest oleic acid molecules were released during friction process. The carboxylic acid soap film formed by oleic acid played a major role in lubrication, and the alcohol chemisorption film and carbon deposition film formed by the fragments of β-CD played auxiliary and promoting role. They formed a composite lubricating film, which had better tribological performance under certain conditions.

ABSTRACT The densification process and mechanism of a rapid solidification high temperature titanium alloy by hot isostatic pressing has been investigated systemically. The relative density of the hot isostatic pressing (HIP) specimen at 500 ℃ increased from the initial packing density of 64.5% to 81% through approaching and rearrangement of powder particles. The relative density of the specimen HIPed at 500-700 ℃ increased to 97% through plastic deformation of powder particles during which the interparticle contact areas become larger. The relative density of the specimen HIPed at above 700 ℃ increased through powder particles power-law creep and lattice / boundary diffusion.

ABSTRACT Surface-modified polypropylene (PP) cotton with acrylic acid (AA) was prepared by cross-linked grafting copolymerization of AA onto PP filter cotton, using AA as a functional monomer and N, N'-Methylenebisacrylamide (MBA) as a cross-linked agent in the present of UV light, and the cross-linked grafting ratio of PP cotton can reach 220%. The optimum process conditions is: benzophenone (BP) content 0.50 g/100 g AA, MBA content 5.0 g/100 g AA, the mass ratio of AA to PP 5 : 1, and the irradiation time 25 min. The structure of surface-modified PP cotton with AA was characterized with FT-IR. The adsorption behaviors for Cd²⁺ were investigated. The experimental results show that surface-modified PP cotton with AA has a good adsorption capacity and the adsorption ratio reached above 95% when Cd²⁺ concentration was less than 50 mg·L^-1. The adsorption equilibrium data of Cd²⁺ do not obey Langmuir model and Freundlich model in the investigated concentration range.

ABSTRACT Silica sol was prepared by sol-gel method to modify the surface of carbon fiber; the process of spreading for epoxy droplet on parallel carbon fiber sheet was observed; the unidirectional carbon fiber reinforced epoxy resin matrix composites were prepared, and the effect of silica sol modification of carbon fiber on the tensile property of the composites was investigated. The results showed that the wettability of epoxy to the silica sol modified carbon fiber has been improved greatly due to the introduction of polar functional groups such as Si—O—Si and —NH₂. The coating of silica sol improved the adhesion between carbon fiber and epoxy, resulting in an increasement of 62.74% of the lateral tensile strength, comparing with that of the unmodified carbon fiber reinforced composites, but little change of the longitudinal tensile strength. Likewise, the lateral tensile strength of composites from carbon fiber pretreated by nitric acid and subsequently modified by silica sol was increased by 35.27%, comparing with composites from pure nitric acid treated carbon fiber.