Advanced Materials Research Vols. 239-242

Abstract: The metal materials play important roles in the area of the industry. So it is meanful to use some technologies to improve the comprehensive properties of the metal materials. Comparing with other methods, the surface nanocrystalline technology can improve the strength, the hardness, the abrasive resistance and the corrosion resistance of the metal materials. Besides, through the surface nanocrystalline technology, the grain of the organization can be refined, and the lifespan of the fatigue can be prolonged. So, the surface nanocrystalline technology is with widely market application prospect. At present, there are many studies about the surface nanocrystalline technology, and many typical technologies have been applicated in the industrial production successfully, which satisfy the high requirement of the modern industry in some extent. In this article, the principle, the preparation method and the research status of the surface nanocrystalline technology are produced, and the prospection are made.

Abstract: The interfacial microstructure evolution of copper/aluminium laminates with different annealing processes was studied. It was found that the formation and growth of intermetallic compounds in the interface during metallurgical combination process have four stages: the incubation period, the formation of island-like new phases in local areas, the transverse-lengthwise-transverse growth of diffusion zone, the formation of new intermetallic compounds and thickening of diffusion zone.

Abstract: A novel polysiloxane bearing (N,N)-dimethyl-γ-aminopropyl-γ-aminopropyl side groups(ASO-2) was synthesized by copolymerization of octamethylcyclotetrasiloxane with (N,N)-dimethyl-γ-aminopropyl-γ-aminopropyl methyl dimethoxysilane and hexamethyldisiloxane. Chemical structure, film morphology and the softening fabric property of ASO-2 were characterized and investigated by IR, 1H-NMR, SEM, atomic force microscope(AFM) and Kawabata evaluation system(KES).The experiment results indicate that ASO-2 can form a hydrophobic film on both the cotton fiber and silicon wafer surface. The ASO-2 film relatively exhibits a non-homogeneous structure and uneven morphology in its AFM images. Consequently, in 2 μm2 scanning field, the root mean square roughness of ASO-2 film reaches to 0.226 nm, which is 2.69 times rougher as compared with that of N-β-aminoethyl-γ-aminopropyl polysiloxane (ASO-1) film. Application experiments indicate though the tactile of ASO-2 imparted on 100% cotton is somewhat rougher than that of ASO-1, the whiteness and wettability of the cotton treated by ASO-2 are better than those by ASO-1.

Abstract: In order to search for new wear resistant materials used as drilling tools and improve the service life and drilling efficiency, the 7Cr7Mo2V2Si steel was prepared and its abrasive wear behavior and mechanisms were studied under both dry and water wear conditions. The research results show that the wear losses of the 7Cr7Mo2V2Si steel increase with the increase of normal load and sliding speed at both of dry and water wear conditions. The wear losses become greatly increase at high sliding speed and heavy normal load wear conditions. The wear rates of the 7Cr7Mo2V2Si steel at water wear conditions are bigger than those at dry wear conditions. The existence of water will aggravate the wear loss of the steel because water can clean the tribo-interface by taking away the fine powder or debris, which may keep the corundum abrasives protruding and remaining sharp edge state to produce more serious two-body abrasive wear to the steel, and meanwhile the collaborative action of the friction stress and the corrosion may result in stress corrosive wear of the steel. The main wear mechanisms of the 7Cr7Mo2V2Si steel are micro-cutting wear, multi-plastic deformation wear at dry wear conditions and accompanied with stress corrosive wear at water wear conditions.

Abstract: In this paper, we present a strategy for the preparation of Fe-doped TiO₂/SiO₂ aerogel microspheres (Fe-TSAMs) for visible light photocatalysis degradation of methylene blue. A water- in-oil (W/O) emulsion of Span 80–Tween 85/n-heptane–n-butanol/FeCl₃-doped TiO₂/SiO₂ alcoholic sols–formamide was obtained. Wet TiO₂/SiO₂ gel microspheres were prepared by the sol-gel process in the W/O emulsion, then they were dried at ambient pressure condition to prepare Fe-TSAMs. The Fe-TSAMs were characterized by N₂ adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the resultant Fe-TSAMs possess nanoporous network structure comprising TiO₂ and SiO₂ nanoparticles with diameters of 10-20 nm. The Fe-TSAMs have a mean diameter of about 100 μm, an apparent density of 0.26 g/cm³, a specific surface area of 360 m²/g, a pore volume of 1.77 cm³/g and the most probable pore size of 18.7 nm with the porosity of 87.7%. By using methylene blue as a simulated aqueous pollutant, the visible light photocatalysis properties of the Fe-TSAMs were investigated. The results indicate that low concentration Fe ion doping (5 wt%) could avoid the formation of recombination centers for photo-generated electron/hole pairs. Compared with commercial P25 TiO₂ powders, Fe-TSAMs exhibit excellent photocatalytic ability for degradation of methylene blue under visible light region. The Fe-TSAMs could be reclaimed conveniently and the reused Fe-TSAMs also have a good photocatalytic activity.

Abstract: This hydrothermal reaction of tridentate rigid 2,4,6-tris-(benzimidazolyl-2-yl)pyridine (pytbzim) ligand, linear bridging 4,4′-bipyridine (4,4′-bpy) ligand and Zn(II) salts in acetonitrile and water mixed solvents generates a new complex {[Zn₃I₆(4,4′-bpy)(pytbzim)₃].(H₂O)₂.(CH₃CN)}_n. The asymmetry unit of complex contains a [ZnI₂(pytbzim)] and a {[Zn₂I₂(4,4′-bpy)₂(pytbzim)₂] units, which further construct into a three-dimensional supramolecular networks through p-p stacking interaction and rich hydrogen bonds between units and solvents. The solid state photoluminescence studies reveal good fluorescent properties of the pytbzim ligand and Zn(II)-complex at room temperature.

Abstract: Y₂Cu₂O₅/Y₂O₃ (YCO) photocatalysts were prepared using sol-gel method. The photocatalysts were modified by Pt particles to prepare Pt-loaded composite (Pt-YCO) using hydrogen reduction method, and NiO/YCO were synthesized by impregnation method. These obtained samples were characterized by thermogravimetry and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), and ultraviolet visible diffuse reflectance absorption spectra (UV-Vis DRS) techniques. Photocatalytic H₂ evolution activity of the modified photocatalysts has been evaluated from aqueous oxalic acid solution used as sacrificial reagent under simulated sunlight irradiation. The result showed that when the concentration of the photocatalysts is 0.8 g·L^-1， Pt-YCO photocatalyst exhibits higher photocatalytic activity compared with unloaded YCO. The hydrogen production rate is 4.12 mmol·h^-1·g^-1 with 1wt% loading amount of Pt, while the loading content is up to 2.5wt%, the hydrogen production rate of Pt-YCO photocatalyst deecreased instead. Whereas NiO/YCO composite exhibits less photocatalytic activity than that of pure YCO under the same conditions.

Abstract: TiAl/Al₂O₃ in situ composites have been prepared by a reactive hot pressing method from Ti, Al and Nb₂O₅ powders. The phase transformation and the mechanism of synthesis were studied by differential scanning calorimeter (DSC) of starting powers and X-ray diffraction (XRD) of samples hot press sintered at different temperatures from 500 °C to 1300 °C. Scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) was utilized to investigate the morphology characteristics of the products. The resultant in situ formed TiAl/Al₂O₃ composites exhibited multiplex structures containing TiAl, Ti₃Al, Al₂O₃ and NbAl₃ phases. Fine Al₂O₃ particles that act as reinforcing phase are dispersed along the interface of the matrix. The formation of TiAl/Al₂O₃ composite involves many transitional stages. Firstly, Ti and Al reacted to form TiAl₃ and Ti₃Al intermediates, then Nb₂O₅ was reduced by Al to form the Al₂O₃, and finally, the competitive solid-state diffusing reactions among Ti₃Al, TiAl and TiAl₃ produced the final matrix phases of the resultant composite.

Abstract: The epoxy resin-based polymer alloys putty modified by using silicone/nano-TiO₂/MoS₂ micron-particles and nm-TiO₂/μm-Al₂O₃ composite particles were prepared at room temperature. Properties including hardness, friction and wear characteristics are analyzed by means of pin-on-disk testers, scanning electron microscopy (SEM). In addition, the influences of contents of organic silicone on the matrix were investigated via measuring the tensile strength and elongation, thermal stability and microstructure of the cured materials. The results showed that the tensile strength of the cured materials(mass ratio of epoxy resin to TSR144 is 1:1) is 59.12 MPa, elongation = 12.40%, and temperature of 50% weight loss is 414°C, higher than those of pure epoxy resin by 10.58 MPa, 5.59%, and 24°C respectively. Finally, its friction mechanism has been preliminarily discussed.

Abstract: The shark-skin effect motivated from the dermal surface morphology of sharks hastens the imitation and manufacture of the non-smooth drag reduction bionic coating based on shark skin. The fabrication of the bionic shark-skin coating with life-sized scale-like microstructure was presented in this paper. Using hot embossing technology, the direct micro replication of the microstructure on shark skin was investigated for the first time. Modeled after the shark skin sample, the negative structure was directly replicated and printed on PMMA flat plate in the hot embossing process, relied on which the bionic shark-skin coating made of silica gel was fabricated in the end. The preliminary experiment results indicate that this method is a high precision, high throughput, high efficiency and low cost way to fabricate bionic microstructure in micron and submicron scale with good repeatability and availability.