Materials Science Forum Vols. 620-622

Abstract: The Ni-TiN nanocomposite films have been successfully fabricated onto commercial brass copper substrates using dc electroplating technique, and the microstructure and anti-corrosion properties of the optimized Ni-TiN nanocomposite have been respectively characterized using scanning electron microscopy (SEM). The results show that the morphology of Ni-TiN composite film is sensitively dependent on the electroplating current density, the concentration of TiN nanoparticles, the solution stirring speed, the bath temperature and the solution pH value.

Abstract: The electroplating behavior of nanocrystalline CoNiFe soft magnetic thin film with high saturation magnetic flux density and low coercivity was investigated using cyclic voltammetry and chronoamperometry methods in conjunction with the scanning electron microscopy (SEM/EDX) and X-ray diffraction (XRD) techniques. The results show that, the co-deposition of CoNiFe alloy behaves anomalously. And the nucleation/growth process of CoNiFe ternary alloy followed 3D instantaneous mechanism at higher potentials, while in the case of lower potentials it followed 3D progressive mechanism.

Abstract: In this paper, we report the multiferroic and piezoelectric behavior observed in transition-metal doped ZnO films. The experimental results indicated that the Co-doped ZnO films deposited by magnetron sputtering possess a Curie temperature higher than 700K, and the magnetic moments of Co are intimatedly correlated to the doping concentration and the substrate. A giant magnetic moment of 6.1 B/Co is observed in (4 at.%) Co-doped ZnO films. Ferroelectric and ferromagnetic behaviors simultaneously were also obtained in V and Cr doped ZnO films on Pt(111)/Ti/SiO2/Si(100) substrates by reactive sputtering method, revealing a multiferroic nature. The high piezoelectric d33 coefficient 80-120 pm/V has also been achieved by Cr and V substitutions, which could make Cr-doped or V-doped ZnO a promising material in piezoelectric devices.

Abstract: Fluoralkylpolysiloxane modified Polyurethane (FSPU) films with high water contact angle (CA) were prepared. fluoralkylpolysiloxane was obtained using perfluoro octyl sulfuryl fluoride and terminal amino-silicone oil as reactants. Then, the isocyanate end capped PU prepolymer was synthesized by reacting isocyanate with a soft segment mixed by active amino-end-capping fluoralkylpolysiloxane and polyether glycol. The fluoralkylpolysiloxane modified PU films were obtained after the PU prepolymer was cured by 3,3 '- dichloro -4,4' – amino - diphenyl methane (MOCA). The results showed that the modified polyurethane with 10% (mass fraction) PFATPS had a good compatibility, low surface energy, surface water contact angle and surface oil contact angle was improved by 49° and 37° respectively, and heat resistance, water resistance was apparently improved.

Abstract: Porous Ti-Mo alloy samples with different porosities from 52% to 72% were successfully fabricated by the space-holder sintering method. The pore size of the porous Ti-Mo alloy samples were ranged from 200 to 500 μm. The plateau stress and elastic modulus of the porous Ti-Mo alloy samples increases with the decreasing of the porosity. Moreover, an apatite coating on the Ti-Mo alloy after an alkali and heat treatment was obtained through soaking into a simulated body fluid (SBF). The porous Ti-Mo alloy provides promising potential for new implant materials with new bone tissue ingrowth ability, bioactivity and mechanical properties mimicking those of natural bone.

Abstract: In this paper, the conception and classification of Green-growing porous concrete (POC) is introduced. POC is made of single-sized coarse aggregate, Portland cement, admixtures, chemical admixtures, water, et al. It should be properly mixed before cast in mould. Because of its large-pore structure, POC have much ecological and environmental value. In the case of be used as greening concrete which placed in highway side, POC’s compressive strength should be higher than 15MPa, at the same time, its valid porosity content should be at the range of 25% and 30%.

Abstract: In this paper, porous Si3N4 ceramics were fabricated by carbothermal reduction between carbon black and diatomite. Diatomite is a siliceous, sedimentary rock consisting principally of the fossilized skeletal remains of diatom, a unicellular aquatic plant related to the algae. The main ingredient of diatomite is the amorphous active silicon dioxide. The influence of diatomite particle size on the microstructure of sintering bodies was analyzed. XRD analysis demonstrated the formation of Si3N4 except for minor of glass phase. SEM analysis showed that the resultant porous β-Si3N4 ceramics occupied fine microstructure and uniform pore structure.

Abstract: Deformation behavior of lotus-type porous copper with long cylindrical pores aligned in one direction through equal-channel angular extrusion (ECAE) process was investigated using a die with channel angle of 150º. Although the density slightly increased after every pass, the porous structure remains in the process. The Vickers hardness and the compressive yield strength of lotus copper increased through the ECAE process. The compressive yield strength after 3 passes increased up to 10 times larger than that before processing. The deformation of lotus copper takes place by buckling and the shearing of the cell walls. The increase in hardness is considered to be caused by work hardening.

Abstract: With commercial α-Si3N4 and h-BN powders as starting materials, La2O3, Al2O3, Y2O3 as sintering additives, Si3N4/BN composite ceramics with 25vol% h-BN were fabricated by pressureless sintering. Various amounts of La2O3 (0, 2, 4, 8, 15wt%) were added, with constant Y2O3/Al2O3 weight ratio and additives (Y2O3/Al2O3/La2O3) amount. The densification behaviors, α-βtransformation and room-temperature strength of Si3N4/BN composite were investigated. The porosity of samples decreased with La2O3 content increasing, and the lowest porosity of 20.83% was observed for samples containing 4wt% La2O3, then leaded to an increase. The flexural strength of all the specimens increased with the addition up to 4wt% and changed greatly thereafter. The highest room-temperature flexural strength, 272.4MPa, was obtained when 4wt% La2O3 was added. Results of XRD patterns revealed that β-Si3N4 and h-BN existed in all the specimens. No α-Si3N4 was detected, implying thatα- toβ-Si3N4 transformation has been completed during the pressureless sintering process. These results show that the La2O3-Al2O3-Y2O3 system can act as effective sintering additives for pressureless sintered Si3N4/BN composite.

Abstract: New porous materials with hybrid pore structure “Fibers-In-Pores” structure were produced by developing Si3N4 whiskers in pores of partially-sintered silicon by nitriding. Because silicon and Si3N4 have excellent heat resistance, the proposed porous materials are expected to utilize high-temperature applications such as gas filters. Porous silicon was produced by sintering Si powder at 1300°C for 1 h in a stream of Ar gas. Porous Si bodies were nitrided at 1300°C for 1 h with N2 gas to develop long Si3N4 whiskers in pores of partially-sintered silicon. Specific surface area was increased and gas permeability was decreased by applying the nitridation process at 1300°C.