Advanced Materials Research Vols. 631-632

Abstract: In this study, Ni-5wt.%Al coating was fabricated on the 6061-T6 aluminum alloy substrate by twin-wire arc spraying technology. Through different heat treatment process, effect of microstructure and phase structure was studied with different temperature and time. Interface reaction mechanism of alloy coating/substrate and diffusion behavior of elements was discussed. Heat treatment was carried out at 400°C，480°C，550°C and respective for 4h, 24h, 48h. The XRD , SEM and EDS results showed that main phases of Ni-5wt.%Al original coating were composed of Ni solid solution, in addition to a small amount of Al₂O₃, NiO and Al₄Ni₃. Phase composition has basically not changed, interface of the coating/substrate occurred diffusion, which was controlled by the diffusion of Al atoms. Intermetallic compounds of NiAl3 and Ni₂Al₃ were formed in interface of coating/substrate, and interface diffusion area gradually was thickened.

Abstract: Ni_0.5Zn_0.5Fe₂O₄, Ni_0.3Cu_0.2Zn_0.5Fe₂O₄ and Ni_0.4Co_0.2Zn_0.4Fe₂O₄ spinel ferrite nanofibers with 60–100 nm in diameter were fabricated through the sol-gel assisted electrospinning method, followed by calcination at 600°C for 2h in air. The phase structure morphology and element composition of these nanofibers were determined by XRD, FE-SEM and EDS. Magnetic measurements were used to justify the ferromagnetic properties of these nanofibers. Microwave absorption, which was in the range of 2-18 GHz, was studied by a vector network analyzer. The adoption of Cu²⁺ and Co²⁺ substitution was found to improve the microwave absorption in relation to non-substituted NiZn ferrite nanofibers. Reflection loss exceeding –5 dB is obtained between 11 and 18 GHz for silicon rubber composites containing 15 vol% nickel-based ferrite nanofibers with coating thicknesses of 3 mm. The results indicate that the prepared nickel-based ferrite nanofibers possess good electromagnetic wave absorption performance in the Ku band and have great potential as microwave absorber for practical applications.

Abstract: Using silicon powders as raw materials, adding nano-silicon nitride as a diluent and NH₄Cl₃ and FeCl₃ as catalysts, α-phase silicon nitride powders were prepared by direct nitridation method. The silicon powders were first milled with 20% α-Si₃N₄ and 4% NH₄Cl₃ for 30 minutes. Then the mixture was heat-treated at 1300°C for 1 hour in the pure nitrogen gas. The phases and their content of the as-prepared product were detected by X-ray diffraction (XRD) and the microstructure was studied by scanning electron microscope (SEM). The results showed that the product mainly consisted ofα-Si₃N₄ with a mass fraction over 92% and were submicron-sized particles．

Abstract: A kind of new carboxyl and vinyl co-modified silicone oil (Vi-CAS-1) was synthesized with vinyl/amino co-modified silicone oil (Vi-ASO-1) and maleic anhydride (MA) as raw materials. Then 0.03 % Vi-CAS-1 in ethyl acetate solution was used as a finishing agent, the performance of Vi-CAS-1 on dacron fabrics was studied, and the effects of carboxyl equivalent, viscosity and the mole ratio of raw materials such as Vi-ASO-1 to MA on the Vi-CAS-1 performance were also investigated carefully. The results shows that, the elasticity and flexibility of fabrics treated by Vi-CAS-1 significantly increase. And when cooperate with the silicone which contains Si-H (PHMS-0.16 %) in application, the compounded Vi-CAS-1 can improve the fabric water-repellency to some extent, as compared with the fabric treated only with Vi-CAS-1.

Abstract: A spherical humidity control composite material with excellent humidity control performances has been prepared by twice foaming method. The composite comprises a natural polymer derivative (KGM), a porous natural mineral (Halloysite) and an Sodium polyacrylate (PAAS). It has high capacity for moisture adsorption, fast response to humidity changes, and small range for equilibrium humidity control. The moisture adsorption content of the composite material is 1.10 (g/g) of its own weight. The moisture absorption rate is 0.3948 (g/7h•g^-1), and moisture desorption rate is 0.4682 (g/7h•g^-1). The composite material has an equilibrium humidity control ranging from 50%RH to 53%RH. It can reach to the equilibrium levels within 60 minutes. It is suitable for maintaining a proper micro-environment for places such as museums or galleries.

Abstract: Experimental research on calcium alginate fibers thermal degradation and flame retardancy under catalysis of metallic salts was done by limiting oxygen index (LOI), scanning electron microscopy (SEM), and thermogravimetric analysis (TG) methods. LOI results show that with increasing calcium ions content, the flame retardant properties of the calcium alginate fibers improves further. The residues of calcium alginate fibers gradually retained fiber shape and on the surface of the residues the holes reduced, with the calcium ion content increasing. TG indicates temperature at maximum rate of weight loss (T-max) was clearly shifted from 246 °C for alginic acid fibers to 244°C, 236°C, 208°C, 205 °C and 203°C (SCa-1-1# calcium alginate fibers, SCa-2-2# calcium alginate fibers, SCa-3-3# calcium alginate fibers, SCa-4-4# calcium alginate fibers, SCa-5-5# calcium alginate fibers), respectively. The thermal degradation residues at 1000°C for different calcium alginate fibers are 13.7%, 16.1%, 17.2%, 18.2%, 18.4%, 19.2%, separately. Further discussion of the combustion process and flame retardant mechanism is presented.

Abstract: BiFe _1-x Co_xO₃(x= 0-0.3) polycrystalline samples were prepared in order to study the effect of Co substitution on BiFeO₃ structural, magnetic and electric properties, which to the best of our knowledge, the related work has not been reported. The samples were synthesized by a simple solid-state method, which the process contains mortar grind, calcinate, press and sinter. The crystal structures were refined from XRD data in the acentric R3c space group; a second phase CoFe₂O₄ was identified, in increasing amounts with the increase of x. The magnetic moment is greatly improved and the magnetization for BiFe _0.96 Co _0.04 O₃ was found to be 0.756 emu/g.

Abstract: The strain rate sensitivity of neoprene is characterized using a modified split Hopkinson pressure bar (SHPB) system at intermediate (50 s^-1, 100 s^-1) and high (500 s^-1, 1000 s^-1) strain rates. We used two quartz piezoelectric force transducers that were sandwiched between the specimen and experimental bars respectively to directly measure the weak wave signals. A laser gap gage was employed to monitor the deformation of the sample directly. Three kinds of neoprene rubbers (Shore hardness: SHA60, SHA65, and SHA70) were tested using the modified split Hopkinson pressure bar. Experimental results show that the modified apparatus is effective and reliable for determining the compressive stress-strain responses of neoprene at intermediate and high strain rates.

Abstract: In this paper, the tribological properties of the modified PTFE three-layer composites in different humidities were studied. The wear mechanisms of the modified PTFE three-layer composites with and without PI were also analyzed. The test results showed that in the humidity of 15%-75%, the friction coefficients of the composites increased with the humidity increased. At the humidity of 100%, the friction coefficient reduced significantly. With the increase of humidity, the wear of the composites decreased at first and then increased. The smallest wear appeared when the humidity was 45% or 60% for with or without PI composites respectively. And the results also revealed that PI is helpful to improve the wear stability of the composites in different humidities.

Abstract: Four continuous annealing cycles were adopted to get four kinds of multi-phase steels using 0.2C-1.5Si-1.8Mn [wt%] alloyed raw steel and the microstructures and mechanical properties were investigated. The results show that traditional ferrite-martensite dual phase steel has a tensile strength of more than 1000MPa, but has the lowest strength-plastic product of only 18GPa%. The traditional ferrite, bainite and residual austenite TRIP steel has the highest elongation of 31% and hardening exponent of 0.24, but its tensile strength is just over 800MPa. Introducing hard matrix such as acicular bainitc ferrite or martensite to replace the polygonal ferrite matrix, meanwhile introducing metastable austenite, is conducive to obtain high strength and good ductility. Those kinds of modified TRIP steel with hard matrix can reach above 20GPa% of the strength-plastic product on the 1000MPa grade.