Advanced Materials Research Vols. 152-153

Abstract: Pumice was used to make up lightweight aggregate concrete (LWAC). Frost resistance durability of LWAC in 5% Na2SO4 solution was studied. The test results showed that LWAC durability deteriorates more rapidly under freezing-thawing in salt solution than in water. The strength loss of LWAC was reduced by steel fiber and polypropylene fiber regardless of Na2SO4 solution and water. Fly ash and silica fume can improve Interfacial Transition Zone（ITZ）and the frost resistance of fibers reinforcement LWAC dramatically.

Abstract: Bagasse is an abundant agricultural byproduct. The use of bagasse has generated much interest due to its low cost, possibility of environmental protection and use of locally available renewable resources. In this paper, cellulose was dissolved in the ionic liquid （1-butyl-3-methylimidazolium chloride） and regenerated in water. FT-IR and SEM were used to characterize the structure of the original and regenerated cellulose. It was found that the treatment of the original cellulose in the ionic liquid significantly degraded the cellulose and completely destroyed the cellulose crystals. Despite many studies of the chemical modification of cellulose published around the world in this area, only a few have been investigated about the regeneration of sugarcane bagasse. Theoretical basis was established for further research on the application of the regenerated cellulose in material science.

Abstract: The orthogonal test method is used to research effect of the factors on the concrete’s frost resistance performance. The factors include volume fraction of fibers, water-binder ratio, fly ash and water-reducing agent. The results show that the polypropylene fiber influences on the mass loss of concrete noticeably, which can improve the frost resistance of concrete. The match ratio of the concrete is optimized. Finally the best match ratio is found out, which meets strength and frost resistance of concrete.

Abstract: Nano-aluminum, which has high thermal conductivity and good compatibility, was added into paraffin to improve its thermal conductivity. Surface modified technology was adopted and dispersant was used to prepare uniform and stable organic phase-change nano-fluid of paraffin and nano-aluminum. Transient plane source method was used to test the thermal conductivity of the prepared organic phase-change nano-fluid. Results showed that the addition of nano-aluminum largely improved the thermal conductivity of paraffin. After the formula of Lu and Lin was modified, a calculation model for thermal conductivity of the organic phase-change nano-fluid was deduced. And experimental results showed that the results of calculation agreed that of experiment very well.

Abstract: The effects of ground limestone powder on the fluidity, strength and viscosity of reactive powder concrete(RPC) were studied. The results show that, the flexural strength of RPC greatly increases with the increase of the content of ground limestone powder at the W/B of 0.16, 0.18 and 0.20 when ground limestone powder content is less than 30%; for fresh RPC, the maximum compressive strength is 160MPa and the maximum flexural strength is 36.9MPa when the limestone powder content is 158kg/m3 at the W/B of 0.20, with 20cm good fluidity and very compact microstructure; the viscosity of RPC greatly decreases with the addition amount of ground limestone powder, the viscosity of RPC mixture changes from 60,000MPa•S to 18,000MPa•S when cement content decreases from 388kg/m3 to 150kg/m3 and the addition amount of limestone powder increases from 0 to 238kg/m3.

Abstract: The in-situ oxidation technique is an effective method of synthesizing copper matrix composites reinforced by oxide dispersion. In this study, the process of fabricating Cu/Cr2O3 composite by Cr in-situ oxidation in Cu-Cr pre-alloyed powders was investigated. The evolution of the structure formed in the processing of Cu/Cr2O3 composites was characterized by optical microscopy and transmission electron microscopy (TEM). The results show that the sub-solution Cu-Cr alloy powders can be produced by high energy milling, in which Cr powders are first crushed into fine particulates, followed by the formation of Cr sub-solution in copper under the extrusion and impact of high energy grinding balls. In the Cu/Cr2O3 composite fabricated by the Cu-Cr pre-alloyed powders, the Cr2O3 particulates produced exist almost in the original sites of the Cr, and they are dispersed uniformly within the Cu matrix. The distribution of Cr2O3 particulates is similar to that in the full solid solution Cu-Cr powders.

Abstract: Nano-aluminum, which has high thermal conductivity and good compatibility, was added into paraffin to improve its thermal conductivity. Surface modified technology was adopted and dispersant was used to prepare uniform and stable organic phase-change nano-fluid of paraffin and nano-aluminum. Experiments were conducted to test the phase-change temperature and latent heat of the prepared organic phase-change nano-fluid. Results show that the addition of nano-aluminum has no effect on phase-change temperature, but it changes phase-change latent heat of the prepared organic phase-change nano-fluid. Reduced degree of the latent heat is nearly proportional to the quantity of the added nano-aluminum.

Abstract: Electrical discharge machining (EDM) is relatively modern machining process having distinct advantages over other machining processes and able to machine Ti-alloys effectively. This paper attempts to investigate the effects of peak ampere, pulse on time and pulse off time on tool wear rate (TWR) of titanium alloy Ti-6Al-4V in EDM utilizing copper tungsten as an electrode and positive polarity of the electrode. A mathematical model for electrode wear rate is developed in this paper. Design of experiments method and response surface methodology techniques are implemented. The validity test of the fit and adequacy of the proposed models has been carried out through analysis of variance. It can be seen that as the peak current increases the TWR decreases till certain ampere and then increases. The excellent surface finish is investigated in this study at short pulse on time and in contrast the long pulse duration causes the lowest TWR. Long pulse off time provides minimum TWR and the impact of pulse interval on TWR depends on peak current. The result leads to wear rate of electrode and economical industrial machining by optimizing the input parameters.

Abstract: The aim of the present work was to study the feasibility of wet synthesizing hydroxyapatite (HAP) with star-like and high specific surface area. HAP was synthesized by one-step self-assembly process in ionic liquid media under microwave irradiation, and treated at 300, 600, 900 , respectively. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis revealed that HAP was pure crystal phase. Nitrogen adsorption and desorption isotherms (NADI) with a characteristic hysteresis loop further confirmed the existence of uniform micropores or channels of HAP. The BET surface area, pore volume, and pore size distribution were calculated to be 324m2g-1, 0.39cm3g-1, and 3.28 nm, respectively. Scanning electron microscopy (SEM) results indicated that the HAP was of star-shaped morphology. The formation of HAP could be explained by functional ionic liquid as structure-directing template. Well-ordered mesostructure of HAP with star-like might be therefore used as a potential biomaterial for preparation of bone implant materials.

Abstract: In order to gain a deep insight into the mechanism of Ni-doped Mo activated sintering process, the diffusion behavior of Mo-Ni interface was studied utilizing a Mo-Ni diffusion couple. The phase structure and composition on the diffusion layer were characterized and analyzed by means of scanning electron microscope and transmission electron microscope, the self diffusion coefficient and interdiffusion coefficient were calculated. The results show that a diffusion layer is formed between Mo and Ni after sintering at 1223k for 1h, which is comprised of a δ-NiMo intermetallic compound and a limit solid solution containing small amounts of nickel. The self diffusion coefficient and interdiffusion coefficient are 2.068×10-18cm2/s and 4.5×10-12cm2/s, respectively. It is suggested that the diffusion rate of Mo in δ-NiMo intermetallic compound and a limit solid solution containing small amounts of nickel is 106 times bigger than that of self diffusion, and the intermetallic compound layer provides a short diffusion path for Mo activated sintering.