Advanced Materials Research Vols. 488-489

Abstract: The influence of substrate temperature on the UV-Visible-near-IR optical properties, namely the band gap, the Urbach energy and the refractive index of NiO thin films deposited by RF sputtering has been investigated. The optical band gap of thin films showed the blue-shift in the transmission spectra with increase in the substrate temperature which is related to variation in carrier concentration of the deposited films. Urbach energy (EU) values indicate that the films deposited at 400 oC substrate temperature show least structural disorder. The refractive index of the films is found to decrease continuously with increase in the substrate temperature at all photon energies in the visible and near-IR region, and is attributed to the decreasing packing density of the films. Introduction

Abstract: Polymer blends between pristine polypropylene (PP) and post-consumer soft-drink PET bottles (rPET) were prepared using pulverization technique. The polymer mixtures were pulverized, at the amounts of rPET in PP of 0, 10, 15, 20 and 30 phr (parts per hundred of resin) by weight, into powder. In an extruder, the polymer powders were mixed with maleic anhydride-grafted polypropylene (MAPP) and polyethylene wax (PE wax) as a compatibilizer and a processing aid, respectively. The extrudates were prepared into test specimens by injection molding. Physical properties of PP/rPET blends were subsequently investigated. The results pointed out that, for the pulverized blends without compatibilizer, tensile and flexural strength were improved at the lower amount of rPET. The compatibilizing effect of MAPP was exhibited at the higher amount of rPET. The reduction of melt flow index (MFI) may cause difficulties for some processing techniques which required polymers with high MFI. The addition of PE wax successfully brought up the MFI as well as elongation at break while other mechanical properties decreased.

Abstract: The polymer electrolytes were prepared using the solution cast technique. The polymer host consisted of chitosan and poly(ethylene oxide) (PEO). Ammonium nitrate (NH₄NO₃) was added to the blend solution to provide the charge carriers for ionic conduction. The sample containing 40 wt.% NH4NO₃ exhibited a conductivity value of 5.83 × 10-4 S cm-1 at 373 K. Conductivity-temperature relationship for all samples obeyed Arrhenius rule and the activation energy of each samples were obtained. The sample containing 40 wt.% NH₄NO₃ showed the lowest activation energy at 0.29 eV. The conductivity variation for the prepared electrolyte system was explained using the Rice and Roth model. Sample with 40 wt. % NH₄NO₃ exhibited the highest number density and mobility of charge carriers with values of 1.39 × 1020 cm^-3 and 4.60 × 10^-6 cm² V^-1 s^-1 respectively. The increase in conductivity was attributed to the increase in the number density and mobility of charge carriers.

Abstract: The effect of thermal cycling on the martensitic transformation and response characteristics has been studied in bias-SMA spring actuators aged at 350 °C ~ 500 °C. As the number of thermal cycling increases, the Ms temperature of the SMA spring showing only B2→B19' martensitic transformation by aging at 350 or 500 °C goes down. However, SMA spring in which B2→R→B19' martensitic transformation taken place by aging at 400 or 450 °C shows multi-step transformations i.e., M1 and M2 transformations with thermal cycling. The heat flow of M2 transformation increases while the transformation temperature difference between M1 and M2 transformations is enlarged as the number of cycling increases. The recovery displacement and force of bias-SMA spring actuator increase up to the 10th cycle and the extent of increase is the largest at aging temperature of 500 °C. However, both recovery properties decrease after the 10³ or 10⁴ cycles, while the decreasing tendency becomes larger with a rise in aging temperature. Such a change in recovery characteristics of bias-SMA spring actuator with thermal cycling is discussed in connection with training effect or lattice defects introduced during thermal cycling.

Abstract: The accuracy of inverse estimation for viscoelastic material properties is usually affected by two main factors: mechanical model and the initial value of iterations. In our research, a new method based on artificial neural network and modified particle swarm optimization (PSO) is developed to estimate viscoelastic material properties. The artificial neural network is established to model the behavior of viscoelastic materials which has solved the model-dependent problem; and chaos algorithm is also added to PSO algorithm to improve its local escaping ability which helps us solve the initial-value problem. Feasibility of this method is demonstrated by both data from theoretical formula and FEM simulation experiment.

Abstract: We have performed detailed structural, electronic and magnetic properties of high - TC multiferroic CuO using first principles density functional theory. The total energy results revealed that AFM is the most stable magnetic ground state of CuO. The DOS and electronic band structure calculations show that in the absence of on-site Coulomb interaction (U), AFM structure of CuO heads to a metallic state. However, upon incorporating U in the calculations, a band gap of 1.2 eV is recovered. Furthermore, the Born effective charges calculated on Cu does not show any anomalous character.This suggests that the polarization seen in CuO could be attributed to the spin induced AFM ordering effect.

Abstract: Hydraulic fracturing is an effective measure to recover the permeabilityof reservoir and important to enhance oil and gas well production and water injection well. Fracturing fluid is the key factor in the fracture treatments. At present, water-based fracturing fluids are popular, because of low costs and steady performance, which has the largest applications. However, it performs badly in residue. The novel developed clearfrac fluid system named CF1 has lowresidue, cost affectivity, prior temperature resistance properties. Evaluation through a series of lab experiments, the experiments result show that the novel clearfrac fluid system can satisfy with the requirement of low damage and have favorable temperature resistance under 120 ^。C. The damage to the core matrix due to with the broken frac-fluid is low. Prior properties of the novel clear-fracturing fluid are suitable to high temperature and high pressure reservoirs. It is also a novel environmental friendly viscoelastic surfactant fracturing fluid. The development of the novel clear-fracturing fluid for hydraulic fracturing industry is significant.

Abstract: In order to investigate influence of end-groups on thermodynamic property and viscosity of hyperbranched polyether. Three series of hyperbranched polyethers with three different end-groups were studied. These three groups are: hydroxyl, acetate and stearic acid ester. The result confirms the complicated effect of end-groups on properties of hyperbranched polymer. When end-groups change from polar groups of hydroxyl to non-polar groups of acetate, glass transition temperature reduced about 50°C, viscosity reduced sharply too. Glass transition temperature and viscosity all increase with generation rise. When end-groups change from acetate to stearic acid ester, corresponding hyperbranched polyether change from amorphous to crystalline. The crystallization stemmed from long chain structure of end-group, which is easy to form crystalline, its crystalline region molten become main thermodynamic transformation, and obscure the glass transition.

Abstract: With increasing concern about the protection of the environment and the shortage of petroleum resources, the synthesis of polymer materials from renewable biomass resources has attracted a lot of attention. Starch based phenolic resin was prepared via hydrolyzation and condensation of starch at different temperatures from 120 °C to 200 °C. Gel time, apparent activation energies for curing reaction, impact strength, crystal structure and thermal resistance were studied. The results showed that: (1) the apparent activation energy for curing reaction was 19.8 kJ/mol; (2) crystal structure changed as a function of starch hydrolysis; (3) electron microscopy showed the disappearance of starch during the hydrolyzation; (4) the impact strength of starch based phenolic resin was 741 J/m² and residual mass at 600 °C was 40%. These results were compared with those of formaldehyde based phenolic resin, and it was detected that starch could be used to prepare phenolic resin in replacement of formaldehyde

Abstract: At present,the most commonly used polymer is partially hydrolyzed ployacryamide in polymer flooding.Moreover the viscosity of PAM solution is the critical factor of influencing sweep efficiency,which affects the oil production significantly.The viscosity of ployacryamide(PAM) solution is measured by CVRO200 rheometer under low shear rate after different shear time.The results show that the viscosity of PAM solution having the same concentration and hydrolysis degree increases with the molecular weight increasing.The viscosity of ionic PAM solution is far more than that of non-ionic PAM in the case of the same mass concentration.The viscosity of PAM solution decreases significantly with the brine salinity increasing,and ionic PAM is influenced much more seriously than the non-ionic PAM.An increase in temperature and the concentration of sodium hydroxide causes a great reduction of the viscosity of PAM solution,and non-ionic surfactant can lower the viscosity of PAM solution,but the impact is not very serious.Moreover the viscosity of PAM solution reduces obviously with the increase of shear rate and shear time.At the same time,the relevant theoretical interpretation is given.All these might serve definite purpose for the study of oil production.