Advanced Materials Research Vols. 160-162

Abstract: 1J79 alloy was prepared by vacuum electric arc smelting．The crystal growth and the content of impurity was observed by electron probe microanalyzer，and magnetic properties were measured by vibrating sample magnetometer(VSM)．Experimental results show that inclusions in the alloy are fewer and fewer, composition becomes more uniform with the increases of the Mo content, and grain size also becomes larger and larger with the increases of Mo content, to reduce coercivity. The small amount of Mo addition is useful to improve the saturation magnetization and reduce coercivity．

Abstract: CNTs were treated with hydrazine hydrate and diethylenetriamine, respectively. Scanning electron spectroscopy (SEM) observation showed that the doped CNTs kept the length/diameter ratio of pristine CNTs. X-ray photoelectron spectroscopy (XPS) characterized that nitrogen can be doped to CNTs. XPS analysis further indicated that C/N atomic ratio of CNTs treated by hydrazine hydrate is 95/2, four times of CNTs treated by diethylenetriamine, which is 96/0.5. The hydrophilicity for N-doped CNTs (N-CNTs) is much improved and enhanced by increasing N proportion. As electrode material of supercapacitor, nitrogen functional groups contribute pseudo-Faradic capacitance, but its cyclic performance still need to be improved. Thanks to the good hydrophilicity for N-CNTs that improves the wettability of CNTs for electrolyte; the specific capacitance of N-CNTs is still slightly higher than pristine CNTs after cycling.

Abstract: Formaldehyde cross-linked chitosan was used to adsorb sulfate ions from aqueous solution in this study. Batch experiments were conducted to investigate the conditions of the adsorption, the isotherms and kinetics of the adsorption. The optimized conditions of adsorption were as follows: the adsorbent dosage was 0.5g, the equilibrium time was 240min, the initial concentration of sulfate ions was 153.3mg/L, the temperature was 50°Cand the value of pH was 2.2. The maximum adsorption capacity came up to 14.7 mg/g with the adsorption efficiency got to 95.7%. The equilibrium data fitted Langmuir isothermal model well. In addition, the adsorption process could be explained by the second-order kinetic model, and the chemisorption was the limit step for adsorption velocity.

Abstract: The adsorption of cadmium in simulated wastewater by chitosan was investigated. The influence of temperature, contact time and pH on adsorption efficiency of cadmium was examined. Some related mathematical models were used in the fitting of experimental data. The results showed that at room temperature, the optimum pH of adsorption is between 4 and 7. At lower pH values, a strong competition existed between cadmium ions and protons for sorption sites and the sorption efficiency was decreased. After 60 minutes the adsorption equilibrium can be achieved. Chitosan is very effective at removing cadmium with the maximum adsorption capacity is 112.05mg•g-1. The adsorption kinetic curves agree with the pseudo-second-order adsorption kinetic equations and the adsorption isotherms could be well described by Langmuir isotherm equations.

Abstract: With chitosan as the raw material, a new type of resin material is synthesized through formaldehyde crosslinking. The effects of the reactant ratio, the reaction temperature, the reaction time, the stirring rate and the system pH on the cross-linking rate are studied in detail. The resin material is then characterized by means of IR. The experimental results show that the reaction occurs mainly on the amino and the hydroxyl of chitosan. The chitosan-based resin material with good properties of sphericity and acidresistivity can be prepared under the optimal experimental conditions, which are found to be 1:5 for the ratio of chitosan and formaldehyde, 60°C for the temperature, 1 h for the reaction time, 440r/min for the stirring rate and 10 for the pH.

Abstract: In this study, the graft copolymerization of acryalmide and acrylonitrile onto chitosan with K2S2O8-NaHSO3 initiator under N2 interaction is studied and the mechanism is discussed. Compared to the chitosan graft of acrylamide or acrylonitrile, the graft yield and graft efficiency of ternary polymerization increase significantly. The stability and reproducibility are also improved obviously. To be specific, the reaction time, the reaction temperature, the effect of the amount of materials, the concentration of K2S2O8, and the concentration of NaHSO3 on the graft yield and graft efficiency is investigated respectively. The C=C of acrylamide and the acrylonitrile react respectively with -NH2 and C6-OH of chitosan initiated by SO4-•. The experimental results show that the optimal synthesis conditions are given as follows: the reaction time is 6h, the reaction temperature is 60°C, the ratio of m(chitosan):m(acrylamide):m(acrylonitrile) is 1:7:5, the concentration of K2S2O8 is 4.5mmol/L, and the concentration of NaHSO3 is about 2.6mmol/L. Under such conditions the graft yield and graft efficiency can be up to 839.52% and 70.00%, respectively.

Abstract: The density functional theory (DFT) calculations explored the structural optimization and the frequency of N-carboxymethyl chitosan (N-CMCS) and O-carboxymethyl chitosan (O-CMCS). For the isomers, the calculations comparatively were performed. The charge distribution and frontier molecular orbit were analyzed by using the natural bond orbital (NBO) method. The results showed: the two rotational isomers a and b can stably exist, with the stability order a>b; N-carboxymethyl chitosan reaction active sites are concentrated in -OH and -NHCH2COOH, while O-carboxymethyl chitosan reaction active sites are concentrated in -NH2 and -CH2COOH; The water-soluble mechanism of carboxymethyl chitosan was investigated deeply, on the one hand, the presence of carboxymethyl of carboxymethyl chitosan had a tendency to ionize H+, on the other hand the carboxymethyl increased the distance and weakened the hydrogen bonds between molecules, even though Einstein shift H-bond is formed in the carboxymethyl chitosan molecules.

Abstract: The molybdenum alloys doped with various mass fraction zirconium diboride (ZrB2) particles were successfully prepared by using the powder metallurgy technology. The microstructure, hardness and the tensile properties of the pure molybdenum and molybdenum alloys doped with ZrB2 particles were determined at room temperature. Results showed that the addition of zirconium diboride refined the molybdenum grains obviously, meanwhile, molybdenum grain sizes decrease with the increasing of zirconium diboride mass fraction. Measurements on mechanical properties showed that molybdenum alloys doped with ZrB2 particles had higher hardness and strength than pure molybdenum. The analysis and discussion results show that the strengthening mechanisms of ZrB2-doped molybdenum alloys may be attributed to the fine-grain strengthening, particle dispersion strengthening, interfacial-bond strengthening and oxygen reduction strengthening.

Abstract: SiO2 sol sealing agent was developed by hydrolyzing of organic alkoxide, and protective composite coatings were obtained on magnesium alloys AZ31B by micro-arc oxidation (MAO) treatment plus a top coating with sealing agent using dipping-costing technique. SEM observations revealed that SiO2 sol immersed into pores and uniformly covered the surface of MAO coating. XPS analysis indicated that an inorganic SiO2 layer has formed on the surface of MAO coating. The results of potentiodynamic polarization tests showed that corrosion resistance of AZ31B alloys with composite coatings was evidently superior to that of merely MAO coating. The SiO2 layer provided corrosion protection by physically sealing the pores on the MAO coating and acting as a barrier. The composite coatings could suppress the corrosion process by preventing the transferring or diffusing of corrosive ions between magnesium alloys substrate and solution.

Abstract: Based on deposition rate of coatings and ion flux measured by Langmuir probe in sputtering environment, bombardment energy Ec1 of sputtered neutral atoms and bombardment energy Ec2 of bombardment ions accepted by substrate surface micro-area per unit time were calculated. The magnitude of Ec1 and Ec2 was approximately the same, surface diffusing processes of the top layer atoms in the coating were accelerated by the simultaneity action of Ec1 and Ec2, bulk diffusion processes of the atoms under the top layer in the coating were promoted by energy accumulation and temperature rise effect caused by the continuance action of Ec1 and Ec2.