Advanced Materials Research Vols. 774-776

Abstract: This study successfully grafted multiwalled carbon nanotubes (MWCNTs) with carboxyl group (MWCNTs-COOH) via concentrated nitric acid oxidation reaction. The morphologies of MWCNTs oxidized under various conditions and the extent of dispersion of the MWCNTs in the cement matrix were characterized using fourier transform infrared spectroscopy (FTIR). This investigation also optimized the mechanical properties of MWCNTs-OPC cement composites by utilizing pristine MWCNTs (P-MWCNTs) and modified MWCNTs (MWCNTs-COOH) through a combination of dispersion method. Micrographs of MWCNTs incorporated cement samples revealed uniform dispersion of MWCNTs in cement, good interfacial adhesion between MWCNTs and cement, and improved interfacial bonding between MWCNTs-OPC cement at 0.4 wt.% loading. An improved dispersion and hence an improved crosslink interaction between MWCNTs-COOH and cement lead to the stronger shift of the mechanical properties of the cement composites.

Abstract: In this paper, the ultimate, proximate and component analyses of the Daxinganling larch bark and xylem were performed and intercompared respectively. The pyrolysis features of the bark and xylem were analyzed by using the differential thermal thermo-gravimetric analyzer (TG). The influences of heating rate on pyrolysis features were discussed. The results show: (i) the content of H is a little more in the xylem than the bark and the content of ash in the bark is two times of the xylem and the content of fixed carbon in the xylem is two times of the bark. The content of alcohol-benzene extract is significantly more in the bark than the xylem and the glarson lignin in the bark is two times of the xylem but the hemicellulose in the xylem is three times of the bark; (ii) the process of the bark pyrolysis has two pyrolysis areas, but the xylem has a only pyrolysis area, however, the main pyrolysis interval of temperature of the bark and xylem are between 420K to 720K, in which the weight-loss of bark is 87-91% of the full weight-loss and the xylem weight-loss is 91-95% of the full weight-loss. (iii) the DTG peak of the xylem is behind 25 K of bark, and the DTG peak of the bark is-0.47 but the xylem-0.93. (iv) the curves of the TG and DTG move to the side of the higher temperature a bit following the heating rate increased, while the main pyrolysis areas are wider.

Abstract: Pure powdery high molecular weight polyacrylonitrile (HMW-PAN) copolymers were firstly synthesized by aqueous deposited polymerization (ADP) technique employing 2,2'-Azobis (isobutyramidine) dihydrochloride (AIBA) as initiator and itaconic acid (IA) as comonomer. Various PAN polymers were obtained through changing different polymerization parameters. It is indicated that with the increase of total monomer concentration, initiator concentration, reaction temperature and reaction time, polymerization conversions of PAN copolymers all increased. While the molecular weights become greater with the increase of total monomer concentration. With the increase of initiator concentration and reaction temperature (under higher reaction temperature region), the molecular weights decreased. However, the molecular weights only had very little decrease at the end of long extension of reaction time.

Abstract: Shaking-flask experiments and electrochemical tests were conducted to study the bioleaching of marmatite with mixed cultures of mesophilic bacteria. The effects of copper ions and the surfactant, o-phenylenediamines (OPD) on the bioleaching were investigated. The electrochemical mechanism of the bioleaching was researched through cyclic voltammetry and chronoamperometry. The results show that the decrease in leaching rate was associated with a passive film (elemental sulfur) formed on the surface of marmatite in the leaching course. It was found that, however, the passive film dissolved readily under high potential conditions or with the bacterial action. Especially, in the presence of bacteria, the decomposition of the passive film was accelerated by adding either copper ions or OPD, leading to a significant increase in the bioleaching rate of marmatite.

Abstract: Corrosion of the steel affects seriously its mechanical performance. Based on the finite element methods, strength tensile properties of corroded steel were studied. Pit shapes and pit depths, pit locations, etc on the mechanical behavior of steel were studied mainly. Pit depth is major cause of produce rust steel mechanical performance degradation, because there is an obvious stress concentration phenomenon around pit, cause steel mechanics performance degraded significantly. Pit shapes and lengths may also be affected steel mechanical properties.

Abstract: Conditions of phase transitions in systems of identical ferromagnetic spherical nanoparticles randomly distributed in metal nonmagnetic matrix and superlattices of small number of nanoparticles with the Ruderman-Kittel-Kasuya-Yosida interaction are researched. In the framework of the Ising model the behavior of superspins is well described with the random interaction field method. The alteration of the effective magnetic moment due to the change in volume affects the choice of the magnetic state of the system: ferromagnetic spin glass or antiferromagnetic spin glass. The ground state of superlattice depends on the distance between particles.

Abstract: The cone index is one of the important indicators that can describe the comprehensive physical characteristics of lunar regolith. Its closely related to the sink and sideslip of lunar rover and also has widely used in prediction the trafficability, adhesion property, tractive performance of lunar rover. Based on component method, a kind of low gravity simulator, the tiltable test-bed has been built. This study has got the stable low gravity along axial direction and measured the penetration resistance characteristics of JLU-2 in different gravity through tests. The results shows that the gravity environment has an obvious impact on the cone index of lunar soil simulant, CI values reduce with the decreasing of gravity environment. Namely, in the low gravity condition, it shows weaker resistance ability for a foreign object to penetrate into. The result has important application value of prepare, optimize and risk assessment in walking mechanism of lunar rover and the sampling mechanism.

Abstract: In this paper, the magnetic graphene oxide (Fe₃O₄@GO) has been successfully prepared by decomposition of Iron (III) acetylacetonate in the mixture solution of triethylene glycol and GO. atomic force microscope, TEM, XRD and superconducting quantum interference device were used to characterize the material. The results showed that the magnetic Fe₃O₄ nanoparticles modified graphene oxide has been obtained, and it has superparamagnetism with magnetization saturation of 16.4emu/g. the Fe₃O₄@GO has a good sustained-release performance, and vitro cytotoxicity confirmed that its security for Fe₃O₄@ GO as a potential drug carrier.

Abstract: Mesoporous silica nanoparticles (MSNs), with controllable pore size at wider range (2-13 nm) and particle size about 100 nm, have been successfully prepared using different templates. N₂ adsorptiondesorption isotherms, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the material. The results showed that the MSNs have high specific surface area, controllable pore-size and the pore volume, and uniform particle size. Their drug delivery properties were investigated. It was found that the amount of loading DOX is increased with surface area, and the multi-release experiments showed that they had a sustained-release property; MSNs with larger pore size had the larger amount of DOX.

Abstract: Attapulgite was modified with different methods and used as support to immobilize β-glucosidase. Effects of enzyme dosage, pH, temperature and time in immobilization on stabilities of immobilized β-glucosidase were investigated. The results showed that the optimum immobilization conditions of β-glucosidase on organic modification attapulgite were as follows: enzyme dosage 3600 U/g, temperature 50 °C, time 60 min and pH 5.0. The thermal and storage stabilities of immobilized β-glucosidase were improved significantly.