Preparation and photocatalytic application of high temperature stabilized ZrSiO4@TiO2 hybrid nanostructure

A new ZrSiO4@TiO2 hybrid nanostructure was prepared by a heterogeneous flocculation method. Phytic acid was introduced to modify the surface charging of the components for hybrid assembly. The obtained powder was coated on ceramic tiles and fired at 900 ℃ to fabricate photocatalytic ceramic. Experimental results show that anatase TiO2 in the composite powder has high thermal stability until 1 200 ℃. ZrSiO4 matrix prevents the mass transfer of anatase TiO2 at high temperature and greatly retards the phase transition of anatase to rutile. Besides, the photocatalytic ceramic shows apparent activities for the degradation of methyl orange under ultra-violet irradiation.     

Preparation and properties of multi-wall carbon nanotube/SiC composites by aqueous tape casting

MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramethylammonium hydroxide as the dispersant. The stability of MWCNTs/SiC slur-ries was studied and characterized in terms of zeta potential and rheology measurements. The relative density of the composite was about 98% after hot-pressing at 1850℃ (at 25 MPa in Ar for 30 min). The hardness of the composites decreased with the increase in MWCNTs content. The flexural strength and the fracture toughness were 742.17 MPa and 4.63 MPa·m1/2, respectively when the MWCNTs content was 0.25 wt%. Further increase in MWCNTs content to 0.50 wt% did not lead to the increase in mechanical properties. Most of MWCNTs were found to be located at SiC grain boundaries and the pull out of the MWCNTs was observed.     

Thermodynamic analysis of the Ti-Al-N system

Motivated by the application of (Ti, Al)N alloy compound in the coating layer, the ternary phase diagram of Ti-Al-N was analyzed by the calculation of the phase diagram (CALPHAD) technique. The isothermal sections of the Ti-Al-N ternary system were constructed and compared with the literature experimental results. The thermodynamic parameters of the Ti-Al-N ternary sys- tem and the related Ti-N and Al-N binary systems were adopted from literatures, whereas, those of the Ti-Al binary from the literatures were adjusted according to both the ternary and the binary phase equilibria. The consistency between the calculated results and the experimental data shows that considering the ternary thermodynamic relationship, the adjustments to the thermodynamic parameters of the related binaries are necessary.     

Preparation of aluminum foam sandwich by rolling-bonding/powder metallurgy foaming technology

Aluminum foam sandwich was prepared by rolling-bonding/powder metallurgical foaming technology, and the effects of rolling on bond strength of face sheet/powders and powder density were studied. Moreover, the foaming agent, TiH2, was heat treated and a certain amount of Mg was added into powder in an attempt to understand how the stability and uniformity of foam was improved. The experimental results show that the foaming precursors with ideal quality were obtained by rolling-bonding process. When rolling reduction is 67%, the consistency of powders reach to 99.87%. Throughout consideration of the bonding of face sheet/ core layer powders and deformation characteristic of powders, the optimum rolling reduction is 60%-70%. Cracks and drainage during foaming were inhibited by heat treatment of foaming agent TiH2 and the addition of a certain amount of Mg. The optimum heat treatment way of TiH2 is that heat preserving 1 hour at 450 ℃; the amount of adding Mg is 1wt%.     

Solid State Reaction Synthesis and Thermoelectric Properties ofMg_2Si doped with Sb and Te

Doped with Sb and Te, Mg2Si based compounds were prepared respectively by solid state reaction at 823 K for 8 h. Effects of dopants of Sb and Te on the structure and thermoelectric properties of the compounds were investigated. By calculating the values of the electrical conductivity for Sb-doped sample, the mechanism of electric conduction at 625 K is different. The figure of merit for sample doped with 0.4 wt% Te at500K is 2.4 × 10-3W/mK2,and it reaches 3. 3 ×10-3 W/mK2 at 650K for the sample doped with 0. 5wt% Sb. The values are more than 1.4 times and 2.3 times of the pure Mg2 Si sample.     

Effects of Fe Modified Na_2WO_4 Additive on the Hydrogen Storage Properties of MgH_2

A Fe modified Na_2WO_4 compound was synthesized by a solution impregnation method and was ball-milled with MgH_2 to constitute a novel MgH_2-Fe_2O_3/Na_2WO_4 composite. The effects of the Fe_2O_3/Na_2WO_4 additive on the hydrogen storage properties of MgH_2 together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH_2+20 wt% Fe_2O_3/Na_2WO_4 was almost 5 times that of pure MgH_2. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH_2. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH_2. It was worth noting that the MgH_2+20 wt% Fe/Na_2WO_4 presented the lower dehydrogenation reaction activation energy(Ea) of 35.9 kJ·mol-1 compared to that of pure MgH_2. The active MgWO4, Mg2 FeH6 and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH_2.     

Photocatalytic Activity of Porous Magnesium Oxychloride Cement Combined with AC/TiO_2 Composites

As a decorative material, magnesium oxychloride cement was used as a photocatalyst supporter to purify the pollutants indoors. Due to excellent adsorption properties of activated carbon(AC), the photocatalytic composties, TiO_2/AC, were prepared and introduced into the porous magnesium oxychloride cement(PMOC) substrate to composite a sort of photocatalytic cementitious material(PCM). The optimal composite processes were assessed by gas chromatograph, using toluene as the target. By comparing the perspective of toluene purification and thorough decomposition, it can be found that the optimal mass ratio for TiO_2/AC composites is 4/25, and the heat treatment to TiO_2/AC sample at 350 ℃ can play the optimal synergetic role of adsorbents in photocatalytic process. The synergistic effect of TiO_2, AC and magnesium oxychloride cement(MOC) was also evaluated by gas chromatograph. One-take molding process was adopted to introduce the TiO_2/AC into PMOC substrate, and its optimal mass fraction was 4 wt%, while the appropriate density of substrate was 0.35 g/cm3. Toluene degradation showed that the prepared PCM can degrade pollutants efficiently. The appropriate treatment process of TiO_2/AC, mass of TiO_2/AC, substrate density, and stable pore structure should be coordinated to maximize the adsorption-photodegradation performance. The combination of photocatalytic materials, adsorbents, and building materials provided a new idea for the application of photocatalysis.     

Removal and utilization of calcite existed in scheelite by preparation of calcium sulfate whiskers

In order to eliminate the effect of calcite associated with scheelite on the scheelite flotation, hydrochloric acid was used to dissolve the calcite, and the soaking solution was used to prepare CaSO_4 whiskers by hydrothermal reaction with sulfuric acid at ambient pressure. First, the condition experiments of preparing CaSO_4 whiskers by using CaCl_2 and H_2SO_4 were carried out to optimize reaction parameters of the crystallization process. The optimal conditions were: at 102 ℃ reaction temperature, 0,5 mol/L reactant concentration and 60 min reaction time. Then based on the condition experiments and considering keeping acid concentration stable for achieving HCl recycling, Calcium sulfate whiskers with the average diameter of 1.41 μm and the average aspect ratio of 109 were prepared by the soaking solution after evaporating to half of its volume and 1.0 mol/L H_2SO_4 at 102 ℃ for 60 min: After ion exchange processing,the filtrate could be used as HCl in the process of HCl dissolution.     

Crystal Structure and Hydrogen Storage Behaviors of Mg/MoS_2 Composites from Ball Milling

The Mg/MoS_2 composites were prepared by ball milling under argon atmosphere,and the effect of MoS_2 on the crystal structure and hydrogen storage properties of Mg was investigated.It is found that 10 wt% of MoS_2 is sufficient to prevent particle aggregation and cold welding during the milling process.The crystallite size of Mg will remain constant at slightly less than 38.8 nm with the milling process due to the size confinement effect of MoS_2.The dehydrogenation temperature of MgH_2 is reduced to 390.4-429.4 ℃ due to the crystallite size reduction.Through fitting by Johnson-Mehl-Avrami model,it is found that Mg crystal grows by three dimension controlled by interface transformation during the process of MgH_2 decomposition.MoS_2 has a weak catalyst effect on the decomposition of MgH_2 and activation energy of 148.9 k J/mol is needed for the dehydrogenation process calculated by the Arrhenius equation.     

Preparation and self-assembly of chitosan/carbon microsphere composite

Carbon-based films were synthesized by self-assembly of chitosan-encapsulated carbon microsphere (CMS@CS) composite. First, carbon microspheres (CMSs) prepared by chemical vapor deposition were modified by HNO3 and H2O2. Second, oxidized CMSs were modified by chitosan (CS). Finally, CMS@CS was self-assembled by vertical deposition, in which suspension concentration and deposition temperature on the quality of self-assembling film were investigated. Field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetry, and Fourier transformation infrared spectrometry were employed to characterize the morphology and structure of the samples. The results show that CMSs modified by CS had uniform particle size and good dispersion, CMS@CS was self-assembled into a dense film, the film thickened with increasing suspension concentration at fixed temperature, and more ordered film was obtained at 1 wt% of suspension concentration and 50 ℃. The ultraviolet-visible absorption spectra show that the absorbance of CMS@CS film grew steadily with increasing suspension concentration and that the CMSs with oxygen-containing groups have a good assembling performance to form composite films with CS.     

Synthesis of Organic Modified SiC_w/PVDF Composite Membrane and Its Dielectric Properties under Low Temperature

Cetyltrimethylammonium bromide(CTAB) was incorporated into silicon carbide whiskers(SiC_w) to improve their hydrophobicity. The solution casting method was employed to develop composite membranes of polyvinylidene fluoride(CTAB-SiC_w/PVDF) with different feed ratios. FT-IR spectroscopic studies proved that CTAB was successfully incorporated into the SiC_w. SiC_w phase structure was maintained after modification by CTAB according to XRD results. SEM studies indicated that the surface became smoother with CTAB dispersal in the PVDF membrane. The dielectric properties of the composite membranes containing various amounts of CTAB-SiC_w were measured at low temperature. It was found that the dielectric constant of the composite membranes with 13.0 wt% whiskers reached a maximum value of 25 at low frequency, and decreased to nine at high frequency(from 500 Hz to 1 MHz) at 0 ℃. The dielectric loss of each composite membrane increased with increasing temperature and reached a maximum value. The value shifted with corresponding frequency increases. In addition, the dielectric loss reached a maximum value of 0.2 when 16.7 wt% of CTAB-SiC_w was fed at each frequency(from-30 ℃ to 10 ℃). At room temperature, the dielectric constant could be maintained at 42 and the loss factor decreased to 0.8 at 100 Hz when 13.0 wt% of CTABSiC_w was incorporated. Additionally, TGA experiments indicated that the decomposition temperature of a PVDF membrane was increased by 10 ℃ and its heat resistance was improved by adding 13.0 wt% of CTAB-SiC_w. This PVDF composite membrane has potential for use as an insulator and capacitor.     

Properties of functionalized graphene/room temperature vulcanized silicone rubber composites prepared by an In-situ reduction method

Functionalized graphene oxide (FGO) was prepared by treating graphene oxide with γ-aminopropyl triethoxysilane (KH-550) before the mixture was dispersed into α, ω-dihydroxy polydimethylsiloxane to get room temperature vulcanized (RTV) silicone rubber composites by solution casting. The cured composites were then reduced with hydrazine hydrate to obtain functionalized graphene (FG)/RTV silicone rubber composites. The structures of FGO and the resultant composites were characterized by atomic force microscopy, FT-IR spectra and X-ray diffraction. KH-550 was found to be grafted onto graphene sheets, leading to an increased interlayer spacing. Significant improvements in thermal and mechanical properties were obtained. Both the FGO/RTV silicone rubber composite contain 1.0 wt% of FGO, and its reduced product showed an increase of one-step weight loss temperature with 61 ℃ and 133 ℃ higher than that of pure silicone rubber. Tensile strength and elongation at break of FG/RTV silicone rubber composite (with 0.5 wt% FGO content) increased by 175% and 67%, respectively, compared with those of pure silicone rubber.     

Complete splitting process of steel fiber reinforced concrete at intermediate strain rate

The complete splitting process of steel fiber reinforced concrete （SFRC） at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with lnstron 1342 materials testing machine was given, and the experiment principle and the loading mode of cubic split specimen were introduced. During the experiment, 30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm, designed and prepared according to C20 class SFRC with different volume fractions of steel fiber （0, 1%, 2%, 3%, 4%） were tested and analyzed. At the same time, the size effect of SFRC at intermediate strain rate was investigated. The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate. When the steel fiber content increases from 0 to 4%, the splitting strength of SFRC increases from 100% to 261%, i.e. increasing by 161% compared with that of the common concrete. The loading rate increases from 1.33 kN/s to 80.00 kN/s, and the splitting tensile strength increases by 43.55%.     

The Mixed-Alkali Effect on The Resistance of Glass to Water

Based on the composition of float glass, the resistance of glass to water, in which a small amount of K2O (0-1.0 wt% ) was substituted for equivalent amount of Na2O, was investigated by means of glass grains testing. The components extracted from the glass and total alkalinities in extraction solution were determined by atomic absorption spectroscopy and neutralizing method, respectively. The composition of the glass was 14.4 K2O Na2O, 4.0MgO, 8.2CaO, 1.4Al2 O3, 72.0 SiO2, and the minimum extraction ratio of oxides (maximum durability) occurred at a K2 O/Na2O ratio of 0.051( by weight) due to the presence of the mixed-alkali effect. The relative extraction ratio of alkali oxides (R2O) was greater than that of alkaline earth oxides (RO) . By means of mixed-alkali effect and lowing relative contents of R2O in the glass, the resistance of float glass to water was improved and its mildew-proof ability was therefore increased.     

Effect of heating on hydrogen retention in C-SiC coatings

C-SiC coatings were prepared on stainless steel with magnetron sputtering deposition followed by Argon ion bombardment. These samples were implanted by 5 keV hydrogen ion beam. SEM, SIMS and IR transmission were utilized to study the mechanism and the stability of hydrogen retention of C-SiC coatings. Comparison was made between the samples with and without removing Argon by heating then followed by H^＋ ion implantation. The results show that removal of argon by heating can improve the hydrogen retention of the C-SiC coatings. The thermal stability of hydrogen barrier for the C-SiC coatings was investigated, it is found that the property of hydrogen retention for the C-SiC coatings is still good after heating at 573 K, but it becomes worse after heating at 873 K, and it loses after heating at 1 173 K.     

Fabrication of solid-phase-sintered SiC-based composites with short carbon fibers

Solid-phase-sintered Si C-based composites with short carbon fibers（Csf/SSi C） in concentrations ranging from 0 to 10wt% were prepared by pressureless sintering at 2100°C. The phase composition, microstructure, density, and flexural strength of the composites with different Csf contents were investigated. SEM micrographs showed that the Csf distributed in the SSi C matrix homogeneously with some gaps at the fiber/matrix interfaces. The densities of the composites decreased with increasing Csf content. However, the bending strength first increased and then decreased with increasing Csf content, reaching a maximum value of 390 MPa at a Csf content of 5wt%, which was 60 MPa higher than that of SSi C because of the pull-out strengthening mechanism. Notably, Csf was graphitized and damaged during the sintering process because of the high temperature and reaction with boron derived from the sintering additive B4C; this graphitization degraded the fiber strengthening effect.     

Preparation of CaO-Al2O3-SiO2 system glass from molten blast furnace slag

To use the potential heat of molten blast furnace slag completely, a CaO-Al2O3-SiO2 system glass （MSG） was prepared from the molten industrial slag. The corresponding method proposed in this study utilized both slag and its potential heat, improving the production rate and avoiding the environmental pollution. Using appropriate techniques, an MSG with uniform color and superior performances was produced. Based on the experimental results and phase diagram, the chemical composition of MSG by mass is obtained as follows：CaO 27%-33%, SiO2 42%-51%, Al2O3 11%-14%, MgO 6%-8%, and Na2O＋K2O 1%-4%. Thermodynamic processes of MSG preparation were analyzed, and the phases and microstructures of MSG were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that alkali metal oxides serve as the fluxes, calcium oxide serves as the stabilizer, and alumina reinforces the Si-O network. XRD and SEM analyses show that, the prepared MSG displays the glass-feature patterns, the melting process is more complete, and the melt viscosity is lowered with an increase in calcium oxide content;however, a continuous increase in slag content induces the crystalli-zation of glass, leading to the formation of glass subphase. The optimum content of molten slag in MSG is 67.37wt%. With respect to bend-ing strength and acid/alkali resistance, the performance of MSG is better than that of ordinary marble.     

Thermal behavior and Rheologieal Properties of PANI-DBSA/PAN Blends

Conducting blends of polyacrylonitrile （PAN） copolymer and dodecylbenzene sulfonic acid doped polyaniline （PANI-DBSA） were prepared by solution blending of the two components. By means of various characterization methods including differential scanning calorimetry （DSC）, thermogravimetric analysis （TGA）, transmission electron microscopy （TEM） and cone-plate rheometry, the effects of PANI-DBSA content on the thermal behavior, morphological and rheological properties of the blends were investigated. A single and composition-dependent /＇g was found for each of all blends and the thermal stability of PANI-DBSA/PAN was superior to that of both pure Co-PAN and PANI- DBSA. Rheological results show that the apparent viscosity of blend solution decreased at low PANI- DBSA content （2.5 wt%） while increased at high PANI-DBSA content （7.5wt%-10 wt%）. Moreover, the shear-thinning appeared more distinctly with the incorporation of PANI-DBSA into the blend solutions especially at a high shear rate.     

Zn^2＋ Release Performance in Simulated Uterine Solution and Surface Characteristics of ZnO/LDPE Nanocomposites

Zinc oxide/low-density polyethylene （LDPE） nanocomposites were prepared for intrauterine devices. The change of Zn^2＋ release rates of nanocomposites （ doped with various mass fractions of zinc oxide nanoparticles between 5wt% and 65 wt% ） for 264 days in a simulated uterine solution were investigated. The resuits show that initial burst phases are followed by near zero-order release phases. SEM technique was employed to observe the surface morphology of the 45wt% ZnO/ LDPE composite. Elements and phases on the surface of the nanocomposite after incubation were also analyzed by EDX and XRD respectively. The experimental results show that incrustation formation does not occur after incubation.     

Thermal behavior and Rheological Properties of PANI-DBSA/PAN Blends

Conducting blends of polyacrylonitrile (PAN) copolymer and dodecylbenzene sulfonic acid doped polyaniline (PANI-DBSA) were prepared by solution blending of the two components. By means of various characterization methods including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and cone-plate rheometry, the effects of PANI-DBSA content on the thermal behavior, morphological and rheological properties of the blends were investigated. A single and composition-dependent Tg was found for each of all blends and the thermal stability of PANI-DBSA/PAN was superior to that of both pure Co-PAN and PANI- DBSA. Rheological results show that the apparent viscosity of blend solution decreased at low PANI- DBSA content (2.5 wt%) while increased at high PANI-DBSA content (7.5wt%-10 wt%). Moreover, the shear-thinning appeared more distinctly with the incorporation of PANI-DBSA into the blend solutions especially at a high shear rate.