Preparation and thermoelectric properties of SiO<Subscript>2</Subscript>/<Emphasis Type="Italic">β</Emphasis>-Zn<Subscript>4</Subscript>Sb<Subscript>3</Subscript> nanocomposite materials

A series of SiO₂/β-Zn₄Sb₃ core-shell composite particles with 3, 6, 9, and 12 nm of SiO₂ shell in thickness were prepared by coating β-Zn₄Sb₃ microparticles with SiO₂ nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution. SiO₂/β-Zn₄Sb₃ nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering (SPS) method. Microstructure, phase composition, and thermoelectric properties of SiO₂/β-Zn₄Sb₃ nanocomposite thermoelectric materials were systemically investigated. The results show that β-Zn₄Sb₃ microparticles are uniformly coated by SiO₂ nanoparticles, and no any phase transformation reaction takes place during SPS process. The electrical and thermal conductivity gradually decreases, and the Seebeck coefficient increases compared to that of β-Zn₄Sb₃ bulk material, but the increment of Seebeck coefficient in high temperature range remarkably increases. The thermal conductivity of SiO₂/β-Zn₄Sb₃ nanocomposite material with 12 nm of SiO₂ shell is the lowest and only 0.56 W·m⁻¹·K⁻¹ at 460 K. As a result, the ZT value of the SiO₂/β-Zn₄Sb₃ nanocomposite material reaches 0.87 at 700 K and increases by 30%.     

Magnetism regulation of (In<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>O<Subscript>3</Subscript> semiconductors prepared by sol-gel method

Fe doped In₂O₃ samples (In_1−x Fe _x )₂O₃ (x=0, 0.05, 0.1, 0.2 and 0.3) on glass substrate were prepared by sol-gel method. The XRD results demonstrate that the solubility of Fe ions in In₂O₃ matrix is around 20%, above which impurity phase can be observed. The transmittance of the samples with x=0, 0.05, 0.1 and 0.2 are above 80% in the visible region while the transimittance of the glass is 90%. The transmittance curves slightly red-shifts as x increasing. All of the samples except x=0 are ferromagnetic at room temperature. The highest saturation magnetization moment is reached in the sample x=0.2 with 330 emu/cm³, and the coercive force is 169 Oe which is also the largest in our samples. The results indicate that the addition of Fe ions could tune the structure, the ferromagnetism and optical property in the In₂O₃ matrix.     

Adsorption performances and refrigeration application of adsorption working pair of CaCl<Subscript>2</Subscript>−NH<Subscript>3</Subscript>

The adsorption performance of CaCl₂−NH₃ is studied under the condition of different expansion spaces for adsorbent, and the relationships between adsorption performance of CaCl₂−NH₃ and the phenomena of swelling and agglomeration during adsorption are researched. It is found that the performance stability is related to the ratio of expansion space to the volume of adsorbent r _as, and the performance attenuation is serious in the case of large r _as. Severe adsorption hysteresis exists in the process of adsorption and desorption at the same evaporating and condensing temperatures, which is related to the stability constant of chemical reaction. This phenomenon cannot be explained by the theory of physical adsorption. Moderate agglomeration will be beneficial to the formation of ammoniate complex; the magnitude of expansion space will affect adsorption performance. Analysis shows that the activated energy needed in the process of adsorption for the sample with r _as. of 2∶1 is less than that for the sample with r _as of 3∶1. The refrigeration performance of CaCl₂−NH₃ is predicted from experiments. The cooling capacity of one adsorption cycle is about 945.4 kJ/kg for the adsorbent with an r _as of 2∶1 at the evaporating temperature of 0°C.     

Dendrite crystal morphology evolution mechanism of <Emphasis Type="Italic">β</Emphasis>-BaB<Subscript>2</Subscript>O<Subscript>4</Subscript> crystal

Existence of [B₃-O₆]³⁻ hexagonal ring growth unit in melt solution of β-BaB₂O₄ crystal was proved by the results of high temperature Raman measurements. A morphology evolution process of β-BaB₂O₄ crystal was observed by a high temperature in-situ observation device. The crystal morphology varied with the supersaturation of growth melt solution. The mechanism of β-BaB₂O₄ crystal morphology evolution was analyzed through the growth unit model. Supported by the National Natural Science Foundation of China (Grant No. 60808026) and the Nanjing University of Aeronautics and Astronautics Scientific Research Fund (Grant No. S0764-081)     

Structure and infrared radiation property of Co<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> ferrites by XAFS analysis

Co_1−x Zn _x Fe₂O₄ ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found that infrared radiance show a nonlinear change with x, exhibiting the infrared radiance of this material improved and the average radiance in the 8–14 μm waveband reached 0.91. The Co³⁺ and Zn²⁺ ions are found to occupy both tetrahedral and octahedral sites, and correspondingly, the fraction of Fe³⁺ ions in B-site decreases nonlinearly in ferrites. The lattice parameters are found to concern with Zn²⁺, and the activation energy deduces from crystal strain and crystal vibrate increases with content Zn²⁺. The redistribution of the Co³⁺ and Zn²⁺ ions between tetrahedral and octahedral sites is related to the providing a selective tetrahedral and octahedral sites infrared radiance of Co_1−x Zn _x Fe₂O₄ ceramics with increasing x.     

Low temperature synthesis of nano porous 12CaO∙7Al<Subscript>2</Subscript>O<Subscript>3</Subscript> powder by hydrothermal method

Single-phase insulating 12CaO?7Al₂O₃ (C12A7) powder was synthesized using an optimized hydrothermal method. Pure phase of C12A7 was got at a comparatively lower temperature (c.a. 300 °C) than that has been previously reported. The crystallite size of the synthesized C12A7 powder was 7±2 nm. The surface area values calculated for all the samples at a synthesis temperature range of 250-800 °C for 5 h were in the range of about 19-24 m²/g, with pore sizes of 12-20 nm. This low-temperature-based synthetic strategy along with nano porous structures and a high surface area value can facilitate catalyst application.     

Structures and properties of La<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>MnO<Subscript>3+σ</Subscript>-z SBA-15 (z=0, 1, 2, 4) perovskite catalysts

Mesoporous La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite oxides were synthesized via hard-templating with ordered mesoporous silica SBA-15 as the template. The as-prepared samples were characterized by XRD, SEM, AFM, BET, and XPS and the catalytic activity was tested for CO oxidation. The wide-angle XRD patterns showed that La_0.8Sr_0.2MnO_3+σ perovskite was formed. The SEM and AFM analyses exhibited that La_0.8Sr_0.2MnO_3+σ by hard-templating method had much smaller particle size (18 nm) than that (40 nm) by the sol-gel method. The perovskite-type oxides La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) also displayed a higher BET surface area from 70 to 143.7 m²/g and a disordered mesostructure from nitrogen sorption analysis, as well as a small-angle XRD pattern. Moreover, the La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite exhibited a much higher activity in CO oxidation than the conventional La_0.8Sr_0.2MnO_3+σ perovskite. Further analysis by the means of XPS techniques indicated that the existence of high content of O_ads/O_latt species contributed to the high activity.     

Forming mechanism and morphology of CaSO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O by SEM-EDS and ICP

To promote the development of 3D printing materials, gypsum powders used in 3D printing were analyzed in detail through SEM-EDS and ICP. The forming mechanism and morphology of CaSO₄? χH₂O powders were analyzed and confirmed. Furthermore, the printing mechanism of gypsum powders was analyzed and discussed. According to the results of SME-EDS analysis and ICP detection, the factors affecting the forming accuracy, strength, surface quality and reliability of CaSO₄? χH₂O crystal were found in this paper. Adding a variety of additives to change the performance of calcium sulfate would be the further research.     

Pore structure of new composite adsorbent SiO<Subscript>2</Subscript>·<Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O· <Emphasis Type="Italic">y</Emphasis>CaCl<Subscript>2</Subscript> with high uptake of water from air

A new composite adsorbent SiO₂·xH₂O·yCaCl₂ which is composed of macro-porous silica gel and calcium chloride is introduced. In order to analyze its adsorption theory, adsorption and desorption isotherms, BET surface areas, pore volumes and average pore diameters of macro-porous silica gel and four composite adsorbent samples with different CaCl₂ content are measured using SEM and Asap2010 apparatus. From the adsorption isotherms, desorption isotherms and lag loops, it can be deduced that the main pore structure in macro-porous silica gel and the new composite adsorbent have two shapes: taper with one top open and taper or hyperbolic taper with both ends open. Based on the analysis of pore diameter distribution and lag loop, a sketch map showing calcium chloride filled in pore of macro-porous silica gel is presented. The adsorption isotherms at 25°C are measured. Experimental results show that the new composite adsorbent can adsorb more water than common adsorbents (macro-porous silica gel, micro-porous silica gel and synthetic zeolite 13X). In the light of the results of pore structure, adsorption isotherms and lyolysis phenomenon are analyzed.     

<Emphasis Type="Italic">In-situ</Emphasis> growth and photoluminescence of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> cone-like nanowires on the surface of Ga substrates

β-Ga₂O₃ cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750–1000°C for 2 h in air. The controllable synthesis of β-Ga₂O₃ nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesized products were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the β-Ga₂O₃ nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30–100 nm and 0.5–1.5 μm, respectively. A possible mechanism was also proposed to account for the formation of β-Ga₂O₃ cone-like nanowires. Photoluminescence spectra of the β-Ga₂O₃ nanowires obtained at different temperatures were measured at room temperature, and a strong blue photoluminescence with peaks at 430 and 460 nm and a weak red photoluminescence with peak at 713 nm were observed. The blue light emission intensity decreases with increasing the reaction temperature, however, the red light emission intensity hardly changes. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants, etc., respectively. Supported by the National Natural Science Foundation of China (Grant No. 20573072) and Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060718010)     

Effect of Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>B/<Emphasis Type="Italic">α</Emphasis>-Fe nanocomposite permanent magnets with a combined Co and Nb additions

Influence of Co+Nb on the Nd₈Fe₈₂Co₃Nb₁B₆ nanocomposite magnets was investigated by adding Co element combined with Nb element. Results show that the high temperature stability of two phases is increased. Adding Co+Nb could improve the glass forming ability of the alloy, reduce the size of grains, increase the exchange coupling ability of two phases, and obviously increase the magnetic properties of the alloy. The optimal magnetic properties are B _r=1.14 T, H _cj=320 kA/m, (BH)max-109.3 kJ/m³.     

Melt-spun Al<Subscript>70−<Emphasis Type="Italic">X</Emphasis></Subscript>Si<Subscript>30</Subscript>Mn<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript> (<Emphasis Type="Italic">X</Emphasis>=0, 3, 5, 7, 10) anode in lithium-ion batteries

Al_70−X Si₃₀Mn _X (X=0, 3, 5, 7, 10, mol%) ribbons were prepared by melt spinning. A supersaturated solid solution of Si and Mn in fcc Al and some microstructures consisting of nano grains were obtained. Some alloys with nano-sized grains exhibited high discharge capacities and favorable cycle properties. The capacity of more than 400 mAh/g could be obtained in melt-spun Al₆₇Si₃₀Mn₃ alloy after 20 cycles and more than 300 mAh/g after 40 cycles. Li/Si and Li/Al compounds in the anodes of pure Al and pure Si were not detected in Al-Si-Mn alloys inserted by Li. It is considered that the formation of the supersaturated solid solution and refinement of microstructures have prevented the alloys from the forming the compounds with superfluous Li. As a result, the electrochemical properties have been improved. Supported by the National Natural Science Foundation of China (Grant No. 50371066)     

Analysis methods of SrTiO<Subscript>3</Subscript> ceramic’s electricity performance

The effect of oxidizing-heat-treatment conditions on the electricity performance of doped SrTiO3 ceramic is analyzed by using the theory of grey neural network. Based on the number of main parameters, the model of GNNM （1,1）, GNNM （1,2）, GNNM （1,3） is used to analyze and construct the corresponding model of GNNM （2,1） gray neural network. It can reach the required precision by calculating.     

Novel wide band gap alloyed semiconductors, <Emphasis Type="Italic">x</Emphasis>(LiGaO<Subscript>2</Subscript>)<Subscript>1/2</Subscript>-(1−<Emphasis Type="Italic">x</Emphasis>)ZnO,and fabrication of their thin films

Oxide semiconductor alloys of x(LiGaO₂)_1/2-(1−x)ZnO were fabricated by the solid state reaction between β-LiGaO₂ and ZnO and rf-magnetron sputtering. For the solid state reaction, the wurtzite-type single phases were obtained in the composition range of x⩽0.38. The formation range of the alloys was wider than that of the (Mg_1−x Zn _x )O system, because the β-LiGaO₂ possesses a wurtzite-derived structure and approximately the same lattice constants with ZnO. The electrical resistivity and energy band gap of the 0.38(LiGaO₂)_1/2-0.62ZnO alloyed ceramic were 0.45 Ωcm and 3.7 eV, respectively, at room temperature. For the alloying by sputtering, the films consisting of the wurtzite-type single phase were obtained over the entire composition range of x(LiGaO₂)_1/2-(1−x)ZnO. The energy band gap was controllable in the range from 3.3 to 5.6 eV. For the as-deposited film fabricated using the 0.4(LiGaO₂)_1/2-0.6ZnO alloyed ceramic target, the energy band gap was 3.74 eV, and the electrical resistivity, carrier density and the Hall mobility at room temperature were 3.6 Ωcm, 3.4×10¹⁷ cm⁻³ and 5.6 cm² V⁻¹ s⁻¹, respectively.     

Analysis of Mg content of Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O film grown on sapphire substrates by plasma-assisted molecular beam epitaxy

The Mg content of Zn_1−x Mg _x O film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.     

Synthesis and electrochemical behaviors of <Emphasis Type="Italic">α</Emphasis>-MoO<Subscript>3</Subscript> nanobelts/carbon nanotubes composites for lithium ion batteries

α-MoO₃ nanobelts/carbon nanotubes (CNTs) composites were synthesized by simple hydrothermal method followed by CNTs incorporating, and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge testing techniques were employed to evaluate the electrochemical behaviors of α-MoO₃ nanobelts /CNTs composites. The results exhibited that compared to bare α-MoO₃ nanobelts, the α-MoO₃ nanobelts/CNTs composites have better electrochemical performances as cathode materials for lithium ion battery, maintaining a reversible specific capacity of 222.2 mAh/g at 0.3 C after 50 cycles, and 74.1% retention of the first reversible capacity. In addition, the Rct value of the α-MoO₃ nanobelts/ CNTs is 13 Ω, much lower than 66 Ω of the bare α-MoO₃ nanobelts. The better electrochemical performances of the α-MoO₃ nanobelts /CNTs composites can be attributed to the effects of the high conductive CNTs network.     

Chitosan and <Emphasis Type="Italic">β</Emphasis>-cyclodextrin microspheres as pulmonary sustained delivery systems

Chitosan and β-cyclodextrin were used to prepare microspheres with theophylline for pulmonary delivery by spray drying method. The characteristics, mucociliotoxicity, permeation rate and drug release were studied. The drug entrapments of microspheres Ⅰ, Ⅱ and Ⅲ were from 35.70% to 21.09% and 13.33%, while yields and encapsulation efficiencies were higher than 45% and about 90% respectively. The microspheres possessed low tap densities （0.34-0.48 g/cm^3）, appropriate diameters （3.35-3.94 μm） and theoretical aerodynamics diameters （2.20-3.04 μm）. SEM images showed the microspheres were spherical with smooth or wrinkled surface surfaces. FT-IR demonstrated theophylline had formed hydrogen bonds with chitosan and fl-cyclodextrin. The microspheres could effectively reduce the ciliotoxicity and easy to penetrate the memberine. The in vitro release of the microspheres was related to the ratio of drug/polymer and microspheres Ⅱ had a prolong release, providing the release of 72.00% in 12 h. The results suggestes that chitosan/β-cyclodextrin microspheres Ⅱ are a promising carrier as sustained release for pulmonary delivery.     

Stability of <Emphasis Type="Italic">γ</Emphasis>′ multimodal microstructure in a Ni-based powder metallurgy superalloy

Multimodal size distribution of γ′ phase was obtained in a slow-cooling experiment following supersolvus solution treatment (1191°C). The morphology of the secondary γ′ particles exhibited splitting and protrusion instabilities. In the subsequent aging process (815°C), reverse coarsening was observed, i.e., the average precipitate size decreased with increasing aging time. Reverse coarsening slows the coarsening rate of the precipitates, increases the hardness of the alloy, and greatly improves the morphological stability of the γ′ phase.     

Stability control of steer by wire system based on <Emphasis Type="Italic">μ</Emphasis> synthesis robust control

The uncertainty influences may result in performance deterioration and instability to the steer by wire (SBW) system. Thus, it must make the control system keep robust stability from uncertainty, and have good robustness. In order to effectively restrain the interference and improve steering stability, this paper presents a μ synthesis robust controller based on SBW system, which considers the effect of model uncertainty and external disturbance on the system dynamics. Taking the ideal yaw rate tracking, interference suppression and excellent robustness as the control objectives, the μ synthesis robust controller is designed using linear fractional transformation theory to deal with the uncertainty. Then, it is testified through time domain and robustness simulation analysis. Simulation results show that the proposed controller can not only ensure robustness and robust stability of the system quite well, but improve handling stability of the vehicle effectively. The results of this study provide certain theoretical basis for the research and application of SBW system.     

Preparation of <Emphasis Type="Italic">γ</Emphasis>-methacryloxypropyl Trimethoxy Silane Cross-linked PDMS Membrane for Pervaporation Recovery of Butanol

The present study aimed to improve the pervaporation (PV) performances of polydimethylsiloxane (PDMS) membranes by using special cross-linkers. The γ-methacryloxypropyl trimethoxy silane (KH-570) cross-linked PDMS membranes were fabricated and characterized by FTIR, TGA, WCA, DSC, SEM, and swelling properties. Experimental results showed that the separation factor of the membrane increased slightly with the feed temperature whereas permeate flux increased. Butanol flux increased slowly with the feed concentration while the water flux decreased. The overall result indicated that the separation factor decreased slowly with the feed concentration. The membrane, with a thickness of 55 μm, showed a total flux of 308.4 g/m²h with a separation factor of 26.8 at 70 °C, and butanol permeability reached 11.13×10⁵ Barrer with a membrane selectivity of 56.0.