不同制备方法所得PEN纤维的结构性能比较

利用高速纺丝法与纺丝拉伸一步法两种不同的方法制备聚萘二甲酸乙二酯 ( PEN)纤维 ,以DSC、X射线衍射、声速、力学测试等手段分析其结构、热学及力学性能并进行比较。结果表明 :以上两种纺丝法所制备 PEN纤维的晶型、晶粒尺寸不同 ;在所采用的高速纺丝速度范围内 ,分别以 6,7,8km/m in的速度纺制的试样结构性能基本相同 ;而纺丝拉伸一步法中不同的拉伸倍数对纤维的取向度影响较大 ,进而使杨氏模量、断裂强度和断裂伸长率变化较大     

Structural, electrochemical and thermal properties of LiNi0.8−yTiyCo0.2O2 as cathode materials for lithium ion battery

Multiple substitution compounds with the formula LiNi_0.8−yTi_yCo_0.2O₂ (0≤y≤0.1) were synthesized by sol-gel method using citric acid as a chelating agent. The effects of titanium substitution on the structural, electrochemical and thermal properties of the cathode materials are investigated. A solid solution phase (R-3m) is observed in the range of 0≤y≤0.1 for the titanium-doped materials. X-ray photoelectron spectroscopy (XPS) shows that there are Ni³⁺, Ni²⁺, Co³⁺, Co²⁺ and Ti⁴⁺ five transition metal ions in titanium-doped materials. Rietveld refinement of X-ray diffraction (XRD) patterns indicates that titanium substitution changes the materials’ structure with different cationic distribution. An increase of the Ni/Co amount in the 3a Li site is found with the addition of titanium amount. An improved cycling performance is observed for titanium-doped cathode materials, which is interpreted to a significant suppression of phase transitions and lattice changes during cycling. The thermal stability of titanium-doped materials is also improved, which can be attributed to its lower oxidation ability and enhanced structural stability at delithiated state.     

Preparation and properties of deep dye fibers from poly(ethylene terephthalate)/SiO2 nanocomposites by in situ polymerization

In this study, poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were synthesized by in situ polymerization and melt‐spun to fibers. The superfine structure and properties of PET/SiO₂ fibers were studied in detail by means of TEM, DSC, SEM, and a universal tensile machine. According to the TEM, SiO₂ nanoparticles were well dispersed in the PET matrix at a size level of 10–20 nm. The DSC results indicated that the SiO₂ nanoparticles might act as a marked nucleating agent promoting the crystallization of the PET matrix from melt but which inhibited the crystallization from the glassy state, owing to the “crosslink” interaction between the PET and SiO₂ nanoparticles. The tensile strength of 5.73 MPa was obtained for the fiber from PET/0.1 wt % SiO₂, which was 17% higher than that of the pure PET. The fibers were treated with aqueous NaOH. SEM photographs showed that more and deeper pits were introduced onto PET fibers, which provided shortcuts for disperse dye and diffused the reflection to a great extent. According to the K/S values, the color strength of the dyeing increased with increasing SiO₂ content. It is found that the deep dyeability of PET fibers was improved greatly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Increase of N2O Fluxes in Agricultural Peat and Sandy Soil under Elevated CO2 Concentration: Concomitant Changes in Soil Moisture, Groundwater Table and Biomass Production of Phleum pratense

The effects of elevated atmospheric CO₂ concentration on soil moisture, N₂O fluxes, and biomass production of Phleum pratense were studied in the laboratory. Farmed peat and sandy soil mesocosms sown with P. pratense were fertilized with a commercial fertilizer. In peat soil 10 g N m⁻² of commercial fertilizer were added and in sandy soil 15 g N m⁻². In both experiments, soil moisture was regulated with deionized water; 18 mesocosms were tended to keep equally moist, and the other 18 were watered with equal amounts of water. Nine mesocosms from both watering treatments were grown under ambient (360 μmol mol⁻¹) CO₂ concentration and the remaining nine under doubled (720 μmol mol⁻¹) CO₂. N₂O efflux was monitored using a closed chamber technique and a gas chromatograph. The elevated supply of CO₂ increased production of above- and belowground biomass, soil moisture and N₂O fluxes, but decreased the total N content in the aboveground biomass, especially for the sandy soil. In similar water levels, N₂O efflux from the sandy soil was the same magnitude as that from the peat soil. In addition to moisture, N availability was the main limiting factor for N₂O production, but C availability also seemed to regulate the denitrification activity. In addition to an increase in C availability the increase in the N₂O efflux under the raised CO₂ concentration also required a simultaneous increase in soil moisture.     

Ionic liquids as electrolytes

Salts having a low melting point are liquid at room temperature, or even below, and form a new class of liquids usually called room temperature ionic liquids (RTIL). Information about RTILs can be found in the literature with such key words as: room temperature molten salt, low-temperature molten salt, ambient-temperature molten salt, liquid organic salt or simply ionic liquid. Their physicochemical properties are the same as high temperature ionic liquids, but the practical aspects of their maintenance or handling are different enough to merit a distinction. The class of ionic liquids, based on tetraalkylammonium cation and chloroaluminate anion, has been extensively studied since late 1970s of the XX century, following the works of Osteryoung. Systematic research on the application of chloroaluminate ionic liquids as solvents was performed in 1980s. However, ionic liquids based on aluminium halides are moisture sensitive. During the last decade an increasing number of new ionic liquids have been prepared and used as solvents. The general aim of this paper was to review the physical and chemical properties of RTILs from the point of view of their possible application as electrolytes in electrochemical processes and devices. The following points are discussed: melting and freezing, conductivity, viscosity, temperature dependence of conductivity, transport and transference numbers, electrochemical stability, possible application in aluminium electroplating, lithium batteries and in electrochemical capacitors.     

Synthesis and characterization of Li ion conducting La2/3−xLi3xTiO3 by a polymerizable complex method

Ultrafine lithium ion conducting La_2/3−xLi_3xTiO₃ (x = 0.11, LLT) powder was synthesized by a simple polymerizable complex method based on the Pechini-type process. The formation mechanism, homogeneity and microstructure of the samples were investigated by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD analysis indicated the formation of pure perovskite-type phase. The powder synthesized at a temperature as low as 900 °C in a much shorter time than solid-state reaction method was well crystallized. The lithium ion conductivity of the LLT ceramics sintered at 1200 °C was found to be 9 × 10⁻⁴ S/cm at room temperature.     

Combustion and structure formation in the Ti-Ta-C-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> system

Biocompatible composites (Ti, Ta)C _x + Ca₃(PO₄)₂ for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca₃(PO₄)₂ mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have little or no influence on the burning velocity U and combustion temperature T _c. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.      

F离子掺杂TiO2的性能研究

以NH4F为掺杂剂，采用溶胶-凝胶法制备F离子掺杂型TiO2光催化剂，对其进行XRD、XPS和PL表征，结果表明，F离子掺杂ToO2由于Ti—F配位体的形成而能抑制金红石相的生成，同时F离子掺杂能增加TiO2表面缺陷浓度并降低Ti2P键的结合能，另外，由于F离子能取代Ti—OH配位体而降低了表面羟基氧浓度．光催化研究结果表明，F离子掺杂提高了TiO2光催化活性近1．5倍．     

Oxyfuel boiler design in a lignite-fired power plant

In the context of CO₂ capture and storage, the oxyfuel technology provides a promising option applicable in centralised power production schemes. This technology is based on combustion with pure oxygen instead of air and the flue gas mainly consists of CO₂ and H₂O. The work presented in this paper is focused in the application of the oxyfuel technology in a lignite-fired power plant. Significant design issues are the required extended flue gas recirculation in order to provide the ballasting effect of the absent N₂ and moderate the furnace temperatures. Therefore, a modified design of heat exchange surfaces of the oxyfuel steam boiler was formulated and was compared to a conventional air-fired boiler. A typical modern Greek air-fired power plant has been used as reference. The dominating factors that affect the dimensioning of the oxyfuel boiler are the higher radiative heat transfer - due to the high concentrations of CO₂ and H₂O in the flue gas - and the different flue gas mass flow, compared to a conventional air-fired boiler. For the determination of the thermodynamic cycle characteristics, simulations were made with the use of a thermodynamic cycle calculation software [Stamatelopoulos GN. Calculation and optimisation of power plant thermodynamic cycles, VDI-Regulations, Series 6, Nr. 340. Braunchweig, Mechanical Engineering Department; 1996 [in German]].