The thermal behavior and kinetic parameters of decomposition reaction of limestone in a temperature-programmed mode were investigated by means of TG. The experimental results show that the kinetic model functions in different forms for the thermal decomposition reactions of different limestone grain sizes in dispersing state under the atmosphere of static air are 4(1−α)3/4 for small size limestone and (1−α) for large size limestone. Information was obtained on the relationship among the decomposition temperature, decomposition time, decomposition fraction, decomposition reaction rate constant and grain size of limestone.
A preparation technology of chloride contaminated resistant concrete was presented. The newly developed non-steady-state migration test method was employed for the evaluation of chloride ions diffusion coefficient of the concrete. The experimental results show that this method has a good correlation with the traditional NT Build 443 method, and it provides an effective and quick approach to assess the resistant capacity of concrete against chloride ions.
The eco-material composition is not well-distributed in preparation. The eco-material samples were taken for computer image analysis, and its particle numbers and appearance parameters were measured. Based on the mechanism of connective mixing and diffusion, the particles distribution was simulated by a computer using the random walk with Levy flight. The results show that the eco-material microstructure simulated by a computer has an idealized porous structure. The particles distribution has a cluster characteristic that changes with the different size and number of particles in Levy flight trajectory. Each cluster consists of a collection of clusters and shows a structure of self-similar cluster, hence presents a well-defined fractal property. The results obtained from SEM observation are in good agreement with the numerical simulations, and show that the convective mixing presents in the Levy flight walk.
The ground powders with the same particle size distribution and the same mean particle diameter were prepared by five different types of mills. The flowability index (FI) and the particle shape indices, namely, Wadell's working sphericity Φ w and circularity Φ C, of five kinds of test powders were measured. The effect of the comminuting mechanisms on the flowability of ground powders was investigated, and the relationship between the flowability of ground powders and the particle shape indices was analyzed. The experimental results show that the ground powders obtained by collision have irregular particle shapes and smooth surfaces, showing a high flow-ability. On the other hand, though the particle obtained by grinding is close to a spherical particle, but it has a rugged surface, and shows a bad flowability. Furthermore, the flowability index is more correlated with the circularity than the working sphericity is. This means that the surface roughness is more effective in determining the flowability of powders than the roundness is.
The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn packed with activated carbon at pH 9.0. The nickel was eluted from the minicolumn with 10% (v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10mL was obtained. The detection limit (DL) of nickel with the use of the preconcentration method was 13ng·g−1 in the original solid sample. The precision for 10 replicate determinations at 150ng·g−1 nickel concentration was 5.2% relative standard deviation (RSD). The calibration graph was linear with a correlation coefficient of r=0.9996 up to concentration of 660ng·g−1 nickel.
A new complex [Cu(C12H8N2)2]1.5PW12O40·1.5H2O was synthesized under hydrothermal conditions. The complex was characterized by the elemental analysis, SEM, X-ray powder diffraction analysis, IR, UV-Vis spectroscopy, and TG thermal analysis, respectively. The experimental result shows that the heteropolyanion is of a Keggin structure containing coordinated cations. Photochromism studies show that the electron transfer takes place from the organic compound to the heteropolyanion.
A tentative idea of developing a liquid-catalytic system on methanol anode oxidation was proposed by analyzing the characteristics of methanol anode oxidation in direct methanol fuel cell. The kinetics of methanol oxidation at a glassy carbon electrode in the presence of nicotinamide adenine dinucleotide (NAD+) was investigated. It is found that the current density of methanol oxidation increases greatly and the electrochemical reaction impedance reduces obviously in the presence of NAD+ compared with those in the absence of NAD+. The catalytic activity of NAD+ is sensitive to temperature. When the temperature preponderates over 45°C, NAD+ is out of function of catalysis for methanol oxidation, which is probably due to the denaturation of NAD+ at a relatively high temperature.
The process for face milling of (α+β) titanium alloy while using minimum quantity librication (MQL) as the cooling technique was optimized by using of the Taguchi method to improve characteristics. The cutting speed, feed rate, and depth of cut were optimized with consideration of multiple performance characteristics including tool life, volume removed and surface roughness. The experimental results show that the multiple performance characteristics can be simultaneously improved through this approach, and the feed rate is the most influential cutting parameter in the face milling of titanium alloys.
To study the effect of chitosan-gelatin blends on the growth and proliferation of in vitro cultured bone marrow stromal cells (BMSCs) and explore a new carrier for the application of tissure engineering, cells from long bones of young rabbitsaged less than two weeks were expanded in vitro for one week and seeded onto the surface of pure chitosan and chitosan-gelatin blends. Cells attached to and proliferated on both pure chitosan and chitosan-gelatin blends were monitored with the aid of an inverted light microscope and a scanning electron microscope. The cell viability was monitored by MTT after 2, 4, 6, 8 days seeding. BMSCs could be attached to and proliferated on both pure chitosan and chitosan-gelatin blends and remain their morphologies seen in vivo. Chitosan-gelatin blends could promote BMSCs to proliferate (P<0.01). It is confirmed that chitosan-gelatin blends maintain the bioactivity feature of chitosan and even enhance the growth and proliferation of in vitro cultured BMSCs because of the adding of gelatin. It is a potential carrier for the delivery of cells tissue engineering.
The optical properties of matrix of porous glasses and phase-separated glasses were investigated by visible spectroscopy and infrared spectroscopy. The experimental results show that, both the porous glasses and phase-separated glasses have very good light transmission in visible light region that wavelenth is longer than 560 nm. The micropores of porous glasses and the boron-rich phase of phase-separated glasses have strong Rayleigh scatter effects on the visible light, the largest scatter occurrs at 360–370 nm; the thicker the glasses, the larger the light scattering. Thus, the pare size distribution and the size of heterogeneous micro zone in boron-rich phase of phase-separated glasses can be measured. After coupled into porours glasses, the most intense absorption of hydrated ions of [Co(H2O)6]2+ shifts from 508nm to 515nm. The production of the most intense absorption and the red shift were owed to Jahn-Teller effect of octahedral field formed by six H2O molecular and perturbation effect resulted by microporous of porous glasses for its physics-chemical circumstance. As a result, the porous glasses are perfect optical function materials in visible region, which can be assembled by chemical method.
The dynamics of phase separation in two-dimensional binary fluid with low-middle densities was investigated by molecular dynamics simulation. The spinodal decomposition region for symmetric systems may be divided into the diffusive and kinematic region. At an elevated temperature, the motion of particles is diffusive. At a middle temperature, the kinematic mechanism takes effect on the systems with middle density, and the diffusive mechanism holds only for the dilute system. At a low temperature, the phase separation obeys the kinematic mechanism in a wide range of density. For asymmetric systems, the growth of particles A (majority) is different from that of particles B (minority). The diffusive and kinematic regions for the majority are similar to those of symmetric system. The growth exponent for the minority is related to its absolute density and temperature because of its small density.
A SiCw/Al composite was fabricated through a squeeze cast route and cold rolled to about 30%, 50% and 70% reduction in thickness, respectively. The length of whiskers in the composite before and after rolling was examined using SEM. Some of the rolled composites were annealed by recrystallizing to remove the work hardening of the matrix alloy. The hardness of the rolled and annealed SiCw/Al composites was examined and then associated with the change of the whisker length and the work hardening of the matrix alloy. It was found that the hardness was a function of the degree of cold rolling. For the cold rolled composites, with the increase in the degree of cold rolling, the hardness increases at furst, and decreases when the degree of cold rolling exceeds 50%. For the annealed ones, however, the hardness decreases monotonously with the increase in rolling degree. The different changes in hardness between the rolled and annealed composites could be attributed to a result of the competition between the work hardening of the matrix resulting from the cold rolling and the work softening arising from the change of whisker length.
A new kind of in-situ ceramic consolidation molding process was investigated on the basis of the characteristics of starch swelling in water and gelatinizing when heated. The SiC ceramic suspension containing about 50vol% solids loading and about 3wt% starch can be cast and molded into various complex-shape SiC ceramic parts in a water-thermostat. The dry shrinkage of the green body was less than 1.0% when the solid volume fraction of SiC suspension was up to 52.5%. The density and pore size were homogeneously distributed inside the biscuits. Soaked with melt silicon in a vacuum arc furnace, the biscuits were turn into SiC ceramic materials with homogeneous structure and high performances.
The nanosized Ca3Co2O6 powder was synthesized via sol-gel process. The phase composition was characterized by means of X-ray diffraction. Polycrystalline samples of Ca3Co2O6 were prepared by a sintering procedure of nanosized power. The seebeck coefficient and electrical conductivity of the samples were measured from 450K up to 750K. The results show that the Seebeck coefficient increases with the increasing temperature. The electronic structures were calculated using the self-consistent full-potential linearized augmented plane-wave (LAPW) method within the density functional theory. The relationship between thermoelectric property and electronic structures was discussed.
High-yielding low-cost vanadium oxide nanotubes were prepared by hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discovered to determine the content of V (IV) in vanadium oxide nanotubes by thermogravimetric analysis (TGA). This method can be extended to determine the content of low oxidation state in other transition metal oxide nanomaterials.
The homogeneous glass sample for the (1−x)As2S3−xCdBr2, where x=0.015, 0.035, 0.05, was prepared by the conventional melt-quenched method. Amorphous (1−x)As2S3−xCdBr2 alloys were determined by X-ray diffraction, thermal comprehensive analysis and Raman scattering. The glass transition temperature (Tg) decreases a bit with the addition of CdBr2. Based on the experimental data, the microstructure is considered to be the discrete molecule species of AsBr3 and Cd−S atomic bonds or clusters are homogeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges.
The microstructural evolution and phase transformations of mechanically stirred non-dendritic ZA27 alloy during partial remelting were studied by using scanning electron microscopy and X-ray diffraction technique. The partial remelting temperature was 460°C and lower than the stirring temperature of 465°C. So the microstructure with globular grains needed for semi-solid forming can not be obtained and the starting primary nondendritic grains change in turn to connect non-dendritic grains, long chain-like structures and finally to coarsen connect grains. However, the small near-equiaxed grains between the primary non-dendritic grains are evolved into small globular grains gradually, some of which are also attached to the primary non-dendritic grains during the subsequent heating. The X-ray diffraction results show that a series of phase transformations, α+ν+ε→β, ν+β→L, β→α′+L, α+η+ɛ→α′ and α′→L, occur successively during this process. The main reason why the starting primary non-dendritic grains do not separate into the needed independent globular grains is that the reactions of ν+β→L and α′→L do not occur or occurr incompletely in the layers used to connect the primary nondendritic grains.
The dielectric ceramics with a main crystal phase of MgTiO3 and additional crystal phase of CaTiO3 were prepared by the conventional electronic ceramics technology. The structures of MgTiO3 are ilmenite-type, and belong to hexagonal syngony. The ratio of MgTiO3 to CaTiO3 can be adjusted to gain a zero temperature coefficient of ɛ and a higher ɛ for the system. The effects of B2O3 doping on the dielectric properties of MgTiO3-CaTiO3 (MCT) ceramics were investigated. The addition of B2O3 decreases the sintering temperature and results in rapid densification without obvious negative effect on the Q values of the system (Q=1/tan δ). B2O3 exists as liquid phase in the sintering process, promoting the reactions as a sintering agent.
By making castings that pick up gas from moisture in red sand molds, the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al−25% Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw” tendency. In addition to primary silicon refinement, the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.
A theoretical model was presented to calculate the laser intensity distribution and the particle temperatures at different sites of the workpiece in the laser cladding process. By using this model, the effects of the powder feeding rate on the laser intensity distribution and the particle temperatures were investigated, the calculated results under the condition of different injection angles were also plotted. It is shown that with increasing the injection angle, the laser intensity distributions are similar but the peak value of the laser intensity decreases. Simultaneously, the peak value of the particle temperature increases and the distribution of the particle temperatures gets central symmetrical gradually. These tests results should be considered in model of laser cladding due to their subtle effects on the dynamic processes in laser molten pool.
Some properties of nano SiO2 modified PVF adhesive were studied. The experimental results show that nano SiO2 can improve the properties of PVF adhesive very well. Meanwhile the modification mechanism of nano SiO2 to PVF adhesive and the applications of this adhesive in paper-plastic composite, concrete and fire-proof paint were discussed by using IR and XRD determination.
Neoprene latex modified emulsified bitumen and fine aggregate are used to prepare a new type of stress-absorbed material, which has strong ability of anti-reflective cracking on asphalt concrete over layer-constructed upon a semi-rigid type base course or cement concrete pavement block. Experimental results demonstrate the stress-absorbed material have excellent mechanical properties including a low modulus of elasticity, high ultimate tensile stress and strain, and a strong distortion ability. Stress concentration in asphalt over layer originated by temperature changes and traffic loads can be alleviated.
The properties of high performance color hardener (HPCH) and the mechanism were studied. HPCH is a composite system, which is composed of cementitious and auxiliary cementing materials, composite additives, abrasion resistance component (aggregate) and pigment. The porosity and pore structure of the material are obviously improved due to the activation, filling and adsorption of auxiliary cementing materials, thus resulting in a great increase of binding capacity for ions in HPCH and the obstacles of ion migrating. The density of material structure, bonding capacity of cementitious material to the abrasion-resisting component and the corrosion resistance are greatly and effectively improved by adding the auxiliary cementing materials and compound additives. According to the tests of dry shrinkage, sulphate resistance, chloride permeability and Ca(OH)2 content distribution, the property superiority of HPCH is analyzed. The mechanism of materials modification of HPCH is explained from the microscopic point of view by testing the pore structure and pore distribution via the mercury intrusion pressure method.
Effects of water to binder ratio (mW/mB), types and addition content of mineral admixtures on the autogenous relative humidity (ARH) change of concrete resulting from self-desiccation were studied. The parameters of coefficient of mineral self-desiccation-effect k and efficient water to binder ratio re were proposed, and experimental results were fitted non-linearly and analyzed using these proposed parameters. The experimental results indicate that ARH reduction of concrete at different ages increases with the decrease of mW/mB. The ARH change laws of concrete with mW/mB lower than 0.4 can be expressed with a non-linear equation. The extent of the effect of types and addition content of mineral admixtures on ARH reduction of concrete resulting from self-desiccation can be reflected by the non-linear equation with the parameter of efficient water to binder ratio re effectively.
Granular wastes have negative effects on the environment due to contamination. On the other hand, stony components in granular wastes have a potential good perspectives for utilization in civil engineering works as secondary raw building materials. To reuse such materials without environmental risks, all contaminants must be removed or reduced to an acceptable level. Therefore liberation of materials is an important step in waste treatment. For this purpose, separation and cleansing techniques are suitable. Based on the analysis of contaminants in wastes, it is discussed how to select suitable techniques. The rules for technique selection and processes for quality improvement are set up. To evaluate the environmental quality and technical quality of output products, it is necessary to check leaching behaviours and physical properties.
A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structure of ERF. Combining the scheme of the classical conductivity model for the single-chain structure, a new formula for the prediction of the shear yield stress of ERF was set up. The influences of the separation distance of the particles, the volume fraction of the particles and the applied electric field on the shear yield stress were investigated.
The theory calculation formula is deduced about stress distribution in cross section and changes in Martensite percentages with the section height of random section shape bar under the action of the bending moment according to the Brinson's Constitutive Relation. The bar's energy dissipation capability under circulation of bending moment was analyzed and the calculation theory was set up. By using MATLAB program and the numerical calculation for uniform rectangle cross section bar, the relationships among the maximal stress and strain on cross section edge with bend load, the stress and Martensite percent's with cross section height, the energy dissipation capability with cross section height, and the energy dissipation capability with maximal strain on cross section edge are gained, also those curves are discused. It is put forward that the SMA material can be used for passive structure vibration control to dissipate energy of bend load.
In order to understand the change regulation of residual stress during multi-repaired welding to provide theoretical guidance for correct repaired welding procedure and improvement of joint properties, and to simulate the magnitude and distribution of residual stress using the finite element method (FEM). A model of temperature field of weld-repaired using FEM, which was simplified, was established. The weld stress consists of thermal stress and organization stress. Models of the thermal stress and organization stress were described. ANSYS, a software of finite element, was applied to calculate the stress, BHW35 steel was taken as an example, the simulated and experimental results for the 1st, 3rd and 5th weld-repaired were analyzed, the simulated results are in good agreement with experimental results. It can be concluded that the residual stress in the weld center changes little, and the high residual stress exists in HAZ. And in the same place, the more repaired weld, the higher residual stress, and the area of residual stress becomes wider.
Cordierite precursor was obtained through a process, which involved the decomposition of metal nitrates on the surface of ultrafine carbon black powder between 100–300°C and the gasification of the carbon black at higher temperature in air. The average size of the particles, which were heat-treated at 700°C for 10h, is about 1020 nm, and the specific surface area is about 129 m2/g. The experimental results show that the ultra-fine particles of cordierite precursor can be produced by this process. The precursor powder was calcined at different temperatures. X-ray diffraction examination indicates that β-quartz is crystallized from the amorphous matrix around 850°C firstly and then MgO-Al2O3 spinel and α-cordierite appears. Above 1000°C, MgO-Al2O3 spinel and cristobalite disappear gradually and form an intermediate phase (sapphirine). At around 1300°C, the main phase is α-cordierite, and no other phase is detected.
A method of fuzzy modeling based on fuzzy clustering and Kalman filtering was proposed for predicting Ms temperature from chemical composition for martensitic stainless steel. The membership degree of each sample was calculated by the fizzy clustering algorithm. Kalman filtering was used to identify the consequent parameters. Only Grade 95 steel are available for training and validation, and the fuzzy model is valid for the following element concentration ranges (wt%): 0.01<C<0.7; 0<Si<1.0; 0.10<Mn<1.25; 11.5<Cr<17.5; 0<Ni<2.5; 0<Mo<1.0. Compared with that of several empirical models reported, the accuracy of the fuzzy model was almost 5 times higher than that of the best empirical model. Furthermore, the compositional dependences of Ms were successfully determined and compared with those of the empirical formulae. It was found that the specific element dependences were a function of the overall composition, something could not easily be found using conventional statistics.