Search

Gel-mediated crystallization is a common system to produce self-organized materials, which is fundamental to the development of bottom-up approaches to functional complex materials. Mineralization in hydrogel matrices nevertheless remains empirical in the generation of crystallization products with tailored heterogeneous structures. We demonstrate that the employment of the hydrogels with proper cationic diffusivity can trigger the consecutive growth of oriented, granular-rhombohedral heterogeneous structures. The controllable morphogenesis leads to continuous calcitic CaCO3 films comprising spatial heterogeneity, where epitaxial match assumedly favors the successive deposition of both granular and rhombohedral layers. The scenario of consecutive growth is disclosed, where the thickness of the granular layers can become a valuable indicator to reflect the retardancy degree of crystallization. The evaluation of the physicochemical properties of the hydrogels finally establishes a direct correlation between the cationic diffusivity of the hydrogels and the appearance of the heterogeneous structures. The current work therefore sheds light on the implementation of rational morphogenetic approaches to crystalline materials with tailored complex architectures.

Strength, microstructure and austenitic grain size of a hot formed steel WHT1300HF after simulative hot stamping were studied by using universal testing machine for materials and optical microscopy. The results show that the yield strength of the hot stamping parts presented the tendency of earlier decrease and later increase with the extension of holding time, tensile strength was first reduced and then hold above 1400 MPa. In addition, the microstructure of the hot stamping parts was lath martensite, and martensite lath length and packet width increases with the heating temperature increased from 850 °C to 1050 °C. Especially, the effect of heat temperature on the original austenite grain size was more obvious, such as the austenite grains grew up quickly with the increase of heating temperature, and the original austenite grain diameter was 37.8 μm when the temperature reached 1050 °C.

The surface of hot-dip galvanized high strength low alloy (HSLA) steel easily occurs orange peel in the deformation process. On the other hand, the defects possess a specific directivity and sits at approximately a 45-degree angle to the sheet steel rolling direction. The microstructures and properties of steel specimens with the orange peel defects and the normal were analyzed, which results showed that their microstructures consist of ferrite and few granular pearlite. The yield point elongation of the HSLA steel resulted in the orange peel defects on the surface of sheet stamping and it is associated with skin rolling and stretch rolling process. Further studied on the fine microstructures by means of SEM and electron back scatter diffraction (EBSD) techniques, which was apparent for the defect steel that the orange peel defects were resulted from weak favorable {111} texture might be the key factors aggravating the formation of orange peel defects. It can be concluded that the formation of Cottrell atmospheres caused the yield point elongation by the interaction between dislocation and diffusive solute atoms as basic reason and the directivity of the orange peel defects was related with the LUDERS slip forming. The yield point elongation can be eliminated to avoid the orange peel defects beyond to 1.8% skin-rolling and stretch rolling method with an appropriate annealing technology.

The effect of different annealing temperature on microstructure and properties of the hot-stamping boron steel were studied.The results show that the yield strength of the test steel is reduced with increasing annealing temperature, only at 790°C,the specimen yield strength increased slightly, and showed a significant downward trend after 790°C.The specimen tensile strength and hardness with the change of the same trend when annealing temperature changes.And through the test we can see,at 760°C ,the test steel has entered a two-phase region,the test steel gain ferrite and pearlite when it is annealed below the temperature,it is easy to appear martensite microstructure when it is annealed in the higher temperature,and lead to the strength and hardness of the rise.

The high strength high plasticity high beneficial textile cold-rolling steel with 540MPa tensile strength 27% elongation 1.67 (111) textile index is developed in industry. The experimental results show that the ferrite fine grain around 5μm supports the properties of both high strength and plasticity, while the ferrite with percentage more than 90% leads to high elongation, and the large number second precipitation phase NbC with uniform fine size around 10nm is helpful to fine ferrite grain and form strong（111）textile fiber.

Micro-arc oxidation coating on ZAlSi12Cu2Mg1 alloy were prepared in Na2SiO3 electrolyte, effects of C6H8O7 and C3H8O3 as additive on resistances of micro-arc oxidation coatings were investigated. Results show that coatings containing completest ceramic particles were obtained on alloys surface processed in electrolyte solution including 2.0 g/L C6H8O7 additive, the size of micro-arc wholes becomes larger with more C6H8O7, and it has improved with 1ml/L C3H8O3 in the solution. The results of XRD analysis indicates that the coatings are mainly composed of alumina and mullite. EDS analysis showed the element contains sodium, oxygen, silicon and aluminum. Wear resistance of coating were increased by adding C3H8O3.

Using micro-arc oxidation technology in preparation Ti6Al4V alloy surface oxidation film, adding to the electrolyte H2O2, influence of H2O2 addition amount of oxidation film characteristics has been studied. The results show that, H2O2 addition amount of 4.0 g·L-1, positive critical arcs voltage minimum, for 338 V. SEM analysis showed that, electrolyte of H2O2 addition amount by 1.0 g·L-1 increased to 4.0 g·L-1, film hole diameter after decreasing, micro-arc oxidation film layer of density increases. Oxidation film surface roughness reduced to 7.619 when H2O2 addition amount for 4 g·L-1. With H2O2 addition amount from 1.0 g·L-1 increased to 4.0 g·L-1, micro-arc oxidation film in the wear process mass loss is reduced, wear resistance for promotion.

The experiment and finite element analysis were made to determine the pin-load distribution of multiple countersunk bolted single-lap joints. In the experiment, the pin-load fractions were evaluated indirectly by the lap-sheet surface strains collected from a few rows of strain gages. The joint strains and pin-load distribution were also obtained directly in the finite element analysis. The calculated strains correlated well with the experiment. Nevertheless, the pin-load fraction results of the both techniques are quite different. The further analysis revealed that the procedure of transforming the measured strains into pin loads is not reliable, since the intrinsic additional bending had not been taken into account. Therefore the appropriate way to determine the pin-load distribution should be the numerical analysis validated by the strain measurement. The another attempt showed that the pin-load distribution can be evaluated by the finite element modeling of two-dimensional shells and beams as well with satisfied accuracy.

In view of the fact that the two-dimensional square pore network model screened many microstructure features and transfer characteristics inside porous media, a fractal pore network model for unsteady drying process of natural porous body was developed on the base of fractal geometry theory and transport process principle, which took various factors into consideration, such as the liquid-phase flow, vapor-phase diffusion, temperature gradient, and pore microstructure characteristic.

In order to validate the model established in reference [1], a drying experimental study was conducted, and numerical simulation was carried out under the same environmental condition. The experiment and simulation results indicated that the fractal pore network model could explain the drying process of real porous media effectively, the drying curve of fractal models was more consistent with the real drying curve than that of regular models, and its moisture fields well reflected the drying kinetics characteristic of real porous media. There was no correlation between the pore fractal dimension and the drying time, and the simulation result of unsteady-state heat transfer was more consistent with a real drying process than that of steady-state heat transfer for the convective thermal drying.

Taking the sand bed as the simulated object, a pore network model for drying of real porous media is developed by applying the invasion percolation theory and transport process principle, which fused the physical parameters of sand bed, such as porosity, pore mean diameter, pore size distribution, into the model parameters. The experiment and simulation results indicated that this model could explain the drying process of sand bed well. The throat size distribution has a great effect on the drying process.

The research is conducted to analyze the micro structure of TiC/7075, a composite material and to study its wear properties. TiC/7075 composites produced under different sintering temperatures and with different particle contents are prepared with the help of the powder metallurgy technology. The result shows that with the increase of the TiC content, the microstructure of TiC/7075 composites tend to have the form of equiaxed crystal. The microstructure of the composite material with 8% of TiC shows the uniform and fine properties, making it have the properties of the equiaxed crystal. The hardness and the wear resistance increase with the increase of the content of TiC. Also with the increase of the sintering temperature, the sharp edge of the hole becomes smooth. The wear resistance of TiC/7075 composites is superior to 7075 matrix alloy, and the wear mechanism of TiC/7075 composites is adhesive wear and abrasive wear.

A pore network model for drying of grain materials was established on the base of pore network theory and transport process principle, and a corn drying experiment was conducted to verify the validity of this model. The experiment and simulation results indicated that this model could explain the drying process of grain materials well. There is a significant difference between the corn and pore vapor temperature, and it is unreasonable to confuse the two kinds of temperature. The particle size distribution has a great effect on the drying process. The higher the uneven degree of particle size distribution was, the slower the grain materials were dried and the more unbalanced the moisture distribution appeared.

Using fly ash from the power plant and SiO2 as the main raw materials, glass-ceramic was prepared by melting method. By means of DSC, XRD and SEM, the crystallizations of CaO-Al2O3-SiO2 system glass-ceramic were studied. The results show that it is more and more difficult to crystallize as the content of SiO2 increases. When the content of SiO2 reaches to 41.5%, the crystal nucleus form in the form of shuttle shape, the crystals develop in the same direction for a certain zone. But the crystals develop into hexagon shape finally when they are heated for 1 h at 1100°Cafter nucleation at 780°C.The developed crystals are anorthite. The sizes of crystals are between 1- 1.5μm, their microhardness can reach HV804.

7075 matrix alloy was fabricated by in-situ reaction liquidus curve casting method, and its as-cast microstructure was analyzed, the wear properties of these composites and matrix alloy were studied under the different conditions. The results show that the wear resistance of TiC/7075 composites is superior to 7075 matrix alloy in the same conditions (with same load or rotating velocity). Because of introduction of particle reinforcements, the wear resistance of the composite is enhanced by 1.5～4 times than that of its matrix. In addition, the wear mass loss of TiC/7075 composites increases almost with increase of load, but decreases with increase of rotating velocity. The wear resistance of the composites increases slightly at low load and high rotating velocity. The SEM analysis of the worn-out surface indicates that the wear mechanism of TiC/7075 composites is mainly abrasive wear.

In this paper, with sodium carbonate as an auxiliary agent in the fly ash, the mixtures were sintered at 880°C for 90 min, then dissolved by different concentrations of sulfuric acid respectively for extracting the hydrated silica. The results show that when the activated ash fly is dissolved by different concentrations of sulfuric acid, the dissolution rates of ash fly increase with the concentration of sulfuric acid increasing. Impurities of aluminum and iron atoms are present in an orderly array of micro-andalusite structure in the generative hydrated silica. When they are dissolved by sulfuric acid for 2%(wt%), the orderly structure is destroyed obviously, and the aluminum and iron atoms are separated out. The purity of hydrated silica can reach 99.9%.

The die-cast AZ91D magnesium alloy (mass fraction: Al 8.5-9.5%, Zn 0.5-0.9%, Mn 0.17-0.40%, Si 0.05%, Fe 0.004, balance Mg) was used as the substrate material in the present work. The dimension of the rectangular samples was 30 mm 20 mm 3 mm. Prior to ABSTRACT Ceramic coatings were fabricated on AZ91D Mg-alloy substrate by microarc oxidation in Na2SiO3- NaOH-Na2EDTA electrolytes with and without C3H8O3 addition. The effects of different concentrations of C3H8O3 contained in the electrolyte on coatings thickness were investigated. The surface morphologies, RMS roughness, phase compositions and corrosion resistance property of the ceramic coatings were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and electrochemical corrosion test respectively. It is found that the addition of C3H8O3 into silicate electrolyte leads to increase of the unit-area adsorptive capacity of the negative ions at anode-electrolyte interface and thus improves the compactness and corrosion resistance of the MAO coating. The coating thickness decreases gradually with the increase of concentrations of C3H8O3 in the electrolyte. The oxide coating formed in base electrolyte containing 4 mL/L C3H8O3 exhibits the best surface appearance, the lowest surface RMS roughness (174 nm) and highest corrosion resistance. In addition, both ceramic coatings treated in base electrolyte with and without C3H8O3 are mainly composed of periclase MgO and forsterite Mg2SiO4 phase, but no diffraction peak of Mg phase is found in the patterns.

In this paper, in order to predict the residual deformation of thick spherical structure, a welding program is compiled in APDL language based on Ansys and a numerical welding experiment of a welding example is carried out. The temperature field of welding was simulated firstly, then a thermal-structure coupling analysis was carried out, and at last the residual stress and deformation after welding were got. After that, the numerical experiment result was compared with physical experiment one. The comparative analysis shows that the numerical simulation fits well with physical experiment. On the basis of that, a three-dimensional numerical experiment of a thick spherical shell structure was carried out to get the changing rule of stress and deformation of a thick spherical shell structure during welding. The research is of great value to the prediction of residual deformation and high precision machining.

Objective The purpose of this study is to explore the growth, differentiation and osteogeneration of bone marrow stromal cells (BMSCs) on partially demineralized bone matrix (pDBM) and to generate bone tissue by tissue engineering approach in vivo. Methods Demineralized bone was processed from femur head of Shanghai white swine. Calcium content, porosity and pore size was measured respectively. In vitro osteogenic differentiated human BMSCs of passage 3 were seeded in pDBM. Adhesive rate of cells to pDBM was calculated 24hours after seeding. Distribution, growth and proliferation of BMSCs on pDBM were observed with fluorescent DiI labeling. Matrix disposition was analyzed with SEM observation. Cell-material complex was implanted subcutaneously in nude mice. The implants were harvested at 8, 12 weeks post surgery and samples were observed by H&E staining. Results BMSCs adhered well on the material and the distribution of cells was uniform. The adhesive rate is 99.1%±1%. New bone formation was observed in implant of 8, 12 weeks respectively. The newly formed bone was generated on the surface of the residual material and a layer of cells with typical characteristic of osteoblast was observed to adhere on the surface of the new bone. Conclusion With good biocompatibility to hBMSCs, pDBM could serve as ideal scaffold for bone tissue engineering both in vitro and in vivo.

In this study, grooving and cutting tests were carried out to evaluate cutting performance of soda-lime glass using an ultra-precision lathe with a single-crystal diamond tool. The machined workpiece surface topography, chip formation, and surface roughness were examined using SEM and AFM. Tool wear was measured using a Nomarski microscope. Experimental results indicate that with the depth of cut increasing, there is a ductile-brittle transition in cutting of soda-lime glass materials. Under different cutting conditions, two types of surfaces are achieved: ductile cutting surface and fractured surface. Chips always formed in an irregular and discontinuous shape. Cutting modes have a significant effect on the machined workpiece surface roughness. Tool wear mainly occurs on the flank face and its wear mechanism is dominated by abrasion. Ductile cutting can be achieved when the undeformed chip thickness is less than a critical value.

Micro bore finishing for metal and ceramic materials has been a challenge in the manufacturing industry. Unfortunately, little is understood about how to polish a micro bore and how to assess its inner wall quality because it is difficult to access the micro bore for either polishing or measurement. This article reports on a feasibility study of the abrasive flow polishing of micro bores of 260 similar to 500-mum diameters and 25 similar to 50 length/diameter ratios for both metal and ceramic materials. An abrasive flow polishing machine was designed and built with turbulent flow characteristics. Polishing of steel S45C bores of 400- and 500-mum diameters, stainless steel 304 bores of 500-mum diameter, and zirconia bores of 260-mum diameter was conducted. Surface roughness and topography of the polished inner walls of micro bores were characterized using profilometry and optical interferometry from the three-dimensional point of view. Significant reduction in surface roughness of the micro bore inner walls has been made in the polishing processes. The results indicate that it is feasible to apply the abrasive flow polishing technology for metal and ceramic micro bores of diameters of 260 mum or larger and the length/diameter ratios of 25 or higher. It is found that surface roughness of the polished micro bore inner walls decreases with an increase of the abrasive flow passes.

KTiOPO4 samples were implanted by Bi+ ions with energies from 100 to 350 keV in increments of 50 keV. The depth distribution and diffusion behavior of implanted Bi+ into KTiOPO4 were investigated by normal and oblique incidence Rutherford backscattering. The results show that the maximum difference between experimental and calculated values of the mean projected range is less than 22%; the experimental range straggling somewhat deviates from the prediction by TRIM'98. After annealing, the redistributions of implanted Bi+ ions in KTiOPO4 do not obey Fick’s law, and there is a segregation process to the surface for 700 °C annealing. After 800 °C annealing for 30 min, most of the segregated Bi+ ions had evaporated, and the distribution of the remaining Bi+ ions became flat.

2.0 MeV Au+ ions were implanted into different Si substrates with a fluence of 2×1015 ions/cm2 at room temperature with different angles of incidence. Tested Si substrates are amorphized Si, amorphous Si film and crystal Si. The mean projected range, range straggling and lateral spread have been studied by Rutherford backscattering (RBS). The results show that (1) the experimental mean projected range is larger than the value predicted by TRIM (transport of ions in matter) by around 20%; (2) the experimental range straggling and lateral spread deviate significantly from the TRIM predictions; (3) after the correlation between nuclear and electronic stopping is included, the agreement between experimental and calculated values is markedly improved.

Polyimide (C22H10N2O5)n was implanted with Bi+ and Fe+ ions at different energies, doses, and angles. The depth distribution of implanted Bi+ and Fe+ ions in polyimide was measured by Rutherford backscattering. The results show: (1) For the case of 2×1015 Bi+ ions/cm2, the depth distribution was nearly Gaussian for both energies; for the case of 1×1016 Bi+ ions/cm2, diffusion behavior during implantation is observed. (2) For the case of 1×1016 Fe+ions/cm2, the depth distribution was Gaussian for 200 keV, and the depth distributions of the as-implanted Fe+ ions become bimodal and have a split behavior under 0° and 45° for 350 keV. (3) For a regular distribution, the experimental mean-projected range is in good agreement with the calculated value, within less than 6%, the experimental range straggling is larger than the calculated one based on TRIM'98.

Polyimide (C22H10N2O5)n films were irradiated at room temperature by 200, and 300 keV Yb+ and 400 keV Er+. The dose was 1×1015 ions/cm2. The Rutherford backscattering technique has been used to study the diffusion behavior and the depth distribution of implanted Yb+ and Er+ in polyimide (C22H10N2O5)n. The results show that (1) for the sample annealed at lower temperature, the migration of Yb+ and Er+ into the overlying polyimide is faster than into the undamaged polyimide, but there is a significant non-Fickian tail extending deep into the undamaged polyimide film, (2) oxygen loss was observed, and (3) the depth distributions of “as implanted” Yb+ and Er+ were nearly Gaussian in all cases. The x-ray photoelectron spectroscopy was used to study the structural modification. After ion implantation, the binding energy of carbon 1s, nitrogen 1s and oxygen 1s in polyimide was decreased.

It was reported [1] that a preferential c -axis orientation exists in Tl-1223 bulk superconductor with a nominal composition of (Tl 0.5 Pb 0.5 )(Sr 0.8 Ba 0.1 ) 2 Ca 2 Cu 3 O z . Now the condition under which the preferential orientation can form and the factors which lead to preferential orientation have been investigated. The results indicated that, in the (Tl 0.5 Pb 0.5 )(Sr 2− x Ba x ) Ca 2 Cu 3 O z system with Sr content increasing and Ba content decreasing, the distance between atoms in the a - b -plane shortens more drastically than that between adjacent atoms along the c -axis, and when x decreases to 0.2, the bond strength between atoms in the a - b -plane becomes much stronger, and then the crystalline grains grow preferentially in the a - b crystallographic direction and show a plate-like shape. Later, these platelets realign at the partial-melting stage due to the existing liquid phase, so the preferential c -axis orientation is obtained.

The interference effect of periodic negative and positive refractive index multilayer thin films is investigated. The ultra-wide reflective band and rippleless in transition region are presented great different from the normal multilayer thin film coatings.