The structures and dielectric properties of Ba6−3xNd8+2xTi18O54 system(x=2.3) doped with different contents of Bi2O3, whose final molecular formula is Ba6−3x(Nd1−yBi y)8+2xTi18O54 were investigated. It is indicated that the dielectric constant increases greatly whereas Q value( f 0=4 GHz) decreases with the increase of Bi2O3 content. However, the temperature coefficient could be controlled below 0±30×10−6/°C in the experiment. These phenomena are related to the appearance of a new phase, Bi4Ti3O12, which has high dielectric constant. Also, that Bi3+(0.13 nm) substitutes for Nd3+(0.099 5 nm) will increase the unit cell volume, which will lead to the enlargement of the octahedron B site occupied by Ti4+. So the spontaneous polarization of Ti4+ ions will be strengthened. Besides, Bi3+ will fill up some vacancies which Ba2+ or Nd3+ ions leave in two A1 sites and four A2 sites. More positive ions polarize, which also contributes to higher dielectric constant. The samples got with the optimium properties are sintered at 1 200 °C for 4 h, when y=0.25, ε≈.110, Q≈5 400(f 0=4 GHz), TCC=−4.7× 10−6/°C; When y=0.3, ε≈120, Q≈5 000(f 0=4 GHz), TCC=−24×10−6/°C.
The residual formaldehyde (HCHO) in fabric was degraded using photo-catalysis assisted by the compound catalyst of nano-TiO2 and nano-ZnO. The effects of several factors on the degradation, such as the composing of catalyst, irradiation time, pH value and the H2CHO concentration of the immersed solution were investigated. Results showed that H2CHO of the immersed solution had degraded 93% after 5 h irradiation, and the degradation ratio of formaldehyde could be improved and the aging of the fabric can be avoided with the addition of ZnO nanoparticles and pH value of the immersed-fibric solution. The fabric with residual formaldehyde about 1 800 γ/g can be efficiently treated to satisfy the China National Standard (GB/2912.1-1998) with the photo-catalytic degradation.
SMn xZn1−xFe2O4 (x=1,0.9,0.8,0.7,0.6,0.5,0.25,0) nanoparticles were prepared by ball-milling hydrothermal and investigated by X-ray diffraction, DTG and TEM. Nanocrystallite grain size was determined by X-ray linewidth to be from 63 Å to 274 Å. The thermal properties indicate absorbed water still remain at low temperature, crystalline wate will be decomposed from 230 °C to 260 °C, partial Mn2+ will be oxidized near 730 °C. TEM shows the ferrite particles pocess a spherical morphology and uniform nanosize.
Pure TiO2 thin films and iron doped TiO2 thin films on glass substrate were prepared by sol-gel method, and characterized by X-ray diffractometer (XRD), thermo-gravimetric analysis (TG-DSC), high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and UV-Vis spectroscopy, respectively. The experimental results show that the pure TiO2 thin films and iron doped TiO2 thin films can destroy most of the escherichia coli and bacillus subtillis under the irradiation of 365 nm UV-light. However, the iron doped TiO2 thin film is a better photocatalyst than pure TiO2 thin film. The ultrastructural studies provide direct evidences for understanding the bactericidal mechanism of the TiO2 photocatalyst.
Several batches of NiCr alloy thin films with different thickness were prepared in a multi-targets magnetron sputtering apparatus by changing sputtering time while keeping sputtering target power of Ni and Cr fixed. Then the as-deposited films were characterized by energy-dispersive X-Ray spectrometer (EDX), Atomic Force Microscope (AFM) and four-point probe (FPP) to measure surface grain size, roughness and sheet resistance. The film thickness was measured by Alpha-Step IQ Profilers. The thickness dependence of surface roughness, lateral grain size and resistivity was also studied. The experimental results show that the grain size increases with film thickness and the surface roughness reaches the order of nanometer at all film thickness. The as-deposited film resistivity decreases with film thickness.
The microstructured surface of materials were fabricated by a two-step acid-base catalyzed sol-gel process. In fluorinated polymer with PTFE doping, the well-proportioned composite sols were prepared using sol-gel processing under the hydrochloric acid and deficiency of water conditions. After the substrate was coated by composite sols, and the gelation treatment on the surface of composite coating, the micrometer-scale and nanometer-scale hierarchical structures were formed in surface layer of material. XPS and TEM technologies were employed to identify that the gelation occurs just on the surface of composite coating. The morphology of coating surface was observed by SEM and AFM technologies. The microstructured surface of material can be fabricated using this inexpensive and easily controlled method on low surface energy resin materials, the super-hydrophobic coatings materials can be prepared.
NdTbCo/Cr amorphous films with high perpendicular magnetic anisotropy were prepared onto glass substrates by rf magnetron sputtering. The effects of Nd substitution on the magnetic and magneto-optical properties of TbCo/Cr films were investigated. It was found that partial Tb substitution by Nd would increase the saturation magnetization and the Kerr rotation angle, change the temperature dependence of magneto-optical characteristics. These results can be explained by the ferrimagnetic structure of the rare earth-transition metal alloy. When the magnetic layer composition was (Nd0.265Tb0.735)31Co69, a saturation magnetization of 247 emu/cm3 and a coercivity of 3.8 kOe at room temperature could be obtained.
The influences of mass concentration of nickel chloride hexahydrate, sodium borohydride, ethylenediamine, pH value, bath temperature on deposition rate were studied with orthogonal experiments by a series of pre-treatments on micro-diamond particle, and the optimized parameters were obtained. Both the morphology and the composition of original diamond and the diamond with Ni-B coating were analyzed by SEM and XRD respectively. The SEM image shows that the spherical Ni-B particle is coated upon diamond. XRD pattern shows that the coating compositions are Ni and Ni2B.
A new process to synthesize polycrystalline samples of Sr14Cu24O41 was presented. Firstly, dry gel powder of Sr14Cu24O41 was synthesized by the citrates sol-gel method, using Sr(NO3)2, Cu(NO3)2, ethylene glycol and citrate acid as raw materials. Then, polycrystalline samples of Sr14Cu24O41 were prepared by solid-state reaction. Thermal Gravimetric and Differential Thermal Analysis(TG-DTA) showed that the temperature for solid-state reaction is at 942 °C. The samples are identified to be single phase by X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM). The SEM pictures showed that the first-step particles were at even size of about 100 nm by this technique. The electronic transport measurements showed that the doping compound were semiconductor with a crossover temperature T ρ. in the Arrhenius plot of the resistivity versus temprature.
The effect of silicon on synthesis of Ti3AlC2 by spark plasma sintering (SPS) from TiC/Ti/Al powders was investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for phase identification and microstructure evaluation. The results show that addition of silicon can considerably accelerate the synthesis reaction of Ti3AlC2 and fully dense, essentially single-phase (purity >98%) polycrystalline Ti3AlC2 could be successfully obtained by sintering 2TiC/1Ti/1Al/0.2Si powders at 1 200–1 250 °C under a pressure of 30 MPa. SEM photographs show that the obtained Ti3AlC2 samples from mixtures powders are in plane-shape with a size of about 2–5 μm and 10–25 μm in the thickness dimension and elongated dimension, respectively.
As a part of the green process for manufacturing chromium compounds, two steps are involved in the synthesis of ultra-fine Cr2O3 powders: the first is the hydrogen reduction of K2CrO4 into intermediate trivalent (Cr3+) or tetravalent (Cr4+) chromium compounds; the second is the decomposing of the intermediate into Cr2O3 by heat treating. The intermediate is well characterized by means of SEM, XRD, and XPS. The possible reaction mechanism of the process is analyzed.
To develop a software to predict the evolution of microstructure and the development of mechanical properties during the heat treatment of cast aluminum alloys, we modeled the redistribution of solute during the solution treatment of multicomponent alloys. The predictions of solidifi cation simulation software or the results of experiment provided the initial microstructure and solute distribution for simulation of heat treatment. Binary through quinary aluminum alloys with silicon, copper, magnesium, and iron were modeled. The basic model assumed local equilibrium (no undercooling due to nucleation or growth) and computed diffusion in the solid constituents during solidification. The evolution of microstructure during solution treatment was followed by qualitative and quantitative metallography. The results of simulation for the ternary alloy Al-7%Si-3.5%Cu were compared to experimental observation.
Ordered zinc oxide (ZnO) rod arrays with very high orientation were fabricated on Si substrates by using a solution method. The substrate surfaces were functionalized by Self-Assembly Monolayers (SAMs). In the very early growth stage, the oriented ZnO crystals had already grown, which appeared to be the main reason why ZnO nanorods showed very high orientation. The un-dense and un-uniform SAMs provided a surface that was heterogeneous to ZnO nucleation. Consequently, highly oriented ZnO rods were selectively grown on the “coin-like” SAM-uncovered regions. The route developed here can provide some helpful information to control the nucleation and orientation of ZnO in aqueous solution. Also, the site-selective growth mechanisms can indicate a clue to grow patterned highly oriented ZnO nanorod arrays by the organic template.
Effects of calcium addition and electromagnetic stirring on the microstructure of AZ91 magnesium alloy and refinement mechanism were investigated. The results show that calcium addition ranging from 0.1wt% to 0.3 wt% does not lead to formation of any new phases but cause the refi nement of as-cast microstructure.However, combined calcium alloying and electromagnetic stirring significantly decrease the grain size, change the morphologies of the β-Mg17Al12 phases,and reduce their volume percentage. The minimum grain size of AZ91 alloy is obtained in the case of the addition of 0.2 wt%Ca with exciting voltage of 100 V. The microstructural refi nement is attributed to the increase of the degree of undercooling and nucleation temperature of primary α-Mg phases on the basis of DTA analysis results.
Some new heteropolyoxometalates of large organic cations with molybdotungstosilicic acids (general formula: (CTMA)4SiMo xW12−xO40⋅mH2O⋅nDMF, x=0,2,4,6,8,10,12) were prepared by the reaction of cetyltrimethylammonium bromide (CTMAB,C16H33N(CH3)3Br) with H4SiMo xW12−xO40(x=0,2,4,6,8,10,12) in aqueous solution and recrystallization in DMF, and characterized by elemental analysis, IR spectra,TG-DTA and XRD techniques. The IR spectrum confirms the presence of Keggin structure and organic cations in these compounds, and it is indicated that the stretching vibration of the M-Od, M-Ob-M and Si-Oa becomes more red-shifted when molybdenum is gradually substituted for the tungsten atom. In particular, the thermal decomposition of the heteropolyoxometalates was studied in nitrogen atmosphere. The TG-DTA curves show that their thermal behaviors not only contain the release of water molecule, DMF molecule, CTMA and its fragments but also contains simultaneous collapse of Keggin anion. Their end products of the thermal decomposition are the mixture of WO3, MoO3 and SiO2. And from the final decomposition temperature of view, it is found that the thermal stability of these compounds gradually is decreased when the number of molybdenum atoms is increased.
The effectiveness of the corrosion protection of Nafion/Dimethysulfoxid (DMSO) organic coatings for AM50 magnesium alloy prepared by simple immersion and heat treatment was investigated. Its corrosion resistance and morphologies of the Nafion/DMSO organic coatings were studied by electrochemical corrosion testing and optical microscopy. The results show that Nafion/DMSO organic coatings can improve the corrosion resistance of AM50 magnesium alloy effectively. Also, the corrosion resistance increases with the surface density of the organic coatings.
The kinetics equation of deposition rate was implemented to help explain some of the mechanisms responsible for structures observed during the deposition of CoFeB films on poly-ester plastic. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient, confidence interval, residual error and confidence interval were confirmed by computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2–10 GHz range. At 2 GHz, the permeability, magnetic loss of the electroless CoFeB films were 304,76.6 respectively as the concentration of reducer is 1 g·L−1.
An acrylate emulsion was modified by adding vinyltriisopropoxy silane (trade name C-1706). By adding the multiple emulsifier which consists of an anionic emulsifier, sodium dodecyl benzene sulfonate (SDBS) and nonionic emulsifier, octyl phenolic divinyl oxide (OP-10), the acrylosilane microemulsion was synthesized by seeded emulsion polymerization. The influential factors including the kind and the adding amount of emulsifiers and the monomer variety of alkoxy silane and the added methods which influence on the properties of the microemulsion were investigated. It is found that SDBS and OP-10 as multiple emulsifiers with mass ratio of 1:1 and the adding amount of 2.5%–3.5% can act on co-effect for emulsion polymerization. The C-1706 possesses bulky isopropoxy substituent that can reduce hydrolysis reactivity during the polymerization process, so as to not only make the process smoothly but also advance the store stability of the emulsion. Moreover, the latter-addition mode of C-1706 can restrain its hydrolysis activity and polycondensation reaction during the polymerization process of the emulsion. The structure, the film cross section, the particle size and its distribution of the microemulsion were analyzed by the Fourier Transform Infrared Ray Spectrum (FTIR), Scanning Electron Microscopy (SEM) and a particle size analyzer,respectively. The results show that the particle diameter of the modified microemulsion can be controlled between 50 and 70 nm and its film hardness is 7.3. Only adding 1.5% of C-1706 into the system of emulsion polymerization can apparently improve the weathering resistance of the microemulsion, which undergo degradation with chromatism(ΔE) is 1.6 after 3 600 hours of QUV-aging.
Polycrystalline Sr5LnTi3Ta7O30 (Ln=La, Nd, Sm and Y) ceramics were prepared as single-phase materials through conventional solid-state ceramics method. The structure was characterized by X-ray diffraction method and scanning electron microscopy (SEM). The dielectric properties were measured from room temperature to 400 °C. All compounds are paraelectric phases adopting the filled tetragonal tungsten bronze (TB) structure at room temperature. At 1 MHz their dielectric constant (ε r) varied from 109 to 139, dielectric loss changed from 0.003 3 to 0.005 8, and the temperature coefficients of the dielectric constant (τ ε) moved from −710 to −880×10−6 °C−1.
Stable and single-dispersed hydroxyapatite (HAP) nanoparticles were synthesized with ultrasonic-assisted method. HAP nanoparticles were characterized by dynamic light scattering, XRD (X-ray diffraction) and TEM (Transmission Electron Microscopy). The effect of HAP nanoparticles on the K562 human myelogenous leukemia cell line was investigated by MTT assay and cell count test, and the mechanism was studied through the changes of cell cycle and ultrastructure. The results showed that HAP nanoparticles inhibited the proliferation of K562 cells dramatically in vitro. HAP nanoparticles entered the cytoplasm of K562 cells and the cells were arrested at G2/M phase, thus, the cells died directly.
A new kind of fiber optic oxygen sensing material based on the fluorescence quenching of Ru(bpy)3Cl2 was prepared by the themo-polymerization method. The ruthenium dye was immobilized in N, N-methylene bisacrylamide(MBBA) polymer by physically trapping while MBBA was covalently cross-linked on the glass micro-beads by NaHSO3-O2-MnSO4 initiator system. The lock-in amplifyication technology was used for the detection of their sensing properties. The influences of indicator concentration, glass micro-beads diameter, post polymerization time, concentration and reaction time of glutaraldehyde on the properties of sensing materials were studied. To optimize the influencing factors to the sensing materials, the indicator concentration of 0.7 g/L, glass micro-beads diameter of 0.3 mm, post polymerization time of 5 h were achieved. The immobilization stability of ruthenium dye and the performance of the sensing materials were improved by the new polymerization system. An absolute detection limit of 3×10-6 (V/V) and the response time of 10 s were obtained. This kind of sensing materials has good stability and their life time is 2 years.
A novel bioactive and bioresorbable PDLLA/chondroitin sulfate/chitosan scaffold was prepared via layer-by-layer(LBL) electrostatic-self-assembly (ESA) and the thermally induced phase separation (TIPS) technique. Chondroitin sulfate and chitosan were alternately deposited on the activated PDLLA substrate. The deposition process was monitored by UV-Vis absorbance spectroscopy. After frozen and lyophilized, the scaffold was characterized by attenuated total reflection (ATR)-FT-IR, XPS, SEM and AFM. The results showed that the scaffold was modified uniformly with a dense inner layer with few detectable pores and a porous sponge outer layer with the pore size about 5 μm, there was an obvious across section and the average thickness of each layer was about 9.4 nm.
Novel catalysts of phosphotungstic heteropolyacids (PW12) supported on neutral alumina were prepared by assistance of ultrasound and plasma treatment. The prepared catalysts were characterized by FT-IR pyridine adsorption (Py-IR), temperature programmed desorption of Pyridine (Py-TPD), BET and X-ray diffraction (XRD), and their catalytic performances were evaluated by the cationic polymerization of tetrahydrofuran. The results indicate that plasma treatment remarkably increases the surface acidity of the prepared catalyst while ultrasonic treatment induces PW12 to uniformly disperse on the support surface and expose more active sites for the acid catalytic reaction. A higher catalytic activity (69.7%) is obtained on the novel catalyst, which significantly outstripped that on the conventional sample (57.5%).
A novel current feed style, alternating pulse current, was proposed in electrocoagulation aiming at preventing the passivation of electrode materials. The open circuit potential (OCP) measurements after anodic and cathodic potentiodynamic polarization showed that cathodic polarization could activate Al electrode. The surface of Al electrode after alternating pulse current electrocoagulation was investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), and the results indicate that passivation of Al is not observed. Furthermore, the simulated wastewater treatment tests show that alternating pulse current electrocoagulation has a visible energy saving effect and is worthy of generalization.
The durability of epoxy resin coating was studied under environments with relative humidity (RH) of 98%–100%, at 55 °C for 900 h, at 65 °C for 700 h and at 75 °C for 400 h, respectively. Peel strength test, dynamical mechanical thermal analysis (DMTA), infrared spectroscopy (IR) and energy dispersive X-ray spectroscopy (EDX) were employed for measurements. Peel strength indicated the development of adhesive property of the coating, DMTA indicated the development of physical property, IR revealed the development of chemical structure, and EDX showed surface element change of the coating. All these results show a good timetemperature equivalence characteristic between humidity aging time and temperature.
Electrical measurement was employed to investigate the early hydration characteristics of cement pastes with different dosages of superplasticizer in the same W/C ratio. The hyperbolic method was applied to analyze the electrical resistivity development. The peak point (P h) on the hyperbolic curve could be easily read. The time (t h) to reach the point Ph had strong relations with the setting time. th was delayed with the increment of the dosage of superplasticizer. The time th was used to plot the relationship between the initial setting time and fi nal setting time. The hyperbolic equation was established to predict the ultimate resistivity. The retardation effect of the superplasticizer was confirmed in the same W/C ratio by setting time and isothermal heat evolution.
The influences of natural sand, manufactured-sand (MS) and stone-dust (SD) in the manufactured-sand on workability, compressive strength, elastic modulus, drying shrinkage and creep properties of high-strength concrete (HSC) were tested and compared. The results show that the reasonable content (7%–10.5%) of SD in MS will not deteriorate the workability of MS-HSC. It could even improve the workability. Moreover, the compressive strength increases gradually with the increasing SD content,and the MSHSC with low SD content (smaller than 7%) has the elastic modulus which approaches that of the natural sand HSC, but the elastic modulus reduces when the SD content is high. The influence of the SD content on drying shrinkage performance of MS-HSC is closely related to the hydration age. The shrinkage rate of MS-HSC in the former 7 d age is higher than that of the natural sand HSC, but the difference of the shrinkage rate in the late age is not marked. Meanwhile the shrinkage rate reduces as the fly ash is added; the specific creep and creep coefficient of MS-HSC with 7% SD are close to those of the natural sand HSC.
The mechanical properties of several kinds of coal gangue calcined with limestone were Researched so as to find the optimum way of calcinations with limestone. Microstructure and property of hydration process of cement pastes containing added-calcium coal gangue were analyzed by means of scanning electron microscope (SEM) and method of mercury in trusion poremeasurement (MIP), etc. The experiment can approve those results: when proper amounst of gypsum and fluorite were taken as mineralizers in the course of calcinations of added-calcium coal gangue, activity of coal gangue can be effectively improved. The results of mechanical property and structural characteristic such as hydration process, hydration product and microstructure etc. of cement pastes containing added-calcium coal gangue are consistent.
According to the design requirement and on the basis of the principle that the thermal expansion coeffi cient of the support structure should match with that of the mirror, a lightweight silicon carbide primary mirror assembly was designed. Finite element analysis combined with the parameter-optimized method was used during the design. Lightweight cell and rigid rib structure were used for the mirror assembly. The static, dynamic and thermal properties of the primary mirror assembly were analyzed. It is shown that after optimization, the lightweight ratio of the silicon carbide mirror is 52.5%, and the rigidity of the silicon carbide structure is high enough to support the required mirror. When temperature changes, the deformation of the mirror surface is in proportion to the temperature difference.
A modified testing system characterized by full automation, steady operation and high accuracy of strain and stress measurements was developed to determine the cracking tendency of high strength concrete (HSC) in restrained condition at early ages. The shrinkage stress and the tensile creep behavior of HSC at early ages were investigated. The infl uence of W/C ratio and curing conditions on the early-age shrinkage stress and tensile creep was evaluated. It was found that the lower W/C ratio and drying curing condition resulted in higher shrinkage stress, stress induced tensile creep and greater cracking tendency.
The self-monitoring application of asphalt concrete containing graphite and carbon fibers using indirect tensile test and wheel rolling test were introduced. The experiment results indicate that this kind of pitch-based composite is effective for strain/stress self-monitoring. In the indirect tensile test, for a completely conductive asphalt concrete specimen, the piezoresistivity was very weak and slightly positive, which meant the resistivity increase with the increment of tensile strain at all stress/strain amplitudes, with the gage factor as high as 6. The strain self-sensing ability was superior in the case of higher graphite content. However, when the conductive concrete was embedded into common asphalt concrete specimen as a partial structure function, the piezoresistivity was positive at all stress/strain amplitudes and with the gage factor of 13, which was much higher than that of completely conductive specimen. Thus, the strain self-sensing ability was superior when conductive asphalt concrete was taken in as a partial structure function. In the wheel-rolling test, the piezoresistivity was highly positive. At any stress amplitude, the piezoresistivity was strong, with the gage factor as high as 100, which was higher for a stress amplitude of 0.7 MPa than that of 0.5 MPa.
The rule of infant age concrete strength development under low temperature and complex affecting factors is researched. An efficient and reliable mathematical forecast model is set up to predict the infant age concrete antifreeze critical strength under low temperature at construction site. On the basis of the revision of concrete equivalent coefficient under complex influencing factors, least-squares curve-fitting method is applied to approximate the concrete strength under standard curing and the forecast formula of concrete compressive strength could be obtained under natural temperature condition by various effects. When the amounts of double-doped are 10% fly ashes and 4% silica fumes as cement replacement, the antifreeze critical strength changes form 3.5–4.1MPa under different low temperature curing. The equivalent coefficient correction formula of concrete under low temperature affected by various factors could be obtained. The obtained equivalent coefficient is suitable for calculating the strength which is between 10% to 40% of standard strength and the curing temperature from 5–20 °C. The forecast value of concrete antifreeze critical strength under low temperature could be achieved by combining the concrete antifreeze critical strength value with the compressive strength forecast of infant age concrete under low temperature. Then the theory for construction quality control under low temperature is provided.
In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution (pH=2), hydraulic acid solution (pH=3) were applied as the corrosive medium. 6 series of corrosion tests, including 111 specimens, were carried out. Mechanical properties of all the corroded specimens were tested respectively. Compressive properties of the corroded specimens (e.g. compressive strength, stress-strain relation, elastic modulus etc.) were achieved. Taking the strength degradation ratio and strain energy loss as damage index, effects of the corrosion solution on the compressive property of corroded concrete were discussed in detail. Relationship between the damage index and corrosion state of specimens were achieved.
SAfter leached from municipal solid waste landfill was treated by recirculation, the concentration of pollutants decreases greatly, and the moisture content of the solid waste in landfill site was increased and waste stabilization rate was accelerated. Compared with traditional treatment methods, this method offers more important practical values, including short investment, enhanced treatment efficiency and facilitated operation and management. The experimental results indicated that a 99.9% removal of ammonia nitrogen and an 80.5% removal of COD were obtained, when hydraulic power surface load is 15.92 L/m2·d, and organic surface load is 25.54 g/m2·d.