Ca xBa1−xTiO3 (CBT) fine particles doped with red luminescence center of Pr3+ ions (Pr: CBT) were successfully synthesized by salt assisted spray pyrolysis (SASP) process. Scanning electronic microscope (SEM) and laser scattering analysis demonstrate that salt can be removed from the surface of particles by washing with Milli-Q water and the particles can be further separated by ball-milling to get well-dispersed Pr3+ ions doped CBT fine particles. The luminescence properties, such as photoluminescence (PL) and mechanoluminescence (ML), of as-synthesized Pr: CBT particles were investigated. For Pr: CBT fine particles with different Ca molar ratios, all the samples show one emission at 612 nm, with increasing Ca molar ratio, PL intensity of Pr: CBT fine particles become stronger and stronger. When pressure was loaded on the Pr: CBT pellet, mechanoluminescence(ML) emission was measured. The results show that the ML intensity is proportional to the applied pressure.
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%.
A simple sonochemical route for the surface coating of titanium dioxide on cadmium sulfide nanocrystal was reported. After 2 h ultrasonic irradiation treatment, the mixture of CdS nanocrystals and tetrabutyl titanate in an aqueous medium yielded CdS/TiO2 nanocrystals composites with core/shell structure. The thickness of TiO2 layer with smooth interface could be easily controlled via changing the concentration of the precursors and the time of irradiation. The core/shell nanocrysrals were characterized by X-ray diffraction, transmission electron microscope and UV-vis spectrometry techniques. The prepared semiconductor composites with particular band structure present appealing properties especially in photochemical activity.
Ti-Si-N composite coatings were synthesized on a novel combining cathode and middle-frequency magnetron sputtering system, designed on an industrial scale. Ti was produced from the arc target and Si from magnetron target during deposition. The influences of negative bias voltage and Si content on the hardness and microstructure of the coatings were investigated. The composite coatings prepared under optimized conditions were characterized to be nc-TiN/a-Si3N4 structure with grain sizes of TiN ranging from 8–15 nm and exhibited a high hardness of 40 GPa. The enhancement of the hardness is suggested to be caused by the nanograin-amorphous structure effects.
LiMn2O4 thin films of different thickness were derived from solution deposition and heat treated by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the films were examined by galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy. LiMn2O4 thin films of different thickness derived from solution deposition and rapid thermal annealing are homogeneous and crack free with the grain size between 20 nm and 50 nm. The specific capacity of these films is between 42 and 47 µAh·cm2·µm−1. The capacity decreases with the increase of discharge current density. The capacity loss per cycle increases from 0.012% to 0.16% after being cycled 50 times as the film thickness increases from 0.18 µm to 1.04 µm. The lithium diffusion coefficients of these films are in the same order of 10−11 cm2·s−1.
The influences of concentration and modulus of sodium silicate solution and curing mode on the phase composition, microstructure and strength development in the geopolymers prepared using Class F fly ash were investigated. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and MAS NMR were utilized. Results show that the compressive strength increases as sodium silicate solution modulus increases, but when modulus exceeds 1.4, the compressive strength decreases, and it decreases markedly while the modulus is greater than 2.0. The compressive strength was improved by the increase of sodium silicate solution concentration. When the concentration is 32%, the compressive strength reaches the maximum, then it reduces as concentration increasing. Elevated temperature can increase the strength of samples that synthesized from sodium silicate solution with 32% concentration and modulus 1.2. Compared to the strength of the sample cured at 50 °C, the strength of the samples cured at 65 °C and 80 °C are higher at 1 d and 3 d, but the same at 7 d. At high temperature, prolonged curing time will decrease the strength. Long precuring at room temperature before application of heat is beneficial for strength development, and there is about 50% increase in strength of the samples cured at 1 d precuring and 2 d elevated temperature as compared to the strengths of the samples cured for 3 d at elevated temperatures or cured for 28 d at room temperature. The main product of reaction in the geopolymeric material is amorphous alkali aluminosilicate gel.
The glass forming region of Bi2O3-B2O3-BaO ternary system was investigated. A serial of glass samples with high Bi2O3 content in Bi2O3-B2O3-BaO system were prepared by using conventional melting and quenching meld, and the refractive indexes and absorption spectra of samples were measured. It is found that the refractive index of samples as well as the UV absorption increase with the increase of BaO content. According to the Tauc law, optical band gap E opg which is assumed to be the effective energy band gap E g is calculated and decreases with the increasing BaO content, and the ratio of E g/E opg is 1.3.
The fabrication process of Cu/Al2O3/MgF2/Au double-barrier metal/insulator/metal junction (DMIMJ) was introduced, and more stable light emission from this junction was successfully observed. The light emission physical mechanism of the junction was discussed. Results show that light emission spectrum of this structure locates at wavelength of 250–700 nm with two peaks at around 460 nm and 640 nm, which moves towards shorter wavelength region in comparison with that of the Al/Al2O3/Au junction. The light emission efficiency of this junction ranges from 0.7×10−5–2.0×10−5, which is 1 to 2 orders higher than that of the single-barrier Al/Al2O3/Au junction. The improved properties of this structure should be due to the electrons resonant tunneling effect in the double-barrier.
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.
An experiment was designed to prepare isotropic pyrocarbon by thermal gradient chemical vapor deposition apparatus. The deposition was performed under ambient atmosphere at 1400 °C, with natural gas volume flow of 3.5 m3/h for 80 h. The results show that the thickness and the bulk density of the deposit are about 1.95 g/cm3 and 10 mm, respectively. The microstructure of the deposit was examined by polarized light microscopy and scanning electron microscopy, which shows that the deposit is constituted of sphere isotropic pyrocarbon, pebble pyrocarbon and laminar pyrocarbon.
Al2O3/TiAl composites were successfully fabricated by hot-press-assisted exothermic dispersion method with elemental powder mixtures of Ti, Al TiO2 and Nb2O5, and the microstructure and mechanical properties were investigated. The results indicate the fine Al2O3 particles tend to disperse on the grain boundaries. The grain size of TiAl matrix decreases and the hardness increases with increasing Nb2O5 content. The bending strength and fracture toughness reach to a maximum when Nb2O5 content is 6 wt%, under 642 MPa and 6.69 MPa·m1/2, respectively. Based on the fractography and the observation of crack propagation path, it is concluded that the strengthening and toughening of such composites at room temperature can be attributed to the refinement of the TiAl matrix, the deflection behavior in the crack propagation and the dispersion of Al2O3 particles.
A new method of recycling aluminum and iron in boiler slag derived from plants that use coal as fuel was presented. The new method can integrate efficient extraction and reuse of the leached pellets together. An elemental analysis of aqueous solutions leached by sulfuric acid was conducted by the EDTA-Na2-ZnCl2 titration method, and the components and microstructures of the samples were examined by means of XRF, XRD and SEM. An aluminum extraction efficiency of 86.50% was achieved when the sintered pellets were leached using 4 mol·L−1 H2SO4 with solid/liquid ratio(m/V) of 1:5 at 80 °C for 24 h. An iron extraction efficiency of 94.60% was achieved under the same condition for the maximum extraction efficiency of Al. The extraction efficiency of Al and Fe increased with temperature, leaching time and acidity. The concentration of alumina and iron hydroxide in the final product was determined to be 99.12% and 92.20% respectively. This product of alumina would be used directly for the production of metallic aluminum.
Tungsten bronze (TB) type potassium strontium niobate KSr2Nb5O15 was prepared by solid-state reaction method, and was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse spectrum. The photocatalyst shows high photocatalytic activity of photodegrading acid red G. The effects of photocatalyst dosage and initial concentration of acid red G on the photodegradation process were studied. The kinetics of photocatalytic degradation of acid red G by KSr2Nb5O15 catalyst follows the first order reaction.
Fe68Zr20B12 amorphous alloy was prepared by mechanical alloying(MA) method and annealed at different temperatures. Microstructures and magnetic properties of Fe68Zr20B12 alloys as-milled and annealed at 693, 843, 943 and 993 K were studied. The raw powders(Fe, Zr, B) formed b. c. c. α-Fe solid solution at early stages of MA and then transformed into amorphous alloy. Grain size(D) of Fe68Zr20B12 alloys increases with increasing annealing temperature and keeps at nanometer level. The specific saturation magnetization(σ s) increases with increasing annealing temperature from 300 K to 943 K, and then decreases with annealing temperature at 993 K because of the precipitation of Fe3B.
Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 °C, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 µm, shape factor is 0.83, and mean thickness of network carbide is 5.21 µm.
Neural Stem Cells (NSCs) were incubated with self-assembled hydrogel from IKVAV-containing peptide amphiphile (IKVAV-PA) for one week. The cytocompatibility of hydrogel was evaluated. NSCs were seeded in three-dimensional (3D) hydrogels (Experimental Group, EG) or surface of coverslips (Control Group, CG), double-labeled with Calcein-AM and PI. A growth curve of cells was obtained according to CCK-8. TEM study of hydrogel revealed a network of nanofibers. NSCs began to proliferate after 24 h of incubation, and formed bigger neurospheres at 48 h in EG than in CG. Cell proliferation activity was higher in EG than in CG (P<0.05). The self-assembled Hydrogel had good cytocompatibility and promoted the proliferation of NSCs.
CTBN-EP prepolymers were synthesized from CTBN and epoxy resin under the catalysis of HTMAB. FTIR analyses indicate the formation of ester group between the carboxyl group of CTBN and the oxirane group of epoxy resin. The viscosity of modified prepolymer increases with CTBN content increasing, but the epoxy value of the prepolymer decreases greatly. DSC analyses verify that CTBN affects the curing process of CTBN-EP/PEA system. Mechanical testing presents the improved toughness of CTBN-EP/PEA curings for the decrease of tensile strength, flexural strength and compressive strength, and increase of impact strength and elongation-at-break with the CTBN content increasing. SEM micrographs show the rubber phase with many holes in diameter about 0.5–1.5 µm is formed when CTBN content is lower than 10 phr. However, the pattern of SEM graph shows some stalactite-like strips when CTBN content is higher than 15 phr. Furthermore, the SEM image of 25 phr CTBN sample forms a kind of co-continuous structure.
Flame retardant epoxy resins were prepared by a simple mixed method using ammonium aluminum carbonate hydroxy hydrate (AACHH) as a halogen-free flame retardant. The prepared samples were characterized by X-ray diffraction, thermogravimetric and differential scanning calorimetry, scanning electron microscope and limiting oxygen index(LOI) experiments. Effects of AACHH content on LOI of epoxy resins/AACHH composite and flame retardant mechanism were investigated and discussed. Results show that AACHH exhibites excellent flame-retardant properties in epoxy resin(EP). When the content of AACHH was 47.4%, the LOI of EP reached 32.2%. Moreover, the initial and terminal decomposition temperature of EP increased by 48°C and 40 °C, respectively. The flame retarded mechanism of AACHH is due to the synergic flame retardant effects of diluting, cooling, decomposition resisting and obstructing.
K16 and RGD-containing peptide was used to modify the surface of three-dimensional PLGA-(ASP-PEG) matrix, then the modified PLGA-(ASP-PEG) was incubated in modified simulated body fluid (SBF). The biomineralization of the modified PLGA-(ASP-PEG) was explored, and the peptide was synthesized with solid phase synthesis technology and linked covalently to PLGA-(ASP-PEG) through cross-linker (Sulfo-LC-SPDP), which was characterized with XPS. The modified PLGA-(ASP-PEG) (Experiment group, EG) and PLGA-(ASP-PEG) (Control group, CG) were all incubated into SBF for 10 d, and the growth of hydroxyapatite (HA) nanocrystals was confirmed with XRD, EDS and SEM. HPLC shows that peptide purity is 94.13%, while MS analysis shows that molecular value of peptide is 2741.26. Binding energy of the sulphur in EG was 164 eV is detected by XPS, and the ratio of carbon and sulphur is 99.746:0.1014. SEM analysis demonstrates the better growth of bonelike HA nanocrystals in EG than that in CG. The component of mineral in EG consisted mainly of hydroxyapatite containing low crystalline nanocrystals, and the Ca/P ratio is about 1.60, which is similar to that of natural bone, while the Ca/P ratio in CG is 1.52. PLGA-(ASP-PEG) modified with peptide provided enough functional groups for biomineralization, and possessed the bonelike structure.
A simple, and homogeneous detection system for human IgG based on the optical properties of aggregated gold nanoparticles probes were investigated. When gold nanoparticles with about 13 nm in diameter were modified by goat anti-human IgG, the addition of human IgG could change the absorption of colloidal gold solution, and the absorption intensity at 740 nm depended on the amount of human IgG. The aggregation of gold nanoparticles was also validated using transmission electron microscopy (TEM). A series of experiments were carried out to study the effects of pH value, the reaction temperature, and non-specific adsorption on the assay. A dynamic range of 10–500 µg/3 mL human IgG was observed. The new bioassay could be used for the rapid and homogeneous detection of antibodies in bioanalytical chemistry.
Rigid polyurethane foams were fabricated with five kinds of liquefied sugarcane bagasse polyols (LBP). The foams derived from sugarcane bagasse were investigated by thermogravimetric analysis (TGA), and the thermal degradation data were analyzed using the Coast-Redfern method and Ozawa method to obtain the reaction order and activation energy. The results indicate that the sugarcane bagasse-foams exhibit an excellent heat-resistant property, whereas their pyrolysis procedures are quite complicated. The reaction as first order only takes place from 250 to 400 °C, and the pyrolysis activation energies vary from 20 to 140 kJ/mol during the whole pyrolysis process.
The changes of induced bone with four kinds of Ca-P ceramics after 2 years implantation in the dorsal muscles of rabbits were investigated. After 2 years implantation, mature bone (with a lamellar structure after the remodeling process) with bone marrow was observed in HA1100 (HA, micro+macro porous), HA900 (HA, micro+macro porous) and BCP (HA/TCP=7:3, micro+ macro porous), and no bone formation was observed in HA1200 (HA, macro porous) ceramics. The induced bone neither disappeared nor grew uncontrollably, and was seen inside the pores of the implants or on the outer surface under the fibrous layer after 2 years. No bone formation was observed in the soft tissues distant from the implants. These results indicate that heterotopic bone formation induced by Ca-P materials did not give rise to uncontrolled growth over time, and the induced bone is limited to the inside or around the implants. Moreover, ectopic bone formation on the outer surface of the implants was detected in rabbits after 2 years.
Formation and growth of the intermediate phases in the Ni-Al diffusion couples prepared by pouring technique were investigated. Electron probe microanalysis, scanning electron microscopy and X-ray diffraction were used to characterize the product phases in the joints. The results show that two intermediate phases form in the sequence of NiAl3 and Ni2Al3 during solidification. After annealed, Ni2Al3 and NiAl3 still exist in the joints of the couples. The reasons for the formation of Ni2Al3 and NiAl3, as well as the absence of NiAl, Ni5Al3 and Ni3Al were discussed, respectively. The growth kinetics of both product phase layers indicates that their growth obeys the parabolic rate law. The activation energies and frequency factors for NiAl3 and Ni2Al3 phases were also calculated according to the Arrhenius equation.
50CrVA cold-rolled spring steel strip was used to fabricate the diaphragm of the automotive horn. The material parameters which were taken into account in the design of the diaphragm involve elongation, elastic limit, Young’s modulus, yield strength and tensile strength. The tempering process was carried out in order to enable the diaphragm to possess the excellent mechanical properties, such as high elastic limit, high fatigue strength and perfect stress relaxation resistance. As a nonlinear information processing system, the backpropagation artificial neural network (BPANN) was applied to predict and simulate the relationship between the mechanical properties of the diaphragm and the tempering process parameters. Experimental results show that a BPANN with 3-8-5 architecture is capable of predicting the relationship between the mechanical properties of the diaphragm and the tempering temperature successfully and lays the profound foundations for optimizing the design of the diaphragm. BPANN simulation results show that the tempering temperature ranging from 380 to 420 °C contributes to enhancing the comprehensive mechanical properties of the diaphragm including high Young’s modulus, high elastic limit and high fatigue strength.
Three kinds of superalloys were prepared by spray deposited process. The analysis results of microstructures and mechanical properties indicate that the spray deposited preforms with higher integral densification and the oxygen content in each kind of superalloy was very low. The microstructures are consisted of fine grain without dendritic equi-axed. The spray deposited superalloys possessed good ductility. The forging experiment displays that even though the once deformation of spray deposited GH742 alloy more than 60%, the crack can not be found. Meanwhile, the mechanical properties of spray deposited superalloys are significantly increased.
The microstructure with uniform equiaxed fine gain was obtained by the thermo-mechanical processing (TMP) for the 5083 Al alloy (Al-4.56%Mg–0.61%Mn) plate. Uniaxial tensile test was carried out at a temperature range of 500–570 °C and a strain rate range of 4.17×10−4 s−1−1×10−2 s−1. Maximum tensile elongation 530% was obtained at 550 °C and strain rate $\dot \varepsilon $ = 4.17 × 10−4 s−1. Dislocations were observed in grain interiors and at grain boundaries during uniaxial tensile deformation by transmission electronic microscopy (TEM), respectively. Results show that the grain boundary sliding (GBS) accommodated by dislocation motion is the principal reason for superplastic deformation. The cavities and fracture were observed during uniaxial tensile deformation of the alloy by scanning electronic microscopy (SEM), indicating that linkage of cavities in large region would induce failure of the material. Moreover, presence of liquid phase at grain boundary also affects the superplastic deformation and behavior of cavities.
Six kinds of polyurethane (PU) elastomers were prepared based on different polyesters, polyethers and chain extenders. The structure, mechanical properties and cold resistant properties of PU were systematically investigated by FTIR, XRD, DMTA, universal testing machine and flex ductility machine. The results show that T g of soft segment is the main factor of the cold resistant properties of polyurethane elastomer. Compared with the same relative molecular mass of the polyester and the polyether, the polyether flexibility is better, the glass transition temperature (T g) is lower and the cold resistant properties is remarkable, for example the cold resistant properties of PU based on poly (tetramethylene glycol), 1, 4-BG and MDI achieves the fifth level. The physics performances of polyurethane elastomers, such as breakdown strength, Young’s modulus and the cold resistant properties, are all superior.
The V-K catalysts were produced on porous α-alumina substrate by a solution impregnation route and the compositions and catalytic activities for soot oxidation were studied by XRD, TG/DTG, DSC and TPR. According to the catalytic activity studies, the catalytic activity of the crystalline phases is in the order: KNO3+KVO3>K3V5O14+KVO3. The appearance of excessive KHCO3 phase will lead to the deterioration of catalytic activity when the catalysts contain higher KNO3 content. It is also found that when the K:V molar ratio is higher than 1:1, the prepared catalysts show a strong CO2 absorption characteristic and this behavior will become gradually significant with the increasing of K:V molar ratio. Considerable amount of absorbed CO2 are strongly bonded to the crystal lattice with onset desorption temperature of 200 °C.
The Al-Ca-Ba glass system with good chemical durability was firstly investigated as the scintillators host. Luminescence properties of Ce3+ ions in this glass were studied, and obvious red shift and larger stokes shift with respect to others system were investigared. The excellent physical property such as high density and large refractive index implies this glass as an important material for the high quality scintillating fiber.
Two aspects of studies were carried out: 1) synthesis of geopolymer by using fly ash and metakaolin; 2) Immobilization behaviors of fly ash based geopolymer in a presence of Pb and Cu ions. As for the synthesis of fly ash based geopolymer, 4 different fly ash content (10%, 30%, 50%, 70%) and 3 types of curing regimes (standard curing, steam curing and autoclave curing) were investigated to obtain the optimum synthesis condition based on the compressive and flexural strength. The experimental results show that geopolymer, containing 30% fly ash and synthesized at steam curing (80° for 8 h), exhibits higher mechanical strengths. The compressive and flexural strengths of fly ash based geopolymer reach 32.2 MPa and 7.15 MPa, respectively. Additionally, Infrared (IR) and X-ray diffraction (XRD) techniques were used to characterize the microstructure of the fly ash geopolymer. IR spectra shows that the absorptive band at 1086 cm−1 shifts to lower wave number around 1033 cm−1, and the 6-coordinated Al transforms into 4-coordination during the synthesis of fly ash based geopolymer. The resulting geopolymeric products were X-ray amorphous materials. As for immobilization of heavy metals, the leaching tests were employed to investigate the immobilization behaviors of the fly ash based geopolymer synthesized under the above optimum condition. The leaching tests showed that fly ash based geopolymer can effectively immobilize Cu and Pb heavy metal ions, and the immobilization efficiency reached 90% greater when heavy metals were incorporated in the fly ash geopolymer in the range of 0.1% to 0.3%. The Pb exhibits better immobilization efficiency than the Cu, especially in the case of large dosages of heavy metals.
The mineral admixture slurry was made by wet-discharged fly-ash (WDFA) promoted by matrix bonding component (MBC), and the strengths, hydration products change (XRD, SEM) of cement paste made by the slurry were studied. The results indicate that in the process of wet-milling preparation, there is a prime proportion (70:30) between wet-discharged fly-ash and matrix bonding component in the slurry. The physical activation of wet-milling and chemical activation of modified agents accelerate the hydration of cement including the cement and mineral which has not hydrated completely in the matrix bonding component. And the hydrated part of matrix bonding component can play the function of inducing crystallization, which can accelerate secondary hydration reaction of fly-ash.
Effect of TiO2 content on the burnability of clinker with high C3S were investigated by determination of free lime in final product, and the clinker phase formation, microstructural features of C3S and the solubility of TiO2 in C3S were further studied by XRD, SEM/EDS analysis. TiO2 accelerates the combination of free lime in the samples, free lime content decreases obviously with TiO2 increasing up to 2% and almost remains above 2%. A new phase CaO·TiO2 was found when TiO2 was up to 3%, and samples with TiO2 displayed well-formed uniform size hexagonal C3S crystal. The limit of solubility of TiO2 in C3S at 1400 °C is about 1.7%.
Belite-rich cement (BRC) can be made at lower temperature, but it has unsatisfactory reactivity. The crystal structure of dicalcium silicate (C2S) was modified by solutionizing some additional irons. By adding barium sulfate (BaSO4) in the raw meals, the clinkers were easier to be burnt, and the compressive strength of BaSO4-modified BRC was considerably improved. The distortion of the crystal structure of C2S was confirmed by the interplanar distance change and nuclear magnetic resonance (NMR) of 29Si in C2S. An effective way was found to activate C2S and to broaden the application field of Belite-rich cement.
The influence of lightweight aggregate (LWA) pre-wetting on the chemical bound water and pore structure of the paste around aggregate as well as concrete permeability were investigated. The results show that, in early age the dry LWA has significant effect on the formation of dense paste around it and improving the concrete impermeability. However the prewetted LWA has strong water-releasing effect in later age, which increases the hydration degree of the paste around it, and makes the adjacent paste develop a structure with low porosity and finer aperture, furthermore the concrete impermeability can be improved. It is suggested that, as for concrete with low durability requirement, the LWA without pre-wetting treatment can be used as long as meet the workability requirement of fresh concrete, the good impermeability of concrete can be gained as well. As for concrete with high durability requirement, the prewetted LWA should be used, and the pre-wetting time should be extended as long as possible, in order to optimize the concrete structure in long term, and improve the concrete durability.
High performance cement based composite materials was prepared by adding epoxy emulsion. The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory. This epoxy emulsion has advantages over other emulsion, such as dehydrated slightly, and, well film formation abilities. The mechanical properties corruptness resistance and structure of epoxy emulsion modified cement mortars were studied. Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength. The corruptness resistance of all modified mortars is better than the unmodified mortar. The polymer film forms the bridge phases between the matrix and the aggregate regions, and forms a three-dimension structure in the cement hydration system, which improves the mechanical properties of modified mortars.
Layered steel fiber reinforced rubber concrete (LSFRRC), a new type of pavement concrete based on the requirements of national standard were experimentally researched. The different properties of flexural-tensile strength from plain concrete (PC), rubber concrete (RC), layered steel fiber reinforced concrete (LSFRC) and LSFRRC were presented. Experimental results show that the tensile strength of LSFRRC is improved by 4.12% compared with PC, by 13.75% compared with RC. The load-deflection curve on flexural-tensile propertiesis put forward. The flexural-tensile toughness index I10 of LSFRRC is improved 10.32 times compared with PC.