Activated carbon aerogels(ACAs) derived from sol-gel polycondensation of resorcinol (R) and formaldehyde (F) were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy (SEM) and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge-discharge rate and long cycle life (about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2). Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.
The aging properties of advanced composite T300/5405 which soaked in 15# hydraulic oil, 4010 lubricating oil, RP-3 kerosene and AHC-1 cleaner were studied. The absorption and mechanical properties of the composites were measured, and the scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and the infrared analysis (IR) were used to investigate the properties’ changes of the composite. The aging mechanism of composite T300/5405 was also discussed. The experimental results show that the absorption of the composite in AHC-1 was the biggest, and the other three mediums had little effect on the composites. The mechanical properties declined in the aging. The composites have undergone chemical change in the test; T g rose or declined after the aging, and the AHC-1 cleaner and 4010 lubricating oil had the greatest influence on the T g.
PAN fibers pre-oxidized at 240 °C, 260 °C, 280 °C, 300 °C were treated in 8 T, 12 T, 16 T high magnetic fields, respectively. The experimental result implied that there were two kinds of magnetic units cyan and carbon-nitrogen heterocycle in pre-oxidized PAN fibers, and the movement of magnetic units resulted in changes of orientation structure of pre-oxidized PAN fibers in high magnetic fields. Overall orientation increased with increase of magnetic field intensity and extension of processing time, whereas change of crystalline orientation depended on magnetic field intensity and content of carbon-nitrogen heterocycle due to the competition of two magnetic units. Furthermore, magnetic fields induced the conversion from amorphous region to crystal region and improved crystalline properties of pre-oxidized PAN fibers.
One-dimensional cerium phosphate (CePO4) nanorods were successfully synthesized by a facile and simple solvothermal method at 150 °C for 12 h, using Ce(NO3)3·6H2O and NaH2PO4·2H2O as the starting materials. Phase and morphologie of the as-synthesized CePO4 products, characterized by XRD, FESEM, and TEM, were proved to be perfect and uniform hexagonal CePO4 nanorods with aspect ratio of more than 100. The photoluminescence (PL) spectrometer was used to investigate the optical properties of the as-synthesized hexagonal CePO4 nanorods.
The phase of pyrochlore Gd2Zr2O7 used for immobilization of Pu (IV) was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd2Zr2−xCe xO7 (0.0 ⩽ x ⩽ 2.0) were synthesized via a high temperature solid reaction method with Gd2O3 and ZrO2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 + 0.00825 x (0.2 ⩽ x ⩽ 2.0), while V = 0.14668 + 0.00711 x (0.2 ⩽ x ⩽ 2.0) was also achieved.
A series of mesoporous phosphotungstic acid/alumina composites (HPW/Al2O3) with various HPW contents were synthesized by evaporation-induced self-assembly method. These composites were characterized by nitrogen adsorption-desorption, TEM, FTIR, and UV-vis, and were tested as catalysts in oxidation desulfurization of model fuel composed of dibenzothiophene (DBT) and hydrocarbon, using H2O2 as the oxidant. These composites exhibited high activity in catalytic oxidation of DBT in model fuel and good reusing ability. The best performance was achieved by using the mesoporous HPW/Al2O3 with 15wt% HPW content, which resulted in a DBT conversion of 98% after 2 h reaction at 343 K, and it did not show significant activity degradation after 3 recycles. Characterization results showed that the mesoporous structure of alumina and the Keggin structure of HPW were preserved in the formed composite. These results suggested that HPW/Al2O3 could be a promising catalyst in oxidative desulfurization process.
Ni-Ag/TiC composite coating was prepared on the 45 steel substrates by means of laser cladding. Microstructure and wear properties of composite coatings were analyzed using optical microscopy, field emission scanning electron microscopy and wear machine. The experimental results show that defects, such as cracks and pores, do not occur in the laser-cladded Ni-Ag/TiC composite coating and 45 steel substrate, and they present good metallurgical bonding between them. Compared with Ni/TiC composite coating, microhardness values of the two coatings do not present evident differences. The wear experiment result shows that Ni-Ag/TiC composite coated with Ag possesses low friction coefficient and good wear resistance compared with Ni/TiC composite coating.
The effect of Al2O3 doping on the microstructure and electrical properties of the ZnO-Pr6O11-Co3O4-MnCO3-Y2O3 system was investigated in the range of 0.0–0.1mol%. The results reveal that Al2O3 doping has slight influence on the densification process. The microstructure of the ceramics comprises of ZnO phase, ZnAl2O4 spine phase and Pr-rich phases. The addition of Al2O3 greatly affects the electrical properties. The varistor voltage (E 1mA/cm 2) of ZPCMYAl samples decreases over a wide range from 5 530 V/cm to 1 844 V/cm with the increasing Al2O3 content. The nonlinear exponent(α) increases with the increasing Al2O3 content to 0.01mol%, whereas it is decreased by the further doping. The ZPCMYAl-based varistor ceramics with 0.01mol% Al2O3 exhibit the best electrical properties, with the nonlinear exponent (α) attaining the highest value of 33.4 and the lowest leakage current of 2.7 μA. The capacitance-voltage (C-V) measurement shows that the donor density (N d) at the grain boundaries increase from 1.58×1018 to 3.15×1018 cm−3, the barrier height (φ b) increases from 1.60 to 2.36 eV, and the depletion layer width (t) decreases from 24.9 to 21.6 nm.
We investigated the deformation behaviors of Zr65Cu17.5Ni10Al7.5 in superplastic forming in silicon mould via numerical modeling and experiments. The data needed for the constitutive formulation were obtained from compressive tests to establish a material library for finite-element simulation using a DEFORM 3D software. A constant speed forming process of a micro gear was modeled where the loading force, feature size and amount of deformation in the micro gear in silicon mould were analyzed in detail for the optimal requirements of micro gear forming and the protection of silicon mould. Guided by the modeling parameters, an amorphous metal micro gear was successfully obtained by our home-made superplastic forming system with the optimized parameters (temperature of 683 K, top speed of 0.003 mm/s until the load force reaching limiting value at 1960 N, and a gradually decelerating process for holding the force to the end). Our work gives a good example for optimization of superplastic forming and fabrication of BMGs in microparts.
The tribological properties of TiAl-Ti3SiC2 composites (TMC) against Si3N4 ceramic ball pair at room temperature were investigated through the determination of friction coefficients and wear rates, and the morphologies and compositions of wear debris, worn surfaces of TMC and Si3N4 ceramic ball were analyzed. The experimental results showed that TMC with 15wt% Ti3SiC2 exhibited relatively excellent tribological properties. The solid-phase self-lubricating tribo-layers formed on the worn surfaces of both TMC with 15wt% Ti3SiC2 and Si3N4 ceramic ball, which was beneficial to the lower friction coefficient and wear rate.
The microscopic structure of waste can aluminum material was researched by adding Al5TiB refining agent, La-Ce rare earth and mixed rare earth modifiers, and the microstructure and mechanical performance of the modified aluminum material were studied. The experimental results show that the optimal refiner addition amount is 1.1wt%; the material performance can be significantly improved when the content of La-Ce rare earth ranges to a certain degree, but the mixed rare earth barely affects the refinement effect of the aluminum. When being homogenized, the mixed rare earth plays more obvious role in refining the aluminum material than La-Ce rare earth. The optimal plan is modifying the aluminum material with 3wt% mixed rare earth and homogenizing with annealing temperature of 580 °C, annealing time of 12 hours and heating rate of 5 °C/min while refining the material with 1.1wt% Al-5Ti-1B.
In order to study the properties of sintered copper powder shaped charge liner, the copper powder, whose particle size was below 20 μm, was chosen as the main material. The mixed powders were directly pressed into the desired shape of the shaped charge liner by the top direct-pressure way. The microscopic morphology of the spinning shaped charge liner, the sintered and non-sintered powder liners, and the particle properties of the copper powder were studied with scanning electron microscopy. The experimental results showed that the irregular copper powder could get together effectively and sintering could improve the compactness of the powder liner effectively. The wall thickness and density of the non-sintered and sintered liner were also tested, and it shows that sintering causes the wall thickness thinned and the density improved. The penetration depths of non-sintered powder liner, sintered powder liner and the spinning copper plate liner were tested with different standoff respectively, showing that the penetration properties of sintered powder liner are well.
The hydration properties of cement-GGBS-fly ash blended binder and cement-GGBS-steel slag blended binder were compared. The experimental results show that the hydration rate of cement-GGBS-steel slag blended binder is higher than that of cement-GGBS-fly ash blended binder within 28 days, but lower than the latter after 28 days. The hydration of cement-GGBS-steel slag blended binder tends to produce more Ca(OH)2 than the hydration of cement-GGBS-fly ash blended binder, especially at late ages. Cement-GGBS-steel slag mortar exhibits higher strength than cement-GGBS-fly ash mortar within 28 days, but at late ages, it exhibits similar compressive strength with cement-GGBS-fly ash mortar and even slightly lower bending strength than cement-GGBS-fly ash mortar. Cement-GGBS-steel slag paste has finer early pore structure but coarser late pore structure than cement-GGBS-fly ash paste. Cement-GGBS-steel slag paste can get satisfied late pore structure and cement-GGBS-steel slag mortar can get satisfied late strength as compared with pure cement paste and pure cement mortar, respectively.
The adsorbing effect of calcined layered double hydroxide (CLDH) for chloride ions in simulated concrete pore (SCP) solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl− and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio ([Cl−]/[OH−]) of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with Cl−, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.
The mechanical property of a novel expanded polystyrene cement-based material (EPS-C), which was prepared by compressing semi-dry materials molding, was investigated. The compressive behavior was analyzed by compression tests to gain the energy absorbed during failure. Performance for impact resistance was tested by a self-made device. The results figures out that the EPS-C has good toughness and can reach strain of 0.7 without failure. The stress-strain curve is quite different from that of normal EPS concrete. It can be divided into three stages and in the third stage the compressing exhibits the highest energy absorption. With the rising of cement ratio, the impact force absorption (IFA) decreases first and then increases. The impact energy absorption (IEA) increases first and then decreases. The lowest IFA and the highest IEA appear at the cement dosage from 233 g/L to 267 g/L and from 233 g/L to 300 g/L, respectively.
Red cement-based decorative mortars were prepared with different content electroplating sludge containing Pb (EPSP), and their colors, water absorption, strengths, hydration characteristics and heavy metal leachabilities were investigated. The experimental results show that EPSP can adjust the mortar color well as the red pigments exclusively used in the decorative mortars. EPSP will result in the increase of water absorption, but the mortar produced with 5% EPSP still has the very satisfactory water absorption. The mortars with EPSP are provided with nearly the same compressive, flexural and tensile bond strengths as those of the control. EPSP has no notable influence on the paste hydration. But it can densify the mortar microstructures. It is also evident that heavy metal concentrations in leachates of the mortars with EPSP are far lower than the recommended in the GB5085.3-2007.
The high-temperature phase transition of tobermorite was investigated by TGA/DSC, X-ray diffraction and Infrared spectroscopy (IR), respectively. The experimental results showed that Si-OH bonds were cleaved at 724 °C and dehydroxylation occured at the same time, implying that the crystal structure of tobermorite was broken. As a result, the dehydroxylation tobermorite was metastable state, exhibiting obviously hydrolysis activity. The suspension was alkaline and Ca2+ ions content reached a maximum value 4.76% after heat treatment at 724 °C. The dehydroxylation tobermorite had potential reactive activity due to the strong hydrolysis activity. The disordered structure recombined to wollastonite, and the crystal structure became ordering and stable at 861 °C Finally, 2M-wollastonite structure can be found in the sample as the temperature reached up to 1 000 °C.
Under saturation dosage of all kinds of SP, the free water amount was examined by centrifuge. The distribution of solution and flocculation microstructures in fresh cement paste was observed in three-dimensional space by confocal laser scanning microscope(CLSM). Results indicate that SP can increase the free water amount by destroying the flocculated cement particle structure and different free water amount is released by different kinds of SP. The changes of the size of flocculation structures and the dispersion of solution were obviously detected with confocal laser scanning microscope: the size of flocculation structures was smaller and more dispersed in fresh cement paste with polycarboxylate superplasticizer, but the size of flocculation structures was bigger and cannot be dispersed uniformly in fresh cement paste with others SP. The multi-level flocculation structures theoretical model of fresh cement paste was then set up. The theory indicates that different kinds of SP with different dispersion strength will open the flocculation structures at different levels, which in turn present different water reducing rate.
Organic-based materials are often used as the coating of metal oilcans. But they need to be sprayed several times in the whole life of oilcans because of the short-life of organic components. To overcome this problem, a type of long-life flexible cement-based anti-corrosion material used on the surface of metal oilcans was developed according to the principle that the steel reinforced concrete can remain the same life with buildings. The materials with different formulas composed of acrylic emulsion, cement and other additives were prepared. Because the ratios of polymer to cement played the decisive role in the adhesion and anti-corrosion characteristics, their effects on the physical performances were investigated by comparing the mechanical properties, anti-corrosion and anti-aging properties. The relationship between microstructure and macroscopic properties was also discussed.
Based on the principle of ENV 196-4 “Methods of testing cement — Part 4: Quantitative determination of constituents” or Chinese Standard GB/12960-2007 “Quantitative measurement of mineral admixtures in cement”, methods were developed for quantitative determination of fly ash, slag and limestone powder in fresh cement pastes, mortars and concretes. Limestone powder was determined using thermal analysis method. The residue content of fly ash on an 80-um sieve, and silt contents of aggregate were also considered during the quantitative determination of mineral composition of quaternary cementitious system. With the developed methods, the deviations between the measured and the actual mineral contents of the constituent in the cementitious material in fresh cement paste, mortar and concrete, were within 3%.
This paper introduced a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of cement paste was investigated, in which three kinds of admixtures were taken into account including viscosity modifying admixture (VMA), silica fume (SF), and shrinkage-reducing admixture (SRA). The experimental results indicate that the dynamic elastic modulus of cement paste increases with decreasing water-cement ratio. The addition of SF increases the dynamic elastic modulus, however, the overdosage of VMA causes its reduction. SRA reduces the dynamic elastic modulus at early age without affecting it in later period. Finally, a multiscale micromechanics approach coupled with a hydration model CEMHYD3D and percolation theory is utilized to predict the elastic modulus of cement paste, and the predictive results by the model are in accordance with the experimental data.
The applicability of the rapid iodide migration test was systematically studied. Comparative experimental tests of different test conditions, including several external voltages, test durations, concrete ages and mixing proportions, were carried out to make clear the transport behaviors of iodide under parallel electric fields. Numerical simulations were also done using the finite element method to found the correlation between chloride and iodide transport behaviors. The test and numerical results show that the chloride transport behaviors of RIM and RCM tests have a good correlation under the several conditions used in the present paper. Moreover, the influence of external conditions (external voltages, test durations) on the test results is small. Thus, it can be concluded that the RIM method is available to determine the chloride penetration resistance of the chloride-eroded structural concrete.
The adsorption amount, ζ-potential of cement particles and fluidity of cement paste were tested to research the competitive adsorption between naphthalene superplasticizer (FDN) and STPP. The experimental results showed that the presence of STPP could significantly improve the fluidity of cement paste and reduce the fluidity loss with FDN. There existed a competitive adsorption between STPP and FDN. STPP and calcium ions formed complexes; they preferentially adsorbed onto surface of cement particles and preempt adsorption points of FDN; and it reduced adsorption amount of FDN. In the absence of STPP, saturation adsorption amount of FDN was 5.93 mg/g; but when the dosage of STPP was 0.1%, it reduced to 4.3 mg/g (about 72.5%). The adsorption amount of FDN was reduced by STPP, but ζ-potential of cement particles enhanced and fluidity of cement paste increased because of strong negative charge effect of the complexes. Adsorption of the complexes would delay Ca2+ into liquid and inhibit formation of active adsorption points. Then, content of FDN in liquid increased with the addition of STPP and ζ-potential of cement particles became stable. In this way, fluidity loss of cement paste reduced.
A composite rejuvenator was used for the rejuvenation of aged asphalt in comparison with the common rejuvenator. The effects of the rejuvenators on the performance and microstructure of the aged asphalt were investigated by physical properties tests, dynamic shear rheometer and atomic force microscopy. The results indicate that the physical and rheological properties of the aged asphalt are restored more significantly by the composite rejuvenator than the common rejuvenator, which can be ascribed to the effective recovery of microstructure of the aged asphalt. The composite rejuvenator has the potential to be used for the rejuvenation of severely aged asphalt since it can restore the colloidal structure of the aged asphalt effectively through composition regulation and chemical reactions between the composite rejuvenator and asphaltenes.
The relationships between microstructure and melting temperature of slag containing different heavy metals (Zn, Cu, Pb and Cr) were studied. Furthermore, the corresponding solidification mechanism and rule of heavy metals were analyzed by microscopic tests during melting and reconstructing process. Based on preliminary results, three conclusions were derived. Firstly, pure slag would begin to melt when the temperature reached 1 180 °C; however, Zn did not play any fluxing action. Secondly, upon adding Cu and Pb, the initial melting temperature of slag decreased by 5–8 °C and their fluxing effect was observed. Thirdly, the initial melting temperature and the reaction time for slag decreased by 22 °C and 6 s respectively after adding Cr; the fluxing action was significant under Cr. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscope (FTIR) analyses showed that the above heavy metals had little influence on the reconstruction of slag. Toxicity characteristic leaching procedure (TCLP) leaching tests showed a good solidification effect of the heavy metals with melting slag, fixation rate of Zn, Cu, Pb and Cr was 36.3%, 24.6%, 9.2% and 93.2%, respectively. The leaching toxicity of the heavy metals met the requirements for environmental emission after solidification treatment.
The blend films with gelatin and poly(vinyl alcohol) (PVA) were prepared by a solution casting method. The compatibility between gelatin and PVA in the blend films was investigated. The transmittance, Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), thermogravimetry analysis (TG), and differential scanning calorimetry (DSC) were employed to characterize the resultant blend films. According to optic result, the opacity of the blend film at the ratio of 20/80 (w/w, Gel to PVA) was the lowest, indicating the best compatibility between Gel and PVA at the ratio. The results of IR, XRD, DSC, and TG revealed an intensive interaction and good compatibility between them in the blend film at the ratio. The mechanical properties and solubility showed that PVA content in the blend films obviously affected the elongation at break and solubility. The mechanical properties and water resistance of gelatin film may be improved by the introduction of PVA.
Nanoscale ionic materials(NIMS) based on carbon black(CB) were prepared through a facile method. Firstly, CB was oxidized in the mixture of nitric acid and sulfuric acid, resulting in a large amounts of -COOH on surface of CB. Then oxidized CB was grafted by polyetheramine through neutralization reaction between -COOH of CB and -NH2-of polyetheramine, and CB derivatives were obtained. This surface-functionalized CB can behave as liquid at ambient temperature in the absence of solvent by carefully varying the components. FTIR and thermaogravimetric analysis confirmed that the successively grafting of polyetheramine. TEM revealed the monodisperse core-shell structure of CB derivatives particles. The viscoelasticity of CB derivatives were closely related to the molecular weight and loading of polyetheramine. The unique core-shell and ionic structure and flowability of these CB derivatives could guide our future work on obtaining NIMs with tunable and controllable properties and broaden its commercial applications.
Perfluorinated alkyl silicone oil (PFASO) was successfully synthesized from N-ethyl-N-hydroxylethyl perfluorinated octane sulfonamide, succinic anhydride and amino silicone oil by esterification and amide reaction at moderate temperature in the presence of different catalysts. The chemical structure of the synthesized samples was characterized by Fourier transform infrared spectroscopy (FT-IR), the relative molecular mass(MM) and molecular mass distribution(MMD) of PFASO were tested by gel filtration chromatography(GFC). A commercial epoxy resin (DGEBA) was modified with PFASO, with the content of PFASO 1–5 phr. Thermo-gravimetric analysis (TGA), impact tests, scanning electron microscope (SEM) and water contact angle test were applied to provide accurate results on the thermal stability, toughness and hydrophobicity of PFASO/epoxy complex. The experimental results reveal that epoxy resins can be successfully modified by adding a small amount of as-synthesized modifiers via simple direct mixing, and verify that the as-synthesized modifier can improve the toughness and hydrophobicity of epoxy resin without sacrificing its thermal properties.
The corrosion behaviors of ultra-high strength steel 30CrMnSiNi2A in sodium chloride solution were studied by weight loss and electrochemical methods. The morphology of corrosion products was observed using scanning electron microscopy(SEM) and the composition was analyzed using an energy dispersive spectroscopy(EDS) and X-Ray diffraction (XRD). The experimental results showed that the corrosion came from pitting corrosion and the rust layer was composed of outer rust layer γ-FeOOH and inner rust layer Fe2O3 with a little β-FeOOH. The correlation between corrosion rate and test time accorded with exponential rule. The corrosion current measured by polarization methods was higher than that calculated by weight loss method after a long-time immersion, the main reason was that β-FeOOH and γ-Fe2O3 transformed by γ-FeOOH led to overestimating corrosion rate. The processes of corrosion prophase were obtained from XRD and EIS results. The corrosion product, Fe(OH)2 formed at the initial stage stayed at a non-steady state and then consequently transferred to γ-FeOOH, γ-Fe2O3 or β-FeOOH.
By means of Miedema formation enthalpy model with Toop model, the excess free-energy, enthalpies of formation, excess entropies and activity values of all components of Mg-Al-Y ternary alloy were calculated with computer programming. The experimental results show that enthalpies of formation, excess free-energy and excess entropies of the ternary alloy are negative in the whole content range, the minimum values at 1 123 K are all obtained at x Al=55%, x Y=45%, x Mg=0%, which are −37.969, −30.961 kJ/mol and −6.24 J/(mol·k) respectively. Activity curves show that the activity values of Al and Y in Mg-Al-Y ternary alloy rapidly decrease with the decrease of molar fraction, the values of which are very small when the molar fraction decreases to 0.4. It means that there is a strong interaction between Al and Y and stable compounds can be form in the Mg-Al-Y ternary alloy system.
The softening behavior of Inconel 718 alloy at different temperatures was studied using two-stage interrupted compression method on Gleeble1500D thermal stimulator, and the 2% offset method was applied to analyze the experimental dates. Finally, the static recrystallization fraction was obtained. At the same times, optical microscope (OM) and transmission electron microscopy (TEM) were employed to investigate the microstructure characteristic. The experimental results showed that the recrystallization was more sensitive to temperature than holding time. The recrystallization process finished quickly above 1 050 °C, and significantly prolonged below 1 025 °C. Additionally, the dynamical model of static recrystallization follows the Avrami equation. The nucleating mechanism was characterized by bulging at grain boundary and merging of sub-grain.
The purpose of this study was to use a three-component photoinitiation system comprising 1wt% CQ (camphorquinone), 2wt% DMAEMA (2-(dimethylamino) ethyl meth acrylate) and 2wt% Ph2I+PF6 − (diphenyliodonium hexafluorophosphate) to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis (3-methacrylate-2-hydroxy propyl) ether (BisS-GMA) with the expanding monomer unsaturated spiro orthoesters 2-methylene-1,4,6-trispiro[4,4] nonane (MTOSN), for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker’s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanical properties.
The apatite-coated chitosan microspheres were fabricated by incubating chitosan in five times simulated body fluid. The apatite deposited on the microspheres was similar to natural bone mineral, as demonstrated by scanning electron microscopy, X-ray diffraction spectra and Fourier transformed-infrared spectroscopy analyses. Rat bone marrow-derived mesenchymal stem cells (BMSCs) were seeded on apatite-coated microspheres to investigate the effect of this scaffold on cell proliferation and differentiation. BMSCs seeded on uncoated microspheres were served as a control. In vivo experiment was evaluated by transplanting the microspheres loaded with or without BMSCs in 5-mm cranial defects of Wistar rats. Bone regeneration was investigated via micro-CT and histological analysis. It was found that apatite-coated chitosan microspheres could significantly promote the proliferation and alkaline phosphatase activity of BMSCs compared with uncoated microspheres. Histological slices and Micro-CT images at 8 weeks revealed much better regeneration of bone in the apatite-coated microspheres loaded with BMSCs than the control. In addition, the defect filled with pure microspheres induced little new bone formation. Our findings suggest that the apatite-coated chitosan microspheres scaffold is a promising carrier of stem cells for cranial bone tissue engineering.
The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6Al4V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystallinity and morphologies of deposits were influenced by depositing temperature (100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C, respectively). The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6Al4V surface when the depositing temperature is 100 °C. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.
The potential of combining bioactive glass(MBG) and silk fibroin(SF) together as a new drug delivery system was evaluated. The three-dimensional porous scaffolds were selected as the form of SF, and sol-gel method was adopted to fabricate MBG in this study. The characteristic of the synthesized material was measured by transmission electron microscopy and scanning electron microscopy. In vitro evaluation of drug delivery was carried out in terms of drug loading and drug release. And aspirin was chosen as the drug for scaffolds to carry out in vitro tests and repair BALB/C mice calvarial defects. Bone formation was examined by microcomputed tomography. The experimental results show that MBG/silk scaffolds have better physiochemical properties compared with silk scaffolds. In comparison to pure silk scaffolds, MBG/silk scaffolds enhance the drug loading efficiency, release rate in vitro and promote bone regeneration in vivo. Thus we conclude that MBG/silk scaffold is a more efficient drug delivery system than pure silk scaffolds.
The nano-TiO2 particles were prepared by liquid hydrolysis method and characterized using XRD. Its antibacterial activity against two representative bacterial, Escherichia coli and Staphylococcus aureus, was also studied. The experimental results showed that the nano-TiO2 calcinated at 600–700 °C contained the obvious anatase phase and exerted excellent antibacterial activity. The feature of antibacterial activity of nano-TiO2 was non-strains specificity and exerted best antibacterial activity at concentration of 0.8 g/L.
This study aimed to evaluate the effect of three inorganic materials:casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), calcium sodium phosphosilicate (CSP) and sodium fluoride (NaF) on their remineralization potential. CPP-ACP, CSP and NaF were applicated in demineralized enamel for 4 h and then all enamel samples were immersed in remineralization solution. After 10 days, all samples were prepared for microhardness test, scanning electron microscopy (SEM) observation and the elemental level (%) analysis by energy dispersive X-ray spectroscopy (EDX). The surface microhardness (SMH) values of three experimental groups were significantly higher than that of control group (P<0.05). The SMH value of NaF group was significantly higher than other experimental groups (P<0.05). The SEM micrographs showed that three remineralization materials caused distinct morphological changes and remineralized deposits were different from each other. EDX elemental analysis showed that there were significant differences in the Ca (wt%) and Ca:P molar ratio of the enamel layer among control and experimental groups. The Ca (wt%) and Ca:P molar ratio in NaF group were significantly higher than those of other experimental groups. There were no significant differences in P (wt%) among control and experimental groups (P<0.05). Three remineralization materials used in our study had the potential of remineralizing the demineralized enamel. NaF is the best and most feasible choice to be used in remineralizing the demineralized enamel.