W-doped TiO2 supported by hybrid carbon nanomaterials of multi-walled carbon nanotubes and C60 fullerene was synthesized by a simple hydrothermal method. The material displayed high visible light photocatalytic activity. X-ray diffraction, field emission transmission electron microscopy, ultra violet/visible light absorption and photoluminescence spectroscopy were used to characterize the material as photocatalyst. Photocatalytic activity on the degradation of Rhodamine B dye in an aqueous solution under ultraviolet light and visible light irradiation was also studied. The experimental results indicated that the photocatalytic activity of the material was much higher than that of pure TiO2 or Degussa P25 TiO2.
The hybrid particles composed of hydroxyapatite (HAp) and ferrite (γ-Fe2O3) were synthesized by two-step precipitation method. The effect of reaction temperature on the morphology of the hybrids was also studied. The resultant hybrids were characterized by transmission electron microscopy (TEM) and X-ray diffraction analysis(XRD). It was found that γ-Fe2O3 nanoparticles dispersed within the HAp matrix and these hybrids had a feather-like or spherical morphology when synthesized at 90 °C or room temperature, respectively. The magnetic properties of the hybrid showed good superparamagnetic feature, and they could be controlled by the external magnetic field.
Graphene was produced via a soft chemistry synthetic route for lithium ion battery applications. The sample was characterized by X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy and transmission electron microscopy, respectively. The electrochemical performances of graphene as anode material were measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The experimental results showed that the graphene possessed a thin wrinkled paper-like morphology and large specific surface area (342 m2·g−1). The first reversible specific capacity of the graphene was as high as 905 mA·h·g−1 at a current density of 100 mA·g−1. Even at a high current density of 1000 or 2000 mA·g−1, the graphene maintained good cycling stability, indicating that it is a promising anode material for high-performance lithium ion batteries.
Effect of solution concentration on the structures and corrosion inhibition behavior of γ-APS films fabricated on surface of low carbon steel was systematically studied by EIS, RA-IR, and AFM. The experimental results indicated that the impedance of γ-APS silane treated substrates and the cross-linking degree of γ-APS films gradually increased with the increasing solution concentration. There was some noticeable transformation in molecular orientation and protective performance of γ-APS films when solution concentration was above 10vol%. High cross-linking degree and changes in molecular orientation generated γ-APS films with excellent protective performance and ordered arrangement.
Nest-like and multilayered-disk-like Bi2WO6 photocatalysts were synthesized through a hydrothermal strategy using thiourea and acetic acid as complexing agents. The nest-like Bi2WO6 showed excellent visible-light-driven photocatalytic performance, and it could decompose rhodamine B(RhB) within 100 minutes. This excellent performance resulted from its special microstructure and the relatively large surface area.
Novel microcellular foams using thin plasticized PC sheet were prepared by compression molding. The measurement results showed that T g of plasticized PC was decreased and the molecular chain mobility was increased. Decrease in T g and increase in chains mobility were contributed to the widen of foaming temperature window. Effects of processing conditions on cell size, cell density and relative density were also investigated. The experimental results show that the temperature, tributyl citrate and foaming agent content have more effects on the structures and morphology of the plasticized PC microcellular foam. Effects of experimental conditions on cell size distribution have also been discussed.
Distribution expressions of total gas pressure and partial water vapor pressure along the channel direction were established based on lumped model by analyzing pressure loss in the channel and gas diffusion in the layer. The mechanism of droplet formation in the flow channel was also analyzed. Effects of the relative humidity, working temperature and stoichiometry on liquid water formation were discussed in detail. Moreover, the force equilibrium equation of the droplet in the flow channel was deduced, and the critical flow velocity for the water droplet removal was also addressed. The experimental results show that the threshold position of the liquid droplet is far from the inlet with the increase of temperature, and it decreases with the increase of the inlet total pressure. The critical flow velocity decreases with the increase of the radius and the working pressure.
The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes (SWCNTs) are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics (MSM) into finite element method (FEM), the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption (SEA) of SWCNTs is 1–2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications.
TiAlN solar selective absorbing coatings which were deposited on 304L stainless steel using cathodic arc evaporation method were annealed under non-vacuum at different temperatures with different times. The optical properties (absorptance and emittance) of the coatings were measured by a spectrophotometer. It was found that, after being annealed for 2 hours at different temperatures, the absorptance of the coatings reached the highest value of 0.92 at 700 °C while the emittance got the lowest value of 0.38 at 800 °C. When the coatings were annealed at 600 °C for 24 hours, the optical properties changed to 0.92/0.44 (absorptance/ emittance). By measuring the structure, morphology, elements and surface roughness of the coatings, it was found that both the elemental composition and the surface roughness of the coatings changed as a result of annealing, and these changes caused the change of the optical properties of the coatings.
A new type of the nanometer particles and epoxy/bismaleimide-triazine nanocomposites were prepared using a nanometer silica (nano-SiO2), a 4,5-epoxycyclohexane 1,2-dicarboxylic acid dilycidyl (TDE-85) epoxy resin, a 4,4′-bismaleimidodiphenymethane (BMI) and a bisphenol a dicyanate (BADCy). The properties of nano-SiO2/TDE-85/BMI/BADCy composites, such as mechanical and thermal properties, were systemically investigated in detail by mechanical measurement, scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The experimental results showed that the addition of the appropriate amount of nano-SiO2 could improve the impact strength and the flexural strength of the nano-SiO2/TDE-85/BMI/BADCy composites. Simultaneously, the thermal stability of the blends was found to be higher than that of the TDE-85/BMI/BADCy copolymers.
A simple procedure was presented to directly synthesize Zn1−xCd xS (0⩽x⩽1) quantum dots (QDs) in aqueous solution. QDs’ structures and properties were characterized by TEM (transmission electron microscopy), XRD (X-ray diffraction) and fluorescence microscopy. For those as-synthesized Zn1−xCd xS QDs, when the molar ratio between Zn and Cd changed from 1 to 0, its photoluminescence (PL) emission peak shifted from 430 nm to 675 nm. PL emission quantum efficiency was up to 15%. The experiment results demonstrated that those alloyed QDs showed a good biocompatibility and could be used as labelling materials in cell biology.
Novel poly(thioether imide)s were synthesized by 2,5-dimercapto-1,3,4-thiadiazole, and aromatic heterocyclic chlorodiimids through nucleophilic substitution reaction as alkali catalysts were presented. The poly(thioether imide)s exhibited good thermal property. The glass transition temperatures of polymers were around 373 °C, and 10% weight loss temperatures were in the range of 450–500 °C in nitrogen/air atmosphere. Meanwhile, the chloroform dilute solutions of these polymers could show strong UV-vis absorption peaks at about 289 nm. After being protonated by inorganic acids (HCl), the new shoulder absorption peaks were observed at 350 nm. The PL absorption bands of polymer solutions were in the region of 350–550 nm, which showed the green-yellow fluorescence.
SiCp/Al-Mg metal matrix composites were manufactured by semi-solid stirring technique. The composites were remelted and then solidified under different pressures to study the solidification behavior of composites by differential thermal analysis, scanning electron microscopy, and transmission electron microscopy. The experimental results show that SiCp reinforcements can not act as heterogeneous nucleation sites for α(Al), and an interfacial layer composed of MgAl2O4 spinel and Si-rich phase existed at Al/SiCp interface. The undercooling of the matrix alloy was improved by the pressure applied, resulting in the grain of matrix alloy refining. The X-ray diffraction pattern of composites testified that the matrix alloy exhibited a certain preferred orientation during solidification. In addition, with increasing the pressure for solidification, the pored defects in the composites decreased, while the relative density, hardness and compressive strength increased. Therefore, the microstructure and mechanical properties of the composites were improved by pressure placed during the solidification of SiCp/Al-Mg composites.
This project was aimed to evaluate the chloride permeability and corrosion behavior of cement-based composites which comprised fibers and silica fume in the mixes. Resistivity, polarization resistance, ponding and rapid chloride penetration results of specimens were obtained through tests. Test results indicate that resistivity, open circuit potentials and direct current polarization of specimens with w/b ratio of 0.35 are higher than those of specimens with w/b ratio of 0.55. For length-diameter ratio of 65, resistivity and direct current polarization of specimens with fiber length of 35 mm were similar to those of 60 mm. In addition, the open circuit potentials of specimens with fiber length of 60 mm were slightly higher that those of 35 mm. The resistivity decreased with increasing steel fiber content, and the open circuit potential and direct current polarization increased with increasing steel fiber content. The specimens containing silica fume were found to provide higher resistivity, open circuit potentials and direct current polarization than the control specimens. The incorporation of steel fiber and silica fume in composites achieved more significantly decreases in resistivity and increases in direct current polarization than steel fiber composites or silica fume composites. The penetration depth and six-hour total charge passed of specimens for w/b ratio of 0.35 were lower than those for w/b ratio of 0.55. For length-diameter ratio of 65, the penetration depth of specimens for fiber length of 35 mm was similar to that of 60 mm. The penetration depth decreased with increased steel fiber content in the composites. By regression analysis, a good correlation between open circuit potential and direct current polarization, and chloride penetration depth and direct current polarization.
Hydroxypropyl methylcellulose (HPMC) and amphoteric polyacrylamide (ACPAM) were respectively used to prepare engineered cementitious composite (ECC) which exhibits strain-hardening behavior under uniaxial tension. The connections between cement paste structure and the performance of the composite in fresh and hardened state were investigated, aiming at achieving the desirable workability at a given solids concentration. The experimental results of viscosity and microstructure of cement pastes show that the intimate connections between flocculation groups lead to the growing increase in viscosity. The results of deformability and fiber dispersion demonstrate that fiber dispersion coefficient is a comprehensive index which can reflect the performance of deformability as well as uniformity. And the desirable fresh mixture can be achieved by optimizing the viscosity of cement paste. At last, the ductile strain-hardening performance of the ECC prepared with HPMC or ACPAM was investigated through uniaxial tensile test.
Self-compacting concrete (SCC) was used for the filling layer of CRTSIII plate ballastless track, which needs excellent workability. The rheological properties of SCC cement paste containing chemical admixtures (CA) such as polycarboxylate-based superplasticizer (PCE), air-entraining agent (AE) and defoamer (DF) were investigated using a Brookfield R/S SST2000 soft solid tester with a vane geometry spindle. The cementitious materials were designed as one, two and, three components systems by addition of ordinary portland cement (OPC) with these chemical admixtures. The rheological properties of one-component system (PCE paste) were improved with increasing the content of PCE. For two components systems of PCE-AE and PCE-DF, yield stress and plastic viscosity reduced firstly and increased afterward with the increasing of AE content. And the plastic viscosity reached the optimum when the content of AE is 0.004wt%. In general, the trend of yield stress and plastic viscosity decreased with the increasing of the DF content. For three components systems, PCE-AE-DF systems, the rheological properties were improved compared with the sample with AE or DF, which attributed to mixes of the active components mentioned above (CA) which could have a synergetic effect.
For lack of laboratory and field performance data on stabilization of reclaimed asphalt pavement (RAP) aggregate and stabilized soil (S) for road bases and subbases construction, the influences of RAP/S ratio, cement and fly ash content, modifying agent (MA) on the compact, unconfined compressive strength, indirect tensile strength and water stability of the CIR mixtures were investigated. The experimental results showed that the maximum dry density and the optimum moisture content of the mixture changed significantly with the RAP/S ratio and cement-fly ash content. Unconfined compressive strength, indirect tensile strength and water stability were improved significantly by the addition of MA, and the water stability was improved by nearly 20% on average. Scanning electron microscopy(SEM) images indicated that MA accelerated the hydration of cement-fly ash system. Needle-like AFt and fibrous C-S-H gel were observed in the mixtures, which resulted in the cementation effect among the CIR mixture particles and a more compact microstructure. All these could be the cause of high strength of the CIR mixtures with MA.
In situ monitoring of the microstructure evolution of cement mortar in accelerated carbonation reaction for different carbonation ages was carried out by X-ray computed tomography (XCT). And the carbonation degrees of different time were measured by the volume fraction of uncarbonated and carbonated parts. Meanwhile, we presented a model for the carbonation of cement mortar by means of X-ray computed tomography (XCT). Based on the principles of chemical engineering processes, the reacted products become a solid inert ash layer. Finally, the model was validated with results of accelerated carbonation of cement mortar. The model is thus able to reasonably predict the carbonation phenomena for accelerated conditions.
In order to study the effects of loading condition and temperature on the dynamic properties of asphalt mixtures, the dynamic loading tests on different loading condition (various speeds and loads under a certain roughness) and temperature conditions were performed. The experimental result show that the dynamic properties of asphalt mixtures are influenced by vehicle load and speed, besides, the effects of temperature on dynamic properties of asphalt mixture are significant.
In order to study how to correctly apply the two different time dependencies to service life prediction models, the definition of parameters in the time dependent equation using the long-term test method and the short-term test method, and its relationship were discussed. The experimental results show that, as the two time dependencies have different meanings, they have different manners when handled in service life prediction models. Time dependency of chloride diffusion coefficients in concrete was obtained by fitting experimental data. A large number of accurate experimental data were required to fit the formula of time dependency to ensure the accuracy of service life prediction model.
Yb:YAG nanopowders were synthesized by the alcohol-water co-precipitation method adding MgO as sintering additives. Appropriate amount of MgO adding can restrict the agglomeration and reduce the particle size of Yb:YAG powders. When the MgO content was 0.04wt%, well-dispersed Yb:YAG powders with ellipsoidal particles of less than 100 nm diameter were obtained. The experimental results showed the valence variation of doping ion Yb3+ would not appear when adding MgO as sintering additives, so ceramics showed colorless transparent instead of green due to Yb2+ color center using traditional SiO2 as additives. The transmission of the sintered Yb:YAG ceramics can reach 80.6% even without annealing. Ceramic morphology showed that the grains had uniform-distribution with the size of 10 μm or so, and no impurity and pore existed in the grain boundary and crystalline while using optimal sintering conditions.
Targeting the problem of available water conservation in sand fixation, the sand-fixing and grass-planting materials were prepared with clay modified by emulsifying vegetable waxes and octylphenol polyoxyethylene ether (OP4). The water retention property was studied in simulating desertification environmental climate and the materials were characterized by means of UV-Vis, SEM, FTIR, XRD and TGA measurements. The experimental result showed that the materials had excellent water retention properties, due to that vegetable waxes adhered evenly to clay particle surfaces, made the clay pores changing from hydrophilic to hydrophobic and so inhibited the water evaporation. Grass-planting experiment showed that, with reasonable mass ratio of clay, vegetable waxes and surfactant, the materials not only inhibited water evaporation but also maintained sound air permeability so shat the germination rate and survival rate of grass were significantly improved.
A cordierite was synthesized from calcined bauxite, talcum, and quartz. The properties and microstructure of the cordierite sintered samples were characterized by Archimedes’ method, thermal dilatometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and so on. The experimental results showed that calcined bauxite could broaden the range of synthesizing temperature from 1300 °C to 1420 °C and get pure cordierite. The bulk density and linear thermal expansion coeffi cient of the sample synthesized at 1420 °C for 2 h were 1.97 g·cm−3 and 2.1×10−6 °C−1, respectively. The XRD analysis showed that the major crystalline phase was α-cordierite with almost no glassy matters, the SEM images illustrated a small vent hole and the size were 5–100 μm, the well-grown hexagonal and granular cordierite grains had the sizes distributed among 0.1–8 μm, and providing high mechanical strength and lower linear thermal expansion coeffi cient.
Copolymerization of chitosan selectively grafted by polyethylene glycol was prepared. Chitosan was selectively grafted by monomethoxy polyethylene glycol(mPEG-OH), which contained a hydroxyl group combining with hexamethylene diisocyanate(HDI) to form a novel macromonomer namely monomethoxy polyethylene glycol isocyanate(mPEG-NCO) containing a isocyanate group with higher chemical activity in ethyl glyoxalate solution absolutely without water. The selective grafted copolymerization of Chitosan with mPEG-NCO was conducted under heterogeneous conditions as suspension in dimethylformamide. The hydrophilic copolymers of chitosan were prepared by condensation reaction of isocyanate group on mPEGNCO with hydroxy groups on chitosan chains because amino groups on chitosan chains were protected by complexion formation with copper ions. The effect of reaction condition on the grafting extents was discussed. Swelling properties of mPEG-g-CS were researched. The graft copolymer mPEG-g-CS was characterized by the infrared spectra. The experimental result showed that the copper ions were very effective to protect amino groups from condensation reaction. The swelling degree in water increases with adding of grafting ratio. The maximum swelling degree was up to above 132% when the grafting ratio was about 270%. The graft copolymer can be soluble partially in pure water.
Bridge polycarboxylate superplasticizers(PCs) with crosslink structure were synthesized by using polyethyleneglycol di-acrylate(PEGdA), replacing partial polyethyleneglycol mono-acrylate (PEGmA) as crosslinking agent. Structures of bridge PCs were analyzed by gel permeation chromatography, and dispersion ability was evaluated by cement paste dispersity variation on time and rheology test. The experimental results showed that, molecular weight(MW) of bridge PCs increased with increase of PEGdA proportion, and MW distribution curve changed from Gaussian to flat like, which meant notable increase of highly crosslinked copolymer. Bridge PCs led to decreased initial cement paste dispersity and better dispersity retention due to slow releasing. Further research showed that, PEGdA proportion had slight effect on polymerization degree of backbone, MW distribution of backbone deviated from Gaussian distribution and shoulder peaks appeared on distribution curve when PEGdA increased.
CaCu3Ti4O12 (CCTO) ceramics doped with Zr4+ were prepared. Effects of Zr4+ on microstructure, dielectric properties and conduction behavior of CaCu3Ti4−xZr xO12 (x=0, 0.05, 0.10, 0.20) ceramics were studied in the frequency range of 10–106 Hz. Grain size and dielectric loss of Zr4+-doped CCTO ceramic decreased compared with pure CCTO. The loss tangent (tanδ) of CaCu3Ti4−xZr xO12 (x=0.20) ceramic droped to 0.05 at a frequency of 1 kHz, which was reduced by 55% compared with pure CCTO ceramic. The mechanism effect of electrical conductivity on dielectric loss of Zr4+-doping CCTO ceramics was also discussed.
The Co2O3-doping effect on the formation of 3CaO·3Al2O3·CaSO4 from CaCO3-Al2O3-CaSO4·2H2O mixtures was investigated by means of SO2 emission behavior, chemical analysis, X-ray diffraction, differential thermal analysis and scanning electron microscopy. The experimental results show that Co2O3 addition increases the reactivity of the CaCO3-Al2O3-CaSO4·2H2O system significantly, by reducing SO2 emissions in combustion and f-CaO contents in the clinkers, promoting the nucleation and growth of 3CaO· 3Al2O3·CaSO4, and intensifying the formation of 3CaO·3Al2O3·CaSO4. Moreover, Co2O3 addition lowers the formation temperature of 3CaO·3Al2O3·CaSO4 by 18 °C, and similarly increases the thermal stability of it at a wider temperature range.
Sliding friction and wear behavior of two different grain-size aluminas (average grain size = 0.6 and 2 μm) was studied in physiological saline environment. Relationship between time and wear loss was observed. The wear loss volume increased with increased sliding time and fine-grained alumina exhibits a lower value. In the initial wear-in period, grains pull-out caused by grain-boundary microcracking is the dominant wear mechanism of submicron grained alumina. In the case of alumina of large grain size, intergranular and transgranular fracture is the basic wear mechanism. As the sliding time increases, compaction of wear debris on sliding surface of fine and coarsen alumina determines the wear characteristics.
Three-dimensional (3D) five-directional braided (SiO2) f/SiO2 composites were prepared by silicasol-infiltration-sintering (SIS) method. The flexural properties and microstructures were studied. The flexural strength and flexural elastic modulus were found to be 73 MPa and 12 GPa, respectively. The results of stress vs deflection curve and SEM examinations revealed that the fracture mechanism of 3D, five-directional braided (SiO2) f/SiO2 composite was a mixture mode of ductile and brittle. The ductile mode was attributed to the weak bonding strength of fiber/matrix at low temperature. The brittle fracture might be caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process.
Varying the flow rate of natural gas from 50 to 80 to 120 l/h, isotropic pyrocarbon produced by hot wall chemical vapor deposition at 1000 °C were examined by X-ray diffraction and Raman spectroscopy. The X-ray data were evaluated by Scherrer equation, and the intensity ratio of D to G band derived from Raman data was used to evaluate the lateral extension of isotropic pyrocarbon. The experimental results show that the d 002-spacing of isotropic pyrocarbon decreases from 0.3499 nm to 0.3451 nm, while the stack height increases from 6.5 to 8.4 nm with the increase of flow rate of natural gas. The intensity ratio of D to G band and lateral extension of isotropic pyrocarbon increases with natural gas flow rate increasing. After heat treatment, all the crystallite parameters (stack height, lateral extension, and d 002-spacing) decrease, indicating the improvement of the arrangement of the basic structural units of isotropic pyrocarbon.
A new permanent magnetic separator was introduced to treat the ores with the characteristics of weak magnetic iron minerals and in a fine size range. The new machine was applied to the iron removal from potash feldspar. The effects of the magnetic field intensity, pulp density and grinding fineness on the iron removal were investigated. The optimized operation parameters were achieved and listed as follows: the −0.074 mm content is 85%, the pulp density is 45% and the magnetic field strength is 2T. A close test of middles regrinding was also carried out to improve concentrate yield. The data show that the grade of TFe(total iron) in potash feldspar product decreased from 1.31% to 0.21% and the concentrate yield reached 85.32%. All the results indicated that the traditonal high-intensity electromagnetic separators can be betterly substituted by the new permanent magnetic separator. This study may provide the theoretical evidence for iron removal from potash feldspar.
The corrosion process of phenolic epoxy coated tinplate in energy drink was investigated by in-situ electrochemical impedance spectroscopy(EIS) and electrochemical noise(EN) techniques. The experimental results indicate that the degradation process of novolac epoxy coated tinplate in energy drink can be divided into three main stages: organic coating wetted by the beverage; corrosion initiation beneath the organic coating; and corrosion extension process. It was proposed that the tin coating and carbon steel were mainly corroded by organic acids in energy drink through the pores of the organic coating. After the tin coating was corroded, the carbon steel started to corrode due to its higher electrochemical activity and became to be the dominated corrosion reaction.
The products of expanded polypropylene(EPP) is widely explored and used. the PP modification methods, the preparation methods of EPP and the molding technology of EPP were reviewed. The application of EPP in the field of sporting equipment were also discussed. This paper may provide theoretical foundation for the applications and developments of EPP.
The low-melting phosphate glass was prepared for production of glass binders for protective coating of steel slab. Effects of different O/P ratios on glass structures and properties were analyzed. Differential thermal analysis (DTA) and infrared spectroscopy (IR) techniques were applied for low-melting glass binder. It was found that the glass transition temperature(T g) was about 300 °C and softening temperature(T f) was about 480 °C. The choice of O/P ratio was very important to the glass transition and softening temperatures. When more P=O bonds existed in the glass networks, P-O-P bond angle was deformed with decreasing of the ratio of O/P. The coatings could adhere to the substrates instantaneously at 800 °C when the content of binder exceeded 3wt%. The optimal content of glass binder was 5wt%.
In situ A356-x%PVF (particle volume fraction) ZrB2 (x=1, 3, 5) composites were prepared via magneto-chemistry in situ reaction and the dry sliding wear properties of the composites were investigated. The experimental results show that ZrB2 reinforcement particle is obtained and its morphology mainly present in spherical and regular hexagon. Wear test results show that the values of wear weight loss of the composites decrease with the increase of value under a given sliding time and a certain load of 60 N. Especially, when x=5, the weight loss of the as-prepared composite is 43.1 mg, which is only 36.4% to that of A356 alloy, 118 mg. The wear mechanism is changed from adhesion wear to adhesion wear and abrasive wear and then to abrasive wear with the increase of x value.
Microstructures and tensile properties of Mg-6Zn-1Y-1Ce alloy extruded in a temperature range between 300 °C and 400 °C were investigated. The yield strength of the material increased as the extrusion temperature decreased due to grain refinement. The yield strengths and grain sizes of extruded samples met Hall-Petch equation. The microstructure of the alloy extruded at 300 °C had a bimodal grain size distribution with an average grain size of 2.7 μm and showed a yield strength of 327 MPa with an elongation of 9%. The fine-grained microstructures were attributed to the dynamic recrystallization and the pinning effect of fine strengthening particles.
To investigate the bacterial colonization on zirconium oxide and titanium surfaces in vivo quantitatively using a confocal laser scanning microscope (CLSM). Ten samples of zirconium oxide ceramic and commercially pure titanium were fabricated and polished using silicon carbide abrasive paper. One sample from each group was evaluated topographic pattern under a scanning electron microscope. One sample from each group was to evaluate roughness using a profilometer. Eight volunteers were selected. The samples were cemented at the buccal surfaces of upper first molars. All samples were removed after 48 hours, immersed in SYTO-9 and propidium iodide fluorescent to stain for adherent bacteria and observed with CLSM. Fewer bacteria were observed in zirconia group than titanium group. However, there was no statistical difference between two groups. The experimental results demonstrate that zirconium oxide may be considered as a promising material for dental implant abutments.
Gelatin ceftiofur alkali microsphere was prepared to observe its characteristics and evaluate preservation conditions. The glutaraldehyde was increased and the carboxylic methyl chitosan was added to improve the microsphere. The experimental results show microspheres have a better morphology surface and fairly regular structure with 4% glutaraldehyde. The average particle size is 15.84 μm and particle size distribution is narrow which shows a good uniformity. Microsphere size was affected by the stirrer speed, dosing ratio and curing degree. The greater drug loaded is, the better microspheres loading is; but with the increase of drug loading rate, the entrapment efficiency increases first and then decreases. The drug release rate of the microsphere is 24.90% in 0.5 h and 84.90% in 48 h, when CMC-GMs with 4% curing agent is 32.03% in 0.5 h and 88.44% in 48 h. So Gms embedding of ceftiofur alkali are better than CMC-GM. The stability tests show that strong light, high temperature, high humidity have a great influence on the microspheres.