Nickel tartrate precursor particles were synthesized by the liquid phase precipitation method in an ethanol-water-ammonia mixed solution, with tartaric acid and using nickel chlorate as raw materials, with the pH value controlled at 4.0, and the temperature controlled at 50 °C. Nickel particles with complicated morphology were prepared by the decomposition of nickel taratrate precursor particles at temperatures of 360, 380 and 400 °C, respectively. The study of infrared spectroscopy (IR) indicated that the product was pure nickel tartrate. The studies of the atomic absorption spectrometry (AAS) and organic elemental analysis (OEA) indicated that the molar ratio of Ni2+ to (C4H4O6)2− is close to 1:1. The studies of the differential scanning calorimeter and thermo-gravimetric analysis (DSC-TG) indicated that the chemical formula Ni2(C4H4O6)2·5H2O was confirmed. The studies of X-ray diffractions (XRD) indicated that the silvery white metal powders were pure Ni, with a face-centered cubic crystal structure. The images of scanning electron microscopy (SEM) showed that the morphology of metal Ni particles was obvious spherical and radiate. The diameter of nickel tartrate particles was about 60 μm, which consisted of many nanolathes; and the diameter of metal Ni particles was about 30 μm, which consisted of many lathes about 0.5 μm in thickness.
Dy2(WO4)3 powders were synthesized through liquid-phase reaction. The structure transformation of Dy2(WO4)3 powders were analyzed by differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The optical absorption and photoluminescence properties were characterized by UV-vis-infra diffuse reflectance spectra and fluorescence spectra. The Dy2(WO4)3 host could absorb deep UV light and transfer the energy of UV light to Dy3+ ions, which convert the high-energy UV light to blue light (482 nm, 4 F 9/2→6 H 15/2) and yellow light (547 nm, 4 F 9/2→6 H 13/2). The Dy2(WO4)3 powders could also absorb near UV light and exhibit blue and yellow emissions near 482 and 547 nm, respectively. Heat treating promoted the crystallization and regulated the micro-structure of Dy2(WO4)3 hosts. The bands of W-Od anti-symmetric stretching vibration exhibited red shift with the increasing of sintering temperature. The W-Ob-W groups tended to combine with each other to form W-Oc-W groups after heat treating. These regulation of micro-structure had influence on the luminescent color of Dy2(WO4)3. The samples could emit yellow-green, white-yellow and white light under the excitation of 350 nm after being treated at 600, 800 and 1 000 °C, respectively. The prepared Dy2(WO4)3 powders have potential to act as UV absorber for solar cell to improve the conversion efficiency and also exhibit potential for white light LED.
Ternary In-rich Al xIn1−xN films were successfully grown on Si (111) and (0001) sapphire substrates by radio-frequency magnetron sputtering on a relatively Al-rich Al xIn1−xN layer after AlN buffer. X-ray diffraction (XRD) patterns of the films indicate highly c axis-oriented wurtzite structure and the indium content of about 0.76 has been evaluated according to the Vegard’s law. An Al-rich Al xIn1−xN transition layer was formed between the ultimate In-rich Al xIn1−xN film and the AlN buffer, which served as a further buffer to alleviate mismatch. X-ray photoelectron spectroscopy (XPS) depth profiling analyses confirm the alternative of indium and aluminum composition and the unavoidable oxygen impurities from surface to bulk. Owing to high indium content, obvious E 2 H and InN-like A 1 (LO) phonon model accompanying with slight AlN-like A 1 (LO) phonon model are observed. Hall effect measurements demonstrate n-type electrical conductivity in these alloys with carrier concentrations n=1019 cm−3. The strain in In-rich Al xIn1−xN films can be significantly reduced by introducing an Al-rich interlayer, facilitating the improvement of film quality for diverse device applications.
Amorphous ribbons of the alloy Fe73.5Si13.5B9Cu1Nb1V2 were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry (DSC) measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami (JMA) equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nucleation rate. The variation of soft magnetic properties of nanocrystalline Fe73.5Si13.5B9Cu1Nb1V2 alloy powder cores as a function of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.
Titanium aluminum carbide (Ti3AlC2 and Ti2AlC) powders were synthesized from TiH2 powders instead of Ti powders as Ti source by a tube furnace under argon atmosphere without preliminary dehydrogenation. 95 wt% pure Ti3AlC2 powders were synthesized from TiH2/1.1Al/2TiC at 1 450 °C for 120 min. High-purity Ti2AlC powders were also prepared from 3TiH2/1.5Al/C and 2TiH2/1.5Al/TiC powders at 1 400 °C for 120 min. The as-synthesized samples were porous and easy to be ground into powders. Sn or Si additives in starting materials increased the purity of synthesized Ti3AlC2 obviously and expanded the temperature range for the synthesis of Ti3AlC2. With Si or Sn as additives, high pure Ti3AlC2 was synthesized at 1 200 °C for 60 min from TiH2/x Si/Al/2TiC and TiH2/x Sn/Al/2TiC (x = 0.1, 0.2), respectively.
The effects of atmospheres and precursors on MnO x/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NO x conversion activity in ammonia selective catalytic reduction (NH3-SCR) reactions. Results showed that the manganese carbonate (MC) precursor caused mainly Mn2O3, while the manganese nitrate (MN) precursor resulted primarily in MnO2 and the manganese sulfate (MS) precursor was unchanged. The manganese acetate (MA) precursor leaded obtaining a mixture of Mn2O3 and Mn3O4. NO x conversion decreased in the following order: MA/TiO2 > MC/TiO2 > MN/TiO2 > MS/TiO2 > P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO x conversion decreased with calcination atmospheres: Nitrogen> Air> Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.
Epitaxial (0001)-oriented Zn1−xCo xO ( x= 0.01, 0.05 and 0.1) thin films were grown on c-sapphire substrates by pulsed laser deposition. The XRD analysis, optical transmittance and XPS measurements revealed that the Co2+ substituted Zn2+ ions were incorporated into the lattice of ZnO in Zn1−xCo xO thin films. The electrical properties measurements revealed that the Co concentration had a nonmonotonic influence on the electrical properties of the Zn1−xCo xO thin films due to the defects resulted from imperfections induced by Co substitution. The resistivity remarkably increased and the carrier concentration remarkably decreased in Zn1−xCo xO thin films after oxygen annealing at 600 ° under 15 Pa O2 pressure for 60 mins. Room-temperature ferromagnetic was observed and the ferromagnetic Co amount was smaller than the nominal Co concentration for Zn1−xCo xO samples before oxygen annealing. After oxygen annealing, the Zn1−xCo xO thin films exhibited paramagnetic behavior. It is suggested that the room-temperature ferromagnetic of Zn1−xCo xO thin films may attribute to defects or carriers induced mechanism.
CaO-Al2O3-SiO2 system float glasses were melted at an elevated temperature, and about 60% of the total energy was occupied by melting and clarification stage. In order to reduce the melting temperature of the float glasses, Bi2O3 was added as fluxing agent. The structure and some melting properties such as the influence of the addition of the oxidation bismuth on the properties of float glass melt, melting temperature, and the structure of glass were studied. The results showed that the basic structure was not changed with the addition of Bi2O3 from 0.5% to 2%. The viscosity of the glass melt decreased with the addition of Bi2O3 obviously, as the viscosity of the glass melt was 1.35 Pa·s, the temperature was reduced by about 30 °C from sample A1 to sample A5. With the increasing of Bi2O3, the bending strength of glass was reduced and the transmisivity of glass samples had no change in visible light range, and the transmissivity of the glass samples was more than 88%. The ultraviolet cut-off length showed red shift with the addition of Bi2O3. With the increasing of Bi2O3, the water resistance of the glass samples was improved.
Two types of high-purity synthetic silica glasses were annealed with different processes in precision annealing furnace. The thermal stress and structure of samples were analyzed by two types of stress instruments and Fourier transform infrared spectrometer. After being annealed at 1 070 °C for 6 days and then cooled slowly, optical path difference (OPD) caused by stress in the center and edge of Type III silica glass with a diameter of 150 mm and thickness of 50 mm decreased from 6 to 2 nm/cm. Meanwhile, with the same annealing process, fictive temperature of small-size Type III glass decreased to 939 °C, and structural stability of silica glass was improved. In addition, after being annealed at 1 100 °C for 5 hours and then cooled slowly, internal stress in Type IV silica glass with a thickness of 1 mm was basically eliminated, and its fictive temperature decreased from 1 421 to 966 °C.
The crystallization kinetics of 38.0CaO-38.0Al2O3-10.5BaO-6.5MgO-6.0Y2O3-1.0(Na2O+K2O) (wt%) glass was studied by differential scanning calorimeter (DSC) and X-ray diffraction (XRD) techniques. The results showed that DSC curves of calcium aluminate glass have a single glass transition temperature followed by one crystallization peak for the heating rates β = 5 K/min and two crystallization temperatures T p1 and T p2 for β ≥ 10 K/min. The activation energies of crystallization obtained from the Gao-Wang model of the first exothermal peak and the second exothermal peak of calcium aluminate glass are 340 and 662 kJ/mol, respectively. The Avrami exponents of the both crystallization peaks are approximately 2, indicating the twodimensional crystalline growth during its transformation from amorphous to crystalline. Ca12Al14O33, Ca3Al2O6 and unknown crystalline phases firstly appear when calcium aluminate glass is heat-treated. With the extending of heat-treatment duration, BaAl2O4 phase comes out.
The pechini method was used to synthesize antimony-doped tin oxide (ATO) nanoparticles, and the subsequent solution co-blend was employed to fabricate ATO/PVB nanocomposites. Uv-Vis-NIR spectra show that the addition of ATO nano particles can significantly enhance the thermal insulating efficiency of ATO/PVB nanocomposites. With the increase of ATO content, the thermal insulating efficiency is increased. Uv is almost fully absorbed by all ATO/PVB nanocomposites. Vis transmittance-haze spectra reveal that ATO/PVB nanocomposites exhibit higher Vis transmittance of over 72.7% and lower haze of below 2% when ATO content is in the range of 0.1 wt%–0.5 wt%. The thermal insulating tests indicate that in comparison with the pure PVB film, nanocomposite films with 0.1 wt%–0.5 wt% ATO can reduce temperature of 1–3 °C, suggesting that this novel nanocomposite can be used for energy-saving glass.
The hydrophobic silica aerogel (SiO2 aerogel) was prepared by in situ polymerization sol-gel method and ethanol supercritical drying, with tetraethoxysilane (TEOS) as silica source, phenyltriethoxysilane (PTES) as modifier, ethanol as solvent and ammonia as catalyst. The effects of n(PTES)/n(TOES) were investigated on gel time, structure, and hydrophobicity. The SiO2 aerogel was measured by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of n(PTES)/n(TOES) were also studied on adsorption property of pentane, hexane, heptane, octane, benzene, toluene, o-xylene, nitromethane, nitroethane, and nitrobenzene. The adsorption intensity of SiO2 aerogel was compared with that of activated carbon. The results show, with the increasing of n(PTES)/n(TOES), the surface area, pore volume, and pore size of SiO2 aerogel decreased, gel time and hydrophobicity increased, and the contact angle could be 154° with n(PTES)/n(TOES)=0.7. The adsorption intensity of SiO2 aerogel with n(PTES)/n(TOES)=0.5 was bigger than that of activated carbon with an average 5.84 times of 10 organic liquid. The adsorption intensity of aerogel with n(PTES)/n(TOES) =0.1 was the best one in all samples with the average 8.33 times compared with that of activated carbon.
We adopted a notch method to study the influence of crack width (macro level) on chloride transport and binding of cracked concrete under a non-steady state migration test. The results show that migration coefficient of cracked concrete increases with increasing crack width up to a critical value (0.43 mm), for the whole concrete or the area close to crack; the increase of migration coefficient could be independent from crack parameter when a critical crack width is reached. For chloride binding, Langmuir isotherms of cracked concrete samples exhibit the similar decreasing trend as crack width increases from 0.27 to 1.96 mm. The increased current value could be responsible for the trend based on the hypothesis of electric force.
The effect of curing regime on the distribution of Al3+ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance(NMR) with deconvolution technique. The results indicate that the tetrahedral coordination Al3+ incorporated in C-S-H structure mainly originate from the Al3+ incorporated in the alite and belite phases in the Portland cement. The curing regime of constant temperature of 20 °C is beneficial to the octahedral coordination Al3+ transforming to tetrahedral coordination Al3+ incorporated in C-S-H structure. However, at curing regime of variable temperature, the temperature rising process is more advantageous to the transformation from ettringite to monosulphate, substitution of Al3+ for Si4+ in the C-S-H structure and the formation of the third aluminate hydrate (TAH) than that at constant temperature of 20 °C. The high temperature of 60 °C in the holding temperature process promotes the decomposition of ettringite, and enhances the consumption of the Al3+ incorporated in C-S-H phases and the Al3+ in TAH for the monosulphate forming. The temperature decreasing promotes the transformation from monosulphate to ettringite, and increases the consumption of the Al3+ incorporated in C-S-H phases, and then increases the quantity of the TAH.
To investigate the effect of different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads, the beams were exposed in indoor, freeze/thaw cycles and immersed in alkaline solution at elevated temperature. The bars were carefully extracted from the beams and tested in order to evaluate residual tensile properties. The results show that the tensile strength decreased significantly in the highly aggressive conditions but not in the natural conditions. The effect of GFRP bars casting in concrete beams demonstrated approximately 2.5% decrease of tensile strength caused by pore water environment in concrete beams on basis of those of the original bars. The effect of sustained loading plus work cracks demonstrated about 10.5% tensile strength decrease on basis of those of the bars only casted in concrete beams. The effect of environments under sustained loading plus work cracks demonstrated about 17% tensile strength decrease caused by a saturated solution of Ca(OH)2 and 60±2 °C tap water (pH=12–13) and about 8% tensile strength decrease caused by freezing and thawing cycle (F/T), both on basis of those of the bars of the indoor beams only under sustained loading plus work cracks. The results demonstrate the effects of the tensile strengths under different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads.
The feasibility of high calcium fly ash (CFA)-based geopolymers to fix heavy metals were studied. The CFA-based geopolymers were prepared from CFA, flue gas desulfurization gypsum (FGDG), and water treatment residual (WTR). The static leaching showed that heavy metals concentrations from CFAbased geopolymers were lower than their maximum concentration limits according to the U.S. environmental protection law. And the encapsulated and fixed ratios of heavy metals by the CFA-based geopolymers were 96.02%–99.88%. The dynamic real-time leaching experiment showed that concentration of Pb (II) was less than 1.1 μg / L, Cr (VI) less than 3.25 mg / L, while Hg (II) less than 4.0 μg / L. Additionally, dynamic accumulated leaching concentrations were increased at the beginning of leaching process then kept stable. During the dynamic leaching process, heavy metals migrated and accumulated in an area near to the solid-solution interface. When small part of heavy metals in “the accumulated area” breached through the threshold value of physical encapsulation and chemical fixation they migrated into solution. The dynamic leaching ratios and effective diffusion coefficients of heavy metals from CFA-based geopolymer were very low and the long-term security of heavy metals in CFA-based geopolymer was safe.
Accelerated carbonation experiments about the development of carbonation rates of ordinary Portland cement concrete under different artificial climates were carried out. Six water cement ratios and six climate condition combinations of temperature and relative humidity were used. Results indicate that changes of concrete carbonation rate with environmental temperature agree the Arrhenius law well, which suggests concrete carbonation rate has obvious dependence on temperature. The higher the temperature is, the more quickly the concrete carbonates, and at the same time it is also affected by environmental relative humidity. Thereafter, the apparent activation energy E a of concrete carbonation reaction was obtained, ranging from 16.8 to 20.6 kJ/mol corresponding 0.35–0.74 water cement ratio, and lower water cement ratio will cause the apparent activation energy increase. Concrete carbonation rates will increase 1.1–1.69 times as temperature increase every 10 °C at the temperature range of 10 to 60 °C.
Organic epoxy matrices have been widely used in the FRP reinforcing technique, but they have serious disadvantages of poor high-temperature resistance. An inorganic adhesive is invented to replace the organic adhesive. For the inorganic adhesive at normal temperature and different high temperatures, the microstructure and phase composition are investigated by means of X-ray diffraction (XRD) and SEM respectively. Results show that inorganic adhesive can resist at least 600 °C high temperature. Fire-resistance performance of inorganic adhesive can meet the requirements of fiber reinforced polymer (FRP) strengthened RC structures.
We used micro-XCT(X-ray computed tomography) to in-situ investigate the microstructure evolution of hardened binder paste containing different contents (0%, 30%, 50% and 70%) of blast-furnace slag at different carbonation time (0, 3, 7 and 14 days), respectively. The carbonation front shape, the degrees of carbonation and cracks spatial distribution were studied for hardened binder paste containing BFS. In addition, the porosity and pore volume distribution of macro-pore were measured at different carbonation ages. The results reveal that the degree of carbonation at different times can be measured by the volume fraction of the uncarbonated and carbonated parts.
Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were ‘long component’ and ‘short component’. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated.
Proper parameters for image taking and minimum field number for image processing were investigated to evaluate volume fraction of unhydrated cement(UHC) in both neat cement paste and slag blended cement paste. Our research suggested that magnification 250× was sufficient for the two pastes, and accelerating voltage should be set as 15 kV and 20 kV for BSE image taking of neat cement paste and slag blended cement paste respectively; the minimum field number increased while the total imaging area stayed the same as the magnification increased within certain statistical bias.
The influences of silica fume and aluminum sulfate on hydration process of sulfoaluminate cement were carried out by ring flow, setting time, hydration heat, XRD and DTG analyses. In addition, mortar mixtures with different functional additives have been studied through compressive strength, flexural strength, volume stability at early age and porosity characterization tests. The results show that the addition of silica fume and aluminum sulfate reduces the fluidity and shortens the setting time of sulfoaluminate cement paste, promoting hydration process and increasing hydration products at early age. In the case of appropriate proportion of mortar, the inclusion of hydroxy propyl methyl cellulose, dispersible polypropylene fiber and organic silicon kind of defoamer can control segregation and bleeding, improve mechanical strength and volume stability at early age, and modify the pore distribution of sulfoaluminate cement mortar, respectively. The sulfoaluminate cement mortar can carry out gravitational grouting in the absence of outside force, the compressive strength of 2 hours and 24 hours have reached 26 and 58 MPa respectively, and have good microexpansion and tiny pore distribution characterization.
A new method to prepare radiation shielding functional aggregate is described, and an appropriate mix ratio and a reasonable calcinated condition was engaged. The γ-ray shielding capability of both the new functional aggregates and some other nature aggregates had been measured. The linear attenuation coefficients (µ, cm−1) of these aggregates had been calculated at photon energies from 1 keV to 10GeV using XCOM program, and measured at the photon energies of 662 keV, showing good agreement between experimental and calculated results. The results show that the γ-ray shielding capacity of the new functional aggregates has been improved substantially compared with basalt, almost equal to serpentine and high-titanium slag, and up to 80% to barite.
The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using warm vertical compaction and treated with distilled water, 2.5% NaOCl, 17% EDTA and 2.5% NaOCl; or 17% EDTA, 2.5% NaOCl, and ultrasonic agitation (U/E/N treatment). Subsequently, radicular dentin surfaces were observed under scanning electron microscopy (SEM). RelyX Fiber Posts were cemented in the treated canals by using RelyX U100, and thin-slice push-out test and SEM observation of coronal and apical regions of the specimens were performed. Data were analyzed using two-way ANOVA and Tukey’s HSD posthoc tests, and the percentage of failure type was calculated. Ultrasonic/EDTA/NaOCl irrigation showed the maximum effectiveness in removing the smear layer and debris on the dentin surface. The apical bond strength of the experimental groups was significantly higher than that of the control group (P< 0.05). Adhesive failure between cement and dentin was the most common mode of failure. No obvious RDIZ or resin tag was detected. Chemical irrigants facilitated the bonding of these fiber posts, and ultrasonic activation improved retention. Future studies should evaluate the effectiveness of irrigation on fiber post push-out strength in fatigue cycling condition.
Fe2O3@polypyrrole nanotubes (Fe2O3@PPy nanotubes) have been successfully prepared by in-situ polymerization of the pyrrole on the surface of Fe2O3 nanotubes (Fe2O3-NTs), via using L-Lysine as modified surfactant. Hollow PPy nanotubes were also produced by dissolution of the Fe2O3 core from the core/shell composite nanotubes with 1 mol·L−1 HCl. Scanning electron microscopy(SEM), transmission electron microscope (TEM), selective-area electron diffraction (SAED), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy(FT-IR) confirmed the formation of Fe2O3-NTs and Fe2O3@PPy core/shell nanotubes. Its catalytic properties were investigated under the ultrasound. The results of UV-vis spectroscopy (UV) demonstrated Rhodamine B (RhB) can be efficiently degraded by Fe2O3 @PPy nanotubes.
Rule of similarity and latex compounding techniques were combined for the first time to prepare natural rubber/nanosilica (NR/SiO2) nanocomposite with core-shell nanosilica-poly (methyl methacrylate) (SiO2-PMMA) particles and PMMA-modified natural rubber matrix (NR-PMMA). The microstructure of SiO2 and nanocomposites with different SiO2 contents was characterized by fourier transform infrared spectroscopy (FTIR); the morphology of nanocomposites was investigated with scanning electron microscopy (SEM); the tensile strength was characterized by tensile testing machine and the thermal stability of composites was studied by thermal gravimetric analysis. Results showed that PMMA chains have successfully grafted onto the surface of SiO2, and the core-shell SiO2-PMMA nanoparticles and NR-PMMA latex have been perfectly incorporated. SiO2-PMMA nanoparticles are evenly distributed over the NR matrix with an average size in the range of 60–100 nm at the low content (SiO2≤ 3 wt%), while aggregations are apparently observed when 5 wt% SiO2 is loaded. In addition, NR/SiO2 composities possess a considerable improvement in ageing resistance compared with the pure NR. The tensile strength of composite increases from 6.99 to 12.72 MPa, reaching the highest value at a 0.5 wt% SiO2 loading, and then the figure decreases gradually because of the aggregation of SiO2 nanoparticles. It is anticipated that the reported process is to provide a simple and economic way for preparing NR composites.
A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes’ law. Acrylonitrilebutadiene-styrene/Cu (ABS/Cu) gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 1015 Ω at ABS rich side, while that declined to 105 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vol%–4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.
A novel starch-based hybrid hydrogel was formed by physical and mild steps. Firstly, aqueous solution of a mixture of starch maleic half-ester (SM) and poly(vinyl alcohol) (PVA) was subjected to freezing-thawing cycles to generate a physical functional SM/PVA hydrogel. Subsequently, the SM/PVA/HA hybrid hydrogel was obtained through the alternate soaking process. The structure and morphology of the hydrogels were examined with Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). It was found that the existence of carboxylic groups on SM chains not only enabled SM/PVA hydrogel to be pH-sensitive, but also enhanced the formation of hydroxyapatite in the hydrogel via chelating calcium ions onto the matrix.
Super plasticizer was synthesized by using coal coking by product washing oil and industrial naphthalene. The results show that sulfonationt time (2.5 h), sulfonation temperature (160 °C) and condensation time (5.0 h) are key factors. Adding oxidizing agent MO in the course of synthesis can decrease the emission of SO2 in exhaust (20%). Compared with NF, NF-30 have some advantages in lower cost, high water reducing rate (19.7%) and optimum early strengths. Moreover, TGA-DTA and SEM analysis were adopted to research the NF-30 modified concrete on hydyation mechanism. The analysis show that, compared with NF, there are a large number of hydration products such as Ca (OH)2, C-S-H, AFt etc of NF-30, the structure of NF-30 is dense and the performance is good.
Acetanilide (AC), adipic acid (AA) and potassium hydrogen phthalate (PHP) were chosen as additives to accelerate PVC crystallization and improve its mechanical properties. The influences of the additives and annealing on the crystallization behavior, micromorphology and the tensile properties were investigated by the thermal analysis, scanning electron microscopy (SEM) and the tensile test. Based on the analysis results, it was concluded that the melting peaks ranging from 110 to 200 °C and 200 to 240 °C were caused by the fusion of the fringed micelle crystals and chain-folded crystals respectively. AC advanced the fringed micelle crystal to develop, while AA and PHP promoted obviously the chain-folded crystal to grow. The addition of the foreign additives did not change the growth pattern of PVC crystallites, the growth of the micelle crystal was favorable at 110 °C, and the chain-folded crystal was developed at higher temperature. For PVC/AA and PVC/PHP, when annealed at 110 °C, a regular nest like network was formed, the crystallinity and the crystallite size were increased as well, and as a result, the tensile strength, Young’s modulus and the elongation at break point were improved simultaneously and greatly.
The high-temperature friction and wear properties of TiAl alloys and Ti2AlN/TiAl composites (TTC) in contact with nickel-based superalloy were studied. The results showed that, at 800 and 1 000 °C, the coefficient of the friction (COF) decreased with the increase of sliding velocity and the wear loss of the TTC decreased with the increase of volume fraction of Ti2AlN. The wear mechanisms of the pairs are adhesive wear and the wear debris mainly comes from the contacting nickel-based superalloy. The intergranular fracture and the cracking of the phase boundary in the lamellar structure are the wear mode of TiAl alloy. The wear mode of TTC is phase boundary fracture and adhesive spalling. The abrasive resistance of TTC is slightly higher than that of TiAl alloy.
A TiAlN coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature (RT) and 650 °C. The results reveal that the TiAlN coating is compact, on which a small number of large particle and pits are present. The Ti/Al atomic ratio in the coating is about 0.94. The average hardness of the coating is 1 868 HV0.1 and the interface bonding force between TiAlN coating and the substrate is about 31 N. The elastic modulus and the strength of the steel are improved by the deposition of TiAlN coating. The influence of the TiAlN coating on the tensile properties of the steel can be ignored at both RT and 650 °C. Moreover, there is no obvious decrease of the fatigue limit of substrate when the steel is coated by the coating at the investigated temperature.
Nickel-titanium shape memory alloy (NiTi SMA) which possesses crystal structure of B2 austenite at room temperature was subjected to plastic deformation at low temperature (−150 °C) by means of local canning compression. The microstructural evolution of NiTi SMA at the different deformation degree was investigated by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). At the deformation degree by 15%, a high density of dislocations occurs in the deformed NiTi sample. At the deformation degree by 25%, the deformed NiTi sample exhibits the martensite morphology due to the pinning of dislocations at the grain boundaries. At the deformation degree by 50%, a small amount of nanocrystalline phase arises in the deformed NiTi sample. At the deformation degree by 80%, severe plastic deformation (SPD) leads to the occurrence of a great deal of amorphous and nanocrystalline phase.
The corrosion behavior of C100 steel in simulated environments with high H2S and CO2 content was studied through high-temperature and high-pressure autoclave, and the H2S stress corrosion cracking (SSC) resistance of C100 steel was evaluated by SSC tests. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) technique were employed to characterize the corrosion products and the metal matrix. The results indicate that all of the corrosion products in this investigation are mainly composed of different types of iron sulfide such as Fe0.95S, FeS0.9, Fe0.985S, Fe7S8 and FeS, and the absence of iron carbonate in the corrosion scales suggests that the corrosion process is governed by H2S corrosion. The corrosion rate decreases in the initial stage and then increases with the enhancement of the temperature. There exists a minimum corrosion rate at about 110 °C. Under the partial pressure of H2S lower than 9 MPa, the corrosion rate decreases with the increase of $P_{H_2 S} $ While over 9 MPa, a higher $P_{H_2 S} $ will result in a faster corrosion process. When the applied stress is 72%, 80% and 85% of actual yield strength (AYS), all tested specimens show no crack, which reveals a superior SSC resistance.
In order to increase antibacterial abilities and avoid the aggregation of nanoparticle, Ag-ZnO nanocomposites were studied in the network structure which contains bonds, and these bonds are formed by hydrolysis reaction between Ti(TBOU)4(TBOT) and the water that in Persimmon tannin solution. The size and morphology of Ag-ZnO nanocomposites were investigated by scanning electron microscopy (SEM) and field emission scanning electron microscopy(FE-SEM). The antibacterial properties of nanocomposites were examined by minimal bactericidal concentration(MBC). Results showed that this kind of antibacterial nanocomposites composites(ANPs) have excellent antibacterial abilities and without aggregation.
The elemental tellurium nanoparticles (TeNPs) — sucrose sol was prepared by the reaction of sodium tellurite with ascorbic acid in sucrose aqueous solution. The results indicated that TeNPs were dispersion excellent in the TeNPs — sucrose sol and the morphology of TeNPs was needle-like with about 70 nm in width and 500 nm in length. The antioxidant activity of the TeNPs — sucrose sol in vitro was estimated by pyrogallol autoxidation method, Fenton method and oxygen radical absorbance capacity (ORAC) assay. The results showed that a certain amount of TeNPs — sucrose sol could effectively scavenge superoxide anion free radical and hydroxyl free radical with scavenging rates of 73 % and 57 %, respectively. ORAC assay was used to measure the total antioxidant capacity of TeNPs — sucrose sol. The order of ORAC values was 2.25 μmol·L−1 TeNPs — 0.025 % sucrose sol > 0.025 % sucrose > 2.25 μmol·L−1 Na2TeO3 > 1.63 μmol·L−1 ascorbic acid. The results suggested that the TeNPs — sucrose sol had the excellent antioxidant activity and TeNPs were the dominating contributors to antioxidant capacity of the TeNPs — sucrose sol.
The system of SiO2-CaO-P2O5 bioactive glasses (BG) were successfully synthesized by microemulsion approach. X-ray diffraction (XRD),scanning electron micro scopy(SEM) and energy dispersive X-ray (EDX) analyses, transmission electron microscopy(TEM),Fourier transform infrared spectroscopy (FTIR), BET N2 gas adsorption analysis techniques were utilized in order to evaluate the phase composition, dimension, morphology, interconnectivity of pores and particle size of the synthesized BG respectiveely. The biocompatibility of BG was assessed by using dimethylthiazol diphenyl tetrazolium bromide (MTT).The BG scaffolds were implanted in rabbit mandibles and studied histologically. The results showed that the BG with a particle size less than 100 nm was prepared successfully. The measured BET specific surface area and pore volume was 113.9 m2/g and 0.28 cm3/g respectively. Cell cultures revealed that BG has been shown to have good biocompatibility and is also beneficial to the survival of Schwann cells, which can promote cell proliferation in vivo assay indicating that the BG can promote osteoconductivity.