The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.
The FeNip/PP nanocomposites were successfully prepared by the two-step blending method and the permeable layer interface with thickness of 2 to 10 nm was formed on the surface of nanopowders. The interface is composed of the lattice and molecular chain, in which the polypropylene molecular chain enters the lattice defects and forms a cross-linked structure. The interface causes the FeNi nanopowders to be well compatible with the polypropylene matrix and uniformly dispersed in the matrix, and significantly improves the mechanical properties of composites. The tensile strength of 2wt% FeNip/PP composites reached 38 MPa, 23% higher than that of pure PP resin. The shielding performance of 20wt% FeNip/PP composites reached 9.8 dB in the frequency range of 1-100 MHz.
The amorphous I/Au composite nanoflms were prepared by low vacuum direct current sputtering (LVDCS) method. The optimized preparation technologies contain growth pressure, time, gaseous environment and annealing conditions. The maximum fuorescence emission (λ em max) of I/Au nanoflms was observed at wavelength of 375 nm, and the intensity of fuorescence emission peak of annealed I/Au flms was smaller than that of unannealed one due to fewer amorphous Au nanoparticles, caused by annealing treatment. In the UV-Vis absorption spectra, the intensity of UV-Vis absorption peak of annealed I/ Au nanoflms is larger than that of the unannealed one. This work also developed a new way to grow I/Au composite fuorescent thin flms.
A novel method was presented to create composite micelles of amphiphilic copolymers and Ag nanoparticles (NPs) in a three-dimensional co-flow focusing microfluidic device (3D CFMD). Self-assembly of the copolymers was initiated by the fast mixing of water and a blend dispersion of hydrophobic Ag NPs and amphiphilic copolymers. At the same time, the hydrophobic Ag NPs enter the core of copolymer micelles, based on the hydrophobic interaction. The copolymer-Ag NPs composite micelles have a core-shell structure with copolymer shell and Ag NPs core. COMSOL Multiphysics is used to simulate the concentration distribution of copolymers and Ag NPs under different flow rates. Co-assembly microfluidic conditions are determined based on simulation results. Under suitable microfluidic conditions, both block copolymers and gradient copolymers can co-assemble with hydrophobic Ag NPs to form composite micelles, respectively. This microfluidic coassembly method will have a good prospect in the preparation of composite micelles of amphiphilic copolymers and metal nanoparticles.
BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength.
A high production efficiency synthesis method was used to produce a stacked vanadium nitride nanoparticle structure with an inexpensive raw material as an anode material and high surface area polystyrene was used the cathode material for lithium ion hybrid capacitors. The Li-HCs cell displayed an excellent specific capacitance of 64.2 F·g-1 at a current density of 0.25 A·g-1 and a wide potential window of 0.01 to 3.5 V. Furthermore, the device exhibited a high energy density of 109.3 W·h·kg-1 at a power density of 512.3 W·kg-1 and retained an energy density of 69.2 W·h·kg-1 at a high power density of 3 498.9 W·kg-1 at 2 A·g-1. Due to the short synthesis time and simple raw materials, this method is suitable for industrial production.
Cetyltrimethylammonium bromide (CTAB) was incorporated into silicon carbide whiskers (SiC w) to improve their hydrophobicity. The solution casting method was employed to develop composite membranes of polyvinylidene fluoride (CTAB-SiC w/PVDF) with different feed ratios. FT-IR spectroscopic studies proved that CTAB was successfully incorporated into the SiC w. SiC w phase structure was maintained after modification by CTAB according to XRD results. SEM studies indicated that the surface became smoother with CTAB dispersal in the PVDF membrane. The dielectric properties of the composite membranes containing various amounts of CTAB-SiC w were measured at low temperature. It was found that the dielectric constant of the composite membranes with 13.0wt% whiskers reached a maximum value of 25 at low frequency, and decreased to nine at high frequency (from 500 Hz to 1 MHz ) at 0 ℃. The dielectric loss of each composite membrane increased with increasing temperature and reached a maximum value. The value shifted with corresponding frequency increases. In addition, the dielectric loss reached a maximum value of 0.2 when 16.7wt% of CTAB-SiC w was fed at each frequency (from -30 ℃ to 10 ℃). At room temperature, the dielectric constant could be maintained at 42 and the loss factor decreased to 0.8 at 100 Hz when 13.0wt% of CTABSiC w was incorporated. Additionally, TGA experiments indicated that the decomposition temperature of a PVDF membrane was increased by 10 ℃ and its heat resistance was improved by adding 13.0wt% of CTAB-SiC w. This PVDF composite membrane has potential for use as an insulator and capacitor.
Microstructure, texture and hardness evolutions of Al-Mg-Si-Cu alloy during annealing treatment were studied by microstructure, texture and hardness characterization in the present study. The experimental results show that microstructure, texture and hardness will change to some extent with the increase of annealing temperature. The microstructure transforms from the elongated bands to elongated grains first, and then the grains grow continuously. The texture transforms from the initial deformation texture b fiber to recrystallization texture mainly consisting of CubeND {001}<310> and P {011}<122> orientations first, and then the recrystallization texture may be enhanced continuously as a result of the grain growth. Hardness decreases slowly at first, and then decreases sharply and increases significantly finally. Besides, the particle distributions also have great changes. As the annealing temperature increases, they increase firstly as a result of precipitation, and then gradually disappear as a result of dissolution. Finally, the effect of annealing temperature on microstructure, texture and hardness evolutions is discussed.
Microstructure evolution and properties of hot-extruded Inconel 625 alloy were investigated at different creep temperatures, aging time and strain rates. The experimental results indicate that the Inconel 625 alloy exhibits an excellent creep resistance at 700 °C and below. When the creep temperature rises to 750 °C, the creep resistance falls drastically due to the failure of phase transformation strengthening and the precipitation of a large amount of δ phase and σ phase at the grain boundary. The special temperature-sensitive characteristics of Inconel 625 alloy play a very important role in its fracture. When the strain rate is 8.33×10−3 s−1, the strength of the specimen is higher than that of other parameters attributed to the effect of phase transformation strengthening. With the increase of Ni3 (Al, Ti), the phase transformation strengthening inhibits thickening of the stacking faults into twins and improves the overall mechanical properties of the alloy. With the increase of the aging time, the granular Cr-rich M23C6 carbides continue to precipitate at the grain boundary, which hinders the movement of the dislocations and obviously increases the strength of the samples. Especially, the yield strength increases several times.
The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature (T g) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and T g shifted towards to higher temperature.
The titanium carbide phase was synthesized in laser melted-pool in situ as the reinforced particles of nickel based composite coating on Ti-6Al-4V alloy surface using the nickel and graphite blending powder by laser cladding. The microstructure investigation showed that the petals-shaped particles and granular particles were two main morphology of titanium carbide particles. And a few spiral-shaped titanium carbide pattern and eutectic titanium carbide appeared on the cross-sections of the coating. The spiral-shaped titanium carbide pattern composed of some slender arc-shape titanium carbide particles and the eutectic titanium carbide was fine. The morphology and distribution of the spiral-shaped titanium carbide patterns and eutectic titanium carbide confrmed that their growth mechanism was the dissolution-precipitation mechanism and was affected by the convection behavior of the laser melted pool. The spiral-shaped titanium carbide pattern would precipitate out the high-temperature melts under high-speed convection. The eutectic titanium carbide would precipitate out when the melts stopped convection or dropped to eutectic temperature.
Ag-modified TiO2 nanoflowers were prepared using a two-step process. The experimental process is green and free from contamination and can be synthesized directly at room temperature. Compared with pure TiO2, Ag-modified TiO2 enhances the absorption of visible light and effectively promotes the detachment of photoelectron pairs, Ag-TiO2 has a significantly enhanced visible light response activity to photodecomposition of methyl orange (MO). It is shown that the strong interaction between Ag nanoparticles and TiO2 enhances the photocatalytic activity of TiO2 nanoflowers. The self-made open-air reactor was used to test the photocatalytic performance of different samples. The results showed that Ag-modified TiO2 nanoflowers had excellent photodegradation ability. After repeated photodegradation of MO, Ag-modified TiO2 nanoflowers showed good stability.
The viability of using polypropylene fibers (PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete aggregate (RCA). Mixes with different RCA replacement ratios and different PPF content were designed and tested. The test results showed that the addition of PPF did not change significantly the compressive strength and the density of the concrete, but slightly decreased its modulus of elasticity and Poisson’s ratio. The drop in the splitting tensile strength and the flexural strength due to RCA inclusions was to a large extent compensated by the PPF addition. The water absorption decreased and the percent voids increased with increased PPF addition. Correlations between the RCA content, the PPF content and the properties of concrete were studied. Useful regression models were proposed to predict the properties of concrete in relevant ranges of RCA and PPF content.
Fly ash (FA) was utilized to hydrothermally synthesize FA based Al-substituted tobermorites, and was combined with raw materials of FA and municipal solid waste incineration fly ash (MSWI) to hydrothermally synthesize FA-MSWI based Al-substituted tobermorites. Then optimum samples named FA-T and FM-T were selected, correspondingly. Their intrinsic properties as well as their solidification / stabilization and adsorption of heavy metals were studied. The experimental results showed that the specific surface area of FA-T and FM-T was 28.259 m2/g and 45.939 m2/g, respectively. Their pore size distribution, particle size distribution, and median particle size were approximately the same. FA-T and FM-T both had great potential of solidification / stabilization heavy metal to dispose hazardous solid waste. Further, FA-T and FM-T also showed good adsorption efficiency for heavy metals Pb2+ and Cu2+ as adsorbent to treat waste water.
Aiming to investigate the mix design of eco-friendly UHPC with supplementary cementitious materials and coarser aggregates, we comprehensively studied the workability, microstructure, porosity, compressive strength, flexural strength, and Young’s modulus of UHPC. Relationship between compressive strength and Young’s modulus was obtained eventually. It is found that the compressive strength, flexural strength, and Young’s modulus of UHPC increase by 19.01%, 10.81%, and 5.99%, respectively, when 40wt% cement is replaced with supplementary cementitious materials. The relationship between compressive strength and Young’s modulus of UHPC is an exponential form.
Ba0.6Sr0.4TiO3 ceramic was synthesized by the sol-gel method combined with the solidstate reaction. Phase composition and microstructure analyses indicate that pure BST phase with aggregated nanograins can be achieved. The dielectric properties change with sintering temperature, and reach the maximum at suitable temperatures. The highest dielectric constant of 4351 is obtained at 100 Hz for 1 275 ℃ sintered sample that is 2 times greater than that of the original sample, which indicates the dielectric properties can be modulated by grain size and density. The results show that Ba0.6Sr0.4TiO3 is a promising candidate for microwave applications.
To study the effect of atmospheric pressure on the properties of fresh and hardened air-entrained concrete, three kinds of air entraining agents were used for preparing air-entrained concrete in the plateaus (Lhasa, 61 kPa) and the plains (Beijing, 101 kPa). Air content, slump, compressive strength and pore structure of the three air-entrained concretes were tested in these two places. It is found that the air content of concrete under low atmospheric pressure (LAP) is 4%-36% lower than that of concrete under normal atmospheric pressure (NAP), which explaines the decrease of slump for air-entrained concrete under LAP. Pore number of hardened concrete under LAP is reduced by 48%-69%. While, the proportion of big pores (pore diameter >1 200 μm) and air void spacing factor are increased by 1.5%-7.3% and 51%-92%, respectively. The deterioration of pore structure results in a 3%-9% reduction in the compressive strength of concrete. From the results we have obtained, it can be concluded that the increase of critical nucleation energy of air bubbles and the decrease of volumetric compressibility coefficient of air in the concrete are responsible for the variation of air content and pore structure of concrete under LAP.
Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m3.
In this paper, scrap rubber powder (SRP), azodicarbonamide (ADC) as foaming agent and double-component epoxy resins (ER) as binder were used to prepare porous sound-absorbing material of rubber foam composite (RFC) by hot-pressing process. Response surface methodology (RSM) was employed to evaluate three process variables, i e, specimen thickness (A), ADC dosage (B) and foaming temperature (C), and to establish two polynomial function model equation between sound absorption coeffcient (α) and three process factors (A, B, C) at middle and low frequency 250 Hz, 500 Hz, 800 Hz, 1 000 Hz to determine the optimal preparation condition of RFC. The statistical analysis of results demonstrated that specimen thickness (A) exerted signifcant impact on sound absorption properties of RFC. And the optimum prepared condition of RFC was 10 mm specimen thickness, 3.00 g ADC dosage, and approximately 196–foaming temperature. Under optimal condition, sound absorption coeffcient of RFC could reach 5.68% (250 Hz), 7.67% (500 Hz), 20.73% (800 Hz), 18.71% (1 000 Hz), coinciding with the predicted values 5.70% (250 Hz), 7.69% (500 Hz), 20.77% (800 Hz), 18.74% (1 000 Hz) from the predicted polynomial function model, which exhibited that RSM could be used to optimize the preparation process of sound-absorbing materials.
Crystallization characteristic of periclase in clinker and effect of Mg2+ on hydrate of cement pastes were investigated. Morphologies and relative content of periclase were characterized with scanning electron microscopy and X-ray diffraction. Derivative thermogravimetry analysis and backscattered electron imaging were used to characterize the effect of Mg2+ on hydrate of cement pastes. The experimental results show that in ample space, periclase forms octahedron structure, and subhedral or anhedral crystal is formed in limited space. Due to the accelerated burning temperature and prolonged holding time, coarse pericalase crystals are formed. Mg(OH)2 particle thickness increases due to faster crystal growth rate along c axis at later age. Mg2+ can substitute Ca2+ in C-S-H or C-A-H to form magnesium silicate hydrate(M-S-H) or magnesium aluminate hydrate(M-A-H), and the substitution extent for C-A-H is higher than that for C-S-H. Cured in 80 °C water, the decalcification rate of C-A-H in pastes is higher than that cured in 50 °C water. M-A-H with an atomic Mg/Al ratio of 2 is formed through substitution of Ca by Mg in C-A-H.
In order to reflect truly the damage evolution mechanism of weak muddy intercalation in dry-wet cycles, two typical weak muddy intercalations were selected for dry-wet cycles. The mineral changes of specimens were analyzed via X-ray diffraction after dry-wet cycles. By combining in-situ SEM and digital image processing (DIP), the damage evolution process and damage characteristic parameters of each stage were obtained. The experimental results indicate that the hydration and dissolution of minerals can not be a determinant factor in structure damage. The micro-structural damage is due to disintegration of mineral aggregates, leading to changes in the number and size of cracks and pores. The damage degree of specimens is related to its initial structure, and the micro-structural damage intensifies and finally tends to stabilize with cycle times increased.
The sulfate ions immobilization behavior of calcined layered double hydroxides (CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.
SnO2/AgIO4 hybrids were fabricated by an in-situ synthetic method at room temperature. The structure, morphology, light response range, separation efficiency of the electron-hole pairs and elements of the as-synthesized samples were characterized by adopting X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy, respectively. The synergistically photocatalytic degradation mechanism of the as-synthesized composites was also proposed. The experimental results reveal that under the visible light irradiation the as-synthesized SnO2/AgIO4 hybrids can enhance the photocatalytic degradation efficiency of rhodamine B compared to pure samples. With increasing the molar ratios of AgIO4 to SnO2, it displays the trend of first increasing and then decreasing. When it is 1:2 in 150 min, the as-prepared hybrids have the highest degradation efficiency of 93.1%, which increases by 6550.0%, 30.5%, and 1505.0% compared to those of pure SnO2, AgIO4, and TiO2 (P25), respectively. Moreover, the Sn-O-Ag cross-linking bonds are formed at the interfaces of SnO2 and AgIO4. In addition, superoxide anion radicals and holes play a major role in the process of photodegradation.
Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the property of the sample, such as porosity, compressive strength and room-temperature thermal conductivity were explored. The experimental results show that the 3D skeleton structure of the sample was constructed by the randomly arranged mullite fibers and inorganic particles. The content of alumina can be adjusted effectively by impregnation times and it increases with increasing impregnation cycles. The thermal conductivity and compressive strength can also be controlled via tailored impregnation cycles. The compressive strength of fibrous ceramic ranged from 1.03 MPa to 5.31 MPa, while the porosity decrease slightly from 85.3% to 73.8%. In the same time, the thermal conductivity increase from 0.037 W/(m·K) to 0.217 W/(m·K), indicating that the fibrous ceramic with high impressive and low thermal conductivity can be fabricated by impregnation method.
The grain refinement mechanism and texture evolution of electromagnetically formed polycrystalline Cu sheets were investigated using the electron back-scattered diffraction (EBSD) technique. It is found that the average grain size decreases from 35.88 μm to 8.77 μm. The grain refinement was mainly attributed to dynamic recrystallization (DRX) at the grain boundary regions of bulged Cu samples where the inhomogeneous dislocation density and the large lattice misorientation were observed. The DRX mechanisms at the grain boundaries were discussed with respect to the strain-induced grain boundary migration nucleation. Moreover, the orientation distribution function (ODF) of the sample with the strain of 50% demonstrated a strong {110}<211> texture and a relatively weak {001}<100> texture. The texture evolution was discussed using the plastic work values of the grains with various orientations, which were calculated according to the Taylor model and the virtual work principle. The experimental results show that the expended plastic work of the grains with {110} orientation is 9.69 MPa, which is distinctly higher than those of the grains with the {001} and {111} orientations. This indicates that the formation of the {110} orientated texture would be preferred with increasing strain in good agreement with the experimental result.
Al foam sandwich panel (AFS) with metallic bonding was fabricated by foaming a hotpressed three-layer composite with two steel facesheets and a melt route precursor as core. The melt route precursor was fabricated by dispersing undecomposed blowing agent into molten Al, followed by solidification. Microstructures of the joints during fabrication process were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Static three-point bending was conducted to evaluate joint quality of the AFS. It was found that a primary bonding was achieved by hot-pressing and significant diffusion layer of Fe-Al intermetallic compounds was sustained between steel and Al foam core by foaming. Damage modes of the AFS under three-point bending were dominated by indentation, plastic hinges, core shear and crack. Delamination between steel and foam was absent, implying that reliable metallic bonding was achieved. This method allows for producing large-scale AFS with steel facesheets.
A recrystallization and partial melting (RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion experiments were conducted to comparatively investigate the optimum extrusion process parameters. Commercial 7075Al alloy samples were frstly extruded with varying extrusion ratios below the recrystallization temperature followed by homogenization, then these samples were reheated to the semi-solid state and held in the range of 5 to 50 minutes. The experimental results show that varying process cause the difference in the deformation degree and microstructure for as-extruded samples, resulting in various semi-solid microstructure. It is verifed that the formation of equiaxed grains in semi-solid microstructure depends on recrystallization behavior of extruded samples during partial melting. Both relative high extrusion temperature and low extrusion ratio lead to high volume fraction of recrystallized area, thus entirely equiaxed solid grains in semi-solid 7075Al alloy samples can be obtained finally. In addition, Ostwald ripening was determined as the dominate coarsening mechanism of solid grains in semi-solid state for this 7075 Al alloy during the RAP route. The infuence of pre-deformation on recrystallization behavior of this 7075 Al alloy was discussed in detail.
The addition of high Ti (>0.1%) in microalloyed bainitic high strength steel was designed, and the precipitation morphology of steels with different Ti, Nb, and V contents was studied by utilizing transmission electron microscopy (TEM). Based on the classical nucleation-crystal growth theory and the Johnson-Mehl-Avrami equation, the precipitation thermodynamic and kinetic model of second phase particles in austenite was established in the form of (Nb x,V y,Ti z)C, and the complex precipitation mechanism of second phase particles was emphatically studied. The experimental results show that the complex precipitation particles could be divided into two categories: the coarser particles with about 100 nm grain size and the independent complex precipitation particles in the form of (Nb,V,Ti)C with 35-50 nm grain size. The latter has a better precipitation strengthening effect, and the calculated PTT curve shows a typical “C” shape. When the deformed storage energy is 3 820 J·;mol-1, the fastest precipitation temperature of calculated PTT curve is 925 °C, and the calculated result is essentially consistent with experimental values. The increase of Ti content increased the nose point temperature and expanded the range of fastest precipitation temperature.
Influence mechanism of sulfide ions (S2-) during manganese electrodeposition from sulphate electrolyte was investigated. Under the experimental conditions, S2- ion concentration and electrolyte pH represented significant multiple effects on the cathode current efficiency. Scanning electron microscope (SEM) indicated that electrodeposition manganese layer (EML) became refinement as S2- ion concentration was increased. X-ray Diffraction (XRD) displayed that S2- ion had negligible influence on the preferred orientation of the crystalline layer of the EML. S2- ion had no influence on the chemical composition of EML. S2- ion could improve the corrosion resistance of EML. The interaction mechanism of S2- ion with manganese electrodeposition was systematically explored by analysing E-pH diagram, cyclic voltammetry curve, cathode polarization curve and electrochemical impedance method.
V-Cr-Al-O nanospheres were successfully synthesized using V2O5, Al(OH)3, CrO3, and H2C2O42O as the starting materials by a facile one-pot hydrothermal approach. Several techniques containing X-ray powder diffraction, hydrogen temperature programmed reduction, scanning electron microscopy were used to characterize the composition, morphology and redox property of V-Cr-Al-O nanospheres. The catalytic behavior of prepared nanospheres on the thermal decomposition of AP was investigated by the thermogravimetric analysis and differential thermal analysis (TG/DTA). The experimental results show that the thermal decomposition temperature of AP in the presence of V-Cr-Al-O nanospheres is to 395 °C (decreased by 35 °C), which proves better catalyst for the thermal decomposition of AP.
An effect of heating and stirring in a facile wet chemical route to synthesize entangled nanofibrous mesh of doped polyaniline (PANI) was reported. The structural, morphological, and optical properties of PANI nano-fibers were found to be dependent on synthesis temperature and stirring. The XRD analysis confirms nano PANI formation with 2θ peaks around 15°, 21°, and 25° for (011), (020), and (200) crystal planes, respectively. The average crystallite size varies between 25 nm to 60 nm due to change in synthesis conditions. The SEM analysis reveals the clustered granule formation for PANI sample synthesized at 28 and 60 ° under continuous stirring, whereas, unstirred synthesis at 60 ° shows entangled nano-fibrous mesh morphology. The TGA study shows better thermal stability for PANI mesh over granular PANI. The FTIR spectra validates the emeraldine salt PANI formation with peaks corresponding to C-H, C-N, N=Q=N, N=B=N, and N-H vibration bands. The UV-Vis analysis shows the major absorbance peaks around λ: 340 nm (π-π* transition of benzenoid ring), and λ: 800 nm (π-π*, polaron-π*, π-polaron transitions). The dense entangled nano-fibrous coating of PANI synthesized at 60 ° without stirring shows highest electrical conductivity of 3.79 S·cm-1.
Bis[2-(3,4-epoxycyclohexyl)ethyl]octamethyltetrasiloxane is also called diepoxycyclohexylethyl octamethyltetrasiloxane. In the present paper, diepoxycyclohexylethyl octamethyltetrasiloxane was synthesized, and the synthesized product was characterized by FTIR and 1HMR. The synthesized product was compounded with some acrylates and an expoxide as well as photoinitiators to obtain a 3D printing stereolithography resin (3DSLR111). The properties of 3DSLR111 and its UV-cured samples were investigated by some instruments and equipments. The experimental results show that the critical exposure (E c) of 3DSLR111 is 10.1 mJ/cm2, its penetration depth (D p) is 0.15 mm, and its viscosity at 30 °C is 319 mPa·s. Some samples were printed with 3DSLR111, and their linear shrinkage and warping factor were evaluated. The linear shrinkage and the curl distortion factor are less than 0.80% and 7.30%, respectively, which indicates that the sample printed with 3DSLR111 has high accuracy, and that the synthesized diepoxycyclohexylethyl octamethyltetrasiloxane can be well applied to the preparation of the photosensitive resin for stereolithography 3D printing.
In the presence of titanium dioxide powder, cross-linking reaction between commercial polyvinyl alcohol (PVA)-based macromonomer and acrylic acid (AA) was initiated with potassium persulfate in an emulsifying system. As a result, PVA-AA/TiO2 composite gel particles were obtained. The morphology and composition of the particles were analyzed with scanning electron microscopy (SEM), energy scattering x-ray spectroscopy (EDS), Fourier infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The analysis results confirmed that the particles were the expected ones. TiO2 was dispersed homogeneously within the spheroidal particles. Compared to the control gel, the composite gel particles not only contained Ti element but also showed higher thermal stability. In addition, the photo-catalytic behavior of the particles for the degradation of methyl orange contained in aqueous solution was examined. The particles exhibited photo-catalytic characteristic for the degradation of the model dye, which could be modulated by simply varying the amount of cross-linking agent or TiO2. The photo-catalytic degradation percentage of methyl orange maintained at 91%-96% after using the particles three times, which indicated that TiO2 could played its role repeatedly via being fixated within polyvinyl alcohol-based gel.
A simple strategy was developed to prepare a tough, self-healing, antibacterial and moldable hydrogel by introducing the natural polyphenolic compound tannic acid (TA) as a cross-linking center for hydrogen bonds. Polyvinyl alcohol (PVA)-TA hydrogel was prepared by physical mixing using PVA as a main component and TA as a cross-linker. There were two types of physical cross linking bonds in the PVA-TA hydrogel network, which were weaker hydrogen bonds between PVA molecular chains and stronger hydrogen bonds between PVA and TA molecules. The mechanical properties and self-healing ability could be adjusted by changing the contents of PVA and TA. The hydrogel possessed not only high mechanical strength (305 kPa tensile strength and 864 kPa compressive strength), moldability and excellent self-healing properties (95% self-healing efficiency) but also good antibacterial abilities against S. aureus and E. coli. In addition, after soaking the dried hydrogel in 90 ℃ deionized water for 4 h, they could also regain their self-healing ability to a certain extent. The hydrogels have potential applications in the biomedical fields.
A dual-receptor targeting delivery system based on acid-cleavage hydrazone bond was developed in the study. The characters of CMCS-hyd-CUR-EGFR- mAb were identifed. The in vitro release studies revealed that this drug delivery system was acid-sensitive, and the self-assembled nanoparticles which were spherical. The in vitro results indicated that the dual-receptor targeting nanoparticles could be faster internalized into the Cal-27 cells via receptor-mediated endocytosis, which exhibited better antitumor activity than the one-receptor nanoparticles. The experimental results clearly reveal that CMCS-hyd-CUR-EGFR mAb provides a novel way for drug delivery in oral cancer treatment.