Nanocomposite cation exchange membranes (CEMs) were prepared by adding various loadings of functionalized silica nanoparticles to the sulfonated polyethersulfone (sPES) polymeric matrix. The silica nanoparticles were functionalized by mercaptopropyl (F 1, IEC=0), propylsulfonic acid (F 2, IEC= 2.71), and sulfonic acid (F 3, IEC=2.84). The properties of prepared membranes were investigated by varying the loadings of functionalized silica nanoparticles. Applying functionalized nanoparticles provides additional ion exchange groups and enhances water contents as well as conductivities and permselectivities of the membranes. The maximum IEC of 1.9 meq.g-1 was obtained for the membrane having 3wt% F 3 nanoparticles and the maximum conductivity of 0.237 S·cm-1 was achieved for the membrane having 2wt% F 3 nanoparticles, which were 19.6% and 64% higher than the corresponding values for sPES membrane, respectively. The excellent properties of the nanocomposite cation-exchange membranes make them appropriate candidates for electrodialysis and desalination processes.
Impurities from the raw materials, the grinding and the homogenization of the raw materials, the kiln instability and the complexity of the cooling step, all these factors make it difficult to obtain a perfect evaluation of the mineralogical composition of Portland clinker. We studied the limitations of the most commonly used quantitative methods and recommend some procedures to obtain reliable and reproducible results of quantitative analyses. Different clinker samples (provided by the Bizerte Cement Company (Tunisia)) were subjected to an elemental analysis by X-ray fluorescence and the mineralogical composition was determined by the Bogue calculation and by X-ray powder diffraction combined with the Rietveld method (Different softwares were used: XPert High Score Plus version 2.0 and TOPAS version 4.2). We then compared the results obtained by the Rietveld method and the Bogue calculation to the specific peak areas of each phase. The content of each phase, determined by the Rietveld method, varied proportionally to the change in peak area; a significant difference in these results was found by using the elementary Bogue calculation.
In order to obtain a safe, reliable, long-lived battery system without use of flammable, volatile, and relatively unstable organic liquid-based electrolytes, lithium garnet oxides with formulas Li7-xLa3Zr2-xTa xO12 (x=0.2-1) were synthesized by the solid state reaction method. Single cubic phases were observed in the composition x range between 0.2 and 1. The lattice parameters decreased with the addition of Ta due to the smaller ionic radius of Ta5+ compared with that of Zr4+, following the Vegard’s law. The total conductivity of the x = 0.3 composition is 6.03×10-5 S·cm-1 at room temperature with an activation energy of 0.30 eV. These lithium garnet oxides exhibit lithium ionic transport that is relevant to lithium battery application.
NiCr2O4 (NCO) spinel composites with different Mn/Ni atomic ratios (Mn/Ni = 0.05, 0.10, 0.15, and 0.20) were synthesized via solid state reaction method. Phase compositions and microstructure of samples were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The TG-DSC curves showed that the appropriate baking temperature for Mn-doped NCO spinel preparation was approximately 1 320 °C. X-ray diffraction patterns exhibited the formation of NCO spinel with Fd-3m space group. Valence state of the Mn ions was determined from 2p and 3s X-ray photoelectron spectra. Manganese ions were mostly in divalent and trivalent states, and the ratio of Mn2+/Mn3+ was 0.78-0.98. Fourier transform infrared spectroscopy (FTIR) was used to analyze the spectral emissivity of Mn doped NCO spinel. It was revealed that the infrared emissivity of Mn-doped NCO spinel in 1.8-5 μm could be significantly enhanced with increasing content of Mn2+, reaching as high as 0.9398. Mn-doped NCO spinel showed excellent radiation performance and good prospect in high emissivity applications in the temperature range of 800-1 200 °C.
The longitude tensile properties of 3-Dimension-4-directional(3D-4d) braided C/SiC composites(CMCs) were investigated with the help of a double scale model. This model involves micro-scale and unit-cell scale. In micro-scale, the tensile properties of fiber tows which involves matrix cracking, interfacial debonding, and fiber failure are studied. The unit-cell scale model can reflect the braided structure and simulate the tensile properties of 3D-4d CMCs by introducing the tensile properties of fiber tows into it. Quasi-static tensile tests of 3D-4d braided CMCs were performed on a PWS-100 test system. The predicted tensile stress-strain curve by the double scale model is in good agreement with that of the experimental results.
Hydroxyl terminated polybutadiene (HTPB) based polyurethane (PU)-polystyrene (PS) interpenetrating polymer network (IPN) was prepared and characterized by FTIR, TGA, WCA, swelling experiments, and SEM. The IPN was used for pervaporation (PV) recovery of butanol. Both the permeation flux and separation factor increased with feed temperature, and both water and butanol fluxes increased with feed concentration while no obvious effect of concentration on separation factor was found. Through the formation of IPN structure, the total flux of HTPB based PU increased greatly with the decrease of separation factor. At the feed temperature of 60 °C, the IPN membrane obtained a total flux of 613.3 g/m2h with a separation factor of 6.15.
We reported the synthesis of nitrogen-doped carbon using surface-attached polyelectrolyte layers as precursors. The synthesized material has a large surface area of 800 m2·g-1 with uniformed pore distribution. Benefitfed from the high pyridinic nitrogen content, the synthesized nitrogen-doped porous carbon material exhibits promising electrocatalytic activity toward oxygen reduction reactions in acidic medium and very high stability against continuous cyclic voltammetry scans. The experimental results demonstrate that surface-attached polyelectrolyte layers are promising carbon and nitrogen sources for the formation of heteroatom-doped porous carbon materials.
Tensile properties of epoxy casts together with shape memory alloy (SMA), glass (GF) and carbon (CF) woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy (SEM) and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.
TiAlSiN coating was deposited on H13 hot work mould steel using cathodic arc ion plating (CAIP). The surface-interface morphologies and phases of the obtained coating were analyzed using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively, and the morphologies, distributions of chemical elements and profiles of worn tracks were also researched using scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and optical microscope (OM), respectively. The friction-wear performances of TiAlSiN coating under oil lubricated and dry fiction conditions were investigated, and the wear mechanisms of TiAlSiN coating were discussed. The experimental results show that the coating is primarily composed of (Ti, Al)N, AlTiN, and TiN hard phases, Si3N4 exists between the (Ti, Al)N crystal grains, increasing the coating microhardness to 3200HV. The TiAlSiN coating has excellent performances of reducing friction and wear resistance, the average coefficient of friction (COF) of TiAlSiN coating under oil lubricated condition is only 0.05, lowered than the average COF of 0.211 under dry friction condition, the wear rate decreases by about 81.2% compared with that under dry friction condition. The wear mechanism of TiAlSiN coating under oil lubricated and dry friction conditions is composed of abrasive wear, fatigue wear, and abrasive wear, respectively. The internal friction of oil lubrication is a main factor of decreasing fatigue wear.
Palygorskite/paraffin phase-change composites were prepared by the combination of purified palygorskite clay and sliced paraffin. Then, this composite was used in the Trombe wall to improve its energy storage ability. Further, its energy storage ability was compared to that of ordinary concrete wall through contrastive test. The experiments show that palygorskite clay is a type of clay mineral with strong adsorption ability, and the purity of natural palygorskite clay can reach up to 97.1% after certain purification processes. Paraffin is well adsorbed by palygorskite, and the test results show that the optimal adsorption ratio is palygorskite: paraffin = 2:1 (mass ratio). Palygorskite/paraffin phase change composites can be obtained by using palygorskite as the adsorbing medium to adsorb paraffin. The composite materials exhibit good heat storage (release) performance, which can store heat with increasing environment temperature and release heat with decreasing temperature. This property not only increases the inertia to environment temperature change, but also promotes the energy migration in different time and space, thus achieving a certain energy-saving effect. The application of palygorskite/paraffin phase change composite materials to the Trombe wall can significantly reduce the fluctuation of indoor temperature and enhance the thermal inertia of indoor environment. From the aspect of energy storage effect, the Trombe wall fabricated using PCMs is significantly superior to the concrete wall with the same thickness.
The effect of pressure-induced flow (PIF) processing on the mechanical properties of non-continuous carbon fiber (CF) reinforced polyphenylene sulfide (PPS) composites was investigated. A series of CF/PPS composites under different processing conditions were prepared through PIF-processing. SEM observations showed that the interfaces adhesion between CFs and PPS became stronger and ductile fracture mainly occurred in PPS matrix. This brought to a great increase of both strength and toughness by about 2 folds, when the composites were processed at 240 °C and under 263 MPa. The results in differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements indicated more regular crystalline structures and orientation of lamellae formed during PIF-processing.
In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field (B-LBSF) was successfully fabricated in this work. Through boron doping in the LBSF, much higher doping concentration was observed for the B-LBSF over the Al-LBSF. Higher doping concentration in the LBSF is expected to lead to better rear passivation and lower rear contact resistance. Based on one thousand pieces of solar cells for each type, it was found that the rear passivated crystalline silicon solar cells with B-LBSF showed statistical improvement in their photovoltaic properties over those with Al-LBSF.
The fatigue behavior of 30WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.
Three-dimensional hierarchical Co3O4 microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment. Photocatalytic properties measurements revealed that the photocatalystic activities of CuO/Co3O4 composites (Co3O4 microstructures decorated with CuO) were enhanced while those of Ag2O/Co3O4 composites (Co3O4 microstructures decorated with Ag2O) were reduced, when compared with those of pure hierarchical Co3O4 microstructures toward the degradation of methyl orange. In addition, CuO/Co3O4 composites exhibited an excellent recyclability ability of photodegradation. The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability. With the increase of the loaded Ag2O and CuO dosages deposited on the Co3O4 microstructures surface, the specific capacitance values of the composites were increased. Ag2O/Co3O4 composite electrodes showed higher specific capacitance values and better cycling stability than CuO/Co3O4 composite ones.
Three different curing temperatures (20 °C, 40 °C, and 60 °C) were set, so that the nonevaporable water (w n) contents of plain cement pastes cured at these three temperatures were measured to determine the hydration degree of cement. Tests were carried out to compare the pore structure and strength of cement paste, as well as the strength and permeability of concrete under different temperature curing conditions when their cements were cured to the same hydration degree. The experimental results show that either at a relatively low hydration degree (w n=15%) or high hydration degree (w n=16.5%), elevated curing temperature has little influence on the hydration products of cement paste, while it has a negative influence on the pore structure and compressive strength of cement paste. However, this negative effect is weaker at high hydration degree. The large capillary pore (>100 nm) volumes of cement pastes remain almost the same at high hydration degree, regardless of curing temperatures. As for the concrete, elevated curing temperature also has negative influence on its compressive strength development, at both low hydration degree and high hydration degree. And this negative effect is stronger than that on cement paste’s compressive strength at the same hydration degree. On the whole, elevated curing temperature has little influence on the resistance of concrete to chloride ion penetration.
Drying shrinkage of thermal insulation mortar with glazed hollow beads was measured by a vertical length comparator, and the influences of fly ash with different contents (0, 18%, 36%, and 54% were used) on the long-term drying shrinkage were discussed. The mass loss was measured by the weighting method and the pore structure was characterized using three different methods, including the light microscopy, the mercury intrusion porosimetry (MIP), and the nitrogen adsorption/desorption (NAD) experiments, and the correlations among them were researched. The results show that drying shrinkage process of thermal insulation mortar includes three steps with increasing curing time: the acceleration period (before 7 d), the deceleration period (7-365 d), and the metastable period (after 365 d). Drying shrinkage in the first stage (7 d before) increases quickly owing to the fast water loss, and its development in the last two stages is attributed to the increment of the pore volume of mortar with the radius below 50 nm, especially the increment of the pore volume fraction of the pore radius within the size range between 7.3 nm and 12.3 nm. There is no change in the drying shrinkage development trend of mortar with fly ash addition, and three steps in the service life, but fly ash addition in the mortar restrains its value. There is a linear relationship between the drying shrinkage and fly ash content, which means that drying shrinkage reduces with fly ash addition.
Yield stress development of cement paste is potentially governed by percolation of 3-dimensional links formed by hydration products on the surface of the particles. It rises steadily at a gradual rate before a sudden increase in rate of growth. In this study, a method was proposed to predict the yield stress development based on the diameter of spread (D) of mini slump cone test and gradient from electrical resistivity measurement (K m). To evaluate the significance of (D) and (K m) in terms of yield stress, they were quantitatively compared to the initial yield stress (τ 0) and rate of yield stress growth (K) obtained from a rheometer. A mathematical relationship between the yield stress of cement paste, diameter of spread and electrical resistivity characteristic gradient was developed. The equation developed can be used as an alternative method to estimate yield stress of cement paste.
A self-crosslinkable liquid highly branched polycarbosilane (LHBPCS) with 5.07% vinyl group and a C/Si ratio of 1.33 was used as the precursor to prepare SiC ceramic material. Microwave heating technique and conventional heating method were applied for the heating treatment process. It was found that, compared with conventional heating method, microwave heating technique could enhance the crystallinity of SiC ceramic material with small grain size at much lower curing temperature and within shorter time. In addition, the SiO2 additive could lead to less α-SiC and excess carbon, but worsen the crystallinity of β-SiC in the final samples.
The objective of this work was to study the properties of bamboo charcoal and cement-based composite materials and their microstructure. The pastes with various bamboo charcoals were prepared and the relative properties such as setting times and strength were tested and the microstructures and pore characteristics of pastes with various bamboos were also studied. The experimental results indicated that bamboo charcoal affects the setting times of cement paste, but the introduction of water reducer relieves this condition. Bamboo charcoal also poses an impact on the hardened paste strength. The prominent strength decrease is found when more and larger size bamboo charcoal is mixed into the cement paste. Bamboo charcoal alters the paste microstructure and increases the porosity and pore volume, but it increases the pores with the diameter of less than 50 μm. The pastes with various bamboo charcoals are given with the good functions such as adjusting humidity and adsorption.
We investigated the temperature dependency of the dynamic mechanical properties of cement asphalt paste by the dynamic mechanical thermal analysis (DMTA) method. The experimental results show that the dynamic mechanical properties of cement asphalt pastes are sensitive to temperature due to the inclusion of asphalt, and may go through different states within a temperature range of -40 °C to 60 °C, which is different from that of pure cement and asphalt. As the temperature of the cement asphalt paste increases, a considerable change of dynamic mechanical properties, including storage modulus (E’), loss modulus (E”) and loss factor (tanδ) is observed. Moreover, the influence of asphalt to cement (A/C) ratio on the temperature sensitivity of the dynamic mechanical properties of cement asphalt composites was investigated. The temperature dependency of cement asphalt composites is ascribed to the temperature dependency of the asphalt and its interaction with cement paste. A simple fractional model is proposed to describe the viscoelastic behavior of cement asphalt composites.
The geopolymer samples were prepared with smelting waste slag of non-ferrous metal as the raw material and water glass as the activator. The effect of modulus of water glass and water binder ratio on the compressive strength was studied. The results show that the strength of the geopolymer activated by water glass with modulus of 1.1 and water binder ratio of 0.28 can maintain an increasing trend in the 90 curing days. Through the analyses with XRD, SEM (EDS), and FTIR, the main reaction products are found to be geopolymer gels, which bond the crystalline minerals to provide strength. The molecular chains of amorphous phase in slag become shorter after depolymerization-polycondensation.
To analyze the influence of new compound admixture on shotcrete performance, the ordinary Portland cement pr425 was used as matrix components. The optimum proportion of admixture was obtained by analyzing the influence of content on cement setting time and compressive strength. The microstructure of cement test block and the mechanism of reducing dust of composite macromolecule admixture were analyzed by scanning electron microscopy and infrared spectroscopy. It was shown that the ratio of polyacrylic acid was 0.02%. The ratio of J85 accelerator was 5%. The ratio of bentonite was 4.5% in composite admixture. The most optimal content of admixture in the slurry was 7%. The compound coagulant formed by additive together with C3A, C4AF which provided nucleation for hydration and crystallization of C3S and C3S, and played an active role to promote the activity of the mineral admixture in cement, and increased the elastic modulus of C-S-H gel and accelerated the hydration process of portland cement. Bentonite and polyacrylic acid promote the wettability, cohesiveness and workability of cement paste in the process of hydration. The formation of cement test block gel was even. The interface between the matrix phase and the aggregate phase was not obvious which ensured the matching between the matrix and the aggregate phase. The addition of bentonite formed hydrogen bonds in cement paste and improved the cohesiveness of the system. The J-85 accelerator promoted the combination of aluminate and gypsum which hindered the formation of calcium carbide around the cement particles which made cement rapid condensation. Polyacrylic acid mainly changed the strength of hydroxyl absorption peak in cement paste to improve the initial strength of cement test block. The addition of new admixtures promoted the process of cement hydration to be more thorough and affected the later strength development of concrete by affecting the formation of calcium carbonate stone.
Ribbon-like Cu doped V6O13 was synthesized via a simple solvothermal approach followed by heat treatment in air. As an cathode material for lithium ion battery, the ribbon-like Cu doped V6O13 electrode exhibited good capacity retention with a reversible capacity of over 313 mAh·g−1 for up to 50 cycles at 0.1 C, as well as a high charge capacity of 306 mAh·g−1 at a high current rate of 1 C, in comparison to undoped V6O13 electrode (267 mAh·g−1 at 0.1C and 273 mAh·g−1 at 1 C). The high rate capability and better cycleability of the doped electrode can be attributed to the influence of the Cu ions on the mophology and the electronic conductivity of V6O13 during the lithiation and delithiation process.
A new research method was proposed(A/S method) to study the components and properties of reclained asphalt mixture (RAP). The RAP was divided into two main parts, one was marked with A that included all the reclaimed old asphalt materials(including some parts of particle materials covered by asphalt), the other was marked with S which mainly included works soil in the road structure. The actual working conditions were simulated by this kind of new method, and the adaption between the RAP properties, A/S, and the content of cementitious materials were studied. The research indicated that the real working condition could be simulated effectively by means of A/S method. It was also showed that high content of cement could improve the overall performance of RAP significantly, but it would have a negative effect on the properties of RAP if the types and sizes of aggregate particles in RAP mixture were too single. The optimum water content and maximum dry density could not be regarded as the primary basis to evaluate the overall performance of RAP, when S=0 in the experiments, although the maximum density of samples was bigger than that with A/S=1/1, the samples were not strong enough and they were easy to collapse, which indicated that component design of RAP played a great role in improving the overall properties of RAP and the comprehensive tests should be considered to evaluate the stability of RAP. Low frequency load in high temperature environment had the negative effect on the overall stability of RAP, and factors such as the loading state of the materials, the hydration degree of cementitious materials, and the aggregate gradation in the mixture were the determining factors for improving the overall performance of RAP.
As a kind of special material in geotechnical engineering, the mudded weak interlayer plays a crucial part in slope stability. In this paper, we presented a method to determine the threshold value of section micrographs of the mudded weak interlayer in slope during its meso-structure qualification process. Some soil tests, scanning electron microscopy (SEM) and image segmentation technology were performed to fulfill our purpose. Specifically, the relation between 3D-porosity and the threshold was obtained by least square fitting of the threshold-porosity curves and a simplified pore equivalent model. Using this relation and the 3D-porosity determined by soil experiments, we can figure out the polynomial equation of the threshold value. The threshold values obtained by the other existing methods in literature were employed to validate our present results.
Fe3O4-octadecyltrichlorosilane (Fe3O4-OTS) was synthesized and used to remove dyes in a competitive system. Fe3O4-OTS was prepared by slow hydrolysis of OTS in cyclohexane on the surface of Fe3O4 obtained through coprecipitation method. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and contact angle analyzer (CA) were used to analyze the properties of Fe3O4-OTS. Methyl orange (MO) and methylene blue (MB) were selected as model molecules to study the influence mechanism of pH and ionic strength on competitive adsorption. The results of EDS and CA indicated that Fe3O4 was modified successfully with OTS on the surface. Silicon appeared and carbon content increased obviously on the surface of adsorbent. Contact angle of adsorbent increased from 0° to 107° after being modified by OTS. Fe3O4-OTS showed good separation for MO and MB in competitive system, which has potential to separate dyes in sewage. Separation factor (β B O) changed from 18.724 to 0.017, when pH changed from 7 to 12, revealing that MO and MB could be separated almost thoroughly by Fe3O4-OTS. pH could change the surface charge of Fe3O4-OTS and structure of dyes, and thus change the interactions of competitive system indirectly. Even though hydrophobic interaction was enhanced, ionic strength reduced the difference of electrostatic interaction between dyes and Fe3O4-OTS. So it is unfavorable to separate dyes with opposite charges when ionic strength increases. These findings may provide theoretical guidances to separate two-component dye pollutants.
7XXX series aluminium alloys generally present low weldability by fusion welding methods because of the sensitivity to weld solidification cracking, vaporization of strengthening alloys and other defects in the fusion zone. Friction stir welding (FSW) can be deployed successfully with aluminium alloys. We presented the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of SSM7075 joints. Semi solid plates were butt-welded by FSW at a rotation speed of 1110 r/min, welding speeds of 70 and 110 mm/min. Solution treatment, artificial aging, and T6 (solution treatment and artificial aging combined) were applied to the welded joints, each with three samples. It was found that the T6 joints at the speed of 70 mm/min yielded the highest tensile strength of 459.23 MPa. This condition best enhanced the mechanical properties of FSW SSM7075 aluminium alloy joints.
The effect of high-energy electropulsing-ultrasonic surface treatment (EUST) on the surface properties and the microstructure evolution of C45E4 steel was investigated. Refined microstructure and reduced surface roughness were obtained owing to the surface nanocrystallization process. Compared with the ultrasonic surface treatment (UST), the impact depth of the surface strengthened layer was increased by 40% to 700 μm after EUST. The average grain size of the surface nanocrystallization layer was reduced to 30-50 nm. The surface roughness of the C45E4 steel was reduced to 0.25 μm, and the surface microhardness was dramatically enhanced to 460 HV. The improvement of microstructure and micro-hardness at ambient temperature was likely attributed to the acceleration of atomic diffusion and the enhancement of plastic deformation ability in the surface strengthened layer under the influence of electropulsing. Due to the electropulsing-assisted ultrasonic strengthening effect, the surface nanocrystallization in this ultrafast procedure was noticeably enhanced.
This work aimed to in-situ monitor the atmospheric corrosion of steels exposed to Zhoushan offshore environment by using electrochemical noise (EN) technique. A portable EN monitoring system was established and two electrochemical probes (named as Q235B and T91) were designed. Experimental results indicated that the noise resistance of T91 steel was higher than that of Q235B steel, revealing that the corrosion resistance of T91 was higher than that of Q235B. A 60-day monitoring result indicated that the noise resistance was well correlated with the weight loss data. Wavelet analyses results of EN data indicated that Q235B underwent uniform corrosion and T91 suffered from localized corrosion, which was further confirmed by the surface observation. It is concluded that EN can be used as a new method to identify the corrosion form and corrosion resistance in atmospheric conditions.
The effects of biaxial tensile pre-strain on the forming limit of DP590 high-strength steel under high strain rate were investigated. The stress-strain curves of DP590 steel sheet under the biaxial tensile of different load ratios were obtained. The forming limit diagrams (FLDs) of DP590 steel sheet under biaxial tensile pre-strain and electromagnetic hybrid forming were established. Results showed that the biaxial tensile pre-strain had significant effects on the formability of DP590 steel. The pre-strain in a certain range improved the forming limit of DP590 steel under high rate, and the forming limit increased with the pre-strain. The pre-strain in the same direction of high rate increased the forming limit of the final deformation under complex strain paths conditions, but the pre-strain in the vertical direction decreased the minor strain under the high strain rate.
Macroscopic texture and microscopic orientation in hot-rolled and annealed sheets of non-oriented electrical steel were studied by XRD and EBSD techniques. The microstructure of hot-rolled and annealed samples was studied by OM. Experimental results indicate that a strong heredity is observed in texture evolution between hot-rolled texture and annealed texture. Typical elements have a large effect on the recrystallization microstructure and texture distribution. The texture distribution through thickness is highly affected by recrystallization in hot rolled sheets. The recrystallization is boosted by Si and Al. Goss grains originate from cracked initial <100> columnar grains. {110}<112>, {112}<111> and {111}<112> grains are related to Goss grains. In subsurface lay of hot rolled sheets, Al can strengthen Goss texture and weaken copper-type texture. {112}<111> texture and {110}<112> texture are strengthened by Si. In the central layers, {100}<001> texture and {111}<121> texture are weakened by Al. {100}<011> texture is increased by Al. Si can increase the proportion of γ-fiber texture and decrease that of {100}<011> texture. In annealed texture, {100}<001> texture and Goss texture are decreased by Al and Si. γ-fiber texture is increased by Si and {111}<121> texture is preferentially increased by Al. The recrystallized grain size is increased and iron loss of annealed sheets is reduced by Al and Si, which means that the magnetic properties are optimized by the Al and Si content.
A new low-cost corrosion-resistant rebar (HRB400R) was designed and fabricated by chromium micro-alloying. The effects of Cr on the passivation and corrosion behavior of this rebar in the simulated concrete pore solutions were studied systematically, and its improved corrosion resistance was revealed. In the Cl--free saturated Ca(OH)2 solution, the HRB400R rebar presented nearly the same passive film and similar passivation ability compared to the common carbon steel rebar. In the long-term immersion corrosion test in the Cl--contained Ca(OH)2 solution, the HRB400R rebar presented improved corrosion resistance and obvious longer passivation-maintaining period. Micro-alloying of Cr element in the rebar matrix enhanced its corrosion resistance against Cl--attack and retarded the corrosion initiation in the matrix. In the alkaline NaCl salt spraying test, the HRB400R rebar also presented obviously lower mass-loss rate. The enrichment of Cr element in the rust layer improved its retardant effect to the penetration of aggressive medium, and decreased the corrosion propagation rate of the rebar.
We discussed the oxidation differential and mechanisms on different planes of pyrite. The experimental results show that the oxidation priority is: (222) plane> (200) plane> (200) plane, and there is no direct correlation between the crystal plane index, the atom numbers, and the oxidation priority. However, with more exchanged charge among atoms, the oxidation could be conducted more easily, and the distribution rule of the electric charge conforms with the variation trend of adsorption energy, which will provide more overall cognition on the oxidation mechanism of pyrite from the atomic scale.
Hot compression tests on AZ40 magnesium alloy were conducted on a Gleeble 1500d hot simulation testing machine in a deformation temperature range of 330 °C-420 °C and a strain rate range of 0.002-2 s-1. Hot deformation behaviors were investigated on the basis of the analysis of the flow stressstrain curves, constitutive equation, and processing map. The stress exponent and apparent activation energy were calculated to be 5.821 and 173.96 kJ/mol, respectively. Deformation twins and cracks located in grain boundaries were generated at 330 °C and 0.02 s-1, which are associated with a high strain rate and a limited number of available slip systems. With increasing temperature and decreasing strain rate, the twins disappeared and the degree of dynamic recrystallization increased. The alloy was completely dynamically recrystallized at 420 °C and 0.002 s-1, with a homogenous grain size of approximately 13.7 μm. The instability domains of the deformation behavior can be recognized by processing maps. By considering the processing maps and characterizing the microstructure, the optimum hot deformation parameters in this experiment were determined to be 420 °C and 0.002 s-1.
The correlation between the internal friction behaviour of Zr55Al10Ni5Cu30 BMG samples and their quenching temperatures was investigated. It was found that, below the glass transition temperature, the activation energy decreased with increasing quenching temperature, but in the surpercooled liquid region the activation energy tended to be enhanced with a further increase in the quenching temperature. Besides, there were both anelastic and viscoelastic relaxation for the amorphous alloys. The anelastic behaviour would change into viscoelastic relaxation easily for the samples prepared at higher temperature.
A modulated photoluminescence nanosensor was developed for the quantitative detection of formaldehyde with nitrogen-doped graphene quantum dots and melamine. The sensing system was based on the different activated effects of melamine and hydrogen peroxide on the photoluminescence intensity of nitrogen-doped graphene quantum dots. Under the optimal conditions, the modulated photoluminescence sensing system can be used to detect formaldehyde with a good linear relationship between the nitrogen-doped graphene quantum dots photoluminescence difference and the concentration of formaldehyde. The novel sensing system provided new directions for the detection of formaldehyde with high selectivity and quick response.
A new type of adjustable nozzle with an annulus clearance between the surfaces of a revolved solid and the matched hole was analyzed, which contained matching parts, regulating parts, guiding elements, and sealing part. The general regulating function of the adjustable nozzle was derived and the regulating and matching characteristics were also analyzed. Through the analysis, it was concluded that the matching-profile curve of either the revolved body or matched hole should be chosen as a straight line in order to keep the linear regulating feature. Moreover, the multi-annulus-clearance nozzle was designed, and some experiments were carried out on preparing budesonide particles with the nozzle. According to the experimental results, it was proved that the annulus nozzles is practical in preparing micro-particles by supercritical fluid precipitation method.
This work aimed to develop an intelligent multi-target tracking hyaluronic acid-RGD-chlorambucil-quantum dots (HA-RGD-CLB-QDs) drug delivery system. After deacetylated, hyaluronic acid was reacted with anticancer drug chlorambucil, RGD, and quantum dots to obtain the HA-RGD-CLB-QDs drug delivery system. The characterization by FT-IR, 1H NMR, TEM, XPS, DLS, and UV-vis absorption and fluorescence spectra show that the system is successfully constructed with an average particle size of about 70 nm. The results of the drug release profile show that that the system has a pH and enzyme sensitive controlled release behaviour. Moreover, cellular uptake and toxicity results show that the system has an ideal dual receptor-mediated endocytosis pathway that significantly enhances the efficacy of CLB tumor therapy and has a lower toxicity to normal cells.The system shows the potential application as a carrier for cancer therapy.
A micromechanical model based on discrete element method (DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating three-dimensional aggregates that can reflect the realistic geometry such as shape, size and fracture surface of aggregate particles was developed using a user-defined procedure coded with FISH language in particle flow code in three-dimensions (PFC3D). The parallel-bond model (PBM), linear contact model (LCM), and slip model(SM), whose sets of micro parameters were obtained by comparing experimental tests with numerical simulation results, were used to characterize the internal contact behavior of asphalt mixture. Digital asphalt mixture specimens were used to simulate the effects of aggregate size and specimen scale on the cracking behavior by the indirect tensile (IDT) test. Some conclusions can be drawn as follows: Both cracks and IDT strength decrease with increasing aggregate size. However, the heterogeneity of contact-force distribution augments with increasing aggregate size, especially with 13.2-16 mm aggregate. The aggregate size of 4.75-9.5 mm dominates in forming skeleton structure for asphalt mixture. The IDT strength decreases and cracks augment with increasing sample scale. The crack growth can be well interpreted from the perspective of energy analysis. The conclusions show that the proposed micromechanical model is suitable for the simulation of crack propagation. This study provides an assistant tool to further study the cracking behavior of particle-reinforced composites material such as asphalt mixture and Portland cement concrete.
The gas-phase dehydration of glycerol was conducted over HPW/MCM-41 catalysts, which were prepared by impregnation of different amount of H3PW12O40 (HPW) on the MCM-41 support. The samples were characterized by XRD, N2 physisorption, FTIR, NH3-TPD, and pyridine-FTIR measurements. N2 physisorption results suggested that the uniform framework of MCM-41 could still be well maintained after modified with HPW. Pyridine-FTIR experiments indicate that HPW modified MCM-41 can generate rich Brønsted acid sites. Moreover, Brønsted acid sites facilitated to improve acrolein selectivity. Under the optimized reaction conditions: 40wt% HPW loading, 20% glycerol concentration, and 320 °C reaction temperature, the glycerol conversion and acrolein selectivity reach 85% and 80%, respectively.