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The effects of heat treatment on the mechanical properties of plain-woven SiC/SiC composites at 927 °C and 1200 °C in argon were evaluated through tensile tests at room temperature and at elevated temperature on the as-received and heat-treated plain-woven SiC/SiC composites, respectively. Heat treatment can improve the mechanical properties of composites at room temperature due to the release of thermal residual stress. Although heat treatment can damage the fiber, the effect of this damage on the mechanical properties of composites is generally less than the effect of thermal residual stress. Heat treatment will graphitize the pyrolytic carbon interface and reduce its shear strength. Testing temperature will affect the expansion or contraction of the components in the composites, thereby changing the stress state of the components. This study can provide guidance for the optimization of processing of ceramic matrix composites and the structural design in high-temperature environments.

The transverse constitutive relationship of warp yarns and weft yarns was established separately. A new analytical expression considering the coupling effect of fiber/matrix interface debonding damage was proposed to simulate the transverse elastic modulus of warp yarns. The validation using the finite element method shows that the analytical expression has good accuracy. The transverse cracking of single weft yarn and weft yarn attached to warp yarn was simulated with the finite element method, and the transverse constitutive relationship in these two cases was simulated. The transverse constitutive relationship of single weft yarn shows obvious brittleness, while the transverse constitutive relationship of weft yarn attached to warp yarn shows obvious toughness. The transverse constitutive relationship of warp yarns and weft yarns established in this paper can contribute to establish the three-dimensional constitutive relationship of yarns in the multi-scale modeling of the mechanical behavior of plain-woven ceramic matrix composites.

In the present study, the fatigue behavior and damage evolution of SiC/SiC minicomposites at elevated temperatures in oxygen-free environment are investigated which are important for their application and are still unclear. The high-temperature fatigue test platform is developed and the fatigue stress-life curve and the stress-strain response are obtained. The test result shows that the life of the material at elevated temperature is shorter than that at room temperature under the same stress level. Moreover, the hysteresis loop width and the residual strain increase with the increasing of the cycles while the hysteresis modulus decreases during the fatigue cycling. The evolution process of matrix cracks is observed using the real-time remote detection system. It is found that matrix cracking is insensitive to the cyclic loading which is similar to room temperature and is due to that the degeneration of the interfacial shear stress reduces the area of high stress in matrix. The fiber/matrix interfacial shear stress under different cycles is determined based on the fatigue modulus of each hysteresis loop. The result shows a fatigue enhancement phenomenon for the interface which is not observed at room temperature.

The sensitivity of strength via temperature for SiC/SiC composites and SiC fibers in an oxygen-free environment is studied through experimental investigation and theoretical analysis. Tensile tests are performed on SiC/SiC minicomposites at room temperature, 500 and 1000 ℃ in an oxygen-free environment. A high-efficiency method is proposed to obtain the high-temperature strength distribution of SiC fibers. The experimental results show that the sensitivity of strength via temperature is high for SiC fibers but low for SiC/SiC minicomposites. To explain this phenomenon, the strength model of minicomposites is developed. The theoretical analysis reveals that the low sensitivity of strength via temperature for minicomposites results from that the influences of the changes of the Weibull parameters m and σ0 at elevated temperatures are offset.

To study the thermal decomposition of Al/ZrH2/PTFE with different Al particle size as well as mechanical strength and impact sensitivity under medium and low strain rates, molding-vacuum sintering was adopted to prepare four groups of power materials and cylindrical specimens with different Al particle size. The active decomposition temperature of ZrH2 was obtained by TG-DSC, and the quasi-static mechanics/reaction characteristics as well as the impact sensitivity of the specimen were studied respectively by quasi-static compression and drop-hammer test. The results show that the yield strength of the material decreased with the increase of the Al particle size, while the compressive strength, failure strain and toughness increased first and then decreased, which reached the maximum values of 116.61 MPa, 191%, and 119.9 MJ/m respectively when the Al particle size is 12∼14 μm because of particle size grading. The specimens with the highest strength and toughness formed circumferential open cracks and reacted partly when pressed. Those with developmental cracks formed inside did not react. It is considered that fracture of specimens first triggered initial reaction between Al and PTFE to release an amount of heat. Then ZrH2 was activated and decomposed, and participated in subsequent reaction to generate ZrC. The impact sensitivity of the specimens decreased with the increase of Al particle size.

To predict the fatigue limit of ceramic matrix minicomposites, the fatigue behaviour of SiC/SiC minicomposites was studied by plotting the L-N curve obtained from fatigue tests. An efficient mathematical model was established based on micromechanics analysis to predict the fatigue limit of these materials. Based on the fatigue failure mechanism, the interfacial shear stress of the SiC/SiC minicomposites decreases as the number of cycles increases because of matrix cracking, interfacial debonding, interfacial slipping, and interfacial wear. In the fatigue limit state, the PyC interface debonds completely and the SiC/SiC minicomposite is fully supported by the fibres. A fatigue limit prediction model was proposed based on the fatigue limit state. To improve the accuracy of the model, a procedure was devised to determine the probability of fibre filaments that break owing to the imposed stress, considering the possibility that the fibre filaments of the SiC/SiC minicomposites were broken during the manufacturing process. In general, there was good agreement between the experimental and predicted fatigue limits, with an error of ~5%.

Thermite serves as a kind of representative energetic material, which is extensively applied in the civil and military fields. In this paper, PTFE/Al/Fe2O3, PTFE/Al/MnO2 and PTFE/Al/MoO3, solid fluorine-containing thermite with different PTFE content, were successfully fabricated by referring to the traditional thermite and adding PTFE as a binder or matrix. Quasi-static compression tests were performed to investigate the mechanical and reactive behavior of fluorine-containing thermite. SEM and XRD were employed to analyze and characterize the energetic composites and reaction residuals. The results show that all types of fluorine-containing thermite exhibited different mechanical behavior. PTFE/Al/MnO2 exhibited the lowest yield strength and strain hardening modulus, but the highest compressive strength and toughness. With the increase of PTFE content, the strength of fluorine-containing thermite improved. No reaction occurred when the PTFE content was 60 vol%, while fluorine-containing thermite with a PTFE content of 80 vol% experienced a severe exothermic reaction under quasi-static compression. The ignition of PTFE/Al/MoO3 and PTFE/Al/Fe2O3 actually attributed to the reaction of Al and PTFE, and the reaction between Al and Fe2O3 or MoO3 was not excited due to the insufficient input energy. The thermite reaction between Al and MnO2, as well as the reaction of MnO2 and PTFE, was induced because PTFE/Al/MnO2 possessed excellent ductility and absorbed the most energy during compression, accompanied with the production of Mn and MnF2.

The performance of the hydrophilic diamond fixed-abrasive lapping pad has great effects on successive lapping quality. In this research, orthogonal experiment method was applied to research...

The strength of plain-woven SiC/SiC composites was predicted with the multi-scale method. Firstly, a three-dimensional unit cell was used to characterize the geometric structure of plain-woven SiC/SiC composites. Secondly, the yarns were seen as minicomposites, whose axial mechanical properties were obtained by the shear-lag model, and the fiber defect model was adopted to simulate the failure process of minicomposites. The strength of plain-woven SiC/SiC composites predicted with the multi-scale method is in good agreement with the experimental result. Besides, the effects of heat treatment and load-carrying capacity of broken fiber on the strength of plain-woven SiC/SiC composites were evaluated, and the effect of woven geometry structure was also evaluated.

The titanium body porcelain was synthesised through sol–gel using borate–silicate system. The porcelain was characterised by X-ray diffraction (XRD), scanning electron microscope and three-point fl...

A constitutive model of SiC/SiC composites is developed which considers fiber failure and broken fibers’ load carrying capability. To obtain the in situ properties of SiC fibers, tensile tests are performed on the heat-treated fibers. A more universal fiber strength model is developed to describe the strength distribution of SiC fibers. In the constitutive model of SiC/SiC composites, the stress distribution of broken fibers is analyzed. To validate the in situ fiber strength distribution and the constitutive model, a tensile test is performed on SiC/SiC minicomposites. The predicted strength and stress-strain response of SiC/SiC minicomposites are in good agreement with the experimental results. The numerical calculations show that fiber failure nearly has no effect on the nonlinearity of SiC/SiC composites although the strength of composites will increase to infinity without fiber failure, and that the strength of the composites will decrease greatly if broken fibers do not carry the load.

The mesoscopic model of fibre-reinforced composites can provide key geometric and material related information for predicting the mechanical properties of composite components. In this study, an approach to build a mesoscale preform of a plain-weave composite component with complex geometry was established. This was achieved via parameterisation and integration - with a set of parameters, related to the preform geometry, and a macroscopic geometrical model, of the composite component, as the inputs. In this method, tow centrelines were simulated as sinusoids in curvilinear coordinates. A simplified model of the tow section is proposed at the mesoscale. Based on this method, the geometry of the plain-weave preform at the mesoscale can be obtained integrally according to the macroscopic shape of the component input. The credibility of this proposed method was verified with similar microscopic observations and experiments conducted in other studies. The applicability of this approach to a more complex component was also investigated. Finally, a characteristic layer was established to analyse the material aperiodicity in a complex component.

Star-like nano-ZrO2 has been synthesized using Zr(NO3)4·5H2O as zirconium source by a hydrothermal process without any template and surfactant. The structure of the as-prepared ZrO2 powder was investigated by multiple advanced analytical methods. The results showed that CH3COO− and NO3− had great effects on the formation of star-like ZrO2 nanostructures. The as-prepared ZrO2 had a superior catalytic activity, and the reason for it was analyzed by UV-Vis diffuse reflectance spectroscopy. The effect of raw material ratios on the photocatalytic property of ZrO2 was studied. The synthesized ZrO2 showed a narrow bandgap (3.50–3.85 eV) and an excellent photocatalytic activity, and the degradation of RhB was up to nearly 100% in 30 min with this photocatalyst.

A new in situ strength model of carbon fibers was developed based on the distribution of defects to predict the stress-strain response and the strength of C/SiC composites. Different levels of defects in the fibers were considered in this model. The defects in the fibers were classified by their effects on the strength of the fiber. The strength of each defect and the probability that the defect appears were obtained from the tensile test of single fibers. The strength model of carbon fibers was combined with the shear-lag model to predict the stress-strain responses and the strengths of fiber bundles and C/SiC minicomposites. To verify the strength model, tensile tests were performed on fiber bundles and C/SiC minicomposites. The predicted and experimental results were in good agreement. Effects of the fiber length, the fiber number and the heat treatment on the final strengths of fiber bundles and C/SiC minicomposites were also discussed.

Novel Bi2O4/BiOBr heterojunctions were fabricated via a chemical etching process. BiOBr nanosheets could be in-situ generated in Bi2O4 micro-rods, which greatly improved the interface quality. The photocatalytic performance of samples was evaluated by the degradation of rhodamine B(RhB) and methyl orange (MO) under visible light irradiation. The results showed that Bi2O4/BiOBr heterojunctions displayed higher photocatalytic activity than pure Bi2O4 and BiOBr, and 99.3% MO could be degraded in 60 min over 0.4BB (~ 33.3 mol% BiOBr) sample. The effective separation and transfer of the photogenerated electrons and holes were believed to be the main factor for the enhanced activity, and the holes (h+) and ·O2− radicals were confirmed to be the main active species. This work offers an effective route to the fabrication of Bi2O4/BiOBr heterojunctions with high interface quality for photocatalytic applications.

By in-situ oxidative polymerization method, a novel flower-like polyaniline/graphitic carbon nitride (PANI/g-C3N4) nanocomposite was successfully synthesized. In comparison with single PANI, PANI/g-C3N4 displayed enhanced electrochemical performance which had a specific capacitance of 584.3 F g−1 and 81.91% of capacitance retention after 1000 cycles at 1 A g−1. This work demonstrated a simple strategy of improving the specific capacitance and cycling stability of polymer electrodes and may be extended to other similar systems.

The fatigue life of plain-woven SiC/SiC composites was predicted with the multi-scale method by combining the micromechanical model with the mesoscale finite element model. The micromechanical constitutive relationship of yarns under variable amplitude loading was derived, and the mesoscale finite element model was established by choosing the minimum repeatable unit as the unit cell. The degradation of interface shear stress was obtained by fitting the secant modulus of hysteresis loop, and the fiber random fracture model based on the global load sharing model was adopted to simulate the fatigue failure of the yarns. To improve the prediction speed of fatigue life, the number of fatigue cycles increases exponentially. The fatigue life of plain-woven SiC/SiC composites predicted with the multi-scale method are in good agreement with the experimental results.

The in situ elastic modulus and strength distribution of carbon fibers in C/SiC composites were studied. To obtain the in situ property data, fibers were heat treated according to the fabrication process of C/SiC composites. Tensile tests were performed on the single fibers and fiber bundles. The equivalent in situ modulus and strength were proposed considering the loose and unparallel fibers in the composites. The experimental and numerical results showed that the equivalent elastic modulus and average strength of in situ fibers are much lower than that of the original fibers. In addition, the equivalent strength distribution of in situ fibers is more dispersive.

Novel g-C3N4 decorated Bi2O4 heterojuction photocatalysts were prepared via a hydrothermal method. The obtained samples were characterized by using XRD, SEM, EDS mapping, FT-IR, XPS and DRS. After the introduction of g-C3N4, g-C3N4 nanostructure was evenly distributed on Bi2O4 nanorods, forming heterojunction composites with staggered band alignments. The photocatalytic performance was evaluated by the degradation of methyl orange under visible light irradiation. The g-C3N4/Bi2O4 composites exhibited significantly enhanced photocatalytic activity. Among them, 10CB sample displayed the highest degradation efficiency, whose apparent rate constant was 2.2 and 11.8 times higher than that of Bi2O4 and g-C3N4, respectively. Besides, by combining Bi2O4 with g-C3N4, the composites showed decent photochemical stability. It was assumed that the enhanced photocatalytic activity and photostability could be ascribed to the formation of heterojunction, which effectively promoted the separation and transfer of photogenerated charge carriers.

To investigate the mechanical properties of pressed and sintered PTFE/Al/Ni (polytetrafluoroethylene/aluminum/nickel) composite, uniaxial quasi-static and dynamic compression experiments were conducted at strain rates from 10−2 to 3 × 103/s. The prepared samples were tested by an electrohydraulic press with 300 kN loading capacity and a split Hopkinson pressure bar (SHPB) device at room temperature. Experimental results show that PTFE/Al/Ni composite exhibits evident strain hardening and strain rate hardening. Additionally, a bilinear relationship between stress and $${\text{log(}}\dot{\varepsilon } )$$ is observed. The experimental data were fit to Johnson-Cook constitutive model, and the results are in well agreement with measured data.

Gradual matrix closure and its effects on the constitutive behavior of SiC/SiC composites are examined in the present study. Real-time matrix crack detection and a macroscopic loading–unloading tensile test are performed on SiC/SiC minicomposites. To verify the effects of matrix crack closure, stress-strain responses under loading and unloading with and without crack closure are discussed. The experimental and numerical results show that matrix cracks close gradually upon unloading, and gradual matrix closure greatly reduces the unloading stiffness.

To realise wide-band stealth of radar absorbing material, a special-shaped honeycomb radar absorbing structure within nested cone-shaped scattering configuration is designed. Based on the HS theory and the impedance matching design, the rule about the influence of the geometry parameter and electromagnetic parameter on the absorbing performance is analysed. In addition, the reflectivity performance is analysed on the condition of oblique incidence angles. By optimising the geometry parameters of the special-shaped honeycomb structure and designing the multilayer composite structure based on impedance matching theory, the results indicate that the two absorbing peaks can be formed for the special-shaped honeycomb radar absorbing structure, and the reflectivity is improved for both the vertical and oblique incidence angles.

A self-healing coating with UV-shielding property was prepared in this paper. The self-healing property was based on the inclusion between a host (&beta, CD-TiO2) and a guest HEMA-Ad). After inclusion of the host and guest, the host&ndash, guest complex (HEMA-Ad/&beta, CD-TiO2) was polymerized with other reactive monomers (HEMA and BA) to obtain the final coating. The coating had good hydrophobicity (water contact angle &gt, 90&deg, moisture absorption rate &lt, 2%) and excellent UV-shielding performance (ultra-violet protect factor &gt, 90%), and could be firmly bonded to a soft substrate. In addition, the coating had good self-healing property, which means that cracks in the material can recover many times after being damaged and that the UV-shielding ability can be fully restored with the self-healing process.

To study the effect of the addition of potassium perchlorate (KClO4) on the performance of nano thermites, Al/Bi2O3 nano thermites with different mass fraction (wt%) of KClO4 was made by ultrasonic dispersion method. Then, all samples were tested by SEM, DSC and rapid excitation ignition. DSC results showed Al/Bi2O3/10 wt%KClO4 had the highest heat release. Compared with Al/Bi2O3, the heat release increased by 28.32%. The results of activation energy calculations showed Al/Bi2O3/30 wt%KClO4 had the lowest activation energy (Ea). Its activation energy was reduced by 30%, mere about 149.17 KJ mol−1. Finally, it can be seen from the combustion situation that the addition of KClO4 reduced the intensity of burning. This work found a way to increase the heat release or reduce the activation energy of nano thermites by controlling the amount of KClO4 added.

A strength model of the matrix element is developed for SiC/SiC composites to predict the matrix cracking process. A strength formula of the matrix element is presented. Modeling results using the previously introduced critical matrix strain energy criterion and the probabilistic-statistical approach are also examined. To verify these models, real-time matrix crack detection and a macroscopic tensile test are performed on SiC/SiC minicomposites. A comparison between the predicted and experimentally obtained results shows that the present strength model is better than the two above methods.

Strain has valuable effects on the formation of the growth and the photo electronic properties of Ge/Si quantum dots (QDs), and it is important to understand the distribution of strain and the other properties of Ge/Si QDs theoretically. In this work, a method based on the Green’s function technique is used to solve elastic equations and the strain of different QDs shapes is calculated by a numerical algorithm. The strain of QDs which array in different density is analyzed and the strain of hemispherical QDs is compared with pyramidal QDs in calculations.

Erbium (Er) doped Bi24O31Br10 samples were successfully prepared by using a solvothermal method. The samples were characterized by XRD, XPS, SEM, TEM, BET, DRS, PL and EIS. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) and methyl orange (MO) under visible light irradiation. The result shows that Er dopant induces a significant improvement in the photocatalytic activity. 1.0% Er–Bi24O31Br10 sample exhibits the best photocatalytic performance. The enhanced photocatalytic activity is attributed to the effective trapping of photogenerated electron by Er3+ ion and the up-conversion process resulting from Er dopant. In addition, it is found that holes and super-oxide radicals play main role in the photocatalytic degradation of RhB and MO.

The fatigue behavior of 2D needled C/SiC CMCs at room temperature was studied. The residual tensile properties were determined for the run-out condition set for the fatigue testing. It is noted that the 2D needled C/SiC CMCs achieve ~20% enhancement of the ultimate tensile strength after fatigue loading with fiber pull-out present. This enhancement of residual properties is not widely observed and reported for CMCs. The increase in residual tensile properties correlates with the applied fatigue stress. The procedures for testing and the mechanics for the increased strength after fatigue testing are discussed. This is supplemented with microstructure observations. The prior fatigue loading results in more full-developed micro-damage and a more uniform stress state in the fibers of needled C/SiC CMCs, so the load capability of post-fatigue specimens is stronger than the as-received ones with extremely uneven pre-loading in fibers. Keywords: Ceramic Matrix Composites, Fatigue strengthening, Residual strength, Stress level, Microstructural mechanism

The supercapacitors with conventional multilayer structure exhibit a large contact resistance and tend to delaminate because of the relative displacement under external force. Herein, the all-in-one flexible supercapacitors are fabricated by integrating chemically crosslinked hydrogel electrolytes with conducting copolymer electrodes. The hydrogel electrolyte is prepared by chemically crosslinking reaction of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) with glutaraldehyde (GA) where the hydroxyl groups (-OH) of PVA and PEG react with aldehyde groups (-CHO) of GA to form acetal or hemiacetal in sulphuric acid solution. The prepared hydrogel electrolyte exhibits better mechanical properties (tensile strength of 36 KPa under strain of 117%) and remarkable ionic conductivity (67.1 mS cm−1) than pure PVA hydrogel. Based on this gel electrolyte, a novel flexible supercapacitor with an all-in-one (electrode-electrolyte-electrode) configuration is designed by in situ polymerization of poly (pyrrole-co-aniline) onto PVA/PEG gel electrolyte to achieve exceptional electrochemical performance. This all-in-one configuration can maintain fast charge-carrier transportation and good structural stability. The resulting device shows a large specific capacitance of 773 mF cm−2 at the current density of 0.2 mA cm−2, excellent energy density (54 μWh cm−2) and power density (100 μW cm−2). Under different bending angles or 1000 bending cycles, the capacitance of the device is maintained at 100% which owing to the all-in-one configuration can overcome the relative displacement and avoid the loss of electroactive materials from gel electrolytes when the device is bent. These findings present potential applications in flexible, wearable and smart energy storage devices.

In order to control heat and smoke release of the intumescent flame retardant (IFR) epoxy coating on steel during fire hazard, a little amount of zirconium nitride (ZrN) of 1～3 wt% was introduced into the coating. The back temperature test showed it used about 46.1 min for the steel plate coated with IFR coating without ZrN to reach 580 °C, however by using of 3 wt% ZrN, the time was prolonged to 61 min, indicating the steel structure can be kept for more than 15 min. The result is very important to the safety of steel structure, meaning more escape time during a fire hazard. Furthermore in cone test, the coating containing ZrN exhibited more control on heat and smoke release. For example, compared with the IFR coating containing no ZrN, coating containing 3 wt% ZrN cut more than 20.3% total heat release (THR) and 40.0% smoke production (SPR). The graphitization degree increase of char was documented by Raman spectrum; and in XRD patterns some special peaks of ZrP2O7 and Ti0.8Zr0.2P2O7 was found in char, all the results indicated ZrN participated into the charring with IFR and TiO2 together and then promote formation of more compact char structure.

This study presents numerical simulations of a unidirectional ceramic matrix composite (CMC) plate under different loads considering the effect of fluid-structure interaction (FSI). The two-scale method was used in the dynamic simulation of CMC plate. The shear-lag model considering the damage modes of CMCs was used to simulate the constitutive behavior in the micro-scale. The explicit dynamic finite element method was used to simulate the dynamic response in the macro-scale. The dynamic responses of CMC plate under impulse and harmonic load were simulated. The incompressible Navier-Stokes equations were employed in the simulation of fluid. The dynamic response of CMC plate with FSI was solved based on the staggered method. The effect of fluid on the dynamic response of CMC plate was discussed.

In order to explore the best formula of flame-type high-energy burner, this paper selects 7 groups of flame-type high-energy burners with good stability, high energy and a wide range of raw materials based on the existing literature and patents. The Gibbs free energy Values of 7 groups of formulations at different temperatures were calculated by using the chemical thermodynamic formula, and the changes in Gibbs free energy Values of 7 groups of formulations were drawn, which provided a basis for the calculation of reaction rate k value by Eyring equation. Then, according to the calculation theory of chemical reaction calorific value, the heat of reaction of 7 different formulations at different temperatures was calculated. The results show that the Gibbs free energy value of Al/MnO2 in the seven groups of formulations is much smaller than that of the other groups in the same reaction temperature environment, and decreases with increasing temperature. According to the Arrhenius formula and the Eyring equation, the reaction rate of Al/MnO2 is the fastest in each group. When the other conditions are constant, the reaction enthalpy of Al/MnO2 is the smallest in each group, therefor the heat released by the reaction is the most. In summary, under the same quality conditions, the Al/MnO2 flame type high energy burner formulation has the fastest reaction rate and the most heat release, which provides theoretical guidance for experimental design and practice.

An important result of our investigations of the fatigue response of Ceramic Matrix Composites (CMCs) is the modeling of the residual strength after fatigue loading. According to the experimental results, the residual tensile strength of 2D needled CMCs firstly increases and then decreases as the number of fatigue cycles increases. Based on the microstructure observations and the wear-in/wear-out mechanisms presented by previous researchers, a model is developed here to characterize the residual strength vs. the number of fatigue cycles for the composites. After parameter identification, the presented model describes the change of the residual strength quite well.

The distribution of slip regions on the fiber–matrix interface of unidirectional fiber-reinforced ceramic matrix composites is described to simulate the constitutive behavior under arbitrary loading and unloading. The appearance and disappearance of forward and reverse slip regions are discussed and the stress distribution when there are any number of forward and reverse slip regions is also provided. The interface slipping and constitutive behavior after closure of matrix cracks under compressive loading are analyzed. Based on the distribution model of slip regions, the stress–strain response of unidirectional fiber-reinforced ceramic matrix composites under arbitrary loading and unloading is calculated.

In this study, a finite element method was developed based on X-ray computer tomography to predict the elastic modulus of needle carbon-fiber-reinforced ceramic matrix composites with voids randomly existing in the material. In these pictures, every pixel point contains all of the information of the components that we need, including voids. Using this information, the mechanical properties of components can be obtained, then a finite element model with voids was built and the predicted results fit well with the experiments. In addition, a volume average method was developed to determine the proper representative volume element size to reduce the computing time without losing the accuracy.

BiPO4/BiOBr p–n junction photocatalysts were successfully synthesized via a facile one-pot solvothermal method. The products were characterized by XRD, FE-SEM, HRTEM, XPS, DRS, PL and EIS. The obtained BiPO4/BiOBr composites were constructed by inlaying BiPO4 nanoparticles into BiOBr hierarchical microspheres. Compared with BiPO4 and BiOBr, they exhibited significantly enhanced visible light photocatalytic activity towards the degradation of Rhodamine B (RhB). Among them, 10% BiPO4/BiOBr showed the maximum value of the activity, whose degradation rate was about three times higher than that of pure BiOBr. The enhanced photocatalytic activity could be attributed to the formation of the BiPO4/BiOBr p–n junction, which resulted in the effective separation and transfer of photogenerated electron–hole pairs. Moreover, the trapping experiments confirmed that O2− and h+ were the main active species responsible for the degradation of RhB.

Temper embrittlement tends to occur in the turbine rotor after long running, which refers to the decrease in notch toughness of alloy steels in a certain temperature range (e.g., 400°C to 600°C). The severity of temper embrittlement must be monitored timely to avoid further damagement, and the fracture appearance transition temperature (FATT50) is commonly used as an indicator parameter to characterize the temper embrittlement. Compared with conventional destructive methods (e.g., small punch test), nondestructive approaches have drawn significant attention in predicting the material degradation in turbine rotor steels without impairing the integrity of the components. In this paper, laboratory experiments were carried out based on a nondestructive method, electrochemical impedance spectroscopy (EIS), with groups of lab-charged specimens for predicting the temper embrittlement (FATT50) of turbine rotor steel. The results show that there was a linear relationship of interfacial impedance of the specimens and their FATT50values. The predictive error based on the experiment study is within the range of ±15°C, indicating the predicting model is precise, effective, and reasonable.

Selective laser melting (SLM) manufactures components through the overlapping of multi-track and multi-layer molten pools of metal powders, resulting in two types of molten pool boundaries (MPBs), “layer–layer” and “track–track” MPBs, remaining in SLM parts. The microstructure of MPBs exhibits a complex and regular spatial topological structure. There is a coarse grain zone below the MPBs and nonmetallic elements (C, O, Si) near the MPBs are in an unstable state. Long and thin columnar grains with the same orientations distribute on two sides of the “layer–layer” MPBs, whereas the columnar grains on both sides of “track–track” MPBs have different orientations. The “track–track” MPBs are short and intersect with “layer–layer” MPBs at some points and form acute angles, where cracks are initiated when applied with external loads. The effect of the MPBs on microscopic slipping, macroscopic ductility and fracture mechanism of the SLM parts made along different directions, which were exerted a tensile loading in the as-built condition without heat treatment, was analyzed and evaluated using slip theory and experiments. The results reveal that the MPBs have a significant impact on the microscopic slipping at the loading, macroscopic plastic behavior and fracture mode, and are one of the main reasons for the obvious anisotropy and low ductility of SLM parts.

The fabrication and evaluation of a glassy carbon electrode (GCE) modified with ordered mesopo- rous carbon (OMC), 2-mercaptoethanesulfonate (MES)- tethered polyaniline (PANI) and bismuth for simultane- ous determination of trace Cd 2 + and Pb 2 + by differential pulse anodic stripping voltammetry (DPASV) are pre- sented here. The morphology and electrochemical proper- ties of the fabricated electrode were respectively charac- terized by scanning electron microscopy (SEM) and elec- trochemical impedance spectroscopy (EIS). Experimental parameters such as PANI disposition, preconcentration potential, preconcentration time and bismuth concentra- tion were optimized. Under optimum conditions, the fab- ricated electrode exhibited linear calibration curves ranged from 1 to 120 nM for Cd 2 + and Pb 2 + . The limits of detection (LOD) were 0.26 nM for Cd 2 + and 0.16 nM for Pb 2 + (S/N = 3), respectively. Additionally, repeatabili- ty, reproducibility, interference and application were also investigated, and the proposed electrode exhibited excel- lent performance. The proposed method could be extend- ed for the development of other new sensors for heavy metal determination.

Cobalt nanoparticles-embedded magnetic ordered mesoporous carbon (Co/OMC), prepared through a simple method involving infusing and calcination, was used as a highly effective adsorbent for rhodamine B (Rh B) removal. Several techniques, including SEM, HRTEM, nitrogen adsorption–desorption isotherms, XRD, Raman spectra, EDX, zeta potential and VSM measurement, were applied to characterize the adsorbent. Batch tests were conducted to investigate the adsorption performance. The adsorption capacity of the resultant adsorbent was relatively high compared with raw ordered mesoporous carbon (OMC) and reached an equilibrium value of 468 mg/g at 200 mg/L initial Rh B concentration. Removal efficiency even reached 96% within 25 min at 100 mg/L initial Rh B concentration. Besides, the adsorption amount increased with the increase of solution pH, adsorbent dose and initial Rh B concentration. Kinetics study showed that the adsorption agreed well with pseudo-second-order model ( R 2 = 0.999) and had a significant correlation with intra-particle diffusion model in the both two adsorption periods. Furthermore, thermodynamics research indicated that the adsorption process was endothermic and spontaneous in nature. The adsorption isotherms fitted well with Langmuir model, demonstrating the formation of mono-molecular layer on the surface of Co/OMC during adsorption process. The results confirmed that Co/OMC has the potential superiority in removal of Rh B from aqueous solution.

There is a risk of InGaZnO thin film transistor (IGZO TFT) failure, especially electro-static discharge (ESD) damage of gate driver on array (GOA) circuits, due to the combination of Cu interconnect, InGaZnO (IGZO) active layer and SiNx/SiO2 insulating layer used to realize large-scale ultra-high resolution display. It is found that the IGZO TFT damage position caused by ESD occurs between the source/drain metal layer and the gate insulator. The Cu metal of gate electrode diffuses into the gate insulator of SiNx/SiO2. The closer to the ESD damage area the IGZO TFT is, the more serious the negative bias of its threshold voltage (Vth) is until the device is fully turned on. The IGZO TFT with a large channel width-to-length ratio(W/L) in GOA circuit results in a serious negative bias of threshold voltage. In this paper, the ESD failure problem of GOA circuit in the IGZO TFT backplane is systematically analyzed by combining the ESD device level analysis with the system level analysis, which combines IGZO TFT device technology, difference in metal density between GOA region and active area on backplane, non-uniform thickness distribution of gate metal layer and gate insulator and so on. In the analysis of ESD device level, we propose that the diffusion of Cu metal from gate electrode into SiNx/SiO2 leads to the decrease of effective gate insulator layer, and that the built-in space charge effect leads to the decrease of the anti-ESD damage ability of IGZO TFT. In the analysis of ESD system level, we propose that the density of metal layers in GOA region is 4.5 times higher than that in active area of display panel, which makes the flatness of metal layer in GOA region worse. The non-uniformity of thickness of Cu metal film, SiNx film and SiO2 film around glass substrate lead to the position dependence of the anti-ESD damage ability of IGZO TFT in the GOA region. If there is a transition zone of film thickness change in IGZO TFT with large area, the ESD failure will occur easily. Accordingly, we propose to split large area IGZO TFT into several sub-TFT structures, which can effectively improve the ESD failure.

The InGaZnO thin film transistor (IGZO TFT) backplane combined with Cu interconnection has nearly an order of magnitude lower in the ability to withstand voltage than that of traditional a-Si TFT backplane on the production line. The breakdown voltage of Mo/Cu interconnection between data line and gate line is only about 60% of that of traditional a-Si TFT backplane. The electrostatic discharge (ESD) breakdown of Mo/Cu:SiNx/SiO2:Mo/Cu structure has become an important factor affecting the normal display of IGZO TFT ultra high definition (UHD) panel. We find that the anti-ESD damage ability of IGZO TFT devices needs matching with the anti-ESD damage ability of interlayer Cu interconnection in order to achieve a high-robustness IGZO TFT backplane. The position of ESD damage in IGZO TFT backplane is commonly in the climbing place where the data line crosses the scanning line. In this paper, a Cu diffusion model is proposed to explain the mechanism for the ESD failure of interlayer Cu interconnection. The Cu metal in gate line diffuses into SiNx/SiO2 gate insulator, and Cu metal at the corner of data line, where the date line crosses the gate line, diffuses into SiO2 film on the date line. The selection conditions of three kinds of protection architectures for ESD protection circuits around Cu interconnection, i.e. R-type, R-half-type, and Diode-type protection architectures, are proposed. On the basis of process optimization such as Cu metal film forming and Cu metal interface treatment, an ESD protection method for the Cu interconnection periphery of IGZO TFT backplane with high robustness is proposed. For the stable production process of IGZO TFT, combined with the design window of ESD protection circuit, the peripheral ESD protection circuit of Cu interconnect is designed with diode-type protection circuit on the IGZO TFT backplane of large-sized UHD and QUHD panel, which effectively improves the effect of interlayer Cu interconnection of IGZO TFT backplane on ESD damage. Through the production verification, it is proved that the metal diffusion of Cu interconnection on IGZO TFT backplane is the fundamental reason for reducing the anti-ESD damage ability of Mo/Cu:SiNx/SiO2:Mo/Cu structure. The rationality of the proposed ESD damage model for interlayer Cu interconnection is verified, which provides a theoretical basis for subsequent IGZO TFT backplane design with high robustness.

Today, silicon material plays an irreplaceable role in microelectronic of the information industry, however it don`t have a good emission characteristics. In order to explore the emission character, we calculated the electrons structure, absorbance of silicon doped with C, Si, Ge, Sn and Pb by the first-principles methods.

The binding energy, electronic structure and optical properties of ultrathin single-layer silicon nanosheets passivated with H-, H3C-, H2-N and HS-cluster were calculated using density functional theory based on plane-wave ultra-soft pseudopotential respectively. Firstly, the most stable configuration was selected from passivated configurations according to the lowest energy principle after calculating their total energies. Secondly the density of state and the band structure of the different passivated systems were calculated. It was found that different passivation clusters could affect the forbidden band, furthermore the passivated HS-cluster could notably decrease the width of forbidden band through electron transfer. Finally, the light absorption and reflection properties were also investigated. All results were conducive to the development of silicon-based optoelectronic devices.