Under the current technological conditions, inclusions have become inevitable in steel. To investigate the impact of micron inclusions on the mechanical properties of metals, vacuum arc melting was used to control the mass fractions (contents) of micron Al₂O₃ powder at 0%, 0.2%, 0.6%, 1%, and 2%, thereby preparing samples with different contents of micron inclusions. Statistical analysis of inclusion sizes via computed tomography imaging and scanning electron microscopy (SEM) revealed that most inclusions had a size of <5 μm. Moreover, the quantity of inclusions proportionally increased with increasing Al₂O₃ content. Mechanical properties were tested using the indentation method; the test results indicated that the addition of a certain amount of micron inclusions can enhance the mechanical performance of a metal. However, when the Al₂O₃ content exceeded 1%, the tensile strength increase slowed down and the yield strength decreased. SEM observations revealed that at high Al₂O₃ content, inclusions tended to agglomerate into large inclusions or clusters, which caused local stress concentration. This phenomenon in turn negatively affected the strengthening effect of the micron inclusions on the mechanical properties of the investigated metal.

Herein, a wet-mixing process was used to improve the dispersion of fillers in nitrile latex by incorporating three types of accelerators: trialkyl chlorides (TACs), tetramethylthiuram disulfide (TMTD), and zinc dibenzyldithiocarbamate (ZTC). These accelerators were added to cost-effective and readily available nitrile latex, followed by mixing, coagulation, washing, and drying to obtain nitrile rubber nitrile butadiene rubber (NBR). A novel rapidly-vulcanized NBR was developed using the properties of NBR3445F and NBR3345 as reference standards, and the effects of different types and dosages of accelerators on the vulcanization characteristics, mechanical properties, and microstructure of the developed NBR were studied. Results showed that compared with conventional rapidly vulcanized NBR, the developed NBR with 2 parts of accelerator TAC (TAC-2) exhibited 4.7 s higher vulcanization speed, a 138% higher tensile strength, and 59% higher tear strength. This NBR also exhibited substantially higher overall performance than NBRs with the other two accelerators, ZTC and TMTD. These findings were well aligned with the microstructural characteristics observed in scanning electron microscopy image. Based on the premise of ensuring rapid vulcanization speed and safe processing performance, TAC, an accelerator with better performance, can be selected to manufacture a rapidly vulcanized NBR, providing a technical path and an experimental basis for the development of related materials.

With the development of intensive farming，the requirements for the living environment of livestock and poultry have become increasingly stringent. During the hot summer months，the demand for highly effective antibacterial curtain paper is particularly urgent. In this study，we used the in situ ultraviolet light irradiation method to successfully introduce Ag nanoparticles into an antibacterial curtain paper. The addition of an appropriate amount of Ag not only improved the filtration performance of the curtain paper，which can effectivly filter the impurities and microorganisms in the air，but also significantly enhanced its mechanical properties，especially the durability and stability. In addition，it even increased its bactericidal efficiency to 100%. This achievement is expected to enhance the filtration and antibacterial effectiveness of existing curtain papers in farms and provides significant theoretical guidance for the development of related products.

The three-position mechanism represents a critical mechanical component in ultra-high voltage switch circuit breakers，with the copper nut serving as a pivotal element. Premature failure of this component can significantly compromise the operational stability and longevity of the circuit breaker. This comprehensive investigation employs advanced analytical techniques to elucidate the underlying fracture mechanisms of the copper nut. Utilizing a multifaceted analytical approach，the study systematically examined the fracture morphology and material characteristics. Optical microscopy，scanning electron microscopy，and metallographic microscopy were employed to scrutinize the fracture surface and microstructural features. Complementary analyses using X-ray fluorescence spectrometry and electronic universal testing machine characterized the material’s compositional and mechanical properties. The investigation revealed critical insights into the failure mechanism. Multiple crack initiation sites were identified within the fracture zone，characterized by coarse grain structures and an extensive network of precipitate particles localized at grain boundaries. The failure mode was definitively classified as cumulative fatigue damage. The primary crack source originated at the diameter transition of the shaft pin root’a structural stress concentration zone that represents the most vulnerable point in the copper nut’s mechanical design. The findings underscore the importance of structural geometry and material microstructure in predicting and mitigating mechanical failure in critical electromechanical components.

As a common flame retardant, ammonium polyphosphate (APP) can considerably improve the flame retardancy of rubber, but the molecular structure of APP shows that it contains a large number of ammonium phosphate groups, rendering it highly hygroscopic. To address this hygroscopic issue of APP, microencapsulated APP (MF201) was obtained by coating APP microcapsules with melamine resin. Although MF201 can solve the hygroscopic issue of APP, the presence of microencapsulated shells may affect the properties of rubber. To study the difference between the two flame retardants, APP and MF201 were introduced into a natural rubber/butadiene rubber (NR/BR) composite to investigate their impacts on the hardness, flame retardancy, wear resistance, and other physical and mechanical properties of NR/BR composites. The results show that the addition of APP and MF201 can improve the flame retardancy, hardness, mechanical properties, and wear resistance of NR/BR composites. Due to the plasticizing effect of the melamine resin shell, the hardness of NR/BR composites decreases slightly when MF201 is added. Furthermore, APP and MF201 improve the flame retardancy of NR/BR composites to the same extend. For example, 45 phr APP and MF201 increase the limiting oxygen index of NR/BR composites to 25.5% and their UL-94 combustion rating to HB. In addition, the effects of APP and MF201 on wear resistance are basically the same. The NR/BR composites with MF201 added have lower hardness and higher elongation at break. Therefore, the microencapsulated shell did not change the flame retardant and wear resistance of APP to NR/BR composites, but increased the elongation at break and reduced the hardness.

To improve the corrosion resistance of traditional pure Zn coatings, we used 30 mm diameter Q195 welded pipes as the substrate and prepared a series of hot-dip galvanized alloy coatings by adding trace amounts of alloy elements such as Al, Ni, and Re to the Zn bath. First, the main factors affecting corrosion resistance were identified through a four-factor and three-level orthogonal experiment. Then, the experiment was further improved for the primary factors, and single-factor experiments were conducted to obtain the optimal parameter combination. Finally, the microstructure characteristics and corrosion resistance of the coating were studied and analyzed using methods such as high and low temperature humidity test, neutral salt spray test, metallographic analysis, and scanning electron microscopy. Results indicate that the introduction of alloying elements suppresses the growth of ζ layer, which makes the coating structure compact, and improves the corrosion resistance of the coating. The coating prepared in this study could remain rustless throughout a 72 h salt spray test and a 120 h humidity test. The process for preparing the alloy coating is same as the existing production process for traditional Zn coatings.

Although regression analysis can predict some drape indicators, they have problems such as low prediction accuracy and the inability to calculate some indicators. To overcome these issues, this study proposes a new method using genetic algorithm to optimize BP neural network (GA-BP neural network) to improve the prediction accuracy of real fabric drape. In this study, we designed a GA-BP neural network model, selected 100 pure cotton woven fabric samples from the fabric database, including 80 training samples, 10 test samples, and 10 validation samples, used the genetic algorithm to optimize the parameters of the neural network, and used correlation analysis to optimize sample input parameters to improve the prediction performance of the model. The results of the drape coefficient prediction for the 10 test samples show that compared with the traditional BP neural network, the average absolute percentage error of the BP neural network optimized by the genetic algorithm decreased from 12.74% to 7.03%. Furthermore, we used an empirical equation to identify error cycles and concluded that the optimal number of hidden layer nodes is 9. This study indicates that the GA-BP neural network can effectively improve the accuracy of fabric drape prediction and has important application value for the virtualization of fabric drape performance.

In order to study the welding methods suitable for metal bipolar plates, 0.1 mm 316L stainless steel was welded by four common bipolar plate welding methods : laser welding, vacuum diffusion welding, brazing and ultrasonic welding.The potentiodynamic polarization curves of four kinds of welded joints were measured by using CHI-604E electrochemical workstation. The electrochemical corrosion properties of four kinds of welded joints were compared, and the electrochemical corrosion behavior was analyzed by combining microstructure and chemical composition.It is found that the corrosion resistance of vacuum diffusion welded joints and laser welded joints is strong, and the corrosion resistance of ultrasonic welded joints and brazed joints is weak.The post-weld deformation of four kinds of welded specimens was measured by laser spectral confocal microscope. Under the action of fixture, the deformation of laser welded specimens was smaller than that of other specimens.The welding time and welding process used in the welding process of the four welding methods were compared.After comprehensive comparison, laser welding is finally determined as the best choice for these four common metal bipolar plate welding methods.

SF₆ is widely used in high-voltage insulated equipment due to its excellent insulating properties. High-voltage insulated equipment faces the problem of insulation aging during its long-term operation, which can reduce the stability and safety of energy power equipment. When partial discharge occurs, SF₆ decomposes under high-voltage and temperature into various species, such as SO₂, SO₂F₂, HF, and H₂S. Based on the first principle, a novel two-dimensional semiconductor pristine GeO₂ monomolecular layer, which has a strong adsorption capacity for SF₆ decomposed gases, is proposed in this study. Results show that this pristine GeO₂ monomolecular layer provides an ideal amount of charge transfer and work function during the adsorption process. The detection of the SF₆ decomposed gases by the novel two-dimensional GeO₂, which is a gas-sensitive semiconductor material, allows us to identify the operational status and degree of insulation of high-voltage insulated equipment, which is crucial for maintaining the reliability and stability of power systems.

Phthalonitrile resin is new type of high-temperature resistant thermosetting resin system that has attracted wide attention owing to its excellent thermal and oxidative stability, flame retardancy, and mechanical properties as well as low expansion coefficient, dielectric constant, and dielectric loss. To improve its manufacturability and meet stringent environmental performance requirements, extensive research has been conducted worldwide on the modification of the phthalonitrile system. This paper reviews the research progress of the phthalonitrile system from the aspects of molecular structure design and curing methods and mechanisms along with its applications in electrical components, adhesives, etc. Moreover, the paper discusses the opportunities and challenges faced by phthalonitrile as a new type of special functional resin material, aiming to provide insights for research in relevant fields.

The existing fatigue life prediction of asphalt mixtures is mostly based on traditional fatigue equation fitting; however, due to the multidirectionality of pavement structure and the complexity of materials, the prediction accuracy is often not satisfactory. Therefore, this article establishes an optimized neural network-based model for predicting the strength and fatigue life of asphalt mixtures using indoor indirect tensile tests and verifies the accuracy of the prediction model. The experimental results show that the accuracy of Genetic Algorithm-Back Propagation neural network to predict the fatigue mechanical properties for asphalt mixture is within 4%, which is far superior to traditional fatigue prediction equations and can be used as an effective method to obtain data on the fatigue characteristics of asphalt mixtures.

Radiative-cooling nylon is a filament with a passive radiative cooling function and is made of high-infrared-emitting inorganic particle SiO₂ and infrared-transmitting material polyamide 6 (PA6) using the industrial melt spinning method. In this study, the surface morphology, aggregated structure, chemical composition, mechanical properties, thermal properties, and surface friction properties of three types of radiative-cooling nylon filaments and an ordinary nylon filament were compared. The thermal conductivity, cool feeling at instant contact, and indoor cooling performance of the four knitted fabrics were further tested. The results show that the knitted fabric interwoven with the radiative-cooling PA6/PE sheath-core composite yarn, which is spun with SiO₂-added radiative-cooling PA6 as the skin material and polyethylene (PE) as the core material, and radiative-cooling nylon filament with circular cross-section demonstrate the best thermal conductivity and cooling performance. Its infrared thermal imaging temperature was approximately 1.8 ℃ higher than that of the ordinary nylon knitted fabric, indicating that the knitted fabric exhibits a higher infrared transmittance and better cooling effect. Thus, the radiative-cooling nylon knitted fabric possesses excellent radiative cooling performance and wearability and can be used for the development of radiative-cooling textiles.

Titanium alloys possess excellent properties like low density, high specific strength, and corrosion resistance. So, these alloys are widely used in the aerospace. With the development of aerospace, the usage ratio of such alloys is one of the criteria to measure whether the aerospace equipment is advanced or not. Because these alloys show low hardness and wear resistance, fretting wear becomes an important cause for the failure of titanium alloy parts. To improve the fretting wear resistance, laser cladding was used to produce a coating on the surface of TC4 alloy in this study. The results showed that the hardness and wear resistance of TC4 alloy were improved by laser cladding Ti-Al powder.

The flame retardants aluminum diethylphosphinate (ADP) and aluminum hypophosphite (ALHP) were introduced into natural rubber (NR) and butadiene rubber (BR) to prepare the composites. In this study, we compared the effects of the two flame retardants on the processing characteristics, physical properties, flame retardancy, mechanical properties, and abrasion resistance of the composites. Results showed that both flame retardants delayed the vulcanization of the composites, increased the Mooney viscosity. ADP exhibited a more evident increase in Mooney viscosity than ALHP. When ADP and ALHP was added at 45 phr, the limiting oxygen index (LOI) of the composites increased from 22.1% to 28.7% and 24.5%, respectively. The addition of ADP and ALHP reduced the rebound resilience of the composites, but increased hardness of it. The flame retardants reduced the tensile strength, elongation at break, and tear strength of the composites. Both flame retardants had an adverse effect on the abrasion resistance, with the abrasion loss of the composites increasing by 100% and 85% at 45 phr of ADP and ALHP, respectively. When graphene is used as a carbonization agent for ADP-containing composites, it can improve the flame retardancy without affecting the abrasion resistance. ADP and ALHP have different degrees of influence on the properties of NR/BR composites. Due to the high carbon content of ADP and volatilization by heat, the flame retardancy of NR/BR composites is greatly improved. But the tensile strength and abrasion resistance of the composites are lower than that of the ALHP-containing composites.

Along with the long preparation cycle time and high cost of conventional preparation methods, the inherent high thermal conductivity of TiCoSb Half-Heusler alloy limited its commercial application. Herein, Ti_1-xNb_xCoSb Half-Heusler alloys with low thermal conductivity were successfully prepared by microwave synthesis combined with rapid hot-pressing sintering, which substantially shortened the preparation cycle and increased the density of TiCoSb Half-Heusler alloys. Furthermore, we studied the effects of Nb substitution at Ti sites on the phase composition, composition distribution, and thermoelectric transport properties of Ti_1-xNb_x CoSb Half-Heusler thermoelectric materials. Additionally, the figure of merit(ZT) of Ti_1-xNb_x CoSb samples were considerably optimized under the combined effects of increasing power factor and decreasing lattice thermal conductivity. The results showed that the Ti_0.93Nb_0.07CoSb sample had a maximum ZT of 0.1 at 725 K, which was two orders of magnitude higher than that of the TiCoSb sample prepared by the same process.

In this paper, graphene prepared by liquid-phase stripping assisted by tannic acid achieved better dispersion than ordinary graphene. The new graphene can meet the requirements of low cost, high output, and environmental protection. Graphene-SiO₂ hybrid materials were obtained by reacting SiO₂ treated with silane coupling agent (KH550) modification and graphene modified with tannic acid to form strong hybridization bonds, and the success of obtaining graphene-SiO₂ hybrid materials was confirmed by infrared spectroscopy. Furthermore, the mechanical properties of graphene-SiO₂ hybrid material in styrene-butadiene/polybutadiene composites were studied. In addition, the mechanical properties and the electrical and thermal conductivity of the blend of conductive carbon black and graphene-SiO₂ hybrid material in styrene-butadiene/polybutadiene composite were investigated. The results show that: at the addition of 1 part per hundred(phr) of graphene-SiO₂ hybrid material, the butadiene/cis rubber composites obtained relatively good wear resistance, if the loading is more than 1 phr, the graphene fillers will easily reaggregate with each other, resulting in an increase in wear volume compared with the blank control group. Moreover, when 8 phrs of self-made graphene were added, the conductivity increased by 1 000 times, and the antistatic properties of rubber composites were considerably improved.

Silica (mainly comprising nano-SiO₂) is widely used in rubber reinforcement owing to its advantages of easy preparation and environmental protection. However, owing to its structural characteristics, silica has poorer dispersion and reinforcement ability than carbon black. The purpose of this paper is to present a proposal to improve the dispersion of silica in rubber using a silane coupling agent and to study the effect of synergistic reinforcement of modified silica and graphene on natural rubber. The hybrid filler KS-TGE was obtained through a Michael addition reaction between graphene modified by dispersant tannic acid and silica (KS) modified by the silane coupling agent KH570. Subsequently, the KS-TGE/NR composites were prepared by mixing KS-TGE with natural rubber. Test results showed that the modified silica improves the dispersion in rubber and the mechanical properties of natural rubber after blending with the hybrid filler prepared using graphene and natural rubber. Compared with unmodified nano-SiO₂/NR, the tensile strength of the modified composites increased by 36.3% and the elongation at break increased by 79.5%. In addition, KS-TGE/NR can maintain excellent elastic and dynamic mechanical properties.

In this paper, the preparation process of N-propylethylenediamine bonded silica gel (PSA) with controllable bonding amount was optimized; the batch repeatability of PSA preparation was examined; and the pilot scale-up experiment of PSA preparation was conducted. The properties of the PSA were investigated by infrared spectroscopy, elemental analysis, and potentiometric titration. The results showed that N—H stretching vibration peaks appeared at 3 460 cm^-1, asymmetric and symmetric stretching vibration peaks of —CH appeared at 2 960 cm^-1 and 2 860 cm^-1, and deformation vibration absorption peaks of —NH₂ appeared at 708 cm^-1, indicating that N-propylethylenediamine was successfully grafted onto the surface of silica gel.Furthermore, with the increasing proportion of silane reagent in the preparation system, the content of carbon, nitrogen, and hydrogen elements and the ion exchange capacity obtained by potentiometric titration showed an upward trend, indicating that the bonding amount of ethylenediamine-N-propyl functional group gradually increased. Moreover, the prepared PSA packing component was separated from the purification column, and the removal efficiency of ginkgolic acid from the extract of ginkgo biloba leaves using PSA with different bonding amounts was investigated. The results showed that PSA had a strong adsorption capacity for ginkgolic acid and could be used to remove ginkgolic acid from the extract of ginkgo biloba leaves, the maximum sample loading volumes for PSA separation and purification columns 2^#, 3^#, 4^#, and 5^# are 21, 22, 23, 24 mL, respectively. In addition, the removal efficiency was found to increase with the increasing amount of ethylenediamine-N-propyl bonding.

Polyvinyl chloride (PVC) foam board is prepared by extrusion foaming of PVC with low polymerization degree, and the PVC foam board is prone to curling movement along the force direction of the molecular chain due to environmental changes, resulting in shrinkage and deformation of the board. Heavy calcium carbonate (HCC) was used as raw material, polyvinyl alcohol (PVA) and tannic acid (TA) were used as modifiers to prepare modified HCC. It was combined with PVC to prepare PVC foam sheets. Infrared spectrometer, differential scanning calorimeter, scanning electron microscope, Vicat softening point tester and universal electronic stretching machine were used to characterize the foamed board, and the effect of modifier dosage on the dimensional stability of the foamed board was discussed. The results show that when the TA content is 3% of HCC, the glass transition temperature of PVC foam board is 88.1 ℃, the temperature of Vicat softening point is 75.21 ℃, and the PVC foam board has excellent dimensional stability, and the cell structure is stable and uniform, and has the best tensile strength of 6.17 MPa. Modified HCC particles have good dispersion, strong binding ability with PVC, and high dimensional stability of PVC foam board can replace the use of wood in home decoration boards, which is of great significance to protect the environment.

A lightweight and cooling woven fabric for summer was developed by selecting and combining different cooling fibers. Twelve samples were produced by selecting polyester/mint blended yarn as warp yarn, nylon fiber as weft yarn and plain, and twill and satin as fabric weave to investigate the impact of different weft yarns and fabric structures on the thermal and moisture comfort properties of the fabrics. The results showed that twill and satin fabrics had better thermal and moisture transfer performance; plain weave fabrics provided a good cooling sensation upon contact; cool nylon indeed enhanced the cooling of the fabric, but it showed poor moisture transfer performance in tightly woven structures. Micro-denier nylon had similar thermal and moisture transfer performance to cool-feel nylon but had lower air permeability and cross-sectional nylon had better moisture transfer performance but lower thermal conductivity.

The energy conversion efficiency of CH₃NH₃PbI₃ (MAPPbI₃) perovskite solar cells is closely related to the quality of the perovskite film. To obtain high quality perovskite films, the film preparation method and process were optimized. It was found that the green solvents, propylene glycol methyl ether acetate and glycerol, can promote nucleation of PbI₂ particles, provide heterogeneous nucleation sites for CH₃NH₃PbI₃ perovskite crystals, and thus facilitate the rapid growth of perovskite crystals. Compared to perovskite films treated with the common toxic solvent chlorobenzene, films treated with propylene glycol methyl ether acetate and glycerol have larger grain size, lower root-mean-square value, and greater surface roughness optimization. This can result in a uniform, full-coverage perovskite film that is close to the perovskite carrier diffusion length. The performance of devices under different treatment conditions was tested and it was found that compared to CH₃NH₃PbI₃ perovskite solar cells treated with chlorobenzene (energy conversion efficiency of 17.86%), the device treated with green solvent glycerol had the highest efficiency of 21.60%, which is an increase of nearly 21%. These experimental results have some reference value and guiding significance for researchers in this field to obtain environmentally friendly high-quality perovskite type solar cells in the future.

Inclusions have an impact on the fatigue strength and fatigue life of steel, but inclusions in large samples cannot be accurately imaged using X-ray micro computer tomo-graphy(X-ray micro-CT). This study provides a novel approach to obtain the three-dimensional morphology of inclusions in large steel samples. To realize the three-dimensional features of inclusions in large alloy samples, this study used a nonaqueous electrolysis method to obtain inclusions; then scanning electron microscopy was performed to observe and analyze the electrolyzed inclusions.Furthermore, the electrolyzed inclusions were aggregated into cylindrical samples and finally scanned with X-ray micro-CT to obtain their three-dimensional information, and the obtained dimensional data of the inclusions were statistically analyzed.

The Exfresh fiber is a new type of modified acrylic fiber with fine denier and antibacterial properties; it is fabricated by adding an antibacterial agent to the spinning stock solution. The surface morphologies, mechanical properties, moisture absorption properties, specific resistance, friction properties, and curling properties of the Exfresh and ordinary acrylic fibers were tested and compared in this study. The elemental composition and chemical bonds of the two fibers were analyzed via X-ray photoelectron spectroscopy (XPS). Furthermore, the moisture-absorbing quick-drying and moisture-absorbing heat-generating properties of the Exfresh blended fabrics were tested. Results showed that the Exfresh fiber featured a circular cross-section, rough longitudinal surface and dense grooves as well as a low linear density, excellent mechanical properties, and high spinnability. Additionally, it has a lower specific resistance and higher friction coefficient than the ordinary acrylic fiber, thereby making it difficult to produce static electricity. Results of the XPS analysis showed that the added antibacterial agent was a quaternary ammonium salt. Additionally, the evaporation rate of an Exfresh fiber-blended fabric is bigger than 0.18 g/h, and its maximum moisture-absorbing heat-generating temperature rise is bigger than 4 ℃. Moreover, it exhibits excellent moisture-absorbing quick-drying and moisture-absorbing heat-generating properties, and can be used to develop multifunctional fabrics.

EKS fiber is a subacrylate fiber with significant hygroscopic-heating properties. In this study, the surface morphologies of EKS and acrylic fibers were compared, and their mechanical properties, friction properties, specific resistance, curling properties, moisture absorption and liberation properties, and hygroscopic-heating properties were tested and analyzed. The results showed that compared with the acrylic fiber, the EKS fiber featured a circular cross section and rough longitudinal structure as well as low breaking strength, friction coefficient, specific resistance and curl rate; moreover, it featured a high linear density, elongation at break, and moisture recovery rate. With the initial absorption rate and liberation rate being 0.39% min^-1 and 8.94% min^-1, respectively, the moisture absorption and liberation rates of the EKS fiber decreased exponentially with time, and the time required to achieve the absorption and liberation balance was longer than that for the acrylic fiber. The EKS fiber exhibited good hygroscopic-heating properties with a maximum hygroscopic-heating value of 8.2 ℃, which was 4.7 ℃ higher than that for the acrylic fiber.

Because TiAl alloys are susceptible to fatigue cracking on their surfaces due to cyclic loading when used at high temperatures, it is necessary to treat their surfaces to improve their mechanical properties. In this study, TiAl alloy was subjected to shot peening tests at room temperature, using 0.2 mm diameter steel shots at 0.7 MPa air pressure. The shot peening simulation studies were conducted using ABAQUS finite element analysis software. Subsequently, the shot-peened specimens were heat treated at different temperatures and holding times. The cross-sectional microstructures of the specimens were observed using a scanning electron microscope (SEM), the residual compressive stresses on the surfaces were measured using an X-ray residual stress meter, and the surface microhardness after heat treatment was measured using a microhardness meter. The results showed that many pits and lamellar protrusions appeared on the surface of TiAl alloy after shot peening, and obvious plastic deformations and numerous deformation twins appeared at the secondary surface. The residual compressive stress on the surface of the TiAl alloy after heat treatment decreased as the holding time and heat treatment temperature increased. Hardness followed a similar trend as the residual stress; however, when the heat treatment temperature was raised to 1 200 ℃, the hardness increased due to the change of metallographic organization and a significant increase inα₂ phase content.

Several high-strength fastening bolts were found broken on a railway steel bridge. Failure analysis of these bolts was performed to determine why they fractured and to prevent future bolt fractures. The fracture morphology, microarea-chemical analysis of the fracture, microstructure and hardness of the bolts, compositional contents, and mechanical properties of the bolt steel were analyzed by using scanning electron microscopy, energy dispersive X-ray spectrometry, optical microscopy, a Rockwell hardness tester, X-ray fluorescence spectrometry, and an electronic universal testing machine, respectively. The results indicate that the compositional contents, hardness, and mechanical properties are consistent with the 20MnTiB steel standard. In addition, dendritic cracks can be observed in the fracture initiation zones of the fastening bolts and the corrosion products in the cracks contain sulfur.The fastening bolts are subjected to cyclic loads in normal working conditions. Therefore, fractures of the fastening bolts were caused by corrosion fatigue fractures under cyclic loads. The cracks initiated at the root of the screw thread or the connecting point between the stud and nut, which are particularly vulnerable to stress corrosion cracks caused by the presence of sulfur.

The effects of four solid-solution treatments on the microstructure and properties of Al-5.6Cu-1.7Mg-0.2Zr-0.1Sr-0.6Ti alloy were studied herein by metallographic structure analysis,SEM(Scanning Electron Microscope) analysis、X-Ray Diffraction,hardness,conductivity,room temperature tensile properties, elongation after fracture and intergranular corrosion resistance. The results show that the grain size increases and with an increase in the solution temperature. The size and quantity of insoluble phase in the alloy decrease with increasing solution temperature when the temperature is less than 520 ℃. When the solid treatment is 510 ℃ for 2 h and then at 520 ℃ for 2 h, the insoluble phase in the alloy begins to increase, and the alloy appears slight overburning, the elongation after fracture and intergranular corrosion resistance become worse, but the tensile strength reaches the highest as 490.14 MPa. The dislocation strength and dislocation contribution decrease with an increase in the solution temperature. The strength effect in the alloy is mainly attributed to the solution strengthening and aging precipitation strengthening.Two different solid-solution treatments (route a:490 ℃ for 2 h and then at 500 ℃ for 2 h; route b: 500 ℃ for 2 h and then at 510 ℃ for 2 h) both can guarantee the mechanical properties(strength and elongation) and intergranular corrosion resistance of the alloy under T6 aging are good; therefore,both of the solid-solution treatments are suitable for preparing Al-5.6Cu-1.7Mg-0.2Zr-0.1Sr-0.6Ti alloy.

Owing to the low visible-light utilization of traditional photocatalysts and the serious problem of photogenerated electron-hole recombination at the bulk/interface, two-dimensional Bi₂WO₆ nanosheets were prepared herein using the hydrothermal method. Based on the principle of energy-level matching, Cu₂S was grown on the surface of the two-dimensional Bi₂WO₆ nanosheets using the hydrothermal method to construct Bi₂WO₆-Cu₂S heterojunctions for improved light absorption. Based on the excellent piezoelectric properties of the nanosheets and the excellent optical absorption and carrier transport properties of the Bi₂WO₆-Cu₂S heterojunctions, a piezo-photoelectric synergistic catalytic system was constructed and the optimal degradation experimental conditions were explored. The Bi₂WO₆-Cu₂S material was successfully applied for the degradation of Rhodamine B(RhB) in water. The results showed that under the synergistic photoelectric-piezoelectric effect, the degradation rate of RhB by the designed Bi₂WO₆-Cu₂S reached 87% in 40 min. This study provides a new way for designing unique heterojunction structures via the synergistic action of photocatalysis and piezoelectric catalysis.

The working surface of a camshaft is easily worn during service, thus seriously affecting the normal operation of the machine. The pitting areas on the working surface of the camshaft were repaired using cold-welding equipment. A metallographic microscope was used to observe the microstructure of the repaired area, and the residual stress distribution and hardness distribution around the repaired areas were determined using an X-ray residual stress tester and a hardness tester, respectively. The results show that the repair welding spot is well combined with the matrix, the carbides precipitated from austenite are dispersed in the matrix structure, the position of the repair welding spot presents the minimum residual stress and the minimum hardness value, and the influence of the repair welding spot on the residual stress and hardness is maintained within around 4 mm of the repaired areas. The camshaft repaired via cold welding meets the service performance requirements.

Polyimide (PI), a type of high temperature-resistant polymer synthesized using dianhydride or diamine, has become one of the most industrialized polymer materials with the highest operating temperature owing to its strong high-temperature resistance property. However, the strength of PI films still needs to be improved for their industrial application. To improve the elongation rate and tensile strength of PI films, different methods, such as adjusting the concentration, ratio, addition method of precursors and the addition amount of biomass fibers, have been tested in our experiments.4,4-Diaminodiphenyl ether and 3,3,4,4-biphenyltetracarboxylic acid dianhydride were used as the precursors for the reaction. Polyamide acid was prepared using the positive addition method in the presence of a cross linker, which was then poured into a Petri dish containing uniform lotus root fiber. The PI film was obtained by calcination. The results showed that the final gage length and elastic modulus of the PI films containing lotus root fiber were lower than those of the pure PI film. Furthermore, PI-2% root-fiber film had a tensile elongation at break of 6.49%, a tensile strength of 67.33 MPa, and a maximum force tolerance.of 57.47 N, which are much higher than those of pure PI film. Thus, the addition of lotus root fiber enhances the mechanical properties of the film.

Herein, we are using polyamide 66 fiber to develop high performance and high quality denim fabric. Using viscose as the outer fiber, polyamide 66 or spandex as the core yarn to make 36.4 and 28.0 tex core-spun yarn as the weft yarn, pure cotton yarn of 36.4 and 28.0 tex as the warp yarn, a rapier loom is used to interweave to make the denim fabric. The strength, wear resistance, elastic recovery, crease recovery, and bending properties of denim fabrics woven from 6 kinds of fabrics waved by polyamide 66 core-spun yarns and spandex core-spun yarns were tested. Through comparative analysis, it is found that the elasticity of polyamide 66 core-spun denim is as good as that of spandex core-spun denim, while its strength and softness are better. Viscose/polyamide 66 (3.33 tex/10 F) core-spun fabric is stronger, more resilient, and softer than viscose/polyamide 66 (3.33 tex/34 F) fabric. Meanwhile, fabrics woven with 36.4 tex yarn have better strength, elasticity, and crease recovery, while fabrics woven with 28.0 tex yarn are softer.

Humidity is a significant environmental parameter in storage, civil explosives business, and other fields. The performance of humidity-sensitive materials directly determines the quality of sensors. Polyimide and polyvinyl alcohol, the most commonly used humidity-sensing materials in optical fiber humidity sensors, were selected as the research objects. The humidity sensors were fabricated by coating two different humidity-sensitive materials on the surface of the fiber Bragg grating and their sensitivity, response time, and long-term stability were tested and compared. Results show that the linearity of the humidity sensor coated with polyimide is 99.98%, the sensitivity is 5.4 pm/%, the response time is 9.7 min, and the maximum wavelength shift is 5.6 pm. The humidity sensor coated with polyvinyl alcohol has a higher sensitivity in the range of relative humidity 60%~90%, which makes polyvinyl alcohol-based humidity sensors more suitable for humidity measurement in high-humidity environments.

The poor mechanical properties of hydrogel electrolytes and the freezing of water at low temperatures affect their ionic conductivity, thereby hindering their application in energy storage devices and electronic conductors. In this study, a type of antifreezing organic hydrogel with high mechanical properties and conductivity is fabricated. The electrolyte was synthesized via free-radical polymerization by adding soy protein isolates and using acrylamide and methacrylic ethyl sulfobetaine as monomers in a mixed solution of dimethyl sulfoxide/H₂O in the presence of lithium chloride. The fabricated hydrogel electrolyte exhibits good ionic conductivity (maximum 37.5 mS/cm), good mechanical properties (maximum stress 69 kPa and maximum strain 762.5%), and high toughness and fatigue resistance. Furthermore, the fabricated electrolyte shows a good response under varying strain and temperature conditions with a wide sensing window and good stability. Additionally, supercapacitors based on this electrolyte show good electrochemical performance between 20 ℃ and -20 ℃. In other words, at 20 ℃, the capacitances of the supercapacitor are 62.1 and 30 F/g at current densities of 0.2 and 5 A/g respectively, while at -20 ℃, the capacitance can maintain 59% of the value obtained at 20 ℃. Moreover, the supercapacitor can maintain 92% of the capacitance after 10 000 cycles, showing good cyclic stability.

In this study,the effects of different Sn contents on the microstructures and mechanical properties of Mg-5Zn-2.5Al-xSn(x=0, 1, 2, 3, 4) (ZAT52x) alloys were investigated. Curves of the mass fraction of liquid versus temperature during solidification of Mg-5Zn-2.5Al-xSn (x=0, 2, 4) (ZAT52x) were calculated using the Thermo-Calc software. It is found that α-Mg, Mg₂Sn (not precipitated when x=0), φ-Mg₂₁(Zn,Al)₁₇, τ-Mg₃₂(Zn,Al)₄₉, and MgZn precipitate in sequence during the solidification of ZAT52x magnesium alloy. As the Sn addition increases, the melting point of the ZAT52x alloy decreases and the amount of the second phases increases, and the tensile strength and elongation of the as-cast ZAT52x increased at first and then decreased. The as-cast ZAT522 alloy exhibits the best mechanical properties with tensile strength of 245.9 MPa and elongation of 14.4%. After extrusion, the ZAT522 alloy exhibits the highest tensile strength (376.2 MPa) and elongation (20.8%), while the ZAT524 alloy shows a more balanced mechanical property with tensile strength, yield strength, and elongation of 363.7 MPa, 260.4 MPa, and 17.9%, respectively.

To determine the degradation pattern of pore structures during concrete damage under different sulfate mass fraction, the freeze-thaw cycle test of concrete under different sulfate mass fraction is performed herein. Using nuclear magnetic resonance technology, the change in porosity during concrete damage is analyzed, in addition to the mass loss and relative dynamic elastic modulus change. The results show that the first peak of T₂ spectrum changes significantly under different sulfate mass fraction. In the same period of the freeze-thaw cycle, the change range of the T₂ spectrum first peak increases with increase in the sulfate mass fraction. An exponential relation exists between the first peak area of T₂ spectrum and the number of freeze-thaw cycles in the salt-freezing environment, and a linear relation exists in the water-freezing environment. There is a linear relation between the development of microporosity and the number of freeze-thaw cycles. There is a significant linear relationship between the porosity and the number of freeze-thaw cycles and sulfate mass fraction. The mass loss and the relative dynamic elastic modulus loss in the salt-freezing environment increase with increase in the sulfate mass fraction.

Herein, a novel type of high efficiency porcelain-aluminum composite solar plate (PACP) was developed, which comprised aluminum alloy matrix plates, flow guide collecting tubes and nanostructure endothermic coatings. The aluminum alloy matrix plate was an integrated structure of circulating pipes and curved fin plates and manufactured through a one-step extrusion process using corrosion-resistant 6063 aluminum alloy. The inner walls of the circulating pipes and diversion collecting pipes were protected by spraying superhydrophobic coating layers. The nanoblack porcelain composite powder was synthesized using black porcelain powders, matting agents, and resin binders. The nanostructure endothermic coating was prepared via electrostatic spraying and a high-temperature curing process. The solar absorptance was up to 0.96. The experimental results showed that the nanostructure endothermic coatings exhibited good thermal stability and would not peel off under long-term adverse environmental conditions. The porcelain-aluminum composite solar plates with an integrated structure exhibited excellent thermal conductivity, and the thermal conductivity efficiency was as high as 0.98. The thermal efficiency of the proposed porcelain-aluminum composite solar collector was approximately 43.6%, which was higher than that of traditional solar collectors, and the manufacturing cost was approximately 14% lower than that of traditional solar collectors. The proposed porcelain-aluminum composite solar collectors have advantages in terms of cost, life, and efficiency and can be used to build large-area solar collector systems to meet current development requirements of the solar energy industry. It has good economic and social benefits and broad application prospects.

The optimal heat-treatment parameters for the high-chromium cast iron blades of shot blasting machine were researched on the basis of the orthogonal experimental design. With the addition of trace elements, vanadium and nano-sized WC/TiC particles, the wear resistance of high-chromium (Cr) cast-iron casting was improved, thus extending its service life. The results indicated that the blades′ hardness was 60 HRC and its best wear resistance was obtained at a quenching soaking time of 3 h while temping at 450 ℃ for 2 h. By adding the trace elements, vanadium and nano-sized WC/TiC particles, the microstructure of the blade was refined, the carbide morphology was changed, and the wear resistence improved by 30%. Results showed that the wear resistance of high-Cr blades can be increased by optimizing the heat-treatment process and the blades′ composition, thereby proving the comprehensive benefit of this study in industrial applications.

In this study, the original vibration signals of an Svenska Kullager-Fabriken (SKF) bearing's inner race, rolling element, and outer race with three fault sizes were extracted from Case Western Reserve University Bearing Data Center. The fault sizes were 0.007, 0.014, and 0.021 in(1 in=2.54 cm). By empirical mode decomposition (EMD), 17 intrinsic mode functions were found. Principal component analysis (PCA) was then conducted, and it was found that the relationship between the fault sizes of the inner and outer races and the first and second principal components could be accurately fitted by principal component fitting formulas. Therefore, the fault sizes can be obtained by real-time monitoring of vibration signals and signal analysis. Finally, the residual life of the bearing with a fault was predicted using the Paris-Erdogan formula and finite element simulation. This study has a significant meaning for prevention of equipment accidents caused by bearing cracks.

In this study, an electromagnetically induced transparent metamaterial structure with four metal lines and a ring is proposed. It exhibits the characteristics of horizontal and vertical polarization insensitivity when the electromagnetic wave is perpendicular to its surface. The characteristics of the metamaterial transmission curve and its surface current distribution have been numerically calculated and simulated. Further, the phase propagation curve and group refractive index are calculated and analyzed. The maximum group refractive index can reach up to 380, indicating that the metamaterial can be used to fabricate slow optical devices. When this metamaterial is used to manufacture a refractive index sensor, the D_FOM value is approximately 20.13, indicating a higher sensitivity compared with those of the existing sensors. Results show that the metamaterial can be applied to manufacture slow optical devices and refractive index sensors.

The optimization and calculation of the phase diagram of a Ti-Nb-Zr ternary system were presented using Pandat software. The Gibbs energy of the pure component was described using the expression provided in the scientific group thermodata Europe database. The substitutional solution and two-sublattice models were used to describe the Gibbs energy of the liquid and solid solution phases, respectively. To improve the description of the Ti-Nb-Zr ternary system, the thermodynamic parameters of the Ti-Nb and Ti-Zr systems were obtained using the PanOptimizer module of Pandat software by considering experimental data on phase equilibrium and published thermodynamic properties. The calculations of the phase equilibrium and thermodynamic properties using the proposed description agreed well with the experimental data. The results have important directive significance to the development of Ti-Nb-Zr ternary system biomedical materials.