We adopted the solution impregnation route with aluminum dihydrogen phosphate solution as liquid medium for effective surface modification on graphite substrate. The mass ratio of graphite to Al(H₂PO₄)₃ changed from 0.5:1 to 4:1, and the impregnation time changed from 1 to 7 h. The typical composite phase change thermal storage materials doped with the as-treated graphite were fabricated using form-stable technique. To investigate the oxidation and anti-oxidation behavior of the impregnated graphite at high temperatures, the samples were put into a muffle furnace for a cyclic heat test. Based on SEM, EDS, DSC techniques, analyses on the impregnated technique suggested an optimized processing conditions of a 3 h impregnation time with the ratio of graphite: Al(H₂PO₄)₃ as 1:3 for graphite impregnation treatment. Further investigations on high-temperature phase change heat storage materials doped by the treated graphite suggested excellent oxidation resistance and thermal cycling performance.

The low-melting glass of Bi₂O₃-B₂O₃-SiO₂ (BiBSi) system was used for the first time for laser sealing of vacuum glazing. Under the condition of constant boron content, how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated. In addition, the relationships between laser power, low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed. The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass, leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion. During laser sealing, the copper ions in the low-melting glass play an endothermic role. A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass. The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio, but shows a linear correlation with the content of divalent copper ions. The greater the concentration of divalent copper ions, the greater the absorbance of the low-melting glass, and the lower the laser power required for laser sealing. The shear strength of the low melting glass solder after laser sealing was tested, and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.

To analyze the impact of bubbles on the mechanical behavior of glasses, by controlling the refining time, we prepared three borosilicate glasses with the same composition and different porosity. By the analysis software integrated within the optical microscope, the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified. From the hardness and crack initiation resistance (C _R), we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.

To improve the catalytic performance of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) towards carbon soot, we utilized the impregnation method to incorporate Ag into the prepared LSCF catalyst. We conducted a series of characterization tests and evaluated the soot catalytic activity of the composite catalyst by comparing it with the LaCoO₃ group, LaFeO₃ group, and catalyst-free group. The results indicate that the Ag-LSCF composite catalyst exhibits the highest soot catalytic activity, with the characteristic temperature values of 376.3, 431.1, and 473.9 °C at 10 %, 50 %, and 90 % carbon soot conversion, respectively. These values are 24.8, 20.2, and 23.1 °C lower than those of the LSCF group. This also shows that LSCF can improve the catalytic activity of soot after compounding with Ag, and reflects the necessity of using catalysts in soot combustion reaction. XPS characterization and BET test show that Ag-LSCF has more abundant surface-adsorbed oxygen species, larger specific surface area and pore volume than LSCF, which also proves that Ag-LSCF has higher soot catalytic activity.

CuO nanoparticles were successfully synthesized via a two-jet electrospun method, and then screen-printed on silver-carbon electrodes, forming CuO-modified Ag-C (CuO/Ag-C) disposable strip electrodes. In natural environment condition for glucose detection, the obtained CuO/Ag-C electrodes show a high sensitivity of 540 nA·mM⁻¹·cm⁻², and a low limit of detection (0.68 mM) in a wide linear response range of 0.68 mM and 3 mM (signal/noise = 3), respectively. In addition, the CuO/Ag-C electrodes also exhibit excellent anti-interference, air stability and repeatability. As a result, the fabrication of CuO nanoparticles via an electrospun process and the technique of screen-printed electrodes are of great significance for glucose detection.

Cu-Mn co-doped CeO₂ photocatalyst was successfully synthesized by the sol-gel method to assess its capability in degrading tetracycline. XRD and TEM results showed that Cu and Mn were successfully co-doped into CeO₂ without forming heterostructure, XPS and photoelectrochemical results revealed that Mn ions doping amplified the generation of photo-induced charge carriers, while Cu ions doping significantly facilitated the interfacial charge transfer process. Notably, the optimized Cu₃Mn₂CeO₂ nanoparticles exhibited the highest TC removal efficiency, achieved a rate of 78.18% and maintained a stable cycling performance.

This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate (C₃S). The method combines the hydration simulation, thermodynamic calculation, and finite element analysis to examine the effects of pore solution, including effect of electrochemical potential, effect of chemical activity, and effect of mechanical interactions between ions, on the chloride effective diffusion coefficient of hydrated C₃S paste. The results indicate that the effect of electrochemical potential on chloride diffusion becomes stronger with increasing hydration age due to the increase in the content of hydrated calcium silicate; as the hydration age increases, the effect of chemical activity on chloride diffusion weakens when the number of diffusible elements decreases; the effect of mechanical interactions between ions on chloride diffusion decreases with the increase of hydration age.

In order to study the characteristics of pure fly ash-based geopolymer concrete (PFGC) conveniently, we used a machine learning method that can quantify the perception of characteristics to predict its compressive strength. In this study, 505 groups of data were collected, and a new database of compressive strength of PFGC was constructed. In order to establish an accurate prediction model of compressive strength, five different types of machine learning networks were used for comparative analysis. The five machine learning models all showed good compressive strength prediction performance on PFGC. Among them, R ², MSE, RMSE and MAE of decision tree model (DT) are 0.99, 1.58, 1.25, and 0.25, respectively. While R ², MSE, RMSE and MAE of random forest model (RF) are 0.97, 5.17, 2.27 and 1.38, respectively. The two models have high prediction accuracy and outstanding generalization ability. In order to enhance the interpretability of model decision-making, we used importance ranking to obtain the perception of machine learning model to 13 variables. These 13 variables include chemical composition of fly ash (SiO₂/Al₂O₃, Si/Al), the ratio of alkaline liquid to the binder, curing temperature, curing durations inside oven, fly ash dosage, fine aggregate dosage, coarse aggregate dosage, extra water dosage and sodium hydroxide dosage. Curing temperature, specimen ages and curing durations inside oven have the greatest influence on the prediction results, indicating that curing conditions have more prominent influence on the compressive strength of PFGC than ordinary Portland cement concrete. The importance of curing conditions of PFGC even exceeds that of the concrete mix proportion, due to the low reactivity of pure fly ash.

The available test methods for optimal moisture content of cold recycled mixture (CRM) as well as its bulk specific gravity, and theoretical maximum relative density were analyzed in this work. Some test improvements were suggested to improve test control of the CRM road performance based on the discovered flaws. Besides, the properties of reclaimed asphalt pavement (RAP), including the content of old asphalt, penetration index, passing rate of 4.75 mm sieve, and gradation change rate after extraction, were examined. The effects of RAP characteristics on splitting tensile strength, water stability, the high- and low-temperature performance of emulsified asphalt CRM were studied. The results show that the optimum moisture content of CRM should be determined when the compaction work matches the specimen’s molding work. Among the analyzed methods of bulk specific gravity assessment, the dry-surface and CoreLok methods provide more robust and accurate results than the wax-sealing method, while the dry-surface method is the most cost-efficient. The modified theoretical maximum relative density test method is proposed, which can reduce the systematic error of the vacuum test method. The following RAP-CRM trends can be observed. The lower the content of old asphalt and the smaller the change rate of gradation, the smaller the voids and the better the water stability of CRM. The greater the penetration of old asphalt, the higher the fracture work and low-temperature splitting strength. The greater the penetration, the higher the passing rate of 4.75 mm sieve after extraction, and the worse the high-temperature performance of CRM.

This study aimed to address the challenges of solid waste utilization, cost reduction, and carbon reduction in the treatment of deep-dredged soil at Xuwei Port in Lianyungang city of China. Past research in this area was limited. Therefore, a curing agent made from powdered shells was used to solidify the dredged soil in situ. We employed laboratory orthogonal tests to investigate the physical and mechanical properties of the powdered shell-based curing agent. Data was collected by conducting experiments to assess the role of powdered shells in the curing process and to determine the optimal ratios of powdered shells to solidified soil for different purposes. The development of strength in solidified soil was studied in both seawater and pure water conditions. The study revealed that the strength of the solidified soil was influenced by the substitution rate of powdered shells and their interaction with cement. Higher cement content had a positive effect on strength. For high-strength solidified soil, the recommended ratio of wet soil: cement: lime: powdered shells were 100:16:4:4, while for low-strength solidified soil, the recommended ratio was 100:5.4:2.4:0.6. Seawater, under appropriate conditions, improved short-term strength by promoting the formation of expansive ettringite minerals that contributed to cementation and precipitation. These findings suggest that the combination of cement and powdered shells is synergistic, positively affecting the strength of solidified soil. The recommended ratios provide practical guidance for achieving desired strength levels while considering factors such as cost and carbon emissions. The role of seawater in enhancing short-term strength through crystal formation is noteworthy and can be advantageous for certain applications. In conclusion, this research demonstrates the potential of using a powdered shell-based curing agent for solidifying dredged soil in an environmentally friendly and cost-effective manner. The recommended ratios for different strength requirements offer valuable insights for practical applications in the field of soil treatment, contributing to sustainable and efficient solutions for soil management.

The pre-wetting of aggregate surface is a means to improve the interface performance of SBS modified asphalt and aggregate. The effect of pre-wetting technology on the interaction between SBS modified asphalt and aggregate was analyzed by molecular dynamics simulation. The diffusion coefficient and concentration distribution of SBS modified asphalt on aggregate surface are included. The simulation results show that the diffusion coefficient of the aggregate surface of SBS modified asphalt is increased by 47.6% and 70.5% respectively after 110# asphalt and 130# asphalt are pre-wetted. The concentration distribution of SBS modified asphalt on the aggregate surface after pre-wetting is more uniform. According to the results of interface energy calculation, the interface energy of SBS modified bitumen and aggregate can be increased by about 5% after pre-wetting. According to the results of molecular dynamics simulation, the pre-wetting technology can effectively improve the interface workability of SBS modified bitumen and aggregate, so as to improve the interface performance.

The chloride penetration resistance of cement-based grout materials was improved by nano-silica emulsion. Specimens of mixtures containing different nano-silica particles or emulsions were exposed in sodium chloride solutions of specific concentrations with different test ages. Hardened properties of the mixes were assessed in terms of weight loss and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) of mixes were performed to analysis the phase evolution and microstructure. The results demonstrated that the introduction of nano-SiO₂ emulsion significantly decreased the compressive strength loss and calcium hydroxide (CH) crystal content of hydration production, and then enhanced the resistance of cement-based grouting materials to chloride ion penetration. This improvement derives from the filling and pozzolanic effects of nano-SiO₂ particles, which were incorporated via an emulsion and attributed to a well dispersion in grouting matrix.

The effects of liquid-solid ratio and reaction time on the leaching rate of magnesium at room temperature were investigated, as well as the effects of the molar ratio of MgO/MgCl₂, the amount of water added, and the amount of acid-impregnated slag dosed on the compressive strength and water resistance of LR-MOC. The results showed that the magnesium element in the boron mud could be maximally leached under the conditions of 1:1 concentration of hydrochloric acid at room temperature, liquid-solid ratio of 2.5 mL·g⁻¹, and reaction time of 5 h, and the main products were amorphous SiO₂ as well as a small amount of magnesium olivine which had not been completely reacted. The LR-MOC prepared using the acid-soaked mixture could reach a softening coefficient of 0.85 for 28 d of water immersion when the molar ratio of MgO/MgCl₂ was 2.2, the amount of water added was 0 g, and the acid-soaked slag dosing was 40 wt%, which also led to an appreciable late-strength, with an increase of 19.4% in compressive strength at 28 d compared to that at 7 d. Unlike previous studies, LR-MOC prepared in this way has a final strength phase that is not the more easily hydrolysed 3-phase but the lath-like 5-phase. For this phenomenon, we analyzed the mechanism and found that, during the acid leaching process, a part of amorphous SiO₂ dissolved in the acid leaching solution formed a silica sol, in which Mg²⁺ played a bridging role to make the silica sol more stable. With the addition and hydrolysis of MgO, the silica sol gel coagulation slows down, providing a capping layer to inhibit the hydrolysis of the 5-phase crystals and providing some strength after coagulation. The amorphous SiO₂ in the other part of the acid-impregnated slag generated M-S-H gel with Mg²⁺ and OH⁻, which synergised with the dense structure composed of interlocking crystals to improve the water resistance of LR-MOC.

A ternary early-strengthening agent consisting of calcium formate + triethanolamine + lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength. The optimum ratio of the three early-strengthening agents was determined as 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate by response surface methodology. The effects of the ternary early-strengthening agent composed of calcium formate + triethanolamine(TEA)+ lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength, fluidity, and setting time, and the microstructural characterizations of X-ray powder diffractometer(XRD), thermogravimetry (TG-DSC) and scanning electron microscopy (SEM). The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multiperformance composite admixture for cementitious materials. The best performance was obtained with the compounding scheme of 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate ternary early-strengthening agent and 0.05% quercetin. The compressive strength of 1, 3, 7, and 28 d are 94.8%, 39.8%, 42%, and 28% higher than those of the blank group, respectively. The initial time and final setting time are 41 and 57 minutes, respectively. According to the microscopic analysis, the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin, which forms skeleton support while thickening and solidifying the cement slurry, which enhances the early compressive strength of the cement-based materials.

Carbon fibre, steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties. The electrically conductive cementitious materials with different volume dosages were analysed through compressive and flexural strength, electrochemical impedance spectroscopy and temperature rise tests. An equivalent circuit model was established to study the electrically conductive heat generation mechanism in the electrically conductive cementitious composites. The results indicate that the mechanical properties of cementitious composite materials with a ternary conductive phase are better than those of pristine cementitious materials because the fibrous filler improves their mechanical properties. However, the incorporation of graphite in the material reduces its strength. Introducing fibrous and point-like conductive phase materials into the cementitious material enhances the overall conductive pathway and considerably reduces the electrical resistance of the cementitious material, enhancing its conductive properties. The volume ratios of carbon fibre, steel fibre and graphite that achieve an optimal complex doping in the cementitious material were 0.35%, 0.6% and 6%, respectively. This was determined using the mutation point of each circuit element parameter as the percolation threshold. In addition, at a certain safety voltage, there is a uniform change between the internal and surface temperatures of the conductive cementitious material, and the heating effect in this materialis is considerably better than that in the pristine cementitious material.

Three types of activators such as sodium hydroxide, calcium oxide and triethanolamine (TEA) are used to establish different activation environments to address the problems associated with the process of activating fly ash paste. We conducted mechanical tests and numerical simulations to understand the evolution of microstructure, and used environmental scanning electron microscopy (ESEM) and energy dispersive spectroscopy (EDS) techniques to analyze the microenvironments of the samples. The mechanical properties of fly ash paste under different activation conditions and the changes in the microstructure and composition were investigated. The results revealed that under conditions of low NaOH content (1%–3%), the strength of the sample increased significantly. When the content exceeded 4%, the rate of increase in strength decreased. Based on the results, the optimal NaOH content was identified, which was about 4%. A good activation effect, especially for short-term activation (3–7 d), was achieved using TEA under high doping conditions. The activation effect was poor for long-term strength after 28 days. The CaO content did not significantly affect the degree of activation achieved. The maximum effect was exerted when the content of CaO was 2%. The virtual cement and concrete testing laboratory (VCCTL) was used to simulate the hydration process, and the results revealed that the use of the three types of activators accelerated the formation of Ca(OH)₂ in the system. The activators also corroded the surface of the fly ash particles, resulting in a pozzolanic reaction. The active substances in fly ash were released efficiently, and hydration was realized. The pores were filled with hydration products, and the microstructure changed to form a new frame of paste filling that helped improve the strength of fly ash paste.

The paper presents experimental investigation results of crack pattern change in cement pastes caused by external sulfate attack (ESA). To visualize the formation and development of cracks in cement pastes under ESA, an X-ray computed tomography ( X-ray CT) was used, i e, the tomography system of Zeiss Xradia 510 versa. The results indicate that X-CT can monitor the development process and distribution characteristics of the internal cracks of cement pastes under ESA with attack time. In addition, the C₃A content in the cement significantly affects the damage mode of cement paste specimens during sulfate erosion. The damage of ordinary Portland cement (OPC) pastes subjected to sulfate attack with high C₃A content are severe, while the damage of sulfate resistant Portland cement (SRPC) pastes is much smaller than that of OPC pastes. Furthermore, a quadratic function describes the correlation between the crack volume fraction and development depth for two cement pastes immermed in sulfate solution.

This study investigates the mechanism of action of representative molecules of basalt fibers on the healing of water-soaked asphalt. Thermodynamic parameters, morphological characteristics, interfacial healing energy, and interfacial healing strength were analyzed using molecular dynamics and macroscopic tests under different time, temperature, and water conditions to evaluate the specific states and critical conditions involved in self-healing. The results indicate that basalt-fiber molecules can induce rearrangement and a combination of water-soaked asphalt at the healing interface. Hydroxyl groups with different bonding states increase the interfacial adsorption capacity of water-soaked asphalt. The interaction between basalt fiber molecules and water molecules leads to a “hoop” phenomenon, while aromatics-2 molecules exhibit a “ring band aggregation” phenomenon. The former reduces the miscibility of water and asphalt molecules, while the latter causes slow diffusion of the components. Furthermore, a micro-macro dual-scale comparison of interfacial healing strength was conducted at temperatures of 297.15 and 312.15 K to identify the strength transition point and critical temperature of 299.4 K during the self-healing process of basalt-fiber modified water-soaked asphalt.

Paste and mortar specimens were prepared with sulfoaluminate cement (SAC), P·O 42.5 ordinary Portland cement (OPC), and standard sand, and mixed and cured with pure water and artificial seawater, respectively. The mechanical properties of mortar specimens were tested. Hydration and microstructure of paste specimens were also investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), and ²⁷Al nuclear magnetic resonance (NMR), respectively. The results indicate that SAC mortar samples mixed and cured by seawater have faster strength growth before 28 d and higher compressive strength than OPC mortar samples. Compared to curing in deionized water, the hydration products of SAC are somewhat coarser when cured in simulated seawater. The evolution of aluminum phase hydration products during the hydration process of SAC mixed and cured in simulated seawater is quite different from that of OPC. From 3 to 28 d, the content of each aluminum phase hydration product in SAC paste cured in simulated seawater changed little, while that in OPC paste changed significantly; for example, from 7 to 28 d, the content of ettringite (AFt) in OPC paste increased significantly. This type of AFt formed loosely, harming the mortar’s microstructure.

In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure, a series of high-strength manufactured sand concrete (HMC) are prepared by taking the manufactured sand lithology (tuff, limestone, basalt, granite), stone powder content (0, 5%, 10%, 15%) and concrete strength grade (C60, C80, C100) as variables. The evolution of mechanical properties of HMC and the correlation between cubic compressive strength and other mechanical properties are studied. Compared to river sand, manufactured sand enhances the cubic compressive strength, axial compressive strength and elastic modulus of concrete, while its potential microcracks weaken the flexural strength and splitting tensile strength of concrete. Stone powder content displays both positive and negative effects on mechanical properties of HMC, and the stone powder content is suggested to be less than 10%. The empirical formulas between cubic compressive strength and other mechanical properties are proposed.

We have described in detail the effects of nano-SiO₂, nano-CaCO₃, carbon nanotubes, and nano-Al₂O₃ on geopolymer concrete from the perspectives of macro mechanics and microstructure. The existing research results show that the mechanism of nano-materials on geopolymer concrete mainly includes the filling effect, nucleation effect, and bridging effect, the appropriate amount of nano-materials can be used as fillers to reduce the porosity of geopolymer concrete, and can also react with Ca(OH)₂ to produce C-S-H gel, thereby improving the mechanical properties of geopolymer concrete. The optimum content of nano-SiO₂ is between 1.0% and 2.0%. The optimum content of nano-CaCO₃ is between 2.0% and 3.0%. The optimum content of carbon nanotubes is between 0.1% and 0.2%. The optimum content of nano-Al₂O₃ is between 1.0% and 2.0%. The main problems existing in the research and application of nanomaterial-modified geopolymer concrete are summarized, which lays a foundation for the further application of nanomaterial in geopolymer concrete.

Traditional machine learning (ML) encounters the challenge of parameter adjustment when predicting the compressive strength of reclaimed concrete. To address this issue, we introduce two optimized hybrid models: the Bayesian optimization model (B-RF) and the optimal model (Stacking model). These models are applied to a data set comprising 438 observations with five input variables, with the aim of predicting the compressive strength of reclaimed concrete. Furthermore, we evaluate the performance of the optimized models in comparison to traditional machine learning models, such as support vector regression (SVR), decision tree (DT), and random forest (RF). The results reveal that the Stacking model exhibits superior predictive performance, with evaluation indices including R ²=0.825, MAE=2.818 and MSE=14.265, surpassing the traditional models. Moreover, we also performed a characteristic importance analysis on the input variables, and we concluded that cement had the greatest influence on the compressive strength of reclaimed concrete, followed by water. Therefore, the Stacking model can be recommended as a compressive strength prediction tool to partially replace laboratory compressive strength testing, resulting in time and cost savings.

This study identified castor oil and phosphate ester as effective retarders through setting time, tensile, and flexural tests, and determined their optimal dosages. The mechanism by which phosphate ester affects the setting time of polyurethane was further investigated using molecular dynamics simulations. Fourier transform infrared spectroscopy was also employed to systematically study the physical and chemical interactions between phosphate esters and polyurethane materials. The results demonstrate that a 1% concentration of phosphate ester provides the most effective retarding effect with minimal impact on the strength of polyurethane. When phosphate ester is added to the B component of the two-component polyurethane system, its interaction energy with component A decreases, as do the diffusion coefficient and aggregation degree of component B on the surface of component A. This reduction in interaction slows the setting time. Additionally, the addition of phosphate ester to polyurethane leads to the disappearance or weakening of functional groups, indicating competitive interactions within the phosphate ester components that inhibit the reaction rate.

A new modified blend ultrafiltration (UF) membrane with good hydrophilicity, high porosity and excellent anti-fouling performance was developed by using carboxylic multi-walled carbon nanotube (CMWCNT) as casting solution additive. Furthermore, a composite nanofiltration (NF) membrane with large water flux and good retention rate was fabricated by using the PVDF/CMWCNT blend UF membrane as the substrate, and polyvinyl alcohol (PVA), β-cyclodextrin (β-CD) and polyethylenimine (PEI) as the coating solution. The results show that with the appropriate addition of CMWCNT in the casting solution, the surface roughness, porosity and recovery rate of the PVDF/CMWCNT blend UF membrane is obviously increased. The water flux of blend UF membrane is significantly improved when the CMWCNT content increases from 0 wt% to 0.2 wt%. The water flux of blend UF membrane with 0.2 wt% CMWCNT is 162.7 L/(m²·h), which is 44.3% higher than that of the pure PVDF membrane. When β-CD content is 0.8 wt%, the retention rate of Congo red by PVDF/CMWCNT/β-CD composite NF membrane reaches 98.7%, which is 28.3% higher than that of single PVA/PEI modified membrane. This research will provide a new idea and simple method for developing novel high-performance composite NF membranes.

To prepare a conductive polymer actuator with decent performance, a self-built experimental platform for the preparation of polypyrrole film is employed. One of the essential goals is to examine the mechanical characteristics of the actuator in the presence of various combinations of process parameters, combined with the orthogonal test method of “four factors and three levels”. The bending and sensing characteristics of actuators of various sizes are methodically examined using a self-made bending polypyrrole actuator. The functional relationship between the bending displacement and the output voltage signal is established by studying the characteristics of the actuator sensor subjected to various degrees of bending. The experimental results reveal that the bending displacement of the actuator tip almost exhibits a linear variation as a function of length and width. When the voltage reaches 0.8 V, the bending speed of the actuator tends to be stable. Finally, the mechanical properties of the self-assembled polypyrrole actuator are verified by the design and fabrication of the microgripper.

The mechanical and thermodynamic properties of W-Ti alloys ( including W₁₅Ti₁, W₁₄Ti₂, W₁₂Ti₄ and W₈Ti₈ alloys) were investigated by the first-principles approach based on density functional theory. The results indicate that W-Ti alloys except W₈Ti₈ are thermodynamically stable. The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration. However, their B/G ratios and Poisson’s ratios exceed those of pure tungsten, suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys. The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten, indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys. Nevertheless, elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys. This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.

In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming, a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets. At the same time, the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets. In this work, the bulging process of the tailor-welded overlapping sheets was taken as the research object. Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification. The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality. When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength, the deformation of the tailor-welded sheets are more uniform, the offset of the weld seam is minimal, the limit bulging height is maximal, and the forming quality is optimal.

The constant amplitude loading fatigue tests were carried out on the 6061/7075 aluminum alloy TIG fillet welded lap specimens in this study, and the weld seam cross-section hardness was measured. The experimental results show that most specimens mainly failed at the 7075 side weld toes even though the base material tensile strength of 7075 is higher than that of 6061. The maximum stress-strain concentration in the two finite element models is located at the 7075 side weld toe, which is basically consistent with the actual fracture location. The weld zone on the 7075 side experiences severe material softening, with a large gradient. However, the Vickers hardness value on the 6061 side negligibly changes and fluctuates around 70 HV. No obvious defects are found on the fatigue fracture, but a large number of secondary cracks appear. Cracks germinate from the weld toe and propagate in the direction of the plate thickness. Weld reinforcement has a serious impact on fatigue life. Fatigue life will decrease exponentially as the weld reinforcement increases under low stress. It is found that the notch stress method can give a better fatigue life prediction for TIG weldments, and the errors of the predicted results are within the range of two factors, while the prediction accuracy decreases under low stress. The equivalent structural stress method can also be used for fatigue life prediction of TIG weldments, but the errors of prediction results are within the range of three factors, and the accuracy decreases under high stress.

Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing, in which the evolution of magnetic properties, grain orientations and precipitates were studied. To illustrate the Zener factor, the diameter and number density of precipitates of interrupted testing samples were statistically calculated. The effect of precipitate ripening on the Goss texture and magnetic property was investigated. Data indicated that the trend of Zener factor was similar under different heating rates, first increasing and then decreasing, and that the precipitate maturing was greatly inhibited as the heating rate increased. Secondary recrystallization was developed at the temperature of 1 010 °C when a heating rate of 5 °C/h was used, resulting in Goss, Brass and {110} <227> oriented grains growing abnormally and a magnetic induction intensity of 1.90T. Furthermore, increasing the heating rate to 20 °C/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture. However, when the heating rate was extremely fast, such as 40 °C/h, poor secondary recrystallization was developed with many island grains, corresponding to a decrease in magnetic induction intensity to 1.87 T. At a suitable heating rate of 20 °C/h, the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1 020 °C were found among the experimental variables in this study. The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates, leading to the deviation and dispersion of Goss texture, thereby reducing the magnetic properties.

In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying (LSA). Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W₂C (specimen A), Mn+NiWC (specimen B) and Mn+SiC (specimen C) powders were fabricated to improve the wear and corrosion behavior of 1Cr18Ni9Ti steel blades in high speed mixers. Microstructure evolution, phases, element distribution, microhardness, wear and corrosion behavior of the laser alloyed layers were investigated. Results indicated that high Mn steel matrix composites with undissolved W₂C, WC and other in-situ formed carbides were formed by LSA with Mn+W₂C and Mn+NiWC while SiC totally dissolved into the high Mn matrix when adding Mn+SiC. Ni as the binding phase in Ni-WC powder decreased the crack sensitivity of the alloyed layer as compared with the addition of W₂C powder. An improvement in average microhardness was achieved in the matrix in specimen A, B and C, with the value of 615, 602 and 277 HV_0.5, while that of the substrate was 212 HV_0.5. The increase of microhardness, wear and corrosion resistance is highly corelated to microstructure, formed phases, type and content of carbides, micro-hardness and toughness of the alloyed layers.

This paper describes severe plastic deformation (SPD) procedures, which are utilized to form an ultrafine-grained structure in metallic biomaterials. During the SPD process, a solid material sample is subjected to very high loads without a significant change in sample dimensions. In the present work, the high-pressure torsion (HPT) process, as one of the SPD techniques, which achieves a high degree of deformation and ensures refinement of the microstructure, will be discussed in more detail. Considering that grain size control is accepted as a method to obtain materials with desired characteristics, an overview of the properties of ultrafine-grained titanium-based biomaterials to be used in medicine is given. Moreover, particular attention is dedicated to the influences of HPT process parameters, primarily hydrostatic pressure, and number of revolutions during torsion, on the grain size and physical and mechanical characteristics (modulus of elasticity, microhardness, and tensile properties), corrosion resistance, and biocompatibility of the titanium-based biomaterials. A review of the literature indicates that titanium-based materials obtained by the SPD process show improved mechanical and physical properties without losing biocompatibility and corrosion resistance, which suggests that these methods of obtaining implants are something that should be further developed in the future.