The utilization of magnetic nanofluids as the base carrier fluid of magnetorheological fluids represents an effective approach to enhance the magnetorheological effect. However, achieving highly stable nano-composite magnetorheological fluids remains a significant challenge, encompassing both the synthesis of magnetic nanofluids and the prevention of composite particle agglomeration. In this study, Fe₃O₄ silicone oil-based magnetic nanofluids were prepared using silane coupling agent KH550 as a dispersant, followed by a novel process of co-coating dispersants to obtain nano-composite magnetorheological fluids. The surface morphology, physical phase composition and magnetic properties were characterized and analyzed using XRD, FI-IR, TEM, FE-SEM and VSM. The sedimentation stability and redispersibility of the novel nano-composite magnetorheological fluids were investigated. The results show that surface modification of micron-sized particles significantly enhances the stability and redispersibility of the nano-composite magnetorheological fluids, with optimal sedimentation stability and redispersibility observed at nanoparticle volume fraction of 8%. Furthermore, the novel nano-composite magnetorheological fluids demonstrate superior temperature resistance, remaining stable within the temperature range form -40 ℃ to 120 ℃over extended durations. Rheological properties of novel nano-composite magnetorheological fluid were also investigated demonstrating higher off-state viscosity and magnetorheological effect in comparison to conventional magnetorheological fluids. Moreover, both static and dynamic yield stresses increase with nanoparticle concentration and magnetic field strength.

In order to study the effect of temperature on the recovery stress and mechanical properties of iron-based shape memory alloys (Fe-SMA), experiments on the temperature-related mechanical properties of Fe-SMA and their influence laws were carried out. Firstly, the effects of different activation temperatures on the recovery stress of Fe-SMA rods were investigated by pre-stretching and activation experiments, and an empirical ontological model of recovery stress-temperature of Fe-SMA was established on the basis of experimental studies. Secondly, secondary heating experiments were carried out to investigate the effects of different activation temperatures, additional loads, and exposure temperatures on the recovery stress of Fe-SMA rods. Finally, the mechanical properties of Fe-SMA rods after high temperature were investigated by monotonic tensile experiments. The results show that the established model of Fe-SMA recovery stress-temperature can effectively simulate the relationship between recovery stress and temperature of Fe-SMA. During the secondary heating process, when the activation temperature is lower than 200 ℃, Fe-SMA has a high stress retention ratio, and the stress loss of Fe-SMA rods increases with the elevated of the additional load and the exposure temperature. After experiencing high temperature, the residual shape memory effect induces higher stresses in Fe-SMA rods compared to the initial stresses. The modulus of elasticity and ultimate strength exhibit relative stability, whereas the yield strength experiences a slight increase with rising exposure temperatures. This investigation serves as a reference for informing the fire-resistant design and utilization of Fe-SMA members in academic discourse.

As a kind of intelligent fluid with both magnetic and fluidity properties, magnetorheological fluids have been widely used in many fields. Bidisperse magnetorheological fluids, with their excellent settling stability, redispersing ability and magnetorheological properties, are one of the most promising directions for the future development of magnetorheological fluids. In light of the research progress in recent years, the stabilisation mechanism of bidisperse magnetorheological fluids is highlighted, and the magnetorheological properties of bidisperse magnetorheological fluids are reviewed based on microstructural evolution, experimental influencing factors, and intrinsic mechanics models. Finally, the industrial application of bidisperse magnetorheological fluids is proposed.

In an effort to enhance the research efficiency of magnetorheological fluid (MRF) sedimentation stability and to improve the current reliance on experimental measurement for assessing sedimentation performance, this paper employs a kinetic approach to simulate a microscale mechanical model for magnetic particles. We propose a simulation method for MRF sedimentation under zero magnetic field conditions and validate it through inductance-based sedimentation detection experiments. Since MRF sedimentation occurs in the absence of a magnetic field, we extend the microscale mechanical model, originally developed under the influence of a magnetic field, by introducing the effects of Brownian and van der Waals forces. The simulation method is parameterized with MRF-specific values and compared against experimental data obtained through inductance-based sedimentation detection. The results demonstrate that the introduced simulation method, incorporating Brownian and van der Waals forces, accurately predicts MRF sedimentation rates, effectively addressing the time-consuming nature of current investigations into MRF sedimentation stability.

In this work, morphology control of In₂O₃ gas sensing materials was realized through controlling the hydrothermal synthesis conditions, and In₂O₃ with zero to three dimensional morphologies (nanoparticles, nanorods, nanosheets, and microspheres) were prepared directionally. The morphology, structure, and chemical properties of In₂O₃ were characterized by various methods, and their gas sensing performances toward NO₂ were systematically investigated. The gas sensing test results showed that NO₂ gas sensing performances were significantly improved through morphology control. Among them, In₂O₃ microspheres with the largest surface area and chemisorbed oxygen species exhibited the optimum gas sensing performances to NO₂, and the sensor fabricated with In₂O₃ microspheres reached a high response of 695 to 5.0×10^-6 NO₂ under 100 ℃ and can detect NO₂ down to 0.2×10^-6, showing high selectivity and reliable repeatability. Finally, the influential mechanism of In₂O₃ morphology control on NO₂ gas sensing performances was further discussed.

The traditional NiTi alloy has been widely used in many fields due to its superelasticity, shape memory effect and excellent biocompatibility. For example, it has been prepared into orthodontic arch wire and vascular stent in the biomedical field. However, biomedical equipment needs precision and miniaturization, and the traditional NiTi alloy has been unable to keep up with the development. The nanocrystalline NiTi alloy after severe plastic deformation has better tensile, compressive strength, plasticity and fatigue properties than the traditional coarse and ultra-fine grained NiTi alloy. It is expected to expand the scope of application in the biomedical field. Nanocrystalline NiTi alloy can be used in the manufacture of new medical devices and orthopedic biomaterials. The combination of NiTiAg with Ag not only has excellent mechanical properties, but also has antibacterial effect. W-NiTi composite material is formed by combining with W nanowire/belt to improve the radiation opacity and make the positioning and deployment of instruments and implants in the human body easier. In recent years, there is also a new surface modification technology, ultrasonic nanocrystalline surface modification, which produces nanocrystalline on the surface of NiTi alloy to improve fatigue and corrosion resistance. This paper mainly introduces the application of existing NiTi alloys and the application prospect of nanocrystalline NiTi alloys in biomedical field.

In order to provide a basis for optimizing the heat treatment process of Ni-rich Ti-Ni shape memory alloys, the effects of annealing and aging processes on the microstructure, phase transformation type, phase transformation temperature and temperature hysteresis of Ni-rich Ti-Ni alloys were investigated by optical microscope, TEM and differential scanning calorimetry with Ti-50.8Ni alloy wire as the object. After annealing at 350~800 ℃ for 5~120 min in Ti-50.8Ni alloy wire, with the increase of annealing temperature and time, the reversion, recrystallization and grain growth of the alloy occur, the recrystallization temperature is about 600 ℃, and the microstructure morphology changes from fibrous to equiaxed. The transformation types of the alloy change from B2→R→B19′/B19′→R→B2 to B2→R→B19′/B19′→B2 to B2→B19′/B19′→B2 (B2-parent phase, CsCl type; R-R phase, rhombohedral; B19′-martensite phase, monoclinic) upon cooling/heating. The R transformation temperature θ_R increases first and then decreases, and the maximum value 35.2 ℃ is obtained in the alloy annealed at 400 ℃. The martensite (M) transformation temperature θ_M increases, the temperature hysteresis of M transformation Δθ_M decreases, and the temperature hysteresis of R transformation Δθ_R is about 4 ℃. After aging at 300-500 ℃ for 0.5-50 h in Ti-50.8Ni alloy, with the increase of annealing temperature and time, the evolution role of the morphology of Ti₃Ni₄ precipitates is fine particle →needle-shape →plate-shape. The transformation types of the alloys aged at 300 ℃ and 500 ℃ are B2→R→B19′/B19′→R→B2 and B2→R→B19′/B19′→B2, respectively, and the ones of the alloys aged at 400 ℃ change from B2→R→B19′/B19′→R→B2 to B2→R→B19′/B19′→B2. The θ_R300, θ_R400, θ_R500, θ_M300 and θ_M500 increase. The θ_M400 decreases first and then increases, and the minimum value -121.4 ℃ is obtained in the alloy aged at 400 ℃ for 1 h. The Δθ_M300 and Δθ_M400 increase first and then decrease, and the maximum value 70.5 ℃ and 129.4 ℃ are obtained in the alloys aged at 300 ℃ for 5 h and at 400 ℃ for 1 h, respectively. The Δθ_M500 decreases, and the Δθ_R300 and Δθ_R400 are about 4 ℃.

The stability of magnetorheological fluids (MRF) plays a very important role in the realization of magnetorheological fluid functions, while magnetorheological fluids have become the most widely used materials with its flexible, controllable and stable characteristics. The applications of magnetorheological fluids in mechanical transmission, precision machining, medicine, civil engineering and other fields and their principles are reviewed, along with a summary comparison of various methods for testing the settling stability of magnetorheological fluids. Focusing on the influencing factors of the settling stability of magnetorheological fluids, the influence of additives on the settling stability of magnetorheological fluids is compared and analyzed from the perspective of settling rate by summarizing the mechanism of action of different types of additives. It is also pointed out that changing the structure of magnetic particles and forming low-density composites mainly improve the settling performance of magnetorheological fluids by increasing the friction between magnetic particles and base carrier fluid and reducing the density difference between magnetic particles and base carrier fluid. Finally, the future development trend of magnetorheological fluids is pointed out.

4D printing technology is a variable characteristics rapid prototyping technology, which is mainly based on 3D printing. It additively manufactures the desired object with intelligent materials. The molding firmware can be stimulated by the external environment, in terms of its shape, structure or function of the time dimension changes. Since the technology was proposed, it has attracted the attention of a large number of scholars. With the continuous deepening of research on 4D printing technology, this technology plays a significant advantage in the interdisciplinary integration. This paper first reviews the research status of shape memory intelligent materials in 4D printing, and then elaborates the application research of 4D printing technology based on shape memory intelligent materials in the fields of medical, bionic, military and life product manufacturing. Finally it looks forward to the potential applications and challenges of 4D printing shape memory intelligent materials in the future development.

Shape memory polymer with 4D printing is a smart material that can change the shape of an object over time based on 3D printing. In this work, polyester acrylates were exploited to improve the performance of shape memory based on acrylate, and printed samples with shape memory polymer of polyester acrytate/epoxy acrylate were prepared. The effects of prepolymer ratio and diluent amount on shape memory and mechanical properties were investigated systematically. The results demonstrated that when polyester acrytate/bisphenol A epoxy acrylate was 1∶2, the maximum tensile strength was 30.5 MPa and elastic modulus was 286.38 MPa. While the prepolymer ratio was 1∶2 and the diluent mass fraction was 50 wt%, the shape memory polymer maintained a stable shape recovery rate of 99.3%-99.8% under the 14-folding experiments of water bath. The 4D printed samples recovered to 180° in 4 s at 85 ℃ water bath temperature, showing good performance of shape memory.

Because of the outbreak of COVID-19 pandemic, the disinfectants have become a daily necessity. The chlorine gas is an important industrial raw material for disinfectants. And the demand of chlorine gas is increasing. As is known to all, chlorine gas is a toxic gas and harmful to health. However, the gas sensors based on common metal oxide semiconductor are not sensitive to low concentrations of chlorine gas. Therefore, it is of great significance to develop the gas sensing materials based on metal oxide semiconductor that are high sensitivity to trace leakage of chlorine gas. In this work, In₂O₃ microtubules were synthesized by bio-template method with degreasing cotton. In₂O₃ microtubules was simply treated with NaBH₄ reduction and In₂O₃ microtubules with abundant oxygen vacancies were successfully prepared at room temperature. The effects of the method on the crystal structure, morphology and oxygen vacancies were investigated by means of XRD, SEM, XPS and EPR. The results showed that this method could effectively enhance the concentration of oxygen vacancies in In₂O₃ materials without the destruction on crystal structure and morphology. In the gas sensing tests, the gas response of In₂O₃ microtubules with NaBH₄ treatment was about 13 times higher than In₂O₃ microtubules to the same low concentration of chlorine gas. In another word, the In₂O₃ microtubules were more sensitive to low concentration of chlorine gas after NaBH₄ treatment. According to the analysis of gas sensing mechanism, chlorine gas molecule was not only directly adsorbed on the material surface but also oxygen vacancies of material surface. Thus it can be seen that the oxygen vacancies on material surface played an important role in chlorine gas-sensing performance. Because there are more oxygen vacancies in the In₂O₃ microtubules treated by NaBH₄ than the untreated, the In₂O₃ microtubules with abundant oxygen vacancies exhibited excellent sensitivity to low concentration chlorine gas.

In order to develop a Ti-Ni base shape memory alloy with narrow temperature hysteresis and stable properties, Ti-45Ni-5Cu-0.3Cr (atomic fraction) shape memory alloy wires were designed and manufactured. The matensitic transformation and shape memory behaviors of annealed and aged Ti-45Ni-5Cu-0.3Cr alloy were studied and the effect of the deformation temperature on the shape memory behaviors of the alloy was investigatied by differential scanning calorimeter and microcomputer-controlled electronic universal testing machine. It shows that the one-step reversible matensitic transformation of A→M/M→A (A-parent phase B2, CsCl; M-matensite B19′, monoclinic) occurs in the Ti-45Ni-5Cu-0.3Cr alloy annealed at 350-700 ℃ for 0.5 h and aged at 300-600 ℃ for 1-50 h upon cooling/heating. The martensitic transformation temperature is stable, and changes in the range of 14-21 ℃. The temperature hysteresis is narrow, and changes in the range of 17-21 ℃. At the room temperature, both annealed and aged Ti-45Ni-5Cu-0.3Cr alloys exhibit shape memory effect and the shape memory behavior is stable. With the increase of deformation temperature, the stress-strain plateau stress increases, the residual strain decreases, the alloy characteristics change from shape memory effect to superelasticity, and the transition temperature is between 50 ℃ and 60 ℃ in Ti-45Ni-5Cu-0.3Cr alloy.

Shape memory alloy is a kind of metal intelligent material which can change phase under the action of temperature and pressure. It has been widely used in transportation, aerospace, biomedicine and many other fields. With the continuous improvement of advanced engineering technology for the intelligent and functional diversification of metal structure materials, the traditional mechanical transmission structure shows disadvantages such as poor stability and complex structure, which are increasingly difficult to meet the needs of the present stage. Shape memory alloy has attracted great attention by virtue of its excellent mechanical properties. It is urgent to analyze its multi-field application in order to promote the interdisciplinary integration and the formation of a complete knowledge system. In this paper, we review application frontier of shape memory alloy in automobile industry, aerospace, biomedical, and building at home and abroad, analyze research progress of basic features such as shape memory effect, superelasticity, high damping property, biocompatibility and elastothermal effect, and discuss the shortcomings of shape memory alloy research at present and the future application prospect and development direction.

In this experiment, non-consumable vacuum arc furnace was selected to melt the alloy ingot, and the phase structure and magnetostrictive properties of the alloy were studied. The results show that the Fe81Ga19-XAlX alloy is still dominated by A2 phase after the addition of Al element to the Fe-Ga alloy to replace the occupying of Ga element. The basic structure of the alloy is α-Fe core cubic structure, and the grains change from slender irregular polygons to long columnar crystals, and the orientation of the columnar crystals is significantly enhanced. When x=3.5, the saturation magnetostrictive value of the alloy is 202×10^-6, which is about four times of that when x=0. The improvement of magnetostrictive properties is mainly attributed to the preferred orientation of phase A2 along [100] of Fe-Ga alloy doped with Al and the lattice distortion caused by Al atom entering the lattice of Fe-Ga alloy.

Fe-Ga magnetostrictive coating is prepared by high velocity oxy-fuel spraying (HVOF) process as a sensitive element in magnetostrictive guided wave sensors. The effects of different heat treatment temperatures from 300 ℃ to 700 ℃ on the quality of Fe-Ga coatings are investigated, and the microstructure and properties of the coatings are analyzed by SEM, XRD and magnetostrictive tester. Results show that the Fe-Ga coating maintains a single A2 phase structure during the heat treatment process. The deformed grains in the particles gradually recrystallize at the temperature ranging from 300 to 600 ℃, and completed recrystallization occurs at 700 ℃. The magnetostrictive properties increase with the increase of heat treatment temperature, and the corresponding saturation magnetic field gradually decreases. The maximum magnetostriction reaches 46 ppm with the coating annealed at 700 ℃. This study shows that appropriate annealing process can improve the magnetostrictive properties, which is a guideline for the preparation of high-efficiency transducer materials.

MXenes, a novel family of two-dimensional transition metal carbides/nitrides, as two-dimensional materials, have large specific surface areas and diverse surface terminations. The surface of MXenes can adsorb gas molecules, which can change the conductivity of MXenes. Hence, MXenes can be used as novel gas sensitive materials. This paper reviews the gas sensing properties and applications of MXenes (Ti₃C₂ MXene, V₂C MXene, Mo₂C MXene and etc.) from the theoretical and experimental perspectives, summarizes the gas responses of different MXenes, analyzes the gas sensitive mechanisms, concludes the advantages and disadvantages of MXenes as gas sensitive materials and outlooks the future applications of MXenes in the area of gas sensors.

Fe-Ga magnetostrictive alloy powder with particle size of 10-150 μm is prepared by aerosolization method using pure Fe and Ga metals as raw materials, and Fe-Ga coating is prepared by high velocity oxy-fuel spraying (HVOF) process. The microstructure and properties of the coating are characterized by the SEM, X-ray diffraction, indentation tester, tensile tester and the magnetostrictive tester. The results show that the aerosolized powder has a single α-Fe phase and high powder sphericity. The Fe-Ga powder with a particle size of 30-60 μm is selected as the raw material for HVOF, and the prepared coating has a typical lamellar structure with dense bonding and pores in local areas, and the average porosity is less than 1.2%. The coating with different thicknesses still maintains the structure of α-Fe phase, but there is a shift in diffraction peaks, and no other new phase are formed. The micro-hardness distribution of the coating is uniform, and the average hardness is higher than 4.5 GPa. The interface bonding between coating and substrate is good with the bonding strength higher than 70 MPa. The magnetostriction coefficient of Fe-Ga coating with a thickness of 400 μm is 30×10^-6, indicating the feasibility of preparing magnetostrictive coatings by HVOF, which is expected to realize the long-term online monitoring of magnetostrictive guided waves.

4D printing is an additive manufacturing technology based on stimuli-responsive materials. Although 4D printing is mainly on the basis of 3D printing, the manufactured objects are no longer static in 4D printing. Under external stimuli containing heat, light, magnetism, electricity, pH and so on, the shape, properties or functions of the objects designed by 3D printing can change with time. Stimuli-responsive shape memory materials (SMMs) can be fabricated with 4D printing, which demonstrates the various merits such simple process to manufacture, powerful ability to transform, diverse stimuli-modalities, and so on. In this work, we focus on introducing the research progress of 4D printed shape memory alloys (SMAs), shape memory polymers (SMPs) and shape memory hydrogels (SMHs). At the end of this review, the problems and application prospect of 4D printing technology are discussed.

The optical gas-sensitive effect is the interaction between the material surface and the detection gas, causing a change in material optical properties and thus detecting the gas content. It is a gas content detection method with high sensitivity and reliability. Metal oxide semiconductors are often used as optical gas-sensitive materials due to their active electronic properties near the forbidden band. HCHO is a common indoor air pollutant and is the main source of indoor gas enviro nment pollution. In this paper, we analyze the reasons for the optical gas-sensitive properties change of adsorbed formaldehyde molecules on rutile TiO₂ (110) surface, which doped by C, Ru and C/Ru co-doped respectively. It is found that the 2p and 4d electrons of impurity elements act in concert to significantly improving the material gas-sensitive properties. The material surface structures, density of states, Mulliken populations, optical properties and selectivity are analyzed by using first principle plane wave super-soft pseudopotential method based on density generalized theory. The studies have shown that the impurity elements enhance rutile surface oxidation under formaldehyde gas enviro nment. And the surface optical gas-sensitive effect with C/Ru co-doping is the most significant. Therefore, the C/Ru co-doped surface has better optical gas-sensitive sensing properties, and the sensitive detection of low concentration of HCHO is an effective detection method.

The development of gas sensor technology has a positive effect on the development of human society. Recent studies have shown that atomic-level dispersed materials have ultra-high activity, unique electronic structure and quantum size effect, etc. Therefore, loading certain single atoms on certain gas-sensing materials will significantly improve the gas-sensing properties. This article reviews the preparation and characterization techniques of single atom materials in recent years and their research progress in gas sensors, and analyzes the performance advantages of single atom materials, single-atom loading strategies, analysis methods, gas sensitivity and mechanisms, etc. The existing problems and the future development trend of single atom material based gas sensors are discussed, and finally some relevant opinions on the application and development of single atom materials in gas sensors are put forward.

The base fluid is an important factor affecting the performance of magnetorheological fluids. Compared with traditional base fluids, ionic liquids have moderate viscosity and polarity, and can be used as base fluids for preparing new magnetorheological fluids. In this paper, 1-octyl-3-methylimidazole tetrafluoroborate ionic liquid is used as the base liquid, and carbonyl iron powder is used as the dispersed phase particles to prepare a magnetorheological fluid with a particle volume fraction of 20%. Performance comparison of magnetorheological fluids is investigated. The rheological test results show that the maximum shear yield stress of the ionic liquid-based magnetorheological fluid at 436 kA/m is 29% higher than that of the silicone oil-based magnetorheological fluid. The ionic liquid-based magnetorheological fluid has a more significant Magnetorheological effect.

In order to solve the problems of non-renewable and non-degradable of the traditional shape memory polymer (SMP) based on synthetic polymer, more attention is payed to the development and application of natural polymer based SMP. In this study, natural polymers of cellulose and agarose are used as raw materials, alkali/urea aqueous solution serves as co solvent and epichlorohydrin is used as crosslinking agent. After blending, crosslinking, washing and drying, cellulose/agarose composite films with different ratios are successfully prepared. The shape memory performance of the composite films is characterized. The wet composite films and the hot water soaked composite films are fixed at a set angle through different angles of mold, respectively. The wet film is dried at room temperature, and the composite film soaked in hot water is solidified at low temperature, and then the composite films fixed at a certain angle are obtained. After, the composite films with the certain angle are put into water and hot water, and the composite films returns to the initial shape. The shape fixation rate and recovery rate of the composite film are calculated by the certain angle and recovery angle. The results show that the films have good shape memory properties for water stimulation through the formation and breaking of hydrogen bonds, and the destruction and formation of agarose crystals also show good shape memory behavior to thermal stimulation. The shape fixation rate and shape recovery rate are above 95% and 84% in water induction, and 58% and 85% in hot water induction. Besides, it is found that with the increase of the agarose, the mechanical properties change. The tensile strength of the dry film and wet film decrease from 132 MPa and 5.4 MPa to 101 MPa and 1.9 MPa, and the elongation at break increase from 14.2% and 133.8% to 20.3% and 195.2%, respectively. At the same time, the structure of the composite film is uniform, and the transmittance is more than 90%. This work can provide a new idea for the development of natural polymer based SMP.

Acetone is widely used in industry and laboratories, and the detection of acetone is very important. ZnFe₂O₄ is a spinel-type ternary metal oxide with excellent gas response and can be widely used in gas sensors. In this paper, a simple one-step hydrothermal method was used to prepare spherical ZnFe₂O₄ gas-sensing materials. The morphology, chemical composition, specific surface area, etc. of the material were analyzed by XRD, XPS, SEM, TEM, N₂ adsorption-analyzer, and the gas-sensing performance was studied with acetone as the target gas. The results show that the ZnFe₂O₄ nanospheres are self-assembled from nanoparticles and have a large specific surface area. The ZnFe₂O₄ based gas sensor has a response of 65.74 to acetone at the optimal working temperature of 150 ℃, excellent selectivity, stability and repeatability, but the gas response gradually decreases with the increase of humidity.

PVAc latex-based shape memory polymers(SMP) with high strain and recovery ratio are fabricated by formation of poly(vinyl acetate) (PVAc) core and polystyrene(PS) shell through acrylonitrile grafting (PVAc-AN/PS) in emulsion polymerization. It is exhibited that the morphology-controllable “protuberances” on the latex core could be acted as observable “net-point” during the shape memory cycle. The morphology of PVAc-AN/PS particles with core-shell structure is characterized by scanning electron microscope and transmission electron microscope, and the morphological evolution of the PVAc-AN/PS latex particles varying with the quantity of PS is investigated. The shape memory performance of PVAC-AN/PS latex film is explored by uniaxial stretch shape memory cycle experiment, demonstrating that the shape recovery ratio of the PVAc-AN/PS latex film is effectively improved by adjusting the amount of St added during the polymerization. The experimental results show that PVAc-AN/PS core-shell latex film possesses high strain more than 1500% with shape recovery ratio of 85% or more. Therefore, this study provides a new approach for designing “net-point” in shape memory effect of polymers and regulating the shape memory performance of polymers.

Cobalt ferrite substituted with Zn²⁺ and Zr⁴⁺ are prepared by sol-gel auto-combustion method using spent Li-ion batteries as raw materials. The crystal structure, morphology, magnetic properties and magnetostrictive properties are explored. The results show that the substituted samples are spinel structure and the morphology of the samples changes compared with cobalt ferrite. With the increase of zinc-zirconium substituting amount, the saturation magnetization, maximum magnetostriction coefficient and maximum strain derivative of the samples firstly increase and then decrease. At the substituting amount x=0.050, the saturation magnetization and maximum strain derivative of the sample at a lower magnetic field strength are 87.56 Am²/kg and -1.81×10^-9 A^-1m, respectively. It is beneficial to the application of ferrite magnetostrictive materials on the pressure sensors and actuators.

Cyclic tensile tests of shape memory alloy bars with four different diameters were conducted. The effects of heat treatment, cyclic loading-unloading numbers, strain amplitude on the mechanicalbehaviour of SMA bars were analyzed. The mechanical parameters such as residual strain, energy dissipation per cycle, secant stiffness, equivalent damping ratio were studied with different strain amplitude and cyclic loading-unloading numbers. The experimental results indicate that the phase transformation stress was higher when the heat treatment scheme was 400 ℃ for 15 min for 14 mm SMA bar. The mechanical properties were basically stable after 5 cyclic loading-unloading cycles, which should be considered in engineering applications. The test results provided a basis for the use of large size SMA bars in self-centering structures.

Volatile organic amines are toxic and harmful,which pose a serious threat to the ecological environment and public safety.The rapid detection of organic amines is of great significance for environmental pollution prevention,food safety monitoring and even medical diagnosis.Based on the research progress of tin dioxide semiconductor materials in the detection of organic amine,the formation of heterojunctions between tin dioxide and metal oxides,metal sulfides,carbon materials and organic polymer reported recently,and the effects of heterojunctions on amine-gas sensing performance were summarized.The other materials possessing heterojunctions and their applications in amine-gas sensing fields were prospected.

With the development of human beings and the progress of society,people pay more and more attention to the environmental problems,especially the detection of toxic and harmful gases.Metal oxide gas sensors can solve this problem.Metal oxide semiconductor gas sensor has been widely studied and applied because of its small size,low cost,convenient use and quick response.Tungsten trioxide (WO₃),as a typical n-type semiconductor gas sensing material,has attracted wide attention in the detection of various toxic and harmful gases due to its unique gas sensing properties.The structure and morphology of sensing materials,the exposed crystal facets,the introduction of oxides and noble metals play a key role in improving the gas sensing performance of materials.Therefore,in this paper,the recent studies on the synthesis,interface control,modification methods,gas sensing properties and related mechanisms of one-dimensional,two-dimensional and three-dimensional WO₃ materials were summarized,the existing problems in the research process of gas sensor based on WO₃ at present were put forward,and its future development trend was prospected.

The phase transformation behaviors of Ti-45Ni-5Cu and Ti-50Ni shape memory alloy wires annealed at 350～700 ℃ were comparatively investigated by X-ray diffractometry and differential scanning calorimetry. The composition phases of Ti-45Ni-5Cu and Ti-50Ni alloy wires were all monoclinic martensite B19′. With increasing annealing temperature, the phase transformation type of Ti-50Ni shape memory alloy wire changed from B2→R→B19′/B19′→B2 type to B2→B19′/B19′→B2 type upon cooling/heating (B2, CsCl; R, rhombohedral; B19′, monoclinic). The reverse martensitic transformation temperature changed in the range of 72～80 ℃, and the temperature hysteresis changed in the range of 41～33 ℃. The phase transformation type of Ti-45Ni-5Cu shape memory alloy wire was B2→B19′/B19′→B2 type constantly upon cooling/heating, the reverse martensitic transformation temperature changed in the range of 46～65 ℃, and the temperature hysteresis changed in the range of 22～24 ℃. Comparing with Ti-50Ni shape memory alloy wire, the phase transformation type was stable, the phase transformation temperature was low, and the temperature hysteresis was narrow in the Ti-45Ni-5Cu shape memory alloy wire. The Ti-45Ni-5Cu shape memory alloy with narrow temperature hysteresis could be used to make temperature sensitive actuators.

In this paper, bimetallic MOF(ZnCo-MOF) materials containing a small amount of metal element Co was prepared by a facile solution reaction at room temperature. The effects of calcinations temperature and composition on morphology and specific surface area were studied. The optimized synthesis process was adopted as heating rate of 1 ℃/min and sintering temperature/time of 600 ℃/3. The structures and morphologies of the porous materials were characterized by means of XRD, FESEM, TGA and BET. The gas-sensitive properties of the porous nanomaterials with or without Co prepared at different sintering temperatures to acetone were studied and compared. The results show that 1.5% Co-doped ZnO porous materials sintered under 600 ℃/3 h had the best gas sensing properties. The response value of the porous materials to acetone gas of 50 ×10^-6 could reach 54 at the optimum operating temperature of 270 ℃, limit of detection was calculated to be 0.3 ×10^-6, and owned the advantages of low operating temperature, high sensitivity and good selectivity.

The effect of aging temperature (T_ag) on the microstructure, phase transformation, tensile property, and shape memory behavior of Ti-51.1Ni shape memory alloy aged at 300 ℃, 400 ℃, 500 ℃, 600 ℃ for 1 h, respectively, were investigated by XRD, optical microscope, TEM, differential scanning calorimetry and tensile test. The phase composition at room temperature of Ti-51.1Ni alloy aged at 300-600 ℃ was parent phase B2, martensite B19′ and precipitated phase Ti₃Ni₄. The morphology of microstructure was equiaxed, and Ti₃Ni₄ precipitations appeared in the microstructure. With increasing T_ag, the morphology of Ti₃Ni₄ changed from punctate to flaky. With increasing T_ag, the phase transformation type of Ti-51.1Ni alloy changed from A→R/R→A to A→R→M/M→A to A→M/M→A (A-parent phase B2, CsCl; R-R phase, rhombohedral; M-martensite B19′, monoclinic) upon cooling/heating. The R phase transformation temperature (T_R) increased and the M transformation temperature (T_M) decreased after aged at 500 ℃. With increasing T_ag, the tensile strength of the alloy increased firstly and then decreased. The elongation of the alloy decreased firstly and then increased. The alloys aged at 300 ℃ and 400 ℃ showed superelasticity (SE), and the alloy aged at 500 ℃ and 600 ℃ showed shape memory effect (SME)+ SE. In order to make Ti-51.1Ni alloy show SE at room temperature, the alloy need to be aged at 300 ℃ or 400 ℃, and to make the alloy show SME at room temperature, the alloy need to be aged at 500 ℃.

Formaldehyde is a typical indoor pollution gas, which harms people's health seriously. ZnSnO₃ is a ternary metal oxide with a perovskite structure and is widely used in gas sensing materials. In this paper, different rGO-doped ZnSnO₃ composites were successfully synthesized by one-step hydrothermal method. XRD, FTIR, SEM, TGA, XPS and BET methods were adopted to characterize the structure, morphology, thermal stability, chemical composition, and specific surface area of composite materials, and the gas sensing properties to different target gases, such as ethanol, acetone, ammonia, Benzene and formaldehyde, were also investigated. The experimental results showed that the rGO-doped ZnSnO₃ could effectively improve the gas sensitivity of ZnSnO₃. Among them, the 4%rGO/ZnSnO₃ composite had the highest sensitivity to 30×10^-6 formaldehyde gas (38.9), fast response recovery time (112s, 15s) and good selectivity and stability.

With the rapid development of shape memory composites, polyvinyl alcohol (PVA) based shape memory composites with good biocompatibility are receiving widespread attention. The preparation method of PVA based shape memory composites, such as physical blending methods of solution casting, cyclic freezing and thawing, in-situ polymerization blending, physical embedding, laminating, coprecipitating, and blending followed by supercritical drying and chemical crosslinking methods were introduced. The characteristics and research progress of above-mentioned preparing methods were also discussed in details. The related application research and progress of PVA based shape memory composites on biomedical fields, such as drug sustained release, scaffolds for tissue engineering and photosensor were analyzed and discussed. Finally, it was proposed that the development of PVA based composites with multi-stimulus response and multi-functionality would be the research trend of shape memory composite materials in the future. PVA based shape memory composite materials with excellent comprehensive properties would play an important role in the field of biomedical composite materials.

In this paper, NiO/In₂O₃ nanocomposites were prepared by hydrothermal and water bath method. The nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Characterization results show that the NiO nanosheets were uniformly grown on the surface of In₂O₃ nanospheres with the diameter of 200-300 nm, and the thickness of NiO nanosheets was about 20 nm. Gas-sensing tests exhibit that the sensor response to 10×10^-6 formaldehyde was about 20 at 220 ^oC with the fast response time (about 4 s) and recovery time (about 16 s), and good reproducibility and selectivity. Some possible mechanisms were further discussed based on the hierarchical structure and p-n heterojunction.

Carboxymethyl chitosan is widely used in biomedical field due to its good water solubility and biocompatibility. In this paper, N-isopropylacrylamide was grafted onto carboxymethyl chitosan by free radical combination method under the action of initiator potassium persulfate with natural degradable polymer carboxymethyl chitosan as carrier. Then, a new photo-thermal sensitive carboxymethyl chitosan microsphere loaded with photosensitizer indocyanine green(ICG) was prepared by emulsion crosslinking method under the crosslinking effect of vanillin. Fourier transform infrared(FT-IR), nuclear magnetic resonance(¹H-NMR) and scanning electron microscope(SEM) were used to characterize the structure of the copolymer and the morphology of the microspheres. The effects of oil-water ratio, rotation speed, vanillin and emulsification time on the drug loading rate of adriamycin in the nanospheres were investigated, and their photothermal properties were also studied. The experimental results shows that Fourier transform infrared(FTIR) and nuclear magnetic(¹H-NMR) analysis proved that N-isopropylacrylamide was successfully grafted onto carboxymethyl chitosan. Scanning electron microscopy showed that the appearance of the nanospheres was spherical, with uniform distribution and an average particle size of 143 nm. The drug loading rate of microspheres with oil-water ratio of 20∶1, rotating speed of 600 r/min, vanillin content of 1 mL and emulsifying time of 3 h was the highest 19.32%. At the same time, the nano microspheres could slowly release drugs in a targeted manner and had good photothermal sensitivity. The nano microspheres had wide application prospects in the fields of drug controlled release, drug carriers and the like.

Firstly, Ni-Mn-Ga-Co alloy powders with different particle sizes were prepared by ball milling. Then, porous Ni-Mn-Ga-Co magnetic shape memory alloy with foamed structure was successfully prepared by 3D printing technology. Microstructure, phase structure, phase transformation and related magnetic properties of the alloy were studied by means of SEM, DSC and XRD. The results showed that the alloy powders with different particle sizes obtained by ball milling and sieving were irregular in shape. Ni-Mn-Ga-Co alloy powder had a non-modulated tetragonal martensite structure at room temperature, and its characteristic peak was very obvious. The DSC curves of Ni-Mn-Ga-Co alloys showed wide-peak phase transition, and the addition of Co had little effect on the initial martensitic transformation temperature (Ms), but the Curie temperature (Tc) of Ni-Mn-Ga-Co alloys had a significant increase. The maximum saturation magnetization of the magnetic alloys prepared by sintering with 50-100 μm alloy powder was 68 Am²/kg. The smaller the particle size of the alloy powder, the higher the density of the sintered porous Ni-Mn-Ga-Co magnetic shape memory alloy. When the particle size of alloy powder was less than 50 μm, the density could reach 90%, and when the particle size of alloy powder was 50-100 μm, the density was only 75%. Compared with the alloy powder with smaller particle size, the magnetic alloy produced by the alloy powder with larger particle size had higher magnetic induction strain capacity, which was because the foam structure could effectively reduce the internal and external constraints, thereby improving the induced strain of magnetic field.

In this paper, the effect of surfactant on the settling stability of magnetorheological fluid was mainly studied. The differences in the properties of magneto-rheological fluid samples with different kinds and mass fraction of surfactants were analyzed through experiments to explore the influence of surfactant HLB value on the anti-settling stability of magneto-rheological fluid. It was found that the settling stability of magneto-rheological fluid was improved with the decrease of HLB value. In addition, the concept of contact angle was also introduced to analyze the influence of measuring dispersed particles on wettability of base liquid in the preparation process of magnetorheological fluid, and to explore a new evaluation method based on magnetorheological fluid's anti-settling stability.

In this work, harmonic loss and magnetostriction of thin gauge grain-oriented silicon steel (0.23 mm) were studied by simulating the invigorative magnetic field of 3-7 th harmonic superposition conditions. Meanwhile, evolution law of magnetic domain structure of the material was also explored. The results indicate that harmonic superposition could result in increases of hysteresis loop area and number of hysteresis cycles, as well as change reinforce of magnetic flux density in the samples. Magnetic hysteresis loss and eddy current loss increased continuously with enhancement of harmonic frequency or content, which brought sizeable addictional loss to the sample. Iron loss under 30% harmonic superposition of 5th harmonic increased by 89.7% compared with fundamental frequency. Harmonics caused decreases of width of 180°magnetic domains which could result in decreases of valume fraction of 90°domains and increases of magnetostrictive amplitudes λ_p-p. At the same time, the butterfly curves were distorted.

Different proportions (0, 1%, 3%, 5%, 7%, 9wt%) of hierarchical g-C₃N₄/SnO₂ heterostructures were synthesized by one-step hydrothermal method. The crystal structure, morphology and optical properties of the materials were investigated by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM and TEM), BET specific surface area measurement and photoluminescence spectroscopy (PL). Meanwhile, the gas sensing performances of g-C₃N₄/SnO₂ nanostructures were investigated towards ethanol. The results showed that the gas response of 5wt% g-C₃N₄/SnO₂ based sensor was 77.5×10^-6 to 40×10^-6 ethanol at the optimum working temperature of 270 ℃, which was about 8.4 times higher than that of the pure SnO₂. Finally, the enhanced gas sensing mechanism of the g-C₃N₄/SnO₂ nanocomposite was discussed.

In order to research the ΔE effect of giant magnetostrictive materials, a magnetization model considering the effects of dynamic stress and coefficient changes was proposed by combining the Jiles-Atherton model with the magnetoelastic effect. The magnetic field-magnetization relationship and stress-magnetization relationship of giant magnetostrictive materials under external magnetic field and compressive stress were modeled respectively. According to Hooke's law and the second domain-rotation model, the total strain of materials under the combined action of stress and magnetic field were calculated, and the strain-stress loop of materials under different external magnetic fields were obtained. By calculating the slope of the strain-stress curve, the elastic modulus versus stress curve of the magnetostrictive material under different applied magnetic fields was obtained. A stress test device was built to test the magnetization-stress response and strain-stress response of Terfenol-D under different applied magnetic fields. The test results were basically consistent with the model calculation results. The results show that the ΔE effect was the result of the balance of magnetic field energy and stress anisotropy. The maximum elastic modulus variation of Terfenol-D reached 513%. The research results provided theoretical basis and control methods for the design of variable stiffness of new electromechanical systems.