- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
Ceramic matrix composites(CMC) have excellent application potential in the aerospace field as thermal structure material. The introduction of continuous fibers solves the problem of high brittleness of ceramics, and the interphase. A micro area between fiber and matrix, plays an important role in guaranteeing the high toughness of CMC. In the last decades, relevant research mainly has focused on the relationships between the interphase and the macroscopic mechanical properties of CMC. Due to the limitation of characterization technology, it is difficult to study deeply the micro-mechanical behavior in the interface region.With the development of micro-nano mechanical testing and focused ion beam (FIB) technology, the characterization of CMC interfacial layer bonding strength and its failure behavior have gradually increased in recent years. On this basis, the interphase roles, the influencing factors of interfacial shear strength and the regulation mechanism of interphase were reviewed. The current methods of testing interface shear strength by direct or indirect means were summarized. The applicable conditions and differences of fiber push-out/push-in and micro pillar compression methods were summarized empathetically. The progress in failure mechanism of the interfacial zone was revealed, and some remaining problems were pointed out. The fiber push-out/push-in test can reflect the influence of matrix stress on the interfacial shear strength, but the test results might be influenced by external factors.And the micro pillar compression test primarily reflects the intrinsic properties of the interphase, and can't reflect the influence of the matrix stress on the interfacial shear strength, nor can it reflect the fiber pull-out process.Finally, the future research directions are prospected: further expanding the characterization methods of the mechanical behavior of the interface micro-zone, while clarifying the influence mechanism between the micro-mechanical behavior and the macroscopic mechanical properties, and establishing relevant models, ultimately achieving the optimization of the interfacial zone of CMC.
With the continuous development of the aerospace field, the service conditions of high temperature structural components such as metal and carbon materials are increasingly harsh. The service life of high temperature structural components can be effectively improved by preparing silicon-based ceramic coatings on the surface of high temperature structural components and giving them special properties through appropriate processes. In recent years, the polymer precursors conversion ceramic coating has gradually become a novel method for preparing inorganic coatings. The new approach has the advantage of excellent processability and functional scalability, which gets more and more attention from researchers. The research progress of high temperature resistant ceramic coatings based on silicon-containing polymeric precursors was reviewed in this paper. Firstly, the preparation of ceramic coatings from the polymers was introduced, including the influences of silicon-based polymer precursors, fillers, coating and pyrolysis process on the structure and properties of the obtained coatings. Then, the applications of polymer-derived ceramic coatings in high temperature protection fields, such as anti-oxidation, environmental barrier and thermal barrier coatings were discussed. Finally, The problems in improving coating performance and defect control of polymer ceramic coatings were pointed out, and the development direction of polymer ceramic coatings was prospected, for example, by introducing ultra-high temperature elements such as Hf, Zr, Ta into silicon-based precursors, improving the temperature resistance level of ceramic coatings, and developing new efficient ceramic technology to improve the existing efficiency and applicability.
With the development of modern science and technology, the demand for survivability of high-speed aircraft is constantly increasing. Its nose cone, wing, tail nozzle and other high-temperature components are easily exposed. In order to hide the high temperature parts of high-speed aircraft, the high temperature application of wave absorbing materials has attracted the attention of researchers. High temperature absorbing ceramic materials can realize the application in the above background. In order to provide the basis for analyzing and improving the problems of limited high temperature degree and narrow absorption bandwidth of ceramic absorbing materials, the absorbing mechanism of ceramic absorbing materials with high temperature resistance was described with the influence of temperature. The high temperature absorbing ceramic materials and coatings can be classified into carbide ceramics, nitride ceramics, oxide ceramics and polymer conversion ceramics. Based on this classification, the electromagnetic wave loss mechanism of ceramic absorbing materials and coatings, and their absorbing properties under high temperature conditions were summarized in this paper.In addition, it is pointed out that the future high temperature absorbing ceramic materials should improve the existing materials' low high temperature resistance and narrow effective absorption band width so as to strengthen its service ability.
Polymer derived ceramics (PDCs) technology has the advantages of simple manufacturing and adjustable composition, providing an effective way to prepare new types of ceramics. However, due to the escape of tiny molecules during the pyrolysis process, the pore defects are formed, and amorphous polymer derived SiCNO ceramics (PDCs SiCNO ceramics) produced by precursor technique have poor mechanical properties. To solve the aforementioned problems, enhancement of the polymer-derived ceramics is achieved by adding a second phase (particles reinforcement) to the ceramic matrix. A method was proposed to obtain ZrO2 reinforced PDCs-SiCNO composite ceramics (PDCs-SiCNO-ZrO2) by ball-milling of polyvinylsilazane (PVSZ) and ZrO2 followed by pyrolyzing. The phase structure and mechanical properties of PDCs-SiCNO-ZrO2 composite ceramics were investigated, respectively. The results show that the introduced ZrO2 fillers are embedded in the matrix of PDCs-SiCNO ceramic as a reinforcement, which not only can effectively reduce the linear shrinkage, but also greatly enhance the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics. PDCs-SiCNO-ZrO2 composite ceramics with a 10%(mass fraction) ZrO2 addition have the flexural and compressive strengths of 197.03 MPa and 375.2 MPa, which are 64% and 267% greater than those of PDCs-SiCNO ceramics. The highest hardness value can reach 20.92 GPa, and the fracture toughness can reach 2.76 MPa·m1/2. The addition of appropriate content of ZrO2 contributes to the densification of the PDCs-SiCNO ceramic matrix, which enhances the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics.
Piezoelectric acceleration sensors are used for monitoring the vibration state of high-temperature components of some important technical equipment, such as aero engines and heavy gas turbines. These sensors require a high Curie temperature piezoelectric ceramic as a sensitive element, and "lead-free"electronic components are an urgent requirement for environmental protection. Gd/Mn co-doped high-temperature lead-free piezoelectric ceramics((0.67BiFeO3-0.33Ba1-xGdxTiO3)+0.5%(mass fraction)MnO2, x=0-0.02, BF-BT) were prepared by a traditional solid-state reaction process. The effects of doping concentration x of Gd3+ on the phase composition, microstructure, piezoelectric property, dielectric relaxation behavior and AC impedance characteristic of BF-BTceramics were investigated. The results show that all samples have pure perovskite structure with coexistence of tripartite phase (R) and tetragonal phase (T), and the T phase content increases with the increasing Gd3+ doping concentration. Moderate amount(x < 0.02)of Gd3+ dopant diffusing into the perovskite lattice would also promote the grain growth of BF-BT ceramics. Gd3+ doped samples exhibit enhanced relaxation phase transition behavior. The phase transition temperature (Tm) decreases with the increase of x, while the dielectric relaxation degree (ΔTrelax) increases with the increase of x. The R-CPE equivalent circuit model has been utilized to match the complex impedance spectra(Cole-Cole diagrams) of the BF-BTceramics, indicating that the AC impedance of samples at high temperature is mainly contributed by the grain boundary. The activation energy of dielectric relaxation increases with the increasing Gd3+ doping concentration, demonstrating the substitution of Gd3+ for Ba2+ can reduce the donor doping effect.In general, when x=0.01, the sample exhibits the optimized electrical properties, including TC=425 ℃, d33=126 pC/N, kp=25.9%, and tanδ=0.059. The Gd3+ doped BF-BTceramics are expected to be used as a promising high-temperature piezoelectric material.
ZnO-Bi2O3-Co2O3-NiO-Mn3O4-SiO2-Cr2O3 varistor ceramics were prepared by solid-phase sintering method.The effects of different doping amounts of Cr2O3 on the microstructure and electrical properties of ZnO varistor ceramics were investigated, and the phases, microstructures and electrical properties of samples were characterized. The results indicate that the addition of Cr2O3 effectively inhibits the abnormal growth of ZnO grains, enhances the uniformity of grain distribution, reduces the ZnO grain resistance and increases the grain boundary resistance.In the range of 0%-0.21% (molar fraction, the same below) of Cr2O3 addition, the nonlinear coefficient of the varistor ceramics increases first and then decreases as the addition amount increases. When the Cr2O3 doping amount is 0.14%, the ZnO varistor ceramics exhibit excellent electrical properties, with a potential gradient E1 mA=216 V·mm-1, leakage current JL=0.36 μA·cm-2, nonlinear coefficient α=25, residual voltage ratio K=1.815, and aging coefficient Kct=0.647. In addition, the initial U1 mA value of varistor ceramics still maintains 96.75% after impacted by 100 kA pulse current twice with 4/10 μs waveform. The Cr2O3 doped ZnO varistor ceramics demonstrate excellent impulse stability and significant application potential for lightning arresters of power distribution systems.
Photoelectrocatalytic technology is one of the most promising methods to solve the problems of environmental pollution and energy shortage.Based on the photoelectrochemical properties of semiconductor minerals or the natural physical characteristics of non-semiconductor minerals, the photoelectrocatalytic mineral materials were constructed by compositing mineral with photoelectrocatalytic functional body, with the characteristics of low cost, good environmental compatibility and excellent property, which have received wide attention in the new field of mineral utilization. On the basis of limiting whether the research of photoelectrocatalytic mineral materials belong to the scope of mineral application, the mineral components and characteristics of the photoelectrocatalytic mineral materials were introduced, their classification, preparation methods, as well as the enhanced mechanism of catalytic activity by minerals were discussed. Finally, the research status of photoelectrocatalytic mineral materials used in the treatment of wastewater, hydrogen evolution by photoelectrocatalysis water splitting, CO2 energy utilization were summarized. It is pointed out that attention should be paid to the intrinsic photoelectric properties of minerals, the establishment of the relationship between material composite structures and efficiency, and the clarification of the mechanism by which material mineralogical properties affect photocatalysis. The application research of photocatalysis mineral materials in new energy, chemical synthesis, and mineral/microbial interactions should be expanded.
Carbon/carbon (C/C) three-dimensional textile composites are widely used in aerospace, rail transit, photovoltaic thermal field and other high temperature components due to their strong designability, excellent mechanical properties and high temperature resistance. However, the internal yarn structure of C/C three-dimensional textile composites is complex and has high porosity, showing a high degree of anisotropy and heterogeneity. These factors will bring great difficulties in revealing the mechanical properties and damage mechanism. Therefore, starting from practical applications, the research status of C/C three-dimensional textile composites is reviewed in recent years from three aspects: micro reconstruction, mechanical performance characterization, and numerical simulation. The aim is to provide important support for the integrated preparation of C/C three-dimensional textile composites structure and function, the exploration of deep learning models, and the construction of progressive damage testing platforms in high-temperature experimental environments.
The forming technology of surface micropattern structure was widely used in practical manufacturing as a means to texture the surface of materials and to promote advanced and functional materials. The main methods of surface micropattern forming include hot embossing, chemical etching, electrical discharge machining(EDM), photolithography and 3D printing depending on the application areas of materials. The different surface micropattern structure forming techniques and the basic principles of preparing surface texturise functional materials were reviewed, and their practical applications in photovoltaics, electronic information, intelligent manufacturing, ultra-precision manufacturing and other fields were listed. The characteristics and scope of application of different surface micropattern structure forming technologies are summarized, and the key problems faced in realizing the surface texturisation and functionalization of materials are put forward, which provides certain reference for the micromachining technology of surface micropattern structures.
Metastable β type Ti-34Nb-4Zr-0.3O(mass fraction/%)alloy (TNZO) was prepared by vacuum arc melting, single-phase hot forging and cold rolling. The cold-rolled TNZO alloys were aged at low-temperature of 250 ℃ and 300 ℃ in order to reveal the effect of aging temperature and time on the precipitation behavior of ω phase and the mechanical properties of the alloys. The results show that ω phase precipitates in nanometer size as a result of low temperature aging which leads to the increase of strength and elastic modulus of the alloys. ω phase is easy to coarsen and agglomerate when the alloy is aged at 300 ℃, which results in the rapid drop of the elongation and embrittlement of the alloy. Short time aging at 250 ℃ could make the ω phase precipitated dispersedly with small volume fraction, enabling the alloy to have excellent comprehensive properties of high strength, low modulus, ultra-high elasticity and good plasticity and show a broad application prospect in the field of aerospace elastic titanium alloys and medical implant titanium alloys.
The medium and high volume fraction SiCp/Al composites were prepared by hot isostatic pressing powder metallurgy process with volume fractions of 35%, 45% and 55% using 2024 and 6061 aluminum alloys as the matrix, respectively. The effect of matrix alloy and SiC volume fraction on the mechanical properties of the composites was investigated. The results show that with the same SiC volume fraction, composites with 2024 aluminum alloy matrix have higher bending strength and elastic modulus, while composites with 6061 aluminum alloy matrix present higher fracture strain. Meanwhile, the mechanical properties of composites with 2024 and 6061 alumium alloy matrix present the same trend as SiC volume fraction increases. The bending strength increases at first and then decreases, with the maximum values of composites with volume fraction of 45% being 656.54 MPa and 548.00 MPa, respectively. However, the elastic modulus continuous increases and reaches maximum for SiCp/2024Al and SiCp/6061Al composites with volume fraction of 55% being 202 GPa and 188 GPa, respectively. The effect of differences in matrix alloys on mechanical properties is more significant at lower volume fractions, and increasing the volume fraction will weaken this difference. According to the theoretical formulas calculation, Orowan mechanism has negligible strengthening effect for the composites with micron-grade SiC particle.The strengthening effect of other types of reinforcement mechanisms can be enhanced on different levels with the increase of the volume fraction of the reinforcement, wherein the contribution of geometrically necessary dislocations and thermal mismatch reinforcement to the yield strength of materials is always dominant.
The effect of different solution temperatures (1140, 1160 ℃ and 1180 ℃) and cooling conditions (AC, FC-900 ℃+AC, FC) on the microstructures and mechanical properties of K439B alloy were investigated using metallographic microscopy and field emission scanning electron microscopy (FE-SEM). The results show that the optical microstructures and morphology of γ' precipitates are similar and the width of grain boundary slightly increases after increasing the solution temperature. When cooled with AC, γ' precipitates are uniformly distributed and the average size is 50.7 nm; when cooled with FC-900 ℃+AC, the larger γ' precipitates of 250-510 nm are precipitated at the interdendritic area region and near the grain boundary, exhibiting a bimodal γ' microstructure; when cooled with FC, the volume fraction of larger γ' precipitates increases and the content of granular M23C6 carbides at grain boundary improves. The stress rupture life of K439B alloy at 815 ℃/379 MPa is enhanced after reducing the cooling rate, while different solution parameters have little effect on the room-temperature tensile property.
In order to study the effect of aging strengthening on the wear mechanism and frictional deformation behavior of rare earth magnesium alloys, GW83 (Mg-8Gd-3Y-0.5Zr, mass fraction/%) rare earth magnesium alloy was prepared by extrusion process. The electronic universal testing machine was used to evaluate the alloy's mechanical properties.The optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to examine the alloy's microstructure.The ball-on-disc dry sliding friction testing machine was used to examine the wear resistance. The results show that after aging treatment (T5), a large amount of β′ precipitated phases are precipitated in the alloy. The hardness and tensile strength of the alloy are 124.1HV and 420.31 MPa, respectively, which are significantly higher than those in the extruded state (O state). As the load increases, the friction coefficient of the alloy decreases and the wear rate increases. Aging treatment can significantly improve the wear resistance of GW83 alloy, which is related to changes in wear mechanism and degree of friction deformation. Under a load of 5-10 N, the main wear mechanisms of both samples are abrasion, oxidation, and adhesive wear. When the load increases to 20 N, the main wear mechanism of the O state sample changes to delamination wear, while the transition load of the T5 sample is 80 N. T5 heat treatment significantly reduces the degree of surface metal deformation and deformation layer thickness caused by friction, thereby reducing the generation of friction cracks.
In order to study the corrosion resistance of three different superhydrophobic coatings (MZS-1, MZS-2 and ZnO@ZIF-8) on AZ91D magnesium alloy surface in 5% (mass fraction) NaCl solution. The microstructure, wettability and corrosion resistance of the superhydrophobic composite coating were tested and characterized by field emission scanning electron microscope, static contact angle tester, electrochemical workstation and salt spray tester, respectively. The results show that the corrosion of the superhydrophobic coatings does not occur until 192 h after salt spray treatment among the three types of superhydrophobic coatings, and the corrosion of the MZS-1 superhydrophobic coating is the most serious. The surface pitting of the MZS-2 superhydrophobic coating doesn't occur until 240 h later, and the contact angle is still high after salt spray treatment, so the corrosion resistance of the MZS-2 composite coating is the best.The polarization curve tests indicate that the corrosion current density of three superhydrophobic coatings are still one order of magnitude lower than that of the metal matrix after salt spray treatment for 240 h, showing excellent corrosion resistance. The superhydrophobic coating can effectively increase the corrosion resistance of metal materials.It can effectively prevent the infiltration of corrosive ions and provide long-term protection for the matrix because of its water repellency.
The morphology and phase stability of precipitated phases are essential for regulating mechanical properties of alloys. The (FeNiCoCr)90Al5Ti5 high entropy alloy was prepared by low-speed ball milling and hot-press sintering method, and the effects of high-temperature (1150 ℃) and medium-temperature (850 ℃) aging treatment on the types, morphology, distribution and mechanical properties of precipitated phases in the alloy were investigated. The results show that the compressive strain of the prepared alloy reaches 47%, and the yield strength and ultimate compressive strength are 948 MPa and 1684 MPa, respectively. The high strength is due to the strengthening effect of the L12 structure nano-precipitation phases within the crystal. After aging at 850 ℃ for 10 h, the L12 precipitated phases grow into equiaxed grains with a size exceeding 10 μm, and some of them transform into a thin lamellar HCP structure η phases, which leads to the decrease of the yield strength and ultimate compressive strength of the alloy. After aging at 1150 ℃ for 2 h, the intracrystalline L12 nano-precipitated phases completely redissolve, which leads to a drastic decrease in the yield strength and ultimate compressive strength of the alloy.
To improve the interfacial properties of poly-p-phenylenebenzobisoxazole(PBO) fiber/epoxy resin (EP)composites, the surfaces of acidified PBO fibers were coated with the sizing agents of waterborne polyurethane modified using γ-aminopropyltriethoxysilane(KH550). The surface chemical composition of PBO fibers was characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). Scanning electron microscopy (SEM)was employed to characterize the surface morphology of PBO fibers and the tear surface morphology of PBO/EP composites. Furthermore, the mechanical properties of single PBO fibers and PBO/EP composites were analyzed. The results show that the active groups on the surfaces of PBO fibers increase significantly with the values of O/C(atomic ratio)from 0.16 to 0.25 after being coated with the sizing agents, and the defects on the surfaces of PBO fibers can be repaired effectively. By adjusting the contents and structure of the sizing agents on the fibers, the interlaminar shear strength and tensile strength of PBO/EP unidirectional composites reach 41.3 MPa and 1.70 GPa, respectively. In contrast to the untreated ones, the interlaminar shear strength and tensile strength of modified composites increase by 44.9% and 15.6%, respectively.
SiCp/2024Al composite was prepared by semi-solid stirring casting, and the distribution of SiCp was regulated by multi-step deformation of hot extrusion and multi-direction forging (MDF). The effects of SiCp distribution on the microstructure and properties of SiCp/2024Al composite ware studied. The results show that hot extrusion deformation cause SiCp to distribute along the extrusion direction (ED). After multi-directional forging, SiCp distribution is improved significantly, and it changes from directional distribution to uniform distribution. After 1MDF, the SiCp distribution along the ED changes to disordered distribution, and the mechanical properties of the material are sharply decreased. After 3MDF, the distribution uniformity of SiCp is improved, and the mechanical properties of the material are greatly improved. When the forging passes increase to 6, the distribution uniformity of SiCp is further improved, the mechanical properties of the material decrease with the partial SiCp breaking. When the forging number is 3, the mechanical properties of the composite are optimal, with yield strength, ultimate tensile strength and elongation are 264 MPa, 387 MPa and 7%, respectively. Compared with the directionally distributed composite, the uniform distribution of SiCp effectively relieves the local stress concentration, and the matrix alloy stores more dislocation. In addition, when the distribution uniformity of SiCp is improved, the Al2Cu phase is also refined. The diffuse distribution of Al2Cu phase hinders the slip of dislocation, resulting in a uniformly distributed composite with a higher work hardening rate and internal stress. In order to study the effect of SiCp distribution on softening behavior of composites, cyclic stress relaxation experiments are carried out. In the process of stress cycling, the uniformly distributed SiCp/2024Al composites with uniform distribution of SiCp and Al2Cu phases exhibit a better stress relaxation resistance.
Due to the small size of commercial BN crystal and the unique interlayer interaction of BN, the traditional exfoliate method makes it difficult to fabricate BN nanosheets (BNNSs) with high aspect ratio (> 5000). High aspect ratio BNNSs were obtained by sintering ammonium borane and centrifugal separation of the sintering products. The synthesis mechanism and structure of BN nanosheets were characterized by FTIR, TG, TEM and XRD. The results show that the cross-linking and dehydrogenation of ammonium borane begin when the temperature is over 80 ℃. Hydrogen releasing results in the formation of foam structure during the cross link process of ammonium borune, and finally the inorganic process was completed at 1000 ℃ to obtain the BN foam containing BNNSs. The as-prepared BNNSs are hexagonal crystal structure, with a thickness of about 1.5 nm and an average width of 30 μm. The width-thickness ratio reaches 20000. The high aspect ratio BNNSs were introduced to polyvinyl alcohol (PVA) to prepare the BNNS/PVA composite film. The composite film shows significant improvement in thermal conductivity and mechanical properties, fully explains the application advantages of high aspect ratio BNNSs in the field of BN based composites.
Hydrogel is an ideal material for cartilage repair, but it is difficult for artificial materials to achieve ultra-low friction coefficient of cartilage at present. The amphoteric ion anionic double crosslinked P(AAm-co-AAc-co-SBMA-co-AMPS)/Fe3+hydrogel was synthesized by using the amphoteric monomer [2-(methacryloxy) ethyl] dimethyl-(3-sulfopropyl)(SBMA) and the anionic monomer 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The frictional tests were conducted in water and PBS to evaluate the effects of zwitterionic and anionic groups on the coefficient of friction (CoF). The results show that the physical crosslinking point introduced by SBMA and AMPS can improve the compressive strength of hydrogel, and achieve a low CoF (0.04) in water, In addition, it is observed that CoF further decreases to 0.015 in PBS, and the decrease of CoF is caused by the highly hydrated upper layer of hydrogel produced during PBS soaking.
CoxBy alloy with high hardness and high melting point has wide range of applications in many fields because of its stable chemical property, high strength, and good thermal stability. In this work, the thermodynamic and electrical properties of five CoxBy alloys (CoB, Co2B, Co3B, Co23B6 and Co5B16), were studied and compared based on a first-principles approach. The elastic constant and related mechanical property of the binary alloys were calculated by using the energy-strain method, and the thermodynamic properties such as the Debye temperature (ΘD) and the coefficient of thermal expansion (α) within a finite temperature were calculated based on the quasi-simple harmonic Debye model. By comparing the mechanical parameters of the binary alloys, it is found that the comprehensive mechanical property of the CoB alloy is the best among the studied alloys; the state density mapping indicates that all five CoxB y alloys have good metallicity and electrical conductivity, and have some potential applications in the field of electrode materials. In Co3B and Co23B6 alloys, there is a resonance peak between the d electron orbital of Co atom and the p electron orbital of B atom, indicating that there is a significant chemical bond between Co—B.The study complements the gap of thermomechanical property parameters of CoxBy binary alloys and provides a theoretical reference for the design and application of Co based or Co—B binary alloy materials.
The closed-cycle process will generate a large number of radioactive aerosols, and its high humidity, high acidity, and high radioactivity lead to rapid failure and high replacement frequency of glass fiber high-efficiency filters. In order to solve the above problems, hydrophobic modification of the traditional glass fiber filter material was proposed to improve its tolerance to severe conditions. The low surface energy modifier (polydimethylsiloxane) was used to realize the chemical hydrophobicity of filter material. The microstructure was constructed by introducing SiO2 nanoparticles to further improve hydrophobicity. The modification effect was analyzed by means of SEM, FTIR and contact angle measuring instrument, and the filtration performance of the modified filter material was further studied. The research results show that the modification can effectively improve the hydrophobicity of the glass fiber filter material and improve its moisture resistance. The static contact angle of the simply chemically modified filter material can reach 146°, and the modified filter material after the introduction of SiO2 nanoparticles exhibit an angle of more than 150°. When the mass fraction of polydimethylsiloxane and SiO2 nanoparticles is 2.0% and 0.5%, respectively, the corresponding filter material GF-PS-0.5 shows the best acid resistance, which is mainly due to the synergy of chemical hydrophobicity and microstructural hydrophobicity. The hydrophobicity of GF-PS-0.5 remains stable after a sufficient amount of γ-irradiation, indicating its good radiation resistance. The modified filter material maintains excellent filtration performance, and the filtration efficiency exceeds 99.99%. The modification process can improve the tolerance of the glass fiber filter material without influencing the filtration performance, showing a good application prospect.
The wood was used as raw material to obtain the wood skeleton by matrix-removal. And the high-strength wood-based composite hydrogels with PVA/PAM double network structure were constructed by in-situ polymerization. The change rules of macro/micro functional morphological characteristics, mechanical properties, optical properties and chemical composition of the wood-based composite hydrogels were systematically investigated by adjusting the mass ratio of PVA and PAM in the hydrogel system. The results show that introducing a small amount of PVA into the PAM/wood skeleton composite hydrogels and constructing a double network structure can effectively enhanced the mechanical properties of the wood-based composite hydrogels. As a result, the wood-based composite hydrogels show tensile properties with a maximum tensile strength and fracture elongation of 16.47 MPa and 11.61%. Furthermore, the wood-based composite hydrogel is used as a flexible substrate with a conductivity of 1.8 S/m to assemble and build sensor components. The results indicate that the flexible sensor exhibits stable and repeatable relative current signal changes under a variety of deformations.
In order to expand the application of polypropylene (PP) in 3D printing technology and improve its mechanical properties, PP/polyethylene terephthalate (PET) blend filaments were prepared by extruding PP with PET using melt blending. The rheological behavior, crystallization structure, melting and crystallization behavior, microstructure, mechanical properties of the filament blends and 3D printed samples with different mixing ratios of PP, PET were analyzed. The results show that the viscosity of PP/PET blends decreases with the increase of shear rate and exhibits shear thinning behavior. PET acts as a nucleating agent and does not change the crystal shape of PP during PP crystallization. The melting temperature of PP is about 150 ℃, and the crystallization temperature increases with the increase of PET concentrations. The PP matrix and PET dispersed phase have obvious "sea-island" structure, in which PET is the "island" phase, with a diameter of 2-5 μm. With the increase of PET concentrations, the tensile strength of filament blends is improved. Simultaneously, the tensile strength and the impact strength of the 3D printed samples is improved. However, the mechanical properties of 3D printed samples are generally lower than those of filament blends due to interlayer interaction.
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