- 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)
Polymeric foams have become essential items due to their excellent properties. Open-cell foams are widely used in the fields of sound-absorbing, biomedicine, optics, conduction, etc. In particular, polymer nanocomposites offer modern medicine new opportunities for generating products for antibacterial treatment, tissues engineering, cancer therapy, medical imaging, dental applications and drug delivery, etc. In this paper, the preparation methods, foaming mechanism and application fields of open-cell foams were described, as well as new developments in recent years. Finally, the main problems in the process of material preparation and application were summarized and the future development trend of polymer blending, formation of micro-nano composites, coating of high-barrier materials and polymer modification for the preparation of high-performance open-cell polymer foams was forecasted.
Nowadays, water shortage has become a severe issue all over the world, especially in some arid and undeveloped areas. In nature, many creatures can collect water from fog which can provide a source of inspiration to develop novel and functional water-collecting materials. Recently, as an increasingly hot research topic, bioinspired materials with water collection have captured vast scientific attentions into both practical applications and fundamental researches. In this paper, the mechanism of water collection of Namib desert beetle, cactus and spider silk was summarized, and the synthesis, function and water collection efficiency of corresponding biomimetic materials were described, as well as new developments in recent years. Finally, conclusions and outlook concerning the main problems and development trends of bionic water-collecting materials in the process of preparation and application were presented.
After the Fukushima accident, there is an urgent need to develop fuel cladding materials to meet the performance requirements of materials under severe accident conditions, and therefore greatly improving the accident tolerance of nuclear power plants. Although the macroscopic thermal neutron absorption capture cross-section of the FeCrAl alloy is much higher than that of zirconium alloy, however, its good corrosion resistance, high temperature mechanical properties and radiation damage resistance in severe accident conditions make it become a candidate material of accident-tolerant fuel cladding. Currently, the performance of various industrial FeCrAl alloys can not meet the requirements of materials for nuclear power plants. Therefore, the FeCrAl alloy needs to be optimized in order to obtain a better performance. The research progress of corrosion behavior, mechanical properties, microstructural evolution and mechanical properties under irradiation, weldability and processability of FeCrAl alloys are summarized systematically. Meanwhile, the corrosion mechanism at high temperatures and the reasons for the change of microstructure and mechanical properties of FeCrAl alloy are analyzed. Besides, the main problems of FeCrAl alloy of high temperature corrosion behavior, weldability, workability and the future research directions are proposed.
Bio-based gallic acid epoxy resin(GAER)was prepared by gallic acid as main raw material. Nano-ZnO surface modification by KH-550 was used to prepare KH550-nano-ZnO. In addition, it was combined with the bio gallic acid epoxy resin(GAER), GAER/KH550-nano-ZnO composite coating was prepared by using succinic anhydride as curing agent. The changes of microstructure before and after modification of nano-ZnO were characterized. The curing process of succinic anhydride/GAER system was studied by differential scanning calorimeter. The effects of the KH550-nano-ZnO content on the mechanical properties, the thermal properties, dynamic mechanical properties and the antibacterial properties of the coating film were tested. The results show that the addition of proper amount of KH550-nano-ZnO can increase the glass transition temperature (Tg) of the system and improve the impact resistance of coating surface. The hardness and thermal stability of the coating are increased and the adhesion is decreased with the increased content of KH550-nano-ZnO. The initial thermal decomposition temperature (T5%) of the composite coating is higher 12.6-15.4℃ than that of pure GAER. When the content of KH550-nano-ZnO is 2%(mass fraction), the Tg is increased by 30.7℃ compared with pure GAER resin. The anti-bacterial rate of the KH550-nano-ZnO/GAER cured coating to Escherichia coli and Staphylococcus aureus reaches 99.99%.
A simple synthetic method of poly(hexamethylene guanidine hydrochloride) grafted hollow nano-silica (HSN-PHMG), a novel antibacterial material, was proposed. The water dispersibility and antibacterial property of HSN grafting of PHMG were improved. The hollow structure of nano-silica was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis were used to characterize the successful grafting of PHMG and the mass fraction of PHMG is about 9.5% in HSN-PHMG. Antibacterial test using Escherichia coil (E.coil) and Staphylococcus aureus (S.aureus) as test strains and the results show that the minimum inhibitory concentration (MIC) of HSN-PHMG on E.coil and S.aureus are all 32 mg/L; E.coil can be completely killed within 2 h when the concentration of HSN-PHMG is 64 mg/L.
Using organic solvent in traditional polymer filtration membrane is easy to cause environ-mental pollution.The silk was uniformly grafted with polyacrylonitrile using zinc chloride aqueous sol-ution as the solvent. The nano-TiO2 was blended into the mixture and the casting solution was pre-pared. The TiO2 blended silk fibroin grafted PAN (SF-g-PAN/TiO2) filtration membrane was pre-pared using water as the coagulation bath. The membrane was characterized by scanning electron micr-oscopy and infrared spectroscopy. The hydrophilic, anti-fouling and mechanical properties of SF-g-PAN membranes with different TiO2contents were studied. The rejection performance of dyes with different molecular weight by the SF-g-PAN/TiO2 membrane was investigated. The results show that the mechanical properties of the SF-g-PAN/TiO2 filtration membranes increase firstly and then dec-rease with the increase of TiO2 content. When the content of TiO2 is 1%(mass fraction), the mech-anical and hydrophilic properties of the SF-g-PAN/TiO2 membrane are the best; the rejection of the dyes whose molecular weight is more than 660 is greater than 96%, with the flux of 80 L/(m2·h) at 0.10 MPa.
Polymethacrylimide foams were prepared by free radical bulk polymerization with butyl methacrylate (BMA), acrylamide (AM) as the reactive monomer, acrylic acid (AA) as the third monomer and crosslinker at different heat treatment time. The structure and properties were characterized by FTIR, SEM, TGA and DSC. The results show that with the increase of heat treatment time of BMA/AM/AA copolymer, the rearrangement reaction between molecular chains produces a six-membered imide ring. After cross-linking and solidification, PMI foam is obtained. The characteristic absorption peaks are in good agreement with the literature values. After heat treatment for 5 h, a dense closed cell foam with a pore diameter of 100-200 μm is obtained, which has good mechanical properties, compressive strength of 8.160 MPa and tensile strength of 12.95 MPa. The glass transition temperature (Tg) of the foam is 255℃, the thermal decomposition temperature Td10 is as high as 280℃ when the thermal mass loss is 10%, and the foam still retains more than 80% at 345℃, and the thermal conductivity is 0.05424 W/(m·K). It is indicated that the foam with excellent high temperature resistance and thermal insulation properties is obtained after heat treatment of the copolymer for 5 h.
Fluoroacrylate/polyurethane composite emulsion (FPAPU) were synthesized by miniemulsion polymerization. The effect of four kinds of materials with different surface properties (aluminum plate, stainless steel plate, PTFE plate and glass plate) on the self-organized gradient distribution structure of fluorine-containing components in FPAPU latex film was studied. The results show that the gradient structure is not obvious when the film is formed on aluminum and stainless steel plate respectively. The gradient structure is obvious when the film is formed on PTFE and glass substrate respectively. Especially for the film formed on the glass plate, the content of fluorinated component is increased from film-substrate (F-S) surface to film-air (F-A) surface, and the difference of both sides of the film is obvious. The surface free energy difference can reach 11.71 mN/m. The apparent stratification structure is formed from F-S surface to F-A surface, and F-A surface is relatively rough. The film formed on glass substrate has excellent hydrophobicity and oleophobicity, and the contact angle of water and oil (diiodomethane) on which can reach 121.6ånd 90.6°respectively.
The tribological properties of garaphene and graphene oxide (GO) as water based additives were investigated for AZ31 Magnesium alloy cold rolling. The morphology and composition of surfaces were characterized by field emission scanning electron microscopy(FESEM) and Raman spectrum. The lubricating mechanism of graphene and graphene oxide(GO) as water-based additives was explored. The results indicate that the best tribological response of the magnesium alloy/steel pairs evaluated is obtained when GO and graphene at a concentration of 0.5%(mass fraction) is added to water. The friction coefficients of graphene nanofluids and GO nanofluids are 0.132 and 0.038, and the wear volumes are 23.1 mm3 and 2.59 mm3. Furthermore, the cold-rolling tests show that the application of GO nanofluids leads to a significant reduction in the rolling force and an improvement in the surface quality of sheets. Under the same testing conditions, the lubricating performance of GO nanofluids are superior to graphene nanofluids, which attributes to the superior dispersion in the water and prominent wetting of the GO nanofluids on the magnesium alloy surface.
In order to further enhance the performance of the AlSi10Mg parts fabricated by selective laser melting, the WC/AlSi10Mg composite with 0.1%WC(mass fraction) was obtained by mixing the nano-WC and AlSi10Mg in mixing machine, and the specimen block was fabricated by the selective laser melting machine. By comparing the AlSi10Mg specimens fabricated by the same process, the effects of nano-WC on the microstructure formation and evolution of the microstructure and the mechanical properties of the microstructure were investigated. The results show that the WC/AlSi10Mg powder has good sphericity and the particle size distribution is concentrated in 20-60 μm. The WC/AlSi10Mg sample has the density of over 99% and hardness of about 158.89HV, which is 14.58% higher than that of the AlSi10Mg sample. The WC/AlSi10Mg samples grow uniformly and densely, with obvious molten pool lines. The inside of the crystal grain is α-Al matrix, and the boundary is a eutectic Si phase interposed with WC. The yield strength of the WC/AlSi10Mg sample reaches 337.75 MPa, the ultimate strength is as high as 514.00 MPa, and the elongation is 3.78%. Compared with the same process, AlSi10Mg samples are increased by 4.73%, 6.25% and 35.97%, respectively. Therefore, SLM-processed WC/AlSi10Mg composite parts have better application prospects than AlSi10Mg parts.
High energy ball milling and spark plasma sintering(SPS) were used to make high density pure W bulk, the relative density of samples can reach more than 97.0%. TZM alloy powder was laid on the surface of the W bulk, SPS was used to sinter TZM and join W with TZM at the same time. This experiment realized the joining between W bulk and TZM powder without interlayer. The effects of sintering temperature and cooling rate on the microstructure and mechanical properties of W/TZM alloy joints were investigated.The results show that W is well joined with TZM alloy, and there are no holes, microcracks and unwelded defects in the interface. When the sintering temperature is within the scope of 1400-1600℃, W/TZM joints shear strength increases with the increase of sintering temperature. The shear strength of the joints obtained by rapid cooling is higher than that of the joints with slow cooling at the same sintering temperature. When the sintering temperature is 1600℃ and taken rapid cooling, the shear strength of joint is higher than that of the other samples, the maximum shear strength is 159.7 MPa.
Ni-Ag nanoparticles were prepared by DC arc-discharge plasma method, using the compacted micron-sized powders of Ni and Ag as the raw targets. The content of Ni in Ni-Ag nanoparticles samples was 70.54%(mass fraction). The particles' sizes were mainly in range of 30-70 nm. The results indicate that the resistivity of compressed Ni-Ag powders has low resistivity of 5.36×10-5 Ω·cm. The conductive ink is prepared by using of Ni-Ag nanoparticles (70.54% of Ni) as the additive. An ink line is drew on a polyimide sheet matrix, subsequently dried and sintered at elevated temperatures under protective atmosphere of Ar. The electrical property testing results of sintering samples show dense structure and good conductivity over 300℃. It is indicated that the resistivity of the sintered sample declines with the temperature rising, i.e. 1.83×10-3 Ω·cm at sintering temperature of 450℃ which is much lower than that of the ink line of pure Ni nanoparticles.
The variation in phase parameter and mechanical properties of specific positions (gauge and grip) of the P92 steel specimens tested at 625℃ and 110-180 MPa was studied by SEM-BSE, EDS, EBSD, TEM and multiphase separation technology (MPST). The results show that highly stressed regions near fracture surface in the gauge portion are of higher volume fractions of M23C6 carbide and Laves phase, higher coarsening/widening trend of M23C6 carbides/martensite laths, and lower concen-tration of Cr and W elements and smaller percentage of low angle grain boundaries in the matrix as compared to a stress-free condition at the gripped end. It is evident that all these changes lead to the transformation of martensite into ferrite and hardness decreasing. It is indicated through this study that the changes in microstructure and mechanical properties of the stress-free sample cannot actually reflect the real changes of the samples stressed at the same aging temperature and time.
Hollow polymer spheres (HPS) were firstly prepared through a hydrothermal method using phenolic precursor and styrene as starting materials.HPS was treated with phosphorous trichloride via a Friedel-Crafts reaction to obtain phosphorus-containing cross-linked polymer.After carbonization and KOH activation, P-doped hollow porous carbon spheres (AP-HCS) were prepared.FT-IR, TG, SEM, TEM, Raman, BET and XPS, and so on, were used to characterize the composition, structure and morphology of polymer and carbon spheres.The capacitance performance was also tested in 1 mol/L H2SO4electrolyte.The results show that AP-HCS has specific surface area of 2177 m2/g, exhibits good capacitance performance of 288 F/g at the current density of 1 A/g.After charging and discharging for 5000 times at the current density of 5 A/g, the 88.9% capacity is retained, showing good capacitance performance.
Lithium-rich manganese-based materials have attracted much attention because of their high charge-discharge capacity. In order to solve the problems of low coulombic efficiency, poor cycling performance and poor rate capability, lithium-ion conductor Li2ZrO3 with three-dimensional Li+ channel was employed to coat lithium-rich manganese-based cathode material Li[Li0.2Ni0.2Mn0.6]O2. According to the structure and morphological analysis, different amounts of Li2ZrO3 were successfully coated on the surface of the sample. When the thickness of the coating layer is 3 nm (1% coating amount, mass fraction), the electrochemical performance of the composite material is significantly improved. The first discharge specific capacity is 271.5 mAh·g-1 and the first coulombic efficiency is 72.4%. The first irreversible capacity loss is obviously reduced. The discharge specific capacity at 0.5 C is 191.5 mAh·g-1 and the capacity retention is 89.5%. The specific capacity at 5 C is 75 mAh·g-1 and the rate performance is improved. The results show that a uniform thickness of Li2ZrO3 coating layer can form a core-shell structure on the surface of the sample to make the sample more stable. It can reduce surface side reactions and prevent the formation of thicker SEI films. All of these results benefit from the high conductivity, high electrochemical stability and good lithium ion conductivity of Li2ZrO3 coating layer.
The cobalt hydroxides were in situ synthesized via hydrothermal method with carbon fiber derived from cotton as substrate using cobalt nitrate as cobalt precursor and hexamethylenetetramine as precipitation agent. The morphology and structure of the materials were characterized by scanning electron microscope(SEM), X-ray diffraction(XRD) and IR spectra, respectively. The electroch-emical performance of the samples was analyzed by electrochemical tests such as cyclic voltammetry, galvanostatic charge and discharge and AC impedance. The XRD and SEM results show that, the obtained cobalt hydroxide grown in situ on the carbon fiber substrate is flower-like and α-phase. The electrochemical performance tests display that the specific capacitance of the flower-like cobalt hydroxide is 650 F/g at the current density of 1 A/g, and the retention rate of 67% can be kept with the current density of 10 A/g. The above results illustrate that the flower-like cobalt hydroxide has excellent electrochemical performance, mainly due to its unique structure and morphology, which significantly improves the stability of the electrode material, the diffusion rate of ions and the transport efficiency of electrons.
The spherical and dense alumina nanoparticles were used to prepare alumina microcrystalline ceramics. The effect of granulation and sintering parameters on the microstructure and mechanical properties of the ceramics was studied. The results show that fine green body can be obtained with the addition of 0.8% (mass fraction) PVA, and the density of green body can also be improved. With the increase of sintering temperature from 1400℃ to 1550℃, the density is increased from 74.1% to 97.5%, while the grain size of the ceramics is only increased gradually from 0.6 μm to 1.4 μm owing to the stable spherical shape and the uniformly packed pores. With the increase of holding time from 30 min to 120 min at 1550℃, the porosity is decreased from 4.8% to 0.4%, and the grain size is then increased from 1.2 μm to 2.7 μm. Besides, the sintering activation energy of the employed spheres is 788 kJ/mol, which proves that the particles are inactive during earlier and medium stage of sintering, and the spheres are benefit to obtain microcrystalline ceramics. The ceramic sintered at 1550℃ for 90 min has a density of 98.9%, an average grain size of 1.6 μm, a hardness of 26.4 GPa and a bending strength of 574 MPa.
In the application of ceramic 3D printing technology based on extrusion process, it was found that different extrusion methods have important influence on the controllability of the discharging speed, which leads to obvious difference in the surface quality and the success rate of printing samples. For this problem, two kinds of extruding devices with plunger and screw were selected. Under the basic conditions of Bingham viscoelastic fluid slurry and 0.6 mm nozzle diameter, the 3D printing effect of the two kinds of equipment was compared and analyzed by combining the printing test data and the simulation discharge velocity curve. The results show that the discharging speed of screw extrusion method decreases below 30% than that of the original in 0.03 s, the time required to reach this discharge speed by the plunger extrusion method is 2.4 s. The discharge amount of the plunger extrusion method is 3 times that of the screw extruder method in 0.27 s after the slurry feed is stopped. The flow field analysis shows that the different driving principle of the two extrusion methods under viscoelastic slurry condition is the main reason for this difference.
Photocurable coal-series kaolin slurry was prepared based on photocurable resin system. The rheological properties of the slurry were characterized by a rheometer. The effect of dispersant and plasticizer addition on the rheological properties of the slurry was studied. The results show that oleic acid as a dispersant has the effect of reducing the viscosity of the slurry. When the mass fraction of oleic acid added is 1% of the kaolin powder, the viscosity of the slurry is the lowest, while the viscosity of the 40%(volume fraction) kaolin slurry is 49.56 Pa·s. Adding plasticizer PEG-300 can further reduce the viscosity of the slurry. The viscosity of the slurry decreases with the addition of plasticizer. When the plasticizer is added in the mass fraction of 20% of the photosensitive resin, the viscosity of the slurry decreases to 19.77 Pa·s, at which the requirement for good recoating is well met. The slurry with optimized rheological properties is formed in a stereolithography apparatus. After debinding and sintering, kaolin ceramics with complex shape are obtained.
Hot dip plating was used to prepare Pb40Sn60 and Pb37Sn63 low melting point alloy coatings on copper wires to improve the properties of weldability and corrosion resistance, and the microstructure and phase composition were examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Resistivity, mechanical properties and corrosion resistance of the alloy were investigated by the tests of electrical resistivity, tensile and neutral salt spray. The results show that the Pb40Sn60 and Pb37Sn63 alloy coatings are all composed of α phase and β phase, the resistivity of PbSn alloy coatings are all higher than that of copper substrate, the resistivity of Pb40Sn60 alloy coating is 2.6832×10-3Ω·m and Pb37Sn63 alloy coating is 2.5929×10-3 Ω·m. Hardness, strength and plasticity of copper after hot dipped PbSn alloy coatings all decrease, surface hardness of Pb40Sn60 and Pb37Sn63 alloy coatings is respectively 13.4HV0.2 and 12.6HV0.2, tensile strength is respectively 193 MPa and 180 MPa, elongation is respectively 35% and 37%. PbSn alloy coatings on copper wire have good properties of conductivity, mechanical and corrosion resistance. With the decrease of Pb content or the increase of Sn content, the relative amount of α phase is reduced and relative amount of β phase increases in the PbSn alloy coating, resistivity, hardness and strength are all reduced, plasticity increases slightly, its corrosion resistance is enhanced. The corrosion rate of Pb40Sn60 alloy coatings is higher than that of Pb37Sn63 alloy coatings, the corrosion rate of Pb40Sn60 alloy coating is 2.44×10-2 g·cm-2·a-1 and Pb37Sn63 alloy coatings is 3.65×10-3 g·cm-2·a-1, and the corrosion resistance of Pb40Sn60 alloy coatings is relatively poor. The corrosion resistance of α phase is poor than that of β phase, the corrosion degree of α phase is more serious than that of β phase in PbSn alloy coating.
The Cu2ZnSnS4 thin film has advantages of naturally abundant elements and high absorption coefficient, which make it an ideal absorber material for thin film solar cell. The periodic metal precursors of Cu2ZnSnS4 were deposited by magnetron sputtering. Then, the Cu2ZnSnS4 thin films were fabricated by two-step sulfurization treatment of the periodic precursors. The effects of the first step sulfurization (pre-sulfurization) on the properties of Cu2ZnSnS4 thin films were studied. The results indicate that the pre-sulfurization treatment can promote the sulfurization reactions of periodic precursors. The crystallinities of Cu2ZnSnS4 thin films with pre-sulfurization are superior to that of Cu2ZnSnS4 thin film without pre-sulfurization. When the pre-sulfurization temperature is 350℃, the increase of pre-sulfurization time is beneficial to the sulfurization reactions of precursors and inhibition of Sn-loss. However, an overlong pre-sulfurization time leads to easy formations of secondary phases in the final thin films, which affect the properties of Cu2ZnSnS4 thin films. The pre-sulfurization temperature of 350℃ and pre-sulfurization time of 10 min can get the best crystallinity of Cu2ZnSnS4 thin film with Cu-poor and Zn-rich composition and void-free surface.
The surface treatment was carried out on the surface of materials of A473M martensitic stainless steel axle sleeve by rolling technology, aiming to investigate the effect on its mechanical properties. The surface morphology and roughness, residual stress, microhardness, tensile and fatigue property were systematically studied using the SEM, white light interferometer, X-ray diffractometer, microhardness tester, EBSD, tensile tester and fatigue tester. The results show that the surface roughness of rolling specimen reduces significantly, which is about 1/5 of that of turning surface. The residual compression stress is induced near surface by rolling processing, the maximum value can reach up to 946 MPa and the residual compression stress decreases along with the depth. The thickness of the residual compression stress layer is about 200 μm. In addition, the rolling surface microhardness can be improved by 30% compared with that of turning surface and the hardened layer can be about 200 μm. As for mechanical properties, the tensile strength, yield strength and elongation of rolling specimens increase about 40%, 22% and 8% respectively compared with that of turning specimens. The fatigue life increases from 5.4×104 cycles to 1×107 cycles after rolling processing. The mechanical properties of the rolled material significantly improve, and the fatigue life significantly increases.
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