Polyether ether ketone(PEEK)-based continuous glass fiber reinforced thermoplastic composite offers advantages such as high strength,electrical insulation,and heat insulation.Parts manufactured using this composite an...Polyether ether ketone(PEEK)-based continuous glass fiber reinforced thermoplastic composite offers advantages such as high strength,electrical insulation,and heat insulation.Parts manufactured using this composite and 3D printing have promising applications in aerospace,automobile,rail transit,etc.In this paper,a high-temperature melt impregnation method was used to successfully prepare the 3D printing prepreg filaments of the aforementioned composite.In the FDM 3D printing equipment,a nozzle of high thermal conductivity and wear-resistant copper alloy and a PEEK-based carbon fiber thermoplastic composite build plate with uniform temperature control were innovatively introduced to effectively improve the quality of 3D printing.The porosity of the 3D printed samples produced from the composite prepreg filament was analyzed under different printing parameters,and the mechanical properties and fracture mechanism of the printed parts were studied.The results show that the printing layer thickness,printing speed,printing temperature and build plate temperature have varying effects on the porosity of printed parts,which in turn affects tensile strength and the interlaminar shear strength(ILSS).When the printing layer thickness is 0.4 mm,printing speed is 2 mm/s,nozzle temperature is 430℃ and build plate temperature is 150℃,the tensile strength and ILSS of the composite printed parts reach their maximum values of 463.76 and 24.95 MPa,respectively.Microscopic analysis of the fracture morphology of the tensile specimens reveals that the 3D printed CGF/PEEK composite sample has three types of fracture mode,which are single filament bundle fracture,fracture mode of delamination,and fracture failure of the sample at the cross-section.The essence of the above three kinds of fracture mode is the difference of the interface bonding force of 3D printed CGF/PEEK composites.The fracture failure at the cross-section is that the continuous glass fibers in the composite are pulled out until they break,which is the main form of the failure of the composite under tensile load.The interfacial region of the composite is prone to microscopic defects such as voids and delamination during 3D printing,which become the most vulnerable link of the composite.Understanding the relationship between voids and fracture behavior lays a foundation for defect suppression and performance improvement of subsequent printed parts.展开更多
The refining effect and mechanism of Sb on Mg2Si and the microstructure of the matrix were investigated.The results indicate that there are Mg3Sb2 particles in the composites with the addition of Sb,and Mg3Sb2 can pro...The refining effect and mechanism of Sb on Mg2Si and the microstructure of the matrix were investigated.The results indicate that there are Mg3Sb2 particles in the composites with the addition of Sb,and Mg3Sb2 can promote the formation of fine polygonal type Mg2Si by providing nucleation site.Meanwhile,the grain size of Sb modified alloy is finer than that of the matrix. The improved microstructure results in the improvement of mechanical properties.The ultimate tensile strength is increased by 12.2%with the addition of 0.8%Sb.展开更多
It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to ful...It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to fully densify the AIN/BN composites in this work. Microstructure, mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated. The results show that the microstructure of composites is fine and homogenous, and the AIN/BN composites exhibit high mechanical properties. To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites, a heat treating methodology was introduced through gas pressure sintering （GPS）. This processing was significantly beneficial to enhancing the thermal conductivity of the specimen. The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.展开更多
The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially ...The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially impregnating sisal fibres(S)with organosolv lignin(LO),organosolv lignin and glutaraldehyde(LOG),Kraft lignin(LK)and Kraft lignin and glutaraldehyde(LKG).The fibre modifications were verified by FTIR-ATR and SEM analyzes,and the presence of lignin on the surface of the fibres was evidenced,confirming the effectiveness of the treatments.The mechanical,thermal(by TGA)and water absorption properties of the fibres before and after the modifications were also investigated.After treatment,the modified fibres presented an expressive reduction of the water absorption and did not show significant changes in the mechanical properties when compared with the natural unmodified sisal fibre(SNAT).It was verified an increase in the thermal stability of the treated fibres which can be attributed to the insertion of lignin on the fibres.To evaluate the performance of the fibres in the cementitious composites,cement plates(CP)were produced with different treated fibres(CP-SLOG,CP-SLO,CP-SLKG,CP-SLK)and fibres without treatment(CP-SNAT).The composites were evaluated concerning to the water absorption,porosity and mechanical properties.The fractured regions were also investigated by SEM.All composites prepared showed similar values of absorption and porosity indexes.From the mechanical properties,the composites prepared with modified fibres showed a significant increase in the modulus of rupture and modulus of elasticity compared with CP-SNAT,while toughness was similar to all samples.From the SEM images,it was observed that the modified fibres immersed in the cementitious plates showed no degradation,indicating that the impregnation of lignin acted as a protective agent of the fibres.Therefore,the treatments of the fibres with lignin led to a significant improvement in the properties of the composites generating a treatment with potential for industrial application.展开更多
A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experime...A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experimental data in a SiCw/Al-Li T6 composite and the published experimental data on different SiCw/Al T6 composites and also compared with the previous shear lag models and the other theoretical models.展开更多
We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-mo...We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.展开更多
To achieve simultaneous improvement in wear resistance and corrosion resistance,we propose a novel strategy to successfully develop Mg matrix composites containing blocky primary Mg_(2)Si with small size instead of un...To achieve simultaneous improvement in wear resistance and corrosion resistance,we propose a novel strategy to successfully develop Mg matrix composites containing blocky primary Mg_(2)Si with small size instead of undesirable dendrite shape and large size.The tribological and corrosion behavior of Mg_(2)Si/AZ91 unmodified and modified with 2.0wt.%Sb was subsequently and systematically investigated.The results show that Sb addition can significantly modify the morphology of primary Mg_(2)Si to blocky polygon with smaller size of 12-25μm,but has less effect onα-Mg grain size.Compared with unmodified composite,Sb modified Mg_(2)Si/AZ91 composite has higher Brinell hardness and nearly unchanged microhardness of the matrix.Sb modified composite exhibits a 26%lower wear loss than unmodified composite suggesting the greatly improved wear resistance.Microstructure analyses indicate that the main wear mechanism of composites is dominated by abrasive wear,and Sb addition can decrease the width and depth of grooves,resulting in a weakened abrasive wear behavior.Additionally microcracks initiation on Sb modified Mg_(2)Si particles can be restricted during the sliding friction process because of higher toughness and blocky polygonal shape induced by Sb doping,which is responsible for the improved wear resistance.Interestingly,Sb modified Mg_(2)Si/AZ91composite also demonstrates a superior corrosion resistance than unmodified composite due to the decrease of calculated corrosion rate from1.57 mm/y to 0.74 mm/y,reduced by 52.8%.Such improvement is closely related to the reduced susceptibility to micro-galvanic corrosion,which is attributed to the reduced volta potential difference of Mg_(2)Si relative to the Mg matrix,from 365 mV to 210 mV.展开更多
Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix...Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix interface apparently decreased with decreasing a pore diameter,and consequently a new idea of microspace modification concept was proposed for controllingfracture behavior of C/C composites. Four types of C/C composites with various pore structureswere fabricated by hot-pressing, and their fracture behavior was investigated by three pointbending tests. The fracture behavior of the C/C composites was changed from brittle one topseudo ductile one with decreasing the pore diameter. This result supported the validity of themicrospace modification concept proposed in this paper.展开更多
The effects of RE, V, Ti and B on the microstructure and properties of high chromium cast iron containing 3% molybdenum under as-cast and heat treatment conditions were investigated with the method of comparing experi...The effects of RE, V, Ti and B on the microstructure and properties of high chromium cast iron containing 3% molybdenum under as-cast and heat treatment conditions were investigated with the method of comparing experiments. The results show that with the increase of RE content, the primary austenite of high chromium cast iron is obviously refined. The morphology of carbide is changed from netlike and lath to small multiangular isolated blocks or massive blocks, the isolated degree of carbide is improved obviously, and the size is significantly refined. The addition of V and B into high chromium cast iron can refine the microstmcture, reduce coarse columnar crystals and make the carbide smaller and uniform. Through composite modification with RE, V, Ti and B, the hardness, wear resistance and impact toughness of high chromium cast iron are increased conspicuously. After heat treatment, the hardness of high chromium iron is increased significantly, but the toughness and wear resistance do not show great improvement.展开更多
Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistanc...Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistance,and biocompatibility.PEEK and its composites have found extensive applications across various fields,including machinery,aerospace,military equipment,electronics,and biomedicine,positioning themselves as promising substitutes for traditional metal structures.Nevertheless,achieving optimal performance and functional molding of PEEK and its composites presents a formidable challenge,given their inherent characteristics,such as semi-crystallinity,high melting temperature,heightened viscosity,low dielectric coefficient,and hydrophobic properties.In this paper,we present a comprehensive review of the molding methods and processes of PEEK and its composites,including extrusion molding,hot compression molding,injection molding,and 3D printing.We also introduce typical innovative applications within the fields of mechanics,electricity,and biomedicine while elucidating methodologies that leverage the distinctive advantages of PEEK and its composites.Additionally,we summarize research findings related to manipulating the properties of PEEK and its composites through the optimization of machine parameters,process variables,and material structural adjustments.Finally,we contemplate the prevailing development trends and outline prospective avenues for further research in the advancement and molding of PEEK and its composites.展开更多
To improve the flame resistance of polypropylene(PP)/carbon fiber(CF)composite materials,triazine char-forming agent(TCA)was compounded with ammonium polyphosphate(APP)or modified APP(CS-APP)in a 2:1 ratio to prepare ...To improve the flame resistance of polypropylene(PP)/carbon fiber(CF)composite materials,triazine char-forming agent(TCA)was compounded with ammonium polyphosphate(APP)or modified APP(CS-APP)in a 2:1 ratio to prepare intumescent flame retardant(IFR)and the modified intumescent flame retardant(CS-IFR)in this paper.Flame retardancy and thermal degradation behaviors of the composites modified by IFR and CS-IFR were characterized by Fourier Transform Infrared(FTIR),contact angle measurement,oxygen index(OI),vertical burning tests(UL-94),thermogravimetric analyer(TGA),and thermogravimetric analyzer coupled with Fourier transform infrared(TG-FTIR).It was found that 25.0 phr of IFR and 24.0 phr of CS-IFR could improve the LOI value of PP/CF composites to 28.3%and 28.9%,respectively.At the same time,a UL-94 V-0 rating was achieved.The experimental results show that the IFR and CS-IFR prepared could effectively improve the flame retardancy and thermostability of PP/CF composites,and they would greatly expand the application range of PP/CF composite materials.展开更多
In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase...In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase.Microstructure and morphology of Mg_(2)Si were observed by synchrotron X-ray to-mography and TEM,and first-principles calculations were also performed to testify the effect of Eu mod-ification.Results show that the size of primary Mg_(2)Si particles decreases and eutectic Mg_(2)Si phase trans-forms from lamellar to fibrous by Eu addition.After heat treatment,sharp angles of primary Mg_(2)Si par-ticles passivate,and eutectic Mg_(2)Si dissolves and appears to be short dot-like.Meanwhile,nano-sizedβ"phase precipitates in the matrix.For morphology of Mg_(2)Si with Eu modification,TEM results show that Eu impedes the growing of Mg_(2)Si,which is verified by first-principles calculations that Eu atom preferentially adsorbs on Mg_(2)Si{100}facet.The adsorption and suppression growing of Mg_(2)Si transform the morphology of Mg_(2)Si and thus improve the elongation.UTS and elongation of the heat-treated Eu modified composites are 281 MPa and 8.4%,which improved 81%and 200%compared to the as-cast Al-15%Mg_(2)Si composite.The strengthening mechanism mainly results from precipitation strengthening of nano-sizedβ"precipitates in the heat-treated composite.展开更多
Al2O3 ceramic powder was applied to modify the large pores defects on the surface of the porous metal Ti support,in situ oxidation method was a convenient method to prepare defect free ceramic/Ti composite membranes o...Al2O3 ceramic powder was applied to modify the large pores defects on the surface of the porous metal Ti support,in situ oxidation method was a convenient method to prepare defect free ceramic/Ti composite membranes on this basis.In situ oxidation conditions experimental results show that the best condition for preparing the TiO2-Al2O3/Ti composite membrane is under 800°C for 2 h,and the microstructure and pore sizes of the TiO2-Al2O3/Ti composite membranes are affected obviously.The thickness and composition of the TiO2/Ti composite membranes are determined by SEM and XRD completely.The pore size distribution of the composite membrane is measured by bubble pressure method,the most probable aperture is about 3.12μm,while the average pore size of defect free TiO2-Al2O3/Ti is about 3.23μm.After ultrasonic treatment,the slight weight change of membranes reveals no observable change,which indicates that TiO2-Al2O3/Ti composite membranes maintain a good stability.展开更多
Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance...Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy（SEM） and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2 wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.展开更多
The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive...The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...展开更多
This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of prim...This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt%resulted in a loss of modification, possibly due to the formation of Al8 MgB iS i4 compound before the precipitation of the primary Mg2 Si. Additionally, the structure of the pseudo-eutectic Mg2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al5 Fe Si（β）, Al2Cu（θ） and Al5Cu2Mg8Si6（Q） intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg2 Si particles.展开更多
Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface o...Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface of SiCp and the interface between SiCp and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO2-C on the surface of SiCp and Al at the SiCp-Al interface at 1 050 ℃. Besides, the process of Na3 AlF6 melting, dissolving and then contacting with Al2 O3 formed the NaF-AlF3-Al2 O3 system, which generated OAlF2-, promoting the dessolution of Al2 O3 film on the surface of Al powder. Na3 AlF6 meets the needs of chemical reaction in TiO2-C-Al system at the SiCpAl interface in the way of offering more molten Al. After 0.75 wt% Na3 AlF6 was added into raw materials, the whole TiO2-C film and most SiO2 film were destroyed and the interfacial bonding between SiCp and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al4 C3 phase formed in the system. At this time, the flexure strength and density of samples presented optimal values, reaching up to 106.5 MPa and 90.77% respectively.展开更多
A new type composite of high efficiency sound attenuation was cured. The superfine tungsten powder, plasticizerand stabilizer are added into the PVC resin and blended in the mixing chamber of a HAAKE rheometer. The ef...A new type composite of high efficiency sound attenuation was cured. The superfine tungsten powder, plasticizerand stabilizer are added into the PVC resin and blended in the mixing chamber of a HAAKE rheometer. The effect ofthe filler modification is considered in the composite cure. The properties of modified composite and unmodified oneare studied by SEM morphology viewing, acoustic and mechanical measurement. The test results indicate that thereason of the better soundproof and mechanical properties is the particle uniform dispersion and stronger adhesion.展开更多
Organic dyes based hybrid organic-inorganic luminescent nanomaterials with high quantum efficiency, good physical or chemical stability, and favorable biocompatibility, have attracted growing attention recently becaus...Organic dyes based hybrid organic-inorganic luminescent nanomaterials with high quantum efficiency, good physical or chemical stability, and favorable biocompatibility, have attracted growing attention recently because of their important applications in the areas of biomedical imaging, chemical sensors, and light-emitting diodes(LEDs). Nevertheless, conventional fluorescence molecules suffer from aggregation-caused quenching(ACQ) when they are doped into inorganic nanomaterials. Aggregation-induced emission(AIE) is an abnormal and intriguing fluorescent phenomenon that has aroused increasing interest for various applications especially in biomedical fields. Compared with conventional organic dyes, the AIE-active molecules will emit more intense fluorescence in their aggregates or solid states. It provides an elegant route to overcome the drawbacks of conventional organic molecules. Over the past few decades, the fabrication and surface modification of various organic-inorganic luminescent composites doped with AIE-active molecules have been reported. Therefore, it is highly desirable to summarize these advances. In this review, recent advances and progress in constructing various AIEgens-doped organic-inorganic hybrid nanocomposites and their subsequent surface modification were summarized. We hope this review could further promote the research of AIE-active functional materials.展开更多
Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium di...Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium dioxide particles, the titanium dioxide particles were surface-modified with a silicane coupling agent, methacryloylpropyltrimethoxysilicane. Polymer encapsulation in the presence of either modified-titanium dioxide particles or unmodified-titanium dioxide particles was carried out by dispersion polymerization of styrene, divinylbenzene in ethanol medium with polyvinylpyrroliclone as stabilizer, and 2, 2＇-azobis（isobutyronitrile） as initiator. The modified-titanium dioxide was analyzed with Fourier-transform infrared spectroscopy（FTIR）, UV-Vis spectrophotometer, thermo-gravimetric analysis and transmission microscope. The polymer encapsulation of modified-titanium dioxide and unmodified-titanium dioxide particles was confirmed with FTIR and transmission electron microscope. Results show that compared with unmodified-titanium dioxide, modified-titanium dioxide is more suitable for preparing inorganic core/orclanic shell composites.展开更多
基金supported by the National Key Research and Development Program Project of China(Grant No.2018YFB1106700).
文摘Polyether ether ketone(PEEK)-based continuous glass fiber reinforced thermoplastic composite offers advantages such as high strength,electrical insulation,and heat insulation.Parts manufactured using this composite and 3D printing have promising applications in aerospace,automobile,rail transit,etc.In this paper,a high-temperature melt impregnation method was used to successfully prepare the 3D printing prepreg filaments of the aforementioned composite.In the FDM 3D printing equipment,a nozzle of high thermal conductivity and wear-resistant copper alloy and a PEEK-based carbon fiber thermoplastic composite build plate with uniform temperature control were innovatively introduced to effectively improve the quality of 3D printing.The porosity of the 3D printed samples produced from the composite prepreg filament was analyzed under different printing parameters,and the mechanical properties and fracture mechanism of the printed parts were studied.The results show that the printing layer thickness,printing speed,printing temperature and build plate temperature have varying effects on the porosity of printed parts,which in turn affects tensile strength and the interlaminar shear strength(ILSS).When the printing layer thickness is 0.4 mm,printing speed is 2 mm/s,nozzle temperature is 430℃ and build plate temperature is 150℃,the tensile strength and ILSS of the composite printed parts reach their maximum values of 463.76 and 24.95 MPa,respectively.Microscopic analysis of the fracture morphology of the tensile specimens reveals that the 3D printed CGF/PEEK composite sample has three types of fracture mode,which are single filament bundle fracture,fracture mode of delamination,and fracture failure of the sample at the cross-section.The essence of the above three kinds of fracture mode is the difference of the interface bonding force of 3D printed CGF/PEEK composites.The fracture failure at the cross-section is that the continuous glass fibers in the composite are pulled out until they break,which is the main form of the failure of the composite under tensile load.The interfacial region of the composite is prone to microscopic defects such as voids and delamination during 3D printing,which become the most vulnerable link of the composite.Understanding the relationship between voids and fracture behavior lays a foundation for defect suppression and performance improvement of subsequent printed parts.
基金Project（50765005）supported by the National Natural Science Foundation of China
文摘The refining effect and mechanism of Sb on Mg2Si and the microstructure of the matrix were investigated.The results indicate that there are Mg3Sb2 particles in the composites with the addition of Sb,and Mg3Sb2 can promote the formation of fine polygonal type Mg2Si by providing nucleation site.Meanwhile,the grain size of Sb modified alloy is finer than that of the matrix. The improved microstructure results in the improvement of mechanical properties.The ultimate tensile strength is increased by 12.2%with the addition of 0.8%Sb.
基金the National Natural Science Foundation of China(No.50232020)Wuhan University of Technology(No.471-38650199)
文摘It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to fully densify the AIN/BN composites in this work. Microstructure, mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated. The results show that the microstructure of composites is fine and homogenous, and the AIN/BN composites exhibit high mechanical properties. To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites, a heat treating methodology was introduced through gas pressure sintering （GPS）. This processing was significantly beneficial to enhancing the thermal conductivity of the specimen. The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.
文摘The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially impregnating sisal fibres(S)with organosolv lignin(LO),organosolv lignin and glutaraldehyde(LOG),Kraft lignin(LK)and Kraft lignin and glutaraldehyde(LKG).The fibre modifications were verified by FTIR-ATR and SEM analyzes,and the presence of lignin on the surface of the fibres was evidenced,confirming the effectiveness of the treatments.The mechanical,thermal(by TGA)and water absorption properties of the fibres before and after the modifications were also investigated.After treatment,the modified fibres presented an expressive reduction of the water absorption and did not show significant changes in the mechanical properties when compared with the natural unmodified sisal fibre(SNAT).It was verified an increase in the thermal stability of the treated fibres which can be attributed to the insertion of lignin on the fibres.To evaluate the performance of the fibres in the cementitious composites,cement plates(CP)were produced with different treated fibres(CP-SLOG,CP-SLO,CP-SLKG,CP-SLK)and fibres without treatment(CP-SNAT).The composites were evaluated concerning to the water absorption,porosity and mechanical properties.The fractured regions were also investigated by SEM.All composites prepared showed similar values of absorption and porosity indexes.From the mechanical properties,the composites prepared with modified fibres showed a significant increase in the modulus of rupture and modulus of elasticity compared with CP-SNAT,while toughness was similar to all samples.From the SEM images,it was observed that the modified fibres immersed in the cementitious plates showed no degradation,indicating that the impregnation of lignin acted as a protective agent of the fibres.Therefore,the treatments of the fibres with lignin led to a significant improvement in the properties of the composites generating a treatment with potential for industrial application.
文摘A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experimental data in a SiCw/Al-Li T6 composite and the published experimental data on different SiCw/Al T6 composites and also compared with the previous shear lag models and the other theoretical models.
基金Funded by Changsha Natural Science Foundation(No.kq2208270)。
文摘We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.
基金Natural Science Basic Research Program of Shaanxi(2022JQ-331)Fundamental Research Funds for the Central Universities(xjh03202101503)+1 种基金China Postdoctoral Science Foundation(2021M692518)National Key Research and Development Program of China(2021YFB3701204)。
文摘To achieve simultaneous improvement in wear resistance and corrosion resistance,we propose a novel strategy to successfully develop Mg matrix composites containing blocky primary Mg_(2)Si with small size instead of undesirable dendrite shape and large size.The tribological and corrosion behavior of Mg_(2)Si/AZ91 unmodified and modified with 2.0wt.%Sb was subsequently and systematically investigated.The results show that Sb addition can significantly modify the morphology of primary Mg_(2)Si to blocky polygon with smaller size of 12-25μm,but has less effect onα-Mg grain size.Compared with unmodified composite,Sb modified Mg_(2)Si/AZ91 composite has higher Brinell hardness and nearly unchanged microhardness of the matrix.Sb modified composite exhibits a 26%lower wear loss than unmodified composite suggesting the greatly improved wear resistance.Microstructure analyses indicate that the main wear mechanism of composites is dominated by abrasive wear,and Sb addition can decrease the width and depth of grooves,resulting in a weakened abrasive wear behavior.Additionally microcracks initiation on Sb modified Mg_(2)Si particles can be restricted during the sliding friction process because of higher toughness and blocky polygonal shape induced by Sb doping,which is responsible for the improved wear resistance.Interestingly,Sb modified Mg_(2)Si/AZ91composite also demonstrates a superior corrosion resistance than unmodified composite due to the decrease of calculated corrosion rate from1.57 mm/y to 0.74 mm/y,reduced by 52.8%.Such improvement is closely related to the reduced susceptibility to micro-galvanic corrosion,which is attributed to the reduced volta potential difference of Mg_(2)Si relative to the Mg matrix,from 365 mV to 210 mV.
文摘Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix interface apparently decreased with decreasing a pore diameter,and consequently a new idea of microspace modification concept was proposed for controllingfracture behavior of C/C composites. Four types of C/C composites with various pore structureswere fabricated by hot-pressing, and their fracture behavior was investigated by three pointbending tests. The fracture behavior of the C/C composites was changed from brittle one topseudo ductile one with decreasing the pore diameter. This result supported the validity of themicrospace modification concept proposed in this paper.
基金supported by the Harbin Scientific Research Fund for Young Scholars (No.2005AFQXJ030)the Harbin Science and Technology Project (No.2002AA5CG026)the Foundation of Heilong-jiang Educational Committee (No.11511051)
文摘The effects of RE, V, Ti and B on the microstructure and properties of high chromium cast iron containing 3% molybdenum under as-cast and heat treatment conditions were investigated with the method of comparing experiments. The results show that with the increase of RE content, the primary austenite of high chromium cast iron is obviously refined. The morphology of carbide is changed from netlike and lath to small multiangular isolated blocks or massive blocks, the isolated degree of carbide is improved obviously, and the size is significantly refined. The addition of V and B into high chromium cast iron can refine the microstmcture, reduce coarse columnar crystals and make the carbide smaller and uniform. Through composite modification with RE, V, Ti and B, the hardness, wear resistance and impact toughness of high chromium cast iron are increased conspicuously. After heat treatment, the hardness of high chromium iron is increased significantly, but the toughness and wear resistance do not show great improvement.
基金supported by the National Key R&D Program of China(No.2022YFC2401903)the“Pioneer”and the“Leading Goose”R&D Program of Zhejiang Province(No.2023C01170)+1 种基金the National Natural Science Foundation of China(No.52205424)the Key Project of Science and Technology Innovation 2025 of Ningbo(No.2023Z029),China.
文摘Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistance,and biocompatibility.PEEK and its composites have found extensive applications across various fields,including machinery,aerospace,military equipment,electronics,and biomedicine,positioning themselves as promising substitutes for traditional metal structures.Nevertheless,achieving optimal performance and functional molding of PEEK and its composites presents a formidable challenge,given their inherent characteristics,such as semi-crystallinity,high melting temperature,heightened viscosity,low dielectric coefficient,and hydrophobic properties.In this paper,we present a comprehensive review of the molding methods and processes of PEEK and its composites,including extrusion molding,hot compression molding,injection molding,and 3D printing.We also introduce typical innovative applications within the fields of mechanics,electricity,and biomedicine while elucidating methodologies that leverage the distinctive advantages of PEEK and its composites.Additionally,we summarize research findings related to manipulating the properties of PEEK and its composites through the optimization of machine parameters,process variables,and material structural adjustments.Finally,we contemplate the prevailing development trends and outline prospective avenues for further research in the advancement and molding of PEEK and its composites.
基金Funded by the Program for New Century Excellent Talents in University of Ministry of Education of China(NCET-12-0912)。
文摘To improve the flame resistance of polypropylene(PP)/carbon fiber(CF)composite materials,triazine char-forming agent(TCA)was compounded with ammonium polyphosphate(APP)or modified APP(CS-APP)in a 2:1 ratio to prepare intumescent flame retardant(IFR)and the modified intumescent flame retardant(CS-IFR)in this paper.Flame retardancy and thermal degradation behaviors of the composites modified by IFR and CS-IFR were characterized by Fourier Transform Infrared(FTIR),contact angle measurement,oxygen index(OI),vertical burning tests(UL-94),thermogravimetric analyer(TGA),and thermogravimetric analyzer coupled with Fourier transform infrared(TG-FTIR).It was found that 25.0 phr of IFR and 24.0 phr of CS-IFR could improve the LOI value of PP/CF composites to 28.3%and 28.9%,respectively.At the same time,a UL-94 V-0 rating was achieved.The experimental results show that the IFR and CS-IFR prepared could effectively improve the flame retardancy and thermostability of PP/CF composites,and they would greatly expand the application range of PP/CF composite materials.
基金the National Natural Science Foun-dation of China(No.U21A2042)the National Science Fund for Distinguished Young Scholars of China(No.51825401).
文摘In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase.Microstructure and morphology of Mg_(2)Si were observed by synchrotron X-ray to-mography and TEM,and first-principles calculations were also performed to testify the effect of Eu mod-ification.Results show that the size of primary Mg_(2)Si particles decreases and eutectic Mg_(2)Si phase trans-forms from lamellar to fibrous by Eu addition.After heat treatment,sharp angles of primary Mg_(2)Si par-ticles passivate,and eutectic Mg_(2)Si dissolves and appears to be short dot-like.Meanwhile,nano-sizedβ"phase precipitates in the matrix.For morphology of Mg_(2)Si with Eu modification,TEM results show that Eu impedes the growing of Mg_(2)Si,which is verified by first-principles calculations that Eu atom preferentially adsorbs on Mg_(2)Si{100}facet.The adsorption and suppression growing of Mg_(2)Si transform the morphology of Mg_(2)Si and thus improve the elongation.UTS and elongation of the heat-treated Eu modified composites are 281 MPa and 8.4%,which improved 81%and 200%compared to the as-cast Al-15%Mg_(2)Si composite.The strengthening mechanism mainly results from precipitation strengthening of nano-sizedβ"precipitates in the heat-treated composite.
基金Projects(212006065,21666018)supported by the National Natural Science Foundation of China
文摘Al2O3 ceramic powder was applied to modify the large pores defects on the surface of the porous metal Ti support,in situ oxidation method was a convenient method to prepare defect free ceramic/Ti composite membranes on this basis.In situ oxidation conditions experimental results show that the best condition for preparing the TiO2-Al2O3/Ti composite membrane is under 800°C for 2 h,and the microstructure and pore sizes of the TiO2-Al2O3/Ti composite membranes are affected obviously.The thickness and composition of the TiO2/Ti composite membranes are determined by SEM and XRD completely.The pore size distribution of the composite membrane is measured by bubble pressure method,the most probable aperture is about 3.12μm,while the average pore size of defect free TiO2-Al2O3/Ti is about 3.23μm.After ultrasonic treatment,the slight weight change of membranes reveals no observable change,which indicates that TiO2-Al2O3/Ti composite membranes maintain a good stability.
基金Funded by the National Natural Science Foundation of China(Nos.11302054 and 11472086)the Hong Kong,Macao and Taiwan Science and Technology Cooperation Projects of Ministry of Science and Technology of China(No.2014DFH50060)+1 种基金the Natural Science Foundation of Heilongjiang Province of China(No.A2015012)the Fundamental Research Funds for the Central Universities(GK2010260256)
文摘Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy（SEM） and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2 wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.
基金the Natural Science Foundation of Jiangxi Province (No. 0650047)the Science and Technology Program of the Education Department of Jiangxi Province,China(No.GJJ08268).
文摘The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...
文摘This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt%resulted in a loss of modification, possibly due to the formation of Al8 MgB iS i4 compound before the precipitation of the primary Mg2 Si. Additionally, the structure of the pseudo-eutectic Mg2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al5 Fe Si（β）, Al2Cu（θ） and Al5Cu2Mg8Si6（Q） intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg2 Si particles.
文摘Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface of SiCp and the interface between SiCp and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO2-C on the surface of SiCp and Al at the SiCp-Al interface at 1 050 ℃. Besides, the process of Na3 AlF6 melting, dissolving and then contacting with Al2 O3 formed the NaF-AlF3-Al2 O3 system, which generated OAlF2-, promoting the dessolution of Al2 O3 film on the surface of Al powder. Na3 AlF6 meets the needs of chemical reaction in TiO2-C-Al system at the SiCpAl interface in the way of offering more molten Al. After 0.75 wt% Na3 AlF6 was added into raw materials, the whole TiO2-C film and most SiO2 film were destroyed and the interfacial bonding between SiCp and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al4 C3 phase formed in the system. At this time, the flexure strength and density of samples presented optimal values, reaching up to 106.5 MPa and 90.77% respectively.
文摘A new type composite of high efficiency sound attenuation was cured. The superfine tungsten powder, plasticizerand stabilizer are added into the PVC resin and blended in the mixing chamber of a HAAKE rheometer. The effect ofthe filler modification is considered in the composite cure. The properties of modified composite and unmodified oneare studied by SEM morphology viewing, acoustic and mechanical measurement. The test results indicate that thereason of the better soundproof and mechanical properties is the particle uniform dispersion and stronger adhesion.
基金financially supported by the National Natural Science Foundation of China (Nos. 21564006, 21561022, 21644014, 21788102, and 21865016)
文摘Organic dyes based hybrid organic-inorganic luminescent nanomaterials with high quantum efficiency, good physical or chemical stability, and favorable biocompatibility, have attracted growing attention recently because of their important applications in the areas of biomedical imaging, chemical sensors, and light-emitting diodes(LEDs). Nevertheless, conventional fluorescence molecules suffer from aggregation-caused quenching(ACQ) when they are doped into inorganic nanomaterials. Aggregation-induced emission(AIE) is an abnormal and intriguing fluorescent phenomenon that has aroused increasing interest for various applications especially in biomedical fields. Compared with conventional organic dyes, the AIE-active molecules will emit more intense fluorescence in their aggregates or solid states. It provides an elegant route to overcome the drawbacks of conventional organic molecules. Over the past few decades, the fabrication and surface modification of various organic-inorganic luminescent composites doped with AIE-active molecules have been reported. Therefore, it is highly desirable to summarize these advances. In this review, recent advances and progress in constructing various AIEgens-doped organic-inorganic hybrid nanocomposites and their subsequent surface modification were summarized. We hope this review could further promote the research of AIE-active functional materials.
基金Supported by National High Technology Research and Development Program of China (863 Program) (No. 2004AA302010) and Natural Science Foundation of Tianjin (No. 043186411) .
文摘Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium dioxide particles, the titanium dioxide particles were surface-modified with a silicane coupling agent, methacryloylpropyltrimethoxysilicane. Polymer encapsulation in the presence of either modified-titanium dioxide particles or unmodified-titanium dioxide particles was carried out by dispersion polymerization of styrene, divinylbenzene in ethanol medium with polyvinylpyrroliclone as stabilizer, and 2, 2＇-azobis（isobutyronitrile） as initiator. The modified-titanium dioxide was analyzed with Fourier-transform infrared spectroscopy（FTIR）, UV-Vis spectrophotometer, thermo-gravimetric analysis and transmission microscope. The polymer encapsulation of modified-titanium dioxide and unmodified-titanium dioxide particles was confirmed with FTIR and transmission electron microscope. Results show that compared with unmodified-titanium dioxide, modified-titanium dioxide is more suitable for preparing inorganic core/orclanic shell composites.
