In order to improve mechanical properties of TiAlNb alloys,different contents of silicon were added into Ti48Al6Nb alloy.The Ti48Al6NbxSi (x=0,0.1,0.2,0.3,0.4 and 0.5,at.%) alloys were prepared by vacuum arc melting.T...In order to improve mechanical properties of TiAlNb alloys,different contents of silicon were added into Ti48Al6Nb alloy.The Ti48Al6NbxSi (x=0,0.1,0.2,0.3,0.4 and 0.5,at.%) alloys were prepared by vacuum arc melting.The phase constitution,microstructure evolution and mechanical properties of the alloys were studied.Results show that the Ti48Al6NbxSi alloys consist of γ-TiAl phase,α2-Ti3Al phase and B2 phase,and Ti5Si3 silicide phase is formed when the addition of silicon is higher than 0.3at.%.The addition of silicon leads to the decrease in γ phase and increase in α2 phase.The formation of silicide decreases the amount of Nb dissolved in the TiAl matrix,and therefore decreases B2 phase.Compressive tests show that the ultimate strength of the alloys increases from 2,063 MPa to 2,281 MPa with an increase in silicon from 0 to 0.5at.%,while the fracture strain decreases from 34.7% to 30.8%.The increase of compressive strength and decrease of fracture strain can be attributed to the decrease of B2 phase and the formation of Ti5Si3 phase by the addition of silicon.The strengthening mechanism is changed from solid solution strengthening when the addition of silicon is less than 0.3at.% to combination of solid solution strengthening and secondary phase strengthening when the addition of silicon is higher than 0.3at.%.展开更多
Co1-x-yNix+ySb3-xSnx polycrystals were fabricated by vacuum melting combined with hot-press sintering. The effect of alloying on the thermoelectric properties of unfilled skutterudite CO1-xNixSb3-xSnx was investigate...Co1-x-yNix+ySb3-xSnx polycrystals were fabricated by vacuum melting combined with hot-press sintering. The effect of alloying on the thermoelectric properties of unfilled skutterudite CO1-xNixSb3-xSnx was investigated. A leap of electrical conductivity from the Co0.93Ni0.07Sb2.93Sn0.07 sample to the Co0.88Ni0.12Sb288Sn0.12 sample occurs during the measurement of electrical conductivity, indicating the adjustment of band structure by proper alloying. The results show that alloying enhances the power factor of the materials. On the basis of alloying, the thermoelectric properties of Coo.88Nio.12Sb2.ssSno.12 are improved by Ni-doping. The thermal conductivities of Ni-doping samples have no reduction, but their power factors have obvious enhancement. The power factor of Co0.81Ni0.09Sb2.88Sn0.12 reaches 3.0 mW-m-1·K-2 by Ni doping. The dimensionless thermoelectric figure of merit reaches 0.55 at 773 K for the unfilled Co0.81Ni0.19 Sb2.88Sn0.12,展开更多
Two kinds of CoCrNi composite coatings,CoCrNiMo and CoCrNiMoBC,were prepared by laser cladding on the base metal of 304 stainless steel.The wear and corrosion properties of the coatings were studied by wear tests and ...Two kinds of CoCrNi composite coatings,CoCrNiMo and CoCrNiMoBC,were prepared by laser cladding on the base metal of 304 stainless steel.The wear and corrosion properties of the coatings were studied by wear tests and electrochemical tests.Results show that the addition of B_(4)C promotes the generation of the ceramic phase,and therefore improving the microhardness of the coating and enhancing its wear resistance,while simutaneously keeps its excellent corrosion resistance.Energy dispersive X-ray spectrometry analysis shows that the chromium distribution in the two coatings is relatively uniform,which is beneficial for corrosion resistance.Scanning Kelvin probe microscopy results reveal that the potential difference between dendrites and interdendrites is only 20 mV,which leads to a relatively low driving force for galvanic corrosion.Observation through the atomic-scale high-resolution transmission electron microscopy shows that the fundamental reason for the high wear and corrosion resistance of the coating is the excellent coherent interface between the two phases,which reduces the interface energy and potential difference and thus improving its corrosion resistance.展开更多
To strengthen the face-centered-cubic(FCC)type CoCrFeNi high-entropy alloy(HEA)by in-situ reinforced phase,(CoCrFeNi)_(100-x)(NbB_(2))_(x)(x=0,2,4,6,8,at.%)alloys were prepared.Phase constitution,microstructure,tensil...To strengthen the face-centered-cubic(FCC)type CoCrFeNi high-entropy alloy(HEA)by in-situ reinforced phase,(CoCrFeNi)_(100-x)(NbB_(2))_(x)(x=0,2,4,6,8,at.%)alloys were prepared.Phase constitution,microstructure,tensile mechanical properties of the alloys were studied,and the mechanisms were discussed.Results show that the microstructure of all the reinforced alloys consists of the matrix FCC phase,Laves phase,and(Cr_(3)Fe)B_(x) phase.The eutectic structure and(Cr_(3)Fe)B_(x) phases are formed in the interdendritic region,and the eutectic structure is composed of Laves and FCC phases.When x increases from 0 to 8,i.e.,with increase of Nb and B elements,the volume fraction of Laves and(Cr_(3)Fe)B_(x) phases increases gradually from 0 to 5.84%and 8.3%,respectively.Tensile testing results show that the ultimate strength of the alloys increases gradually from 409 MPa to 658 MPa,while the fracture strain decreases from 75%to 1.6%.Fracture analysis shows that the crack originates from the(Cr_(3)Fe)B_(x) phase.The CoCrFeNi alloys are mainly strengthened by the second phase(Laves phase and boride phase).展开更多
The intensification of energy crises and environmental pollution inspire researchers’attention to environment-friendly SnTe thermoelectric materials.In this work,we achieved a lower lattice thermal conductivity and o...The intensification of energy crises and environmental pollution inspire researchers’attention to environment-friendly SnTe thermoelectric materials.In this work,we achieved a lower lattice thermal conductivity and optimized the power factor via the synergistic optimization of bonding characteristic,VSn,and resonant level for the SnTe system,respectively.Pb-introduction produces weak bonding strength,mass fluctuation,and stress distortion,which result in lower thermal conductivity.The lowest lattice thermal conductivity achieves 0.66 W m^(–1) K^(–1) at 773 K.Further introduced VSn relieves loss of electrical conductivity caused by Pb-introduction,and it also makes the bigger g(E)and up-shift of resonance level.The VSn,enhanced g(E),and resonant level make electrical conductivity and Seebeck coefficient enhance simultaneously.Finally,the further optimization of thermal and electronic transport performance contributes to a higher ZT value of∼0.86 at 773 K in the Sn_(0.685)Pb_(0.285)In_(0.015)Te_(0.7)Se_(0.3) sample.The strategy of bonding characteristic,VSn,and resonant level synergistic engineering will be widely applicable to various TE systems for achieving better thermoelectric performance.展开更多
In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 mon...In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 month and 24 months differ significantly.The corrosion rate after 1 month during the summer season was 19.82 g/m^(2)·year and it decreased to 13.87 g/m^(2)·year after two years’exposure.Corrosion is initiated with pitting corrosion and then evolved to uniform corrosion with prolonging exposure time.The skyward surface exhibited a much severe corrosion than that of the groundward surface,attributed to the long-term existence of the adsorbed electrolyte layer.The corrosion products formed on the alloy exposed in Antarctica environment were MgCO_(3)·3H_(2)O,MgCO_(3)·5H_(2)O and Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O,with the MgCO_(3)·3H_(2)O as the dominant phase in the initial stage and the Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O as the dominant phase after long-term exposure.展开更多
A Zn-AI layered double hydroxide (ZnAI-LDH) coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly(lactic acid)...A Zn-AI layered double hydroxide (ZnAI-LDH) coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly(lactic acid) (PLA) coating was sealed on the top layer of the ZnAI-LDH coating using vacuum freeze-drying. The characteristics of the ZnAI-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ZnAI-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAI-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.展开更多
A superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XR...A superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XRD, FT- IR and XPS. The corrosion resistance of the prepared coatings was studied using potentiodynamic polarization and electrochemical impedance spectrum. The results revealed that the superhydrophobic surface considerably improved the corrosion-resistant performance of the LDH coatings on the aluminum alloy substrate. The formation mechanism of the superhydrophobic surface was proposed.展开更多
Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable ...Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the degradation, implants, resulting from the arises a major concern. Micro arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA)coating on biomedical Mg- 1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate pH variation in an appropriate range. Surface morphologies were discerned using SEM EMPA. AM corrosion resistance was evaluated via electrochemical Polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predomlnantly consisted of MgO, Mg2SiO4 and YzO3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5-7.8 The neutrallzation caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The reSult designates that MAOI PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.展开更多
Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coating...Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the MglAl/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively, The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210℃. The diffusion mechanism of the interfaces of MglAI and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.展开更多
The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, E...The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, EPMA, X-ray EDS, XRD and FTIR. The corrosion behavior was evaluated using weight-loss measurement, hydrogen evolution, electrochemical and pH measurements, The results demonstrate that the microstructure for both ZMT614-1,5Nd alloy and ZMT614-0.5Y alloy is characterized by α-Mg and intermetallic compounds, most of which are distributed along the grain boundaries. These second phases contain Mg2Zn, Mg2Zn11, Mg2Sn and single metal Mn, together with Mg12Nd phase for the ZMT614-1.5Nd alloy, and with Mg24Y5 phase for the ZMT614-0.5Y alloy. Honeycomb-like corrosion product layers form. The corrosion resistance of the ZMT614-0.5Y alloy is higher than that of the ZMT614-1.5Nd alloy, which is ascribed to the addition of the element Y into the alloy delaying the corrosion initiation in comparison to that of Nd element in the alloy.展开更多
In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques char...In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques characterized the as-synthesized ZnO/NiO composites and pure ZnO.The p-NiO/n-ZnO junctions formed between adjacent ZnO and NiO nanoparticles,improving the gas sensing performance.The ZnO/NiO composite with the Ni:Zn atomic ratio of 7.42:100 exhibited the best iso-propanol sensing properties.Compared to pure ZnO,it showed high selectivity and sensitivity(R_(a)/R_(g)=221.3 toward 400×10^(-6)isopropanol),fast response rate(less than 10 s),short recovery time,and simultaneously low operating temperature.Also,the ZnO/NiO composite exhibited a wide sensing range(1×10^(-6)-1000×10^(-6))to isopropanol and processed good long-term stability.The experimental results suggested the potential application in fabricating efficient isopropanol sensors using this ZnO/NiO composite.The enhanced isopropanol sensing mech-anism is also discussed in charge transfer between heterojunctions,surface area,and surface defects.展开更多
Porous Zn2 Ti04-ZnO microtubes have been successfully fabricated using chemical precipitation followed by a calcination process using a carbon fiber template.The porous Zn_(2)TiO_(4)-ZnO micro tubes with a diameter o...Porous Zn2 Ti04-ZnO microtubes have been successfully fabricated using chemical precipitation followed by a calcination process using a carbon fiber template.The porous Zn_(2)TiO_(4)-ZnO micro tubes with a diameter of~4μm consisted of Zn_(2)TiO_(4) and ZnO nanoparticles.These displayed worm-like pore structures.Carbon fibers played an important role during the porous Zn_(2)TiO_(4)-ZnO microtube formation process.The porous and hollow structure of Zn_(2)TiO_(4)-ZnO provided abundant active sensing sites and channels for gas adsorption and diffusion.The porous Zn_(2)TiO_(4)-ZnO microtubes exhibited improved gas sensing properties for acetone when compared with pure ZnO.The Zn_(2)TiO_(4)-ZnO sensor response was 33.4 for 100μg·ml^(-1) acetone at the optimum operating temperature(370℃).This was~2.7 times higher than that of pure ZnO.Additionally,the as-prepared porous Zn_(2)TiO_(4)-ZnO microtubes displayed sufficient long-term acetone stability and selectivity.This showed the potential application for acetone detection.The enhanced Zn_(2)TiO_(4)-ZnO gas sensing properties are due to the unique heterogeneous and porous structure,which was analyzed using the porous and band structure.展开更多
NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the ...NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the NiCrxMoy alloy coatings were investigated using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,electrochemical tests,X-ray photoelectron spectroscopy,microhardness,and nanoindentation tests.As the Cr content increased,the phase composition of the coatings changed from a single face-centered cubic(FCC)structure to a dual-phase structure coexisting with body-centered cubic(BCC)and FCC structures,while the addition of Mo promoted the precipitation ofσphase.The appearance of a homogeneous dual-phase structure and some amount ofσphase played a positive role in the corrosion resistance of NiCrxMoy coatings.Cr^3+ ions and Mo^6+ ions in the passive film enhanced the stability of the coatings.The nanoindentation tests showed that the nanohardness(6.71 GPa)and elastic modulus(184.40 GPa)of BCC phase were higher than those of the FCC phase(5.19 GPa and 155.26 GPa,respectively).Overall,the BCC phase andσphase improved the mechanical properties of the coatings.展开更多
The corrosion resistance of magnesium alloys can be improved using functional surface modification such as hydrophobic treatment.In this study,a hierarchical hydroxide zinc carbonate(HZC) film was fabricated on AZ31...The corrosion resistance of magnesium alloys can be improved using functional surface modification such as hydrophobic treatment.In this study,a hierarchical hydroxide zinc carbonate(HZC) film was fabricated on AZ31 magnesium alloy via a simple chemical-bath deposition process using urea aqueous solution.The morphologies,compositions and corrosion resistance of the hydrophobic film were analyzed using scanning electron microscopy,X-ray diffraction and Fourier transform infrared spectrometer,and electrochemical measurements as well.The results revealed that the HZC film displayed flower-like protrusions and had a thickness of approximately 100 um.The fluoroalkylsilane(FAS)-modified HZC film exhibited a hydrophobic property with a water contact angle of 131.3°.The FAS/HZC film significantly improved the corrosion resistance of the AZ31 alloy due to hierarchical structures and hydrophobic modification.展开更多
The NiAl–TiC–TiB2 composites were processed by self-propagating high-temperature synthesis(SHS) method using raw powders of Ni, Al, Ti, B4 C, TiC, and TiB2, and their microstructure and micro-hardness were investi...The NiAl–TiC–TiB2 composites were processed by self-propagating high-temperature synthesis(SHS) method using raw powders of Ni, Al, Ti, B4 C, TiC, and TiB2, and their microstructure and micro-hardness were investigated. The TiC–TiB2 in NiAl matrix, with contents from 10 to 30 wt%, emerged with the use of two methods: in situ formed and externally added. The results show that all final products are composed of three phases of NiAl, TiC, and TiB2. The microstructures of NiAl–TiC–TiB2 composites with in situ-formed TiC and TiB2 are fine, and all the three phases are distributed uniformly. The grains of NiAl matrix in the composites have been greatly refined, and the micro-hardness of NiAl increases from 381 HV100 to 779 HV100. However, the microstructures of NiAl–TiC–TiB2 composites with externally added TiC and TiB2 are coarse and inhomogeneous, with severe agglomeration of TiC and TiB2 particles. The samples containing externally added 30 wt% TiC–TiB2attain the micro-hardness of 485 HV100. The microstructure evolution and fracture mode of the two kinds of NiAl–TiC–TiB2 composites are different.展开更多
Open-celled porous (TiB2-Al2O3)/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis (SHS). Effects of 10Al-3B2O3-3TiO2 conten...Open-celled porous (TiB2-Al2O3)/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis (SHS). Effects of 10Al-3B2O3-3TiO2 contents (0-20 wt%) on the pore structures and the quasi-static compressive behaviors of the resultant materials were investigated. The porous (TiBE-Al2O3)/NiAl composites exhibit composite pore structure consisting of homogeneously distributed and interconnected millimeter pores and micropores. The millimeter pores virtually inherit the shape and size of carbamide particles, while the pore size of micropores increases with increasing the 10Al-3BEO3-3TiO2 content. Depending on the volume fraction of the carbamide, the porosity of the porous materials can be easily controlled in a range of 55%-85%. When the porosity is about 72%, the compressive strengths of porous NiAl and porous (TiBE-Al203)/NiAl composite with 15% 10Al-3B2O3-3TiO2 in green compact are 19 and 32 MPa, and the corresponding strains are 2.9% and 5.7%, respectively. Furthermore, the quasi-static compressive behavior of porous (TiB2-AlEO3)/NiAl composites can be estimated by Gibson-Ashby model.展开更多
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51825401 and 52001114)the State Key Laboratory of Materials Processing and Die&Mould Technology(P2020-023)the Guangdong Introducing Innovative and Entrepreneurial Teams,China(2016ZT06G025).
基金Project(51772176)supported by the National Natural Science Foundation of ChinaProject(tspd20161006)supported by Taishan Scholarship of Climbing Plan,ChinaProject(2015AA034404)supported by National High-tech Research and Development Program of China
基金the National Natural Science Foundation of China(Grant Nos.51825401,51971121,52001114)the Scientific Research Fund of State Key Laboratory of Materials Processing and Die&Mould Technology(Grant No.P2020-023)Henan Provincial Department of Science and Technology Research Project(Grant No.182102110096)。
文摘In order to improve mechanical properties of TiAlNb alloys,different contents of silicon were added into Ti48Al6Nb alloy.The Ti48Al6NbxSi (x=0,0.1,0.2,0.3,0.4 and 0.5,at.%) alloys were prepared by vacuum arc melting.The phase constitution,microstructure evolution and mechanical properties of the alloys were studied.Results show that the Ti48Al6NbxSi alloys consist of γ-TiAl phase,α2-Ti3Al phase and B2 phase,and Ti5Si3 silicide phase is formed when the addition of silicon is higher than 0.3at.%.The addition of silicon leads to the decrease in γ phase and increase in α2 phase.The formation of silicide decreases the amount of Nb dissolved in the TiAl matrix,and therefore decreases B2 phase.Compressive tests show that the ultimate strength of the alloys increases from 2,063 MPa to 2,281 MPa with an increase in silicon from 0 to 0.5at.%,while the fracture strain decreases from 34.7% to 30.8%.The increase of compressive strength and decrease of fracture strain can be attributed to the decrease of B2 phase and the formation of Ti5Si3 phase by the addition of silicon.The strengthening mechanism is changed from solid solution strengthening when the addition of silicon is less than 0.3at.% to combination of solid solution strengthening and secondary phase strengthening when the addition of silicon is higher than 0.3at.%.
基金financially supported by the National Natural Science Foundation of China (Nos.50801054 and 51072104)the Research Award Fund for Outstanding Young Scientists in Shandong Province,China (No.BS2011CL031)
文摘Co1-x-yNix+ySb3-xSnx polycrystals were fabricated by vacuum melting combined with hot-press sintering. The effect of alloying on the thermoelectric properties of unfilled skutterudite CO1-xNixSb3-xSnx was investigated. A leap of electrical conductivity from the Co0.93Ni0.07Sb2.93Sn0.07 sample to the Co0.88Ni0.12Sb288Sn0.12 sample occurs during the measurement of electrical conductivity, indicating the adjustment of band structure by proper alloying. The results show that alloying enhances the power factor of the materials. On the basis of alloying, the thermoelectric properties of Coo.88Nio.12Sb2.ssSno.12 are improved by Ni-doping. The thermal conductivities of Ni-doping samples have no reduction, but their power factors have obvious enhancement. The power factor of Co0.81Ni0.09Sb2.88Sn0.12 reaches 3.0 mW-m-1·K-2 by Ni doping. The dimensionless thermoelectric figure of merit reaches 0.55 at 773 K for the unfilled Co0.81Ni0.19 Sb2.88Sn0.12,
基金support of the National Natural Science Foundation of China(No.51971121)the National Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers(CN)(No.U2106216)+1 种基金the Taishan Scholarship of Climbing Plan(No.tspd20161006)the Major Special Science and Technology Projects in Shandong Province(Nos.2019JZZY010303,2019JZZY010360).
文摘Two kinds of CoCrNi composite coatings,CoCrNiMo and CoCrNiMoBC,were prepared by laser cladding on the base metal of 304 stainless steel.The wear and corrosion properties of the coatings were studied by wear tests and electrochemical tests.Results show that the addition of B_(4)C promotes the generation of the ceramic phase,and therefore improving the microhardness of the coating and enhancing its wear resistance,while simutaneously keeps its excellent corrosion resistance.Energy dispersive X-ray spectrometry analysis shows that the chromium distribution in the two coatings is relatively uniform,which is beneficial for corrosion resistance.Scanning Kelvin probe microscopy results reveal that the potential difference between dendrites and interdendrites is only 20 mV,which leads to a relatively low driving force for galvanic corrosion.Observation through the atomic-scale high-resolution transmission electron microscopy shows that the fundamental reason for the high wear and corrosion resistance of the coating is the excellent coherent interface between the two phases,which reduces the interface energy and potential difference and thus improving its corrosion resistance.
基金supported by the National Natural Science Foundation of China(No.51825401).
文摘To strengthen the face-centered-cubic(FCC)type CoCrFeNi high-entropy alloy(HEA)by in-situ reinforced phase,(CoCrFeNi)_(100-x)(NbB_(2))_(x)(x=0,2,4,6,8,at.%)alloys were prepared.Phase constitution,microstructure,tensile mechanical properties of the alloys were studied,and the mechanisms were discussed.Results show that the microstructure of all the reinforced alloys consists of the matrix FCC phase,Laves phase,and(Cr_(3)Fe)B_(x) phase.The eutectic structure and(Cr_(3)Fe)B_(x) phases are formed in the interdendritic region,and the eutectic structure is composed of Laves and FCC phases.When x increases from 0 to 8,i.e.,with increase of Nb and B elements,the volume fraction of Laves and(Cr_(3)Fe)B_(x) phases increases gradually from 0 to 5.84%and 8.3%,respectively.Tensile testing results show that the ultimate strength of the alloys increases gradually from 409 MPa to 658 MPa,while the fracture strain decreases from 75%to 1.6%.Fracture analysis shows that the crack originates from the(Cr_(3)Fe)B_(x) phase.The CoCrFeNi alloys are mainly strengthened by the second phase(Laves phase and boride phase).
基金supported by the National Natural Science Foundation of China(Nos.U2106216,51971121)the Natural Science Foundation of Shandong Province(Grant No.ZR2020ME012)。
文摘The intensification of energy crises and environmental pollution inspire researchers’attention to environment-friendly SnTe thermoelectric materials.In this work,we achieved a lower lattice thermal conductivity and optimized the power factor via the synergistic optimization of bonding characteristic,VSn,and resonant level for the SnTe system,respectively.Pb-introduction produces weak bonding strength,mass fluctuation,and stress distortion,which result in lower thermal conductivity.The lowest lattice thermal conductivity achieves 0.66 W m^(–1) K^(–1) at 773 K.Further introduced VSn relieves loss of electrical conductivity caused by Pb-introduction,and it also makes the bigger g(E)and up-shift of resonance level.The VSn,enhanced g(E),and resonant level make electrical conductivity and Seebeck coefficient enhance simultaneously.Finally,the further optimization of thermal and electronic transport performance contributes to a higher ZT value of∼0.86 at 773 K in the Sn_(0.685)Pb_(0.285)In_(0.015)Te_(0.7)Se_(0.3) sample.The strategy of bonding characteristic,VSn,and resonant level synergistic engineering will be widely applicable to various TE systems for achieving better thermoelectric performance.
基金The authors acknowledgement the Excellent Youth Science Fund of Shandong Province(No.ZR2022YQ44)the Fundamental Research Funds for the Central Universities(No.201762008).
文摘In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 month and 24 months differ significantly.The corrosion rate after 1 month during the summer season was 19.82 g/m^(2)·year and it decreased to 13.87 g/m^(2)·year after two years’exposure.Corrosion is initiated with pitting corrosion and then evolved to uniform corrosion with prolonging exposure time.The skyward surface exhibited a much severe corrosion than that of the groundward surface,attributed to the long-term existence of the adsorbed electrolyte layer.The corrosion products formed on the alloy exposed in Antarctica environment were MgCO_(3)·3H_(2)O,MgCO_(3)·5H_(2)O and Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O,with the MgCO_(3)·3H_(2)O as the dominant phase in the initial stage and the Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O as the dominant phase after long-term exposure.
文摘A Zn-AI layered double hydroxide (ZnAI-LDH) coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly(lactic acid) (PLA) coating was sealed on the top layer of the ZnAI-LDH coating using vacuum freeze-drying. The characteristics of the ZnAI-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ZnAI-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAI-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.
基金financially supported by the National Natural Science Foundation of China(No.21306214)the Doctoral Program Foundation of the State Education Ministry(No. 20133718120003)+2 种基金the Applied Basic Research Foundation of Qingdao(No.13-1-4-217-jch)the Scientific Research Foundation of Shandong for Outstanding Young Scientists(No.BS2013CL009)SDUST Research Fund(No.2014TDJH104)
文摘A superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XRD, FT- IR and XPS. The corrosion resistance of the prepared coatings was studied using potentiodynamic polarization and electrochemical impedance spectrum. The results revealed that the superhydrophobic surface considerably improved the corrosion-resistant performance of the LDH coatings on the aluminum alloy substrate. The formation mechanism of the superhydrophobic surface was proposed.
基金This research was financially supported by the National Natural Science Foundation of China (Grant No. 51241001), Shandong Provincial Natural Science Foundation, China (ZR2011E MM004), SDUST Research Fund (2014TDJH 104), Joint innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources, and Shandong Province as well as Taishan Scholarship Project of Shandong Province (TS20110828). Thanks go to Prof. Rong-Shi Chen and the members of his group at Institute of Metals Research, Chinese Academy of Sciences for the preparation of the ingots.
文摘Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the degradation, implants, resulting from the arises a major concern. Micro arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA)coating on biomedical Mg- 1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate pH variation in an appropriate range. Surface morphologies were discerned using SEM EMPA. AM corrosion resistance was evaluated via electrochemical Polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predomlnantly consisted of MgO, Mg2SiO4 and YzO3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5-7.8 The neutrallzation caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The reSult designates that MAOI PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.
基金Acknowledgements This research was financially supported by the National Natural Science Foundation of China (Grant No. 51241001), Shandong Provincial Natural Science Foundation, China (ZR2011 EMM004), Taishan Scholarship Project of Shandong Province (TS20110828), SDUST Research Fund (2014TDJH104), Joint Innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources, and Shandong Province. Thanks go to Dr. Jun CHEN, Dr. Donghua YANG and Dr. Zhenlin WANG in Chongqing University of Technology for the help in the sample preparation, corrosion and scratch tests.
文摘Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the MglAl/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively, The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210℃. The diffusion mechanism of the interfaces of MglAI and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.
基金Acknowledgements This research was financially supported by the National Natural Science Foundation of China (Grant No. 5124 1001 ), the Natural Science Foundation of Shandong Province (Grant No. ZR2011EMM004), the Open Foundation of State Key Laboratory for Corrosion and Protection (Grant No. SKLCP21012KF03), SDUST Research Fund and Taishan Scholarship Project of Shandong Provincc (Grant No. TS20110828).
文摘The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, EPMA, X-ray EDS, XRD and FTIR. The corrosion behavior was evaluated using weight-loss measurement, hydrogen evolution, electrochemical and pH measurements, The results demonstrate that the microstructure for both ZMT614-1,5Nd alloy and ZMT614-0.5Y alloy is characterized by α-Mg and intermetallic compounds, most of which are distributed along the grain boundaries. These second phases contain Mg2Zn, Mg2Zn11, Mg2Sn and single metal Mn, together with Mg12Nd phase for the ZMT614-1.5Nd alloy, and with Mg24Y5 phase for the ZMT614-0.5Y alloy. Honeycomb-like corrosion product layers form. The corrosion resistance of the ZMT614-0.5Y alloy is higher than that of the ZMT614-1.5Nd alloy, which is ascribed to the addition of the element Y into the alloy delaying the corrosion initiation in comparison to that of Nd element in the alloy.
基金financially supported by the Distinguished Taishan Scholars in Climbing Plan (No. tspd20161006)the Major-Special Science and Technology Projects in Shandong Province(Nos.2019JZZY010303 and 2019JZZY010360)Shandong Provincial Natural Science Foundation (No. ZR2019MEM049)。
文摘In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques characterized the as-synthesized ZnO/NiO composites and pure ZnO.The p-NiO/n-ZnO junctions formed between adjacent ZnO and NiO nanoparticles,improving the gas sensing performance.The ZnO/NiO composite with the Ni:Zn atomic ratio of 7.42:100 exhibited the best iso-propanol sensing properties.Compared to pure ZnO,it showed high selectivity and sensitivity(R_(a)/R_(g)=221.3 toward 400×10^(-6)isopropanol),fast response rate(less than 10 s),short recovery time,and simultaneously low operating temperature.Also,the ZnO/NiO composite exhibited a wide sensing range(1×10^(-6)-1000×10^(-6))to isopropanol and processed good long-term stability.The experimental results suggested the potential application in fabricating efficient isopropanol sensors using this ZnO/NiO composite.The enhanced isopropanol sensing mech-anism is also discussed in charge transfer between heterojunctions,surface area,and surface defects.
基金financially supported by the Distinguished Taishan Scholars in Climbing Plan(No.tspd20161006)Shandong Provincial Natural Science Foundation(No.ZR2019MEM049)+1 种基金the National Natural Science Foundation of China(Nos.51772176 and 51971121)Shandong Province Key Laboratory of Mine Mechanical Engineering(No.2019KLMM101)。
文摘Porous Zn2 Ti04-ZnO microtubes have been successfully fabricated using chemical precipitation followed by a calcination process using a carbon fiber template.The porous Zn_(2)TiO_(4)-ZnO micro tubes with a diameter of~4μm consisted of Zn_(2)TiO_(4) and ZnO nanoparticles.These displayed worm-like pore structures.Carbon fibers played an important role during the porous Zn_(2)TiO_(4)-ZnO microtube formation process.The porous and hollow structure of Zn_(2)TiO_(4)-ZnO provided abundant active sensing sites and channels for gas adsorption and diffusion.The porous Zn_(2)TiO_(4)-ZnO microtubes exhibited improved gas sensing properties for acetone when compared with pure ZnO.The Zn_(2)TiO_(4)-ZnO sensor response was 33.4 for 100μg·ml^(-1) acetone at the optimum operating temperature(370℃).This was~2.7 times higher than that of pure ZnO.Additionally,the as-prepared porous Zn_(2)TiO_(4)-ZnO microtubes displayed sufficient long-term acetone stability and selectivity.This showed the potential application for acetone detection.The enhanced Zn_(2)TiO_(4)-ZnO gas sensing properties are due to the unique heterogeneous and porous structure,which was analyzed using the porous and band structure.
基金financially supported by the Distinguished Taishan Scholars in Climbing Plan(No.tspd2O161OO6)the National Natural Science Foundation of China(Nos.51772176 and 51971121).
文摘NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the NiCrxMoy alloy coatings were investigated using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,electrochemical tests,X-ray photoelectron spectroscopy,microhardness,and nanoindentation tests.As the Cr content increased,the phase composition of the coatings changed from a single face-centered cubic(FCC)structure to a dual-phase structure coexisting with body-centered cubic(BCC)and FCC structures,while the addition of Mo promoted the precipitation ofσphase.The appearance of a homogeneous dual-phase structure and some amount ofσphase played a positive role in the corrosion resistance of NiCrxMoy coatings.Cr^3+ ions and Mo^6+ ions in the passive film enhanced the stability of the coatings.The nanoindentation tests showed that the nanohardness(6.71 GPa)and elastic modulus(184.40 GPa)of BCC phase were higher than those of the FCC phase(5.19 GPa and 155.26 GPa,respectively).Overall,the BCC phase andσphase improved the mechanical properties of the coatings.
基金supported by the National Natural Science Foundation of China(No.51241001)SDUST Research Fund(No.2014TDJH104)+3 种基金Taishan Scholarship Project of Shandong Province(No.TS20110828)Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents(No.2013RCJJ006)Scientific Research Foundation of Shandong for Outstanding Young Scientist(No.BS2013CL009)Applied Basic Research Foundation of Qingdao(No.13-1-4-188-jch)
文摘The corrosion resistance of magnesium alloys can be improved using functional surface modification such as hydrophobic treatment.In this study,a hierarchical hydroxide zinc carbonate(HZC) film was fabricated on AZ31 magnesium alloy via a simple chemical-bath deposition process using urea aqueous solution.The morphologies,compositions and corrosion resistance of the hydrophobic film were analyzed using scanning electron microscopy,X-ray diffraction and Fourier transform infrared spectrometer,and electrochemical measurements as well.The results revealed that the HZC film displayed flower-like protrusions and had a thickness of approximately 100 um.The fluoroalkylsilane(FAS)-modified HZC film exhibited a hydrophobic property with a water contact angle of 131.3°.The FAS/HZC film significantly improved the corrosion resistance of the AZ31 alloy due to hierarchical structures and hydrophobic modification.
基金financially supported by the National Natural Science Foundation of China(Nos.51072104 and 51272141)Tai Shan Scholars Project of Shandong Province,China(No.ts20110828)
文摘The NiAl–TiC–TiB2 composites were processed by self-propagating high-temperature synthesis(SHS) method using raw powders of Ni, Al, Ti, B4 C, TiC, and TiB2, and their microstructure and micro-hardness were investigated. The TiC–TiB2 in NiAl matrix, with contents from 10 to 30 wt%, emerged with the use of two methods: in situ formed and externally added. The results show that all final products are composed of three phases of NiAl, TiC, and TiB2. The microstructures of NiAl–TiC–TiB2 composites with in situ-formed TiC and TiB2 are fine, and all the three phases are distributed uniformly. The grains of NiAl matrix in the composites have been greatly refined, and the micro-hardness of NiAl increases from 381 HV100 to 779 HV100. However, the microstructures of NiAl–TiC–TiB2 composites with externally added TiC and TiB2 are coarse and inhomogeneous, with severe agglomeration of TiC and TiB2 particles. The samples containing externally added 30 wt% TiC–TiB2attain the micro-hardness of 485 HV100. The microstructure evolution and fracture mode of the two kinds of NiAl–TiC–TiB2 composites are different.
基金financially supported by the Natural Science Foundation of Shandong Province (No.ZR2014EMM009)the Public School Visiting Fund of Shandong University of Science and Technology
文摘Open-celled porous (TiB2-Al2O3)/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis (SHS). Effects of 10Al-3B2O3-3TiO2 contents (0-20 wt%) on the pore structures and the quasi-static compressive behaviors of the resultant materials were investigated. The porous (TiBE-Al2O3)/NiAl composites exhibit composite pore structure consisting of homogeneously distributed and interconnected millimeter pores and micropores. The millimeter pores virtually inherit the shape and size of carbamide particles, while the pore size of micropores increases with increasing the 10Al-3BEO3-3TiO2 content. Depending on the volume fraction of the carbamide, the porosity of the porous materials can be easily controlled in a range of 55%-85%. When the porosity is about 72%, the compressive strengths of porous NiAl and porous (TiBE-Al203)/NiAl composite with 15% 10Al-3B2O3-3TiO2 in green compact are 19 and 32 MPa, and the corresponding strains are 2.9% and 5.7%, respectively. Furthermore, the quasi-static compressive behavior of porous (TiB2-AlEO3)/NiAl composites can be estimated by Gibson-Ashby model.