Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence.Here,a unique structured hybrid catalyst composed of Fe_(3)O_(4) nanoparticles intimately dispersed inside an acidic zeol...Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence.Here,a unique structured hybrid catalyst composed of Fe_(3)O_(4) nanoparticles intimately dispersed inside an acidic zeolite is developed.1 to 4 nm sized Fe_(3)O_(4) nanoparticles end up evenly dispersed in an acidic and slightly mesoporous Al-ZSM-5 based on Fe_(3)O_(4) restructuring during co-hydro thermal synthesis using organosilane modification.A very high aromatic productivity of 214 mmolaromatics h^(-1) gFe^(-1) can be obtained with a remarkable 62%aromatic selectivity in hydrocarbons.This catalyst has excellent sintering resistance ability and maintains stable aromatics production over 570 h.The synthetic insights that postulate a mechanism for the metastable oxide-zeolite reorganization during hydrothermal synthesis could serve as a generic route to sinter-resistant oxide-zeolite composite materials with uniform,well-dispersed oxide nanoparticles in close intimacy with-and partially confined in-a zeolite matrix.展开更多
In order to enhance the sintering resistance of lanthanum aluminate based high emissivity coatings,Ca^(2+)-Fe^(3+)doped LaAlO_(3)/ZrO_(2)specimens were prepared by solid state sintering using La_(2)O_(3),Al_(2)O_(3),C...In order to enhance the sintering resistance of lanthanum aluminate based high emissivity coatings,Ca^(2+)-Fe^(3+)doped LaAlO_(3)/ZrO_(2)specimens were prepared by solid state sintering using La_(2)O_(3),Al_(2)O_(3),CaCO_(3) and Fe_(2)O_(3) as raw materials,extra-adding fused Y_(2)O_(3)-stabilized ZrO_(2)(0,5%,10%,and 15%,by mass),ball milling,pre-calcining,pressing into shapes and sintering at 1600℃for 2 h.The effect of the ZrO_(2)addition on the properties of lanthanum aluminate based high emissivity coatings was explored.It is concluded that ZrO_(2)does not react with LaAlO_(3),which can inhibit the sintering of the specimens.With the increase of the ZrO_(2),addition,the linear shrinkage rate and the thermal conductivity decrease significantly,while the emissivity decreases,but the emissivity of all the specimens is all higher than 0.9.The optimal addition of ZrO_(2),is 10%.展开更多
Three kinds of full compositional distribution (from 0 to 100wt%W) W/Cu FGMs (functionally graded materials) with high density is fabricated by resistance sintering under ultra-high pressure. Microstructure analys...Three kinds of full compositional distribution (from 0 to 100wt%W) W/Cu FGMs (functionally graded materials) with high density is fabricated by resistance sintering under ultra-high pressure. Microstructure analysis showed that the good grading composition of all FGMs has been obtained. The sintering mechanism of W is mainly solid state sintering. Thermal shock test in air demonstrated that the grading at the interface between W and Cu is effective for the reduction of thermal stress, but obvious transver- se and vertical cracks occur in the pure W layer. The oxidation of the W60Cu40 layer and the W40Cu60 layer is heavier than that of the other layers.展开更多
Six-layered W-TiC/Cu functionally graded materials were fabricated by resistance sintering under ultra-high pressure and exposed in the edge plasma of HT-7 tokamak. Microstruc- ture morphologies show that the TiC part...Six-layered W-TiC/Cu functionally graded materials were fabricated by resistance sintering under ultra-high pressure and exposed in the edge plasma of HT-7 tokamak. Microstruc- ture morphologies show that the TiC particles distribute homogeneously in the W matrix, strength- ening the grain boundary, while gradient layers provide a good compositional transition from W- TiC to Cu. After about 360 shots in the HT-7 tokamak, clear surface modification can be observed after plasma exposure, and the addition of nano TiC particles is beneficial to the improvement of plasma loads resistance of W.展开更多
High-insulation,long-life thermal barrier coatings(TBCs)decrease the service temperature of superalloys and improve the service life of gas turbines.Improvement in the thermal insulation properties of the coating main...High-insulation,long-life thermal barrier coatings(TBCs)decrease the service temperature of superalloys and improve the service life of gas turbines.Improvement in the thermal insulation properties of the coating mainly depends on the optimization of the TBC structure.An important challenge for TBCs is maintaining a high performance during thermal exposure without degradation,as the pore-rich structure of the topcoat would inevitably be transformed by sintering.A low-thermalconductivity anti-sintering coating can overcome the tradeoff between thermal insulation and sinter degradation.In this review,the design,preparation,and serviceability evaluation of a low-thermal-conductivity anti-sintering coating will be discussed.Furthermore,directions for potential development are introduced.This paper provides a comprehensive understanding of the structured tailoring of TBCs for better thermal insulation and anti-sintering performance.展开更多
Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we...Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we report a new and facile strategy to confine Ru and/or Co nanoparticles(NPs) in the channels of N-doped carbon using benzoic acid to guide the deposition location of Ru.The developed catalyst with confined RuCo alloy particles exhibits high resistance against Ru sintering and displays excellent activity and long term stability for NH3 synthesis,achieving an NH3 synthesis rate of up to 18.9 mmol NH_(3) gcat^(-1)h^(-1)at 400℃,which is ca.2.25 times that of the catalyst prepared without confinement(with metal deposited on the support surface).In the latter case,there is an increase of nanoparticle size from 2.52 to 4.25 nm together with ca.48% decrease of NH_(3) synthesis rate after 68 h at 400℃.This study provides a new avenue for simple fabrication of precious-metal-based catalysts that are highly resistant against sintering,specifically suitable for low-temperature synthesis of ammonia with outstanding efficiency.展开更多
Al-Cr-Fe alloy containing quasicrystals has been consolidated using spark plasma sintering(SPS). Its corrosion resistance properties were comparatively investigated with pure Al by electrochemical methods in 3.5 wt%...Al-Cr-Fe alloy containing quasicrystals has been consolidated using spark plasma sintering(SPS). Its corrosion resistance properties were comparatively investigated with pure Al by electrochemical methods in 3.5 wt% NaCl solution. Their corrosion current density was also compared with that of three commercial steels-316 stainless steel, AISI 440C stainless steel and AISI H13 tool steel. Al-Cr-Fe alloy exhibits nobler corrosion potential and evident passivation with a potential range of around 150 mV while no passivation of pure Al sample is seen. The corrosion resistance of Al-Cr-Fe alloy is less than that of pure Al, but is close to that of 316 stainless steel and superior to that of AISI 440C stainless steel and AISI H13 tool steel.展开更多
Equiatomic CuZrAl and CuZrAlTi medium entropy alloys were designed and synthesized by mechanical alloying and spark plasma sintering technique.The alloying behavior,phase evolutions,microstructures and properties of s...Equiatomic CuZrAl and CuZrAlTi medium entropy alloys were designed and synthesized by mechanical alloying and spark plasma sintering technique.The alloying behavior,phase evolutions,microstructures and properties of samples were investigated by X-ray diffraction,differential scanning calorimetry,field emission scanning electron microscopy,microscopy/Vickers hardness testing and electrochemical polarization measurement.The results indicate that the final products of as-milled alloys consist of amorphous phases.Ti addition improves the glass forming ability of as-milled alloys.The as-sintered CuZrAl alloy contains face-centered cubic(fcc)solid solution,Al_(1.05)Cu_(0.95) Zr and AlZr_2 phases at different sintering temperatures.With Ti addition,the as-sintered sample is only composed of intermetallics at 690°C,while fcc1,fcc2 and CuTi3phases are formed at 1100°C.CuZrAlTi-1100°C alloy exhibits the highest hardness value of 1173HV0.2owing to the high sintering density,solid solution strengthening and homogeneous precipitation of nano-size crystalline phase.CuZrAlTi-690°C alloy presents a similar corrosion resistance with304 Lstainless steel in seawater solution and further possesses the lower corrosion rate.展开更多
We report a facile strategy to synthesize intermetallic nanoparticle (iNP) electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles (NPs). ZIF-8...We report a facile strategy to synthesize intermetallic nanoparticle (iNP) electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles (NPs). ZIF-8 serves not only as precursor for N-doped carbon (NC), but also as Zn source for the formation of intermetallic or alloy NPs with the encapsulated metals. The resulting sub-4 nm PtZn iNPs embedded in NC exhibit high sintering resistance up to 1,000℃. Importantly, the present methodology allows fine-tuning of both composition (e.g., PdZn and RhZn iNPs, as well as AuZn and RuZn alloy NPs) and size (2.4, 3.7, and 5.4 nm PtZn) of the as-formed bimetallic NPs. To the best of our knowledge, this is the first report of a metal-organic framework (MOF) with multiple functionalities, such as secondary metal source, carbon precursor, and size-regulating reagent, which promote the formation of iNPs. This work opens a new avenue for the synthesis of highly uniform and stable iNPs.展开更多
Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sin...Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.展开更多
基金supported financially by the National Natural Science Foundation of China(51776206)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01N092)+4 种基金the National Key R&D Program of China(2018YFB1501504)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX20_0095)the Fundamental Research Funds for the Central Universities(3203002104D)the Research Foundation-Flanders(FWO,grant 12E8617N)for funding and KU Leuven grant C14/20/086visiting scholar(2017-20202)at the Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences。
文摘Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence.Here,a unique structured hybrid catalyst composed of Fe_(3)O_(4) nanoparticles intimately dispersed inside an acidic zeolite is developed.1 to 4 nm sized Fe_(3)O_(4) nanoparticles end up evenly dispersed in an acidic and slightly mesoporous Al-ZSM-5 based on Fe_(3)O_(4) restructuring during co-hydro thermal synthesis using organosilane modification.A very high aromatic productivity of 214 mmolaromatics h^(-1) gFe^(-1) can be obtained with a remarkable 62%aromatic selectivity in hydrocarbons.This catalyst has excellent sintering resistance ability and maintains stable aromatics production over 570 h.The synthetic insights that postulate a mechanism for the metastable oxide-zeolite reorganization during hydrothermal synthesis could serve as a generic route to sinter-resistant oxide-zeolite composite materials with uniform,well-dispersed oxide nanoparticles in close intimacy with-and partially confined in-a zeolite matrix.
基金Zhongyuan Science and Technology Innovation Leading Talents(224200510006)NSFC-Henan Joint Fund funded project(U1904217).
文摘In order to enhance the sintering resistance of lanthanum aluminate based high emissivity coatings,Ca^(2+)-Fe^(3+)doped LaAlO_(3)/ZrO_(2)specimens were prepared by solid state sintering using La_(2)O_(3),Al_(2)O_(3),CaCO_(3) and Fe_(2)O_(3) as raw materials,extra-adding fused Y_(2)O_(3)-stabilized ZrO_(2)(0,5%,10%,and 15%,by mass),ball milling,pre-calcining,pressing into shapes and sintering at 1600℃for 2 h.The effect of the ZrO_(2)addition on the properties of lanthanum aluminate based high emissivity coatings was explored.It is concluded that ZrO_(2)does not react with LaAlO_(3),which can inhibit the sintering of the specimens.With the increase of the ZrO_(2),addition,the linear shrinkage rate and the thermal conductivity decrease significantly,while the emissivity decreases,but the emissivity of all the specimens is all higher than 0.9.The optimal addition of ZrO_(2),is 10%.
基金This work was financially supported by the National Natural Science Foundation of China (No.50301001)
文摘Three kinds of full compositional distribution (from 0 to 100wt%W) W/Cu FGMs (functionally graded materials) with high density is fabricated by resistance sintering under ultra-high pressure. Microstructure analysis showed that the good grading composition of all FGMs has been obtained. The sintering mechanism of W is mainly solid state sintering. Thermal shock test in air demonstrated that the grading at the interface between W and Cu is effective for the reduction of thermal stress, but obvious transver- se and vertical cracks occur in the pure W layer. The oxidation of the W60Cu40 layer and the W40Cu60 layer is heavier than that of the other layers.
基金supported by National Natural Science Foundation of China (No.11175205)
文摘Six-layered W-TiC/Cu functionally graded materials were fabricated by resistance sintering under ultra-high pressure and exposed in the edge plasma of HT-7 tokamak. Microstruc- ture morphologies show that the TiC particles distribute homogeneously in the W matrix, strength- ening the grain boundary, while gradient layers provide a good compositional transition from W- TiC to Cu. After about 360 shots in the HT-7 tokamak, clear surface modification can be observed after plasma exposure, and the addition of nano TiC particles is beneficial to the improvement of plasma loads resistance of W.
基金financially supported by the Natural Science Basic Research Program of Shaanxi(No.2019JQ380)the Fundamental Research Funds for the Central Universities,CHD(No.300102500102)
文摘High-insulation,long-life thermal barrier coatings(TBCs)decrease the service temperature of superalloys and improve the service life of gas turbines.Improvement in the thermal insulation properties of the coating mainly depends on the optimization of the TBC structure.An important challenge for TBCs is maintaining a high performance during thermal exposure without degradation,as the pore-rich structure of the topcoat would inevitably be transformed by sintering.A low-thermalconductivity anti-sintering coating can overcome the tradeoff between thermal insulation and sinter degradation.In this review,the design,preparation,and serviceability evaluation of a low-thermal-conductivity anti-sintering coating will be discussed.Furthermore,directions for potential development are introduced.This paper provides a comprehensive understanding of the structured tailoring of TBCs for better thermal insulation and anti-sintering performance.
基金supported by the National Science Fund for Distinguished Young Scholars of China(21825801)the National Natural Science Foundation of China(21972019)Fujian Outstanding Youth Fund(2019J06011)。
文摘Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we report a new and facile strategy to confine Ru and/or Co nanoparticles(NPs) in the channels of N-doped carbon using benzoic acid to guide the deposition location of Ru.The developed catalyst with confined RuCo alloy particles exhibits high resistance against Ru sintering and displays excellent activity and long term stability for NH3 synthesis,achieving an NH3 synthesis rate of up to 18.9 mmol NH_(3) gcat^(-1)h^(-1)at 400℃,which is ca.2.25 times that of the catalyst prepared without confinement(with metal deposited on the support surface).In the latter case,there is an increase of nanoparticle size from 2.52 to 4.25 nm together with ca.48% decrease of NH_(3) synthesis rate after 68 h at 400℃.This study provides a new avenue for simple fabrication of precious-metal-based catalysts that are highly resistant against sintering,specifically suitable for low-temperature synthesis of ammonia with outstanding efficiency.
文摘Al-Cr-Fe alloy containing quasicrystals has been consolidated using spark plasma sintering(SPS). Its corrosion resistance properties were comparatively investigated with pure Al by electrochemical methods in 3.5 wt% NaCl solution. Their corrosion current density was also compared with that of three commercial steels-316 stainless steel, AISI 440C stainless steel and AISI H13 tool steel. Al-Cr-Fe alloy exhibits nobler corrosion potential and evident passivation with a potential range of around 150 mV while no passivation of pure Al sample is seen. The corrosion resistance of Al-Cr-Fe alloy is less than that of pure Al, but is close to that of 316 stainless steel and superior to that of AISI 440C stainless steel and AISI H13 tool steel.
基金the financial support from the National Natural Science Foundation of China(No.51671095)Key Research Development Program of Shandong Province of China(No.2015GGx102016)
文摘Equiatomic CuZrAl and CuZrAlTi medium entropy alloys were designed and synthesized by mechanical alloying and spark plasma sintering technique.The alloying behavior,phase evolutions,microstructures and properties of samples were investigated by X-ray diffraction,differential scanning calorimetry,field emission scanning electron microscopy,microscopy/Vickers hardness testing and electrochemical polarization measurement.The results indicate that the final products of as-milled alloys consist of amorphous phases.Ti addition improves the glass forming ability of as-milled alloys.The as-sintered CuZrAl alloy contains face-centered cubic(fcc)solid solution,Al_(1.05)Cu_(0.95) Zr and AlZr_2 phases at different sintering temperatures.With Ti addition,the as-sintered sample is only composed of intermetallics at 690°C,while fcc1,fcc2 and CuTi3phases are formed at 1100°C.CuZrAlTi-1100°C alloy exhibits the highest hardness value of 1173HV0.2owing to the high sintering density,solid solution strengthening and homogeneous precipitation of nano-size crystalline phase.CuZrAlTi-690°C alloy presents a similar corrosion resistance with304 Lstainless steel in seawater solution and further possesses the lower corrosion rate.
文摘We report a facile strategy to synthesize intermetallic nanoparticle (iNP) electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles (NPs). ZIF-8 serves not only as precursor for N-doped carbon (NC), but also as Zn source for the formation of intermetallic or alloy NPs with the encapsulated metals. The resulting sub-4 nm PtZn iNPs embedded in NC exhibit high sintering resistance up to 1,000℃. Importantly, the present methodology allows fine-tuning of both composition (e.g., PdZn and RhZn iNPs, as well as AuZn and RuZn alloy NPs) and size (2.4, 3.7, and 5.4 nm PtZn) of the as-formed bimetallic NPs. To the best of our knowledge, this is the first report of a metal-organic framework (MOF) with multiple functionalities, such as secondary metal source, carbon precursor, and size-regulating reagent, which promote the formation of iNPs. This work opens a new avenue for the synthesis of highly uniform and stable iNPs.
基金supported financially by the National Natural Science Foundation of China(Nos.U1537212,51971013,51590894and 51425102)the National Key Research and Development Program of China(No.2016YFB0300901)。
文摘Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.