Ceramic foams were prepared using red mud and fly ash as raw materials with sodium borate as sintering aid agent,starchand MnO2as foaming agent,respectively.The influence of the amount of starch or MnO2on the crystall...Ceramic foams were prepared using red mud and fly ash as raw materials with sodium borate as sintering aid agent,starchand MnO2as foaming agent,respectively.The influence of the amount of starch or MnO2on the crystalline phase,pore morphologyand physical–chemical porosities was studied.The results showed that the main crystal phases of samples with starch addition andMnO2addition were sodalite phase Na6(AlSiO4)6and Na8(SiAlO4)6MnO4,respectively.The SEM images showed that the variation ofporous structure was mainly dominated by the addition of foaming agent.With the increase of foaming agent,the samples exhibitedbetter comprehensive properties:bulk density of0.59?0.96g/cm3,porosity of41.82%?63.51%,water absorption of3.16%?9.17%,compressive strength of4.22?8.38MPa,flexural strength of2.44?5.82MPa,acid resistance of95.59%?99.60%,alkali resistance of99.82%?99.99%.Based on these properties,the ceramic foams can be used in building field.展开更多
Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foami...Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foaming agent during sintering.The effect of the BA/FA mass ratio on the phase composition,pore morphology,pore size distribution,physical properties,and glass structure was investigated,with results showing that with the increase in the BA/FA ratio,the content of the glass phase,Si-O-Si,and Q3Si units decrease gradually.The glass transmission temperature of the mixture was also reduced.When combined,the glass viscosity decreases,causing bubble coalescence and uneven pore distribution.Glass ceramic foams with uniform spherical pores are fabricated.When the content of BA,FA,and PS are 35wt%,45wt%,and 20wt%,respectively,contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm3,porosity of 56.01%,and compressive strength exceeding 16.23 MPa.This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.展开更多
The introduction of porous structures into high-entropy ceramics is expected to further improve its thermal insulation performance.In this work,a series of novel rare-earth-niobate high-entropy ceramic foams((Dy_(0.2)...The introduction of porous structures into high-entropy ceramics is expected to further improve its thermal insulation performance.In this work,a series of novel rare-earth-niobate high-entropy ceramic foams((Dy_(0.2)Ho_(0.2)Y_(0.2)Er_(0.2)Yb_(0.2))_(3)NbO_(7))with hierarchical pore structures were prepared by a particle-stabilized foaming method.Atomic-scale analysis reveals that high entropy causes atom displacement and lattice distortion.The high-entropy ceramic foams exhibit high porosity(90.13%-96.13%)and ultralow thermal conductivity(0.0343-0.0592 W/(m·K))at room temperature.High-entropy ceramic foam prepared by a 20 wt%slurry sintered at 1500℃has the porosity of 96.12%and extremely low thermal conductivity of 0.0343 W/(m·K).The existence of walls and secondary pores contributes to reduced thermal conductivity.There is a temperature difference of over 800℃between frontside and backside of the sample under fire resistance test.The research indicates that these as-prepared high-entropy ceramic foams are expected to be promising thermal insulation materials.展开更多
Crushable ceramic foams are more suitable to be used as an arrestor material applied in engineered materials arresting system （EMAS） for airport runway for their properties of widely controllable strength, negligibl...Crushable ceramic foams are more suitable to be used as an arrestor material applied in engineered materials arresting system （EMAS） for airport runway for their properties of widely controllable strength, negligible crushing-rebounding behavior, durability, and chemically-inert composition, comparing with traditional concrete foams. The synthesis of ceramic foams adopted direct-foaming method and used an animal protein as foaming agent. Kaolin, talc powder and alumina were the main raw materials. Effects of the ratios of raw materials, calcination temperatures, heating rates, holding time, viscosities of potyvinyl alcohol （PVA） solution as well as the amounts of protein foaming agent and water on microscopic structure, densities, compressive strength and open porosities of ceramic foams were investigated systematically. The results indicate that ceramic foams with typical pore sizes 100-300 μm, open porosities from 73.1% to 91.5%, densities from 0.25 to 0.62 g.cm-3, compressive strength from 0.19 to 4.89 MPa, are obtained by properly adjusting the parameters mentioned above. And the mechanical strength meets the requirement for the EMAS for airport runway. In addition, good correlations are observed among compressive strength, open porosity, microscopic structure, and crystal phase. Furthermore, the possibility of producing the general dimensions of such aircraft arresting components with the proposed method was also discussed.展开更多
With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase compos...With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase composition, the acid–base properties, and the microstructure, were analyzed by XRD, SEM, Py-IR, and BET techniques. The performance of the ZrO2 polycrystalline ceramic foam catalyst in a tubular reactor was investigated via biodiesel synthesis using S. wilsoniana oil and methanol. The effects of reaction conditions(i.e., reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil) on transesterification efficiency were investigated, and the reaction conditions were optimized using RSM. The optimum reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil were determined to be 290 ℃, 10 MPa, and 4:1, respectively. Under this condition, the FAME content in the product oil reached 98.38%. The performance of the ZrO2 polycrystalline ceramic foam catalyst synthesized in this work for biodiesel synthesis from S. wilsoniana oil with a moisture content of 7.1% and an acid value of 130.697 mg KOH/g was examined, and the FAME content in the product oil was found to be 93% and 97.67%, respectively. The FAME content in the product oil exceeded 97% after five consecutive cycles(12 h per cycle of use) of the catalyst. The proposed catalyst represents a new type of solid catalyst with excellent acid resistance, water resistance, esterification efficiency, and catalytic stability.展开更多
In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network mo...In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template （F）, centrifugal acceleration （v） and sintering temperature （T）, while the only output was the ultimate compressive strength （（7）. According to the registered BP model, the effects of F, v, T on 0 were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.展开更多
The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obta...The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.展开更多
Based on the assumption of a local non-equilibrium of heat transfer between a solid matrix and gas,a mathematic model of coal mine methane combustion in a porous medium was established,as well the solid-gas boundary c...Based on the assumption of a local non-equilibrium of heat transfer between a solid matrix and gas,a mathematic model of coal mine methane combustion in a porous medium was established,as well the solid-gas boundary conditions.We simulated numerically the flame propagation characteristics.The results show that the flame velocity in ceramic foam is higher than that of free laminar flows;the maximum flame velocity depends on the combined effects of a radiation extinction coefficient and convection heat transfer in ceramic foam and rises with an increase in the chemical equivalent ratio.The radiation extinction coefficient cannot be used alone to determine the heat regeneration effects in the design of ceramic foam burners.展开更多
The importance of purification for aluminum and aluminum alloy casting was outlined. By comparing ceramic foam filters （CFF） in China and overseas, the existing problems and challenges of China＇ s CFF for aluminum ...The importance of purification for aluminum and aluminum alloy casting was outlined. By comparing ceramic foam filters （CFF） in China and overseas, the existing problems and challenges of China＇ s CFF for aluminum were given. Measures to improve the performance of CFF were put forward based on material, preparation process, utility evaluation, etc.展开更多
Casting defects that are closely related to entrapped air bubbles and metallic oxides occur very frequently in the sand mold casting process. Many researchers have shown that these defects can be reduced by adopting a...Casting defects that are closely related to entrapped air bubbles and metallic oxides occur very frequently in the sand mold casting process. Many researchers have shown that these defects can be reduced by adopting an appropriate gating system design. However, it is difficult for field engineers to identify a specific gating system that is more appropriate for their products. In this study, we tried to draw a comparison between two gating system designs with and without a ceramic foam filter. The ceramic foam filter was added to the horizontal runner just after the down sprue to prevent air bubble generation and reduce turbulence without a change of gating system design. The water modeling experiment was conducted with four different amounts of the initial volumes of water in the reservoir to verify the effects of initial pouring velocity. The results of the experiment applying the filter showed remarkably changed flow characteristics. The use of the filter was found to convert the flow pattern of water in the desired direction. The ceramic foam filter performed well to reduce flow velocity and stabilize the water stream.The flow pattern without a filter can be improved significantly even with the the use of just a 10 PPI irregular filter. Although the study confirmed that use of the filter may change the flow characteristics, it needs to be noted that the use of the ceramic filter alone cannot solve all the problems caused by a poorly designed gating system.展开更多
This study investigated the potential application of a zirconium oxide （ZrO2） ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor （GDNF）. Three sets of ZrO2 ceramic foams...This study investigated the potential application of a zirconium oxide （ZrO2） ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor （GDNF）. Three sets of ZrO2 ceramic foams with different pore densities of 10, 20, and 30 pores per linear inch （PPI） were prepared to support a 3D culturing system. After primary astrocytes were cultured in these systems, production yields of GDNF were evaluated. The biomaterial bio- compatibility, cell proliferation and activation of cellular signaling pathways in GDNF synthesis and secretion in the culturing systems were also assessed and compared with a conventional culturing system. In this study, we found that the ZrO2 ceramic foam culturing system was biocompatible, using which the GDNF yields were elevated and sustained by stimulated cell proliferation and activation of signaling pathways in astrocytes cultured in the system. In conclusion, the ZrO2 ceramic foam is promising for the development of a GDNF mass production device for Parkinson＇s disease treatment.展开更多
A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separat...A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation ofa Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness （533 and 633 K） were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.展开更多
The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to...The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.展开更多
Conventional Ceramic Foam Filter(CFF)technology has some difficulties in removing fine particulates(e.g.<20 μm)from liquid aluminium.In the present work the filtration behaviour of 30,50 and 80 ppi CFF filters hav...Conventional Ceramic Foam Filter(CFF)technology has some difficulties in removing fine particulates(e.g.<20 μm)from liquid aluminium.In the present work the filtration behaviour of 30,50 and 80 ppi CFF filters have been studied in the presence of magnetic fields in the range of 0.06-0.2T,produced by induction coils operated at 50 Hz. A feed recipe containing 90 wt.%of the aluminium alloy A356 doped with 10 wt.%A356 composite,containing 15 wt% SiC particles with a particle size ranging from 13 to 23 μm,was used.When the results obtained for the experiments conducted under the influence of a magnetic field where compared with similar reference gravity filtration experiments profound changes were observed in the distribution of particulates within,over and below the filter.Significant improvements in the wetting behaviour of the liquid metal to the CFF surface were also observed.It is believed that a successful change in filtration mechanisms is obtained as a result of the presence of the Lorentz forces and the metal recirculation produced by the magnetic field.The magnitude of the Lorentz forces,i.e.the magnetic pressure,are in the present work discussed in relation to the filtration results,and quantified based on experimental data and validated 2D axial symmetric Finite Element Modelling(FEM).展开更多
Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influe...Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influences of SiC and magnesia content,the sintering temperatures on ceramic properties were discussed.Alumina-based foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times.Its main phases after 1 hour sintering at 1 500℃ consist of alumina,silicon carbide,spinel and mullite.展开更多
Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural ...Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.展开更多
In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount o...In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount of flux(talc and potassium feldspar)and foaming agent silicon carbide(SiC).The effects of the steel slag addition(equivalent replacement of coal gangue,5%,10%,15%,20%,25%,30%,and 35%,by mass)and flux addition(fixing the total addition of talc and potassium feldspar at 20 mass%,replacing potassium feldspar with talc in equal amount of 0,5%,10%,15%,and 20%,by mass)on the physical properties,microstructure and phase composition of the foamed ceramics were studied.The results show that:(1)with the increase of steel slag additions,the addition of SiO_(2) in the skeleton structure decreases,the addition of CaO,MgO and other oxides increases,and the viscosity decreases;excessive steel slag addition is not conducive to the formation of moderate-size and uniform distributed pores due to the low addition of SiO_(2);the steel slag addition shall not exceed 30%;(2)the influence of talc and potassium feldspar flux on the foamed ceramics is mainly to change the contents of alkali metal oxides,as well as Al_(2)O_(3) and SiO_(2) which constitute the ceramic skeleton;(3)the optimum foamed ceramic formulation is m(coal gangue):m(steel slag):m(potassium feldspar):m(talc)=50:30:10:10,extra-adding 0.1 mass%SiC.展开更多
Increasing porosity is one of the most direct ways to improve the thermal insulation and dielectric properties of materials.Until now,many wet methods for preparing Si_(3)N_(4) ceramic foams usually face the problems ...Increasing porosity is one of the most direct ways to improve the thermal insulation and dielectric properties of materials.Until now,many wet methods for preparing Si_(3)N_(4) ceramic foams usually face the problems of complex rheology,long period,and expensive cost,and the reported pore sizes of Si_(3)N_(4) ceramic foams are typically micron-grade,resulting in a lack of competitiveness in thermal insulation and wave-transparent applications.In this paper,the Si_(3)N_(4)@SiO_(2) ceramic foams were prepared using an efficient dry-method,which combined three processes of low temperature chemical vapor deposition(LTCVD),template,and isostatic pressing.The method has the advantages of simple operation and short preparation period,and can realize near-net size molding and mass production.In addition,the evolution mechanisms of honeycomb microstructure and composition of Si_(3)N_(4)@SiO_(2) ceramic foam during sintering were studied by chemical reaction thermodynamics.The as-prepared Si_(3)N_(4)@SiO_(2) ceramic foam possesses low density(0.377 g·cm^(-3)),high compressive strength(7.5 MPa),low thermal conductivity(0.0808 W·m^(-1)·K^(-1)),and excellent dielectric properties(ε<1.32,tanδ<0.009)in the frequency range of 8-18 GHz,and its maximum working temperature in air can reach up to 1100℃.It will be recommended to be applied in the interlayer of Si_(3)N_(4) ceramic radome to improve its thermal insulation and electromagnetic wave transparency performances.展开更多
To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of ...To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of three different pore densities.The biaxial method is validated by characterization of mechanical parameters,and the in-situ fracture process is validated by a digital image correlation,followed by a formula correction for effective tensile strength with consideration of discrete crack paths.For experimental setup curved loading platens,compliant pad and intermediate quasi-static loading rate are proposed for guaranteeing tensile failure under a radial compressive load.Tensile strength,fracture energy,and brittleness increase with the foam pore density,and the fracture behavior is a balanced result of materials and foam structural support strength.An analytical model of splitting tensile strength with structural parameters is derived,which implies its dependence on cell size and critical stress intensity factor of strut materials.展开更多
A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite mater...A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage density and high thermal conductivity, it is suit for energy storage under high temperature.展开更多
基金Project(K1003027-11) supported by the Key Project Foundation of Science and Technology Plans of Changsha,China
文摘Ceramic foams were prepared using red mud and fly ash as raw materials with sodium borate as sintering aid agent,starchand MnO2as foaming agent,respectively.The influence of the amount of starch or MnO2on the crystalline phase,pore morphologyand physical–chemical porosities was studied.The results showed that the main crystal phases of samples with starch addition andMnO2addition were sodalite phase Na6(AlSiO4)6and Na8(SiAlO4)6MnO4,respectively.The SEM images showed that the variation ofporous structure was mainly dominated by the addition of foaming agent.With the increase of foaming agent,the samples exhibitedbetter comprehensive properties:bulk density of0.59?0.96g/cm3,porosity of41.82%?63.51%,water absorption of3.16%?9.17%,compressive strength of4.22?8.38MPa,flexural strength of2.44?5.82MPa,acid resistance of95.59%?99.60%,alkali resistance of99.82%?99.99%.Based on these properties,the ceramic foams can be used in building field.
基金the National key R&D projects(Nos.2019YFC1907101,2019YFC1907103,2017YFB0702304)the Key R&D project in Ningxia Hui Autonomous Region(No.2020BCE01001)+5 种基金the National Natural Science Foundation of China(No.51672024)the Xijiang Innovation and Entrepreneurship Team(No.2017A0109004)the Program of China Scholarships Coun-cil(No.201806465040)the Fundamental Research Funds for the Central Universities(Nos.FRF-IC-19-007,FRF-IC-19-017Z,FRF-MP-19-002,FRF-TP-19-003B1,FRF-GF-19-032B,and 06500141)the State Key Laboratory for Ad-vanced Metals and Materials(No.2019Z-05)the Integ-ration of Green Key Process Systems MIIT.
文摘Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foaming agent during sintering.The effect of the BA/FA mass ratio on the phase composition,pore morphology,pore size distribution,physical properties,and glass structure was investigated,with results showing that with the increase in the BA/FA ratio,the content of the glass phase,Si-O-Si,and Q3Si units decrease gradually.The glass transmission temperature of the mixture was also reduced.When combined,the glass viscosity decreases,causing bubble coalescence and uneven pore distribution.Glass ceramic foams with uniform spherical pores are fabricated.When the content of BA,FA,and PS are 35wt%,45wt%,and 20wt%,respectively,contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm3,porosity of 56.01%,and compressive strength exceeding 16.23 MPa.This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.
基金supported by the National Natural Science Foundation of China(No.52072301)the State Key Laboratory of Solidification Processing(NPU)(No.2021-TS-08)+3 种基金the State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KFZD202102)the China-Poland International Collaboration Fund of National Natural Science Foundation of China(No.51961135301)the Fundamental Research Funds for the Central Universities(No.D5000210722)State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(No.P2020–009)。
文摘The introduction of porous structures into high-entropy ceramics is expected to further improve its thermal insulation performance.In this work,a series of novel rare-earth-niobate high-entropy ceramic foams((Dy_(0.2)Ho_(0.2)Y_(0.2)Er_(0.2)Yb_(0.2))_(3)NbO_(7))with hierarchical pore structures were prepared by a particle-stabilized foaming method.Atomic-scale analysis reveals that high entropy causes atom displacement and lattice distortion.The high-entropy ceramic foams exhibit high porosity(90.13%-96.13%)and ultralow thermal conductivity(0.0343-0.0592 W/(m·K))at room temperature.High-entropy ceramic foam prepared by a 20 wt%slurry sintered at 1500℃has the porosity of 96.12%and extremely low thermal conductivity of 0.0343 W/(m·K).The existence of walls and secondary pores contributes to reduced thermal conductivity.There is a temperature difference of over 800℃between frontside and backside of the sample under fire resistance test.The research indicates that these as-prepared high-entropy ceramic foams are expected to be promising thermal insulation materials.
基金Funded partly by the National Natural Science Foundation of China(No.51202151)
文摘Crushable ceramic foams are more suitable to be used as an arrestor material applied in engineered materials arresting system （EMAS） for airport runway for their properties of widely controllable strength, negligible crushing-rebounding behavior, durability, and chemically-inert composition, comparing with traditional concrete foams. The synthesis of ceramic foams adopted direct-foaming method and used an animal protein as foaming agent. Kaolin, talc powder and alumina were the main raw materials. Effects of the ratios of raw materials, calcination temperatures, heating rates, holding time, viscosities of potyvinyl alcohol （PVA） solution as well as the amounts of protein foaming agent and water on microscopic structure, densities, compressive strength and open porosities of ceramic foams were investigated systematically. The results indicate that ceramic foams with typical pore sizes 100-300 μm, open porosities from 73.1% to 91.5%, densities from 0.25 to 0.62 g.cm-3, compressive strength from 0.19 to 4.89 MPa, are obtained by properly adjusting the parameters mentioned above. And the mechanical strength meets the requirement for the EMAS for airport runway. In addition, good correlations are observed among compressive strength, open porosity, microscopic structure, and crystal phase. Furthermore, the possibility of producing the general dimensions of such aircraft arresting components with the proposed method was also discussed.
基金the financial support from the National Natural Science Foundation of China (No. 21266022, No. 21466022)the National High Technology Research and Development Program 863 (2014AA022002, 2012AA101800-03, 2012AA021205-6, 2012AA021704)+1 种基金the Key Programs of the National Laboratory (No. SKLFZZB-201312)the International Science & Technology Cooperation Program of China (2014DFA61040)
文摘With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase composition, the acid–base properties, and the microstructure, were analyzed by XRD, SEM, Py-IR, and BET techniques. The performance of the ZrO2 polycrystalline ceramic foam catalyst in a tubular reactor was investigated via biodiesel synthesis using S. wilsoniana oil and methanol. The effects of reaction conditions(i.e., reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil) on transesterification efficiency were investigated, and the reaction conditions were optimized using RSM. The optimum reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil were determined to be 290 ℃, 10 MPa, and 4:1, respectively. Under this condition, the FAME content in the product oil reached 98.38%. The performance of the ZrO2 polycrystalline ceramic foam catalyst synthesized in this work for biodiesel synthesis from S. wilsoniana oil with a moisture content of 7.1% and an acid value of 130.697 mg KOH/g was examined, and the FAME content in the product oil was found to be 93% and 97.67%, respectively. The FAME content in the product oil exceeded 97% after five consecutive cycles(12 h per cycle of use) of the catalyst. The proposed catalyst represents a new type of solid catalyst with excellent acid resistance, water resistance, esterification efficiency, and catalytic stability.
基金financially supported by the Innovation Research Team Program of the Ministry of Education(IRT0713)the Key Laboratory of New Materials in Automobile of Liaoning Province(grant No.201016201)Doctoral Initiating Project of Liaoning Province Foundation for Natural Sciences,China
文摘In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template （F）, centrifugal acceleration （v） and sintering temperature （T）, while the only output was the ultimate compressive strength （（7）. According to the registered BP model, the effects of F, v, T on 0 were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.
基金supported by the National Natural Science Foundation of China (50672014)Innovation Research Team Program of the Ministry of Education (IRT0713)
文摘The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.
基金supported by the National Natural Science Foundation of China (No.50534090)the Science Foundation of China University of Mining and Technology (No.0E061046)
文摘Based on the assumption of a local non-equilibrium of heat transfer between a solid matrix and gas,a mathematic model of coal mine methane combustion in a porous medium was established,as well the solid-gas boundary conditions.We simulated numerically the flame propagation characteristics.The results show that the flame velocity in ceramic foam is higher than that of free laminar flows;the maximum flame velocity depends on the combined effects of a radiation extinction coefficient and convection heat transfer in ceramic foam and rises with an increase in the chemical equivalent ratio.The radiation extinction coefficient cannot be used alone to determine the heat regeneration effects in the design of ceramic foam burners.
文摘The importance of purification for aluminum and aluminum alloy casting was outlined. By comparing ceramic foam filters （CFF） in China and overseas, the existing problems and challenges of China＇ s CFF for aluminum were given. Measures to improve the performance of CFF were put forward based on material, preparation process, utility evaluation, etc.
文摘Casting defects that are closely related to entrapped air bubbles and metallic oxides occur very frequently in the sand mold casting process. Many researchers have shown that these defects can be reduced by adopting an appropriate gating system design. However, it is difficult for field engineers to identify a specific gating system that is more appropriate for their products. In this study, we tried to draw a comparison between two gating system designs with and without a ceramic foam filter. The ceramic foam filter was added to the horizontal runner just after the down sprue to prevent air bubble generation and reduce turbulence without a change of gating system design. The water modeling experiment was conducted with four different amounts of the initial volumes of water in the reservoir to verify the effects of initial pouring velocity. The results of the experiment applying the filter showed remarkably changed flow characteristics. The use of the filter was found to convert the flow pattern of water in the desired direction. The ceramic foam filter performed well to reduce flow velocity and stabilize the water stream.The flow pattern without a filter can be improved significantly even with the the use of just a 10 PPI irregular filter. Although the study confirmed that use of the filter may change the flow characteristics, it needs to be noted that the use of the ceramic filter alone cannot solve all the problems caused by a poorly designed gating system.
基金Project supported by the National Natural Science Foundation of China(Nos.81171262 and 81371473)
文摘This study investigated the potential application of a zirconium oxide （ZrO2） ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor （GDNF）. Three sets of ZrO2 ceramic foams with different pore densities of 10, 20, and 30 pores per linear inch （PPI） were prepared to support a 3D culturing system. After primary astrocytes were cultured in these systems, production yields of GDNF were evaluated. The biomaterial bio- compatibility, cell proliferation and activation of cellular signaling pathways in GDNF synthesis and secretion in the culturing systems were also assessed and compared with a conventional culturing system. In this study, we found that the ZrO2 ceramic foam culturing system was biocompatible, using which the GDNF yields were elevated and sustained by stimulated cell proliferation and activation of signaling pathways in astrocytes cultured in the system. In conclusion, the ZrO2 ceramic foam is promising for the development of a GDNF mass production device for Parkinson＇s disease treatment.
基金financially supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia and is a result of projects No. 34033 and No. 34023
文摘A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation ofa Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness （533 and 633 K） were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.
基金financially supported by the Natural Science Foundation of Liaoning Province(No.:201102090)the Doctoral Initiating Project of Liaoning Province Foundation for Natural Sciences,China(No.:20111068)+2 种基金the High School Development Plan for Distinguished Young Scholars of Liaoning Province Education Committee(No.:LJQ2012056)the National High-Tech Research and Development Program of China("863"Program,No.:2011AA060102)the International Science and Technology Cooperation Program of China,(No.:2011DFR50270)
文摘The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.
基金Item Sponsored by RIRA (Remelting and Inclusion Refining of Aluminium) Project Funded by the Norwegian Research Council (NRC) -BIP Project No.179947/I40
文摘Conventional Ceramic Foam Filter(CFF)technology has some difficulties in removing fine particulates(e.g.<20 μm)from liquid aluminium.In the present work the filtration behaviour of 30,50 and 80 ppi CFF filters have been studied in the presence of magnetic fields in the range of 0.06-0.2T,produced by induction coils operated at 50 Hz. A feed recipe containing 90 wt.%of the aluminium alloy A356 doped with 10 wt.%A356 composite,containing 15 wt% SiC particles with a particle size ranging from 13 to 23 μm,was used.When the results obtained for the experiments conducted under the influence of a magnetic field where compared with similar reference gravity filtration experiments profound changes were observed in the distribution of particulates within,over and below the filter.Significant improvements in the wetting behaviour of the liquid metal to the CFF surface were also observed.It is believed that a successful change in filtration mechanisms is obtained as a result of the presence of the Lorentz forces and the metal recirculation produced by the magnetic field.The magnitude of the Lorentz forces,i.e.the magnetic pressure,are in the present work discussed in relation to the filtration results,and quantified based on experimental data and validated 2D axial symmetric Finite Element Modelling(FEM).
基金The project is supported by National Natural Science Foundation of China:50334030PhD Fund of Liaoning Province:20041010.
文摘Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influences of SiC and magnesia content,the sintering temperatures on ceramic properties were discussed.Alumina-based foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times.Its main phases after 1 hour sintering at 1 500℃ consist of alumina,silicon carbide,spinel and mullite.
基金supported by the National Natural Science Foundation of China(Grant Nos.52102113,52231007)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2021160)the Creative Research Foundation of TSCM。
文摘Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.
文摘In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount of flux(talc and potassium feldspar)and foaming agent silicon carbide(SiC).The effects of the steel slag addition(equivalent replacement of coal gangue,5%,10%,15%,20%,25%,30%,and 35%,by mass)and flux addition(fixing the total addition of talc and potassium feldspar at 20 mass%,replacing potassium feldspar with talc in equal amount of 0,5%,10%,15%,and 20%,by mass)on the physical properties,microstructure and phase composition of the foamed ceramics were studied.The results show that:(1)with the increase of steel slag additions,the addition of SiO_(2) in the skeleton structure decreases,the addition of CaO,MgO and other oxides increases,and the viscosity decreases;excessive steel slag addition is not conducive to the formation of moderate-size and uniform distributed pores due to the low addition of SiO_(2);the steel slag addition shall not exceed 30%;(2)the influence of talc and potassium feldspar flux on the foamed ceramics is mainly to change the contents of alkali metal oxides,as well as Al_(2)O_(3) and SiO_(2) which constitute the ceramic skeleton;(3)the optimum foamed ceramic formulation is m(coal gangue):m(steel slag):m(potassium feldspar):m(talc)=50:30:10:10,extra-adding 0.1 mass%SiC.
基金supported by the Special Project of Science and Technology Cooperation and Exchange of Shanxi Province(No.202204041101014)the National Key Research and Development Program of China(No.2023YFB3811302)+1 种基金the Jinzhong University Research Funds for Doctor(No.JUD2023014)the Shanxi Provincial Key Research and Development Project(No.2022ZDYF027).
文摘Increasing porosity is one of the most direct ways to improve the thermal insulation and dielectric properties of materials.Until now,many wet methods for preparing Si_(3)N_(4) ceramic foams usually face the problems of complex rheology,long period,and expensive cost,and the reported pore sizes of Si_(3)N_(4) ceramic foams are typically micron-grade,resulting in a lack of competitiveness in thermal insulation and wave-transparent applications.In this paper,the Si_(3)N_(4)@SiO_(2) ceramic foams were prepared using an efficient dry-method,which combined three processes of low temperature chemical vapor deposition(LTCVD),template,and isostatic pressing.The method has the advantages of simple operation and short preparation period,and can realize near-net size molding and mass production.In addition,the evolution mechanisms of honeycomb microstructure and composition of Si_(3)N_(4)@SiO_(2) ceramic foam during sintering were studied by chemical reaction thermodynamics.The as-prepared Si_(3)N_(4)@SiO_(2) ceramic foam possesses low density(0.377 g·cm^(-3)),high compressive strength(7.5 MPa),low thermal conductivity(0.0808 W·m^(-1)·K^(-1)),and excellent dielectric properties(ε<1.32,tanδ<0.009)in the frequency range of 8-18 GHz,and its maximum working temperature in air can reach up to 1100℃.It will be recommended to be applied in the interlayer of Si_(3)N_(4) ceramic radome to improve its thermal insulation and electromagnetic wave transparency performances.
基金support from the National Natural Science Foundation of China(Nos.U21A2058 and U22A20127)the German Research Foundation(Collaborative Research Center 920,Multi-Functional Filters for Metal Melt Filtration-A Contribution toward Zero Defect Materials)are appreciated.The author Claudia Voigt would like to thank the Federal Ministry of Education and Research(BMBF)for supporting these investigations as part of the junior research group PurCo(No.03XP0420).
文摘To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of three different pore densities.The biaxial method is validated by characterization of mechanical parameters,and the in-situ fracture process is validated by a digital image correlation,followed by a formula correction for effective tensile strength with consideration of discrete crack paths.For experimental setup curved loading platens,compliant pad and intermediate quasi-static loading rate are proposed for guaranteeing tensile failure under a radial compressive load.Tensile strength,fracture energy,and brittleness increase with the foam pore density,and the fracture behavior is a balanced result of materials and foam structural support strength.An analytical model of splitting tensile strength with structural parameters is derived,which implies its dependence on cell size and critical stress intensity factor of strut materials.
基金Funded by the "863" Hi-Tech Research and Development Program of China (2008AA05Z418)
文摘A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage density and high thermal conductivity, it is suit for energy storage under high temperature.
