Carbon-and silica-based nanomaterials possess a set of merits including large surface area,good structural stability,diversified morphology,adjustable structure,and biocompatibility.These outstanding features make the...Carbon-and silica-based nanomaterials possess a set of merits including large surface area,good structural stability,diversified morphology,adjustable structure,and biocompatibility.These outstanding features make them widely applied in different fields.However,limited by the surface free energy effect,the current studies mainly focus on the symmetric structures,such as nanospheres,nanoflowers,nanowires,nanosheets,and core-shell structured composites.By comparison,the asymmetric structure with ingenious adjustability not only exhibits a larger effective surface area accompanied with more active sites,but also enables each component to work independently or corporately to harness their own merits,thus showing the unusual performances in some specific applications.The current review mainly focuses on the recent progress of design principles and synthesis methods of asymmetric carbon-and silica-based nanomaterials,and their applications in energy storage,catalysis,and biomedicine.Particularly,we provide some deep insights into their unique advantages in related fields from the perspective of materials’structure-performance relationship.Furthermore,the challenges and development prospects on the synthesis and applications of asymmetric carbon-and silica-based nanomaterials are also presented and highlighted.展开更多
During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples ...During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents.The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated.Results show that the sintering level and the content ofα-cristobalite in the surface layer are significantly higher than that of the sample interior.A considerable number of microcracks are found in the surface layer due to theβtoα-phase transition of cristobalite.As the sodium content in the alumina powder decreases,the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease,which is beneficial to the thermal expansion and flexural strength at ambient temperature.The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks,but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.展开更多
Paperboard is an environment-friendly multi-layer material widely used for packaging applications. However, for food packaging paperboard lacks essential barrier properties towards oxygen and water vapor. Conventional...Paperboard is an environment-friendly multi-layer material widely used for packaging applications. However, for food packaging paperboard lacks essential barrier properties towards oxygen and water vapor. Conventional solutions to enhance these barrier properties (e.g. paperboard film coating with synthetic polymers) require special manufacturing facilities and difficult the end-of-life disposal and recycling of the paperboard. Paperboard coating with silica-based formulations is an eco-friendly alternative hereby disclosed. Silica-nanocoatings were prepared by sol-gel synthesis, with or without the addition of Zn(2)-Al-NO3 layered double hydroxides (LDHs), and applied on the surface (ca 2 g/m2) of industrial paperboard samples by a roll-to-roll technique. The physicochemical features of silica-nanocoatings were studied by FTIR-ATR, SEM/EDS, XRD analysis and surface energy measurements. The barrier properties of uncoated and silica-coated paperboard were accessed by water vapor transmission rate (WVTR) and oxygen permeability (Jo2) measurements. The best barrier results were obtained for paperboard coated with a mixture of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES), with and without the incorporation of LDHs.展开更多
In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize ph...In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina pro- moted crystallization of fused silica during sintering at 1180-1220 ℃ and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 ~C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 ℃. In addition, deflection resis- tance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry （SEMJEDS） analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite.展开更多
Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating pre...Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman＇s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir Hinshelwood （LH） recombination （Tw 〈 620 K） to Eley Rideal （ER） replacement （620 K 〈 Tw 〈 1350 K）, and then to 02 desorption （Tw 〉 1350 K）. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature （HT） range, while the surface coverage of physisorption areas varies within quite low temperature （LT） range （Tw 〈 250 K）. Recommended evaluation of partial parameters is also given.展开更多
Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed wave...Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating（AWG） with 2% refractive index difference and a four-channel top-illuminated positive-intrinsicnegative photodetector（PD） array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 Gb E data center interconnections.展开更多
Silica-based ceramic cores have been widely used to fabricate aero-engine hollow blades due to their moderate high temperature mechanical properties and excellent leachability.In this study,silica-based ceramics with ...Silica-based ceramic cores have been widely used to fabricate aero-engine hollow blades due to their moderate high temperature mechanical properties and excellent leachability.In this study,silica-based ceramics with SiC fiber addition were prepared via stereolithography,and the influence of SiC fiber content on mechanical properties of the obtained silica-based ceramics was investigated.With the increase of SiC fiber content,linear shrinkage gradually decreased,while room temperature flexural strength and high temperature flexural strength first increased and then decreased.As SiC fiber content increased to 4.0 wt%,linear shrinkage was reduced to 0.62%resulting from the oxidation of SiC.Furthermore,room temperature flexural strength was improved from 11.79 MPa to 23.83 MPa and high temperature flexural strength was enhanced from 15.64 MPa to 34.62 MPa with 4.0 wt%SiC fiber addition due to the reinforcement of fibers and the enhancedβ-cristobalite content,which meets the need of ceramic cores.Therefore,it demonstrates the capability of fabricating high-performance and high-precision silica-based ceramic cores reinforced by SiC fibers via stereolithography for rapid manufacturing of hollow blades.展开更多
The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by lase...The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by laser powder bed fusion(LPBF)combined with vacuum infiltration(VI).To enhance the infiltration effect,the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100℃.Results showed that a large number of silica particles infiltrated into the pre-sintered bodies.The infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of grains.Nevertheless,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the porosity.ZrSiO_(4) grains could hinder the propagation of cracks due to their high strength.When the addition of ZrSiO_(4) was 10 wt.%,room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1(the mass ratio of silica sol to silica powder was 10:1)reached 17.21 MPa due to the reinforcement of sintering necks.Moreover,high-temperature flexural strength reached 13.90 MPa.Therefore,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.展开更多
Colloidal nanoparticles with anisotropic architectures have attracted a variety of interest and attention due to different physical and chemical properties compared with the isotropic counterparts,making them promisin...Colloidal nanoparticles with anisotropic architectures have attracted a variety of interest and attention due to different physical and chemical properties compared with the isotropic counterparts,making them promising candidates in many fundamental studies and practical applications.Particularly,carbon and silica-based anisotropic nanoparticles can be one stand out by combing both intrinsic merits of carbons and silica,such as structural stability,biocompatibility,large surface area,and ease of functionalization with the anisotropic structural complexity.In this review,we aim to provide an updated summary of the research related to the anisotropic carbon and silica-based nanostructures,covering both their synthesis and applications.展开更多
We have summarized our recent work in the area of novel silica-based optical fibers, which can be classified into two types: silica optical fiber doped with special elements including Bi, Al, and Ce, and micro-structu...We have summarized our recent work in the area of novel silica-based optical fibers, which can be classified into two types: silica optical fiber doped with special elements including Bi, Al, and Ce, and micro-structured multi-core fibers. For element-doped optical fiber, the Bi/Al co-doped silica fibers could exhibit a fluorescence spectrum covering the wavelength range between 1000 and 1400 nm with a full width at half maximum(FWHM) of about 150 nm, which enables its use in fiber amplifiers and laser systems. The Ce-doped fiber's center wavelengths of excitation and emission are about 340 and 430 nm, respectively. The sapphire-derived fiber(SDF) with high alumina dopant concentration in the core can form mullite through heating and cooling with arc-discharge treatment. This SDF can be further developed for an intrinsic Fabry-Perot interferometric that can withstand 1200 ℃, which allows it to be used in high-temperature sensing applications. Owing to the strong evanescent field, microstructured multi-core fiber can be used in a wide range of applications in biological fiber optic sensing, chemical measurement, and interference-related devices. Coaxial-core optical fiber is another novel kind of silica-based optical fiber that has two coaxial waveguide cores and can be used for optical trapping and micro-particle manipulation by generating a highly focused conical optical field. The recent developments of these novel fibers are discussed.展开更多
The effects of temperature and pressure on the steam reforming of methane （CH4＋H2O→← 3H2＋CO） were investigated in a membrane reactor （MR） with a hydrogen permeable membrane. The studies used a novel silica-bas...The effects of temperature and pressure on the steam reforming of methane （CH4＋H2O→← 3H2＋CO） were investigated in a membrane reactor （MR） with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition （CVD） technique with a permeance for H2 of 6.0×10^-8 mol·m^-2.s^-1.Pa^-1 at 923 K. The results in a packed-bed reactor （PBR） were compared to those of the membrane reactor at various temperatures （773-923 K） and pressures （1-20 atm, 101.3-2026.5 kPa） using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73× 10^-6 mol·g^-1 .s^-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10^-6 mol·g^-1.s^-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.展开更多
[Objectives]To establish a non-toxic and efficient method for extracting DNA and total RNA from peanuts and laying a solid foundation for the molecular biology study of peanuts.[Methods]Based on the principle and meth...[Objectives]To establish a non-toxic and efficient method for extracting DNA and total RNA from peanuts and laying a solid foundation for the molecular biology study of peanuts.[Methods]Based on the principle and method of purifying nucleic acids by silica gel adsorption at high salt and low pH condition,a non-toxic and efficient method to extract peanut DNA and total RNA using cetyltrimethyl ammonium bromide(CTAB)extraction solution was designed.The quality and purity of nucleic acids were detected by agarose gel electrophoresis and nucleic acids protein analyzer,respectively.The quality of DNA was further verified by enzyme digestion and PCR amplification using molecular marker techniques.The quality of total RNA was further verified by reverse transcription(RT)-PCR of actin gene and cDNA-SCoT gene differential display technique.[Results]The agarose gel electrophoresis test showed that the peanut DNA extracted by a low-toxic and effective method is free of contamination and degradation.Through the detection by the nucleic acid protein analyzer,the DNA concentration,yield,A260/A280 and A260/A230 of 5 peanut varieties were 419.6-498.2 ng/μL,20.98-24.91μg/g,1.89-1.96 and 2.03-2.28,respectively.The DNA was of high quality and can be completely digested by EcoRI restriction enzymes,and also can be used for SCoT and SRAP molecular marker technology analysis.The RNA extracted from different tissues of peanuts showed no visible DNA bands by non-denaturing agarose gel electrophoresis.The separated 28S bands were brighter than 18S.The ratio of A260/A280 and A260/A230 showed that the RNA quality was good and can be used for reverse transcription,RT-PCR of actin gene and amplification of cDNA-SCoT gene differential display technique.[Conclusions]This experiment established a low-toxic and effective method for extracting DNA and total RNA from peanuts.Compared with traditional methods,this method is more time-saving and cheaper than commercial kits.The most important point is that this method does not use toxic reagents such as phenol,chloroform and isopropanol.Thus,it is expected to be widely applied in molecular biology research.展开更多
In the contemporary context,tetracycline is widely utilized as a prevalent antibiotic in various facets of life.However,the excessive use of antibiotics has caused visible environmental consequences.Henceforth,the sci...In the contemporary context,tetracycline is widely utilized as a prevalent antibiotic in various facets of life.However,the excessive use of antibiotics has caused visible environmental consequences.Henceforth,the scientific community has increasingly focused on developing catalysts that exhibit exceptional efficacy in the proficient degradation of tetracycline.In this study,a novel nanomaterial was developed to encapsulate Cd Te quantum dots(QDs)with a SiO_(2)shell.The distinct synthesis approach generated a composite material that showed heterogeneity and considerably increased the contact area with contaminants.Consequently,the transfer of photoelectron to the SiO_(2)spheres was significantly improved,leading to a more efficient separation during the catalytic process.The study investigated how different factors,such as the loading of the catalyst,the initial concentration of tetracycline,p H levels,and the wight ratio of Cd Te QDs(SiO_(2)+Cd Te QDs)affected the effectiveness of photocatalytic tetracycline degradation.The findings indicated that the optimal degradation efficiency was observed at a catalyst concentration of 0.25 g/L and a solution p H of 9,leading to an impressive degradation rate of 96%within a mere 2 h timeframe.展开更多
A novel macroporous silica-based hexagonal tungsten oxide （h-WO3/SiO2） with exchangeable sodium cations located in hex- agonal tunnel structure was synthesized by a facile hydrothermal treatment of sodium tungstate ...A novel macroporous silica-based hexagonal tungsten oxide （h-WO3/SiO2） with exchangeable sodium cations located in hex- agonal tunnel structure was synthesized by a facile hydrothermal treatment of sodium tungstate dihydrate with 1 mol/L HCl solution. Utilization of the h-WO3/SiO2 adsorbent to remove aqueous strontium was investigated under the condition of various pH values, contact time, the initial concentration of metal ions, salt ion concentration, and coexisting ions. According to the experimental data, Sr2＋ adsorption equilibrium was achieved within 15 min in acidic solution, and the maximum removal ca- pacity of Sr2＋ occurred at pH 4. The kinetic adsorption of Sr2＋ on h-WO3/SiO2 was controlled by pseudo second-order model, and the saturated adsorption of Sr2＋ on h-WO3/SiO2 was better described by Langmuir and Redlich-Peterson isotherm models compared with the Freundlich isotherm model. The distribution coefficient of St2＋ was more than 2000 cm3/g in the presence of Ca2＋, Mg2＋, La3＋, and Eu3＋, indicating that the h-WO3/SiO2 showed excellent selectivity towards Sr2＋ in pH 4.展开更多
基金support from the Shuguang Program supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(18SG035)Shanghai Engineering Research Center of Advanced Thermal Functional Materials(Shanghai Polytechnic University).
文摘Carbon-and silica-based nanomaterials possess a set of merits including large surface area,good structural stability,diversified morphology,adjustable structure,and biocompatibility.These outstanding features make them widely applied in different fields.However,limited by the surface free energy effect,the current studies mainly focus on the symmetric structures,such as nanospheres,nanoflowers,nanowires,nanosheets,and core-shell structured composites.By comparison,the asymmetric structure with ingenious adjustability not only exhibits a larger effective surface area accompanied with more active sites,but also enables each component to work independently or corporately to harness their own merits,thus showing the unusual performances in some specific applications.The current review mainly focuses on the recent progress of design principles and synthesis methods of asymmetric carbon-and silica-based nanomaterials,and their applications in energy storage,catalysis,and biomedicine.Particularly,we provide some deep insights into their unique advantages in related fields from the perspective of materials’structure-performance relationship.Furthermore,the challenges and development prospects on the synthesis and applications of asymmetric carbon-and silica-based nanomaterials are also presented and highlighted.
基金funded by the Shenzhen Development and Reform Commission Project(SZDRC 20181000)made possible through funding from the Wedge Central South Research Institute,Chinasupported by the State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,China。
文摘During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents.The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated.Results show that the sintering level and the content ofα-cristobalite in the surface layer are significantly higher than that of the sample interior.A considerable number of microcracks are found in the surface layer due to theβtoα-phase transition of cristobalite.As the sodium content in the alumina powder decreases,the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease,which is beneficial to the thermal expansion and flexural strength at ambient temperature.The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks,but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.
基金Authors acknowledge the financial support from NANOBARRIER EU FP7 project(FP7-NMP-2011-LARGE-5,ref.N˚280759) CICECO-Aveiro Institute of Materials grant financed by FCT(PEst-C/CTM/LA0011/2013)The financial support from the project CICECO-Aveiro Institute of Materials(Ref.FCT UID/CTM/50011/2013)is greatly acknowledged.
文摘Paperboard is an environment-friendly multi-layer material widely used for packaging applications. However, for food packaging paperboard lacks essential barrier properties towards oxygen and water vapor. Conventional solutions to enhance these barrier properties (e.g. paperboard film coating with synthetic polymers) require special manufacturing facilities and difficult the end-of-life disposal and recycling of the paperboard. Paperboard coating with silica-based formulations is an eco-friendly alternative hereby disclosed. Silica-nanocoatings were prepared by sol-gel synthesis, with or without the addition of Zn(2)-Al-NO3 layered double hydroxides (LDHs), and applied on the surface (ca 2 g/m2) of industrial paperboard samples by a roll-to-roll technique. The physicochemical features of silica-nanocoatings were studied by FTIR-ATR, SEM/EDS, XRD analysis and surface energy measurements. The barrier properties of uncoated and silica-coated paperboard were accessed by water vapor transmission rate (WVTR) and oxygen permeability (Jo2) measurements. The best barrier results were obtained for paperboard coated with a mixture of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES), with and without the incorporation of LDHs.
文摘In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina pro- moted crystallization of fused silica during sintering at 1180-1220 ℃ and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 ~C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 ℃. In addition, deflection resis- tance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry （SEMJEDS） analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite.
基金co-supported by the National Natural Science Foundation of China (No. 51306204)the Natural Science Foundation of Hunan Province (No. 13JJ2002)
文摘Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman＇s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir Hinshelwood （LH） recombination （Tw 〈 620 K） to Eley Rideal （ER） replacement （620 K 〈 Tw 〈 1350 K）, and then to 02 desorption （Tw 〉 1350 K）. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature （HT） range, while the surface coverage of physisorption areas varies within quite low temperature （LT） range （Tw 〈 250 K）. Recommended evaluation of partial parameters is also given.
基金supported by the National High Technology Research and Development Program of China(No.2015AA016902)the National Natural Science Foundation of China(Nos.61435013 and 61405188)K.C.Wong Education Foundation
文摘Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating（AWG） with 2% refractive index difference and a four-channel top-illuminated positive-intrinsicnegative photodetector（PD） array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 Gb E data center interconnections.
基金supported by National Science and Technology Major Project(no.2017-Ⅶ-0008-0102)National Natural Science Foundation of China(no.51975230)Fundamental Research Funds for the Central Universities(nos.2019kfy XMPY020,2020kfy FPZX003,2018KFYYXJJ030,2019kfy XKJC011)。
文摘Silica-based ceramic cores have been widely used to fabricate aero-engine hollow blades due to their moderate high temperature mechanical properties and excellent leachability.In this study,silica-based ceramics with SiC fiber addition were prepared via stereolithography,and the influence of SiC fiber content on mechanical properties of the obtained silica-based ceramics was investigated.With the increase of SiC fiber content,linear shrinkage gradually decreased,while room temperature flexural strength and high temperature flexural strength first increased and then decreased.As SiC fiber content increased to 4.0 wt%,linear shrinkage was reduced to 0.62%resulting from the oxidation of SiC.Furthermore,room temperature flexural strength was improved from 11.79 MPa to 23.83 MPa and high temperature flexural strength was enhanced from 15.64 MPa to 34.62 MPa with 4.0 wt%SiC fiber addition due to the reinforcement of fibers and the enhancedβ-cristobalite content,which meets the need of ceramic cores.Therefore,it demonstrates the capability of fabricating high-performance and high-precision silica-based ceramic cores reinforced by SiC fibers via stereolithography for rapid manufacturing of hollow blades.
基金financially supported by National Science and Technology Major Project(No.2017-Ⅶ−0008-0102)National Nat-ural Science Foundation of China(No.51975230)Fundamental Research Funds for the Central Universities(Nos.2019kfyXMPY020,2020kfyFPZX003,2018KFYYXJJ030 and 2019kfyXKJC011)。
文摘The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by laser powder bed fusion(LPBF)combined with vacuum infiltration(VI).To enhance the infiltration effect,the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100℃.Results showed that a large number of silica particles infiltrated into the pre-sintered bodies.The infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of grains.Nevertheless,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the porosity.ZrSiO_(4) grains could hinder the propagation of cracks due to their high strength.When the addition of ZrSiO_(4) was 10 wt.%,room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1(the mass ratio of silica sol to silica powder was 10:1)reached 17.21 MPa due to the reinforcement of sintering necks.Moreover,high-temperature flexural strength reached 13.90 MPa.Therefore,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.
基金the National Key R&D Program of China (No. 2016YFA0202900)the National Natural Science Foundation of China (Nos.21622308 and 21872121)+1 种基金Key Program Supported by the Natural Science Foundation of Zhejiang Province,China (No. LZ18B060002)the Fundamental Research Funds for the Central Universities (No.2017XZZX002-16) are greatly appreciated.
文摘Colloidal nanoparticles with anisotropic architectures have attracted a variety of interest and attention due to different physical and chemical properties compared with the isotropic counterparts,making them promising candidates in many fundamental studies and practical applications.Particularly,carbon and silica-based anisotropic nanoparticles can be one stand out by combing both intrinsic merits of carbons and silica,such as structural stability,biocompatibility,large surface area,and ease of functionalization with the anisotropic structural complexity.In this review,we aim to provide an updated summary of the research related to the anisotropic carbon and silica-based nanostructures,covering both their synthesis and applications.
基金Project supported by the National Natural Science Foundation of China(Nos.61735009,61535004,and 61827819)
文摘We have summarized our recent work in the area of novel silica-based optical fibers, which can be classified into two types: silica optical fiber doped with special elements including Bi, Al, and Ce, and micro-structured multi-core fibers. For element-doped optical fiber, the Bi/Al co-doped silica fibers could exhibit a fluorescence spectrum covering the wavelength range between 1000 and 1400 nm with a full width at half maximum(FWHM) of about 150 nm, which enables its use in fiber amplifiers and laser systems. The Ce-doped fiber's center wavelengths of excitation and emission are about 340 and 430 nm, respectively. The sapphire-derived fiber(SDF) with high alumina dopant concentration in the core can form mullite through heating and cooling with arc-discharge treatment. This SDF can be further developed for an intrinsic Fabry-Perot interferometric that can withstand 1200 ℃, which allows it to be used in high-temperature sensing applications. Owing to the strong evanescent field, microstructured multi-core fiber can be used in a wide range of applications in biological fiber optic sensing, chemical measurement, and interference-related devices. Coaxial-core optical fiber is another novel kind of silica-based optical fiber that has two coaxial waveguide cores and can be used for optical trapping and micro-particle manipulation by generating a highly focused conical optical field. The recent developments of these novel fibers are discussed.
文摘The effects of temperature and pressure on the steam reforming of methane （CH4＋H2O→← 3H2＋CO） were investigated in a membrane reactor （MR） with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition （CVD） technique with a permeance for H2 of 6.0×10^-8 mol·m^-2.s^-1.Pa^-1 at 923 K. The results in a packed-bed reactor （PBR） were compared to those of the membrane reactor at various temperatures （773-923 K） and pressures （1-20 atm, 101.3-2026.5 kPa） using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73× 10^-6 mol·g^-1 .s^-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10^-6 mol·g^-1.s^-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.
基金Projects of National Natural Science Foundation of China(3166042831960409+2 种基金31960416)Projects of Guangxi Natural Science Foundation of China(2018GXNSFDA281027,2018GXNSFDA294004,2017GXNSFAA198032)Science and Technology Development Fund Project of Guangxi Academy of Agricultural Sciences(Gui Nong Ke 2018YM06,Gui Nong Ke 2017JZ13,31960409,Gui Nong Ke 2018YT12).
文摘[Objectives]To establish a non-toxic and efficient method for extracting DNA and total RNA from peanuts and laying a solid foundation for the molecular biology study of peanuts.[Methods]Based on the principle and method of purifying nucleic acids by silica gel adsorption at high salt and low pH condition,a non-toxic and efficient method to extract peanut DNA and total RNA using cetyltrimethyl ammonium bromide(CTAB)extraction solution was designed.The quality and purity of nucleic acids were detected by agarose gel electrophoresis and nucleic acids protein analyzer,respectively.The quality of DNA was further verified by enzyme digestion and PCR amplification using molecular marker techniques.The quality of total RNA was further verified by reverse transcription(RT)-PCR of actin gene and cDNA-SCoT gene differential display technique.[Results]The agarose gel electrophoresis test showed that the peanut DNA extracted by a low-toxic and effective method is free of contamination and degradation.Through the detection by the nucleic acid protein analyzer,the DNA concentration,yield,A260/A280 and A260/A230 of 5 peanut varieties were 419.6-498.2 ng/μL,20.98-24.91μg/g,1.89-1.96 and 2.03-2.28,respectively.The DNA was of high quality and can be completely digested by EcoRI restriction enzymes,and also can be used for SCoT and SRAP molecular marker technology analysis.The RNA extracted from different tissues of peanuts showed no visible DNA bands by non-denaturing agarose gel electrophoresis.The separated 28S bands were brighter than 18S.The ratio of A260/A280 and A260/A230 showed that the RNA quality was good and can be used for reverse transcription,RT-PCR of actin gene and amplification of cDNA-SCoT gene differential display technique.[Conclusions]This experiment established a low-toxic and effective method for extracting DNA and total RNA from peanuts.Compared with traditional methods,this method is more time-saving and cheaper than commercial kits.The most important point is that this method does not use toxic reagents such as phenol,chloroform and isopropanol.Thus,it is expected to be widely applied in molecular biology research.
基金supported by National Natural Science Foundation of China(No.51976081)open research fund program of State Key Laboratory of Eco-hydraulics in Northwest Arid RegionXi’an University of Technology(Grant No.2022KFKT-4)
文摘In the contemporary context,tetracycline is widely utilized as a prevalent antibiotic in various facets of life.However,the excessive use of antibiotics has caused visible environmental consequences.Henceforth,the scientific community has increasingly focused on developing catalysts that exhibit exceptional efficacy in the proficient degradation of tetracycline.In this study,a novel nanomaterial was developed to encapsulate Cd Te quantum dots(QDs)with a SiO_(2)shell.The distinct synthesis approach generated a composite material that showed heterogeneity and considerably increased the contact area with contaminants.Consequently,the transfer of photoelectron to the SiO_(2)spheres was significantly improved,leading to a more efficient separation during the catalytic process.The study investigated how different factors,such as the loading of the catalyst,the initial concentration of tetracycline,p H levels,and the wight ratio of Cd Te QDs(SiO_(2)+Cd Te QDs)affected the effectiveness of photocatalytic tetracycline degradation.The findings indicated that the optimal degradation efficiency was observed at a catalyst concentration of 0.25 g/L and a solution p H of 9,leading to an impressive degradation rate of 96%within a mere 2 h timeframe.
基金supported by the National Natural Science Foundation of China (21261140335)
文摘A novel macroporous silica-based hexagonal tungsten oxide （h-WO3/SiO2） with exchangeable sodium cations located in hex- agonal tunnel structure was synthesized by a facile hydrothermal treatment of sodium tungstate dihydrate with 1 mol/L HCl solution. Utilization of the h-WO3/SiO2 adsorbent to remove aqueous strontium was investigated under the condition of various pH values, contact time, the initial concentration of metal ions, salt ion concentration, and coexisting ions. According to the experimental data, Sr2＋ adsorption equilibrium was achieved within 15 min in acidic solution, and the maximum removal ca- pacity of Sr2＋ occurred at pH 4. The kinetic adsorption of Sr2＋ on h-WO3/SiO2 was controlled by pseudo second-order model, and the saturated adsorption of Sr2＋ on h-WO3/SiO2 was better described by Langmuir and Redlich-Peterson isotherm models compared with the Freundlich isotherm model. The distribution coefficient of St2＋ was more than 2000 cm3/g in the presence of Ca2＋, Mg2＋, La3＋, and Eu3＋, indicating that the h-WO3/SiO2 showed excellent selectivity towards Sr2＋ in pH 4.
