Unidirectional porous AlN ceramics(UP-AlNs)have attracted great attention for their wide applications in catalyst supports,filters and composite reinforcements.However,traditional fabrication processes usually require...Unidirectional porous AlN ceramics(UP-AlNs)have attracted great attention for their wide applications in catalyst supports,filters and composite reinforcements.However,traditional fabrication processes usually require high temperature and long production cycle.Herein,UP-AlNs were successfully fabricated via the combination of tertiary butyl alcohol(TBA)-based freeze casting and combustion synthesis route using Al and AlN powders as raw materials.The microstructure,open porosity,thermal conductivity and compressive strength of UP-AlNs can be manipulated by synergistically regulating the AlN diluent content and Al/AlN solid loading of the freezing slurries.The optimal UP-AlNs exhibited controllable structure wavelength(λ)and open porosity in a wide range of 21.1-47.1μm and 54.2%-86.0%,respectively.In addition,the corresponding products also possessed anisotropic thermal conductivity and compressive strength.This novel route for the fabrication of UP-AlNs has the advantages of low cost,energy-saving and high efficiency,which shows significant promise for industrial applications.展开更多
Graphene oxide(GO)is widely used in the construction and application of various 2 D membrane-based materials due to its unique colloidal structure.Herein,we demonstrate that micrometer-sized particles can make up free...Graphene oxide(GO)is widely used in the construction and application of various 2 D membrane-based materials due to its unique colloidal structure.Herein,we demonstrate that micrometer-sized particles can make up freestanding membranes enabled by the extraordinary amphiphilic and polymer-like properties of graphene oxide through freeze casting.The 2 D macromolecule,GO could well wrap the particles for better uniformity and stability in either dispersion or membrane.Importantly,freeze casting plays an important role in avoiding the severe aggregation of micrometer-sized particles in the solventremoving process.After reduction,the membrane exhibits good electrical conductivity while maintaining its integral structure,which can be directly used as a freestanding binder-free electrode.This work provides a universal approach to fabricate freestanding membranes with various micrometersized materials for energy storage.展开更多
Digital patternless freeze-casting technology is a new approach for obtaining frozen sand moulds using digital milling technology. The change law of tensile strength and air permeability of frozen sand moulds (100-mes...Digital patternless freeze-casting technology is a new approach for obtaining frozen sand moulds using digital milling technology. The change law of tensile strength and air permeability of frozen sand moulds (100-mesh and 200-mesh silica sand, and zircon sand moulds) under different freezing temperatures and water contents was studied. Results show that with the decrease of freezing temperature and the increase of water contents, the tensile strength and air permeability of the sand moulds are gradually improved. Meanwhile, computed tomography technology was used to characterize the shape and size of the water film between the sand particles mixed with 4wt.% water. The results show that in silica sand moulds, the form of water film is lumpy, and 200-mesh silica sand moulds have more water films and higher proportion of small-sized water films than 100-mesh silica sand moulds, while in zircon sand moulds, the form of water film is membranous. At the same freezing temperature and water content, the tensile strength of zircon sand mould is the highest, and 100-mesh silica sand mould is the lowest. A comparative solidification experiment of A356 aluminum alloy was carried out in frozen sand mould and resin sand mould. The results show that the primary α-Al phase appears in the form of equiaxed and eutectic silicon phase is needle-like in freezing sand mould casting, but the primary α-Al phase grows in the form of dendrites, and the eutectic silicon phase is coarse needle-like in the resin sand mould casting. The difference of microstructure is caused by the different cooling rate. The cooling rate of A356 aluminum alloy in frozen sand mould is higher than that in resin sand mould.展开更多
In tissue engineering(TE),tissue-inducing scaffolds are a promising solution for organ and tissue repair owing to their ability to attract stem cells in vivo,thereby inducing endogenous tissue regeneration through top...In tissue engineering(TE),tissue-inducing scaffolds are a promising solution for organ and tissue repair owing to their ability to attract stem cells in vivo,thereby inducing endogenous tissue regeneration through topological cues.An ideal TE scaffold should possess biomimetic cross-scale structures,similar to that of natural extracellular matrices,at the nano-to macro-scale level.Although freeform fabrication of TE scaffolds can be achieved through 3D printing,this method is limited in simultaneously building multiscale structures.To address this challenge,low-temperature fields were adopted in the traditional fabrication processes,such as casting and 3D printing.Ice crystals grow during scaffold fabrication and act as a template to control the nano-and micro-structures.These microstructures can be optimized by adjusting various parameters,such as the direction and magnitude of the low-temperature field.By preserving the macro-features fabricated using traditional methods,additional micro-structures with smaller scales can be incorporated simultaneously,realizing cross-scale structures that provide a better mimic of natural organs and tissues.In this paper,we present a state-of-the-art review of three low-temperature-field-assisted fabrication methods—freeze casting,cryogenic3D printing,and freeze spinning.Fundamental working principles,fabrication setups,processes,and examples of biomedical applications are introduced.The challenges and outlook for low-temperature-assisted fabrication are also discussed.展开更多
Porous Y2Si05 ceramic was fabricated by freeze casting with tert-butyl alcohol as solvent. The porous Y2SiO5 ceramic possessed long straight pore structure. With decreasing solid loading from 20 to 10 vol.%, the poros...Porous Y2Si05 ceramic was fabricated by freeze casting with tert-butyl alcohol as solvent. The porous Y2SiO5 ceramic possessed long straight pore structure. With decreasing solid loading from 20 to 10 vol.%, the porosity of the Y2SiO5 ceramic increased linearly from 45% to Y2%, while the compressive strength declined from 23.2 to 3.2 MPa. The thermal conductivity of Y2SiO5 decreased from 2.34 W/mK for the dense bulk to 0.05 W/mK for the porous body with a porosity of 57%.展开更多
To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and inter...To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and interfacial bonding.By pressure infiltration of the molten alloy into the freeze-cast porous ceramic skeleton,the 2024Al/B_(4)C-TiB_(2)composites with a laminate-reticular hierarchical structure were produced.Compared with 2024Al/B_(4)C composite,adding initial TiH_(2)improved the flexural strength and valid fracture toughness from(484±27)to(665±30)MPa and(19.3±1.5)to(32.7±1.8)MPa·m^(1/2),respectively.This exceptional damage resistance ability was derived from multiple extrinsic toughening mechanisms including uncracked-ligament bridging,crack branching,crack propagation and crack blunting,and more importantly,the fracture model transition from single to multiple crack propagation.This strategy opens a pathway for improving the wettability and interfacial bonding of Al/B_(4)C composites,and thus produces nacre-inspired materials with optimized damage tolerance.展开更多
Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ...Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ultra-low resilience after compression.Some methods can realize a well-aligned structure,however,they involve high costs and complex technology.Herein,a 3 D graphene hybrid aerogel with an anisotropic open-cell and well-oriented structure is realized by unidirectional freeze casting,which combines the‘soft’(e.g.graphene oxide,Tween-80)and‘hard’(e.g.graphene assembly)components to realize full recovery after flattening.A graphene aerogel annealed at a moderate temperature(200℃)can possess superhydrophilicity and outstanding wet-resilience properties,including after being pressed under40 MPa.Furthermore,the graphene aerogel annealed at a high temperature of 1500℃exhibits excellent thermal conductivity enhancement efficiency in polydimethylsiloxane(PDMS).The resultant nanocomposites clearly demonstrate anisotropic thermal conductivity and promising applications as thermal interface materials.This strategy offers new insights into the design and fabrication of 3 D multifunctional graphene aerogels.展开更多
This work aimed to prepare the nanospike surface-modified bionic porous titanium implants that feature favorableosteointegration performance and anti-bacterial functions.The implant was prepared using freeze casting,a...This work aimed to prepare the nanospike surface-modified bionic porous titanium implants that feature favorableosteointegration performance and anti-bacterial functions.The implant was prepared using freeze casting,and nanospikesurface-modification of the implant was performed using thermal oxidation.The pore morphology and size,mechanical properties,and osteogenic performance of the implants were analyzed and discussed.The results showed that when the volume ratio of titaniumpowder in slurry was set to be10%,the porosity,pore diameter,compressive strength,and elastic modulus of the porous sampleswere(58.32±1.08)%,(126.17±18.64)μm,(58.51±20.38)MPa and(1.70±0.52)GPa,respectively.When the porous sample wassintered at a temperature of1200°C for1h,these values were(58.24±1.50)%,(124.16±13.64)μm,(54.77±27.55)MPa and(1.63±0.30)GPa,respectively.The nanospike surface-modified bionic porous titanium implants had favorable pore morphology andsize,mechanical properties and osteointegration performance through technology optimization,and showed significant clinicalapplication prospect.展开更多
Building high-performance aerogels with biomass-derived rather than fossil-derived polymers is an eco-friendlier option given the increasingly serious sustainability issues.Chitosan(CS)aero-gels with oriented pore str...Building high-performance aerogels with biomass-derived rather than fossil-derived polymers is an eco-friendlier option given the increasingly serious sustainability issues.Chitosan(CS)aero-gels with oriented pore structures exhibit broad application prospects owing to light weight,high porosity,and favorable bioactivity,but the dominating drawback in low mechanical strength greatly hinders their functional advantages.In this study,two types of silk microfibers with simi-lar diameter yet different aspect ratios(1-3(denoting as SmSF)and 50-100(denoting as LmSF))were used as fillers to reinforce CS aerogels prepared by directional freeze casting.The distinc-tion of SmSF and LmSF in size led to their notable variations in distribution pattern,as SmSF embedded within the individual CS lamellae while LmSF traversed throughout the adjacent CS lamellae,which in consequence significantly influence their mechanical reinforcing efficiency.The compressive strength values could be improved from 61.67 kPa(pure CS aerogel)to 82.13 kPa(SmSF/CS aerogel)and 165.03 kPa(LmSF/CS aerogel),respectively,attributing to the tran-sition in deformation mechanisms from a bending-to crumpling-dominated mode.In addition,the embedding or bridging structure could also change the liquid transportation property of CS aerogels.The results of this study demonstrated the feasibility of applying filler-size-mediated strategy for material structural optimization.展开更多
The efficiency of water electrolysis is significantly affected by the bubbles on the surface and inside the electrode.To enhance the gas-liquid transfer within the porous electrodes,we developed an innovative design t...The efficiency of water electrolysis is significantly affected by the bubbles on the surface and inside the electrode.To enhance the gas-liquid transfer within the porous electrodes,we developed an innovative design termed dual-aligned porous electrode(D-APE),achieved by integrating magnetic alignment with freeze casting techniques.This paper investigates the hydrogen evolution performance of porous electrodes prepared using four different methods:evaporation,magnetic-aligned evaporation,freeze casting,and dual-aligned methods.The findings demonstrate that the magnetic-aligned process effectively alters the electrode structure,resulting in improved hydrogen evolution performance.Notably,among all the examined electrodes,the D-APE exhibits the highest hydrogen evolution performance,with further enhancements observed with prolonged the time of magnetic alignment.Furthermore,a comparison is made between electrodes prepared using the freeze casting method and the dual-aligned method at various thickness.The results show that the thinner D-APE exhibits excellent hydrogen evolution performance at high current density.Moreover,the D-APE demonstrates significantly improved material utilization rates compared to the conventional freeze casting method,offering promising prospects for enhancing the efficiency of water electrolysis.展开更多
基金supported by the National Natural Science Foundation of China(No.51872222)the Shaanxi Innovation Capacity Support Program(2018TD-031)the Xi’an Municipal Science and Technology Project(2020KJRC0056)。
文摘Unidirectional porous AlN ceramics(UP-AlNs)have attracted great attention for their wide applications in catalyst supports,filters and composite reinforcements.However,traditional fabrication processes usually require high temperature and long production cycle.Herein,UP-AlNs were successfully fabricated via the combination of tertiary butyl alcohol(TBA)-based freeze casting and combustion synthesis route using Al and AlN powders as raw materials.The microstructure,open porosity,thermal conductivity and compressive strength of UP-AlNs can be manipulated by synergistically regulating the AlN diluent content and Al/AlN solid loading of the freezing slurries.The optimal UP-AlNs exhibited controllable structure wavelength(λ)and open porosity in a wide range of 21.1-47.1μm and 54.2%-86.0%,respectively.In addition,the corresponding products also possessed anisotropic thermal conductivity and compressive strength.This novel route for the fabrication of UP-AlNs has the advantages of low cost,energy-saving and high efficiency,which shows significant promise for industrial applications.
文摘Graphene oxide(GO)is widely used in the construction and application of various 2 D membrane-based materials due to its unique colloidal structure.Herein,we demonstrate that micrometer-sized particles can make up freestanding membranes enabled by the extraordinary amphiphilic and polymer-like properties of graphene oxide through freeze casting.The 2 D macromolecule,GO could well wrap the particles for better uniformity and stability in either dispersion or membrane.Importantly,freeze casting plays an important role in avoiding the severe aggregation of micrometer-sized particles in the solventremoving process.After reduction,the membrane exhibits good electrical conductivity while maintaining its integral structure,which can be directly used as a freestanding binder-free electrode.This work provides a universal approach to fabricate freestanding membranes with various micrometersized materials for energy storage.
基金This work was financially supported by the National Science Found for Distinguished Young Scholars(No.51525503).
文摘Digital patternless freeze-casting technology is a new approach for obtaining frozen sand moulds using digital milling technology. The change law of tensile strength and air permeability of frozen sand moulds (100-mesh and 200-mesh silica sand, and zircon sand moulds) under different freezing temperatures and water contents was studied. Results show that with the decrease of freezing temperature and the increase of water contents, the tensile strength and air permeability of the sand moulds are gradually improved. Meanwhile, computed tomography technology was used to characterize the shape and size of the water film between the sand particles mixed with 4wt.% water. The results show that in silica sand moulds, the form of water film is lumpy, and 200-mesh silica sand moulds have more water films and higher proportion of small-sized water films than 100-mesh silica sand moulds, while in zircon sand moulds, the form of water film is membranous. At the same freezing temperature and water content, the tensile strength of zircon sand mould is the highest, and 100-mesh silica sand mould is the lowest. A comparative solidification experiment of A356 aluminum alloy was carried out in frozen sand mould and resin sand mould. The results show that the primary α-Al phase appears in the form of equiaxed and eutectic silicon phase is needle-like in freezing sand mould casting, but the primary α-Al phase grows in the form of dendrites, and the eutectic silicon phase is coarse needle-like in the resin sand mould casting. The difference of microstructure is caused by the different cooling rate. The cooling rate of A356 aluminum alloy in frozen sand mould is higher than that in resin sand mould.
基金National Natural Science Foundation Council of China(Grant No.52305359)Hubei Provincial Natural Science Foundation of China(Grant No.2023AFB141)National Medical Products Administration Key Laboratory for Dental Materials(PKUSS20240401)。
文摘In tissue engineering(TE),tissue-inducing scaffolds are a promising solution for organ and tissue repair owing to their ability to attract stem cells in vivo,thereby inducing endogenous tissue regeneration through topological cues.An ideal TE scaffold should possess biomimetic cross-scale structures,similar to that of natural extracellular matrices,at the nano-to macro-scale level.Although freeform fabrication of TE scaffolds can be achieved through 3D printing,this method is limited in simultaneously building multiscale structures.To address this challenge,low-temperature fields were adopted in the traditional fabrication processes,such as casting and 3D printing.Ice crystals grow during scaffold fabrication and act as a template to control the nano-and micro-structures.These microstructures can be optimized by adjusting various parameters,such as the direction and magnitude of the low-temperature field.By preserving the macro-features fabricated using traditional methods,additional micro-structures with smaller scales can be incorporated simultaneously,realizing cross-scale structures that provide a better mimic of natural organs and tissues.In this paper,we present a state-of-the-art review of three low-temperature-field-assisted fabrication methods—freeze casting,cryogenic3D printing,and freeze spinning.Fundamental working principles,fabrication setups,processes,and examples of biomedical applications are introduced.The challenges and outlook for low-temperature-assisted fabrication are also discussed.
文摘Porous Y2Si05 ceramic was fabricated by freeze casting with tert-butyl alcohol as solvent. The porous Y2SiO5 ceramic possessed long straight pore structure. With decreasing solid loading from 20 to 10 vol.%, the porosity of the Y2SiO5 ceramic increased linearly from 45% to Y2%, while the compressive strength declined from 23.2 to 3.2 MPa. The thermal conductivity of Y2SiO5 decreased from 2.34 W/mK for the dense bulk to 0.05 W/mK for the porous body with a porosity of 57%.
基金financially supported by the National Natural Science Foundation of China(Nos.51502053,52072091,51621091)Heilongjiang Touyan Team,China。
文摘To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and interfacial bonding.By pressure infiltration of the molten alloy into the freeze-cast porous ceramic skeleton,the 2024Al/B_(4)C-TiB_(2)composites with a laminate-reticular hierarchical structure were produced.Compared with 2024Al/B_(4)C composite,adding initial TiH_(2)improved the flexural strength and valid fracture toughness from(484±27)to(665±30)MPa and(19.3±1.5)to(32.7±1.8)MPa·m^(1/2),respectively.This exceptional damage resistance ability was derived from multiple extrinsic toughening mechanisms including uncracked-ligament bridging,crack branching,crack propagation and crack blunting,and more importantly,the fracture model transition from single to multiple crack propagation.This strategy opens a pathway for improving the wettability and interfacial bonding of Al/B_(4)C composites,and thus produces nacre-inspired materials with optimized damage tolerance.
基金financially supported by the National Natural Science Foundation of China(No.U19A20105)。
文摘Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ultra-low resilience after compression.Some methods can realize a well-aligned structure,however,they involve high costs and complex technology.Herein,a 3 D graphene hybrid aerogel with an anisotropic open-cell and well-oriented structure is realized by unidirectional freeze casting,which combines the‘soft’(e.g.graphene oxide,Tween-80)and‘hard’(e.g.graphene assembly)components to realize full recovery after flattening.A graphene aerogel annealed at a moderate temperature(200℃)can possess superhydrophilicity and outstanding wet-resilience properties,including after being pressed under40 MPa.Furthermore,the graphene aerogel annealed at a high temperature of 1500℃exhibits excellent thermal conductivity enhancement efficiency in polydimethylsiloxane(PDMS).The resultant nanocomposites clearly demonstrate anisotropic thermal conductivity and promising applications as thermal interface materials.This strategy offers new insights into the design and fabrication of 3 D multifunctional graphene aerogels.
基金Projects(51290295,51305464) supported by the National Natural Science Foundation of ChinaProject(2016JJ6156) supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(2016JC2064) supported by the Key Research and Development Program of Hunan Province,ChinaProject(20130162120094) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘This work aimed to prepare the nanospike surface-modified bionic porous titanium implants that feature favorableosteointegration performance and anti-bacterial functions.The implant was prepared using freeze casting,and nanospikesurface-modification of the implant was performed using thermal oxidation.The pore morphology and size,mechanical properties,and osteogenic performance of the implants were analyzed and discussed.The results showed that when the volume ratio of titaniumpowder in slurry was set to be10%,the porosity,pore diameter,compressive strength,and elastic modulus of the porous sampleswere(58.32±1.08)%,(126.17±18.64)μm,(58.51±20.38)MPa and(1.70±0.52)GPa,respectively.When the porous sample wassintered at a temperature of1200°C for1h,these values were(58.24±1.50)%,(124.16±13.64)μm,(54.77±27.55)MPa and(1.63±0.30)GPa,respectively.The nanospike surface-modified bionic porous titanium implants had favorable pore morphology andsize,mechanical properties and osteointegration performance through technology optimization,and showed significant clinicalapplication prospect.
基金supported by National Natural Science Foundation of China(No.52103149)State of Sericulture Industry Tech-nology System(No.CARS-18-ZJ0501)+2 种基金Zhejiang Provincial Science and Technology Plans(No.2021C02072-6)China Postdoctoral Science Foundation(No.2023M743064)Zhejiang University Start-up Fund.
文摘Building high-performance aerogels with biomass-derived rather than fossil-derived polymers is an eco-friendlier option given the increasingly serious sustainability issues.Chitosan(CS)aero-gels with oriented pore structures exhibit broad application prospects owing to light weight,high porosity,and favorable bioactivity,but the dominating drawback in low mechanical strength greatly hinders their functional advantages.In this study,two types of silk microfibers with simi-lar diameter yet different aspect ratios(1-3(denoting as SmSF)and 50-100(denoting as LmSF))were used as fillers to reinforce CS aerogels prepared by directional freeze casting.The distinc-tion of SmSF and LmSF in size led to their notable variations in distribution pattern,as SmSF embedded within the individual CS lamellae while LmSF traversed throughout the adjacent CS lamellae,which in consequence significantly influence their mechanical reinforcing efficiency.The compressive strength values could be improved from 61.67 kPa(pure CS aerogel)to 82.13 kPa(SmSF/CS aerogel)and 165.03 kPa(LmSF/CS aerogel),respectively,attributing to the tran-sition in deformation mechanisms from a bending-to crumpling-dominated mode.In addition,the embedding or bridging structure could also change the liquid transportation property of CS aerogels.The results of this study demonstrated the feasibility of applying filler-size-mediated strategy for material structural optimization.
基金supported by the National Natural Science Foundation of China under Grant(No.52076131).
文摘The efficiency of water electrolysis is significantly affected by the bubbles on the surface and inside the electrode.To enhance the gas-liquid transfer within the porous electrodes,we developed an innovative design termed dual-aligned porous electrode(D-APE),achieved by integrating magnetic alignment with freeze casting techniques.This paper investigates the hydrogen evolution performance of porous electrodes prepared using four different methods:evaporation,magnetic-aligned evaporation,freeze casting,and dual-aligned methods.The findings demonstrate that the magnetic-aligned process effectively alters the electrode structure,resulting in improved hydrogen evolution performance.Notably,among all the examined electrodes,the D-APE exhibits the highest hydrogen evolution performance,with further enhancements observed with prolonged the time of magnetic alignment.Furthermore,a comparison is made between electrodes prepared using the freeze casting method and the dual-aligned method at various thickness.The results show that the thinner D-APE exhibits excellent hydrogen evolution performance at high current density.Moreover,the D-APE demonstrates significantly improved material utilization rates compared to the conventional freeze casting method,offering promising prospects for enhancing the efficiency of water electrolysis.
