Highly stretchable carbon aerogels.

PubMed

Guo, Fan; Jiang, Yanqiu; Xu, Zhen; Xiao, Youhua; Fang, Bo; Liu, Yingjun; Gao, Weiwei; Zhao, Pei; Wang, Hongtao; Gao, Chao

2018-02-28

Carbon aerogels demonstrate wide applications for their ultralow density, rich porosity, and multifunctionalities. Their compressive elasticity has been achieved by different carbons. However, reversibly high stretchability of neat carbon aerogels is still a great challenge owing to their extremely dilute brittle interconnections and poorly ductile cells. Here we report highly stretchable neat carbon aerogels with a retractable 200% elongation through hierarchical synergistic assembly. The hierarchical buckled structures and synergistic reinforcement between graphene and carbon nanotubes enable a temperature-invariable, recoverable stretching elasticity with small energy dissipation (~0.1, 100% strain) and high fatigue resistance more than 10 6 cycles. The ultralight carbon aerogels with both stretchability and compressibility were designed as strain sensors for logic identification of sophisticated shape conversions. Our methodology paves the way to highly stretchable carbon and neat inorganic materials with extensive applications in aerospace, smart robots, and wearable devices.

Polyaniline-Coated Activated Carbon Aerogel/Sulfur Composite for High-performance Lithium-Sulfur Battery

NASA Astrophysics Data System (ADS)

Tang, Zhiwei; Jiang, Jinglin; Liu, Shaohong; Chen, Luyi; Liu, Ruliang; Zheng, Bingna; Fu, Ruowen; Wu, Dingcai

2017-12-01

An activated carbon aerogel (ACA-500) with high surface area (1765 m2 g-1), pore volume (2.04 cm3 g-1), and hierarchical porous nanonetwork structure is prepared through direct activation of organic aerogel (RC-500) with a low potassium hydroxide ratio (1:1). Based on this substrate, a polyaniline (PANi)-coated activated carbon aerogel/sulfur (ACA-500-S@PANi) composite is prepared via a simple two-step procedure, including melt-infiltration of sublimed sulfur into ACA-500, followed by an in situ polymerization of aniline on the surface of ACA-500-S composite. The obtained ACA-500-S@PANi composite delivers a high reversible capacity up to 1208 mAh g-1 at 0.2C and maintains 542 mAh g-1 even at a high rate (3C). Furthermore, this composite exhibits a discharge capacity of 926 mAh g-1 at the initial cycle and 615 mAh g-1 after 700 cycles at 1C rate, revealing an extremely low capacity decay rate (0.48‰ per cycle). The excellent electrochemical performance of ACA-500-S@PANi can be attributed to the synergistic effect of hierarchical porous nanonetwork structure and PANi coating. Activated carbon aerogels with high surface area and unique three-dimensional (3D) interconnected hierarchical porous structure offer an efficient conductive network for sulfur, and a highly conductive PANi-coating layer further enhances conductivity of the electrode and prevents the dissolution of polysulfide species.

Nitrogen and Fluorine-Codoped Carbon Nanowire Aerogels as Metal-Free Electrocatalysts for Oxygen Reduction Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Shaofang; Zhu, Chengzhou; Song, Junhua

2017-07-11

The development of active, durable, and low-cost catalysts to replace noble metal-based materials is highly desirable to promote the sluggish oxygen reduction reaction in fuel cells. Herein, nitrogen and fluorine-codoped three-dimensional carbon nanowire aerogels, composed of interconnected carbon nanowires, were synthesized for the first time by a hydrothermal carbonization process. Owing to their porous nanostructures and heteroatom-doping, the as-prepared carbon nanowire aerogels, with optimized composition, present excellent electrocatalytic activity that is comparable to commercial Pt/C. Remarkably, the aerogels also exhibit superior stability and methanol tolerance. This synthesis procedure paves a new way to design novel heteroatomdoped catalysts.

Method for producing hydrophobic aerogels

DOEpatents

Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

1999-01-01

A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

The monolithic carbon aerogels and aerogel composites for electronics and thermal protection applications

NASA Astrophysics Data System (ADS)

Lu, Sheng; Guo, Hui; Zhou, Yugui; Liu, Yuanyuan; Jin, Zhaoguo; Liu, Bin; Zhao, Yingmin

2017-09-01

Monolithic carbon aerogels have been prepared by condensation polymerization and high temperature pyrolysis. The morphology of carbon aerogels are characterized by SEM. The pore structure is characterized by N2 adsorption-desorption technique. Monolithic carbon aerogels are mesoporous nanomaterials. Carbon fiber reinforced carbon aerogel composites are prepared by in-situ sol-gel process. Fiber reinforced carbon aerogel composites are of high mechanical strength. The thermal response of the fiber reinforced aerogel composite samples are tested in an arc plasma wind tunnel. Carbon aerogel composites show good thermal insulation capability and high temperature resistance in inert atmosphere even at ultrahigh temperature up to 1800 °C. The results show that they are suitable for applications in electrodes for supercapacitors/ Lithium-ion batteries and aerospace thermal protection area.

Wood-Derived Ultrathin Carbon Nanofiber Aerogels.

PubMed

Li, Si-Cheng; Hu, Bi-Cheng; Ding, Yan-Wei; Liang, Hai-Wei; Li, Chao; Yu, Zi-You; Wu, Zhen-Yu; Chen, Wen-Shuai; Yu, Shu-Hong

2018-06-11

Carbon aerogels with 3D networks of interconnected nanometer-sized particles exhibit fascinating physical properties and show great application potential. Efficient and sustainable methods are required to produce high-performance carbon aerogels on a large scale to boost their practical applications. An economical and sustainable method is now developed for the synthesis of ultrathin carbon nanofiber (CNF) aerogels from the wood-based nanofibrillated cellulose (NFC) aerogels via a catalytic pyrolysis process, which guarantees high carbon residual and well maintenance of the nanofibrous morphology during thermal decomposition of the NFC aerogels. The wood-derived CNF aerogels exhibit excellent electrical conductivity, a large surface area, and potential as a binder-free electrode material for supercapacitors. The results suggest great promise in developing new families of carbon aerogels based on the controlled pyrolysis of economical and sustainable nanostructured precursors. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Super high-rate fabrication of high-purity carbon nanotube aerogels from floating catalyst method for oil spill cleaning

NASA Astrophysics Data System (ADS)

Khoshnevis, Hamed; Mint, Sandar Myo; Yedinak, Emily; Tran, Thang Q.; Zadhoush, Ali; Youssefi, Mostafa; Pasquali, Matteo; Duong, Hai M.

2018-02-01

In this study, we apply an advanced floating catalyst method to fabricate carbon nanotube (CNT) aerogels at super high deposition rate for oil spill cleaning. The aerogels consist of 3D porous network of stacking double-walled CNT bundles with low catalyst impurity (9%) and high thermal stability (650 °C). With high porosity, surface areas, and water contact angles, the CNT aerogels exhibit a high oil adsorption of up to 107 g/g and good reusability of up to four adsorption-burning cycles. This work suggests that the lightweight, porous, and super hydrophobic CNT aerogels can be promising sorbent materials for environmental applications.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

1997-01-01

Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (<50 m.sup.2 /gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, J.L.; Tran, T.D.; Feikert, J.H.; Mayer, S.T.

1997-06-10

Fabrication is described for conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive deionization, and waste treatment. Electrodes fabricated from low surface area (<50 m{sup 2}/gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon composites with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to high surface area carbons, fuel cell electrodes can be produced. 1 fig.

1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

PubMed

Hao, Pin; Tian, Jian; Sang, Yuanhua; Tuan, Chia-Chi; Cui, Guanwei; Shi, Xifeng; Wong, C P; Tang, Bo; Liu, Hong

2016-09-15

The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg -1 and 47.5 Wh kg -1 at a power density of 400 W kg -1 , respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

Porous silicon nanocrystals in a silica aerogel matrix

PubMed Central

2012-01-01

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation. PMID:22805684

Porous silicon nanocrystals in a silica aerogel matrix.

PubMed

Amonkosolpan, Jamaree; Wolverson, Daniel; Goller, Bernhard; Polisski, Sergej; Kovalev, Dmitry; Rollings, Matthew; Grogan, Michael D W; Birks, Timothy A

2012-07-17

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation.

Nano-micro carbon spheres anchored on porous carbon derived from dual-biomass as high rate performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Liu, Shaobo; Zhao, Yang; Zhang, Baihui; Xia, Hui; Zhou, Jianfei; Xie, Wenke; Li, Hongjian

2018-03-01

Hierarchical nano-micro carbon spheres@rice straw-derived porous carbon composites are successfully synthesized by the in situ decoration of the porous carbon with carbon spheres from glucose under the assistance of cetyltrimethyl ammonium bromide micelles and further activated by KOH. The scanning electron microscope images clearly show the carbon spheres disperse homogeneously and orderly onto the surface and in the inner macropores of the porous carbon. The diameter of the carbon spheres varies from 475 nm to 1.6 μm, which can be easily controlled by introducing extra inducing agent. The optimal composites exhibit a large specific surface area (1122 m2 g-1), rich content of oxygen (14.2 wt %), and tunable hierarchical porous structure. When used as supercapacitor electrodes, the novel composites with abundant fruits present a high specific capacitance of 337 F g-1 at 1 A g-1, excellent rate retention of 83% from 1 to 20 A g-1 and a good cycling stability with 96% capacitance retention after 10000 cycles. In this strategy, the thought of shared ion-buffering reservoirs is proposed and the mutual promotion effects between the carbon spheres and porous carbon in the composites are also practically demonstrated to contribute the enhanced electrochemical performances.

Carbon aerogels by pyrolysis of TEMPO-oxidized cellulose

NASA Astrophysics Data System (ADS)

Zhang, Sizhao; Feng, Jian; Feng, Junzong; Jiang, Yonggang; Ding, Feng

2018-05-01

Although carbon aerogels derived from naturally occurring materials have been developed extensively, a reasonable synthetic approach using cellulose-resource remains unclear. Here, we report a strategy to prepare carbon aerogels originated from cellulose position-selectively oxidized by TEMPO-oxidized process. Contrary to non-TEMPO-oxidized cellulose-derived carbon aerogels (NCCA) with relative loose structure, TEMPO-oxidized cellulose-derived carbon aerogels (TCCA) with tight fibrillar-continuous network are monitored, suggesting the importance of TEMPO-oxidized modification towards creating the architecture of subsequently produced carbon aerogels. TCCA endows a higher BET area despite owning slightly dense bulk density comparing with that of NCCA. The structural texture of TCCA could be maintained in a way in comparison to TEMPO-oxidized cellulose-derived aerogel, due to the integration and aggregation effect by losing the electric double layer repulsion via ionization of the surface carboxyl groups. FTIR and XPS analyses signify the evidence of non-functionalized carbon-skeleton network formation in terms of TCCA. Further, the mechanism concerning the creation of carbon aerogels is also established. These findings not only provide new insights into the production of carbon aerogels but also open up a new opportunity in the field of functional carbon materials.

Freeze-Dried Carbon Nanotube Aerogels for High-Frequency Absorber Applications.

PubMed

Anoshkin, Ilya V; Campion, James; Lioubtchenko, Dmitri V; Oberhammer, Joachim

2018-06-13

A novel technique for millimeter wave absorber material embedded in a metal waveguide is proposed. The absorber material is a highly porous carbon nanotube (CNT) aerogel prepared by a freeze-drying technique. CNT aerogel structures are shown to be good absorbers with a low reflection coefficient, less than -12 dB at 95 GHz. The reflection coefficient of the novel absorber is 3-4 times lower than that of commercial absorbers with identical geometry. Samples prepared by freeze-drying at -25 °C demonstrate resonance behavior, while those prepared at liquid nitrogen temperature (-196 °C) exhibit a significant decrease in reflection coefficient, with no resonant behavior. CNT absorbers of identical volume based on wet-phase drying preparation show significantly worse performance than the CNT aerogel absorbers prepared by freeze-drying. Treatment of the freeze-dried CNT aerogel with n- and p-dopants (monoethanolamine and iodine vapors, respectively) shows remarkable improvement in the performance of the waveguide embedded absorbers, reducing the reflection coefficient by 2 dB across the band.

Self-Assembled Fe-N-Doped Carbon Nanotube Aerogels with Single-Atom Catalyst Feature as High-Efficiency Oxygen Reduction Electrocatalysts

DOE PAGES

Zhu, Chengzhou; Fu, Shaofang; Song, Junhua; ...

2017-02-06

In this study, self-assembled M–N-doped carbon nanotube aerogels with single-atom catalyst feature are for the first time reported through one-step hydrothermal route and subsequent facile annealing treatment. By taking advantage of the porous nanostructures, 1D nanotubes as well as single-atom catalyst feature, the resultant Fe–N-doped carbon nanotube aerogels exhibit excellent oxygen reduction reaction electrocatalytic performance even better than commercial Pt/C in alkaline solution.

Nitrogen-doped carbon aerogels for electrical energy storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, Patrick; Montalvo, Elizabeth; Baumann, Theodore F.

Disclosed here is a method for making a nitrogen-doped carbon aerogel, comprising: preparing a reaction mixture comprising formaldehyde, at least one nitrogen-containing resorcinol analog, at least one catalyst, and at least one solvent; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel; and thermally annealing the dry gel to produce the nitrogen-doped carbon aerogel. Also disclosed is a nitrogen-doped carbon aerogel obtained according to the method and a supercapacitor comprising the nitrogen-doped carbon aerogel.

Hierarchical Nafion enhanced carbon aerogels for sensing applications

NASA Astrophysics Data System (ADS)

Weng, Bo; Ding, Ailing; Liu, Yuqing; Diao, Jianglin; Razal, Joselito; Lau, King Tong; Shepherd, Roderick; Li, Changming; Chen, Jun

2016-02-01

This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG monoliths performed well as a gas sensor and as a biosensor with high sensitivity and selectivity. The remarkable sensitivity of 8.52 × 103 μA mM-1 cm-2 was obtained in dopamine (DA) detection, which is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template. These outstanding properties make the NECAG a promising electrode candidate for a wide range of applications. Further in-depth investigations are being undertaken to probe the structure-property relationship of NECAG monoliths prepared under various conditions.This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG

Ultralight boron nitride aerogels via template-assisted chemical vapor deposition

PubMed Central

Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

2015-01-01

Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 °C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m2 g−1, 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm−3, much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools. PMID:25976019

Ultralight boron nitride aerogels via template-assisted chemical vapor deposition.

PubMed

Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

2015-05-15

Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 (°)C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m(2) g(-1), 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm(-3), much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools.

Ultralight super-hydrophobic carbon aerogels based on cellulose nanofibers/poly(vinyl alcohol)/graphene oxide (CNFs/PVA/GO) for highly effective oil-water separation.

PubMed

Xu, Zhaoyang; Zhou, Huan; Tan, Sicong; Jiang, Xiangdong; Wu, Weibing; Shi, Jiangtao; Chen, Peng

2018-01-01

With the worsening of the oil-product pollution problem, oil-water separation has attracted increased attention in recent years. In this study, a porous three-dimensional (3D) carbon aerogel based on cellulose nanofibers (CNFs), poly(vinyl alcohol) (PVA) and graphene oxide (GO) was synthesized by a facile and green approach. The resulting CNF/PVA/GO aerogels were synthesized through an environmentally friendly freeze-drying process and then carbonized to yield CNF/PVA/GO carbon aerogels with low density (18.41 mg cm -3 ), high porosity (98.98%), a water contact angle of 156° (super-hydrophobic) and high oil absorption capacity (97 times its own weight). The carbonization treatment of the CNF/PVA/GO aerogel not only improved the hydrophobic properties but also enhanced the adsorption capacity and specific surface area. Given the many good performance characteristics and the facile preparation process of carbon aerogels, these materials are viable candidates for use in oil-water separation and environmental protection.

Polyimide Cellulose Nanocrystal Composite Aerogels

NASA Technical Reports Server (NTRS)

Nguyen, Baochau N.; Meador, Mary Ann; Rowan, Stuart; Cudjoe, Elvis; Sandberg, Anna

2014-01-01

Polyimide (PI) aerogels are highly porous solids having low density, high porosity and low thermal conductivity with good mechanical properties. They are ideal for various applications including use in antenna and insulation such as inflatable decelerators used in entry, decent and landing operations. Recently, attention has been focused on stimuli responsive materials such as cellulose nano crystals (CNCs). CNCs are environmentally friendly, bio-renewable, commonly found in plants and the dermis of sea tunicates, and potentially low cost. This study is to examine the effects of CNC on the polyimide aerogels. The CNC used in this project are extracted from mantle of a sea creature called tunicates. A series of polyimide cellulose nanocrystal composite aerogels has been fabricated having 0-13 wt of CNC. Results will be discussed.

Carbon aerogel electrodes for direct energy conversion

DOEpatents

Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

1997-01-01

A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome.

Conductivity enhancement of carbon aerogel by modified gelation using self additive

NASA Astrophysics Data System (ADS)

Singh, Ashish; Kohli, D. K.; Bhartiya, Sushmita; Singh, Rashmi; Rajak, Gaurav; Singh, M. K.; Karnal, A. K.

2018-04-01

Carbon aerogels having high surface area and open pore structure are being studied for many electrochemical applications such as fuel cells and super capacitors. Moderate electrical conductivity of resorcinol - formaldehyde (R-F) derived carbon aerogel limits its utility in these applications. The current manuscript briefs about the synthesis of composite carbon aerogel using carbon aerogel itself as additive during gelation of water based carbon aerogel and study the effect on its conductivity and surface properties. The additive carbon aerogel was synthesized and pre-treated at higher temperature to achieve enhancement in conductivity. The composite carbon aerogel (CCA) samples were characterized for surface area properties, morphology, electrical conductivity and specific capacitance. The surface area properties of CCA showed improvement and specific surface area of ˜1798 m2/g with total pore volume of 1.7 cm3/g. was obtained. The electrical conductivity of the composite carbon aerogel with 5 wt % additive showed improvement over the plain carbon aerogel with respective values of 144 S/m and 128 S/m. The specific capacitance evaluated for CA and CCA are 102 and 118 F/g at scan rate of 10mV/s with improvement of ˜16%.

Towards an aerogel-based coating for aerospace applications: reconstituting aerogel particles via spray drying

NASA Astrophysics Data System (ADS)

Bheekhun, N.; Abu Talib, A. R.; Mustapha, S.; Ibrahim, R.; Hassan, M. R.

2016-10-01

Silica aerogel is an ultralight and highly porous nano-structured ceramic with its thermal conductivity being the lowest than any solids. Although aerogels possess fascinating physical properties, innovative solutions to tackle today's problems were limited due to their relative high manufacturing cost in comparison to conventional materials. Recently, some producers have brought forward quality aerogels at competitive costs, and thereby opening a panoply of applied research in this field. In this paper, the feasibility of spray-drying silica aerogel to tailor its granulometric property is studied for thermal spraying, a novel application of aerogels that is never tried before in the academic arena. Aerogel-based slurries with yttria stabilised zirconia as a secondary ceramic were prepared and spray-dried according to modified T aguchi experimental design in order to appreciate the effect of both the slurry formulation and drying conditions such as the solid content, the ratio of yttria stabilised zirconia:aerogel added, the amount of dispersant and binder, inlet temperature, atomisation pressure and feeding rate on the median particle size of the resulting spray-dried powder. The latter was found to be affected by all the aforementioned independent variables at different degree of significance and inclination. Based on the derived relationships, an optimised condition to achieve maximum median particle size was then predicted.

Carbon aerogel electrodes for direct energy conversion

DOEpatents

Mayer, S.T.; Kaschmitter, J.L.; Pekala, R.W.

1997-02-11

A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes is described, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome. 1 fig.

Prospect of Thermal Insulation by Silica Aerogel: A Brief Review

NASA Astrophysics Data System (ADS)

Hasan, Mohammed Adnan; Sangashetty, Rashmi; Esther, A. Carmel Mary; Patil, Sharanabasappa B.; Sherikar, Baburao N.; Dey, Arjun

2017-10-01

Silica aerogel is a unique ultra light weight nano porous material which offers superior thermal insulation property as compared to the conventional thermal insulating materials. It can be applied not only for ground and aerospace applications but also in low and high temperatures and pressure regimes. Aerogel granules and monolith are synthesized by the sol-gel route while aerogel based composites are fabricated by the reinforcement of fibers, particle and opacifiers. Due to the characteristic brittleness (i.e., poor mechanical properties) of monolith or bulk aerogel, it is restricted in several applications. To improve the mechanical integrity and flexibility, usually different fibers are reinforced with aerogel and hence it can be used as flexible thermal insulation blankets. Further, to achieve effective thermal insulation behaviour particularly at high temperature, often opacifiers are doped with silica aerogel. In the present brief review, the prospects of bulk aerogel and aerogel based composites are discussed for the application of thermal insulation and thermal stability.

Monte Carlo Study on Carbon-Gradient-Doped Silica Aerogel Insulation.

PubMed

Zhao, Y; Tang, G H

2015-04-01

Silica aerogel is almost transparent for wavelengths below 8 µm where significant energy is transferred by thermal radiation. The radiative heat transfer can be restricted at high temperature if doped with carbon powder in silica aerogel. However, different particle sizes of carbon powder doping have different spectral extinction coefficients and the doped carbon powder will increase the solid conduction of silica aerogel. This paper presents a theoretical method for determining the optimal carbon doping in silica aerogel to minimize the energy transfer. Firstly we determine the optimal particle size by combining the spectral extinction coefficient with blackbody radiation and then evaluate the optimal doping amount between heat conduction and radiation. Secondly we develop the Monte Carlo numerical method to study radiative properties of carbon-gradient-doped silica aerogel to decrease the radiative heat transfer further. The results indicate that the carbon powder is able to block infrared radiation and thus improve the thermal insulating performance of silica aerogel effectively.

3D dual-confined sulfur encapsulated in porous carbon nanosheets and wrapped with graphene aerogels as a cathode for advanced lithium sulfur batteries

DOE PAGES

Hou, Yang; Li, Jianyang; Gao, Xianfeng; ...

2016-03-15

Although lithium–sulfur (Li–S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and the insulating nature of sulfur. Here, we report a rationally designed Li–S cathode with a dual-confined configuration formed by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transportmore » and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior electrochemical performance, including a large reversible capacity of 1328 mA h g -1 in the first cycle, excellent cycling stability (maintaining a reversible capacity of 647 mA h g -1 at 0.2 C after 300 cycles) with nearly 100% Coulombic efficiency, and a high rate capability of 512 mA h g -1 at 8 C for 30 cycles, which is among the best reported rate capabilities.« less

Lightweight and efficient microwave absorbing materials based on walnut shell-derived nano-porous carbon.

PubMed

Qiu, Xu; Wang, Lixi; Zhu, Hongli; Guan, Yongkang; Zhang, Qitu

2017-06-08

Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with a subsequent potassium hydroxide activation of walnut shells and the microwave absorption properties have also been investigated. The obtained samples have large specific surface areas with numerous micropores and nanopores. The sample activated at 600 °C with a specific surface area of 736.2 m 2 g -1 exhibits the most enhanced microwave absorption performance. It has the maximum reflection loss of -42.4 dB at 8.88 GHz and the effective absorption bandwidth (reflection loss below -10 dB) is 1.76 GHz (from 8.08 GHz to 9.84 GHz), corresponding to a thickness of 2 mm. Additionally, the effective absorption bandwidth can reach 2.24 GHz (from 10.48 GHz to 12.72 GHz) when the absorber thickness is 1.5 mm. Three-dimensional porous architecture, interfacial polarization relaxation loss, and the dipolar relaxation loss make a great contribution to the excellent microwave absorption performance. In contrast, the non-activated sample with lower specific surface area (435.3 m 2 g -1 ) has poor microwave absorption performance due to a poor dielectric loss capacity. This comparison highlights the role of micropores and nanopores in improving the dielectric loss property of porous carbon materials. To sum up, porous biomass carbon has great potential to become lightweight microwave absorbers. Moreover, KOH is an efficient activation agent in the fabrication of carbonaceous materials.

Behavior of silica aerogel networks as highly porous solid solvent media for lipases in a model transesterification reaction.

PubMed

El Rassy, H; Perrard, A; Pierre, A C

2003-03-03

Highly porous silica aerogels with differing balances of hydrophobic and hydrophilic functionalities were studied as a new immobilization medium for enzymes. Two types of lipases from Candida rugosa and Burkholderia cepacia were homogeneously dispersed in wet gel precursors before gelation. The materials obtained were compared in a simple model reaction: transesterification of vinyl laurate by 1-octanol. To allow a better comparison of the hydrophobic/hydrophilic action of the solid, very open aerogel networks with traditional organic hydrophobic/hydrophilic liquid solvents, this reaction was studied in mixtures containing different proportions of 2-methyl-2-butanol, isooctane, and water. The results are discussed in relation to the porous and hydrophobic nature of aerogels, characterized by nitrogen adsorption. It was found that silica aerogels can be considered as "solid" solvents for the enzymes, able to provide hydrophobic/hydrophilic characteristics different from those prevailing in the liquid surrounding the aerogels. A simple mechanism of action for these aerogel networks is proposed.

On the correlation between the porous structure and the electrochemical response of powdered and monolithic carbon aerogels as electrodes for capacitive deionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macías, C., E-mail: carlosmacias@nanoquimia.com; Lavela, P.; Rasines, G.

2016-10-15

The combined effect of resorcinol/catalyst (100≤R/C≤800) and resorcinol/water (0.04≤R/W≤0.13) molar ratio on the textural and capacitive properties of carbon aerogels with potential application for capacitive deionization has been evaluated. Activated and pyrolyzed aerogels were synthesized by the sol-gel polymerization of resorcinol-formaldehyde mixtures and dried in supercritical conditions. Data show that high R/C and R/W molar ratios lead to materials with large pores in the mesopore range, whereas the surface area and micropore volumes remain somewhat the same. The activation of the aerogels increased the differences in the specific surface and micropore volumes due to the development of microporosity. This effectmore » was more remarkable for the samples with low R/C whatever the R/W ratio, indicating that the carbon aerogel obtained using high amounts of catalyst are more prone to be activated. Regarding the electrochemical features of the aerogels, low capacitance values were measured in aerogels combining low R/W and high R/C and reciprocally low R/C and high R/W molar ratios, due to their higher resistance. Polarization resistances were found to be slightly higher for the pyrolyzed than for activated aerogels, and followed a decreasing trend with the mesoporosity, indicating the outstanding contribution of the mesoporous network to provide a good kinetic response. The desalting capacity of monolithic aerogels showed a simultaneous dependence with the surface area and the resistivity of the electrodes, pointing out the importance of performing electrochemical measurements in adequate cell configurations (i.e., desalting units) upon the intended application. - Graphical abstract: The textural properties of carbon aerogels are strongly influenced by the synthesis parameters precursor to catalyst (R/C) and water (R/C) ratios. The volumetric capacitance measured in a symmetric cell with monolithic electrodes of carbon aerogel strongly correlates with

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

DOEpatents

Pekala, R.W.

1996-09-17

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1,000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1,050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

DOEpatents

Pekala, Richard W.

1995-01-01

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

DOEpatents

Pekala, R.W.

1995-12-19

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes{<=}1000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

DOEpatents

Pekala, Richard W.

1996-01-01

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Water extractable arabinoxylan aerogels prepared by supercritical CO2 drying.

PubMed

Marquez-Escalante, Jorge; Carvajal-Millan, Elizabeth; Miki-Yoshida, Mario; Alvarez-Contreras, Lorena; Toledo-Guillén, Alma Rosa; Lizardi-Mendoza, Jaime; Rascón-Chu, Agustín

2013-05-14

Water extractable arabinoxylan (WEAX) aerogels were prepared by extracting the solvent from the alcogels (WEAX hydrogels with an alcohol as the solvent) with carbon dioxide under supercritical conditions. WEAX aerogels were characterized using scanning electron microscopy and adsorption and desorption nitrogen isotherms. The micrographs indicate a heterogeneous porous network structure in WEAX aerogel. Adsorption/desorption nitrogen isotherms of this material were type IV, which confirm that this material possess a mesoporous structure. WEAX aerogels rehydration capability was evaluated and the water absorption mechanism was determined. The WEAX aerogels water absorption mechanism was non-Fickian (n = 0.54).

Versatile Three-Dimensional Porous Cu@Cu2 O Aerogel Networks as Electrocatalysts and Mimicking Peroxidases.

PubMed

Ling, Pinghua; Zhang, Qiang; Cao, Tingting; Gao, Feng

2018-06-04

A facile strategy is presented to form 3D porous Cu@Cu 2 O aerogel networks by self-assembling Cu@Cu 2 O nanoparticles with the diameters of ca. 40 nm for constructing catalytic interfaces. Unexpectedly, the prepared Cu@Cu 2 O aerogel networks display excellent electrocatalytic activity to glucose oxidation at a low onset potential of ca. 0.25 V. Moreover, the Cu@Cu 2 O aerogels also can act as mimicking-enzymes including horseradish peroxidase and NADH peroxidase, and show obvious enzymatic catalytic activities to the oxidation of dopamine (DA), o-phenyldiamine (OPD), 3,3,5,5-tetramethylbenzidine (TMB), and dihydronicotinamide adenine dinucleotide (NADH) in the presence of H 2 O 2 . These 3D Cu@Cu 2 O aerogel networks are a new class of porous catalytic materials as mimic peroxidases and electrocatalysts and offer a novel platform to construct catalytic interfaces for promising applications in electrochemical sensors and artificial enzymatic catalytic systems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Engineering Polymer Nanocomoposite Aerogels for Energy Storage and Harvesting

NASA Astrophysics Data System (ADS)

Zheng, Qifeng

Various porous polymer nanocomposite aerogels were synthesized using an environmentally friendly freeze-drying process. These polymer nanocomposite aerogels exhibit ultralow densities, high porosities, high specific surface areas and high flexibility. The advantages of these polymer nanocomposites aerogels for energy storage and energy harvesting applications have been demonstrated. Flexible supercapacitors (SCs) are particularly attractive for energy storage applications due to their high power densities and long life cycles. A novel type of highly flexible and all-solid-state SCs using cellulose nanofibril (CNF)-reduced graphene oxide (RGO)-carbon nanotube (CNT) aerogels as electrodes was developed. Due to the porous structure of the CNF/RGO/CNT aerogel electrodes, and the excellent electrolyte absorption properties of the CNFs present in the electrodes, the resulting all-solid-state SCs exhibited excellent electrochemical performance, superior flexibility and cycle stability. To further increase the capacitances and energy densities, pseudocapacitive materials (i.e., MoO3) were incorporated to prepare the free-standing and highly flexible CNF-RGO-molybdenum oxynitride (MoOxNy) aerogel film electrode. Supercapacitors made with the CNF/RGO/MoOxNy aerogel electrodes exhibited outstanding specific capacitances and remarkable energy densities in different electrolytes while maintaining the high power densities and superior cycle stability. Flexible nanogenerators (NGs) that can harvest ubiquitous mechanical energy from ambient environments have attracted significant attention during the past decade. A novel, simple, cost-effective, and scalable technique was developed to fabricate high-performance flexible compact NGs using porous CNF-poly(dimethylsiloxane) (PDMS) aerogel film. Under external stress, the resulting NGs exhibited very stable and high output signals. We hypothesized that the remarkable electric outputs would not only be attributable to the intrinsic

Reinforcement of bacterial cellulose aerogels with biocompatible polymers

PubMed Central

Pircher, N.; Veigel, S.; Aigner, N.; Nedelec, J.M.; Rosenau, T.; Liebner, F.

2014-01-01

Bacterial cellulose (BC) aerogels, which are fragile, ultra-lightweight, open-porous and transversally isotropic materials, have been reinforced with the biocompatible polymers polylactic acid (PLA), polycaprolactone (PCL), cellulose acetate (CA), and poly(methyl methacrylate) (PMMA), respectively, at varying BC/polymer ratios. Supercritical carbon dioxide anti-solvent precipitation and simultaneous extraction of the anti-solvent using scCO2 have been used as core techniques for incorporating the secondary polymer into the BC matrix and to convert the formed composite organogels into aerogels. Uniaxial compression tests revealed a considerable enhancement of the mechanical properties as compared to BC aerogels. Nitrogen sorption experiments at 77 K and scanning electron micrographs confirmed the preservation (or even enhancement) of the surface-area-to-volume ratio for most of the samples. The formation of an open-porous, interpenetrating network of the second polymer has been demonstrated by treatment of BC/PMMA hybrid aerogels with EMIM acetate, which exclusively extracted cellulose, leaving behind self-supporting organogels. PMID:25037381

Silicon Oxycarbide Aerogels for High-Temperature Thermal Insulation

NASA Technical Reports Server (NTRS)

Evans, Owen; Rhine, Wendell; Coutinho, Decio

2010-01-01

This work has shown that the use of SOC-A35 leads to aerogel materials containing a significant concentration of carbidic species and limited amorphous free carbon. Substitution of the divalent oxide species in silica with tetravalent carbidic carbon has directly led to materials that exhibit increased network viscosity, reduced sintering, and limited densification. The SiOC aerogels produced in this work have the highest carbide content of any dense or porous SiOC glass reported in the literature at that time, and exhibit tremendous long-term thermal stability.

Aerogel Projects Ongoing in MSFC's Engineering Directorate

NASA Technical Reports Server (NTRS)

Shular, David A.; Smithers, Gweneth A.; Plawsky, Joel L.; Whitaker, Ann F. (Technical Monitor)

2000-01-01

When we speak of an aerogel material, we are referring more to process and structure am to a specific substance. Aerogel, considered the lightest solid material, has been made from silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more recently. However, aerogel can be made from almost any type of substance, even lead. Because an aerogel is mostly air (about 99 %), the solid substance used will affect the weight very little. The term "aerogel" connotes the sol-gel process used to manufacture the material. The aerogel begins as a liquid "sol," becomes a solid "alcogel," and is then dried to become an "aerogel." The final product has a unique structure, useful for exploitation. It is an "open pore" system with nano-sized particles and pores, has very high surface area, and is highly interconnected. Besides low weight, aerogels have ultimate (lowest) values in other properties: thermal conductivity, refractive index, sound speed, and dielectric constant. Aerogels were first prepared in 1931 by Steven Kistler, who used a supercritical drying step to replace the liquid in a gel with air, preserving the structure (1). Kistler's procedure involved a water-to-alcohol exchange step; in the 1970's, this step was eliminated when a French investigator introduced the use of tetramethylorthosilicate. Still, alcohol drying involved dangerously high temperatures and pressures. In the 1980's, the Microstructured Materials Group at Berkeley Laboratory found that the alcohol in the gel could be replaced with liquid carbon dioxide before supercritical drying, which greatly improved safety (2). 'Me most recent major contribution has been that of Deshpande, Smith and Brinker in New Mexico, who are working to eliminate the supercritical drying step (3). When aerogels were first being developed, they were evaporatively dried. However, the wet gel, when dried, underwent severe shrinkage and cracking; this product was termed "xerogel." When the

Nano-casted Metal Oxide Aerogels as Dual Purpose Structural Components for Space Exploration

NASA Technical Reports Server (NTRS)

Vassilaras, Plousia E.

2004-01-01

NASA missions and space exploration rely on strong, ultra lightweight materials. Such materials are needed for building up past and present space vehicles such as the Sojourner Rover (1997) or the two MERs (2003), but also for a number of components and/or systems including thermal insulators, Solar Sails, Rigid Aeroshells, and Ballutes. The purpose of my internship here at Glenn Research Center is to make dual purpose materials; materials that in addition to being lightweight have electronic, photophysical and magnetic properties and, therefore, act as electronic components and sensors as well as structural components. One type of ultra lightweight material of great interest is aerogels, which have densities ranging from 0.003 g/cc to 0.8 g/cc . However, aerogels are extremely fragile and, as a result, have limited practical applications. Recently, Glenn Research Center has developed a process of nano-casting polymers onto the inorganic network of silica-based aerogels increasing the strength 300 fold while only increasing the density 3 fold. By combining the process of nano-casting polymers with inorganic oxide networks other than silica, we are actively pursuing lightweight dual purpose materials. To date, thirty different inorganic oxide aerogels have been prepared using either standard sol-gel chemistry or a non-alkoxide method involving metal chloride precursors and an epoxide; epichlorohydrin, propylene oxide or trimethylene oxide, as proton scavengers. More importantly, preliminary investigations show that the residual surface hydroxyl groups on each of these inorganic oxide aerogels can be successfully crosslinked with urethane. In addition to characterizing physical and mechanical properties such as density, strength and flexibility, each of these metal oxide aerogels are being characterized for thermal and electronic conductivity and magnetic and optical properties.

Ultra-fine Pt nanoparticles on graphene aerogel as a porous electrode with high stability for microfluidic methanol fuel cell

NASA Astrophysics Data System (ADS)

Kwok, Y. H.; Tsang, Alpha C. H.; Wang, Yifei; Leung, Dennis Y. C.

2017-05-01

Platinum-decorated graphene aerogel as a porous electrode for flow-through direct methanol microfluidic fuel cell is introduced. Ultra-fine platinum nanoparticles with size ranged from diameter 1.5 nm-3 nm are evenly anchored on the graphene nanosheets without agglomeration. The electrode is characterized by scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. Catalytic activity is confirmed by cyclic voltammetry. The electroactive surface area and catalytic activity of platinum on graphene oxide (Pt/GO) are much larger than commercial platinum on carbon black (Pt/C). A counterflow microfluidic fuel cell is designed for contrasting the cell performance between flow-over type and flow-through type electrodes using Pt/C on carbon paper and Pt/GO, respectively. The Pt/GO electrode shows 358% increment in specific power compared with Pt/C anode. Apart from catalytic activity, the effect of porous electrode conductivity to cell performance is also studied. The conductivity of the porous electrode should be further enhanced to achieve higher cell performance.

Poly(vinyl alcohol)/cellulose nanofibril hybrid aerogels with an aligned microtubular porous structure and their composites with polydimethylsiloxane

Treesearch

Tianliang Zhai; Qifeng Zheng; Zhiyong Cai; Lih-Sheng Turng; Hesheng Xia; Shaoqin Gong

2015-01-01

Superhydrophobic poly(vinyl alcohol) (PVA)/ cellulose nanofibril (CNF) aerogels with a unidirectionally aligned microtubular porous structure were prepared using a unidirectional freeze-drying process, followed by the thermal chemical vapor deposition of methyltrichlorosilane. The silanized aerogels were characterized using various techniques including scanning...

Ultralight Graphene/Carbon Nanotubes Aerogels with Compressibility and Oil Absorption Properties

PubMed Central

Zhao, Da; Yu, Li; Liu, Dongxu

2018-01-01

Graphene aerogels have many advantages, such as low density, high elasticity and strong adsorption. They are considered to be widely applicable in many fields. At present, the most valuable research area aims to find a convenient and effective way to prepare graphene aerogels with excellent properties. In this work graphene/carbon nanotube aerogels are prepared through hydrothermal reduction, freeze-drying and high temperature heat treatment with the blending of graphene oxide and carbon nanotubes. A new reducing agent-ascorbic acid is selected to explore the best preparation process. The prepared aerogels have compression and resilience and oil absorption properties due to the addition of carbon nanotubes as designed. PMID:29690559

Ultralight Graphene/Carbon Nanotubes Aerogels with Compressibility and Oil Absorption Properties.

PubMed

Zhao, Da; Yu, Li; Liu, Dongxu

2018-04-22

Graphene aerogels have many advantages, such as low density, high elasticity and strong adsorption. They are considered to be widely applicable in many fields. At present, the most valuable research area aims to find a convenient and effective way to prepare graphene aerogels with excellent properties. In this work graphene/carbon nanotube aerogels are prepared through hydrothermal reduction, freeze-drying and high temperature heat treatment with the blending of graphene oxide and carbon nanotubes. A new reducing agent-ascorbic acid is selected to explore the best preparation process. The prepared aerogels have compression and resilience and oil absorption properties due to the addition of carbon nanotubes as designed.

Reinforcement of bacterial cellulose aerogels with biocompatible polymers.

PubMed

Pircher, N; Veigel, S; Aigner, N; Nedelec, J M; Rosenau, T; Liebner, F

2014-10-13

Bacterial cellulose (BC) aerogels, which are fragile, ultra-lightweight, open-porous and transversally isotropic materials, have been reinforced with the biocompatible polymers polylactic acid (PLA), polycaprolactone (PCL), cellulose acetate (CA), and poly(methyl methacrylate) (PMMA), respectively, at varying BC/polymer ratios. Supercritical carbon dioxide anti-solvent precipitation and simultaneous extraction of the anti-solvent using scCO2 have been used as core techniques for incorporating the secondary polymer into the BC matrix and to convert the formed composite organogels into aerogels. Uniaxial compression tests revealed a considerable enhancement of the mechanical properties as compared to BC aerogels. Nitrogen sorption experiments at 77K and scanning electron micrographs confirmed the preservation (or even enhancement) of the surface-area-to-volume ratio for most of the samples. The formation of an open-porous, interpenetrating network of the second polymer has been demonstrated by treatment of BC/PMMA hybrid aerogels with EMIM acetate, which exclusively extracted cellulose, leaving behind self-supporting organogels. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Polyolefin-Based Aerogels

NASA Technical Reports Server (NTRS)

Lee, Je Kyun; Gould, George

2012-01-01

An organic polybutadiene (PB) rubberbased aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection, exhibiting the flexibility, resiliency, toughness, and durability typical of the parent polymer, yet with the low density and superior insulation properties associated with the aerogels. The rubbery behaviors of the PB rubber-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogel insulation materials. Additionally, with higher content of hydrogen in their structure, the PB rubber aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. Since PB rubber aerogels also exhibit good hydrophobicity due to their hydrocarbon molecular structure, they will provide better performance reliability and durability as well as simpler, more economic, and environmentally friendly production over the conventional silica or other inorganic-based aerogels, which require chemical treatment to make them hydrophobic. Inorganic aerogels such as silica aerogels demonstrate many unusual and useful properties. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven one promising approach, providing a conveniently fielded form factor that is relatively robust toward handling in industrial environments compared to silica aerogel monoliths. However, the flexible silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain applications. Although the cross-linked organic aerogels such as resorcinol-formaldehyde (RF), polyisocyanurate, and cellulose aerogels show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient

Flexible and porous cellulose aerogels/zeolitic imidazolate framework (ZIF-8) hybrids for adsorption removal of Cr(IV) from water

NASA Astrophysics Data System (ADS)

Bo, Shaoguo; Ren, Wenjing; Lei, Chao; Xie, Yuanbo; Cai, Yurong; Wang, Shunli; Gao, Junkuo; Ni, Qingqing; Yao, Juming

2018-06-01

The low cost of adsorption treatment of heavy metal ions in water has been extensively studied. In this paper, we have demonstrated a facile method of combining two emerging materials cellulose aerogels (CA) and metal-organic frameworks (MOFs) into one highly functional aerogel to adsorption removal of heavy metal ions from water, by entrapping MOF particles into a flexible and porous CA. The resultant hybrid cellulose aerogels had a highly porous structure with zeolitic imidazolate framework-8 (ZIF-8) loadings can reach 30 wt%. The hybrid cellulose aerogels (named as ZIF-8@CA) show good adsorption capacity for Cr(Ⅵ). The adsorption process of ZIF-8@CA is better described by pseudo-second-order kinetic model and Langmuir isotherm, with maximum monolayer adsorption capacity of 41.8 mg g-1 for Cr(Ⅵ), whose adsorption capacity has greatly improved when compared with a single CA or ZIF-8. Thus, such a flexible and durable hybrid cellulose aerogel is a very prospective material for metal ions cleanup and industrial wastewater purification.

Mechanics of Nanostructured Porous Silica Aerogel Resulting from Molecular Dynamics Simulations.

PubMed

Patil, Sandeep P; Rege, Ameya; Sagardas; Itskov, Mikhail; Markert, Bernd

2017-06-08

Silica aerogels are nanostructured, highly porous solids which have, compared to other soft materials, special mechanical properties, such as extremely low densities. In the present work, the mechanical properties of silica aerogels have been studied with molecular dynamics (MD) simulations. The aerogel model of 192 000 atoms was created with different densities by direct expansion of β-cristobalite and subjected to series of thermal treatments. Because of the high number of atoms and improved modeling procedure, the proposed model was more stable and showed significant improvement in the smoothness of the resulting stress-strain curves in comparison to previous models. Resulting Poisson's ratio values for silica aerogels lie between 0.18 and 0.21. The elasticity moduli display a power law dependence on the density, with the exponent estimated to be 3.25 ± 0.1. These results are in excellent agreement with reported experimental as well as computational values. Two different deformation scenarios have been discussed. Under tension, the low-density aerogels were more ductile while the denser ones behaved rather brittle. In the compression simulations of low-density aerogels, deformation occurred without significant increase in stress. However, for high densities, atoms offer a higher resistance to the deformation, resulting in a more stiff response and an early densification. The relationship between different mechanical parameters has been found in the cyclic loading simulations of silica aerogels with different densities. The residual strain grows linearly with the applied strain (≥0.16) and can be approximated by a phenomenological relation ϵ p = 1.09ϵ max - 0.12. The dissipation energy also varies with the compressive strain according to a power law with an exponent of 2.31 ± 0.07. Moreover, the tangent modulus under cyclic loading varies exponentially with the compressive strain. The results of the study pave the way toward multiscale modeling of silica

Infinite Coordination Polymer Nano- and Micro-Particles

DTIC Science & Technology

2015-06-12

Mirkin, Tobin J. Marks, Joseph T. Hupp. SiO2 Aerogel-templated, Porous TiO2 Photoanodes for Enhanced Performances in Dye-Sensitized Solar Cells ...nano-scale ICPs and their selective surface functionalization, we examined if indeed these ICP-DNA hybrid structures could enter cells and...surface functionalization. In particular, we aimed to utilize this fundamental understanding for the realization of nano-scale ICP-biomolecule hybrids

Green and facile fabrication of carbon aerogels from cellulose-based waste newspaper for solving organic pollution.

PubMed

Han, Shenjie; Sun, Qingfeng; Zheng, Huanhuan; Li, Jingpeng; Jin, Chunde

2016-01-20

Carbon-based aerogel fabricated from waste biomass is a potential absorbent material for solving organic pollution. Herein, the lightweight, hydrophobic and porous carbon aerogels (CAs) have been synthesized through freezing-drying and post-pyrolysis by using waste newspaper as the only raw materials. The as-prepared CAs exhibited a low density of 18.5 mg cm(-3) and excellent hydrophobicity with a water contact angle of 132° and selective absorption for organic reagents. The absorption capacity of CA for organic compounds can be 29-51 times its own weight. Moreover, three methods (e.g., squeezing, combustion, and distillation) can be employed to recycle CA and harvest organic pollutants. Combined with waste biomass as raw materials, green and facile fabrication process, excellent hydrophobicity and oleophilicity, CA used as an absorbent material has great potential in application of organic pollutant solvents absorption and environmental protection. Copyright © 2015 Elsevier Ltd. All rights reserved.

Refining cocoon to prepare (N, S, and Fe) ternary-doped porous carbon aerogel as efficient catalyst for the oxygen reduction reaction in alkaline medium

NASA Astrophysics Data System (ADS)

Li, Changqing; Sun, Fengzhan; Lin, Yuqing

2018-04-01

Various advanced sulfur doped Fe-N-C non-noble metal catalysts of oxygen reduction reaction (ORR) have been recently designed and reported with excellent catalytic activity. Herein, we refined cocoon with several steps to form silk fibroin solution, treated with iron salt to prepare an easy available, heteroatom (N, S, and Fe) ternary-doped, porous carbon aerogel (HDCA). Heteroatom existed in organic compounds in silk fibroin endow active site for ORR of the resultant carbon frameworks. Moreover, the amino acids presented in silk fibroin acted as ligands, functioning with Fe ions to form FeNx coordination compounds, which also served as active sites towards ORR. The synthesized HDCA electrocatalysts, especially HDCA-800 (obtained at 800 °C) displayed excellent catalytic activity with onsets, half-wave potential of 0.94 V, 0.79 V and higher limited current density of 3.80 mA cm-2 through a near four-electron reduction pathway with an average electron transferred number of 3.86, making them promising alternatives for state-of-the-art ORR electrocatalysts in fuel cell field. The porous structure with synergistic effect of N and S heteroatom doping has been proposed to play a key role in facilitating the desired ORR reaction.

Bacterial cellulose-based sheet-like carbon aerogels for the in situ growth of nickel sulfide as high performance electrode materials for asymmetric supercapacitors.

PubMed

Zuo, Lizeng; Fan, Wei; Zhang, Youfang; Huang, Yunpeng; Gao, Wei; Liu, Tianxi

2017-03-30

Electroactive materials, such as nickel sulfide (NiS), with high theoretical capacities have attracted broad interest to fabricate highly efficient supercapacitors. Preventing aggregation and increasing the conductivity of NiS particles are key challenging tasks to fully achieve excellent electrochemical properties of NiS. One effective approach to solve these problems is to combine NiS with highly porous and conductive carbon materials such as carbon aerogels. In this study, a green and facile method for the in situ growth of NiS particles on bacterial cellulose (BC)-derived sheet-like carbon aerogels (CAs) has been reported. CA prepared by the dissolution-gelation-carbonization process was used as a framework to construct NiS/CA composite aerogels with NiS uniformly decorated on the pore walls of CA. It was found that the NiS/CA composite aerogel electrodes exhibit excellent capacitive performance with high specific capacitance (1606 F g -1 ), good rate capacitance retention (69% at 10 A g -1 ), and enhanced cycling stability (91.2% retention after 10 000 continuous cyclic voltammetry cycles at 100 mV s -1 ). Furthermore, asymmetric supercapacitors (ASCs) were constructed utilizing NiS/CA composite and CA as the positive and negative electrode materials, respectively. Through the synergistic effect of three-dimensional porous structures and conductive networks derived from CA and the high capacitive performance offered by NiS, the ASC device exhibited an energy density of ∼21.5 Wh kg -1 and a power density of 700 W kg -1 at the working voltage of 1.4 V in 2 M KOH aqueous solution. The ASC device also showed excellent long-term cycle stability with ∼87.1% specific capacitance retention after 10 000 cycles of cyclic voltammetry scans. Therefore, the NiS/CA composite shows great potential as a promising alternative to high-performance electrode materials for supercapacitors.

Facile synthesis of hierarchical porous VOx@carbon composites for supercapacitors.

PubMed

Zhao, Chunxia; Cao, Jinqiao; Yang, Yunxia; Chen, Wen; Li, Junshen

2014-08-01

Hierarchical or micro-nano structured porous VOx@carbon composites were synthesized by a one-step method using phenolic resin as the carbon precursor and ammonium metavanadate as the source of vanadium oxides. The effects of the vanadium source loading on the microstructure and electrochemical properties of the composites were investigated. X-ray diffraction results showed that as the vanadium oxides source loading increased, vanadium oxides in the composites changed oxidation states from V2O3 to mixed states of V2O3 and VO2. Electrochemical test results indicated that the micro-nano porous structure of the composites could facilitate the ion diffusion in the rich porous structure and then promote the electrochemical reaction. More importantly, we found that vanadium oxides greatly enhanced the electrochemical performance of the materials, due to the faradic capacitance generated from vanadium oxide nanoparticles. A maximum specific capacitance of 171 F/g was obtained from VOx@carbon composite with vanadium loading of ∼44 wt%. Further increasing the VOx loading over this fraction was not beneficial. Our results suggested that hierarchical porous VOx@carbon composites were promising candidates for supercapacitor applications. Copyright © 2013 Elsevier Inc. All rights reserved.

Hierarchical porous carbon materials prepared using nano-ZnO as a template and activation agent for ultrahigh power supercapacitors.

PubMed

Wang, Haoran; Yu, Shukai; Xu, Bin

2016-09-20

Hierarchical porous carbon materials with high surface areas and a localized graphitic structure were simply prepared from sucrose using nano-ZnO as a hard template, activation agent and graphitization catalyst simultaneously, which exhibit an outstanding high-rate performance and can endure an ultrafast scan rate of 20 V s -1 and ultrahigh current density of 1000 A g -1 .

Coherent-Interface-Assembled Ag2O-Anchored Nanofibrillated Cellulose Porous Aerogels for Radioactive Iodine Capture.

PubMed

Lu, Yun; Liu, Hongwei; Gao, Runan; Xiao, Shaoliang; Zhang, Ming; Yin, Yafang; Wang, Siqun; Li, Jian; Yang, Dongjiang

2016-10-26

Nanofibrillated cellulose (NFC) has received increasing attention in science and technology because of not only the availability of large amounts of cellulose in nature but also its unique structural and physical features. These high-aspect-ratio nanofibers have potential applications in water remediation and as a reinforcing scaffold in composites, coatings, and porous materials because of their fascinating properties. In this work, highly porous NFC aerogels were prepared based on tert-butanol freeze-drying of ultrasonically isolated bamboo NFC with 20-80 nm diameters. Then nonagglomerated 2-20-nm-diameter silver oxide (Ag 2 O) nanoparticles (NPs) were grown firmly onto the NFC scaffold with a high loading content of ∼500 wt % to fabricate Ag 2 O@NFC organic-inorganic composite aerogels (Ag 2 O@NFC). For the first time, the coherent interface and interaction mechanism between the cellulose I β nanofiber and Ag 2 O NPs are explored by high-resolution transmission electron microscopy and 3D electron tomography. Specifically, a strong hydrogen between Ag 2 O and NFC makes them grow together firmly along a coherent interface, where good lattice matching between specific crystal planes of Ag 2 O and NFC results in very small interfacial straining. The resulting Ag 2 O@NFC aerogels take full advantage of the properties of the 3D organic aerogel framework and inorganic NPs, such as large surface area, interconnected porous structures, and supreme mechanical properties. They open up a wide horizon for functional practical usage, for example, as a flexible superefficient adsorbent to capture I - ions from contaminated water and trap I 2 vapor for safe disposal, as presented in this work. The viable binding mode between many types of inorganic NPs and organic NFC established here highlights new ways to investigate cellulose-based functional nanocomposites.

Hybrid aerogel-derived Sn-Ni alloy immobilized within porous carbon/graphene dual matrices for high-performance lithium storage.

PubMed

Zhang, Hao; Zhang, Mengru; Zhang, Meiling; Zhang, Lin; Zhang, Anping; Zhou, Yiming; Wu, Ping; Tang, Yawen

2017-09-01

Nanoporous networks of tin-based alloys immobilized within carbon matrices possess unique structural and compositional superiorities toward lithium-storage, and are expected to manifest improved strain-accommodation and charge-transport capabilities and thus desirable anodic performance for advanced lithium-ion batteries (LIBs). Herein, a facile and scalable hybrid aerogel-derived thermal-autoreduction route has been developed for the construction of nanoporous network of SnNi alloy immobilized within carbon/graphene dual matrices (SnNi@C/G network). When applied as an anode material for LIBs, the SnNi@C/G network manifests desirable lithium-storage performances in terms of specific capacities, cycle life, and rate capability. The facile aerogel-derived route and desirable Li-storage performance of the SnNi@C/G network facilitate its practical application as a high-capacity, long-life, and high-rate anode material for advanced LIBs. Copyright © 2017 Elsevier Inc. All rights reserved.

Aerogel and xerogel composites for use as carbon anodes

DOEpatents

Cooper, John F [Oakland, CA; Tillotson, Thomas M [Tracy, CA; Hrubesh, Lawrence W [Pleasanton, CA

2008-08-12

Disclosed herein are aerogel and xerogel composite materials suitable for use as anodes in fuel cells and batteries. Precursors to the aerogel and xerogel compounds are infused with inorganic polymeric materials or carbon particles and then gelled. The gels are then pyrolyzed to form composites with internal structural support.

Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

NASA Technical Reports Server (NTRS)

Leventis, Nicholas

2006-01-01

Aerogels comprise a class of low-density, high porous solid objects consisting of dimensionally quasi-stable self-supported three-dimensional assemblies of nanoparticles. Aerogels are pursued because of properties above and beyond those of the individual nanoparticles, including low thermal conductivity, low dielectric constant and high acoustic impedance. Possible applications include thermal and vibration insulation, dielectrics for fast electronics, and hosting of functional guests for a wide variety of optical, chemical and electronic applications. Aerogels, however, are extremely fragile materials, hence they have found only limited application in some very specialized environments, for example as Cerenkov radiation detectors in certain types of nuclear reactors, aboard spacecraft as collectors of hypervelocity particles (refer to NASA's Stardust program) and as thermal insulators on planetary vehicles on Mars (refer to Sojourner Rover in 1997 and Spirit and Opportunity in 2004). Along these lines, the X-Aerogel is a new NASA-developed strong lightweight material that has resolved the fragility problem of traditional (native) aerogels. X-Aerogels are made by applying a conformal polymer coating on the surfaces of the skeletal nanoparticles of native aerogels (see Scanning Electron Micrographs). Since the relative amounts of the polymeric crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by the templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by remplated casting of polymer on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralighweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the the thermal conductivity of styrofoam. X-Aerogels

Aerogel-supported filament

DOEpatents

Wuest, Craig R.; Tillotson, Thomas M.; Johnson, III, Coleman V.

1995-01-01

The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces.

Effects of nanoparticle shape on the morphology and properties of porous CdSe assemblies (aerogels).

PubMed

Yu, Hongtao; Brock, Stephanie L

2008-08-01

We demonstrate the effect of differently shaped CdSe nanoscale building blocks (dots, rods, branched nanoparticles, and hyperbranched nanoparticles) on the morphologies, surface characteristics, and optical properties of resultant porous CdSe nanostructured aerogels. Monolithic CdSe aerogels were produced by controlled oxidative removal of surface thiolate ligands from differently shaped CdSe nanoparticles to yield a wet gel, followed by CO(2) supercritical drying. The X-ray diffraction data show that the resultant CdSe aerogels maintain the crystalline phase of the building blocks without significant grain growth. However, the transmission electron microscopy images indicate that the morphology of CdSe aerogels changes from a colloid-type morphology to a polymer-type morphology when the building block changes from dot to rod or the branched nanoparticle. The morphology of the CdSe aerogel assembled from hyperbranched nanoparticles appears to be intermediate between the colloid-type and the polymer-type. Nitrogen physisorption measurements suggest that the surface areas and porosity are a direct function of the shape of the primary building blocks, with aerogels formed from rods or branched particles exhibiting the greatest surface areas (>200 m(2)/g) and those prepared from hyperbranched nanoparticles exhibiting the least (<100 m(2)/g). Band gap measurements and photoluminescence studies show that the as-prepared CdSe aerogels retain to a large extent the intrinsic quantum confinement of the differently shaped building blocks, despite being connected into a 3D network.

Crystalline boron nitride aerogels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.

This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxidemore » and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.« less

Polyimide Aerogels and Porous Membranes for Ultrasonic Impedance Matching to Air

NASA Technical Reports Server (NTRS)

Swank, Aaron J.; Sands, Obed S.; Meador, Mary Ann B.

2014-01-01

This work investigates acoustic impedance matching materials for coupling 200 kHz ultrasonic signals from air to materials with similar acoustic properties to that of water, flesh, rubber and plastics. Porous filter membranes as well as a new class of cross-linked polyimide aerogels are evaluated. The results indicate that a single impedance matching layer consisting of these new aerogel materials will recover nearly half of the loss in the incident-to-transmitted ultrasound intensity associated with an air/water, air/flesh or air/gelatin boundary. Furthermore, the experimental results are obtained where other uncertainties of the "real world" are present such that the observed impedance matching gains are representative of real-world applications. Performance of the matching layer devices is assessed using the idealized 3-layer model of infinite half spaces, yet the experiments conducted use a finite gelatin block as the destination medium.

Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solid-state supercapacitors.

PubMed

Zheng, Qifeng; Cai, Zhiyong; Ma, Zhenqiang; Gong, Shaoqin

2015-02-11

A novel type of highly flexible and all-solid-state supercapacitor that uses cellulose nanofibril (CNF)/reduced graphene oxide (RGO)/carbon nanotube (CNT) hybrid aerogels as electrodes and H2SO4/poly(vinyl alcohol) (PVA) gel as the electrolyte was developed and is reported here. These flexible solid-state supercapacitors were fabricated without any binders, current collectors, or electroactive additives. Because of the porous structure of the CNF/RGO/CNT aerogel electrodes and the excellent electrolyte absorption properties of the CNFs present in the aerogel electrodes, the resulting flexible supercapacitors exhibited a high specific capacitance (i.e., 252 F g(-1) at a discharge current density of 0.5 A g(-1)) and a remarkable cycle stability (i.e., more than 99.5% of the capacitance was retained after 1000 charge-discharge cycles at a current density of 1 A g(-1)). Furthermore, the supercapacitors also showed extremely high areal capacitance, areal power density, and energy density (i.e., 216 mF cm(-2), 9.5 mW cm(-2), and 28.4 μWh cm(-2), respectively). In light of its excellent electrical performance, low cost, ease of large-scale manufacturing, and environmental friendliness, the CNF/RGO/CNT aerogel electrodes may have a promising application in the development of flexible energy-storage devices.

Pressure-Sensitive and Conductive Carbon Aerogels from Poplars Catkins for Selective Oil Absorption and Oil/Water Separation.

PubMed

Li, Lingxiao; Hu, Tao; Sun, Hanxue; Zhang, Junping; Wang, Aiqin

2017-05-31

Multifunctional carbon aerogels that are both highly compressible and conductive have broad potential applications in the range of sound insulator, sensor, oil absorption, and electronics. However, the preparation of such carbon aerogels has been proven to be very challenging. Here, we report fabrication of pressure-sensitive and conductive (PSC) carbon aerogels by pyrolysis of cellulose aerogels composed of poplars catkin (PC) microfibers with a tubular structure. The wet PC gels can be dried directly in an oven without any deformation, in marked contrast to the brittle nature of traditional carbon aerogels. The resultant PSC aerogels exhibit ultralow density (4.3 mg cm -3 ), high compressibility (80%), high electrical conductivity (0.47 S cm -1 ), and high absorbency (80-161 g g -1 ) for oils and organic liquids. The PSC aerogels have potential applications in various fields such as elastomeric conductors, absorption of oils from water and oil/water separation, as the PSC aerogels feature simple preparation process with low-cost biomass as the precursor.

Efficiently dense hierarchical graphene based aerogel electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Xin; Lu, Chengxing; Peng, Huifen; Zhang, Xin; Wang, Zhenkun; Wang, Gongkai

2016-08-01

Boosting gravimetric and volumetric capacitances simultaneously at a high rate is still a discrepancy in development of graphene based supercapacitors. We report the preparation of dense hierarchical graphene/activated carbon composite aerogels via a reduction induced self-assembly process coupled with a drying post treatment. The compact and porous structures of composite aerogels could be maintained. The drying post treatment has significant effects on increasing the packing density of aerogels. The introduced activated carbons play the key roles of spacers and bridges, mitigating the restacking of adjacent graphene nanosheets and connecting lateral and vertical graphene nanosheets, respectively. The optimized aerogel with a packing density of 0.67 g cm-3 could deliver maximum gravimetric and volumetric capacitances of 128.2 F g-1 and 85.9 F cm-3, respectively, at a current density of 1 A g-1 in aqueous electrolyte, showing no apparent degradation to the specific capacitance at a current density of 10 A g-1 after 20000 cycles. The corresponding gravimetric and volumetric capacitances of 116.6 F g-1 and 78.1 cm-3 with an acceptable cyclic stability are also achieved in ionic liquid electrolyte. The results show a feasible strategy of designing dense hierarchical graphene based aerogels for supercapacitors.

Self-Assembled Fe-N-Doped Carbon Nanotube Aerogels with Single-Atom Catalyst Feature as High-Efficiency Oxygen Reduction Electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Chengzhou; Fu, Shaofang; Song, Junhua

Finely controlled synthesis of high active and robust non-precious metal catalysts with excellent electrocatalytic efficiency towards oxygen reduction reaction is extremely vital for successful implementation of fuel cells and metal batteries. Unprecedented oxygen reduction reaction electrocatalytic performances and the diversified synthetic procedure in term of favorable structure/morphology characteristics make transition metals-derived M–N–C (M=Fe, Co) structures the most promising nanocatalysts. Herein, using the nitrogen-containing small molecular and inorganic salt as precursors and ultrathin tellurium nanowires as templates, we successfully synthesized a series of well-defined M-N-doped hollow carbon nanowire aerogels through one step hydrothermal route and subsequent facile annealing treatment. Taking advantagemore » of the porous nanostructures, one-dimensional building block as well as homogeneity of active sites, the resultant Fe-N-doped carbon hollow nanowire aerogels exhibited excellent ORR electrocatalytic performance even better than commercial Pt/C in alkaline solution, holding great potential in fuel cell applications.« less

Aerogel-supported filament

DOEpatents

Wuest, C.R.; Tillotson, T.M.; Johnson, C.V. III

1995-05-16

The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces. 6 Figs.

Preparation and characterisation of CNF/MWCNT carbon aerogel as efficient adsorbents.

PubMed

Xu, Zhaoyang; Jiang, Xiangdong; Tan, Sicong; Wu, Weibing; Shi, Jiangtao; Zhou, Huan; Chen, Peng

2018-06-01

In recent years, carbon aerogels have attracted much attention in basic research and as potential applications in many fields. Herein, the authors report a novel approach using bamboo powder as raw material to fabricate cellulose nanofibers (CNFs)/multi-walled carbon nanotubes (MWCNTs) carbon aerogels by a simple dipping and carbonisation process. The developed material exhibits many exciting properties including low density (0.056 g cm -3 ), high porosity (95%), efficient capability for separation of oily droplets from water, and high adsorption capacity for a variety of oils and organic solvents by up to 110 times its own weight. Furthermore, the CNF/MWCNT carbon aerogels (CMCA) can be recycled many times by distillation and combustion, satisfying the requirements of practical oil-water separation. Taken together with its economical, environmentally benign manufacturing process, sustainability of the precursor and versatility of material, the CMCA developed in this study will be a promising candidate for addressing the problems arising from the spills of oily compounds.

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

PubMed Central

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-01-01

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding. PMID:26067176

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance.

PubMed

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-06-11

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

NASA Astrophysics Data System (ADS)

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-06-01

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

Super-hydrophobic fluorine containing aerogels

DOEpatents

Coronado, Paul R [Livermore, CA; Poco, John F [Livermore, CA; Hrubesh, Lawrence W [Pleasanton, CA

2007-05-01

An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.

[Ambient pressure synthesis and characterization of silica aerogel as adsorbent for dieldrin].

PubMed

Sha, Wei; Liu, Rui-ping; Liu, Hui-juan; Qu, Jiu-hui

2008-12-01

Hydrophobic silica aerogels were prepared from cheap waterglass precursors via surface modification of wet gels and ambient pressure drying route. Its adsorption capacity of Dieldrin, a typical of persistent organic pollutants (POPs), was examined. It is characterized via BET, FTIR, and DSC-TGA. The silica aerogels were highly hydrophobic with contact angles of 135 degrees-142 degrees, and the hydrophobicity of the aerogels could be maintained up to the temperature of 380 degrees C. The silica aerogels were porous with, pore size distribution of 17.5-23.4 nm, porosity of 94.8%-95.6%, and surface area of 444-560 m2 x g(-1). The results of adsorption experiments indicated that the hydrophobic aerogels could remove 84% of dieldrin from aqueous solution within 4 h; the adsorption process followed the pseudo-second-order kinetics process. Based on the adsorption equilibrium results, the adsorption capacity of silica aerogel was 11 times bigger than by active carbon.

Polyimide Aerogel Thin Films

NASA Technical Reports Server (NTRS)

Meador, Mary Ann; Guo, Haiquan

2012-01-01

Polyimide aerogels have been crosslinked through multifunctional amines. This invention builds on "Polyimide Aerogels With Three-Dimensional Cross-Linked Structure," and may be considered as a continuation of that invention, which results in a polyimide aerogel with a flexible, formable form. Gels formed from polyamic acid solutions, end-capped with anhydrides, and cross-linked with the multifunctional amines, are chemically imidized and dried using supercritical CO2 extraction to give aerogels having density around 0.1 to 0.3 g/cubic cm. The aerogels are 80 to 95% porous, and have high surface areas (200 to 600 sq m/g) and low thermal conductivity (as low as 14 mW/m-K at room temperature). Notably, the cross-linked polyimide aerogels have higher modulus than polymer-reinforced silica aerogels of similar density, and can be fabricated as both monoliths and thin films.

Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

PubMed

Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

2016-02-01

This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2018-04-03

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2014-08-19

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Instrumentation for Nano-porous, Nano-particulate Geopolymeric Materials Research

DTIC Science & Technology

2008-11-04

and their composites . This grant was used to procure equipment to synthesize and characterize the nano- and meso-porous geopolymers , and study their...and meso-porosity and microstructure of geopolymers and their composites is part of an ongoing research project in the PIs research group, which has...the synthesis and processing of geopolymers and geopolymer composites . The attritor mill enables synthesis Technical Report of nano-sized high

Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

NASA Technical Reports Server (NTRS)

Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

2013-01-01

This presentation discussed the potential advantages of developing Slotted Waveguide Arrays using polyimide aerogels. Polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aerospace antenna systems. PI aerogels are highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties. For slotted waveguide array applications, there are significant advantages in mass that more than compensate for the slightly higher loss of the aerogel filled waveguide when compared to state of practice commercial waveguide.

Concrete surface with nano-particle additives for improved wearing resistance to increasing truck traffic.

DOT National Transportation Integrated Search

2012-07-01

This study focused on the use of nanotechnology in concrete to improve the wearing resistance of concrete. The nano : materials used were polymer cross-linked aerogels, carbon nanotubes, and nano-SiO2, nano-CaCO3, and nano-Al2O3 : particles. As an in...

Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores.

PubMed

Zhu, Cheng; Liu, Tianyu; Qian, Fang; Han, T Yong-Jin; Duoss, Eric B; Kuntz, Joshua D; Spadaccini, Christopher M; Worsley, Marcus A; Li, Yat

2016-06-08

Graphene is an atomically thin, two-dimensional (2D) carbon material that offers a unique combination of low density, exceptional mechanical properties, thermal stability, large surface area, and excellent electrical conductivity. Recent progress has resulted in macro-assemblies of graphene, such as bulk graphene aerogels for a variety of applications. However, these three-dimensional (3D) graphenes exhibit physicochemical property attenuation compared to their 2D building blocks because of one-fold composition and tortuous, stochastic porous networks. These limitations can be offset by developing a graphene composite material with an engineered porous architecture. Here, we report the fabrication of 3D periodic graphene composite aerogel microlattices for supercapacitor applications, via a 3D printing technique known as direct-ink writing. The key factor in developing these novel aerogels is creating an extrudable graphene oxide-based composite ink and modifying the 3D printing method to accommodate aerogel processing. The 3D-printed graphene composite aerogel (3D-GCA) electrodes are lightweight, highly conductive, and exhibit excellent electrochemical properties. In particular, the supercapacitors using these 3D-GCA electrodes with thicknesses on the order of millimeters display exceptional capacitive retention (ca. 90% from 0.5 to 10 A·g(-1)) and power densities (>4 kW·kg(-1)) that equal or exceed those of reported devices made with electrodes 10-100 times thinner. This work provides an example of how 3D-printed materials, such as graphene aerogels, can significantly expand the design space for fabricating high-performance and fully integrable energy storage devices optimized for a broad range of applications.

Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying

NASA Astrophysics Data System (ADS)

Tian, H. Y.; Buckley, C. E.; Mulè, S.; Paskevicius, M.; Dhal, B. B.

2008-11-01

Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 °C was also activated in a carbon dioxide atmosphere at 900 °C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of <0.35 ± 0.07 to 0.55 ± 0.05 nm were present, and TEM measurements and nitrogen adsorption showed that larger mesopores were also present. Hydrogen storage properties of the CA were also investigated. An activated sample with a Brunauer-Emmett-Teller surface area of 1539 ± 20 m2 g-1 displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

Removal of bromide and iodide anions from drinking water by silver-activated carbon aerogels.

PubMed

Sánchez-Polo, M; Rivera-Utrilla, J; Salhi, E; von Gunten, U

2006-08-01

The aim of this study is to analyze the use of Ag-doped activated carbon aerogels for bromide and iodide removal from drinking water and to study how the activation of Ag-doped aerogels affects their behavior. It has been observed that the carbonization treatment and activation process of Ag-doped aerogels increased the surface area value ( [Formula: see text] ), whereas the volume of meso-(V(2)) and macropores (V(3)) decreased slightly. Chemical characterization of the materials revealed that carbonization and especially activation process considerably increased the surface basicity of the sample. Original sample (A) presented acidic surface properties (pH(PZC)=4.5) with 21% surface oxygen, whereas the sample that underwent activation showed mainly basic surface chemical properties (pH(PZC)=9.5) with only 6% of surface oxygen. Carbonization and especially, activation process considerable increased the adsorption capacity of bromide and iodide ions. This would mainly be produced by (i) an increase in the microporosity of the sample, which increases Ag-adsorption sites available to halide anions, and (ii) a rise of the basicity of the sample, which produces an increase in attractive electrostatic interactions between the aerogel surface, positively charged at the working pH (pH(solution)aerogels in water treatment, adsorption of bromide and iodide was studied under dynamic conditions using waters from Lake Zurich. Results obtained showed that the carbonization and activation processes increased the adsorptive capacity of the aerogel sample. However, results showed that the adsorption capacity of the aerogel samples studied was considerably lower in water from Lake Zurich. Results showed X(0.02) (amount adsorbed to initial breakthrough) values of 0.1 and 4.3 mg/g for chloride anion and dissolved organic carbon (DOC), respectively, during bromide adsorption process in water from Lake Zurich

Desalination with Carbon Aerogel Electrodes

DTIC Science & Technology

1996-12-04

Desalination with Carbon Aerogel Electrodes Joseph C. Farmer, Jeffrey H Richardson and David V Fix Chemistry and Materials Science Department Lawrence...Department of Interior, 190 pages, May (1966). 9. A. M. Johnson, A. W. Venolia, J. Newman, R. G. Wilbourne , C. M. Wong,, W. S. Gillam, S. Johnson, R. H...200 056, 31 pages, March (1970). 10. A. M. Johnson, A. W. Venolia, R. G. Wilbourne , J. Newman, "The Electrosorb Process for Desalting Water," Marquardt

Adsorption and desorption performance of benzene over hierarchically structured carbon-silica aerogel composites.

PubMed

Dou, Baojuan; Li, Jinjun; Wang, Yufei; Wang, Hailin; Ma, Chunyan; Hao, Zhengping

2011-11-30

Hierarchically structured carbon-silica aerogel (CSA) composites were synthesized from cheap water glass precursors and granulated activated carbon via a post-synthesis surface modification with trimethylchlorosilane (TMCS) and a low-cost ambient pressure drying procedure. The resultant CSA composites possess micro/mesoporous structure and hydrophobic surface. The adsorption and desorption performance of benzene on carbon-silica aerogel composite (CSA-2) under static and dynamic conditions were investigated, comparing with pure silica aerogel (CSA-0) and microporous activated carbon (AC). It was found that CSA-2 has high affinity towards aromatic molecules and fast adsorption kinetics. Excellent performance of dynamic adsorption and desorption observed on CSA-2 is related to its higher adsorption capacity than CSA-0 and less mass transfer resistance than AC, arising from the well-developed microporosity and open foam mesostructure in the CSA composites. Copyright © 2011 Elsevier B.V. All rights reserved.

Highly Porous, Rigid-Rod Polyamide Aerogels with Superior Mechanical Properties and Unusually High Thermal Conductivity.

PubMed

Williams, Jarrod C; Nguyen, Baochau N; McCorkle, Linda; Scheiman, Daniel; Griffin, Justin S; Steiner, Stephen A; Meador, Mary Ann B

2017-01-18

We report here the fabrication of polyamide aerogels composed of poly-p-phenylene-terephthalamide, the same backbone chemistry as DuPont's Kevlar. The all-para-substituted polymers gel without the use of cross-linker and maintain their shape during processing-an improvement over the meta-substituted cross-linked polyamide aerogels reported previously. Solutions containing calcium chloride (CaCl 2 ) and para-phenylenediamine (pPDA) in N-methylpyrrolidinone (NMP) at low temperature are reacted with terephthaloyl chloride (TPC). Polymerization proceeds over the course of 5 min resulting in gelation. Removal of the reaction solvent via solvent exchange followed by extraction with supercritical carbon dioxide provides aerogels with densities ranging from 0.1 to 0.3 g/cm 3 , depending on the concentration of calcium chloride, the formulated number of repeat units, n, and the concentration of polymer in the reaction mixture. These variables were assessed in a statistical experimental study to understand their effects on the properties of the aerogels. Aerogels made using at least 30 wt % CaCl 2 had the best strength when compared to aerogels of similar density. Furthermore, aerogels made using 30 wt % CaCl 2 exhibited the lowest shrinkage when aged at elevated temperatures. Notably, whereas most aerogel materials are highly insulating (thermal conductivities of 10-30 mW/m K), the polyamide aerogels produced here exhibit remarkably high thermal conductivities (50-80 mW/(m K)) at the same densities as other inorganic and polymer aerogels. These high thermal conductivities are attributed to efficient phonon transport by the rigid-rod polymer backbone. In conjunction with their low cost, ease of fabrication with respect to other polymer aerogels, low densities, and high mass-normalized strength and stiffness properties, these aerogels are uniquely valuable for applications such as lightweighting in consumer electronics, automobiles, and aerospace where weight reduction is

Nano/macro porous bioactive glass scaffold

NASA Astrophysics Data System (ADS)

Wang, Shaojie

Bioactive glass (BG) and ceramics have been widely studied and developed as implants to replace hard tissues of the musculo-skeletal system, such as bones and teeth. Recently, instead of using bulk materials, which usually do not degrade rapidly enough and may remain in the human body for a long time, the idea of bioscaffold for tissue regeneration has generated much interest. An ideal bioscaffold is a porous material that would not only provide a three-dimensional structure for the regeneration of natural tissue, but also degrade gradually and, eventually be replaced by the natural tissue completely. Among various material choices the nano-macro dual porous BG appears as the most promising candidate for bioscaffold applications. Here macropores facilitate tissue growth while nanopores control degradation and enhance cell response. The surface area, which controls the degradation of scaffold can also be tuned by changing the nanopore size. However, fabrication of such 3D structure with desirable nano and macro pores has remained challenging. In this dissertation, sol-gel process combined with spinodal decomposition or polymer sponge replication method has been developed to fabricate the nano-macro porous BG scaffolds. Macropores up to 100microm are created by freezing polymer induced spinodal structure through sol-gel transition, while larger macropores (>200um) of predetermined size are obtained by the polymer sponge replication technique. The size of nanopores, which are inherent to the sol-gel method of glass fabrication, has been tailored using several approaches: Before gel point, small nanopores are generated using acid catalyst that leads to weakly-branched polymer-like network. On the other hand, larger nanopores are created with the base-catalyzed gel with highly-branched cluster-like structure. After the gel point, the nanostructure can be further modified by manipulating the sintering temperature and/or the ammonia concentration used in the solvent

Dynamics of Photoexcitation and Photocatalysis at Nanostructured Carbon Interfaces

DTIC Science & Technology

2015-07-14

nanotubes with a sacrificial polymer and eliminating the polymer using a critical point drying process. This process creates aerogel structures that...Bindl DJ, Jacobberger RM, Wu M-Y, Singha Roy S, Arnold MS, Semiconducting Carbon Nanotube Aerogel Bulk Heterojunction Solar Cells, Small 10 (16), pp...ACS Nano 2015, 9 (1), 564-572. Ye Y, Bindl DJ, Jacobberger RM, Wu M-Y, Singha Roy S, Arnold MS, Semiconducting Carbon Nanotube Aerogel Bulk

Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying.

PubMed

Tian, H Y; Buckley, C E; Mulè, S; Paskevicius, M; Dhal, B B

2008-11-26

Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 °C was also activated in a carbon dioxide atmosphere at 900 °C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of <0.35 ± 0.07 to 0.55 ± 0.05 nm were present, and TEM measurements and nitrogen adsorption showed that larger mesopores were also present. Hydrogen storage properties of the CA were also investigated. An activated sample with a Brunauer-Emmett-Teller surface area of 1539 ± 20 m(2) g(-1) displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

Three-dimensional multichannel aerogel of carbon quantum dots for high-performance supercapacitors.

PubMed

Lv, Lingxiao; Fan, Yueqiong; Chen, Qing; Zhao, Yang; Hu, Yue; Zhang, Zhipan; Chen, Nan; Qu, Liangti

2014-06-13

A three-dimensional (3D) carbon quantum dot (CQD) aerogel has been prepared by in situ assembling CQDs in the sol-gel polymerization of resorcinol (R) and formaldehyde (F) and subsequently pyrolyzing the formed CQD gel. Compared to the supercapacitor based on the CQD-free aerogel, the supercapacitor fabricated with the CQD aerogel showed 20-fold higher specific capacitance (294.7 F g(-1) at the current density of 0.5 A g(-1)) and an excellent stability over 1000 consecutive charge-discharge cycles.

Three-dimensional multichannel aerogel of carbon quantum dots for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Lv, Lingxiao; Fan, Yueqiong; Chen, Qing; Zhao, Yang; Hu, Yue; Zhang, Zhipan; Chen, Nan; Qu, Liangti

2014-06-01

A three-dimensional (3D) carbon quantum dot (CQD) aerogel has been prepared by in situ assembling CQDs in the sol-gel polymerization of resorcinol (R) and formaldehyde (F) and subsequently pyrolyzing the formed CQD gel. Compared to the supercapacitor based on the CQD-free aerogel, the supercapacitor fabricated with the CQD aerogel showed 20-fold higher specific capacitance (294.7 F g-1 at the current density of 0.5 A g-1) and an excellent stability over 1000 consecutive charge-discharge cycles.

Bioinspired Synthesis of Monolithic and Layered Aerogels.

PubMed

Han, Xiao; Hassan, Khalil T; Harvey, Alan; Kulijer, Dejan; Oila, Adrian; Hunt, Michael R C; Šiller, Lidija

2018-06-01

Aerogels are the least dense and most porous materials known to man, with potential applications from lightweight superinsulators to smart energy materials. To date their use has been seriously hampered by their synthesis methods, which are laborious and expensive. Taking inspiration from the life cycle of the damselfly, a novel ambient pressure-drying approach is demonstrated in which instead of employing low-surface-tension organic solvents to prevent pore collapse during drying, sodium bicarbonate solution is used to generate pore-supporting carbon dioxide in situ, significantly reducing energy, time, and cost in aerogel production. The generic applicability of this readily scalable new approach is demonstrated through the production of granules, monoliths, and layered solids with a number of precursor materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aerogel and xerogel composites for use as carbon anodes

DOEpatents

Cooper, John F.; Tillotson, Thomas M.; Hrubesh, Lawrence W.

2010-10-12

A method for forming a reinforced rigid anode monolith and fuel and product of such method. The method includes providing a solution of organic aerogel or xerogel precursors including at least one of a phenolic resin, phenol (hydroxybenzene), resorcinol(1,3-dihydroxybenzene), or catechol(1,2-dihydroxybenzene); at least one aldehyde compound selected from the group consisting of formaldehyde, acetaldehyde, and furfuraldehyde; and an alkali carbonate or phosphoric acid catalyst; adding internal reinforcement materials comprising carbon to said precursor solution to form a precursor mixture; gelling said precursor mixture to form a composite gel; drying said composite gel; and pyrolyzing said composite gel to form a wettable aerogel/carbon composite or a wettable xerogel/carbon composite, wherein said composites comprise chars and said internal reinforcement materials, and wherein said composite is suitable for use as an anode with the chars being fuel capable of being combusted in a molten salt electrochemical fuel cell in the range from 500 C to 800 C to produce electrical energy. Additional methods and systems/compositions are also provided.

Carbothermal transformation of a graphitic carbon nanofiber/silica aerogel composite to a SiC/silica nanocomposite.

PubMed

Lu, Weijie; Steigerwalt, Eve S; Moore, Joshua T; Sullivan, Lisa M; Collins, W Eugene; Lukehart, C M

2004-09-01

Carbon nanofiber/silica aerogel composites are prepared by sol-gel processing of surface-enhanced herringbone graphitic carbon nanofibers (GCNF) and Si(OMe)4, followed by supercritical CO2 drying. Heating the resulting GCNF/silica aerogel composites to 1650 degrees C under a partial pressure of Ar gas initiates carbothermal reaction between the silica aerogel matrix and the carbon nanofiber component to form SiC/silica nanocomposites. The SiC phase is present as nearly spherical nanoparticles, having an average diameter of ca. 8 nm. Formation of SiC is confirmed by powder XRD and by Raman spectroscopy.

Electrodes Based on Carbon Aerogels Partially Graphitized by Doping with Transition Metals for Oxygen Reduction Reaction

PubMed Central

Abdelwahab, Abdalla; Castelo-Quibén, Jesica; Vivo-Vilches, José F.; Pérez-Cadenas, María; Maldonado-Hódar, Francisco J.

2018-01-01

A series of carbon aerogels doped with iron, cobalt and nickel have been prepared. Metal nanoparticles very well dispersed into the carbon matrix catalyze the formation of graphitic clusters around them. Samples with different Ni content are obtained to test the influence of the metal loading. All aerogels have been characterized to analyze their textural properties, surface chemistry and crystal structures. These metal-doped aerogels have a very well-developed porosity, making their mesoporosity remarkable. Ni-doped aerogels are the ones with the largest surface area and the smallest graphitization. They also present larger mesopore volumes than Co- and Fe-doped aerogels. These materials are tested as electro-catalysts for the oxygen reduction reaction. Results show a clear and strong influence of the carbonaceous structure on the whole electro-catalytic behavior of the aerogels. Regarding the type of metal doping, aerogel doped with Co is the most active one, followed by Ni- and Fe-doped aerogels, respectively. As the Ni content is larger, the kinetic current densities increase. Comparatively, among the different doping metals, the results obtained with Ni are especially remarkable. PMID:29690602

Surface modified aerogel monoliths

NASA Technical Reports Server (NTRS)

Leventis, Nicholas (Inventor); Johnston, James C. (Inventor); Kuczmarski, Maria A. (Inventor); Meador, Mary Ann B. (Inventor)

2013-01-01

This invention comprises reinforced aerogel monoliths such as silica aerogels having a polymer coating on its outer geometric surface boundary, and to the method of preparing said aerogel monoliths. The polymer coatings on the aerogel monoliths are derived from polymer precursors selected from the group consisting of isocyanates as a precursor, precursors of epoxies, and precursors of polyimides. The coated aerogel monoliths can be modified further by encapsulating the aerogel with the polymer precursor reinforced with fibers such as carbon or glass fibers to obtain mechanically reinforced composite encapsulated aerogel monoliths.

Benzimidazole Based Aerogel Materials

NASA Technical Reports Server (NTRS)

Rhine, Wendell E. (Inventor); Mihalcik, David (Inventor)

2016-01-01

The present invention provides aerogel materials based on imidazoles and polyimidazoles. The polyimidazole based aerogel materials can be thermally stable up to 500 C or more, and can be carbonized to produce a carbon aerogel having a char yield of 60% or more, specifically 70% or more. The present invention also provides methods of producing polyimidazole based aerogel materials by reacting at least one monomer in a suitable solvent to form a polybenzimidazole gel precursor solution, casting the polybenzimidazole gel precursor solution into a fiber reinforcement phase, allowing the at least one gel precursor in the precursor solution to transition into a gel material, and drying the gel materials to remove at least a portion of the solvent, to obtain an polybenzimidazole-based aerogel material.

Highly porous and mechanically strong ceramic oxide aerogels

NASA Technical Reports Server (NTRS)

Johnston, James C. (Inventor); Leventis, Nicholas (Inventor); Ilhan, Ulvi F. (Inventor); Meador, Mary Ann B. (Inventor); Fabrizio, Eve F. (Inventor)

2012-01-01

Structurally stable and mechanically strong ceramic oxide aerogels are provided. The aerogels are cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions. The functional groups can be hydroxyl groups, which are native to ceramic oxides, or they can be non-hydroxyl functional groups that can be decorated over the internal surfaces of the ceramic oxide network. Methods of preparing such mechanically strong ceramic oxide aerogels also are provided.

Highly porous and mechanically strong ceramic oxide aerogels

NASA Technical Reports Server (NTRS)

Fabrizio, Eve F. (Inventor); Leventis, Nicholas (Inventor); Ilhan, Ulvi F. (Inventor); Meador, Mary Ann B. (Inventor); Johnston, James C. (Inventor)

2010-01-01

Structurally stable and mechanically strong ceramic oxide aerogels are provided. The aerogels are cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions. The functional groups can be hydroxyl groups, which are native to ceramic oxides, or they can be non-hydroxyl functional groups that can be decorated over the internal surfaces of the ceramic oxide network. Methods of preparing such mechanically strong ceramic oxide aerogels also are provided.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle.

PubMed

Zhuo, Hao; Hu, Yijie; Tong, Xing; Chen, Zehong; Zhong, Linxin; Lai, Haihong; Liu, Linxiang; Jing, Shuangshuang; Liu, Qingzhong; Liu, Chuanfu; Peng, Xinwen; Sun, Runcang

2018-05-01

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon XANES Data from Six Aerogel Picokeystones Cut from the Top and Bottom Sides of the Stardust Comet Sample Tray

NASA Technical Reports Server (NTRS)

Wirick, S.; Flynn, G. J.; Frank, D.; Sandford, S. A.; Zolensky, M. E.; Tsou, P.; Peltzer, C.; Jacobsen, C.

2009-01-01

Great care and a large effort was made to minimize the amount of organic matter contained within the flight aerogel used to collect Comet 81P/Wild 2 samples. Even so, by the very nature of the production process and silica aerogel s affinity for volatile organics keeping silica aerogel free from organics is a monumental task. Silica aerogel from three production batches was flown on the Stardust sample return mission. All 3 types had layered densities varying from 5mg/ml to 50 mg/ml where the densest aerogel was farthest away from the collection area. A 2 step gelation process was used to make the flight aerogel and organics used in this process were tetraethylorthosilicate, ethanol and acetonitrile. Both ammonium hydroxide and nitric acid were also used in the aerogel production process. The flight aerogel was baked at JPL at 300 C for 72 hours, most of the baking was done at atmosphere but twice a day the oven was pumped to 10 torr for hour [1]. After the aerogel was baked it was stored in a nitrogen purged cabinet until flight time. One aerogel cell was located in the SRC away from any sample collection area as a witness to possible contamination from out gassing of the space craft, re-entry gases and any other organic encounter. This aerogel was aerogel used in the interstellar collection sample tray and is the least dense of the 3 batches of aerogel flown. Organics found in the witness tile include organics containing Si-CH3 bonds, amines and PAHS. Besides organic contamination, hot spots of calcium were reported in the flight aerogel. Carbonates have been detected in comet 81P/Wild2 samples . During preflight analyses, no technique was used to analyze for carbonates in aerogel. To determine if the carbonates found in 81P/Wild2 samples were from the comet, it is necessary to analyze the flight aerogel for carbonate as well as for organics.

Influence of Aerogel Morphology and Reinforcement Architecture on Gas Convection in Aerogel Composites

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.; Meyer, Matthew; Guo, Haiquan; Rogers, Richard B.; DeMange, Jeffrey J.; Richardson, Hayley

2016-01-01

A variety of thermal protection applications require lightweight insulation capable of withstanding temperatures well above 900 C. Aerogels offer extremely low-density thermal insulation due to their mesoporous structure, which inhibits both gas convection and solid conduction. Silica aerogel systems are limited to use temperatures of 600-700 C, above which they sinter. Alumina aerogels maintain a porous structure to higher temperatures than silica, before transforming to -alumina and densifying. We have synthesized aluminosilicate aerogels capable of maintaining higher surface areas at temperatures above 1100 C than an all-alumina aerogel using -Boehmite as the aluminum source and tetraethoxysilane (TEOS) as the silicon source. The pore structure of these aerogels varies with thermal exposure temperature and time, as the aluminosilicate undergoes a variety of phase changes to form transition aluminas. Transformation to -alumina is inhibited by incorporation of silica into the alumina lattice. The aerogels are fragile, but can be reinforced using a large variety of ceramic papers, felts or fabrics. The objective of the current study is to characterize the influence of choice of reinforcement and architecture on gas permeability of the aerogel composites in both the as fabricated condition and following thermal exposure, as well as understand the effects of incorporating hydrophobic treatments in the composites.

Biomass-derived sponge-like carbonaceous hydrogels and aerogels for supercapacitors.

PubMed

Wu, Xi-Lin; Wen, Tao; Guo, Hong-Li; Yang, Shubin; Wang, Xiangke; Xu, An-Wu

2013-04-23

As a newly developed material, carbon gels have been receiving considerable attention due to their multifunctional properties. Herein, we present a facile, green, and template-free route toward sponge-like carbonaceous hydrogels and aerogels by using crude biomass, watermelon as the carbon source. The obtained three-dimensional (3D) flexible carbonaceous gels are made of both carbonaceous nanofibers and nanospheres. The porous carbonaceous gels (CGs) are highly chemically active and show excellent mechanical flexibility which enable them to be a good scaffold for the synthesis of 3D composite materials. We synthesized the carbonaceous gel-based composite materials by incorporating Fe3O4 nanoparticles into the networks of the carbonaceous gels. The Fe3O4/CGs composites further transform into magnetite carbon aerogels (MCAs) by calcination. The MCAs keep the porous structure of the original CGs, which allows the sustained and stable transport of both electrolyte ions and electrons to the electrode surface, leading to excellent electrochemical performance. The MCAs exhibit an excellent capacitance of 333.1 F·g(-1) at a current density of 1 A·g(-1) within a potential window of -1.0 to 0 V in 6 M KOH solution. Meanwhile, the MCAs also show outstanding cycling stability with 96% of the capacitance retention after 1000 cycles of charge/discharge. These findings open up the use of low-cost elastic carbon gels for the synthesis of other 3D composite materials and show the possibility for the application in energy storage.

Flame Retardant Effect of Aerogel and Nanosilica on Engineered Polymers

NASA Technical Reports Server (NTRS)

Williams, Martha K.; Smith, Trent M.; Roberson, Luke B.; Yang, Feng; Nelson, Gordon L.

2010-01-01

Aerogels are typically manufactured vIa high temperature and pressure-critical-point drying of a colloidal metal oxide gel filled with solvents. Aerogel materials derived from silica materials represent a structural morphology (amorphous, open-celled nanofoams) rather than a particular chemical constituency. Aerogel is not like conventional foams in that it is a porous material with extreme microporosity and composed of individual features only a few nanometers in length with a highly porous dendriticlike structure. This unique substance has unusual properties such as low thermal conductivity, refractive index and sound suppression; in addition to its exceptional ability to capture fast moving dust. The highly porous nature of the aerogel's structure provides large amounts of surface area per unit weight. For instance, a silica aerogel material with a density of 100 kilograms per cubic meters can have surface areas of around 800 to 1500 square meters per gram depending on the precursors and process utilized to produce it. To take advantage of the unique properties of silica aerogels, especially the ultra light weight and low thermal conductivity, their composites with various engineering polymers were prepared and their flammability was investigated by Cone Calorimetry. The flammability of various polystyrene/silica aerogel nanocomposites were measured. The combination of these nanocomposites with a NASA patented flame retardant SINK were also studied. The results were compared with the base polymer to show the differences between composites with different forms of silica.

Advanced Aerogel Technology

NASA Technical Reports Server (NTRS)

Jones, Steven

2013-01-01

The JPL Aerogel Laboratory has made aerogels for NASA flight missions, e.g., Stardust, 2003 Mars Exploration Rovers and the 2011 Mars Science Laboratory, as well as NASA research projects for the past 14 years. During that time it has produced aerogels of a range of shapes, sizes, densities and compositions. Research is ongoing in the development of aerogels for future sample capture and return missions and for thermal insulation for both spacecraft and scientific instruments. For the past several years, the JPL Aerogel Laboratory has been developing, producing and testing a new composite material for use as the high temperature thermal insulation in the Advanced Sterling Radioisotope Generator (ASRG) being developed by Lockheed Martin and NASA. The composite is made up of a glass fiber felt, silica aerogel, Titania powder, and silica powder. The oxide powders are included to reduce irradiative heat transport at elevated temperatures. These materials have thermal conductivity values that are the same as the best commercially produced high temperature insulation materials, and yet are 40% lighter. By greatly reducing the amount of oxide powder in the composite, the density, and therefore for the value of the thermal conductivity, would be reduced. The JPL Aerogel Laboratory has experimented with using glass fiber felt, expanded glass fiber felt and loose fibers to add structural integrity to silica aerogels. However, this work has been directed toward high temperature applications. By conducting a brief investigation of the optimal combination of fiber reinforcement and aerogel density, a durable, extremely efficient thermal insulation material for ambient temperature applications would be produced. If a transparent thermal insulation is desired, then aerogel is an excellent candidate material. At typical ambient temperatures, silica aerogel prevents the transport of heat via convection and conduction due to its highly porous nature. To prevent irradiative thermal

Cellulose-derived carbon aerogels supported goethite (α-FeOOH) nanoneedles and nanoflowers for electromagnetic interference shielding.

PubMed

Wan, Caichao; Jiao, Yue; Qiang, Tiangang; Li, Jian

2017-01-20

We describe a rapid and facile chemical precipitation method to grow goethite (α-FeOOH) nanoneedles and nanoflowers on the carbon aerogels which was obtained from the pyrolysis of cellulose aerogels. When evaluated as electromagnetic interference (EMI) shielding materials, the α-FeOOH/cellulose-derived carbon aerogels composite displays the highest SE total value of 34.0dB at the Fe 3+ /Fe 2+ concentration of 0.01M, which is about 4.8 times higher than that of the individual α-FeOOH (5.9dB). When the higher or lower Fe 3+ /Fe 2+ concentrations were used, the EMI shielding performance deterioration occurred. The integration of α-FeOOH with the carbon aerogels transforms the reflection-dominant mechanism for α-FeOOH into the adsorption-dominant mechanism for the composite. The adsorption-dominant mechanism undoubtedly makes contribution to alleviating secondary radiation, which is regarded as more attractive alternative for developing electromagnetic radiation protection products. Copyright © 2016 Elsevier Ltd. All rights reserved.

Controlled synthesis of flexible graphene aerogels macroscopic monolith as versatile agents for wastewater treatment

NASA Astrophysics Data System (ADS)

Dong, Shuying; Xia, Longji; Guo, Teng; Zhang, Fangyuan; Cui, Lingfang; Su, Xianfa; Wang, Dong; Guo, Wei; Sun, Jianhui

2018-07-01

Emerging applications for environmental purification require agents that not only possess high decontamination efficiency, but also are capable of withstanding mechanical deformation without secondary pollution and degradation of performance. To this end, we have controlled synthesis of mechanically flexible graphene aerogel (GA) by vacuum freeze-drying of their hydrogel precursors obtained from heating the aqueous mixtures of graphene oxide (GO) and Vitamin C (VC) without stirring. Through the adaptable process conditions, such as the particle size of carbon, GO concentration, dosage of reducing agent and solution pH, the highly porous, ultralight and mechanically flexible GA are synthesized. Owing to the porous, robust and stable structure, the resulting GA show very promising performance in water purification including enrichment of organic liquid solvents (alcohols, oil and alkanes), removal of hexavalent chromium Cr(VI) and purified industrial wastewater, as well as flexible conductors. The successful creation of the GA may provide new insights into the design of carbon-based aerogels for various applications, as the GA can be prepared via a very simple procedure and available in macroscopic diverse morphologies with tunable porosity.

3D hierarchical porous graphene aerogel with tunable meso-pores on graphene nanosheets for high-performance energy storage

PubMed Central

Ren, Long; Hui, K. N.; Hui, K. S.; Liu, Yundan; Qi, Xiang; Zhong, Jianxin; Du, Yi; Yang, Jianping

2015-01-01

New and novel 3D hierarchical porous graphene aerogels (HPGA) with uniform and tunable meso-pores (e.g., 21 and 53 nm) on graphene nanosheets (GNS) were prepared by a hydrothermal self-assembly process and an in-situ carbothermal reaction. The size and distribution of the meso-pores on the individual GNS were uniform and could be tuned by controlling the sizes of the Co3O4 NPs used in the hydrothermal reaction. This unique architecture of HPGA prevents the stacking of GNS and promises more electrochemically active sites that enhance the electrochemical storage level significantly. HPGA, as a lithium-ion battery anode, exhibited superior electrochemical performance, including a high reversible specific capacity of 1100 mAh/g at a current density of 0.1 A/g, outstanding cycling stability and excellent rate performance. Even at a large current density of 20 A/g, the reversible capacity was retained at 300 mAh/g, which is larger than that of most porous carbon-based anodes reported, suggesting it to be a promising candidate for energy storage. The proposed 3D HPGA is expected to provide an important platform that can promote the development of 3D topological porous systems in a range of energy storage and generation fields. PMID:26382852

Highly porous ceramic oxide aerogels having improved flexibility

NASA Technical Reports Server (NTRS)

Guo, Haiquan (Inventor); Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

2012-01-01

Ceramic oxide aerogels having improved flexibility are disclosed. Preferred embodiments exhibit high modulus and other strength properties despite their improved flexibility. The gels may be polymer cross-linked via organic polymer chains to further improve strength properties, without substantially detracting from the improved flexibility. Methods of making such aerogels are also disclosed.

Chitin Liquid-Crystal-Templated Oxide Semiconductor Aerogels.

PubMed

Chau, Trang The Lieu; Le, Dung Quang Tien; Le, Hoa Thi; Nguyen, Cuong Duc; Nguyen, Long Viet; Nguyen, Thanh-Dinh

2017-09-13

Chitin nanocrystals have been used as a liquid crystalline template to fabricate layered oxide semiconductor aerogels. Anisotropic chitin liquid crystals are transformed to sponge-like aerogels by hydrothermally cross-linked gelation and lyophilization-induced solidification. The hydrothermal gelation of chitin aqueous suspensions then proceeds with peroxotitanate to form hydrogel composites that recover to form aerogels after freeze-drying. The homogeneous peroxotitanate/chitin composites are calcined to generate freestanding titania aerogels that exhibit the nanostructural integrity of layered chitin template. Our extended investigations show that coassembling chitin nanocrystals with other metal-based precursors also yielded semiconductor aerogels of perovskite BaTiO 3 and CuO x nanocrystals. The potential of these materials is great to investigate these chitin sponges for biomedicine and these semiconductor aerogels for photocatalysis, gas sensing, and other applications. Our results present a new aerogel templating method of highly porous, ultralight materials with chitin liquid crystals.

Toward Aerogel Electrodes of Superior Rate Performance in Supercapacitors through Engineered Hollow Nanoparticles of NiCo2O4

PubMed Central

Li, Jianjiang; Chen, Shuai; Zhu, Xiaoyi; She, Xilin; Liu, Tongchao; Zhang, Huawei; Komarneni, Sridhar

2017-01-01

Abstract A biomass‐templated pathway is developed for scalable synthesis of NiCo2O4@carbon aerogel electrodes for supercapacitors, where NiCo2O4 hollow nanoparticles with an average outer diameter of 30–40 nm are conjoined by graphitic carbon forming a 3D aerogel structure. This kind of NiCo2O4 aerogel structure shows large specific surface area (167.8 m2 g−1), high specific capacitance (903.2 F g−1 at a current density of 1 A g−1), outstanding rate performance (96.2% capacity retention from 1 to 10 A g−1), and excellent cycling stability (nearly without capacitance loss after 3000 cycles at 10 A g−1). The unique structure of the 3D hollow aerogel synergistically contributes to the high performance. For instance, the 3D interconnected porous structure of the aerogel is beneficial for electrolyte ion diffusion and for shortening the electron transport pathways, and thus can improve the rate performance. The conductive carbon joint greatly enhances the specific capacity, and the hollow structure prohibits the volume changes during the charge–discharge process to significantly improve the cycling stability. This work represents a giant step toward the preparation of high‐performance commercial supercapacitors. PMID:29270344

Toward Aerogel Electrodes of Superior Rate Performance in Supercapacitors through Engineered Hollow Nanoparticles of NiCo2O4.

PubMed

Li, Jianjiang; Chen, Shuai; Zhu, Xiaoyi; She, Xilin; Liu, Tongchao; Zhang, Huawei; Komarneni, Sridhar; Yang, Dongjiang; Yao, Xiangdong

2017-12-01

A biomass-templated pathway is developed for scalable synthesis of NiCo 2 O 4 @carbon aerogel electrodes for supercapacitors, where NiCo 2 O 4 hollow nanoparticles with an average outer diameter of 30-40 nm are conjoined by graphitic carbon forming a 3D aerogel structure. This kind of NiCo 2 O 4 aerogel structure shows large specific surface area (167.8 m 2 g -1 ), high specific capacitance (903.2 F g -1 at a current density of 1 A g -1 ), outstanding rate performance (96.2% capacity retention from 1 to 10 A g -1 ), and excellent cycling stability (nearly without capacitance loss after 3000 cycles at 10 A g -1 ). The unique structure of the 3D hollow aerogel synergistically contributes to the high performance. For instance, the 3D interconnected porous structure of the aerogel is beneficial for electrolyte ion diffusion and for shortening the electron transport pathways, and thus can improve the rate performance. The conductive carbon joint greatly enhances the specific capacity, and the hollow structure prohibits the volume changes during the charge-discharge process to significantly improve the cycling stability. This work represents a giant step toward the preparation of high-performance commercial supercapacitors.

In vivo ultrasonic detection of polyurea crosslinked silica aerogel implants.

PubMed

Sabri, Firouzeh; Sebelik, Merry E; Meacham, Ryan; Boughter, John D; Challis, Mitchell J; Leventis, Nicholas

2013-01-01

Polyurea crosslinked silica aerogels are highly porous, lightweight, and mechanically strong materials with great potential for in vivo applications. Recent in vivo and in vitro studies have demonstrated the biocompatibility of this type of aerogel. The highly porous nature of aerogels allows for exceptional thermal, electric, and acoustic insulating capabilities that can be taken advantage of for non-invasive external imaging techniques. Sound-based detection of implants is a low cost, non-invasive, portable, and rapid technique that is routinely used and readily available in major clinics and hospitals. In this study the first in vivo ultrasound response of polyurea crosslinked silica aerogel implants was investigated by means of a GE Medical Systems LogiQe diagnostic ultrasound machine with a linear array probe. Aerogel samples were inserted subcutaneously and sub-muscularly in a) fresh animal model and b) cadaveric human model for analysis. For comparison, samples of polydimethylsiloxane (PDMS) were also imaged under similar conditions as the aerogel samples. Polyurea crosslinked silica aerogel (X-Si aerogel) implants were easily identified when inserted in either of the regions in both fresh animal model and cadaveric model. The implant dimensions inferred from the images matched the actual size of the implants and no apparent damage was sustained by the X-Si aerogel implants as a result of the ultrasonic imaging process. The aerogel implants demonstrated hyperechoic behavior and significant posterior shadowing. Results obtained were compared with images acquired from the PDMS implants inserted at the same location.

Investigation of Polyurea-Crosslinked Silica Aerogels as a Neuronal Scaffold: A Pilot Study

PubMed Central

Sabri, Firouzeh; Cole, Judith A.; Scarbrough, Michael C.; Leventis, Nicholas

2012-01-01

Background Polymer crosslinked aerogels are an attractive class of materials for future implant applications particularly as a biomaterial for the support of nerve growth. The low density and nano-porous structure of this material combined with large surface area, high mechanical strength, and tunable surface properties, make aerogels materials with a high potential in aiding repair of injuries of the peripheral nervous system. However, the interaction of neurons with aerogels remains to be investigated. Methodology In this work the attachment and growth of neurons on clear polyurea crosslinked silica aerogels (PCSA) coated with: poly-L-lysine, basement membrane extract (BME), and laminin1 was investigated by means of optical and scanning electron microscopy. After comparing the attachment and growth capability of neurons on these different coatings, laminin1 and BME were chosen for nerve cell attachment and growth on PCSA surfaces. The behavior of neurons on treated petri dish surfaces was used as the control and behavior of neurons on treated PCSA discs was compared against it. Conclusions/Significance This study demonstrates that: 1) untreated PCSA surfaces do not support attachment and growth of nerve cells, 2) a thin application of laminin1 layer onto the PCSA discs adhered well to the PCSA surface while also supporting growth and differentiation of neurons as evidenced by the number of processes extended and b3-tubulin expression, 3) three dimensional porous structure of PCSA remains intact after fixing protocols necessary for preservation of biological samples and 4) laminin1 coating proved to be the most effective method for attaching neurons to the desired regions on PCSA discs. This work provides the basis for potential use of PCSA as a biomaterial scaffold for neural regeneration. PMID:22448239

Preparation, Characterization and Activity of a Peptide-Cellulosic Aerogel Protease Sensor from Cotton

PubMed Central

Edwards, J. Vincent; Fontenot, Krystal R.; Prevost, Nicolette T.; Pircher, Nicole; Liebner, Falk; Condon, Brian D.

2016-01-01

Nanocellulosic aerogels (NA) provide a lightweight biocompatible material with structural properties, like interconnected high porosity and specific surface area, suitable for biosensor design. We report here the preparation, characterization and activity of peptide-nanocellulose aerogels (PepNA) made from unprocessed cotton and designed with protease detection activity. Low-density cellulosic aerogels were prepared from greige cotton by employing calcium thiocyanate octahydrate/lithium chloride as a direct cellulose dissolving medium. Subsequent casting, coagulation, solvent exchange and supercritical carbon dioxide drying afforded homogeneous cellulose II aerogels of fibrous morphology. The cotton-based aerogel had a porosity of 99% largely dominated by mesopores (2–50 nm) and an internal surface of 163 m2·g−1. A fluorescent tripeptide-substrate (succinyl-alanine-proline-alanine-4-amino-7-methyl-coumarin) was tethered to NA by (1) esterification of cellulose C6 surface hydroxyl groups with glycidyl-fluorenylmethyloxycarbonyl (FMOC), (2) deprotection and (3) coupling of the immobilized glycine with the tripeptide. Characterization of the NA and PepNA included techniques, such as elemental analysis, mass spectral analysis, attenuated total reflectance infrared imaging, nitrogen adsorption, scanning electron microscopy and bioactivity studies. The degree of substitution of the peptide analog attached to the anhydroglucose units of PepNA was 0.015. The findings from mass spectral analysis and attenuated total reflectance infrared imaging indicated that the peptide substrate was immobilized on to the surface of the NA. Nitrogen adsorption revealed a high specific surface area and a highly porous system, which supports the open porous structure observed from scanning electron microscopy images. Bioactivity studies of PepNA revealed a detection sensitivity of 0.13 units/milliliter for human neutrophil elastase, a diagnostic biomarker for inflammatory diseases. The

Preparation, Characterization and Activity of a Peptide-Cellulosic Aerogel Protease Sensor from Cotton.

PubMed

Edwards, J Vincent; Fontenot, Krystal R; Prevost, Nicolette T; Pircher, Nicole; Liebner, Falk; Condon, Brian D

2016-10-26

Nanocellulosic aerogels (NA) provide a lightweight biocompatible material with structural properties, like interconnected high porosity and specific surface area, suitable for biosensor design. We report here the preparation, characterization and activity of peptide-nanocellulose aerogels (PepNA) made from unprocessed cotton and designed with protease detection activity. Low-density cellulosic aerogels were prepared from greige cotton by employing calcium thiocyanate octahydrate/lithium chloride as a direct cellulose dissolving medium. Subsequent casting, coagulation, solvent exchange and supercritical carbon dioxide drying afforded homogeneous cellulose II aerogels of fibrous morphology. The cotton-based aerogel had a porosity of 99% largely dominated by mesopores (2-50 nm) and an internal surface of 163 m²·g -1 . A fluorescent tripeptide-substrate (succinyl-alanine-proline-alanine-4-amino-7-methyl-coumarin) was tethered to NA by (1) esterification of cellulose C6 surface hydroxyl groups with glycidyl-fluorenylmethyloxycarbonyl (FMOC), (2) deprotection and (3) coupling of the immobilized glycine with the tripeptide. Characterization of the NA and PepNA included techniques, such as elemental analysis, mass spectral analysis, attenuated total reflectance infrared imaging, nitrogen adsorption, scanning electron microscopy and bioactivity studies. The degree of substitution of the peptide analog attached to the anhydroglucose units of PepNA was 0.015. The findings from mass spectral analysis and attenuated total reflectance infrared imaging indicated that the peptide substrate was immobilized on to the surface of the NA. Nitrogen adsorption revealed a high specific surface area and a highly porous system, which supports the open porous structure observed from scanning electron microscopy images. Bioactivity studies of PepNA revealed a detection sensitivity of 0.13 units/milliliter for human neutrophil elastase, a diagnostic biomarker for inflammatory diseases. The

Effect of Nano Silica on the Physical Property of Porous Concrete Pavement

NASA Astrophysics Data System (ADS)

Yusak, Mohd Ibrahim Mohd; Ezree Abdullah, Mohd; Putra Jaya, Ramadhansyah; Rosli Hainin, Mohd; Ibrahim, Mohd Haziman Wan

2017-08-01

Rice husk can be categorized as an organic waste material from paddy industries. Silica is a major inorganic element of the rice husk. The aim of present study is to evaluate the effect of Nano silica on the physical properties of porous concrete pavement. Rice husk has been burned in the furnace (650°C for 6 hours) and ground for four different grinding times (33, 48, 63 and 81 hours). Five types of mixes were prepared to evaluate the different Nano silica grinding time. A Nano silica dosage of 10% by weight of binder was used throughout the experiments. The physical properties were examined through compressive strength, transmission electron microscopy and x-ray fluorescence. The experimental results indicate that the different Nano size gives a different effect to porous concrete strength. Based on the results obtained, Nano silica ground for 63 hours (65.84nm) gives the best result and performance to porous concrete pavement specimens.

The adsorption of rare earth ions using carbonized polydopamine nano shells

DOE PAGES

Sun, Xiaoqi; Luo, Huimin; Mahurin, Shannon Mark; ...

2016-01-07

Herein we report the structure effects of nano carbon shells prepared by carbonized polydopamine for rare earth elements (REEs) adsorption for the first time. The solid carbon sphere, 60 nm carbon shell and 500 nm carbon shell were prepared and investigated for adsorption and desorption of REEs. The adsorption of carbon shells for REEs was found to be better than the solid carbon sphere. The effect of acidities on the adsorption and desorption properties was discussed in this study. The good adsorption performance of carbon shells can be attributed to their porous structure, large specific surface area, amine group andmore » carbonyl group of dopamine.« less

In Vivo Ultrasonic Detection of Polyurea Crosslinked Silica Aerogel Implants

PubMed Central

Sabri, Firouzeh; Sebelik, Merry E.; Meacham, Ryan; Boughter, John D.; Challis, Mitchell J.; Leventis, Nicholas

2013-01-01

Background Polyurea crosslinked silica aerogels are highly porous, lightweight, and mechanically strong materials with great potential for in vivo applications. Recent in vivo and in vitro studies have demonstrated the biocompatibility of this type of aerogel. The highly porous nature of aerogels allows for exceptional thermal, electric, and acoustic insulating capabilities that can be taken advantage of for non-invasive external imaging techniques. Sound-based detection of implants is a low cost, non-invasive, portable, and rapid technique that is routinely used and readily available in major clinics and hospitals. Methodology In this study the first in vivo ultrasound response of polyurea crosslinked silica aerogel implants was investigated by means of a GE Medical Systems LogiQe diagnostic ultrasound machine with a linear array probe. Aerogel samples were inserted subcutaneously and sub-muscularly in a) fresh animal model and b) cadaveric human model for analysis. For comparison, samples of polydimethylsiloxane (PDMS) were also imaged under similar conditions as the aerogel samples. Conclusion/significance Polyurea crosslinked silica aerogel (X-Si aerogel) implants were easily identified when inserted in either of the regions in both fresh animal model and cadaveric model. The implant dimensions inferred from the images matched the actual size of the implants and no apparent damage was sustained by the X-Si aerogel implants as a result of the ultrasonic imaging process. The aerogel implants demonstrated hyperechoic behavior and significant posterior shadowing. Results obtained were compared with images acquired from the PDMS implants inserted at the same location. PMID:23799093

Mechanical performance of porous concrete pavement containing nano black rice husk ash

NASA Astrophysics Data System (ADS)

Ibrahim, M. Y. Mohd; Ramadhansyah, P. J.; Rosli, H. Mohd; Ibrahim, M. H. Wan

2018-01-01

This paper presents an experimental research on the performance of nano black rice husk ash on the porous concrete pavement properties. The performance of the porous concrete pavement mixtures was investigated based on their compressive strength, flexural strength, and splitting tensile strength. The results indicated that using nano material from black rice husk ash improved the mechanical properties of porous concrete pavement. In addition, the result of compressive, flexural, and splitting tensile strength was increased with increasing in curing age. Finally, porous concrete pavement with 10% replacement levels exhibited an excellent performance with good strength compared to others.

Low density, resorcinol-formaldehyde aerogels

DOEpatents

Pekala, R.W.

1989-10-10

The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer clusters. The covalent crosslinking of these clusters produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density [<=]100 mg/cc; cell size [<=]0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 [angstrom]. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

Preparation and Reinforcement of Dual‐Porous Biocompatible Cellulose Scaffolds for Tissue Engineering

PubMed Central

Pircher, Nicole; Fischhuber, David; Carbajal, Leticia; Strauß, Christine; Nedelec, Jean‐Marie; Kasper, Cornelia; Rosenau, Thomas

2015-01-01

1 Biocompatible cellulose‐based aerogels composed of nanoporous struts, which embed interconnected voids of controlled micron‐size, have been prepared employing temporary templates of fused porogens, reinforcement by interpenetrating PMMA networks and supercritical carbon dioxide drying. Different combinations of cellulose solvent (Ca(SCN)2/H2O/LiCl or [EMIm][OAc]/DMSO) and anti‐solvent (EtOH), porogen type (paraffin wax or PMMA spheres) and porogen size (various fractions in the range of 100–500 μm) as well as intensity of PMMA reinforcement have been investigated to tailor the materials for cell scaffolding applications. All aerogels exhibited an open and dual porosity (micronporosity >100 μm and nanoporosity extending to the low micrometer range). Mechanical properties of the dual‐porous aerogels under compressive stress were considerably improved by introduction of interpenetrating PMMA networks. The effect of the reinforcing polymer on attachment, spreading, and proliferation of NIH 3T3 fibroblast cells, cultivated on selected dual‐porous aerogels to pre‐evaluate their biocompatibility was similarly positive. PMID:26941565

Preparation and Reinforcement of Dual-Porous Biocompatible Cellulose Scaffolds for Tissue Engineering.

PubMed

Pircher, Nicole; Fischhuber, David; Carbajal, Leticia; Strauß, Christine; Nedelec, Jean-Marie; Kasper, Cornelia; Rosenau, Thomas; Liebner, Falk

2015-09-01

1Biocompatible cellulose-based aerogels composed of nanoporous struts, which embed interconnected voids of controlled micron-size, have been prepared employing temporary templates of fused porogens, reinforcement by interpenetrating PMMA networks and supercritical carbon dioxide drying. Different combinations of cellulose solvent (Ca(SCN) 2 /H 2 O/LiCl or [EMIm][OAc]/DMSO) and anti-solvent (EtOH), porogen type (paraffin wax or PMMA spheres) and porogen size (various fractions in the range of 100-500 μm) as well as intensity of PMMA reinforcement have been investigated to tailor the materials for cell scaffolding applications. All aerogels exhibited an open and dual porosity (micronporosity >100 μm and nanoporosity extending to the low micrometer range). Mechanical properties of the dual-porous aerogels under compressive stress were considerably improved by introduction of interpenetrating PMMA networks. The effect of the reinforcing polymer on attachment, spreading, and proliferation of NIH 3T3 fibroblast cells, cultivated on selected dual-porous aerogels to pre-evaluate their biocompatibility was similarly positive.

Aerogels for Thermal Insulation of Thermoelectric Devices

NASA Technical Reports Server (NTRS)

Sakamoto, Jeffrey; Fleurial, Jean-Pierre; Snyder, Jeffrey; Jones, Steven; Caillat, Thierry

2006-01-01

Silica aerogels have been shown to be attractive for use as thermal-insulation materials for thermoelectric devices. It is desirable to thermally insulate the legs of thermoelectric devices to suppress lateral heat leaks that degrade thermal efficiency. Aerogels offer not only high thermal- insulation effectiveness, but also a combination of other properties that are especially advantageous in thermoelectric- device applications. Aerogels are synthesized by means of sol-gel chemistry, which is ideal for casting insulation into place. As the scale of the devices to be insulated decreases, the castability from liquid solutions becomes increasingly advantageous: By virtue of castability, aerogel insulation can be made to encapsulate devices having any size from macroscopic down to nanoscopic and possibly having complex, three-dimensional shapes. Castable aerogels can permeate voids having characteristic dimensions as small as nanometers. Hence, practically all the void space surrounding the legs of thermoelectric devices could be filled with aerogel insulation, making the insulation highly effective. Because aerogels have the lowest densities of any known solid materials, they would add very little mass to the encapsulated devices. The thermal-conductivity values of aerogels are among the lowest reported for any material, even after taking account of the contributions of convection and radiation (in addition to true thermal conduction) to overall effective thermal conductivities. Even in ambient air, the contribution of convection to effective overall thermal conductivity of an aerogel is extremely low because of the highly tortuous nature of the flow paths through the porous aerogel structure. For applications that involve operating temperatures high enough to give rise to significant amounts of infrared radiation, opacifiers could be added to aerogels to reduce the radiative contributions to overall effective thermal conductivities. One example of an opacifier is

The kinetic enhancement of hydrogen cycling in NaAlH(4) by melt infusion into nanoporous carbon aerogel.

PubMed

Stephens, Robert D; Gross, Adam F; Van Atta, Sky L; Vajo, John J; Pinkerton, Frederick E

2009-05-20

Enhanced kinetic performance and reversibility have been achieved with uncatalyzed NaAlH4 by incorporation into nanoporous carbon aerogel. Aerogel with a pore size distribution peaked at 13 nm and a pore volume of 0.8 cm(3) g(-1) was filled with NaAlH4 to 94% capacity by melt infusion at 189 degrees C under 183 bar H(2) gas overpressure. Dehydrogenation to NaH + Al with reasonable kinetics was accomplished at 150 degrees C, well below the NaAlH4 melting temperature (183 degrees C), compared to hydrogen release above 230 degrees C for bulk uncatalyzed NaAlH4. Uncatalyzed bulk samples did not rehydrogenate under laboratory conditions, whereas NaAlH4 in a carbon aerogel host was readily rehydrogenated at approximately 160 degrees C and 100 bar H(2) to approximately 85% of its initial capacity. Ball-milled NaAlH4 catalyzed with 4 mol% TiCl3 showed somewhat better kinetics compared to the infused aerogel; nevertheless, the large kinetic enhancement obtained by incorporation into carbon aerogel, even in the absence of a catalyst, demonstrates the substantial benefit of confining the NaAlH4 to nanoscale dimensions.

Optical shock waves in silica aerogel.

PubMed

Gentilini, S; Ghajeri, F; Ghofraniha, N; Di Falco, A; Conti, C

2014-01-27

Silica aerogels are materials well suited for high power nonlinear optical applications. In such regime, the non-trivial thermal properties may give rise to the generation of optical shock waves, which are also affected by the structural disorder due to the porous solid-state gel. Here we report on an experimental investigation in terms of beam waist and input power, and identify various regimes of the generation of wave-breaking phenomena in silica aerogels.

High Temperature Aerogels for Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.; Mbah, Godfrey C.

2008-01-01

High temperature aerogels in the Al2O3-SiO2 system are being investigated as possible constituents for lightweight integrated thermal protection system (TPS) designs for use in supersonic and hypersonic applications. Gels are synthesized from ethoxysilanes and AlCl3.6H2O, using an epoxide catalyst. The influence of Al:Si ratio, solvent, water to metal and water to alcohol ratios on aerogel composition, morphology, surface area, and pore size distribution were examined, and phase transformation on heat treatment characterized. Aerogels have been fabricated which maintain porous, fractal structures after brief exposures to 1000 C. Incorporation of nanofibers, infiltration of aerogels into SiC foams, use of polymers for crosslinking the aerogels, or combinations of these, offer potential for toughening and integration of TPS with composite structure. Woven fabric composites having Al2O3-SiO2 aerogels as a matrix also have been fabricated. Continuing work is focused on reduction in shrinkage and optimization of thermal and physical properties.

Low density, resorcinol-formaldehyde aerogels

DOEpatents

Pekala, Richard W.

1991-01-01

The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "Clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density.ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100.circle.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

Low density, resorcinol-formaldehyde aerogels

DOEpatents

Pekala, Richard W.

1989-01-01

The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density .ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 .ANG.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

PubMed Central

Sinkó, Katalin

2010-01-01

Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of porous materials can be tailored by variations in synthesis conditions (e.g., the type of precursors, catalyst, and surfactants; the ratio of water/precursor; the concentrations; the medium pH; and the solvent). The objectives of this review are to summarize and elucidate the effects of chemical conditions on the nanoporous structure of sol-gel derived silicate aerogels.

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

PubMed Central

Harper-Leatherman, Amanda S.; Pacer, Elizabeth R.; Kosciuszek, Nina D.

2016-01-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol–gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development. PMID:26967257

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity.

PubMed

Harper-Leatherman, Amanda S; Pacer, Elizabeth R; Kosciuszek, Nina D

2016-03-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol-gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development.

Property control of graphene aerogels by in situ growth of silicone polymer

NASA Astrophysics Data System (ADS)

Zhou, Shuai; Zhou, Xiang; Hao, Gazi; Jiang, Wei; Wang, Tianhe

2018-05-01

Modulation of the density (from 3.5 to 64 mg cm-3), hydrophobicity and oil-uptake capability of graphene aerogels in extensive ranges were achieved by reacting (3-Mercaptopropyl)trimethoxysilane (MPS) with graphene oxide solutions under heating. The reaction allowed a characteristic silicone substructure to be formed on graphene and joint the graphene layers firmly together. With the increase of MPS concentrations (≤ca. 0.2 vol%), the nano silicone polymer grown on graphene functioned as a "linker" and "spacer", leading to a substantial decrease of the aerogel density. Because of the formation of silicone polymer and the characteristic nano-micro substructures on the backbones of graphene aerogels, the graphene aerogels exhibited a high hydrophobicity with the water contact angle consistently exceeding 142 degrees. Functionalized graphene aerogels with a density of 3.5 mg cm-3 were conveniently fabricated that displayed an extraordinary oil absorption capacity, 182 times for lubricating oil and 143 times for n-hexane of its own weight. Furthermore, the aerogels maintained their ultra-high absorption capability even after 20 absorption-distillation cycles, due to structural integrity held by the strong interfacial adhesion between graphene sheets and polymer chains of aerogels. This study offers a promising graphene aerogels and also provides a strategy for fabricating extra low dense functional materials.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-10-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g-1 present high specific capacities of the 308 and 200 F g-1 in KOH electrolyte at current densities of 0.1 and 10 A g-1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g-1 at 0.1 A g-1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors.

PubMed

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-10-16

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m(2) g(-1) present high specific capacities of the 308 and 200 F g(-1) in KOH electrolyte at current densities of 0.1 and 10 A g(-1), respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g(-1) at 0.1 A g(-1) and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

PubMed Central

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-01-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g−1 present high specific capacities of the 308 and 200 F g−1 in KOH electrolyte at current densities of 0.1 and 10 A g−1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g−1 at 0.1 A g−1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry. PMID:26472144

Carbon Papers and Aerogels Based on Graphene Layers and Chitosan: Direct Preparation from High Surface Area Graphite.

PubMed

Barbera, Vincenzina; Guerra, Silvia; Brambilla, Luigi; Maggio, Mario; Serafini, Andrea; Conzatti, Lucia; Vitale, Alessandra; Galimberti, Maurizio

2017-12-11

In this work, carbon papers and aerogels based on graphene layers and chitosan were prepared. They were obtained by mixing chitosan (CS) and a high surface area nanosized graphite (HSAG) in water in the presence of acetic acid. HSAG/CS water dispersions were stable for months. High resolution transmission electron microscopy revealed the presence of few graphene layers in water suspensions. Casting or lyophilization of such suspensions led to the preparation of carbon paper and aerogel, respectively. In X-ray spectra of both aerogels and carbon paper, peaks due to regular stacks of graphene layers were not detected: graphene with unaltered sp 2 structure was obtained directly from graphite without the use of any chemical reaction. The composites were demonstrated to be electrically conductive thanks to the graphene. Chitosan thus makes it possible to obtain monolithic carbon aerogels and flexible and free-standing graphene papers directly from a nanosized graphite by avoiding oxidation to graphite oxide and successive reduction. Strong interaction between polycationic chitosan and the aromatic substrate appears to be at the origin of the stability of HSAG/CS adducts. Cation-π interaction is hypothesized, also on the basis of X-ray photoelectron spectroscopy findings. This work paves the way for the easy large-scale preparation of carbon papers through a method that has a low environmental impact and is based on a biosourced polymer, graphene, and water.

Synthesis and structural characteristics of high surface area TiO2 aerogels by ultrasonic-assisted sol-gel method

NASA Astrophysics Data System (ADS)

Qingge, Feng; Huidong, Cai; Haiying, Lin; Siying, Qin; Zheng, Liu; Dachao, Ma; Yuyang, Ye

2018-02-01

TiO2 aerogel is a unique three-dimensional porous nano-particle material with the characteristics of high specific surface area and good light transmittance. In this paper, a novel method involving ultrasonic-assisted sol-gel, solvent exchange, and vacuum drying was successfully developed to synthesis the TiO2 aerogel. The morphology and properties of the prepared TiO2 aerogels were characterized by the Brunauer-Emmett-Teller theory (BET), x-ray diffraction, field-emission scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis-differential thermal analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy. The adsorption and photocatalytic activity of TiO2 aerogels was evaluated by monitoring the degradation of Rhodamine B solution. Our results indicated that: (1) with an optimum ratio of Ti:H2O = 8:1 the BET surface area, average pore diameter, and total pore volume of TiO2 aerogel are enhanced to 563.6 m2 g-1, 3.01 nm, and 0.42 cm3 g-1, respectively; (2) the TiO2 aerogels possessed controllable crystal form depending on the thermal treatments conditions. The crystal face (101) of anatase, complete anatase, mixed state of anatase and rutile, and rutile were obtained by increasing the temperature from 200 °C-300 °C, from 400 °C-500 °C, 600 °C, and from 700 °C-1000 °C, respectively; and (3) the excellent catalytic activity of the as-prepared TiO2 aerogels for the ultraviolet photolytic degradation of Rhodamine B had attributed to the synergistic effect of adsorption and photoactivity.

Tailoring mechanical properties of aerogels for aerospace applications.

PubMed

Randall, Jason P; Meador, Mary Ann B; Jana, Sadhan C

2011-03-01

Silica aerogels are highly porous solid materials consisting of three-dimensional networks of silica particles and are typically obtained by removing the liquid in silica gels under supercritical conditions. Several unique attributes such as extremely low thermal conductivity and low density make silica aerogels excellent candidates in the quest for thermal insulation materials used in space missions. However, native silica aerogels are fragile at relatively low stresses. More durable aerogels with higher strength and stiffness are obtained by proper selection of silane precursors and by reinforcement with polymers. This paper first presents a brief review of the literature on methods of silica aerogel reinforcement and then discusses our recent activities in improving not only the strength but also the elastic response of polymer-reinforced silica aerogels. Several alkyl-linked bis-silanes were used in promoting flexibility of the silica networks in conjunction with polymer reinforcement by epoxy.

Preparation of Mn, Ni, Co ferrite highly porous silica nanocomposite aerogels by an urea-assisted sol-gel procedure.

PubMed

Loche, Danilo; Casula, Maria F; Falqui, Andrea; Marras, Sergio; Corrias, Anna

2010-02-01

The preparation of highly porous MnFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposite aerogels with high purity and homogeneity was successfully achieved by a sol-gel procedure involving urea-assisted co-gelation of the precursor phases firstly applied for the synthesis of CoFe2O4-SiO2. This method allows fast gelation, giving rise to aerogels with 97% porosity. The structural, morphological and textural characterization as a function of thermal treatments was carried out by a multitechnique approach confirming that, as in the case of CoFe2O4-SiO2, the formation of single nanocrystals of manganese ferrite and nickel ferrite with spinel structure occurs after heating at 750 degrees C and is complete at 900 degrees C when the high porosity typical of aerogels is still retained. Thermogravimetric analysis (TG), differential thermal analysis (DTA), N2-physisorption at 77 K, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) indicate that the compositional homogeneity, crystallite size, thermal stability, and porosity are controlled by the sol-gel parameters of the preparation.

Multifunctional carbon nano-paper composite

NASA Astrophysics Data System (ADS)

Zhang, Zhichun; Chu, Hetao; Wang, Kuiwen; Liu, Yanjv; Leng, Jinsong

2013-08-01

Carbon Nanotube (CNT), for its excellent mechanical, electrical properties and nano size, large special surface physical property, become the most promising material. But carbon nanotube can still fabricated in micro dimension, and can't be made into macro size, so to the carbon nanotube filled composite can't explore the properties of the CNT. Carbon nano-paper is made of pure CNT, with micro pore, and it turn micro sized CNT into macro shaped membrane. Based on the piezo-resistivity and electrical conductivity of the carbon nano-paper, we used the carbon nano-paper as functional layers fabricate functional composite, and studies its strain sensing, composite material deicing and shape memory polymer (SMP) material electric actuation performance. The results shown that the resin can pregnant the nano paper, and there was good bond for nano paper and composite. The functional composite can monitoring the strain with high sensitivity comparing to foil strain gauge. The functional composite can be heated via the carbon nano paper with low power supply and high heating rate. The composite has good deicing and heat actuation performance to composite material. For the good strain sensing, electric conductivity and self-heating character of the carbon nano-paper composite, it can be used for self sensing, anti lightning strike and deicing of composite materials in aircrafts and wind turbine blades.

Highly porous ceramic oxide aerogels having improved flexibility

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

2012-01-01

Ceramic oxide aerogels incorporating periodically dispersed flexible linkages are provided. The flexible linkages impart greater flexibility than the native aerogels without those linkages, and have been shown to reduce or eliminate the need for supercritical CO.sub.2-mediated drying of the corresponding wet gels. The gels may also be polymer cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions.

Low density, resorcinol-formaldehyde aerogels

DOEpatents

Pekala, R.W.

1988-05-26

The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer ''clusters''. The covalent crosslinking of these ''clusters'' produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density less than or equal to100 mg/cc; cell size less than or equal to0.1 microns). The aerogels are transparent,dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 A/degree/. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron. 1 fig., 1 tab.

A three-dimensional self-assembled SnS 2 -nano-dots@graphene hybrid aerogel as an efficient polysulfide reservoir for high-performance lithium–sulfur batteries

DOE PAGES

Luo, Liu; Chung, Sheng-Heng; Manthiram, Arumugam

2018-01-01

A free-standing self-assembled graphene aerogel embedded with SnS 2 nano-dots (SnS 2 -ND@G) is established as an efficient substrate for high-loading sulfur cathodes with synergistically physical and chemical polysulfide-trapping capability.

A three-dimensional self-assembled SnS 2 -nano-dots@graphene hybrid aerogel as an efficient polysulfide reservoir for high-performance lithium–sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Liu; Chung, Sheng-Heng; Manthiram, Arumugam

A free-standing self-assembled graphene aerogel embedded with SnS 2 nano-dots (SnS 2 -ND@G) is established as an efficient substrate for high-loading sulfur cathodes with synergistically physical and chemical polysulfide-trapping capability.

Hydrogen crystallization in low-density aerogels.

PubMed

Kucheyev, S O; Van Cleve, E; Johnston, L T; Gammon, S A; Worsley, M A

2015-04-07

Crystallization of liquids confined in disordered low-density nanoporous scaffolds is poorly understood. Here, we use relaxation calorimetry to study the liquid-solid phase transition of H2 in a series of silica and carbon (nanotube- and graphene-based) aerogels with porosities ≳94%. Results show that freezing temperatures of H2 inside all the aerogels studied are depressed but do not follow predictions of the Gibbs-Thomson theory based on average pore diameters measured by conventional gas sorption techniques. Instead, we find that, for each material family investigated, the depression of average freezing temperatures scales linearly with the ratio of the internal surface area (measured by gas sorption) and the total pore volume derived from the density of aerogel monoliths. The slope of such linear dependences is, however, different for silica and carbon aerogels, which we attribute to microporosity of carbons and the presence of macropores in silica aerogels. Our results have important implications for the analysis of pore size distributions of low-density nanoporous materials and for controlling crystallization of fuel layers in targets for thermonuclear fusion energy applications.

High specific surface area aerogel cryoadsorber for vacuum pumping applications

DOEpatents

Hill, Randal M.; Fought, Eric R.; Biltoft, Peter J.

2000-01-01

A cryogenic pumping system is provided, comprising a vacuum environment, an aerogel sorbent formed from a carbon aerogel disposed within the vacuum environment, and cooling means for cooling the aerogel sorbent sufficiently to adsorb molecules from the vacuum environment onto the aerogel sorbent. Embodiments of the invention include a liquid refrigerant cryosorption pump, a compressed helium cryogenic pump, a cryopanel and a Meissner coil, each of which uses carbon aerogel as a sorbent material.

Evaluating Dimethyldiethoxysilane for use in Polyurethane Crosslinked Silica Aerogels

NASA Technical Reports Server (NTRS)

Randall, Jason P.; Meador, Mary Ann B.; Jana, Sadhan C.

2008-01-01

Silica aerogels are highly porous materials which exhibit exceptionally low density and thermal conductivity. Their "pearl necklace" nanostructure, however, is inherently weak; most silica aerogels are brittle and fragile. The strength of aerogels can be improved by employing an additional crosslinking step using isocyanates. In this work, dimethyldiethoxysilane (DMDES) is evaluated for use in the silane backbone of polyurethane crosslinked aerogels. Approximately half of the resulting aerogels exhibited a core/shell morphology of hard crosslinked aerogel surrounding a softer, uncrosslinked center. Solid state NMR and scanning electron microscopy results indicate the DMDES incorporated itself as a conformal coating around the outside of the secondary silica particles, in much the same manner as isocyanate crosslinking. Response surface curves were generated from compression data, indicating levels of reinforcement comparable to that in previous literature, despite the core/shell morphology.

Starch-based aerogels: airy materials from amylose-sodium palmitate inclusion complexes

USDA-ARS?s Scientific Manuscript database

Aerogels are a class of interesting low density porous materials prepared by replacing the water phase contained within a hydrogel with a gas phase while maintaining the three dimensional network structure of the gel. The investigation of starch and hydrocolloid-based aerogels has received attentio...

Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

PubMed

Park, Yong Seob; Choi, Won Seek; Yi, Junsin; Lee, Jaehyeong

2014-05-01

Anodic Aluminum Oxide (AAO) template prepared in acid electrolyte possess regular and highly anisotropic porous structure with pore diameter range from five to several hundred nanometers, and with a density of pores ranging from 10(9) to 10(11) cm(-2). AAO can be used as microfilters and templates for the growth of CNTs and metal or semiconductor nanowires. Varying anodizing conditions such as temperature, electrolyte, applied voltage, anodizing and widening time, one can control the diameter, the length, and the density of pores. In this work, we deposited Al thin film by radio frequency magnetron sputtering method to fabricate AAO nano template and synthesized multi-well carbon nanotubes on a glass substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). AAO nano-porous templates with various pore sizes and depths were introduced to control the dimension and density of CNT arrays. The AAO nano template was synthesize on glass by two-step anodization technique. The average diameter and interpore distance of AAO nano template are about 65 nm and 82 nm. The pore density and AAO nano template thickness are about 2.1 x 10(10) pores/cm2 and 1 microm, respectively. Aligned CNTs on the AAO nano template were synthesized by MPECVD at 650 degrees C with the Ni catalyst layer. The length and diameter of CNTs were grown 2 microm and 50 nm, respectively.

Highly compressible 3D periodic graphene aerogel microlattices

PubMed Central

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

2015-01-01

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications. PMID:25902277

Highly compressible 3D periodic graphene aerogel microlattices

DOE PAGES

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; ...

2015-04-22

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young’s modulimore » of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Ultimately, adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.« less

Transparent, Superflexible Doubly Cross-Linked Polyvinylpolymethylsiloxane Aerogel Superinsulators via Ambient Pressure Drying.

PubMed

Zu, Guoqing; Shimizu, Taiyo; Kanamori, Kazuyoshi; Zhu, Yang; Maeno, Ayaka; Kaji, Hironori; Shen, Jun; Nakanishi, Kazuki

2018-01-23

Aerogels have many attractive properties but are usually costly and mechanically brittle, which always limit their practical applications. While many efforts have been made to reinforce the aerogels, most of the reinforcement efforts sacrifice the transparency or superinsulating properties. Here we report superflexible polyvinylpolymethylsiloxane, (CH 2 CH(Si(CH 3 )O 2/2 )) n , aerogels that are facilely prepared from a single precursor vinylmethyldimethoxysilane or vinylmethyldiethoxysilane without organic cross-linkers. The method is based on consecutive processes involving radical polymerization and hydrolytic polycondensation, followed by ultralow-cost, highly scalable, ambient-pressure drying directly from alcohol as a drying medium without any modification or additional solvent exchange. The resulting aerogels and xerogels show a homogeneous, tunable, highly porous, doubly cross-linked nanostructure with the elastic polymethylsiloxane network cross-linked with flexible hydrocarbon chains. An outstanding combination of ultralow cost, high scalability, uniform pore size, high surface area, high transparency, high hydrophobicity, excellent machinability, superflexibility in compression, superflexibility in bending, and superinsulating properties has been achieved in a single aerogel or xerogel. This study represents a significant progress of porous materials and makes the practical applications of transparent flexible aerogel-based superinsulators realistic.

Nano-crystalline porous tin oxide film for carbon monoxide sensing

NASA Technical Reports Server (NTRS)

Liu, Chung-Chiun (Inventor); Savinell, Robert F. (Inventor); Jin, Zhihong (Inventor)

2000-01-01

A tin oxide sol is deposited on platinum electrodes (12) of a sensor (10). The sol is calcined at a temperature of 500 to 800.degree. C. to produce a thin film of tin oxide with a thickness of about 150 nm to 2 .mu. and having a nano-crystalline structure with good stability. The sensor rapidly detects reducing gases, such as carbon monoxide, or hydrocarbons and organic vapors. Sensors using films calcined at around 700.degree. C. have high carbon monoxide selectivity with a response time of around 4 minutes and a recovery time of 1 minute, and therefore provide good detection systems for detection of trace amounts of pollutants such as toxic and flammable gases in homes, industrial settings, and hospitals.

Transparent, flexible supercapacitors from nano-engineered carbon films.

PubMed

Jung, Hyun Young; Karimi, Majid B; Hahm, Myung Gwan; Ajayan, Pulickel M; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Transparent, flexible supercapacitors from nano-engineered carbon films

PubMed Central

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications. PMID:23105970

Transparent, flexible supercapacitors from nano-engineered carbon films

NASA Astrophysics Data System (ADS)

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-10-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Gold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces

PubMed Central

2016-01-01

Three-dimensional (3D) porous metal nanostructures have been a long sought-after class of materials due to their collective properties and widespread applications. In this study, we report on a facile and versatile strategy for the formation of Au hydrogel networks involving the dopamine-induced 3D assembly of Au nanoparticles. Following supercritical drying, the resulting Au aerogels exhibit high surface areas and porosity. They are all composed of porous nanowire networks reflecting in their diameters those of the original particles (5–6 nm) via electron microscopy. Furthermore, electrocatalytic tests were carried out in the oxidation of some small molecules with Au aerogels tailored by different functional groups. The beta-cyclodextrin-modified Au aerogel, with a host–guest effect, represents a unique class of porous metal materials of considerable interest and promising applications for electrocatalysis. PMID:26751502

Porous Cross-Linked Polyimide Networks

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Guo, Haiquan (Inventor)

2015-01-01

Porous cross-linked polyimide networks are provided. The networks comprise an anhydride end-capped polyamic acid oligomer. The oligomer (i) comprises a repeating unit of a dianhydride and a diamine and terminal anhydride groups, (ii) has an average degree of polymerization of 10 to 50, (iii) has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups, and (iv) has been chemically imidized to yield the porous cross-linked polyimide network. Also provided are porous cross-linked polyimide aerogels comprising a cross-linked and imidized anhydride end-capped polyamic acid oligomer, wherein the oligomer comprises a repeating unit of a dianhydride and a diamine, and the aerogel has a density of 0.10 to 0.333 g/cm.sup.3 and a Young's modulus of 1.7 to 102 MPa. Also provided are thin films comprising aerogels, and methods of making porous cross-linked polyimide networks.

Hydrogen Crystallization in Low-Density Aerogels

DOE PAGES

Kucheyev, S. O.; Van Cleve, E.; Johnston, L. T.; ...

2015-03-17

Crystallization of liquids confined in disordered low-density nanoporous scaffolds is poorly understood. Here in this work, we use relaxation calorimetry to study the liquid–solid phase transition of H 2 in a series of silica and carbon (nanotube- and graphene-based) aerogels with porosities ≳94%. Results show that freezing temperatures of H 2 inside all the aerogels studied are depressed but do not follow predictions of the Gibbs–Thomson theory based on average pore diameters measured by conventional gas sorption techniques. Instead, we find that, for each material family investigated, the depression of average freezing temperatures scales linearly with the ratio of themore » internal surface area (measured by gas sorption) and the total pore volume derived from the density of aerogel monoliths. The slope of such linear dependences is, however, different for silica and carbon aerogels, which we attribute to microporosity of carbons and the presence of macropores in silica aerogels. In conclusion, our results have important implications for the analysis of pore size distributions of low-density nanoporous materials and for controlling crystallization of fuel layers in targets for thermonuclear fusion energy applications.« less

Emerging Hierarchical Aerogels: Self-Assembly of Metal and Semiconductor Nanocrystals.

PubMed

Cai, Bin; Sayevich, Vladimir; Gaponik, Nikolai; Eychmüller, Alexander

2018-06-19

Aerogels assembled from colloidal metal or semiconductor nanocrystals (NCs) feature large surface area, ultralow density, and high porosity, thus rendering them attractive in various applications, such as catalysis, sensors, energy storage, and electronic devices. Morphological and structural modification of the aerogel backbones while maintaining the aerogel properties enables a second stage of the aerogel research, which is defined as hierarchical aerogels. Different from the conventional aerogels with nanowire-like backbones, those hierarchical aerogels are generally comprised of at least two levels of architectures, i.e., an interconnected porous structure on the macroscale and a specially designed configuration at local backbones at the nanoscale. This combination "locks in" the inherent properties of the NCs, so that the beneficial genes obtained by nanoengineering are retained in the resulting monolithic hierarchical aerogels. Herein, groundbreaking advances in the design, synthesis, and physicochemical properties of the hierarchical aerogels are reviewed and organized in three sections: i) pure metallic hierarchical aerogels, ii) semiconductor hierarchical aerogels, and iii) metal/semiconductor hybrid hierarchical aerogels. This report aims to define and demonstrate the concept, potential, and challenges of the hierarchical aerogels, thereby providing a perspective on the further development of these materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Depolarized haze of nano-porous AAO film via porosity and aspect control

NASA Astrophysics Data System (ADS)

Tseng, Chun-Wei; Lin, Yung-Hsiang; Cheng, Chih-Hsien; Lin, Gong-Ru

2018-01-01

Multiple scattering induced haze and depolarization effects of nano-porous AAO films controlled by detuning the porosity and aspect ratio of the nano holes are investigated. The nano-porous AAO film with its porosity increasing from 12.6% to 19.3% enhances the scattering of the incident laser beam with its maximal scattering angle enlarged from 5° to 8° under TM-mode incidence and from 6° to 10° under TE-mode incidence. Because of multiple scattering within the porous holes of the AAO, the depolarization on the reflected beam by transferring its electric field from horizontal to the vertical such that the polarization ratio is degraded with a randomized haze. The porosity of AAO surface broadens from 12.6% to 19.3% when increasing the bias voltage from 40 to 60 V during the second-step of the electro-chemical anodization process, which essentially adjusts the polarization ratio under TM-mode and TE-mode incidences raise from 0.31 to 0.35 and from 0.32 to 0.48, respectively. The depolarized haze of the nano-porous AAO film is correlated with its porosity and aspect ratio controlled by the pore size and etched depth of the AAO. Under TM-mode incidence, the simulated polarization ratio increases from 0.35 to 0.38, which correlates well with experimental results. In contrast, the experiment result slightly deviates from the theoretical prediction as the TE-mode field interacts more surface area than the TM-mode field does. Such a nano-porous AAO exhibits tunable depolarized haze via the control porosity and aspect ratio, which is particularly suitable to serve as the catalytic buffer for synthesizing the hydrophobic and hazed solar energy converters.

Aerogel sorbents

DOEpatents

Begag, Redouane; Rhine, Wendell E.; Dong, Wenting

2018-04-03

The current invention describes methods and compositions of various sorbents based on aerogels of various silanes and their use as sorbent for carbon dioxide. Methods further provide for optimizing the compositions to increase the stability of the sorbents for prolonged use as carbon dioxide capture matrices.

Aerogel sorbents

DOEpatents

Begag, Redouane; Rhine, Wendell E; Dong, Wenting

2016-04-05

The current invention describes methods and compositions of various sorbents based on aerogels of various silanes and their use as sorbent for carbon dioxide. Methods further provide for optimizing the compositions to increase the stability of the sorbents for prolonged use as carbon dioxide capture matrices.

A three-dimensional carbon nano-network for high performance lithium ion batteries

DOE PAGES

Tian, Miao; Wang, Wei; Liu, Yang; ...

2014-11-20

Three-dimensional (3D) network structure has been envisioned as a superior architecture for lithium ion battery (LIB) electrodes, which enhances both ion and electron transport to significantly improve battery performance. Herein, a 3D carbon nano-network is fabricated through chemical vapor deposition of carbon on a scalably manufactured 3D porous anodic alumina (PAA) template. As a demonstration on the applicability of 3D carbon nano-network for LIB electrodes, the low conductivity active material, TiO 2, is then uniformly coated on the 3D carbon nano-network using atomic layer deposition. High power performance is demonstrated in the 3D C/TiO 2 electrodes, where the parallel tubesmore » and gaps in the 3D carbon nano-network facilitates fast Li ion transport. A large areal capacity of ~0.37 mAh·cm –2 is achieved due to the large TiO 2 mass loading in the 60 µm-thick 3D C/TiO 2 electrodes. At a test rate of C/5, the 3D C/TiO 2 electrode with 18 nm-thick TiO 2 delivers a high gravimetric capacity of ~240 mAh g –1, calculated with the mass of the whole electrode. A long cycle life of over 1000 cycles with a capacity retention of 91% is demonstrated at 1C. In this study, the effects of the electrical conductivity of carbon nano-network, ion diffusion, and the electrolyte permeability on the rate performance of these 3D C/TiO 2 electrodes are systematically studied.« less

Assembly of phosphide nanocrystals into porous networks: formation of InP gels and aerogels.

PubMed

Hitihami-Mudiyanselage, Asha; Senevirathne, Keerthi; Brock, Stephanie L

2013-02-26

The applicability of sol-gel nanoparticle assembly routes, previously employed for metal chalcogenides, to phosphides is reported for the case of InP. Two different sizes (3.5 and 6.0 nm) of InP nanoparticles were synthesized by solution-phase arrested precipitation, capped with thiolate ligands, and oxidized with H₂O₂ or O₂/light to induce gel formation. The gels were aged, solvent-exchanged, and then supercritically dried to obtain aerogels with both meso- (2-50 nm) and macropores (>50 nm) and accessible surface areas of ∼200 m²/g. Aerogels showed higher band gap values relative to precursor nanoparticles, suggesting that during the process of assembling nanoparticles into 3D architectures, particle size reduction may have taken place. In contrast to metal chalcogenide gelation, InP gels did not form using tetranitromethane, a non-oxygen-transferring oxidant. The requirement of an oxygen-transferring oxidant, combined with X-ray photoelectron spectroscopy data showing oxidized phosphorus, suggests gelation is occurring due to condensation of phosphorus oxoanionic moieties generated at the interfaces. The ability to link discrete InP nanoparticles into a 3D porous network while maintaining quantum confinement is expected to facilitate exploitation of nanostructured InP in solid-state devices.

Directionally Antagonistic Graphene Oxide-Polyurethane Hybrid Aerogel as a Sound Absorber.

PubMed

Oh, Jung-Hwan; Kim, Jieun; Lee, Hyeongrae; Kang, Yeonjune; Oh, Il-Kwon

2018-06-21

Innovative sound absorbers, the design of which is based on carbon nanotubes and graphene derivatives, could be used to make more efficient sound absorbing materials because of their excellent intrinsic mechanical and chemical properties. However, controlling the directional alignments of low-dimensional carbon nanomaterials, such as restacking, alignment, and dispersion, has been a challenging problem when developing sound absorbing forms. Herein, we present the directionally antagonistic graphene oxide-polyurethane hybrid aerogel we developed as a sound absorber, the physical properties of which differ according to the alignment of the microscopic graphene oxide sheets. This porous graphene sound absorber has a microporous hierarchical cellular structure with adjustable stiffness and improved sound absorption performance, thereby overcoming the restrictions of both geometric and function-orientated functions. Furthermore, by controlling the inner cell size and aligned structure of graphene oxide layers in this study, we achieved remarkable improvement of the sound absorption performance at low frequency. This improvement is attributed to multiple scattering of incident and reflection waves on the aligned porous surfaces, and air-viscous resistance damping inside interconnected structures between the urethane foam and the graphene oxide network. Two anisotropic sound absorbers based on the directionally antagonistic graphene oxide-polyurethane hybrid aerogels were fabricated. They show remarkable differences owing to the opposite alignment of graphene oxide layers inside the polyurethane foam and are expected to be appropriate for the engineering design of sound absorbers in consideration of the wave direction.

Aerogel Projects Ongoing in MSFC's Engineering Directorate

NASA Technical Reports Server (NTRS)

Shular, D. A.; Smithers, G. A.; Plawsky, J. L.

2001-01-01

When we speak of an aerogel material, we are referring more to process and structure than to a specific substance. Aerogel, considered the lightest solid material, has been made from silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more recently. However, aerogel can be made from almost any type of substance, even lead. Because an aerogel is mostly air (about 99%), the solid substance used will affect the weight very little. The problem with aerogels is their low tensile strength and lack of elasticity. Therefore, the challenge is to find ways to make the stronger or ways to circumvent the strength issue. Organic aerogels have slightly higher strength than base silica aerogels, while the carbonized version has three to five times the break strength of the base aerogel.

Polyimide aerogels cross-linked through amine functionalized polyoligomeric silsesquioxane.

PubMed

Guo, Haiquan; Meador, Mary Ann B; McCorkle, Linda; Quade, Derek J; Guo, Jiao; Hamilton, Bart; Cakmak, Miko; Sprowl, Guilherme

2011-02-01

We report the first synthesis of polyimide aerogels cross-linked through a polyhedral oligomeric silsesquioxane, octa(aminophenyl)silsesquioxane (OAPS). Gels formed from polyamic acid solutions of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), bisaniline-p-xylidene (BAX) and OAPS were chemically imidized and dried using supercritical CO(2) extraction to give aerogels having density around 0.1 g/cm(3). The aerogels are greater than 90 % porous, have high surface areas (230 to 280 m(2)/g) and low thermal conductivity (14 mW/m-K at room temperature). Notably, the polyimide aerogels cross-linked with OAPS have higher modulus than polymer reinforced silica aerogels of similar density and can be fabricated as both monoliths and thin films. Thin films of the aerogel are flexible and foldable making them an ideal insulation for space suits, and inflatable structures for habitats or decelerators for planetary re-entry, as well as more down to earth applications.

Improvements to the Synthesis of Polyimide Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Nguyen, Baochau N.; Guo, Haiquan; Vivod, Stephanie; He, Zuhui; Malow, Ericka; Silva, Rebecca

2011-01-01

Cross-linked polyimide aerogels are viable approach to higher temperature, flexible insulation for inflatable decelerators. Results indicate that the all-polyimide aerogels are as strong or stronger than polymer reinforced silica aerogels at the same density. Currently, examining use of carbon nanofiber and clay nanoparticles to improve performance. Flexible, polyimide aerogels have potential utility in other applications such as space suits, habitats, shelter applications, etc. where low dusting is desired

Robust superhydrophobic bridged silsesquioxane aerogels with tunable performances and their applications.

PubMed

Wang, Zhen; Wang, Dong; Qian, Zhenchao; Guo, Jing; Dong, Haixia; Zhao, Ning; Xu, Jian

2015-01-28

Aerogels are a family of highly porous materials whose applications are commonly restricted by poor mechanical properties. Herein, thiol-ene chemistry is employed to synthesize a series of novel bridged silsesquioxane (BSQ) precursors with various alkoxy groups. On the basis of the different hydrolyzing rates of the methoxy and ethoxy groups, robust superhydrophobic BSQ aerogels with tailorable morphology and mechanical performances have been prepared. The flexible thioether bridge contributes to the robustness of the as-formed aerogels, and the property can be tuned on the basis of the distinct combinations of alkoxy groups with the density of the aerogels almost unchanged. To the best of our knowledge, the lowest density among the ambient pressure dried aerogels is obtained. Further, potential application of the aerogels for oil/water separation and acoustic materials has also been presented.

The effect of brushing with nano calcium carbonate and calcium carbonate toothpaste on the surface roughness of nano-ionomer

NASA Astrophysics Data System (ADS)

Anisja, D. H.; Indrani, D. J.; Herda, E.

2017-08-01

Nanotechnology developments in dentistry have resulted in the development of nano-ionomer, a new restorative material. The surface roughness of restorative materials can increase bacteria adhesion and lead to poor oral hygiene. Abrasive agents in toothpaste can alter tooth and restorative material surfaces. The aim of this study is to identify the effect of brushing with nano calcium carbonate, and calcium carbonate toothpaste on surface roughness of nano-ionomer. Eighteen nano-ionomer specimens were brushed with Aquabidest (doubledistilled water), nano calcium carbonate and calcium carbonate toothpaste. Brushing lasted 30 minutes, and the roughness value (Ra) was measured after each 10 minute segment using a surface roughness tester. The data was analyzed using repeated ANOVA and one-way ANOVA test. The value of nano-ionomer surface roughness increased significantly (p<0.05) after 20 minutes of brushing with the nano calcium carbonate toothpaste. Brushing with calcium carbonate toothpaste leaves nano-ionomer surfaces more rugged than brushing with nano calcium carbonate toothpaste.

Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Fabrizio, Eve F.; Ilhan, Faysal; Dass, Amala; Zhang, Guo-Hui; Vassilaras, Plousia; Johnston, J. Chris; Leventis, Nicholas

2005-01-01

The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

Porous Si spheres encapsulated in carbon shells with enhanced anodic performance in lithium-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hui; Wu, Ping, E-mail: zjuwuping@njnu.edu.cn; Shi, Huimin

2014-07-01

Highlights: • In situ magnesiothermic reduction route for the formation of porous Si@C spheres. • Unique microstructural characteristics of both porous sphere and carbon matrix. • Enhanced anodic performance in term of cycling stability for lithium-ion batteries. - Abstract: A novel type of porous Si–C micro/nano-hybrids, i.e., porous Si spheres encapsulated in carbon shells (porous Si@C spheres), has been constructed through the pyrolysis of polyvinylidene fluoride (PVDF) and subsequent magnesiothermic reduction methodology by using SiO{sub 2} spheres as precursors. The as-synthesized porous Si@C spheres have been applied as anode materials for lithium-ion batteries (LIBs), and exhibit enhanced anodic performance inmore » term of cycling stability compared with bare Si spheres. For example, the porous Si@C spheres are able to exhibit a high reversible capacity of 900.0 mA h g{sup −1} after 20 cycles at a current density of 0.05 C (1 C = 4200 mA g{sup −1}), which is much higher than that of bare Si spheres (430.7 mA h g{sup −1})« less

Polyurea-Based Aerogel Monoliths and Composites

NASA Technical Reports Server (NTRS)

Lee, Je Kyun

2012-01-01

aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection for government and commercial applications. The rubbery polyureabased aerogel exhibits little dustiness, good flexibility and toughness, and durability typical of the parent polyurea polymer, yet with the low density and superior insulation properties associated with aerogels. The thermal conductivity values of polyurea-based aerogels at lower temperature under vacuum pressures are very low and better than that of silica aerogels. Flexible, rubbery polyurea-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogels, including polyisocyanurate aerogels, which are generally prepared with the one similar component to polyurethane rubber aerogels. Additionally, with higher content of hydrogen in their structures, the polyurea rubber-based aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. The aerogel materials also demonstrate good hydrophobicity due to their hydrocarbon molecular structure. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven to be one promising approach, providing a conveniently fielded form factor that is relatively robust in industrial environments compared to silica aerogel monoliths. However, the flexible, silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain application environments. Although the cross - linked organic aerogels, such as resorcinol- formaldehyde (RF), polyisocyanurate, and cellulose aerogels, show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient radiation shielding materials due

Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage

NASA Astrophysics Data System (ADS)

Prakash, Sai S.; Brinker, C. Jeffrey; Hurd, Alan J.; Rao, Sudeep M.

1995-03-01

HIGHLY porous inorganic films have potential applications as dielectric materials, reflective and anti-reflective coatings, flat-panel displays, sensors, catalyst supports and super-insulating architectural glazings1-3. Aerogels4 are the most highly porous solids known, and can now be prepared from inorganic5 and organic6,7 precursors with volume-fraction porosities of up to 99.9% (ref. 8). Aerogels are normally prepared by supercritical extraction of the pore fluid from a wet gel1, which prevents the network collapse that is otherwise induced by capillary forces. But supercritical processing is expensive, hazardous and incompatible with the processing requirements of many potential applications,thus severely restricting the commercial exploitation of aerogels. Here we describe a means of preparing aerogels by a simple dip-coating method at ambient pressure without the need for supercriti-cal extraction. We add surface groups to the inorganic gel which make drying shrinkage reversible9: as the solvent is withdrawn, the gel springs back to a porous state. We can generate aerogel films with 98.5% porosity using this approach. We anticipate that it will greatly expand the commercial applications of these materials.

Electrostatic-Assisted Liquefaction of Porous Carbons

DOE PAGES

Li, Peipei; Schott, Jennifer A.; Zhang, Jinshui; ...

2017-10-10

Porous liquids are a newly developed porous material that combine unique fluidity with permanent porosity, which exhibit promising functionalities for a variety of applications. However, the apparent incompatibility between fluidity and permanent porosity makes the stabilization of porous nanoparticle with still empty pores in the dense liquid phase a significant challenging. For this study, by exploiting the electrostatic interaction between carbon networks and polymerized ionic liquids, we demonstrate that carbon-based porous nanoarchitectures can be well stabilized in liquids to afford permanent porosity, and thus opens up a new approach to prepare porous carbon liquids. Furthermore, we hope this facile synthesismore » strategy can be widely applicated to fabricate other types of porous liquids, such as those (e.g., carbon nitride, boron nitride, metal–organic frameworks, covalent organic frameworks etc.) also having the electrostatic interaction with polymerized ionic liquids, evidently advancing the development and understanding of porous liquids.« less

Migration of carbon dioxide included micro-nano bubble water in porous media and its monitoring

NASA Astrophysics Data System (ADS)

Takemura, T.; Hamamoto, S.; Suzuki, K.; Koichi, O.

2017-12-01

The distributed CO2 storage is the small scale storage and its located near the emission areas. In the distributed CO2 storage, the CO2 is neutralized by sediment and underground water in the subsurface region (300-500m depth). Carbon dioxide (CO2) included micro-nano bubbles is one approach in neutralizing CO2 and sediments by increasing CO2 volume per unit volume of water and accelerating the chemical reaction. In order to design underground treatment for CO2 gas in the subsurface, it is required to elucidate the behavior of CO2 included micro-nano bubbles in the water. In this study, we carried out laboratory experiment using the soil tank, and measure the amount of leakage of CO2 gas at the surface. In addition, the process of migration of carbon dioxide included micro-nano bubble was monitored by the nondestructive method, wave velocity and resistivity.

Polyvinyl alcohol (PVA)-cellulose nanofibril (CNF)-multiwalled carbon nanotube (MWCNT) hybrid organic aerogels with superior mechanical properties

Treesearch

Qifeng Zheng; Alireza Javadi; Ronald Sabo; Zhiyong Cai; Shaoqin Gong

2013-01-01

Polyvinyl alcohol (PVA)–cellulose nanofibril (CNF)–multiwalled carbon nanotube (MWCNT) hybrid organic aerogels were prepared using an environmentally friendly freeze-drying process with renewable materials. The material properties of these “green” hybrid aerogels were characterized extensively using various techniques. It was found that adding a small amount of CNFs...

Highly stable multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) core-shell composites with three-dimensional porous nano-network for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Zhou, Haihan; Han, Gaoyi; Chang, Yunzhen; Fu, Dongying; Xiao, Yaoming

2015-01-01

A facile and feasible electrochemical polymerization method has been used to construct the multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (MWCNTs@PEDOT/PSS) core-shell composites with three-dimensional (3D) porous nano-network microstructure. The composites are characterized with Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. This special core-shell nanostructure can significantly reduce the ions diffusion distance and the 3D porous nano-network microstructure effectively enlarges the electrode/electrolyte interface. The electrochemical tests including cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy tests are performed, the results manifest the MWCNTs@PEDOT/PSS core-shell composites have superior capacitive behaviors and excellent cyclic stability, and a high areal capacitance of 98.1 mF cm-2 is achieved at 5 mV s-1 cyclic voltammetry scan. Furthermore, the MWCNTs@PEDOT/PSS composites exhibit obviously superior capacitive performance than that of PEDOT/PSS and PEDOT/Cl electrodes, indicating the effective composite of MWCNTs and PEDOT noticeably boosts the capacitive performance of PEDOT-based electrodes for electrochemical energy storage. Such a highly stable core-shell 3D network structural composite is very promising to be used as electrode materials for the high-performance electrochemical capacitors.

Super-hierarchical porous carbons derived from mixed biomass wastes by a stepwise removal strategy for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Peng, Lin; Liang, Yeru; Dong, Hanwu; Hu, Hang; Zhao, Xiao; Cai, Yijing; Xiao, Yong; Liu, Yingliang; Zheng, Mingtao

2018-02-01

The synthesis and energy storage application of hierarchical porous carbons with size ranging from nano-to micrometres has attracted considerable attention all over the world. Exploring eco-friendly and reliable synthesis of hierarchical porous carbons for supercapacitors with high energy density and high power is still of ongoing challenge. In this work, we report the design and synthesis of super-hierarchical porous carbons with highly developed porosity by a stepwise removal strategy for high-rate supercapacitors. The mixed biomass wastes of coconut shell and sewage sludge are employed as raw material. The as-prepared super-hierarchical porous carbons present high surface areas (3003 m2 g-1), large pore volume (2.04 cm3 g-1), appropriate porosity, and outstanding electrochemical performance. The dependence of electrochemical performance on structural, textural, and functional properties of carbons engineered by various synthesis strategies is investigated in detail. Moreover, the as-assembled symmetrical supercapacitor exhibits high energy density of 25.4 Wh kg-1 at a power density of 225 W kg-1 and retains 20.7 Wh kg-1 even at a very high power of 9000 W kg-1. This work provides an environmentally benign strategy and new insights to efficiently regulate the porosity of hierarchical porous carbons derived from biomass wastes for energy storage applications.

Hugoniots of aerogels involving carbon and resorcinol formaldehyde

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrubesh, L H; Ree, F H; Schmidt, R D

1999-06-24

Recently, a first-order phase transition is predicted in liquid carbon using atomistic simulation and Brenner's bond order potential. There are also experimental data suggesting a possibility for a first-order phase transition. In light of this, a thermochemical equilibrium code (CHEQ) is used to provide guidance to experiments to find a liquid-liquid phase change in carbon foam and carbon-rich aerogel, resorcinol formaldehyde. Isotherms and Hugoniots were computed based on the previous analysis by van Thiel and Ree. The present calculations predict the liquid-liquid-graphite triple point to be at 5000 K and 5.2 GPa and its critical point to be at 6000more » K and 8.8 GPa. The present Hugoniot calculations suggest that the liquid-liquid phase transition may be detected by performing a shock experiment with initial density of approximately 0.15 gm/cm{sup 3}.« less

Characterization of pure and composite resorcinol formaldehyde aerogels doped with silver

NASA Astrophysics Data System (ADS)

Attia, S. M.; Abdelfatah, M. S.; Mossad, M. M.

2017-07-01

A series of Resorcinol Formaldehyde (RF) aerogels composites with nanoparticles of sliver were prepared by the sol-gel method at different concentrations doped silver. FTIR spectra of pure and composite RF aerogels show six absorption bands attributed to -OH groups bonded to the benzene ring, stretching of -CH2- bonds and aromatic ring stretching. FTIR results ensured that sliver particles do not interact with aerogel network. UV-visible spectrum of pure silver show an absorbance peak at 420 nm attributed to the surface plasmon excitation of sliver Nano spheres. UV-visible spectral of pure and composite RF aerogels shows a steep decrease of absorption with wavelength after 500 nm, making sample’s color reddish brown. TEM and SEM images of pure and composite RF aerogels revealed that the textural arrangement of RF aerogels can be described as densely packed small nodules.

High rate capacitive performance of single-walled carbon nanotube aerogels

DOE PAGES

Van Aken, Katherine L.; Pérez, Carlos R.; Oh, Youngseok; ...

2015-05-30

Single-walled carbon nanotube (SWCNT) aerogels produced by critical-point-drying of wet-gel precursors exhibit unique properties, such as high surface-area-to-volume and strength-to-weight ratios. They are free-standing, are binder-free, and can be scaled to thicknesses of more than 1 mm. In this paper, we examine the electric double layer capacitive behavior of these materials using a common room temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI). Electrochemical performance is assessed through galvanostatic cycling, cyclic voltammetry and impedance spectroscopy. Results indicate stable capacitive performance over 10,000 cycles as well as an impressive performance at high charge and discharge rates, due to accessible pore networks andmore » enhanced electronic and ionic conductivities of SWCNT aerogels. Finally, these materials can find applications in mechanically compressible and flexible supercapacitor devices with high power requirements.« less

1-Dimensional AgVO3 nanowires hybrid with 2-dimensional graphene nanosheets to create 3-dimensional composite aerogels and their improved electrochemical properties

NASA Astrophysics Data System (ADS)

Liang, Liying; Xu, Yimeng; Lei, Yong; Liu, Haimei

2014-03-01

Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability.Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability. Electronic supplementary information (ESI) available: Preparation, characterization, SEM images, XRD patterns, and XPS of AgVO3/GAs. See DOI: 10.1039/c3nr06899d

Composite Aerogel Multifoil Protective Shielding

NASA Technical Reports Server (NTRS)

Jones, Steven M.

2013-01-01

New technologies are needed to survive the temperatures, radiation, and hypervelocity particles that exploration spacecraft encounter. Multilayer insulations (MLIs) have been used on many spacecraft as thermal insulation. Other materials and composites have been used as micrometeorite shielding or radiation shielding. However, no material composite has been developed and employed as a combined thermal insulation, micrometeorite, and radiation shielding. By replacing the scrims that have been used to separate the foil layers in MLIs with various aerogels, and by using a variety of different metal foils, the overall protective performance of MLIs can be greatly expanded to act as thermal insulation, radiation shielding, and hypervelocity particle shielding. Aerogels are highly porous, low-density solids that are produced by the gelation of metal alkoxides and supercritical drying. Aerogels have been flown in NASA missions as a hypervelocity particle capture medium (Stardust) and as thermal insulation (2003 MER). Composite aerogel multifoil protective shielding would be used to provide thermal insulation, while also shielding spacecraft or components from radiation and hypervelocity particle impacts. Multiple layers of foil separated by aerogel would act as a thermal barrier by preventing the transport of heat energy through the composite. The silica aerogel would act as a convective and conductive thermal barrier, while the titania powder and metal foils would absorb and reflect the radiative heat. It would also capture small hypervelocity particles, such as micrometeorites, since it would be a stuffed, multi-shock Whipple shield. The metal foil layers would slow and break up the impacting particles, while the aerogel layers would convert the kinetic energy of the particles to thermal and mechanical energy and stop the particles.

Aerogel to simulate delamination and porosity defects in carbon-fiber reinforced polymer composites

NASA Astrophysics Data System (ADS)

Juarez, Peter; Leckey, Cara A. C.

2018-04-01

Representative defect standards are essential for the validation and calibration of new and existing inspection techniques. However, commonly used methods of simulating delaminations in carbon-fiber reinforced polymer (CFRP) composites do not accurately represent the behavior of the real-world defects for several widely-used NDE techniques. For instance, it is common practice to create a delamination standard by inserting Polytetrafluoroethylene (PTFE) in between ply layers. However, PTFE can transmit more ultrasonic energy than actual delaminations, leading to an unrealistic representation of the defect inspection. PTFE can also deform/wrinkle during the curing process and has a thermal effusivity two orders of magnitude higher than air (almost equal to that of a CFRP). It is therefore not effective in simulating a delamination for thermography. Currently there is also no standard practice for producing or representing a known porosity in composites. This paper presents a novel method of creating delamination and porosity standards using aerogel. Insertion of thin sheets of solid aerogel between ply layers during layup is shown to produce air-gap-like delaminations creating realistic ultrasonic and thermographic inspection responses. Furthermore, it is shown that depositing controlled amounts of aerogel powder can represent porosity. Micrograph data verifies the structural integrity of the aerogel through the composite curing process. This paper presents data from multiple NDE methods, including X-ray computed tomography, immersion ultrasound, and flash thermography to the effectiveness of aerogel as a delamination and porosity simulant.

Flexible aerogel composite for mechanical stability and process of fabrication

DOEpatents

Coronado, Paul R.; Poco, John F.

2000-01-01

A flexible aerogel and process of fabrication. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4-5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

Flexible aerogel composite for mechanical stability and process of fabrication

DOEpatents

Coronado, Paul R.; Poco, John F.

1999-01-01

A flexible aerogel and process of fabrication. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4-5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

Graphene-carbon nanotube composite aerogel for selective detection of uric acid

NASA Astrophysics Data System (ADS)

Zhang, Feifei; Tang, Jie; Wang, Zonghua; Qin, Lu-Chang

2013-12-01

Graphene and single-walled carbon nanotube (SWNT) composite aerogel has been prepared by hydrothermal synthesis. The restacking of graphene is effectively reduced by SWNTs inserted in between graphene layers in order to make available more active sites and reactive surface area. Electrochemical experiments show that the graphene-SWNT composite electrode has superior catalytic performance in selective detection of uric acid (UA).

Surfactant-free synthesis of silica aerogel microspheres with hierarchically porous structure.

PubMed

Zhang, Yulu; Wang, Jin; Zhang, Xuetong

2018-04-01

In this work, we developed a new method to synthesize silica aerogel microspheres via ambient pressure drying (APD) process without applying any surfactants and mechanical stirring. An ethanol solution of partially hydrolyzed, partially condensed silica (CS) was used as precursor in the synthesis, the water-repellent n-Heptane as solvent, while the water-soluble ammonia gas (NH 3 ) as catalyst. After a fast sol-gel process and APD process, aerogel microspheres were obtained in the form of white powder with packing density ranged from 62 mg/cm 3 to 230 mg/cm 3 for different samples. The SEM images exhibited fine spherical morphology for these aerogel microparticles, and their statistical average particle diameter ranged from 0.8 μm to 1.5 μm. Besides, according to the analysis of N 2 adsorption-desorption isotherms, the BET surface area of these aerogel microspheres was in the range of 800-960 m 2 /g, and a considerable volume of micropores was detected along with the abundant mesospores in these microspheres, which was further confirmed by the TEM image and SAXS curve. Based on the very limited solubility of NH 3 in the reaction system, a non-emulsion formation mechanism was proposed to illustrate the formation of these aerogel microspheres. Copyright © 2018 Elsevier Inc. All rights reserved.

Hyper-elastic modeling and mechanical behavior investigation of porous poly-D-L-lactide/nano-hydroxyapatite scaffold material.

PubMed

Han, Quan Feng; Wang, Ze Wu; Tang, Chak Yin; Chen, Ling; Tsui, Chi Pong; Law, Wing Cheung

2017-07-01

Poly-D-L-lactide/nano-hydroxyapatite (PDLLA/nano-HA) can be used as the biological scaffold material in bone tissue engineering as it can be readily made into a porous composite material with excellent performance. However, constitutive modeling for the mechanical response of porous PDLLA/nano-HA under various stress conditions has been very limited so far. In this work, four types of fundamental compressible hyper-elastic constitutive models were introduced for constitutive modeling and investigation of mechanical behaviors of porous PDLLA/nano-HA. Moreover, the unitary expressions of Cauchy stress tensor have been derived for the PDLLA/nano-HA under uniaxial compression (or stretch), biaxial compression (or stretch), pure shear and simple shear load by using the theory of continuum mechanics. The theoretical results determined from the approach based on the Ogden compressible hyper-elastic constitutive model were in good agreement with the experimental data from the uniaxial compression tests. Furthermore, this approach can also be used to predict the mechanical behaviors of the porous PDLLA/nano-HA material under the biaxial compression (or stretch), pure shear and simple shear. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanically Strong Lightweight Materials for Aerospace Applications (x-aerogels)

NASA Technical Reports Server (NTRS)

Leventis, Nicholas

2005-01-01

The X-Aerogel is a new NASA-developed strong lightweight material made by reacting the mesoporous surfaces of 3-D networks of inorganic nanoparticles with polymeric crosslinkers. Since the relative amount of the crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by templated casting of polymeric precursors on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralightweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the thermal conductivity of styrofoam. XAerogels have been demonstrated with several polymers such as polyurethanes/polyureas, epoxies and polyolefins, while crosslinking of approximately 35 different oxide aerogels yields a wide variety of dimensionally stable, porous lightweight materials with interesting structural, magnetic and optical properties. X-Aerogels are evaluated for cryogenic rocket fuel storage tanks and for Advanced EVA suits, where they will play the dual role of the thermal insulator/structural material. Along the same lines, major impact is also expected by the use of X-Aerogels in structural components/thermal protection for small satellites, spacecrafts, planetary vehicles and habitats.

Synthesis and characterization of a nanocrystalline diamond aerogel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.

2011-07-06

Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel's void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material revealmore » the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel.« less

Characterization of stoichiometric nanocrystalline spinel ferrites dispersed on porous silica aerogel.

PubMed

Casula, M F; Concas, G; Congiu, F; Corrias, A; Loche, D; Marras, C; Spano, G

2011-11-01

Stoichiometric magnetic nanosized ferrites MFe2O4 (M = Mn, Co, Ni) were prepared in form of nearly spherical nanocrystals supported on a highly porous silica aerogel matrix, by a sol-gel procedure. X-ray diffraction and transmission electron microscopy indicate that these materials are made out of non-agglomerated ferrite nanocrystals having size in the 5-10 nm range. Investigation by Mössbauer Spectroscopy was used to gain insights on the superparamagnetic relaxation and on the inversion degree. Magnetic ordering at room temperature varies from superparamagnetic in the NiFe2O4 sample, highly blocked (approximately 70%) in the MnFe2O4 sample and nearly fully blocked in the CoFe2O4 sample. A fitting procedure of the Mössbauer data has been used in order to resolve the spectrum into the tetrahedral and octahedral components; in this way, an inversion degree of 0.68 (very close to bulk values) was obtained for 6 nm silica-supported CoFe2O4 nanocrystals.

Self-Expansion Construction of Ultralight Carbon Nanotube Aerogels with a 3D and Hierarchical Cellular Structure.

PubMed

Luo, Yufeng; Luo, Shu; Wu, Hengcai; Li, Mengya; Wang, Ke; Yan, Lingjia; Jiang, Kaili; Li, Qunqing; Fan, Shoushan; Wang, Jiaping

2017-07-01

A novel and simple strategy is developed to construct ultralight and 3D pure carbon nanotube (CNT) aerogels by the spontaneous expansion of superaligned CNT films soaked in a piranha (mixed H 2 SO 4 and H 2 O 2 ) solution, followed by cryodesiccation. The macroscopic CNT aerogels have an extremely low apparent density (0.12 mg cm -3 ), ultrahigh porosity (99.95%), high specific surface area (298 m 2 g -1 ), and a hierarchical cellular structure with giant and ultrathin CNT sheets as cell walls. The pure CNT aerogels show high adsorption abilities for various kinds of solvents, and have great potential in widespread applications such as energy storage, catalysis, and bioengineering. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent Advances in Research on the Synthetic Fiber Based Silica Aerogel Nanocomposites

PubMed Central

Ślosarczyk, Agnieszka

2017-01-01

The presented paper contains a brief review on the synthesis and characterization of silica aerogels and its nanocomposites with nanofibers and fibers based on a literature study over the past twenty years and my own research. Particular attention is focused on carbon fiber-based silica aerogel nanocomposites. Silica aerogel is brittle in nature, therefore, it is necessary to improve this drawback, e.g., by polymer modification or fiber additives. Nevertheless, there are very few articles in the literature devoted to the synthesis of silica aerogel/fiber nanocomposites, especially those focusing on carbon fibers and nanofibers. Carbon fibers are very interesting materials, namely due to their special properties: high conductivity, high mechanical properties in relation to very low bulk densities, high thermal stability, and chemical resistance in the silica aerogel matrix, which can help enhance silica aerogel applications in the future. PMID:28336876

Recent Advances in Research on the Synthetic Fiber Based Silica Aerogel Nanocomposites.

PubMed

Ślosarczyk, Agnieszka

2017-02-16

The presented paper contains a brief review on the synthesis and characterization of silica aerogels and its nanocomposites with nanofibers and fibers based on a literature study over the past twenty years and my own research. Particular attention is focused on carbon fiber-based silica aerogel nanocomposites. Silica aerogel is brittle in nature, therefore, it is necessary to improve this drawback, e.g., by polymer modification or fiber additives. Nevertheless, there are very few articles in the literature devoted to the synthesis of silica aerogel/fiber nanocomposites, especially those focusing on carbon fibers and nanofibers. Carbon fibers are very interesting materials, namely due to their special properties: high conductivity, high mechanical properties in relation to very low bulk densities, high thermal stability, and chemical resistance in the silica aerogel matrix, which can help enhance silica aerogel applications in the future.

Monolithic cobalt-doped carbon aerogel for efficient catalytic activation of peroxymonosulfate in water.

PubMed

Hu, Peidong; Long, Mingce; Bai, Xue; Wang, Cheng; Cai, Caiyun; Fu, Jiajun; Zhou, Baoxue; Zhou, Yongfeng

2017-06-15

As an emerging carbonaceous material, carbon aerogels (CAs) display a great potential in environmental cleanup. In this study, a macroscopic three-dimensional monolithic cobalt-doped carbon aerogel was developed by co-condensation of graphene oxide sheets and resorcinol-formaldehyde resin in the presence of cobalt ions, followed by lyophilization, carbonization and thermal treatment in air. Cobalt ions were introduced as a polymerization catalyst to bridge the organogel framework, and finally cobalt species were retained as both metallic cobalt and Co 3 O 4 , wrapped by graphitized carbon layers. The material obtained after a thermal treatment in air (CoCA-A) possesses larger BET specific surface area and pore volume, better hydrophilicity and lower leaching of cobalt ions than that without the post-treatment (CoCA). Despite of a lower loading of cobalt content and a larger mass transfer resistance than traditional powder catalysts, CoCA-A can efficiently eliminate organic contaminants by activation of peroxymonosulfate with a low activation energy. CoCA-A can float beneath the surface of aqueous solution and can be taken out completely without any changes in morphology. The monolith is promising to be developed into an alternative water purification technology due to the easily separable feature. Copyright © 2017 Elsevier B.V. All rights reserved.

One-pot mass preparation of MoS2/C aerogels for high-performance supercapacitors and lithium-ion batteries.

PubMed

Zhang, Yan; He, Ting; Liu, Guanglei; Zu, Lianhai; Yang, Jinhu

2017-07-20

In this paper, we report the successful design and synthesis of a hierarchically porous MoS 2 /C composite aerogel by simple one-pot mass preparation. The synthesis involves the in situ formation of MoS 2 nanosheets on agarose molecular chains, the gelation of MoS 2 -deposited agarose monomers to generate a composite hydrogel, and in situ transformation of the composite hydrogel into a MoS 2 /C composite aerogel through carbonization. This composite aerogel can be used as a high-performance electrode material for supercapacitors and lithium-ion batteries. When tested as a supercapacitor electrode, it achieves a high specific capacitance of 712.6 F g -1 at 1 A g -1 and 97.3% capacity retention after 13 000 cycles at 6 A g -1 . In addition, as a lithium-ion battery electrode, it exhibits a superior rate capability (653.2 mA h g -1 at 0.1 A g -1 and 334.5 mA h g -1 at 5.0 A g -1 ) and an ultrahigh capacity retention of nearly 100% after 1000 cycles at 1 A g -1 . These performances may be ascribed to the unique structure of the MoS 2 /C composite aerogel, such as hierarchical pores, (002) plane-expanded MoS 2 and interconnected carbon networks embedded uniformly with MoS 2 nanosheets. This work may provide a general and simple approach for mass preparation of composite aerogel materials and pave the way for promising materials applied in both supercapacitors and lithium-ion batteries.

Spatially confined synthesis of SiOx nano-rod with size-controlled Si quantum dots in nano-porous anodic aluminum oxide membrane.

PubMed

Pai, Yi-Hao; Lin, Gong-Ru

2011-01-17

By depositing Si-rich SiOx nano-rod in nano-porous anodic aluminum oxide (AAO) membrane using PECVD, the spatially confined synthesis of Si quantum-dots (Si-QDs) with ultra-bright photoluminescence spectra are demonstrated after low-temperature annealing. Spatially confined SiOx nano-rod in nano-porous AAO membrane greatly increases the density of nucleated positions for Si-QD precursors, which essentially impedes the route of thermally diffused Si atoms and confines the degree of atomic self-aggregation. The diffusion controlled growth mechanism is employed to determine the activation energy of 6.284 kJ mole(-1) and diffusion length of 2.84 nm for SiO1.5 nano-rod in nano-porous AAO membrane. HRTEM results verify that the reduced geometric dimension of the SiOx host matrix effectively constrain the buried Si-QD size at even lower annealing temperature. The spatially confined synthesis of Si-QD essentially contributes the intense PL with its spectral linewidth shrinking from 210 to 140 nm and its peak intensity enhancing by two orders of magnitude, corresponding to the reduction on both the average Si-QD size and its standard deviation from 2.6 to 2.0 nm and from 25% to 12.5%, respectively. The red-shifted PL wavelength of the Si-QD reveals an inverse exponential trend with increasing temperature of annealing, which is in good agree with the Si-QD size simulation via the atomic diffusion theory.

Lightweight, Mesoporous, and Highly Absorptive All-Nanofiber Aerogel for Efficient Solar Steam Generation.

PubMed

Jiang, Feng; Liu, He; Li, Yiju; Kuang, Yudi; Xu, Xu; Chen, Chaoji; Huang, Hao; Jia, Chao; Zhao, Xinpeng; Hitz, Emily; Zhou, Yubing; Yang, Ronggui; Cui, Lifeng; Hu, Liangbing

2018-01-10

The global fresh water shortage has driven enormous endeavors in seawater desalination and wastewater purification; among these, solar steam generation is effective in extracting fresh water by efficient utilization of naturally abundant solar energy. For solar steam generation, the primary focus is to design new materials that are biodegradable, sustainable, of low cost, and have high solar steam generation efficiency. Here, we designed a bilayer aerogel structure employing naturally abundant cellulose nanofibrils (CNFs) as basic building blocks to achieve sustainability and biodegradability as well as employing a carbon nanotube (CNT) layer for efficient solar utilization with over 97.5% of light absorbance from 300 to 1200 nm wavelength. The ultralow density (0.0096 g/cm 3 ) of the aerogel ensures that minimal material is required, reducing the production cost while at the same time satisfying the water transport and thermal-insulation requirements due to its highly porous structure (99.4% porosity). Owing to its rationally designed structure and thermal-regulation performance, the bilayer CNF-CNT aerogel exhibits a high solar-energy conversion efficiency of 76.3% and 1.11 kg m -2 h -1 at 1 kW m -2 (1 Sun) solar irradiation, comparable or even higher than most of the reported solar steam generation devices. Therefore, the all-nanofiber aerogel presents a new route for designing biodegradable, sustainable, and scalable solar steam generation devices with superb performance.

The Compressive Behavior of Isocyanate-crosslinked Silica Aerogel at High Strain Rates

NASA Technical Reports Server (NTRS)

Luo, H.; Lu, H.; Leventis, N.

2006-01-01

Aerogels are low-density, highly nano-porous materials. Their engineering applications are limited due to their brittleness and hydrophilicity. Recently, a strong lightweight crosslinked silica aerogel has been developed by encapsulating the skeletal framework of amine-modified silica aerogels with polyureas derived by isocyanate. The mesoporous structure of the underlying silica framework is preserved through conformal polymer coating, and the thermal conductivity remains low. Characterization has been conducted on the thermal, physical properties and the mechanical properties under quasi-static loading conditions. In this paper, we present results on the dynamic compressive behavior of the crosslinked silica aerogel (CSA) using a split Hopkinson pressure bar (SHPB). A new tubing pulse shaper was employed to help reach the dynamic stress equilibrium and constant strain rate. The stress-strain relationship was determined at high strain rates within 114-4386/s. The effects of strain rate, density, specimen thickness and water absorption on the dynamic behavior of the CSA were investigated through a series of dynamic experiments. The Young's moduli (or 0.2% offset compressive yield strengths) at a strain rate approx.350/s were determined as 10.96/2.08, 159.5/6.75, 192.2/7.68, 304.6/11.46, 407.0/20.91 and 640.5/30.47 MPa for CSA with densities 0.205, 0.454, 0.492, 0.551,0.628 and 0.731 g/cu cm, respectively. The deformation and failure behaviors of a native silica aerogel with density (0.472 g/cu cm ), approximately the same as a typical CSA sample were observed with a high speed digital camera. Digital image correlation technique was used to determine the surface strains through a series of images acquired using high speed photography. The relative uniform axial deformation indicated that localized compaction did not occur at a compressive strain level of approx.17%, suggesting most likely failure mechanism at high strain rate to be different from that under quasi

Enhancing substrate utilization and power production of a microbial fuel cell with nitrogen-doped carbon aerogel as cathode catalyst.

PubMed

Tardy, Gábor Márk; Lóránt, Bálint; Lóka, Máté; Nagy, Balázs; László, Krisztina

2017-07-01

Catalytic efficiency of a nitrogen-doped, mesoporous carbon aerogel cathode catalyst was investigated in a two-chambered microbial fuel cell (MFC) applying graphite felt as base material for cathode and anode, utilizing peptone as carbon source. This mesoporous carbon aerogel containing catalyst layer on the cathode increased the maximum power density normalized to the anode volume to 2.7 times higher compared to the maximum power density obtained applying graphite felt cathode without the catalyst layer. At high (2 and 3) cathode/anode volume ratios, maximum power density exceeded 40 W m -3 . At the same time, current density and specific substrate utilization rate increased by 58% resulting in 31.9 A m -3 and 18.8 g COD m -3  h -1 , respectively (normalized to anode volume). Besides the increase of the power and the rate of biodegradation, the investigated catalyst decreased the internal resistance from the range of 450-600 to 350-370 Ω. Although Pt/C catalyst proved to be more efficient, a considerable decrease in the material costs might be achieved by substituting it with nitrogen-doped carbon aerogel in MFCs. Such cathode still displays enhanced catalytic effect.

Functionalization of biomass carbonaceous aerogels: selective preparation of MnO2@CA composites for supercapacitors.

PubMed

Ren, Yumei; Xu, Qun; Zhang, Jianmin; Yang, Hongxia; Wang, Bo; Yang, Daoyuan; Hu, Junhua; Liu, Zhimin

2014-06-25

Functionalized porous carbon materials with hierarchical structure and developed porosity coming from natural and renewable biomass have been attracting tremendous attention recently. In this work, we present a facile and scalable method to synthesize MnO2 loaded carbonaceous aerogel (MnO2@CA) composites via the hydrothermal carbonaceous (HTC) process. We employ two reaction systems of the mixed metal ion precursors to study the optimal selective adsorption and further reaction of MnO2 precursor on CA. Our experimental results show that the system containing KMnO4 and Na2S2O3·5H2O exhibits better electrochemical properties compared with the reaction system of MnSO4·H2O and (NH4)2S2O8. For the former, the obtained MnO2@CA displays the specific capacitance of 123.5 F·g(-1). The enhanced supercapacitance of MnO2@CA nanocomposites could be ascribed to both electrochemical contributions of the loaded MnO2 nanoparticles and the porous structure of three-dimensional carbonaceous aerogels. This study not only indicates that it is vital for the reaction systems to match with porous carbonaceous materials, but also offers a new fabrication strategy to prepare lightweight and high-performance materials that can be used in energy storage devices.

Liquid-solid phase transition of hydrogen and deuterium in silica aerogel

NASA Astrophysics Data System (ADS)

Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O.

2014-10-01

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H2 and D2 in an ˜85%-porous base-catalyzed silica aerogel. We find that liquid-solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ˜4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H2 and D2 confined inside the aerogel monolith. Results for H2 and D2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

Synthesis and characterization of a nanocrystalline diamond aerogel

PubMed Central

Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Kilcoyne, A. L. David; Wang, Yinmin; Willey, Trevor M.; Visbeck, Kenneth S.; Fakra, Sirine C.; Evans, William J.; Zaug, Joseph M.; Satcher, Joe H.

2011-01-01

Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel’s void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material reveal the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel. PMID:21555550

Sol-Gel assembly of CdSe nanoparticles to form porous aerogel networks.

PubMed

Arachchige, Indika U; Brock, Stephanie L

2006-06-21

A detailed study of CdSe aerogels prepared by oxidative aggregation of primary nanoparticles (prepared at room temperature and high temperature conditions, >250 degrees C), followed by CO2 supercritical drying, is described. The resultant materials are mesoporous, with an interconnected network of colloidal nanoparticles, and exhibit BET surface areas up to 224 m2/g and BJH average pore diameters in the range of 16-32 nm. Powder X-ray diffraction studies indicate that these materials retain the crystal structure of the primary nanoparticles, with a slight increase in primary particle size upon gelation and aerogel formation. Optical band gap measurements and photoluminescence studies show that the as-prepared aerogels retain the quantum-confined optical properties of the nanoparticle building blocks despite being connected into a 3-D network. The specific optical characteristics of the aerogel can be further modified by surface ligand exchange at the wet-gel stage, without destroying the gel network.

Ultra-lightweight and highly porous carbon aerogels from bamboo pulp fibers as an effective sorbent for water treatment

NASA Astrophysics Data System (ADS)

Yuan, Wei; Zhang, Xiaofang; Zhao, Jiangqi; Li, Qingye; Ao, Chenghong; Xia, Tian; Zhang, Wei; Lu, Canhui

Sorbents derived from biomass provide a novel approach to settle issues of organic solvent and/or oil leakage. In this work, a novel carbon aerogel (CA) was prepared as sorbents using the cheap and abundant bamboo pulp fibers as precursors through the pyrolysis method. The CA displayed an ultra-low density (5.65 mg cm-3), high hydrophobicity (water contact angle of 135.9°) and a large specific surface area (379.39 m2 g-1) as well as great mechanical properties. The absorption capacities of CA for organic solvents/oils were extraordinary (50-150 g/g). Particularly, its absorption on organic solvents was superior to many other bio-based CAs. The reusability of CA was also found impressive. For over five absorption-desorption cycles, the CA still showed excellent absorption behaviors on organic solvents and oils. Importantly, the fabrication process of CA is quite simple and environmentally friendly, demonstrating high potentials for future water treatment applications.

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

NASA Astrophysics Data System (ADS)

Zhu, Zhigang; Song, Wenhui; Burugapalli, Krishna; Moussy, Francis; Li, Ya-Li; Zhong, Xiao-Hua

2010-04-01

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 µm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 °C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 µM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.

Enhanced electrochemical capacitance and oil-absorbability of N-doped graphene aerogel by using amino-functionalized silica as template and doping agent

NASA Astrophysics Data System (ADS)

Du, Yongxu; Liu, Libin; Xiang, Yu; Zhang, Qiang

2018-03-01

The development of novel energy storage devices with high power density and energy density is highly desired. However, as a promising material, the strong π-π interaction of graphene inhibits its applications. Herein, we provide a new approach that amino-functionalized silica are used as both templates to prevent the restacking of the graphene sheets and doping agents simultaneously. The microstructures, porous properties and chemical composition of the resulted N-doped reduced graphene oxide (RGO) aerogels, characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, indicate that the amount of SiO2-NH2 has profound effects on the surface area and carbon activity of the graphene sheets. Benefiting from the large specific surface area of 481.8 m2 g-1, low series resistances and high nitrogen doping content (4.4 atom%), the as-fabricated 3D hierarchical porous N-doped RGO aerogel electrode exhibits outstanding electrochemical performance in aqueous and organic electrolyte, such as ultrahigh specific capacitances of 350 F g-1 at a current density of 1 A g-1 and excellent reversibility with a cycling efficiency of 88% after 10000 cycles. In addition, the N-doped RGO aerogels possess high oil-absorbability with long recyclability.

Polymer-Coated Graphene Aerogel Beads and Supercapacitor Application.

PubMed

Ouyang, An; Cao, Anyuan; Hu, Song; Li, Yanhui; Xu, Ruiqiao; Wei, Jinquan; Zhu, Hongwei; Wu, Dehai

2016-05-04

Graphene aerogels are highly porous materials with many energy and environmental applications; tailoring the structure and composition of pore walls within the aerogel is the key to those applications. Here, by freeze casting the graphene oxide sheets, we directly fabricated freestanding porous graphene beads containing radially oriented through channels from the sphere center to its surface. Furthermore, we introduced pseudopolymer to make reinforced, functional composite beads with a unique pore morphology. We showed that polymer layers can be coated smoothly on both sides of the pore walls, as well as on the junctions between adjacent pores, resulting in uniform polymer-graphene-polymer sandwiched structures (skeletons) throughout the bead. These composite beads significantly improved the electrochemical properties, with specific capacitances up to 669 F/g and good cyclic stability. Our results indicate that controlled fabrication of homogeneous hierarchical structures is a potential route toward high performance composite electrodes for various energy applications.

Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.

PubMed

Donius, Amalie E; Liu, Andong; Berglund, Lars A; Wegst, Ulrike G K

2014-09-01

Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C. Copyright © 2014 Elsevier Ltd. All rights reserved.

Liquid–solid phase transition of hydrogen and deuterium in silica aerogel

DOE PAGES

Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O.

2014-10-30

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H 2 and D 2 in an ~85%-porous base-catalyzed silica aerogel. In this work, we find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ~4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H 2 and D 2 confined inside the aerogel monolith. Lastly, results formore » H 2 and D 2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.« less

Liquid–solid phase transition of hydrogen and deuterium in silica aerogel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O., E-mail: kucheyev@llnl.gov

2014-10-28

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H{sub 2} and D{sub 2} in an ∼85%-porous base-catalyzed silica aerogel. We find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ∼4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H{sub 2} and D{sub 2} confined inside the aerogel monolith. Results for H{sub 2} and D{sub 2}more » are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.« less

Investigation of bioactivity and cell effects of nano-porous sol-gel derived bioactive glass film

NASA Astrophysics Data System (ADS)

Ma, Zhijun; Ji, Huijiao; Hu, Xiaomeng; Teng, Yu; Zhao, Guiyun; Mo, Lijuan; Zhao, Xiaoli; Chen, Weibo; Qiu, Jianrong; Zhang, Ming

2013-11-01

In orthopedic surgery, bioactive glass film coating is extensively studied to improve the synthetic performance of orthopedic implants. A lot of investigations have confirmed that nano-porous structure in bioactive glasses can remarkably improve their bioactivity. Nevertheless, researches on preparation of nano-porous bioactive glasses in the form of film coating and their cell response activities are scarce. Herein, we report the preparation of nano-porous bioactive glass film on commercial glass slide based on a sol-gel technique, together with the evaluation of its in vitro bioactivity through immersion in simulated body fluid and monitoring the precipitation of apatite-like layer. Cell responses of the samples, including attachment, proliferation and osteogenic differentiation, were also investigated using BMSCS (bone marrow derived mesenchymal stem cells) as a model. The results presented here provide some basic information on structural influence of bioactive glass film on the improvement of bioactivity and cellular effects.

Supported porous carbon and carbon-CNT nanocomposites for supercapacitor applications

NASA Astrophysics Data System (ADS)

Schopf, Dimitri; Es-Souni, Mohammed

2016-03-01

Supported porous carbon and porous carbon-MWCNT-nanocomposite films are produced by pyrolysis of porous polyvinylidene fluoride (PVDF) or porous PVDF-MWCNT-nanocomposite films on thermally resistant substrates. All films are characterized by SEM, RAMAN and XRD. The application of these films as supercapacitors is explored with outstanding supercapacitance values ranging from 80 to 120 F g-1 (up to 70 mF cm-2) in a three-electrode set-up in 1 M KOH, depending on microstructure. Additionally, the implementation of porous nanocarbon-MWCNT-nanocomposite films as electrodes in a symmetrical supercapacitor device is investigated. In all cases, long-term charge-discharge stability is demonstrated.

Synthesis and characterization of porous CaCO3 micro/nano-particles

NASA Astrophysics Data System (ADS)

Achour, A.; Arman, A.; Islam, M.; Zavarian, A. A.; Basim Al-Zubaidi, A.; Szade, J.

2017-06-01

Porous CaCO3 particles, both micro and nano sized, were synthesized in a mixture of Ca(OH)2, hyaluronic acid (HA), glycine, NaOH and NaCl solution with supercritical carbon dioxide. The particles were characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscope, Raman spectroscope (RS), X-ray photoelectron spectroscope (XPS) and scanning electron microscope techniques. All these techniques showed that the particles crystallize into only one CaCO3 structure, namely the vaterite phase. In addition, FTIR, RS and XPS indicated the presence of residual reactive species i.e. glycine, NaCl, and HA. The XRD results confirmed the presence of NaCl and γ-glycine, which is a crystalline material. Moreover, the HA seems to be mostly embedded in the bulk of the micro-particles. Such materials are promising for biomedical applications such as drug delivery.

Synthesis and Characterization of Highly Crystalline Graphene Aerogels

DOE PAGES

Worsley, Marcus A.; Pham, Thang T.; Yan, Aiming; ...

2014-10-06

Aerogels are used in a broad range of scientific and industrial applications due to their large surface areas, ultrafine pore sizes, and extremely low densities. Recently, a large number of reports have described graphene aerogels based on the reduction of graphene oxide (GO). Though these GO-based aerogels represent a considerable advance relative to traditional carbon aerogels, they remain significantly inferior to individual graphene sheets due to their poor crystallinity. Here, we report a straightforward method to synthesize highly crystalline GO-based graphene aerogels via high-temperature processing common in commercial graphite production. The crystallization of the graphene aerogels versus annealing temperature ismore » characterized using Raman and X-ray absorption spectroscopy, X-ray diffraction, and electron microscopy. Nitrogen porosimetry shows that the highly crystalline graphene macrostructure maintains a high surface area and ultrafine pore size. Because of their enhanced crystallinity, these graphene aerogels exhibit a ~200 °C improvement in oxidation temperature and an order of magnitude increase in electrical conductivity.« less

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

PubMed Central

Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yang, Fan

2018-01-01

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future. PMID:29385745

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

PubMed

Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

2018-01-30

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Self-Assembled Nano-FeO(OH)/Reduced Graphene Oxide Aerogel as a Reusable Catalyst for Photo-Fenton Degradation of Phenolic Organics.

PubMed

Liu, Renlan; Xu, Yiming; Chen, Baoliang

2018-06-19

Fabrication of visible-light-responsive, macroscopic photo-Fenton catalysts is crucial for wastewater treatment. Here, we report a facile fabrication method for nano-FeO(OH)/reduced graphene oxide aerogels (FeO(OH)-rGA) equipped with a stable macrostructure and a high efficiency for catalytic degradation of phenolic organics. The structure of FeO(OH)/rGA was characterized by SEM, TEM, XPS, Raman analysis. The FeO(OH) is the main constituent of ferrihydrite, which dispersed in the graphene aerogel with a particle size of ∼3 nm can efficiently activate H 2 O 2 to generate abundant •OH. The excellent performance of the FeO(OH)/rGO aerogel was specifically exhibited by the outstanding catalyst activity, sustained mineralization and eminent reaction rate for phenolic organics. A synergy effect between FeO(OH) and graphene aerogel was observed, which came from the extensive electron transfer channels and active sites of the 3D graphene aerogel and the visible-light-activated FeO(OH) and H 2 O 2 consistently producing •OH. The FeO(OH)/rGA could be reused for 10 cycles without a reduction in the catalytic activity and had less iron leaching, which guarantees that the active ingredient remains in the gel. Moreover, the FeO(OH)/rGA induced photo-Fenton degradation of 4-chlorophenol under near neutral pH conditions because the tight connection of FeO(OH) with the rGO aerogel results in less iron leaching and prevents the generation of Fe(OH) 3 . The 4-chlorophenol was completely removed in 80 min with a 0.074 min -1 rate constant in the FeO(OH)-rGA/H 2 O 2 photo-Fenton system under visible-light irradiation, and mineralization rate was up to 80% after 6 h. Oxidative •OH can continuously attack 4-chlorophenol, 2,4,6-trichlorophenol and bisphenol A without selectivity. These results lay a foundation for highly effective and durable photo-Fenton degradation of phenolic organics at near neutral pH and sufficient activation of H 2 O 2 for future applications.

An X-ray absorption spectroscopy study of the inversion degree in zinc ferrite nanocrystals dispersed on a highly porous silica aerogel matrix.

PubMed

Carta, D; Marras, C; Loche, D; Mountjoy, G; Ahmed, S I; Corrias, A

2013-02-07

The structural properties of zinc ferrite nanoparticles with spinel structure dispersed in a highly porous SiO(2) aerogel matrix were compared with a bulk zinc ferrite sample. In particular, the details of the cation distribution between the octahedral (B) and tetrahedral (A) sites of the spinel structure were determined using X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the zinc ferrite spinel structures varies with particle size. In particular, in the bulk microcrystalline sample, Zn(2+) ions are at the tetrahedral sites and trivalent Fe(3+) ions occupy octahedral sites (normal spinel). When particle size decreases, Zn(2+) ions are transferred to octahedral sites and the degree of inversion is found to increase as the nanoparticle size decreases. This is the first time that a variation of the degree of inversion with particle size is observed in ferrite nanoparticles grown within an aerogel matrix.

Three dimensional nitrogen-doped graphene aerogels functionalized with melamine for multifunctional applications in supercapacitors and adsorption

NASA Astrophysics Data System (ADS)

Xing, Ling-Bao; Hou, Shu-Fen; Zhou, Jin; Zhang, Jing-Li; Si, Weijiang; Dong, Yunhui; Zhuo, Shuping

2015-10-01

In present work, we demonstrate an efficient and facile strategy to fabricate three-dimensional (3D) nitrogen-doped graphene aerogels (NGAs) based on melamine, which serves as reducing and functionalizing agent of graphene oxide (GO) in an aqueous medium with ammonia. Benefiting from well-defined and cross-linked 3D porous network architectures, the supercapacitor based on the NGAs exhibited a high specific capacitance of 170.5 F g-1 at 0.2 A g-1, and this capacitance also showed good electrochemical stability and a high degree of reversibility in the repetitive charge/discharge cycling test. More interestingly, the prepared NGAs further exhibited high adsorption capacities and high recycling performance toward several metal ions such as Pb2+, Cu2+ and Cd2+. Moreover, the hydrophobic carbonized nitrogen-doped graphene aerogels (CNGAs) showed outstanding adsorption and recycling performance for the removal of various oils and organic solvents.

3D Networked Tin Oxide/Graphene Aerogel with a Hierarchically Porous Architecture for High-Rate Performance Sodium-Ion Batteries.

PubMed

Xie, Xiuqiang; Chen, Shuangqiang; Sun, Bing; Wang, Chengyin; Wang, Guoxiu

2015-09-07

Low-cost and sustainable sodium-ion batteries are regarded as a promising technology for large-scale energy storage and conversion. The development of high-rate anode materials is highly desirable for sodium-ion batteries. The optimization of mass transport and electron transfer is crucial in the discovery of electrode materials with good high-rate performances. Herein, we report the synthesis of 3 D interconnected SnO2 /graphene aerogels with a hierarchically porous structure as anode materials for sodium-ion batteries. The unique 3 D architecture was prepared by a facile in situ process, during which cross-linked 3 D conductive graphene networks with macro-/meso-sized hierarchical pores were formed and SnO2 nanoparticles were dispersed uniformly on the graphene surface simultaneously. Such a 3 D functional architecture not only facilitates the electrode-electrolyte interaction but also provides an efficient electron pathway within the graphene networks. When applied as anode materials in sodium-ion batteries, the as-prepared SnO2 /graphene aerogel exhibited high reversible capacity, improved cycling performance compared to SnO2 , and promising high-rate capability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sorption of pollutants by porous carbon, carbon nanotubes and fullerene- an overview.

PubMed

Gupta, Vinod K; Saleh, Tawfik A

2013-05-01

The quality of water is continuously deteriorating due to its increasing toxic threat to humans and the environment. It is imperative to perform treatment of wastewater in order to remove pollutants and to get good quality water. Carbon materials like porous carbon, carbon nanotubes and fullerene have been extensively used for advanced treatment of wastewaters. In recent years, carbon nanomaterials have become promising adsorbents for water treatment. This review attempts to compile relevant knowledge about the adsorption activities of porous carbon, carbon nanotubes and fullerene related to various organic and inorganic pollutants from aqueous solutions. A detailed description of the preparation and treatment methods of porous carbon, carbon nanotubes and fullerene along with relevant applications and regeneration is also included.

High-volumetric performance aligned nano-porous microwave exfoliated graphite oxide-based electrochemical capacitors.

PubMed

Ghaffari, Mehdi; Zhou, Yue; Xu, Haiping; Lin, Minren; Kim, Tae Young; Ruoff, Rodney S; Zhang, Q M

2013-09-20

Ultra-high volumetric performance electrochemical double layer capacitors based on high density aligned nano-porous microwave exfoliated graphite oxide have been studied. Elimination of macro-, meso-, and larger micro-pores from electrodes and controlling the nano-morphology results in very high volumetric capacitance, energy, and power density values. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Nanofiber Incorporated Silica Based Aerogels with Di-Isocyanate Cross-Linking

NASA Technical Reports Server (NTRS)

Vivod, Stephanie L.; Meador, Mary Ann B.; Capadona, Lynn A.; Sullivan, Roy M.; Ghosn, Louis J.; Clark, Nicholas; McCorkle, Linda

2008-01-01

Lightweight materials with excellent thermal insulating properties are highly sought after for a variety of aerospace and aeronautic applications. (1) Silica based aerogels with their high surface area and low relative densities are ideal for applications in extreme environments such as insulators for the Mars Rover battery. (2) However, the fragile nature of aerogel monoliths prevents their widespread use in more down to earth applications. We have shown that the fragile aerogel network can be cross-linked with a di-isocyanate via amine decorated surfaces to form a conformal coating. (3) This coating reinforces the neck regions between secondary silica particles and significantly strengthens the aerogels with only a small effect on density or porosity. Scheme 1 depicts the cross-linking reaction with the di-isocyanate and exhibits the stages that result in polymer cross-linked aerogel monoliths.

Synthesis and characterization of Fe{sub 3}O{sub 4}: Porous carbon nanocomposites for biosensor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arora, Manju, E-mail: marora@nplindia.org; Zargar, R. A., E-mail: rayeesphy12@gmail.com

2015-08-28

Fe{sub 3}O{sub 4}:Porous carbon (Fe{sub 3}O{sub 4}:PC) nano-magnetic composites were prepared by using different weight fractions of acid treated PC by the chemical co-precipitation route and annealed at 573 K, 773 K and 973 K temperatures in inert N{sub 2} gas atmosphere for 2 hrs to obtain desired stoichiometry of nanocomposites. The structural, morphological and magnetic properties of these composites were characterized by powder XRD, TEM, EPR and VSM analytical techniques. The crystallinity of the composites, g-value and spin concentration increases with increasing annealing temperature. TEM images confirmed the formation of nanosized ferrite nanoprticles whose size increases from 23 nm to 54 nm on increasingmore » annealing temperature. Porous carbon increases porosity, coercivity and reduces saturation magnetization of these prepared nanocomposites.« less

Octahedral Tin Dioxide Nanocrystals Anchored on Vertically Aligned Carbon Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries.

PubMed

Liu, Mingkai; Liu, Yuqing; Zhang, Yuting; Li, Yiliao; Zhang, Peng; Yan, Yan; Liu, Tianxi

2016-08-11

A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared via a simple and efficient directional freezing method. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional graphene/carbon nanotube (GCNT) composites. Vertically aligned pores can effectively prevent the emersion of "closed" pores which cannot load the active SnO2 nanoparticles, further ensure quick immersion of electrolyte throughout the aerogel, and can largely shorten the transport distance between lithium ions and active sites of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good interconnected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1190 mAh/g with good long-term cycling stability up to 1000 times was achieved. This work provides a promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices.

Octahedral Tin Dioxide Nanocrystals Anchored on Vertically Aligned Carbon Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Liu, Mingkai; Liu, Yuqing; Zhang, Yuting; Li, Yiliao; Zhang, Peng; Yan, Yan; Liu, Tianxi

2016-08-01

A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared via a simple and efficient directional freezing method. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional graphene/carbon nanotube (GCNT) composites. Vertically aligned pores can effectively prevent the emersion of “closed” pores which cannot load the active SnO2 nanoparticles, further ensure quick immersion of electrolyte throughout the aerogel, and can largely shorten the transport distance between lithium ions and active sites of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good interconnected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1190 mAh/g with good long-term cycling stability up to 1000 times was achieved. This work provides a promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices.

Monolithic Nickel (II) Oxide Aerogels Using an Organic Epoxide: The Importance of the Counter Ion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gash, A E; Satcher, J H; Simpson, R L

2004-01-13

The synthesis and characterization of nickel (II) oxide aerogel materials prepared using the epoxide addition method is described. The addition of the organic epoxide propylene oxide to an ethanolic solution of NiCl{sub 2} 6H{sub 2}O resulted in the formation of an opaque light green monolithic gel and subsequent drying with supercritical CO{sub 2} gave a monolithic aerogel material of the same color. This material has been characterized using powder X-ray diffraction, electron microscopy, elemental analysis, and nitrogen adsorption/desorption analysis. The results indicate that the nickel (II) oxide aerogel has very low bulk density (98 kg/m{sup 3} ({approx}98 %porous)), high surfacemore » area (413 m{sup 2}/g), and has a particulate-type aerogel microstructure made up of very fine spherical particles with an open porous network. By comparison, a precipitate of Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} is obtained when the same preparation is attempted with the common Ni(NO{sub 3}){sub 2} 6H{sub 2}O salt as the precursor. The implications of the difference of reactivity of the two different precursors are discussed in the context of the mechanism of gel formation via the epoxide addition method. The synthesis of nickel (II) oxide aerogel, using the epoxide addition method, is especially unique in our experience. It is our first example of the successful preparation of a metal oxide aerogel using a metal divalent metal ion and may have implications for the application of this method to the preparation of aerogels or nanoparticles of other divalent metal oxides. To our knowledge this is the first report of a monolithic pure nickel (II) oxide aerogel materials.« less

Preparation of Silica Aerogel from TEOS

PubMed

Tamon; Kitamura; Okazaki

1998-01-15

Silica alcogels were synthesized by the sol-gel polymerization of tetraethylorthosilicate (TEOS). In the synthesis, HCl and NH3 were used as hydrolysis and condensation catalysts. The gelation time became short and the visible light transmittance increased with increasing the amount of HCl or lengthening the hydrolysis time. The alcogels were dried under supercritical conditions with carbon dioxide, and silica aerogels were obtained. As a result of characterization by visible light transmission and N2 adsorption, the aerogels are mesoporous materials with high surface areas. The experimental results suggest that the aerogel properties are not influenced by the drying conditions such as extraction temperature, extraction time, depressurizing temperature, and depressurizing rate. On the other hand, the properties are changed under the conditions of sol-gel polymerization. In the preparation of highly transparent aerogels with high surface areas and large pore volumes, it is necessary to synthesize highly transparent alcogels. It is found that the visible light transmittance of alcogels is an index for preparing aerogels from TEOS. Copyright 1998 Academic Press. Copyright 1998Academic Press

Mesoporous fluorocarbon-modified silica aerogel membranes enabling long-term continuous CO2 capture with large absorption flux enhancements.

PubMed

Lin, Yi-Feng; Chen, Chien-Hua; Tung, Kuo-Lun; Wei, Te-Yu; Lu, Shih-Yuan; Chang, Kai-Shiun

2013-03-01

The use of a membrane contactor combined with a hydrophobic porous membrane and an amine absorbent has attracted considerable attention for the capture of CO2 because of its extensive use, low operational costs, and low energy consumption. The hydrophobic porous membrane interface prevents the passage of the amine absorbent but allows the penetration of CO2 molecules that are captured by the amine absorbent. Herein, highly porous SiO2 aerogels modified with hydrophobic fluorocarbon functional groups (CF3 ) were successfully coated onto a macroporous Al2 O3 membrane; their performance in a membrane contactor for CO2 absorption is discussed. The SiO2 aerogel membrane modified with CF3 functional groups exhibits the highest CO2 absorption flux and can be continuously operated for CO2 absorption for extended periods of time. This study suggests that a SiO2 aerogel membrane modified with CF3 functional groups could potentially be used in a membrane contactor for CO2 absorption. Also, the resulting hydrophobic SiO2 aerogel membrane contactor is a promising technology for large-scale CO2 absorption during the post-combustion process in power plants. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synergic mechanism of adsorption and metal-free catalysis for phenol degradation by N-doped graphene aerogel.

PubMed

Ren, Xiaohua; Guo, Huanhuan; Feng, Jinkui; Si, Pengchao; Zhang, Lin; Ci, Lijie

2018-01-01

3D porous N-doped reduced graphene oxide (N-rGO) aerogels were synthesized by a hydrothermal reduction of graphene oxide (GO) with urea and following freeze-drying process. N-rGO aerogels have a high BET surface of 499.70 m 2 /g and a high N doping content (5.93-7.46 at%) including three kinds of N (graphitic, pyridinic and pyrrolic). Their high catalytic performance for phenol oxidation in aqueous solution was investigated by catalytic activation of persulfate (PS). We have demonstrated that N-rGO aerogels are promising metal-free catalysts for phenol removal. Kinetics studies indicate that phenol degradation follows first-order reaction kinetics with the reaction rate constant of 0.16799 min -1 for N-rGO-A(1:30). Interestingly, the comparison of direct catalytic oxidation with adsorption-catalytic oxidation experiments indicates that adsorption plays an important role in the catalytic oxidation of phenol by decreasing the phenol degradation time. Spin density and adsorption modeling demonstrates that graphitic N in N-rGO plays the most important role for the catalytic performance by inducing high positive charge densities to adjacent carbon atoms and facilitating phenol adsorption on these carbon sites. Furthermore, the activation mechanism of persulfate (PS) on N-rGO was first investigated by DFT method and PS can be activated to generate strongly oxidative radical (SO 4 · - ) by transferring electrons to N-rGO. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of silica aerogel monoliths with controlled specific surface areas and pore sizes

NASA Astrophysics Data System (ADS)

Gao, Bingying; Lu, Shaoxiang; Kalulu, Mulenga; Oderinde, Olayinka; Ren, Lili

2017-07-01

To replace traditional preparation methods of silica aerogels, a small-molecule 1,2-epoxypropane (PO) has been introduced into the preparation process instead of using ammonia as the cross-linking agent, thus generating a lightweight, high porosity, and large surface area silica aerogel monolithic. We put forward a simple solution route for the chemical synthesis of silica aerogels, which was characterized by scanning electron microscopy (SEM), TEM, XRD, FTIR, thermogravimetric analysis (TGA) and the Brunauer-Emmett-Teller (BET) method In this paper, the effect of the amount of PO on the microstructure of silica aerogels is discussed. The BET surface areas and pore sizes of the resulting silica aerogels can be freely adjusted by changing the amount of PO, which will be helpful in promoting the development of silica aerogels to fabricate other porous materials with similar requirements. We also adopted a new organic solvent sublimation drying (OSSD) method to replace traditional expensive and dangerous drying methods such as critical point drying and freeze drying. This simple approach is easy to operate and has good repeatability, which will further facilitate actual applications of silica aerogels.

Bioinspired Ultralight Inorganic Aerogel for Highly Efficient Air Filtration and Oil-Water Separation.

PubMed

Zhang, Yong-Gang; Zhu, Ying-Jie; Xiong, Zhi-Chao; Wu, Jin; Chen, Feng

2018-04-18

Inorganic aerogels have been attracting great interest owing to their distinctive structures and properties. However, the practical applications of inorganic aerogels are greatly restricted by their high brittleness and high fabrication cost. Herein, inspired by the cancellous bone, we have developed a novel kind of hydroxyapatite (HAP) nanowire-based inorganic aerogel with excellent elasticity, which is highly porous (porosity ≈ 99.7%), ultralight (density 8.54 mg/cm 3 , which is about 0.854% of water density), and highly adiabatic (thermal conductivity 0.0387 W/m·K). Significantly, the as-prepared HAP nanowire aerogel can be used as the highly efficient air filter with high PM 2.5 filtration efficiency. In addition, the HAP nanowire aerogel is also an ideal candidate for continuous oil-water separation, which can be used as a smart switch to separate oil from water continuously. Compared with organic aerogels, the as-prepared HAP nanowire aerogel is biocompatible, environmentally friendly, and low-cost. Moreover, the synthetic method reported in this work can be scaled up for large-scale production of HAP nanowires, free from the use of organic solvents. Therefore, the as-prepared new kind of HAP nanowire aerogel is promising for the applications in various fields.

Synthesis of hierarchically porous perovskite-carbon aerogel composite catalysts for the rapid degradation of fuchsin basic under microwave irradiation and an insight into probable catalytic mechanism

NASA Astrophysics Data System (ADS)

Wang, Yin; Wang, Jiayuan; Du, Baobao; Wang, Yun; Xiong, Yang; Yang, Yiqiong; Zhang, Xiaodong

2018-05-01

3D hierarchically porous perovskites LaFe0.5M0.5O3-CA (M = Mn, Cu) were synthesized by a two-step method using PMMA as template and supporting with carbon aerogel, which were characterized with SEM, TEM, XRD, XPS and FT-IR spectroscopy. The as-prepared composites were used in microwave (MW) catalytic degradation of fuchsin basic (FB) dye wastewater. Batch experiment results showed that the catalytic degradation of FB could be remarkably improved by coating with CA. And LaFe0.5Cu0.5O3-CA exhibited higher catalytic performance than LaFe0.5Mn0.5O3-CA, which had a close connection with the activity of substitution metal ion in B site of the catalysts. The FB removal fit pseudo-first-order model and the degradation rate constant increased with initial pH value and MW powder while decreases with initial FB concentration. All catalysts presented favorable recycling and stability in the repeated experiment. Radical scavenger measurements indicated that hydroxyl radicals rather than surface peroxide and hole played an important role in the catalytic process, and its quantity determined the degradation of FB. Furthermore, both Cu and Fe species were involved in the formation of active species, which were responsible to the excellent performance of the LaFe0.5Cu0.5O3-CA/MW system. Therefore, LaFe0.5Cu0.5O3-CA/MW showed to be a promising technology for the removal of organic pollutants in wastewater treatment applications.

Multiresponsive Graphene-Aerogel-Directed Phase-Change Smart Fibers.

PubMed

Li, Guangyong; Hong, Guo; Dong, Dapeng; Song, Wenhui; Zhang, Xuetong

2018-06-14

Wearable devices and systems demand multifunctional units with intelligent and integrative functions. Smart fibers with response to external stimuli, such as electrical, thermal, and photonic signals, etc., as well as offering energy storage/conversion are essential units for wearable electronics, but still remain great challenges. Herein, flexible, strong, and self-cleaning graphene-aerogel composite fibers, with tunable functions of thermal conversion and storage under multistimuli, are fabricated. The fibers made from porous graphene aerogel/organic phase-change materials coated with hydrophobic fluorocarbon resin render a wide range of phase transition temperature and enthalpy (0-186 J g -1 ). The strong and compliant fibers are twisted into yarn and woven into fabrics, showing a self-clean superhydrophobic surface and excellent multiple responsive properties to external stimuli (electron/photon/thermal) together with reversible energy storage and conversion. Such aerogel-directed smart fibers promise for broad applications in the next-generation of wearable systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Drug release from nanoparticles embedded in four different nanofibrillar cellulose aerogels.

PubMed

Valo, Hanna; Arola, Suvi; Laaksonen, Päivi; Torkkeli, Mika; Peltonen, Leena; Linder, Markus B; Serimaa, Ritva; Kuga, Shigenori; Hirvonen, Jouni; Laaksonen, Timo

2013-09-27

Highly porous nanocellulose aerogels prepared by freeze-drying from various nanofibrillar cellulose (NFC) hydrogels are introduced as nanoparticle reservoirs for oral drug delivery systems. Here we show that beclomethasone dipropionate (BDP) nanoparticles coated with amphiphilic hydrophobin proteins can be well integrated into the NFC aerogels. NFCs from four different origins are introduced and compared to microcrystalline cellulose (MCC). The nanocellulose aerogel scaffolds made from red pepper (RC) and MCC release the drug immediately, while bacterial cellulose (BC), quince seed (QC) and TEMPO-oxidized birch cellulose-based (TC) aerogels show sustained drug release. Since the release of the drug is controlled by the structure and interactions between the nanoparticles and the cellulose matrix, modulation of the matrix formers enable a control of the drug release rate. These nanocomposite structures can be very useful in many pharmaceutical nanoparticle applications and open up new possibilities as carriers for controlled drug delivery. Copyright © 2013 Elsevier B.V. All rights reserved.

Highly-sensitive electrochemical sensing platforms for food colourants based on the property-tuning of porous carbon.

PubMed

Cheng, Qin; Xia, Shanhong; Tong, Jianhua; Wu, Kangbing

2015-08-05

It is very challenging to develop highly-sensitive analytical platforms for toxic synthetic colourants that widely added in food samples. Herein, a series of porous carbon (PC) was prepared using CaCO3 nanoparticles (nano-CaCO3) as the hard template and starch as the carbon precursor. Characterizations of scanning electron microscopy and transmission electron microscopy indicated that the morphology and porous structure were controlled by the weight ratio of starch and nano-CaCO3. The electrochemical behaviours of four kinds of widely-used food colourants, Sunset yellow, Tartrazine, Ponceau 4R and Allura red, were studied. On the surface of PC samples, the oxidation signals of colourants enhanced obviously, and more importantly, the signal enhancement abilities of PC were also dependent on the starch/nano-CaCO3 weight ratio. The greatly-increased electron transfer ability and accumulation efficiency were the main reason for the enhanced signals of colourants, as confirmed by electrochemical impedance spectroscopy and chronocoulometry. The prepared PC-2 sample by 1:1 starch/nano-CaCO3 weight ratio was more active for the oxidation of food colourtants, and increased the signals by 89.4-fold, 79.3-fold, 47.3-fold and 50.7-fold for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. As a result, a highly-sensitive electrochemical sensing platform was developed, and the detection limits were 1.4, 3.5, 2.1 and 1.7 μg L(-1) for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. The practical application of this new sensing platform was demonstrated using drink samples, and the detected results consisted with the values that obtained by high-performance liquid chromatography. Copyright © 2015 Elsevier B.V. All rights reserved.

Two-Dimensional Porous Carbon: Synthesis and Ion-Transport Properties.

PubMed

Zheng, Xiaoyu; Luo, Jiayan; Lv, Wei; Wang, Da-Wei; Yang, Quan-Hong

2015-09-23

Their chemical stability, high specific surface area, and electric conductivity enable porous carbon materials to be the most commonly used electrode materials for electrochemical capacitors (also known as supercapacitors). To further increase the energy and power density, engineering of the pore structures with a higher electrochemical accessible surface area, faster ion-transport path and a more-robust interface with the electrolyte is widely investigated. Compared with traditional porous carbons, two-dimensional (2D) porous carbon sheets with an interlinked hierarchical porous structure are a good candidate for supercapacitors due to their advantages in high aspect ratio for electrode packing and electron transport, hierarchical pore structures for ion transport, and short ion-transport length. Recent progress on the synthesis of 2D porous carbons is reported here, along with the improved electrochemical behavior due to enhanced ion transport. Challenges for the controlled preparation of 2D porous carbons with desired properties are also discussed; these require precise tuning of the hierarchical structure and a clarification of the formation mechanisms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characteristics of Sodium Polyacrylate/Nano-Sized Carbon Hydrogel for Biomedical Patch.

PubMed

Park, Jong-Kyu; Seo, Sun-Kyo; Cho, Seungkwan; Kim, Han-Sung; Lee, Chi-Hwan

2018-03-01

Conductive hydrogels were prepared for biomedical patch in order to improve the electrical conductivity. Sodium polyacrylate and nano-sized carbon were mixed and fabricated by aqueous solution gelation process in various contents of nano-sized carbon with 0.1, 0.5, 1.0 and 2.0 wt%. Sodium polyacrylate/nano-sized carbon conductive hydrogels were investigated by molecular structure, surface morphology and electrical conductivity. The conductivity of the hydrogel/nano-sized carbon conductive hydrogel proved to be 10% higher than conductive hydrogel without nano-sized carbon. However, it was founded that conductive hydrogels with nano-sized carbon content from 0.5 up to 2.0 wt% were remarkably decreased. This may be due to the non-uniform distribution of nano-sized carbon, resulting from agglomerates of nano-sized carbon. The developed hydrogel is intended for use in the medical and cosmetic fields that is applicable to supply micro-current from device to human body.

Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors.

PubMed

Huang, Haijian; Wang, Xing; Tervoort, Elena; Zeng, Guobo; Liu, Tian; Chen, Xi; Sologubenko, Alla; Niederberger, Markus

2018-03-27

A general method for preparing nano-sized metal oxide nanoparticles with highly disordered crystal structure and their processing into stable aqueous dispersions is presented. With these nanoparticles as building blocks, a series of nanoparticles@reduced graphene oxide (rGO) composite aerogels are fabricated and directly used as high-power anodes for lithium-ion hybrid supercapacitors (Li-HSCs). To clarify the effect of the degree of disorder, control samples of crystalline nanoparticles with similar particle size are prepared. The results indicate that the structurally disordered samples show a significantly enhanced electrochemical performance compared to the crystalline counterparts. In particular, structurally disordered Ni x Fe y O z @rGO delivers a capacity of 388 mAh g -1 at 5 A g -1 , which is 6 times that of the crystalline sample. Disordered Ni x Fe y O z @rGO is taken as an example to study the reasons for the enhanced performance. Compared with the crystalline sample, density functional theory calculations reveal a smaller volume expansion during Li + insertion for the structurally disordered Ni x Fe y O z nanoparticles, and they are found to exhibit larger pseudocapacitive effects. Combined with an activated carbon (AC) cathode, full-cell tests of the lithium-ion hybrid supercapacitors are performed, demonstrating that the structurally disordered metal oxide nanoparticles@rGO||AC hybrid systems deliver high energy and power densities within the voltage range of 1.0-4.0 V. These results indicate that structurally disordered nanomaterials might be interesting candidates for exploring high-power anodes for Li-HSCs.

Porous block nanofiber composite filters

DOEpatents

Ginley, David S.; Curtis, Calvin J.; Miedaner, Alexander; Weiss, Alan J.; Paddock, Arnold

2016-08-09

Porous block nano-fiber composite (110), a filtration system (10) and methods of using the same are disclosed. An exemplary porous block nano-fiber composite (110) includes a porous block (100) having one or more pores (200). The porous block nano-fiber composite (110) also includes a plurality of inorganic nano-fibers (211) formed within at least one of the pores (200).

Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds.

PubMed

Zanin, H; Rosa, C M R; Eliaz, N; May, P W; Marciano, F R; Lobo, A O

2015-06-14

Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.

Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds

NASA Astrophysics Data System (ADS)

Zanin, H.; Rosa, C. M. R.; Eliaz, N.; May, P. W.; Marciano, F. R.; Lobo, A. O.

2015-05-01

Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.

Mechanism of drug release from silica-gelatin aerogel-Relationship between matrix structure and release kinetics.

PubMed

Veres, Péter; Kéri, Mónika; Bányai, István; Lázár, István; Fábián, István; Domingo, Concepción; Kalmár, József

2017-04-01

Specific features of a silica-gelatin aerogel (3 wt.% gelatin content) in relation to drug delivery has been studied. It was confirmed that the release of both ibuprofen (IBU) and ketoprofen (KET) is about tenfold faster from loaded silica-gelatin aerogel than from pure silica aerogel, although the two matrices are structurally very similar. The main goal of the study was to understand the mechanistic background of the striking difference between the delivery properties of these closely related porous materials. Hydrated and dispersed silica-gelatin aerogel has been characterized by NMR cryoporometry, diffusiometry and relaxometry. The pore structure of the silica aerogel remains intact when it disintegrates in water. In contrast, dispersed silica-gelatin aerogel develops a strong hydration sphere, which reshapes the pore walls and deforms the pore structure. The drug release kinetics was studied on a few minutes time scale with 1s time resolution. Simultaneous evaluation of all relevant kinetic and structural information confirmed that strong hydration of the silica-gelatin skeleton facilitates the rapid desorption and dissolution of the drugs from the loaded aerogel. Such a driving force is not operative in pure silica aerogels. Copyright © 2017 Elsevier B.V. All rights reserved.

The control of ice crystal growth and effect on porous structure of konjac glucomannan-based aerogels.

PubMed

Ni, Xuewen; Ke, Fan; Xiao, Man; Wu, Kao; Kuang, Ying; Corke, Harold; Jiang, Fatang

2016-11-01

Konjac glucomannan (KGM)-based aerogels were prepared using a combination of sol-gel and freeze-drying methods. Preparation conditions were chosen to control ice crystal growth and aerogel structure formation. The ice crystals formed during pre-freezing were observed by low temperature polarizing microscopy, and images of aerogel pores were obtained by scanning electron microscopy. The size of ice crystals were calculated and size distribution maps were drawn, and similarly for aerogel pores. Results showed that ice crystal growth and aerogel pore sizes may be controlled by varying pre-freezing temperatures, KGM concentration and glyceryl monostearate concentration. The impact of pre-freezing temperatures on ice crystal growth was explained as combining ice crystal growth rate with nucleation rate, while the impacts of KGM and glyceryl monostearate concentration on ice crystal growth were interpreted based on their influences on sol network structure. Copyright © 2016 Elsevier B.V. All rights reserved.

Fabrication of a high-density nano-porous structure on polyimide by using ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Ma, Yong-Won; Jeong, Myung Yung; Lee, Sang-Mae; Shin, Bo Sung

2016-03-01

A new approach for fabricating a high-density nano-porous structure on polyimide (PI) by using a 355-nm UV laser is presented here. When PI was irradiated by using a laser, debris that had electrical conductivity was generated. Accordingly, that debris caused electrical defects in the field of electronics. Thus, many researchers have tried to focus on a clean processing without debris. However, this study focused on forming a high density of debris so as to fabricate a nano-porous structure consisting of nanofibers on the PI film. A PI film with closed pores and open pores was successfully formed by using a chemical blowing agent (azodicarbonamide, CBA) in an oven. Samples were precured at 130 °C and cured at 205 °C in sequence so that the closed pores might not coalesce in the film. When the laser irradiated the PI film with closed pores, nanofibers were generated because polyimide was not completely decomposed by photochemical ablation. Our results indicated that a film with micro-closed pores, in conjunction with a 355-nm pulsed laser, can facilitate the fabrication of a high-density nano-porous structure.

Sulfur-Containing Organic-Inorganic Hybrid Gel Compositions and Aerogels

NASA Technical Reports Server (NTRS)

Evans, Owen R (Inventor); Deshpande, Kiranmayi (Inventor); Dong, Wenting (Inventor)

2017-01-01

Methods and materials are described for preparing organic-inorganic hybrid gel compositions where a sulfur-containing cross-linking agent covalently links the organic and inorganic components. The gel compositions are further dried to provide porous gel compositions and aerogels. The mechanical and thermal properties of the dried gel compositions are also disclosed.

Sulfur-Containing Organic-Inorganic Hybrid Gel Compositions and Aerogels

NASA Technical Reports Server (NTRS)

Deshpande, Kiranmayi (Inventor); Evans, Owen R. (Inventor); Dong, Wenting (Inventor)

2015-01-01

Methods and materials are described for preparing organic-inorganic hybrid gel compositions where a sulfur-containing cross-linking agent covalently links the organic and inorganic components. The gel compositions are further dried to provide porous gel compositions and aerogels. The mechanical and thermal properties of the dried gel compositions are also disclosed.

Imaging samples in silica aerogel using an experimental point spread function.

PubMed

White, Amanda J; Ebel, Denton S

2015-02-01

Light microscopy is a powerful tool that allows for many types of samples to be examined in a rapid, easy, and nondestructive manner. Subsequent image analysis, however, is compromised by distortion of signal by instrument optics. Deconvolution of images prior to analysis allows for the recovery of lost information by procedures that utilize either a theoretically or experimentally calculated point spread function (PSF). Using a laser scanning confocal microscope (LSCM), we have imaged whole impact tracks of comet particles captured in silica aerogel, a low density, porous SiO2 solid, by the NASA Stardust mission. In order to understand the dynamical interactions between the particles and the aerogel, precise grain location and track volume measurement are required. We report a method for measuring an experimental PSF suitable for three-dimensional deconvolution of imaged particles in aerogel. Using fluorescent beads manufactured into Stardust flight-grade aerogel, we have applied a deconvolution technique standard in the biological sciences to confocal images of whole Stardust tracks. The incorporation of an experimentally measured PSF allows for better quantitative measurements of the size and location of single grains in aerogel and more accurate measurements of track morphology.

Organic aerogel microspheres

DOEpatents

Mayer, Steven T.; Kong, Fung-Ming; Pekala, Richard W.; Kaschmitter, James L.

1999-01-01

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Incorporation of noble metals into aerogels

DOEpatents

Hair, Lucy M.; Sanner, Robert D.; Coronado, Paul R.

1998-01-01

Aerogels or xerogels containing atomically dispersed noble metals for applications such environmental remediation. New noble metal precursors, such as Pt--Si or Pd(Si--P).sub.2, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

Supercritical fluid extraction as a means of reducing the carbon contamination inherent in samples of silica aerogel destined for the capture of CHON cosmic dust particles in space

NASA Astrophysics Data System (ADS)

Huang, H.-P.; Wright, I. P.; Gilmour, I.; Pillinger, C. T.

1994-11-01

Silica aerogel represents an ideal material for use as a cosmic dust capture medium. Its low density enables impacting particles to decelerate and stop within a small quality of the material, but without any severe heating. Hence the particles, which remain unmelted, can subsequently be removed and studied. Since a large proportion of the prospective cosmic dust is likely to be enriched in elements such as carbon and hydrogen (typically 5 wt% C, 20 wt% H2O), it is imperative that the aerogel used in the capture cell contains minimal quantities of these elements. Unfortunately the lowest density aerogels contain carbon at levels of 5 wt%; water is present in even greater amounts. Thus, techniques need to be identified to remove these contaminants. Herein, an attempt is made to use supercritical fluid extraction to remove carbon (and water). The investigation was tried to identify the most suitable parameters (i.e. CO2 density, solvating power using single or multiple extractions, use of modifier, etc.) necessary for removal of contaminants. A set of conditions was derived which was able to remove 90% of carbon contaminants from an aerogel of 0.12 g/cu cm density. This involved the use of multiple extractions with gradient temperatures (i.e. variable CO2 density), but without the use of a methanol modifier. Unfortunately, the same technique was less efficacious at removing carbon from aerogels with densities less than 0.12 g/cu cm. At present the extraction procedure has only been tried on a laboratory scale, but clearly this could be scaled-up in the future.

The possible crossover effects of NaNO3 confined in porous media: From bulk to clusters

NASA Astrophysics Data System (ADS)

Mu, R.; Jin, F.; Morgan, S. H.; Henderson, D. O.; Silberman, E.

1994-05-01

Differential scanning calorimetry (DSC) and Raman spectra are reported for NaNO3 bulk and for NaNO3 confined in porous silica with pore radii, rp=2.5, 5, 10, 20 nm. Raman spectra are also given for a 6 M solution of NaNO3. The melting transition for the confined NaNO3 exhibits a 1/rp dependence where rp is the pore radius for rp≳5 nm. No melting transition is observed for NaNO3 confined in 2.5 nm pores. Above this pore size, their appears to be a deviation in the melting transition dependence on rp. The internal modes observed in the Raman spectra for the confined material are in agreement with those of the bulk solid except for a feature observed on the low frequency side of the ν1 band. The external TO mode observed at 100 cm-1 and the librational mode at 175 cm-1 for NaNO3 both decrease in intensity and broaden as rp decreases and both bands disappear at rp=2.5 nm. An additional peak at 70 cm-1 not observed in the solution or bulk NaNO3 spectra appears in the spectra of confined NaNO3 and increases in intensity as rp decreases. We assign this band to a new phase of NaNO3 which is stabilized by the surface hydroxyl groups of the porous silica. For NaNO3 confined in pores, rp≤2.5 nm, we suggest that NaNO3 exists as disordered aggregates.

Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel.

PubMed

Cerkauskaite, Ausra; Drevinskas, Rokas; Rybaltovskii, Alexey O; Kazansky, Peter G

2017-04-03

We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

Constructing three-dimensional porous graphene-carbon quantum dots/g-C3N4 nanosheet aerogel metal-free photocatalyst with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

He, Huijuan; Huang, Langhuan; Zhong, Zijun; Tan, Shaozao

2018-05-01

Photocatalysis has been widely considered to be an effective way for solving the worldwide environmental pollution issues. Herein, a new type of three-dimensional (3D) ternary graphene-carbon quantum dots/g-C3N4 nanosheet (GA-CQDs/CNN) aerogel visible-light-driven photocatalyst was synthesized via a two-step hydrothermal method. In this unique ternary photocatalyst, both carbon quantum dots (CQDs) and reduced graphene oxide (rGO) could improve the visible light absorption and promote the charge separation. Furthermore, reduced graphene oxide (rGO) could act as a supportor for the 3D framework. Such a ternary system overcame the drawbacks of bulk g-C3N4 (BCN) and achieved the enhanced photocatalytic activity and long-term stability. As a result, the methyl orange (MO) removal ratio of GA-CQDs/CNN-24% was up to 91.1%, which was about 7.6 times higher than that of bulk g-C3N4 (BCN) under the identical conditions. Moreover that GA-CQDs/CNN-24% exhibited inappreciable loss of photocatalytic activity after four-cycle degradation processes. Finally, the photocatalytic mechanism of GA-CQDs/CNN-24% was interpreted both theoretically and experimentally.

Highly effective removal of basic fuchsin from aqueous solutions by anionic polyacrylamide/graphene oxide aerogels.

PubMed

Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Chen, Long; Hu, Song; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

2015-09-01

Novel anionic polyacrylamide/graphene oxide aerogels were prepared by a freeze drying method and used to remove basic fuchsin from aqueous solutions. These aerogels were sponge-like solid with lightweight, fluffy and porous structure. The batch adsorption experiments were carried out to study the effect of various parameters, such as the solution pH, adsorbent dose, contact time and temperature on adsorption properties of basic fuchsin onto anionic polyacrylamide/graphene oxide aerogels. The kinetics of adsorption corresponded to the pseudo-second-order kinetic model. The Langmuir adsorption isotherm was suitable to describe the equilibrium adsorption process. The maximum adsorption capacity was up to 1034.3 mg/g, which indicated that anionic polyacrylamide/graphene oxide aerogels were promising adsorbents for removing dyes pollutants from aqueous solution. Copyright © 2015 Elsevier Inc. All rights reserved.

Three dimensional macroporous architectures and aerogels built of carbon nanotubes and/or graphene: synthesis and applications.

PubMed

Nardecchia, Stefania; Carriazo, Daniel; Ferrer, M Luisa; Gutiérrez, María C; del Monte, Francisco

2013-01-21

Carbon nanotubes and graphene are some of the most intensively explored carbon allotropes in materials science. This interest mainly resides in their unique properties with electrical conductivities as high as 10(4) S cm(-1), thermal conductivities as high as 5000 W m(-1) K and superior mechanical properties with elastic moduli on the order of 1 TPa for both of them. The possibility to translate the individual properties of these monodimensional (e.g. carbon nanotubes) and bidimensional (e.g. graphene) building units into two-dimensional free-standing thick and thin films has paved the way for using these allotropes in a number of applications (including photocatalysis, electrochemistry, electronics and optoelectronics, among others) as well as for the preparation of biological and chemical sensors. More recently and while recognizing the tremendous interest of these two-dimensional structures, researchers are noticing that the performance of certain devices can experience a significant enhancement by the use of three-dimensional architectures and/or aerogels because of the increase of active material per projected area. This is obviously the case as long as the nanometre-sized building units remain accessible so that the concept of hierarchical three-dimensional organization is critical to guarantee the mass transport and, as consequence, performance enhancement. Thus, this review aims to describe the different synthetic processes used for preparation of these three-dimensional architectures and/or aerogels containing either any or both allotropes, and the different fields of application in which the particular structure of these materials provided a significant enhancement in the efficacy as compared to their two-dimensional analogues or even opened the path to novel applications. The unprecedented compilation of information from both CNT- and graphene-based three-dimensional architectures and/or aerogels in a single revision is also of interest because it allows

Incorporation of noble metals into aerogels

DOEpatents

Hair, L.M.; Sanner, R.D.; Coronado, P.R.

1998-12-22

Aerogels or xerogels containing atomically dispersed noble metals for applications such as environmental remediation are disclosed. New noble metal precursors, such as Pt--Si or Pd(Si--P){sub 2}, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

An environmentally benign route for the development of compressible, thermally insulating and fire retardant aerogels through self-assembling the silk fibroin biopolymer inside the silica structure - An approach towards 3D printing of aerogels.

PubMed

Maleki, Hajar; Montes, Susan; Hayati-Roodbari, Nastaran; Putz, Florian; Huesing, Nicola

2018-06-04

Thanks to the exceptional materials properties of silica aerogels, this fascinating highly porous material has found high performance and real-life applications in various modern industries. However, a requirement for a broadening of these applications is based on the further improvement of their properties especially with regard to mechanical strength and post-synthesis processability with minimum compromise to the other physical properties. Here, we report an entirely novel, simple and aqueous based synthesis approach to prepare mechanically robust aerogel hybrids by co-gelation of silk fibroin (SF) biopolymer, extracted from silkworm cocoons. The synthesis is based on a one-step sequential processes of acid catalysis (physical) crosslinking of the SF biopolymer and simultaneous polycondensation of tetramethyl orthosilicate (TMOS), in the presence of 5-(trimethoxysilyl)pentanoic acid (TMSPA) as a coupling agent and subsequent solvent exchange and supercritical drying. Extensive characterizations by solid-state 1H-NMR, 29Si-NMR, and 2D 1H-29Si heteronuclear correlation (HETCOR) MAS NMR spectroscopy as well as various microscopic techniques (SEM, TEM) and mechanical assessment, confirmed the molecular-level homogeneity of the hybrid nanostructure. The developed silica-SF aerogel hybrids contained an improved set of material properties, such as low density (ρb, average = 0.11 - 0.2 g cm-3), high porosity (~90%), high specific surface area (~ 400-800 m2 g-1), excellent flexibility in compression (up to 80% of strain) with three-order of magnitude improvement in the Young's modulus over that of pristine silica aerogels. In addition, the silica-SF hybrid aerogels are fire retardant and demonstrated excellent thermal insulation performance with thermal conductivities (λ) of (0.033-0.039 Wm-1 K-1). As a further advantage, the formulated hybrid silica-SF aerogel showed an excellent printability in the wet state using a micro-extrusion based 3D printing approach. The

Aerogels Derived from Polymer Nanofibers and Their Applications.

PubMed

Qian, Zhenchao; Wang, Zhen; Zhao, Ning; Xu, Jian

2018-03-08

Aerogels are gels in which the solvent is supplanted by air while the pores and networks are largely maintained. Owing to their low bulk density, high porosity, and large specific surface area (SSA), aerogels are promising for many applications. Various inorganic aerogels, e.g., silica aerogels, are intensively studied. However, the mechanical brittleness of common inorganic aerogels has seriously restricted their applications. In the past decade, nanofibers have been developed as building blocks for the construction of aerogels to improve their mechanical property. Unlike traditional frameworks constructed by interconnected particles, nanofibers can form chemically cross-linked and/or physically entangled 3D skeletons, thus showing flexibility instead of brittleness. Therefore, excellent elasticity and toughness, ultralow density, high SSA, and tunable chemical composition can be expected for the polymer nanofiber-derived aerogels (PNAs). In this review, recent research progress in the fabrication, properties, and applications of PNAs is summarized. Various nanofibers, including nanocelluloses, nanochitins, and electrospun nanofibers are included, as well as carbon nanofibers from the corresponding organic precursors. Typical applications in supercapacitors, electrocatalysts for oxygen reduction reaction, flexible electrodes, oil absorbents, adsorbents, tissue engineering, stimuli-responsive materials, and catalyst carriers, are presented. Finally, the challenges and future development of PNAs are discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aerogel Development

NASA Technical Reports Server (NTRS)

Sahai, Rashmi K.

2005-01-01

Aerogel is one of the most promising materials of the future. It's unique properties, including high porosity, transparency, very high thermal tolerance, and environmental friendliness give it the potential of replacing many different products used in society today. However, the market for aerogel is still very limited because of the cost of producing the material and its fragility. The principle objective of my project has been to find new ways to apply aerogel in order to increase its practicality and appeal to different aspects of society. More specifically, I have focused on finding different chemicals that will coat aerogel and increase its durability. Because aerogel is so fragile and will crumble under the pressure of most coatings this has been no easy task. However, by experimenting with many different coatings and combinations of aerogel properties, I have made several significant discoveries. Aerogel (ideally, high density and hydrophobic) can be coated with several acrylic polymers, including artist's gel and nail polish. These materials provide a protective layering around the aerogel and keep it from breaking as easily. Because fragility is one of the main reasons applications of aerogel are limited, these discoveries will hopefully aid in finding future applications for this extraordinary material.

Synthesis of Porous Carbon Monoliths Using Hard Templates.

PubMed

Klepel, Olaf; Danneberg, Nina; Dräger, Matti; Erlitz, Marcel; Taubert, Michael

2016-03-21

The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m²·g -1 . The pore system comprised macro-, meso-, and micropores. These pores were hierarchically arranged. The pore system was created by the complex interplay of the actions of both the template and the activating agent as well. On the other hand, zeolite-made template shapes allowed for the preparation of microporous carbon monoliths with a high volumetric specific surface area. This feature could be beneficial if carbon monoliths must be integrated into technical systems under space-limited conditions.

Synthesis of Porous Carbon Monoliths Using Hard Templates

PubMed Central

Klepel, Olaf; Danneberg, Nina; Dräger, Matti; Erlitz, Marcel; Taubert, Michael

2016-01-01

The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m2·g−1. The pore system comprised macro-, meso-, and micropores. These pores were hierarchically arranged. The pore system was created by the complex interplay of the actions of both the template and the activating agent as well. On the other hand, zeolite-made template shapes allowed for the preparation of microporous carbon monoliths with a high volumetric specific surface area. This feature could be beneficial if carbon monoliths must be integrated into technical systems under space-limited conditions. PMID:28773338

Organic aerogel microspheres

DOEpatents

Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

1999-06-01

Organic aerogel microspheres are disclosed which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonstick gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Aerogels in Chemical Engineering: Strategies Toward Tailor-Made Aerogels.

PubMed

Smirnova, Irina; Gurikov, Pavel

2017-06-07

The present review deals with recent advances in the rapidly growing field of aerogel research and technology. The major focus of the review lies in approaches that allow tailoring of aerogel properties to meet application-driven requirements. The decisive properties of aerogels are discussed with regard to existing and potential application areas. Various tailoring strategies, such as modulation of the pore structure, coating, surface modification, and post-treatment, are illustrated by results of the last decade. In view of commercialization of aerogel-based products, a panorama of current industrial aerogel suppliers is given, along with a discussion of possible alternative sources for raw materials and precursors. Finally, growing points and perspectives of the aerogel field are summarized.

Facile Fabrication of Nanofibrillated Chitin/Ag2O Heterostructured Aerogels with High Iodine Capture Efficiency.

PubMed

Gao, Runan; Lu, Yun; Xiao, Shaoliang; Li, Jian

2017-06-27

Nanofibrillated chitin/Ag 2 O aerogels were fabricated for radioiodine removal. Chitin was first fabricated into nanofibers with abundant acetyl amino groups (-NHCOCH 3 ) on the surface. Then, highly porous chitin nanofiber (ChNF) aerogels were obtained via freeze-drying. The ChNF aerogels exhibited a low bulk density of 2.19 mg/cm 3 and a high specific surface area of 179.71 m 2 /g. Ag 2 O nanoparticles were evenly anchored on the surfaces of ChNF scaffolds via strong interactions with -NHCOCH 3 groups, subsequently yielding Ag 2 O@ChNF heterostructured aerogels. The composites were used as efficient absorbents to remove radioiodine anions from water and capture a high amount of I 2 vapor in the forms of AgI and iodine molecules. The adsorption capacity of the composite monoliths can reach up to 2.81 mmol/g of I - anions. The high adsorbability of the composite monolithic aerogel signifies its potential applications in radioactive waste disposal.

Mesoporous MnO2/carbon aerogel composites as promising electrode materials for high-performance supercapacitors.

PubMed

Li, Gao-Ren; Feng, Zhan-Ping; Ou, Yan-Nan; Wu, Dingcai; Fu, Ruowen; Tong, Ye-Xiang

2010-02-16

MnO(2) as one of the most promising candidates for electrochemical supercapacitors has attracted much attention because of its superior electrochemical performance, low cost, and environmentally benign nature. In this Letter, we explored a novel route to prepare mesoporous MnO(2)/carbon aerogel composites by electrochemical deposition assisted by gas bubbles. The products were characterized by energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The MnO(2) deposits are found to have high purity and have a mesoporous structure that will optimize the electronic and ionic conductivity to minimize the total resistance of the system and thereby maximize the performance characteristics of this material for use in supercapacitor electrodes. The results of nitrogen adsorption-desorption experiments and electrochemical measurements showed that these obtained mesoporous MnO(2)/carbon aerogel composites had a large specific surface area (120 m(2)/g), uniform pore-size distribution (around 5 nm), high specific capacitance (515.5 F/g), and good stability over 1000 cycles, which give these composites potential application as high-performance supercapacitor electrode materials.

3D Synergistical MXene/Reduced Graphene Oxide Aerogel for a Piezoresistive Sensor.

PubMed

Ma, Yanan; Yue, Yang; Zhang, Hang; Cheng, Feng; Zhao, Wanqiu; Rao, Jiangyu; Luo, Shijun; Wang, Jie; Jiang, Xueliang; Liu, Zhitian; Liu, Nishuang; Gao, Yihua

2018-04-24

A piezoresistive sensor based on ultralight and superelastic aerogel is reported to fabricate MXene/reduced graphene oxide (MX/rGO) hybrid 3D structures and utilize their pressure-sensitive characteristics. The MX/rGO aerogel not only combines the rGO's large specific surface area and the MXene's (Ti 3 C 2 T x ) high conductivity but also exhibits rich porous structure, which leads to performance better than that of single-component rGO or MXene in terms of the pressure sensor. The large nanosheets of rGO can prevent the poor oxidization of MXene by wrapping MXene inside the aerogel. More importantly, the piezoresistive sensor based on the MX/rGO aerogel shows extremely high sensitivity (22.56 kPa -1 ), fast response time (<200 ms), and good stability over 10 000 cycles. The piezoresistive sensor based on the MX/rGO hybrid 3D aerogel can easily capture the signal below 10 Pa, thus clearly testing the pulse of an adult at random. Based on its superior performance, it also demonstrates potential applications in measuring pressure distribution, distinguishing subtle strain, and monitoring healthy activity.

Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solid-state supercapacitors

Treesearch

Qifeng Zheng; Zhiyong Cai; Zhenqiang Ma; Shaoqin Gong

2015-01-01

A novel type of highly flexible and all-solid-state supercapacitor that uses cellulose nanofibril (CNF)/reduced graphene oxide (RGO)/carbon nanotube (CNT) hybrid aerogels as electrodes and H2SO4 poly (vinyl alcohol) PVA gel as the electrolyte was developed and is reported here. These flexible solid-state supercapacitors...

Bonding Unidirectional Carbon Nanotube with Carbon for High Performance

DTIC Science & Technology

2015-06-24

the longest time of 80 minutes had an aerogel -like density, with CNT packing density lower than even the as-grown CNT array. This highly porous nature...nanotube foams with ultralow densities. Unlike other routes for fabrication of CNT aerogels , foam and sponges, this processing method allows the fast

Method for nano-pumping using carbon nanotubes

DOEpatents

Insepov, Zeke [Darien, IL; Hassanein, Ahmed [Bolingbrook, IL

2009-12-15

The present invention relates generally to the field of nanotechnology, carbon nanotubes and, more specifically, to a method and system for nano-pumping media through carbon nanotubes. One preferred embodiment of the invention generally comprises: method for nano-pumping, comprising the following steps: providing one or more media; providing one or more carbon nanotubes, the one or more nanotubes having a first end and a second end, wherein said first end of one or more nanotubes is in contact with the media; and creating surface waves on the carbon nanotubes, wherein at least a portion of the media is pumped through the nanotube.

Single-layer nano-carbon film, diamond film, and diamond/nano-carbon composite film field emission performance comparison

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaoping, E-mail: wxpchina64@aliyun.com, E-mail: wxpchina@sohu.com; Shanghai Key Laboratory of Modern Optical System, Shanghai 200093; Wang, Jinye

A series of single-layer nano-carbon (SNC) films, diamond films, and diamond/nano-carbon (D/NC) composite films have been prepared on the highly doped silicon substrate by using microwave plasma chemical vapor deposition techniques. The films were characterised by scanning electron microscopy, Raman spectroscopy, and field emission I-V measurements. The experimental results indicated that the field emission maximum current density of D/NC composite films is 11.8–17.8 times that of diamond films. And the field emission current density of D/NC composite films is 2.9–5 times that of SNC films at an electric field of 3.0 V/μm. At the same time, the D/NC composite film exhibitsmore » the advantage of improved reproducibility and long term stability (both of the nano-carbon film within the D/NC composite cathode and the SNC cathode were prepared under the same experimental conditions). And for the D/NC composite sample, a high current density of 10 mA/cm{sup 2} at an electric field of 3.0 V/μm was obtained. Diamond layer can effectively improve the field emission characteristics of nano-carbon film. The reason may be due to the diamond film acts as the electron acceleration layer.« less

Method of low pressure and/or evaporative drying of aerogel

DOEpatents

Mayer, S.T.; Kaschmitter, J.L.; Pekala, R.W.

1995-05-30

A process is described whereby Resorcinol/Formaldehyde (RF) aerogel having a density of about 0.4--1.2 g/cc can be manufactured using a simple air drying procedure. This process is inherently simpler, quicker, and less expensive than the more conventional supercritical or subcritical CO{sub 2} extraction procedures. RF aerogels can be used as produced, such as in insulation applications, or pyrolyzed to form carbon aerogels with a density of about 0.9 g/cc for use in applications such as batteries, supercapacitors, etc.

Method of low pressure and/or evaporative drying of aerogel

DOEpatents

Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

1995-01-01

A process whereby Resorcinol/Formaldehyde (RF) aerogel having a density of about 0.4-1.2 g/cc can be manufactured using a simple air drying procedure. This process is inherently simpler, quicker, and less expensive than the more conventional supercritical or subcritical CO.sub.2 extraction procedures. RF aerogels can be used as produced, such as in insulation applications, or pyrolyzed to form carbon aerogels with a density of about 0.9 g/cc for use in applications such as batteries, supercapacitors, etc.

Chitosan-graphene oxide films and CO2-dried porous aerogel microspheres: Interfacial interplay and stability.

PubMed

Frindy, Sana; Primo, Ana; Ennajih, Hamid; El Kacem Qaiss, Abou; Bouhfid, Rachid; Lahcini, Mohamed; Essassi, El Mokhtar; Garcia, Hermenegildo; El Kadib, Abdelkrim

2017-07-01

The intimate interplay of chitosan (CS) and graphene oxide (GO) in aqueous acidic solution has been explored to design upon casting, nanostructured "brick-and-mortar" films (CS-GO-f) and by acidic-to-basic pH inversion, porous CO 2 -dried aerogel microspheres (CS-GO-m). Owing to the presence of oxygenated functional groups in GO, good-quality crack-free hybrid films were obtained. Mechanical properties were improved independently of the GO content and it was found that a 20wt% loading affords hybrid film characterized with a Young modulus three times superior to that reached with the same loading of layered clay. The presence of graphene oxide was found to be detrimental for the thermal stability of the polysaccharide at T <350°C, a fact attributed to the well-established decomposition of the oxygenated functional groups of the graphene sheets. Irrespective to the graphene oxide loading, chitosan-graphene oxide mixture preserves the gelation memory of the polysaccharide. Supercritical drying of the resulting soft hydrogels provides macroporous network with surface areas ranging from 226m 2 g -1 to 554m 2 g -1 . XPS and RAMAN analyses evidenced the selective reduction of GO sheets inside of these microspheres, affording the hitherto unknown macroporous chitosan-entangled-reduced graphene oxide (CS-rGO-m) aerogels. Improvement in both hydrothermal stability (under water reflux) and chemical stability (under acidic conditions) have been noticed for chitosan-graphene oxide microspheres with respect to non-modified chitosan and chitosan-clay bio-hybrids, a result rooted in the substantial hydrophobic character imparted by the addition of graphenic material to the polysaccharide skeleton. In essence, this contribution demonstrates that graphene oxide loading do not disturb neither the filmogenicity of chitosan nor its gelation ability and constitutes a promising route for novel chitosan-based functional hybrid materials. Copyright © 2017 Elsevier Ltd. All rights

Robust, Flexible and Lightweight Dielectric Barrier Discharge Actuators Using Nanofoams/Aerogels

NASA Technical Reports Server (NTRS)

Siochi, Emilie J. (Inventor); Sauti, Godfrey (Inventor); Wilkinson, Stephen P. (Inventor); Guo, Haiquan N. (Inventor); Xu, Tian-Bing (Inventor); Meador, Mary Ann B. (Inventor)

2015-01-01

Robust, flexible, lightweight, low profile enhanced performance dielectric barrier discharge actuators (plasma actuators) based on aerogels/nanofoams with controlled pore size and size distribution as well as pore shape. The plasma actuators offer high body force as well as high force to weight ratios (thrust density). The flexibility and mechanical robustness of the actuators allows them to be shaped to conform to the surface to which they are applied. Carbon nanotube (CNT) based electrodes serve to further decrease the weight and profile of the actuators while maintaining flexibility while insulating nano-inclusions in the matrix enable tailoring of the mechanical properties. Such actuators are required for flow control in aeronautics and moving machinery such as wind turbines, noise abatement in landing gear and rotary wing aircraft and other applications.

Cobalt sulfide aerogel prepared by anion exchange method with enhanced pseudocapacitive and water oxidation performances.

PubMed

Gao, Qiuyue; Shi, Zhenyu; Xue, Kaiming; Ye, Ziran; Hong, Zhanglian; Yu, Xinyao; Zhi, Mingjia

2018-05-25

This work introduces the anion exchange method into the sol-gel process for the first time to prepare a metal sulfide aerogel. A porous Co 9 S 8 aerogel with a high surface area (274.2 m 2 g -1 ) and large pore volume (0.87 cm 3 g -1 ) has been successfully prepared by exchanging cobalt citrate wet gel in thioacetamide and subsequently drying in supercritical ethanol. Such a Co 9 S 8 aerogel shows enhanced supercapacitive performance and catalytic activity toward oxygen evolution reaction (OER) compared to its oxide aerogel counterpart. High specific capacitance (950 F g -1 at 1 A g -1 ), good rate capability (74.3% capacitance retention from 1 to 20 A g -1 ) and low onset overpotential for OER (220 mV) were observed. The results demonstrated here have implications in preparing various sulfide chalcogels.

Cobalt sulfide aerogel prepared by anion exchange method with enhanced pseudocapacitive and water oxidation performances

NASA Astrophysics Data System (ADS)

Gao, Qiuyue; Shi, Zhenyu; Xue, Kaiming; Ye, Ziran; Hong, Zhanglian; Yu, Xinyao; Zhi, Mingjia

2018-05-01

This work introduces the anion exchange method into the sol-gel process for the first time to prepare a metal sulfide aerogel. A porous Co9S8 aerogel with a high surface area (274.2 m2 g‑1) and large pore volume (0.87 cm3 g‑1) has been successfully prepared by exchanging cobalt citrate wet gel in thioacetamide and subsequently drying in supercritical ethanol. Such a Co9S8 aerogel shows enhanced supercapacitive performance and catalytic activity toward oxygen evolution reaction (OER) compared to its oxide aerogel counterpart. High specific capacitance (950 F g‑1 at 1 A g‑1), good rate capability (74.3% capacitance retention from 1 to 20 A g‑1) and low onset overpotential for OER (220 mV) were observed. The results demonstrated here have implications in preparing various sulfide chalcogels.

Ambient Dried Aerogels

NASA Technical Reports Server (NTRS)

Jones, Steven M.; Paik, Jong-Ah

2013-01-01

A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks

NASA Technical Reports Server (NTRS)

Miller, Sandi; Leventis, Nicholas; Johnston, J. Chris; Meador, Michael

2006-01-01

GRC research has led to the development of epoxy-clay nanocomposites with 60-70% lower gas permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. More recent work has produced new composites with more than a 100-fold reduction in helium permeability. Use of these advanced, high barrier composites would eliminate the need for a liner in composite cryotanks, thereby simplifying construction and reducing propellant leakage. Aerogels are attractive materials for use as cryotank insulation because of their low density and low thermal conductivity. However, aerogels are fragile and have poor environmental stability, which have limited their use to certain applications in specialized environments (e.g., in certain types of nuclear reactors as Cerenkov radiation detectors, and as thermal insulators aboard space rovers on Mars). New GRC developed polymer crosslinked aerogels (X-Aerogels) retain the low density of conventional aerogels, but they demonstrate a 300-fold increase in their mechanical strength. Currently, our strongest materials combine a density of approx. 0.45 g/cc, a thermal conductivity of approx. 0.04 W/mK and a compressive strength of 185 MPa. Use of these novel aerogels as insulation materials/structural components in combination with the low permeability of epoxy-clay nanocomposites could significantly reduce cryotank weight and improve durability.

Coupling Mo2C@C core-shell nanocrystals on 3D graphene hybrid aerogel for high-performance lithium ion battery

NASA Astrophysics Data System (ADS)

Xin, Hailin; Hai, Yang; Li, Dongzhi; Qiu, Zhaozheng; Lin, Yemao; Yang, Bo; Fan, Haosen; Zhu, Caizhen

2018-05-01

Hybrid aerogel by dispersing Mo2C@C core-shell nanocrystals into three-dimensional (3D) graphene (Mo2C@C-GA) has been successfully prepared through two-step methods. Firstly, carbon-coated MoO2 nanocrystals uniformly anchor on 3D graphene aerogel (MoO2@C-GA) via hydrothermal reaction. Then the MoO2@C-GA precursor is transformed into Mo2C@C-GA after the following carbonization process. Furthermore, the freeze-drying step plays an important role in the resulting pore size distribution of the porous networks. Moreover, graphene aerogels exhibit extremely low densities and superior electrical properties. When evaluated as anode material for lithium ion battery, Mo2C@C-GA delivers excellent rate capability and stable cycle performance when compared with C-GA and Mo2C nanoparticles. Mo2C@C-GA exhibits the initial discharge capacity of 1461.4 mA h g-1 at the current density of 0.1 A g-1, and retains a reversible capacity of 1089.8 mA h g-1 after 100 cycles at a current density of 0.1 A g-1. Even at high current density of 5 A g-1, a discharge capacity of 623.5 mA h g-1 can be still achieved. The excellent performance of Mo2C@C-GA could be attributed to the synergistic effect of Mo2C@C nanocrystals and the 3D graphene conductive network.

Comparison of porous and nano zinc oxide for replacing high-dose dietary regular zinc oxide in weaning piglets

PubMed Central

Long, Lina; Chen, Jiashun; Zhang, Yonggang; Liang, Xiao

2017-01-01

The aim of this study was to compare the effect of dietary supplementation with low dose of porous and nano zinc oxide (ZnO) on weaning piglets, and to evaluate the possibility of using them as an alternative to high dose of regular ZnO. Piglets were randomly allocated into four treatment groups fed with four diets: (1) basal diet (NC), (2) NC+ 3000 mg/kg ZnO (PC), (3) NC + 500 mg/kg porous ZnO (HiZ) and (4) NC + 500 mg/kg nano ZnO (ZNP). The result showed that piglets in HiZ group had less diarrhea than ZNP group (P < 0.05). Besides, there was no significant difference between PC, HiZ and ZNP groups in terms of serum malondialdeyhde (MDA) concentration and glutathione peroxidase (GSH-Px) activity (P > 0.05). Analysis of trace metal elements revealed that piglets fed with high dose of regular ZnO had the highest Zn level in kidney (P < 0.05), which may induce kidney stone formation. Additionally, a decrease in ileal crypt depth was observed in PC, HiZ and ZNP group, suggesting an effective protection against intestinal injury. Results of mRNA analysis in intestine showed that ZNP supplementation had better effects on up-regulated trefoil factor 3 (TFF3) and nuclear factor erythroid 2-related factor 2 (Nrf2) levels in duodenum and jejunum than HiZ did (P < 0.05), implying that nano ZnO may possess higher anti-inflammatory capacity than porous ZnO. In conclusion, dietary supplementation with low dose of porous and nano ZnO had similar (even better) effect on improving growth performance and intestinal morphology, reducing diarrhea and intestinal inflammatory as high dose of regular ZnO in weaning piglets. Compared with nano ZnO, porous ZnO had better performance on reducing diarrhea but less effect on up-regulation of intestinal TFF3 and Nrf2. PMID:28792520

Superhydrophobic Silicon Nanocrystal-Silica Aerogel Hybrid Materials: Synthesis, Properties, and Sensing Application.

PubMed

Kehrle, Julian; Purkait, Tapas K; Kaiser, Simon; Raftopoulos, Konstantinos N; Winnacker, Malte; Ludwig, Theresa; Aghajamali, Maryam; Hanzlik, Marianne; Rodewald, Katia; Helbich, Tobias; Papadakis, Christine M; Veinot, Jonathan G C; Rieger, Bernhard

2018-04-24

Silicon nanocrystals (SiNCs) are abundant and exhibit exquisitely tailorable optoelectronic properties. The incorporation of SiNCs into highly porous and lightweight substrates such as aerogels leads to hybrid materials possessing the attractive features of both materials. This study describes the covalent deposition of SiNCs on and intercalation into silica aerogels, explores the properties, and demonstrates a prototype sensing application of the composite material. SiNCs of different sizes were functionalized with triethoxyvinylsilane (TEVS) via a radical grafting approach and subsequently used for the synthesis of photoluminescent silica hybrids. The resulting SiNC-containing aerogels possess high porosities, SiNC-based size-dependent photoluminescence, transparency, and a superhydrophobic macroscopic surface. The materials were used to examine the photoluminescence response toward low concentrations of 3-nitrotoluene (270 μM), demonstrating their potential as a sensing platform for high-energy materials.

Study on Locally Confined Deposition of Si Nanocrystals in High-Aspect-Ratio Si Nano-Pillar Arrays for Nano-Electronic and Nano-Photonic Applications II

DTIC Science & Technology

2010-12-03

photoluminescence characteristics of equivalent-size controlled silicon quantum dots by employing a nano-porous aluminum oxide membrane as the template for growing...synthesis of Si quantum dots (Si-QDs) embedded in low-temperature (500oC) annealed Si-rich SiOx nano-rod deposited in nano-porous anodic aluminum oxide ...characteristics of the equivalent-size controlled Si-QDs by employing the nano-porous AAO membrane as the template for growing Si-rich SiOx nano-rods

Porous Ni3(NO3)2(OH)4 nano-sheets for supercapacitors: Facile synthesis and excellent rate performance at high mass loadings

NASA Astrophysics Data System (ADS)

Shi, Mingjie; Cui, Mangwei; Kang, Litao; Li, Taotao; Yun, Shan; Du, Jing; Xu, Shoudong; Liu, Ying

2018-01-01

For supercapacitors, pores in electrode materials can accelerate chemical reaction kinetics by shortening ion diffusion distances and by enlarging electrolyte/electrode interfaces. This article describes a simple one-step route for the preparation of pure-phase porous Ni3(NO3)2(OH)4 nano-sheets by directly heating a mild Ni(NO3)2 and urea solution. During heating, urea decomposed into NH3·H2O, which provided a suitable alkaline environment for the formation of Ni3(NO3)2(OH)4 nano-sheets. Meanwhile, the side product, NH4NO3, created numerous pores as a pore-forming agent. After NH4NO3 removal, the specific surface areas and pore volumes of products were boosted by ∼180-times (from 0.61 to 113.12 m2/g) and ∼90-times (from 3.40 × 10-3 to 3.17 × 10-1 m2/g), respectively. As a cathode material of supercapacitor, the porous Ni3(NO3)2(OH)4 nano-sheets exhibited a high specific capacitance of 1094 F/g at an ultrahigh mass loading of 17.55 mg/cm2, leading to an impressive areal capacitance of 19.2 F/cm2. Furthermore, a Ni3(NO3)2(OH)4 nano-sheet//commercial active carbon asymmetric supercapacitor was constructed and delivered an energy density of 33.2 Wh/Kg at a power density of 190.5 W/Kg, based on the mass of active materials on both electrodes.

Nitrogen-doped hierarchical porous carbon microsphere through KOH activation for supercapacitors.

PubMed

Jiang, Jingui; Chen, Hao; Wang, Zhao; Bao, Luke; Qiang, Yiwei; Guan, Shiyou; Chen, Jianding

2015-08-15

A porous carbon microsphere with moderate specific surface area and superior specific capacitance for supercapacitors is fabricated from polyphosphazene microsphere as the single heteroatoms source by the carbonization and subsequent KOH activation under N2 atmosphere. With KOH activation, X-ray photoelectron spectroscopy analysis confirms that the phosphorus of polyphosphazene microsphere totally vanishes, and the doping content of nitrogen and its population of various functionalities on porous carbon microsphere surface are tuned. Compared with non-porous carbon microsphere, the texture property of the resultant porous carbon microsphere subjected to KOH activation has been remarkably developed with the specific surface area growing from 315 to 1341 m(2) g(-1)and the pore volume turning from 0.17 to 0.69 cm(3) g(-1). Prepared with the KOH/non-porous carbon microsphere weight ratio at 1.0, the porous carbon microsphere with moderate specific surface area of 568 m(2) g(-1), exhibits intriguing electrochemical behavior in 1 M H2SO4 aqueous electrolyte, with superior specific capacitance (278 F g(-1) at 0.1 A g(-1)), good rate capability (147 F g(-1) remained at 10 A g(-1)) and robust cycling durability (No capacitance loss after 5000 cycles). The promising electrochemical performance could be ascribed to the synergy of nitrogen heteroatom functionalities and the porous morphology. Copyright © 2015 Elsevier Inc. All rights reserved.

Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

NASA Astrophysics Data System (ADS)

Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon

2014-05-01

A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution ( i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested (-2°C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

Hydrothermal Carbonization of Microalgae (Chlorococcum sp.) for Porous Carbons With High Cr(VI) Adsorption Performance.

PubMed

Sun, Yuanyuan; Liu, Chang; Zan, Yifan; Miao, Gai; Wang, Hao; Kong, Lingzhao

2018-04-12

Porous carbon adsorbents were prepared from microalgae (Chlorococcum sp.) via directly hydrothermal carbonization coupled with KOH or NH 3 activation for Cr(VI) adsorption. KOH-activated porous carbons exhibit high Cr(VI) adsorption capacities than those obtained via NH 3 modification (370.37 > 95.70 mg/g). The superior Cr(VI) adsorption capacity is due to high surface areas (1784 m 2 /g) and pore volumes of porous carbon with mesoporous and macroporous structures. The Cr(VI) adsorption result was well fitted to the Langmuir model, showing that the removal of Cr(VI) was attributed to the monolayer adsorption of activity site on carbon surface.

Use of Nanofibers to Strengthen Hydrogels of Silica, Other Oxides, and Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Capadona, Lynn A.; Hurwitz, Frances; Vivod, Stephanie L.; Lake, Max

2010-01-01

Research has shown that including up to 5 percent w/w carbon nanofibers in a silica backbone of polymer crosslinked aerogels improves its strength, tripling compressive modulus and increasing tensile stress-at-break five-fold with no increase in density or decrease in porosity. In addition, the initial silica hydrogels, which are produced as a first step in manufacturing the aerogels, can be quite fragile and difficult to handle before cross-linking. The addition of the carbon nanofiber also improves the strength of the initial hydrogels before cross-linking, improving the manufacturing process. This can also be extended to other oxide aerogels, such as alumina or aluminosilicates, and other nanofiber types, such as silicon carbide.

On hydrophilicity improvement of the porous anodic alumina film by hybrid nano/micro structuring

NASA Astrophysics Data System (ADS)

Wang, Weichao; Zhao, Wei; Wang, Kaige; Wang, Lei; Wang, Xuewen; Wang, Shuang; Zhang, Chen; Bai, Jintao

2017-09-01

In both, laboratory and industry, tremendous attention is paid to discover an effective technique to produce uniform, controllable and (super) hydrophilic surfaces over large areas that are useful in a wide range of applications. In this investigation, by combing porous anodic alumina (PAA) film with nano-structures and microarray of aluminum, the hydrophilicity of hybrid nano-micro structure has been significantly improved. It is found some factors can affect the hydrophilicity of film, such as the size and aspect ratio of microarray, the thickness of nano-PAA film etc. Comparing with pure nano-PAA films and microarray, the hybrid nano-micro structure can provide uniform surface with significantly better hydrophilicity. The improvement can be up to 84%. Also, this technique exhibits good stability and repeatability for industrial production. By optimizing the thickness of nano-PAA film and aspect ratio of micro-structures, super-hydrophilicity can be reached. This study has obvious prospect in the fields of chemical industry, biomedical engineering and lab-on-a-chip applications.

Photocatalytic activity of self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition

NASA Astrophysics Data System (ADS)

Shi, Pengjun; Li, Xibo; Zhang, Qiuju; Yi, Zao; Luo, Jiangshan

2018-04-01

A well-separated and oriented TiO2 nano-columns arrays with porous structure were fabricated by the oblique angle sputter deposition technique and subsequently annealing at 450 °C in Ar/O2 mixed atmosphere. The deposited substrate was firstly modified by a template of self-assembled close-packed arrays of 500 nm-diameter silica (SiO2) spheres. Scanning electronic microscopic (SEM) images show that the porous columnar nanostructure is formed as a result of the geometric shadowing effect and surface diffusion of the adatoms in oblique angle deposition (OAD). X-ray diffraction (XRD) measurements reveal that the physically OAD film with annealing treatment are generally mixed phase of rutile and anatase TiO2 polymorphic forms. The morphology induced absorbance and band gap tuning by different substrates was demonstrated by the UV–vis spectroscopy. The well-separated one-dimensional (1D) nano-columns array with specific large porous surface area is beneficial for charge separation in photocatalytic degradation. Compared with compact thin film, such self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition performed an enhanced visible light induced photocatalytic activity by decomposing methyl orange (MO) solution. The well-designed periodic array-structured porous TiO2 films by using modified patterned substrates has been demonstrated significantly increased absorption edge in the UV-visible light region with a narrower optical band gap, which are expected to be favorable for application in photovoltaic, lithium-ion insertion and photocatalytic, etc.

Self-assembly of three-dimensional interconnected graphene-based aerogels and its application in supercapacitors.

PubMed

Ji, Chen-Chen; Xu, Mao-Wen; Bao, Shu-Juan; Cai, Chang-Jun; Lu, Zheng-Jiang; Chai, Hui; Yang, Fan; Wei, Hua

2013-10-01

Homogeneously distributed self-assembling hybrid graphene-based aerogels with 3D interconnected pores, employing three types of carbohydrates (glucose, β-cyclodextrin, and chitosan), have been fabricated by a simple hydrothermal route. Using three types of carbohydrates as morphology oriented agents and reductants can effectively tailor the microstructures, physical properties, and electrochemical performances of the products. The effects of different carbohydrates on graphene oxide reduction to form graphene-based aerogels with different microcosmic morphologies and physical properties were also systemically discussed. The electrochemical behaviors of all graphene-based aerogel samples showed remarkably strong and stable performances, which indicated that all the 3D interpenetrating microstructure graphene-based aerogel samples with well-developed porous nanostructures and interconnected conductive networks could provide fast ionic channels for electrochemical energy storage. These results demonstrate that this strategy would offer an easy and effective way to fabricate graphene-based materials. Copyright © 2013 Elsevier Inc. All rights reserved.

A robust salt-tolerant superoleophobic alginate/graphene oxide aerogel for efficient oil/water separation in marine environments

NASA Astrophysics Data System (ADS)

Li, Yuqi; Zhang, Hui; Fan, Mizi; Zheng, Peitao; Zhuang, Jiandong; Chen, Lihui

2017-04-01

Marine pollution caused by frequent oil spill accidents has brought about tremendous damages to marine ecological environment. Therefore, the facile large-scale preparation of three-dimensional (3D) porous functional materials with special wettability is in urgent demand. In this study, we report a low-cost and salt-tolerant superoleophobic aerogel for efficient oil/seawater separation. The aerogel is prepared through incorporating graphene oxide (GO) into alginate (ALG) matrix by using a facile combined freeze-drying and ionic cross-linking method. The 3D structure interconnected by ALG and GO ensures the high mechanical strength and good flexibility of the developed aerogel. The rough microstructure combined with the hydrophilicity of the aerogel ensures its excellent underwater superoleophobic and antifouling properties. High-content polysaccharides contained in the aerogel guarantees its excellent salt-tolerant property. More impressively, the developed aerogel can retain its underwater superoleophobicity even after 30 days of immersion in seawater, indicating its good stability in marine environments. Furthermore, the aerogel could separate various oil/water mixtures with high separation efficiency (>99%) and good reusability (at least 40 cycles). The facile fabrication process combined with the excellent separation performance makes it promising for practical applications in marine environments.

Micro- and nano-porous surface patterns prepared by surface-confined directional melt crystallization of solvent

NASA Astrophysics Data System (ADS)

Kim, Byoung Soo; Kim, Hyun Jin; An, Suyeong; Chi, Sangwon; Kim, Junseok; Lee, Jonghwi

2017-07-01

Recently, numerous attempts have been made to engineer micro- and nano-porous surface patterns or to develop convenient preparation methods for the practical applications of self-cleaning surfaces, water-repellent surfaces, novel textures, etc. Herein, we introduce a simple, cheap, and repeatable crystallization-based method to produce porous surface structures, on any surface of already fabricated polymeric materials. Contact of the solvent phase with cooled polymer surfaces enabled the limited dissolution of the surfaces and the subsequent extremely fast melt crystallization of the solvent. After removing the crystals, various micro- and nano-porous patterns were obtained, whose pore sizes ranged over three orders of magnitude. Pore depth was linearly dependent on the dissolution time. Crystal growth was mainly directed normal to the surfaces, but it was also controlled in-plane, resulting in cylindrical or lamellar structures. Superhydrophobic surfaces were successfully prepared on both polystyrene and polycarbonate. This process offers a novel surface engineering tool for a variety of polymer surfaces, whose topology can be conveniently controlled over a wide range by crystal engineering.

Synthesis and electromagnetic interference shielding of cellulose-derived carbon aerogels functionalized with α-Fe2O3 and polypyrrole.

PubMed

Wan, Caichao; Li, Jian

2017-04-01

Eco-friendly cellulose-derived carbon aerogels (CDCA) were employed as porous substrate to integrate with α-Fe 2 O 3 and polypyrrole (PPy) via pyrolysis and vapor-phase polymerization. The SEM and TEM observations present that the wrinkled PPy sheets and the α-Fe 2 O 3 nanoparticles were well dispersed in CDCA. The strong interactions (such as hydrogen bonding) between the substrate and the nanomaterials were demonstrated by the FTIR and XPS analysis. When utilized as electromagnetic interference (EMI) shielding materials, the α-Fe 2 O 3 /PPy/CDCA (FPCA) composite has the highest total shielding effectiveness (SE total ) of 39.4dB, about 2.0, 2.9, and 1.3 times that of the acid-treated CDCA (19.3dB), PPy (13.6dB), and α-Fe 2 O 3 /CDCA (29.3dB), respectively. Moreover, the shielding effectiveness due to absorption accounts for 78.2%-84.2% of SE total for FPCA, indicative of the absorption-dominant shielding mechanism contributing to alleviating secondary radiation. These features make the composite a useful alternative candidate for EMI shielding. Copyright © 2017 Elsevier Ltd. All rights reserved.

Strongly coupled inorganic-nano-carbon hybrid materials for energy storage.

PubMed

Wang, Hailiang; Dai, Hongjie

2013-04-07

The global shift of energy production from fossil fuels to renewable energy sources requires more efficient and reliable electrochemical energy storage devices. In particular, the development of electric or hydrogen powered vehicles calls for much-higher-performance batteries, supercapacitors and fuel cells than are currently available. In this review, we present an approach to synthesize electrochemical energy storage materials to form strongly coupled hybrids (SC-hybrids) of inorganic nanomaterials and novel graphitic nano-carbon materials such as carbon nanotubes and graphene, through nucleation and growth of nanoparticles at the functional groups of oxidized graphitic nano-carbon. We show that the inorganic-nano-carbon hybrid materials represent a new approach to synthesize electrode materials with higher electrochemical performance than traditional counterparts made by simple physical mixtures of electrochemically active inorganic particles and conducting carbon materials. The inorganic-nano-carbon hybrid materials are novel due to possible chemical bonding between inorganic nanoparticles and oxidized carbon, affording enhanced charge transport and increased rate capability of electrochemical materials without sacrificing specific capacity. Nano-carbon with various degrees of oxidation provides a novel substrate for nanoparticle nucleation and growth. The interactions between inorganic precursors and oxidized-carbon substrates provide a degree of control over the morphology, size and structure of the resulting inorganic nanoparticles. This paper reviews the recent development of inorganic-nano-carbon hybrid materials for electrochemical energy storage and conversion, including the preparation and functionalization of graphene sheets and carbon nanotubes to impart oxygen containing groups and defects, and methods of synthesis of nanoparticles of various morphologies on oxidized graphene and carbon nanotubes. We then review the applications of the SC

Carbon Nanotube Networks Reinforced by Silver Nanowires with Improved Optical Transparency and Conductivity

NASA Astrophysics Data System (ADS)

Martine, Patricia; Fakhimi, Azin; Lin, Ling; Jurewicz, Izabela; Dalton, Alan; Zakhidov, Anvar A.; Baughman, Ray H.

2015-03-01

We have fabricated highly transparent and conductive free-standing nanocomposite thin film electrodes by adding silver nanowires (AgNWs) to dry-spun Multiwall Carbon Nanotube (MWNT) aerogels. This nanocomposite exhibits desirable properties such as high optical transmittance, excellent flexibility and enhanced electrical conductivity. The incorporation of the AgNWs to the MWNT aerogels was accomplished by using a spray coating method. The optical transparency and sheet resistance of the nanocomposite was tuned by adjusting the concentration of AgNWs, back pressure and nozzle distance of the spray gun to the MWNT aerogel during deposition. As the solvent evaporated, the aerogel MWNT bundles densified via surface tension which caused the MWNT bundles to collapse. This adjustable process was responsible in forming well defined apertures that increased the nanocomposite's transmittance up to 90 percent. Via AgNWs percolation and random interconnections between separate MWNT bundles in the aerogel matrix, the sheet resistance decreased from 1 K ohm/sq to less than 100 ohm/sq. Alan G. MacDiarmid NanoTech Institute

KOH catalysed preparation of activated carbon aerogels for dye adsorption.

PubMed

Ling, Sie King; Tian, H Y; Wang, Shaobin; Rufford, Thomas; Zhu, Z H; Buckley, C E

2011-05-01

Organic carbon aerogels (CAs) were prepared by a sol-gel method from polymerisation of resorcinol, furfural, and hexamethylenetetramine catalysed by KOH at around pH 9 using ambient pressure drying. The effect of KOH in the sol-gel on CA synthesis was studied. It was found that addition of KOH prior to the sol-gel polymerisation process improved thermal stability of the gel, prevented the crystallinity of the gel to graphite, increased the microporosity of CA and promoted activation of CA. The CAs prepared using the KOH catalyst exhibited higher porosity than uncatalysed prepared samples. Activation in CO(2) at higher temperature also enhanced the porosity of CAs. Adsorption tests indicated that the CAs were effective for both basic and acid dye adsorption and the adsorption increased with increasing surface area and pore volume. The kinetic adsorption of dyes was diffusion control and could be described by the second-order kinetic model. The equilibrium adsorption of dyes was higher than activated carbon. Copyright © 2011 Elsevier Inc. All rights reserved.

Three-dimensional barium-sulfate-impregnated reduced graphene oxide aerogel for removal of strontium from aqueous solutions

NASA Astrophysics Data System (ADS)

Jang, Jiseon; Lee, Dae Sung

2018-06-01

A three-dimensional barium-sulfate-impregnated reduced graphene oxide (BaSO4-rGO) aerogel was successfully synthesized by a facile one-step hydrothermal method and was used as an adsorbent to remove strontium from aqueous solutions. The characterized elemental composition, crystal structure, and morphology of the prepared aerogel confirmed that barium sulfate particles were firmly anchored on the surface of the rGO sheets and exhibited a porous 3D structure with a high surface area of 129.37 m2/g. The mass ratio of BaSO4 in the BaSO4-rGO aerogel substantially affected strontium adsorption, and the optimal BaSO4/rGO ratio was found to be 1:1. The synthesized BaSO4-rGO aerogel not only reached adsorption equilibrium within 1 h, but also showed much higher adsorption capacity than an rGO aerogel. The experimental data were well fitted to a pseudo-second-order kinetic model and the adsorption behavior followed the Langmuir isotherm. The adsorption capacity of strontium on BaSO4-rGO aerogels remained relatively high even under ionic competition in simulated seawater. These results showed that the BaSO4-rGO aerogel is an efficient and promising adsorbent for the treatment of strontium in aqueous solutions.

Hybrid aerogel rigid ceramic fiber insulation and method of producing same

NASA Technical Reports Server (NTRS)

Barney, Andrea O. (Inventor); Heng, Vann (Inventor); Oka, Kris Shigeko (Inventor); Santos, Maryann (Inventor); Zinn, Alfred A. (Inventor); Droege, Michael (Inventor)

2004-01-01

A hybrid insulation material comprises of porous ceramic substrate material impregnated with nanoporous material and method of making the same is the topic of this invention. The porous substrate material has bulk density ranging from 6 to 20 lb/ft.sup.3 and is composed of about 60 to 80 wt % silica (SiO.sub.2) 20 to 40 wt % alumina (Al.sub.2 O.sub.3) fibers, and with about 0.1 to 1.0 wt % boron-containing constituent as the sintering agent. The nanoporous material has density ranging from 1.0 to 10 lb/ft.sup.3 and is either fully or partially impregnated into the substrate to block the pores, resulting in substantial reduction in conduction via radiation and convention. The nanoporous material used to impregnate the fiber substrate is preferably formed from a precursor of alkoxysilane, alcohol, water, and an acid or base catalyst for silica aerogels, and from a precursor of aluminum alkoxide, alcohol, water, and an acid or base catalyst for alumina aerogels.

Effects of Carbonization Parameters of Moso-Bamboo-Based Porous Charcoal on Capturing Carbon Dioxide

PubMed Central

Jhan, Jhih-Wei; Cheng, Yi-Ming; Cheng, Hau-Hsein

2014-01-01

This study experimentally analyzed the carbon dioxide adsorption capacity of Moso-bamboo- (Phyllostachys edulis-) based porous charcoal. The porous charcoal was prepared at various carbonization temperatures and ground into powders with 60, 100, and 170 meshes, respectively. In order to understand the adsorption characteristics of porous charcoal, its fundamental properties, namely, charcoal yield, ash content, pH value, Brunauer-Emmett-Teller (BET) surface area, iodine number, pore volume, and powder size, were analyzed. The results show that when the carbonization temperature was increased, the charcoal yield decreased and the pH value increased. Moreover, the bamboo carbonized at a temperature of 1000°C for 2 h had the highest iodine sorption value and BET surface area. In the experiments, charcoal powders prepared at various carbonization temperatures were used to adsorb 1.854% CO2 for 120 h. The results show that the bamboo charcoal carbonized at 1000°C and ground with a 170 mesh had the best adsorption capacity, significantly decreasing the CO2 concentration to 0.836%. At room temperature and atmospheric pressure, the Moso-bamboo-based porous charcoal exhibited much better CO2 adsorption capacity compared to that of commercially available 350-mesh activated carbon. PMID:25225639

Method of producing carbon coated nano- and micron-scale particles

DOEpatents

Perry, W. Lee; Weigle, John C; Phillips, Jonathan

2013-12-17

A method of making carbon-coated nano- or micron-scale particles comprising entraining particles in an aerosol gas, providing a carbon-containing gas, providing a plasma gas, mixing the aerosol gas, the carbon-containing gas, and the plasma gas proximate a torch, bombarding the mixed gases with microwaves, and collecting resulting carbon-coated nano- or micron-scale particles.

Hierarchical porous carbon microspheres derived from porous starch for use in high-rate electrochemical double-layer capacitors.

PubMed

Du, Si-Hong; Wang, Li-Qun; Fu, Xiao-Ting; Chen, Ming-Ming; Wang, Cheng-Yang

2013-07-01

Porous starch was used as a precursor for hierarchical porous carbon microspheres. The preparation consisted of stabilisation, carbonisation and KOH activation, and the resultant hierarchical porous carbon microspheres had a large BET surface area of 3251 m(2)g(-1). Due to the large surface area and the hierarchical pore structure, electrodes made of the hierarchical porous carbon microsphere materials had high specific capacitances of 304 Fg(-1) at a current density of 0.05 Ag(-1) and 197 Fg(-1) at a current density of 180 Ag(-1) when used in a symmetric capacitor with 6M KOH as the electrolyte. After 10,000 cycles, the capacitor still exhibited a stable performance with a capacitance retention of 98%. These results indicate that porous starch is an excellent precursor to prepare high performance electrode materials for EDLCs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Gas anti-solvent precipitation assisted salt leaching for generation of micro- and nano-porous wall in bio-polymeric 3D scaffolds.

PubMed

Flaibani, Marina; Elvassore, Nicola

2012-08-01

The mass transport through biocompatible and biodegradable polymeric 3D porous scaffolds may be depleted by non-porous impermeable internal walls. As consequence the concentration of metabolites and growth factors within the scaffold may be heterogeneous leading to different cell fate depending on spatial cell location, and in some cases it may compromise cell survival. In this work, we fabricated polymeric scaffolds with micro- and nano-scale porosity by developing a new technique that couples two conventional scaffold production methods: solvent casting-salt leaching and gas antisolvent precipitation. 10-15 w/w solutions of a hyaluronic benzyl esters (HYAFF11) and poly-(lactic acid) (PLA) were used to fill packed beds of 0.177-0.425 mm NaCl crystals. The polymer precipitation in micro and nano-porous structures between the salt crystals was induced by high-pressure gas, then its flushing extracted the residual solvent. The salt was removed by water-wash. Morphological analysis by scanning electron microscopy showed a uniform porosity (~70%) and a high interconnectivity between porous. The polymeric walls were porous themselves counting for 30% of the total porosity. This wall porosity did not lead to a remarkable change in compressive modulus, deformation, and rupture pressure. Scaffold biocompatibility was tested with murine muscle cell line C2C12 for 4 and 7 days. Viability analysis and histology showed that micro- and nano-porous scaffolds are biocompatible and suitable for 3D cell culture promoting cell adhesion on the polymeric wall and allowing their proliferation in layers. Micro- and nano-scale porosities enhance cell migration and growth in the inner part of the scaffold. Copyright © 2012 Elsevier B.V. All rights reserved.

Method for nanoencapsulation of aerogels and nanoencapsulated aerogels produced by such method

NASA Technical Reports Server (NTRS)

Sullivan, Thomas A. (Inventor)

2007-01-01

A method for increasing the compressive modulus of aerogels comprising: providing aerogel substrate comprising a bubble matrix in a chamber; providing monomer to the chamber, the monomer comprising vapor phase monomer which polymerizes substantially free of polymerization byproducts; depositing monomer from the vapor phase onto the surface of the aerogel substrate under deposition conditions effective to produce a vapor pressure sufficient to cause the vapor phase monomer to penetrate into the bubble matrix and deposit onto the surface of the aerogel substrate, producing a substantially uniform monomer film; and, polymerizing the substantially uniform monomer film under polymerization conditions effective to produce polymer coated aerogel comprising a substantially uniform polymer coating substantially free of polymerization byproducts.Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating, said polymer coated aerogel comprising porosity and having a compressive modulus greater than the compressive modulus of the aerogel substrate, as measured by a 100 lb. load cell at 1 mm/minute in the linear range of 20% to 40% compression.

3D hybrid-porous carbon derived from carbonization of metal organic frameworks for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Bao, Weizhai; Mondal, Anjon Kumar; Xu, Jing; Wang, Chengyin; Su, Dawei; Wang, Guoxiu

2016-09-01

We report a rational design and synthesis of 3D hybrid-porous carbon with a hierarchical pore architecture for high performance supercapacitors. It contains micropores (<2 nm diameter) and mesopores (2-4 nm), derived from carbonization of unique porous metal organic frameworks (MOFs). Owning to the synergistic effect of micropores and mesopores, the hybrid-porous carbon has exceptionally high ion-accessible surface area and low ion diffusion resistance, which is desired for supercapacitor applications. When applied as electrode materials in supercapacitors, 3D hybrid-porous carbon demonstrates a specific capacitance of 332 F g-1 at a constant charge/discharge current of 500 mA g-1. The supercapacitors can endure more than 10,000 cycles without degradation of capacitance.

Lignocellulose-derived porous phosphorus-doped carbon as advanced electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Yi, Jianan; Qing, Yan; Wu, ChuTian; Zeng, Yinxiang; Wu, Yiqiang; Lu, Xihong; Tong, Yexiang

2017-05-01

Engineering porous heteroatom-doped carbon nanomaterials with remarkable capacitive performance is highly attractive. Herein, a simple and smart method has been developed to synthesize phosphorus (P) doped carbon with hierarchical porous structure derived from lignocellulose. Hierarchically porous P doped carbon is readily obtained by the pyrolysis of lignocellulose immersed in ZnCl2/NaH2PO4 aqueous solution, and exhibits excellent capacitive properties. The as-obtained P doped porous carbon delivers a significant capacitance of 133 F g-1 (146 mF cm-2) at a high current density of 10 A g-1 with outstanding rate performance. Furthermore, the P doped carbon electrode yields a long-term cycling durability with more than 97.9% capacitance retention after 10000 cycles as well. A symmetric supercapacitor with a maximum energy density of 4.7 Wh kg-1 is also demonstrated based on these P doped carbon electrodes.

Asphalt-derived high surface area activated porous carbons for carbon dioxide capture.

PubMed

Jalilov, Almaz S; Ruan, Gedeng; Hwang, Chih-Chau; Schipper, Desmond E; Tour, Josiah J; Li, Yilun; Fei, Huilong; Samuel, Errol L G; Tour, James M

2015-01-21

Research activity toward the development of new sorbents for carbon dioxide (CO2) capture have been increasing quickly. Despite the variety of existing materials with high surface areas and high CO2 uptake performances, the cost of the materials remains a dominant factor in slowing their industrial applications. Here we report preparation and CO2 uptake performance of microporous carbon materials synthesized from asphalt, a very inexpensive carbon source. Carbonization of asphalt with potassium hydroxide (KOH) at high temperatures (>600 °C) yields porous carbon materials (A-PC) with high surface areas of up to 2780 m(2) g(-1) and high CO2 uptake performance of 21 mmol g(-1) or 93 wt % at 30 bar and 25 °C. Furthermore, nitrogen doping and reduction with hydrogen yields active N-doped materials (A-NPC and A-rNPC) containing up to 9.3% nitrogen, making them nucleophilic porous carbons with further increase in the Brunauer-Emmett-Teller (BET) surface areas up to 2860 m(2) g(-1) for A-NPC and CO2 uptake to 26 mmol g(-1) or 114 wt % at 30 bar and 25 °C for A-rNPC. This is the highest reported CO2 uptake among the family of the activated porous carbonaceous materials. Thus, the porous carbon materials from asphalt have excellent properties for reversibly capturing CO2 at the well-head during the extraction of natural gas, a naturally occurring high pressure source of CO2. Through a pressure swing sorption process, when the asphalt-derived material is returned to 1 bar, the CO2 is released, thereby rendering a reversible capture medium that is highly efficient yet very inexpensive.

Three-Dimensionally Hierarchical Graphene Based Aerogel Encapsulated Sulfur as Cathode for Lithium/Sulfur Batteries

PubMed Central

Li, Haipeng; Sun, Liancheng; Wang, Zhuo; Zhang, Yongguang; Tan, Taizhe; Wang, Gongkai

2018-01-01

A simple and effective method was developed to obtain the electrode for lithium/sulfur (Li/S) batteries with high specific capacity and cycling durability via adopting an interconnected sulfur/activated carbon/graphene (reduced graphene oxide) aerogel (S/AC/GA) cathode architecture. The AC/GA composite with a well-defined interconnected conductive network was prepared by a reduction-induced self-assembly process, which allows for obtaining compact and porous structures. During this process, reduced graphene oxide (RGO) was formed, and due to the presence of oxygen-containing functional groups on its surface, it not only improves the electronic conductivity of the cathode but also effectively inhibits the polysulfides dissolution and shuttle. The introduced activated carbon allowed for lateral and vertical connection between individual graphene sheets, completing the formation of a stable three-dimensionally (3D) interconnected graphene framework. Moreover, a high specific surface area and 3D interconnected porous structure efficiently hosts a higher amount of active sulfur material, about 65 wt %. The designed S/AC/GA composite electrodes deliver an initial capacity of 1159 mAh g−1 at 0.1 C and can retain a capacity of 765 mAh g−1 after 100 cycles in potential range from 1 V to 3 V. PMID:29373525

Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels.

PubMed

Boday, Dylan J; Stover, Robert J; Muriithi, Beatrice; Keller, Michael W; Wertz, Jason T; Defriend Obrey, Kimberly A; Loy, Douglas A

2009-07-01

Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density.

Molecular dynamics study of nano-porous materials—Enhancement of mobility of Li ions in lithium disilicate

NASA Astrophysics Data System (ADS)

Habasaki, Junko

2016-11-01

In several nano-porous materials and their composites, enhancement of ionic conductivity has been reported and several mechanisms having different origins have been proposed so far. In the present work, ionic motion of Li ions in porous lithium disilicates is examined by molecular dynamics simulation in the constant volume conditions and the enhancement of the dynamics is predicted. Structures and dynamics of ions in a nano-porous system were characterized and visualized to clarify the mechanism of the enhancement. The diffusion coefficient of Li ions has shown the maximum in the medium density (and porosity) region, and near the maximum, shortening of the nearly constant loss region in the mean squared displacement of ions as well as changes of the structures of the coordination polyhedra, LiOx is found. It suggests that the loosening of the cage, which increases the jump rate of ions, is an origin of the enhancement. When larger (but still in a nano-scale) voids are formed with a further decrease of density, more tight cages are reconstructed and the diffusion coefficient decreases again. These behaviors are closely related to the residual stress in the system. It is noteworthy that the explanation is not based on the percolation of the path only or formation of boundaries, although the former also affects the dynamics.

Preparation of ultrasmall porous carbon nanospheres by reverse microemulsion-hydrothermal method

NASA Astrophysics Data System (ADS)

Wang, Jiasheng; Zhao, Yahong; Wang, Wan-Hui; Bao, Ming

Porous carbon nanospheres (CNSs) have wide applications. A big challenge in materials science is synthesis of discrete ultrasmall porous carbon nanospheres. Herein, we report a facile reverse microemulsion-hydrothermal method to prepare discrete porous CNSs. The obtained CNSs possess an average diameter of 20nm and pores of 0.7nm and 3.4nm. Our work has provided a convenient method for the controllable synthesis of ultrasmall porous CNSs with potential applications.

Versatile fabrication of a superhydrophobic and ultralight cellulose-based aerogel for oil spillage clean-up.

PubMed

Zhang, Hui; Li, Yuqi; Xu, Yaoguang; Lu, Zexiang; Chen, Lihui; Huang, Liulian; Fan, Mizi

2016-10-12

To deal with marine oil spillage and chemical leakage issues, a highly efficient absorbent (cellulose based aerogel) with a low density (ρ < 0.034 g cm -3 , φ > 98.5%) and high mechanical strength was fabricated via a novel physical-chemical foaming method, plasma treatment and subsequent silane modification process. This aerogel has a perfect 3D skeleton and interconnected pores similar to honeycomb, which are favorable to oil adsorption and storage. More importantly, without introducing additional micro/nanoparticles, the rough micro/nano structure of the surface was directly constructed using plasma irradiation in this study. The low surface energy substrate was further introduced using a simple physical-soaking method and the resulting aerogel exhibited excellent superhydrophobicity (WCA > 156°) and superoleophilicity (OCA = 0°), which can selectively and efficiently absorb various oils or organic solvents from polluted water. In addition, this aerogel has a high storage capacity and absorption capacity (up to 4300% and 99% of its weight and volume, respectively). More interestingly, this aerogel exhibits excellent mechanical abrasion resistance and corrosion resistance even in strong acid, alkali solution and salt marine environment. The aerogel could be reused more than 30 times after removal of the absorbed oil by rinsing with ethanol.

The effect of magnetohydrodynamic nano fluid flow through porous cylinder

NASA Astrophysics Data System (ADS)

Widodo, Basuki; Arif, Didik Khusnul; Aryany, Deviana; Asiyah, Nur; Widjajati, Farida Agustini; Kamiran

2017-08-01

This paper concerns about the analysis of the effect of magnetohydrodynamic nano fluid flow through horizontal porous cylinder on steady and incompressible condition. Fluid flow is assumed opposite gravity and induced by magnet field. Porous cylinder is assumed had the same depth of porous and was not absorptive. The First thing to do in this research is to build the model of fluid flow to obtain dimentional governing equations. The dimentional governing equations are consist of continuity equation, momentum equation, and energy equation. Furthermore, the dimensional governing equations are converted to non-dimensional governing equation by using non-dimensional parameters and variables. Then, the non-dimensional governing equations are transformed into similarity equations using stream function and solved using Keller-Box method. The result of numerical solution further is obtained by taking variation of magnetic parameter, Prandtl number, porosity parameter, and volume fraction. The numerical results show that velocity profiles increase and temperature profiles decrease when both of the magnetic and the porosity parameter increase. However, the velocity profiles decrease and the temperature profiles increase when both of the magnetic and the porosity parameter increase.

A robust salt-tolerant superoleophobic alginate/graphene oxide aerogel for efficient oil/water separation in marine environments

PubMed Central

Li, Yuqi; Zhang, Hui; Fan, Mizi; Zheng, Peitao; Zhuang, Jiandong; Chen, Lihui

2017-01-01

Marine pollution caused by frequent oil spill accidents has brought about tremendous damages to marine ecological environment. Therefore, the facile large-scale preparation of three-dimensional (3D) porous functional materials with special wettability is in urgent demand. In this study, we report a low-cost and salt-tolerant superoleophobic aerogel for efficient oil/seawater separation. The aerogel is prepared through incorporating graphene oxide (GO) into alginate (ALG) matrix by using a facile combined freeze-drying and ionic cross-linking method. The 3D structure interconnected by ALG and GO ensures the high mechanical strength and good flexibility of the developed aerogel. The rough microstructure combined with the hydrophilicity of the aerogel ensures its excellent underwater superoleophobic and antifouling properties. High-content polysaccharides contained in the aerogel guarantees its excellent salt-tolerant property. More impressively, the developed aerogel can retain its underwater superoleophobicity even after 30 days of immersion in seawater, indicating its good stability in marine environments. Furthermore, the aerogel could separate various oil/water mixtures with high separation efficiency (>99%) and good reusability (at least 40 cycles). The facile fabrication process combined with the excellent separation performance makes it promising for practical applications in marine environments. PMID:28397862

Polyolefin-based aerogels

NASA Technical Reports Server (NTRS)

Gould, Gerogle L. (Inventor); Lee, Je Kyun (Inventor)

2010-01-01

The present invention relates to cross-linked polyolefin aerogels in simple and fiber-reinforced composite form. Of particular interest are polybutadiene aerogels. Especially aerogels derived from polybutadienes functionalized with anhydrides, amines, hydroxyls, thiols, epoxies, isocyanates or combinations thereof.

Interaction between carboxyl-functionalized carbon black nanoparticles and porous media

NASA Astrophysics Data System (ADS)

Kim, Song-Bae; Kang, Jin-Kyu; Yi, In-Geol

2015-04-01

Carbon nanomaterials, such as carbon nanotubes, fullerene, and graphene, have received considerable attention due to their unique physical and chemical characteristics, leading to mass production and widespread application in industrial, commercial, and environmental fields. During their life cycle from production to disposal, however, carbon nanomaterials are inevitably released into water and soil environments, which have resulted in concern about their health and environmental impacts. Carbon black is a nano-sized amorphous carbon powder that typically contains 90-99% elemental carbon. It can be produced from incomplete combustion of hydrocarbons in petroleum and coal. Carbon black is widely used in chemical and industrial products or applications such as ink pigments, coating plastics, the rubber industry, and composite reinforcements. Even though carbon black is strongly hydrophobic and tends to aggregate in water, it can be dispersed in aqueous media through surface functionalization or surfactant use. The aim of this study was therefore to investigate the transport behavior of carboxyl-functionalized carbon black nanoparticles (CBNPs) in porous media. Column experiments were performed for potassium chloride (KCl), a conservative tracer, and CBNPs under saturated flow conditions. Column experiments was conducted in duplicate using quartz sand, iron oxide-coated sand (IOCS), and aluminum oxide-coated sand (AOCS) to examine the effect of metal (Fe, Al) oxide presence on the transport of CBNPs. Breakthrough curves (BTCs) of CBNPs and chloride were obtained by monitoring effluent, and then mass recovery was quantified from these curves. Additionally, interaction energy profiles for CBNP-porous media were calculated using DLVO theory for sphere-plate geometry. The BTCs of chloride had relative peak concentrations ranging from 0.895 to 0.990. Transport parameters (pore-water velocity v, hydrodynamic dispersion coefficient D) obtained by the model fit from the

A peptide derivatized cellulosic aerogel from cotton as a point of care diagnostic protease sensor

USDA-ARS?s Scientific Manuscript database

Lightweight aerogels are highly porous with usually very small pore size making them suitable for a variety of potential applications as sensors including deformation strain, humidity, organic vapors, thermal, and optical sensing properties. However, little has been reported on their use as biosenso...

Starch aerogel beads obtained from inclusion complexes prepared from high amylose starch and sodium palmitate

USDA-ARS?s Scientific Manuscript database

Starch aerogels are a class of low density highly porous renewable materials currently prepared from retrograded starch gels and are of interest for their good surface area, porosity, biocompatibility, and biodegradability. Recently, we have reported on starches containing amylose-fatty acid salt h...

Ultrafast Sol-Gel Synthesis of Graphene Aerogel Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Mathew; Hu, Matthew; Manandhar, Sandeep

2015-12-01

Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirmsmore » the reduction of the GO in the aerogels to sp2 carbon crystallites with no residual carbon–nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.« less

Study on Thermal Conductivities of Aromatic Polyimide Aerogels.

PubMed

Feng, Junzong; Wang, Xin; Jiang, Yonggang; Du, Dongxuan; Feng, Jian

2016-05-25

Polyimide aerogels for low density thermal insulation materials were produced by 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride, cross-linked with 1,3,5-triaminophenoxybenzene. The densities of obtained polyimide aerogels are between 0.081 and 0.141 g cm(-3), and the specific surface areas are between 288 and 322 m(2) g(-1). The thermal conductivities were measured by a Hot Disk thermal constant analyzer. The value of the measured thermal conductivity under carbon dioxide atmosphere is lower than that under nitrogen atmosphere. Under pressure of 5 Pa at -130 °C, the thermal conductivity is the lowest, which is 8.42 mW (m K)(-1). The polyimide aerogels have lower conductivity [30.80 mW (m K)(-1)], compared to the value for other organic foams (polyurethane foam, phenolic foam, and polystyrene foam) with similar apparent densities under ambient pressure at 25 °C. The results indicate that polyimide aerogel is an ideal insulation material for aerospace and other applications.

Method of patterning an aerogel

DOEpatents

Reed, Scott T [Edgewood, NM

2012-07-24

A method for producing a pattern in an aerogel disposed as a coating on a substrate comprises exposing the aerogel coating to the vapors of a hydrophobic silane compound, masking the aerogel coating with a shadow photomask and irradiating the aerogel coating with ultraviolet (UV) irradiation. The exposure to UV through the shadow mask creates a pattern of hydrophobic and hydrophilic regions in the aerogel coating. Etching away the hydrophilic regions of the aerogel coating, preferably with a 1 molar solution of sodium hydroxide, leaves the unwetted and unetched hydrophobic regions of the aerogel layer on the substrate, replicating the pattern of the photomask. The hydrophobic aerogel pattern can be further exposed to UV irradiation if desired, to create a hydrophilic aerogel pattern.

Effects of pore size, implantation time and nano-surface properties on rat skin ingrowth into percutaneous porous titanium implants

PubMed Central

Farrell, Brad J.; Prilutsky, Boris I.; Ritter, Jana M.; Kelley, Sean; Popat, Ketul; Pitkin, Mark

2013-01-01

The main problem of percutaneous osseointegrated implants is poor skin-implant integration, which may cause infection. This study investigated the effects of pore size (Small, 40–100 microns and Large, 100–160 microns), nanotubular surface treatment (Nano), and duration of implantation (3 and 6 weeks) on skin ingrowth into porous titanium. Each implant type was percutaneously inserted in the back of 35 rats randomly assigned to 7 groups. Implant extrusion rate was measured weekly and skin ingrowth into implants was determined histologically after harvesting implants. It was found that all 3 types of implants demonstrated skin tissue ingrowth of over 30% (at week 3) and 50% (at weeks 4–6) of total implant porous area under the skin; longer implantation resulted in greater skin ingrowth (p<0.05). Only one case of infection was observed (infection rate 2.9%). Small and Nano groups showed the same implant extrusion rate which was lower than the Large group rate (0.06±0.01 vs. 0.16 ± 0.02 cm/week; p<0.05). Ingrowth area was comparable in the Small, Large and Nano implants. However, qualitatively, the Nano implants showed greatest cellular inhabitation within first three weeks. We concluded that percutaneous porous titanium implants allow for skin integration with the potential for a safe seal. PMID:23703928

Fast and Minimal-Solvent Production of Superinsulating Silica Aerogel Granulate.

PubMed

Huber, Lukas; Zhao, Shanyu; Malfait, Wim J; Vares, Sirje; Koebel, Matthias M

2017-04-18

With their low thermal conductivity (λ), silica aerogels can reduce carbon emissions from heating and cooling demands, but their widespread adoption is limited by the high production cost. A one-pot synthesis for silica aerogel granulate is presented that drastically reduces solvent use, production time, and global warming potential. The inclusion of the hydrophobization agent prior to gelation with a post-gelation activation step, enables a complete production cycle of less than four hours at the lab scale for a solvent use close to the theoretical minimum, and limits the global warming potential. Importantly, the one-pot aerogel granulate retains the exceptional properties associated with silica aerogel, mostly λ=14.4±1.0 mW m -1 ⋅K -1 for the pilot scale materials, about half that of standing air (26 mW m -1 ⋅K -1 ). The resource-, time-, and cost-effective production will allow silica aerogels to break out of its niche into the mainstream building and industrial insulation markets. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-Assembled 3D Graphene-Based Aerogel with Co3 O4 Nanoparticles as High-Performance Asymmetric Supercapacitor Electrode.

PubMed

Xie, Lijing; Su, Fangyuan; Xie, Longfei; Li, Xiaoming; Liu, Zhuo; Kong, Qingqiang; Guo, Xiaohui; Zhang, Yaoyao; Wan, Liu; Li, Kaixi; Lv, Chunxiang; Chen, Chengmeng

2015-09-07

Using graphene oxide and a cobalt salt as precursor, a three-dimensional graphene aerogel with embedded Co3 O4 nanoparticles (3D Co3 O4 -RGO aerogel) is prepared by means of a solvothermal approach and subsequent freeze-drying and thermal reduction. The obtained 3D Co3 O4 -RGO aerogel has a high specific capacitance of 660 F g(-1) at 0.5 A g(-1) and a high rate capability of 65.1 % retention at 50 A g(-1) in a three-electrode system. Furthermore, the material is used as cathode to fabricate an asymmetric supercapacitor utilizing a hierarchical porous carbon (HPC) as anode and 6 M KOH aqueous solution as electrolyte. In a voltage range of 0.0 to 1.5 V, the device exhibits a high energy density of 40.65 Wh kg(-1) and a power density of 340 W kg(-1) and shows a high cycling stability (92.92 % capacitance retention after 2000 cycles). After charging for only 30 s, three CR2032 coin-type asymmetric supercapacitors in series can drive a light-emitting-diode (LED) bulb brightly for 30 min, which remains effective even after 1 h. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemically Layered Porous Solids

NASA Technical Reports Server (NTRS)

Koontz, Steve

1991-01-01

Aerogels and other porous solids in which surfaces of pores have chemical properties varying with depth below macroscopic surfaces prepared by sequences of chemical treatments. Porous glass or silica bead treated to make two depth zones having different chemical properties. Beads dropped along tube filled with flowing gas containing atomic oxygen, generated in microwave discharge. General class of materials treatable include oxides of aluminum, silicon, zirconium, tin, titanium, and nickel, and mixtures of these oxides. Potential uses of treated materials include chromatographic separations, membrane separations, controlled releases of chemicals, and catalysis.

Graphene aerogels

DOEpatents

Pauzauskie, Peter J; Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H; Biener, Juergen

2015-03-31

Graphene aerogels with high conductivity and surface areas including a method for making a graphene aerogel, including the following steps: (1) preparing a reaction mixture comprising a graphene oxide suspension and at least one catalyst; (2) curing the reaction mixture to produce a wet gel; (3) drying the wet gel to produce a dry gel; and (4) pyrolyzing the dry gel to produce a graphene aerogel. Applications include electrical energy storage including batteries and supercapacitors.

Structure-Property Relationships in Porous 3-D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Capadona, Lynn A.; McCorkle, Linda; Padadopoulos, Demetrios S.; Leventis, Nicholas

2007-01-01

Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications because of their low density and high mesoporosity. However, their inherent fragility has restricted use of aerogel monoliths to applications where they are not subject to any load. We have previously reported cross-linking the mesoporous silica structure of aerogels with di-isocyanates, styrenes or epoxies reacting with amine decorated silica surfaces. These approaches have been shown to significantly increase the strength of aerogels with only a small effect on density or porosity. Though density is a prime predictor of properties such as strength and thermal conductivity for aerogels, it is becoming clear from previous studies that varying the silica backbone and size of the polymer cross-link independently can give rise to combinations of properties which cannot be predicted from density alone. Herein, we examine the effects of four processing parameters for producing this type of polymer cross-linked aerogel on properties of the resulting monoliths. We focus on the results of C-13 CP-MAS NMR which gives insight to the size and structure of polymer cross-link present in the monoliths, and relates the size of the cross-links to microstructure, mechanical properties and other characteristics of the materials obtained.

Structure-Property Relationships in Porous 3-D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Capadona, Lynn A.; McCorkle, Linda; Papadopoulos, Demetrios S.; Leventis, Nicholas

2007-01-01

Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications because of their low density and high mesoporosity. However, their inherent fragility has restricted use of aerogel monoliths to applications where they are not subject to any load. We have previously reported cross-linking the mesoporous silica structure of aerogels with di-isocyanates, styrenes or epoxies reacting with amine decorated silica surfaces. These approaches have been shown to significantly increase the strength of aerogels with only a small effect on density or porosity. Though density is a prime predictor of properties such as strength and thermal conductivity for aerogels, it is becoming clear from previous studies that varying the silica backbone and size of the polymer cross-link independently can give rise to combinations of properties which cannot be predicted from density alone. Herein, we examine the effects of four processing parameters for producing this type of polymer cross-linked aerogel on properties of the resulting monoliths. We focus on the results of 13C CP-MAS NMR which gives insight to the size and structure of polymer cross-link present in the monoliths, and relates the size of the cross-links to microstructure, mechanical properties and other characteristics of the materials obtained.

A Co-Precursor Approach Coupled with a Supercritical Modification Method for Constructing Highly Transparent and Superhydrophobic Polymethylsilsesquioxane Aerogels.

PubMed

Lei, Chaoshuai; Li, Junning; Sun, Chencheng; Yang, Hailong; Xia, Tao; Hu, Zijun; Zhang, Yue

2018-03-30

Polymethylsilsesquioxane (PMSQ) aerogels obtained from methyltrimethoxysilane (MTMS) are well-known high-performance porous materials. Highly transparent and hydrophobic PMSQ aerogel would play an important role in transparent vacuum insulation panels. Herein, the co-precursor approach and supercritical modification method were developed to prepare the PMSQ aerogels with high transparency and superhydrophobicity. Firstly, benefiting from the introduction of tetramethoxysilane (TMOS) in the precursor, the pore structure became more uniform and the particle size was decreased. As the TMOS content increased, the light transmittance increased gradually from 54.0% to 81.2%, whereas the contact angle of water droplet decreased from 141° to 99.9°, ascribed to the increase of hydroxyl groups on the skeleton surface. Hence, the supercritical modification method utilizing hexamethyldisilazane was also introduced to enhance the hydrophobic methyl groups on the aerogel's surface. As a result, the obtained aerogels revealed superhydrophobicity with a contact angle of 155°. Meanwhile, the developed surface modification method did not lead to any significant changes in the pore structure resulting in the superhydrophobic aerogel with a high transparency of 77.2%. The proposed co-precursor approach and supercritical modification method provide a new horizon in the fabrication of highly transparent and superhydrophobic PMSQ aerogels.

Aerogel-clad optical fiber

DOEpatents

Sprehn, Gregory A.; Hrubesh, Lawrence W.; Poco, John F.; Sandler, Pamela H.

1997-01-01

An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency.

Preparation and Performance of Porous Polymer Electrolytes Doped with Nano-Al₂O₃.

PubMed

Jiang, Qingbai; Liang, Bo; Tang, Siqi; Chen, Xu

2018-03-01

Porous polymer electrolytes (PPEs) doped with nano-Al2O3 were prepared by a joint application of ultrasonic treatment and control evaporation in vacuum oven. The morphology, pore size distribution, thermal, electrochemical and mechanical properties of the PPEs were investigated. The porosity distribution of PPEs was uniform and their pore size was relatively modest. The total resistance (Rt) of PPEs with 10% Al2O3 is only 9 Ω at 80 °C. The maximum tensile strength of the PPEs membranes reached to 24.43 MPa. The results show that nano-Al2O3 can improve the comprehensive performance of PPEs without compromising their conductivity and diplayed the good application prospects of Al2O3-modified PPEs for lithium-ion batteries.

Electron Beam Analysis of Micrometeoroids Captured in Aerogel as Stardust Analogues

NASA Technical Reports Server (NTRS)

Graham, G. A.; Sheffield-Parker, J.; Bradley, P.; Kearsley, A. T.; Dai, Z. R.; Mayo, S. C.; Teslich, N.; Snead, C.; Westphal, A. J.; Ishii, H.

2005-01-01

In January 2004, NASA s Stardust spacecraft passed through the tail of Comet 81P/Wild-2. The on-board dust flux monitor instrument indicated that numerous micro- and nano-meter sized cometary dust particles were captured by the dedicated silica aerogel capture cell. The collected cometary particles will be returned to Earth in January 2006. Current Stardust analogues are: (i) Light-gas-gun accelerated individual mineral grains and carbonaceous meteoritic material in aerogels at the Stardust encounter velocity ca.approximately 6 kilometers per second. (ii) Aerogels exposed in low-Earth orbit (LEO) containing preserved cosmic dust grains. Studies of these impacts offer insight into the potential state of the captured cometary dust by Stardust and the suitability of various analytical techniques. A number of papers have discussed the application of sophisticated synchrotron analytical techniques to analyze Stardust particles. Yet much of the understanding gained on the composition and mineralogy of interplanetary dust particles (IDPs) has come from electron microscopy studies. Here we discuss the application of scanning electron microscopy (SEM) for Stardust during the preliminary phase of post-return investigations.

Aerogel-clad optical fiber

DOEpatents

Sprehn, G.A.; Hrubesh, L.W.; Poco, J.F.; Sandler, P.H.

1997-11-04

An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency. 4 figs.

Effect of Porosity Parameters and Surface Chemistry on Carbon Dioxide Adsorption in Sulfur-Doped Porous Carbons.

PubMed

Wang, En-Jie; Sui, Zhu-Yin; Sun, Ya-Nan; Ma, Zhuang; Han, Bao-Hang

2018-05-22

In this work, a series of highly porous sulfur-doped carbons are prepared through physical activation methods by using polythiophene as a precursor. The morphology, structure, and physicochemical properties are revealed by a variety of characterization methods, such as scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and nitrogen sorption measurement. Their porosity parameters and chemical compositions can be well-tuned by changing the activating agents (steam and carbon dioxide) and reaction temperature. These sulfur-doped porous carbons possess specific surface area of 670-2210 m 2 g -1 , total pore volume of 0.31-1.26 cm 3 g -1 , and sulfur content of 0.6-4.9 atom %. The effect of porosity parameters and surface chemistry on carbon dioxide adsorption in sulfur-doped porous carbons is studied in detail. After a careful analysis of carbon dioxide uptake at different temperatures (273 and 293 K), pore volumes from small pore size (less than 1 nm) play an important role in carbon dioxide adsorption at 273 K, whereas surface chemistry is the key factor at a higher adsorption temperature or lower relative pressure. Furthermore, sulfur-doped porous carbons also possess good gas adsorption selectivity and excellent recyclability for regeneration.

Cellulose Nanofibrils Aerogel Cross-Linked by Poly(vinyl alcohol) and Acrylic Acid for Efficient and Recycled Adsorption with Heavy Metal Ions.

PubMed

She, Jiarong; Tian, Cuihua; Wu, Yiqiang; Li, Xianjun; Luo, Sha; Qing, Yan; Jiang, Zheng

2018-06-01

Cellulose nanofibrils (CNFs), disintegrated from natural fibers, are promising alternatives in wastewater purification for the porous structure and numerous hydroxyls. The pristine CNFs aerogel has limited mechanical strength and are vulnerable to collapse when exposed to water. In this work, eco-friendly and recycled CNFs aerogel adsorbents were successfully prepared using cellulose nanofibrils (CNFs), which cross-linked by poly(vinyl alcohol) (PVA) and acrylic acid (AA). The combination of PVA and AA endowed CNFs aerogel strong three-dimensional porous structure and desirable adsorption properties. The heavy metal ions were adsorbed on the CNFs-PVA-AA (CPA) adsorbents efficiently and the maximum adsorption capacities for Cu2+ and Pb2+ approached 30.0 mg/g and 131.5 mg/g, respectively. The CPA adsorbent also showed excellent reusability and their adsorption capacities maintained 89% and 88% for Cu2+ and Pb2+ after 5 repeated uses. The adsorption of these heavy metal ions were confirmed to follow pseudo-second-order kinetic and Langmuir isotherm model. The functions of C ═ O and -OH were the major adsorption sites. Chemical adsorption combined with the porous physical adsorption made the CPA to be excellent adsorbent for the removal of heavy metal ions in wastewater.

Nano-solenoid: helicoid carbon-boron nitride hetero-nanotube

NASA Astrophysics Data System (ADS)

Zhang, Zi-Yue; Miao, Chunyang; Guo, Wanlin

2013-11-01

As a fundamental element of a nanoscale passive circuit, a nano-inductor is proposed based on a hetero-nanotube consisting of a spiral carbon strip and a spiral boron nitride strip. It is shown by density functional theory associated with nonequilibrium Green function calculations that the nanotube exhibits attractive transport properties tunable by tube chirality, diameter, component proportion and connection manner between the two strips, with excellent `OFF' state performance and high current on the order of 10-100 μA. All the hetero-nanotubes show negative differential resistance. The transmission peaks of current are absolutely derived from the helicoid carbon strips or C-BN boundaries, giving rise to a spiral current analogous with an energized nano-solenoid. According to Ampere's Law, the energized nano-solenoid can generate a uniform and tremendous magnetic field of more than 1 tesla, closing to that generated by the main magnet of medical nuclear magnetic resonance. Moreover, the magnitude of magnetic field can be easily modulated by bias voltage, providing great promise for a nano-inductor to realize electromagnetic conversion at the nanoscale.As a fundamental element of a nanoscale passive circuit, a nano-inductor is proposed based on a hetero-nanotube consisting of a spiral carbon strip and a spiral boron nitride strip. It is shown by density functional theory associated with nonequilibrium Green function calculations that the nanotube exhibits attractive transport properties tunable by tube chirality, diameter, component proportion and connection manner between the two strips, with excellent `OFF' state performance and high current on the order of 10-100 μA. All the hetero-nanotubes show negative differential resistance. The transmission peaks of current are absolutely derived from the helicoid carbon strips or C-BN boundaries, giving rise to a spiral current analogous with an energized nano-solenoid. According to Ampere's Law, the energized nano

High-strength porous carbon and its multifunctional applications

DOEpatents

Wojtowicz, Marek A; Rubenstein, Eric P; Serio, Michael A; Cosgrove, Joseph E

2013-12-31

High-strength porous carbon and a method of its manufacture are described for multifunctional applications, such as ballistic protection, structural components, ultracapacitor electrodes, gas storage, and radiation shielding. The carbon is produced from a polymer precursor via carbonization, and optionally by surface activation and post-treatment.

Cellulose aerogels functionalized with polypyrrole and silver nanoparticles: In-situ synthesis, characterization and antibacterial activity.

PubMed

Wan, Caichao; Li, Jian

2016-08-01

Green porous and lightweight cellulose aerogels have been considered as promising candidates to substitute some petrochemical host materials to support various nanomaterials. In this work, waste wheat straw was collected as feedstock to fabricate cellulose hydrogels, and a green inexpensive NaOH/polyethylene glycol solution was used as cellulose solvent. Prior to freeze-drying treatment, the cellulose hydrogels were integrated with polypyrrole and silver nanoparticles by easily-operated in-situ oxidative polymerization of pyrrole using silver ions as oxidizing agent. The tri-component hybrid aerogels were characterized by scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, and X-ray diffraction. Moreover, the antibacterial activity of the hybrid aerogels against Escherichia coli (Gram-negative), Staphylococcus aureus (Gram-positive) and Listeria monocytogenes (intracellular bacteria) was qualitatively and quantitatively investigated by parallel streak method and determination of minimal inhibitory concentration, respectively. This work provides an example of combining cellulose aerogels with nanomaterials, and helps to develop novel forms of cellulose-based functional materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal conductivity of aerogel blanket insulation under cryogenic-vacuum conditions in different gas environments

NASA Astrophysics Data System (ADS)

E Fesmire, J.; Ancipink, J. B.; Swanger, A. M.; White, S.; Yarbrough, D.

2017-12-01

Thermal conductivity of low-density materials in thermal insulation systems varies dramatically with the environment: cold vacuum pressure, residual gas composition, and boundary temperatures. Using a reference material of aerogel composite blanket (reinforcement fibers surrounded by silica aerogel), an experimental basis for the physical heat transmission model of aerogel composites and other low-density, porous materials is suggested. Cryogenic-vacuum testing between the boundary temperatures of 78 K and 293 K is performed using a one meter cylindrical, absolute heat flow calorimeter with an aerogel blanket specimen exposed to different gas environments of nitrogen, helium, argon, or CO2. Cold vacuum pressures include the full range from 1×10-5 torr to 760 torr. The soft vacuum region, from about 0.1 torr to 10 torr, is complex and difficult to model because all modes of heat transfer - solid conduction, radiation, gas conduction, and convection - are significant contributors to the total heat flow. Therefore, the soft vacuum tests are emphasized for both heat transfer analysis and practical thermal data. Results for the aerogel composite blanket are analyzed and compared to data for its component materials. With the new thermal conductivity data, future applications of aerogel-based insulation systems are also surveyed. These include Mars exploration and surface systems in the 5 torr CO2 environment, field joints for vacuum-jacketed cryogenic piping systems, common bulkhead panels for cryogenic tanks on space launch vehicles, and liquid hydrogen cryofuel systems with helium purged conduits or enclosures.

Facile and green fabrication of cellulosed based aerogels for lampblack filtration from waste newspaper.

PubMed

Fan, Peidong; Yuan, Yali; Ren, Junkai; Yuan, Bin; He, Qian; Xia, Guangmei; Chen, Fengxia; Song, Rui

2017-04-15

In this study, the lightweight, hydrophobic and porous cellulose-based aerogels (CAGs) were synthesized through a freeze-drying process using waste newspaper as the only raw material. After crosslinking with glutaraldehyde and treatment with trimethylchlorosilane (TMCS) using a simple thermal chemical vapor deposition process, the resulting CAGs became hydrophobic and oleophilic. Furthermore, the as-prepared CAGs exhibited a low density (17.4-28.7mgcm -3 ) and mesoporous inner-structure. All these properties attributed the novel aerogel not only with a good adsorption capability of oils and organic solvents, including kerosene, nitrobenzene, and chloroform, but also an excellent filtration capacity of lampblack. Copyright © 2017 Elsevier Ltd. All rights reserved.

Purity and cleanness of aerogel as a cosmic dust capture medium

NASA Technical Reports Server (NTRS)

Tsou, P.; Fleming, R. H.; Lindley, P. M.; Craig, A. Y.; Blake, D.

1994-01-01

The capability for capturing micrometeoroids intact through laboratory simulations and in space in passive underdense silica aerogel offers a valuable tool for cosmic dust research. The integrity of the sample handling medium can substantially modify the integrity of the sample. Intact capture is a violent hypervelocity event: the integrity of the capturing medium can cause even greater modification of the sample. Doubts of the suitability of silica aerogel as a capture medium were raised at the 20th LPSC, and questions were raised again at the recent workshop on Particle Capture, Recovery, and Velocity Trajectory Measurement Technologies. Assessment of aerogel's volatile components and carbon contents have been made. We report the results of laboratory measurements of the purity and cleanliness of silica aerogel used for several Sample Return Experiments flown on the Get Away Special program.

Cellulose Nanofibril Based-Aerogel Microreactors: A High Efficiency and Easy Recoverable W/O/W Membrane Separation System

PubMed Central

Zhang, Fang; Ren, Hao; Dou, Jing; Tong, Guolin; Deng, Yulin

2017-01-01

Hereby we report a novel cellulose nanofirbril aerogel-based W/O/W microreactor system that can be used for fast and high efficient molecule or ions extraction and separation. The ultra-light cellulose nanofibril based aerogel microspheres with high porous structure and water storage capacity were prepared. The aerogel microspheres that were saturated with stripping solution were dispersed in an oil phase to form a stable water-in-oil (W/O) suspension. This suspension was then dispersed in large amount of external waste water to form W/O/W microreactor system. Similar to a conventional emulsion liquid membrane (ELM), the molecules or ions in external water can quickly transport to the internal water phase. However, the microreactor is also significantly different from traditional ELM: the water saturated nanocellulose cellulose aerogel microspheres can be easily removed by filtration or centrifugation after extraction reaction. The condensed materials in the filtrated aerogel particles can be squeezed and washed out and aerogel microspheres can be reused. This novel process overcomes the key barrier step of demulsification in traditional ELM process. Our experimental indicates the novel microreactor was able to extract 93% phenol and 82% Cu2+ from external water phase in a few minutes, suggesting its great potential for industrial applications. PMID:28059153

Cellulose Nanofibril Based-Aerogel Microreactors: A High Efficiency and Easy Recoverable W/O/W Membrane Separation System

NASA Astrophysics Data System (ADS)

Zhang, Fang; Ren, Hao; Dou, Jing; Tong, Guolin; Deng, Yulin

2017-01-01

Hereby we report a novel cellulose nanofirbril aerogel-based W/O/W microreactor system that can be used for fast and high efficient molecule or ions extraction and separation. The ultra-light cellulose nanofibril based aerogel microspheres with high porous structure and water storage capacity were prepared. The aerogel microspheres that were saturated with stripping solution were dispersed in an oil phase to form a stable water-in-oil (W/O) suspension. This suspension was then dispersed in large amount of external waste water to form W/O/W microreactor system. Similar to a conventional emulsion liquid membrane (ELM), the molecules or ions in external water can quickly transport to the internal water phase. However, the microreactor is also significantly different from traditional ELM: the water saturated nanocellulose cellulose aerogel microspheres can be easily removed by filtration or centrifugation after extraction reaction. The condensed materials in the filtrated aerogel particles can be squeezed and washed out and aerogel microspheres can be reused. This novel process overcomes the key barrier step of demulsification in traditional ELM process. Our experimental indicates the novel microreactor was able to extract 93% phenol and 82% Cu2+ from external water phase in a few minutes, suggesting its great potential for industrial applications.

A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Koch, J. A.; Haugh, M. J.

2016-07-15

A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX–6 (C{sub 20}H{sub 30}) aerogel are discussed in this manuscript.

A multi-wavelength, high-contrast contact radiography system for the study of low density aerogel foams

DOE PAGES

Opachich, Y.P.; Koch, J.A.; Haugh, M. J.; ...

2017-07-01

A multi wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility (NIF) and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ~10.3% accuracy with ~30 μm spatial resolution. The system description, performance and measurement results collected using a 17.8 mg/cc carbon based JX–6 (C 20H 30) aerogel are discussed in this manuscript.

Preparation of the Lentinus edodes-based porous biomass carbon by hydrothermal method for capacitive desalination

NASA Astrophysics Data System (ADS)

Yan, Junbin; Zhang, Hexuan; Xie, Zhengzheng; Liu, Jianyun

2017-08-01

Biomass carbon materials were prepared by hydrothermal method using Lentinus edodes, followed by activation by ZnCl2 at high carbonization temperature. SEM and contact angle test show that ZnCl2 has a significant effect on the surface morphology and properties of porous carbon materials. Using the porous carbon as electrodes of the capacitor, the specific capacitance of the porous carbon material was found to be 247.6 F/g. The desalination amount of porous carbon material in capacitor cell was 12.9 mg/g, being the 1.9 times of that of the commercial activated carbon.

Strong White Photoluminescence from Carbon-Incorporated Silicon Oxide Fabricated by Preferential Oxidation of Silicon in Nano-Structured Si:C Layer

NASA Astrophysics Data System (ADS)

Vasin, Andriy V.; Ishikawa, Yukari; Shibata, Noriyoshi; Salonen, Jarno; Lehto, Vesa-Pekka

2007-05-01

A new approach to development of light-emitting SiO2:C layers on Si wafer is demonstrated. Carbon-incorporated silicon oxide was fabricated by three-step procedure: (1) formation of the porous silicon (por-Si) layer by ordinary anodization in HF:ethanol solution; (2) carbonization at 1000 °C in acetylene flow (formation of por-Si:C layer); (3) oxidation in the flow of moisturized argon at 800 °C (formation of SiO2:C layer). Resulting SiO2:C layer exhibited very strong and stable white photoluminescence at room temperature. It is shown that high reactivity of water vapor with nano-crystalline silicon and inertness with amorphous carbon play a key role in the formation of light-emitting SiO2:C layer.

Mechanical Properties of Aerogels

NASA Technical Reports Server (NTRS)

Parmenter, Kelly E.; Milstein, Frederick

1995-01-01

Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response

Compression molding of aerogel microspheres

DOEpatents

Pekala, Richard W.; Hrubesh, Lawrence W.

1998-03-24

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50-800 kg/m.sup.3 (0.05-0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization.

Computational materials chemistry for carbon capture using porous materials

NASA Astrophysics Data System (ADS)

Sharma, Abhishek; Huang, Runhong; Malani, Ateeque; Babarao, Ravichandar

2017-11-01

Control over carbon dioxide (CO2) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO2 capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO2 separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO2 capture are discussed.

Preparing silica aerogel monoliths via a rapid supercritical extraction method.

PubMed

Carroll, Mary K; Anderson, Ann M; Gorka, Caroline A

2014-02-28

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10(-3) molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

PubMed Central

Gorka, Caroline A.

2014-01-01

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes. PMID:24637334

High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes

PubMed Central

Im, Hyeongwook; Kim, Taewoo; Song, Hyelynn; Choi, Jongho; Park, Jae Sung; Ovalle-Robles, Raquel; Yang, Hee Doo; Kihm, Kenneth D.; Baughman, Ray H.; Lee, Hong H.; Kang, Tae June; Kim, Yong Hyup

2016-01-01

Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application. When normalized to the cell cross-sectional area, a maximum power output of 6.6 W m−2 is obtained for a 51 °C inter-electrode temperature difference, with a Carnot-relative efficiency of 3.95%. The importance of electrode purity, engineered porosity and catalytic surfaces in enhancing the thermocell performance is demonstrated. PMID:26837457

Porous carbons prepared by direct carbonization of MOFs for supercapacitors

NASA Astrophysics Data System (ADS)

Yan, Xinlong; Li, Xuejin; Yan, Zifeng; Komarneni, Sridhar

2014-07-01

Three porous carbons were prepared by direct carbonization of HKUST-1, MOF-5 and Al-PCP without additional carbon precursors. The carbon samples obtained by carbonization at 1073 K were characterized by XRD, TEM and N2 physisorption techniques followed by testing for electrochemical performance. The BET surface areas of the three carbons were in the range of 50-1103 m2/g. As electrode materials for supercapacitor, the MOF-5 and Al-PCP derived carbons displayed the ideal capacitor behavior, whereas the HKUST-1 derived carbon showed poor capacitive behavior at various sweep rates and current densities. Among those carbon samples, Al-PCP derived carbons exhibited highest specific capacitance (232.8 F/g) in 30% KOH solution at the current density of 100 mA/g.

Particle Tracks in Aerogel

NASA Image and Video Library

2005-11-03

In an experiment using a special air gun, particles are shot into aerogel at high velocities. Closeup of particles leaving a carrot-shaped trail in the aerogel are shown here. Aerogel was used on NASA Stardust spacecraft.

ZnFe2O4 nanoparticles dispersed in a highly porous silica aerogel matrix: a magnetic study.

PubMed

Bullita, S; Casu, A; Casula, M F; Concas, G; Congiu, F; Corrias, A; Falqui, A; Loche, D; Marras, C

2014-03-14

We report the detailed structural characterization and magnetic investigation of nanocrystalline zinc ferrite nanoparticles supported on a silica aerogel porous matrix which differ in size (in the range 4-11 nm) and the inversion degree (from 0.4 to 0.2) as compared to bulk zinc ferrite which has a normal spinel structure. The samples were investigated by zero-field-cooling-field-cooling, thermo-remnant DC magnetization measurements, AC magnetization investigation and Mössbauer spectroscopy. The nanocomposites are superparamagnetic at room temperature; the temperature of the superparamagnetic transition in the samples decreases with the particle size and therefore it is mainly determined by the inversion degree rather than by the particle size, which would give an opposite effect on the blocking temperature. The contribution of particle interaction to the magnetic behavior of the nanocomposites decreases significantly in the sample with the largest particle size. The values of the anisotropy constant give evidence that the anisotropy constant decreases upon increasing the particle size of the samples. All these results clearly indicate that, even when dispersed with low concentration in a non-magnetic and highly porous and insulating matrix, the zinc ferrite nanoparticles show a magnetic behavior similar to that displayed when they are unsupported or dispersed in a similar but denser matrix, and with higher loading. The effective anisotropy measured for our samples appears to be systematically higher than that measured for supported zinc ferrite nanoparticles of similar size, indicating that this effect probably occurs as a consequence of the high inversion degree.

Compression molding of aerogel microspheres

DOEpatents

Pekala, R.W.; Hrubesh, L.W.

1998-03-24

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner is disclosed. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50--800 kg/m{sup 3} (0.05--0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization. 4 figs.

Robust and Stable Cu Nanowire@Graphene Core-Shell Aerogels for Ultraeffective Electromagnetic Interference Shielding.

PubMed

Wu, Shiting; Zou, Mingchu; Li, Zhencheng; Chen, Daqin; Zhang, Hui; Yuan, Yongjun; Pei, Yongmao; Cao, Anyuan

2018-06-01

Cu nanowires (CuNWs) are considered as a promising candidate to develop high performance metal aerogels, yet the construction of robust and stable 3D porous structures remains challenging which severely limits their practical applications. Here, graphene-hybridized CuNW (CuNW@G) core-shell aerogels are fabricated by introducing a conformal polymeric coating and in situ transforming it into multilayered graphene seamlessly wrapped around individual CuNWs through a mild thermal annealing process. The existence of the outer graphene shell reinforces the 3D bulk structure and significantly slows down the oxidation process of CuNWs, resulting in improved mechanical property and highly stable electrical conductivity. When applied in electromagnetic interference shielding, the CuNW@G core-shell aerogels exhibit an average effectiveness of ≈52.5 dB over a wide range (from 8.2 to 18 GHz) with negligible degradation under ambient conditions for 40 d. Mechanism analysis reveals that the graphene shell with functional groups enables dual reflections on the core-shell and a multiple dielectric relaxation process, leading to enhanced dielectric loss and energy dissipation within the core-shell aerogels. The flexible core-shell-structured CuNW@G aerogels, with superior mechanical robustness and electrical stability, have potential applications in many areas such as advanced energy devices and functional composites. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of HF acid catalyst concentration on properties of aerogel low-k thin films

NASA Astrophysics Data System (ADS)

Gaikwad, A. S.; Gupta, S. A.; Mahajan, A. M.

2016-08-01

The effect of hydrofluoric acid (HF) catalyst concentration in coating solution on chemical, physical and structural properties of silica aerogel thin films was investigated. The aerogel films were synthesized by using a sol-gel spin coating method followed by aging in ethanol and CO2 supercritical drying. The refractive index (RI) is observed to be reduced from 1.32 to 1.13 and porosity percentage increased from 30.21% to 71.64% in accordance with increasing HF concentration. Deposition of silica aerogel was confirmed from Fourier transform infrared spectroscopy measurement. The nanoporous nature of deposited films was confirmed from field effect scanning electron microscopy and observed pore diameter is in the range of 3.33 to 6.69 nm. The nanoporous nature of the film was also validated from atomic force microscopy and root mean square roughness was observed to be increased from 2.31 nm to 3.2 nm with increasing acid catalyst concentration in the coating solution. The calculated dielectric constant from CV measurement of fabricated metal-insulator-semiconductor structure for the silica aerogel formed at 0.8 ml HF concentration is observed to be 1.73. These deposited nanoporous silica aerogel low-k films with lower k value and smaller pore size have application as interlayer dielectric materials to minimize the disadvantages of porous materials.

Strength-controllable graphene oxide amphiprotic aerogels as highly efficient carrier for anionic and cationic azo molecules

NASA Astrophysics Data System (ADS)

Xiong, Jiaqing; Jiao, Chenlu; Xu, Sijun; Tao, Jin; Zhang, Desuo; Lin, Hong; Chen, Yuyue

2015-06-01

Ice-bath self-assembly was employed to fabricate the GO/AP-MCC/CS aerogel based on natural materials. The components are amphiprotic microcrystalline cellulose (AP-MCC), chitosan (CS), and graphene oxide (GO), which act as the main framework, auxiliary framework and adhesive, respectively. The results of characterization determines the components form the GO/AP-MCC/CS aerogel according to chemical interactions. The mechanical properties depend largely on the mass ratio of AP-MCC/CS, which can be regulated by controlling the contents of AP-MCC and CS. The resultant GO/AP-MCC/CS aerogel was observed possessing three-dimensional (3D) interpenetrating porous networks with wrinkled structure on the inner wall, which provide a good encapsulation capacity for the guest molecules. As expected, owing to the amphiprotic properties and large specific surface area, GO/AP-MCC/CS aerogel exhibits high-efficiency load capacity for both anionic (CR) and cationic azo molecules (MB), which can reach up to about 132.2 mg/g for CR and 123.2 mg/g for MB, respectively.

Biomass-derived porous carbon modified glass fiber separator as polysulfide reservoir for Li-S batteries.

PubMed

Selvan, Ramakrishnan Kalai; Zhu, Pei; Yan, Chaoi; Zhu, Jiadeng; Dirican, Mahmut; Shanmugavani, A; Lee, Yun Sung; Zhang, Xiangwu

2018-03-01

Biomass-derived porous carbon has been considered as a promising sulfur host material for lithium-sulfur batteries because of its high conductive nature and large porosity. The present study explored biomass-derived porous carbon as polysulfide reservoir to modify the surface of glass fiber (GF) separator. Two different carbons were prepared from Oak Tree fruit shells by carbonization with and without KOH activation. The KOH activated porous carbon (AC) provides a much higher surface area (796 m 2  g -1 ) than pyrolized carbon (PC) (334 m 2  g -1 ). The R factor value, calculated from the X-ray diffraction pattern, revealed that the activated porous carbon contains more single-layer sheets with a lower degree of graphitization. Raman spectra also confirmed the presence of sp 3 -hybridized carbon in the activated carbon structure. The COH functional group was identified through X-ray photoelectron spectroscopy for the polysulfide capture. Simple and straightforward coating of biomass-derived porous carbon onto the GF separator led to an improved electrochemical performance in Li-S cells. The Li-S cell assembled with porous carbon modified GF separator (ACGF) demonstrated an initial capacity of 1324 mAh g -1 at 0.2 C, which was 875 mAh g -1 for uncoated GF separator (calculated based on the 2nd cycle). Charge transfer resistance (R ct ) values further confirmed the high ionic conductivity nature of porous carbon modified separators. Overall, the biomass-derived activated porous carbon can be considered as a promising alternative material for the polysulfide inhibition in Li-S batteries. Copyright © 2017 Elsevier Inc. All rights reserved.

Micropore engineering of carbonized porous aromatic framework (PAF-1) for supercapacitors application.

PubMed

Li, Yanqiang; Roy, Soumyajit; Ben, Teng; Xu, Shixian; Qiu, Shilun

2014-07-07

Micropore engineering of porous carbons on the effect of capacitance was explored using a carbonized porous aromatic framework (PAF-1). The porous carbons obtained through different carbonization methods show different pore structures enabling us to do this. The capacitance was measured both in aqueous electrolyte and different organic electrolytes. The porous carbons prepared by KOH activation show both high microporous volume, which is beneficial for charge storage, and mesoporous volume, which is devoted to fast ion diffusion in the pores; properties which are highly desirable. It shows a capacitance as high as 280 F g(-1) and 203 F g(-1) at a current density of 1 A g(-1) in 6.0 M KOH and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI), respectively. We also demonstrate the effect of diffusion and that of geometric packing of the electrolyte ions in the pores, where a commensurate match of the electrolyte ions with the pores of carbonized materials control and influence significantly the capacitance of these materials.

3D Aerogel of Graphitic Carbon Nitride Modified with Perylene Imide and Graphene Oxide for Highly Efficient Nitric Oxide Removal under Visible Light.

PubMed

Hu, Jundie; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

2018-05-01

3D materials are considered promising for photocatalytic applications in air purification because of their large surface areas, controllability, and recyclability. Here, a series of aerogels consisting of graphitic-carbon nitride (g-C 3 N 4 ) modified with a perylene imide (PI) and graphene oxide (GO) are prepared for nitric oxide (NO) removal under visible-light irradiation. All of the photocatalysts exhibit excellent activity in NO removal because of the strong light absorption and good planarity of PI-g-C 3 N 4 coupled with the favorable charge transport properties of GO, which slow the recombination of electron-hole pairs. The aerogel containing thiophene displays the most efficient NO removal of the aerogel series, with a removal ratio of up to 66%. Density functional theory calculations are conducted to explain this result and recycling experiments are carried out to verify the stability and recyclability of these photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Versatile Cellulose-Based Carbon Aerogel for the Removal of Both Cationic and Anionic Metal Contaminants from Water.

PubMed

Alatalo, Sara-Maaria; Pileidis, Filoklis; Mäkilä, Ermei; Sevilla, Marta; Repo, Eveliina; Salonen, Jarno; Sillanpää, Mika; Titirici, Maria-Magdalena

2015-11-25

Hydrothermal carbonization of cellulose in the presence of the globular protein ovalbumin leads to the formation of nitrogen-doped carbon aerogel with a fibrillar continuous carbon network. The protein plays here a double role: (i) a natural source of nitrogen functionalities (2.1 wt %) and (ii) structural directing agent (S(BET) = 38 m(2)/g). The applicability in wastewater treatment, namely, for heavy metal removal, was examined through adsorption of Cr(VI) and Pb(II) ion solely and in a mixed bicomponent aqueous solutions. This cellulose-based carbogel shows an enhanced ability to remove both Cr(VI) (∼68 mg/g) and Pb(II) (∼240 mg/g) from the targeted solutions in comparison to other carbon materials reported in the literature. The presence of competing ions showed little effect on the adsorption efficiency toward Cr(VI) and Pb(II).

Systematic studies of tannin–formaldehyde aerogels: preparation and properties

PubMed Central

Amaral-Labat, Gisele; Szczurek, Andrzej; Fierro, Vanessa; Pizzi, Antonio; Celzard, Alain

2013-01-01

Gelation of tannin–formaldehyde (TF) solutions was systematically investigated by changing pH and concentration of TF resin in water. In this way we constructed the TF phase diagram, from which chemical hydrogels could be described, and also synthesized thermoreversible tannin-based hydrogels. Conditions of non-gelation were also determined. Hydrogels were dried in supercritical CO2, leading to a broad range of TF aerogels. The latter were investigated for volume shrinkage, total porosity, micro-, meso- and macropore volumes, Brunauer–Emmett–Teller (BET) surface area, microscopic texture, mechanical and thermal properties. All these properties are discussed in relation to each other, leading to an accurate and self-consistent description of these bioresource-based highly porous materials. The conditions for obtaining the highest BET surface area or mesopore volume were determined and explained in relation to the preparation conditions. The highest BET surface area, 880 m2 g−1, is remarkably high for organic aerogels derived from a natural resource. PMID:27877559

Systematic studies of tannin-formaldehyde aerogels: preparation and properties

NASA Astrophysics Data System (ADS)

Amaral-Labat, Gisele; Szczurek, Andrzej; Fierro, Vanessa; Pizzi, Antonio; Celzard, Alain

2013-02-01

Gelation of tannin-formaldehyde (TF) solutions was systematically investigated by changing pH and concentration of TF resin in water. In this way we constructed the TF phase diagram, from which chemical hydrogels could be described, and also synthesized thermoreversible tannin-based hydrogels. Conditions of non-gelation were also determined. Hydrogels were dried in supercritical CO2, leading to a broad range of TF aerogels. The latter were investigated for volume shrinkage, total porosity, micro-, meso- and macropore volumes, Brunauer-Emmett-Teller (BET) surface area, microscopic texture, mechanical and thermal properties. All these properties are discussed in relation to each other, leading to an accurate and self-consistent description of these bioresource-based highly porous materials. The conditions for obtaining the highest BET surface area or mesopore volume were determined and explained in relation to the preparation conditions. The highest BET surface area, 880 m2 g-1, is remarkably high for organic aerogels derived from a natural resource.

Recent Advances in Porous Carbon Materials for Electrochemical Energy Storage.

PubMed

Wang, Libin; Hu, Xianluo

2018-06-18

Climate change and the energy crisis have promoted the rapid development of electrochemical energy-storage devices. Owing to many intriguing physicochemical properties, such as excellent chemical stability, high electronic conductivity, and a large specific surface area, porous carbon materials have always been considering as a promising candidate for electrochemical energy storage. To date, a wide variety of porous carbon materials based upon molecular design, pore control, and compositional tailoring have been proposed for energy-storage applications. This focus review summarizes recent advances in the synthesis of various porous carbon materials from the view of energy storage, particularly in the past three years. Their applications in representative electrochemical energy-storage devices, such as lithium-ion batteries, supercapacitors, and lithium-ion hybrid capacitors, are discussed in this review, with a look forward to offer some inspiration and guidelines for the exploitation of advanced carbon-based energy-storage materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prototype Aerogel Insulation for Melamine-Foam Substitute: Critical Space Station Express Rack Technology

NASA Technical Reports Server (NTRS)

Noever, David A.; Sibille, Laurent; Smith, David; Cronise, Raymond

1998-01-01

There is a current lack of environmentally acceptable foams to insulate Long-Duration Human Spaceflight Missions, including the experimental Express Rack for the Space Station. A recent 60-day manned test in a sealed chamber at Johnson Space Center (JSC) was nearly aborted, because of persistently high formaldehyde concentrations in the chamber. Subsequent investigation showed that the source was melamine foam (used extensively for acoustic insulation). The thermal and acoustic potential for melamine-foam substitutes is evaluated for scale-up to a silica-based foam and aerogel, which is environmentally benign for long duration space flight. These features will be discussed in reference to an aerogel prototype to: 1) assemble material strength data for various formulated aerogels, both silica and organic carbon aerogels; 2) assemble the aerogel into panels of mylar/vacuum-encapsulated rigid boards which can be molded in various shapes and rigidities; and 3) describe a process for space applications for formaldehyde-free, long duration thermal and acoustic insulators.

Aerogels made of chitosan and chondroitin sulfate at high degree of neutralization: Biological properties toward wound healing.

PubMed

Concha, Miguel; Vidal, Alejandra; Giacaman, Annesi; Ojeda, Javier; Pavicic, Francisca; Oyarzun-Ampuero, Felipe A; Torres, César; Cabrera, Marcela; Moreno-Villoslada, Ignacio; Orellana, Sandra L

2018-02-09

In this study, highly neutralized, highly porous, and ultralight polymeric aerogels prepared from aqueous colloidal suspensions of chitosan (CS) and chondroitin sulfate (ChS) nanocomplexes, formulated as quasi-equimolar amounts of both, are described. These aerogels were designed as healing agents under the inspiration of minimizing the amount of matter applied to wounds, reducing the electrostatic potential of the material and avoiding covalent cross-linkers in order to decrease metabolic stress over wounds. Aerogels synthesized under these criteria are biocompatible and provide specific properties for the induction of wound healing. They do not affect neither the metabolic activity of cultured 3T3 fibroblasts nor the biochemical parameters of experimental animals, open wounds close significantly faster and, unlike control wounds, complete reepithelialization and scarring can be attained 14 days after surgery. Because of its hydration abilities, rapid adaptation to the wound bed and the early accelerator effect of wound closure, the CS/ChS aerogels appear to be functional inducers of the healing. Previous information show that CS/ChS aerogels improve wound bed quality, increase granulation tissue and have pain suppressive effect. CS/ChS aerogels are useful as safe, inexpensive and easy to handle materials for topical applications, such as skin chronic wounds. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Cellulose nanofiber aerogel as a promising biomaterial for customized oral drug delivery

PubMed Central

Bhandari, Jyoti; Mishra, Harshita; Mishra, Pawan Kumar; Wimmer, Rupert; Ahmad, Farhan J; Talegaonkar, Sushama

2017-01-01

Cellulose nanofiber (CNF) aerogels with favorable floatability and mucoadhesive properties prepared by the freeze-drying method have been introduced as new possible carriers for oral controlled drug delivery system. Bendamustine hydrochloride is considered as the model drug. Drug loading was carried out by the physical adsorption method, and optimization of drug-loaded formulation was done using central composite design. A very lightweight-aerogel-with-matrix system was produced with drug loading of 18.98%±1.57%. The produced aerogel was characterized for morphology, tensile strength, swelling tendency in media with different pH values, floating behavior, mucoadhesive detachment force and drug release profiles under different pH conditions. The results showed that the type of matrix was porous and woven with excellent mechanical properties. The drug release was assessed by dialysis, which was fitted with suitable mathematical models. Approximately 69.205%±2.5% of the drug was released in 24 hours in medium of pH 1.2, whereas ~78%±2.28% of drug was released in medium of pH 7.4, with floating behavior for ~7.5 hours. The results of in vivo study showed a 3.25-fold increase in bioavailability. Thus, we concluded that CNF aerogels offer a great possibility for a gastroretentive drug delivery system with improved bioavailability. PMID:28352172

Construct 3D porous hollow Co3O4 micro-sphere: A potential oxidizer of nano-energetic materials with superior reactivity

NASA Astrophysics Data System (ADS)

Wang, Jun; Zheng, Bo; Qiao, Zhiqiang; Chen, Jin; Zhang, Liyuan; Zhang, Long; Li, Zhaoqian; Zhang, Xingquan; Yang, Guangcheng

2018-06-01

High energy density and rapid reactivity are the future trend for nano-energetic materials. Energetic performance of nano-energetic materials depends on the interfacial diffusion and mass transfer during the reacted process. However, the development of desired structure to significantly enhance reactivity still remains challenging. Here we focused on the design and preparation of 3D porous hollow Co3O4 micro-spheres, in which gas-blowing agents (air) and maximize interfacial interactions were introduced to enhance mass transport and reduce the diffusion distance between the oxidizer and fuel (Aluminum). The 3D hierarchical Co3O4/Al based nano-energetic materials show a low-onset decomposition temperature (423 °C), and high heat output (3118 J g-1) resulting from porous and hollow nano-structure of Co3O4 micro-spheres. Furthermore, 3D hierarchical Co3O4/Al arrays were directly fabricated on the silicon substrate, which was fully compatible with silicon-based microelectromechanical systems to achieve functional nanoenergetics-on-a-chip. This approach provides a simple and efficient way to fabricate 3D ordered nano-energetic arrays with superior reactivity and the potential on the application in micro-energetic devices.

Thermal management of thermoacoustic sound projectors using a free-standing carbon nanotube aerogel sheet as a heat source.

PubMed

Aliev, Ali E; Mayo, Nathanael K; Baughman, Ray H; Avirovik, Dragan; Priya, Shashank; Zarnetske, Michael R; Blottman, John B

2014-10-10

Carbon nanotube (CNT) aerogel sheets produce smooth-spectra sound over a wide frequency range (1-10(5) Hz) by means of thermoacoustic (TA) sound generation. Protective encapsulation of CNT sheets in inert gases between rigid vibrating plates provides resonant features for the TA sound projector and attractive performance at needed low frequencies. Energy conversion efficiencies in air of 2% and 10% underwater, which can be enhanced by further increasing the modulation temperature. Using a developed method for accurate temperature measurements for the thin aerogel CNT sheets, heat dissipation processes, failure mechanisms, and associated power densities are investigated for encapsulated multilayered CNT TA heaters and related to the thermal diffusivity distance when sheet layers are separated. Resulting thermal management methods for high applied power are discussed and deployed to construct efficient and tunable underwater sound projector for operation at relatively low frequencies, 10 Hz-10 kHz. The optimal design of these TA projectors for high-power SONAR arrays is discussed.

Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity.

PubMed

Si, Yang; Wang, Xueqin; Dou, Lvye; Yu, Jianyong; Ding, Bin

2018-04-01

Ultralight aerogels that are both highly resilient and compressible have been fabricated from various materials including polymer, carbon, and metal. However, it has remained a great challenge to realize high elasticity in aerogels solely based on ceramic components. We report a scalable strategy to create superelastic lamellar-structured ceramic nanofibrous aerogels (CNFAs) by combining SiO 2 nanofibers with aluminoborosilicate matrices. This approach causes the random-deposited SiO 2 nanofibers to assemble into elastic ceramic aerogels with tunable densities and desired shapes on a large scale. The resulting CNFAs exhibit the integrated properties of flyweight densities of >0.15 mg cm -3 , rapid recovery from 80% strain, zero Poisson's ratio, and temperature-invariant superelasticity to 1100°C. The integral ceramic nature also provided the CNFAs with robust fire resistance and thermal insulation performance. The successful synthesis of these fascinating materials may provide new insights into the development of ceramics in a lightweight, resilient, and structurally adaptive form.

Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity

PubMed Central

Wang, Xueqin; Dou, Lvye; Yu, Jianyong

2018-01-01

Ultralight aerogels that are both highly resilient and compressible have been fabricated from various materials including polymer, carbon, and metal. However, it has remained a great challenge to realize high elasticity in aerogels solely based on ceramic components. We report a scalable strategy to create superelastic lamellar-structured ceramic nanofibrous aerogels (CNFAs) by combining SiO2 nanofibers with aluminoborosilicate matrices. This approach causes the random-deposited SiO2 nanofibers to assemble into elastic ceramic aerogels with tunable densities and desired shapes on a large scale. The resulting CNFAs exhibit the integrated properties of flyweight densities of >0.15 mg cm−3, rapid recovery from 80% strain, zero Poisson’s ratio, and temperature-invariant superelasticity to 1100°C. The integral ceramic nature also provided the CNFAs with robust fire resistance and thermal insulation performance. The successful synthesis of these fascinating materials may provide new insights into the development of ceramics in a lightweight, resilient, and structurally adaptive form. PMID:29719867

Infiltrated carbon foam composites

NASA Technical Reports Server (NTRS)

Lucas, Rick D. (Inventor); Danford, Harry E. (Inventor); Plucinski, Janusz W. (Inventor); Merriman, Douglas J. (Inventor); Blacker, Jesse M. (Inventor)

2012-01-01

An infiltrated carbon foam composite and method for making the composite is described. The infiltrated carbon foam composite may include a carbonized carbon aerogel in cells of a carbon foam body and a resin is infiltrated into the carbon foam body filling the cells of the carbon foam body and spaces around the carbonized carbon aerogel. The infiltrated carbon foam composites may be useful for mid-density ablative thermal protection systems.

Method of manufacturing aerogel composites

DOEpatents

Cao, W.; Hunt, A.J.

1999-03-09

Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel.

Method of manufacturing aerogel composites

DOEpatents

Cao, Wanqing; Hunt, Arlon Jason

1999-01-01

Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel.

High surface area aerogels for energy storage and efficiency