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1

Aerogels Insulate Against Extreme Temperatures  

NASA Technical Reports Server (NTRS)

In 1992, NASA started to pursue the development of aerogel for cryogenic insulation. Kennedy Space Center awarded Small Business Innovation Research (SBIR) contracts to Aspen Systems Inc., of Marlborough, Massachusetts, that resulted in a new manufacturing process and a new flexible, durable, easy-to-use form of aerogel. Aspen Systems formed Aspen Aerogels Inc., in Northborough, Massachusetts, to market the product, and by 2009, the company had become the leading provider of aerogel in the United States, producing nearly 20 million square feet per year. With an array of commercial applications, the NASA-derived aerogel has most recently been applied to protect and insulate people s hands and feet.

2010-01-01

2

Composite flexible blanket insulation  

NASA Technical Reports Server (NTRS)

An improved composite flexible blanket insulation is presented comprising top silicon carbide having an interlock design, wherein the reflective shield is composed of single or double aluminized polyimide and wherein the polyimide film has a honeycomb pattern.

Kourtides, Demetrius A. (inventor); Lowe, David M. (inventor)

1994-01-01

3

Analysis and testing of multilayer and aerogel insulation configurations  

SciTech Connect

Multilayer insulation systems that have robust operational characteristics have long been a goal of many research projects. Such thermal insulation systems may need to offer some degree of structural support and/or mechanical integrity during loss of vacuum scenarios while continuing to provide insulative value to the vessel. Aerogel-based composite blankets can be the best insulation materials in ambient pressure environments; in high vacuum, the thermal performance of aerogel improves by about one order of magnitude. Standard multilayer insulation (MLI) is typically 50% worse at ambient pressure and at soft vacuum, but as much as two or three orders of magnitude better at high vacuum. Different combinations of aerogel blanket and multilayer insulation materials have been tested at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Analysis performed at Oak Ridge National Laboratory showed an importance to the relative location of the MLI and aerogel blankets. Apparent thermal conductivity testing under cryogenicvacuum conditions was performed to verify the analytical conclusion. Tests results are shown to be in agreement with the analysis which indicated that the best performance is obtained with aerogel layers located in the middle of the blanket insulation system.

Johnson, W L [NASA Kennedy Space Center, Kennedy Space Center, Florida; Demko, Jonathan A [ORNL; Fesmire, J. E. [NASA Kennedy Space Center, Kennedy Space Center, Florida

2010-01-01

4

Aerogel beads as cryogenic thermal insulation system  

Microsoft Academic Search

An investigation of the use of aerogel beads as thermal insulation for cryogenic applications was conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Steady-state liquid nitrogen boiloff methods were used to characterize the thermal performance of aerogel beads in comparison with conventional insulation products such as perlite powder and multilayer insulation (MLI). Aerogel beads produced by Cabot

J. E. Fesmire; S. D. Augustynowicz; S. Rouanet

2002-01-01

5

Aerogels Insulate Missions and Consumer Products  

NASA Technical Reports Server (NTRS)

Aspen Aerogels, of Northborough, Massachusetts, worked with NASA through an SBIR contract with Kennedy Space Center to develop a robust, flexible form of aerogel for cryogenic insulation for space shuttle launch applications. The company has since used the same manufacturing process developed under the SBIR award to expand its product offerings into the more commercial realms, making the naturally fragile aerogel available for the first time as a standard insulation that can be handled and installed just like standard insulation.

2008-01-01

6

Aerogel Based Insulation for High Temperature Industrial Processes.  

National Technical Information Service (NTIS)

Under this program, Aspen Aerogels has developed an industrial insulation called Pyrogel HT, which is 4-5 times more thermally efficient than current non-aerogel technology. Derived from nanoporous silica aerogels, Pyrogel HT was specifically developed to...

O. Evans

2011-01-01

7

Fibrous-Ceramic/Aerogel Composite Insulating Tiles  

NASA Technical Reports Server (NTRS)

Fibrous-ceramic/aerogel composite tiles have been invented to afford combinations of thermal-insulation and mechanical properties superior to those attainable by making tiles of fibrous ceramics alone or aerogels alone. These lightweight tiles can be tailored to a variety of applications that range from insulating cryogenic tanks to protecting spacecraft against re-entry heating. The advantages and disadvantages of fibrous ceramics and aerogels can be summarized as follows: Tiles made of ceramic fibers are known for mechanical strength, toughness, and machinability. Fibrous ceramic tiles are highly effective as thermal insulators in a vacuum. However, undesirably, the porosity of these materials makes them permeable by gases, so that in the presence of air or other gases, convection and gas-phase conduction contribute to the effective thermal conductivity of the tiles. Other disadvantages of the porosity and permeability of fibrous ceramic tiles arise because gases (e.g., water vapor or cryogenic gases) can condense in pores. This condensation contributes to weight, and in the case of cryogenic systems, the heat of condensation undesirably adds to the heat flowing to the objects that one seeks to keep cold. Moreover, there is a risk of explosion associated with vaporization of previously condensed gas upon reheating. Aerogels offer low permeability, low density, and low thermal conductivity, but are mechanically fragile. The basic idea of the present invention is to exploit the best features of fibrous ceramic tiles and aerogels. In a composite tile according to the invention, the fibrous ceramic serves as a matrix that mechanically supports the aerogel, while the aerogel serves as a low-conductivity, low-permeability filling that closes what would otherwise be the open pores of the fibrous ceramic. Because the aerogel eliminates or at least suppresses permeation by gas, gas-phase conduction, and convection, the thermal conductivity of such a composite even at normal atmospheric pressure is not much greater than that of the fibrous ceramic alone in a vacuum.

White, Susan M.; Rasky, Daniel J.

2004-01-01

8

Aerogel insulation systems for space launch applications  

NASA Astrophysics Data System (ADS)

New developments in materials science in the areas of solution gelation processes and nanotechnology have led to the recent commercial production of aerogels. Concurrent with these advancements has been the development of new approaches to cryogenic thermal insulation systems. For example, thermal and physical characterizations of aerogel beads under cryogenic-vacuum conditions have been performed at the Cryogenics Test Laboratory of the NASA Kennedy Space Center. Aerogel-based insulation system demonstrations have also been conducted to improve performance for space launch applications. Subscale cryopumping experiments show the thermal insulating ability of these fully breathable nanoporous materials. For a properly executed thermal insulation system, these breathable aerogel systems are shown to not cryopump beyond the initial cooldown and thermal stabilization phase. New applications are being developed to augment the thermal protection systems of space launch vehicles, including the Space Shuttle External Tank. These applications include a cold-boundary temperature of 90 K with an ambient air environment in which both weather and flight aerodynamics are important considerations. Another application is a nitrogen-purged environment with a cold-boundary temperature of 20 K where both initial cooldown and launch ascent profiles must be considered. Experimental results and considerations for these flight system applications are discussed.

Fesmire, J. E.

2006-02-01

9

Aerogel insulation applications for liquid hydrogen launch vehicle tanks  

NASA Astrophysics Data System (ADS)

Solutions to thermal insulation problems using aerogel beads were demonstrated for space launch vehicles using a model of the space shuttle external tank's liquid hydrogen (LH 2) intertank. Test results using liquid helium show that with aerogel, the nitrogen mass inside the intertank is greatly reduced and free liquid nitrogen is eliminated. Physisorption within the aerogel was also investigated, showing that the sorption ratio (liquid nitrogen to aerogel beads) is about 62%. The insulating effectiveness of the aerogel shows that cryopumping is driven by thermal communication between warm and cold surfaces. This technology can solve heat transfer problems and augment existing thermal protection systems on launch vehicles.

Fesmire, J. E.; Sass, J. P.

2008-05-01

10

Nanogel Aerogel as Load Bearing Insulation for Cryogenic Systems  

NASA Astrophysics Data System (ADS)

Load support structures in cryogenic storage, transport and processing systems are large contributors to the total heat leak of the system. Conventional insulation systems require the use of these support members in order to stabilize the process fluid enclosure and prevent degradation of insulation performance due to compression. Removal of these support structures would substantially improve system efficiency. Nanogel aerogel insulation performance is tested at vacuum pressures ranging from high vacuum to atmospheric pressure and under loads from loosely packed to greater than 10,000 Pa. Insulation performance is determined using boil-off calorimetry with liquid nitrogen as the latent heat recipient. Two properties of the aerogel insulation material suit it to act as a load bearing ``structure'' in a process vessel: (1) Ability to maintain thermal performance under load; (2) Elasticity when subjected to load. Results of testing provide positive preliminary indication that these properties allow Nanogel aerogel to effectively be used as a load bearing insulation in cryogenic systems.

Koravos, J. J.; Miller, T. M.; Fesmire, J. E.; Coffman, B. E.

2010-04-01

11

Ceramic electrical insulators for liquid metal blankets  

Microsoft Academic Search

A systematic evaluation of ceramic electrical insulators for a self-cooled, liquid-lithium\\/vanadium-alloy blanket has been conducted to identify the most promising candidates as well as the data needs. Fifteen oxides and nitrides are included in this evaluation; all of them have been assessed against a common set of technical requirements, low activation and cost. Among these materials, CaO, MgO, BN, and

Y. Y. Liu; D. L. Smith

1986-01-01

12

Process for Forming Transparent Aerogel Insulating Arrays.  

National Technical Information Service (NTIS)

An improved supercritical drying process for forming transparent silica aerogel arrays is described. The process is of the type utilizing the steps of hydrolyzing and condensing aloxides to form alcogels. A subsequent step removes the alcohol to form aero...

P. H. Tewari A. J. Hunt

1985-01-01

13

Thin Thermal-Insulation Blankets for Very High Temperatures  

NASA Technical Reports Server (NTRS)

Thermal-insulation blankets of a proposed type would be exceptionally thin and would endure temperatures up to 2,100 C. These blankets were originally intended to protect components of the NASA Solar Probe spacecraft against radiant heating at its planned closest approach to the Sun (a distance of 4 solar radii). These blankets could also be used on Earth to provide thermal protection in special applications (especially in vacuum chambers) for which conventional thermal-insulation blankets would be too thick or would not perform adequately.

Choi, Michael K.

2003-01-01

14

Thin Thermal-Insulation Blankets for Very High Temperatures  

NASA Technical Reports Server (NTRS)

Thermal-insulation blankets of a proposed type would be exceptionally thin and would endure temperatures up to 2,100 C. These blankets were originally intended to protect components of the NASA Solar Probe spacecraft against radiant heating at its planned closest approach to the Sun (a distance of 4 solar radii). These blankets could also be used on Earth to provide thermal protection in special applications (especially in vacuum chambers) for which conventional thermal-insulation blankets would be too thick or would not perform adequately. A blanket according to the proposal (see figure) would be made of molybdenum, titanium nitride, and carbon- carbon composite mesh, which melt at temperatures of 2,610, 2,930, and 2,130 C, respectively. The emittance of molybdenum is 0.24, while that of titanium nitride is 0.03. Carbon-carbon composite mesh is a thermal insulator. Typically, the blanket would include 0.25-mil (.0.00635-mm)-thick hot-side and cold-side cover layers of molybdenum. Titanium nitride would be vapor-deposited on both surfaces of each cover layer. Between the cover layers there would be 10 inner layers of 0.15-mil (.0.0038-mm)-thick molybdenum with vapor-deposited titanium nitride on both sides of each layer. The thickness of each titanium nitride coat would be about 1,000 A. The cover and inner layers would be interspersed with 0.25-mil (0.00635-mm)-thick layers of carbon-carbon composite mesh. The blanket would have total thickness of 4.75 mils (approximately equal to 0.121 mm) and an areal mass density of 0.7 kilograms per square meter. One could, of course, increase the thermal- insulation capability of the blanket by increasing number of inner layers (thereby unavoidably increasing the total thickness and mass density).

Choi, Michael K.

2003-01-01

15

Thermal resistance and compressive strain of underwater aerogel syntactic foam hybrid insulation at atmospheric and elevated hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The purpose of this study was to present a new underwater thermal insulation designed for flexibility and high thermal resistance. The insulation was a hybrid composite of two constituents: syntactic foam and an insulating aerogel blanket. Methods for treating and combining the constituents into a hybrid insulation of several designs are presented. A final configuration was selected based on high thermal resistance and was tested for thermal resistance and compressive strain to a pressure of 1.2 MPa (107 msw, meters of sea water) for five continuous pressure cycles. The thermal resistance and compressive strain results were compared to foam neoprene and underwater pipeline insulation. It was found that the hybrid insulation has a thermal resistance significantly higher than both foam neoprene and underwater pipeline insulation at atmospheric and elevated hydrostatic pressures (1.2 MPa). The total thermal resistance of the hybrid insulation decreased 32% at 1.2 MPa and returned to its initial value upon decompression. It was concluded that the hybrid insulation, with modifications, could be used for wetsuit construction, shallow underwater pipeline insulation, or any underwater application where high thermal resistance, flexibility, and resistance to compression are desired.

Bardy, Erik; Mollendorf, Joseph; Pendergast, David

2006-05-01

16

Synthesis of silica aerogel blanket by ambient drying method using water glass based precursor and glass wool modified by alumina sol  

Microsoft Academic Search

Silica aerogel blankets have been synthesized by ambient drying technique using cheap water glass as the silica source and glass wool modified by alumina sol. One step solvent exchange and surface modification were simultaneously conducted by immersing the wet hydrogel blanket in EtOH\\/TMCS\\/hexane solution. The synthesized silica aerogel blanket was light with the density of 0.143–0.104g\\/cm3 and 89.4–95% porosity. The

J. Chandradass; Sung Kang; Dong-sik Bae

2008-01-01

17

Polymethylsilsesquioxane-cellulose nanofiber biocomposite aerogels with high thermal insulation, bendability, and superhydrophobicity.  

PubMed

Polymethylsilsesquioxane-cellulose nanofiber (PMSQ-CNF) composite aerogels have been prepared through sol-gel in a solvent containing a small amount of CNFs as suspension. Since these composite aerogels do not show excessive aggregation of PMSQ and CNF, the original PMSQ networks are not disturbed. Composite aerogels with low density (0.020 g cm(-3) at lowest), low thermal conductivity (15 mW m(-1) K(-1)), visible light translucency, bending flexibility, and superhydrophobicity thus have been successfully obtained. In particular, the lowest density and bending flexibility have been achieved with the aid of the physical supporting effect of CNFs, and the lowest thermal conductivity is comparable with the original PMSQ aerogels and standard silica aerogels. The PMSQ-CNF composite aerogels would be a candidate to practical high-performance thermal insulating materials. PMID:24865571

Hayase, Gen; Kanamori, Kazuyoshi; Abe, Kentaro; Yano, Hiroyuki; Maeno, Ayaka; Kaji, Hironori; Nakanishi, Kazuki

2014-06-25

18

Double layered tailorable advanced blanket insulation  

NASA Technical Reports Server (NTRS)

An advanced flexible reusable surface insulation material for future space shuttle flights was investigated. A conventional fly shuttle loom with special modifications to weave an integral double layer triangular core fabric from quartz yarn was used. Two types of insulating material were inserted into the cells of the fabric, and a procedure to accomplish this was developed. The program is follow up of a program in which single layer rectangular cell core fabrics are woven and a single type of insulating material was inserted into the cells.

Falstrup, D.

1983-01-01

19

Heat insulation performance, mechanics and hydrophobic modification of cellulose-SiO2 composite aerogels.  

PubMed

Cellulose-SiO2 composite hydrogel was prepared by combining the NaOH/thiourea/H2O solvent system and the immersion method with controlling the hydrolysis-fasculation rate of tetraethyl orthosilicate (TEOS). The hydrophobic composite aerogels were obtained through the freeze-drying technology and the cold plasma modification technology. Composite SiO2 could obviously reduce the thermal conductivity of cellulose aerogel. The thermal conductivity could be as low as 0.026 W/(mK). The thermal insulation mechanism of the aerogel material was discussed. Composite SiO2 reduced hydrophilicity of cellulose aerogel, but environmental humidity had a significant influence on heat insulation performance. After hydrophobic modification using CCl4 as plasma was conducted, the surface of composite aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 132°. The modified composite aerogel still kept good heat insulation performance. This work provided a foundation for the possibility of applying cellulose-SiO2 composite aerogel in the insulating material field. PMID:23987346

Shi, Jianjun; Lu, Lingbin; Guo, Wantao; Zhang, Jingying; Cao, Yang

2013-10-15

20

Tailorable advanced blanket insulation using aluminoborosilicate and alumina batting  

NASA Technical Reports Server (NTRS)

Two types of Tailorable Advanced Blanket Insulation (TABI) flat panels for Advanced Space Transportation Systems were produced. Both types consisted of integrally woven, 3-D fluted core having parallel faces and connecting ribs of Nicalon yarns. The triangular cross section flutes of one type was filled with mandrels of processed Ultrafiber (aluminoborosilicate) stitchbonded Nextel 440 fibrous felt, and the second type wall filled with Saffil alumina fibrous felt insulation. Weaving problems were minimal. Insertion of the fragile insulation mandrels into the fabric flutes was improved by using a special insertion tool. An attempt was made to weave fluted core fabrics from Nextel 440 yarns but was unsuccessful because of the yarn's fragility. A small sample was eventually produced by an unorthodox weaving process and then filled with Saffil insulation. The procedures for setting up and weaving the fabrics and preparing and inserting insulation mandrels are discussed. Characterizations of the panels produced are also presented.

Calamito, Dominic P.

1989-01-01

21

Polyolefin-Based Aerogels  

NASA Technical Reports Server (NTRS)

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 radiation shielding materials due to their lower content of hydrogen element. The present invention relates to maleinized polybutadiene (or polybutadiene adducted with maleic anhydride)- based aerogel monoliths and composites, and the methods for preparation. Hereafter, they are collectively referred to as polybutadiene aerogels. Specifically, the polybutadiene aerogels of the present invention are prepared by mixing a maleinized polybutadiene resin, a hardener containing a maleic anhydride reactive group, and a catalyst in a suitable solvent, and maintaining the mixture in a quiescent state for a sufficient period of time to form a polymeric gel. After aging at elevated temperatures for a period of time to provide uniformly stronger wet gels, the micro porous maleinized polybutadiene- based aerogel is then obtained by removing interstitial solvent by supercritical drying. The mesoporous maleinized polybutadiene-based aerogels contain an open-pore structure, which provides inherently hydrophobic, flexible, nearly unbreakable, less dusty aerogels with excellent thermal and physical properties. The materials can be used as thermal and acoustic insulation, radiation shielding, and vibration-damping materials. The organic PB-based rubber aerogels are very flexible, no-dust, and hydrophobic organics that demonstrated the following ranges of typical properties: densities of 0.08 to 0.255 grams per cubic centimeters, shrinkage factor (raerogel/rtarget) = 1.2 to 2.84, and thermal conductivity values of 20.0 to 35.0 mW/m-K.

Lee, Je Kyun; Gould, George

2012-01-01

22

Flexible Aerogel as a Superior Thermal Insulation for High Temperature Superconductor Cable Applications  

NASA Astrophysics Data System (ADS)

High temperature superconducting (HTS) cables are an advanced technology that can both strengthen and improve the national electrical distribution infrastructure. HTS cables require sufficient cooling to overcome inherent low temperature heat loading. Heat loads are minimized by the use of cryogenic envelopes or cryostats. Cryostats require improvement in efficiency, reliability, and cost reduction to meet the demanding needs of HTS conductors (1G and 2G wires). Aspen Aerogels has developed a compression resistant aerogel thermal insulation package to replace compression sensitive multi-layer insulation (MLI), the incumbent thermal insulation, in flexible cryostats for HTS cables. Oak Ridge National Laboratory tested a prototype aerogel package in a lab-scale pipe apparatus to measure the rate of heat invasion. The lab-scale pipe test results of the aerogel solution will be presented and directly compared to MLI. A compatibility assessment of the aerogel material with HTS system components will also be presented. The aerogel thermal insulation solution presented will meet the demanding needs of HTS cables.

White, S.; Demko, J.; Tomich, A.

2010-04-01

23

Spray-on technique simplifies fabrication of complex thermal insulation blanket  

NASA Technical Reports Server (NTRS)

Spray-on process constructs molds used in forming sections of thermal insulation blankets. The process simplifies the fabrication of blankets by eliminating much of the equipment formerly required and decreasing the time involved.

Bond, W. E. G.; Raymond, R.

1966-01-01

24

A blanket design, apparatus, and fabrication techniques for the mass production of multilayer insulation blankets for the Superconducting Super Collider  

SciTech Connect

The multilayer insulation (MLI) system for the Superconducting Super Collider (SSC) consists of full cryostat length assemblies of aluminized polyester film fabricated in the form of blankets and installed as blankets to the 4.5K cold mass and the 20K and 80K thermal radiation shields. Approximately 40,000 MLI blankets will be required in the 10,000 cryogenic devices comprising the SSC accelerator. Each blanket is nearly 17 meters long and 1.8 meters wide. This paper reports the blanket design, an apparatus, and the fabrication method used to mass produce pre-fabricated MLI blankets. Incorporated in the blanket design are techniques which automate quality control during installation of the MLI blankets in the SSC cryostat. The apparatus and blanket fabrication method insure consistency in the mass produced blankets by providing positive control of the dimensional parameters which contribute to the thermal performance of the MLI blanket. By virtue of the fabrication process, the MLI blankets have inherent features of dimensional stability three-dimensional uniformity, controlled layer density, layer-to-layer registration, interlayer cleanliness, and interlayer material to accommodate thermal contraction differences. 11 refs., 6 figs., 1 tab.

Gonczy, J.D.; Boroski, W.N.; Niemann, R.C.; Otavka, J.G.; Ruschman, M.K.; Schoo, C.J.

1989-09-01

25

Aerogel-Based Insulation for Industrial Steam Distribution Systems.  

National Technical Information Service (NTIS)

Thermal losses in industrial steam distribution systems account for 977 trillion Btu/year in the US, more than 1% of total domestic energy consumption. Aspen Aerogels worked with Department of Energy's Industrial Technologies Program to specify, develop, ...

J. Williams

2011-01-01

26

Prototype Aerogel Insulation for Melamine-Foam Substitute: Critical Space Station Express Rack Technology  

NASA Technical Reports Server (NTRS)

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.

Noever, David A.; Sibille, Laurent; Smith, David; Cronise, Raymond

1998-01-01

27

Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels  

NASA Technical Reports Server (NTRS)

Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the carboxyl groups of the organic phase. The polymerization process has been adapted to create interpenetrating PMA and silica-gel networks from monomers and prevent any phase separations that could otherwise be caused by an overgrowth of either phase. Typically, the resulting PMA/silica aerogel, without or with fiber reinforcement, has a density and a thermal conductivity similar to those of pure silica aerogels. However, the PMA enhances mechanical properties. Specifically, flexural strength at rupture is increased to 102 psi (=0.7 MPa), about 50 times the flexural strength of typical pure silica aerogels. Resistance to compression is also increased: Applied pressure of 17.5 psi (=0.12 MPa) was found to reduce the thicknesses of several composite PMA/silica aerogels by only about 10 percent.

Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

2010-01-01

28

Aerogel applications  

Microsoft Academic Search

Aerogel materials possess a wide variety of exceptional properties, hence a striking number of applications have developed for them. Many of the commercial applications of aerogels such as catalysts, thermal insulation, windows, and particle detectors are under development and new applications have been publicized since the ISA4 Conference in 1994: e.g., supercapacitors, insulation for heat storage in automobiles, electrodes for

Lawrence W. Hrubesh

1998-01-01

29

Thermo-hygric properties of a newly developed aerogel based insulation rendering for both exterior and interior applications  

Microsoft Academic Search

A new kind of rendering based on silica aerogel granulates was developed showing a high performance namely a low thermal conductivity and a low vapour transmission resistance, a combination of characteristics unachieved by existing renderings. This insulation rendering has a clear advantage over insulation boards which need a plane subsurface, adjustment, gluing and even fastening by means of dowels. A

Th. Stahl; S. Brunner; M. Zimmermann; K. Ghazi Wakili

30

Thermal Performance of Composite Flexible Blanket Insulations for Hypersonic Aerospace Vehicles  

NASA Technical Reports Server (NTRS)

This paper describes the thermal performance of a Composite Flexible Blanket Insulation (C.F.B.I.) considered for potential use as a thermal protection system or thermal insulation for future hypersonic vehicles such as the National Aerospace Plane (N.A.S.P.). Thermophysical properties for these insulations were also measured including the thermal conductivity at various temperatures and pressures and the emissivity of the fabrics used in the flexible insulations. The thermal response of these materials subjected to aeroconvective heating from a plasma arc is also described. Materials tested included two surface variations of the insulations, and similar insulations coated with a Protective Ceramic Coating (P.C.C.). Surface and backface temperatures were measured in the flexible insulations and on Fibrous Refractory Composite Insulation (F.R.C.I.) used as a calibration model. The uncoated flexible insulations exhibited good thermal performance up to 35 W/sq cm. The use of a P.C.C. to protect these insulations at higher heating rates is described. The results from a computerized thermal analysis model describing thermal response of those materials subjected to the plasma arc conditions are included. Thermal and optical properties were determined including thermal conductivity for the rigid and flexible insulations and emissivity for the insulation fabrics. These properties were utilized to calculate the thermal performance of the rigid and flexible insulations at the maximum heating rate.

Kourtides, Demetrius A.

1993-01-01

31

Electrically insulating coatings for V-Li self-cooled blanket in a fusion system  

SciTech Connect

The blanket system is one of the most important components in a fusion reactor because it has a major impact on both the economics and safety of fusion energy. The primary functions of the blanket in a deuterium/tritium-fueled fusion reactor are to convert the fusion energy into sensible heat and to breed tritium for the fuel cycle. The liquid-metal blanket concept requires an electrically insulating coating on the first-wall structural material to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Based on the thermodynamics of interactions between the coating and the liquid lithium on one side and the structural V-base alloy on the other side, several coating candidates are being examined to perform the insulating function over a wide range of temperatures and lithium chemistries.

Natesan, K.; Reed, C. B.; Uz, M.; Park, J. H.; Smith, D. L.

2000-05-17

32

Thermal Insulator of Porous SiC/SiC Composites for Fusion Blanket System  

NASA Astrophysics Data System (ADS)

For fusion energy realization, attractive energy conversion system and fuel supply system are essentially required. The current ITER test blanket module study has dual coolant lithium lead (DCLL) system as the attractive blanket option. The concept of making ceramic thermal insulation panels for DCLL blanket has been presented, however, realistic material systems have not been proven so far. This work is trying to present the porous SiC/SiC thermal insulation panel based on the current NITE-method technology. Typical panels with through thickness and in-plane channels and porosities tailored were designed, fabricated and evaluated, successfully. Thermal conductivity of those panels were controlled, as designed, and the tailoring capability of thermal conductivity by NITE-method was presented. This concept and technology can satisfy the basic material requirements as well as economical requirements and large scale production requirements.

Satori, Kouichi; Kishimoto, Hirotatsu; Park, Joon-Soo; Jung, Hun-Chea; Lee, Young-Ju; Kohyama, Akira

2011-10-01

33

Hybrid aerogel rigid ceramic fiber insulation and method of producing same  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

34

Technical applications of aerogels.  

National Technical Information Service (NTIS)

Aerogel materials posses such a wide variety of exceptional properties that a striking number of applications have developed for them. Many of the commercial applications of aerogels such as catalysts, thermal insulation, windows, and particle detectors a...

L. W. Hrubesh

1997-01-01

35

Development of tailorable advanced blanket insulation for advanced space transportation systems  

NASA Technical Reports Server (NTRS)

Two items of Tailorable Advanced Blanket Insulation (TABI) for Advanced Space Transportation Systems were produced. The first consisted of flat panels made from integrally woven, 3-D fluted core having parallel fabric faces and connecting ribs of Nicalon silicon carbide yarns. The triangular cross section of the flutes were filled with mandrels of processed Q-Fiber Felt. Forty panels were prepared with only minimal problems, mostly resulting from the unavailability of insulation with the proper density. Rigidizing the fluted fabric prior to inserting the insulation reduced the production time. The procedures for producing the fabric, insulation mandrels, and TABI panels are described. The second item was an effort to determine the feasibility of producing contoured TABI shapes from gores cut from flat, insulated fluted core panels. Two gores of integrally woven fluted core and single ply fabric (ICAS) were insulated and joined into a large spherical shape employing a tadpole insulator at the mating edges. The fluted core segment of each ICAS consisted of an Astroquartz face fabric and Nicalon face and rib fabrics, while the single ply fabric segment was Nicalon. Further development will be required. The success of fabricating this assembly indicates that this concept may be feasible for certain types of space insulation requirements. The procedures developed for weaving the ICAS, joining the gores, and coating certain areas of the fabrics are presented.

Calamito, Dominic P.

1987-01-01

36

Applications for silica aerogel products  

Microsoft Academic Search

Aerogels, nanoporous lightweight materials, were discovered more than 60 years ago. The supercritical manufacturing process and expensive raw materials typically used to produce aerogels prohibited commercialization on an industrial scale. Recently, a commercially attractive ambient pressure production process was developed which will allow broader commercialization of silica aerogel products. Some aerogel products for insulation applications and their preparation is described.

M. Schmidt; F Schwertfeger

1998-01-01

37

Ambient Dried Aerogels  

NASA Technical Reports Server (NTRS)

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.

Jones, Steven M.; Paik, Jong-Ah

2013-01-01

38

Mechanical Properties of Aerogels.  

National Technical Information Service (NTIS)

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 c...

K. E. Parmenter F. Milstein

1995-01-01

39

Thermal properties of organic and inorganic aerogels  

Microsoft Academic Search

Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. This paper examines the three major contributions to thermal transport through porous materials; solid, gaseous, and radiative, to identify how to reduce the thermal conductivity of air-filled aerogels. We find that significant improvements in the thermal insulation property of aerogels are

Lawrence W. Hrubesh; Richard W. Pekala

1994-01-01

40

Fabrication and performance of AIN insulator coatings for application in fusion reactor blankets  

SciTech Connect

The liquid-metal blanket concept for fusion reactors requires an coating on the first-wall structural material to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Based on the thermodynamics of interactions betwen the coating and the liquid lithium on one side and the structural V-base alloy on the other side, an AIN coating was selected as a candidate. Detailed investigations were conducted on the fabrication, metallurgical microstructure, compatibility in liquid Li, and electrical characteristics of AIN material obtained from several sources. Lithium compatibility was studied in static systems by exposing AIN-coated specimens to liquid Li for several time periods. Electrical resistance was measured at room temperature on the specimens before and after exposure to liquid Li. The results obtained in this study indicate that AIN is a viable coating from the standpoint of chemical compatibility in Li, electrical insulation, and ease of fabrication; for these reasons, the coating should be examined further for fusion reactor applications.

Natesan, K.

1995-09-01

41

A comparison of the thermal resistance of a foam neoprene wetsuit to a wetsuit fabricated from aerogel-syntactic foam hybrid insulation  

Microsoft Academic Search

The purpose of this study was to compare the thermal resistance of a wetsuit fabricated from aerogel-syntactic foam hybrid insulation developed by Bardy et al [1] to a foam neoprene wetsuit. The thermal resistance of the hybrid wetsuit and a foam neoprene wetsuit was measured on a human test subject in water at 0.25 MPa (15.25 msw) of hyperbaric pressure.

Erik Bardy; Joseph Mollendorf; David Pendergast

2006-01-01

42

Sintering behaviour of alumina-modified silica aerogels  

Microsoft Academic Search

A main problem for the applicability of silica aerogels as thermal insulation materials at temperatures above 600°C is viscous sintering, which may lead to a significant density increase with time. Modification of silica aerogels via integration of alumina yields aerogels with increased stability against sintering. The onset of sintering of alumina silica aerogels occurs at about 900°C compared with about

R. Saliger; T. Heinrich; T. Gleissner; J. Fricke

1995-01-01

43

Epoxy Crosslinked Silica Aerogels (X-Aerogels)  

NASA Technical Reports Server (NTRS)

NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

2004-01-01

44

Improvements to the Synthesis of Polyimide Aerogels  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

45

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

NASA Technical Reports Server (NTRS)

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 have been demonstrated with several polymers such as polyurethanes/polyureas, epoxies and polyolefins, while crosslinking of approximately 35 different oxide aerogels yields a range of dimensionally stable, porous lightweight materials with unique combinations of structural, magnetic and optical properties. The main theme in materials development for space exploration is multifunction. For example, use of one material for thermal insulation/structural component will free weight for useful payload. In that regard, X-aerogels are evaluated at NASA for cryogenic fuel storage tanks and for spacesuits. Along the same lines, major impact fro X-Aerogels is also expected in commercial applications for thermal/acoustic insulation, in catalytic reformers and converters, in filtration membranes and membranes for fuel cells, as platforms for optical, electrical and magnetic sensors, and as lightweight structural component for aircraft and satellites.

Leventis, Nicholas

2006-01-01

46

Beta Cloth Durability Assessment for Space Station Freedom (SSF) Multi-Layer Insulation (MLI) Blanket Covers.  

National Technical Information Service (NTIS)

MLI blankets for the Space Station Freedom (SSF) must comply with general program requirements and recommendations for long life and durability in the low-Earth orbit (LEO) environment. Atomic oxygen and solar ultraviolet/vacuum ultraviolet are the most i...

J. Le S. Jacobs S. L. Koontz

1993-01-01

47

Simplified Waterproofing of Aerogels  

NASA Technical Reports Server (NTRS)

A relatively simple silanization process has been developed for waterproofing or rewaterproofing aerogels, xerogels, and aerogel/tile composites, and other, similar low-density, highly microporous materials. Such materials are potentially attractive for a variety of applications especially for thermal-insulation panels that are required to be thin and lightweight. Unfortunately, such materials are also hydrophilic and tend to collapse after adsorbing water from the air. Hence, an effective means of waterproofing is necessary to enable practical exploitation of aerogels and the like. Older processes for waterproofing aerogels are time-consuming, labor-intensive, and expensive, relative to the present process. Each of the older processes includes a number of different chemical treatment steps, and some include the use of toxic halogenated surface-modifying compounds, pressures as high as hundreds of atmospheres, and/or temperatures as high as 1,000 C.

Hsu, Ming-Ta S.; Chen, Timothy S.; White, Susan; Rasky, Daniel J.

2003-01-01

48

Mechanical Properties of Aerogels  

NASA Technical Reports Server (NTRS)

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 of reinforced aerogels can be fully understood, more tests of unreinforced aerogels are necessary. Unreinforced aerogels are of particular use because their birefringent nature allows for visual determination of stress fields during mechanical testing. The success of any future tests depends on the availability of a large supply of quality specimens with well-documented preparation and storage histories.

Parmenter, Kelly E.; Milstein, Frederick

1995-01-01

49

Beta cloth durability assessment for Space Station Freedom (SSF) Multi-Layer Insulation (MLI) blanket covers  

NASA Technical Reports Server (NTRS)

MLI blankets for the Space Station Freedom (SSF) must comply with general program requirements and recommendations for long life and durability in the low-Earth orbit (LEO) environment. Atomic oxygen and solar ultraviolet/vacuum ultraviolet are the most important factors in the SSF natural environment which affect materials life. Two types of Beta cloth (Teflon coated woven glass fabric), which had been proposed as MLI blanket covers, were tested for long-term durability in the LEO environment. General resistance to atomic oxygen attack and permeation were evaluated in the high velocity atomic oxygen beam system at Los Alamos National Laboratories. Long-term exposure to the LEO environment was simulated in the laboratory using a radio frequency oxygen plasma asher. The plasma asher treated Beta cloth specimens were tested for thermo-optical properties and mechanical durability. Space exposure data from the Long Duration Exposure Facility and the Intelsat Solar Array Coupon were also used in the durability assessment. Beta cloth fabricated to Rockwell specification MBO 135-027 (Chemglas 250) was shown to have acceptable durability for general use as an MLI blanket cover material in the LEO environment while Sheldahl G414500 should be used only in locations which are protected from direct Ram atomic oxygen.

Koontz, Steven L.; Jacobs, Stephen; Le, Julie

1993-01-01

50

Beta cloth durability assessment for Space Station Freedom (SSF) Multi-Layer Insulation (MLI) blanket covers  

SciTech Connect

MLI blankets for the Space Station Freedom (SSF) must comply with general program requirements and recommendations for long life and durability in the low-Earth orbit (LEO) environment. Atomic oxygen and solar ultraviolet/vacuum ultraviolet are the most important factors in the SSF natural environment which affect materials life. Two types of Beta cloth (Teflon coated woven glass fabric), which had been proposed as MLI blanket covers, were tested for long-term durability in the LEO environment. General resistance to atomic oxygen attack and permeation were evaluated in the high velocity atomic oxygen beam system at Los Alamos National Laboratories. Long-term exposure to the LEO environment was simulated in the laboratory using a radio frequency oxygen plasma asher. The plasma asher treated Beta cloth specimens were tested for thermo-optical properties and mechanical durability. Space exposure data from the Long Duration Exposure Facility and the Intelsat Solar Array Coupon were also used in the durability assessment. Beta cloth fabricated to Rockwell specification MBO 135-027 (Chemglas 250) was shown to have acceptable durability for general use as an MLI blanket cover material in the LEO environment while Sheldahl G414500 should be used only in locations which are protected from direct Ram atomic oxygen.

Koontz, S.L.; Jacobs, S.; Le, J.

1993-03-01

51

Aerogel Composites: Strong and Waterproof  

NASA Technical Reports Server (NTRS)

Aerogels are exotic materials having superior thermal and physical properties with great potential for both space and industrial uses. Although aerogels are excellent low-density insulators with unique acoustic and optical properties, their commercialization potential is currently limited by moisture absorption, fragility, and cost. This paper describes useful, easily scaled-up solutions to the first two of these three problems. The waterproofing and water-repellent method described here is a cheaper and simpler improvement over previous permanent methods.

White, Susan; Hsu, Ming-ta; Arnold, James O. (Technical Monitor)

1999-01-01

52

Experimental study of the influences of degraded vacuum on multilayer insulation blankets  

NASA Astrophysics Data System (ADS)

The paper presented experimental investigation on the heat transfer of MLI with different rarefied gases at different pressures. The investigations were carried out using an innovative static liquid nitrogen boil-off rate measurement system in the case of the small temperature perturbations of cold and warm boundaries. The heat fluxes for a number of inert and some polyatomic gases have been analyzed at different heat transfer conditions ranging from molecular to continuum regime, apparent thermal conductivities of the multilayer insulation were measured over a wide range of temperature (77 K-300 K) and pressure (10 -3-10 5 Pa) using the apparatus. The experimental results indicated that under degraded vacuum condition, the influences of rarefied gas on the MLI thermal performance very depend on the gas rarefaction degree which impacted by the MLI vacuum degree. Under the condition of molecular regime heat transfer, the MLI thermal performance was greatly influenced by gas energy accommodation coefficients (EAC), when under the continuum regime, the performances depend on the thermal conductivity of rarefied gas itself. Compared to the results of N 2, Ar, CO 2, Air and He as interstitial gases in the MLI, Ar was the better selection as space gas because of its low EAC and thermal conductivity characteristics on the different vacuum condition ranging from high pressure to vacuum. So different residual gases can be utilized according to the vacuum level and gas energy accommodation coefficient, in order to improve the insulation performance of low vacuum MLI.

Sun, P. J.; Wu, J. Y.; Zhang, P.; Xu, L.; Jiang, M. L.

2009-12-01

53

Material Properties for Fiber-Reinforced Silica Aerogels  

NASA Technical Reports Server (NTRS)

Ceramic fiber-reinforced silica aerogels are novel materials for high performance insulation, including thermal protection materials. Experimental data are presented for the thermal and mechanical properties, showing the trends exhibited over a range of fiber loadings and silica aerogel densities. Test results are compared to that of unreinforced bulk aerogels.

White, Susan; Rouanet, Stephane; Moses, John; Arnold, James O. (Technical Monitor)

1994-01-01

54

Aerogels in Space-Based Applications  

NASA Technical Reports Server (NTRS)

Aerogel materials have two major space applications. Aerogels have already been used in Shuttle-based experiments to capture micrometeorites for earth-based investigation of the captured particles. To exploit the well-known low thermal conductivity of these materials, the use of aerogels for thermal insulation of spacecraft is under investigation. This paper will draw on published information about aerogels and other materials, and will include only noncritical technology. No discussion will be included of specific chemical processing techniques or of advanced, technologically critical concepts.

White, Susan M.; Arnold, James O. (Technical Monitor)

1994-01-01

55

Thermal properties of organic and inorganic aerogels  

SciTech Connect

Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. This paper examines the three major contributions to thermal transport through porous materials; solid, gaseous, and radiative, to identify how to reduce the thermal conductivity of air-filled aerogels. We find that significant improvements in the thermal insulation property of aerogels are possible by; (i) employing materials with a low intrinsic solid conductivity, (ii) reducing the average pore size within aerogels, and (iii) affecting an increase of the infrared extinction in aerogels. Theoretically, polystyrene is the best of the organic materials and zirconia is the best inorganic material to use for the lowest achievable conductivity. Significant reduction of the thermal conductivity for all aerogel varieties is predicted with only a modest decrease of the average pore size. This might be achieved by modifying the sol-gel chemistry leading to aerogels. For example, a thermal resistance value of [ital R]=20 per inch would be possible for an air-filled resorcinol-formaldehyde aerogel at a density of 156 kg/m[sup 3], if the average pore size was less than 35 nm. An equation is included which facilitates the calculation of the optimum density for the minimum total thermal conductivity, for all varieties of aerogels.

Hrubesh, L.W.; Pekala, R.W. (Chemistry and Material Science Department, Lawrence Livermore National Laboratory, Livermore, California 94551-9900 (United States))

1994-03-01

56

Dielectric properties and electronic applications of aerogels  

SciTech Connect

Among their other exceptional properties, aerogels also exhibits unusual dielectric properties due to their nano-sized structures and high porosities. For example, our measurements of the dielectric constants and loss tangents for several aerogel varieties at microwave frequencies show that they both vary linearly with the aerogel density, indicating that the dielectric behavior of aerogels is more gas-like than solid-like. We have also measured the dielectric strength of silica aerogels and find that they are better than ceramics for high voltage insulation. The low dielectric constants and loss tangents of aerogels, along with their controllable thermal expansion properties, make them desirable materials for use as thin films in high speed integrated digital and microwave circuitry.

Hrubesh, L.W.; Pekala, R.W.

1993-07-01

57

Aerogel Derived Nanostructured Thermoelectric Materials  

SciTech Connect

America’s dependence on foreign sources for fuel represents a economic and security threat for the country. These non renewable resources are depleting, and the effects of pollutants from fuels such as oil are reaching a problematic that affects the global community. Solar concentration power (SCP) production systems offer the opportunity to harness one of the United States’ most under utilized natural resources; sunlight. While commercialization of this technology is increasing, in order to become a significant source of electricity production in the United States the costs of deploying and operating SCP plants must be further reduced. Parabolic Trough SCP technologies are close to meeting energy production cost levels that would raise interest in the technology and help accelerate its adoption as a method to produce a significant portion of the Country’s electric power needs. During this program, Aspen Aerogels will develop a transparent aerogel insulation that can replace the costly vacuum insulation systems that are currently used in parabolic trough designs. During the Phase I program, Aspen Aerogels will optimize the optical and thermal properties of aerogel to meet the needs of this application. These properties will be tested, and the results will be used to model the performance of a parabolic trough HCE system which uses this novel material in place of vacuum. During the Phase II program, Aspen Aerogels will scale up this technology. Together with industry partners, Aspen Aerogels will build and test a prototype Heat Collection Element that is insulated with the novel transparent aerogel material. This new device will find use in parabolic trough SCP applications.

Wendell E Rhine, PI; Dong, Wenting; Greg Caggiano, PM

2010-10-08

58

Polyurea Aerogels.  

National Technical Information Service (NTIS)

Polyurea aerogels as well as methods for preparing the same are disclosed. One method involves mixing a polyisocyanate with a polyamine in a solvent and supercritically drying the resultant gel. Polyoxyalkyleneamine are a preferred type of the polyamines....

J. K. Lee

2006-01-01

59

Synthesis and physico-chemical properties of organic aerogels  

NASA Astrophysics Data System (ADS)

Basically, an organic aerogel is any aerogel with a framework consists of organic polymers. The organic aerogels are fabricated by the sol-gel polymerization of resorcinol with formaldehyde, followed by exchanging with acetone, and then with liquid CO2 and drying under CO2 supercritical conditions. The organic aerogels obtained by this process exhibits themselves as an insulators i.e. they possesses high resistance to the flow of current through them. These obtained aerogels when heated at elevated temperatures of about 1100 °C they becomes conducting, demonstrates themselves a low resistance of the order of 4?.

Kavale, Mahendra S.; Parale, V. G.; Rao, A. Venkateswara; Wagh, P. B.; Gupta, Satish C.

2013-06-01

60

Improved Aluminized Multilayer Insulation  

NASA Technical Reports Server (NTRS)

In blanket of insulating material, layers of aluminized Mylar polyethylene terephthalate separated by spacers cause mutliple reflections of thermal radiation and impede passage of radiation through blanket. Insulating quality of blanket proportional to number of functional aluminized radiation-shield surfaces in assembly.

Tepper, Edward H.

1988-01-01

61

Polyimide Cellulose Nanocrystal Composite Aerogels  

NASA Technical Reports Server (NTRS)

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.

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

2014-01-01

62

Aerogel commercialization: Technology, markets and costs  

SciTech Connect

Commercialization of aerogels has been slow due to several factors including cost and manufacturability issues. The technology itself is well enough developed as a result of work over the past decade by an international-community of researchers. Several extensive substantial markets appear to exist for aerogels as thermal and sound insulators, if production costs can keep prices in line with competing established materials. The authors discuss here the elements which they have identified as key cost drivers, and they give a prognosis for the evolution of the technology leading to reduced cost aerogel production.

Carlson, G.; Lewis, D.; McKinley, K.; Richardson, J.; Tillotson, T.

1994-10-07

63

Composite Silica Aerogels Opacified with Titania  

NASA Technical Reports Server (NTRS)

A further improvement has been made to reduce the high-temperature thermal conductivities of the aerogel-matrix composite materials described in Improved Silica Aerogel Composite Materials (NPO-44287), NASA Tech Briefs, Vol. 32, No. 9 (September 2008), page 50. Because the contribution of infrared radiation to heat transfer increases sharply with temperature, the effective high-temperature thermal conductivity of a thermal-insulation material can be reduced by opacifying the material to reduce the radiative contribution. Therefore, the essence of the present improvement is to add an opacifying constituent material (specifically, TiO2 powder) to the aerogel-matrix composites.

Paik, Jon-Ah; Sakamoto, Jeffrey; Jones, Steven; Fleurial, Jean-Pierre; DiStefano, Salvador; Nesmith, Bill

2009-01-01

64

Polyolefin-based aerogels  

NASA Technical Reports Server (NTRS)

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.

Lee, Je Kyun (Inventor); Gould, Gerogle L. (Inventor)

2010-01-01

65

Mechanical Properties of Aerogels. Final Report  

SciTech Connect

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.

Parmenter, K.E.; Milstein, F.

1995-01-01

66

Novel load responsive multilayer insulation with high in-atmosphere and on-orbit thermal performance  

NASA Astrophysics Data System (ADS)

Aerospace cryogenic systems require lightweight, high performance thermal insulation to preserve cryopropellants both pre-launch and on-orbit. Current technologies have difficulty meeting all requirements, and advances in insulation would benefit cryogenic upper stage launch vehicles, LH2 fueled aircraft and ground vehicles, and provide capabilities for sub-cooled cryogens for space-borne instruments and orbital fuel depots. This paper reports the further development of load responsive multilayer insulation (LRMLI) that has a lightweight integrated vacuum shell and provides high thermal performance both in-air and on-orbit. LRMLI is being developed by Quest Product Development and Ball Aerospace under NASA contract, with prototypes designed, built, installed and successfully tested. A 3-layer LRMLI blanket (0.63 cm thick, 77 K cold, 295 K hot) had a measured heat leak of 6.6 W/m2 in vacuum and 40.6 W/m2 in air at one atmosphere. In-air LRMLI has an 18× advantage over Spray On Foam Insulation (SOFI) in heat leak per thickness and a 16× advantage over aerogel. On-orbit LRMLI has a 78× lower heat leak than SOFI per thickness and 6× lower heat leak than aerogel. The Phase II development of LRMLI is reported with a modular, flexible, thin vacuum shell and improved on-orbit performance. Structural and thermal analysis and testing results are presented. LRMLI mass and thermal performance is compared to SOFI, aerogel and MLI over SOFI.

Dye, S.; Kopelove, A.; Mills, G. L.

2012-04-01

67

Surface modified aerogel monoliths  

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

68

Nearly Seamless Vacuum-Insulated Boxes  

NASA Technical Reports Server (NTRS)

A design concept, and a fabrication process that would implement the design concept, have been proposed for nearly seamless vacuum-insulated boxes that could be the main structural components of a variety of controlled-temperature containers, including common household refrigerators and insulating containers for shipping foods. In a typical case, a vacuum-insulated box would be shaped like a rectangular parallelepiped conventional refrigerator box having five fully closed sides and a hinged door on the sixth side. Although it is possible to construct the five-closed-side portion of the box as an assembly of five unitary vacuum-insulated panels, it is not desirable to do so because the relatively high thermal conductances of the seams between the panels would contribute significant amounts of heat leakage, relative to the leakage through the panels themselves. In contrast, the proposal would make it possible to reduce heat leakage by constructing the five-closed-side portion of the box plus the stationary portion (if any) of the sixth side as a single, seamless unit; the only remaining seam would be the edge seal around the door. The basic cross-sectional configuration of each side of a vacuum-insulated box according to the proposal would be that of a conventional vacuum-insulated panel: a low-density, porous core material filling a partially evacuated space between face sheets. However, neither the face sheets nor the core would be conventional. The face sheets would be opposite sides of a vacuum bag. The core material would be a flexible polymer-modified silica aerogel of the type described in Silica/Polymer and Silica/Polymer/Fiber Composite Aero - gels (MSC-23736) in this issue of NASA Tech Briefs. As noted in that article, the stiffness of this core material against compression is greater than that of prior aerogels. This is an important advantage because it translates to greater retention of thickness and, hence, of insulation performance when pressure is applied across the thickness, in particular, when the space between the face sheets is evacuated, causing the core material to be squeezed between the face sheets by atmospheric pressure. Fabrication of a typical vacuum-insulated box according to the proposal would begin with fabrication of a cross-shaped polymer-modified aerogel blanket. The dimensions of the cross would be chosen so that (1) the central rectangular portion of the cross would form the core for the back of the box and (2) the arms of the cross could be folded 90 from the back plane to form the cores of the adjacent four sides of the box. Optionally, the blanket could include tabs for joining the folded sides of the blanket along mating edges and tabs that could serve as hinges for the door. Vacuum bags in the form of similar five-sided boxes would be made of a suitable polymeric film, one bag to fit the outer core surface, the other to fit the inner core surface. By use of commercially available film-sealing equipment, these box-shaped bags would be seamed together to form a single vacuum bag encasing the box-shaped core. Also, a one-way valve would be sealed to the bag. Through this valve, the interior of the bag would be evacuated to a pressure between 1 and 10 torr (approximately between 0.13 and 1.3 kPa). The polymer-modified aerogel core material is known to perform well as a thermal insulator in such a partial vacuum.

Stepanian, Christopher J.; Ou, Danny; Hu, Xiangjun

2010-01-01

69

Saddle Blanket  

USGS Multimedia Gallery

This is one of many saddle blankets from Dr. J.D. Love. The blanket has some felt decoration along the edges and is in particularily good condition. Saddle Blankets were used under saddles or pack saddles to provide comfort for animals used to carry equipment. Object ID: USGS-000011...

2009-07-22

70

Melamine-formaldehyde aerogels.  

National Technical Information Service (NTIS)

The ability to tailor the structure and properties of aerogels at the nanometer scale opens up exciting possibilities for these unique, low density materials. Traditional inorganic aerogels have been formed from the hydrolysis and condensation of metal al...

C. T. Alviso R. W. Pekala

1991-01-01

71

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

NASA Technical Reports Server (NTRS)

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.

Leventis, Nicholas

2005-01-01

72

Compression of aerogels  

Microsoft Academic Search

When an aerogel is pressurized in a mercury porosimeter, the network is compressed, but no mercury enters the pores. Therefore, porosimetry cannot be used to measure the pore size distribution in an aerogel, but it does provide a measure of the bulk modulus of the network. For silica aerogels, the network is linearly elastic under small strains, then exhibits yield

George W. Scherer; Douglas M. Smith; Xiaomei Qiu; Julie M. Anderson

1995-01-01

73

Glazings with granular aerogel  

Microsoft Academic Search

Double glazing units filled with granular aerogel open up new applications in the fields of daylighting systems and passive solar architecture. Silica aerogel has ideal characteristics for solar thermal applications. High transparency for solar radiation is combined with extremely low thermal conductivity. The chemical company BASF (D) is developing a granular form of aerogel, which will be introduced to the

Joerg J. Dengler; Volker Wittwer

1994-01-01

74

Highly Insulating Windows with a U-value less than 0.6 W/m2K  

SciTech Connect

U.S. households rely primarily on three sources of energy: natural gas, electricity, and fuel oil. In the past several decades, electricity consumption by households has grown dramatically, and a significant portion of electricity used in homes is for lighting. Lighting includes both indoor and outdoor lighting and is found in virtually every household in the United States. In 2001, according to the US Energy Information Administration, lighting accounted for 101 billion kWh (8.8 percent) of U.S. household electricity use. Incandescent lamps, which are commonly found in households, are highly inefficient sources of light because about 90 percent of the energy used is lost as heat. For that reason, lighting has been one focus area to increase the efficiency of household electricity consumption. Windows have several functions, and one of the main functions is to provide a view to the outside. Daylighting is another one of windows main functions and determines the distribution of daylight to a space. Daylighting windows do not need to be transparent, and a translucent daylighting window is sufficient, and often desired, to diffuse the light and make the space more environmentally pleasing. In homes, skylights are one source of daylighting, but skylights are not very energy efficient and are inseparably linked to solar heat gain. In some climates, added solar heat gains from daylighting may be welcome; but in other climates, heat gain must be controlled. More energy efficient skylights and daylighting solutions, in general, are desired and can be designed by insulating them with aerogels. Aerogels are a highly insulating and transparent material in its pure form. The overall objective for this project was to prepare an economical, translucent, fiber-reinforced aerogel insulation material for daylighting applications that is durable for manufacturing purposes. This advanced insulation material will increase the thermal performance of daylighting windows, while satisfying constraints such as durability, cost, user acceptance, size limits, and environmental safety concerns. The energy efficient daylighting window will consist of a translucent and resilient aerogel panel sandwiched between glass panes in double glazed windows. Compared to the best windows available today, the double glazed translucent windows with 1/2-inch aerogel inserts will have a U-value of 1.2 W/m{sup 2} K (0.211 BTU/ft{sup 2} h F) without any coating or low conductivity fill gases. These windows will be more effective than the windows with an Energy Star rating of U-2 W/m{sup 2} K and could be made even more efficient by using low-e coated glass glazings and inert gas fills. This report summarizes the work accomplished on Cooperative Agreement DE-FC26-03NT41950. During this project, Aspen Aerogels made transparent and translucent aerogels from TMOS and TEOS. We characterized the transparency of the aerogels, reinforced the transparent aerogels with fibers and prepared large translucent aerogel panels and blankets. We also conducted an initial market study for energy efficient translucent windows. A lab-scale process was developed that could be scaled-up to manufacture blankets of these translucent aerogels. The large blankets prepared were used to fabricate prototype translucent windows and skylights. The primary goal of this project was to develop transparent, resilient, hydrophobic silica aerogels that have low thermal conductivities (R-10/inch) to be used to produce aerogel insulated double-glazing windows with a U value of 0.6 W/m{sup 2}K. To meet this objective we developed a process and equipment to produce blankets of translucent, hydrophobic aerogel. We focused on silica, organically-modified silica aerogels (Ormosils), and fiber reinforced silica aerogels due to the appreciable expertise in silica sol-gel processing available with the personnel at Aspen Aerogels, and also due to the quantity of knowledge available in the scientific literature. The project was conducted in three budget periods, herein called BP1, BP2 and BP3.

Wendell Rhine; Ying Tang; Wenting Dong; Roxana Trifu; Reduane Begag

2008-11-30

75

Carbon nanomaterials in silica aerogel matrices  

SciTech Connect

Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

Hamilton, Christopher E [Los Alamos National Laboratory; Chavez, Manuel E [Los Alamos National Laboratory; Duque, Juan G [Los Alamos National Laboratory; Gupta, Gautam [Los Alamos National Laboratory; Doorn, Stephen K [Los Alamos National Laboratory; Dattelbaum, Andrew M [Los Alamos National Laboratory; Obrey, Kimberly A D [Los Alamos National Laboratory

2010-01-01

76

Uncooled thin film pyroelectric IR detector with aerogel thermal isolation  

DOEpatents

A monolithic infrared detector structure which allows integration of pyroelectric thin films atop low thermal conductivity aerogel thin films. The structure comprises, from bottom to top, a substrate, an aerogel insulating layer, a lower electrode, a pyroelectric layer, and an upper electrode layer capped by a blacking layer. The aerogel can offer thermal conductivity less than that of air, while providing a much stronger monolithic alternative to cantilevered or suspended air-gap structures for pyroelectric thin film pixel arrays. Pb(Zr.sub.0.4 Ti.sub.0.6)O.sub.3 thin films deposited on these structures displayed viable pyroelectric properties, while processed at 550.degree. C.

Ruffner, Judith A. (Albuquerque, NM); Bullington, Jeff A. (Albuquerque, NM); Clem, Paul G. (Albuquerque, NM); Warren, William L. (Albuquerque, NM); Brinker, C. Jeffrey (Albuquerque, NM); Tuttle, Bruce A. (Albuquerque, NM); Schwartz, Robert W. (Seneca, SC)

1999-01-01

77

Surfactant doped silica aerogels dried at supercritical pressure  

NASA Astrophysics Data System (ADS)

By combining the molecular silica precursor methyltrimethoxysilane (MTMS) with methanol, water and Tween-80 solution, we get surfactant-doped silica alcogels. The wet alcogels can be exchanged with methanol and then supercritically extracted with nitrogen to produce surfactant-doped silica aerogels (SDSAs). SDSAs represent a new class of aerogels that are composed of aggregated submicron porous particles that have tunable interparticle nanoporosity. As we increased the percentage of surfactant, the physical properties of silica aerogels changes. In this study we characterized the SDSAs by SEM for morphological study, FTIR for the material composition, contact angle for hydrophobicity determination and thermal conductivity measurements are carried out for thermal insulation application.

Parale, V. G.; Mahadik, D. B.; Kavale, M. S.; Rao, A. Venkateswara; Vhatkar, R. S.; Wagh, P. B.; Gupta, Satish C.

2013-02-01

78

Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

79

Monolithic nanoporous crystalline aerogels.  

PubMed

Monolithic aerogels can be easily obtained by drying physical gels formed by linear uncross-linked polymers. Preparation methods, structure, and properties of these physically cross-linked polymeric aerogels are reviewed, with particular emphasis to those whose cross-linking knots are crystallites and, more in particular, crystallites exhibiting nanoporous-crystalline forms. The latter aerogels present beside disordered amorphous micropores (typical of all aerogels) also all identical nanopores of the crystalline phases. Their outstanding guest transport properties combined with low material cost, robustness, durability, and ease of handling and recycle make these aerogels suitable for applications in chemical separations, purification, and storage as well as in biomedicine. Scientific, technological, and industrial perspectives for monolithic nanoporous-crystalline polymeric aerogels are also discussed. PMID:23913316

Daniel, Christophe; Longo, Simona; Ricciardi, Rosa; Reverchon, Ernesto; Guerra, Gaetano

2013-08-01

80

Dielectric properties of aerogels  

Microsoft Academic Search

We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel

L. W. Hrubesh; L. E. Keene; V. R. Latorre

1993-01-01

81

Method of casting aerogels  

DOEpatents

The invention describes a method for making monolithic castings of transparent silica aerogel with densities in the range from 0.001 g/cm[sup 3] to 0.6 g/cm[sup 3]. Various shapes of aerogels are cast in flexible polymer molds which facilitate removal and eliminate irregular surfaces. Mold dimensions are preselected to account for shrinkage of aerogel which occurs during the drying step of supercritical extraction of solvent. 2 figures.

Poco, J.F.

1993-09-07

82

Elastic nonlinearity of aerogels  

NASA Astrophysics Data System (ADS)

We have investigated the sound propagation in SiO2 aerogels and three types of organic aerogels: resorcinol formaldehyde, melamine formaldehyde, and vitreous carbon. The main parameter determining the sound velocity is the aerogel density; however, the bond strength and cross linking also influence the stiffness of these materials. Furthermore, we show that at least two types of low-density aerogels become less stiff and consequently the sound velocity is lowered when the specimens are uniaxially compressed. We explain this in terms of a model for the internal structure.

Gross, J.; Fricke, J.; Pekala, R. W.; Hrubesh, L. W.

1992-06-01

83

Aerogel derived catalysts  

SciTech Connect

Aerogels area class of colloidal materials which have high surface areas and abundant mesoporous structure. SiO{sub 2} aerogels show unique physical, optical and structural properties. When catalytic metals are incorporated in the aerogel framework, the potential exists for new and very effective catalysts for industrial processes. Three applications of these metal-containing SiO{sub 2} aerogels as catalysts are briefly reviewed in this paper--NO{sub x} reduction, volatile organic compound destruction, and partial oxidation of methane.

Reynolds, J. G., LLNL

1996-12-11

84

In Vivo Ultrasonic Detection of Polyurea Crosslinked Silica Aerogel Implants  

PubMed Central

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.

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

2013-01-01

85

Melamine-formaldehyde aerogels  

DOEpatents

Organic aerogels that are transparent and essentially colorless are prepared from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porosity, ultrafine cell/pore sizes, and optical clarity. 3 figs.

Pekala, R.W.

1992-01-14

86

Melamine-formaldehyde aerogels  

DOEpatents

Organic aerogels that are transparent and essentially colorless are prepa from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porsity, ultrafine cell/pore sizes, and optical clarity.

Pekala, Richard W. (Pleasant Hill, CA)

1992-01-01

87

Nanoengineering Strong Silica Aerogels  

Microsoft Academic Search

ABSTRACT In the quest for strong lightweight materials, silica aerogels would be very attractive, if they were not fragile. The strength of silica aerogel monoliths has been improved by a factor of over 100 through cross-linking the nanoparticle building blocks of preformed silica hydrogels with poly(hexamethylene diisocyanate). Composite monoliths are much less hygroscopic than native silica, and they do not

Nicholas Leventis; Chariklia Sotiriou-Leventis; Guohui Zhang; Abdel-Monem M. Rawashdeh

2002-01-01

88

Chitin Nanowhisker Aerogels  

PubMed Central

Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043–0.113 g cm?3), high porosities (up to 97 %), surface areas of up to 261 m2 g?1, and mechanical properties at the high end of other reported values (modulus between 7 and 9.3 MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4 %.

Heath, Lindy; Zhu, Lifan; Thielemans, Wim

2013-01-01

89

Chitin nanowhisker aerogels.  

PubMed

Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2 ). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043-0.113?g?cm(-3) ), high porosities (up to 97?%), surface areas of up to 261?m(2) ?g(-1) , and mechanical properties at the high end of other reported values (modulus between 7 and 9.3?MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4?%. PMID:23335426

Heath, Lindy; Zhu, Lifan; Thielemans, Wim

2013-03-01

90

Dielectric properties of aerogels  

SciTech Connect

We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m[sup 3]. For the same range of densities, the measured loss tangents vary linearly between values of 2[times]10[sup [minus]4] and 7[times]10[sup [minus]2]. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 7% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

Hrubesh, L.W.; Keene, L.E.; Latorre, V.R. (Chemistry and Material Sciences Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1993-07-01

91

Carbon aerogels for electrochemical applications  

Microsoft Academic Search

A major advantage of highly crosslinked, organic aerogels is the ability to transform many of these materials into electrically conductive carbon aerogels. Carbon aerogels have been formed as monoliths, microspheres, irregularly-shaped powders, and thin film composites. In all cases, the carbon aerogels retain their high surface area (400–800 m2\\/g) and ultrafine cell\\/pore size (<100 nm). Carbon aerogels are being examined

R. W. Pekala; J. C. Farmer; C. T. Alviso; T. D. Tran; S. T. Mayer; J. M. Miller; B. Dunn

1998-01-01

92

Method for producing hydrophobic aerogels  

SciTech Connect

A method is described 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.

Hrubesh, L.W.; Poco, J.F.; Coronado, P.R.

1999-12-21

93

Mechanically Strong, Lightweight Porous Materials Developed (X-Aerogels)  

NASA Technical Reports Server (NTRS)

Aerogels are attractive materials for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other materials. Potential NASA applications for these materials include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these materials. These issues have severely hampered the application of aerogels in NASA missions.

Leventis, Nicholas

2005-01-01

94

Edge-to-edge assembled graphene oxide aerogels with outstanding mechanical performance and superhigh chemical activity.  

PubMed

Aerogels, an extremely important aggregation state of various self-assembled nanoscale building blocks, have great potential in fields ranging from energy storage to thermal insulation. However, the porosity of aerogels makes them mechanically weak in most cases, and the chemical activity of the resulting aerogel needs consideration. Herein, chemically crosslinked graphene oxide (GO) 3D aerogels with large specific surface areas (up to 850 m(2) g(-1) ), outstanding mechanical performance (up to 20 MPa Young's modulus, 1 MPa yield strength and 45 J g(-1) specific energy adsorption), and superhigh chemical activity (toward some reducing gases such as H2 S, HI, and SO2 ), are fabricated by assembling 2D GO sheets edge-to-edge into uniform, 3D hydrogel networks with subsequent supercritical fluid drying. These aerogels are superior to other 3D frameworks (e.g. graphene aerogels) assembled via partial overlapping of the basal planes of the 2D building blocks. PMID:23512583

Huang, Huan; Chen, Pengwan; Zhang, Xuetong; Lu, Yun; Zhan, Wanchu

2013-04-22

95

Probing the Geometry and Interconnectivity of Pores in Organic Aerogels Using Hyperpolarized 129Xe NMR Spectroscopy  

SciTech Connect

Aerogels represent a class of novel open-pore materials with high surface area and nanometer pore sizes. They exhibit extremely low mass densities, low thermal conductivity, good acoustic insulation, and low dielectric constants. These materials have potential applications in catalysis, advanced separation techniques, energy storage, environmental remediation, and as insulating materials. Organic aerogels are stiffer and stronger than silica aerogels and are better insulators with higher thermal resistance. Resorcinol-Formaldehyde (RF) aerogels are typically prepared through the base-catalyzed sol-gel polymerization of resorcinol with formaldehyde in aqueous solution to produce gels, which are then dried in supercritical CO2.1,2 The [resorcinol]/ [catalyst] (R/C) ratio of the starting sol-gel solution has been determined to be the dominant factor that affects the properties of RF aerogels. Since the unique microstructures of aerogels are responsible for their unusual properties, characterizing the detailed porous structures and correlating them with the processing parameters are vital to establish rational design principles for novel organic aerogels with tailored properties. In this communication we report the first use of hyperpolarized (HP) 129Xe NMR to probe the geometry and interconnectivity of pores in RF aerogels and to correlate these with synthetic conditions. Our work demonstrates that HP 129Xe NMR is so far the only method for accurately measuring the free volume-to-surface-area (Vg/S) ratios for soft mesoporous materials without using any geometric models.

Moudrakovski, Igor L.; Wang, Li Q.; Baumann, T.; Satcher, J. H.; Exarhos, Gregory J.; Ratcliffe, C. I.; Ripmeester, J. A.

2004-04-28

96

Carbon aerogel composites prepared by ambient drying and using oxidized polyacrylonitrile fibers as reinforcements.  

PubMed

Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m(-1) K(-1) at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system. PMID:22047011

Feng, Junzong; Zhang, Changrui; Feng, Jian; Jiang, Yonggang; Zhao, Nan

2011-12-01

97

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

98

Blanket technology  

Microsoft Academic Search

It was concluded that systems requirements would force a reassessment of the conventional approach to interconnecting cells into blanket or array modules. Defense applications (hardening) were identified as the key requirement that would force a movement away from the standard method (solder) of forming array circuits. The panel also agreed that requirements associated with the impending NASA Space Station and

J. Scott-Monck

1982-01-01

99

Silica aerogel-polymer nanocomposites and new nanoparticle syntheses  

NASA Astrophysics Data System (ADS)

Aerogels are extremely high surface area, low density materials with applications including thermal and acoustic insulators, radiation detectors and cometary dust particle traps. However, their low density and aggregate structure makes them extremely fragile and practically impossible to machine or handle without breaking. This has led to the development of aerogel composites with enhanced mechanical properties through the addition of polymers or surface modifiers. To date, attempts to strengthen aerogels have come with significant increases in density and processing time. Here I will describe our search for a solution to these problems with our invention using methyl cyanoacrylate chemical vapor deposition (CVD) to strengthen silica, aminated silica and bridged polysilsesquioxane aerogels. This approach led to a strength improvement of the composites within hours and the strongest composite prepared had a 100x strength improvement over the precursor aerogel. We also developed the first approach to control the molecular weight of the polymers that reinforce silica aerogels using surface-initiated atom transfer radical polymerization (SI-ATRP). Although PMMA reinforcement of silica aerogels improved the mechanical properties, further strength improvements were achieved by cross-linking the grafted PMMA. Additionally, we developed the first silica aerogels reinforced with polyaniline nanofibers that were strong and electrically conductive. Reinforcing silica aerogels with polyaniline allowed them to be used as a sensor for the detection of protonating and deprotonating gaseous species. Finally we developed a new approach for the synthesis of silica and bridged polysilsesquioxane spheres using a surfactant free synthesis. This approach allowed for the first in-situ incorporation of base sensitive functionalities during the sol-gel polymerization.

Boday, Dylan Joseph

100

Polyimide Aerogels with Three-Dimensional Cross-Linked Structure  

NASA Technical Reports Server (NTRS)

Polyimide aerogels with three-dimensional cross-linked structure are made using linear oligomeric segments of polyimide, and linked with one of the following into a 3D structure: trifunctional aliphatic or aromatic amines, latent reactive end caps such as nadic anhydride or phenylethynylphenyl amine, and silica or silsesquioxane cage structures decorated with amine. Drying the gels supercritically maintains the solid structure of the gel, creating a polyimide aerogel with improved mechanical properties over linear polyimide aerogels. Lightweight, low-density structures are desired for acoustic and thermal insulation for aerospace structures, habitats, astronaut equipment, and aeronautic applications. Aerogels are a unique material for providing such properties because of their extremely low density and small pore sizes. However, plain silica aerogels are brittle. Reinforcing the aerogel structure with a polymer (X-Aerogel) provides vast improvements in strength while maintaining low density and pore structure. However, degradation of polymers used in cross-linking tends to limit use temperatures to below 150 C. Organic aerogels made from linear polyimide have been demonstrated, but gels shrink substantially during supercritical fluid extraction and may have lower use temperature due to lower glass transition temperatures. The purpose of this innovation is to raise the glass transition temperature of all organic polyimide aerogel by use of tri-, tetra-, or poly-functional units in the structure to create a 3D covalently bonded network. Such cross-linked polyimides typically have higher glass transition temperatures in excess of 300 400 C. In addition, the reinforcement provided by a 3D network should improve mechanical stability, and prevent shrinkage on supercritical fluid extraction. The use of tri-functional aromatic or aliphatic amine groups in the polyimide backbone will provide such a 3D structure.

Panek, John

2010-01-01

101

Silica modified cellulosic aerogels  

Microsoft Academic Search

\\u000a Abstract  Shaped cellulosic aerogels—as the ‘young’ generation succeeding the well-established silica and synthetic polymer-based aerogels—are\\u000a intriguing materials that feature properties similar to those of their antecessors combined with the additional advantages\\u000a and characteristics of the re-growing biopolymer cellulose. Reinforced shaped cellulosic aerogels consisting of two interpenetrating\\u000a networks of cellulose and silica were prepared from shaped cellulose solutions by (1) regenerating (reprecipitating)

Marco Litschauer; Marie-Alexandra Neouze; Emmerich Haimer; Ute Henniges; Antje Potthast; Thomas Rosenau; Falk Liebner

2011-01-01

102

Activated carbon aerogels  

SciTech Connect

Activated carbon aerogels were obtained from the CO{sub 2} activation of the carbon aerogels. The adsorption isotherms of nitrogen on activated carbon aerogels at 77 K were measured and analyzed by the high-resolution {alpha}{sub s} plot to evaluate their porosities. The {alpha}{sub s} plot showed an upward deviation from linearity below {alpha}{sub s} = 0.5, suggesting that the presence of micropores becomes more predominant with the extent of the activation. Activation increased noticeably the pore volume and the surface area (the maximum value: 2600 m{sup 2}.g{sup -1}) without change of the basic network structure of primary particles. Activated carbon aerogels had a bimodal pore size distribution of uniform micropores and mesopores. 16 refs., 2 figs., 1 tab.

Hanzawa, Y.; Kaneko, K. [Chiba Univ. (Japan)] [Chiba Univ. (Japan); Pekala, R.W. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States); Dresselhaus, M.S. [Massachusetts Inst. of Technology, Cambridge, MA (United States)] [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-12-25

103

Hydrophobic silica aerogels  

Microsoft Academic Search

Hydrophobic silica aerogels were produced by the -Si(Me)3 (trimethylsilyl substituent: TMS) modification of alcogels followed by CO2 supercritical drying. The structure of trimethylsilyl modified silica aerogel (TMSA) was the silica matrix produced by hydrolysis and condensation of only tetramethoxysilane (TMOS). TMS was modified on the surface of the silica matrix. TMSA was extremely moisture-resistant. The density, size, and transparency of

H. Yokogawa; M. Yokoyama

1995-01-01

104

Method of casting aerogels  

DOEpatents

The invention describes a method for making monolithic castings of transparent silica aerogel with densities in the range from 0.001 g/cm.sup.3 to 0.6 g/cm.sup.3. Various shapes of aerogels are cast in flexible polymer molds which facilitate removal and eliminate irregular surfaces. Mold dimensions are preselected to account for shrinkage of alcogel which occurs during the drying step of supercritical extraction of solvent.

Poco, John F. (Livermore, CA)

1993-01-01

105

Improved multilayer insulation applications. [spacecraft thermal control  

NASA Technical Reports Server (NTRS)

Multilayer insulation blankets used for the attenuation of radiant heat transfer in spacecraft are addressed. Typically, blanket effectiveness is degraded by heat leaks in the joints between adjacent blankets and by heat leaks caused by the blanket fastener system. An approach to blanket design based upon modular sub-blankets with distributed seams and upon an associated fastener system that practically eliminates the through-the-blanket conductive path is described. Test results are discussed providing confirmation of the approach. The specific case of the thermal control system for the optical assembly of the Space Telescope is examined.

Mikk, G.

1982-01-01

106

Organic aerogel microspheres and fabrication method therefor  

DOEpatents

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.

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

1996-04-16

107

Comparative study of aerogels obtained from differently prepared nanocellulose fibers.  

PubMed

This article describes the fabrication of nanocellulose fibers (NCFs) with different morphologies and surface properties from biomass resources as well as their self-aggregation into lightweight aerogels. By carefully modulating the nanofibrillation process, four types of NCFs could be readily fabricated, including long aggregated nanofiber bundles, long individualized nanofibers with surface C6 -carboxylate groups, short aggregated nanofibers, and short individualized nanofibers with surface sulfate groups. Free-standing lightweight aerogels were obtained from the corresponding aqueous NCF suspensions through freeze-drying. The structure of the aerogels could be controlled by manipulating the type of NCFs and the concentration of their suspensions. A possible mechanism for the self-aggregation of NCFs into two- or three-dimensional aerogel nanostructures was further proposed. Owing to web-like structure, high porosity, and high surface reactivity, the NCF aerogels exhibited high mechanical flexibility and ductility, and excellent properties for water uptake, removal of dye pollutants, and the use as thermal insulation materials. The aerogels also displayed sound-adsorption capability at high frequencies. PMID:24420495

Chen, Wenshuai; Li, Qing; Wang, Youcheng; Yi, Xin; Zeng, Jie; Yu, Haipeng; Liu, Yixing; Li, Jian

2014-01-01

108

Two Dimensional Heat Transfer around Penetrations in Multilayer Insulation  

NASA Technical Reports Server (NTRS)

The objective of this task was to quantify thermal losses involving integrating MLI into real life situations. Testing specifically focused on the effects of penetrations (including structural attachments, electrical conduit/feedthroughs, and fluid lines) through MLI. While there have been attempts at quantifying these losses both analytically and experimentally, none have included a thorough investigation of the methods and materials that could be used in such applications. To attempt to quantify the excess heat load coming into the system due to the integration losses, a calorimeter was designed to study two dimensional heat transfer through penetrated MLI. The test matrix was designed to take as many variables into account as was possible with the limited test duration and system size. The parameters varied were the attachment mechanism, the buffer material (for buffer attachment mechanisms only), the thickness of the buffer, and the penetration material. The work done under this task is an attempt to measure the parasitic heat loads and affected insulation areas produced by system integration, to model the parasitic loads, and from the model produce engineering equations to allow for the determination of parasitic heat loads in future applications. The methods of integration investigated were no integration, using a buffer to thermally isolate the strut from the MLI, and temperature matching the MLI on the strut. Several materials were investigated as a buffer material including aerogel blankets, aerogel bead packages, cryolite, and even an evacuated vacuum space (in essence a no buffer condition).

Johnson, Wesley L.; Kelly, Andrew O.; Jumper, Kevin M.

2012-01-01

109

Flexible Polyimide Aerogel Cross-linked by Poly(maleic Anhydride-alt-alkylene)  

NASA Technical Reports Server (NTRS)

Aerogels are potential materials for aerospace applications due to their lower thermal conductivity, lighter weight, and low dielectric constant. However, silica aerogels are restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extreme aerospace environments. In order to fit the needs of aerospace applications, developing new thermal insulation materials that are flexible, and moisture resistant is needed. To this end, we fabricated a series of polyimide aerogels crosslinked with different poly(maleic anhydride-alt-alkylene)s as seen in Scheme 1. The polyimide oligomers were made with 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), and different diamines or diamine combinations. The resulting aerogels have low density (0.06 gcm3 to 0.16 gcm3) and high surface area (240-440 m2g). The effect of the different backbone structures on density, shrinkage, porosity, surface area, mechanical properties, moisture resistance and thermal properties will be discussed. These novel polyalkylene-imide aerogels may be potential candidates for applications such as space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Scheme 1. Network of polyimide aerogels crosslinked with deifferent poly(maleic anhydride).

Guo, Haiquan; Meador, Mary Ann B.; Wilkewitz, Brittany Marie

2014-01-01

110

Cryogenic Insulation Systems  

NASA Technical Reports Server (NTRS)

The results of a comparative study of cryogenic insulation systems performed are presented. The key aspects of thermal insulation relative to cryogenic system design, testing, manufacturing, and maintenance are discussed. An overview of insulation development from an energy conservation perspective is given. Conventional insulation materials for cryogenic applications provide three levels of thermal conductivity. Actual thermal performance of standard multilayer insulation (MLI) is several times less than laboratory performance and often 10 times worse than ideal performance. The cost-effectiveness of the insulation system depends on thermal performance; flexibility and durability; ease of use in handling, installation, and maintenance; and overall cost including operations, maintenance, and life cycle. Results of comprehensive testing of both conventional and novel materials such as aerogel composites using cryostat boil-off methods are given. The development of efficient, robust cryogenic insulation systems that operate at a soft vacuum level is the primary focus of this paper.

Augustynowicz, S. D.; Fesmire, J. E.; Wikstrom, J. P.

1999-01-01

111

Bonding aerogels with polyurethanes  

SciTech Connect

Aerogels, porous silica glasses with ultra-fine cell size (30nm), are made by a solution gelation (sol-gel) process. The resulting gel is critical point dried to densities from 0.15--0.60 g/cc. This material is machinable, homogeneous, transparent, coatable and bondable. To bond aerogel an adhesive should have long cure time, no attack on the aerogel structure, and high strength. Several epoxies and urethanes were examined to determine if they satisfied these conditions. Bond strengths above 13 psi were found with double bubble and DP-110 epoxies and XI-208/ODA-1000 and Castall U-2630 urethanes. Hardman Kalex Tough Stuff'' A-85 hardness urethane gave 18 psi bond strength. Hardman A-85, Tuff-Stuff'' was selected for further evaluation because it produced bond strengths comparable to the adherend cohesive strength. 5 refs., 2 figs.

Matthews, F.M.; Hoffman, D.M.

1989-11-01

112

Evaluation of Aerogel Materials for High-Temperature Batteries  

SciTech Connect

Siiica aerogels have 1/3 the thermal conductivity of the best commercial composite insulations, or ~13 mW/m-K at 25°C. However, aerogels are transparent in the near IR region of 4-7 µm, which is where the radiation peak from a thermal-battery stack occurs. Titania and carbon- black powders were examined as thermal opacifiers, to reduce radiation at temperatures between 300°C and 600°C, which spans the range of operating temperature for most thermal batteries. The effectiveness of the various opacifiers depended on the loading, with the best overall results being obtained using aerogels filled with carbon black. Fabrication and strength issues still remain, however.

Ashley, Carol S.; Guidotti, Ronald A.; Reed, Scott T.; Reinhardt, Frederick W.

1999-05-04

113

Polyvinyl alcohol-cellulose nanofibrils-graphene oxide hybrid organic aerogels.  

PubMed

Hybrid organic aerogels consisting of polyvinyl alcohol (PVA), cellulose nanofibrils (CNFs), and graphene oxide nanosheets (GONSs) were prepared using an environmentally friendly freeze-drying process. The material properties of these fabricated aerogels were measured and analyzed using various characterization techniques including compression testing, scanning electron microscopy, thermogravimetric (TGA) analysis, Brunauer-Emmet-Teller (BET) surface area analysis, and contact angle measurements. These environmentally friendly, biobased hybrid organic aerogels exhibited a series of desirable properties including a high specific compressive strength and compressive failure strain, ultralow density and thermal conductivity, good thermal stability, and moisture resistance, making them potentially useful for a broad range of applications including thermal insulation. PMID:23789837

Javadi, Alireza; Zheng, Qifeng; Payen, Francois; Javadi, Abdolreza; Altin, Yasin; Cai, Zhiyong; Sabo, Ronald; Gong, Shaoqin

2013-07-10

114

Gas permeability of carbon aerogels  

SciTech Connect

Carbon aerogels are synthesized via the aqueous polycondensation of resorcinol with formaldehyde, followed by supercritical drying and subsequent pyrolysis at 1050 [degree]C. As a result of their interconnected porosity, ultrafine cell/pore size, and high surface area, carbon aerogels have many potential applications such as supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, the permeability of carbon aerogels was calculated from equations based upon Darcy's law. Our measurements show that carbon aerogels have permeabilities on the order of 10[sup [minus]12] to 10[sup [minus]10] cm[sup 2] over the density range from 0.05--0.44 g/cm[sup 3]. Like many other aerogel properties, the permeability of carbon aerogels follows a power law relationship with density, reflecting differences in the average mesopore size. Comparing the results from this study with the permeability of silica aerogels reported by other workers, we found that the permeability of aerogels is governed by a simple universal flow equation. This paper discusses the relationship between permeability, pore size, and density in carbon aerogels.

Kong, F.; LeMay, J.D.; Hulsey, S.S.; Alviso, C.T.; Pekala, R.W. (Chemistry and Materials Science Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1993-12-01

115

Traditional, state-of-the-art and future thermal building insulation materials and solutions – Properties, requirements and possibilities  

Microsoft Academic Search

The advantages and disadvantages of the thermal building insulation materials and solutions have been treated. Both traditional, state-of-the-art and possible materials and solutions beyond these have been investigated. Examples of these may be mineral wool, expanded polystyrene, extruded polystyrene, polyurethane, vacuum insulation panels, gas insulation panels, aerogels, and future possibilities like vacuum insulation materials, nano insulation materials and dynamic insulation

Bjørn Petter Jelle

2011-01-01

116

Nanofibrillar cellulose aerogels  

Microsoft Academic Search

Highly porous aerogels consisting of cellulose nanofibrils were prepared by dissolution\\/regeneration of cellulose in aq. calcium thiocyanate followed by regeneration and carefully controlled drying. The influence of drying method (regular freeze drying, rapid freeze drying, and solvent exchange drying) on resulting porosity was studied by electron microscopy and nitrogen adsorption. While regular freeze drying caused significant coalescence of microfibrillar units,

Hao Jin; Yoshiharu Nishiyama; Masahisa Wada; Shigenori Kuga

2004-01-01

117

Glazings with granular aerogel  

NASA Astrophysics Data System (ADS)

Double glazing units filled with granular aerogel open up new applications in the fields of daylighting systems and passive solar architecture. Silica aerogel has ideal characteristics for solar thermal applications. High transparency for solar radiation is combined with extremely low thermal conductivity. The chemical company BASF (D) is developing a granular form of aerogel, which will be introduced to the market in the near future. The application potential of this material in window systems was tested as part of a CEC-JOULE project in co-operation with four other industrial companies and two research institutes under the leadership of the Fraunhofer-Institut fur Solare Energiesysteme (FhG-ISE) in Freiburg. A typical u-value for a double glazed window with a 16 mm thick layer of granular aerogel is 1.0 W m-2 K-1, the solar transmission for diffuse light is about 45%. Both parameters are variable over a wide range depending on the particle size distribution, thickness of the layer and choice of the filling gas. First window elements were tested in different applications. Realized installations are presented.

Dengler, Joerg J.; Wittwer, Volker

1994-09-01

118

Cellulose-based aerogels  

Microsoft Academic Search

New organic aerogels were prepared using cellulose derivatives as precursors. The elaboration process and the structural characterisations of these porous cellulose-based materials are described in the present study. Series of monolithic gels were synthesised in acetone by crosslinking cellulose acetate with a non-toxic isocyanate via sol–gel route, using tin-based catalyst. Gelation times (ranging from 15 to 150min) were significantly dependent

F. Fischer; A. Rigacci; R. Pirard; S. Berthon-Fabry; P. Achard

2006-01-01

119

Highly Insulating Windows with a U-Value Less than 0.6 W/m2K, (Final).  

National Technical Information Service (NTIS)

The overall objective for this project was to prepare an economical, translucent, fiber-reinforced aerogel insulation material for daylighting applications that is durable for manufacturing purposes. This advanced insulation material will increase the the...

B. Reduane D. Wenting R. Wendell T. Roxana T. Ying

2008-01-01

120

Aerogels—Preparation, properties, applications  

Microsoft Academic Search

About 1000 papers on aerogels have been published so far, with nearly 200 now being added per year. These numbers demonstrate the attraction which these low density materials exert on physicists, chemists and material scientists. With respect to basic science the (fractal) structure, the dynamics, the low temperature thermal properties and the interaction of guest molecules with the aerogel skeleton

Jochen Fricke; Andreas Emmerling

121

Thermally Emitting Iron Aerogel Composites.  

National Technical Information Service (NTIS)

Aerogels are a class of materials with extremely high surface area and porosity. An exothermic reaction that takes place on the hundreds of square meters/gram of aerogel surface area could result in substantial thermal emission. Here we report various air...

C. Merzbacher R. Bernstein Z. Homrighaus D. Rolison

2000-01-01

122

Superfluid 3He in Aerogel  

Microsoft Academic Search

We report measurements of the superfluid density and transition temperature of 3He confined within 98.2% open aerogel. Both the superfluid fraction and the temperature at which the superfluid is manifested are suppressed strongly from their bulk values. The results suggest that the aerogel reduces the order parameter by a mechanism other than as a diffusely scattering surface.

J. V. Porto; J. M. Parpia

1995-01-01

123

Aerogels: production, characterization, and applications  

Microsoft Academic Search

Aerogels are unique materials with many fascinating properties. A scientific curiosity since being prepared in the 1930's, today's research has focused on potential applications and more economic production routes. In this paper, we present a historic review of aerogels while bringing the reader up-to-date on the latest technological developments.

J. Fricke; T Tillotson

1997-01-01

124

Cosmic Dust Collection in Aerogel  

Microsoft Academic Search

Aerogel is an ultra-low-density material that can be used to capture small particles incident upon it at speeds in excess of 1 km s1. This permits capture of cosmic dust in space where the high speeds usually result in destructive impact events. The performance of aerogel in laboratory impact tests is described. Completely intact capture is rare; most studies show

Mark J. Burchell; Giles Graham; Anton Kearsley

2006-01-01

125

Synthesis of high porosity, monolithic alumina aerogels  

SciTech Connect

Many non-silica aerogels are notably weak and fragile in monolithic form. Particularly, few monolithic aerogels with densities less than 50kg/m3 have any significant strength. It is especially difficult to prepare uncracked monoliths of pure alumina aerogels that are robust and moisture stable. In this paper, we discuss the synthesis of strong, stable, monolithic, high porosity (>98% porous) alumina aerogels, using a two-step sol-gel process. The alumina aerogels have a polycrystalline morphology that results in enhanced physical properties. Most of the measured physical properties of the alumina aerogels are superior to those for silica aerogels for equivalent densities.

Poco, J F; Satcher, J H; Hrubesh, L W

2000-09-20

126

Fusion blanket high-temperature heat transfer  

SciTech Connect

Deep penetration of 14 MeV neutrons makes two-temperature region blankets feasible. A relatively low-temperature (approx. 300/sup 0/C) metallic structure is the vacuum/coolant pressure boundary, while the interior of the blanket, which is a simple packed bed of nonstructural material, operates at very high temperatures (>1000/sup 0/C). The water-cooled shell structure is thermally insulated from the steam-cooled interior. High-temperature steam can dramatically increase the efficiency of electric power generation, as well as produce hydrogen and oxygen-based synthetic fuels at high-efficiency.

Fillo, J.A.

1983-01-01

127

Method for producing metal oxide aerogels having densities less than 0. 02 g/cc  

DOEpatents

A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm[sup 3] to those with a density of more than 0.8 g/cm[sup 3], by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm[sup 3]. High temperature, direct supercritical extraction of the liquid phase of the gel produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, homogeneous silica aerogels with a density of less than 0.02 to higher than 0.8 g/cm[sup 3], with high thermal insulation capacity, improved mechanical strength and good optical transparency, are described. 7 figures.

Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

1994-01-04

128

Method for producing metal oxide aerogels having densities less than 0.02 g/cc  

DOEpatents

A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm.sup.3 to those with a density of more than 0.8 g/cm.sup.3, by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm.sup.3. High temperature, direct supercritical extraction of the liquid phase of the gel produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, homogeneous silica aerogels with a density of less than 0.02 to higher than 0.8 g/cm.sup.3, with high thermal insulation capacity, improved mechanical strength and good optical transparency, are described.

Tillotson, Thomas M. (Tracy, CA); Poco, John F. (Livermore, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Thomas, Ian M. (Livermore, CA)

1994-01-01

129

Nanoencapsulated aerogels produced by monomer vapor deposition and polymerization  

NASA Technical Reports Server (NTRS)

Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating. In an embodiment, the polymer coated aerogel is comprised of a porosity and has a compressive modulus greater than the compressive modulus of the aerogel substrate.

Sullivan, Thomas A. (Inventor)

2011-01-01

130

Super-hydrophobic fluorine containing aerogels  

DOEpatents

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.

Coronado, Paul R. (Livermore, CA); Poco, John F. (Livermore, CA); Hrubesh, Lawrence W. (Pleasanton, CA)

2007-05-01

131

Monolayer coated aerogels and method of making  

DOEpatents

Aerogels having a monolayer coating are described. The aerogel and a monolayer forming precursor are provided in a supercritical fluid, whereupon the aerogel and the monolayer forming precursor are reacted in said supercritical fluid to form a covalent bond between the aerogel and the monolayer forming precursor. Suitable aerogels are ceramic oxides such as silica, alumina, aluminosilicate, and combinations thereof. Suitable monolayer forming precursors include alkyl silanes, chlorosilanes, boranes, chloroboranes, germanes, and combinations thereof. The method may also include providing a surface preparation agent such as water, or hydroetching an aerogel to enhance the coating of the monolayer.

Zemanian, Thomas Samuel (Richland, WA); Fryxell, Glen (Kennwick, WA); Ustyugov, Oleksiy A. (Spokane, WA)

2006-03-28

132

Dynamics of capillary condensation in aerogels  

SciTech Connect

Dynamics of capillary condensation of liquid {sup 4}He in various density silica aerogels was investigated systematically. Interfaces were clearly visible when bulk liquid was rapidly sucked into the aerogel. Time evolution of the interface positions was consistent with the Washburn model and their effective pore radii were obtained. Condensation was a single step in a dense aerogel and two steps in a low density aerogel. Crossover between the two types of condensation was observed in an intermediate density aerogel. Variety of the dynamics may be the manifestation of the fractal nature of aerogels which had a wide range of distribution of pore radii.

Nomura, R.; Miyashita, W.; Yoneyama, K.; Okuda, Y. [Department of Condensed Matter Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8551 (Japan)

2006-03-15

133

The EU advanced dual coolant blanket concept  

Microsoft Academic Search

The advanced dual coolant (A-DC) blanket is one of the EU advanced concepts to be investigated in the frame of the long-term power plant conceptual study (PPCS). Its basic concept—following the ARIES-ST concept—is based on the use of helium-cooled ferritic steel structure, the self-cooled Pb–17Li breeding zone, and SiC\\/SiC flow channel inserts. The latter serves as electrical and thermal insulators

Prachai Norajitra; Leo Bühler; Ulrich Fischer; Siegfried Malang; Gunter Reimann; Horst Schnauder

2002-01-01

134

Composite aerogels for sensing applications  

NASA Astrophysics Data System (ADS)

Composite aerogels are nanoscale mesoporous materials that retain both the meso- and nanoscopic properties of each component. Colloidal metal-silica aerogels (in which the colloidal metal is Au or Pt) exhibit both the transparency and porosity of silica aerogel and the optical behavior of the metal colloid. The silica aerogel essentially acts as a transparent matrix for the isolated metal colloids, which remain accessible to external reagents. Sensing elements adsorbed to the surface of the metal in colloidal Au-silica aerogels are also addressable. For dyes with absorption spectra complementary to that of the metal plasmon resonance, spectral changes due to alteration of the dye environment may be optically monitored. By dispersing the metal colloids in an about-to-gel silica sol, the properties of the metal colloid (i.e. size, which determines the position and FWHM of the plasmon resonance) can be tailored prior to immobilization. The ability to modify the colloidal metal surface either prior to or following gelation in the silica matrix coupled with gentle processing conditions permit modification of the metal surface with, for example, temperature-sensitive biomolecules. Composite colloidal metal-silica aerogels therefore provide a novel method for the nanoscale engineering of optical sensors with rapid response times due to the high mesoporosity of the silica matrix.

Anderson, Michele L.; Rolison, Debra R.; Merzbacher, Celia I.

1999-06-01

135

Design and test evaluation of a solid cryogen cooler insulation system  

Microsoft Academic Search

A computer design analysis and a calorimeter test were performed on a multilayer insulation system used with a cylindrical fiberglass support for application to a solid cryogen cooler. The analysis included the effect of the lateral penetrating support and lateral heat flow in the insulation blankets. The insulation blankets and a simulated support were installed on a near full-size calorimeter

J. E. Ahern; T. W. Lawson

1978-01-01

136

Apparent Thermal Conductivity Of Multilayer Insulation  

NASA Technical Reports Server (NTRS)

Mathematical model of apparent or effective thermal conductivity between two successive layers of multilayer thermal insulation (MLI) offers potential for optimizing performance of insulation. One gains understanding of how each physical mechanism contributes to overall flow of heat through MLI blanket. Model helps analyze engineering tradeoffs among such parameters as number of layers, thicknesses of gaps between layers, types of spacers placed in gaps, weight, overall thickness, and effects of foregoing on apparent thermal conductivity through blanket.

Mcintosh, Glen E.

1995-01-01

137

Ultralight multiwalled carbon nanotube aerogel.  

PubMed

Ultralight multiwalled carbon nanotube (MWCNT) aerogel is fabricated from a wet gel of well-dispersed pristine MWCNTs. On the basis of a theoretical prediction that increasing interaction potential between CNTs lowers their critical concentration to form an infinite percolation network, poly(3-(trimethoxysilyl) propyl methacrylate) (PTMSPMA) is used to disperse and functionalize MWCNTs where the subsequent hydrolysis and condensation of PTMSPMA introduces strong and permanent chemical bonding between MWCNTs. The interaction is both experimentally and theoretically proven to facilitate the formation of a MWCNT percolation network, which leads to the gelation of MWCNT dispersion at ultralow MWCNT concentration. After removing the liquid component from the MWCNT wet gel, the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm(3) is obtained. The MWCNT aerogel has an ordered macroporous honeycomb structure with straight and parallel voids in 50-150 ?m separated by less than 100 nm thick walls. The entangled MWCNTs generate mesoporous structures on the honeycomb walls, creating aerogels with a surface area of 580 m(2)/g which is much higher than that of pristine MWCNTs (241 m(2)/g). Despite the ultralow density, the MWCNT aerogels have an excellent compression recoverable property as demonstrated by the compression test. The aerogels have an electrical conductivity of 3.2 × 10(-2) S·cm(-1) that can be further increased to 0.67 S·cm(-1) by a high-current pulse method without degrading their structures. The excellent compression recoverable property, hierarchically porous structure with large surface area, and high conductivity grant the MWCNT aerogels exceptional pressure and chemical vapor sensing capabilities. PMID:21090673

Zou, Jianhua; Liu, Jianhua; Karakoti, Ajay Singh; Kumar, Amit; Joung, Daeha; Li, Qiang; Khondaker, Saiful I; Seal, Sudipta; Zhai, Lei

2010-12-28

138

Raman Scattering in Silica and Silicophosphate Aerogels  

Microsoft Academic Search

Silicate aerogels are versatile, lightweight, and highly porous materials which are formed by the critical point drying of gelled organic silicate solutions. Aerogels have a complicated microstructure consisting of small nano -scale grains linked together into chains and higher-order clusters. Both silica and silicophosphate aerogels were fabricated for this study. Their bulk density was measured and their morphology was characterized

Barbara L. Walden

1991-01-01

139

Vacuum-dried robust bridged silsesquioxane aerogels.  

PubMed

Robust aerogels derived from a thiol-ene clicked bridged silsesquioxane precursor are obtained by a facile vacuum-drying method. With rather low densities, the flexible aerogels are still robust enough to bear at least 20 repeating compressions and further functionalization by wet doping. The durability and facile preparation procedure promise the aerogels' wider practical applications. PMID:23784876

Wang, Zhen; Dai, Zhen; Wu, Junjie; Zhao, Ning; Xu, Jian

2013-08-27

140

Low RF Reflectivity Spacecraft Thermal Blanket by Using High-Impedance Surface Absorbers  

NASA Astrophysics Data System (ADS)

A technique for designing a low-RF reflectivity thermal blanket is presented. Multi-layer insulation (MLI) blankets are employed to stabilize the temperature on spacecraft unit but they can be responsible of passive intermodulation products and high-mutual coupling between antennas since they are realized with metallic materials. The possibility to replace the last inner layer of a MLI blanket with an ultra-thin absorbing layer made of high-impedance surface absorber is discussed.

Costa, F.; Monorchio, A.; Carrubba, E.; Zolesi, V.

2012-05-01

141

Surge current and electron swarm tunnel tests of thermal blanket and ground strap materials  

NASA Technical Reports Server (NTRS)

The results are described of a series of current conduction tests with a thermal control blanket to which grounding straps have been attached. The material and the ground strap attachment procedure are described. The current conduction tests consisted of a surge current examination of the ground strap and a dilute flow, energetic electron deposition and transport through the bulk of the insulating film of this thermal blanket material. Both of these test procedures were used previously with thermal control blanket materials.

Hoffmaster, D. K.; Inouye, G. T.; Sellen, J. M., Jr.

1977-01-01

142

Thermal Conductivity of Powder Insulations Below 180 K  

Microsoft Academic Search

We have measured the thermal conductivity of aerogel beads and glass microspheres at average temperatures ranging from 30 K to 180 K. The measuring device consists of two closed, concentric cylinders suspended inside of a vacuum insulated cryostat. The insulation being tested occupies the annular space between the cylinders. A single stage Gifford-McMahon cryocooler, thermally anchored to the outer cylinder,

M. N. Barrios; Y. S. Choi; S. W. van Sciver

2008-01-01

143

High Temperature Aerogels in the Al2O3-SiO2 System  

NASA Technical Reports Server (NTRS)

Al2O3-SiO2 aerogels are of interest as constituents of thermal insulation systems for use at high temperatures. Al2O3 and mullite aerogels are expected to crystallize at higher temperatures than their SiO2 counterparts, hence avoiding the shrinkages that accompany the formation of lower temperature SiO2 phases and preserving pore structures into higher temperature regimes. The objective of this work is to determine the influence of processing parameters on shrinkage, gel structure (including surface area, pore size and distribution) and pyrolysis behavior.

Hurwitz, Frances I.; Aranda, Denisse V.; Gallagher, Meghan E.

2008-01-01

144

Biodegradable pectin/clay aerogels.  

PubMed

Biodegradable, foamlike materials based on renewable pectin and sodium montmorillonite clay were fabricated through a simple, environmentally friendly freeze-drying process. The addition of multivalent cations (Ca(2+) and Al(3+)) resulted in apparent cross-linking of the polymer and enhancement of aerogel properties. The compressive properties increased as the solid contents (both pectin and clay) increased; moduli in the range of 0.04-114 MPa were obtained for materials with bulk densities ranging from 0.03 g/cm(3) to 0.19 g/cm(3), accompanied by microstructural changes from a lamellar structure to a cellular structure. Biodegradability of the aerogels was investigated by detecting CO2 release for 4 weeks in compost media. The results revealed that pectin aerogels possess higher biodegradation rates than wheat starch, which is often used as a standard for effective biodegradation. The addition of clay and multivalent cations surprisingly increased the biodegradation rates. PMID:23406325

Chen, Hong-Bing; Chiou, Bor-Sen; Wang, Yu-Zhong; Schiraldi, David A

2013-03-13

145

Synergistic hybrid organic-inorganic aerogels.  

PubMed

A class of inorganic-organic hybrid mesoporous aerogel structure was synthesized by growing gel in a gel. In Type 1, silica gels were grown inside the macropores of thermoreversible syndiotactic polystyrene (sPS) gel, while Type 2 hybrid aerogels were obtained by thermoreversible gelation of sPS chains in the mesopores of preformed silica gel. The hybrid gels were converted into aerogels by exchanging the solvent with liquid carbon dioxide followed by supercritical drying. The hybrid aerogels presented cocontinuous networks of pearl-necklace silica particles and crystalline strands of sPS and exhibited the "petal effect" due to the presence of superhydrophobic sPS and hygroscopic silica. The compressive modulus and compressive strain show large enhancements over sPS and silica aerogels indicating synergy, although Type 1 hybrid aerogels were found to be more robust. The hybrid aerogels showed fast absorption and high absorption capacity for a representative hydrocarbon liquid. PMID:23773123

Wang, Xiao; Jana, Sadhan C

2013-07-10

146

MHD considerations for a self-cooled liquid lithium blanket  

SciTech Connect

The magnetohydrodynamic (MHD) effects can present a feasibility issue for a self-cooled liquid metal blanket of magnetically confined fusion reactors, especially inboard regime of a tokamak. This pressure drop can be significantly reduced by using insulated wall structure. A self-healing insulating coating has been identified, which will reduce the pressure drop by more than a factor of 10. The future research direction to further quantify the performance of this coating is also outlined.

Sze, D.K.; Mattas, R.F.; Hull, A.B.; Picologlou, B.F.; Smith, D.L.

1992-03-01

147

Restoration of blanket peatlands.  

PubMed

There is concern that ecosystem services provided by blanket peatlands have come under threat due to increasing degradation. Blanket peatlands are subject to a wide range of drivers of degradation and are topographically variable. As a result, many degradation forms can develop, including those resulting from eroding artificial drainage, incising gullies and areas of bare peat. Many degraded blanket peatlands have undergone restoration measures since the turn of the century. However, there has been little formal communication of the techniques used and their success. Using practitioner knowledge and a review of the available literature, this paper discusses the methodologies used for restoring sloping blanket peatlands. It then considers current understanding of the impact of restoration on blanket peatland ecosystem services. There is a paucity of research investigating impacts of several common restoration techniques and much more is needed if informed management decisions are to be made and funding is to be appropriately spent. Where data are available we find that restoration is largely beneficial to many ecosystem services, with improvements being observed in water quality and ecology. However, the same restoration technique does not always result in the same outcomes in all locations. The difference in response is predominantly due to the spatial and temporal heterogeneity inherent in all blanket peatlands. Peatland practitioners must take this variability into account when designing restoration strategies and monitoring impact. PMID:24384281

Parry, Lauren E; Holden, Joseph; Chapman, Pippa J

2014-01-15

148

Prediction of Mechanical Properties of Aerogels using a Multifractal Multidimensional Multiscaling Approach  

NASA Astrophysics Data System (ADS)

Aerogels, produced by sol-gel technologies, have several applications in sensors, high energy particle physics, catalysis, heat insulation, supercapacitors, heat storage devices, high efficiency windows, among others. These applications take advantage of the outstanding properties these materials present as a result of their structure. However, the low mechanical properties that these materials present as result of the process, limits their commercial applications. In this dissertation, it is investigated the relationship between the processing conditions and mechanical properties of these materials computationally. The prediction of the effective properties for these materials is a daunting task because of their complex structure. Aerogels's structure is not homogeneous nor periodic, but rather amorphous, nanostructured, and highly porous, making the traditional techniques used to study other materials inapplicable. This dissertation presents the prediction of mechanical properties of aerogels calculated by a novel Multifractal Multidimensional Multiscaling Approach (MMMA) developed here. MMMA consists on recursively calculating the effective properties of the material along several scales. Since aerogels and structures produced by sol-gel technologies present a multifractal character, it is shown that MMMA is applicable to predict the effective properties of these materials. The implementation of MMMA requires a fractal characterization of the structure. For this, computational scattering experiments were performed on structures resembling aerogels. The structures resembling aerogels were produced computationally incorporating the chemistry and the physical phenomena involved in the formation process. MMMA was used to predict the mechanical properties of silica aerogels for different processing conditions. Thus, mechanical properties, scattering experiments, and processing conditions were investigated and correlated in this work.

Campo Schickler, Fritz Andres

149

Purging of a Tank-Mounted Multilayer Insulation System by Gas Diffusion.  

National Technical Information Service (NTIS)

The investigation was conducted on a multilayer insulation (MLI) system mounted on a spherical liquid hydrogen propellant tank. The MLI consisted of two blankets of insulation each containing 15 double-aluminized Mylar radiation shields separated by doubl...

I. E. Sumner

1978-01-01

150

Structural heat pipe. [for spacecraft wall thermal insulation system  

NASA Technical Reports Server (NTRS)

A combined structural reinforcing element and heat transfer member is disclosed for placement between a structural wall and an outer insulation blanket. The element comprises a heat pipe, one side of which supports the outer insulation blanket, the opposite side of which is connected to the structural wall. Heat penetrating through the outer insulation blanket directly reaches the heat pipe and is drawn off, thereby reducing thermal gradients in the structural wall. The element, due to its attachment to the structural wall, further functions as a reinforcing member.

Ollendorf, S. (inventor)

1974-01-01

151

Aerogels derived from multifunctional organic monomers  

SciTech Connect

Traditional inorganic aerogels are mad via the hydrolysis and condensation of metal alkoxides. Recently, we reported the synthesis of organic aerogels based upon the aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde. The former materials can also be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. In both the inorganic and organic systems, the structure and properties of the dried aerogel are dictated by polymerization conditions. Factors such as pH, reactant ratio, and temperature influence the crosslinking chemistry and growth processes taking place prior to gelation. The ability to tailor the structure and properties of aerogels at the nanometer scale opens up exciting possibilities for these novel materials. This paper addresses the chemistry-structure-property relationships of organic aerogels. 22 refs., 7 figs.

Pekala, R.W.; Alviso, C.T.; Kong, F.M.; Hulsey, S.S.

1991-09-01

152

Hypervelocity impact experiments on aerogel dust collector  

Microsoft Academic Search

Laboratory hypervelocity impact experiments were conducted to verify the performance of aerogel dust collectors used for gathering meteoroids and space debris in the near-Earth environment and to derive the relationships of various parameters characterizing the projectile with morphology of tracks left by the penetrating projectile in the aerogel collector pad. Silica aerogel collectors of 0.03 g\\/cm3 density were impacted at

Yukihito Kitazawa; Akira Fujiwara; Toshihiko Kadono; Kichiro Imagawa; Yutaka Okada; Kazuo Uematsu

1999-01-01

153

Ultralight and highly compressible graphene aerogels.  

PubMed

Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials. PMID:23418081

Hu, Han; Zhao, Zongbin; Wan, Wubo; Gogotsi, Yury; Qiu, Jieshan

2013-04-18

154

ITER breeding blanket design  

SciTech Connect

A breeding blanket design has been developed for ITER to provide the necessary tritium fuel to achieve the technical objectives of the Enhanced Performance Phase. It uses a ceramic breeder and water coolant for compatibility with the ITER machine design of the Basic Performance Phase. Lithium zirconate and lithium oxide am the selected ceramic breeders based on the current data base. Enriched lithium and beryllium neutron multiplier are used for both breeders. Both forms of beryllium material, blocks and pebbles are used at different blanket locations based on thermo-mechanical considerations and beryllium thickness requirements. Type 316LN austenitic steel is used as structural material similar to the shielding blanket. Design issues and required R&D data are identified during the development of the design.

Gohar, Y.; Cardella, A.; Ioki, K.; Lousteau, D.; Mohri, K.; Raffray, R.; Zolti, E. [ITER Joint Central Team, Garching (Germany)] [and others

1995-12-31

155

Light Water Seed Blanket Reactor.  

National Technical Information Service (NTIS)

A seed blanket light water breeder reactor and a light water seed blanket thorium burner reactor have been considered. Both these proposals make use of geometry control in order to regulate reactivity. (Atomindex citation 11:538563)

1979-01-01

156

Improving the thermal performance of single-glazed windows using translucent granular aerogel  

Microsoft Academic Search

Cost-effective materials, products and installation methods are required to improve the energy efficiency of the UK's existing building stock. The aim of this paper is to assess the potential for high-performance translucent granular aerogel insulation to be retrofitted over single glazing to reduce heat loss without blocking out all of the useful natural light. In situ testing of a 10-mm-thick

Mark Dowson; David Harrison; Salmaan Craig; Zachary Gill

2011-01-01

157

Control of mesoporous structure of organic and carbon aerogels  

Microsoft Academic Search

Resorcinol-formaldehyde (RF) aerogels were synthesized via the sol-gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution and followed by supercritical drying with carbon dioxide. Mesoporous carbon aerogels were then obtained by pyrolyzing the RF aerogels in an inert atmosphere. The control of mesoporous structure of the aerogels was studied by changing the amount of resorcinol (R), formaldehyde

H. Tamon; H. Ishizaka; T. Araki; M. Okazaki

1998-01-01

158

Aerogel composites using chemical vapor infiltration  

Microsoft Academic Search

A new method to produce novel composite materials based on the use of aerogels as a starting material is described. Using chemical vapor infiltration, a variety of solid materials were thermally deposited into the open pore structure of aerogel. The resulting materials possess new and unusual properties including photoluminescence, magnetism and altered optical properties. An important characteristic of this preparation

Arlon J. Hunt; Michael R. Ayers; Wanqing Cao

1995-01-01

159

Synthesis of High Porosity, Monolithic Alumina Aerogels.  

National Technical Information Service (NTIS)

Many non-silica aerogels are notably weak and fragile in monolithic form. Particularly, few monolithic aerogels with densities less than 50kg/m3 have any significant strength. It is especially difficult to prepare uncracked monoliths of pure alumina aerog...

J. F. Poco J. H. Satcher L. W. Hrubesh

2000-01-01

160

Silica aerogel captures cosmic dust intact  

Microsoft Academic Search

The mesostructure of silica aerogel resembles strings of pearls, ranging in size from 10 to 100 Å. This fine mesostructure transmits nearly 90% of incident light in the visible, while providing sufficiently gentle dissipation of the kinetic energy of hypervelocity cosmic dust particles to permit their intact capture. In 1987, silica aerogel was introduced as a capture medium to take

Peter Tsou

1995-01-01

161

Structure of random porous materials: Silica aerogel  

Microsoft Academic Search

Using small-angle x-ray scattering, we show that porous silica aerogel has a fractal backbone structure. The observed structure is traced to the underlying chemical (polymerization) and physical (colloid aggregation) growth processes. Comparison of scattering curves for aerogel with silica aggregates confirms this interpretation.

Dale Schaefer; Keith Keefer

1986-01-01

162

Carbon aerogels for catalysis applications: An overview  

Microsoft Academic Search

Carbon aerogels are nanostructured carbons obtained from the carbonization of organic aerogels, which are prepared from the sol–gel polycondensation of certain organic monomers. These materials have a great versatility both at the nanoscopic level in terms of their pore texture and at the macroscopic level in terms of their form. Thus, the surface area, pore volume, and pore size distribution

C. Moreno-Castilla; F. J. Maldonado-Hódar

2005-01-01

163

Transparent monolithic metal ion containing nanophase aerogels  

Microsoft Academic Search

The formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at

Risen W. M. Jr; X. Hu; S. Ji; K. Littrell

1999-01-01

164

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

NASA Technical Reports Server (NTRS)

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.

Vassilaras, Plousia E.

2004-01-01

165

Tailoring the properties of organic aerogels  

SciTech Connect

We have recently succeeded in producing a new class of organic (or carbon) aerogels whose electrical, mechanical, and other properties are superior to those of the metal alkoxides. By tailoring properties to specific applications, we hope to achieve aerogels with even better performance. We have already tested carbon aerogels for use in inertial-confinement fusion targets and are currently studying applications to other technologies, such as battery electrodes, catalyst supports, and gas filters. In several of these applications, the permeability of the carbon aerogels-that is, their resistance to fluid flow-is crucial to their performance. Here, we describe briefly the synthesis of organic aerogels and present the results of our permeability studies.

Not Available

1993-05-01

166

Physics of Interplanetary Dust Collection with Aerogel  

NASA Technical Reports Server (NTRS)

This report presents the results of research undertaken to study various problems associated with hypervelocity capture of dust particles in aerogel. The primary topics investigated were the properties of shocked aerogel and the requirements for reliable capture of particles on the STARDUST mission. In particular, the viscosity of shocked aerogel has been an open question. The results presented here suggest that the viscosity of aerogel at high impact velocities is negligible, although there remains some uncertainty about lower velocities. The model adopted for viscosity treats the mixture of polymeric silica and decomposition products and finds that, for particle velocities of 6-7 km/s, the viscosity is similar to that typical of light gasses at STP. Expressions for the Hugoniot of aerogel as a function of density were also obtained from the available data. All aerogels of interest for cosmic dust collectors have very similar shock velocity-particle velocity Hugoniot curves. The strength behavior of aerogel for low-speed penetration was measured, but further work is needed to study the proper way to apply this to the issue of terminal deceleration of a dust particle. Preliminary calculations designed to maximize the penetration depths were performed to determine the required density of aerogel to reliably stop a particle in a 3 cm thickness of aerogel (the path length expected for a normal impact into the STARDUST collector). In order to stop a particle of density rho(sub p) and diameter d(sub p), the mean density of the aerogel collector should be no less than that given by the expression bar rho(sub 0) = 1.085 X 10(exp -4 )rho(sub p)d(sub p), for densities measured in g/ cu cm and the particle diameter measured in micrometers.

Anderson, William W.

1998-01-01

167

Multipurpose hardened spacecraft insulation  

NASA Technical Reports Server (NTRS)

A Multipurpose Hardened Spacecraft Multilayer Insulation (MLI) system was developed and implemented to meet diverse survivability and performance requirements. Within the definition and confines of a MLI assembly (blanket), the design: (1) provides environmental protection from natural and induced nuclear, thermal, and electromagnetic radiation; (2) provides adequate electrostatic discharge protection for a geosynchronous satellite; (3) provides adequate shielding to meet radiated emission needs; and (4) will survive ascent differential pressure loads between enclosed volume and space. The MLI design is described which meets these requirements and design evolution and verification is discussed. The application is for MLI blankets which closeout the area between the laser crosslink subsystem (LCS) equipment and the DSP spacecraft cabin. Ancillary needs were implemented to ease installation at launch facility and to survive ascent acoustic and vibration loads. Directional venting accommodations were also incorporated to avoid contamination of LCS telescope, spacecraft sensors, and second surface mirrors (SSMs).

Steimer, Carlos H.

1990-01-01

168

Mechanically strong, flexible polyimide aerogels cross-linked with aromatic triamine.  

PubMed

Polyimide gels are produced by cross-linking anhydride capped polyamic acid oligomers with aromatic triamine in solution and chemically imidizing. The gels are then supercritically dried to form nanoporous polyimide aerogels with densities as low as 0.14 g/cm(3) and surface areas as high as 512 m(2)/g. To understand the effect of the polyimide backbone on properties, aerogels from several combinations of diamine and dianhydride, and formulated oligomer chain length are examined. Formulations made from 2,2'-dimethylbenzidine as the diamine shrink the least but have among the highest compressive modulus. Formulations made using 4,4'-oxydianiline or 2,2'dimethylbenzidine can be fabricated into continuous thin films using a roll to roll casting process. The films are flexible enough to be rolled or folded back on themselves and recover completely without cracking or flaking, and have tensile strengths of 4-9 MPa. Finally, the highest onset of decomposition (above 600 °C) of the polyimide aerogels was obtained using p-phenylene diamine as the backbone diamine with either dianhydride studied. All of the aerogels are suitable candidates for high-temperature insulation with glass transition temperatures ranging from 270-340 °C and onsets of decomposition from 460-610 °C. PMID:22233638

Meador, Mary Ann B; Malow, Ericka J; Silva, Rebecca; Wright, Sarah; Quade, Derek; Vivod, Stephanie L; Guo, Haiquan; Guo, Jiao; Cakmak, Miko

2012-02-01

169

Facile preparation of monolithic ?-carrageenan aerogels.  

PubMed

To the best of our knowledge, it is the first study reporting the synthesis of monolithic ?-carrageenan aerogels with meso- and macroporous structures, being unique in physical and chemical properties. We demonstrate a novel method to synthesize ?-carrageenan aerogels in which potassium thiocyanate was used as the source of specific ions. Aerogels were characterized by envelope density analysis, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. By varying the concentration of ?-carrageenan between 0.5 and 3 wt%, the envelope density can be linearly increased from 40 to 160 kg m?³. The sulphate functional groups in the wet gel and the specific ions are the key factors controlling the volume shrinkage of aerogels which average about 66%. The aerogels exhibit a fibrillar structure similar to cellulose aerogels. The fibril thickness was observed to be 10-15 nm and the specific surface area was about 230 m² g?¹. The existing meso- and macroporous structures were confirmed by nitrogen adsorption-desorption isotherm analysis and scanning electron microscopy. The aerogels were completely pure, free of specific ions and confirmed to be amorphous by powder X-ray diffraction. Hence, these porous materials can provide a matrix with a chelating function which can be used as a host in many applications. PMID:24718695

Ganesan, Kathirvel; Ratke, Lorenz

2014-05-14

170

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

NASA Technical Reports Server (NTRS)

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.

Sullivan, Thomas A. (Inventor)

2007-01-01

171

Low density, resorcinol-formaldehyde aerogels  

DOEpatents

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.

Pekala, R.W.

1989-10-10

172

Synthesis and characterization of vanadium oxide aerogels  

Microsoft Academic Search

Vanadium pentoxide aerogels were synthesized by supercritical drying with CO2. The aerogels were prepared using a variety of sol compositions from the system VO(OC3H7)3\\/H2O\\/acetone. The materials were found to be of fairly low density (0.04-0.1 g\\/cm3) with surface areas in the range of 300–400 m2\\/g. Chemical and structural studies indicate that the aerogels are hydrated oxides of composition V2O5 ·

F. Chaput; B. Dunn; P. Fuqua; K. Salloux

1995-01-01

173

Waterproofing Nanostructured Aerogel-Ceramic Fiber Composites  

NASA Technical Reports Server (NTRS)

Aerogels are nanoporous materials which can be used to enhance the transport properties of ceramic fiber materials, to exploit their unique properties such as high porosity, large surface area, low density and low thermal conductivity. Numerous applications have been investigated. major obstacle to commercialization is that the structure of aerogels collapses due to the adsorption of water. simple and relatively cheap process has been developed to waterproof silica, alumina and alumina-silica and carbon aerogels and composites incorporating them. Previous waterproofing methods are short lived or expensive and time consuming.

White, Susan; Hsu, Ming Ta; Arnold, Jim (Technical Monitor)

2001-01-01

174

Low density, resorcinol-formaldehyde aerogels  

DOEpatents

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.

Pekala, R.W.

1988-05-26

175

Low density, resorcinol-formaldehyde aerogels  

DOEpatents

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.

Pekala, Richard W. (Pleasant Hill, CA)

1991-01-01

176

Low density, resorcinol-formaldehyde aerogels  

DOEpatents

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.

Pekala, Richard W. (Pleasant Hill, CA)

1989-01-01

177

Ruthenium / aerogel nanocomposits via Atomic Layer Deposition  

SciTech Connect

We present a general approach to prepare metal/aerogel nanocomposites via template directed atomic layer deposition (ALD). In particular, we used a Ru ALD process consisting of alternating exposures to bis(cyclopentadienyl)ruthenium (RuCp{sub 2}) and air at 350 C to deposit metallic Ru nanoparticles on the internal surfaces of carbon and silica aerogels. The process does not affect the morphology of the aerogel template and offers excellent control over metal loading by simply adjusting the number of ALD cycles. We also discuss the limitations of our ALD approach, and suggest ways to overcome these.

Biener, J; Baumann, T F; Wang, Y; Nelson, E J; Kucheyev, S O; Hamza, A V; Kemell, M; Ritala, M; Leskela, M

2006-08-28

178

Aerogels as catalysts and catalyst supports  

SciTech Connect

Aerogels have been used as catalysts since the 1930`s. These materials are interesting because their high surface area means more active sites for gas/ solid interactions. Aerogels have important applications as catalyst supports and are stable as well, which is a real advantage for designing catalytic materials. The author discusses some recent work in his laboratory on developing aerogels as catalytic materials. An important step in preparing these materials is supercritical extraction with CO{sub 2}. Preparation and properties of titania, niobia, and titania-zirconia systems are discussed.

Ko, E.I. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

1993-04-01

179

Aerogel Cherenkov Detector Prototype Experiments  

NASA Astrophysics Data System (ADS)

Studying the additional flavor degree of freedom in the H(e,e'K^+) and H(e,e'K^+) reactions allows for exceptional insight into the transition from hadronic to partonic degrees of freedom in exclusive processes, specifically the reaction mechanism underlying strangeness production. To carry out strangeness physics experiments, the Nuclear Physics Group at Catholic University of America is building an Aerogel Cherenkov detector to be used at Jefferson Lab. To study the detector performance a prototype was built and experiments were carried out using several component configurations. One important aspect of the prototype is the photocathode uniformity of the large diameter photomultiplier tube: its effect on the detector is best studied with the prototype using the aerogel material and reflective detector box for Cerenkov photons in diffusive reflections. Another important aspect of the detector performance, therefore, is the effect of different reflective materials for the detector box wall lining. In this presentation I will present the results from these tests of the effect of the photomultiplier tubes and reflective surfaces on overall detector performance, as well as the modeling of the detector in the GEANT4 framework.

Rothgeb, Laura

2012-10-01

180

Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R  

Microsoft Academic Search

The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double

Robert J. Stochl; Richard H. Knoll

1991-01-01

181

Structure-property relationships of carbon aerogels  

SciTech Connect

Of the organic reactions in sol-gel polymerizations, the most studied reaction is the aqueous polycondensation of resorcinol with formaldehyde; the resulting crosslinked gels are supercritically dried from CO{sub 2} to give resorcinol-formaldehyde (RF) aerogels. These aerogels can be pyrolyzed to form vitreous carbon monoliths with black color, high porosity, ultrafine cell/pore size, high surface area, and interconnected particles of the organic precursor. The structure and properties of the carbon aerogels depend on R/C (resorcinol/catalyst) ratio of starting solution, pyrolysis temperature, and chemical activation. Each variable is discussed. Carbon aerogels provide an almost ideal electrode material (in double-layer capacitors) owing to low electrical resistivity (<40 mohm-cm), controllable pore size distribution (5--500 {angstrom}), and high volumetric surface areas ({approximately}500 m{sup 2}/cm{sup 3}).

Pekala, R.W.; Alviso, C.T.; Kong, F.M.

1993-12-01

182

Optical shock waves in silica aerogel.  

PubMed

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. PMID:24515173

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

2014-01-27

183

Process for preparing polymer reinforced silica aerogels  

NASA Technical Reports Server (NTRS)

Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

2011-01-01

184

Single-wall carbon nanotube aerogels  

NASA Astrophysics Data System (ADS)

Aerogels of single-wall carbon nanotubes (SWNTs) were created by freeze drying and critical point drying of aqueous SWNT gels. The resulting aerogels maintain the strongly-connected three-dimensional SWNT network of the original gel and have density less than 0.1 g/cm3. While these pure SWNT aerogels are self-supporting, reinforcement with small amounts of added polyvinylalcohol (PVA) produces much stronger structures that are easy to handle. Electrical conductivity of order 1 S/cm is observed in the self-supporting aerogels, and similar conductivity can be achieved in PVA-reinforced aerogels through additional processing. The aerogels can be backfilled with polymers such as epoxy to create composite materials that retain the high conductivity of the network. Other potential applications for these structures, such as sensors, actuators, and thermoelectric devices, are currently being explored. This work is supported by grants from NSF (MRSEC DMR05-20020 and DMR-0505048) and NASA NAG8-2172.

Bryning, M. B.; Islam, M. F.; Hough, L. A.; Yodh, A. G.

2006-03-01

185

High Temperature Aerogels for Thermal Protection Systems  

NASA Technical Reports Server (NTRS)

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.

Hurwitz, Frances I.; Mbah, Godfrey C.

2008-01-01

186

MARS high-temperature blanket  

SciTech Connect

The MARS high temperature blanket is designed for the dual applications of either high efficiency electricity production or process heat for synthetic fuel production. Other blanket design goals are tritium self-sufficiency, low tritium inventory, more than 40% of the blanket energy extracted at high energy, long lifetime in the neutron environment, no use of reactive liquid metals, minimization of long term activation and use of characterized materials and fabrication techniques. This challenging set of goals has been met with a novel blanket design that uses radial zoning and the unique properties of the lead-lithium eutectic, Pb/sub 83/Li/sub 17/, as a coolant/neutron multiplier/breeder. During the first year of MARS, the blanket design was optimized for electricity production. A reoptimization for the synthetic fuel application is in progress.

Gordon, J.D.; Berwald, D.H.; Flanders, B.A.

1982-12-01

187

Sol-gel route to very high porosity silica aerogels.  

National Technical Information Service (NTIS)

This report discusses the preparation and characterization of very high porosity silica aerogels. The data presented here suggests a microstructure for the very high porosity silica aerogel that differs from the bead-like structure proposed for single-ste...

L. W. Hrubesh T. M. Tillotson J. F. Poco

1991-01-01

188

Synthesis and Properties of Vanadium Oxide Aerogel Films.  

National Technical Information Service (NTIS)

The fine colloid size, high surface area and controllable density of vanadium oxide aerogels make these materials interesting candidates for lithium insertion electrodes. Thin films of vanadium oxide aerogels were prepared using an alkoxide precursor sol ...

H. P. Wong B. Dunn K. Salloux F. Chaput M. W. Breiter

1996-01-01

189

Resorcinol-Formaldehyde Aerogels and Their Carbonized Derivatives.  

National Technical Information Service (NTIS)

Organic aerogels are produced from the supercritical drying of resorcinol-formaldehyde gels. The aerogels have continuous porosity with cell/pore sizes <1000 /angstrom/. Their morphology consists of interconnected colloidal-like particles with diameters o...

R. W. Pekala F. M. Kong

1988-01-01

190

Eureka! Aerogel capture of meteoroids in space  

NASA Technical Reports Server (NTRS)

Light gas gun studies have shown that 6 km/s solid mineral and glass test particles can be successively captured in 0.05 g cm(exp -3) aerogel without severe heating or fragmentation. In spite of this work, there has been uncertainty in the performance of aerogel for hypervelocity capture of real meteoroids. Natural impacts differ from simulations in that the particles are likely to be structurally weak and they typically impact at higher velocity that can be simulated in the laboratory. We are fortunate now to have had two successful capture experiments using aerogel exposed in space. These experiments provide fundamental data for the assessment of the value of silica aerogel for capture of hypervelocity meteoroids from spacecraft. The first experiment used 0.02 g cm(exp -3) aerogel flown on the lid of a Shuttle Get Away Special canister. During its 9 day exposure, the 0.165 m(exp 2) of aerogel in this Sample Return Experiment (SRE) captured two long 'carrot-shaped' tracks and one highly fractured bowl shaped 'crater'. The second collection was with 0.04 m(exp 2) of 0.05 g cm(exp -3) aerogel exposed on ESA's Eureca freeflying spacecraft that was exposed for 11 months before recovery by the Shuttle. The Eureca aerogel exposure consisted of four 10x10 cm module trays that were part of the TiCCE meteoroid collector built by the University of Kent at Canterbury. To date we have found ten 'carrot-shaped' tracks and two 'craters' on this experiment. The longest tracks in both exposures are over 2 mm long. Two of the TiCCE modules had a 0.1 micron Al film suspended a millimeter above the aerogel. On these modules several of the projectiles fragmented during passage through the film producing fields of carrot shaped tracks from the resulting miniature 'meteor' shower. Most of the tracks in these showers have observable particles at their ends. We have extracted one of the carrot track meteoroids and mounted it in epoxy for sectioning. So far the examination of these 14 impacts suggests that low density aerogel is a magic and highly effective media for intact capture of hypervelocity particles in space.

Brownlee, D. E.; Horz, F.; Hrubsch, L.; Mcdonnell, J. A. M.; Tsou, P.; Williams, J.

1994-01-01

191

Neutron Radioscopic Measurement of Water Adsorption Coefficients in Aerogels  

Microsoft Academic Search

In this work, neutron radioscopy was utilized to investigate water vapor uptake by a hydrophilic silica aerogel. Aerogel is an unusual porous material, produced by a sol-gel process that results in a solid material with a unique microstructure composed of nanometer-size particles and pores. Aerogels have an extraordinarily large internal surface area which is accessible via open pores, making them

D. A. Bostain; J. S. Brenizer Jr; P. M. Norris

2002-01-01

192

Thin aerogel films for optical, thermal, acoustic and electronic applications  

Microsoft Academic Search

Aerogels are a special class of continuously porous solid materials which are characterized by nanometer size particles and pores. Typically, aerogels are made using sol-gel chemistry to form a solvent filled, high porosity gel that is dried by removing the solvent without collapsing the tenuous solid phase. As bulk materials, aerogels are known to have many exceptional, and even some

L. W Hrubesh; J. F Poco

1995-01-01

193

Controllability of pore characteristics of resorcinol–formaldehyde carbon aerogel  

Microsoft Academic Search

Resorcinol–formaldehyde (RF) aerogels were synthesized by sol–gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution, followed by drying with supercritical carbon dioxide. The RF carbon aerogels were prepared by carbonizing the RF aerogels at a high temperature under a nitrogen atmosphere. On changing the catalyst species and the catalyst ratios in synthesizing the RF hydrogels, we investigated

Toshihide Horikawa; Jun'ichi Hayashi; Katsuhiko Muroyama

2004-01-01

194

THEORETICAL STUDY OF A NEW MATERIAL FOR FILTERS: AEROGELS  

Microsoft Academic Search

Aerogels are highly porous materials made by removing the liquid phase of a dilute suspension of solids by taking off the vapor under super-critical temperature and pressure conditions. The aerogel structure has a skeleton of nanometer-size elements forming pores that are tens of nanometers in dimension. In some cases the structure of the aerogel arises from clusters having fractal geometry.

DOUGLAS W. COOPER

1989-01-01

195

Nanoindentation on hybrid organic\\/inorganic silica aerogels  

Microsoft Academic Search

The hybrid organic\\/inorganic silica aerogels experiment a drastic mechanical change into rubber behaviour in relation with the pure inorganic silica aerogel as a brittle material. Aerogels were prepared by sol–gel process and drying by venting off the supercritical ethanol, no degradation of the organic polymer was detected. TEOS (tetraethoxysiloxane) and PDMS (polydimethylsiloxane) were used as inorganic and organic precursors, respectively.

N. de la Rosa-Fox; V. Morales-Flórez; J. A. Toledo-Fernández; M. Piñero; R. Mendoza-Serna; L. Esquivias

2007-01-01

196

Blanket comparison and selection study. Volume II  

SciTech Connect

This volume contains extensive data for the following chapters: (1) solid breeder tritium recovery, (2) solid breeder blanket designs, (3) alternate blanket concept screening, and (4) safety analysis. The following appendices are also included: (1) blanket design guidelines, (2) power conversion systems, (3) helium-cooled, vanadium alloy structure blanket design, (4) high wall loading study, and (5) molten salt safety studies. (MOW)

Not Available

1983-10-01

197

Thermal conductivity of thermal-battery insulations  

SciTech Connect

The thermal conductivities of a variety of insulating materials used in thermal batteries were measured in atmospheres of argon and helium using several techniques. (Helium was used to simulate the hydrogen atmosphere that results when a Li(Si)/FeS{sub 2} thermal battery ages.) The guarded-hot-plate method was used with the Min-K insulation because of its extremely low thermal conductivity. For comparison purposes, the thermal conductivity of the Min-K insulating board was also measured using the hot-probe method. The thermal-comparator method was used for the rigid Fiberfrax board and Fiberfrax paper. The thermal conductivity of the paper was measured under several levels of compression to simulate the conditions of the insulating wrap used on the stack in a thermal battery. The results of preliminary thermal-characterization tests with several silica aerogel materials are also presented.

Guidotti, R.A.; Moss, M.

1995-08-01

198

Tritiation of aerogel matrices: T sub 2 O, tritiated organics and tritium exchange on aerogel surfaces  

SciTech Connect

Three methods for incorporation of tritium into the phoshor/aerogel matrix have been demonstrated: (1) adsorption of T{sub 2}O by the aerogel, (2) incorporation of tritiated organic into the pores of the aerogel and (3) isotopic exchange of tritium from T{sub 2} gas for the H residing on the surface of the aerogel. Adsorption of T{sub 2}O produces the brightest light (4.4 fL) to date but the tritium is loosely bound. Incorporation of tritiated organics into the pores of the aerogel produces less that theoretical luminance and intensity diminishes rapidly due to precipitation and darkening of the organic from radiation damage. Isotopic exchange produces a stable lamp by tritiating H sites on the surface of the aerogel. A lamp with stable luminance of 1.1 fL has been produced; a theoretical limit for a mono-layer coverage fo the aerogel surface is 2 to 3 fL. 7 refs., 4 figs., 2 tabs.

Ellefson, R.E.; Gill, J.T. (EG and G Mound Applied Technologies, Miamisburg, OH (USA)); Shepodd, T.J. (Sandia Labs., Livermore, CA (USA)); Leonard, L.E. (USDOE, Washington, DC (USA))

1990-01-01

199

High resolution transmission electron microscopy of melamine-formaldehyde aerogels and silica aerogels  

SciTech Connect

The goal of the high resolution transmission electron microscopy (HRTEM) was to image the structure of two tetramethyl orthosilicate (TMOS) and two melamine-formaldehyde (MF) aerogels at the single polymer chain level{sup 1,2}. With this level of structural resolution we hoped to interrelate each aerogel's structure with its physical properties and its method of synthesis. Conventional single-step base catalysed TMOS aerogels show strings of spheroidal particles linked together with minimal necking. The spheroidal particles range from 86--132 {Angstrom} and average 113{plus minus}10 {Angstrom} in diameter{sup 2}. In contrast the TMOS aerogels reported on here were made by a two step method. After extended silica chains are grown in solution under acidic conditions with a substoichiometric amount of water, the reaction is stopped and the methanol hydrolysed from TMOS is removed. Then base catalysis and additional water are added to cause gel formation is a nonalcoholic solvent. The MF aerogels were prepared for HRTEM by fracturing them on a stereo microscope stage with razor knife so that fractured pieces with smooth flat surfaces could be selected for platinum-carbon replication. The two silica (TMOS) aerogels were both transparent and difficult to see. These aerogels were fractured on a stereo microscope stage with tweezers. 6 refs., 4 figs.

Ruben, G.C. (Dartmouth Coll., Hanover, NH (United States). Dept. of Biological Sciences)

1991-09-01

200

Multipurpose Thermal Insulation Test Apparatus  

NASA Technical Reports Server (NTRS)

A multi-purpose thermal insulation test apparatus is used for testing insulation materials, or other components. The test apparatus is a fluid boil-off calorimeter system for calibrated measurement of the apparent thermal conductivity (k-value) of a specimen material at a fixed vacuum level. The apparatus includes an inner vessel for receiving a fluid with a normal boiling point below ambient temperature, such as liquid nitrogen, enclosed within a vacuum chamber. A cold mass assembly, including the inner vessel and thermal guards, is suspended from the top of the vacuum chamber. Handling tools attach to the cold mass assembly for convenient manipulation of the assembly and for the installation or wrapping of insulation test materials. Liquid nitrogen is typically supplied to the inner vessel using a fill tube with funnel. A single port through the top of the vacuum chamber facilitates both filling and venting. Aerogel composite stacks with reflective films are fastened to the top and the bottom of the inner vessel as thermal guards. The comparative k-value of the insulation material is determined by measuring the boil-off flow rate of gas, the temperature differential across the insulation thickness, and the dimensions (length and diameters) of the test specimen.

Fesmire, James E. (Inventor); Augustynowicz, Stanislaw D. (Inventor)

2002-01-01

201

Volatiles in interplanetary dust particles and aerogels  

NASA Technical Reports Server (NTRS)

Volatiles measured in 25 interplanetary dust particles (IDPs) are a mixture of both indigenous materials and contaminants associated with the collection and processing of the ODPs prior to analysis. Most IDPs have been collected in the stratosphere using a silicone oil/freon mixture (20:1 ratio) coated on collector plates. Studies have shown that silicone oil, freon and hexane residues remain with the ODPs, despite attempts to clean the IDPs. Analysis of the IDPs with the LMMS-technique produces spectra with a mixture of indigeneous and contaminants components. The contamination signal can be identified and removed; however, the contamination signal may obscure some of the indigeneous component's signal. Employing spectra stripping techniques, the indigenous volatile constituents associated with the IDPs can be identified. Volatiles are similar to those measured in CI or CM carbonaceous chondrites. Collection of IDPs in low-Earth orbit utilizing a Cosmic Dust Collection Facility attached to Space Station Freedom has been proposed. The low-density material aerogel has been proposed as a collection substrate for IDPs. Our studies have concentrated on identifying volatile contaminants that are associated with aerogel. We have found that solvents used for the preparation of aerogel remain in aerogel and methods must be developed for removing the entrapped solvents before aerogels can be used for an IDP collection substrate.

Gibson, E. K., Jr.; Harmetz, C. P.

1991-01-01

202

The Aerocapacitor: A carbon aerogel based supercapacitor  

NASA Astrophysics Data System (ADS)

During the 1980's, a wide variety of carbon foams, formed by the pyrolysis of polymeric foams, were developed at several Department of Energy Laboratories. These foams are known for their monolithic structure and the ability to tailor their critical parameters (e.g. porosity, density). Lawrence Livermore National Laboratory (LLNL) exclusively developed a unique type of carbon foam, known as carbon aerogels. Carbon aerogels are a special class of open-cell foams with (1) homogeneous ultrafine particle and pore size, (2) very large useful surface area per unit volume, and (3) monolithic structure, that yields (4) excellent electrical conductivity due to the intimate connection of the particles. We have applied carbon aerogels to make an 'Aerocapacitor'; a high power- and energy-density electrochemical double layer capacitor (EDLC) that uses carbon aerogels as electrodes. Carbon aerogel surface areas range from about 100 to 700 m(sup 2)/cc (as measured by BET analysis), with bulk densities of 0.05 to 1.0 g/cm(sup 3) and their morphology allows stored energy to be released rapidly, resulting in high power-densities.

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

1992-12-01

203

Water extractable arabinoxylan aerogels prepared by supercritical CO2 drying.  

PubMed

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). PMID:23673527

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

2013-01-01

204

Effective emittance measurements on clamshell-wrapped multi-layer insulation for half inch tubing  

NASA Astrophysics Data System (ADS)

The three clamshell-wrapped multi-layer insulation (MLI) blankets for Space Station external fuel lines have been subjected to effective emittance measurements. Tube target temperatures were of the order of 110 to -40 F. While blanket no. 1 was modeled after that currently used on the Space Shuttle Orbiter, the no. and no. 3 blankets were designed to reduce heat leakage through minimization of EVA flap material.

Stobb, C. A.

1993-07-01

205

Anisotropic Aerogels for Studying Superfluid 3He  

NASA Astrophysics Data System (ADS)

It may be possible to stabilize new superfluid phases of 3He with anisotropic silica aerogels. We discuss two methods that introduce anisotropy in the aerogel on length scales relevant to superfluid 3He. First, anisotropy can be induced with uniaxial strain. A second method generates anisotropy during the growth and drying stages. We have grown cylindrical ˜98% aerogels with anisotropy indicated by preferential radial shrinkage after supercritical drying and find that this shrinkage correlates with small angle x-ray scattering (SAXS). The growth-induced anisotropy was found to be ˜90° out of phase relative to that induced by strain. This has implications for the possible stabilization of superfluid phases with specific symmetry.

Pollanen, J.; Blinstein, S.; Choi, H.; Davis, J. P.; Lippman, T. M.; Lurio, L. B.; Halperin, W. P.

2007-09-01

206

High strength air-dried aerogels  

DOEpatents

A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

Coronado, Paul R.; Satcher, Jr., Joe H.

2012-11-06

207

Nucleation and Avalanche of 4He Crystals in Aerogel  

NASA Astrophysics Data System (ADS)

Dynamical transition of 4He crystals in aerogel was reported recently (Nomura et al. Phys. Rev. Lett. 101:175703, 2008). Bare aerogel, which was placed in the bulk 4He crystals, was used in the report. 4He crystals inside the aerogel grew via creep at high temperatures and via avalanche at low temperatures owing to the competition between thermal fluctuation and quenched disorder. Crystal-liquid interface advanced from the edge to inside of the aerogel. Crystal has a greater density than liquid so that the extra mass has to be transported in the crystallization process. It is not known how the mass is transported in the aerogel. To find a clue to this issue, we did an experiment with aerogel in a glass tube so that the aerogel had contact with the bulk on only one surface. In this case, a similar dynamical transition was observed at low temperatures. In the avalanche region, however, 4He crystals did not grow from the outer surface of the aerogel but nucleated at various sites inside the aerogel. This means that crystallization in aerogel does not occur by the forced invasion of 4He crystal but by a process of the bulk crystal once being melted and transported to increase the pressure of the liquid in the aerogel. Thus, a mass transport mechanisms for the crystallization has been revealed by this observation.

Ueno, Ken-Ichi; Masumoto, Ryota; Mimori, Tomohiro; Osawa, Aiko; Nomura, Ryuji; Okuda, Yuichi

2010-02-01

208

Incorporation of noble metals into aerogels  

DOEpatents

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.

Hair, Lucy M. (Livermore, CA); Sanner, Robert D. (Livermore, CA); Coronado, Paul R. (Livermore, CA)

1998-01-01

209

Incorporation of noble metals into aerogels  

DOEpatents

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.

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

1998-12-22

210

Assessment of alkali metal coolants for the ITER blanket  

NASA Astrophysics Data System (ADS)

The blanket system is one of the most important components of a fusion reactor because it has a major impact on both the economics and safety of fusion energy. The primary functions of the blanket in a deuterium/tritium-fueled fusion reactor are to convert the fusion energy into sensible heat and to breed tritium for the fuel cycle. The blanket comparison and selection study, conducted earlier, described the overall comparative performance of different blanket concepts, including liquid metal, molten salt, water, and helium. This paper will discuss the ITER requirements for a self-cooled blanket concept with liquid lithium and for indirectly cooled concepts that use other alkali metals such as NaK. The paper addresses the thermodynamics of interactions between the liquid metals (e.g., lithium and NaK) and structural materials (e.g., V-base alloys), together with associated corrosion/compatibility issues. Available experimental data are used to assess the long-term performance of the first wall in a liquid metal environment. Other key issues include development of electrical insulator coatings on the first-wall structural material to MHD pressure drop, and tritium permeation/inventory in self-cooled and indirectly cooled concepts. Acceptable types of coatings (based on their chemical compatibility and physical properties) are identified, and surface-modification avenues to achieve these coatings on the first wall are discussed. The assessment examines the extent of our knowledge on structural materials performance in liquid metals and identifies needed research and development in several of the areas in order to establish performance envelopes for the first wall in a liquid-metal environment.

Natesan, K.; Reed, C. B.; Mattas, R. F.

1994-06-01

211

Assessment of alkali metal coolants for the ITER blanket  

SciTech Connect

The blanket system is one of the most important components of a fusion reactor because it has a major impact on both the economics and safety of fusion energy. The primary functions of the blanket in a deuterium/tritium-fueled fusion reactor are to convert the fusion energy into sensible heat and to breed tritium for the fuel cycle. The Blanket Comparison and Selection Study, conducted earlier, described the overall comparative performance of different blanket concepts, including liquid metal, molten salt, water and helium. This paper will discuss the ITER requirements for a self-cooled blanket concept with liquid lithium and for indirectly cooled concepts that use other alkali metals such as NaK. The paper addresses the thermodynamics of interactions between the liquid metals (e.g., lithium and NaK) and structural materials (e.g., V-base alloys), together with associated corrosion/compatibility issues. Available experimental data are used to assess the long-term performance of the first wall in a liquid metal environment. Other key issues include development of electrical insulator coatings on the first-wall structural material to MHD pressure drop, and tritium permeation/inventory in self-cooled and indirectly cooled concepts. Acceptable types of coatings (based on their chemical compatibility and physical properties) are identified, and surface-modification avenues to achieve these coatings on the first wall are discussed. The assessment examines the extent of our knowledge on structural materials performance in liquid metals and identifies needed research and development in several of the areas in order to establish performance envelopes for the first wall in a liquid-metal environment.

Natesan, K.; Reed, C.B.; Mattas, R.F.

1994-06-01

212

Multiscale Computer Simulation of Tensile and Compressive Strain in Polymer- Coated Silica Aerogels  

NASA Technical Reports Server (NTRS)

While the low thermal conductivities of silica aerogels have made them of interest to the aerospace community as lightweight thermal insulation, the application of conformal polymer coatings to these gels increases their strength significantly, making them potentially useful as structural materials as well. In this work we perform multiscale computer simulations to investigate the tensile and compressive strain behavior of silica and polymer-coated silica aerogels. Aerogels are made up of clusters of interconnected particles of amorphous silica of less than bulk density. We simulate gel nanostructure using a Diffusion Limited Cluster Aggregation (DLCA) procedure, which produces aggregates that exhibit fractal dimensions similar to those observed in real aerogels. We have previously found that model gels obtained via DLCA exhibited stress-strain curves characteristic of the experimentally observed brittle failure. However, the strain energetics near the expected point of failure were not consistent with such failure. This shortcoming may be due to the fact that the DLCA process produces model gels that are lacking in closed-loop substructures, compared with real gels. Our model gels therefore contain an excess of dangling strands, which tend to unravel under tensile strain, producing non-brittle failure. To address this problem, we have incorporated a modification to the DLCA algorithm that specifically produces closed loops in the model gels. We obtain the strain energetics of interparticle connections via atomistic molecular statics, and abstract the collective energy of the atomic bonds into a Morse potential scaled to describe gel particle interactions. Polymer coatings are similarly described. We apply repeated small uniaxial strains to DLCA clusters, and allow relaxation of the center eighty percent of the cluster between strains. The simulations produce energetics and stress-strain curves for looped and nonlooped clusters, for a variety of densities and interaction parameters.

Good, Brian

2009-01-01

213

From Green Aerogels to Porous Graphite by Emulsion Gelation of Acrylonitrile.  

National Technical Information Service (NTIS)

Porous carbons, including carbon (C-) aerogels, are technologically important materials, while polyacrylonitrile (PAN) is the main industrial source of graphite fiber. Graphite aerogels are synthesized herewith pyrolytically from PAN aerogels, which in tu...

A. G. Sadekar A. N. Bang C. A. Wisner S. S. Mahadik Z. J. Larimore

2012-01-01

214

Polyolefin-Based Aerogels (PAT-APPL-11-287 777).  

National Technical Information Service (NTIS)

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, hyd...

G. L. Gould J. K. Lee

2005-01-01

215

An emerging platform for drug delivery: aerogel based systems.  

PubMed

Over the past few decades, advances in "aerogel science" have provoked an increasing interest for these materials in pharmaceutical sciences for drug delivery applications. Because of their high surface areas, high porosities and open pore structures which can be tuned and controlled by manipulation of synthesis conditions, nanostructured aerogels represent a promising class of materials for delivery of various drugs as well as enzymes and proteins. Along with biocompatible inorganic aerogels and biodegradable organic aerogels, more complex systems such as surface functionalized aerogels, composite aerogels and layered aerogels have also been under development and possess huge potential. Emphasis is given to the details of the aerogel synthesis and drug loading methods as well as the influence of synthesis parameters and loading methods on the adsorption and release of the drugs. Owing to their ability to increase the bioavailability of low solubility drugs, to improve both their stability and their release kinetics, there are an increasing number of research articles concerning aerogels in different drug delivery applications. This review presents an up to date overview of the advances in all kinds of aerogel based drug delivery systems which are currently under investigation. PMID:24394377

Ulker, Zeynep; Erkey, Can

2014-03-10

216

Analysis of thermal performance of penetrated multi-layer insulation  

NASA Technical Reports Server (NTRS)

Results of research performed for the purpose of studying the sensitivity of multi-layer insulation blanket performance caused by penetrations through the blanket are presented. The work described in this paper presents the experimental data obtained from thermal vacuum tests of various penetration geometries similar to those present on the Hubble Space Telescope. The data obtained from these tests is presented in terms of electrical power required sensitivity factors referenced to a multi-layer blanket without a penetration. The results of these experiments indicate that a significant increase in electrical power is required to overcome the radiation heat losses in the vicinity of the penetrations.

Foster, Winfred A., Jr.; Jenkins, Rhonald M.; Yoo, Chai H.; Barrett, William E.

1988-01-01

217

Analysis of thermal performance of penetrated multi-layer insulation  

NASA Astrophysics Data System (ADS)

Results of research performed for the purpose of studying the sensitivity of multi-layer insulation blanket performance caused by penetrations through the blanket are presented. The work described in this paper presents the experimental data obtained from thermal vacuum tests of various penetration geometries similar to those present on the Hubble Space Telescope. The data obtained from these tests is presented in terms of electrical power required sensitivity factors referenced to a multi-layer blanket without a penetration. The results of these experiments indicate that a significant increase in electrical power is required to overcome the radiation heat losses in the vicinity of the penetrations.

Foster, Winfred A., Jr.; Jenkins, Rhonald M.; Yoo, Chai H.; Barrett, William E.

1988-06-01

218

Ambient-pressure silica aerogel films.  

National Technical Information Service (NTIS)

Very highly porous (aerogel) silica films with refractive index in the range 1.006--1.05 (equivalent porosity 98.5--88%) were prepared by an ambient-pressure process. It was shown earlier using in situ ellipsometric imaging that the high porosity of these...

S. S. Prakash C. J. Brinker A. J. Hurd

1994-01-01

219

Manufacturing complex silica aerogel target components  

SciTech Connect

Aerogel is a material used in numerous components in High Energy Density Physics targets. In the past these components were molded into the proper shapes. Artifacts left in the parts from the molding process, such as contour irregularities from shrinkage and density gradients caused by the skin, have caused LANL to pursue machining as a way to make the components.

Defriend Obrey, Kimberly Ann [Los Alamos National Laboratory; Day, Robert D [Los Alamos National Laboratory; Espinoza, Brent F [Los Alamos National Laboratory; Hatch, Doug [Los Alamos National Laboratory; Patterson, Brian M [Los Alamos National Laboratory; Feng, Shihai [Los Alamos National Laboratory

2008-01-01

220

Resorcinol-formaldehyde and carbon aerogel microspheres.  

National Technical Information Service (NTIS)

Aerogels are a unique class of materials possessing an open-cell structure with ultrafine cells/pores (<100nm), high surface area (400--1100 m(sup 2)/g), and a solid matrix composed of interconnected particles, fibers, or platelets with characteristic dim...

C. T. Alviso R. W. Pekela J. Gross X. Lu R. Caps

1996-01-01

221

Removable fibrous glass insulation fitted to complex equipment shapes results in $178,000/yr savings  

SciTech Connect

In early 1980, PPG Industries embarked on a general plant energy conservation effort at its Lake Charles, LA plant where chlor-alkalis, various chlorinated hydrocarbons, and vinyl chloride monomer are manufactured. Company engineers sought a means of insulating process steam components that, because of their complex shapes, were not (and normally are not) insulated. These components included flanges on heat exchanger heads and reboilers, steam valves in process areas, manways and other equipment. PPG plant engineers specified removable, reusable blanket insulation. The blankets are constructed of a fibrous glass mat form insulation encased in a silicone-impregnated glass cloth or similar weather barrier. Each insulation blanket was custom-made for its particular equipment shape and service application to ensure a close fit and optimal energy efficiency. Insulation thickness, type of weather barrier, and mesh were specified according to intended use. For protection from abrasion or puncture, some of the blankets also were covered with stainless steel, Monel, or Inconel wire mesh. Overall, the blankets provide high strength, durability, low thermal conductivity ratings, and an operating range of up to 1200/sup 0/F. Reduced maintenance costs and improved worker productivity have been evidenced since installing the blanket insulation. Further, PPG has increased energy efficiency. Project savings were tracked for 30 months (insulation and installation costs vs. fuel and maintenance savings) and revealed annual plant savings of $178,000-$130,000 in energy savings and $48,000 in maintenance savings. With the cost of the insulation blankets being about $125,000, PPG recovered its investment in under a year.

Not Available

1985-08-01

222

Lightweight Thermal Insulation for a Liquid-Oxygen Tank  

NASA Technical Reports Server (NTRS)

A proposed lightweight, reusable thermal-insulation blanket has been designed for application to a tank containing liquid oxygen, in place of a non-reusable spray-on insulating foam. The blanket would be of the multilayer-insulation (MLI) type and equipped with a pressure-regulated nitrogen purge system. The blanket would contain 16 layers in two 8-layer sub-blankets. Double-aluminized polyimide 0.3 mil (.0.008 mm) thick was selected as a reflective shield material because of its compatibility with oxygen and its ability to withstand ionizing radiation and high temperature. The inner and outer sub-blanket layers, 1 mil (approximately equals 0.025 mm) and 3 mils (approximately equals 0.076 mm) thick, respectively, would be made of the double-aluminized polyimide reinforced with aramid. The inner and outer layers would provide structural support for the more fragile layers between them and would bear the insulation-to-tank attachment loads. The layers would be spaced apart by lightweight, low-thermal-conductance netting made from polyethylene terephthalate.

Willen, G. Scott; Lock, Jennifer; Nieczkoski, Steve

2005-01-01

223

Cryogenic insulation  

Microsoft Academic Search

Midwesco Enterprise, Inc, has developed an improved insulator for use with LNG pipelines that practically satisfies the theoretical promise of a satisfactory insulator, is relatively inexpensive, does not require periodic reevacuation (as does vacuum-type insulation), and offers a coefficient of thermal expension sufficiently low to prevent cracking at the cold face next to the line (unlike polyurethane foam). This new

Hallwood

1974-01-01

224

Insulation Station  

NSDL National Science Digital Library

In this physical sciences activity, learners explore insulation. Leaners investigate how insulation can be used to slow down the conduction of heat from one side of a wall to the other. Learners are challenged with designing the best way to insulate a cup to prevent ice cubes from melting.

Television, Twin C.

2013-01-01

225

Magnetization and spin diffusion of liquid 3He in aerogel  

NASA Astrophysics Data System (ADS)

We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of He3 in aerogel, including both elastic and inelastic scattering of He3 quasiparticles, and compare these results with data for He3 in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the “dirty” B phase of He3 in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density.

Sauls, J. A.; Bunkov, Yu. M.; Collin, E.; Godfrin, H.; Sharma, P.

2005-07-01

226

Evaluating Dimethyldiethoxysilane for use in Polyurethane Crosslinked Silica Aerogels  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

227

Non-silica aerogels as hypervelocity particle capture materials  

NASA Astrophysics Data System (ADS)

The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle capture and return missions would expand the scientific value of these missions. Alumina, titania, germania, zirconia, tin oxide, and resorcinol/formaldehyde aerogels were produced and impact tested with 20, 50, and 100?m glass microspheres to determine the suitability of different non-silica aerogels as hypervelocity particle capture mediums. It was found that non-silica aerogels do perform as efficient hypervelocity capture mediums, with alumina, zirconia, and resorcinol/formaldehyde aerogels proving to be the best of the materials tested.

Jones, Steven M.

2010-01-01

228

Catalytic graphitization of carbon aerogels by transition metals  

SciTech Connect

Carbon aerogels and Cr-, Fe-, Co-, and Ni-containing carbon aerogels were obtained by pyrolysis, at temperatures between 500 and 1,800 C, of the corresponding aerogels prepared by the sol-gel method from polymerization of resorcinol with formaldehyde. All samples were characterized by mercury porosimetry, nitrogen adsorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Results obtained show that carbon aerogels are, essentially, macroporous materials that maintain large pore volumes even after pyrolysis at 1,800 C. For pyrolysis at temperatures higher than 1,000 C, the presence of the transition metals produced graphitized areas with three-dimensional stacking order, as shown by HRTEM, XRD, and Raman spectroscopy. HRTEM also showed that the metal-carbon containing aerogels were formed by polyhedral structures. Cr and Fe seem to be the best catalysts for graphitization of carbon aerogels.

Maldonado-Hodar, F.J.; Moreno-Castilla, C.; Rivera-Utrilla, J.; Hanzawa, Y.; Yamada, Y.

2000-05-02

229

Thermal performance measurements of a 100 percent polyester MLI (multilayer insulation) system for the Superconducting Super Collider  

SciTech Connect

The plastic materials used in the multilayer insulation (MLI) blankets of the superconducting magnets of the Superconducting Super Collider (SSC) are comprised entirely of polyesters. This paper reports on tests conducted in three separate experimental blanket arrangements. The tests explore the thermal performance of two candidate blanket joint configurations each employing a variation of a stepped-butted joint nested between sewn blanket seams. The results from the joint configurations are compared to measurements made describing the thermal performance of the basic blanket materials as tested in an ideal joint configuration. Twenty foil sensors were incorporated within each test blanket to measure interstitial layer and joint layer temperatures. Heat flux and thermal gradients are reported for high and degraded insulating vacuums, and during transient and steady state conditions. In complement with this paper is an associate paper bearing the same title head but with the title extension Part 1: Instrumentation and experimental preparation (300K-80K)'. 5 refs., 8 figs., 2 tabs.

Gonczy, J.D.; Boroski, W.N.; Niemann, R.C.

1989-09-01

230

Neutron Radioscopic Measurement of Water Adsorption Coefficients in Aerogels  

Microsoft Academic Search

.    In this work, neutron radioscopy was utilized to investigate water vapor uptake by a hydrophilic silica aerogel. Aerogel\\u000a is an unusual porous material, produced by a sol-gel process that results in a solid material with a unique microstructure\\u000a composed of nanometer-size particles and pores. Aerogels have an extraordinarily large internal surface area which is accessible\\u000a via open pores,

D. A. Bostain; P. M. Norris

2002-01-01

231

Energy loss and impact cratering in aerogels: theory and experiment  

Microsoft Academic Search

Aerogel collectors have been deployed in low-Earth orbit to collect orbital debris and micrometeorites. An array of silica aerogel collectors is currently en-route back to Earth following an encounter with the Comet Wild-2 on board the Stardust spacecraft. Stardust is returning, for laboratory analysis, cometary and interstellar dust grains which impacted into the aerogel collectors at hypervelocities. While the morphology

Gerardo Domínguez; Andrew J. Westphal; Steven M. Jones; Mark L. F. Phillips

2004-01-01

232

Catalytic graphitization of carbon aerogels by transition metals  

Microsoft Academic Search

Carbon aerogels and Cr-, Fe-, Co-, and Ni-containing carbon aerogels were obtained by pyrolysis, at temperatures between 500 and 1,800 C, of the corresponding aerogels prepared by the sol-gel method from polymerization of resorcinol with formaldehyde. All samples were characterized by mercury porosimetry, nitrogen adsorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Results obtained show that

F. J. Maldonado-Hodar; C. Moreno-Castilla; J. Rivera-Utrilla; Y. Hanzawa; Y. Yamada

2000-01-01

233

Multiplier, moderator, and reflector materials for lithium-vanadium fusion blankets.  

SciTech Connect

The self-cooled lithium-vanadium fusion blanket concept has several attractive operational and environmental features. In this concept, liquid lithium works as the tritium breeder and coolant to alleviate issues of coolant breeder compatibility and reactivity. Vanadium alloy (V-4Cr-4Ti) is used as the structural material because of its superior performance relative to other alloys for this application. However, this concept has poor attenuation characteristics and energy multiplication for the DT neutrons. An advanced self-cooled lithium-vanadium fusion blanket concept has been developed to eliminate these drawbacks while maintaining all the attractive features of the conventional concept. An electrical insulator coating for the coolant channels, spectral shifter (multiplier, and moderator) and reflector were utilized in the blanket design to enhance the blanket performance. In addition, the blanket was designed to have the capability to operate at high loading conditions of 2 MW/m{sup 2} surface heat flux and 10 MW/m{sup 2} neutron wall loading. This paper assesses the spectral shifter and the reflector materials and it defines the technological requirements of this advanced blanket concept.

Gohar, Y.; Smith, D. L.

1999-10-07

234

Effect of Ultra Violet Radiation on Surface Properties: Comparison of RTV 655 and Silica--Based Aerogels  

NASA Astrophysics Data System (ADS)

The broad spectrum of ultra violet (UV) radiation causes material property changes such as chalkiness, brittleness, color change, and ultimately complete mechanical failure. UV radiation is also known to modify the surface charge state of insulators. These effects are intensified for materials used in space exploration due to the lack of an atmosphere. In this work, we compare the radiation response and the material properties of RTV 655 (existing calibration targets material on Phoenix Mars Lander) and silica-based aerogels. The extreme light-weight and ability to color-code aerogels makes this material a candidate for the next generation of calibration targets. The radiation response of both materials will be studied using Kelvin Probe, UV-VIS spectrophotometry, and ESR techniques.

Sinden-Redding, Mackenzie; Sabri, Firouzeh

2009-11-01

235

Electronic detection of focused Cherenkov rings from aerogel  

NASA Astrophysics Data System (ADS)

The recent development of highly transparent aerogel has permitted its use as a Cherenkov radiator in a focused (non-Rayleigh-scattered) mode. We report on the optical properties of this aerogel obtained by observation of Cherenkov rings with single-electron-sensitive phototubes. The dependence on aerogel radiator thickness of the number of Cherenkov ring hit points and background is shown and compared to expectations. A 5 cm thick radiator of this aerogel will permit {?}/{K} identification up to 20 GeV/c.

De Leo, R.; Lagamba, L.; Manzari, V.; Nappi, E.; Scognetti, T.; Alemi, M.; Becker, H.; Forty, R.; Adachi, I.; Suda, R.; Sumiyoshi, T.; Leone, A.; Perrino, R.; Matteuzzi, C.; Seguinot, J.; Ypsilantis, T.; Cisbani, E.; Frullani, S.; Garibaldi, F.; Iodice, M.; Urciuoli, G. M.

1997-02-01

236

Raman Scattering in Silica and Silicophosphate Aerogels.  

NASA Astrophysics Data System (ADS)

Silicate aerogels are versatile, lightweight, and highly porous materials which are formed by the critical point drying of gelled organic silicate solutions. Aerogels have a complicated microstructure consisting of small nano -scale grains linked together into chains and higher-order clusters. Both silica and silicophosphate aerogels were fabricated for this study. Their bulk density was measured and their morphology was characterized by transmission electron microscopy and scanning electron microscopy. Finally, Raman spectra were taken over the range 5-1100 cm ^{-1}. For aerogels the Raman scattering curve can be separated into three different spectroscopic (and hence length-scale regimes). At very low frequencies (5-70 cm ^{-1}), Raman spectra reveal a "particle band" that arises from the discrete particulate character of the gels at very small size scales. The location of the particle band maximum was related to the particle size, as confirmed by TEM measurements of the nanoscale structure in the aerogels. Increasing the amount of time a wet gel was allowed to age before being dried caused the particle peak to sharpen and grow in intensity, reflecting the ongoing condensation of lightly crosslinked silica tetrahedra within and along the surfaces of the particles. The scattering at intermediate frequencies (30 -200 cm^{-1}), which arises from modes within the elementary particles, followed a power law in frequency of the sort predicted for the vibrations of self-similar fractal structures. The power law exponent changed with the initial gel preparation conditions and decreased as age time increased. Spectra at higher frequencies imply an abundance of cyclical ring structures and Si-OH bonds which, along with the peaks characteristic of bulk silica glass, grew and became better defined with increasing age time. This provided a physical picture for the origin of intermediate scale disorder. The addition of P_2O _5 affected the aerogel microstructure. Like silicon, phosphorus is a network former which readily bonds with oxygen in a tetrahedral configuration. The addition of phosphorus, even at very low concentrations, reduced the mean particle size. This was demonstrated both by the TEM micrographs and by the change in position of the particle peak in Raman scattering.

Walden, Barbara L.

237

Liquid lithium blanket processing studies  

Microsoft Academic Search

The sorption of tritium on yttrium from flowing molten lithium and the subsequent release of tritium from yttrium for regeneration of the metal sorbent were investigated to evaluate the feasibility of such a tritium-recovery process for a fusion reactor blanket of liquid lithium. In initial experiments with the forced convection loop, yttrium samples were contacted with lithium at 300 C.

J. B. Talbot; S. D. Clinton

1979-01-01

238

Magnetic hydrophobic nanocomposites: Silica aerogel/maghemite  

NASA Astrophysics Data System (ADS)

Magnetic hydrophobic aerogels (MHA) in the form of nanocomposites of silica and maghemite (?-Fe2O3) were prepared by one step sol-gel procedure followed by supercritical solvent extraction. Silica alcogels were obtained from TEOS, MTMS, methanol and H2O, and Fe(III) nitrate as magnetic precursor. The hydrophobic property was achieved using the methytrimethoxysilane (MTMS) as co-precursor for surface modification. The so produced nanocomposite aerogels are monolithic, hydrophobic and magnetic. The interconnected porous structure hosts ?6 nm size ?-Fe2O3 particles, has a mean pore diameter of 5 nm, and a specific surface area (SSA) of 698 m²/g. Medium range structure of MHA is determined by SAXS, which displays the typical fractal power law behavior with primary particle radius of ?1 nm. Magnetic properties of the nanoparticle ensembles hosted in them are studied by means of dc-magnetometry.

Mendoza Zélis, P.; Fernández van Raap, M. B.; Socolovsky, L. M.; Leyva, A. G.; Sánchez, F. H.

2012-08-01

239

High resolution patterning of silica aerogels  

SciTech Connect

Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag{sup +} ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 {micro}m, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed by Ag clusters with a size of several {micro}m, separated by thin layers of silica.

Bertino, M.F.; Hund, J.F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A.T.; Terry, J. (UMR-MUST); (IIT)

2008-10-30

240

Nanoparticle iron–titanium oxide aerogels  

Microsoft Academic Search

Nanostructured iron oxide–titania aerogel materials have been prepared by sol–gel polymerization of iron acetylacetonate with titanium butoxide and supercritical drying. Their structural properties, including particle morphology, crystalline phase, bond linkage and surface area, were varied by addition of ferric oxide into the titania matrix, as characterized by means of HRTEM, XRD, FT-IR and the BET method. X-ray photoelectron spectra (XPS)

Chien-Tsung Wang; Shih-Hung Ro

2007-01-01

241

Method for making monolithic metal oxide aerogels  

DOEpatents

Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The containment vessel is enclosed within an aqueous atmosphere that is above the supercritical temperature and pressure of the solvent of the metal alkoxide solution.

Coronado, Paul R. (Livermore, CA)

1999-01-01

242

The Pore Structure Determination of Carbon Aerogels  

Microsoft Academic Search

The detailed adsorption isotherms of nitrogen on carbon aerogels at 77 K were measured. The N2 adsorption isotherm had a marked hysteresis. The adsorption isotherms were analyzed by high resolution as-plots to evaluate their porosity. The as-plots showed an explicit upward deviation from the linearity below as = 0.5, suggesting the presence of micropores. The mesoporosity and microporosity were separately

Y. Hanzawa; K. Kaneko; N. Yoshizawa; R. W. Pekala; M. S. Dresselhaus

1998-01-01

243

Computer Simulation of Fracture in Aerogels  

NASA Technical Reports Server (NTRS)

Aerogels are of interest to the aerospace community primarily for their thermal properties, notably their low thermal conductivities. While the gels are typically fragile, recent advances in the application of conformal polymer layers to these gels has made them potentially useful as lightweight structural materials as well. In this work, we investigate the strength and fracture behavior of silica aerogels using a molecular statics-based computer simulation technique. The gels' structure is simulated via a Diffusion Limited Cluster Aggregation (DLCA) algorithm, which produces fractal structures representing experimentally observed aggregates of so-called secondary particles, themselves composed of amorphous silica primary particles an order of magnitude smaller. We have performed multi-length-scale simulations of fracture in silica aerogels, in which the interaction b e e n two secondary particles is assumed to be described by a Morse pair potential parameterized such that the potential range is much smaller than the secondary particle size. These Morse parameters are obtained by atomistic simulation of models of the experimentally-observed amorphous silica "bridges," with the fracture behavior of these bridges modeled via molecular statics using a Morse/Coulomb potential for silica. We consider the energetics of the fracture, and compare qualitative features of low-and high-density gel fracture.

Good, Brian S.

2006-01-01

244

Cutting Silica Aerogel for Particle Extraction  

NASA Technical Reports Server (NTRS)

The detailed laboratory analyses of extraterrestrial particles have revolutionized our knowledge of planetary bodies in the last three decades. This knowledge of chemical composition, morphology, mineralogy, and isotopics of particles cannot be provided by remote sensing. In order to acquire these detail information in the laboratories, the samples need be intact, unmelted. Such intact capture of hypervelocity particles has been developed in 1996. Subsequently silica aerogel was introduced as the preferred medium for intact capturing of hypervelocity particles and later showed it to be particularly suitable for the space environment. STARDUST, the 4th NASA Discovery mission to capture samples from 81P/Wild 2 and contemporary interstellar dust, is the culmination of these new technologies. In early laboratory experiments of launching hypervelocity projectiles into aerogel, there was the need to cut aerogel to isolate or extract captured particles/tracks. This is especially challenging for space captures, since there will be many particles/tracks of wide ranging scales closely located, even collocated. It is critical to isolate and extract one particle without compromising its neighbors since the full significance of a particle is not known until it is extracted and analyzed. To date, three basic techniques have been explored: mechanical cutting, lasers cutting and ion beam milling. We report the current findings.

Tsou, P.; Brownlee, D. E.; Glesias, R.; Grigoropoulos, C. P.; Weschler, M.

2005-01-01

245

Cellulose nanofibrils aerogels generated from jute fibers.  

PubMed

In this work, we report the cellulose nanofibrils extracted from the pristine jute fibers via the pretreatments followed by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and mechanical disintegration. The effects of pretreatments by using the NaOH solution and dimethyl sulfoxide solvent on the fiber morphology and macro/micro-structures were investigated by polarizing microscope and synchrotron radiation wide/small-angle X-ray scattering (WAXS/SAXS). The cellulose nanofibrils exhibit a diameter ranging from 5 nm to 20 nm and a length of several micrometers, which have been assembled into cellulose aerogels by the lyophilization of as-prepared nanofibrils dispersions with various concentrations. The results indicated that the hierarchical structures of as-prepared cellulose aerogels were dependent on the dispersion concentrations. The WAXS results show that the typical cellulose aerogels are coexistence of cellulose I and cellulose II, which has a great promise for many potential applications, such as pharmaceutical, liquid filtration, catalysts, bio-nanocomposites, and tissue engineering scaffolds. PMID:24815398

Lin, Jinyou; Yu, Liangbo; Tian, Feng; Zhao, Nie; Li, Xiuhong; Bian, Fenggang; Wang, Jie

2014-08-30

246

Electrochemical characterization of vanadium pentoxide aerogels  

NASA Astrophysics Data System (ADS)

The growing demand for autonomous, high power, energy storage devices has fueled the development of novel cathode materials for secondary lithium batteries. This research was focused on the electrochemical characterization and optimization of a new vanadium oxide aerogel cathode material. This new aerogel, intercalation compound (LixV2O 5) has been synthesized with a surface area of approximately 420 m 2/g and has been shown to exhibit capacities on the order of 350 mAh/g. Traditional electrochemical characterization methods (cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy) in conjunction with a newly developed scanning probe microscopy technique (liquid atomic force microscopy---contact mode and non-contact magnetic AC mode) were used to obtain in-situ morphological data on the V2 O5 cathode during cell cycling. The finding from these experiments, along with scanning electron microscopy and Fourier transform infrared spectroscopy data were used to develop a new cathode synthesis technique where cycling efficiency was increased by approximately 60% for the first five cycles. A second experimental goal of this dissertation involves the fabrication of thick-film, rechargeable V2O5 aerogel cells. These cells were tested in a pulse discharge fashion for powering piezoelectric, micro-electro-mechanical systems. These thin film cells were also evaluated as an autonomous power supply in a mechanical integrity (structural health) monitoring system (chirp source).

Salloux, Kurt

247

Composite flexible insulation for thermal protection of space vehicles  

NASA Technical Reports Server (NTRS)

A composite flexible blanket insulation (CFBI) system considered for use as a thermal protection system for space vehicles is described. This flexible composite insulation system consists of an outer layer of silicon carbide fabric, followed by alumina mat insulation, and alternating layers of aluminized polyimide film and aluminoborosilicate scrim fabric. A potential application of this composite insulation would be as a thermal protection system for the aerobrake of the aeroassist space transfer vehicle (ASTV). It would also apply to other space vehicles subject to high convective and radiative heating during atmospheric entry. The thermal performance of this composite insulation as exposed to a simulated atmospheric entry environment in a plasma arc test facility is described. Other thermophysical properties which affect the thermal response of this composite insulation is included. It shows that this composite insulation is effective as a thermal protection system at total heating rates up to 30.6 W/sq cm.

Kourtides, Demetrius A.; Tran, Huy K.; Chiu, S. Amanda

1991-01-01

248

Characterization of the microstructures of organic and carbon aerogels based upon mixed cresol–formaldehyde  

Microsoft Academic Search

Organic aerogels were synthesized via the sol–gel polycondensation of mixed cresol with formaldehyde in a slightly basic aqueous solution followed by supercritical drying with carbon dioxide. Carbon aerogels are generated by pyrolysis of organic aerogels in inert atmosphere at high temperature. Obvious chemical and physical changes can take place within aerogel microstructures during the pyrolysis process. IR combined with TGA,

Wen-Cui Li; An-Hui Lu; Shu-Cai Guo

2001-01-01

249

Nanostructure control of carbon aerogels and the application in lithium ion cells  

Microsoft Academic Search

Carbon aerogels are derived via a sol-gel process with resorcinol and formodehyde and subsequent pyrolysis of the precursor (RF) aerogels. Due to their high surface area, electrically conducting network and chemical inertness, carbon aerogels can be considered ideal electrodes in rechargeable batteries. In this paper the optimization of the preparation and structure controlling of carbon aerogels are studied. The influence

Shen Jun; Han Weina; Mi Yijie; Wu Guangming; Zhou Bin; Zhang Zhihua; Ni Xingyuan; Niu Xixian; Wang Guoqing; Wang Peiqing; Wang Qingfeng

2008-01-01

250

Non-silica aerogels as hypervelocity particle capture materials  

Microsoft Academic Search

The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle

Steven M. Jones

2010-01-01

251

Determination of mesopore size of aerogels from thermal conductivity measurements  

Microsoft Academic Search

A novel method to determine the average mesopore size of aerogels was developed. This method is based on the findings that the heat transfer through the gas phase in porous materials is strongly affected by the size of mesopores. Polyisocyanurate aerogels were synthesized and the thermal conductivity of these materials was investigated from vacuum to ambient pressure using the transient

Ok-Joo Lee; Kun-Hong Lee; Tae Jin Yim; Sun Young Kim; Ki-Pung Yoo

2002-01-01

252

Highly porous ceramic oxide aerogels having improved flexibility  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

253

Compressed Silica Aerogels for the Study of Superfluid 3He  

NASA Astrophysics Data System (ADS)

We have performed Small Angle X-ray Scattering (SAXS) on uniaxially strained aerogels and measured the strain-induced structural anisotropy. We use a model to connect our SAXS results to anisotropy of the 3He quasiparticle mean free path in aerogel.

Pollanen, J.; Choi, H.; Davis, J. P.; Blinstein, S.; Lippman, T. M.; Lurio, L. B.; Mulders, N.; Halperin, W. P.

2006-09-01

254

Temperature and moisture dependence of dielectric constant for silica aerogels.  

National Technical Information Service (NTIS)

The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500 deg C. However, due to the open porosity and la...

L. H. Hrubesh

1997-01-01

255

Organic aerogels from the polycondensation of resorcinol with formaldehyde  

Microsoft Academic Search

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 are processed under supercritical conditions to obtain low density, organic aerogels ( ? 0.1 g cm-3). The aerogels are transparent, dark red in colour, and consist of interconnected colloidal-like particles with diameters of

R. W. Pekala

1989-01-01

256

Carbon aerogels derived from cresol–resorcinol–formaldehyde for supercapacitors  

Microsoft Academic Search

The objective of the present paper is to demonstrate the possibility to synthesize mixed carbon aerogels (denoted CmRF) from cresol (Cm), resorcinol (R) and formaldehyde (F), as an alternative economic route to the classical RF synthesis. These porous carbon aerogels can be used as electrode materials for supercapacitors with a high volume-specific capacitance. Organic precursor gels were synthesized via polycondensation

Wencui Li; G Reichenauer; J Fricke

2002-01-01

257

Tailoring of morphology and surface properties of syndiotactic polystyrene aerogels.  

PubMed

This study evaluates a method for rendering syndiotactic polystyrene (sPS) aerogels hydrophilic using polyethylene oxide (PEO) of different molecular weights. The highly porous sPS aerogels are inherently hydrophobic although applications involving absorption of moisture and removal of particulate solids may benefit from the high surface area of sPS aerogels provided some degree of hydrophilicity is induced in these materials. In this work, sPS gels are prepared by thermo-reversible gelation in tetrahydrofuran in the presence of PEO. The gels are dried under supercritical conditions to obtain aerogels. The aerogels are characterized by scanning electron microscopy, nitrogen-adsorption porosimetry, helium pycnometry, and contact angle measurements. The data reveal that the pore structures and surface energy can be controlled by varying the concentration and molecular weight of PEO and using different cooling rates during thermo-reversible gelation. In the first case, sPS aerogels, aerogels containing PEO of a low molecular weight or low concentration show superhydrophobic surface presenting the "lotus effect". In the second case, PEO at a higher concentration or with higher molecular weight forms phase-separated domains yielding new hydrophilic macropores (>10 ?m) in the aerogel structures. These macropores contribute to the superhydrophobic surface with the "petal effect". The cooling rate during gelation shows a strong influence on these two cases. PMID:23573990

Wang, Xiao; Jana, Sadhan C

2013-05-01

258

Fiducial Marks for Location of Particles in Aerogel  

NASA Technical Reports Server (NTRS)

If an extraterrestrial sample is captured in aerogel as a collection of particles, it is important to be able to consistently locate individual grains when changing instruments or laboratories. We report on a feasibility study for applying fiducial marks to aerogel nondestructively so that the marks can eventually be used with optical, X-ray or other (manual or automated) location techniques.

Jurewicz, A. J. G.; Tsapin, A. I.; Jones, S. M.

2004-01-01

259

Organic and composite aerogels through ring opening metathesis polymerization (ROMP)  

NASA Astrophysics Data System (ADS)

Aerogels are open-cell nanoporous materials, unique in terms of low density, low thermal conductivity, low dielectric constants and high acoustic attenuation. Those exceptional properties stem from their complex hierarchical solid framework (agglomerates of porous, fractal secondary nanoparticles), but they also come at a cost: low mechanical strength. This issue has been resolved by crosslinking silica aerogels with organic polymers. The crosslinking polymer has been assumed to form a conformal coating on the surface of the skeletal framework by covalent bridging elementary building blocks. However, "assuming" is not enough: for correlating nanostructure with bulk material properties, it is important to know the exact location of the polymer on the aerogel backbone. For that investigation, we synthesized a new norbornene derivative of triethoxysilane (Si-NAD) that can be attached to skeletal silica nanoparticles. Those norbornene-modified silica aerogels were crosslinked with polynorbornene by ring opening metathesis polymerization (ROMP). The detailed correlation between nanostructure and mechanical strength was probed with a wide array of characterization methods ranging from molecular to bulk through nano. Subsequently, it was reasoned that since the polymer dominates the exceptional mechanical properties of polymer crosslinked aerogels, purely organic aerogels with the same nanostructure and interparticle connectivity should behave similarly. That was explored and confirmed by: (a) synthesis of a difunctional nadimide monomer (bis-NAD), and preparation of robust polyimide aerogels by ROMP of its norbornene end-caps; and, (b) synthesis of dimensionally stable ROMP-derived polydicyclopentadiene aerogels by grafting the nanostructure with polymethylmethacrylate (PMMA) via free radical chemistry.

Mohite, Dhairyashil P.

260

Transverse sound in aerogel with liquid 4He  

NASA Astrophysics Data System (ADS)

An experiment was performed to measure transverse sound resonances in a square slab of aerogel filled with liquid 4He. Resonances have been observed both in the superfluid and normal phase. The dynamics of the system was modelled by combining the equations of two-fluid hydrodynamics of helium with those of elasticity of aerogel.

Berkutov, I. B.; Babuin, S.; Golov, A. I.

2003-05-01

261

Vanadium oxide aerogels: Nanostructured materials for enhanced energy storage  

Microsoft Academic Search

The synthesis, chemistry, local structure and electrochemical properties of vanadium oxide xerogels and aerogels have much in common. The one difference in their respective synthesis routes, the means by which solvent is removed, has a significant influence on the resulting morphology. The high surface area, nanodimensional solid phase, short diffusion paths and interconnected mesoporosity of the aerogels exert a profound

Veronica Augustyn; Bruce Dunn

2010-01-01

262

Morphology and thermal conductivity of model organic aerogels  

Microsoft Academic Search

The intersection volume of two independent 2-level cut Gaussian random fields\\u000ais proposed to model the open-cell microstructure of organic aerogels. The\\u000aexperimentally measured X-ray scattering intensity, surface area and solid\\u000athermal conductivity of both polymeric and colloidal organic aerogels can be\\u000aaccounted for by the model.

Anthony P. Roberts

1997-01-01

263

Compressed Silica Aerogels for the Study of Superfluid 3He  

SciTech Connect

We have performed Small Angle X-ray Scattering (SAXS) on uniaxially strained aerogels and measured the strain-induced structural anisotropy. We use a model to connect our SAXS results to anisotropy of the 3He quasiparticle mean free path in aerogel.

Pollanen, J.; Choi, H.; Davis, J. P.; Blinstein, S.; Lippman, T. M.; Halperin, W. P. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Lurio, L. B. [Department of Physics, Northern Illinois University, DeKalb, IL 60115 (United States); Mulders, N. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

2006-09-07

264

Thermal Conductivity of Powder Insulations Below 180 K  

NASA Astrophysics Data System (ADS)

We have measured the thermal conductivity of aerogel beads and glass microspheres at average temperatures ranging from 30 K to 180 K. The measuring device consists of two closed, concentric cylinders suspended inside of a vacuum insulated cryostat. The insulation being tested occupies the annular space between the cylinders. A single stage Gifford-McMahon cryocooler, thermally anchored to the outer cylinder, cools the apparatus to a desired temperature range. A heater mounted on the inner cylinder generates uniform heat flux through the insulating material between the two cylinders. During each measurement, a temperature difference of roughly 10 K across the insulation is maintained. Fourier's law of heat conduction is used to relate the temperature difference between the two cylinders and the applied heating power to a bulk effective thermal conductivity of the powder insulation. Data were collected for aerogel beads between 30 K and 80 K and for glass bubbles between 30 K and 180 K. Results are compared to data from the literature.

Barrios, M. N.; Choi, Y. S.; van Sciver, S. W.

2008-03-01

265

Deformation of silica aerogels during adsorption of helium and neon  

NASA Astrophysics Data System (ADS)

Fluids confined in aerogel, especially ^3He and ^4He, have been intensely studied for over a decade. Because of the low surface tensions of these fluids, capillary forces are small and the resulting deformation of the aerogel is usually neglected. However, high porosity aerogels are very compressible and large volume changes have been seen^1 during adsorption of nitrogen, which has a much higher surface tension. We have used a linear variable differential transformer (LVDT) to measure the deformation of aerogels as fluids capillary condense within them. Our measurements are taken along isotherms near the critical points of neon and helium and show small volume changes in the aerogel during adsorption and desorption. 1. G. Reichenauer and G.W. Scherer, J. Non-Cryst. Solids 277 (2000) 162.

Herman, Tobias; Beamish, John

2004-03-01

266

Evaluation of low cost/high temperature insulation, July 1974 - June 1975  

NASA Technical Reports Server (NTRS)

Six fiber products and six insulation blankets comprising silica, alumina, zirconia, mullite, and mixed ceramic systems were subjected to furnace exposures up to 500 hours at temperatures of 1000 to 1600 C and evaluated for chemical and dimensional stability and for changes in thermal conductivity. Alumina, zirconia, and mullite fibers were fabricated into reusable surface insulation (RSI) tile by water-felting and reimpregnation with ethyl silicate. Specimens were exposed to 25 thermal cycles at 1200 C and 1400 C and a pressure of 10 and 32 torr, respectively. Production costs for 930 sq m (10,000 sq ft) of blanket insulation and of alumina RSI tile were developed.

Strauss, E. L.

1975-01-01

267

Composite ceria-coated aerogels and methods of making the same  

SciTech Connect

Ceria-coated aerogels can include an aerogel support material having a stabilized ceria coating thereon. The ceria coating can be formed by solution or vapor deposition of alcogels or aerogels. Additional catalytic metal species can also be incorporated into the coating to form multi-metallic compounds having improved catalytic activity. Further, the ceria coated aerogels retain high surface areas at elevated temperatures. Thus, improvements in catalytic activity and thermal stability can be achieved using these ceria-coated composite aerogels.

Eyring, Edward M; Ernst, Richard D; Turpin, Gregory C; Dunn, Brian C

2013-05-07

268

High resolution transmission electron microscopy of melamine-formaldehyde aerogels and silica aerogels.  

National Technical Information Service (NTIS)

The goal of the high resolution transmission electron microscopy (HRTEM) was to image the structure of two tetramethyl orthosilicate (TMOS) and two melamine-formaldehyde (MF) aerogels at the single polymer chain level(sup 1,2). With this level of structur...

G. C. Ruben

1991-01-01

269

Aerogel Keystones: Extraction Of Complete Hypervelocity Impact Events From Aerogel Collectors  

Microsoft Academic Search

In January 2006, the Stardust mission will return the first samples from a solid solar-system body since Apollo, and the first samples of contemporary interstellar dust ever collected. Although sophisticated laboratory instruments exist for the analysis of Stardust samples, techniques for the recovery of particles and particle residues from aerogel collectors remain primitive. Here we describe our recent progress in

Andrew J. Westphal; Christopher J. Snead; Anna L. Butterworth; Giles A. Graham; John P. Bradley; Saÿsa Bajt; Patrick G. Grant; Graham Bench; Sean Brennan; P Piannetta

2003-01-01

270

Aerogel keystones: Extraction of complete hypervelocity impact events from aerogel collectors  

Microsoft Academic Search

In January 2006, the Stardust mission will return the first samples from a solid solar system body beyond the Moon and the first samples of contemporary interstellar dust ever collected. Although sophisticated laboratory instruments exist for the analysis of Stardust samples, techniques for the recovery of particles and particle residues from aerogel collectors remain primitive. Here, we describe our recent

Andrew J. Westphal; Christopher Snead; Anna Butterworth; Giles A. Graham; John P. Bradley; Sasa Bajt; Patrick G. Grant; Graham Bench; Sean Brennan; Piero Pianetta

2004-01-01

271

Analysis of multilayer insulation between 80K and 300K  

SciTech Connect

A model has been developed that can be used to determine the temperature distribution and heat transfer through a multilayer insulation (MLI) blanket. Predictions from the model were compared with a series of temperature measurements made during laboratory experiments and during a test of five superconducting magnets (dipoles) installed in a string and tested at Fermi National Accelerator Laboratory, FNAL (ER Test).

Augustynowicz, S.D.; Demko, J.A. [Superconducting Super Collider Lab., Dallas, TX (United States); Datskov, V.I. [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Lab. of High Energy

1993-07-01

272

Fusion blankets for high efficiency power cycles  

SciTech Connect

Definitions are given of 10 generic blanket types and the specific blanket chosen to be analyzed in detail from each of the 10 types. Dimensions, compositions, energy depositions and breeding ratios (where applicable) are presented for each of the 10 designs. Ultimately, based largely on neutronics and thermal hyraulics results, breeding an nonbreeding blanket options are selected for further design analysis and integration with a suitable power conversion subsystem.

Powell, J R; Fillo, J A; Horn, F L; Lazareth, O W; Usher, J L

1980-04-01

273

Low technology high tritium breeding blanket concept  

SciTech Connect

The main function of this low technology blanket is to produce the necessary tritium for INTOR operation with minimum first wall coverage. The INTOR first wall, blanket, and shield are constrained by the dimensions of the reference design and the protection criteria required for different reactor components and dose equivalent after shutdown in the reactor hall. It is assumed that the blanket operation at commercial power reactor conditions and the proper temperature for power generation can be sacrificed to achieve the highest possible tritium breeding ratio with minimum additional research and developments and minimal impact on reactor design and operation. A set of blanket evaluation criteria has been used to compare possible blanket concepts. Six areas: performance, operating requirements, impact on reactor design and operation, safety and environmental impact, technology assessment, and cost have been defined for the evaluation process. A water-cooled blanket was developed to operate with a low temperature and pressure. The developed blanket contains a 24 cm of beryllium and 6 cm of solid breeder both with a 0.8 density factor. This blanket provides a local tritium breeding ratio of approx.2.0. The water coolant is isolated from the breeder material by several zones which eliminates the tritium buildup in the water by permeation and reduces the changes for water-breeder interaction. This improves the safety and environmental aspects of the blanket and eliminates the costly process of the tritium recovery from the water. 12 refs., 13 tabs.

Gohar, Y.; Baker, C.C.; Smith, D.L.; Billone, M.C.; Cha, Y.S.; Clemmer, R.; Finn, P.A.; Hassanein, A.M.; Johnson, C.E.; Liu, Y.

1987-10-01

274

Toughened Thermal Blanket for MMOD Protection  

NASA Technical Reports Server (NTRS)

Thermal blankets are used extensively on spacecraft to provide passive thermal control of spacecraft hardware from thermal extremes encountered in space. Toughened thermal blankets have been developed that greatly improve protection from hypervelocity micrometeoroid and orbital debris (MMOD) impacts. These blankets can be outfitted if so desired with a reliable means to determine the location, depth and extent of MMOD impact damage by incorporating an impact sensitive piezoelectric film. Improved MMOD protection of thermal blankets was obtained by adding selective materials at various locations within the thermal blanket. As given in Figure 1, three types of materials were added to the thermal blanket to enhance its MMOD performance: (1) disrupter layers, near the outside of the blanket to improve breakup of the projectile, (2) standoff layers, in the middle of the blanket to provide an area or gap that the broken-up projectile can expand, and (3) stopper layers, near the back of the blanket where the projectile debris is captured and stopped. The best suited materials for these different layers vary. Density and thickness is important for the disrupter layer (higher densities generally result in better projectile breakup), whereas a highstrength to weight ratio is useful for the stopper layer, to improve the slowing and capture of debris particles.

Christiansen, Eric L.; Lear, Dana M.

2014-01-01

275

Packed fluidized bed blanket for fusion reactor  

DOEpatents

A packed fluidized bed blanket for a fusion reactor providing for efficient radiation absorption for energy recovery, efficient neutron absorption for nuclear transformations, ease of blanket removal, processing and replacement, and on-line fueling/refueling. The blanket of the reactor contains a bed of stationary particles during reactor operation, cooled by a radial flow of coolant. During fueling/refueling, an axial flow is introduced into the bed in stages at various axial locations to fluidize the bed. When desired, the fluidization flow can be used to remove particles from the blanket.

Chi, John W. H. (Mt. Lebanon, PA)

1984-01-01

276

75 FR 11557 - Woven Electric Blankets From China  

Federal Register 2010, 2011, 2012, 2013

...No. 731-TA-1163 (Final)] Woven Electric Blankets From China AGENCY: United States...less-than-fair-value imports from China of woven electric blankets, provided for in subheading...semi- finished, and unassembled woven electric blankets, including woven electric...

2010-03-11

277

Globally anisotropic high porosity silica aerogels  

NASA Astrophysics Data System (ADS)

We discuss two methods by which high porosity silica aerogels can be engineered to exhibit global anisotropy. First, anisotropy can be introduced with axial strain. In addition, intrinsic anisotropy can result during growth and drying stages and, suitably controlled, it can be correlated with preferential radial shrinkage in cylindrical samples. We have performed small angle X-ray scattering (SAXS) to characterize these two types of anisotropy. We show that global anisotropy originating from either strain or shrinkage leads to optical birefringence and that optical cross-polarization studies are a useful characterization of the uniformity of the imposed global anisotropy.

Pollanen, J.; Shirer, K.; Blinstein, S.; Davis, J.; Choi, H.; Lippman, T.; Halperin, W.; Lurio, L.

2008-10-01

278

Hypervelocity capture of meteoritic particles in nonsilica aerogels  

NASA Astrophysics Data System (ADS)

Abstract- The Stardust mission captured particles from the comet 81P/Wild 2 in gradient density silica aerogel and returned the collected samples to earth in 2006. The analyses of these particles have revealed several new insights into the formation of our solar system. However, since the aerogel used as the capture material was silica, the elemental analyses of the silica-rich particles were made more complicated in certain ways due to the mixing of the silicon of the particles and that of the aerogel. By using a nonsilica aerogel, future elemental analyses of silica-rich particles captured in aerogel could be made more straightforward. Resorcinol/formaldehyde (RF), alumina, and zirconia aerogels were impact tested with meteoritic fragments and the captured fragments were mapped with synchrotron-based X-ray microprobe (XRM) and the particles were analyzed with X-ray fluorescence (XRF). The resorcinol/formaldehyde aerogel proved to be the best capture material, in that it could be keystoned and XRF could be used to locate and analyze particles that were less than 10 ?m.

Jones, Steven M.; Flynn, George

2011-09-01

279

Temperature and moisture dependence of dielectric constant for silica aerogels  

SciTech Connect

The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500{degrees}C. However, due to the open porosity and large surface areas for aerogels, their dielectric constants are strongly affected by moisture and temperature. This paper presents data for the dielectric constants of silica aerogels as a function of moisture content at 25{degrees}C, and as a function of temperature, for temperatures in the range from 25{degrees}C to 450{degrees}C. Dielectric constant data are also given for silica aerogels that are heat treated in dry nitrogen at 500{degrees}C, then cooled to 25{degrees}C for measurements in dry air. All measurements are made on bulk aerogel spheres at 22GHz microwave frequency, using a cavity perturbation method. The results of the dependence found here for bulk materials can be inferred to apply also to thin films of silica aerogels having similar nano-structures and densities.

Hrubesh, L.H., LLNL

1997-03-01

280

Beryllium in the ITER blanket  

SciTech Connect

This paper consists of viewgraphs used in a presentation on the application of beryllium in breeding blankets for ITER and JET. The paper brings together data on the physical, thermal, mechanical, and chemical properties of beryllium and beryllium oxide for this type of application, as well as issues of compatibility with construction materials, and irradiation experience. It includes the results from testing programs carried out to arrive at some of the information, including fabrication work, irradiation experiments, and sample tests performed both in and out of the irradiation piles.

Billone, M.C.

1995-01-01

281

Highly porous and mechanically strong ceramic oxide aerogels  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

282

Highly porous and mechanically strong ceramic oxide aerogels  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

283

Aerogel and ferroelectric dielectric materials for plasma actuators  

NASA Astrophysics Data System (ADS)

This paper presents performance evaluation of two thick materials with extreme permittivity as dielectric barrier discharge actuators. Specifically, the use of silica aerogels and ferroelectrics is investigated. Due to high polarizability of the ferroelectric material the supplied power manifests itself primarily as heat generation with no measurable thrust. The silica aerogel, however, has a significant impact on thrust saturation as compared with other dielectrics reported to date. Specifically, the silica aerogel is found to have an order of magnitude better thrust to actuator weight ratio than acrylic and twice than that of Kapton with no power penalty, making it potentially useful for small vehicle applications.

Durscher, Ryan; Roy, Subrata

2012-01-01

284

Pairing states of superfluid 3He in uniaxially anisotropic aerogel  

NASA Astrophysics Data System (ADS)

Stable pairing states of superfluid 3He in aerogel are examined in the case with a global uniaxial anisotropy which may be created by applying a uniaxial stress to the aerogel. Due to such a global anisotropy, the stability region of an Anderson-Brinkman-Morel (ABM) pairing state becomes wider. In a uniaxially stretched aerogel, the pure polar pairing state with a horizontal line node is predicted to occur, as a three-dimensional superfluid phase, over a measurable width just below the superfluid transition at Tc (P) . A possible relevance of the present results to the case with no global anisotropy is also discussed.

Aoyama, Kazushi; Ikeda, Ryusuke

2006-02-01

285

Thermal Insulation  

NASA Technical Reports Server (NTRS)

Commercially known as Solimide, Temptronics, Inc.'s thermal insulation has application in such vehicles as aircraft, spacecraft and surface transportation systems (i.e. rapid transit cars, trains, buses, and ships) as acoustical treatment for door, wall, and ceiling panels, as a means of reducing vibrations, and as thermal insulation (also useful in industrial equipment). Product originated from research conducted by Johnson Space Center on advanced flame-resistant materials for minimizing fire hazard in the Shuttle and other flight vehicles.

1984-01-01

286

Low technology high tritium breeding blanket concept  

Microsoft Academic Search

The main function of this low technology blanket is to produce the necessary tritium for INTOR operation with minimum first wall coverage. The INTOR first wall, blanket, and shield are constrained by the dimensions of the reference design and the protection criteria required for different reactor components and dose equivalent after shutdown in the reactor hall. It is assumed that

Y. Gohar; C. C. Baker; D. L. Smith; M. C. Billone; Y. S. Cha; R. Clemmer; P. A. Finn; A. M. Hassanein; C. E. Johnson; Y. Liu

1987-01-01

287

Nucleonic Aspects of the LINUS Imploding Blanket.  

National Technical Information Service (NTIS)

Nucleonic analyses have been performed for the Naval Research Laboratory's imploding-liner fusion reactor concept called LINUS. Mixtures of Pb and LiPb were used for the liquid metal liner (blanket), with blanket thickness, LiPb fraction, and Cd poisoning...

D. J. Dudziak

1978-01-01

288

ARIES-IV Nested Shell Blanket Design.  

National Technical Information Service (NTIS)

The ARIES-IV Nested Shell Blanket (NSB) Design is an alternate blanket concept of the ARIES-IV low activation helium-cooled reactor design. The reference design has the coolant routed in the poloidal direction and the inlet and outlet plena are located at...

C. P. C. Wong K. Redler E. E. Reis R. Will E. Cheng

1993-01-01

289

An overview of dual coolant Pb-17Li breeder first wall and blanket concept development for the US ITER-TBM design  

SciTech Connect

An attractive blanket concept for the fusion reactor is the dual coolant Pb-17Li liquid (DCLL) breeder design. Reduced activation ferritic steel (RAFS) is used as the structural material. Helium is used to cool the first wall and blanket structure, and the self-cooled breeder Pb-17LI is circulated for power conversion and for tritium breeding. A SiCf/SiC composite insert is used as the magnetohydrodynamic (MHD) insulation to reduce the impact from the MHD pressure drop of the circulating Ph-17Li and as the thermal insulator to separate the high temperature Pb-17Li from the helium cooled RAFS structure.

Wong, Clement; Malang, S.; Sawan, M.; Dagher, Mohamad; Smolentsev, S.; Merrill, Brad; Youssef, M.; Reyes, Susanna; Sze, Dai Kai; Morley, Neil B.; Sharafat, Shahran; Calderoni, P.; Sviatoslavsky, G.; Kurtz, Richard J.; Fogarty, Paul J.; Zinkle, Steven J.; Abdou, Mohamed A.

2006-02-01

290

Multiscale Computer Simulation of Failure in Aerogels  

NASA Technical Reports Server (NTRS)

Aerogels have been of interest to the aerospace community primarily for their thermal properties, notably their low thermal conductivities. While such gels are typically fragile, recent advances in the application of conformal polymer layers to these gels has made them potentially useful as lightweight structural materials as well. We have previously performed computer simulations of aerogel thermal conductivity and tensile and compressive failure, with results that are in qualitative, and sometimes quantitative, agreement with experiment. However, recent experiments in our laboratory suggest that gels having similar densities may exhibit substantially different properties. In this work, we extend our original diffusion limited cluster aggregation (DLCA) model for gel structure to incorporate additional variation in DLCA simulation parameters, with the aim of producing DLCA clusters of similar densities that nevertheless have different fractal dimension and secondary particle coordination. We perform particle statics simulations of gel strain on these clusters, and consider the effects of differing DLCA simulation conditions, and the resultant differences in fractal dimension and coordination, on gel strain properties.

Good, Brian S.

2008-01-01

291

Method for net-shaping using aerogels  

DOEpatents

A method of net-shaping using aerogel materials is provided by first forming a sol, aging the sol to form a gel, with the gel having a fluid component and having been formed into a medium selected from the group consisting of a powder, bulk material, or granular aerobeads, derivatizing the surface of the gel to render the surface unreactive toward further condensation, removing a portion of the fluid component of the final shaped gel to form a partially dried medium, placing the medium into a cavity, wherein the volume of said medium is less that the volume of the cavity, and removing a portion of the fluid component of the medium. The removal, such as by heating at a temperature of approximately less than 50.degree. C., applying a vacuum, or both, causes the volume of the medium to increase and to form a solid aerogel. The material can be easily removed by exposing the material to a solvent, thereby reducing the volume of the material. In another embodiment, the gel is derivatized and then formed into a shaped medium, where subsequent drying reduces the volume of the shaped medium, forming a net-shaping material. Upon further drying, the material increases in volume to fill a cavity. The present invention is both a method of net-shaping and the material produced by the method.

Brinker, C. Jeffrey (Albuquerque, NM); Ashey, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM); Sriram, Chunangad S. (Indianapolis, IN); Harris, Thomas M. (Tulsa, OK)

2001-01-01

292

Blanket materials for DT fusion reactors  

SciTech Connect

This paper presents an overview of the critical materials issues that must be considered in the development of a tritium breeding blanket for a tokamak fusion reactor that operates on the D-T-Li fuel cycle. The primary requirements of the blanket system are identified and the important criteria that must be considered in the development of blanket technology are summarized. The candidate materials are listed for the different blanket components, e.g., breeder, coolant, structure and neutron multiplier. Three blanket concepts that appear to offer the most potential are: (1) liquid-metal breeder/coolant, (2) liquid-metal breeder/separate coolant, and (3) solid breeder/separate coolant. The major uncertainties associated with each of the design concepts are discussed and the key materials R and D requirements for each concept are identified.

Smith, D.L.

1981-01-01

293

Effect of Cyclic Aeroconvective Heating on Flexible Thermal Insulations  

NASA Technical Reports Server (NTRS)

This paper describes the effect of cyclic aeroconvective heating on the thermal performance of ceramic flexible insulations considered for potential use as thermal protection systems or thermal insulations for future hypersonic vehicles such as the Reusable Launch Vehicles (RLV's) and other applications where structures require thermal protection from severe heating. The thermal response of these materials after exposure to cyclic aeroconvective heating from a plasma arc is described. The thermal insulations evaluated were Composite Flexible Blanket Insulations composed of an outer layer of aluminoborosilicate fabric and alumina insulation. The insulations were evaluated with and without a high emissivity coating. These insulations were exposed to the plasma arc stream for nine minutes reaching surface temperatures of 1150 C and a heat flux of 10.5 W/sq cm. Insulations were exposed three, six, or nine times in order to demonstrate reusability and to determine the effect oi coatings on the surface durability of these insulations. Test results demonstrated the capability of these insulations to protect either composite or metallic structures from high heating environments. It is shown that high emittance coatings reduce backface temperatures. The durability of these insulations when impacted at low velocities was also demonstrated. The interaction of the coatings with the ceramic fibers was characterized. An analytical thermal model was utilized to correlate experimental thermal test results with calculated values.

Kourtides, Demetrius A.; Zambrano, Brian; Kowalski, Tom; Rasky, Daniel J. (Technical Monitor)

1995-01-01

294

Mechanically Strong, Lightweight Porous Materials Developed (X-Aerogels).  

National Technical Information Service (NTIS)

Aerogels are attractive materials for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other materials. Potential NASA applications for these materials ...

N. Leventis

2005-01-01

295

Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong.  

National Technical Information Service (NTIS)

The mesoporous surfaces of tetramethylorthosilicate (TMOS)-derived silica aerogels have been modified with amines by co-polymerization of TMOS with aminopropyltriethoxysilane (APTES). The amine sites have become anchors for crosslinking the nanoparticles ...

M. A. B. Meador E. F. Fabrizio F. Ilhan A. Dass

2005-01-01

296

Capacitive, deionization with carbon aerogel electrodes: Carbonate, sulfate, and phosphate.  

National Technical Information Service (NTIS)

A process for the capacitive deionization (CDI) of water with a stack of carbon aerogel electrodes has been developed by Lawrence Livermore National Laboratory. Unlike ion exchange, electricity is used instead of chemicals for regeneration of the system. ...

J. C. Farmer D. V. Fix G. V. Mack R. W. Pekala J. F. Poco

1995-01-01

297

Silica aerogel: An intrinsically low dielectric constant material.  

National Technical Information Service (NTIS)

Silica aerogels are highly porous solids having unique morphologies in wavelength of visible which both the pores and particles have sizes less than the wavelength of visible light. This fine nanostructure modifies the normal transport mechanisms within a...

L. W. Hrubesh

1995-01-01

298

Graphene nanoribbon aerogels unzipped from carbon nanotube sponges.  

PubMed

Graphene nanoribbon aerogels are fabricated by directly unzipping multi-walled carbon nanotube sponges. These fascinating materials have potential applications as high performance nanocomposites and supercapacitor electrodes. PMID:24496883

Peng, Qingyu; Li, Yibin; He, Xiaodong; Gui, Xuchun; Shang, Yuanyuan; Wang, Chunhui; Wang, Chao; Zhao, Wenqi; Du, Shanyi; Shi, Enzheng; Li, Peixu; Wu, Dehai; Cao, Anyuan

2014-05-28

299

Forced-air patient warming blankets disrupt unidirectional airflow.  

PubMed

We have recently shown that waste heat from forced-air warming blankets can increase the temperature and concentration of airborne particles over the surgical site. The mechanism for the increased concentration of particles and their site of origin remained unclear. We therefore attempted to visualise the airflow in theatre over a simulated total knee replacement using neutral-buoyancy helium bubbles. Particles were created using a Rocket PS23 smoke machine positioned below the operating table, a potential area of contamination. The same theatre set-up, warming devices and controls were used as in our previous study. This demonstrated that waste heat from the poorly insulated forced-air warming blanket increased the air temperature on the surgical side of the drape by > 5°C. This created convection currents that rose against the downward unidirectional airflow, causing turbulence over the patient. The convection currents increased the particle concentration 1000-fold (2 174 000 particles/m(3) for forced-air warming vs 1000 particles/m(3) for radiant warming and 2000 particles/m(3) for the control) by drawing potentially contaminated particles from below the operating table into the surgical site. Cite this article: Bone Joint J 2013;95-B:407-10. PMID:23450029

Legg, A J; Hamer, A J

2013-03-01

300

Hypervelocity capture of meteoritic particles in nonsilica aerogels  

Microsoft Academic Search

Abstract- The Stardust mission captured particles from the comet 81P\\/Wild 2 in gradient density silica aerogel and returned the collected samples to earth in 2006. The analyses of these particles have revealed several new insights into the formation of our solar system. However, since the aerogel used as the capture material was silica, the elemental analyses of the silica-rich particles

Steven M. Jones; George Flynn

2011-01-01

301

AEM and HREM evaluation of carbon nanostructures in silica aerogels  

SciTech Connect

Nanostructured carbon has been deposited in silica aerogels by chemical vapor infiltration using acetylene or ferrocene at moderate temperatures. Using analytical electron microscopy and high-resolution electron microscopy, we have observed various carbon rings and nanotubes in the silica aerogel-based carbon composite. Both X-ray microanalysis and nano-probe diffraction techniques have been used to confirm the presence of those carbon nanostructures. Morphologies and structural properties of the carbon nanotubes and rings have also been examined in detail.

Song, X.Y.; Cao, W.; Hunt, A.J.

1994-04-01

302

Structure of organic aerogels. 1. Morphology and scaling  

Microsoft Academic Search

Small-angle X-ray scattering is used to determine the structure of nanoporous organic aerogels made by the base-catalyzed polymerization of resorcinol and formaldehyde. This study probes the effect of several variables on the morphology of the supercritically dried aerogels including catalyst concentration, monomer concentration, acid aging, and pyrolysis. In addition, the development of structure during polymerization and aging of the precursor

R. W. Pekala; D. W. Schaefer

1993-01-01

303

Morphology and electrochemistry of ruthenium\\/carbon aerogel nanostructures  

Microsoft Academic Search

The structure-property relationships of nanostructured Ru\\/carbon aerogel composite materials have been evaluated. These new materials were prepared via a novel two-step metal vapor impregnation method which enables one to control the Ru loading through repetition of the process. The resulting microstructure is characterized by highly dispersed Ru particles (â20--30 â« in diameter) attached to the carbon aerogel surface and distributed

J. M. Miller; B. Dunn

1999-01-01

304

Models for Superfluid H3e in Aerogel  

Microsoft Academic Search

Several recent experiments find evidence of superfluidity of 3He in\\u000a98%-porous aerogel. The primary effect of the aerogel is that it scatters the\\u000aquasiparticles of 3He. We find that many experimental findings are\\u000aquantitatively understood by a relatively simple model that takes into account\\u000astrong inhomogeneity of the scattering on a length scale of 100 nm.

E. V. Thuneberg; S. K. Yip; M. Fogelstrom; J. A. Sauls

1998-01-01

305

Impact Features and Projectile Residues in Aerogel Exposed on Mir  

Microsoft Academic Search

Approximately 0.63 m2 of SiO2-based aerogel (0.02 g cm?3) was exposed for 18 months on the Mir Station to capture hypervelocity particles from both man-made and natural sources. Optical inspection revealed two major classes of hypervelocity impact features in the aerogel: (1) long, carrot-shaped tracks, well known from laboratory impact experiments, that exhibit a depth- (t) to-diameter (D) relationship of

F. Hörz; M. E. Zolensky; R. P. Bernhard; T. H. See; J. L. Warren

2000-01-01

306

New organic aerogels based upon a phenolic-furfural reaction  

Microsoft Academic Search

The aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde are two proven synthetic routes for the formation of organic aerogels. A new type of organic aerogel based upon a phenolic-furfural (PF) reaction was recently discovered. This sol?gel polymerization has a major advantage over past approaches since it can be conducted in alcohol (e.g., 1-propanol), thereby eliminating

R. W Pekala; C. T Alviso; X Lu; J Gross; J Fricke

1995-01-01

307

Hydrodynamic Property of Oscillating Superfluid 3He in Aerogel  

SciTech Connect

The investigation of the superfluidity of liquid 3He in aerogel of 97.5% and 98.5% porosities using the fourth sound resonance technique revealed two distinct observations. First, the superfluid transition temperature TC and the superfluid density {rho}s/{rho} of 3He in aerogel are greatly suppressed. Second, the sound attenuation does not depend on temperature at higher temperatures, but monotonically diminishes with decreasing temperature at lower temperatures.

Obara, K.; Nago, Y.; Yano, H.; Ishikawa, O.; Hata, T. [Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Yokogawa, H.; Yokoyama, M. [Advanced Technology Research Laboratory, Matsushita Electric Works, Ltd. (Japan)

2006-09-07

308

Hydrodynamic Property of Oscillating Superfluid 3He in Aerogel  

NASA Astrophysics Data System (ADS)

The investigation of the superfluidity of liquid 3He in aerogel of 97.5% and 98.5% porosities using the fourth sound resonance technique revealed two distinct observations. First, the superfluid transition temperature TC and the superfluid density ?s/? of 3He in aerogel are greatly suppressed. Second, the sound attenuation does not depend on temperature at higher temperatures, but monotonically diminishes with decreasing temperature at lower temperatures.

Obara, K.; Nago, Y.; Yano, H.; Ishikawa, O.; Hata, T.; Yokogawa, H.; Yokoyama, M.

2006-09-01

309

Silica aerogel: An intrinsically low dielectric constant material  

SciTech Connect

Silica aerogels are highly porous solids having unique morphologies in wavelength of visible which both the pores and particles have sizes less than the wavelength of visible light. This fine nanostructure modifies the normal transport mechanisms within aerogels and endows them with a variety of exceptional physical properties. For example, aerogels have the lowest measured thermal conductivity and dielectric constant for any solid material. The intrinsically low dielectric properties of silica aerogels are the direct result of the extremely high achievable porosities, which are controllable over a range from 75% to more than 99.8 %, and which result in measured dielectric constants from 2.0 to less than 1.01. This paper discusses the synthesis of silica aerogels, processing them as thin films, and characterizing their dielectric properties. Existing data and other physical characteristics of bulk aerogels (e.g., thermal stablity, thermal expansion, moisture adsorption, modulus, dielectric strength, etc.), which are useful for evaluating them as potential dielectrics for microelectronics, are also given.

Hrubesh, L.W.

1995-04-01

310

ADVANCED HIGH PERFORMANCE SOLID WALL BLANKET CONCEPTS  

SciTech Connect

OAK A271 ADVANCED HIGH PERFORMANCE SOLID WALL BLANKET CONCEPTS. First wall and blanket (FW/blanket) design is a crucial element in the performance and acceptance of a fusion power plant. High temperature structural and breeding materials are needed for high thermal performance. A suitable combination of structural design with the selected materials is necessary for D-T fuel sufficiency. Whenever possible, low afterheat, low chemical reactivity and low activation materials are desired to achieve passive safety and minimize the amount of high-level waste. Of course the selected fusion FW/blanket design will have to match the operational scenarios of high performance plasma. The key characteristics of eight advanced high performance FW/blanket concepts are presented in this paper. Design configurations, performance characteristics, unique advantages and issues are summarized. All reviewed designs can satisfy most of the necessary design goals. For further development, in concert with the advancement in plasma control and scrape off layer physics, additional emphasis will be needed in the areas of first wall coating material selection, design of plasma stabilization coils, consideration of reactor startup and transient events. To validate the projected performance of the advanced FW/blanket concepts the critical element is the need for 14 MeV neutron irradiation facilities for the generation of necessary engineering design data and the prediction of FW/blanket components lifetime and availability.

WONG, CPC; MALANG, S; NISHIO, S; RAFFRAY, R; SAGARA, S

2002-04-01

311

Insulation Material  

NASA Technical Reports Server (NTRS)

Manufactured by Hitco Materials Division of Armco, Inc. a ceramic fiber insulation material known as Refrasil has been used extensively as a heat-absorbing ablative reinforcement for such space systems as rocket motor nozzles, combustion chambers, and re-entry shields. Refrasil fibers are highly porous and do not melt or vaporize until fibers exceed 3,100 degrees Fahrenheit. Due to these and other properties, Refrasil has found utility in a number of industrial high temperature applications where glass, asbestos and other materials fail. Hitco used this insulation to assist Richardson Co., Inc. in the manufacturing of hard rubber and plastic molded battery cases.

1984-01-01

312

A fast reactor core concept using an internal blanket  

Microsoft Academic Search

A new core concept using an internal blanket, which is one type of heterogeneous core, has been developed. The core employs a disk-shaped internal blanket at the axial central region of the core. This internal blanket extends radially all the way through the core to the external blanket and is arranged so that its thickness is greater in the radial

K. Kawashima; K. Inoue; S. Kobayashi

1981-01-01

313

Imbibition of Liquid Helium in Aerogels  

NASA Astrophysics Data System (ADS)

We report optical measurements of the imbibition of liquid helium in a sample of silica aerogel with 90 % porosity. Both direct imaging and light scattering experiments were performed to determine the dynamics and the properties of the liquid-gas interface in both the normal and superfluid phases of liquid helium. In the normal phase, a classical Lucas Washburn behavior is observed for the rise of the imbibition front while the behavior in the superfluid phase is markedly different, as the fluid invades the sample from all sides with a constant speed. In both phases, the interface is rough, leading to light scattering. In addition, condensation ahead of the imbibition front is observed at low temperature in the superfluid phase.

Spathis, P.; Delga, A.; Malheiro, C.; Wolf, P. E.

2013-06-01

314

Monolithic three-dimensional electrochemical energy storage system on aerogel or nanotube scaffold  

DOEpatents

A monolithic three-dimensional electrochemical energy storage system is provided on an aerogel or nanotube scaffold. An anode, separator, cathode, and cathodic current collector are deposited on the aerogel or nanotube scaffold.

Farmer, Joseph C; Stadermann, Michael

2013-11-12

315

Desalting in wastewater reclamation using capacitive deionization with carbon aerogel electrodes.  

National Technical Information Service (NTIS)

Capacitive deionization with carbon aerogel electrodes is an efficient and economical new process for removing salt and impurities from water. Carbon aerogel is a material that enables the successful purification of water because of its high surface area,...

J. H. Richardson J. C. Farmer D. V. Fix J. A. H. de Pruneda G. V. Mack

1996-01-01

316

Silica Aerogel for Use in Cosmic Dust Collectors Utilized in the Tanpopo Mission  

NASA Astrophysics Data System (ADS)

We are developing silica aerogels for use in cosmic dust collectors utilized in the Tanpopo mission. In this paper, we present the recent development of a box-framing aerogel in contamination-controlled environments.

Tabata, M.; Yano, H.; Kawai, H.; Imai, E.; Hashimoto, H.; Yokobori, S.; Yamagishi, A.; Tanpopo Working Group

2013-11-01

317

Window insulator  

SciTech Connect

An insulator for mounting to a window. A pair of plastic layers including a plurality of partitions positioned therebetween form air pockets between the layers. A plurality of suction cups and suction grooves arranged in rows on one outer surface of the sheet removably secure the sheet to a window. The sheet includes a circumferentially extending recessed portion receiving the window frame.

Nesbitt, W. A.

1985-10-01

318

An assessment of critical thermal-hydraulic problems in a deuterium-tritium solid breeder blanket  

SciTech Connect

Steady-state thermal-hydraulic analyses were carried out for the DEMO/STARFIRE fusion reactor based on solid breeder blankets and pressurized water as the coolant. The results of the parametric studies show that a coolant in-tube design, i.e., coolant tubes embedded in solid breeder blanket, with a contact resistance between the coolant tube and the solid breeder tailored to maintain the operating temperature window (i.e., the maximum and the minimum temperature imposed on the solid breeder) is viable. However, design of such a solid breeder blanket will present serious challenges because of uncertainty in the thermophysical properties of breeder materials, the narrow operating temperature window, the close manufacturing tolerances necessary to control the gap conductance, the sensitivity of tritium inventory and tritium extraction to breeder temperature distribution, and the deleterious effect of neutron irradiation on breeder material properties. The study shows that even modest uncertainties in the thermal conductivity of solid breeders, interfacial gap conductances, and operating power levels can have significant impact on blanket design. Therefore, the designer should include the expected variations in these parameters. Experimental programs are needed to quantify the above factors and to develop methods (e.g., insulated coatings) for gap conductance control and in situ recovery of tritium via helium purge gas channels.

Misra, B.; Clemmer, R.G.; Smith, D.L.

1983-09-01

319

European blanket development for a demo reactor.  

National Technical Information Service (NTIS)

There are four breeding blanket concepts for a fusion DEMO reactor under development within the framework of the fusion technology programme of the European Union (EU). This paper describes the design of these concepts, the accompanying R + D programme an...

L. Giancarli E. Proust S. Malang M. Dalle Donne L. Anzidei

1994-01-01

320

Granulation in Upflow Anaerobic Sludge Blanket Reactor,  

National Technical Information Service (NTIS)

The experiment was designed to study Upflow Anaerobic Sludge Blanket (UASB) reactor and to evaluate a methane fermentation process for the treatment of wastewater. The essential feature of the UASB process is high activity of anaerobic bacterial mass in t...

T. Hoaki T. Tomozawa S. Kaneko

1987-01-01

321

APT target-blanket fabrication development  

SciTech Connect

Concepts for producing tritium in an accelerator were translated into hardware for engineering studies of tritium generation, heat transfer, and effects of proton-neutron flux on materials. Small-scale target- blanket assemblies were fabricated and material samples prepared for these performance tests. Blanket assemblies utilize composite aluminum-lead modules, the two primary materials of the blanket. Several approaches are being investigated to produce large-scale assemblies, developing fabrication and assembly methods for their commercial manufacture. Small-scale target-blanket assemblies, designed and fabricated at the Savannah River Site, were place in Los Alamos Neutron Science Center (LANSCE) for irradiation. They were subjected to neutron flux for nine months during 1996-97. Coincident with this test was the development of production methods for large- scale modules. Increasing module size presented challenges that required new methods to be developed for fabrication and assembly. After development, these methods were demonstrated by fabricating and assembling two production-scale modules.

Fisher, D.L.

1997-06-13

322

Multifractal framework based on blanket method.  

PubMed

This paper proposes two local multifractal measures motivated by blanket method for calculation of fractal dimension. They cover both fractal approaches familiar in image processing. The first two measures (proposed Methods 1 and 3) support model of image with embedded dimension three, while the other supports model of image embedded in space of dimension three (proposed Method 2). While the classical blanket method provides only one value for an image (fractal dimension) multifractal spectrum obtained by any of the proposed measures gives a whole range of dimensional values. This means that proposed multifractal blanket model generalizes classical (monofractal) blanket method and other versions of this monofractal approach implemented locally. Proposed measures are validated on Brodatz image database through texture classification. All proposed methods give similar classification results, while average computation time of Method 3 is substantially longer. PMID:24578664

Paskaš, Milorad P; Reljin, Irini S; Reljin, Branimir D

2014-01-01

323

Multifractal Framework Based on Blanket Method  

PubMed Central

This paper proposes two local multifractal measures motivated by blanket method for calculation of fractal dimension. They cover both fractal approaches familiar in image processing. The first two measures (proposed Methods 1 and 3) support model of image with embedded dimension three, while the other supports model of image embedded in space of dimension three (proposed Method 2). While the classical blanket method provides only one value for an image (fractal dimension) multifractal spectrum obtained by any of the proposed measures gives a whole range of dimensional values. This means that proposed multifractal blanket model generalizes classical (monofractal) blanket method and other versions of this monofractal approach implemented locally. Proposed measures are validated on Brodatz image database through texture classification. All proposed methods give similar classification results, while average computation time of Method 3 is substantially longer.

Paskas, Milorad P.; Reljin, Irini S.; Reljin, Branimir D.

2014-01-01

324

Liquid-vapor critical behavior in silica aerogel  

NASA Astrophysics Data System (ADS)

Fluids in porous media provide a testing ground for the effects of disorder and confinement on phase transitions and critical phenomena. Specifically, highly porous silica aerogel with its tenuous solid structure has allowed low temperature physicists to probe the effect of dilute fixed impurities on both the 4He superfluid transition and the 3He superfluid transition. Both systems have yielded exciting results and work is ongoing, especially on 3He in aerogel. This thesis explores the effect of aerogel on another transition---the liquid-vapor transition near the liquid-vapor critical point. In dense porous media, the liquid-vapor transition is usually described as capillary condensation---a process which assigns surface tension a primary role in determining the thermodynamic state of the system. However, aerogels are often so diffuse (less than 5% silica by volume---the rest is open space) that it becomes difficult to speak of pore size and meniscus shape as one would in a denser porous medium. As one approaches the liquid-vapor critical point, thermal fluctuations within the fluid grow until they exceed the scale of the aerogel strands and pores themselves. In this regime one cannot expect surface tension to control the thermodynamics of the system---it is instead in a regime where thermal fluctuations may govern its behavior. In the past there were even suggestions that the addition of aerogel might shift the character of the transition into another universality class. The following chapters present data collected on helium and neon in aerogel near their respective liquid-vapor critical points. While the behavior of the fluid at low temperatures is consistent with the pictures provided by capillary condensation, closer to the critical point they are incompatible and remain somewhat unexplained. Evidence for a shift in universality class was not found---in fact there was very little evidence for a macroscopic equilibrium transition of any type.

Herman, Tobias Kent

325

Chemically Active Aerogel-Fly Ash Composites for Mercury Clean-Up  

Microsoft Academic Search

To aid the development of IGCC technologies, the unique properties of aerogels were exploited to research purifying systems for H 2S, NOx and Hg that are durable and efficient. Aerogels can be used to capture hot gases based on their high surface areas and great tendency to form composites with various other sorbents or structural supports. Silica aerogels are at

Uschi M. Graham; Gerald Thomas

326

Morphological effects on the transport and magnetic properties of polymeric and colloidal carbon aerogels  

SciTech Connect

The temperature-dependent conductivity, magnetoresistance, magnetic susceptibility, and room-temperature Raman scattering of carbon aerogel samples with different morphologies and various grain sizes are studied. In particular, carbon aerogels with a [ital polymeric] morphology are studied and compared with [ital colloidal] carbon aerogels. The conductivity exhibits an exp[[minus] [radical][ital T][sub 0]/[ital T

Reynolds, G.A.M. (Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Fung, A.W.P. (Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Wang, Z.H. (Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Dresselhaus, M.S. (Department of Physics, and Department of Electrical Engineering Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Pekala, R.W. (Department of Chemistry and Materials Science, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1994-12-15

327

Characteristics of cometary dust tracks in Stardust aerogel and laboratory calibrations  

Microsoft Academic Search

The cometary tray of the NASA Stardust spacecraft's aerogel collector was examined to study the dust captured during the 2004 flyby of comet 81P\\/Wild 2. An optical scan of the entire collector surface revealed 256 impact features in the aerogel (width >100 mum). Twenty aerogel blocks (out of a total of 132) were removed from the collector tray for a

M. J. Burchell; S. A. J. Fairey; P. Wozniakiewicz; D. E. Brownlee; F. Hörz; A. T. Kearsley; T. H. See; P. Tsou; A. Westphal; S. F. Green; J. M. Trigo-Rodríguez; G. Domingúez

2008-01-01

328

Size control and characterization of spherical carbon aerogel particles from resorcinol–formaldehyde resin  

Microsoft Academic Search

Spherical resorcinol–formaldehyde (RF) aerogel particles were synthesized by emulsion polymerization of resorcinol with formaldehyde in a slightly basic aqueous solution, followed by supercritical drying with carbon dioxide. RF carbon aerogel particles were prepared by carbonizing of the RF aerogel particles at a high temperature under a nitrogen atmosphere. By changing the viscosity of the RF sol added to the cyclohexane

Toshihide Horikawa; Jun’ichi Hayashi; Katsuhiko Muroyama

2004-01-01

329

Aerogel as a Sample Collector and Sample Mount for Transmission XRD Analysis  

NASA Technical Reports Server (NTRS)

Silica aerogel can be used for dust collection and in situ X-ray analysis. Aerogels can be less absorbing than Be, and it is feasible to obtain X-ray transmission factors >50% using typical aerogels together with a 100-micrometer Be backing foil. Additional information is contained in the original extended abstract.

Bish, D. L.; Vaniman, D. T.; Chipera, S. J.; Yen, A. S.; Jones, S. M.

2001-01-01

330

Preparation of controlled porosity carbon aerogels for energy storage in rechargeable lithium oxygen batteries  

Microsoft Academic Search

Porous carbon aerogels are prepared by polycondensation of resorcinol and formaldehyde catalyzed by sodium carbonate followed by carbonization of the resultant aerogels in an inert atmosphere. Pore structure of carbon aerogels is adjusted by changing the molar ratio of resorcinol to catalyst during gel preparation and also pyrolysis under Ar and activation under CO2 atmosphere at different temperatures. The prepared

Mojtaba Mirzaeian; Peter J. Hall

2009-01-01

331

Liquid metal breeder-coolant blanket concept  

SciTech Connect

This paper discusses the results and conclusions of a self-cooled, liquid-metal design for a D-T fusion reactor, which is part of the Blanket Comparison and Selection Study (BCSS). The effort reported in this paper emphasizes the inboard blanket of a tokamak since the problem is most severe in this region. The work on a self-cooled TMR is also reported.

Sze, D.K.; Cha, Y.S.; Gohar, Y.; Majumdar, S.; Picologlou, P.; Smith, D.L.

1984-01-01

332

Effects of overlaps, stitches, and patches on multilayer insulation.  

NASA Technical Reports Server (NTRS)

The effects of spacecraft installation-type discontinuities on aluminized Mylar multilayer insulation have been measured using an electrically heated cylindrical calorimeter. The experimental results have been reproducible within plus or minus 10% or better for identical blankets and less than plus or minus 5% for the same blanket. Good blanket performance can be obtained using short interleaving for joints, eliminating stitched seams, and using small patches, particularly over the hot side of stitches. The heat loss through stitching is excessive but highly localized. Analytical models matched to thermocouple test results are presented. The manner in which radiation and conduction participate in heat transfer adjacent to discontinuities is indicated. High lateral heat transfer is also established as an important phenomenon in the vicinity of a discontinuity.

Stimpson, L. D.; Jaworski, W.

1972-01-01

333

Cryogenic Insulation  

NASA Technical Reports Server (NTRS)

Kevin Rivers, Thermal Structures Branch, checks electronic wiring on a test panel for a cryogenic insulation system. The thermal-mechanical testing is being done for Lockheed Martin as part of the X-33 Reusable Launch Vehicle (RLV) program. The foam panel, encased in an aluminum alloy, will be subjected to very low and very high temperatures and then be placed under heavyloads as part of the testing. Material in this panel may be used as part of an RLV fuel tank.

1996-01-01

334

High Porosity Silica Aerogels Engineered for Superfluid ^3He Research  

NASA Astrophysics Data System (ADS)

Silica aerogel is a network of strands with a diameter of 3 nm and average separation ?a 30 -- 100 nm. Low-density aerogel can be used to introduce disorder in superfluid ^3He because the superfluid coherence length is of the same order as ?a. We have developed novel sample growth and preparation techniques for producing aerogels for a variety of measurements on superfluid ^3He. In particular, it has been proposed that anisotropic aerogels can be used to understand the stability of the A-like superfluid ^3He phases [1, 2]. We can introduce anisotropy in aerogel on length scales relevant to superfluid ^3He. Anisotropy can be induced with uniaxial strain, or alternatively, during growth and drying stages. We have performed small angle x-ray scattering to probe these two types of anisotropy and find that uniaxial strain can be used to tune between them. [1] C.L. Vicente, et al., Phys. Rev. B. 72, 094519 (2005). [2] K. Aoyama and R. Ikeda, Phys. Rev. B 73, 060504(R) (2006).

Pollanen, J.; Blinstein, S.; Choi, H.; Davis, J. P.; Lippman, T. M.; Shirer, K. R.; Halperin, W. P.; Lurio, L. B.

2007-03-01

335

Reinforcement of silica aerogels using silane-end-capped polyurethanes.  

PubMed

Proper selection of silane precursors and polymer reinforcements yields more durable and stronger silica aerogels. This paper focuses on the use of silane-end-capped urethane prepolymer and chain-extended polyurethane for reinforcement of silica aerogels. The silane end groups were expected to participate in silica network formation and uniquely determine the amounts of urethanes incorporated into the aerogel network as reinforcement. The aerogels were prepared by one-step sol-gel process from mixed silane precursors tetraethoxysilane, aminopropyltriethoxysilane (APTES), and APTES-end-capped polyurethanes. The morphology and mechanical and surface properties of the resultant aerogels were investigated in addition to elucidation of chemical structures by solid-state (13)C and (29)Si nuclear magnetic resonance. Modification by 10 wt % APTES-end-capped chain-extended polyurethane yielded a 5-fold increase in compressive modulus and 60% increase in density. APTES-end-capped chain-extended polyurethane was found to be more effective in enhancement of mechanical properties and reduction of polarity. PMID:23611433

Duan, Yannan; Jana, Sadhan C; Lama, Bimala; Espe, Matthew P

2013-05-21

336

On the deceleration of cometary fragments in aerogel  

NASA Astrophysics Data System (ADS)

Determining the thermal history of the cometary grains captured by the Stardust mission presents a difficult problem. We consider two simplified models for the deceleration of hypervelocity particles captured in aerogel; both models assume a velocity squared drag force. The first model assumes that the mass of the particle remains constant during capture and the second that mass is lost due to ablation of the particle through interactions with the aerogel. It is found that the constant mass model adequately reproduces the track lengths, found from experiments by Hörz et al. in 2008, that impacted aluminium oxide spheres into aerogel at hypervelocities ~6 km s-1. Deceleration in aerogel heats volatile particles such as organic ices to high temperatures greater than 1,000 K, for durations of ~1 ?s: more than sufficient to completely ablate the particle. Refractory particles also experience significant heating greater than 2500 K, greater than the particle's melting point, over similar timescales. This suggests that the fragments recovered to Earth by the Stardust mission were considerably altered by hypersonic capture by aerogel, and so limits the amount of information that can be obtained regarding the formation of mineral and organic particles within Kuiper Belt comets.

Coulson, S. G.

2009-01-01

337

Dielectric and other properties of polyimide aerogels containing fluorinated blocks.  

PubMed

The dielectric and other properties of a series of low-density polyimide block copolymer aerogels have been characterized. Two different anhydride-capped polyimide oligomers were synthesized: one from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4'-oxidianiline (ODA) and the other from biphenyl-3,3',4,4'-tetracarboxylic dianhydride and ODA. The oligomers were combined with 1,3,5-triaminophenoxybenzene to form a block copolymer networked structure that gelled in under 1 h. The polyimide gels were supercritically dried to give aerogels with relative dielectric constants as low as 1.08. Increasing the amount of 6FDA blocks by up to 50% of the total dianhydride decreased the density of the aerogels, presumably by increasing the free volume and also by decreasing the amount of shrinkage seen upon processing, resulting in a concomitant decrease in the dielectric properties. In this study, we have also altered the density independent of fluorine substitution by changing the polymer concentration in the gelation reactions and showed that the change in dielectric due to density is the same with and without fluorine substitution. The aerogels with the lowest dielectric properties and lowest densities still had compressive moduli of 4-8 MPa (40 times higher than silica aerogels at the same density), making them suitable as low dielectric substrates for lightweight antennas for aeronautic and space applications. PMID:24483208

Meador, Mary Ann B; McMillon, Emily; Sandberg, Anna; Barrios, Elizabeth; Wilmoth, Nathan G; Mueller, Carl H; Miranda, Félix A

2014-05-14

338

Comparison of lithium and the eutectic lead lithium alloy, two candidate liquid metal breeder materials for self-cooled blankets  

SciTech Connect

Liquid metals are attractive candidates for both near-term and long-term fusion applications. The subjects of this comparison are the differences between the two candidate liquid metal breeder materials Li and LiPb for use in breeding blankets in the areas of neutronics, magnetohydrodynamics, tritium control, compatibility with structural materials, heat extraction system, safety, and required R&D program. Both candidates appear to be promising for use in self-cooled breeding blankets which have inherent simplicity with the liquid metal serving as both breeders and coolant. The remaining feasibility question for both breeder materials is the electrical insulation between liquid metal and duct walls. Different ceramic coatings are required for the two breeders, and their crucial issues, namely self-healing of insulator cracks and radiation induced electrical degradation are not yet demonstrated. Each liquid metal breeder has advantages and concerns associated with it, and further development is needed to resolve these concerns.

Malang, S. [Kernforschungszentrum Karlsruhe GmbH (Germany); Mattas, R. [Argonne National Lab., IL (United States)

1994-06-01

339

Suitability of silica aerogel as a capture medium for interplanetary dust  

NASA Technical Reports Server (NTRS)

Impact experiments using silica aerogel as a deceleration and capture medium for interplanetary dust are reported. A rough correlation is noted between increasing particle track lengths and decreasing aerogel density, and there is a poor correlation of track lengths with impact velocity at laboratory attainable velocities of 5-7 km/s. It is concluded that aerogel track lengths should not be used as velocity indicators. Chemical analyses are also reported of aerogel samples used in this study in order to assess the risks concerning contamination of interplanetary dust particles by the silica aerogel capture medium. It is demonstrated that this material is impressively clean.

Barrett, R. A.; Zolensky, M. E.; Hoerz, F.; Lindstrom, D. J.; Gibson, E. K.

1992-01-01

340

Summary report for ITER task - T68: MHD facility preparation for Li/V blanket option  

SciTech Connect

A key feasibility issue for the ITER Vanadium/Lithium breeding blanket is the question of insulator coatings. Design calculations show that an electrically insulating layer is necessary to maintain an acceptably low MHD pressure drop. To enable experimental investigations of the MHD performance of candidate insulator materials and the technology for putting them in place, the room-temperature ALEX (Argonne`s Liquid Metal EXperiment) NaK facility was upgraded to a 300{degrees}C lithium system. The objective of this upgrade was to modify the existing facility to the minimum extent necessary, consistent with providing a safe, flexible, and easy to operate MHD test facility which uses lithium at ITER-relevant temperatures, Hartmann numbers, and interaction parameters. The facility was designed to produce MHD pressure drop data, test section voltage distributions, and heat transfer data for mid-scale test sections and blanket mockups. The system design description for this lithium upgrade of the ALEX facility is given in this document.

Reed, C.B.; Haglund, R.C.; Miller, M.E. [and others

1995-08-01

341

Superfluid transition to ABM state of 3He in aerogel  

NASA Astrophysics Data System (ADS)

Stability of the ABM pairing state in aerogel is studied in order to identify the equal-spin pairing (ESP) state of superfluid 3He there close to the transition temperature Tc(P). It is shown by examining Tc(P) beyond the mean-field approximation that the quenched disorder makes the normal to ABM transition point higher compared with that of the normal to BW transition over a wider pressure range than in the bulk case. If the ESP state in 3He in aerogel is the ABM state, the present result naturally explains why the ESP state in aerogel at least upon cooling is realized even at lower pressures than the so-called PCP in the bulk case.

Aoyama, Kazushi; Ikeda, Ryusuke

2005-08-01

342

Stable low-loss optical nanofibres embedded in hydrophobic aerogel.  

PubMed

Nanofibres, optical fibres narrower than the wavelength of light, degrade in hours on exposure to air. We show that encapsulation in hydrophobic silica aerogel (refractive index 1.05) provides protection and stability (over 2 months) without sacrificing low attenuation, strong confinement and accessible evanescent field. The measured attenuation was <0.03 dB/mm, over 10 × lower than reported with other encapsulants. This enables many nanofibre applications based on their extreme small size and strong external evanescent field, such as optical sensors, nonlinear optics, nanofibre circuits and high-Q resonators. The aerogel is more than a waterproof box, it is a completely-compatible gas-permeable material in intimate contact with the nanofibre and hydrophobic on both the macroscopic and molecular scales. Its benefits are illustrated by experiments on gas sensing (exploiting the aerogel's porosity) and supercontinuum generation (exploiting its ultra-low index). PMID:21263617

Xiao, Limin; Grogan, M D W; Wadsworth, W J; England, R; Birks, T A

2011-01-17

343

Synthesis of transparent and hydrophobic TMOS based silica aerogels  

NASA Astrophysics Data System (ADS)

In this paper, the preparation of tetramethoxysilane (TMOS) based silica aerogels, by sol-gel process with varying the molar ratio of silylating agent are reported. The optimal molar ratio of precursors TMOS: MeOH: NH4OH was kept constant at 5:14.2:0.93 × 10-4, respectively, and concentration of silylating agent, hexamethyldisiloxane (HMDSO) were varied from 2% to 12% of the solvent. The retrieved aerogels have been characterized by apparent density, % porosity, Thermal conductivity, Fourier Transform Infrared Spectroscopy (FTIR), Thermo-gravimetric and Differential Scanning Calorimetry (TGA-DSC) and contact angle measurements. The effect of humidity on silica aerogels has been studied. The thermal analysis indicates thermal stability of hydrophobicity retains up to 329 °C.

Mahadik, D. B.; Rao, A. Venkateswara; Wagh, P. B.; Gupta, Satish C.

2013-06-01

344

Fourth Sound Measurement of Superfluid 3He in Aerogel  

NASA Astrophysics Data System (ADS)

The fourth sound resonance experiment has been done on liquid 3He in 98.5% porosity aerogel. Aerogel was grown inside the pores among the sintered silver powder to avoid the vibration of the aerogel strands by the sound experiment. The measurement was performed at zero magnetic field and 27 bar. We observed the phase transition between the A-like and B-like phases and also their coexistent state. The A-like to B-like phase transition occurs not at a temperature but within a temperature band. In this band, the A-like phase gradually converts to the B-like phase. Possible picture of the coexistent state is discussed.

Nago, Y.; Obara, K.; Kado, R.; Yano, H.; Ishikawa, O.; Hata, T.

2007-09-01

345

Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames  

NASA Astrophysics Data System (ADS)

We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (-g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in -g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in -g flames, which reduces the time to gel for nanoparticles by ?106 s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.

Chakrabarty, Rajan K.; Novosselov, Igor V.; Beres, Nicholas D.; Moosmüller, Hans; Sorensen, Christopher M.; Stipe, Christopher B.

2014-06-01

346

The Thermal Performance of Several Australian Fibrous Insulating Materials  

Microsoft Academic Search

The thermal conductivity of fibrous insulation materials most com monly used in Australian buildings has been measured over a range of typical densi ties and thicknesses. Correlating equations for thermal conductivity as a function of density have been derived for each material.The materials studied have included batt or blanket form (low-density fibreglass, sheep's wool, and polyester fibre) and loose-fill form

J. G. Symons; R. E. Clarke; J. V. Peirce

1995-01-01

347

Study of lithium diffusion through vanadium pentoxide aerogel  

NASA Astrophysics Data System (ADS)

Good electrode materials play an important part in rechargeable Li batteries. In this paper, safe and inexpensive vanadium pentoxide (V2O5) aerogel materials were used as cathode materials. We discussed preparation of the films and lithium ion diffusion at the interface between the cathode and electrolyte by potential-step current transient technique and digital simulations. The results showed that diffusion coefficient (DLi) of the V2O5 aerogel film was 9.18×10-14cm2/s and exchange current was 12.5×10-6A at potential step 3.6~3.5VLi/Li+.

Wang, Airong; Wu, Guangming; Yang, Hui-yu; Zhang, Ming-xia; Fang, Xingmei; Yang, Xiao-yun; Zhou, Bin; Shen, Jun

2008-03-01

348

Highly porous ceramic oxide aerogels having improved flexibility  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

349

Synthesis of highly crystalline sp2-bonded boron nitride aerogels.  

PubMed

sp(2)-Bonded boron nitride aerogels are synthesized from graphene aerogels via carbothermal reduction of boron oxide and simultaneous nitridation. The color and chemical composition of the original gel change dramatically, while structural features down to the nanometer scale are maintained, suggesting a direct conversion of the carbon lattice to boron nitride. Scanning and transmission electron microscopies reveal a foliated architecture of wrinkled sheets, a unique morphology among low-density, porous BN materials. The converted gels display a high degree of chemical purity (>95%) and crystalline order and exhibit unique cross-linking structures. PMID:24011289

Rousseas, Michael; Goldstein, Anna P; Mickelson, William; Worsley, Marcus A; Woo, Leta; Zettl, Alex

2013-10-22

350

Ultrasound propagation in dense aerogels filled with liquid 4He  

NASA Astrophysics Data System (ADS)

Longitudinal ultrasound propagation was studied in dense aerogels filled with liquid 4He. Sound velocity and attenuation were measured at the frequency of 6 MHz in both normal and superfluid phases. Pressure dependence of velocity and attenuation were also studied. Studied aerogels had porosities about 85%. They had two different types of structure, tangled strand structure and aggregated particles structure. The pore size distributions were narrow. Reduction of superfluid transition temperature mainly depended on not porosity but mean pore size. The structure of gel played an important role in sound velocity and attenuation.

Matsumoto, K.; Ohmori, K.; Abe, S.; Kanamori, K.; Nakanishi, K.

2012-12-01

351

RICH with multiple aerogel layers of different refractive index  

NASA Astrophysics Data System (ADS)

A proximity focusing ring imaging Cherenkov detector with multiple aerogel radiator layers is studied. In situations where limited space is available and a compact RICH detector is required, the use of a nonhomogeneous, multiple refractive index radiator offers a possibility for improving the resolution. Experimental investigations of the relevant parameters, i.e. single photon Cherenkov angle uncertainty and number of detected photons per ring, are presented for different aerogel radiator configurations. The results are promising and appear to satisfy the requirements for the forthcoming upgrade of the particle identification system of the Belle detector.

Korpar, S.; Adachi, I.; Fratina, S.; Fukushima, T.; Gorišek, A.; Iijima, T.; Kawai, H.; Konishi, H.; Kozakai, Y.; Križan, P.; Matsumoto, T.; Mazuka, Y.; Nishida, S.; Ogawa, S.; Ohtake, S.; Pestotnik, R.; Saitoh, S.; Seki, T.; Stanovnik, A.; Sumiyoshi, T.; Uchida, Y.; Unno, Y.; Yamamoto, S.

2005-11-01

352

Complete book of insulating  

SciTech Connect

Insulating makes significant energy conservation possible at relatively modest cost for most householders. Chapters presented are: Making Your Home into an Island; Understanding Heat Flow in Buildings; Weatherstripping and Caulking; Properties of Insulating Materials; Retrofitting Insulation; Installing Insulation in New Buildings; Coping with Other Energy Losers; and Laws, Government Programs, and Codes Affecting Insulation.

Albright, R.; Gay, L.; Stiles, J.; Worman, E.C.; Worman, N.P.; Zak, D.

1980-01-01

353

Multilayer insulation (MLI) in the Superconducting Super Collider: A practical engineering approach to physical parameters governing MLI thermal performance  

SciTech Connect

Multilayer insulation (MLI) is employed in cryogenic devices to control the heat load of those devices. The physics defining the thermal performance of an MLI system is extremely complex due to the thermal dynamics of numerous interdependent parameters which in themselves contribute differently depending on whether boundary conditions are transient or steady-state. The Multilayer Insulation system for the Superconducting Super Collider (SSC) consists of full cryostat length assemblies of aluminized polyester film, fabricated in the form of blankets, and installed as blankets to the 4.5K cold mass, and the 20K and 80K thermal radiation shields. Approximately 40,000 blankets will be required in the 10,000 cryogenic devices comprising the SSC accelerator. Each blanket will be nearly 56 feet long by 6 feet wide and will consist of as many as 32 reflective and 31 spacer layers of material. Discussed are MLI material choices, and the physical parameters which contribute to the operational performance of MLI systems. Disclosed is a method for fabricating MLI blankets by employing a large diameter winding mandrel having a circumference sufficient for the required blanket length. The blanket fabrication method assures consistency in mass produced MLI blankets by providing positive control of the dimensional parameters which contribute to the MLI blanket thermal performance. The fabrication method can be used to mass produce prefabricated MLI blankets that by virtue of the product have inherent features of dimensional stability, three-dimensional uniformity, controlled layer density, layer-to-layer registration, interlayer cleanliness, and interlayer material to accommodate thermal contraction differences. 9 refs., 4 figs., 2 tabs.

Gonczy, J.D.; Boroski, W.N.; Niemann, R.C.

1989-03-01

354

The requirements for processing tritium recovered from liquid lithium blankets: The blanket interface  

SciTech Connect

We have initiated a study to define a blanket processing mockup for Tritium Systems Test Assembly. Initial evaluation of the requirements of the blanket processing system have been started. The first step of the work is to define the condition of the gaseous tritium stream from the blanket tritium recovery system. This report summarizes this part of the work for one particular blanket concept, i.e., a self-cooled lithium blanket. The total gas throughput, the hydrogen to tritium ratio, the corrosive chemicals, and the radionuclides are defined. The key discoveries are: the throughput of the blanket gas stream (including the helium carrier gas) is about two orders of magnitude higher than the plasma exhaust stream;the protium to tritium ratio is about 1, the deuterium to tritium ratio is about 0.003;the corrosion chemicals are dominated by halides;the radionuclides are dominated by C-14, P-32, and S-35;their is high level of nitrogen contamination in the blanket stream. 77 refs., 6 figs., 13 tabs.

Clemmer, R.G.; Finn, P.A.; Greenwood, L.R.; Grimm, T.L.; Sze, D.K.; Bartlit, J.R.; Anderson, J.L.; Yoshida, H.; Naruse

1988-03-01

355

Thermally distinct ejecta blankets from Martian craters  

NASA Astrophysics Data System (ADS)

A study of Martian ejecta blankets is carried out using the high-resolution thermal IR/visible data from the Termoskan instrument aboard Phobos '88 mission. It is found that approximately 100 craters within the Termoskan data have an ejecta blanket distinct in the thermal infrared (EDITH). These features are examined by (1) a systematic examination of all Termoskan data using high-resolution image processing; (2) a study of the systematics of the data by compiling and analyzing a data base consisting of geographic, geologic, and mormphologic parameters for a significant fraction of the EDITH and nearby non-EDITH; and (3) qualitative and quantitative analyses of localized regions of interest. It is noted that thermally distinct ejecta blankets are excellent locations for future landers and remote sensing because of relatively dust-free surface exposures of material excavated from depth.

Betts, B. H.; Murray, B. C.

1993-06-01

356

Quality of Fissile Fuel Bred in a Fusion Reactor Blanket.  

National Technical Information Service (NTIS)

Neutronic calculations were made of a hybrid CTR blanket consisting of uranium and thorium fuel. The calculational model is described. Transmutation calculations for the UO sub 2 blanket were performed for a number of irradiation times ranging from 100 to...

B. R. Leonard U. P. Jenquin

1976-01-01

357

The conversion of a room temperature NaK loop to a high temperature MHD facility for Li/V blanket testing  

SciTech Connect

The Vanadium/Lithium system has been the recent focus of ANL`s Blanket Technology Pro-ram, and for the last several years, ANL`s Liquid Metal Blanket activities have been carried out in direct support of the ITER (International Thermonuclear Experimental Reactor) breeding blanket task area. A key feasibility issue for the ITER Vanadium/Lithium breeding blanket is the Near the development of insulator coatings. Design calculations, Hua and Gohar, show that an electrically insulating layer is necessary to maintain an acceptably low magneto-hydrodynamic (MHD) pressure drop in the current ITER design. Consequently, the decision was made to convert Argonne`s Liquid Metal EXperiment (ALEX) from a 200{degrees}C NaK facility to a 350{degrees}C lithium facility. The upgraded facility was designed to produce MHD pressure drop data, test section voltage distributions, and heat transfer data for mid-scale test sections and blanket mockups at Hartmann numbers (M) and interaction parameters (N) in the range of 10{sup 3} to 10{sup 5} in lithium at 350{degrees}C. Following completion of the upgrade work, a short performance test was conducted, followed by two longer multiple-hour, MHD tests, all at 230{degrees}C. The modified ALEX facility performed up to expectations in the testing. MHD pressure drop and test section voltage distributions were collected at Hartmann numbers of 1000.

Reed, C.B.; Haglund, R.C.; Miller, M.E.; Nasiatka, J.R. [Argonne National Lab., IL (United States); Kirillov, I.R.; Ogorodnikov, A.P.; Preslitski, G.V.; Goloubovitch, G.P. [Efremov (D.V.) Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation); Xu, Zeng Yu [Southwestern Inst. of Physics (China). Fusion Technology and Materials Div.

1996-12-31

358

Lightweight Insulated Footwear.  

National Technical Information Service (NTIS)

Compound formulations having good low temperature flexibility were developed for the outsole, upper and outer skin of the lightweight insulated boot. The proper insulation thickness for the entire boot was determined from foot insulation test data to prod...

R. A. Mazzeo

1971-01-01

359

Cryogenic Insulation Development.  

National Technical Information Service (NTIS)

Multilayer insulations for long term cryogenic storage are described. The devulted in an insulation concept using lightweight radiation shields, separated by low conductive Dacron fiber tufts. The insulation is usually referred to as Superfloc. The fiber ...

K. E. Leonhard

1972-01-01

360

Some new ideas for Tandem Mirror blankets  

SciTech Connect

The Tandem Mirror Reactor, with its cylindrical central cell, has led to numerous blanket designs taking advantage of the simple geometry. Also many new applications for fusion neutrons are now being considered. To the pure fusion electricity producers and hybrids producing fissile fuel, we are adding studies of synthetic fuel producers and fission-suppressed hybrids. The three blanket concepts presented are new ideas and should be considered illustrative of the breadth of Livermore's application studies. They are not meant to imply fully analyzed designs.

Neef, W.S. Jr.

1981-10-12

361

Markov Blanket Feature Selection for Support Vector Machines  

Microsoft Academic Search

Based on Information Theory, optimal feature selection should be carried out by searching Markov blankets. In this paper, we formally analyze the current Markov blanket dis- covery approach for support vector machines and propose to discover Markov blankets by performing a fast heuris- tic Bayesian network structure learning. We give a suffi- cient condition that our approach will improve the

Jianqiang Shen; Lida Li; Weng-keen Wong

2008-01-01

362

Development of fusion blanket technology for the DEMO reactor  

Microsoft Academic Search

The viability of various materials and blanket designs for use in nuclear fusion reactors can be tested using computer simulations and as parts of the test blanket modules within the International Thermonuclear Experimental Reactor (ITER) facility. The work presented here focuses on blanket model simulations using the Monte Carlo simulation package MCNPX (Computational Physics Division Los Alamos National Laboratory, 2010)

B. R. Colling; S. D. Monk

363

Fractal Studies on Titanium-Silica Aerogels using SMARTer  

SciTech Connect

Power-law scattering approximation has been employed to reveal the fractal structures of solid-state titanium-silica aerogel samples. All small-angle neutron scattering (SANS) measurements were performed using 36 meters SANS BATAN spectrometer (SMARTer) at the neutron scattering laboratory (NSL) in Serpong, Indonesia. The mass fractal dimension of titanium-silica aerogels at low scattering vector q range increases from -1.4 to -1.92 with the decrease of acid concentrations during sol-gel process. These results are attributed to the titanium-silica aerogels that are growing to more polymeric and branched structures. At high scattering vector q range the Porod slope of -3.9 significantly down to -2.24 as the roughness of particle surfaces becomes higher. The cross over between these two regimes decreases from 0.4 to 0.16 nm{sup -1} with the increase of acid concentrations indicating also that the titanium-silica aerogels are growing.

Putra, E. Giri Rachman; Ikram, A.; Bharoto; Santoso, E. [Neutron Scattering Laboratory, BATAN, Kawasan Puspiptek Serpong, Tangerang 15314 (Indonesia); Fang, T. Chiar; Ibrahim, N. [Department of Physics, Faculty of Science Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor (Malaysia); Mohamed, A. Aziz [Materials Technology Group, Industrial Technology Division Agensi Nuklear Malaysia, 43000 Kajang (Malaysia)

2008-03-17

364

Preparation and flammability of poly(vinyl alcohol) composite aerogels.  

PubMed

Poly(vinyl alcohol) (PVOH)-based aerogel composites with nanoscale silica, halloysite, montmorillonite (MMT), and laponite were prepared via a freeze-drying method. The PVOH/MMT and PVOH/laponite composites exhibit higher compressive moduli than the PVOH/SiO2 or PVOH/halloysite samples. Layered microstructures were observed for the samples except with PVOH/laponite, which showed irregular network morphologies. Thermogravimetric analysis of the aerogel samples showed increased thermal stability with the addition of nanofillers. The heat release measured by cone calorimetry, smoke release, and carbon monoxide production of the aerogel composites are all significantly decreased with the addition of nanofillers; these values are much lower than those for commercial expanded polystyrene foam. The fillers did not lead to obvious increases in the limiting oxygen index values, and the corresponding time to ignition values decrease. The ability to adjust the nanofiller levels in these foamlike aerogel composites allows for specific tuning of these products for fire safety. PMID:24731187

Chen, Hong-Bing; Wang, Yu-Zhong; Schiraldi, David A

2014-05-14

365

Capture of Particles in Hypervelocity Impacts in Aerogel  

NASA Astrophysics Data System (ADS)

The capture in aerogel of 106 lm diameter glass beads is investigated for impact speeds of 1 to 7.5 km s-1. Three different aerogel densities were used, 60, 96 and 180 kg m-3. It was found that the length of the penetration track in the aerogel increases with speed until a maximum is reached. Above the maximum speed the track length decreases. This behaviour is similar to that which has previously been observed for particles impacting polystyrene foams and porous alumina. Whilst track length was not found to be an unambiguous indicator of impact speed, the excavated track volume was found to be a suitable indictor of speed. Further, it was possible to estimate the original particle size by measurements of the track volume and entrance hole size. In addition sub-100 um diameter particles composed of various minerals were fired into aerogel and the characterisation of the particles in situ by use of a Raman spectrometer was evaluated. This was found to work well, giving vibrational spectra essentially similar to those of the bulk minerals, thus providing a mineralogical rather than an elemental signature for the captured particles.

Burchell, M. J.; Creighton, J. A.; Cole, M. J.; Mann, J.; Kearsley, A. T.

2001-02-01

366

New organic aerogels based upon a phenolic-furfural reaction  

SciTech Connect

The aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde are two proven synthetic routes for the formation of organic aerogels. Recently, we have discovered a new type of organic aerogel based upon a phenolic-furfural (PF) reaction. This sol-gel polymerization has a major advantage over past approaches since it can be conducted in alcohol (e.g., 1-propanol), thereby eliminating the need for a solvent exchange step prior to supercritical drying from carbon dioxide. The resultant aerogels are dark brown in color and can be converted to a carbonized version upon pyrolysis in an inert atmosphere. BET surface areas of 350--600 m{sup 2}/g have been measured, and transmission electron microscopy reveals an interconnected structure of irregularly-shaped particles or platelets with {approximately}10 nm dimensions. Thermal conductivities as low as 0.015 W/m-K have been recorded for PF aerogels under ambient conditions. This paper describes the chemistry-structure-property relationships of these new materials in detail.

Hrubesh, L.W.

1994-09-01

367

Quantum Fluid Dynamics of Rotating Superfluid 3He in Aerogel  

NASA Astrophysics Data System (ADS)

Superfluid 3He A-like and B-like phases in 98% aerogel have been studied under rotation up to 2 ? rad/s by using cw-NMR and Homogeneous Pressing Domain (HPD) NMR at 29 mT and 3.0 MPa. Triplet superfluid 3He has continuous symmetries whose degeneracies are lifted by small perturbations of magnetic field, boundary condition of the sample cell, counterflow and global anisotropies of aerogel. We report NMR results of the two typical samples in aerogel under rotation, which are almost identical in the phase diagram, T c and the critical velocity of the multiplication of vortex but are very different in textures and responses to the flow with each other. One samples (S-D) is slightly compressed by squeezing and thermal stress and thus has global anisotropic deformation along the sample axis. The other cell (S-H) has randomly(not uniaxially)-oriented global anisotropy. In the S-D, we observed a large negative shift in cw-NMR and spin wave and HPD in the B-like phase. Comparing textures determined by NMR and its response to the counterflows between two samples, we discuss how the long-range order of the continuous symmetry and textures are controlled by orientation effects due to global anisotropy in aerogel.

Kunimatsu, Takayuki; Matsubara, Akira; Izumina, Ken; Sato, Toshihiro; Kubota, Minoru; Takagi, Takeo; Bunkov, Yuriy M.; Mizusaki, Takao

2008-02-01

368

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

National Technical Information Service (NTIS)

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...

N. Leventis

2005-01-01

369

Electrosorption of Ions from Aqueous Solutions by Nanostructured Carbon Aerogel  

Microsoft Academic Search

Electrosorption is generally defined as potential-induced adsorption on the surface of charged electrodes. After polarization of the electrodes, ions are removed from the electrolyte solution by the imposed electric field and adsorbed onto the surface of the electrodes. Experimental and modeling studies were conducted using two types of carbon aerogel composites of different surface areas to provide a better understanding

Tung-Yu Ying; Kun-Lin Yang; Sotira Yiacoumi; Costas Tsouris

2002-01-01

370

Hydrophobic waterglass based aerogels without solvent exchange or supercritical drying  

Microsoft Academic Search

The usual production of silica aerogels include supercritical drying and expensive raw materials like tetraethoxysilane which prohibit a commercialization. To avoid the costs of supercritical drying one can modify the internal surface with a silation agent. Hydrophobization of the lyogel makes it possible to dry at ambient pressure. The next step is to use waterglass as a cheaper silica source.

F. Schwertfeger; D. Frank; M. Schmidt

1998-01-01

371

Enhanced thermal characterization of silica aerogels through molecular dynamics simulation  

NASA Astrophysics Data System (ADS)

Porous structures of silica aerogels are generated using classical molecular dynamics, with the Tersoff potential, which has been re-parametrized for modeling silicon dioxides. This work demonstrates that this potential is superior to the widely used BKS potential in terms of characterizing the thermal conductivities of amorphous silica, by comparing the vibrational density of states with previous experimental studies. Aerogel samples of increasing densities are obtained through an expanding, heating and quenching process. Reverse non-equilibrium molecular dynamics is applied at each density to determine the thermal conductivity. A power-law fit of the results is found to accurately reflect the power-law variation found in experimental bulk aerogels. The results are also of the same order of magnitude as experimental bulk aerogels, but they are consistently higher. By analyzing the pore size distribution on different simulation length scales, we show that such a disparity is due to finite sizes of pores that can be represented, where increasing simulation length scales lead to an increase in the largest pore size that can be modeled.

Yeo, J. J.; Liu, Z. S.; Ng, T. Y.

2013-10-01

372

Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles  

Microsoft Academic Search

Improved electrically powered artificial muscles are needed for generating force, moving objects, and accomplishing work. Carbon nanotube aerogel sheets are the sole component of new artificial muscles that provide giant elongations and elongation rates of 220% and (3.7 × 104)% per second, respectively, at operating temperatures from 80 to 1900 kelvin. These solid-state-fabricated sheets are enthalpic rubbers having gaslike density

Ali E. Aliev; Jiyoung Oh; Mikhail E. Kozlov; Alexander A. Kuznetsov; Shaoli Fang; Alexandre F. Fonseca; Raquel Ovalle; Márcio D. Lima; Mohammad H. Haque; Yuri N. Gartstein; Mei Zhang; Anvar A. Zakhidov; Ray H. Baughman

2009-01-01

373

Porous silicon nanocrystals in a silica aerogel matrix  

PubMed Central

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.

2012-01-01

374

Porous silicon nanocrystals in a silica aerogel matrix  

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

375

Reinforcement of bacterial cellulose aerogels with biocompatible polymers.  

PubMed

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. PMID:25037381

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

2014-10-13

376

Nuclear magnetic resonance studies of resorcinol-formaldehyde aerogels.  

PubMed

In this article, we report a detailed study of resorcinol-formaldehyde (RF) aerogels prepared under different processing conditions, [resorcinol]/[catalyst] (R/C) ratios in the starting sol-gel solutions, using continuous flow hyperpolarized (129)Xe NMR in combination with solid-state (13)C and two-dimensional wide-line separation (2D-WISE) NMR techniques. The degree of polymerization and the mobility of the cross-linking functional groups in RF aerogels are examined and correlated with the R/C ratios. The origin of different adsorption regions is evaluated using both coadsorption of chloroform and 2D EXSY (129)Xe NMR. A hierarchical set of Xe exchange processes in RF aerogels is found using 2D EXSY (129)Xe NMR. The exchange of Xe gas follows the sequence (from fastest to slowest): mesopores with free gas, gas in meso- and micropores, free gas with micropores, and, finally, among micropore sites. The volume-to-surface-area (V(g)/S) ratios for aerogels are measured for the first time without the use of geometric models. The V(g)/S parameter, which is related both to the geometry and the interconnectivity of the pore space, has been found to correlate strongly with the R/C ratio and exhibits an unusually large span: an increase in the R/C ratio from 50 to 500 results in about a 5-fold rise in V(g)/S. PMID:16852369

Moudrakovski, Igor L; Ratcliffe, Christopher I; Ripmeester, John A; Wang, Li-Qiong; Exarhos, Gregory J; Baumann, Theodore F; Satcher, Joe H

2005-06-01

377

AGING AND IODINE LOADING OF SILVER-FUNCTIONALIZED AEROGELS  

SciTech Connect

Engineered silver-functionalized silica aerogels are being investigated for their application in off-gas treatment at a used nuclear fuel reprocessing facility. Reprocessing will release several key volatile radionuclides, including iodine-129. To achieve regulatory compliance, iodine-129 must be removed from any off-gas stream prior to environmental discharge. Silver-functionalized aerogels have been demonstrated to have high iodine capture capacity, high porosity and potential for conversion into a waste form. Capture materials used in off-gas treatment may be exposed to a heated, high humidity, acidic gas stream for months. Extended exposure to this stream could affect sorbent performance. It was the aim of this study to evaluate what impacts might be observed when Ag0-functionalized aerogels prepared at Pacific Northwest National Laboratory were contacted with a dry air stream for up to 6 months and then used to adsorb iodine from a synthetic off-gas stream. Results demonstrate that there is some loss of iodine capture capacity caused by aging, but that this loss is not as marked as for aging of more traditional iodine sorbents, such as silver-impregnated mordenite. Specifically, aging silver-functionalized aerogel under a dry air stream for up to 6 months can decrease its iodine capacity from 41wt% to 32wt%.

Bruffey, Stephanie H [ORNL; Jubin, Robert Thomas [ORNL; Anderson, Kaara K [ORNL; Walker Jr, Joseph Franklin [ORNL

2013-01-01

378

Extreme synthesis and chemical doping of diamond aerogel  

NASA Astrophysics Data System (ADS)

Amorphous carbon aerogels have attracted much interest in recent years due to their low density, large intrinsic surface areas (>1000 m^2/g), large pore volume, low dielectric constant, and high strength. We use high-pressure (˜20 GPa) laser-heating (>600 C) within a diamond anvil cell (DAC) to convert the amorphous network of a low-density (40mg/cc) carbon aerogel into an ultrananocrystalline diamond aerogel. Photoluminescence spectroscopy and confocal time-correlated single-photon counting indicate the recovered material contains both negatively-charged and neutral nitrogen-vacancy (NV) complexes. Synchrotron scanning transmission x-ray microscopy (STXM) is used to compare the carbon electronic density-of-states of the amorphous starting material with the recovered diamond aerogel with ˜100 meV energy resolution. Finally, we use nanoscale secondary ion mass spectrometry to investigate doping of the resorcinol-formaldehyde starting material with the aim of chemically tuning heteroatomic point defects within this diamond material system.

Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Wang, Yinmin; Kilcoyne, A. L. D.; Weber, Peter K.; Willey, Trevor M.; Visbeck, Kenneth S.; Evans, William J.; Satcher, Joe H., Jr.

2010-03-01

379

Nuclear Magnetic Resonance Studies of Resorcinol-Formaldehyde Aerogels  

SciTech Connect

In this article we report a detailed study of resorcinol-formaldehyde (RF) aerogels prepared under different processing conditions, [resorcinol]/[catalyst] (R/C) ratios in the starting sol-gel solutions, using continuous flow hyperpolarized 129Xe NMR in combination with solid-state 13C and two-dimensional wide-line separation (2D-WISE) NMR techniques. The degree of polymerization and the mobility of the cross-linking functional groups in RF aerogels are examined and correlated with the R/C ratios. The origin of different adsorption regions is evaluated using both co-adsorption of chloroform and 2D EXSY 129Xe NMR. A hierarchical set of Xe exchange processes in RF aerogels is found using 2D EXSY 129Xe NMR. The exchange of Xe gas follows the sequence (from fastest to slowest): mesopores with free gas, gas in meso- and micro-pores, free gas with micropores, and, finally, among micropore sites. The volume-to-surface-area (Vg/S) ratios for aerogels are measured for the first time without the use of geometric models. The Vg/S parameter, which is related both to the geometry and the interconnectivity of the pore space, has been found to correlate strongly with the R/C ratio and exhibits an unusually large span: an increase in the R/C ratio from 50 to 500 results in about a 5-fold rise in Vg/S.

Moudrakovski, Igor L.; Ratcliffe, C I.; Ripmeester, J A.; Wang, Li Q.; Exarhos, Gregory J.; Baumann, T; Satcher, J H.

2005-06-09

380

Nitridation under ammonia of high surface area vanadium aerogels  

SciTech Connect

Vanadium pentoxide gels have been obtained from decavanadic acid prepared by ion exchange on a resin from ammonium metavanadate solution. The progressive removal of water by solvent exchange in supercritical conditions led to the formation of high surface area V{sub 2}O{sub 5}, 1.6H{sub 2}O aerogels. Heat treatment under ammonia has been performed on these aerogels in the 450-900 deg. C temperature range. The oxide precursors and oxynitrides have been characterized by XRD, SEM, TGA, BET. Nitridation leads to divided oxynitride powders in which the fibrous structure of the aerogel is maintained. The use of both very low heating rates and high surface area aerogel precursors allows a higher rate and a lower threshold of nitridation than those reported in previous works. By adjusting the nitridation temperature, it has been possible to prepare oxynitrides with various nitrogen enrichment and vanadium valency states. Whatever the V(O,N) composition, the oxidation of the oxynitrides in air starts between 250 and 300 deg. C. This determines their potential use as chemical gas sensors at a maximum working temperature of 250 deg. C.

Merdrignac-Conanec, Odile [Laboratoire Verres et Ceramiques, UMR CNRS 6512, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France)]. E-mail: odile.merdrignac@univ-rennes1.fr; El Badraoui, Khadija [Laboratoire Verres et Ceramiques, UMR CNRS 6512, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France); L'Haridon, Paul [Laboratoire Verres et Ceramiques, UMR CNRS 6512, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France)

2005-01-15

381

Insulation Testing Using Cryostat Apparatus with Sleeve  

NASA Technical Reports Server (NTRS)

The method and equipment of testing continuously rolled insulation materials is presented in this paper. Testing of blanket and molded products is also facilitated. Materials are installed around a cylindrical copper sleeve using a wrapping machine. The sleeve is slid onto the vertical cold mass of the cryostat. The gap between the cold mass and the sleeve measures less than 1 mm. The cryostat apparatus is a liquid nitrogen boiloff calorimeter system that enables direct measurement of the apparent thermal conductivity (k-value) of the insulation system at any vacuum level between 5 x 10(exp -5) and 760 torr. Sensors are placed between layers of the insulation to provide complete temperature-thickness profiles. The temperatures of the cold mass (maintained at 77.8 kelvin (K)), the sleeve (cold boundary temperature (CBT)), the insulation outer surface (warm boundary temperature (WBT)), and the vacuum can (maintained at 313 K by a thermal shroud) are measured. Plots of CBT, WBT, and layer temperature profiles as functions of vacuum level show the transitions between the three dominant heat transfer modes. For this cryostat apparatus, the measureable heat gain is from 0.2 to 20 watts. The steady-state measurement of k-value is made when all temperatures and the boiloff rate are stable.

Fesmire, J. E.; Augustynowicz, S. D.

1999-01-01

382

Effects of continents on Earth cooling: Thermal blanketing and depletion in radioactive elements  

NASA Astrophysics Data System (ADS)

Estimate of mantle heat flow under continental shields are very low, indicating a strong insulating effect of continents on mantle heat loss. This effect is investigated with a simple approach: continents are introduced in an Earth cooling model as perfect thermal insulators. Continental growth rate has then a strong influence on mantle cooling. Various continental growth models are tested and are used to compute the mantle depletion in radioactive elements as a function of continental crust extraction. Results show that the thermal blanketing effect of continents strongly affects mantle cooling, and that mantle depletion must be taken into account in order not to overestimate mantle heat loss. In order to obtain correct oceanic heat flow for present time, continental growth must begin at least 3 Gy ago and steady-state for continental area must be reached for at least 1.5 Gy in our cooling model.

Grigné, Cécile; Labrosse, Stéphane

383

27 CFR 40.67 - Blanket bond.  

Code of Federal Regulations, 2013 CFR

...tobacco products operates more than one factory he may, in lieu of filing separate...of § 40.134, for any or all of the factories. The total amount of any blanket bond...satisfaction of any liability incurred at any factory covered by the bond. (72 Stat....

2013-04-01

384

The European breeding blanket design for ITER  

Microsoft Academic Search

In the frame of the ITER Engineering Design Activity (EDA), the European Home Team (EU HT), in collaboration with the Joint Central Team (JCT) and the three other HTs, has contributed to the development of a joint water-cooled solid breeder blanket design concept for the ITER Enhanced Performance Phase. In early 1997 the EU HT gradually arrived at a different

M. Ferrari; W. Danner; A. Bianchij; G. Celentano; D. Cepraga; A. Cheyne; M. Dalle Donne; L. De Stefanis; M. Eid; J.-M. Gay; W. Gulden; H. Jahn; F. Lucca; X. Masson; G. Mazzone; J. Mustoe; L. Petrizzi; T. Pinna; M. Pirozzi; A. Pizuto; Y. Poitevin; M. Roccella; F. Scaffidi-Argentina; D. Sherwood; F. Zacchia

1997-01-01

385

Characterization of aerogel and Photomultiplier Tubes for the 12-GeV Hall C Kaon Aerogel Detector at Jefferson Lab  

NASA Astrophysics Data System (ADS)

Thomas Jefferson National Accelerator Facility's upgrade from 6-GeV to 12-GeV beam energy requires a new magnetic spectrometer for Hall C. At 6 GeV the High Momentum Spectrometer (HMS) made use of an aerogel threshold Cherenkov detector for particle identification of p/K/p. The HMS is not designed to operate at momenta greater than 7 GeV/c, instead a Super High Momentum Spectrometer (SHMS) will be constructed. An aerogel threshold Cherenkov detector needs to be included in the new spectrometer as well. Pions, kaons and protons of sufficient velocity produce Cherenkov radiation when passing through media with low indices of refraction. Aerogels with n = 1.020 and n = 1.030 will be used for p/K/p separation. A diffusion box, lined with millipore, will collect the light from the Cherenkov radiation. Photomultiplier tubes (PMTs) will then detect the light and convert the photons into an electrical signal that electronics will then be able to interpret. This presentation will show the dependence of the aerogel's signal strength on thickness of stack as well as the PMTs' gain dependence on high voltage.

Wood, Kevin

2011-10-01

386

Parametric Weight Comparison of Advanced Metallic, Ceramic Tile, and Ceramic Blanket Thermal Protection Systems  

NASA Technical Reports Server (NTRS)

A parametric weight assessment of advanced metallic panel, ceramic blanket, and ceramic tile thermal protection systems (TPS) was conducted using an implicit, one-dimensional (I-D) finite element sizing code. This sizing code contained models to account for coatings fasteners, adhesives, and strain isolation pads. Atmospheric entry heating profiles for two vehicles, the Access to Space (ATS) vehicle and a proposed Reusable Launch Vehicle (RLV), were used to ensure that the trends were not unique to a certain trajectory. Ten TPS concepts were compared for a range of applied heat loads and substructural heat capacities to identify general trends. This study found the blanket TPS concepts have the lightest weights over the majority of their applicable ranges, and current technology ceramic tiles and metallic TPS concepts have similar weights. A proposed, state-of-the-art metallic system which uses a higher temperature alloy and efficient multilayer insulation was predicted to be significantly lighter than the ceramic tile stems and approaches blanket TPS weights for higher integrated heat loads.

Myers, David E.; Martin, Carl J.; Blosser, Max L.

2000-01-01

387

Preparation of hydrophobic granular silica aerogels and adsorption of phenol from water  

NASA Astrophysics Data System (ADS)

Granular silica aerogels with different degrees of hydrophobicity were prepared via sol-gel synthesis followed by drying at ambient pressure. The effects of preparation conditions, including pH and modification time, on aerogel characterization were investigated. The aerogels were characterized using nitrogen adsorption at 77 K. We found that the aerogel was a nano-structured material with high specific surface area and high porosity. The aerogels were used for phenol adsorption from water. The effects of hydrophobicity degree, phenol concentration, and contact time were studied. Batch kinetic and isotherm studies were carried out to evaluate the effects of contact time and phenol concentration. The Freundlich model and the pseudo-second-order fitted the experimental data. The results also indicated that the phenol adsorption process involved both boundary layer diffusion and intraparticle diffusion. When the equilibrium concentration of phenol was 290 mg L-1, the adsorption of phenol on the aerogel was 142 mg g-1.

Qin, Guotong; Yao, Yuan; Wei, Wei; Zhang, Tao

2013-09-01

388

Magnetization and spin diffusion of liquid {sup 3}He in aerogel  

SciTech Connect

We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of {sup 3}He in aerogel, including both elastic and inelastic scattering of {sup 3}He quasiparticles, and compare these results with data for {sup 3}He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the 'dirty' B phase of {sup 3}He in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density.

Sauls, J. A. [Centre de Recherches sur les Tres Basses Temperatures, Centre National de la Recherche Scientifique, Laboratoire Associe a l'Universite J. Fourier, Boite Postale 166, 38042 Grenoble Cedex 9 (France); Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States); Bunkov, Yu.M.; Collin, E.; Godfrin, H. [Centre de Recherches sur les Tres Basses Temperatures, Centre National de la Recherche Scientifique, Laboratoire Associe a l'Universite J. Fourier, Boite Postale 166, 38042 Grenoble Cedex 9 (France); Sharma, P. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

2005-07-01

389

Sound Insulation in Buildings  

NASA Astrophysics Data System (ADS)

Sound insulation between the different rooms inside a building or to the outside is a very complex problem. First, the airborne sound insulation of ceilings, walls, doors and windows is important. Second, a sufficient structure-borne sound insulation, also called impact sound insulation, for the ceilings, has to be provided especially. Finally, the service equipment should be sufficiently quiet.

Gösele, K.; Schröder, E.

390

Multiple density layered insulator  

DOEpatents

A multiple density layered insulator for use with a laser is disclosed which provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation. 4 figs.

Alger, T.W.

1994-09-06

391

Multiple density layered insulator  

DOEpatents

A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.

Alger, Terry W. (Tracy, CA)

1994-01-01

392

Properties of cryogenic insulants  

Microsoft Academic Search

High vacuum, cold gases and liquids, and solids are the principal insulating materials for superconducting apparatus. All these insulants have been claimed to show fairly good intrinsic dielectric performance under laboratory conditions where small scale experiments in the short term range are typical. However, the insulants must be integrated into large scaled insulating systems which must withstand any particular stressing

J. Gerhold

1998-01-01

393

Insulation Materials Investigation  

NSDL National Science Digital Library

Students test the insulation properties of different materials by timing how long it takes ice cubes to melt in the presence of various insulating materials. Students learn about the role that thermal insulation materials can play in reducing heat transfer by conduction, convection and radiation, as well as the design and implementation of insulating materials in construction and engineering.

University Of Houston

394

The compressive behavior of isocyanate-crosslinked silica aerogel at high strain rates  

Microsoft Academic Search

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

H. Luo; H. Lu; N. Leventis

2006-01-01

395

High-porosity aerogels of high specific surface area prepared from nanofibrillated cellulose (NFC)  

Microsoft Academic Search

Low-density aerogels based on nanofibrillated cellulose (NFC) from wood pulp were prepared from NFC aqueous dispersions using solvent exchange from water to tert-butanol followed by tert-butanol freeze-drying. In the present study, the dispersion of NFC nanofibers in the hydrocolloid was very well preserved in the aerogels. The “effective” diameter of the NFC nanofibers in the aerogels is around 10–18nm corresponding

Houssine Sehaqui; Qi Zhou; Lars A. Berglund

2011-01-01

396

Structure of carbon aerogels near the gelation limit of the resorcinol–formaldehyde precursor  

Microsoft Academic Search

Resorcinol–formaldehyde (RF) gels with a very high molar ratio of resorcinol\\/catalyst (R\\/C), e.g., 1500 and a low relative molar mass content of resorcinol+formaldehyde (RF-ratio) of about 30% can be ambient pressure dried with minimal shrinkage. The resulting RF-aerogels exhibit average cluster and pore sizes >50 nm. Upon pyrolysis the RF-aerogels are transformed into carbon aerogels exhibiting the same morphology of

R. Petricevic; G Reichenauer; V Bock; A Emmerling; J Fricke

1998-01-01

397

Interference coating by hydrophobic aerogel-like SiO 2 thin films  

Microsoft Academic Search

The present paper presents a novel method of preparation of hydrophobic aerogel-like SiO2 thin films by means of a two-step acid\\/base derived silica sol at an ambient pressure without any supercritical drying. Crack free aerogel-like SiO2 thin films having thickness of 100–400nm, and refractive indices of 1.13–1.25 have been obtained upon heating at different temperatures. By using the silica aerogel-like

Qinyuan Zhang; J. Wang; G. Wu; J. Shen; S. Buddhudu

2001-01-01

398

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

Microsoft Academic Search

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 (SN2), whereas the volume of meso-(V2)

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

2006-01-01

399

Characterization and electrochemical performance of graphene-containing carbon aerogel for supercapacitor.  

PubMed

Graphene-containing carbon aerogel was prepared by a polycondensation of resorcinol with formaldehyde using chemically exfoliated graphene oxide in ambient conditions, and its electrochemical performance as an electrode for supercapacitor was examined. The effect of pH in the preparation of RFGO (resorcinol-formaldehyde and graphene oxide) solution on the physical and electrochemical properties of graphene-containing carbon aerogel was investigated. For comparison, graphene-free carbon aerogel was also prepared. Among the samples, graphene-containing carbon aerogel prepared at pH 6.5 showed the highest BET surface area (733 m2/g) and the largest pore volume (1.39 cm3/g) with well-developed porous structure. Electrochemical properties of graphene-containing carbon aerogel and graphene-free carbon aerogel electrodes were measured by cyclic voltammetry at a scan rate of 10 mV/sec and by charge/discharge test at constant current of 1 A/g in 6 M KOH electrolyte. From cyclic voltammetry measurements, it was found that graphene-containing carbon aerogel prepared at pH 6.5 showed higher specific capacitance than graphene-free carbon aerogel (63 F/g vs. 54 F/g). Specific capacitance calculated by charge/discharge test also revealed that graphene-containing carbon aerogel prepared at pH 6.5 showed higher specific capacitance than graphene-free carbon aerogel (85 F/g vs. 79 F/g). Thus, electrochemical performance of graphene-containing carbon aerogel prepared at pH 6.5 could be enhanced by adding graphene into carbon aerogel. PMID:24266169

Lee, Yoon Jae; Park, Hai Woong; Hong, Ung Gi; Song, In Kyu

2013-12-01

400

Effect of reduction temperature on the preparation of zero-valent iron aerogels for trichloroethylene dechlorination  

Microsoft Academic Search

Zero-valent iron (ZVI) aerogels have been synthesized by sol-gel method and supercritical CO2 drying, followed by H2 reduction in the temperature range of 350–500 °C. When applied to trichloroethylene (TCE) dechlorination, the ZVI aerogel\\u000a reduced at 370 °C showed the highest performance in the conditions employed in this study. Thus, the effect of reduction temperature\\u000a in preparing ZVI aerogels has

Jihye Ryu; Dong Jin Suh; Young-Kwon Park; Young-Woong Suh

2008-01-01

401

Aerogel VO x \\/MgO catalysts for oxidative dehydrogenation of propane  

Microsoft Academic Search

VOx\\/MgO aerogel catalysts were synthesized using three different preparation methods: by mixing the aerogel MgO support with dry ammonium vanadate, by vanadium deposition from a precursor solution in toluene, and by hydrolysis of a mixture of vanadium and magnesium alkoxides followed by co-gelation and supercritical drying. The latter aerogel technique allowed us to synthesize mixed vanadium–magnesium hydroxides with the surface

Ilya V. Mishakov; Aleksey A. Vedyagin; Alexander F. Bedilo; Vladimir I. Zaikovskii; Kenneth J. Klabunde

2009-01-01

402

Composite flexible insulation for thermal protection of space vehicles  

NASA Technical Reports Server (NTRS)

A composite flexible blanket insulation (CFBI) system considered for use as a thermal protection system for space vehicles is described. This flexible composite insulation system consists of an outer layer of silicon carbide fabric, followed by alumina mat insulation, and alternating layers of aluminized polyimide film and aluminoborosilicate scrim fabric. A potential application of this composite insulation would be as a thermal protection system for the aerobrake of the Aeroassist Space Transfer Vehicle (ASTV). It would also apply to other space vehicles subject to high convective and radiative heating during atmospheric entry. The thermal performance of this composite insulation as exposed to a simulated atmospheric entry environment in a plasma arc test facility is described. Other thermophysical properties which affect the thermal response of this system are also described. Analytical modeling describing the thermal performance of this composite insulation is included. It shows that this composite insulation is effective as a thermal protection system at total heating rates up to 30.6 W/sq cm.

Kourtides, Demetrius A.; Tran, Huy K.; Chiu, S. Amanda

1992-01-01

403

Thermal performance of various multilayer insulation systems below 80K  

SciTech Connect

The SSC collider dipole cryostat consists of a vacuum shell operating at room temperature, two thermal shields operating near 80K and 20K respectively, and the superconducting magnet assembly operating near 4K. The cryostat design incorporates multilayer insulation (MLI) blankets to limit radiant heat transfer into the 80K and 20K thermal shields. Also, an MLI blanket is used to impede heat transfer through residual gas conduction into the 4K superconducting magnet assembly. A measurement facility at Fermilab has been used to experimentally optimize the thermal insulation system for the dipole cryostat. Previous thermal measurements have been used to define the 80K MLI system configuration and verify system performance. With the 80K MLI system defined, the current effort has focused on experimentally defining the optimum insulation scheme for the 20K thermal shield. The SSC design specification requires that radiant heat transfer be limited to 0.093 W/m{sup 2} at an insulating vacuum of 10{sup {minus}6}torr.

Boroski, W.N.; Nicol, T.H.; Schoo, C.J.

1992-04-01

404

Thermal performance of various multilayer insulation systems below 80K  

SciTech Connect

The SSC collider dipole cryostat consists of a vacuum shell operating at room temperature, two thermal shields operating near 80K and 20K respectively, and the superconducting magnet assembly operating near 4K. The cryostat design incorporates multilayer insulation (MLI) blankets to limit radiant heat transfer into the 80K and 20K thermal shields. Also, an MLI blanket is used to impede heat transfer through residual gas conduction into the 4K superconducting magnet assembly. A measurement facility at Fermilab has been used to experimentally optimize the thermal insulation system for the dipole cryostat. Previous thermal measurements have been used to define the 80K MLI system configuration and verify system performance. With the 80K MLI system defined, the current effort has focused on experimentally defining the optimum insulation scheme for the 20K thermal shield. The SSC design specification requires that radiant heat transfer be limited to 0.093 W/m[sup 2] at an insulating vacuum of 10[sup [minus]6]torr.

Boroski, W.N.; Nicol, T.H.; Schoo, C.J.

1992-04-01

405

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)  

NASA Astrophysics Data System (ADS)

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

Hernández, Rebeca; Nogales, Aurora; Sprung, Michael; Mijangos, Carmen; Ezquerra, Tiberio A.

2014-01-01

406

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS).  

PubMed

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles. PMID:24437913

Hernández, Rebeca; Nogales, Aurora; Sprung, Michael; Mijangos, Carmen; Ezquerra, Tiberio A

2014-01-14

407

Leftover Superfluid 4He in Aerogel and Its Crystallization by Cooling  

NASA Astrophysics Data System (ADS)

Using a variable volume cell, we were able to crystallize 4He in aerogels at a constant temperature. The entire crystallization process was monitored visually owing to the transparency of the aerogel. Two different crystallization processes of 4He in aerogels were observed: creep at high temperatures and avalanche at low temperatures. In a 96 % porosity aerogel, we noticed that 4He remained liquid in some parts of the cell even though other parts of the aerogel were completely crystallized. Once such a situation was formed, the application of additional pressure did not further crystallize the liquid. This is presumably because a supply path of 4He atoms from the bulk crystal was blocked by the crystals in the aerogel. This leftover liquid, however, was found to begin to crystallize via avalanches when cooled below a particular temperature. If the crystallization pressure in aerogel is temperature independent at low temperatures as the bulk crystallization pressure, the crystallization by cooling is rather unusual. Possible explanations would be a decrease of the crystallization pressure in aerogel in the low temperature region, or the supersolidity of crystals in aerogel playing some role in mass transport.

Matsuda, Hirofumi; Ochi, Aguri; Isozaki, Rei; Nomura, Ryuji; Okuda, Yuichi

2013-05-01

408

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

409

Enhanced thermal transport in carbon aerogel nanocomposites containing double-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report thermal conductivity measurements of a carbon aerogel nanocomposite containing double-walled carbon nanotubes. The nanocomposites were prepared by the sol-gel polymerization of resorcinol with formaldehyde in aqueous suspension containing a surfactant-stabilized dispersion of double-walled carbon nanotubes. Subsequent drying and pyrolysis resulted in free-standing monolithic carbon aerogel nanocomposites with uniform dispersions of carbon nanotubes. The monoliths were characterized by high-resolution scanning electron microscopy and thermal conductivity measurements via the transient hot-wire method. Enhanced thermal conductivities were observed for carbon aerogel nanocomposites relative to pristine carbon aerogels. The details of these results are discussed in comparison with theory and literature.

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

2009-04-01

410

Strong-coupling effects in superfluid He3 in aerogel  

NASA Astrophysics Data System (ADS)

Effects of impurity scatterings on the strong-coupling (SC) contribution, stabilizing the ABM (axial) pairing state, to the quartic term of the Ginzburg-Landau free energy of superfluid He3 are theoretically studied to examine recent observations suggestive of an anomalously small SC effect in superfluid He3 in aerogels. To study the SC corrections, two approaches are used. One is based on a perturbation in the short-range repulsive interaction, and the other is a phenomenological approach used previously for the bulk liquid by Sauls and Serene [Phys. Rev. B 24, 183 (1981)]. It is found that the impurity scattering favors the BW pairing state and shrinks the region of the ABM pairing state in the T-P phase diagram. In the phenomenological approach, the resulting shrinkage of the ABM region is especially substantial and, if assuming an anisotropy over a large scale in aerogel, leads to justifying the phase diagrams determined experimentally.

Aoyama, Kazushi; Ikeda, Ryusuke

2007-09-01

411

Penetration of various projectiles into low-density aerogels  

NASA Astrophysics Data System (ADS)

A large number of cometary dust particles were captured with low-density silica aerogels in NASA Stardust Mission. The dust particles penetrate into the aerogels and form various track shapes. In order to derive quantitative properties of the dust particles from the morphology of the tracks, we should understand the penetration mechanism and construct track formation models, which connect the impact conditions and the track shapes. It is essential to experimentally observe the track formation process to construct the models. A large number of experiments of penetration into low-density media have been carried out, but there are a few studies on the in-situ observation of penetration process. In this study, we report the results of the observation of the penetration process using a high-speed camera for various types of projectiles. Various projectiles made different track shapes. We analyze the track growth of both projectile penetration depth and diameter.

Kadono, T.; Niimi, R.; Okudaira, K.; Hasegawa, S.; Tabata, M.; Tsuchiyama, A.

2011-12-01

412

An Aerogel ?erenkov Detector with High Rate Capability  

NASA Astrophysics Data System (ADS)

The excitation spectra of medium mass hypernuclei will be studied by the (e,e'K^+) reaction at a new spectrometer system to be deployed at Jefferson Lab by the E01-011 collaboration. The high background rates expected require an efficient trigger level particle identification. An aerogel ?erenkov detector will be employed for pion suppression. This detector is being developed and built at Florida International University. It will consist of three layers of segmented aerogel ?erenkov detectors. A prototype consisting of one segment only has been built and recently was tested in a mixed hadron beam at KEK. On average, roughly 20 photoelectrons have been observed for pions with 1.2 GeV/c momentum. After presenting the design and the results from the prototype, we will discuss the expected performance characteristics of the full system under the predicted experimental conditions.

Carl, Michael; Reinhold, Joerg

2002-10-01

413

Bulbous tracks arising from hypervelocity capture in aerogel  

NASA Astrophysics Data System (ADS)

The capture of 81P/Wild 2 cometary particles in aerogel with a well-defined impact velocity (6.1 km s-1) has provided a wealth of data concerning the composition of Jupiter-family comets. To interpret this data we must understand the capture processes in the aerogel. A major category of tracks are those with bulbous cavities lined with particle fragments. We present a new model to account for the production of these “turnip”-shaped impact cavities. The model uses a thermodynamic approach in order to account for the likely expansion of vapors from particles rich in volatile species. Volume measurements of some of the largest Stardust tracks analysed so far, together with theoretical considerations, indicate that for the majority of Stardust cometary aggregate particle impacts, fragmentation of relatively weak impactors (combined with radial expansion of the resulting subgrains) is the leading cause of bulbous track production, while volatile release of vapors played a secondary role.

Trigo-Rodríguez, J. M.; Domínguez, G.; Burchell, M. J.; Hörz, F.; Llorca, J.

2008-02-01

414

Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles  

NASA Astrophysics Data System (ADS)

Improved electrically powered artificial muscles are needed for generating force, moving objects, and accomplishing work. Carbon nanotube aerogel sheets are the sole component of new artificial muscles that provide giant elongations and elongation rates of 220% and (3.7 × 104)% per second, respectively, at operating temperatures from 80 to 1900 kelvin. These solid-state-fabricated sheets are enthalpic rubbers having gaslike density and specific strength in one direction higher than those of steel plate. Actuation decreases nanotube aerogel density and can be permanently frozen for such device applications as transparent electrodes. Poisson’s ratios reach 15, a factor of 30 higher than for conventional rubbers. These giant Poisson’s ratios explain the observed opposite sign of width and length actuation and result in rare properties: negative linear compressibility and stretch densification.

Aliev, Ali E.; Oh, Jiyoung; Kozlov, Mikhail E.; Kuznetsov, Alexander A.; Fang, Shaoli; Fonseca, Alexandre F.; Ovalle, Raquel; Lima, Márcio D.; Haque, Mohammad H.; Gartstein, Yuri N.; Zhang, Mei; Zakhidov, Anvar A.; Baughman, Ray H.

2009-03-01

415

Aerogel RICH for forward PID at Belle II  

NASA Astrophysics Data System (ADS)

For the Belle II spectrometer we are preparing a proximity focusing RICH with aerogel as the radiator. It will be positioned in the forward direction of the spectrometer in the small space between the drift chamber and the electromagnetic calorimeter inside a strong magnetic field of 1.5 T. The Hybrid Avalanche Photo Diode used as a photo sensor, is able to detect single photons with a high efficiency, can operate in the magnetic field and is resistant to the expected neutron and gamma fluxes in the detector. By detecting more than 11 photons per incident 4 GeV/c pion, with 15 mrad single photon Cherenkov angle resolution, the designed aerogel RICH should enable an efficient separation of kaons from pions in the wide range of particle momenta from 0.5 GeV/c up to 4 GeV/c.

Pestotnik, R.; Adachi, I.; Hara, K.; Higuchi, M.; Iijima, T.; Iwata, S.; Kakuno, H.; Kawai, H.; Kawasaki, T.; Korpar, S.; Križan, P.; Kumita, T.; Mori, W.; Nishida, S.; Ogawa, S.; Šantelj, L.; Sakashita, Y.; Seljak, A.; Sumiyoshi, T.; Tabata, M.; Takagaki, H.; Yusa, Y.; Verheyden, R.

2013-12-01

416

High Resolution, Single-Step Patterning of Silica Aerogels  

NASA Technical Reports Server (NTRS)

Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag' ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 km, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed of Ag clusters with a size of several pm, separated by thin layers of silica.

Bertino, M. F.; Hund, J. F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A. T.; Terry, J.

2003-01-01

417

Equation-Of Measurements in Ta2O5 Aerogel  

NASA Astrophysics Data System (ADS)

Highly porous samples of tantalum pentoxide (Ta2O5) aerogel were compressed from initial densities of 0.1, 0.15, and 0.25 g/cm3 by shock waves with strengths between 0.3 and 3 Mbar. The compressed material was between 5 and 15 times as dense as the unshocked aerogels with temperatures of ~5 eV (~58,000 K). These strong shock loadings were produced by the OMEGA Laser System at the Laboratory of Laser Energetics. The shocked states were diagnosed with the OMEGA velocity interferometer system for any reflector. When the compression measurements are compared to an available high-energy-density equation-of-state model, it is found that the model underestimates the level of compression achieved by shock loading below a Mbar.

Miller, J. E.; Boehly, T. R.; Meyerhofer, D. D.; Eggert, J. H.

2007-12-01

418

Ceramic helium-cooled blanket test module  

Microsoft Academic Search

The design of RF DEMO-relevant ceramic helium cooled blanket test module (CHC BTM) for testing in international thermonuclear experimental reactor (ITER) is under consideration. The RF concept of DEMO BTM is based upon the breeder inside tube (BIT)-concept. This concept suggests the use of solid breeding ceramic material, helium as coolant and tritium purge-gas, ferrite–martensite steel as structural material, and

A Leshukov; V Kovalenko; G Shatalov; G Goroshkin; A Obukhov

2000-01-01

419

Chicxulub Ejecta Blanket Deposits From Belize  

NASA Technical Reports Server (NTRS)

The Chicxulub impact into a thick sequence of carbonates and sulfates released over a trillion tons of volatiles. The importance of the explosive release of such a large mass of volatiles has been greatly underestimated in studies of ejecta depositional processes. Proximal Chicxulub ejecta blanket deposits recent discovered on Albion Island in Belize provide a key to understanding the role of volatile-rich target material during large impact events.

Ocampo, A.

1995-01-01

420

Progress on the TAURO blanket system  

Microsoft Academic Search

TAURO is a self-cooled Pb?17Li blanket for Fusion Power Reactors (FPRs) using SiCf\\/SiC composites structures. It has been developed with the objective to achieve both passive safety and high thermal efficiency. The Pb?17Li outlet temperature exceeds 850°C. A Brayton cycle is envisaged for power conversion and the possibility of hydrogen production is addressed. This paper recalls the main features of

H Golfier; G Aiello; M Futterer; L Giancarli; A Li-Puma; Y Poitevin; J Szczepanski

2002-01-01

421

Silica xerogels and aerogels synthesized with ionic liquids  

Microsoft Academic Search

The synthesis of silica gels with ionic liquids (IL) as either additives or co-solvents is described. The wet gels were either dried by supercritical CO2 or by evaporation to obtain aerogels or xerogels, respectively. The effects of two ionic liquids: 1-butyl-3-methyl imidazolium tetrafluororate (IL1) and 1-butyl-4-methyl pyridinium tetrafluoroborate (IL2), on the structural and textural characteristics of gels were investigated. IL2

Ali Karout; Alain. C. Pierre

2007-01-01

422

Multifunctional, ultra-flyweight, synergistically assembled carbon aerogels.  

PubMed

All carbon aerogels (up to 1000 cm(3)) with ultralow density (down to 0.16 mg cm(-3)) and temperature-invariant (-190-900 °C) super-elasticity are fabricated by facile assembling of commercial carbon nanotubes (CNTs) and chemically-converted giant graphene sheets, on the basis of the synergistic effect between elastic CNTs ribs and giant graphene cell walls. PMID:23418099

Sun, Haiyan; Xu, Zhen; Gao, Chao

2013-05-14

423

Preparation-morphology-performance relationships in cobalt aerogels as supercapacitors.  

PubMed

The ability to direct the morphology of cobalt sol-gel materials by using the simple synthetic parameters in epoxide-driven polycondensations has been dramatically demonstrated, and the influence of such morphological differences upon the supercapacity of the materials has been explored. Precursor salt, epoxide, and solvent all influence the speed of the sol-gel transition and the size and shape of the features observed in the as-prepared materials, thereby leading to highly varied microstructures including spheres, sponge-like networks, and plate assemblies of varied size. These morphological features of the as-prepared cobalt aerogels were observed for the first time by high resolution scanning electron microscopy (HRSEM). The as-prepared aerogel materials were identified by powder X-ray diffraction and thermogravimetry as weakly crystalline or amorphous cobalt basic salts with the general formula Co(OH)(2-n)X(n) where X = Cl or NO3 according to the precursor salt used in the synthesis. For all samples, the morphology was preserved through mild calcining to afford spinel phase Co3O4 in a variety of microstructures. Wide-ranging specific surface areas were determined for the as-prepared and calcined phases by physisorption analysis in agreement with the morphologies observed by HRSEM. The Co3O4 aerogels were evaluated for their supercapacitive performance by cyclic voltammetry. The various specimens exhibit capacitances ranging from 110 to 550 F g(-1) depending upon the attributes of the particular aerogel material, and the best specimen was found to have good cycle stability. These results highlight the epoxide-driven sol-gel condensation as a versatile preparative route that provides wide scope in materials' properties and enables the analysis of structure-performance relationships in metal oxide materials. PMID:24417220

Peterson, Geneva R; Hung-Low, Fernando; Gumeci, Cenk; Bassett, Will P; Korzeniewski, Carol; Hope-Weeks, Louisa J

2014-02-12

424

Structure and self-similarity of silica aerogels  

Microsoft Academic Search

Small-angle neutron scattering from silica aerogels reveals that they form mutually self-similar volume fractals for a wide range of densities and preparations. The fractal dimension is D=2.40+\\/-0.03. The fractal behavior extends down to near-molecular sizes. Indication for a volume-to-surface fractal crossover is also obtained. These results apply to neutrally prepared or acid-catalyzed materials. Base-catalyzed gels have widely different properties.

René Vacher; Thierry Woignier; Jacques Pelous; Eric Courtens

1988-01-01

425

Design of the APT Target/Blanket  

NASA Astrophysics Data System (ADS)

The Accelerator Production of Tritium Target/Blanket system is composed of a separated tungsten spallation target surrounded by a lead moderator, as well as attendant heat removal systems. The system is housed in a building located at the end of a 1.3 km long linear accelerator, which can produce a 100 mA proton beam up to 1700 MeV (170MW). The beam is expanded by a rastering system to a 0.19m x 190.m shape before passing through an Inconel window and impacting the heavy-water cooled tungsten target. Neutrons produced in the tungsten by the spallation process are further multiplied and moderated in a surrounding light-water cooled lead blanket. Neutron capture in tubes of Helium-3 gas inserted in the blanket produce tritium which is removed on a continual basis in an adjacent Tritium Separation Facility (TSF). The APT T/B is a robust design based on existing technology. Where possible, proven materials and component designs are used. To accommodate uncertainties in predicted lifetimes, the design is modularized to allow for a straightforward replacement of spent components. The thermal hydraulic design is well within allowable limits and due to the low temperature and pressure systems, offers additional safety and reliability benefits. The safety by design process has incorporated passive design features, redundancy, and defense in depth to provide adequate protection of both the worker and the public.

Cappiello, M. W.

1998-04-01

426

Nuclear Analysis of an ITER Blanket Module  

NASA Astrophysics Data System (ADS)

ITER blanket system is the reactor's plasma-facing component, it is mainly devoted to provide the thermal and nuclear shielding of the Vacuum Vessel and external ITER components, being intended also to act as plasma limiter. It consists of 440 individual modules which are located in the inboard, upper and outboard regions of the reactor. In this paper attention has been focused on to a single outboard blanket module located in the equatorial zone, whose nuclear response under irradiation has been investigated following a numerical approach based on the Monte Carlo method and adopting the MCNP5 code. The main features of this blanket module nuclear behaviour have been determined, paying particular attention to energy and spatial distribution of the neutron flux and deposited nuclear power together with the spatial distribution of its volumetric density. Moreover, the neutronic damage of the structural material has also been investigated through the evaluation of displacement per atom and helium and hydrogen production rates. Finally, an activation analysis has been performed with FISPACT inventory code using, as input, the evaluated neutron spectrum to assess the module specific activity and contact dose rate after irradiation under a specific operating scenario.

Chiovaro, P.; Di Maio, P. A.; Parrinello, V.

2013-08-01

427

A comparison of mechanical properties and scaling law relationships for silica aerogels and their organic counterparts  

SciTech Connect

Aerogels are a special class of open-cell foams derived from the supercritical extraction of highly crosslinked, inorganic or organic gels. The resultant materials have ultrafine cell/pore sizes (< 100 nm), high surface areas (350--1000m{sup 2}/g), and a microstructure composed of interconnected colloidal-like particles or polymeric chains with characteristic diameters of 10 nm. TEM and SAXS show that this microstructure is sensitive to variations in processing conditions that influence crosslinking chemistry and growth processes prior to gelation. Traditional silica aerogels are prepared via the hydrolysis and condensation of tetramethoxy silane (TMOS) or tetraethoxy silane (TEOS). Factors such as pH and the (H{sub 2}O)/(TMOS) ratio affect the microstructure of the dried aerogel. It is generally accepted that polymeric' silica aerogels result from acid catalysis while colloidal'silica aerogels result from base catalysis. Recently, Hrubesh and Tillotson developed a new condensed silica' procedure for obtaining silica aerogels with densities as low as 0.004g/cc, i.e. only 3{times} the density of air. Organic aerogels are formed from the aqueous, polycondensation of (1) resorcinol/formaldehyde or (2) melamine/formaldehyde. The microstructure of the resorcinol-formaldehyde (RF) aerogels is dictated by the amount of base catalyst used in the sol-gel polymerization. In addition, these materials can be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. Melamine- formaldehyde (MF) aerogels that are both colorless and transparent are only formed under acidic conditions (i.e. pH = 1--2). In this paper, the microstructural dependence and scaling law relationships for the compressive modulus of silica, carbon, RF, and MF aerogels will be discussed in detail. 17 refs., 1 fig.

Pekala, R.W.; Hrubesh, L.W.; Tillotson, T.M.; Alviso, C.T.; Poco, J.F.; LeMay, J.D.

1990-08-01

428

Optically transparent silica aerogels based on sodium silicate by a two step sol-gel process and ambient pressure drying  

NASA Astrophysics Data System (ADS)

Interest in improving the optical transmission of sodium silicate-based aerogels by ambient pressure drying led to the synthesis of aerogels using a two-step sol-gel process. To produce optically transparent silica aerogel granules, NH4F (1 M) and HCl (4 M) were used as hydrolyzing and condensation catalysts, respectively. The silica aerogels were characterized by their bulk density, porosity (%), contact angle and thermal conductivity. Optical transmission of as synthesized aerogels was studied by comparing the photos of aerogel granules. Scanning electron microscopic study showed the presence of fractal structures in these aerogels. The degree of transparency in two step sol-gel process-based aerogels is higher than the conventional single step aerogels. The N2 adsorption-desorption analysis depicts that the two step sol-gel based aerogels have large surface areas. Optically transparent silica aerogels with a low density of ˜0.125 g/cc, low thermal conductivity of ˜0.128 W/mK and higher Brunauer, Emmett, and Teller surface area of ˜425 m2/g were obtained by using NH4F (1 M), HCl (4 M), and a molar ratio of Na2SiO3::H2O::trimethylchlorosilane of 1::146.67::9.46. The aerogels retained their hydrophobicity up to 500 °C.

Bangi, Uzma K. H.; Jung, In-Keun; Park, Chang-Sun; Baek, Seungsu; Park, Hyung-Ho

2013-04-01

429

Porous structure of organic and carbon aerogels synthesized by sol-gel polycondensation of resorcinol with formaldehyde  

Microsoft Academic Search

Organic aerogels were synthesized via the sol-gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution and followed by supercritical drying with carbon dioxide. As a result of characterization by nitrogen adsorption, the resorcinol-formaldehyde (RF) aerogels were mesoporous materials with high surface areas and had few micropores. The surface area of the RF aerogel was controlled by the

H. Tamon; H. Ishizaka; M. Mikami; M. Okazaki

1997-01-01

430

Carbon aerogel based electrode material for EAP actuators  

NASA Astrophysics Data System (ADS)

In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and poly(vinylidene-co-hexafluoropropylene) (PVdF(HFP)). Actuators were made by using layer-by-layer casting method and they work as a bending actuators. Carbon aerogel is synthesized from 5- methylresorcinol, which is a waste product in oil-shale industry. It makes the material "environmentally green". Carbon aerogels have a very low density and considerable specific surface area. It is generally understood that the large interfacial surface area of electrodes gives rise to better actuation performance; therefore, designing actuators with high specific surface area electrodes is of interest. The assembled three layer actuators require low voltage to operate and work steadily in open air due to non-volatile electrolyte. The electromechanical and electrical characteristics of prepared actuators were examined and compared to our previously reported actuators based on the carbide-derived carbon and activated carbon electrodes. The differences in actuation performance were analyzed in the context of pore characteristics and degree of graphitization of carbons. The gas sorption measurements were performed to characterize pore size distribution. These actuators show high strain, low back-relaxation and low power consumption and they are good for slow-response applications compared to carbon nanotube actuators.

Kaasik, Friedrich; Torop, Janno; Peikolainen, Anna-Liisa; Koel, Mihkel; Aabloo, Alvo

2011-03-01

431

Ultralow percolation threshold in aerogel and cryogel templated composites.  

PubMed

We demonstrate a novel concept for preparing percolating composites with ultralow filler content by utilizing nanofiller-loaded aerogel and cryogels as a conductive template. This concept is investigated for several porous systems, including resorcinol-formaldehyde (RF), silica, and polyacrylamide (PAM) gels, and both graphene and carbon nanotubes are utilized as nanofiller. In each case, a stable, aqueous nanofiller dispersion is mixed with a sol-gel precursor and polymerized to form a hydrogel, which can then be converted to an aerogel by critical point drying or cryogel by freeze-drying. Epoxy resin is infused into the pores of the gels by capillary action without disrupting the monolithic structure. We show that conductive graphene/epoxy composites are formed with a very low graphene loading; a percolation threshold as low as 0.012 vol % is obtained for graphene-RF cryogel/epoxy composite. This is the lowest reported threshold of any graphene-based nanocomposites. Similar values are achieved in other aerogel and nanofiller systems, which demonstrates the versatility of this method. PMID:23927050

Irin, Fahmida; Das, Sriya; Atore, Francis O; Green, Micah J

2013-09-10

432

Lunar and Planetary Science XXXV: Interplanetary Dust and Aerogel  

NASA Technical Reports Server (NTRS)

Contents include the following: Isotopically Primitive Interplanetary Dust Particles of Cometary Origin: Evidence from Nitrogen Isotopic Compositions. The Solar Nebula s First Accretionary Particles (FAPs) Are They Preserved in Collected Interplanetary Dust Samples? On the Origin of GEMS. An Analytical SuperSTEM for Extraterrestrial Materials Research. Sub-Micrometer Scale Minor Element Mapping in Interplanetary Dust Particles: A Test for Stratospheric Contamination. First Report of Taenite in an Asteroidal Interplanetary Dust Particle: Flash-heating Simulates Nebular Dust Evolution. FTIR Analyses of IDPs: Comparison with the InfraRed Spectra of the Interstellar Medium. Mineralogical Study of Hydrated IDPs: X-Ray Diffraction and Transmission Electron Microscopy. Focused Ion Beam Recovery and Analysis of Interplanetary Dust Particles (IDPs) and Stardust Analogues. Technique for Concentration of Carbonaceous Material from Aerogel Collectors Using HF-Vapor Etching. Synchrotron X-Ray Analysis of Captured Particle Residue in Aerogel. In-Situ Analyses of Earth Orbital Grains Trapped in Aerogel, Using Synchrotron X-Ray Microfluorescence Techniques. Igneous Rims on Micrometeorites and the Sizes of Chondrules in Main Belt Asteroids.

2004-01-01

433

Application of High-Performance Aerogel Insulating Materials (Analysis & Test Results)  

SciTech Connect

The NCSX stellarator core design is built around a 3-period, highly shaped plasma with an assembly of four magnet systems, the TF coils (TF), the Modular Coils (MC), the PF Coils (PF), and the Trim Coils, that surrounds an all welded Vacuum Vessel (VV). The VV features approximately 100 ports for heating, pumping, diagnostics, and maintenance access. The entire system is surrounded by a cryostat to permit operation of the coils at liquid nitrogen temperature. The VV and coils are assembled in 120 segments. The VV segments must be placed inside the MC by sliding the coils over each end of the vessel subassembly. Installation of the port extensions is done after this operation. They are slipped through access holes in the MC onto port stubs and welded on from inside. Figures 1 & 2 illustrate the assembly of the MC over a VV section and installation of TF and port extensions to complete a sector of the VV.

Goranson, Paul L [ORNL; Freudenberg, Kevin D [ORNL; McGinnis, William Dean [ORNL; Dudek, L. [Princeton Plasma Physics Laboratory (PPPL); Zarnstorff, M. C. [Princeton Plasma Physics Laboratory (PPPL)

2009-01-01

434

An overview of dual coolant Pb-17Li breeder first wall and blanket concept development for the US ITER-TBM design  

SciTech Connect

An attractive blanket concept for the fusion reactor is the dual coolant Pb-17Li liquid (DCLL) breeder design. Reduced activation ferritic steel (RAFS) is used as the structural material. Helium is used to cool the first wall and blanket structure, and the self-cooled breeder Pb-17Li is circulated for power conversion and for tritium breeding. A SiCf/SiC composite insert is used as the magnetohydrodynamic (MHD) insulation to reduce the impact from the MHD pressure drop of the circulating Pb-17Li and as the thermal insulator to separate the high temperature Pb-17Li from the helium cooled RAFS structure. For the reference tokamak power reactor design, this blanket concept has the potential of satisfying the design limits of RAFS while allowing the feasibility of having a high Pb-17Li outlet temperature of 700 C. We have identified critical issues for the concept, some of which include the first wall design, the assessment of MHD effects with the SiC-composite flow coolant insert, and the extraction and control of the bred tritium from the Pb-17Li breeder. R&D programs have been proposed to address these issues. At the same time we have proposed a test plan for the DCLL ITER-Test Blanket Module program.

Wong, C C; Malang, S; Sawan, M; Dagher, M; Smolentsev, S; Merrill, B; Youssef, M; Reyes, S; Sze, D D; Morley, N B; Sharafat, S; Calderoni, P; Sviatoslavsky, G; Kurtz, R; Fogarty, P; Zinkle, S; Abdou, M

2005-05-13

435

An overview of dual coolant Pb-17Li breeder first wall and blanket concept development for the US ITER-TBM design  

SciTech Connect

An attractive blanket concept for the fusion reactor is the dual coolant Pb-17Li liquid (DCLL) breeder design. Reduced activation ferritic steel (RAFS) is used as the structural material. Helium is used to cool the first wall and blanket structure, and the self-cooled breeder Pb-17Li is circulated for power conversion and for tritium breeding. A SiCf/SiC composite insert is used as the magnetohydrodynamic (MHD) insulation to reduce the impact from the MHD pressure drop of the circulating Pb-17Li and as the thermal insulator to separate the high temperature Pb-17Li from the helium cooled RAFS structure. For the reference tokamak power reactor design, this blanket concept has the potential of satisfying the design limits of RAFS while allowing the feasibility of having a high Pb-17Li outlet temperture of 700C. We have identified critical issues for the concept, some of which inlude the first wall design, the assessment of MHD effectrs with the SiC-composite flow coolant insert, and the extraction and control of the bred tritium from the Pb-17Li breeder. R&D programs have been proposed to address these issues. At the same time, we have proposed a test plan for the DCLL ITER-Test Blanket Module program.

Wong, Clement; Malang, S.; Sawan, M.; Dagher, Mohamad; Smolentsev, S.; Merrill, Brad; Youssef, M.; Reyes, Susanna; Sze, Dai Kai; Morley, Neil B.; Sharafat, Shahran; Calderoni, P.; Sviatoslavsky, G.; Kurtz, Richard J.; Fogarty, Paul J.; Zinkle, Steven J.; Abdou, Mohamed A.

2006-07-05

436

Solid breeder blanket option for the ITER conceptual design  

Microsoft Academic Search

A solid-breeder, water-cooled blanket option based on a multilayer configuration was developed for the ITER (International Thermonuclear Experimental Reactor). The blanket uses beryllium for neutron multiplication and lithium oxide for tritium breeding. The material forms are sintered products for both materials with 0.8 density factor. The lithium-6 enrichment is 90%. The blanket can accommodate a factor of two change in

Y. Gohar; H. Attaya; M. C. Billone; P. Finn; S. Majumdar; L. R. Turner; C. C. Baker; B. E. Nelson; R. Raffray

1989-01-01

437

Electric and magnetic field exposure associated with electric blankets  

SciTech Connect

electric blankets may be important contributors to the public's overall exposure to 60 Hz electric and magnetic fields (EMFs) since they are common appliances that are used close to the body for long periods of time. This report describes a series of experimental and computer analyses characterizing various aspects of EMF exposure from electric blankets in use prior to Fall 1990. Almost of electric blankets were found to use on/off controllers with cycle periods of minutes. Calculations of magnetic fields within the body show that, when blankets are heating, flux densities averaged over the whole body range from 15--33 mG during the on'' cycle with typical values of 22 mG. Duty cycles are predicted to vary widely from user-to-user, with typical values of perhaps 40%. Given typical blanket usage patterns, the long-term body-averaged magnetic field exposure from blankets is expected to be comparable to that form other EMF sources for a significant fraction of the blanket-using population. No significant differences were found between time-averaged magnetic field exposures from blankets with metal alloy and plastic polymer heating elements. Blankets with alloy and polymer heating elements did differ significantly in electric field exposure. Calculations show that the unperturbed field 5 cm above flat blankets range from 60--150 V/m for alloy heating cables and unperturbed field 5 cm above flat blankets range from 60--150 V/m for alloy heating cables and 10--40 V/m polymer cables. Starting in Fall 1990, electric blanket manufactures introduced new designs that produce much smaller magnetic fields. These are expected to replace the current in-use stock at a rate of 10--15% per year.

Florig, H.K.; Hoburg, J.F. (Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Engineering and Public Policy)

1991-12-01

438

Optimization of an Aerogel Cerenkov Detector Having a Mirror Light Collection System.  

National Technical Information Service (NTIS)

Cerenkov detectors with silica aerogel of refractive index 1.03 as the radiator have been tested in a particle beam at the CERN Proton Synchrotron. With a detector surface of 22 x 50 cm exp 2 and 9 cm thickness of aerogel, the number of photoelectrons was...

K. E. Johansson T. Aakesson J. Norrby

1979-01-01

439

Model Calculation of Orientational Effect of Deformed Aerogel on the Order Parameter of Superfluid 3He  

NASA Astrophysics Data System (ADS)

Theory of Rainer and Vuorio of small objects in superfluid 3He is applied for calculation of the average orientational effect of a deformed aerogel on the order parameter of 3He. The minimum deformation which stabilizes the ordered state is evaluated both for specular and diffusive scattering of quasiparticles by the strands of aerogel.

Surovtsev, E. V.; Fomin, I. A.

2008-02-01

440

Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates  

Microsoft Academic Search

Nanostructured biological materials inspire the creation of materials with tunable mechanical properties. Strong cellulose nanofibrils derived from bacteria or wood can form ductile or tough networks that are suitable as functional materials. Here, we show that freeze-dried bacterial cellulose nanofibril aerogels can be used as templates for making lightweight porous magnetic aerogels, which can be compacted into a stiff magnetic

R. T. Olsson; M. A. S. Azizi Samir; G. Salazar-Alvarez; L. Belova; V. Ström; L. A. Berglund; O. Ikkala; J. Nogués; U. W. Gedde

2010-01-01

441

Controlling the growth of palladium aerogels with high-performance toward bioelectrocatalytic oxidation of glucose.  

PubMed

We report the controllable synthesis of Pd aerogels with high surface area and porosity by destabilizing colloidal solutions of Pd nanoparticles with variable concentrations of calcium ions. Enzyme electrodes based on Pd aerogels co-immobilized with glucose oxidase show high activity toward glucose oxidation and are promising materials for applications in bioelectronics. PMID:24475875

Wen, Dan; Herrmann, Anne-Kristin; Borchardt, Lars; Simon, Frank; Liu, Wei; Kaskel, Stefan; Eychmüller, Alexander

2014-02-19

442

Monolithic composites of silica aerogels by reactive supercritical deposition of hydroxy-terminated poly(dimethylsiloxane).  

PubMed

Monolithic composites of silica aerogels with hydroxyl-terminated poly(dimethylsiloxane) (PDMS(OH)) were developed with a novel reactive supercritical deposition technique. The method involves dissolution of PDMS(OH) in supercritical CO2 (scCO2) and then exposure of the aerogel samples to this single phase mixture of PDMS(OH)-CO2. The demixing pressures of the PDMS(OH)-CO2 binary mixtures determined in this study indicated that PDMS(OH) forms miscible mixtures with CO2 at a wide composition range at easily accessible pressures. Upon supercritical deposition, the polymer molecules were discovered to react with the hydroxyl groups on the silica aerogel surface and form a conformal coating on the surface. The chemical attachment of the polymer molecules on the aerogel surface were verified by prolonged extraction with pure scCO2, simultaneous deposition with superhydrophobic and hydrophilic silica aerogel samples and ATR-FTIR analysis. All of the deposited silica aerogel samples were obtained as monoliths and retained their transparency up to around 30 wt % of mass uptake. PDMS(OH) molecules were found to penetrate all the way to the center of the monoliths and were distributed homogenously throughout the cylindrical aerogel samples. Polymer loadings as high as 75.4 wt % of the aerogel mass could be attained. It was shown that the polymer uptake increases with increasing exposure time, as well as the initial polymer concentration in the vessel. PMID:24168319

Sanli, D; Erkey, C

2013-11-27

443

Three-dimensional textural and compositional analysis of particle tracks and fragmentation history in aerogel  

NASA Astrophysics Data System (ADS)

We report analyses of aerogel tracks using (1 synchrotron X-ray computed microtomography (XRCMT), (2) laser confocal scanning microscopy (LCSM), and (3) synchrotron radiation X-ray fluorescence (SRXRF) of particles and their paths resulting from simulated hypervelocity impacts (1-2), and a single ~1 mm aerogel track from the Stardust cometary sample collector (1-3). Large aerogel pieces can be imaged sequentially, resulting in high spatial resolution images spanning many tomographic fields of view (‘lambda-tomography’). We report calculations of energy deposited, and tests on aromatic hydrocarbons showing no alteration in tomography experiments. Imaging at resolutions from ~17 to ~1 micron/pixel edge (XRCMT) and to <100 nm/ pixel edge (LCSM) illustrates track geometry and interaction of particles with aerogel, including rifling, particle fragmentation, and final particle location. We present a 3-D deconvolution method using an estimated point-spread function for aerogel, allowing basic corrections of LCSM data for axial distortion. LCSM allows rapid, comprehensive, non-destructive, high information return analysis of tracks in aerogel keystones, prior to destructive grain extraction. SRXRF with LCSM allows spatial correlation of grain size, chemical, and mineralogical data. If optical methods are precluded in future aerogel capture missions, XRCMT is a viable 3D imaging technique. Combinations of these methods allow for complete, nondestructive, quantitative 3-D analysis of captured materials at high spatial resolution. This data is fundamental to understanding the hypervelocity particle-aerogel interaction histories of Stardust grains.

Ebel, D. S.; Greenberg, M.; Rivers, M. L.; Newville, M.

2009-11-01

444

Three-dimensional textural and compositional analysis of particle tracks and fragmentation history in aerogel  

SciTech Connect

We report analyses of aerogel tracks using (1) synchrotron X-ray computed microtomography (XRCMT), (2) laser confocal scanning microscopy (LCSM), and (3) synchrotron radiation X-ray fluorescence (SRXRF) of particles and their paths resulting from simulated hypervelocity impacts (1-2), and a single {approx}1 mm aerogel track from the Stardust cometary sample collector (1-3). Large aerogel pieces can be imaged sequentially, resulting in high spatial resolution images spanning many tomographic fields of view ('lambda-tomography'). We report calculations of energy deposited, and tests on aromatic hydrocarbons showing no alteration in tomography experiments. Imaging at resolutions from -17 to -1 micron/pixel edge (XRCMT) and to <100 nm/pixel edge (LCSM) illustrates track geometry and interaction of particles with aerogel, including rifling, particle fragmentation, and final particle location. We present a 3-D deconvolution method using an estimated point-spread function for aerogel, allowing basic corrections of LCSM data for axial distortion. LCSM allows rapid, comprehensive, non-destructive, high information return analysis of tracks in aerogel keystones, prior to destructive grain extraction. SRXRF with LCSM allows spatial correlation of grain size, chemical, and mineralogical data. If optical methods are precluded in future aerogel capture missions, XRCMT is a viable 3D imaging technique. Combinations of these methods allow for complete, nondestructive, quantitative 3-D analysis of captured materials at high spatial resolution. This data is fundamental to understanding the hypervelocity particle-aerogel interaction histories of Stardust grains.

Ebel, Denton S.; Greenberg, Michael; Rivers, Mark L.; Newville, Matthew; (AMNH)

2010-05-04

445

Frequency dependence of fast mode ultrasound attenuation of liquid 4He in aerogel  

Microsoft Academic Search

In our previous work, anomalous sound attenuation in superfluid phase was observed in liquid 4He filled in 97.0 % porous aerogel using longitudinal ultrasound at the frequency of 10 MHz. To understand the nature of the observed anomaly one needs to know the viscous coupling between normal component and aerogel strands. As far as the viscous penetration depth depends on

K. Matsumoto; H. Tsuboya; K. Ohmori; S. Abe; H. Suzuki; D. A. Tayurskii

2009-01-01

446

Determination of the permeability of carbon aerogels by gas flow measurements  

SciTech Connect

Carbon aerogels are synthesized via the polycondensation of resorcinol and formaldehyde, followed by supercritical drying and pyrolysis at 1050{degree}C in nitrogen. Because of their interconnected porosity, ultrafine cell structure and high surface area, carbon aerogels have many potential applications, such as in supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, we calculated the permeability of carbon aerogels from equations based upon Darcy's law. Our measurements show that carbon aerogels have apparent permeabilities on the order of 10{sup {minus}12}to 10{sup {minus}10} cm{sup 2} for densities ranging from 0.44 to 0.05 g/cm{sup 3}. Like their mechanical properties, the permeability of carbon aerogels follows a power law relationship with density and average pore size. Such findings help us to estimate the average pore sizes of carbon aerogels once their densities are known. This paper reveals the relationships among permeability, pore size and density in carbon aerogels.

Kong, F.M.; Hulsey, S.S.; Alviso, C.T.; Pekala, R.W.

1992-04-01

447

Determination of the permeability of carbon aerogels by gas flow measurements  

SciTech Connect

Carbon aerogels are synthesized via the polycondensation of resorcinol and formaldehyde, followed by supercritical drying and pyrolysis at 1050{degree}C in nitrogen. Because of their interconnected porosity, ultrafine cell structure and high surface area, carbon aerogels have many potential applications, such as in supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, we calculated the permeability of carbon aerogels from equations based upon Darcy`s law. Our measurements show that carbon aerogels have apparent permeabilities on the order of 10{sup {minus}12}to 10{sup {minus}10} cm{sup 2} for densities ranging from 0.44 to 0.05 g/cm{sup 3}. Like their mechanical properties, the permeability of carbon aerogels follows a power law relationship with density and average pore size. Such findings help us to estimate the average pore sizes of carbon aerogels once their densities are known. This paper reveals the relationships among permeability, pore size and density in carbon aerogels.

Kong, F.M.; Hulsey, S.S.; Alviso, C.T.; Pekala, R.W.

1992-04-01

448

Silica reusable surface insulation  

NASA Technical Reports Server (NTRS)

A reusable silica surface insulation material is provided by bonding amorphous silica fibers with colloidal silica at an elevated temperature. The surface insulation is ordinarily manufactured in the form of blocks (i.e., tiles).

Goldstein, H. E.; Smith, M.; Leiser, D. B. (inventors)

1976-01-01

449

Insulation for Piping.  

National Technical Information Service (NTIS)

A foamed insulation for cryogenic pipe lines comprised of a pair of preformed, semicircular foamed insulation half-sections is described. The faying surfaces are coated with a polyurethane adhesive and bonded together about the pipe. The faying surfaces o...

G. Lerma

1975-01-01

450

Foam Thermal Insulation.  

National Technical Information Service (NTIS)

The report covers the testing of two different types of foam thermal insulation materials using certain proprietary coatings. The purpose of these tests was to determine the suitability of these materials as thermal insulation for shipboard construction c...

R. E. Buzhardt

1967-01-01

451

Current Trends of Blanket Research and Development in Japan 5.The Frontiers of Research on Fusion Blanket Technology  

NASA Astrophysics Data System (ADS)

Current topics concerning blanket technology are reviewed. In the chemical engineering/chemistry area, the qualitative and quantitative effects of mass transfer steps of tritium is important in the understanding of the behavior of bred tritium in the solid breeder blanket system. Such phenomena as adsorption, isotope exchange reactions, and water formation reaction at the grain surface produce profound effects on the behavior of the bred tritium in the blanket. Regarding the liquid system, the physical or chemical properties of Li, Li17Pb83 and Flibe as liquid blanket materials were compared. Some recent studies were introduced regarding tritium recovery from the liquid blanket materials, impurity removal from salts, ceramic coating of structural materials, and the vapor pressure of mixtures of metals or salts. Thermal hydraulic topics in relation to several candidate power reactor concepts are summarized. Emphasis is laid on the simultaneous removal of heat and tritium from the blanket and some aspects of forming effective power cycles are developed.

Nishikawa, Masabumi; Fukada, Satoshi; Shimizu, Akihiko; Iguchi, Tetsuo

452

Statistical topological insulators  

NASA Astrophysics Data System (ADS)

We define a class of insulators with gapless surface states protected from localization due to the statistical properties of a disordered ensemble, namely, due to the ensemble's invariance under a certain symmetry. We show that these insulators are topological, and are protected by a Z2 invariant. Finally, we prove that every topological insulator gives rise to an infinite number of classes of statistical topological insulators in higher dimensions. Our conclusions are confirmed by numerical simulations.

Fulga, I. C.; van Heck, B.; Edge, J. M.; Akhmerov, A. R.

2014-04-01

453

Carbon quantum dot-functionalized aerogels for NO2 gas sensing.  

PubMed

Silica aerogels functionalized with strongly fluorescent carbon quantum dots were first prepared and used for simple, sensitive, and selective sensing of NO2 gas. In the presence of ethanol, homemade silica aerogels with a large specific surface area of 801.17 m(2)/g were functionalized with branched polyethylenimine-capped quantum dots (BPEI-CQDs) with fluorescence quantum yield higher than 40%. The prepared porous CQD-aerogel hybrid material could maintain its excellent fluorescence (FL) activity in its solid state. The FL of CQD-aerogel hybrid material could be selectively and sensitively quenched by NO2 gas, suggesting a promising application of the new FL-functionalized aerogels in gas sensing. PMID:23905622

Wang, Ruixue; Li, Geli; Dong, Yongqiang; Chi, Yuwu; Chen, Guonan

2013-09-01

454

X-ray radiographic technique for measuring density uniformity of silica aerogel  

NASA Astrophysics Data System (ADS)

This paper proposes a new X-ray radiographic technique for measuring density uniformity of silica aerogels used as radiator in proximity-focusing ring-imaging Cherenkov detectors. To obtain high performance in a large-area detector, a key characteristic of radiator is the density (i.e. refractive index) uniformity of an individual aerogel monolith. At a refractive index of n=1.05, our requirement for the refractive index uniformity in the transverse plane direction of an aerogel tile is |?(n-1)/(n-1)|<4% in a focusing dual layer radiator (with different refractive indices) scheme. We applied the radiographic technique to evaluate the density uniformity of our original aerogels from a trial production and that of Panasonic products (SP-50) as a reference, and to confirm they have sufficient density uniformity within ±1% along the transverse plane direction. The measurement results show that the proposed technique can quantitatively estimate the density uniformity of aerogels.

Tabata, Makoto; Hatakeyama, Yoshikiyo; Adachi, Ichiro; Morita, Takeshi; Nishikawa, Keiko