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All sources NASA NTRS DOE OSTI

NASA NTRS2003

Thin Thermal-Insulation Blankets for Very High Temperatures

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.↗

NASA NTRS2017

Thermal Insulation System for Non-Vacuum Applications Including a Multilayer Composite

The thermal insulation system of the present invention is for non-vacuum applications and is specifically tailored to the ambient pressure environment with any level of humidity or moisture. The thermal insulation system includes a multilayered composite including i) at least one thermal insulation layer and at least one compressible barrier layer provided as alternating, successive layers, and ii) at least one reflective film provided on at least one surface of the thermal insulation layer and/or said compressible barrier layer. The different layers and materials and their combinations are designed to provide low effective thermal conductivity for the system by managing all modes of heat transfer. The thermal insulation system includes an optional outer casing surrounding the multilayered composite. The thermal insulation system is particularly suited for use in any sub-ambient temperature environment where moisture or its adverse effects are a concern. The thermal insulation system provides physical resilience against damaging mechanical effects including compression, flexure, impact, vibration, and thermal expansion/contraction.

Fesmire, James E.↗

DOE OSTI2020

Porous thermally insulating compositions containing hollow silica particles

A thermally insulating composition comprising hollow spherical silica particles and a coating of a material having a thermal conductivity of less than 0.3 W/m·K on surfaces of said silica particles. In particular embodiments, the low conductivity coating material may be a polymer, such as polystyrene or polyvinylpyrrolidone, or the low conductivity coating material may be a quaternary ammonium salt of the Formula (1), i.e., R1R2R3R4N+A−, with at least one of R1, R2, R3, and R4 being an alkyl group containing at least ten carbon atoms (and A− is a counter anion), or the low conductivity coating material may be phenyl-C61-butyric acid methyl ester covalently bound to the hollow spherical silica particles. Also described herein is a method of thermally insulating a surface by applying a coating of the thermally insulating composition, described above, onto the surface.

36 MATERIALS SCIENCE↗

NASA NTRS1982

Thermally Insulated Glove With Good Tactility

Thermally insulated glove contains short, closely-spaced elastomeric pins that insulate without impairing flexibility. By confining pins to the inter-joint areas of palm, fingers and back of the hand, joint mobility is retained. Glove thermal-insulation requirements dictate the relationships among pin length, pin diameter, and number of pins per unit surface length.

Balinskas, R.↗

DOE OSTI2021

Critical roles of pores and moisture in sustainable nanocellulose-based super-thermal insulators

In a recent report in Matter, Bergström and co-workers describe a novel thermal transport behavior that subverts this assumption of porous materials. In their work, the authors describe a nanocellulose-based foam that features ultrahigh porosity (> 99.6%) and aligned µm-scale pores (10–100 µm) whose radial thermal conductivity (i.e., perpendicular to the pore alignment) is close to that of free air in the dry state. Furthermore, the radial thermal conductivity of the cellulose-based foam can be reduced to ~14 mW/(m·K) when the relative humidity is ~35%. Super-thermal insulators, which demonstrate a thermal conductivity below that of stationary air (~ 25 mW/(m·K), 20 ºC, 1.0 atm), are needed to minimize heat loss in various applications (e.g., buildings, thermal energy storage tanks, cold chain packaging, etc.) to mitigate the energy crisis and reduce carbon emissions. Introducing pores into a material is a facile and effective way to achieve low thermal conductivity as pores can suppress thermal transport through solids by reducing the cross-sectional area and increasing the tortuosity of the heat transfer pathway. In porous structures there are two kinds of pores: open and closed. While increased porosity can reduce heat conduction through solids with an open porous structure, the improved gas conduction creates a competing effect that simultaneously elevates the heat transfer. Therefore, the thermal conductivity of a material with µm-scale open pores is usually larger than that of stationary air. Reducing the pore size to less than the mean free path of air (~ 70 nm, 20 ºC, 1.0 atm) can effectively reduce gas conduction, enabling the material to achieve a thermal conductivity below that of stationary air. However, high cost of the nanosized raw materials and time-consuming fabrication processes limit the large-scale applications of nanoporous thermal insulators. Meanwhile, closed pores can block heat transport only through the continuous gas phase. As a result, the thermal conductivity of a closed porous structure can theoretically be much smaller than that of stationary air if the solid conduction can also be suppressed by (1) lowering the solid content of the material, (2) reducing the thermal conductivity of the building blocks of the material, and/or (3) increasing interfacial thermal resistance between neighboring building blocks. Most processes used to generate porous structures (e.g., supercritical drying, freeze drying) involve a solvent that escapes the material. Therefore, it is difficult to create pores and isolate them simultaneously, preventing the fabrication of super-thermal insulators with closed pores.

36 MATERIALS SCIENCE↗

NASA NTRS1996

Lightweight, Thermally Insulating Structural Panels

Lightweight, thermally insulating panels that also serve as structural members developed. Honeycomb-core panel filled with low-thermal-conductivity, opacified silica aerogel preventing convection and minimizes internal radiation. Copper coating on face sheets reduces radiation. Overall thermal conductivities of panels smaller than state-of-art commercial non-structurally-supporting foam and fibrous insulations. On Earth, panels suitable for use in low-air-pressure environments in which lightweight, compact, structurally supporting insulation needed; for example, aboard high-altitude aircraft or in partially evacuated panels in refrigerators.

Eisen, Howard J.↗

DOE OSTI2020

Porous thermally insulating compositions containing hollow spherical nanoparticles

A method of thermally insulating a surface, the method comprising applying a coating of a thermally insulating composition onto said surface, wherein said thermally insulating composition comprises: (i) hollow spherical nanoparticles having a mean particle size of less than 800 nm in diameter and a particle size distribution in which at least 90% of the hollow spherical nanoparticles have a size within ±20% of said mean particle size, and a first layer of cationic or anionic molecules attached to said surfaces of the hollow spherical nanoparticles; and (ii) a second layer of molecules of opposite charge to the first layer of molecules, wherein said second layer of molecules of opposite charge are ionically associated with said first layer of molecules, wherein the molecules in said second layer have at least eight carbon atoms.

36 MATERIALS SCIENCE↗

NASA NTRS1968

Cryogenic thermal insulation Patent

Development of thermal insulation material for insulating liquid hydrogen tanks in spacecraft

Middleton, R. L.↗

NASA NTRS1999

Waterproof Silicone Coatings of Thermal Insulation and Vaporization Method

Thermal insulation composed of porous ceramic material can be waterproofed by producing a thin silicone film on the surface of the insulation by exposing it to volatile silicone precursors at ambient conditions. When the silicone precursor reactants are multi-functional siloxanes or silanes containing alkenes or alkynes carbon groups higher molecular weight films can be produced. Catalyst are usually required for the silicone precursors to react at room temperature to form the films. The catalyst are particularly useful in the single component system e.g. dimethylethoxysilane (DNMS) to accelerate the reaction and decrease the time to waterproof and protect the insulation. In comparison to other methods, the chemical vapor technique assures better control over the quantity and location of the film being deposited on the ceramic insulation to improve the waterproof coating.

Cagliostro, Domenick E.↗

NASA NTRS1979

Thermal insulation protection means

A system for providing thermal insulation for portions of a spacecraft which do not exceed 900 F during ascent or reentry relative to the earth's atmosphere is described. The thermal insulation is formed of relatively large flexible sheets of needled Nomex felt having a flexible waterproof coating. The thickness of the felt is sized to protect against projected temperatures and is attached to the structure by a resin adhesive. Vent holes in the sheets allow ventilation while maintaining waterproofing. The system is heat treated to provide thermal stability.

Dotts, R. L.↗

NASA NTRS2003

Thin Thermal-Insulation Blankets for Very High Temperatures

Choi, Michael K.↗

NASA NTRS2004

Methods of Testing Thermal Insulation and Associated Test Apparatus

The system and method for testing thermal insulation uses a cryostatic insulation tester having a vacuum chamber and a cold mass including a test chamber and upper and lower guard chambers adjacent thereto. The thermal insulation is positioned within the vacuum chamber and adjacent the cold mass. Cryogenic liquid is supplied to the test chamber, upper guard and lower guard to create a first gas layer in an upper portion of the lower guard chamber and a second gas layer in an upper portion of the test chamber. Temperature are sensed within the vacuum chamber to test the thermal insulation.

Fesmire, James E.↗

NASA NTRS2006

Aerogels for Thermal Insulation of Thermoelectric Devices

Silica aerogels have been shown to be attractive for use as thermal-insulation materials for thermoelectric devices. It is desirable to thermally insulate the legs of thermoelectric devices to suppress lateral heat leaks that degrade thermal efficiency. Aerogels offer not only high thermal- insulation effectiveness, but also a combination of other properties that are especially advantageous in thermoelectric- device applications. Aerogels are synthesized by means of sol-gel chemistry, which is ideal for casting insulation into place. As the scale of the devices to be insulated decreases, the castability from liquid solutions becomes increasingly advantageous: By virtue of castability, aerogel insulation can be made to encapsulate devices having any size from macroscopic down to nanoscopic and possibly having complex, three-dimensional shapes. Castable aerogels can permeate voids having characteristic dimensions as small as nanometers. Hence, practically all the void space surrounding the legs of thermoelectric devices could be filled with aerogel insulation, making the insulation highly effective. Because aerogels have the lowest densities of any known solid materials, they would add very little mass to the encapsulated devices. The thermal-conductivity values of aerogels are among the lowest reported for any material, even after taking account of the contributions of convection and radiation (in addition to true thermal conduction) to overall effective thermal conductivities. Even in ambient air, the contribution of convection to effective overall thermal conductivity of an aerogel is extremely low because of the highly tortuous nature of the flow paths through the porous aerogel structure. For applications that involve operating temperatures high enough to give rise to significant amounts of infrared radiation, opacifiers could be added to aerogels to reduce the radiative contributions to overall effective thermal conductivities. One example of an opacifier is carbon black, which absorbs infrared radiation. Another example of an opacifier is micron- sized metal flakes, which reflect infrared radiation. Encapsulation in cast aerogel insulation also can help prolong the operational lifetimes of thermoelectric devices that must operate in vacuum and that contain SiGe or such advanced skutterudite thermoelectric materials as CoSb3 and CeFe3.5Co0.5Sb12. The primary cause of deterioration of most thermoelectric materials is thermal decomposition or sublimation (e.g., sublimation of Sb from CoSb3) at typical high operating temperatures. Aerogel present near the surface of CoSb3 can impede the outward transport of Sb vapor by establishing a highly localized, equilibrium Sb vapor atmosphere at the surface of the CoSb3.

Sakamoto, Jeffrey↗

NASA NTRS2008

Hybrid Multifoil Aerogel Thermal Insulation

This innovation blends the merits of multifoil insulation (MFI) with aerogel-based insulation to develop a highly versatile, ultra-low thermally conductive material called hybrid multifoil aerogel thermal insulation (HyMATI). The density of the opacified aerogel is 240 mg/cm3 and has thermal conductivity in the 20 mW/mK range in high vacuum and 25 mW/mK in 1 atmosphere of gas (such as argon) up to 800 C. It is stable up to 1,000 C. This is equal to commercially available high-temperature thermal insulation. The thermal conductivity of the aerogel is 36 percent lower compared to several commercially available insulations when tested in 1 atmosphere of argon gas up to 800 C.

Sakamoto, Jeffrey↗

NASA NTRS1984

Thermal Insulation

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.

Source record↗

NASA NTRS2003

Thermal insulating conformal blanket

The conformal thermal insulating blanket may have generally rigid batting material covered by an outer insulating layer formed of a high temperature resistant woven ceramic material and an inner insulating layer formed of a woven ceramic fiber material. The batting and insulating layers may be fastened together by sewing or stitching using an outer mold layer thread fabricated of a high temperature resistant material and an inner mold layer thread of a ceramic fiber material. The batting may be formed to a composite structure that may have a firmness factor sufficient to inhibit a pillowing effect after the stitching to not more than 0.03 inch. The outer insulating layer and an upper portion of the batting adjacent the outer insulating layer may be impregnated with a ceramic coating material.

Barney, Andrea↗

NASA NTRS2009

Improved Aerogel Vacuum Thermal Insulation

An improved design concept for aerogel vacuum thermal-insulation panels calls for multiple layers of aerogel sandwiched between layers of aluminized Mylar (or equivalent) poly(ethylene terephthalate), as depicted in the figure. This concept is applicable to both the rigid (brick) form and the flexible (blanket) form of aerogel vacuum thermal-insulation panels. Heretofore, the fabrication of a typical aerogel vacuum insulating panel has involved encapsulation of a single layer of aerogel in poly(ethylene terephthalate) and pumping of gases out of the aerogel-filled volume. A multilayer panel according to the improved design concept is fabricated in basically the same way: Multiple alternating layers of aerogel and aluminized poly(ethylene terephthalate) are assembled, then encapsulated in an outer layer of poly(ethylene terephthalate), and then the volume containing the multilayer structure is evacuated as in the single-layer case. The multilayer concept makes it possible to reduce effective thermal conductivity of a panel below that of a comparable single-layer panel, without adding weight or incurring other performance penalties. Implementation of the multilayer concept is simple and relatively inexpensive, involving only a few additional fabrication steps to assemble the multiple layers prior to evacuation. For a panel of the blanket type, the multilayer concept, affords the additional advantage of reduced stiffness.

Ruemmele, Warren P.↗

DOE OSTI2025

Advancing the Understanding of Snow Accumulation, Melting, and Associated Thermal Insulation Using Spatially Dense Snow Depth and Temperature Time Series

Snow thermal insulation is a critical factor influencing ground thermal dynamics and associated biogeochemical processes. We analyzed the spatiotemporal variability of snow accumulation, melting, and thermal insulation dynamics using spatially dense, collocated snow depth and ground interface temperature time series over two consecutive years. We demonstrated that considering late‐winter snow depth alone was insufficient to fully capture the complexity in snow and insulation dynamics. The influence of vegetation and topography on snow depth distribution varied over the season, across sites and years. We found that deep snow with a long melting period had a substantial impact on thawing n‐factors. To better predict snow insulation effects, we proposed a new weighted snow depth metric that integrates mean daily snow depth and air temperature throughout the cold season. Our results provide insights for developing space‐time remote sensing products and evaluating the representation of snow and permafrost processes in Earth system models.

54 ENVIRONMENTAL SCIENCES↗