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The lowest-density silica nanofoam weighs 1,000 g/m 3, [59] which is the evacuated version of the record-aerogel of 1,900 g/m 3. [60] The density of air is 1,200 g/m 3 (at 20 °C and 1 atm). [61] The silica solidifies into three-dimensional, intertwined clusters that make up only 3% of the volume. Conduction through the solid is therefore very low.
Typical R-values are given for various materials and structures as approximations based on the average of available figures and are sorted by lowest value. R-value at 1 m gives R-values normalised to a 1 metre (3 ft 3 in) thickness and sorts by median value of the range.
The R-value is the building industry term [3] for thermal resistance "per unit area." [4] It is sometimes denoted RSI-value if the SI units are used. [5] An R-value can be given for a material (e.g., for polyethylene foam), or for an assembly of materials (e.g., a wall or a window). In the case of materials, it is often expressed in terms of R ...
Based on a typical k-value of 0.007 W/(m·K), the R-value of a typical 25-millimetre-thick (1 in) VIP would be 3.5 m 2 ·K/W (20 h·ft 2 ·°F/BTU). To provide the same R-value, 154 millimetres (6 in) of rockwool or 84 millimetres (3 in) of rigid polyurethane foam panel would be required.
The effectiveness of bulk insulation is commonly evaluated by its R-value, of which there are two – metric (SI) (with unit K⋅W −1 ⋅m 2) and US customary (with unit °F⋅ft 2 ⋅h/BTU), the former being 0.176 times the latter numerically, or the reciprocal quantity the thermal conductivity or U-value W⋅K −1 ⋅m −2.
Boron nitride aerogel is an aerogel made of highly porous boron nitride (BN). It typically consists of a mixture of deformed boron nitride nanotubes and nanosheets . It can have a density as low as 0.6 mg/cm 3 and a specific surface area as high as 1050 m 2 /g, and therefore has potential applications as an absorbent , catalyst support and gas ...
SEAgel (Safe Emulsion Agar gel) is one of a class of high-tech foam materials known as aerogels.It is an excellent thermal insulator and among the least dense solids known. . SEAgel was invented by Robert Morrison at the Lawrence Livermore National Laboratory in 19
Note that the especially high molar values, as for paraffin, gasoline, water and ammonia, result from calculating specific heats in terms of moles of molecules. If specific heat is expressed per mole of atoms for these substances, none of the constant-volume values exceed, to any large extent, the theoretical Dulong–Petit limit of 25 J⋅mol ...