VACUUM FLASK WITH TIN PHOSPHORUS OXIDE SEALING GLASS
Metal-walled vacuum flasks including tin phosphorus oxide sealing glass, and methods of sealing an exhaust aperture for a metal-walled vacuum flask, including disposing a tin phosphorus oxide sealing glass frit adjacent the exhaust aperture, applying a vacuum to the metal-walled vacuum flask; and raising a temperature of the sealing glass frit under the vacuum sufficiently that the sealing glass flows and seals the exhaust aperture.
1 . A method of sealing an exhaust aperture for a metal-walled vacuum flask, comprising:
disposing a sealing glass frit adjacent the exhaust aperture, wherein the sealing glass is a tin phosphorus oxide glass;
applying a vacuum to the metal-walled vacuum flask; and
raising a temperature of the sealing glass frit under the vacuum sufficiently that the sealing glass flows and seals the exhaust aperture.
2 . The method of claim 1 , wherein disposing the tin phosphorus oxide sealing glass frit includes disposing a sealing glass frit including glass having the formula SnO.P 2 O 5 .
3 . The method of claim 1 , wherein disposing the sealing glass frit includes disposing a sealing glass frit that is substantially lead-free.
4 . The method of claim 1 , further comprising loading the metal-walled vacuum flask into a vacuum furnace for heating.
5 . The method of claim 4 , further comprising preheating the vacuum furnace prior to loading the metal-walled vacuum flask into the vacuum furnace.
6 . The method of claim 4 , further comprising preheating the vacuum furnace to at least about 250° C. prior to loading the metal-walled vacuum flask into the vacuum furnace.
7 . The method of claim 1 , wherein raising the temperature of the sealing glass frit includes heating the sealing glass frit to a temperature above the glass transition temperature (T g ) of the sealing glass frit.
8 . The method of claim 7 , further comprising holding the sealing glass at a temperature above the glass transition temperature of the sealing glass for at least about 100 minutes.
9 . The method of claim 7 , wherein raising the temperature of the sealing glass frit includes heating the vacuum furnace to approximately 600° C.
10 . The method of claim 9 , further comprising holding the vacuum furnace at approximately 600° C. for approximately 100 to approximately 120 minutes.
11 . The method of claim 9 , further comprising cooling the vacuum furnace to approximately 270° C.
12 . A metal-walled vacuum flask, comprising
a metal inner bottle and a metal outer bottle;
wherein a neck portion of the inner bottle is connected to a neck portion of the outer bottle to form an enclosed space between the inner bottle and said outer bottle;
wherein the enclosed space is substantially evacuated; and
wherein an aperture in the outer bottle used to evacuate the enclosed space is sealed by a tin phosphorus oxide sealing glass.
13 . A metal-walled vacuum flask having an inner bottle and an outer bottle, prepared by a method comprising:
disposing a sealing glass frit adjacent an exhaust aperture in the outer bottle, wherein the sealing glass is a tin phosphorus oxide glass;
applying a vacuum to the metal-walled flask; and
raising a temperature of the sealing glass frit under a vacuum sufficiently that the sealing glass flows and seals the exhaust aperture.
14 . The metal-walled vacuum flask of claim 13 , wherein disposing the tin phosphorus oxide sealing glass frit includes disposing a sealing glass frit wherein the glass has the formula SnO.P 2 O 5 .
15 . The metal-walled vacuum flask of claim 10 , wherein the vacuum is applied to the metal-walled flask and the temperature of the sealing glass frit is raised above the glass transition temperature (T g ) of the sealing glass frit while the metal-walled flask is disposed in a vacuum furnace.