Vacuum flask with tin phosphorus oxide sealing glass

Abstract

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.

What is claimed is: 
     
         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.