Glass-to-metal joint for a solar receiver

Abstract

A glass-to-metal sealing device of a solar receiver has a metal collar and a glass cylinder to be sealed together. The glass cylinder is made of a borosilicate glass having a coefficient of thermal expansion within the range of [3.1, 3.5]·10 −6 ° C. −1 in a temperature range of [50, 450]° C. The metal collar s made of an austenitic alloy having a coefficient of thermal expansion in the range of [3.5, 6.0]·10 −6 ° C. −1 in the temperature range of [50, 450]° C. The end portion of the metal collar is beveled so as to increase its mechanical flexibility and, further, the end portion of the metal collar is processed via a thermal treatment in order to establish a bond between the metal and the glass surfaces.

1 - 12 . (canceled) 
     
     
         13 . A glass-to-metal sealing device of a solar receiver, the device comprising:
 a metal collar and a glass cylinder to be sealed to one another;   said glass cylinder being formed of a borosilicate glass having a coefficient of thermal expansion in a range of [3.1, 3.5] 10 −6 ° C. −1  in a temperature range of [50, 450]° C.;   said metal collar being formed of an austenitic alloy having a coefficient of thermal expansion in a range of [3.5, 6.0] 10 −6 ° C. −1  in the temperature range of [50, 450]° C.;   said metal collar having a beveled end portion for increasing a mechanical flexibility thereof; and   said end portion of said metal collar being processed via a thermal treatment in order to establish a bond between the metal of said metal collar and glass surfaces of said class cylinder.   
     
     
         14 . The glass-to-metal sealing device according to  claim 13 , wherein said beveled end portion of said metal collar is defined by longitudinal sections having a trapezoidal shape with a minor base at a free end of said metal collar. 
     
     
         15 . The glass-to-metal sealing device according to  claim 14 , wherein a ratio between a length of the minor base and a length of a major base of the trapezoidal shape is greater than 0.25. 
     
     
         16 . The glass-to-metal sealing device according to  claim 15 , wherein the length of the major base lies in a range of [0.3, 0.6] mm and the length of the minor base lies in a range of [0.15, 0.3] mm. 
     
     
         17 . The glass-to-metal sealing device according to  claim 14 , wherein lateral sides (L1, L2) of the trapezoidal shape enclose an angle in a range of [0.5, 10] degrees. 
     
     
         18 . The glass-to-metal sealing device according to  claim 13 , wherein said austenitic alloy of said metal collar has a concentration of nickel and cobalt contents to satisfy an ASTM F15/DIN 17745 norm. 
     
     
         19 . The glass-to-metal sealing device according to  claim 13 , wherein the thermal treatment processing said end portion of said metal collar is an oxidation treatment generating on the metal surface a glass-dedicated oxide layer. 
     
     
         20 . The glass-to-metal sealing device according to  claim 19 , wherein the glass-dedicated oxide layer has a thickness spanning a range of [0.3, 3.0] μm and a penetration in a metal matrix in a range of [1.5,18.0] μm. 
     
     
         21 . The glass-to-metal sealing device according to  claim 20 , wherein the glass-dedicated oxide is an iron oxide. 
     
     
         22 . The glass-to-metal sealing device according to  claim 21 , wherein the iron oxide is selected from the group consisting of FeO, Fe 3 C 4 , and a mixture of FeO and Fe 3 C 4 . 
     
     
         23 . A method of producing a glass-to-metal sealing device of a solar receiver, the device including a metal collar and a glass cylinder to be sealed together, the method comprising the following steps:
 a) providing, as a glass for the glass cylinder, a borosilicate glass having a coefficient of thermal expansion in a range of [3.1, 3.5] 10 −6 ° C. −1  in a temperature range of [50, 450]° C.;   b) providing, as a metal of the metal collar, an austenitic alloy having a coefficient of thermal expansion in a range of [3.5, 6.0] 10 −6 ° C. −1  in the temperature range of [50, 450]° C.;   c) beveling an end portion of the metal collar so as to increase a mechanical flexibility thereof;   d) processing the end portion of the metal collar via a thermal treatment for establishing a bond between the metal and glass surfaces; and   e) sealing together the end collar portions of the glass cylinder and the metal collar.   
     
     
         24 . A tubular solar receiver, comprising an outer glass tube and an inner metal tube connected to one another via the glass-to-metal sealing device according to  claim 13 .