Thermal emittance coating for x-ray tube target

Claim 2

An x-ray tube anode comprising a refractory metal target with a surface region for being impinged by electrons to produce X radiation and a coating distinct from said region for enhancing the thermal emittance of said target, said coating consisting a fused metal oxide ceramic having a minimum melting point at approximately 1580° C. and fused at no greater then approximately 1750° C. so that an adherent coating is retained during anode operation, said fused metal oxide ceramic consisting essentially of Al 2 O 3 , ZrO 2 , and TiO 2 , except for incidental impurities.

Claim 3

The anode of claim 1 wherein the refractory metal target is a molybdenum alloy.

Claim 4

The anode of claim 1 wherein the refractory metal target is a tungsten alloy.

Claim 5

The anode of claim 1 wherein the refractory metal target is of composite construction having a refractory metal layer physically supported on a refractory substrate exhibiting greater thermal conductance.

Claim 6

The anode of claim 1 wherein the surface region of the refractory metal target coated with the metal oxide ceramic is roughened before coating.

Claim 7

The anode of claim 1 wherein the metal oxide ceramic comprises the composition within perimeter ABCDEF of FIG. 1.

Claim 8

The anode of claim 6 wherein the metal oxide ceramic consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight percent up to about 40 weight percent ZrO 2 and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidental impurities.

Claim 9

The anode of claim 7 wherein the metal oxide ceramic consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 and approximately 10 weight percent Al 2 O 3 , except for incidental impurities.

Claim 10

An x-ray tube anode comprising a refractory metal target with a surface region for being impinged by electrons to produce X radiation and a coating distinct from said region for enhancing thermal emittance of said target, said coating resulting from fusion in situ at a pressure of 10 -5 Torr or lower and at a temperature no greater than approximately 1750° C. a metal oxide physical mixture consisting essentially of Al 2 O 3 , ZrO 2 and TiO 2 to produce a metal oxide ceramic exhibiting a minimum melting point of approximately 1580°C. which retains adherence to the coated anode during anode operation.

Claim 11

An x-ray tube anode comprising a refractory metal target with a surface region for being impinged by electrons to produce X radiation and a coating distinct from said region for enhancing thermal emittance of said target, said coating resulting from fusion in situ at a pressure of 10 -5 Torr or lower and at a temperature no greater than approximately 1750° C. a metal oxide physical mixture consisting essentially of Al 2 O 3 , ZrO 2 and TiO 2 to produce a metal oxide ceramic exhibiting a minimum melting point of approximately 1580°C. which retains adherence to the coated anode during anode operation.

Claim 12

The anode of claim 9 wherein the metal oxide ceramic consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight up to about 40 weight percent ZrO 2 , and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidental impurities.

Claim 13

The anode of claim 10 wherein the metal oxide ceramic consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 , and approximately 10 weight percent Al 2 O 3 , except for incidental impurities.

Claim 14

A coating for enhancing thermal emittance of a refractory metal article to which said coating is applied, said coating comprising the fused product of heating a metal oxide physical mixture consisting essentially of TiO 2 , ZrO 2 , and Al 2 O 3 , except for incidental impurities to an elevated temperature no greater than approximately 1750° C. for a sufficient time period to fuse said mixture and provide a metal oxide ceramic with a minimum melting point of approximately 1580° C. which retains adherence to the coated refractory metal article when heated to elevated temperatures.

Claim 15

A coating for enhancing thermal emittance of a refractory metal article to which said coating is applied, said coating comprising the fused product of heating a metal oxide physical mixture consisting essentially of TiO 2 , ZrO 2 , and Al 2 O 3 , except for incidental impurities to an elevated temperature no greater than approximately 1750° C. for a sufficient time period to fuse said mixture and provide a metal oxide ceramic with a minimum melting point of approximately 1580° C. which retains adherence to the coated refractory metal article when heated to elevated temperatures.

Claim 16

A coating as in claim 12 wherein the metal oxide ceramic consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight percent up to about 40 weight percent ZrO 2 , and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidential impurities.

Claim 17

A coating as in claim 13 wherein the metal oxide ceramic consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 , and approximately 10 weight percent Al 2 O 3 , except for incidental purities.

Claim 18

A coating as in claim 12 wherein said metal oxide physical mixture is first deposited on the surface of said article by plasma spraying in an inert atmosphere to produce an unfused product and thereafter fused at a temperature no greater than approximately 1750° C. in a vacuum atmosphere of 10 -5 Torr or lower.

Claim 19

A coating as in claim 15 wherein said article being coated is a refractory metal x-ray tube anode.

Claim 20

A coating as in claim 16 wherein the surface of said refractory metal x-ray tube anode being coated is roughened before coating.

Claim 23

A method as in claim 18 wherein said metal oxide mixture consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight percent up to about 40 weight percent ZrO 2 , and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidental impurities.

Claim 24

A method as in claim 19 wherein said metal oxide mixture consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 , and approximately 10 weight percent Al 2 O 3 , except for incidental impurities.

Claim 25

A method as in claim 18 wherein said refractory metal x-ray tube anode surface being coated is roughened before coating.

Claim 26

A method as in claim 21 wherein the roughening of said refractory metal x-ray tube anode surface is achieved by sandblasting.

Claim 27

A method as in claim 18 wherein said metal oxide mixture is deposited on the x-ray tube anode surface by spraying with a plasma gun.

Claim 28

An improved rotating anode x-ray tube construction comprising: (a) a sealed evacuated glass envelope incorporating cathode and anode structural assemblies to generate X radiation within said glass envelope, (b) said cathode structural assembly including an electron emissive filament operatively associated with means to focus an electron beam generated by said filament upon the anode structural assembly, (c) said anode structural assembly including a refractory metal target for impingement of said electron beam thereon to produce X radiation, and (d) further structural means disposed within said glass envelope to cause relative rotation between said cathode assembly and refractory metal target, wherein the improvement comprises providing a surface coating from the region impinged by said electron beam to enhance the thermal emittance from said target, said surface coating consisting of a fused metal oxide ceramic having a minimum melting point of approximately 1580° C. and fused at no greater than approximately 1750° C. so that an adherent coating is retained during operation of the refractory metal target, said fused metal oxide ceramic consisting essentially of TiO 2 , ZrO 2 and Al 2 O 3 , except for incidental impurities.

Claim 29

An improved rotating anode x-ray tube construction comprising: (a) a sealed evacuated glass envelope incorporating cathode and anode structural assemblies to generate X radiation within said glass envelope, (b) said cathode structural assembly including an electron emissive filament operatively associated with means to focus an electron beam generated by said filament upon the anode structural assembly, (c) said anode structural assembly including a refractory metal target for impingement of said electron beam thereon to produce X radiation, and (d) further structural means disposed within said glass envelope to cause relative rotation between said cathode assembly and refractory metal target, wherein the improvement comprises providing a surface coating from the region impinged by said electron beam to enhance the thermal emittance from said target, said surface coating consisting of a fused metal oxide ceramic having a minimum melting point of approximately 1580° C. and fused at no greater than approximately 1750° C. so that an adherent coating is retained during operation of the refractory metal target, said fused metal oxide ceramic consisting essentially of TiO 2 , ZrO 2 and Al 2 O 3 , except for incidental impurities.

Claim 30

A rotating anode x-ray tube as in claim 24 wherein the cathode assembly remains stationary during tube operation and the anode assembly rotates with respect thereto.

Claim 31

A rotating anode x-ray tube as in claim 24 wherein the fused metal oxide ceramic consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight percent up to about 40 weight percent ZrO w , and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidental impurities.

Claim 32

A rotating anode x-ray tube as in claim 24 wherein the fused metal oxide ceramic consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 , and approximately 10 weight percent Al 2 O 3 , except for incidental impurities.

Claim 33

A rotating anode x-ray tube as in claim 26 wherein said coating results from fusing in situ at a pressure of 10 -5 Torr or lower and at a temperature no greater than approximately 1750° C. a metal oxide physical mixture consisting essentially of TiO 2 , ZrO 2 and Al 2 O 3 , except for incidental impurities, wherein said metal oxide ceramic further exhibits a minimum melting point of approximately 1580° C. and remains adherent to the refractory metal target during operation.

Claim 34

In a radiographic imaging system utilizing a rotating anode x-ray tube, a scintillator body to convert the x-rays to an optical image, and photodetection means coupled thereto for converting said optical image to an electronic display thereof, the improvement wherein the anode of said x-ray tube comprises a refractory metal target with a surface region for impingement of electrons thereon to produce X radiation and a coating distinct from said region for enhancing the thermal emittance of said target, the improvement wherein said coating consists of a fused metal oxide ceramic having a minimum melting point of approximately 1580° C. and fused at no greater than approximately 1750° C. so as to remain adherent to the refractory metal target during operation, said fused metal oxide ceramic consisting essentially of TiO 2 , ZrO 2 and Al 2 O 3 , except for incidental impurities.

Claim 35

In a radiographic imaging system utilizing a rotating anode x-ray tube, a scintillator body to convert the x-rays to an optical image, and photodetection means coupled thereto for converting said optical image to an electronic display thereof, the improvement wherein the anode of said x-ray tube comprises a refractory metal target with a surface region for impingement of electrons thereon to produce X radiation and a coating distinct from said region for enhancing the thermal emittance of said target, the improvement wherein said coating consists of a fused metal oxide ceramic having a minimum melting point of approximately 1580° C. and fused at no greater than approximately 1750° C. so as to remain adherent to the refractory metal target during operation, said fused metal oxide ceramic consisting essentially of TiO 2 , ZrO 2 and Al 2 O 3 , except for incidental impurities.

Claim 36

A radiographic imaging system as in claim 29 wherein the fused metal oxide ceramic consists essentially of from about 40 weight percent up to about 70 weight percent TiO 2 , from about 20 weight percent up to about 40 weight percent ZrO 2 , and from about 10 weight percent up to about 20 weight percent Al 2 O 3 , except for incidental impurities.

Claim 37

A radiographic imaging system as in claim 30 wherein the fused metal oxide ceramic consists essentially of approximately 50 weight percent TiO 2 , approximately 40 weight percent ZrO 2 and approximately 10 weight percent Al 2 O 3 , except for incidental impurities.

Claim 38

A radiographic imaging system as in claim 29 which further includes means for digital recording of said optical image.

Claim 39

A radiographic imaging system as in claim 29 which further includes digital processing means to enhance the quality of said optical image.