X-RAY AND GAMMA-RAY SHIELDING GLASS

Abstract

An X-ray and gamma-ray shielding glass, including the following components in weight-%: 10-35% SiO.sub.2; 60-70% PbO; 0-8% B.sub.2O.sub.3; 0-10% Al.sub.2O.sub.3; 0-10% Na.sub.2O; 0-10% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0-2% Sb.sub.2O.sub.3; 0-6% BaO; and 0.05-2% ZrO.sub.2.

Claims

1. An X-ray and gamma-ray shielding glass, comprising the following components in weight-%: 10-35% SiO.sub.2; 60-70% Pb0; 0-8% B.sub.2O.sub.3; 0-10% Al.sub.2O.sub.3; 0-10% Na.sub.2O; 0-10% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0-2% Sb.sub.2O.sub.3; 0-6% BaO; and 0.05-2% ZrO.sub.2.

2. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass includes the following composition in weight-%: 20-30% SiO.sub.2; 60-67% PbO; 1-5% B.sub.2O.sub.3; 0% Al.sub.2O.sub.3; 0.05-2% Na.sub.2O; 0.1-3% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0.1-0.5% Sb.sub.2O.sub.3; 0% BaO; and 0.1-2% ZrO.sub.2.

3. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass includes the following composition in weight-%: 20-30% SiO.sub.2; 60-65% PbO; 1.5-2.5% B.sub.2O.sub.3; 0-3% Al.sub.2O.sub.3; 05-2% Na.sub.2O; 1-3% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0.1-0.5% Sb.sub.2O.sub.3; 0% BaO; and 0.5-2% ZrO.sub.2.

4. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass includes the following composition in weight-%: 20-30% SiO.sub.2; 60-65% PbO; 1.55-2.5% B.sub.2O.sub.3; 0% Al.sub.2O.sub.3; 0.05-2% Na.sub.2O; 0.1-3% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0.1-0.5% Sb.sub.2O.sub.3; 0% BaO; and 1-2% ZrO.sub.2.

5. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass is BaO-free, except for contaminants.

6. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass also includes at least one of 1-8 weight-% B.sub.2O.sub.3, 0.5-6 weight-% B.sub.2O.sub.3, and 1-5 weight-% B.sub.2O.sub.3.

7. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein the composition is selected so that a kinetic of crystallization dØ/dt is at least one of less than 0.2 μm/min., less than 0.1 μm/min., less than 0.05 μm/min., and less than 0.02 μm/min.

8. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein except for contaminants, the glass does not contain at least one of SrO and MgO.

9. The X-ray and gamma-ray shielding glass composition according to claim 1, wherein said glass includes the following composition in weight-%: 25-35% SiO.sub.2; 60-70% PbO; 0.5-2% Na.sub.2O; 0.5-3% K.sub.2O; 0,5-0,75% Sb.sub.2O.sub.3; 0.5-5% ZrO.sub.2; and 0-5% BaO; and in that except for contaminants, the composition is free of B.sub.2O.sub.3, SrO, As.sub.2O.sub.3.

10. A glass plate, comprising the following components in weight-%: 10-35% SiO.sub.2; 60-70% PbO; 0-8% B.sub.2O.sub.3; 0-10% Al.sub.2O.sub.3; 0-10% Na.sub.2O; 0-10% K.sub.2O; 0-0.3% As.sub.2O.sub.3; 0-2% Sb.sub.2O.sub.3; 0-6% BaO; and 0.05-2% ZrO.sub.2, wherein the glass plate has a thickness in the rage of 5 μm to 50 mm.

11. The glass plate according to claim 10, wherein said thickness is in the range of 25 μm to 20 mm.

12. The glass plate according to claim 10, wherein said thickness is in the range of 0.8 mm to 10 mm.

13. The glass plate according to claim 10, wherein at a thickness of 10 mm and a wavelength of 400 nm, the glass plate has a transmission which is at least one of >50%, >70%, >75%, and >80%.

14. The glass plate according to claim 13, wherein at a thickness of 10 mm and a wavelength of 400 nm, the glass plate has a transmission in the range of 75% to 90%.

15. A method to produce gamma-ray shielding glass plates, wherein the method comprises the following steps: providing a glass composition including the following components in weight-%: 10-35% SiO.sub.2, 60-70% PbO, 0-8% B.sub.2O.sub.3, 0-10% Al.sub.2O.sub.3, 0-10% Na.sub.2O, 0-10% K.sub.2O, 0-0.3% As.sub.2O.sub.3, 0-2% Sb.sub.2O.sub.3, 0-6% BaO, and 0.05-2% ZrO.sub.2; drawing a glass ribbon with a thickness in the range of 0.8 mm to 20 mm upwards from a melt against gravitational force, guiding the glass ribbon by a plurality of rolls; running the glass ribbon through a cooling section; and cutting the glass ribbon into glass plates.

16. The method according to claim 15, wherein said thickness of the glass ribbon is in the range of 0.8 mm to 10 mm.

17. A method to produce gamma-ray shielding glass plates, wherein the method comprises the following steps: providing a glass composition including the following components in weight-%: 10-35% SiO.sub.2, 60-70% PbO, 0-8% B.sub.2O.sub.3, 0-10% AlO.sub.3, 0-10% Na.sub.2O, 0-10% K.sub.2O, 0-0.3% As.sub.2O.sub.3, 0-2% Sb.sub.2O.sub.3, 0-6% BaO, and 0.05-2% ZrO.sub.2; drawing a glass ribbon with a thickness in the range of 25 μm-1.1 mm downwards from a melt with the gravitational force, guiding the glass ribbon by a plurality of rolls; running the glass ribbon through a cooling section; and cutting the glass ribbon into glass plates.

18. The method according to claim 15, wherein the method is performed so that a kinetic of crystallization of the glass composition dØ/dt is at least one of less than 0.3 μm/min., less than 0.2 μm/min., less than 0.1 μm/min., less than 0.05 μm/min., and less than 0.02 μm/min.

19. The method according to claim 17, wherein the method is performed so that a kinetic of crystallization of the glass composition dØ/dt is at least one of less than 0.3 μm/min., less than 0.2 μm/min., less than 0.1 μm/min., less than 0.05 μm/min., and less than 0.02 μm/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0071] FIG. 1 illustrates a device for determining the crystallization kinetic;

[0072] FIG. 2a illustrates the behavior of the crystallization kinetic dØ/dt in μm/min. relative to temperature, that correlates with the viscosity in dPa.Math.s for glass per example 1 in Table 1, whereby the abscissa is logarithmically divided;

[0073] FIG. 2b illustrates the behavior of the crystallization kinetic dØ/dt in μm/min. relative to temperature, that correlates with the viscosity in dPa.Math.s for a glass according to comparative example 1 in Table 1, whereby the abscissa is logarithmically divided; and

[0074] FIG. 3 illustrates a device for an up-draw-process.

[0075] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrates embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0076] For two embodiments with a ZrO.sub.2 content of 1 weight-% according to the invention, the increased resistance to a weight loss due to the influence of an aqueous solution according to DIN ISO 695 is shown below in comparison with comparative examples. To demonstrate the resistance, the surface weight loss, the so-called surface ablation in mg/100 cm.sup.2 is determined by three-hour cooking in a mixture of same volume shares of a sodium hydroxide solution of 1 mol/l and sodium-carbonate solution with a concentration of 0.5 mol/l.

[0077] A first composition of a glass according to the invention includes: [0078] 4.29 weight-% BaO [0079] 0.55 weight-% K.sub.2O [0080] 0.06 weight-% Na.sub.2O [0081] 65.68 weight-% PbO [0082] 0.28 weight-% Sb.sub.2O.sub.3 [0083] 28.12 weight-% SiO.sub.2 [0084] 1.02 weight-% ZrO.sub.2

[0085] For this, a value of 240 mg/100 cm.sup.2 surface ablation is measured according to ISO DIN 695.

[0086] An alternative composition of a glass according to the invention includes: [0087] 2.46 weight-% B.sub.2O.sub.3 [0088] 2.52 weight-% K.sub.2O [0089] 1.48 weight-% Na.sub.2O [0090] 60.67 weight-% PbO [0091] 0.25 weight-% Sb.sub.2O.sub.3 [0092] 31.32 weight-% SiO.sub.2 [0093] 1.00 weight-% ZrO.sub.2

[0094] This alternative glass has a value for the surface ablation of 291 mg/100 cm.sup.2 (according to ISO DIN 695). Because of the low crystallization tendency, the alternative glass can be drawn in the up-draw as well as in the down-draw process.

[0095] Moreover, the glass according to example 1, as well as the glass according to example 2 has a high transmission of more than 75% at 400 nm wavelength and a plate thickness of 10 mm.

[0096] In contrast to above glasses, the comparative glasses have a ZrO.sub.2-content of 0 weight-%. For these glasses without ZrO.sub.2, the weight loss at 591 mg/100 cm.sup.2 or 564 mg/100 cm.sup.2 respectively is almost twice as high as for the inventive glasses with a ZrO.sub.2 content of 1 weight-%. As can be seen from the comparative examples, the hydrolytic resistance is surprisingly increased by the ZrO.sub.2-content according to the invention. This is also clarified by Table 1 below, when viewing comparative examples 1 and 2.

TABLE-US-00001 TABLE 1 Comparison Comparison Weight-% Example 1 Example 1 Example 2 Example 2 Example 3 Example 4 B.sub.2O.sub.3 0 2.49 2.46 2.46 2.07 1.89 Al.sub.2O.sub.3 0 0 0 1 0 0 BaO 4.29 0 0 0 0 0 K.sub.2O 0.55 2.54 2.52 2.52 2.12 1.94 Na.sub.2O 0.06 1.49 1.48 1.48 1.24 1.14 PbO 6.68 61.29 60.67 60.68 66.96 69.74 Sb.sub.2O.sub.3 0.28 0.25 0.25 0.25 0.21 0.19 SiO.sub.2 28.12 31.94 31.62 31.62 26.56 24.33 ZrO.sub.2 1.02 0 1 0 0.84 0.77 Σ: 100 100 100 100 100 100 Alkaline solution A3 A3 A3 A3 — — DIN ISO 695 class Resistance per DIN ISO 695 240 591 291 564 — — weight loss mg/100 cm.sup.2 Transmission (thickness = 10 mm) 0.802 0.847 0.821 0.825 0.798 0.7507 λ = 400 nm: Max dØ/dt μm/min. (log(η) 0.250 (4.87) 0.015 (7.17) — (—) — (—) 0.011 (4.84) 0.061 (5.41) log (dPa .Math. s)) (retention time = 16 hrs.)

[0097] The lye class of the alkali resistance according to ISO 695 is stated in Table 1 for example 1 and example 2, as well as for the comparison examples, as well as the resistance according to ISO 695 against a weight loss in mg/100 cm.sup.2. As can be seen in Table 1, the weight loss for example 1 and example 2 is only half as great than that of the comparison examples. This is due to the ZrO.sup.2 content in the glass compositions. It is further shown in the Table that the transmission of a 10 mm thick plate and a wavelength of λ=400 nm is greater than 75%. In current example 2 a transmission of 0.82 is achieved. Moreover, the maximum crystallization rate dØ/dt is specified in Table 1 for the various glass compositions. The specified value specifies herein the crystallization rate in μm/min after 16 hours. Also, stated, in parenthesis after the crystallization rate is the viscosity of the melt in log(dPa.Math.s). As can be seen in Table 1, in example 1 that contains BaO, the crystallization rate is very high at a viscosity of log η=4.87 log(dPa.Math.s). The high crystallization rate calls for a rapid formation of crystals in a glass according to example 1, with 4.29 weight-% BaO, resulting in that the glass is difficult to produce. A glass of this type can be produced through casting, since a draw process of such glass compositions is eliminated.

[0098] Also specified are examples 3 and 4 for zirconium based lead glasses according to the invention which are also characterized by a high transmission at 400 nm wavelength. Examples 2 and 3 with a lead content <67 weight-% are also specified. Glasses with a lead content <67 weight-% and a BaO-content of 0 weight-% are characterized by a very low crystallization tendency, resulting in being easy to draw and high transmission.

[0099] FIG. 1 illustrates schematically a device to determine the crystallization kinetic. The device includes a plate 1 with uniformly spaced apart recesses 3. Glass samples 5 are inserted into the recesses and are thermalized at different temperatures for 16 hours in a gradient kiln, contingent upon the arrangement of recesses 5. In FIG. 1 this is identified with Phase 1. After thermalization, glass samples 5 are illuminated with the assistance of a microscope 7 with polarized light and from the measurement with the microscope the average size of the crystals is determined and from this in turn the crystal growth kinetic dØ/dt for each recess temperature. This is identified as Phase 2 in FIG. 1. The measurements are performed in a temperature range between 500° C. and 1000° C. Since in measurements in a gradient kiln can only be performed in a 200° C. wide temperature range, the temperatures are recorded gradually in 200° C. steps.

[0100] FIG. 2a illustrates the crystallization kinetic subject to the viscosity for the glass with the composition from example 1, according to Table 1. The greatest crystallization kinetic dØ/dt results from approximately 0.25 μm/min. at a viscosity η of approximately equal to 10.sup.5 dPa.Math.s (log(η)=5 log(dPa.Math.s). As can be seen in FIG. 2a, the crystallization kinetic in the viscosity range of η=10.sup.5 dPa.Math.s to 10.sup.6.5 dPa.Math.s (respectively log(η)=5 log(dPa.Math.s) and log(η)=6.5(log(dPa.Math.s) that is used for draw processes like the up-draw process is so high that drawing the glass composition is not possible. The reason for this is the high BaO content.

[0101] In contrast to the composition according to example 1, the composition according to example 2 can be produced in a draw process. The reason for this is the presence of B.sub.2O.sub.3 in the composition according to example 2. B.sub.2O.sub.3 lowers the crystallization kinetic drastically so that the glass can be produced in a draw process. This also applies to examples 3 and 4 with a B.sub.2O.sub.3 content of 1 to 3 weight-% B.sub.2O.sub.3 whose crystallization rate is below 0.1 μm/min.

[0102] The draw characteristic of the glass according to the comparison example 1 can be gathered from the crystallization kinetic dØ/dt per FIG. 2b.

[0103] FIG. 2b illustrates the crystallization kinetic subject to the viscosity for the glass with the composition per comparison example 1, according to Table 1. The greatest crystallization kinetic dØ/dt results from approximately 0.015 μm/min. at a viscosity η of approximately equal to 10.sup.7.17 dPa.Math.s (log(η)=7.17 log (dPa.Math.s).

[0104] As can be seen in FIG. 2b, the crystallization kinetic in the viscosity range ofη=10.sup.5 dPa.Math.s to 10.sup.6.5 dPa.Math.s (respectively log(η)=5 log(dPa.Math.s) and log(η)=6.5 log(dPa.Math.s) which is used for draw processes like the up-draw process is practically at 0, so that the glass according to comparison example 1 can be easily drawn in contrast to the glass according to example 1. This is due to the fact that the glass composition is BaO-free with the exception of contaminants. This also applies to the composition according to example 2, which is why this glass can also be drawn easily.

[0105] FIG. 3 illustrates a device for implementation of an up-draw process, for example for a glass composition according to comparison example 1. The melt with the inventive glass composition is identified as 100 and the draw nozzle through which the melt is drawn as 103. Refractory wall of the draw tank is identified as 105. A glass ribbon 107 is guided upwards over rolls 109 and is cooled in a cooling section. The glass ribbon thus drawn in an upward directed draw process, the so-called up-draw process has a thickness in the range of 0.8-20 mm.

[0106] The glass composition according to the present invention offers a glass composition for the first time that is characterized by high hydrolytic resistance, as shown by the examples in contrast to the comparison tests.

[0107] The glasses moreover have a low crystallization tendency and such crystallization kinetic that it is possible to draw such glass compositions—for example without limitation thereto—in an up-draw process into glass ribbons or glass plates having high transmission, for example greater than 75%, for example greater than 80% at 400 nm wavelength and a 10 mm thick plate. The plates produced from the inventive glass compositions moreover are characterized by a high transmission greater than 75%, for example greater than 80% at 400 nm wavelength with 10 mm thick plates.

[0108] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.