DE2010683C - Devitrification-resistant borosilicate glass with low intrinsic radioactivity and high permeability up to 350 nm as well as good processability - Google Patents

Description

The invention relates to glass compositions with very low intrinsic radioactivity, the high permeability up to 350 nm and good verjirheitharkeit exhibit.

Such a glass is available in various forms, e.g. B. for pipes. Pistons. Vials, needed, especially for radiochemical work and for the manufacture of radiation measuring devices. The following factors are a prerequisite for the suitability of such a glass:

10

1. Low self-radioactivity,

2. high light transmission in the visible and short-wave range up to 350 nm,

3. good devitrification resistance,

4. good processability, d. H. low toughness, and especially suitability for automatic processing.

The aim of the present invention is a n ^ ° ^a glass composition, which leads to a glass having the aforementioned properties.

This aim is achieved according to the invention with a glass composition which is free of potassium oxide and has the following composition in percent by weight: ^a 5

SiO ₂ 65 to 66%

B ₂ O ₃ 12%

Ai ₂ O ₃ 5%

Na ₂ O 6 to 6.5%, ₀

ZnO 5 to 8%

BaO 3 to 6%

Total ZnO + BaO 11%

Replacing the barium oxide with calcium oxide would lead to somewhat tougher glasses, so that the addition of barium oxide should be given preference. Adding more than 8 percent by weight of zinc oxide worsens the devitrification resistance. The glasses according to the invention have a higher by about 20 x units thermal expansion / have a comparatively known borosilicate glasses that contain no 2wertigen metal oxides and expansion coefficient at 32-10 'C ^0. The toughness of the glasses according to the invention is therefore 115 and 175 ° C. lower in the softening [EW) and processing range [Va) , ie they are significantly softer in terms of processing.

To achieve high light transmission in the short-wave range, the presence of a reducing agent such as sugar or charcoal powder of 0.05 to 0.15 percent by weight in the mixture is advantageous. At the same time, it is necessary to use raw materials that are as pure as possible in order to reduce the UV light transmission through coloring substances such as Fe ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ . CeO ₂ to be kept as low as possible.

An additional introduction of a maximum of 0.30 percent by weight of common salt (NaCl) and 0.20 percent by weight of fluorine (F) as sodium _{silicofluoride (Na 1 SiF 11} ) is suitable for refining this glass, which must be melted without oxidizing agents.

The reducing agent and refining agent components are. as already stated, additionally introduced, see above that they add up to a percentage over 100.

The measurement of the self-radioactivity of the glass can, for. B. with the help of a / J anticoincidence counter (low backgrouiid counter). The device measures // - rays and partly also i \ - and y-rays. The zero rate of the counter with which the measurements were carried out was 0.7 pulses / min.

The glasses according to the invention give pulse rates of 0.1 to 0.4 pulses / min., Which corresponds to a potassium disintegration rate of 0.25 to 0.9 disintegrations / min '· gramrrr ¹ . It is therefore to be addressed as a glass with extremely low self-acitivity.

The fluctuation range of the pulse rates is determined by contamination of the glass raw materials and the ff. B. are contained in potassium oxide (K ¹⁰ ) and can also be contained in barium compounds (those of the uranium series). It is therefore necessary to check the glass raw materials to be used for these disturbing impurities before use. Certain ff.-materials generally used for the melt internals show high radioactive impurities, ie they give high pulse rates. It turned out that not potassium compounds, but uranium and radium compounds and their secondary products are responsible. For the production of a glass with low intrinsic radioactivity, it is therefore also necessary that the ff.-material of the melting units also have a low intrinsic radioactivity.

Example of a preferred composition of the mixture in percent by weight with the physical and chemical property values

SiO ₁ 65.50 ° /,

B _t O ₈ 12.00%

AI ₂ O ₃ 5.00 ° / "

Na ₂ 0 6,50 ° / _o

ZnO 8.00 ° / ₀

BaO 3.00% / ₀

NaCl 0.30%

F 0.20%

Sugar 0.05%

> Purifying agents Reducing agent

total

Weight percent .. 100.55%

.% 10 ⁷ (20 to 300 ° C) / ⁰ C 52

Tg ( ⁰ C); /; - 10 ^{13 6} poise 520

Ew [ ⁰ C); η ~ 10 'Poise 735

Va ( ⁰ C); η ~ W Poise 1090 Density (g / cem) 2.48

7 "tioo (° C); <f = ■ 1 · 10" Ω-cm 200

Crystallization maximum ( ⁰ C) 880

Krist. Maximum speed (μηι / Μίη.) 0.10

Transmission for 1 mm thickness and 35Onm (%)> 90

Pulses / min 0.1 to 0.4 Hydrol. Best, according to DIN 12111 0.014

(1st Class)

Acid resistance according to DIN 12116 2.5

(2nd class)

Lye best. according to DIN 52322 170

(IM. Class)

Embodiment according to the above composition

Required raw material quantities for 100 kg calculated glass:

65.50 kg of sand (Sipur quality). 21.30 kg of boric acid. 7.60 kg alumina hydrate, 11.00 kg soda, 8.00 kg zinc

oxide (quality white seal), 3.90 kg barium carbonate, 0.30 kg table salt. 0.33 kg sodium silicate fluoride, 0.05 kg of sugar.

Melting temperature 1440 to 1460 ° C

Lauteri temperature 1460 to 1480 ³ C

Decay temperature .. 1150 to 1170 ³ C

for Dannerrohrzug and automatic blow molding machine

Cooling temperature 530 to 540 ³ C,

¹ I, up to 2 hours

Claims (2)

Patent claims: 1. Decay-resistant borosilicate glass with low intrinsic radioactivity and high permeability up to 350 .mu.m as well as good processability, characterized in that it is free of potassium oxide and is melted from a mixture calculated on the oxide basis of the following composition in percent by weight: SiO, 65 to 66 "/ ,, B ₂ O ₃ AUO ₃ Well, O ZnO BaO Total ZnO BaO '- la 6 to 5 to 3 to 1 1 ° / ¹ ι / o 6.5 "' 8 ° / n 6 ⁿ / " 2. Glass according to claim 1, characterized in that it is melted from a mixture calculated on the basis of oxide and having the following composition in percent by weight: such as 65.50 "/"
12.00 β / _β B ₂ O ₃ 5.00% Al ₁ O ₃ 6.50 ° / ₀ Na ₂ O 8.00 ° / ₀ ZnO 3.00 ⁰ U BaO 0.30% NaCl 0.20 ° / ₀ FaIsNa ₁ SiF, 0.05 ° / ₀ Sugar