【発明の詳細な説明】[Detailed description of the invention]
＜産業上の利用分野＞
本発明は天然に大量に存在し、現在あまり多く
は利用されていないシラスをはじめとする火山ガ
ラス質堆積物を有効利用し、負の熱膨張係数を有
するガラスを製造する方法に関し、本発明で得ら
れるガラスは、その粉末を通常の正の熱膨張係数
を有するガラスあるいはセラミツク粉末等と適量
混合し、加熱焼結して無膨張焼結体を得る、又は
それ単味で加熱した際に収縮する事が望まれる部
材を得る等従来のガラスが具備していなかつた新
規な用途に活用出来るものである。
＜従来の技術＞
火山ガラス質堆積物はSiO2を主成分として約
70重量％、その他にAl2O3，Na2O，K2O等を含
む一種のけい酸塩であり、我が国に広く分布して
おり、その利用方法も多く研究されている。例え
ば南九州に広く分布する火山ガラス質堆積物の一
種であるシラスの利用方法の一つとしてガラスへ
の応用があり、特公昭52−17338号公報で示され
る様な方法が提案されている。この特公昭52−
17338号公報で示されるのは、シラスに対して
CaO，ZrO2及びZnOを添加して、耐アルカリ性
に富んだガラスを製造しようとする方法である。
本発明者等も先に、火山ガラス質堆積物に対し
添加する物質の量や熱処理条件を適宜調整する事
で強度が大なるガラスの製造方法を開発、特許出
願をなした（特願昭60−266651号）。
ところでこれらのガラスは全て熱膨張係数は正
であり、熱膨張係数が約80×10-71／℃位の大き
な値を示すガラス程強度が大で、熱膨張係数の大
きさと強度とは正比例する傾向にある事が判つ
た。
しかるに耐熱衝撃性を考慮すれば出来る限り熱
膨張の少ない材料が好ましい為に、強度は大であ
るが熱膨張係数は小あるいは全く熱膨張をしない
という材料があれば好都合である。
＜発明が解決しようとする問題点＞
本発明は強度は大で、熱膨張が小あるいは全く
熱膨張をしない材料の原料としたり、又それ単味
で加熱により収縮する部材として用いる負の熱膨
張係数を有するガラスの製造法を提供する事を目
的とする。
＜問題点を解決する為の手段＞
上記本発明の目的を達成する為の手段は次の如
くである。即ちAl2O3粉末14〜30重量％、Li2O粉
末７〜15重量％、残部火山ガラス質堆積物粉末か
らなる配合の混合粉末を、加熱溶融した後、歪除
去処理を施し、更に550〜800℃の温度下で12〜24
時間再加熱した後徐冷することを特徴とする負の
熱膨張係数を有する結晶化ガラスの製造法であ
る。
上記混合粉末中のAl2O3やLi2Oは、ガラス中に
ユークリプタイト（Li2O・Al2O3・2SiO2）やβ
―スポデユーメン（Li2O・Al2O3・2SiO2）結晶
の生成過程、及びこれらの結晶の相転移時の収縮
性を利用して負の熱膨張係数を有するガラスを得
る為であり、Al2O314重量％未満あるいはLi2O7
重量％未満では必要な量の上記結晶の生成がな
く、一方Al2O3が30重量％を越えると融点が高く
なり過ぎ、又Li2Oが15重量％を越えると融点が
低下し過ぎ結晶が粗大化し得られるガラスの強度
低下が激しいが為に、Al2O3は14〜30重量％、
Li2Ｏは７〜15重量％が望ましい。
又再加熱時の温度及び時間は、後述する実施例
の結果から出来る限り短時間処理でしかも得られ
るガラスの熱膨張係数が負の値となる範囲で選定
した。
＜実施例及び作用＞
以下本発明の実施例を示す。
実施例 １
この実施例は、火山ガラス質堆積物として鹿児
島県吉田町に産する所謂吉田シラスを用いた。そ
の吉田シラスの化学組成を下記第１表に示す。こ
の様な吉田シラスの未水洗品粉末63.56ｇに対し、
市販Al2O3粉末31.61ｇ、市販Li2O11.86ｇを調合
して混合粉末を得た。該混合粉末の化学組成を同
じく下記第１票に示す。
<Industrial Application Field> The present invention effectively utilizes volcanic glassy deposits such as whitebait, which exists in large quantities in nature but is currently not widely used, to produce glass with a negative coefficient of thermal expansion. Regarding the method of producing the glass obtained in the present invention, the powder is mixed with an appropriate amount of glass or ceramic powder having a normal positive coefficient of thermal expansion, and the mixture is heated and sintered to obtain a non-expandable sintered body. It can be used for new applications that conventional glass does not have, such as obtaining a member that is desired to shrink when heated. <Conventional technology> Volcanic glassy deposits are mainly composed of SiO 2 and contain approximately
It is a type of silicate containing 70% by weight, and also contains Al 2 O 3 , Na 2 O, K 2 O, etc., and is widely distributed in Japan, and its usage is being studied extensively. For example, one method of using whitebait, which is a type of volcanic glassy deposit widely distributed in southern Kyushu, is to apply it to glass, and a method as shown in Japanese Patent Publication No. 17338/1983 has been proposed. This special public service, Showa 52-
What is shown in Publication No. 17338 is for whitebait
This method attempts to produce glass with high alkali resistance by adding CaO, ZrO 2 and ZnO. The present inventors have also previously developed a method for manufacturing glass with increased strength by appropriately adjusting the amount of substances added to volcanic glassy deposits and heat treatment conditions, and filed a patent application (Patent Application No. 1983). −266651). By the way, all of these glasses have positive thermal expansion coefficients, and the glass with a larger thermal expansion coefficient of about 80 x 10 -7 1/°C has higher strength, and the size of the thermal expansion coefficient and strength are directly proportional. It has been found that there is a tendency to However, considering thermal shock resistance, it is preferable to use a material with as little thermal expansion as possible, so it would be advantageous to have a material that has high strength but has a small coefficient of thermal expansion or no thermal expansion at all. <Problems to be Solved by the Invention> The present invention can be used as a raw material for materials that have high strength and have little or no thermal expansion, or can be used as a material that shrinks when heated. The purpose of this invention is to provide a method for manufacturing glass having a coefficient of coefficient. <Means for solving the problems> The means for achieving the above object of the present invention are as follows. That is, a mixed powder with a composition of 14 to 30% by weight of Al 2 O 3 powder, 7 to 15% by weight of Li 2 O powder, and the remainder volcanic glassy deposit powder is heated and melted, then subjected to strain removal treatment, and further heated to 550% by weight. 12-24 under the temperature of ~800℃
This is a method for producing crystallized glass having a negative coefficient of thermal expansion, which is characterized by reheating for a period of time and then slowly cooling. Al 2 O 3 and Li 2 O in the above mixed powder are eucryptite (Li 2 O・Al 2 O 3・2SiO 2 ) and β
- This is to obtain glass with a negative coefficient of thermal expansion by utilizing the formation process of spodumene (Li 2 O・Al 2 O 3・2SiO 2 ) crystals and the shrinkage properties of these crystals during phase transition. 2 O 3 less than 14% by weight or Li 2 O7
If Al 2 O 3 is less than 30% by weight, the melting point will be too high, and if Li 2 O is more than 15% by weight, the melting point will be too low and crystals will not form. Al 2 O 3 is 14 to 30% by weight because the glass becomes coarse and the strength of the resulting glass is severely reduced.
The content of Li 2 O is preferably 7 to 15% by weight. Further, the temperature and time during reheating were selected from the results of the examples described later in such a range that the treatment was as short as possible and the thermal expansion coefficient of the glass obtained was a negative value. <Examples and effects> Examples of the present invention will be shown below. Example 1 In this example, so-called Yoshida shirasu produced in Yoshida-cho, Kagoshima Prefecture as a volcanic glassy deposit was used. The chemical composition of Yoshida whitebait is shown in Table 1 below. For 63.56g of unwashed powder of Yoshida whitebait,
A mixed powder was obtained by blending 31.61 g of commercially available Al 2 O 3 powder and 11.86 g of commercially available Li 2 O. The chemical composition of the mixed powder is also shown in Sheet 1 below.
【表】
なお上記混合粉末は、吉田シラス59.39重量％、
Al2O329.53重量％、Li2O11.08重量％の組合せと
なる。
この様な組成の混合粉末を、白金皿に入れ電気
炉内で1600℃，１時間加熱溶融しカレツトを造
り、該カレツトを74ｍ以下に粉枠し、再び白金皿
に入れ電気炉内で1600℃，１時間加熱溶融した後
歪除去処理を行つた。この歪除去処理は、上記電
気炉とは別の予め500℃に保持した炉内に収納さ
れたステンレス容器内にコークス粉を入れ、該コ
ークス粉の中にカーボン製底板及びカーボン製の
分割式側板用仕切板を入れそれら底板と仕切板と
により囲まれる内部空間に、上記白金皿内の溶融
状混合物を注入し、施蓋状態下に30分間保持後徐
冷するという方法を採つた。
この様にして得られたガラスを切断、研磨して
５×５×15（mm）の試料を作り、その後500〜800
℃の各点に12時間及び24時間保持した後徐冷した
製品の熱膨張係数を図面に示す。
この図面に示す結果から、24時間保持の場合は
550℃で、熱膨張係数は負の値となり、580〜600
℃間でその絶対値が最も大きくなり、以後温度を
上げるに従つて絶対値が序々に小さくなつている
が、800℃迄はいずれも負の値を示している事、
及び12時間程の場合には24時間の場合と比し、全
体的に高温側へ移行し、かつ熱膨張係数の絶対値
は小となつてはいるが、800℃迄はいずれも負の
値を示している事が判る。
実施例 ２
上記第１表に示した吉田シラス末水洗品粉末
86.07ｇ、市販Al2O3粉末15.41ｇ、市販Li2O粉末
8.03ｇを調合し下記第２表に示す如き組成の混合
粉末を得た。[Table] The above mixed powder contains 59.39% by weight of Yoshida Shirasu,
This is a combination of 29.53% by weight of Al 2 O 3 and 11.08% by weight of Li 2 O. The mixed powder with this composition was placed in a platinum dish and heated and melted at 1,600°C in an electric furnace for 1 hour to form a cullet.The cullet was shaped into a powder frame of 74 m or less, and then placed in a platinum dish again and heated at 1,600°C in an electric furnace. After heating and melting for 1 hour, strain removal treatment was performed. In this strain removal process, coke powder is placed in a stainless steel container housed in a furnace that is pre-maintained at 500°C, separate from the electric furnace, and a carbon bottom plate and a carbon split side plate are placed inside the coke powder. A method was adopted in which the molten mixture in the platinum dish was poured into the internal space surrounded by the bottom plate and the partition plate, kept covered for 30 minutes, and then slowly cooled. The glass obtained in this way was cut and polished to make 5 x 5 x 15 (mm) samples, and then 500 to 800
The drawing shows the coefficient of thermal expansion of the product that was kept at each temperature for 12 and 24 hours and then slowly cooled. From the results shown in this drawing, in the case of 24-hour retention,
At 550℃, the coefficient of thermal expansion is negative, 580-600
The absolute value is the largest between ℃ and 800℃, and the absolute value gradually decreases as the temperature increases, but all values are negative up to 800℃.
In the case of about 12 hours, the overall temperature shifts to the higher temperature side compared to the case of 24 hours, and the absolute value of the coefficient of thermal expansion becomes smaller, but all values are negative up to 800℃. It can be seen that it shows. Example 2 Yoshida whitebait powder washed with water shown in Table 1 above
86.07g, commercially available Al 2 O 3 powder 15.41g, commercially available Li 2 O powder
8.03g was mixed to obtain a mixed powder having the composition shown in Table 2 below.
【表】
なお上記混合粉末は、吉田シラス78.6重量％，
Al2O314.1重量％、Li2O7.3重量％の組み合わせと
なる。
この様な組成の混合粉末を、上記実施例１と同
一条件下に、加熱溶融してカレツトを得る→カレ
ツトを粉枠し再び加熱溶融→歪除去処理→徐冷し
て得たガラスから、同じく５×５×15（mm）の試
料を作り、該試料を600℃，24時間再加熱した後
に徐冷して得た製品につき、その熱膨張係数を測
定した結果、−18×10-71／℃であつた。
＜発明の効果＞
以上述べて来た如く、本発明によれば従来では
存在しなかつた負の熱膨張係数を有するガラスを
得る事が出来る。従つてこのガラスを再度粉枠し
通常の正の熱膨張係数を有するガラスやセラミツ
ク粉と適量組合わせた原料粉末を焼結すれば、そ
の組み合わせに応じ熱膨張が非常に少ないあるい
は全く熱膨張をしない焼結体を得る事が可能で、
その焼結体の強度は本発明方法で得られるガラス
に組み合わせる相手材により維持すればよいので
高強度の焼結体を得る事も出来る。
従つて温度変化によりその寸法精度が変化しな
い事が要求される部材、又は逆に温度上昇に伴い
収縮する事が要求される部材への応用が出来るも
のである。[Table] The above mixed powder contains 78.6% by weight of Yoshida whitebait,
This is a combination of 14.1% by weight of Al 2 O 3 and 7.3% by weight of Li 2 O. A mixed powder having such a composition is heated and melted under the same conditions as in Example 1 to obtain a cullet.The cullet is then heated and melted again in a powder frame. A 5 x 5 x 15 (mm) sample was made, and the sample was reheated at 600°C for 24 hours and then slowly cooled.The thermal expansion coefficient of the product was measured and found to be -18 x 10 -7 1 /℃. <Effects of the Invention> As described above, according to the present invention, it is possible to obtain a glass having a negative coefficient of thermal expansion, which did not exist in the past. Therefore, if this glass is powder-framed again and the raw material powder is sintered in combination with an appropriate amount of ordinary glass or ceramic powder that has a positive coefficient of thermal expansion, depending on the combination, the thermal expansion will be very small or there will be no thermal expansion at all. It is possible to obtain a sintered body that does not
Since the strength of the sintered body can be maintained by the mating material combined with the glass obtained by the method of the present invention, a high-strength sintered body can be obtained. Therefore, it can be applied to members whose dimensional accuracy is required not to change due to temperature changes, or conversely, to members whose dimensional accuracy is required to shrink as the temperature rises.
【図面の簡単な説明】[Brief explanation of drawings]
図面は本発明実施例１で得たガラスの熱膨張係
数を示すグラフ。
The drawing is a graph showing the thermal expansion coefficient of the glass obtained in Example 1 of the present invention.