著者

幾原 雄一 栗下 裕明 吉永 日出男

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.95, no.1102, pp.638-645, 1987-06-01

被引用文献数

9 18

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In order to in vestigate the effect of grain boundary structure on the high-temperature strength of SiC, three kinds of SiC materials were prepared by pressureless sintering; material A with sintering aids of B+C, material B with B+C+AlN, and material C without any sintering aid. Their strength was measured by three-point bending at temperatures from room temperature to 2070K. The grain boundary structure was observed by HR-TEM. The following results were obtained.<br>(1) The strength of material A increases with increasing temperature up to 2070K. The fracture mode is transgranular at all temperatures studied. At the grain boundaries observed, a non-crystalline phase of 2-5nm in thickness is always found. This phase is thought to be either a compound of B and C or an extended grain boundary.<br>(2) The strength of material B increases up to 1770K, but above that temperature it decreases rapidly. The fracture mode also changes at that temperature from transgranular to intergranular. There exists also a 2-5nm thick non-crystalline phase at grain boundaries. The boundary phase is thought to be a compound in the system B-C-AlN. Above 1770K this phase is considered to flow viscously under stress to bring about boundary sliding which causes the strength to decrease.<br>(3) The strength of material C is almost independent of temperature. There exists again a 3-5nm thick non-crystalline phase at grain boundaries, but the boundary phase is thought to be an extended grain boundary.<br>(4) The dihedral angles observed in material C are frequently much larger than the critical angle of 60°. This observation is against the Prochazka's thermodynamic limitation, γ_gb/γ_sv<√3. The large dihedral angles may come from the existence of a grain boundary phase, which lowers the boundary energy.<br>(5) Densification of materials A and B is thought to proceed by the diffusion through the grain boundary phases.

著者

余語 利信 松雄 茂 中 重治

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.95, no.1097, pp.94-98, 1987-01-01

被引用文献数

8

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Highly pure boron nitride of low crystallinity could be synthesized from triammoniadecaborane and ammonia below 800°C under atmospheric pressure. Triammoniadecaborane reacted with ammonia at temperatures between 300° and 450°C, and formed an amorphous solid containing BN, NH and BH bonds. According to the data of IR spectrum, the BH absorption band at 2500cm^-1 decreased in intensity with increasing temperature, and disappeared at 800°C. The 800cm^-1 band assigned to the BNB bonding increased in intensity from 700° to 800°C. The degree of alignment of the B₃N₃ hexagonal layer increased as the reaction time increased from 2h to 10h at 800°C. The X-ray diffraction profiles of the product formed at 800°C for 10h showed the broad diffractions centered at 2θ=25.5° and 42.0° (Cu Kα). The crystallization of boron nitride synthesized at 800°C for 10h proceeded above 1180°C. The 100 reflection of hexagonal boron nitride was separated from the broad 10 diffraction of the specimen heated at 1550°C for 2h. The lattice constant (c⁰) and size of crystallite (L^c) of the specimen were 6.735 and 220Å, respectively, after heating at 1550°C under atmospheric pressure for 2h. The size of crystallite increased from 320 to 830Å as the temperature increased from 1100°C to 1500°C under 2.0GPa for 10min heating. Boron nitride synthesized by heating at 800°C for 10h crystallized to hexagonal boron nitride when heated at 1500°C and 2.0GPa for 10min.

著者

村瀬 嘉夫 加藤 悦朗

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.86, no.993, pp.225-229, 1978-05-01

被引用文献数

1 6

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Zr(OH)₄について沈殿の生成条件, 乾燥条件, 試料の形状及び熱処理ふん囲気などが熱分解により生成するZrO₂の結晶構造に与える影響を検討し, 水蒸気の作用について新しい知見を得た. Zr(OH)₄沈殿の生成条件は結果にほとんど影響を与えない. 沈殿の乾燥に長時間を要すると乾燥完了までの沈殿の老化 (γ化) のために熱分解後のZrO₂に単斜結晶の量が増大する. 塊状試料の熱分解や昇温速度の小さい熱分解では沈殿の老化 (γ化) や自ら発生する水蒸気の影響をうけやすく単斜ZrO₂の結晶量が増大する. Zr(OH)₄を水蒸気中で熱処理すると単斜ZrO₂が結晶化し, 水蒸気の少ない減圧下では正方ZrO₂のみが結晶化する. この水蒸気の影響は無定形ZrO₂の生成過程よりそれからの結晶化過程において顕著である. この結果から水蒸気中では正方と単斜ZrO₂の表面エネルギーの差が小さくなると考えられる.

著者

佐々木 茂弌

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.68, no.780, pp.283-294, 1960-12-01

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For the purpose of investigating the effective way of preventing the thermal fracture of various bricks for bottom casting pit in teeming of molten steel, the equation of thermal shock resistance has been deduced from thermal stress equation, and the physical-mechanlcal properties of various bricks have been determined by testing. On the basis of the results obtained, considerations have been made concerning the effect of these properties and the size of each brick on thermal shock resistance.<br>Important results obtained are summarized as follows:<br>i) In the thermal stress equation σ=<i>E</i>α/(1-μ)⋅(θ₀-Θ)⋅<i>f</i>, thermal shock resistance (R) are expressed in σ_max/σ′, putting σ′ as max. thermal stress in tension, <i>f</i>′ as factor <i>f</i> corresponding to σ′, σ_max as max. tensile strength of a brick.<br>ii) Heat-transfer coefficient from molten steel flowing at temperature θ₀ to the surface of the brick at temperature Θ being in contact with molten steel flow is very large, and therefore, thermal shock resistance is expressed by the following two equations.<br>In the earliest stage, when heat does'nt begin to flow within a brick:<br><i>R</i>₂′=σ_max/<i>E</i>⋅(1-μ)/α⋅1/(θ₀-Θ)<br>In the next stage, when heat flows within a brick:<br><i>R</i>₁′=σ_max/<i>E</i>⋅(1-μ)/α⋅1/(θ₀-Θ)⋅(<i>kt</i>^1/2/γ)^<i>a</i><br>or <i>R</i>₁′=σ_max/<i>E</i>⋅(1-μ)/α⋅1/(θ₀-Θ)⋅(<i>K</i>/<i>γh</i>)^<i>a</i>′<br>iii) The relation between the mechanical properties and porosity may be expressed by a hyperbolic curve.<br>iv) The ratio of bending strength to Young's modulus, an effective factor for increasing thermal shock resistance, is larger in pyrophillite-clay brick than that in grog-clay brick. This ratio shows a trend to decrease with increasing porosity. It is presumed from the data in technical literatures that this ratio is approximately constant at high temperature below the critical temperature of pyroplastic property.<br>v) Based on the equation of thermal shock resistance determined in the case of runner brick, it is estimated that bending strength/Young's modulus ratio, linear thermal-expansion coefficient (α), poisson's ratio (μ) and temperature difference (θ₀-Θ) have an influence of first power. On the other hand, the thermal conductivity (<i>K</i>), specific heat (<i>C</i>_ρ), density (ρ) and wall thickness (γ) have an infiuence of 0.040 and 0.081 powers, respectively, on thermal shock resistance. In addition, considerations have been made concerning the degree of the effect of porosity, which is in functional relation to mechanical properties and thermal conductivity, on the thermal shock resistance.<br>vi) It is presumed that there is a limit in the improvement of thermal shock resistance by changing the properties of a fire clay brick and that most important factor for the prevention of thermal fracture is the moderate pyroplastic property.

著者

久保 靖

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.71, no.808, 1963-04-01

著者

柿谷 悟 藤坂 正良

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.66, no.750, pp.133-139, 1958-06-01

被引用文献数

3

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In order to build up a background to the relative difficulty for burning the different raw materials in cement production the solid phase reactions between SiO₂ and either CaCO₃ or BaCO₃ at the temperatures ranging 500°-800°C were studied by measuring the amount of CO₂ liberated during the reaction. Then, applying the figures so obtained into the Jander's equation for solid phase reaction the authors have tried to work out the rate constants as well as the activation energies. However, it was found out that there were many examples which failed to fit in the equation, probably, due to the additional CO₂ liberated by simple thermal dissociation of the carbonates.<br>On the other hand, W. E. S. Turner et al. have suggested the acceleration of thermal dissociation of CaCO₃ when it was mixed with the powder of silica or of pure gold. The same trend was confirmed to exist also in the case of BaCO₃.<br>Furthermore, the investigation of X-ray diffraction pattern has revealed that the reaction products of CaCO₃ and SiO₂ obtained by heating at 700°C in air for 242 hours was not wollastonite (βCaO⋅SiO₂) but larnite (β2CaO⋅SiO₂).

著者

藤井 欽二郎

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.73, no.841, 1965-09-01

著者

前仏 忠

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.88, no.1018, 1980-06-01

著者

浜野 健也

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.72, no.830, 1964-12-01

著者

関口 秀一

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.82, no.951, 1974-11-01

著者

門間 英毅 上野 精一 堤 正幸 金澤 孝文

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.86, no.1000, pp.590-597, 1978-12-01

被引用文献数

16 19

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α-Ca₃(PO₄)₂ 粉末-H₂O系分散液を種々のpHに調製し, これをそのままあるいは反応中のpHを一定保持しながら, 80℃で主に2時間の加温処理を行った. 得られた固相分の結晶相とpH条件との関係を明らかにし, 更にアパタイト生成物に関しては, 反応pH条件とCa/P比, 構成イオン種, 加熱変化及び粒子形態などとの関連を検討した.<br>反応中のpHを一定に保持してもしなくても, pHが約4.6以上であればアパタイト単一相になり, これ以下pH 4.3までは短冊状結晶のアパタイトとオクタカルシウムホスフェートとの混合相になり, pH 4.2-3.0では角板状のCaHPO₄を主体としていた. アパタイト単一相の場合の結晶は, 保持pH値を変えることによって板状あるいは花片状及び柱状のおのおのの形態に成長した. pHを一定保持しない場合にはすべて花片状であった. 反応中のpHが高いほど, アパタイトへの転化は遅くなるけれども, アパタイトのCa/P比は増大しやすくなった. 高Ca/P比のアパタイトになるほど, 含水量やHPO₄^2-含量の減少と, OH^-含量及び結晶性の増大が認められた. アパタイトの含水状態, 含有HPO₄^2-の脱水縮合温度はオクタカルシウムホスフェートのそれらと類似していた。

著者

中村 雅彦

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.86, no.996, 1978-08-01

著者

林 国郎 福井 雅男 上井 勲

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.89, no.1028, pp.165-170, 1981-04-01

被引用文献数

4

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ワラストナイト結晶の転移温度以上で焼成されたワラストナイト磁器の誘電特性の劣化原因を究明するために行った実験結果は, 次のように要約される.<br>その劣化の原因が, ワラストナイトの結晶型によるものかを調べるために, 高純度のβ-, 及びα-CaO・SiO₂を合成し, 分散法を用いて, 粉末状態で誘電率 (ε) と誘電正接 (tanδ) を測定したところ, β型では6.5, 及び4.2×10^-4, α型では8.6, 及び5.0×10^-4となり, 両者の特性にはほとんど差を認めることができなかった. 次に, ホットプレスによって得たち密焼結体により, 誘電特性を比較したところ, β型焼結体のε, 及びtanδは7.4, 及び3.9×10^-4で, α型焼結体では8.4, 及び4.4×10^-4となり, 結晶型による差はなく, このことが特性の劣化の原因でないことが分った.<br>そこで, 磁器の内部微細組織の観察を行った結果, 高温焼成において磁器中に生じたα型結晶と, ガラス質母相の熱膨張係数の差により, 冷却時に母相中に発生したと思われるクラックが, 誘電特性を劣化させる原因になったものと考えられる.

著者

千野 英春

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.87, no.1011, 1979-11-01

著者

門間 英毅 金澤 孝文

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.84, no.968, pp.53-57, 1976-04-01

被引用文献数

50 102

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α-燐酸カルシウムの水和反応が塩基性液中, 100℃以下で生じることを見出した. 反応は温度およびpH低下とともに遅くなり, 室温およびpH約5以下ではほとんど進行しなかった. 水和反応生成物は硬化体として得られた. 十分に水和させた生成物は, Ca/Pモル比=1.5のカルシウム欠損水酸アパタイトであると同定された. このアパタイト中には水分子, OH^-およびHPO₄^2-のHとして約4.7%の水成分が含まれていた. アパタイト構造は700℃までの加熱によって全含有水分の約75%を揮発させても安定であった. このときHPO₄^2-の消滅とP₂O₇^4-の生成とが確認された. 残りの水分は, OH^-の除去とβ-燐酸カルシウムの生成とを伴って, 755℃で急激に放出された. アパタイト-燐酸カルシウム分解反応の見掛け活性化エネルギーは65kcal/molであった.

著者

木村 邦夫 陣内 和彦 諌山 幸男

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.80, no.918, pp.84-91, 1972-02-01

被引用文献数

12 11

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In view of good properties of hollow glass micro-sphere such as lightness, thermal insulating and sound arresting properties, high melting point and incombustibility and ability to increase quantity, some new composites of unparalleled characteristics are being developed by mixing them into plastics, carbon, cement, lime and its kind and metals. For instance they are now being used in diverse fields for making synthetic wood, master model, electric accessories, materials of low thermal conductivity ceramics, including aircraft materials and submarine diver-ship materials, and their demand is rapidly increasing. So, some methods to produce them have been invented already, but as the processes of them are rather complicated and the materials are expensive, the production become very expensive, too. Hereon, we authors discovered that hollow glass micro-sphere can be produced from the "Shirasu", which is acidic volcanic ejecta and one of the unutilized mineral resources distributes widely in southern Kyushu and other districts in Japan, through simple and inexpensive method. Incidentally, we will call it as "Silas Balloons". We made up an apparatus for calcining of raw material, and investigated the conditions for production of Silas Balloons, bubbling and expansive mineral component in Shirasu, the effectiveness of processing of raw material and producibility of Silas Balloons from some Shirasu produced in various districts, and measured general characteristics of Silas Balloons. And following results have been obtained. 1) Using the Shirasu as the material, it is optimum to calcine it at a temperature about 1000℃ shortly within 60 seconds. 2) Maximum size of calcining material is 300μ to obtain hollow glass microsphere. 3) It has been found that bubbling and expansive mineral component in the Shirasu is volcanic glass, and more accurately, the effective H_2O contained in it is estimated the bubbling agent. 4) Enriching the volcanic glass in the material through processing of raw material, especially through classification and magnetic separation, yield of Silas Balloons has considerably increased. 5) Some Shirasu produced in various districts would be able to be used as materials of Silas Balloons. 6) Compared with the known micro-sphere heretofore such as Microballoons of Emerson and Cuming Inc., Silas Balloons is superior to the former in its strength, melting point and hygroscopic property, though inferior to the former in its appearance.

著者

橋本 謙一

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.73, no.837, 1965-05-01

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.67, no.766, 1959-10-01

著者

高橋 一郎 宇佐美 三郎 中門 公明 宮田 寛 志田 茂

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.93, no.1076, pp.186-194, 1985-04-01

被引用文献数

26 18

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各種の微小欠陥を付加したSi₃N₄とSiCの強度試験を行うとともに, 他の実験結果も併せて整理し, 欠陥寸法, 切欠き半径と強度の関係を求めた. その結果, 実際の機械部品で対象とするような100μm程度以下の微小な欠陥では, 破壊靱性値<i>K</i>_ICを一定とする線形破壊力学による評価結果は非安全側を与え, この傾向は結晶粒径の大きい材料ほど大であることが明らかとなった. 表面加工傷, 空孔, 人工欠陥等の各種の欠陥についての実験結果は, その形状効果を補正した等価き裂長さを用いることによって, 欠陥寸法と強度の関係は同一に取り扱うことができた. また, 各種セラミックスについての強度試験結果を, 等価き裂長さと平均結晶粒径の比<i>a</i>_e/<i>d</i>と小さいき裂と大きいき裂の臨界応力拡大係数の比<i>K</i>_C/<i>K</i>_ICの関係で整理すると, 材料の種類によらずほぼ同一の関係となることが明らかになった. この関係は本報で提案した結晶破壊モデルから導かれる関係式で比較的よく説明され, 更に平滑材における結晶粒径と強度の関係及び切欠き半径と強度の関係についても, 本モデルによる関係式で実験値の傾向は良く表された.

著者

河村 淳一 速水 久治 有吉 騏三郎 細井 映司

出版者

公益社団法人日本セラミックス協会

雑誌

窯業協會誌 (ISSN:18842127)

巻号頁・発行日

vol.81, no.935, pp.263-270, 1973-07-01

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Packing behavior of the dry ramming mixes by method with stick penetration were in good agreement with calculations of author's previous report. Also, attempts at removal tendency of intermediate component were not so effective for obtaining a closer packing.<br>It was shown that the <i>q</i> value of closest packing (=q_ρm) might shift to a lower value when the stick penetration times becames larger, and the q_ρm could be expressed as hyperbolic function of stick penetration times.<br>Another intensified packing experiment of the dry mixes was shown that the q_ρm was inversely proportioned to the maximum particle-size, and that a closer packing was obtained as the particle were more spherical in shape.<br>In packing experiment of the wet ramming mixes, the behavior by light ramming was similar to that of dry mixes, however, the packing intensity dependence and the maximum particle-size dependence on the q_ρm was not so much as that of dry mixes, and the shift of the q_ρm was lower than that of dry mixes.<br>A different tendency about packing behavior by heavy ramming and press moulding of wet mixes was observed, that the q_ρm might shift to a higher value as the intensity of packing operation got higher, probably as a result of the crushing and defacement of grains.<br>From these results, it might be concluded that the factors of the degree of packing for magnesia ramming mixes was moisture and binder, particle-shape, mechanical properties of magnesia clinker grain, maximum particle-size or extension of distribution, grading of particle-size, and intensity of packing operation.