40～90℃の温和な条件のソフト溶液反応により, 非晶質シリカ被覆カルシア固溶セリアナノ粒子を合成し, 光化学特性について検討した.カルシアはセリア中に約20mol%であり, カルシアの固溶により粒成長が抑制され, 粒径2～4nmのナノ粒子が生成された.カルシア固溶によるセリアの微粒化により, 薄膜透過スペクトルでは, 紫外線吸収能が向上するとともに可視部の透明性も向上した.セリアの酸化触媒活性は, カルシアの固溶およびシリカの被覆のいずれでも低減でき, カルシア固溶により, 酸化触媒活性低減のために必要なシリカ被覆量を減少できた.なお, 光触媒活性はセリアおよびカルシア固溶セリアのいずれもチタニアと比較しいちじるしく低かった.

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加熱-冷却の繰り返しによる酸化マグネシウム (MgO) セラミックスの力学的性質の変化について検討した.試料には平均結晶粒子径が34.8μm, 12.8μm, および0.65μmの3種類の高密度MgOセラミックス (相対密度 : 99.0%以上) を使用した.これらの室温における曲げ強度 (平均) はそれぞれ185MPa, 219MPa, および276MPaであった.基準温度を900℃に設定し, 温度差を100℃から500℃の間で変化させ, MgOセラミックスに対して赤外線加熱により加熱-冷却を繰り返した.加熱-冷却速度は100℃・min^-1または200℃・min^-1に設定した.MgO試験片の残留曲げ強度は温度差と加熱-冷却サイクルの増大にともなって減少した.また, これらの減少傾向はMgO試験片の平均結晶粒径がもっとも小さく (0.65μm), 加熱-冷却速度が速い (200℃・min^-1) 場合にもっとも顕著に認められた.温度差の増加にともなう残留曲げ強度の低下は水急冷法によって熱衝撃を加えた場合に顕著に認められたが, 赤外線加熱法のような比較的温和な条件の場合にも類似の挙動があらわれた.

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Modification of hexagonal-type mesoporous silica via intercalation of PVA and its adsorption properties were investigated. The hexagonal-type mesoporous silica was formed from Si (OC₂H₅) ₄ and self-assembly of C₁₆H₃₃N (CH₃) ₃Br. In order to intercalate PVA, the produced mesoporous silica was dipped into PVA aqueous solution with stirring, followed by firing at 300-800°C in N₂ atmosphere for immobilization of PVA. Thickness of PVA layer in intercalated mesoporous silica was evaluated from its composition and thermogravimetry. The thickness of around 0.1 nm was found to decrease with elevating the firing temperature and the carbonization fraction of the layer increased linearly. The adsorption properties were investigated by using O₂ and N₂ gases at 25°C. The ratio of adsorption volume, O₂/N₂, decreased apparently depending on firing temperature. Since the decrease of the ratio was in agreement with the amount of PVA that was not carbonized yet, the adsorption ability of O₂ was considered to be attributed to organic species.

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Calcium ferrite mono-nitrate hydrate (hereafter abbreviated as CFMNH) obtained at 60°C by a reaction between Ca (OH) ₂ suspension and Fe (NO₃) ₃ solution was characterized by XRD, FT-IR, DTA-TG and SEM-EDX. The synthesized CFMNH was the puseudo-hexagonal layer compound with basal spacing of 1.04 nm which is equivalent to half of the lattice constant c. By heating CFMNH below 100°C, this basal spacing was decreased from 1.04 nm at room temperature through 0.86 nm at 60°C to 0.80 nm at 100°C. These CFMNHs were also indexed tentatively as puseudo-hexagonal symmetry.
To study change of basal spacing with pH, 1.04 nm CFMNH suspension was stirred for 1 hour at room temperature in various pH solutions adjusted from about 12 to 13 with NaOH. The basal spacing of CFMNH decreased from 1.04 nm to 0.76 nm with increase of pH. The 0.76 nm spacing of CFMNH was finally settled to 0.80 nm by a longer aging process. The three types of CFMNH with different basal spacings were obtained by pH control as well as by thermal dehydration. However, the chemical composition and structure of 0.80 nm CFMNH obtained at room temperature by pH control were different from those of 0.80 nm CFMNH obtained by thermal dehydration in terms of carbonate contents, degree of hydrogen bond and stacking mode of layers.

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