鉄に富むマグネシオを高温高圧から常温常圧へ回収し，透過電顕で観察したところ，従来報告例のない格子定数が通常のマグネシオの2倍の超構造が見いだされたので，それについて報告する．

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A cylindrical wüstite pellet was thermally synthesized. The lattice constant of wüstite (4.307Å) in the pellet indicated that the amount of cationic vacancy was very small. It was also found that the magnetite in the pellet had a larger constant (8.52Å) than the stoichiometric one (8.390Å). The pellet was placed on a vitreous silica rod and heated at 1150°C for 24 hrs under A gas. As a result of the heating, a new crystalline phase was formed in the silica rod. The reacted wüstite pellet was separated from the silica at the surface of contact and was filed nearly parallel to the surface. The filings thus obtained from each layer of wüstite pellet were analyzed by using X-ray diffractometer. The nearer to the contact surface, the smaller the lattice constants for both the iron oxides. The largest constant for those oxides was comparable to the values observed befor the reaction. From the present experimental results the author obtained the following conclusions：(1) Wüstite which had reacted with silica might be expressed as Fe_1−yO indicating lesser (or no) cationic vacancy as compared with the iron saturated wustite Fe_1−xO (y<x). (2) Consequently, as the reaction proceeded the cationic vacancy was accumulated in the wüstite in the neighborhood of the contact surface; therefore, the lattice constant of this wüstite became smaller. (3) When the wüstite was saturated with the vacancy, magnetite was precipitated. This magnetite had a lattice constant comparable with the stoichiometric one.

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Atomic level observations have been made for the commensurate phase P″of Fe0.902O and the incommensurate phase P′of Fe0.920O by means of the high resolution electron microscopy. The crystal structure of the P″phase is monoclinic and belongs to the space group P2₁/m. The vacancy cluster is made of two vacancy tetrahedra with a common edge and contains no iron atom at the tetrahedral sites. In the real crystal, however, several kinds of structural disorder are introduced. [Jap. J. Appl. Phys. 24, L723 (1985) ] . In the P′phase, the cluster arrangement is almost cubic. The P′is essentially incommensurate without any domain structure.

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巨岩石型惑星深部に存在するMgSiO₃やCaSiO₃の存在様式を理解するためにチタン酸塩をアナログに高圧高温実験を行った。FeTiO₃を出発物質にして、約85 GPa、2500 Kまでにイルメナイト相(約0-20 GPa)、ペロブスカイト相(約20-30 GPa)、CaTi₂O₄型Fe₂TiO₄相 + OI型TiO₂相(約30-44 GPa、高温側)、型FeO相 + OI型TiO₂相(約30-44 GPa、低温側)、型FeO相 + 斜方晶系FeTi₃O₇相(約44 GPa以上)が出現し、さらに約170 GPa、2000 K以上の条件で新たな相が出現することが判明した。

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炭素を0.05%含む純鉄を大気中700°Cで9 min加熱し鋼表面に20 μm前後の厚みの鉄スケ－ルを生成させ、450°Cで30～180 min加熱して変態させた試料について、多軸回折装置を用いて侵入深さ一定sin²ψ法（侵入深さ各40、60、80 μm）により鉄とマグネタイトの残留応力深さ分布測定を室温でex-situに行った。未変態ならびに変態させた試料では、どのX線侵入深さにおいても鉄に残留応力の存在が認められなかった。マグネタイト相では未変態状態の残留応力は小さいが変態スケ－ルで残留圧縮応力を示唆する結果を得た。

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下部マントルは主に(Mg,Fe)SiO3ペロブスカイトとマグネシオで構成されていると考えられており、これらの相中のFe含有量は密度や相転移などに影響を及ぼすと考えられる。したがって、これらの相中のFe含有量を知ることはマントルダイナミクスを理解するうえで非常に重要である。このような理由から、(Mg,Fe)SiO3ペロブスカイトとマグネシオ間のFeとMg分配については、これまでに多くの研究がなされている。しかし、温度依存性については系統的に調べられたものは少ない。そこで本研究では、高温高圧実験により、広い温度範囲で(Mg,Fe)SiO3ペロブスカイトとマグネシオ間のFeとMgの分配を決定した。高温高圧実験には愛媛大学設置のマルチアンビル型高圧発生装置を使用し、_から_24 GPa、1400℃から2000℃の条件下で実験を行った。出発物質には(Mg0.91Fe0.09)2SiO4組成のSan Carlos olivine、合成したFo80、Fo70、Fo60を粉末にしたものを使用した。回収した試料はSEM、EDS、微小部Ｘ線回折装置を用いて相の同定と化学組成の分析を行った。本実験の結果、(Mg,Fe)SiO3ペロブスカイトとマグネシオ間の分配係数KD=(Fe/Mg)Pv/ (Fe/Mg)Mwは温度の増加と共に大きくなり、San Carlos olivine においては、1400℃から2000℃の間で0.19から0.34へと変化した。また、ある一つの温度において、温度保持時間によってKDは変化した。　本研究の結果から、温度は(Mg,Fe)SiO3ペロブスカイトとマグネシオ間のFeとMgの分配に大きく影響を及ぼすことがわかった。これは、下部マントルのダイナミクスを推定する場合、この効果を考慮する必要があることを示している。また、温度保持時間による分配係数の変化から、相間の化学平衡状態について検討する。

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MgO is added as a flux to iron-ores in the sintering and pelletising processes. MgO diffused into wustite influences the reduction of wustite. In order to understand the dissolution rate of MgO, diffusion experiments were conducted by means of the FeO-MgO diffusion couple method. The diffusivity \ ildeD was obtained in the range of Fe cation-site fraction (N_Fe) from 0.3 to 0.85 and relatively lower temperatures (1188∼1529 K). \ ildeD increases exponentially with N_Fe in the range of N_Fe from 0.3 to 0.6, but in the range more than 0.6, the increasing tendency becomes weak gradually. The variation of \ ildeD with N_Fe can be interpreted due to the facts that \ ildeD is proportional to 1.6 powers of vacant cation-site fraction (N_V) and that the N_V increases exponentially with an increase in N_Fe, but the increase in N_V shows the tendency to be suppressed in the range of N_Fe more than 0.6. The experimental results can be represented by the equation, log\ ildeD=A(logP_O2+8)+B. A and B are shown in Figs. 5 and 6, respectively.

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焼結ダイヤモンドアンビルを用いたマルチアンビル装置により、50GPa程度の圧力下までのパイロライト組成の相関係・元素分配・密度変化を、X線その場観察および急冷回収試料の分析によりおこなった。また、得られた試料のいくつかにおいて、主要相であるMgペロフスカイトおよびマグネシオのFeの価数をメスバワー分光およびEELSにより決定した。これら２相の間のFe分配は40GPa程度を境に大きく変化することが見い出されたが、これはマグネシオ中の2価Feの相対的濃集により説明でき、Feの高スピン-低スピン転移に関連づけられる。またパイロライトの密度は地震学的モデルと良く一致し、下部マントルの化学組成として適切であることが示された。

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The reduction rate of liquid wustite contained in an iron crucible under Ar-CO, CO-CO₂ or Ar-CO-CO₂ gas mixtures has been measured by using thermobalance at 1 400 and 1 450°C. The experimental region of partial pressure of CO was P_CO=0.02 -0.18 atm (Ar-CO) and P_CO=0.07-0.84 atm (Ar-CO-CO₂ and CO-CO₂).
The apparent reduction rate became constant in the region of gas flow rate above 2.5 l/min. Under this experimental condition, the rate of reduction was controlled by the chemical reaction at the interface, and was expressed by the following equation :
r=k_c(K_e-α)P_CO (g-oxygen/cm²·s),
where K_e and α are the equilibrium constant of the reaction among gas, liquid wustite and solid iron, and P_CO2/P_CO in the gas phase, respectively. The apparent rate constant of the chemical reaction, k_c, was expressed by the following equation :
k_c=1.18 exp(-24 300/RT) (g-oxygen/cm²·s·atm).
The reduction rate of liquid wustite with CO was 6 times larger than that of solid wustite.

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Solid state bonding of Fe and Al₂O₃ using an wüstite (written as FeO hereafter) interlayer was carried out by hot pressing at 1450 K for 3.6 ks in a vacuum of 10⁻³ Pa under pressure of 29.3 MPa. The interfaces between bonded materials Fe/FeO/Al₂O₃ were investigated by means of EPMA, X-ray diffractometry and TEM. (001) plane of an Fe single crystal was oxidized, in order to determine the micro-compositional variation at the FeO/Fe interface by AES and XPS. The change in the ratio of the Auger peak heights I_O(503)⁄I_Fe(703) and the chemical shift ΔE of the Fe(2p_3⁄2) depending on the distance from the oxidized Fe surface were measured by using Ar⁺ etching. It was found that in the region between 10 and 230 nm from the surface, I_O⁄I_Fe was constant (=FeO). But in the region from 230 to 420 nm (T-region), it gradually and linearly decreased with increasing distance, until it began to drop exponentially to zero (=Fe). At the FeO/Al₂O₃ interface a new reaction layer about 6 μm in thickness was formed, which had a spinel type structure with the lattice parameter of 0.8171 nm showing broad diffraction lines. But electron diffraction photographs of the new reaction layer showed a hallow pattern. Tensile strength values of Fe/FeO/Fe and Al₂O₃/FeO/Al₂O₃ were 7.4 and 5.9 MPa, respectively, when the interlayer FeO was 300 μm in thickness, and they were 53.9 and 30.4 MPa, respectively, when the thickness was 50 μm. Fracture was observed not at the interfaces or in the T-region but in the brittle interlayer FeO in both cases of Fe and Al₂O₃. Therefore, it is clear that the T-region or the new reaction layer contributes to the FeO/Fe or FeO/Al₂O₃ bonding, respectively.

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The reduction rate of liquid wustite in contact with solid iron with inert gas(N₂, Ar or He)-hydrogen mixture was measured by using the thermobalance at 1 400, 1 450°C.
(1) The apparent reduction rate of liquid wustite with hydrogen was proportional to P_H2.
(2) The apparent reduction rate was affected by the gas flow rate over the range of this experiment. The rate of chemical reaction between liquid wustite and hydrogen was so fast that the overall reduction was controlled by mass transfer in the stagnant film of gas phase in the range of flow rate, V<4l/min(N₂-H₂ and Ar-H₂ mixture) or V<7l/min(He-H₂ mixture). However, in the range of V=728l/min with He-H₂ mixture, reduction was controlled by both two steps, i.e., mass transfer in gas phase and chemical reaction at the interface. The chemical reaction rate at the interface was estimated to be 1.6×10^-2(g-oxygen/cm²·s·atm).
(3) The chemical reaction rate estimated was about 20 times larger than that of solid wustite obtained in the present work.

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The reduction of dense wustite crystals quenched from the molten state has been studied over the temperature range from 600° to 1 00°C in order to investigate the rate controlling step of the intial stage of reduction. The reduction rate was calculated from the weight change of the specimen measured by a thermobalance. The change in iron concentration and the rerief of the surface of specimen with time were observed with an Electron Probe Micro-Analyzer (EPMA) and an optical microscope. The reduction rate was expressed by the rectilinear law R=k₁t at the initial stage, and then by the parabolic law R=k₂t^1/2 at the middle stage of reduction process.
As long as the rectilinear law was valid, the number of point-like reduced irons increased on the surface of specimen. As the reduction proceeded furthermore, the diameter of point-like reduced irons became large. When the point-like irons were contacted with each other, the specimen surface was completely covered with reduction iron. When the surface of specimen was covered with reduction iron, the reduction rate equation was changed to the paraboric law.
It is concluded that the overall reduction rate can not be expressed by only one general equation for dense iron oxide, “Fe O”, because the micro-mechanism of the reduction process is not same for these three stages.

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のCO-H₂混合ガスによる還元速度に関して,未反応核モデルに基づく数式モデルを展開した.このモデルにおいて,
(1)還元鉄を触媒とする水性ガスシフト反応を考慮に入れた.
(2)ガス境膜および生成鉄層内のガスの拡散速度は多成分系のSTEFAN-MAXWELLの式によつて推算した.
緻密なの薄板のCO-H₂混合ガスによる還元実験を1000℃において行い,そのデータをこの数式モデルを用いて解析した.その結果,次のことがわかつた.
(1)水性ガスシフト反応の影響は無視できるほど小さい.
(2)還元速度のガス濃度への依存性は加成性から負に偏倚する.その理由はガス境膜および生成鉄層における拡散抵抗の寄与が大きいためである.

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This study was performed to ascertain the authors’ consideration that the magnitude of the flux of cation vacancy diffusing into the reaction interface may determine the morphology of reduced iron. Wustite plates of about 1.5 mm thickness and wustite foils produced by the unidirectional oxidation of iron foils of 200, 70 and 25 μm thicknesses in situ were used as specimens. In the reduction of wustite plates, pores were formed in wustite before iron formation, and thereafter iron was formed on the pores. A region of the highest reduction degree was located not on the exterior surface in contact with the reducing gas but in a place distant from the surface. In the reduction of wustite foils, the reaction interface receiving the in-flux of vacancies advances much more rapidly than that not receiving it. The effect of cation vacancies diffusing into the interface on the distance between iron nuclei and the elongation rate of pores in wustite was discussed.

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