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In the past decades, ceramic matrix composites (CMCs) have been attracting much attention for high-temperature structural applications. Ceramics are characterized by high hardness, high corrosion resistance, high heat resistance, high wear resistance, and low thermal expansion to be used for turbine blades of aircraft engines and others. It is important to not only improve fracture toughness but also creep and creep-fatigue resistances for high-temperature structures. In this study, SiC particles, SiC whiskers, α-alumina (Al_2O_3) particles, Ni particles, Ti powders, and SUS304 powders were prepared and added to partially stabilized zirconia (PSZ) for enhancement of high-temperature strength of the materials through the interaction due to the stress-induced transformation of PSZ and strengthening by the additives. The effects of the additives on the strengthening of PSZ were investigated on nano-, micro- and macro-scale mechanical properties at elevated temperatures. Nano- and micro-scale indentation hardness, elastic modulus and damping properties were evaluated using high-temperature nanoindentation equipment. For macro scale properties, biaxial bending tests were conducted at RT and 300℃. The effect of the additives on mechanical characteristics of PSZ were investigated by a coupling of nano-, micro- and macroscale analysis at elevated temperatures.

上顎前歯をオールセラミッククラウンで修復した症例。上顎前歯の不良補綴物による審美障害を主訴に来院した患者に、シリカ系セラミックスとジルコニアを用いて修復した。オールセラミッククラウンの製作にあたり、天然歯の形態と色調の再現が重要である。審美的、機能的、生物学的適合性に満足を得るためには、診断用ワックスアップ、プロビジョナルレストレーション、支台歯形成、歯肉圧排などが重要なファクターであると考えられる。, The long term follows up case reports of all ceramic restoration for anterior. The patients had esthetically unacceptable anterior crowns. The case of restorations used silicate ceramics and zirconia for anterior teeth. In making all-ceramic crowns, it is necessary to reproduce the shape and color near to those of the natural tooth. We should not overlook the importance of diagnostic waxing-up, provisional restoration, tooth preparation, gingival retraction and others, for the satisfaction of excellent esthetic, function and biocompatibility.

ジルコニアに対するレジンセメントの接着強度に及ぼす真空紫外線（VUV）照射の影響について検討した。接触角はVUV 未照射（80.18±3.2°）、照射直後（1分後）（34.2±6.2°）を示し、照射直後に有意に減少した（p ＜ 0.05）。X線光電子分光（XPS）測定から、VUV照射後にジルコニアにOH基が導入されたことが示唆された。本研究では、VUV照射がジルコニアセラミックスに対するレジンセメントの接着強度に及ぼす影響を評価した。剪断試験より、VUV未照射（4.36±1.6MPa）と照射（7.10±4.4MPa）の条件では、照射により有意に接着強さが向上した。照射直後では、②シラン含有プライマー（12.82±3.4MPa）は、①AZプライマー（5.42±2.0MPa）および③シランなしプライマー（5.2±2.0MPa）に対して有意に接着力は向上した。本研究では、VUV照射直後のシラン処理が、ジルコニアとレジンセメントとの接着強度を有意に向上させることが示唆された。これは、シランに結合する可能性のあるOH基が存在することにより説明できる。, Influence of vacuum ultraviolet (VUV) irradiation on the bond strength of resin cement on zirconia was investigated. The contact angle was shown as VUV Unirradiated (80.18±3.2°) and immediately after irradiated (1minute) (34.2±6.2°). Irradiation group showed significantly lower mean contact angle values unirradiated group (p＜0.05). X-ray photoelectron spectroscopic (XPS) analysis suggested that OH terminals were introduced on zirconia after VUV irradiation. This study evaluated the effect of vacuum ultraviolet (VUV) irradiation on the shear bond strength of resin cement to zirconia ceramics. The means and standard deviations of bond strength (MPa±S.D.) per group were as follows: unirradiated group (4.36±1.6MPa), Irradiation group (7.10±4.4MPa). Immediately after irradiation ②Silane containing primer (12.82±3.4MPa), ①AZ Primer (5.42±2.0MPa), ③Primer without silane (5.2±2.0MPa). Irradiation group showed significantly higher mean bond values unirradiated group (p＜0.05). Immediately after irradiation ②Silane containing primer group showed significantly higher mean bond values ①AZ Primer group and ③Primer without silane group. Within the limitations of this study, the finding that the bond strength between zirconia and resin cement was significantly greater with primers containing silane by the VUV. This finding could be accounted by the presence of OH terminals, which can couple to silane, resulting in the increase of bond strength.

Ceramics / metal functionally graded materials (FGMs) have been attracting much attention as composite materials that are intended for application to high-temperature structures. This study fucuses on toughening of ceramics and their matrix composites, which are building blocks of the FGMs. Partially stabilized zirconia (PSZ) with toughening additives such as Ni particles, Inconel fibers, SiC particles, SiC whiskers and a-alumina (Al_2O_3) particles were fabricated by spark plasma sintering (SPS). Toughening mechanisms were investigated based on their micro and macro-scale mechanical properties and microstructures. Disk bending tests, producing balanced biaxial loading conditions, were conducted probing bending strength at macro scales, while Vickers hardness tests were carried out to estimate fracture toughness and examine toughening mechanisms at micro scales. In addition, using a nanoindentation tester, hardness, elastic modulus, and creep properties were investigated at elevated temperatures (RT and 300℃). The results demonstrated that toughness of ZrO_2 increased by adding Ni particles, Inconel fibers and Al_2O_3 particles. Addition of Al_2O_3 particles highly enhanced disk bending strength and deformability.

Magnesium (Mg) has the lowest density among practical metals and has excellent specific stiffness and strength characteristics. Carbon nanotube (CNT) reinforced Mg matrix composites have been attracting much attention as an effective material composing light-weight structures in automobile and aerospace industries. However, CNT fibers tend to be intricately entangled with each other, which lead to exhibit unexpected low mechanical properties of the composites. In this study, CNT reinforced Mg composites have been fabricated using powder metallurgical techniques with spark plasma sintering (SPS) methods. CNTs have been subjected to ultrasonic treatment and mixed with fine powder of ZrO_2 to obtain uniform dispersion of CNTs in Mg matrix. In addition, metals with low melting points have been added to fill voids and cracks around CNTs. Three-point bending test results demonstrated that CNT/ Mg composites with both low melting point metal, Sn, and fine powders, ZrO_2, exhibited the highest maximum bending stresses among the composites and pure Mg. Flexural modulus have been also highly improved.

The dip-coating method of ceria-zirconia supported Cu catalyst prepared by coprecipitation and impregnation method on cordierite and SiC honeycombs was investigated. The preparation conditions of slurry for dip-coating were controlled by（1）the ratio of catalyst powder and binder powder,（2）the ratio of mixed powder and solvent, and（3）solvent. By adjusting these condition, uniform layer was formed successfully. For coating on SiC honeycomb, ethanol as solvent to prepare the slurry influenced forming the layer, because of its high wettability. The thickness of coat layer cordierite and SiC honeycomb were 8-9 μm and 10-13 μm on, respectively. The honeycomb catalysts showed the same activity as catalyst powder. It was indicated that homogeneous coat was obtained, and all of the coated catalyst on each honeycomb functioned.

歯科材料の進歩に伴い高強度なセラミックスによるメタルフリー修復が試みられているが、フレームのセラミックスと前装陶材の接着強度が問題視されている。本研究では脆性材料の引張強さを求めるダイアメトラル試験法の試験片形状をコントロールしたFlattened diametral bond（FDB）試験法を接着評価の題材とし、有限要素法により解析した。 ジルコニアと歯科用陶材の接合の接着耐久性をダイアメトラル圧縮試験法で評価するため、3種類の解析モデルを設計した。解析モデル1では直径10mm のジルコニア円柱の上下を平坦にしたFDB 試験用の試験片を準備し、長さの影響を調べた。次にジルコニア／陶材の半円状接合試験片をシミュレートし、均等に10μm の変位を与えた場合（解析モデル2）と均等に55N を負荷した場合（解析モデル3）を想定した。各々のジルコニア／陶材の界面での剥離に影響するせん断方向への応力分布について検討を行った。 解析モデル1からは試験片長さの影響が明らかにされ、長さ1mm では応力分布が一様であった。したがって、解析モデル2，3では1mm でシミュレーションを行った。解析モデル2で上方の平坦な部位から変位（ひずみ）を与えたところ、変位量が一定の場合には材質の物性による掛かる負荷の想定値が変わるため、次に解析モデル3として上端からの均等な応力値を付加する想定で有限要素解析を行った。その結果、3－D有限要素解析はジルコニア／陶材の接合界面に対して垂直方向に均一な引張応力が生じることを示した。 以上のことから上下面を平坦に加工して行うFDB 試験法は材料間の接合界面に一様な引張方向への応力を発生させることが可能と考えられ、異種材料の接合界面を評価する上で臨床的に有効な手法ではないかと考えられた。

Fe-doped ceria-zirconia Zr x Ce 0.95-x Fe 0.05 O 2-δ (where x=0, 0.20, 0.40, 0.60, 0.80, and 0.95), and Tb-doped ceria-zirconia Zr x Ce 0.95-x Tb 0.05 O 2-δ (where x=0, 0.20, 0.40, 0.60, 0.80, and 0.95) powder samples were synthesized by a coprecipitation method and heated at 900oC and 1230oC. The samples were characterized by XRD, colorimetric assessment and UV-Vis diffuse reflectance spectroscopy. Furthermore, the color glazes obtained by adding the samples to the basic glaze were heated at 1230oC in air, and evaluated by colorimetric assessment. In Fe-doped ceria zirconia samples heated at 900oC, the red color varied to orange and yellow with increasing x in Zr x Ce 0.95-x Fe 0.05 O 2-δ . However, the glazes containing them (with Zr) changed from warm color into pale like celadon. In Tb-doped ceria zirconia samples, the dark brown color varied to yellow-brown and orange with increasing x in Zr x Ce 0.95-x Tb 0.05 O 2-δ . The glazes containing them showed orange or pale yellow color. These warm colored materials show high durability against high temperature and environmental friendly properties, so the application as ceramic pigments can be expected.

大連結子の具備条件は、強固でたわまない事であり、現在は金属が用いられている。一方、歯科用ジルコニアは高い生体親和性、審美性を有し、高強度であるため、ブリッジの臨床に導入されている。そこで本研究では、イットリア添加部分安定化ジルコニア(ZR-Y、Y-TZP)とコバルト・クロム合金の4点曲げ試験における最大荷重と最大荷重時の変形量の比較、検討を行った。ZR-Yは変形量は小さいものの、最大荷重が著しく小さかった。Y-TZPはコバルト・クロム合金と同等の最大荷重を示し、変形量は小さかった。そのためY-TZPでは従来の金属と同様に大連結子に応用できることが示唆された。

CONiCrNY was pressureless plasma-sprayed on a substrate of nickel-base superalloy as a bond coating. Under the substrate rotation, zirconia with 4mol% yttria was coated as the top coating by the electron beam-physical vapor deposition (EB-Pun). The rotation speed of the substrate was 5, 10 and 20rpm. The top coating was made by the columnar structure which consisted of the core part and the peripheral part, The top of the core part had a pyramidal shape made by piling up the zirconia (111) planes. The peripheral part showed feather-like structure, which was made by growth of the zirconia and directions. For the specimen with 20rpm, the in-plane residual stress was small within the range from-20 to 30MPa, the out-of-plane residual stress was a very small compression. By the increase in the rotation speed, the column becomes thick and the inter-columnar space becomes large. The substrate rotation is useful for the reduction of the residual stresses in the EB-PVD thermal barrier coaling.

The Ni-based superalloy IN738LC was used as the substrate material, and CoNiCrAIY powder was pressureless plasma-sprayed on the substrate as the bond coating. Zirconia was coated as the top coating by the electron beam-physical vapor deposition (EB-PVD) method. In the EB-PVD process, the specimens were kept at 1223K and rotated with 5rpm, 10rpm and 20rpm. According to the microscopic observation and the result of the pole figures, the top coalings had a columnar structure, which was made by the piling up of (111) planes. The cross section of the column had a diamond shape, and its diagonal was parallel to the rotation axis. The residual stress on the surface of the top coatings was evaluated by the X-ray diffraction method. Each diffraction profile was separated into the 133 and the 331peak, and the residual stress was measured by the sin^2Ψ method. The measured residual stresses were-76.7MPa for 5rpm, -63.0MPa for 10rpm and -25.1MPa for 20rpm.

Specimens of tetragonal zirconia containing 3 mol % Y_2O_3 (Y-TZP) were ground with a diamond wheel of grain number 200/230. The residual stress and the monoclinic content were measured by the X-ray diffraction method. The bending stress was applied in the directions parallel and perpendicular to the grinding direction of the specimen. The residual stress on the ground surface was compressive, and the compression zone extended to about 30 μm in depth. The monoclinic content on the ground surface was raised to 7 to 8 percent. The bending strength increased in both directions because of the residual compressive stress near the surface introduced by grinding. For ground specimens, defects at the nucleation site of bending fracture were pores or coarse grains, but not grinding defects. Since the lower content of Y_2O_3 near the nucleation site raised the toughness of the material, the fracture toughness for fracture from small defects was larger than that of the single edge precracked specimen. The increase in the Weibull modulus due to grinding was discussed on the basis of fracture mechanics.

超高温・高熱応力負荷のような苛酷環境での連続使用が可能な超耐熱材料として、傾斜機能材料の開発が進められている。これは、一種のセラミック/金属複合材料であるが、この設計・合成に必要な物性値のデータベース作成において、各材料の破壊強度特性評価システムの開発が重要な課題である。室温から超高温にわたる機械的性質の評価が可能な試験方法を確立した。これまで金属材料の延性-脆性遷移温度評価に用いられていた小型パンチ(SP)試験法を室温で脆性材料にも適用できるように改良した、改良型小型パンチ(MSP)試験法を開発し、その詳細を報告した。ジルコニア/ステンレス鋼複合材料について実験し、破壊靭性値と破壊応力から、応力拡大係数の推定ができることを明かにした。さらに、アコースティック・エミッション(AE)法を併用した室温における破壊靭性試験とMSP試験との結果から、セラミックス単体材、ジルコニア/ステンレス鋼、およびステンレス鋼繊維強化複合材料について、荷重-変位曲線に対応したAE信号の発生特性を比較し、かつ走査電子顕微鏡観結果も加味して、材料の微視的破壊過程を明かにした。また、異なる種々の製造方法(粒子法、溶射法、自己発熱法)で試作したセラミック/金属複合材料について、高温でのSP/MSP試験を実施し、それぞれの製造法および材料の組合わせにより、高温強度特性に大きな違いが現われることを示した。, Modified Small Punch (MSP) method is developed for fracture characteristics evaluation of brittle materials and test results are reported. The MSP method is developed by the modification of Small Punch (SP) method, which was developed to evaluate the ductility and brittleness transition temperature of ductile metal materials. Testing procedures and test results of SP method and MSP method are compared using Zirconium and stainless steel composite materials. Reproducibility of test results and bending and yield strength test results from both methods are correlated. Fracture mechanisms for ceramic materials, Zirconium and stainless steel composite material, and Zirconium and stainless steel fiber reinforced composite material are studied by using yield strength method and MSP method together with acoustic emission test. Microscopic fracture mechanisms for these materials are also studied by the use of electronic scanning microscopic observations. Several ceramic materials and ceramic/metal composite materials at high temperature of 1873 K are studied and test results from SP method and MSP method are compared., 資料番号: AA0004166002, レポート番号: NAL SP-17

次の2論文を掲載する。(1)FGM開発のためのSP/MSP試験法。この研究は、1987年より科学技術振興調整費による総合課題として、産学官30余の研究機関が参加し、材料設計分科会、構造制御分科会、および特性評価分科会の提携のもとに推進されている。各研究機関が独自に信頼性のあるデータを収集できる目的のために傾斜機能材料特有の評価方法について順次評価を進めてきた。開発途上の傾斜機能材料については、従来のJIS試験法に対応する大型の試験片を合成することが困難である。ここに提案する方法は微小試験片でも有効な機械的特性値を取得し、早期に材料設計グループにフィードバックし、最適な材料設計に資することを目的に開発整備された試験法である。(2)セラミックス/金属複合材料のための破壊特性評価システムの開発に関する研究。これは付録として掲載されている。, This report is composed of two related papers: The first one is specification on MSP (Modified Small Punch) method and the second one is research paper on the evaluation of MSP method using ceramic materials as testing material. The first is titled as SP (Small Punch) and MSP (Modified Small Punch) tests for the evaluation of FGM (Functionally Gradient Materials) and defines testing apparatus, preparation method and dimensions of test pieces, and testing procedures. The second one is titled as research on the development of fracture characteristics evaluation system for ceramics and metal composite materials. In this paper fracture characteristics of ceramics/metal composite materials are evaluated using newly developed MSP method and the results are compared with those obtained by using conventional SP method. Microscopic fracture processes are observed by the acoustic emission method. The testing temperature was varied to high temperature of 1873 K., 資料番号: AA0004166000, レポート番号: NAL SP-17

application/pdf, 論文(Article)

Growth of ZrO2 whiskers by the reaction of ZrCl4 and O2 or H2O was examined at 1100°-1300℃. Only powder products were obtained at temperatures below 1200℃ in both reaction systems. At 1250°-1300℃, however, monoclinic whiskers or needle crystals were produced. In ZrCl4-O2 system, the whiskers were grown on a mullite substrate together with flaky materials, bricky crystals and powder. Optimum conditions for the whisker growth were ZrCl4 1-3%, O2 0.25-0.35%, and total flow rate of the reactant gas 40-60 cm3/min. The size of the whiskers was 0.1-2μm in width and 10-100μm in length. The growth axis was the direction or perpendicular to the (104) plane. In ZrCl4-H2O system, no whiskers were formed on the substrate, but needle crystals (whisker-like) and powder were obtained at the outlet of the reaction tube. The monoclinic needles were very minute, their dimension being 0.05-0.5μm in width and 0.5-3μm in length. The growthe axis was the direction or perpendicular to the (104), (113) or (211) plane. Optimum conditions were ZrCl4 2-5%, H2O 3-4%, and total flow rate of the reactant 30-60 cm3/min. Electron microsopic observation revealed that the whiskers and the needles had no particles on the tops, suggesting that both of them grew by a VS mechanism.

2017