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This study aimed to evaluate the effect of three pretreatment conditioners and surface preparations on a composite resin adhesive for a gold alloy. Cast disk specimens were made and bonded with RelyX Unicem luting agent under six surface conditions: 1) polished with No.600 carbide paper, 2) air-abraded with alumina, 3) Alloy Primer metal conditioner was applied after alumina-abrasion, 4) Monobond Plus multipurpose conditioner was applied after alumina-abrasion, 5) M. L. Primer metal conditioner was applied after alumina-abrasion, and 6) Rocatec multipurpose silica-coating system was applied. The bond strengths were determined before and after thermocycling (50,000 cycles). The bond strengths of the alumina-abrasion group were significantly decreased after thermocycling. The Rocatec and M. L. Primer exhibited higher bond strengths than other treatments. The application of metal conditioners and multipurpose surface preparations was recommended for improved bonding between the evaluated adhesive resin and gold alloy.

The purpose of the present study was to evaluate the efficacy of pretreatment on the bonding durability between titanium casting and two acrylic adhesives. Cast titanium disk specimens treated with four polymer-metal bonding systems as follow: 1) air-abraded with 50-70 μm alumina, 2) 1)+Alloy Primer, 3) 1)+M.L. Primer and 4) tribochemical silica/silane coating system (Rocatec System). The specimens were bonded with M bond or Super-bond C&B adhesive. The shear bond strengths were determined before and after thermocycling (20,000 cycles). The surface characteristics after polishing, and for the 1) and 4) preparations were determined. The bond strengths for all combinations significantly decreased after thermocycling. The combination of Super-bond C&B adhesive and 2) led to significantly higher bond strength than the other preparations after thermocycling. The maximum height of the profile parameters for the polishing group was lower than other preparations.

Purpose: The aim of this study is to evaluate a newly developed polymethyl methacrylate (PMMA) powder. Methods: The particle size distribution, surface area, and particle shape of both new and traditional powders were compared. The shear bond strength of the resin cement with the new powder to a silver-palladium-copper-gold alloy was determined and compared to that for a cement with the traditional powder. Also, the weight of mixture held by the brush at one time of both powders was also calculated and compared as an index of mixability. Results: The surface area of the new powder was smaller than that of the traditional powder, while the particles size distributions were similar. The new powder included various-sized spherical particles as well as irregular particles, while the traditional powder consisted of only irregular particles. The new powder showed significantly higher mixability, although its bond strength was not significantly different from that of traditional powder. Conclusion: The results of this study show that the interminglement of spherical and irregular particles cannot influence the bond strength to the alloy but is helpful to improve the working properties., Journal of Prosthodontic Research, 55(4), pp.193-198; 2011

症例の概要：患者は62歳の女性．上下顎臼歯部欠損による咀嚼障害を主訴に本院を受診した．下顎臼歯部欠損に対して違和感により可撤性部分床義歯を受け入れられなかったためインプラント支持による固定性義歯により機能回復を行った．考察：遊離端欠損に対して違和感の訴えが強く使用できなかった可撤性部分床義歯ではなくインプラント支持による固定性義歯を応用したことにより安定した臼歯部咬合が得られたと思われる． 3年が経過するが特に大きな問題は認められない．結論：本症例は上顎が可撤性，下顎は固定性義歯により欠損補綴を行った．患者の満足度も高く，機能的にも良好な結果が得られた．

This study aimed to evaluate the bonding behavior of two acrylic resin adhesives joined to titanium-aluminum-niobium (Ti-6Al-7Nb) alloy primed with two metal conditioners. Cast Ti-6Al-7Nb alloy disks were air-abraded with alumina and bonded with six combinations of two resin adhesives (Super-Bond C&B and Multi Bond) and three surface conditions (Alloy Primer, M.L. Primer, and unprimed control). Shear bond strengths were determined both before and after 20,000 thermal cycles. The tri-n-butylborane initiated Super-Bond C and B resin exhibited greater bond strength than the BPO-amine initiated Multi-Bond resin. Both the Alloy Primer with a hydrophobic phosphate and the M.L. Primer with a phosphonoacetate effectively improved the 24-hour bond strength of Multi-Bond resin as well as the post-thermocycling bond strength of Super-Bond C and B resin.

The purpose of the present study was to evaluate the bond strength and durability of four bonding systems joined to a prefabricated porcelain material (Vita Celay Blanks). Two sizes of porcelain block were bonded with one of the following systems: (1) Clapearl Bonding Agent and Clapearl DC; (2) Imperva Porcelain Primer and Imperva Dual; (3) Monobond S and Variolink II; or (4) Tokuso Ceramics Primer and Bistite II. Shear bond strength was measured after 24-hour immersion in water and after subsequent thermocycling. The average pre- and post-thermocycling bond strengths in MPa (n=8) were: 52.5 and 42.5 for bonding system (1), 47.7 and 32.8 for (2), 55.0 and 48.8 for (3), and 51.5 and 25.6 for (4). Although prethermocycling results were not statistically different from each other, Group (3) exhibited the greatest strength after thermocycling.

A couple of zinc oxide (ZnO) single crystals with single boundaries (ZnO-ZnO single-contacts) are fabricated by the traditional vapor reaction method and their electrical properties are characterized. The ZnO-ZnO single-contacts obtained show nonlinear current-voltage (I-V) characteristics without varistor-forming constituents. Some of the ZnO-ZnO single-contacts show pronounced nonlinear I-V characteristics with negative resistance. The I-V characteristics of the ZnO-ZnO single-contacts are apparently similar to those of ZnO varistors; however, there are marked differences in the electric structure of the boundaries between the ZnO-ZnO single-contacts and ZnO varistors. The capacitance-voltage (C-V) relations of the ZnO-ZnO single-contacts are quite different from that of ZnO varistors and no evidence for the formation of double Schottky barriers at the boundary region are found. A very slow response to current stress is a feature of ZnO-ZnO single-contacts and it is suggested that any thermal processes including Joule heat would modify the carrier transport efficiency through the boundaries.

This investigation was carried out in order to evaluate ammonium hydrogen fluoride (AHF) and cupric chloride (CC) as components of a metal etchant. The surface of cast titanium-aluminum-niobium (Ti-6Al-7Nb) was air-abraded with alumina, etched for 10 s, and rinsed with water. A phosphate or a thiophosphate primer was applied to the bonding area, and an acrylic rod was bonded to the specimen with a tri-n-butylborane-initiated self-curing luting agent. Shear bond strengths were determined after thermocycling (4 degrees C and 60 degrees C) for 10,000 cycles. The average bond strength was significantly influenced by thermocycling, AHF, and primer, but was not influenced by CC. The maximum average bond strengths were obtained when the etchant consisted of 5mass% AHF, with and without 0.3mass% CC. Microphotographs showed that numerous micropits were created on the etched surface, suggesting increased micromechanical retention. In conclusion, chemical etching with 5mass% AHF significantly improved the durability of resin bonding to Ti-6Al-7Nb.

The purpose of the current study was to evaluate the bonding characteristics of super-elastic titanium-nickel (Ti-Ni) alloy castings. Disk specimens were cast from a Ti-Ni alloy (Ti-50.85Ni mol%) using an arc centrifugal casting machine. High-purity titanium and nickel specimens were also prepared as experimental references. The specimens were air-abraded with alumina, and bonded with an adhesive resin (Super-Bond C & B). A metal conditioner containing a phosphate monomer (Cesead II Opaque Primer) was also used for priming the specimens. Post-thermocycling average bond strengths (MPa) of the primed groups were 41.5 for Ti-Ni, 30.4 for Ti and 19.5 for Ni, whereas those of the unprimed groups were 21.6 for Ti, 19.3 for Ti-Ni and 9.3 for Ni. Application of the phosphate conditioner elevated the bond strengths of all alloy/metals (P < 0.05). X-ray fluorescence analysis revealed that nickel was attached to the debonded resin surface of the resin-to-nickel bonded specimen, indicating that corrosion of high-purity nickel occurred at the resin-nickel interface. Durable bonding to super-elastic Ti-Ni alloy castings can be achieved with a combination of a phosphate metal conditioner and a tri-n-butylborane-initiated adhesive resin.

The purpose of the current study was to evaluate the adhesive performance of metal conditioners when used for bonding between auto-polymerizing methacrylic resins and a titanium alloy. Disk specimens were cast from a titanium-aluminum-niobium (Ti-6Al-7Nb) alloy, air-abraded with alumina, and bonded with 24 combinations of eight metal conditioners (Acryl Bond, ACB; All-Bond 2 Primer B, ABB; Alloy Primer, ALP; Cesead II Opaque Primer, COP; Metafast Bonding Liner, MBL; Metal Primer II, MPII; MR Bond, MRB; Super-Bond liquid, SBL) and three autopolymerizing methacrylic resins (Repairsin, RE; Super-Bond C & B, SB; Tokuso Rebase; TR). Unprimed specimens were used as controls. Shear bond strengths were determined both before and after thermocycling (4-60 degrees C, 20, 000 cycles). The ALP-SB group recorded the greatest post-thermocycling bond strength (21.8 MPa) followed by the COP-SB group (17.8 MPa) and the MPII-SB group. The post-thermocycling bond strengths of the unprimed-SB group and the ALP-RE group were statistically comparable. No significant differences were found among the nine TR resin groups, and these groups showed the lowest bond strength. In conclusion, the use of one of the three conditioners (ALP, COP, and MPII) in combination with the SB resin is recommended for bonding the Ti-6Al-7Nb alloy.

The purpose of the present study was to evaluate the surface preparation effects of eight metal conditioners and an adhesive system on bonding between a prosthodontic composite material and cast titanium. Eight primers designed for conditioning base metal alloys (Acryl Bond, All-Bond 2 Primer B, Alloy Primer, Cesead II Opaque Primer, Eye Sight Opaque Primer, Metafast Bonding Liner, Metal Primer II, and MR Bond) as well as a surface modification technique (Siloc) were assessed. Disk specimens cast from titanium (T-Alloy H) were either primed with one of the eight primers or treated with the Siloc system, and then bonded with a light-activated composite material (Artglass). Bond durability was evaluated by thermocycling (4 and 60 degrees C, 1 min each, 20, 000 cycles). After thermocycling, two groups either primed with the Cesead II Opaque Primer material or treated with the Siloc system exhibited significantly greater bond strength (20.0 and 19.0 MPa) than the other groups (0.2-12.6 MPa, P < 0.05). These two systems are considered to be useful for improving bonding between the titanium and the composite material tested.

Design of intelligent material with self-diagnosing function for preventing fatal fracture of the structural material is achieved by hybrid composites consisting of fiber tows or powders in carbon material with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. CPGFRP/GFRP (carbon powder dispersed in glass-fiber-reinforced plastics/glass-fiber-reinforced plastics) composites are superior to CFGFRP (carbon-fiber and glass-fiber-reinforced plastics) composites in respect of their capability of damage monitoring by measuring change in electrical resistance from the early stage of damage, but the former is inferior to the latter as an application because of the difficulties of mass production and high cost. CFGFRP composites are already commercially used as sensor rods for diagnosing the health of concrete structures in skyscrapers in the architectural field or in security walls for preventing an invader in the security field. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improving the reliability of material.

A consistent bond between the metal framework and the luting agent is desired when resin-bonded prostheses are constructed with titanium. The purpose of this study was to evaluate three different metal primers on titanium bonding. Two sources of titanium (machined 99.9% titanium and cast Titan Ingot JS2) were used. Disk specimens were bonded with eight combinations of three primers and two luting agents (Panavia 21 and Super-Bond C&B), including two controls. Shear bond strengths were determined after 24-h water storage and after 10,000 cycles of thermocycling. Bond strengths were influenced by thermocycling, primer, luting agent and their combinations, but no significant differences were found between the machined 99.9% titanium and the cast ingot. The thione-phosphate dual functional primer (Alloy Primer) was comparable to the phosphate primer (Cesead II Opaque Primer) and the thiophosphate primer (Metal Primer II) for bonding the titanium metals examined. The most durable bond was obtained in three combinations of these primers and one luting agent (Super-Bond C&B).

SiC-fiber/Si3N4-matrix composites (CMC) which contained W fiber (Wf), Ti fiber (Tif) or Si3N4-TiN phase ([SiN-TiN]) as an electrically conductive phase were fabricated by hot-pressing in N2. Electrical resistance change (ΔR) was measured in bending tests including loading-unloading and cyclic tests. The CMC-Wf showed little ΔR in deformation regions and discontinuous ΔR at the fracture of whole material. The ΔR of the CMC-Tif was observed in small displacement because of brittle TiN formation during the hot-pressing, but residual ΔR after loading-unloading and cyclic tests was slight in this material. The CMC-[SiN-TiN] possessed the best sensitivity of ΔR among the three kinds of materials. At unloaded state, the CMC-[SiN-TiN] had clearly residual ΔR, which increased obviously with increasing the number of cycles. These results could be qualitatively understood by conductive pass amputation in percolation structure of TiN particles in the matrix phase of the CMC. The self-diagnosis function of fracture detection in the CMCs would be applicable into the damage evaluation of important materials and structures.

昨今の技術は複雑になりすぎている弊害が目立つ。環境にも人にも優しい技術は簡明なものである。複雑さを回避し簡明な技術を構築・設計するためのコンセプトと手法を材料開発を例にとって説明する。キーワードは発音を「けん」とする漢字群, 賢 (=建=検=兼=健=倹=圏) である。簡明化を通じ技術を市民のものにする運動を展開している。

Brevity is the soul of future in technology. We have to avoid spaghetti syndromes of modern technology. For this purpose intelligent materials must be developed. Yanagida proposes ken-materilas to meet the requirement for the future technology. Authorities have to find novel concepts to make technology more easily understood to avoid unnecessary confusion. Integration is an important key word. Improvement of structural reliability and capability of self-damage monitoring may be achieved if we design so beforehand. This opens a new field of materials design in composite materials. Typical case is a concrete structure reinforced by CFGFRP (carbon fiber and glass fiber co-reinforced plastic) bars. This may be extended to diagnose damage of fragile materials such as ceramics used for heat engine component and concrete piles. R & D is conducted by Ken-materials Research Consortium led by Yanagida.

The CuO/ZnO heterocontact is made by stacking CuO and ZnO porous ceramics and its catalytic activity for CO oxidation reaction is evaluated as a function of applied bias. Its catalytic activity is strongly depend on the dc applied bias and when the reverse bias (CuO-, ZnO+) is applied to the heterocontact, the amount of the produced \hboxCO2 from the catalytic interface rapidly increases, while it decreases when forward bias is applied. The magnitude of the enhancement of the catalytic activity by reverse applied bias is extremely large (30% for −2.0 V at 320°C), comparing with the results in the gradient composition CuO/ZnO heterocontact. The p-i-n structure is suggested as to the electronic structure of the CuO-ZnO contact interfaces and supposing p-i-n structure, the surface Fermi level position of CuO and ZnO are guessed to move as a function of applied bias. The catalytic reaction over CuO make a large contribute to the whole catalytic reaction at the CuO/ZnO heterocontact and it would be modified by the applied voltage dependent surface Fermi level position of CuO. The working mechanisms of such phenomena are qualitatively discussed by the electronic theory of catalyst proposed by Wolkenstein.

In the starting step of durability testing, the elements removed in relaxing from each electric side because of the measuring of impedance and velocity by ultrasonic wave and density of elements. The electromechanical coupling factor decreased with an increase in resonance resistance. The decrease of velocity was shown due to submicron-crack and residual stress caused by lattice mismatch that occurred by domain switching. The occurrences of submicron-crack and residual stress were suggested by the decrease of pellets bending strength. From these results, the total discussion was performed for the degradation process.

Carbon powders (CP) and carbon fiber (CF) were introduced into glass fiber reinforced plastics (GFRP) composites to obtain fracture detection function. The specimens were evaluated through the relation between a load-displacement curve and an electrical resistance change curve in three point bending test. CP containing GFRP (CPGFRP) has a sensitivity of electrical resistance change at much lower load level than CF containing GFRP (CPGFRP). In loading/unloading tests, CPGFRP showed a large amount of residual electrical resistance which enables the estimation of loading hysteresis.

Fatigue tests of ceramics are usually performed under cyclic stress. However, piezoelectric materials are used under an applied electric field and stresses are caused by the displacement. It is very important to understand the relation between the fatigue behavior and the compositional conditions. S-N curves of fatigue test in an applied electric field were composed of two curves having different gradients, acceleration was observed in the range of many time cycles. Fatigue behavior of piezoelectric ceramics considers accumulative fatigue which shows markedly decrease of strength caused by internal-crack with domain switching.

The CuO/ZnO heterocontacts for carbon monoxide (CO) gas sensors were made using CuO ceramics with different histories, and their gas sensing characteristics were evaluated. The CuO/ZnO heterocontact made by the quenched CuO sintered compact showed enhanced CO and CO{sub 2} gas sensitivity, while that made by slowly cooled CuO showed no selective CO gas-sensing characteristics with no CO{sub 2} gas sensitivity. The quenched CuO ceramics were thermodynamically stable but the slowly cooled ones were not; therefore the adsorbed CO molecules on the quenched CuO are thought to be stable and have longer lifetimes. The specific reaction between the adsorbed CO on CuO and adsorbed oxygen on ZnO would be promoted by long lifetime adsorbed CO on CuO and that may be the origin of the enhanced CO gas sensitivity of the quenched-CuO/ZnO heterocontact. The concentrations of cation vacancies of the quenched CuO ceramics can be controlled by controlling the firing temperatures. However, when the CuO ceramics for the CuO/ZnO heterocontact were made by firing and quenching, the ability to be selective in CO gas sensing of the heterocontact was not easily controlled by the control of the defect concentrations of the CuO ceramics.

Ultrafine spherical particles of γ-Al 2 O 3 containing 4 at% magnesium and pure γ-Al 2 O 3 were prepared by evaporating metal Al in air. Consequently, both particles were heated at 1400°C for 6 h in a vacuum. TEM observations showed that the Mg-doped γ-Al 2 O 3 particles were much more stable than the pure γ-Al 2 O 3 particles. The role of Mg atoms on the stability is discussed mainly based on the results obtained by high-resolution electron microscopy and energy dispersive X-ray spectroscopy.

This paper reports some experimental results on a concave piezoelectric element, conical backing and first amplifier for high-sensitivity and wide-band AE transducer. The piezoelectric element, conceived according to a “resonance dispersion” design, was fabricated based on piezoelectric ceramics/polymer 1-3 connectivity composites by Newnham. To control ringing characteristics, the backing was conical in shape. The first amplifier was inserted in a FET zero-bias amplifier in a cable connecter. The AE transducer had half sensitivity and a wider resonance frequency (100kHz-1.9MHz) than a conventional type AE transducer (resonance frequency; 180kHz). The residual noise was 20μVp-p (10kHz-50MHz) at first stage amplifier, the measurement of hold level was able to reduce the noise to 10μV with a wide frequency. Using this AE transducer, AE measurement with a high-sensitivity and wide-band was realized in material testings.

The NO and NO2 responding properties of Nd2CuO4−y thick film prepared by citrating process were investigated by measuring electrical conductance in air and N2 at 400 °C. The conductance was decreased by NO and was increased by NO2 with quick response and recovery time, which suggests that the Nd2CuO4−y thick film is applicable to be a sensing element for NO and NO2 gases. The NOx responding properties in N2 showed a different behavior from those in air, which suggests that NO and NO2 responding mechanisms and their surface reactions are greatly affected by existing oxygen. Nitrate-like species were observed in N (1s) X-ray photoelectron spectra of Nd2CuO4−y thick film after NOx treatment. The charges of NOx adsorbates inferred from X-ray photoelectron spectroscopy analysis were consistent with those expected from conductance changes induced by the introductions of NOx in air.

Hardened gypsum is chosen as a simple model of hardened cement materials and an analogy between the mechanical and dielectric strength distributions is investigated. Both of the strengths are evaluated in terms of Weibull statistics and a two-parameter Weibull function is adopted for both of the strength distributions. Both plots show good coincidence which is independent of the water content used during the mixing of hemihydrate gypsum powder for hardening. The hardened gypsum sheets made with 70 wt% of water, have mechanical and dielectric strength distributions that show two different behaviours in the Weibull plots, however, both the plots agree with each other. From our results, it is concluded that the mechanical strength distribution of hardened gypsum can be evaluated in terms of the dielectric strength distribution, which can be easily measured from a breakdown test.

CuO–ZnO composites were fabricated by heating with infiltrating a cupric solution into a porous ZnO matrix. The composites possess a nonlinear, rectifying current–voltage character due to the presence of a p–n junction produced by the CuO and ZnO semiconductors. This junction is essential for the creation of voltage-dependent sensing properties of humidity and flammable gases. The forward current (CuO: positive bias) greatly increased with increasing the relative humidity, while the reverse current only slightly increased with an equivalent increase in the relative humidity. This asymmetric current change with the humidity is similar to that observed for conventional CuO and ZnO sintered specimens heterocontact produced by mechanically pressing the specimens together. The current was increased by the introduction of CO and H2 (4000 p.p.m.) at 250°C, with the current increase due to CO exceeding that of the H2 in the measured bias region within ±6 V. The utility of the new processing method for forming p–n semiconductor junctions open to the atmosphere has been shown.

Strain-dependent electrical conduction has been observed in the system NiO-CaO. xNiO.(1 - x)CaO solid solutions are fabricated by a traditional solid-reaction method. When the 0.03NiO.0.97CaO solid solution is annealed at 1000°C, excess NiO is excluded and precipitates on the surface or intergrain layers. When compressive stress is applied to the specimen, the electrical conductivity increases with an increase in the applied stress. The magnitude of the conductivity change exceeds 50% during 15 MPa loading at 800°C. The presence of a precipitated NiO layer over the xNiO. (1 - x)CaO phase is suggested to be the origin of the applied stress-dependent electrical conductivity.

Objective: The shear bond strengths of two hard chairside reline resin materials and an auto-polymerizing denture base resin material to cast Ti and a Co-Cr alloy treated using four conditioning methods were investigated. Material And Methods: Disk specimens (diameter 10 mm and thickness 2.5 mm) were cast from pure Ti and Co-Cr alloy. The specimens were wet-ground to a final surface finish of 600 grit, air-dried, and treated with the following bonding systems: 1) air-abraded with 50-70-μm grain alumina (CON); 2) 1) + conditioned with a primer, including an acidic phosphonoacetate monomer (MHPA); 3) 1) + conditioned with a primer including a diphosphate monomer (MDP); 4) treated with a tribochemical system. Three resin materials were applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles. Results: The strengths decreased after thermocycling for all combinations. Among the resin materials assessed, the denture base material showed significantly (p, Journal of Applied Oral Science, 21(4), pp.320-326; 2013

Semiconductive carbon fibers suitable for infrared-ray sensor materials were prepared by final heat treatments at 600--700 C in an atmosphere with a controlled oxygen-gas (O{sub 2}) concentration, and the influence of O{sub 2} concentration on the electrical properties and surface composition/microstructure was investigated. Resistivities at 20 C were almost equal and independent of the O{sub 2} concentration of heat treatment in all cases, but the thermistor constant decreased as the O{sub 2} concentration increased. Carbon fibers heat-treated in O{sub 2}-mixed nitrogen gas (N{sub 2}) exhibited higher surface oxygen concentrations than did those treated in pure N{sub 2}, and surface microstructures differed between the two fibers. A high-voltage pulse application more effectively decreased resistivity in fibers heat-treated in an atmosphere with a higher O{sub 2} concentration. Apparently, control of the O{sub 2} concentration in the heat-treatment atmosphere and high-voltage pulse application can produce a desirable resistivity and thermistor constant independently in carbon fibers.

An extensive characterization has been carried out for copper oxide (CuO)/zinc oxide (ZnO) heterocontacts having carbon monoxide gas selectivity. We have focused on p-type semiconducting CuO, using sodium as a dopant, which is a key material for CuO/ZnO heterocontacts having carbon monoxide gas selectivity. It is shown that this heterocontact responds quickly and selectively to CO. XRD results show that, by adding 1 mol% Na 2 CO 3 to pure CuO, the monoclinic lattice constants a and b and the angle β increase, but the lattice constant c decreases. The electrical conductivity is measured as a function of temperature for pure CuO and for CuO with 1 mol% Na 2 CO 3 . The resistivity of pure CuO is higher than that of CuO(Na) by three orders of magnitude at 250°C. The capacitance is measured for pure CuO/ZnO and CuO(Na)/ ZnO heterocontacts in pure dry air and in air with H 2 or CO. The increase of capacitance in response to CO is larger than the H 2 response in the CuO(Na)/ZnO heterocontact, but the reverse result is found in the pure CuO/ZnO heterocontact. It is concluded from XPS results that chemisorbed oxygen is less prevalent on the surface of the CuO(Na) than on the pure CuO surface.

Mechanical and electrical properties of zirconia-based alumina composites as solid electrolyte used in solid oxide fuel cells (SOFC) were examined, in which the alumina addition and its morphology were changed. The bending strength increased with the addition of 0.38 μm alumina up to 30 mol%, then decreased. In this sample the ionic conductivities almost remained constant up to 30 mol%.

Screening fields, at or below which 10%, 30% and 50% of TiO2 ceramic samples would break electrically, were applied to samples which show single-mode strength distribution. After these high-voltage screenings, the surviving samples were subjected to mechanical strength measurement and the resultant strength distributions were compared with the original distributions. This high-voltage screening was also applied to model ceramics samples composed of titania with two different relative densities. The effect of high-voltage screening and the correlation between mechanical and dielectric strengths are discussed.

Thin SnO 2 films of about 10 nm thickness were prepared by sputtering on SiO 2 /Si substrates, and the effects of an external electric field from the substrate on the conductance of the SnO 2 film were investigated at 26°C and up to 300°C. The apparent conductance of the SnO 2 film increased with a positive substrate bias and decreased with a negative substrate bias. These field effects became more evident with larger bias and in SnO 2 films with a lower carrier concentration. By using metal oxide semiconductor theory, the results are attributed to the formation of a depletion and an accumulation layers in the SnO 2 film under a negative and a positive bias, respectively. The influence of electron traps in the SnO 2 film on its apparent conductance was suggested from calculations of these field effects. At temperatures above 150°C, slow changes in the conductance with time were observed under a constant negative bias. From the results measured in N 2 and in air, it was suggested that the amount or types of surface oxygen adsorbates changed under a negative electric field. These results indicate the possibility of controlling the electrical properties and the surface reactions of SnO 2 films by an external electric field.

Single crystals of (Ba0.96-xLnxSr0.04)TiO3 (Ln=La, Gd) were grown over a composition range of x=0.001 to 0.03. Electrical resistivities of the single crystals were measured by the DC four-probe method. The temperature dependence of resistivities of these crystals changed from semiconductive to metallic at the Curie temperature (TC). Although the room temperature resistivities of Gd-doped single crystals were independent of Gd concentration of 1 to 3%, they decreased monotonically with increasing the dopant concentration after annealing in a reducing atmosphere.

The bending behaviour of a piezoelectric actuator consisting of a dense PZT (Pb0.995Nb0.01(Zr0.53Ti0.47)0.99O3) plate and a porous ZnO (ZnO + 10 mol% NiO + 0.2 mol% Li2O) plate in response to reducing-gas (CO, H2) atmospheres has been investigated. The actuator is prepared by bonding the dense PZT and press-formed ZnO disks using a hot-press technique with glass frits at the interface. The PZT and ZnO plates, cut off from the hot-pressed body, have high resistivities of the same level in air but only the ZnO showed a decrease in resistivity on introduction of reducing gas at 250 °C. An applied d.c. electric field is confirmed to concentrate on the PZT part of the PZT/ZnO actuator on introduction of reducing gases. The shrinkage caused by a d.c. bias at the PZT side of the actuator increases due to the concentration of electric field, and then the actuator shows a change of bending displacement from 3 μm in air to 7 μm in 0.40 vol.% air-balanced CO gas under 250 kV m−1. It is found that the applied voltage is distributed to both plates in air, but concentrates in the PZT part in reducing-gas atmosphere due to a decrease in resistance of the ZnO part.

The electrical anisotropy of layer-structured bismuth titanate (Bi 4 Ti 3 O 12 ) has been investigated by measurements of Seebeck coefficient, dielectric permittivity, DC conductivity, and complex impedance on single- and polycrystalline samples, and a plausible explanation for the origin of dielectric anomaly below Curie temperature has been suggested. A large anisotropy in the dielectric permittivity, DC conductivity and activation energy for charge transport was observed between the parallel/perpendicular direction to the bismuth oxide layer ((Bi 2 O 2 ) 2+ layer. Complex impedance and modulus spectroscopy on single crystals in the direction perpendicular to the bismuth oxide layer below the Curie temperature confirmed that there are large differences in the electrical resistivity and, in particular, capacitance between the parallel/perpendicular direction to the bismuth oxide layer, which is assumed to be due to the difference in the electrical nature of the bismuth oxide layer and the pseudo-perovskite block. The dielectric anomaly below the Curie temperature is thought to originate from the space charge due to the thermally agitated polarization fluctuation.

The sintering of fibrous BaTiO3 powder particles was investigated. Special emphasis was given to the role of particle orientation in the compact on densification and microstructure development. Compacts were made by dry-pressing. During the initial stage of sintering, the fibrous particles rearranged and bundles of particles were formed. The volume of pores between bundles of particles decreased on further heating. Grain growth started when the sintered density reached ca. 56% of the theoretical density. Higher temperatures of sintering increased the degree of the crystal axis orientation. Thus, highly orientated sintered bodies with high densities were prepared by heating at 1500 °C.

The surface properties of copper oxide (CuO) were discussed for considering the working mechanism of a CuO/ZnO heterocontact gas sensor having carbon monoxide (CO) gas selectivity. We focused on p-type semiconducting CuO, using sodium as a dopant, which is a key material for selective CO gas sensing and its surface properties were characterized by XPS, TPD and FT-IR analyses. It was found that the Cu/O ratio of the 1mol% Na2CO3-added CuO surface was higher than that of pure CuO surface by XPS analysis. By TPD analysis, it was found that CO was adsorbed more strongly on 1mol% Na2CO3-added CuO than on pure CuO. By the in situ IR measurement of CO adsorbed on the surface of 1mol% Na2CO3-added CuO specimen under 300°C, we found two asymmetric bands of CO, whereas an asymmetric streching CO2 band was found on IR measurement of pure CuO specimen. It was confirmed that Cu atoms on pure CuO surface exposed to CO at 300°C changed from Cu2+ to Cu1+ or Cu0, in contrast to Cu atoms on 1mol% Na2CO3-added CuO surface, which changed to Cu2+. The electrical conductivity was measured as a function of temperature for pure CuO, CuO with 1mol% Na2CO3 and ZnO specimens. The resistivity of ZnO was larger than that of pure CuO and CuO with 1mol% Na2CO3 by three and six orders of magnitude at 250°C, respectively. A working mechanism of CuO(Na)/ZnO heterocontact gas sensor was elucidated in order to explain its high CO selectivity.

The humidity-sensing electrical properties of heterocontacts betweenp-type La2CuO4andn-type ZnO semiconductors, and of the single oxides, as a comparison, were studied. The heterocontacts was prepared by mechanically pressing sintered disks of the two oxides. The electrical characterization of the heterocontacts was carried out using dc and ac measurements at various relative humidity (RH) values, in order to evaluate the sensing mechanisms and the electrical properties of thesep-njunctions. Their humidity sensitivity was explained in terms of the variation of the barrier height at thep-njunctions, due to the saturation of the original interface states by physisorbed water, which leads to the release of trapped electrons, resulting in an increase in the forward current. The higher the number of interface states, the higher the RH-sensitivity of the heterocontacts. Electrochemical impedance spectroscopy (EIS) measurements showed, at 90% RH, a distribution of capacitances with different relaxation times, which may be caused by the electrolysis of water molecules atp-njunction sites. For their use as humidity sensors, they showed a response of 4 orders of magnitude in the whole RH range tested, and a fast response time. The response of the heterocontacts was bias-dependent, tunable by externally applied electric field. They also have stand-by capability and a self-cleaning mechanism, which allow them to be described as intelligent materials.

The complex impedance of a CuO/ZnO oxide semiconductor heterocontact was studied by applying a dc bias voltage in a mixture of CO or H2 (4000 ppm) in air between 250° and 400°C. The frequency dependence of reactance showed a minimum peak, and the absolute value of the reactance and the frequency giving the peak both changed in a different manner, depending on the presence of a reducing gas of either CO and H2, and also the dc bias. Sensing properties could be tuned to detect both CO and H2 gases in air or to detect only H2 gas in air, by selecting the measuring frequency and the applied dc bias at 400°C. Additional resistance and capacitance specific to the ambient gases were introduced to the interface impedance of the semiconductors, and then were estimated from impedance measurements. Tunable gas sensing was possible when the product of the resistance and the capacitance components in the interface had varying values, dependent on gas species and dc bias. This paper proposes this new method of tunable gas sensing that uses the complex impedance characteristics of a heterocontact. In addition, the mechanisms of the tuning function are discussed.

Heterocontacts between p-type La2CuO4 and n-type ZnO semiconductors have been prepared by mechanically pressing sintered discs of the two oxides. Their humidity-sensing electrical properties are evaluated using d.c. and a.c. measurements at various relative humidity (rh) values. The current-voltage (I—V) curves, measured in dry and wet N2 or O2, are typical of p-n diodes at all rh values. The current versus rh sensitivity of the heterocontacts is bias dependent. The influence of the original adsorbates on the rh sensitivity is proved. Higher rh sensitivities of the heterocontacts are measured in oxygen, where a larger number of interface states is present. Electrochemical impedance spectroscopy (EIS) measurements, carried out in dry and wet air, show that the higher the rh, the higher the interface capacitance and the lower the interface resistance. EIS spectra are dependent on the d.c. bias applied, which mainly affects the resistence. At 90% rh, a distribution of capacitances with different relaxation time is found, which may be caused by the electrolysis of water molecules at p-n junction sites.

The a.c. impedances of a CuO(Na)/ZnO heterocontact have been investigated under a d.c. bias voltage (−10 to + 10 V) in CO- and H 2 -containing atmospheres at 250°C. The reactance (imaginary component of the impedance) shows characteristic changes depending on the gas species, measuring frequency and applied d.c. bias. By tuning the measuring frequency under a d.c. bias of −1 and −3 V, CO sensitivities higher than that obtained by d.c. measurements and high CO selectivity are obtained. the reactance changes are related to changes in both the resistance and capacitance components of the interface impedance. The product of the interface resistance and capacitance is found to be an effective index for the evaluation of gas selectivity in heterocontact-type gas sensors.

Electrically equivalent circuits for the paraelectric phase of layer-structured BaBi4Ti4O15 single crystals in the parallel and perpendicular directions to the (Bi2O2)2+ layer were identified by complex impedance and modulus analysis at 600 to 767°C. The same form of single semicircle in complex impedance plots for both directions could be differentiated by using complex modulus plots. The equivalent circuits for the parallel and perpendicular directions to the (Bi2O2)2+ layer were identified as a single parallel RC circuit and two parallel RC circuits in a series array, respectively.