Resource recovery of inorganic solid waste, such as waste incineration fly ash, cupola dust discharged from foundries, and nickel metal hydride battery waste, have been investigated. From results, tobermorite (Al-substituted tobermorite) and zeolitic compounds (zeolites A and P), which exhibit removal characteristics for toxic cations, were prepared from waste incineration fly ash by hydrothermal treatment in the presence of NaOH solution. Pretreatment of waste incineration fly ash with water washing and heating at 800°C was essential for preparing reproducible tobermorite as a major product at 180°C, while pretreatment with HCl solution, in addition to water washing and heating at 800°C, was essential for preparing reproducible zeolites A and P, as major products at 60-120°C. The H₂S sorptive property of cupola dust was induced by spinel-type nanocrystals composed of transition elements in the dust at room temperature in existence of water vapor, and drastically enhanced by NaOH treatments at 80-125°C to extract the spinel-type nanocrystals from amorphous SiO₂ matrix. The further examination revealed that the water adsorbed on the surface of the spinel-type nanocrystals played a role as a sorptive field. The Ni-based compound (w-NiO) was prepared from nickel metal hydride battery waste by a series of acid and base treatments. The CH₄ conversion over w-NiO was superior to that over regent NiO (r-NiO) for the CH₄ dry reforming, and exhibited an unusual behavior. The differences of catalytic activities between w-NiO and r-NiO were attributed to carbon deposition by side reactions and sinterability of the resulting Ni from NiO.

抄録全体を表示

A variety of layered transition metal oxides and layered double hydroxides have been exfoliated into unilamellar nanosheets such as Ti_0.91O₂, Ca₂Nb₃O₁₀, MnO₂, and M_1-x^IIAl_x(OH)₂ (M^II=Mg, Co, Zn, Ni). The exfoliation was promoted via the high degree of swelling driven by intercalation of quaternary ammonium ions for the layered oxides and solvation with formamide for the hydroxides. Various characterizations revealed very high two-dimensional anisotropy for the nanosheets thus obtained; a thickness of around 1 nm vs. a lateral size of submicrometers or larger. These nanosheets can be assembled or organized through various solution-phase processings to produce a range of nanostructured materials. Addition of electrolytes into a colloidal suspension of nanosheets promotes their restacking, yielding a flocculate. The combination of nanosheets and some counterions through this route led to a range of nanocomposites which exhibited fluorescent, photocatalytic, and electrochemical properties. On the other hand, the nanosheets can be deposited layer-by-layer with suitable polyelectrolytes to produce multilayer ultrathin films, in which the nanoarchitecture can be precisely controlled. The multilayer films of Ti_0.91O₂ and MnO₂ nanosheets showed photoinduced superhydrophilicity and electrochromic properties, respectively. Furthermore, the films of ferromagnetic titania nanosheets such as Ti_0.8Co_0.2O₂ and Ti_0.6Fe_0.4O₂ were found to show very high magneto-optical properties at room temperature.

抄録全体を表示

Perovskite ferroelectrics have been used for many piezoelectric and dielectric applications. The responses of perovskite ferroelectrics to the applied electric field, such as strains and electric displacements, are not proportional to the strength of electric field but generally show a non-linear behavior. This paper reviews previous studies on non-linear piezoelectric and dielectric responses mainly done by the author’s research group. The mechanism generating non-linear responses is the domain-wall motion and the dipole fluctuation in the polar nano-regions of relaxors. Some experimental results of the electric-field induced strains of PZT ceramics and the non-linear dielectric behaviors of relaxors including dielectric used in multi-layered ceramic capacitors (MLCCs) are presented. The non-linear piezoelectric and dielectric behaviors of perovskite ferroelectrics are discussed to find the key issues for piezoelectric actuators and MLCCs used in future applications.

抄録全体を表示

The relationship between electrical conductivity and dielectric constant was investigated for 10 atom%Sm doped CeO₂ (Ce_0.9Sm_0.1O_2-δ), which is a typical oxide-ion conductor. Computer simulation clarified that anomalously large dielectric constant originated from the superimposition of both Debye-type dipole and interfacial polarization between electrolyte and electrode. The interfacial polarization was proportional to the inverse of the frequency, suggesting the accumulation of oxide ions at the interfacial sites with high-energy barriers due to the oxide-ion conduction. Ac conductivity (σ_ac) at high temperatures and high frequencies agreed with the σ_dc value, but lowered in such a frequency region that the Debye-type polarization appeared. The activation energy for σ_dc agreed with those for Debye-type polarization and interfacial polarization, suggesting that these thermal exciting processes originate from oxide-ion diffusion.

抄録全体を表示

N-doped TiO₂ nanotubes were prepared by a wet process and with an additional thermal treatment. Firstly, titanate nanotubes were prepared by a hydrothermal chemical method. Then the obtained nanotubes were immersed in a 0.5 mol/L NH₃ solution for different periods. Finally, the resulted products were calcinated at high temperature to complete the substitution of O by N. The prepared N-doped nanotubes had an anatase structure and a large specific surface area. For those N-doped TiO₂ nanotubes, a significant shift of the absorption edge to a lower energy region and a notable decomposition of methyl orange in an aqueous solution under visible light irradiation were observed. The most visible light active catalysts were those immersed in a 0.5 mol/L NH₃ solution for 10 h and then calcinated at 400°C for 1 h.

抄録全体を表示

Calcium sulfonate, a detergent/dispersant component in lubricating oils, greatly increase the friction coefficient of TiO₂ added Fe₂O₃-Al₂O₃ ceramics under boundary lubricating conditions. ESCA studies showed that the average thickness of an organic thin film sticking to the surface of wear tracks was thicker than that away from wear tracks, and the concentrations of Ca, S and P were much higher in the wear track than those off the wear track, suggesting that most of the -SO₃-Ca-OH groups in sulfonate remained unchanged. It is concluded that oil containing rich calcium compounds possibly formed a layer, blocking other oily additives with which the surface would have been wettable. This is assumed to increase the friction coefficient of the TiO₂ added Fe₂O₃-Al₂O₃ ceramics.

抄録全体を表示

Au loaded TiO₂ (Au/TiO₂) ceramic thick film catalyst was integrated on a micro Thermoelectric Gas Sensor (TGS). We have investigated the catalytic activity of the Au/TiO₂ catalyst for CO oxidation and the CO sensing performance of the micro-TGS with this catalyst. CO started to burn when the Au/TiO₂ catalyst was exposed to 1 vol% CO in air at an operating temperature of 150°C, which was detected by the output voltage of the TGS. A good linearity between the CO concentrations in air (from 250 ppm to 1 vol%) and the voltage signal of the sensor (from 0.15 mV to 5.0 mV) was obtained at an operating temperature of 200°C.

抄録全体を表示

Carbothermal reduction and nitridation (CRN) process was utilized to prepare magnesium aluminum oxynitride (MgAlON) and the influence of reaction variables, such as heating temperature, soaking time and the source of carbon, on the formation of MgAlON was investigated. In addition, the density of samples prepared under different route was compared. The results show that volatile gases, Mg (g) in chief, lead to variation in lattice constant and chemical composition at high temperature, and decrease the sintering effect. Since high temperature and low CO partial pressure are favorable to the CRN reaction in view of thermodynamic reason and high temperature also favors the transport of gases, the rate of CRN reaction increases with the increasing temperature. Due to the difference in reactivity between graphite and carbon black, CRN reaction may be the rate controlling step when graphite is used and solid solution of AlN may be the controlling step when carbon black is utilized. CRN reaction can increase surface energy of reaction materials and results in higher final density. However, gases in the system retard the densification effect.

抄録全体を表示

Silver was introduced into borosilicate glass by a classical staining process under varying conditions of temperature and time. The spectroscopic features of the stained glasses were examined by studying absorption, photoluminescence and electron paramagnetic resonance properties. The diffusion parameters (diffusion coefficient and diffusion activation energy) of silver ions were calculated based on elemental analysis data from an inductively coupled plasma (ICP) spectrometry, and from line scan profiles from energy dispersion X-ray analysis (EDX).

抄録全体を表示

Porous cordierite ceramics with controlled porosity were fabricated via a reaction sintering using expandable microspheres as sacrificial templates and ceramics-filled polysiloxane as a precursor for cordierite ceramics. The influence of the sintering temperature, the template content, and the additive composition on the microstructure, porosity, and compressive strength has been investigated. The results showed that the template content, the sintering temperature, and the sintering additive composition have a significant effect on the porosity. By controlling the template content, the sintering temperature, and the sintering additive composition, it was possible to produce porous cordierite ceramics possessing a wide range of porosities ranging from 11% to 72%. The compressive strength was influenced by both the porosity and the additive composition. The compressive strength of the porous cordierite ceramics containing 6 mass% kaolin as a sintering additive was~150 MPa at 35% porosity.

抄録全体を表示

The precursor for rod-like TiO₂ was successfully prepared by the hydrolysis of titanium isopropoxide dissolved in diols such as 1,3-butanediol, 1,3-propanediol and 1,2-propanediol. The square rod TiO₂, whose typical size was estimated to be 1.5 μm long and 0.3 μm in width, was easily synthesized by the calcination of precursors at 500°C in air. TEM observation indicated that the square rod TiO₂ was ensemble of nano-sized anatase TiO₂ particles (approximately 20 nm), and a large surface area thus was achieved. The square rod TiO₂ powder exhibited the high catalytic performance in the complete photo-oxidation of acetaldehyde to CO₂ and water, and the activity was as high as that of TiO₂ (Degusa, P-25).

抄録全体を表示

Flake-type Ni powder was studied to enable further thinning of the MLCC Ni electrode. Considering the manufacturing process for the present ceramic capacitor, it is necessary to make the firing shrinkage action of what similar to that of a dielectric green sheet. Nickel flake paste with added organometallic acid salt of the same composition as nickel flake powder and ceramics was considered. According to the results of our study, the sintering of electrode paste films is inhibited when using Ni flake paste with an organometallic acid salt in contrast to using Ni spherical paste. A similar result has been obtained by observing of the surface structure of sintered bodies.

抄録全体を表示

Conventionally the manufacturing of ceramic parts consists of various processes such as pulverization of raw materials, dispersion, mixing, drying, shape forming, removal of organic binder, sintering and machining. We proposed new manufacturing processes using microwave technique, a technique named “compact process,” for the significant enhancement of manufacturing speed and ultimate improvement of productivity of ceramics fabrication, in which the complicated operations are reduced to simplified processes. In this report, the effects on the characteristics of sintered body and decreasing of energy consumption by compact process will be discussed.

抄録全体を表示

Silicon carbide (SiC) powder was prepared by heating a mixture of fullerene and silicon powders at 900-1000 K for 24 h with a Na flux. X-ray and electron diffraction revealed that the obtained powder was β-SiC. The agglomerates of SiC particles with a size of a few dozen nm were observed by transmission electron microscopy. The specific surface area and mean particle size of the SiC powder prepared at 1000 K were 12 m²/g and 88 nm, respectively.

抄録全体を表示

(Sr_1-xBa_x)MnO₃ (0.0≤x≤0.5) was synthesized using a standard ceramic technique which has a four-layered hexagonal (4H) structure with space group P6₃/mmc. The oxygen content for this is 3.000±0.001 for x=0.0-0.3, 2.982±0.001 for x=0.4, and 2.972±0.001 for x=0.5. The lattice constants (a and c) increase linearly with increasing x. From Rietveld analysis at room temperature, both the Mn-O(1) distance and the Mn-O(2)-Mn angle increase with increasing x, while the Mn-O(2) distance decreases with increasing x. Based on measurements of magnetic susceptibility, 4H-(Sr_1-xBa_x)MnO₃ exhibits antiferromagnetism, and T_N decreases slightly from ≈276 K (x=0.0) to ≈264 K (x=0.5).

抄録全体を表示

Sintering property of cation substituted LaCrO₃ system could be improved by simultaneous substitution of Ca and Sr for La site. It was revealed that grain size and their distribution increased by Ca and/or Sr substitution, resulting in 80% and 87% sintering density of La_0.75Ca_0.05Sr_0.20CrO₃ and La_0.70Ca_0.05Sr_0.25CrO₃, respectively. Electrical conductivity and activation energy of La_0.70Ca_0.05Sr_0.25CrO₃ are nearly equal to those of La_0.7Ca_0.35CrO₃, which has already been employed as an interconnector of SOFC or as a material for a high temperature heater. We regard that La_0.70Ca_0.05Sr_0.25CrO₃ with high electrical conductivity has promising properties for various electrical applications since it is free from structural phase transition involving discrete volume variation.

抄録全体を表示