Showing papers by "Kikuo Okuyama published in 2000"
TL;DR: In this article, spray pyrolysis was applied to the preparation of fine YAG:Ce phosphor particles, and the characteristics of particles such as crystallinity, morphology, and photoluminescence were investigated.
216 citations
TL;DR: In this paper, the structure of the α and β modifications of poly(tetramethylene succinate) (PTMS) were analyzed by X-ray diffraction: the β form appeared with an application of stress.
199 citations
TL;DR: In this article, zinc sulfide particles 20-40 nm in diameter were prepared by electrically driven spray pyrolysis, and the initially highly charged drops formed were neutralized by bipolar ions from a radioactive source to increase the overall transmission efficiency through a reactor furnace.
163 citations
TL;DR: In this article, the influence of operating parameters on the morphology of particles prepared by spray pyrolysis was investigated using a temperature-graded laminar flow aerosol reactor.
Abstract: The influence of operating parameters on the morphology of particles prepared by spray pyrolysis was investigated using a temperature-graded laminar flow aerosol reactor Experimentally, zirconia particles were prepared by spray pyrolysis using an aqueous solution of zirconyl hydroxide chloride Hollow particles were formed if the reactor temperature was high, the temperature gradient was too large, the flow rate of carrier gas was high, and the initial solute concentration was low A numerical simulation of the pyrolysis process was developed using a combination of two previous models The simulation results compared well with the experimental results
155 citations
TL;DR: In this paper, a monomer for the synthesis of soluble polyimides with high thermal stability, i-BPDA, was proposed and an efficient method of its preparation was developed.
85 citations
TL;DR: In this article, low-pressure differential mobility analysis was used to study the aerosol formed during 1064-nm pulsed Nd 3+ ǫ:YAG laser ablation of a solid cesium iodide (CsI) target.
41 citations
TL;DR: A unified model for electrical conduction in both the insulator particle solid state ionic and conducting particle insulator matrix composites was introduced for the first time in this article, where the basic formulation of effective medium approximation was reconsidered by replacing the site conductivities with the contact conductivities as well as the probability of site occupation with the probability for contact development.
Abstract: A unified model is introduced for the first time for electrical conduction in both the insulator particle‐solid‐state ionic and conducting particle‐insulator matrix composites. In the model, the basic formulation of effective medium approximation is reconsidered by replacing the site conductivities with the contact conductivities as well as the probability of site occupation with the probability of contact development. The model predictions are in agreement with the available experimental data. © 2000 The Electrochemical Society. All rights reserved.
36 citations
TL;DR: In this paper, a differential mobility analyzer (DMA) based on the DMA devised by Seto et al. and a Faraday cup electrometer was used for measurement of nanometer-sized particles at a few hundred Pa.
33 citations
TL;DR: In this article, the time-dependent change in the concentrations of organic species adsorbed on a silicon wafer surface is modeled using numerical calculations based on rate theory, which can describe and predict the actual increase and decrease in the surface concentrations of propionic acid ester, siloxane (D9), and di(2−ethylhexyl)phthalate.
Abstract: For the first time, the time‐dependent change in the concentrations of organic species adsorbed on a silicon wafer surface is modeled using numerical calculations based on rate theory. An equation composed of the adsorption rate from the gas phase to the silicon wafer surface and the desorption rate from the silicon wafer surface is developed accounting for competitive processes in a multicomponent system. This equation can describe and predict the actual increase and decrease in the surface concentrations of propionic acid ester, siloxane (D9), and di(2‐ethylhexyl)phthalate. It is also indicated that the organic species having a large adsorption rate with a small desorption rate remains in significant abundance on the silicon wafer surface for a very long period after cleaning. © 2000 The Electrochemical Society. All rights reserved.
31 citations
TL;DR: In this paper, the roles of ammonium bicarbonate and ammonium ammonium dioxide (NH3) in the preparation of Ni particles from NiCl2 · 6H2O aqueous solution by ultrasonic spray pyrolysis were investigated.
Abstract: The roles of NH3 · H2O and NH4HCO3 in the preparation of Ni particles from NiCl2 · 6H2O aqueous solution by ultrasonic spray pyrolysis were investigated. The results showed that both ammonia and ammonium bicarbonate had a remarkable influence on the solution chemistry and the resulting particles, and could significantly modify the reaction pathway. After the addition of these additives to the precursor solution, intermediate NiO was formed initially, followed by reduction to metallic Ni in the presence of a reductive gas. H2 is a powerful reducing agent; however, metallic Ni could also be obtained in the absence of H2 in the carrier gas. In the latter case, it was shown that NH3 was primarily responsible for Ni formation. A description of the mechanisms and processes of Ni formation during spray pyrolysis is proposed.
28 citations
TL;DR: In this paper, the green luminescent Zn2SiO4:Mn having size of 0.3-1.3 µm was directly prepared by spray pyrolysis without post-annealing processes.
Abstract: Particles of the green luminescent Zn2SiO4:Mn having size of 0.3–1.3 µm was directly prepared by spray pyrolysis without post-annealing processes. Characteristics of as-prepared particles such as crystallinity, morphology, and photoluminescence were investigated. Zn2SiO4:Mn particles with spherical morphology, non-aggregation, and having pure willemite was formed at a temperature of 1000–1300°C. The luminescence of the Mn2+ ion in Zn2SiO4 shows an emission band in the 525 nm when excited by 254 nm light.
TL;DR: In this paper, the effects of gas-phase nucleation in the plasma enhanced chemical vapor deposition process and its effects on thin film surface morphology were studied experimentally for a conventional radio frequency plasma reactor using tetraethylorthosilicate (TEOS) vapor and oxygen gases.
Abstract: Particle generation by gas-phase nucleation in the plasma enhanced chemical vapor deposition process and its effects on thin film surface morphology were studied experimentally for a conventional radio frequency plasma reactor using tetraethylorthosilicate (TEOS) vapor and oxygen gases. The particles suspended in the plasma space and deposited on the film were observed simultaneously by in situ laser light scattering methods and an ex situ scanning electron microscopic method. The generated particles were trapped in the plasma/sheath boundary under all four experimental conditions, in which TEOS concentrations were 0.5 and 5.0 vol % and reactor pressures were 66.7 and 533.3 Pa (0.5 and 4.0 Torr). The size and amount of particles and the film morphology were found to depend on the TEOS concentration and the reactor pressure. Under the conditions in which highly concentrated particles were generated in plasma, dome-like structures of 50–400 nm in diameter were observed on the thin film surface. The average size of the dome-like structure was comparable to that of the particles generated in plasma.
TL;DR: In this paper, an analytical expression for the electrical conductivity of porous silicon has been obtained, which demonstrates that the overall temperature dependence of electrical conductivities cannot be described by a single Arrhenius relationship, and there is a change in the electrical transport mechanism at a critical temperature.
TL;DR: In this paper, the electrical conductivity of nanocrystals is investigated by using a hybrid approach that treats the electronic structure of a nanocrystal quantum mechanically, and the transport of electrons semiclassically.
TL;DR: In this paper, the thermal condition in a rapid thermal processing (RTP) system using circular infrared lamps is systematically studied, for the first time, based on the direct approach model using a ray trace simulation.
Abstract: The thermal condition in a rapid thermal processing (RTP) system using circular infrared lamps is systematically studied, for the first time, based on the direct approach model using a ray trace simulation. This study focuses specifically on the temperature profile influenced by the connector, which is the dark region inevitably occupying a small part of the circular infrared lamp. Since the rays emitted from the lamp are distributed over the concentric circle region formed by the cylindrical reflectors, the influence of no radiation from the connector is significantly decreased resulting in the formation of a very shallow valley in the temperature profile of the silicon substrate below the connector. This conclusion is consistent with the actual applicability of the RTP system using the circular infrared lamps for very large diameter silicon substrates.
TL;DR: In this paper, a new method to coat iron oxide particles with carbon black using an adhesive agent is reported, and magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance.
Abstract: Magnetic particles with finer size, higher coercive force, higher blackness, and lower electrical resistance are required to produce better magnetic tape materials. A new method to coat iron oxide particles with carbon black using an adhesive agent is reported in this paper. Magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of ∼20% and a reduction in electrical resistance of ∼1 order of magnitude relative to conventionally prepared tapes are achieved when ∼5% of the particle weight is carbon black. Surface smoothness and the orientation ratio are also improved because the dispersibility of these particles in magnetic lacquer is better than that of uncoated magnetic iron oxide particles. Higher electromagnetic performance relative to the conventionally prepared layers is also obtained. TEM photographs indicate that all the carbon black is firmly bound to the surface of the magnetic iron oxide particles in a distinct layer.
TL;DR: In this paper, a theory for the electrical conduction of solid polymer electrolytes in the entire range of temperatures, by considering the fluctuation of the melting temperature and by the application of the statistical theory of gelation, is introduced, which contains the expected Arrhenius and VTF dependence as the asymptotic limits at low and high temperatures.
TL;DR: Fujimoto et al. as mentioned in this paper presented a numerical simulation for film formation by cluster/particle co-deposition in the atmospheric-pressure chemical vapor deposition and compared the simulation results with experimentally obtained growth rates and surface morphologies of films prepared from four organic silicon vapors.
Abstract: In order to confirm the previously developed numerical simulation for film formation by cluster/particle co-deposition in the atmospheric-pressure chemical vapor deposition [Fujimoto et al..: J. Appl. Phys. 85 (1999) 4196], simulation results were compared with experimentally obtained growth rates and surface morphologies of films prepared from four organic silicon vapors [tetraethylorthosilicate (TEOS), triethoxysilane (TRIES), tetramethylorthosilicate (TMOS), and octamethylcyclotetrasiloxane (OMCTS)] and ozone gas using a flow-type vertical tube reactor. For TEOS, TRIES and TMOS, the simulation results could explain reasonably experimentally determined film growth rate, particle deposition rate and surface morphology of film when natural convection did not occur in the reactor. However, the numerical simulation could not estimate film formation from OMCTS.
TL;DR: In this article, a new liquid source chemical vapor deposition process was introduced for preparing (Ba, Sr)TiO 3 (BST) thin films from Ba(DPM) 2 (tetraglyme), Sr (DPM), BaTiO3, and TiO 3, and it was demonstrated that in the formation of BST films, the three precursors, TiO 2, BaTi2, and SrTiO, react and produce deposits or intermediates independently.
Abstract: A new liquid source chemical vapor deposition process is introduced for preparing (Ba, Sr)TiO 3 (BST) thin films from Ba(DPM) 2 (tetraglyme), Sr(DPM) 2 (tetraglyme), and Ti(DPM) 2 (i-OC 3 H 7 ) 2 (DPM = dipivaloylmethanato) dissolved in butylacetate. The film deposition mechanism as well as the BST film growth rate are determined by studying the film formation and the associated chemical reaction kinetics as a function of temperature and gas flow rates. It is demonstrated that in the formation of BST films, the three precursors, TiO 2 , BaTiO 3 , and SrTiO 3 , react and produce deposits or intermediates independently. The deposition rate of BST films is the summation of the respective growth rates of the BaO, SrO, and TiO 2 films. The gas-phase decomposition reactions of the precursors, rather than their surface reactions on the substrate, dominate the BST film growth rate. The kinetics of the three overall chemical reactions to produce the oxide films of Ba, Sr, and Ti are determined by comparing the experimental film deposition rates and the numerical results. The suggested chemical reaction kinetics and the reaction rate constants are expected to be important in the design of metallorganic chemical vapor deposition reactors for BST films.
Patent•
10 Mar 2000
TL;DR: In this article, a method for producing metallic particulate powder by using an atomizing thermal decomposition solution was proposed. But this method is not suitable for the high purity and dispersibility of metallic particles.
Abstract: PROBLEM TO BE SOLVED: To provide a method of producing metallic particulate powder by which dense, spherical metallic particulate powder excellent in dispersibility and high in purity can be obtained SOLUTION: In this method for producing metallic particulate powder, an aqueous solution of nickel acetate or an aqueous solution of nickel formate or an aqueous solution of copper acetate or an aqueous solution of copper formate is used as atomizing thermal decomposition solution, and spherical metallic particulate powder is obtained by an atomizing thermal decomposition method
21 May 2000
TL;DR: In this article, a theoretical model for considering the size dispersity effect on the conduction development and percolation limit is presented. And the model suggests an innovative route for processing new conductive adhesives with ultralow per-colation limits.
Abstract: A well known approach for reducing the electrical percolation threshold of an electrically conductive material is to mix the relatively small sized conducting fillers with the relatively large sized inert particles. The percolation limit in terms of the volume fraction of conducting particles is known to decrease with increasing ratio of the mean size between the small and large particles. However, both the small conducting and large inert particles rarely exist as monodispersed, rather, there is a respective size distribution for each of them. Such a size distribution is expected to affect the development of conductivity as well as the percolation threshold. The first theoretical model for considering such a size dispersity effect on the conduction development and the percolation limit is reported. It is shown that the present model not only includes all the previous ones for considering only the particle size ratio effect, it considers the respective role played by the ratio of mean particle size, the size dispersity and the volume fraction on the electrical conduction development and the percolation limit. The model suggests an innovative route for processing new conductive adhesives with ultralow percolation limits. Other implications for manufacturing electrically conductive adhesives are also discussed.
02 Apr 2000
TL;DR: In this article, the Clausius-Mosotti equation was used to determine the enhancement of polymeric composites as a function of volume fraction of particles, and it was shown that the enhancement increases with the particle volume fraction.
Abstract: Polymeric composites of high dielectric constants find many applications in microelectronics and optics It is experimentally known that the interaction of dielectric particles dispersed in a polymeric composite can lead to an enhancement of the dielectric constant of the composite relative to that as predicted by Clausius-Mosotti equation A model for determining this enhancement as a function of volume fraction of particles is introduced It is shown that the enhancement increases with the particle volume fraction, which is consistent with the experimental evidence Our theoretical results lead to the development of a viable means for enhancing the dielectric constant of composites by thermally poling under a sufficiently high electric field
TL;DR: In this paper, a low pressure differential mobility analyzer (LPDMA) is used for low pressure differential mobility analysis (LDA) and the results show that LDA is effective in low pressure environments.
Abstract: 窒素気流中で大気圧場で発生させたAgナノ粒子を対象として, 分級部の短い新しいタイプのウイーン大学型の減圧用微分型静電分級器 (Low Pressure Differential Mobility Analyzer, LPDMA) を用いて, Agナノ粒子のその場サイズ測定および分級特性試験を123～300Torrの減圧場において系統的に行った. 160Torrの減圧場で本LPDMAで測定した体積平均径DV, DMAは, Agナノ粒子の粒径6～15nmの範囲において, LPDMA入口でサンプリングした粒子を透過型電子顕微鏡 (TEM) で観察して求めた体積平均径DV, TEMよりも約7%程度大きいものの, 良い相関を示した.また, 160Torrの減圧場において本LPDMAを用いて6～25nmの範囲で, シースガスとエアロゾルガス流量比を5: 1で分級した際の設定径は, 分級後サンプリングしてTEM観察した粒子から求めた粒径よりも約14%程度大きいものの, 同様に良い相関を示した. その際, 分級前のサンプリング粒子のTEM像から求めた粒径から算出した幾何標準偏差は1.34～1.50の範囲であるのに対して, 分級後のサンプリング粒子像から算出したそれは1.08～1.17の範囲であり, ブラウン拡散による分級のブロードニングを無視してLPDMA流量比から算出した理論値 (1.093) とほぼ一致した. 以上の結果より, 123～300Torrの減圧場における6～25nmのナノ粒子の粒径測定, 分級操作が, 本LPDMAシステムを用いて十分可能であることを実証した.
Journal Article•
TL;DR: In this paper, the authors propose a method to improve the quality of the data collected by the data collection system by using the information of the user's behavior and the data gathered by the system itself.
Abstract: 環状赤外線放射加熱炉の加熱分布を直接レイトレース法により解析し, 反射鏡の役割と基板の反射率の影響などを考察した. 環状赤外線光源に沿って設けられた円筒鏡は光源直下の赤外線吸収量を増大させるだけでなく, 円筒鏡に沿って同心円状に赤外線吸収効率を増大させ, 同心円状の基板の赤外線吸収量分布の均一性を向上させる働きをしていると考えられる. 更に, 光源に隣接する円筒鏡だけでなく, その外側の円筒鏡によっても赤外線吸収効率が向上されることが把握された. 基板の反射率が大きくなると共に, そして光源と基板の距離の増大と共に赤外線吸収量は減少し, 赤外線吸収量分布はなだらかになることが把握された. 熱による基板からの放射光は, 放射光が発した位置の近傍に戻るものが多く, 基板の外周ほど加熱炉外へ逃げ易いことが計算により定量的に確認された.
Patent•
[...]
07 Jan 2000
TL;DR: In this paper, a small current meter capable of reducing the noise in a current to be measured is provided, where external threads 16a are carved on the outer surface of an end part of the bar-shaped member 16, projecting downward from a fixed ring 17, and internal threads 21a are inscribed on the inner surface of the receiving part 21 by thread connection.
Abstract: PROBLEM TO BE SOLVED: To provide a small current meter capable of reducing effectively the noise in a current to be measured SOLUTION: A bar-shaped member 16 is installed projectingly from the bottom surface 18a of a plate 18 of a Faraday cup 10, and a receiving part 21 is installed on the upper surface 25a of an outer box 25 of a preamplifier device 20 In this case, external threads 16a are carved on the outer surface of an end part of the bar-shaped member 16, projecting downward from a fixed ring 17, and internal threads 21a are carved on the inner surface of the receiving part 21, and the bar-shaped member 16 is connected to the receiving part 21 by thread connection A shield ring 22, encircling the connection part between the bar-shaped member 16 and the receiving part 21, is interposed between the bottom surface 18a of the plate 18 and the upper surface 25a of the outer box 25, to thereby shield an electromagnetic wave entering the connection part between the bar-shaped member 16 and the receiving part 21