Electrical characterization of homoepitaxial diamond p–n junction

Electrical properties of homoepitaxial diamond p–n⁺ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 10⁵ at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density N_i of the p–n⁺ junction is not uniform and N_i at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce N_i at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n⁺ interface and incorporating during the growth of p-type layer, which makes to reduce N_i at the vicinity of the p–n⁺ interface.     

Crystallization process and magnetic properties of Fe100−x,B x (10 ≦ × ≦ 35) amorphous alloys and supersaturated state of boron inα-Fe

Amorphous specimens of Fe_100–x B _x were prepared in the range 10 × 35 at % B by a single-roller method. The crystallization process and the boron concentration dependence of the Curie temperature were examined by differential scanning calorimetry, X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. Two-step crystallization was observed in specimens with× < 17: amorphous amorphous + boron-supersaturated b c c phase (-Fe(B)) t-Fe₃B +-Fe. A single-Fe(B) phase was not observed. The transition temperature from t-Fe₃B to stable (-Fe + t-Fe₂B) sensitively depends on the boron content in the alloys. The crystallization temperature (T _x) of the amorphous alloys was almost unchanged for 17 × 31, but increased remarkably at high boron concentrations of× 33, where the decomposition products consisted of t-Fe₂B and o-FeB. The Curie temperature (T _c) of the amorphous phase was as low as 480 K at× = 10, increased with increasing boron content up to 820 K and then decreased in the high boron concentration alloys of× > 28. A single-Fe(B) phase was not detected in the as-quenched specimens of× = 8 and 10. The phase coexisted with the o-Fe₃B and amorphous phases. The lattice parameter of the phase was 0.2861₀ nm which was smaller than that of pure iron by 2/1000, indicating the substitutional occupation of boron atoms in the b c c lattice.     

Effect of cation structure on the electrochemical and thermal properties of ion conductive polymers obtained from polymerizable ionic liquids

Several onium cations having vinyl group formed ionic liquids after coupling with bis(trifluoromethanesulfonyl)imide. These monomers were polymerized, and the relation between onium cation structure and properties of thus polymerized ionic liquids was investigated. The polymerized ionic liquid having ethylimiadzolium cation unit showed the highest ionic conductivity of around 10⁻⁴ S cm⁻¹ at 30 °C among the obtained polymers reflecting the lowest glass transition temperature of −59 °C. These polymers were thermally stable and their decomposition temperatures were about 350 °C. The ionic conductivity of the polymerized ionic liquids decreased by both the addition of lithium bis(trifluoromethanesulfonyl)imide and the polymerization in the presence of cross-linker. However, the polymerized ionic liquid having 1-methylpiperidinium cation structure showed good lithium ion transference number of 0.43 at room temperature.     

An Advanced Oscillation Mixing Method for Improving the Cooling Uniformity in Quenching

In quenching, the cooling uniformity is most important to diminish distortion occurring on work pieces. As a trial to accomplish uniform cooling, therefore, there exist various mixing methods of a quenchant and the quenchant circulation with an external pump has so far been the well accepted mixing method. However, this study proposes an advanced oscillation mixing method that can improve more the cooling uniformity in quenching. The proposed method includes a stirrer in oscillating motion, so that the simultaneous oscillating and mixing movements of the stirrer are considered to provide efecfively the uniform cooling characteristics for the quenchant. In comparison with the case of the circulation pump mixing, the investigation using the oscillation mixing method has demonstrated the following two experimental facts:(1) the short vapor blanket stage caused by the quick breakage of the oil vapor blanket and (2) the reduced variation of the quenching distortion.     

A Recommendation System Keeping Both Precision and Recall by Extraction of Uninteresting Information

A recommendation system which recommends interesting information to the target user must guarantee high precision and recall. However, there is trade-off between precision and recall. In this paper, we propose a web page recommendation method balancing both of them by take advantage of uninteresting information. The proposed method extracts the interest and uninterest indicators from not only historical interesting web pages but also uninteresting ones in a target genre. The historical interesting and uninteresting information is derived based on the browsing time and bookmarking. The proposed method can keep precision and recall by excluding the uninteresting information from the recommended ones based on the interest and uninterest indicators. The experimental result proved that the proposed method can improve the precision and recall than an existing method.     

Catalytic Performance of Aged Rh/CeO2–ZrO2 for NO–C3H6–O2 Reaction Under a Stoichiometric Condition

The activity of Rh/CeO₂ for NO reduction by C₃H₆ was gradually deceased by mixing with ZrO₂ until 68 mol%. Rh supported on CeO₂–ZrO₂ with higher OSC was found to show lower catalytic activity. High OSC of CeO₂–ZrO₂ would probably stabilize the surface of Rh in oxidized state, resulting in low activity and low efficiency of C₃H₆ utilization for NO reduction. In situ FT-IR spectroscopy suggested that mononitrosyl species such as Rh(NO)^δ? and Rh(NO)^δ+ are reaction intermediates in the NO–C₃H₆–O₂ reaction over Rh/CeO₂–ZrO₂ catalysts.     

Monte Carlo simulation of stress corrosion cracking on a smooth surface of sensitized stainless steel type 304

Stress corrosion cracking (SCC) on a smooth surface of structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under combination of material, stress and corrosive environment. In this paper, a Monte Carlo simulation of the SCC process is proposed based on stochastic properties for micro crack initiation and concepts in fracture mechanics for crack coalescence and propagation. The procedure is as follows: The possible number of grain-sized micro cracks which can be initiated is set for a given space and initiation times for all cracks are assigned by random numbers based on exponential distribution. Sites and sizes of cracks are assigned by uniform random numbers and normal random numbers, respectively. Coalescence and propagation of cracks are determined based on fracture mechanics. The emphasis in the model is put on the influence of semi-elliptical surface cracks. Numerical simulations are carried out based on the results of creviced-bent-beam tests for sensitized stainless steel type 304 under high-temperature and high-purity water containing dissolved oxygen and the influence of micro crack initiation rate and coalescence condition on the simulation results is discussed.     

Viscoelastic behavior of poly(butyl methacrylate) densely grafted on silica nanoparticles

A series of poly(butyl methacrylate)s (PBMAs) with various molar masses (33 000–270 000 g mol^?1), which were densely grafted on fumed silica nanoparticles (PBMA–SiO₂), were synthesized by surface‐initiated atom transfer radical polymerization. The dynamic viscoelastic behavior of PBMA–SiO₂ was systematically investigated in the solid and molten states with oscillatory strains, and compared to that of a conventional nanocomposite (PBMA/SiO₂). The storage moduli of PBMA–SiO₂ and PBMA/SiO₂ are equivalent in the solid state, whereas the storage modulus of PBMA–SiO₂ is lower than that of PBMA/SiO₂ in the molten state, especially at high silica loading. This is because the formation of a network structure composed of the silica nanoparticles in PBMA–SiO₂ is strongly suppressed by the polymer brushes on the particles. In contrast, even at low silica loading, the PBMA–SiO₂ system exhibits a gel‐like behavior resulting from a steric repulsion between the composite particles, because all of the tethered polymers behave as bound polymers. Copyright © 2011 Society of Chemical Industry     

Effect of mixing ratio on bactericidal action of MgO–CaO powders

MgO–CaO powders were prepared with different molar ratios (MgO/CaO) at 1400 °C for 2 h in air. By using the powder samples obtained, the change in bactericidal effect as a function of MgO–CaO composition was studied by colony count method. From the XRD measurements, it was found that CaO solid solution was formed by the replacement of Mg²⁺ ion with larger Ca²⁺ ion. However, no formation of MgO solid solution was observed. The average particle size and the specific surface area of the samples used in this study were about 0.2 m and 10.5m²g^–1, respectively. The pH values of physiological saline containing powder samples increased with the increase of CaO content, and the value reached 12.1 in sample with the molar ratio (MgO/CaO) of 0.25. From the results of bactericidal tests for Staphylococcus aureus, it was found that the bactericidal effect increased with the increase of CaO content in the samples.     

Preparation of Lead Lanthanum Zirconate Titanate (PLZT, (Pb,La)(Zr,Ti)O3) Fibers by Sol-Gel Method

Lead lanthanum zirconate titanate (PLZT, (Pb,La)(Zr,-Ti)O₃) ceramic fibers were prepared by the sol-gel method from a solution of lead acetate trihydrate, lanthanum isopropoxide, zirconium n -propoxide, and titanium isopropoxide that contained 2-methoxyethanol as the solvent. The sols obtained from the solution were concentrated at 156°-174°C for 2 h. Concentration at higher temperatures resulted in more-viscous sols of higher specific gravities. The concentration resulted in the formation of spinnable sols, which had viscosities >10⁵ mPas and exhibited Newtonian flow properties. These spinnable sols were formed to be so stable that no change in viscosity and spinnability was observed for more than three months when stored in a sealed container at room temperature. Gel-to-ceramic fiber conversion was investigated by means of X-ray diffractometry, infrared spectroscopy, and thermal analysis. Single-phase perovskite PLZT ceramic fibers 5-200 μm in diameter and >20 cm in length were obtained. Scanning electron microscopy (SEM) observation and Brunauer-Emmett-Teller (BET) measurement showed that heat treatment of the fibers at a lower rate resulted in the formation of fibers of denser microstructure. Although the SEM image of the cross section of the fibers revealed a relatively dense microstructure and a laser beam could be transmitted through a fiber 6 mm in length, BET measurement of the fibers indicated that the fibers had more than a few percent of open porosities, and scattering of light was observed in the laser-beam guiding test.