Optimization of interface structures in crystalline silicon heterojunction solar cells

In heterojunction solar cells consisting of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si), suppression of epitaxial growth at the heterointerface is found to be crucial to achieve high solar cell efficiencies. In order to avoid the epitaxial growth, wide-gap hydrogenated amorphous silicon oxide (a-SiO:H) has been applied to the heterojunction solar cells. We have fabricated a-SiO:H/c-Si solar cells using n-type and p-type c-Si substrates and demonstrated that incorporation of the a-SiO:H i layer prevents the harmful epitaxial growth at the heterointerface completely.     

Thermal and electrical conduction properties of vertically aligned carbon nanotubes produced by water-assisted chemical vapor deposition

We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe–Ti–O nanoparticles as catalyst. Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct-current four-terminal method, respectively. The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors. The electrical resistance shows a T^−1/4 temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping.     

Palladium‐Catalyzed Hydroxymethylation of Aryl‐ and Heteroarylboronic Acids using Aqueous Formaldehyde

Cyclometallated NHC palladium complexes prepared from palladium(II) acetate [Pd(OAc)₂] and unsymmetrical 1,3‐diarylimidazolinium salts catalyzed the hydroxymethylation of (hetero)arylboronic acids using an excess amount of formalin to afford (hetero)arylmethanols in good to satisfactory yields.

     

Evidence of Oxygen Ferromagnetism in ZnO Based Materials

Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.     

Thin reduced graphene oxide interlayer with a conjugated block copolymer for high performance non-volatile ferroelectric polymer memory

Polymer ferroelectric-gate field effect transistors (Fe-FETs) employing ferroelectric polymer thin films as gate insulators are highly attractive as a next-generation non-volatile memory. For minimizing gate leakage current of a device which arises from electrically defective ferroelectric polymer layer in particular at low operation voltage, the materials design of interlayers between the ferroelectric insulator and gate electrode is essential. Here, we introduce a new solution-processed interlayer of conductive reduced graphene oxides (rGOs) modified with a conjugated block copolymer, poly(styrene-block-paraphenylene) (PS-b-PPP). A FeFET with a solution-processed p-type oligomeric semiconducting channel and ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) insulator exhibited characteristic source–drain current hysteresis arising from ferroelectric polarization switching of a PVDF-TrFE insulator. Our PS-b-PPP modified rGOs (PMrGOs) with conductive moieties embedded in insulating polymer matrix not only significantly reduced the gate leakage current but also efficiently lowered operation voltage of the device. In consequence, the device showed large memory gate voltage window and high ON/OFF source–drain current ratio with excellent data retention and read/write cycle endurance. Furthermore, our PMrGOs interlayers were successfully employed to FeFETs fabricated on mechanically flexible substrates with promising non-volatile memory performance under repetitive bending deformation.     

Thermodynamic analysis for the controllability of elements in the recycling process of metals

This study presents the results of chemical thermodynamic analysis on the distribution of elements in the smelting process of metallic materials to examine the controllability of impurities in the pyrometallurgical technique. The results of the present work can give an answer against the frequently given question; "Which impurity element can be removable in metallurgical process?" or "How far can the impurity level be controlled?". The proposed method was applied to estimate the distribution of 29 elements for a copper converter and 26 elements for a steel-making process and shows the distribution tendency of elements among the gas, slag, and metal phases as well as clarifying which metals can be recovered or removed from secondary resources in metallurgical processes. The effects of temperature, oxygen partial pressure, and slag composition on the distribution ratio of elements were also evaluated, and the removal limit or controllability of impurity in these two processes was presented. This study results in thermodynamic features of various elements in the pyrometallurgical process and also shows, even by varying process parameters such as temperature and oxygen partial pressure, no drastic improvement of removal efficiency should be expected, except for lead and tin in copper.     

Use of electrolyzed water ice for preserving freshness of pacific saury (Cololabis saira)

The effects of electrolyzed water ice (EW-ice), compared with traditional tap water ice (TW-ice), on the microbiological, chemical, and sensory quality of Pacific saury (Cololabis saira) stored for a period of up to 30 days at 4 degrees C were evaluated. EW-ice with active chlorine at a concentration of 34 mg/kg was prepared from weak acidic electrolyzed water, whose pH, oxidation-reduction potential, and chlorine content were 5, 866 mV, and 47 mg/liter, respectively. Microbiological analysis showed that EW-ice, compared with TW-ice, markedly inhibited the growth of both aerobic and psychrotrophic bacteria in saury flesh during refrigerated storage, primarily because of the action of active chlorine. Chemical analysis revealed that EW-ice retarded the formation of volatile basic nitrogen and thiobarbituric acid-reactive substances and reduced the accumulation of alkaline compounds in the fish flesh in comparison with TW-ice. Sensory analysis confirmed that the freshness of saury was better preserved in EW-ice than in TW-ice and showed that the saury stored in EW-ice had a shelf life that was about 4 to 5 days longer than the fish stored in TW-ice.     

The effect of heat sealing temperature on the properties of OPP/CPP heat seal. I. Mechanical properties

The effect of heat sealing temperature on the mechanical properties and morphology of OPP/CPP laminate films was investigated. The laminated films were placed in an impulse type heat sealing machine with both CPP sides facing each other. The temperatures investigated ranged from 100 to 250°C. T‐peel and tensile tests in combination with SEM were used to characterize the heat seals. A minimum seal initiation temperature of 120°C was identified for OPP/CPP laminate heat sealing. Peel strength increased sharply from zero at 110°C to maximum at 120°C, after which a gradual decrease was observed. Tensile strength initially increased until 120°C, after which it gradually decreased until 170°C and assumed a constant value beyond that. The initial rise has been associated to cold crystallization, while the reduction between 120°C and 170°C was due to relaxation in molecular orientation. Beyond 170°C, all the orientation in the laminate has been lost so orientation effects are nullified. Morphological studies with SEM revealed that seals were partially formed at lower temperatures, while the laminates were totally fused together at high temperatures, with intermediate temperatures showing properties that lie in between. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 753–760, 2005     

Effects of External Stress on Defect Annihilation and Bubble Swelling During Annealing of Neutron-Irradiated Silicon Carbide

Silicon carbide ceramics fabricated by three different methods were neutron-irradiated in the Japan Materials Testing Reactor and were subsequently annealed free from stresses or under compressive external stresses. The macroscopic length monotonically decreased with annealing above the irradiation temperature, when annealing was performed below ∼1300°C. This decrease was not affected by the external stresses. However, annealing above ∼1300°C led to an increase in length in B-containing SiC. The expansion was caused by the formation and growth of He bubbles at grain boundaries. The growth occurred by flow of vacancies into bubbles. The compressive stress retarded the expansion along the loading direction. This retardation was compensated by a length incrase along the lateral direction. The effect of external stresses was discussed by considering differently oriented He bubbles. One bubble was stress favored and the other stress unfavored. The stress determined the diffusional flow of vacancy-He atom complexes between the favored and unfavored bubbles which were caused by anisotropic expansion under a directional stress.     

Effect of heat‐sealing temperature on the properties of OPP/CPP heat seals. Part II. Crystallinity and thermomechanical properties

The crystalline structure of the heat‐sealed part of oriented polypropylene (OPP) and cast polypropylene (CPP) films was investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy, and thermal mechanical analysis (TMA). The relationship between the crystalline structure and the mechanical properties was analyzed. It was found that the high total crystallinity of both OPP and CPP gave rise to good mechanical properties and that the orientation of the crystalline structure in the OPP film also was an important factor. The optimum condition for heat sealing was the temperature at which total crystallinity was highest while still retaining the crystalline orientation of OPP. The assessment of crystalline orientation by TMA is an innovation initiated by the authors. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 513–519, 2006