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Sample records for additive si source

  1. Size and shape effect of SiC source/drain on strained Si.

    PubMed

    Byeon, D S; Kim, S W; Ko, D H

    2014-10-01

    Strained Si is used to enhance carrier mobility in MOSFET devices. Epi-grown Si(1-x)C(x) as a source/drain induces strain on a channel because its lattice constant is smaller than Si. The distribution of stress varies with the layout of the device and can involve gate length, source/drain width, elevation height, etc. In this work, we report on how these parameters effect channel strain by employing the Finite Element Method. A 3-dimensional model and anisotropic properties such as the elastic constant and Poisson's ratio were adopted for high accuracy. Si0.983C0.017 was used as the source/drain on a Si substrate. The lateral channel strain was calculated based on a 30-90 nm gate length, a 30-90 nm source/drain width and 0-30 nm elevated source/drain shapes. The results showed that, when the gate length is longer, the channel strain is lower. On the other hand, source/drain width affects channel strain in a reverse manner. For models with the same gate length and source/drain width: 30, 60, 90 nm, the average channel strain is lower when the gate length and source/drain width are shorter. An additional parameter, namely, source/drain elevation height, was also studied. Interestingly, the effect of elevated shape is dependent on gate length and source/drain width.

  2. Refinement of Eutectic Si Phase in Al-5Si Alloys with Yb Additions

    NASA Astrophysics Data System (ADS)

    Li, J. H.; Suetsugu, S.; Tsunekawa, Y.; Schumacher, P.

    2013-02-01

    A series of Al-5 wt pct Si alloys with Yb additions (up to 6100 ppm) have been investigated using thermal analysis and multiscale microstructure characterization techniques. The addition of Yb was found to cause no modification effect to a fibrous morphology involving Si twinning; however, a refined plate-like eutectic structure was observed. The Al2Si2Yb phase was observed with Yb addition level of more than 1000 ppm. Within the eutectic Al and Si phases, the Al2Si2Yb phase was also found as a precipitation from the remained liquid. No Yb was detected in the α-Al matrix or plate-like Si particle, even with Yb addition up to 6100 ppm. The absence of Yb inside the eutectic Si particle may partly explain why no significant Si twinning was observed along {111}Si planes in the eutectic Si particle. In addition, the formation of the thermodynamic stable YbP phases is also proposed to deteriorate the potency of AlP phase in Al alloys. This investigation highlights to distinguish the modification associated with the ever present P in Al alloys. We define modification as a transition from faceted to fibrous morphology, while a reduction of the Si size is termed refinement.

  3. Removal of B from Si by Hf addition during Al-Si solvent refining process.

    PubMed

    Lei, Yun; Ma, Wenhui; Sun, Luen; Wu, Jijun; Dai, Yongnian; Morita, Kazuki

    2016-01-01

    A small amount of Hf was employed as a new additive to improve B removal in the electromagnetic solidification refinement of Si with an Al-Si melt, because Hf has a very strong affinity for B. The segregation ratio of Hf between the solid Si and Al-Si melt was estimated to range from 4.9 × 10(-6) to 8.8 × 10(-7) for Al concentrations of 0 to 64 at.%, respectively. The activity coefficient of Hf in solid Si at its infinite dilution was also estimated. A small addition of Hf (<1025 parts per million atoms, ppma) significantly improved the B removal. It was confirmed that the use of an increased Hf addition, slower cooling rate, and Al-rich Al-Si melt as the refining solvent removed B more efficiently. B in Si could be removed as much as 98.2% with 410 ppma Hf addition when the liquidus temperature of the Al-Si melt was 1173 K and the cooling rate was 4.5-7.6 K min(-1). The B content in Si could be controlled from 153 ppma to 2.7 ppma, which meets the acceptable level for solar-grade Si.

  4. Removal of B from Si by Hf addition during Al–Si solvent refining process

    PubMed Central

    Lei, Yun; Ma, Wenhui; Sun, Luen; Wu, Jijun; Dai, Yongnian; Morita, Kazuki

    2016-01-01

    Abstract A small amount of Hf was employed as a new additive to improve B removal in the electromagnetic solidification refinement of Si with an Al–Si melt, because Hf has a very strong affinity for B. The segregation ratio of Hf between the solid Si and Al–Si melt was estimated to range from 4.9 × 10−6 to 8.8 × 10−7 for Al concentrations of 0 to 64 at.%, respectively. The activity coefficient of Hf in solid Si at its infinite dilution was also estimated. A small addition of Hf (<1025 parts per million atoms, ppma) significantly improved the B removal. It was confirmed that the use of an increased Hf addition, slower cooling rate, and Al-rich Al–Si melt as the refining solvent removed B more efficiently. B in Si could be removed as much as 98.2% with 410 ppma Hf addition when the liquidus temperature of the Al–Si melt was 1173 K and the cooling rate was 4.5–7.6 K min–1. The B content in Si could be controlled from 153 ppma to 2.7 ppma, which meets the acceptable level for solar-grade Si. PMID:27877853

  5. B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

    NASA Astrophysics Data System (ADS)

    Lei, Yun; Ma, Wenhui; Sun, Luen; Dai, Yongnian; Morita, Kazuki

    2016-02-01

    This study investigated a new process of enhancing B removal by adding small amounts of Zr in the electromagnetic solidification refinement of Si with Si-Al melt. B in Si was removed by as much as 97.2 pct by adding less than 1057 ppma Zr, and the added Zr was removed by as much as 99.7 pct. In addition, Zr is more effective in enhancing B removal than Ti in the same electromagnetic solidification refining process.

  6. Hole mobility in strained Si/SiGe/vicinal Si(110) grown by gas source MBE

    NASA Astrophysics Data System (ADS)

    Arimoto, Keisuke; Yagi, Sosuke; Yamanaka, Junji; Hara, Kosuke O.; Sawano, Kentarou; Usami, Noritaka; Nakagawa, Kiyokazu

    2017-06-01

    Strained Si/SiGe heterostructures were grown on vicinal Si(110) substrates by using gas-source MBE, and relationship between structural aspects and effective hole mobility was investigated. The surface inclination was found to be effective in obtaining smoother surface. By growing the film at different substrate temperatures, samples which were significantly different in surface morphology and crystalline defects were obtained. Under a certain condition, the strain in the SiGe layer was found to be relaxed mainly by microtwin formation. It was found that this strain relaxation pathway was favorable for pMOSFETs with [1 ̅10 ] channel. As a result, the effective hole mobility as high as 350 cm2/Vs was achieved on conventional Si substrate.

  7. Synthesis and structural property of Si nanosheets connected to Si nanowires using MnCl2/Si powder source

    NASA Astrophysics Data System (ADS)

    Meng, Erchao; Ueki, Akiko; Meng, Xiang; Suzuki, Hiroaki; Itahara, Hiroshi; Tatsuoka, Hirokazu

    2016-08-01

    Si nanosheets connected to Si nanowires were synthesized using a MnCl2/Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH4 or SiCl4. The existence of the Si nanosheets connected to the Si<111> nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of <211> perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.

  8. Effect of Si addition on secondary hardening of alloy steels

    NASA Astrophysics Data System (ADS)

    Cho, Ki Sub; Kwon, Hoon

    2017-07-01

    In this work, the precipitation kinetics of secondary carbides in Si-bearing steels was examined via calorimetric analysis coupled with the Johnson-Mehl-Avrami kinetic model. In particular, the properties of two commercial high-speed steels (10V and ASP 23), which contained the secondary carbides described by the formulas MC/M23C6 and MC/M23C6/M6C, respectively, were investigated and compared with those of PSD and AISI D2 steels. The obtained results revealed that the presence of Si in alloys not only inhibited the precipitation of the cementite phase, but also accelerated the precipitation kinetics of the secondary carbides. Using the obtained magnitudes of the thermodynamic driving force for complete precipitation in the metastable systems formed under para-equilibrium and ortho-equilibrium conditions, it was found that the addition of Si decreased the stability of the system produced under para-equilibrium conditions and, therefore, enabled the diffusion of interstitial carbon species at low temperatures as well as rapid aging during the secondary hardening reaction.

  9. Scalable Production of Si Nanoparticles Directly from Low Grade Sources for Lithium-Ion Battery Anode.

    PubMed

    Zhu, Bin; Jin, Yan; Tan, Yingling; Zong, Linqi; Hu, Yue; Chen, Lei; Chen, Yanbin; Zhang, Qiao; Zhu, Jia

    2015-09-09

    Silicon, one of the most promising candidates as lithium-ion battery anode, has attracted much attention due to its high theoretical capacity, abundant existence, and mature infrastructure. Recently, Si nanostructures-based lithium-ion battery anode, with sophisticated structure designs and process development, has made significant progress. However, low cost and scalable processes to produce these Si nanostructures remained as a challenge, which limits the widespread applications. Herein, we demonstrate that Si nanoparticles with controlled size can be massively produced directly from low grade Si sources through a scalable high energy mechanical milling process. In addition, we systematically studied Si nanoparticles produced from two major low grade Si sources, metallurgical silicon (∼99 wt % Si, $1/kg) and ferrosilicon (∼83 wt % Si, $0.6/kg). It is found that nanoparticles produced from ferrosilicon sources contain FeSi2, which can serve as a buffer layer to alleviate the mechanical fractures of volume expansion, whereas nanoparticles from metallurgical Si sources have higher capacity and better kinetic properties because of higher purity and better electronic transport properties. Ferrosilicon nanoparticles and metallurgical Si nanoparticles demonstrate over 100 stable deep cycling after carbon coating with the reversible capacities of 1360 mAh g(-1) and 1205 mAh g(-1), respectively. Therefore, our approach provides a new strategy for cost-effective, energy-efficient, large scale synthesis of functional Si electrode materials.

  10. Effect of Si addition on AC and DC magnetic properties of (Fe-P)-Si alloy

    NASA Astrophysics Data System (ADS)

    Gautam, Ravi; Prabhu, D.; Chandrasekaran, V.; Gopalan, R.; Sundararajan, G.

    2016-05-01

    We report a new (Fe-P)-Si based alloy with relatively high induction (1.8-1.9 T), low coercivity (< 80 A/m), high resistivity (˜38 μΩ cm) and low core loss (217 W/kg @ 1 T/1 kHz) comparable to the commercially available M530-50 A5 Si-steel. The attractive magnetic and electrical properties are attributed to i) the two phase microstructure of fine nano precipitates of Fe3P dispersed in α-Fe matrix achieved by a two-step heat-treatment process and ii) Si addition enhancing the resistivity of the α-Fe matrix phase. As the alloy processing is by conventional wrought metallurgy method, it has the potential for large scale production.

  11. Two New SiO Maser Sources in High-Mass Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yun, Youngjoo; Kim, Jaeheon; Liu, Tie; Kim, Kee-Tae; Choi, Minho

    2016-08-01

    Silicon monoxide (SiO) masers are rare in star-forming regions, with the exception of five known SiO maser sources. However, we detected two new SiO maser sources from infrared-loud clumps of the high-mass star-forming regions G19.61-0.23 and G75.78+0.34. High angular resolution observations toward G19.61-0.23 suggest that the deeply embedded young stellar object (YSO) of SMA1 is powering the SiO masers. In addition, the SiO v = 1, J = 1 \\to 0 line shows four spike features, while the v = 2 maser shows combined features of one spike and broad wing components, implying energetic activities of the YSO of SMA1 in the G19.61-0.23 hot molecular core. The SiO v = 0, J = 2 \\to 1 emission shows bipolar outflows in the NE-SW direction with respect to the center of the SiO maser source. A high angular resolution map of the SiO v = 1, J = 2 \\to 1 maser in G75.78+0.34 shows that the SiO maser is associated with the CORE source at the earliest stage of high-mass star formation. Therefore, the newly detected SiO masers and their associated outflows will provide good probes for investigating this early high-mass star formation.

  12. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR SiO MASER SOURCES

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon E-mail: jhkim@kasi.re.kr

    2012-11-01

    We carried out simultaneous observations of four maser lines, SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23}, toward 83 known SiO maser sources without H{sub 2}O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H{sub 2}O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H{sub 2}O maser emission without SiO maser emission was detected from one source. Therefore, H{sub 2}O maser emission was newly detected from 15 sources. SiO maser emission without H{sub 2}O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H{sub 2}O maser emission detected. SiO v = 2 maser emission was detected from nine sources without v = 1 maser detection. The SiO v = 2 maser sources without the v = 1 maser detections need to be investigated, with a large number of v = 2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H{sub 2}O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H{sub 2}O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H{sub 2}O masers are discussed in IRAS two-color diagrams.

  13. Optimum condition to fabricate 5-10 nm SiO2/Si structure using advanced nitric acid oxidation of Si method with Si source

    NASA Astrophysics Data System (ADS)

    Imamura, Kentaro; Matsumoto, Taketoshi; Kobayashi, Hikaru

    2012-12-01

    A low temperature (≦120 °C) fabrication method to form relatively thick SiO2/Si structure with a Si source has been developed using the advanced nitric acid oxidation of Si (NAOS) method, and the formation mechanism has been investigated. The reaction mechanism consists of direct oxidation of Si, dissolution of Si sources, and surface reaction of the dissolved Si species. The dissolved Si species is present in HNO3 solutions as mono-silicic acid and reacts with oxidizing species formed by decomposition of HNO3 on an ultrathin SiO2 layer (i.e., 1.4 nm) produced by the direct oxidation of Si substrates with HNO3 solutions. To achieve a uniform thickness of SiO2 layer with a smooth surface, HNO3 solutions with concentrations higher than 60 wt. % are needed because the dissolved Si species polymerizes in HNO3 solutions when the concentration is below 60 wt. %, resulting in the formation of SiO2 particles in HNO3, which are deposited afterwards on the SiO2 layer. In spite of the low temperature formation at 120 °C, the electrical characteristics of the advanced NAOS SiO2 layer formed with 68 wt. % HNO3 and subsequent post-metallization anneal at 250 °C are nearly identical to those of thermal oxide formed at 900 °C.

  14. Refinement of Eutectic Si in High Purity Al-5Si Alloys with Combined Ca and P Additions

    NASA Astrophysics Data System (ADS)

    Ludwig, Thomas Hartmut; Li, Jiehua; Schaffer, Paul Louis; Schumacher, Peter; Arnberg, Lars

    2015-01-01

    The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the recalescence undercooling, respectively. Optical microscopy, SEM, EPMA, and TEM were employed to characterize the resultant microstructures. It was found that 250 ppm Ca addition to Al-5Si wt pct alloys with higher P contents leads to a significant increase of the eutectic droplet undercooling. For low or moderate cooling rates, the TEM results underline that Ca additions do not promote Si twinning. Thus, a higher twin density cannot be expected in Ca containing Al-Si alloys after, e.g., sand casting. Consequently, a refinement of the eutectic Si from coarse flake-like to fine plate-like structure, rather than a modification of the eutectic Si to a fibrous morphology, was achieved. This strongly indicates that the main purpose of Ca additions is to counteract the coarsening effect of the eutectic Si imposed by higher P concentrations. Significant multiple Si twinning was observed in melt-spun condition; however, this can be attributed to the higher cooling rate. After DSC heating (slow cooling), most of Si twins disappeared. Thus, the well-accepted impurity-induced twinning mechanism may be not valid in the case of Ca addition. The possible refinement mechanisms were discussed in terms of nucleation and growth of eutectic Si. We propose that the pre-eutectic Al2Si2Ca phase and preferential formation of Ca3P2 deactivate impurity particles, most likely AlP, poisoning the nucleation sites for eutectic Si.

  15. Effect of addition of Si on thermal and electrical properties of Al-Si-Al2O3 composites

    NASA Astrophysics Data System (ADS)

    Cao, R.; Jiang, J. X.; Wu, C.; Jiang, X. S.

    2017-06-01

    Al-5wt.%Si-Al2O3, Al-10wt.%Si-Al2O3, Al-20wt.%Si-Al2O3 composites were fabricated by powder metallurgy and in-situ reactive synthesis technology. The impact of the addition of Si on the thermal and electrical properties was tested and analysed for vary in silicon content in Al-Si-Al2O3 composites. Results show that both thermal expansion coefficient and thermal conductivity decreased as silicon content increased because Si and Al2O3 dispersed in the Al matrix uniformly to suppress the high thermal expansion of Al to a large extent as well as the interfacial thermal resistance which led to the decline in thermal conductivity. Electrical resistivity increased when silicon content was increased because low thermal expansion coefficient particles of Si and Al2O3 severely damaged the continuity of the Al matrix which hindered movement of electron in the matrix.

  16. The improved mechanical properties of β-CaSiO3 bioceramics with Si3N4 addition.

    PubMed

    Pan, Ying; Zuo, Kaihui; Yao, Dongxu; Yin, Jinwei; Xin, Yunchuan; Xia, Yongfeng; Liang, Hanqin; Zeng, Yuping

    2015-03-01

    The motivation of this study is to investigate the effect of Si3N4 addition on the sinterability of β-CaSiO3 ceramics. β-CaSiO3 ceramics with different content of Si3N4 were prepared at the sintering temperature ranging from 1000°C to 1150°C. The results showed that Si3N4 can be successfully used as sintering additive by being oxidized to form SiO2. The β-CaSiO3 ceramics with 3wt% Si3N4 sintered at 1100°C revealed flexural strength, hardness and fracture toughness of 157.2MPa, 4.4GPa and 2.3MPam(1/2) respectively, which was much higher than that of pure β-CaSiO3 ceramics (41.1MPa, 1.0GPa, 1.1MPam(1/2)). XRD analysis and SEM observation indicated that the main phase maintained to be β-phase after sintering. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Formation of Si nanowires by the electrochemical reduction of SiO2 with Ni or NiO additives.

    PubMed

    Fang, Sheng; Wang, Han; Yang, Juanyu; Yu, Bing; Lu, Shigang

    2016-08-15

    Various morphologies of silicon nanowires (SiNWs) were successfully prepared by the electrochemical reduction of silica mixed with different additives (Au, Ag, Fe, Co, Ni, and NiO, respectively). Straight SiNWs were extensively obtained by the electro-reduction of porous Ni/SiO2 blocks in molten CaCl2 at 900 °C. The SiNWs had a wide diameter distribution of 80 to 350 nm, and the Ni-Si droplets were found on the tips of the nanowires. The growth mechanism of SiNWs was investigated, which could reveal that the nano-sized Ni-Si droplets formed at the Ni/SiO2/CaCl2 three-phase interlines. Based on the mechanism proposed, NiO particles with sub-micrometer size were selected as the additive, and straight SiNWs with diameters of 60 to 150 nm were also prepared via the electrochemical process.

  18. Alternative current source based Schottky contact with additional electric field

    NASA Astrophysics Data System (ADS)

    Mamedov, R. K.; Aslanova, A. R.

    2017-07-01

    Additional electric field (AEF) in the Schottky contacts (SC) that covered the peripheral contact region wide and the complete contact region narrow (as TMBS diode) SC. Under the influence of AEF is a redistribution of free electrons produced at certain temperatures of the semiconductor, and is formed the space charge region (SCR). As a result of the superposition of the electric fields SCR and AEF occurs the resulting electric field (REF). The REF is distributed along a straight line perpendicular to the contact surface, so that its intensity (and potential) has a minimum value on the metal surface and the maximum value at a great distance from the metal surface deep into the SCR. Under the influence of AEF as a sided force the metal becomes negative pole and semiconductor - positive pole, therefore, SC with AEF becomes an alternative current source (ACS). The Ni-nSi SC with different diameters (20-1000 μm) under the influence of the AEF as sided force have become ACS with electromotive force in the order of 0.1-1.0 mV, which are generated the electric current in the range of 10-9-10-7 A, flowing through the external resistance 1000 Ohm.

  19. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR SiO AND H{sub 2}O MASER SOURCES. I

    SciTech Connect

    Kim, Jaeheon; Cho, Se-Hyung; Oh, Chung Sik; Byun, Do-Young E-mail: cho@kasi.re.k E-mail: bdy@kasi.re.k

    2010-05-15

    We present the results of simultaneous observations of both SiO and H{sub 2}O masers toward 166 known SiO and H{sub 2}O maser sources using the Korean VLBI Network Yonsei 21 m radio telescope during 2009 June. Both SiO and H{sub 2}O maser emission were detected from 112 sources giving a detection rate of 67% at one epoch observation. SiO-only maser emission was detected from 42 sources, while H{sub 2}O-only maser emission was detected from four sources. Most of the SiO masers appear around the stellar velocity, while H{sub 2}O masers show different characteristics compared with SiO masers. There are more than 20 sources that show a one-way peak or double peaks with respect to the stellar velocity and SiO maser peak velocity. The H{sub 2}O maser peak and integrated intensity ratios with respect to those of SiO (v = 1) show increasingly larger values from Mira variables, to OH/IR stars, to semi-regular variables. In addition, the IRAS two-color diagram of SiO and H{sub 2}O maser observational results is discussed.

  20. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Regional Offices. In addition, NRC Functional Organization Charts, NUREG-0325, contains detailed... NUCLEAR REGULATORY COMMISSION STATEMENT OF ORGANIZATION AND GENERAL INFORMATION Introduction § 1.3 Sources of additional information. (a) A statement of the NRC's organization, policies, procedures...

  1. Mushroom-free selective epitaxial growth of Si, SiGe and SiGe:B raised sources and drains

    NASA Astrophysics Data System (ADS)

    Hartmann, J. M.; Benevent, V.; Barnes, J. P.; Veillerot, M.; Lafond, D.; Damlencourt, J. F.; Morvan, S.; Prévitali, B.; Andrieu, F.; Loubet, N.; Dutartre, D.

    2013-05-01

    We have evaluated various Cyclic Selective Epitaxial Growth/Etch (CSEGE) processes in order to grow "mushroom-free" Si and SiGe:B Raised Sources and Drains (RSDs) on each side of ultra-short gate length Extra-Thin Silicon-On-Insulator (ET-SOI) transistors. The 750 °C, 20 Torr Si CSEGE process we have developed (5 chlorinated growth steps with four HCl etch steps in-between) yielded excellent crystalline quality, typically 18 nm thick Si RSDs. Growth was conformal along the Si3N4 sidewall spacers, without any poly-Si mushrooms on top of unprotected gates. We have then evaluated on blanket 300 mm Si(001) wafers the feasibility of a 650 °C, 20 Torr SiGe:B CSEGE process (5 chlorinated growth steps with four HCl etch steps in-between, as for Si). As expected, the deposited thickness decreased as the total HCl etch time increased. This came hands in hands with unforeseen (i) decrease of the mean Ge concentration (from 30% down to 26%) and (ii) increase of the substitutional B concentration (from 2 × 1020 cm-3 up to 3 × 1020 cm-3). They were due to fluctuations of the Ge concentration and of the atomic B concentration [B] in such layers (drop of the Ge% and increase of [B] at etch step locations). Such blanket layers were a bit rougher than layers grown using a single epitaxy step, but nevertheless of excellent crystalline quality. Transposition of our CSEGE process on patterned ET-SOI wafers did not yield the expected results. HCl etch steps indeed helped in partly or totally removing the poly-SiGe:B mushrooms on top of the gates. This was however at the expense of the crystalline quality and 2D nature of the ˜45 nm thick Si0.7Ge0.3:B recessed sources and drains selectively grown on each side of the imperfectly protected poly-Si gates. The only solution we have so far identified that yields a lesser amount of mushrooms while preserving the quality of the S/D is to increase the HCl flow during growth steps.

  2. 17 CFR 38.801 - Additional sources for compliance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

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    Code of Federal Regulations, 2014 CFR

    2014-04-01

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    Code of Federal Regulations, 2014 CFR

    2014-04-01

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    Code of Federal Regulations, 2014 CFR

    2014-04-01

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    2014-04-01

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  7. 17 CFR 38.801 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.801 Section 38.801 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Governance Fitness Standards § 38.801 Additional sources for compliance...

  8. 17 CFR 38.351 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.351 Section 38.351 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Emergency Authority § 38.351 Additional sources for compliance. Applicants and...

  9. 17 CFR 37.801 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 37.801 Section 37.801 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION SWAP EXECUTION FACILITIES Emergency Authority § 37.801 Additional sources for compliance. A swap...

  10. 17 CFR 38.1001 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.1001 Section 38.1001 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Antitrust Considerations § 38.1001 Additional sources for compliance. Applicants...

  11. 17 CFR 37.1101 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 37.1101 Section 37.1101 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION SWAP EXECUTION FACILITIES Antitrust Considerations § 37.1101 Additional sources for compliance. A swap...

  12. 17 CFR 37.601 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 37.601 Section 37.601 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION SWAP EXECUTION FACILITIES Position Limits or Accountability § 37.601 Additional sources for compliance...

  13. 17 CFR 38.851 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.851 Section 38.851 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Conflicts of Interest § 38.851 Additional sources for compliance. Applicants and...

  14. 17 CFR 38.751 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.751 Section 38.751 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Dispute Resolution § 38.751 Additional sources for compliance. Applicants and...

  15. 17 CFR 37.408 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 37.408 Section 37.408 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION SWAP EXECUTION FACILITIES Monitoring of Trading and Trade Processing § 37.408 Additional sources...

  16. 17 CFR 38.201 - Additional sources for compliance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Additional sources for compliance. 38.201 Section 38.201 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Contracts Not Readily Subject to Manipulation § 38.201 Additional sources...

  17. 17 CFR 38.201 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Additional sources for compliance. 38.201 Section 38.201 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Contracts Not Readily Subject to Manipulation § 38.201 Additional sources...

  18. Enhanced magnetic behaviors of CoPt nanoparticles by addition of SiO{sub 2}

    SciTech Connect

    Wang, Yaxin; Zhang, Xiaolong; Liu, Yang; Jiang, Yuhong; Zhang, Yongjun; Yang, Jinghai

    2014-05-01

    Equiatomic L1{sub 0} CoPt alloy nanoparticles (NPs) with various contents of SiO{sub 2} are synthesized by the simple sol–gel method. The SiO{sub 2} additions restrain the growth of grain and hinder the agglomeration formation. The coercivity increases first and then decreases with SiO{sub 2} addition. Compared to the 0 μl-SiO{sub 2} CoPt NPs, the higher ordering degree and better magnetic properties are obtained by the addition of amount 10 μl SiO{sub 2} in our sample. And the coercivity is two times as large as that of 0 μl-SiO{sub 2} NPs. When the addition of SiO{sub 2} is more than 10 μl, the deteriorated magnetic properties are ascribed to the transformation from hard magnetically phase to soft magnetically phase due to the decrease of particle size. - Graphical abstract: L1{sub 0} CoPt alloy nanoparticles with various contents of SiO{sub 2} are synthesized by sol–gel method. The effects of SiO{sub 2} on the structure and magnetic properties of CoPt nanoparticles are investigated. - Highlights: • The L1{sub 0} CoPt–SiO{sub 2} nanoparticles (NPs) were synthesized by sol–gel method. • Effects of SiO{sub 2} content on the structure and magnetic properties were investigated. • The addition of SiO{sub 2} restrained the growth of particle size. • CoPt–10 μl SiO{sub 2} NPs showed a higher ordering degree and better magnetic properties.

  19. Study of Heterogeneous Nucleation of Eutectic Si in High-Purity Al-Si Alloys with Sr Addition

    NASA Astrophysics Data System (ADS)

    Zarif, Muhammad; McKay, Brian; Schumacher, Peter

    2011-06-01

    Al-5 wt pct Si master-alloys with controlled Sr and/or P addition/s were produced using super purity Al 99.99 wt pct and Si 99.999 wt pct materials in an arc melter. The master-alloy was melt-spun resulting in the production of thin ribbons. The Al matrix of the ribbons contained entrained Al-Si eutectic droplets that were subsequently investigated. Differential scanning calorimetry, thermodynamic calculations, and transmission electron microscopy techniques were employed to examine the effect of the Sr and P additions on eutectic undercoolings and nucleation phenomenon. Results indicate that, unlike P, Sr does not promote nucleation. Increasing Sr additions depressed the eutectic nucleation temperature. This may be a result of the formation of a Sr phase that could consume or detrimentally affect potent AlP nucleation sites.

  20. Modification of Mo-Si alloy microstructure by small additions of Zr.

    PubMed

    Mousa, M; Wanderka, N; Timpel, M; Singh, S; Krüger, M; Heilmaier, M; Banhart, J

    2011-05-01

    Molybdenum and its alloys are potential materials for high-temperature applications. However, molybdenum is susceptible to embrittlement because of oxygen segregation at the grain boundaries. In order to alleviate the embrittlement small amounts of zirconium were alloyed to a solid solution of Mo-1.5Si alloy. Two Mo-based alloys, namely Mo-1.5Si and Mo-1.5Si-1Zr, were investigated by the complementary high-resolution methods transmission electron microscopy and atom probe tomography. The Mo-1.5Si alloy shows a polycrystalline structure with two silicon-rich intermetallic phases Mo(5)Si(3) and Mo(3)Si located at the grain boundaries and within the grains. In addition, small clusters with up to 10 at% Si were found within the molybdenum solid solution. Addition of a small amount of zirconium to Mo-1.5Si leads to the formation of two intermetallic phases Mo(2)Zr and MoZr(2), which are located at the grain boundaries as well as within the interior of the grain. Transmission electron microscopy shows that small spherical Mo-Zr-rich precipitates (<10nm) decorate the grain boundaries. The stoichiometry of the small precipitates was identified as Mo(2)Zr by atom probe tomography. No Si-enriched small precipitates were detected in the Mo-1.5Si-1Zr alloy. It is concluded that the presence of zirconium hinders their formation.

  1. Sintering and properties of Si3N4 with and without additives by HIP treatment

    NASA Technical Reports Server (NTRS)

    Kuratani, S.; Shimada, M.; Koizumi, M.

    1986-01-01

    Hot Isostatic Pressing (HIP) of Si3N4 powders with and without additives was performed using a glass container, and various kinds of pressureless-sintered Si3N4 were HIP'ed without a container. The effects of HIP treatment on density, microstructure, flexural strength, microhardness, and fracture toughness on Si3N4 ceramics were studied. Using a glass container it was difficult to reach theoretical density. The microhardness of HIP'ed Si3N4 without additives was low, and the fracture toughness of HIP'ed Si3N4 with and without additives was 22 to 25 W/m-K, and it decreased with increasing the amount of additives. The density and flexural strength, and hardness of pressureless-sintered Si3N4 which contained Al2O and Y2O3 as oxide additives were remarkably improved by HIP treatment using nitrogen as a pressure transmitting gas. It is very important to select the sintering conditions for fabricating the presintered body of Si3N4 in order to improve the mechanical properties of Si3N4 by HIP treatment.

  2. Influence of Si Addition on Quenching Sensitivity and Formation of Nano-Precipitate in Al-Mg-Si Alloys.

    PubMed

    Kim, JaeHwang; Hayashi, Minoru; Kobayashi, Equo; Sato, Tatsuo

    2016-02-01

    The age-hardening is enhanced with the high cooling rate since more vacancies are formed during quenching, whereas the stable beta phase is formed with the slow cooling rate just after solid solution treatment resulting in lower increase of hardness during aging. Meanwhile, the nanoclusters are formed during natural aging in Al-Mg-Si alloys. The formation of nanoclusters is enhanced with increasing the Si amount. High quench sensitivity based on mechanical property changes was confirmed with increasing the Si amount. Moreover, the nano-size beta" phase, main hardening phase, is more formed by the Si addition resulting in enhancement of the age-hardening. The quench sensitivity and the formation behavior of precipitates are discussed based on the age-hardening phenomena.

  3. Silicon purification using a Cu-Si alloy source

    NASA Technical Reports Server (NTRS)

    Powell, R. C.; Tejedor, P.; Olson, J. M.

    1986-01-01

    Production of 99.9999% pure silicon from 98% pure metallurgical grade (MG) silicon by a vapor transport filtration process (VTP) is described. The VTF process is a cold wall version of an HCl chemical vapor transport technique using a Si:Cu3Si alloy as the silicon source. The concentration, origin, and behavior of the various impurities involved in the process were determined by chemically analyzing alloys of different purity, the slag formed during the alloying process, and the purified silicon. Atomic absorption, emission spectrometry, inductively coupled plasma, spark source mass spectrometry, and secondary ion mass spectroscopy were used for these analyses. The influence of the Cl/H ratio and the deposition temperature on the transport rate was also investigated.

  4. The Effects of Si Addition on Electrical Degradation of ZnO Varistors

    NASA Astrophysics Data System (ADS)

    Satoi, Yohei; Hirai, Hideki; Yoshino, Hiroyuki; Yoshikado, Shinzo

    The effects of Si addition on the electrical degradation of the ZnO varistors were investigated by voltage-current (V-I ), capacitance-voltage (C-V ) methods, and Isothermal Capacitance Transient Spectroscopy (ICTS). The nonlinearity index α for the Bi-Mn-Si-added ZnO varistors didn’t show the remarkable change but that for the Bi-Co-Si-added ZnO varistors decreased by Si addition. Values of α after electrical degradation showed the local maximum at approximately 700molppm for Bi-Mn-added ZnO varistors and at approximately 500molppm for Bi-Co-added ZnO varistors. It is found that the electrical degradation can be hindered at these optimum Si contents. EC-ET showed the local maximum at the optimum Si content similar to α for the Bi-Mn-Al-added ZnO varistors but those for Bi-Co-Si-added ZnO varistors showed the local minimum at the optimum Si content contrary to α for Bi-Co-Al-added ZnO varistors. The density Nis of the interface trap levels obtained by C-V characteristics and ICTS for both kinds of ZnO varistor showed the local minimum at the optimum Si content similar to Al added Bi-Mn-added and Bi-Co-added ZnO varistors.

  5. In situ toughened SiC ceramics with Al-B-C additions and oxide-coated SiC platelet/SiC composites

    SciTech Connect

    Cao, J. |

    1996-12-01

    This work aimed at fabrication and characterization of high toughness SiC ceramics through the applications of in situ toughening and SiC platelet reinforcement. The processing-microstructure-property relations of hot pressed SiC with Al, B, and C additions (designated as ABC-SiC) were investigated. Through a liquid phase sintering mechanism, dense SiC was obtained by hot pressing at a temperature as low as 1,700 C with 3 wt% Al, 0.6 wt% B, and 2 wt% C additions. These sintering aids also enhanced the {beta}-to-{alpha} (3C-to-4H) phase transformation, which promoted SiC grains to grow into plate-like shapes. Under optimal processing conditions, the microstructure exhibited high-aspect-ratio plate-shaped grains with a thin (< 1 nm) Al-containing amorphous grain boundary film. The mechanical properties of the toughened SiC and the composites were evaluated in comparison with a commercial Hexoloy SiC under identical test conditions. The C-curve behavior was examined using the strength-indentation load relationship and compared with that directly measured using precracked compact tension specimens. The in situ toughened ABC-SiC exhibited much improved flaw tolerance and a significantly rising R-curve behavior. A steady-state toughness in excess of 9 MPam{sup 1/2} was recorded for the ABC-SiC in comparison to a single valued toughness below 3 MPam{sup 1/2} for the Hexoloy. Toughening in the ABC-SiC was mainly attributed to grain bridging and subsequent pullout of the plate-shaped grains. The high toughness ABC-SiC exhibited a bend strength of 650 MPa with a Weibull modulus of 19; in comparison, the commercial SiC showed a bend strength of 400 MPa with a Weibull modulus of 6. Higher fracture toughness was also achieved by the reinforcement of SiC platelets, encapsulated with alumina, yttria, or silica, in a SiC matrix.

  6. Fabrication and characterization of Si3N4 ceramics without additives by high pressure hot pressing

    NASA Technical Reports Server (NTRS)

    Shimada, M.; Tanaka, A.; Yamada, T.; Koizumi, M.

    1984-01-01

    High pressure hot-pressing of Si3N4 without additives was performed using various kinds of Si3N4 powder as starting materials, and the relation between densification and alpha-beta phase transformation was studied. The temperature dependences of Vickers microhardness and fracture toughness were also examined. Densification of Si3N4 was divided into three stages, and it was found that densification and phase transformation of Si3N4 under pressure were closely associated. The results of the temperature dependence of Vickers microhardness indicated that the high-temperature hardness was strongly influenced not only by the density and microstructure of sintered body but also by the purity of starting powder. The fracture toughness values of Si3N4 bodies without additives were 3.29-4.39 MN/m to the 3/2 power and independent of temperature up to 1400 C.

  7. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  8. Optical investigations of β-FeSi2 with and without Cr addition

    NASA Astrophysics Data System (ADS)

    Rebien, M.; Henrion, W.; Stauss, P.; Diesner, K.; Panknin, D.

    2001-11-01

    Thin films of semiconducting iron disilicide (β-FeSi2) with up to 8 at. % Cr addition grown on Si(001) and Si(111) substrates were studied by spectroscopic ellipsometry as well as transmission and reflection measurements at room temperature. The dielectric function was deduced in the interband spectral range. In molecular beam epitaxy (MBE) preparation part of the Fe atoms were substituted by Cr during deposition. For a low Cr amount in the doping range up to ˜0.4 at.%, Cr was found to modify epitaxial growth on Si(111) substrates with a change in dominating β-FeSi2 grain orientation. Higher amounts of Cr lead to the precipitation of CrSi2, which was detected optically and confirmed by x-ray diffraction measurements, and a deterioration of film morphology. Furthermore, β-FeSi2 thin films were implanted with Cr and subsequently annealed at various temperatures. In these samples also CrSi2 was detected. The results suggest that it is impossible to produce β-(Fe1-x,Crx)Si2 alloys (x>0.003) by MBE or ion implantation.

  9. Thermoelectric Properties of MnSi1.7 Films with Addition of Aluminum and Carbon

    NASA Astrophysics Data System (ADS)

    Hou, Q. R.; Liang, D.; Feng, X.; Zhao, W.; Chen, Y. B.; He, Y. J.

    Polycrystalline higher manganese silicide (MnSi1.7, HMS) films with addition of aluminum and carbon are prepared on thermally-oxidized silicon substrates by electron beam evaporation and magnetron sputtering, respectively. An aluminum intermediate layer and a carbon cap layer are used as the doping sources. It is found that both the Seebeck coefficient and electrical resistivity are dependent on the amount of aluminum and carbon added to the films. The Seebeck coefficient changes a little in the temperature range 300 to 433 K and decreases considerably above 433 K when aluminum is added to the film. When carbon is added to the film, however, the Seebeck coefficient increases slightly. With addition of aluminum and carbon, the resistivity decreases. As a result, the thermoelectric power factor increases, especially for films with carbon addition. Several activation energies (0.022-0.20 eV) are observed from the curves of logarithm of resistivity versus reciprocal temperature. The larger activation energies of 0.35 and 0.51 eV are consistent with the energy band gaps for higher manganese silicides.

  10. An electrostatic Si e-gun and a high temperature elemental B source for Si heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Scarinci, F.; Casella, A.; Lagomarsino, S.; Fiordelisi, M.; Strappaveccia, P.; Gambacorti, N.; Grimaldi, M. G.; Xue, LiYing

    1996-08-01

    In this paper we present two kind of sources used in Si MBE growth: a Si source where an electron beam is electrostatically deflected onto a Si rod and a high temperature B source to be used for p-doping. Both sources have been designed and constructed at IESS. The Si source is constituted of a Si rod mounted on a 3/4″ flange with high-voltage connector. A W filament held at high voltage (up to 2000 V) is heated by direct current. Electrons from the filament are electrostatically focused onto the Si rod which is grounded. This mounting allows a minimum heating dispersion and no contamination, because the only hot objects are the Si rod and the W filament which is mounted in such a way that it cannot see the substrate. Growth rates of 10 Å/min on a substrate at 20 cm from the source have been measured. Auger and LEED have shown no contamination. The B source is constituted of a graphite block heated by direct current. A pyrolitic graphite crucible put in the graphite heater contains the elemental B. The cell is water cooled and contains Ta screens to avoid heat dispersion. It has been tested up to a temperature of 1700°C. P-doped Si 1- xGe x layers have been grown and B concentration has been measured by SIMS. A good control and reproducibility has been attained.

  11. Fabrication of highly dense SiN4 ceramics without additives by high pressure sintering

    NASA Technical Reports Server (NTRS)

    Takatori, K.; Shimade, M.; Koizumi, M.

    1984-01-01

    Silicon nitride (Si3N4) is one of candidate materials for the engineering ceramics which is used at high temperatures. The mechanical strengths of hot pressed or sintered Si2N4 ceramics containing some amount of additives, however, are deteriorated at elevated temperatures. To improve the high temperature strength of Si3N4 ceramics, an attempt to consolidate Si3N4 without additives was made by high pressure sintering technique. Scanning electron micrographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully self-bonded sintered bodies were 310N sq m at room temperature and 174N/sq m at 1200 C.

  12. SiGN-SSM: open source parallel software for estimating gene networks with state space models.

    PubMed

    Tamada, Yoshinori; Yamaguchi, Rui; Imoto, Seiya; Hirose, Osamu; Yoshida, Ryo; Nagasaki, Masao; Miyano, Satoru

    2011-04-15

    SiGN-SSM is an open-source gene network estimation software able to run in parallel on PCs and massively parallel supercomputers. The software estimates a state space model (SSM), that is a statistical dynamic model suitable for analyzing short time and/or replicated time series gene expression profiles. SiGN-SSM implements a novel parameter constraint effective to stabilize the estimated models. Also, by using a supercomputer, it is able to determine the gene network structure by a statistical permutation test in a practical time. SiGN-SSM is applicable not only to analyzing temporal regulatory dependencies between genes, but also to extracting the differentially regulated genes from time series expression profiles. SiGN-SSM is distributed under GNU Affero General Public Licence (GNU AGPL) version 3 and can be downloaded at http://sign.hgc.jp/signssm/. The pre-compiled binaries for some architectures are available in addition to the source code. The pre-installed binaries are also available on the Human Genome Center supercomputer system. The online manual and the supplementary information of SiGN-SSM is available on our web site. tamada@ims.u-tokyo.ac.jp.

  13. Evaluation of Exogenous siRNA Addition as a Metabolic Engineering Tool for Modifying Biopharmaceuticals

    PubMed Central

    Tummala, Seshu; Titus, Michael; Wilson, Lee; Wang, Chunhua; Ciatto, Carlo; Foster, Donald; Szabo, Zoltan; Guttman, Andras; Li, Chen; Bettencourt, Brian; Jayaraman, Muthuswamy; Deroot, Jack; Thill, Greg; Kocisko, David; Pollard, Stuart; Charisse, Klaus; Kuchimanchi, Satya; Hinkle, Greg; Milstein, Stuart; Myers, Rachel; Wu, Shiaw-Lin; Karger, Barry; Rossomando, Anthony

    2012-01-01

    Traditional metabolic engineering approaches, including homologous recombination, zinc finger nucleases, and short hairpin RNA (shRNA), have previously been employed to generate biologics with specific characteristics that improve efficacy, potency, and safety. An alternative approach is to exogenously add soluble small interfering RNA (siRNA) duplexes, formulated with a cationic lipid, directly to cells grown in shake flasks or bioreactors, This approach has the following potential advantages : no cell line development required, ability to tailor mRNA silencing by adjusting siRNA concentration, simultaneous silencing of multiple target genes, and potential temporal control of down regulation of target gene expression. In this study, we demonstrate proof of concept of the siRNA feeding approach as a metabolic engineering tool in the context of increasing monoclonal antibody afucosylation. First, potent siRNA duplexes targeting fut8 and gmds were dosed into shake flasks with cells that express an anti-CD20 monoclonal antibody. Dose response studies demonstrated the ability to titrate the silencing effect. Furthermore, siRNA addition resulted in no deleterious effects on cell growth, final protein titer, or specific productivity. In bioreactors, antibodies produced by cells following siRNA treatment exhibited improved functional characteristics compared to antibodies from untreated cells, including increased levels of afucosylation (63%), a 17-fold improvement in FCgRIIIa binding, and an increase in specific cell lysis by up to 30%, as determined in an ADCC assay. In addition, standard purification procedures effectively cleared the exogenously added siRNA and transfection agent. Moreover, no differences were observed when other key product quality structural attributes were compared to untreated controls. These results establish that exogenous addition of siRNA represents a potentially novel metabolic engineering tool to improve biopharmaceutical function and

  14. Effect of Additional Elements of Al-Si Filler Alloy on Flowability and Clearance Fillability

    NASA Astrophysics Data System (ADS)

    Edo, Masakazu; Yoshino, Michihide; Kuroda, Shuu

    Aluminum alloys are widely used for automotive heat exchangers manufactured by brazing processes. All joint gaps must be filled with Al-Si filler metal to prevent the leak of refrigerant. Recently, brazing of heat exchanger components has become difficult due to the decrease in the thickness of the brazing sheets. Since the fluidity of Al-Si molten metal is very high, the flow of molten filler metal sometimes causes dissolution of the base metal or defect of joints. In this study, we investigated the effect of additional elements (such as Mn, Fe, Ti and Zr) of Al-Si filler metal on the flowability and clearance fillability using our original evaluation model. The results indicated that the addition of Mn or Ti improved the clearance fillability significantly. We clarified the mechanism that additional elements change the properties of molten filler metal, by measuring the viscosity of each filler metal and observing the solidified microstructure.

  15. Additive manufacturing of Ti-Si-N ceramic coatings on titanium

    NASA Astrophysics Data System (ADS)

    Zhang, Yanning; Sahasrabudhe, Himanshu; Bandyopadhyay, Amit

    2015-08-01

    In this study, Laser Engineered Net Shaping (LENSTM) was employed towards Additive Manufacturing/3D Printing of Ti-Si-N coatings with three different Ti-Si ratios on commercially pure titanium (cp-Ti) substrate. Microstructural analysis, phase analysis using X-ray diffraction, wear resistance and hardness measurements were done on LENS™ processed 3D printed coatings. Coatings showed graded microstructures and in situ formed phases. Results showed that microstructural variations and phase changes influence coating's hardness and wear resistance directly. High hardness values were obtained from all samples' top surface where the hardness of coatings can be ranked as 90% Ti-10% Si-N coating (2093.67 ± 144 HV0.2) > 100% Ti-N coating (1846 ± 68.5 HV0.2) > 75% Ti-25% Si-N coating (1375.3 ± 61.4 HV0.2). However, wear resistance was more dependent on inherent Si content, and samples with higher Si content showed better wear resistance.

  16. Enhanced thermoelectric properties of Mg2Si by addition of TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Cederkrantz, D.; Farahi, N.; Borup, K. A.; Iversen, B. B.; Nygren, M.; Palmqvist, A. E. C.

    2012-01-01

    The effects on the thermoelectric properties of Mg2Si when adding TiO2 nanoparticles have been evaluated experimentally. A batch of Mg2Si was prepared through direct solid state reaction and divided into portions which were mechanically mixed with different amounts of TiO2 nanoparticles ranging from 0.5 to 3 vol% and subsequently sintered to disks. All materials showed n-type conduction and the absolute value of the Seebeck coefficient was reduced with increasing amount of TiO2 added, while the electrical resistivity was greatly reduced. The thermal conductivity was surprisingly little affected by the addition of the nanoparticles. An optimum value of the thermoelectric figure-of-merit ZT = TS2σ/k was found for the addition of 1 vol% TiO2, showing almost three times higher ZT value than that of the pure Mg2Si. Larger TiO2 additions resulted in lower ZT values and with 3 vol% added TiO2 the ZT was comparable to the pure Mg2Si. The sintering process resulted in reduction or chemical reaction of all TiO2 to TiSi2 and possibly elemental titanium as well as reduced TiOx. The increased electrical conductivity and the decreased Seebeck coefficient were found due to an increased charge carrier concentration, likely caused by the included compounds or titanium-doping of the Mg2Si matrix. The low observed effect on the thermal conductivity of the composites may be explained by the relatively higher thermal conductivity of the included compounds, counter-balancing the expected increased grain boundary scattering. Alternatively, the introduction of compounds does not significantly increase the concentration of scattering grain boundaries.

  17. Volume 3a - Area Source Methods - Additional Documents

    EPA Pesticide Factsheets

    Nonpoint (area) source emission reference materials from the Emissions Inventory Improvement Program (EIIP). Provides nonpoint source guidance on ammonia emissions from natural landscapes, fertilized soils, and nonagricultural sources.

  18. Effects of Ar and O2 additives on SiO2 etching in C4F8-based plasmas

    NASA Astrophysics Data System (ADS)

    Li, Xi; Ling, Li; Hua, Xuefeng; Fukasawa, Masanaga; Oehrlein, Gottlieb S.; Barela, Marcos; Anderson, Harold M.

    2003-01-01

    Gas mixtures based on C4F8 are promising for the development of high-performance SiO2 plasma etching processes. Measurements of important gas phase species, thin film etching rates and surface chemistry changes were performed for inductively coupled plasmas fed with C4F8/Ar and C4F8/O2 gas mixtures. The addition of Ar to C4F8 causes a strong increase of the plasma density relative to that of pure C4F8 (by up to a factor of 4× at 90% Ar). For O2 addition the changes in plasma density are small up to 90% O2 relative to pure C4F8. Infrared laser absorption spectroscopy was used to determine the absolute densities of neutral CF, CF2 and COF2 radical species as a function of the gas composition. The densities of CF and CF2 were enhanced for certain operating conditions when Ar was added to C4F8 as long as the amount of Ar remained below 20%. For instance, the partial pressure of CF was 0.1 mTorr for a 20 mTorr 1400 W source power discharge for pure C4F8, and increased to 0.13 mTorr at 20% Ar. Above 20% Ar it decreased, roughly following the gas dilution. The CF2 partial pressure was about 5 mTorr for the same conditions, and increased by about 10% at 20% Ar. Above 20% Ar the CF2 partial pressure decreased roughly linearly with the amount of Ar added, to about 2 mTorr at 50% Ar. Of particular interest was the analysis of the difference in behavior of CF, CF2 and COF2 partial pressures over SiO2 and Si surfaces, with and without rf bias power (in the latter case a self-bias voltage of -100 V was used). For pure C4F8 discharges at 20 mTorr and 1400 W inductive power without rf bias the partial pressures of CF, CF2 and COF2 radicals are comparable over SiO2 and Si surfaces. Upon applying a rf bias, the CF2 partial pressure over a SiO2 surface is reduced much more strongly than for a Si surface. The overall reduction appears to be consistent with the relative SiO2/Si etch rate ratios observed for these conditions. These results indicate that CF2 is consumed during the

  19. Spent yeast as natural source of functional food additives

    PubMed

    Rakowska, Rita; Sadowska, Anna; Dybkowska, Ewa; Świderski, Franciszek

    Spent yeasts are by-products arising from beer and wine production which over many years have been chiefly used as feed additives for livestock. They contain many valuable and bioactive substances which has thereby generated much interest in their exploitation. Up till now, the main products obtained from beer-brewing yeasts are β-glucans and yeast extracts. Other like foodstuffs include dried brewer’s yeast, where this is dried and the bitterness removed to be fit for human consumption as well as mannan-oligosaccharides hitherto used in the feed industry. β-glucans constitute the building blocks of yeast cell walls and can thus be used in human nutrition as dietary supplements or serving as food additives in functional foods. β-glucans products obtained via post-fermentation of beer also exhibit a high and multi-faceted biological activity where they improve the blood’s lipid profile, enhance immunological status and have both prebiotic and anti-oxidant properties. Yeast extracts are currently being used more and more to enhance flavour in foodstuffs, particularly for meat and its products. Depending on how autolysis is carried out, it is possible to design extracts of various meat flavours characteristic of specific meats. Many different flavour profiles can be created which may be additionally increased in combination with vegetable extracts. Within the food market, yeast extracts can appear in various guises such as liquids, pastes or powders. They all contain significant amounts of glutamic acid, 5’-GMP and 5’-IMP nucleotides together with various amino acids and peptides that act synergistically for enhancing the flavour of foodstuff products. Recent studies have demonstrated additional benefits of yeast extracts as valuable sources of amino acids and peptides which can be used in functional foods and dietary supplements. These products possess GRAS status (Generally Recognised As Safe) which thereby also adds further as to why they should be used

  20. Eutectic Morphology of Al-7Si-0.3Mg Alloys with Scandium Additions

    NASA Astrophysics Data System (ADS)

    Pandee, Phromphong; Gourlay, C. M.; Belyakov, S. A.; Ozaki, Ryota; Yasuda, Hideyuki; Limmaneevichitr, Chaowalit

    2014-09-01

    The mechanisms of Al-Si eutectic refinement due to scandium (Sc) additions have been studied in an Al-7Si-0.3Mg foundry alloy. The evolution of eutectic microstructure is studied by thermal analysis and interrupted solidification, and the distribution of Sc is studied by synchrotron micro-XRF mapping. Sc is shown to cause significant refinement of the eutectic silicon. The results show that Sc additions strongly suppress the nucleation of eutectic silicon due to the formation of ScP instead of AlP. Sc additions change the macroscopic eutectic growth mode to the propagation of a defined eutectic front from the mold walls opposite to the heat flux direction similar to past work with Na, Ca, and Y additions. It is found that Sc segregates to the eutectic aluminum and AlSi2Sc2 phases and not to eutectic silicon, suggesting that impurity-induced twinning does not operate. The results suggest that Sc refinement is mostly caused by the significantly reduced silicon nucleation frequency and the resulting increase in mean interface growth rate.

  1. Strength and microstructure of sintered Si3N4 with rare-earth-oxide additions

    NASA Technical Reports Server (NTRS)

    Sanders, W. A.; Mieskowski, D. M.

    1985-01-01

    Room temperature, 700-, 1000-, 1200-, and 1370-C examinations of the effect of 1.7-2.6 mol pct rare earth oxide additions to sintered Si3N4 are conducted. While the room temperature-1000 C bend strengths were higher for this material with Y2O3 additions than with CeO2, La2O3, or Sm2O3, the reverse was true at 1200-1370 C. This phenomenon is explained on the basis of microstructural differences, since quantitative microscopy of SEM replicas showed the Si3N4-Y2O3 composition to contain both a higher percentage of elongated grains and a coarser microstructure than the other three alternatives. The elongated grains appear to increase this composition's low temperature strength irrespective of microstructural coarseness; this coarseness, however, decreases strength relative to the other compositions at higher temperatures.

  2. Synchrotron Radiation Irradiation Effects for SiHn on Si(100) Surface in the Synchrotron Radiation Stimulated Si Gas Source Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Yoshigoe, Akitaka; Nagasono, Mitsuru; Mase, Kazuhiko; Urisu, Tsuneo

    1995-12-01

    SiH n on Si (100) surfaces during synchrotron radiation (SR) stimulated gas source molecular beam epitaxy (SR-GSMBE) using Si2H6 gas (1.0×10-3 Torr) are investigated in situ by means of infrared reflection absorption spectroscopy using CoSi2 buried metal layer substrates (BML-IRAS) in the low substrate temperature region (400° C-140° C). It has been found that SiH2 and SiH3 on the surface are easily decomposed by SR to SiH and the decomposition rate of SiH is extremely slow. The decomposition reaction cross sections for SiH2 and SiH3 for the total irradiating photon flux have been evaluated to be 5.7×10-20 cm2 and 1.7×10-19 cm2, respectively. Experimental results are discussed, considering the model of the localized multihole excitation and its quenching.

  3. Additional experiments relative to the shelf life of Li(Si)/FeS2 thermal batteries

    NASA Astrophysics Data System (ADS)

    Searcy, J. Q.; Armijo, J. R.

    1985-02-01

    A continuing effort to develop a new thermal battery technology based on the Li(Si)/FeS2 electrochemical couple is reported. The results relate to the long shelf life requirement for thermal batteries designed by Sandia, and include topics relevant to leakage through the hermetic seal and accelerated aging experiments with materials new to the technology. Conclusions relevant to leakage through the hermetic seal are that the maximum leak rate must not exceed 1.8 x 10(-7) w, where w is the grams of Li(Si) contained by a battery, and that a bomb type leak test can be designed that is adequate for most Li(Si)/FeS2 batteries. Conclusions relevant to long term compatibility of new materials include the following: nickel is not compatible with the iron disulfide in the cathode; the CaSi2 additive used to suppress the initial voltage transient does not react or degrade during accelerated aging experiments, but the use of that material can lead to an increase in the variability of the activated lives, especially for long life batteries; Grafoil current collectors used with the cathode do not degrade in accelerated aging experiments.

  4. Modification of the surface morphology of 4H-SiC by addition of Sn and Al in solution growth with SiCr solvents

    NASA Astrophysics Data System (ADS)

    Komatsu, Naoyoshi; Mitani, Takeshi; Hayashi, Yuichiro; Kato, Tomohisa; Harada, Shunta; Ujihara, Toru; Okumura, Hajime

    2017-01-01

    For solution growth of 4H-SiC with Si0.6-x-yCr0.4AlxSny solvents, the changes in surface morphology and polytype induced by the addition of Sn and Al to the Si0.6Cr0.4 solvent were investigated. Growth with Si0.6Cr0.4 solvents resulted in a rough surface covered with large macrosteps that were several micrometers high, and the polytype of the grown layer transformed to 6H and 15R-SiC. The surface roughening and polytype instability were suppressed when more than 2 at% Al was added to the SiCr0.4 solvent. We also found that the combined addition of both 2-4 at% Sn and 0.5-1 at% Al resulted in smooth surface morphology. We discussed the modification of the surface morphology of 4H-SiC caused by the additives in terms of the wetting properties of the solvents. Based on the results of experiments and thermodynamic calculations, the addition of both Sn and Al increased the liquid/solid interfacial energy. Because the two-dimensional nucleation energy increases with the interfacial energy, we conclude that smooth step flow growth of 4H-SiC was achieved by lowering the frequency of two-dimensional nucleation on the growth surface.

  5. Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas

    SciTech Connect

    Nordmark, H.; Holmestad, R.; Nagayoshi, H.; Matsumoto, N.; Nishimura, S.; Terashima, K.; Marioara, C. D.; Walmsley, J. C.; Ulyashin, A.

    2009-02-15

    Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi{sub 2} particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H{sub 2} flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi{sub 2} particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiH{sub x} species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi{sub 2} particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi{sub 2} particles on their tips as well as sometimes being incorporated into their structure.

  6. Percolation model with an additional source of disorder

    NASA Astrophysics Data System (ADS)

    Kundu, Sumanta; Manna, S. S.

    2016-06-01

    The ranges of transmission of the mobiles in a mobile ad hoc network are not uniform in reality. They are affected by the temperature fluctuation in air, obstruction due to the solid objects, even the humidity difference in the environment, etc. How the varying range of transmission of the individual active elements affects the global connectivity in the network may be an important practical question to ask. Here a model of percolation phenomena, with an additional source of disorder, is introduced for a theoretical understanding of this problem. As in ordinary percolation, sites of a square lattice are occupied randomly with probability p . Each occupied site is then assigned a circular disk of random value R for its radius. A bond is defined to be occupied if and only if the radii R1 and R2 of the disks centered at the ends satisfy a certain predefined condition. In a very general formulation, one divides the R1-R2 plane into two regions by an arbitrary closed curve. One defines a point within one region as representing an occupied bond; otherwise it is a vacant bond. The study of three different rules under this general formulation indicates that the percolation threshold always varies continuously. This threshold has two limiting values, one is pc(sq) , the percolation threshold for the ordinary site percolation on the square lattice, and the other is unity. The approach of the percolation threshold to its limiting values are characterized by two exponents. In a special case, all lattice sites are occupied by disks of random radii R ∈{0 ,R0} and a percolation transition is observed with R0 as the control variable, similar to the site occupation probability.

  7. Densification of Reaction Bonded Silicon Nitride with the Addition of Fine Si Powder Effects on the Sinterability and Mechanical Properties

    SciTech Connect

    Lee, Sea-Hoon; Cho, Chun-Rae; Park, Young-Jo; Ko, Jae-Woong; Kim, Hai-Doo; Lin, Hua-Tay; Becher, Paul F

    2013-01-01

    The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain Lu2O3-SiO2 additives were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering (GPS) at 1850oC through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at 1950oC. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped the compaction of green bodies and induced the formation of fine Si3N4 particles after nitridation and sintering at and above 1600oC. The amount of residual SiO2 within the specimens was not strongly affected by adding fine Si powder because most of the SiO2 layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of the specimens were 991 MPa and 8.0 MPa m1/2, respectively.

  8. ITEP Bernas ion source with additional electron beam

    SciTech Connect

    Kulevoy, T.V.; Kuibeda, R.P.; Petrenko, S.V.; Batalin, V.A.; Pershin, V.I.; Kropachev, G.N.; Hershcovitch, A.; Johnson, B.M.; Gushenets, V.I.; Oks, E.M.; Poole, H.J.

    2006-03-15

    A joint research and development program is underway to develop steady-state intense ion sources for the two energy extremes of MeV and hundreds of eV. For the MeV range the investigations were focused on charge-state enhancement for ions generated by the modified Bernas ion sources. Based on the previously successful ITEP experience with the e-metal vapor vacuum arc ion source [e.g., Batalin et al., Rev. Sci. Instrum. 75, 1900 (2004)], the injection of a high-energy electron beam into the Bernas ion source discharge region is expected to enhance the production of high charge states. Presented here are construction details and studies of electron-beam influence on the enhancement of ion-beam charge states generated by the modified Bernas ion source.

  9. Si diffusion and intermixing in AlGaAs/GaAs structures using buried impurity sources

    SciTech Connect

    Beernink, K.J.; Thornton, R.L.; Anderson, G.B.; Emanuel, M.A.

    1995-05-08

    Si diffusion and impurity-induced layer intermixing from a buried impurity source have been studied by transmission electron microscopy and secondary ion mass spectroscopy of isolated, Si-doped GaAs layers in an undoped Al{sub 0.4}Ga{sub 0.6}As/GaAs superlattice and by photoluminescence measurements on Si-doped GaAs quantum wells with undoped Al{sub 0.4}Ga{sub 0.6}As barriers. In annealed samples, the Si profile suggests a Si diffusion process involving multiply ionized column III vacancies. The width of the resulting Si profile and the spatial extent and completeness of intermixing strongly depend on the initial Si concentration in the doped layer.

  10. Radiation safety attached to radioactive sources management - additional aspects

    SciTech Connect

    Kositsyn, V.F.

    1993-12-31

    Radiation sources are used in many scientific areas. Safety management requirements are determined for them with guarantee of the international and national dose limits unexceeding. As a rule, such dose limits are being developed concerning the type, energy, and flux of main radiation. Lack of knowledge of these attendant radiations can put personnel in danger. The study of the attendant neutron and gamma-radiations for plutonium 128 alpha sources was made.

  11. Improvement of low-humidity performance of PEMFC by addition of hydrophilic SiO 2 particles to catalyst layer

    NASA Astrophysics Data System (ADS)

    Jung, Un Ho; Park, Ki Tae; Park, Eun Hee; Kim, Sung Hyun

    Hydrophilic SiO 2 particles are added to the catalyst layer of a fuel cell membrane-electrode assembly (MEA) to improve wettability and performance at low-humidity conditions. The SiO 2 added MEAs are prepared by spraying technique and the contact angle is measured by the sessile drop method. The effects of SiO 2 additions of 0, 20, 40 and 60 wt.% (based on Pt/C) are investigated for various relative humidity levels in the anode and the cathode. The increased wettability of the cathode catalyst layer exerts an adverse effect on cell performance by causing flooding; this result demonstrates the hydrophilicity of SiO 2. With 40 wt.% addition of SiO 2 to the anode catalyst layer, the current density at 0.6 V and 0% relative humidity of the anode is 93% of that at 100% relative humidity. By comparison, the performance of a cell using a MEA with no added SiO 2 is only 85% of that at 0% relative humidity. A MEA with SiO 2 addition in the anode gives a higher performance at 60% relative humidity of the cathode than one with an undoped MEA. Increased wettability of the anode catalyst layer caused by SiO 2 addition renders it easy to absorb water from back diffusion.

  12. Influence of phosphine flow rate on Si growth rate in gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Gao, F.; Huang, D. D.; Li, J. P.; Lin, Y. X.; Kong, M. Y.; Sun, D. Z.; Li, J. M.; Lin, L. Y.

    2000-12-01

    As reported by other authors, we have also observed that the Si growth rate decreases with increasing phosphine (PH 3) flow rate in gas source Si molecular beam epitaxy using phosphorous (P) as a n-type dopant. Why small quantity PH 3 can affect Si growth rate? Up to now, the quantitative characterization of PH 3 flow influence on Si growth rate is little known. In this letter, the PH 3 influence will be analyzed in detail and a model considering strong P surface segregation and its absorption of hydrogen will be proposed to characterize the effect.

  13. Additive Effects on Si3n4 Oxidation/Volatilization in Water Vapor

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Robinson, R. Craig; Fox, Dennis S.; Wenglarz, Richard A.; Ferber, Mattison K.

    2002-01-01

    Two commercially available additive-containing silicon nitride materials were exposed in four environments which range in severity from dry oxygen at 1 atm pressure, and low gas velocity to an actual turbine engine. Oxidation and volatilization kinetics were monitored at temperatures ranging from 1066 to 1400 C. The main purpose of this paper is to examine the surface oxide morphology resulting from the exposures. It was found that the material surface was enriched in rare earth silicate phases in combustion environments when compared to the oxides formed on materials exposed in dry oxygen. However, the in situ formation of rare earth disilicate phases offered little additional protection from the volatilization of silica observed in combustion environments. It was concluded that externally applied environmental barrier coatings are needed to protect additive-containing silicon nitride materials from volatilization reactions in combustion environments. Introduction Si3N4 is proposed for use as components, such as vanes, in turbine applications. Tens of thousands of hours of life are needed for both land-based turbines and aeropropulsion applications. Additive-containing SisN4 materials are

  14. Microwaves as an energy source for producing beta-SiC.

    PubMed

    Aguilar, J; Rodríguez, J; Hinojosa, M

    2001-01-01

    This work describes the production of silicon carbide using microwaves as the energy source, which was supplied by means of variable power, up to 2000 Watts, magnetron operating at 2.45 GHz. The obtained samples were analyzed by means of X-ray diffraction and observed with electron microscopy (SEM). Temperatures achieved were around 2000 degrees C, which is the upper limit for the beta-SiC growth regime, before getting other SiC polytypes. Analysis of different portions of the sample showed that beta-SiC was the only formed compound, although free SiO2 and graphite were also present. Observations made by SEM demonstrated different crystal growth regime, meaning that thermal conditions were not totally uniform. The amount of beta-SiC found and the relative simplicity of the device prove that production of this material from silica and graphite is possible by applying microwaves as an energy source.

  15. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES

    SciTech Connect

    Kim, Jaeheon; Cho, Se-Hyung; Kim, Sang Joon E-mail: cho@kasi.re.kr

    2013-01-01

    We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.

  16. Additional muon calculations for the SLC positron source

    SciTech Connect

    Nelson, W.R.; McCall, R.C.

    1985-04-23

    This note is an update to the muon calculations presented in CN-221 and takes into account: (1) a more complete muon production and transport model, including an estimate of wide angle production based on experimental data, (2) additional earth shielding that will be added on top and both sides of the 2/3 tunnel areas, and (3) a detailed analysis of the earth profile as it pertains to shielding in the direction of the SLAC site boundary. The highest annual dose at the SLAC boundary is found to be 13 mrem/year (4000 hours of operation at 50 kW), and this occurs at a horizontal angle of 0 degrees and a vertical angle of 3.6 degrees relative to the incident beam direction. Although the shielding criteria is 10 mrem/year at the site boundary, the radiation transport model becomes somewhat conservative at large distances from the shield, which should bring the 13 mrem/year number actually well below the criteria. This point is also about 28 feet above the roadway. Extension of this line may strike the ground in the Christmas tree farm beyond the SLAC boundary but there will be additional attenuation due to distance. We do not recommend that any additional shielding be added at this time. 4 refs., 1 fig.

  17. Enhancement-mode Ga2O3 MOSFETs with Si-ion-implanted source and drain

    NASA Astrophysics Data System (ADS)

    Wong, Man Hoi; Nakata, Yoshiaki; Kuramata, Akito; Yamakoshi, Shigenobu; Higashiwaki, Masataka

    2017-04-01

    Enhancement-mode β-Ga2O3 metal-oxide-semiconductor field-effect transistors with low series resistance were achieved by Si-ion implantation doping of the source/drain contacts and access regions. An unintentionally doped Ga2O3 channel with low background carrier concentration that was fully depleted at a gate bias of 0 V gave rise to a positive threshold voltage without additional constraints on the channel dimensions or device architecture. Transistors with a channel length of 4 µm delivered a maximum drain current density (I DS) of 1.4 mA/mm and an I DS on/off ratio near 106. Nonidealities associated with the Al2O3 gate dielectric as well as their impact on enhancement-mode device performance are discussed.

  18. Modifying Si-based consolidants through the addition of colloidal nano-particles

    NASA Astrophysics Data System (ADS)

    Ksinopoulou, E.; Bakolas, A.; Moropoulou, A.

    2016-04-01

    The modification of silicon-based stone consolidants has been the subject of many scientific studies aiming to overcome the commonly reported drawbacks of these materials, such as the tendency to shrink and crack during drying. The addition of nano-particle dispersions into silica matrix has been found to enhance their effectiveness in several ways. Objective of the current research was to study the preparation of particle-modified consolidants (PMC), consisting of an ethyl silicate matrix (TEOS) loaded with colloidal silica (SiO2) nano-particles and oxide titania (TiO2) particles. The effect of the polyacrylic acid on the dispersion stability was also investigated, by varying its concentration into PMC samples. The prepared materials were allowed to dry in two different relative humidity environments and then evaluated based on their stability in the sol phase, the aggregation sizes, determined through dynamic light scattering, the % solids content and their morphological characteristics, observed via scanning electron microscopy (SEM-EDAX). Mercury intrusion porosimetry was also applied to investigate the microstructural characteristics and differences between the prepared consolidants. Significant role in the final form of the material is played by both the initial molar ratios in the mixtures, as well as the conditions where the drying and aging takes place. Based on the results, the three-component PMCs appear to be promising in stone consolidation, as they show a reduction in cracking and shrinkage during drying and a more porous network, compared with the siliceous material, or the two-component TEOS-SiO2 formulation.

  19. a-Si:H solar cells: SiH(2)Cl(2) as a source gas and a-SiGe:H alloys

    NASA Astrophysics Data System (ADS)

    Payne, Adam More

    This thesis gives an overview of the reasons why solar cells are a necessity in this world of carbon constrained energy use. The most important factors upon which to work to improve the competitiveness of photovoltaic generated electricity with conventional, fossil fuel based generation are the cost of the solar cell and the cell conversion efficiency. The two main technical thrusts of this thesis--DCS as a source gas and a-SiGe:H alloys--attacked two aspects of these problems. a-SiGe:H is used in multijunction cells to achieve higher efficiencies and DCS can be used to increase the deposition rate of a-Si:H thus decreasing the time it takes to make a solar cell. We review the various experimental methods used to investigate the optical and electronic properties of a-Si:H thin films as well as the methods used to measure solar cell efficiency and determine the effectiveness of the various portions of a solar cell. Using DCS as a source gas helped us increase the deposition rate by factor of 5 while maintaining the film quality; however chlorinated intrinsic films had higher defect densities and lower photoconductivity than standard a-Si:H films. Use of DCS to deposit i-layers of a solar cell led us to the discovery that Cl enhances the doping efficiency of B in a-Si:H. The enhanced doping of a-SiC:H as the p-layer of a solar cell increased the cell's efficiency from 7.1% to 7.8%. A-SiGe:H alloys were investigated over a range of Tauc gaps from 1.7 eV down to 1.0 eV. The optical and electronic properties of these films were investigated as well as their incorporation in solar cells. Different bandgap graded structures were used in the i-layer of a solar cell with the conclusion that the bathtub shaped i-layer yields the highest stabilized efficiency. An attempt was made to fabricate solar cells using cathode-deposited a-SiGe:H alloys as the i-layer in collaboration with Harvard University. The cells fabricated could neither prove nor disprove the effectiveness of

  20. Influence of Si addition on the microstructure and mechanical properties of Ti-35Nb alloy for applications in orthopedic implants.

    PubMed

    Tavares, A M G; Ramos, W S; de Blas, J C G; Lopes, E S N; Caram, R; Batista, W W; Souza, S A

    2015-11-01

    In the development of new materials for orthopedic implants, special attention has been given to Ti alloys that show biocompatible alloy elements and that are capable of reducing the elastic modulus. Accordingly, Ti-Nb-Si alloys show great potential for application. Thus, this is a study on the microstructures and properties of Ti-35Nb-xSi alloys (x=0, 0.15, 0.35 and 0.55) (wt%) which were thermally treated and cooled under the following conditions: furnace cooling (FC), air cooling (AC), and water quenching (WQ). The results showed that Si addition is effective to reduce the density of omega precipitates making beta more stable, and to produce grain refinement. Silicides, referred as (Ti,Nb)3Si, were formed for alloys containing 0.55% Si, and its formation presumably occurred during the heating at 1000°C. In all cooling conditions, the hardness values increased with the increasing of Si content, as a result from the strong Si solid solution strengthening effect, while the elastic modulus underwent a continuous reduction due to the reduction of omega precipitates in beta matrix. Lower elastic moduli were observed in water-quenched alloys, which concentration of 0.15% Si was more effective in their reduction, with value around 65 GPa. Regarding Ti-35Nb-xSi alloys (x=0, 0.15 and 0.35), the "double yield point" phenomenon, which is typical of alloys with shape memory effect, was observed. The increase in Si concentration also produced an increase from 382 MPa to 540 MPa in the alloys' mechanical strength. Ti-35Nb-0.55Si alloy, however, showed brittle mechanical behavior which was related to the presence of silicides at the grain boundary.

  1. Effect of copper addition on the glass forming ability in Pd-Si binary amorphous alloying system

    NASA Astrophysics Data System (ADS)

    Wang, Xutong; Zeng, Mo; Nollmann, Niklas; Wilde, Gerhard; Tian, Zhuang; Tang, Chengying

    2017-09-01

    The effect of copper addition on the glass forming ability in Pd-Si amorphous alloys was systematically studied by X-ray diffraction and differential scanning calorimeter with a binary alloy series of Pd81+xSi19-x (x=0, 1, 1.5, 2, 2.5, 3, 4) and a ternary alloy series of Pd83.5-xCuxSi16.5 (x=0, 2, 4, 6, 8, 10, 12). It has been found that the critical size of the Pd-Si alloys could be improved significantly from 8mm to 15mm and ΔTx could be enhanced from 18.7 K to 54.7 K with the addition of copper. The determined activation energy demonstrates that Cu additions improve the thermal stability of the system significantly. The different results of the measured criteria to evaluate the GFA for the Pd-Si and the Pd-Cu-Si alloys may be linked to a different crystallization behavior. The enhanced GFA is linked to a more thermodynamically stable liquid and a reduction of atomic diffusion in the ternary alloy by Cu addition.

  2. Aberration-corrected HAADF-STEM investigations of precipitate structures in Al-Mg-Si alloys with low Cu additions

    NASA Astrophysics Data System (ADS)

    Saito, Takeshi; Marioara, Calin D.; Andersen, Sigmund J.; Lefebvre, Williams; Holmestad, Randi

    2014-02-01

    Precipitates in a lean Al-Mg-Si alloy with low Cu addition (~0.10 wt.%) were investigated by aberration-corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Most precipitates were found to be disordered on the generally ordered network of Si atomic columns which is common for the metastable precipitate structures. Fragments of known metastable precipitates in the Al-Mg-Si-(Cu) alloy system are found in the disordered precipitates. It was revealed that the disordered precipitates arise as a consequence of coexistence of the Si-network. Cu atomic columns are observed to either in-between the Si-network or replacing a Si-network column. In both cases, Cu is the center in a three-fold rotational symmetry on the Si-network. Parts of unit cells of Q‧ phase were observed in the ends of a string-type precipitates known to extend along dislocation lines. It is suggested that the string-types form by a growth as extension of the B‧/Q‧ precipitates initially nucleated along dislocation lines. Alternating Mg and Si columns form a well-ordered interface structure in the disordered Q‧ precipitate. It is identical to the interface of the Q‧ parts in the string-type precipitate.

  3. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    SciTech Connect

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D. Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M.; Bednarcik, J.; Michalikova, J.

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  4. Addition of poly (propylene glycol) to multiblock copolymer to optimize siRNA delivery

    PubMed Central

    Dai, Zhi; Arévalo, Maria T; Li, Junwei; Zeng, Mingtao

    2014-01-01

    Previous studies have examined different strategies for siRNA delivery with varying degrees of success. These include use of viral vectors, cationic liposomes, and polymers. Several copolymers were designed and synthesized based on blocks of poly(ethylene glycol) PEG, poly(propylene glycol) PPG, and poly(l-lysine). These were designated as P1, P2, and P3. We studied the copolymer self-assembly, siRNA binding, particle size, surface potential, architecture of the complexes, and siRNA delivery. Silencing of GFP using copolymer P3 to deliver GFP-specific siRNA to Neuro-2a cells expressing GFP was almost as effective as using Lipofectamine 2000, with minimal cytotoxicity. Thus, we have provided a new copolymer platform for siRNA delivery that we can continue to modify for improved delivery of siRNA in vitro and eventually in vivo. PMID:24424156

  5. Addition of poly (propylene glycol) to multiblock copolymer to optimize siRNA delivery.

    PubMed

    Dai, Zhi; Arévalo, Maria T; Li, Junwei; Zeng, Mingtao

    2014-01-01

    Previous studies have examined different strategies for siRNA delivery with varying degrees of success. These include use of viral vectors, cationic liposomes, and polymers. Several copolymers were designed and synthesized based on blocks of poly(ethylene glycol) PEG, poly(propylene glycol) PPG, and poly(l-lysine). These were designated as P1, P2, and P3. We studied the copolymer self-assembly, siRNA binding, particle size, surface potential, architecture of the complexes, and siRNA delivery. Silencing of GFP using copolymer P3 to deliver GFP-specific siRNA to Neuro-2a cells expressing GFP was almost as effective as using Lipofectamine 2000, with minimal cytotoxicity. Thus, we have provided a new copolymer platform for siRNA delivery that we can continue to modify for improved delivery of siRNA in vitro and eventually in vivo.

  6. Microstructures and Properties of Carbon Refractories for Blast Furnaces with SiO2 and Al Additions

    NASA Astrophysics Data System (ADS)

    Li, Yawei; Chen, Xilai; Sang, Shaobai; Li, Yuanbing; Jin, Shengli; Zhao, Lei; Ge, Shan

    2010-08-01

    Microstructures and properties of carbon refractories specimens for blast furnaces with SiO2 and Al additions were investigated after coking for 3 hours at 1400 °C with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray, mercury porosimetry, and a thermal properties analyzer. Additives can influence the matrix structures and improve the properties of specimens. SiO2 additions decreased the mean pore diameter and tremendously increased <1- μm pore volume by filling in the pores and matrix, resulting in an increased particle packing density. Addition of Al improved the thermal conductivity by the in-situ formation of well-developed Al4C3, AlN, and SiC whiskers. With double addition of SiO2 + Al, not only the mean pore diameter decreased but also the thermal conductivity; <1- μm pore volume and cold crushing strength increased by combining the above mentioned superiority of single additive; and more SiC formed, providing greater assistance to improve such material properties.

  7. Effect of Y addition on crystallization behavior and soft-magnetic properties of Fe78Si9B13 ribbons

    NASA Astrophysics Data System (ADS)

    Zhanwei, Liu; Dunbo, Yu; Kuoshe, Li; Yang, Luo; Chao, Yuan; Zilong, Wang; Liang, Sun; Kuo, Men

    2017-08-01

    A series of amorphous Fe-Si-B ribbons with various Y addition were prepared by melt-spinning. The effect of Y addition on crystallization behavior, thermal and magnetic properties was systematically investigated. With the increase of Y content, the initial crystallization temperature shifted to a higher temperature, indicating that the thermal stability of amorphous state in Fe-Si-B-Y ribbon is enhanced compared to that of Fe-Si-B alloy. Meanwhile, compared to the two exothermic peaks in the samples with lower Y content, a new exothermic peak was found in the ribbons with Y content higher than 1 at%, which corresponded to the decomposition of metastable Fe3B phase. Among all the alloys, Fe76.5Si9B13Y1.5 alloy exhibits optimized magnetic properties, with high saturation magnetization Ms of 187 emu/g and low coercivity HcJ of 7.6 A/m.

  8. Si1-yCy/Si(001) gas-source molecular beam epitaxy from Si2H6 and CH3SiH3: Surface reaction paths and growth kinetics

    NASA Astrophysics Data System (ADS)

    Foo, Y. L.; Bratland, K. A.; Cho, B.; Desjardins, P.; Greene, J. E.

    2003-04-01

    In situ surface probes and postdeposition analyses were used to follow surface reaction paths and growth kinetics of Si1-yCy alloys grown on Si(001) by gas-source molecular-beam epitaxy from Si2H6/CH3SiH3 mixtures as a function of C concentration y (0-2.6 at %) and temperature Ts (500-600 °C). High-resolution x-ray diffraction reciprocal lattice maps show that all layers are in tension and fully coherent with their substrates. Film growth rates R decrease with both y and Ts, and the rate of decrease in R as a function of y increases rapidly with Ts. In situ isotopically tagged D2 temperature-programmed desorption (TPD) measurements reveal that C segregation during steady-state Si1-yCy(001) growth results in charge transfer from Si surface dangling bonds to second-layer C atoms, which have a higher electronegativity than Si. From the TPD results, we obtain the coverage θSi*(y,Ts) of Si* surface sites with C backbonds as well as H2 desorption energies Ed from both Si and Si* surface sites. θSi* increases with increasing y and Ts in the kinetically limited segregation regime while Ed decreases from 2.52 eV for H2 desorption from Si surface sites with Si back bonds to 2.22 eV from Si* surface sites. This leads to an increase in the H2 desorption rate, and hence should yield higher film deposition rates, with increasing y and/or Ts during Si1-yCy(001) growth. The effect, however, is more than offset by the decrease in Si2H6 reactive sticking probabilities at Si* surface sites. Film growth rates R(Ts,JSi2H6,JCH3SiH3) calculated using a simple transition-state kinetic model, together with measured kinetic parameters, were found to be in excellent agreement with the experimental data.

  9. Antimony-assisted carbonization of Si(111) with solid source molecular beam epitaxy

    SciTech Connect

    Hackley, Justin; Richardson, Christopher J. K.; Sarney, Wendy L.

    2013-11-15

    The carbonization of an antimony-terminated Si (111) surface in a solid source molecular beam epitaxy system is presented. Reflection high-energy electron diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy are used to characterize samples grown with and without antimony termination. It is shown that the antimony-terminated surface promotes the formation of thin, smooth and continuous SiC films at a relatively low temperature of 800 °C.

  10. Improvement of sag resistance by the addition of tungsten in Si-Cr-Mo-V steels

    SciTech Connect

    Nam, W.J.; Lee, C.S.; Ban, D.Y.

    1997-06-01

    The sag resistance of automobile suspension springs is defined, in general, as the resistance to the plastic deformation of springs during repeated loading in service. Since it is one of the most important properties required for high strength spring steels, earlier works on high strength spring steels have concentrated on the improvement of the sag resistance by adding alloying elements or by changing processing treatments. However, the effect of W, a carbide former, on the sag resistance has not been clarified yet. It is, therefore, of interest to investigate the effect of the W addition on the sag resistance. The evaluation of the sag resistance is usually performed by direct static and dynamic tests on prototype springs. However, such a direct method leads to high costs and long testing time. Thus, Furr has proposed the torsional Bauschinger test as one of convenient testing methods, which is related to the Bauschinger effect. He has also shown that the size of hysteresis loops generated in the torsional Bauschinger test has a close relationship with the sag resistance of springs. Ohara, et al. have investigated the correlation between a direct testing on prototype springs and the torsional Bauschinger test, and have shown that a larger loop area in the torsional Bauschinger test represents a higher sag resistance. In view of the foregoing, the purposes of this investigation are to examine the effects of the W addition on (a) the microstructural evolution during tempering and (b) the sag resistance, using the torsional Bauschinger test, for 0.6C-1.5Si-0.5Cr-0.1Mo-0.2V (wt.%) spring steels.

  11. Improved magneto-caloric effect of the Gd50Co50 metallic glass by minor Si addition

    NASA Astrophysics Data System (ADS)

    Tang, B. Z.; Yu, P.; Ding, D.; Wu, C.; Xia, L.

    2017-02-01

    In the present work, we studied the effect of minor Si addition on the magneto-caloric effect (MCE) of the Gd50Co50 metallic glass. The Gd50Co50-xSix (x=2, 5) as-spun ribbons show typical amorphous characteristics in structure and magneto-caloric behaviors. The peak values for the magnetic entropy change (-ΔSmpeak) of the Gd50Co50-xSix (x=0, 2, 5) metallic glasses increase significantly with the addition of Si. The mechanism for the enhanced MCE by minor addition of Si was investigated by revealing the relationship between -ΔSmpeak and the Curie temperature in the Gd-Co-based amorphous ribbons.

  12. The influence of Ti additions on the mechanical and electrochemical behavior of β-Ta5Si3 nanocrystalline coating

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Cheng, Jian; Jiang, Shuyun; Munroe, Paul; Xie, Zong-Han

    2017-10-01

    In this study, the effects of Ti substitutional additions on the mechanical and electrochemical corrosion behavior of β-Ta5Si3 were investigated through both theoretical calculation and experiment. Initially, first-principles calculations, based on density functional theory, were used to guide compositional design, according to the calculation of mechanical parameters (for example, bulk modulus, shear modulus, Young's modulus, the shear modulus/bulk modulus ratio and Poisson's ratio). This analysis showed that optimum mechanical performance may be achieved through Ta atoms in the Ta20Si12 unit cell being replaced by two Ti atoms. Subsequently, both the binary β-Ta5Si3 coating and the optimized Ti-alloyed β-Ta5Si3 coating (i.e., β-(Ta0.902Ti0.098)5Si3) were deposited onto Ti-6Al-4V substrates using a double cathode glow discharge plasma method. Both as-deposited coatings exhibited a tetragonal crystal structure with fine equiaxed grains ∼4 nm in diameter. The mechanical properties of the coatings were determined by both nanoindentation and Vickers indentation techniques, and their electrochemical corrosion behavior was examined by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis in naturally aerated 0.9 wt.% NaCl solution at 37 °C. These investigations showed that the addition of Ti significantly improved the damage resistance of β-Ta5Si3, with little negative impact on its corrosion resistance.

  13. Improved thermal and electrical design for an all-Si thermoelectric micropower source

    NASA Astrophysics Data System (ADS)

    Donmez, I.; Salleras, M.; Calaza, C.; Gadea, G.; Morata, A.; Tarancón, A.; Fonseca, L.

    2017-05-01

    This work presents current achievements on the fabrication and characterization of an all-Si based planar thermoelectric microgenerator. Ordered dense arrays of Vapor-Liquid-Solid (VLS) grown p-type Si nanowires (Si NWs) are integrated in predefined thermally isolated microstructures as nanostructured thermoelectric active material. Optimizations in device processing and architecture that improved both thermal and electrical performances of the microgenerator resulted in a 70 fold increase in power output. Furthermore, the performance of microgenerators with Si NWs is compared to that of microgenerators with micron-sized Si beams as active material. Additionally, a 60 fold improvement in power output is observed by placing a cold-finger on top of the thermally isolated microstructure to demonstrate the effect of a heat exchanger, which is currently being implemented on the microgenerator.

  14. C incorporation and segregation during Si 1- yC y/Si( 0 0 1 ) gas-source molecular beam epitaxy from Si 2H 6 and CH 3SiH 3

    NASA Astrophysics Data System (ADS)

    Foo, Y. L.; Bratland, K. A.; Cho, B.; Soares, J. A. N. T.; Desjardins, P.; Greene, J. E.

    2002-08-01

    We have used in situ D 2 temperature-programmed desorption (TPD) to probe C incorporation and surface segregation kinetics, as well as hydrogen desorption pathways, during Si 1- yC y(0 0 1) gas-source molecular beam epitaxy from Si 2H 6/CH 3SiH 3 mixtures at temperatures Ts between 500 and 650 °C. Parallel D 2 TPD results from C-adsorbed Si(0 0 1) wafers exposed to varying CH 3SiH 3 doses serve as reference data. Si 1- yC y(0 0 1) layer spectra consist of three peaks: first-order β 1 at 515 °C and second-order β 2 at 405 °C, due to D 2 desorption from Si monodeuteride and dideuteride phases, as well as a new second-order C-induced γ 1 peak at 480 °C. C-adsorbed Si(0 0 1) samples with very high CH 3SiH 3 exposures yielded a higher-temperature TPD feature, corresponding to D 2 desorption from surface C atoms, which was never observed in Si 1- yC y(0 0 1) layer spectra. The Si 1- yC y(0 0 1) γ 1 peak arises due to desorption from Si monodeuteride species with C backbonds. γ 1 occurs at a lower temperature than β 1 reflecting the lower D-Si * bond strength, where Si * represents surface Si atoms bonded to second-layer C atoms, as a result of charge transfer from dangling bonds. The total integrated monohydride (β 1+γ 1) intensity, and hence the dangling bond density, remains constant with y indicating that C does not deactivate surface dangling bonds as it segregates to the second-layer during Si 1- yC y(0 0 1) growth. Si * coverages increase with y at constant Ts and with Ts at constant y. The positive Ts-dependence shows that C segregation is kinetically limited at Ts⩽650 °C. D 2 desorption activation energies from β 1, γ 1 and β 2 sites are 2.52, 2.22 and 1.88 eV.

  15. Influence of Ti and La Additions on the Formation of Intermetallic Compounds in the Al-Zn-Si Bath

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Gu, Qin-Fen; Li, Qian; Lu, Hu-Sheng

    2016-12-01

    The effect of Ti and La additions on the formation of intermetallic compounds (IMCs) in the galvalume (55Al-Zn-1.6Si wt pct) bath was investigated experimentally and further studied with first-principles calculation. The studied baths contain: 1 wt pct Fe, with Ti content ranging from 0.05 to 0.15 wt pct and La content ranging from 0.05 to 0.30 wt pct. Combination of the experimental results with the thermodynamic analysis shows that the solubility of Fe in the alloy bath decreases with an increase of Ti content, which results in the formation of mass dross. Compared with the Ti-containing alloy, La promotes the formation of τ 5 phase (Fe2Al8Si). When both Ti and La are added, Fe4Al13, τ 5, τ 6 (β-Al4.5FeSi), TiAl3, and Ti2Al20La phases were observed. Since these IMCs would consume more Si in the bath, the decrease of Si content with Ti and La additions is more significant than that of the bath without these additions. Furthermore, the formation mechanism of Ti/TiAl3/Ti2La20La core-shell structure in the coating bath is proposed. This study has implications for strategic design of industry hot-dip production with exceptional mechanical properties of Al alloy coating.

  16. Effect of carbon addition on elevated temperature crack growth resistance in (Mo,W)Si[sub 2]-SiC[sub p] composite

    SciTech Connect

    Ramamurty, U. . Division of Engineering); Suresh, S. . Dept. of Materials Science and Engineering); Petrovic, J.J. . Materials Science and Technology Division)

    1994-10-01

    Experimental results on subcritical crack growth behavior of hot-pressed MoSi[sub 2]-50 mol% WSi[sub 2] alloy reinforced with 30 vol% SiC particles in the temperature range 1,200--1,300 C are presented. The effect of 2 wt % C addition on the stable crack growth resistance of this composite was investigated under both static and cyclic loading conditions. The results indicate that the addition off carbon to the composite improves the subcritical crack growth resistance under both static and cyclic loads and increases the elevated temperature capabilities of the (Mo, W) Si[sub 2] composite. Increasing the temperature from 1,200 to 1,300 C is found to increase the crack growth velocities with a concomitant decrease in the crack growth initiation thresholds. Electron microscopy of the crack-tip region indicates that the stable crack growth process is influenced primarily by interfacial cavitation. At 1,300 C, deformation processes such as twinning of the SiC particles and dislocation motion within the matrix grains appear to play an active role in determining the crack growth kinetics. The role of glassy phase in influencing the high-temperature fracture behavior and its implications for design of the microstructure of the brittle materials are discussed.

  17. GaAs nanowires on Si substrates grown by a solid source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ihn, Soo-Ghang; Song, Jong-In; Kim, Young-Hun; Lee, Jeong Yong

    2006-07-01

    High-quality Au-catalyzed GaAs nanowires were grown on Si substrates by vapor-liquid-solid growth in a solid source molecular beam epitaxy system. X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy reveal that the GaAs nanowires were epitaxially grown on Si substrates with uniform diameters along the nanowires. While GaAs nanowires on Si(111) and (001) substrates were mainly grown along the ⟨111⟩ direction with zinc-blende and wurtzite structures, unusual GaAs nanowires grown along ⟨001⟩ with a pure zinc-blende structure were also observed. Strong photoluminescence was observed from GaAs nanowires grown on a Si(001) substrate at room temperature.

  18. Effect of Zn and Mn Additions on the Wear Resistance of Cast Alloy Mg - 5% Al - 1% Si

    NASA Astrophysics Data System (ADS)

    Cug, Harun; Ahlatci, Hayrettin

    2017-07-01

    The effect of additions of Zn and Mn (from 0.5 to 4%) on the microstructure of alloy Mg - 5% Al - 1% Si is studied by the methods of x-ray diffractometry and light and scanning electron microscopy. The strength parameters are determined in tensile and wear tests. It is shown that particles of Mg2Si precipitate in the matrix and particles of Mg17Al12 precipitate on grain boundaries upon the introduction of low contents of Zn and Mn. Phases MgZn and Al6Mn precipitate at a high content of the additions. An optimum concentration of Zn and Mn is chosen for raising the wear resistance of alloy Mg - 5% Al - 1% Si.

  19. Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition.

    PubMed

    Yao, Maoqing; Cong, Sen; Arab, Shermin; Huang, Ningfeng; Povinelli, Michelle L; Cronin, Stephen B; Dapkus, P Daniel; Zhou, Chongwu

    2015-11-11

    Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due to their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates to achieve monolithic integration of solar cell materials that are not lattice-matched. Here, we report the first realization of nanowire-on-Si tandem cells with the observation of voltage addition of the GaAs nanowire top cell and the Si bottom cell with an open circuit voltage of 0.956 V and an efficiency of 11.4%. Our simulation showed that the current-matching condition plays an important role in the overall efficiency. Furthermore, we characterized GaAs nanowire arrays grown on lattice-mismatched Si substrates and estimated the carrier density using photoluminescence. A low-resistance connecting junction was obtained using n(+)-GaAs/p(+)-Si heterojunction. Finally, we demonstrated tandem solar cells based on top GaAs nanowire array solar cells grown on bottom planar Si solar cells. The reported nanowire-on-Si tandem cell opens up great opportunities for high-efficiency, low-cost multijunction solar cells.

  20. Synergistic Effect of MoS₂ and SiO₂ Nanoparticles as Lubricant Additives for Magnesium Alloy-Steel Contacts.

    PubMed

    Xie, Hongmei; Jiang, Bin; Hu, Xingyu; Peng, Cheng; Guo, Hongli; Pan, Fusheng

    2017-06-23

    The tribological performances of the SiO₂/MoS₂ hybrids as lubricant additives were explored by a reciprocating ball-on-flat tribometer for AZ31 magnesium alloy/AISI 52100 bearing steel pairs. The results demonstrated that the introduction of SiO₂/MoS₂ hybrids into the base oil exhibited a significant reduction in the friction coefficient and wear volume as well as an increase in load bearing capacity, which was better than the testing results of the SiO₂ or MoS₂ nanolubricants. Specifically, the addition of 0.1 wt % nano-SiO₂ mixed with 1.0 wt % nano-MoS₂ into the base oil reduced the friction coefficient by 21.8% and the wear volume by 8.6% compared to the 1.0 wt % MoS₂ nanolubricants. The excellent lubrication behaviors of the SiO₂/MoS₂ hybrid nanolubricants can be explained by the micro-cooperation of different nanoparticles with disparate morphology and lubrication mechanisms.

  1. Theoretical study on the mechanism for the addition reaction of SiH(3) with propylene and acetic acid.

    PubMed

    Liu, Yongjun; Wang, Zhiguo; Suo, Yourui

    2006-11-16

    To explore the reactivities of alkene (-CH=CH(2)) and carboxy (-COOH) group with H-Si under UV irradiation, the addition mechanism for the reactions of SiH(3) radical with propylene and acetic acid was studied by using the B3LYP/6-311++G(d,p) method. Based on the surface energy profiles, the dominant reaction pathways can be established; i.e., SiH(3) adds to the terminal carbon atom of the alkene (-CH=CH(2)) to form an anti-Markovnikov addition product, or adds to the oxygen atom of the carboxy group (-COOH) to form silyl acetate (CH(3)-COOSiH(3)). Because the barrier in the reaction of the carboxy group (39.9 kJ/mol) is much larger than that of alkene (11.97 kJ/mol), we conclude that the reaction of bifunctional molecules (e.g., omega-alkenoic acid) with H-Si under irradiation condition is highly selective; i.e., the alkene group (-CH=CH(2)) reacts with SiH(3) substantially faster than the carboxyl group (-COOH), which agrees well with the experimental results. This provides the possibility of preparing carboxy-terminated monolayers on silicon surface from omega-alkenoic acids via direct photochemical reaction.

  2. Effect of Copper and Zirconium Addition on Properties of Fe-Co-Si-B-Nb Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Ikram, Haris; Khalid, Fazal Ahmad; Akmal, Muhammad; Abbas, Zameer

    2017-07-01

    In this research work, iron-based bulk metallic glasses (BMGs) have been fabricated, characterized and compared with Fe-Si alloy. BMG alloys of composition ((Fe0.6Co0.4)0.75B0.20Si0.05)96Nb4) were synthesized by suction casting technique using chilled copper die. Effect of copper and zirconium addition on magnetic, mechanical, thermal and electrochemical behavior of ((Fe0.6Co0.4)0.75B0.20Si0.05)96Nb4 BMGs was investigated. Furthermore, effect of annealing on nano-crystallization and subsequently on magnetic and mechanical behavior was also analyzed. Amorphousness of structure was evidenced by XRD analysis and microscopic visualization, whereas nano-crystallization behavior was identified by peak broadening of XRD patterns. Magnetic properties, measured by vibrating sample magnetometer, were found to be improved for as-cast BMG alloys by copper addition and further enhanced by nano-crystallization after annealing. Mechanical properties were observed to be increased by zirconium addition while slightly declined by copper addition. Potentiodynamic polarization analysis manifested the positive role of zirconium in enhancing corrosion resistance of BMGs in acidic, basic and brine mediums. Moreover, mechanical properties and corrosion analysis results affirmed the superiority of BMG alloys over Fe-Si alloy.

  3. Effect of ternary additions on the oxidation resistance of Ti{sub 5}Si{sub 3}

    SciTech Connect

    Thom, A.J.; Akinc, M. |

    1995-10-01

    Refractory intermetallic silicides are receiving increasing consideration for use as high temperature structural materials. Ti{sub 5}Si{sub 3}-based compositions are attractive due to their ability to incorporate a variety of interstitial ternary additions. These ternary additions present a unique opportunity to potentially tailor physical properties. Previous experimental work has shown that these additions significantly increase the otherwise poor oxidation resistance of undoped Ti{sub 5}Si{sub 3} above 700 C. Recent experimental work by the authors on the oxidation of small atom doped Ti{sub 5}Si{sub 3} is discussed. Interstitial additions of boron, carbon, and oxygen substantially improve the isothermal oxidation resistance of Ti{sub 5}Si{sub 3} at 1,000 C. In contrast, added nitrogen does not provide significant improvement. Even up to 1,306 C, interstitial oxygen imparts excellent oxidation resistance with a mass gain of 1.1 mg/cm{sup 2} after 240 hours.

  4. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  5. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  6. Using Si depletion in aerosol to identify the sources of crustal dust in two Chinese megacities

    NASA Astrophysics Data System (ADS)

    Zhao, Qing; He, Kebin; Rahn, Kenneth A.; Ma, Yongliang; Yang, Fumo; Duan, Fengkui

    2010-07-01

    Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM 2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM 2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%-65% when using the average abundance of Al in crust (6%-8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004-2006. This result can help resolve the contradictory findings on this topic that have been presented earlier.

  7. 5 CFR 3601.103 - Additional exceptions for gifts from outside sources.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Additional exceptions for gifts from outside sources. 3601.103 Section 3601.103 Administrative Personnel DEPARTMENT OF DEFENSE SUPPLEMENTAL... gifts from outside sources. In addition to the gifts which come within the exceptions set forth in 5 CFR...

  8. The Effect of SiC Particle Addition During FSW on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Abbasi, M.; Abdollahzadeh, A.; Bagheri, B.; Omidvar, H.

    2015-12-01

    Welding and joining of magnesium alloys exert a profound effect on magnesium application expansion, especially in ground and air transportations where large-size, complex components are required. Due to specific physical properties of magnesium, its welding requires great control. In general, the solid-state nature of friction stir welding (FSW) process has been found to produce a low concentration of defects. In the current research, specimens from AZ31 magnesium alloy were welded together using the friction stir process with previously inserted SiC powder particles in the nugget zone. In other words, during the FSW process, the pre-placed SiC particles were stirred throughout the nugget zone of the weld. The results indicated that proper values of rotation and translation speeds led to good appearance of weld zone and suitable distribution of SiC particles producing increased weld strength. The comparison of the microstructures and mechanical properties of FS-welded AZ31 with those of FS-welded one using pre-placed SiC particles showed that the addition of SiC particles decreased the grain size and increased the strength and the formability index.

  9. Influence of addition of Si in FeAl alloys: Theory

    NASA Astrophysics Data System (ADS)

    Apiñaniz, E.; Legarra, E.; Plazaola, F.; Garitaonandia, J. S.

    The magnetic behaviour of Fe-based magnetic systems has been studied theoretically and experimentally for many years [E.P. Wohlfath, K.H.J. Buschow, Handbook of Ferromagnetic Materials, vol. 4, North-Holland Elsevier Science Publishers, Amsterdam, New York, Oxford, Tokyo, 1988 (Chapter 1)]. Starting with Al dissolved in Fe, the first stable structure is the D03 cubic structure and it exists over the range 23-37 at% Al. In this range these alloys present interesting magnetic properties. The other stable compound existing over a wide range of composition is FeAl which is also cubic, with the B2 structure (CsCl), and it exists over the range 37-50 at% Al. On the other hand, the FeAlSi alloys show the D03 structure, but do not show the B2 structure. The effect of Si in these alloys is double; on the one hand, it contributes to the decrease of the lattice parameter which, as reported by Nogues et al. [Phys. Rev. B 74 (2006) 024407], has a major influence on the magnetism and, on the other hand, having one more p electron than the Al atom, it promotes the charge transfer from Si to Fe atoms, as reported by Legarra et al. [Hyperfine Interact. 169 (2006) 1217-1222]. In this work, we perform ab-initio electronic calculations by means of tight binding linear muffin-tin orbital (TBLMTO) and Vienna Ab-initio Simulation Package (VASP) in order to study the magnetic contribution of Si/Al substitution in the FeAl alloys.

  10. High efficiency 4H-SiC betavoltaic power sources using tritium radioisotopes

    SciTech Connect

    Thomas, Christopher; Portnoff, Samuel; Spencer, M. G.

    2016-01-04

    Realization of an 18.6% efficient 4H-silicon carbide (4H-SiC) large area betavoltaic power source using the radioisotope tritium is reported. A 200 nm 4H-SiC P{sup +}N junction is used to collect high-energy electrons. The electron source is a titanium tritide (TiH{sup 3}{sub x}) foil, or an integrated titanium tritide region formed by the diffusion of tritium into titanium. The specific activity of the source is directly measured. Dark current measured under short circuit conditions was less than 6.1 pA/cm{sup 2}. Samples measured with an external tritium foil produced an open circuit voltage of 2.09 V, short circuit current of 75.47 nA/cm{sup 2}, fill factor of 0.86, and power efficiency of 18.6%. Samples measured with an integrated source produced power efficiencies of 12%. Simulations were done to determine the beta spectrum (modified by self absorption) exiting the source and the electron hole pair generation function in the 4H-SiC. The electron-hole pair generation function in 4H-SiC was modeled as a Gaussian distribution, and a closed form solution of the continuity equation was used to analyze the cell performance. The effective surface recombination velocity in our samples was found to be 10{sup 5}–10{sup 6 }cm/s. Our analysis demonstrated that the surface recombination dominates the performance of a tritium betavoltaic device but that using a thin P{sup +}N junction structure can mitigate some of the negative effects.

  11. High efficiency 4H-SiC betavoltaic power sources using tritium radioisotopes

    NASA Astrophysics Data System (ADS)

    Thomas, Christopher; Portnoff, Samuel; Spencer, M. G.

    2016-01-01

    Realization of an 18.6% efficient 4H-silicon carbide (4H-SiC) large area betavoltaic power source using the radioisotope tritium is reported. A 200 nm 4H-SiC P+N junction is used to collect high-energy electrons. The electron source is a titanium tritide (TiH3x) foil, or an integrated titanium tritide region formed by the diffusion of tritium into titanium. The specific activity of the source is directly measured. Dark current measured under short circuit conditions was less than 6.1 pA/cm2. Samples measured with an external tritium foil produced an open circuit voltage of 2.09 V, short circuit current of 75.47 nA/cm2, fill factor of 0.86, and power efficiency of 18.6%. Samples measured with an integrated source produced power efficiencies of 12%. Simulations were done to determine the beta spectrum (modified by self absorption) exiting the source and the electron hole pair generation function in the 4H-SiC. The electron-hole pair generation function in 4H-SiC was modeled as a Gaussian distribution, and a closed form solution of the continuity equation was used to analyze the cell performance. The effective surface recombination velocity in our samples was found to be 105-106 cm/s. Our analysis demonstrated that the surface recombination dominates the performance of a tritium betavoltaic device but that using a thin P+N junction structure can mitigate some of the negative effects.

  12. Effects of La addition on the microstructure and tensile properties of Al-Si-Cu-Mg casting alloys

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Pan, Ye; Wu, Ji-li; Tao, Shi-wen; Chen, Yu

    2015-04-01

    The effects of La addition on the microstructure and tensile properties of B-refined and Sr-modified Al-11Si-1.5Cu-0.3Mg casting alloys were investigated. With a trace addition of La (0.05wt%-0.1wt%), the mutual poisoning effect between B and Sr can be neutralized by the formation of LaB6 rather than SrB6. By employing a La/B weight ratio of 2:1, uniform microstructures, which are characterized by well refined α-Al grains and adequately modified eutectic Si particles as well as the incorporation of precipitated strengthening intermetallics, are obtained and lead to appreciable tensile properties with an ultimate tensile strength of 270 MPa and elongation of 5.8%.

  13. The source of dissolved silicon in soil surface solutions of a temperate forest ecosystem: Ge/Si and Si isotope ratios as biogeochemical tracers

    NASA Astrophysics Data System (ADS)

    Cornelis, J.; Delvaux, B.; Cardinal, D.; André, L.; Ranger, J.; Opfergelt, S.

    2010-12-01

    solutions evolve towards lighter values (-1.38 and -2.05 ‰) and higher Ge/Si ratios (2.7 µmol/mol) relative to granite bedrock. This suggests a partial dissolution of 28Si and Ge-enriched secondary clays minerals incorporated by bioturbation in organic-rich horizons, with a fractionation releasing preferentially light Si isotopes. Without considering that organic acids promote dissolution of minerals, clay minerals detected in the organic layer (vermiculite, chlorite, illite and Ca-montmorillonite) are not stable and could have been partially dissolved and transformed in the chemical environment of forest floor. Sources of H4SiO4 in forest floor solutions are influenced by tree species which control the extent of clay-sized minerals mixed in organic horizons by bioturbation and, to a lesser extent, the Si recycling by forest vegetation.

  14. Stabilizing Nanosized Si Anodes with the Synergetic Usage of Atomic Layer Deposition and Electrolyte Additives for Li-Ion Batteries.

    PubMed

    Hy, Sunny; Chen, Yi-Hsiu; Cheng, Ho-Ming; Pan, Chun-Jern; Cheng, Ju-Hsiang; Rick, John; Hwang, Bing-Joe

    2015-07-01

    A substantial increase in charging capacity over long cycle periods was made possible by the formation of a flexible weblike network via the combination of Al2O3 atomic layer deposition (ALD) and the electrolyte additive vinylene carbonate (VC). Transmission electron microscopy shows that a weblike network forms after cycling when ALD and VC were used in combination that dramatically increases the cycle stability for the Si composite anode. The ALD-VC combination also showed reduced reactions with the lithium salt, forming a more stable solid electrolyte interface (SEI) absent of fluorinated silicon species, as evidenced by X-ray photoelectron spectroscopy. Although the bare Si composite anode showed only an improvement from a 56% to a 45% loss after 50 cycles, when VC was introduced, the ALD-coated Si anode showed an improvement from a 73% to a 11% capacity loss. Furthermore, the anode with the ALD coating and VC had a capacity of 630 mAh g(-1) after 200 cycles running at 200 mA g(-1), and the bare anode without VC showed a capacity of 400 mAh g(-1) after only 50 cycles. This approach can be extended to other Si systems, and the formation of this SEI is dependent on the thickness of the ALD that affects both capacity and stability.

  15. Spectral aspects of the determination of Si in organic and aqueous solutions using high-resolution continuum source or line source flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Kowalewska, Zofia; Pilarczyk, Janusz; Gościniak, Łukasz

    2016-06-01

    High-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) was applied to reveal and investigate spectral interference in the determination of Si. An intensive structured background was observed in the analysis of both aqueous and xylene solutions containing S compounds. This background was attributed to absorption by the CS molecule formed in the N2O-C2H2 flame. The lines of the CS spectrum at least partially overlap all five of the most sensitive Si lines investigated. The 251.611 nm Si line was demonstrated to be the most advantageous. The intensity of the structured background caused by the CS molecule significantly depends on the chemical form of S in the solution and is the highest for the most-volatile CS2. The presence of O atoms in an initial S molecule can diminish the formation of CS. To overcome this S effect, various modes of baseline fitting and background correction were evaluated, including iterative background correction (IBC) and utilization of correction pixels (WRC). These modes were used either independently or in conjunction with least squares background correction (LSBC). The IBC + LSBC mode can correct the extremely strong interference caused by CS2 at an S concentration of 5% w:w in the investigated solution. However, the efficiency of this mode depends on the similarity of the processed spectra and the correction spectra in terms of intensity and in additional effects, such as a sloping baseline. In the vicinity of the Si line, three lines of V were recorded. These lines are well-separated in the HR-CS FAAS spectrum, but they could be a potential source of overcorrection when using line source flame atomic absorption spectrometry (LS FAAS). The expected signal for the 251.625 nm Fe line was not registered at 200 mg L- 1 Fe concentration in the solution, probably due to the diminished population of Fe atoms in the high-temperature flame used. The observations made using HR-CS FAAS helped to establish a "safe" level

  16. Microstructural developments in pressureless-sintered US -SiC materials with Al, B, and C additions

    SciTech Connect

    Shinozaki, S.; Donlon, W.T.; Hangas, J.; Juterbock, B.N.; Peters, C.R.; Williams, R.M.

    1985-10-01

    Fine-grained US -SiC powder with various combinations of Al, B, and C additions was pressureless-sintered to near-theoretical density and investigated using analytical electron microscopy. The additions were found to enhance the US -to- phase transformation and subsequent basal growth of -SiC, as confirmed by quantitative X-ray diffraction analysis. Formation of graphite was reduced when Al was present in the carbon-rich regions because fine Al4C3 particles formed. For low sintering temperatures, Al was distributed in amorphous carbon as Al4C3 particles, whereas at high sintering temperature (>1800C) Al was concentrated in pores and along grain boundaries as an Al-rich second phase. This phase was identified as mostly Al8B4C7 by energy-dispersive X-ray analysis, electron energy-loss spectroscopy, and selectedarea diffraction analysis. Formation of homogeneous microstructures and rapid polytypic transformation in this material may be explained by the homogeneous Al distribution at relatively low temperature, the local crystallographic coherency of the and US -phases, diffusion of the Al-rich second phase on the basal plane of -SiC, and formation of an Al4C3 layer grown epitaxially.

  17. Na@SiO2-Mediated Addition of Organohalides to Carbonyl Compounds for the Formation of Alcohols and Epoxides

    PubMed Central

    Kapoor, Mohit; Hwu, Jih Ru

    2016-01-01

    Alcohols and epoxides were generated by the addition of organohalides to carbonyl compounds in the presence of sodium metal impregnated with silica gel (Na@SiO2) in THF at 25 °C through a radical pathway. Under the same conditions, Schiff bases were also successfully converted to the corresponding amines. Furthermore, the reaction of aldehydes with α-haloesters or 4-(chloromethyl)-coumarin with the aid of Na@SiO2 generated trans epoxides. An unprecedented mechanism is proposed for their formation. The advantages associated with these new reactions include: (1) products are obtained in good-to-excellent yields, (2) reactions are completed at room temperatures in a short period of time (<2.0 h), (3) it is unnecessary to perform the reactions under anhydrous conditions, and (4) the entire process requires only simple manipulations. PMID:27853277

  18. Na@SiO2-Mediated Addition of Organohalides to Carbonyl Compounds for the Formation of Alcohols and Epoxides

    NASA Astrophysics Data System (ADS)

    Kapoor, Mohit; Hwu, Jih Ru

    2016-11-01

    Alcohols and epoxides were generated by the addition of organohalides to carbonyl compounds in the presence of sodium metal impregnated with silica gel (Na@SiO2) in THF at 25 °C through a radical pathway. Under the same conditions, Schiff bases were also successfully converted to the corresponding amines. Furthermore, the reaction of aldehydes with α-haloesters or 4-(chloromethyl)-coumarin with the aid of Na@SiO2 generated trans epoxides. An unprecedented mechanism is proposed for their formation. The advantages associated with these new reactions include: (1) products are obtained in good-to-excellent yields, (2) reactions are completed at room temperatures in a short period of time (<2.0 h), (3) it is unnecessary to perform the reactions under anhydrous conditions, and (4) the entire process requires only simple manipulations.

  19. Additivity of kinetic and potential energy contributions in modification of graphene supported on SiO2

    NASA Astrophysics Data System (ADS)

    Zhang, Xitong; Zhao, Shijun; Wang, Yuyu; Xue, Jianming

    2017-04-01

    The damage production induced by MeV highly charged ions (HCI) irradiations in graphene supported on a SiO2 substrate is investigated using molecular dynamics method. We get results in agreement with our recent experiments. We find that the electronic energy loss and potential energy deposition have similar effects on the defects creation in SiO2 substrate-supported graphene and both mechanisms of energy deposition seem to contribute in an additive way. The influences of the energy deposition depth and radius are studied. Only the energy deposited below the surface within 2.5 nm will induce the damage in graphene. Hence, the HCI can be a powerful tool to induce defects in graphene without causing deep damage of the substrate. When charge of incident Xeq+ is above 30, a nanopore is formed and the size of nanopore in graphene can be controlled by changing the incident charge state.

  20. A high performance Ge/Si0.5Ge0.5/Si heterojunction dual sources tunneling transistor with a U-shaped channel

    NASA Astrophysics Data System (ADS)

    Li, Wei; Liu, Hongxia; Wang, Shulong; Wang, Qianqiong; Chen, Shupeng

    2017-06-01

    In this paper, a new Ge/Si0.5Ge0.5/Si heterojunction dual sources tunneling transistor with a U-shaped channel (Ge_DUTFET) is proposed and investigated by Silvaco-Atlas simulation. The line tunneling perpendicular to channel and point tunneling parallel to channel simultaneously occur on both sides of the gate. The Ge is chosen as the source region material to increase the line tunneling current. The designed heterojunction between the Ge source and Si channel decreases the point tunneling barrier width to enhance the point tunneling current. And this heterojunction can also promote the Ge_DUTFET to occur point tunneling at the small gate voltage, which makes it obtain the smaller turn-on voltage. Furthermore, the Si0.5Ge0.5 buffer layer is also helpful for the enhancement of performance. The simulation results reveal that Ge_DUTFET has the better performance compared with the Si_DUTFET. The on-state current and average subthreshold swing of Ge_DUTFET are 1.11 × 10-5A/μm and 35.1mV/dec respectively. The max cut-off frequency (fT) and gain bandwidth product (GBW) are 26.6 GHz and 16.6 GHz respectively. The fT and GBW of the Ge_DUTFET are respectively increased by ∼27.4% and ∼84.3% compared with the Si_DUTFET.

  1. Temperature dependence of a microstructured SiC coherent thermal source

    NASA Astrophysics Data System (ADS)

    Hervé, Armande; Drévillon, Jérémie; Ezzahri, Younès; Joulain, Karl; De Sousa Meneses, Domingos; Hugonin, Jean-Paul

    2016-09-01

    By ruling a grating on a polar material that supports surface phonon-polaritons such as silicon carbide (SiC), it is possible to create directional and monochromatic thermal sources. So far, most of the studies have considered only materials with room temperature properties as the ones tabulated in Palik's handbooks. Recently, measurements have provided experimental data of the SiC dielectric function at different temperatures. Here we study, numerically, the effect of the temperature dependence of the dielectric function on the thermal emission of SiC gratings (1D grating, in a first approach), heated at different temperatures. When materials are heated, the position of the grating emissivity peak shifts towards higher wavelength values. A second consequence of the temperature dependence of optical properties is that room temperature designed gratings are not optimal for higher temperatures. However, by modifying the grating parameters, it is possible to find an emission peak, with a maximum of emissivity near 1, for each temperature. We tried first to catch some patterns in the emissivity variation. Then, we obtained a grating, which leads to an optimum emissivity for all available temperature data for SiC.

  2. Synthesis of Si-Ge nanoscale structures via deposition of single-source (GeH3)4-nSiHn hydrides

    NASA Astrophysics Data System (ADS)

    Hu, Changwu; Tsong, I. S. T.; D'Costa, V.; Menéndez, J.; Crozier, P. A.; Tolle, J.; Kouvetakis, J.

    2005-08-01

    Growth of nanoscale islands with distinct Si0.33Ge0.67, Si0.25Ge0.75, and Si0.20Ge0.80 compositions and uniform sizes is conducted on Si(100) via dehydrogenation of the single-source hydrides (H3Ge)2SiH2, (H3Ge)3SiH, and (H3Ge)4Si, respectively. High-spatial-resolution electron energy loss spectroscopy and Raman spectroscopy indicate homogeneous elemental concentrations within and among islands and confirm that their Si-Ge content is predetermined by the stoichiometry of the corresponding precursors. Z-contrast electron microscopy reveals distinct and perfectly epitaxial islands with atomically sharp interfaces grown via a smooth and continuous wetting layer ˜10Å thick. Cross-sectional electron microscopy shows monomodal distributions of islands with defect-free microstructures. Low-energy electron microscopy studies of the film formation reveal that the growth proceeds via the Stranski-Krastanov mode. Assemblies of coherent quantum dots with highly controlled Ge-rich concentrations produced by this method are desirable for their potentially useful optical properties.

  3. Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

    2000-01-01

    Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

  4. Hydrogen incorporation during deposition of a-Si:H from an intense source of SiH{sub 3}

    SciTech Connect

    Van de Sanden, M.C.M.; Severens, R.J.; Kessels, W.M.M.; Van de Pas, F.; Van Ijzendoorn, L.; Schram, D.C.

    1997-07-01

    The incorporation of hydrogen during the fast deposition of a-Si:H from an expanding thermal arc is investigated by means of isotope labeling of the precursor gases silane and hydrogen. It is found that hydrogen in a-Si:H originates dominantly from the silyl radical. A small fraction of the hydrogen in a-Si:H is due to exchange reaction of atomic hydrogen in the plasma with hydrogen chemisorbed on the surface during growth.

  5. Structure and high-temperature properties of Ti5Si3 with interstitial additions

    SciTech Connect

    Williams, Jason

    1999-12-01

    This study was motivated by the fact that previous research on the structure and properties of Ti5Si3 showed unacceptably inconsistent results. The primary reason for these inconsistencies was interstitial contamination of Ti5Si3 by carbon, nitrogen and oxygen. Thus, this study measured the effects that these interstitial atoms have on some of the previously reported properties. These properties include crystalline structure, thermal expansion anisotropy, electronic structure and bonding, and high temperature oxidation resistance. In Chapter 2 of this study, the lattice parameters and atomic positions of Ti5Si3 as a function of carbon, nitrogen or oxygen content were measured via x-ray and neutron diffraction. Comparing these lattice parameters to those reported in other studies on supposedly pure Ti5Si3 confirmed that the majority of the previous studies had samples with a considerable amount of interstitial impurities. In fact, the lattice parameter trends given in Chapter 2 can be used to estimate the types and level of impurities in these studies. Furthermore, Chapter 2 discusses how atomic positions change as interstitial atoms are incorporated into the lattice. These changes in atomic separations suggest that strong bonds form between the interstitial atoms and the surrounding titanium atoms. This is in full agreement with the electronic structure calculations given in Chapter 4. These calculations show that bonding does occur between titanium d-states and interstitial atom p-states at the expense of bonding between some of the titanium and silicon atoms. In addition, carbon seems to be the most strongly bonded interstitial atom. Knowledge of the exact interstitial content and its effect on bonding is important because Chapters 3 and 5 have shown that interstitial atoms have a marked effect on the thermal expansion and oxidation resistance. As discussed in Chapter 3, all

  6. Mechanism of the addition of nonenolizable aldehydes and ketones to (Di)metallenes (R(2)X=YR(2), X = Si, Ge Y = C, Si, Ge): a density functional and multiconfigurational perturbation theory study.

    PubMed

    Mosey, Nicholas J; Baines, Kim M; Woo, Tom K

    2002-11-06

    The mechanism of the addition of nonenolizable aldehydes and ketones to group 14 (di)metallenes has been examined through a theoretical study of the addition of formaldehyde to Si=C, Ge=C, Si=Si, Si=Ge, and Ge=Ge bonds at the B3LYP/6-311++G(d,p) and CAS-MCQDPT2/6-31++G(d,p) levels of theory. The reaction pathways located can be grouped as either involving the formation of singlet diradical or zwitterionic intermediates or as concerted processes. Within each group of reaction pathways, several different mechanisms have been located, with not all mechanisms being available to all of the (di)metallenes. It was found that for reactions in which a Si-O bond results (i.e., addition to Si=C, Si=Si, and Si=Ge) both diradical and zwitterionic intermediates are possible; however, the formation of diradical intermediates was not found for reactions that result in the formation of a Ge-O bond (addition to Ge=C and Ge=Ge). The underlying cause of this pathway selectivity is examined, as well as the effect of solvent on the relative energies of the pathways. The results of the study shed light on the cause of experimentally obtained results regarding the mechanism of the reaction of (di)metallenes with nonenolizable ketones and aldehydes.

  7. Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting

    NASA Astrophysics Data System (ADS)

    Ahmad, M.; Ali, G.; Ahmed, Ejaz; Haq, M. A.; Akhter, J. I.

    2011-06-01

    Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

  8. Influence of Li-B-Si Additions on the Sintering and Microwave Dielectric Properties of Ba-Nd-Ti Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Duan, Shuxin; Sun, Shumeng; Li, Hao; Mi, Yuean; Zhou, Xiaohua; Zhang, Shuren

    2013-12-01

    Li2O-B2O3-SiO2 (LBS) synthesized via a solid-state reaction process was chosen as a novel sintering aid for tungsten-bronze-type Ba4Nd9.3Ti18O54 (BNT) ceramic. The effects of LBS additions on the sintering behaviors, microstructures, and microwave dielectric properties of the BNT ceramic have been investigated, indicating that LBS addition obviously lowered the sintering temperature of the BNT ceramic without damaging its microwave dielectric properties. BNT ceramic doped with 3 wt.% and 4 wt.% LBS addition could be well sintered at 975°C and 950°C for 3 h and had excellent properties: ɛ r = 65.99, Q × f = 4943 GHz ( f = 4.4 GHz), τ f = 19 ppm/°C, and ɛ r = 64.56, Q × f = 4929 GHz ( f = 4.3 GHz), τ f = 11 ppm/°C, respectively.

  9. Reduction in secondary dendrite arm spacing in cast eutectic Al-Si piston alloys by cerium addition

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Asmael, M. B. A.; Shahizan, N. R.; Gandouz, S.

    2017-01-01

    The effects of Ce on the secondary dendrite arm spacing (SDAS) and mechanical behavior of Al-Si-Cu-Mg alloys were investigated. The reduction of SDAS at different Ce concentrations was evaluated in a directional solidification experiment via computer-aided cooling curve thermal analysis (CA‒CCTA). The results showed that 0.1wt%-1.0wt% Ce addition resulted in a rapid solidification time, Δ t s, and low solidification temperature, Δ T S, whereas 0.1wt% Ce resulted in a fast solidification time, Δ t a-Al, of the α-Al phase. Furthermore, Ce addition refined the SDAS, which was reduced to approximately 36%. The mechanical properties of the alloys with and without Ce were investigated using tensile and hardness tests. The quality index ( Q) and ultimate tensile strength of (UTS) Al-Si-Cu-Mg alloys significantly improved with the addition of 0.1wt% Ce. Moreover, the base alloy hardness was improved with increasing Ce concentration.

  10. Influence of Co addition on the magnetocaloric effect of FeCoSiAlGaPCB amorphous alloys

    SciTech Connect

    Franco, V.; Borrego, J.M.; Conde, A.; Roth, S.

    2006-03-27

    The FeCoSiAlGaPCB alloys can be prepared as bulk amorphous materials, with outstanding mechanical properties and increased electrical resistivity. These features can be beneficial for their application as a magnetic refrigerant. The influence of Co addition on the magnetic entropy change of the alloy has been studied. This compositional modification displaces the temperature of the peak entropy change closer to room temperature, but reduces the refrigerant capacity of the material. For the Co-free alloy, the peak entropy change is increased with respect to a Finemet alloy containing Mo, but its refrigerant capacity is not enhanced.

  11. Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

    1989-01-01

    Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.

  12. Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

    1989-01-01

    Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.

  13. Flexible Solar Cells Using Doped Crystalline Si Film Prepared by Self-Biased Sputtering Solid Doping Source in SiCl4/H2 Microwave Plasma.

    PubMed

    Hsieh, Ping-Yen; Lee, Chi-Young; Tai, Nyan-Hwa

    2016-02-01

    We developed an innovative approach of self-biased sputtering solid doping source process to synthesize doped crystalline Si film on flexible polyimide (PI) substrate via microwave-plasma-enhanced chemical vapor deposition (MWPECVD) using SiCl4/H2 mixture. In this process, P dopants or B dopants were introduced by sputtering the solid doping target through charged-ion bombardment in situ during high-density microwave plasma deposition. A strong correlation between the number of solid doping targets and the characteristics of doped Si films was investigated in detail. The results show that both P- and B-doped crystalline Si films possessed a dense columnar structure, and the crystallinity of these structures decreased with increasing the number of solid doping targets. The films also exhibited a high growth rate (>4.0 nm/s). Under optimal conditions, the maximum conductivity and corresponding carrier concentration were, respectively, 9.48 S/cm and 1.2 × 10(20) cm(-3) for P-doped Si film and 7.83 S/cm and 1.5 × 10(20) cm(-3) for B-doped Si film. Such high values indicate that the incorporation of dopant with high doping efficiency (around 40%) into the Si films was achieved regardless of solid doping sources used. Furthermore, a flexible crystalline Si film solar cell with substrate configuration was fabricated by using the structure of PI/Mo film/n-type Si film/i-type Si film/p-type Si film/ITO film/Al grid film. The best solar cell performance was obtained with an open-circuit voltage of 0.54 V, short-circuit current density of 19.18 mA/cm(2), fill factor of 0.65, and high energy conversion of 6.75%. According to the results of bending tests, the critical radius of curvature (RC) was 12.4 mm, and the loss of efficiency was less than 1% after the cyclic bending test for 100 cycles at RC, indicating superior flexibility and bending durability. These results represent important steps toward a low-cost approach to high-performance flexible crystalline Si film

  14. 75 FR 74773 - Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-01

    ...EPA is issuing a regulation to require monitoring and reporting of greenhouse gas emissions from additional sources of fluorinated greenhouse gases, including electronics manufacturing, fluorinated gas production, electrical equipment use, electrical equipment manufacture or refurbishment, as well as importers and exporters of pre-charged equipment and closed-cell foams. This rule requires monitoring and reporting of greenhouse gases for these source categories only for sources with carbon dioxide equivalent emissions, imports, or exports above certain threshold levels. This rule does not require control of greenhouse gases.

  15. Radio optical reference frame. 6: Additional source positions in the northern hemisphere

    NASA Technical Reports Server (NTRS)

    Fey, A. L.; Russell, J. L.; De Vegt, C.; Zacharias, N.; Johnston, K. J.; Ma, C.; Hall, D. M.; Holdenried, E. R.

    1994-01-01

    Radio and optical positions for northern hemisphere extragalactic sources are reported. Milliarcsecond (mas) accurate radio positions of 106 sources north of -2 deg declination are derived from Mark III Very Long Baseline Interferometry (VLBI) observations taken during ten experiments from 1990 January through 1990 October. The results presented supplement an ongoing project to define and maintain an all-sky radio/optical reference frame of 400 or more extragalactic sources with mas accurate radio and optical positions. Radio positions for 34 new sources are presented along with improved radio positions for 72 sources already in the reference frame catalog. An additional nine sources have been determined to be unsuitable reference frame objects. Radio observations of nine calibration sources tie the new positions to the existing catalogue. The radio positions of the new sources have formal mean errors of approximately 0.7 mas in right ascension and approximately 1.0 mas in declination. Sources for which we report improved radio positions now have formal mean errors of approximately 0.5 mas in both coordinates, an improvement in some cases by as much as 75%. Positions in the FK5 system have also been obtained for the optical counterparts of an additional five northern hemisphere radio sources using prime focus plates from the Kitt Peak National Observatory's 4 m telescope and a Ritchey-Chretien focus plate from the Calar Alto 2.2 m telescope. The optical positions have internal accuracies of about 0.03 sec and differ from the radio positions by about 0.07 sec on the average.

  16. Understanding Influence of MoSi2 Addition (5 Weight Percent) on Tribological Properties of TiB2

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Amartya; Raju, G. B.; Basu, Bikramjit

    2008-12-01

    In densifying engineering ceramics such as TiB2 using nonmetallic sinter additives, it is important to assess the influence of the addition of sinter-aid on the properties of TiB2. The present article reports how a small addition of MoSi2 (5 wt pct) sinter-aid enhances the wear resistance of TiB2 at mode-I fretting contact. This has been confirmed using a series of unlubricated wear tests on hot-pressed ceramics using two different counterbodies, viz. bearing steel and WC-6 wt pct Co cemented carbide, under identical testing conditions. Steady-state coefficient of friction (COF) against steel counterbody has been found to noticeably vary in the range of 0.5 to 1, with variation in load or MoSi2 addition. However, insignificant variation in COF (˜0.5) has been recorded during fretting against WC-Co. Furthermore, lower wear rate (˜10-6 mm3/Nm) is measured against the cemented carbide, as compared to that against steel (˜10-5 mm3/Nm). It has been observed that the material removal of TiB2-based ceramics against steel involves tribochemical wear as well as abrasive wear, and the occurrence of tribochemical wear is explained in terms of various feasible reactions at the tribological interface. Lower contact area, resulting in reduced adhesive wear, along with the absence of additional tribochemical wear, has been attributed to lower wear rate as observed after fretting against the harder (WC-Co) counterbody. A number of possible reactions along with their thermodynamic feasibility are discussed to explain the tribochemical wear at the interface of the mating couple. Irrespective of counterbody or material composition, the measured wear volume exhibits linear dependency on abrasion parameter, confirming the role of material parameters on the contribution of abrasive wear to the material removal/damage of the investigated materials.

  17. The Influence of Sintering Temperature on the Microwave Dielectric Properties of Mg2SiO4 Ceramics with CaO-B2O3-SiO2 Addition

    NASA Astrophysics Data System (ADS)

    Yang, Hongyu; Li, Enzhu; Sun, Chengli; Duan, Shuxin; Yuan, Ying; Tang, Bin

    2017-02-01

    Conventional solid-state methods were used to synthesize Mg2SiO4 ceramic at relatively low sintering temperatures with the assistance of CaO-B2O3-SiO2 (CBS) glass. The effects of the CBS additions on the sintering behavior, crystal structures, microstructures, and microwave dielectric properties of Mg2SiO4 ceramic have been investigated in detail. The results indicate that the addition of CBS glass lowered the sintering temperature of Mg2SiO4 ceramic significantly. The Mg2SiO4 ceramic with 7 wt.% CBS addition sintered at 1325°C for 4 h shows excellent microwave dielectric properties: ɛ r = 6.47, Q × f = 16,552 GHz, τ f = -23.34 ppm/°C.

  18. A fundamental study of the oxidation behavior of SI primary reference fuels with propionaldehyde and DTBP as an additive

    NASA Astrophysics Data System (ADS)

    Johnson, Rodney

    In an effort to combine the benefits of SI and CI engines, Homogeneous Charge Compression Ignition (HCCI) engines are being developed. HCCI combustion is achieved by controlling the temperature, pressure, and composition of the fuel and air mixture so that autoignition occurs in proper phasing with the piston motion. This control system is fundamentally more challenging than using a spark plug or fuel injector to determine ignition timing as in SI and CI engines, respectively. As a result, this is a technical barrier that must be overcome to make HCCI engines applicable to a wide range of vehicles and viable for high volume production. One way to tailor the autoignition timing is to use small amounts of ignition enhancing additives. In this study, the effect of the addition of DTBP and propionaldehyde on the autoignition behavior of SI primary reference fuels was investigated. The present work was conducted in a new research facility built around a single cylinder Cooperative Fuels Research (CFR) octane rating engine but modified to run in HCCI mode. It focused on the effect of select oxygenated hydrocarbons on hydrocarbon fuel oxidation, specifically, the primary reference fuels n-heptane and iso-octane. This work was conducted under HCCI operating conditions. Previously, the operating parameters for this engine were validated for stable combustion under a wide range of operating parameters such as engine speeds, equivalence ratios, compression ratios and inlet manifold temperature. The stable operating range under these conditions was recorded and used for the present study. The major focus of this study was to examine the effect of the addition of DTBP or propionaldehyde on the oxidation behavior of SI primary reference fuels. Under every test condition the addition of the additives DTBP and propionaldehyde caused a change in fuel oxidation. DTBP always promoted fuel oxidation while propionaldehyde promoted oxidation for lower octane number fuels and delayed

  19. Development ceramic composites based on Al2O3, SiO2 and IG-017 additive

    NASA Astrophysics Data System (ADS)

    Kurovics, E.; Shmakova, A.; Kanev, B.; Gömze, L. A.

    2017-02-01

    Based on high purity alumina and quartz powders and IG-017 bio-original additives the authors have developed new ceramic composite materials for different industrial purposes. The main goal was to fine a material and morphological structures of high performance ceramic composites as frames for development complex materials for extreme consumptions in the future. For this the mixed powders of Al2O3 , SiO2 and IG-017 bio-original additive were uniaxially pressed at different compaction pressures into disc shapes and were sintered in electric kiln under air (1) and nitrogrn (2) atmosphere. The grain size distributions of the raw materials were determined by laser granulometry. There thermo-physical properties were also determined by derivatography. The prepared and sintered specimens were tested on geometrical sizes, microstructure and morphology by scanning electron microscopy, porosity and water absorption. In this work the authors present the results of their research and investigation.

  20. Enhanced luminescence properties of CaTiO(3):Pr(3+) phosphor with addition of SiO(2) by solid-state reaction.

    PubMed

    Chen, Rui; Chen, Donghua

    2014-06-05

    Red phosphors CaTiO3:Pr(3+) with addition of SiO2 were prepared by solid-state reaction technique (SS). The effect of SiO2 on the crystalline phase, surface morphology and luminescence properties of CaTiO3:Pr(3+) was studied by X-ray diffractometer, transmission electron microscope, brightness meter and photoluminescence spectrometer, respectively. The results indicated that the content of SiO2 has influence on luminescence intensity, initial brightness and persistent time of samples. The red phosphor CaTi0.5Si0.5O3:Pr(3+) exhibited the optimal luminescence properties.

  1. Photon-assisted field emission from a Si tip at addition of an AC low voltage

    NASA Astrophysics Data System (ADS)

    Zaporozhchenko, A. V.; Chernov, S. V.; Odnodvorets, L. V.; Stetsenko, B. V.; Nepijko, S. A.; Elmers, H. J.; Schönhense, G.

    2015-07-01

    We investigated the field emission current from a p-type silicon tip with large resistivity of 4 × 103 Ω cm for light illumination with a photon energy of 1.3 eV and tip-anode voltages of 0.7-5.0 kV. Additional AC voltage with amplitude 30-60 V and frequency varying in the range of 10-107 Hz was applied to the tip which resulted in variations of emission current. We investigated the dependence of this phenomenon on the AC signal parameters, light intensity and temperature. The resonant-like frequency dependence of the emission current is because the tip acts as a driven plasmonic resonator. The results represent an important step forward for the development of high-frequency display systems based on electron field emission.

  2. 76 FR 36339 - Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs: Extension of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-22

    ... AGENCY 40 CFR Part 98 RIN A2060 Mandatory Reporting of Greenhouse Gases: Additional Sources of... Mandatory Greenhouse Gas Reporting Rule. Consequently, this action extends three of the deadlines in Subpart.... Carole Cook, Climate Change Division, Office of Atmospheric Programs (MC-6207J), Environmental...

  3. SiC detectors for radiation sources characterization and fast plasma diagnostic

    NASA Astrophysics Data System (ADS)

    Cannavò, A.; Torrisi, L.

    2016-09-01

    Semiconductor detectors based on SiC have been investigated to characterize the radiations (photons and particles) emitted from different sources, such as radioactive sources, electron guns, X-ray tubes and laser-generated plasmas. Detectors show high response velocity, low leakage current, high energy gap and high radiation hardness. Their high detection efficiency permits to use the detectors in spectroscopic mode and in time-of-flight (TOF) approach, generally employed to monitor low and high radiation fluxes, respectively. Using the laser start signal, they permit to study the properties of the generated plasma in vacuum by measuring accurately the particle velocity and energy using pulsed lasers at low and high intensities. Possible applications will be reported and discussed.

  4. Adsorption mechanisms of isoxazole and oxazole on Si(100)-2 × 1 surface: Si-N dative bond addition vs. [4+2] cycloaddition

    NASA Astrophysics Data System (ADS)

    Kumer Ghosh, Manik; Choi, Cheol Ho

    2011-12-01

    The surface reaction pathways of isoxazole and oxazole on Si(100)-2 × 1 surface were theoretically investigated. They both form a weakly bound Si-N dative bond adduct on Si(100)-2 × 1 surface. In the case of isoxazole, the barrierlessly formed Si-N adduct is the most important surface product, that cannot be easily converted into other species. On the other hand, a facile concerted [4+2]CC cycloaddition without involving the initial Si-N dative bond adduct was also found in the case of oxazole adsorption. The existence of Diels-Alder reactions is attributed to the particular arrangement of the two heteroatoms of oxazole in such a way that the two Si-C σ-bonds can be formed in a [4+2] fashion. In short, the unique geometric arrangements and electronegativity of these similar heteroatomic molecules yielded distinctively different surface reaction characteristics.

  5. Effects of additional HONO sources on visibility over the North China Plain

    NASA Astrophysics Data System (ADS)

    Li, Ying; An, Junling; Gultepe, Ismail

    2014-09-01

    The objective of the present study was to better understand the impacts of the additional sources of nitrous acid (HONO) on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain (NCP) during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry (WRF/Chem) model were performed, including three additional HONO sources: (1) the reaction of photo-excited nitrogen dioxide (NO * 2) with water vapor; (2) the NO2 heterogeneous reaction on aerosol surfaces; and (3) HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% (3-4 km) in local urban areas of the NCP. Monthly-mean concentrations of NO{3/-}, NH{4/+}, SO{4/2-} and PM2.5 were increased by 20%-52% (3-11 μg m-3), 10%-38%, 6%-10%, and 6%-11% (9-17 μg m-3), respectively; and in urban areas, monthly-mean accumulationmode number concentrations (AMNC) and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NO x and aerosols.

  6. Beamforming for directional sources: additional estimator and evaluation of performance under different acoustic scenarios.

    PubMed

    Bouchard, Christian; Havelock, David I; Bouchard, Martin

    2011-04-01

    Beamforming is done with an array of sensors to achieve a directional or spatially-specific response by using a model of the arriving wavefront. Conventionally, a plane wave or point source model is used and this can cause decreased array gain or even total breakdown of beamforming when the source is directional. To avoid this, the authors proposed in recent work an alternative beamforming method which defines a set of "sub-beamformers," each designed to respond to a different spatial mode of the source. The outputs of the individual sub-beamformers are combined in a weighted sum to give an overall output of better quality than that of a monopole beamformer. This paper extends the previous work by introducing an additional estimator for the weighted sum and by presenting simulation results to demonstrate the relative performance of the proposed method and the different estimators for a directional source in the presence of diffuse noise, reverberation, and an interfering source. Gain optimization subject to a constraint on the white-noise gain with the proposed beamforming method is also introduced. Generally, when beamforming on directional sources, the proposed method outperforms beamforming with a point source model when the input signal-to-noise ratio (SNR) is 0 dB or higher.

  7. Synthesis of high-performance Li2FeSiO4/C composite powder by spray-freezing/freeze-drying a solution with two carbon sources

    NASA Astrophysics Data System (ADS)

    Fujita, Yukiko; Iwase, Hiroaki; Shida, Kenji; Liao, Jinsun; Fukui, Takehisa; Matsuda, Motohide

    2017-09-01

    Li2FeSiO4 is a promising cathode active material for lithium-ion batteries due to its high theoretical capacity. Spray-freezing/freeze-drying, a practical process reported for the synthesis of various ceramic powders, is applied to the synthesis of Li2FeSiO4/C composite powders and high-performance Li2FeSiO4/C composite powders are successfully synthesized by using starting solutions containing both Indian ink and glucose as carbon sources followed by heating. The synthesized composite powders have a unique structure, composed of Li2FeSiO4 nanoparticles coated with a thin carbon layer formed by the carbonization of glucose and carbon nanoparticles from Indian ink. The carbon layer enhances the electrochemical reactivity of the Li2FeSiO4, and the carbon nanoparticles play a role in the formation of electron-conducting paths in the cathode. The composite powders deliver an initial discharge capacity of 195 and 137 mAh g-1 at 0.1 C and 1 C, respectively, without further addition of conductive additive. The discharge capacity at 1 C is 72 mAh g-1 after the 100th cycle, corresponding to approximately 75% of the capacity at the 2nd cycle.

  8. Use of additional fission sources or scattering sources to model inward axial leakages in fast-reactor analysis

    SciTech Connect

    Grimm, K.N.; Meneghetti, D.

    1981-10-01

    When calculations of flux are done in less than three dimensions, bucklings are normally used to model leakages (flows) in the dimensions for which the flux is not calculated. If the net leakage for a given energy group is outward (positive), the buckling is positive, and buckling methods work well. However, if the new leakage for a given energy group is inward (negative), the buckling is negative and can lead to numerical instabilities (oscillations in the iterative flux calculation). This report discusses two equivalent nonbuckling methods to model inward leakages. One method (the chi/sub g/ method) models these incoming neutrons by additional fission sources. The other method (the ..sigma../sub s/(1 ..-->.. g) method) models them by increased downscatter sources. The derivation of the two methods is shown, and the flux spectra obtained by their use are compared with those obtained from two-dimensional (RZ) calculations.

  9. The Effect of Chilling and Ce Addition on the Microstructure and Mechanical Properties of Al-23Si Alloy

    NASA Astrophysics Data System (ADS)

    Vijeesh, V.; Narayan Prabhu, K.

    2017-01-01

    The present work involves the study of the effect of varying concentration of Ce addition on microstructure and mechanical properties of Al-23%Si alloys. Melt-treated alloys were solidified in copper, brass, stainless steel molds to assess the effect of cooling rate. The effect on microstructure was assessed by measuring the fineness of primary silicon and eutectic silicon particle characteristics. The Ce melt treatment transformed the coarse and irregular primary silicon into refined polyhedral silicon crystals, and the effect was more significant at higher cooling rates. Although the melt treatment had refined the eutectic silicon at lower cooling rates, it did not show any considerable effect on the eutectic silicon at higher cooling rates. The mechanical properties of the alloy increased significantly with increase in cooling rates and cerium concentration. Analysis of the results and literature reveals that the refined primary silicon was formed as a result of an invariant reaction between Ce compounds and primary silicon at higher temperatures.

  10. Effect of Titanium Addition on the Elemental Partitioning Behavior of Silicon in Ni-19 At. Pct Al- xSi- yTi Alloys

    NASA Astrophysics Data System (ADS)

    Kuo, Li-Yin; Chang, Yao-Jen; Yeh, An-Chou

    2017-08-01

    We have investigated the effect of Ti addition on the partitioning behavior of Si in Ni-19 at. pct Al- xSi- yTi alloys ( x = 1.0 to 2.5 at. pct and y = 0.0 to 2.0 at. pct). The elemental partition ratios between the γ and γ' phases were determined by electron probe microanalysis. The results indicate that an increase in the Ti content increases the partitioning tendency of Si in the γ matrix. However, Si was preferentially partitioned in the γ' phase after 816 hours aging at 1373 K (1100 °C). Interestingly, a CALPHAD-based simulation also predicted the tendency of Si to partition in the γ phase with increasing Ti content. However, Si was predicted to preferentially partition in the γ matrix. First-principles calculations suggest that Ti atoms can replace Si atoms in the γ' phase and reject Si atoms into the face-centered cubic γ matrix. Furthermore, the partitioning behavior of Si could also be influenced by the presence of point defects and the volume fraction of the γ' phase.

  11. Carbon source utilization profiles suggest additional metabolic interactions in a synergistic linuron-degrading bacterial consortium.

    PubMed

    Horemans, Benjamin; Smolders, Erik; Springael, Dirk

    2013-04-01

    A bacterial triple-species consortium that synergistically metabolizes the phenylurea herbicide linuron was studied to determine whether synergy is extended toward the metabolism of other C-sources. The metabolic performance and range of the individual consortium members were compared with those of paired and three-species combinations in Biolog GN2 MicroPlate assays. The strain combinations showed an increase in the rate and extent of utilization of 80% of the C-sources that were utilized by either one or more of the individual consortium members and the additional utilization of eight C-sources for which oxidation was not observed for the individual strains. When one of the three strains was replaced by bacterial strains 'foreign' to the consortium, either belonging to the same genus or to other genera, mainly antagonistic effects occurred. The data suggest that the consortium members cooperate in the metabolism of C-sources in addition to linuron. This feature can contribute in consolidating consortium composition when linuron is absent or present at low concentrations.

  12. Influence of Indium-Tin Oxide Additive on the Sintering Process and Conductivity of Na3Zr2Si2PO12 Solid Electrolyte

    NASA Astrophysics Data System (ADS)

    Chen, Dan; Luo, Fa; Gao, Lu; Zhou, Wancheng; Zhu, Dongmei

    2017-07-01

    Because of the poor sintering ability and low phase purity limit in the application of a Na3Zr2Si2PO12 solid electrolyte, it is important to find an effective way to obtain a pure and dense Na3Zr2Si2PO12 ceramic at reduced temperature. In this study, high conductive indium-tin oxide (ITO) was innovatively used as the sintering additive to improve the purity and density of the Na3Zr2Si2PO12 ceramic. The influence of ITO additive on density, phase, microstructure and conductivity of the Na3Zr2Si2PO12 ceramic was investigated. Archimedes method, x-ray diffraction, scanning electron microcopy and complex impedance spectroscopy were used as experimental techniques to evaluate the effect of the additive. The results show that the ITO sintering additive increases not only the purity and density but also the conductivity of the Na3Zr2Si2PO12 ceramic. The Na3Zr2Si2PO12 ceramic with 3 wt.% ITO additive sintered at 1150°C for 4 h possesses a high density of 3.15 g/cm3 and good conductivity of (3.95 ± 0.12) × 10-4 S/cm.

  13. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-05-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  14. Enhanced post-denitrification without addition of an external carbon source in membrane bioreactors.

    PubMed

    Vocks, M; Adam, C; Lesjean, B; Gnirss, R; Kraume, M

    2005-09-01

    This study investigates a post-denitrification process without the addition of an external carbon source combined with an enhanced biological phosphorus removal (EBPR) in a membrane bioreactor (MBR). Three trial plants, with two different process configurations, were operated on two different sites, and a variety of accompanying batch tests were conducted. It was shown that even without dosing of an external carbon source, denitrification rates (DNR) much above endogenous rates could be obtained in post-denitrification systems. Furthermore, the anaerobic reactor located ahead of the process had a positive impact on the DNR. Given these surprising results, the project team decided to identify the carbon source used by the microorganisms in the post-denitrification process. Batch tests could demonstrate that lysis products do not play a major role as a C-source for post-denitrification. The following hypothesis was proposed to explain the observations: the glycogen, internally stored by the substrate accumulating bacteria, if anaerobic conditions are followed by aerobic conditions could act as carbon source for denitrification in post-denitrification system. First exploratory batch tests, where the glycogen evolution was monitored, corroborate this assumption.

  15. Effect of tin addition on the distribution of phosphorus and metallic impurities in Si-Al alloys

    NASA Astrophysics Data System (ADS)

    Tang, Tianyu; Lai, Huixian; Sheng, Zhilin; Gan, Chuanhai; Xing, Pengfei; Luo, Xuetao

    2016-11-01

    Metallurgical grade silicon was purified through solvent refining method by adding tin to the Si-Al alloy. The distribution of phosphorus and metallic impurities in the resulting Si-Al-Sn melts was investigated. Compared with the primary Si and the eutectic αAl+Si, the phosphorus and metallic impurities were more distinctly distributed in the βSn phase, which was always accompanied by needle-like intermetallic β-Al5SiFe compounds. To improve the phosphorus and metallic impurity removal ratios, Si-Al-Sn ternary alloys with different composition were investigated. The phosphorus removal ratio increased with the aluminum and tin content in the Si-Al-Sn ternary alloy. Compared to increasing the Al content and keeping the Si/Sn ratio fixed, the impurity removal ratios were higher when the Sn content was increased to the same mass percentage and the Si/Al ratio was kept fixed in the Si-Al-Sn melt.

  16. Effect of the working gas of the ion-assisted source on the optical and mechanical properties of SiO2 films deposited by dual ion beam sputtering with Si and SiO2 as the starting materials.

    PubMed

    Wu, Jean-Yee; Lee, Cheng-Chung

    2006-05-20

    Silicon and fused-silica targets are used as the starting materials for depositing silicon oxide (SiO2) films. The SiO2 films are prepared by a dual ion beam sputtering deposition system with a main ion source and an ion-assisted source with different working gases. The films deposited are then examined and compared by using a visible spectrophotometer, a Fourier-transform IR spectrophotometer, an atomic force microscope, and contact angle instruments. A Twyman-Green interferometer is employed to study the film stress by phase-shift interferometry. All the SiO2 films show excellent optical properties with extra-low extinction coefficients (below 2x10(-5)) and have no water absorption. When the working gas is O2 for the ion-assisted source, the deposited SiO2 films show good properties in terms of stress and roughness and with a good molecular bonding structure order for both targets. However, SiO2 films deposited from the fused-silica target had a larger contact angle, while those deposited from the silicon target had 2.5 times the deposition rate.

  17. Effects of h-BN addition on microstructures and mechanical properties of β-CaSiO3 bioceramics.

    PubMed

    Pan, Ying; Yao, Dongxu; Zuo, Kaihui; Xia, Yongfeng; Yin, Jinwei; Liang, Hanqin; Zeng, Yuping

    2016-09-01

    The main purpose of this study consists in investigating the effects of h-BN addition on the sinterability of β-CaSiO3 (β-CS) bioceramics. β-CS bioceramics with different contents of h-BN were prepared at the sintering temperature ranging from 800°C to 1100°C. The results showed that h-BN can be successfully used as sintering additive by being oxidized to form low melting point B2O3 related glassy phase and enhanced the flexural strength by the formation of rod-like β-CS grains. β-CS bioceramics with 1wt% h-BN sintered at 1000°C revealed flexural strength and fracture toughness of 182.2MPa and 2.4MPam(1/2) respectively, which were much higher than that of pure β-CS bioceramics (30.2MPa, 0.53MPam(1/2)) fabricated in the same processing condition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Evaluating the time and source of hydrocarbon additions to soils using lead isotopes and historical changes in industrial lead sources

    SciTech Connect

    Hurst, R.W. California State Univ., Los Angeles, CA )

    1994-04-01

    Isotopic analysis of anthropogenic Pb in well-dated, southern California coastal sediments have been integrated with historical changes in ore Pb sources to produce calibration curves (206Pb/207Pb vs. time) that allow us to model the time anthropogenic Pb was added to a soil horizon. The major, historical sources of anthropogenic Pb in southern California are fossil fuels (e.g. gasoline). Hence, Pb model ages (LABILE model; Los Angeles Borderland Industrial Lead) provide time constraints on Pb deposition from fossil fuel combustion via airborne deposition, runoff, and/or sewage outfall in this region. The correlation between the LABILE model age and known times of anthropogenic Pb additions at 17 specific sites is good (r = 0.978); the accuracy of the method ranges from one to five years in the post-1960 time interval. Factors influencing accuracy include analytical uncertainties in Pb isotopic measurements ([<=]0.1%), the scatter in isotopic ratios of anthropogenic Pb (circa 0.2%), and the uncertainty in the sediment age used to calibrate the method (0-15 yr). At one site three statistically distinguishable events were identified; they correlate with residential development (1968), airborne vehicular Pb deposition (1983), and site remediation (1991). Gasoline incursions at two tests sites have been dated accurately ([+-] 1 yr). The limitations of the LABILE model (geographic, age, types of hydrocarbons, and industry to which it applies) are now under investigation.

  19. The Effect of Crystallinity of Carbon Source on Mechanically Activated Carbothermic Synthesis of Nano-Sized SiC Powders

    NASA Astrophysics Data System (ADS)

    Moshtaghioun, B. M.; Monshi, A.; Abbasi, M. H.; Karimzadeh, F.

    2013-02-01

    The relevance of the structure of carbon materials and milling on the carbothermic reduction of silica to produce nano-sized silicon carbide (SiC) was studied. Graphite (crystalline) and metallurgical coke (mainly amorphous) were chosen as carbon precursors that were mixed with amorphous pure nano-sized SiO2 and milled for different times. The SiC yield at 1450 °C for l h was influenced by the degree of milling. Extending the milling time increased SiC formation in both cases. Although some extensive milling converted both sources of carbon into amorphous phase, the amount of synthesized SiC from graphite was about 4.5-3 times higher than coke with increased extent of milling. Graphite is converted from stable crystalline state into the amorphous phase, so it absorbs more activation energy of milling and fresher active centers are created, while the already amorphous coke absorbs less energy and thus less fresh active centers are created. This energy difference acts as a driving force, resulting in higher yield of nano-sized SiC when graphite is used as carbon source.

  20. Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies

    NASA Astrophysics Data System (ADS)

    Reynolds, R. J.; Haffner, L. M.; Tufte, S. L.

    1999-11-01

    Spatial variations of the [S II]/Hα and [N II]/Hα line intensity ratios observed in the gaseous halo of the Milky Way and other galaxies are inconsistent with pure photoionization models. They appear to require a supplemental heating mechanism that increases the electron temperature at low densities, ne. This would imply that in addition to photoionization, which has a heating rate per unit volume proportional to n2e, there is another source of heat with a rate per unit volume proportional to a lower power of ne. One possible mechanism is the dissipation of interstellar plasma turbulence, which, according to Minter & Spangler, heats the ionized interstellar medium in the Milky Way at a rate of ~1×10-25ne ergs cm-3 s-1. If such a source were present, it would dominate over photoionization heating in regions where ne<~0.1 cm-3, producing the observed increases in the [S II]/Hα and [N II]/Hα intensity ratios at large distances from the galactic midplane as well as accounting for the constancy of [S II]/[N II], which is not explained by pure photoionization. Other supplemental heating sources, such as magnetic reconnection, cosmic rays, or photoelectric emission from small grains, could also account for these observations, provided they supply ~10-5 ergs s-1 per square centimeter of the Galactic disk to the warm ionized medium.

  1. Effect of argon additive on H- density and temperature in volume negative ion source

    NASA Astrophysics Data System (ADS)

    Ivanov, A. A.; Bacal, M.; Rouillé, C.; Nishiura, M.; Sasao, M.

    2004-05-01

    Various plasma parameters were measured for several hydrogen-argon mixtures in the multicusp H- ion source Camembert III, equipped with tantalum filaments. The density and the temperature of electrons were measured with the Langmuir probe situated in the center of the source and associated with the photodetachment diagnostics. The two-laser photodetachment diagnostics was used to obtain the temperatures of the two negative ion populations. At low hydrogen pressure (0.8 mTorr) a small concentration of argon additive enhances the hydrogen negative ion density (by approximately 60%), it also increases the electron density. The negative ion population fractions having the high- and low-temperature values behave differently when varying the total pressure in pure hydrogen and in hydrogen with argon additive. Several possible explanations of the drastic change of the relative ratio of negative ion populations when the argon fraction is increased, are proposed. Another interesting phenomenon observed during the experiments is the decrease with time of the H- density in the presence of argon. After adding the argon during the time interval of ˜1 h the H- density goes down and finally establishes at a minimum value. The final H- density is lower than the H- density in pure hydrogen plasma before adding argon. This "poisoning" is discussed in terms of wall production of vibrationally excited H2 molecules.

  2. Simultaneous Observatinos of H2O and SiO Masers Toward Known Extragalactic Water Maser Sources

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yoon, Dong-Hwan; Kim, Jaeheon; Byun, Do-Young; Wagner, Jan

    2015-12-01

    We observe ten known 22 GHz H_{2}O maser galaxies during February 19-22, 2011 using the 21 m Tamna telescope of the Korean VLBI Network and a new wide-band digital spectrometer. Simultaneously we searched for 43 GHz SiO v = 1, 2, J = 1-0 maser emission. We detect H_{2}O maser emission towards five sources (M 33, NGC 1052, NGC 1068, NGC 4258, M 82), with non-detections towards the remaining sources (UGC 3193, UGC 3789, Antennae H_{2}O-West, M 51, NGC 6323) likely due to sensitivity. Our 22 GHz spectra are consistent with earlier findings. Our simultaneous 43 GHz SiO maser search produced non-detections, yielding - for the first time - upper limits on the 43 GHz SiO maser emission in these sources at a 3 σ sensitivity level of 0.018 K-0.033 K (0.24 Jy-0.44 Jy) in a 1.75 km s^{-1} velocity resolution. Our findings suggest that any 43 GHz SiO masers in these sources (some having starburst-associated H_{2}O kilomasers) must be faint compared to the 22 GHz H_{2}O maser emission.

  3. Accelerated Source-Encoding Full-Waveform Inversion with Additional Constraints

    NASA Astrophysics Data System (ADS)

    Boehm, C.; Fichtner, A.; Ulbrich, M.

    2014-12-01

    We present a flexible framework of Newton-type methods for constrained full-waveform inversion in the time domain. Our main goal is (1) to incorporate additional prior knowledge by using general constraints on the model parameters and (2) to reduce the computational costs of solving the inverse problem by tailoring source-encoding strategies to Newton-type methods.In particular, we apply the Moreau-Yosida regularization to handle the constraints and use a continuation strategy to adjust the regularization parameter. Furthermore, we propose a semismooth Newton method with a trust-region globalization that relies on second-order adjoints to compute the Newton system with a matrix-free preconditioned conjugate gradient solver. The costs of conventional FWI approaches scale proportionally with the number of seismic sources. Here, source-encoding strategies that trigger different sources simultaneously have been proven to be a successful tool to trade a small loss of information for huge savings of computational time to solve the inverse problem. This is particularly interesting for our setting as one iteration of Newton's methods using the full Hessian is considerably more expensive than quasi-Newton methods like L-BFGS. To this end, we discuss a sample average approximation model that is accelerated by using inexact Hessian information based on mini-batches of the samples. Furthermore, we compare its performance with stochastic descent schemes. Here, the classical stochastic gradient method is accelerated by an L-BFGS preconditioner and moreover, the stability of this stochastic preconditioner is enhanced by using the Hessian instead of only gradient information.Numerical results are presented for problems in geophysical exploration on reservoir-scale.

  4. A 10-kW SiC Inverter with A Novel Printed Metal Power Module With Integrated Cooling Using Additive Manufacturing

    SciTech Connect

    Chinthavali, Madhu Sudhan; Ayers, Curtis William; Campbell, Steven L; Wiles, Randy H; Ozpineci, Burak

    2014-01-01

    With efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wide band gap semiconductors including silicon carbide (SiC) have been identified as possibly being a partial solution. This paper focuses on the development of a 10-kW all SiC inverter using a high power density, integrated printed metal power module with integrated cooling using additive manufacturing techniques. This is the first ever heat sink printed for a power electronics application. About 50% of the inverter was built using additive manufacturing techniques.

  5. SEI Formation and Interfacial Stability of a Si Electrode in a LiTDI-Salt Based Electrolyte with FEC and VC Additives for Li-Ion Batteries.

    PubMed

    Lindgren, Fredrik; Xu, Chao; Niedzicki, Leszek; Marcinek, Marek; Gustafsson, Torbjörn; Björefors, Fredrik; Edström, Kristina; Younesi, Reza

    2016-06-22

    An electrolyte based on the new salt, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), is evaluated in combination with nano-Si composite electrodes for potential use in Li-ion batteries. The additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are also added to the electrolyte to enable an efficient SEI formation. By employing hard X-ray photoelectron spectroscopy (HAXPES), the SEI formation and the development of the active material is probed during the first 100 cycles. With this electrolyte formulation, the Si electrode can cycle at 1200 mAh g(-1) for more than 100 cycles at a coulombic efficiency of 99%. With extended cycling, a decrease in Si particle size is observed as well as an increase in silicon oxide amount. As opposed to LiPF6 based electrolytes, this electrolyte or its decomposition products has no side reactions with the active Si material. The present results further acknowledge the positive effects of SEI forming additives. It is suggested that polycarbonates and a high LiF content are favorable components in the SEI over other kinds of carbonates formed by ethylene carbonate (EC) and dimethyl carbonate (DMC) decomposition. This work thus confirms that LiTDI in combination with the investigated additives is a promising salt for Si electrodes in future Li-ion batteries.

  6. Flat Panel Light Source with Lateral Gate Structure Based on SiC Nanowire Field Emitters

    PubMed Central

    Youh, Meng-Jey; Tseng, Chun-Lung; Jhuang, Meng-Han; Chiu, Sheng-Cheng; Huang, Li-Hu; Gong, Jyun-An; Li, Yuan-Yao

    2015-01-01

    A field-emission light source with high luminance, excellent luminance uniformity, and tunable luminance characteristics with a novel lateral-gate structure is demonstrated. The lateral-gate triode structure comprises SiC nanowire emitters on a Ag cathode electrode and a pair of Ag gate electrodes placed laterally on both sides of the cathode. The simple and cost-effective screen printing technique is employed to pattern the lateral-gates and cathode structure on soda lime glass. The area coverage of the screen-printed cathode and gates on the glass substrate (area: 6 × 8 cm2) is in the range of 2.04% – 4.74% depending on the set of cathode-gate electrodes on the substrate. The lateral-gate structure with its small area coverage exhibits a two-dimensional luminance pattern with high brightness and good luminance uniformity. A maximum luminance of 10952 cd/cm2 and a luminance uniformity of >90% can be achieved with a gate voltage of 500 V and an anode voltage of 4000 V, with an anode current of 1.44 mA and current leakage to the gate from the cathode of about 10%. PMID:26042359

  7. Simultaneous Purification and Perforation of Low-Grade Si Sources for Lithium-Ion Battery Anode.

    PubMed

    Jin, Yan; Zhang, Su; Zhu, Bin; Tan, Yingling; Hu, Xiaozhen; Zong, Linqi; Zhu, Jia

    2015-11-11

    Silicon is regarded as one of the most promising candidates for lithium-ion battery anodes because of its abundance and high theoretical capacity. Various silicon nanostructures have been heavily investigated to improve electrochemical performance by addressing issues related to structure fracture and unstable solid-electrolyte interphase (SEI). However, to further enable widespread applications, scalable and cost-effective processes need to be developed to produce these nanostructures at large quantity with finely controlled structures and morphologies. In this study, we develop a scalable and low cost process to produce porous silicon directly from low grade silicon through ball-milling and modified metal-assisted chemical etching. The morphology of porous silicon can be drastically changed from porous-network to nanowire-array by adjusting the component in reaction solutions. Meanwhile, this perforation process can also effectively remove the impurities and, therefore, increase Si purity (up to 99.4%) significantly from low-grade and low-cost ferrosilicon (purity of 83.4%) sources. The electrochemical examinations indicate that these porous silicon structures with carbon treatment can deliver a stable capacity of 1287 mAh g(-1) over 100 cycles at a current density of 2 A g(-1). This type of purified porous silicon with finely controlled morphology, produced by a scalable and cost-effective fabrication process, can also serve as promising candidates for many other energy applications, such as thermoelectrics and solar energy conversion devices.

  8. Fe and Fe+2%Si targets as ion sources via UV laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Lorusso, A.; Krása, J.; Láska, L.; Nassisi, V.; Velardi, L.

    2009-08-01

    In the last years the ion component of a laser-produced plasma has been considered and studied as an object to provide high-density ion sources, which can be applied in many fields such as laser-induced implantation. In this work a KrF laser beam of 108 W/cm2 irradiance was focused onto single-crystalline Fe and single-crystalline Fe with 2% of Si targets and the characteristics of both free expanding laser-produced plasmas were compared. The time-of-flight (TOF) method was applied to determine the ion charge yield at various laser fluences and the ion angular spread. The analyses of TOF spectra showed a synergetic effect of the silicon admixture in target material on the Fe ions production. Besides, this admixture was also responsible of the increasing of the plasma temperature which corresponds in turn to the increasing of the average kinetic energy of the particles as well as of the more collimated ion distribution.

  9. Addition of water across Si-Ir bonds in iridium complexes with κ-P,P,Si (biPSi) pincer ligands.

    PubMed

    García-Camprubí, Alba; Martín, Marta; Sola, Eduardo

    2010-11-15

    Electrophiles such as Me(+), Ag(+), or protons react with the five-coordinate Ir(III) complex [IrClH(biPSi)] (biPSi = κ-P,P,Si-Si(Me){(CH(2))(3)PPh(2)}(2)) by abstracting its chloride ligand. The resulting species can be stabilized by a variety of L ligands to give the cationic complexes [IrH(biPSi)L(2)](+). The derivative [IrH(biPSi)(NCMe)(2)](+) has been subjected to a kinetic study regarding the facile dissociations of its acetonitrile ligands. The presence of water changes the course of the reaction producing dihydride complexes that contain the silanol ligand κ-O,P,P-HOSi(Me){(CH(2))(3)PPh(2)}(2) (biPSiOH). The water activation product [IrH(2)(biPSiOH)(NCMe)](CF(3)SO(3)) undergoes insertion reactions with ethylene and phenylacetylene. The use of hydrolyzable fluorinated counterions such as PF(6)(-) or BF(4)(-) further modifies the reaction by provoking the incorporation of fluoride at the silicon atom of the former biPSi ligand. The dihydride resulting after such a process, [IrH(2)(biPSiF)(NCMe)(2)]BF(4) (biPSiF = κ-P(2)-FSi(Me){(CH(2))(3)PPh(2)}(2)), displays a trans-chelating diphosphine ligand. When dehydrogenating the Ir center, spontaneously or using ethylene as hydrogen acceptor, the diphosphine backbone undergoes a Si-C bond cleavage leading to a new Ir(III) species with κ-P,Si and κ-C,P chelate ligands.

  10. Styrofoam Debris as a Source of Hazardous Additives for Marine Organisms.

    PubMed

    Jang, Mi; Shim, Won Joon; Han, Gi Myung; Rani, Manviri; Song, Young Kyoung; Hong, Sang Hee

    2016-05-17

    There is growing concern over plastic debris and their fragments as a carrier for hazardous substances in marine ecosystem. The present study was conducted to provide field evidence for the transfer of plastic-associated chemicals to marine organisms. Hexabromocyclododecanes (HBCDs), brominated flame retardants, were recently detected in expanded polystyrene (styrofoam) marine debris. We hypothesized that if styrofoam debris acts as a source of the additives in the marine environment, organisms inhabiting such debris might be directly influenced by them. Here we investigated the characteristics of HBCD accumulation by mussels inhabiting styrofoam. For comparison, mussels inhabiting different substrates, such as high-density polyethylene (HDPE), metal, and rock, were also studied. The high HBCD levels up to 5160 ng/g lipid weight and the γ-HBCD dominated isomeric profiles in mussels inhabiting styrofoam strongly supports the transfer of HBCDs from styrofoam substrate to mussels. Furthermore, microsized styrofoam particles were identified inside mussels, probably originating from their substrates.

  11. Statistical addition method for external noise sources affecting HF-MF-LF systems

    NASA Astrophysics Data System (ADS)

    Neudegg, David

    2001-01-01

    The current statistical method for the addition of external component noise sources in the LF, MF, and lower HF band (100 kHz to 3 MHz) produces total median noise levels that may be less than the largest-component median in some cases. Several case studies illustrate this anomaly. Methods used to sum the components rely on their power (decibels) distributions being represented as normal by the statistical parameters. The atmospheric noise component is not correctly represented by its decile values when it is assumed to have a normal distribution, causing anomalies in the noise summation when components are similar in magnitude. A revised component summation method is proposed, and the way it provides a more physically realistic total noise median for LF, MF, and lower HF frequencies is illustrated.

  12. Effects of Zr, In and SiC Addition on the Critical Current in Filamentary MgB2 Superconductors by Suspension Spinning

    NASA Astrophysics Data System (ADS)

    Goto, T.; Katoh, H.; Watanabe, K.; Nishijima, G.

    2004-06-01

    We have examined the effects of Zr, In and nanoscale SiC addition on the field dependence of transport Jc for filamentary MgB2 superconductors at 4.2 K in magnetic field up to 14 T. Suspension spinning of commercially available MgB2, and Zr, In or nanoscale SiC powders was used to fabricate a long superconducting MgB2 wire. The as-drawn filaments were pressed and pyrolyzed to remove volatile components. The filamentary samples were then cold-pressed, enveloped by an iron sheet with Mg powder or with a pellet of mixed powder of Mg and B, and vacuum-sealed in a fused quartz tube and sintered. The Jc of the sample was strongly dependent on the sintering condition and addition content. 10 at% In addition enhanced the Jc at magnetic fields up to 8 T for the sample sintered with Mg powder. 5 at% SiC addition in the sample sintered with a pellet of Mg and B powders improved the Jc at fields of more than 7 T and the zero resistivity at 4.2 K was maintained by applying the field of 14 T. The magnetization for the samples was also measured at 4.2 K in magnetic fields up to 5 T by using SQUID magnetometer. The addition of Zr and SiC enhanced the magnetic Jc value.

  13. On the Asymmetric Splitting of CBED HOLZ Lines under the Gate of Recessed SiGe Source/Drain Transistors

    NASA Astrophysics Data System (ADS)

    Benedetti, A.; Bender, H.

    The behaviour of the CBED HOLZ line splitting under the gate of transistor structures with recessed SiGe in the source/drain regions is investigated. Structures with nitride/oxide dummy gates or with poly gates and nitride spacers are studied. In the gate region as well as below the SiGe, splitting of the HOLZ lines in the CBED patterns is observed with increasing magnitude towards the interface. The splitting under the gate shows an asymmetry for equivalent lines which inverts along horizontal cutlines under the gate. The behaviour is explained by a 3-dimensional relaxation of the stress.

  14. Basal plane dislocation multiplication via the Hopping Frank-Read source mechanism in 4H-SiC

    NASA Astrophysics Data System (ADS)

    Wang, H.; Wu, F.; Byrappa, S.; Sun, S.; Raghothamachar, B.; Dudley, M.; Sanchez, E. K.; Hansen, D.; Drachev, R.; Mueller, S. G.; Loboda, M. J.

    2012-04-01

    Synchrotron white beam x-ray topography (SWBXT) observations are reported of single-ended Frank-Read sources in 4H-SiC. These result from inter-conversion between basal plane dislocations (BPDs) and threading edge dislocations (TEDs) brought about by step interactions on the growth interface resulting in a dislocation comprising several glissile BPD segments on parallel basal planes interconnected by relatively sessile TED segments. Under stress, the BPD segments become pinned by the TED segments producing single ended Frank-Read sources. Since the BPDs appear to "hop" between basal planes, this apparently dominant multiplication mechanism for BPDs in 4H-SiC is referred to as the "Hopping" Frank-Read source mechanism.

  15. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys.

    PubMed

    Gebhardt, T; Music, D; Ekholm, M; Abrikosov, I A; Vitos, L; Dick, A; Hickel, T; Neugebauer, J; Schneider, J M

    2011-06-22

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Néel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  16. Addition of surfactants in ozonated water cleaning for the suppression of functional group formation and particle adhesion on the SiO2 surface

    NASA Astrophysics Data System (ADS)

    Yang, Jahyun; Im, Kyungtaek; Lim, Sangwoo

    2011-04-01

    Various kinds of surfactants were added to a cleaning solution and deionized (DI) water, and their effect on the suppression of organic function group formation and particle adhesion to a SiO2 surface was analyzed using multi-internal reflection Fourier transform infrared spectroscopy. The results implied that attached organic functional groups are affected by the chemical structure of a surfactant in DI water. Furthermore, the addition of anionic glycolic acid ethoxylate 4-tert-butylphenyl ether (GAE4E) is the most effective in terms of preventing organic group attachment and particle adhesion to the SiO2 surface, whether it was added to the cleaning solution or post-cleaning rinse water, with or without polystyrene latex particles. Moreover, it was possible to completely prevent particle adhesion to the SiO2 surface with the proper addition of GAE4E in DIO3 solution.

  17. Depth distribution of Frank loop defects formed in ion-irradiated stainless steel and its dependence on Si addition

    NASA Astrophysics Data System (ADS)

    Chen, Dongyue; Murakami, Kenta; Dohi, Kenji; Nishida, Kenji; Soneda, Naoki; Li, Zhengcao; Liu, Li; Sekimura, Naoto

    2015-12-01

    Although heavy ion irradiation is a good tool to simulate neutron irradiation-induced damages in light water reactor, it produces inhomogeneous defect distribution. Such difference in defect distribution brings difficulty in comparing the microstructure evolution and mechanical degradation between neutron and heavy ion irradiation, and thus needs to be understood. Stainless steel is the typical structural material used in reactor core, and could be taken as an example to study the inhomogeneous defect depth distribution in heavy ion irradiation and its influence on the tested irradiation hardening by nano-indentation. In this work, solution annealed stainless steel model alloys are irradiated by 3 MeV Fe2+ ions at 400 °C to 3 dpa to produce Frank loops that are mainly interstitial in nature. The silicon content of the model alloys is also tuned to change point defect diffusion, so that the loop depth distribution influenced by diffusion along the irradiation beam direction could be discussed. Results show that in low Si (0% Si) and base Si (0.42% Si) samples the depth distribution of Frank loop density quite well matches the dpa profile calculated by the SRIM code, but in high Si sample (0.95% Si), the loop number density in the near-surface region is very low. One possible explanation could be Si's role in enhancing the effective vacancy diffusivity, promoting recombination and thus suppressing interstitial Frank loops, especially in the near-surface region, where vacancies concentrate. By considering the loop depth distribution, the tested irradiation hardening is successfully explained by the Orowan model. A hardening coefficient of around 0.30 is obtained for all the three samples. This attempt in interpreting hardening results may make it easier to compare the mechanical degradation between different irradiation experiments.

  18. Analytical methods for SiO2 and other inorganic oxides in titanium dioxide or certain silicates for food additive specifications.

    PubMed

    Mutsuga, Motoh; Sato, Kyoko; Hirahara, Yoshichika; Kawamura, Yoko

    2011-04-01

    An analytical method has been developed for the detection of SiO(2) and other oxides in titanium dioxide and certain silicates used in food additives using inductively coupled plasma (ICP) atomic emission spectrometry without hydrofluoric acid. SiO(2) and other oxides in titanium dioxide or certain silicates were resolved by alkali fusion with KOH and boric acid and then dissolved in dilute hydrochloric acid as a test solution for ICP. The recovery of SiO(2) and Al(2)O(3) added at 0.1 and 1.0%, respectively, in TiO(2) was 88-104%; coefficient of variation was <4%. The limit of determination of SiO(2) and Al(2)O(3) was about 0.08%, and the accuracy of the ICP method was better than that of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) test method. The recovery of SiO(2) and other oxides in silicates was 95-107% with a coefficient of variation of <4%. Using energy dispersive X-ray fluorescence spectrometry (EDX) with fundamental parameter determination, the content of SiO(2) and other oxide in titanium dioxide and silicate showed good agreement with the ICP results. ICP with alkali fusion proved suitable as a test method for SiO(2), Al(2)O(3) and other oxides in titanium dioxide and certain silicates, and EDX proves useful for screening such impurities in titanium dioxide and componential analysis of certain silicates.

  19. Source/drain eSiGe engineering for FinFET technology

    NASA Astrophysics Data System (ADS)

    Peng, Jianwei; Qi, Yi; Lo, Hsien-Ching; Zhao, Pei; Yong, Chloe; Yan, Jianghu; Dou, Xinyuan; Zhan, Hui; Shen, Yanping; Regonda, Suresh; Hu, Owen; Yu, Hong; Joshi, Manoj; Adams, Charlotte; Carter, Rick; Samavedam, Srikanth

    2017-09-01

    Epitaxy growth loading effect—the growth rate difference between device macros due to their local open ratio difference—is an important consideration for device design and thus process optimization. A poor loading process leads to device performance delta across macros. For eSiGe on FinFETs, we found that optimized eSiGe on FinFETs saturates as the eSiGe diamond pins at fin top surface and the fin-sidewall-spacer (FSS). The eSiGe diamond size measured by lateral CD does not increase with deposition time, but it linearly correlates to cavity depth and FSS pushdown. In principle, the eSiGe loading effect can be addressed with an extended growth time until every device macros saturates. However, it is found that, the epitaxy growth related defects, measured by abnormal eSiGe and unwanted growth, can also be elevated to an unacceptable level for a longer deposition time. Thus, the eSiGe loading process still needs to be optimized for an improved process window. In this work, an optimized eSiGe process achieves reduced loading between 2-fin and 40-fin macros and thus a smaller pFET performance gap between the two device macros.

  20. Synergistic Effect of MoS2 and SiO2 Nanoparticles as Lubricant Additives for Magnesium Alloy–Steel Contacts

    PubMed Central

    Xie, Hongmei; Jiang, Bin; Hu, Xingyu; Peng, Cheng; Guo, Hongli; Pan, Fusheng

    2017-01-01

    The tribological performances of the SiO2/MoS2 hybrids as lubricant additives were explored by a reciprocating ball-on-flat tribometer for AZ31 magnesium alloy/AISI 52100 bearing steel pairs. The results demonstrated that the introduction of SiO2/MoS2 hybrids into the base oil exhibited a significant reduction in the friction coefficient and wear volume as well as an increase in load bearing capacity, which was better than the testing results of the SiO2 or MoS2 nanolubricants. Specifically, the addition of 0.1 wt % nano-SiO2 mixed with 1.0 wt % nano-MoS2 into the base oil reduced the friction coefficient by 21.8% and the wear volume by 8.6% compared to the 1.0 wt % MoS2 nanolubricants. The excellent lubrication behaviors of the SiO2/MoS2 hybrid nanolubricants can be explained by the micro-cooperation of different nanoparticles with disparate morphology and lubrication mechanisms. PMID:28644394

  1. Effect of SiC and Graphite Particulates Addition on Wear Behaviour of Al2219 Alloy Hybrid Composites

    NASA Astrophysics Data System (ADS)

    Nagaral, Madeva; Shivananda, B. K.; Jayachandran; Auradi, V.; Kori, S. A.

    2016-09-01

    In this investigation wear behaviour of A12219 alloy reinforced with SiC and graphite particulates were studied. The percentage of silicon carbide and graphite as reinforcements were varied from 2 wt.% to 4 wt.% in steps of 2. Energy dispersive spectroscopy and scanning electron microphotographs were used to confirm the presence of SiC and graphite particulates and its uniform distribution over the aluminum matrix. Wear behaviour of aluminum alloy Al2219 reinforced with silicon carbide and graphite fabricated by stir casting process was investigated. The wear properties of the metal matrix composites were studied by performing dry sliding wear test using a pin-on-disc wear tester. The experiments were conducted at a constant sliding velocity of 1.73m/s over a load of 2kg. The results showed that the wear resistance of Al2219-2%SiC-2% graphite and Al2219-4%SiC-4% graphite composites were better than the unreinforced alloy. The wear in terms of weight loss and wear rate was found to decrease with the increasing the weigh percentages of SiC and graphite. To study the dominant sliding wear mechanism worn surfaces were analyzed using scanning electron microscopy.

  2. InCl3/Me3SiCl-catalyzed direct Michael addition of enol acetates to α,β-unsaturated ketones.

    PubMed

    Onishi, Yoshiharu; Yoneda, Yuki; Nishimoto, Yoshihiro; Yasuda, Makoto; Baba, Akio

    2012-11-16

    The direct Michael addition of enol acetates to α,β-unsaturated ketones was achieved using a combination of Lewis acid catalysts, InCl(3) and Me(3)SiCl, which furnished stable enol-form products that could be further transformed into functionalized 1,5-diketones by reactions with various electrophiles.

  3. Improving High-Temperature Tensile and Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloys Through Micro-additions of Ti, V, and Zr

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2015-07-01

    High-temperature tensile and low-cycle fatigue tests were performed to assess the influence of micro-additions of Ti, V, and Zr on the improvement of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in the as-cast condition. Addition of transition metals led to modification of microstructure where in addition to conventional phases present in the Al-7Si-1Cu-0.5Mg base, new thermally stable micro-sized Zr-Ti-V-rich phases Al21.4Si4.1Ti3.5VZr3.9, Al6.7Si1.2TiZr1.8, Al2.8Si3.8V1.6Zr, and Al5.1Si35.4Ti1.6Zr5.7Fe were formed. The tensile tests showed that with increasing test temperature from 298 K to 673 K (25 °C to 400 °C), the yield stress and tensile strength of the present studied alloy decreased from 161 to 84 MPa and from 261 to 102 MPa, respectively. Also, the studied alloy exhibited 18, 12, and 5 pct higher tensile strength than the alloy A356, 354 and existing Al-Si-Cu-Mg alloy modified with additions of Zr, Ti, and Ni, respectively. The fatigue life of the studied alloy was substantially longer than those of the reference alloys A356 and the same Al-7Si-1Cu-0.5Mg base with minor additions of V, Zr, and Ti in the T6 condition. Fractographic analysis after tensile tests revealed that at the lower temperature up to 473 K (200 °C), the cleavage-type brittle fracture for the precipitates and ductile fracture for the matrix were dominant while at higher temperature fully ductile-type fracture with debonding and pull-out of cracked particles was identified. It is believed that the intermetallic precipitates containing Zr, Ti, and V improve the alloy performance at increased temperatures.

  4. Assessment of open source software for CBCT in detecting additional mental foramina.

    PubMed

    Santos, Oséas; Pinheiro, Lucas Rodrigues; Umetsubo, Otávio Shoiti; Sales, Marcelo Augusto Oliveira; Cavalcanti, Marcelo Gusmão Paraíso

    2013-01-01

    The purpose of this study was to evaluate which post-processing imaging protocol would be better to analyze the additional mental foramen (AMF) in preoperative planning with cone-beam computed tomography (CBCT) exams, and to test reproducibility of measurements, using open source software (OsiriX). The software was used to detect the cases of AMF from among 58 exams for dental implant planning in edentulous mandible areas-three cases were found. The case images were submitted to qualitative analysis using 2D orthogonal MPR, 3D-MPR and 3D volume rendering protocols by two oral and maxillofacial radiologists. Quantitative analysis used the 3D-MPR protocol; the closed polygon tool measured the mental foramen (MF) and the AMF areas; the length tool measured the distance between foramina. The measurements were performed independently by the examiners, at two different times. Intra- and interexaminer agreement was assessed using the intraclass correlation coefficient. The panoramic view did not show the MF and the AMF clearly. The AMF could be detected in the parasagittal view. 2D Orthogonal MPR was effective to observe the AMF in some cases. The 3D-MPR and 3D view protocols were the most effective to locate and analyze the AMF. In conclusion, a 3D view improves visualization when anatomical points are not clearly visible. 3D-MPR was considered a more effective post-processing imaging protocol to observe foramina relationships. The high reproducibility of measurements for anatomical MF variations was established using specific tools featured in open source software for CBCT. OsiriX is realistic and recommended for preoperative planning.

  5. Fabrication of Source/Drain Electrodes for a-Si:H Thin-Film Transistors Using a Single Cu Alloy Target

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Lee, C. Y.; Nam, H. S.; Lee, J. G.; Yang, H. J.; Ho, W. J.; Jeong, J. Y.; Koo, D. H.

    2011-11-01

    A Cu alloy/Cu alloy oxide bilayer structure was formed on an n +-a-Si:H substrate using a single Cu alloy target. It was employed for the source/drain electrodes in the fabrication of a-Si:H thin-film transistors with good electrical performance, high thermal stability, and good adhesion. Transmission electron microscopy and electron energy-loss spectroscopy analyses revealed that the initial sputtering of the Cu alloy in O2/Ar allowed for preferential oxidation of Si and the formation of a SiO x /Cu-supersaturated a-Si:H bilayer at the copper oxide-a-Si:H interface. This bilayer turned into an SiO x /Cu3Si bilayer after annealing at 300°C. It provided a stable contact structure with low contact resistance.

  6. Effect of silicon (Si) particles addition on melting temperature, intermetallic compound formation and solderability of Sn-Cu-Ni composite solder paste

    NASA Astrophysics Data System (ADS)

    Said, R. M.; Salleh, M. A. A. Mohd; Ramli, M. I. I.; Saud, N.

    2017-04-01

    The effect of silicon (Si) particles addition on the melting temperature, intermetallic compound (IMC) layer formation and solderability of Sn-Cu-Ni solder joint were investigated. The melting temperature of mixture solder paste was studied by using Differential Scanning Calorimeter (DSC). Solderability of solder paste was evaluated through the contact angle of solder paste on Cu substrate. The interfacial morphology of monolithic and composite solder paste was characterized metallographically. The wettability and IMC thickness of Sn-Cu-Ni composite solder paste was reduced compared to the monolithic solder paste. Overall, the Si particles improved the physical properties and solderability of Sn-Cu-Ni composite solder paste.

  7. Effects of Additives on Electrochemical Growth of Cu Film on Co/SiO2/Si Substrate by Alternating Underpotential Deposition of Pb and Surface-Limited Redox Replacement by Cu

    NASA Astrophysics Data System (ADS)

    Fang, J. S.; Lin, L. Y.; Wu, C. L.; Cheng, Y. L.; Chen, G. S.

    2017-08-01

    The effects of additives to an acidic electrolyte for electrochemical deposition of copper film to prevent corrosion of the Co/SiO2/Si substrate have been investigated. A sacrificial Pb layer was formed by underpotential deposition (UPD), then a Cu layer was prepared using surface-limited redox replacement (SLRR) to exchange the UPD-Pb layer in an acidic copper electrolyte with trisodium citrate, sodium perchlorate, and ethylenediamine as additives. The additives significantly affected the replacement of UPD-Pb by Cu and prevented galvanic corrosion of the Co/SiO2/Si substrate in the acidic Cu electrolyte. The results showed that both sodium perchlorate and ethylenediamine reduced the corrosion of the Co substrate and resulted in Cu film with low electrical resistivity. However, residual Pb was present in the Cu film when using trisodium citrate, as the citrate ions slowed copper displacement. The proposed sequential UPD-Pb and SLRR-Cu growth method may enable electrochemical deposition for fabrication of Cu interconnects on Co substrate from acidic Cu electrolyte.

  8. Effect of C and Ce addition on the microstructure and magnetic property of the mechanically alloyed FeSiBAlNi high entropy alloys

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Axinte, Eugen; Zhao, Zhengfeng; Wang, Yan

    2016-09-01

    The effects of elemental addition, C and Ce, on the microstructure, thermal property and magnetic property of mechanically alloyed FeSiBAlNi (based-W5) high entropy alloys (HEAs) have been investigated in depth in the present work. The amorphous HEAs have been successfully fabricated by mechanical alloying. The results reveal that Ce addition obviously shortens the formation time of fully amorphous phase, therefore leading to the enhanced glass forming ability (GFA) of the based-W5. The final products of as-milled FeSiBAlNiC alloy consist of the main amorphous phase and a small amount of Si nanocrystals. In addition, C and Ce addition are both beneficial to enhance the thermal stability. The coercivity force (Hc) of the tested samples lies in the range of 50-378 Oe, suggesting the semi-hard magnetic property. The saturation magnetization (Ms) becomes decreased with increasing the milling time. C addition effectively increases Ms exhibiting the good magnetic property, however, Ce addition presents the negative effect. It should be noted that the amorphous phase tends to be formed when the radius ratio (Rr) is larger than 1, and the GFA is enhanced with increasing Rr and valence electron concentration.

  9. Development of a Mo-Si-B coating for Nb-based Alloys and the Effects of Zr Additions to Mo-Si-B Coatings for Enhanced Oxidation Protection in Ultra-High Temperature Applications

    NASA Astrophysics Data System (ADS)

    Lu-Steffes, Otto John

    Higher efficiencies and reduced emissions performance of fossil fuel energy systems are achieved with increasing operation temperatures. This increase in operating temperature requires the use of materials with higher melting points such as refractory metal alloys. However, refractory metals suffer from catastrophic oxidation in this type of environment. Thus, oxidation protection for refractory metal alloys is a crucial step in developing next generation ultra-high temperature materials. To meet this challenge, an oxidation resistant coating for Nb based alloys has been designed as well as the incorporation of zirconium into the Mo-Si-B coating to provide further corrosion protection and a reduction in temperature for the underlying multi-layered structure. Niobium samples coated with a Mo-Si-B coating demonstrate enhanced oxidation protection compared to samples only coated with Si-B. Thermogravimetric analysis testing at 1300°C for 24 hours for both the Mo-Si-B coated Nb and Nb-based alloys show enhanced oxidation protection with mass changes of 0.44 mg/cm2 and 0.55 mg/cm2, respectively, compared to the uncoated alloy that had a mass change of 87.6 mg/cm2. To demonstrate the design concept for a coating with thermal barrier behavior, Zr is added to the Mo-Si-B coating through the pack cementation technique. The resulting coating shows that the Zr reacts with the aluminosilica top layer to form Zr silicides and ZrO2. Upon oxidation, the coating forms a mixed top layer composed of borosilica, ZrO2 and ZrSiO 4. Oxidation testing of the Zr modified Mo-Si-B coating exhibits low mass change indicating that the coating provides oxidation protection and that the Zr additions do not interfere with the oxidation protection of the Mo-Si-B coating. Finite element modeling using object oriented finite element analysis of the coating structures yielded an evaluation of the mechanical and thermal properties of the coatings, providing insight into the thermal performance and

  10. Independent and Additive Effects of Different Sources of Fluoride and Dental Fluorosis.

    PubMed

    Celeste, Roger Keller; Luz, Patricia Blaya

    2016-01-01

    To investigate the contribution of different sources of fluoride related to dental fluorosis. This population-based, matched, case-control study (67 pairs) used a representative sample of 271 schoolchildren. Dental fluorosis was measured using Dean's index. Children's caregivers were interviewed about nine risk factors. Data were analyzed using conditional logistic regression. The prevalence of questionable cases was 18.8 percent, and the prevalence of very mild, mild, or moderate cases of dental fluorosis was 11.5 percent, with no severe case. Age of start of toothbrushing, drinking water from wells, frequency of toothbrushing, type of tooth-paste, standard/ children's mouthrinse usage, and fluoride supplements were not significant (P>0.15). Drinking water from wells and using supplements were underpowered (N less than six). Children who frequently ate toothpaste had an odds ratio of 5.56 (95% confidence interval (CI) 1.75 to 17.73) times more fluorosis; those applying toothpaste to cover the bristles had 5.55 times more fluorosis (95% CI 1.44 to 21.42); and those using an adult size toothbrush had 3.17 times more flurosis (95% CI 1.15 to 8.71). There was a significant additive interaction (P<0.01). In a community with water fluoridation, the factors associated with dental fluorosis are intentional toothpaste ingestion and tooth-paste applied on the whole toothbrush.

  11. Elite sport is not an additional source of distress for adolescents with high stress levels.

    PubMed

    Gerber, Markus; Holsboer-Trachsler, Edith; Pühse, Uwe; Brand, Serge

    2011-04-01

    This study examined whether participation in elite sport interacts with stress in decreasing or increasing symptoms of depression and anxiety among adolescents, and further, whether the interplay between participation in high-performance sport and stress is related to the perceived quality of sleep. 434 adolescents (278 girls, 156 boys; age: M = 17.2 yr.) from 15 "Swiss Olympic Sport Classes" and 9 conventional classes answered a questionnaire and completed a 7-day sleep log. Analyses of covariance showed that heightened stress was related to more depressive symptoms and higher scores for trait-anxiety. Moreover, those classified as having poor sleep by a median split cutoff reported higher levels of depressive symptoms. No significant (multivariate) main effects were found for high-performance sport athletes. Similarly, no significant two- or three-way interaction effects were found. These results caution against exaggerated expectations concerning sport participation as a stress buffer. Nevertheless, participation in high-performance sport was not found to be an additional source of distress for adolescents who reported high stress levels despite prior research that has pointed toward such a relationship.

  12. Enhancement of programming speed on gate-all-around poly-silicon nanowire nonvolatile memory using self-aligned NiSi Schottky barrier source/drain

    NASA Astrophysics Data System (ADS)

    Ho, Ching-Yuan; Chang, Yaw-Jen; Chiou, Y. L.

    2013-08-01

    The programming characteristics of gate-all-around silicon-oxide-nitride-oxide silicon (SONOS) nonvolatile memories are presented using NiSi/poly-Si nanowires (SiNW) Schottky barrier (SB) heterojunctions. The non-uniform thermal stress distribution on SiNW channels due to joule heating affected the carrier transport behavior. Under a high drain voltage, impact ionization was found as a large lateral field enhances carrier velocity. As gate voltage (Vg) increased, the difference in the drain current within a range of various temperature conditions can be mitigated because a high gate field lowers the SB height of a NiSi source/SiNW/NiSi drain junction to ensure efficient hot-carrier generation. By applying the Fowler-Nordheim programming voltage to the SONOS nanowire memory, the SB height (Φn = 0.34 eV) could be reduced by image force; thus, hot electrons could be injected from SB source/drain electrodes into the SiN storage node. To compare both SiNW and Si nanocrystal SONOS devices, the SB SiNW SONOS device was characterized experimentally to propose a wider threshold-voltage window, exhibiting efficient programming characteristics.

  13. Solar neutrinos and the influences of opacity, thermal instability, additional neutrino sources, and a central black hole on solar models

    NASA Technical Reports Server (NTRS)

    Stothers, R. B.; Ezer, D.

    1972-01-01

    Significant quantities that affect the internal structure of the sun are examined for factors that reduce the temperature near the sun's center. The four factors discussed are: opacity, central black hole, thermal instability, and additional neutrino sources.

  14. The Effect of SiO2 Addition on the Characteristics of CuFe2O4 Ceramics for NTC Thermistor

    NASA Astrophysics Data System (ADS)

    Wiendartun, Syarif, D. Gustaman

    2008-03-01

    The effect of SiO2 addition on the characteristics of CuFe2O4 ceramics for NTC thermistors has been studied. The ceramics were produced by pressing a homogeneous mixture of CuO, Fe3O4 and SiO2 (0-0.75 w/o) powders in appropriate proportions to produce CuFe2O4 based ceramics and sintering the pressed powder at 1100 °C for 2 hours in air. Electrical characterization was done by measuring electrical resistivity of the ceramics at various temperatures (25 °C-100 °C). Microstructure and structural analyses were also carried out by using optical microscopy and X-ray diffraction (XRD), respectively. The XRD analyses showed that the CuFe2O4 and SiO2 added-CuFe2O4 ceramics have crystal structure of cubic spinel. The presence of second phase could not be identified from the XRD analyses. According to the electrical data, it was known that the SiO2 addition increased the thermistor constant (B) and the room temperature electrical resistivity (ρRT). The value of B and ρRT of the produced CuFe2O4 ceramics namely B = 2548-3308 ° K and ρRT = 291-9400 ohm's, fitted market requirement.

  15. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-08-01

    Rapidly solidified hypoeutectic Al-10Si- xMg ( x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  16. Microstructure and hydrothermal corrosion behavior of NITE-SiC with various sintering additives in LWR coolant environments

    DOE PAGES

    Parish, Chad M.; Terrani, Kurt A.; Kim, Young -Jin; ...

    2016-11-28

    Nano-infiltration and transient eutectic phase (NITE) sintering was developed for fabrication of nuclear grade SiC composites. We produced monolithic SiC ceramics using NITE sintering, as candidates for accident-tolerant fuels in light-water reactors (LWRs). In this work, we exposed three different NITE chemistries (yttria-alumina [YA], ceria-zirconia-alumina [CZA], and yttria-zirconia-alumina [YZA]) to autoclave conditions simulating LWR coolant loops. The YZA was most corrosion resistant, followed by CZA, with YA being worst. High-resolution elemental analysis using scanning transmission electron microscopy (STEM) X-ray mapping combined with multivariate statistical analysis (MVSA) datamining helped explain the differences in corrosion. YA-NITE lost all Al from the corrodedmore » region and the ytttria reformed into blocky precipitates. The CZA material lost all Al from the corroded area, and the YZA – which suffered the least corrosion –retained some Al in the corroded region. Lastly, the results indicate that the YZA-NITE SiC is most resistant to hydrothermal corrosion in the LWR environment.« less

  17. Microstructure and hydrothermal corrosion behavior of NITE-SiC with various sintering additives in LWR coolant environments

    SciTech Connect

    Parish, Chad M.; Terrani, Kurt A.; Kim, Young -Jin; Koyanagi, Takaaki; Katoh, Yutai

    2016-11-28

    Nano-infiltration and transient eutectic phase (NITE) sintering was developed for fabrication of nuclear grade SiC composites. We produced monolithic SiC ceramics using NITE sintering, as candidates for accident-tolerant fuels in light-water reactors (LWRs). In this work, we exposed three different NITE chemistries (yttria-alumina [YA], ceria-zirconia-alumina [CZA], and yttria-zirconia-alumina [YZA]) to autoclave conditions simulating LWR coolant loops. The YZA was most corrosion resistant, followed by CZA, with YA being worst. High-resolution elemental analysis using scanning transmission electron microscopy (STEM) X-ray mapping combined with multivariate statistical analysis (MVSA) datamining helped explain the differences in corrosion. YA-NITE lost all Al from the corroded region and the ytttria reformed into blocky precipitates. The CZA material lost all Al from the corroded area, and the YZA – which suffered the least corrosion –retained some Al in the corroded region. Lastly, the results indicate that the YZA-NITE SiC is most resistant to hydrothermal corrosion in the LWR environment.

  18. ADDITIONAL OBSERVATIONS OF PLANETS AND QUASI-STELLAR RADIO SOURCES AT 3 MM,

    DTIC Science & Technology

    MERCURY ( PLANET ), VENUS( PLANET ), PERIODIC VARIATIONS, RADIO ASTRONOMY, SPECTRUM SIGNATURES...EXTRATERRESTRIAL RADIO WAVES, SOURCES), GALAXIES, BLACKBODY RADIATION, BRIGHTNESS, TEMPERATURE, MARS( PLANET ), JUPITER( PLANET ), SATURN( PLANET

  19. Delayed plastic relaxation limit in SiGe islands grown by Ge diffusion from a local source

    SciTech Connect

    Vanacore, G. M.; Zani, M.; Tagliaferri, A.; Nicotra, G.; Bollani, M.; Bonera, E.; Montalenti, F.; Picco, A.; Boioli, F.; Capellini, G.; Isella, G.; Osmond, J.

    2015-03-14

    The hetero-epitaxial strain relaxation in nano-scale systems plays a fundamental role in shaping their properties. Here, the elastic and plastic relaxation of self-assembled SiGe islands grown by surface-thermal-diffusion from a local Ge solid source on Si(100) are studied by atomic force and transmission electron microscopies, enabling the simultaneous investigation of the strain relaxation in different dynamical regimes. Islands grown by this technique remain dislocation-free and preserve a structural coherence with the substrate for a base width as large as 350 nm. The results indicate that a delay of the plastic relaxation is promoted by an enhanced Si-Ge intermixing, induced by the surface-thermal-diffusion, which takes place already in the SiGe overlayer before the formation of a critical nucleus. The local entropy of mixing dominates, leading the system toward a thermodynamic equilibrium, where non-dislocated, shallow islands with a low residual stress are energetically stable. These findings elucidate the role of the interface dynamics in modulating the lattice distortion at the nano-scale, and highlight the potential use of our growth strategy to create composition and strain-controlled nano-structures for new-generation devices.

  20. Recrystallization of atomically balanced amorphous pockets in Si: A source of point defects

    SciTech Connect

    Marques, Luis A.; Pelaz, Lourdes; Lopez, Pedro; Santos, Ivan; Aboy, Maria

    2007-10-15

    We use classical molecular dynamics simulation techniques to study the regrowth behavior of amorphous pockets in Si. We demonstrate that crystallization depends on the morphology of the pocket-crystal interface. Although our simulated amorphous pockets had not any excess nor deficit of atoms with respect to perfect crystal, after regrowth we found residual defects. Most of them are single Si interstitials and vacancies, but also larger defects have been encountered. We have determined their atomic structures and calculated their formation energies. These complexes are more stable than amorphous pockets, and may trigger the formation of extended defects or favor damage accumulation.

  1. Characterization of Ultra High Temperature Ceramics via Transmission Electron Microscopy. Part 2: UHTCs sintered with addition of TaSi2

    DTIC Science & Technology

    2010-01-21

    hafnium diborides and carbides belong to the class of materials defined UHTCs (Ultra-High-Temperature-Ceramics). These materials are of particular...are finally compared to composites sintered with addition of the same amount of MoSi2. FA8655-09-M-4002 8 1. Introduction Zirconium, hafnium ... alloying elements. High temperatures decrease the liquid surface tension and promote wettability. Also, the spreading rate towards equilibrium is enhanced

  2. 40 CFR 60.4247 - What parts of the mobile source provisions apply to me if I am a manufacturer of stationary SI...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... provisions apply to me if I am a manufacturer of stationary SI internal combustion engines or a manufacturer... Standards of Performance for Stationary Spark Ignition Internal Combustion Engines Mobile Source Provisions... SI internal combustion engines or a manufacturer of equipment containing such engines?...

  3. 40 CFR 60.4247 - What parts of the mobile source provisions apply to me if I am a manufacturer of stationary SI...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... provisions apply to me if I am a manufacturer of stationary SI internal combustion engines or a manufacturer... Standards of Performance for Stationary Spark Ignition Internal Combustion Engines Mobile Source Provisions... SI internal combustion engines or a manufacturer of equipment containing such engines?...

  4. 40 CFR 60.4247 - What parts of the mobile source provisions apply to me if I am a manufacturer of stationary SI...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... provisions apply to me if I am a manufacturer of stationary SI internal combustion engines or a manufacturer... Standards of Performance for Stationary Spark Ignition Internal Combustion Engines Mobile Source Provisions... SI internal combustion engines or a manufacturer of equipment containing such engines?...

  5. 40 CFR 60.4247 - What parts of the mobile source provisions apply to me if I am a manufacturer of stationary SI...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... provisions apply to me if I am a manufacturer of stationary SI internal combustion engines or a manufacturer... Standards of Performance for Stationary Spark Ignition Internal Combustion Engines Mobile Source Provisions... SI internal combustion engines or a manufacturer of equipment containing such engines?...

  6. 40 CFR 60.4247 - What parts of the mobile source provisions apply to me if I am a manufacturer of stationary SI...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... provisions apply to me if I am a manufacturer of stationary SI internal combustion engines or a manufacturer... Standards of Performance for Stationary Spark Ignition Internal Combustion Engines Mobile Source Provisions... SI internal combustion engines or a manufacturer of equipment containing such engines?...

  7. Effects of ultrasonic agitation and surfactant additive on surface roughness of Si (111) crystal plane in alkaline KOH solution.

    PubMed

    Jiao, Qingbin; Tan, Xin; Zhu, Jiwei; Feng, Shulong; Gao, Jianxiang

    2016-07-01

    In the silicon wet etching process, the "pseudo-mask" formed by the hydrogen bubbles generated during the etching process is the reason causing high surface roughness and poor surface quality. Based upon the ultrasonic mechanical effect and wettability enhanced by isopropyl alcohol (IPA), ultrasonic agitation and IPA were used to improve surface quality of Si (111) crystal plane during silicon wet etching process. The surface roughness Rq is smaller than 15 nm when using ultrasonic agitation and Rq is smaller than 7 nm when using IPA. When the range of IPA concentration (mass fraction, wt%) is 5-20%, the ultrasonic frequency is 100 kHz and the ultrasound intensity is 30-50 W/L, the surface roughness Rq is smaller than 2 nm when combining ultrasonic agitation and IPA. The surface roughness Rq is equal to 1 nm when the mass fraction of IPA, ultrasound intensity and the ultrasonic frequency is 20%, 50 W and 100 kHz respectively. The experimental results indicated that the combination of ultrasonic agitation and IPA could obtain a lower surface roughness of Si (111) crystal plane in silicon wet etching process. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

    NASA Astrophysics Data System (ADS)

    Javidani, M.; Arreguin-Zavala, J.; Danovitch, J.; Tian, Y.; Brochu, M.

    2016-12-01

    This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro- and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of 80° to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

  9. Effect of Mg/B ratio on the superconductivity of MgB2 bulk with SiC addition

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Dou, S. X.; Lu, C.; Zhou, S. H.; Li, W. X.

    2010-03-01

    To improve the self-field critical current density (Jc) and critical temperature (Tc) in SiC-doped MgB2 , optimization of the nominal Mg/B mixing ratio has been performed. The effects of the nominal Mg/B mixing ratio (x:2) on the superconductivity, Raman spectra, current transport properties, and flux pinning mechanisms in MgB2 with 10 wt.% SiC doping were investigated systematically, with x varied from 1 to 1.2. It has been found that the sample with the Mg/B ratio of 1.15:2 exhibited the best Jc performance for all fields (0-8.5 T), and its Tc was also enhanced. The optimized Mg/B ratio diminished the interband scattering caused by Mg or B vacancies, and in turn, increased Tc . The connectivity and disorder were increased in the Mg1.15B2 sample. Both of these were responsible for the improved Jc under all the fields examined.

  10. Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

    NASA Astrophysics Data System (ADS)

    Javidani, M.; Arreguin-Zavala, J.; Danovitch, J.; Tian, Y.; Brochu, M.

    2017-04-01

    This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro- and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of 80° to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

  11. Meta-analysis on Methane Mitigating Properties of Saponin-rich Sources in the Rumen: Influence of Addition Levels and Plant Sources

    PubMed Central

    Jayanegara, Anuraga; Wina, Elizabeth; Takahashi, Junichi

    2014-01-01

    Saponins have been considered as promising natural substances for mitigating methane emissions from ruminants. However, studies reported that addition of saponin-rich sources often arrived at contrasting results, i.e. either it decreased methane or it did not. The aim of the present study was to assess ruminal methane emissions through a meta-analytical approach of integrating related studies from published papers which described various levels of different saponin-rich sources being added to ruminant feed. A database was constructed from published literature reporting the addition of saponin-rich sources at various levels and then monitoring ruminal methane emissions in vitro. Accordingly, levels of saponin-rich source additions as well as different saponin sources were specified in the database. Apart from methane, other related rumen fermentation parameters were also included in the database, i.e. organic matter digestibility, gas production, pH, ammonia concentration, short-chain fatty acid profiles and protozoal count. A total of 23 studies comprised of 89 data points met the inclusion criteria. The data obtained were subsequently subjected to a statistical meta-analysis based on mixed model methodology. Accordingly, different studies were treated as random effects whereas levels of saponin-rich source additions or different saponin sources were considered as fixed effects. Model statistics used were p-value and root mean square error. Results showed that an addition of increasing levels of a saponin-rich source decreased methane emission per unit of substrate incubated as well as per unit of total gas produced (p<0.05). There was a decrease in acetate proportion (linear pattern; p<0.001) and an increase in propionate proportion (linear pattern; p<0.001) with increasing levels of saponin. Log protozoal count decreased (p<0.05) at higher saponin levels. Comparing between different saponin-rich sources, all saponin sources, i.e. quillaja, tea and yucca saponins

  12. Meta-analysis on Methane Mitigating Properties of Saponin-rich Sources in the Rumen: Influence of Addition Levels and Plant Sources.

    PubMed

    Jayanegara, Anuraga; Wina, Elizabeth; Takahashi, Junichi

    2014-10-01

    Saponins have been considered as promising natural substances for mitigating methane emissions from ruminants. However, studies reported that addition of saponin-rich sources often arrived at contrasting results, i.e. either it decreased methane or it did not. The aim of the present study was to assess ruminal methane emissions through a meta-analytical approach of integrating related studies from published papers which described various levels of different saponin-rich sources being added to ruminant feed. A database was constructed from published literature reporting the addition of saponin-rich sources at various levels and then monitoring ruminal methane emissions in vitro. Accordingly, levels of saponin-rich source additions as well as different saponin sources were specified in the database. Apart from methane, other related rumen fermentation parameters were also included in the database, i.e. organic matter digestibility, gas production, pH, ammonia concentration, short-chain fatty acid profiles and protozoal count. A total of 23 studies comprised of 89 data points met the inclusion criteria. The data obtained were subsequently subjected to a statistical meta-analysis based on mixed model methodology. Accordingly, different studies were treated as random effects whereas levels of saponin-rich source additions or different saponin sources were considered as fixed effects. Model statistics used were p-value and root mean square error. Results showed that an addition of increasing levels of a saponin-rich source decreased methane emission per unit of substrate incubated as well as per unit of total gas produced (p<0.05). There was a decrease in acetate proportion (linear pattern; p<0.001) and an increase in propionate proportion (linear pattern; p<0.001) with increasing levels of saponin. Log protozoal count decreased (p<0.05) at higher saponin levels. Comparing between different saponin-rich sources, all saponin sources, i.e. quillaja, tea and yucca saponins

  13. Formation of deoxidization products in iron ingot by the addition of Al, Si, and/or Mn (M-5)

    NASA Technical Reports Server (NTRS)

    Fukazawa, Akira

    1993-01-01

    The objective of this work is to examine the morphology, composition, and distribution of deoxidation products in iron and iron-10 percent Ni alloy ingots. The deoxidation agents Si, Mn, Al, and their mixtures are selected to investigate the formation mechanism of the deoxidation products and to compare the differences of oxide formation among these agents in microgravity. After the experiment in space, the tested specimens are going to be analyzed by the use of the latest physical and/or chemical analytical equipment, and the information obtained will be a great help for the comprehension of the formation of oxide inclusion in steel for practical purposes, and also for the study of the solidification mechanism theory in the theoretical field.

  14. Measurement and Analysis of Porosity in Al-10Si-1Mg Components Additively Manufactured by Selective Laser Melting

    SciTech Connect

    Rao, Suraj; Cunningham, Ross; Ozturk, Tugce; Rollett, Anthony D.

    2016-10-18

    Aluminum alloys are candidate materials for weight critical applications because of their excellent strength and stiffness to weight ratio. However, defects such as voids decrease the strength and fatigue life of these alloys, which can limit the application of Selective Laser Melting. In this study, the average volume fraction, average size, and size distribution of pores in Al10-Si-1Mg samples built using Selective Laser Melting have been characterized. Synchrotron high energy X-rays were used to perform computed tomography on volumes of order one cubic millimeter with a resolution of approximately 1.5 μm. Substantial variations in the pore size distributions were found as a function of process conditions. Even under conditions that ensured that all locations were melted at least once, a significant number density was found of pores above 5 μm in diameter.

  15. Impacts of carbon source addition on denitrification and phosphorus uptake in enhanced biological phosphorus removal systems.

    PubMed

    Begum, Shamim A; Batista, Jacimaria R

    2013-01-01

    In this study, simultaneous denitrification and phosphorus (P) removal were investigated in batch tests using nitrified mixed liquor and secondary wastewater influent from a full-scale treatment plant and different levels of acetate and propionate as supplemental carbon sources. Without supplemental carbon source, denitrification occurred at low rate and P release and P uptake was negatively affected (i.e., P removal of only 59.7%). When acetate and propionate were supplied, denitrification and P release occurred simultaneously under anoxic conditions. For acetate and propionate at a C/N stoichiometric ratio of 7.6, P release was negatively affected by denitrification. For acetate, the percent P removal and denitrification were very similar for C/N ratios of 22 (5X stoichiometric) and 59 (10X stoichiometric). For propionate, both percent P removal and denitrification deteriorated for C/N ratios of 22 (5X stoichiometric) and 45 (10X stoichiometric). It was observed that carbon source added in excess to stoichiometric ratio was consumed in the aerobic zone, but P was not taken up. This implies that PAO bacteria may utilize the excess carbon source in the aerobic zone rather than their polyhydroxyalkanoate (PHA) reserves, thereby promoting deterioration of the system.

  16. 36 CFR 1290.3 - Sources of assassination records and additional records and information.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... IMPLEMENTATION OF THE PRESIDENT JOHN F. KENNEDY ASSASSINATION RECORDS COLLECTION ACT OF 1992 (JFK ACT) § 1290.3..., historical societies, and other similar organizations; (e) Individuals who possess such records by virtue of..., who have obtained such records from sources identified in paragraphs (a) through (e) of this section...

  17. 36 CFR 1290.3 - Sources of assassination records and additional records and information.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... IMPLEMENTATION OF THE PRESIDENT JOHN F. KENNEDY ASSASSINATION RECORDS COLLECTION ACT OF 1992 (JFK ACT) § 1290.3..., historical societies, and other similar organizations; (e) Individuals who possess such records by virtue of..., who have obtained such records from sources identified in paragraphs (a) through (e) of this section...

  18. A FEATURE MOVIE OF SiO EMISSION 20-100 AU FROM THE MASSIVE YOUNG STELLAR OBJECT ORION SOURCE I

    SciTech Connect

    Matthews, L. D.; Greenhill, L. J.; Goddi, C.; Humphreys, E. M. L.; Chandler, C. J.; Kunz, M. W.

    2010-01-01

    We present multi-epoch Very Long Baseline Array imaging of the {sup 28}SiO v = 1 and v = 2, J = 1-0 maser emission toward the massive young stellar object (YSO) Orion Source I. Both SiO transitions were observed simultaneously with an angular resolution of approx0.5 mas (approx0.2 AU for d = 414 pc) and a spectral resolution of approx0.2 km s{sup -1}. Here we explore the global properties and kinematics of the emission through two 19-epoch animated movies spanning 21 months (from 2001 March 19 to 2002 December 10). These movies provide the most detailed view to date of the dynamics and temporal evolution of molecular material within approx20-100 AU of a massive (approx>8 M{sub sun}) YSO. As in previous studies, we find that the bulk of the SiO masers surrounding Source I lie in an X-shaped locus; the emission in the south and east arms is predominantly blueshifted, and emission in the north and west is predominantly redshifted. In addition, bridges of intermediate-velocity emission are observed connecting the red and blue sides of the emission distribution. We have measured proper motions of over 1000 individual maser features and found that these motions are characterized by a combination of radially outward migrations along the four main maser-emitting arms and motions tangent to the intermediate-velocity bridges. We interpret the SiO masers as arising from a wide-angle bipolar wind emanating from a rotating, edge-on disk. The detection of maser features along extended, curved filaments suggests that magnetic fields may play a role in launching and/or shaping the wind. Our observations appear to support a picture in which stars with masses as high as at least 8 M{sub sun} form via disk-mediated accretion. However, we cannot yet rule out that the Source I disk may have been formed or altered following a recent close encounter.

  19. Optical spectroscopy of p-GaAs nanopillars on Si for monolithic integrated light sources

    NASA Astrophysics Data System (ADS)

    Morales, J. S. D.; Gandan, S.; Ren, D.; Ochalski, Tomasz J.; Huffaker, Diana L.

    2017-02-01

    In this work, we study the optical properties and emission dynamics of the novel nanostructure p-GaAs nanopillars (NPs) on Si. The integration of III-V optoelectronics on Si substrates is essential for next-generation high-speed communications. NPs on Si are good candidates as gain media in monolithically integrated small-scale lasers on silicon. In order to develop this technology, an in-depth knowledge of the NP structure is necessary to resolve its optimal optical properties. The optical characterization which has been carried out consists of the emission analysis for different NP geometries. We measured NPs with different combinations of pitch (of the order of a few μm) and diameter (of the order of tens of nm). A comparison of intensities for the various NPs provides us with the most efficient geometry. The quality of the crystal grown has been studied from temperature-dependent photoluminescence (PL). A red shift and a significant reduction of the intensity of the NP emission are observed with an increase in temperature. The results also show the presence of two non-radiative recombination channels when the intensity peaks at different temperatures are analyzed with the activation energy function.

  20. Influences of Na2O and K2O Additions on Electrical Conductivity of CaO-MgO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Zheng, Wei-Wei; Chou, Kuo-Chih

    2017-04-01

    The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts.

  1. Influences of Na2O and K2O Additions on Electrical Conductivity of CaO-MgO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Zheng, Wei-Wei; Chou, Kuo-Chih

    2017-01-01

    The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts.

  2. Epitaxy of Si1- x C x via ultrahigh-vacuum chemical vapor deposition using Si2H6, Si3H8, or Si4H10 as Si precursors

    NASA Astrophysics Data System (ADS)

    Koo, Sangmo; Jang, Hyunchul; Ko, Dae-Hong

    2017-09-01

    In this study, disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H10) were used as Si precursors for the growth of Si1- x C x epilayers, and the growth properties of the layers were compared. The use of a higher-order silane significantly increased the growth rates of the Si1- x C x epilayers at a processing temperature of 650 °C. In addition, a higher growth rate realized by using a higher-order silane promoted an increase in the substitutional carbon concentration in the Si1- x C x epilayers owing to the additional injection of a C-source gas (SiH3CH3) and the incorporation of C atoms into substitutional sites. The differences in growth properties between Si precursors were explained on the basis of reaction mechanisms.

  3. Hidden sources of phosphorus: presence of phosphorus-containing additives in processed foods.

    PubMed

    Lou-Arnal, Luis M; Arnaudas-Casanova, Laura; Caverni-Muñoz, Alberto; Vercet-Tormo, Antonio; Caramelo-Gutiérrez, Rocío; Munguía-Navarro, Paula; Campos-Gutiérrez, Belén; García-Mena, Mercedes; Moragrera, Belén; Moreno-López, Rosario; Bielsa-Gracia, Sara; Cuberes-Izquierdo, Marta

    2014-01-01

    An increased consumption of processed foods that include phosphorus-containing additives has led us to propose the following working hypothesis: using phosphate-rich additives that can be easily absorbed in processed foods involves a significant increase in phosphorus in the diet, which may be considered as hidden phosphorus since it is not registered in the food composition tables. The quantity of phosphorus contained in 118 processed products was determined by spectrophotometry and the results were contrasted with the food composition tables of the Higher Education Centre of Nutrition and Diet, those of Morandeira and those of the BEDCA (Spanish Food Composition Database) Network. Food processing frequently involves the use of phosphoric additives. The products whose label contains these additives have higher phosphorus content and higher phosphorus-protein ratio. We observed a discrepancy with the food composition tables in terms of the amount of phosphorus determined in a sizeable proportion of the products. The phosphorus content of prepared refrigerated foods hardly appears in the tables. Product labels provide little information on phosphorus content. We observed a discrepancy in phosphorus content in certain foods with respect to the food composition tables. We should educate our patients on reviewing the additives on the labels and on the limitation of processed foods. There must be health policy actions to deal with the problem: companies should analyse the phosphorus content of their products, display the correct information on their labels and incorporate it into the food composition tables. Incentives could be established to prepare food with a low phosphorus content and alternatives to phosphorus-containing additives.

  4. Surface segregation and growth-mode transitions during the initial stages of Si growth on Ge(001)2 × 1 by cyclic gas-source molecular beam epitaxy from Si2H6

    NASA Astrophysics Data System (ADS)

    Tsu, R.; Xiao, H. Z.; Kim, Y.-W.; Hasan, M.-A.; Birnbaum, H. K.; Greene, J. E.; Lin, D.-S.; Chiang, T.-C.

    1994-01-01

    Surface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2×1 by cyclic gas-source molecular beam epitaxy from Si2H6 has been investigated using in situ reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy, electron-energy-loss spectroscopy, and scanning tunneling microscopy, combined with post-deposition high-resolution cross-sectional transmission electron microscopy. The layers were deposited using repetitive cycles consisting of saturation Si2H6 dosing at room temperature, followed by annealing for 1 min at 550 °C. Film growth was observed to proceed via a mixed Stranski-Krastanov mode. Single-step-height two-dimensional growth was obtained for nominal Si deposition thicknesses tSi up to ≂1.5 monolayers (ML). However, the upper layer remained essentially pure Ge which segregated to the surface through site exchange with deposited Si as H was desorbed. At higher tSi, the Ge coverage decreased slowly, the surface roughened, and two-dimensional multilayer island growth was observed for tSi up to ≂7.5 ML, where bulk reflections in RHEED patterns provided evidence for the evolution of three-dimensional island formula.

  5. A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Reynolds, J. E.; Jauncey, D. L.; De Vegt, C.; Zacharias, N.; Ma, C.; Fey, A. L.; Johnston, K. J.; Hindsley, R.; Hughes, J. A.

    1994-01-01

    We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

  6. A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Reynolds, J. E.; Jauncey, D. L.; De Vegt, C.; Zacharias, N.; Ma, C.; Fey, A. L.; Johnston, K. J.; Hindsley, R.; Hughes, J. A.

    1994-01-01

    We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

  7. Food additives and environmental chemicals as sources of childhood behavior disorders

    SciTech Connect

    Weiss, B.

    1982-01-01

    The Feingold hypothesis postulates that many children who exhibit disturbed behavior improve on a diet devoid of certain food additives. Its validity has been examined on the basis of controlled trails. The total evidence, although not wholly consistent, nevertheless suggests that the hypothesis is, in principle, correct. Such a conclusion poses difficult problems and new issues for etiology, treatment, toxicology, and regulation.

  8. Fracture mode, microstructure and temperature-dependent elastic moduli for thermoelectric composites of PbTe-PbS with SiC nanoparticle additions

    NASA Astrophysics Data System (ADS)

    Ni, Jennifer E.; Case, Eldon D.; Schmidt, Robert D.; Wu, Chun-I.; Hogan, Timothy P.; Trejo, Rosa M.; Lara-Curzio, Edgar; Kanatzidis, Mercouri G.

    2013-12-01

    Twenty-six (Pb0.95Sn0.05Te)0.92(PbS)0.08-0.055% PbI2-SiC nanoparticle (SiCnp) composite thermoelectric specimens were either hot pressed or pulsed electric current sintered (PECS). Bloating (a thermally induced increase in porosity, P, for as-densified specimens) was observed during annealing at temperatures >603 K for hot-pressed specimens and PECS-processed specimens from wet milled powders, but in contrast seven out of seven specimens densified by PECS from dry milled powders showed no observable bloating following annealing at temperatures up to 936 K. In this study, bloating in the specimens was accessed via thermal annealing induced changes in (i) porosity measured by scanning electron microscopy on fractured specimen surfaces, (ii) specimen volume and (iii) elastic moduli. The moduli were measured by resonant ultrasound spectroscopy. SiCnp additions (1-3.5 vol.%) changed the fracture mode from intergranular to transgranular, inhibited grain growth, and limited bloating in the wet milled PECS specimens. Inhibition of bloating likely occurs due to cleaning of contamination from powder particle surfaces via PECS processing which has been reported previously in the literature.

  9. Selective Laser Melting Additive Manufacturing of TiC/AlSi10Mg Bulk-form Nanocomposites with Tailored Microstructures and Properties

    NASA Astrophysics Data System (ADS)

    Gu, Dongdong; Wang, Hongqiao; Chang, Fei; Dai, Donghua; Yuan, Pengpeng; Hagedorn, Yves-Christian; Meiners, Wilhelm

    The nanoscale TiC particle reinforced AlSi10Mg nanocomposite parts were produced by selective laser melting (SLM) additive manufacturing process. The influence of laser energy density (LED) on densification behavior, microstructural evolution, microhardness and wear properties of SLM-processed TiC/AlSi10Mg nanocomposites was studied. It showed that the near fully dense nanocomposite parts (>98% theoretical density) were achieved with increasing the applied LED. The TiC reinforcement in SLM-processed parts experienced a microstructural change from the standard nanoscale particle morphology (the average size 77-93 nm) to the relatively coarsened submicron structure (the mean particle size 154 nm) as the LED increased.The sufficiently high densification rate combined with the homogeneousdistribution of nanoscale TiC reinforcement throughout the matrix led to a high microhardness of 181.2 HV0.2, a considerably low coefficient of friction (COF) of 0.36, and a reduced wear rate of 2.94×10-5 mm3N-1m-1 for SLM-processed TiC/AlSi10Mg nanocomposite parts.

  10. Fracture mode, microstructure and temperature-dependent elastic moduli for thermoelectric composites of PbTe PbS with SiC nanoparticle additions

    SciTech Connect

    Ni, Jennifer E; Case, Eldon D; Hogan, Timophy P.; Trejo, Rosa M; Lara-Curzio, Edgar; Kanatzidis, Mercouri G.

    2013-01-01

    Twenty-six (Pb0.95Sn0.05Te)0.92(PbS)0.08 0.055% PbI2 SiC nanoparticle (SiCnp) composite thermoelectric specimens were either hot pressed or pulsed electric current sintered (PECS). Bloating (a thermally induced increase in porosity, P, for as-densified specimens) was observed during annealing at temperatures >603 K for hot-pressed specimens and PECS-processed specimens from wet milled powders, but in contrast seven out of seven specimens densified by PECS from dry milled powders showed no observable bloating following annealing at temperatures up to 936 K. In this study, bloating in the specimens was accessed via thermal annealing induced changes in (i) porosity measured by scanning electron microscopy on fractured specimen surfaces, (ii) specimen volume and (iii) elastic moduli. The moduli were measured by resonant ultrasound spectroscopy. SiCnp additions (1 3.5 vol.%) changed the fracture mode from intergranular to transgranular, inhibited grain growth, and limited bloating in the wet milled PECS specimens. Inhibition of bloating likely occurs due to cleaning of contamination from powder particle surfaces via PECS processing which has been reported previously in the literature.

  11. Common genetic variants, acting additively, are a major source of risk for autism

    PubMed Central

    2012-01-01

    Background Autism spectrum disorders (ASD) are early onset neurodevelopmental syndromes typified by impairments in reciprocal social interaction and communication, accompanied by restricted and repetitive behaviors. While rare and especially de novo genetic variation are known to affect liability, whether common genetic polymorphism plays a substantial role is an open question and the relative contribution of genes and environment is contentious. It is probable that the relative contributions of rare and common variation, as well as environment, differs between ASD families having only a single affected individual (simplex) versus multiplex families who have two or more affected individuals. Methods By using quantitative genetics techniques and the contrast of ASD subjects to controls, we estimate what portion of liability can be explained by additive genetic effects, known as narrow-sense heritability. We evaluate relatives of ASD subjects using the same methods to evaluate the assumptions of the additive model and partition families by simplex/multiplex status to determine how heritability changes with status. Results By analyzing common variation throughout the genome, we show that common genetic polymorphism exerts substantial additive genetic effects on ASD liability and that simplex/multiplex family status has an impact on the identified composition of that risk. As a fraction of the total variation in liability, the estimated narrow-sense heritability exceeds 60% for ASD individuals from multiplex families and is approximately 40% for simplex families. By analyzing parents, unaffected siblings and alleles not transmitted from parents to their affected children, we conclude that the data for simplex ASD families follow the expectation for additive models closely. The data from multiplex families deviate somewhat from an additive model, possibly due to parental assortative mating. Conclusions Our results, when viewed in the context of results from genome

  12. Effects of the addition of different nitrogen sources in the tequila fermentation process at high sugar concentration.

    PubMed

    Arrizon, J; Gschaedler, A

    2007-04-01

    To study the effect of the addition of different nitrogen sources at high sugar concentration in the tequila fermentation process. Fermentations were performed at high sugar concentration (170 g l(-1)) using Agave tequilana Weber blue variety with and without added nitrogen from different sources (ammonium sulfate; glutamic acid; a mixture of ammonium sulfate and amino acids) during the exponential phase of growth. All the additions increased the fermentation rate and alcohol efficiency. The level of synthesis of volatile compounds depended on the source added. The concentration of amyl alcohols and isobutanol were decreased while propanol and acetaldehyde concentration increased. The most efficient nitrogen sources for fermentation rate were ammonium sulfate and the mixture of ammonium sulfate and amino acids. The level of volatile compounds produced depended upon types of nitrogen. The synthesis of some volatile compounds increased while others decreased with nitrogen addition. The addition of nitrogen could be a strategy for improving the fermentation rate and efficiency in the tequila fermentation process at high sugar Agave tequilana concentration. Furthermore, the sensory quality of the final product may change because the synthesis of the volatile compounds is modified.

  13. Addition of dietary fiber sources to shakes reduces postprandial glycemia and alters food intake.

    PubMed

    Galvão Cândido, Flávia; Silva Ton, Winder Tadeu; Gonçalves Alfenas, Rita de Cássia

    2014-09-15

    Introducción: Obesidad y diabetes de tipo 2 pueden ser controlados por alimentos capaces de modular la ingesta de alimentos y la glucemia. Objetivos: Se investigó si la adición de alimentos fuentes de fibra o fasolamina a batidos puede controlar la ingesta de alimentos y reducir la glucemia posprandial. Métodos: Estudio aleatorizado, simple ciego, de diseño cruzado (ingesta de alimentos:n=22; glucemia:n=10). Cinco batidos con cantidades similares de macronutrientes (C - control batido, SA - salvado de avena batido, L - linaza batido, FB - extracto de frijol blanco batido y PI - harina de plátano no maduro batido) fueron consumidos en cinco días no consecutivos. Las participantes registraron la ingesta de alimentos en las 24 horas subsiguientes. La glucosa en sangre se midió a 0 (inmediatamente antes), 15, 30, 45, 60, 90 y 120 minutos después de la ingestión de cada batido y se calcularon las áreas incrementales bajo las curvas (AIBC). Resultados: En comparación a C, hubo un aumento significativo en la ingesta de fibra después de que el consumo de SA(+17,9g), SL(+19,1g), y PI(+12,6g), y en la grasa después del consumo de SA(+25,4g). Se encontró una reducción no significativa de la ingesta diaria de energía en L (1524kJ, P=0,10) en comparación con C. Hubo una reducción del 43% en el AIBC (P=0,03) en respuesta al consumo PI. Conclusiones: Harina de plátano no maduro reduce la respuesta glucémica posprandial de batidos casi a la mitad. El efecto de salvado de avena y linaza en la ingesta de alimentos requiere mayor investigación en estudios a largo plazo.

  14. Medication is an additional source of phosphate intake in chronic kidney disease patients.

    PubMed

    Sultana, J; Musazzi, U M; Ingrasciotta, Y; Giorgianni, F; Ientile, V; Fontana, A; Minghetti, P; Perrotta, M; Santoro, D; Savica, V; Trifirò, G

    2015-10-01

    Hyperphosphatemia increases the risk of cardiovascular morbidity but the use of medicines as a source of phosphate has not been investigated yet. This study aims to explore the use of absorbable phosphate-containing drugs in CKD patients. Incident CKD patients were identified within the Arianna database (containing data from 158,510 persons in Caserta (Southern Italy) registered with 123 general practitioners) from 2005 to 2011. Drugs prescribed to these patients were classified as phosphate-containing based on the summary of product characteristics (SPC), PubChem and Micromedex. The number and duration of prescriptions for these drugs as well as the overall intake of phosphate were estimated. Out of 1989 CKD patients, 1381 (70%) were prescribed 266 medicinal products containing absorbable phosphate over a median follow-up of 6 years (interquartile range (IQR) = 5.2-6.0). Most patients were prescribed ATC A (650; 47.1%) and C (660; 47.8%) phosphate-containing drug products targeting the gastrointestinal and cardiovascular system for a median of 232 (IQR: 56-656) and 224 (IQR: 56-784) days respectively. Several medications, especially chronically prescribed ones, contain absorbable phosphate. This study's findings confirm the relevance of medicines as a phosphate source for the first time. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Nanoscale η-NiSi formation via ion irradiation of Si/Ni/Si

    NASA Astrophysics Data System (ADS)

    Banu, Nasrin; Satpati, Biswarup; Bhukta, Anjan; Dev, B. N.

    2017-01-01

    Nickel monosilicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node complementary metal-oxide-semiconductor technology. We have investigated the formation of nanoscale NiSi by ion irradiation of Si (˜5 nm)/Ni(˜15 nm)/Si, grown in an ultrahigh vacuum environment. Irradiation was carried out at room temperature with 1 MeV Si+ ions. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed for analysis. With increasing ion fluence, ion beam mixing occurs and more and more Si is incorporated into the Ni layer, and this layer gets amorphized. At an even higher fluence, a recrystallized uniform nickel monosilicide (η-NiSi) layer is formed. Several planar spacings of different Miller indices of η-NiSi have been observed in XRD and TEM. Additionally, an interesting amorphization and recrystallization behavior has been observed in the substrate Si with increasing ion fluence. To our knowledge, this has never been observed in ion irradiation of bare Si in decades of work in this area. This kind of amorphization/recrystallization in Si is apparently Ni-induced. Irradiation displaces Ni and produces a distribution of Ni in amorphized Si. Irradiation at a higher fluence produces two recrystallized Si bands in amorphous Si with concomitant accumulation of Ni at the amorphous/crystalline interfaces. On a further increase in irradiation fluence, the recrystallized Si bands again pass through amorphization and recrystallization. The total thickness of recrystallized, as well as amorphous Si, shows an oscillatory behavior as a function of ion fluence.

  16. Reduction of CO2 diffuse emissions from the traditional ceramic industry by the addition of Si-Al raw material.

    PubMed

    González, I; Barba-Brioso, C; Campos, P; Romero, A; Galán, E

    2016-09-15

    The fabrication of ceramics can produce the emission of several gases, denominated exhaust gases, and also vapours resulting from firing processes, which usually contain metals and toxic substances affecting the environment and the health of workers. Especially harmful are the diffuse emissions of CO2, fluorine, chlorine and sulphur from the ceramics industry, which, in highly industrialized areas, can suppose an important emission focus of dangerous effects. Concerning CO2, factories that use carbonate-rich raw materials (>30% carbonates) can emit high concentrations of CO2 to the atmosphere. Thus, carbonate reduction or substitution with other raw materials would reduce the emissions. In this contribution, we propose the addition of Al-shales to the carbonated ceramic materials (marls) for CO2 emission reduction, also improving the quality of the products. The employed shales are inexpensive materials of large reserves in SW-Spain. The ceramic bodies prepared with the addition of selected Al-shale to marls in variable proportions resulted in a 40%-65% CO2 emission reduction. In addition, this research underlines at the same time that the use of a low-price raw material can also contribute to obtaining products with higher added value. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Investigating the addition of SiO₂-CaO-ZnO-Na₂O-TiO₂ bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity.

    PubMed

    Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W

    2015-11-01

    Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability. © The Author(s) 2015.

  18. Cytotoxicity of Au, ZnO and SiO₂ NPs using in vitro assays with mussel hemocytes and gill cells: Relevance of size, shape and additives.

    PubMed

    Katsumiti, Alberto; Arostegui, Inmaculada; Oron, Miriam; Gilliland, Douglas; Valsami-Jones, Eugenia; Cajaraville, Miren P

    2016-01-01

    Metal-bearing nanoparticles (NPs) possess unique physico-chemical characteristics that make them useful for an increasing number of industrial products and applications, but could also confer them a higher toxicity due to their higher reactivity compared to bulk forms of the same materials. There is a considerable interest in the use of in vitro techniques in environmentally relevant species, such as marine mussels, to evaluate NPs toxicity. In the present work, mussel hemocytes and gill cells were used to assess the potential toxic effects of Au, ZnO and SiO2 NPs with different sizes and shapes in parallel with their respective ionic and bulk forms and additives used in the NPs preparations. Cytotoxicity (neutral red and MTT assays) was screened at a wide range of concentrations, and LC50 values were calculated. Uptake of fluorescently labeled SIO2 NPs of 27 nm by hemocytes was also investigated. Au, ZnO and SiO2 NPs were less toxic than the corresponding ionic forms but more toxic than the bulk forms. ZnO NPs were the most toxic NPs tested which could be related with their capacity to release free ions. SiO2 NPs were not taken up by hemocytes and were not toxic to either hemocytes or gill cells. Size-dependent toxicity was found for Au NPs. Shape influenced the cytotoxicity of ZnO NPs. Finally, the presence of the additives Na-citrate and Ecodis P90 contributed to the toxicity of Au and ZnO NPs, respectively. As a general conclusion, solubility appears to play a key role in NPs toxicity to mussel cells.

  19. Evaluation of lubricating oil preparation procedures for the determination of Al, Ba, Mo, Si and V by high-resolution continuum source FAAS.

    PubMed

    Amorim Filho, Volnei Resta; Gomes Neto, José Anchieta

    2009-01-01

    Microwave-assisted acid decomposition and oil-in-water emulsification were evaluated as sample pretreatment procedures to determine Al, Ba, Mo, Si and V in lubricating oils by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Average recoveries of Al, Ba and V in oil digests (107, 103 and 101%) were close to those obtained for emulsions prepared in kerosene medium (94, 113 and 95%). Average recoveries for Mo were close to 105 and 46% for emulsions and digests, respectively. Improved average recoveries (101%) were obtained for Mo in digests using the analyte addition technique. Silicon was successfully quantified only in digested samples. Limits of quantification for Al, Ba, Mo and V were 1.4, 31.5, 1.5 and 11.4-fold lower than those obtained by line-source FAAS. Enhanced sensitivity, multi-elemental capability, and high sample throughput are among the main advantages of HR-CS FAAS in comparison with the line-source FAAS technique.

  20. Oxidation of ZrB2 and ZrB2-SiC Ceramics With Tungsten Additions (Preprint)

    DTIC Science & Technology

    2009-02-01

    Parthasarathy et al. have developed a mechanistic model that describes both the structural evolution and the rate-limiting steps at various stages of...based on the possibility of modifying the microstructure of the ZrO2 scale (29). Specifically, WO3 forms a eutectic with ZrO2 at ~1275°C...studies on liquid phase sintering of ZrO2 with additions of WO3 were conducted by mixing four, six, or ten mole percent WO3 (99.995%, Aldrich

  1. Wood decomposition in Amazonian hydropower reservoirs: An additional source of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Abril, Gwenaël; Parize, Marcelo; Pérez, Marcela A. P.; Filizola, Naziano

    2013-07-01

    Amazonian hydroelectric reservoirs produce abundant carbon dioxide and methane from large quantities of flooded biomass that decompose anaerobically underwater. Emissions are extreme the first years after impounding and progressively decrease with time. To date, only water-to-air fluxes have been considered in these estimates. Here, we investigate in two Amazonian reservoirs (Balbina and Petit Saut) the fate of above water standing dead trees, by combining a qualitative analysis of wood state and density through time and a quantitative analysis of the biomass initially flooded. Dead wood was much more decomposed in the Balbina reservoir 23 years after flooding than in the Petit Saut reservoir 10 years after flooding. Termites apparently played a major role in wood decomposition, occurring mainly above water, and resulting in a complete conversion of this carbon biomass into CO2 and CH4 at a timescale much shorter than reservoir operation. The analysis of pre-impounding wood biomass reveals that above-water decomposition in Amazonian reservoirs is a large, previously unrecognized source of carbon emissions to the atmosphere, representing 26-45% of the total reservoir flux integrated over 100 years. Accounting for both below- and above-water fluxes, we could estimate that each km2 of Amazonian forest converted to reservoir would emit over 140 Gg CO2-eq in 100 years. Hydropower plants in the Amazon should thus generate 0.25-0.4 MW h per km2 flooded area to produce lower greenhouse gas emissions than gas power plants. They also have the disadvantage to emit most of their greenhouse gases the earliest years of operation.

  2. High Temperature Thermoplastic Additive Manufacturing Using Low-Cost, Open-Source Hardware

    NASA Technical Reports Server (NTRS)

    Gardner, John M.; Stelter, Christopher J.; Yashin, Edward A.; Siochi, Emilie J.

    2016-01-01

    Additive manufacturing (or 3D printing) via Fused Filament Fabrication (FFF), also known as Fused Deposition Modeling (FDM), is a process where material is placed in specific locations layer-by-layer to create a complete part. Printers designed for FFF build parts by extruding a thermoplastic filament from a nozzle in a predetermined path. Originally developed for commercial printers, 3D printing via FFF has become accessible to a much larger community of users since the introduction of Reprap printers. These low-cost, desktop machines are typically used to print prototype parts or novelty items. As the adoption of desktop sized 3D printers broadens, there is increased demand for these machines to produce functional parts that can withstand harsher conditions such as high temperature and mechanical loads. Materials meeting these requirements tend to possess better mechanical properties and higher glass transition temperatures (Tg), thus requiring printers with high temperature printing capability. This report outlines the problems and solutions, and includes a detailed description of the machine design, printing parameters, and processes specific to high temperature thermoplastic 3D printing.

  3. Sump additives as a source of bioaerosols in a school building.

    PubMed

    Thorne, P S

    1993-04-01

    An investigation was launched following complaints of poor air quality and building-related illness in a public elementary school. Occlusion of air intakes put the building under negative pressure and caused vents from a below-ground sump to become air intakes. Outside air drawn through the sump pit traveled into the adjacent main air handling unit and was disseminated throughout the building. Sump additives introduced in an attempt to counteract foul odors contained spores of Bacillus species, which appeared as bioaerosols throughout the school. Viable microbial sampling identified B subtilis, B cereus, and B licheniformis in the sump room and classrooms at levels as high as 760 colony forming units/m3 (CFU/m3). Concentrations of CO2 in classrooms were 1250 ppm, indicating inadequate makeup air. Remediation was accomplished by opening the air intakes, isolating the sump room from the air handling system, venting the sump to the outside, and flushing the sump with fresh water on a regular basis.

  4. The influence of Si addition in 55AlZn bath on the coating structures obtained in the batch hot-dip metallization

    NASA Astrophysics Data System (ADS)

    Mendala, J.

    2011-05-01

    One of the methods of increasing the corrosion resistance of zinc coatings is the application of zinc and aluminium alloy baths in the metallization process. The coatings obtained are characterized by much better corrosion resistance thanks to the combination of aluminium properties, i.e. the barrier protection provided by naturally created aluminium oxides, with the capacity to protect the steel substrate, which is characteristic of zinc coatings. Zinc coatings with 55 wt. % Al and an addition of Si have gained industrial importance. The introduction of a third alloying component into the metallization bath is a technological addition, the aim of which is to reduce and possibly inhibit the aluminium diffusion towards the substrate. The article presents the results of the examination of coatings obtained in a 55AlZn bath at varied parameters of the technological process, as well as the specification of silicon addition influence on the structure and chemical composition of the coatings, and on the kinetics of growth. The coatings were obtained in three temperatures: 620, 640 and 660°C, and the process was conducted in a 55 wt. % Al bath with Si content of 0, 0.8 and 1.6 wt. % respectively, the remaining content was Zn. For the purposes of evaluating the microstructure and thickness of the coatings obtained, examinations on a light microscope were conducted. In order to determine the chemical composition of the coatings obtained, an EDS analysis was conducted. Quantitative examination of the chemical composition was carried out on the selected cross-sections of samples with coatings considered to be representative ones, using a SEM with a microanalysis system. Moreover, the linear distribution of elements on the cross-sections of the chosen coatings was determined. It is possible to state that the addition of silicon to 55AlZn baths allows reducing the uncontrolled growth of a layer. The layers obtained are more uniform, continuous and they show good adhesion to

  5. Growth of Hexagonal Columnar Nanograin Structured SiC Thin Films on Silicon Substrates with Graphene–Graphitic Carbon Nanoflakes Templates from Solid Carbon Sources

    PubMed Central

    Liu, Xingfang; Sun, Guosheng; Liu, Bin; Yan, Guoguo; Guan, Min; Zhang, Yang; Zhang, Feng; Chen, Yu; Dong, Lin; Zheng, Liu; Liu, Shengbei; Tian, Lixin; Wang, Lei; Zhao, Wanshun; Zeng, Yiping

    2013-01-01

    We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition system (LPCVD). The GGNs are small plates with lateral sizes of around 100 nm and overlap each other, and are made up of nanosized multilayer graphene and graphitic carbon matrix (GCM). Long and straight SiC nanograins with hexagonal shapes, and with lateral sizes of around 200–400 nm are synthesized on the GGNs, which form compact SiC thin films. PMID:28809227

  6. Mo/Si multilayer-coated amplitude-division beam splitters for XUV radiation sources

    PubMed Central

    Sobierajski, Ryszard; Loch, Rolf Antonie; van de Kruijs, Robbert W. E.; Louis, Eric; von Blanckenhagen, Gisela; Gullikson, Eric M.; Siewert, Frank; Wawro, Andrzej; Bijkerk, Fred

    2013-01-01

    Amplitude-division beam splitters for XUV radiation sources have been developed and extensively characterized. Mo/Si multilayer coatings were deposited on 50 nm-thick SiN membranes. By changing the multilayer structure (periodicity, number of bilayers, etc.) the intensity of the reflected and transmitted beams were optimized for selected incident radiation parameters (wavelength, incident angle). The developed optical elements were characterized by means of XUV reflectometry and transmission measurements, atomic force microscopy and optical interferometry. Special attention was paid to the spatial homogeneity of the optical response and reflected beam wavefront distortions. Here the results of the characterization are presented and improvements required for advanced applications at XUV free-electron lasers are identified. A flatness as low as 4 nm r.m.s. on 3 × 3 mm beam splitters and 22 nm r.m.s. on 10 × 10 mm beam splitters has been obtained. The high-spatial-frequency surface roughness was about 0.7–1 nm r.m.s. The middle-spatial-frequency roughness was in the range 0.2–0.8 nm r.m.s. The reflection and transmission of the beam splitters were found to be very homogeneous, with a deviation of less than 2% across the full optical element. PMID:23412481

  7. Source Distribution Method for Unsteady One-Dimensional Flows With Small Mass, Momentum, and Heat Addition and Small Area Variation

    NASA Technical Reports Server (NTRS)

    Mirels, Harold

    1959-01-01

    A source distribution method is presented for obtaining flow perturbations due to small unsteady area variations, mass, momentum, and heat additions in a basic uniform (or piecewise uniform) one-dimensional flow. First, the perturbations due to an elemental area variation, mass, momentum, and heat addition are found. The general solution is then represented by a spatial and temporal distribution of these elemental (source) solutions. Emphasis is placed on discussing the physical nature of the flow phenomena. The method is illustrated by several examples. These include the determination of perturbations in basic flows consisting of (1) a shock propagating through a nonuniform tube, (2) a constant-velocity piston driving a shock, (3) ideal shock-tube flows, and (4) deflagrations initiated at a closed end. The method is particularly applicable for finding the perturbations due to relatively thin wall boundary layers.

  8. Optimizing external carbon source addition in domestics wastewater treatment based on online sensoring data and a numerical model.

    PubMed

    Wang, Qibin; Chen, Qiuwen; Chen, Jing

    2017-06-01

    The removal of total nitrogen in wastewater treatment plants (WWTPs) is often unsatisfactory for a variety of reasons. One possible measure to improve nitrogen removal is the addition of external carbon. However, the amount of carbon addition is directly related to WWTP operation costs, highlighting the importance of accurately determining the amount of external carbon required. The objective of this study was to obtain a low nitrate concentration in the anoxic zone of WWTPs efficiently and economically by optimizing the external carbon source dosage. Experiments were conducted using a pilot-scale pre-denitrification reactor at a Nanjing WWTP in China. External carbon source addition based on online monitoring of influent wastewater quality and a developed nitrification-denitrification numerical model was investigated. Results showed that carbon addition was reduced by 47.7% and aeration costs were reduced by 8.0% compared with those using a fixed-dose addition mode in the pilot reactor. The obtained technology was applied to the full-scale Jiangxinzhou WWTP in Nanjing with promising results.

  9. High-rate RPECVD of a-Si:H films by means of a VHF resonant plasma source

    SciTech Connect

    Blum, T.; Suchaneck, G.; Kuske, J.; Stephan, U.; Kottwitz, A.; Beyer, W.

    1996-12-31

    Thin film polycrystalline silicon on large-area glass substrate is a promising material for low-cost high efficiency solar cells. High deposition rate (up to 5 nm/s) a-Si:H films suitable for recrystallization were deposited using a {lambda}/4 helical resonator source. Refractive index, Tauc-gap, photo- and dark conductivities were measured for film characterization. The metastable behavior was characterized by the light-induced degradation of the photoconductivity. Hydrogen content and bonding configuration were analyzed by IR absorption and mass separated thermal fusion transients, film microstructure was studied by intentionally incorporating carbon and oxygen. Most of the hydrogen is located on internal surfaces in the otherwise dense material. Differences between the deposition from the highly excited plasma and the conventional remote PECVD process are discussed.

  10. Direct Growth of CdTe on a (211) Si Substrate with Vapor Phase Epitaxy Using a Metallic Cd Source

    NASA Astrophysics Data System (ADS)

    Iso, Kenji; Gokudan, Yuya; Shiraishi, Masumi; Murakami, Hisashi; Koukitu, Akinori

    2017-10-01

    We successfully performed epitaxial CdTe growth on a Si (211) substrate with vapor-phase epitaxy using a cost-effective metallic cadmium source as a group-II precursor. The thermodynamic data demonstrate that the combination of metallic Cd and diisopropyl-telluride (DiPTe) with a H2 carrier gas enables the growth of CdTe crystals. A CdTe single crystal with a (422) surface orientation was obtained when a growth temperature between 600°C and 650°C was employed. The surface morphology and crystalline quality were improved with increasing film thickness. The full-width at half-maximum of the x-ray rocking curves with a film thickness of 15.7 μm for the skew-symmetrical (422) and asymmetrical (111) reflection were 528 arcsec and 615 arcsec, respectively.

  11. Effect of additional sample bias in Meshed Plasma Immersion Ion Deposition (MPIID) on microstructural, surface and mechanical properties of Si-DLC films

    NASA Astrophysics Data System (ADS)

    Wu, Mingzhong; Tian, Xiubo; Li, Muqin; Gong, Chunzhi; Wei, Ronghua

    2016-07-01

    Meshed Plasma Immersion Ion Deposition (MPIID) using cage-like hollow cathode discharge is a modified process of conventional PIID, but it allows the deposition of thick diamond-like carbon (DLC) films (up to 50 μm) at a high deposition rate (up to 6.5 μm/h). To further improve the DLC film properties, a new approach to the MPIID process is proposed, in which the energy of ions incident to the sample surface can be independently controlled by an additional voltage applied between the samples and the metal meshed cage. In this study, the meshed cage was biased with a pulsed DC power supply at -1350 V peak voltage for the plasma generation, while the samples inside the cage were biased with a DC voltage from 0 V to -500 V with respect to the cage to study its effect. Si-DLC films were synthesized with a mixture of Ar, C2H2 and tetramethylsilane (TMS). After the depositions, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy and nanoindentation were used to study the morphology, surface roughness, chemical bonding and structure, and the surface hardness as well as the modulus of elasticity of the Si-DLC films. It was observed that the intense ion bombardment significantly densified the films, reduced the surface roughness, reduced the H and Si contents, and increased the nanohardness (H) and modulus of elasticity (E), whereas the deposition rate decreased slightly. Using the H and E data, high values of H3/E2 and H/E were obtained on the biased films, indicating the potential excellent mechanical and tribological properties of the films. In this paper, the effects of the sample bias voltage on the film properties are discussed in detail and the optimal bias voltage is presented.

  12. Addition of Si-H and B-H bonds and redox reactivity involving low-coordinate nitrido-vanadium complexes.

    PubMed

    Thompson, Rick; Tran, Ba L; Ghosh, Soumya; Chen, Chun-Hsing; Pink, Maren; Gao, Xinfeng; Carroll, Patrick J; Baik, Mu-Hyun; Mindiola, Daniel J

    2015-03-16

    In this study we enumerate the reactivity for two molecular vanadium nitrido complexes of [(nacnac)V≡N(X)] formulation [nacnac = (Ar)NC(Me)CHC(Me)(Ar)(-), Ar = 2,6-(CHMe2)2C6H3); X(-) = OAr (1) and N(4-Me-C6H4)2 (Ntolyl2) (2)]. Density functional theory calculations and reactivity studies indicate the nitride motif to have nucleophilic character, but where the nitrogen atom can serve as a conduit for electron transfer, thus allowing the reduction of the vanadium(V) metal ion with concurrent oxidation of the incoming substrate. Silane, H2SiPh2, readily converts the nitride ligand in 1 into a primary silyl-amide functionality with concomitant two-electron reduction at the vanadium center to form the complex [(nacnac)V{N(H)SiHPh2}(OAr)] (3). Likewise, addition of the B-H bond in pinacolborane to the nitride moiety in 2 results in formation of the boryl-amide complex [(nacnac)V{N(H)B(pinacol)}(Ntolyl2)] (4). In addition to spectroscopic data, complexes 3 and 4 were also elucidated structurally by single-crystal X-ray diffraction analysis. One-electron reduction of 1 with 0.5% Na/Hg on a preparative scale allowed for the isolation and structural determination of an asymmetric bimolecular nitride radical anion complex having formula [Na]2[(nacnac)V(N)(OAr)]2 (5), in addition to room-temperature solution X-band electron paramagnetic resonance spectroscopic studies.

  13. A comparative study of Si-containing electrolyte additives for lithium ion battery: Which one is better and why is it better

    NASA Astrophysics Data System (ADS)

    Wang, Kang; Xing, Lidan; Zhu, Yunmin; Zheng, Xiongwen; Cai, Dandan; Li, Weishan

    2017-02-01

    Influence of two Si-containing electrolyte additives, tris(trimethylsilyl)borate (TMSB) and tris(trimethylsilyl)phosphate (TMSP), on the cyclic stability of high voltage LiNi0.5Mn1.5O4 electrode has been systematically studied in this work. The capacity retention of LiNi0.5Mn1.5O4 cycling in STD (1M LiPF6/EC: EMC = 3:7), TMSB- and TMSP-containing electrolytes is 23%, 85% and 71% after 600 cycles at 1C rate, respectively, revealing that the ability of TMSB on improving the cyclic performance of LiNi0.5Mn1.5O4 is superior to that of TMSP. Experimental and theoretical characterizations show that the preferential reaction of both TMSB and TMSP generates thin and uniform film on LiNi0.5Mn1.5O4 surface, which effectively suppress the continuous oxidation reaction of electrolyte. While the film generated from TMSB, which contains B and Si-rich compounds, shows better ability on restraining the growth of interfacial resistance during cycling, resulting in better cyclic stability of LiNi0.5Mn1.5O4 than that of TMSP.

  14. Effect of CeO2, MgO and Y2O3 additions on the sinterability of a milled Si3N4 with 14.5 wt% SiO2

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1981-01-01

    The sinterability of alpha Si3N4 with 0-5.07 equivalent per cent of CeO2, MgO, or Y2O3 has been studied in the temperature range 1650-1820 C by density measurements and X-ray diffraction analysis. Maximum densities were obtained in the range 1765-1820 C and were 99.6% of theoretical with 2.5% CeO2; 98.5% of theoretical with 1.24 to 1.87% MgO, and 99.2% of theoretical with 2.5% Y2O3. Densities 94% or more of theoretical value were obtained with as little as 0.62 equivalent per cent additive.

  15. Effect of powder characteristics on gas-pressure sintering of Si{sub 3}N{sub 4} with rare earth additives

    SciTech Connect

    Tiegs, T.N.; Nunn, S.D.; Walls, C.A.; Barker, D.; Davisson, C.; Jones, P.J.

    1993-09-01

    Several Si{sub 3}N{sub 4} powders, synthesized by various methods and having different surface areas, oxygen contents and impurity levels, were examined. During early stage densification, all powders showed similar shrinkage with the diimide ederived powder exhibiting delayed {alpha}/{beta} transformation compared to the other powders. The diimide and gas-phase derived powders achieved the highest final densities. Improved densification was observed by increasing the oxygen content and this also resulted in high toughness for some materials with rare earth apatite additives. However, the increased oxygen resulted in reduced high temperature strength. Fracture toughnesses (K{sub Ic}) up to 10 MPa{radical}m were obtained for some compositions.

  16. Nonlinear source-filter coupling due to the addition of a simplified vocal tract model for excised larynx experiments

    PubMed Central

    Smith, Benjamin L.; Nemcek, Steven P.; Swinarski, Krzysztof A.; Jiang, Jack J.

    2013-01-01

    Objectives Traditional excised larynx dissection and setup calls for the removal of all supraglottal structures, eliminating any source-filter interactions that measurably affect the acoustic properties of phonation. We introduce a simplified vocal tract model that can be used in excised larynx experiments and tested the nonlinear source-filter interactions that are present with the addition of highly-coupled, supraglottal structures. Methods Aerodynamic and acoustic data were measured at phonation threshold pressure (PTP) and +25% PTP in ten excised canine larynges using a modified dissection technique. PTP and phonation threshold flow (PTF) were defined as the pressure and flow at the phonation onset; phonation threshold power (PTW) is the product of these values. Data were recorded for four experimental conditions: PTP without vocal tract; +25% PTP without vocal tract; PTP with vocal tract; +25% PTP with vocal tract. Differences in PTP, PTF, and PTW were evaluated. For trials conducted at +25%PTP, differences in airflow were evaluated. Results PTP (p = 0.009) and PTW (p = 0.002) were significantly reduced with the addition of the novel vocal tract. A reduction in PTF was also present with the vocal tract (p = 0.021) but airflow was not significantly reduced in +25% PTP trials (p = 0.196). Conclusion The proposed vocal tract can be used with complete larynges when conducting excised larynx experiments. The effects of nonlinear source-filter interaction were observed during trials with the vocal tract, as evidenced by changes in threshold aerodynamic parameters. PMID:23490131

  17. InAs nanowire growth modes on Si (111) by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Robson, M. T.; LaPierre, R. R.

    2016-02-01

    InAs nanowires (NWs) were grown on silicon substrates by gas source molecular beam epitaxy using five different growth modes: (1) Au-assisted growth, (2) positioned (patterned) Au-assisted growth, (3) Au-free growth, (4) positioned Au-assisted growth using a patterned oxide mask, and (5) Au-free selective-area epitaxy (SAE) using a patterned oxide mask. Optimal growth conditions (temperature, V/III flux ratio) were identified for each growth mode for control of NW morphology and vertical NW yield. The highest yield (72%) was achieved with the SAE method at a growth temperature of 440 °C and a V/III flux ratio of 4. Growth mechanisms are discussed for each of the growth modes.

  18. Modeling the Effect of External Carbon Source Addition under Different Electron Acceptor Conditions in Biological Nutrient Removal Activated Sludge Systems.

    PubMed

    Hu, Xiang; Wisniewski, Kamil; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

    2016-02-16

    The aim of this study was to expand the International Water Association Activated Sludge Model No. 2d (ASM2d) to predict the aerobic/anoxic behavior of polyphosphate accumulating organisms (PAOs) and "ordinary" heterotrophs in the presence of different external carbon sources and electron acceptors. The following new aspects were considered: (1) a new type of the readily biodegradable substrate, not available for the anaerobic activity of PAOs, (2) nitrite as an electron acceptor, and (3) acclimation of "ordinary" heterotrophs to the new external substrate via enzyme synthesis. The expanded model incorporated 30 new or modified process rate equations. The model was evaluated against data from several, especially designed laboratory experiments which focused on the combined effects of different types of external carbon sources (acetate, ethanol and fusel oil) and electron acceptors (dissolved oxygen, nitrate and nitrite) on the behavior of PAOs and "ordinary" heterotrophs. With the proposed expansions, it was possible to improve some deficiencies of the ASM2d in predicting the behavior of biological nutrient removal (BNR) systems with the addition of external carbon sources, including the effect of acclimation to the new carbon source.

  19. Si/SiC-based DD hetero-structure IMPATTs as MM-wave power-source: a generalized large-signal analysis

    NASA Astrophysics Data System (ADS)

    Mukherjee, Moumita; Tripathy, P. R.; Pati, S. P.

    2015-06-01

    A full-scale, self-consistent, non-linear, large-signal model of double-drift hetero-structure IMPATT diode with general doping profile is derived. This newly developed model, for the first time, has been used to analyze the large-signal characteristics of hexagonal SiC-based double-drift IMPATT diode. Considering the fabrication feasibility, the authors have studied the large-signal characteristics of Si/SiC-based hetero-structure devices. Under small-voltage modulation (∼ 2%, i.e. small-signal conditions) results are in good agreement with calculations done using a linearised small-signal model. The large-signal values of the diode's negative conductance (5 × 106 S/m2), susceptance (10.4 × 107 S/m2), average breakdown voltage (207.6 V), and power generating efficiency (15%, RF power: 25.0 W at 94 GHz) are obtained as a function of oscillation amplitude (50% of DC breakdown voltage) for a fixed average current density. The large-signal calculations exhibit power and efficiency saturation for large-signal (> 50%) voltage modulation and thereafter decrease gradually with further increasing voltage-modulation. This generalized large-signal formulation is applicable for all types of IMPATT structures with distributed and narrow avalanche zones. The simulator is made more realistic by incorporating the space-charge effects, realistic field and temperature dependent material parameters in Si and SiC. The electric field snap-shots and the large-signal impedance and admittance of the diode with current excitation are expressed in closed loop form. This study will act as a guide for researchers to fabricate a high-power Si/SiC-based IMPATT for possible application in high-power MM-wave communication systems.

  20. Growth processes in the initial stage of Ge films on (811)Si surfaces by GeH4 source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Koide, Y.; Zaima, S.; Itoh, K.; Ohshima, N.; Yasuda, Y.

    1990-09-01

    The growth process in the initial stage of growth of Ge films on (811)Si substrate surfaces by GeH4 source molecular-beam epitaxy has been studied by in situ reflection high-energy electron diffraction observation. It has been found that a strained film by the monolayer overgrowth mode is formed initially with an epitaxial relationship of the parallel orientation, and that plate-shaped Ge islands with (811) facets are grown early in the growth, but that the predominant facet changes to {311} and the (100) planes with further growth. These growth processes are similar to those of Ge films on (100)Si surfaces reported previously. It is concluded that Ge islands with {811} facets are energetically stable in the initial stage of the island growth on the (811)Si surfaces as well as on the (100)Si surfaces.

  1. On the extraction of the external drain and source resistors and effective channel length in Si-MOSFET

    NASA Astrophysics Data System (ADS)

    Joodaki, M.

    2015-09-01

    This paper focuses on the extraction of drain/source resistance and effective channel length (Leff) of the silicon MOSFET in the linear drain current region. Leff is expressed as a function of drain/source resistance, drain current, threshold voltage, drain voltage, and body-effect coefficient. Using this definition, an additional component of drain/source resistance in the linear drain current region, inversion charge reduction resistance (RΔQ), is introduced which results from the influence of drain/source resistors, internal source/body voltage and drain voltage on the total inversion charge. Finally, a new method for extraction of the drain/source resistance is developed. In this method several parameters that have impact on device behavior are considered. The parameters include gate voltage dependency, short channel effects, and poly gate length dependency. The results presented here are not only very useful for accurate device modeling and characterization, but are also vital to better understanding of the device physics. Furthermore, they can describe shortcomings of the other methods which use devices of different gate lengths. The extracted linear model provides less than 1.07% and 3.3% average absolute error and maximum error, respectively, for all seven devices under test over the gate voltage range of 0.75-2 V.

  2. On the Additional Absorption of Radio Emission from Discrete Cosmic Sources Under HF Modification of the Lower Ionosphere

    NASA Astrophysics Data System (ADS)

    Bezrodny, V. G.; Charkina, O. V.; Yampolski, Yu. M.

    2015-12-01

    The possibilities of modification of a weakly ionized plasma are investigated theoretically and experimentally within different electron density behavior models. The dependence of the additional absorption of radiation of discreet cosmic sources Cassiopeia A and Cygnus A in the artificially disturbed ionospheric D-region on the amplitude of heating signal during the special measuring campaigns of February and October 2008 has been analyzed. The ionosphere has been modified with using the world most powerful HAARP heater, Alaska, USA. The 64 beam riometer located in the immediate vicinity of the heater was used as the recording system.

  3. Effect of cerium addition on casting/chill interfacial heat flux and casting surface profile during solidification of Al-14%Si alloy

    NASA Astrophysics Data System (ADS)

    Vijeesh, V.; Prabhu, K. N.

    2016-03-01

    In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (Ra) and arithmetical mean of the absolute departures of the waviness profile from the centre line (Wa) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35µm and 13µm respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.

  4. Analysis of the effect of sidewall on the performance of 6H-SiC Schottky barrier source/drain NMOSFETs

    NASA Astrophysics Data System (ADS)

    Tang, Xiao-Yan; Zhang, Yi-Men; Zhang, Yu-Ming; Gao, Jin-Xia

    2004-07-01

    Between source/drain and gate of SiC Schottky barrier source/drain MOSFET (SiC SBSD-MOSFET), there must be a sidewall as isolation. The width of sidewall strongly affects on the device performance. In this paper the effect of sidewall on the performance of 6H-SiC SBSD-NMOSFET is simulated with the 2D simulator MEDICI. The simulated results show that a sidewall with width less than 0.1mum slightly affects the device performance. However, when the width of sidewall exceeds 0.1mum, the conduction does not occur until the drain voltage is high enough and saturation current sharply decreases. The effect of the sidewall on device performance can be reduced by decreasing the doping concentration in the epitaxial layer.

  5. Si1-yGey or Ge1-zSnz Source/Drain Stressors on Strained Si1-xGex-Channel P-Type Field-Effect Transistors: A Technology Computer-Aided Design Study

    NASA Astrophysics Data System (ADS)

    Eneman, Geert; De Keersgieter, An; Witters, Liesbeth; Mitard, Jerome; Vincent, Benjamin; Hikavyy, Andriy; Loo, Roger; Horiguchi, Naoto; Collaert, Nadine; Thean, Aaron

    2013-04-01

    The interaction between two stress techniques, strain-relaxed buffers (SRBs) and epitaxial source/drain stressors, is studied on short, Si1-xGex- and Ge-channel planar transistors. This work focuses on the longitudinal channel stress generated by these two techniques. Unlike for unstrained silicon-channel transistors, for strained channels on top of a strain-relaxed buffer a source/drain stressor without recess generates similar longitudinal channel stress than source/drain stressors with a deep recess. The least efficient stress transfer is obtained for source/drain stressors with a small recess that removes only the strained channel, not the substrate underneath. These trends are explained by a trade-off between elastic relaxation of the strained-channel during source/drain recess and the increased stress generation of thicker source/drain stressors. For Ge-channel pFETs, GeSn source/drains and Si1-xGex strain-relaxed buffers are efficient stressors for mobility enhancement. The former is more efficient for gate-last schemes than for gate-first, while the stress generated by the SRB is found to be independent of the gate-scheme.

  6. Precise Perforation and Scalable Production of Si Particles from Low-Grade Sources for High-Performance Lithium Ion Battery Anodes.

    PubMed

    Zong, Linqi; Jin, Yan; Liu, Chang; Zhu, Bin; Hu, Xiaozhen; Lu, Zhenda; Zhu, Jia

    2016-11-09

    Alloy anodes, particularly silicon, have been intensively pursued as one of the most promising anode materials for the next generation lithium-ion battery primarily because of high specific capacity (>4000 mAh/g) and elemental abundance. In the past decade, various nanostructures with porosity or void space designs have been demonstrated to be effective to accommodate large volume expansion (∼300%) and to provide stable solid electrolyte interphase (SEI) during electrochemical cycling. However, how to produce these building blocks with precise morphology control at large scale and low cost remains a challenge. In addition, most of nanostructured silicon suffers from poor Coulombic efficiency due to a large surface area and Li ion trapping at the surface coating. Here we demonstrate a unique nanoperforation process, combining modified ball milling, annealing, and acid treating, to produce porous Si with precise and continuous porosity control (from 17% to 70%), directly from low cost metallurgical silicon source (99% purity, ∼ $1/kg). The produced porous Si coated with graphene by simple ball milling can deliver a reversible specific capacity of 1250 mAh/g over 1000 cycles at the rate of 1C, with Coulombic efficiency of first cycle over 89.5%. The porous networks also provide efficient ion and electron pathways and therefore enable excellent rate performance of 880 mAh/g at the rate of 5C. Being able to produce particles with precise porosity control through scalable processes from low-grade materials, it is expected that this nanoperforation may play a role in the next generation lithium ion battery anodes, as well as many other potential applications such as optoelectronics and thermoelectrics.

  7. Effect of Nano-Si3N4 Additives and Plasma Treatment on the Dry Sliding Wear Behavior of Plasma Sprayed Al2O3-8YSZ Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Gou, Junfeng; Zhang, Jian; Zhang, Qiwen; Wang, You; Wang, Chaohui

    2017-04-01

    In this paper, the effect of nano-Si3N4 additives and plasma treatment on the wear behavior of Al2O3-8YSZ ceramic coatings was studied. Nano-Al2O3, nano-8YSZ (8 wt.% Y2O3-stabilized ZrO2) and nano-Si3N4 powders were used as raw materials to fabricate four types of sprayable feedstocks. Plasma treatment was used to improve the properties of the feedstocks. The surface morphologies of the ceramic coatings were observed. The mechanical properties of the ceramic coatings were measured. The dry sliding wear behavior of the Al2O3-8YSZ coatings with and without Si3N4 additives was studied. Nano-Si3N4 additives and plasma treatment can improve the morphologies of the coatings by prohibiting the initiation of micro-cracks and reducing the unmelted particles. The hardness and bonding strength of AZSP (Al2O3-18 wt.% 8YSZ-10 wt.% Si3N4-plasma treatment) coating increased by 79.2 and 44% compared to those of AZ (Al2O3-20 wt.% 8YSZ) coating. The porosity of AZSP coating decreased by 85.4% compared to that of AZ coating. The wear test results showed that the addition of nano-Si3N4 and plasma treatment could improve the wear resistance of Al2O3-8YSZ coatings.

  8. Effect of Nano-Si3N4 Additives and Plasma Treatment on the Dry Sliding Wear Behavior of Plasma Sprayed Al2O3-8YSZ Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Gou, Junfeng; Zhang, Jian; Zhang, Qiwen; Wang, You; Wang, Chaohui

    2017-02-01

    In this paper, the effect of nano-Si3N4 additives and plasma treatment on the wear behavior of Al2O3-8YSZ ceramic coatings was studied. Nano-Al2O3, nano-8YSZ (8 wt.% Y2O3-stabilized ZrO2) and nano-Si3N4 powders were used as raw materials to fabricate four types of sprayable feedstocks. Plasma treatment was used to improve the properties of the feedstocks. The surface morphologies of the ceramic coatings were observed. The mechanical properties of the ceramic coatings were measured. The dry sliding wear behavior of the Al2O3-8YSZ coatings with and without Si3N4 additives was studied. Nano-Si3N4 additives and plasma treatment can improve the morphologies of the coatings by prohibiting the initiation of micro-cracks and reducing the unmelted particles. The hardness and bonding strength of AZSP (Al2O3-18 wt.% 8YSZ-10 wt.% Si3N4-plasma treatment) coating increased by 79.2 and 44% compared to those of AZ (Al2O3-20 wt.% 8YSZ) coating. The porosity of AZSP coating decreased by 85.4% compared to that of AZ coating. The wear test results showed that the addition of nano-Si3N4 and plasma treatment could improve the wear resistance of Al2O3-8YSZ coatings.

  9. Influence of ternary addition of transition elements (Cr, Si and Mn) on the microstructure and magnetic properties of nano-structured CuCo alloy

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Chabri, S.; Basumallick, A.; Chattopadhyay, P. P.

    2012-09-01

    The current state of studies presents the effect of ternary addition of transition elements such as Mn, Cr and Si (10 wt%) on the mechanically driven non-equilibrium solubility of 40 wt% Co containing Cu-Co alloy. X-ray powder diffraction analysis indicates that addition of Mn has been found to be the most effective in enhancing the solubility and formation of a complete solid solution between Co and Cu in a short duration (30 h) of ball milling. The microstructure of the ball milled CuCoMn alloy was found to be stable after the isothermal annealing up to a temperature of 450 °C for 1 h. The magnetic properties such as magnetic saturation, coercivity and remanence of ball milled CuCo alloy in the presence of Mn significantly altered after annealing in the temperature range 350-650 °C for 1 h. The best combination of magnetic properties of CuCoMn alloy has been found after annealing at 550 °C for 1 h.

  10. Large-scale sequencing reveals 21U-RNAs and additional microRNAs and endogenous siRNAs in C. elegans.

    PubMed

    Ruby, J Graham; Jan, Calvin; Player, Christopher; Axtell, Michael J; Lee, William; Nusbaum, Chad; Ge, Hui; Bartel, David P

    2006-12-15

    We sequenced approximately 400,000 small RNAs from Caenorhabditis elegans. Another 18 microRNA (miRNA) genes were identified, thereby extending to 112 our tally of confidently identified miRNA genes in C. elegans. Also observed were thousands of endogenous siRNAs generated by RNA-directed RNA polymerases acting preferentially on transcripts associated with spermatogenesis and transposons. In addition, a third class of nematode small RNAs, called 21U-RNAs, was discovered. 21U-RNAs are precisely 21 nucleotides long, begin with a uridine 5'-monophosphate but are diverse in their remaining 20 nucleotides, and appear modified at their 3'-terminal ribose. 21U-RNAs originate from more than 5700 genomic loci dispersed in two broad regions of chromosome IV-primarily between protein-coding genes or within their introns. These loci share a large upstream motif that enables accurate prediction of additional 21U-RNAs. The motif is conserved in other nematodes, presumably because of its importance for producing these diverse, autonomously expressed, small RNAs (dasRNAs).

  11. Nonlinear source-filter coupling due to the addition of a simplified vocal tract model for excised larynx experiments.

    PubMed

    Smith, Benjamin L; Nemcek, Steven P; Swinarski, Krzysztof A; Jiang, Jack J

    2013-05-01

    Traditional excised larynx dissection and setup calls for the removal of all supraglottal structures, eliminating any source-filter interactions that measurably affect the acoustic properties of phonation. We introduce a simplified vocal tract model that can be used in the excised larynx experiments and tested the nonlinear source-filter interactions that are present with the addition of highly coupled, supraglottal structures. Aerodynamic and acoustic data were measured at phonation threshold pressure (PTP) and +25% PTP in 10 excised canine larynges using a modified dissection technique. PTP and phonation threshold flow (PTF) were defined as the pressure and flow at the phonation onset; phonation threshold power (PTW) is the product of these values. Data were recorded for four experimental conditions: PTP without vocal tract; +25% PTP without vocal tract; PTP with vocal tract; and +25% PTP with vocal tract. Differences in PTP, PTF, and PTW were evaluated. For trials conducted at +25% PTP, differences in airflow were evaluated. PTP (P = 0.009) and PTW (P = 0.002) were significantly reduced with the addition of the novel vocal tract. A reduction in PTF was also present with the vocal tract (P = 0.021), but airflow was not significantly reduced in +25% PTP trials (P = 0.196). The proposed vocal tract can be used with complete larynges when conducting excised larynx experiments. The effects of nonlinear source-filter interaction were observed during trials with the vocal tract, as evidenced by changes in threshold aerodynamic parameters. Copyright © 2013 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

  12. Influence of TiB2 Addition on the Precipitation Kinetics in Al-7Si-0.3Mg In Situ TiB2 Composites

    NASA Astrophysics Data System (ADS)

    Nandam, S. H.; Murty, B. S.; Sankaran, S.

    2015-07-01

    Precipitation behavior of the Al-7Si-0.3Mg/TiB2 in situ composites was investigated using differential scanning calorimetry and transmission electron microscopy, and it was found that Si precipitation is accelerated with increase in TiB2 content. Non-isothermal kinetic analysis clearly showed a decrease in the precipitation kinetics of the overaged metastable precipitates in the Mg2Si precipitation sequence.

  13. Xylem-Transported Glucose as an Additional Carbon Source for Leaf Isoprene Formation in Quercus Robur L.

    NASA Astrophysics Data System (ADS)

    Graus, M.; Kreuzwieser, J.; Schnitzler, J.; Wisthaler, A.; Hansel, A.; Rennenberg, H.

    2003-04-01

    Isoprene is emitted from mature, photosynthesizing leaves of many plant species, particularly of trees. Current interest in understanding the biochemical and physiological mechanisms controlling isoprene formation is caused by the important role isoprene plays in atmospheric chemistry. Isoprene reacts with hydroxyl radicals (OH) thereby generating oxidizing agents such as ozone and organic peroxides. Ozone causes significant deterioration in air quality and can pose threats to human health therefore its control is a major goal in Europe and the United States. In recent years, much progress has been made in elucidating the pathways of isoprene biosynthesis. Nevertheless the regulatory mechanisms controlling isoprene emission are not completely understood. Light and temperature appear to be the main factors controlling short-term variations in isoprene emission. Exposure of plants to C-13 labeled carbon dioxide showed instantaneous assimilated carbon is the primary carbon source for isoprene formation. However, variations in diurnal and seasonal isoprene fluxes, which cannot be explained by temperature, light, and leaf development led to the suggestion that alternative carbon sources may exist contributing to isoprene emissions. The aim of the present study was to test whether xylem-transported carbohydrates act as additional sources for isoprene biosynthesis. For this purpose, [U-C-13] alpha-D-glucose was fed to photosynthesizing leaves via the xylem of Quercus robur L. seedlings and the incorporation of glucose derived C-13 into emitted isoprene was monitored in real time using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). A rapid incorporation of C-13 from xylem-fed glucose into single (mass 70) and double (mass 71) C-13 labeled isoprene molecules was observed after a lag phase of approximately 5 to 10 minutes. This incorporation was temperature dependent and was highest (up to 13% C-13 of total carbon emitted as isoprene) at the temperature optimum of

  14. Xylem-transported Glucose as an Additional Carbon Source for Leaf Isoprene Formation in Quercus Robur L.

    NASA Astrophysics Data System (ADS)

    Graus, M.; Wisthaler, A.; Hansel, A.; Kreuzwieser, J.; Rennenberg, H.; Schnitzler, J.

    2002-12-01

    Isoprene is emitted from mature, photosynthesizing leaves of many plant species, particularly of trees. Current interest in understanding the biochemical and physiological mechanisms controlling isoprene formation is caused by the important role isoprene plays in atmospheric chemistry. Isoprene reacts with hydroxyl radicals (OH) thereby generating oxidizing agents such as ozone and organic peroxides. Ozone causes significant deterioration in air quality and can pose threats to human health therefore its control is a major goal in Europe and the United States. In recent years, much progress has been made in elucidating the pathways of isoprene biosynthesis. Nevertheless the regulatory mechanisms controlling isoprene emission are not completely understood. Light and temperature appear to be the main factors controlling short-term variations in isoprene emission. Exposure of plants to 13CO2 showed instantaneous assimilated carbon is the primary carbon source for isoprene formation. However, variations in diurnal and seasonal isoprene fluxes, which cannot be explained by temperature, light, and leaf development led to the suggestion that alternative carbon sources may exist contributing to isoprene emissions. The aim of the present study was to test whether xylem-transported carbohydrates act as additional sources for isoprene biosynthesis. For this purpose, [U-13C]α-D-glucose was fed to photosynthesizing leaves via the xylem of {Quercus} {robur} L. seedlings and the incorporation of glucose derived 13C into emitted isoprene was monitored in real time using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). A rapid incorporation of 13C from xylem-fed glucose into single (mass 70) and double (mass 71) 13C-labeled isoprene molecules was observed after a lag phase of approximately 5 to 10 minutes. This incorporation was temperature dependent and was highest (up to 13 % 13C of total carbon emitted as isoprene) at the temperature optimum of isoprene emission (40 - 42

  15. Ge/Si, Ca/Sr and 87Sr/86Sr tracers of biogeochemical sources and cycling of Si and Ca at the Shale Hills CZO

    NASA Astrophysics Data System (ADS)

    Derry, L. A.; Meek, K.; Sparks, J. P.

    2014-12-01

    Plant uptake and cycling of nutrients is commonly the largest flux of nutrients in terrestrial ecosystems. Hydrologic and other losses are offset by inputs from atmospheric deposition and weathering. We measured elemental and isotopic compositions from soil solution, soil exchange complex, leaves and sapwater from two canopy species, soil and rock samples, and stream and ground waters at the Shale Hills CZO. Xylem fluid and leaf samples have similar Ge/Si < 1 μmo/mol, consistent with fractionation at the root-soil water interface. Ge/Si in soil waters is higher Ge/Si near the surface and increases over the growing season, indicating preferential uptake of Si. Ca/Sr in leaves of Quercus are significantly higher (450±150) than for Acer (200±100), and Ca/Sr is generally higher in leaves than in xylem, consistent with Ca uptake during transpiration. 87Sr/86Sr in both are similar for a given site, implying that the trees access similar pools of Sr and Ca, although there are site-to-site differences. Data on litterfall rates and transpiration rates yield similar estimates of plant cycling of Ca and Si. 87Sr/86Sr in soil solutions from ridgtop and swale sites are well explained by mixing Sr derived from shale and atmospheric deposition. Valley bottom soil solutions and stream and groundwater samples include Sr and Ca derived from dissolution of diagenetic carbonates, found in drill cuttings. A preliminary estimate of the Sr and Ca stream fluxes and isotopic mass balances imply propagation of a carbonate weathering front of ca. 200 m/Ma, faster than previously reported regolith weathering advance rates based on on cosmogenic nuclides and U series (Jin et al., 2010; Ma et al., 2010). These rates are not strictly comparable and differences are at least in part consistent with the greater depth of the carbonate weathering front (Brantley et al, 2013). The data for Ca, Sr, Si and Ge in soil, soil solutions and stream waters reflects the interaction of slower weathering

  16. Additively manufactured MEMS multiplexed coaxial electrospray sources for high-throughput, uniform generation of core-shell microparticles.

    PubMed

    Olvera-Trejo, D; Velásquez-García, L F

    2016-10-18

    This study reports the first MEMS multiplexed coaxial electrospray sources in the literature. Coaxial electrospraying is a microencapsulation technology based on electrohydrodynamic jetting of two immiscible liquids, which allows precise control with low size variation of the geometry of the core-shell particles it generates, which is of great importance in numerous biomedical and engineering applications, e.g., drug delivery and self-healing composites. By implementing monolithic planar arrays of miniaturized coaxial electrospray emitters that work uniformly in parallel, the throughput of the compound microdroplet source is greatly increased, making the microencapsulation technology compatible with low-cost commercial applications. Miniaturized core-shell particle generators with up to 25 coaxial electrospray emitters (25 emitters cm(-2)) were fabricated via stereolithography, which is an additive manufacturing process that can create complex microfluidic devices at a small fraction of the cost per device and fabrication time associated with silicon-based counterparts. The characterization of devices with the same emitter structure but different array sizes demonstrates uniform array operation. Moreover, the data demonstrate that the per-emitter current is approximately proportional to the square root of the flow rate of the driving liquid, and it is independent of the flow rate of the driven liquid, as predicted by the theory. The core/shell diameters and the size distribution of the generated compound microparticles can be modulated by controlling the flow rates fed to the emitters.

  17. Reduction of Methane Emission during Slurry Storage by the Addition of Effective Microorganisms and Excessive Carbon Source from Brewing Sugar.

    PubMed

    Bastami, Mohd Saufi B; Jones, Davey L; Chadwick, David R

    2016-11-01

    Storing livestock manure is the primary stage of manure management where microbial processes and chemical reactions result in the release of methane (CH), nitrous oxide (NO), ammonia (NH), and carbon dioxide (CO). This study examined the reduction of CH emissions from slurry storage under two temperatures (cool [10°C] and warm [30°C]) when a glucose-rich substrate (brewing sugar) and activated effective microorganisms were applied at 10% (w/w) and 5% (v/w), respectively. Brewing sugar addition influenced microbial anaerobic respiration, resulting in a reduction of slurry pH to <5.0, through "self-acidification" caused by lactic acid production. Subsequently, CH emissions were significantly reduced by 87 and 99% in the cool and warm environments, respectively. The effective microorganism treatment did not change the chemical characteristics of the slurry but reduced CH emissions by 17 and 27% ( < 0.05) in the cool and warm environments, respectively. These results suggest that self-acidification after addition of a carbon source may be a promising alternative to slurry acidification using concentrated acids.

  18. Effect of impurities of Fe and Si on the structure and strengthening upon annealing of the Al-0.2% Zr-0.1% Sc alloys with and without Y additive

    NASA Astrophysics Data System (ADS)

    Pozdniakov, A. V.; Aitmagambetov, A. R.; Makhov, S. V.; Napalkov, V. I.

    2017-05-01

    The effect of impurities of Fe and Si on the microstructure and kinetics of the change in the hardness during annealing of the cast Al-0.2% Zr-0.1% Sc and Al-0.2% Zr-0.1% Sc-0.2% Y alloys has been studied. It has been found that the presence of the impurities of Fe and Si in the Al-0.2% Zr-0.1% Sc alloy leads to a partial binding of scandium into the (Al, Fe, Si, Sc) and (Al, Fe, Sc) phases of crystallization origin and to the corresponding depletion of the aluminum solid solution of Sc. It has been shown that as a result, the strengthening is significantly decreases upon annealing. The addition of 0.2% Y into the Al-0.2% Zr-0.1% Sc alloy with impurities of Fe and Si leads to the formation of the Al3Y and (Al, Y, Fe, Si) phases, whereas Sc is completely dissolved in the aluminum solid solution. It has been shown that the addition of Y leads to an increase in the thermal stability of the alloys during annealing at temperatures of 250, 300, and 370°C and eliminates the negative effect of impurities of Fe and Si.

  19. The investigation of effect of organic carbon sources addition in anaerobic-aerobic (low dissolved oxygen) sequencing batch reactor for nutrients removal from wastewaters.

    PubMed

    Zheng, Xiong; Tong, Juan; Li, Hongjing; Chen, Yinguang

    2009-05-01

    The effect of addition of organic carbon sources (acetic acid and waste activated sludge alkaline fermentation liquid) on anaerobic-aerobic (low dissolved oxygen, 0.15-0.45 mg/L) biological municipal wastewater treatment was investigated. The results showed that carbon source addition affected not only the transformations of polyhydroxyalkanoates (PHA), glycogen, nitrogen and phosphorus, but the net removal of nitrogen and phosphorus. The removal efficiencies of TN and TP were, respectively, 61% and 61% without organic carbon source addition, 81% and 95% with acetic acid addition, and 83% and 97% with waste activated sludge alkaline fermentation liquid addition. It seems that the alkaline fermentation liquid of waste biosolids generated in biological wastewater treatment plant can be used to replace acetic acid as an additional carbon source to improve the anaerobic-aerobic (low dissolved oxygen) municipal wastewater nutrients removal although its use was observed to cause a slight increase of effluent BOD and COD concentrations.

  20. Oxidation Resistance, Electrical and Thermal Conductivity, and Spectral Emittance of Fully Dense HfB2 and ZrB2 with SiC, TaSi2, and LaB6 Additives

    DTIC Science & Technology

    2012-01-26

    decreased with increasing SiC concentration. EDS patterns show zirconium along with silicon in the glassy surface layer for the specimen with 15.3 mol... SiC , but only silicon in the glassy layer for the specimen with 29.7 mol% SiC . Glassy surface layer and oxide underlayer thicknesses as a function of...Oxidation of Zirconium Diboride- Silicon Carbide at 1500◦C in a Low Partial Pressure of Oxygen, J. Am. Ceram. Soc., 89 [10] 3240-45 (2006). [7] A. K

  1. Process optimizations to recessed e-SiGe source/drain for performance enhancement in 22 nm all-last high-k/metal-gate pMOSFETs

    NASA Astrophysics Data System (ADS)

    Qin, Changliang; Wang, Guilei; Hong, Peizhen; Liu, Jinbiao; Yin, Huaxiang; Yin, Haizhou; Ma, Xiaolong; Cui, Hushan; Lu, Yihong; Meng, Lingkuan; Xiang, Jinjuan; Zhong, Huicai; Zhu, Huilong; Xu, Qiuxia; Li, Junfeng; Yan, Jian; Zhao, Chao; Radamson, Henry H.

    2016-09-01

    In this paper, the technology of recessed embedded SiGe (e-SiGe) source/drain (S/D) module is optimized for the performance enhancement in 22 nm all-last high-k/metal-gate (HK/MG) pMOSFETs. Different Si recess-etch techniques were applied in S/D regions to increase the strain in the channel and subsequently, improve the performance of transistors. A new recess-etch method consists of a two-step etch method is proposed. This process is an initial anisotropic etch for the formation of shallow trench followed by a final isotropic etch. By introducing the definition of the upper edge distance (D) between the recessed S/D region and the channel region, the process advantage of the new approach is clearly presented. It decreases the value of D than those by conventional one-step isotropic or anisotropic etch of Si. Therefore, the series resistance is reduced and the channel strain is increased, which confirmed by the simulation results. The physical reason of D reducing is analyzed in brief. Applying this recess design, the implant conditions for S/D extension (SDE) are also optimized by using a two-step implantation of BF2 in SiGe layers. The overlap space between doping junction and channel region has great effect on the device's performance. The designed implantation profile decreases the overlap space while keeps a shallow junction depth for a controllable short channel effect. The channel resistance as well as the transfer ID-VG curves varying with different process conditions are demonstrated. It shows the drive current of the device with the optimized SDE implant condition and Si recess-etch process is obviously improved. The change trend of on-off current distributions extracted from a series of devices confirmed the conclusions. This study provides a useful guideline for developing high performance strained PMOS SiGe technology.

  2. Self-catalyzed core-shell GaAs/GaNAs nanowires grown on patterned Si (111) by gas-source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    La, Rui; Liu, Ren; Yao, Weichuan; Chen, Renjie; Jansson, Mattias; Pan, Janet L.; Buyanova, Irina A.; Xiang, Jie; Dayeh, Shadi A.; Tu, Charles W.

    2017-08-01

    We report structural studies on the epitaxial growth of GaAs/GaNAs core-shell nanowires (NWs) on patterned Si (111) substrates by self-catalyzed selective area growth using Gas-Source Molecular Beam Epitaxy. Epitaxial growth conditions were obtained using a combination of dry and time-sensitive wet etching of the SiO2 growth mask and native SiO2 layer, respectively. We found that higher growth temperatures resulted in a higher yield for the epitaxial growth of patterned self-catalyzed GaAs NWs on Si with an optimal temperature of 690 °C. The GaNAs shell growth at 500 °C was found to be conformal and maintained an epitaxial and dislocation-free interface with both the Si substrate and the GaAs nanowire. The micro-photoluminescence (μ-PL) measurement at 6 K revealed two bands peaking at 1.45 and 1.17 eV, which could be emission from the GaAs core and GaNAs shell. Transmission electron microscopy showed the zincblende crystal structure of GaAs and GaAs/GaNAs core-shell NWs with minimal twinning near the base of the GaAs nanowires and at the tips of the GaAs/GaNAs core/shell nanowires. This study illustrates the feasibility of the epitaxial growth of patterned GaAs with dilute nitride shells on Si substrates, which would have potential for Si-friendly intermediate band solar cells and telecom emitters.

  3. Improved dual-energy material discrimination for dual-source CT by means of additional spectral filtration

    PubMed Central

    Primak, A. N.; Ramirez Giraldo, J. C.; Liu, X.; Yu, L.; McCollough, C. H.

    2009-01-01

    The use of additional spectral filtration for dual-energy (DE) imaging using a dual-source CT (DSCT) system was investigated and its effect on the material-specific DEratio was evaluated for several clinically relevant materials. The x-ray spectra, data acquisition, and reconstruction processes for a DSCT system (Siemens Definition) were simulated using information provided by the system manufacturer, resulting in virtual DE images. The factory-installed filtration for the 80 kV spectrum was left unchanged to avoid any further reductions in tube output, and only the filtration for the high-energy spectrum was modified. Only practical single-element filter materials within the atomic number range of 40≤Z≤83 were evaluated, with the aim of maximizing the separation between the two spectra, while maintaining similar noise levels for high- and low-energy images acquired at the same tube current. The differences between mean energies and the ratio of the 140 and 80 kV detector signals, each integrated below 80 keV, were evaluated. The simulations were performed for three attenuation scenarios: Head, body, and large body. The large body scenario was evaluated for the DE acquisition mode using the 100 and 140 kV spectra. The DEratio for calcium hydroxyapatite (simulating bone or calcifications), iodine, and iron were determined for CT images simulated using the modified and factory-installed filtration. Several filter materials were found to perform well at proper thicknesses, with tin being a good practical choice. When image noise was matched between the low- and high-energy images, the spectral difference in mean absorbed energy using tin was increased from 25.7 to 42.7 keV (head), from 28.6 to 44.1 keV (body), and from 20.2 to 30.2 keV (large body). The overlap of the signal spectra for energies below 80 keV was reduced from 78% to 31% (head), from 93% to 27% (body), and from 106% to 79% (large body). The DEratio for the body attenuation scenario increased from 1

  4. Integration of Highly Strained SiGe in Source and Drain with HK and MG for 22 nm Bulk PMOS Transistors

    NASA Astrophysics Data System (ADS)

    Wang, Guilei; Luo, Jun; Qin, Changliang; Liang, Renrong; Xu, Yefeng; Liu, Jinbiao; Li, Junfeng; Yin, Huaxiang; Yan, Jiang; Zhu, Huilong; Xu, Jun; Zhao, Chao; Radamson, Henry H.; Ye, Tianchun

    2017-02-01

    In this study, the integration of SiGe selective epitaxy on source/drain regions and high-k and metal gate for 22 nm node bulk pMOS transistors has been presented. Selective Si1- x Ge x growth (0.35 ≤ × ≤ 0.40) with boron concentration of 1-3 × 1020 cm-3 was used to elevate the source/drain. The main focus was optimization of the growth parameters to improve the epitaxial quality where the high-resolution x-ray diffraction (HRXRD) and energy dispersive spectrometer (EDS) measurement data provided the key information about Ge profile in the transistor structure. The induced strain by SiGe layers was directly measured by x-ray on the array of transistors. In these measurements, the boron concentration was determined from the strain compensation of intrinsic and boron-doped SiGe layers. Finally, the characteristic of transistors were measured and discussed showing good device performance.

  5. Integration of Highly Strained SiGe in Source and Drain with HK and MG for 22 nm Bulk PMOS Transistors.

    PubMed

    Wang, Guilei; Luo, Jun; Qin, Changliang; Liang, Renrong; Xu, Yefeng; Liu, Jinbiao; Li, Junfeng; Yin, Huaxiang; Yan, Jiang; Zhu, Huilong; Xu, Jun; Zhao, Chao; Radamson, Henry H; Ye, Tianchun

    2017-12-01

    In this study, the integration of SiGe selective epitaxy on source/drain regions and high-k and metal gate for 22 nm node bulk pMOS transistors has been presented. Selective Si1-x Ge x growth (0.35 ≤ × ≤ 0.40) with boron concentration of 1-3 × 10(20) cm(-3) was used to elevate the source/drain. The main focus was optimization of the growth parameters to improve the epitaxial quality where the high-resolution x-ray diffraction (HRXRD) and energy dispersive spectrometer (EDS) measurement data provided the key information about Ge profile in the transistor structure. The induced strain by SiGe layers was directly measured by x-ray on the array of transistors. In these measurements, the boron concentration was determined from the strain compensation of intrinsic and boron-doped SiGe layers. Finally, the characteristic of transistors were measured and discussed showing good device performance.

  6. α-SiC nanoscale transit-time diodes: performance of the photo-irradiated terahertz sources at elevated temperature

    NASA Astrophysics Data System (ADS)

    Mukherjee, Moumita; Mazumder, Nilratan; Roy, Sitesh Kumar

    2010-05-01

    The effects of elevated junction temperature on the terahertz (THz) frequency characteristics of α-(hexagonal, 4H and 6H) silicon carbide (SiC) based double-drift region (DDR, p++ p n n++ type) impact ionization avalanche transit-time (IMPATT) devices are studied and compared for the first time through simulation experiments. This study reveals that at 300 K < T < 600 K, a 4H-SiC IMPATT diode may yield 3.5 W of output power (efficiency (η) ~ 8.6%) at 1.3 THz, while its 6H-SiC counterpart can deliver 3 W of output power (η = 6.3%) at 1.2 THz. It is interesting to observe that at elevated temperature, the performance of a 6H-SiC IMPATT diode degrades more in comparison with its 4H-SiC counterpart. These comparative analyses reveal the superiority of 4H-SiC diodes over their 6H-SiC counterparts, and thus establish the potential of the former as a high-power THz IMPATT oscillator even in harsh environments. Mobile space charge effects and the effect of positive series resistance on the high-temperature performance of the THz devices are also simulated, and it is found that series resistance reduces the output power level of the diodes by at least 15.0%. Moreover, the effects of increased junction temperature on the photo-sensitivity of top mounted (TM) and flip chip (FC) α-SiC IMPATTs are also investigated using a modified simulation technique. The device operating frequencies, under TM illumination configuration, shifts upward by at least 40.0 GHz, whereas the operating frequency shifts upward by at least 100.0 GHz under FC illumination configuration. The simulation results and the proposed experimental methodology presented here may be used for realizing optically controlled α-SiC transit-time devices for application in THz communication.

  7. Addition of a worm leachate as source of humic substances in the drinking water of broiler chickens.

    PubMed

    Gomez-Rosales, S; de L Angeles, M

    2015-02-01

    The objective of this research was to evaluate the growth performance, the apparent ileal digestibility of nitrogen and energy, the retention of nutrients and the apparent metabolizable energy corrected to zero nitrogen retention (AMEn) in broiler chickens supplemented with increasing doses of a worm leachate (WL) as a source of humic substances (HS) in the drinking water. In Exp. 1, 140 male broilers were penned individually and assigned to four WL levels (0%, 10%, 20%, and 30%) mixed in the drinking water from 21 to 49 days of age. Water was offered in plastic bottles tied to the cage. In Exp. 2, 600 male broilers from 21 to 49 days of age housed in floor pens were assigned to three levels of WL (0%, 10%, and 20%) mixed in the drinking water. The WL was mixed with tap water in plastic containers connected by plastic tubing to bell drinkers. The results of both experiments were subjected to analysis of variance and polynomial contrasts. In Exp. 1, the daily water consumption was similar among treatments but the consumption of humic, fulvic, and total humic acids increased linearly (p<0.01) as the WL increased in the drinking water. The feed conversion (p<0.01) and the ileal digestibility of energy, the excretion of dry matter and energy, the retention of dry matter, ash and nitrogen and the AMEn showed quadratic responses (p<0.05) relative to the WL levels in drinking water. In Exp. 2, the increasing level of WL in the drinking water had quadratic effects on the final body weight, daily weight gain and feed conversion ratio (p<0.05). The addition of WL as a source of HS in the drinking water had beneficial effects on the growth performance, ileal digestibility of energy, the retention of nutrients as well on the AMEn in broiler chickens; the best results were observed when the WL was mixed at levels of 20% to 30% in the drinking water.

  8. Addition of a Worm Leachate as Source of Humic Substances in the Drinking Water of Broiler Chickens

    PubMed Central

    Gomez-Rosales, S.; de L. Angeles, M.

    2015-01-01

    The objective of this research was to evaluate the growth performance, the apparent ileal digestibility of nitrogen and energy, the retention of nutrients and the apparent metabolizable energy corrected to zero nitrogen retention (AMEn) in broiler chickens supplemented with increasing doses of a worm leachate (WL) as a source of humic substances (HS) in the drinking water. In Exp. 1, 140 male broilers were penned individually and assigned to four WL levels (0%, 10%, 20%, and 30%) mixed in the drinking water from 21 to 49 days of age. Water was offered in plastic bottles tied to the cage. In Exp. 2, 600 male broilers from 21 to 49 days of age housed in floor pens were assigned to three levels of WL (0%, 10%, and 20%) mixed in the drinking water. The WL was mixed with tap water in plastic containers connected by plastic tubing to bell drinkers. The results of both experiments were subjected to analysis of variance and polynomial contrasts. In Exp. 1, the daily water consumption was similar among treatments but the consumption of humic, fulvic, and total humic acids increased linearly (p<0.01) as the WL increased in the drinking water. The feed conversion (p<0.01) and the ileal digestibility of energy, the excretion of dry matter and energy, the retention of dry matter, ash and nitrogen and the AMEn showed quadratic responses (p<0.05) relative to the WL levels in drinking water. In Exp. 2, the increasing level of WL in the drinking water had quadratic effects on the final body weight, daily weight gain and feed conversion ratio (p<0.05). The addition of WL as a source of HS in the drinking water had beneficial effects on the growth performance, ileal digestibility of energy, the retention of nutrients as well on the AMEn in broiler chickens; the best results were observed when the WL was mixed at levels of 20% to 30% in the drinking water. PMID:25557817

  9. In situ sol-gel composition of multicomponent hybrid precursors to luminescent novel unexpected microrod of Y 2SiO 5:Eu 3+ employing different silicate sources

    NASA Astrophysics Data System (ADS)

    Huang, Honghua; Yan, Bing

    2004-12-01

    Y 2SiO 5 doped with Eu 3+ were in situ synthesized by a hybrid precursor assembly sol-gel technology employing four different silicate sources, 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM result shows that there exist some novel unexpected morphological microrod structures owing to using the crosslinking reagents other than TEOS as silicate source. The photoluminescent properties of Y 2SiO 5:Eu 3+ have been studied as a function of Eu 3+ doping concentration. A cross-relaxation process between identical Eu 3+ ions results in the quenching of the 5D 1 emission for high concentration sample.

  10. 77 FR 12226 - Sadex Corp.; Filing of Food Additive Petition (Animal Use); Electron Beam and X-Ray Sources for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-29

    ... Petition (Animal Use); Electron Beam and X-Ray Sources for Irradiation of Poultry Feed and Poultry Feed... regulations be amended to provide for the safe use of electron beam and x-ray sources for irradiation of... use of electron beam and x- ray sources for irradiation of poultry feed and poultry feed ingredients...

  11. Sources and Sinks of Se, As, Si, P and N in an Urban Stream, San Diego Creek, Irvine, California, USA

    NASA Astrophysics Data System (ADS)

    Meixner, T.; Hibbs, B.; Moller, J.; Walker, J.

    2006-05-01

    Continuing concern about arsenic and selenium in the environment has encouraged many studies of the origins and fate of these trace elements in the environment. Few studies have focused on the fate of selenium and arsenic in streams in general and none to our knowledge have focused on urban streams. In this study we integrate field measurements of surface water and groundwater chemical composition, measurements of stream oxidation and reduction conditions with end-member mixture analysis (EMMA) of stream water sources. EMMA was conducted for San Diego Creek at Campus Drive in Irvine California. This creek is heavily impacted by a groundwater nitrogen, selenium and arsenic source. The contaminants are of environmental interest in the basin, nitrogen for eutrophication impacts in the stream and in the receiving water body, Newport Bay, selenium for its ecological impact, and arsenic for its potential impact on drinking water supplies. The potential sources of streamwater to San Diego Creek were urban runoff, agricultural runoff, dilute groundwaters, moderately saline groundwaters and saline groundwaters. Each source water had different chemical compositions in selenium, arsenic, nitrogen species as well as a suite of hydrologically conservative chemical constituents. We used the EMMA results and the estimated end-member contributions to determine potential in-stream losses of non-conservative dissolved chemicals such as selenium, arsenic, silica, nitrogen and phosphorus. The results of this analysis indicate a seasonal pattern of in-stream loss for nitrogen, phosphorus, selenium and silica with greater losses during the summer and smaller losses during the winter. Notably arsenic was not lost during in-stream transport. Additionally while nitrogen showed loss from streamflow throughout the year selenium showed a net input of selenium from in-stream sources during winter months. This result indicates that nitrogen loss in the stream was a true loss while selenium loss

  12. Single-source-precursor synthesis of dense SiC/HfCxN1-x-based ultrahigh-temperature ceramic nanocomposites

    NASA Astrophysics Data System (ADS)

    Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; GuillonPresent Address: Forschungszentrum Jülich, Institut Für Energie-Und Klimaforschung 1: Werkstoffsynthese Und Herstellungsverfahren, Wilhelm-Johnen-Straße, D.-52425 Jülich., Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

    2014-10-01

    A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1-x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1-x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1-x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm-1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm-1.A novel single-source precursor was synthesized by the reaction of an allyl hydrido

  13. Using additional external inputs to forecast water quality with an artificial neural network for contamination event detection in source water

    NASA Astrophysics Data System (ADS)

    Schmidt, F.; Liu, S.

    2016-12-01

    Source water quality plays an important role for the safety of drinking water and early detection of its contamination is vital to taking appropriate countermeasures. However, compared to drinking water, it is more difficult to detect contamination events because its environment is less controlled and numerous natural causes contribute to a high variability of the background values. In this project, Artificial Neural Networks (ANNs) and a Contamination Event Detection Process (CED Process) were used to identify events in river water. The ANN models the response of basic water quality sensors obtained in laboratory experiments in an off-line learning stage and continuously forecasts future values of the time line in an on-line forecasting step. During this second stage, the CED Process compares the forecast to the measured value and classifies it as regular background or event value, which modifies the ANN's continuous learning and influences its forecasts. In addition to this basic setup, external information is fed to the CED Process: A so-called Operator Input (OI) is provided to inform about unusual water quality levels that are unrelated to the presence of contamination, for example due to cooling water discharge from a nearby power plant. This study's primary goal is to evaluate how well the OI fits into the design of the combined forecasting ANN and CED Process and to understand its effects on the online forecasting stage. To test this, data from laboratory experiments conducted previously at the School of Environment, Tsinghua University, have been used to perform simulations highlighting features and drawbacks of this method. Applying the OI has been shown to have a positive influence on the ANN's ability to handle a sudden change in background values, which is unrelated to contamination. However, it might also mask the presence of an event, an issue that underlines the necessity to have several instances of the algorithm run in parallel. Other difficulties

  14. Effect of P addition on glass forming ability and soft magnetic properties of melt-spun FeSiBCuC alloy ribbons

    NASA Astrophysics Data System (ADS)

    Xu, J.; Yang, Y. Z.; Li, W.; Chen, X. C.; Xie, Z. W.

    2016-11-01

    The dependency of phosphorous content on the glass forming ability, thermal stability and soft magnetic properties of Fe83.4Si2B14-xPxCu0.5C0.1 (x=0,1,2,3,4) alloys was investigated. The experimental results showed that the substitution of B by P increased the glass forming ability in this alloy system. The Fe83.4Si2B10P4Cu0.5C0.1 alloy shows a fully amorphous character. Thermal stability of melt-spun ribbons increases and temperature interval between the first and second crystallization peaks enlarges with the increase of P content. And the saturation magnetic flux density (Bs) shows a slight increase with the increase of P content. The Fe83.4Si2B11P3Cu0.5C0.1 nanocrystalline alloy exhibits a high Bs about 200.6 emu/g. The Bs of fully amorphous alloy Fe83.4Si2B10P4Cu0.5C0.1 drops dramatically to 172.1 emu/g, which is lower than that of other nanocrystallines. Low material cost and excellent soft magnetic properties make the FeSiBPCuC alloys promise soft magnetic materials for industrial applications.

  15. Effects of waste eggshells and SiC addition on specific strength and thermal expansion of hybrid green metal matrix composite.

    PubMed

    Sharma, Satpal; Dwivedi, Shashi Prakash

    2017-03-18

    Chicken eggshell waste is an industrial byproduct, and its disposal constitutes a serious environmental hazard. Chicken eggshell can be used in commercial products to produce new materials with low cost and density. Low density material which can sustain at higher temperature is a remarkable area of research. Keeping these facts in the mind, the present investigation aims to study the physical behaviour, specific strength and thermal expansion of AA2014/SiC/carbonized eggshell hybrid green metal matrix composites. Microstructure of hybrid green metal matrix shows that the reinforcement particles (SiC particulates and carbonized eggshells particles) are uniformly distributed in the matrix AA2014 alloy. Specific strength for the composites containing 2.5wt.% SiC and up to 7.5wt.% carbonized eggshell was observed to be higher than that of the other selected composites. While for the same composition (AA2014/2.5% SiC/7.5% carbonized eggshell composites), porosity was observed lower than other selected composites. The results revealed that sample of AA2014/2.5% SiC/7.5% carbonized eggshell showed minimum cross sectional area reduction after the thermal expansion at 450°C among all the selected samples. Overall costs of hybrid metal matrix composites were also calculated.

  16. Study on the lifetime of Mo/Si multilayer optics with pulsed EUV-source at the ETS

    NASA Astrophysics Data System (ADS)

    Schürmann, Mark; Yulin, Sergiy; Nesterenko, Viatcheslav; Feigl, Torsten; Kaiser, Norbert; Tkachenko, Boris; Schürmann, Max C.

    2011-06-01

    As EUV lithography is on its way into production stage, studies of optics contamination and cleaning under realistic conditions become more and more important. Due to this fact an Exposure Test Stand (ETS) has been constructed at XTREME technologies GmbH in collaboration with Fraunhofer IOF and with financial support of Intel Corporation. This test stand is equipped with a pulsed DPP source and allows for the simultaneous exposure of several samples. In the standard set-up four samples with an exposed area larger than 35 mm2 per sample can be exposed at a homogeneous intensity of 0.25 mW/mm2. A recent update of the ETS allows for simultaneous exposures of two samples with intensities up to 1.0 mW/mm2. The first application of this alternative set-up was a comparative study of carbon contamination rates induced by EUV radiation from the pulsed source with contamination rates induced by quasicontinuous synchrotron radiation. A modified gas-inlet system allows for the introduction of a second gas to the exposure chamber. This possibility was applied to investigate the efficiency of EUV-induced cleaning with different gas mixtures. In particular the enhancement of EUV-induced cleaning by addition of a second gas to the cleaning gas was studied.

  17. Field-scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as an oxygen source with moisture and nutrient addition. Appendices. Doctoral thesis

    SciTech Connect

    Miller, R.N.

    1990-01-01

    This document contains appendices regarding a reprint on a field scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as a oxygen source with moisture and nutrient addition.

  18. Addition of SiC Particles to Ag Die-Attach Paste to Improve High-Temperature Stability; Grain Growth Kinetics of Sintered Porous Ag

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Nagao, Shijo; Suganuma, Katsuaki

    2015-10-01

    To improve the high-temperature reliability of sintered Ag joints, three types of silicon carbide particle (SiCp) of different size and morphology were added to Ag micron-flake paste. Quality sintered joints between Cu dummy chips and Cu substrate were obtained at a relatively low temperature (250°C), in air, under low load (0.4 MPa), and 35 MPa die-shear strength was achieved. High-temperature stability was investigated by means of aging tests at 150, 200, and 250°C for 500 h, and by thermal cycling between -50°C and 250°C for up to 170 cycles. The best distribution and compatibility with porous sintered Ag structures was observed for sub-micron SiC particles with an average diameter of 600 nm. After high-temperature storage for 500 h at 250°C, mean Ag grain size of the SiC-containing joints was unchanged whereas that for pure sintered Ag increased from 1.1 to 2.5 μm. Ag joints containing the optimum amount (2 wt.%) of SiCp retained their original strength (20 MPa) after storage at 250°C for 500 h. The shear strength of Ag joints without added SiCp decreased from 27 to 7 MPa after 500 h because of grain growth, which obeyed the classical parabolic law. Grain growth in pure Ag joints is discussed in terms of a temperature-dependent exponent n and activation energy Q. Our SiCp-containing joints resisted the grain growth that induces interfacial cracks during thermal cycling.

  19. Abiologic silicon isotope fractionation between aqueous Si and Fe(III)-Si gel in simulated Archean seawater: Implications for Si isotope records in Precambrian sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Zheng, Xin-Yuan; Beard, Brian L.; Reddy, Thiruchelvi R.; Roden, Eric E.; Johnson, Clark M.

    2016-08-01

    Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope exchange kinetics and equilibrium fractionation factors in systems that are pertinent to Precambrian marine conditions. Using the three-isotope method and an enriched 29Si tracer, a series of experiments were conducted to constrain Si isotope exchange kinetics and fractionation factors between amorphous Fe(III)-Si gel, a likely precursor to Precambrian jaspers and BIFs, and aqueous Si in artificial Archean seawater under anoxic conditions. Experiments were conducted at room temperature, and in the presence and absence of aqueous Fe(II) (Fe(II)aq). Results of this study demonstrate that Si solubility is significantly lower for Fe-Si gel than that of amorphous Si, indicating that seawater Si concentrations in the Precambrian may have been lower than previous estimates. The experiments reached ˜70-90% Si isotope exchange after a period of 53-126 days, and the highest extents of exchange were obtained where Fe(II)aq was present, suggesting that Fe(II)-Fe(III) electron-transfer and atom-exchange reactions catalyze Si isotope exchange through breakage of Fe-Si bonds. All experiments except one showed little change in the instantaneous solid-aqueous Si isotope fractionation factor with time, allowing extraction of equilibrium Si isotope fractionation factors through extrapolation to 100% isotope exchange. The equilibrium 30Si/28Si fractionation between Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -2.30 ± 0.25‰ (2σ) in the absence of Fe(II)aq. In the case where Fe(II)aq was present, which resulted in addition of ˜10% Fe(II) in the final solid, creating a mixed Fe(II)-Fe(III) Si gel, the equilibrium fractionation between Fe(II)-Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -3.23 ± 0.37‰ (2σ). Equilibrium

  20. Observations of SiO toward OMC-1 - A new outflow source 1.5 arcmin south of Orion-KL?

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Friberg, P.

    1987-01-01

    Observations of the J = 2-1 transition of thermal SiO have been carried out toward OMC-1. Approximately 1.5 arcmin south of the KL nebula and IRc2, a new moderately strong source of SiO emission with T(a)-asterisk of about 1 K has been detected. The emission appears to be confined to a region 30 arcsec or less in size and shows evidence of high-velocity wings extending + or - 12-15 km/s from line center, which may indicate the presence of an embedded star in its early stages. The SiO J - 2-1 line was sought at other positions in OMC-1 but was not detected except at (3N, 1E), where a weak narrow line was observed. Derived column densities and abundances at the 1.5-arcmin S, (3N, 1E), and KL positions suggest that SiO formation is favored in regions where outflows and high temperatures are present.

  1. Al( sup 2 P) l brace SiH sub 4 r brace complex and photoreversible oxidative addition/reductive elimination reaction Al( sup 2 P) l brace SiH sub 4 r brace leftrightarrow SiH sub 3 AlH. 1. Al( sup 2 P) l brace SiH sub 4 r brace complex

    SciTech Connect

    Lefcourt, M.A.; Ozin, G.A. )

    1991-04-04

    Matrix-isolation investigations were carried out on samples consisting of individual aluminum atoms dispersed throughout silane (SiH{sub 4})-containing matrices and other related substrate materials at 12 K. UV-vis and EPR spectroscopies helped in the determination of a ground-state complex between {sup 2}P Al atoms and SiH{sub 4} molecules appearing upon matrix formation. The substitution of SiD{sub 4} for SiH{sub 4} caused narrowing of the absorptions associated with aluminum in both the experimental techniques employed, giving further support for the existence of ground-state complex. Further characterization of the complex was aided by results obtained from EPR spectral simulations and a series of ab initio self-consistent-field geometry optimization calculations. The EPR spectral simulations allowed g values, hyperfine splittings, and atomic orbital spin densities to be reported for the complex along with the ab initio results which supported the choice of a three-center, two-electron Al({eta}{sup 2}-SiH{sub 4}) side-on 'agostic' interaction scheme as the most probable bonding picture for the aluminum/silane ground-state complex.

  2. Spark Plasma Sintering of α/β Si3N4 Ceramics with MgO-Al2O3 and MgO-Y2O3 as Sintering Additives

    NASA Astrophysics Data System (ADS)

    Yu, F. L.; Bai, Y.; Han, P. D.; Shi, Q. L.; Ni, S.; Wu, J. H.

    2016-12-01

    In the present work, the α/β Si3N4 ceramics were fabricated by spark plasma sintering (SPS) at 1400-1500 °C for 6 min with 3wt.%MgO + 5wt.%Al2O3 and 3wt.%MgO + 5wt.%Y2O3 as sintering additives. The results showed that the phase composition, microstructure and mechanical properties of α/β Si3N4 ceramics were highly dependent on the type of sintering additive. The incomplete phase transformation from α to β occurred in the presence of an oxynitride (Mg-Al(Y)-Si-O-N) liquid phase. Compared with MgO-Al2O3, MgO-Y2O3 can significantly improve the β conversion rate of as-sintered α/β Si3N4 ceramics. And the as-sintered ceramics using MgO + Al2O3 as sintering additives had higher mechanical properties.

  3. Effect of Si addition on the structural, microstructural and magnetic properties of (Fe70Al30)100-xSix nanostructured powders elaborated by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Hemmous, M.; Guittoum, A.; Kezrane, M.; Boukherroub, N.; Martínez-Blanco, D.; Gorria, P.; Blanco, J. A.; Souami, N.; Fenineche, N.

    2017-10-01

    In the present work, nanocrystalline (Fe70Al30)100-xSix (x = 0, 5, 10, 15 and 20 at.%) powders were prepared by mechanical alloying for a fixed milling time of 72 h. The powder samples were characterized in terms of structural evolution, morphological changes and magnetic behavior. The X-ray diffraction measurements reveal that all the samples are of (bcc) single phase with an average crystallite size less than 22 nm. Besides, the lattice parameter decreases with Si content (x) up to the solubility limit of Si atoms into the α-Fe lattice where it remains independent of the composition. The magnetic data obtained by Vibrating Sample Magnetometer showed that the saturation magnetization decreases monotonously with Si content increasing x, whereas coercivity which not only depends on composition but also on structure of the sample decreases to a minimum of 20.3 Oe at x = 10 at.% and increases abruptly at the higher x value (x = 20 at.%). Mössbauer spectroscopy analyses indicated that the sample with x = 5 at.% exhibits a fully ferromagnetic behavior and that beyond this concentration, the content of the ferromagnetic phase gradually decreases due to the non magnetic nature of Si.

  4. Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt

    NASA Astrophysics Data System (ADS)

    El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

    2014-10-01

    The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside α-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of α-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of

  5. Growth and photoluminescence of self-catalyzed GaP/GaNP core/shell nanowires on Si(111) by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kuang, Y. J.; Sukrittanon, S.; Li, H.; Tu, C. W.

    2012-01-01

    We report a study on self-catalyzed GaP/GaNP core/shell nanowires (NWs) grown on Si(111) by gas-source molecular beam epitaxy. Scanning electron microscopy images show that vertical and uniform GaP NWs and GaP/GaNP core/shell NWs are grown on Si(111). The density ranges from ˜1 × 107 to ˜5 × 108 cm-2 across the substrate. Typical diameters are ˜110 nm for GaP NWs and ˜220 nm for GaP/GaNP NWs. Room temperature photoluminescence (PL) signal from the GaP/GaNP core/shell NWs confirms that N is incorporated in the shell and the average N content is ˜0.9%. The PL low-energy tail is significantly reduced, compared to bulk GaNP.

  6. In situ sol-gel composition of multicomponent hybrid precursor to hexagon-like Zn 2SiO 4:Tb 3+ microcrystalline phosphors with different silicate sources

    NASA Astrophysics Data System (ADS)

    Huang, Honghua; Yan, Bing

    2006-02-01

    Zn 2SiO 4 doped with Tb 3+ were in situ synthesized by a modified sol-gel technology with the assembly hybrid precursor employed four different silicate sources, i.e. 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM result shows that there exist some novel unexpected micromorphological structures of hexagon-like with the dimension of 0.5-1.0 μm. The photoluminescent properties of Zn 2SiO 4:Tb 3+ phosphors have been studied as a function of Tb 3+ doping concentration. Cross-relaxation process between identical Tb 3+ ions results in the quenching of the 5D 3 emission for high concentration sample.

  7. Effect of SiO2 addition on photocatalytic activity, water contact angle and mechanical stability of visible light activated TiO2 thin films applied on stainless steel by a sol gel method

    NASA Astrophysics Data System (ADS)

    Momeni, Mansour; Saghafian, Hasan; Golestani-Fard, Farhad; Barati, Nastaran; Khanahmadi, Amirhossein

    2017-01-01

    Nanostructured N doped TiO2/20%SiO2 thin films were developed on steel surface via sol gel method using a painting airbrush. Thin films then were calcined at various temperatures in a range of 400-600 °C. The effect of SiO2 addition on phase composition and microstructural evolution of N doped TiO2 films were studied using XRD and FESEM. Optical properties, visible light photocatalytic activity, hydrophilic behavior, and mechanical behavior of the films were also investigated by DRS, methylene blue degradation, water contact angle measurements, and nanoscratch testing. Results indicated that the band gap energy of N doped TiO2/SiO2 was increased from 2.93 to 3.09 eV. Crack formation during calcination was also significantly promoted in the composite films. All composite films demonstrated weaker visible light photocatalytic activities and lower mechanical stability in comparison with N doped TiO2 films. Moreover, the N doped TiO2/SiO2 film calcined at 600 °C showed undesirable hydrophilic behavior with a water contact angle of 57° after 31 h of visible light irradiation. Outcomes of the present study reveal some different results to previous reports on TiO2/SiO2 films. In general, we believe the differences in substrate material as well as application in visible light are the main reasons for the above mentioned contradiction.

  8. Luminescence of Nanoporous Si and ALD-Deposited ZnO on Nanoporous Si Substrate

    NASA Astrophysics Data System (ADS)

    Pham, Vuong-Hung; Tam, Phuong Dinh; Dung, Nguyen Huu; Nguyen, Duy-Hung; Huy, Pham Thanh

    2017-08-01

    This paper reports the attempt at synthesizing nanoporous silicon (Si) with a dendritic-like structure and atomic layer deposition (ALD) of ZnO on nanoporous Si to control light emission intensity and emission center by applying an optimum voltage, etching time and thickness of ZnO layer. The dendritic-like structure of nanoporous Si was formed with low etching voltages of 5-10 V. Fourier transform infrared absorption spectra of the nanoporous Si reveals that the intensities of hydride stretching, SiH2 scissor mode and Si-O-Si vibration peak increase with the increasing of etching time. The formation of a thick dendritic-like structure with an increasing SiH2 bond resulted in significant enhancement of luminescence. In addition, the ALD-deposited ZnO layer on nanoporous Si resulted in light emission from both ZnO and nanoporous Si under a single excitation source. These results suggest the potential application of an ALD-deposited ZnO layer on nanoporous Si in designing materials for advanced optoelectronics.

  9. Fabrication and measurement of devices in Si/SiGe nanomembranes

    NASA Astrophysics Data System (ADS)

    Mohr, Robert

    Silicon/silicon-germanium (Si/SiGe) heterostructures are useful as hosts for gated quantum dots. The quality of the as-grown Si/SiGe heterostructure has a large impact on the final quality of the quantum dot as a qubit host. For many years, quantum dots have been fab- ricated on strain-graded heterostructures. Commonly used strain-graded heterostructures inevitably develop plastic defects that lead to interface roughness, crosshatch, and mosaic tilt. All of these factors are sources of disorder in Si/SiGe quantum electronics. In this dissertation, I report the fabrication of Hall bars and gated quantum dots on heterostructures grown on fully elastically relaxed SiGe nanomembranes, rather than strain-graded heterostructures. I report measurements of Hall bars demonstrating the creation of two-dimensional electron gases in these structures. I report the fabrication procedures used to create pairs of Hall bars and quantum dots on individual membranes. In addition, I explain a general process flow for the creation of Si/SiGe quantum devices. I focus especially on an ion-implantation technique I implemented for the fabrication of Hall bars and quantum dots in Si/SiGe heterostructures without modulation doping layers.

  10. Luminescence of Nanoporous Si and ALD-Deposited ZnO on Nanoporous Si Substrate

    NASA Astrophysics Data System (ADS)

    Pham, Vuong-Hung; Tam, Phuong Dinh; Dung, Nguyen Huu; Nguyen, Duy-Hung; Huy, Pham Thanh

    2017-03-01

    This paper reports the attempt at synthesizing nanoporous silicon (Si) with a dendritic-like structure and atomic layer deposition (ALD) of ZnO on nanoporous Si to control light emission intensity and emission center by applying an optimum voltage, etching time and thickness of ZnO layer. The dendritic-like structure of nanoporous Si was formed with low etching voltages of 5-10 V. Fourier transform infrared absorption spectra of the nanoporous Si reveals that the intensities of hydride stretching, SiH2 scissor mode and Si-O-Si vibration peak increase with the increasing of etching time. The formation of a thick dendritic-like structure with an increasing SiH2 bond resulted in significant enhancement of luminescence. In addition, the ALD-deposited ZnO layer on nanoporous Si resulted in light emission from both ZnO and nanoporous Si under a single excitation source. These results suggest the potential application of an ALD-deposited ZnO layer on nanoporous Si in designing materials for advanced optoelectronics.

  11. Determination of europium content in Li2SiO3(Eu) by neutron activation analysis using Am-Be neutron source.

    PubMed

    Naik, Yeshwant; Tapase, Anant Shamrao; Mhatre, Amol; Datrik, Chandrashekhar; Tawade, Nilesh; Kumar, Umesh; Naik, Haladhara

    2016-12-01

    Circulardiscs of Li2SiO3 doped with europium were prepared and a new activation procedure for the neutron dose estimation in a breeder blanket of fusion reactor is described. The amount of europium in the disc was determined by neutron activation analysis (NAA) using an isotopic neutron source. The average neutron absorption cross section for the reaction was calculated using neutron distribution of the Am-Be source and available neutron absorption cross section data for the (151)Eu(n,γ)(152m)Eu reaction, which was used for estimation of europium in the pallet. The cross section of the elements varies with neutron energy, and the flux of the neutrons in each energy range seen by the nuclei under investigation also varies. Neutron distribution spectrum of the Am-Be source was worked out prior to NAA and the effective fractional flux for the nuclear reaction considered for the flux estimation was also determined.

  12. Site selectivity and reversibility in the reactions of titanium hydrazides with Si-H, Si-X, C-X and H+ reagents: Ti=N(α) 1,2-silane addition, Nβ alkylation, Nα protonation and σ-bond metathesis.

    PubMed

    Tiong, Pei Jen; Nova, Ainara; Schwarz, Andrew D; Selby, Jonathan D; Clot, Eric; Mountford, Philip

    2012-02-28

    We report a combined experimental and computational comparative study of the reactions of the homologous titanium dialkyl- and diphenylhydrazido and imido compounds Cp*Ti{MeC(N(i)Pr)(2)}(NNR(2)) (R = Me (1) or Ph (2)) and Cp*Ti{MeC(N(i)Pr)(2)}(NTol) (3) with silanes, halosilanes, alkyl halides and [Et(3)NH][BPh(4)]. Compound 1 underwent reversible Si-H 1,2-addition to Ti=N(α) with RSiH(3) (experimental ΔH ca. -17 kcal mol(-1)), and irreversible addition with PhSiH(2)X (X = Cl, Br). DFT found that the reaction products and certain intermediates were stabilised by β-NMe(2) coordination to titanium. The Ti-D bond in Cp*Ti{MeC(N(i)Pr)(2)}(D){N(NMe(2))SiD(2)Ph} underwent σ-bond metathesis with BuSiH(3) and H(2). Compound 1 reacted with RR'SiCl(2) at N(α) to transfer both Cl atoms to Ti; 2 underwent a similar reaction. Compound 3 did not react with RSiH(3) or alkyl halides but formed unstable Ti=N(α) 1,2-addition or N(α) protonation products with PhSiH(2)X or [Et(3)NH][BPh(4)]. Compound 1 underwent exclusive alkylation at N(β) with RCH(2)X (R = H, Me or Ph; X = Br or I) whereas protonation using [Et(3)NH][BPh(4)] occurred at N(α). DFT studies found that in all cases electrophile addition to N(α) (with or without NMe(2) chelation) was thermodynamically favoured compared to addition to N(β).

  13. Experimental investigation of thermo-optic effects in SiC and Si photonic crystal nanocavities.

    PubMed

    Yamada, Shota; Song, Bong-Shik; Asano, Takashi; Noda, Susumu

    2011-10-15

    We experimentally investigate and compare the thermo-optic effects of silicon carbide (SiC) and silicon (Si) photonic crystal nanocavities on their resonant wavelengths over a temperature range of 25 °C to nearly 200 °C by using a laser source with a wavelength close to the telecommunication wavelength range of 1550 nm. The measured results clearly show that the shift in the resonant wavelength of the SiC cavity is significantly (by a factor of 3) less than that of the Si cavity for the same ambient temperature changes. In addition, the measured results provide direct estimates of the thermo-optic coefficients (dn/dT) for thin SiC and Si as 3.87×10(-5)/°C and 1.60×10(-4)/°C, respectively, for this temperature range.

  14. AlN and AlGaN layers grown on Si(111) substrate by mixed-source hydride vapor phase epitaxy method

    NASA Astrophysics Data System (ADS)

    Jeon, Hunsoo; Jeon, Injun; Lee, Gang Seok; Bae, Sung Geun; Ahn, Hyung Soo; Yang, Min; Yi, Sam Nyung; Yu, Young Moon; Honda, Yoshio; Sawaki, Nobuhiko; Kim, Suck-Whan

    2017-01-01

    High Al-composition AlGaN and AlN epilayers were grown directly on Si(111) substrate by a hydride vapor phase epitaxy (HVPE) method with a melted mixed source in a graphite boat set in a source zone with high temperatures of T = 700 and 800 °C, respectively. The presence of the Ga material in the mixed source of Ga and Al promoted the growth of AlN and AlGaN epilayers in the growth zone. When the temperature in the source zone was 800 °C, the crystalline quality of the AlN and AlGaN epilayers increased as the ratio of Ga to Al increased, and the optimum mix ratio of Ga to Al for the growth of AlN epilayers was approximately 0.35-0.42, obtained from a numerical fitting analysis of the X-ray diffraction (XRD) data for these epilayers. It appears that they can be grown directly by our melted-mixed-source HVPE method in a high-temperature source zone.

  15. Improved source assessment of Si, Al and related mineral components to PM10 based on a daily sampling procedure.

    PubMed

    Peng, Ge; Puxbaum, Hans; Bauer, Heidi; Jankowski, Nicole; Shi, Yao

    2010-01-01

    Samples obtained from an industrialized valley in the East Alpine region were collected daily for a half year and analyzed using X-ray fluorescence to examine the elements Si, Al, Fe, Ca, Mg, Na, K, Zn, P, S and Cl. Some factors affecting the changes of these elements were considered, including time, elemental correlations, weekday, weekend and seasonal changes. Diagnostic analysis provided an insight into a decoupling behavior that occursin siliceous and carbonates minerals. A decrease in Si and Al and an increase in carbonates, Na, K, Zn and P were observed during the cold season. However, a consistently high correlation of Si and Al was observed in all seasons. It was established that such high levels originated from street surface abrasion. The increase in variability and absolute levels of carbonates during the cold season was demonstrated by adding carbonates to the street surface as gritting material to increase the grip on snowy surfaces. A marked increase in Na and Cl was observed in winter which may have been caused by thaw salt that is widely used in winter in Austria. This was associated with a significant increase in K, Zn, and P in the cold season that was the result of domestic space heating with wood. PM10 levels in December were 12 microg/m3 and were higher than levels detected in July. It was established that such high levels originated from mineral oxides, wood smoke, and inorganic ionic material(s).

  16. Stem effect of a Ce3+ doped SiO2 optical dosimeter irradiated with a 192Ir HDR brachytherapy source

    NASA Astrophysics Data System (ADS)

    Carrara, Mauro; Tenconi, Chiara; Guilizzoni, Roberta; Borroni, Marta; Cavatorta, Claudia; Cerrotta, Annamaria; Fallai, Carlo; Gambarini, Grazia; Vedda, Anna; Pignoli, Emanuele

    2014-11-01

    Fiber-optic-coupled scintillation dosimeters are characterized by their small active volume if compared to other existing systems. However, they potentially show a greater stem effect, especially in external beam radiotherapy where the Cerenkov effect is not negligible. In brachytherapy, due to the lower energies and the shorter high dose range of the employed sources, the impact of the stem effect to the detector accuracy might be low. In this work, the stem effect of a Ce3+ doped SiO2 scintillation detector coupled to a SiO2 optical fiber was studied for high dose rate brachytherapy applications. Measurements were performed in a water phantom at changing source-detector mutual positions. The same irradiations were performed with a passive optical fiber, which doesn't have the dosimeter at its end. The relative contribution of the passive fiber with respect to the uncorrected readings of the detector in each one of the investigated source dwell positions was evaluated. Furthermore, the dosimeter was calibrated both neglecting and correcting its response for the passive fiber readings. The obtained absolute dose measurements were then compared to the dose calculations resulting from the treatment planning system. Dosimeter uncertainties with and without taking into account the passive fiber readings were generally below 2.8% and 4.3%, respectively. However, a particular exception results when the source is positioned near to the optical fiber, where the detector underestimates the dose (-8%) or at source-detector longitudinal distances higher than 3 cm. The obtained results show that the proposed dosimeter might be adopted in high dose rate prostate brachytherapy with satisfactory accuracy, without the need for any stem effect correction. However, accuracy further improves by subtraction of the noise signal produced by the passive optical fiber.

  17. A γ-ray detector with a silicon photomultiplier (SiPM) readout for neutron diffraction experiments at spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Festa, G.; Pietropaolo, A.; Reali, E.; Grazzi, F.; Schooneveld, E. M.

    2010-03-01

    Standard detectors for neutron diffraction experiments are typically 3He filled proportional counters. Indeed, in the near future the 3He availability will be greatly reduced, so the R&D activity on alternative neutron counters is a very important issue to be addressed. Scintillator detectors could be considered as one of these alternatives. In this context, a prototype thermal neutron counter composed of a yttrium-aluminium-perovskite scintillator crystal coupled to a silicon photomultiplier (SiPM) and a standard photomultiplier tube (PMT) was used in time of flight neutron diffraction experiments on the INES spectrometer at the ISIS spallation neutron source. Neutron detection was realized by attaching the crystal to a natural cadmium sheet, used as a (n, γ) converter. Results show that the SiPM-based readout detection system has promising performances with respect to that based on a standard PMT. Diffraction patterns recorded with the 3He tubes' neutron counters in use on INES allowed a comparative assessment of the SiPM-based device for time of flight neutron diffraction experiments, with respect to the standard detection technique.

  18. Fluorescence enhancement of single-phase red-blue emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors via Dy3+ addition for plant cultivation

    NASA Astrophysics Data System (ADS)

    Liu, Ling-Yun; Wang, Da-Jian; Mao, Zhi-Yong; Liu, Yan-Hua; Li, Xue-Zheng; Lu, Qi-Fei

    2009-01-01

    Fluorescence enhancement of red and blue concurrently emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors for plant cultivation has been investigated by Dy3+ addition. The Ba3MgSi2O8:Eu2+,Mn2+,Dy3+(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy3+ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation.

  19. Synthesis of MgO-CaO-Al2O3-SiO2 nanocomposite powder by polymeric complex method as a novel sintering additive of AlN ceramics

    NASA Astrophysics Data System (ADS)

    Lee, Hwa-Jun; Cho, Woo-Seok; Kim, Hyeong Jun; Pan, Wei; Shahid, Mohammad; Ryu, Sung-Soo

    2016-09-01

    A MgO-CaO-Al2O3-SiO2 (MCAS) nanocomposite powder with a particle size of 50 nm and a specific surface area of 40.6 m2/g was successfully synthesized via heat-treatment of polymeric precursors containing Mg, Ca, Al and Si in air at 700 °C for 5 h. It was characterized as a novel sintering additive for the densification AlN ceramics at a low temperature below 1600 °C. It was found that the nanosized MCAS powder was suitable for the densification of AlN ceramics. In particular, full densification could be achieved when only 1.0 wt% MCAS additive-doped AlN powder compact was sintered for 1 h at 1600 °C, and a thermal conductivity of 84 W/m·K was attained.

  20. Work Function Tuning and Doping Optimization of 22-nm HKMG Raised SiGe/SiC Source-Drain FinFETs

    NASA Astrophysics Data System (ADS)

    Rezali, F. A. Md; Rasid, M. A. S. Abd; Othman, N. A. F.; Hatta, S. Wan Muhamad; Soin, N.

    2017-01-01

    The basic requirements on process design of extremely scaled devices involve appropriate work function and tight doping control due to their significant effect on the threshold voltage as well as other critical electrical parameters such as drive current and leakage. This paper presents a simulation study of 22-nm fin field-effect transistor (FinFET) performance based on various process design considerations including metal gate work function (WF), halo doping (N halo), source/drain doping (N sd), and substrate doping (N sub). The simulations suggest that the n-type FinFET (nFinFET) operates effectively with lower metal gate WF while the p-type FinFET (pFinFET) operates effectively with high metal gate WF in 22-nm strained technology. Further investigation shows that the leakage reduces with increasing N halo, decreasing N sd, and increasing N sub. Taguchi and Pareto analysis-of-variance approaches are applied using an L27 orthogonal array combined with signal-to-noise ratio analysis to determine the best doping concentration combination for 22-nm FinFETs in terms of threshold voltage (V t), saturation current (I on), and off-state current (I off). Since there is a tradeoff between I on and I off, the design with the nominal-is-best V t characteristic is proposed, achieving nominal V t of 0.259 V for the nFinFET and -0.528 V for the pFinFET. Pareto analysis revealed N halo and N sub to be the dominant factor for nFinFET and pFinFET performance, respectively.

  1. Work Function Tuning and Doping Optimization of 22-nm HKMG Raised SiGe/SiC Source-Drain FinFETs

    NASA Astrophysics Data System (ADS)

    Rezali, F. A. Md; Rasid, M. A. S. Abd; Othman, N. A. F.; Hatta, S. Wan Muhamad; Soin, N.

    2017-03-01

    The basic requirements on process design of extremely scaled devices involve appropriate work function and tight doping control due to their significant effect on the threshold voltage as well as other critical electrical parameters such as drive current and leakage. This paper presents a simulation study of 22-nm fin field-effect transistor (FinFET) performance based on various process design considerations including metal gate work function (WF), halo doping ( N halo), source/drain doping ( N sd), and substrate doping ( N sub). The simulations suggest that the n-type FinFET ( nFinFET) operates effectively with lower metal gate WF while the p-type FinFET ( pFinFET) operates effectively with high metal gate WF in 22-nm strained technology. Further investigation shows that the leakage reduces with increasing N halo, decreasing N sd, and increasing N sub. Taguchi and Pareto analysis-of-variance approaches are applied using an L27 orthogonal array combined with signal-to-noise ratio analysis to determine the best doping concentration combination for 22-nm FinFETs in terms of threshold voltage ( V t), saturation current ( I on), and off-state current ( I off). Since there is a tradeoff between I on and I off, the design with the nominal-is-best V t characteristic is proposed, achieving nominal V t of 0.259 V for the nFinFET and -0.528 V for the pFinFET. Pareto analysis revealed N halo and N sub to be the dominant factor for nFinFET and pFinFET performance, respectively.

  2. Observations on the Influence of Secondary Me Oxides Additives (Me=Si,Al, Mg) on the Microstructural Evolution and Mechanical Behavior of Silicon Nitride Ceramics Containing RE2O3 (RE=La, Gd, Lu)

    SciTech Connect

    Becher, Paul F; Averill, Frank; Lin, Hua-Tay; Waters, Shirley B; Shibata, Naoya; Painter, Gayle S; van Benthem, Klaus

    2010-01-01

    The evolution of β Si3N4 microstructures is influenced by the adsorption of rare earth elements at grain surfaces and by the viscosity of the intergranular phases. Theoretical and STEM studies show that the RE atoms exhibit different tendencies to segregate from the liquid phase to grain surfaces and different binding strengths at these surfaces. When combined with MgO (or Al2O3) secondary additions, the rare earth additives are combined in low viscosity intergranular phases during densification and the α to β phase transformation and microstructural evolution are dominated by the RE adsorption behavior. On the other hand, a much higher viscosity intergranular phase forms when the RE2O3 are combined with SiO2. While the rare earth adsorption behavior remains the same, the phase transformation and microstructure are now dominated by Si3N4 solubility and transport in the high liquid phase. By understanding these additive effects, one can develop reinforced microstructures leading silicon nitride ceramics with greatly improved mechanical behavior.

  3. Al( sup 2 P) l brace SiH sub 4 r brace complex and photoreversible oxidative addition/reductive elimination reaction Al( sup 2 P) l brace SiH sub 4 r brace leftrightarrow SiH sub 3 AlH. 2. Al( sup 2 P) l brace SiH sub 4 r brace leftrightarrow SiH sub 3 AlH reaction

    SciTech Connect

    Lefcourt, M.A.; Ozin, G.A. )

    1991-04-04

    Brief 400-nm photolysis of 1:10 silane/argon matrices containing monatomically isolated aluminum results in the formation of the insertion product silylaluminum hydride (SiH{sub 3}AlH), most likely via an oxidative addition mechanism. The techniques of UV-vis, EPR, and infrared spectroscopy enabled the identification and characterization of this molecule. The photolytic generation of this species paralleled the formation of methylaluminum hydride (CH{sub 3}AlH) studied previously in the authors laboratory. EPR spectral simulations and ab initio self-consistent-field molecular orbital (SCF MO) calculations were employed to help in the characterization of silylaluminum hydride. The EPR spectral parameters extracted from the raw data via the computer simulations, along with subsequently calculated atomic orbital spin densities, determined that the molecule was a bent, orthorhombic species. The SCF MO calculated bond angle at the Al atom was shown to be 118.80{degree}. Secondary photolysis of the aluminum/silane matrix sample resulted in the conversion of the insertion product back to that of the ground-state complex most likely by a reductive elimination mechanism.

  4. Biochemical methane potential from sewage sludge: Effect of an aerobic pretreatment and fly ash addition as source of trace elements.

    PubMed

    Huiliñir, César; Pinto-Villegas, Paula; Castillo, Alejandra; Montalvo, Silvio; Guerrero, Lorna

    2017-06-01

    The effect of aerobic pretreatment and fly ash addition on the production of methane from mixed sludge is studied. Three assays with pretreated and not pretreated mixed sludge in the presence of fly ash (concentrations of 0, 10, 25, 50, 250 and 500mg/L) were run at mesophilic condition. It was found that the combined use of aerobic pretreatment and fly ash addition increases methane production up to 70% when the fly ash concentrations were lower than 50mg/L, while concentrations higher than 250mg/L cause up to 11% decrease of methane production. For the anaerobic treatment of mixed sludge without pretreatment, the fly ash improved methane generation at all the concentrations studied, with a maximum of 56%. The removal of volatile solids does not show an improvement compared to the separate use of an aerobic pre-treatment and fly ash addition. Therefore, the combined use of the aerobic pre-treatment and fly ash addition improves only the production of methane. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Effects of MgO and Al2O3 Addition on Redox State of Chromium in CaO-SiO2-CrO x Slag System by XPS Method

    NASA Astrophysics Data System (ADS)

    Wang, Li-jun; Yu, Ji-peng; Chou, Kuo-chih; Seetharaman, Seshadri

    2015-08-01

    The effects of MgO and Al2O3 on the redox state of chromium in CaO-SiO2-CrO x system have been investigated at 1873 K (1600 °C) under Ar-CO-CO2 atmosphere and analyzed by means of X-ray photoelectron spectroscopy. From the analysis of the Cr 2p core level spectra, it was found that both Cr(II) and Cr(III) exist simultaneously in CaO-MgO/Al2O3-SiO2-CrO x , and the quantitative ratio Cr(II)/Cr(III) has been obtained by deducing from the area under the computer-resolved peaks. Substitutions of CaO by MgO, SiO2 by Al2O3 favored the Cr(II) state existing in the system in the composition ranges of 3 to 10 wt pct MgO and 5 to 20 pct Al2O3. Meanwhile, from the analysis of the O1s spectra in CaO-MgO-SiO2-CrO x , it was found that the ratio of the non-bridging oxygen content increased first due to the CrO contribution to the electron distribution uniformly as O- at MgO low content. Afterward, it went to decreasing with continuing addition of MgO because ionic contribution of MgO is less than that of CaO and the influence of the CrO clustering on the non-Bridging oxygen is limited due to only 5 wt pct CrO x . In CaO-Al2O3-SiO2-CrO x system, Cr(II) acts as a network modifier to compensate Al3+ charge balance to make the structure stable, so the non-bridge oxygen in this system continues decreasing.

  6. Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

    NASA Astrophysics Data System (ADS)

    Jiao, Zengbao; Li, Hongxiang; Wu, Yuan; Gao, Jingen; Wang, Shanlin; Yi, Seonghoon; Lu, Zhaoping

    2010-03-01

    Glass formation, mechanical and magnetic properties of the Fe76- x C7.0Si3.3B5.0P8.7Mo x ( x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635-3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10-1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

  7. Effect of minor Cu addition on phase evolution and magnetic properties of {[(Fe0.5Co0.5)0.75Si0.05B0.20]0.96Nb0.04}100-x Cux alloys

    NASA Astrophysics Data System (ADS)

    Li, R.; Stoica, M.; Eckert, J.

    2009-01-01

    {[(Fe0.5Co0.5)0.75Si0.05B0.20]0.96Nb0.04}100-xCux (x = 0, 1, 1.5 and 2) alloys with different rapid solidification conditions were prepared by copper mold casting and melt spinning. The structures, the thermal and the magnetic properties were studied by X-ray diffraction, differential scanning calorimetry and vibrating sample magnetometry, respectively. Minor Cu addition obviously depresses the glass-forming ability of the alloys (critical glassy diameter dc < 1 mm) compared with [(Fe0.5Co0.5)0.75Si0.05B0.20]96 Nb4 (dc = 3 mm). The effect of Cu addition on the evolution of crystalline phases corresponding to different rapid solidification conditions was evaluated. The existence of (Fe,Co), (Fe,Co)3B, (Fe,Co)2B and (Fe,Co)23B6 crystalline phases in {[(Fe0.5Co0.5)0.75Si0.05B0.20]0.96 Nb0.04}100-x Cux alloys influences the saturation magnetization compared with the corresponding glassy alloys.

  8. Recent Additions in the Modeling Capabilities of an Open-Source Wave Energy Converter Design Tool: Preprint

    SciTech Connect

    Tom, N.; Lawson, M.; Yu, Y. H.

    2015-04-20

    WEC-Sim is a midfidelity numerical tool for modeling wave energy conversion devices. The code uses the MATLAB SimMechanics package to solve multibody dynamics and models wave interactions using hydrodynamic coefficients derived from frequency-domain boundary-element methods. This paper presents the new modeling features introduced in the latest release of WEC-Sim. The first feature discussed conversion of the fluid memory kernel to a state-space form. This enhancement offers a substantial computational benefit after the hydrodynamic body-to-body coefficients are introduced and the number of interactions increases exponentially with each additional body. Additional features include the ability to calculate the wave-excitation forces based on the instantaneous incident wave angle, allowing the device to weathervane, as well as import a user-defined wave elevation time series. A review of the hydrodynamic theory for each feature is provided and the successful implementation is verified using test cases.

  9. Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources.

    PubMed

    Sobierajski, R; Bruijn, S; Khorsand, A R; Louis, E; van de Kruijs, R W E; Burian, T; Chalupsky, J; Cihelka, J; Gleeson, A; Grzonka, J; Gullikson, E M; Hajkova, V; Hau-Riege, S; Juha, L; Jurek, M; Klinger, D; Krzywinski, J; London, R; Pelka, J B; Płociński, T; Rasiński, M; Tiedtke, K; Toleikis, S; Vysin, L; Wabnitz, H; Bijkerk, F

    2011-01-03

    We investigated the damage mechanism of MoN/SiN multilayer XUV optics under two extreme conditions: thermal annealing and irradiation with single shot intense XUV pulses from the free-electron laser facility in Hamburg - FLASH. The damage was studied "post-mortem" by means of X-ray diffraction, interference-polarizing optical microscopy, atomic force microscopy, and scanning transmission electron microscopy. Although the timescale of the damage processes and the damage threshold temperatures were different (in the case of annealing it was the dissociation temperature of Mo2N and in the case of XUV irradiation it was the melting temperature of MoN) the main damage mechanism is very similar: molecular dissociation and the formation of N2, leading to bubbles inside the multilayer structure.

  10. In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

    SciTech Connect

    Matsui, Kunio; Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Sato, Masugu

    2011-05-15

    The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

  11. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N 2O

    NASA Astrophysics Data System (ADS)

    Moseman-Valtierra, Serena; Gonzalez, Rosalinda; Kroeger, Kevin D.; Tang, Jianwu; Chao, Wei Chun; Crusius, John; Bratton, John; Green, Adrian; Shelton, James

    2011-08-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N 2O, CH 4, and CO 2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N 2O, CH 4 and respiratory CO 2 fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO 3 equivalent to 1.4 g N m -2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N 2O and CH 4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N 2O in July 2009 averaged -33 μmol N 2O m -2 day -1. However, within 1 h of nutrient additions, N 2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH 4 fluxes were not significantly affected. N 2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 μmol N 2O m -2 day -1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N 2O and CH 4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N 2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N 2O and CH 4 fluxes observed, exceeded half

  12. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N2O

    USGS Publications Warehouse

    Moseman-Valtierra, Serena; Gonzalez, Rosalinda; Kroeger, Kevin D.; Tang, Jianwu; Chao, Wei Chun; Crusius, John; Bratton, John; Green, Adrian; Shelton, James

    2011-01-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N2O, CH4, and CO2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N2O, CH4 and respiratory CO2fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO3 equivalent to 1.4 g N m−2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N2O and CH4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N2O in July 2009 averaged −33 μmol N2O m−2 day−1. However, within 1 h of nutrient additions, N2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH4 fluxes were not significantly affected. N2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 μmol N2O m−2 day−1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N2O and CH4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N2O and CH4 fluxes observed, exceeded half

  13. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N2O

    USGS Publications Warehouse

    Moseman-Valtierra, S.; Gonzalez, R.; Kroeger, K.D.; Tang, J.; Chao, W.C.; Crusius, J.; Bratton, J.; Green, A.; Shelton, J.

    2011-01-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N2O, CH4, and CO2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N2O, CH4 and respiratory CO2 fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO3 equivalent to 1.4 g N m-2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N2O and CH4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N2O in July 2009 averaged -33 ??mol N2O m-2 day-1. However, within 1 h of nutrient additions, N2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH4 fluxes were not significantly affected. N2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 ??mol N2O m-2 day-1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N2O and CH4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N2O and CH4 fluxes observed, exceeded half the magnitude of typical

  14. SHRIMP-SI Multiple Sulfur Isotope Analysis of Sulfides from Brazilian Deposits: Analytical Capability to Resolve Single Grain Textural Complexities and Distinct Sulfur Sources

    NASA Astrophysics Data System (ADS)

    Ireland, T. R.; Teles, G. D. S.; Chemale, F., Jr.; Avila, J.

    2016-12-01

    The Archean atmosphere is thought to be several times more reducing than the present day atmosphere, and the occurrence of Mass Independent Fractionation of Sulfur isotopes (MIF-S) in sulfides of sedimentary and volcanogenic rocks older than 2.45 Ga reinforces it. The most accepted mechanism to generate MIF-S requires photochemical reactions with volcanogenic SO2 in an anoxic atmosphere (O2 levels <10-5 PAL). The identification of MIF-S, noted as ∆33S and ∆36S, requires precise measurements of less abundant 33S and 36S isotopes, which were first attained by bulk isotope analyses. However, in-situ analysis has become essential, as many of ancient sulfide samples have suffered post-depositional processes, and their primary isotopic signature from the atmosphere are now overprinted by mass-dependent fractionation processes. High-precision and resolution in situ measurements of 32S, 33S, 34S and 36S in sulfides can be achieved by SHRIMP-SI, which allows isotopic determinations with internal errors better than 0.05‰ for ∆33S and 0.2‰ for ∆36S (2SE), and reproducibility about 0.1‰ for ∆33S and better than 0.5‰ for ∆36S (2SD). Examples of the SHRIMP-SI capability are provided by multiple sulfur isotope analysis of samples from Brazil, the Au-(U) and pyrite deposits of Jacobina Basin and the massive sulfide deposits of the 3.3 Ga Mundo Novo Greenstone Belt. The level of precision and spatial resolution achievable with SHRIMP-SI allowed the isotopic distinction between sedimentary and post-depositional pyrites in Jacobina Basin, as well as the identification of different sulfur sources in the Mundo Novo Greenstone Belt VMS deposits.

  15. An additional source of uncertainty and bias in digital spectral estimates near the Nyquist frequency. [in clear air turbulence time series analysis

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.

    1986-01-01

    An additional source of bias and uncertainty in digital spectral estimates near the Nyquist frequency is discovered which is produced by the fact that the finite width main lobe of the spectral window is periodic with period of 2(omega sub c), equal to 4pi times the Nyquist frequency. For estimates near omega sub c, contributions from frequencies near -(omega sub c) are found to appear even for a sufficiently sampled bandlimited time history. In real-world applications, this source should be significant if the number of data points is small, and it should be of even more importance if the signal is not strictly bandlimited.

  16. Effects of boron addition on a-Si(90)Ge(10):H films obtained by low frequency plasma enhanced chemical vapour deposition.

    PubMed

    Pérez, Arllene M; Renero, Francisco J; Zúñiga, Carlos; Torres, Alfonso; Santiago, César

    2005-06-29

    Optical, structural and electric properties of (a-(Si(90)Ge(10))(1-y)B(y):H) thin film alloys, deposited by low frequency plasma enhanced chemical vapour deposition, are presented. The chemical bonding structure has been studied by IR spectroscopy, while the composition was investigated by Raman spectroscopy. A discussion about boron doping effects, in the composition and bonding of samples, is presented. Transport of carriers has been studied by measurement of the conductivity dependence on temperature, which increases from 10(-3) to 10(1) Ω(-1) cm(-1) when the boron content varies from 0 to 50%. Similarly, the activation energy is between 0.62 and 0.19 eV when the doping increases from 0 to 83%. The optical properties have been determined from the film's optical transmission, using Swanepoel's method. It is shown that the optical gap varies from 1.3 to 0.99 eV.

  17. Influence of Na2SiO3 addition on surface microstructure and cavitation damage characteristics for plasma electrolytic oxidation of Al-Mg alloy

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Hyung; Son, Chang-Ryeon; Kim, Seong-Jong

    2016-01-01

    Recently, plasma electrolytic oxidation (PEO) has emerged as a promising surface modification technique to improve surface properties of Al alloys. In this study, PEO coating process for Al-Mg alloy was conducted with two different electrolyte solutions under the same electrical parameters: one was potassium hydroxide (KOH) aqueous solution, and the other involved potassium hydroxide aqueous solution with sodium silicate (Na2SiO3). The surface morphology was observed with scanning electron microscope (SEM) and elemental compositions were identified with energy dispersive spectroscopy (EDS) analysis. The chemical structures of PEO coatings were identified by X-ray diffraction analysis. Cavitation experiment was performed using ultrasonic vibratory cavitation erosion testing apparatus. Cavitation damage of PEO coatings was characterized using SEM and three-dimensional (3D) microscope. The result indicated that the surface of Al-Mg alloy were successfully modified having complete different surface morphologies by changing electrolyte composition. It was found that the surface morphology had a great influence on the cavitation damage behavior of PEO coating.

  18. Populations of Dalapon-decomposing Bacteria in Soil as Influenced by Additions of Dalapon or Other Carbon Sources

    PubMed Central

    Burge, Wylie D.

    1969-01-01

    The numbers of bacteria capable of decomposing the herbicide dalapon were determined for five soils by the most-probable-number method. Before treatment of the soils with dalapon, the numbers varied from 1,000 to 10,000 cells per g of soil. Incubation of the soils with dalapon resulted in large increases (100-fold) in two of three soils in which dalapon was decomposed rapidly. Lack of increase in numbers in spite of rapid decomposition in the other soil probably indicated breakdown by a chemical process or decomposition by fungi. In the remaining two soils, in which decomposition was slow in one and did not occur in the other, the initial numbers were at the low end of the range and the increase was small on incubation with dalapon. Addition of ground alfalfa or ground corn plant material to a soil did not result in significant increases in the numbers of dalapon-decomposing bacteria, either during or after decomposition of the plant material. Glucose depressed the rate of breakdown of dalapon in the soil and increased dalapon-decomposing Bacillus species rather than Arthrobacter and Agrobacterium species, which were found to increase on incubation with dalapon itself. The most-probable-number method appears to be a valuable tool for pesticide-ecology studies. PMID:5772393

  19. J-type Carbon Stars: A Dominant Source of 14N-rich Presolar SiC Grains of Type AB

    NASA Astrophysics Data System (ADS)

    Liu, Nan; Stephan, Thomas; Boehnke, Patrick; Nittler, Larry R.; O'D. Alexander, Conel M.; Wang, Jianhua; Davis, Andrew M.; Trappitsch, Reto; Pellin, Michael J.

    2017-07-01

    We report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB (14N/15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%-15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.

  20. Investigating the impact of source/drain doping dependent effective masses on the transport characteristics of ballistic Si-nanowire field-effect-transistors

    SciTech Connect

    Nag Chowdhury, Basudev; Chattopadhyay, Sanatan

    2014-03-28

    This article studies the impact of doping dependent carrier effective masses of the source/drain regions on transport properties of Si-nanowire field effect transistors within ballistic limit. The difference of carrier effective mass in channel and that in the source/drain regions leads to a misalignment of respective sub-bands and forms non-ideal contacts. Such non-idealities are incorporated by modifying the relevant self-energies which control the effective electronic transport from source to drain through the channel. Non-ideality also arises in the nature of local density of states in the channel due to sub-band misalignment, resulting to a reduction of drain current by almost 50%. The highest values of drain current, leakage current, and their ratio are obtained for the S/D doping concentrations of 3 × 10{sup 20} cm{sup −3}, 8 × 10{sup 20} cm{sup −3}, and 2 × 10{sup 20} cm{sup −3}, respectively, for the nanowire of length 10 nm and diameter of 3 nm. Interestingly, the maximum of sub-threshold swing, minimum of threshold voltage, and the maximum of leakage current are observed to be apparent at the same doping concentration.

  1. Fabrication and characteristics of an nc-Si/c-Si heterojunction MOSFETs pressure sensor.

    PubMed

    Zhao, Xiaofeng; Wen, Dianzhong; Li, Gang

    2012-01-01

    A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances of the four nc-Si/c-Si heterojunction MOSFETs form a Wheatstone bridge. When the additional pressure is P, the nc-Si/c-Si heterojunction MOSFETs pressure sensor can measure this additional pressure P. The experimental results show that when the supply voltage is 3 V, length-width (L:W) ratio is 2:1, and the silicon membrane thickness is 75 μm, the full scale output voltage of the pressure sensor is 15.50 mV at room temperature, and pressure sensitivity is 0.097 mV/kPa. When the supply voltage and L:W ratio are the same as the above, and the silicon membrane thickness is 45 μm, the full scale output voltage is 43.05 mV, and pressure sensitivity is 2.153 mV/kPa. Therefore, the sensor has higher sensitivity and good temperature characteristics compared to the traditional piezoresistive pressure sensor.

  2. Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Hu, J H; Chen, C Z

    2014-02-01

    Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants.

  3. The influence of Ga additions on electric and magnetic properties of Co{sub 47}Fe{sub 21}B{sub 21}Si{sub 5}Nb{sub 6} alloy in crystal and liquid states

    SciTech Connect

    Sidorov, V. Rojkov, I.; Mikhailov, V.; Svec, P.; Janickovic, D.

    2015-08-17

    The influence of small additions of gallium on electric resistivity and magnetic susceptibility of the bulk glass forming Co{sub 47}Fe{sub 20.9}B{sub 21.2}Si{sub 4.6}Nb{sub 6.3} alloy was studied in a wide temperature range up to 1830 K. Gallium atoms were found to increase resistivity but decrease susceptibility of the alloy. The suppositions about clusters surrounding Ga atoms in the melt and new GFA criterion are given.

  4. Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

    PubMed

    Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

    2006-03-01

    New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

  5. Reducing contralateral SI activity reveals hindlimb receptive fields in the SI forelimb-stump representation of neonatally amputated rats.

    PubMed

    Pluto, Charles P; Chiaia, Nicolas L; Rhoades, Robert W; Lane, Richard D

    2005-09-01

    In adult rats that sustained forelimb amputation on the day of birth, >30% of multiunit recording sites in the forelimb-stump representation of primary somatosensory cortex (SI) also respond to cutaneous hindlimb stimulation when cortical GABA(A+B) receptors are blocked (GRB). This study examined whether hindlimb receptive fields could also be revealed in forelimb-stump sites by reducing one known source of excitatory input to SI GABAergic neurons, the contralateral SI cortex. Corpus callosum projection neurons connect homotopic SI regions, making excitatory contacts onto pyramidal cells and interneurons. Thus in addition to providing monosynaptic excitation in SI, callosal fibers can produce disynaptic inhibition through excitatory synapses with inhibitory interneurons. Based on the latter of these connections, we hypothesized that inactivating the contralateral (intact) SI forelimb region would "unmask" normally suppressed hindlimb responses by reducing the activity of SI GABAergic neurons. The SI forelimb-stump representation was first mapped under normal conditions and then during GRB to identify stump/hindlimb responsive sites. After GRB had dissipated, the contralateral (intact) SI forelimb region was mapped and reversibly inactivated with injections of 4% lidocaine, and selected forelimb-stump sites were retested. Contralateral SI inactivation revealed hindlimb responses in approximately 60% of sites that were stump/hindlimb responsive during GRB. These findings indicate that activity in the contralateral SI contributes to the suppression of reorganized hindlimb receptive fields in neonatally amputated rats.

  6. Kinetics of the addition of olefins to Si-centered radicals: the critical role of dispersion interactions revealed by theory and experiment.

    PubMed

    Johnson, Erin R; Clarkin, Owen J; Dale, Stephen G; DiLabio, Gino A

    2015-06-04

    Solution-phase rate constants for the addition of selected olefins to the triethylsilyl and tris(trimethylsilyl)silyl radicals are measured using laser-flash photolysis and competition kinetics. The results are compared with predictions from density functional theory (DFT) calculations, both with and without dispersion corrections obtained from the exchange-hole dipole moment (XDM) model. Without a dispersion correction, the rate constants are consistently underestimated; the errors increase with system size, up to 10(6) s(-1) for the largest system considered. Dispersion interactions preferentially stabilize the transition states relative to the separated reactants and bring the DFT-calculated rate constants into excellent agreement with experiment. Thus, dispersion interactions are found to play a key role in determining the kinetics for addition reactions, particularly those involving sterically bulky functional groups.

  7. Influences of TiO2 Addition on the Crystallization Behavior, Microstructure, and Magnetic Properties of Li2O-MnO2-Fe2O3-CaO-P2O5-SiO2 Glasses

    NASA Astrophysics Data System (ADS)

    Cheng, Huy-Zu; Lin, Huey-Jiuan; Wang, Moo-Chin; Wang, Chien-Fa; Hsi, Chi-Shiung; Zhao, XiuJian; Jiang, Hong; Li, Chang-Jiu; Lu, Peng

    2015-05-01

    Influences of TiO2 addition on the phase transformation, microstructure, and magnetic properties of Li2O-MnO2-Fe2O3-CaO-P2O5-SiO2 (LMFCPS) glass have been studied using DTA, XRD, SEM, EDS, TEM, SAED, and SQUID. When LMFCPS glass, with and without TiO2 content, is crystallized at 1123 K (850 °C) for 2 hours, the magnetite (FeFe2O4), β-wollastonite (β-CaSiO3), lithium orthophosphate (Li3PO4), and triphylite (Li(Mn0.5Fe0.5)PO4) phases are formed. The β-wollastonite and lithium silicate formed with evident directionality were observed in the LMFCPS glass-ceramics without adding TiO2. However, when the LMFCPS glass with various TiO2 content is crystallized at 1123 K (850 °C) for 16 hours, very small remnant magnetic induction and coercive field hysteresis loops were found showing the ferromagnetic property in a magnetic field smaller than 2000 Oe. Additionally, when LMFCPS glass with various TiO2 contents is crystallized at 1123 K (850 °C) for 16 hours, the glass-ceramics showed super-paramagnetic property in a magnetic field of 60 kOe due to the small grains of the iron-rich phases.

  8. Fe-doped semi-insulating GaN with solid Fe source grown on (110) Si substrates by NH3 molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Noh, Young Kyun; Lee, Sang Tae; Kim, Moon Deock; Oh, Jae Eung

    2017-02-01

    Iron doped GaN layers were grown on (110) Si substrates by ammonia molecular beam epitaxy (MBE) using solid elemental iron as a source. Specular films with concentrations up to 1×1020 cm-3, as determined by secondary ion mass spectroscopy, were grown, unlike a limited incorporation of Fe into GaN by metal-rich rf plasma MBE. The Fe concentration in the film showed an exponential dependence on the inverse of source temperature with an activation energy of 3.4 eV, which agrees well to the reported value for the sublimation of Fe. A 1.5 μm thick GaN film with a sheet resistance of 1 GΩ/sq. was obtained by compensating unintentional residual donors with a small Fe concentration of 1×1017 cm-3. X-ray diffraction rocking curves indicated high crystalline quality, very similar to an undoped film, showing that the Fe incorporation required to obtain the semi-insulating film properties did not affect the structural properties of the film. The low-temperature PL spectra of highly resistive and semi-insulating Fe:GaN in the range of 1017 1018 cm-3 show dominant exciton emissions and enhanced donor-acceptor-pair (DAP) emissions, implying that Fe ions contribute to the DAP transition between donor levels and Fe-related acceptor levels, possibly compensating the residual donors to achieve the semi-insulating electrical properties.

  9. Boron Nitride Obtained from Molecular Precursors: Aminoboranes Used as a BN Source for Coatings, Matrix, and Si 3N 4-BN Composite Ceramic Preparation

    NASA Astrophysics Data System (ADS)

    Thévenot, F.; Doche, C.; Mongeot, H.; Guilhon, F.; Miele, P.; Cornu, D.; Bonnetot, B.

    1997-10-01

    Aminoboranes, pure or partially converted into aminoborazines using thermal or aminolysis polymerization, have been used as boron nitride precursors. An amorphous BN preceramic is obtained when pyrolysed up to 1000°C that can be stabilized using further annealing up to 1400°C or crystallized into h-BN above 1700°C. These molecular precursors have been used to prepare carbon fiber/BN matrix microcomposites to get an efficient BN coating on graphite and as a BN source in Si3N4/BN composite ceramic. The properties of these new types of samples have been compared with those obtained by classical processes. The boron nitride obtained from these precursors is a good sintering agent during the hot-pressing of the samples. However, the crystallinity of BN, even sintered up to 1800°C, remains poor. In fact, most of the mechanical properties of the composite ceramic (density, porosity, hardness) are clearly improved and the aminoboranes can be considered as convenient boron nitride sources and helpful sintering agents in hot-pressing technology.

  10. Sintering oxide ceramics based on AI2O3 and ZrO2, activated by MgO, TiO2 and SiO2 additives

    NASA Astrophysics Data System (ADS)

    Matrenin, S. V.; Zenin, B. S.; Tayukin, R. V.

    2016-11-01

    The positive effect of the addition of MgO and TiO2 in an amount of no more than 1 wt. % on sintering and physico-mechanical properties of alumina ceramics is established. Addition of 5% of SiO2 to A12O3 provides the mechanism of liquid phase sintering of ceramics, which leads to increase in its density and strength up to 480 MPa. In ceramic system A12O3 - ZrO2 - Y2O3 highest level of physical and mechanical properties of the composition had a hypereutectic composition 16.6% A12O3 - 76% Z1O2 - 7.4% Y2O3. In this composition two mechanisms of hardening are realized simultaneously, such as transformational hardening by t- m - ZrO2 transition and dispersion strengthening with high-modulus particles of α- A12O3.

  11. Screening landraces for additional sources of field resistance to cassava mosaic disease and green mite for integration into the cassava improvement program.

    PubMed

    Raji, Adebola; Ladeinde, Oluseyi; Dixon, Alfred

    2008-03-01

    Twelve cassava landraces were evaluated for sources of resistance genes to diseases and pests of major economic importance in Africa. The objective was to assess their levels of field resistance to mosaic disease (ACMD), bacterial blight (CBB), anthracnose (CAD), and green mite (CGM), compared to TMS30572, an elite cultivar widely adopted in Africa. Considerable genotypic variation was observed among cultivars for resistance to ACMD and CGM but not for CBB and CAD. The lowest mean incidence of 12% and severity of 1.8 on a scale of 1-5 for ACMD was recorded for Atu, a landrace with farmer acceptable qualities. In comparison, the improved cultivar, TMS 30572, had a mean disease incidence of 72% and a severity score of 2.8. Another landrace, MS-20 had the lowest CGM damage score (2.1) while TMS 30572 emerged as one of the susceptible cultivars with a damage score of 3. Additional sources of resistance to ACMD and CGM that may possibly be better than the popular improved cultivar, TMS 30572, were identified in this study. These could serve as novel sources of additional genes to complement existing resources for elite cassava breeding in Africa.

  12. Ultrahigh B doping ({<=}10{sup 22} cm{sup -3}) during Si(001) gas-source molecular-beam epitaxy: B incorporation, electrical activation, and hole transport

    SciTech Connect

    Glass, G.; Kim, H.; Desjardins, P.; Taylor, N.; Spila, T.; Lu, Q.; Greene, J. E.

    2000-03-15

    Si(001) layers doped with B concentrations C{sub B} between 1x10{sup 17} and 1.2x10{sup 22} cm{sup -3} (24 at %) were grown on Si(001)2x1 at temperatures T{sub s}=500-850 degree sign C by gas-source molecular-beam epitaxy from Si{sub 2}H{sub 6} and B{sub 2}H{sub 6}. C{sub B} increases linearly with the incident precursor flux ratio J{sub B{sub 2}}{sub H{sub 6}}/J{sub Si{sub 2}}{sub H{sub 6}} and B is incorporated into substitutional electrically active sites at concentrations up to C{sub B}{sup *}(T{sub s}) which, for T{sub s}=600 degree sign C, is 2.5x10{sup 20} cm{sup -3}. At higher B concentrations, C{sub B} increases faster than J{sub B{sub 2}}{sub H{sub 6}}/J{sub Si{sub 2}}{sub H{sub 6}} and there is a large and discontinuous decrease in the activated fraction of incorporated B. However, the total activated B concentration continues to increase and reaches a value of N{sub B}=1.3x10{sup 21} cm{sup -3} with C{sub B}=1.2x10{sup 22} cm{sup -3}. High-resolution x-ray diffraction (HR-XRD) and reciprocal space mapping measurements show that all films, irrespective of C{sub B} and T{sub s}, are fully strained. No B precipitates or misfit dislocations were detected by HR-XRD or transmission electron microscopy. The lattice constant in the film growth direction a{sub (perpendicular} {sub sign)} decreases linearly with increasing C{sub B} up to the limit of full electrical activation and continues to decrease, but nonlinearly, with C{sub B}>C{sub B}{sup *}. Room-temperature resistivity and conductivity mobility values are in good agreement with theoretical values for B concentrations up to C{sub B}=2.5x10{sup 20} and 2x10{sup 21} cm{sup -3}, respectively. All results can be explained on the basis of a model which accounts for strong B surface segregation to the second-layer with a saturation coverage {theta}{sub B,sat} of 0.5 ML (corresponding to C{sub B}=C{sub B}{sup *}). At higher C{sub B} (i.e., {theta}{sub B}>{theta}{sub B,sat}), B accumulates in the upper layer as

  13. Zircon Hf isotopic constraints on the mantle source of felsic magmatic rocks in the Phan Si Pan uplift and Tu Le basin, northern Vietnam

    NASA Astrophysics Data System (ADS)

    Usuki, T.; Lan, C.; Tran, T.; Pham, T.; Wang, K.

    2013-12-01

    Permian plume-related rocks, such as picrites, flood basalts and silicic volcanic rocks occur in northern Vietnam. This area was displaced 600 km southeastward along the Ailao Shan-Red River fault during mid-Tertiary in response to the India-Eurasia collision. The original location of the area was situated at the central Emeishan Large Igneous Province (ELIP) in SW China before Tertiary. The picrites and flood basalts in northern Vietnam have been investigated by many authors and are comparable with the ELIP. While, felsic magmatisms in northern Vietnam has been poorly studied. Zircon U-Pb age and Hf isotopic data are useful to compare the felsic magmatism in northern Vietnam with that in the ELIP, because the magmatisms of the ELIP had a characteristic time period (260-250 Ma) and the Hf isotopes show a remarkable mantle signature. Therefore, this study carried out in-situ U-Pb ages and Hf isotopic compositions for 300 zircon grains in eighteen granitoids and rhyolites in Phan Si Pan uplift and Tu Le basin in northern Vietnam. Zircons from the granitoids and rhyolites occasionally show development of {101} pyramid and {100} prism crystal facies, suggesting typical zircons crystallized from high temperature alkaline granite. 206Pb/238U ages of granitoid and rhyolite yield consistently in a narrow range of 260 to 250 Ma, which coincides with those from peralkaline to metaluminous granites in the ELIP. ɛHf(t) values of zircons in rhyolites and granites of this study dominate in the range of +5 to +10, which is consistent with those from the ELIP. U-Pb ages and Hf isotopic compositions of zircons indicate that felsic magmatic rocks in the Phan Si Pan uplift and Tu La basin have been derived from the same mantle source with the ELIP.

  14. Addition Reactions of Me3 SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O, S, and N Ligands.

    PubMed

    Yang, Zhi; Yi, Yafei; Zhong, Mingdong; De, Sriman; Mondal, Totan; Koley, Debasis; Ma, Xiaoli; Zhang, Dongxiang; Roesky, Herbert W

    2016-05-10

    The reaction of one equivalent of LAlH2 (1; L=HC(CMeNAr)2 , Ar=2,6-iPr2 C6 H3 , β-diketiminate ligand) with two equivalents of 2-mercapto-4,6-dimethylpyrimidine hydrate resulted in LAl[(μ-S)(m-C4 N2 H)(CH2 )2 ]2 (2) in good yield. Similarly, when N-2-pyridylsalicylideneamine, N-(2,6-diisopropylphenyl)salicylaldimine, and ethyl 3-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxylate were used as starting materials, the corresponding products LAl[(μ-O)(o-C6 H4 )CN(C5 NH4 )]2 (3), LAlH[(μ-O)(o-C4 H4 )CN(2,6-iPr2 C6 H3 )] (4), and LAl[(μ-NH)(o-C8 SH8 )(COOC2 H5 )]2 (5) were isolated. Compounds 2-5 were characterized by (1) H and (13) C NMR spectroscopy as well as by single-crystal X-ray structural analysis. Surprisingly, compounds 2-5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN).

  15. The effect of fluoroethylene carbonate additive content on the formation of the solid-electrolyte interphase and capacity fade of Li-ion full-cell employing nano Si-graphene composite anodes

    NASA Astrophysics Data System (ADS)

    Bordes, Arnaud; Eom, KwangSup; Fuller, Thomas F.

    2014-07-01

    When fluoroethylene carbonate (FEC) is added to the ethylene carbonate (EC)-diethyl carbonate (DEC) electrolyte, the capacity and cyclability of full-cells employing Si-graphene anode and lithium nickel cobalt aluminum oxide cathode (NCA) cathode are improved due to formation of a thin (30-50 nm) SEI layer with low ionic resistance (∼2 ohm cm2) on the surface of Si-graphene anode. These properties are confirmed with electrochemical impedance spectroscopy and a cross-sectional image analysis using Focused Ion Beam (FIB)-SEM. Approximately 5 wt.% FEC in EC:DEC (1:1 wt.%) shows the highest capacity and most stability. This high capacity and low capacity fade is attributed to a more stable SEI layer containing less CH2OCO2Li, Li2CO3 and LiF compounds, which consume cyclable Li. Additionally, a greater amount of polycarbonate (PC), which is known to form a more robust passivation layer, thus reducing further reduction of electrolyte, is confirmed with X-ray photoelectron spectroscopy (XPS).

  16. Ionized Gas Kinematics around an Ultra-luminous X-Ray Source in NGC 5252: Additional Evidence for an Off-nuclear AGN

    NASA Astrophysics Data System (ADS)

    Kim, Minjin; Ho, Luis C.; Im, Myungshin

    2017-08-01

    The Seyfert 2 galaxy NGC 5252 contains a recently identified ultra-luminous X-ray (ULX) source that has been suggested to be a possible candidate off-nuclear low-mass active galactic nucleus. We present follow-up optical integral-field unit observations obtained using Gemini Multi-Object Spectrographs on the Gemini-North telescope. In addition to confirming that the ionized gas in the vicinity of the ULX is kinematically associated with NGC 5252, the new observations reveal ordered motions consistent with rotation around the ULX. The close coincidence of the excitation source of the line-emitting gas with the position of the ULX further suggests that ULX itself is directly responsible for the ionization of the gas. The spatially resolved measurements of [N ii] λ6584/Hα surrounding the ULX indicate a low gas-phase metallicity, consistent with those of other known low-mass active galaxies but not that of its more massive host galaxy. These findings strengthen the proposition that the ULX is not a background source but rather that it is the nucleus of a small, low-mass galaxy accreted by NGC 5252.

  17. Ellipsometric study of Si(0.5)Ge(0.5)/Si strained-layer superlattices

    NASA Technical Reports Server (NTRS)

    Sieg, R. M.; Alterovitz, S. A.; Croke, E. T.; Harrell, M. J.

    1993-01-01

    An ellipsometric study of two Si(0.5)Ge(0.5)/Si strained-layer super lattices grown by MBE at low temperature (500 C) is presented, and results are compared with x ray diffraction (XRD) estimates. Excellent agreement is obtained between target values, XRD, and ellipsometry when one of two available Si(x)Ge(1-x) databases is used. It is shown that ellipsometry can be used to nondestructively determine the number of superlattice periods, layer thicknesses, Si(x)Ge(1-x) composition, and oxide thickness without resorting to additional sources of information. It was also noted that we do not observe any strain effect on the E(sub 1) critical point.

  18. Ellipsometric study of Si(0.5)Ge(0.5)/Si strained-layer superlattices

    NASA Technical Reports Server (NTRS)

    Sieg, R. M.; Alterovitz, S. A.; Croke, E. T.; Harrell, M. J.

    1993-01-01

    We present an ellipsometric study of two Si(0.5)Ge(0.5)/Si strained-layer superlattices grown by MBE at low temperature (500 C), and compare our results with X-ray diffraction (XRD) estimates. Excellent agreement is obtained between target values, XRD, and ellipsometry when one of two available Si(x)Ge(1-x) databases is used. We show that ellipsometry can be used to nondestructively determine the number of superlattice periods, layer thicknesses, Si(x)Ge(1-x) composition, and oxide thickness without resorting to additional sources of information. We also note that we do not observe any strain effect on the E1 critical point.

  19. Effect of ZnO addition on bioactive CaO-SiO2-P2O5-CaF2 glass-ceramics containing apatite and wollastonite.

    PubMed

    Kamitakahara, M; Ohtsuki, C; Inada, H; Tanihara, M; Miyazaki, T

    2006-07-01

    Some ceramics show bone-bonding ability, i.e. bioactivity. Apatite formation on ceramics is an essential condition to bring about direct bonding to living bone when implanted into bony defects. A controlled surface reaction of the ceramic is an important factor governing the bioactivity and biodegradation of the implanted ceramic. Among bioactive ceramics, glass-ceramic A-W containing apatite and wollastonite shows high bioactivity, as well as high mechanical strength. In this study, glass-ceramics containing zinc oxide were prepared by modification of the composition of the glass-ceramic A-W. Zinc oxide was selected to control the reactivity of the glass-ceramics since zinc is a trace element that shows stimulatory effects on bone formation. Glass-ceramics were prepared by heat treatment of glasses with the general composition: xZnOx(57.0-x)CaOx35.4SiO(2)x7.2P(2)O(5)x0.4CaF(2) (where x=0-14.2mol.%). Addition of ZnO increased the chemical durability of the glass-ceramics, resulting in a decrease in the rate of apatite formation in a simulated body fluid. On the other hand, the release of zinc from the glass-ceramics increased with increasing ZnO content. Addition of ZnO may provide bioactive CaO-SiO(2)-P(2)O(5)-CaF(2) glass-ceramics with the capacity for appropriate biodegradation, as well as enhancement of bone formation.

  20. Weakening of Sisbnd Si bonding in exohydrogenated Si60 nanoclusters

    NASA Astrophysics Data System (ADS)

    Bainglass, Edan; Mayfield, Cedric L.; Huda, Muhammad N.

    2017-09-01

    We performed density functional theory (DFT) analyses of several hollow cage-like Si60 nanoclusters and found a favoring of exohydrogenation in terms of reduced binding energies in all the structures except the Si60 fullerene. Further investigation into the effects of exohydrogenation on the Sisbnd Si bonding network revealed a level of weakening in Sisbnd Si bonds. A correlation was established between the magnitude of this weakening and the success of exohydrogenation in stabilizing the nanocluster. In addition, we found a slightly bent chain of individual Si20 units to exhibit the lowest binding energy among the present group of Si60 clusters studied here.

  1. Increasing fermentation efficiency at high sugar concentrations by supplementing an additional source of nitrogen during the exponential phase of the tequila fermentation process.

    PubMed

    Arrizon, Javier; Gschaedler, Anne

    2002-11-01

    In the tequila industry, fermentation is traditionally achieved at sugar concentrations ranging from 50 to 100 g x L(-1). In this work, the behaviour of the Saccharomyces cerevisiae yeast (isolated from the juices of the Agave tequilana Weber blue variety) during the agave juice fermentation is compared at different sugar concentrations to determine if it is feasible for the industry to run fermentation at higher sugar concentrations. Fermentation efficiency is shown to be higher (above 90%) at a high concentration of initial sugar (170 g x L(-1)) when an additional source of nitrogen (a mixture of amino acids and ammonium sulphate, different than a grape must nitrogen composition) is added during the exponential growth phase.

  2. Polyvinyl alcohol gelation: A structural locking-up agent and carbon source for Si/CNT/C composites as high energy lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Chen, Dingqiong; Liao, Wenjuan; Yang, Yang; Zhao, Jinbao

    2016-05-01

    A novel polyvinyl alcohol (PVA) hydrogel method is developed to synthesize Si/CNT/C composites. The Si nanoparticles and CNTs are 'position' locked up by PVA hydrogel in a simple aqueous solution process, and then the Si-CNT-PVA hydrogel has pyrolyzed to form Si/CNT/C composites. In this unique structured Si/CNT/C composites, the CNTs form a porous network acting both as conductive agent for electron transfer and buffer space to accommodate huge Si volume change during lithiation/delithiation process, while the coating layer of carbon carbonized from polyvinyl alcohol (PVA) hydrogel is conducive to stabilize the interweaved composite structure. The complex structures of Si/CNT/C composites and their electrochemical properties are presented in this paper. The Si/CNT/C composites exhibit an initial reversible capacity of nearly 800 mAhg-1, an excellent capacity retention of 97.1% after 100 cycles at the rate of 0.1 C, and high capacity retention even at high current rate.

  3. MoSi2-Base Composites

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    2003-01-01

    Addition of 30 to 50 vol% of Si3N4 particulate to MoSi2 eliminated its low temperature catastrophic failure, improved room temperature fracture toughness and the creep resistance. The hybrid composite SCS-6/MoSi2-Si3N4 did not show any matrix cracking and exhibited excellent mechanical and environmental properties. Hi-Nicalon continuous fiber reinforced MoSi2-Si3N4 also showed good strength and toughness. A new MoSi2-base composite containing in-situ whisker-type (Beta)Si3N4 grains in a MoSi2 matrix is also described.

  4. Determination of additivity of apparent and standardized ileal digestibility of amino acids in diets containing multiple protein sources fed to growing pigs.

    PubMed

    Xue, P C; Ragland, D; Adeola, O

    2014-09-01

    An experiment was conducted in growing pigs to investigate the additivity of apparent ileal digestibility (AID) or standardized ileal digestibility (SID) of CP and AA in mixed diets containing multiple protein sources. Using the determined AID or SID for CP and AA in corn, soybean meal (SBM), corn distillers' dried grains with solubles (DDGS), or canola meal (CM), the AID or SID for 4 mixed diets based on corn-SBM, corn-SBM-DDGS, corn-SBM-CM, or corn-SBM-DDGS-CM were predicted and compared with determined AID or SID, respectively. Eighteen growing pigs (initial BW = 61.3 ± 5.5 kg) were surgically fitted with T-cannulas and assigned to a duplicated 9 × 4 incomplete Latin square design with 9 diets and 4 periods. The 9 experimental diets consisted of a nitrogen-free diet (NFD) to estimate basal ileal endogenous loss (BEL) of AA, 4 semipurified diets to determine the AID and SID of CP and AA in the 4 ingredients, and 4 mixed diets to test the additivity of AID and SID. Chromic oxide was added as an indigestible marker. Pigs were fed 1 of the 9 diets during each 7-d period, and ileal digesta were collected on d 6 and 7, from 0800 to 1800 h. The analyzed AA levels for the mixed diets were close to the calculated values based on the AA composition of each ingredient. The results revealed that the predicted SID were consistent with determined values, except for Leu, Thr, Asp, Cys, Pro, and Ser in the corn-SBM diet and Met and Cys in the corn-SBM-DDGS diet. The determined AID for total AA and Arg, His, Trp, Gly, and Pro in the corn-SBM diet were greater (P < 0.05) than predicted. For the corn-SBM-DDGS diet, the determined AID were greater (P < 0.05) than predicted AID for CP, total AA, and all AA except for Arg, Leu, and Pro. In the corn-SBM-CM diet, the determined AID were greater (P < 0.05) than predicted AID for Arg, Cys, and Gly. When compared with determined values, predicted AID in the corn-SBM-DDGS-CM diet were lower (P < 0.05) for total AA and Arg, Met, Cys, and

  5. Effect of glucose addition and N sources in defined media on fibrolytic activity profiles of Neocallimastix sp. YQ1 grown on corn stover.

    PubMed

    Yang, H J; Yue, Q

    2012-08-01

    Cleavage of plant cell wall arabinoxylans occurs by the action of ferulic acid esterase (FAE) and acetyl esterase (AE), which cleave feruloyl groups substituted at the 5'-OH group of arabinosyl residues and acetyl groups substituted at O-2/O-3 of the xylan backbone, respectively. In this study, we examined the enzyme profiles of the anaerobic rumen fungus Neocallimastix sp. YQ1 for FAE, AE and polysaccharide hydrolases when grown on corn stover, a lignin-rich waste biomaterial. A 2 × 4 factorial experiment in 10-days pure cultures was used to test glucose addition (G(+) : glucose at 1.0 g/l, G(-) : no glucose) and four N sources (N1: 1.0 g/l yeast extract, 1.0 g/l tryptone and 0.5 g/l (NH(4))(2) SO(4); N2: 2.8 g/l yeast extract and 0.5 g/l (NH(4))(2) SO(4) ; N3: 1.6 g/l tryptone and 0.5 g/l (NH(4))(2) SO(4); N4: 1.4 g/l tryptone and 1.7 g/l yeast extract) in defined media. The optimal combinations of glucose and N sources to promote FAE and AE activity were G(+) N2 and G(+) N4, respectively. The peak activities of FAE and AE occurred on days 9 and 10, respectively. Addition of glucose and an increase in yeast extract and/or tryptone to a Hungate's medium favoured fungal production of volatile fatty acids, which could be just a consequence of more organic matter available to digest. This suggests that enzymatic release of ferulic acid by a synergistic action of lignin hydrolytic esterase and polysaccharide hydrolases may be essential for plant cell wall biodegradation in the rumen. © 2011 Blackwell Verlag GmbH.

  6. Stress engineering in GaN structures grown on Si(111) substrates by SiN masking layer application

    SciTech Connect

    Szymański, Tomasz Wośko, Mateusz; Paszkiewicz, Bogdan; Paszkiewicz, Regina

    2015-07-15

    GaN layers without and with an in-situ SiN mask were grown by using metal organic vapor phase epitaxy for three different approaches used in GaN on silicon(111) growth, and the physical and optical properties of the GaN layers were studied. For each approach applied, GaN layers of 1.4 μm total thickness were grown, using silan SiH{sub 4} as Si source in order to grow Si{sub x}N{sub x} masking layer. The optical micrographs, scanning electron microscope images, and atomic force microscope images of the grown samples revealed cracks for samples without SiN mask, and micropits, which were characteristic for the samples grown with SiN mask. In situ reflectance signal traces were studied showing a decrease of layer coalescence time and higher degree of 3D growth mode for samples with SiN masking layer. Stress measurements were conducted by two methods—by recording micro-Raman spectra and ex-situ curvature radius measurement—additionally PLs spectra were obtained revealing blueshift of PL peak positions with increasing stress. The authors have shown that a SiN mask significantly improves physical and optical properties of GaN multilayer systems reducing stress in comparison to samples grown applying the same approaches but without SiN masking layer.

  7. Spectrometric analysis of process etching solutions of the photovoltaic industry--determination of HNO3, HF, and H2SiF6 using high-resolution continuum source absorption spectrometry of diatomic molecules and atoms.

    PubMed

    Bücker, Stefan; Acker, Jörg

    2012-05-30

    The surface of raw multicrystalline silicon wafers is treated with HF-HNO(3) mixtures in order to remove the saw damage and to obtain a well-like structured surface of low reflectivity, the so-called texture. The industrial production of solar cells requires a consistent level of texturization for tens of thousands of wafers. Therefore, knowing the actual composition of the etch bath is a key element in process control in order to maintain a certain etch rate through replenishment of the consumed acids. The present paper describes a novel approach to quantify nitric acid (HNO(3)), hydrofluoric acid (HF), and hexafluosilicic acid (H(2)SiF(6)) using a high-resolution continuum source graphite furnace absorption spectrometer. The concentrations of Si (via Si atom absorption at the wavelength 251.611 nm, m(0),(Si)=130 pg), of nitrate (via molecular absorption of NO at the wavelength 214.803 nm, [Formula: see text] ), and of total fluoride (via molecular absorption of AlF at the wavelength 227.46 nm, m(0,F)=13 pg) were measured against aqueous standard solutions. The concentrations of H(2)SiF(6) and HNO(3) are directly obtained from the measurements. The HF concentration is calculated from the difference between the total fluoride content, and the amount of fluoride bound as H(2)SiF(6). H(2)SiF(6) and HNO(3) can be determined with a relative uncertainty of less than 5% and recoveries of 97-103% and 96-105%, respectively. With regards to HF, acceptable results in terms of recovery and uncertainty are obtained for HF concentrations that are typical for the photovoltaic industry. The presented procedure has the unique advantage that the concentration of both, acids and metal impurities in etch solutions, can be routinely determined by a single analytical instrument.

  8. Optimization of anaerobically digested distillery molasses spent wash decolorization using soil as inoculum in the absence of additional carbon and nitrogen source.

    PubMed

    Adikane, H V; Dange, M N; Selvakumari, K

    2006-11-01

    The aim of this study was to achieve maximum decolorization of molasses spent wash (MSW) in absence of any additional carbon or nitrogen source using soil as inoculum. Soil samples were collected from the MSW disposal site. Colored soil samples exhibited higher pH, sugar and protein as compare to less colored samples. A decolorization of 69% was obtained using 10% (w/v) soil and 12.5% (v/v) MSW after 7 days incubation. Optimized parameters including days--6 days, pH--6, MSW--12.5% and soil concentration--40%, were obtained for maximum decolorization. A decolorization of 81% was achieved using 10% soil and 12.5% MSW after 18 days incubation in absence of any media supplement. Nearly 12% reduction in decolorization activity of the soil sample was observed over a period of 12 months when stored at 6 degrees C. It could be concluded that the decolorization of MSW might be achieved using soil as inoculum without addition of chemical amendments.

  9. Construction and characterization of spherical Si solar cells combined with SiC electric power inverter

    NASA Astrophysics Data System (ADS)

    Oku, Takeo; Matsumoto, Taisuke; Hiramatsu, Kouichi; Yasuda, Masashi; Shimono, Akio; Takeda, Yoshikazu; Murozono, Mikio

    2015-02-01

    Spherical silicon (Si) photovoltaic solar cell systems combined with an electric power inverter using silicon carbide (SiC) field-effect transistor (FET) were constructed and characterized, which were compared with an ordinary Si-based converter. The SiC-FET devices were introduced in the direct current-alternating current (DC-AC) converter, which was connected with the solar panels. The spherical Si solar cells were used as the power sources, and the spherical Si panels are lighter and more flexible compared with the ordinary flat Si solar panels. Conversion efficiencies of the spherical Si solar cells were improved by using the SiC-FET.

  10. Characterization of high-dose and high-energy implanted gate and source diode and analysis of lateral spreading of p gate profile in high voltage SiC static induction transistors

    NASA Astrophysics Data System (ADS)

    Onose, Hidekatsu; Kobayashi, Yutaka; Onuki, Jin

    2017-03-01

    The effect of the p gate dose on the characteristics of the gate-source diode in SiC static induction transistors (SIT) was investigated. It was found that a dose of 1.5 × 1014 cm-2 yields a pn junction breakdown voltage higher than 60 V and good forward characteristics. A normally on SiC SIT was fabricated and demonstrated. A blocking voltage higher than 2.0 kV at a gate-source voltage of -50 V and on-resistance of 70 mΩ cm2 were obtained. Device simulations were performed to investigate the effect of the lateral spreading. By comparing the measured I-V curves with simulation results, the lateral spreading factor was estimated to be about 0.5. The lateral spreading detrimentally affected the electrical properties of the SIT made using implantations at energies higher than 1 MeV.

  11. The Banhadão Alkaline Complex, Southeastern Brazil: source and evolution of potassic SiO2-undersaturated high-Ca and low-Ca magmatic series

    NASA Astrophysics Data System (ADS)

    Ruberti, Excelso; Enrich, Gaston E. R.; Azzone, Rogério G.; Comin-Chiaramonti, Piero; de Min, Angelo; Gomes, Celso B.

    2012-01-01

    The Cretaceous Banhadão alkaline complex in southeastern Brazil presents two potassic SiO2-undersaturated series. The high-Ca magmatic series consist of initially fractionated olivine (Fo92-91) + diopside (Wo48-43En49-35Ae0-7), as evidenced by the presence of xenocrysts and xenoliths. In that sequence, diopside (Wo47-38En46-37Ae0-8) + phlogopite + apatite + perovskite (Prv>92) crystallized to form the phlogopite melteigite and led to the Ca enrichment of the magma. Diopside (Wo47-41En32-24 Ae3-14) continued to crystallize as an early mafic mineral, followed by nepheline (Ne74.8-70.1Ks26.3-21.2Qz7.6-0.9) and leucite (Lc65-56) and subsequently by melanite and potassic feldspar (Or85-99Ab1-7) to form melanite ijolites, wollastonite-melanite urtites and melanite-nepheline syenites. Melanite-pseudoleucite-nepheline syenites are interpreted to be a leucite accumulation. Melanite nephelinite dykes are believed to represent some of the magmatic differentiation steps. The low-Ca magmatic series is representative of a typical fractionation of aegirine-augite (Wo36-29En25-4Ae39-18) + alkali feldspar (Or57-96Ab3-43) + nepheline (Ne76.5-69.0Ks19.9-14.4Qz15.1-7.7) + titanite from phonolite magma. The evolution of this series from potassic nepheline syenites to sodic sodalite syenites and sodalitolites is attributed to an extensive fractionation of potassic feldspar, which led to an increase of the NaCl activity in the melt during the final stages forming sodalite-rich rocks. Phonolite dykes followed a similar evolutionary process and also registered some crustal assimilation. The mesocratic nepheline syenites showed interactions with phlogopite melteigites, such as compatible trace element enrichments and the presence of diopside xenocrysts, which were interpreted to be due to a mixing/mingling process of phonolite and nephelinite magmas. The geochemical data show higher TiO2 and P2O5 contents and lower SiO2 contents for the high-Ca series and different LILE evolution trends

  12. Dual-source dual-energy CT with additional tin filtration: Dose and image quality evaluation in phantoms and in-vivo

    PubMed Central

    Primak, Andrew N.; Giraldo, Juan Carlos Ramirez; Eusemann, Christian D.; Schmidt, Bernhard; Kantor, B.; Fletcher, Joel G.; McCollough, Cynthia H.

    2010-01-01

    Purpose To investigate the effect on radiation dose and image quality of the use of additional spectral filtration for dual-energy CT (DECT) imaging using dual-source CT (DSCT). Materials and Methods A commercial DSCT scanner was modified by adding tin filtration to the high-kV tube, and radiation output and noise measured in water phantoms. Dose values for equivalent image noise were compared among DE-modes with and without tin filtration and single-energy (SE) mode. To evaluate DECT material discrimination, the material-specific DEratio for calcium and iodine were determined using images of anthropomorphic phantoms. Data were additionally acquired in 38 and 87 kg pigs, and noise for the linearly mixed and virtual non-contrast (VNC) images compared between DE-modes. Finally, abdominal DECT images from two patients of similar sizes undergoing clinically-indicated CT were compared. Results Adding tin filtration to the high-kV tube improved the DE contrast between iodine and calcium as much as 290%. Pig data showed that the tin filtration had no effect on noise in the DECT mixed images, but decreased noise by as much as 30% in the VNC images. Patient VNC-images acquired using 100/140 kV with added tin filtration had improved image quality compared to those generated with 80/140 kV without tin filtration. Conclusion Tin filtration of the high-kV tube of a DSCT scanner increases the ability of DECT to discriminate between calcium and iodine, without increasing dose relative to SECT. Furthermore, use of 100/140 kV tube potentials allows improved DECT imaging of large patients. PMID:20966323

  13. Effect of Bi(Mg1/2Ti1/2)O3 addition on the electrical properties of Si-Mn modified on SrTiO3

    NASA Astrophysics Data System (ADS)

    Roh, Yoon-ah; Masaki, Takaki; Yoon, Dae-Ho

    2015-05-01

    Single-Crystalline Strontium titanate (SrTiO3) has been widely used in many fields such as catalyst, semiconductors and dielectrics. SrTiO3 is a typical perovskite-type oxide, the physical properties of which strongly depend on its chemical composition, structure, shape, size, and crystallinity. In this work, the effects of Bi(Mg1/2Ti1/2)O3 addition on the nanostructure and the dielectric properties of Si-Mn modified SrTiO3 were investigated to develop nano-sized particles and low-temperature-fired SrTiO3-based ceramics with stable temperature characteristics. The dielectric constant of SrTiO3-Bi(Mg1/2Ti1/2)O3 was found to range from 900 to 1200 at 1 kHz for samples sintered at 1200°C. This new composition, SrTiO3-Bi(Mg1/2Ti1/2)O3, can be applied as a nano-sized dielectric materials in various fields.

  14. Effect of high-pressure/temperature (HP/T) treatments of in-package food on additive migration from conventional and bio-sourced materials.

    PubMed

    Mauricio-Iglesias, M; Jansana, S; Peyron, S; Gontard, N; Guillard, V

    2010-01-01

    Migration was assessed during and after two high-pressure/temperature (HP/T) treatments intended for a pasteurization (800 MPa for 5 min, from 20 to 40 degrees C) and a sterilization treatment (800 MPa for 5 min, from 90 to 115 degrees C) and were compared with conventional pasteurization and sterilization, respectively. The specific migration of actual packaging additives used as antioxidants and ultraviolet light absorbers (Irganox 1076, Uvitex OB) was investigated in a number of food-packaging systems combining one synthetic common packaging (LLDPE) and a bio-sourced one (PLA) in contact with the four food-simulating liquids defined by European Commission regulations. After standard HP/T processing, migration kinetics was followed during the service life of the packaging material using Fourier transform infrared spectrometer (FTIR) spectroscopy. LLDPE withstood the high-pressure sterilization, whereas it melted during the conventional sterilization. No difference was observed on migration from LLDPE for both treatments. In the case of PLA, migration of Uvitex OB was very low or not detectable for all the cases studied.

  15. [Underreporting of tuberculosis in the Information System on Notifiable Diseases (SINAN): primary default and case detection from additional data sources using probabilistic record linkage].

    PubMed

    Pinheiro, Rejane Sobrino; Andrade, Vanusa de Lemos; Oliveira, Gisele Pinto de

    2012-08-01

    This study aimed to analyze underreporting of tuberculosis (TB) cases in the Information System on Notifiable Diseases (SINAN), based on the following data sources: Mortality Information System (SIM), Registry and Follow-up Book for TB Case Treatment (LPATB), and Laboratory Registry Book (LRLAB). Probabilistic record linkage was used between the SIM (2007-2008) and SINAN (2002-2008). A search was conducted in LPATB and LRLAB (2007-2008) for cases not recorded in SINAN. There were 125 deaths, of which 44.8% were not recorded in SINAN. In LPATB, 58 cases (5.1%) were in treatment and were not reported in SINAN. LRLAB showed 32 smear-positive cases not reported to SINAN and without treatment, representing primary default. Addition of the retrieved cases, led to a 14.6% increase in the incidence rate in 2007 and 11.6% in 2008. Underreporting of deaths from or with TB in the Mortality Information System and primary default revealed difficulties in access to adequate and timely treatment, calling for rethinking of strategies to detect cases for timely treatment.

  16. Estimating PM2.5 Concentrations in Xi'an City Using a Generalized Additive Model with Multi-Source Monitoring Data

    PubMed Central

    Song, Yong-Ze; Yang, Hong-Lei; Peng, Jun-Huan; Song, Yi-Rong; Sun, Qian; Li, Yuan

    2015-01-01

    Particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) represents a severe environmental problem and is of negative impact on human health. Xi'an City, with a population of 6.5 million, is among the highest concentrations of PM2.5 in China. In 2013, in total, there were 191 days in Xi’an City on which PM2.5 concentrations were greater than 100 μg/m3. Recently, a few studies have explored the potential causes of high PM2.5 concentration using remote sensing data such as the MODIS aerosol optical thickness (AOT) product. Linear regression is a commonly used method to find statistical relationships among PM2.5 concentrations and other pollutants, including CO, NO2, SO2, and O3, which can be indicative of emission sources. The relationships of these variables, however, are usually complicated and non-linear. Therefore, a generalized additive model (GAM) is used to estimate the statistical relationships between potential variables and PM2.5 concentrations. This model contains linear functions of SO2 and CO, univariate smoothing non-linear functions of NO2, O3, AOT and temperature, and bivariate smoothing non-linear functions of location and wind variables. The model can explain 69.50% of PM2.5 concentrations, with R2 = 0.691, which improves the result of a stepwise linear regression (R2 = 0.582) by 18.73%. The two most significant variables, CO concentration and AOT, represent 20.65% and 19.54% of the deviance, respectively, while the three other gas-phase concentrations, SO2, NO2, and O3 account for 10.88% of the total deviance. These results show that in Xi'an City, the traffic and other industrial emissions are the primary source of PM2.5. Temperature, location, and wind variables also non-linearly related with PM2.5. PMID:26540446

  17. Estimating PM2.5 Concentrations in Xi'an City Using a Generalized Additive Model with Multi-Source Monitoring Data.

    PubMed

    Song, Yong-Ze; Yang, Hong-Lei; Peng, Jun-Huan; Song, Yi-Rong; Sun, Qian; Li, Yuan

    2015-01-01

    Particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) represents a severe environmental problem and is of negative impact on human health. Xi'an City, with a population of 6.5 million, is among the highest concentrations of PM2.5 in China. In 2013, in total, there were 191 days in Xi'an City on which PM2.5 concentrations were greater than 100 μg/m3. Recently, a few studies have explored the potential causes of high PM2.5 concentration using remote sensing data such as the MODIS aerosol optical thickness (AOT) product. Linear regression is a commonly used method to find statistical relationships among PM2.5 concentrations and other pollutants, including CO, NO2, SO2, and O3, which can be indicative of emission sources. The relationships of these variables, however, are usually complicated and non-linear. Therefore, a generalized additive model (GAM) is used to estimate the statistical relationships between potential variables and PM2.5 concentrations. This model contains linear functions of SO2 and CO, univariate smoothing non-linear functions of NO2, O3, AOT and temperature, and bivariate smoothing non-linear functions of location and wind variables. The model can explain 69.50% of PM2.5 concentrations, with R2 = 0.691, which improves the result of a stepwise linear regression (R2 = 0.582) by 18.73%. The two most significant variables, CO concentration and AOT, represent 20.65% and 19.54% of the deviance, respectively, while the three other gas-phase concentrations, SO2, NO2, and O3 account for 10.88% of the total deviance. These results show that in Xi'an City, the traffic and other industrial emissions are the primary source of PM2.5. Temperature, location, and wind variables also non-linearly related with PM2.5.

  18. Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe-Mg2Si, SiGe-FeSi2

    NASA Astrophysics Data System (ADS)

    Nozariasbmarz, Amin; Roy, Palash; Zamanipour, Zahra; Dycus, J. Houston; Cabral, Matthew J.; LeBeau, James M.; Krasinski, Jerzy S.; Vashaee, Daryoosh

    2016-10-01

    Thermoelectric properties of nanostructured FeSi2, Mg2Si, and SiGe are compared with their nanocomposites of SiGe-Mg2Si and SiGe-FeSi2. It was found that the addition of silicide nanoinclusions to SiGe alloy maintained or increased the power factor while further reduced the thermal conductivity compared to the nanostructured single-phase SiGe alloy. This resulted in ZT enhancement of Si0.88Ge0.12-FeSi2 by ˜30% over the broad temperature range of 500-950 °C compared to the conventional Si0.80Ge0.20 alloy. The Si0.88Ge0.12-Mg2Si nanocomposite showed constantly increasing ZT versus temperature up to 950 °C (highest measured temperature) reaching ZT ˜ 1.3. These results confirm the concept of silicide nanoparticle-in-SiGe-alloy proposed earlier by Mingo et al. [Nano Lett. 9, 711-715 (2009)].

  19. Effect of energy source and xylanase addition on energy metabolism, performance, chemical body composition and total body electrical conductivity (TOBEC) of broilers.

    PubMed

    Dänicke, S; Halle, I; Strobel, E; Franke, E; Jeroch, H

    2001-10-01

    Three diets containing either no supplemented fat (LF), 12% soybean oil (SO) or 12% coconut oil (CO) were fed to broilers to examine energy utilization in two experiments. Heat production and energy retained as fat and protein were measured in the first experiment using a respiration technique in combination with C- and N-balance and controlled (pair-fed) feeding conditions. Growth performance, carcass composition, chemical body composition and total body electrical conductivity (TOBEC) were evaluated in a second experiment under ad libitum feeding conditions (from hatching to day 35). Moreover, each of the three diet types was tested with or without the addition of a xylanase-containing enzyme preparation in the growth experiment. Energy utilization (experiment 1), expressed as the ratio between total retained energy and metabolizable energy intake, amounted to 0.33, 0.36 and 0.39 in LF-, SO- and CO-fed groups, respectively. Applying ad libitum feeding conditions in the second experiment caused a significant reduction in feed intake and weight gain in broilers fed the CO-diet. The feed-to-gain ratio was significantly lower in birds given the fat-supplemented diets. The highest degree of fatness as indicated by the highest percentage of abdominal and visceral fat and by highest total fat content was found in birds fed the CO-diet. The higher the body protein content and the lower the body fat content, the higher the TOBEC value should be. This was confirmed when LF-fed broilers were compared to their CO-fed counterparts. However, fat type seemed to be related to TOBEC values since SO-fed broilers had similar TOBEC values as CO-fed birds, whereas chemical body composition was comparable to LF-fed broilers. Xylanase addition significantly increased weight gain up to 21 days of age and decreased the feed-to-gain ratio slightly, whereas none of the other parameters were influenced by this treatment. An interaction between energy source and enzyme supplementation was

  20. Inductively coupled plasma spectrometry: Noise characteristics of aerosols, application of generalized standard additions method, and Mach disk as an emission source

    SciTech Connect

    Luan, Shen

    1995-10-06

    This dissertation is focused on three problem areas in the performance of inductively coupled plasma (ICP) source. The noise characteristics of aerosols produced by ICP nebulizers are investigated. A laser beam is scattered by aerosol and detected by a photomultiplier tube and the noise amplitude spectrum of the scattered radiation is measured by a spectrum analyzer. Discrete frequency noise in the aerosol generated by a Meinhard nebulizer or a direct injection nebulizer is primarily caused by pulsation in the liquid flow from the pump. A Scott-type spray chamber suppresses white noise, while a conical, straight-pass spray chamber enhances white noise, relative to the noise seen from the primary aerosol. Simultaneous correction for both spectral interferences and matrix effects in ICP atomic emission spectrometry (AES) can be accomplished by using the generalized standard additions method (GSAM). Results obtained with the application of the GSAM to the Perkin-Elmer Optima 3000 ICP atomic emission spectrometer are presented. The echelle-based polychromator with segmented-array charge-coupled device detectors enables the direct, visual examination of the overlapping lines Cd (1) 228.802 nm and As (1) 228.812 nm. The slit translation capability allows a large number of data points to be sampled, therefore, the advantage of noise averaging is gained. An ICP is extracted into a small quartz vacuum chamber through a sampling orifice in a water-cooled copper plate. Optical emission from the Mach disk region is measured with a new type of echelle spectrometer equipped with two segmented-array charge-coupled-device detectors, with an effort to improve the detection limits for simultaneous multielement analysis by ICP-AES.

  1. The effectiveness of power-generating complexes constructed on the basis of nuclear power plants combined with additional sources of energy determined taking risk factors into account

    NASA Astrophysics Data System (ADS)

    Aminov, R. Z.; Khrustalev, V. A.; Portyankin, A. V.

    2015-02-01

    The effectiveness of combining nuclear power plants equipped with water-cooled water-moderated power-generating reactors (VVER) with other sources of energy within unified power-generating complexes is analyzed. The use of such power-generating complexes makes it possible to achieve the necessary load pickup capability and flexibility in performing the mandatory selective primary and emergency control of load, as well as participation in passing the night minimums of electric load curves while retaining high values of the capacity utilization factor of the entire power-generating complex at higher levels of the steam-turbine part efficiency. Versions involving combined use of nuclear power plants with hydrogen toppings and gas turbine units for generating electricity are considered. In view of the fact that hydrogen is an unsafe energy carrier, the use of which introduces additional elements of risk, a procedure for evaluating these risks under different conditions of implementing the fuel-and-hydrogen cycle at nuclear power plants is proposed. Risk accounting technique with the use of statistical data is considered, including the characteristics of hydrogen and gas pipelines, and the process pipelines equipment tightness loss occurrence rate. The expected intensities of fires and explosions at nuclear power plants fitted with hydrogen toppings and gas turbine units are calculated. In estimating the damage inflicted by events (fires and explosions) occurred in nuclear power plant turbine buildings, the US statistical data were used. Conservative scenarios of fires and explosions of hydrogen-air mixtures in nuclear power plant turbine buildings are presented. Results from calculations of the introduced annual risk to the attained net annual profit ratio in commensurable versions are given. This ratio can be used in selecting projects characterized by the most technically attainable and socially acceptable safety.

  2. [Iron and zinc in vitro potential availability in an infant diet with fortified bread with different iron sources or with the addition of different iron absorption promoters].

    PubMed

    Binaghi, María J; Cagnasso, Carolina E; Pellegrino, Nestor R; Drago, Silvina R; González, Rolando; Ronayne, Patricia A; Valencia, Mirta E

    2011-09-01

    Home-made diets are the most frequently used complementary foods. In the present work we evaluated iron and zinc availability in a usually consumed infant diet containing either iron-fortified bread with different iron sources: ferrous sulfate, ferrous bisglycinate, NaFeEDTA. We also used non-fortified bread with absorption promoters: ascorbic acid, sodium citrate, Na2EDTA, combined with different beverages. The diet (potato, pumpkin, grits, bread, and apple) was combined with water, milk, tea, a soft drink and an orange-based artificial drink. Mineral dialyzability (D) as an indicator of potential availability was determined using an in vitro method. Statistical analysis was performed by ANOVA, and a posteriori Tukey test. There were no significant differences in FeD between diets with ferrous sulfate or ferrous bisglycinate fortified bread; in NaFeEDTA fortified bread it increased significantly (p<0.05). Iron D increase was greater in diets with bread containing absorption promoters than in those with fortified bread. The orange-based artificial drink increased FeD, while tea and milk decreased it significantly (p < 0.05). Zinc D increased significantly when the bread was fortified either with ferrous sulfate or NaFeEDTA, but remained unchanged in diets with ferrous bisglycinate fortified bread. The addition of tea or milk decreased ZnD while the orange-based artificial drink increased it significantly (p < 0.05). Regarding absorption promoters, the greater values both in FeD and ZnD were observed in diets with iron nonfortified bread containing Na2EDTA.

  3. The Multi-allelic Genetic Architecture of a Variance-Heterogeneity Locus for Molybdenum Concentration in Leaves Acts as a Source of Unexplained Additive Genetic Variance

    PubMed Central

    Forsberg, Simon K. G.; Andreatta, Matthew E.; Huang, Xin-Yuan; Danku, John; Salt, David E.; Carlborg, Örjan

    2015-01-01

    Genome-wide association (GWA) analyses have generally been used to detect individual loci contributing to the phenotypic diversity in a population by the effects of these loci on the trait mean. More rarely, loci have also been detected based on variance differences between genotypes. Several hypotheses have been proposed to explain the possible genetic mechanisms leading to such variance signals. However, little is known about what causes these signals, or whether this genetic variance-heterogeneity reflects mechanisms of importance in natural populations. Previously, we identified a variance-heterogeneity GWA (vGWA) signal for leaf molybdenum concentrations in Arabidopsis thaliana. Here, fine-mapping of this association reveals that the vGWA emerges from the effects of three independent genetic polymorphisms that all are in strong LD with the markers displaying the genetic variance-heterogeneity. By revealing the genetic architecture underlying this vGWA signal, we uncovered the molecular source of a significant amount of hidden additive genetic variation or “missing heritability”. Two of the three polymorphisms underlying the genetic variance-heterogeneity are promoter variants for Molybdate transporter 1 (MOT1), and the third a variant located ~25 kb downstream of this gene. A fourth independent association was also detected ~600 kb upstream of MOT1. Use of a T-DNA knockout allele highlights Copper Transporter 6; COPT6 (AT2G26975) as a strong candidate gene for this association. Our results show that an extended LD across a complex locus including multiple functional alleles can lead to a variance-heterogeneity between genotypes in natural populations. Further, they provide novel insights into the genetic regulation of ion homeostasis in A. thaliana, and empirically confirm that variance-heterogeneity based GWA methods are a valuable tool to detect novel associations of biological importance in natural populations. PMID:26599497

  4. Sol-gel synthesis and luminescence of unexpected microrod crystalline Ca 5La 5(SiO 4) 3(PO 4) 3O 2:Dy 3+ phosphors employing different silicate sources

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Huang, Honghua

    2007-08-01

    Ca5La5(SiO4)3(PO4)3O2 doped with Dy3+ were synthesized by sol-gel technology with hybrid precursor employed four different silicate sources, 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM diagraphs show that there exist some novel unexpected morphological structures of microrod owing to the crosslinking reagents than TEOS as silicate source for their amphipathy template effect. X-ray pictures confirm that Ca5La5(SiO4)3(PO4)3O2:Dy3+ compound is formed by a pure apatitic phase. The Dy3+ ions could emit white light in Ca5La5(SiO4)3(PO4)3O2 compound, and the ratio of Y/B is 1.1, when the Dy3+ doped concentration is 1.0 mol%.

  5. Effect of combined addition of nano-SiC and nano-Ho2O3 on the in-field critical current density of MgB2 superconductor

    NASA Astrophysics Data System (ADS)

    Varghese, Neson; Vinod, K.; Chattopadhyay, M. K.; Roy, S. B.; Syamaprasad, U.

    2010-01-01

    MgB2 superconducting samples added with nano-Ho2O3 (n-Ho2O3) and/or nano-SiC (n-SiC) have been prepared by an in situ solid state reaction method to investigate and compare the combined and individual effects of n-SiC and n-Ho2O3 on a crystal structure, critical temperature (TC), and critical current density (JC) of MgB2. All the doped samples exhibit significantly enhanced in-field JC and the codoped sample with 2.5 wt % n-Ho2O3 and 5 wt % n-SiC gives the best performance in in-field JC, and the enhancement is around 100 times and 2 times greater than the undoped and monodoped n-SiC samples, respectively, at 5 K and 8 T. For the n-SiC added sample, lattice distortions due to C substitution on the B site and the formation of reacted phase Mg2Si as flux pinners cause enhanced JC up to the maximum field studied (8 T). While in the n-Ho2O3 added sample, a reacted phase HoB4 having a strong magnetic moment forms, without any substitution at the Mg or B site, which acts as a flux pinner in order to enhance the in-field JC. Accordingly the best codoped sample exhibits these combined benefits of n-SiC and n-Ho2O3 in MgB2 superconductor.

  6. SI Notes.

    ERIC Educational Resources Information Center

    Nelson, Robert A.

    1983-01-01

    Discusses legislation related to SI (International Systems of Units) in the United States. Indicates that although SI metric units have been officially recognized by law in the United States, U.S. Customary Units have never received a statutory basis. (JN)

  7. Astrometrically registered simultaneous observations of the 22 GHz H{sub 2}O and 43 GHz SiO masers toward R Leonis Minoris using KVN and source/frequency phase referencing

    SciTech Connect

    Dodson, Richard; Rioja, María J.; Jung, Tae-Hyun; Sohn, Bong-Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung-Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo-Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; and others

    2014-11-01

    Oxygen-rich asymptotic giant branch (AGB) stars can be intense emitters of SiO (v = 1 and 2, J = 1 → 0) and H{sub 2}O maser lines at 43 and 22 GHz, respectively. Very long baseline interferometry (VLBI) observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned H{sub 2}O and v = 1 and v = 2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. We present phase-referenced simultaneous spectral-line VLBI images for the SiO v = 1 and v = 2, J = 1 → 0, and H{sub 2}O maser emission around the AGB star R LMi, obtained from the Korean VLBI Network (KVN). The simultaneous multi-channel receivers of the KVN offer great possibilities for astrometry in the frequency domain. With this facility, we have produced images with bona fide absolute astrometric registration between high-frequency maser transitions of different species to provide the positions of the H{sub 2}O maser emission and the center of the SiO maser emission, hence reducing the uncertainty in the proper motions for R LMi by an order of magnitude over that from Hipparcos. This is the first successful demonstration of source frequency phase referencing for millimeter VLBI spectral-line observations and also where the ratio between the frequencies is not an integer.

  8. SiS nanosheets as a promising anode material for Li-ion batteries: a computational study.

    PubMed

    Kong, Qingquan; Feng, Wei; Wang, Qingyuan; Gan, Li-Yong; Sun, Chenghua

    2017-03-22

    Recently, a two-dimensional Pma2-SiS monolayer has been predicted to show promising electronic properties [Nano Lett., 2015, 16, 1110]. However, it is suggested that Pma2-SiS is not suitable as an anode for Li-ion batteries [J. Power Sources, 2016, 331, 391]. By employing density functional theory calculations, we find that an ultrahigh theoretical specific capacity of 893.4 mA h g(-1) can be achieved in Pma2-SiS due to the strong bonding between Li and the S atoms released from Si-S bond breakage. Additionally, the low barrier of Li-diffusion (0.08 eV) along the Si-Si bond direction and the moderate average voltage (1.12 V) of the Li intercalation suggest that Pma2-SiS is promising as an anode material for Li-ion battery applications.

  9. Diffuse and point sources of silica in the Seine River watershed.

    PubMed

    Sferratore, Agata; Garnier, Josette; Billen, Gilles; Conley, Daniel I; Pinault, Séverine

    2006-11-01

    Dissolved silica (DSi) is believed to enter aquatic ecosystems primarily through diffuse sources by weathering. Point sources have generally been considered negligible, although recent reports of DSi inputs from domestic and industrial sources suggest otherwise. In addition, particulate amorphous silica (ASi) inputs from terrestrial ecosystems during soil erosion and in vegetation can dissolve and also be a significant source of DSi. We quantify here both point and diffuse sources of DSi and particulate ASi to the Seine River watershed. The total per capita point source inputs of Si (DSi + ASi) were found to be 1.0 and 0.8 g Si inhabitant(-1) d(-1) in raw and treated waters of the Achères wastewater treatment plant, in agreement with calculations based on average food intake and silica-containing washing products consumption. A mass balance of Si inputs and outputs for the Seine drainage network was established for wet and dry hydrological conditions (2001 and 2003, respectively). Diffuse sources of Si are of 1775 kg Si km(-2) y(-1) in wet conditions and 762 kg Si km(-2) y(-1) in dry conditions, with the proportion of ASi around 6%. Point sources of Si from urban discharge can contribute to more than 8% of the total Si inputs at the basin scale in hydrologically dry years. An in-stream retention of 6% of total inputs in dry conditions and 12% in wet conditions is inferred from the budget.

  10. Absorption in a-Si/SiO2 Superlattices

    NASA Astrophysics Data System (ADS)

    Kilpelä, O.; Karppinen, M.; Novikov, S.; Sokolov, V.; Yliniemi, S.

    a-Si/SiO2 superlattices were grown on quartz by MBD (Molecular Beam Deposition) using in situ oxidation by an RF-plasma source. The a-Si layer thicknesses were varied from 0.5-2.5nm while the SiO2 layer thicknesses (1.0nm) were kept constant. Optical transmission and reflection measurements were performed on these samples at room temperature. The recorded spectra were then analyzed with a commercial optical thin film analysis program. The band gaps were derived from constant-n and non-constant-n forms of Tauc and Cody laws. The observed blueshift of the band gap, with decreasing a-Si layer thickness, is attributed to quantum confinement in the a-Si sublayers.

  11. High throughput production of nanocomposite SiO x powders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Homma, Keiichiro; Kambara, Makoto; Yoshida, Toyonobu

    2014-04-01

    Nanocomposite Si/SiO x powders were produced by plasma spray physical vapor deposition (PS-PVD) at a material throughput of 480 g h-1. The powders are fundamentally an aggregate of primary ˜20 nm particles, which are composed of a crystalline Si core and SiO x shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiO x vapors, followed by disproportionation reaction of nucleated SiO x nanoparticles. When CH4 was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiO x shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g-1 after 100 cycles at the same time.

  12. Total ionizing dose effects of Ge channel pFETs with raised Si0.55Ge0.45 source/drain

    SciTech Connect

    Hachtel, Jordan A.; Chisholm, Matthew F.; Pantelides, Sokrates T.; Wang, Liang; Zhang, En Xia; Schrimpf, Ronald D.; Fleetwood, Daniel M.; Duan, Guo Xing; Zhang, Cher Xuan; Reed, Robert A.; Samsel, Isaak K.; Alles, Michael L.; Witters, Lisbeth; Collaert, Nadine; Linten, Dimitri; Mitard, Jerome; Galloway, Kenneth F.

    2015-12-01

    The total ionizing dose response of Ge channel pFETs with raised Si0.55Ge0.45 source/drain is investigated under different radiation bias conditions. Threshold-voltage shifts and transconductance degradation are noticeable only for negative-bias (on state) irradiation, and are mainly due to negative bias-temperature instability (NBTI). Here, nonmonotonic leakage changes during irradiation are observed, which are attributed to the competition of radiation-induced field transistor leakage and S/D junction leakage.

  13. Improving the homogeneity of alternating current-drive atmospheric pressure dielectric barrier discharges in helium with an additional low-amplitude radio frequency power source: A numerical study

    SciTech Connect

    Wang Qi; Sun Jizhong; Zhang Jianhong; Wang Dezhen; Liu Liying

    2013-04-15

    It was proposed in this paper that the homogeneity of the atmospheric pressure discharge driven by an ac power source could be improved by applying an auxiliary low-amplitude rf power source. To verify the idea, a two-dimensional fluid model then was applied to study the atmospheric discharges in helium driven by ac power, low-amplitude rf power, and combined ac and low-amplitude rf power, respectively. Simulation results confirmed that an auxiliary rf power could improve the homogeneity of a discharge driven by an ac power source. It was further found that there existed a threshold voltage of the rf power source leading to the transition from inhomogeneous to homogeneous discharge. As the frequency of the rf power source increased from 2 to 22 MHz, the magnitude of the threshold voltage dropped first rapidly and then to a constant value. When the frequency was over 13.56 MHz, the magnitude of the threshold voltage was smaller than one-sixth of the ac voltage amplitude under the simulated discharge parameters.

  14. SiC Nanoparticles Toughened-SiC/MoSi2-SiC Multilayer Functionally Graded Oxidation Protective Coating for Carbon Materials at High Temperatures

    NASA Astrophysics Data System (ADS)

    Abdollahi, Alireza; Ehsani, Naser; Valefi, Zia; Khalifesoltani, Ali

    2017-05-01

    A SiC nanoparticle toughened-SiC/MoSi2-SiC functionally graded oxidation protective coating on graphite was prepared by reactive melt infiltration (RMI) at 1773 and 1873 K under argon atmosphere. The phase composition and anti-oxidation behavior of the coatings were investigated. The results show that the coating was composed of MoSi2, α-SiC and β-SiC. By the variations of Gibbs free energy (calculated by HSC Chemistry 6.0 software), it could be suggested that the SiC coating formed at low temperatures by solution-reprecipitation mechanism and at high temperatures by gas-phase reactions and solution-reprecipitation mechanisms simultaneously. SiC nanoparticles could improve the oxidation resistance of SiC/MoSi2-SiC multiphase coating. Addition of SiC nanoparticles increases toughness of the coating and prevents spreading of the oxygen diffusion channels in the coating during the oxidation test. The mass loss and oxidation rate of the SiC nanoparticle toughened-SiC/MoSi2-SiC-coated sample after 10-h oxidation at 1773 K were only 1.76% and 0.32 × 10-2 g/cm3/h, respectively.

  15. SI and Non-SI Units of Concentration: A Truce?

    ERIC Educational Resources Information Center

    Rich, Ronald L.

    1986-01-01

    Questions the current usage of the International System of Units (called SI units) in representing chemical notation and terminology. Suggests several additions to the system that relate to concentrations. Outlines new symbols for distinguishing between "concentration" and "molality." Includes tables to illustrate the proposed SI units. (TW)

  16. Hydrogen-induced crystallization of amorphous Si thin films. II. Mechanisms and energetics of hydrogen insertion into Si-Si bonds

    SciTech Connect

    Valipa, Mayur S.; Sriraman, Saravanapriyan; Aydil, Eray S.; Maroudas, Dimitrios

    2006-09-01

    We report a detailed study of the mechanisms and energetics of hydrogen (H) insertion into strained Si-Si bonds during H-induced crystallization of hydrogenated amorphous Si (a-Si:H) thin films. Our analysis is based on molecular-dynamics (MD) simulations of exposure of a-Si:H films to H atoms from a H{sub 2} plasma through repeated impingement of H atoms. Hydrogen atoms insert into Si-Si bonds as they diffuse through the a-Si:H film. Detailed analyses of the evolution of Si-Si and Si-H bond lengths from the MD trajectories show that diffusing H atoms bond to one of the Si atoms of the strained Si-Si bond prior to insertion; upon insertion, a bridging configuration is formed with the H atom bonded to both Si atoms, which remain bonded to each other. After the H atom leaves the bridging configuration, the Si-Si bond is either further strained, or broken, or relaxed, restoring the Si-Si bond length closer to the equilibrium bond length in crystalline Si. In some cases, during its diffusion in the a-Si:H film, the H atom occupies a bond-center position between two Si atoms that are not bonded to each other; after the H diffuses away from this bond-center position, a Si-Si bond is formed between these previously nonbonded Si atoms. The activation energy barrier for the H insertion reaction depends linearly on both the initial strain in the corresponding Si-Si bond and a strain factor that takes into account the additional stretching of the Si-Si bond in the transition-state configuration. The role of the H insertion reactions in the structural relaxation of the a-Si:H network that results in disorder-to-order transitions is discussed.

  17. Chemical vapor deposition of Si:C and Si:C:P films-Evaluation of material quality as a function of C content, carrier gas and doping

    NASA Astrophysics Data System (ADS)

    Dhayalan, Sathish Kumar; Loo, Roger; Hikavyy, Andriy; Rosseel, Erik; Bender, Hugo; Richard, Olivier; Vandervorst, Wilfried

    2015-09-01

    Incorporation of source-drain stressors (S/D) for FinFETs to boost the channel mobility is a promising scaling approach. Typically SiGe:B S/D stressors are used for p FinFETs and Si:C:P S/D stressors for n FinFETs. The deposition of such Si:C:P S/D stressors requires a low thermal budget to freeze the C in substitutional sites and also to avoid problems associated with surface reflow of Si fins. In this work, we report the material properties of Si:C and Si:C:P epitaxial layers grown by chemical vapor deposition, in terms of their defectivity and C incorporation as a function of different process conditions. The undoped Si:C layers were found to be defect free for total C contents below 1%. Above this concentration defects were incorporated and the defect density increased with increasing C content. Abrupt epitaxial breakdown occurred beyond a total C content of 2.3% resulting in amorphous layers. P doping of Si:C layers brought down the resistivity and also thicker Si:C:P films underwent epitaxial breakdown. Additionally, the use of nitrogen instead of hydrogen as carrier gas resulted in an increase of the growth rate and substitutional C incorporation both by a factor of two, while the surface defect density reduced.

  18. Endotaxial Si nanolines in Si(001):H

    NASA Astrophysics Data System (ADS)

    Owen, James; Bianco, François; Köster, Sigrun A.; Mazur, Daniel; Renner, Christoph; Bowler, David

    2011-03-01

    The study of one dimensional wires is of great interest in the area of low-dimensional physics, and these structures also have potential applications in future nanodevices. A perfectly straight nanoline embedded in a H-terminated silicon surface has been fabricated by a process of hydrogenation of a Bi nanoline surface using an atomic H beam source, and comprises a triangular core of Si embedded in the top five layers of the Si substrate. The defect density of this nanoline is extremely low, and being H- terminated, it is stable in air for limited periods of time. Scanning Tunnelling Microscopy experimental data and Density Functional Theory calculations have been used to determine the atomic structure of this nanoline, so-called the Haiku Stripe, and have revealed that there exists a 1D state localised to the nanoline core, lying just above the conduction band minimum. This work is supported by the Swiss National Science Fundation.

  19. Optoelectronic III-V Heterostructures on SI Substrates

    DTIC Science & Technology

    1990-09-14

    V optoelectronic devices operating at wavelengths (i.e., A > 1.2 microns) requiring a transparent substrate or monolithic waveguides. In addition to... integration of InP and related compounds with Si previously.’ The buffer layer was then capped with an un- would allow the combining of optical sources...modulators, doped InP active layer of 4/pm thickness grown at 480 C and detectors operating at 1.3 and 1.55 /m with Si integrated and 1 um/h. Reflection

  20. An inside job for siRNAs.

    PubMed

    Golden, Daniel E; Gerbasi, Vincent R; Sontheimer, Erik J

    2008-08-08

    Among the three main categories of small silencing RNAs in insects and mammals-siRNAs, miRNAs, and piRNAs-siRNAs were thought to arise primarily from exogenous sources, whereas miRNAs and piRNAs arise from endogenous loci. Recent work in flies and mice reveals several classes of endogenous siRNAs (endo-siRNAs) that contribute to functions previously reserved for miRNAs and piRNAs, including gene regulation and transposon suppression.

  1. Effect of zinc cations on the kinetics of supramolecular assembly and the chirality of porphyrin J-aggregates† †Electronic supplementary information (ESI) available: UV/Vis spectral changes during metallation (SI1) and demetallation (SI2) of TPPS, RLS profiles (SI3), fluorescence emission decay and time resolved and fluorescence anisotropy (SI4), m and n kinetic parameters as a function of Zn(ii) (SI5), ICP-OES analysis experimental conditions (Table SI1), and acquisition parameters for ICP-OES analysis (Table SI2). See DOI: 10.1039/c6sc02686a Click here for additional data file.

    PubMed Central

    Romeo, A.; Zagami, R.; Pollicino, G.; Pasternack, R. F.

    2017-01-01

    Dilute aqueous solutions of anionic meso-4-sulfonatophenyl-porphyrin (TPPS) extract zinc(ii) ions from glass or quartz surfaces at room temperature and efficiently form the corresponding metal complex (ZnTPPS). The partial or complete formation of ZnTPPS has been probed by UV/Vis spectroscopy and both static and time-resolved fluorescence. The source of zinc(ii) ions has been clearly identified through inductively coupled plasma optical emission spectrometry. The presence of increasing amounts of ZnTPPS slows down the rate of TPPS J-aggregate formation in acid solution. This influences the nucleation step and has a profound impact on the onset of chirality in these species. This evidence indicates the important role of this adventitious metal ion in the interpretation of various spectroscopic and kinetic data for the self-assembly of the TPPS porphyrin and provides some insights into controversial findings on their chirality. The use of this metal derivative as the starting compound for in situ formation of monomeric TPPS is suggested. PMID:28451233

  2. Food additives

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/002435.htm Food additives To use the sharing features on this page, please enable JavaScript. Food additives are substances that become part of a food ...

  3. SI: The Stellar Imager

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2006-01-01

    The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI s prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

  4. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  5. Reduction of hysteresis losses in the magnetic refrigerant La0.8Ce0.2Fe11.4Si1.6 by the addition of boron

    NASA Astrophysics Data System (ADS)

    Shamba, P.; Debnath, J. C.; Zeng, R.; Wang, J. L.; Campbell, S. J.; Kennedy, S. J.; Dou, S. X.

    2011-04-01

    In an effort to improve the magnetocaloric effects of the NaZn13-type La0.8Ce0.2Fe11.4Si1.6 compound, the effect of boron doping on the magnetic properties and magnetocaloric properties has been investigated. The magnetic entropy change (ΔSM) for the La0.8Ce0.2Fe11.4Si1.6 compound, obtained for a field change of 0-5 T using the Maxwell relation exhibits a spike and appears to be overestimated and is thus corrected by using the Clausius-Clapeyron equation (CC). The ΔSM determined from the CC equation is estimated to be 19.6 J kg-1K-1. However, large hysteretic losses which are detrimental to the magnetic refrigeration efficiency occur in the same temperature range. In this work, we report a significant reduction in hysteretic losses by doping the La0.8Ce0.2Fe11.4Si1.6 compound with a small amount of boron to obtain La0.8Ce0.2Fe11.4Si1.6Bx compounds. The hysteresis loss decreases from 131.5 to 8.1 J kg -1 when x increases from 0 to 0.3, while ΔSM, obtained for a field change of 0-5 T, varies from 19.6 to 15.9 J kg-1K-1. This also simultaneously shifts the TC from 174 to 184 K and significantly improves the effective refrigerant capacity (RCeff) of the material from 164 to 305 J kg-1.

  6. Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Meng, X G; Chen, C Z

    2014-06-01

    A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell.

  7. Role of surface-reaction layer in HBr/fluorocarbon-based plasma with nitrogen addition formed by high-aspect-ratio etching of polycrystalline silicon and SiO2 stacks

    NASA Astrophysics Data System (ADS)

    Iwase, Taku; Matsui, Miyako; Yokogawa, Kenetsu; Arase, Takao; Mori, Masahito

    2016-06-01

    The etching of polycrystalline silicon (poly-Si)/SiO2 stacks by using VHF plasma was studied for three-dimensional NAND fabrication. One critical goal is achieving both a vertical profile and high throughput for multiple-stack etching. While the conventional process consists of multiple steps for each stacked layer, in this study, HBr/fluorocarbon-based gas chemistry was investigated to achieve a single-step etching process to reduce process time. By analyzing the dependence on wafer temperature, we improved both the etching profile and rate at a low temperature. The etching mechanism is examined considering the composition of the surface reaction layer. X-ray photoelectron spectroscopy (XPS) analysis revealed that the adsorption of N-H and Br was enhanced at a low temperature, resulting in a reduced carbon-based-polymer thickness and enhanced Si etching. Finally, a vertical profile was obtained as a result of the formation of a thin and reactive surface-reaction layer at a low wafer temperature.

  8. [Prevalence of dental fluorosis and additional sources of exposure to fluoride as risk factors to dental fluorosis in schoolchildren of Campeche, Mexico].

    PubMed

    Beltrán-Valladares, Perla Rubí; Cocom-Tun, Héctor; Casanova-Rosado, Juan Fernando; Vallejos-Sánchez, Ana Alicia; Medina-Solís, Carlo Eduardo; Maupomé, Gerardo

    2005-01-01

    To determine the prevalence and severity of dental fluorosis, and to evaluate supplementary fluoride sources as potential risk factors to fluorosis in school children aged 6-9. A cross-sectional study was carried out in 320 children attending elementary schools protected by a public preventive dental program in the city of Campeche, Mexico. A self-administered questionnaire directed to the mothers was delivered through the schools and collected in the same way. The examiners were trained and calibrated (kappa > 0.90) in modified Dean's Index. The fluorosis community index (FCI) was calculated. Bivariate analyses were made with Chi2 test; odds ratios (OR) and 95% confidence intervals were calculated. Logistic regression was used in the final model. Fluorosis prevalence was 56.3%, with very mild fluorosis present in 45% of children, mild in 10%, and severe in just 1.3%. The FCI was 0.7. The multivariate model showed that the effect of the supplementary fluoride sources was different between children that started brushing with toothpaste before two years of age (OR = 6.15; IC 95% = 2.03-18.67) and after (OR = 2.14; IC 95% = 1.16-3.94). Fluorosis prevalence was high for mild modalities, and low for more severe levels. According to FCI the dental fluorosis constitute a public health problem in the studied sample. Exposure to diverse fluoride sources -above and beyond the fluoridated salt program- was a risk factor for dental fluorosis in this community. Results suggest that toothpaste use in children two years of age and younger should be cautious, limited to follow current guidelines, and supervised by parents to minimize the risk of dental fluorosis.

  9. Breeding Pierce’s disease resistant table and raisin grapes and the development of markers for additional sources of resistance 2008

    USDA-ARS?s Scientific Manuscript database

    Twenty-two seedless x seedless crosses to develop additional BC2 and BC3 V. arizonica and BC1 SEUS BD5-117 families were made in 2008. Powdery mildew resistance was included in five of these crosses. These crosses produced 5,148 berries, 8,824 ovules and 1,861 embryos. Nine seeded BC1 crosses bas...

  10. The Stellar Imager (SI) Vision Mission and the Benefits of an Ares V Launch

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth F.

    2008-01-01

    The Stellar Imager (SI) is a UV/Optical, Space-Based Interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. SI is a "Flagship and Landmark Discovery Mission" in the 2005 Heliophysics Roadmap and a potential implementation of the UVOI in the 2006 Science Program for NASA's Astronomy and Physics Division. In this paper we briefly discuss the science goals, technology needs, and baseline design of the SI Mission, and then describe the benefits to the mission that a launch on an Ares V, with its larger payload shroud, would produce. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.

  11. Substrate-Free Self-Assembled SiOx-Core Nanodots from Alkylalkoxysilane as a Multicolor Photoluminescence Source for Intravital Imaging

    PubMed Central

    Lin, Pei-Ying; Hsieh, Chiung-Wen; Kung, Mei-Lang; Hsieh, Shuchen

    2013-01-01

    Intravital fluorescence imaging has great potential in biological and biomedical research, as it provides the ability to directly observe biological structures and processes in their natural state. Contrast agents for intravital imaging applications should exhibit good biocompatibility, multiphoton fluorescence, and long emission. Carbon nanodots and semiconductor nanocrystals meet these requirements in most cases, with the added benefit that their properties can be ‘tuned' for specific applications by controlling the size and surface chemistry of the nanoparticles. Here, we report on a simple heat-assisted strategy to fabricate SiOx-core self-assembled nanodots using self-assembled monolayer (SAM) materials. Our results demonstrate that substrate-free self-assembled nanodots from alkylalkoxysilane exhibit controllable structural and chemical characteristics that are well suited for applications in biological, biomedical, and clinical research, and may find further use in optoelectronic and sensor devices. PMID:23609156

  12. Switchable resonant hyperpolarization transfer to 29Si spins in natural silicon

    NASA Astrophysics Data System (ADS)

    Dluhy, Phillip; Salvail, Jeff Z.; Saeedi, Kamyar; Thewalt, Mike L. W.; Simmons, Stephanie

    2015-05-01

    Silicon nano- and microparticles containing polarized 29Si spins are promising inexpensive and biocompatible medical imaging agents, particularly for magnetic resonance imaging (MRI). Maximizing out-of-equilibrium polarization (i.e., hyperpolarization) of the 29Si nuclear spins as efficiently as possible is critical for such an application. Here we identify and exploit a frequency-matched resonant transfer process between easily hyperpolarized bulk 31P and otherwise insensitive 29Si nuclear spins in natural silicon, boosting the 29Si signal to over 200 times its thermal equilibrium signal. This technique could be used in tandem with microwave-based hyperpolarization schemes for even higher efficiencies. Lastly, this hyperpolarization buildup process does not necessarily introduce an additional source of decoherence; after hyperpolarization the resonant transfer process can be switched off to recover the ultralong lifetimes of 29Si spins for in vivo imaging.

  13. Graphene synthesis on SiC: Reduced graphitization temperature by C-cluster and Ar-ion implantation

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Li, H.; Zhang, Z. D.; Wang, Z. S.; Zhou, S. Y.; Wang, Z.; Li, T. C.; Liu, J. R.; Fu, D. J.

    2015-08-01

    Thermal decomposition of SiC is a promising method for high quality production of wafer-scale graphene layers, when the high decomposition temperature of SiC is substantially reduced. The high decomposition temperature of SiC around 1400 °C is a technical obstacle. In this work, we report on graphene synthesis on 6H-SiC with reduced graphitization temperature via ion implantation. When energetic Ar, C1 and C6-cluster ions implanted into 6H-SiC substrates, some of the Si-C bonds have been broken due to the electronic and nuclear collisions. Owing to the radiation damage induced bond breaking and the implanted C atoms as an additional C source the graphitization temperature was reduced by up to 200 °C.

  14. Gluten-free bread with an addition of freeze-dried red and purple potatoes as a source of phenolic compounds in gluten-free diet.

    PubMed

    Gumul, Dorota; Ziobro, Rafał; Ivanišová, Eva; Korus, Anna; Árvay, Július; Tóth, Tomáš

    2017-02-01

    The basis for gluten-free diet is often gluten-free bread, which is usually characterized by a low-nutritional value, and lacks any pro-health properties. Only after an introduction of gluten-free raw materials, containing high level of bioactive compounds it would be possible to obtain the product with a pro-health potential. The aim of the study was to analyze the content of bioactive compounds (total phenolic content, phenolic acids, flavonoids, flavonols, anthocyanins and carotenoids) in gluten-free bread prepared with 5% addition of freeze-dried red and purple potatoes as well as to assess their antioxidant potential. Summarizing, among the analyzed gluten-free breads with an addition of freeze-dried red and purple potatoes, the best results could be obtained by using variety Magenta Love (red potato), which provided the highest levels of phenolic compounds and carotenoids and also antioxidant and antiradical activity.

  15. Surface morphology evolution of amorphous Fe Si layers upon thermal annealing

    NASA Astrophysics Data System (ADS)

    Sun, C. M.; Tsang, H. K.; Wong, S. P.; Ke, N.; Hark, S. K.

    2008-04-01

    Changes in the surface morphology of ion-beam-synthesized amorphous Fe-Si layers after rapid thermal annealing (RTA) and furnace annealing (FA) were investigated using atomic force microscopy and transmission electron microscopy. Completely amorphous Fe-Si layers were formed by Fe implantation at a dosage of 5 × 1015 cm-2 using a metal vapour vacuum arc ion source under 80 kV extraction voltage and cryogenic temperature. After RTA at 850 °C, β-FeSi2 precipitates in Si are completely aggregated from this amorphous Fe-Si layer and the surface of the implanted layer remains flat. To date, no obvious photoluminescence (PL) spectrum has been reported from RTA treated β-FeSi2 precipitates. However, after annealing at 850 °C for 40 s, high-quality β-FeSi2 precipitates in Si are obtained which clearly show 1.5 µm PL at 80 K for the first time. Even though additional long-term FA at 850 °C can enhance PL intensity to a limited extent, the longer thermal treatment induces the outdiffusion of β-FeSi2 precipitates and degrades the surface flatness.

  16. Si light-emitting device in integrated photonic CMOS ICs

    NASA Astrophysics Data System (ADS)

    Xu, Kaikai; Snyman, Lukas W.; Aharoni, Herzl

    2017-07-01

    The motivation for integrated Si optoelectronics is the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive biochemical sensors in the environmental control or medicine leads to the development of integrated high resolution sensors. Here CMOS-compatible Si light-emitting device structures are presented for investigating the effect of various depletion layer profiles and defect engineering on the photonic transition in the 1.4-2.8 eV. A novel Si device is proposed to realize both a two-terminal Si-diode light-emitting device and a three-terminal Si gate-controlled diode light-emitting device in the same device structure. In addition to the spectral analysis, differences between two-terminal and three-terminal devices are discussed, showing the light emission efficiency change. The proposed Si optical source may find potential applications in micro-photonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry.

  17. Comparison of low frequency charge noise in identically patterned Si/SiO{sub 2} and Si/SiGe quantum dots

    SciTech Connect

    Freeman, Blake M.; Schoenfield, Joshua S.; Jiang, HongWen

    2016-06-20

    We investigate and compare the charge noise in Si/SiO{sub 2} and Si/SiGe gate defined quantum dots with identically patterned gates by measuring the low frequency 1/f current noise through the biased quantum dots in the coulomb blockade regime. The current noise is normalized and used to extract a measurement of the potential energy noise in the system. Additionally, the temperature dependence of this noise is investigated. The measured charge noise in Si/SiO{sub 2} compares favorably with that of the SiGe device as well as previous measurements made on other substrates suggesting Si/SiO{sub 2} is a potential candidate for spin based quantum computing.

  18. Potential N2O Emissions from the Tanks of Bromeliads Suggest an Additional Source of N2O in the Neotropics.

    PubMed

    Suleiman, Marcel; Brandt, Franziska B; Brenzinger, Kristof; Martinson, Guntars O; Braker, Gesche

    2016-12-06

    We studied the propensity of the tank bromeliad Werauhia gladioliflora to emit the greenhouse gas nitrous oxide (N2O) at current and at increased N deposition levels in the range of predicted future scenarios. Potential production rates and net accumulation of N2O from tank substrate corresponded to N availability. N2O was produced in excess at all N levels due to a low level of N2O reductase activity which agreed well with a low abundance of N2O reducers compared to nitrite reducers. Transcriptional activation, however, indicated that expression of denitrification genes may be enhanced with increasing N supply eventually leading to more efficient N2O turnover with potential for adaptation of denitrifier communities to higher N levels. Our findings indicate that tank bromeliads may constitute a novel source of N2O in Neotropical forest canopies but further studies are required to understand the size and significance of in situ N2O fluxes from tank bromeliads to the environment.

  19. Potential biofuel additive from renewable sources--Kinetic study of formation of butyl acetate by heterogeneously catalyzed transesterification of ethyl acetate with butanol.

    PubMed

    Ali, Sami H; Al-Rashed, Osama; Azeez, Fadhel A; Merchant, Sabiha Q

    2011-11-01

    Butyl acetate holds great potential as a sustainable biofuel additive. Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is eco-friendly and offers several advantages over the commonly used Fischer Esterification. The Amberlite IR 120- and Amberlyst 15-catalyzed transesterification is studied in a batch reactor over a range of catalyst loading (6-12 wt.%), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15-333.15K). A butanol mole fraction of 0.2 in the feed is found to be optimum. Amberlite IR 120 promotes faster kinetics under these conditions. The transesterifications studied are slightly exothermic. The moles of solvent sorbed per gram of catalyst decreases (ethanol>butanol>ethyl acetate>butyl acetate) with decrease in solubility parameter. The dual site models, the Langmuir Hinshelwood and Popken models, are the most successful in correlating the kinetics over Amberlite IR 120 and Amberlyst 15, respectively.

  20. Kilogram-scale production of SnO(2) yolk-shell powders by a spray-drying process using dextrin as carbon source and drying additive.

    PubMed

    Choi, Seung Ho; Kang, Yun Chan

    2014-05-05

    A simple and general method for the large-scale production of yolk-shell powders with various compositions by a spray-drying process is reported. Metal salt/dextrin composite powders with a spherical and dense structure were obtained by spray drying and transformed into yolk-shell powders by simple combustion in air. Dextrin plays a key role in the preparation of precursor powders for fabricating yolk-shell powders by spray drying. Droplets containing metal salts and dextrin show good drying characteristics even in a severe environment of high humidity. Sucrose, glucose, and polyvinylpyrrolidone are widely used as carbon sources in the preparation of metal oxide/carbon composite powders; however, they are not appropriate for large-scale spray-drying processes because of their caramelization properties and adherence to the surface of the spray dryer. SnO2 yolk-shell powders were studied as the first target material in the spray-drying process. Combustion of tin oxalate/dextrin composite powders at 600 °C in air produced single-shelled SnO2 yolk-shell powders with the configuration SnO2 @void@SnO2 . The SnO2 yolk-shell powders prepared by the simple spray-drying process showed superior electrochemical properties, even at high current densities. The discharge capacities of the SnO2 yolk-shell powders at a current density of 2000 mA g(-1) were 645 and 570 mA h g(-1) for the second and 100th cycles, respectively; the corresponding capacity retention measured for the second cycle was 88 %. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Mechanism for Si-Si Bond Rupture in Single Molecule Junctions.

    PubMed

    Li, Haixing; Kim, Nathaniel T; Su, Timothy A; Steigerwald, Michael L; Nuckolls, Colin; Darancet, Pierre; Leighton, James L; Venkataraman, Latha

    2016-12-14

    The stability of chemical bonds can be studied experimentally by rupturing single molecule junctions under applied voltage. Here, we compare voltage-induced bond rupture in two Si-Si backbones: one has no alternate conductive pathway whereas the other contains an additional naphthyl pathway in parallel to the Si-Si bond. We show that in contrast to the first system, the second can conduct through the naphthyl group when the Si-Si bond is ruptured using an applied voltage. We investigate this voltage induced Si-Si bond rupture by ab initio density functional theory calculations and molecular dynamics simulations that ultimately demonstrate that the excitation of molecular vibrational modes by tunneling electrons leads to homolytic Si-Si bond rupture.

  2. Diminution of 2,3,5-triphenyltetrazolium chloride toxicity on Listeria monocytogenes growth by iron source addition to the culture medium.

    PubMed

    Junillon, Thomas; Flandrois, Jean-Pierre

    2014-04-01

    Tetrazolium salts (TTZ) such as 2,3,5-triphenyltetrazolium chloride (TTC) are readily reduced by bacterial populations of various genus. The reduced form of these redox indicators is conspicuously colored allowing a quick and easy detection of growth. The studies are mainly confined to Gram negative bacteria because of an important toxic effect of tetrazolium salts on Gram positive bacteria. Indeed, we observed an important impact of different tetrazolium salts on Listeria monocytogenes growth, curiously limited to an increase in the duration of the lag phase. In this study, we demonstrate that increasing the iron concentration in a medium containing TTC leads to a significant decrease of the lag phase. L. monocytogenes growth was kinetically measured and growth parameters were estimated using the Baranyi model. While lag phase diminution was found to be iron concentration dependent, growth rate was not affected. Addition of iron enables growth of some strains totally inhibited by a 0.4 g/l of TTC and for the other a significant reduction of the latency is observed. The nature of the mechanism resulting in a decrease of the observed lag phase remains unclear. Then, the use of iron supplementation may be proposed to overcome the inhibitory effect of TTC on L. monocytogenes. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Addition of thiols to the double bond of dipeptide C-terminal dehydroalanine as a source of new inhibitors of cathepsin C.

    PubMed

    Lenartowicz, Paweł; Makowski, Maciej; Oszywa, Bartosz; Haremza, Kinga; Latajka, Rafał; Pawełczak, Małgorzata; Kafarski, Paweł

    2017-08-01

    Addition of thiols to double bond of glycyl-dehydroalanine and phenyl-dehydroalanine esters provided micromolar inhibitors of cathepsin C. The structure-activity studies indicated that dipeptides containing N-terminal phenylalanine exhibit higher affinity towards the enzyme. A series of C-terminal S-substituted cysteines are responsible for varying interaction with S1 binding pocket of cathepsin C. Depending on diastereomer these compounds most likely act as slowly reacting substrates or competitive inhibitors. This was proved by TLC analysis of the medium in which interaction of methyl (S)-phenylalanyl-(R,S)-(S-adamantyl)cysteinate (7i) with the enzyme was studied. Molecular modeling enabled to establish their mode of binding showed that S2 pocket is long and narrow and accommodates phenyl group of phenylalanine while significantly spacious sites located at the surface of the enzyme (one of them being S1 pocket) bind the adamantyl moiety oriented in different direction for each stereoisomer. Finally replacement of carboxymethyl moiety of methyl (S)-phenylalanyl-(R,S)-(S-phenyl)cysteinate (7c) with nitrile group provided about 650-times more potent inhibitor of cathepsin C indicating that the studied C-terminal S-substituted cysteines are good activity probes for S1 binding pocket of this enzyme. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  4. Effect of the addition of zero valent iron (Fe(0)) on the batch biological sulphate reduction using grass cellulose as carbon source.

    PubMed

    Mulopo, Jean; Schaefer, L

    2013-12-01

    Mineral mining generates acidic, saline, metal-rich mine waters, often referred to as acid mine drainage (AMD). Treatment of AMD and recovering saleable products during the treatment process are a necessity since water is, especially in South Africa, a scarce commodity. The aim of the study presented here was to investigate the effect of zero valent iron (Fe(0)) on the biological removal of sulphate from AMD in batch reactors. The performance of the reactors was assessed by means of sulphate reduction, chemical oxygen demand (COD), volatile fatty acid (VFA) utilisation and volatile suspended solids (VSS) concentration. To this end, three batch reactors, A, B and C (volume 2.5 L), were operated similarly with the exception of the addition of grass cuttings and iron filings. Reactors A and B received twice as much grass (100 g) as C (50 g). Reactor A received no iron filings to act as a control, while reactors B and C received 50-g iron filings for the experimental duration. The results showed that Fe(0) appears to provide sustained sulphate removal when sufficient grass substrate is available. In reactors A and C, sulphate removal efficiency was higher when the COD concentration was lower due to utilisation. In reactor B, sulphate removal efficiency was accompanied by an accumulation of COD as hydrogen (H2) provided by the Fe(0) was utilised for sulphate reduction. Furthermore, these results showed the potential of Fe(0) to enhance the participation of microorganisms in sulphate reduction.

  5. Identification of the light-independent phosphoserine pathway as an additional source of serine in the cyanobacterium Synechocystis sp. PCC 6803.

    PubMed

    Klemke, Friederike; Baier, Antje; Knoop, Henning; Kern, Ramona; Jablonsky, Jiri; Beyer, Gabriele; Volkmer, Thomas; Steuer, Ralf; Lockau, Wolfgang; Hagemann, Martin

    2015-05-01

    L-serine is one of the proteinogenic amino acids and participates in several essential processes in all organisms. In plants, the light-dependent photorespiratory and the light-independent phosphoserine pathways contribute to serine biosynthesis. In cyanobacteria, the light-dependent photorespiratory pathway for serine synthesis is well characterized, but the phosphoserine pathway has not been identified. Here, we investigated three candidate genes for enzymes of the phosphoserine pathway in Synechocystis sp. PCC 6803. Only the gene for the D-3-phosphoglycerate dehydrogenase is correctly annotated in the genome database, whereas the 3-phosphoserine transaminase and 3-phosphoserine phosphatase (PSP) proteins are incorrectly annotated and were identified here. All enzymes were obtained as recombinant proteins and showed the activities necessary to catalyse the three-step phosphoserine pathway. The genes coding for the phosphoserine pathway were found in most cyanobacterial genomes listed in CyanoBase. The pathway seems to be essential for cyanobacteria, because it was impossible to mutate the gene coding for PSP in Synechocystis sp. PCC 6803 or in Synechococcus elongatus PCC 7942. A model approach indicates a 30-60% contribution of the phosphoserine pathway to the overall serine pool. Hence, this study verified that cyanobacteria, similar to plants, use the phosphoserine pathway in addition to photorespiration for serine biosynthesis. © 2015 The Authors.

  6. Inherent paramagnetic defects in layered Si/SiO{sub 2} superstructures with Si nanocrystals

    SciTech Connect

    Jivanescu, M.; Stesmans, A.; Zacharias, M.

    2008-11-15

    An extensive electron spin resonance (ESR) analysis has been carried out on structures comprised of Si nanoparticles ({approx}2 nm across) embedded in a regular pattern in an amorphous SiO{sub 2} matrix, fabricated by the SiO/SiO{sub 2} superlattice approach, with the intent to reveal and quantify occurring paramagnetic defects. The as-grown state is found to exhibit only a Si dangling bond (DB) signal, which through combination of first and second harmonic X-, K-, and Q-band observations in combination with computer spectra simulation, could be conclusively disentangled as solely comprised of overlapping powder pattern spectra of P{sub b(0)} and P{sub b1} defects, the archetypal intrinsic defects of the Si/SiO{sub 2} interface, with no evidence for a D line (Si DBs in disordered Si). This indicates a full crystalline system of randomly oriented Si nanocrystals (NCs). The P{sub b(0)}/P{sub b1} defect system, pertaining to the NC-Si/SiO{sub 2} interfaces, is found to be both qualitatively and quantitatively much alike that of standard (high-quality) thermal Si/SiO{sub 2}. The system is inherent, remaining unaffected by subsequent UV/vacuum UV irradiations. Relying on the known properties of P{sub b}-type defects in standard microscopic Si/SiO{sub 2}, the data would comply with Si nanocrystallites, in average, predominantly bordered by (111) and (100) facets, perhaps with morphology, schematically, of [100] truncated (111) octahedrons. Based on independent NC particles counting, there appears a P{sub b}-type center at {approx}71% of the Si NCs indicating the latter to be comprised of two subsystems-with or without an incorporated strain relaxing interface defect-which in that case will exhibit drastically different defect-sensitive properties, such as, e.g., photoluminescence (PL). Upon additional optical irradiation, two more defects appear, i.e., the SiO{sub 2}-associated E{sub {gamma}}{sup '} and EX centers, where the observed density of the former, taken as

  7. Synthesis of epitaxial Si(100) nanowires on Si(100) substrate using vapor liquid solid growth in anodic aluminum oxide nanopore arrays

    NASA Astrophysics Data System (ADS)

    Shimizu, T.; Senz, S.; Shingubara, S.; Gösele, U.

    2007-06-01

    The synthesis of epitaxial Si nanowires with growth direction parallel to Si [100] on Si(100) substrate was demonstrated using a combination of anodic aluminum oxide (AAO) template, catalytic gold film sandwiched between the template and the Si(100) substrate and vapor-liquid-solid growth using SiH4 as the Si source. After growing out from the AAO nanopores, most Si nanowires changed their diameter and growth direction into larger diameter and <111> direction.

  8. Absence of quantum confinement effects in the photoluminescence of Si3N4-embedded Si nanocrystals

    NASA Astrophysics Data System (ADS)

    Hiller, D.; Zelenina, A.; Gutsch, S.; Dyakov, S. A.; López-Conesa, L.; López-Vidrier, J.; Estradé, S.; Peiró, F.; Garrido, B.; Valenta, J.; Kořínek, M.; Trojánek, F.; Malý, P.; Schnabel, M.; Weiss, C.; Janz, S.; Zacharias, M.

    2014-05-01

    Superlattices of Si-rich silicon nitride and Si3N4 are prepared by plasma-enhanced chemical vapor deposition and, subsequently, annealed at 1150 °C to form size-controlled Si nanocrystals (Si NCs) embedded in amorphous Si3N4. Despite well defined structural properties, photoluminescence spectroscopy (PL) reveals inconsistencies with the typically applied model of quantum confined excitons in nitride-embedded Si NCs. Time-resolved PL measurements demonstrate 105 times faster time-constants than typical for the indirect band structure of Si NCs. Furthermore, a pure Si3N4 reference sample exhibits a similar PL peak as the Si NC samples. The origin of this luminescence is discussed in detail on the basis of radiative defects and Si3N4 band tail states in combination with optical absorption measurements. The apparent absence of PL from the Si NCs is explained conclusively using electron spin resonance data from the Si/Si3N4 interface defect literature. In addition, the role of Si3N4 valence band tail states as potential hole traps is discussed. Most strikingly, the PL peak blueshift with decreasing NC size, which is often observed in literature and typically attributed to quantum confinement (QC), is identified as optical artifact by transfer matrix method simulations of the PL spectra. Finally, criteria for a critical examination of a potential QC-related origin of the PL from Si3N4-embedded Si NCs are suggested.

  9. NGSI student activities in open source information analysis in support of the training program of the U.S. DOE laboratories for the entry into force of the additional protocol

    SciTech Connect

    Sandoval, M Analisa; Uribe, Eva C; Sandoval, Marisa N; Boyer, Brian D; Stevens, Rebecca S

    2009-01-01

    In 2008 a joint team from Los Alamos National Laboratory (LANL) and Brookhaven National Laboratory (BNL) consisting of specialists in training of IAEA inspectors in the use of complementary access activities formulated a training program to prepare the U.S. Doe laboratories for the entry into force of the Additional Protocol. As a major part of the support of the activity, LANL summer interns provided open source information analysis to the LANL-BNL mock inspection team. They were a part of the Next Generation Safeguards Initiative's (NGSI) summer intern program aimed at producing the next generation of safeguards specialists. This paper describes how they used open source information to 'backstop' the LANL-BNL team's effort to construct meaningful Additional Protocol Complementary Access training scenarios for each of the three DOE laboratories, Lawrence Livermore National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory.

  10. Using JVLA Observations of SiO Masers to Probe the Extended Atmosphere of an AGB Star: W Hydrae

    NASA Astrophysics Data System (ADS)

    Kamieneski, Patrick S.; Matthews, Lynn D.

    2015-01-01

    The Asymptotic Giant Branch star W Hydrae (W Hya) is known to be a strong source of silicon monoxide (SiO) masers in its extended atmosphere. Jansky Very Large Array imaging observations obtained in February 2014 were used to target eleven SiO J=1-0 rotational transitions near 43 GHz. The vibrational ground state (v=0) lines for the 28SiO, 29SiO, and 30SiO isotopologues were successfully detected, as were the v=1,2,3 lines for 28SiO. Non-detections included the v=1,2 transitions for 29SiO and 30SiO, and the v=4 line for 28SiO. We will summarize the relative shape, size, and intensity of the emission regions of the detected transitions. We have discovered spatially extended ground-state 28SiO emission in a region located approximately 300 to 600 milliarcseconds (projected distance of 34 to 69 AU) from the star. We will discuss a saddle-like distribution and a small gradient in the velocity field for the 28SiO v=1 line, which may help to confirm the existence of a bipolar outflow in W Hya. Additionally, our results indicate that the observed transitions have differing spatial distributions. Peak 28SiO v=1,2,3 emission primarily occupies a region 12 - 42 mas (projected distance of 1.4 - 4.8 AU) west of the star, while the 29SiO and 30SiO isotopologues are located in disparate regions around 45 - 70 mas (5.2 - 8.1 AU) to the northwest of the star.This work was sponsored by a grant from the National Science Foundation Research Experience for Undergraduate program to MIT Haystack Observatory.

  11. Discovery of a Plains Caldera Complex and Extinct Lava Lake in Arabia Terra, Mars: Implications for the Discovery of Additional Highland Volcanic Source Regions

    NASA Technical Reports Server (NTRS)

    Bleacher, Jacob; Michalski, Joseph

    2012-01-01

    Several irregularly shaped topographic depressions occur near the dichotomy boundary in northern Arabia Terra, Mars. The geomorphology of these features suggests that they formed by collapse, opposed to meteor impact. At least one depression (approx.55 by 85 km) displays geologic features indicating a complex, multi-stage collapse history. Features within and around the collapse structure indicate volcanic processes. The complex occurs within Hesperian ridged plains of likely volcanic origin and displays no crater rim or evidence for ejecta. Instead the depression consists of a series of circumferential graben and down-dropped blocks which also display upper surfaces similar to ridged plain lavas. Large blocks within the depression are tilted towards the crater center, and display graben that appear to have originally been linked with circumferential graben outside of the complex related to earlier collapse events. A nearly 700 m high mound exists along a graben within the complex that might be a vent. The deepest depression displays two sets of nearly continuous terraces, which we interpret as high-stands of a drained lava lake. These features appear similar to the black ledge described during the Kilauea Iki eruption in 1959. A lacustrine origin for the terraces seems unlikely because of the paucity of channels found in or around the depression that could be linked to aqueous surface processes. In addition, there is no obvious evidence for lacustrine sediments within the basin. Together with the presence of significant faulting that is indicative of collapse we conclude that this crater complex represents a large caldera formed in the Late Noachian to Early Hesperian. Other linear and irregular depressions in the region also might be linked to ancient volcanism. If that hypothesis is correct, it suggests that northern Arabia Terra could contain a large, previously unrecognized highland igneous province. Evacuation of magma via explosive and effusive activity

  12. Effects of different fibre sources and fat addition on cholesterol and cholesterol-related lipids in blood serum, bile and body tissues of growing pigs.

    PubMed

    Kreuzer, M; Hanneken, H; Wittmann, M; Gerdemann, M M; Machmuller, A

    2002-04-01

    Knowledge is limited on the efficacy of hindgut-fermentable dietary fibre to reduce blood, bile and body tissue cholesterol levels. In three experiments with growing pigs the effects of different kinds and levels of bacterially fermentable fibre (BFS) on cholesterol metabolism were examined. Various diets calculated to have similar contents of metabolizable energy were supplied for complete fattening periods. In the first experiment, a stepwise increase from 12 to 20% BFS was performed by supplementing diets with fermentable fibre from sugar beet pulp (modelling hemicelluloses and pectin). Beet pulp, rye bran (modelling cellulose) and citrus pulp (pectin) were offered either independently or in a mixture in the second experiment. These diets were opposed to rations characterized in carbohydrate type by starch either mostly non-resistant (cassava) or partly resistant (maize) to small intestinal digestion. The third experiment was planned to explore the interactions of BFS from citrus pulp with fat either through additional coconut oil/palm kernel oil blend or full-fat soybeans. In all experiments the increase of the BFS content was associated with a constant (cellulose) or decreasing (hemicelluloses, pectin) dietary proportion of non-digestible fibre. In experiment 1 an inverse dose-response relationship between BFS content and cholesterol in blood serum and adipose tissue as well as bile acid concentration in bile was noted while muscle cholesterol did not respond. In experiment 2 the ingredients characterized by cellulose and hemicelluloses/pectin reduced cholesterol-related traits relative to the low-BFS-high-starch controls whereas, except in adipose tissue cholesterol content, the pectinous ingredient had the opposite effect. However, the changes in serum cholesterol mainly affected HDL and not LDL cholesterol. Adipose tissue cholesterol also was slightly lower with partly resistant starch compared to non-resistant starch in the diet. Experiment 3 showed that

  13. SiC JFET Transistor Circuit Model for Extreme Temperature Range

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2008-01-01

    A technique for simulating extreme-temperature operation of integrated circuits that incorporate silicon carbide (SiC) junction field-effect transistors (JFETs) has been developed. The technique involves modification of NGSPICE, which is an open-source version of the popular Simulation Program with Integrated Circuit Emphasis (SPICE) general-purpose analog-integrated-circuit-simulating software. NGSPICE in its unmodified form is used for simulating and designing circuits made from silicon-based transistors that operate at or near room temperature. Two rapid modifications of NGSPICE source code enable SiC JFETs to be simulated to 500 C using the well-known Level 1 model for silicon metal oxide semiconductor field-effect transistors (MOSFETs). First, the default value of the MOSFET surface potential must be changed. In the unmodified source code, this parameter has a value of 0.6, which corresponds to slightly more than half the bandgap of silicon. In NGSPICE modified to simulate SiC JFETs, this parameter is changed to a value of 1.6, corresponding to slightly more than half the bandgap of SiC. The second modification consists of changing the temperature dependence of MOSFET transconductance and saturation parameters. The unmodified NGSPICE source code implements a T(sup -1.5) temperature dependence for these parameters. In order to mimic the temperature behavior of experimental SiC JFETs, a T(sup -1.3) temperature dependence must be implemented in the NGSPICE source code. Following these two simple modifications, the Level 1 MOSFET model of the NGSPICE circuit simulation program reasonably approximates the measured high-temperature behavior of experimental SiC JFETs properly operated with zero or reverse bias applied to the gate terminal. Modification of additional silicon parameters in the NGSPICE source code was not necessary to model experimental SiC JFET current-voltage performance across the entire temperature range from 25 to 500 C.

  14. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  15. Phosphazene additives

    DOEpatents

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  16. Tailoring of Boehmite-Derived Aluminosilicate Aerogel Structure and Properties: Influence of Ti Addition

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Guo, Haiquan; Sheets, Erik J.; Miller, Derek R.; Newlin, Katy N.

    2010-01-01

    Aluminosilicate aerogels offer potential for extremely low thermal conductivities at temperatures greater than 900 C, beyond where silica aerogels reach their upper temperature limits. Aerogels have been synthesized at various Al:Si ratios, including mullite compositions, using Boehmite (AlOOH) as the Al source, and tetraethoxy orthosilicate as the Si precursor. The Boehmite-derived aerogels are found to form by a self-assembly process of AlOOH crystallites, with Si-O groups on the surface of an alumina skeleton. Morphology, surface area and pore size varies with the crystallite size of the starting Boehmite powder, as well as with synthesis parameters. Ternary systems, including Al-Si-Ti aerogels incorporating a soluble Ti precursor, are possible with careful control of pH. The addition of Ti influences sol viscosity, gelation time pore structure and pore size distribution, as well as phase formation on heat treatment.

  17. Electroluminescence from Si/SiGe quantum cascade emitters

    NASA Astrophysics Data System (ADS)

    Paul, D. J.; Lynch, S. A.; Bates, R.; Ikonic, Z.; Kelsall, R. W.; Harrison, P.; Norris, D. J.; Liew, S. L.; Cullis, A. G.; Murzyn, P.; Pidgeon, C.; Arnone, D. D.; Robbins, D. J.

    2003-03-01

    Intersubband electroluminescence results are presented from Si/SiGe quantum cascade emitters at 3.2 THz and at temperatures up to 150 K. The effect of adding doping into the active quantum wells was studied in addition to reduced barrier widths from previous measurements. While the current through the sample is increased by the addition of doping, the emitted power is reduced through additional free carrier absorption and Coulombic scattering. Free electron laser measurements confirm the intersubband transitions in the quantum wells of the cascade devices and produce non-radiative lifetimes of ∼20 ps between 4 and 150 K.

  18. A detailed coupled-mode-space non-equilibrium Green's function simulation study of source-to-drain tunnelling in gate-all-around Si nanowire metal oxide semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Seoane, N.; Martinez, A.

    2013-09-01

    In this paper we present a 3D quantum transport simulation study of source-to-drain tunnelling in gate-all-around Si nanowire transistors by using the non-equilibrium Green's function approach. The impact of the channel length, device cross-section, and drain and gate applied biases on the source-to-drain tunnelling is examined in detail. The overall effect of tunnelling on the ID-VG characteristics is also investigated. Tunnelling in devices with channel lengths of 10 nm or less substantially enhances the off-current. This enhancement is more important at high drain biases and at larger cross-sections where the sub-threshold slope is substantially degraded. A less common effect is the increase in the on-current due to the tunnelling which contributes as much as 30% of the total on-current. This effect is almost independent of the cross-section, and it depends weakly on the studied channel lengths.

  19. Controlling deposition of nanoparticles by tuning surface charge of SiO2 by surface modifications† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra22412a Click here for additional data file.

    PubMed Central

    Eklöf, Johnas; Gschneidtner, Tina; Lara-Avila, Samuel; Nygård, Kim

    2016-01-01

    The self-assembly of nanoparticles on substrates is relevant for a variety of applications such as plasmonics, sensing devices and nanometer-sized electronics. We investigate the deposition of 60 nm spherical Au nanoparticles onto silicon dioxide (SiO2) substrates by changing the chemical treatment of the substrate and by that altering the surface charge. The deposition is characterized by scanning electron microscopy (SEM). Kelvin probe force microscopy (KPFM) was used to characterize the surface workfunction. The underlying physics involved in the deposition of nanoparticles was described by a model based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory combined with random sequential adsorption (RSA). The spatial statistical method Ripley's K-function was used to verify the DLVO–RSA model (ERSA). The statistical results also showed that the adhered particles exhibit a short-range order at distances below ~300 nm. This method can be used in future research to predict the deposition densities of charged nanoparticles onto charged surfaces. PMID:28066544

  20. SEMICONDUCTOR TECHNOLOGY: SBH adjustment characteristic of the dopant segregation process for NiSi/n-Si SJDs

    NASA Astrophysics Data System (ADS)

    Haiping, Shang; Qiuxia, Xu

    2010-05-01

    By means of analyzing the I-V characteristic curve of NiSi/n-Si Schottky junction diodes (NiSi/n-Si SJDs), abstracting the effective Schottky barrier height (varphiB, eff) and the ideal factor of NiSi/n-Si SJDs and measuring the sheet resistance of NiSi films (RNiSi), we study the effects of different dopant segregation process parameters, including impurity implantation dose, segregation annealing temperature and segregation annealing time, on the varphiB, eff of NiSi/n-Si SJDs and the resistance characteristic of NiSi films. In addition, the changing rules of varphiB, eff and RNiSi are discussed.

  1. Carbon Diffusion through SiO2 from a Hydrogenated Amorphous Carbon Layer and Accumulation at the SiO2/Si Interface

    NASA Astrophysics Data System (ADS)

    Krafcsik, Olga H.; Vida, György; Pócsik, István; Josepovits, Katalin V.; Deák, Péter

    2001-04-01

    Carbon diffusion in a SiO2/Si system was investigated. The source was provided by chemical vapor deposition of a hydrogenated amorphous carbon layer onto the oxide at low temperature. From layers with low oxygen content, no carbon outdiffusion was detected up to 1190°C@. If the O content was high, the diffusion would start suddenly at 1140°C, and carbon accumulation would be found on the Si side of the SiO2/Si interface in the form of SiC precipitates. These results are interpreted by assuming oxygen-assisted dissociation of carbon atoms from the carbon layer in form of CO molecules, fast CO diffusion through SiO2 and an exothermic reaction of CO with Si. No carbon segregation was found in SiO2. Consequences of carbon island formation during SiC oxidation are pointed out.

  2. Synthesis of several millimeters long SiC-SiO2 nanowires by a catalyst-free technique

    NASA Astrophysics Data System (ADS)

    Dong, Shun; Li, Minglun; Hu, Ping; Cheng, Yuan; Sun, Boqian

    2016-11-01

    In situ synthesis of ultra-long SiC-SiO2 nanowires were successfully conducted with the raw materials of silicon and phenolic resin by an effective and catalyst-free technique. Several millimeters long SiC-SiO2 nanowires with the diameters in the range of 50-200 nm were mainly composed of Si, C and a small amount of O, and the formation of several millimeters long SiC-SiO2 nanowires was attributed to a low flow rate and carbon sources supplied continuously by the pyrolysis of phenolic resin. A catalyst-free vapor-solid (VS) growth mechanism was proposed to illustrate the growth process of ultra-long SiC-SiO2 nanowires in present experiment, which provides a promising method for in situ fabrication of SiC-SiO2 nanowires as reinforcements into composites.

  3. Electric field assisted low-temperature growth of SiGe on insulating films for future TFT

    NASA Astrophysics Data System (ADS)

    Miyao, Masanobu; Kanno, Hiroshi; Sadoh, Taizoh

    2008-02-01

    Development of new semiconductors with high mobility is strongly needed to realize future system-in-displays. To achieve this, we have been investigating electric field assisted metal-induced lateral crystallization (MILC) of a-Si 1-XGe X (0SiGe with all Ge fractions. In addition, thin-film transistors (TFTs) with Schottky source and drain structures were fabricated, which showed good ambipolar operation characteristics. Present paper reviews such our recent progress of electric field assisted low temperature SiGe growth and discusses the possible application to TFTs with high speed operation.

  4. Recycling of Al-Si die casting scraps for solar Si feedstock

    NASA Astrophysics Data System (ADS)

    Seo, Kum-Hee; Jeon, Je-Beom; Youn, Ji-Won; Kim, Suk Jun; Kim, Ki-Young

    2016-05-01

    Recycling of aluminum die-casting scraps for solar-grade silicon (SOG-Si) feedstock was performed successfully. 3 N purity Si was extracted from A383 die-casting scrap by using the combined process of solvent refining and an advanced centrifugal separation technique. The efficiency of separating Si from scrap alloys depended on both impurity level of scraps and the starting temperature of centrifugation. Impurities in melt and processing temperature governed the microstructure of the primary Si. The purity of Si extracted from the scrap melt was 99.963%, which was comparable to that of Si extracted from a commercial Al-30 wt% Si alloy, 99.980%. The initial purity of the scrap was 2.2% lower than that of the commercial alloy. This result confirmed that die-casting scrap is a potential source of high-purity Si for solar cells.

  5. Thermal Evaporation Synthesis and Optical Properties of ZnS Microbelts on Si and Si/SiO2 Substrates

    NASA Astrophysics Data System (ADS)

    Nguyen, V. N.; Khoi, N. T.; Nguyen, D. H.

    2017-06-01

    In this study, we report on the differences in optical properties of zinc sulfide (ZnS) microbelts grown on Si and Si/SiO2 substrates by a thermal evaporation method. Our investigation suggests that the composition and luminescence of the microbelts are dependent on the growth substrate. Field emission scanning electron microscopy images show the formation of nanoparticles with a diameter of 300-400 nm on ZnS microbelts grown on Si substrate. In addition, energy dispersive x-ray spectroscopy analysis combined with x-ray diffraction and Raman measurements reveal the existence of Si on these microbelts which may bond with O to form SiO2 or amorphous silica. In contrast, no Si presents on the microbelts grown on Si/SiO2 substrate. Moreover, photoluminescence measurement at 300 K shows a narrow emission peak in the near-ultraviolet region from microbelts grown on Si/SiO2 substrate but a broad emission band with multi-peaks from microbelts grown on Si substrate. The origin of the luminescence distinction between microbelts is discussed in terms of the differences in the growth substrates and compositions.

  6. An electrostatic ion pump with nanostructured Si field emission electron source and Ti particle collectors for supporting an ultra-high vacuum in miniaturized atom interferometry systems

    NASA Astrophysics Data System (ADS)

    Basu, Anirban; Velásquez-García, Luis F.

    2016-12-01

    We report a field emission-based, magnetic-less ion pump architecture for helping maintain a high vacuum within a small chamber that is compatible with miniaturized cold-atom interferometry systems. A nanostructured silicon field emitter array, with each nano-sharp tip surrounded by a self-aligned proximal gate electrode, is used to generate a surplus of electrons that cause impact ionization of gas molecules. A two-stage cylindrical electron collector, made of titanium, is used to increase the travel distance of the electrons, augmenting the ionization probability; gas ionization is subsequently followed by gettering of the ions by a negatively charged, annular-shaped titanium electrode. A proof-of-concept pump prototype was characterized using a 25 cm3 stainless steel vacuum chamber backed up by an external turbomolecular pump, a diaphragm pump, and a standard ion pump. Pumping action was observed with the electrostatic pump operating alone after an initial rapid rise of the chamber pressure due to electron/ion scrubbing. In addition, running the electrostatic pump in combination with the standard ion pump results in a lower vacuum level compared to the vacuum level produced by the standard ion pump acting alone. A proposed reduced-order model accurately predicts the functional dependence of the pressure versus time data and provides a good estimate of the characteristic pumping time constant inferred from the experiments.

  7. Facile Synthesis of Si@SiC Composite as an Anode Material for Lithium-Ion Batteries.

    PubMed

    Ngo, Duc Tung; Le, Hang T T; Pham, Xuan-Manh; Park, Choong-Nyeon; Park, Chan-Jin

    2017-09-18

    Here, we propose a simple method for direct synthesis of a Si@SiC composite derived from a SiO2@C precursor via a Mg thermal reduction method as an anode material for Li-ion batteries. Owing to the extremely high exothermic reaction between SiO2 and Mg, along with the presence of carbon, SiC can be spontaneously produced with the formation of Si. The synthesized Si@SiC was composed of well-mixed SiC and Si nanocrystallites. The SiC content of the Si@SiC was adjusted by tuning the carbon content of the precursor. Among the resultant Si@SiC materials, the Si@SiC-0.5 sample, which was produced from a precursor containing 4.37 wt % of carbon, exhibits excellent electrochemical characteristics, such as a high first discharge capacity of 1642 mAh g(-1) and 53.9% capacity retention following 200 cycles at a rate of 0.1C. Even at a high rate of 10C, a high reversible capacity of 454 mAh g(-1) was obtained. Surprisingly, at a fixed discharge rate of C/20, the Si@SiC-0.5 electrode delivered a high capacity of 989 mAh g(-1) at a charge rate of 20C. In addition, a full cell fabricated by coupling a lithiated Si@SiC-0.5 anode and a LiCoO2 cathode exhibits excellent cyclability over 50 cycles. This outstanding electrochemical performance of Si@SiC-0.5 is attributed to the SiC phase, which acts as a buffer layer that stabilizes the nanostructure of the Si active phase and enhances the electrical conductivity of the electrode.

  8. {sup 13}C chemical shift anisotropies for carbonate ions in cement minerals and the use of {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR in studies of Portland cement including limestone additions

    SciTech Connect

    Sevelsted, Tine F.; Herfort, Duncan

    2013-10-15

    {sup 13}C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed {sup 13}C MAS or {sup 13}C({sup 1}H) CP/MAS NMR spectra (9.4 T or 14.1 T) for {sup 13}C in natural abundance. The variation in the {sup 13}C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in {sup 13}C MAS NMR spectra. However, it is shown that by combining {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends {sup 29}Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in {sup 27}Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •{sup 13}C chemical shift anisotropies for inorganic carbonates from {sup 13}C MAS NMR. •Narrow {sup 13}C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase.

  9. Growth of chemically deposited ZnO and ZnO-SiO2 on Pt buffered Si substrate

    NASA Astrophysics Data System (ADS)

    Peguit, A. D. M. V.; Candidato, R. T., Jr.; Bagsican, F. R. G.; Odarve, M. K. G.; Jabian, M. E.; Sambo, B. R. B.; Vequizo, R. M.; Alguno, A. C.

    2015-06-01

    Growing ZnO on Si via low-cost CBD is difficult owing to the large lattice mismatch between ZnO and Si and the intricate control of nanoparticle aggregation. In this work, a Pt buffer layer and addition of SiO2 on the chemical solution were introduced. The effect of these parameters on the resulting morphology and composition were investigated using SEM-EDX and FTIR. Pt-coated Si showed higher density of ZnO nanostructure growth than bare Si due to the additional nucleation sites provided by Pt. Moreover, SiO2 addition resulted to a different ZnO nanostructure.

  10. Structural Characterization of Polycrystalline 3C-SiC Films Prepared at High Rates by Atmospheric Pressure Plasma Chemical Vapor Deposition Using Monomethylsilane

    NASA Astrophysics Data System (ADS)

    Kakiuchi, Hiroaki; Ohmi, Hiromasa; Nakamura, Ryota; Aketa, Masatoshi; Yasutake, Kiyoshi

    2006-10-01

    Polycrystalline cubic silicon carbide (3C-SiC) films were deposited at a relatively low temperature of 1070 K on Si(001) substrates by atmospheric pressure plasma chemical vapor deposition. Monomethylsilane (CH3SiH3) was used as the single source. CH4 and SiH4 dual sources were also used to compare deposition characteristics. Under the present deposition conditions, very high deposition rates of more than 3 nm/s were obtained. The structure of the SiC films was evaluated by reflection high-energy electron diffraction, Fourier transform infrared absorption spectroscopy and cross-sectional transmission electron microscopy. In addition, optical emission spectroscopy was employed to study the chemical reactions in the CH4/SiH4 and CH3SiH3 plasmas. The results showed that increasing H2 concentration is essential in forming a high quality 3C-SiC film by enhancing the hydrogen elimination reaction at the film-growing surface. From the optical emission spectra, it was found that atomic hydrogen generated by adding H2 in the plasma increase the amount of principal precursors for the film growth. The utilization of CH3SiH3 also led to a higher concentration of principal precursors in the plasma, enhancing the incorporation of Si-C bonds into the film. As a consequence of simultaneously using a high H2 concentration and the CH3SiH3 single source, the columnar growth of 3C-SiC crystallites was achieved.

  11. Si/SiGe MMIC's

    NASA Astrophysics Data System (ADS)

    Luy, Johann-Friedrich; Strohm, Karl M.; Sasse, Hans-Eckard; Schueppen, Andreas; Buechler, Josef; Wollitzer, Michael; Gruhle, Andreas; Schaeffler, Friedrich; Guettich, Ulrich; Klaassen, Andreas

    1995-04-01

    Silicon-based millimeter-wave integrated circuits (SIMMWIC's) can provide new solutions for near range sensor and communication applications in the frequency range above 50 GHz. This paper gives a survey on the state-of-the-art performance of this technology and on first applications. The key devices are IMPATT diodes for mm-wave power generation and detection in the self-oscillating mixer mode, p-i-n diodes for use in switches and phase shifters, and Schottky diodes in detector and mixer circuits. The silicon/silicon germanium heterobipolar transistor (SiGe HBT) with f(sub max) values of more than 90 GHz is now used for low-noise oscillators at Ka-band frequencies. First system applications are discussed.

  12. Development of SiAlON materials

    NASA Technical Reports Server (NTRS)

    Layden, G. K.

    1979-01-01

    Cold pressing and sintering techniques were used to produce ceramic test specimens in which the major phase was either Si3N4 or a solid solution having the beta Si3N4 structure. Additional components were incorporated to promote liquid phase sintering. Glass and/or crystalline phase were consequently retained in boundaries between Si3N4 grains which largely determined the physical properties of the bodies. Systems investigated most extensively included R-Si-Al-O-N (R = rare earth element) Zr-Si-Al-O-N, Y-Si-Be-O-N, and R1-R2-Si-O-N. Room temperature and 1370 C modulus of ruptured, 1370 C creep, and oxidation behavior are discussed in terms of phase relationships in a parent quinery, and relavent oxide systems.

  13. Si-H bond activation at {(NHC)₂Ni⁰} leading to hydrido silyl and bis(silyl) complexes: a versatile tool for catalytic Si-H/D exchange, acceptorless dehydrogenative coupling of hydrosilanes, and hydrogenation of disilanes to hydrosilanes.

    PubMed

    Schmidt, David; Zell, Thomas; Schaub, Thomas; Radius, Udo

    2014-07-28

    The unique reactivity of the nickel(0) complex [Ni2(iPr2Im)4(COD)] (1) (iPr2Im = 1,3-di-isopropyl-imidazolin-2-ylidene) towards hydrosilanes in stoichiometric and catalytic reactions is reported. A series of nickel hydrido silyl complexes cis-[Ni(iPr2Im)2(H)(SiH(n-1)R(4-n))] (n = 1, 2) and nickel bis(silyl) complexes cis-[Ni(iPr2Im)2(SiH(n-1)R(4-n))2] (n = 1, 2, 3) were synthesized by stoichiometric reactions of 1 with hydrosilanes H(n)SiR(4-n), and fully characterized by X-ray diffraction and spectroscopic methods. These hydrido silyl complexes are examples where the full oxidative addition step is hindered. They have, as a result of the remaining Si-H interactions, remarkably short Si-H distances and feature a unique dynamic behavior in solution. Cis-[Ni(iPr2Im)2(H)(SiMePh2)] (cis-5) shows in solution at room temperature a dynamic site exchange of the NHC ligands, H-D exchange with C6D6 to give the deuteride complex cis-[Ni(iPr2Im)2(D)(SiMePh2)] (cis-5-D), and at elevated temperatures an irreversible isomerization to trans-[Ni(iPr2Im)2(D)(SiMePh2)] (trans-5-D). Reactions with sterically less demanding silanes give cis-configured bis(silyl) complexes accompanied by the release of dihydrogen. These complexes display, similarly to the hydrido silyl complexes, interestingly short Si-Si distances. Complex 1 reacts with 4 eq. HSi(OEt)3, in contrast to all the other silanes used in this study, to give the trans-configured bis(silyl) complex trans-[Ni(iPr2Im)2Ni(Si(OEt)3)2] (trans-12). The addition of two equivalents of Ph2SiH2 to 1 results, at elevated temperatures, in the formation of the dinuclear complex [{(iPr2Im)Ni-μ(2)-(HSiPh2)}2] (6). This diamagnetic, formal Ni(I) complex exhibits a long Ni-Ni bond in the solid state, as established by X-ray diffraction. The capability of the electron rich {Ni(iPr2Im)2} complex fragment to activate Si-H bonds was applied catalytically in the deuteration of Et3Si-H to Et3Si-D employing C6D6 as a convenient deuterium source

  14. Liquid chromatography coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry and post-column addition of metal salt solutions as a powerful tool for the metabolic profiling of Fusarium oxysporum.

    PubMed

    Cirigliano, Adriana M; Rodriguez, M Alejandra; Gagliano, M Laura; Bertinetti, Brenda V; Godeas, Alicia M; Cabrera, Gabriela M

    2016-03-25

    Fusarium oxysporum L11 is a non-pathogenic soil-borne fungal strain that yielded an extract that showed antifungal activity against phytopathogens. In this study, reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry (API-QTOF-MS) was applied for the comprehensive profiling of the metabolites from the extract. The employed sources were electrospray (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). Post-column addition of metal solutions of Ca, Cu and Zn(II) was also tested using ESI. A total of 137 compounds were identified or tentatively identified by matching their accurate mass signals, suggested molecular formulae and MS/MS analysis with previously reported data. Some compounds were isolated and identified by NMR. The extract was rich in cyclic peptides like cyclosporins, diketopiperazines and sansalvamides, most of which were new, and are reported here for the first time. The use of post-column addition of metals resulted in a useful strategy for the discrimination of compound classes since specific adducts were observed for the different compound families. This technique also allowed the screening for compounds with metal binding properties. Thus, the applied methodology is a useful choice for the metabolic profiling of extracts and also for the selection of metabolites with potential biological activities related to interactions with metal ions.

  15. Fusion of Si28+Si28,30: Different trends at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Montagnoli, G.; Stefanini, A. M.; Esbensen, H.; Jiang, C. L.; Corradi, L.; Courtin, S.; Fioretto, E.; Grebosz, J.; Haas, F.; Jia, H. M.; Mazzocco, M.; Michelagnoli, C.; Mijatović, T.; Montanari, D.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Torresi, D.

    2014-10-01

    Background: The fusion excitation function of the system Si28+Si28 at energies near and below the Coulomb barrier is known only down to ≃15 mb. This precludes any information on both coupling effects on sub-barrier cross sections and the possible appearance of hindrance. For Si28+Si30 even if the fusion cross section is measured down to ≃50 μb, the evidence of hindrance is marginal. Both systems have positive fusion Q values. While Si28 has a deformed oblate shape, Si30 is spherical. Purpose: We investigate 1. the possible influence of the different structure of the two Si isotopes on the fusion excitation functions in the deep sub-barrier region and 2. whether hindrance exists in the Si+Si systems and whether it is strong enough to generate an S-factor maximum, thus allowing a comparison with lighter heavy-ion systems of astrophysical interest. Methods: Si28 beams from the XTU Tandem accelerator of the INFN Laboratori Nazionali di Legnaro were used. The setup was based on an electrostatic beam separator, and fusion evaporation residues (ER) were detected at very forward angles. Angular distributions of ER were measured. Results: Fusion cross sections of Si28+Si28 have been obtained down to ≃600 nb. The slope of the excitation function has a clear irregularity below the barrier, but no indication of a S-factor maximum is found. For Si28+Si30 the previous data have been confirmed and two smaller cross sections have been measured down to ≃4 μb. The trend of the S-factor reinforces the previous weak evidence of hindrance. Conclusions: The sub-barrier cross sections for Si28+Si28 are overestimated by coupled-channels calculations based on a standard Woods-Saxon potential, except for the lowest energies. Calculations using the M3Y+repulsion potential are adjusted to fit the Si28+Si28 and the existing Si30+Si30 data. An additional weak imaginary potential (probably simulating the effect of the oblate Si28 deformation) is required to fit the low-energy trend of

  16. Endotaxial Si nanolines in Si(001):H

    NASA Astrophysics Data System (ADS)

    Bianco, F.; Owen, J. H. G.; Köster, S. A.; Mazur, D.; Renner, Ch.; Bowler, D. R.

    2011-07-01

    We present a detailed study of the structural and electronic properties of a self-assembled silicon nanoline embedded in the H-terminated silicon (001) surface, known as the Haiku stripe. The nanoline is a perfectly straight and defect-free endotaxial structure of huge aspect ratio; it can grow micrometer long at a constant width of exactly four Si dimers (1.54 nm). Another remarkable property is its capacity to be exposed to air without suffering any degradation. The nanoline grows independently of any step edges at tunable densities from isolated nanolines to a dense array of nanolines. In addition to these unique structural characteristics, scanning tunneling microscopy and density functional theory reveal a one-dimensional state confined along the Haiku core. This nanoline is a promising candidate for the long-sought-after electronic solid-state one-dimensional model system to explore the fascinating quantum properties emerging in such reduced dimensionality.

  17. Crystallization of amorphous Si nanoclusters in SiO(x) films using femtosecond laser pulse annealings.

    PubMed

    Korchagina, T T; Gutakovsky, A K; Fedina, L I; Neklyudova, M A; Volodin, V A

    2012-11-01

    The SiO(x) films of various stoichiometries deposited on Si substrates with the use of the co-sputtering from two separate Si and SiO2 targets were annealed by femtosecond laser pulses. Femtosecond laser treatments were applied for crystallization of amorphous silicon nanoclusters in the silicon-rich oxide films. The treatments were carried out with the use of Ti-Sapphire laser with wavelength 800 nm and pulse duration about 30 fs. Regimes of crystallization of amorphous Si nanoclusters in the initial films were found. Ablation thresholds for SiO(x) films of various stoichiometries were discovered. The effect of laser assisted formation of a-Si nanoclusters in the non-stoichiometric dielectric films with relatively low concentration of additional Si atoms was also observed. This approach is applicable for the creation of dielectric films with semiconductor nanoclusters on non-refractory substrates.

  18. Are dangling bond centers important interface traps in 4H-SiC metal oxide semiconductor field effect transistors?

    NASA Astrophysics Data System (ADS)

    Anders, M. A.; Lenahan, P. M.; Lelis, A. J.

    2016-10-01

    Silicon carbide (SiC) based metal-oxide-semiconductor field-effect transistors (MOSFETs) have great promise in high power and high temperature applications. Unfortunately, effective channel mobilities remain disappointingly low, typically about 30 cm2/Vs. A major contributor to the disappointing effective channel mobilities is the presence of substantial densities of interface traps at the SiC/SiO2 interface. Many investigators have invoked silicon or carbon dangling bonds to be the dominating source of these interface defects, but very little, if any, direct experimental evidence exists to support this assumption in the SiC/SiO2 system. Cantin et al. [Phys. Rev. Lett. 92, 1 (2004)] have used conventional electron paramagnetic resonance measurements on porous oxidized SiC structures to measure the g tensor for the SiC/SiO2 interface carbon dangling bond. These results provide a particularly straightforward means to search for the presence of carbon dangling bonds in fully processed SiC MOSFETs using electrically detected magnetic resonance. Additionally, simple theory provides guidance to search for silicon dangling bond defects. In this study, we utilize K band electrically detected magnetic resonance via spin dependent charge pumping measurements in which almost all of the SiC band gap at the SiC/SiO2 interface is accessed. Although quite high signal to noise measurements are achieved, we are unable to detect any trace of the carbon dangling bond spectra. However, in very poor quality p-channel devices, we observe a spectrum which could be consistent with silicon dangling bonds. Other defect centers are clearly present and we conclude that these other centers dominate the interface trap density of states.

  19. Interfacial SiO2 scavenging kinetics in HfO2 gate stack

    NASA Astrophysics Data System (ADS)

    Li, Xiuyan; Nishimura, Tomonori; Toriumi, Akira

    2016-11-01

    In this paper, Si and oxygen diffusions as well as SiO2 reduction reaction in HfO2/SiO2/Si stacks are examined in detail for fully understanding the SiO2-IL scavenging process. A 29Si isotope tracing experiment confirms that Si in SiO2-IL is mostly emitted from the HfO2 surface. In addition, the reaction of oxygen from SiO2 with VO in HfO2 is suggested. Furthermore, it is reported that the Si substrate is not changed at all in the SiO2-IL scavenging by simultaneously comparing a Si surface between with and without scavenged parts. Based on these results, a kinetic model for the SiO2-IL scavenging in HfO2/SiO2/Si stacks is proposed.

  20. Microstructure and Hot Oxidation Resistance of SiMo Ductile Cast Irons Containing Si-Mo-Al

    NASA Astrophysics Data System (ADS)

    Ibrahim, Mervat M.; Nofal, Adel; Mourad, M. M.

    2016-12-01

    SiMo ductile cast irons are used as high-temperature materials in automotive components, because they are microstructurally stable at high operating temperatures. The effect of different amounts of Si and Mo as well as the addition of 3 wt pct Al on the microstructure, high-temperature oxidation, and mechanical properties of SiMo ductile cast iron was studied. Dilatometric measurements of SiMo ductile iron exhibited obvious differences in the transformation temperature A 1 due to presence of Al and the increase of Si. The microstructure of the SiMo alloys without Al addition showed outstanding nodularity and uniform nodule distribution. However, by adding 3 wt pct Al to low Si-SiMo ductile iron, some compacted graphite was observed. The results of oxidation experiments indicated that high Si-SiMo ductile iron containing 4 and 4.9 wt pct Si had superior resistance to lower Si-SiMo and SiMo ductile iron containing 3 wt pct Al. The results showed also that with increasing Si up to 4.9 wt pct or by replacing a part of Si with 3 wt pct Al, tensile strength increased while elongation and impact toughness decreased.

  1. Microstructure and Hot Oxidation Resistance of SiMo Ductile Cast Irons Containing Si-Mo-Al

    NASA Astrophysics Data System (ADS)

    Ibrahim, Mervat M.; Nofal, Adel; Mourad, M. M.

    2017-04-01

    SiMo ductile cast irons are used as high-temperature materials in automotive components, because they are microstructurally stable at high operating temperatures. The effect of different amounts of Si and Mo as well as the addition of 3 wt pct Al on the microstructure, high-temperature oxidation, and mechanical properties of SiMo ductile cast iron was studied. Dilatometric measurements of SiMo ductile iron exhibited obvious differences in the transformation temperature A 1 due to presence of Al and the increase of Si. The microstructure of the SiMo alloys without Al addition showed outstanding nodularity and uniform nodule distribution. However, by adding 3 wt pct Al to low Si-SiMo ductile iron, some compacted graphite was observed. The results of oxidation experiments indicated that high Si-SiMo ductile iron containing 4 and 4.9 wt pct Si had superior resistance to lower Si-SiMo and SiMo ductile iron containing 3 wt pct Al. The results showed also that with increasing Si up to 4.9 wt pct or by replacing a part of Si with 3 wt pct Al, tensile strength increased while elongation and impact toughness decreased.

  2. Oxidation of TaSi2-Containing ZrB2-SiC Ultra-High Temperature Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Smith, Jim; Levine, Stanley R.; Lorincz, Jonathan; Reigel, Marissa

    2010-01-01

    Hot pressed coupons of composition ZrB2-20 v% SiC-5 v% TaSi2 and ZrB2-20 v% SiC-20 v% TaSi2 were oxidized in stagnant air at temperatures of 1627 and 1927C for one, five and ten 10-minute cycles. The oxidation reactions were characterized by weight change kinetics, x-ray diffraction, and SEM/EDS. Detailed WDS/microprobe quantitative analyses of the oxidation products were conducted for the ZrB2-20 v% SiC-20 v% TaSi2 sample oxidized for five 10-minute cycles at 1927C. Oxidation kinetics and product formation were compared to ZrB2-20 v% SiC with no TaSi2 additions. It was found that the 20 v% TaSi2 composition exhibited improved oxidation resistance relative to the material with no TaSi2 additions at 1627C. However, for exposures at 1927C less oxidation resistance and extensive liquid phase formation were observed compared to the material with no TaSi2 additions. Attempts to limit the liquid phase formation by reducing the TaSi2 content to 5 v% were unsuccessful. In addition, the enhanced oxidation resistance at 1627C due to 20 v% TaSi2 additions was not achieved at the 5 v% addition level. The observed oxidation product evolution is discussed in terms of thermodynamics and phase equilibria for the TaSi2-containing ZrB2-SiC material system. TaSi2-additions to ZrB2-SiC at any level are not recommended for ultra-high temperature (>1900C) applications due to excessive liquid phase formation.

  3. The Basic SI Model

    ERIC Educational Resources Information Center

    Hurley, Maureen; Jacobs, Glen; Gilbert, Melinda

    2006-01-01

    A general overview of the SI model is provided, including the SI philosophy, essential components of the program, program structures, key roles, outcomes, and evaluation. A review of what we have learned about the importance of planning SI sessions, providing ongoing training for leaders, conducting regular SI program assessments, and implementing…

  4. Screening of additives in plastics with high resolution time-of-flight mass spectrometry and different ionization sources: direct probe injection (DIP)-APCI, LC-APCI, and LC-ion booster ESI.

    PubMed

    Ballesteros-Gómez, Ana; Jonkers, Tim; Covaci, Adrian; de Boer, Jacob

    2016-04-01

    Plastics are complex mixtures consisting of a polymer and additives with different physico-chemical properties. We developed a broad screening method to elucidate the nature of compounds present in plastics used in electrical/electronic equipment commonly found at homes (e.g., electrical adaptors, computer casings, heaters). The analysis was done by (a) solvent extraction followed by liquid chromatography coupled to high accuracy/resolution time-of-flight mass spectrometry (TOFMS) with different ionization sources or (b) direct analysis of the solid by ambient mass spectrometry high accuracy/resolution TOFMS. The different ionization methods showed different selectivity and sensitivity for the different compound classes and were complementary. A variety of antioxidants, phthalates, UV filters, and flame retardants were found in most samples. Furthermore, some recently reported impurities or degradation products derived from flame retardants were identified, such as hydroxylated triphenyl phosphate and tetrabromobisphenol A monoglycidyl ether.

  5. Visible light emission from MBD-grown {Si}/{SiO2} superlattices

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Sinkkonen, J.; Kilpelä, O.; Gastev, S. V.

    1997-05-01

    {Si}/{SiO2} superlattices were grown by MBD using in situ oxidation by RF-plasma source. Room temperature photoluminescence (PL) was observed in the spectral range 1.9-2.3 eV. PL spectra show blueshifts due to the quantum confinement of the energy states in ultrathin silicon layers.

  6. High temperature compounds for turbine vanes. [of SiC, Si3N4, and Si composites

    NASA Technical Reports Server (NTRS)

    Rhodes, W. H.; Cannon, R. M., Jr.

    1974-01-01

    Fabrication and microstructure control studies were conducted on SiC, Si3N and composites based on Si3N. Charpy mode impact testing to 2400 F established that Si3N4/Mo composites have excellent potential. Attempts to fabricate composites of Si3N4 with superalloys, both by hot pressing and infiltration were largely unsuccessful in comparison to using Mo, Re, and Ta which are less reactive. Modest improvements in impact strength were realized for monolithic Si3N4; however, SiC strengths increased by a factor of six and now equal values achieved for Si3N4. Correlations of impact strength with material properties are discussed. Reduced MgO densification aid additions to Si3N4 were found to decrease densification kinetics, increase final porosity, decrease room temperature bend strength, increase high temperature bend strength, and decrease bend stress rupture properties. The decrease in bend strength at high temperature for fine grain size SiC suggested that a slightly larger grain size material with a nearly constant strength-temperature relation may prove desirable in the creep and stress rupture mode.

  7. Low Activation Joining of SiC/SiC Composites for Fusion Applications: Tape Casting TiC+Si Powders

    SciTech Connect

    Henager, Charles H.; Kurtz, Richard J.; Canfield, Nathan L.; Shin, Yongsoon; Luscher, Walter G.; Mansurov, Jirgal; Roosendaal, Timothy J.; Borlaug, Brennan A.

    2013-08-06

    The use of SiC composites in fusion environments likely requires joining of plates using reactive joining or brazing. One promising reactive joining method uses solid-state displacement reactions between Si and TiC to produce Ti3SiC2 + SiC. We continue to explore the processing envelope for this joint for the TITAN collaboration in order to produce optimal joints to undergo irradiation studies in HFIR. One noted feature of the joints produced using tape-calendared powders of TiC+Si has been the large void regions that have been apparently unavoidable. Although the produced joints are very strong, these voids are undesirable. In addition, the tapes that were made for this joining were produced about 20 years ago and were aging. Therefore, we embarked on an effort to produce some new tape cast powders of TiC and Si that could replace our aging tape calendared materials.

  8. Ion Beam Synthesis Of Metal - Silicon Carbide - Si Multilayer Structures

    NASA Astrophysics Data System (ADS)

    Lindner, J. K. N.; Tsang, W. M.; Stritzker, B.; Wong, S. P.

    2003-08-01

    High doses of Ti, Ni, Mo, or W ions were implanted at elevated temperatures either conventionally or using a MEVVA ion source into ion beam synthesized Si/SiC/Si or SiC/Si layer structures in order to create metallic layers contacting the SiC. The depth distribution of metal atoms and the formation of silicide and carbide phases as well as the formation of cavities at the lower SiC/Si interface are studied by Rutherford backscattering spectroscopy (RBS) and cross-sectional transmission electron microscopy (XTEM). A brief survey of the effects ocurring in the ion beam metallization of SiC films is given and the benefit of using ion beams for metallization of thin films is elucidated.

  9. Modification of Mg{sub 2}Si in Mg–Si alloys with gadolinium

    SciTech Connect

    Ye, Lingying; Hu, Jilong Tang, Changping; Zhang, Xinming; Deng, Yunlai; Liu, Zhaoyang; Zhou, Zhile

    2013-05-15

    The modification effect of gadolinium (Gd) on Mg{sub 2}Si in the hypereutectic Mg–3 wt.% Si alloy has been investigated using optical microscope, scanning electron microscope, X-ray diffraction and hardness measurements. The results indicate that the morphology of the primary Mg{sub 2}Si is changed from coarse dendrite into fine polygon with the increasing Gd content. The average size of the primary Mg{sub 2}Si significantly decreases with increasing Gd content up to 1.0 wt.%, and then slowly increases. Interestingly, when the Gd content is increased to 4.0 and 8.0 wt.%, the primary and eutectic Mg{sub 2}Si evidently decrease and even disappear. The modification and refinement of the primary Mg{sub 2}Si is mainly attributed to the poisoning effect. The GdMg{sub 2} phase in the primary Mg{sub 2}Si is obviously coarsened as the Gd content exceeds 2.0 wt.%. While the decrease and disappearance of the primary and eutectic Mg{sub 2}Si are ascribed to the formation of vast GdSi compound. Therefore, it is reasonable to conclude that proper Gd (1.0 wt.%) addition can effectively modify and refine the primary Mg{sub 2}Si. - Highlights: ► Proper Gd (1.0 wt.%) addition can effectively modify and refine the primary Mg{sub 2}Si. ► We studied the reaction feasibility between Mg and Si, Gd and Si in Mg–Gd–Si system. ► We explored the modification mechanism of Gd modifier on Mg{sub 2}Si.

  10. Binding waste anthracite fines with Si-containing materials as an alternative fuel for foundry cupola furnaces.

    PubMed

    Huang, He; Fox, John T; Cannon, Fred S; Komarneni, Sridhar; Kulik, Joseph; Furness, Jim

    2011-04-01

    An alternative fuel to replace foundry coke in cupolas was developed from waste anthracite fines. Waste anthracite fines were briquetted with Si-containing materials and treated in carbothermal (combination of heat and carbon) conditions that simulated the cupola preheat zone to form silicon carbide nanowires (SCNWs). SCNWs can provide hot crushing strengths, which are important in cupola operations. Lab-scale experiments confirmed that the redox level of the Si-source significantly affected the formation of SiC. With zerovalent silicon, SCNWs were formed within the anthracite pellets. Although amorphous Si (+4) plus anthracite formed SiC, these conditions did not transform the SiC into nanowires. Moreover, under the test conditions, SiC was not formed between crystallized Si (+4) and anthracite. In a full-scale demonstration, bricks made from anthracite fines and zerovalent silicon successfully replaced a part of the foundry coke in a full-scale cupola. In addition to saving in fuel cost, replacing coke by waste anthracite fines can reduce energy consumption and CO2 and other pollution associated with conventional coking.

  11. A soft x-ray photoemission study of the chemisorption and reaction of diethylsilane on Si(100)

    SciTech Connect

    Lapiano-Smith, D.A.; Himpsel, F.J.; Terminello, L.J.

    1993-06-01

    Soft x-ray synchrotron radiation was utilized as the excitation source in a high-resolution photoemission experiment on chemisorption and subsequent reaction of diethylsilane on the Si(100) surface. We have found that diethylsilane chemisorbs dissociatively to form Si-CH{sub 2}CH{sub 3} surface species on Si(100) following a room temperature exposure. These species are identified by two very sharp peaks observed in the valence band spectra positioned at 17.9 and 14.3 eV binding energy. In addition, C 1s core level spectra, measured following exposures of Si(100) substrates as a function of surface temperature, show that carbon, in some form, exists on the Si surface following exposures at every temperature from room temperature to about 600C. While only {minus}CH{sub 2}CH{sub 3}, ethyl groups are observed on the surface at room temperature, these species appear to partially dehydrogenate at 300C, producing a mixture of {minus}CH{sub 2}CH{sub 3} groups and other intermediate carbonaceous species. At a growth temperature of about 400C the intermixing of elemental carbon with Si begins. At higher temperatures, we observe the continued degradation of diethylsilane to produce a Si + C alloy on the surface at 600C. Results indicate that diethylsilane has potential as a molecular precursor for SiC formation by chemical vapor deposition techniques.

  12. Slurry sampling high-resolution continuum source electrothermal atomic absorption spectrometry for direct beryllium determination in soil and sediment samples after elimination of SiO interference by least-squares background correction.

    PubMed

    Husáková, Lenka; Urbanová, Iva; Šafránková, Michaela; Šídová, Tereza

    2017-12-01

    In this work a simple, efficient, and environmentally-friendly method is proposed for determination of Be in soil and sediment samples employing slurry sampling and high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS-ETAAS). The spectral effects originating from SiO species were identified and successfully corrected by means of a mathematical correction algorithm. Fractional factorial design has been employed to assess the parameters affecting the analytical results and especially to help in the development of the slurry preparation and optimization of measuring conditions. The effects of seven analytical variables including particle size, concentration of glycerol and HNO3 for stabilization and analyte extraction, respectively, the effect of ultrasonic agitation for slurry homogenization, concentration of chemical modifier, pyrolysis and atomization temperature were investigated by a 2(7-3) replicate (n = 3) design. Using the optimized experimental conditions, the proposed method allowed the determination of Be with a detection limit being 0.016mgkg(-1) and characteristic mass 1.3pg. Optimum results were obtained after preparing the slurries by weighing 100mg of a sample with particle size < 54µm and adding 25mL of 20% w/w glycerol. The use of 1μg Rh and 50μg citric acid was found satisfactory for the analyte stabilization. Accurate data were obtained with the use of matrix-free calibration. The accuracy of the method was confirmed by analysis of two certified reference materials (NIST SRM 2702 Inorganics in Marine Sediment and IGI BIL-1 Baikal Bottom Silt) and by comparison of the results obtained for ten real samples by slurry sampling with those determined after microwave-assisted extraction by inductively coupled plasma time of flight mass spectrometry (TOF-ICP-MS). The reported method has a precision better than 7%. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Effect of protein source and protease addition on performance, blood metabolites and nutrient digestibility of turkeys fed on low-protein diets from 28 to 55 d post hatch.

    PubMed

    Shahir, M H; Rahimi, R; Taheri, H R; Heidariniya, A; Baradaran, N; Asadi Kermani, Z

    2016-06-01

    The objective of this study was to investigate the effect of a monocomponent protease and dietary inclusion of canola meal (CM) and poultry by-product meal (PBM) on growth performance, carcass characteristics and blood metabolites of turkeys fed on low crude protein (CP) diets from 28 to 55 d post hatch. Experimental treatments included control, maize-soybean meal diet including 258.3 g/kg CP; negative control 1 (NC1), maize-soybean meal diet with reduced CP (232.4 g/kg); NC2, control diet (CP, 258.3 g/kg) including CM (80 g/kg) and PBM (80 g/kg); NC3, maize-soybean meal diet with reduced CP (232.4 g/kg) including CM (80 g/kg) and PBM (80 g/kg). Also, the NC1 + P and NC3 + P diets were created by addition of protease enzyme (30 000 units/kg of diet) to the NC1 and NC3 diets, respectively. The NC3 group had lower body weight gain (BWG) compared to those fed on the control diet, and no improvement with enzyme addition (NC3 + P) was achieved. The protease addition to the NC1 diet (NC1 + P) improved BWG to the level of the control diet. The NC1 group had higher feed conversion ratio (FCR) compared to the control and NC3 + P, but protease addition to the NC1 diet improved FCR. Protease addition to the low CP diets resulted in higher nitrogen (N) retention than in the control and NC2 groups. Also, the NC1 + P and NC3 + P diets increased apparent ileal digestibility (AID) of CP compared to the control group. It was concluded that addition of CM (up to 80 g/kg) and PBM (up to 80 g/kg) to turkey diets had no negative effect on growth performance from 28 to 55 d of age. The NC1 + P group achieved the BWG of the control group which was partially due to increases in N retention and AID of CP, but the NC3 + P group failed to recover the growth losses. This difference implies that the efficacy of the protease may depend upon the protein source in the ration.

  14. Improved nucleic acid descriptors for siRNA efficacy prediction

    PubMed Central

    Sciabola, Simone; Cao, Qing; Orozco, Modesto; Faustino, Ignacio; Stanton, Robert V.

    2013-01-01

    Although considerable progress has been made recently in understanding how gene silencing is mediated by the RNAi pathway, the rational design of effective sequences is still a challenging task. In this article, we demonstrate that including three-dimensional descriptors improved the discrimination between active and inactive small interfering RNAs (siRNAs) in a statistical model. Five descriptor types were used: (i) nucleotide position along the siRNA sequence, (ii) nucleotide composition in terms of presence/absence of specific combinations of di- and trinucleotides, (iii) nucleotide interactions by means of a modified auto- and cross-covariance function, (iv) nucleotide thermodynamic stability derived by the nearest neighbor model representation and (v) nucleic acid structure flexibility. The duplex flexibility descriptors are derived from extended molecular dynamics simulations, which are able to describe the sequence-dependent elastic properties of RNA duplexes, even for non-standard oligonucleotides. The matrix of descriptors was analysed using three statistical packages in R (partial least squares, random forest, and support vector machine), and the most predictive model was implemented in a modeling tool we have made publicly available through SourceForge. Our implementation of new RNA descriptors coupled with appropriate statistical algorithms resulted in improved model performance for the selection of siRNA candidates when compared with publicly available siRNA prediction tools and previously published test sets. Additional validation studies based on in-house RNA interference projects confirmed the robustness of the scoring procedure in prospective studies. PMID:23241392

  15. SiC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION

    SciTech Connect

    Paul K.T. Liu

    2001-10-16

    This technical report summarizes our activities conducted in Yr II. In Yr I we successfully demonstrated the feasibility of preparing the hydrogen selective SiC membrane with a chemical vapor deposition (CVD) technique. In addition, a SiC macroporous membrane was fabricated as a substrate candidate for the proposed SiC membrane. In Yr II we have focused on the development of a microporous SiC membrane as an intermediate layer between the substrate and the final membrane layer prepared from CVD. Powders and supported thin silicon carbide films (membranes) were prepared by a sol-gel technique using silica sol precursors as the source of silicon, and phenolic resin as the source of carbon. The powders and films were prepared by the carbothermal reduction reaction between the silica and the carbon source. The XRD analysis indicates that the powders and films consist of SiC, while the surface area measurement indicates that they contain micropores. SEM and AFM studies of the same films also validate this observation. The powders and membranes were also stable under different corrosive and harsh environments. The effects of these different treatments on the internal surface area, pore size distribution, and transport properties, were studied for both the powders and the membranes using the aforementioned techniques and XPS. Finally the SiC membrane materials are shown to have satisfactory hydrothermal stability for the proposed application. In Yr III, we will focus on the demonstration of the potential benefit using the SiC membrane developed from Yr I and II for the water-gas-shift (WGS) reaction.

  16. a-Si:F and a-Si:F:H prepared by ion-beam-assisted reactive deposition

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Brodie, D. E.

    1992-08-01

    a-Si:F and a-Si:F:H films have been prepared by ion-beam-assisted deposition using SiF4, SiH4+Ar, or SiF4+SiH4 as the gases for the ion source. Fluorine in a-Si eliminates some dangling bonds, increases the optical gap, and decreases the dark conductivity. The results are influenced mainly by the ion-beam energy used. The a-Si:F films do not exhibit an activated conductivity even up to 150 °C, and no photoconductivity could be detected. However, film properties were significantly improved when a very small amount of H was added to the a-Si:F and much less than 1 at. % H produced films that were photoconducting and had activated conductivities. The properties of these a-Si:F:H are strongly dependent on both the fluorine concentration CF and the hydrogen concentration CH. The deposition rate decreases with increasing SiF4 content in the source gas, and neither CF nor CH vary linearly with the change in the source gas ratio SiH4/(SiF4+SiH4). Hence, CH must be known and controlled in order to evaluate the effect of fluorine on the film's properties. By studying a series of a-Si:F:H samples containing the same CH, it is noted that incorporating some F does improve the film's electrical properties. Annealing experiments suggest that an observed peak at 2100 cm-1 in the IR spectra of these a-Si:F:H films is not completely due to SiH2, as has been suggested by others.

  17. Direct observation of nanometer-scale strain field around CoSi{sub 2}/Si interface using scanning moiré fringe imaging

    SciTech Connect

    Kim, Suhyun; Jung, Younheum; Jung Kim, Joong; Byun, Gwangseon; Lee, Sunyoung; Lee, Heabum

    2014-04-21

    We report the use of scanning moiré fringe (SMF) imaging through high-angle annular dark-field scanning transmission electron microscopy (STEM) to measure the strain field around a CoSi{sub 2} contact embedded in the source and drain (S/D) region of a transistor. The atomic arrangement of the CoSi{sub 2}/Si (111) interface was determined from the high-resolution (HR)-STEM images, and the strain field formed around the S/D region was revealed by nanometer-scale SMFs appearing in the STEM image. In addition, we showed that the strain field in the S/D region measured by SMF imaging agreed with results obtained via peak-pairs analysis of HR-STEM images.

  18. Experimental Investigations on the effect of Additive on the Tensile Properties of Fiber Glass Fabric Lamina

    NASA Astrophysics Data System (ADS)

    Nava Sai Divya, A.; Raghu Kumar, B., Dr; Lakshmi Narayana, G., Dr

    2017-09-01

    The main objective of this work is to investigate the effect of additives on tensile behaviour of fiber glass fabric at lamina level to explore an alternative skin material for the outer body of aerospace applications and machines. This experimental work investigates the effect of silica concentration in epoxy resin lapox L-12 on the tensile properties of glass fabric lamina of 4H-satin weave having 3.6 mm thickness. The lamina was prepared by using hand lay-up method and tests were conducted on it. Various tensile properties values obtained from experimentation were compared for four glass fiber lamina composites fabricated by adding the silica powder to resin bath. The effect of variations in silica concentration (0% SiO2, 5% SiO2, 10% SiO2 and 15% SiO2) on the tensile properties of prepared material revealed that maximum stiffness was obtained at 15% and yield strength at 10% SiO2 concentration in glass fiber lamina. Increasing the silica concentration beyond 10% had led to deterioration in the material properties. The experimentation that was carried out on test specimen was reasonably successful as the effect of silica powder as an additive in glass fiber lamina enhanced the mechanical properties up to certain limit. The underpinning microscopic behaviour at the source of these observations will be investigated in a follow up work.

  19. Green synthesis of Si-incorporated hydroxyapatite using sodium metasilicate as silicon precursor and in vitro antibiotic release studies.

    PubMed

    Abinaya Sindu, P; Kolanthai, Elayaraja; Suganthi, R V; Thanigai Arul, K; Manikandan, E; Catalani, Luiz H; Narayana Kalkura, S

    2017-10-01

    The aim of the current study is to synthesize nanosized silicon incorporated HAp (Si-HAP) using sodium metasilicate as the silicon source. The sol-gel derived samples were further subjected to microwave irradiation. Incorporation of Si into HAp did not alter the HAp phase, as confirmed by the X-ray diffraction analysis (XRD). Moreover, variation in the lattice parameters of the Si-incorporated HAp indicates that Si is substituted into the HAp lattice. The decrease in the intensity of the peaks attributed to hydroxyl groups, which appeared in the FTIR and Raman spectra of Si-HAp, further confirms the Si substitution in HAp lattices. The silicon incorporation enhanced the nanorods length by 70%, when compared to that of pure HAp. Microwave irradiation improved the crystallinity of Si-HAp when compared to as-synthesized Si-HAp samples. As-synthesized Si-incorporated HAp sample showed an intense blue emission under UV excitation. Microwave irradiation reduced the intensity of blue emission and exhibited red shift due to the reduction of defects in the Si-HAp crystal. The morphological change from rod to spherical and ribbon-like forms was observed with an increase in silicon content. Further, Si-HAp exhibited better bioactivity and low dissolution rate. Initially there was a burst release of amoxicillin from all the samples, subsequently it followed a sustained release. The microwave-irradiated HAp showed extended period of sustained release than that of as-synthesized HAp and Si-HAp. Similarly, the microwave-irradiated Si-incorporated samples exhibited prolonged drug release, as compared to that of the as-synthesized samples. Hence, Si-HAp is rapidly synthesized by a simple and cost effective method without inducing any additional phases, as compared to the conventional sintering process. This study provides a new insight into the rapid green synthesis of Si-HAp. Si-HAp could emerge as a promising material for the bone tissue replacement and as a drug delivery system

  20. Synthesis of ZnO-SiO2 nanocomposite particles and their characterization by sonochemical method

    NASA Astrophysics Data System (ADS)

    Widiyastuti, W.; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng; Okuyama, Kikuo

    2017-05-01

    ZnO-SiO2 nanocomposite particles were prepared by sonochemical method under continuous ultrasound irradiation for an hour. Zinc nitrate and sodium silicate were used as zinc oxide and silica sources, respectively. Silica concentration was varied to investigate the effect of silica on the characteristics of the generated composite particles and they were also compared to ZnO particles. Morphology, crystallinity, chemical bonding analysis, photoluminescence spectra, and photocatalytic activity were characterized by scanning electron microscopy (SEM), X-Ray diffraction, Fourier Transform Infrared (FTIR), luminescence spectrophotometer, and UV-Vis spectrophotometer, respectively. Nanorod structures were observed for pure ZnO, ZnO-SiO2 particles with 250 ppm and 750 ppm silica addition during synthesis. Spherical agglomerated particles were found for particle with 0.1 M silica addition. The crystalline size and photocalytic activity decreased with the silica addition. A strongest chemical bonding for ZnO and SiO2 was also observed for particle with 0.1 M silica addition based on FTIR spectra. However, the highest photoluminescence emission by excitation wavelength at 250 nm, was observed for ZnO-SiO2 particles with 750 ppm silica addition with emission peak at 515 nm wavelength.

  1. Mo-Si alloy development

    SciTech Connect

    Liu, C.T.; Heatherly, L.; Wright, J.L.

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  2. Strong enhancement of high-field critical current properties and irreversibility field of MgB2 superconducting wires by coronene active carbon source addition via the new B powder carbon-coating method

    NASA Astrophysics Data System (ADS)

    Ye, Shu Jun; Matsumoto, Akiyoshi; Chao Zhang, Yun; Kumakura, Hiroaki

    2014-08-01

    We report an effective carbon-containing additive, coronene (C24H12), for MgB2 superconducting wires. We used B powder coated with C24H12 to fabricate MgB2 wires using the powder-in-tube (PIT) and internal Mg diffusion (IMD) processes. The in-field critical current properties are strongly enhanced for both PIT- and IMD-processed MgB2 wires. For PIT MgB2 wires, a critical current density (Jc) value of 1.8 × 104 A cm-2 is obtained at 4.2 K and 10 T. For IMD MgB2 wires, we obtained a Jc of 1.07 × 105 A cm-2 and an engineering Jc (Je) of 1.12 × 104 A cm-2 at 4.2 K and 10 T. These Jc and Je values are similar to the highest values reported for MgB2 wires thus far. Furthermore, the irreversibility field, Birr, determined with a current density criterion of 100 A cm-2, is strongly enhanced to 25 T at 4.2 K, which is also the highest value reported for MgB2 superconducting wires thus far. Coronene is an active carbon source for MgB2 superconducting wires because (1) coronene has a high carbon content (96 wt%) with a small amount of hydrogen (impurity), (2) the decomposition temperature for coronene is near the reaction temperature between Mg and B, and (3) uniform dispersion of coronene on the B surface can be obtained due to the melting point of coronene being lower than the decomposition temperature. Carbon substitution for B caused by the coronene active carbon source is mainly responsible for the high field critical current properties and the high Birr obtained in this work.

  3. Calcium addition at the Hubbard Brook Experimental Forest increases sugar storage, antioxidant activity and cold tolerance in native red spruce (Picea rubens)

    Treesearch

    Joshua M. Halman; Paul G. Schaberg; Gary J. Hawley; Christopher Eagar

    2008-01-01

    In fall (November 2005) and winter (February 2006), we collected current-year foliage of native red spruce (Picea rubens Sarg.) growing in a reference watershed and in a watershed treated in 1999 with wollastonite (CaSiO3, a slow-release calcium source) to simulate preindustrial soil calcium concentrations (Ca-addition...

  4. Analysis of the dynamics of reactions of SiCl2 at Si(100) surfaces

    NASA Astrophysics Data System (ADS)

    Anzai, Keisuke; Kunioshi, Nílson; Fuwa, Akio

    2017-01-01

    The dynamics of reactions of SiCl2 at Si(100) surfaces was investigated through the molecular orbital method at the B3LYP/6-31G(d,p) level of theory, with the surface being modeled using clusters of silicon atoms. The intradimer adsorption of a SiCl2 molecule proceeded with no energy barrier, and in the structure of the product of the adsorption reaction the Si atom of the SiCl2 adsorbate formed a triangular structure with the two Si atoms of the surface dimer, in agreement with theoretical predictions published recently in the literature for a small cluster. However, the dynamics reported in this work indicates that SiCl2 undergoes molecular adsorption at the silicon surface, in contrast with the dissociative adsorption suggested by some available kinetic models. Intradimer adsorption of a second SiCl2 molecule, and interdimer adsorptions of a first, a second, and a third SiCl2 molecule were also seen to proceed without significant energy barriers, suggesting that the formation of the first additional layer of silicon atoms on the surface would be fast if the adsorption of SiCl2 were the only type of reaction proceeding in the system. The diffusion of the SiCl2 adsorbate over the surface and its desorption from the surface were found to have comparable activation energies, so that these reactions are expected to compete at high temperatures.

  5. Uniform SiGe/Si quantum well nanorod and nanodot arrays fabricated using nanosphere lithography

    PubMed Central

    2013-01-01

    This study fabricates the optically active uniform SiGe/Si multiple quantum well (MQW) nanorod and nanodot arrays from the Si0.4Ge0.6/Si MQWs using nanosphere lithography (NSL) combined with the reactive ion etching (RIE) process. Compared to the as-grown sample, we observe an obvious blueshift in photoluminescence (PL) spectra for the SiGe/Si MQW nanorod and nanodot arrays, which can be attributed to the transition of PL emission from the upper multiple quantum dot-like SiGe layers to the lower MQWs. A possible mechanism associated with carrier localization is also proposed for the PL enhancement. In addition, the SiGe/Si MQW nanorod arrays are shown to exhibit excellent antireflective characteristics over a wide wavelength range. These results indicate that SiGe/Si MQW nanorod arrays fabricated using NSL combined with RIE would be potentially useful as an optoelectronic material operating in the telecommunication range. PMID:23924368

  6. Effects of SiC whiskers and particles on precipitation in aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Papazian, John M.

    1988-12-01

    The age-hardening precipitation reactions in aluminum matrix composites reinforced with discontinuous SiC were studied using a calorimetric technique. Composites fabricated with 2124, 2219, 6061, and 7475 alloy matrices were obtained from commercial sources along with unreinforced control materials fabricated in a similar manner. The 7475 materials were made by a casting process while the others were made by powder metallurgy: the SiC reinforcement was in the form of whiskers or particulate. It was found that the overall age-hardening sequence of the alloy was not changed by the addition of SiC, but that the volume fractions of various phases and the precipitation kinetics were substantially modified. Precipitation and dissolution kinetics were generally accelerated. A substantial portion of this acceleration was found to be due to the powder metallurgy process employed to make the composites, but the formation kinetics of some particular precipitate phases were also strongly affected by the presence of SiC. It was observed that the volume fraction of GP zones able to form in the SiC containing materials was significantly reduced. The presence of SiC particles also caused normally quench insensitive materials such as 6061 to become quench sensitive. The microstructural origins of these effects are discussed.

  7. Recent progress in Si thin film technology for solar cells

    NASA Astrophysics Data System (ADS)

    Kuwano, Yukinori; Nakano, Shoichi; Tsuda, Shinya

    1991-11-01

    Progress in Si thin film technology 'specifically amorphous Si (a-Si) and polycrystalline Si (poly-Si) thin film' for solar cells is summarized here from fabrication method, material, and structural viewpoints. In addition to a-Si, primary results on poly-Si thin film research are discussed. Various applications for a-Si solar cells are mentioned, and consumer applications and a-Si solar cell photovoltaic systems are introduced. New product developments include see-through solar cells, solar cell roofing tiles, and ultra-light flexible solar cells. As for new systems, air conditioning equipment powered by solar cells is described. Looking to the future, the proposed GENESIS project is discussed.

  8. Growth of cobalt and cobalt disilicide on Si(100)

    NASA Astrophysics Data System (ADS)

    Gallego, J. M.; Miranda, R.; Molodtsov, S.; Laubschat, C.; Kaindl, G.

    1990-12-01

    The growth of Co on Si(100) and the initial stages of the formation of cobalt suicides have been studied by means of a multitechnique approach. Adsorption of Co on Si(100) at room temperature does not result in reaction and formation of a few ML-thick CoSi 2 overlayer, contrary to adsorption on (111) surfaces. Rather, a layer-by-layer growth of metallic Co with some Si interdiffused is observed. The formation of CoSi 2 requires annealing to 350°C, a temperature much lower than in the (111) surface. Annealing to 600° C results in additional Si-enrichment at the surface produced by disruption of the CoSi 2 overlayer. The thin CoSi 2 "template" layer, which is crucial to achieve epitaxial growth, contains Si at the outer surface, as demonstrated by chemical titration.

  9. Improving Thermomechanical Properties of SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.; Bhatt, Ramakrishna T.

    2006-01-01

    Today, a major thrust toward improving the thermomechanical properties of engine components lies in the development of fiber-reinforced silicon carbide matrix composite materials, including SiC-fiber/SiC-matrix composites. These materials are lighter in weight and capable of withstanding higher temperatures, relative to state-of-the-art metallic alloys and oxide-matrix composites for which maximum use temperatures are in the vicinity of 1,100 C. In addition, the toughness or damage tolerance of the SiC-matrix composites is significantly greater than that of unreinforced silicon-based monolithic ceramics. For successful application in advanced engine systems, the SiC-matrix composites should be able to withstand component service stresses and temperatures for the desired component lifetimes. Inasmuch as the high-temperature structural lives of ceramic materials are typically limited by creep-induced growth of flaws, a key property required of such composite materials is high resistance to creep under conditions of use. Also, the thermal conductivity of the materials should be as high as possible so as to minimize component thermal gradients and thermal stresses. A state-of-the-art SiC-matrix composite is typically fabricated in a three-step process: (1) fabrication of a component-shaped architectural preform reinforced by thermally stable high-performance fibers, (2) chemical-vapor infiltration (CVI) of a fiber-coating material such as boron nitride (BN) into the preform, and (3) infiltration of an SiC-based matrix into the remaining porosity in the preform. Generally, the matrices of the highest-performing composites are fabricated by initial use of a CVI SiC matrix component that is typically more thermally stable and denser than matrix components formed by processes other than CVI. As such, the initial SiC matrix component made by CVI provides better environmental protection to the coated fibers embedded within it. Also, the denser CVI SiC imparts to the

  10. Growth and characterization of GaN thin films on Si(111) substrates using SiC intermediate layer

    SciTech Connect

    Lim, K.Y.; Lee, K.J.; Park, C.I.; Kim, K.C.; Choi, S.C.; Lee, W.H.; Suh, E.K.; Yang, G.M.; Nahm, K.S.

    2000-07-01

    GaN films have been grown atop Si-terminated 3C-SiC intermediate layer on Si(111) substrates using low pressure metalorganic chemical vapor deposition (LP-MOCVD). The SiC intermediate layer was grown by chemical vapor deposition (CVD) using tetramethylsilane (TMS) as the single source precursor. The Si terminated SiC surface was obtained by immediately flow of SiH{sub 4} gas after growth of SiC film. LP-MOCVD growth of GaN on 3C-SiC/Si(111) was carried out with trimethylgallium (TMG) and NH{sub 3}. Single crystalline hexagonal GaN layers can be grown on Si terminated SiC intermediate layer using an AlN or GaN buffer layer. Compared with GaN layers grown using a GaN buffer layer, the crystal qualities of GaN films with AlN buffer layers are extremely improved. The GaN films were characterized by x-ray diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). Full width at half maximum (FWHM) of double crystal x-ray diffraction (DCXD) rocking curve for GaN (0002) on 3C-SiC/Si(111) was 890 arcsec. PL near band edge emission peak position and FWHM at room temperature are 3.38 eV and 79.35 meV, respectively.

  11. Chemical reactivity of SiC fibre-reinforced SiC with beryllium and lithium ceramic breeder materials

    NASA Astrophysics Data System (ADS)

    Kleykamp, H.

    2000-12-01

    SiC fibre-reinforced SiC fabrics (f-SiC/SiC) are considered for structural materials of advanced fusion blanket concepts. Priority tasks are compatibility studies of SiC with Li breeder ceramics and the Be neutron multiplier. Isothermal and anisothermal powder reactions by DTA up to 1220°C were examined between Li 4SiO 4, Li 2ZrO 3 and Li 2TiO 3, respectively, and SiC and SiC/SiO 2 mixtures, respectively. The SiC/SiO 2 mixture simulated the chemical state of Nicalon fibres. Solid state reactions between SiC and Be pellets were studied by capsule experiments. The reaction products Be 2C and Si were observed between the initial phases after annealing at 800°C and 900°C. A parabolic time law with a chemical diffusion coefficient D˜=2.6×10 -15 m 2/s of Be in the products was deduced at 900°C. Additional oxygen released from SiO 2 as a component of the simulated fibres oxidised the reaction products via the gas phase by formation of a Be 2SiO 4 layer. All reactions are kinetically hindered below 700°C.

  12. Effect of oxygen on ion-beam induced synthesis of SiC in silicon

    NASA Astrophysics Data System (ADS)

    Artamonov, V. V.; Valakh, M. Ya.; Klyui, N. I.; Melnik, V. P.; Romanyuk, A. B.; Romanyuk, B. N.; Yuhimchuk, V. A.

    1999-01-01

    The properties of Si-structures with a buried silicon carbide (SiC) layer created by high-dose carbon implantation into Cz-Si or Fz-Si wafers followed by high-temperature annealing were studied by Raman and infrared spectroscopy. The effect of additional oxygen implantation on the peculiarities of SiC layer formation was also studied. It was shown that under the same implantation and post-implantation annealing conditions the buried SiC layer is more effectively formed in Cz-Si or in Si (Cz-or Fz-) subjected to additional oxygen implantation. So we can conclude that oxygen in silicon promotes the SiC layer formation due to SiO x precipitate creation and accommodation of the crystal volume in the region where SiC phase is formed. Carbon segregation and amorphous carbon film formation on SiC grain boundaries were revealed.

  13. SiS in Circumstellar Shells

    NASA Astrophysics Data System (ADS)

    Sahai, R.; Wootten, A.; Clegg, R. E. S.

    1985-07-01

    The author has observed the spectrum of SiS toward the Mira variable IRC+10216, and made a detailed model incorporating a radial SiS abundance gradient due to photodissociation by interstellar UV (Sahai, Wootten, and Clegg 1984). The sensitive search for SiS J = 7-6 and J = 6-5 lines in other carbon-rich, oxygen-rich, and S-type envelopes has revealed three new sources, CIT 6, CRL 2688 and IRC+20370, all of which are carbon-rich.

  14. Advanced Si IR detectors using molecular beam epitaxy

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Jones, E. W.; George, T.; Ksendzov, A.; Huberman, M. L.

    1991-01-01

    SiGe/Si heterojunction internal photoemission (HIP) long wavelength infrared (LWIR) detectors have been fabricated by MBE. The SiGe/Si HIP detector offers a tailorable spectral response in the long wavelength infrared regime by varying the SiGe/Si heterojunction barrier. Degenerately doped p(+) SiGe layers were grown using elemental boron, as the dopant source allows a low growth temperature. Good crystalline quality was achieved for boron-doped SiGe due to the reduced growth temperature. The dark current density of the boron-doped HIP detectors was found to be thermionic emission limited. HIP detectors with a 0.066 eV were fabricated and characterized using activation energy analysis, corresponding to a 18 micron cutoff wavelength. Photoresponse of the detectors at wavelengths ranging from 2 to 12 microns has been characterized with corresponding quantum efficiencies of 5 - 0.1 percent.

  15. Advanced SI IR detectors using molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lin, T. L.; Jones, E. W.; George, T.; Ksendzov, A.; Huberman, M. L.

    1991-12-01

    SiGe/Si heterojunction internal photoemission (HIP) long wavelength infrared (LWIR) detectors have been fabricated by MBE. The SiGe/Si HIP detector offers a tailorable spectral response in the long wavelength infrared regime by varying the SiGe/Si heterojunction barrier. Degenerately doped p(+) SiGe layers were grown using elemental boron, as the dopant source allows a low growth temperature. Good crystalline quality was achieved for boron-doped SiGe due to the reduced growth temperature. The dark current density of the boron-doped HIP detectors was found to be thermionic emission limited. HIP detectors with a 0.066 eV were fabricated and characterized using activation energy analysis, corresponding to a 18 micron cutoff wavelength. Photoresponse of the detectors at wavelengths ranging from 2 to 12 microns has been characterized with corresponding quantum efficiencies of 5 - 0.1 percent.

  16. Theoretically predicted and experimentally determined effects of the Si/(Si + C) gas phase ratio on the growth and character of monocrystalline beta silicon carbide films

    NASA Astrophysics Data System (ADS)

    Kim, H. J.; Davis, R. F.

    1986-10-01

    The effects of the Si/(Si + C) ratio in the reaction gas stream on the growth and properties of monocrystalline beta-SiC films grown on Si(100) substrates via chemical vapor deposition have been theoretically and experimentally studied. The amounts of condensed phases of beta-SiC and Si, and the partial pressures of the remaining Si and C-containing gases as a function of the Si/(Si + C) ratio in the source gases have been initially obtained from thermodynamic calculations using the 'SOLGASMIX-PV' computer program. Complementary and comparative experimental growth studies have shown that inclusion-free films having maximum values in growth rate and carrier concentration and a minimum value of resistivity were obtained near Si/(Si + C) = 0.5.

  17. SiC device development for high temperature sensor applications

    NASA Technical Reports Server (NTRS)

    Shor, J. S.; Goldstein, David; Kurtz, A. D.; Osgood, R. M.

    1992-01-01

    Progress made in the processing and characterization of 3C-SiC for high temperature sensor applications is reviewed. Piezoresistance properties of silicon carbide and the temperature coefficient of resistivity of n-type beta-SiC are presented. In addition, photoelectrical etching and dopant selective etch-stops in SiC and high temperature Ohmic contacts for n-type beta-SiC sensors are discussed.

  18. FT-IR analysis of high temperature annealing effects in a-SiC:H thin films

    NASA Astrophysics Data System (ADS)

    Frischmuth, Tobias; Schneider, Michael; Grille, Thomas; Schmid, U.

    2017-06-01

    Hydrogenated amorphous SiC (a-SiC:H) is an attractive material for MEMS applications where high robustness or operation in harsh environments is targeted. In previous publications, it was demonstrated, that the properties of a-SiC:H thin films can be tailored over a wide range by changing the auxiliary table excitation power of a dual plasma source deposition process using an inductively coupled plasma-enhanced chemical vapour deposition system. In this work, the annealing behavior of dual plasma source deposited a-SiC:H thin films under argon atmosphere is investigated by using Fourier transform infrared (FT-IR) spectroscopy for chemical analysis. All investigated layers show a decrease of hydrogen containing bonds (X-Hx) and an increase of Si-C bonds with increasing annealing temperature in the FT-IR spectrum. This behaviour is directly linked to the effusion of hydrogen from the thin films at elevated temperatures. In addition, films deposited at higher auxiliary plasma power show more X-Hx and less Si-C bonds, indicating a higher hydrogen amount in those films. All layers shrink with increasing annealing temperature due to the effusion of hydrogen with a stronger shrink at higher PT values caused by the increased hydrogen amount. This shrink also leads to a densification of the thin films.

  19. Tunable, broadband and high-efficiency Si/Ge hot luminescence with plasmonic nanocavity array

    NASA Astrophysics Data System (ADS)

    Qi, Gongmin; Zhang, Miao; Wang, Lin; Mu, Zhiqiang; Ren, Wei; Li, Wei; Di, Zengfeng; Wang, Xi

    2016-06-01

    In addition to the massive application in the electronics industry for decades, silicon has been considered as one of the best candidates for the photonics industry. However, a high-efficiency, broadband light source is still a challenge. In this paper, we theoretically propose a Si/Ge based platform consisting of plasmonic nanocavity array to realize the tunable, broadband, and high-efficiency Si/Ge hot luminescence from infrared to visible region with large luminescence enhancement (about 103). It is demonstrated that the large luminescence enhancement is due to the resonance between the intrinsic hot luminescence and the plasmonic nanocavity modes with ultra-small effective mode volumes. And, the size and Ge composition of Si 1 - x Ge x nanowire can be tuned to realize the tunable and broadband luminescence. This study gives rise to many applications in silicon photonics, like ultrafast optical communications, sensors, and on-chip spectral measurements.

  20. Metal Additive Manufacturing: A Review of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.