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Sample records for ag-au solid solution

  1. Formation of one-dimensional Ag-Au solid solution colloids with Au nanorods as seeds, their alloying mechanisms, and surface plasmon resonances

    NASA Astrophysics Data System (ADS)

    Guo, Tao; Tan, Yiwei

    2012-12-01

    In this work, one dimensional (1D) Ag-Au solid solution nanoalloys were synthesized by rapidly diffusing Ag into the preformed Au nanorod (AuNR) seeds at ambient temperature in aqueous solution. By varying the molar ratio of AgCl/AuNR (in gold atoms), two kinds of 1D Ag-Au alloy nanostructures with a narrow size distribution--AgAu nanowires and Ag33Au67 nanorods--could be obtained in high yields when NaCl and polyvinylpyrrolidone (PVP) were used as an additive and capping reagent, respectively. Based on HRTEM imaging combined with a series of control experiments, it is conceivable that vacancy/defect-motivated interdiffusion of Ag and Au atoms coupled with oxidative etching is a crucial stage in the mechanism responsible for this room-temperature alloying process, and the subsequent conjugation of the fused Ag-Au alloyed nanostructures is associated with the formation of the AgAu nanowires. The resulting 1D Ag-Au nanoalloys form stable colloidal dispersions and show unique localized surface plasmon resonance (LSPR) peaks in the ensemble extinction spectra.In this work, one dimensional (1D) Ag-Au solid solution nanoalloys were synthesized by rapidly diffusing Ag into the preformed Au nanorod (AuNR) seeds at ambient temperature in aqueous solution. By varying the molar ratio of AgCl/AuNR (in gold atoms), two kinds of 1D Ag-Au alloy nanostructures with a narrow size distribution--AgAu nanowires and Ag33Au67 nanorods--could be obtained in high yields when NaCl and polyvinylpyrrolidone (PVP) were used as an additive and capping reagent, respectively. Based on HRTEM imaging combined with a series of control experiments, it is conceivable that vacancy/defect-motivated interdiffusion of Ag and Au atoms coupled with oxidative etching is a crucial stage in the mechanism responsible for this room-temperature alloying process, and the subsequent conjugation of the fused Ag-Au alloyed nanostructures is associated with the formation of the AgAu nanowires. The resulting 1D Ag-Au

  2. Formation of one-dimensional Ag-Au solid solution colloids with Au nanorods as seeds, their alloying mechanisms, and surface plasmon resonances.

    PubMed

    Guo, Tao; Tan, Yiwei

    2013-01-21

    In this work, one dimensional (1D) Ag-Au solid solution nanoalloys were synthesized by rapidly diffusing Ag into the preformed Au nanorod (AuNR) seeds at ambient temperature in aqueous solution. By varying the molar ratio of AgCl/AuNR (in gold atoms), two kinds of 1D Ag-Au alloy nanostructures with a narrow size distribution--AgAu nanowires and Ag(33)Au(67) nanorods--could be obtained in high yields when NaCl and polyvinylpyrrolidone (PVP) were used as an additive and capping reagent, respectively. Based on HRTEM imaging combined with a series of control experiments, it is conceivable that vacancy/defect-motivated interdiffusion of Ag and Au atoms coupled with oxidative etching is a crucial stage in the mechanism responsible for this room-temperature alloying process, and the subsequent conjugation of the fused Ag-Au alloyed nanostructures is associated with the formation of the AgAu nanowires. The resulting 1D Ag-Au nanoalloys form stable colloidal dispersions and show unique localized surface plasmon resonance (LSPR) peaks in the ensemble extinction spectra.

  3. One-step Solution Processing of Ag, Au and Pd@MXene Hybrids for SERS

    NASA Astrophysics Data System (ADS)

    Satheeshkumar, Elumalai; Makaryan, Taron; Melikyan, Armen; Minassian, Hayk; Gogotsi, Yury; Yoshimura, Masahiro

    2016-08-01

    We report on one-step hybridization of silver, gold and palladium nanoparticles from solution onto exfoliated two-dimensional (2D) Ti3C2 titanium carbide (MXene) nanosheets. The produced hybrid materials can be used as substrates for surface-enhanced Raman spectroscopy (SERS). An approximate analytical approach is also developed for the calculation of the surface plasmon resonance (SPR) frequency of nanoparticles immersed in a medium, near the interface of two dielectric media with different dielectric constants. We obtained a good match with the experimental data for SPR wavelengths, 440 nm and 558 nm, respectively for silver and gold nanoparticles. In the case of palladium, our calculated SPR wavelength for the planar geometry was 160 nm, demonstrating that non-spherical palladium nanoparticles coupled with 2D MXene yield a broad, significanlty red-shifted SPR band with a peak at 230 nm. We propose a possible mechanism of the plasmonic hybridization of nanoparticles with MXene. The as-prepared noble metal nanoparticles on MXene show a highly sensitive SERS detection of methylene blue (MB) with calculated enhancement factors on the order of 105. These findings open a pathway for extending visible-range SERS applications of novel 2D hybrid materials in sensors, catalysis, and biomedical applications.

  4. One-step Solution Processing of Ag, Au and Pd@MXene Hybrids for SERS.

    PubMed

    Satheeshkumar, Elumalai; Makaryan, Taron; Melikyan, Armen; Minassian, Hayk; Gogotsi, Yury; Yoshimura, Masahiro

    2016-08-25

    We report on one-step hybridization of silver, gold and palladium nanoparticles from solution onto exfoliated two-dimensional (2D) Ti3C2 titanium carbide (MXene) nanosheets. The produced hybrid materials can be used as substrates for surface-enhanced Raman spectroscopy (SERS). An approximate analytical approach is also developed for the calculation of the surface plasmon resonance (SPR) frequency of nanoparticles immersed in a medium, near the interface of two dielectric media with different dielectric constants. We obtained a good match with the experimental data for SPR wavelengths, 440 nm and 558 nm, respectively for silver and gold nanoparticles. In the case of palladium, our calculated SPR wavelength for the planar geometry was 160 nm, demonstrating that non-spherical palladium nanoparticles coupled with 2D MXene yield a broad, significanlty red-shifted SPR band with a peak at 230 nm. We propose a possible mechanism of the plasmonic hybridization of nanoparticles with MXene. The as-prepared noble metal nanoparticles on MXene show a highly sensitive SERS detection of methylene blue (MB) with calculated enhancement factors on the order of 10(5). These findings open a pathway for extending visible-range SERS applications of novel 2D hybrid materials in sensors, catalysis, and biomedical applications.

  5. One-step Solution Processing of Ag, Au and Pd@MXene Hybrids for SERS

    PubMed Central

    Satheeshkumar, Elumalai; Makaryan, Taron; Melikyan, Armen; Minassian, Hayk; Gogotsi, Yury; Yoshimura, Masahiro

    2016-01-01

    We report on one-step hybridization of silver, gold and palladium nanoparticles from solution onto exfoliated two-dimensional (2D) Ti3C2 titanium carbide (MXene) nanosheets. The produced hybrid materials can be used as substrates for surface-enhanced Raman spectroscopy (SERS). An approximate analytical approach is also developed for the calculation of the surface plasmon resonance (SPR) frequency of nanoparticles immersed in a medium, near the interface of two dielectric media with different dielectric constants. We obtained a good match with the experimental data for SPR wavelengths, 440 nm and 558 nm, respectively for silver and gold nanoparticles. In the case of palladium, our calculated SPR wavelength for the planar geometry was 160 nm, demonstrating that non-spherical palladium nanoparticles coupled with 2D MXene yield a broad, significanlty red-shifted SPR band with a peak at 230 nm. We propose a possible mechanism of the plasmonic hybridization of nanoparticles with MXene. The as-prepared noble metal nanoparticles on MXene show a highly sensitive SERS detection of methylene blue (MB) with calculated enhancement factors on the order of 105. These findings open a pathway for extending visible-range SERS applications of novel 2D hybrid materials in sensors, catalysis, and biomedical applications. PMID:27557838

  6. Hardness of cubic solid solutions

    PubMed Central

    Gao, Faming

    2017-01-01

    We demonstrate that a hardening rule exists in cubic solid solutions with various combinations of ionic, covalent and metallic bonding. It is revealed that the hardening stress ∆τFcg is determined by three factors: shear modulus G, the volume fraction of solute atoms fv, and the size misfit degree δb. A simple hardening correlation in KCl-KBr solid-solution is proposed as ∆τFcg = 0.27 G. It is applied to calculate the hardening behavior of the Ag-Au, KCl-KBr, InP-GaP, TiN-TiC, HfN-HfC, TiC-NbC and ZrC-NbC solid-solution systems. The composition dependence of hardness is elucidated quantitatively. The BN-BP solid-solution system is quantitatively predicted. We find a hardening plateau region around the x = 0.55–0.85 in BNxP1−x, where BNxP1−x solid solutions are far harder than cubic BN. Because the prediction is quantitative, it sets the stage for a broad range of applications. PMID:28054659

  7. Hardness of cubic solid solutions

    NASA Astrophysics Data System (ADS)

    Gao, Faming

    2017-01-01

    We demonstrate that a hardening rule exists in cubic solid solutions with various combinations of ionic, covalent and metallic bonding. It is revealed that the hardening stress ∆τFcg is determined by three factors: shear modulus G, the volume fraction of solute atoms fv, and the size misfit degree δb. A simple hardening correlation in KCl-KBr solid-solution is proposed as ∆τFcg = 0.27 G. It is applied to calculate the hardening behavior of the Ag-Au, KCl-KBr, InP-GaP, TiN-TiC, HfN-HfC, TiC-NbC and ZrC-NbC solid-solution systems. The composition dependence of hardness is elucidated quantitatively. The BN-BP solid-solution system is quantitatively predicted. We find a hardening plateau region around the x = 0.55–0.85 in BNxP1‑x, where BNxP1‑x solid solutions are far harder than cubic BN. Because the prediction is quantitative, it sets the stage for a broad range of applications.

  8. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaffin, Elise; O'Connor, Ryan T.; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ˜410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  9. Solid Solutions

    NASA Astrophysics Data System (ADS)

    Lee, Go-Eun; Kim, Il-Ho; Lim, Young Soo; Seo, Won-Seon; Choi, Byeong-Jun; Hwang, Chang-Won

    2014-06-01

    Since Bi2Te3 and Bi2Se3 have the same crystal structure, they form a homogeneous solid solution. Therefore, the thermal conductivity of the solid solution can be reduced by phonon scattering. The thermoelectric figure of merit can be improved by controlling the carrier concentration through doping. In this study, Bi2Te2.85Se0.15:D m (D: dopants such as I, Cu, Ag, Ni, Zn) solid solutions were prepared by encapsulated melting and hot pressing. All specimens exhibited n-type conduction in the measured temperature range (323 K to 523 K), and their electrical conductivities decreased slightly with increasing temperature. The undoped solid solution showed a carrier concentration of 7.37 × 1019 cm-3, power factor of 2.1 mW m-1 K-1, and figure of merit of 0.56 at 323 K. The figure of merit ( ZT) was improved due to the increased power factor by I, Cu, and Ag dopings, and maximum ZT values were obtained as 0.76 at 323 K for Bi2Te2.85Se0.15:Cu0.01 and 0.90 at 423 K for Bi2Te2.85Se0.15:I0.005. However, the thermoelectric properties of Ni- and Zn-doped solid solutions were not enhanced.

  10. Isomorphism and solid solutions among Ag- and Au-selenides

    NASA Astrophysics Data System (ADS)

    Palyanova, Galina A.; Seryotkin, Yurii V.; Kokh, Konstantin A.; Bakakin, Vladimir V.

    2016-09-01

    Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag2-xAuxSe with a step of x=0.25 (0≤x≤2) to 1050 °C and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag2Se - Ag1.94Au0.06Se, fischesserite Ag3AuSe2 - Ag3.2Au0.8Se2 and gold selenide AuSe - Au0.94Ag0.06Se. Solid solutions and AgAuSe phases were added to the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe.

  11. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    NASA Astrophysics Data System (ADS)

    Porobova, Svetlana; Markova, Tat'jana; Klopotov, Vladimir; Klopotov, Anatoliy; Loskutov, Oleg; Vlasov, Viktor

    2016-01-01

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen's law.

  12. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    SciTech Connect

    Porobova, Svetlana Loskutov, Oleg; Markova, Tat’jana; Klopotov, Vladimir; Klopotov, Anatoliy; Vlasov, Viktor

    2016-01-15

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

  13. Near infrared Ag/Au alloy nanoclusters: tunable photoluminescence and cellular imaging.

    PubMed

    Wang, Chuanxi; Xu, Lin; Xu, Xiaowei; Cheng, Hao; Sun, Hongchen; Lin, Quan; Zhang, Chi

    2014-02-15

    The fluorescent nanomaterials play an important role in cellular imaging. Although the synthesis of fluorescent metal nanoclusters (NCs) have been developing rapidly, there are many technical issues in preparing metal alloy NCs. Herein, we used a facile galvanic replacement reaction to prepare Ag/Au alloy NCs. The characterizations of UV, PL, HRTEM, EDX and XPS confirm one fact the Ag/Au alloy NCs are carried out. As-prepared Ag/Au alloy NCs display near-infrared (NIR) fluorescence centered at 716 nm and show tunable luminescence from visible red (614 nm) to NIR (716 nm) by controlling the experimental Ag/Au ratios. Moreover, as-prepared Ag/Au alloy NCs are protected by glutathione (GSH) whose some functional groups including thiol, carboxyl and amino groups make the as-prepared alloy NCs exhibit good dispersion in aqueous solution, high physiological stability and favorable biocompatibility. Together with NIR fluorescence, these advantages make alloy NCs be promising candidate in biological labeling.

  14. Corrosion resistance evaluation of Pd-free Ag-Au-Pt-Cu dental alloys.

    PubMed

    Fujita, Takeshi; Shiraishi, Takanobu; Takuma, Yasuko; Hisatsune, Kunihiro

    2011-01-01

    The corrosion resistance of nine experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.9% NaCl solution was investigated using cyclic voltammetry (CV), optical microscopy, and scanning electron microscopy (SEM). CV measurements revealed that the breakdown potential (E(bd)) and zero current potential (E(zc)) increased with increasing Au/(Au+Ag) atomic ratio. Thus, the Au/(Au+Ag) atomic ratio, but not the Cu content, influenced the corrosion resistance of Ag-Au-Pt-Cu alloys. After the forward scan of CV, both optical and scanning electron microscope images showed that in all the experimental alloys, the matrix phase was corroded but not the second phase. From corrosion resistance viewpoint, the Ag-Au-Pt-Cu alloys seemed to be suitable for clinical application.

  15. Electrostatic assembles and optical properties of Au CdTe QDs and Ag/Au CdTe QDs

    NASA Astrophysics Data System (ADS)

    Yang, Dongzhi; Wang, Wenxing; Chen, Qifan; Huang, Yuping; Xu, Shukun

    2008-09-01

    Au-CdTe and Ag/Au-CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.

  16. Mixed oxide solid solutions

    DOEpatents

    Magno, Scott; Wang, Ruiping; Derouane, Eric

    2003-01-01

    The present invention is a mixed oxide solid solution containing a tetravalent and a pentavalent cation that can be used as a support for a metal combustion catalyst. The invention is furthermore a combustion catalyst containing the mixed oxide solid solution and a method of making the mixed oxide solid solution. The tetravalent cation is zirconium(+4), hafnium(+4) or thorium(+4). In one embodiment, the pentavalent cation is tantalum(+5), niobium(+5) or bismuth(+5). Mixed oxide solid solutions of the present invention exhibit enhanced thermal stability, maintaining relatively high surface areas at high temperatures in the presence of water vapor.

  17. Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability.

    PubMed

    Lee, Habeom; Hong, Sukjoon; Lee, Jinhwan; Suh, Young Duk; Kwon, Jinhyeong; Moon, Hyunjin; Kim, Hyeonseok; Yeo, Junyeob; Ko, Seung Hwan

    2016-06-22

    Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices.

  18. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    EPA Science Inventory

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  19. Tuning the SERS Response with Ag-Au Nanoparticle-Embedded Polymer Thin Film Substrates.

    PubMed

    Rao, V Kesava; Radhakrishnan, T P

    2015-06-17

    Development of facile routes to the fabrication of thin film substrates with tunable surface enhanced Raman scattering (SERS) efficiency and identification of the optimal conditions for maximizing the enhancement factor (EF) are significant in terms of both fundamental and application aspects of SERS. In the present work, polymer thin films with embedded bimetallic nanoparticles of Ag-Au are fabricated by a simple two-stage protocol. Ag nanoparticles are formed in the first stage, by the in situ reduction of silver nitrate by the poly(vinyl alcohol) (PVA) film through mild thermal annealing, without any additional reducing agent. In the second stage, aqueous solutions of chloroauric acid spread on the Ag-PVA thin film under ambient conditions, lead to the galvanic displacement of Ag by Au in situ inside the film, and the formation of Ag-Au particles. Evolution of the morphology of the bimetallic nanoparticles into hollow cage structures and the distribution of Au on the nanoparticles are revealed through electron microscopy and energy dispersive X-ray spectroscopy. The localized surface plasmon resonance (LSPR) extinction of the nanocomposite thin film evolves with the Ag-Au composition; theoretical simulation of the extinction spectra provides insight into the observed trends. The Ag-Au-PVA thin films are found to be efficient substrates for SERS. The EF follows the variation of the LSPR extinction vis-à-vis the excitation laser wavelength, but with an offset, and the maximum SERS effect is obtained at very low Au content; experiments with Rhodamine 6G showed EFs on the order of 10(8) and a limit of detection of 0.6 pmol. The present study describes a facile and simple fabrication of a nanocomposite thin film that can be conveniently deployed in SERS investigations, and the utility of the bimetallic system to tune and maximize the EF.

  20. Integrated logic gate for fluorescence turn-on detection of histidine and cysteine based on Ag/Au bimetallic nanoclusters-Cu²⁺ ensemble.

    PubMed

    Sun, Jian; Yang, Fan; Zhao, Dan; Chen, Chuanxia; Yang, Xiurong

    2015-04-01

    By means of employing 11-mercaptoundecanoic acid (11-MUA) as a reducing agent and protecting ligand, we present straightforward one-pot preparation of fluorescent Ag/Au bimetallic nanoclusters (namely AgAuNCs@11-MUA) from AgNO3 and HAuCl4 in alkaline aqueous solution at room temperature. It is found that the fluorescence of AgAuNCs@11-MUA has been selectively quenched by Cu(2+) ions, and the nonfluorescence off-state of the as-prepared AgAuNCs@11-MUA-Cu(2+) ensemble can be effectively switched on upon the addition of histidine and cysteine. By incorporating Ni(2+) ions and N-ethylmaleimide, this phenomenon is further exploited as an integrated logic gate and a specific fluorescence turn-on assay for selectively and sensitively sensing histidine and cysteine has been designed and established based on the original noncovalent AgAuNCs@11-MUA-Cu(2+) ensemble. Under the optimal conditions, histidine and cysteine can be detected in the concentration ranges of 0.25-9 and 0.25-7 μM; besides, the detection limits are found to be 87 and 111 nM (S/N = 3), respectively. Furthermore, we demonstrate that the proposed AgAuNCs@11-MUA-based fluorescent assay can be successfully utilized for biological fluids sample analysis.

  1. Thermodynamic Properties of Liquid Ag-Au-Sn Alloys

    NASA Astrophysics Data System (ADS)

    Hindler, M.; Knott, S.; Mikula, A.

    2010-10-01

    The thermodynamic properties of liquid Ag-Au-Sn alloys were studied with an electromotive force (EMF) method using the eutectic mixture of KCl/LiCl as a liquid electrolyte. Activities of Sn in the liquid alloys were measured at three cross-sections with constant molar ratios of Ag:Au = 2:1, 1:1, and 1:2 with tin in the concentration range between 20 at.% and 90 at.% from the liquidus of the samples up to 1030 K. The integral Gibbs energies at 973 K and the integral enthalpies were calculated by Gibbs-Duhem integration.

  2. Study on antibacterial activity of chemically synthesized PANI-Ag-Au nanocomposite

    NASA Astrophysics Data System (ADS)

    Boomi, Pandi; Prabu, Halliah Gurumallesh; Manisankar, Paramasivam; Ravikumar, Sundaram

    2014-05-01

    Pristine polyaniline (PANI), PANI-Ag, PANI-Au and PANI-Ag-Au nanocomposites have been successfully synthesized by chemical oxidative polymerization method using aniline as monomer, ammonium persulphate as oxidant and metal (Ag, Au and Ag-Au) colloids. UV-Vis analysis exhibited surface Plasmon resonances of Ag, Au, Ag-Au nanoparticles. FT-IR spectra revealed the shift in peak position of N-H stretching. X-ray diffraction (XRD) results confirm the presence of Ag, Au and Au-Ag nanoparticles. HR-TEM images show nanosizes of Ag, Au, Ag-Au and the incorporation of such nanoparticles into the PANI matrix. Pristine PANI, PANI-Ag, PANI-Au and PANI-Ag-Au nanocomposites were tested for antibacterial activity by agar well diffusion method. PANI-Ag-Au nanocomposite exhibited higher antibacterial activity against both gram-positive [Streptococcus sp. (MTCC 890), Staphylococcus sp. (MTCC 96)] and gram-negative bacteria [Escherichia coli (MTCC 1671) and Klebsiella sp. (MTCC 7407)] when compared with PANI-Ag nanocomposite, PANI-Au nanocomposite and pristine PANI. The novelty of this study is the polymer-bimetal synthesis and its antibacterial potential.

  3. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported.

  4. Preparation of Ag/Au bimetallic nanostructures and their application in surface-enhanced fluorescence.

    PubMed

    Dong, Jun; Ye, Yanyan; Zhang, Wenhui; Ren, Zebin; Huo, Yiping; Zheng, Hairong

    2015-11-01

    An effective substrate for surface-enhanced fluorescence, which consists of cluster Ag/Au bimetallic nanostructures on a copper surface, was synthesized via a multi-stage galvanic replacement reaction of a Ag cluster in a chlorauric acid (HAuCl4) solution at room temperature. The fabricated silver/gold bimetallic cluster were found to yield large surface-enhanced fluorescence (SEF) enhancement factors for rhodamine 6G probe molecules deposited on the substrate, and also the fluorescence efficiency is critically dependent on the period of nanostructure growth. With the help of proper control reaction conditions, such as the reaction time, and concentration of reaction solutions, the maximum fluorescence enhanced effect was obtained. Therefore, the bimetallic nanostructure substrate also can be adapted to studies in SEF, which will expand the application of SEF.

  5. Interfacial reactions in the Sn-Ag/Au couples

    NASA Astrophysics Data System (ADS)

    Chen, Sinn-Wen; Yen, Yee-Wen

    2001-09-01

    Ag-Sn alloys are one of the most promising lead-free solders. Their reactions with Au substrates have been examined by using the reaction couple technique. Sn-3.5wt.%Ag/Au and Sn-25wt.%Ag/Au couples have been prepared and reacted at 120, 150, 180 and 200 C for various lengths of time. Three phases, δ-AuSn, ɛ2-AuSn2, and η-AuSn4, are found in all the couples. The thickness of the reaction layers inccreases with higher temperatures and longer reaction time, and their growth rates are described by using the parabolic law. Arrhenius equation is used to describe the temperature dependence of the growth rates. The activation energy of the growth of the intermetallic layers in both kinds of the reaction couples is similar and is determined to be 76.74 KJ/mole. Based on the reaction path knowledge and interfacial morphology, it is concluded that Sn is the fastest diffusion species in the couples.

  6. Facile synthesis of Ag@Au core-sheath nanowires with greatly improved stability against oxidation.

    PubMed

    Yang, Miaoxin; Hood, Zachary D; Yang, Xuan; Chi, Miaofang; Xia, Younan

    2017-02-07

    We report a facile synthesis of Ag@Au core-sheath nanowires through the conformal deposition of Au atoms onto the surface of pre-synthesized Ag nanowires. The resulting Ag@Au nanowires showed morphology and optical properties almost identical to the pristine Ag nanowires, but with greatly improved stability under different corrosive environments.

  7. STRUCTURE AND PROPERTIES OF SOLID SOLUTIONS.

    DTIC Science & Technology

    Contents: solid solution strengthening and strain aging in Ag-base Al alloys; solid solution strengthening and aging in Cu-base Al alloys; solid ... solution strengthening in NaCl-base NaBr solutions; short-range order; solid solution strength in the gold-silver system.

  8. Tarnish resistance evaluation of experimental Pd-free Ag-Au-Pt-Cu dental alloys.

    PubMed

    Takuma, Yasuko; Shiraishi, Takanobu; Fujita, Takeshi; Hisatsune, Kunihiro

    2010-05-01

    This study evaluated the tarnish resistance of eight experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.1% Na(2)S aqueous solution at 37 degrees C. Color measurements of the plate samples were made using a computerized spectrophotometer before and after immersion in the test solution for up to 72 hours. Tarnish discoloration was evaluated using the color difference vector, DeltaE*, in the CIELAB color space. Microstructural observation of each sample through an optical microscope revealed the matrix phase as the major constituent and second-phase small grains in the matrix phase. Selective tarnish discoloration occurred in the matrix, and fractional area of the matrix to the whole surface area was influenced by the sum of Au and Ag concentrations. The DeltaE* value significantly decreased with increasing Au/(Au+Ag) atomic ratio. In conclusion, the Au/(Au+Ag) ratio in an alloy and the fractional area of the matrix were found to be primary and auxiliary factors affecting the tarnish resistance of the experimental alloys.

  9. Probing the rupture of a Ag atomic junction in a Ag-Au mixed electrode

    NASA Astrophysics Data System (ADS)

    Kim, Taekyeong

    2015-09-01

    We probed that the atomic junction in Ag part ruptures during stretching of atomic sized contacts of Ag-Au mixed electrodes, resulting in Ag-Ag electrodes through a scanning tunneling microscope breaking junction (STM-BJ) technique. We observed that the conductance and tunneling decay constant for a series of amine-terminated oligophenyl molecular junctions are essentially the same for the Ag-Au mixed and the Ag-Ag electrodes. We also found the molecular plateau length and the evolution patterns with the Ag-Au mixed electrodes are similar to those with Ag-Ag electrodes rather than the Au-Au electrodes in the molecular junction elongation. This result is attributed to the smaller binding energy of Ag atoms compared to that of Au atoms, so the Ag junction part is more easily broken than that of Au part in stretching of Ag-Au mixed electrodes. Furthermore, we successfully observed that the rupture force of the atomic junction for the Ag-Au mixed electrodes was identical to that for the Ag-Ag electrodes and smaller than that for the Au-Au electrodes. This study may advance the understanding of the electrical and the mechanical properties in molecular devices with Ag and Au electrodes in future.

  10. Germanium-silicon solid solutions

    NASA Technical Reports Server (NTRS)

    Zemskov, V. S.; Kubasov, V. N.; Belokurova, I. N.; Titkov, A. N.; Shulpina, I. L.; Safarov, V. I.; Guseva, N. B.

    1977-01-01

    An experiment on melting and directional crystallization of an antimony (Sb) doped germanium silicon (GeSi) solid solution was designed for the Apollo-Soyuz Test Project (ASTP) to study the possibility of using zero-g conditions for obtaining solid-solution monocrystals with uniformly distributed components. Crystallization in the zero-g environment did not occur under ideal stationary growth and segregation conditions. Crystallization under zero-g conditions revealed the heterogeneous nature of Si and Sb distribution in the cross sections of crystals. The presence of the radial thermal gradient in the multipurpose furnace could be one of the reasons for such Si and Sb distribution. The structure of space-grown crystals correlates with the nature of heterogeneities of Si and Sb distribution in crystals. The type of surface morphology and the contour observed in space-grown crystals were never observed in ground-based crystals and indicate the absence of wetting of the graphitized walls of the ampoule by the melt during melting and crystallization.

  11. Growth of Solid Solution Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.; Holland, L. R.

    1985-01-01

    The major objective of this program is to determine the conditions under which single crystals of solid solutions can be grown from the melt in a Bridgman configuration with a high degree of chemical homogeneity. The central aim is to assess the role of gravity in the growth process and to explore the possible advantages for growth in the absence of gravity. The alloy system being investigated is the solid solution semiconductor with x-values appropriate for infrared detector applications in Hg sub (1-x) Cd sub x Te the 8 to 14 micro m wavelength region. Both melt and Te-solvent growth are being considered. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. Experimental facilities have been established for the purification, casting, and crystal growth of the alloy system. Facilities have been also established for the metallurgical, compositional, electric and optical characterization of the alloys. Crystals are being grown by the Bridgman-Stockbarger method and are analyzed by various experimental techniques to evaluate the effects of growth conditions on the longitudinal and radial compositional variations and defect densities in the crystals.

  12. Phase equilibria in the Ag-Au-In system at 500°C

    NASA Astrophysics Data System (ADS)

    Ptashkina, E. A.; Romanova, A. G.; Pavlenko, A. S.; Kabanova, E. G.; Kuznetsov, V. N.

    2017-02-01

    Phase equilibria in Ag-Au-In system at 500°C are investigated by means of electron microscopy, electron probe microanalysis, and X-ray powder diffraction. The part of the system's isothermal cross section with an indium content of up to 50 at % is constructed.

  13. Partitioning of platinum-group elements (PGE) and chalcogens (Se, Te, As, Sb, Bi) between monosulfide-solid solution (MSS), intermediate solid solution (ISS) and sulfide liquid at controlled fO2-fS2 conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yanan; Brenan, James

    2015-06-01

    In order to better understand the behavior of highly siderophile elements (HSEs: Os, Ir, Ru, Rh, Pt, Pd, Au, Re), Ag, Pb and chalcogens (As, Se, Sb, Te and Bi) during the solidification of sulfide magmas, we have conducted a series of experiments to measure partition coefficients (D values) between monosulfide solid solution (MSS) and sulfide melt, as well as MSS and intermediate solid solution (ISS), at 0.1 MPa and 860-926 °C, log fS2 -3.0 to -2.2 (similar to the Pt-PtS buffer), with fO2 controlled at the fayalite-magnetite-quartz (FMQ) buffer. The IPGEs (Os, Ir, Ru), Rh and Re are found to be compatible in MSS relative to sulfide melt with D values ranging from ∼20 to ∼5, and DRe/DOs of ∼0.5. Pd, Pt, Au, Ag, Pb, as well as the chalcogens, are incompatible in MSS, with D values ranging from ∼0.1 to ∼1 × 10-3. For the same metal/sulfur ratio, D values for the IPGEs, Rh and Re are systematically larger than most past studies, correlating with higher oxygen content in the sulfide liquid, reflecting the significant effect of oxygen on increasing the activity coefficients for these elements in the melt phase. MSS/ISS partitioning experiments reveal that Ru, Os, Ir, Rh and Re are partitioned into MSS by a factor of >50, whereas Pd, Pt, Ag, Au and the chalcogens partition from weakly (Se, As) to strongly (Ag, Au) into ISS. Uniformly low MSS- and ISS- melt partition coefficients for the chalcogens, Pt, Pd, Ag and Au will lead to enrichment in the residual sulfide liquid, but D values are generally too large to reach early saturation in Pt-Pd-chalcogen-rich accessory minerals, based on current solubility estimates. Instead, these phases likely precipitate at the last dregs of crystallization. Modeled evolution curves for the PGEs and chalcogens are in reasonably good agreement with whole-rock sulfide compositions for the McCreedy East deposit (Sudbury, Ontario), consistent with an origin by crystallization of MSS, then MSS + ISS from sulfide magma.

  14. SERS activity studies of Ag/Au bimetallic films prepared by galvanic replacement.

    PubMed

    Wang, Chaonan; Fang, Jinghuai; Jin, Yonglong

    2012-10-01

    Ag films on Si substrates were fabricated by immersion plating, which served as sacrificial materials for preparation of Ag/Au bimetallic films by galvanic replacement method. SEM images displayed that the sacrificial Ag films presenting island morphology experienced interesting structural evolution process during galvanic replacement reaction, and nano-scaled holes were formed in the resultant bimetallic films. SERS measurements using crystal violet as an analyte showed that SERS intensities of bimetallic films were enhanced significantly compared with that of pure Ag films and related mechanisms were discussed. Immersion plating experiment carried out on Ag films on PEN substrates fabricated by photoinduced reduction method further confirmed that galvanic replacement is an easy method to fabricate Ag/Au bimetallic and a potential approach to improve the SERS performance of Ag films.

  15. Energetic, electronic, and thermal effects on structural properties of Ag-Au nanoalloys.

    PubMed

    Chen, Fuyi; Johnston, Roy L

    2008-01-01

    Using a genetic algorithm global optimization approach combined with density functional theory calculations, a search has been made for the lowest energies of (AgAu)(m) nanoalloys with 20-150 atoms (diameters of 1.0-2.0 nm). A total of 31 decahedra, 35 icosahedra, and 2 close-packed motifs are identified in two icosahedral windows and one Marks-decahedral window. These structural motifs have twinned, capped, defective, and distorted atomic packing compared to classical clusters, such as the icosahedron. The magic numbers, atomic ordering, electronic structure, and melting behavior are further studied, and a new poly-nanocrystalline decahedral motif, Ag(44)Au(44), is found to have high structural, electronic, and thermal stability. Our results show that alloying can lead to a remarkable stabilization of local order and provide a comprehensive model for the structures and properties of Ag-Au nanoalloys.

  16. Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Hareesh, K.; Joshi, R. P.; D. V., Sunitha; Bhoraskar, V. N.; Dhole, S. D.

    2016-12-01

    One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV-vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5-19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp2 domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

  17. Real-time imaging and elemental mapping of AgAu nanoparticle transformations.

    PubMed

    Lewis, E A; Slater, T J A; Prestat, E; Macedo, A; O'Brien, P; Camargo, P H C; Haigh, S J

    2014-11-21

    We report the controlled alloying, oxidation, and subsequent reduction of individual AgAu nanoparticles in the scanning transmission electron microscope (STEM). Through sequential application of electron beam induced oxidation and in situ heating and quenching, we demonstrate the transformation of Ag-Au core-shell nanoparticles into: AgAu alloyed, Au-Ag core-shell, hollow Au-Ag2O core-shell, and Au-Ag2O yolk-shell nanoparticles. We are able to directly image these morphological transformations in real-time at atomic resolution and perform energy dispersive X-ray (EDX) spectrum imaging to map changing elemental distributions with sub-nanometre resolution. By combining aberration corrected STEM imaging and high efficiency EDX spectroscopy we are able to quantify not only the growth and coalescence of Kirkendall voids during oxidation but also the compositional changes occurring during this reaction. This is the first time that it has been possible to track the changing distribution of elements in an individual nanoparticle undergoing oxidation driven shell growth and hollowing.

  18. A (25)Mg, (89)Y and (115)In solid state MAS NMR study of YT2X and Y(T0.5T'0.5)2X (T/T' = Pd, Ag, Au; X = Mg, In) Heusler phases.

    PubMed

    Benndorf, Christopher; Stein, Sebastian; Heletta, Lukas; Kersting, Marcel; Eckert, Hellmut; Pöttgen, Rainer

    2016-12-20

    Yttrium-transition metal-magnesium (indium) Heusler phases YPd2Mg, YPd2In, YAg2Mg, YAg2In, YAu2Mg, and YAu2In and their quaternary compounds (solid solutions) Y(Pd0.5Ag0.5)2Mg, Y(Pd0.5Ag0.5)2In, Y(Pd0.5Au0.5)2Mg, Y(Pd0.5Au0.5)2In, Y(Ag0.5Au0.5)2Mg and Y(Ag0.5Au0.5)2In were synthesized from the elements in sealed niobium ampoules in a high-frequency furnace or by arc-melting, respectively. All compounds crystallize with the cubic MnCu2Al type structure (Heusler phase), space group Fm3[combining macron]m. The structure of Y(Ag0.39Au0.61)2Mg was refined from single crystal X-ray diffractometer data: a = 689.97(5) pm, wR2 = 0.0619, 52 F(2) values, 6 parameters. Magnetic susceptibility measurements show Pauli paramagnetic behavior for all samples. The compounds were investigated by (25)Mg, (89)Y and (115)In solid state MAS NMR spectroscopy. Large positive resonance shifts are observed for all nuclei. A review of the present data in the context of literature data on isotypic Heusler phases with Cd and Sn indicates that the (89)Y shifts show a correlation with the electronegativity of the main group atoms (Mg, Cd, In, Sn). The solid solutions Y(Ag1-xTx)2Mg (x = 0.1, 0.25, 0.33, 0.5; T = Pd, Au) clearly show Vegard-like behavior concerning their lattice parameters, and their main group element resonance shifts arising from spin and orbital contributions are close to the interpolated values of the corresponding end-member compounds.

  19. Single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

    1974-01-01

    The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

  20. Solution-solid-solid mechanism: superionic conductors catalyze nanowire growth.

    PubMed

    Wang, Junli; Chen, Kangmin; Gong, Ming; Xu, Bin; Yang, Qing

    2013-09-11

    The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire.

  1. Determination of anthracene on Ag-Au alloy nanoparticles/overoxidized-polypyrrole composite modified glassy carbon electrodes.

    PubMed

    Mailu, Stephen N; Waryo, Tesfaye T; Ndangili, Peter M; Ngece, Fanelwa R; Baleg, Abd A; Baker, Priscilla G; Iwuoha, Emmanuel I

    2010-01-01

    A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode (PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO(3) and HAuCl(4) using C(6)H(5)O(7)Na(3) as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20-50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10(-6) to 3.56 × 10(-4) M with a detection limit of 1.69 × 10(-7) M. The proposed method was simple, less time consuming and showed a high sensitivity.

  2. Computer simulation of concentrated solid solution strengthening

    NASA Technical Reports Server (NTRS)

    Kuo, C. T. K.; Arsenault, R. J.

    1976-01-01

    The interaction forces between a straight edge dislocation moving through a three-dimensional block containing a random array of solute atoms were determined. The yield stress at 0 K was obtained by determining the average maximum solute-dislocation interaction force that is encountered by edge dislocation, and an expression relating the yield stress to the length of the dislocation and the solute concentration is provided. The magnitude of the solid solution strengthening due to solute atoms can be determined directly from the numerical results, provided the dislocation line length that moves as a unit is specified.

  3. Probing the Ag, Au, and Cu electrode/pyridine-α-hydroxymethyl biphenyl phosphine oxide isomer interface with SERS

    NASA Astrophysics Data System (ADS)

    Pięta, Ewa; Proniewicz, Edyta; Boduszek, Bogdan; Olszewski, Tomasz K.; Nattich-Rak, Małgorzata; Kim, Younkyoo

    2015-04-01

    The potential-dependent surface enhanced Raman scattering (SERS) and generalized two-dimensional correlation analysis (G2DCA) methods were used to characterize three pyridine-α-hydroxymethyl biphenyl phosphine oxide isomers: (diphenylphosphoryl)(pyridine-2-yl)methanol (α-Py), (diphenylphosphoryl)(pyridine-3-yl)methanol (β-Py), and (diphenylphosphoryl)(pyridine-4-yl)methanol (γ-Py). The aforementioned compounds were deposited onto Ag, Au, and Cu electrode surfaces under different applied electrode potentials in an aqueous solution at physiological pH. On the basis of the enhancement, broadening, and shift in wavenumbers of individual bands, the geometry of the investigated molecules and influence of substituent position on the adsorption mode (in the α-(2-), β-(3-), and γ-(4-) positions), electrode type, and applied electrode potential were examined. It was found that the SERS spectra are dominated by bands assigned to phenyl (Ph) and pyridine (Py) ring vibrations. However, some differences in the arrangement of the aforementioned fragments were observed with changes to the type of the metal surface and the applied electrode potential.

  4. Molecular dynamics simulation of joining process of Ag-Au nanowires and mechanical properties of the hybrid nanojoint

    SciTech Connect

    Ding, Su; Tian, Yanhong Jiang, Zhi; He, Xiaobin

    2015-05-15

    The nanojoining process of Ag-Au hybrid nanowires at 800K was comprehensively studied by virtue of molecular dynamics (MD) simulation. Three kinds of configurations including end-to-end, T-like and X-like were built in the simulation aiming to understand the nanojoining mechanism. The detailed dynamic evolution of atoms, crystal structure transformation and defects development during the nanojoining processes were performed. The results indicate that there are two stages in the nanojoining process of Ag-Au nanowires which are atom diffusion and new bonds formation. Temperature is a key parameter affecting both stages ascribed to the energy supply and the optimum temperature for Ag-Au nanojoint with diameter of 4.08 nm has been discussed. The mechanical properties of the nanojoint were examined with simulation of tensile test on the end-to-end joint. It was revealed that the nanojoint was strong enough to resist fracture at the joining area.

  5. Corrosion properties of Ag-Au-Cu-Pd system alloys containing indium.

    PubMed

    Hattori, Masayuki; Tokizaki, Teruhiko; Matsumoto, Michihiko; Oda, Yutaka

    2010-01-01

    In this study, the corrosion resistance of Ag-Au-Cu-Pd system alloys consisting of 5 or 10 mass% indium was evaluated. Levels of element release and tarnish were determined and electrochemical measurements performed. Results were compared with those for commercial silver-palladium-gold alloy. In terms of electrochemical behavior, the transpassive potential of these experimental alloys was 168-248mV. Experimental alloys with 25 mass% Au showed similar corrosion resistance to control gold-silver-palladium alloy. Amount of released elements was 14-130microg/cm(2) at 7 days, which is in the allowable range for dental alloys. Addition of indium to Ag-Au-Cu-10mass%Pd system alloys was effective in increasing resistance to tarnish and alloys containing 10 mass% of indium showed a minimal decrease in L(*) values after immersion. These findings indicate that 25Au-37.5Ag-15Cu-10Pd-2Zn-10In-0.5Ir alloy is applicable in dental practice.

  6. Nanowire networks and hollow nanospheres of Ag-Au bimetallic alloys at room temperature.

    PubMed

    Hurtado, R Britto; Cortez-Valadez, M; Arizpe-Chávez, H; Flores-Lopez, N S; Álvarez, Ramón A B; Flores-Acosta, M

    2017-03-17

    Due to their physicochemical properties, metallic nanoalloys have potential applications in biomedicine, electrocatalysis and electrochemical sensors, among many other fields. New alternative procedures have emerged in order to reduce production costs and the use of toxic substances. In this study we present a novel low-toxicity synthesis method for the fabrication of nanowire networks (NWNs) and Ag-Au hollow nanospheres. The synthesis process is performed at room temperature without any sophisticated equipment, such as special cameras or furnaces, etc. Transmission electron microscopy showed that the NWNs contain random alloys with a diameter of between 10-13 nm. The radius for the hollow nanospheres is approximately located between 70-130 nm. The absorption bands in the UV-vis spectrum associated with the surface plasmon in Ag-Au bimetallic nanoparticles are highlighted at 385 nm for the NWNs and 643 nm for the hollow nanospheres. The study was performed with low-toxicity substances, such as rongalite, ascorbic acid and sucrose, and showed high efficiency for the fabrication of these types of nanostructures, as well as good stability for long periods of time.

  7. Component conversion from pure Au nanorods to multiblock Ag-Au-Ag nanorods assisted by Pt nanoframe templates

    NASA Astrophysics Data System (ADS)

    Lee, Sangji; Jang, Hee-Jeong; Jang, Ho Young; Kim, Seong Kyu; Park, Sungho

    2016-06-01

    We developed a new method for synthesizing multiblock Ag-Au-Ag nanorods using Pt nanoframes that had been deposited on the edges of Au nanorod seeds. As a function of Au etching time, the length of the Au nanorod decreased symmetrically starting from the two ends, leading to the formation of empty inner space at the ends. Subsequent reduction of Ag ions could be selectively performed in the inner space confined by Pt nanoframes and the resulting Ag-Au-Ag nanorods exhibited characteristic LSPR modes originating from each block component (in a transverse direction) and SPR coupling (in a longitudinal direction). The high quality of the resulting multiblock nanorods enabled observation of the longitudinal quadrupole mode that was induced by Ag-Au SPR coupling in a long axis. The mode exhibited high sensitivity in accordance with the change in the surrounding media, demonstrating great potential for sensor applications.We developed a new method for synthesizing multiblock Ag-Au-Ag nanorods using Pt nanoframes that had been deposited on the edges of Au nanorod seeds. As a function of Au etching time, the length of the Au nanorod decreased symmetrically starting from the two ends, leading to the formation of empty inner space at the ends. Subsequent reduction of Ag ions could be selectively performed in the inner space confined by Pt nanoframes and the resulting Ag-Au-Ag nanorods exhibited characteristic LSPR modes originating from each block component (in a transverse direction) and SPR coupling (in a longitudinal direction). The high quality of the resulting multiblock nanorods enabled observation of the longitudinal quadrupole mode that was induced by Ag-Au SPR coupling in a long axis. The mode exhibited high sensitivity in accordance with the change in the surrounding media, demonstrating great potential for sensor applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03484e

  8. Au-Ag@Au Hollow Nanostructure with Enhanced Chemical Stability and Improved Photothermal Transduction Efficiency for Cancer Treatment.

    PubMed

    Jiang, Tongtong; Song, Jiangluqi; Zhang, Wenting; Wang, Hao; Li, Xiaodong; Xia, Ruixiang; Zhu, Lixin; Xu, Xiaoliang

    2015-10-07

    Despite the fact that Au-Ag hollow nanoparticles (HNPs) have gained much attention as ablation agents for photothermal therapy, the instability of the Ag element limits their applications. Herein, excess Au atoms were deposited on the surface of a Au-Ag HNP by improving the reduction power of l-ascorbic acid (AA) and thereby preventing the reaction between HAuCl4 and the Ag element in the Au-Ag alloy nanostructure. Significantly, the obtained Au-Ag@Au HNPs show excellent chemical stability in an oxidative environment, together with remarkable increase in extinction peak intensity and obvious narrowing in peak width. Moreover, finite-difference time-domain (FDTD) was used to simulate the optical properties and electric field distribution of HNPs. The calculated results show that the proportion of absorption cross section in total extinction cross section increases with the improvement of Au content in HNP. As predicted by the theoretical calculation results, Au-Ag@Au nanocages (NCs) exhibit a photothermal transduction efficiency (η) as high as 36.5% at 808 nm, which is higher than that of Au-Ag NCs (31.2%). Irradiated by 808 nm laser at power densities of 1 W/cm(2), MCF-7 breast cancer cells incubated with PEGylated Au-Ag@Au NCs were seriously destroyed. Combined together, Au-Ag@Au HNPs with enhanced chemical stability and improved photothermal transduction efficiency show superior competitiveness as photothermal agents.

  9. Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate

    PubMed Central

    Jun Yin, Hong; Yang Chen, Zhao; Mei Zhao, Yong; Yang Lv, Ming; An Shi, Chun; Long Wu, Zheng; Zhang, Xin; Liu, Luo; Li Wang, Ming; Jun Xu, Hai

    2015-01-01

    Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br– and I–), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10−8  M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface. PMID:26412773

  10. Relativistic effects on the nuclear magnetic shielding in the MF (M=Cu, Ag, Au) series

    SciTech Connect

    David, Jorge; Restrepo, Albeiro

    2007-11-15

    Relativistic effects on the nuclear magnetic shielding {sigma}(M) of the series of diatomics MF (M=Cu, Ag, Au) are calculated and analyzed using the Dirac-Hartree-Fock (DHF) method in the random phase approximation (RPA). Significant differences due to relativistic effects on the shielding constant {sigma}(M) are found in this series of atoms. The high electronegativity of the fluorine atom works in conjunction with the spin-orbit coupling to increase the calculated value for {sigma}(Au). An unusually large diamagnetic contribution to the shielding constant is observed. Nonrelativistic nuclear magnetic shielding [{sigma}{sup NR}(M)] shows very good linear correlation with the nuclear charge (Z) of the metal, while the relativistic shielding [{sigma}{sup rel}(M)] varies as Z{sup 2.26}.

  11. Communication: Kinetics of chemical ordering in Ag-Au and Ag-Ni nanoalloys

    NASA Astrophysics Data System (ADS)

    Calvo, F.; Fortunelli, A.; Negreiros, F.; Wales, D. J.

    2013-09-01

    The energy landscape and kinetics of medium-sized Ag-Au and Ag-Ni nanoalloy particles are explored via a discrete path sampling approach, focusing on rearrangements connecting regions differing in chemical order. The highly miscible Ag27Au28 supports a large number of nearly degenerate icosahedral homotops. The transformation from reverse core-shell to core-shell involves large displacements away from the icosahedron through elementary steps corresponding to surface diffusion and vacancy formation. The immiscible Ag42Ni13 naturally forms an asymmetric core-shell structure, and about 10 eV is required to extrude the nickel core to the surface. The corresponding transformation occurs via a long and smooth sequence of surface displacements. For both systems the rearrangement kinetics exhibit Arrhenius behavior. These results are discussed in the light of experimental observations.

  12. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

    1999-01-01

    The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

  13. Chitosan stabilized Ag-Au nanoalloy for colorimetric sensing and 5-Fluorouracil delivery.

    PubMed

    E A K, Nivethaa; S, Dhanavel; Narayanan, V; A, Stephen

    2017-02-01

    Fluorescent CS/Ag-Au (chitosan/silver-gold) nanocomposite containing different weight percentage of Ag and Au was synthesized using the chemical reduction method. 5-Fluorouracil (5-FU) encapsulated nanocomposite was also synthesized and its cytotoxicity towards breast cancer cell lines (MCF-7) studied. The XRD pattern of the nanocomposite shows peaks of chitosan, silver and gold. The peaks corresponding to gold and silver indicate the face centered cubic structure of silver and gold nanoparticles. The polymer matrix nanocomposite structure with chitosan as the matrix and silver-gold as the filler phase is evident from the high resolution transmission electron microscopy (HRTEM) images and an increase in particle size from∼5nm to about 12nm is noticeable on encapsulation of 5-Fluorouracil (5-FU). The presence of fluorine in the case of 5-FU encapsulated nanocomposite and the presence of reflections corresponding to 5-FU in the SAED pattern confirms the encapsulation of 5-FU into the nanocomposite, which is also confirmed by elemental mapping. The presence of a single surface plasmon resonance (SPR) peak in the case of the nanocomposite in a position in between the SPR bands of pure silver and gold nanoparticles confirms the formation of Ag-Au alloy and the elemental mapping results obtained for the nanocomposite also supports the UV-vis results. The photoluminescence (PL) spectrum clearly shows an emission peak in the near infrared region (700-900nm), which makes the nanocomposite suitable for use in cellular imaging. The application of the nanocomposite as a colorimetric sensor was also studied and it was found to be useful for the specific detection of mercury (Hg) without much interference and the detection limit was found to be 5.0×10(-8)M.

  14. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Corell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1998-01-01

    The objective of this study is to conduct the Earth-based research sufficient to successfully propose a flight experiment (1) to experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in conductive melts as this applies to the bulk growth of solid solution semiconducting materials in the reduced gravitational levels available in low Earth orbit and (2) to assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during space processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system was chosen because it has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit high growth rates compared to many other commonly studied alloy semiconductors. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. Some compositional anomalies observed by us in magnetic grown crystals can only be explained by TEMC; this has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface.

  15. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Croell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1999-01-01

    The objective of this study is to: (1) experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in electrically conductive melts as this applies to the bulk growth of solid solution semiconducting materials; and (2) assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit reasonable growth rates. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. TEMC has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface. In conclusion, magnetic fields up to 5 Tesla are sufficient to eliminate time-dependent convection in silicon floating zones and possibly Bridgman growth of Ge-Si alloys. In both cases, steady convection appears to be more significant for mass transport than diffusion, even at 5 Tesla in the geometries used here. These results are corroborated in both growth configurations by calculations.

  16. Enzymatic plasmonic engineering of Ag/Au bimetallic nanoshells and their use for sensitive optical glucose sensing.

    PubMed

    He, Haili; Xu, Xiaolong; Wu, Haoxi; Jin, Yongdong

    2012-04-03

    Enzyme works for plasmonic nanostructure: an interesting enzyme-responsive hybrid Ag/Au-GOx bimetallic nanoshell (NS) system is reported, in which control over the enzyme reaction of glucose oxidase (GOx) can automatically fine-tune the morphology (from complete NS to porous NS) and optical properties of the hybrid nanostructure. The phenomenon is further exploited as a new platform for sensitive optical glucose sensing.

  17. Formation of recent Pb-Ag-Au mineralization by potential sub-surface microbial activity

    NASA Astrophysics Data System (ADS)

    Tornos, Fernando; Velasco, Francisco; Menor-Salván, César; Delgado, Antonio; Slack, John F.; Escobar, Juan Manuel

    2014-08-01

    Las Cruces is a base-metal deposit in the Iberian Pyrite Belt, one of the world’s best-known ore provinces. Here we report the occurrence of major Pb-Ag-Au mineralization resulting from recent sub-surface replacement of supergene oxyhydroxides by carbonate and sulphide minerals. This is probably the largest documented occurrence of recent microbial activity producing an ore assemblage previously unknown in supergene mineralizing environments. The presence of microbial features in the sulphides suggests that these may be the first-described natural bacteriomorphs of galena. The low δ13C values of the carbonate minerals indicate formation by deep anaerobic microbial processes. Sulphur isotope values of sulphides are interpreted here as reflecting microbial reduction in a system impoverished in sulphate. We suggest that biogenic activity has produced around 3.1 × 109 moles of reduced sulphur and 1010 moles of CO2, promoting the formation of ca. 1.19 Mt of carbonates, 114,000 t of galena, 638 t of silver sulphides and 6.5 t of gold.

  18. Physico-chemical and antimicrobial properties of co-sputtered Ag Au/PTFE nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Zaporojtchenko, V.; Podschun, R.; Schürmann, U.; Kulkarni, A.; Faupel, F.

    2006-10-01

    In this work, we used co-sputtering of noble metals together with polytetrafluorethylene (PTFE) as a method for producing antibacterial metal/polymer nanocomposite coatings, where the precious metals are only incorporated in a thin surface layer. Moreover, they are finely dispersed as nanoparticles, thus saving additional material and providing a very large effective surface for metal ion release. Nanocomposite films with thickness between 100 and 300 nm were prepared with a wide range of metal filling between 10 and 40%. The antimicrobial effect of the nanocomposite coatings was evaluated by means of two different assays. The bactericidal activity due to silver release from the surface was determined by a modification of conventional disc diffusion methods. Inhibition of bacterial growth on the coated surface was investigated through a modified proliferation assay. Staphylococcus aureus and S. epidermidis were used as test bacteria, as these species commonly cause infections associated with medical polymer devices. The antibacterial efficiency of the coatings against different bacteria was demonstrated at extremely small noble metal consumption: Au: ~1 mg m-2 and Ag: ~0.1 g m-2. The maximum ability for having an antibacterial effect was shown by the Ag-Au/PTFE nanocomposite, followed by the Ag/PTFE nanocomposite.

  19. Formation of recent Pb-Ag-Au mineralization by potential sub-surface microbial activity.

    PubMed

    Tornos, Fernando; Velasco, Francisco; Menor-Salván, César; Delgado, Antonio; Slack, John F; Escobar, Juan Manuel

    2014-08-06

    Las Cruces is a base-metal deposit in the Iberian Pyrite Belt, one of the world's best-known ore provinces. Here we report the occurrence of major Pb-Ag-Au mineralization resulting from recent sub-surface replacement of supergene oxyhydroxides by carbonate and sulphide minerals. This is probably the largest documented occurrence of recent microbial activity producing an ore assemblage previously unknown in supergene mineralizing environments. The presence of microbial features in the sulphides suggests that these may be the first-described natural bacteriomorphs of galena. The low δ(13)C values of the carbonate minerals indicate formation by deep anaerobic microbial processes. Sulphur isotope values of sulphides are interpreted here as reflecting microbial reduction in a system impoverished in sulphate. We suggest that biogenic activity has produced around 3.1 × 10(9) moles of reduced sulphur and 10(10) moles of CO2, promoting the formation of ca. 1.19 Mt of carbonates, 114,000 t of galena, 638 t of silver sulphides and 6.5 t of gold.

  20. Dual-frequency plasmon lasing modes in active three-layered bimetallic Ag/Au nanoshells

    NASA Astrophysics Data System (ADS)

    Wu, DaJian; Wu, XueWei; Cheng, Ying; Jin, BiaoBing; Liu, XiaoJun

    2015-11-01

    The optical properties of three-layered silver-gold-silica (SGS) nanoshells with gain have been investigated theoretically by using Mie theory. Surface plasmon amplification by stimulated emission of radiation (spaser) phenomena can be observed at two plasmon modes of the active SGS nanoshell in the visible region. It is found with the decrease in the radius of the inner Ag core that the critical value of ɛg″(ωg ) for the super-resonance of the low-energy mode increases first and then decreases while that for the high-energy mode decreases. An interesting overlap between the two curves for the critical value of ɛg″(ωg ) can be found at a special core radius. At this point, two super-resonances can be achieved concurrently at the low- and high-energy modes of the active SGS nanoshell with the same gain coefficient. This dual-frequency spaser based on the bimetallic Ag/Au nanoshell may be an efficient candidate for designing the nanolaser.

  1. Ag/Au/Polypyrrole Core-shell Nanowire Network for Transparent, Stretchable and Flexible Supercapacitor in Wearable Energy Devices

    NASA Astrophysics Data System (ADS)

    Moon, Hyunjin; Lee, Habeom; Kwon, Jinhyeong; Suh, Young Duk; Kim, Dong Kwan; Ha, Inho; Yeo, Junyeob; Hong, Sukjoon; Ko, Seung Hwan

    2017-02-01

    Transparent and stretchable energy storage devices have attracted significant interest due to their potential to be applied to biocompatible and wearable electronics. Supercapacitors that use the reversible faradaic redox reaction of conducting polymer have a higher specific capacitance as compared with electrical double-layer capacitors. Typically, the conducting polymer electrode is fabricated through direct electropolymerization on the current collector. However, no research have been conducted on metal nanowires as current collectors for the direct electropolymerization, even though the metal nanowire network structure has proven to be superior as a transparent, flexible, and stretchable electrode platform because the conducting polymer’s redox potential for polymerization is higher than that of widely studied metal nanowires such as silver and copper. In this study, we demonstrated a highly transparent and stretchable supercapacitor by developing Ag/Au/Polypyrrole core-shell nanowire networks as electrode by coating the surface of Ag NWs with a thin layer of gold, which provide higher redox potential than the electropolymerizable monomer. The Ag/Au/Polypyrrole core-shell nanowire networks demonstrated superior mechanical stability under various mechanical bending and stretching. In addition, proposed supercapacitors showed fine optical transmittance together with fivefold improved areal capacitance compared to pristine Ag/Au core-shell nanowire mesh-based supercapacitors.

  2. Synthesis of multifunctional Ag@Au@phenol formaldehyde resin particles loaded with folic acids for photothermal therapy.

    PubMed

    Yang, Ping; Xu, Qi-Zhi; Jin, Sheng-Yu; Lu, Yang; Zhao, Yang; Yu, Shu-Hong

    2012-07-23

    Multifunctional Ag@Au@ phenol formaldehyde resin (PFR) particles loaded with folic acids (FA) have been designed for killing tumor cells through photothermy conversion under the irradiation of near-infrared (NIR) light. Possessing the virtue of good fluorescence, low toxicity, and good targeting, the nanocomposite consists of an Ag core, an Au layer, a PFR shell, and folic acids on the PFR shell. The Ag@PFR core-shell structure can be prepared with a simple hydrothermal method after preheating. We then filled the PFR shell with a layer of Au by heating and modified the shell with polyelectrolyte to change its surface charge state. To capture tumor cells actively, FA molecules were attached onto the surface of the Ag@Au@PFR particles in the presence of 1-ethyl-3-(3-dimethly aminopropyl) carbodiimide (EDAC) and N-hydroxysuccinimide (NHS). Owing to the excellent property of Au NPs and Ag NPs as photothermal conversion agents, the Ag@Au@ PFR@FA particles can be utilized to kill tumor cells when exposed to NIR light.

  3. Ag/Au/Polypyrrole Core-shell Nanowire Network for Transparent, Stretchable and Flexible Supercapacitor in Wearable Energy Devices.

    PubMed

    Moon, Hyunjin; Lee, Habeom; Kwon, Jinhyeong; Suh, Young Duk; Kim, Dong Kwan; Ha, Inho; Yeo, Junyeob; Hong, Sukjoon; Ko, Seung Hwan

    2017-02-03

    Transparent and stretchable energy storage devices have attracted significant interest due to their potential to be applied to biocompatible and wearable electronics. Supercapacitors that use the reversible faradaic redox reaction of conducting polymer have a higher specific capacitance as compared with electrical double-layer capacitors. Typically, the conducting polymer electrode is fabricated through direct electropolymerization on the current collector. However, no research have been conducted on metal nanowires as current collectors for the direct electropolymerization, even though the metal nanowire network structure has proven to be superior as a transparent, flexible, and stretchable electrode platform because the conducting polymer's redox potential for polymerization is higher than that of widely studied metal nanowires such as silver and copper. In this study, we demonstrated a highly transparent and stretchable supercapacitor by developing Ag/Au/Polypyrrole core-shell nanowire networks as electrode by coating the surface of Ag NWs with a thin layer of gold, which provide higher redox potential than the electropolymerizable monomer. The Ag/Au/Polypyrrole core-shell nanowire networks demonstrated superior mechanical stability under various mechanical bending and stretching. In addition, proposed supercapacitors showed fine optical transmittance together with fivefold improved areal capacitance compared to pristine Ag/Au core-shell nanowire mesh-based supercapacitors.

  4. Ag/Au/Polypyrrole Core-shell Nanowire Network for Transparent, Stretchable and Flexible Supercapacitor in Wearable Energy Devices

    PubMed Central

    Moon, Hyunjin; Lee, Habeom; Kwon, Jinhyeong; Suh, Young Duk; Kim, Dong Kwan; Ha, Inho; Yeo, Junyeob; Hong, Sukjoon; Ko, Seung Hwan

    2017-01-01

    Transparent and stretchable energy storage devices have attracted significant interest due to their potential to be applied to biocompatible and wearable electronics. Supercapacitors that use the reversible faradaic redox reaction of conducting polymer have a higher specific capacitance as compared with electrical double-layer capacitors. Typically, the conducting polymer electrode is fabricated through direct electropolymerization on the current collector. However, no research have been conducted on metal nanowires as current collectors for the direct electropolymerization, even though the metal nanowire network structure has proven to be superior as a transparent, flexible, and stretchable electrode platform because the conducting polymer’s redox potential for polymerization is higher than that of widely studied metal nanowires such as silver and copper. In this study, we demonstrated a highly transparent and stretchable supercapacitor by developing Ag/Au/Polypyrrole core-shell nanowire networks as electrode by coating the surface of Ag NWs with a thin layer of gold, which provide higher redox potential than the electropolymerizable monomer. The Ag/Au/Polypyrrole core-shell nanowire networks demonstrated superior mechanical stability under various mechanical bending and stretching. In addition, proposed supercapacitors showed fine optical transmittance together with fivefold improved areal capacitance compared to pristine Ag/Au core-shell nanowire mesh-based supercapacitors. PMID:28155913

  5. Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

    PubMed

    Li, Zongbing; Miao, Xiangmin; Xing, Ke; Peng, Xue; Zhu, Aihua; Ling, Liansheng

    2016-06-15

    A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg(2+) detection with a detection limit of 3.6 pM. Importantly, the methodology has high selectivity for Hg(2+) detection.

  6. PdAgAu alloy with high resistance to corrosion by H2S

    SciTech Connect

    Braun, Fernando; Miller, James B.; Gellman, Andrew J.; Tarditi, Ana M.; Fleutot, Benoit; Kondratyuk, Petro; Cornaglia, Laura M.

    2012-12-01

    PdAgAu alloy films were prepared on porous stainless steel supports by sequential electroless deposition. Two specific compositions, Pd83Ag2Au15 and Pd74Ag14Au12, were studied for their sulfur tolerance. The alloys and a reference Pd foil were exposed to 1000 H2S /H2 at 623 K for periods of 3 and 30 hours. The microstructure, morphology and bulk composition of both nonexposed and H2S-exposed samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). XRD and SEM analysis revealed time-dependent growth of a bulk Pd{sub 4}S phase on the Pd foil during H2S exposure. In contrast, the PdAgAu ternary alloys displayed the same FCC structure before and after H2S exposure. In agreement with the XRD and SEM results, sulfur was not detected in the bulk of either ternary alloy samples by EDS, even after 30 hours of H2S exposure. X-ray photoelectron spectroscopy (XPS) depth profiles were acquired for both PdAgAu alloys after 3 and 30 hours of exposure to characterize sulfur contamination near their surfaces. Very low S 2p and S 2s XPS signals were observed at the top-surfaces of the PdAgAu alloys, and those signals disappeared before the etch depth reached ~ 10 nm, even for samples exposed to H2S for 30 hours. The depth profile analyses also revealed silver and gold segregation to the surface of the alloys; preferential location of Au on the alloys surface may be related to their resistance to bulk sulfide formation. In preliminary tests, a PdAgAu alloy membrane displayed higher initial H{sub 2} permeability than a similarly prepared pure Pd sample and, consistent with resistance to bulk sulfide formation, lower permeability loss in H2S than pure Pd.

  7. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    SciTech Connect

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-05-16

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  8. End-Member Formulation of Solid Solutions and Reactive Transport

    SciTech Connect

    Lichtner, Peter C.

    2015-09-01

    A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.

  9. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

    2001-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

  10. Enhancement of chitosan-graphene oxide SPR sensor with a multi-metallic layers of Au-Ag-Au nanostructure for lead(II) ion detection

    NASA Astrophysics Data System (ADS)

    Kamaruddin, Nur Hasiba; Bakar, Ahmad Ashrif A.; Yaacob, Mohd Hanif; Mahdi, Mohd Adzir; Zan, Mohd Saiful Dzulkefly; Shaari, Sahbudin

    2016-01-01

    We demonstrate the enhancement of surface plasmon resonance (SPR) technique by implementing a multi-metallic layers of Au-Ag-Au nanostructure in the chitosan-graphene oxide (CS-GO) SPR sensor for lead(II) ion detection. The performance of the sensor is analyzed via SPR measurements, from which the sensitivity, signal-to-noise ratio and repeatability are determined. The nanostructure layers are characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We showed that the proposed structure has increased the shift in the SPR angle up to 3.5° within the range of 0.1-1 ppm due to the enhanced evanescent field at the sensing layer-analyte interface. This sensor also exhibits great repeatability which benefits from the stable multi-metallic nanostructure. The SNR value of 0.92 for 5 ppm lead(II) ion solution and reasonable linearity range up to that concentration shows that the tri-metallic CS-GO SPR sensor gives a good response towards the lead(II) ion solution. The CS-GO SPR sensor is also sensitive to at least a 10-5 change in the refractive index. The results prove that our proposed tri-metallic CS-GO SPR sensor demonstrates a strong performance and reliability for lead(II) ion detection in accordance with the standardized lead safety level for wastewater.

  11. Compositional Segregation in Unidirectionally Solidified Solid Solution Crystals

    NASA Technical Reports Server (NTRS)

    Wang, J. C.

    1983-01-01

    A computer program was developed to model compositional segregation in unidrectionally solidified solid-solution-semiconducting crystals. The program takes into account the variations of the interface segregation constant and solidification rate with composition. Calculations are performed for the HgCdTe solid solution system that is compared with experimental data.

  12. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

    1999-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the

  13. Special quasirandom structures for perovskite solid solutions

    NASA Astrophysics Data System (ADS)

    Jiang, Zhijun; Nahas, Yousra; Xu, Bin; Prosandeev, Sergey; Wang, Dawei; Bellaiche, Laurent

    2016-11-01

    Special quasirandom structures (SQS) are presently generated for disordered (A‧1-x {{\\text{A}}\\prime \\prime} x )BX3 and A(B‧1-x {{\\text{B}}\\prime \\prime} x )X3 perovskite solid solutions, with x  =  1/2 as well as 1/3 and 2/3. These SQS configurations are obtained by imposing that the so-called Cowley parameters are as close to zero as possible for the three nearest neighboring shells. Moreover, these SQS configurations are slightly larger in size than those available in the literature for x  =  1/2, mostly because of the current capabilities of atomistic techniques. They are used here within effective Hamiltonian schemes to predict various properties, which are then compared to those associated with large random supercells, in a variety of compounds, namely (Ba1-x Sr x )TiO3, Pb(Zr1-x Ti x )O3, Pb(Sc0.5Nb0.5)O3, Ba(Zr1-x Ti x )O3, Pb(Mg1/3Nb2/3)O3 and (Bi1-x Nd x )FeO3. It is found that these SQS configurations can reproduce many properties of large random supercells of most of these disordered perovskite alloys, below some finite material-dependent temperature. Examples of these properties are electrical polarization, anti-phase and in-phase octahedral tiltings, antipolar motions, antiferromagnetism, strain, piezoelectric coefficients, dielectric response, specific heat and even the formation of polar nanoregions (PNRs) in some relaxors. Some limitations of these SQS configurations are also pointed out and explained.

  14. A highly sensitive hydrogen peroxide sensor based on (Ag-Au NPs)/poly[o-phenylenediamine] modified glassy carbon electrode.

    PubMed

    Shamsipur, Mojtaba; Karimi, Ziba; Amouzadeh Tabrizi, Mahmoud

    2015-11-01

    Herein, the poly(o-phenylenediamine) decorated with gold-silver nanoparticle (Ag-Au NPs) nanocomposite modified glassy carbon was used for the determination of hydrogen peroxide. Electrochemical experiments indicated that the proposed sensor possesses an excellent sensitivity toward the reduction of hydrogen peroxide. The resulting sensor exhibited a good response to hydrogen peroxide over linear range from 0.2 to 60.0μM with a limit of detection of 0.08μM, good reproducibility, long-term stability and negligible interference from ascorbic acid, uric acid and dopamine. The proposed sensor was successfully applied to the determination of hydrogen peroxide in human serum sample.

  15. Ag/Au bi-metallic film based color surface plasmon resonance biosensor with enhanced sensitivity, color contrast and great linearity.

    PubMed

    Li, Chung-Tien; Lo, Kun-Chi; Chang, Hsin-Yun; Wu, Hsieh-Ting; Ho, Jennifer H; Yen, Ta-Jen

    2012-01-01

    In wavelength surface plasmon resonance (SPR) biosensor, the manipulation of SPR dispersion relation by Ag/Au bi-metallic film was first time implemented. Due to the enhanced resonant wavelength shift and the sharper SPR slope of using Ag/Au bi-metallic film, the illuminated color of reflection shows one order of magnitude greater contrast than conventional SPR biosensors. Such an Ag/Au bi-metallic film based color SPR biosensor (CSPRB) allows the detail bio-interactions, for example 100 nM streptavidin, to be distinguished by directly observing the color change of reflection through naked eyes rather than the analysis of spectrometer. In addition to the enhanced sensitivity and color contrast, this CSPRB also possesses a great linear detection range up to 0.0254 RIU, which leading to the application of point-of-care tests.

  16. Structural analysis of 5-fluorouracil and thymine solid solutions

    NASA Astrophysics Data System (ADS)

    Vogt, Frederick G.; Vena, Joseph A.; Chavda, Manisha; Clawson, Jacalyn S.; Strohmeier, Mark; Barnett, Maria E.

    2009-08-01

    Solid-state analysis with powder X-ray diffraction (PXRD), solid-state NMR (SSNMR), and other spectroscopic and physical methods can provide detailed structural information about organic and pharmaceutical cocrystals. In this study, a range of solid-state analysis methods are used to characterize co-crystallized solid solutions of 5-fluorouracil and thymine. 1H, 13C and 19F SSNMR and PXRD methods are used to study the structure and disorder present in a solid solution previously prepared by solution evaporation methods; here the solid solution is prepared over a wider stoichiometric range by solvent-drop grinding techniques. Long-range perturbations of key chemical shifts are detectable by SSNMR, indicating that the solid solution is not random. Cross-polarization and heteronuclear correlation SSNMR experiments between 1H, 13C, and 19F nuclei offer insight into the structure of this solid solution, and density functional theory (DFT) methods are applied to calculate lattice energies and NMR properties in order to understand the population of the two primary disordered sites in the crystal structure. In addition, a second solid solution of 5-fluorouracil and thymine is reported and analyzed. This solid solution, which was produced by solvent-drop grinding experiments and characterized by SSNMR and powder X-ray diffraction methods, is determined to be an isostructural phase to that of anhydrous thymine with the inclusion of 5-fluorouracil defects. A similar effect does not occur under excess 5-fluorouracil conditions; instead, phase-separated Form 1 of 5-fluorouracil and anhydrous thymine are obtained. DFT calculations are applied to offer a possible explanation for this disparity.

  17. Solid solution hardening of molecular crystals: tautomeric polymorphs of omeprazole.

    PubMed

    Mishra, Manish Kumar; Ramamurty, Upadrasta; Desiraju, Gautam R

    2015-02-11

    In the context of processing of molecular solids, especially pharmaceuticals, hardness is an important property that often determines the manufacturing steps employed. Through nanoindentation studies on a series of omeprazole polymorphs, in which the proportions of the 5- and 6-methoxy tautomers vary systematically, we demonstrate that solid-solution strengthening can be effectively employed to engineer the hardness of organic solids. High hardness can be attained by increasing lattice resistance to shear sliding of molecular layers during plastic deformation.

  18. Plurality of inherent states in equiatomic solid solutions

    NASA Astrophysics Data System (ADS)

    Demkowicz, M. J.

    2017-03-01

    We show that single-crystal, equiatomic solid solutions of Lennard-Jones particles have a plurality of inherent states: mechanically stable configurations with identical lattice site occupancies, yet distinct potential-energy minima. External loading triggers transitions between inherent states via localized shear transformations. A plurality of inherent states and mechanically activated transitions between them make equiatomic solid solutions an unusual form of matter: one that is crystalline like single-component metals, yet exhibits localized shear transformations like metallic glasses.

  19. Analytical Solution for Isentropic Flows in Solids

    NASA Astrophysics Data System (ADS)

    Heuzé, Olivier

    2009-12-01

    In the XIXth century, Riemann gave the equations system and the exact solution for the isentropic flows in the case of the ideal gas. But to our knowledge, nothing has been done to apply it to condensed media. Many materials of practical interest, for instance metals, obey to the linear law D = c+s u, where D is the shock velocity, u the particle velocity, and c and s properties of the material. We notice that s is strongly linked to the fundamental derivative. This means that the assumption of constant fundamental derivative is useful in this case, as it was with the isentropic gamma in the Riemann solution. Then we can apply the exact Riemann solution for these materials. Although the use of the hypergeometric function is complicated in this case, we obtain a very good approximation with the development in power series.

  20. Solid state synthesis, crystal growth and optical properties of urea and p-chloronitrobenzene solid solution

    SciTech Connect

    Rai, R.N.; Kant, Shiva; Reddi, R.S.B.; Ganesamoorthy, S.; Gupta, P.K.

    2016-01-15

    Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB and UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal. - Highlights: • The hygroscopic character of urea was modified by making the solid solutionSolid solution formation is support by elemental, powder- and single crystal XRD • Crystal of solid solution has higher SHG signal and mechanical stability. • Refractive index and band gap of solid solution crystal have determined.

  1. Synthesis of highly fluorescent metal (Ag, Au, Pt, and Cu) nanoclusters by electrostatically induced reversible phase transfer.

    PubMed

    Yuan, Xun; Luo, Zhentao; Zhang, Qingbo; Zhang, Xinhai; Zheng, Yuangang; Lee, Jim Yang; Xie, Jianping

    2011-11-22

    This paper reports a simple and scalable method for the synthesis of highly fluorescent Ag, Au, Pt, and Cu nanoclusters (NCs) based on a mild etching environment made possible by phase transfer via electrostatic interactions. Using Ag as a model metal, a simple and fast (total synthesis time < 3 h) phase transfer cycle (aqueous → organic (2 h incubation) → aqueous) has been developed to process originally polydisperse, nonfluorescent, and unstable Ag NCs into monodisperse, highly fluorescent, and extremely stable Ag NCs in the same phase (aqueous) and protected by the same thiol ligand. The synthetic protocol was successfully extended to fabricate highly fluorescent Ag NCs protected by custom-designed peptides with desired functionalities (e.g., carboxyl, hydroxyl, and amine). The facile synthetic method developed in this study should largely contribute to the practical applications of this new class of fluorescence probes.

  2. Chemical noise produced by equilibrium adsorption/desorption of surface pyridine at Au-Ag-Au bimetallic atom-scale junctions studied by fluctuation spectroscopy.

    PubMed

    Hwang, Tai-Wei; Branagan, Sean P; Bohn, Paul W

    2013-03-20

    The chemical noise contained in conductance fluctuations resulting from adsorption and desorption of pyridine at Au-Ag-Au bimetallic atom-scale junctions (ASJs) exhibiting ballistic electron transport is studied using fluctuation spectroscopy. ASJs are fabricated by electrochemical Ag deposition in a Au nanogap to produce a high-conductance Ag quantum wire, followed by electromigration-induced thinning in pyridine solution to create stable ASJs. The conductance behavior of the resulting ASJs is analyzed by sequential autocorrelation and Fourier transform of the current-time data to yield the power spectral density (PSD). In these experiments the PSDs from Ag ASJs in pyridine exhibit two main frequency regions: 1/f noise originating from resistance fluctuations of the junction itself at low frequencies, and a Lorentzian noise component arising from molecular adsorption/desorption fluctuations at higher frequencies. The characteristic cutoff frequency of the Lorentzian noise component determines the relaxation time of molecular fluctuations, which, in turn, is sensitive to the kinetics of the adsorption/desorption process. The kinetics are found to depend on concentration and on the adsorption binding energy. The junction size (<5G0), on the other hand, does not affect the kinetics, as the cutoff frequency remains unchanged. Concentration-dependent adsorption free energies are interpreted as arising from a distribution of binding energies, N(E(b)), on the Ag ASJ. Other observations, such as long lifetime ASJs and two-level fluctuations in conductance, provide additional evidence for the integral role of the adsorbate in determining ASJ reorganization dynamics.

  3. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.

  4. Forces between hydrophobic solids in concentrated aqueous salt solution.

    PubMed

    Mastropietro, Dean J; Ducker, William A

    2012-03-09

    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108°. Thus, in 1 M salt solution, it is unnecessary to invoke the presence of a hydrophobic force at separations greater than 5 nm. Through measurement in salt solution, we avoid the necessity of accounting for large electrostatic forces that frequently occur in pure water and may obscure resolution of other forces.

  5. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An experimental study was conducted to determine whether alloy softening in Fe alloys is dependent on electron concentration and to provide a direct comparison of alloy softening and hardening in several binary Fe alloy systems having the same processing history. Alloy additions to Fe included the elements in the Periods 4-6 and the Groups IV-VIII with the exception of technetium. A total of 19 alloy systems was investigated, and hardness testing was the primary means of evaluation. Testing was carried out at four temperatures over a homologous temperature range of 0.043-0.227 times the absolute melting temperature of unalloyed Fe. Major conclusions are that the atomic radius ratio of solute-to-Fe is the key factor in controlling low-temperature hardness of the binary Fe alloys and that alloy softening rates at 77 K and alloy hardening rates at 411 K are correlated with this atomic radius ratio for 15 of the binary alloy systems. Mechanisms of alloy softening and hardening are proposed.

  6. Suppression of vacancy cluster growth in concentrated solid solution alloys

    SciTech Connect

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; Bei, Hongbin; Weber, William J.; Zhang, Yanwen

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solution alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.

  7. KNH2-KH: a metal amide-hydride solid solution.

    PubMed

    Santoru, Antonio; Pistidda, Claudio; Sørby, Magnus H; Chierotti, Michele R; Garroni, Sebastiano; Pinatel, Eugenio; Karimi, Fahim; Cao, Hujun; Bergemann, Nils; Le, Thi T; Puszkiel, Julián; Gobetto, Roberto; Baricco, Marcello; Hauback, Bjørn C; Klassen, Thomas; Dornheim, Martin

    2016-09-27

    We report for the first time the formation of a metal amide-hydride solid solution. The dissolution of KH into KNH2 leads to an anionic substitution, which decreases the interaction among NH2(-) ions. The rotational properties of the high temperature polymorphs of KNH2 are thereby retained down to room temperature.

  8. Preparation of Sic/AIN Solid Solutions Using Organometallic Precursors

    DTIC Science & Technology

    1989-02-15

    studies suggested that RAINH phase separation from the liquid polycarbosilane might be avoided by carrying out the pyrolyses at elevated temperatures, where... Pyrolyses Involving [Aethvl 2AMN21 3 In the last few months of this program, an alternative route to SiC/AlN solid solutions was discovered which obviates the

  9. Brazing method produces solid-solution bond between refractory metals

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Brazing two refractory metals by diffusion bonding minimizes distortion and avoids excessive grain growth in the metals. This method requires the selection of an interface metal that forms intermediate low-melting eutectics or solid solutions with the metals to be brazed.

  10. On the solution of a lubrication problem with particulate solids

    NASA Technical Reports Server (NTRS)

    Dai, F.; Khonsari, M. M.

    1991-01-01

    The lubrication characteristic of a fluid with solid particles is studied using the continuum theory of mixtures. The governing equations are formulated and appropriate boundary conditions are introduced for an arbitrary-shaped lubricant film thickness. As a special case, closed-form analytical perturbation solutions for pressure and shear stress are obtained for a mixture of a conventional oil and solid particles with small values of solid-volume fraction sheared in the clearance space of an infinitely long slider bearing. It is found that when compared with a pure fluid, the mixture of the fluid and solid generates a higher pressure and therefore a higher load-carrying capacity with the added advantage of a reduction in the coefficient of friction.

  11. Ag@Au core-shell nanoparticles synthesized by pulsed laser ablation in water: Effect of plasmon coupling and their SERS performance.

    PubMed

    Vinod, M; Gopchandran, K G

    2015-01-01

    Ag@Au core-shell nanoparticles are synthesised by pulsed laser ablation in water using low energy laser pulses. The plasmon characteristics of these core-shell nanoparticles are found to be highly sensitive to the thickness of Au coating. In the synthesis, at first silver nanocolloid was prepared by ablating Ag target and then it is followed by ablation of Au target for different time durations to form Ag@Au core-shell nanostructures. The effect of plasmon-plasmon coupling on the absorption spectra is investigated by decreasing the effective distance between the nanoparticles. This is achieved by reducing the total volume of the colloidal suspension by simple evaporation of water, the solvent used. The suitability of these core-shell nanostructures for application as surface enhanced Raman scattering substrates are tested with crystal violet as probe molecules. Influence of plasmon coupling on the enhancement of Raman bands is found to be different for different bands.

  12. The IP6 micelle-stabilized small Ag cluster for synthesizing Ag-Au alloy nanoparticles and the tunable surface plasmon resonance effect

    NASA Astrophysics Data System (ADS)

    Wang, Na; Wen, Ying; Wang, Yao; Zhang, Rui; Chen, Xiyao; Ling, Bo; Huan, Shuangyan; Yang, Haifeng

    2012-04-01

    The stable small Ag seeds (size in diameter < 10 nm) were obtained in the presence of inositol hexakisphosphoric (IP6) micelles. Then Ag-Au bimetallic nanoparticles were synthesized through a replacement reaction with the rapid interdiffusion process between such small Ag seeds in nanoclusters and HAuCl4. Adjusting the dosage of HAuCl4 resulted in different products, which possessed unique surface plasmon resonances (SPR). The morphologies of the as-made nanoparticles were observed using transmission electron microscopy and field emission scanning electron microscopy and their compositions were determined by energy-dispersive x-ray spectroscopy. Among them, the Ag-Au alloy nanoparticles with the cauliflower-like structure had a suitable SPR for highly sensitive Raman detection application as a surface-enhanced Raman scattering (SERS) substrate with a long-term stability of six months.

  13. Suppression of vacancy cluster growth in concentrated solid solution alloys

    DOE PAGES

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; ...

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solutionmore » alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.« less

  14. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt).

    PubMed

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-24

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  15. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt)

    NASA Astrophysics Data System (ADS)

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-01

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  16. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt)

    PubMed Central

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-01-01

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties. PMID:28233838

  17. Au-Ag-Au double shell nanoparticles-based localized surface plasmon resonance and surface-enhanced Raman scattering biosensor for sensitive detection of 2-mercapto-1-methylimidazole.

    PubMed

    Liao, Xue; Chen, Yanhua; Qin, Meihong; Chen, Yang; Yang, Lei; Zhang, Hanqi; Tian, Yuan

    2013-12-15

    In this paper, Au-Ag-Au double shell nanoparticles were prepared based on the reduction of the metal salts HAuCl4 and AgNO3 at the surface of seed particles. Due to the synergistic effect between Au and Ag, the hybrid nanoparticles are particularly stable and show excellent performances on the detection of 2-mercapto-1-methylimidazole (methimazole). The binding of target molecule at the surface of Au-Ag-Au double shell nanoparticles was demonstrated based on both localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) spectra. The LSPR intensity is directly proportional to the methimazole concentration in the range of 0.10-3.00×10(-7) mol L(-1). The SERS spectrum can be applied in identification of methimazole molecule. The LSPR coupled with SERS based on the Au-Ag-Au double shell nanoparticles would be very attractive for the quantitative determination and qualitative analysis of the analytes in medicines.

  18. A first principle study of encapsulated and functionalized silicon nanotube of chirality (6,6) with monoatomically thin metal wires of Ag, Au and Cu

    NASA Astrophysics Data System (ADS)

    Kumar Chandel, Surjeet; Kumar, Arun; Ahluwalia, P. K.; Sharma, Raman

    2015-04-01

    First principle calculations have been performed to study the influence of interaction of monoatomically thin metal nanowires of Ag, Au and Cu placed inside (encapsulation) and outside (functionalization) the silicon nanotube having armchair conformation with chirality (6,6). The cohesive energy for all the encapsulated and functionalized systems under study was found to be almost same. In comparison to the pristine silicon nanotube (SiNT) which is found to be semiconducting in nature, all the encapsulated and functionalized systems of SiNT are found to be metallic in nature. The calculated electronic band structures show that the conductance in case of Ag, Au and Cu nanowires encapsulation is 2G0. However, its value for functionalized Ag, Au and Cu nanowires is found to be 1G0, 2G0 and 4G0 for the outside positioning of nanowires respectively. Optical properties of all the encapsulated and functionalized SiNTs have been studied. All the systems under study show reflectivity in the infrared (IR) region and behave as non-absorbing transparent conductors in the visible region.

  19. Interdiffusion in Ternary Magnesium Solid Solutions of Aluminum and Zinc

    DOE PAGES

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; ...

    2016-01-11

    Al and Zn are two of the most common alloying elements in commercial Mg alloys, which can improve the physical properties through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of these and other microstructural design relevant to Mg-alloy development. However, there is a lack of multicomponent diffusion data available for Mg alloys. Through solid-to-solid diffusion couples, diffusional interactions of Al and Zn in ternary Mg solid-solution at 400° and 450 °C were examined by an extension of the Boltzmann-Matano analysis based on Onsager s formalism. Concentration profiles of Mg-Al-Zn ternary alloys were determinedmore » by electron probe microanalysis, and analyzed to determine the ternary interdiffusion coefficients as a function of composition. Zn was determined to interdiffuse the fastest, followed by Mg and Al. Appreciable diffusional interactions among Mg, Al, and Zn were observed by variations in sign and magnitude of cross interdiffusion coefficients. In particular, Zn was found to significantly influence the interdiffusion of Mg and Al significantly: the and ternary cross interdiffusion coefficients were both negative, and large in magnitude, in comparison to and , respectively. Al and Mg were observed influence the interdiffusion of Mg and Al, respectively, with positive and interdiffusion coefficients, but their influence on the Zn interdiffusion was negligible.« less

  20. Interdiffusion in Ternary Magnesium Solid Solutions of Aluminum and Zinc

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2016-01-11

    Al and Zn are two of the most common alloying elements in commercial Mg alloys, which can improve the physical properties through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of these and other microstructural design relevant to Mg-alloy development. However, there is a lack of multicomponent diffusion data available for Mg alloys. Through solid-to-solid diffusion couples, diffusional interactions of Al and Zn in ternary Mg solid-solution at 400° and 450 °C were examined by an extension of the Boltzmann-Matano analysis based on Onsager s formalism. Concentration profiles of Mg-Al-Zn ternary alloys were determined by electron probe microanalysis, and analyzed to determine the ternary interdiffusion coefficients as a function of composition. Zn was determined to interdiffuse the fastest, followed by Mg and Al. Appreciable diffusional interactions among Mg, Al, and Zn were observed by variations in sign and magnitude of cross interdiffusion coefficients. In particular, Zn was found to significantly influence the interdiffusion of Mg and Al significantly: the and ternary cross interdiffusion coefficients were both negative, and large in magnitude, in comparison to and , respectively. Al and Mg were observed influence the interdiffusion of Mg and Al, respectively, with positive and interdiffusion coefficients, but their influence on the Zn interdiffusion was negligible.

  1. Evaluation of experimental parameters for growth of homogeneous solid solutions

    NASA Astrophysics Data System (ADS)

    Scheel, Hans J.; Swendsen, Robert H.

    2001-12-01

    In this paper, we discuss the experimental conditions required to grow large two-component crystals from homogeneous solid solutions. Building on the work of Burton, Prim, and Slichter and that of Van Erk, we are able to establish that the concentration fluctuations for diffusion-limited growth are rather insensitive to hydrodynamic fluctuations. This enables a crystal grower to take advantage of forced convection to optimize growth rates without aggravating the striation problem.

  2. Characteristics of photosensors based on solid solutions of AII BVIcompounds

    NASA Astrophysics Data System (ADS)

    Lubegin, Gennady V.; Gusliannikov, Vladimir V.

    1999-10-01

    In the work there are submitted the results of the research of photosensors on a base of solid solutions of A(superscript II)B(superscript VI) compounds for measurement and control of intensity of low-level light in narrow areas of spectrum. The basic principles of technological process of manufacturing of injection photo diodes are described. The results of measurements of voltage-current characteristics and spectral characteristics of photo diodes, received in laboratory technological process with the various contents of cadmy and zinc in ZnCd(subscript 1-x)S(subscript x) solid solutions, and also sulfur and selen in CdS(subscript 1-x)Se(subscript x) solid solutions are submitted. The investigation results have shown, that photosensors work at low positive bias voltage, do not require cooling, have high sensitivity in a maximum and narrow selectivity. In CdS(subscript 1-x)Se(subscript x)- photosensors the photosensitive protecting coverage of transparent films on the base of As(subscript 2)S(subscript 3) compounds is applied. The opportunity of creation of a wide discrete range of photo diodes with the sensitivity in range from near ultraviolet up to near infrared area of spectrum is shown.

  3. Solid-solution nanocrystallite formation by high-energy milling.

    PubMed

    Kwon, Hanjung; Jung, Suna; Cho, Sung-Wook; Kil, Dae-Sup; Roh, Ki-Min; Lim, Jae-Won

    2013-09-01

    Solid-solution nanocrystalline powders were prepared by the high-energy milling of Ti alloys with graphite. The B1 structure (NaCl-like structure) phases, (Ti, Cr)C and (Ti, Al)C, were formed during the milling process of Ti-Cr + graphite and Ti-Al + graphite, and the synthetic procedures were investigated in terms of the phase evolution from XRD data. The (Ti, Al)C phase was obtained after milling for 20 hr at BPR = 40:1 (under a more severe condition), while the (Ti, Cr)C phase formed after milling for 20 hr at BPR = 20:1 (a relatively soft condition). The difference in the tendency to create a solid solution with Ti in the B1 structure caused a difference in the synthetic behavior of (Ti, Al)C and (Ti, Cr)C. In other words, (Ti, Cr)C is formed earlier than (Ti, Al)C during milling because the atomic size of Cr (0.166 nm) is similar to that of Ti (0.176 nm), which leads to the straightforward formation of the solid-solution (Ti, Cr)C as compared to when (Ti, Al)C is used. As a result, the crystallite size of the (Ti, Al)C phase (2-3 nm) synthesized at a later stage becomes smaller than that of the (Ti, Cr)C phase (5 10 nm) formed at an earlier stage during milling.

  4. Flow-based solution-liquid-solid nanowire synthesis

    NASA Astrophysics Data System (ADS)

    Laocharoensuk, Rawiwan; Palaniappan, Kumaranand; Smith, Nickolaus A.; Dickerson, Robert M.; Werder, Donald J.; Baldwin, Jon K.; Hollingsworth, Jennifer A.

    2013-09-01

    Discovered almost two decades ago, the solution-liquid-solid (SLS) method for semiconductor nanowire synthesis has proven to be an important route to high-quality, single-crystalline anisotropic nanomaterials. In execution, the SLS technique is similar to colloidal quantum-dot synthesis in that it entails the injection of chemical precursors into a hot surfactant solution, but mechanistically it is considered the solution-phase analogue to vapour-liquid-solid (VLS) growth. Both SLS and VLS methods make use of molten metal nanoparticles to catalyse the nucleation and elongation of single-crystalline nanowires. Significantly, however, the methods differ in how chemical precursors are introduced to the metal catalysts. In SLS, precursors are added in a one-off fashion in a flask, whereas in VLS they are carried by a flow of gas through the reaction chamber, and by-products are removed similarly. The ability to dynamically control the introduction of reactants and removal of by-products in VLS synthesis has enabled a degree of synthetic control not possible with SLS growth. We show here that SLS synthesis can be transformed into a continuous technique using a microfluidic reactor. The resulting flow-based SLS (`flow-SLS') platform allows us to slow down the synthesis of nanowires and capture mechanistic details concerning their growth in the solution phase, as well as synthesize technologically relevant axially heterostructured semiconductor nanowires, while maintaining the propensity of SLS for accessing ultrasmall diameters below 10 nm.

  5. Origin of epithermal Ag-Au-Cu-Pb-Zn mineralization in Guanajuato, Mexico

    NASA Astrophysics Data System (ADS)

    Mango, Helen; Arehart, Greg; Oreskes, Naomi; Zantop, Half

    2014-01-01

    The Guanajuato epithermal district is one of the largest silver producers in Mexico. Mineralization occurs along three main vein systems trending dominantly northwest-southeast: the central Veta Madre, the La Luz system to the northwest, and the Sierra system to the east. Mineralization consists dominantly of silver sulfides and sulfosalts, base metal sulfides (mostly chalcopyrite, galena, sphalerite, and pyrite), and electrum. There is a broad zonation of metal distribution, with up to 10 % Cu+Pb+Zn in the deeper mines along the northern and central portions of the Veta Madre. Ore occurs in banded veins and breccias and as stockworks, with gangue composed dominantly of quartz and calcite. Host rocks are Mesozoic sedimentary and intrusive igneous rocks and Tertiary volcanic rocks. Most fluid inclusion homogenization temperatures are between 200 and 300 °C, with salinities below 4 wt.% NaCl equivalent. Fluid temperature and salinity decreased with time, from 290 to 240 °C and from 2.5 to 1.1 wt.% NaCl equivalent. Relatively constant fluid inclusion liquid-to-vapor ratios and a trend of decreasing salinity with decreasing temperature and with increasing time suggest dilution of the hydrothermal solutions. However, evidence of boiling (such as quartz and calcite textures and the presence of adularia) is noted along the Veta Madre, particularly at higher elevations. Fluid inclusion and mineralogical evidence for boiling of metal-bearing solutions is found in gold-rich portions of the eastern Sierra system; this part of the system is interpreted as the least eroded part of the district. Oxygen, carbon, and sulfur isotope analysis of host rocks, ore, and gangue minerals and fluid inclusion contents indicate a hydrothermal fluid, with an initial magmatic component that mixed over time with infiltrating meteoric water and underwent exchange with host rocks. Mineral deposition was a result of decreasing activities of sulfur and oxygen, decreasing temperature, increasing p

  6. Extended Hansen approach: calculating partial solubility parameters of solid solutes.

    PubMed

    Wu, P L; Beerbower, A; Martin, A

    1982-11-01

    A multiple linear regression method, known as the extended Hansen solubility approach, was used to estimate the partial solubility parameters, delta d, delta p, and delta h for crystalline solutes. The method is useful, since organic compounds may decompose near their melting points, and it is not possible, to determine solubility parameters for these solid compounds by the methods used for liquid solvents. The method gives good partial and total solubility parameters for naphthalene; with related compounds, less satisfactory results were obtained. At least three conditions, pertaining to the regression equation and the solvent systems, must be met in order to obtain reasonable solute solubility parameters. In addition to providing partial solubility parameters, the regression equations afford a calculation of solute solubility in both polar and nonpolar solvents.

  7. Structuring by field enhancement of glass, Ag, Au, and Co thin films using short pulse laser ablation

    SciTech Connect

    Ulmeanu, M.; Zamfirescu, M.; Rusen, L.; Luculescu, C.; Moldovan, A.; Stratan, A.; Dabu, R.

    2009-12-01

    Single pulse laser ablation of glass, Ag, Au, and Co thin films was experimentally investigated with a laser pulse width of 400 ps at a wavelength of 532 nm both in the far and near fields. In the far-field regime, the electromagnetic field results from a focused laser beam, while the near-field regime is realized by a combination of the focused laser beam incident on a spherical colloidal particle. For the near-field experiments we have used polystyrene colloidal particles of 700 nm diameter self-assembled or spin coated on top of the surfaces. Laser fluences applied are in the range of 0.01-10 J/cm{sup 2}. The diameter and the morphologies of the ablated holes were investigated by optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy. The dependence of the shape of the holes reflects the fluence regime and the thermophysical properties, i.e., melting temperature and thermal diffusivity of the surfaces involved in the experiments. We give quantitative data about the fluence threshold, diameter, and depth ablation dependence for the far and near fields and discuss their values with respect to the enhancement factor of the intensity of the electromagnetic field due to the use of the colloidal particles. Theoretical estimations of the intensity enhancement were done using the finite-difference time-domain method by using the RSOFT software. The application of near fields allows structuring of the surfaces with structure dimension in the order of 100 nm and even below.

  8. Improving the dissolution rate of poorly water soluble drug by solid dispersion and solid solution: pros and cons.

    PubMed

    Chokshi, Rina J; Zia, Hossein; Sandhu, Harpreet K; Shah, Navnit H; Malick, Waseem A

    2007-01-01

    The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

  9. Multiparametric dissolution of thorium-cerium dioxide solid solutions.

    PubMed

    Claparede, Laurent; Clavier, Nicolas; Dacheux, Nicolas; Mesbah, Adel; Martinez, Julien; Szenknect, Stéphanie; Moisy, Philippe

    2011-11-21

    The dissolution of Th(1-x)Ce(x)O(2) solid solutions samples prepared by thermal conversion of oxalate precursors was studied by varying independently several parameters (such as chemical composition, leachate acidity, leaching temperature, firing temperature, and crystallization state). The relative effects of these parameters on the normalized dissolution rate were examined. Either the obtained partial order related to the proton activity (n = 0.50 ± 0.01) or the activation energy (E(A) = 57 ± 6 kJ.mol(-1)) suggested that the dissolution was mainly driven by surface reactions occurring at the solid/liquid interface. Conversely to that observed for Th(1-x)U(x)O(2) and Ce(1-x)Nd(x)O(2-x/2) solid solutions, the chemical composition did not induce strong modifications of the chemical durability of the leached samples. While the initial normalized dissolution rate slightly depended on the elimination of crystal defects for firing temperatures below 800 °C, it was mainly independent of the crystallite size (T ≥ 900 °C). The role of crystal defects (then that of preparation conditions) appeared thus important to consider since they contributed to modifications of the normalized dissolution rates of the same order of magnitude than that of the leachate acidity.

  10. Crystallization in solid solution-aqueous solution systems: Thermodynamic and kinetic approaches

    SciTech Connect

    Shtukenberg, A. G. Punin, Yu. O.; Azimov, P. Ya.

    2010-03-15

    A new phenomenological approach is proposed to describe the crystallization kinetics in solid solution-aqueous solution binary systems. The phase diagrams, equilibria, and quasie-quilibria are considered within this approach. The crystallization kinetics near the true equilibrium and the crystallization features at large deviations from equilibrium are discussed on this basis. Special attention is paid to possible interactions in a solution with a seed crystal placed in it. In particular, the interactions leading to the seed's crystal growth or dissolution and to a possible exchange or metasomatic reactions are considered. In addition, the effect of the generated mismatch stress on the crystal growth rate and composition is analyzed.

  11. One-pot synthesis of M (M = Ag, Au)@SiO2 yolk-shell structures via an organosilane-assisted method: preparation, formation mechanism and application in heterogeneous catalysis.

    PubMed

    Chen, Yu; Wang, Qihua; Wang, Tingmei

    2015-05-21

    We demonstrate the fabrication of yolk-shell catalysts consisting of a single M (M = Ag, Au) nanoparticle encapsulated within a hollow mesoporous organosilica shell via an organosilane-assisted strategy. The advantages of our method lie in its good controllability of the void space as well as the thickness of the mesoporous shell. The M@CTAB/SiO2 synthesized through a modified Stöber method can transform to yolk-shell structures after adding (3-aminopropyl)trimethoxysilane (APTMS)/TEOS or (3-aminopropyl)triethoxysilane (APTES)/TEOS into the synthetic medium. We give unambiguous evidence that the middle CTAB/SiO2 layer transforms into a less dense APTMS-rich organic-inorganic layer which was selectively removed in alkaline aqueous solution, while the amino-functionalized hybrid shells remain intact. Moreover, we discuss the role of alkylamino groups in the shell in the transformation from Ag@SiO2 nanorattles to hollow structures when impregnating the as-synthesized Ag@SiO2 nanorattles in HAuCl4 aqueous solution. The nanorattles also exhibit high catalytic activity for the catalytic reduction of p-nitrophenol.

  12. Interfacial Free Energy of Cu-Co Solid Solutions

    NASA Astrophysics Data System (ADS)

    Zhevnenko, S. N.

    2013-06-01

    The surface energies of Cu-Co solid solutions in hydrogen atmosphere were measured. The measurements were performed on pure copper and copper alloys containing 0.45, 0.7, 1.4, 2.25, 2.50, and 2.8 at. pct Co and 4.1 at. pct Co for the temperature range 1245 K to 1349 K (972 °C to 1076 °C). The experiments were conducted using the zero creep method for 18 mcm foils. The modified method allowed " in situ" determining of the surface energy. It was shown that the surface energy increases as the concentration increases up to 1.4 at. pct Co and then decreases. Such extreme behavior was obtained by the direct method for the first time in a solid metallic system.

  13. Grain Size Hardening Effects in Mg-Gd Solid Solutions

    NASA Astrophysics Data System (ADS)

    Nagarajan, Devarajan; Cáceres, Carlos H.; Griffiths, John R.

    2016-11-01

    Pure Mg and alloys with 0.4, 1.3, and 3.8 at. pct Gd were cast with grain sizes between 700 and 35 µm and tested in tension and compression after solid solution heat treatment and quenching. The grain structure of the castings was random, that is, there was no preferred orientation, unlike the situation in extrusions and forgings usually reported in the literature. The results are compared to earlier work on Mg-Zn alloys. A tension-compression asymmetry in which the yield strength in compression is less than in tension was observed in pure Mg but was reversed for the concentrated alloys. The Hall-Petch stress intensity factor, k, first increased then decreased with the amount of Gd in solution. It is noted that defining the friction stress by extrapolating the data to infinite grain size should be treated with caution in Mg and its alloys: nevertheless, a rationale involving solid solution softening/hardening and twinning is offered for the observed values of the friction stress. The reversion of the tension-compression asymmetry is explained by the operation of { {10bar{1}1} } (contraction) twinning in the concentrated alloys in place of { {10bar{1}2} } (extension) twinning in pure Mg and the dilute alloys. It is argued that the activation of { {10bar{1}1} } twinning in the more concentrated alloys accounts for their lower k-value.

  14. First-principles electronic structure of the delafossites ABO 2 (A=Cu, Ag, Au; B=Al, Ga, Sc, In, Y): evolution of d 10-d 10 interactions

    NASA Astrophysics Data System (ADS)

    Kandpal, Hem Chandra; Seshadri, Ram

    2002-08-01

    While bonding between d 10 atoms and ions in molecular systems has been well studied, less attention has been paid to interactions between such seemingly closed shell species in extended inorganic solids. In this contribution, we present visualizations of the electronic structures of the delafossites ABO 2 (A = Cu, Ag, Au) with particular emphasis on the nature of d 10-d 10 interactions in the close packed plane of the coinage metal ion. We find that on going from Cu to Ag to Au, the extent of bonding between A and A increases. However, the structures (in terms of distances) of these compounds are largely determined by the strongly ionic B IIIO interaction and for the larger B ions Sc, In and Y, the A atoms are sufficiently well-separated that AA bonding is almost negligible. We also analyze some interesting differences between Ag and Au, including the larger AO covalency of the Au. The trends in electronic structure suggest that the Ag and Au compounds are not good candidate transparent conducting oxides.

  15. Room-Temperature Tensile Behavior of Oriented Tungsten Single Crystals with Rhenium in Dilute Solid Solution

    DTIC Science & Technology

    1966-01-01

    SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION Sby M. Garfinkle Lewis Research Center Cleveland, Ohio 20060516196 NATIONAL AERONAUTICS AND...WITH RHENIUM IN DILUTE SOLID SOLUTION By M. Garfinkle Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by...ORIENTED TUNGSTEN SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION * by M. Garfinkle Lewis Research Center SUMMARY Tungsten single crystals

  16. Features of luminescence of liquid and solid solutions of dibenzopyrenequinnone

    SciTech Connect

    Nurmukhametov, R.N.; Baskakova, Z.M.; Khachatorova, G.T.; Mil'khiker, P.D.

    1986-01-01

    This paper reports on a study of the fluorescence characteristics of DBPQ in liquid and solid media with various polarities. The absorption, fluorescence, and fluorescence excitation spectra of the dye are investigated in a series of solvents and polymeric matrices. In liquid solutions, no new fluorescence band appears. The unusual fluorescence properties of DBPQ can be attributed to inversion of closely positioned energy levels of the S..pi pi..* and Tn..pi..* states under the influence of the medium and on the ability of the dye molecules to be photoreduced to the leuco form.

  17. REVIEWS OF TOPICAL PROBLEMS: Diffusive decomposition of solid solutions

    NASA Astrophysics Data System (ADS)

    Slezov, V. V.; Sagalovich, V. V.

    1987-01-01

    The present status of the theory of the late stage of diffusive decomposition of multicomponent solid solutions, owing to diffusive interaction of macrodefects, is reviewed. Methods for solving the systems of equations describing the decomposition process are analyzed. The evolution of the critical dimensions of precipitates and the transformation of an arbitrary distribution function into a universal function for different mechanisms of mass transfer are studied in detail. The conditions for coexistence of phases in the presence of decomposition of multicomponent systems are examined. The results of the theory are compared with experiment.

  18. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  19. Temperature dependence of nucleation rate in a binary solid solution

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Philippe, T.; Duguay, S.; Blavette, D.

    2012-12-01

    The influence of regression (partial dissolution) effects on the temperature dependence of nucleation rate in a binary solid solution has been studied theoretically. The results of the analysis are compared with the predictions of the simplest Volmer-Weber theory. Regression effects are shown to have a strong influence on the shape of the curve of nucleation rate versus temperature. The temperature TM at which the maximum rate of nucleation occurs is found to be lowered, particularly for low interfacial energy (coherent precipitation) and high-mobility species (e.g. interstitial atoms).

  20. Electronic origin of solid solution softening in bcc molybdenum alloys.

    PubMed

    Medvedeva, N I; Gornostyrev, Yu N; Freeman, A J

    2005-04-08

    The intrinsic mechanism of solid solution softening in bcc molybdenum alloys due to 5d transition metal additions is investigated on the basis of ab initio electronic-structure calculations that model the effect of alloying elements on the generalized stacking fault (GSF) energies. We demonstrate that additions with an excess of electrons (Re, Os, Ir, and Pt) lead to a decrease in the GSF energy and those with a lack of electrons (Hf and Ta) to its sharp increase. Using the generalized Peierls-Nabarro model for a nonplanar core, we associate the local reduction of the GSF energy with an enhancement of double kink nucleation and an increase of the dislocation mobility, and we reveal the electronic reasons for the observed dependence of the solution softening on the atomic number of the addition.

  1. Energetics of Rare Earth Doped Uranium Oxide Solid Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Lei

    The physical and chemical properties of UO2 nuclear fuels are affected as fission products accumulate during irradiation. The lanthanides, a main group of fission products, form extensive solid solutions with uranium oxide in the fluorite structure. Thermodynamic studies of such solid solutions had been performed to obtain partial molar free energies of oxygen as a function of dopant concentration and temperature; however, direct measurement of formation enthalpies was hampered by the refractory nature of these oxides. In this work, high temperature oxide melt solution calorimetry was utilized to study the thermochemistry of various rare earth doped uranium oxide LnxU 1-xO2-0.5x+y (Ln = La, Y, Nd) over a wide range of dopant concentrations and oxygen contents. The sintered solid solutions were carefully characterized to determine their phase purity, chemical composition, and uranium oxidation state, with most of the materials in the oxygen excess regime. The enthalpies of formation of LnxU1-xO2-0.5x+y were calculated from the calorimetric data. The oxidation enthalpies of these solid solutions are similar to that of UO2. The formation enthalpies from constituent oxides (LnO1.5, UO2, and UO3) become increasingly negative with addition of dopant cations and appear relatively independent of the uranium oxidation state (oxygen content) when the type and concentration of the dopants are the same. This is valid in the oxygen excess regime; thus an estimation of formation enthalpies of LnxU1-xO2 materials can be made. The formation enthalpies from elements of hyperstoichiometric LnxU1-xO 2-0.5x+y materials obtained from calorimetric measurements are in good agreement with those calculated from free energy data. A direct comparison between the formation enthalpies from calorimetric study and computational research using density functional theory was also performed. The experimental and computational energies of LnxU 1-xO2 (Ln = La, Y, Nd) generally agree within 10 k

  2. Kinetics of the cellular decomposition of supersaturated solid solutions

    NASA Astrophysics Data System (ADS)

    Ivanov, M. A.; Naumuk, A. Yu.

    2014-09-01

    A consistent description of the kinetics of the cellular decomposition of supersaturated solid solutions with the development of a spatially periodic structure of lamellar (platelike) type, which consists of alternating phases of precipitates on the basis of the impurity component and depleted initial solid solution, is given. One of the equations, which determines the relationship between the parameters that describe the process of decomposition, has been obtained from a comparison of two approaches in order to determine the rate of change in the free energy of the system. The other kinetic parameters can be described with the use of a variational method, namely, by the maximum velocity of motion of the decomposition boundary at a given temperature. It is shown that the mutual directions of growth of the lamellae of different phases are determined by the minimum value of the interphase surface energy. To determine the parameters of the decomposition, a simple thermodynamic model of states with a parabolic dependence of the free energy on the concentrations has been used. As a result, expressions that describe the decomposition rate, interlamellar distance, and the concentration of impurities in the phase that remain after the decomposition have been derived. This concentration proves to be equal to the half-sum of the initial concentration and the equilibrium concentration corresponding to the decomposition temperature.

  3. Solid-solution semiconductor nanowires in pseudobinary systems.

    PubMed

    Liu, Baodan; Bando, Yoshio; Liu, Lizhao; Zhao, Jijun; Masanori, Mitome; Jiang, Xin; Golberg, Dmitri

    2013-01-09

    Pseudobinary solid-solution semiconductor nanowires made of (GaP)(1-x)(ZnS)(x), (ZnS)(1-x)(GaP)(x) and (GaN)(1-x)(ZnO)(x) were synthesized based on an elaborative compositional, structural, and synthetic designs. Using analytical high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS), we confirmed that the structure uniformity and a lattice match between the two constituting binary components play the key roles in the formation of quaternary solid-solution nanostructures. Electrical transport measurements on individual GaP and (GaP)(1-x)(ZnS)(x) nanowires indicated that a slight invasion of ZnS in the GaP host could lead to the abrupt resistance increase, resulting in the semiconductor-to-insulator transition. The method proposed here may be extended to the rational synthesis of many other multicomponent nanosystems with tunable and intriguing optoelectronic properties for specific applications.

  4. Zn₃P₂-Zn₃As₂ solid solution nanowires.

    PubMed

    Im, Hyung Soon; Park, Kidong; Jang, Dong Myung; Jung, Chan Su; Park, Jeunghee; Yoo, Seung Jo; Kim, Jin-Gyu

    2015-02-11

    Semiconductor alloy nanowires (NWs) have recently attracted considerable attention for applications in optoelectronic nanodevices because of many notable properties, including band gap tunability. Zinc phosphide (Zn3P2) and zinc arsenide (Zn3As2) belong to a unique pseudocubic tetragonal system, but their solid solution has rarely been studied. Here In this study, we synthesized composition-tuned Zn3(P1-xAsx)2 NWs with different crystal structures by controlling the growth conditions during chemical vapor deposition. A first type of synthesized NWs were single-crystalline and grew uniformly along the [110] direction (in a cubic unit cell) over the entire compositional range (0 ≤ x ≤ 1) explored. The use of an indium source enabled the growth of a second type of NWs, with remarkable cubic-hexagonal polytypic twinned superlattice and bicrystalline structures. The growth direction of the Zn3P2 and Zn3As2 NWs was also switched to [111] and [112], respectively. These structural changes are attributable to the Zn-depleted indium catalytic nanoparticles which favor the growth of hexagonal phases. The formation of a solid solution at all compositions allowed the continuous tuning of the band gap (1.0-1.5 eV). Photocurrent measurements were performed on individual NWs by fabricating photodetector devices; the single-crystalline NWs with [110] growth direction exhibit a higher photoconversion efficiency compared to the twinned crystalline NWs with [111] or [112] growth direction.

  5. Irradiation-induced composition patterns in binary solid solutions

    SciTech Connect

    Dubey, Santosh; El-Azab, Anter

    2013-09-28

    A theoretical/computational model for the irradiation-driven compositional instabilities in binary solid solutions has been developed. The model is suitable for investigating the behavior of structural alloys and metallic nuclear fuels in a reactor environment as well as the response of alloy thin films to ion beam irradiation. The model is based on a set of reaction-diffusion equations for the dynamics of vacancies, interstitials, and lattice atoms under irradiation. The dynamics of these species includes the stochastic generation of defects by collision cascades as well as the defect reactions and diffusion. The atomic fluxes in this model are derived based on the transitions of lattice defects. The set of reaction-diffusion equations are stiff, hence a stiffly stable method, also known as the Gear method, has been used to numerically approximate the equations. For the Cu-Au alloy in the solid solution regime, the model results demonstrate the formation of compositional patterns under high-temperature particle irradiation, with Fourier space properties (Fourier spectrum, average wavelength, and wavevector) depending on the cascade damage characteristics, average composition, and irradiation temperature.

  6. Formation of solid solutions between racemic and enantiomeric citalopram oxalate.

    PubMed

    de Diego, Heidi Lopez; Bond, Andrew D; Dancer, Robert James

    2011-05-01

    The X-ray powder diffractograms of racemic citalopram oxalate and (S)-citalopram oxalate are very similar, but the melting point of the racemate is higher than that of the pure enantiomer. The higher melting point indicates that the racemate is a racemic compound, rather than a conglomerate. The crystal structure of the enantiomer contains two molecules of (S)-citalopram in the asymmetric unit. The conformation of the two molecules is different but they approximate mirror images of each other if the aromatic groups are interchanged. The crystal structure of the racemate is essentially isostructural with that of the enantiomer, having almost the same cell parameters but containing a crystallographic inversion centre that is not retained in the enantiomer structure. The closely-comparable crystal structures permit solid solutions to be formed between racemic and enantiomeric citalopram oxalate. Phase diagrams of the (R)-citalopram and (S)-citalopram oxalate system are constructed, and they show that solid solutions are formed at all ratios of the two enantiomers.

  7. Self-field ac losses of a twisted multifilamentary (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape

    NASA Astrophysics Data System (ADS)

    Friend, C. M.; Huang, Y. B.

    2000-06-01

    Self-field loss measurements at 77 K on a superconducting (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape with twisted filaments are presented. Using the first- and third-harmonic components of the electric field, the hysteretic losses are separated from the total loss. At peak transport currents less than half the critical current, the hysteretic losses are considerably reduced. However, sizable nonhysteretic losses are also observed. At higher currents, the hysteretic loss increases, dominating the total loss, and is similar to that for an untwisted tape.

  8. Solid state synthesis, crystal growth and optical properties of urea and p-chloronitrobenzene solid solution

    NASA Astrophysics Data System (ADS)

    Rai, R. N.; Kant, Shiva; Reddi, R. S. B.; Ganesamoorthy, S.; Gupta, P. K.

    2016-01-01

    Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB and UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal.

  9. Creep Behavior of Solid Solution Strengthened Y3Al5O12

    DTIC Science & Technology

    2007-11-02

    DATES COVERED Final Technical Report 15 Feb 97 to 29 Aug 97 4. TITLE AND SUBTITLE Creep Behavior of Solid Solution Strengthened Y3A15012 6...Final Report Title: Creep Behavior of Solid Solution Strengthened Y3AI5012 Award Number: F49620-97-1-0097 For the period of: 2/14/97-8/31/97...been investigated at present in these oxides is through the formation of solid solution alloys. For the case of oxides two different possible solid

  10. Reaction paths and equilibrium end-points in solid-solution aqueous-solution systems

    USGS Publications Warehouse

    Glynn, P.D.; Reardon, E.J.; Plummer, L.N.; Busenberg, E.

    1990-01-01

    Equations are presented describing equilibrium in binary solid-solution aqueous-solution (SSAS) systems after a dissolution, precipitation, or recrystallization process, as a function of the composition and relative proportion of the initial phases. Equilibrium phase diagrams incorporating the concept of stoichiometric saturation are used to interpret possible reaction paths and to demonstrate relations between stoichiometric saturation, primary saturation, and thermodynamic equilibrium states. The concept of stoichiometric saturation is found useful in interpreting and putting limits on dissolution pathways, but there currently is no basis for possible application of this concept to the prediction and/ or understanding of precipitation processes. Previously published dissolution experiments for (Ba, Sr)SO4 and (Sr, Ca)C??O3orth. solids are interpreted using equilibrium phase diagrams. These studies show that stoichiometric saturation can control, or at least influence, initial congruent dissolution pathways. The results for (Sr, Ca)CO3orth. solids reveal that stoichiometric saturation can also control the initial stages of incongruent dissolution, despite the intrinsic instability of some of the initial solids. In contrast, recrystallisation experiments in the highly soluble KCl-KBr-H2O system demonstrate equilibrium. The excess free energy of mixing calculated for K(Cl, Br) solids is closely modeled by the relation GE = ??KBr??KClRT[a0 + a1(2??KBr-1)], where a0 is 1.40 ?? 0.02, a1, is -0.08 ?? 0.03 at 25??C, and ??KBr and ??KCl are the mole fractions of KBr and KCl in the solids. The phase diagram constructed using this fit reveals an alyotropic maximum located at ??KBr = 0.676 and at a total solubility product, ???? = [K+]([Cl-] + [Br-]) = 15.35. ?? 1990.

  11. Solid state and solution nitrate photochemistry: photochemical evolution of the solid state lattice.

    PubMed

    Asher, Sanford A; Tuschel, David D; Vargson, Todd A; Wang, Luling; Geib, Steven J

    2011-05-05

    We examined the deep UV 229 nm photochemistry of NaNO(3) in solution and in the solid state. In aqueous solution excitation within the deep UV NO(3)¯ strong π → π* transition causes the photochemical reaction NO(3)¯ → NO(2)¯ + O·. We used UV resonance Raman spectroscopy to examine the photon dose dependence of the NO(2)¯ band intensities and measure a photochemical quantum yield of 0.04 at pH 6.5. We also examined the response of solid NaNO(3) samples to 229 nm excitation and also observe formation of NO(2)¯. The quantum yield is much smaller at ∼10(-8). The solid state NaNO(3) photochemistry phenomena appear complex by showing a significant dependence on the UV excitation flux and dose. At low flux/dose conditions NO(2)¯ resonance Raman bands appear, accompanied by perturbed NO(3)¯ bands, indicating stress in the NaNO(3) lattice. Higher flux/dose conditions show less lattice perturbation but SEM shows surface eruptions that alleviate the stress induced by the photochemistry. Higher flux/dose measurements cause cratering and destruction of the NaNO(3) surface as the surface layers are converted to NO(2)¯. Modest laser excitation UV beams excavate surface layers in the solid NaNO(3) samples. At the lowest incident fluxes a pressure buildup competes with effusion to reach a steady state giving rise to perturbed NO(3)¯ bands. Increased fluxes result in pressures that cause the sample to erupt, relieving the pressure.

  12. Ag@Au concave cuboctahedra: A unique probe for monitoring Au-catalyzed reduction and oxidation reactions by surface-enhanced Raman spectroscopy

    DOE PAGES

    Zhang, Jiawei; Winget, Sarah A.; Wu, Yiren; ...

    2016-01-26

    In this paper, we report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au3+ by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets. The concave cuboctahedramore » embrace excellent SERS activity that is more than 70-fold stronger than that of the original Ag cuboctahedra at an excitation wavelength of 785 nm. The concave cuboctahedra also exhibit remarkable stability in the presence of an oxidant such as H2O2 because of the protection by a complete Au shell. These two unique attributes enable in-situ SERS monitoring of the reduction of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) by NaBH4 through a 4,4'-dimercaptoazobenzene (trans-DMAB) intermediate and the subsequent oxidation of 4-ATP back to trans-DMAB upon the introduction of H2O2.« less

  13. Ag@Au concave cuboctahedra: A unique probe for monitoring Au-catalyzed reduction and oxidation reactions by surface-enhanced Raman spectroscopy

    SciTech Connect

    Zhang, Jiawei; Winget, Sarah A.; Wu, Yiren; Su, Dong; Sun, Xiaojun; Xie, Zhao -Xiong; Qin, Dong

    2016-01-26

    In this paper, we report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au3+ by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets. The concave cuboctahedra embrace excellent SERS activity that is more than 70-fold stronger than that of the original Ag cuboctahedra at an excitation wavelength of 785 nm. The concave cuboctahedra also exhibit remarkable stability in the presence of an oxidant such as H2O2 because of the protection by a complete Au shell. These two unique attributes enable in-situ SERS monitoring of the reduction of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) by NaBH4 through a 4,4'-dimercaptoazobenzene (trans-DMAB) intermediate and the subsequent oxidation of 4-ATP back to trans-DMAB upon the introduction of H2O2.

  14. A coupled-cluster study on the noble gas binding ability of metal cyanides versus metal halides (metal = Cu, Ag, Au).

    PubMed

    Pan, Sudip; Gupta, Ashutosh; Saha, Ranajit; Merino, Gabriel; Chattaraj, Pratim K

    2015-11-05

    A coupled-cluster study is carried out to investigate the efficacy of metal(I) cyanide (MCN; M = Cu, Ag, Au) compounds to bind with noble gas (Ng) atoms. The M-Ng bond dissociation energy, enthalpy change, and Gibbs free energy change for the dissociation processes producing Ng and MCN are computed to assess the stability of NgMCN compounds. The Ng binding ability of MCN is then compared with the experimentally detected NgMX (X = F, Cl, Br) compounds. While CuCN and AgCN have larger Ng binding ability than those of MCl and MBr (M = Cu, Ag), AuCN shows larger efficacy toward bond formation with Ng than that of AuBr. Natural bond orbital analysis, energy decomposition analysis in conjunction with the natural orbital for chemical valence theory, and the topological analysis of the electron density are performed to understand the nature of interaction occurring in between Ng and MCN. The Ng-M bonds in NgMCN are found comprise an almost equal contribution from covalent and electrostatic types of interactions. The different electron density descriptors also reveal the partial covalent character in the concerned bonds.

  15. Au@Ag/Au nanoparticles assembled with activatable aptamer probes as smart "nano-doctors" for image-guided cancer thermotherapy.

    PubMed

    Shi, Hui; Ye, Xiaosheng; He, Xiaoxiao; Wang, Kemin; Cui, Wensi; He, Dinggeng; Li, Duo; Jia, Xuekun

    2014-08-07

    Although nanomaterial-based theranostics have increased positive expectations from cancer treatment, it remains challenging to develop in vivo "nano-doctors" that provide high-contrast image-guided site-specific therapy. Here we designed an activatable theranostic nanoprobe (ATNP) via self-assembly of activatable aptamer probes (AAPs) on Au@Ag/Au nanoparticles (NPs). As both quenchers and heaters, novel Au@Ag/Au NPs were prepared, showing excellent fluorescence quenching and more effective near-infrared photothermal therapy than Au nanorods. The AAP comprised a thiolated aptamer and a fluorophore-labeled complementary DNA; thus, the ATNP with quenched fluorescence in the free state could realize signal activation through target binding-induced conformational change of the AAP, and then achieve on-demand treatment under image-guided irradiation. By using S6 aptamer as the model, in vitro and in vivo studies of A549 lung cancer verified that the ATNP greatly improved imaging contrast and specific destruction, suggesting a robust and versatile theranostic strategy for personalized medicine in future.

  16. Nucleation of the diamond phase in aluminium-solid solutions

    NASA Technical Reports Server (NTRS)

    Hornbogen, E.; Mukhopadhyay, A. K.; Starke, E. A., Jr.

    1993-01-01

    Precipitation was studied from fcc solid solutions with silicon, germanium, copper and magnesium. Of all these elements only silicon and germanium form diamond cubic (DC) precipitates in fcc Al. Nucleation of the DC structure is enhanced if both types of atom are dissolved in the fcc lattice. This is interpreted as due to atomic size effects in the prenucleation stage. There are two modes of interference of fourth elements with nucleation of the DC phase in Al + Si, Ge. The formation of the DC phase is hardly affected if the atoms (for example, copper) are rejected from the (Si, Ge)-rich clusters. If additional types of atom are attracted by silicon and/or germanium, DC nuclei are replaced by intermetallic compounds (for example Mg2Si).

  17. Dielectric properties of the multicomponent PZT-type solid solution

    NASA Astrophysics Data System (ADS)

    Bochenek, Dariusz; Niemiec, Przemysław; Adamczyk, Małgorzata; Machnik, Zbigniew; Dercz, Grzegorz

    2015-10-01

    In this paper the multicomponent PZT-type solid solution doped by barium, calcium, strontium, bismuth and germanium with composition: Pb0.975Ba0.01Ca0.01Sr0.005(Zr0.52Ti0.48)O3 + 1.4 wt.% Bi2O3 + 0.3 wt.% GeO obtained by hot uniaxial pressing method is described. The results of structural, dielectric, ferroelectric and electromechanical studies of these ceramics are presented. It has been stated that introduction to the basic composition PZT admixtures of the barium, calcium, strontium, bismuth and germanium has a positive effect on the electro-physic parameters of obtained ceramic samples. This material has good microstructure, with high value of the dielectric permittivity (with the high temperature of phase transition) as well as low dielectric losses. It allows considering this material as elements for low frequency and high temperature electromechanical transducers.

  18. Lattice thermal conductivity of nanograined half-Heusler solid solutions

    SciTech Connect

    Geng, Huiyuan Meng, Xianfu; Zhang, Hao; Zhang, Jian

    2014-05-19

    We report a phenomenological model of atomic weight, lattice constant, temperature, and grain size to calculate the high-temperature lattice thermal conductivity of nanograined solid solutions. The theoretical treatment developed here is reasonably consistent with the experimental results of n-type MNiSn and p-type MCoSb alloys, where M is the combination of Hf, Zr, and Ti. For disordered half-Heusler alloys with moderated grain sizes, we predict that the reduction in lattice thermal conductivity due to grain boundary scattering is independent of the scattering parameter, which characterizes the phonon scattering cross section of point defects. In addition, the lattice thermal conductivity falls off with temperature as T{sup –1∕2} around the Debye temperature.

  19. A solid dielectric gated graphene nanosensor in electrolyte solutions.

    PubMed

    Zhu, Yibo; Wang, Cheng; Petrone, Nicholas; Yu, Jaeeun; Nuckolls, Colin; Hone, James; Lin, Qiao

    2015-03-23

    This letter presents a graphene field effect transistor (GFET) nanosensor that, with a solid gate provided by a high-κ dielectric, allows analyte detection in liquid media at low gate voltages. The gate is embedded within the sensor and thus is isolated from a sample solution, offering a high level of integration and miniaturization and eliminating errors caused by the liquid disturbance, desirable for both in vitro and in vivo applications. We demonstrate that the GFET nanosensor can be used to measure pH changes in a range of 5.3-9.3. Based on the experimental observations and quantitative analysis, the charging of an electrical double layer capacitor is found to be the major mechanism of pH sensing.

  20. Crystal-chemical features of the solid solutions

    SciTech Connect

    Titov, V.V.; Kesler, Ya.A.; Gordeev, I.V.; Mozhaev, A.P.

    1988-04-01

    The unusual magnetic properties of the solid solutions of CuCr/sub 2/S/sub 4/ in Cu/sub 0.5/Mo/sub 0.5/Cr/sub 2/S/sub 4/ (M = Al, Ga, In) are closely related to the crystal chemistry of these compounds. Specimens for structural investigation were obtained by solid-phase synthesis in evacuated quartz capsules. X-ray phase analysis of all the compounds was made by the powder method in a DRON-1 diffractometer with Cu K..cap alpha.. filtered radiation. The experimental confirmation of the ordering of the cations in the tetrahedral sublattice of the investigated spinels was obtained by the authors from their IR absorption spectra taken in the range 400-33 cm/sup /minus/1/. The presence of seven intense absorption bands in the spectra of the specimens indicates that these materials belong to the space group F/anti/43m, i.e., that there is ordering in the A sublattice. Their investigation led them to the conclusion that in a number of cases the vibrational spectra of the crystals are more sensitive in the investigation of atomic ordering than the spectra of x-ray and neutron diffraction, in agreement with the theoretical predictions.

  1. Thermal expansion of solid solutions in apatite binary systems

    SciTech Connect

    Knyazev, Alexander V.; Bulanov, Evgeny N. Korokin, Vitaly Zh.

    2015-01-15

    Graphical abstract: Thermal dependencies of volume thermal expansion parameter for with thermal expansion diagrams for Pb{sub 5}(PO{sub 4}){sub 3}F{sub x}Cl{sub 1−x}. - Highlights: • Solid solutions in three apatitic binary systems were investigated via HT-XRD. • Thermal expansion coefficients of solid solutions in the systems were calculated. • Features of the thermal deformation of the apatites were described. • Termoroentgenography is a sensitive method for the investigation of isomorphism. - Abstract: High-temperature insitu X-ray diffraction was used to investigate isomorphism and the thermal expansion of apatite-structured compounds in three binary systems in the entire temperature range of the existence of its hexagonal modifications. Most of the studied compounds are highly expandable (α{sub l} > 8 × 10{sup 6} (K{sup −1})). In Pb{sub 5}(PO{sub 4}){sub 3}F–Pb{sub 5}(PO{sub 4}){sub 3}Cl system, volume thermal expansion coefficient is independence from the composition at 573 K. In Pb{sub 5}(PO{sub 4}){sub 3}Cl–Pb{sub 5}(VO{sub 4}){sub 3}Cl, the compound with equimolar ratio of substituted atoms has constant volume thermal expansion coefficient in temperature range 298–973 K. Ca{sub 5}(PO{sub 4}){sub 3}Cl–Pb{sub 5}(PO{sub 4}){sub 3}Cl system is characterized by the most thermal sensitive composition, in which there is an equal ratio of isomorphic substituted atoms.

  2. Purification of uranothorite solid solutions from polyphase systems

    NASA Astrophysics Data System (ADS)

    Clavier, Nicolas; Szenknect, Stéphanie; Costin, Dan Tiberiu; Mesbah, Adel; Ravaux, Johann; Poinssot, Christophe; Dacheux, Nicolas

    2013-10-01

    The mineral coffinite, nominally USiO4, and associated Th1-xUxSiO4 uranothorite solid solutions are of great interest from a geochemical point of view and in the case of the direct storage of spent nuclear fuels. Nevertheless, they clearly exhibit a lack in the evaluation of their thermodynamic data, mainly because of the difficulties linked with their preparation as pure phases. This paper thus presents physical and chemical methods aiming to separate uranothorite solid solutions from oxide additional phases such as amorphous SiO2 and nanometric crystallized Th1-yUyO2. The repetition of centrifugation steps envisaged in first place was rapidly dropped due to poor recovery yields, to the benefit of successive washings in acid then basic media. Under both static and dynamic flow rates (i.e. low or high rate of leachate renewal), ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy) analyses revealed the systematic elimination of Th1-yUyO2 in acid media and of SiO2 in basic media. Nevertheless, two successive steps were always needed to reach pure samples. On this basis, a first cycle performed in static conditions was chosen to eliminate the major part of the accessory phases while a second one, in dynamic conditions, allowed the elimination of the residual impurities. The complete purification of the samples was finally evidenced through the characterization of the samples by the means of PXRD (Powder X-Ray Diffraction), SEM (Scanning Electron Microscopy) observations and X-EDS (X-Ray Energy Dispersive Spectroscopy) analyses.

  3. The effect of solute distribution on the strain rate sensitivity of solid solutions

    NASA Astrophysics Data System (ADS)

    Xu, Zhijie

    Several aspects of the physics of the interaction of mobile solute atoms and dislocations in dilute solid solution alloys are studied in this thesis. Solute is added to pure metals in order to improve their strength. Alloying also leads to a number of other effects, some of which are undesirable. For example, it leads to reduced ductility and may cause plastic instabilities. Both of these limit material formability. Here, understanding is added regarding the physical basis of these phenomena. Reduced formability is associated with the occurrence of plastic instabilities which are caused either by low strain hardening or by low (negative) strain rate sensitivity (SRS). The current study is focused on the second effect. The strain rate sensitivity has an instantaneous component (always positive), which is associated with the thermally activated motion of dislocations, and a transient component (which may be either positive or negative), which is associated with the correlated motion of dislocations and solute. Negative SRS results when the transient component is sufficiently negative and is presumably due to clustering of solute at dislocations. The study has a multiscale nature. On the nanoscale, the formation of solute clusters at stationary dislocation cores is studied using Monte Carlo simulations and EAM potentials in an Al-Mg alloy. The size of the thermodynamically stable cluster and the binding energy of the dislocation to its cluster are evaluated as a function of the average solute concentration and temperature. Such data enter all existing constitutive models of DSA. On the mesoscale, we investigate how solute structures (concentration fluctuations) defined on longer length scales affect dislocation motion and hence the strain rate sensitivity of the material. This investigation is performed using 2D dislocation dynamics simulations. On the macroscopic scale, parametric constitutive modeling is used to investigate the effect of mesoscopic solute structures

  4. ON THE THERMODYNAMICS OF SOLID INTRUSION SOLUTIONS WITH BODY-CENTERED CUBIC LATTICE

    DTIC Science & Technology

    THE PROPERTIES OF AN ELASTICALLY DEFORMED SOLID INTRUSION SOLUTION WITH BODY - CENTERED CUBIC LATTICE, UNBALANCED WITH RESPECT TO ENERGETICALLY DIFFERENT POSITIONS OF THE ATOMS OF THE DISSOLVED SUBSTANCE.

  5. Investigation of Propellant and Explosive Solid Solution Systems II X-Ray Studies

    DTIC Science & Technology

    1978-03-01

    A\\Yj* ^\\C/*^ ^ 1 tatf AD 7t ott w AD-E400 125 TECHNICAL REPORT ARLCD-TR-77066 INVESTIGATION OF PROPELLANT AND EXPLOSIVE SOLID SOLUTION SYSTEMS...Report ARLCD-TR-77066 2. GOVT ACCESSION NO. *. TITLE (and Subtitle) INVESTIGATION OF PROPELLANT AND EXPLOSIVE SOLID SOLUTION SYSTEMS II X-RAY...Interplanar spacings and x-ray diffraction 9 intensities of AP, KP and their physical mixtures and solid solutions 4 X-ray data of 3 AN: KP solid solution and

  6. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    NASA Astrophysics Data System (ADS)

    Hovis, Guy; Abraham, Tony; Hudacek, William; Wildermuth, Sarah; Scott, Brian; Altomare, Caitlin; Medford, Aaron; Conlon, Maricate; Morris, Matthew; Leaman, Amanda; Almer, Christine; Tomaino, Gary; Harlov, Daniel

    2015-04-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear, but as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV ), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  7. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    NASA Astrophysics Data System (ADS)

    Hovis, G. L.; Abraham, T.; Hudacek, W.; Wildermuth, S.; Scott, B.; Altomare, C.; Medford, A.; Conlon, M.; Morris, M.; Leaman, A.; Almer, C.; Tomaino, G.; Harlov, D. E.

    2014-12-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear but, as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  8. Stability region of the liebermannite-lingunite solid solution

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Irifune, T.; Ohfuji, H.; Shinmei, T.; DU, W.

    2015-12-01

    Aluminosilicate hollandite, with the chemical formula of (K,Na)AlSi3O8, is a potential host mineral of K and Na in the deep Earth [1,2]. The Na hollandite end member is called lingunite, and the K hollandite end member was named liebermannite recently. Phase relations in the system KAlSi3O8-NaAlSi3O8 under conditions of the Earth mantle transition zone and uppermost lower mantle [3,4] are essential to understanding the behavior of the liebermannite-lingunite solid solution under high pressure and high temperature, however, it is still not clear whether or not the end members can form complete solid solutions with the hollandite structure under some conditions. Previous high pressure experiments obtained the K hollandite with the limited Na content up to 50 mol % [3,4], while the Na-rich hollandite with the Na content of about 80 mol % was discovered in some meteorites [5,6]. Here we report our successful synthesis of the Na-rich hollandite with the Na content of 78 mol % at 22 GPa, 2273 K, the same condition under which the Na-rich hollandite found in the meteorite was inferred to be formed during the shock event [5]. Phase relations around 22 GPa at 1873 and 2273 K determined by our experiments indicate the solubility of NaAlSi3O8 in K hollandite is sensitive to both pressure and temperature, especially around the pressure corresponding to the dissociation of jadeite into the calcium ferrite type NaAlSiO4and stishovite, and there may be a stability region for the Na hollandite end member at temperatures slightly higher than 2273 K. Our improved phase relations provide a reasonable access to estimate the composition of hollandite in the Earth's interior and a supportive evidence to interpret the formation of the Na-rich hollandite found in meteorites via phase equilibria. [1] Irifune T., Ringwood A.E. and Hibberson W.O. (1994) Earth Planet. Sci. Lett. 126: 351-368. [2] Ishii T., Kojitani H. and Akaogi M. (2012) Earth Planet. Sci. Lett. 357-358: 34-41. [3] Yagi A

  9. Sustainable solutions for solid waste management in Southeast Asian countries.

    PubMed

    Ngoc, Uyen Nguyen; Schnitzer, Hans

    2009-06-01

    Human activities generate waste and the amounts tend to increase as the demand for quality of life increases. Today's rate in the Southeast Asian Nations (ASEANs) is alarming, posing a challenge to governments regarding environmental pollution in the recent years. The expectation is that eventually waste treatment and waste prevention approaches will develop towards sustainable waste management solutions. This expectation is for instance reflected in the term 'zero emission systems'. The concept of zero emissions can be applied successfully with today's technical possibilities in the agro-based processing industry. First, the state-of-the-art of waste management in Southeast Asian countries will be outlined in this paper, followed by waste generation rates, sources, and composition, as well as future trends of waste. Further on, solutions for solid waste management will be reviewed in the discussions of sustainable waste management. The paper emphasizes the concept of waste prevention through utilization of all wastes as process inputs, leading to the possibility of creating an ecosystem in a loop of materials. Also, a case study, focusing on the citrus processing industry, is displayed to illustrate the application of the aggregated material input-output model in a widespread processing industry in ASEAN. The model can be shown as a closed cluster, which permits an identification of opportunities for reducing environmental impacts at the process level in the food processing industry. Throughout the discussion in this paper, the utilization of renewable energy and economic aspects are considered to adapt to environmental and economic issues and the aim of eco-efficiency. Additionally, the opportunities and constraints of waste management will be discussed.

  10. Sustainable solutions for solid waste management in Southeast Asian countries

    SciTech Connect

    Uyen Nguyen Ngoc Schnitzer, Hans

    2009-06-15

    Human activities generate waste and the amounts tend to increase as the demand for quality of life increases. Today's rate in the Southeast Asian Nations (ASEANs) is alarming, posing a challenge to governments regarding environmental pollution in the recent years. The expectation is that eventually waste treatment and waste prevention approaches will develop towards sustainable waste management solutions. This expectation is for instance reflected in the term 'zero emission systems'. The concept of zero emissions can be applied successfully with today's technical possibilities in the agro-based processing industry. First, the state-of-the-art of waste management in Southeast Asian countries will be outlined in this paper, followed by waste generation rates, sources, and composition, as well as future trends of waste. Further on, solutions for solid waste management will be reviewed in the discussions of sustainable waste management. The paper emphasizes the concept of waste prevention through utilization of all wastes as process inputs, leading to the possibility of creating an ecosystem in a loop of materials. Also, a case study, focusing on the citrus processing industry, is displayed to illustrate the application of the aggregated material input-output model in a widespread processing industry in ASEAN. The model can be shown as a closed cluster, which permits an identification of opportunities for reducing environmental impacts at the process level in the food processing industry. Throughout the discussion in this paper, the utilization of renewable energy and economic aspects are considered to adapt to environmental and economic issues and the aim of eco-efficiency. Additionally, the opportunities and constraints of waste management will be discussed.

  11. Relaxor-based solid solutions for piezoelectric and electrostrictive applications

    NASA Astrophysics Data System (ADS)

    Alberta, Edward F.

    This thesis explores the dielectric, piezoelectric, and electrostrictive properties of a number of relaxor ferroelectric-based solid solution systems. The components of these solid solution systems have a variety of characteristics ranging from normal- to relaxor- to anti-ferroelectric. Some of the relaxor end-members investigated were Pb(In1/2Nb1/2)O3 [PIN], Pb(In1/2Ta1/2)O3 [PIT], Pb(Sc 1/2Nb1/2)O3 [PSN], Pb(Ni1/3Nb 2/3)O3 [PNN], Pb(Mg1/3Nb2/3)O 3 [PMN], and Pb(Zn1/3Nb2/3)O3 [PZN]. Several of these systems have Curie temperatures [Tc] that are among the highest known for MPB compositions. Some examples are PIN-0.38PT with a Tc of 319°C, PIT-0.38PT with a Tc of 248°C, and PSN 0.42PT with a Tc of 254°C. While these are slightly lower that those of typically found in PZT, the temperature dependence of the piezoelectric properties was found to be minimal. The electromechanical coupling coefficients were largely unchanged upon heating to as high as 150°C. This is approximately equal to the Tc of PMN-PT and PZN-PT and significantly exceeds the generally accepted maximum operating temperature for these materials. Many of the materials studied were found to have very large electromechanical coupling factors and produce extraordinarily high field-induced strains. Both PSN-0.42PT and PNN-0.15PZ-0.34PT were found to produce strain levels of ˜0.30% under unipolar drive with limited hysteresis. Peak-to-peak strain levels of as much as 0.60% were possible under bipolar drive conditions. Both of these MPB compositions had very large piezoelectric properties, with the slightly larger values of d33 = 810pC/N, kp = 0.69, kt = 0.56, and k33 = 0.80 occurring in PNN-PZ-PT. Each of the MPB compositions studied has features that can be exploited for specific applications. The combination of high Tc and coercive field found in both PIN-PT and Bi(Ni1/2T1/2)O3 -PT should allow these materials to be used at high drive levels and/or at high temperatures. The high strain, low hysteresis

  12. Magnetic properties of Co-Cu metastable solid solution alloys

    NASA Astrophysics Data System (ADS)

    Fan, Xu; Mashimo, Tsutomu; Huang, Xinsheng; Kagayama, Tomoko; Chiba, Akira; Koyama, Keiichi; Motokawa, Mitsuhiro

    2004-03-01

    Metastable solid solution alloy powders and bulk alloys in the cobalt(Co)-copper(Cu) (10 90 mol % Co) system, which is an almost immiscible system at the ambient state, were prepared by mechanical alloying (MA) and shock compression. All MA-treated powders showed the x-ray diffraction patterns of a single phase of fcc structure. The lattice parameter increases with Cu concentration and is fundamentally on the line with Vegard’s law. The magnetization curves of CoxCu100-x (x=20 80) metastable bulk alloys at room temperature showed ferromagnetism, while the one of Co10Cu90 system showed paramagnetism. The saturation magnetic moment (Ms) curve versus electron numbers per atom at 0 K was found to be similar to the Slater-Pauling curves of other transition-metal binary systems and decreased with increasing Cu concentration and approached zero at about 28.8 electrons per atom. The magnetoresistance ratio at room temperature increased with Cu content in the ferromagnetic region, while the one of the paramagnetic Co10Cu90 alloy was negligibly small.

  13. Vacancy diffusion in magnetite-hercynite solid solution

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeru; Nakamura, Akio; Shimizu, Toshiaki; Fueki, Kazuo

    1983-11-01

    To extend the chemical relaxation technique to ternary oxide systems, theoretical analysis was made to obtain an expression for the chemical diffusion coefficient in terms of the vacancy diffusion coefficient. An equation, D˜ = [ {C O}/{(C 1 + C 2) }] D v( {1}/{2})( {∂ ln P( O2) }/{∂ ln C v}) , was derived. This is similar to the one for the binary oxide system. Chemical relaxation experiments were made on the magnetite-hercynite solid solutions, (Fe 1- yAl y) 3-δO 4 with y = 0.0, 0.067, 0.133, and 0.20, at temperatures between 1300 and 1400°C. The vacancy diffusion coefficient decreased remarkably with an increase in y. The activation energy was found to be 20.8 ± 3.7, 33.5 ± 4.2, 50.4 ± 3.6, and 66.3 ± 4.5 kcal/mole for y = 0.0, 0.067, 0.133, and 0.20, respectively. A strong dependence on y was also found. The dependence of the vacancy diffusion coefficient on y was interpreted to indicate that the jump frequency of cation vacancies is decreased by the introduction of aluminium ion.

  14. Solidification and crystal growth of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  15. Intrinsic luminescence centers in scandia, yttria, and their solid solutions

    NASA Astrophysics Data System (ADS)

    Solomonov, V. V.; Spirina, A. V.; Spirin, A. V.; Paranin, S. N.

    2016-11-01

    Pulsed cathodoluminescence (PCL) of Y2O3 and Sc2O3 powders, as well as of ceramic samples of binary (11 mol % Sc2O3-ZrO2 and 10 mol % Y2O3-ZrO2) and ternary ( xSc2O3-(10-x)Y2O3-ZrO2) ( x = 5, 6, 7, 8 mol %) solid solutions are studied in the range of 300-850 nm at room temperature. In Y2O3 and Sc2O3, series of strong narrow luminescence bands emitted by surface bound radicals ...0 ...0 >-Y= O and ...0 ...0 >-Sc= O are found. The PCL spectra of xSc2O3-(10-x)Y2O3-ZrO2 ceramic samples showed the same series of narrow bands at 543, 551, 555, 572, 583, 594, 614, and 639 nm as the yttrium oxide spectra. The existence of these luminescence bands, which correspond to the emission of the ...0 ...0 >-Y= O radical, and the absence of the emission lines of the ...0 ...0 >-Sc= O radical indicate that yttrium ions, due to their larger radius, are the first that are displaced to the surface of crystallites in these systems, which is accompanied by the formation of the second phase in subsurface layers.

  16. Global optimization of bimetallic cluster structures. II. Size-matched Ag-Pd, Ag-Au, and Pd-Pt systems.

    PubMed

    Rossi, Giulia; Ferrando, Riccardo; Rapallo, Arnaldo; Fortunelli, Alessandro; Curley, Benjamin C; Lloyd, Lesley D; Johnston, Roy L

    2005-05-15

    Genetic algorithm global optimization of Ag-Pd, Ag-Au, and Pd-Pt clusters is performed. The 34- and 38-atom clusters are optimized for all compositions. The atom-atom interactions are modeled by a semiempirical potential. All three systems are characterized by a small size mismatch and a weak tendency of the larger atoms to segregate at the surface of the smaller ones. As a result, the global minimum structures exhibit a larger mixing than in Ag-Cu and Ag-Ni clusters. Polyicosahedral structures present generally favorable energetic configurations, even though they are less favorable than in the case of the size-mismatched systems. A comparison between all the systems studied here and in the previous paper (on size-mismatched systems) is presented.

  17. Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al{sub 2}O{sub 3}(0001) substrates

    SciTech Connect

    Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

    2007-05-01

    Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al{sub 2}O{sub 3}(0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively.

  18. Alloying Solid Solution Strengthening of Fe-Ga Alloys: A First-Principle Study

    DTIC Science & Technology

    2006-01-01

    effect from alloying additions of Nb, Mo, V, Cr and Co in cubic solid solution of Fe-Ga alloys. Mayer bond order "BO" values were used to evaluate the...that transition metal Nb achieves the best strengthening effect in Fe-Ga alloys. The solid solution strengthening follows a trend from larger to

  19. The behavior of Gliclazide in solution and in the solid state: a case of organic compound presenting a solid-solution structure.

    PubMed

    Santa María, Dolores; Claramunt, Rosa M; Alkorta, Ibon; Elguero, José

    2009-06-01

    The structure of the hypoglycemic agent Gliclazide has been studied by (1)H, (13)C, and (15)N NMR in solution (CDCl(3) and DMSO-d(6)) and in the solid state. In the solid state, the compound crystallizes as an EZ isomer without dynamic properties. In CDCl(3) solution, the structure is still EZ but with a slow nitrogen inversion about the pyrrolidine nitrogen: two invertomers have been observed and characterized. In DMSO-d(6), the rate is faster and only averaged signals were observed. GIAO calculated absolute shieldings were used to confirm the nature of the observed species. In the solid state, Gliclazide presents the phenomenon of solid-solution with two disordered conformations present in the crystal at a 90:10 ratio.

  20. Investigation of droplet collisions for solutions with different solids content

    NASA Astrophysics Data System (ADS)

    Kuschel, Matthias; Sommerfeld, Martin

    2013-02-01

    The collision behaviour of droplets and the collision outcome are investigated for high viscous polymer solutions. For that purpose, two droplet chains produced by piezoelectric droplet generators are directed towards each other at a certain angle so that individual droplet pairs collide. For recording the collision event, one double-image and one high-speed CCD camera were used. One camera is positioned perpendicular to the collision plane recording the outcome of the collision, and the second camera is aligned parallel to the collision plane to assure that the droplet chains are exactly in one plane. A new approach for tracking droplets in combination with an extended particle tracking velocimetry algorithm has been developed. Time-resolved series of pictures were used to analyse the dynamics of droplet collisions. The three different water soluble substances were saccharose and 1-Ethenyl-2-pyrrolidone (PVP) with different molecular weights (K17, K30). The solvent was demineralised water. The solids contents ranged from 20 to 60 %, 5 to 25 % and 5 to 35 %, yielding dynamic viscosities in the range of 2-60 mPa s. Results were collected for different pairs of impact angles and Weber numbers in order to establish common collision maps for characterising the outcomes. Here, relative velocities between 0.5 and 4 m/s and impact parameters in the interval from 0 to 1 for equal-sized droplets (Δ = 1) have been investigated. Additionally, satellite formation will be discussed exemplarily for K30. A comparison with common models of different authors (Ashgriz and Poo in J Fluid Mech 221:183-204, 1990; Estrade et al. in Int J Heat Fluid Flow 20:486-491, 1999) mainly derived for low viscous droplets revealed that the upper limit of their validity is given by an Ohnesorge number of Oh = 0.115 and a capillary number of Ca = 0.577. For higher values of these non-dimensional parameters and hence higher dynamic viscosities, these models are unable to predict correctly the

  1. Solid solution, phase separation, and cathodoluminescence of GaP-ZnS nanostructures.

    PubMed

    Liu, Baodan; Bando, Yoshio; Dierre, Benjamin; Sekiguchi, Takashi; Golberg, Dmitri; Jiang, Xin

    2013-09-25

    Quaternary solid-solution nanowires made of GaP and ZnS have been synthesized through well-designed synthetic routines. The as-synthesized GaP-ZnS solid-solution nanowires exhibit decent crystallinity with the GaP phase as the host, while a large amount of twin structural defects are observed in ZnS-rich nanowires. Cathodoluminescence studies showed that GaP-rich solid-solution nanowires have a strong visible emission centered at 600 nm and the ZnS-rich solid-solution nanowires exhibited a weak emission peak in the UV range and a broad band in the range 400-600 nm. The formation mechanism, processes, and optical emissions of GaP-ZnS solid-solution nanowires were discussed in detail.

  2. Solid-solution aqueous-solution equilibria: thermodynamic theory and representation

    USGS Publications Warehouse

    Glynn, P.D.; Reardon, E.J.

    1990-01-01

    Thorstenson and Plummer's (1977) "stoichiometric saturation' model is reviewed, and a general relation between stoichiometric saturation Kss constants and excess free energies of mixing is derived for a binary solid-solution B1-xCxA: GE = RT[ln Kss - xln(xKCA) - (l-x)ln((l-x)KBA)]. This equation allows a suitable excess free energy function, such as Guggenheim's (1937) sub-regular function, to be fitted from experimentally determined Kss constants. Solid-phase free energies and component activity-coefficients can then be determined from one or two fitted parameters and from the endmember solubility products KBA and KCA. A general form of Lippmann's (1977,1980) "solutus equation is derived from an examination of Lippmann's (1977,1980) "total solubility product' model. Lippmann's ??II or "total solubility product' variable is used to represent graphically not only thermodynamic equilibrium states and primary saturation states but also stoichiometric saturation and pure phase saturation states. -from Authors

  3. Solid lipid nanoparticles suspension versus commercial solutions for dermal delivery of minoxidil.

    PubMed

    Padois, Karine; Cantiéni, Céline; Bertholle, Valérie; Bardel, Claire; Pirot, Fabrice; Falson, Françoise

    2011-09-15

    Solid lipid nanoparticles have been reported as possible carrier for skin drug delivery. Solid lipid nanoparticles are produced from biocompatible and biodegradable lipids. Solid lipid nanoparticles made of semi-synthetic triglycerides stabilized with a mixture of polysorbate and sorbitan oleate were loaded with 5% of minoxidil. The prepared systems were characterized for particle size, pH and drug content. Ex vivo skin penetration studies were performed using Franz-type glass diffusion cells and pig ear skin. Ex vivo skin corrosion studies were realized with a method derived from the Corrositex(®) test. Solid lipid nanoparticles suspensions were compared to commercial solutions in terms of skin penetration and skin corrosion. Solid lipid nanoparticles suspensions have been shown as efficient as commercial solutions for skin penetration; and were non-corrosive while commercial solutions presented a corrosive potential. Solid lipid nanoparticles suspensions would constitute a promising formulation for hair loss treatment.

  4. Evolution of mixed surfactant aggregates in solutions and at solid/solution interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Rui

    Surfactant systems have been widely used in such as enhanced oil recovery, waste treatment and metallurgy, etc., in order to solve the problem of global energy crisis, to remove the pollutants and to generate novel energy resources. Almost all surfactant systems are invariably mixtures due to beneficial and economic considerations. The sizes and shapes of aggregates in solutions and at solid/solution interfaces become important, since the nanostructures of mixed aggregates determine solution and adsorption properties. A major hurdle in science is the lack of information on the type of complexes and aggregates formed by mixtures and the lack of techniques for deriving such information. Using techniques such as analytical ultracentrifuge, small angle neutron scattering, surface tension, fluorescence, cryo-TEM, light scattering and ultrafiltration, the nanostructures of aggregates of sugar based n-dodecyl-beta-D-maltoside (DM) and nonionic pentaethyleneglycol monododecyl ether or nonyl phenol ethoxylated decyl ether (NP-10) and their mixtures have been investigated to prove the hypothesis that the aggregation behavior is linked to packing of the surfactant governed by the molecular interactions as well as the molecular structures. The results from both sedimentation velocity and sedimentation equilibrium experiments suggest coexistence of two types of micelles in nonyl phenol ethoxylated decyl ether solutions and its mixtures with n-dodecyl-beta-D-maltoside while only one micellar species is present in n-dodecyl-beta-D-maltoside solutions, in good agreement with those from small angle neutron scattering, cryo-TEM, light scattering and ultrafiltration. Type I micelles were primary micelles at cmc while type II micelles were elongated micelles. On the other hand, the nanostructures of mixed surface aggregates have been quantitatively predicted for the first time using a modified packing index. As a continuation of the Somasundaran-Fuersteneau adsorption model, a

  5. Kinetic analysis for formation of Cd1-xZnxSe solid-solution nanocrystals.

    PubMed

    Sung, Yun-Mo; Lee, Yong-Ji; Park, Kyung-Soo

    2006-07-19

    Kinetic analysis on the nanocrystal solid-solution formation was performed by heat treating CdSe/ZnSe core/shell nanocrystals, synthesized via a typical TOP/TOPO approach, at different temperatures for different time periods. X-ray diffraction (XRD) peak shifts in Cd1-xZnxSe cores according to the solid-solution treatments were monitored and used for the estimation of the lattice parameter change. The degree of solid-solution formation was determined considering the compositional variation in Cd1-xZnxSe cores, which was obtained from the Vegard's law. The degree of solid-solution formation (x) was applied to Jander analysis, and an Arrhenius-type plot was produced using the slopes of Jander plots. The activation energy for solid-solution formation was determined as approximately 152 kJ/mol, which evidently indicates that the diffusion of Zn2+ ions in the CdSe-ZnSe system is the governing mechanism for the Cd1-xZnxSe solid-solution formation. The Jander equation to predict the solid-solution formation kinetics for the CdSe/ZnSe core/shell systems was completed using the reaction rate constant (k).

  6. Synthesis of the bismuth oxyhalide solid solutions with tunable band gap and photocatalytic activities.

    PubMed

    Ren, Kuaixia; Liu, Jie; Liang, Jie; Zhang, Kun; Zheng, Xiao; Luo, Hongde; Huang, Yunbo; Liu, Pujun; Yu, Xibin

    2013-07-14

    Three series of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions were systematically synthesized through a low-temperature precipitation. These solid solutions were characterized by XRD, FESEM, TEM, EDS, UV-vis spectra, nitrogen sorption/desorption, and PL. The tunable band gaps of the as-prepared solid solutions were realized via only changing the molar ratio of two halide ions. Meanwhile, the influence of citric acid in the formations of controllable morphological structures was discussed to study the growth mechanism of solid solutions. The photocatalytic activities of the bismuth oxyhalide solid solutions have also been investigated by the degradation of Rhodamine-B (RhB) under visible light irradiation. The optimized solid solutions possess higher photocatalytic activity than pure ones [BiOM (M = Cl, Br, I)] due to the broadened range of visible light response and the reduced recombination rate of electron-holes pairs. The results show that the synthesis of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions have profound significance for the design of the novel photocatalyst materials.

  7. Analysis of solid solutions stability in scheelite-type molybdates and tungstates

    SciTech Connect

    Zhuravlev, V.D.; Reznitskikh, O.G.; Velikodnyi, Yu.A.; Patrusheva, T.A.; Sivtsova, O.V.

    2011-10-15

    Mutual solubility of bivalent metal molybdates and tungstates with scheelite structure was theoretically estimated by calculating formation enthalpies and the maximal decomposition temperatures of solid solutions at different temperatures. The theoretical stability of continuous solid solutions in binary systems of bivalent metal molybdates and tungstates was found to be higher than reported literature data. After cooling down continuous substitution solid solution should remain in following systems: CaMoO{sub 4}-CdMoO{sub 4}, SrMoO{sub 4}-MMoO{sub 4} (M=Ba, Pb), BaMoO{sub 4}-PbMoO{sub 4}, SrWO{sub 4}-MWO{sub 4} (M=Ca, Pb), and BaWO{sub 4}-PbWO{sub 4}. There is a probability that at room temperature in systems CaMoO{sub 4}-SrMoO{sub 4,} CaWO{sub 4}-PbWO{sub 4}, and BaWO{sub 4}-SrWO{sub 4} the single homogeneity region may decompose to limited solid solutions. It was shown experimentally that a continuous series of scheelite-structure solid solutions M{sub 1-x}M{sup I}{sub x}TO{sub 4} can be formed via citrate synthesis at temperatures below 500 deg. S. - Graphical abstract: Calculated boundaries of solid solutions in BaWO{sub 4}-CaWO{sub 4} (1) and PbMoO{sub 4}-CaMoO{sub 4} (2) systems. Highlights: > Stability of solid solutions molybdates and tungstates has been investigated. > The ionic model for isovalent substitutions was used. > In 'polyhedral substitution model' enthalphies of mixing were calculated. > Most of the examined series of solid solutions is stable at room temperatures. > Solid solutions M{sub 1-x}M{sup I}{sub x}Mo(W)O{sub 4} (x=0-1) were formed via citrate synthesis below 500 S.

  8. Investigation of compositional segregation during unidirectional solidification of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Wang, J. C.

    1982-01-01

    Compositional segregation of solid solution semiconducting alloys in the radial direction during unidirectional solidification was investigated by calculating the effect of a curved solid liquid interface on solute concentration at the interface on the solid. The formulation is similar to that given by Coriell, Boisvert, Rehm, and Sekerka except that a more realistic cylindrical coordinate system which is moving with the interface is used. Analytical results were obtained for very small and very large values of beta with beta = VR/D, where V is the velocity of solidification, R the radius of the specimen, and D the diffusivity of solute in the liquid. For both very small and very large beta, the solute concentration at the interface in the solid C(si) approaches C(o) (original solute concentration) i.e., the deviation is minimal. The maximum deviation of C(si) from C(o) occurs for some intermediate value of beta.

  9. Al and Zn Impurity Diffusion in Binary and Ternary Magnesium Solid-Solutions

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Magnesium alloys are considered for implementation into structural components where energy-efficiency and light-weighting are important. Two of the most common alloying elements in magnesium alloys are Aluminum and Zinc. The present work examines impurity diffusion coefficients of Al and Zn in Mg(Zn) and Mg(Al) binary solid solutions, respectively. Experimental investigation is carried out with ternary diffusion couples with polycrystalline alloys. Concentration profiles were measured by electron microprobe micro-analysis and the impurity diffusion coefficients were determined by the Hall Method. Results of Al and Zn impurity diffusion in Mg solid solutions are reported, and examined as a function of composition of Mg solid solution.

  10. The Effect of Hydrogen on the Solid Solution Strengthening and Softening of Nickel.

    DTIC Science & Technology

    1981-11-01

    Afl-A108 654e ILLINOIS UNIV AT URBANA DEPT OF METALLURGY AND MININS--ETC F/6 11/6 THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRFNSTNFNING ANfl...RESOLUTION TEST CHART NATIONAL HUR[AU OF STANDARDS 1963 A, " , ..... . .... .. i ....... .. .. . t , LEVEL THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING...Availability Codes IIAvail and/or Dist Special THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING AND SOFTENING OF NICKEL J. Eastman, F. Heuhaum, T

  11. Synthesis of (U,Zr)C solid solutions under exothermic conditions. Revision

    SciTech Connect

    Wang, Lily L.; Moore, H.G.; Gladson, J.W.

    1993-10-01

    The reactions of forming (U,Zr)C solid solutions from their elemental components or similarly less stable reactants such as UC{sub 2} are strongly exothermic due to the high stability of these solid solutions. A simple approach of utilizing this heat of formation energy to assist the solid solution reaction process is intimately mix the less stable reactant powders and pressed them into compact; the compact is then heated to the ignition temperature of the reaction. The feasibility of this reaction method to synthesize (U,Zr) solid solutions has been demonstrated in this study. The preliminary results also show that both the initial composition and the heating rate have a significant effect on the nature of the reaction process. As expected the degree of powder mixing was also found to affect the completeness of the reaction.

  12. Infrared Spectra of Simple Inorganic Ion Pairs in Solid Solution: A Physical Inorganic Chemistry Experiment.

    ERIC Educational Resources Information Center

    Miller, Philip J.; Tong, William G.

    1980-01-01

    Presents a physical inorganic experiment in which large single crystals of the alkali halides doped with divalent ion impurities are prepared easily. Demonstrates the ion pairing of inorganic ions in solid solution. (CS)

  13. THE ROLE OF ELECTRON CONFIGURATION ON PROPERTIES IN DILUTE SOLID SOLUTION ALLOYS

    DTIC Science & Technology

    THE ROLE OF ELECTRON CONFIGURATION ON THE PROPERTIES OF DILUTE SOLID SOLUTION ALLOYS IS DISCUSSED IN TERMS OF THE EFFECT OF DILUTE IMPURITIES ON THE RECRYSTALLIZATION CHARACTERISTICS OF PURE METALLIC ELEMENTS.

  14. Planet Patrol. An Educational Unit on Solid Waste Solutions for Grades 4-6.

    ERIC Educational Resources Information Center

    Shively, Patti J.; And Others

    This educational unit on solid waste solutions is intended to convey to students an understanding of the four methods of solid waste handling, in priority order, as recommended by the Environmental Protection Agency: (1) reduction in the volume of waste produced; (2) recycling and composting; (3) waste combustion, i.e., incineration of waste; and…

  15. CoSb3-IrSb3 solid solutions: preparation and characterization

    NASA Astrophysics Data System (ADS)

    Borshchevsky, Alex; Fleurial, Jean-Pierre; Allevato, Eugene; Caillat, Thierry

    1994-08-01

    The binary antimonide compounds of the skutterudite family have a good potential for thermoelectric applications as recent results at the Jet Propulsion Laboratory (JPL) have shown. However, the room temperature thermal conductivity of these materials is about 10 Wm-1K-1 with an estimated 80% contribution from the lattice. To achieve maximum ZT values, the lattice thermal conductivity needs to be lowered. Because the lattice thermal conductivity of solid solutions can substantially decrease due to the addition of point defect phonon scattering (all state of the art thermoelectric materials are solid solutions), a study of the formation of solid solutions between the antimonide skutterudite compounds is of interest. The existence of CoP3-CoAs3 and CoAs3-CoSb3 solid solutions was already reported in the literature. The preparation and characterization of both p-type and n-type CoSb3-IrSb3 solid solutions by several techniques is reviewed in this paper. The homogeneity of the samples and the existence of solid solutions were investigated using mass density measurements, X-ray diffractometry, microprobe analysis and optical microscopy. The thermal conductivity, the electrical resistivity, and the Hall mobility were measured from 25 to 500 °C. Experimental results showed that solid solutions were successfully formed in a wide range of compositions. Some immiscibility was observed but may be due to the preparation conditions. The changes in the thermoelectric properties indicated the influence of a strong point defect scattering, resulting in large decreases in Hall mobility and thermal conductivity. The potential for high ZT values in CoSb3-IrSb3 solid solutions is discussed.

  16. Superficial composition in binary solid solutions A(B): Drastic effect of pure element surface tensions

    NASA Astrophysics Data System (ADS)

    Rolland, A.; Aufray, B.

    1985-10-01

    This paper deals with a comparative study of surface segragation of Pb and Ni respectively from Ag(Pb)(111) and Ag(Ni)(111) solid solutions. A high level of segregation of the solute is observed for both systems characterized by very low solute solubility. However, the superficial composition strongly depends on the relative surface tensions of the pure elements: the solute atoms are strictly on superficial sites when γ solute is smaller than γ solvent; in contrast uppermost layer consists purely of solvent when γ solute is greater than γ solvent. Two schematic distributions in close proximity to the surface are proposed in the last case.

  17. Experimental study of loss mechanisms of AgAu/PbBi-2223 tapes with twisted filaments under perpendicular AC magnetic fields at power frequencies

    NASA Astrophysics Data System (ADS)

    Martínez, E.; Yang, Y.; Beduz, C.; Huang, Y. B.

    2000-05-01

    AC losses under perpendicular AC fields have been measured at 77 K and power frequencies for multifilamentary AgAu (10 wt.%)/Bi-2223 tapes with filaments twisted at different pitches. Using simultaneous measurements of the first and higher harmonics of the voltage induced in the pick-up coil, the main loss contributions (superconductor and coupling current losses) have been obtained separately. At power frequencies, twisting produces the desired uncoupling of the filaments at fields lower than the coupling field, which has also been determined experimentally. In the uncoupled-filament regime, the superconductor losses are reduced strongly with respect to the untwisted tapes. The reduction of the total loss with twisting is also observed. However, due to the important contribution of the coupling current losses for this field orientation, a very small pitch (<5 mm) is necessary for a considerably lower loss than that of untwisted tapes. The dependence of the coupling field and coupling current losses on the twist pitch has been analysed and compared with the theoretical predictions.

  18. Solid-solute phase equilibria in aqueous solution: VII. A re-interpretation of magnesian calcite stabilities

    NASA Astrophysics Data System (ADS)

    Königsberger, Erich; Gamsjäger, Heinz

    1992-11-01

    It is proposed to model magnesian calcites thermodynamically as dilute solid solutions of MgCO 3 in CaCO 3 according to the Unified Interaction Parameter Formalism ( BALE and PELTON, Met. Trans. A21A, 1997-2002, 1990). In this case both stoichiometric saturation and precipitation data of synthetic magnesian calcites taken from literature can consistently be explained.

  19. Oversolubility in the microvicinity of solid-solution interfaces.

    PubMed

    Bergonzi, Isabelle; Mercury, Lionel; Simon, Patrick; Jamme, Frédéric; Shmulovich, Kirill

    2016-06-01

    Water-solid interactions at the macroscopic level (beyond tens of nanometers) are often viewed as the coexistence of two bulk phases with a sharp interface in many areas spanning from biology to (geo)chemistry and various technological fields (membranes, microfluidics, coatings, etc.). Here we present experimental evidence indicating that such a view may be a significant oversimplification. High-resolution infrared and Raman experiments were performed in a 60 × 20 μm(2) quartz cavity, synthetically created and initially filled with demineralized water. The IR mapping (3 × 3 μm(2) beam size) performed using the SOLEIL synchrotron radiation source displays two important features: (i) the presence of a dangling free-OH component, a signature of hydrophobic inner walls; (ii) a shift of the OH-stretching band which essentially makes the 3200 cm(-1) sub-band predominate over the usual main component at around 3400 cm(-1). Raman maps confirmed these signatures (though less marked than IR's) and afforded a refined spatial distribution of this interfacial signal. This spatial resolution, statistically treated, results in a puzzling image of a 1-3 μm thick marked-liquid layer along the entire liquid-solid interface. The common view is then challenged by this strong evidence that a μm-thick layer analogous to an interphase forms at the solid-liquid interface. The thermodynamic counterpart of the vibrational shifts amounts to around +1 kJ mol(-1) at the interface with a rapidly decreasing signature towards the cavity centre, meaning that vicinal water may form a reactive layer, of micrometer thickness, expected to have an elevated melting point, a depressed boiling temperature, and enhanced solvent properties.

  20. Control of molecular rotor rotational frequencies in porous coordination polymers using a solid-solution approach.

    PubMed

    Inukai, Munehiro; Fukushima, Tomohiro; Hijikata, Yuh; Ogiwara, Naoki; Horike, Satoshi; Kitagawa, Susumu

    2015-09-30

    Rational design to control the dynamics of molecular rotors in crystalline solids is of interest because it offers advanced materials with precisely tuned functionality. Herein, we describe the control of the rotational frequency of rotors in flexible porous coordination polymers (PCPs) using a solid-solution approach. Solid-solutions of the flexible PCPs [{Zn(5-nitroisophthalate)x(5-methoxyisophthalate)1-x(deuterated 4,4'-bipyridyl)}(DMF·MeOH)]n allow continuous modulation of cell volume by changing the solid-solution ratio x. Variation of the isostructures provides continuous changes in the local environment around the molecular rotors (pyridyl rings of the 4,4'-bipyridyl group), leading to the control of the rotational frequency without the need to vary the temperature.

  1. The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation

    SciTech Connect

    Fleming, P.G.; Holmes, J.D.; Otway, D.J.; Morris, M.A.

    2011-09-15

    Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La{sub 2}O{sub 3} phase. - Graphical abstract: The suggested mechanism for the formation of dual fluorite phase particles, where Step 1 corresponds to room temperature aging, Step 2; heating the solution to 90 deg. C, Step 3; cooling of the solution to room temperature, Step 4; calcination to 500 deg. C, Step 5; calcination to 700 deg. C and Step 6; calcination to 1300 deg. C. The terminology of e.g. La{sub 1-x}Ce{sub x}(OH){sub 3} is used to indicate the formation of a mixed oxy-hydroxy participate rather than a definitive assignment of stoichiometry. Similarly, La{sub 1-y}Ce{sub y}O{sub 2} only implies a mixed solid solution. Highlights: > Mol% of prepared Ce-La oxides did not follow that of reactant mol%. > Complex reaction pathway found to be dependent on metal solution concentrations. > At certain concentrations core shell particles were found to form. > A reaction model was produced based on cationic solubility. > Report lanthana solubility higher than previously reported in CeO{sub 2}.

  2. Precipitation in Al–Mg solid solution prepared by solidification under high pressure

    SciTech Connect

    Jie, J.C.; Wang, H.W.; Zou, C.M.; Wei, Z.J.; Li, T.J.

    2014-01-15

    The precipitation in Al–Mg solid solution containing 21.6 at.% Mg prepared by solidification under 2 GPa was investigated. The results show that the γ-Al{sub 12}Mg{sub 17} phase is formed and the β′ phase cannot be observed in the solid solution during ageing process. The precipitation of γ and β phases takes place in a non-uniform manner during heating process, i.e. the γ and β phases are first formed in the interdendritic region, which is caused by the inhomogeneous distribution of Mg atoms in the solid solution solidified under high pressure. Peak splitting of X-ray diffraction patterns of Al(Mg) solid solution appears, and then disappears when the samples are aged at 423 K for different times, due to the non-uniform precipitation in Al–Mg solid solution. The direct transformation from the γ to β phase is observed after ageing at 423 K for 24 h. It is considered that the β phase is formed through a peritectoid reaction of α + γ → β which needs the diffusion of Mg atoms across the interface of α/γ phases. - Highlights: • The γ phase is formed and the β′ phase is be observed in Al(Mg) solid solution. • Peak splitting of XRD pattern of Al(Mg) solid solution appears during aged at 150 °C. • The β phase is formed through a peritectoid reaction of α + γ → β.

  3. Ab initio identified design principles of solid-solution strengthening in Al.

    PubMed

    Ma, Duancheng; Friák, Martin; von Pezold, Johann; Raabe, Dierk; Neugebauer, Jörg

    2013-04-01

    Solid-solution strengthening in six Al-X binary systems is investigated using first-principle methods. The volumetric mismatch parameter and the solubility enthalpy per solute were calculated. We derive three rules for designing solid-solution strengthened alloys: (i) the solubility enthalpy per solute is related to the volumetric mismatch by a power law; (ii) for each annealing temperature, there exists an optimal solute-volume mismatch to achieve maximum strength; and (iii) the strengthening potential of high volumetric mismatch solutes is severely limited by their low solubility. Our results thus show that the thermodynamic properties of the system (here Al-X alloys) set clear upper bounds to the achievable strengthening effects owing to the reduced solubility with increasing volume mismatch.

  4. Colloidal quantum dot solids for solution-processed solar cells

    NASA Astrophysics Data System (ADS)

    Yuan, Mingjian; Liu, Mengxia; Sargent, Edward H.

    2016-03-01

    Solution-processed photovoltaic technologies represent a promising way to reduce the cost and increase the efficiency of solar energy harvesting. Among these, colloidal semiconductor quantum dot photovoltaics have the advantage of a spectrally tuneable infrared bandgap, which enables use in multi-junction cells, as well as the benefit of generating and harvesting multiple charge carrier pairs per absorbed photon. Here we review recent progress in colloidal quantum dot photovoltaics, focusing on three fronts. First, we examine strategies to manage the abundant surfaces of quantum dots, strategies that have led to progress in the removal of electronic trap states. Second, we consider new device architectures that have improved device performance to certified efficiencies of 10.6%. Third, we focus on progress in solution-phase chemical processing, such as spray-coating and centrifugal casting, which has led to the demonstration of manufacturing-ready process technologies.

  5. Functional Ceramic Ferroelectromagnetic Materials in Single Phase Solid-Solutions

    DTIC Science & Technology

    2007-12-05

    materials of 99.9% purity ( Aldrich) ( Bi2O3 , La2O3, PbO, Fe2O3, TiO2) were weighed in a stochiometirc proportion and ball milled in acetone medium for...Aldrich) ( Bi2O3 , MgO, ZrO2, PbO, Fe2O3, TiO2) were weighed in a stochiometirc proportion and ball milled in acetone medium for 24 hours.The mixture...prepared using conventional solid- state reaction route. The raw materials of 99.9% purity ( Aldrich) ( Bi2O3 , La2O3, PbO, Fe2O3, TiO2) were weighed in a

  6. Surface Defects Enhanced Visible Light Photocatalytic H2 Production for Zn-Cd-S Solid Solution.

    PubMed

    Zhang, Xiaoyan; Zhao, Zhao; Zhang, Wanwan; Zhang, Guoqiang; Qu, Dan; Miao, Xiang; Sun, Shaorui; Sun, Zaicheng

    2016-02-10

    In order to investigate the defect effect on photocatalytic performance of the visible light photocatalyst, Zn-Cd-S solid solution with surface defects is prepared in the hydrazine hydrate. X-ray photoelectron spectra and photoluminescence results confirm the existence of defects, such as sulfur vacancies, interstitial metal, and Zn and Cd in the low valence state on the top surface of solid solutions. The surface defects can be effectively removed by treating with sulfur vapor. The solid solution with surface defect exhibits a narrower band gap, wider light absorption range, and better photocatalytic perfomance. The optimized solid solution with defects exhibits 571 μmol h(-1) for 50 mg photocatalyst without loading Pt as cocatalyst under visible light irradiation, which is fourfold better than that of sulfur vapor treated samples. The wavelength dependence of photocatalytic activity discloses that the enhancement happens at each wavelength within the whole absorption range. The theoretical calculation shows that the surface defects induce the conduction band minimum and valence band maximum shift downward and upward, respectively. This constructs a type I junction between bulk and surface of solid solution, which promotes the migration of photogenerated charges toward the surface of nanostructure and leads to enhanced photocatalytic activity. Thus a new method to construct highly efficient visible light photocatalysts is opened.

  7. Organic solid solution composed of two structurally similar porphyrins for organic solar cells.

    PubMed

    Zhen, Yonggang; Tanaka, Hideyuki; Harano, Koji; Okada, Satoshi; Matsuo, Yutaka; Nakamura, Eiichi

    2015-02-18

    A solid solution of a 75:25 mixture of tetrabenzoporphyrin (BP) and dichloroacenaphtho[q]tribenzo[b,g,l]porphyrin (CABP) forms when they are generated in a matrix of (dimethyl(o-anisyl)silylmethyl)(dimethylphenylsilylmethyl)[60]fullerene. This solid solution provides structural and optoelectronic properties entirely different from those of either pristine compounds or a mixture at other blending ratios. The use of this BP:CABP solid solution for organic solar cell (OSC) devices resulted in a power conversion efficiency (PCE) value higher by 16 and 300% than the PCE values obtained for the devices using the single donor BP and CABP, respectively, in a planar heterojunction architecture. This increase originates largely from the increase in short circuit current density, and hence by enhanced charge carrier separation at the donor/acceptor interface, which was probably caused by suitable energy level for the solid solution state, where electronic coupling between the two porphyrins occurred. The results suggest that physical and chemical modulation in solid solution is beneficial as an operationally simple method to enhance OSC performance.

  8. Tuning the Luminescent Properties of a Ag/Au Tetranuclear Complex Featuring Metallophilic Interactions via Solvent-Dependent Structural Isomerization.

    PubMed

    Donamaría, Rocío; Gimeno, M Concepción; Lippolis, Vito; López-de-Luzuriaga, José M; Monge, Miguel; Olmos, M Elena

    2016-11-07

    In this paper the reaction products of the basic gold(I) species [Au(C6Cl5)2](-) against the acid salt Ag(OClO3) in the presence of the S-donor macrocyclic ligand 1,4,7-trithiacyclononane ([9]aneS3) are studied in different solvents. Two different isomers of stoichiometry [{Au(C6Cl5)2}Ag([9]aneS3)]2 were isolated depending on the solvent used, dichloromethane or tetrahydrofuran, which show different luminescence in the solid state. X-ray diffraction studies of these compounds reveals that both show the same heteropolynuclear Ag···Au···Au···Ag system but with different Au···Au interaction distances and different relative positions of the cationic fragment [Ag([9]aneS3)](+) in the structure with respect the bimetallic Au···Au core. This work includes a study of the optical properties of both isomers, as well as time-dependent density functional theory calculations that were performed to determine the origin of their different luminescence.

  9. Regional setting and characteristics of the Neoproterozoic Wadi Hamama Zn-Cu-Ag-Au prospect: evidence for an intra-oceanic island arc-hosted volcanogenic hydrothermal system

    NASA Astrophysics Data System (ADS)

    Abd El-Rahman, Yasser; Surour, Adel A.; El-Manawi, Abdel Hamid W.; El-Dougdoug, Abdel-Monem A.; Omar, Sayed

    2015-04-01

    The Wadi Hamama area is a volcanogenic Zn-Cu-Au-Ag prospect. It is hosted by a Neoproterozoic bimodal-mafic sequence, which comprises basalt, dacite and rhyolite along with volcaniclastic rocks. The rocks have a low-K tholeiitic affinity and are enriched in large ion lithophile elements over high field strength elements, which indicated their formation in an intra-oceanic island arc tectonic setting. The area was intruded by a tonalite-trondhjemite body, which has an intra-oceanic island arc affinity and later by diorite, which has a cordilleran-margin geochemical affinity. These rock units were intruded by post-tectonic granite dykes, which have a within-plate geochemical signature. There is a quartz-carbonate horizon extending along the contact between the basalt and the volcaniclastic rocks, mainly banded and lapilli tuffs. This horizon is of exhalative origin and is underlain by a mushroom-shaped alteration zone extending from the horizon down to the massive basalt. The footwall alteration is characterized by a silica-rich core surrounded by a thick chlorite sheath. Both the quartz-carbonate horizon and the footwall-altered rocks enclose historical trenches and pits. Sulfide-rich core samples are enriched in Zn, relative to Cu, and in Ag, which indicates the low-temperature nature of the hydrothermal system. The prospect was affected by supergene processes, which led to the widespread occurrence of secondary copper minerals and gold enrichment relative to the leached base metals, especially Zn. The prospect formed through a limited rifting of an intra-oceanic island arc which resulted in the formation of a small-scale volcanogenic Zn-Cu-Ag-Au prospect.

  10. Charge distribution and local structure of americium-bearing thorium oxide solid solutions.

    PubMed

    Carvajal-Nunez, U; Prieur, D; Vitova, T; Somers, J

    2012-11-05

    The electronical and structural properties of Th(0.80)Am(0.20)O(2-x) materials have been studied by the coupling of X-ray diffraction and X-ray absorption spectroscopy techniques. A substoichiometric fluorite Th(IV)(0.80)Am(III)(0.20)O(1.90) solid solution is found following sintering in moisturized Ar-H(2). In contrast, heating of this sample in air leads to a nondefective fluorite Th(IV)(0.80)Am(IV)(0.20)O(2.00) solid solution. The structures of these solid solution compounds were fully characterized by assessing the interatomic distances, the coordination numbers, and the structural disorder. The effect of the sintering atmosphere on these crystallographical parameters and on the cation valences has been determined and the capability of ThO(2) to accommodate tri- and tetravalent actinides in the fluorite structure assessed.

  11. Visualization of the atomic structure of solid solutions with the NaCl structure

    NASA Astrophysics Data System (ADS)

    Babanov, Yu. A.; Ponomarev, D. A.; Ustinov, V. V.

    2015-04-01

    It has been shown how an atomic cluster for a solid solution with a rock salt structure can be constructed using the Pauling model. Simulation has been performed for 343000 ions of Ni x Zn1 - x O3 ( x = 0, 0.3, 0.5, 0.7, 1.0) oxide substitutional solid solutions. Coordinates of all cluster ions are obtained and distribution functions of ion pairs (Ni-O, Ni-Ni, Ni-Zn, Zn-Zn, Zn-O, O-O) are constructed as functions of distance. The shape of the normal distribution indicates the existence of bounded chaos in the system of oxide solid solutions. The width of the Gaussian distribution function is determined by the difference of metal ionic radii. The results are in agreement with both X-ray diffraction and EXAFS spectroscopy data.

  12. Isotope Labeling for Solution and Solid-State NMR Spectroscopy of Membrane Proteins

    PubMed Central

    Verardi, Raffaello; Traaseth, Nathaniel J.; Masterson, Larry R.; Vostrikov, Vitaly V.; Veglia, Gianluigi

    2013-01-01

    In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578

  13. Catalytic properties of nanoscale iron-doped zirconia solid-solution aerogels.

    PubMed

    Chen, Lifang; Hu, Juncheng; Richards, Ryan M

    2008-05-16

    Nanoscale iron-doped zirconia solid-solution aerogels are prepared via a simple ethanol thermal route using zirconyl nitrate and iron nitrate as starting materials, followed by a supercritical fluid drying process. Structural characteristics are investigated by means of powder X-ray diffraction (XRD), thermal analyses (TG/DTA), N(2) adsorption measurements and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the resulting iron-doped solid solutions are metastable tetragonal zirconia which exhibit excellent dispersibility and high solubility of iron oxide. Further, when the Fe:(Fe+Zr) ratio x is lower than 0.10, all of the Fe(3+) ions can be incorporated into ZrO(2) by substituting Zr(4+) to form Zr(1-) (x)Fe(x)O(y) solid solutions. Moreover, for the first time, an additional hydroxyl group band that is not present in pure ZrO(2) is observed by DRIFTS for the Zr(Fe)O(2) solid solution. This is direct evidence of Fe(3+) ions incorporated into ZrO(2). These Zr(1-) (x)Fe(x)O(y) solid solutions are excellent catalysts for the solvent-free aerobic oxidation of n-hexadecane using air as the oxidant under ambient conditions. The Zr(0.8)Fe(0.2)O(y) solid-solution catalyst demonstrates the best catalytic properties, with the conversion of n-hexadecane reaching 36.2 % with 48 % selectivity for ketones and 24 % selectivity for alcohols and it can be recycled five times without significant loss of activity.

  14. Crystal Chemistry of MgAl2O4 Spinel Solid Solution

    NASA Astrophysics Data System (ADS)

    Yoshiasa, Akira; Maekawa, Hidemi; Sugiyama, Kazumasa

    Considerable efforts have been devoted to the structural studies of spinel group minerals or type compounds because of their importance as constituents of the Earth’s crust and mantle. Despite their simple structures, many spinel type compounds exhibit complex disordering phenomena involving the mixing of cation on two sites, which have important consequences for both thermodynamic and physical properties. The cation distributions and the structural variation in MgAl2-xGaxO4 solid-solution have been clarified using 27Al MAS NMR measurements and single crystal X-ray diffraction. The determined local distance in the solid solution corresponds with the bond distance expected from the effective ionic radii except Al-O distance in the tetrahedral site. We have revealed that the Al-O distance in the tetrahedral site in spinel solid solution is about 0.15 Å longer than the expected value. Boron is the same group element as Al and Ga and its ionic radius is considerably small. Single crystals of MgAl2-xBxO4 spinel were synthesized under high pressure and high temperature. The maximum content of boron was about x = 0.13 at 1273 K and 11 GPa. The smallest B ion occupies the octahedral site in top priority in the spinel solid solution of the Mg-Al-B systems. The B3+ ions can replace considerably bigger Al3+ ion under pressure. These spinel solid-solutions are largely disordered crystals. Only the positional shifts of oxygen ion have been relaxing the disorder in the solid solution.

  15. Ferroelectromagnetic solid solutions on the base piezoelectric ceramic materials for components of micromechatronics

    NASA Astrophysics Data System (ADS)

    Bochenek, Dariusz; Zachariasz, Radosław; Niemiec, Przemysław; Ilczuk, Jan; Bartkowska, Joanna; Brzezińska, Dagmara

    2016-10-01

    In the presented work, a ferroelectromagnetic solid solutions based on PZT and ferrite powders have been obtained. The main aim of combination of ferroelectric and magnetic powders was to obtain material showing both electric and magnetic properties. Ferroelectric ceramic powder (in amount of 90%) was based on the doped PZT type solid solution while magnetic component was nickel-zinc ferrite Ni1-xZnxFe2O4 (in amount of 10%). The synthesis of components of ferroelectromagnetic solid solutions was performed using the solid phase sintering. Final densification of synthesized powder has been done using free sintering. The aim of the work was to obtain and examine in the first multicomponent PZT type ceramics admixed with chromium with the following chemical composition Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3 and next ferroelectromagnetic solid solution based on a PZT type ferroelectric powder (Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3) and nickel-zinc ferrite (Ni0.64Zn0.36Fe2O4), from the point of view of their mechanical and electric properties, such as: electric permittivity, ε; dielectric loss, tanδ; mechanical losses, Q-1; and Young modulus, E.

  16. Controlled Living Nanowire Growth: Precise Control over the Morphology and Optical Properties of AgAuAg Bimetallic Nanowires.

    PubMed

    Mayer, Martin; Scarabelli, Leonardo; March, Katia; Altantzis, Thomas; Tebbe, Moritz; Kociak, Mathieu; Bals, Sara; García de Abajo, F Javier; Fery, Andreas; Liz-Marzán, Luis M

    2015-08-12

    Inspired by the concept of living polymerization reaction, we are able to produce silver-gold-silver nanowires with a precise control over their total length and plasmonic properties by establishing a constant silver deposition rate on the tips of penta-twinned gold nanorods used as seed cores. Consequently, the length of the wires increases linearly in time. Starting with ∼210 nm × 32 nm gold cores, we produce nanowire lengths up to several microns in a highly controlled manner, with a small self-limited increase in thickness of ∼4 nm, corresponding to aspect ratios above 100, whereas the low polydispersity of the product allows us to detect up to nine distinguishable plasmonic resonances in a single colloidal solution. We analyze the spatial distribution and the nature of the plasmons by electron energy loss spectroscopy and obtain excellent agreement between measurements and electromagnetic simulations, clearly demonstrating that the presence of the gold core plays a marginal role, except for relatively short wires or high-energy modes.

  17. Controlled Living Nanowire Growth: Precise Control over the Morphology and Optical Properties of AgAuAg Bimetallic Nanowires

    PubMed Central

    2015-01-01

    Inspired by the concept of living polymerization reaction, we are able to produce silver–gold–silver nanowires with a precise control over their total length and plasmonic properties by establishing a constant silver deposition rate on the tips of penta-twinned gold nanorods used as seed cores. Consequently, the length of the wires increases linearly in time. Starting with ∼210 nm × 32 nm gold cores, we produce nanowire lengths up to several microns in a highly controlled manner, with a small self-limited increase in thickness of ∼4 nm, corresponding to aspect ratios above 100, whereas the low polydispersity of the product allows us to detect up to nine distinguishable plasmonic resonances in a single colloidal solution. We analyze the spatial distribution and the nature of the plasmons by electron energy loss spectroscopy and obtain excellent agreement between measurements and electromagnetic simulations, clearly demonstrating that the presence of the gold core plays a marginal role, except for relatively short wires or high-energy modes. PMID:26134470

  18. Structural and magnetic properties of mechanically alloyed Co 20Cu 80 solid solution

    NASA Astrophysics Data System (ADS)

    Yoo, Y. G.; Yang, D. S.; Yu, S. C.; Kim, W. T.; M. Lee, J.

    1999-08-01

    Microstructural change during the mechanical alloying of Co 20Cu 80 has been studied by X-ray diffractometry (XRD) and extended X-ray absorption fine structure (EXAFS) techniques. EXAFS analysis shows clearly the formation of supersaturated Co 20Cu 80 solid solution with FCC crystal structure during mechanical alloying, which is in good agreement with XRD analysis. Magnetic properties also have been studied by SQUID magnetometer from 4 to 290 K. The supersaturated Co 20Cu 80 solid solution shows wide distribution in Co cluster size due to the continuous blocking of Co cluster as a function of temperature.

  19. Exciton mobility edge in CdS 1-xSe x solid solutions

    NASA Astrophysics Data System (ADS)

    Permogorov, S.; Reznitsky, A.; Verbin, S.; Lysenko, V.

    1983-07-01

    Low temperature emission spectra of localized excitons in CdS 1-xSe x solid solutions under the monochromatic excitation with tunable laser have been studied. It has been found that the luminescence of localized excitons has a high degree of linear polarization with respect to the polarization direction of exciting light. This polarization reflects the "hidden" anisotropy of macroscopically isotropic localized exciton system and strongly depends on the frequency of exciting light. Study of this dependence has permitted for the first time a determination of position of the "mobility edge" for exciton migration in disordered semiconductor solid solution.

  20. Magnetism and Solid Solution Effects in NiAI (40% AI) Alloys

    SciTech Connect

    Liu, Chain T; Fu, Chong Long; Chisholm, Matthew F; Thompson, James R; Krcmar, Maja; Wang, Xun-Li

    2007-01-01

    The solid solution effects of ternary additions of transition elements in intermetallic Ni-40% Al were investigated by both experimental studies and theoretical calculations. Co solute atoms when sitting at Ni sublattice sites do not affect the lattice parameter and hardening behavior of Ni-40Al. On the other hand, Fe, Mn, and Cr solutes, which are mainly on Al sublattice sites, substantially expand the lattice parameter and produce an unusual solid solution softening effect. First-principles calculations predict that these solute atoms with large unfilled d-band electrons develop large magnetic moments and effectively expand the lattice parameter when occupying Al sublattice sites. The theoretical predictions were verified by both electron loss-energy spectroscopy (EELS) analyses and magnetic susceptibility measurements. The observed softening behavior can be explained quantitatively by the replacement of Ni anti-site defects (potent hardeners) by Fe, Mn, and Cr anti-site defects with smaller atom size mismatch between solute and Al atoms. This study has led to the identification of magnetic interaction as an important physical parameter affecting the solid solution hardening in intermetallic alloys containing transition elements.

  1. Activities of the components in a spinel solid solution of the Fe-Al-O system

    NASA Astrophysics Data System (ADS)

    Lykasov, A. A.; Kimyashev, A. A.

    2011-09-01

    The conditions of the equilibrium between the Fe3O4-FeAl2O4 solution and wustite are determined by measuring the EMF of galvanic cells containing a solid electrolyte, and the activities of the components in the Fe3O4-FeAl2O4 solution are calculated by treating the results of the experiment on the equilibrium between the spinel solution and wustite. Their properties are found to be different from those of ideal solutions at temperatures of 1000-1300 K. A significant positive deviation from the Raoult's law is believed to indicate the tendency of the solution to decompose. The experimental data are treated in terms of the theory of regular solutions, assuming the energy of mixing to be a function of temperature only. The critical temperature of decomposition for the Fe3O4-FeAl2O4 solution is found to be 1084 K.

  2. First-principles investigation of solute-hydrogen interaction in a α-Ti solid solution

    NASA Astrophysics Data System (ADS)

    Hu, Q. M.; Xu, D. S.; Yang, R.; Li, D.; Wu, W. T.

    2002-08-01

    In this paper, a first-principles method is used to calculate the interaction energy between substitutional solute atoms and hydrogen in α-Ti. The results show that simple metal (SM) solute atoms are repulsive to H and therefore are detraps for H, whereas transition metal (TM) solute atoms, with smaller sizes than that of the host atoms, attract H and provide traps for H. The relationship between the interaction energy and lattice distortion as well as the electronic structure is investigated. The SM-H and TM-H interactions are dominated by different factors. The repulsive interaction between SM atoms and H is mainly due to the hybridization between the electrons of SM atoms and H when they are close to each other. The interaction between the TM solutes and H is attributable to the atomic size effect, and can be described satisfactorily by Matsumoto's strain field relaxation model. From the solute-H interaction energy and available measured terminal solubility of hydrogen (TSH), the relationship between the solute trapping of hydrogen and TSH in α-Ti is discussed. No coherent relationship is found between the theoretical hydrogen trapping effect and the experimental TSH in α-Ti alloys.

  3. REMOVAL OF SOLIDS FROM HIGHLY ENRICHED URANIUM SOLUTIONS USING THE H-CANYON CENTRIFUGE

    SciTech Connect

    Rudisill, T; Fernando Fondeur, F

    2009-01-15

    Prior to the dissolution of Pu-containing materials in HB-Line, highly enriched uranium (HEU) solutions stored in Tanks 11.1 and 12.2 of H-Canyon must be transferred to provide storage space. The proposed plan is to centrifuge the solutions to remove solids which may present downstream criticality concerns or cause operational problems with the 1st Cycle solvent extraction due to the formation of stable emulsions. An evaluation of the efficiency of the H-Canyon centrifuge concluded that a sufficient amount (> 90%) of the solids in the Tank 11.1 and 12.2 solutions will be removed to prevent any problems. We based this conclusion on the particle size distribution of the solids isolated from samples of the solutions and the calculation of particle settling times in the centrifuge. The particle size distributions were calculated from images generated by scanning electron microscopy (SEM). The mean particle diameters for the distributions were 1-3 {micro}m. A significant fraction (30-50%) of the particles had diameters which were < 1 {micro}m; however, the mass of these solids is insignificant (< 1% of the total solids mass) when compared to particles with larger diameters. It is also probable that the number of submicron particles was overestimated by the software used to generate the particle distribution due to the morphology of the filter paper used to isolate the solids. The settling times calculated for the H-Canyon centrifuge showed that particles with diameters less than 1 to 0.5 {micro}m will not have sufficient time to settle. For this reason, we recommend the use of a gelatin strike to coagulate the submicron particles and facilitate their removal from the solution; although we have no experimental basis to estimate the level of improvement. Incomplete removal of particles with diameters < 1 {micro}m should not cause problems during purification of the HEU in the 1st Cycle solvent extraction. Particles with diameters > 1 {micro}m account for > 99% of the

  4. Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State.

    PubMed

    Reddy, G N Manjunatha; Huqi, Aida; Iuga, Dinu; Sakurai, Satoshi; Marsh, Andrew; Davis, Jeffery T; Masiero, Stefano; Brown, Steven P

    2017-02-16

    The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet-based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H⋅⋅⋅N and N-H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D (1) H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible-further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K(+) , Sr(2+) ) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase.

  5. Interdiffusion and impurity diffusion in polycrystalline Mg solid solution with Al or Zn

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Interdiffusion and impurity diffusion in Mg binary solid solutions, Mg(Al) and Mg(Zn) were investigated at temperatures ranging from 623 to 723 K. Interdiffusion coef cients were determined via the Boltzmann Matano Method using solid-to-solid diffusion couples assembled with polycrystalline Mg and Mg(Al) or Mg(Zn) solid solutions. In addition, the Hall method was employed to extrapolate the impurity diffusion coef cients of Al and Zn in pure polycrystalline Mg. For all diffusion couples, electron micro-probe analysis was utilized for the measurement of concentration pro les. The interdiffusion coef cient in Mg(Zn) was higher than that of Mg(Al) by an order of magnitude. Additionally, the interdiffusion coef cient increased signi cantly as a function of Al content in Mg(Al) solid solution, but very little with Zn content in Mg(Zn) solid solution. The activation energy and pre-exponential factor for the average effective interdiffusion coef cient in Mg(Al) solid solution were determined to be 186.8 ( 0.9) kJ/mol and 7.69 x 10-1 ( 1.80 x 10-1) m2/s, respectively, while those determined for Mg(Zn) solid solution were 139.5 ( 4.0) kJ/mol and 1.48 x 10-3 ( 1.13 x 10-3) m2/s. In Mg, the Zn impurity diffusion coef cient was an order of magnitude higher than the Al impurity diffusion coef cient. The activation energy and pre-exponential factor for diffusion of Al impurity in Mg were determined to be 139.3 ( 14.8) kJ/mol and 6.25 x 10-5 ( 5.37 x 10-4) m2/s, respectively, while those for diffusion of Zn impurity in Mg were determined to be 118.6 ( 6.3) kJ/mol and 2.90 x 10-5 ( 4.41 x 10-5) m2/s.

  6. Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

    DOE PAGES

    Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; ...

    2016-01-01

    We investigate Irradiation-induced damage accumulation in Ni0.8Fe0.2 and Ni0.8Cr0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

  7. Preparation and Analysis of Solid Solutions in the Potassium Perchlorate-Permanganate System.

    ERIC Educational Resources Information Center

    Johnson, Garrett K.

    1979-01-01

    Describes an experiment, designed for and tested in an advanced inorganic laboratory methods course for college seniors and graduate students, that prepares and analyzes several samples in the nearly ideal potassium perchlorate-permanganate solid solution series. The results are accounted for by a theoretical treatment based upon aqueous…

  8. Thermal transport properties of halide solid solutions: Experiments vs equilibrium molecular dynamics

    NASA Astrophysics Data System (ADS)

    Gheribi, Aïmen E.; Salanne, Mathieu; Chartrand, Patrice

    2015-03-01

    The composition dependence of thermal transport properties of the (Na,K)Cl rocksalt solid solution is investigated through equilibrium molecular dynamics (EMD) simulations in the entire range of composition and the results are compared with experiments published in recent work [Gheribi et al., J. Chem. phys. 141, 104508 (2014)]. The thermal diffusivity of the (Na,K)Cl solid solution has been measured from 473 K to 823 K using the laser flash technique, and the thermal conductivity was deduced from critically assessed data of heat capacity and density. The thermal conductivity was also predicted at 900 K in the entire range of composition by a series of EMD simulations in both NPT and NVT statistical ensembles using the Green-Kubo theory. The aim of the present paper is to provide an objective analysis of the capability of EMD simulations in predicting the composition dependence of the thermal transport properties of halide solid solutions. According to the Klemens-Callaway [P. G. Klemens, Phys. Rev. 119, 507 (1960) and J. Callaway and H. C. von Bayer, Phys. Rev. 120, 1149 (1960)] theory, the thermal conductivity degradation of the solid solution is explained by mass and strain field fluctuations upon the phonon scattering cross section. A rigorous analysis of the consistency between the theoretical approach and the EMD simulations is discussed in detail.

  9. Linear structural evolution induced tunable photoluminescence in clinopyroxene solid-solution phosphors.

    PubMed

    Xia, Zhiguo; Zhang, Yuanyuan; Molokeev, Maxim S; Atuchin, Victor V; Luo, Yi

    2013-11-22

    Clinopyroxenes along the Jervisite (NaScSi2O6)-Diopside (CaMgSi2O6) join have been studied, and a solid-solution of the type (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 has been identified in the full range of 0 ≤ x ≤ 1. The powder X-ray patterns of all the phases indicate a structural similarity to the end compounds and show smooth variation of structural parameters with composition. The linear structural evolution of iso-structural (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 solid-solutions obeying Vegard's rule has also been examined and verified by high resolution transmission electron microscopy (HRTEM). The continuous solid-solutions show the same structural type, therefore the photoluminescence spectra of Eu(2+) doped samples possess the superposition of spectral features from blue-emitting component (CaMgSi2O6:Eu(2+)) and yellow-emitting one (NaScSi2O6:Eu(2+)). This indicates that the spectroscopic properties of (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 clinopyroxene solid-solutions are in direct relations with structural parameters, and it is helpful for designing color-tunable photoluminescence with predetermined parameters.

  10. Magnetic properties of solid solutions based on UFe 10Si 2

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Andreev, A. V.; Shiokawa, Y.; Miyashita, J.

    2002-04-01

    Magnetization of interstitial (UFe 10Si 2C x) and substitution (U 1- xR xFe 10Si 2, R=Nd, Er) solid solutions based on UFe 10Si 2 has been studied as a function of magnetic field and temperature on aligned powders. The results point to the considerable contribution of the U sublattice to the magnetic anisotropy.

  11. Thermal transport properties of halide solid solutions: Experiments vs equilibrium molecular dynamics

    SciTech Connect

    Gheribi, Aïmen E. Chartrand, Patrice; Salanne, Mathieu

    2015-03-28

    The composition dependence of thermal transport properties of the (Na,K)Cl rocksalt solid solution is investigated through equilibrium molecular dynamics (EMD) simulations in the entire range of composition and the results are compared with experiments published in recent work [Gheribi et al., J. Chem. phys. 141, 104508 (2014)]. The thermal diffusivity of the (Na,K)Cl solid solution has been measured from 473 K to 823 K using the laser flash technique, and the thermal conductivity was deduced from critically assessed data of heat capacity and density. The thermal conductivity was also predicted at 900 K in the entire range of composition by a series of EMD simulations in both NPT and NVT statistical ensembles using the Green-Kubo theory. The aim of the present paper is to provide an objective analysis of the capability of EMD simulations in predicting the composition dependence of the thermal transport properties of halide solid solutions. According to the Klemens-Callaway [P. G. Klemens, Phys. Rev. 119, 507 (1960) and J. Callaway and H. C. von Bayer, Phys. Rev. 120, 1149 (1960)] theory, the thermal conductivity degradation of the solid solution is explained by mass and strain field fluctuations upon the phonon scattering cross section. A rigorous analysis of the consistency between the theoretical approach and the EMD simulations is discussed in detail.

  12. Exact Solution of the Two-Level System and the Einstein Solid in the Microcanonical Formalism

    ERIC Educational Resources Information Center

    Bertoldi, Dalia S.; Bringa, Eduardo M.; Miranda, E. N.

    2011-01-01

    The two-level system and the Einstein model of a crystalline solid are taught in every course of statistical mechanics and they are solved in the microcanonical formalism because the number of accessible microstates can be easily evaluated. However, their solutions are usually presented using the Stirling approximation to deal with factorials. In…

  13. Hydrogen-storage properties of solid-solution alloys of immiscible neighboring elements with Pd.

    PubMed

    Kusada, Kohei; Yamauchi, Miho; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Kubota, Yoshiki

    2010-11-17

    Rh and Ag are the elements neighboring Pd, which is well known as a hydrogen-storage metal. Although Rh and Ag do not possess hydrogen-storage properties, can Ag-Rh alloys actually store hydrogen? Ag-Rh solid-solution alloys have not been explored in the past because they do not mix with each other at the atomic level, even in the liquid phase. We have used the chemical reduction method to obtain such Ag-Rh alloys, and XRD and STEM-EDX give clear evidence that the alloys mixed at the atomic level. From the measurements of hydrogen pressure-composition isotherms and solid-state (2)H NMR, we have revealed that Ag-Rh solid-solution alloys absorb hydrogen, and the total amount of hydrogen absorbed reached a maximum at the ratio of Ag:Rh = 50:50, where the electronic structure is expected to be similar to that of Pd.

  14. The synthesis and chemical durability of Nd-doped single-phase zirconolite solid solutions

    NASA Astrophysics Data System (ADS)

    Cai, Xin; Teng, Yuancheng; Wu, Lang; Zhang, Kuibao; Huang, Yi

    2016-10-01

    Nd-doped single-phase zirconolite solid solutions was synthesized by solid-state reaction and following two steps of acid treatment. The phase composition, microstructure, and chemical durability of the zirconolite solid solutions were investigated. About 15 at% Nd was successfully stabilized into the zirconolite. The element mapping images of Ca, Zr, Nd and Ti show that all the elements are almost distributed homogeneously in the zirconolite waste forms. Product Consistency Test (PCT) was conducted under different pH values (pH = 5, 7 and 9) to evaluate the chemical durability of the Nd-doped zirconolite waste forms. The normalized element release rate of Ca (LRCa) in pH = 5 medium is higher than that of pH = 7 and 9, while the LRNd value remains almost unchanged under different pH values. The LRNd value is as low as 10-5 g m-2 d-1 after 42 days.

  15. Electrocatalytic hydrogenation of 5-hydroxymethylfurfural in acidic solution.

    PubMed

    Kwon, Youngkook; Birdja, Yuvraj Y; Raoufmoghaddam, Saeed; Koper, Marc T M

    2015-05-22

    Electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) is studied on solid metal electrodes in acidic solution (0.5 M H2 SO4 ) by correlating voltammetry with on-line HPLC product analysis. Three soluble products from HMF hydrogenation are distinguished: 2,5-dihydroxymethylfuran (DHMF), 2,5-dihydroxymethyltetrahydrofuran (DHMTHF), and 2,5-dimethyl-2,3-dihydrofuran (DMDHF). Based on the dominant reaction products, the metal catalysts are divided into three groups: (1) metals mainly forming DHMF (Fe, Ni, Cu, and Pb), (2) metals forming DHMF and DMDHF depending on the applied potentials (Co, Ag, Au, Cd, Sb, and Bi), and (3) metals forming mainly DMDHF (Pd, Pt, Al, Zn, In, and Sb). Nickel and antimony are the most active catalysts for DHMF (0.95 mM cm(-2) at ca. -0.35 VRHE and -20 mA cm(-2) ) and DMDHF (0.7 mM cm(-2) at -0.6 VRHE and -5 mA cm(-2) ), respectively. The pH of the solution plays an important role in the hydrogenation of HMF: acidic condition lowers the activation energy for HMF hydro-genation and hydrogenates the furan ring further to tetrahydrofuran.

  16. Different routes towards oscillatory zoning in the growth of solid solutions.

    PubMed

    Lubashevsky, Ihor; Mues, Tanja; Heuer, Andreas

    2008-10-01

    Oscillatory zoning, i.e., self-formation of spatial quasiperiodic oscillations in the composition of solid growing from aqueous solution, is analyzed theoretically. Keeping in mind systems like (Ba,Sr)SO4 , we propose a one-dimensional model that takes into account the nonideality of the solid solution and the system asymmetry, in particular, reflecting itself in different solubilities for such systems. Based on a linear stability analysis, different parameter regions can be identified. Even an ideal solution with a sufficiently large asymmetry can display oscillatory zoning. Numerical simulations complement the linear stability analysis as well as the qualitative consideration of the instability development and reveal the nature of the limit cycles.

  17. Thermodynamic considerations in solid adsorption of bound solutes for patient support in liver failure.

    PubMed

    Patzer, John F

    2008-07-01

    New detoxification modes of treatment for liver failure that use solid adsorbents to remove toxins bound to albumin in the patient bloodstream are entering clinical evaluations, frequently in head-to-head competition. While generally effective in reducing toxin concentration beyond that obtainable by conventional dialysis procedures, the solid adsorbent processes are largely the result of heuristic development. Understanding the principles and limitations inherent in competitive toxin binding, albumin versus solid adsorbent, will enhance the design process and, possibly, improve detoxification performance. An equilibrium thermodynamic analysis is presented for both the molecular adsorbent recirculating system (MARS) and fractionated plasma separation, adsorption, and dialysis system (Prometheus), two advanced systems with distinctly different operating modes but with similar equilibrium limitations. The Prometheus analysis also applies to two newer approaches: sorbent suspension reactor and microsphere-based detoxification system. Primary results from the thermodynamic analysis are that: (i) the solute-albumin binding constant is of minor importance to equilibrium once it exceeds about 10(5) L/mol; (ii) the Prometheus approach requires larger solid adsorbent columns than calculated by adsorbent solute capacity alone; and (iii) the albumin-containing recycle stream in the MARS approach is a major reservoir of removed toxin. A survey of published results indicates that MARS is operating under mass transfer control dictated by solute-albumin equilibrium in the recycle stream, and Prometheus is approaching equilibrium limits under current clinical protocols.

  18. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple formula for the thermal conductivity of a quaternary solid solution

    NASA Astrophysics Data System (ADS)

    Nakwaski, W.

    1988-11-01

    An analysis is made of the thermal conductivity of quaternary solid solutions (alloys) allowing for their disordered structure on the basis of a phenomenological analysis proposed by Abeles. This method is applied to a quaternary solid solution In1 - xGaxAsyP1 - y. A simple analytic expression is derived for the thermal conductivity of this material.

  19. Study of Decomposition of a Highly Supersaturated Solid Solution of a Granulated Alloy, Al-1, 5Cr-1, 5Zr,

    DTIC Science & Technology

    The mechanism and kinetics of decomposition of a highly supersaturated solid solution in an alloy is of importance in stating the proper technology...that during annealing up to 250 C, there is a great density of dislocations. A hypothesis is presented concerning the structural changes occurring at heating the highly supersaturated solid solution of this alloy.

  20. Thermodynamics and solubility of (UxNp1-x) O2(am) solid solution in the carbonate system

    SciTech Connect

    Rai, Dhanpat; Hess, Nancy J.; Yui, Mikazu; Felmy, Andrew R.; Moore, D. A.

    2004-12-31

    SUMMARY-The formation of a solid solution can significantly affect the solubility of a minor component. The objectives of this study were to determine the nature of U(IV) and Np(IV) solid solutions and their thermodynamic properties. For this purpose...

  1. Uncertainties associated with lacking data for predictions of solid-solution partitioning of metals in soil.

    PubMed

    Le, T T Yen; Hendriks, A Jan

    2014-08-15

    Soil properties, i.e., pH and contents of soil organic matter (SOM), dissolved organic carbon (DOC), clay, oxides, and reactive metals, are required inputs to both mechanistic and empirical modeling in assessing metal solid-solution partitioning. Several of these properties are rarely measured in site-specific risk assessment. We compared the uncertainties induced by lacking data on these soil properties in estimating metal soil solution concentrations. The predictions by the Orchestra framework were more sensitive to lacking soil property data than the predictions by the transfer functions. The deviations between soil solution concentrations of Cd, Ni, Zn, Ba, and Co estimated with measured SOM and those estimated with generic SOM by the Orchestra framework were about 10 times larger than the deviations in the predictions by the transfer functions. High uncertainties were induced by lacking data in assessing solid-solution partitioning of oxy-anions like As, Mo, Sb, Se, and V. Deviations associated with lacking data in predicting soil solution concentrations of these metals by the Orchestra framework reached three-to-six orders of magnitude. The solid-solution partitioning of metal cations was strongly influenced by pH and contents of organic matter, oxides, and reactive metals. Deviations of more than two orders of magnitude were frequently observed between the estimates of soil solution concentrations with the generic values of these properties and the estimates based on the measured data. Reliable information on these properties is preferred to be included in the assessment by either the Orchestra framework or transfer functions.

  2. On the difference of equilibrium constants of DNA hybridization in bulk solution and at the solid-solution interface.

    PubMed

    Oliviero, Giulio; Federici, Stefania; Colombi, Paolo; Bergese, Paolo

    2011-01-01

    The origin of the difference between the equilibrium (affinity) constants of ligand-receptor binding in bulk solution and at a solid-solution interface is discussed in terms of Gibbsian interfacial thermodynamics. It results that the difference is determined by the surface work that the ligand-receptor interaction spends to accommodate surface binding, and in turn that the value of the surface equilibrium constant (strongly) depends on the surface that confines the event. This framework consistently describes a wide set of experimental observations of DNA surface hybridization, correctly predicting that within the surface work window for DNA hybridization, that ranges from -90 to 75 kJ mol(-1), the ratio between surface and bulk equilibrium constants ranges from 10(-16) to 10(13), spanning 29 orders of magnitude.

  3. Structural, vibrational, and thermochemical properties of the monazite-type solid solution La1-xPrxPO4

    NASA Astrophysics Data System (ADS)

    Hirsch, A.; Kegler, P.; Alencar, I.; Ruiz-Fuertes, J.; Shelyug, A.; Peters, L.; Schreinemachers, C.; Neumann, A.; Neumeier, S.; Liermann, H.-P.; Navrotsky, A.; Roth, G.

    2017-01-01

    The monazite-type solid solution La1-xPrxPO4 was synthesized by solid-state reaction and extensively investigated using electron microprobe and thermogravimetric analyses, differential scanning and high-temperature oxide melt solution calorimetry, powder X-ray diffraction, infrared and Raman spectroscopy. Lattice parameters and Ln-O bond lengths show a decrease with increasing Pr content. A small excess volume is observed for the solid solution. IR spectra of the solid solution members present no detectable differences, while a blue shift of the PO4-related modes is seen in the Raman data. This shift can be attributed to the lanthanide contraction. Within errors, calorimetry data show no systematic deviation from an ideal behavior, though one might interpret the data as an indication of a slightly asymmetric mixture. All data indicate that deviations from ideality of the solid solution - if present - are very small.

  4. A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state.

    PubMed

    Bencini, Andrea; Berni, Emanuela; Bianchi, Antonio; Fornasari, Patrizia; Giorgi, Claudia; Lima, Joao C; Lodeiro, Carlos; Melo, Maria J; de Melo, J Seixas; Parola, Antonio Jorge; Pina, Fernando; Pina, Joao; Valtancoli, Barbara

    2004-07-21

    The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.

  5. Thermodynamic properties of carbon in b.c.c. and f.c.c. iron-silicon-carbon solid solutions.

    NASA Technical Reports Server (NTRS)

    Chraska, P.; Mclellan, R. B.

    1971-01-01

    The equilibrium between hydrogen-methane gas mixtures and Fe-Si-C solid solutions has been investigated both as a function of temperature and carburizing gas composition. The thermodynamic properties of the carbon atoms in both b.c.c. and f.c.c. solid solution have been derived from the equilibrium measurements. The results found have been compared with those of earlier investigations and with the predictions of recent theoretical models on ternary solid solutions containing both substitutional and interstitial solute atoms.

  6. Thermodynamic analysis of the concentration profiles of epitaxial layers of nonideal solid solutions

    SciTech Connect

    Kazakov, A.I.; Kishmar, I.N.; Mokritskii, V.A.; Yakubovskii, M.V.

    1988-03-01

    Based on thermodynamic analysis employing the quasiregular approach a mathematical model of the process of equilibrium crystallization of nonideal three-component solid solutions of compounds of the type A/sup III/B/sup V/ from a restricted volume of a solution in a melt was constructed. This model enables calculation of the distribution of the components over the thickness of the epitaxial layer for low rates of cooling of the solution in a melt. The computer calculations of the concentration profiles of the epitaxial layers of Ga/sub 1-x/Al/sub x/ agreed well with the experimental data for thicknesses of the epitaxial layers up to 20 ..mu..m. For high rates of cooling the mass transfer in the volume of the solution in a melt must be taken into account.

  7. A combined analytical solution for Chemical Exchange Saturation Transfer and semi-solid Magnetization Transfer

    PubMed Central

    Zaiss, Moritz; Zu, Zhongliang; Xu, Junzhong; Schuenke, Patrick; Gochberg, Daniel F.; Gore, John C.; Ladd, Mark E.; Bachert, Peter

    2015-01-01

    Off-resonant radiofrequency irradiation in tissue indirectly lowers the water signal by saturation transfer processes: On the one hand, there are selective chemical exchange saturation transfer (CEST) effects originating from exchanging endogenous protons resonating a few ppm from water; on the other hand, there is the broad semi-solid magnetization transfer (MT) originating from immobile protons associated with the tissue matrix with kHz line-widths. Recently it was shown that endogenous CEST contrasts can be strongly affected by the MT background so that corrections are needed to derive accurate estimates of CEST effects. Herein we show that a full analytical solution of the underlying Bloch-McConnell equations for both MT and CEST provides insights into their interaction and suggests a simple means to isolate their effects. The presented analytical solution, based on the eigenspace solution of the Bloch-McConnell equations, extends previous treatments by allowing arbitrary line-shapes for the semi-solid MT effects and simultaneously describing multiple CEST pools in the presence of a large MT pool for arbitrary irradiation. The structure of the model indicates that semi-solid MT and CEST effects basically add up inversely in determining the steady-state Z-spectrum, as previously shown for direct saturation and CEST effects. Implications for existing previous CEST analyses in the presence of a semi-solid MT are studied and discussed. It turns out that to accurately quantify CEST contrast, a good reference Z-value, the observed longitudinal relaxation rate of water, and the semi-solid MT pool size fraction, must all be known. PMID:25504828

  8. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys.

    PubMed

    Zhang, Yanwen; Stocks, G Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C; Wang, Lumin; Béland, Laurent K; Stoller, Roger E; Samolyuk, German D; Caro, Magdalena; Caro, Alfredo; Weber, William J

    2015-10-28

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications.

  9. Structure and magnetic properties of metastable Co-Cu solid solution nanowire arrays fabricated by electrodeposition

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Li, Fashen; Wang, Ying; Song, Lijing

    2006-08-01

    Nanowire arrays of the metastable Cox Cu1-x (0.20 x 0.85) solid solution system which can not be obtained by equilibrium methods, were prepared by electrodeposition in pores of anodic aluminum oxide (AAO) template, and subsequently annealed at different temperatures. The as-deposited samples all show single phase of fcc structure, and lattice parameters decrease with the increase of Co content and fundamentally accord with Vegard's law. The phase transition with heat treatment was investigated by X-ray diffraction and differential thermal analysis (DTA) which further confirmed the formation of solid solution. With Co content increasing, the coercivity along nanowire axis for as-deposited samples increases, but it decreases for the annealed samples at 700 °C. This phenomenon was explained considering the interaction of Co particles through Cu in nanowires after phase separation.

  10. Accelerated exploration of multi-principal element alloys with solid solution phases.

    PubMed

    Senkov, O N; Miller, J D; Miracle, D B; Woodward, C

    2015-03-05

    Recent multi-principal element, high entropy alloy (HEA) development strategies vastly expand the number of candidate alloy systems, but also pose a new challenge--how to rapidly screen thousands of candidate alloy systems for targeted properties. Here we develop a new approach to rapidly assess structural metals by combining calculated phase diagrams with simple rules based on the phases present, their transformation temperatures and useful microstructures. We evaluate over 130,000 alloy systems, identifying promising compositions for more time-intensive experimental studies. We find the surprising result that solid solution alloys become less likely as the number of alloy elements increases. This contradicts the major premise of HEAs--that increased configurational entropy increases the stability of disordered solid solution phases. As the number of elements increases, the configurational entropy rises slowly while the probability of at least one pair of elements favouring formation of intermetallic compounds increases more rapidly, explaining this apparent contradiction.

  11. Accelerated exploration of multi-principal element alloys with solid solution phases

    NASA Astrophysics Data System (ADS)

    Senkov, O. N.; Miller, J. D.; Miracle, D. B.; Woodward, C.

    2015-03-01

    Recent multi-principal element, high entropy alloy (HEA) development strategies vastly expand the number of candidate alloy systems, but also pose a new challenge—how to rapidly screen thousands of candidate alloy systems for targeted properties. Here we develop a new approach to rapidly assess structural metals by combining calculated phase diagrams with simple rules based on the phases present, their transformation temperatures and useful microstructures. We evaluate over 130,000 alloy systems, identifying promising compositions for more time-intensive experimental studies. We find the surprising result that solid solution alloys become less likely as the number of alloy elements increases. This contradicts the major premise of HEAs—that increased configurational entropy increases the stability of disordered solid solution phases. As the number of elements increases, the configurational entropy rises slowly while the probability of at least one pair of elements favouring formation of intermetallic compounds increases more rapidly, explaining this apparent contradiction.

  12. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    SciTech Connect

    Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-10-28

    A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel to binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.

  13. Point defect concentrations and solid solution hardening in NiAl with Fe additions

    SciTech Connect

    Pike, L.M.; Chang, Y.A.; Liu, C.T.

    1997-08-01

    The solid solution hardening behavior exhibited when Fe is added to NiAl is investigated. This is an interesting problem to consider since the ternary Fe additions may choose to occupy either the Ni or the Al sublattice, affecting the hardness at differing rates. Moreover, the addition of Fe may affect the concentrations of other point defects such as vacancies and Ni anti-sites. As a result, unusual effects ranging from rapid hardening to solid solution softening are observed. Alloys with varying amounts of Fe were prepared in Ni-rich (40 at. % Al) and stoichiometric (50 at. % Al) compositions. Vacancy concentrations were measured using lattice parameter and density measurements. The site occupancy of Fe was determined using ALCHEMI. Using these two techniques the site occupancies of all species could be uniquely determined. Significant differences in the defect concentrations as well as the hardening behavior were encountered between the Ni-rich and stoichiometric regimes.

  14. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    PubMed Central

    Zhang, Yanwen; Stocks, G. Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-01-01

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications. PMID:26507943

  15. Flexible, Luminescent Metal-Organic Frameworks Showing Synergistic Solid-Solution Effects on Porosity and Sensitivity.

    PubMed

    Liu, Si-Yang; Zhou, Dong-Dong; He, Chun-Ting; Liao, Pei-Qin; Cheng, Xiao-Ning; Xu, Yan-Tong; Ye, Jia-Wen; Zhang, Jie-Peng; Chen, Xiao-Ming

    2016-12-23

    Mixing molecular building blocks in the solid solution manner is a valuable strategy to obtain structures and properties in between the isostructural parent metal-organic frameworks (MOFs). We report nonlinear/synergistic solid-solution effects using highly related yet non-isostructural, phosphorescent Cu(I) triazolate frameworks as parent phases. Near the phase boundaries associated with conformational diversity and ligand heterogeneity, the porosity (+150 %) and optical O2 sensitivity (410 times, limit of detection 0.07 ppm) can be drastically improved from the best-performing parent MOFs and even exceeds the records hold by precious-metal complexes (3 ppm) and C70 (0.2 ppm).

  16. Isomorphism and solid solution as shown by an accurate high-resolution diffraction experiment.

    PubMed

    Poulain, Agnieszka; Kubicki, Maciej; Lecomte, Claude

    2014-12-01

    High-resolution crystal structure determination and spherical and multipolar refinement enabled an organic solid solution of 1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole-5-carbonitrile and 5-bromo-1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole to be found, which would not normally be revealed using only standard resolution data (ca 0.8 Å), as the disordered part is only visible at high resolution. Therefore, this new structure would have been reported as just another polymorphic form, even more reasonably as isostructural with other derivatives. To the best of our knowledge this is the first example of organic solid solution modelled via charge density Hansen-Coppens formalism and analysed by means of quantum theory of atoms in molecules (QTAIM) theory.

  17. Tunable catalytic activity of solid solution metal-organic frameworks in one-pot multicomponent reactions.

    PubMed

    Aguirre-Díaz, Lina María; Gándara, Felipe; Iglesias, Marta; Snejko, Natalia; Gutiérrez-Puebla, Enrique; Monge, M Ángeles

    2015-05-20

    The aim of this research is to establish how metal-organic frameworks (MOFs) composed of more than one metal in equivalent crystallographic sites (solid solution MOFs) exhibit catalytic activity, which is tunable by virtue of the metal ions ratio. New MOFs with general formula [InxGa1-x(O2C2H4)0.5(hfipbb)] were prepared by the combination of Ga and In. They are isostructural with their monometal counterparts, synthesized with Al, Ga, and In. Differences in their behavior as heterogeneous catalysts in the three-component, one pot Strecker reaction illustrate the potential of solid solution MOFs to provide the ability to address the various stages involved in the reaction mechanism.

  18. Preparation of Li2S-P2S5 solid electrolyte from N-methylformamide solution and application for all-solid-state lithium battery

    NASA Astrophysics Data System (ADS)

    Teragawa, Shingo; Aso, Keigo; Tadanaga, Kiyoharu; Hayashi, Akitoshi; Tatsumisago, Masahiro

    2014-02-01

    Electrode-solid electrolyte composite materials for all-solid-state lithium batteries were prepared by coating of the Li2S-P2S5 solid electrolyte onto LiCoO2 particles using a N-methylformamide (NMF) solution of 80Li2S·20P2S5 (mol%) solid electrolyte. SEM and EDX analysis showed that the Li2S-P2S5 solid electrolyte was uniformly coated on LiCoO2 particles. The all-solid-state cell using the LiCoO2 particles coated with the solid electrolyte showed higher charge-discharge capacity than the cells using uncoated LiCoO2 particles.

  19. Solution-Liquid-Solid Synthesis of Hexagonal Nickel Selenide Nanowire Arrays with a Nonmetal Catalyst.

    PubMed

    Xu, Kun; Ding, Hui; Jia, Kaicheng; Lu, Xiuli; Chen, Pengzuo; Zhou, Tianpei; Cheng, Han; Liu, Si; Wu, Changzheng; Xie, Yi

    2016-01-26

    Inorganic nanowire arrays hold great promise for next-generation energy storage and conversion devices. Understanding the growth mechanism of nanowire arrays is of considerable interest for expanding the range of applications. Herein, we report the solution-liquid-solid (SLS) synthesis of hexagonal nickel selenide nanowires by using a nonmetal molecular crystal (selenium) as catalyst, which successfully brings SLS into the realm of conventional low-temperature solution synthesis. As a proof-of-concept application, the NiSe nanowire array was used as a catalyst for electrochemical water oxidation. This approach offers a new possibility to design arrays of inorganic nanowires.

  20. Photoinduced processes in solid polymer solutions of dyes in an interference field of laser radiation

    SciTech Connect

    Sizykh, A G; Tarakanova, E A

    1998-12-31

    An investigation was made of the relationships governing the photochemical mechanism of formation of light-induced gratings in solid polymer solutions of a dye with a high quantum yield of the triplet states. The combined analysis of the results of real and numerical experiments was made for a solution of eosin K in gelatin. The protonation rate constant of the dye was measured and the dependence of the diffraction efficiency on the duration of irradiation was explained taking diffusion of the dye into account. A method was proposed for determination of the duffusion coefficient in a spatially modified interference field of the laser radiation. The diffusion coefficients were found. (nonlinear optical phenomena)

  1. Solution-Processed Ambipolar Organic Thin-Film Transistors by Blending p- and n-Type Semiconductors: Solid Solution versus Microphase Separation.

    PubMed

    Xu, Xiaomin; Xiao, Ting; Gu, Xiao; Yang, Xuejin; Kershaw, Stephen V; Zhao, Ni; Xu, Jianbin; Miao, Qian

    2015-12-30

    Here, we report solid solution of p- and n-type organic semiconductors as a new type of p-n blend for solution-processed ambipolar organic thin film transistors (OTFTs). This study compares the solid-solution films of silylethynylated tetraazapentacene 1 (acceptor) and silylethynylated pentacene 2 (donor) with the microphase-separated films of 1 and 3, a heptagon-embedded analogue of 2. It is found that the solid solutions of (1)x(2)1-x function as ambipolar semiconductors, whose hole and electron mobilities are tunable by varying the ratio of 1 and 2 in the solid solution. The OTFTs of (1)0.5(2)0.5 exhibit relatively balanced hole and electron mobilities comparable to the highest values as reported for ambipolar OTFTs of stoichiometric donor-acceptor cocrystals and microphase-separated p-n bulk heterojunctions. The solid solution of (1)0.5(2)0.5 and the microphase-separated blend of 1:3 (0.5:0.5) in OTFTs exhibit different responses to light in terms of absorption and photoeffect of OTFTs because the donor and acceptor are mixed at molecular level with π-π stacking in the solid solution.

  2. X-ray diffraction study of gold nitride films: Observation of a solid solution phase

    NASA Astrophysics Data System (ADS)

    Alves, L.; Hase, T. P. A.; Hunt, M. R. C.; Brieva, A. C.; Šiller, L.

    2008-12-01

    The structure of nitride containing gold films produced by reactive ion sputtering and nitrogen plasma etching is investigated using x-ray photoelectron spectroscopy and x-ray diffraction. It is found that gold nitride is a solid solution of nitrogen atoms dissolved in a fcc gold matrix. Differences between the strain and lattice parameters of gold and gold nitride films were observed and are explained by interstitial nitrogen present in the latter.

  3. Properties of solid solutions, doped film, and nanocomposite structures based on zinc oxide

    NASA Astrophysics Data System (ADS)

    Lashkarev, G. V.; Shtepliuk, I. I.; Ievtushenko, A. I.; Khyzhun, O. Y.; Kartuzov, V. V.; Ovsiannikova, L. I.; Karpyna, V. A.; Myroniuk, D. V.; Khomyak, V. V.; Tkach, V. N.; Timofeeva, I. I.; Popovich, V. I.; Dranchuk, N. V.; Khranovskyy, V. D.; Demydiuk, P. V.

    2015-02-01

    A study of the properties of materials based on the wide bandgap zinc oxide semiconductor, which are promising for application in optoelectronics, photovoltaics and nanoplasmonics. The structural and optical properties of solid solution Zn1-xCdxO films with different cadmium content, are studied. The samples are grown using magnetron sputtering on sapphire backing. Low-temperature photoluminescence spectra revealed emission peaks associated with radiative recombination processes in those areas of the film that have varying amounts of cadmium. X-ray phase analysis showed the presence of a cadmium oxide cubic phase in these films. Theoretical studies of the solid solution thermodynamic properties allowed for a qualitative interpretation of the observed experimental phenomena. It is established that the growth of the homogeneous solid solution film is possible only at high temperatures, whereas regions of inhomogeneous composition can be narrowed through elastic deformation, caused by the mismatch of the film-backing lattice constants. The driving forces of the spinodal decomposition of the Zn1-xCdxO system are identified. Fullerene-like clusters of Znn-xCdxOn are used to calculate the bandgap and the cohesive energy of ZnCdO solid solutions. The properties of transparent conductive ZnO films, doped with Group III donor impurities (Al, Ga, In), are examined. It is shown that oxygen vacancies are responsible for the hole trap centers in the zinc oxide photoconductivity process. We also examine the photoluminescence properties of metal-ZnO nanocomposite structures, caused by surface plasmons.

  4. Saturation magnetization in supersaturated solid solution of Co-Cu alloy

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Kajikawa, Kota; Hakamada, Masataka; Mabuchi, Mamoru

    2009-10-01

    The magnetovolume effect has been investigated using a supersaturated solid solution of a Co-19 at. %Cu alloy processed by electrodeposition. The enhanced saturation magnetization of the Co-Cu alloy was attributed to both metastable fcc Co and lattice expansion. The density functional theory using the CASTEP code revealed that an enhanced magnetic moment due to the magnetovolume effect is obtained in fcc Co, but not in hcp Co.

  5. Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

    SciTech Connect

    Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; Weber, William J.

    2016-01-01

    We investigate Irradiation-induced damage accumulation in Ni0.8Fe0.2 and Ni0.8Cr0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

  6. Molecular tectonics: crystal engineering of mixed valence Fe(II)/Fe(III) solid solutions.

    PubMed

    Dechambenoit, Pierre; Ferlay, Sylvie; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2010-02-14

    Based on isostructurality between crystals formed upon combining the dicationic tecton 2 with either M(3)Fe(III)(CN)(6) or M(4)Fe(II)(CN)(6) (M = Cs), a rare example of an H-bonded mixed valence Fe(ii)-Fe(iii) solid solution ((Cs(2)2(3)-[Fe(II)(CN)(6)](2))(0.83)(2(3)-[Fe(III)(CN)(6)](2))(0.17))) and curious necklace-like composite crystals were generated.

  7. A novel quaternary solid solution photo-absorber material for photoelectrochemical hydrogen generation.

    PubMed

    Hong, Tiantian; Liu, Zhifeng; Yan, Weiguo; Wang, Bo; Zhang, Xueqi; Liu, Junqi; Wang, Junkai; Han, Jianhua

    2015-09-14

    We report a novel quaternary solid solution (Ag-Cu-Sb-S or ACSS) serving as a photo-absorber material in the photoelectrochemical field for the first time, and ZnO/ACSS nanoarrays exhibited a photocurrent density of 4.45 mA cm(-2). The research indicates that ZnO/ACSS composite structures have enormous potential in PEC hydrogen generation systems.

  8. Investigation of Self-Organized Nanoheterostructure Properties in InGaAsP Solid Solutions

    DTIC Science & Technology

    1998-06-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012787 TITLE: Investigation of Self-Organized Nanoheterostructure ... nanoheterostructure properties in InGaAsP solid solutions I S. Tarasov, 1. N. Arsent’ev, N. A. Bert, L. S. Vavilova, V.A. Kapitonov, A. V. Murashova...organized InGaAsP nanoheterostructures grown on InP and GaAs substrates have been investigated by photoluminescence and transmission electron microscopy

  9. Experimental and theoretical investigation of Cr1-xScxN solid solutions for thermoelectrics

    NASA Astrophysics Data System (ADS)

    Kerdsongpanya, Sit; Sun, Bo; Eriksson, Fredrik; Jensen, Jens; Lu, Jun; Koh, Yee Kan; Nong, Ngo Van; Balke, Benjamin; Alling, Björn; Eklund, Per

    2016-12-01

    The ScN- and CrN-based transition-metal nitrides have recently emerged as a novel and unexpected class of materials for thermoelectrics. These materials constitute well-defined model systems for investigating mixing thermodynamics, phase stability, and band structure aiming for property tailoring. Here, we demonstrate an approach to tailor their thermoelectric properties by solid solutions. The trends in mixing thermodynamics and densities-of-states (DOS) of rocksalt-Cr1-xScxN solid solutions (0 ≤ x ≤ 1) are investigated by first-principles calculations, and Cr1-xScxN thin films are synthesized by magnetron sputtering. Pure CrN exhibits a high power factor, 1.7 × 10-3 W m-1 K-2 at 720 K, enabled by a high electron concentration thermally activated from N vacancies. Disordered rocksalt-Cr1-xScxN solid solutions are thermodynamically stable, and calculated DOS suggest the possibility for power-factor improvement by Sc3d orbital delocalization on Cr3d electrons giving decreasing electrical resistivity, while localized Cr3d orbitals with a large DOS slope may yield an improved Seebeck coefficient. Sc-rich solid solutions show a large improvement in power factor compared to pure ScN, and all films have power factors above that expected from the rule-of-mixture. These results corroborate the theoretical predictions and enable tailoring and understanding of structure-transport-property correlations of Cr1-xScxN.

  10. Precipitation of Ordered Phases in Metallic Solid Solutions: A Synergistic Clustering and Ordering Process (Preprint)

    DTIC Science & Technology

    2011-07-01

    of such concurrent clustering and ordering processes in metallic solid solutions including Fe-Al [4], Ni-Al [5,6], Ni-Ti [7,8], and Cu -Ti [9,10...ordering reaction to take place. The proposition is that since the Cu -15Ni-8Sn alloy composition cannot undergo congruent ordering, spinodal...interpretation of their results. For example, Wendt and Hassan noted from [14] that in samples of the quenched alloy that have been briefly aged

  11. High-Performance Hydrogen Evolution from MoS2(1-x) P(x) Solid Solution.

    PubMed

    Ye, Ruquan; del Angel-Vicente, Paz; Liu, Yuanyue; Arellano-Jimenez, M Josefina; Peng, Zhiwei; Wang, Tuo; Li, Yilun; Yakobson, Boris I; Wei, Su-Huai; Yacaman, Miguel Jose; Tour, James M

    2016-02-17

    A MoS2(1-x) P(x) solid solution (x = 0 to 1) is formed by thermally annealing mixtures of MoS2 and red phosphorus. The effective and stable electrocatalyst for hydrogen evolution in acidic solution holds promise for replacing scarce and expensive platinum that is used in present catalyst systems. The high performance originates from the increased surface area and roughness of the solid solution.

  12. CSBB-ConeExclusion, adapting structure based solution virtual screening to libraries on solid support.

    PubMed

    Shave, Steven; Auer, Manfred

    2013-12-23

    Combinatorial chemical libraries produced on solid support offer fast and cost-effective access to a large number of unique compounds. If such libraries are screened directly on-bead, the speed at which chemical space can be explored by chemists is much greater than that addressable using solution based synthesis and screening methods. Solution based screening has a large supporting body of software such as structure-based virtual screening tools which enable the prediction of protein-ligand complexes. Use of these techniques to predict the protein bound complexes of compounds synthesized on solid support neglects to take into account the conjugation site on the small molecule ligand. This may invalidate predicted binding modes, the linker may be clashing with protein atoms. We present CSBB-ConeExclusion, a methodology and computer program which provides a measure of the applicability of solution dockings to solid support. Output is given in the form of statistics for each docking pose, a unique 2D visualization method which can be used to determine applicability at a glance, and automatically generated PyMol scripts allowing visualization of protein atom incursion into a defined exclusion volume. CSBB-ConeExclusion is then exemplarically used to determine the optimum attachment point for a purine library targeting cyclin-dependent kinase 2 CDK2.

  13. Characterizing SiC-AlN semiconductor solid solutions with indirect and direct bandgaps

    NASA Astrophysics Data System (ADS)

    Dallaeva, Dinara; Ramazanov, Shikhgasan; Ramazanov, Gusejn; Akhmedov, Ramazan; Tománek, Pavel

    2015-01-01

    The objective of the study is to characterize the dependence of the optical properties of solid solutions of silicon carbide and aluminum nitride on composition. Even small differences in composition provide manipulation of band gap features over a wide range. Data for this paper were collected by X-ray diffraction, photoluminescence and absorption spectroscopy. The evolution of the observed optical properties as a result of compositional changes were studied. X-ray studies confirm the presence of a(SiC)1-x(AlN)x solid solution. Investigation of absorption spectra shows the optical band gap of the sample with composition (SiC)0,88(AlN)0,12 is 3.5eV, and 4.24 eV for the (SiC)0,36(AlN)0,64 solid solution. The photoluminescence spectra demonstrate the strong dependence of the spectra on composition x. The experimental results are in agreement with theory. These data demonstrate the optimization of optical properties for particular optoelectronic applications by varying the (SiC)1-x(AlN)xcomposition.

  14. Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

    NASA Astrophysics Data System (ADS)

    Vidyasagar, K.; Gopalakrishnan, J.; Rao, C. N. R.

    1985-06-01

    Precursor solid solutions provide convenient routes for preparing complex metal oxides. Hydroxide solid solutions of the general formula Ln1- xMx(OH) 3 (where Ln = La or Nd and M = Al, Cr, Fe, Co, or Ni) and La 1- x- yM' xM″ y(OH) 3 (where M' = Ni and M″ = Co or Cu) crystallize in the rare earth trihydroxide structure and can be decomposed at relatively low temperatures to yield complex metal oxides. Several oxides of the type LaNiO 3, NdNiO 3, LaNi 1- xCo xO 3, and LaNi 1- xCu xO 3 have been prepared by the hydroxide precursor route. Thermal decomposition of cyanide precursors of the type Ln[ M1- xM' x(CN) 6] · 5H 2O and Ln1- xLn' x[ M(CN) 6] · 5H 2O yields the quaternary oxides which are not readily made by ceramic methods. Nitrate solid solution precursors of the type Ba 1- xPb x(NO 3) 2, Sr 1- xPb x(NO 3) 2, and BaSrPb(NO 3) 6 have been used for preparing several interesting oxides such as BaPbO 3, Ba 2PbO 4, and BaSrPbO 4.

  15. Controls of carbonate mineralogy and solid-solution of Mg in calcite: evidence from spelean systems

    SciTech Connect

    Gonzalez, L.A.; Lohmann, K.C.

    1985-01-01

    Precipitation of carbonate minerals in spelean systems occurs under a wide range of fluid chemistry, Mg-Ca ratios, alkalinities, pH and temperatures; thus, spelean systems provide ideal settings to determine factors controlling the mineralogy of precipitated carbonates and solid-solution of Mg in calcite. Cave waters and actively-precipitating carbonate speleothems were collected from Carlsbad Caverns National Park, New Mexico and the Mammoth-Flint Cave System, Kentucky. Carbonate mineralogy of precipitated phases was determined by x-ray diffraction, and major and minor element composition of waters and accompanying minerals were determined by Atomic Absorption Spectrophotometry. Results demonstrate that at a constant CO3 concentration the precipitation threshold for calcite to aragonite is controlled dominantly by the Mg/Ca ratio of the ambient fluid. Aragonite precipitation is favored by high Mg/Ca ratios. Conversely, with increasing CO3 concentration at constant fluid Mg/Ca ratios, calcite is preferentially precipitated. Solid-solution of Mg in calcite is positively correlated with both increased Mg/Ca ratios and CO3 concentrations. These data suggest that Mg contents of calcite can not be defined solely in terms of a homogeneous distribution coefficient. Rather, Mg concentrations can be also be affected by the CO3 concentration and degree of calcite saturation, suggesting that the rate of crystal growth also plays and important role in Mg solid-solution in calcites.

  16. Solid solution partitioning of Sr 2+, Ba 2+, and Cd 2+ to calcite

    NASA Astrophysics Data System (ADS)

    Tesoriero, Anthony J.; Pankow, James F.

    1996-03-01

    Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr 2+, Ba 2+, and Cd 2+ to calcite (CaCO 3(s)). The distribution coefficient of a divalent metal ion Me 2+ for partitioning from an aqueous solution into calcite is given by DMe = ( XMeCO 3(s)/[Me 2+])/( XCaCO 3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25 °C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ± 0.003, 0.012 ± 0.005, and 1240 ± 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd 2+ will be strongly retarded in aquifers containing calcite; Sr 2+ and Ba 2+ will not be retarded nearly as much.

  17. Local structure in the disordered solid solution of cis- and trans-perinones.

    PubMed

    Teteruk, Jaroslav L; Glinnemann, Jürgen; Heyse, Winfried; Johansson, Kristoffer E; van de Streek, Jacco; Schmidt, Martin U

    2016-06-01

    The cis- and trans-isomers of the polycyclic aromatic compound perinone, C26H12N4O2, form a solid solution (Vat Red 14). This solid solution is isotypic to the crystal structures of cis-perinone (Pigment Red 194) and trans-perinone (Pigment Orange 34) and exhibits a combined positional and orientational disorder: In the crystal, each molecular position is occupied by either a cis- or trans-perinone molecule, both of which have two possible molecular orientations. The structure of cis-perinone exhibits a twofold orientational disorder, whereas the structure of trans-perinone is ordered. The crystal structure of the solid solution was determined by single-crystal X-ray analysis. Extensive lattice-energy minimizations with force-field and DFT-D methods were carried out on combinatorially complete sets of ordered models. For the disordered systems, local structures were calculated, including preferred local arrangements, ordering lengths, and probabilities for the arrangement of neighbouring molecules. The superposition of the atomic positions of all energetically favourable calculated models corresponds well with the experimentally determined crystal structures, explaining not only the atomic positions, but also the site occupancies and anisotropic displacement parameters.

  18. Solid Solution Photocatalyst with Spontaneous Polarization Exhibiting Low Recombination Toward Efficient CO2 Photoreduction.

    PubMed

    Zhou, Peng; Wang, Xin; Yan, Shicheng; Zou, Zhigang

    2016-08-23

    Decreasing the recombination of photogenerated carriers is a major challenge for efficiently converting solar energy into chemical energy by photocatalysis. Here, we have demonstrated that growth of a polar GaN:ZnO solid solution single crystal along its polarization axis is beneficial to efficient separation of photogenerated carriers, owing to the periodic potential barriers and wells generated from the periodically positive and negative atom arrangements in crystal structure. Local charge imbalance caused by replacing Ga(3+) with Zn(2+) leads to a polarization vector in the {0 0 0 1} planes of GaN:ZnO solid solution, thus forming a 1 D electron transport path along [2 1‾  1‾  0] in the {0 0 0 1} planes of GaN:ZnO solid solution to decrease recombination. Shorting the hole-transport distance by synthesizing porous nanoplates can further decrease recombination under the polarization field and improve the performance of polar photocatalyst in photoreduction of CO2 into CH4 .

  19. Solid solution partitioning of Sr2+, Ba2+, and Cd2+ to calcite

    USGS Publications Warehouse

    Tesoriero, A.J.; Pankow, J.F.

    1996-01-01

    Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr2+, Ba2+, and Cd2+ to calcite (CaCO3(s)). The distribution coefficient of a divalent metal ion Me2+ for partitioning from an aqueous solution into calcite is given by DMe = (XMeCO3(s)/[Me2+])/(XCaCO3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25??C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ?? 0.003, 0.012 ?? 0.005, and 1240 ?? 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd2+ will be strongly retarded in aquifers containing calcite; Sr2+ and Ba2+ will not be retarded nearly as much.

  20. Contrasting fluids and reservoirs in the contiguous Marcona and Mina Justa iron oxide-Cu (-Ag-Au) deposits, south-central Perú

    NASA Astrophysics Data System (ADS)

    Chen, Huayong; Kyser, T. Kurtis; Clark, Alan H.

    2011-10-01

    The Marcona-Mina Justa deposit cluster, hosted by Lower Paleozoic metaclastic rocks and Middle Jurassic shallow marine andesites, incorporates the most important known magnetite mineralization in the Andes at Marcona (1.9 Gt at 55.4% Fe and 0.12% Cu) and one of the few major iron oxide-copper-gold (IOCG) deposits with economic Cu grades (346.6 Mt at 0.71% Cu, 3.8 g/t Ag and 0.03 g/t Au) at Mina Justa. The Middle Jurassic Marcona deposit is centred in Ica Department, Perú, and the Lower Cretaceous Mina Justa Cu (Ag, Au) prospect is located 3-4 km to the northeast. New fluid inclusion studies, including laser ablation time-of-flight inductively coupled plasma mass spectrometry (LA-TOF-ICPMS) analysis, integrated with sulphur, oxygen, hydrogen and carbon isotope analyses of minerals with well-defined paragenetic relationships, clarify the nature and origin of the hydrothermal fluid responsible for these contiguous but genetically contrasted deposits. At Marcona, early, sulphide-free stage M-III magnetite-biotite-calcic amphibole assemblages are inferred to have crystallized from a 700-800°C Fe oxide melt with a δ18O value from +5.2‰ to +7.7‰. Stage M-IV magnetite-phlogopite-calcic amphibole-sulphide assemblages were subsequently precipitated from 430-600°C aqueous fluids with dominantly magmatic isotopic compositions (δ34S = +0.8‰ to +5.9‰; δ18O = +9.6‰ to +12.2‰; δD = -73‰ to -43‰; and δ13C = -3.3‰). Stages M-III and M-IV account for over 95% of the magnetite mineralization at Marcona. Subsequent non-economic, lower temperature sulphide-calcite-amphibole assemblages (stage M-V) were deposited from fluids with similar δ34S (+1.8‰ to +5.0‰), δ18O (+10.1‰ to +12.5‰) and δ13C (-3.4‰), but higher δD values (average -8‰). Several groups of lower (<200°C, with a mode at 120°C) and higher temperature (>200°C) fluids can be recognized in the main polymetallic (Cu, Zn, Pb) sulphide stage M-V and may record the involvement of

  1. A decontamination system for chemical weapons agents using a liquid solution on a solid sorbent.

    PubMed

    Waysbort, Daniel; McGarvey, David J; Creasy, William R; Morrissey, Kevin M; Hendrickson, David M; Durst, H Dupont

    2009-01-30

    A decontamination system for chemical warfare agents was developed and tested that combines a liquid decontamination reagent solution with solid sorbent particles. The components have fewer safety and environmental concerns than traditional chlorine bleach-based products or highly caustic solutions. The liquid solution, based on Decon Greentrade mark, has hydrogen peroxide and a carbonate buffer as active ingredients. The best solid sorbents were found to be a copolymer of ethylene glycol dimethacrylate and n-lauryl methacrylate (Polytrap 6603 Adsorber); or an allyl methacrylate cross-linked polymer (Poly-Pore E200 Adsorber). These solids are human and environmentally friendly and are commonly used in cosmetics. The decontaminant system was tested for reactivity with pinacolyl methylphosphonofluoridate (Soman, GD), bis(2-chloroethyl)sulfide (Mustard, HD), and S-(2-diisopropylaminoethyl) O-ethyl methylphosphonothioate (VX) by using NMR Spectroscopy. Molybdate ion (MoO(4)(-2)) was added to the decontaminant to catalyze the oxidation of HD. The molybdate ion provided a color change from pink to white when the oxidizing capacity of the system was exhausted. The decontaminant was effective for ratios of agent to decontaminant of up to 1:50 for VX (t(1/2) < or = 4 min), 1:10 for HD (t(1/2) < 2 min with molybdate), and 1:10 for GD (t(1/2) < 2 min). The vapor concentrations of GD above the dry sorbent and the sorbent with decontamination solution were measured to show that the sorbent decreased the vapor concentration of GD. The E200 sorbent had the additional advantage of absorbing aqueous decontamination solution without the addition of an organic co-solvent such as isopropanol, but the rate depended strongly on mixing for HD.

  2. Structures in solid state and solution of dimethoxy curcuminoids: regioselective bromination and chlorination

    PubMed Central

    2013-01-01

    Background Several papers described the structure of curcumin and some other derivatives in solid and in solution. In the crystal structure of curcumin, the enol H atom is located symmetrically between both oxygen atoms of the enolone fragment with an O···O distance of 2.455 Å, which is characteristic for symmetrical H-bonds. In the solution, the geometry of the enolone fragment is attributed to the inherent disorder of the local environment, which solvates one of the basic sites better than the other, stabilizing one tautomer over the other. In this paper, how the position of methoxy groups in dimethoxy curcuminoids influence the conformation of molecules and how the halogen atoms change it when they are bonded at α-position in keto-enol part of molecules is described. Results Six isomers of dimethoxy curcuminoids were prepared. Conformations in solid state, which were determined by X-ray single crystallography and 1H MAS and 13C CPMAS NMR measurements, depend on the position of methoxy groups in curcuminoid molecules. In solution, a fast equilibrium between both keto-enol forms exists. A theoretical calculation finding shows that the position of methoxy groups changes the energy of HOMO and LUMO. An efficient protocol for the highly regioselective bromination and chlorination leading to α-halogenated product has been developed. All α-halogenated compounds are present mainly in cis keto-enol form. Conclusions The structures in solid state of dimethoxy curcuminoids depend on the position of methoxy groups. The NMR data of crystalline solid samples of 3,4-diOCH3 derivative, XRD measurements and X-ray structures lead us to the conclusion that polymorphism exists in solids. The same conclusion can be done for 3,5-diOCH3 derivative. In solution, dimethoxy curcuminoids are present in the forms that can be described as the coexistence of two equivalent tautomers being in fast equilibrium. The position of methoxy groups has a small influence on the enolic hydrogen

  3. Transport properties of dilute α -Fe (X ) solid solutions (X = C, N, O)

    NASA Astrophysics Data System (ADS)

    Schuler, Thomas; Nastar, Maylise

    2016-06-01

    We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute solid solution into intrinsic cluster Onsager matrices, and extract from them flux-coupling ratios, mobilities, and association-dissociation rates for each cluster. The formalism is applied to vacancy-interstitial solute pairs in α -Fe (V X pairs, X = C, N, O), with ab initio based thermodynamic and kinetic parameters. Convergence of the cluster mobility contribution gives a controlled estimation of the cluster definition distance, taking into account both its thermodynamic and kinetic properties. Then, the flux-coupling behavior of each V X pair is discussed, and qualitative understanding is achieved from the comparison between various contributions to the Onsager matrix. Also, the effect of low-activation energy second-nearest-neighbor interstitial solute jumps around a vacancy on these results is addressed.

  4. Differences in physical chemistry and dissolution rate of solid particle aerosols from solution pressurised inhalers.

    PubMed

    Buttini, Francesca; Miozzi, Michele; Balducci, Anna Giulia; Royall, Paul G; Brambilla, Gaetano; Colombo, Paolo; Bettini, Ruggero; Forbes, Ben

    2014-04-25

    Solution composition alters the dynamics of beclomethasone diproprionate (BDP) particle formation from droplets emitted by pressurised metered dose inhalers (pMDIs). The hypothesis that differences in inhaler solutions result in different solid particle physical chemistry was tested using a suite of complementary calorimetric techniques. The atomisation of BDP-ethanol solutions from commercial HFA-pMDI produced aerodynamically-equivalent solid particle aerosols. However, differences in particle physico-chemistry (morphology and solvate/clathrate formation) were detected by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and supported by hot stage microscopy (HSM). Increasing the ethanol content of the formulation from 8 to 12% (w/w), which retards the evaporation of propellant and slows the increase in droplet surface viscosity, enhanced the likelihood of particles drying with a smooth surface. The dissolution rate of BDP from the 12% (w/w) ethanol formulation-derived particles (63% dissolved over 120 min) was reduced compared to the 8% (w/w) ethanol formulation-derived particles (86% dissolved over 120 min). The addition of 0.01% (w/w) formoterol fumarate or 1.3% (w/w) glycerol to the inhaler solution modified the particles and reduced the BDP dissolution rate further to 34% and 16% dissolved in 120 min, respectively. These data provide evidence that therapeutic aerosols from apparently similar inhaler products, including those with similar aerodynamic performance, may behave non-equivalently after deposition in the lungs.

  5. Energetics of a uranothorite (Th1–xUxSiO4) solid solution

    DOE PAGES

    Guo, Xiaofeng; Szenknect, Stephanie; Mesbah, Adel; ...

    2016-10-11

    High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO4)x–(ThSiO4)1–x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. Furthermore, variations in unit cell parameters and negative excess volumes of mixing, coupled with stronglymore » exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.« less

  6. Study of solid-solution hardening in binary aluminium-based alloys

    NASA Astrophysics Data System (ADS)

    Draissia, Mohamed; Debili, Mohamed-Yacine

    2005-09-01

    Solid-solution formation in binary aluminium-based alloys is due essentially to the combined effects of the size and valence of solvent and solute atoms, as expected by the four Hume-Rothery rules. The lattice parameter of aluminium in the solid solution of the sputtered Al-Fe films is [Al-a (Å)=4.052-6.6×10-3Y]. The increasing and decreasing evolution of the lattice parameter of copper [Cu-a (Å)=3.612+1.8×10-3Z] and aluminium [Al-a (Å)=4.048-1.6×10-3X] in the sputtered Al-1.8 to 92.5 at. % Cu films is a result of the difference in size between the aluminium and copper atoms. The low solubility of copper in aluminium (<1.8 at % Cu) is due to the valences of solvent and solute atoms in contrast with other sputtered films prepared under similar conditions, such as Al-Mg (20 at. % Mg), Al-Ti (27 at. % Ti), Al-Cr (5at. % Cr) and Al-Fe (5.5 at. % Fe) where the solubility is due to the difference in size.

  7. Structural investigations of aroylhydrazones derived from nicotinic acid hydrazide in solid state and in solution

    NASA Astrophysics Data System (ADS)

    Galić, Nives; Brođanac, Ivan; Kontrec, Darko; Miljanić, Snežana

    2013-04-01

    Structural forms of aroylhydrazones derived from nicotinic acid hydrazide have been studied in the solid state by FT-IR spectroscopy and in solution by NMR, UV-Vis and ATR spectroscopy. The studied compounds were N'-benzylidene-3-pyridinecarbohydrazide (1), N'-(2,4-dihydroxyphenylmethylidene)-3-pyridinecarbohydrazide (2), N'-(5-chloro-2-hydroxyphenylmethylidene)-3-pyridinecarbohydrazide (3), and N'-(3,5-dichloro-2-hydroxymethoxyphenylmethylidene)-3-pyridinecarbohydrazide (4). The compound 1 adopted the most stable ketoamine form (form I, sbnd COsbnd NHsbnd Ndbnd Csbnd ) in the solid state as well as in various organic solvents. In mixtures of organic solvents with water the UV-Vis and ATR spectra implied intermolecular hydrogen bonding of 1 with water molecules. The presence of both tautomeric forms I and II (form II, sbnd COHdbnd Nsbnd Ndbnd Csbnd ) was proposed for the solid substance and highly concentrated solutions of 2, whereas form I was detected as the predominant one in diluted solutions. For compounds 3 and 4 a coexistence of forms I and III (form III, sbnd COsbnd NHsbnd NHsbnd Cdbnd Csbnd COsbnd ) was noticed in the solid state and in polar protic organic solvents. The conversion to form III was induced by increasing the water content in the solvent mixtures. This process was the most pronounced for compound 4. When exposed to daylight, an appearance of a new band was observed during time in the UV-Vis spectrum of 4 in organic solvent/water 1/1 mixtures, which implied that tautomeric interconversion was most likely followed by E/Z isomerisation.

  8. Efficient screening of 2D molecular polymorphs at the solution-solid interface

    NASA Astrophysics Data System (ADS)

    Lee, Shern-Long; Adisoejoso, Jinne; Fang, Yuan; Tahara, Kazukuni; Tobe, Yoshito; Mali, Kunal S.; de Feyter, Steven

    2015-03-01

    Formation of multiple polymorphs during two-dimensional (2D) crystallization of organic molecules is more of a routine occurrence than rarity. Although such diverse crystalline structures provide exciting possibilities for studying crystal engineering in 2D, predicting the occurrence of polymorphs for a given building block is often non-trivial. Moreover, there is scarcity of methods that can experimentally verify the presence of such crystalline polymorphs in a straightforward fashion. Here we demonstrate a relatively simple experimental approach for screening of 2D polymorphs formed at the solution-solid interface. The strategy involves use of solution flow produced by contacting a piece of tissue paper to the sample to generate a lateral density gradient along the substrate surface. In situ generation of such gradient allows rapid discovery and nanoscale separation of multiple 2D polymorphs in a single experiment. The concept is demonstrated using three structurally different building blocks that differ in terms of intermolecular interactions responsible for 2D crystal formation. The method described here represents a powerful tool for efficient screening of 2D polymorphs formed at the solution-solid interface.Formation of multiple polymorphs during two-dimensional (2D) crystallization of organic molecules is more of a routine occurrence than rarity. Although such diverse crystalline structures provide exciting possibilities for studying crystal engineering in 2D, predicting the occurrence of polymorphs for a given building block is often non-trivial. Moreover, there is scarcity of methods that can experimentally verify the presence of such crystalline polymorphs in a straightforward fashion. Here we demonstrate a relatively simple experimental approach for screening of 2D polymorphs formed at the solution-solid interface. The strategy involves use of solution flow produced by contacting a piece of tissue paper to the sample to generate a lateral density

  9. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    SciTech Connect

    Xie, Miao; Mohammadi, Reza; Turner, Christopher L.; Kaner, Richard B.; Kavner, Abby; Tolbert, Sarah H.

    2015-07-29

    In this paper, we explore the hardening mechanisms in WB4-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under nonhydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB4 solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  10. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    SciTech Connect

    Xie, Miao; Turner, Christopher L.; Mohammadi, Reza; Kaner, Richard B. E-mail: akavner@ucla.edu Tolbert, Sarah H. E-mail: akavner@ucla.edu; Kavner, Abby E-mail: akavner@ucla.edu

    2015-07-27

    In this work, we explore the hardening mechanisms in WB{sub 4}-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under non-hydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB{sub 4} solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  11. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    DOE PAGES

    Xie, Miao; Mohammadi, Reza; Turner, Christopher L.; ...

    2015-07-29

    In this paper, we explore the hardening mechanisms in WB4-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under nonhydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB4 solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  12. A Study of Diffusivity in the BCC Solid Solution of Nb-Al and Nb-Ti-Al System

    DTIC Science & Technology

    1990-01-01

    A STUDY OF DIFFUSIVITY IN THE BCC SOLID SOLUTION OF Nb-Al AND Nb-Ti-Al SYSTEM P DTIC ELECTE NOV 3o01993 A- J.BY JOSE GUADALUPE LUIS RUIZ APARICIO A...analysis was employed for the evaluation of composition profiles in all the diffusion couples. Tne interdiffusion coefficient for the 0 solid solution of Nb...system suggest that Ti is the fastest element in the J0 solid solution . Qualitatively the penetration tendencies correlate with the melting point of

  13. Solid-solution CrCoCuFeNi high-entropy alloy thin films synthesized by sputter deposition

    DOE PAGES

    An, Zhinan; Jia, Haoling; Wu, Yueying; ...

    2015-05-04

    The concept of high configurational entropy requires that the high-entropy alloys (HEAs) yield single-phase solid solutions. However, phase separations are quite common in bulk HEAs. A five-element alloy, CrCoCuFeNi, was deposited via radio frequency magnetron sputtering and confirmed to be a single-phase solid solution through the high-energy synchrotron X-ray diffraction, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. The formation of the solid-solution phase is presumed to be due to the high cooling rate of the sputter-deposition process.

  14. Long-term behavior of refractory thorium-plutonium dioxide solid solutions

    NASA Astrophysics Data System (ADS)

    Claparede, Laurent; Guigue, Mireille; Jouan, Gauthier; Nadah, Nassima; Dacheux, Nicolas; Moisy, Philippe

    2017-01-01

    The long-term behavior of Th0.87Pu0.13O2 was examined in nitric acid concentrations. The normalized dissolution rates after 3380 days, range from (1.4 ± 0.2) × 10-6 g m-2 d-1 in 5 M HNO3 down to (3.2 ± 0.4) × 10-8 g m-2 d-1 in 10-3 M HNO3, which confirms the high chemical durability of this solid solution. The amounts of plutonium measured in solution lead to 0.9% and 2.1% of dissolved solid in 1 M and 5 M HNO3, respectively. In such conditions, the time required to reach the full dissolution of the material varies from 430 years (5 M HNO3) to 18,000 years (10-3 M HNO3). Moreover, the partial order related to the proton activity (n = 0.45 ± 0.03) suggests that the dissolution is mainly driven by surface reactions occurring at the solid/liquid interface. The characterization of the leached samples by SEM shows small microstructural modifications (i.e. detachment of crystallites) and the absence of neoformed phase while from PXRD, the unit cell parameter and crystallite size are not significantly affected.

  15. B-site substituted solid solutions on the base of sodium-bismuth titanate

    NASA Astrophysics Data System (ADS)

    Ishchuk, V. M.; Gusakova, L. G.; Kisel, N. G.; Kuzenko, D. V.; Spiridonov, N. A.; Sobolev, V. L.

    The paper presents results of studies of the formation of phases during the solid-state synthesis in the [(Na0.5Bi0.5)0.80Ba0.20](Ti1-yBy)O3 system of solid solutions with B-site substitutions. The substitutions by zirconium, tin and ion complexes (In0.5Nb0.5) and (Fe0.5Nb0.5) have been studied. It has been found that the synthesis is a multi-step process associated with the formation of a number of intermediate phases (depending on the compositions and calcination temperatures). Single-phase solid solutions have been produced at the calcination temperatures in the interval 1000-1100∘C. An increase in the substituting ions concentration leads to a linear increase of the crystal cell size. At the same time, the tolerance factor gets reduced boosting the stability of the antiferroelectric phase as compared to that of the ferroelectric phase.

  16. Luminescence properties of the Ca-alpha-sialon:Eu solid solution

    NASA Astrophysics Data System (ADS)

    Pawlik, Tomasz; Michalik, Daniel; Sopicka-Lizer, Malgorzata; Lisiecki, Radosław; Adamczyk, Barbara; Pławecki, Materusz; Mieszczak, Łukasz; Walerczyk, Wiktoria

    2016-09-01

    The Ca,Eu-α-sialon powders with the mixed solid solution composition have been manufactured via the solid-state reaction process in flowing nitrogen in a graphite furnace at a relatively low temperature of 1650 °C without an external overpressure. XRD data with Rielveld refinement and XPS measurements were used for characterization of the lattice constants and the surface chemical composition. The monophase Ca-Eu-α-sialon was obtained with the nominal composition of Eu0.048Ca0.702Si7.75Al2.25O0.75N15.25. The highest emission intensity in a yellow-orange region at 590 nm and quantum efficiency of 66% was found for this pure Ca,Eu-α-sialon. Estimation of m,n values from the lattice constant and EDS results showed a small deviation from the nominal composition of designed α-sialon. XPS results demonstrated significant changes of the chemical composition in the oxidized surface of phosphor particles. Possible reasons of emission redshift and relationship between the actual solid solution composition and luminescence properties are discussed in terms of simultaneous presence of Eu2+ and Eu3+ ions in the sialon crystal lattice and residual oxynitride glass.

  17. Supramolecular stabilization of metastable tautomers in solution and the solid state.

    PubMed

    Juribašić, Marina; Bregović, Nikola; Stilinović, Vladimir; Tomišić, Vladislav; Cindrić, Marina; Sket, Primož; Plavec, Janez; Rubčić, Mirta; Užarević, Krunoslav

    2014-12-22

    This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non-heterocyclic, tautomeric solids. Quantum-chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3-methoxysalicylaldehyde and 2-amino-3-hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen-bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid-state and solvent-mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions.

  18. Optical characterization of CdSe quantum dots with metal chalcogenide ligands in solutions and solids

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Q.; Cao, X. A.

    2011-07-01

    The exchange of the original organic ligands of colloidal CdSe core and CdSe/CdS/ZnS core/multishell quantum dots (QDs) with inorganic metal chalcogenide ligands (SnS44-) resulted in carrier delocalization in solutions and enhanced inter-QD electronic coupling in solids, as inferred from peak redshift and broadening of the absorption and photoluminescence (PL) spectra. The SnS4-capped QDs retained strong excitonic absorption but suffered significant PL quenching. Mild thermal treatment below 350 °C transformed the SnS4 ligands into a more conductive phase, leading to stronger coupling yet complete PL quenching. These findings suggest that QD solids with metal chalcogenide ligands may have high quantum yields of photocurrent generation and can be used as functional blocks in thin-film solar cells for efficient solar energy conversion.

  19. Modelling of solid polymer and direct methanol fuel cells: Phenomenological equations and analytical solutions

    NASA Astrophysics Data System (ADS)

    Kauranen, P. S.

    1993-04-01

    In the solid state concept of a direct methanol fuel cell (DMFC), methanol is directly oxidized at the anode of a solid polymer electrolyte fuel cell (SPEFC). Mathematical modelling of the transport and reaction phenomena within the electrodes and the electrolyte membrane is needed in order to get a closer insight into the operation of the fuel cell. In the work, macro-homogenous porous electrode and dilute solution theories are used to derive the phenomenological equations describing the transport and reaction mechanisms in a SPEFC single cell. The equations are first derived for a conventional H2/air SPEFC, and then extended for a DMFC. The basic model is derived in a one dimensional form in which it is assumed that species transport take place only in the direction crossing the cell sandwich. In addition, two dimensional descriptions of the catalyst layer are reviewed.

  20. Multivalent-Counterion-Induced Surfactant Multilayer Formation at Hydrophobic and Hydrophilic Solid-Solution Interfaces.

    PubMed

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun; Xu, Hui; Tucker, Ian M; Petkov, Jordan T; Sivia, Devinderjit S

    2015-06-23

    Surface multilayer formation from the anionic-nonionic surfactant mixture of sodium dodecyl dioxyethylene sulfate, SLES, and monododecyl dodecaethylene glycol, C12E12, by the addition of multivalent Al(3+) counterions at the solid-solution interface is observed and characterized by neutron reflectivity, NR. The ability to form surface multilayer structures on hydrophobic and hydrophilic silica and cellulose surfaces is demonstrated. The surface multilayer formation is more pronounced and more well developed on the hydrophilic and hydrophobic silica surfaces than on the hydrophilic and hydrophobic cellulose surfaces. The less well developed multilayer formation on the cellulose surfaces is attributed to the greater surface inhomogeneities of the cellulose surface which partially inhibit lateral coherence and growth of the multilayer domains at the surface. The surface multilayer formation is associated with extreme wetting properties and offers the potential for the manipulation of the solid surfaces for enhanced adsorption and control of the wetting behavior.

  1. Joule-Thomson Inversion in Vapor-Liquid-Solid Solution Systems

    NASA Astrophysics Data System (ADS)

    Nichita, Dan Vladimir; Pauly, Jerome; Daridon, Jean-Luc

    2009-07-01

    Solid phase precipitation can greatly affect thermal effects in isenthalpic expansions; wax precipitation may occur in natural hydrocarbon systems in the range of operating conditions, the wax appearance temperature being significantly higher (as high as 350 K) for hyperbaric fluids. Recently, methods for calculating the Joule-Thomson inversion curve (JTIC) for two-phase mixtures, and for three-phase vapor-liquid-multisolid systems have been proposed. In this study, an approach for calculating the JTIC for the vapor-liquid-solid solution systems is presented. The JTIC is located by tracking extrema and angular points of enthalpy departure variations versus pressure at isothermal conditions. The proposed method is applied to several complex synthetic and naturally occurring hydrocarbon systems. The JTIC can exhibit several distinct branches (which may lie within two- or three-phase regions or follow phase boundaries), multiple inversion temperatures at fixed pressure, as well as multiple inversion pressures at given temperature.

  2. Solution- and solid-phase oligosaccharide synthesis using glucosyl iodides: a comparative study.

    PubMed

    Lam, Son N; Gervay-Hague, Jacquelyn

    2002-11-19

    Glycosyl iodide donors have been used in both solid- and solution-phase syntheses yielding alpha-(1 --> 6)-linked glucosyl oligomers in highly efficient protocols. While the solid-phase strategy offers advantages in terms of ease of purification, it requires a total of 7.5 equiv of donor and approximately 12 h to complete the incorporation of one monosaccharide unit. In contrast, solution-phase methods require only 2.5 equiv of donor and 2-3 h reaction time per glycosylation. Moreover, since the reactions are virtually quantitative (> 90%) column chromatography of the material is facile. The overall advantages of solution-phase oligosaccharide synthesis were further illustrated in the convergent synthesis of a hexamer (methoxycarbonylmethyl 6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl-(1 --> 6)-tetrakis-(2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl-(1 --> 6))-2,3,4-tri-O-benzyl-1-thio-alpha-D-glucopyranoside) that was constructed from dimer donor iodides in a two-plus-two and a two-plus-four fashion.

  3. Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes.

    PubMed

    Dabb, Serin L; Messerle, Barbara A; Otting, Gottfried; Wagler, Jörg; Willis, Anthony

    2008-01-01

    The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.

  4. Microstructural and Electrical Characterization of Barium Strontium Titanate-Based Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition

    DTIC Science & Technology

    2003-04-03

    Strontium Titanate-Based Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition DISTRIBUTION: Approved for public...Society H2.4 Microstructural and Electrical Characterization of Barium Strontium Titanate- based Solid Solution Thin Films Deposited on Ceramic...investigated and report the microstructural and electrical characterization of selected barium strontium titanate-based solid solution thin films

  5. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Sugama, Toshifumi

    1993-01-01

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR).sub.n (wherein M is Ti, Zr, Ge or Al; R is CH.sub.3, C.sub.2 H.sub.5 or C.sub.3 H.sub.7 ; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., <1000.degree. C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  6. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Sugama, Toshifumi

    1992-01-01

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR).sub.n (wherein M is Ti, Zr, Ge or Al; R is CH.sub.3, C.sub.2 H.sub.5 or C.sub.3 H.sub.7 ; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., <1000.degree. C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  7. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Toshifumi Sugama.

    1993-04-06

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR)[sub n] (wherein M is Ti, Zr, Ge or Al; R is CH[sub 3], C[sub 2]H[sub 5] or C[sub 3]H[sub 7]; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., < 1,000 C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  8. Leaching heavy metals in municipal solid waste incinerator fly ash with chelator/biosurfactant mixed solution.

    PubMed

    Xu, Ying; Chen, Yu

    2015-07-01

    The chelator [S,S]-ethylene diamine disuccinic acid, citric acid, and biosurfactant saponin are selected as leaching agents. In this study, the leaching effect of saponin mixed with either ethylene diamine disuccinic acid or citric acid on the levels of copper, zinc, lead, and cadmium in municipal solid waste incinerator fly ash is investigated. Results indicate that saponin separately mixed with ethylene diamine disuccinic acid and citric acid exhibits a synergistic solubilisation effect on copper, zinc, lead, and cadmium leaching from fly ash. However, saponin and ethylene diamine disuccinic acid mixed solution exhibits a synergistic solubilisation effect that is superior to that of a saponin and citric acid mixed solution. The extraction rate of heavy metal in fly ash leached with a saponin and chelator mixed solution is related to the pH of the leaching solution, and the optimal range of the pH is suggested to be approximately neutral. After leaching with a saponin and chelator mixed solution, copper, zinc, lead, and cadmium contents significantly decreased (p < 0.05) in the extractable or acid-soluble and reducible fractions. By adopting the proposed approach, the leaching concentrations of copper, zinc, lead, and cadmium in treated fly ash are in accordance with Standard for Pollution Control on the Security Landfill Site for Hazardous Wastes GB18598-2001.

  9. Multifunctional imidazobenzothiadiazole probe displaying solvatofluorochromism and ability to form ion-pair complexes in solid state and in solution.

    PubMed

    Alfonso, María; Fernández, Israel; Tárraga, Alberto; Molina, Pedro

    2015-05-15

    Fluorescent solid 5-pyridylimidazobenzothiadiazole displays a remarkable solvatofluorochromism and with Zn(AcO)2 and Cd(AcO)2, either in solution or under solvent-free conditions, forms ion-pair complexes that in the solid state can be discriminated and separated by fluorescence measurements and selective extraction with diethyl ether or chloroform.

  10. Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

    NASA Astrophysics Data System (ADS)

    de Julián Fernández, C.; Mattei, G.; Paz, E.; Novak, R. L.; Cavigli, L.; Bogani, L.; Palomares, F. J.; Mazzoldi, P.; Caneschi, A.

    2010-04-01

    Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

  11. SOLID SOLUTION CARBIDES ARE THE KEY FUELS FOR FUTURE NUCLEAR THERMAL PROPULSION

    NASA Technical Reports Server (NTRS)

    Panda, Binayak; Hickman, Robert R.; Shah, Sandeep

    2005-01-01

    Nuclear thermal propulsion uses nuclear energy to directly heat a propellant (such as liquid hydrogen) to generate thrust for space transportation. In the 1960 s, the early Rover/Nuclear Engine for Rocket Propulsion Application (NERVA) program showed very encouraging test results for space nuclear propulsion but, in recent years, fuel research has been dismal. With NASA s renewed interest in long-term space exploration, fuel researchers are now revisiting the RoverMERVA findings, which indicated several problems with such fuels (such as erosion, chemical reaction of the fuel with propellant, fuel cracking, and cladding issues) that must be addressed. It is also well known that the higher the temperature reached by a propellant, the larger the thrust generated from the same weight of propellant. Better use of fuel and propellant requires development of fuels capable of reaching very high temperatures. Carbides have the highest melting points of any known material. Efforts are underway to develop carbide mixtures and solid solutions that contain uranium carbide, in order to achieve very high fuel temperatures. Binary solid solution carbides (U, Zr)C have proven to be very effective in this regard. Ternary carbides such as (U, Zr, X) carbides (where X represents Nb, Ta, W, and Hf) also hold great promise as fuel material, since the carbide mixtures in solid solution generate a very hard and tough compact material. This paper highlights past experience with early fuel materials and bi-carbides, technical problems associated with consolidation of the ingredients, and current techniques being developed to consolidate ternary carbides as fuel materials.

  12. Ab Initio Calculations and Synthesis of Sc2InC-Y2InC Solid Solution

    DTIC Science & Technology

    2010-02-03

    tribological materials. It will study a solid solution of this fascinating new class of nanolaminated materials using both theoretical and experimental means...Sc2InC-Y2InC solid solution using ab initio calculations and 2) to synthesize Sc2InC-Y2InC thin films using magnetron sputtering and to determine the correlation between composition, structure, and mechanical properties thereof.

  13. PZT-like structural phase transitions in the BiFeO3-KNbO3 solid solution.

    PubMed

    Lennox, Robert C; Taylor, Daniel D; Vera Stimpson, Laura J; Stenning, Gavin B G; Jura, Marek; Price, Mark C; Rodriguez, Efrain E; Arnold, Donna C

    2015-06-21

    Despite the high prominence of the perovskites BiFeO(3) and KNbO(3) the solid solution between the two has received little attention. We report a detailed neutron and synchrotron X-ray powder diffraction, and Raman spectroscopy study which demonstrates an R3c→P4mm→Amm2 series of structural phase transitions similar to that exhibited by the PbZrO(3)-PbTiO(3) solid solution.

  14. Synthesis of dental enamel-like hydroxyapatite through solution mediated solid-state conversion.

    PubMed

    Zhang, Junling; Jiang, Dongliang; Zhang, Jingxian; Lin, Qingling; Huang, Zhengren

    2010-03-02

    An ordered dental enamel-like structure of hydroxyapatite (HAp) was achieved through a solution mediated solid-state conversion process with organic phosphate surfactant and gelatin as the mediating agent. Transmission electron microscopy (TEM) tests demonstrated uniform sizes in the obtained apatite nanorods which arranged in parallel to each other along the c-axis and formed organized microarchitectural units over 10 microm in size. The sizes of the synthetic hydroxyapatite nanorods were similar to that observed in enamel from human teeth. The formation and regulation of the orientation and size of HAp nanorods might lead to a better understanding of the biomineralization process for the preparation of high performance biomaterials.

  15. NMR in Chevrel-phase solid solution Mo 6Se 8- xTe x

    NASA Astrophysics Data System (ADS)

    Hamard, C.; Le Floch, M.; Peña, O.; Wojakowski, A.

    1999-01-01

    The Mo 6Se 8-Mo 6Te 8 solid solution was studied by X-ray diffraction, magnetic susceptibility and 77Se and 125Te NMR. Dynamic studies show that substitution occurs differently when Se replaces Te in Mo 6Te 8 than when Te replaces Se in Mo 6Se 8. Selenium first fills the high-symmetry sites and then it becomes statistically distributed on the 6f positions of the R3¯ symmetry. In the second case, Te occupies randomly the 8 X sites of the Mo 6X 8 structure, creating large perturbations of the 125Te NMR spectra over the whole range of x.

  16. Solid-Solution Alloying of Immiscible Ru and Cu with Enhanced CO Oxidation Activity.

    PubMed

    Huang, Bo; Kobayashi, Hirokazu; Yamamoto, Tomokazu; Matsumura, Syo; Nishida, Yoshihide; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kawaguchi, Shogo; Kubota, Yoshiki; Kitagawa, Hiroshi

    2017-03-24

    We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts.

  17. Synthesis and characterization of the LDH hydrotalcite-pyroaurite solid-solution series

    SciTech Connect

    Rozov, K.; Berner, U.; Taviot-Gueho, C.; Leroux, F.; Renaudin, G.; Kulik, D.; Diamond, L.W.

    2010-08-15

    A layered double hydroxide (LDH) hydrotalcite-pyroaurite solid-solution series Mg{sub 3}(Al{sub x}Fe{sub 1-x})(CO{sub 3}){sub 0.5}(OH){sub 8} with 1 - x = 0.0, 0.1...1.0 was prepared by co-precipitation at 23 {+-} 2 {sup o}C and pH = 11.40 {+-} 0.03. The compositions of the solids and the reaction solutions were determined using ICP-OES (Mg, Al, Fe, and Na) and TGA techniques (CO{sub 3}{sup 2-}, OH{sup -}, and H{sub 2}O). Powder X-ray diffraction was employed for phase identification and determination of the unit cell parameters a{sub o} and c{sub o} from peak profile analysis. The parameter a{sub o} = b{sub o} was found to be a linear function of the composition. This dependency confirms Vegard's law and indicates the presence of a continuous solid-solution series in the hydrotalcite-pyroaurite system. TGA data show that the temperatures at which interlayer H{sub 2}O molecules and CO{sub 3}{sup 2-} anions are lost, and at which dehydroxylation of the layers occurs, all decrease with increasing mole fraction of iron within the hydroxide layers. Features of the Raman spectra also depend on the iron content. The absence of Raman bands for Fe-rich members (x{sub Fe} > 0.5) is attributed to possible fluorescence phenomena. Based on chemical analysis of both the solids and the reaction solutions after synthesis, preliminary Gibbs free energies of formation have been estimated. Values of {Delta}G{sup o}{sub f}(hydrotalcite) = - 3773.3 {+-} 51.4 kJ/mol and {Delta}G{sup o}{sub f}(pyroaurite) = - 3294.5 {+-} 95.8 kJ/mol were found at 296.15 K. The formal uncertainties of these formations constants are very high. Derivation of more precise values would require carefully designed solubility experiments and improved analytical techniques.

  18. Atomistic simulation of local structure and mixing properties of mineral solid solutions

    NASA Astrophysics Data System (ADS)

    Urusov, V. S.

    2009-04-01

    At present there are several ways to simulate solid solution structure and properties by using ab initio as well as semi-empirical (atomistic) approaches [1]. The main problem of each approach is a reasonable representation of random distribution of atoms substituting each other over common positions. A procedure in operation here used large supercells and generation of most disordered atomic configurations for some selected compositions of solid solution (1:1, 1:3, 3:1, 4:1, 1:4, etc.). The following binary systems were studied by such a way: NaCl - KCl [2, 3, 4], CaO - MgO, CaO - SrO, SrO - BaO (supercell 444, 512 atoms) [3], TiO2 - SnO2 (444, 384 atoms), Al2O3 - Cr2O3, Al2O3 - Fe2O3, Fe2O3 - Cr2O3 (441, 480 atoms) [5]. The calculation technique was based on the method of semi-empirical potentials using the GULP program [6]. Potential parameters of ionic (halides) or partially covalent (oxides) interatomic interactions were optimized by using of structural, thermodynamic and elastic properties of pure components. Calculated heat capacities and entropies as a function of temperature were in a good agreement with experimental data. Excess mixing properties (enthalpy, volume, bulk modulus, vibrational entropy) were calculated for different compositions of the solid solutions. This allowed to reproduce Gibbs energy as a function of temperature and composition and estimate critical temperature of decomposition and miscibility gap of a solid solution. Statistical analysis of bond lengths frequencies for the nearest and next-nearest neighbors in (Na0.5K0.5)Cl, (Ca0.5Mg0.5)O, (Ti0.5Sn0.5)O2, (Al1.0Cr1.0)O3 solid solutions revealed a detailed picture of the lattice relaxation. These results were compared with earlier predictions made by phenomenological crystal chemical models [7, 8] and available EXAFS data. References 1. V.S.Urusov. J.Solid State Chem. 2000. V.153. 357. 2. Urusov V.S., Petrova T.G., Leonenko E.V., Eremin N.N. Vestn. Mosc. Univ. 2008

  19. Coinage metals binding as main group elements: structure and bonding of the carbene complexes [TM(cAAC)2] and [TM(cAAC)2](+) (TM = Cu, Ag, Au).

    PubMed

    Jerabek, Paul; Roesky, Herbert W; Bertrand, Guy; Frenking, Gernot

    2014-12-10

    Quantum chemical calculations using density functional theory have been carried out for the cyclic (alkyl)(amino)carbene (cAAC) complexes of the group 11 atoms [TM(cAAC)2] (TM = Cu, Ag, Au) and their cations [TM(cAAC)2](+). The nature of the metal-ligand bonding was investigated with the charge and energy decomposition analysis EDA-NOCV. The calculations show that the TM-C bonds in the charged adducts [TM(cAAC)2](+) are significantly longer than in the neutral complexes [TM(cAAC)2], but the cations have much higher bond dissociation energies than the neutral molecules. The intrinsic interaction energies ΔEint in [TM(cAAC)2](+) take place between TM(+) in the (1)S electronic ground state and (cAAC)2. In contrast, the metal-ligand interactions in [TM(cAAC)2] involve the TM atoms in the excited (1)P state yielding strong TM p(π) → (cAAC)2 π backdonation, which is absent in the cations. The calculations suggest that the cAAC ligands in [TM(cAAC)2] are stronger π acceptors than σ donors. The trends of the intrinsic interaction energies and the bond dissociation energies of the metal-ligand bonds in [TM(cAAC)2] and [TM(cAAC)2](+) give the order Au > Cu > Ag. Calculations at the nonrelativistic level give weaker TM-C bonds, particularly for the gold complexes. The trend for the bond strength in the neutral and charged adducts without relativistic effects becomes Cu > Ag > Au. The EDA-NOCV calculations suggest that the weaker bonds at the nonrelativistic level are mainly due to stronger Pauli repulsion and weaker orbital interactions. The NBO picture of the C-TM-C bonding situation does not correctly represent the nature of the metal-ligand interactions in [TM(cAAC)2].

  20. Phase separation in dilute solutions of 3He in solid 4He

    NASA Astrophysics Data System (ADS)

    Huan, C.; Yin, L.; Xia, J. S.; Candela, D.; Cowan, B. P.; Sullivan, N. S.

    2017-03-01

    We report the results of studies of the phase separation of solid solutions of dilute concentrations of 3He in 4He. The temperatures and the kinetics of the phase separation were determined from NMR experiments for 3He concentrations 1.6 ×10-5solution theory as augmented by Edwards and Balibar [Phys. Rev. B 39, 4083 (1989), 10.1103/PhysRevB.39.4083]. The growth of 3He droplets shows a t1 /3 time dependence at long times consistent with Ostwald ripening.

  1. NEXAFS Chemical State and Bond Lengths of p-Aminobenzoic Acid in Solution and Solid State

    NASA Astrophysics Data System (ADS)

    Stevens, J. S.; Gainar, A.; Suljoti, E.; Xiao, J.; Golnak, R.; Aziz, E. F.; Schroeder, S. L. M.

    2016-05-01

    Solid-state and solution pH-dependent NEXAFS studies allow direct observation of the electronic state of para-aminobenzoic acid (PABA) as a function of its chemical environment, revealing the chemical state and bonding of the chemical species. Variations in the ionization potential (IP) and 1s→π* resonances unequivocally identify the chemical species (neutral, cationic, or anionic) present and the varying local environment. Shifts in σ* shape resonances relative to the IP in the NEXAFS spectra vary with C-N bond length, and the important effect of minor alterations in bond length is confirmed with nitrogen FEFF calculations, leading to the possibility of bond length determination in solution.

  2. Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

    NASA Technical Reports Server (NTRS)

    Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.

    1975-01-01

    Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

  3. Effective distribution coefficients of a binary ideal solid solution controlled by kink kinetics

    NASA Astrophysics Data System (ADS)

    Matsumoto, Naoko; Kitamura, Masao

    2001-01-01

    Effective distribution coefficients of a binary ideal solid solution growing from dilute surroundings are derived for the steady state using a model in which atoms attach and detach only at kink sites on a (0 0 1) surface of a simple cubic crystal. A system of equations is presented to give the step-edge, terrace, and bulk compositions in terms of attachment and detachment frequencies. The total net flux of atoms from the mother phase to kink sites is also formulated as a function of these compositions and the frequencies. Numerical solutions to the system of equations show that the step-edge, terrace, and bulk compositions are different from one another and that the step-edge, terrace, and bulk distribution coefficients will all approach unity from their respective equilibrium values as the total net flux increases.

  4. Exact solution of the two-level system and the Einstein solid in the microcanonical formalism

    NASA Astrophysics Data System (ADS)

    Bertoldi, Dalía S.; Bringa, Eduardo M.; Miranda, E. N.

    2011-11-01

    The two-level system and the Einstein model of a crystalline solid are taught in every course of statistical mechanics and they are solved in the microcanonical formalism because the number of accessible microstates can be easily evaluated. However, their solutions are usually presented using the Stirling approximation to deal with factorials. In this paper, those two models are solved without any approximation, using the gamma function and its derivatives. Exact values are calculated for the entropy, temperature and specific heat, and the relative error between our exact solution and the approximate one using the Stirling approximation. This error is significant for small systems, with a number of particles N ~ 100, as in studies of atomic clusters or nanoscale structures.

  5. Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment

    NASA Astrophysics Data System (ADS)

    Bachmaier, A.; Stolpe, M.; Müller, T.; Motz, C.

    2015-08-01

    Nanocrystalline and ultrafine-grained Cu100-xCox (x = 26 and 76) solid solutions have been prepared by severe plastic deformation (SPD) of elemental powder mixtures. For both concentrations a supersaturated solid solution fcc phase was identified after the deformation process with grain sizes of less than 50 nm for Co rich solutions and around 100 nm for Cu rich solutions. Additionally, synthesis of nanocrystalline materials in the Cu-Co alloy system by electrodeposition has been conducted. Microstructural characterization by scanning and transmission electron microscopy, differential scanning calorimetry, and microhardness measurements are used to investigate the structural evolution, the thermal stability and mechanical properties of the different nanocrystalline Cu-Co alloy materials during isothermal and non-isothermal annealing. In this study it is shown that the phase decomposition of the metastable Cu-Co solid solutions has a significant influence on their thermal stability, which can be linked to the underlying microstructure that forms during annealing.

  6. In situ study of the solid-state formation of U(1-x)Am(x)O(2±δ) solid solution.

    PubMed

    Lebreton, Florent; Belin, Renaud C; Prieur, Damien; Delahaye, Thibaud; Blanchart, Philippe

    2012-09-03

    In order to reduce the nuclear waste inventory and radiotoxicity, U(1-x)Am(x)O(2±δ) materials are promising fuels for heterogeneous transmutation. In this context, they are generally fabricated from UO(2+δ) and AmO(2-δ) dioxide powders. In the subsequent solid solution, americium is assumed to be trivalent whereas uranium exhibits a mixed-valence (+IV/+V) state. However, no formation mechanisms were ever evidenced and, more particularly, it was not possible to know whether the reduction of Am(IV) to Am(III) occurs before the solid-solution formation, or only once it is established. In this study, we used high-temperature X-ray diffraction on a UO(2±δ)/AmO(2-δ) (15 mol %) mixture to observe in situ the formation of the U(1-x)Am(x)O(2±δ) solid solution. We show that UO(2+δ) is, at relatively low temperature (<700 K), oxidized to U(4)O(9-δ), which is likely to be caused by oxygen release from the simultaneous AmO(2-δ) reduction to cubic Am(2)O(3±δ). Cubic Am(2)O(3+δ) then transforms to hexagonal Am(2)O(3) at 1300 K. Thus, the initial Am(IV) is fully reduced to Am(III) before the solid solution starts forming at 1740 K. The UO(2) fluorite phase vanishes after 4 h at 1970 K, indicating that the formation of the solid solution is completed, which proves that this solid solution is formed after the complete reduction of Am(IV) to Am(III).

  7. Coordination chemistry study of hydrated and solvated lead(II) ions in solution and solid state.

    PubMed

    Persson, Ingmar; Lyczko, Krzysztof; Lundberg, Daniel; Eriksson, Lars; Płaczek, Anna

    2011-02-07

    The coordination chemistry of lead(II) in the oxygen donor solvents water, dimethylsulfoxide (dmso, Me(2)SO), N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), N,N'-dimethylpropyleneurea (dmpu), and 1,1,3,3-tetramethylurea (tmu), as well as in the sulfur donor solvent N,N-dimethylthioformamide (dmtf), has been investigated by extended X-ray absorption fine structure (EXAFS) and/or large angle X-ray scattering (LAXS) in solution, and by single crystal X-ray diffraction and/or EXAFS of solid hydrates and solvates. Lead(II) may either form hemidirected complexes with large bond distance distribution and an apparent gap for excess electron density, or holodirected ones with a symmetric coordination sphere with normal bond distance distribution, depending on the strength of antibonding lead 6s/ligand np molecular orbital interactions and ligand-ligand interactions. The crystallographic data show that the solid lead(II) perchlorate and trifluoromethanesulfonate hydrate structures are hemidirected, while the solid lead(II) solvates of dma and dmpu have regular octahedral configuration with holodirected geometry and mean Pb-O bond distances in the range 2.50-2.52 Å. EXAFS data on the hydrated lead(II) ion in aqueous solution show broad bond distance distribution and a lack of inner-core multiple scattering contributions strongly indicating a hemidirected structure. The Pb-O bond distances found both by EXAFS and LAXS, 2.54(1) Å, point to a six-coordinate hydrated lead(II) ion in hemidirected fashion with an unevenly distributed electron density. The results obtained for the dmso solvated lead(II) ion in solution are ambiguous, but for the most part support a six-coordinate hemidirected complex. The mean Pb-O bond distances determined in dmf and dma solution by LAXS, 2.55(1) and 2.48(1) Å, respectively, indicate that in both solvate complexes lead(II) binds six solvent molecules with the former complex being hemidirected whereas the latter is holodirected. The

  8. Spectroscopic study of mimetite-vanadinite solid solution series - preliminary results

    NASA Astrophysics Data System (ADS)

    Janicka, Urszula; Bajda, Tomasz; Topolska, Justyna; Manecki, Maciej

    2014-05-01

    Mimetite Pb5(AsO4)3Cl and vanadinite Pb5(VO4)3Cl are minerals from the Pb-apatites family which belong to the apatite supergroup. Most often they crystalize under hypergenic conditions, in oxidation zones of Pb ore deposits, where they form paragenesis with pyromorphite Pb5(PO4)3Cl. These minerals are used in the techniques of soils reclamation. Their crystal structure allows substituting of metal cations as well as of anionic complexes. Natural mimetite often contains admixture of phosphates and/or vanadates. Similarly, vanadinite contains admixtures of phosphates and/or arsenates. Among the lead apatites, properties of the minerals from pyromorphite-mimetite solid solution series are well known, while the knowledge about the mimetite-vanadinite series is incomplete. The aim of this research was synthesis and spectroscopic characterization of mimetite-vanadinite solid solution series. Mimetite, vanadinite and their solid solution were synthesized from aqueous solutions by dropwise mixing of Pb(NO3)2, Na3VO4, Na2HAsO4×7H2O and NaCl at 25 ºC and pH = 3.5. Products of the syntheses were analyzed by X-Ray diffraction (XRD), Infrared absorption spectroscopy (FTIR) and Raman spectroscopy. The precipitates formed in the syntheses were identified by the XRD method as mimetite, vanadinite and their solid solutions. Other crystalline phases were not present in synthetic precipitates within the detection limit of XRD. In the Mid-IR spectra of mimetite-vanadinite solid solutions series, bands characteristic for vibrations of As-O bonds of the AsO4 tetrahedra and vibrations of V-O bonds of the VO4 tetrahedra were observed. The band corresponding to stretching ν3vibrations of AsO4 and VO4 occured in the range 700-900 cm-1. In the Raman spectra, bands which are characteristic for vibrations of As-O bonds of the AsO4 tetrahedra and vibrations of V-O bonds of the VO4 tetrahedra were also observed. The bands attributed to vibrations in the AsO4 tetrahedra appeared at 880-740 cm

  9. Synthesis, characterization, and enthalpy of mixing of the (Fe,Mg)C0 3 solid solution

    NASA Astrophysics Data System (ADS)

    Chai, L.; Navrotsky, A.

    1996-11-01

    Solid solutions along the magnesite-siderite join have been synthesized from mechanical mixtures of iron oxalate and basic magnesium carbonate using hydrothermal synthesis techniques at 500°C and about 2 kilobars. The double capsule method was used to provide the atmosphere necessary to prevent decomposition and oxidation of the Fe 2+-bearing carbonate. The synthetic samples were characterized by x-ray diffraction (XRD) and thermogravimetric analysis (TGA). Unit cell parameters, determined from x-ray diffraction in step scan mode, show a linear relationship with composition. The compositions and homogeneity of the sample were confirmed by electron microprobe analysis. Enthalpy of mixing was measured using a Calvet-type calorimeter at 770°C. A two step calorimetric method was developed and confirmed to be successful in determining the energetics of the Fe 2+-bearing carbonates. The first step involved decomposition of the sample in an oxygen atmosphere, and then the decomposition of the sample in an oxygen atmosphere, and then the decomposition products (a mixture of a spinel phase, MgFe 2O 4, and MgO or hematite) were dissolved in lead borate solvent in air as the second step. The enthalpies of mixing are slightly positive, with a regular solution parameter of 4.44 ± 0.75 kJ/mol. Under the assumption of regular solution, the phase diagram of the FeC0 3sbnd MgCO 3 system has been calculated, and the critical temperature for exsolution is about -6°C. Thus, the (Fe,Mg) CO 3 solid solution is expected to be complete and nearly ideal in all geological environments.

  10. Synthesis and crystallographic study of Pb-Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

    SciTech Connect

    Zhu Kongjun; Yanagisawa, Kazumichi; Shimanouchi, Rie; Onda, Ayumu; Kajiyoshi, Koji; Qiu Jinhao

    2009-06-03

    The solid solutions in the system of Pb and Sr hydroxyapatite, Sr{sub 10-x}Pb{sub x}HAp (x = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 deg. C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr-Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb{sub 3}O{sub 2}(OH){sub 2} in the Pb(NO{sub 3}){sub 2}.4H{sub 2}O solution before mixing with (NH{sub 4}){sub 2}HPO{sub 4} solution at 160 deg. C, HTMM causes the decrease of crystallization of the samples with high Pb content.

  11. Temperature-dependent vibrational spectra of zinc(II) bis-(N,N'-diethyldithiocarbamate) in solid state and solution

    NASA Astrophysics Data System (ADS)

    Trendafilova, N.; Kellner, R.

    The IR spectra of zinc(II) bis-(N,N'-diethyldithiocarbamate) in the solid state (at 20, 80 and 120°C) as well as in solution (20°C) have been recorded and discussed as to the changes in the zinc coordination sphere that may occur upon heating and dissolution. The decreased number of bands in the high-temperature and in the solution specta as compared with the room temperature solid state spectra has been explained by removal of the intermolecular contacts upon dissolution or thermal averaging in the high temperature solid state.

  12. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    PubMed Central

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-01-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials. PMID:27991504

  13. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    DOE PAGES

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; ...

    2015-10-15

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). Finally, the high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganesemore » doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.« less

  14. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-10-01

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C-H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100-120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140-160 °C, conversion: 3-5%). The high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganese doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C-H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.

  15. Transformation of photophysical properties from solution to solid state in alkoxy-cyano-diphenylacetylene molecules.

    PubMed

    Karunakaran, Venugopal; Prabhu, Deepak D; Das, Suresh; Varughese, Sunil

    2015-07-28

    Detailed photophysical properties of cyano and mono (MA)/bis alkoxy (DA) substituted diphenylacetylene moieties with different alkyl chain lengths (methyl (1), octyl (8) and dodecyl (12)) were investigated in solution and the solid state in an effort to determine the effect of self-aggregation on these properties. The solvated molecules showed a minimal bathochromic shift with an increase of solvent polarity in their absorption spectra, whereas a significant shift was observed in the emission spectra. This could be attributed to the relatively low change in dipole moment between ground and Franck-Condon excited states and luminescence arising from the intramolecular charge transfer state with a dipole moment significantly higher than that of the ground state. In solid state the emission quantum yields of these materials were significantly higher than in solution. For DA1, polymorphic materials with distinct photophysical properties were obtained. The DA1 materials obtained by fast precipitation (DA1) showed broad fluorescence with peaks at 398, 467 and 535 nm upon excitation at different wavelengths. Detailed analysis of absorption, emission and excitation spectra and lifetime experiments indicated that these peaks could be attributed to the monomer, J- and H-type aggregates respectively. Whereas the crystals obtained by slow crystallization (DA1C) showed only one emission peak at around 396 nm attributed to the monomer. This is supported by the single crystal X-ray structure which consists of a monomer molecule having minimal interaction with nearest neighbour molecules.

  16. Electrophysical properties of solid solutions of silver in PbTe

    SciTech Connect

    Sharov, M. K.

    2012-05-15

    The thermopower coefficient {alpha}{sub 0} and the electrical conductivity {sigma} of Pb{sub 1-x}Ag{sub x}Te solid solutions, where x = (0-0.007), are measured at T = 300 K. The hole concentration p is calculated. All samples are of the p type. With increasing silver content, {alpha}{sub 0} decreases, while p and {sigma} increase. For undoped crystals, {alpha}{sub 0} = 251.0 {mu}V/K, p = 1.1 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 165 {Omega}{sup -1} cm{sup -1}. At the silver-solubility limit for x = 0.007, {alpha}{sub 0} = 193.8 {mu}V/K, p = 2.3 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 216 {Omega}{sup -1} cm{sup -1}. The hole concentration in all samples is much lower than the concentration of introduced silver atoms. The hole gas in Pb{sub 1-x}Ag{sub x}Te solid solutions is weakly degenerate in the entire silver-concentration range.

  17. Solid analyte and aqueous solutions sensing based on a flexible terahertz dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Liang, Lan-Ju; Ding, Xin; Yao, Jian-Quan

    2017-02-01

    A high-sensitivity sensing technique was demonstrated based on a flexible terahertz dual-band metamaterial absorber. The absorber has two perfect absorption peaks, one with a fundamental resonance (f1) of the structure and another with a high-order resonance (f2) originating from the interactions of adjacent unit cells. The quality factor (Q) and figure of merit of f2 are 6 and 14 times larger than that of f1, respectively. For the solid analyte, the changes in resonance frequency are monitored upon variation of analyte thickness and index; a linear relation between the amplitude absorption with the analyte thickness is achieved for f2. The sensitivity (S) is 31.2% refractive index units (RIU-1) for f2 and 13.7% RIU-1 for f1. For the aqueous solutions, the amplitude of absorption decreases linearly with increasing the dielectric constant for the ethanol-water mixture of f1. These results show that the designed absorber cannot only identify a solid analyte but also characterize aqueous solutions through the frequency shift and amplitude absorption. Therefore, the proposed absorber is promising for future applications in high-sensitivity monitoring biomolecular, chemical, ecological water systems, and aqueous biosystems.

  18. Influence of fluorine in the synthesis of apatites. Synthesis of solid solutions of hydroxy-fluorapatite.

    PubMed

    Rodríguez-Lorenzo, L M; Hart, J N; Gross, K A

    2003-09-01

    Hydroxy-fluorapatites (OH-FAps) occur biologically in teeth and form the basis for application as biomaterials. This work aims to synthesize a series of fluoride substituted calcium hydroxyapatites (OHAps) to determine how fluoride influences the synthesis and the resulting characteristics of solid solutions. OH-FAPs powders were synthesized with a chemical composition of Ca(10)(PO(4))(6)(OH)(2-x) F(x), with x=0.0, 0.4, 0.8, 1.2, 1.6 and 2.0. The synthesis of partially substituted OHAp yields materials with lower crystallinity and higher specific surface area than OHAp or fluorapatite (FAp). The smallest crystal size of 263A, occurs at less than 50% hydroxyl substitution with fluoride at x=0.4, and the highest surface area of 132m(2)/g occurs at x=0.8. Reaction kinetics occur faster at higher fluoride content, producing the expected Ca/P ratio of 1.67 only for x=2.0. X-ray and IR studies show that OH-FAPs are homogeneous solid solutions instead of mixtures of OHAp and FAp. The presence of a high fluoride concentration increases the driving force for crystal growth during the calcination process.

  19. Manipulation of σy/κ ratio in single phase FCC solid-solutions

    NASA Astrophysics Data System (ADS)

    Lee, J. I.; Oh, H. S.; Park, E. S.

    2016-08-01

    We investigate how to manipulate the ratio between thermal conductivity (κ) and yield strength (σy) in face-centered cubic solid-solutions by varying the number of principal elements (NPEs) and temperature. The influence of NPEs on κ and its electronic (κe) and lattice (κl) contribution is evaluated using the Wiedemann-Franz law. Positive Δκ/ΔT and the highest κl/κe ratio in high-entropy alloys (HEAs) can be understood by considering severe lattice distortion and compositional complexity. Among the solid-solutions from Ni to quinary alloys, the NiCoFeCrMn HEA exhibits the lowest κ. However, σy increases with increasing NPEs and decreasing temperature. Thus, the NiCoFeCrMn HEA exhibits the highest σy/κ ratio, higher than those of representative cryogenic alloys, which can be distinctively increased with a decrease in temperature. These results would give us a guideline on how to manipulate properties using HEA design concept in order to develop idealized cryogenic materials.

  20. Multiple Multidentate Halogen Bonding in Solution, in the Solid State, and in the (Calculated) Gas Phase.

    PubMed

    Jungbauer, Stefan H; Schindler, Severin; Herdtweck, Eberhardt; Keller, Sandro; Huber, Stefan M

    2015-09-21

    The binding properties of neutral halogen-bond donors (XB donors) bearing two multidentate Lewis acidic motifs toward halides were investigated. Employing polyfluorinated and polyiodinated terphenyl and quaterphenyl derivatives as anion receptors, we obtained X-ray crystallographic data of the adducts of three structurally related XB donors with tetraalkylammonium chloride, bromide, and iodide. The stability of these XB complexes in solution was determined by isothermal titration calorimetry (ITC), and the results were compared to X-ray analyses as well as to calculated binding patterns in the gas phase. Density functional theory (DFT) calculations on the gas-phase complexes indicated that the experimentally observed distortion of the XB donors during multiple multidentate binding can be reproduced in 1:1 complexes with halides, whereas adducts with two halides show a symmetric binding pattern in the gas phase that is markedly different from the solid state structures. Overall, this study demonstrates the limitations in the transferability of binding data between solid state, solution, and gas phase in the study of complex multidentate XB donors.

  1. Specific heat critical behavior in Bi1-xSbx solid solutions

    NASA Astrophysics Data System (ADS)

    Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.; Dresselhaus, M. S.

    2016-09-01

    Studies of the specific heat Cp room temperature concentration dependences for the Bi1-xSbx (x = 0-0.12) solid solutions have shown that in the Cp(x) curves, three peaks of Cp are observed near x = 0.015, x = 0.037, and x = 0.07. These peaks are attributed to critical phenomena accompanying second-order concentration phase transitions (PT) from dilute to concentrated solid solutions, to a gapless state, and a semimetal-semiconductor transition, respectively. The numerical values for the critical exponents of the specific heat α for the Cp peaks near x = 0.015 and x = 0.037 have been determined within the framework of fluctuation theory for second-order phase transitions and percolation theory. It was shown that the α values (α = 0.11 ± 0.005) are the same within the margin of error for both peaks and correspond to the values theoretically calculated within the framework of scale-invariant theory for three-dimensional (3D) models and determined experimentally for different physical systems undergoing second-order phase transitions.

  2. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    DOE PAGES

    Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; ...

    2015-10-28

    A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel tomore » binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.« less

  3. Mechanistic study of carvacrol processing and stabilization as glassy solid solution and microcapsule.

    PubMed

    Tackenberg, Markus W; Geisthövel, Carola; Marmann, Andreas; Schuchmann, Heike P; Kleinebudde, Peter; Thommes, Markus

    2015-01-30

    Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients' glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.

  4. Thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6) solid solution.

    PubMed

    Zevalkink, Alex; Swallow, Jessica; Ohno, Saneyuki; Aydemir, Umut; Bux, Sabah; Snyder, G Jeffrey

    2014-11-14

    Zintl phases are attractive for thermoelectric applications due to their complex structures and bonding environments. The Zintl compounds Ca(5)Al(2)In(x)Sb(6)and Ca(5)Al(2)In(x)Sb(6) have both been shown to have promising thermoelectric properties, with zT values of 0.6 and 0.7, respectively, when doped to control the carrier concentration. Alloying can often be used to further improve thermoelectric materials in cases when the decrease in lattice thermal conductivity outweighs reductions to the electronic mobility. Here we present the high temperature thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6)solid solution. Undoped and optimally Zn-doped samples were investigated. X-ray diffraction confirms that a full solid solution exists between the Al and In end-members. We find that the Al : In ratio does not greatly influence the carrier concentration or Seebeck effect. The primary effect of alloying is thus increased scattering of both charge carriers and phonons, leading to significantly reduced electronic mobility and lattice thermal conductivity at room temperature. Ultimately, the figure of merit is unaffected by alloying in this system, due to the competing effects of reduced mobility and lattice thermal conductivity.

  5. Pressureless sintered beta-prime-Si3N4 solid solution - Fabrication, microstructure, and strength

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1977-01-01

    Pressureless sintering of beta-prime-Si3N4 solid solution was studied as a function of temperature using Si3N4, A1N, and Al2O3 as basic constituents. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta-prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 M Pa were achieved at moderate temperature (1000 C), but decreased to 228 M Pa at 1380 C. This substantial strength loss was attributed to a 'glassy' grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

  6. Pressureless sintered beta prime-Si3N4 solid solution: Fabrication, microstructure, and strength

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1977-01-01

    Si3N4, AlN, and Al2O3 were used as basic constituents in a study of the pressureless sintering of beta prime-Si3N4 solid solution as a function of temperature. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 MPa were achieved at moderate temperature (1000 C), but decreased to 228 MPa at 1380 C. This substantial strength loss was attributed to a glassy grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

  7. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  8. Controlling the Electronic Structures of Perovskite Oxynitrides and their Solid Solutions for Photocatalysis.

    PubMed

    Umezawa, Naoto; Janotti, Anderson

    2016-05-10

    Band-gap engineering of oxide materials is of great interest for optoelectronics, photovoltaics, and photocatalysis applications. In this study, electronic structures of perovskite oxynitrides, LaTiO2 N and SrNbO2 N, and solid solutions, (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x , are investigated using hybrid density functional calculations. Band gaps of LaTiO2 N and SrNbO2 N are much smaller than that of SrTiO3 owing to the formation of a N 2p band, which is higher in energy than the O 2p band. The valence- and conduction-band offsets of SrTiO3 /LaTiO2 N and SrTiO3 /SrNbO2 N are computed, and the adequacy for H2 evolution is analyzed by comparing the positions of the band edges with respect to the standard hydrogen electrode (SHE). The band gap of (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x solid solutions are also discussed.

  9. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    PubMed Central

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-01-01

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). The high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganese doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface. PMID:26469151

  10. Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

    NASA Astrophysics Data System (ADS)

    Kula, Anna; Jia, Xiaohui; Mishra, Raj K.; Niewczas, Marek

    2016-12-01

    The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (-269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

  11. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    SciTech Connect

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  12. All-proportional solid-solution Rh-Pd-Pt alloy nanoparticles by femtosecond laser irradiation of aqueous solution with surfactant

    NASA Astrophysics Data System (ADS)

    Sarker, Md. Samiul Islam; Nakamura, Takahiro; Sato, Shunichi

    2015-06-01

    Formation of Rh-Pd-Pt solid-solution alloy nanoparticles (NPs) by femtosecond laser irradiation of aqueous solution in the presence of polyvinylpyrrolidone (PVP) or citrate as a stabilizer was studied. It was found that the addition of surfactant (PVP or citrate) significantly contributed to reduce the mean size of the particles to 3 nm for PVP and 10 nm for citrate, which was much smaller than that of the particles fabricated without any surfactants (20 nm), and improved the dispersion state as well as the colloidal stability. The solid-solution formation of the Rh-Pd-Pt alloy NPs was confirmed by the XRD results that the diffraction pattern was a single peak, which was found between the positions corresponding to each pure Rh, Pd, and Pt NPs. Moreover, all the elements were homogeneously distributed in every particle by STEM-EDS elemental mapping, strongly indicating the formation of homogeneous solid-solution alloy. Although the Rh-Pd-Pt alloy NPs fabricated with PVP was found to be Pt rich by EDS observation, the composition of NPs fabricated with citrate almost exactly preserved the feeding ratio of ions in the mixed solution. To our best knowledge, these results demonstrated for the first time, the formation of all-proportional solid-solution Rh-Pd-Pt alloy NPs with well size control.

  13. ZrB2-HfB2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

    DOE PAGES

    Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

    2016-11-09

    Spark plasma sintered transition metal diborides such as HfB2, ZrB2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H2SO4 and 1 M NaOH electrolytes. HfB2 and ZrB2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H2SO4 were in the range of 0.15 - 0.18 V/decade except for pure HfB2 which showed a Tafel slope of 0.38more » V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of HfxZr1-xB2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.« less

  14. Dissolution of aragonite-strontianite solid solutions in nonstoichiometric Sr (HCO3)2-Ca (HCO3)2-CO2-H2O solutions

    USGS Publications Warehouse

    Plummer, L.N.; Busenberg, E.; Glynn, P.D.; Blum, A.E.

    1992-01-01

    Synthetic strontianite-aragonite solid-solution minerals were dissolved in CO2-saturated non-stoichiometric solutions of Sr(HCO3)2 and Ca(HCO3)2 at 25??C. The results show that none of the dissolution reactions reach thermodynamic equilibrium. Congruent dissolution in Ca(HCO3)2 solutions either attains or closely approaches stoichiometric saturation with respect to the dissolving solid. In Sr(HCO3)2 solutions the reactions usually become incongruent, precipitating a Sr-rich phase before reaching stoichiometric saturation. Dissolution of mechanical mixtures of solids approaches stoichiometric saturation with respect to the least stable solid in the mixture. Surface uptake from subsaturated bulk solutions was observed in the initial minutes of dissolution. This surficial phase is 0-10 atomic layers thick in Sr(HCO3)2 solutions and 0-4 layers thick in Ca(HCO3)2 solutions, and subsequently dissolves and/or recrystallizes, usually within 6 min of reaction. The initial transient surface precipitation (recrystallization) process is followed by congruent dissolution of the original solid which proceeds to stoichiometric saturation, or until the precipitation of a more stable Sr-rich solid. The compositions of secondary precipitates do not correspond to thermodynamic equilibrium or stoichiometric saturation states. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of solid solutions on surfaces of aragonite and strontianite single crystals immersed in Sr(HCO3)2 and Ca(HCO3)2 solutions, respectively. In Sr(HCO3)2 solutions, the XPS signal from the outer ~ 60 A?? on aragonite indicates a composition of 16 mol% SrCO3 after only 2 min of contact, and 14-18 mol% SrCO3 after 3 weeks of contact. The strontianite surface averages approximately 22 mol% CaCO3 after 2 min of contact with Ca(HCO3)2 solution, and is 34-39 mol% CaCO3 after 3 weeks of contact. XPS analysis suggests the surface composition is zoned with somewhat greater enrichment in the outer ~25

  15. Effect of solid solutions and second phases on the thermal conductivity of zirconium diboride ceramics

    NASA Astrophysics Data System (ADS)

    Harrington, Gregory John Kenneth

    The research presented in this dissertation is focused on the thermal conductivity (k) of ZrB2 ceramics. The goal was to develop a better understanding of how various solid solutions and second phases affect the thermal and electrical transport in ZrB2, with a focus on the effect of C, W, and ZrC. The first study showed C additions improved densification and it was proposed that the reduction of boria was the impetus for this result. Boron carbide was formed by the reaction of excess C with reduced B and its formation was mitigated by the addition of ZrH2. This allowed the ZrB2-C binary system to be evaluated for study two. Study two showed the k of ZrB2 is reduced by C in solid solution and as a second phase due to the decrease in the electron contribution to thermal conductivity. Conductivities of 99 (25°C) and 76 W/m*K (2000°C) were obtained for the most pure ZrB2 (0.026 wt% C in solution and 0.2 vol% zirconia) produced in this study, which are the highest reported values for ZrB2 processed using commercial powders since 1980. The third study evaluated the electrical resistivity of ZrB2 up to 1860°C using the van der Pauw technique. Separate linear regimes were observed below and above 950°C, whereas, previous studies assumed a linear relation. Finally the effect of ZrC on the (Zr,W)B2 solid solution was evaluated in study four. The formation of (Zr,W)C initially increased k, but further ZrC additions decreased k. In the end, this research provides both: (1) usable information for the design of future ultra-high temperature ceramic systems; and (2) fundamental research that lays the groundwork for future studies aimed at understanding thermal transport in diboride based materials.

  16. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    DOE PAGES

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; ...

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate heremore » a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the temperature

  17. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; George, Easo P.

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate here a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the

  18. THERMODYNAMICS AND SOLUBILITY OF (UxNp1-x)O2(am) SOLID SOLUTION IN THE CARBONATE SYSTEM

    SciTech Connect

    Rai, Dhanpat; Hess, Nancy J.; Yui, Mikazu; Felmy, Andrew R.; Moore, Dean A.

    2004-03-15

    ABSTRACT -The formation of a solid solution can significantly affect the solubility of a minor component. The objectives of this study were to determine the nature of U(IV) and Np(IV) solid solutions and their thermodynamic properties. For this purpose, co-precipitates of U(IV) and Np(IV) [(UxNp1-x )O2(am), with values for x of 0.95, 0.85, 0.50, 0.15, and 0.05] were prepared, characterized, and used to determine their solubility as a function of K2CO3 concentrations ranging from 1.0 m to 5.0 m in the presence of 0.01 m Na2S2O4 and 0.01 m KOH, and as a function of KHCO3 concentrations ranging from 0.1 m to 0.8 m in the presence of 0.01 m Na2S2O4. The solubility data show that the equilibrium in these systems is reached in <7 days, the solubility-controlling solids are amorphous, and that we were successful in maintaining U and Np in the tetravalent state. A scanning electron microscope equipped with energy dispersive spectrometry and x-ray absorption spectroscopic analyses of the solids indicated the equilibrated co-precipitates to be solid solutions. A close agreement between the thermodynamic predictions, assuming an ideal solid solution, and the experimental solubilities shows that U(IV) and Np(IV) form an ideal solid solution and that non-ideal solid solution behavior for this system can be ruled out.

  19. Cobalt incorporation in calcite: thermochemistry of (Ca,Co)CO3 solid solutions from density functional theory simulations

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Ruiz-Hernández, Sergio E.; Fernández-González, Ángeles; Jiménez, Amalia; de Leeuw, Nora H.; Grau-Crespo, Ricardo

    2015-04-01

    The incorporation of cobalt in mixed metal carbonates is a possible route to the immobilization of this toxic element in the environment. However, the thermodynamics of (Ca,Co)CO3 solid solutions are still unclear due to conflicting data from experiment and from the observation of natural ocurrences. Atomistic computer simulations, which allow the evaluation of thermodynamic properties without the interference of unknown kinetic factors, have been increasingly used in recent years for the investigation of the thermodynamics of mixing and impurity incorporation in carbonate. We report here the results of a computer simulation study of the mixing of calcite (CaCO3) and spherocobaltite (CoCO3), using density functional theory calculations. Our simulations suggest that previously proposed thermodynamic models, based only on observed compositions, significantly overestimate the solubility between the two solids and therefore underestimate the extension of the miscibility gap under ambient conditions. The enthalpy of mixing of the disordered solid solution is strongly positive and moderately asymmetric: calcium incorporation in spherocobaltite is more endothermic than cobalt incorporation in calcite. Ordering of the impurities in (0001) layers is energetically favourable with respect to the disordered solid solution at low temperatures and intermediate compositions, but the ordered phase is still unstable to demixing. The solvus and spinodal lines in the phase diagram using a sub-regular solution model has been also calculated, and conclude that many Ca1-xCoxCO3 mineral solid solutions (with observed compositions of up to x=0.027, and above x=0.93) are metastable with respect to phase separation. The strong non-ideality of this solid solution has an important effect on the solid solution / aqueous solution thermodynamic partitioning: the equilibrium level of substitutional impurities in the endmember solids is always low, regardless of the composition of the aqueous

  20. Solid-State and Solution Metallophilic Aggregation of a Cationic [Pt(NCN)L](+) Cyclometalated Complex.

    PubMed

    Sivchik, Vasily V; Grachova, Elena V; Melnikov, Alexei S; Smirnov, Sergey N; Ivanov, Alexander Yu; Hirva, Pipsa; Tunik, Sergey P; Koshevoy, Igor O

    2016-04-04

    The noncovalent intermolecular interactions (π-π stacking, metallophilic bonding) of the cyclometalated complexes [Pt(NCN)L](+)X(-) (NCN = dipyridylbenzene, L = pyridine (1), acetonitrile (2)) are determined by the steric properties of the ancillary ligands L in the solid state and in solution, while the nature of the counterion X(-) (X(-) = PF6(-), ClO4(-), CF3SO3(-)) affects the molecular arrangement of 2·X in the crystal medium. According to the variable-temperature X-ray diffraction measurements, the extensive Pt···Pt interactions and π-stacking in 2·X are significantly temperature-dependent. The variable concentration (1)H and diffusion coefficients NMR measurements reveal that 2·X exists in the monomeric form in dilute solutions at 298 K, while upon increase in concentration [Pt(NCN)(NCMe)](+) cations undergo the formation of the ground-state oligomeric aggregates with an average aggregation number of ∼3. The photoluminescent characteristics of 1 and 2·X are largely determined by the intermolecular aggregation. For the discrete molecules the emission properties are assigned to metal perturbed IL charge transfer mixed with some MLCT contribution. In the case of oligomers 2·X the luminescence is significantly red-shifted with respect to 1 and originates mainly from the (3)MMLCT excited states. The emission energies depend on the structural arrangement in the crystal and on the complex concentration in solution, variation of which allows for the modulation of the emission color from greenish to deep red. In the solid state the lability of the ligands L leads to vapor-induced reversible transformation 1 ↔ 2 that is accompanied by the molecular reorganization and, consequently, dramatic change of the photophysical properties. Time-dependent density functional theory calculations adequately support the models proposed for the rationalization of the experimental observations.

  1. Solid solution trends that impact electrical design of submicron layers in dielectric capacitors

    NASA Astrophysics Data System (ADS)

    Levi, Roni D.

    It is predictable that future thin layer multilayer dielectrics and thin films embedded capacitors will require higher field and higher reliability performance. This thesis explores the fundamental factors that would limit the high field and reliability performance in thin layer dielectrics based on BaTiO3. Those factors have different origins: On one side, the nature of the metal-dielectric interface was shown to affect the high field dielectric properties of capacitive structures. In addition to that, the intrinsic bulk properties of BaTiO3 based solid solutions affect the high field properties of thin dielectric layers depending on composition and annealing conditions. Both effects were investigated in this study. The temperature dependence of the electrical leakage current density of chemical solution deposited BaTiO3 films on high purity Ni foils was investigated as function of the underlying Ni microstructure. The electrical properties were then characterized on capacitors with and without the presence of Ni grain boundaries. When a Ni grain boundary from the substrate was present in the capacitor used during the electrical measurements, the loss tangent of the capacitor rose rapidly for dc biases exceeding ˜25kV/cm. The critical bias increases to ˜100kV/cm when no substrate grain boundaries are included in the capacitor. In addition, the capacitance-voltage curves are much more symmetric when grain boundaries are absent. This disparity in the electrical behavior was analyzed in terms of the mechanisms of charge conduction across the Ni-dielectric interface. While a reverse biased Schottky emission mechanism dominates the current in areas free of Ni grain boundaries, the Schottky barrier at the cathode is less effective when Ni grain boundaries are present due to local enhancement of the electric field. This, leads to a larger leakage current dominated by the forward biased Schottky barrier at the anode. In addition to the interface influence, the

  2. Computer simulation of the motion of a straight dislocation line in concentrated solid solutions. II. [in fcc alloys

    NASA Technical Reports Server (NTRS)

    Kuo, C. T. K.; Arsenault, R. J.

    1977-01-01

    An investigation was undertaken to determine if the size and modulus interaction of a solute atom with a screw dislocation and the modulus interaction with an edge dislocation contributed to strengthening, in addition to the size interaction with an edge dislocation. The results indicate that the size interaction between solute atom and an edge dislocation accounts for most of the solid solution strengthening in f.c.c. alloys. The contribution to the yield stress from the modulus interaction with an edge dislocation is less than 15%. The interaction between a solute atom and a screw dislocation is much less than that between a solute atom and an edge dislocation.

  3. Iron site occupancies in magnetite-ulvospinel solid solution: A new approach using XMCD

    SciTech Connect

    Pearce, C. I.; Henderson, C. M. B.; Telling, N. D.; Pattrick, R. A.D.; Vaughan, D. J.; Charnock, J. M.; Arenholz, E.; Tuna, F.; Coker, V.S.; Laan, G. van der

    2009-06-22

    Ordering of Fe{sup 3+} and Fe{sup 2+} between octahedral (Oh) and tetrahedral (Td) sites in synthetic members of the magnetite (Fe{sub 3}O{sub 4}) - ulvoespinel (Fe{sub 2}TiO{sub 4}) solid-solution series was determined using Fe L{sub 2,3}-edge X-ray magnetic circular dichroism (XMCD) coupled with electron microprobe and chemical analysis, Ti L-edge spectroscopy, Fe K-edge EXAFS and XANES, Fe{sub 57} Moessbauer spectroscopy, and unit cell parameters. Microprobe analysis, cell edges and chemical FeO determinations showed that the bulk compositions of the samples were stoichiometric magnetite-ulvoespinel solid-solutions. Surface sensitive XMCD showed that the surfaces of these oxide minerals were more sensitive to redox conditions and some samples required re-equilibration with suitable solid-solid buffers. Detailed site-occupancy analysis of these samples gave XMCD-Fe{sup 2+}/Fe{sup 3+} ratios very close to stoichiometric values. L{sub 2,3}-edge spectroscopy showed that Ti{sup 4+} was restricted to Oh sites. XMCD results showed that significant Fe{sup 2+} only entered Td when the Ti content was > 0.40 apfu while Fe{sup 2+} in Oh increased from 1 a.p.f.u in magnetite to a maximum of {approx}1.4 apfu in USP45. As the Ti content increased from this point, the steady increase in Fe{sup 2+} in Td sites was clearly observable in the XMCD spectra, concurrent with a slow decrease in Fe{sup 2+} in Oh sites. Calculated magnetic moments showed a steady decrease from magnetite (4.06 {mu}{sub B}) to USP45 (1.5 {mu}{sub B}) and then a slower decrease towards the value for ulvoespinel (0 {mu}{sub B}). Two of the synthesized samples were also partially maghemitized by re-equilibrating with an oxidizing Ni-NiO buffer and XMCD showed that Fe{sup 2+} oxidation only occurred at Oh sites, with concomitant vacancy formation restricted to this site. This study shows the advantage of using XMCD as a direct measurement of Fe oxidation state in these complex magnetic spinels. These results

  4. Preparation and characterization of carbonated barium-calcium hydroxyapatite solid solutions.

    PubMed

    Yasukawa, Akemi; Ueda, Eiichi; Kandori, Kazuhiko; Ishikawa, Tatsuo

    2005-08-15

    Particles of carbonated barium-calcium hydroxyapatite solid solutions (BaCaHap) with different Ba/(Ba+Ca) (X(Ba)) atomic ratios were prepared by a wet method at 100 degrees C and characterized by various means. The crystal phases and structures of the products strongly depended on the composition of the starting solution, that is, the Ba/(Ba+Ca) atomic ratio ([X(Ba)]) and H3PO4 concentration ([H3PO4]) in the solution. BaCaHap with X(Ba)0.43 could be prepared at [X(Ba)]0.7 by changing [H3PO4], but could never be obtained at [X(Ba)]=0.8-0.95 regardless of [H3PO4]. The carbonated calcium hydroxyapatite particles prepared at [X(Ba)]=0 were fine and short rod-shaped particles (ca. 14x84 nm). With increasing [X(Ba)] from 0 to 0.8, the particles obtained became large spherical agglomerates. The carbonated barium hydroxyapatite particles formed at [X(Ba)]=1 were long rod-shaped agglomerates (ca. 0.2x2 microm) of fine primary particles. The amount of CO2 adsorbed irreversibly on a series of BaCaHaps showed a minimum at (Ba+Ca)/(P+C) atomic ratio of around 1.56, which agreed well with the minimum cation/P ratio obtained for the other hydroxyapatites, as already reported.

  5. Temperature evolution of the crystal structure of Bi1 - xPrxFeO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Karpinsky, D. V.; Troyanchuk, I. O.; Sikolenko, V. V.; Efimov, V.; Efimova, E.; Silibin, M. V.; Chobot, G. M.; Willinger, E.

    2014-11-01

    The crystal structure of solid solutions in the Bi1 - xPrxFeO3 system near the structural transition between the rhombohedral and orthorhombic phases (0.125 ≤ x ≤ 0.15) has been studied. The structural phase transitions induced by changes in the concentration of praseodymium ions and in the temperature have been investigated using X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. It has been established that the sequence of phase transformations in the crystal structure of Bi1 - xPrxFeO3 solid solutions with variations in the temperature differs significantly from the evolution of the crystal structure of the BiFeO3 compounds with the substitution of other rare-earth elements for bismuth ions. The regions of the existence of the single-phase structural state and regions of the coexistence of the structural phases have been determined in the investigation of the crystal structure of the Bi1 - xPrxFeO3 solid solutions. A three-phase structural state has been revealed for the solid solution with x = 0.125 at temperatures near 400°C. The specific features of the structural phase transitions of the compounds in the vicinity of the morphotropic phase boundary have been determined by analyzing the obtained results. It has been found that the solid solutions based on bismuth ferrite demonstrate a significant improvement in their physical properties.

  6. Influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of biodegradable Mg-Zn-Ca alloy

    NASA Astrophysics Data System (ADS)

    Ly, Xuan Nam; Yang, S.; Qin, Y.

    2017-03-01

    The influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of Mg-Zn-Ca alloy was studied in the present investigation by SEM, tensile test, electrochemical and immersion test. The results show that the microstructure of Mg alloys after solid solution treatment significantly changed, a large number of the second phase (Ca2Mg6Zn3, Mg2Ca) dissolved into the α-Mg matrix reaching a supersaturated state, and the grains size was bigger than before solid solution treatment; the mechanical properties were obviously improved. In particular the tensile strength of 0.5wt.% Ca of Mg alloy reached 220MPa and the ductility reached 16.6%. Compared with the as-cast Mg alloys, the corrosion potential after solid-solution treatment slightly shifted negative, but the corrosion current density significantly decreased. After solid solution treatment, the surface corrosion was not serious and the result of weight gain was lower compared with those of the as-cast Mg alloys.

  7. Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L. Niel

    1989-01-01

    The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations () from artificial sea water or NaClMgCl2CaCl2solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0–20 and ∼ 45 mole percent MgCO3) prepared at high calcite supersaturations () from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42−) in the magnesian calcite lattice (point defects) and dislocations (~2 · 109 cm−2). Within each group, the excess free energy of mixing, GE, is described by the mixing model , where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0and A1 for Group I and II solids were evaluated at 25°C. The equilibrium constants of all the solids are closely described by the equation ln , where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and “disordered dolomite”. Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and

  8. Effect of oxygen defects on thermal conductivity of thorium-cerium dioxide solid solutions

    NASA Astrophysics Data System (ADS)

    Muta, Hiroaki; Kado, Hirohisa; Ohishi, Yuji; Kurosaki, Ken; Yamanaka, Shinsuke

    2017-01-01

    Thermal conductivity of thorium-cerium dioxide solid solutions has been measured and analyzed using the relaxation time approximation. Despite the presence of oxygen defects, the partially reduced Th0.8Ce0.2O1.97 exhibited higher thermal conductivity than the stoichiometric one, Th0.8Ce0.2O2.00, showing the same tendency as that previously reported for Th0.7Pu0.3O2-δ. The increase in thermal conductivity with the oxygen defects can be explained by assuming that cerium ions have an average ionic radius of the ionic radii of Ce3+ and Ce4+ in the description of phonon-impurity scattering. This result indicates that the small reduction of (Th,Pu)O2-δ fuel increases the thermal conductivity, especially at high temperatures.

  9. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, Iver E.; Lograsso, Barbara K.; Ellis, Timothy W.

    1994-01-01

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

  10. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

    1994-11-29

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

  11. Variable valence of praseodymium in rare-earth oxide solid solutions

    SciTech Connect

    Kravchinskaya, M.V.; Merezhinskii, K.Y.; Tikhonov, P.A.

    1986-06-01

    Solid solutions of elevated praseodymium oxide content have interesting electrical properties, making them the basis for the manufacture of high-temperature electrically conducting materials. Establishment of the composition-structure-valence state relationships enables control of the material properties. The authors performed investigations using a thermogravimetric apparatus with an electronic microbalance of type EM-5-3M, and using x-ray phase analysis of powders (DRON-1 diffractometer, CuK /SUB alpha/ -radiation). The authors also studied the kinetics of praseodymium oxidation with a thermogravimetric apparatus under isothermal conditions. Evaluation of the results with the equation of Kolmogorov, Erofeev, and Avraam indicates that the process is limited by the chemical oxidation of praseodymium and not by diffusion.

  12. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    NASA Astrophysics Data System (ADS)

    Chow, W. W.; Crawford, M. H.

    2015-10-01

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. A solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.

  13. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    SciTech Connect

    Chow, Weng W.; Crawford, Mary H.

    2015-10-06

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.

  14. Characterization of berkelium(III) dipicolinate and borate compounds in solution and the solid state.

    PubMed

    Silver, Mark A; Cary, Samantha K; Johnson, Jason A; Baumbach, Ryan E; Arico, Alexandra A; Luckey, Morgan; Urban, Matthew; Wang, Jamie C; Polinski, Matthew J; Chemey, Alexander; Liu, Guokui; Chen, Kuan-Wen; Van Cleve, Shelley M; Marsh, Matthew L; Eaton, Teresa M; van de Burgt, Lambertus J; Gray, Ashley L; Hobart, David E; Hanson, Kenneth; Maron, Laurent; Gendron, Frédéric; Autschbach, Jochen; Speldrich, Manfred; Kögerler, Paul; Yang, Ping; Braley, Jenifer; Albrecht-Schmitt, Thomas E

    2016-08-26

    Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state.

  15. Magnetic properties of Ho1- x Lu x B12 solid solutions

    NASA Astrophysics Data System (ADS)

    Gabáni, S.; Gaz̆o, E.; Pristás̆, G.; Takác̆ová, I.; Flachbart, K.; Shitsevalova, N.; Siemensmeyer, K.; Sluchanko, N.

    2013-05-01

    Magnetic properties of the geometrically frustrated antiferromagnet HoB12 (with T N = 7.4 K) modified by substitution of magnetic Ho atoms through non-magnetic Lu ones are presented and discussed. In this case, in Ho1- x Lu x B12 solid solutions, both chemical pressure resulting from different Lu3+ and Ho3+ radii and magnetic dilution take place with increasing Lu content ( x) that change properties of the system. The received results show strong indication for the existence of a quantum critical point near x = 0.9, which separates the region of magnetic order (starting with HoB12 for x = 0) and the nonmagnetic region (ending with superconducting LuB12 for x = 1).

  16. Diffuse scattering measurements of static atomic displacements in crystalline binary solid solutions

    SciTech Connect

    Ice, G.E.; Sparks, C.J.; Jiang, X.; Robertson, L.

    1997-09-01

    Diffuse x-ray scattering from crystalline solid solutions is sensitive to both local chemical order and local bond distances. In short-range ordered alloys, fluctuations of chemistry and bond distances break the long-range symmetry of the crystal within a local region and contribute to the total energy of the alloy. Recent use of tunable synchrotron radiation to change the x-ray scattering contrast between elements has greatly advanced the measurement of bond distances between the three kinds of atom pairs found in crystalline binary alloys. The estimated standard deviation on these recovered static displacements approaches {+-}0.001 {angstrom} (0.0001 nm) which is an order of magnitude more precise than obtained with EXAFS. In addition, both the radial and tangential displacements can be recovered to five near neighbors and beyond. These static displacement measurements provide new information which challenges the most advanced theoretical models of binary crystalline alloys. 29 refs., 8 figs., 2 tabs.

  17. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    DOE PAGES

    Chow, Weng W.; Crawford, Mary H.

    2015-10-06

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages includingmore » low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.« less

  18. Hydration of AMP and ATP molecules in aqueous solution and solid films.

    PubMed

    Faizullin, Dzhigangir; Zakharchenko, Nataliya; Zuev, Yuriy; Puzenko, Alexander; Levy, Evgeniya; Feldman, Yuri

    2013-11-20

    Water enables life and plays a critical role in biology. Considered as a versatile and adaptive component of the cell, water engages a wide range of biomolecular interactions. An organism can exist and function only if its self-assembled molecular structures are hydrated. It was shown recently that switching of AMP/ATP binding to the insulin-independent glucose transporter Human Erythrocyte Glucose Transport Protein (GLUT1) may greatly influence the ratio of bulk and bound water during regulation of glucose uptake by red blood cells. In this paper, we present the results on the hydration properties of AMP/ATP obtained by means of dielectric spectroscopy in aqueous solution and for fully ionized forms in solid amorphous films with the help of gravimetric studies.

  19. Anomalous birefringence in andradite-grossular solid solutions: a quantum-mechanical approach

    NASA Astrophysics Data System (ADS)

    Lacivita, Valentina; D'Arco, Philippe; Orlando, Roberto; Dovesi, Roberto; Meyer, Alessio

    2013-11-01

    The static linear optical properties (refractive indices, birefringence and axial angle) of andradite-grossular (Ca3Fe2Si3O12-Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn-Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1-8 Al for Fe atoms in the primitive cell of andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2 V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.

  20. Atomically resolved three-dimensional structures of electrolyte aqueous solutions near a solid surface.

    PubMed

    Martin-Jimenez, Daniel; Chacon, Enrique; Tarazona, Pedro; Garcia, Ricardo

    2016-07-15

    Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01-1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica.

  1. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    PubMed Central

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules. PMID:28117426

  2. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    NASA Astrophysics Data System (ADS)

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules.

  3. Atomically resolved three-dimensional structures of electrolyte aqueous solutions near a solid surface

    NASA Astrophysics Data System (ADS)

    Martin-Jimenez, Daniel; Chacon, Enrique; Tarazona, Pedro; Garcia, Ricardo

    2016-07-01

    Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01-1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica.

  4. Temperature dependence of the activity of Al in dilute Ni(Al) solid solutions

    SciTech Connect

    Jiang Yong; Smith, J. R.; Evans, A. G.

    2006-12-01

    Activities of dilute Al solid solutions in Ni are determined from a first-principles approach. Both thermal lattice vibration and electronic contributions to free energies are considered and compared. Vibrational contributions tend to dominate the temperature dependencies of the free energies, though electron thermal effects are significant. Calculations show opposing temperature trends for the formation enthalpies and entropies, leading to a partial cancellation of their role in the overall energetics. Nevertheless, their remaining temperature effects are strong. Over the temperature range, 400 K

  5. Covalent binding of biological samples to solid supports for scanning probe microscopy in buffer solution.

    PubMed Central

    Karrasch, S; Dolder, M; Schabert, F; Ramsden, J; Engel, A

    1993-01-01

    Scanning force microscopy allows imaging of biological molecules in their native state in buffer solution. To this end samples have to be fixed to a flat solid support so that they cannot be displaced by the scanning tip. Here we describe a method to achieve the covalent binding of biological samples to glass surfaces. Coverslips were chemically modified with the photoactivatable cross-linker N-5-azido-2-nitrobenzoyloxysuccinimide. Samples are squeezed between derivatized coverslips and then cross-linked to the glass surface by irradiation with ultraviolet light. Such samples can be imaged repeatedly by the scanning force microscope without loss of image quality, whereas identical but not immobilized samples are pushed away by the stylus. Images FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 PMID:8312482

  6. Remanent magnetization of a 'paramagnetic' composition in the ilmenite-hematite solid solution stress

    NASA Technical Reports Server (NTRS)

    Lawson, C. A.; Nord, G. L., Jr.

    1984-01-01

    In the ilmenite-hematite solid solution series, compositions more ilmenite-rich than Ilm(73)Hem(27) are classically thought to be paramagnetic at room temperature. Ilm(80)Hem(20) samples have nevertheless been synthesized that acquire hard saturation remanent and thermoremanent moments. From analysis of AC demagnetization data, the source of the measured remanence is believed to be a single-domain (SD) like material within the IlM(80)Hem(20) grains themselves. On the basis of transmission electron microscope observations, it is suggested that transformation-induced domain boundaries, which in part are enriched in hematite component relative to the bulk composition of the grains, could act as the magnetic carrier of the SD-like remanence.

  7. Compression behavior of quaternary and higher order solid-solution L1(2) trialuminides

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.

    1992-01-01

    Results from preliminary studies undertaken to evaluate the existence of single-phase L1(2) solid solutions between pairs of ternary L1(2) trialuminides are presented. Two-kilogram ingots of selected quaternary compositions were cast, homogenized and forged into pancakes; compression specimens were machined from the forgings and tested as a function of temperature. The results are compared against existing data for the ternary alloys. The ternary L1(2) trialuminides Al66Ti25Mn9, Al67Ti25Cr8, and Al22Ti8Fe3 were found to exhibit continuous solubility in one another. The quaternary Cr-Mn composition does not indicate any strength advantage over its ternary counterparts. The continuous replacement of Mn with Fe enhances the strength of the quaternary compound over the ternary Al66Ti25 Mn9.

  8. Transfer functions for solid-solution partitioning of cadmium for Australian soils.

    PubMed

    de Vries, W; McLaughlin, M J; Groenenberg, J E

    2011-12-01

    To assess transport and ecotoxicological risks of metals, such as cadmium (Cd) in soils, models are needed for partitioning and speciation. We derived regression-based "partition-relations" based on adsorption and desorption experiments for main Australian soil types. First, batch adsorption experiments were carried out over a realistic range of dissolved Cd concentrations in agricultural soils in Australia. Results showed linear sorption relationships, implying the adequacy of using Kd values to describe partitioning. Desorption measurements were then carried out to assess in-situ Kd values and relate these to soil properties The best transfer functions for solid-solution partitioning were found for Kd values relating total dissolved Cd concentration to total soil Cd concentrations, accounting for the variation in pH, SOM contents and DOC concentrations. Model predictions compared well with measurements of an independent data set, but there was a tendency to underestimate dissolved Cd concentrations of highly polluted soils.

  9. SOLIEX: A Novel Solid-Liquid Method of Radionuclides Extraction from Radioactive Waste Solutions - 13486

    SciTech Connect

    Shilova, E.; Viel, P.; Huc, V.

    2013-07-01

    This paper describes recent developments in new solid-liquid extraction method, called SOLIEX, to remove cesium from alkaline solutions. SOLIEX relies on the use of a reversible complexing system comprising a carbon felt bearing molecular traps (calixarenes). This complexing system exhibits a high selectivity for Cs, and is thus expected to be helpful for the treatment of highly diluted cesium wastes even with a high concentration of competing alkali metal cations. As additional advantage, this complexing system can be adapted by molecular engineering to capture other radionuclides, such as Sr, Eu, Am. Finally, this complexing system can be easily and efficiently regenerated by using a cost effective stripping procedure, which limits further generation of waste to meet 'zero liquid' discharge requirements for nuclear facilities. (authors)

  10. Strength, thermal defects, and solid solution hardening in nickel-containing B2 iron aluminides

    SciTech Connect

    Schneibel, J.H.; Munroe, P.R.; Pike, L.M.

    1996-12-31

    Nickel-containing ternary iron aluminides with an aluminum concentration of 45 at.% were investigated with respect to room temperature strength, equilibrium vacancy concentration, and the kinetics of vacancy removal. As compared to binary iron aluminides with the same Al concentration, nickel additions reduce the thermal equilibrium vacancy concentration at 1,273 K, whereas they increase this concentration at 973 K. Furthermore, at low temperatures such as 673 K, nickel additions increase dramatically the time needed to reach vacancy equilibrium. During prolonged annealing at 673 K, the density of <001> dislocations in Fe-45Al-3Ni (at.%) increased by an order of magnitude. This suggests that dislocations act as sinks for vacancies. At the same time, the number density of small (20--50 nm) voids decreased, indicating that they were not stable in the absence of substantial vacancy supersaturations. The findings show also that the solid solution strengthening of iron aluminides due to Ni is much weaker than previously thought.

  11. Two-dimensional solid solution alloy of Bi-Pb binary films on Rh(111)

    NASA Astrophysics Data System (ADS)

    Yuhara, J.; Yokoyama, M.; Matsui, T.

    2011-10-01

    We studied the atomic arrangements and phase diagrams of two-dimensional (2D) Bi-Pb binary films on a Rh(111) surface with low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy. The 2D binary films exhibited incommensurate (4 × 4) LEED patterns with any compositional ratio of Bi:Pb. Atomically resolved STM images revealed that the binary films formed hexagonal, close-packed structures in a 2D solid solution alloy. We found that the 2D binary films followed the Hume-Rothery rule. The interatomic distance decreased linearly from 0.359 nm to 0.342 nm with increasing proportions of Pb. This indicated that the lattice constant of the 2D binary films followed Vegard's law.

  12. Photoelectrochemical properties of CdSe /SUB x/ Te /SUB 1-x/ semiconducting solid solutions

    SciTech Connect

    Kolbasov, G.Y.; Karpov, I.I.; Khanat, L.N.; Pavelets, A.M.

    1986-03-01

    This paper studies the photoelectrochemical properties of polycrystalline films of CdSe /SUB x/ Te /SUB 1-x/ solid solutions at x between 0.5 and 0.8. The spectral dependence of photolectro-chemical current is shown measured with a constant number of light quanta striking CdSe /SUB x/ Te /SUP 1-x/ electrodes with compositions. The results obtained indicate that there is no change in potential drop across the Helmholtz layer when the intensity of the light striking the sample is varied, and that ohmic losses at the photoelectrode are low for the light intensities used. Recombination-type losses of the photogenerated carriers which increae with decreasing superficial band bending are chiefly responsible for the decrease in photocurrent.

  13. Structural and dynamical properties of a new family of solid solutions: ?

    NASA Astrophysics Data System (ADS)

    Bordallo, H. N.; Almairac, R.; Bulou, A.; Nouet, J.

    1996-07-01

    The new solid solutions 0953-8984/8/27/010/img8 have been investigated by different experimental methods in the temperature range 10 K - 300 K. X-ray and calorimetric measurements show that the incommensurate phase characteristic of 0953-8984/8/27/010/img9 is also observed for 0953-8984/8/27/010/img10. Raman spectra were obtained for 0953-8984/8/27/010/img11 and 0953-8984/8/27/010/img12. Two low-frequency, temperature-dependent bands were observed over the whole temperature range investigated. These results are discussed in connection with structural disorder and the presence of precursor effects of an incommensurate phase transition.

  14. Colloidal GaAs quantum wires: solution-liquid-solid synthesis and quantum-confinement studies.

    PubMed

    Dong, Angang; Yu, Heng; Wang, Fudong; Buhro, William E

    2008-05-07

    Colloidal GaAs quantum wires with diameters of 5-11 nm and narrow diameter distributions (standard deviation = 12-21% of the mean diameter) are grown by two methods based on the solution-liquid-solid (SLS) mechanism. Resolved excitonic absorption features arising from GaAs quantum wires are detected, allowing extraction of the size-dependent effective band gaps of the wires. The results allow the first systematic comparison of the size dependences of the effective band gaps in corresponding sets of semiconductor quantum wires and quantum wells. The GaAs quantum wire and well band gaps scale according to the prediction of a simple effective-mass-approximation, particle-in-a-box (EMA-PIB) model, which estimates the kinetic confinement energies of electron-hole pairs in quantum nanostructures of different shapes and confinement dimensionalities.

  15. Hydration of AMP and ATP Molecules in Aqueous Solution and Solid Films

    PubMed Central

    Faizullin, Dzhigangir; Zakharchenko, Nataliya; Zuev, Yuriy; Puzenko, Alexander; Levy, Evgeniya; Feldman, Yuri

    2013-01-01

    Water enables life and plays a critical role in biology. Considered as a versatile and adaptive component of the cell, water engages a wide range of biomolecular interactions. An organism can exist and function only if its self-assembled molecular structures are hydrated. It was shown recently that switching of AMP/ATP binding to the insulin-independent glucose transporter Human Erythrocyte Glucose Transport Protein (GLUT1) may greatly influence the ratio of bulk and bound water during regulation of glucose uptake by red blood cells. In this paper, we present the results on the hydration properties of AMP/ATP obtained by means of dielectric spectroscopy in aqueous solution and for fully ionized forms in solid amorphous films with the help of gravimetric studies. PMID:24264037

  16. Type-II heterojunctions in GaSb-InAs solid solutions: physics and applications

    NASA Astrophysics Data System (ADS)

    Mikhailova, Maya P.; Baranov, Alexej N.; Imenkov, Albert N.; Yakovlev, Yury P.

    1991-03-01

    Staggered-''lineup type II heterojunctions have been realized in Ga In As Sb solid solutions lattice matched. to GaSb as well as ones depending on alloy composition (x1 O. 23 or XinO8O)i n Unique features of type II heterojunctions due to carrier localization and spatial separation on the interface have been experixnen tally observed by electroluminescence generation of coherent radiation and photocurrent gain. Distinctive hallmarks of the narrow-''gap GaSbGaInAsSb heterojunctions have been considered in connection with CV 1-. V and spectral response experiments. Energy band schemes of such structures have been analized. GaSbGaInAsSb heterojunctions with x 0. 80 were found to be type II misaligned ones. Novel optoelectronic devices for midIR spectral range of 1 (lasers LID''s and high-. speed photodiodes) were developed on the base of GaSb-GaInAsSb heterojunctions.

  17. Statistical thermodynamics of non-stoichiometric ceria and ceria zirconia solid solutions.

    PubMed

    Bulfin, B; Hoffmann, L; de Oliveira, L; Knoblauch, N; Call, F; Roeb, M; Sattler, C; Schmücker, M

    2016-08-17

    The thermodynamic redox properties of ceria and ceria zirconia solid solutions are analysed with a new methodology for modelling such systems based on the statistical mechanics of lattice configurations. Experimental thermogravimetric equilibrium data obtained for small non-stoichiometry measurements are combined with literature data to cover a large range of non-stoichiometry (CeO2-δ, δ = 0.001-0.32), temperature (1073-1773 K) and oxygen partial pressure (1-10(-13) bar). A dilute species model of defect clusters , obeying the law of mass action, was sufficient to describe the system over the whole range of conditions, leading to a simple analytical equation of state for the system. This offers new physical insight into the redox properties of ceria based materials, and the theoretical methods developed should also be of great interest for other materials which exhibit continuous oxygen non-stoichiometry similar to ceria, such as perovskite oxides.

  18. Solution-based carbohydrate synthesis of individual solid, hollow, and porous carbon nanospheres using spray pyrolysis.

    PubMed

    Wang, Chengwei; Wang, Yuan; Graser, Jake; Zhao, Ran; Gao, Fei; O'Connell, Michael J

    2013-12-23

    A facile and scalable solution-based, spray pyrolysis synthesis technique was used to synthesize individual carbon nanospheres with specific surface area (SSA) up to 1106 m(2)/g using a novel metal-salt catalyzed reaction. The carbon nanosphere diameters were tunable from 10 nm to several micrometers by varying the precursor concentrations. Solid, hollow, and porous carbon nanospheres were achieved by simply varying the ratio of catalyst and carbon source without using any templates. These hollow carbon nanospheres showed adsorption of to 300 mg of dye per gram of carbon, which is more than 15 times higher than that observed for conventional carbon black particles. When evaluated as supercapacitor electrode materials, specific capacitances of up to 112 F/g at a current density of 0.1 A/g were observed, with no capacitance loss after 20,000 cycles.

  19. Analysis of electrostatic stability and ordering in quaternary perovskite solid solutions

    NASA Astrophysics Data System (ADS)

    Caetano, Clovis; Butler, Keith T.; Walsh, Aron

    2016-04-01

    There are three distinct classes of perovskite structured metal oxides, defined by the charge states of the cations: AIBVO3,AIIBIVO3 , and AIIIBIIIO3 . We investigated the stability of cubic quaternary solid solutions A B O3-A'B'O3 using a model of point-charge lattices. The mixing enthalpies were calculated and compared for the three possible types of combinations of the compounds, both for the random alloys and the ground-state-ordered configurations. The mixing enthalpy of the (I,V)O3-(III,III)O3 alloy is always larger than the other alloys. We found that, different from homovalent alloys, for these heterovalent alloys a lattice constant mismatch between the constituent compounds could contribute to stabilize the alloy. At low temperatures, the alloys present a tendency to spontaneous ordering, forming superlattices consisting of alternated layers of AB O 3 and A'B'O3 along the [110 ] direction.

  20. Polyoxoanion chemistry moves toward the future: From solids and solutions to surfaces

    SciTech Connect

    Klemperer, W.G.; Wall, C.G.

    1998-01-01

    In the context of modern surface science, current understanding of polyoxoanion surface chemistry is truly modest from a structural/mechanistic point of view. Only three techniques have received any attention to date, and none of them has been developed to anywhere near its full potential. The quartz crystal microbalance (QCM) has proven to be a useful qualitative tool for in situ monitoring of polyoxoanion adsorption and adsorption kinetics. A second technique that has shown great potential for in situ study of polyoxoanion surface chemistry at solid-liquid interfaces is modulated infrared spectroscopy. The third and final in situ surface analytical technique that has shown great promise but is yet to be exploited to its full potential is scanning probe microscopy. Sections of the paper discuss scanning probe microscopy; single crystal surfaces; evaporative solution deposition on graphite; electrochemical deposition onto graphite; and self-assembly on metal surfaces.

  1. Flow-Solution-Liquid-Solid Growth of Semiconductor Nanowires: A Novel Approach for Controlled Synthesis

    SciTech Connect

    Hollingsworth, Jennifer A.; Palaniappan, Kumaranand; Laocharoensuk, Rawiwan; Smith, Nickolaus A.; Dickerson, Robert M.; Casson, Joanna L.; Baldwin, Jon K.

    2012-06-07

    Semiconductor nanowires (SC-NWs) have potential applications in diverse technologies from nanoelectronics and photonics to energy harvesting and storage due to their quantum-confined opto-electronic properties coupled with their highly anisotropic shape. Here, we explore new approaches to an important solution-based growth method known as solution-liquid-solid (SLS) growth. In SLS, molecular precursors are reacted in the presence of low-melting metal nanoparticles that serve as molten fluxes to catalyze the growth of the SC-NWs. The mechanism of growth is assumed to be similar to that of vapor-liquid-solid (VLS) growth, with the clear distinctions of being conducted in solution in the presence of coordinating ligands and at relatively lower temperatures (<300 C). The resultant SC-NWs are soluble in common organic solvents and solution processable, offering advantages such as simplified processing, scale-up, ultra-small diameters for quantum-confinement effects, and flexible choice of materials from group III-V to groups II-VI, IV-VI, as well as truly ternary I-III-VI semiconductors as we recently demonstrates. Despite these advantages of SLS growth, VLS offers several clear opportunities not allowed by conventional SLS. Namely, VLS allows sequential addition of precursors for facile synthesis of complex axial heterostructures. In addition, growth proceeds relatively slowly compared to SLS, allowing clear assessments of growth kinetics. In order to retain the materials and processing flexibility afforded by SLS, but add the elements of controlled growth afforded by VLS, we transformed SLS into a flow based method by adapting it to synthesis in a microfluidic system. By this new method - so-called 'flow-SLS' (FSLS) - we have now demonstrated unprecedented fabrication of multi-segmented SC-NWs, e.g., 8-segmented CdSe/ZnSe defined by either compositionally abrupt or alloyed interfaces as a function of growth conditions. In addition, we have studied growth rates as a

  2. Investigating the effect of compression on solute transport through degrading municipal solid waste

    SciTech Connect

    Woodman, N.D. Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

    2014-11-15

    Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.

  3. Nanocrystalline Ce1- x La x O2- δ Solid Solutions Synthesized by Hydrolyzing and Oxidizing

    NASA Astrophysics Data System (ADS)

    Hou, Xueling; Xue, Yun; Han, Ning; Lu, Qianqian; Wang, Xiaochen; Phan, Manh-Huong; Zhong, Yunbo

    2016-05-01

    We undertook a novel batch production approach for the synthesis of CeO2 nanopowders doped with rare earth elements. Solid solution nanopowders of Ce1- x La x O2- δ ( x = 0.15) were successfully synthesized in a large-scale and low-cost production by hydrolyzing and oxidizing Ce-La-C alloys at room temperature and subsequent calcining of their powders at different temperatures (873-1073 K) for 1 h. The Ce-La-C alloys were prepared in a vacuum induction melting furnace. The final products were characterized by x-ray diffraction, transmission electron microscopy, Brunner-Emmet-Teller (BET) surface area analyzer, and Raman spectroscopy. The calculated lattice parameters of the cubic fluorite-type phase of CeO2 tended to increase when La3+ was incorporated into CeO2. The F 2g band shift and the absence of a peak corresponding to La2O3 in the Raman spectra consistently confirmed the incorporation of the La3+ ion into CeO2, and the formation of Ce1- x La x O2- δ solid solutions as manifested by increased oxygen vacancy defects. High-quality Ce1- x La x O2- δ nanopowders of ~10-15 nm diameter with a high BET surface area of ~77 m2 g-1 were obtained. The average crystallite size of Ce1- x La x O2- δ was found to be smaller than that of CeO2 for the same calcination temperature of 1073 K, demonstrating that the introduction of La3+ into CeO2 can stabilize the host lattice and refine the grain size at high temperatures.

  4. Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors

    NASA Astrophysics Data System (ADS)

    Nguyen, An; Gonzalez, Christina M.; Sinelnikov, Regina; Newman, W.; Sun, Sarah; Lockwood, Ross; Veinot, Jonathan G. C.; Meldrum, Al

    2016-03-01

    Silicon quantum dots (Si-QDs) represent a well-known QD fluorophore that can emit throughout the visible spectrum depending on the interface structure and surface functional group. Detection of nitroaromatic compounds by monitoring the luminescence response of the sensor material (typically fluorescent polymers) currently forms the basis of new explosives sensing technologies. Freestanding silicon QDs may represent a benign alternative with a high degree of chemical and physical versatility. Here, we investigate dodecyl and amine-terminated Si-QD luminescence response to the presence of nitrobenzene and dinitrotoluene (DNT) in various solid, solution, and vapor forms. For dinitrotoluene vapor the 3σ detection limit was 6 ppb for monomer-terminated QDs. For nitroaromatics dissolved in toluene the detection limit was on the order of 400 nM, corresponding to ∼100 pg of material distributed over ∼1 cm2 on the sensor surface. Solid traces of nitroaromatics were also easily detectable via a simple ‘touch test’. The samples showed minimal interference effects from common contaminants such as water, ethanol, and acetonitrile. The sensor can be as simple and inexpensive as a small circle of filter paper dipped into a QD solution, with a single vial of QDs able to make hundreds of these sensors. Additionally, a trial fiber-optic sensor device was tested by applying the QDs to one end of a 2 × 2 fiber coupler and exposing them to controlled DNT vapor. Finally, the quenching mechanism was explored via luminescence dynamics measurements and is different for blue (amine) and red (dodecyl) fluorescent silicon QDs.

  5. Solid solution barium–strontium chlorides with tunable ammonia desorption properties and superior storage capacity

    SciTech Connect

    Bialy, Agata; Blanchard, Didier; Vegge, Tejs; Quaade, Ulrich J.

    2015-01-15

    Metal halide ammines are very attractive materials for ammonia absorption and storage—applications where the practically accessible or usable gravimetric and volumetric storage densities are of critical importance. Here we present, that by combining advanced computational materials prediction with spray drying and in situ thermogravimetric and structural characterization, we synthesize a range of new, stable barium-strontium chloride solid solutions with superior ammonia storage densities. By tuning the barium/strontium ratio, different crystallographic phases and compositions can be obtained with different ammonia ab- and desorption properties. In particular it is shown, that in the molar range of 35–50% barium and 65–50% strontium, stable materials can be produced with a practically usable ammonia density (both volumetric and gravimetric) that is higher than any of the pure metal halides, and with a practically accessible volumetric ammonia densities in excess of 99% of liquid ammonia. - Graphical abstract: Thermal desorption curves of ammonia from Ba{sub x}Sr{sub (1−x)}Cl{sub 2} mixtures with x equal to 0.125, 0.25 and 0.5 and atomic structure of Sr(NH{sub 3}){sub 8}Cl{sub 2}. - Highlights: • Solid solutions of strontium and barium chloride were synthesized by spray drying. • Adjusting molar ratios led to different crystallographic phases and compositions. • Different molar ratios led to different ammonia ab-/desorption properties. • 35–50 mol% BaCl{sub 2} in SrCl{sub 2} yields higher ammonia density than any other metal halide. • DFT calculations can be used to predict properties of the mixtures.

  6. BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires with tunable red light emission.

    PubMed

    Lin, Jing; Huang, Yang; Mi, Jiao; Zhang, Xinghua; Lu, Zunming; Xu, Xuewen; Fan, Ying; Zou, Jin; Tang, Chengchun

    2013-10-11

    We report on the controlled growth of novel BN-coated Ca(1-x)Sr(x)S:Eu nanowires via a solid-liquid-solid process. The Ca(1-x)Sr(x)S solid solution forms as one-dimensional nanowires and has been coated with homogeneous protective BN nanolayers. The structure and luminescence properties of this new nanocomposite have been systematically investigated. High-spatial-resolution cathodoluminescence investigations reveal that effective red color tuning has been achieved by tailoring the composition of the Ca(1-x)Sr(x)S nanowires. Moreover, codoping of Ce(3+) and Eu(2+) in the CaS nanowire can induce energy transfer in the matrix and make it possible to obtain enhanced orange color in the nanowires. The BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires are envisaged to be valuable red-emitting nanophosphors and useful in advanced nanodevices and white LEDs.

  7. Smooth and robust solutions for Dirichlet boundary control of fluid-solid conjugate heat transfer problems

    NASA Astrophysics Data System (ADS)

    Yan, Yan; Keyes, David E.

    2015-01-01

    We study a new optimization scheme that generates smooth and robust solutions for Dirichlet velocity boundary control (DVBC) of conjugate heat transfer (CHT) processes. The solutions to the DVBC of the incompressible Navier-Stokes equations are typically nonsmooth, due to the regularity degradation of the boundary stress in the adjoint Navier-Stokes equations. This nonsmoothness is inherited by the solutions to the DVBC of CHT processes, since the CHT process couples the Navier-Stokes equations of fluid motion with the convection-diffusion equations of fluid-solid thermal interaction. Our objective in the CHT boundary control problem is to select optimally the fluid inflow profile that minimizes an objective function that involves the sum of the mismatch between the temperature distribution in the fluid system and a prescribed temperature profile and the cost of the control. Our strategy to resolve the nonsmoothness of the boundary control solution is based on two features, namely, the objective function with a regularization term on the gradient of the control profile on both the continuous and the discrete levels, and the optimization scheme with either explicit or implicit smoothing effects, such as the smoothed Steepest Descent and the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) methods. Our strategy to achieve the robustness of the solution process is based on combining the smoothed optimization scheme with the numerical continuation technique on the regularization parameters in the objective function. In the section of numerical studies, we present two suites of experiments. In the first one, we demonstrate the feasibility and effectiveness of our numerical schemes in recovering the boundary control profile of the standard case of a Poiseuille flow. In the second one, we illustrate the robustness of our optimization schemes via solving more challenging DVBC problems for both the channel flow and the flow past a square cylinder, which use initial

  8. On the Possibility of Formation and Properties of Copper-Silver Solid Solutions Under Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Pilyugin, V. P.; Solodova, I. L.; Tolmachev, T. P.; Antonova, O. V.; Chernyshev, E. G.; Patselov, A. M.

    2016-01-01

    Mechanical alloying of Cu and Ag powders in concentrations Cu1-x-Agx (x at.% = 0.1, 0.2, …, 0.9) under high-pressure torsion is investigated. The alloys obtained have a structure of nanograined nonequilibrium FCC solid solutions with positive deviation from Vegard's law. The hardness of the alloys is 4-6 times higher than of the initial components - copper and silver. The energy and power parameters of treatment of the solid solutions and stages of their formation are calculated from the shear stress measured in situ under high pressure. Thermally induced decomposition of the solid solutions begins from aging under normal conditions, is accelerated upon heating, and ends by short-term heating up to 500°C. It is accompanied by simultaneous development of the processes of gathering recrystallization.

  9. Polarization-sensitive nanowire photodetectors based on solution-synthesized CdSe quantum-wire solids.

    PubMed

    Singh, Amol; Li, Xiangyang; Protasenko, Vladimir; Galantai, Gabor; Kuno, Masaru; Xing, Huili Grace; Jena, Debdeep

    2007-10-01

    Polarization-sensitive photodetectors are demonstrated using solution-synthesized CdSe nanowire (NW) solids. Photocurrent action spectra taken with a tunable white light source match the solution linear absorption spectra of the NWs, showing that the NW network is responsible for the device photoconductivity. Temperature-dependent transport measurements reveal that carriers responsible for the dark current through the nanowire solids are thermally excited across CdSe band gap. The NWs are aligned using dielectrophoresis between prepatterned electrodes using conventional optical photolithography. The photocurrent through the NW solid is found to be polarization-sensitive, consistent with complementary absorption (emission) measurements of both single wires and their ensembles. The range of solution-processed semiconducting NW materials, their facile synthesis, ease of device fabrication, and compatibility with a variety of substrates make them attractive for potential nanoscale polarization-sensitive photodetectors.

  10. Microcosm experiments to study the interaction of solid and solute phases during initial soil development

    NASA Astrophysics Data System (ADS)

    Zimmermann, C.; Chabbi, S.; Schaaf, W.

    2009-04-01

    During the initial phase of soil formation mineral weathering, interactions between the solid and liquid phases as well as accumulation of organic matter play an important role for the development of soil properties and for the establishment of vegetation and the colonization of soil biota. Our study is part of the Transregional Collaborative Research Centre (SFB/TRR 38) ‘Patterns and processes of initial ecosystem development in an artificial catchment' funded by the Deutsche Forschungsgemeinschaft (DFG). The catchment ´Chicken Creeḱ close to Cottbus (Germany) has a size of 6 ha and is composed of a 3-4 m layer of Quaternary loamy to sandy sediments overlying a 1-2 m clay layer. To connect interactions between the soil solid phase and soil solution at the micro-scale with observed processes at the catchment scale we perform microcosm experiments with soil samples from the catchment under controlled laboratory conditions. The microcosm experiments are carried out in a climate chamber at constant 10 °C corresponding to the mean annual temperature of the region. In total 48 soil columns with a diameter of 14.4 cm and height of 30 cm were filled with substrates of two textural compositions reflecting the gradients observed at the catchment and a bulk density of 1.4-1.5 g*cm3. Within the microcosms it is possible to control the gaseous phase and the water fluxes by artificial irrigation. The irrigation runs automated and quasi-continuously four times a day with 6.6 ml each (in total 600 mm*yr-1). Irrigation amount and chemical composition of the artificial rainwater are based on the annual mean at the field site. Litter of two different plant species occurring at the catchment site (Lotus corniculatus, Calamagrostis epigejos) labelled with stable isotopes (δ13C; δ15N) is used for the experiments. All treatments including a control run with four replicates. The gaseous phase in the headspace of the microcosms is analysed continuously for CO2 and N2O contents

  11. Understanding the solution phase chemistry and solid state thermodynamic behavior of pharmaceutical cocrystals

    NASA Astrophysics Data System (ADS)

    Maheshwari, Chinmay

    Cocrystals have drawn a lot of research interest in the last decade due to their potential to favorably alter the physicochemical and biopharmaceutical properties of active pharmaceutical ingredients. This dissertation focuses on the thermodynamic stability and solubility of pharmaceutical cocrystals. Specifically, the objectives are to; (i) investigate the influence of coformer properties such as solubility and ionization characteristics on cocrystal solubility and stability as a function of pH, (ii) to measure the thermodynamic solubility of metastable cocrystals, and study the solubility differences measured by kinetic and equilibrium methods, (iii) investigate the role of surfactants on the solubility and synthesis of cocrystals, (iv) investigate the solid state phase transformation of reactants to cocrystals and the factors that influence the reaction kinetics and, (v) provide models that enable the prediction of cocrystal formation by calculating the free energy of formation for a solid to solid transformation of reactants to cocrystals. Cocrystal solubilities were measured directly when cocrystals were thermodynamically stable, while solubilities were calculated from eutectic concentration measurements when cocrystals were of higher solubility than its components. Cocrystal solubility was highly dependent on coformer solubilities for gabapentin-lactam and lamotrigine cocrystals. It was found that melting point is not a good indicator of cocrystal solubility as solute-solvent interactions quantified by the activity coefficient play a huge role in the observed solubility. Similar to salts, cocrystals also exhibit pHmax, however the salts and cocrystals have different dependencies on the parameters that govern the value of pHmax. It is also shown that cocrystals could provide solubility advantage over salts as lamotrigine-nicotinamide cocrystal hydrate has about 6 fold higher solubility relative to lamotrigine-saccharin salt. In the case of mixtures of solid

  12. Cobalt incorporation in calcite: Thermochemistry of (Ca,Co)CO3 solid solutions from density functional theory simulations

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Ruiz-Hernández, Sergio E.; Fernández-González, Ángeles; Jiménez, Amalia; de Leeuw, Nora H.; Grau-Crespo, Ricardo

    2014-10-01

    The incorporation of cobalt in mixed metal carbonates is a possible route to the immobilisation of this toxic element in the environment. However, the thermodynamics of (Ca,Co)CO3 solid solutions are still unclear due to conflicting data from experiment and from the observation of natural occurrences. We report here the results of a computer simulation study of the mixing of calcite (CaCO3) and spherocobaltite (CoCO3), using density functional theory calculations. Our simulations suggest that previously proposed thermodynamic models, based only on the observed range of compositions, significantly overestimate the solubility between the two solids and therefore underestimate the extension of the miscibility gap under ambient conditions. The enthalpy of mixing of the disordered solid solution is strongly positive and moderately asymmetric: calcium incorporation in spherocobaltite is more endothermic than cobalt incorporation in calcite. Ordering of the impurities in (0001) layers is energetically favourable with respect to the disordered solid solution at low temperatures and intermediate compositions, but the ordered phase is still unstable to demixing. We calculate the solvus and spinodal lines in the phase diagram using a sub-regular solution model, and conclude that many Ca1-xCoxCO3 mineral solid solutions (with observed compositions of up to x = 0.027, and above x = 0.93) are metastable with respect to phase separation. We also calculate solid/aqueous distribution coefficients to evaluate the effect of the strong non-ideality of mixing on the equilibrium with aqueous solution, showing that the thermodynamically-driven incorporation of cobalt in calcite (and of calcium in spherocobaltite) is always very low, regardless of the Co/Ca ratio of the aqueous environment.

  13. Fabrication and Performance of All-Solid-State Chloride Sensors in Synthetic Concrete Pore Solutions

    PubMed Central

    Gao, Xiaojian; Zhang, Jian; Yang, Yingzi; Deng, Hongwei

    2010-01-01

    One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K+, Ca2+, Na+ and SO42− ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments. PMID:22163467

  14. Wetting of a solid substrate by a ``civilized'' model of ionic solutions

    NASA Astrophysics Data System (ADS)

    Oleksy, Anna; Hansen, Jean-Pierre

    2010-05-01

    We use classical density functional theory (DFT) and an explicit solvent description to investigate the wetting and drying behavior of ionic solutions in contact with a charged solid substrate. The solvent is modeled by dipolar hard spheres, while the monovalent ions are oppositely charged hard spheres; cohesion is ensured by a Yukawa attraction between all three species. The free energy functional describing the inhomogeneous solution includes the best available fundamental measure description of excluded volume correlations in a ternary mixture of hard spheres, whereas all electrostatic and cohesive interactions are treated within the mean-field approximation. We find both first and second order wetting transitions which are rather little affected by ions at low and moderate concentrations, compared to the wetting behavior of the pure solvent. A novel drying scenario is predicted, where complete drying is prevented by the electrostatic attraction between a positively charged substrate and the anions, while near a negatively charged substrate, a first order transition with a predrying line is observed. The various scenarios are surprisingly similar to our previous predictions based on a "semiprimitive" model where the solvent particles carry no dipole, but the ion-ion interactions are reduced by a local dielectric permittivity.

  15. A new variable temperature solution-solid interface scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Jahanbekam, Abdolreza; Mazur, Ursula; Hipps, K. W.

    2014-10-01

    We present a new solution-solid (SS) interface scanning tunneling microscope design that enables imaging at high temperatures with low thermal drift and with volatile solvents. In this new design, distinct from the conventional designs, the entire microscope is surrounded in a controlled-temperature and controlled-atmosphere chamber. This allows users to take measurements at high temperatures while minimizing thermal drift. By incorporating an open solution reservoir in the chamber, solvent evaporation from the sample is minimized; allowing users to use volatile solvents for temperature dependent studies at high temperatures. The new design enables the user to image at the SS interface with some volatile solvents for long periods of time (>24 h). An increase in the nonlinearity of the piezoelectric scanner in the lateral direction as a function of temperature is addressed. A temperature dependent study of cobalt(II) octaethylporphyrin (CoOEP) at the toluene/Au(111) interface has been performed with this instrument. It is demonstrated that the lattice parameters remain constant within experimental error from 24 °C to 75 °C. Similar quality images were obtained over the entire temperature range. We report the unit cell of CoOEP at the toluene/Au(111) interface (based on two molecules per unit cell) to be A = (1.36 ± 0.04) nm, B = (2.51 ± 0.04) nm, and α = 97° ± 2°.

  16. Novel cellulose-based amorphous solid dispersions enhance quercetin solution concentrations in vitro.

    PubMed

    Gilley, Andrew D; Arca, Hale Cigdem; Nichols, Brittany L B; Mosquera-Giraldo, Laura I; Taylor, Lynne S; Edgar, Kevin J; Neilson, Andrew P

    2017-02-10

    Quercetin (Q) is a bioactive flavonol with potential to benefit human health. However, Q bioavailability is relatively low, due to its poor aqueous solubility and extensive phase-II metabolism. Strategies to increase solution concentrations in the small intestinal lumen have the potential to substantially increase Q bioavailability, and by extension, efficacy. We aimed to achieve this by incorporating Q into amorphous solid dispersions (ASDs) with cellulose derivatives. Q was dispersed in matrices of cellulose esters including 6-carboxycellulose acetate butyrate (CCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and cellulose acetate suberate (CASub) to afford ASDs that provided stability against crystallization, and pH-triggered release. Blends of CASub and CCAB with the hydrophilic polyvinylpyrrolidone (PVP) further enhanced dissolution. The ASD 10% Q:20% PVP:70% CASub most significantly enhanced Q solution concentration under intestinal pH conditions, increasing area under the concentration/time curve (AUC) 18-fold compared to Q alone. This novel ASD method promises to enhance Q bioavailability in vivo.

  17. Adsorption behavior of hydrophobin and hydrophobin/surfactant mixtures at the solid-solution interface.

    PubMed

    Zhang, Xiaoli L; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Bent, Julian; Cox, Andrew

    2011-09-06

    The adsorption of surface-active protein hydrophobin, HFBII, and HFBII/surfactant mixtures at the solid-solution interface has been studied by neutron reflectivity, NR. At the hydrophilic silicon surface, HFBII adsorbs reversibly in the form of a bilayer at the interface. HFBII adsorption dominates the coadsorption of HFBII with cationic and anionic surfactants hexadecyltrimethyl ammonium bromide, CTAB, and sodium dodecyl sulfate, SDS, at concentrations below the critical micellar concentration, cmc, of conventional cosurfactants. For surfactant concentrations above the cmc, HFBII/surfactant solution complex formation dominates and there is little HFBII adsorption. Above the cmc, CTAB replaces HFBII at the interface, but for SDS, there is no affinity for the anionic silicon surface hence there is no resultant adsorption. HFBII adsorbs onto a hydrophobic surface (established by an octadecyl trimethyl silane, OTS, layer on silicon) irreversibly as a monolayer, similar to what is observed at the air-water interface but with a different orientation at the interface. Below the cmc, SDS and CTAB have little impact upon the adsorbed layer of HFBII. For concentrations above the cmc, conventional surfactants (CTAB and SDS) displace most of the HFBII at the interface. For nonionic surfactant C(12)E(6), the pattern of adsorption is slightly different, and although some coadsorption at the interface takes place, C(12)E(6) has little impact on the HFBII adsorption.

  18. Synthesis and solubility of Pb-Ca and P-As hydroxylapatite solid solutions

    NASA Astrophysics Data System (ADS)

    Puzio, Bartosz; Młynarska, Maria; Motyka, Joanna; Oknińska, Joanna; Mandelt, Agnieszka; Chlebowska, Patrycja; Kwaśniak-Kominek, Monika; Manecki, Maciej

    2016-04-01

    The objective of the study are three solid solution series: - HPY hydroxylpyromorphite Pb5(PO4)3OH - HAP hydroxylapatite Ca5(PO4)3OH - HAP hydroxylapatite Ca5(PO4)3OH - JBM johnbaumite Ca5(AsO4)3OH - JBM johnbaumite Ca5(AsO4)3OH - HMI hydroxylmimetite Pb5(AsO4)3OH The phases were synthesized from aqueous solutions at high pH (over 8) at ambient temperature by dropwise mixing of chemical reagents: Pb(NO3)2, Ca(NO3)2.4H2O, (NH4)H2PO4, and Na2AsHO4.7H2O. The products of all syntheses are crystalline, monomineral fine powders (crystal size less than 1 μm). Their chemical composition is close to theoretical. Systematic shift of XRD peaks and FTIR or Raman bands is observed within the solid solution series. Dissolution experiments were run at 5oC, 25oC, 45oC, and 65oC. An aliquot of 0.5g of each phase was dissolved in 250 mL of 0.05M NH4NO3 (pH between 3 and 5) for about 3 months. In all cases dissolution resulted in increase of pH by about 1. The systems were considered in equilibrium when three consecutive samplings (ca. two weeks apart) resulted in similar concentrations (within 3 standard deviations). The dissolution of all phases in question is incongruent. The amount of precipitating secondary phases was too small for identification. The results of HPY - HAP dissolution experiments are inconclusive due to strongly incongruent dissolution. This is partially in contrary to recent report by Zhu et al. (2015). Systematic increase of solubility is observed in HAP - JBM series. Also, the solubility of these phases increases with the increase of temperature. This is more pronounced for HAP than for JBM. Systematic increase of solubility is also observed in HMI - JBM series. This work is partially funded by AGH research grant no 11.11.140.319 and partially by Polish NCN grant No 2014/01/M/ST10/00355. Zhu,Y., Zhu, Z., Zhao, X., Liang, Y., Huang, Y., 2015. Characterization, dissolution, and solubility of lead hydroxypyromorphite Pb5(PO4)3OH at 25-45oC. Journal of Chemistry

  19. Solution and Solid-State Studies of DNA-Programmable Nanoparticle Single Crystals

    NASA Astrophysics Data System (ADS)

    Auyeung, Evelyn

    This thesis lays the foundation for three main areas that have significantly advanced the field of DNA-programmable nanoparticle assembly: (1) the synthesis of nanoparticle superlattices with novel lattice symmetries (2) post-assembly characterization and applications of superlattices that have been transferred from solution to the solid state and (3) the realization of a slow-cooling strategy for synthesizing faceted nanoparticle single crystals. Together, these advances mark a turning point in the evolution of DNA-programmable assembly from a simple proof-of-concept demonstrated in 1996 to a powerful materials development strategy that has inspired many ongoing investigations in fields including catalysis, plasmonics, and electronics. Chapter 1 begins with an overview of controlled crystallization and its importance across fields including chemistry and materials science. This followed by a description of DNA-programmable assembly and a discussion on its advantages as an assembly strategy. Chapter 2 describes a powerful strategy for synthesizing nanoparticle superlattices using a coreless nanoparticle consisting purely of spherically-oriented oligonucleotides. This "three dimensional spacer approach" allows for the synthesis of nanoparticle superlattices with exotic structures, including one with no mineral equivalent. While DNA is a versatile ligand for nanoparticle assembly, the resulting superlattices are only stable in solution. Chapter 3 addresses these limitations and presents a method for transitioning these materials from solution to the solid state through silica encapsulation. This encapsulation process has transformed the ability to interrogate these materials using electron microscopy, and it has enabled all the studies in subsequent chapters of this thesis. In Chapter 4, a slow-cooling crystallization technique is described that allows for the synthesis of single crystalline microcrystals with well-defined facets from DNA-nanoparticle building blocks

  20. Unprecedented synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution.

    PubMed

    Legrand, Yves-Marie; Gilles, Arnaud; Petit, Eddy; van der Lee, Arie; Barboiu, Mihail

    2011-08-29

    Cyclobutadiene (CBD), the smallest cyclic hydrocarbon bearing conjugated double bonds, has long intrigued chemists because of its chemical characteristics. The question of whether the molecule could be prepared at all has been answered, but the parent compound and its unperturbed derivatives have eluded crystallographic characterization or synthesis "in water". Different approaches have been used to generate and to trap cyclobutadiene in a variety of confined environments: a) an Ar matrix at cryogenic temperatures, b) a hemicarcerand cage enabling the characterization by NMR spectroscopy in solution, and c) a crystalline guanidinium-sulfonate-calixarene G(4)C matrix that is stable enough to allow photoreactions in the solid state. In the latter case, the 4,6-dimethyl-α-pyrone precursor, Me(2)1, has been immobilized in a guanidinium-sulfonate-calixarene G(4)C crystalline network through a combination of non-covalent interactions. UV irradiation of the crystals transforms the entrapped Me(2)1 into a 4,6-dimethyl-Dewar-β-lactone intermediate, Me(2)2, and rectangular-bent 1,3-dimethylcyclobutadiene, Me(2)CBD(R), which are sufficiently stable under the confined conditions at 175 K to allow a conventional structure determination by X-ray diffraction. Further irradiation drives the reaction towards Me(2)3&Me(2)CBD(S)/CO(2) (63.7 %) and Me(2)CBD(R) (37.3 %) superposed crystalline architectures and the amplification of Me(2)CBD(R). The crystallographic models are supported by additional FTIR and Raman experiments in the solid state and by (1)H NMR spectroscopy and ESI mass spectrometry experiments in aqueous solution. Amazingly, the 4,6-dimethyl-Dewar-β-lactone, Me(2)2, the cyclobutadiene-carboxyl zwitterion, Me(2)3, and 1,3-dimethylcyclobutadiene, Me(2)CBD, were obtained by ultraviolet irradiation of an aqueous solution of G(4)C{Me(2)1}. 1,3-Dimethylcyclobutadiene is stable in water at room temperature for several weeks and even up to 50 °C as demonstrated by

  1. Chemically and compositionally modified solid solution disordered multiphase nickel hydroxide positive electrode for alkaline rechargeable electrochemical cells

    DOEpatents

    Ovshinsky, Stanford R.; Corrigan, Dennis; Venkatesan, Srini; Young, Rosa; Fierro, Christian; Fetcenko, Michael A.

    1994-01-01

    A high capacity, long cycle life positive electrode for use in an alkaline rechargeable electrochemical cell comprising: a solid solution nickel hydroxide material having a multiphase structure that comprises at least one polycrystalline .gamma.-phase including a polycrystalline .gamma.-phase unit cell comprising spacedly disposed plates with at least one chemical modifier incorporated around the plates, the plates having a range of stable intersheet distances corresponding to a 2.sup.+ oxidation state and a 3.5.sup.+, or greater, oxidation state; and at least one compositional modifier incorporated into the solid solution nickel hydroxide material to promote the multiphase structure.

  2. The study of magnetic phase diagram of Fe1-xZnxCr2S4 solid solutions

    NASA Astrophysics Data System (ADS)

    Aminov, T. G.; Kirdyankin, D. I.; Shabunina, G. G.; Novotortsev, V. M.

    2013-08-01

    A magnetic phase diagram of Fe1-хZnхCr2S4 solid solutions was studied. The temperature and concentration ranges of existence of magnetoactive phases based on ferrimagnet FeCr2S4 (0≤х≤0.63), antiferromagnet ZnCr2S4 (0.73≤х≤1), and a spin glass (0.63≤х≤0.73) were determined. The concentration dependences of the saturation magnetic moments and Curie temperatures of the solid solutions synthesized were investigated experimentally and theoretically.

  3. Structural stability, mechanical and electronic properties of cubic BC(x)N crystals within a random solid solution model.

    PubMed

    Zhuang, Chunqiang; Zhao, Jijun; Jiang, Xue; Jiang, Xin

    2009-10-07

    We propose a random solution model for cubic BC(x)N (0.21solid solutions are not a simple mixing of diamond and cubic-BN. The computed bandgaps are substantially lower than those of diamond and BN. Compared to BC(2)N, the BC(x)N solids with higher carbon content (x>2) exhibit better structural stability and higher elastic moduli, making them more attractive as potential superhard materials.

  4. Self-catalytic solution-liquid-liquid-solid (SLLS) growth of tapered SnS nanorods

    NASA Astrophysics Data System (ADS)

    Cho, Ki-Hyun; Sung, Yun-Mo

    2013-04-01

    Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could prevent the oxidation of Sn precursors and thus it could facilitate the growth of SnS nanorods, since the surface of Sn clusters and droplets could be momentarily passivated by TOPS molecules. Without addition of extra catalyst nanoparticles, the nucleation and growth of SnS nanorods was induced by liquid Sn droplets. Spherical Sn tips existing at the top of the nanorods evidence the self-catalytic growth. The SLLS growth was proposed based upon the large Sn clusters existing at the bottom of the SnS nanorods in an intermediate stage (5 s) of the growth and the tapered morphology of the nanorods. The growth of SnS nanorods could progress by the upward diffusion of Sn atoms from large liquid Sn clusters along the surface of the SnS nanorods to the interfacial liquid layers (neck area) and the diffusion of S decomposed from TOPS in the solution to the neck area. SnS nanorods showed a direct energy band gap of ~1.6 eV, determined by using the Kubelka-Munk transformation of UV-visible spectra. This self-catalytic SLLS growth produced high-quality and single crystalline SnS nanorods within only 15 s at 290 °C.Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could

  5. Self-catalytic solution-liquid-liquid-solid (SLLS) growth of tapered SnS nanorods.

    PubMed

    Cho, Ki-Hyun; Sung, Yun-Mo

    2013-05-07

    Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could prevent the oxidation of Sn precursors and thus it could facilitate the growth of SnS nanorods, since the surface of Sn clusters and droplets could be momentarily passivated by TOPS molecules. Without addition of extra catalyst nanoparticles, the nucleation and growth of SnS nanorods was induced by liquid Sn droplets. Spherical Sn tips existing at the top of the nanorods evidence the self-catalytic growth. The SLLS growth was proposed based upon the large Sn clusters existing at the bottom of the SnS nanorods in an intermediate stage (5 s) of the growth and the tapered morphology of the nanorods. The growth of SnS nanorods could progress by the upward diffusion of Sn atoms from large liquid Sn clusters along the surface of the SnS nanorods to the interfacial liquid layers (neck area) and the diffusion of S decomposed from TOPS in the solution to the neck area. SnS nanorods showed a direct energy band gap of ∼1.6 eV, determined by using the Kubelka-Munk transformation of UV-visible spectra. This self-catalytic SLLS growth produced high-quality and single crystalline SnS nanorods within only 15 s at 290 °C.

  6. ZrB2-HfB2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

    SciTech Connect

    Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

    2016-11-09

    Spark plasma sintered transition metal diborides such as HfB2, ZrB2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H2SO4 and 1 M NaOH electrolytes. HfB2 and ZrB2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H2SO4 were in the range of 0.15 - 0.18 V/decade except for pure HfB2 which showed a Tafel slope of 0.38 V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of HfxZr1-xB2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.

  7. Chemical composition and acid-base properties of the surface of GaAs-CdS solid solutions

    NASA Astrophysics Data System (ADS)

    Kirovskaya, I. A.; Zemtsov, A. E.

    2007-01-01

    Chemical composition and acid-base properties of the surfaces of GaAs-CdS solid solutions and the constituent binary compounds exposed to air, vacuum, CO, and NH3 were analyzed using mass spectrometry, IR spectrometry, isoelectric-point pH (pHiso) analysis, and mechanochemical methods. Powders and films were prepared from the solid solutions by isothermal diffusion and discrete vacuum evaporation, respectively. XRD and Raman analysis revealed that a solid solution has a sphalerite or wurtzite structure, depending on its composition. The initial surface of all the systems studied exhibited acidic properties: the pH value ranged from 4.9 to 6.45. The surfaces contained Lewis (electron accepting) and Brönsted (adsorbed H2O and CO2 molecules, OH- groups) sites. The acidity of the surface increased upon treatment with CO and decreased upon treatment with NH3. For all types of treatment, the concentration dependence of the acid-base properties of the surface exhibited an extremum. The strongest acidic sites were revealed on the surface of the (GaAs)0.95 (CdS)0.05 solid solution. The adsorption activity of this solution, a promising material for manufacturing gas sensors, was evaluated.

  8. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AIN and InN

    DTIC Science & Technology

    1992-12-01

    AD-A258 804 Final Technical Report Ii Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent...Technical 6/1/86-12/31/92 4. TITLE AND SUBTITLE Growth, Nitrogen Vacancy Reduction and 5. FUNDING NUMBERS Solid Solution Formation in Cubic GaN Thin...According to the structural and chemical analyses, there is no reason to believe that a homogeneous solid solution close to this composition had

  9. Improving the structural consistency of C-S-H solid solution thermodynamic models

    SciTech Connect

    Kulik, Dmitrii A.

    2011-05-15

    Simple aqueous-solid solution models of C-S-H (calcium silicate hydrate) are widely used in studies of cement hydration and waste-cement interactions. Even without a clear structural/mechanistic basis, such thermodynamic models yield a good description of solubility data in [Ca]-C/S space, while only satisfactory in [Si]-C/S, H{sub 2}O-C/S, [Ca]-[Si] spaces and in the 0.1 < C/S < 0.8 range. Here, using a multi-site (sublattice) concept, the ideal solid solution model of C-S-H is revised to make it consistent with the Richardson-Groves structural model of C-S-H and with the modern interpretation of spectroscopic ({sup 29}Si MAS NMR) and solubility data. Consideration of two site substitutions, (1) coupled H{sub 2}OCa{sup 2+} for SiO{sub 2}H{sub 2}{sup 2+} replacement in bridging tetrahedral and adjacent interlayer sites, and (2) substitution of interstitial Ca(OH){sub 2} for a vacancy, leads to a new CSHQ model of (A,B) (C,D)X type composed of two tobermorite-like and two jennite-like end members. Because this ideal sublattice SS model cannot fit solubility data well at 0.8 < C/S < 1.1, a simpler CSH3T model is constructed from a polymeric TobH (CaO){sub 2}(SiO{sub 2}){sub 3}(H{sub 2}O){sub 5}, a dimeric T2C (CaO){sub 3}(SiO{sub 2}){sub 2}(H{sub 2}O){sub 5}, and an ordered pentameric T5C (CaO){sub 2.5}(SiO{sub 2}){sub 2.5}(H{sub 2}O){sub 5} tobermorite-like end members. This solid solution model, limited to the range 0.67 < C/S < 1.5, has a correct built-in dependence of the mean silicate chain length on C/S, yields quite realistic fits to the solubility data, and provides a basis for extensions with foreign cations whose sites in the defect-tobermorite structure of C-S-H are known. To account for C-S-H compositions with C/S > 1.5, CSHQ end members were downscaled to one tetrahedral site and used within the simple mixing model. Despite some loss of structural consistency, the solubility and mean silicate chain length data can be reproduced well with this downscaled

  10. Assessment of a modified and optimised method for determining chemical oxygen demand of solid substrates and solutions with high suspended solid content.

    PubMed

    Raposo, F; de la Rubia, M A; Borja, R; Alaiz, M

    2008-07-15

    A modified approach to determine the chemical oxygen demand (COD) of solid substrates based on the DIN 38414-S9 standard method is proposed. The adapted procedure is assessed and compared with standard methods widely used for water and wastewater such as the American Public Health Association-American Water Works Association-Water Pollution Control Federation (APHA-AWWA-WPCF) standard methods 5220 B-open reflux (SM-OR) and 5220 D-closed reflux colorimetric (SM-CR). Solutions with high suspended concentration of solids, as well as digestates from an anaerobic reactor, were used during the comparative test. For solid substrates, the COD recovery was about 100% when the proposed method was used. For solutions with solid content higher than 20 g TS L(-1), the recovery was only completed when the proposed method was used, showing that the methods traditionally employed are not very appropriate for samples with the described characteristics. For instance, percentages of COD recovery in the ranges of 77.3-87.1% and 89.4-94.1% were achieved when the SM-OR and SM-CR methods were used, respectively.

  11. Thermodynamic Destabilization of Ti-O Solid Solution by H2 and Deoxygenation of Ti Using Mg.

    PubMed

    Zhang, Ying; Fang, Zhigang Zak; Sun, Pei; Zhang, Tuoyang; Xia, Yang; Zhou, Chengshang; Huang, Zhe

    2016-06-08

    Reactive metals including Ti, Zr, Hf, and V, among others, have a strong chemical affinity to oxygen, which makes them difficult to produce and costly to use. It is especially challenging to produce pure or metal alloy powders of these elements when extremely low oxygen content is required, because they have high solubility for oxygen, and the solid solution of these metals with oxygen is often more stable thermodynamically than their oxides. We report a novel thermochemical approach to destabilize Ti(O) solid solutions using hydrogen, thus enabling deoxygenation of Ti powder using Mg, which has not been possible before because of the thermodynamic stability of Ti(O) solid solutions relative to MgO. The work on Ti serves as an example for other reactive metals. Both analytical modeling and experimental results show that hydrogen can indeed increase the oxygen potential of Ti-O solid solution alloys; in other words, the stability of Ti-O solid solutions is effectively decreased, thus increasing the thermodynamic driving force for Mg to react with oxygen in Ti. Because hydrogen can be easily removed from Ti by a simple heat treatment, it is used only as a temporary alloying element to destabilize the Ti-O systems. The thermodynamic approach described here is a breakthrough and is applicable to a range of different materials. This work is expected to provide an enabling solution to overcome one of the key scientific and technological hurdles to the additive manufacturing of metals, which is emerging rapidly as the future of the manufacturing industry.

  12. Comparative analysis of zaleplon complexation with cyclodextrins and hydrophilic polymers in solution and in solid state.

    PubMed

    Jablan, Jasna; Szalontai, Gábor; Jug, Mario

    2012-12-01

    The aim of this work was to investigate the potential synergistic effect of water-soluble polymers (hypromellose, HPMC and polyvinylpyrrolidone, PVP) on zaleplon (ZAL) complexation with parent β-cyclodextrin (βCD) and its randomly methylated derivative (RAMEB) in solution and in solid state. The addition of HPMC to the complexation medium improved ZAL complexation and solubilization with RAMEB (K(ZAL/RAMEB)=156±5M(-1) and K(ZAL/RAMEB/HPMC)=189±8M(-1); p<0.01), while such effect was not observed for βCD (K(ZAL/βCD)=112±2M(-1) and K(ZAL/βCD/HPMC)=119±8M(-1); p>0.05). Although PVP increased the ZAL aqueous solubility from 0.22 to 0.27mg/mL, it did not show any synergistic effects on ZAL solubilization with the cyclodextrins tested. Binary and ternary systems of ZAL with βCD, RAMEB and HPMC were prepared by spray-drying. Differential scanning calorimetry, X-ray powder diffraction and scanning electron microscopy demonstrated a partial ZAL amorphization in spray-dried binary and ternary systems with βCD, while the drug was completely amorphous in all samples with RAMEB. Furthermore, inclusion complex formation in all systems prepared was confirmed by solid-state NMR spectroscopy. The in vitro dissolution rate followed the rank order ZAL/RAMEB/HPMC>ZAL/RAMEB=ZAL/βCD/HPMC>ZAL/βCD≫ZAL, clearly demonstrating the superior performance of RAMEB on ZAL complexation in the solid state and its synergistic effect with HPMC on drug solubility. Surprisingly, when loaded into tablets made with insoluble microcrystalline cellulose, RAMEB complexes had no positive effect on drug dissolution, because HPMC and RAMEB acted as a binders inside the tablets, prolonging their disintegration. Oppositely, the formulation with mannitol, a soluble excipient, containing a ternary RAMEB system, released the complete drug-dose in only 5min, clearly demonstrating its suitability for the development of immediate-release oral formulation of ZAL.

  13. Pressure-volume equation of state for pyrope-almandine solid solutions

    NASA Astrophysics Data System (ADS)

    Nestola, Fabrizio; Milani, Sula; Angel, Ross J.; Pasqual, Daria; Geiger, Charles A.

    2013-04-01

    Garnet is a key phase of Earth's upper mantle and one of the most abundant solid inclusions in diamonds. The pyrope component (Mg3Al2Si3O12, Py) of garnet found in diamonds of peridotitic and eclogitic origin can be as high as about 79 and 43%, respectively and the almandine component (Fe3Al2Si3O12, Al) is about 11 and 33%, respectively. Thus such garnets are largely Py-Al-rich solid solutions (Stachel and Harris, 2008). To determine the depth of formation of diamond-inclusion pairs, precise and accurate thermoelastic parameters for both the diamond and the solid inclusion phase are necessary (e.g. Izraeli et al., 1999; Howell et al., 2010; Nestola et al., 2011; Howell et al., 2012). We are presently investigating the pressure-volume equation of state for a series of synthetic garnets along the binary pyrope-almandine by X-ray single-crystal diffraction using a diamond anvil cell up to a maximum of 8 GPa pressure. We have completed measurements on two crystals of composition Fe3Al2Si3O12 and Fe1.20Mg1.80Al2Si3O12. The equation of state coefficients obtained by fitting a third-order Birch-Murnaghan to the pressure-volume data show that an increase in the pyrope component in garnet causes a slight decrease of the isothermal bulk modulus, KT0, by about 3%, whereas the first pressure derivative term does not vary. Applying our results to obtain the pressure of formation of a natural diamond-garnet pair, and assuming a garnet composition close to Fe1.20Mg1.80Al2Si3O12, we obtain a pressure of encapsulation (or formation if garnet and diamond are syngenetic) of garnet in diamond between 6.5 and 7.0 GPa. References Howell, D., Wood, I.G., Dobson, D.P., Jones, A.P., Nasdala, L., Harris, J.W. (2010) Contrib. Mineral. Petrol., 160, 705-717. Howell, D., Wood, I.G., Nestola, F., Nimis, P., Nasdala, L. (2012) Eur. J. Mineral., ,. Izraeli, E.S., Harris, J.W., Navon, O. (1999) Earth Planet Sci. Lett., 173, 351-360. Nestola, F., Nimis, P., Ziberna, L., Longo, M., Marzoli, A

  14. Dielectric Function and Interband Transitions in Hg{1-x}Zn{x}Te Solid Solutions

    NASA Astrophysics Data System (ADS)

    Castaing, O.; Benhlal, J. T.; Granger, R.; Triboulet, R.

    1996-07-01

    The dielectric function ɛ_r + iɛ_i in Hg{1-x}Znx Te is found, for the first time, at 293 K. It is deduced from spectroscopic ellipsometry measurements for the entire composition range and for photon energies ranging from 0.75 eV to 5.7 eV. A detailed analysis of the chemical treatments leading to the best surfaces which correspond to the highest values of ɛ_i at the E_2 peak is presented. The oxydation of the surface after the last stripping is also studied. The pseudodielectric function is analysed for the critical point model. The variation, with x of the parameters describing the main critical transitions E_0, E_0 + Δ_0, E_1, E_1 + Δ_1 and E_2 are obtained. The results are discussed in relation to the band structure and to the properties of these compounds. La fonction diélectrique ɛ_r + iɛ_i des solutions solides Hg{1-x}ZnxTe est donnée, pour la première fois, à 293 K. Ces résultats sont déduits de mesures d'ellipsométrie spectroscopique dans tout le domaine de composition et pour des énergies de photon allant de 0,75 eV à 5,7 eV. Les traitements chimiques permettant d'obtenir les meilleures surfaces correspondant aux plus fortes valeurs de ɛ_i au pic E_2 sont analysés en détail. De même, l'oxydation de la surface est suivie par ellipsométrie. La fonction pseudodiélectrique est analysée avec le modèle de points critiques. Les variations des paramètres définissant les principales transitions E_0, E_0 + Δ_0, E_1, E_1 + Δ_1 et E_2 sont données en fonction de la composition x. Ces résultats sont discutés en relation avec la structure de bande et les propriétés de ces solutions solides.

  15. Solid solution directionally solidified eutectics: Model systems for structure-property relationships in interfacial fracture

    NASA Astrophysics Data System (ADS)

    Brewer, Luke Nathaniel

    The next generation of high temperature materials for application in aerospace and power generation systems will be required to withstand temperatures well in excess of 1200°C, often in oxidizing atmospheres. Oxide-oxide directionally solidified eutectics (DSE's) have shown promise as high temperature ceramic materials, only to be limited by their lack of fracture toughness at room temperature. In the case of DSE oxide materials, the interfacial fracture behavior has been blamed for the poor performance in the past and is the subject of interest in this work. In this thesis, the solid solution, directionally solidified quaternary eutectic (SS-DSE), Co1-xNixO/ZrO2(CaO), is developed as a model system for the study of interfacial fracture in oxide-oxide DSE's. A variety of structural and mechanical characterization techniques are applied to investigate structure-property relationships for interfacial fracture behavior. The optical floating zone technique was employed for growing both the eutectic crystals and their single crystal counterparts, Co1-x NixO. Co1-xNixO/ZrO2(CaO) was shown to possess the necessary structural elements to serve as a model system for interfacial fracture. Lamellar microstructures were observed for all compositions. The crystallographic relationships between phases evolved as a model solid solution. Interdiffusion of chemical species was minimal, allowing the layers to treated independently. The core of this thesis is dedicated to studying the nature of interfacial fracture behavior in oxide eutectics. This study is motivated by the novel observation of extensive interfacial delamination for the system CoO/ZrO 2(CaO). A transition from interfacial delamination to interfacial penetration is observed for compositions of Co1-xNixO/ZrO 2(CaO) with x > 0.2. The residual stress state in these materials was investigated using X-ray and neutron diffraction-based techniques. The role of plasticity in interfacial fracture was explored using a

  16. Thermodynamic mixing properties and behavior of almandine-spessartine solid solutions

    NASA Astrophysics Data System (ADS)

    Dachs, Edgar; Geiger, Charles A.; Benisek, Artur; Grodzicki, Michael

    2014-01-01

    The heat capacity, Cp, of five solid-solution members of the almandine(Alm)-spessartine(Sps) binary, consisting of three synthetic polycrystalline and two natural single-crystal samples, was measured in the temperature range between 2 and 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. All garnets exhibit a λ-type heat-capacity anomaly at low temperatures resulting from a paramagnetic to antiferromagnetic phase transition. The temperature of the magnetic transition in Fe-rich garnets occurs between those of the two end-members (i.e. 9.2 K for almandine and 6.2 K for spessartine), but lies at lower values between 3.5 and 4.5 K for more Sps-rich compositions with XMngrt>0.5. The calorimetric entropy at 298 K shows mechanical-mixture behavior for Sps-rich garnets and a slight possible negative deviation from such behavior for Alm-rich compositions. At the 2σ level all data are, however, consistent with ideal mixing behavior and the Margules entropy interaction parameter, WS,FeMngrt, is zero for the Alm-Sps binary. Thermodynamic analysis of published high P and T phase-equilibrium Fe-Mn exchange experiments between garnet and ilmenite shows that the excess Gibbs free energy of mixing, ΔGex, for Fe-Mn in garnet is positive and asymmetric towards spessartine. Margules enthalpy interaction parameters of WH,FeMngrt=4170±518 J/cationṡmol and WH,MnFe=1221±588 J/cationṡmol are derived giving a maximum of ΔGex≈0.7 kJ/cationṡmol at XMngrt≈0.6. ΔHex obtained using autocorrelation analysis of published IR spectra of Alm-Sps solid solutions is in reasonable agreement with that derived from phase-equilibrium and calorimetry data. Previous diffraction and spectroscopic results on Alm-Sps garnets and quantum mechanical calculations made on almandine are used to interpret the macroscopic thermodynamic behavior from a microscopic basis. The relevance of the new garnet Fe-Mn mixing model for petrological calculations is demonstrated by

  17. Photocatalytic hydrogen production over solid solutions between BiFeO3 and SrTiO3

    NASA Astrophysics Data System (ADS)

    Lu, Lingwei; Lv, Meilin; Liu, Gang; Xu, Xiaoxiang

    2017-01-01

    Constituting solid solutions has been an appealing means to gain control over various physicochemical properties. In this work, we synthesized a series of SrTiO3-BiFeO3 solid solutions and systematically explored their structural, optical and photocatalytic properties. Our results show that all solid solutions crystallize in a primitive cubic structure and their band gap values can be easily tuned by adjusting molar ratios between SrTiO3 and BiFeO3. Photocatalytic hydrogen production under both full range and visible light irradiation is greatly improved after forming solid solutions. The highest hydrogen production rate obtained is ∼180 μmol/h under full range irradiation (λ ≥ 250 nm) and ∼4.2 μmol/h under visible light irradiation (λ ≥ 400 nm), corresponding to apparent quantum efficiency ∼2.28% and ∼0.10%, respectively. The activity is found to be strongly influenced by surface area and light absorption. Theoretical calculation suggests that Fe contributes to the formation of spin-polarized bands in the middle of original band gap and is responsible for the band gap reduction and visible light photocatalytic activity.

  18. Characterizing the Solid-Solution Coefficient and Plant Uptake Factor of As, Cd and Pb in California Croplands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In risk assessment models, the solid-solution partition coefficient (Kd), and plant uptake factor (PUF), are often employed to model the fate and transport of trace elements in soils. The trustworthiness of risk assessments depends on the reliability of the parameters used. In this study, we exami...

  19. Intramolecular Paternò-Büchi reaction of atropisomeric α-oxoamides in solution and in the solid-state.

    PubMed

    Raghunathan, Ramya; Kumarasamy, Elango; Iyer, Akila; Ugrinov, Angel; Sivaguru, J

    2013-10-07

    Atropisomeric α-oxoamides were synthesized and employed for intramolecular Paternò-Büchi reaction leading to very high enantio- and diastereoselectivity in the bicyclic oxetane photoproduct. A reversal of product selectivity was observed in solution and in the solid-state.

  20. Structural and optical properties of PVP-capped nanocrystalline ZnxCd1-xS solid solutions

    NASA Astrophysics Data System (ADS)

    Askari, Mina; Soltani, Nayereh; Saion, Elias; Yunus, W. Mahmood Mat; Maryam Erfani, H.; Dorostkar, Mahdi

    2015-05-01

    Nanocrystalline ZnxCd1-xS solid solutions were prepared in a microwave-assisted hydrothermal process with gradient distribution of components (x = 0.1, 0.3, 0.5, 0.7, and 0.9). The growth of the cubic-structured quantum dots was observed for all component stoichiometries with the crystallite size between 4.5 and 5.7 nm. The obvious peak shifts have been found in the XRD patterns and the lattice parameters showed linear variation with x increasing. The evolution of the optical properties of obtained solid solutions including absorption and photoemission was also monitored in detail. The solid solutions show a considerable shift in the nanoparticle optical absorption edge from 482 to 343 nm with the increasing of Zn fraction. The band gaps of the solid solutions were estimated to be between 2.94 and 3.40 eV and the position of conduction band was shifted toward more negative potential with x increasing. The photoluminescence spectra showed a broad blue-green emission spreading up to 600 nm with emergence of three dominant peaks belong to sulfur, zinc, and cadmium vacancies.

  1. The formation of supersaturated solid solutions in Fe–Cu alloys deformed by high-pressure torsion

    PubMed Central

    Bachmaier, A.; Kerber, M.; Setman, D.; Pippan, R.

    2012-01-01

    Fully dense bulk nanocomposites have been obtained by a novel two-step severe plastic deformation process in the immiscible Fe–Cu system. Elemental micrometer-sized Cu and Fe powders were first mixed in different compositions and subsequently high-pressure-torsion-consolidated and deformed in a two-step deformation process. Scanning electron microscopy, X-ray diffraction and atom probe investigations were performed to study the evolving far-from-equilibrium nanostructures which were observed at all compositions. For lower and higher Cu contents complete solid solutions of Cu in Fe and Fe in Cu, respectively, are obtained. In the near 50% regime a solid solution face-centred cubic and solid solution body-centred cubic nanograined composite has been formed. After an annealing treatment, these solid solutions decompose and form two-phase nanostructured Fe–Cu composites with a high hardness and an enhanced thermal stability. The grain size of the composites retained nanocrystalline up to high annealing temperatures. PMID:22368454

  2. Virtual Solid Solution Laboratory a tool for quantitative description of mixing and order/disorder effects in minerals

    NASA Astrophysics Data System (ADS)

    Vinograd, V. L.; Gale, J. D.; Winkler, B.

    2006-12-01

    Thermodynamic mixing properties of the majority of pertrologically important mineral phases remain poorly constrained. The Virtual Solid Solution Laboratory (VSSL) is designed to predict unknown mixing properties of solid solutions starting from a well parameterized set of empirical interatomic potentials. The VSSL assists a solid solution modeler in the following tasks: (1) Development of a set of transferable empirical interatomic potentials for a system of interest by fitting to structure and elasticity data of chemically similar minerals; (2) Testing the potentials by comparing the predicted properties of a limited set of ordered structures with the results of quantum mechanical calculations; (3) Static lattice energy calculations on a large set of structures with randomly varied configurations of the exchangeable atoms; (4) Finding a simple equation that describes the energies of the simulated structures. This procedure is known as the cluster expansion (CE); (5) Using the CE model to obtain temperature-dependent mixing properties by Monte Carlo simulations; (6) Calculation of the free energies of mixing by thermodynamic integration of the Monte Carlo results; (7) Calculation of the activity-composition and phase relations from the simulated free energies of mixing. The VSSL results for calcite-magnesite, pyrope-grossular, pyrope-majorite and diopside-jadeite solid solutions are discussed.

  3. Ab initio calculation of excess properties of La1-x(Ln,An)xPO4 solid solutions

    NASA Astrophysics Data System (ADS)

    Li, Yan; Kowalski, Piotr M.; Blanca-Romero, Ariadna; Vinograd, Victor; Bosbach, Dirk

    2014-12-01

    We used ab initio computational approach to predict the excess enthalpy of mixing and the corresponding regular/subregular model parameters for La1-xLnxPO4 (Ln=Ce,…, Tb) and La1-xAnxPO4 (An=Pu, Am and Cm) monazite-type solid solutions. We found that the regular model interaction parameter W computed for La1-xLnxPO4 solid solutions matches the few existing experimental data. Within the lanthanide series W increases quadratically with the volume mismatch between LaPO4 and LnPO4 endmembers (ΔV=VLaPO4-VLnPO4), so that W(kJ/mol)=0.618(. We demonstrate that this relationship also fits the interaction parameters computed for La1-xAnxPO4 solid solutions. This shows that lanthanides can be used as surrogates for investigation of the thermodynamic mixing properties of actinide-bearing solid solutions.

  4. Molten-salt synthesis and composition-dependent luminescent properties of barium tungsto-molybdate-based solid solution phosphors

    NASA Astrophysics Data System (ADS)

    Xiang-Hong, He; Zhao-Lian, Ye; Ming-Yun, Guan; Ning, Lian; Jian-Hua, Sun

    2016-02-01

    Pr3+-activated barium tungsto-molybdate solid solution phosphor Ba(Mo1-zWz)O4:Pr3+ is successfully fabricated via a facile molten-salt approach. The as-synthesized microcrystal is of truncated octahedron and exhibits deep-red-emitting upon blue light excitation. Powder x-ray diffraction and Raman spectroscopy techniques are utilized to investigate the formation of solid solution phosphor. The luminescence behaviors depend on the resulting composition of the microcrystals with fixed Pr3+-doping concentration, while the host lattices remain in a scheelite structure. The forming solid solution via the substitution of [WO4] for [MoO4] can significantly enhance its luminescence, which may be due to the fact that Ba(Mo1-zWz)O4:Pr3+ owns well-defined facets and uniform morphologies. Owing to its properties of high phase purity, well-defined facets, highly uniform morphologies, exceptional chemical and thermal stabilities, and stronger emission intensity, the resulting solid solution phosphor is expected to find potential applications in phosphor-converted white light-emitting diodes (LEDs). Project supported by the Construction Fund for Science and Technology Innovation Group from Jiangsu University of Technology, China, the Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, China (Grant No. KHK1409), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, and the National Natural Science Foundation of China (Grant No. 21373103).

  5. Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation

    PubMed Central

    Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

    2016-01-01

    Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge. PMID:26755070

  6. Thermodynamics of aragonite-strontianite solid solutions: Results from stoichiometric solubility at 25 and 76°C

    USGS Publications Warehouse

    Plummer, L.N.; Busenberg, E.

    1987-01-01

    Neither equilibrium nor stoichiometric saturation is observed at 76°C during laboratory recrystallization of strontianite-aragonite solid solutions even after apparent 100 percent conversion to a narrow secondary composition and demonstration of a nearly constant composition system for periods of 300 hours.

  7. Community Solutions to Solid Waste Pollution. Operation Waste Watch: The New Three Rs for Elementary School. Grade 6. [Second Edition.

    ERIC Educational Resources Information Center

    Virginia State Dept. of Waste Management, Richmond. Div. of Litter & Recycling.

    This publication, the last in a series of seven for elementary schools, is an environmental education curriculum guide with a focus on waste management issues. It contains a unit of exercises selected for sixth grade students focusing on community solutions to solid waste pollution. Waste management activities included in this unit seek to…

  8. Solid state and solution 43Ca NMR of calcium peroxides involved in the disproportionation of hydrogen peroxide by calcium hydroxide.

    PubMed

    Trokiner, Arlette; Bessière, Aurélie; Thouvenot, René; Hau, Damien; Marko, Jean; Nardello, Véronique; Pierlot, Christel; Aubry, Jean-Marie

    2004-06-01

    In order to get some insight into the mechanism of the disproportionation of hydrogen peroxide catalyzed by calcium hydroxide, 43Ca NMR spectra of enriched samples of calcium peroxides and of their precursors have been studied in both solution and solid state. This study demonstrates that no well-defined peroxidized calcium species are formed in solution, showing that the catalytic role of calcium is likely restricted to the solid state. Most of the calcium compounds that could be involved in the catalytic process have been investigated with solid state NMR. The shift and quadrupolar parameters of Ca(OH)2, CaO2.8H2O and CaO2.2H2O2 are reported for the first time. These parameters are different enough to allow the quantitative analysis of a complex mixture of these compounds by NMR.

  9. Novel CX⋯π halogen bonds in complexes of acetylene and its derivatives of Na and MPH3 (M=Cu, Ag, Au) with XCCF (X=Cl, Br, I).

    PubMed

    Zhuo, Hongying; Liu, Mingjuan; Li, Qingzhong; Li, Wenzuo; Cheng, Jianbo

    2014-06-05

    Ab initio calculations have been carried out for a variety of model systems with a T-shaped CX⋯π motif. The CX⋯π interaction of acetylene with the halogen donor molecule XCCF (X=Cl, Br, I) is invariably found to be weak with the interaction energy less than 11kJ/mol in magnitude. Substitution of the two protons in acetylene with more electron-donating sodium atoms increases the π electron density in the CC bond and leads to a substantial enhancement in its interaction with the halogen donor. The calculated interaction energies increase to as much as 73kJ/mol in the case of C2Na2-ICCF. The interaction of XCCF with a model coinage metal ethynide, H3PMCCMPH3 (M=Cu, Ag, Au), is intermediate between these two extremes, and the interaction energy is related to the nature of coinage metals. The CX⋯π halogen bonds have been analyzed with natural bond orbital, atoms in molecules, and energy decomposition.

  10. Ab initio investigation of Ti2Al(C,N) solid solutions

    NASA Astrophysics Data System (ADS)

    Arróyave, Raymundo; Radovic, Miladin

    2011-10-01

    Mn+1AXn phases (M: early transition metal, A: IIIA- or IVA-group element, X: carbon or nitrogen) are layered ternary compounds that possess both metal- and ceramic-like properties with numerous potential applications in bulk and thin film forms, particularly under high-temperature conditions. In this work, we use the cluster expansion formalism to investigate the energetics of C-N interactions across the entire Ti2AlC-Ti2AlN composition range. It is shown that there is a definite tendency for ordering in the C,N sublattice. However, the molar volume and bulk modulus of the ordered structures found along the Ti2AlC-Ti2AlN composition range show small deviations from the (linear) rule of mixing, indicating that despite the ordering tendencies, the C-N interactions are not strong and the solution becomes disordered at relatively low temperatures. Random solid solutions of Ti2AlC1-xNx are simulated using special quasirandom structures (SQS) with x=0.25, 0.50, and 0.75. The thermodynamic properties of these structures are compared to those of the structures found to belong to the ground state through the cluster expansion approach. It is found that the structural properties of these approximations to random alloys do not deviate significantly from Vegard's law. The trend in the structural parameters of these SQS are found to agree well with available experimental data and the predictions of the bulk modulus suggest a very weak alloying effect—with respect to Vegard's law—on the elastic properties of Ti2AlC1-xNx.

  11. Ab initio investigation of Ti{sub 2}Al(C,N) solid solutions

    SciTech Connect

    Arroyave, Raymundo; Radovic, Miladin

    2011-10-01

    M{sub n+1}AX{sub n} phases (M: early transition metal, A: IIIA- or IVA-group element, X: carbon or nitrogen) are layered ternary compounds that possess both metal- and ceramic-like properties with numerous potential applications in bulk and thin film forms, particularly under high-temperature conditions. In this work, we use the cluster expansion formalism to investigate the energetics of C-N interactions across the entire Ti{sub 2}AlC-Ti{sub 2}AlN composition range. It is shown that there is a definite tendency for ordering in the C,N sublattice. However, the molar volume and bulk modulus of the ordered structures found along the Ti{sub 2}AlC-Ti{sub 2}AlN composition range show small deviations from the (linear) rule of mixing, indicating that despite the ordering tendencies, the C-N interactions are not strong and the solution becomes disordered at relatively low temperatures. Random solid solutions of Ti{sub 2}AlC{sub 1-x}N{sub x} are simulated using special quasirandom structures (SQS) with x=0.25, 0.50, and 0.75. The thermodynamic properties of these structures are compared to those of the structures found to belong to the ground state through the cluster expansion approach. It is found that the structural properties of these approximations to random alloys do not deviate significantly from Vegard's law. The trend in the structural parameters of these SQS are found to agree well with available experimental data and the predictions of the bulk modulus suggest a very weak alloying effect--with respect to Vegard's law--on the elastic properties of Ti{sub 2}AlC{sub 1-x}N{sub x}.

  12. Planet Patrol. An Environmental Unit on Solid Waste Solutions for Grades 4-6.

    ERIC Educational Resources Information Center

    Procter and Gamble Educational Services, Cincinnati, OH.

    This classroom unit was developed for use in grades 4-6 to help teach the concept of solid waste management. The teacher's guide provides an overview of the issue of solid waste disposal, a description of government, industry, and consumer roles in resolving the solid waste issue, and four lessons involving sanitary landfills, the reduction of…

  13. The investigation of phenol removal from aqueous solutions by zeolites as solid adsorbents.

    PubMed

    Damjanović, Ljiljana; Rakić, Vesna; Rac, Vladislav; Stošić, Dušan; Auroux, Aline

    2010-12-15

    This work reports results on phenol adsorption from aqueous solutions on synthetic BEA (β) and MFI (ZSM-5) zeolites, studied by heat-flow microcalorimetry. For the sake of comparison, the adsorption was performed on activated carbon, a solid customarily used for removal of phenol from water. The obtained values of heats evolved during phenol adsorption indicate the heterogeneity of active sites present on the investigated systems for the adsorption of phenol. In addition, the amounts of adsorbed pollutant were determined and presented in the form of adsorption isotherms, which were interpreted using Langmuir, Freundlich, Dubinin-Astakov and Sips' equations. The latter was found to express high level of agreement with experimental data. The results obtained in this work reveal that the adsorption of phenol on zeolites depends on both Si/Al ratio and on the pore size. Hydrophobic zeolites that possess higher contents of Si show higher affinities for phenol adsorption. Among investigated zeolites, zeolite β possesses the highest capacity for adsorption of phenol. The possibility of regeneration of used adsorbents was investigated by thermal desorption technique. It has been shown that in the case of β zeolite the majority of adsorbed phenol is easily released in the low temperature region.

  14. Thermophysical properties of Ni-containing single-phase concentrated solid solution alloys

    SciTech Connect

    Jin, Ke; Mu, Sai; An, Ke; Porter, Wallace D.; Samolyuk, German D.; Stocks, George Malcolm; Bei, Hongbin

    2016-12-27

    For this research temperature dependent thermophysical properties, including specific heat capacity, lattice thermal expansion, thermal diffusivity and conductivity, have been systematically studied in Ni and eight Ni-containing single-phase face-centered-cubic concentrated solid solution alloys, at elevated temperatures up to 1273 K. The alloys have similar specific heat values of 0.4–0.5 J·g-1·K-1 at room temperature, but their temperature dependence varies greatly due to Curie and K-state transitions. The lattice, electronic, and magnetic contributions to the specific heat have been separated based on first-principles methods in NiCo, NiFe, Ni-20Cr and NiCoFeCr. The alloys have similar thermal expansion behavior, with the exception that NiFe and NiCoFe have much lower thermal expansion coefficient in their ferromagnetic state due to magnetostriction effects. Calculations based on the quasi-harmonic approximation accurately predict the temperature dependent lattice parameter of NiCo and NiFe with < 0.2% error, but underestimated that of Ni-20Cr by 1%, compared to the values determined from neutron diffraction. In addition, all the alloys containing Cr have very similar thermal conductivity, which is much lower than that of Ni and the alloys without Cr, due to the large magnetic disorder.

  15. Thermophysical properties of Ni-containing single-phase concentrated solid solution alloys

    DOE PAGES

    Jin, Ke; Mu, Sai; An, Ke; ...

    2016-12-27

    For this research temperature dependent thermophysical properties, including specific heat capacity, lattice thermal expansion, thermal diffusivity and conductivity, have been systematically studied in Ni and eight Ni-containing single-phase face-centered-cubic concentrated solid solution alloys, at elevated temperatures up to 1273 K. The alloys have similar specific heat values of 0.4–0.5 J·g-1·K-1 at room temperature, but their temperature dependence varies greatly due to Curie and K-state transitions. The lattice, electronic, and magnetic contributions to the specific heat have been separated based on first-principles methods in NiCo, NiFe, Ni-20Cr and NiCoFeCr. The alloys have similar thermal expansion behavior, with the exception that NiFemore » and NiCoFe have much lower thermal expansion coefficient in their ferromagnetic state due to magnetostriction effects. Calculations based on the quasi-harmonic approximation accurately predict the temperature dependent lattice parameter of NiCo and NiFe with < 0.2% error, but underestimated that of Ni-20Cr by 1%, compared to the values determined from neutron diffraction. In addition, all the alloys containing Cr have very similar thermal conductivity, which is much lower than that of Ni and the alloys without Cr, due to the large magnetic disorder.« less

  16. Electrical and magnetic properties of CuCo and AuCo solid solutions

    NASA Astrophysics Data System (ADS)

    Zibold, G.; Korn, D.

    1981-08-01

    CuCo and AuCo films are quench condensed at cryogenic temperature (4 K). The electrical resistivity and the AC susceptibility are measured at different annealing stages (80 K ≤ T a ≤ 900 K) as a function of temperature and Co concentration, Cu 1-xCo x with x ≤ 0,06 and Au 1-yCo y with y ≤ 0.23. The residual resistivity increases linearly with Co concentration in alloys containing x < 0,03 and y < 0.08. Concerning random solid solutions, the negative slope of the resistivity measured near 5 K is proportional to the square of the Co concentration in the range x < 0,03 and y < 0.02. AC susceptibility measurements of films containing x,y ≤ 0,04 yield small values with respect to magnetic moment p and freezing temperature T f. In CuCo ferromagnetism occurs near x =0,08 whereas in AuCo near y = 0.2. This difference can be ascribed to the smaller lattice constant in Cu as compared to that in Au.

  17. The configurational entropy of mixing of metastable random solid solution in complex multicomponent alloys

    NASA Astrophysics Data System (ADS)

    He, Q. F.; Ye, Y. F.; Yang, Y.

    2016-10-01

    Since the advent of "high-entropy" alloys, the simple ideal mixing rule has been commonly used to calculate the configurational entropy of mixing for these multicomponent alloys. However, there have been increasing experimental evidence reported recently showing that the ideal mixing rule tends to overestimate the configurational entropy of mixing in the multicomponent alloys, particularly at a low temperature. In contrast to the ideal mixing rule, here we provide a formula to assess the configurational entropy of mixing in random solid-solution multicomponent alloys by considering the possible correlations among the constituent elements due to various factors, such as atomic size misfit and chemic bond misfit, which may disturb the potential energy of the system and thus reduce the configurational entropy of mixing. With our entropy formulation, the correlation is explored between the configuration entropy of mixing of different alloys and the general character of the phases formed, such as single- or multiple-phased crystalline phase versus amorphous phase. Being in good agreement with the simulation and experimental results, our work provides an analytical framework that could be further used to explore phase stability in complex multicomponent alloys.

  18. Vibrational spectroscopy of synthetic analogues of ankoleite, chernikovite and intermediate solid solution

    NASA Astrophysics Data System (ADS)

    Clavier, N.; Crétaz, F.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Descostes, M.; Dacheux, N.

    2016-03-01

    Ankoleite (K(UO2)PO4·nH2O), chernikovite (H3O(UO2)PO4·nH2O) and intermediate solid solutions are frequently encountered in the uranium ores that result from the alteration of uranium primary minerals. This paper reports a thorough FTIR and Raman study related to synthetic analogues for these minerals. First, the vibration bands associated to the UO22 + uranyl ion were used to calculate the U = O bond length which appeared in good agreement with the data coming from PXRD. Then, the examination of the phosphate vibration modes in both sets of spectra confirmed the general formulation of the samples and ruled out the presence of hydrogenphosphate groups. Finally, the presence of H2O as well as protonated H3O+ and/or H5O2+ species was also pointed out, and could be used to clearly differentiate the various phases prepared. Vibrational spectroscopy then appeared as an efficient method for the investigation of such analogues of natural samples. It should be particularly relevant when identifying these phases in mineral ores or assemblies.

  19. Growth and Electronic Properties of GaN/ZnO Solid Solution Nanowires

    SciTech Connect

    Han, W.Q.; Zhang, Y.; Nam, C.-Y.; Black, C.T.; Mendez, E.E.

    2010-08-23

    We have grown single-crystal (Ga{sub 1-x}Zn{sub x})(N{sub 1-x}O{sub x}) solid-solution nanowires using nanostructured ZnGa{sub 2}O{sub 4} precursor prepared by a sol-gel method. From electrical transport measurements in individual nanowire field-effect transistors, we have identified the conduction as n-type and obtained a background carrier density (-10{sup 19} cm{sup -3}) and an electron mobility (-1 cm{sup 2}/V s) that are consistent with chemical disorder and a large number of charge traps, as confirmed by the devices photocurrent response. From the dependence of the device photoresponse on incident light wavelength, we have determined the energy band gap of (Ga{sub 0.88}Zn{sub 0.12})(N{sub 0.88}O{sub 0.12}) to be as much as -0.6 eV lower than that of GaN or ZnO.

  20. Adsorption of Cr(VI) and Pb(II) from aqueous solution using agricultural solid waste.

    PubMed

    Geetha, A; Sivakumar, P; Sujatha, M; Palanisamy, P N

    2009-04-01

    Areca nut shell, an agricultural solid waste by-product, has been studied for the removal of heavy metals Cr(VI) and Pb(II) from aqueous solution. Parameters, such as equilibrium time, effect of initial metal ion concentration, effect of pH on the removal, were analyzed. An initial pH of 4.0 was found most favourable for Cr(VI) removal and 5.0 for Pb(II) removal. Two theoretical isotherm models, namely Langmuir and Freundlich, were analyzed for the applicability of the experimental data. The Langmuir adsorption capacity (Q0) was calculated. The results of thermodynamic parameters suggest the exothermic nature of the adsorption. The desorption studies were carried out using dilute hydrochloric acid. Maximum desorption of 88% for Cr(VI) and 91% for Pb(II) were achieved. Areca nut shell waste, the low cost adsorbent is found to be effective in the removal of Cr(VI) and Pb(II) ions, and hence it can be applied for the removal of heavy metals from industrial wastewater.

  1. Transport properties of Ho1- x Lu x B12 solid solutions

    NASA Astrophysics Data System (ADS)

    Gabáni, S.; Bat'ko, I.; Bat'ková, M.; Flachbart, K.; Gaz̆o, E.; Pristás̆, G.; Takác̆ová, I.; Bogach, A. V.; Sluchanko, N. E.; Shitsevalova, N. Yu.

    2013-05-01

    Our studies of Ho1- x Lu x B12 solid solutions have shown that the temperature of antiferromagnetic (AF) order in geometrically frustrated system of HoB12 ( T N = 7.4 K) is linearly suppressed to zero temperature, i.e. T N → 0, as lutetium concentration increases to x→ x c ≈ 0.9. In this contribution, we present original results of electrical resistivity measurements on Ho1- x Lu x B12 single crystalline samples with x = 0, 0.2, 0.5, 0.7, 0.9, 1 in the temperature range 0.06-300 K and in magnetic fields ( B) up to 8 T. Complex B vs T N phase diagrams were received from precise temperature ρ( T) and field ρ( B) dependences of resistivity with several AF phases for x ≤ 0.5 pointing to a possibility of quantum critical point at x c ≈ 0.9. The scattering of conduction electrons in the AF phase and in the paramagnetic phase as well as Hall effect results are analyzed and discussed for various concentrations x, when magnetic dilution increases with the increasing content of nonmagnetic Lu ions in the Ho1- x Lu x B12 system.

  2. Special quasirandom structure modeling of fluorite-structured oxide solid solutions with aliovalent cation substitutions

    NASA Astrophysics Data System (ADS)

    Wolff-Goodrich, Silas; Hanken, Benjamin E.; Solomon, Jonathan M.; Asta, Mark

    2015-07-01

    The accuracy of the special quasirandom structure (SQS) approach for modeling the structure and energetics of fluorite-structured oxide solid solutions with aliovalent cation substitutions is assessed in an ionic-pair potential study of urania and ceria based systems mixed with trivalent rare-earth ions. Mixing enthalpies for SQS supercells containing 96 and 324 lattice sites were calculated using ionic pair potentials for U0.5La0.5O1.75, U0.5Y0.5O1.75, Ce0.5La0.5O1.75, Ce0.5Y0.5O1.75, and Ce0.5Gd0.5O1.75, which all have stoichiometries of pyrochlores. The SQS results were compared to benchmark values for random substitutional disorder obtained using large supercell models. The calculations show significant improvement of the mixing enthalpy for the larger 324 site SQS, which is attributed to a better description of the structural distortions, as characterized by the radial distribution functions in relaxed systems.

  3. Magnetism and structure of Fe Cu binary solid solutions obtained by high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Gorria, P.; Martínez-Blanco, D.; Blanco, J. A.; Pérez, M. J.; González, M. A.; Campo, J.

    2006-10-01

    Martensitic phase transformation is found in various metals, alloys, ceramics and even biological systems. This paper reports on the Fe segregated anomalous α- γ martensitic transformation observed in Fe xCu 100-x binary solid solutions ( x=25 and 50) after subsequent heating-cooling processes. A characteristic observable feature of a martensitic transformation is the microstructure it produces, thermal hysteresis, evolution and metastability. We have analysed the microstructure using neutron thermo-diffraction experiments up to 1100 K. The structural changes of the Fe segregated phase, from bcc to fcc crystal structures, have been followed in detail. The most relevant feature is that the onset of martensite transformation is observed, on heating, more than 100 K below the expected temperature for pure bcc-Fe (1183 K), while the reverse transformation occurs below 900 K on cooling. This anomalous behaviour for the α- γ transformation depends on sample composition, being more important for low Fe contents. Besides that, magnetisation vs. temperature measurements show a clear correlation with structure changes, thus exhibiting thermal hysteresis on heating-cooling cycles. Moreover, a magnetisation enhancement above 550 K is observed on heating, this fact can be attributed to thermal-induced ferromagnetism on isolated γ-Fe precipitates via strong magneto-volume coupling.

  4. Iridium-Tin oxide solid-solution nanocatalysts with enhanced activity and stability for oxygen evolution

    NASA Astrophysics Data System (ADS)

    Li, Guangfu; Yu, Hongmei; Yang, Donglei; Chi, Jun; Wang, Xunying; Sun, Shucheng; Shao, Zhigang; Yi, Baolian

    2016-09-01

    Addressing major challenges from the material cost, efficiency and stability, it is highly desirable to develop high-performance catalysts for oxygen evolution reaction (OER). Herein we explore a facile surfactant-assisted approach for fabricating Irsbnd Sn (Ir/Sn = 0.6/0.4, by mol.) nano-oxide catalysts with good morphology control. Direct proofs from XRD and X-ray photoelectron spectra indicate hydrophilic triblock polymer (TBP, like Pluronic® F108) surfactant can boost the formation of stable solid-solution structure. With the TBP hydrophilic and block-length increase, the fabricated Irsbnd Sn oxides undergoing the rod-to-sphere transition obtain the relatively lower crystallization, decreased crystallite size, Ir-enriched surface and incremental available active sites, all of which can bolster the OER activity and stability. Meanwhile, it is observed that the coupled Ir oxidative etching takes a crucial role in determining the material structure and performance. Compared with commercial Ir black, half-cell tests confirm F108-assistant catalysts with over 40 wt% Ir loading reduction show 2-fold activity enhancement as well as significant stability improvement. The lowest cell voltage using 0.88 mg cm-2 Ir loading is only 1.621 V at 1000 mA cm-2 and 80 °C with a concomitant energy efficiency of 75.8% which is beyond the DOE 2017 efficiency target of 74%.

  5. Atomically resolved three-dimensional structures of electrolyte aqueous solutions near a solid surface

    PubMed Central

    Martin-Jimenez, Daniel; Chacon, Enrique; Tarazona, Pedro; Garcia, Ricardo

    2016-01-01

    Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01–1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica. PMID:27416784

  6. Solid / solution interaction: The effect of carbonate alkalinity on adsorbed thorium

    NASA Astrophysics Data System (ADS)

    LaFlamme, Brian D.; Murray, James W.

    1987-02-01

    Elevated activities of dissolved Th have been found in Soap Lake, an alkaline lake in Eastern Washington. Dissolved 232Th ranges from less than 0.001 to 4.9 dpm/L compared to about 1.3 × 10 -5 dpm/ L in sea water. The enhanced activity in the lake coincides with an increase in carbonate alkalinity. Experiments were conducted to evaluate the effect of pH, ionic strength and carbonate alkalinity on Th adsorption on goethite. Thorium (10 -13 M total) in the presence of 5.22 mg/L α-FeOOH and 0.1 M NaNO 3 has an adsorption edge from pH 2-5. At pH 9.0 ± 0.6 the percent Th absorbed on the solid began to decrease from 100% at 100 meq/L carbonate alkalinity and exhibited no adsorption above 300 meq/L. The experimental data were modeled to obtain the intrinsic adsorption equilibrium constants for Th hydrolysis species. These adsorption constants were incorporated in the model to interpret the observed effect of carbonate alkalinity on Th adsorption. There are two main effects of the alkalinity. To a significant degree the decrease in Th adsorption is due to competition of HCO -3 and CO 2-3 ions for surface sites. Dissolved Th carbonate complexes also contribute to the increase of Th in solution.

  7. Magnetic properties of MnSe1-xTex solid solutions

    NASA Astrophysics Data System (ADS)

    Demidenko, O. F.; Makovetskii, G. I.; Yanushkevich, K. I.; Aplesnin, S. S.; Ryabinkina, L. I.; Romanova, O. B.

    2010-01-01

    Interest in the MnSe1-xTex solid solutions system is caused by the possibility of the orbital ordering existence into the Torb < T < TN temperature range in MnSe and MnTe. Samples in the 0.0 <= x <= 0.4 concentration interval with the step Δx = 0.1 are synthesized. It is established that all synthesized compositions possess the elementary NaCl-type cubic cell. The unit cell parameter a linearly varies from a = 0.546 nm for the composition with x = 0 to a = 0.562 nm for x = 0.4. The magnetic susceptibility temperature dependences are studied. It is determined that Neel's temperature in the investigated samples smoothly decreases from 132 K for MnSe0.9Te0.1 to 118 Script K for MnSe0.6Te0.4 composition. Paramagnetic Curie temperature so decreases with the concentration increase from ΘP = -350 Script K for x =0.1 to ΘP = -270 Script K for x = 0.4. Similarly changes the effective magnetic moment value, decreasing 5.50 Bohr magnetons for MnSe0.9Te0.1 and 5.13 Bohr magnetons for MnSe0.6Te0.4.

  8. Evolution of Quantum Critical Behavior In A Concentrated Ternary Solid Solution: NiCoCrx

    NASA Astrophysics Data System (ADS)

    Sales, Brian; Jin, Ke; Bei, Hongbin; Stocks, Malcolm; Samolyuk, German; May, Andrew; McGuire, Michael

    The face centered cubic (fcc) alloy NiCoCrx with x near 1 is found to be close to the Cr concentration where the ferromagnetic transition temperature, Tc goes to 0. Near this composition these alloys exhibit a resistivity linear in temperature to 2 K, a perfectly linear magnetoresistance, and an excess -TlnT contribution to the low temperature heat capacity. As the Cr concentration is decreased from 1, the Curie temperature and the saturation magnetization, M0, both increase exponentially with x. For x = 0.5, Tc ~ 217 K, but M0 is only 0.26 Bohr magnetons/atom, indicating highly itinerant ferromagnets for 0.5 solid solution fcc alloys are ideal model systems to study the effects of chemical disorder on emergent properties near a quantum critical point. Research supported by the DOE Office of Science, Materials Science and Engineering Division, and the Energy Dissipation to Defect Evolution EFRC.

  9. Removal of Cl adsorbed on Mn-Ce-La solid solution catalysts during CVOC combustion.

    PubMed

    Wang, Xingyi; Ran, Le; Dai, Yu; Lu, Yuanjiao; Dai, Qiguang

    2014-07-15

    Mn-Ce-La oxide-mixed catalysts prepared by the method of complexation followed by calcination at 750°C were tested in the catalytic combustion of chlorobenzene (CB) taken as a model of chlorinated aromatics. XRD analyses show that Mn and La enter CeO2 matrix with a fluorite-like structure to form solid solution. The catalysts with high ratio of Mn/Mn+Ce+La exhibit high activity for CB combustion, due to high oxygen mobility. For all Mn-Ce-La catalysts, deactivation due to Cl adsorption is observed at different temperatures, depending on composition. At 330°C or higher temperature, the removal of Cl species from the surface in the forms of Cl2 (produced through Deacon reaction) and HCl (produced through hydrolysis of Cl) occurs and the activity of catalysts for CB combustion becomes thus stable. Either the addition of water or the increase in gaseous oxygen concentration can promote the removal of Cl species, and thus to increase the activity for CB combustion. High stable activity of Mn-Ce-La catalysts can be related to the combination of good oxidation and Deacon reaction performances.

  10. Experimental measurement of local displacement and chemical pair correlations in crystalline solid solutions

    SciTech Connect

    Sparks, C.L.; Ice, G.E.; Robertson, J.L.; Shaffer, L.B.

    1993-10-01

    Measurement of near-neighbor atomic arrangements in crystalline solid solutions is well established and provides meaningful values for chemical preference of atoms for their near neighbors to beyond the first ten neighboring shells. Static displacements (atomic size) between these atom pairs have mostly been either ignored in the recovery of the local pair preferences or removed by making use of the displacement scattering dependence on momentum transfer. With intense and energy tunable x-ray synchrotron sources, our ability to recover these static displacements between atoms has greatly improved. Data taken with multiple x-ray energies to obtain the contrast necessary to separate like from unlike neighbor pair distances are discussed for the two cases studied to date: A locally ordered Ni{sub 77.5}Fe{sub 22.5} crystal and a locally clustered Fe{sub 53}Cr{sub 47} crystal. Analysis of experimental parameters and data gives the systematic and statistical errors on the recovered parameters. Meaningful atomic displacements from the mean lattice can be measured and recovered. These displacements help us understand material properties and will provide theorists with tests for their calculations.

  11. Two-Dimensional Nb-Based M 4 C 3 Solid Solutions (MXenes)

    DOE PAGES

    Yang, Jian; Naguib, Michael; Ghidiu, Michael; ...

    2015-10-15

    Two new two-dimensional Nb4C3-based solid solutions (MXenes), (Nb0.8,Ti0.2)4C3Tx and (Nb0.8,Zr0.2)4C3Tx (where T is a surface termination) were synthesizedas confirmed by X-ray diffractionfrom their corresponding MAX phase precursors (Nb0.8,Ti0.2)4AlC3 and (Nb0.8,Zr0.2)4AlC3. In our report we discuss Zr-containing MXene. We also studied intercalation of Li ions into these two compositions, and Nb4C3Tx in order to determine the potential of those materials for energy storage applications. Lithiation and delithiation peaks at 2.26 and 2.35 V, respectively, appeared in the case of Nb4C3Tx, but were not present in Nb2CTx. After 20 cycles at a rate of C/4, the specific capacities of (Nb0.8,Ti0.2)4C3Txand (Nb0.8,Ti0.2)4C3Tx weremore » 158 and 132 mAh/g, respectively, both slightly lower than the capacity of Nb4C3Tx.« less

  12. Quantitative Computer Tomography for Determining Composition of Microgravity and Ground Based Solid Solutions

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Engel, H. P.

    1999-01-01

    Advances in x-ray Computer Tomography (CT) have been led by the medical profession, and by evaluation of industrial products, particularly castings. Porosity can readily be determined as a function of the density of a material, and CT is thus an industrially important NDE tool. Providing high purity, 100% dense standards of pure elements and compounds can be fabricated, the composition of solid solution alloys can be determined by measuring the CT number, which is a function of the absorption of the sample. Average densities across slices 1 mm thick can generally be determined to better than 1 percent. With present technology this spatial sensitivity is less than ideal, but important benefits can nevertheless be obtained by using CT, particularly single crystals, prior to making any destructive assault upon the sample. The sample can in fact be examined prior to removal from the mold within which it has been grown and, in the cases of microgravity flight samples, before removal from the cartridge assembly. This greatly assists the researcher in the characterization of the products, particularly as a guide to cutting and sampling. Examples of work with germanium-silicon alloys and mercury cadmium telluride taken with a radioactive cobalt source will be demonstrated.

  13. Inelasticity and precipitation of germanium from a solid solution in Al-Ge binary alloys

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Korchunov, B. N.; Nikanorov, S. P.; Osipov, V. N.

    2015-08-01

    The influence of precipitation of germanium atoms in a solid solution on the dependence of the inelasticity characteristics on the germanium content in aluminum-germanium alloys prepared by directional crystallization has been studied. It has been shown that the Young's modulus defect, the amplitude-dependent decrement, and the microplastic flow stress at a specified cyclic strain amplitude have extreme values at the eutectic germanium content in the alloy. The eutectic composition of the alloy undergoes a ductilebrittle transition. It has been found that there is a correlation between the dependences of the Young's modulus defect, amplitude-dependent decrement, microplastic flow stress, and specific entropy of the exothermal process of germanium precipitation on the germanium content in the hypoeutectic alloy. The concentration dependences of the inelasticity characteristics and their changes after annealing have been explained by the change in the resistance to the motion of intragrain dislocations due to different structures of the Guinier-Preston zones formed during the precipitation of germanium atoms.

  14. Perovskite solid solutions with multiferroic morphotropic phase boundaries and property enhancement

    NASA Astrophysics Data System (ADS)

    Algueró, M.; Amorín, H.; Fernández-Posada, C. M.; Peña, O.; Ramos, P.; Vila, E.; Castro, A.

    2016-05-01

    Recently, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of phases in the BiFeO3-BiCoO3 perovskite binary system, associated with the existence of a discontinuous morphotropic phase boundary (MPB) between multiferroic polymorphs of rhombohedral and tetragonal symmetries. This might be a general property of multiferroic phase instabilities, and a novel promising approach for room temperature magnetoelectricity. We review here our current investigations on the identification and study of additional material systems, alternative to BiFeO3-BiCoO3 that has only been obtained by high pressure synthesis. Three systems, whose phase diagrams were, in principle, liable to show multiferroic MPBs have been addressed: the BiMnO3-PbTiO3 and BiFeO3-PbTiO3 binary systems, and the BiFeO3-BiMnO3-PbTiO3 ternary one. A comprehensive study of multiferroism across different solid solutions was carried out based on electrical and magnetic characterizations, complemented with mechanical and electromechanical measurements. An in-depth structural analysis was also accomplished when necessary.

  15. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution

    NASA Astrophysics Data System (ADS)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-01

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P=16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P41212) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  16. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution.

    PubMed

    Santoro, Mario; Gorelli, Federico A; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-30

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P = 16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P4(1)2(1)2) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  17. Correlated analysis of chemical variations with spectroscopic features of the K-Na jarosite solid solutions relevant to Mars

    NASA Astrophysics Data System (ADS)

    Ling, Zongcheng; Cao, Fengke; Ni, Yuheng; Wu, Zhongchen; Zhang, Jiang; Li, Bo

    2016-06-01

    Detailed chemical, structural and spectroscopic properties of jarosite solid solution minerals are key information for their potential discoveries by future remote sensing and in-situ detections on Mars. We successfully synthesized seven homogeneous K-Na jarosite solid solutions under hydrothermal conditions at 140 °C, whose phase identifications and chemical compositions are confirmed by X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). The chemical ratios of K/(K+Na) in jarosite solid solutions lead to systematic shifts of their characteristic Raman peaks ν1 (SO4)2- (from 1006 to 1011.3 cm-1), ν3 (SO4)2- (from 1100.6 to 1111.2 cm-1), ν2 (SO4)2- (from 434.2 to 444.8 cm-1) with the increase of Na content. While the OH stretching mode decreases with even larger peak position variations (e.g., ∼3410 cm-1 peak shifts from 3410.5 to 3385.7 cm-1) as the K-Na jarosite solid solutions are enriched in Na content. Raman spectroscopic measurements of the seven K-Na jarosite solid solutions enabled us to build a calibration that uses Raman peak positions to estimate K-Na variation in jarosite, which is the key step for their possible applications in the future Raman applications on Mars' missions (e.g., ExoMars and Mars 2020 missions). The band assignments and compositional related variations of their XRD, near-infrared (NIR) and mid-infrared (MIR) spectra also provide informative clues for identifying the jarosite minerals and inferring their composition during martian in-situ and remote sensing measurements.

  18. MBSSAS: A code for the computation of margules parameters and equilibrium relations in binary solid-solution aqueous-solution systems

    USGS Publications Warehouse

    Glynn, P.D.

    1991-01-01

    The computer code MBSSAS uses two-parameter Margules-type excess-free-energy of mixing equations to calculate thermodynamic equilibrium, pure-phase saturation, and stoichiometric saturation states in binary solid-solution aqueous-solution (SSAS) systems. Lippmann phase diagrams, Roozeboom diagrams, and distribution-coefficient diagrams can be constructed from the output data files, and also can be displayed by MBSSAS (on IBM-PC compatible computers). MBSSAS also will calculate accessory information, such as the location of miscibility gaps, spinodal gaps, critical-mixing points, alyotropic extrema, Henry's law solid-phase activity coefficients, and limiting distribution coefficients. Alternatively, MBSSAS can use such information (instead of the Margules, Guggenheim, or Thompson and Waldbaum excess-free-energy parameters) to calculate the appropriate excess-free-energy of mixing equation for any given SSAS system. ?? 1991.

  19. Solution and Solid State Chemistry of Dimolybdenum Fluoroacetates with Ethylenediamine Derivatives

    NASA Astrophysics Data System (ADS)

    Snowden, Kevin Joseph

    Reactions of Mo_2 (O_2 CCF_3)_4, Mo_2O _2CCHF_2)_4, and Mo _2(O_2 CCH_2 F)_4 with the diamines (N,N-dimethylethylene-diamine (udmed), N,N^'-dimethylethylenediamine (sdmed), and N,N,N^',N ^',-tetramethylethylenediamine (tmed)) have been studied. Mo_2(O_2 CCF_3) _4 reacts with udmed in ethanol or acetonitrile to form crystalline (Mo_2(O_2 CCF_3)_3(udmed)_2 ) -(O_2{CCF}_3 ). A single-crystal x-ray study of the orange blades indicate that the complex exists as an ion pair, in which the udmed ligands bind as axial-equatorial chelates to each of the metals. The structure contains hydrogen bonds between the Mo_2 (rm O_2{CCF}_3)_3(udmed) ^+ cation and the free CF_3 {CO}_2^- anion. The compound crystallizes in the monoclinc space group I2/a. The solution reactions of Mo_2( rm O_2{CCF}_3)_4 with udmed, sdmed, and tmed have been studied at -20^circC in ethanol/CD_3CN by ^ {19}F NMR spectroscopy, with Mo _2: diamine ratios up to 1: 8. Udmed displaces on average up to three bridging CF_3{CO}_2 groups from the Mo _2(rm O_2 {CF}_3) _4 core. Sdmed displaces all bridging CF _3{CO}_2 groups. Tmed forms products which on average have two bridging and two free CF_3{CO }_2 groups. The course of these reactions and possible structures of the products are discussed based on spectra and chemical observations. The complex Mo_2(rm O_2 {CCH}_2rm F)_4 reacts with udmed in ethanol to produce crystalline (Mo _2(rm O_2{CCH} _2rm F)_3(udmed)_2 ) -(O_2{CCH}_2 rm F). Solid-state IR establish and single -crystal x-ray studies of the chunky orange crystals show that this compound is much like the trifluoroacetate analogue. The compound crystallizes in monoclinic space group P2 _1/c. The solution reaction reactions of Mo _2(rm O_2{CCHF}_2) _4 with udmed, sdmed, and tmed have been studied at -20^circ C in ethanol/CD_3CN by ^{19}F NMR spectroscopy, with Mo _2: diamine ratios up to 1: 8. Udmed produces appreciable amount of nonbridging and free CHF _2{CO}_2 groups. Sdmed readily displaces all bridging

  20. Convergent solid-phase and solution approaches in the synthesis of the cysteine-rich Mdm2 RING finger domain.

    PubMed

    Vasileiou, Zoe; Barlos, Kostas; Gatos, Dimitrios

    2009-12-01

    The RING finger domain of the Mdm2, located at the C-terminus of the protein, is necessary for regulation of p53, a tumor suppressor protein. The 48-residues long Mdm2 peptide is an important target for studying its interaction with small anticancer drug candidates. For the chemical synthesis of the Mdm2 RING finger domain, the fragment condensation on solid-phase and the fragment condensation in solution were studied. The latter method was performed using either protected or free peptides at the C-terminus as the amino component. Best results were achieved using solution condensation where the N-component was applied with the C-terminal carboxyl group left unprotected. The developed method is well suited for large-scale synthesis of Mdm2 RING finger domain, combining the advantages of both solid-phase and solution synthesis.

  1. Relationships between the solution and solid-state properties of solution-cast low-k silica thin films.

    PubMed

    Chiang, Chao-Ching; Su, Chien-You; Yang, An-Chih; Wang, Ting-Yu; Lee, Wen-Ya; Hua, Chi-Chung; Kang, Dun-Yen

    2016-07-27

    This paper reports on the fabrication of low-k (amorphous) silica thin films cast from solutions without and with two different types of surfactants (TWEEN® 80 and Triton™ X-100) to elucidate the relationships between the structural/morphological features of the casting solutions and the physical properties of the resulting thin films. Cryogenic transmission microscopy (cryo-TEM), static/dynamic light scattering (SLS/DLS), and small-angle X-ray scattering (SAXS) revealed contrasting colloidal dispersion states and phase behavior among the three casting solutions. Casting solution with the Triton™ X-100 surfactant produced stable (>90 days) nanoparticles with good dispersion in solution (mean particle size ∼10 nm) as well as good mesopore volume (characterized by nitrogen physisorption) in powder and thin films of high mechanical strength (characterized by the nanoindentation test). The longer main chain and bulkier side units of the TWEEN® 80 surfactant led to stable micelle-nanoparticle coexisting dispersion, which resulted in the highest mesopore volume in powder and thin films with the lowest dielectric constant (∼3) among the samples in this study. The casting solution without the surfactant failed to produce a stabilized solution or thin films of acceptable uniformity. These findings demonstrate the possibility of fine-tuning low-k silica film properties by controlling the colloidal state of casting solutions.

  2. Structural, vibrational and photoluminescence properties of Sr{sub (1-x)}Pb{sub x}MoO{sub 4} solid solution synthesized by solid state reaction

    SciTech Connect

    Hallaoui, A.; Taoufyq, A.; Arab, M.; Bakiz, B.; Benlhachemi, A.; Bazzi, L.; Valmalette, J-C.; Villain, S.; Guinneton, F.; Gavarri, J-R.

    2016-07-15

    Highlights: • The solid solution Sr{sub (1-x)}Pb{sub (x)}MoO{sub 4} is characterized by X-ray diffraction. • Raman spectroscopy confirm that the solid solution is disordered. • Photoluminescence experiments are carried out under X-ray excitation. • Emission bands can be decomposed into four components between 2.1 and 2.9 eV. • The intensities of emission bands reach a maximum for 0.1 < x < 0.4. - Abstract: In this paper, strontium lead molybdate Sr{sub 1-x}Pb{sub x}MoO{sub 4} polycrystalline samples with 0 ≤ x ≤ 1 were prepared by solid state preparation method at 1000 °C. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-Raman spectroscopy. Their photoluminescence responses were analyzed under X-ray excitation. Rietveld refinements indicate that all the materials present a scheelite-type tetragonal structure. Micro-Raman spectra confirmed the formation of the solid solution with a specific effect due to Sr-O-Mo and Pb-O-Mo links in the scheelite structure. SEM images showed modifications in the shapes and grain sizes as x increased. Broad photoluminescent emission bands were observed in the energy range 2.1–2.9 eV. The emission bands were decomposed into four gaussian components. The intensities of all components presented a strong maximum in the composition range 0.1 < x < 0.4.

  3. Calculation of the standard heat capacity at constant pressure for cobalt ferrite-zinc ferrite solid solutions

    SciTech Connect

    Chachanidze, G.D.; Pavlenishvili, T.A.; Machaladze, T.E.; Khutsishvili, D.I.

    1994-08-01

    Magnetic, electrical, and other properties of Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} solid solutions are widely studied because of their high coercive force and Curie temperature ({Tc}), which makes these compounds applicable in modern electronic devices. However, the information published on their thermodynamic properties is limited. This paper focuses on calculation of the standard heat capacity C{sub p}{sup 0} (298 K) for cobalt zinc ferrites using correlation analysis of the relationship between C{sub p}{sup 0} (298 K) and the saturation magnetic moment {mu}{sub o}. The authors studied the solid solutions Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.2, 0.4, 0.5, 0.6, and 0.8), whose magnetic and thermal parameters, crucial in our calculations, are known to be strongly dependent on the preparation conditions. An equation was derived for calculation of the standard heat capacity at constant pressure from the saturation magnetic moment of Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} solid solutions. The equation allows a satisfactory estimation of the standard heat capacity at 298 Kelvin for any cobalt ferrite-zinc ferrite solid, providing the saturation magnetic moment is available.

  4. Synthesis and structure of Ce1-xEuxPO4 solid solutions for minor actinides immobilization

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohuan; Teng, Yuancheng; Huang, Yi; Wu, Lang; Zeng, Pan

    2014-08-01

    Ce1-xEuxPO4 (x = 0-1) solid solutions were synthesized by the solid state reaction process using europium (Eu) as the surrogate for trivalent minor actinide americium (Am). The effects of calcination temperature, holding time and Eu content on the crystalline phase, microstructure and morphology of Ce1-xEuxPO4 (x = 0-1) were investigated. The monazite-type EuPO4 and CePO4 coexisted after being calcined at 1000 °C for 4 h, suggesting the CePO4 and EuPO4 phases would form initially separately. Pure and single-phase monazite-type Ce1-xEuxPO4 (x = 0-1) powders were obtained at 1300 °C for 4 h. The results of the XRD patterns Rietveld refinement and μ-Raman analysis confirmed the formation of a Ce1-xEuxPO4 (x = 0-1) continuous solid solution. The grain size of Ce0.5Eu0.5PO4 increased obviously as the holding time extended. The Ce, Eu, P and O elements were almost distributed homogeneously in the Ce0.5Eu0.5PO4 solid solution.

  5. Structural, dielectric, and ferroelectric properties of the (1-x)PbTiO₃-xBiAlO₃ solid solution.

    PubMed

    Yu, Huichun; Ren, Wei; Ye, Zuo-Guang

    2010-10-01

    Ferroelectric ceramics derived from the solid solution of (1-x)PbTiO₃-xBiAlO₃ (x = 0, 0.05, 0.10, 0.15, and 0.18) have been synthesized by solid-state reactions. A pure perovskite phase is formed for 0 ≤ x ≤ 0.15. The tetragonality (c/a) of the solid solution decreases with the increasing amount of BiAlO₃. Scanning electron microscopic images reveal a microstructure with a fine grain size of less than 1 μm for the solid solution ceramics (x ≥ 0.05). Compared with pure PbTiOPbTiO₃ ceramics whose high conductivity and poor densification were harmful to their dielectric performance, the ceramics of (1-x)PbTiO₃-xBiAlO₃ are well-densified (with a relative density of up to 93%) and their dielectric and ferroelectric properties are significantly improved with the addition of BiAlO₃, exhibiting reduced dielectric losses, well-developed P-E hysteresis loops (for x = 0.05, 0.10, and 0.15) and a high remnant polarization (P(r)) of 64 μC/cm² (for x = 0.15).

  6. Equilibria involving the reciprocal spinel solid solution (Mg x Fe1- x ) (Al y Cr1- y )2O4: modeling and experiment

    NASA Astrophysics Data System (ADS)

    Jacob, K. T.; Behera, C. K.

    2000-12-01

    Developed in this article is a model for calculating cation distribution and activities in the reciprocal spinel solid solution (Mg X Fe1- X )(Al Y Cr1- Y )2O4 based on octahedral site preference energies of cations independent of composition and temperature, random distribution of ions on tetrahedral and octahedral sites, entropy of randomization of Jahn-Teller distortions associated with Fe2+ ions on the tetrahedral site, and the standard Gibbs energies of formation of the four pure spinel compounds. Enthalpy of mixing of this reciprocal solid solution caused by the large difference of ionic radii of Al3+ and Cr3+ present on the octahedral site was modeled based on experimental data on the binary systems. The tie-line compositions corresponding to the equilibria between the spinel solid solution and the sesquioxide solid solution (Al Z Cr1- Z )2O3 with corundum structure were computed. Values for activities in the corundum solid solution were taken from the literature. The oxygen potential corresponding to the three-phase equilibrium involving metallic iron, the spinel solid solution, and corundum solid solution was computed as a function of composition of the spinel solid solution. The computed results were verified by measurements on nine compositions inside the square representing the reciprocal system. The compositions of coexisting solid solutions were determined by electron-probe microanalysis (EPMA) and lattice parameter measurement using X-ray diffraction (XRD). The activities of FeAl2O4 and FeCr2O4 and oxygen potentials for three-phase equilibria were measured using two independent solid-state cells incorporating a bielectrolyte chain. Both cells gave consistent results within experimental error. The experimental results are in excellent agreement with the computed results, thus validating the model for the reciprocal spinel solid solution.

  7. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AIN and InN

    DTIC Science & Technology

    1992-02-01

    IK AD-A248 058 - - H Final Technical ReportI I Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the...structural and chemical analyses, there is no reason to believe that a homogeneous solid solution close to this composition had formed. Moreover

  8. Crystal Violet Lactone Salicylaldehyde Hydrazone Zn(II) Complex: a Reversible Photochromic Material both in Solution and in Solid Matrix

    NASA Astrophysics Data System (ADS)

    Li, Kai; Li, Yuanyuan; Tao, Jing; Liu, Lu; Wang, Lili; Hou, Hongwei; Tong, Aijun

    2015-09-01

    Crystal violet lactone (CVL) is a classic halochromic dye which has been widely used as chromogenic reagent in thermochromic and piezochromic systems. In this work, a very first example of CVL-based reversible photochromic compound was developed, which showed distinct color change upon UV-visible light irradiation both in solution and in solid matrix. Moreover, metal complex of CVL salicylaldehyde hydrozone was facilely synthesized, exhibiting reversible photochromic properties with good fatigue resistance. It was served as promising solid material for photo-patterning.

  9. Crystal Violet Lactone Salicylaldehyde Hydrazone Zn(II) Complex: a Reversible Photochromic Material both in Solution and in Solid Matrix.

    PubMed

    Li, Kai; Li, Yuanyuan; Tao, Jing; Liu, Lu; Wang, Lili; Hou, Hongwei; Tong, Aijun

    2015-09-28

    Crystal violet lactone (CVL) is a classic halochromic dye which has been widely used as chromogenic reagent in thermochromic and piezochromic systems. In this work, a very first example of CVL-based reversible photochromic compound was developed, which showed distinct color change upon UV-visible light irradiation both in solution and in solid matrix. Moreover, metal complex of CVL salicylaldehyde hydrozone was facilely synthesized, exhibiting reversible photochromic properties with good fatigue resistance. It was served as promising solid material for photo-patterning.

  10. Crystal Violet Lactone Salicylaldehyde Hydrazone Zn(II) Complex: a Reversible Photochromic Material both in Solution and in Solid Matrix

    PubMed Central

    Li, Kai; Li, Yuanyuan; Tao, Jing; Liu, Lu; Wang, Lili; Hou, Hongwei; Tong, Aijun

    2015-01-01

    Crystal violet lactone (CVL) is a classic halochromic dye which has been widely used as chromogenic reagent in thermochromic and piezochromic systems. In this work, a very first example of CVL-based reversible photochromic compound was developed, which showed distinct color change upon UV-visible light irradiation both in solution and in solid matrix. Moreover, metal complex of CVL salicylaldehyde hydrozone was facilely synthesized, exhibiting reversible photochromic properties with good fatigue resistance. It was served as promising solid material for photo-patterning. PMID:26412101

  11. Characterization of interactions between soil solid phase and soil solution in the initial ecosystem development phase

    NASA Astrophysics Data System (ADS)

    Zimmermann, Claudia; Schaaf, Wolfgang

    2010-05-01

    In the initial phase of soil formation interactions between solid and liquid phases and processes like mineral weathering, formation of reactive surfaces and accumulation of organic matter play a decisive role in developing soil properties. As part of the Transregional Collaborative Research Centre (SFB/TRR 38) 'Patterns and processes of initial ecosystem development' in an artificial catchment, these interactions are studied at the catchment 'Chicken Creek' (Gerwin et al. 2009). To link the interactions between soil solid phase and soil solution at the micro-scale with observed processes at the catchment scale, microcosm experiments under controlled laboratory conditions were carried out. Main objectives were to determine the transformation processes of C and N from litter decomposition within the gaseous, liquid and solid phase, the interaction with mineral surfaces and its role for the establishment of biogeochemical cycles. The microcosm experiments were established in a climate chamber at constant 10 ° C. In total 48 soil columns (diameter: 14.4 cm; height: 30 cm) were filled with two different quaternary substrates (sand and loamy sand) representing the textural variation within the catchment at a bulk density of 1.4-1.5 g*cm-3. The columns were automatically irrigated four times a day with 6.6 ml each (corresponding to 600 mm*yr-1). The gaseous phase in the headspace of the microcosms was analysed continuously for CO2 and N2O contents. C and N transformation processes were studied using 13C and 15N labelled litter of two different plant species occurring at the catchment (Lotus corniculatus, Calamagrostis epigejos) that was incorporated into the microcosm surface. All treatments including a control ran with four replicates over a period of 40 weeks. Two additional microcosms act as pure litter controls where substrate was replaced by glass pearls. Litter and substrate were analysed before and after the experiment. Percolate was continuously collected and

  12. Solution chemistry effects on orthophosphate adsorption by cationized solid wood residues.

    PubMed

    Karthikeyan, K G; Tshabalala, Mandla A; Wang, D; Kalbasi, M

    2004-02-01

    Adsorption of orthophosphate anions in aqueous solution by cationized milled solid wood residues was characterized as a function of sorbate-to-sorbent ratio (approximately equal to 0.001-2.58 mmol of P/g substrate), pH (3-9), ionic strength, I (no I control; 0.001 and 0.01 M NaCl), reaction time (4 min to 24 h), and in the presence of other competing anions (0.08-50 mM SO4(2-); 0.08-250 mM NO3-). Sorption isotherms revealed the presence of two kinds of adsorption sites corresponding to high and low binding affinities for orthophosphate anions. Consequently, a two-site Langmuir equation was needed to adequately describe the data over a range of solution conditions. In addition to higher sorption capacity, cationized bark possessed a higher binding energy for orthophosphate anions compared to cationized wood. The sorption capacity and binding energy for bark were 0.47 mmol of P g(-1) and 295.7 L mmol(-1), respectively, and for wood, the corresponding values were 0.27 mmol g(-1) and 61.4 L mmol(-1). Both the sorption capacity and binding energy decreased with increasing I, due to competition from Cl- ions for the available anion-exchange sites. The surface charge characteristics of cationized bark (pHzpc = 7.9) acted in concert with orthophosphate speciation to create a pH-dependent sorption behavior. Orthophosphate uptake was quite rapid and attained equilibrium levels after 3 h. Both SO4(2-) and NO3- influenced percent removal but required high relative competing anion to H2PO4- molar ratios, i.e., 2.5-3 for SO4(2-) and 25 for NO3-, to cause appreciable reduction. These results support our hypothesis that adsorption of orthophosphate anions on cationized bark involves ion exchange and other specific Lewis acid-base interactions.

  13. Optical and morphological characteristics of zinc selenide-zinc sulfide solid solution crystals

    NASA Astrophysics Data System (ADS)

    Singh, N. B.; Su, Ching-Hua; Arnold, Bradley; Choa, Fow-Sen

    2016-10-01

    Experiments were performed to study the effect of point defects on the optical and morphological characteristics of zinc selenide-zinc sulfide ZnSe-ZnS (ZnSexS(1-x)) solid solution crystals grown under terrestrial (1-g) condition. We used the composition ZnSe0.91S0.09 and ZnSe0.73S0.27 for the detailed studies. Crystals of 8 mm and 12 mm diameter were grown using physical vapor transport methods. These crystals did not exhibit gross defects such as voids, bubbles or precipitates. The photoluminescence spectra indicated strong red emission for the 610-630-nm wavelength region in both crystals. This emission could be explained on the basis of high energy irradiation of Zn selenide. For the ZnSe0.73S0.27 crystal, absorption starts at a lower wavelength range (300 nm) when compared to the ZnSe0.91S0.09 crystal presumably due to the much higher bandgap of ZnS than that of ZnSe. Sharp peaks at 451 and 455 nm were observed for both samples corresponding to the band edge transitions, followed by a strong peak at 632 nm. These results were consistent with the observations based on Raman spectroscopy studies. Under 532-nm laser illumination both transverse optical (TO) and longitudinal optical (LO) phonon peaks appeared at Raman shifts of 220 and 280 Δcm-1, respectively. These peaks are similar to those observed for pure ZnSe Raman spectra for which TO and LO occur at 200 and 250 Δcm-1 for the x-axis (first order) polarization.

  14. Thermoelastic properties of grossular-andradite solid solution at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Fan, Dawei; Kuang, Yunqian; Xu, Jingui; Li, Bo; Zhou, Wenge; Xie, Hongsen

    2017-02-01

    The pressure-volume-temperature ( P- V- T) equation of state (EoS) of synthetic grossular (Grs)-andradite (And) solid-solution garnet sample have been measured at high temperature up to 900 K and high pressures up to 22.75 GPa for Grs50And50, by using in situ angle-dispersive X-ray diffraction and diamond anvil cell. Analysis of room-temperature P- V data to a third-order Birch-Murnaghan (BM) EoS yields: V 0 = 1706.8 ± 0.2 Å3, K 0 = 164 ± 2 GPa and K' 0 = 4.7 ± 0.5. Fitting of our P- V- T data by means of the high-temperature third-order BM EoS gives the thermoelastic parameters: V 0 = 1706.9 ± 0.2 Å3, K 0 = 164 ± 2 GPa, K' 0 = 4.7 ± 0.2, (∂K/∂T) P = -0.018 ± 0.002 GPa K-1, and α 0 = (2.94 ± 0.07) × 10-5 K-1. The results also confirm that grossular content increases the bulk modulus of the Grs-And join following a nearly ideal mixing model. The relation between bulk modulus and Grs mole fraction ( X Grs) in this garnet join is derived to be K 0 (GPa) = (163.7 ± 0.7) + (0.14 ± 0.02) X Grs ( R 2 = 0.985). Present results are also compared to previously studies determined the thermoelastic properties of Grs-And garnets.

  15. Electronic properties of surfaces, subsurface layers and interfaces for semiconductor and semimetal solid solutions

    NASA Astrophysics Data System (ADS)

    Romanov, O. V.; Belygh, A. M.; Krasnov, E. L.; Kalenik, V. I.

    1992-05-01

    The electronic and physical-chemical properties of restorded (dDX≤0.5-1.0 nm) surfaces at the depth of the space-charge region and of semiconductor(semimetal)-native anodic oxide (dDX=1.0-100 nm) interfaces have been investigated by the combined field effect in electrolytes (CFEE) method at T = 273-305 K and in metal-oxide-semiconductor (MOS) systems at T = 77-305 K for monocrystalline solid solutions CdxHg1-xTe (0≤x≤0.4) and MnxHg1-xTe (0≤x≤0.24). The interpretation of experimental capacitance-potential and current-potential characteristics has been effectuated allowing for the degeneracy of the electron-hole gas and conduction band non-parabolicity (considered in the Kane approximation). The electronic properties of the surface and subsurface regions have been determined: the forbidden zone (Eg), the thermodynamic equilibrium (ni) and non-equilibrium (nix) carrier concentrations for intrinsic material or the doping level (NA,D) for extrinsic material, the density-of- states effective masses (mcx, mhx), the equilibrium semiconductor(semimetal) surface potential (Vs0) and total electric charge captured at the interface defects (Qtot0), the fast surface states (FSS) density (NSS). The FSS density and the total electric charge at the interface (Qtotox) increase drastically (0.5-2 orders) as a function of the anodic oxide thickness at dOX < 8-12 nm.

  16. Spectroscopy of resonant excitation of exciton luminescence of GaSe-GaTe solid solutions

    NASA Astrophysics Data System (ADS)

    Starukhin, A. N.; Nelson, D. K.; Fedorov, D. L.; Syunyaev, D. K.

    2017-02-01

    The luminescence excitation spectra of localized excitons in GaSe0.85Te0.15 solid solutions have been investigated at the temperature T = 2 K. It has been shown that the excitation spectra of excitons with the localization energy ɛ > 10 mV exhibit an additional maximum M E located on the low-energy side of the maximum corresponding to the free exciton absorption band with n = 1. It has been found that the shift in the position of the maximum M E in the excitation spectrum with respect to the energy of detected photons increases as the energy of detected photons decreases, i.e., with an increase in the localization energy of excitons. Under the resonant excitation of localized excitons by a monochromatic light from the region of the exciton emission band, in the exciton luminescence spectrum on the low-energy side from the excitation line, there is also a maximum of the luminescence ( M L ). The energy distance between the position of the excitation line and the position of the maximum in the luminescence spectrum increases with a decrease in the frequency of the excitation light. The possible mechanisms of the formation of the described structure of the luminescence excitation and exciton luminescence spectra of GaSe0.85Te0.15 have been considered. It has been concluded that the maximum M E in the excitation spectrum and the maximum M L in the luminescence spectrum are attributed to electronic-vibrational transitions with the creation and annihilation of localized excitons, respectively.

  17. Thermoelastic properties of grossular–andradite solid solution at high pressures and temperatures

    SciTech Connect

    Fan, Dawei; Kuang, Yunqian; Xu, Jingui; Li, Bo; Zhou, Wenge; Xie, Hongsen

    2016-09-21

    The pressure–volume–temperature (P–V–T) equation of state (EoS) of synthetic grossular (Grs)–andradite (And) solid-solution garnet sample have been measured at high temperature up to 900 K and high pressures up to 22.75 GPa for Grs50And50, by using in situ angle-dispersive X-ray diffraction and diamond anvil cell. Analysis of room-temperature P–V data to a third-order Birch–Murnaghan (BM) EoS yields: V0 = 1706.8 ± 0.2 Å3, K0 = 164 ± 2 GPa and K'0 = 4.7 ± 0.5. Fitting of our P–V–T data by means of the high-temperature third-order BM EoS gives the thermoelastic parameters: V0 = 1706.9 ± 0.2 Å3, K0 = 164 ± 2 GPa, K'0 = 4.7 ± 0.2, (∂K/∂T)P = -0.018 ± 0.002 GPa K-1, and α0 = (2.94 ± 0.07) × 10-5 K-1. The results also confirm that grossular content increases the bulk modulus of the Grs-And join following a nearly ideal mixing model. The relation between bulk modulus and Grs mole fraction (XGrs) in this garnet join is derived to be K0 (GPa) = (163.7 ± 0.7) + (0.14 ± 0.02) XGrs (R2 = 0.985). Present results are also compared to previously studies determined the thermoelastic properties of Grs-And garnets.

  18. Review of magnetic features observed in (A,A')Ni 2B 2C solid solutions

    NASA Astrophysics Data System (ADS)

    Kuznietz, Moshe; Gonçalves, António P.; Almeida, Manuel

    2002-08-01

    The nickel-borocarbides ANi 2B 2C [A=Y, Ln (lanthanide), An(actinide)], crystallizing in the body-centred tetragonal LuNi 2B 2C-type structure, are classified according to the existence or coexistence of superconducting and antiferromagnetic states (AF). The magnetic features observed in polycrystalline (A,A')Ni 2B 2C solid solutions, adopting the same crystal structure, are reviewed and discussed. Published data on the magnetism in (A,Ln)Ni 2B 2C systems (ANi 2B 2C nonmagnetic, A=Y,La,Lu) indicate a gradual rise in the threshold content, x( m), in (Y 1- xLn x)Ni 2B 2C (Ln=Gd,Tb,Dy,Ho,Er) for the establishment of AF states. (A,A')Ni 2B 2C systems with magnetic end compounds show gradual variation in magnetic features when A and A' are both heavy Ln. The behaviour of (A,A')Ni 2B 2C systems of light A (Pr or U) and heavy A' (Dy or Tm) depends on the magnetic structures of the end compounds. In intermediate compositions, incomplete moment compensation in (Pr,Dy)Ni 2B 2C decreases TN, while different moment directions in the end compounds in (U,Dy)Ni 2B 2C lead to a directional frustration of ordered moments. Such a frustration in (U,Tm)Ni 2B 2C is related to different magnetic structures of the end compounds.

  19. Thermo-compression of pyrope-grossular garnet solid solutions: non-linear compositional dependence

    NASA Astrophysics Data System (ADS)

    Clark, S. M.; Du, W.; Walker, D.

    2014-12-01

    Unit cell parameters of a series of synthetic garnets with the pyrope, grossular, and four intermediate compositions were measured up to about 900K and to 10 GPa using synchrotron X-ray powder diffraction. Coefficients of thermal expansion of pyrope-grossular garnets are in the range 2.10~ 2.74 x 10-5 K-1 and uniformly increase with temperature. Values for the two end members pyrope and grossular are identical within experimental error 2.74±0.05 x 10-5 K-1 and 2.73±0.01 x 10-5 K-1 respectively. Coefficients of thermal expansion for intermediate compositions are smaller than those of end members, and are not linearly dependent on composition. Bulk modulus of grossular is Κ0=164.3(1) GPa (with Κ0' the pressure derivative of the bulk modulus fixed to 5.92) and bulk modulus of pyrope is Κ0=169.2(2) GPa (with Κ0' fixed to 4.4) using a third order Birch-Murnaghan equation of state, which are consistent with previously reported values. The bulk moduli of garnets of intermediate composition are between ~155 and ~160 GPa, smaller than those of the end-members no matter which Κ0' is chosen. The compositional dependence of bulk modulus resembles the compositional dependence of thermal expansion. Intermediate garnets on this binary have large positive excess volume, which makes them more compressible. We find that excess volumes in the pyrope-grossular series remain relatively large even at high pressure (~6GPa) and temperature (~800K), supporting the observation of crystal exsolution on this garnet join. (Ref: Wei Du, Simon Martin Clark, and David Walker (2014) Thermo-compression of pyrope-grossular garnet solid solutions:non-linear compositional dependence. American Mineralogist, In Press).

  20. Laboratory emissivity measurements of the plagioclase solid solution series under varying environmental conditions

    NASA Astrophysics Data System (ADS)

    Donaldson Hanna, K. L.; Thomas, I. R.; Bowles, N. E.; Greenhagen, B. T.; Pieters, C. M.; Mustard, J. F.; Jackson, C. R. M.; Wyatt, M. B.

    2012-11-01

    New laboratory thermal infrared emissivity measurements of the plagioclase solid solution series over the 1700 ˜ 400 cm-1 (6-25 μm) spectral range are presented. Thermal infrared (TIR) spectral changes for fine-particulate samples (0-25 μm) are characterized for the first time under different laboratory environmental conditions: ambient (terrestrial-like), half-vacuum (Mars-like), vacuum, and vacuum with cooled chamber (lunar-like). Under all environmental conditions the Christiansen Feature (CF) is observed to vary in a systematic way with Na-rich end-member (albite) having a CF position at the highest wave number (shortest wavelength) and the Ca-rich end-member (anorthite) having a CF position with the lowest wave number (longest wavelength). As pressure decreases to <10-3 mbar four observations are made: (1) the CF position shifts to higher wave numbers, (2) the spectral contrast of the CF increases relative to the RB, (3) the spectral contrast of the RB in the ˜1200-900 spectral range decreases while the spectral contrast of the RB in the ˜800-400 spectral range either increases or remains the same and (4) the TF disappears. A relationship between the wavelength position of the CF measured under simulated lunar conditions and plagioclase composition (An#) is developed. Although its exact form may evolve with additional data, this linear relationship should be applied to current and future TIR data sets of the Moon. Our new spectral measurements demonstrate how sensitive thermal infrared emissivity spectra of plagioclase feldspars are to the environmental conditions under which they are measured and provide important constraints for interpreting current and future thermal infrared data sets.

  1. Effect of Heat-Treatment and Composition on Structure and Luminescence Properties of Spinel-Type Solid Solution Nanocrystals.

    PubMed

    Sakoda, Kazuki; Hirano, Masanori

    2015-08-01

    The compositional dependence of the structure and properties of spinel-type solid solutions, Zn(A,Ga)2O4 was investigated by comparison with samples hydrothermally prepared and those after heat treatment at 1000 °C in air. Nanocrystalline spinel-type solid solutions in the whole composition range in the ZnAl2O4-ZnGa2O4 system were directly formed from the aqueous precursor solutions of ZnSO4, Al(NO3)3 and Ga(NO3)3 under hydrothermal conditions at 180 °C for 5 h in the presence of tetramethylammonium hydroxide. The incorporation of aluminum into the lattice, Zn(AlxGa1-x)2O4, resulted in lower crystallinity of the spinel. The relationship between the lattice parameter of as-prepared samples and the Al atomic ratio in the spinel composition was slightly apart from the ideal linear relationship that was obtained in the samples after heat treatment at 1000 °C. The optical band gap of both as-prepared solid solutions and those heat treated linearly increased from 4.1~4.2 to 5.25 eV by the incorporation of aluminum ion into the lattice, Zn(AlxGa1-x)2O4. Two main broad-band emission spectra centered at around 360 and 430 nm in the range of 300-600 nm were observed in the spinel solid solutions under excitation at 270 nm, thought their broad-band emission spectra and their peak wavelengths subtly changed depending on the composition and heat treatment.

  2. Formation of III–V ternary solid solutions on GaAs and GaSb plates via solid-phase substitution reactions

    SciTech Connect

    Vasil’ev, V. I.; Gagis, G. S. Kuchinskii, V. I.; Danil’chenko, V. G.

    2015-07-15

    Processes are considered in which ultrathin layers of III–V ternary solid solutions are formed via the delivery of Group-V element vapors to GaAs and GaSb semiconductor plates, with solid-phase substitution reactions occurring in the surface layers of these plates. This method can form defect-free GaAs{sup 1–x}P{sup x}, GaAs{sup x}Sb{sup 1–x}, and GaP{sup x}Sb{sup 1–x} layers with thicknesses of 10–20 nm and a content x of the embedded components of up to 0.04.

  3. (Ca,Sr)CO 3 aqueous-solid solution systems: From atomistic simulations to thermodynamic modelling

    NASA Astrophysics Data System (ADS)

    Kulik, D. A.; Vinograd, V. L.; Paulsen, N.; Winkler, B.

    The uptake of strontium in calcium carbonates is a topic of sustained interest in (radio)geochemistry. The available data on (Ca,Sr)CO 3 aqueous-solid solution (Aq-SS) systems with the calcite ( R3barc) and aragonite ( Pmcn) structures are reconciled using a stepwise approach from atomistic to thermodynamic modelling consisting of: (1) Quantum-mechanical and force-field calculations aimed at the prediction of standard thermodynamic properties of a hypothetical pure SrCO 3( R3barc) compound; (2) Force-field calculations on supercell structures of end members with defects of incoherent atoms in the cluster expansion framework, followed by Monte Carlo simulations of the excess SS mixing properties in both R3barc and Pmcn structures; (3) Thermodynamic modelling of Aq-SS systems with SS phases of both structures using the Gibbs Energy Minimization (GEM) code in two scenarios: (i) aqueous solution in equilibrium with one SS phase of either Pmcn or R3barc structure; (ii) aqueous solution equilibrated with two SS phases having different structures. The (ii) case was investigated using two approaches: (A) The two SS introduced as separate phases, with the excess mixing in each phase described by an own Guggenheim polynomial and (B) End members of different structures combined into a single calcite-strontianite phase using the Darken’s Quadratic Formulation (DQF) mixing model. For the aragonite-strontianite SS system, a nearly symmetric solvus is predicted in good agreement with the available calorimetric and electrochemical data. The solubility data at low Sr concentrations are qualitatively reproduced with the DQF model. For the (Ca,Sr)CO 3 SS with the calcite structure, a slightly asymmetric, moderately positive excess Gibbs free energy of mixing is predicted and shown to agree well with known equilibrium distribution coefficients for trace Sr in calcite and with the predicted solubility product of the hypothetical SrCO 3( R3barc) end member. Although each SS system

  4. Evolution of magnetic properties in the solid solution DyCo1-xNixC2

    NASA Astrophysics Data System (ADS)

    Michor, H.; Levytskyy, V.; Schwarzböck, F.; Babizhetskyy, V.; Kotur, B.

    2015-01-01

    The crystal structure of the solid solution of DyCo1-xNixC2 (0≤x≤1) was investigated by means of X-ray powder diffraction: structure type CeNiC2, space group Amm2, and Pearson symbol oS8. The structural analysis reveals a non-monotonous evolution in particular for the a- and c-lattice constants resulting in a non-linear increase of the unit cell volume due to non-isoelectronic substitution of Co by Ni markedly deviating from Vegard's law. A crossover from ferro- to antiferromagnetic ordering with a significant reduction of the magnetic ordering temperature at intermediate compositions in DyCo1-xNixC2 is observed when varying the Ni-concentration. A crossover from ferro- to antiferromagnetic coupling is also revealed from a sign change of the paramagnetic Curie temperature when proceeding along this solid solution.

  5. Mechanical alloying synthesis of K{sub 2}Bi{sub 8}Se{sub 13}-type solid solutions.

    SciTech Connect

    Toumpas, N.; Kyratsi, T.; Hatzikraniotis, E.; Tsiappos, A.; Pavlidou, E.; Paraskevopoulos, K. M.; Chung, D. Y.; Kanatzidis, M. G.; Materials Science Division; Univ. of Cyprus; Aristotle Univ. Thessaloniki; Northwestern Univ.

    2008-01-01

    Solid solutions of K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} are an interesting series of materials for thermoelectric investigations due to their very low thermal conductivity and highly anisotropic electrical properties. In this work, we aimed to synthesize solid solutions of O-K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} type materials using powder techniques. The synthesis was based on mechanical alloying as well as sintering procedures. The products were studied in terms of structural features, composition and purity with powder x-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Preliminary results on thermoelectric properties as well as IR reflectivity measurements are presented.

  6. Isothermal Decomposition of β-Solid Solution in Titanium Alloy Ti - 10 V - 2Fe - 3Al

    NASA Astrophysics Data System (ADS)

    Illarionov, A. G.; Trubochkin, A. V.; Shalaev, A. M.; Illarionova, S. M.; Popov, A. A.

    2017-03-01

    Regular features of variation of structure, phase composition and hardness characteristics in a β-phase-based titanium alloy Ti - 10 V - 2Fe - 3Al subjected to isothermal treatment in a melt of lead and tin for 5 sec - 32 h at 250 - 800 °C after a hold at 860 °C are considered. The types of the phases precipitated in the process of isothermal decomposition of the high-temperature β-solid solution and the dependences of the lattice constant of the β-phase and of the hardness on the temperature-and-time mode of the treatment are determined. Adiagram of isothermal decomposition of the β-solid solution in alloy Ti - 10 V - 2Fe - 3Al is plotted.

  7. Phase equilibria diagrams, crystal growth peculiarities and Raman investigations of lead and sodium-bismuth tungstate-molybdate solid solutions

    NASA Astrophysics Data System (ADS)

    Lebedev, Andrei V.; Avanesov, Samvel A.; Yunalan, Tyliay M.; Klimenko, Valeriy A.; Ignatyev, Boris V.; Isaev, Vladislav A.

    2016-02-01

    In this paper a comprehensive study of lead and sodium-bismuth tungstate-molybdate solid solutions was carried out, including the clarification of their structural peculiarities and phase diagrams of PbMoO4-PbWO4 and NaBi(MoO4)2-NaBi(WO4)2 systems, the study of spontaneous Raman spectra of these compounds, as well as preliminary experiments on single crystals growth of lead tungstate-molybdate. The linewidths, peak and integral intensities of the totally symmetric Raman vibrations of solid solutions were estimated in comparison with known SRS-active crystals. The conditions of the Czochralski growth of optically transparent lead tungstate-molybdate mixed crystals were found and SRS effect was observed in these crystals when pumping by 12 ns 1064 nm laser pulses.

  8. YbCu2Si2-LaCu2Si2 Solid Solutions with Enhanced Thermoelectric Power Factors

    NASA Astrophysics Data System (ADS)

    Lehr, Gloria J.; Morelli, Donald T.; Jin, Hyungyu; Heremans, Joseph P.

    2015-06-01

    Cryogenic Peltier coolers are ideal for cooling infrared sensors on satellites. To make these thermoelectric devices a realistic option for this application, the efficiency of thermoelectric materials at cryogenic temperatures must be substantially enhanced. Intermediate valence Yb-based compounds have large peaks in the Seebeck coefficient at low temperatures; to optimize these materials this must be understood. We created solid solutions between the intermediate valence compound YbCu2Si2 and an isostructural compound LaCu2Si2 to manipulate the temperature at which the Seebeck coefficient peaks and to maximize zT by reduction of lattice thermal conductivity. An enormous power factor of 110 μW/cm K2 at 100 K and a maximum zT of 0.14 at 125 K were achieved for one of these solid solutions.

  9. Temperature dependence of exciton-surface plasmon polariton coupling in Ag, Au, and Al films on In{sub x}Ga{sub 1−x}N/GaN quantum wells studied with time-resolved cathodoluminescence

    SciTech Connect

    Estrin, Y.; Rich, D. H.; Keller, S.; DenBaars, S. P.

    2015-01-28

    The optical properties and coupling of excitons to surface plasmon polaritons (SPPs) in Ag, Au, and Al-coated In{sub x}Ga{sub 1−x}N/GaN multiple and single quantum wells (SQWs) were probed with time-resolved cathodoluminescence. Excitons were generated in the metal coated SQWs by injecting a pulsed high-energy electron beam through the thin metal films. The Purcell enhancement factor (F{sub p}) was obtained by direct measurement of changes in the temperature-dependent radiative lifetime caused by the SQW exciton-SPP coupling. Three chosen plasmonic metals of Al, Ag, and Au facilitate an interesting comparison of the exciton-SPP coupling for energy ranges in which the SP energy is greater than, approximately equal to, and less than the excitonic transition energy for the InGaN/GaN QW emitter. A modeling of the temperature dependence of the Purcell enhancement factor, F{sub p}, included the effects of ohmic losses of the metals and changes in the dielectric properties due to the temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband critical point transition energies which involve the d-bands of Au and Ag. We show that an inclusion of both intraband and interband effects is essential when calculating the ω vs k SPP dispersion relation, plasmon density of states (DOS), and the dependence of F{sub p} on frequency and temperature. Moreover, the “back bending” in the SPP dispersion relation when including ohmic losses can cause a finite DOS above ω{sub sp} and lead to a measurable F{sub p} in a limited energy range above ω{sub sp}, which can potentially be exploited in plasmonic devices utilizing Ag and Au.

  10. Spectral and electroluminescent properties of coordination compounds of terbium (III) with ibuprofen (in solid form, chloroform solutions, and polyvinylcarbazole films)

    NASA Astrophysics Data System (ADS)

    Samsonova, L. G.; Kopylova, T. N.; Degtyarenko, K. M.; Ponarin, N. V.; Meshkova, S. B.; Zheltvai, I. I.

    2015-08-01

    Spectral properties of terbium (III) complexes with composition of TbL3DL, where L is an anion of d,l-2-(4-isobutylphenyl)propanoic acid (ibuprofen) and DL is 2,2'-dipyridyl (Dipy), 1,10-phenanthroline (Phen), or triphenylphosphine oxide (TPPO), have been studied in a solid form, chloroform solutions, and polyvinylcarbazole (PVC) films. It has been demonstrated that, in PVC films, occupation of the emitting level of terbium (III) involves the participation of polymer. The emission decay lifetimes of terbium in the chloroform solutions and PVC films have been measured. The possibility of the appearance of electroluminescence of complexes in PVC films has been studied.

  11. Solution and solid-supported synthesis of 3,4,5-trisubstituted 1,2,4-triazole-based peptidomimetics.

    PubMed

    Boeglin, Damien; Cantel, Sonia; Heitz, Annie; Martinez, Jean; Fehrentz, Jean-Alain

    2003-11-13

    [reaction: see text] 3,4,5-Trisubstituted 1,2,4-triazoles were synthesized in solution from various thioamides and hydrazides in smooth experimental conditions leading to peptidomimetic scaffolds. This strategy was found to be compatible with the usual peptide synthesis protecting groups. This methodology was then applied on solid support by anchoring alpha-amino acids through their amino function to an activated carbonate resin.

  12. Thermodynamic mixing properties of the UO2-HfO2 solid solution: Density functional theory and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Yuan, Ke; Ewing, Rodney C.; Becker, Udo

    2015-03-01

    HfO2 is a neutron absorber and has been mechanically mixed with UO2 in nuclear fuel in order to control the core power distribution. During nuclear fission, the temperature at the center of the fuel pellet can reach above 1300 K, where hafnium may substitute uranium and form the binary solid solution of UO2-HfO2. UO2 adopts the cubic fluorite structure, but HfO2 can occur in monoclinic, tetragonal, and cubic structures. The distribution of Hf and U ions in the UO2-HfO2 binary and its atomic structure influence the thermal conductivity and melting point of the fuel. However, experimental data on the UO2-HfO2 binary are limited. Therefore, the enthalpies of mixing of the UO2-HfO2 binary with three different structures were calculated in this study using density functional theory and subsequent Monte Carlo simulations. The free energy of mixing was obtained from thermodynamic integration of the enthalpy of mixing over temperature. From the ΔG of mixing, a phase diagram of the binary was obtained. The calculated UO2-HfO2 binary forms extensive solid solution across the entire compositional range, but there are a variety of possible exsolution phenomena associated with the different HfO2 polymorphs. As the structure of the HfO2 end member adopts lower symmetry and becomes less similar to cubic UO2, the miscibility gap of the phase diagram expands, accompanied by an increase in cell volume by 7-10% as the structure transforms from cubic to monoclinic. Close to the UO2 end member, which is relevant to the nuclear fuel, the isometric uranium-rich solid solutions exsolve as the fuel cools, and there is a tendency to form the monoclinic hafnium-rich phase in the matrix of the isometric, uranium-rich solid solution phase.

  13. Thermoelectric properties of n-Bi2Te3 - x - y Se x S y solid solutions under high pressure

    NASA Astrophysics Data System (ADS)

    Korobeinikov, I. V.; Luk'yanova, L. N.; Vorontsov, G. V.; Shchennikov, V. V.; Kutasov, V. A.

    2014-02-01

    The thermoelectric properties of n-Bi2Te3 - x - y Se x S y solid solutions with atomic substitutions in the tellurium sublattice ( x = 0.27, 0.3, y = 0, and x = y = 0.09) have been studied under a pressure to 8 GPa. It has been found that the Seebeck coefficient and the resistance decrease with increasing P, and power factor χ increases in all compositions and becomes maximal at pressures of 2-4 GPa. It has been shown that the power factor χ, which is proportional to the product of the effective mass of the density of states m/m m/m 0 and the charge carrier mobility μ0 in the form ( m/m 0)3/2μ0, increases with increasing pressure mainly due to the increase in the mobility and also depends on the solid solution composition. In the composition with substitution Te → Se + S ( x = y = 0.09), the peculiarity of the dependence of m/m 0 on P in the pressure range corresponding to maximal values of the power factor can be explained by the existence of an electronic topological transition. The increase in the power factor under pressure in n-type Bi2Te3 - x - y Se x S y solid solutions combined with similar data for p-type Bi2 - x Sb x Te3 solid solutions obtained earlier, including the estimations of possible changes in the thermal conductivity with increasing pressure, give grounds to design thermoelements with improved value of the thermoelectric figure-of-merit, which can be 50-70% at pressures of 2-4 GPa.

  14. The local structure of Pd(x)Ce(1-x)O(2-x-δ) solid solutions.

    PubMed

    Gulyaev, R V; Kardash, T Yu; Malykhin, S E; Stonkus, O A; Ivanova, A S; Boronin, A I

    2014-07-14

    PdxCe1-xO2-x-δ solid solutions, which are highly efficient catalysts for the low-temperature oxidation of carbon monoxide, were examined using a set of structural (XRD-PDF, HRTEM, XRD) and spectral (XPS, Raman spectroscopy) methods in combination with quantum-chemical calculations. A comparison of the experimental results and pair distribution function (PDF) modeling data enabled reliable verification of the model of non-isomorphic substitution of Ce(4+) ions by Pd(2+) ions in PdxCe1-xO2-x-δ solid solutions. Palladium ions were shown to be in a near square planar environment with C4v symmetry, which is typical for Pd(2+) ions. Such a near square planar environment was revealed by Raman spectroscopy due to the appearance of the band at ω = 187 cm(-1), which corresponds to the A1 vibrational mode of Pd(2+) ions in [PdO4] subunits. The binding energy of Pd3d5/2 (Eb(Pd3d5/2)) for the Pd(2+) ion in the CeO2 lattice is 1 eV higher than that of Eb(Pd3d5/2) for PdO oxide due to a decrease in the Pd-O distances and the formation of more ionic bonds because of the displacement of Pd(2+) ions with respect to the position of Ce(4+) ions in the fluorite structure. Five structural models of solid solutions are considered in this work. As demonstrated by the DFT calculations, the most realistic model is based on the displacement of palladium ions leading to a near square planar PdO4 environment, which includes water molecules stabilizing the region of anion vacancies in their dissociated state as two hydroxyl groups. The introduction of water molecules in the composition of the PdxCe1-xO2-x-δ solution leads to a decrease in the formation energy and to additional stabilization of palladium in the CeO2 matrix. The formation of PdxCe1-xO2-x-δ solid solutions is accompanied by the dispersing effect caused by distortions of the fluorite structure induced by Pd(2+) ions. The coprecipitation method, which allows Pd(2+) ions to be introduced at the stage of fluorite structure

  15. Solid Solutions of Rare Earth Cations in Mesoporous Anatase Beads and Their Performances in Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Cavallo, Carmen; Salleo, Alberto; Gozzi, Daniele; di Pascasio, Francesco; Quaranta, Simone; Panetta, Riccardo; Latini, Alessandro

    2015-11-01

    Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1-0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J-V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms.

  16. The solution, solid state stability and kinetic investigation in degradation studies of lercanidipine: study of excipients compatibility of lercanidipine.

    PubMed

    Parmar, Nitin; Amin, Saima; Singla, Neelam; Kohli, Kanchan

    2012-01-01

    The objectives of this research were to evaluate the stability of lercanidipine in solution state and solid state and explore the compatibility of drug with oils, surfactants and cosurfactants as excipients. The effect of pH on the degradation in solution state was studied through pH-rate profile of lercanidipine in constant ionic strength buffer solutions in pH range 1-8 which gives the pH of maximum stability. Powdered lercanidipine was stored under 40°C/0%~75% relative humidities (RH) or 0% RH/5~50°C to study the influence of RH and temperature on the stability of lercanidipine in solid state. Binary mixtures of lercanidipine and different excipients were stored at 40°C/75% RH, 40°C and at room temperature for excipient compatibility evaluation. The degradation of lercanidipine at different pH appears to fit a typical first-order reaction, but in solid state, it does not fit any obvious reaction model. Moisture content and temperature both play important roles affecting the degradation rate. Lercanidipine exhibits good compatibility with surfactants, cosurfactants and oils as excipients under stressed conditions of different storage temperature in a 3-week screening study. Moreover, the proposed high-performance liquid chromatography method was utilized to investigate the kinetics of the acidic and alkaline degradation processes of lercanidipine at different temperatures.

  17. Solid Solutions of Rare Earth Cations in Mesoporous Anatase Beads and Their Performances in Dye-Sensitized Solar Cells

    PubMed Central

    Cavallo, Carmen; Salleo, Alberto; Gozzi, Daniele; Di Pascasio, Francesco; Quaranta, Simone; Panetta, Riccardo; Latini, Alessandro

    2015-01-01

    Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1–0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J–V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms. PMID:26577287

  18. A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

    PubMed Central

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

    2015-01-01

    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance. PMID:25619504

  19. First-principles study of band gap engineering via oxygen vacancy doping in perovskite ABB'O₃ solid solutions

    SciTech Connect

    Qi, Tingting; Curnan, Matthew T.; Kim, Seungchul; Bennett, Joseph W.; Grinberg, Ilya; Rappe, Andrew M.

    2011-12-15

    Oxygen vacancies in perovskite oxide solid solutions are fundamentally interesting and technologically important. However, experimental characterization of the vacancy locations and their impact on electronic structure is challenging. We have carried out first-principles calculations on two Zr-modified solid solutions, Pb(Zn1/3Nb2/3)O₃ and Pb(Mg1/3Nb2/3)O₃, in which vacancies are present. We find that the vacancies are more likely to reside between low-valent cation-cation pairs than high-valent cation-cation pairs. Based on the analysis of our results, we formulate guidelines that can be used to predict the location of oxygen vacancies in perovskite solid solutions. Our results show that vacancies can have a significant impact on both the conduction and valence band energies, in some cases lowering the band gap by ≈0.5 eV. The effects of vacancies on the electronic band structure can be understood within the framework of crystal field theory.

  20. First-principles study of band gap engineering via oxygen vacancy doping in perovskite ABB'O₃ solid solutions

    DOE PAGES

    Qi, Tingting; Curnan, Matthew T.; Kim, Seungchul; ...

    2011-12-15

    Oxygen vacancies in perovskite oxide solid solutions are fundamentally interesting and technologically important. However, experimental characterization of the vacancy locations and their impact on electronic structure is challenging. We have carried out first-principles calculations on two Zr-modified solid solutions, Pb(Zn1/3Nb2/3)O₃ and Pb(Mg1/3Nb2/3)O₃, in which vacancies are present. We find that the vacancies are more likely to reside between low-valent cation-cation pairs than high-valent cation-cation pairs. Based on the analysis of our results, we formulate guidelines that can be used to predict the location of oxygen vacancies in perovskite solid solutions. Our results show that vacancies can have a significant impactmore » on both the conduction and valence band energies, in some cases lowering the band gap by ≈0.5 eV. The effects of vacancies on the electronic band structure can be understood within the framework of crystal field theory.« less