WorldWideScience

Sample records for surface o3 depletion

  1. Surface modified Al2O3 in fluorinated polyimide/Al2O3 ...

    Indian Academy of Sciences (India)

    the mechanical and thermal properties of polymers (Li et al. 2010). Herein, we wish to report the synthesis and characte- rization of fluorinated PI–Al2O3 nanocomposite films via in situ polymerization using different contents of surface modified Al2O3 nanoparticles as filler and fluorinated PI as the matrix. PI which was used ...

  2. Photodegradation of phenol on Y2O3 surface

    International Nuclear Information System (INIS)

    Karunakaran, C.; Dhanalakshmi, R.; Anilkumar, P.

    2009-01-01

    Under UV light, phenol degrades on the surface of Y 2 O 3 , an insulator, and the degradation follows first-order kinetics, depends linearly on the light intensity and slows down with pH. The efficiency of degradation is higher with UV-C light than with UV-A light. While particulate anatase TiO 2 , ZnO, ZnS, Fe 2 O 3 , CuO, CdO, and Nb 2 O 5 individually photodegrade phenol, each semiconductor shows synergism when present along with Y 2 O 3 , indicating electron-transfer from phenol adsorbed on Y 2 O 3 to the illuminated semiconductors.

  3. Surface modified Al2O3 in fluorinated polyimide/Al2O3 ...

    Indian Academy of Sciences (India)

    agglomeration. One approach to decrease the aggregation of inorganic Al2O3 is surface modification of these nanoparti- cles with coupling agent which usually has a long alkyl tail and shows a good compatibility with polymer .... ture and spatial distribution of the various components, through direct visualization. Figure 5 ...

  4. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    Administrator

    Page 1. Electronic Supplementary Material. Graphical abstract. Formation and surface characterization of nanostructured Al2O3–TiO2 coatings by Vairamuthu Raj and Mohamed Sirajudeen Mumjitha. (pp 1411–1418).

  5. Surface cation nonstoichiometry in undoped BaTiO3

    International Nuclear Information System (INIS)

    Zhang, Z.; Nowotny, J.; Pigram, P.J.; Lamb, R.N.

    1998-01-01

    This paper considers the effect of high temperature treatment on the local chemistry of the surface region of undoped BaTiO 3 . Segregation-induced cation nonstoichiometry has been investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Samples were thermally treated at 1000 deg C in a tube furnace under different oxygen activities, and then cooled to room temperature at different rates. For slowly cooled samples, Ti enrichment is found in the surface region of oxidised BaTiO 3 , while less Ti segregation occurs in reduced BaTiO3. Increasing the cooling rate reduces the degree of Ti segregation, but it does not change the general behaviour of segregation in either oxidised or reduced BaTiO 3

  6. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    Administrator

    1411. Formation and surface characterization of nanostructured Al2O3–TiO2 coatings. VAIRAMUTHU RAJ* and MOHAMED SIRAJUDEEN MUMJITHA. Advanced Materials ... of the coatings (thickness, growth rate, coating ratio) showed a linear regime with current density and electro- ..... Electronic Supplementary Material.

  7. Study of the solid-solid surface adsorption of Eu2O3 on various Al2O3 supports

    International Nuclear Information System (INIS)

    Liu Rongchuan; Yu Zhi; Zhou Yuan; Yoshitake Yamazaki

    1997-12-01

    Solid-solid surface interactions of Eu 2 O 3 on various oxide substrates are investigated with X-ray and Moessbauer experiments. The results indicate that the interaction of Eu 2 O 3 on the complex support differs from that having simple support. An incorporation model is used to explain how Eu 2 O 3 disperses onto the surface of γ-alumina or η-alumina

  8. LiNbO3 surfaces from a microscopic perspective

    Science.gov (United States)

    Sanna, Simone; Gero Schmidt, Wolf

    2017-10-01

    A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts. Lithium niobate (LiNbO3) is a ferroelectric with a high spontaneous polarization, whose surfaces have a huge and largely unexplored potential. Owing to recent advances in experimental techniques and sample preparation, peculiar and exclusive properties of LiNbO3 surfaces could be demonstrated. For example, water films freeze at different temperatures on differently polarized surfaces, and the chemical etching properties of surfaces with opposite polarization are strongly different. More important, the ferroelectric domain orientation affects temperature dependent surface stabilization mechanisms and molecular adsorption phenomena. Various ab initio theoretical investigations have been performed in order to understand the outcome of these experiments and the origin of the exotic behavior of the lithium niobate surfaces. Thanks to these studies, many aspects of their surface physics and chemistry could be clarified. Yet other puzzling features are still not understood. This review gives a résumé on the present knowledge of lithium niobate surfaces, with a particular view on their microscopic properties, explored in recent years by means of ab initio calculations. Relevant aspects and properties of the surfaces that need further investigation are briefly discussed. The review is concluded with an outlook of challenges and potential payoff

  9. Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Valvidares, Manuel; Huijben, Mark; Yu, Pu; Ramesh, Ramamoorthy; Kortright, Jeffrey

    2010-11-03

    We quantitatively model resonant Ti L2,3 reflectivity Rs,p(q, hn) from several SrTiO3 (001) single crystals having different initial surface preparations and stored in ambient conditions before and between measurements. All samples exhibit unexpected 300 K Rs(hn) - Rp(hn) anisotropy corresponding to weak linear dichroism and tetragonal distortion of the TiO6 octahedra indicating a surface layer with properties different from cubic SrTiO3. Oscillations in Rs(q) confirm a ubiquitous surface layer 2-3 nm thick that evolves over a range of time scales. Resonant optical constant spectra derived from Rs,p(hn) assuming a uniform sample are refined using a single surface layer to fit measured Rs(q). Differences in surface layer and bulk optical properties indicate that the surface is significantly depleted in Sr and enriched in Ti and O. While consistent with the tendency of SrTiO3 surfaces toward non-stoichiometry, this layer does not conform simply to existing models for the near surface region and apparently forms via room temperature surface reactions with the ambient. This new quantitative spectral modeling approach is generally applicable and has potential to study near-surface properties of a variety of systems with unique chemical and electronic sensitivities.

  10. Surface Relaxations, Surface Energies and Electronic Structures of BaSnO3 (001) Surfaces: Ab Initio Calculations

    Science.gov (United States)

    Slassi, A.; Hammi, M.; El Rhazouani, O.

    2017-07-01

    The surface relaxations, surface energies and electronic structures of BaO- and SnO2-terminated BaSnO3 (001) surfaces have been studied by employing the first-principles density functional theory. For both terminations, we find that the upper-layer Ba and Sn atoms move inward, whereas upper-layer O atoms move outward from the surface. Moreover, the largest relaxations are occurred on the first-layer atoms of both terminations. The surface rumpling of BaO-terminated BaSnO3 (001) is slightly less than that of the SnO2-terminated BaSnO3 (001) surface. The surface energies show that both terminated surfaces are energetically stable and favorable. Finally, the surface band gap is slightly decreased for the BaO termination, while it is dramatically decreased for the SnO2 termination.

  11. Photocatalytic Active Bismuth Fluoride/Oxyfluoride Surface Crystallized 2Bi2O3-B2O3 Glass-Ceramics

    Science.gov (United States)

    Sharma, Sumeet Kumar; Singh, V. P.; Chauhan, Vishal S.; Kushwaha, H. S.; Vaish, Rahul

    2018-03-01

    The present article deals with 2Bi2O3-B2O3 (BBO) glass whose photocatalytic activity has been enhanced by the method of wet etching using an aqueous solution of hydrofluoric acid (HF). X-ray diffraction of the samples reveals that etching with an aqueous solution of HF leads to the formation of BiF3 and BiO0.1F2.8 phases. Surface morphology obtained from scanning electron microscopy show granular and plate-like morphology on the etched glass samples. Rhodamine 6G (Rh 6G) has been used to investigate the photocatalytic activity of the as-quenched and etched glasses. Enhanced visible light-driven photocatalytic activity was observed in HF etched glass-ceramics compared to the as-quenched BBO glass. Contact angle of the as-quenched glass was 90.2°, which decreases up to 20.02° with an increase in concentration of HF in the etching solution. Enhanced photocatalytic activity and increase in the hydrophilic nature suggests the efficient treatment of water pollutants by using the prepared surface crystallized glass-ceramics.

  12. Characteristics of surface O3 over Qinghai Lake area in Northeast Tibetan Plateau, China

    International Nuclear Information System (INIS)

    Shen, Zhenxing; Cao, Junji; Zhang, Leiming; Zhao, Zhuzi; Dong, Jungang; Wang, Linqing; Wang, Qiyuan; Li, Guohui; Liu, Suixin; Zhang, Qian

    2014-01-01

    Surface O 3 was monitored continuously during Aug. 12, 2010 to Jul. 21, 2011 at a high elevation site (3200 m above sea level) in Qinghai Lake area (36°58′37″N, 99°53′56″E) in Northeast Tibetan Plateau, China. Daily average O 3 ranged from 21.8 ppbv to 65.3 ppbv with an annual average of 41.0 ppbv. Seasonal average of O 3 followed a decreasing order of summer > autumn > spring > winter. Diurnal variations of O 3 showed low concentrations during daytime and high concentrations during late night and early morning. An intensive campaign was also conducted during Aug. 13–31, 2010 to investigate correlations between meteorological or chemical conditions and O 3 . It was found that O 3 was poorly correlated with solar radiation due to the insufficient NO x in the ambient air, thus limiting O 3 formation under strong solar radiation. In contrast, high O 3 levels always coincided with strong winds, suggesting that stratospheric O 3 and long range transport might be the main sources of O 3 in this rural area. Back-trajectory analysis supported this hypothesis and further indicated the transport of air masses from northwest, northeast and southeast directions. - Highlights: • Surface O 3 was measured in Qinghai Lake area in Northeast Tibetan Plateau, China. • The O 3 chemical formation was under a strong NOx-limited in Qinghai Lake areas. • Stratospheric O 3 and transport might be the main sources of O 3 in this area

  13. Leaf size and surface characteristics of Betula papyrifera exposed to elevated CO2 and O3

    Science.gov (United States)

    Johanna Riikonen; Kevin E. Percy; Minna Kivimaenpaa; Mark E. Kubiske; Neil D. Nelson; Elina Vapaavuori; David F. Karnosky

    2010-01-01

    Betula papyrifera trees were exposed to elevated concentrations of CO2 (1.4 x ambient), O3 (1.2 x ambient) or CO2 + O3 at the Aspen Free-air CO2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied...

  14. Photodegradation of phenol on Y2O3 surface: synergism by semiconductors.

    Science.gov (United States)

    Karunakaran, C; Dhanalakshmi, R; Anilkumar, P

    2009-08-15

    Under UV light, phenol degrades on the surface of Y(2)O(3), an insulator, and the degradation follows first-order kinetics, depends linearly on the light intensity and slows down with pH. The efficiency of degradation is higher with UV-C light than with UV-A light. While particulate anatase TiO(2), ZnO, ZnS, Fe(2)O(3), CuO, CdO, and Nb(2)O(5) individually photodegrade phenol, each semiconductor shows synergism when present along with Y(2)O(3), indicating electron-transfer from phenol adsorbed on Y(2)O(3) to the illuminated semiconductors.

  15. From aggregative adsorption to surface depletion

    DEFF Research Database (Denmark)

    Rother, Gernot; Müter, Dirk; Bock, Henry

    2017-01-01

    Adsorption of a short-chain nonionic amphiphile (C6E3) at the surface of mesoporous silica glass (CPG) was studied by a combination of adsorption measurements and mesoscale simulations. Adsorption measurements covering a wide composition range of the C6E3 + water system show that no adsorption...... occurs up to the critical micelle concentration, at which a sharp increase of adsorption is observed that is attributed to ad-micelle formation at the pore walls. Intriguingly, as the concentration is increased further, the surface excess of the amphiphile begins to decrease and eventually becomes...... negative, which corresponds to preferential adsorption of water rather than amphiphile at high amphiphile concentrations. The existence of such a surface-azeotropic point has not previously been reported in the surfactant adsorption field. Dissipative particle dynamics simulations were performed to reveal...

  16. Fabrication and characterization of fully depleted surface barrier detectors

    International Nuclear Information System (INIS)

    Ray, A.

    2010-01-01

    Fabrication of fully depleted surface barrier type thin detectors needs thin silicon wafer of 20 - 30 μm thickness and flatness of ± 1 μm. Process has been developed for thinning silicon wafers to achieve thickness up to 20 - 30 μm from thicker (0.5 - 0.8 mm) silicon samples. These samples were used to fabricate fully depleted surface barrier detectors using Au contacts on n-type silicon. The detectors were characterized by measuring forward and reverse I-V characteristics and alpha energy spectra of Am-Pu source. (author)

  17. Sorption of U(VI) in surfaces of SrTiO3

    International Nuclear Information System (INIS)

    Ortiz O, H.B.; Ordonez R, E.; Fernandez V, S.M.

    2004-01-01

    In this work is presented the physico chemical characterization and evaluation of those surface properties and of sorption of U on the SrTiO 3 like possible candidate for contention barrier in the deep geological confinement. The made studies showed that the SrTiO 3 presents maximum levels of sorption of positive nature species (mainly UO 2 2+ and UO 2 NO 3 + ). (Author)

  18. Stability of Al2O3 and Al2O3/a-SiNx:H stacks for surface passivation of crystalline silicon

    International Nuclear Information System (INIS)

    Dingemans, G.; Hoex, B.; Sanden, M. C. M. van de; Kessels, W. M. M.; Engelhart, P.; Seguin, R.; Einsele, F.

    2009-01-01

    The thermal and ultraviolet (UV) stability of crystalline silicon (c-Si) surface passivation provided by atomic layer deposited Al 2 O 3 was compared with results for thermal SiO 2 . For Al 2 O 3 and Al 2 O 3 /a-SiN x :H stacks on 2 Ω cm n-type c-Si, ultralow surface recombination velocities of S eff eff 800 deg. C) used for screen printed c-Si solar cells. Effusion measurements revealed the loss of hydrogen and oxygen during firing through the detection of H 2 and H 2 O. Al 2 O 3 also demonstrated UV stability with the surface passivation improving during UV irradiation.

  19. Polarity-induced persistent surface reconstruction in SrRuO3(111) thin films.

    Science.gov (United States)

    Xie, Weimei; Saghayezhian, Mohammad; Gu, M. Q.; Guo, Hangwen; Wu, X. S.; Plummer, E. W.; Zhang, Jiandi

    The surface structural and electronic properties of SrRuO3/SrTiO3\\ (111) as function of the film thickness are investigated. It is found that, though the interface of SRO/STO (111) has no polar mismatch and negligible lattice mismatch, the polar surface of SrRuO3 (111) thin films results in a persistent surface reconstruction. Above 2 unit cells, a (√{ 3} ×√{ 3}) R30° surface reconstruction is observed with both Low energy and reflection high energy electron diffraction. X-ray photoemission spectroscopy shows that the reconstruction is associated with the ordered oxygen vacancies on SrO3-δ terminated surface to compensate the surface polarity. Post annealing in oxygen/ozone mixture restores the p(1 × 1) surface structure, but results in different surface relaxation and enhances the metallicity thus reducing the thickness of dead layer in this material. Supported by U.S. DOE under Grant No. DOE DE-SC0002136.

  20. Resonant soft x-ray scattering from stepped surfaces of SrTiO3

    NARCIS (Netherlands)

    Schlappa, J.; Chang, C.F.; Hu, Z.; Schierle, E.; Ott, H.; Weschke, E.; Kaindl, G.; Huijben, Mark; Rijnders, Augustinus J.H.M.; Blank, David H.A.; Tjeng, L.H.; Schüssler-Langeheine, C.

    2012-01-01

    We studied the resonant diffraction signal from stepped surfaces of SrTiO3 at the Ti 2p ¿ 3d (L2,3) resonance in comparison with x-ray absorption (XAS) and specular reflectivity data. The steps on the surface form an artificial superstructure suitable as a model system for resonant soft x-ray

  1. Characterization of Al2O3 surface passivation of silicon solar cells

    International Nuclear Information System (INIS)

    Albadri, Abdulrahman M.

    2014-01-01

    A study of the passivation of silicon surface by aluminum oxide (Al 2 O 3 ) is reported. A correlation of fixed oxide charge density (Q f ) and interface trap density (D it ) on passivation efficiency is presented. Low surface recombination velocity (SRV) was obtained even by as-deposited Al 2 O 3 films and this was found to be associated to the passivation of interface states. Fourier transfer infrared spectroscopy spectra show the existence of an interfacial silicon oxide thin layer in both as-deposited and annealed Al 2 O 3 films. Q f is found positive in as-deposited films and changing to negative upon subsequent annealing, providing thus an enhancement of the passivation in p-type silicon wafers, associated to field effects. Secondary ion mass spectrometry analysis confirms the correlation between D it and hydrogen concentration at the Al 2 O 3 /Si interface. A lowest SRV of 15 cm/s was obtained after an anneal at 400 °C in nitrogen atmosphere. - Highlights: • Al 2 O 3 provides superior passivation for silicon surfaces. • Atomic layer deposition-Al 2 O 3 was deposited at a low temperature of 200 °C. • A lowest surface passivation velocity of 15 cm/s was obtained after an anneal at 400 °C in nitrogen. • As-deposited Al 2 O 3 films form very thin SiO 2 layer responsible of low interface trap densities. • High negative fixed charge density of (− 2 × 10 12 cm −2 ) was achieved upon annealing at 400 °C

  2. Surface structures and dielectric response of ultrafine BaTiO3 particles

    International Nuclear Information System (INIS)

    Jiang, B.; Peng, J.L.; Bursill, L.A.

    1998-01-01

    Characteristic differences are observed for the dielectric response and microstructures of BaTiO 3 nanoscale fine powders prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition whereas BaTiO 3 prepared via the SAG route remained cubic for all conditions. Atomic resolution images of both varieties showed a high density of interesting surface steps and facets. Computer simulated images of surface structure models showed that the outer (100) surface was typically a BaO layer and that at corners and ledges the steps are typically finished with Ba+2 ions; i.e. the surfaces and steps are Ba-rich. Otherwise the surfaces were typically clean and free of amorphous layers. The relationship between the observed surfaces structures and theoretical models for size effects on the dielectric properties is discussed. (authors)

  3. Polarity compensation mechanisms on the perovskite surface KTaO3(001)

    Science.gov (United States)

    Setvin, Martin; Reticcioli, Michele; Poelzleitner, Flora; Hulva, Jan; Schmid, Michael; Boatner, Lynn A.; Franchini, Cesare; Diebold, Ulrike

    2018-02-01

    An ionic crystal surface can be electrostatically unstable, and the surface must reconstruct in some way to avoid this “polar catastrophe.” Setvin et al. used scanning probe microscopies and density functional theory to study the changes in the polar surface of the perovskite KTaO3. They observed several structural reconstructions as the surface cleaved in vacuum was heated to higher temperatures. These ranged from surface distortions to the formation of oxygen vacancies to the development of KO and TaO2 stripes. Hydroxylation after exposure to water vapor also stabilized the surface.

  4. Effect of surface modification of BiFeO3 on the dielectric, ferroelectric, magneto-dielectric properties of polyvinylacetate/BiFeO3 nanocomposites

    Directory of Open Access Journals (Sweden)

    O. P. Bajpai

    2014-09-01

    Full Text Available Bismuth ferrite (BiFeO3 is considered as one of the most promising materials in the field of multiferroics. In this work, a simple green route as well as synthetic routes has been used for the preparation of pure phase BiFeO3. An extract of Calotropis Gigantea flower was used as a reaction medium in green route. In each case so formed BiFeO3 particles are of comparable quality. These particles are in the range of 50–60 nm and exhibit mixed morphology (viz., spherical and cubic as confirmed by TEM analysis. These pure phase BiFeO3 nanoparticles were first time surface modified effectively by mean of two silylating agent’s viz., tetraethyl orthosilicate (TEOS and (3-Aminopropyltriethoxysilane (APTES. Modified and unmodified BiFeO3 nanoparticles were efficiently introduced into polyvinylacetate (PVAc matrix. It has been shown that nanocomposite prepared by modified BiFeO3 comprise superior dispersion characteristics, improved ferroelectric properties and favorable magneto-dielectric properties along with excellent wettability in compare to nanocomposite prepared by unmodified BiFeO3. These preliminary results demonstrate possible applications of this type of nanocomposites particularly in the field of multiferroic coating and adhesives.

  5. Antimicrobial activity of transition metal acid MoO3 prevents microbial growth on material surfaces

    International Nuclear Information System (INIS)

    Zollfrank, Cordt; Gutbrod, Kai; Wechsler, Peter; Guggenbichler, Josef Peter

    2012-01-01

    Serious infectious complications of patients in healthcare settings are often transmitted by materials and devices colonised by microorganisms (nosocomial infections). Current strategies to generate material surfaces with an antimicrobial activity suffer from the consumption of the antimicrobial agent and emerging multidrug-resistant pathogens amongst others. Consequently, materials surfaces exhibiting a permanent antimicrobial activity without the risk of generating resistant microorganisms are desirable. This publication reports on the extraordinary efficient antimicrobial properties of transition metal acids such as molybdic acid (H 2 MoO 4 ), which is based on molybdenum trioxide (MoO 3 ). The modification of various materials (e.g. polymers, metals) with MoO 3 particles or sol–gel derived coatings showed that the modified materials surfaces were practically free of microorganisms six hours after contamination with infectious agents. The antimicrobial activity is based on the formation of an acidic surface deteriorating cell growth and proliferation. The application of transition metal acids as antimicrobial surface agents is an innovative approach to prevent the dissemination of microorganisms in healthcare units and public environments. Highlights: ► The presented modifications of materials surfaces with MoO 3 are non-cytotoxic and decrease biofilm growth and bacteria transmission. ► The material is insensitive towards emerging resistances of bacteria. ► Strong potential to reduce spreading of infectious agents on inanimate surfaces.

  6. Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks

    Science.gov (United States)

    Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

    2015-03-01

    In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 1012 to 1 × 1012 cm-2 eV-1, the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 1012 cm-2 for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

  7. Fingerprints of surface magnetism in Cr2O3 based exchange bias heterostructures

    Science.gov (United States)

    He, Xi; Wang, Yi; Binek, Ch.

    2009-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic (AF) compounds like Cr2O3 (max. αzz 4ps/m) and also cross-coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. In exchange bias systems the bias field depends critically on the AF interface magnetization. Hence, a strong relation between the latter and the surface magnetization of the free Cr2O3 pinning layer can be expected. Our recent research indicates that there are surface magnetic phase transitions in free Cr2O3 (111) films accompanying surface structural phase transitions. Well defined AF interface magnetization is initialized through ME annealing to T=20K. Subsequently, the interface magnetization is thermally driven through phase transitions at T=120 and 210K. Their effects on the exchange bias are studied in Cr2O3 (111)/CoPt films with the help of polar Kerr and SQUID magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh et al. 2007 Nature Materials 6 21. Financial support by NSF through Career DMR-0547887, MRSEC DMR-0820521 and the NRI.

  8. Surface modification of LiNbO3 and KTa1-xNbxO3 crystals irradiated by intense pulsed ion beam

    Science.gov (United States)

    Cui, Xiaojun; Shen, Jie; Zhong, Haowen; Zhang, Jie; Yu, Xiao; Liang, Guoying; Qu, Miao; Yan, Sha; Zhang, Xiaofu; Le, Xiaoyun

    2017-10-01

    In this work, we studied the surface modification of LiNbO3 and KTa1-xNbxO3 irradiated by intense pulsed ion beam, which was mainly composed of H+ (70%) and Cn+ (30%) at an acceleration voltage of about 450 kV. The surface morphologies, microstructural evolution and elemental analysis of the sample surfaces after IPIB irradiation have been analyzed by scanning electron microscope, atomic force microscope, X-ray diffraction and energy dispersive spectrometer techniques, respectively. The results show that the surface morphologies have significant difference impacted by the irradiation effect. Regular gully damages range from 200 to 400 nm in depth appeared in LiNbO3 under 2 J/cm2 energy density for 1 pulse, block cracking appeared in KTa1-xNbxO3 at the same condition. Surface of the crystals have melted and were darkened with the increasing number up to 5 pulses. Crystal lattice arrangement is believed to be the dominant reason for the different experimental results irradiated by intense pulsed ion beam.

  9. Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell

    OpenAIRE

    Huang, Haibing; Lv, Jun; Bao, Yameng; Xuan, Rongwei; Sun, Shenghua; Sneck, Sami; Li, Shuo; Modanese, Chiara; Savin, Hele; Wang, Aihua; Zhao, Jianhua

    2017-01-01

    This data article is related to the recently published article ‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’ (Huang et al., 2017) [1]. This paper is about passivated emitter and rear cell (PERC) structures and it describes the quality of the Al2O3 rear-surface passivation layer deposited by atomic layer deposition (ALD), in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, g...

  10. Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks

    OpenAIRE

    Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

    2015-01-01

    In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-S...

  11. Al2O3 dielectric layers on H-terminated diamond: Controlling surface conductivity

    Science.gov (United States)

    Yang, Yu; Koeck, Franz A.; Dutta, Maitreya; Wang, Xingye; Chowdhury, Srabanti; Nemanich, Robert J.

    2017-10-01

    This study investigates how the surface conductivity of H-terminated diamond can be preserved and stabilized by using a dielectric layer with an in situ post-deposition treatment. Thin layers of Al2O3 were grown by plasma enhanced atomic layer deposition (PEALD) on H-terminated undoped diamond (100) surfaces. The changes of the hole accumulation layer were monitored by correlating the binding energy of the diamond C 1s core level with electrical measurements. The initial PEALD of 1 nm Al2O3 resulted in an increase of the C 1s core level binding energy consistent with a reduction of the surface hole accumulation and a reduction of the surface conductivity. A hydrogen plasma step restored the C 1s binding energy to the value of the conductive surface, and the resistance of the diamond surface was found to be within the range for surface transfer doping. Further, the PEALD growth did not appear to degrade the surface conductive layer according to the position of the C 1s core level and electrical measurements. This work provides insight into the approaches to establish and control the two-dimensional hole-accumulation layer of the H-terminated diamond and improve the stability and performance of H-terminated diamond electronic devices.

  12. Surface amorphization in Al2O3 induced by swift heavy ion irradiation

    Science.gov (United States)

    Okubo, N.; Ishikawa, N.; Sataka, M.; Jitsukawa, S.

    2013-11-01

    Microstructure in single crystalline Al2O3 developed during irradiation by swift heavy ions has been investigated. The specimens were irradiated by Xe ions with energies from 70 to 160 MeV at ambient temperature. The fluences were in the range from 1.0 × 1013 to 1.0 × 1015 ions/cm2. After irradiations, X-ray diffractometry (XRD) measurements and cross sectional transmission electron microscope (TEM) observations were conducted. The XRD results indicate that in the initial stage of amorphization in single crystalline Al2O3, high-density Se causes the formation of new planes and disordering. The new distorted lattice planes formed in the early stage of irradiation around the fluence of 5.0 × 1013 ions/cm2 for single crystalline Al2O3 irradiated with 160 MeV-Xe ions. Energy dependence on structural modification was also examined in single crystalline Al2O3 irradiated by swift heavy ions. The XRD results indicate that the swift heavy ion irradiation causes the lattice expansion and the structural modification leading to amorphization progresses above the energy around 100 MeV in this XRD study. The TEM observations demonstrated that amorphization was induced in surface region in single crystalline Al2O3 irradiated by swift heavy ions above the fluence expected from the results of XRD. Obvious boundary was observed in the cross sectional TEM images. The crystal structure of surface region above the boundary was identified to be amorphous and deeper region to be single crystal. The threshold fluence of amorphization was found to be around 1.0 × 1014 ions/cm2 in the case over 80 MeV swift heavy ion irradiation and the fluence did not depend on the crystal structures.

  13. Luminescent Properties of Surface Functionalized BaTiO3 Embedded in Poly(methyl methacrylate

    Directory of Open Access Journals (Sweden)

    Sebastian Requena

    2014-01-01

    Full Text Available As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyltriethoxysilane (APTES and mixed with poly(methyl methacrylate/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO3 powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV.

  14. Luminescent Properties of Surface Functionalized BaTiO3 Embedded in Poly(methyl methacrylate)

    Science.gov (United States)

    Requena, Sebastian; Lacoul, Srijan; Strzhemechny, Yuri M.

    2014-01-01

    As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO3 powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV. PMID:28788468

  15. Restoring the magnetism of ultrathin LaMn O3 films by surface symmetry engineering

    Science.gov (United States)

    Peng, J. J.; Song, C.; Li, F.; Gu, Y. D.; Wang, G. Y.; Pan, F.

    2016-12-01

    The frustration of magnetization and conductivity properties of ultrathin manganite is detrimental to their device performance, preventing their scaling down process. Here we demonstrate that the magnetism of ultrathin LaMn O3 films can be restored by a SrTi O3 capping layer, which engineers the surface from a symmetry breaking induced out-of-plane orbital occupancy to the recovered in-plane orbital occupancy. The stabilized in-plane orbital occupancy would strengthen the intralayer double exchange and thus recovers the robust magnetism. This method is proved to be effective for films as thin as 2 unit cells, greatly shrinking the critical thickness of 6 unit cells for ferromagnetic LaMn O3 as demonstrated previously [Wang et al., Science 349, 716 (2015), 10.1126/science.aaa5198]. The achievement made in this work opens up new perspectives to an active control of surface states and thereby tailors the surface functional properties of transition metal oxides.

  16. Surface study and thickness control of thin Al2O3 film on Cu-9%Al(111) single crystal

    International Nuclear Information System (INIS)

    Yamauchi, Yasuhiro; Yoshitake, Michiko; Song Weijie

    2004-01-01

    We were successful in growing a uniform flat Al 2 O 3 film on the Cu-9%Al(111) surface using the improved cleaning process, low ion energy and short time sputtering. The growth of ultra-thin film of Al 2 O 3 on Cu-9%Al was investigated using Auger electron spectroscopy (AES) and a scanning electron microscope (SEM). The Al 2 O 3 film whose maximum thickness was about 4.0 nm grew uniformly on the Cu-9%Al surface. The Al and O KLL Auger peaks of Al 2 O 3 film shifted toward low kinetic energy, and the shifts were related to Schottky barrier formation and band bending at the Al 2 O 3 /Cu-9%Al interface. The thickness of Al 2 O 3 film on the Cu-9%Al surface was controlled by the oxygen exposure

  17. Photochemistry of Methyl Bromide on the α-Cr2O3(0001) Surface

    International Nuclear Information System (INIS)

    Henderson, Michael A.

    2010-01-01

    The photochemical properties of the Cr-terminated α-Cr 2 O 3 (0001) surface were explored using methyl bromide (CH 3 Br) as a probe molecule. CH 3 Br adsorbed and desorbed molecularly from the Cr-terminated α-Cr 2 O 3 (0001) surface without detectable thermal decomposition. Temperature programmed desorption (TPD) revealed a CH 3 Br desorption state at 240 K for coverages up to 0.5 ML, followed by more weakly bound molecules desorbing at 175 K for coverages up to 1 ML. Multilayer exposures led to desorption at ∼130 K. The CH 3 Br sticking coefficient was unity at 105 K for coverages up to monolayer saturation, but decreased as the multilayer formed. In contrast, pre-oxidation of the surface (using an oxygen plasma source) led to capping of surface Cr 3+ sites and near complete removal of CH 3 Br TPD states above 150 K. The photochemistry of chemisorbed CH 3 Br was explored on the Cr-terminated surface using post-irradiation TPD and photon stimulated desorption (PSD). Irradiation of adsorbed CH 3 Br with broad band light from a Hg arc lamp resulted in both photodesorption and photodecomposition of the parent molecule at a combined cross section of ∼10 -22 cm 2 . Parent PSD was indicative of molecular photodesorption, but CH 3 was also detected in PSD and Br atoms were left on the surface, both reflective of photo-induced CH 3 -Br bond dissociation. Use of a 385 nm cut-off filter effectively shut down the photodissociation pathway but not the parent molecule photodesorption process. From these observations it is inferred that d-to-d transitions in α-Cr 2 O 3 , occurring at photon energies 3 Br. It is unclear to what extent band-to-band versus direct CH 3 Br photolysis play in CH 3 -Br bond dissociation initiated by more energetic photons.

  18. Growth and surface modification of LaFeO3 thin films induced by reductive annealing

    International Nuclear Information System (INIS)

    Flynn, Brendan T.; Zhang, Kelvin H.L.; Shutthanandan, Vaithiyalingam; Varga, Tamas; Colby, Robert J.; Oleksak, Richard P.; Manandhar, Sandeep; Engelhard, Mark H.; Chambers, Scott A.; Henderson, Michael A.; Herman, Gregory S.; Thevuthasan, Suntharampillai

    2015-01-01

    Highlights: • LaFeO 3 was grown by molecular beam epitaxy on ZrO 2 :Y 2 O 3 . • The film was highly oriented but not single crystalline. • Angle resolved XPS revealed differences between surface and bulk oxygen. • Annealing the film in vacuum resulted in the sequential reduction of Fe cations. • A greater degree of Fe reduction was found at the surface. - Abstract: The mixed electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO 3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) demonstrated that the film is primarily textured in the [1 0 0] direction and is stoichiometric. High-resolution transmission electron microscopy measurements show regions that are dominated by [1 0 0] oriented LFO grains that are oriented with respect to the substrates lattice. However, selected regions of the film show multiple domains of grains that are not [1 0 0] oriented. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved X-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of LFO materials for catalytic applications

  19. Surface plasmon enhanced organic solar cells with a MoO3 buffer layer.

    Science.gov (United States)

    Su, Zisheng; Wang, Lidan; Li, Yantao; Zhang, Guang; Zhao, Haifeng; Yang, Haigui; Ma, Yuejia; Chu, Bei; Li, Wenlian

    2013-12-26

    High-efficiency surface plasmon enhanced 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane:C70 small molecular bulk heterojunction organic solar cells with a MoO3 anode buffer layer have been demonstrated. The optimized device based on thermal evaporated Ag nanoparticles (NPs) shows a power conversion efficiency of 5.42%, which is 17% higher than the reference device. The improvement is attributed to both the enhanced conductivity and increased absorption due to the near-field enhancement of the localized surface plasmon resonance of Ag NPs.

  20. Effect of Sb2O3 Modified by Various Surface Active Agents on Flame Retardant Properties of PVC Composite

    Directory of Open Access Journals (Sweden)

    XU Jian-lin

    2016-08-01

    Full Text Available Sb2O3 powders were prepared by high energy ball milling using polyethyleneglycol-6000,sodium dodecyl sulfate and OP-10 to modify the surface properties of the powder. The influence of Sb2O3 powders modified by various surface active agents on flame retardant properties of PVC composite materials was studied. The phase composition, morphology and the average particle size of the powders were characterized by XRD and TEM. The particle distribution and flame retardant properties of Sb2O3/PVC composite materials were studied by EDS, limiting oxygen index instrument and vertical burning test. The results show that nanometer Sb2O3 has good dispersion in the PVC matrix because of the higher space steric effect of organic film on the surface of nanometer Sb2O3 when polyethyleneglycol-6000 was used as the surface active agent. While the content of nanometer Sb2O3 is 1.26% in the PVC composite material, the oxygen index of the composite material is 27.1% and the composite material reaches fire retardant grade. Using sodium dodecyl sulfate and OP-10 as surface dispersants, the surface of Sb2O3 powders can not be coated completely. The particle size of Sb2O3 powders are 100nm and 150nm, respectively, The Sb2O3 powders have poor dispersion in the PVC matrix, and even some agglomerating phenomena took place. The oxygen index of Sb2O3/PVC composite materials are 24.7% and 25.3%, respectively, containing 1.26% Sb2O3 powders in Sb2O3/PVC composite material. The materials don't achieve flame retardant level.

  1. Bonding and structure of a reconstructed (001) surface of SrTiO3 from TEM.

    Science.gov (United States)

    Zhu, Guo-zhen; Radtke, Guillaume; Botton, Gianluigi A

    2012-10-18

    The determination of the atomic structure and the retrieval of information about reconstruction and bonding of metal oxide surfaces is challenging owing to the highly defective structure and insulating properties of these surfaces. Transmission electron microscopy (TEM) offers extremely high spatial resolution (less than one ångström) and the ability to provide systematic information from both real and reciprocal space. However, very few TEM studies have been carried out on surfaces because the information from the bulk dominates the very weak signals originating from surfaces. Here we report an experimental approach to extract surface information effectively from a thickness series of electron energy-loss spectra containing different weights of surface signals, using a wedge-shaped sample. Using the (001) surface of the technologically important compound strontium titanate, SrTiO(3) (refs 4-6), as a model system for validation, our method shows that surface spectra are sensitive to the atomic reconstruction and indicate bonding and crystal-field changes surrounding the surface Ti cations. Very good agreement can be achieved between the experimental surface spectra and crystal-field multiplet calculations based on the proposed atomic surface structure optimized by density functional calculations. The distorted TiO(6-x) units indicated by the proposed model can be viewed directly in our high-resolution scanning TEM images. We suggest that this approach be used as a general method to extract valuable spectroscopic information from surface atoms in parallel with high-resolution images in TEM.

  2. Nano surface engineering of Mn 2 O 3 for potential light-harvesting application

    KAUST Repository

    Kar, Prasenjit

    2015-01-01

    Manganese oxides are well known applied materials including their use as efficient catalysts for various environmental applications. Multiple oxidation states and their change due to various experimental conditions are concluded to be responsible for their multifaceted functionality. Here we demonstrate that the interaction of a small organic ligand with one of the oxide varieties induces completely new optical properties and functionalities (photocatalysis). We have synthesized Mn2O3 microspheres via a hydrothermal route and characterized them using scanning electron microscopy (SEM), X-ray diffraction (XRD) and elemental mapping (EDAX). When the microspheres are allowed to interact with the biologically important small ligand citrate, nanometer-sized surface functionalized Mn2O3 (NPs) are formed. Raman and Fourier transformed infrared spectroscopy confirm the covalent attachment of the citrate ligand to the dangling bond of Mn at the material surface. While cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) analysis confirm multiple surface charge states after the citrate functionalization of the Mn2O3 NPs, new optical properties of the surface engineered nanomaterials in terms of absorption and emission emerge consequently. The engineered material offers a novel photocatalytic functionality to the model water contaminant methylene blue (MB). The effect of doping other metal ions including Fe3+ and Cu2+ on the optical and catalytic properties is also investigated. In order to prepare a prototype for potential environmental application of water decontamination, we have synthesized and duly functionalized the material on the extended surface of a stainless steel metal mesh (size 2 cm × 1.5 cm, pore size 150 μm × 200 μm). We demonstrate that the functionalized mesh always works as a "physical" filter of suspended particulates. However, it works as a "chemical" filter (photocatalyst) for the potential water soluble contaminant (MB) in the presence

  3. Surface treatment to form a dispersed Y2O3 layer on Zircaloy-4 tubes

    Science.gov (United States)

    Jung, Yang-Il; Kim, Hyun-Gil; Guim, Hwan-Uk; Lim, Yoon-Soo; Park, Jung-Hwan; Park, Dong-Jun; Yang, Jae-Ho

    2018-01-01

    Zircaloy-4 is a traditional zirconium-based alloy developed for application in nuclear fuel cladding tubes. The surfaces of Zircaloy-4 tubes were treated using a laser beam to increase their mechanical strength. Laser beam scanning of a tube coated with yttrium oxide (Y2O3) resulted in the formation of a dispersed oxide layer in the tube's surface region. Y2O3 particles penetrated the Zircaloy-4 during the laser treatment and were distributed uniformly in the surface region. The thickness of the dispersed oxide layer varied from 50 to 140 μm depending on the laser beam trajectory. The laser treatment also modified the texture of the tube. The preferred basal orientation along the normal to the tube surface disappeared, and a random structure appeared after laser processing. The most obvious result was an increase in the mechanical strength. The tensile strength of Zircaloy-4 increased by 10-20% with the formation of the dispersed oxide layer. The compressive yield stress also increased, by more than 15%. Brittle fracture was observed in the surface-treated samples during tensile and compressive deformation at room temperature; however, the fracture behavior was changed in ductile at elevated temperatures.

  4. Microscopic characterization of Fe nanoparticles formed on SrTiO3(001 and SrTiO3(110 surfaces

    Directory of Open Access Journals (Sweden)

    Miyoko Tanaka

    2016-06-01

    Full Text Available Fe nanoparticles grown on SrTiO3 (STO {001} and {110} surfaces at room temperature have been studied in ultrahigh vacuum by means of transmission electron microscopy and scanning tunnelling microscopy. It was shown that some Fe nanoparticles grow epitaxially. They exhibit a modified Wulff shape: nanoparticles on STO {001} surfaces have truncated pyramid shapes while those on STO {110} surfaces have hexagonal shapes. From profile-view TEM images, approximate values of the adhesion energy of the nanoparticles for both shapes are obtained.

  5. Synergistic impacts of anthropogenic and biogenic emissions on summer surface O3 in East Asia.

    Science.gov (United States)

    Qu, Yu; An, Junling; Li, Jian

    2013-03-01

    A factor separation technique and an improved regional air quality model (RAQM) were applied to calculate synergistic contributions of anthropogenic volatile organic compounds (AVOCs), biogenic volatile organic compounds (BVOCs) and nitrogen oxides (NOx) to daily maximum surface 03 (O3DM) concentrations in East Asia in summer (June to August 2000). The summer averaged synergistic impacts of AVOCs and NOx are dominant in most areas of North China, with a maximum of 60 ppbv, while those of BVOCs and NOx are notable only in some limited areas with high BVOC emissions in South China, with a maximum of 25 ppbv. This result implies that BVOCs contribute much less to summer averaged O3DM concentrations than AVOCs in most areas of East Asia at a coarse spatial resolution (1 degree x 1 degree) although global emissions of BVOCs are much greater than those of AVOCs. Daily maximum total contributions of BVOCs can approach 20 ppbv in North China, but they can reach 40 ppbv in South China, approaching or exceeding those in some developed countries in Europe and North America. BVOC emissions in such special areas should be considered when 03 control measures are taken. Synergistic contributions among AVOCs, BVOCs and NOx significantly enhance O3 concentrations in the Beijing-Tianjin-Tangshan region and decrease them in some areas in South China. Thus, the total contributions of BVOCs to O3DM vary significantly from day to day and from location to location. This result suggests that 03 control measures obtained from episodic studies could be limited for long-term applications.

  6. Research on surface modification and infrared emissivity of In2O3: W thin films

    International Nuclear Information System (INIS)

    Fu, Qiang; Wang, Wenwen; Li, Dongliang; Pan, Jiaojiao

    2014-01-01

    Tungsten-doped indium oxide films (In 2 O 3 : W, IWO) were deposited on glass substrates by DC reactive magnetron sputtering method. The as-deposited IWO films have a minimum resistivity of 6.3 × 10 −4 Ω·cm and an average infrared emissivity of 0.22 in 8–14 μm. The average transmittance is about 90% in visible region and above 81% in near-infrared region. Polystyrene microsphere template and DC magnetron sputtering were used to prepare an Ag micro-grid monolayer on the as-deposited IWO films. After surface modification, the resistivity of the films was reduced by 50% and the average infrared emissivity in 8–14 μm also reduced by 25%. The effects of sphere size and sputtering time on the surface morphology, optical and electrical properties, and infrared emissivity of the IWO thin films were investigated and the mechanism was studied. - Highlights: • High performance In 2 O 3 : W (IWO) films were obtained by DC magnetron sputtering. • Micro-grids on surface were prepared by polystyrene microsphere template method. • Influences of micro-grid size and depth on properties of IWO films were analyzed. • High conductivity and transparency in near-infrared region are obtained

  7. Dynamics of surface screening charges on domains of BiFeO3 films

    Directory of Open Access Journals (Sweden)

    Jun-xing Gu

    2016-01-01

    Full Text Available The dynamics of surface screening charges on BiFeO3 films with pre-written stripe domains was studied with surface potential measurements by Kelvin Probe Force Microscopy. The screening effect decays exponentially over time, and this decay is slower in the arrays with wider domains or larger intervals of domains, indicating that the in-plane diffusion of the surface screening charges plays a major role in the decay dynamics. The good agreement between experimental data and theoretical results based on diffusion-drift model confirms the mechanism of in-plane diffusion of the screening charges in the decay dynamics. Our work could provide a pathway to control the data stability of charge storage by artificially designing the ferroelectric domains.

  8. Polarization dependent Pd deposition structure on LiNbO3 {0001} surface

    Science.gov (United States)

    Kim, Seungchul; Rappe, Andrew M.

    2011-03-01

    We investigate effects of polarization orientation on atomic structure of palladium deposited on lithium niobate (LiNb O3) {0001} surface, using density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations. Adsorption, diffusion, aggregation and clustering process -- include geometries, paths and energies -- of Pd clusters were calculated from DFT simulations. It has been observed that energy barriers of Pd motions on the negatively poled (c-) surface are much larger than those on the positively poled surface (c+), which indicates the Pd motions on the c- surface are much slower than that of c+ surface. We demonstrate, using kMC with kinetic parameters from DFT, very slow motion of Pd on c- surface leads dispersed small clusters or atoms while fast motion on c+ surface leads large clusters, indicating larger Pd-covered area on c- surface than c+ after Pd deposition. This work has been supported by US-DOE (grant DE-FG02-07ER15920), and by AROSR (FA9550-07-1-0397). Computational support was provided by HPCMO of the US-DoD.

  9. A DFT+U investigation of hydrogen adsorption on the LaFeO3(010) surface

    NARCIS (Netherlands)

    Boateng, Isaac W.; Tia, Richard; Adei, Evans; Dzade, N.Y.|info:eu-repo/dai/nl/41249311X; Catlow, C. Richard A.; de Leeuw, Nora H.|info:eu-repo/dai/nl/376421061

    2017-01-01

    The ABO3 perovskite lanthanum ferrite (LaFeO3) is a technologically important electrode material for nickel–metal hydride batteries, energy storage and catalysis. However, the electrochemical hydrogen adsorption mechanism on LaFeO3 surfaces remains under debate. In the present study, we have

  10. Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell

    Directory of Open Access Journals (Sweden)

    Haibing Huang

    2017-04-01

    Full Text Available This data article is related to the recently published article ‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’ (Huang et al., 2017 [1]. This paper is about passivated emitter and rear cell (PERC structures and it describes the quality of the Al2O3 rear-surface passivation layer deposited by atomic layer deposition (ALD, in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, growth per cycle, and film thickness and to the cell efficiency loss mechanisms. This dataset is made public in order to contribute to the limited available public data on industrial PERC cells, to be used by other researchers.

  11. Data of ALD Al2O3rear surface passivation, Al2O3PERC cell performance, and cell efficiency loss mechanisms of Al2O3PERC cell.

    Science.gov (United States)

    Huang, Haibing; Lv, Jun; Bao, Yameng; Xuan, Rongwei; Sun, Shenghua; Sneck, Sami; Li, Shuo; Modanese, Chiara; Savin, Hele; Wang, Aihua; Zhao, Jianhua

    2017-04-01

    This data article is related to the recently published article '20.8% industrial PERC solar cell: ALD Al 2 O 3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%' (Huang et al., 2017) [1]. This paper is about passivated emitter and rear cell (PERC) structures and it describes the quality of the Al 2 O 3 rear-surface passivation layer deposited by atomic layer deposition (ALD), in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, growth per cycle, and film thickness) and to the cell efficiency loss mechanisms. This dataset is made public in order to contribute to the limited available public data on industrial PERC cells, to be used by other researchers.

  12. Nanocomposites of ferroelectric polymers with surface-hydroxylated BaTiO 3 nanoparticles for energy storage applications

    KAUST Repository

    Almadhoun, Mahmoud Nassar Mahmoud

    2012-01-01

    A facile surface hydroxylation treatment using hydrogen peroxide to modify the surface of BaTiO 3 nanofillers dispersed in a ferroelectric copolymer host has been investigated. We demonstrate that the surface functionalization of the BaTiO 3 nanofillers (<100 nm) with hydroxyl groups results in as much as two orders of magnitude reduction in the leakage current of nanocomposite thin-film capacitors. This reduction is observed concurrently with the enhancement of the effective permittivity and breakdown strength of the thin-film nanocomposites. Surface modified BaTiO 3 particles display better dispersion within the polymer matrix, resulting in enhanced relative permittivity and reduced dielectric loss. The dielectric behavior of the nanocomposite films containing up to 30 vol.% BaTiO 3 agreed well with the Bruggeman model. These results demonstrate the potential of facile surface hydroxylation of nanoparticles towards the fabrication of higher energy-density nanocomposites. © 2012 The Royal Society of Chemistry.

  13. Li depletion effects on Li2TiO3 reaction with H2 in thermo-chemical environment relevant to breeding blanket for fusion power plants

    International Nuclear Information System (INIS)

    Alvani, Carlo; Casadio, Sergio; Contini, Vittoria; Giorgi, Rossella; Mancini, Maria Rita; Tsuchiya, Kunihiko; Kawamura, Hiroshi

    2005-07-01

    This is a report of the Working Group in the Subtask on Solid Breeder Blankets under the Implementing Agreement on a Co-operative Programme on Nuclear Technology of Fusion Reactors (International Energy Agency (IEA)). This Working Group (Task F and WG-F) was performed from 2000 to 2004 by a collaboration of European Union (EU) and Japan (JA). In this report, lithium depletion effects on the reaction of lithium titanate (Li 2 TiO 3 ) with hydrogen (H 2 ) in thermo-chemical environment were discussed. The reaction of Li 2 TiO 3 ceramics with H 2 was studied in a thermo-chemical environment simulating (excepting irradiation) that of the hottest pebble-bed zone of breeding-blanket actually designed for fusion power plants. This 'reduction' as performed at 900degC in Ar+0.1%H, purge gas (He+0.1%H 2 being the designed reference') was found to be enhanced by TiO 2 doping of the specimens of simulate 6 Li-burn-up expected to reach 20% at their end-of-life. The reaction rates, however, were so slow to be not significantly extrapolated to the breeder material service time (years). In Ar+3%H 2 , faster reaction rates allowed a better identification of the process evolution (kinetics) by Temperature-Programmed Reduction' (TPR) and 'Oxidation' (TPO), and combined TG-DTA thermal analysis. The reduction of pure Li 4/5 TiO 12/5 spinel phase to Li 4/5 TiO 12/5-y was found to reach in one day the steady state at the O-vacancy concentration y=0.2. Complimentary microscopy (SEM) and spectroscopy (XRD, XPS) techniques were used to characterize the reaction products among which the presence of the orthorhombic Li v TiO 2 (0 ≤ v ≤ 1/2) and Li 2 TiO 3 could be diagnosed. So that the complete spinel reduction to Li 1/2 TiO 2 was obtained according to a scheme involving the Li 1/2 TiO 2 -Li 4/5 TiO 12/5 spinel phase solid solution for which y=3v/(10-5v). The reduction rate of pure meta-titanate to Li 2 TiO 3-x was found much lower (x approx. = 0.01) and even possibly due to the presence

  14. Surface nanostructuring of LiNbO3 by high-density electronic excitations

    International Nuclear Information System (INIS)

    El-Said, A.S.; Wilhelm, R.A.; Facsko, S.; Trautmann, C.

    2013-01-01

    Lithium niobate (LiNbO 3 ) single crystals were irradiated with high energy gold ions (0.5–2.2 GeV) at the UNILAC (GSI) and with 150-keV highly charged xenon ions from an EBIT (Electron Beam Ion Trap, HZDR). The surfaces of the irradiated crystals were analyzed by scanning force microscopy showing very similar topographic changes. Swift heavy ions and slow highly charged ions produce hillock-like nanostructures on the surface. In both cases, the energy deposition of the ions is characterized by dense localized electronic excitations and efficient transfer to the lattice. Furthermore, the irradiation results in a shift in the band gap energy as evidenced by UV–Vis absorption spectroscopy. Specific modifications (e.g. hillock size, energy loss threshold) induced by slow highly charged ions are discussed in comparison with effects due to the electronic energy loss by swift heavy ions

  15. Adsorption of Cu and Pd on alpha-Al2O3(0001) surfaces with different stoichiometries

    DEFF Research Database (Denmark)

    Lodziana, Zbigniew; Nørskov, Jens Kehlet

    2001-01-01

    We report density functional theory calculations of the interaction of Cu and Pd with the (0001) surface of alpha -Al2O3. The interaction of those metals with the oxide surface varies from covalent-like for the aluminum rich surface to ionic-like for the oxygen terminated surface. Stoichiometric...

  16. First principles study of elemental mercury (Hg0) adsorption on low index CoMnO3 surfaces

    International Nuclear Information System (INIS)

    Ji, Wenchao; Su, Pingru; Tang, Qingli; Cheng, Zhiwen; Shen, Zhemin; Fan, Maohong

    2017-01-01

    Highlights: • Hg 0 adsorption on low index CoMnO 3 surface was predicted by DFT method. • Hg 0 is adsorbed on the CoMnO 3 surface with chemisorption interaction. • Hg 0 has highest adsorption energy on CoMnO 3 (1 0 0) surface with Hg-Mn mechanism. • The electron transfer of Hg 0 has positive relationship with adsorption energy. - Abstract: The density functional theory (DFT) is applied to predict elemental mercury (Hg 0 ) adsorption on CoMnO 3 surface for the first time. GGA/PBE functional were selected to determine the potential Hg 0 capture mechanisms. The results show that Hg 0 has good affinity with CoMnO 3 surfaces with chemical adsorption. The adsorption energy of Hg 0 -CoMnO 3 (1 0 0), Hg 0 -CoMnO 3 (1 0 1) and Hg 0 -CoMnO 3 (1 1 0) are −85.225, −72.305 and −70.729 kJ/mol, respectively. The Hg-Mn and Hg-Co mechanisms were revealed on low index surfaces. Hg 0 was oxidized to its valence state of 0.236 on Mn site in CoMnO 3 (1 0 0) surface. The Hg-Co interaction mechanism occurred on Hg 0 -CoMnO 3 (1 0 1) and Hg 0 -CoMnO 3 (1 1 0) with 0.209e − and 0.189e − transformation, respectively. The PDOS analysis shows that Hg-Mn interaction depends on the hybridization of Hg(s- and d-orbitals) and Mn (s-, p- and d- orbitals). However, Hg-Co interaction stems from s- and d- orbitals of Hg, which only overlapping with d- and p- orbital of Co. Both the adsorption energy and electronic structure analysis indicated that CoMnO 3 catalyst performed excellent in Hg 0 oxidation. Exposing CoMnO 3 (1 0 0) is most favorable in Hg 0 control, which provides theoretical instruction on certain crystal plane synthesis in experiment.

  17. Evolution of the SrTiO3 surface electronic state as a function of LaAlO3 overlayer thickness

    Science.gov (United States)

    Plumb, N. C.; Kobayashi, M.; Salluzzo, M.; Razzoli, E.; Matt, C. E.; Strocov, V. N.; Zhou, K. J.; Shi, M.; Mesot, J.; Schmitt, T.; Patthey, L.; Radović, M.

    2017-08-01

    The novel electronic properties emerging at interfaces between transition metal oxides, and in particular the discovery of conductivity in heterostructures composed of LaAlO3 (LAO) and SrTiO3 (STO) band insulators, have generated new challenges and opportunities in condensed matter physics. Although the interface conductivity is stabilized when LAO matches or exceeds a critical thickness of 4 unit cells (uc), other phenomena such as a universal metallic state found on the bare surface of STO single crystals and persistent photon-triggered conductivity in otherwise insulating STO-based interfaces raise important questions about the role of the LAO overlayer and the possible relations between vacuum/STO and LAO/STO interfaces. Here, using angle-resolved photoemission spectroscopy (ARPES) on in situ prepared samples complemented by resonant inelastic X-ray scattering (RIXS), we study how the metallic STO surface state evolves during the growth of a crystalline LAO overlayer. In all the studied samples, the character of the conduction bands, their carrier densities, the Ti3+ crystal field, and the response to photon irradiation bear strong similarities. Nevertheless, we report here that studied LAO/STO interfaces exhibit an instability toward an apparent 2 × 1 folding of the Fermi surface at and above a 4 uc thickness threshold, which distinguishes these heterostructures from bare STO and sub-critical-thickness LAO/STO.

  18. Adsorption of UO22+ in surfaces of SrTiO3

    International Nuclear Information System (INIS)

    Ortiz O, H.B.; Ordonez R, E.; Fernandez V, S.M.

    2005-01-01

    The internationally accepted solution in the administration of the high level radioactive residuals is the multi barrier deep geologic storage which should guarantee that do not exist flights neither transfer of residuals to the atmosphere in time periods of at least 10,000 years. In this confinement type exists the interest to study materials that can be used as engineering barriers as well as the diverse interaction phenomena between these and the radionuclides. In this work it is presented the physicochemical characterization and evaluation of the surface properties and of adsorption of U(VI) in form of UO 2 (NO 3 ) 2 on the SrTiO 3 like possible candidate for contention barrier in the deep geologic confinement. The made studies showed that the SrTiO 3 is stable to temperatures between 0 and 800 C. At the same time it could settle down that the maximum sorption percentages are reached to near pH to the isoelectric point, where chemical species prevail in solution of the type UO 2 (X) - . (Author)

  19. Tuning the electronic properties of LaAlO3/SrTiO3 interfaces by irradiating the LaAlO3 surface with low-energy cluster ion beams

    Science.gov (United States)

    Ridier, Karl; Aureau, Damien; Bérini, Bruno; Dumont, Yves; Keller, Niels; Vigneron, Jackie; Etcheberry, Arnaud; Domengès, Bernadette; Fouchet, Arnaud

    2018-01-01

    We have investigated the effects of low-energy ion beam irradiations using argon clusters on the chemical and electronic properties of LaAlO3/SrTiO3 (LAO/STO) heterointerfaces by combining x-ray photoelectron spectroscopy (XPS) and electrical transport measurements. Due to its unique features, we demonstrate that a short-time cluster ion irradiation of the LAO surface induces significant modifications in the chemical properties of the buried STO substrate with (1) a lowering of Ti atoms oxidation states (from Ti4 + to Ti3 + and Ti2 +) correlated to the formation of oxygen vacancies at the LAO surface and (2) the creation of new surface states for Sr atoms. Contrary to what is generally observed by using higher energy ion beam techniques, this leads to an increase of the electrical conductivity at the LAO/STO interface. Our XPS data clearly reveal the existence of dynamical processes on the titanium and strontium atoms, which compete with the effect of the cluster ion beam irradiation. These relaxation effects are in part attributed to the diffusion of the ion-induced oxygen vacancies in the entire heterostructure since an increase of the interfacial metallicity is also evidenced far from the irradiated area. This paper highlights the possibility of tuning the electrical properties of LAO/STO interfaces by surface engineering, confirming experimentally the intimate connection between LAO chemistry and electronic properties of LAO/STO interfaces.

  20. Λ-Doublet Propensities for Reactions on Competing A' and A″ Potential Energy Surfaces: O(3P) + N2and O(3P) + HCl.

    Science.gov (United States)

    Jambrina, Pablo G; Menéndez, M; Zanchet, A; García, E; Aoiz, F J

    2018-03-15

    This work presents scattering calculations for the O( 3 P) + N 2 ( 1 Σ) → NO( 2 Π) + N( 4 S) and for the O( 3 P) + HCl( 1 Σ) → OH( 2 Π) + Cl( 2 P) reactions with a focus on the prediction of the Λ-doublet populations in which NO and OH are produced. Both reactions can take place on two competing potential energy surfaces of symmetries 3 A' and 3 A″ that correlate reagents with products but with very distinct topographies. As a result, they exhibit very different dynamical behaviors and total reactivity. Using a method that relates the reaction yield on the two competing surfaces to the Λ-doublet populations through the explicit consideration of the stereodynamics of the reaction, we predict that the population of NO and OH on the two Λ-doublet sates is surprisingly similar for both systems. These results contradict the model that assumes that collisions on the 3 A' and 3 A″ would give rise to products in the Π( A') and Π( A″) states, respectively.

  1. Topological states at the (001) surface of SrTiO3

    Science.gov (United States)

    Vivek, Manali; Goerbig, Mark O.; Gabay, Marc

    2017-04-01

    Defect-free SrTiO3 (STO) is a band insulator but angle resolved photoemission spectroscopy (ARPES) experiments have demonstrated the existence of a nanometer thin two-dimensional electron liquid (2DEG) at the (001) oriented surface of this compound. The bulk is a trivial insulator, but our theoretical study reveals that the parity of electronic wave functions in this 2DEG is inverted in the vicinity of special points in reciprocal space where the low-energy dispersion consists of four gapped Dirac cones with a tilted and anisotropic shape. This gives rise to linearly dispersing topological edge states at the one-dimensional boundary. We propose to probe these modes by measuring the Josephson radiation from gapless bound Andreev states in STO based junctions, as it is predicted that they display distinctive signatures of topology.

  2. The atomic surface structure of SrTiO3 (001) studied with synchrotron X-rays

    NARCIS (Netherlands)

    Vonk, V.; Konings, S.; van Hummel, G.J.; Harkema, Sybolt; Graafsma, H

    2005-01-01

    The atomic surface structure of single terminated SrTiO3(0 0 1) (1 × 1) is investigated employing surface X-ray diffraction. In order to obtain these surfaces a special treatment is needed consisting of chemical etching and annealing. Since this is done in an aqueous and subsequently oxygen

  3. Electrochemical corrosion behaviours of pulsed bias MSIP aluminum coating on depleted uranium surface

    International Nuclear Information System (INIS)

    Wang Qingfu; Zhang Pengcheng; Chen Lin; Liu Qinghe; Lang Dingmu; Wang Xiaohong

    2009-01-01

    Aluminum coating was prepared by magnetron sputtering ion plating (MSIP) with pulsed bias on depleted uranium surface. Its electrochemical corrosion behaviours were studied by electrochemical technology, scanning electron microscope (SEM) and X-ray energy dispersive spectroscope (EDS). The corrosion potential of aluminum coating (-534.8 mV) is higher than that of depleted uranium (-641.2 mV). The aluminum coating is a cathodic deposit to depleted uranium. Depleted uranium coated aluminum has much higher polarization resistance,greater magnitude of electrochemical impedance and much lower corrosion current than that of depleted uranium. The aluminum coating has a good corrosion resistance to depleted uranium. Corrosion characteristic of depleted uranium coated aluminum is a typical local corrosion. Meanwhile,the aluminum coating cracks and flakes off from depleted uranium substrate, which deteriorates its anti-corrosion property. Pseudo-diffusion layer on interface between aluminum coating and uranium substrate has some degree of anti-corrosion effect. (authors)

  4. Relation of lifetime to surface passivation for atomic-layer-deposited Al2O3 on crystalline silicon solar cell

    International Nuclear Information System (INIS)

    Cho, Young Joon; Song, Hee Eun; Chang, Hyo Sik

    2015-01-01

    Highlights: • We investigated the relation of potassium contamination on Si solar wafer to lifetime. • We deposited Al 2 O 3 layer by atomic layer deposition (ALD) on Si solar wafer after several cleaning process. • Potassium can be left on Si surface by incomplete cleaning process and degrade the Al 2 O 3 passivation quality. - Abstract: We investigated the relation of potassium contamination on a crystalline silicon (c-Si) surface after potassium hydroxide (KOH) etching to the lifetime of the c-Si solar cell. Alkaline solution was employed for saw damage removal (SDR), texturing, and planarization of a textured c-Si solar wafer prior to atomic layer deposition (ALD) Al 2 O 3 growth. In the solar-cell manufacturing process, ALD Al 2 O 3 passivation is utilized to obtain higher conversion efficiency. ALD Al 2 O 3 shows excellent surface passivation, though minority carrier lifetime varies with cleaning conditions. In the present study, we investigated the relation of potassium contamination to lifetime in solar-cell processing. The results showed that the potassium-contaminated samples, due to incomplete cleaning of KOH, had a short lifetime, thus establishing that residual potassium can degrade Al 2 O 3 surface passivation

  5. Effect of specific surface area of raw material Fe2O3 on magnetic properties of YIG

    Science.gov (United States)

    Huang, Ching-Chien; Zuo, Wei-Zong; Hung, Yung-Hsiung; Huang, Jing-Yi; Kuo, Ming-Feng; Cheng, Chun-Hu

    2018-03-01

    The effect of specific surface area (SSA) of Fe2O3 was investigated while evaluating the raw material of Y3Fe5O12 (yttrium iron garnet (YIG)) preparation. For YIG ferrite, the specific surface area of Fe2O3, rather than average particle size (D50), was found to markedly affect the mixing homogeneity of powders in the mixing procedure and the magnetic properties. Increasing the specific surface area of Fe2O3 resulted in the increase of the remanence (Br) and squareness ratio (SQR); meanwhile, it also caused an obvious reduction in coercivity (HC) for the sintered specimens. An upgrade in the specific surface area of raw material Fe2O3 could further resulted in a decrease in slurry viscosity in the mixing procedure, which promotes slurry mixing homogeneity and further promotes reactivity in the calcination and sintering processes. Consequently, a larger Br and SQR and a smaller HC were obtained. In addition, good ferromagnetic resonance (FMR) line width (i.e., ΔH) properties were also realized as 36.7 Oe at 3.2 GHz using the selected Fe2O3. As found in this study, the strict control of raw material Fe2O3 is critical in tailoring suitable Br and HC for the YIG ferrite manufacturing process.

  6. Surface Passivation of MoO3 Nanorods by Atomic Layer Deposition Towards High Rate Durable Li Ion Battery Anodes

    KAUST Repository

    Ahmed, Bilal

    2015-06-03

    We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in Lithium (Li) ion batteries at high rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2 coated MoO3 electrodes is 68% higher than bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2 coated MoO3 electrodes exhibited specific capacity of 657 mAh/g, on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2 coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li–ions through the passivation layer to the active material. Furthermore, ex–situ HRTEM, X–ray photoelectron spectroscopy (XPS), Raman spectroscopy and X–ray diffraction was carried out to explain the capacity retention mechanism after HfO2 coating.

  7. The Evidence of Giant Surface Flexoelectric Field in (111) Oriented BiFeO3 Thin Film.

    Science.gov (United States)

    Yang, Tieying; Zhang, Xingmin; Chen, Bin; Guo, Haizhong; Jin, Kuijuan; Wu, Xiaoshan; Gao, Xingyu; Li, Zhong; Wang, Can; Li, Xiaolong

    2017-02-15

    In this work, the surface structure of a single-domain epitaxial BiFeO 3 film with (111) orientation was investigated by in situ grazing incidence X-ray diffraction and X-ray reflectivity. We found that a large strain gradient exists in the surface region (2-3 nm) of the BiFeO 3 film. The strain gradient is approximately 10 7 m -1 , which is 2 or 3 orders of magnitude larger than the value inside the film. Moreover, we found that a surface layer with a lower electron density compared with the underlying BiFeO 3 layer exists on the surface of BiFeO 3 film, and this layer exhibits an irreversible surface structure transition occurs at 500 K, which should be associated with the surface flexoelectric field. We considered that this large strain gradient is originated from the surface depolarization field of ferroelectrics. Our results suggest a coupling between the surface structure and the flexoelectricity and imply that the surface layer and properties would be controlled by the strain gradient in ferroelectric films.

  8. High surface O3 episodes in Seoul under different meteorological regimes during KORUS-AQ campaign.

    Science.gov (United States)

    Kim, H.; Lee, M.; Jung, J.; Cho, S.; Shin, H.; Lee, G.; Park, M.; Hong, J.

    2017-12-01

    To examine chemical characteristics of ozone (O3) formation in Seoul Metropolitan Area (SMA), H2O2, PAN, and HONO were measured in conjunction with O3 and its precursors. The experiment was conducted at Olympic Park in Seoul during May 12 June 15, 2016. For the entire experiment period, the high O3 episodes of hourly mean concentration over 100 ppbv occurred on May 20, 23, 25, 29, and 30 and June 10 and 14. These episodes were different in meteorological conditions, precursor strengths, and chemical characteristics. The local influence was dominant under stagnant condition on May 20, 23 and June 10. When stagnant conditions developed over the Korean peninsula, the PBL (Planetary Boundary Layer) height often changed rapidly, leading to abrupt change in O3 and NOx. Particularly the nighttime concentrations of reactive gases such as O3 and NOx were sensitive to the change in PBL height. It is thought to be driven by land-sea breeze circulation. During May 25 28 when air was coming from the Eastern China, O3 was enhanced with aerosols and high SO2 and CO but low NOx concentration. Odd-Oxygen (O3+NO2, OX) ratio indicates the different chemical regimes, particularly at night(8PM - 7AM). O3/OX ratio was close to zero when local influence was dominant due to O3-titration by NOx. In contrast, this ratio was high over 0.6 in Chinese outflow plumes.

  9. Surface resistance of YBa2Cu3O7 films deposited on LaGaO3 substrates

    International Nuclear Information System (INIS)

    Cooke, D.W.; Gray, E.R.; Houlton, R.J.; Javadi, H.H.S.; Maez, M.A.; Bennett, B.L.; Rusnak, B.; Meyer, E.A.; Arendt, P.N.; Beery, J.G.; Brown, D.R.; Garzon, F.H.; Raistriek, I.D.; Bolmaro, B.; Elliott, N.E.; Rollett, A.D.; Klein, N.; Muller, G.; Orbach, S.; Piel, H.; Josefowicz, J.Y.; Rensch, O.B.; Drabeck, L.; Gruner, G.

    1989-01-01

    Superconducting films of YBa 2 Cu 3 O 7 deposited onto LaGaO 3 substrates were prepared by e-beam and magnetron sputtering techniques. Surface resistance measurements made at 22 GHz, 86 GHz, and 148 GHz show that these films are superior to those deposited by similar techniques onto SrTiO 3 . Typical surface resistance values measured at 22 GHz and 12 K are ∼2 m(cgom) with the lowest value being 0.2 m(cgom), which is only 2 to 4 times higher than Nb. The surface resistance is proportional to the square of the measuring frequency

  10. High surface area LaMnO3 nanoparticles enhancing electrochemical catalytic activity for rechargeable lithium-air batteries

    Science.gov (United States)

    Li, Chuanhua; Yu, Zhiyong; Liu, Hanxing; Chen, Kang

    2018-02-01

    To improve sluggish kinetics of ORR and OER (oxygen reduction and evolution reaction) on the air electrode, the high surface area LaMnO3 nanoparticle catalysts were synthesized by sol-gel method. The specific surface area of as-synthesized pure phase LaMnO3 nanoparticles is 21.21 m2 g-1. The onset potential of high surface area LaMnO3 in alkaline solution is -0.0202 V which is comparable to commercial Pt/C. When the assembled high surface area LaMnO3-based lithium-air batteries were measured at 100 mA g-1, the initial discharge specific capacity could reach 6851.9 mA h g-1(carbon). In addition, lithium-oxygen batteries including high surface area LaMnO3 catalysts could be cycled for 52 cycles at 200 mA g-1 under a limited discharge-charge depth of 500 mA h gcarbon-1.

  11. A First Principles Study of H2 Adsorption on LaNiO3(001 Surfaces

    Directory of Open Access Journals (Sweden)

    Changchang Pan

    2017-01-01

    Full Text Available The adsorption of H2 on LaNiO3 was investigated using density functional theory (DFT calculations. The adsorption sites, adsorption energy, and electronic structure of LaNiO3(001/H2 systems were calculated and indicated through the calculated surface energy that the (001 surface was the most stable surface. By looking at optimized structure, adsorption energy and dissociation energy, we found that there were three types of adsorption on the surface. First, H2 molecules completely dissociate and then tend to bind with the O atoms, forming two –OH bonds. Second, H2 molecules partially dissociate with the H atoms bonding to the same O atom to form one H2O molecule. These two types are chemical adsorption modes; however, the physical adsorption of H2 molecules can also occur. When analyzing the electron structure of the H2O molecule formed by the partial dissociation of the H2 molecule and the surface O atom, we found that the interaction between H2O and the (001 surface was weaker, thus, H2O was easier to separate from the surface to create an O vacancy. On the (001 surface, a supercell was constructed to accurately study the most stable adsorption site. The results from analyses of the charge population; electron localization function; and density of the states indicated that the dissociated H and O atoms form a typical covalent bond and that the interaction between the H2 molecule and surface is mainly due to the overlap-hybridization among the H 1s, O 2s, and O 2p states. Therefore, the conductivity of LaNiO3(001/H2 is stronger after adsorption and furthermore, the conductivity of the LaNiO3 surface is better than that of the LaFeO3 surface.

  12. Lead adsorption study on combustion derived γ-Fe2O3 surface

    Indian Academy of Sciences (India)

    Administrator

    Polyvinyl alcohol was used as a fuel for the precursor. The feasibility of the conver- sion of the precursor (as mentioned above) to γ-Fe2O3 through microwave-assisted route is reported. In search of a suitable economic fuel, our use of polyvinyl alcohol has given promising results in the conversion of precursor into γ-Fe2O3.

  13. Surface damages of polycrystalline W and La2O3-doped W induced by high-flux He plasma irradiation

    Science.gov (United States)

    Liu, Lu; Li, Shouzhe; Liu, Dongping; Benstetter, Günther; Zhang, Yang; Hong, Yi; Fan, Hongyu; Ni, Weiyuan; Yang, Qi; Wu, Yunfeng; Bi, Zhenhua

    2018-04-01

    In this study, polycrystalline tungsten (W) and three oxide dispersed strengthened W with 0.1 vol %, 1.0 vol % and 5.0 vol % lanthanum trioxide (La2O3) were irradiated with low-energy (200 eV) and high-flux (5.8 × 1021 or 1.4 × 1022 ions/m2ṡs) He+ ions at elevated temperature. After He+ irradiation at a fluence of 3.0 × 1025/m2, their surface damages were observed by scanning electron microscopy, energy dispersive spectroscopy, scanning electron microscopy-electron backscatter diffraction, and conductive atomic force microscopy. Micron-sized holes were formed on the surface of W alloys after He+ irradiation at 1100 K. Analysis shows that the La2O3 grains doped in W were sputtered preferentially by the high-flux He+ ions when compared with the W grains. For irradiation at 1550 K, W nano-fuzz was formed at the surfaces of both polycrystalline W and La2O3-doped W. The thickness of the fuzz layers formed at the surface of La2O3-doped W is 40% lower than the one of polycrystalline W. The presence of La2O3 could suppress the diffusion and coalescence of He atoms inside W, which plays an important role in the growth of nanostructures fuzz.

  14. Wear Behavior of AZ31/Al2O3 Magnesium Matrix Surface Nanocomposite Fabricated via Friction Stir Processing

    Science.gov (United States)

    Azizieh, Mahdi; Larki, Arsham Norouzi; Tahmasebi, Mehdi; Bavi, Mehdi; Alizadeh, Ehsan; Kim, Hyoung Seop

    2018-03-01

    The aim of this study was to produce magnesium-based surface nanocomposites via friction stir processing and to investigate the effect of tool rotational speed on the microstructure, hardness and wear behavior. The surface of the nanocomposites was characterized using optical and scanning electron microscopes, as well as through microhardness and wear tests. The results indicated that with the increase in rotational speed, the grain size of the surface nanocomposites increased, but its hardness decreased despite the improved distribution of Al2O3 nanoparticles. It was also found that the wear resistance has a direct relation to the distribution of the Al2O3 nanoparticles. Furthermore, the addition of nano-Al2O3 changed the wear mechanism from the adhesive mode in the as-received AZ31 to the abrasive mode in the nanocomposite specimens. The rotational speed of 1400 rpm was an optimum parameter to achieve a suitable composite layer with the highest wear resistance.

  15. Effects of electronic correlation, physical structure, and surface termination on the electronic structure of V2O3 nanowires

    Science.gov (United States)

    Tiano, Amanda L.; Li, Jing-bin; Sutter, Eli; Wong, Stanislaus S.; Fernández-Serra, M.-V.

    2012-09-01

    We report on a density functional theory (DFT) study of the electronic structure of vanadium sesquioxide (V2O3) in both bulk and nanowire form. In particular, our study focuses on the role of spin polarization and electronic correlations, as computed within the local (spin) density approximation (L(S)DA) and the LDA+U formalism. As expected for a mean-field approach such as DFT, our optimized bulk V2O3 structure is shown to be metallic in nature, while an adequate choice of the Hubbard U parameter (U = 4 eV) is enough to open the band gap, making the system insulating. However, this formalism predicts a nonmagnetic insulator, as opposed to the experimentally observed antiferromagnetic structure, to be the ground state. The electronic structure of the V2O3 nanowire system is more complex, and it strongly depends on the surface termination of the structures. Our results show that non-spin-polarized LDA calculations of 001-grown nanowires are metallic in nature. However, LSDA predicts that some surface terminations are half-metals, with a large band gap opening for one of the spins. When LSDA+U was used to study the nanowire model with a closed-shell oxygen surface termination, we observe insulating behavior with no net magnetic moment, with a 104 meV band gap. This is consistent with the experimentally observed gap recently reported in the literature for similar wires. To experimentally address the surface structure of these nanowires, we perform surface specific nano-Auger electron spectroscopy on as-synthesized V2O3 nanowires. Our experimental results show a higher O:V peak ratio (1.93:1) than expected for pure V2O3, thereby suggesting higher oxygen content at the surface of the nanowires. From our results, we conclude that oxygen termination is likely the termination for our as-synthesized V2O3 nanowires.

  16. OZONE PRODUCTION EFFICIENCY AND NOX DEPLETION IN AN URBAN PLUME: INTERPRETATION OF FIELD OBSERVATIONS AND IMPLICATIONS FOR EVALUATING O3-NOX-VOC SENSITIVITY

    Science.gov (United States)

    Ozone production efficiency (OPE) can be defined as the number of ozone (O3) molecules photochemically produced by a molecule of NOx (NO + NO2) before it is lost from the NOx - O3 cycle. Here, we consider observational and modeling techniques to evaluate various operational defi...

  17. Influence of SiO2/Al2O3 Molar Ratio on Phase Composition and Surfaces Quality of Aluminum Silicate Sanitary Glazes in the SiO2-Al2O3-CaO-Na2O System

    Directory of Open Access Journals (Sweden)

    Leśniak M.

    2016-12-01

    Full Text Available This paper presents the results of research on aluminum silicate sanitary glazes in the SiO2-Al2O3-CaO-Na2O system with different SiO2/Al2O3 molar ratio. XRD, SEM-EDS and FITR measurement indicated that SiO2/Al2O3 molar ratio has a significant impact on the phase composition of the obtained glazes. Glass-ceramic glazes were obtained that consisted of both the glass phase and pseudowollastonite (Ca3[SiO3]3 or anorthite (Ca[Al2Si2O8] crystals. Subsequently, the influence of phase composition on surface quality (roughness was examined for the obtained samples. On the basis of the conducted examination of glaze surface roughness was observed that glazes of extreme SiO2/Al2O3 molar ratio are characterized with greatest surface roughness when compared to other glazes.

  18. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    Directory of Open Access Journals (Sweden)

    Wei Xun

    2017-07-01

    Full Text Available Based on first-principles calculations, the BaTiO3(BTO film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

  19. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    Science.gov (United States)

    Xun, Wei; Hao, Xiang; Pan, Tao; Zhong, Jia-Lin; Ma, Chun-Lan; Hou, Fang; Wu, Yin-Zhong

    2017-07-01

    Based on first-principles calculations, the BaTiO3(BTO) film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

  20. Properties of the c-Si/Al2O3 interface of ultrathin atomic layer deposited Al2O3 layers capped by SiNx for c-Si surface passivation

    Science.gov (United States)

    Schuldis, D.; Richter, A.; Benick, J.; Saint-Cast, P.; Hermle, M.; Glunz, S. W.

    2014-12-01

    This work presents a detailed study of c-Si/Al2O3 interfaces of ultrathin Al2O3 layers deposited with atomic layer deposition (ALD), and capped with SiNx layers deposited with plasma-enhanced chemical vapor deposition. A special focus was the characterization of the fixed charge density of these dielectric stacks and the interface defect density as a function of the Al2O3 layer thickness for different ALD Al2O3 deposition processes (plasma-assisted ALD and thermal ALD) and different thermal post-deposition treatments. Based on theoretical calculations with the extended Shockley-Read-Hall model for surface recombination, these interface properties were found to explain well the experimentally determined surface recombination. Thus, these interface properties provide fundamental insights into to the passivation mechanisms of these Al2O3/SiNx stacks, a stack system highly relevant, particularly for high efficiency silicon solar cells. Based on these findings, it was also possible to improve the surface passivation quality of stacks with thermal ALD Al2O3 by oxidizing the c-Si surface prior to the Al2O3 deposition.

  1. Selective hydrothermal synthesis of BiOBr microflowers and Bi2O3 shuttles with concave surfaces

    International Nuclear Information System (INIS)

    Xiao Peipei; Zhu Lingling; Zhu Yongchun; Qian Yitai

    2011-01-01

    Through controlling the amount of NaOH added, BiOBr and Bi 2 O 3 with different shapes were hydrothermally synthesized in the reaction system of Bi(NO 3 ) 3 -hexadecyl trimethyl ammonium bromide (CTAB)-NaOH. As 8 mmol of NaOH was added, BiOBr microflowers constructed of nanoflakes were synthesized. The thickness of these single-crystal nanoflakes was about 20 nm. In the similar condition, when the amount of NaOH added was 28 mmol, Bi 2 O 3 shuttles with concave surfaces were obtained. The length of these shuttles was 100 μm and the diameter at the middle of these shuttles was 50 μm. The photocatalytic activity of as-prepared BiOBr microflowers was evaluated by the degradation of methyl orange (MO) under visible-light irradiation (λ>420 nm), which was up to 96% within 90 min. - Graphical abstract: Through controlling the amount of NaOH added, BiOBr microflowers and Bi 2 O 3 shuttles with concave surfaces were hydrothermally synthesized in the reaction system of Bi(NO 3 ) 3 -hexadecyl trimethyl ammonium bromide (CTAB)-NaOH. Highlights: → BiOBr microflowers constructed of nanoflakes were synthesized hydrothermally. → Bi 2 O 3 shuttles with concave surfaces were also synthesized. → Their formation mechanisms were studied based on the experimental results. → The photocatalytic activity of BiOBr microflowers was evaluated under visible-light irradiation.

  2. [Responses of rice growth and development to elevated near-surface layer ozone (O3) concentration: a review].

    Science.gov (United States)

    Yang, Lian-xin; Wang, Yu-long; Shi, Guang-yao; Wang, Yun-xia; Zhu, Jian-guo

    2008-04-01

    Ozone (O3) is recognized as one of the most important air pollutants. At present, the worldwide average tropospheric O3 concentration has been increased from an estimated pre-industrial level of 38 nl L(-1) (25-45 nl L(-1), 8-h summer seasonal average) to approximately 50 nl L(-1) in 2000, and to 80 nl L(-1) by 2100 based on most pessimistic projections. Oryza sativa L. (rice) is the most important grain crop in the world, and thus, to correctly evaluate how the elevated near-surface layer O3 concentration will affect the growth and development of rice is of great significance. This paper reviewed the chamber (including closed and open top chamber)-based studies about the effects of atmospheric ozone enrichment on the rice visible injury symptoms, photosynthesis, water relationship, phenology, dry matter production and allocation, leaf membrane protective system, and grain yield and its components. Further research directions in this field were discussed.

  3. Cyclone-induced surface ozone and HDO depletion in the Arctic

    Science.gov (United States)

    Zhao, Xiaoyi; Weaver, Dan; Bognar, Kristof; Manney, Gloria; Millán, Luis; Yang, Xin; Eloranta, Edwin; Schneider, Matthias; Strong, Kimberly

    2017-12-01

    Ground-based, satellite, and reanalysis datasets were used to identify two similar cyclone-induced surface ozone depletion events at Eureka, Canada (80.1° N, 86.4° W), in March 2007 and April 2011. These two events were coincident with observations of hydrogen deuterium oxide (HDO) depletion, indicating that condensation and sublimation occurred during the transport of the ozone-depleted air masses. Ice clouds (vapour and crystals) and aerosols were detected by lidar and radar when the ozone- and HDO-depleted air masses arrived over Eureka. For the 2007 event, an ice cloud layer was coincident with an aloft ozone depletion layer at 870 m altitude on 2-3 March, indicating this ice cloud layer contained bromine-enriched blowing-snow particles. Over the following 3 days, a shallow surface ozone depletion event (ODE) was observed at Eureka after the precipitation of bromine-enriched particles onto the local snowpack. A chemistry-climate model (UKCA) and a chemical transport model (pTOMCAT) were used to simulate the surface ozone depletion events. Incorporating the latest surface snow salinity data obtained for the Weddell Sea into the models resulted in improved agreement between the modelled and measured BrO concentrations above Eureka. MERRA-2 global reanalysis data and the FLEXPART particle dispersion model were used to study the link between the ozone and HDO depletion. In general, the modelled ozone and BrO showed good agreement with the ground-based observations; however, the modelled BrO and ozone in the near-surface layer are quite sensitive to the snow salinity. HDO depletion observed during these two blowing-snow ODEs was found to be weaker than pure Rayleigh fractionation. This work provides evidence of a blowing-snow sublimation process, which is a key step in producing bromine-enriched sea-salt aerosol.

  4. O(3P) + C2H4 Potential Energy Surface: Study at the Multireference Level

    Czech Academy of Sciences Publication Activity Database

    West, A. C.; Kretchmer, J. S.; Sellner, B.; Park, K.; Hase, W. L.; Lischka, Hans; Windus, T. L.

    2009-01-01

    Roč. 113, č. 45 (2009), s. 12663-12674 ISSN 1089-5639 Institutional research plan: CEZ:AV0Z40550506 Keywords : hydrogen combustion * multireference methods * O(3P)+C2H4 reaction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.899, year: 2009

  5. Effect of surface oxygen vacancy sites on ethanol synthesis from acetic acid hydrogenation on a defective In2O3(110) surface.

    Science.gov (United States)

    Lyu, Huisheng; Liu, Jiatao; Chen, Yifei; Li, Guiming; Jiang, Haoxi; Zhang, Minhua

    2018-03-07

    Developing a new type of low-cost and high-efficiency non-noble metal catalyst is beneficial for industrially massive synthesis of alcohols from carboxylic acids which can be obtained from renewable biomass. In this work, the effect of active oxygen vacancies on ethanol synthesis from acetic acid hydrogenation over defective In 2 O 3 (110) surfaces has been studied using periodic density functional theory (DFT) calculations. The relative stabilities of six surface oxygen vacancies from O v1 to O v6 on the In 2 O 3 (110) surface were compared. D1 and D4 surfaces with respective O v1 and O v4 oxygen vacancies were chosen to map out the reaction paths from acetic acid to ethanol. A reaction cycle mechanism between the perfect and defective states of the In 2 O 3 surface was found to catalyze the formation of ethanol from acetic acid hydrogenation. By H 2 reduction the oxygen vacancies on the In 2 O 3 surface play key roles in promoting CH 3 COO* hydrogenation and C-O bond breaking in acetic acid hydrogenation. The acetic acid, in turn, benefits the creation of oxygen vacancies, while the C-O bond breaking of acetic acid refills the oxygen vacancy and, thereby, sustains the catalytic cycle. The In 2 O 3 based catalysts were shown to be advantageous over traditional noble metal catalysts in this paper by theoretical analysis.

  6. A Tropical Lake Breeze System : The Effect on Surface NO, NO2, O3, and CO2 Mixing Ratios

    Science.gov (United States)

    Lima Moura, M. A.; Eça D'Almeida Rocha, C. H.; Trebs, I.; Andreae, M. O.; Meixner, F. X.

    2003-04-01

    During the Cooperative LBA Airborne Regional Experiment 2001 (CLAIRE2001, July 2001), we investigated diel variations of nitric oxide (NO), nitrogen dioxide (NO_2), ozone (O_3) and carbon dioxide (CO_2) mixing ratios at Balbina Limnological Station (01^o55'994''S, 59^o28'071''W, Amazonia,Brazil). We applied sensitive and species-specific chemiluminescence (NO, NO_2, O_3) and NDIR (CO_2) analysers to record ambient mixing ratios on 1 min intervals. Simultaneously, we extensively monitored (micro-)meteorological qauntities (air temperature, relative humidity, wind speed and -direction, thermal stratification, rainfall intensity, soil temperatures and moisture, as well as radiation fluxes (global, net, short wave, NO_2 photolysis, and photosynthetic active)). Balbina Limnological Station is located just a few hundred meters south of a 2.360 km^2 hydroelectric power dam (Usina Hidrelétrica de Balbina) and about 100m north from the edge of a primary rainforest. Marked differences in surface albedo and heat storage capacity generate a local wind system, the lake breeze, which advects air from the dam (09:00 to 15:00 local) and from the rainforest (18:00 to 06:00 local), respectively. Generally, we observed marked diel variations of NO, NO_2, O_3, and CO_2 (high/low levels during night/day) and O_3 (low/high levels during night/day). Especially in the tropics, this behaviour is usually related to (a) accumulation of soil emissions (NO, CO_2), chemical reactions (NO, from NO_2-O_3 reaction) and surface destruction (O_3) in a shallow and strong nocturnal boundary layer inversion, and (b) to soil emission (NO), photochemical reactions (NO-NO_2-O_3), dry deposition/plant uptake (NO_2, O_3, and CO_2) and strong turbulent vertical mixing in the daytime mixed layer. However, under the specific conditions of the lake breeze soil emission and dry deposition/ plant uptake can be neglected during daytime. Consequently, the investigation of daytime mixing ratios can be confined to

  7. Relaxation and electronic structure of the V 2O 3(0001) surface: ab initio cluster model studies

    Science.gov (United States)

    Czekaj, I.; Hermann, K.; Witko, M.

    2003-02-01

    The electronic structure and geometric relaxation of the (0001) surface of rhombohedral vanadium sesquioxide, V 2O 3, is studied theoretically with large surface cluster models where ab initio density functional theory is used to characterize charging and bonding. Geometric relaxation in the topmost surface region, up to 5 layers, with its three different bulk terminations is determined by minimizing total energies of the clusters. This yields major relaxation effects depending on the termination. The oxygen layer termination OVV ' exhibits strong relaxation of sub-surface vanadium layers resulting in increased ionic charging at the surface (measured by corresponding atom charges). The metal layer termination VV 'O leads to inwards relaxation of the two topmost vanadium layers by over 40% resulting also in increased surface charging. Ionic charging at the surface is the smallest for the half metal layer V 'OV termination where only the topmost vanadium layer relaxes inwards by 30% in addition to some rearrangement of sub-surface vanadium. This termination is believed to be the most stable of the three relaxed bulk-type terminations based also on analogies with experiments for Cr 2O 3(0001). However, total density-of-states and atom-projected partial densities-of-states curves depend relatively little on surface termination to allow a clear discrimination which could assist an unambiguous experimental identification.

  8. Insight of DFT and ab initio atomistic thermodynamics on the surface stability and morphology of In2O3

    Science.gov (United States)

    Zhang, Minhua; Wang, Wenyi; Chen, Yifei

    2018-03-01

    In2O3 catalysts show remarkable activity and selectivity in methanol synthesis from CO2 hydrogenation. In order to get insight into the surface stability of this catalyst, density functional theory and ab initio atomistic thermodynamics method were used to investigate the surface free energies of various facets as a function of oxygen chemical potential, as well as the influences of temperature, pressure and gas compositions. The results show that the (111) facet presents lowest surface free energy under oxygen-rich condition, while the indium-terminated (100) facet is the most stable one under oxygen-lean condition. Moreover, we applied Wulff construction to determine the equilibrium shape of In2O3 with different oxygen chemical potentials. The equilibrium shape under oxygen-lean condition is cubic, which only expose (100) facet, while, the equilibrium shape under oxygen-rich condition is octahedron, which only expose (111) facet. Meanwhile, the results agree well with what is observed experimentally. It is further predicted that Wulff shape of In2O3 exists in a truncated octahedron morphology in which the (100) surface becomes predominant plane under CO2 hydrogenation reaction conditions.

  9. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    OpenAIRE

    Wei Xun; Xiang Hao; Tao Pan; Jia-Lin Zhong; Chun-Lan Ma; Fang Hou; Yin-Zhong Wu

    2017-01-01

    Based on first-principles calculations, the BaTiO3(BTO) film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investiga...

  10. Airborne lidar measurements of surface ozone depletion over Arctic sea ice

    Directory of Open Access Journals (Sweden)

    J. A. Seabrook

    2013-06-01

    Full Text Available A differential absorption lidar (DIAL for measurement of atmospheric ozone concentration was operated aboard the Polar 5 research aircraft in order to study the depletion of ozone over Arctic sea ice. The lidar measurements during a flight over the sea ice north of Barrow, Alaska, on 3 April 2011 found a surface boundary layer depletion of ozone over a range of 300 km. The photochemical destruction of surface level ozone was strongest at the most northern point of the flight, and steadily decreased towards land. All the observed ozone-depleted air throughout the flight occurred within 300 m of the sea ice surface. A back-trajectory analysis of the air measured throughout the flight indicated that the ozone-depleted air originated from over the ice. Air at the surface that was not depleted in ozone had originated from over land. An investigation into the altitude history of the ozone-depleted air suggests a strong inverse correlation between measured ozone concentration and the amount of time the air directly interacted with the sea ice.

  11. BaTiO3–P(VDF-HFP) nanocomposite dielectrics—Influence of surface modification and dispersion additives

    International Nuclear Information System (INIS)

    Ehrhardt, Claudia; Fettkenhauer, Christian; Glenneberg, Jens; Münchgesang, Wolfram; Pientschke, Christoph; Großmann, Thomas; Zenkner, Mandy; Wagner, Gerald; Leipner, Hartmut S.; Buchsteiner, Alexandra; Diestelhorst, Martin; Lemm, Sebastian; Beige, Horst; Ebbinghaus, Stefan G.

    2013-01-01

    Highlights: • Polymer composites were prepared using a sol–gel synthesized BaTiO 3 . • BaTiO 3 surface hydroxyle groups act as linkers for surfactant molecules. • The effect of chemical adjustment between surfactant and polymer host is studied. • A positive effect of an additional dispersant was found. • Dielectric properties of the resulting composite films are presented. -- Abstract: We report on BaTiO 3 –polymer composites as dielectrics for film capacitors. BaTiO 3 was synthesized by a sol–gel soft-chemistry method leading to spherical nanoparticles with a high degree of surface hydroxyl groups which turned out to be important for the bonding of surfactant molecules. As surfactants, n-octylphosphonic acid and 2,3,4,5,6-pentafluorobenzyl phosphonic acid were used to inhibit particle agglomeration and to improve the wetting behaviour with the polymer. The phosphonic acid-coated BaTiO 3 nanoparticles were dispersed in solutions of poly(vinylidefluoride-co-hexafluoropropylene). Composite films were prepared by the spin-coating technique. A systematic study was performed on the influence of varying oxide fractions, different surfactants and the effect of additional dispersion aids such as sodium dodecyl sulphate or BYK-W 9010 on the quality and dielectric properties of the films obtained. The chemical adjustment of the 2,3,4,5,6-pentaflourobenzyl phosphonic acid within the fluorinated organic host form a more uniform particle distribution and increase relative permittivity of the resulting composite material compared to the unflourinated surfactant. Additionally, an enhancement of the relative permittivity can be realized by adding of dispersants. These two components can increase the relative permittivity by factor 5 compared to the pure polymer material

  12. Surface modifications of crystal-ion-sliced LiNbO3 thin films by low energy ion irradiations

    Science.gov (United States)

    Bai, Xiaoyuan; Shuai, Yao; Gong, Chaoguan; Wu, Chuangui; Luo, Wenbo; Böttger, Roman; Zhou, Shengqiang; Zhang, Wanli

    2018-03-01

    Single crystalline 128°Y-cut LiNbO3 thin films with a thickness of 670 nm are fabricated onto Si substrates by means of crystal ion slicing (CIS) technique, adhesive wafer bonding using BCB as the medium layer to alleviate the large thermal coefficient mismatch between LiNbO3 and Si, and the X-ray diffraction pattern indicates the exfoliated thin films have good crystalline quality. The LiNbO3 thin films are modified by low energy Ar+ irradiation, and the surface roughness of the films is decreased from 8.7 nm to 3.4 nm. The sputtering of the Ar+ irradiation is studied by scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy, and the results show that an amorphous layer exists at the surface of the exfoliated film, which can be quickly removed by Ar+ irradiation. A two-stage etching mechanism by Ar+ irradiation is demonstrated, which not only establishes a new non-contact surface polishing method for the CIS-fabricated single crystalline thin films, but also is potentially useful to remove the residue damage layer produced during the CIS process.

  13. Evaluation of fitting functions for the representation of an O(3P)+H2 potential energy surface. I

    International Nuclear Information System (INIS)

    Wagner, A.F.; Schatz, G.C.; Bowman, J.M.

    1981-01-01

    The DIM surface of Whitlock, Muckerman, and Fisher for the O( 3 P)+H 2 system is used as a test case to evaluate the usefulness of a variety of fitting functions for the representation of potential energy surfaces. Fitting functions based on LEPS, BEBO, and rotated Morse oscillator (RMO) forms are examined. Fitting procedures are developed for combining information about a small portion of the surface and the fitting function to predict where on the surface more information must be obtained to improve the accuracy of the fit. Both unbiased procedures and procedures heavily biased toward the saddle point region of the surface are investigated. Collinear quasiclassical trajectory calculations of the reaction rate constant and one and three dimensional transition state theory rate constant calculations are performed and compared for selected fits and the exact DIM test surface. Fitting functions based on BEBO and RMO forms are found to give quite accurate results

  14. Electrical resistivity surface for FeO-Fe2O3-P2O5 glasses

    Science.gov (United States)

    Vaughan, J. G.; Kinser, D. L.

    1975-01-01

    The dc electrical properties and microstructure of x(FeO-Fe2O3)-(100-x)P2O5 glasses were investigated up to a maximum of x = 75 mol %. Results indicate that, in general, the minimum resistivity of the glass does not occur at equal Fe(2+) and Fe(3+) concentrations, although for the special case where x = 55 mol % the minimum does occur at Fe(2+)/Fe total = 0.5, as reported by other investigators. Evidence presented shows that the position of the minimum resistivity is a function of total iron content. The minimum shifts to glasses richer in Fe(2+) at higher total iron concentrations.

  15. Chromium depletion on the surface of nickel based alloys

    International Nuclear Information System (INIS)

    Dille, E.R.; McDonald, J.L.; Berry, P.

    1988-01-01

    Successful selection of corrosion resistant materials for flue gas desuflurization applications is tricky business at best. Most simulated, accelerated, concentrated corrosion tests try to rank materials to known corrosive condition. If you check the actual data, occasionally you find anomalies such as highly corrosion resistant materials performing below what was expected, while the rest of the group is performing normally. In the field the authors have observed similar results with few acceptable explanations. Recently the authors have found numerous cases of Ni/Cr/Mo alloys with a surface analysis below the ASTM specified range for the element chromium. These surface analysis have been done with a portable X-ray Fluorescent Instrument with the initial results confirmed by an independent laboratory

  16. Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates.

    Science.gov (United States)

    López, Gema; Ortega, Pablo R; Voz, Cristóbal; Martín, Isidro; Colina, Mónica; Morales, Anna B; Orpella, Albert; Alcubilla, Ramón

    2013-01-01

    The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300-1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (S eff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450-1000 nm.

  17. Nanocrystalline BaSnO3 as an Alternative Gas Sensor Material: Surface Reactivity and High Sensitivity to SO2

    Science.gov (United States)

    Marikutsa, Artem; Rumyantseva, Marina; Baranchikov, Alexander; Gaskov, Alexander

    2015-01-01

    Nanocrystalline perovskite-type BaSnO3 was obtained via microwave-assisted hydrothermal route followed by annealing at variable temperature. The samples composition and microstructure were characterized. Particle size of 18–23 nm was unaffected by heat treatment at 275–700 °C. Materials DC-conduction was measured at variable temperature and oxygen concentration. Barium stannate exhibited n-type semiconductor behavior at 150–450 °C with activation energy being dependent on the materials annealing temperature. Predominant ionosorbed oxygen species types were estimated. They were shown to change from molecular to atomic species on increasing temperature. Comparative test of sensor response to various inorganic target gases was performed using nanocrystalline SnO2-based sensors as reference ones. Despite one order of magnitude smaller surface area, BaSnO3 displayed higher sensitivity to SO2 in comparison with SnO2. DRIFT spectroscopy revealed distinct interaction routes of the oxides surfaces with SO2. Barium-promoted sulfate formation favoring target molecules oxidation was found responsible for the increased BaSnO3 sensitivity to ppm-range concentrations of SO2 in air. PMID:28793573

  18. Nanocrystalline BaSnO3 as an Alternative Gas Sensor Material: Surface Reactivity and High Sensitivity to SO2

    Directory of Open Access Journals (Sweden)

    Artem Marikutsa

    2015-09-01

    Full Text Available Nanocrystalline perovskite-type BaSnO3 was obtained via microwave-assisted hydrothermal route followed by annealing at variable temperature. The samples composition and microstructure were characterized. Particle size of 18–23 nm was unaffected by heat treatment at 275–700 °C. Materials DC-conduction was measured at variable temperature and oxygen concentration. Barium stannate exhibited n-type semiconductor behavior at 150–450 °C with activation energy being dependent on the materials annealing temperature. Predominant ionosorbed oxygen species types were estimated. They were shown to change from molecular to atomic species on increasing temperature. Comparative test of sensor response to various inorganic target gases was performed using nanocrystalline SnO2-based sensors as reference ones. Despite one order of magnitude smaller surface area, BaSnO3 displayed higher sensitivity to SO2 in comparison with SnO2. DRIFT spectroscopy revealed distinct interaction routes of the oxides surfaces with SO2. Barium-promoted sulfate formation favoring target molecules oxidation was found responsible for the increased BaSnO3 sensitivity to ppm-range concentrations of SO2 in air.

  19. Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface.

    Science.gov (United States)

    Muratsugu, Satoshi; Kityakarn, Sutasinee; Wang, Fei; Ishiguro, Nozomu; Kamachi, Takashi; Yoshizawa, Kazunari; Sekizawa, Oki; Uruga, Tomoya; Tada, Mizuki

    2015-10-14

    Decarbonylation-promoted Ru nanoparticle formation from Ru3(CO)12 on a basic K-doped Al2O3 surface was investigated by in situ FT-IR and in situ XAFS. Supported Ru3(CO)12 clusters on K-doped Al2O3 were converted stepwise to Ru nanoparticles, which catalyzed the selective hydrogenation of nitriles to the corresponding primary amines via initial decarbonylation, the nucleation of the Ru cluster core, and the growth of metallic Ru nanoparticles on the surface. As a result, small Ru nanoparticles, with an average diameter of less than 2 nm, were formed on the support and acted as efficient catalysts for nitrile hydrogenation at 343 K under hydrogen at atmospheric pressure. The structure and catalytic performance of Ru catalysts depended strongly on the type of oxide support, and the K-doped Al2O3 support acted as a good oxide for the selective nitrile hydrogenation without basic additives like ammonia. The activation of nitriles on the modelled Ru catalyst was also investigated by DFT calculations, and the adsorption structure of a nitrene-like intermediate, which was favourable for high primary amine selectivity, was the most stable structure on Ru compared with other intermediate structures.

  20. Surface dependent structural phase transition in SrTiO 3 observed with spin relaxation of 8Li

    Science.gov (United States)

    Smadella, M.; Salman, Z.; Chow, K. H.; Egilmez, M.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Kreitzman, S. R.; Levy, C. D. P.; MacFarlane, W. A.; Mansour, A. I.; Morris, G. D.; Parolin, T. J.; Pearson, M.; Saadaoui, H.; Song, Q.; Wang, D.

    2009-04-01

    We investigate the 105 K structural phase transition in SrTiO 3 using depth controlled measurements of the spin relaxation of 8Li. The measurements were performed in zero external magnetic field and rely on the local electric field gradient (EFG) at the crystalline implantation site of the 8Li ( I=2) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the EFG in some 8Li implantation sites, resulting in an observable loss of 8Li polarization. This loss of polarization begins at a temperature T*=150 K, indicating there is some loss of cubic symmetry well above the bulk transition. We find that the value of T* is unaffected by the range of implantation depths available (10-150 nm); however, the temperature dependence of the polarization depends on the surface preparation of the SrTiO 3 sample.

  1. The stability of the hydroxylated (0001) surface of alpha-Al2O3

    DEFF Research Database (Denmark)

    Lodziana, Zbigniew; Nørskov, Jens Kehlet; Stoltze, Per

    2003-01-01

    -alumina. The stability of the hydrated surface resolves the discrepancies between the morphology of the alpha-alumina (0001) surface observed under ultra-high vacuum, and at ambient conditions. A method for the calculation of the equilibrium surface stoichiometry is proposed. The proposed approach provides a valuable...... connection between theoretical calculations and experiments with metal oxides....

  2. Impact of regional climate change and future emission scenarios on surface O3 and PM2.5 over India

    Science.gov (United States)

    Pommier, Matthieu; Fagerli, Hilde; Gauss, Michael; Sharma, Sumit; Sinha, Vinay; Ghude, Sachin; Langren, Oskar; Nyiri, Agnes; Wind, Peter

    2017-04-01

    This work aims to study the changes in surface ozone (O3) and fine particulate matter (PM2.5) in a world of changing emissions and climate by focusing on India. Stakeholders in India are already aware about air quality issues but anthropogenic emissions are projected to largely increase for some of the pollutants in the short-term (2030) and medium-term (2050) futures in India, especially if no more policy efforts are made. Only the policies in place before 2014/15 have been taken into account while projecting the future emissions. Current policies have led to decrease in emission intensities, however may not be enough for control of absolute emissions in future. In this study, the regional EMEP/MSC-W chemical transport model is used forced by downscaled meteorological fields at a 50 km resolution following the RCP8.5 greenhouse gas concentration scenario. The reference scenario (for present-day) is evaluated with surface-based measurements. Given the relatively coarse resolution of the meteorological fields used for this comparison with urban observations, the agreement can be considered satisfactory as high correlations with O3 (r=0.9) and PM2.5 (r=0.5 and r=0.8 depending on the data set) are noticed. The bias in PM2.5 is limited (lower than 6%) but the model overestimates the O3 by 35%. Then, this work shows that in the 2050s, the variation in O3 linked to the climate change is mainly due to the change in O3 deposition velocity related to the change in the boundary layer height and, over a few areas, by changes in VOCs. At short term and medium-term, the PM2.5 is predicted to increase due to climate change, by up to 6.5% in the 2050s. This climatic variation is mainly explained by increases in dust, organic matter and secondary inorganic aerosols which are affected by the change in wind speed and precipitations. The large increase in anthropogenic emissions will modify the composition of PM2.5 over India as the secondary inorganic aerosols will be dominant. The

  3. Ultraviolet light depletes surface markers of Langerhans cells

    International Nuclear Information System (INIS)

    Aberer, W.; Schuler, G.; Stingl, G.; Hoenigsmann, H.; Wolff, K.

    1981-01-01

    This report defines the influence of ultraviolet light (UV) on Langerhans cells (LC). Human volunteers and hairless mice (Swiss ha/ha) were exposed to various single and/or cumulative doses of either UV-A, UV-B, or UV-A plus small amounts of UV-B (UV-A (+B)). 24 hr after the last irradiation, morphology of the entire epidermis was evaluated by both light and electron microscopy while LC, in addition, were tested for expression of specific histochemical (ATPase) and functional immunological markers (Ia antigens). In both men and mice, cumulative doses of either 80-120 J/cm2 UV-A (+B) or 1-2 X 100 J/cm2 UV-A resulted in a dramatic reduction of cells exhibiting ATPase and Ia-reactivity. In the UV-B spectrum, single doses of 60-80 mJ/cm2 produced a virtually complete elimination of LC membrane markers. By contrast, pemphigus antigens of keratinocytes were unaffected by these energy doses. Electron microscopy revealed cellular damage of some LC after UV-doses which produce a virtually complete abolition of LC membrane markers. At certain dose ranges (15-30 mJ/cm2 UV-B and 1 x 40 to 2 x 100 J/cm2 UV-A) LC were the only epidermal cells to display morphological damage at the ultrastructural level whereas higher doses affected all epidermal cells. The finding that LC surface markers and to a lesser extent the cells themselves are particularly susceptible to UV irradiation has important implications in view of previous findings that LC are potent stimulators of antigen-specific and allogeneic T cell activation. UV-induced alteration of LC plasma membrane integrity may represent a tool to manipulate adverse immune reactions involving the epidermis

  4. Modelling Cr depletion under a growing Cr2O3 layer on austenitic stainless steel: the influence of grain boundary diffusion

    DEFF Research Database (Denmark)

    Hansson, Anette Nørgaard; Hattel, Jesper Henri; Dahl, Kristian Vinter

    2009-01-01

    The oxidation behaviour of austenitic stainless steels in the temperature range 723–1173K is strongly influenced by the grain size of the oxidizing alloy. In this work the evolution of the concentration profiles of Cr, Ni and Fe in the substrate below a growing Cr2O3 layer is simulated...... according to a parabolic rate law as a consequence of rate limiting diffusion of Cr cations through the oxide layer; the retraction of the oxide/alloy interface associated with the removal of Cr atoms from the substrate is included in the calculations. Numerically, the movement of the oxide/alloy interface...... is formulated such that the initial mesh can be used throughout the calculation. The calculated concentration profiles of the alloying elements emphasize the importance of grain boundaries in supplying Cr from the alloy to the growing oxide layer. For temperatures of 823 and 923K the simulations predict...

  5. Impact of regional climate change and future emission scenarios on surface O3 and PM2.5 over India

    Science.gov (United States)

    Pommier, Matthieu; Fagerli, Hilde; Gauss, Michael; Simpson, David; Sharma, Sumit; Sinha, Vinay; Ghude, Sachin D.; Landgren, Oskar; Nyiri, Agnes; Wind, Peter

    2018-01-01

    Eleven of the world's 20 most polluted cities are located in India and poor air quality is already a major public health issue. However, anthropogenic emissions are predicted to increase substantially in the short-term (2030) and medium-term (2050) futures in India, especially if no further policy efforts are made. In this study, the EMEP/MSC-W chemical transport model has been used to predict changes in surface ozone (O3) and fine particulate matter (PM2.5) for India in a world of changing emissions and climate. The reference scenario (for present-day) is evaluated against surface-based measurements, mainly at urban stations. The evaluation has also been extended to other data sets which are publicly available on the web but without quality assurance. The evaluation shows high temporal correlation for O3 (r = 0.9) and high spatial correlation for PM2.5 (r = 0.5 and r = 0.8 depending on the data set) between the model results and observations. While the overall bias in PM2.5 is small (lower than 6 %), the model overestimates O3 by 35 %. The underestimation in NOx titration is probably the main reason for the O3 overestimation in the model. However, the level of agreement can be considered satisfactory in this case of a regional model being evaluated against mainly urban measurements, and given the inevitable uncertainties in much of the input data.For the 2050s, the model predicts that climate change will have distinct effects in India in terms of O3 pollution, with a region in the north characterized by a statistically significant increase by up to 4 % (2 ppb) and one in the south by a decrease up to -3 % (-1.4 ppb). This variation in O3 is assumed to be partly related to changes in O3 deposition velocity caused by changes in soil moisture and, over a few areas, partly also by changes in biogenic non-methane volatile organic compounds.Our calculations suggest that PM2.5 will increase by up to 6.5 % over the Indo-Gangetic Plain by the 2050s. The increase over India

  6. Impact of regional climate change and future emission scenarios on surface O3 and PM2.5 over India

    Directory of Open Access Journals (Sweden)

    M. Pommier

    2018-01-01

    Full Text Available Eleven of the world's 20 most polluted cities are located in India and poor air quality is already a major public health issue. However, anthropogenic emissions are predicted to increase substantially in the short-term (2030 and medium-term (2050 futures in India, especially if no further policy efforts are made. In this study, the EMEP/MSC-W chemical transport model has been used to predict changes in surface ozone (O3 and fine particulate matter (PM2.5 for India in a world of changing emissions and climate. The reference scenario (for present-day is evaluated against surface-based measurements, mainly at urban stations. The evaluation has also been extended to other data sets which are publicly available on the web but without quality assurance. The evaluation shows high temporal correlation for O3 (r =  0.9 and high spatial correlation for PM2.5 (r =  0.5 and r =  0.8 depending on the data set between the model results and observations. While the overall bias in PM2.5 is small (lower than 6 %, the model overestimates O3 by 35 %. The underestimation in NOx titration is probably the main reason for the O3 overestimation in the model. However, the level of agreement can be considered satisfactory in this case of a regional model being evaluated against mainly urban measurements, and given the inevitable uncertainties in much of the input data.For the 2050s, the model predicts that climate change will have distinct effects in India in terms of O3 pollution, with a region in the north characterized by a statistically significant increase by up to 4 % (2 ppb and one in the south by a decrease up to −3 % (−1.4 ppb. This variation in O3 is assumed to be partly related to changes in O3 deposition velocity caused by changes in soil moisture and, over a few areas, partly also by changes in biogenic non-methane volatile organic compounds.Our calculations suggest that PM2.5 will increase by up to 6.5 % over the Indo

  7. The effect of light soaking on crystalline silicon surface passivation by atomic layer deposited Al2O3

    Science.gov (United States)

    Liao, Baochen; Stangl, Rolf; Mueller, Thomas; Lin, Fen; Bhatia, Charanjit S.; Hoex, Bram

    2013-01-01

    The effect of light soaking of crystalline silicon wafer lifetime samples surface passivated by thermal atomic layer deposited (ALD) Al2O3 is investigated in this paper. Contrary to other passivation materials used in solar cell applications (i.e., SiO2, SiNx), using thermal ALD Al2O3, an increase in effective carrier lifetime after light soaking under standard testing conditions is observed for both p-type (˜45%) and n-type (˜60%) FZ c-Si lifetime samples. After light soaking and storing the samples in a dark and dry environment, the effective lifetime decreases again and practically returns to the value before light soaking. The rate of lifetime decrease after light soaking is significantly slower than the rate of lifetime increase by light soaking. To investigate the underlying mechanism, corona charge experiments are carried out on p-type c-Si samples before and after light soaking. The results indicate that the negative fixed charge density Qf present in the Al2O3 films increases due to the light soaking, which results in an improved field-effect passivation. Numerical calculations also confirm that the improved field-effect passivation is the main contributor for the increased effective lifetime after light soaking. To further understand the light soaking phenomenon, a kinetic model—a charge trapping/de-trapping model—is proposed to explain the time dependent behavior of the lifetime increase/decrease observed under/after light soaking. The trap model fits the experimental results very well. The observed light enhanced passivation for ALD Al2O3 passivated c-Si is of technological relevance, because solar cell devices operate under illumination, thus an increase in solar cell efficiency due to light soaking can be expected.

  8. Structure and electronic properties of the V 2O 3(0001) surface: ab initio density functional theory cluster studies

    Science.gov (United States)

    Czekaj, I.; Witko, M.; Hermann, K.

    2003-02-01

    Electronic properties of the V 2O 3(0001) surface are studied using ab initio density functional theory method. In addition, the nature of surface V-O bonding as well as the electronic states of the structurally different surface oxygen and vanadium sites are discussed and compared with bulk oxygen/vanadium centers. The (0001) surface of vanadium sesquioxide is modeled using clusters of different size where the three ideal bulk-terminated surfaces, denoted as VV 'O (terminated by a double layer of vanadium atoms), V 'OV (terminated by one layer of V atoms), and OVV ' (terminated by one layer of oxygen atoms), are considered. For these surface terminations electronic properties of various surface and bulk centers are discussed. The results confirm bonding in vanadium sesquioxide as a mixture of ionic and covalent characters. Further, charging of structurally non-equivalent surface vanadium and oxygen sites is found to increase with the corresponding coordination number. Large differences in charging between surface and bulk vanadium atoms are found. In addition, the strong interaction between neighboring vanadium ions are observed.

  9. Carrier-Density Control of the SrTiO3 (001) Surface 2D Electron Gas studied by ARPES.

    Science.gov (United States)

    Walker, Siobhan McKeown; Bruno, Flavio Yair; Wang, Zhiming; de la Torre, Alberto; Riccó, Sara; Tamai, Anna; Kim, Timur K; Hoesch, Moritz; Shi, Ming; Bahramy, Mohammad Saeed; King, Phil D C; Baumberger, Felix

    2015-07-08

    The origin of the 2D electron gas (2DEG)stabilized at the bare surface of SrTiO3 (001) is investigated. Using high-resolution angle-resolved photoemission and core-level spectroscopy, it is shown conclusively that this 2DEG arises from light-induced oxygen vacancies. The dominant mechanism driving vacancy formation is identified, allowing unprecedented control over the 2DEG carrier density. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Development of Al2O3 electrospun fibers prepared by conventional sintering method or plasma assisted surface calcination

    Science.gov (United States)

    Mudra, E.; Streckova, M.; Pavlinak, D.; Medvecka, V.; Kovacik, D.; Kovalcikova, A.; Zubko, P.; Girman, V.; Dankova, Z.; Koval, V.; Duzsa, J.

    2017-09-01

    In this paper, the electrospinning method was used for preparation of α-Al2O3 microfibers from PAN/Al(NO3)3 precursor solution. The precursor fibers were thermally treated by conventional method in furnace or low-temperature plasma induced surface sintering method in ambient air. The four different temperatures of PAN/Al(NO3)3 precursors were chosen for formation of α-Al2O3 phase by conventional sintering way according to the transition features observed in the TG/DSC analysis. In comparison, the low-temperature plasma treatment at atmospheric pressure was used as an alternative sintering method at the exposure times of 5, 10 and 30 min. FTIR analysis was used for evaluation of residual polymer after plasma induced calcination and for studying the mechanism of polymer degradation. The polycrystalline alumina fibers arranged with the nanoparticles was created continuously throughout the whole volume of the sample. On the other side the low temperature approach, high density of reactive species and high power density of plasma generated at atmospheric pressure by used plasma source allowed rapid removal of polymer in preference from the surface of fibers leading to the formation of composite ceramic/polymer fibers. This plasma induced sintering of PAN/Al(NO3)3 can have obvious importance in industrial applications where the ceramic character of surface with higher toughness of the fibers are required.

  11. Surface adhesion study of La2O3 thin film on Si and glass substrate for micro-flexography printing

    Science.gov (United States)

    Hassan, S.; Yusof, M. S.; Embong, Z.; Maksud, M. I.

    2017-01-01

    Adhesive property can be described as an interchangeably with some ink and substance which was applied to one surface of two separate items that bonded together. Lanthanum oxide (La2O3) has been used as a rare earth metal candidate as depositing agent or printing ink. This metal deposit was embedded on Silica (Si) wafer and glass substrate using Magnetron Sputtering technique. The choose of Lanthanum oxide as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La2O3 deposited on the surface of Si wafer and glass substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). This research will focus on 3 narrow scan regions which are C 1s, O 1s and La 3d. Further discussion of the spectrum evaluation will be discussed in detail. Here, it is proposed that from the adhesive and surface chemical properties of La is the best on glass substrate which suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal in a practice of micro-flexography printing.

  12. Surface conditions for the observation of metal-insulator transitions on Cr-doped V 2O 3

    Science.gov (United States)

    Toledano, David S.; Metcalf, Patricia; Henrich, Victor E.

    2000-03-01

    Chromium-doped vanadium sesquioxide, (V 1- xCr x) 2O 3, displays two metal-insulator transitions with temperature for 0.005< x<0.0179. The high-temperature (˜300 K) transition occurs in a temperature range that is of interest for catalysis; the physics of the transition is also of fundamental interest. However, so far that transition has been observed only on cleaved samples. Due to the difficulty in obtaining doped single crystals for cleaving, alternate preparation methods are required. (V 0.985Cr 0.015) 2O 3 (0001) was prepared both by scraping with a diamond file and by ion bombardment followed by annealing in oxygen; the resulting surfaces were examined by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) for evidence of the high-temperature metal-insulator transition. Although resistance measurements across the transition temperature showed that a transition had taken place in the bulk, no changes were observed in photoemission spectra of scraped samples; they appeared insulating both above and below the transition. Annealed samples, on the other hand, displayed a clear increase in the density of states at EF, as well as changes in core-level XPS consistent with a metallic surface, as the temperature was lowered through the transition. Sharp (1×1) low energy electron diffraction (LEED) patterns were obtained from annealed surfaces, and Auger spectra showed no evidence of chromium segregation following annealing.

  13. Theoretical investigation of the band alignment of graphene on a polar SrTi O3 (111) surface

    Science.gov (United States)

    Shin, Donghan; Demkov, Alexander A.

    2018-02-01

    Doping graphene layers presents a difficult practical and fundamental problem. We consider theoretically, the possibility of electrostatic doping of graphene by the intrinsic field of a polar substrate. By way of example, we perform density functional theory calculations for a graphene sheet placed on the (111)-oriented perovskite SrTi O3 surface. We find that the Fermi surface moves well below the Dirac point of graphene, resulting simultaneously in a fast conducting channel in graphene, and a slow (large-effective-mass) channel at the oxide surface. Additionally, electrostatic gating may open a way to explore peculiar states that, through the "no crossing," represent a hybrid carrier that exists simultaneously in both materials.

  14. Influence of deposition temperature of thermal ALD deposited Al2O3 films on silicon surface passivation

    Directory of Open Access Journals (Sweden)

    Neha Batra

    2015-06-01

    Full Text Available The effect of deposition temperature (Tdep and subsequent annealing time (tanl of atomic layer deposited aluminum oxide (Al2O3 films on silicon surface passivation (in terms of surface recombination velocity, SRV is investigated. The pristine samples (as-deposited show presence of positive fixed charges, QF. The interface defect density (Dit decreases with increase in Tdep which further decreases with tanl up to 100s. An effective surface passivation (SRV<8 cm/s is realized for Tdep ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized by high thermal budget process (tanl between 10 to 30 min.

  15. Effect of surface reactions on steel, Al2O3 and Si3N4counterparts on their tribological performance with polytetrafluoroethylene filled composites

    NARCIS (Netherlands)

    Shen, J.T.; Top, M.; Ivashenko, O.; Rudolf, P.; Pei, Yutao T.; De Hosson, J.Th.M.

    2015-01-01

    The influence of surface reactions on the tribo-performance of steel, Al2O3 and Si3N4 balls sliding against polytetrafluoroethylene/SiO2/epoxy composites was investigated. Al2O3 ball were found to exhibit the best tribo-performance, namely a low coefficient of friction and the lowest wear rates of

  16. Optimization of Cutting Parameters for Surface Roughness under MQL, using Al2O3 Nanolubricant, during Turning of Inconel 718

    Science.gov (United States)

    Ali, M. A. M.; Khalil, A. N. M.; Azmi, A. I.; Salleh, H. M.

    2017-08-01

    Inconel 718 is a nickel-based alloy commonly used due to its excellent mechanical properties at high temperatures and its elevated corrosion resistance. This material however is difficult to machine due to the high temperature generated during machining, which requires efficient lubrication system. Minimum quantity lubrication (MQL) technique is a more efficient and a more environmentally friendly alternative to conventional flooding lubrication technique. The efficiency and efficacy of this lubrication technique can be further enhanced by adding nano particles and surfactant into the base lubricant. There are currently limited number of studies on the application of minimum quantity lubrication (MQL) technique using nanolubricant with added surfactant in the machining of hard-to-machine materials such as Inconel 718. Consequently, this paper aims to optimize the cutting parameters for surface roughness under minimum quantity lubrication (MQL) condition using surfactant-added Al2O3 nanolubricant during the turning of Inconel 718. The effects of cutting speed, depth of cut and feed rate and their two-way interactions on surface roughness are investigated on the basis of the standard Taguchi’s L9 orthogonal array (OA) design of experiment and the results are assessed using analysis of variance (ANOVA) and signal to noise (S/N) ratio methods to determine the optimal cutting parameter settings as well as the level of significance of the cutting parameters. The optimal surface finish can be observed at the cutting speed of 70 m/min, depth of cut of 0.05 mm and feed rate of 0.05 mm/rev with feed rate being the most significant factor to affect surface finish. Through this study, the application of minimum quantity lubrication (MQL) technique using surfactant-added Al2O3 nanolubricant, has been shown to produce desirable surface finish quality on Inconel 718 with additional economic and ecological benefits.

  17. Reactivity of Surface Nitrates in H2-Assisted SCR of NOx Over Ag/Al2O3 Catalyst

    DEFF Research Database (Denmark)

    Sadokhina, N. A.; Doronkin, Dmitry E.; Baeva, G. N.

    2013-01-01

    The role of nitrate ad-species in H2-assisted SCR over Ag/Al2O3 was compared in NH3-SCR and n-C6H14-SCR processes. It was found that nitrates could be reduced by NH3 or n-C6H14 at similar rates with H2 co-feeding which indicates a common rate-limiting step. However, contributions of surface nitrate...... reduction to the overall NH3-SCR or n-C6H14-SCR are different as revealed by comparing the rates of nitrate reduction with the rates of steady-state processes. The rate of the steady-state n-C6H14-SCR is virtually identical to the rate of surface nitrate reduction suggesting a significant contribution...

  18. Influence of Al2O3 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing

    Directory of Open Access Journals (Sweden)

    L. Suvarna Raju

    2014-12-01

    Full Text Available The influence of three factors, such as volume percentage of reinforcement particles (i.e. Al2O3, tool tilt angle and concave angle of shoulder, on the mechanical properties of Cu–Al2O3 surface composites fabricated via friction stir processing was studied. Taguchi method was used to optimize these factors for maximizing the mechanical properties of surface composites. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. It was found that Al2O3 particles are uniformly dispersed in the stir zone. The tensile properties of the surface composites increased with the increase in the volume percentage of the Al2O3 reinforcement particles. This is due to the addition of the reinforcement particles which increases the temperature of recrystallization by pinning the grain boundaries of the copper matrix and blocking the movement of the dislocations. The observed mechanical properties are correlated with microstructure and fracture features.

  19. Influence of excess sodium ions on the specific surface area formation in a NiO-Al2O3 catalyst prepared by different methods

    Directory of Open Access Journals (Sweden)

    Lazić M.M.

    2008-01-01

    Full Text Available The influence of sodium ions on the specific surface area of a NiO-Al2O3 catalyst in dependence of nickel loading (5, 10, and 20 wt% Ni, temperature of heat treatment (400, 700 and 1100oC and the method of sample preparation was investigated. Low temperature nitrogen adsorption (LTNA, X-ray diffraction (XRD and scanning electron microscopy (SEM were applied for sample characterization. Dramatic differences in the specific surface area were registered between non-rinsed and rinsed Al2O3 and NiO-Al2O3 samples. The lagged sodium ions promote sintering of non-rinsed catalyst samples.

  20. Surface potentials of (001), (012), (113) hematite (α-Fe2O3) crystal faces in aqueous solution.

    Science.gov (United States)

    Chatman, Shawn; Zarzycki, Piotr; Rosso, Kevin M

    2013-09-07

    Hematite (α-Fe2O3) is an important candidate electrode for energy system technologies such as photoelectrochemical water splitting. Conversion efficiency issues with this material are presently being addressed through nanostructuring, doping, and surface modification. However, key electrochemical properties of hematite/electrolyte interfaces remain poorly understood at a fundamental level, in particular those of crystallographically well-defined hematite faces likely present as interfacial components at the grain scale. We report a combined measurement and theory study that isolates and evaluates the equilibrium surface potentials of three nearly defect-free single crystal faces of hematite, titrated from pH 3 to 11.25. We link measured surface potentials with atomic-scale surface topology, namely the ratio and distributions of surface protonation-deprotonation site types expected from the bulk structure. The data reveal face-specific points of zero potential (PZP) relatable to points of zero net charge (PZC) that lie within a small pH window (8.35-8.85). Over the entire pH range the surface potentials show strong non-Nernstian charging at pH extremes separated by a wide central plateau in agreement with surface complexation modeling predictions, but with important face-specific distinctions. We introduce a new surface complexation model based on fitting the entire data set that depends primarily only on the proton affinities of two site types and the two associated electrical double layer capacitances. The data and model show that magnitudes of surface potential biases at the pH extremes are on the order of 100 mV, similar to the activation energy for electron hopping mobility. An energy band diagram for hematite crystallites with specific face expression and pH effects is proposed that could provide a baseline for understanding water splitting performance enhancement effects from nanostructuring, and guide morphology targets and pH for systematic improvements in

  1. Selective generation of laser-induced periodic surface structures on Al2O3-ZrO2-Nb composites

    Science.gov (United States)

    Kunz, Clemens; Bartolomé, José F.; Gnecco, Enrico; Müller, Frank A.; Gräf, Stephan

    2018-03-01

    Laser-induced periodic surface structures (LIPSS) were selectively fabricated on the metal phase of Al2O3-nZrO2-Nb (78.3-1.7-20 vol.%) ceramic matrix composites. For this purpose, sample surfaces were irradiated with fs-laser pulses (τ = 300 fs, λ = 1025 nm) of different laser peak fluences ranging from 0.23 to 0.40 J/cm2. The structured surfaces were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and by measuring the water contact angle. Well-pronounced LIPSS with a period of Λ ≈ 750 nm and a height of h ≈ 263 nm were found solely on the metal phase of the composite when applying the highest fluence whereas no structural and chemical modifications were found on the surface of the ceramic matrix. This can be explained by the different light absorption behaviour of both phases, which results in different ablation thresholds. The water contact angle of composite surfaces was successfully reduced from 68.4° for untreated samples to 40.9° for structured samples. Selectively structured composites with adjustable wettability are of particular interest for biomedical and tribological applications.

  2. Degradation of Reactive Yellow X-RG by O3/Fenton system: response surface approach, reaction mechanism, and degradation pathway.

    Science.gov (United States)

    Shen, Yongjun; Xu, Qihui; Liang, Jun; Xu, Wei

    2016-11-01

    O 3 /Fenton for the treatment of effluent containing Reactive Yellow X-RG is investigated. The response surface methodology is applied to study the main and interactive effects of the parameters. With the initial dye concentration being controlled at 300 mg L -1 , the optimized conditions for wastewater treatment are 3.68, 29.19 and 18.49 mg min -1 for initial pH, mole ratio of [H 2 O 2 ]/[Fe 2+ ] and ozone dosage, respectively. The regression quadratic model well describing the degradation efficiency of O 3 /Fenton process is developed and validated by the analysis of variances, respectively. In addition, a possible pathway for Reactive Yellow X-RG degradation is proposed by detecting the temporal evolution of intermediates in the solution, with the use of some techniques including ultraviolet spectrophotometric method (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC/MS). Meanwhile, every reaction step is given to explain the degradation mechanisms.

  3. Investigating the influence of long-range transport on surface O3 in Nevada, USA, using observations from multiple measurement platforms.

    Science.gov (United States)

    Fine, Rebekka; Miller, Matthieu B; Yates, Emma L; Iraci, Laura T; Gustin, Mae Sexauer

    2015-10-15

    The current United States (US) National Ambient Air Quality Standard (NAAQS) for O3 (75 ppb) is expected to be revised to between 60 and 70 ppb. As the NAAQS becomes more stringent, characterizing the extent of O3 and precursors transported into the US is increasingly important. Given the high elevation, complex terrain, and location in the Intermountain West, the State of Nevada is ideally situated to intercept air transported into the US. Until recently, measurements of O3 and associated pollutants were limited to areas in and around the cities of Las Vegas and Reno. In 2011, the Nevada Rural Ozone Initiative began and through this project 13 surface monitoring sites were established. Also in 2011, the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) began making routine aircraft measurements of O3 and other greenhouse gases in Nevada. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O3 observed in Nevada. Our analyses indicate that stratosphere to troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influence surface observations. The complexity of sources identified here along with the fact that O3 frequently approaches the threshold being considered for a revised NAAQS indicate that interstate and international cooperation will be necessary to achieve compliance with a more stringent regulatory standard. Further, on a seasonal basis we found no significant difference between daily 1-h maximum O3 at surface sites, which ranged in elevation from 888 to 2307 m, and aircraft measurements of O3 O3 across rural Nevada and indicates that column measurements from Railroad Valley, NV are useful in understanding these processes. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Evolution of interface and surface structures of ZnO/Al2 O3 multilayers upon rapid thermal annealing

    Science.gov (United States)

    Liu, H. H.; Chen, Q. Y.; Chang, C. F.; Hsieh, W. C.; Wadekar, P. V.; Huang, H. C.; Liao, H. H.; Seo, H. W.; Chu, W. K.

    2015-03-01

    ZnO ∖Al2O3 multilayers were deposited on sapphires by atomic layer deposition at 85°C. This low substrate temperature ensures good interface smoothness useful for study of interfacial reaction or interdiffusion. Our study aimed at the effects of rapid thermal annealing at different annealing temperatures, times and PAr:PO2. XRR and XRD techniques were used to investigate the kinetics from which various terms of the activation energies could be determined. HR-TEM and electron diffraction were carried out to correlate the microstructures and interfacial alignments as a result of the reactions. AFM were used to assist SEM profiling of the surface morphological evolution in association with the TEM observations.

  5. Titanium Dioxide-Based 64∘ YX LiNbO3 Surface Acoustic Wave Hydrogen Gas Sensors

    Directory of Open Access Journals (Sweden)

    A. Z. Sadek

    2008-01-01

    Full Text Available Amorphous titanium dioxide (TiO2 and gold (Au doped TiO2-based surface acoustic wave (SAW sensors have been investigated as hydrogen gas detectors. The nanocrystal-doped TiO2 films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto 64∘ YX LiNbO3 SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and 310∘C. It was found that gold doping on TiO2 increased the device sensitivity and reduced the optimum operating temperature.

  6. Investigating the influence of long-range transport on surface O3 in Nevada, USA, using observations from multiple measurement platforms

    International Nuclear Information System (INIS)

    Fine, Rebekka; Miller, Matthieu B.; Yates, Emma L.; Iraci, Laura T.; Gustin, Mae Sexauer

    2015-01-01

    The current United States (US) National Ambient Air Quality Standard (NAAQS) for O 3 (75 ppb) is expected to be revised to between 60 and 70 ppb. As the NAAQS becomes more stringent, characterizing the extent of O 3 and precursors transported into the US is increasingly important. Given the high elevation, complex terrain, and location in the Intermountain West, the State of Nevada is ideally situated to intercept air transported into the US. Until recently, measurements of O 3 and associated pollutants were limited to areas in and around the cities of Las Vegas and Reno. In 2011, the Nevada Rural Ozone Initiative began and through this project 13 surface monitoring sites were established. Also in 2011, the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) began making routine aircraft measurements of O 3 and other greenhouse gases in Nevada. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O 3 observed in Nevada. Our analyses indicate that stratosphere to troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influence surface observations. The complexity of sources identified here along with the fact that O 3 frequently approaches the threshold being considered for a revised NAAQS indicate that interstate and international cooperation will be necessary to achieve compliance with a more stringent regulatory standard. Further, on a seasonal basis we found no significant difference between daily 1-h maximum O 3 at surface sites, which ranged in elevation from 888 to 2307 m, and aircraft measurements of O 3 < 2500 m which suggests that similar processes influence daytime O 3 across rural Nevada and indicates that column measurements from Railroad Valley, NV are useful in understanding these processes. - Highlights: • Measurements indicate Asian LRT, STT, and

  7. Depleting groundwater resources mitigating surface freshwater scarcity - a trend in the recent past

    Science.gov (United States)

    Wada, Y.; Van Beek, L. P.; Bierkens, M. F.

    2011-12-01

    During the past decades, human water use more than doubled, yet available surface freshwater resources are finite. As a result, water scarcity has become prevalent in many (semi-)arid regions of the world (e.g., India, Pakistan, North East China, the MENA region). In such regions, the demand often exceeds the available surface freshwater resources primarily due to heavy irrigation which requires large volumes of water in a certain time of the year, when groundwater is additionally used to supplement the deficiency. Excessive groundwater pumping, however, often leads to overexploitation, i.e. groundwater abstraction exceeding groundwater recharge. Here, we quantified globally the impact of depleting groundwater resources on mitigating surface freshwater scarcity and the trend between 1960 and 2000 at a spatial resolution of 0.5 degree. We downscaled available country statistics of groundwater abstraction to 0.5 degree, while we simulated groundwater recharge with the global hydrological model PCR-GLOBWB at the same spatial resolution considering not only natural groundwater recharge but also artificial recharge, i.e. return flow from irrigation. Water scarcity was estimated by confronting computed water demand for livestock, irrigation, industry and households with simulated surface freshwater availability (PCR-GLOBWB) at 0.5 degree. We thus performed a simulation run with/without groundwater pumping to assess the impact on alleviating surface freshwater scarcity. The results indicated that in many of (semi-)arid regions (e.g., North Wet India, North East Pakistan, North East China, West and Central USA, Central Mexico, North Iran, Central Saudi Arabia) large amounts of groundwater abstraction significantly mitigates the intensity of surface freshwater scarcity, while depleting the resources. Our estimate of global groundwater depletion reached close to 280 km3/yr. In most of the MENA region, the intensity of surface freshwater scarcity was eased by 30% up to 50% as

  8. Graphene assisted effective hole-extraction on In2O3:H/CH3NH3PbI3 interface: Studied by modulated surface spectroscopy

    Science.gov (United States)

    Vinoth Kumar, Sri Hari Bharath; Muydinov, Ruslan; Kol'tsova, Tat‘yana; Erfurt, Darja; Steigert, Alexander; Tolochko, Oleg; Szyszka, Bernd

    2018-01-01

    Charge separation in CH3NH3PbI3 (MAPbI3) films deposited on a hydrogen doped indium oxide (In2O3:H) photoelectrode was investigated by modulated surface photovoltage (SPV) spectroscopy in a fixed capacitor arrangement. It was found that In2O3:H reproducibly extracts photogenerated-holes from MAPbI3 films. The oxygen-plasma treatment of the In2O3:H surface is suggested to be a reason for this phenomenon. Introducing graphene interlayer increased charge separation nearly 6 times as compared to that on the In2O3:H/MAPbI3 interface. Furthermore, it is confirmed by SPV spectroscopy that the defects of the MAPbI3 interface are passivated by graphene.

  9. Na-surface segregation and oxygen depletion in particle bombardment of alkaline glasses

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, A.; Marletta, G.; Licciardello, A.; Puglisi, O.

    1988-05-01

    Alkaline glass samples were bombarded by 2 keV Ar ions and neutrals and the surface modification were followed by XPS. Two main effects have been detected after bombardement: (I) a lowering of the Na/Si atomic ratio with a steady state value of about 1/2 of the initial value, and (II) an oxygen depletion. Both effects are independent of the charge state of the projectiles. The sodium concentration profile has been studied by XPS tilting angle technique and it is concluded that bombardment-induced surface segregation occurs and that it is may be responsible for the observed sodium behaviour.

  10. Hydrogenation of furfural at the dynamic Cu surface of CuOCeO2/Al2O3 in vapor phase packed bed reactor

    Science.gov (United States)

    The hydrogenation of furfural to furfuryl alcohol over a CuOCeO2/'-Al2O3 catalyst in a flow reactor is reported. The catalyst was prepared by the wet impregnation of Cu onto a CeO2/'-Al2O3 precursor. The calcined catalyst was then treated with HNO3 to remove surface CuO resulting in a mixed CuCe oxi...

  11. Carbon 1s photoemission line analysis of C-based adsorbate on (111)In2O3 surface: The influence of reducing and oxidizing conditions

    Science.gov (United States)

    Brinzari, V.; Cho, B. K.; Korotcenkov, G.

    2016-12-01

    Synchrotron radiation photoemission study of C 1s line of (111) In2O3 surface was carried out under HV (high vacuum) doses of oxygen, carbon monoxide and water. Gas interaction with the surface was activated by heating of In2O3 monocrystalline film at temperatures of 160 or 250 °C. The study of complex structure of C 1 s line and evolution of its fine components allowed to establish their nature and to propose possible surface adsorbed species and reactions, including a direct chemisorption and dissociation of CO molecules. Reduction or oxidation of the surface determines whether the first (chemisorption) or the second (dissociation) process takes place. The latter is responsible for additional formation of ionosorbed oxygen. Both processes have not been previously reported for In2O3 and for conductive metal oxides.

  12. Correlated electric-field induced reversal of antiferromagnetic order and surface magnetization in magnetoelectric Cr2O3

    Science.gov (United States)

    Wang, Junlei; Singh, Uday; Binek, Christian

    The electric-field-induced Faraday effect in magnetoelectrics comprises a superimposition of linear electric field responses with temperature dependencies of the linear magnetoelectric susceptibility and the antiferromagnetic order parameter. The tunability of the relative strength between the two contributions leads to a table-top set-up allowing to measure voltage-controlled selection and temperature dependence of the antiferromagnetic order parameter. Simultaneous measurement of the polar Kerr effect and the electric-field-induced Faraday effect is utilized to investigate correlated formation and switching of the surface magnetization and bulk antiferromagnetic order in Cr2O3 The correlated reversal of surface or boundary magnetization in response to voltage-controlled reversal of the bulk antiferromagnetic order parameter is of key importance for applications in spintronic devices such as the magnetoelectric MRAM. The Faraday rotation per applied voltage is independent of the sample thickness making the method scalable and versatile for thin film investigations. Scalability, compactness, and simplicity of the data analysis combined with low photon flux requirements make the Faraday approach advantageous for the investigation of the otherwise difficult to access voltage-controlled switching of antiferromagnetic domain states in magnetoelectric thin films. Acknowledgment: This project was supported by SRC through CNFD, an SRC-NRI Center, by C-SPIN, part of STARnet, and by the NSF through MRSEC DMR-0820521.

  13. Characteristics of UV-MicroO3 Reactor and Its Application to Microcystins Degradation during Surface Water Treatment

    Directory of Open Access Journals (Sweden)

    Guangcan Zhu

    2015-01-01

    Full Text Available The UV-ozone (UV-O3 process is not widely applied in wastewater and potable water treatment partly for the relatively high cost since complicated UV radiation and ozone generating systems are utilized. The UV-microozone (UV-microO3, a new advanced process that can solve the abovementioned problems, was introduced in this study. The effects of air flux, air pressure, and air humidity on generation and concentration of O3 in UV-microO3 reactor were investigated. The utilization of this UV-microO3 reactor in microcystins (MCs degradation was also carried out. Experimental results indicated that the optimum air flux in the reactor equipped with 37 mm diameter quartz tube was determined to be 18∼25 L/h for efficient O3 generation. The air pressure and humidity in UV-microO3 reactor should be low enough in order to get optimum O3 output. Moreover, microcystin-RR, YR, and LR (MC-RR, MC-YR, and MC-LR could be degraded effectively by UV-microO3 process. The degradation of different MCs was characterized by first-order reaction kinetics. The pseudofirst-order kinetic constants for MC-RR, MC-YR, and MC-LR degradation were 0.0093, 0.0215, and 0.0286 min−1, respectively. Glucose had no influence on MC degradation through UV-microO3. The UV-microO3 process is hence recommended as a suitable advanced treatment method for dissolved MCs degradation.

  14. Effect of Surface Roughness and Structure Features on Tribological Properties of Electrodeposited Nanocrystalline Ni and Ni/Al2O3 Coatings

    Science.gov (United States)

    Góral, Anna; Lityńska-Dobrzyńska, Lidia; Kot, Marcin

    2017-05-01

    Metal matrix composite coatings obtained by electrodeposition are one of the ways of improving the surfaces of materials to enhance their durability and properties required in different applications. This paper presents an analysis of the surface topography, microstructure and properties (residual stresses, microhardness, wear resistance) of Ni/Al2O3 nanocomposite coatings electrodeposited on steel substrates from modified Watt's-type baths containing various concentrations of Al2O3 nanoparticles and a saccharin additive. The residual stresses measured in the Ni/Al2O3 coatings decreased with an increasing amount of the co-deposited ceramics. It was established that the addition of Al2O3 powder significantly improved the coatings' microhardness. The wear mechanism changed from adhesive-abrasive to abrasive with a rising amount of Al2O3 particles and coating microhardness. Nanocomposite coatings also exhibited a lower coefficient of friction than that of a pure Ni-electrodeposited coating. The friction was found to depend on the surface roughness, and the smoother surfaces gave lower friction coefficients.

  15. Determination of surface and interface magnetic properties for the multiferroic heterostructure Co/BaTiO3 using spleed and arpes.

    Science.gov (United States)

    Borek, St; Braun, J; Minár, J; Kutnyakhov, D; Elmers, H-J; Schönhense, G; Ebert, H

    2016-11-02

    Co/BaTiO3(0 0 1) is one of the most interesting multiferroic heterostructures as it combines different ferroic phases, setting this way the fundamentals for innovative technical applications. Various theoretical approaches have been applied to investigate the electronic and magnetic properties of Co/BaTiO3(0 0 1). Here we determine the magnetic properties of 3 ML Co/BaTiO3 by calculating spin-polarized electron diffraction as well as angle-resolved photoemission spectra, with both methods being well established as surface sensitive techniques. Furthermore, we discuss the impact of altering the BaTiO3 polarization on the spectra and ascribe the observed changes to characteristic details of the electronic structure.

  16. Interface Trap Density Reduction for Al2O3/GaN (0001) Interfaces by Oxidizing Surface Preparation prior to Atomic Layer Deposition.

    Science.gov (United States)

    Zhernokletov, Dmitry M; Negara, Muhammad A; Long, Rathnait D; Aloni, Shaul; Nordlund, Dennis; McIntyre, Paul C

    2015-06-17

    We correlate interfacial defect state densities with the chemical composition of the Al2O3/GaN interface in metal-oxide-semiconductor (MOS) structures using synchrotron photoelectron emission spectroscopy (PES), cathodoluminescence and high-temperature capacitance-voltage measurements. The influence of the wet chemical pretreatments involving (1) HCl+HF etching or (2) NH4OH(aq) exposure prior to atomic layer deposition (ALD) of Al2O3 were investigated on n-type GaN (0001) substrates. Prior to ALD, PES analysis of the NH4OH(aq) treated surface shows a greater Ga2O3 component compared to either HCl+HF treated or as-received surfaces. The lowest surface concentration of oxygen species is detected on the acid etched surface, whereas the NH4OH treated sample reveals the lowest carbon surface concentration. Both surface pretreatments improve electrical characteristics of MOS capacitors compared to untreated samples by reducing the Al2O3/GaN interface state density. The lowest interfacial trap density at energies in the upper band gap is detected for samples pretreated with NH4OH. These results are consistent with cathodoluminescence data indicating that the NH4OH treated samples show the strongest band edge emission compared to as-received and acid etched samples. PES results indicate that the combination of reduced carbon contamination while maintaining a Ga2O3 interfacial layer by NH4OH(aq) exposure prior to ALD results in fewer interface traps after Al2O3 deposition on the GaN substrate.

  17. Fabrication of Al2O3 Nano-Structure Functional Film on a Cellulose Insulation Polymer Surface and Its Space Charge Suppression Effect

    Directory of Open Access Journals (Sweden)

    Jian Hao

    2017-10-01

    Full Text Available Cellulose insulation polymer (paper/pressboard has been widely used in high voltage direct current (HVDC transformers. One of the most challenging issues in the insulation material used for HVDC equipment is the space charge accumulation. Effective ways to suppress the space charge injection/accumulation in insulation material is currently a popular research topic. In this study, an aluminium oxide functional film was deposited on a cellulose insulation pressboard surface using reactive radio frequency (RF magnetron sputtering. The sputtered thin film was characterized by the scanning electron microscopy/energy dispersive spectrometer (SEM/EDS, X-ray photoelectron spectroscopy (XPS, and X-ray diffraction (XRD. The influence of the deposited functional film on the dielectric properties and the space charge injection/accumulation behaviour was investigated. A preliminary exploration of the space charge suppression effect is discussed. SEM/EDS, XPS, and XRD results show that the nano-structured Al2O3 film with amorphous phase was successfully fabricated onto the fibre surface. The cellulose insulation pressboard surface sputtered by Al2O3 film has lower permittivity, conductivity, and dissipation factor values in the lower frequency (<103 Hz region. The oil-impregnated sputtered pressboard presents an apparent space-charge suppression effect. Compared with the pressboard sputtered with Al2O3 film for 90 min, the pressboard sputtered with Al2O3 film for 60 min had a better space charge suppression effect. Ultra-small Al2O3 particles (<10 nm grew on the surface of the larger nanoparticles. The nano-structured Al2O3 film sputtered on the fibre surface could act as a functional barrier layer for suppression of the charge injection and accumulation. This study offers a new perspective in favour of the application of insulation pressboard with a nano-structured function surface against space charge injection/accumulation in HVDC equipment.

  18. Modulation of resistive switching characteristics for individual BaTiO3 microfiber by surface oxygen vacancies

    Science.gov (United States)

    Miao, Zhilei; Chen, Lei; Zhou, Fang; Wang, Qiang

    2018-01-01

    Different from traditional thin-film BaTiO3 (BTO) RRAM device with planar structure, individual microfiber-shaped RRAM device, showing promising application potentials in the micro-sized non-volatile memory system, has not been investigated so far to demonstrate resistive switching behavior. In this work, individual sol-gel BTO microfiber has been formed using the draw-bench method, followed by annealing in different atmospheres of air and argon, respectively. The resistive switching characteristics of the individual BTO microfiber have been investigated by employing double-probe SEM measurement system, which shows great convenience to test local electrical properties by modulating the contact sites between the W probes and the BTO microfiber. For the sample annealed in air, the average resistive ON/OFF ratio is as high as 108, enhanced about four orders in comparison with the counterpart that annealed in Argon. For the sample annealed in argon ambience, the weakened resistive ON/OFF ratio can be attributed to the increased presence of oxygen vacancies in the surface of BTO fibers, and the underlying electrical conduction mechanisms are also discussed.

  19. Longitudinal-Type Leaky Surface Acoustic Wave on LiNbO3 with High-Velocity Thin Film

    Science.gov (United States)

    Matsukura, Fumiya; Uematsu, Masato; Hosaka, Keiko; Kakio, Shoji

    2013-07-01

    The loss reduction of a longitudinal-type leaky surface acoustic wave (LLSAW) by loading with a dielectric thin film with a higher velocity than the substrate is proposed. An aluminum nitride (AlN) thin film was adopted as a high-velocity thin film, and the propagation properties of an LLSAW on an X36°Y-LiNbO3 (LN) substrate were investigated. First, the elastic constants c11 and c44 of an amorphous AlN (a-AlN) thin film deposited by RF magnetron sputtering were determined from the measured phase velocities of two SAW modes with mutually perpendicular particle motion, and they were 78 and 96% of those of a single-crystal AlN thin film. Next, from the theoretical calculation for the LLSAW on X36°Y-LN using the determined constants, it was found that the LLSAW attenuation can be reduced to zero by loading with an a-AlN thin film. Then, the propagation properties of the LLSAW on X36°Y-LN were measured by using an interdigital transducer pair. It was found that the losses due to bulk wave radiation can be reduced by loading with an a-AlN thin film.

  20. Depletion of barium and radium-226 in Black Sea surface waters over the past thirty years

    International Nuclear Information System (INIS)

    Kenison Falkner, K.K.; Edmond, J.M.; O'Neill, D.J.; Todd, J.F.; Moore, W.S.

    1991-01-01

    The nearly landlocked waters of the Black Sea support a valuable fishery, but are also particularly vulnerable to anthropogenic disturbance. Here we use dissolved barium and radium-226 as tracers, to investigate the biogeochemical health of the sea. Both elements are brought to surface waters by vertical mixing of deeper, enriched waters, and by rivers; these inputs should ordinarily be balanced by outflow of surface waters at the Bosphorus, and by biologically mediated removal of 226 Ra-bearing barite. We show, however, that surface-water inventories have been substantially depleted over the past few decades: recent (1988-89) barium concentrations were 1.6 times lower than in 1958 and 1967. These observations suggest that steady-state cycling of these elements has been perturbed by increased primary productivity, presumably fuelled by nutrients from industry and agricultural runoff, and to a lesser extent by decreased fluvial sediment loads owing to extensive impoundment of rivers in the region. (author)

  1. Deposition and characterization of binary Al2O3/SiO2 coating layers on the surfaces of rutile TiO2 and the pigmentary properties

    International Nuclear Information System (INIS)

    Zhang Yunsheng; Yin Hengbo; Wang Aili; Ren Min; Gu Zhuomin; Liu Yumin; Shen Yutang; Yu Longbao; Jiang Tingshun

    2010-01-01

    Binary Al 2 O 3 /SiO 2 -coated rutile TiO 2 composites were prepared by a liquid-phase deposition method starting from Na 2 SiO 3 .9H 2 O and NaAlO 2 . The chemical structure and morphology of binary Al 2 O 3 /SiO 2 coating layers were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, TG-DSC, Zeta potential, powder X-ray diffraction, and transmission electron microscopy techniques. Binary Al 2 O 3 /SiO 2 coating layers both in amorphous phase were formed at TiO 2 surfaces. The silica coating layers were anchored at TiO 2 surfaces via Si-O-Ti bonds and the alumina coating layers were probably anchored at the SiO 2 -coated TiO 2 surfaces via Al-O-Si bonds. The formation of continuous and dense binary Al 2 O 3 /SiO 2 coating layers depended on the pH value of reaction solution and the alumina loading. The binary Al 2 O 3 /SiO 2 -coated TiO 2 composites had a high dispersibility in water. The whiteness and brightness of the binary Al 2 O 3 /SiO 2 -coated TiO 2 composites were higher than those of the naked rutile TiO 2 and the SiO 2 -coated TiO 2 samples. The relative light scattering index was found to depend on the composition of coating layers.

  2. Surface interaction between cubic phase NaNbO3 nanoflowers and Ru nanoparticles for enhancing visible-light driven photosensitized photocatalysis

    Science.gov (United States)

    Chen, Wei; Hu, Yin; Ba, Mingwei

    2018-03-01

    Ru nanoparticles supported on perovskite NaNbO3 with cubic crystal structure and nanoflower-like morphology was prepared by a convenient solvothermal method combined with photo-deposition technique. Crystal structure, chemical component and surface valence states determined by XRD, XPS, TEM and SEM demonstrated the metastable cubic phase of perovskite NaNbO3, and its modified surface by Ru species. Optical and electrochemical analysis, such as UV-vis DRS, OTCS and EIS, indicated the excellent photoelectrochemical properties and the efficient electron transfer of the composites. Compared with naked and Ru-doped NaNbO3, the composite photocatalyst exhibited outstanding performance for the degradation of RhB under visible light irradiation due to the dye self-photosensitization and the surface interaction between Ru metal nanoparticles and semiconductor. In-situ reduction of surface Ru oxide species in the photocatalytic process assisted the further improvement of the photocatalytic activity and stability. Investigation of the main active species during the photocatalysis confirmed the efficient transfer of the photo-generated electrons and the positive effect of oxygen defects in NaNbO3. Finally, possible mechanism of the present visible-light driven photocatalysis was proposed in detail. This work provided an alternative strategy to enhance the visible-light photocatalytic efficiency of the catalyst with wide band gap on the basis of the synergistic effect of dye self-photosensitization, interaction between NaNbO3 and its surface Ru nanoparticles, and the "self-doping" of oxygen defects in NaNbO3.

  3. A study of the effect of surface pretreatment on atomic layer deposited Al2O3 interface with GaN

    Science.gov (United States)

    Gao, Jianyi; Li, Wenwen; Mandal, Saptarshi; Chowdhury, Srabanti

    2017-08-01

    Al2O3 has been an attractive gate dielectric for GaN power devices owing to its large conduction band offset with GaN ( 2.13eV), relatively high dielectric constant ( 9.0) and high breakdown electric field ( 10 MV/cm). Due to exceptional control over film uniformity and deposition rate, atomic layer deposition (ALD) has been widely used for Al2O3 deposition. The major obstacle to ALD Al2O3 on GaN is its high interface-state density (Dit) caused by incomplete chemical bonds, native oxide layer and impurities at the Al2O3/GaN interface. Therefore, an appropriate surface pretreatment prior to deposition is essential for obtaining high-quality interface. In this study, we investigated the effect of TMA, H2O and Ar/N2 plasma pretreatment on Dit and border traps (Nbt). 5 cycles of TMA purge, 5 cycles of H2O purge and Ar/N2 plasma pretreatment were conducted on GaN prior to deposition of ALD Al2O3. Al2O3/GaN metaloxide-semiconductor capacitors (MOSCAPs) were fabricated for the characterization of Dit and Nbt using UV-assisted capacitance-voltage (C-V) technique. The results show that TMA and H2O pretreatment had trivial effects on interface engineering whereas Ar/N2 plasma pretreatment slightly reduced Dit and significantly reduced Nbt.

  4. Temperature Mapping of Air Film-Cooled Thermal Barrier Coated Surfaces Using Cr-Doped GdAlO3 Phosphor Thermography

    Science.gov (United States)

    Eldridge, Jeffrey I.; Shyam, Vikram; Wroblewski, Adam C.; Zhu, Dongming; Cuy, Michael D.; Wolfe, Douglas E.

    2016-01-01

    It has been recently shown that the high luminescence intensity from a Cr-doped GdAlO3 (Cr:GdAlO3) thermographic phosphor enables non-rastered full-field temperature mapping of thermal barrier coating (TBC) surfaces to temperatures above 1000C. In this presentation, temperature mapping by Cr:GdAlO3 based phosphor thermometry of air film-cooled TBC-coated surfaces is demonstrated for both scaled-up cooling hole geometries as well as for actual components in a burner rig test environment. The effects of thermal background radiation and flame chemiluminescence on the measurements are investigated, and advantages of this method over infrared thermography as well as the limitations of this method for studying air film cooling are discussed.

  5. Relationship Between Column-Density and Surface Mixing Ratio: Statistical Analysis of O3 and NO2 Data from the July 2011 Maryland DISCOVER-AQ Mission

    Science.gov (United States)

    Flynn, Clare; Pickering, Kenneth E.; Crawford, James H.; Lamsol, Lok; Krotkov, Nickolay; Herman, Jay; Weinheimer, Andrew; Chen, Gao; Liu, Xiong; Szykman, James; hide

    2014-01-01

    To investigate the ability of column (or partial column) information to represent surface air quality, results of linear regression analyses between surface mixing ratio data and column abundances for O3 and NO2 are presented for the July 2011 Maryland deployment of the DISCOVER-AQ mission. Data collected by the P-3B aircraft, ground-based Pandora spectrometers, Aura/OMI satellite instrument, and simulations for July 2011 from the CMAQ air quality model during this deployment provide a large and varied data set, allowing this problem to be approached from multiple perspectives. O3 columns typically exhibited a statistically significant and high degree of correlation with surface data (R(sup 2) > 0.64) in the P- 3B data set, a moderate degree of correlation (0.16 columns typically exhibited a low to moderate degree of correlation with surface data in each data set. The results of linear regression analyses for O3 exhibited smaller errors relative to the observations than NO2 regressions. These results suggest that O3 partial column observations from future satellite instruments with sufficient sensitivity to the lower troposphere can be meaningful for surface air quality analysis.

  6. Effects of surface chromium depletion on localized corrosion of alloy 825 as a high-level nuclear waste container material

    International Nuclear Information System (INIS)

    Dunn, D.S.; Sridhar, N.; Cragnolino, G.A.

    1995-01-01

    Effects of the chromium-depleted, mill-finished surface on the localized corrosion resistance of alloy 825 (UNS N08825) were investigated. Tests were conducted in solutions based on the ground water at Yucca mountain, Nevada, but with a higher concentration of chloride. Results indicated that breakdown (E p ) and repassivation (E rp ) potentials for mill-finished surfaces were more active than those for polished surfaces. Potentiodynamic polarization tests indicated pits could be initiated on the chromium-depleted surface at potentials of 220 mV SCE in a solution containing 1,000 ppm Cl - at 95 C. Potentiostatic tests identified a similar pit initiation potential for the mill-finished surface. However, under longterm potentiostatic tests, a higher potential of 300 mV SCE was needed to sustain stable pit growth beyond the chromium-depleted layer. An increase in surface roughness also was observed to decrease localized corrosion resistance of the material

  7. Effect of Al_2O_3 Nanoparticles Additives on the Density, Saturated Vapor Pressure, Surface Tension and Viscosity of Isopropyl Alcohol

    Science.gov (United States)

    Zhelezny, Vitaly; Geller, Vladimir; Semenyuk, Yury; Nikulin, Artem; Lukianov, Nikolai; Lozovsky, Taras; Shymchuk, Mykola

    2018-03-01

    This paper presents results of an experimental study of the density, saturated vapor pressure, surface tension and viscosity of Al_2O_3 nanoparticle colloidal solutions in isopropyl alcohol. Studies of the thermophysical properties of nanofluids were performed at various temperatures and concentrations of Al_2O_3 nanoparticles. The paper gives considerable attention to a turbidimetric analysis of the stability of nanofluid samples. Samples of nanofluids remained stable over the range of parameters of the experiments, ensuring the reliability of the thermophysical property data for the Al_2O_3 nanoparticle colloidal solutions in isopropyl alcohol. The studies show that the addition of Al_2O_3 nanoparticles leads to an increase of the density, saturated vapor pressure and viscosity, as well as a decrease for the surface tension of isopropyl alcohol. The information reported in this paper on the various thermophysical properties for the isopropyl alcohol/Al_2O_3 nanoparticle model system is useful for the development of thermodynamically consistent models for predicting properties of nanofluids and correct modeling of the heat exchange processes.

  8. Surface and interface engineering of anatase TiO2 anode for sodium-ion batteries through Al2O3 surface modification and wise electrolyte selection

    Science.gov (United States)

    Li, Tao; Gulzar, Umair; Bai, Xue; Monaco, Simone; Longoni, Gianluca; Prato, Mirko; Marras, Sergio; Dang, Zhiya; Capiglia, Claudio; Proietti Zaccaria, Remo

    2018-04-01

    In the present study, Al2O3 is utilized for the first time as coating agent on nanostructured anatase TiO2 in order to investigate its effect on sodium-ion batteries performance. Our results show that the Al2O3 coating, introduced by a facile two-step approach, provides beneficial effects to the TiO2-based anodes. However, the coated TiO2 still suffers of capacity fading upon cycling when using 1.0 M of NaClO4 in propylene carbonate (PC) as electrolyte. To address this issue, the influence of different electrolytes (NaClO4 salt in various solvents) is further studied. It is found that the modified TiO2 exhibits significant improvements in cycling performance using binary ethylene carbonate (EC) and PC solvent mixture without the need of the commonly used fluoroethylene carbonate (FEC) additive. Under the best configuration, our battery could deliver a high reversible capacity of 188.1 mAh g-1 at 0.1C after 50 cycles, good rate capability up to 5C, and remarkable long-term cycling stability at 1C rate for 650 cycles. This excellent performance can be ascribed to the synergistic effects of surface and interface engineering enabling the formation of a stable and highly ionic conductive interface layer in EC:PC based electrolyte which combines the native SEI film and an 'artificial' SEI layer of irreversibly formed Na-Al-O.

  9. Quantum and Classical Studies of the O(3P)+H2(v=0-3,j=0) > OH + H Reaction Using Benchmark Potential Surface

    National Research Council Canada - National Science Library

    Braunstein, M

    2003-01-01

    ...) studies of the excitation function for O((3)P) + H2(v=0-3,j=0) - OH + H from threshold to 30 kcal/mol collision energy using benchmark potential energy surfaces Rogers et al. J. Phys. Chem. A 104, 2308 (2000). For H(2)(v=0...

  10. Impact of O3or O3/H2O2treatment via a membrane contacting system on the composition and characteristics of the natural organic matter of surface waters.

    Science.gov (United States)

    Stylianou, Stylianos K; Katsoyiannis, Ioannis A; Ernst, Mathias; Zouboulis, Anastasios I

    2017-06-27

    The present study aims to evaluate changes in the structure-composition of natural organic matter (NOM) that occur after the application of bubbleless ozonation or peroxone treatment of surface waters. The oxidation experiments (using 0.5-2 mg O3/mg DOC, or 2:1 O 3 :H 2 O 2 molar ratio) were performed in a continuous mode, using a tubular ceramic membrane contactor. Fluorescence spectroscopy (emission-excitation matrix) and liquid chromatography-organic carbon detection (LC-OCD) were mainly used for the detailed DOC characterization. In brief, the application of single ozonation resulted to high reduction of humic-like peak fluorescence intensities (50-85%) and also to the formation of two new peaks in the region of protein-like components. The co-addition of H 2 O 2 did not present the anticipated increase in the reduction of fluorescence intensity; however, it resulted to the further oxidation of protein-like fluorophores. LC-OCD measurements confirmed the decrease of average molecular weight of NOM during ozone treatment, due to the gradual degradation of biopolymers (14-23%) and humic substances (11-17%) towards building blocks and low molecular weight (LMW) neutrals. Advanced oxidation process (AOP) treatment by the mixture O 3 /H 2 O 2 resulted in the simultaneous decrease of building blocks and LMW neutral concentrations. Conventional batch ozonation and AOP experiments were conducted using ozone-saturated solutions to investigate the effect of different contacting patterns. The results revealed that the different reaction pathways followed during bubbleless and conventional batch experiments may also influence the formation of NOM oxidation intermediates.

  11. Optimization of Pd-B/γ-Al2O3 catalyst preparation for palm oil hydrogenation by response surface methodology (RSM)

    OpenAIRE

    Alshaibani, A. M.; Yaakob, Z.; Alsobaai, A. M.; Sahri, M.

    2014-01-01

    Response surface methodology was used to design and evaluate the experimental variables for Pd-B/γ-Al2O3 catalyst preparation. The catalyst was prepared by impregnation and chemical reduction. Thirteen different samples of the catalyst were prepared at different KOH concentrations and annealed at various temperatures, before applying them in palm oil hydrogenation. Hydrogenation was performed on a 0.12% Pd-B/γ-Al2O3 catalyst at a temperature of 393 K, hydrogen pressure of 500 kPa and agitatio...

  12. Optimization of Pd-B/γ-Al2O3 catalyst preparation for palm oil hydrogenation by response surface methodology (RSM)

    OpenAIRE

    Alshaibani,A. M.; Yaakob,Z.; Alsobaai,A. M.; Sahri,M.

    2014-01-01

    Response surface methodology was used to design and evaluate the experimental variables for Pd-B/γ-Al2O3 catalyst preparation. The catalyst was prepared by impregnation and chemical reduction. Thirteen different samples of the catalyst were prepared at different KOH concentrations and annealed at various temperatures, before applying them in palm oil hydrogenation. Hydrogenation was performed on a 0.12% Pd-B/γ-Al2O3 catalyst at a temperature of 393 K, hydrogen pressure of 500 kPa an...

  13. THE APPLICATION OF STEREOLOGY METHOD FOR ESTIMATING THE NUMBER OF 3D BaTiO3 – CERAMIC GRAINS CONTACT SURFACES

    Directory of Open Access Journals (Sweden)

    Vojislav V Mitić

    2011-05-01

    Full Text Available Methods of stereological study are of great importance for structural research of electronic ceramic materials including BaTiO3-ceramic materials. The broad application of ceramics, based on barium-titanate, in advanced electronics nowadays demands a constant research of its structure, that through the correlation structureproperties, a fundamental in the basic materials properties prognosis triad (technology-structure-properties, leads to further prognosis and properties design of these ceramics. Microstructure properties of BaTiO3- ceramic material, expressed in grains' boundary contact, are of basic importance for electric properties of this material, particularly the capacity. In this paper, a significant step towards establishing control under capacitive properties of BaTiO3-ceramics is being done by estimating the number of grains contact surfaces. Defining an efficient stereology method for estimating the number of BaTiO3-ceramic grains contact surfaces, we have started from a mathematical model of mutual grains distribution in the prescribed volume of BaTiO3-ceramic sample. Since the real microstructure morphology of BaTiO3-ceramics is in some way disordered, spherical shaped grains, using computer-modelling methods, are approximated by polyhedra with a great number of small convex polygons. By dividing the volume of BaTiO3-ceramic sample with the definite number of parallel planes, according to a given pace, into the intersection plane a certain number of grains contact surfaces are identified. According to quantitative estimation of 2D stereological parameters the modelled 3D internal microstructure is obtained. Experiments were made by using the scanning electronic microscopy (SEM method with the ceramic samples prepared under pressing pressures up to 150 MPa and sintering temperature up to 1370°C while the obtained microphotographs were used as a base of confirming the validity of presented stereology method. This paper, by applying

  14. Near-Surface Structural Phase Transition of SrTiO3 Studied with Zero-Field β-Detected Nuclear Spin Relaxation and Resonance

    Science.gov (United States)

    Salman, Z.; Kiefl, R. F.; Chow, K. H.; Hossain, M. D.; Keeler, T. A.; Kreitzman, S. R.; Levy, C. D. P.; Miller, R. I.; Parolin, T. J.; Pearson, M. R.; Saadaoui, H.; Schultz, J. D.; Smadella, M.; Wang, D.; Macfarlane, W. A.

    2006-04-01

    We demonstrate that zero-field β-detected nuclear quadrupole resonance and spin relaxation of low energy Li8 can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO3 single crystal occurs at Tc˜150K, i.e., ˜45K higher than Tcbulk, and that the tetragonal domains formed below Tc are randomly oriented.

  15. The effects of the size of Al2O3 particles in nanolubricant with added SDBS on surface roughness and tool wear during turning of mild steel

    Science.gov (United States)

    Ali, M. A. M.; Khalil, A. N. M.; Azmi, A. I.; Salleh, H. M.

    2017-09-01

    The technology of using Al2O3 nanoparticles in machining seems to solve major machining problems related to friction and heat generation. This achievement is strongly related to the size of particles itself. The purpose of this study is to observe the effects of the size of Al2O3 particles dispersed in solcut base oil with added Sodium Dodecylbenzene Sulfonate (SDBS), during the turning operation of mild steel under Minimum Quantity Lubrication (MQL) condition. The two dependent variables of interest are surface roughness and tool wear. Two different Al2O3 particle sized (600nm and MQL system. The experimental results show that MQL nanolubricant (MQL nanolubricant (600nm) with SDBS.

  16. The dynamics of ultraviolet-induced oxygen vacancy at the surface of insulating SrTiO3(0 0 1)

    International Nuclear Information System (INIS)

    Suwanwong, S.; Eknapakul, T.; Rattanachai, Y.; Masingboon, C.; Rattanasuporn, S.; Phatthanakun, R.; Nakajima, H.; King, P.D.C.; Hodak, S.K.; Meevasana, W.

    2015-01-01

    Highlights: • The dynamics of UV-induced oxygen vacancy is studied from the change of surface resistance. • The formation of 2DEG at the insulating surface of SrTiO 3 is confirmed by ARPES. • The UV-induced change in resistance responds differently to oxygen/gas exposure. • The behavior of resistance recovery suggests an alternative method of low-pressure sensing. - Abstract: The effect of ultra-violet (UV) irradiation on the electronic structure and the surface resistance of an insulating SrTiO 3 (0 0 1) crystal is studied in this work. Upon UV irradiation, we show that the two-dimensional electron gas (2DEG) emerges at the insulating SrTiO 3 surface and there is a pronounced change in the surface resistance. By combining the observations of the change in valance band and the resistance change under different environments of gas pressure and gas species, we find that UV-induced oxygen vacancies at the surface plays a major role in the resistance change. The dynamic of the resistance change at different oxygen pressures also suggests an alternative method of low-pressure sensing.

  17. Investigation of fundamental and high order optical transitions in α-Fe2O3 thin films using surface barrier electroreflectance

    Science.gov (United States)

    Qayyum, H. A.; Al-Kuhaili, M. F.; Durrani, S. M. A.

    2017-10-01

    In this paper, we use surface barrier electroreflectance technique to probe the optical transitions in hematite (α-Fe2O3) thin film. An electric field was induced normal to the surface of α-Fe2O3 thin film in an Ag/α-Fe2O3/Ag based capacitor type structure and the corresponding electroreflectance analysis was performed. Based on the electroreflectance analysis, we observed the fundamental as well as two high order critical points associated with α-Fe2O3. Standard critical point model was used to find the exact energy locations and the broadening parameters associated with these critical points. The existence of the fundamental critical point was further confirmed by the spectrophotometric analysis. The quantitative analysis based on the electro-optic energy confirmed that the obtained electroreflectance spectrum was within the low field regime, and the obtained critical points above the fundamental transition were attributed to the high order transitions of electrons from the valence band to the deep in the conduction band.

  18. Modification of Ag nanoparticles on the surface of SrTiO3 particles and resultant influence on photoreduction of CO2

    Science.gov (United States)

    Shao, Kunjuan; Wang, Yanjie; Iqbal, Muzaffar; Lin, Lin; Wang, Kai; Zhang, Xuehua; He, Meng; He, Tao

    2018-03-01

    Modification of a wide-bandgap semiconductor with noble metals that can exhibit surface plasmon effect is an effective approach to make it responsive to the visible light. In this work, a series of cubic and all-edge-truncated SrTiO3 with and without thermal pretreatment in air are modified by Ag nanoparticles via photodeposition method. The crystal structure, morphology, loading amount of Ag nanoparticles, and optical properties of the obtained Ag-SrTiO3 nanomaterials are well characterized by powder X-ray diffraction, scanning microscope, transmission electron microscope, energy disperse X-ray spectroscopy, ICP-MS and UV-vis diffuse-reflection spectroscopy. The loading amount and size of the Ag nanoparticles can be controlled to some extent by tuning the photodeposition time via growth-dissolution mechanism. The Ag nanoparticles are inclined to deposit on different locations on the surface of cubic and truncated SrTiO3 with and without thermal pretreatment. The resultant SrTiO3 modified by Ag nanoparticles exhibits visible light activity for photocatalytic reduction of CO2, which is closely related to the oxygen vacancy induced by thermal pretreatment, size and amount of Ag nanoparticles. Accordingly, there is an optimized photodeposition time for the synthesis of the photocatalyst that exhibits the highest photocatalytic activity.

  19. Response of Antarctic sea surface temperature and sea ice to ozone depletion

    Science.gov (United States)

    Ferreira, D.; Gnanadesikan, A.; Kostov, Y.; Marshall, J.; Seviour, W.; Waugh, D.

    2017-12-01

    The influence of the Antarctic ozone hole extends all the way from the stratosphere through the troposphere down to the surface, with clear signatures on surface winds, and SST during summer. In this talk we discuss the impact of these changes on the ocean circulation and sea ice state. We are notably motivated by the observed cooling of the surface Southern Ocean and associated increase in Antarctic sea ice extent since the 1970s. These trends are not reproduced by CMIP5 climate models, and the underlying mechanism at work in nature and the models remain unexplained. Did the ozone hole contribute to the observed trends?Here, we review recent advances toward answering these issues using "abrupt ozone depletion" experiments. The ocean and sea ice response is rather complex, comprising two timescales: a fast ( 1-2y) cooling of the surface ocean and sea ice cover increase, followed by a slower warming trend, which, depending on models, flip the sign of the SST and sea ice responses on decadal timescale. Although the basic mechanism seems robust, comparison across climate models reveal large uncertainties in the timescales and amplitude of the response to the extent that even the sign of the ocean and sea ice response to ozone hole and recovery remains unconstrained. After briefly describing the dynamics and thermodynamics behind the two-timescale response, we will discuss the main sources of uncertainties in the modeled response, namely cloud effects and air-sea heat exchanges, surface wind stress response and ocean eddy transports. Finally, we will consider the implications of our results on the ability of coupled climate models to reproduce observed Southern Ocean changes.

  20. Study on influence of Surface roughness of Ni-Al2O3 nano composite coating and evaluation of wear characteristics

    Science.gov (United States)

    Raghavendra, C. R.; Basavarajappa, S.; Sogalad, Irappa

    2018-02-01

    Electrodeposition is one of the most technologically feasible and economically superior techniques for producing metallic coating. The advancement in the application of nano particles has grabbed the attention in all fields of engineering. In this present study an attempt has been made on the Ni-Al2O3nano particle composite coating on aluminium substrate by electrodeposition process. The aluminium surface requires a specific pre-treatment for better adherence of coating. In light of this a thin zinc layer is coated on the aluminium substrate by electroless process. In addition to this surface roughness is an important parameter for any coating method and material. In this work Ni-Al2O3 composite coating were successfully coated by varying the process parameters such as bath temperature, current density and particle loading. The experimentation was performed using central composite design based 20 trials of experiments. The effect of process parameters and surface roughness before and after coating is analyzed on wear rate and coating thickness. The results shown a better wear resistance of Ni-Al2O3 composite electrodeposited coating compared to Ni coating. The particle loading and interaction effect of current density with temperature has greater significant effect on wear rate. The surface roughness is significantly affected the wear behaviour and thickness of coating.

  1. Adsorption of small molecules at the cobalt-doped SrTiO3(001) surface: A first-principles investigation

    Science.gov (United States)

    Carlotto, Silvia; Natile, Marta Maria; Glisenti, Antonella; Vittadini, Andrea

    2015-03-01

    The cobalt-doped SrTiO3 (001) surface and its interaction with small molecules (CO, NO and O2) is investigated by DFT and DFT + U calculations. Structural, electronic, and chemical changes induced by the presence of the cobalt impurity are studied. Similar to what is found for the bulk SrTiO3, cobalt impurities promote the formation of oxygen vacancies and tend to cluster with them. The presence of impurities has a strong influence on adsorption and in particular it gives rise i) to an enhancement of the adsorption energies and ii) to an inversion of the π electron flux from a surface → molecule to a molecule → surface donation. Furthermore, the examined molecular probes have different affinities with surface defects/impurities: whereas the vacancy site is favored for O2and CO, NO is preferentially adsorbed at the Co impurity site. The obtained results provide the basis for further studies of the catalytic properties of Co-doped SrTiO3.

  2. Effective optimization of surface passivation on porous silicon carbide using atomic layer deposited Al2O3

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    2017-01-01

    Porous silicon carbide (B–N co-doped SiC) produced by anodic oxidation showed strong photoluminescence (PL) at around 520 nm excited by a 375 nm laser. The porous SiC samples were passivated by atomic layer deposited (ALD) aluminum oxide (Al2O3) films, resulting in a significant enhancement...... of the PL intensity (up to 689%). The effect of thickness, annealing temperature, annealing duration and precursor purge time on the PL intensity of ALD Al2O3 films was investigated. In order to investigate the penetration depth and passivation effect in porous SiC, the samples were characterized by X...... effective method to enhance the luminescence efficiency of porous SiC....

  3. Ab initio supercell calculations of the (0001) α-Cr2O3 surface with a partially or totally Al-substituted external layer

    International Nuclear Information System (INIS)

    Sun Jizhong; Stirner, Thomas

    2009-01-01

    Ab initio supercell calculations employing the periodic Hartree-Fock formalism are presented of the (0001) α-Cr 2 O 3 surface with a partially or totally Al-substituted external layer. In the simulations a fraction of the Cr atoms at the surface of the chromia slab are replaced by Al atoms, and the Al surface coverage is varied between zero (pure chromia) and 100% (Al-terminated chromia). The surface Al atoms are found to relax inwards considerably, with the magnitude of the relaxation decreasing with increasing Al surface coverage. The calculations also reveal that the surface energy of the slab decreases with increasing Al coverage. Finally, the electronic properties at the surface of the Al-substituted (0001) α-Cr 2 O 3 slabs are investigated. Here the calculations show that the substitution of Cr by Al gives rise to an increase in the covalency of the Al-O bonds compared to slabs of pure alumina. In contrast, the influence of the surface Al atoms on the electrostatic potential in the (0001) plane of metal ions is relatively small. These findings support the utilisation of α-chromia substrates for the templated growth of α-alumina, which is consistent with recent experiments.

  4. Heat generation of surface-modified magnetic γ-Fe2O3 nanoparticles in applied alternating magnetic field

    Science.gov (United States)

    Babič, Michal; Horák, Daniel; Molčan, Matúš; Timko, Milan

    2017-08-01

    In this report, we show preparation of colloidally stable poly(N,N-dimethylacrylamide-co-acrylic acid) (DMA)- and D-mannose (MAN)-coated maghemite nanoparticles and their ability to generate heat in an alternating magnetic field, which could make the particles applicable for hyperthermic therapy of cancer. The particles are obtained by coprecipitation reaction and characterized by transmission electron microscopy, dynamic light scattering, and AC calorimetric measurement of heat generated by the particles. While the dry particles were ca. 10 nm in diameter, their hydrodynamic size in water was within the range of 100 nm. Heating characteristics were measured in an LC circuit with a maximum field intensity of 6.8 kA · m-1 and frequency 190 kHz. The specific absorption rates of γ-Fe2O3, PDM@γ-Fe2O3, and MAN@γ-Fe2O3 nanoparticles were extrapolated to 10 kA · m-1, reaching about 15 W · g-1.

  5. Near-surface hydrogen depletion of diamond-like carbon films produced by direct ion deposition

    Science.gov (United States)

    Markwitz, Andreas; Gupta, Prasanth; Mohr, Berit; Hübner, René; Leveneur, Jerome; Zondervan, Albert; Becker, Hans-Werner

    2016-03-01

    Amorphous atomically flat diamond-like carbon (DLC) coatings were produced by direct ion deposition using a system based on a Penning ion source, butane precursor gas and post acceleration. Hydrogen depth profiles of the DLC coatings were measured with the 15N R-NRA method using the resonant nuclear reaction 1H(15N, αγ)12C (Eres = 6.385 MeV). The films produced at 3.0-10.5 kV acceleration voltage show two main effects. First, compared to average elemental composition of the film, the near-surface region is hydrogen depleted. The increase of the hydrogen concentration by 3% from the near-surface region towards the bulk is attributed to a growth model which favours the formation of sp2 hybridised carbon rich films in the film formation zone. Secondly, the depth at which the maximum hydrogen concentration is measured increases with acceleration voltage and is proportional to the penetration depth of protons produced by the ion source from the precursor gas. The observed effects are explained by a deposition process that takes into account the contributions of ion species, hydrogen effusion and preferential displacement of atoms during direct ion deposition.

  6. Near-surface hydrogen depletion of diamond-like carbon films produced by direct ion deposition

    Energy Technology Data Exchange (ETDEWEB)

    Markwitz, Andreas, E-mail: A.Markwitz@gns.cri.nz [GNS Science, Lower Hutt (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand); Gupta, Prasanth [GNS Science, Lower Hutt (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand); Mohr, Berit [GNS Science, Lower Hutt (New Zealand); Hübner, René [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (Germany); Leveneur, Jerome; Zondervan, Albert [GNS Science, Lower Hutt (New Zealand); Becker, Hans-Werner [RUBION, Ruhr-University Bochum (Germany)

    2016-03-15

    Amorphous atomically flat diamond-like carbon (DLC) coatings were produced by direct ion deposition using a system based on a Penning ion source, butane precursor gas and post acceleration. Hydrogen depth profiles of the DLC coatings were measured with the 15N R-NRA method using the resonant nuclear reaction {sup 1}H({sup 15}N, αγ){sup 12}C (E{sub res} = 6.385 MeV). The films produced at 3.0–10.5 kV acceleration voltage show two main effects. First, compared to average elemental composition of the film, the near-surface region is hydrogen depleted. The increase of the hydrogen concentration by 3% from the near-surface region towards the bulk is attributed to a growth model which favours the formation of sp{sup 2} hybridised carbon rich films in the film formation zone. Secondly, the depth at which the maximum hydrogen concentration is measured increases with acceleration voltage and is proportional to the penetration depth of protons produced by the ion source from the precursor gas. The observed effects are explained by a deposition process that takes into account the contributions of ion species, hydrogen effusion and preferential displacement of atoms during direct ion deposition.

  7. Oxygen tracer diffusion and surface exchange kinetics in Ba0.5Sr0.5Co0.8Fe0.2O3

    NARCIS (Netherlands)

    Berenov, A.; Atkinson, A.; Kilner, J.; Ananyev, M.; Eremin, V.; Porotnikova, N.; Farlenkov, A.; Kurumchin, E.; Bouwmeester, Henricus J.M.; Bucher, E.; Sitte, W.

    2014-01-01

    The oxygen tracer diffusion coefficient, Db⁎, and the oxygen tracer surface exchange coefficient, k, were measured in Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF5582) over the temperature range of 310–800 °C and the oxygen partial pressure range of 1.3 × 10−3–0.21 bar. Several measurement techniques were used:

  8. Optimization of Pd-B/γ-Al2O3 catalyst preparation for palm oil hydrogenation by response surface methodology (RSM

    Directory of Open Access Journals (Sweden)

    A. M. Alshaibani

    2014-03-01

    Full Text Available Response surface methodology was used to design and evaluate the experimental variables for Pd-B/γ-Al2O3 catalyst preparation. The catalyst was prepared by impregnation and chemical reduction. Thirteen different samples of the catalyst were prepared at different KOH concentrations and annealed at various temperatures, before applying them in palm oil hydrogenation. Hydrogenation was performed on a 0.12% Pd-B/γ-Al2O3 catalyst at a temperature of 393 K, hydrogen pressure of 500 kPa and agitation of 500 rpm for 1 h. The iodine value (IV and trans fatty acids (TFAs content responses were measured for each hydrogenated palm oil sample. The predicted models were verified for both responses and found to be statistically adequate. An optimization study was performed on the catalyst preparation variables for minimizing both IV and TFAs content. The Pd-B/γ-Al2O3 prepared under optimized conditions exhibited 47% higher conversion and 22% lower trans-isomerization selectivity than Escat 1241 commercial catalyst. The Pd-B/γ-Al2O3 catalyst preparation variables have a noticeable effect on palm oil hydrogenation conversion and trans-isomerization selectivity.

  9. Enhanced electron mobility at the two-dimensional metallic surface of BaSnO3 electric-double-layer transistor at low temperatures

    Science.gov (United States)

    Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

    2017-05-01

    Wide-bandgap oxides exhibiting high electron mobility hold promise for the development of useful electronic and optoelectronic devices as well as for basic research on two-dimensional electron transport phenomena. A perovskite-type tin oxide, BaSnO3, is currently one of such targets owing to distinctly high mobility at room temperature. The challenge to overcome towards the use of BaSnO3 thin films in applications is suppression of dislocation scattering, which is one of the dominant scattering origins for electron transport. Here, we show that the mobility of the BaSnO3 electric-double-layer transistor reaches 300 cm2 V-1 s-1 at 50 K. The improved mobility indicates that charged dislocation scattering is effectively screened by electrostatically doped high-density charge carriers. We also observed metallic conduction persisting down to 2 K, which is attributed to the transition to the degenerate semiconductor. The experimental verification of bulk-level mobility at the densely accumulated surface sheds more light on the importance of suppression of dislocation scattering by interface engineering in doped BaSnO3 thin films for transparent electrode applications.

  10. Reducing the V2O3(0001) surface through electron bombardment--a quantitative structure determination with I/V-LEED.

    Science.gov (United States)

    Feiten, Felix E; Kuhlenbeck, Helmut; Freund, Hans-Joachim

    2016-01-28

    The (0001) surface of vanadium sesquioxide, V2O3, is terminated by vanadyl groups under standard ultra high vacuum preparation conditions. Reduction with electrons results in a chemically highly active surface with a well-defined LEED pattern indicating a high degree of order. In this work we report the first quantitative structure determination of a reduced V2O3(0001) surface. We identify two distinct surface phases by STM, one well ordered and one less well ordered. I/V-LEED shows the ordered phase to be terminated by a single vanadium atom per surface unit cell on a quasi-hexagonal oxygen layer with three atoms per two-dimensional unit cell. Furthermore we compare the method of surface reduction via electron bombardment with the deposition of V onto a vanadyl terminated film. The latter procedure was previously proposed to result in a structure with three surface vanadium atoms in the 2D unit cell and we confirm this with simulated STM images.

  11. Surface characterization of poly(methylmethacrylate) based nanocomposite thin films containing Al2O3 and TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Lewis, S.; Haynes, V.; Wheeler-Jones, R.; Sly, J.; Perks, R.M.; Piccirillo, L.

    2010-01-01

    Poly(methylmethacrylate) (PMMA) based nanocomposite electron beam resists have been demonstrated by spin coating techniques. When TiO 2 and Al 2 O 3 nanoparticles were directly dispersed into the PMMA polymer matrix, the resulting nanocomposites produced poor quality films with surface roughnesses of 322 and 402 nm respectively. To improve the surface of the resists, the oxide nanoparticles were encapsulated in toluene and methanol. Using the zeta potential parameter, it was found that the stabilities of the toluene/oxide nanoparticle suspensions were 7.7 mV and 19.4 mV respectively, meaning that the suspension was not stable. However, when the TiO 2 and Al 2 O 3 nanoparticles were encapsulated in methanol the zeta potential parameter was 31.9 mV and 39.2 mV respectively. Therefore, the nanoparticle suspension was stable. This method improved the surface roughness of PMMA based nanocomposite thin films by a factor of 6.6 and 6.4, when TiO 2 and Al 2 O 3 were suspended in methanol before being dispersed into the PMMA polymer.

  12. Comparative analysis of the low-energy He + ions scattering on Al and Al 2O 3 surfaces

    Science.gov (United States)

    Fomin, V. M.; Misko, V. R.; Devreese, J. T.; Brongersma, H. H.

    1998-12-01

    Using the Anderson-Muda-Newns approach, the neutralization rate and the ion survival probability have been calculated for the large angle scattering of low-energy He + ions by Al and by Al 2O 3. The two-band model of the electronic energy spectra is applied for the case of alumina. The electron promotion has been shown to play an important role in the processes of the He + ions scattering by aluminum and alumina. The experimentally observed absence of the matrix effect is discussed on the basis of the obtained results.

  13. Comparative analysis of the low-energy He+ ions scattering on Al and Al2O3 surfaces

    International Nuclear Information System (INIS)

    Fomin, V.M.; Misko, V.R.; Devreese, J.T.; Brongersma, H.H.

    1998-01-01

    Using the Anderson-Muda-Newns approach, the neutralization rate and the ion survival probability have been calculated for the large angle scattering of low-energy He + ions by Al and by Al 2 O 3 . The two-band model of the electronic energy spectra is applied for the case of alumina. The electron promotion has been shown to play an important role in the processes of the He + ions scattering by aluminum and alumina. The experimentally observed absence of the matrix effect is discussed on the basis of the obtained results. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  14. Near-surface structural phase transition of SrTiO3 studied with zero-field beta-detected nuclear spin relaxation and resonance.

    Science.gov (United States)

    Salman, Z; Kiefl, R F; Chow, K H; Hossain, M D; Keeler, T A; Kreitzman, S R; Levy, C D P; Miller, R I; Parolin, T J; Pearson, M R; Saadaoui, H; Schultz, J D; Smadella, M; Wang, D; MacFarlane, W A

    2006-04-14

    We demonstrate that zero-field beta-detected nuclear quadrupole resonance and spin relaxation of low energy (8)Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO(3) single crystal occurs at T(c) approximately 150K, i.e., approximately 45K higher than T(c)bulk, and that the tetragonal domains formed below T(c) are randomly oriented.

  15. MILD CHOLESTEROL DEPLETION REDUCES AMYLOID-β PRODUCTION BY IMPAIRING APP TRAFFICKING TO THE CELL SURFACE

    Science.gov (United States)

    Guardia-Laguarta, Cristina; Coma, Mireia; Pera, Marta; Clarimón, Jordi; Sereno, Lidia; Agulló, José M.; Molina-Porcel, Laura; Gallardo, Eduard; Deng, Amy; Berezovska, Oksana; Hyman, Bradley T.; Blesa, Rafael; Gómez-Isla, Teresa; Lleó, Alberto

    2009-01-01

    It has been suggested that cellular cholesterol levels can modulate the metabolism of the amyloid precursor protein (APP) but the underlying mechanism remains controversial. In the current study, we investigate in detail the relationship between cholesterol reduction, APP processing and γ-secretase function in cell culture studies. We found that mild membrane cholesterol reduction led to a decrease in Aβ40 and Aβ42 in different cell types. We did not detect changes in APP intracellular domain or Notch intracellular domain generation. Western blot analyses showed a cholesterol-dependent decrease in the APP C-terminal fragments and cell surface APP. Finally, we applied a fluorescence resonance energy transfer (FRET)-based technique to study APP-Presenilin 1 (PS1) interactions and lipid rafts in intact cells. Our data indicate that cholesterol depletion reduces association of APP into lipid rafts and disrupts APP-PS1 interaction. Taken together, our results suggest that mild membrane cholesterol reduction impacts the cleavage of APP upstream of γ-secretase and appears to be mediated by changes in APP trafficking and partitioning into lipid rafts. PMID:19457132

  16. Investigation of 'surface donors' in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructures: Correlation of electrical, structural, and chemical properties

    Science.gov (United States)

    Ťapajna, M.; Stoklas, R.; Gregušová, D.; Gucmann, F.; Hušeková, K.; Haščík, Š.; Fröhlich, K.; Tóth, L.; Pécz, B.; Brunner, F.; Kuzmík, J.

    2017-12-01

    III-N surface polarization compensating charge referred here to as 'surface donors' (SD) was analyzed in Al2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) heterojunctions using scaled oxide films grown by metal-organic chemical vapor deposition at 600 °C. We systematically investigated impact of HCl pre-treatment prior to oxide deposition and post-deposition annealing (PDA) at 700 °C. SD density was reduced down to 1.9 × 1013 cm-2 by skipping HCl pre-treatment step as compared to 3.3 × 1013 cm-2 for structures with HCl pre-treatment followed by PDA. The nature and origin of SD was then analyzed based on the correlation between electrical, micro-structural, and chemical properties of the Al2O3/GaN interfaces with different SD density (NSD). From the comparison between distributions of interface traps of MOS heterojunction with different NSD, it is demonstrated that SD cannot be attributed to interface trapped charge. Instead, variation in the integrity of the GaOx interlayer confirmed by X-ray photoelectron spectroscopy is well correlated with NSD, indicating SD may be formed by border traps at the Al2O3/GaOx interface.

  17. Room-Temperature Atomic Layer Deposition of Al2 O3 : Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells.

    Science.gov (United States)

    Kot, Malgorzata; Das, Chittaranjan; Wang, Zhiping; Henkel, Karsten; Rouissi, Zied; Wojciechowski, Konrad; Snaith, Henry J; Schmeisser, Dieter

    2016-12-20

    In this work, solar cells with a freshly made CH 3 NH 3 PbI 3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al 2 O 3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al 2 O 3 -covered perovskite films showed enhanced ambient air stability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Magnetic and electrical transport properties of LaBaCo2O(5.5+δ) thin films on vicinal (001) SrTiO3 surfaces.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Collins, Gregory; Wang, Haibin; Bao, Shanyong; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Lin, Yuan; Whangbo, Myung-Hwan

    2013-01-23

    Highly epitaxial LaBaCo(2)O(5.5+δ) thin films were grown on the vicinal (001) SrTiO(3) substrates with miscut angles of 0.5°, 3.0°, and 5.0° to systemically study strain effect on its physical properties. The electronic transport properties and magnetic behaviors of these films are strongly dependent on the miscut angles. With increasing the miscut angle, the transport property of the film changes from semiconducting to semimetallic, which results most probably from the locally strained domains induced by the surface step terraces. In addition, a very large magnetoresistance (34% at 60 K) was achieved for the 0.5°-miscut film, which is ~30% larger than that for the film grown on the regular (001) SrTiO(3) substrates.

  19. Surface Properties and Photocatalytic Activity of KTaO3, CdS, MoS2 Semiconductors and Their Binary and Ternary Semiconductor Composites

    Directory of Open Access Journals (Sweden)

    Beata Bajorowicz

    2014-09-01

    Full Text Available Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD, UV-Vis diffuse reflectance spectroscopy (DRS, scanning electron microscopy (SEM, Brunauer–Emmett–Teller (BET specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  20. A facile peroxo-precursor synthesis method and structure evolution of large specific surface area mesoporous BaSnO3.

    Science.gov (United States)

    Huang, Chuande; Wang, Xiaodong; Shi, Quan; Liu, Xin; Zhang, Yan; Huang, Fei; Zhang, Tao

    2015-04-20

    In this paper, we propose a facile and efficient strategy for synthesizing mesoporous BaSnO3 with a surface area as large as 67 m(2)/g using a peroxo-precursor decomposition procedure. As far as we know, this is the largest surface area reported in literature for BaSnO3 materials and may have a potential to greatly promote the technological applications of this kind of functional material in the area of chemical sensors, NOx storage, and dye-sensitized solar cells. The structure evolution of the mesoporous BaSnO3 from the precursor was followed using a series of techniques. Infrared analysis indicates large amount of protons and peroxo ligands are contained in the peroxo-precursor. Although the crystal structure of the precursor appears cubic according to the analysis of X-ray diffraction data, Raman and Mössbauer spectroscopy results show that the Sn atom is offset from the center of [SnO6] octahedron. After calcination at different temperatures, the precursor gradually transforms into BaSnO3 by release of water and oxygen, and the distortion degree of [SnO6] octahedral decreases. However, a number of oxygen vacancies are generated in the calcined samples, which are further confirmed by the physical property measurement system, and they would lower the local symmetry to some content. The concentration of the oxygen vacancies reduces simultaneously as the calcination temperature increases, and their contributions to the total heat capacity of the sample are calculated based on theoretical analysis of heat capacity data in the temperature region below 10 K.

  1. Investigation of the influence of liquid water films on O3 and PAN deposition on plant leaf surfaces treated with organic / inorganic compounds

    Science.gov (United States)

    Sun, Shang; Moravek, Alexander; von der Heyden, Lisa; Held, Andreas; Kesselmeier, Jürgen; Sörgel, Matthias

    2016-04-01

    Liquid water films on environmental surfaces play an important role in various fields of interest (Burkhardt and Eiden, 1994). For example, the deposition of water soluble trace gases could be increased by surface moisture. Chameides and Stelson (1992) found out that the dissolution of trace gases in airborne particulate matter increases with rising water/solid ratio of the particles. Further, Flechard et al. (1999) concluded that deliquescent salt particles represent a potential sink for trace gases, depending on their chemical property. The formation of surface water films and its influence on the gas deposition was proposed by many previous studies (Fuentes and Gillespie, 1992, Burkhardt and Eiden, 1994, van Hove et al., 1989, Burkhardt et al., 1999, Flechard et al., 1999). In this study we investigate the influence of leaf surface water films on the deposition of O3 and PAN under controlled laboratory conditions. A twin cuvette system described in Sun et al. (2015) was used to control the environmental parameters such as light, temperature, trace gas mixing ratio and humidity. Furthermore, the leaf surface was treated with various organic and inorganic solutions to investigate the influence of deposited compounds on the electrical surface conductance of the leaves and the surface deposition of O3 and PAN at various relative humidities. The result shows that RHcrit, where the electrical surface conductance (G) increases exponentially, was 40 % during the light period and 50 % during the dark period. Furthermore, we observed that the formation of the leaf surface liquid film was depended on the deposited compounds on the leaf cuticles. For the O3 deposition on plants (Quercus ilex) a clear enhancement at rising environmental air humidity under light and dark condition was found. The increase during light conditions can be related partly to increasing stomatal conductance with higher RH. From the non-stomatal deposition measured in dark experiments, we could

  2. Electronic transitions and band offsets in C60:SubPc and C60:MgPc on MoO3 studied by modulated surface photovoltage spectroscopy

    International Nuclear Information System (INIS)

    Fengler, S.; Dittrich, Th.; Rusu, M.

    2015-01-01

    Electronic transitions at interfaces between MoO 3 layers and organic layers of C 60 , SubPc, MgPc, and nano-composite layers of SubPc:C 60 and MgPc:C 60 have been studied by modulated surface photovoltage (SPV) spectroscopy. For all systems, time dependent and modulated SPV signals pointed to dissociation of excitons at the MoO 3 /organic layer interfaces with a separation of holes towards MoO 3 . The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps (E HL ) of C 60 , SubPc, and MgPc and the effective E HL of SubPc:C 60 and MgPc:C 60 were measured. The offsets between the LUMO (ΔE L ) or HOMO (ΔE H ) bands were obtained with high precision and amounted to 0.33 or 0.73 eV for SubPc:C 60 , respectively, and to −0.33 or 0.67 eV for MgPc:C 60 , respectively. Exponential tails below E HL and most pronounced sub-bandgap transitions were characterized and ascribed to disorder and transitions from HOMO bands to unoccupied defect states

  3. Surface structures and compositions of Au-Rh bimetallic nanoclusters supported on thin-film Al2O3/NiAl(100) probed with CO.

    Science.gov (United States)

    Lee, Hsuan; Liao, Zhen-He; Hsu, Po-Wei; Hung, Ting-Chieh; Wu, Yu-Cheng; Lin, Yuwei; Wang, Jeng-Han; Luo, Meng-Fan

    2017-07-28

    The surface structures and compositions of Au-Rh bimetallic nanoclusters on an ordered thin film of Al 2 O 3 /NiAl(100) were investigated, primarily with infrared reflection absorption spectra and temperature-programmed desorption of CO as a probe molecule under ultrahigh-vacuum conditions and calculations based on density-functional theory. The bimetallic clusters were formed by sequential deposition of vapors of Au and Rh onto Al 2 O 3 /NiAl(100) at 300 K. Alloying in the clusters was active and proceeded toward a specific structure-a fcc phase, (100) orientation, and Rh core-Au shell structure, regardless of the order of metal deposition. For Au clusters incorporating deposited Rh, the Au atoms remained at the cluster surface through position exchange and became less coordinated; for deposition in reverse order, deposited Au simply decorated the surfaces of Rh clusters. Both adsorption energy and infrared absorption intensity were enhanced for CO on Au sites of the bimetallic clusters; both of them are associated with the bonding to Rh and also a decreased coordination number of CO-binding Au. These enhancements can thus serve as a fingerprint for alloying and atomic inter-diffusion in similar bimetallic systems.

  4. QCM and AFM Study of atomic scale polishing and roughening of surfaces exposed to nanoparticle suspensions of diamond, Al2O3 and SiO2.

    Science.gov (United States)

    Krim, Jacqueline; Acharya, Biplav; Chestnut, Melanie; Marek, Antonin; Shendarova, Olga; Smirnov, Alex

    The addition of nanoparticles to conventional automotive lubricants is known in many cases to result in increased energy efficiency, but the atomic scale mechanisms leading to the increased efficiency are yet to be established. To explore this issue, we studied surface uptake and nanotribological properties of nanoparticle suspensions of diamond, Al2O3 and SiO2 dispersed in water and/or oil (PAO6) in real time by means of an in situ Quartz Crystal Microbalance (QCM) technique, with a focus on the impact of the suspension on the surface roughness and texture of the QCM electrode and how the results compared to macroscopic reductions in friction and increased energy efficiency for the same materials' combinations. The frequency and dissipative properties (mechanical resistance) of QCM's with both gold and nickel surface electrodes were first studied for immersed samples upon addition of the nanoparticles. Nanodiamonds resulted in an increased mechanical resistance while the addition of Al2O3 and SiO2 nanoparticles resulted in a decreased resistance, indicating a reduced resistance of the fluid to the motion of the QCM. Atomic Force Microscope (AFM) measurements were then performed on the QCM electrodes after exposure to the suspensions, to explore potential polishing and/or roughening effects. The results are closely linked to the macroscopic friction and wear attributes. Work supported by NSF.

  5. Effect of Al2O3 nanolubrication with Sodium Dodecylbenzene Sulfonate (SDBS) on surface roughness and tool wear under MQL during turning of Ti-6AL-4T

    International Nuclear Information System (INIS)

    Ali, M A M; Khalil, A N M; Azmi, A I

    2016-01-01

    The application of coolant reduces the friction and heat generation, which affect the surface finish and tool life, during machining. Recently, nanolubricant opens a new ways of coolant strategy in machining operation. It is well known that suspended nanoparticles without surfactant in base oil tend to agglomerate after a period of time. This paper presents the effects of AEO 3 nanolubricant with surfactant, Sodium Dodecylbenzene Sulfonate (SDBS) on surface roughness and tool wear during turning of titanium alloy, Ti-6AL-4T. The comparison of different coolant strategies, dry cutting, flooding, minimum quantity lubricant (MQL), nanolubricant with and without surfactant are also presented. The results showed that Al 2 O 3 nanolubricant with surfactant, Sodium Dodecylbenzene Sulfonate (SDBS) under MQL exhibits low surface roughness and tool wear rate compared to others. This proved that the addition of surfactant not only improved nanolubricant stability but also machining performance. (paper)

  6. Effect of Al2O3 nanolubrication with Sodium Dodecylbenzene Sulfonate (SDBS) on surface roughness and tool wear under MQL during turning of Ti-6AL-4T.

    Science.gov (United States)

    Ali, M. A. M.; Khalil, A. N. M.; Azmi, A. I.

    2016-02-01

    The application of coolant reduces the friction and heat generation, which affect the surface finish and tool life, during machining. Recently, nanolubricant opens a new ways of coolant strategy in machining operation. It is well known that suspended nanoparticles without surfactant in base oil tend to agglomerate after a period of time. This paper presents the effects of AEO3 nanolubricant with surfactant, Sodium Dodecylbenzene Sulfonate (SDBS) on surface roughness and tool wear during turning of titanium alloy, Ti-6AL-4T. The comparison of different coolant strategies, dry cutting, flooding, minimum quantity lubricant (MQL), nanolubricant with and without surfactant are also presented. The results showed that Al2O3 nanolubricant with surfactant, Sodium Dodecylbenzene Sulfonate (SDBS) under MQL exhibits low surface roughness and tool wear rate compared to others. This proved that the addition of surfactant not only improved nanolubricant stability but also machining performance.

  7. Plasma treatment for influence of cold in different phases of formation of calcium phosphate on the surface of nanocomposite Al2O3/ZrO2

    International Nuclear Information System (INIS)

    Santos, K.H.; Ferreira, J.A.; Osiro, D.; Nascimento, L.I.S.; Pallone, E.M.J.A.; Alves Junior, C.

    2016-01-01

    Among the different techniques used in surface treatment of biomaterials, the plasma has been noted for its ability to promote changes in surface roughness of the treated material. The objective of this study was to evaluate the influence of treatment by plasma in the formation of calcium phosphate nanocomposite on the surface of Al2O3/ZrO2 (5% by vol.). For this, samples were formed, calcined, sintered, surface treated and coated biomimeticamente plasma for 14 days. The surface characterization was performed by confocal microscopy and spectroscopy, Fourier transform infrared (FTIR). After coating, the samples were characterized by FTIR and X-ray diffraction X-ray (XRD). It was observed that the treatments improved surface roughness. Furthermore, regardless of the surface treatment were observed only three phases of calcium phosphates: HA α -TCP and -β-TCP. It is worth noting that depending on the composition, there are variations in the amount of phosphates, as well as the percentages of the different phases. (author)

  8. Inhomogenities of the CDW vector at the (-201) surface of Quasi-1D blue bronze Rb0.3MoO3

    International Nuclear Information System (INIS)

    Brun, C; Machado-Charry, E; Ordejon, P; Canadell, E; Wang, Z Z

    2007-01-01

    Inhomogenities of the b* surface component of the CDW wave vector, probed by LT-UHV-STM, were observed at the (-201) surface of quasi-1D blue bronze Rb 0.3 MoO 3 cleaved in-situ. Whereas on the scale of tens of nanometers, the CDW wave vector might be constant, significant changes were observed on the scale of microns in STM measurement. On the basis of first-principles DFT calculations, it is found that these inhomogenities could be due to a change in the stoichiometry of surface alkali atoms taking place after the cleavage process. It is shown that differences in the stoichiometry of surface alkali atoms change the filling of the partially filled bands of the top most layer. Consequently, in equilibrium with the bulk layers, this results in a local surface potential that changes the surface nesting vector and hence the periodicity of the CDW modulation. The DFT predictions for the changes in surface nesting vector are consistent with the observed experimental inhomogenities probed by STM

  9. Effect of temperature on magnetic and impedance properties of Fe3BO6 of nanotubular structure with a bonded B2O3 surface layer

    Science.gov (United States)

    Kumari, Kalpana; Ram, S.; Kotnala, R. K.

    2018-03-01

    In this investigation, we explore a facile synthesis of Fe3BO6 in the form of small crystallites in the specific shape of nanotubes crystallized from a supercooled liquid Fe2O3-B2O3 precursor. This study includes high resolution transmission electron microscopy (HRTEM) images, magnetic, optical, and impedance properties of the sample. HRTEM images reveal small tubes of Fe3BO6 of 20 nm diameter. A well resolved hysteresis loop appears at 5 K in which the magnetization does not saturate even up to as high field as 50 kOe. It means that the Fe3BO6 nanotubes behave as highly antiferromagnetic in nature in which the surface spins do not align along the field so easily. The temperature dependent impedance describes an ionic Fe3BO6 conductor with a reasonably small activation energy Ea ˜ 0.33 eV. Impedance formalism in terms of a Cole-Cole plot shows a deviation from an ideal Debye-like behavior. We have also reported that electronic absorption spectra are over a spectral range 200-800 nm of wavelengths in order to find out how a bonded surface layer present on the Fe3BO6 crystallites tunes the 3d → 3d electronic transitions in Fe3+ ions.

  10. Development of a New Surface Acoustic Wave Based Gyroscope on a X-112°Y LiTaO3 Substrate

    Directory of Open Access Journals (Sweden)

    Shitang He

    2011-11-01

    Full Text Available A new micro gyroscope based on the surface acoustic wave (SAW gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg−1 s at angular rates of up to 1,000 deg s−1 and good linearity are observed.

  11. Surface spin glass and exchange bias effect in Sm0.5Ca0.5MnO3 manganites nano particles

    Directory of Open Access Journals (Sweden)

    S. K. Giri

    2011-09-01

    Full Text Available In this letter, we report that the charge/orbital order state of bulk antiferromagnetic Sm0.5Ca0.5MnO3 is suppressed and confirms the appearance of weak ferromagnetism below 65 K followed by a low temperature spin glass like transition at 41 K in its nano metric counterpart. Exchange anisotropy effect has been observed in the nano manganites and can be tuned by the strength of the cooling magnetic field (Hcool. The values of exchange fields (HE, coercivity (HC, remanence asymmetry (ME and magnetic coercivity (MC are found to strongly depend on cooling magnetic field and temperature. HE increases with increasing Hcool but for larger Hcool, HE tends to decrease due to the growth of ferromagnetic cluster size. Magnetic training effect has also been observed and it has been analyzed thoroughly using spin relaxation model. A proposed phenomenological core-shell type model is attributed to an exchange coupling between the spin-glass like shell (surrounding and antiferromagnetic core of Sm0.5Ca0.5MnO3 nano manganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructured manganites may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.

  12. Direct observation of the near-surface layer in Pb(Mg1/3Nb2/3)O3 using neutron diffraction

    International Nuclear Information System (INIS)

    Conlon, K.H.; Whan, T.; Fox, J.H.; Luo, H.; Viehland, D.; Li, J.F.; Stock, C.; Shirane, G.

    2004-01-01

    Spatially resolved neutron diffraction as a function of crystal depth in Pb(Mg 1/3 Nb 2/3 )O 3 reveals the presence of a distinct near-surface region where a strong distortion in the lattice exists. A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale ∼100 μm. This confirms a previous assertion, based on a comparison between high-energy x rays and neutrons, that such a near surface region exists in the relaxors. Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed

  13. Optical spectroscopy analysis of the near surface depletion layer in AlGaAs/GaAs heterostructures grown by MBE

    Science.gov (United States)

    Cortes-Mestizo, I. E.; Briones, E.; Yee-Rendón, C. M.; Zamora Peredo, L.; Espinosa-Vega, L. I.; Droopad, R.; Méndez-García, Victor H.

    2017-11-01

    In this work the effects of filling the surface energy states in AlGaAs/GaAs heterostructures on the depletion layer are reported. The depletion layer width was varied from 49 to 10 nm as determined by Raman spectroscopy, allowing to discern their effect on the generation of Franz-Keldysh oscillations observed by photoreflectance spectroscopy. It is found that the photoreflectance modulation process of built-in electric fields at surface is negligible when the surface-levels are filled. This work demonstrates the relationship between the surface-states density, the surface states capability of capture carriers and the layer sequence of the heterostructure. These parameters need to be considered in order to get an adequate analysis of the photoreflectance spectrum of heterostructures. It is shown that if a nearly full-filled condition in the available surface energy levels is established, the Franz-Keldysh oscillations produced by the modulation of the built-in electric field intensity disappears as a result of the reduction in the photogenerated carrier density in the photoreflectance measurement.

  14. Accurate ab initio potential energy surfaces for the 3A'' and 3A' electronic states of the O(3P)+HBr system.

    Science.gov (United States)

    de Oliveira-Filho, Antonio G S; Ornellas, Fernando R; Peterson, Kirk A

    2012-05-07

    In this work, we report the construction of potential energy surfaces for the (3)A('') and (3)A(') states of the system O((3)P) + HBr. These surfaces are based on extensive ab initio calculations employing the MRCI+Q/CBS+SO level of theory. The complete basis set energies were estimated from extrapolation of MRCI+Q/aug-cc-VnZ(-PP) (n = Q, 5) results and corrections due to spin-orbit effects obtained at the CASSCF/aug-cc-pVTZ(-PP) level of theory. These energies, calculated over a region of the configuration space relevant to the study of the reaction O((3)P) + HBr → OH + Br, were used to generate functions based on the many-body expansion. The three-body potentials were interpolated using the reproducing kernel Hilbert space method. The resulting surface for the (3)A('') electronic state contains van der Waals minima on the entrance and exit channels and a transition state 6.55 kcal/mol higher than the reactants. This barrier height was then scaled to reproduce the value of 5.01 kcal/mol, which was estimated from coupled cluster benchmark calculations performed to include high-order and core-valence correlation, as well as scalar relativistic effects. The (3)A(') surface was also scaled, based on the fact that in the collinear saddle point geometry these two electronic states are degenerate. The vibrationally adiabatic barrier heights are 3.44 kcal/mol for the (3)A('') and 4.16 kcal/mol for the (3)A(') state.

  15. Effects of surface chemistry on coagulation of submicron iron oxide particles (α-Fe_2O_3) in water

    OpenAIRE

    Liang, Liyuan

    1988-01-01

    Particles in the colloidal size range, i.e. smaller than 10^(-6) meter, are of interest in environmental science and many other fields of science and engineering. Since aqueous oxide particles have high specific surface areas they adsorb ions and molecules from water, and may remain stable in the aqueous phase with respect to coagulation. Submicron particles collide as a result of their thermal energy, and the effective collision rate is slowed by electric repulsion forces. A key to understan...

  16. High-resolution, high-linearity temperature sensor using surface acoustic wave device based on LiNbO3/SiO2/Si substrate

    Directory of Open Access Journals (Sweden)

    Xiang-Guang Tian

    2016-09-01

    Full Text Available A high-resolution and high-linearity surface acoustic wave (SAW temperature sensor, consisting of a SAW resonator device fabricated on novel X-cut LiNbO3/SiO2/Si piezoelectric substrate and a resonance frequency readout chip using standard 180 nm CMOS technology, is presented for the first time. High temperature performance substrate LiNbO3/SiO2/Si is prepared mainly by ion implantation and wafer bonding at first. RF SAW device with resonance frequency near 900 MHz is designed and fabricated on the substrate. Traditional probe method using network analyzer and the readout chip method are both implemented to characterize the fabricated SAW device. Further measurement of temperature using resonance frequency shift of SAW device demonstrates the feasibility of the combined system as a portable SAW temperature sensor. The obtained frequency-temperature relation of the fabricated device is almost linear. The frequency resolution of the readout chip is 733 Hz and the corresponding temperature accuracy is 0.016 ° C. Resolution of the sensor in this work is superior to most of the commercial temperature measurement sensors. Theory analysis and finite element simulation are also presented to prove the mechanism and validity of using SAW device for temperature detection applications. We conclude that the high-linearity frequency-temperature relation is achieved by the offset between high-order coefficients of LiNbO3 and SiO2 with opposite signs. This work offers the possibility of temperature measuring in ultra-high precision sensing and control applications.

  17. Surface viscoelasticity studies of Gd2O3, SiO2 optical thin films and multilayers using force modulation and force-distance scanning probe microscopy

    International Nuclear Information System (INIS)

    Sahoo, N.K.; Thakur, S.; Senthilkumar, M.; Das, N.C.

    2003-01-01

    The single and multilayer of Gd 2 O 3 and SiO 2 thin films deposited through reactive electron beam evaporation have been studied for their viscoelasticity properties and optical spectral stability using multimode scanning probe microscope and spectrophotometric techniques. A conspicuous changes in viscoelasticity properties and surface topographies have been observed with the Gd 2 O 3 films deposited under various oxygen pressures. The scanning probe measurements on the multilayer filters fabricated using these film materials for laser wavelengths of 248 nm (KrF) and 355 nm (Nd:Yag-III) have shown superior viscoelasticity property, which is not the case with the most conventional multilayers. The results were correlated with the long-term spectral stability that has been studied by recording transmittance spectra of these filters at a time interval of 10 months. Both the multilayer filters have shown excellent temporal spectral stabilities with a relatively better result for the 248 nm reflection filter. Further analysis has shown a very good co-relationship in the spectral stability and viscoelasticity properties in these multilayers

  18. Formation and properties of proton-exchanged and annealed $LiNbO_{3}$ waveguides for surface acoustic wave

    CERN Document Server

    Chien Chuan Cheng; Ying Chung Chen

    2001-01-01

    The proton-exchanged (PE) and annealed PE (APE) z-cut LiNbO/sub 3/ waveguides were fabricated using H/sub 4/P/sub 2/O/sub 7/. The positive strain, c-axis lattice constant change ( Delta c/c), was calculated to be about +0.43%, which was almost independent of the exchanged conditions. The penetration depth of H measured by secondary ion mass spectrometry (SIMS) exhibited a step-like profile, which was assumed to be equal to the waveguide depth (d). The surface acoustic wave (SAW) properties of PE and APE z-cut LiNbO/sub 3/ samples were investigated. The phase velocity (V/sub p/) and electromechanical coupling coefficient (K/sup 2/) of PE samples were significantly decreased by the increase of kd, where k was the wavenumber (2 pi / lambda ). The insertion loss (IL) of PE samples was increased by the increase of kd and became nearly constant at kd >0.064. The temperature coefficient of frequency (TCF) of PE samples allowed an apparent increase with kd, reaching a maximum at kd=0.292, then slightly decreased at h...

  19. O3 Nanoparticles

    KAUST Repository

    Wang, Juan

    2016-11-16

    Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow-bandgap features, the Ti2O3 nanoparticles possess strong light absorption and nearly 100% internal solar–thermal conversion efficiency. Furthermore, Ti2O3 nanoparticle-based thin film shows potential use in seawater desalination and purification.

  20. La and Al co-doped CaMnO3 perovskite oxides: From interplay of surface properties to anion exchange membrane fuel cell performance

    Science.gov (United States)

    Dzara, Michael J.; Christ, Jason M.; Joghee, Prabhuram; Ngo, Chilan; Cadigan, Christopher A.; Bender, Guido; Richards, Ryan M.; O'Hayre, Ryan; Pylypenko, Svitlana

    2018-01-01

    This work reports the first account of perovskite oxide and carbon composite oxygen reduction reaction (ORR) catalysts integrated into anion exchange membrane fuel cells (AEMFCs). Perovskite oxides with a theoretical stoichiometry of Ca0.9La0.1Al0.1Mn0.9O3-δ are synthesized by an aerogel method and calcined at various temperatures, resulting in a set of materials with varied surface chemistry and surface area. Material composition is evaluated by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The perovskite oxide calcined at 800 °C shows the importance of balance between surface area, purity of the perovskite phase, and surface composition, resulting in the highest ORR mass activity when evaluated in rotating disk electrodes. Integration of this catalyst into AEMFCs reveals that the best AEMFC performance is obtained when using composites with 30:70 perovskite oxide:carbon composition. Doubling the loading leads to an increase in the power density from 30 to 76 mW cm-2. The AEMFC prepared with a composite based on perovskite oxide and N-carbon achieves a power density of 44 mW cm-2, demonstrating an ∼50% increase when compared to the highest performing composite with undoped carbon at the same loading.

  1. Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

    Science.gov (United States)

    Perry, Nicola H.; Kim, Jae Jin; Tuller, Harry L.

    2018-01-01

    Abstract We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films. PMID:29511391

  2. Ferromagnetism of Na0.5Bi0.5TiO3 (1 0 0) surface with O2 adsorption

    Science.gov (United States)

    Ju, Lin; Xu, Tongshuai; Zhang, Yongjia; Shi, Changmin; Sun, Li

    2017-08-01

    Na0.5Bi0.5TiO3 (NBT) nanocrystalline powders prepared by sol-gel method with annealing at 900 °C in air 1 h present room-temperature ferromagnetism (FM). The subsequent annealing in vacuum at 900 °C for 30 min weakens the room-temperature FM, while subsequent treatments in oxygen atmosphere at room-temperature enhances the room-temperature FM, indicating that the room-temperature FM may be induced by the adsorbed oxygen on the NBT nanoparticle surface. The adsorption of O2 molecule on the NBT (1 0 0) surface is studied by using density functional theory within local density approximation plus on-site effect method. The physisorption of configuration R5 is the most stable, whereas the chemisorption of O2 is unfavorable at all adsorption sites. The physisorbed O2 molecule on the NBT (1 0 0) surface with a magnetic moment (MM) closes to that for an isolated O2 molecule. The magnetism of configuration R5 is mainly from the O p orbitals. The stable ferromagnetic coupling mechanism is the direct exchange interaction between the nearest-neighbor O2 molecules adsorbed on the surface. The adsorption of O2 molecule on ferroelectric materials may be a promising approach to achieve multiferroic materials.

  3. Gd2O3-doped silica @ Au nanoparticles for in vitro imaging cancer biomarkers using surface-enhanced Raman scattering

    Science.gov (United States)

    Xiao, Lifu; Tian, Xiumei; Harihar, Sitaram; Li, Qifei; Li, Li; Welch, Danny R.; Zhou, Anhong

    2017-06-01

    There has been an interest in developing multimodal approaches to combine the advantages of individual imaging modalities, as well as to compensate for respective weaknesses. We previously reported a composite nano-system composed of gadolinium-doped mesoporous silica nanoparticle and gold nanoparticle (Gd-Au NPs) as an efficient MRI contrast agent for in vivo cancer imaging. However, MRI lacks sensitivity and is unsuitable for in vitro cancer detection. Thus, here we performed a study to use the Gd-Au NPs for detection and imaging of a widely recognized human cancer biomarker, epidermal growth factor receptor (EGFR), in individual human cancer cells with surface-enhanced Raman scattering (SERS). The Gd-Au NPs were sequentially conjugated with a monoclonal antibody recognizing EGFR and a Raman reporter molecule, 4-meraptobenzoic acid (MBA), to generate a characteristic SERS signal at 1075 cm- 1. By spatially mapping the SERS intensity at 1075 cm- 1, cellular distribution of EGFR and its relocalization on the plasma membrane were measured in situ. In addition, the EGFR expression levels in three human cancer cell lines (S18, A431 and A549) were measured using this SERS probe, which were consistent with the comparable measurements using immunoblotting and immunofluorescence. Our SERS results show that functionalized Gd-Au NPs successfully targeted EGFR molecules in three human cancer cell lines and monitored changes in single cell EGFR distribution in situ, demonstrating its potential to study cell activity under physiological conditions. This SERS study, combined with our previous MRI study, suggests the Gd-Au nanocomposite is a promising candidate contrast agent for multimodal cancer imaging.

  4. Template-free construction of hollow α-Fe2O3 hexagonal nanocolumn particles with an exposed special surface for advanced gas sensing properties.

    Science.gov (United States)

    Sun, Linqiang; Han, Xiao; Liu, Kai; Yin, Shan; Chen, Qiaoli; Kuang, Qin; Han, Xiguang; Xie, Zhaoxiong; Wang, Chao

    2015-06-07

    Hollow α-Fe2O3 hexagonal nanocolumn particles (HHCPs) with exposed (101[combining macron]0) and (112[combining macron]5) facets have been synthesized through a hydrothermal method in the absence of templates. The time-dependent experimental results demonstrate that the formation of HHCPs includes four main steps: (1) formation of nanowire precursors, (2) aggregation and conversion to Fe1.833(OH)0.5O2 solid ellipsoid particles (SEPs), (3) dehydration to form hollow ellipsoid particles (HEPs), and (4) recrystallization to HHCPs. Due to their advantages of the hollow structure and the exposed special external and internal surface on the pore structure, the HHCPs exhibit higher gas sensing ability than that of calcined SEPs (CSEPs) and HEPs.

  5. Improvement of leakage current characteristics of Ba0.5Sr0.5TiO3 films by N2O plasma surface treatment

    Science.gov (United States)

    Cho, Hag-Ju; Oh, Sejun; Kang, Chang Seok; Hwang, Cheol Seong; Lee, Byoung Taek; Lee, Ki Hoon; Horii, Hideki; Lee, Sang In; Lee, Moon Yong

    1997-12-01

    The effects of plasma surface treatment, using N2O gas, of Ba0.5Sr0.5TiO3 (BST) film on the leakage current characteristic of a Pt/BST/Pt capacitor were investigated. As a result of exposure of BST film to the plasma, the leakage current density of the BST capacitor decreased by two orders of magnitude in the high voltage region, and higher onset voltage of an abrupt increase in leakage current was observed. The improvement of leakage properties of BST films can be attributed to the elimination of the bulged curve in the leakage current characteristics. Thermal desorption spectroscopy showed that the elimination was closely related to the reduction of carbon content in the BST film.

  6. Effective Surface Passivation of InP Nanowires by Atomic-Layer-Deposited Al2O3with POxInterlayer.

    Science.gov (United States)

    Black, L E; Cavalli, A; Verheijen, M A; Haverkort, J E M; Bakkers, E P A M; Kessels, W M M

    2017-10-11

    III/V semiconductor nanostructures have significant potential in device applications, but effective surface passivation is critical due to their large surface-to-volume ratio. For InP such passivation has proven particularly difficult, with substantial depassivation generally observed following dielectric deposition on InP surfaces. We present a novel approach based on passivation with a phosphorus-rich interfacial oxide deposited using a low-temperature process, which is critical to avoid P-desorption. For this purpose we have chosen a PO x layer deposited in a plasma-assisted atomic layer deposition (ALD) system at room temperature. Since PO x is known to be hygroscopic and therefore unstable in atmosphere, we encapsulate this layer with a thin ALD Al 2 O 3 capping layer to form a PO x /Al 2 O 3 stack. This passivation scheme is capable of improving the photoluminescence (PL) efficiency of our state-of-the-art wurtzite (WZ) InP nanowires by a factor of ∼20 at low excitation. If we apply the rate equation analysis advocated by some authors, we derive a PL internal quantum efficiency (IQE) of 75% for our passivated wires at high excitation. Our results indicate that it is more reliable to calculate the IQE as the ratio of the integrated PL intensity at room temperature to that at 10 K. By this means we derive an IQE of 27% for the passivated wires at high excitation (>10 kW cm -2 ), which constitutes an unprecedented level of performance for undoped InP nanowires. This conclusion is supported by time-resolved PL decay lifetimes, which are also shown to be significantly higher than previously reported for similar wires. The passivation scheme displays excellent long-term stability (>7 months) and is additionally shown to substantially improve the thermal stability of InP surfaces (>300 °C), significantly expanding the temperature window for device processing. Such effective surface passivation is a key enabling technology for InP nanowire devices such as

  7. Depleted uranium

    International Nuclear Information System (INIS)

    Huffer, E.; Nifenecker, H.

    2001-02-01

    This document deals with the physical, chemical and radiological properties of the depleted uranium. What is the depleted uranium? Why do the military use depleted uranium and what are the risk for the health? (A.L.B.)

  8. La(0.8)Sr(0.2)MnO(3-δ) decorated with Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ): a bifunctional surface for oxygen electrocatalysis with enhanced stability and activity.

    Science.gov (United States)

    Risch, Marcel; Stoerzinger, Kelsey A; Maruyama, Shingo; Hong, Wesley T; Takeuchi, Ichiro; Shao-Horn, Yang

    2014-04-09

    Developing highly active and stable catalysts based on earth-abundant elements for oxygen electrocatalysis is critical to enable efficient energy storage and conversion. In this work, we took advantage of the high intrinsic oxygen reduction reaction (ORR) activity of La(0.8)Sr(0.2)MnO(3-δ) (LSMO) and the high intrinsic oxygen evolution reaction (OER) activity of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF) to develop a novel bifunctional catalyst. We used pulsed laser deposition to fabricate well-defined surfaces composed of BSCF on thin-film LSMO grown on (001)-oriented Nb-doped SrTiO3. These surfaces exhibit bifunctionality for oxygen electrocatalysis with enhanced activities and stability for both the ORR and OER that rival the state-of-the-art single- and multicomponent catalysts in the literature.

  9. Ultrahigh nanoparticle stability against salt, pH, and solvent with retained surface accessibility via depletion stabilization.

    Science.gov (United States)

    Zhang, Xu; Servos, Mark R; Liu, Juewen

    2012-06-20

    For many applications, it is desirable to stabilize colloids over a wide range of buffer conditions while still retaining surface accessibility for adsorption and reaction. Commonly used charge or steric stabilization cannot achieve this goal since the former is sensitive to salt and the latter blocks the particle surface. We use depletion stabilization in the presence of high molecular weight polyethylene glycol (PEG) to stabilize a diverse range of nanomaterials, including gold nanoparticles (from 10 to 100 nm), graphene oxide, quantum dots, silica nanoparticles, and liposomes in the presence of Mg(2+) (>1.6 M), heavy metal ions, extreme pH (pH 1-13), organic solvents, and adsorbed nucleosides and drugs. At the same time, the particle surface remains accessible for adsorption of both small molecules and macromolecules. Based on this study, high loading of thiolated DNA was achieved in one step with just 2% PEG 20,000 in 2 h.

  10. Characterization of ion distributions near the surface of sodium-containing and sodium-depleted calcium aluminosilicate glass melts

    International Nuclear Information System (INIS)

    Corrales, Louis R.; Du, Jincheng

    2006-01-01

    The distribution of cation and anion components of sodium containing calcium aluminosilicate glass was studied by classical molecular dynamics simulations in a high temperature melt in the bulk and at the vacuum-melt interface. A significant redistribution of the sodium and non-bridging oxygen ions was observed. Subsequently, a sodium depleted calcium aluminosilicate glass melt was simulated to determine the sensitivity of the redistribution of ions near the vacuum-melt interface to the presence of sodium ions. It is found that the thermodynamic equilibrium condition near a surface favors the enrichment of non-bridging oxygen ions that is closely associated with enrichment of the sodium ions

  11. Modeling and analysis of surface potential of single gate fully depleted SOI MOSFET using 2D-Poisson's equation

    Science.gov (United States)

    Mani, Prashant; Tyagi, Chandra Shekhar; Srivastav, Nishant

    2016-03-01

    In this paper the analytical solution of the 2D Poisson's equation for single gate Fully Depleted SOI (FDSOI) MOSFET's is derived by using a Green's function solution technique. The surface potential is calculated and the threshold voltage of the device is minimized for the low power consumption. Due to minimization of threshold voltage the short channel effect of device is suppressed and after observation we obtain the device is kink free. The structure and characteristics of SingleGate FDSOI MOSFET were matched by using MathCAD and silvaco respectively.

  12. Effects of content and surface hydrophobic modification of BaTiO3 on the cooling properties of ASA (acrylonitrile-styrene-acrylate copolymer)

    Science.gov (United States)

    Xiang, Bo; Zhang, Jun

    2018-01-01

    For the field of cool material, barium titanate (BaTiO3, BT) is still a new member that needs to be further studied. Herein, the effects of both content and surface hydrophobic modification of BT on the cooling properties of acrylonitrile-styrene-acrylate copolymer (ASA) were detailedly investigated, aiming to fabricate composited cool material. Butyl acrylate (BA) was employed to convert the surface of BT from hydrophilic to hydrophobic. The addition of unmodified BT could significantly improve the solar reflectance of ASA, especially when the addition amount is 3 vol%, the near infrared (NIR) reflectance increased from 22.02 to 72.60%. However, serious agglomeration occurred when the addition amount increased to 5 vol% and therefore led to a relatively smaller increase in solar reflectance and an obvious decline in impact strength. After surface hydrophobic modification, the modified BT (M-BT) presented better dispersibility in ASA matrix, which contributed to the improvement of both solar reflectance and impact strength. In addition, the temperature test provided a more sufficient and intuitive way to evaluate the cooling effect of the composited cool materials, and a significant decrease (over 10 °C) could be achieved in the temperature test when M-BT particles were introduced.

  13. Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}.

    Science.gov (United States)

    Altmeyer, Michaela; Jeschke, Harald O; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F; Rozenberg, Marcelo J; Valentí, Roser; Gabay, Marc

    2016-04-15

    Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100  meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.

  14. Surface enhancement of THz wave by coupling a subwavelength LiNbO3slab waveguide with a composite antenna structure.

    Science.gov (United States)

    Zhang, Qi; Qi, Jiwei; Wu, Qiang; Lu, Yao; Zhao, Wenjuan; Wang, Ride; Pan, Chongpei; Wang, Shibiao; Xu, Jingjun

    2017-12-14

    Highly intense terahertz electromagnetic field and efficiently surface localized terahertz field in subwavelength volumes are of vital importance for terahertz photonics integration, also will greatly accelerate the development for integrated applications in biochemical sensing, imaging, terahertz spectroscopy, enhancement of nonlinear effects and even quantum research. In this paper, we achieved large terahertz field enhancement and surface field localization through depositing a pair of Au composite antennas on a LiNbO 3 subwavelength slab waveguide, which can serve as an excellent on-chip platform for terahertz research and application. The antennas consist of two opposing tip-to-tip triangles separated by a gap, and each triangle combines with a strip antenna. Time-resolved imaging and finite-difference time-domain method were used to resolve the characteristics of the designed antennas experimentally and simulatively. Through these methods, we demonstrated outstanding abilities of the platform: leading to a large electric field enhancement, concentrating almost full terahertz energy on the waveguide's surface when they are resonant with the terahertz waves and tunable resonant frequency. These abilities make the subwavelength waveguide coupling with the composite antennas be able to sever as a good integrated device to identify terahertz-sensitive small objects, or an excellent platform to terahertz spectroscopy and quantum research.

  15. Unraveling the role of support surface hydroxyls and its effect on the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion: A theoretical study

    Science.gov (United States)

    Zhang, Riguang; Duan, Tian; Wang, Baojun; Ling, Lixia

    2016-08-01

    The supported Rh-based catalysts exhibit the excellent catalytic performances for syngas conversion to C2 species. In this study, all possible elementary steps leading to C2 species from syngas have been explored to identify the role of support and its surface hydroxyls over Rh/γ-Al2O3 catalyst; Here, the results are obtained using density functional theory (DFT) method. Two models: Rh4 cluster supported on the dry γ-Al2O3(110) surface, D(Rh4), and on the hydroxylated γ-Al2O3(110) surface, H(Rh4), have been used to model Rh/γ-Al2O3 catalyst. Our results show that CO prefers to be hydrogenated to CHO, subsequently, starting from CHO species, CH and CH2 species are the dominate monomers among CHx(x = 1-3) species rather than CH3 and CH3OH on D(Rh4) and H(Rh4) surfaces, suggesting that γ-Al2O3-supported Rh catalyst exhibits the high selectivity towards CHx formation compared to the pure Rh catalyst. On the other hand, D(Rh4) is more favorable for C2 hydrocarbon (C2H2) formation, whereas H(Rh4) surface easily produces C2 hydrocarbon (C2H2) and C2 oxygenates (CHCO,CH2CHO), indicating that the surface hydroxyls of support can affect the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion. Moreover, compared to the pure Rh(111) surface, Rh/γ-Al2O3 catalyst can achieve the excellent catalytic performances for syngas conversion to C2 species.

  16. Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF: Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3

    Directory of Open Access Journals (Sweden)

    U. Pöschl

    2009-12-01

    Full Text Available We present a kinetic double-layer surface model (K2-SURF that describes the degradation of polycyclic aromatic hydrocarbons (PAHs on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl-Rudich-Ammann, 2007 for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc., the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3 ≈ 10−15–10−13 cm3, and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3 ≈ 10−18–10−17 cm2 s−1. The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O ≈ 10−18–10−17 cm3. The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 and physisorption of H2O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O3− ions at the surface. The K2-SURF model enables the calculation of ozone uptake coefficients, γO3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging lead to a strong non-linear dependence of γO3 on time and gas phase composition, with different characteristics

  17. Structure and surface chemistry of Al2O3 coated LiMn2O4 nanostructured electrodes with improved lifetime

    Science.gov (United States)

    Waller, G. H.; Brooke, P. D.; Rainwater, B. H.; Lai, S. Y.; Hu, R.; Ding, Y.; Alamgir, F. M.; Sandhage, K. H.; Liu, M. L.

    2016-02-01

    Aluminum oxide coatings deposited on LiMn2O4/carbon fiber electrodes by atomic layer deposition (ALD) are shown to enhance cathode performance in lithium-ion batteries. With a thin Al2O3 coating derived from 10 ALD cycles, the electrodes exhibit 2.5 times greater capacity retention over 500 cycles at a rate of 1C as well as enhanced rate capability and decreased polarization resistance. Structural and surface studies of the electrodes before and after cycling reveal that a near-surface phenomenon is responsible for the improved electrochemical performance. The crystal structure and overall morphology of the LiMn2O4 electrode are found to be unaffected by electrochemical cycling, both for coated and uncoated samples. However, evidence of Mn diffusion into the ALD coatings is observed from both transmission electron microscopy/energy-dispersive X-ray spectroscopy (TEM-EDS) and X-ray Photoelectron Spectroscopy (XPS) after electrochemical cycling. Furthermore, XPS analysis of the Al 2p photoemission peak for the ALD coated electrodes reveal a significant shift in binding energy and peak shape, suggesting the presence of an Al-O-F compound formed by sequestering HF in the electrolyte. These observations provide new insight toward understanding the mechanism in which ultrathin coatings of amphoteric oxides can inhibit capacity loss for LiMn2O4 cathodes in lithium-ion batteries.

  18. NH3 adsorption on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface: A cluster DFT study

    Science.gov (United States)

    Yan, Zhifeng; Fan, Junyan; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

    2014-01-01

    The adsorption of NH3 on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface has been investigated based on the density functional theory (DFT) method using the clusters models. The calculated results indicate that NH3 could strongly adsorb on both the Lewis and Bronsted acid sites in the form of NH3 species and NH4+ respectively, whereas the adsorption on the Lewis acid site is found to be more favorable energetically than that on the Bronsted acid site. For the Lewis acid site Mulliken population analysis shows a donation of lone pairs from NH3 to the surface and activation of N-H bond. The overlaps of N-s, N-p and Mo-d orbitals suggest the strong interaction between N and Mo atoms. For the Bronsted acid site N-H bond is also activated by the formation of NH4+ species. The hybridizations between H and O atoms as well as N and H atoms are the major reasons for strong chemical adsorption of NH3 and the existence of NH4+ species, which partly attributed to the presence of N-H… O hydrogen bonds. Furthermore, the formation of a second Lewis acid site at adjacent or diagonal site results in slight changes of adsorption stability, structural changes and charge redistributions, suggesting its small influence on NH3 adsorption.

  19. Resistance switching at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Zhao, J.L.; Sun, J.R.

    2010-01-01

    behavior is suggested to be an intrinsic feature of the SrTiO3 single crystal substrates, which mainly originates from the modulation of oxygen ion transfer in SrTiO3 surface by external electric field in the vicinity of interface, whereas the LaAlO3 film acts as a barrier layer. © 2010 American Institute...

  20. The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Brennan, Thomas P; Bakke, Jonathan R; Ding, I-Kang; Hardin, Brian E; Nguyen, William H; Mondal, Rajib; Bailie, Colin D; Margulis, George Y; Hoke, Eric T; Sellinger, Alan; McGehee, Michael D; Bent, Stacey F

    2012-09-21

    Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO(2) active layer and the HTM spiro-OMeTAD. The impact of Al(2)O(3) barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl(4) surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al(2)O(3) deposition. However, only when the TiCl(4) treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al(2)O(3) ALD and the TiCl(4) surface treatment whereas the insulating properties of Al(2)O(3) hinder charge injection and lead to current loss in TiCl(4)-treated devices. The impact of Al(2)O(3) barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al(2)O(3) growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems.

  1. The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells

    KAUST Repository

    Brennan, Thomas P.

    2012-01-01

    Atomic layer deposition (ALD) was used to fabricate Al 2O 3 recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al 2O 3 recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO 2 active layer and the HTM spiro-OMeTAD. The impact of Al 2O 3 barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl 4 surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al 2O 3 deposition. However, only when the TiCl 4 treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al 2O 3 ALD and the TiCl 4 surface treatment whereas the insulating properties of Al 2O 3 hinder charge injection and lead to current loss in TiCl 4-treated devices. The impact of Al 2O 3 barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al 2O 3 growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems. © This journal is the Owner Societies 2012.

  2. COMBINING WLI AND SEM TECHNIQUES TO OBTAIN A 4D SURFACE IMAGE OF A ppHDMSO/AlCeO3 NANOCOMPOSITE

    Directory of Open Access Journals (Sweden)

    Olivier Buchheit

    2011-05-01

    Full Text Available Compositional images from a SEM (scanning electron microscope are sometimes complemented by quantitative topographical data from devices such as an AFM (atomic force microscope or WLI (white light interferometer. Indeed, even if a SEM could provide both kinds of information (composition and topography, the topographical data are incomplete because the SEM does not allow measuring the vertical dimension (i.e., perpendicular to the measurement plane. Thus these two kinds of information are usually measured using two different techniques, and at different locations on the sample. Mean values of surface composition are then linked to mean values of topography, and as a consequence this approach does not allow precisely linking a local topographical peak to its corresponding composition. The present work deals with a SEM/WLI combination methodology, based on the characterization, at the same location, of a nanocomposite (nanoparticles of AlCeO3 dispersed in a plasma-polymerized hexamethyldisiloxane ppHMDSO matrix and deposited by atmospheric plasma on a glass substrate developed for improving anticorrosion properties. SEM images allow the supposition that the protuberances (peaks observed on the surface of a specimen are linked to the nanoparticles dispersed in the polymer coating, but this link is not fully convincing. Thanks to a precise localization method, SEM compositional data and WLI topographical data are here measured at the same location. The recombination of both signals to form a 4D image (3D geometry and 1D composition allows linking protuberances to nanoparticles aggregates without ambiguity. This composite image appears to be an interesting new tool (at the scale of observation, i.e., hundreds of micrometers for the study of nanostructured coatings.

  3. Oxygen Depletion on the Surface of Mercury: Evidence of Silicon Smelting?

    Science.gov (United States)

    McCubbin, F. M.; Vander Kaaden, K. E.; Peplowski, P. N.; Bell, A. S.; Evans, L. G.; Nittler, L. R.; Boyce, J. W.; Keller, L. P.; McCoy, T. J.

    2017-01-01

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft collected data that provided important insights into the structure, chemical makeup, and compositional diversity of Mercury. The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) onboard MESSENGER provided the first detailed chemical analyses of Mercury's surface. Among the many discoveries included several surprising characteristics about the surface of Mercury, including elevated S abundances (up to 4 percent by weight), low Fe abundances (less than 4 percent by weight), and relatively low O abundances (O/Si ratio of 1.40 plus or minus 0.03). The surface chemistry as determined by MESSENGER has been used to identify up to nine distinct geochemical terranes on Mercury. Numerous modeling and experimental efforts have been undertaken to infer the mineralogy and petrology of mercurian lavas and surface materials. However, all of these efforts have presumed valence states for each of the elements according to the following: Si4+, Ti4+, Al3+, Cr2+, Fe2+, Mn2+, Mg2+, Ca2+, Na+, K+, S2-, Cl-. Based on these valence assignments, cations are charged balanced with the anions O2-, S2-, and Cl- and the compositions are recast in terms of oxides, sulfides, and chlorides. Based on these assumptions, the geochemical terranes that have been identified on Mercury yield O/Si wt. ratios ranging from 1.61 to 1.84, which is substantially higher than the preliminary O/Si ratio of 1.40 plus or minus 0.03 determined by the MESSENGER GRS]. We have re-evaluated the O/Si ratio using the entire MESSENGER dataset to reassess its implications for the geochemistry of Mercury.

  4. O3 stars

    International Nuclear Information System (INIS)

    Walborn, N.R.

    1982-01-01

    A brief review of the 10 known objects in this earliest spectral class is presented. Two new members are included: HD 64568 in NGC 2467 (Puppis OB2), which provides the first example of an O3 V((f*)) spectrum; and Sk -67 0 22 in the Large Magellanic Cloud, which is intermediate between types O3 If* and WN6-A. In addition, the spectrum of HDE 269810 in the LMC is reclassified as the first of type O3 III (f*). The absolute visual magnitudes of these stars are rediscussed

  5. Near-surface effects of transient oxidation and reduction on Nb-doped SrTiO3 epitaxial thin films

    Science.gov (United States)

    Chang, C. F.; Chen, Q. Y.; Wadekar, P. V.; Lozano, O.; Wong, M. S.; Hsieh, W. C.; Lin, W. Y.; Ko, H. H.; Lin, Q. J.; Huang, H. C.; Ho, N. J.; Tu, L. W.; Liao, H. H.; Chinta, P. V.; Chu, W. K.; Seo, H. W.

    2014-03-01

    We studied the effects of transient oxidation and reduction of Nb-doped epitaxial thin films through variations of PAr and PO2. The samples were prepared by co-sputtering of Nb and SrTiO3 on LaAlO3 substrates. The Nb-content were varied from 0-33.7%, as determined by PIXE. Contact resistance, sheet resistance, and optical properties are used to discriminate the effects.

  6. O3 and SO2 sensing concept on extended surface of B12N12 nanocages modified by Nickel decoration: A comprehensive DFT study

    Science.gov (United States)

    Rad, Ali Shokuhi; Ayub, Khurshid

    2017-07-01

    Adsorption of SO2 and O3 molecules on pristine boron nitride (B12N12) and Ni-decorated B12N12 nano-cages has been systemically investigated through density functional theory (DFT) methods. Adsorption energies (thermodynamics), bond distances, charge analysis, dipole moments, orbital analysis and density of states are calculated by van der Waals DFT method (MPW1PW91) functional. The adsorption energies of O3 and SO2 on pristine B12N12 are about -143.8 and -14.0 kJ mol-1, respectively. The interaction energies of O3 and SO2 with pristine B12N12 are indicative of chemisorption and physisorption, respectively. Ni-decorated B12N12 (Ni@BN) enhances adsorption of both O3 and SO2 species. The interaction energies for adsorption of SO2 are about -166 and -277 kJ mol-1 whereas the corresponding energies for O3 are -362 and -396 kJ mol-1 for configuration A and B, respectively. These observations show that functionalized B12N12 are highly sensitive toward SO2 and O3 molecules.

  7. Surface Crystallization of Cloud Droplets: Implications for Climate Change and Ozone Depletion

    Science.gov (United States)

    Tabazadeh, A.; Djikaev, Y. S.; Reiss, H.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    The process of supercooled liquid water crystallization into ice is still not well understood. Current experimental data on homogeneous freezing rates of ice nucleation in supercooled water droplets show considerable scatter. For example, at -33 C, the reported freezing nucleation rates vary by as much as 5 orders of magnitude, which is well outside the range of measurement uncertainties. Until now, experimental data on the freezing of supercooled water has been analyzed under the assumption that nucleation of ice took place in the interior volume of a water droplet. Here, the same data is reanalyzed assuming that the nucleation occurred "pseudoheterogeneously" at the air (or oil)-liquid water interface of the droplet. Our analysis suggest that the scatter in the nucleation data can be explained by two main factors. First, the current assumption that nucleation occurs solely inside the volume of a water droplet is incorrect. Second, because the nucleation process most likely occurs on the surface, the rates of nuclei formation could differ vastly when oil or air interfaces are involved. Our results suggest that ice freezing in clouds may initiate on droplet surfaces and such a process can allow for low amounts of liquid water (approx. 0.002 g per cubic meters) to remain supercooled down to -40 C as observed in the atmosphere.

  8. DFT study of Hg adsorption on M-substituted Pd(1 1 1) and PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces

    Science.gov (United States)

    Wang, Jiancheng; Yu, Huafeng; Geng, Lu; Liu, Jianwen; Han, Lina; Chang, Liping; Feng, Gang; Ling, Lixia

    2015-11-01

    The adsorption of Hgn (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd2 shows better Hg adsorption capacity than Pd2/γ-Al2O3, while PdM/γ-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the γ-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/γ-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture.

  9. The effect of radiation-thermal treatment on the physicochemical properties of the Ni-Mo/Al2O3 hydrotreatment catalyst. II. UV-Vis diffuse reflectance spectra of surface compounds after irradiation

    International Nuclear Information System (INIS)

    Solovetskii, Yu.I.; Miroshinichenko, I.I.; Lunin, V.V.

    1993-01-01

    Radiation-thermal damage of the surface and the active metal phases of hydrodesulfurization Ni-Mo/Al 2 O 3 catalysts by a fast electron beam of up to 2.0 MeV energy was studied. UV-Vis diffuse reflectance spectra of the industrial and model coked systems after radiation-thermal treatment were measured. 14 refs., 2 figs

  10. Studies on novel BiyXz-TiO2/SrTiO3 composites: Surface properties and visible light-driven photoactivity

    Science.gov (United States)

    Marchelek, Martyna; Grabowska, Ewelina; Klimczuk, Tomasz; Lisowski, Wojciech; Giamello, Elio; Zaleska-Medynska, Adriana

    2018-03-01

    A series of novel BiyXz-TiO2/SrTiO3 composites were prepared by multistep synthesis route. The as-prepared photocatalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR), Raman spectra and BET analysis. The photocatalytic activity test was performed in aqueous solution of phenol under the irradiation of visible light range (λ ≥ 420 nm). Obtained results revealed that the BiOI_TiO2/SrTiO3 sample exhibit the highest photocatalytic activity under visible irradiation (0.6 μmol/dm3/min). Thus, it was demonstrated that modification of the TiO2/SrTiO3 microspheres by flowers-like structure made of bismuth oxyiodide resulted in enhancement of photocatalytic activity under visible light. The role of active species during the decomposition process of organic compound was investigated using different types of active species scavengers as well as electron paramagnetic resonance analysis (EPR). The study showed that in the BiOI_TiO2/SrTiO3/Vis system the holes (h+) plays relevant role in phenol decomposition. Furthermore, the stability and recyclable properties of obtained BiOI_TiO2/SrTiO3 sample were confirmed during three consecutive processes.

  11. Effect of surface pretreatment in the thermal atomic layer deposition of Al2O3 for passivation of crystal Si solar cells

    Science.gov (United States)

    Li, Meng; Shin, Hong-Sik; Jeong, Kwang-Seok; Oh, Sung-Kwen; Lee, Horyeong; Han, Kyumin; Lee, Yongwoo; Lee, Song-Jae; Lee, Ga-Won; Lee, Hi-Deok

    2014-08-01

    H2O or NH4OH (5%) precursor pretreatment in the chamber was carried out before the thermal atomic layer deposition (ALD) of an Al2O3 passivation layer on p-type crystal Si. It was found that the density of negative oxide fixed charges significantly increased, the Al-O combination at the interface changed, the Al/O atomic at the interface of Al2O3/Si decreased, and the effective lifetime increased. The pretreated samples with changes in the Al-O structure at the interface, which made the interface more oxygen-rich, were believed to be the reason for the improvement of the field effect passivation in Al2O3 passivated crystal Si solar cell applications.

  12. Effect of Sr Content and Strain on Sr Surface Segregation of La1-xSrxCo0.2Fe0.8O3-δas Cathode Material for Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yu, Yang; Ludwig, Karl F; Woicik, Joseph C; Gopalan, Srikanth; Pal, Uday B; Kaspar, Tiffany C; Basu, Soumendra N

    2016-10-12

    Strontium-doped lanthanum cobalt ferrite (LSCF) is a widely used cathode material due to its high electronic and ionic conductivity, and reasonable oxygen surface exchange coefficient. However, LSCF can have long-term stability issues such as surface segregation of Sr during solid oxide fuel cell (SOFC) operation, which can adversely affect the electrochemical performance. Thus, understanding the nature of the Sr surface segregation phenomenon and how it is affected by the composition of LSCF and strain are critical. In this research, heteroepitaxial thin films of La 1-x Sr x Co 0.2 Fe 0.8 O 3-δ with varying Sr content (x = 0.4, 0.3, 0.2) were deposited by pulsed laser deposition (PLD) on single-crystal NdGaO 3 , SrTiO 3 , and GdScO 3 substrates, leading to different levels of strain in the films. The extent of Sr segregation at the film surface was quantified using synchrotron-based total-reflection X-ray fluorescence (TXRF) and atomic force microscopy (AFM). The electronic structure of the Sr-rich phases formed on the surface was investigated by hard X-ray photoelectron spectroscopy (HAXPES). The extent of Sr segregation was found to be a function of the Sr content in bulk. Lowering the Sr content from 40% to 30% reduced the surface segregation, but further lowering the Sr content to 20% increased the segregation. The strain of LSCF thin films on various substrates was measured using high-resolution X-ray diffraction (HRXRD), and the Sr surface segregation was found to be reduced with compressive strain and enhanced with tensile strain present within the thin films. A model was developed correlating the Sr surface segregation with Sr content and strain effects to explain the experimental results.

  13. An Estimating the Effect of Process Parameters on Metal Removal Rate and Surface Roughness in WEDM of Composite Al6063/SiC/Al2O3 by Taguchi Method

    Directory of Open Access Journals (Sweden)

    Himanshu Prasad Raturi

    2017-11-01

    Full Text Available The present study was focused on the fabrication of metal matrix and hybrid metal matrix composites through stir casting process. The Aluminium 6063 was used as base material and SiC/Al2O3 were used as reinforcement with varying weight %. The parametric study on a wire-cut electro discharge machine was carried out by using Taguchi Method. A statistical analysis of variance (ANOVA was performed to identify the process parameters that were statistically significant. It was observed that the MRR decreases with increase in the percentage weight fraction of SiC and Al2O3 particles in the MMCs and HMMCs. Whereas, the surface roughness parameter increases with increase in the percentage weight fraction of SiC and Al2O3 particles due to the hardness of MMCs and HMMCs composites.

  14. Chemical diffusion and oxygen surface transfer of La1-xSrxCoO3-d studied with electrical conductivity relaxation

    NARCIS (Netherlands)

    van der Haar, L.M.; den Otter, M.W.; Morskate, M.; Bouwmeester, Henricus J.M.; Verweij, H.

    2002-01-01

    The chemical diffusion coefficient and oxygen-transfer coefficients of selected compositions in the series $La_1-xSr_xCoO_3-delta$ were studied using the conductivity relaxation technique. Measurements were performed in the temperature range 600-850°C and oxygen partial pressure $10-4$ to 1 bar.

  15. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    In addition, the oscillator energy, disper- sion energy and zero-frequency refractive index values were found from the analysis of the experimental data using. Wemple–DiDomenico single-effective-oscillator model. Keywords. Perovskite; BaTiO3; X-ray diffraction; spectroscopic ellipsometry; refractive index. 1. Introduction.

  16. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    ray diffraction, scanning electron microscopy and ... The structure refinement of BaTi0.5(Fe0.33W0.17)O3 sample was performed in the cubic double and hexagonal setting of the Fm¯3m .... peak Ihex by the following quantitative equations [17]:.

  17. Surface modification of LiCo 1/3Ni 1/3Mn 1/3O 2 with Y 2O 3 for lithium-ion battery

    Science.gov (United States)

    Wu, Feng; Wang, Meng; Su, Yuefeng; Chen, Shi

    The surface of LiCo 1/3Ni 1/3Mn 1/3O 2 cathode material was coated with 1.0 wt.% Y 2O 3 via a simple method to improve the cycling performance for lithium-ion batteries. Cyclic voltammetry showed Y 2O 3-coating inhibited structural change of LiCo 1/3Ni 1/3Mn 1/3O 2 and reaction with the electrolyte on cycling. The Y 2O 3-coated material showed a higher capacity with good cyclability. The discharge capacity of coated sample was 137.5 mAh g -1 at 2.0 mA cm -2 while that of bared one was only 116.2 mAh g -1. The rate of capacity decrease after 20 cycles for the coated sample was 0.7%, much smaller than that of the bared one (2.8%). X-ray photoelectron spectroscopy (XPS) data represented that the presence of two different environmental O1s ions corresponded to the surface-coated Y 2O 3 and core material. ICP-OES and EIS displayed the coating layer could protect the LiCo 1/3Ni 1/3Mn 1/3O 2 from being corroded by the electrolyte and benefit to decrease the cathode charge-transfer resistance at delithiated state.

  18. Inulin as a novel biocompatible coating: evaluation of surface affinities toward CaHPO4, α-Fe2O3, ZnO, CaHPO4@ZnO and α-Fe2O3@ZnO nanoparticles.

    Science.gov (United States)

    Santillán-Urquiza, E; Arteaga-Cardona, F; Hernandez-Herman, E; Pacheco-García, P F; González-Rodríguez, R; Coffer, J L; Mendoza-Alvarez, M E; Vélez-Ruiz, J F; Méndez-Rojas, M A

    2015-12-15

    The introduction of biocompatible coatings onto nanoparticle surfaces can be synthetically challenging. In this work, calcium phosphate (brushite, CaHPO4⋅2H2O), iron oxide (hematite, α-Fe2O3), zinc oxide (ZnO), and CaHPO4@ZnO and α-Fe2O3@ZnO nanoparticles were synthesized and treated with the biocompatible, biodegradable, polysaccharide inulin {(2R,3S,4S,5R)-2-[[(2R,3S,4S,5R)-3,4-dihydroxy-2,5-bis(hydroxymethyl)oxolan-2-yl]oxymethyl]-5-(hydroxymethyl)oxolane-2,3,4-triol} under mild conditions. The products were fully characterized by Fourier transforms infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), dynamic light scattering (DLS), differential thermogravimetric/differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). Surface interactions among hematite and brushite with inulin are weak, but coating the nanoparticle surface with ZnO increased the affinity toward the polysaccharide. Inulin adsorption on the nanoparticle surface was confirmed by thermal and spectroscopic analyses. The nanoparticles had diameters ranging from 50 to 80nm, with nearly spherical morphology. The nanoparticles sizes, stability and solubility in water could make them useful as components for enriched foods. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Free standing TiO2 nanotube array electrodes with an ultra-thin Al2O3 barrier layer and TiCl4 surface modification for highly efficient dye sensitized solar cells

    Science.gov (United States)

    Gao, Xianfeng; Guan, Dongsheng; Huo, Jingwan; Chen, Junhong; Yuan, Chris

    2013-10-01

    Dye sensitized solar cells were fabricated with free standing TiO2 nanotube (TNT) array films, which were prepared by template assisted atomic layer deposition (ALD) with precise wall thickness control. Efforts to improve the photovoltaic performance were made by using Al2O3 barrier layer coating in conjunction with TiCl4 surface modification. An Al2O3 thin layer was deposited on the TNT electrode by ALD to serve as the charge recombination barrier, but it suffers from the drawback of decreasing the photoelectron injection from dye into TiO2 when the barrier layer became too thick. With the TiCl4 treatment in combination with optimal thickness coating, this problem could be avoided. The co-surface treated electrode presents superior surface property with low recombination rate and good electron transport property. A high conversion efficiency of 8.62% is obtained, which is about 1.8 times that of the device without surface modifications.Dye sensitized solar cells were fabricated with free standing TiO2 nanotube (TNT) array films, which were prepared by template assisted atomic layer deposition (ALD) with precise wall thickness control. Efforts to improve the photovoltaic performance were made by using Al2O3 barrier layer coating in conjunction with TiCl4 surface modification. An Al2O3 thin layer was deposited on the TNT electrode by ALD to serve as the charge recombination barrier, but it suffers from the drawback of decreasing the photoelectron injection from dye into TiO2 when the barrier layer became too thick. With the TiCl4 treatment in combination with optimal thickness coating, this problem could be avoided. The co-surface treated electrode presents superior surface property with low recombination rate and good electron transport property. A high conversion efficiency of 8.62% is obtained, which is about 1.8 times that of the device without surface modifications. Electronic supplementary information (ESI) available: UV-Vis spectra of desorbed N719 dyes from

  20. Effect of Phosphine Doping and the Surface Metal State of Ni on the Catalytic Performance of Ni/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    Xiaoru Li

    2015-04-01

    Full Text Available Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P found to improve the catalytic performance significantly because of the formation of Ni2P alloys. However, in the present work we disclose a different catalytic phenomenon for the P-doped Ni/Al2O3 catalyst. We found that doping with P has a significant effect on the state of the active Ni species, and thus improves the selectivity to 1,2-propanediol (1,2-PDO significantly in the hydrogenolysis of glycerol, although Ni-P alloys were not observed in our catalytic system. The structure and selectivity correlations were determined from the experimental data, combining the results of X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, hydrogen temperature-programmed reduction (H2-TPR and ammonia temperature-programmed desorption (NH3-TPD. The presence of NiO species, formed from P-doped Ni/Al2O3 catalyst, was shown to benefit the formation of 1,2-PDO. This was supported by the results of the Ni/Al2O3 catalyst containing NiO species with incomplete reduction. Furthermore, the role the NiO species played in the reaction and the potential reaction mechanism over the P-doped Ni/Al2O3 catalyst is discussed. The new findings in the present work open a new vision for Ni catalysis and will benefit researchers in designing Ni-based catalysts.

  1. Electron beam induced Hg desorption and the electronic structure of the Hg depleted surface of Hg1/sub -//sub x/Cd/sub x/Te

    International Nuclear Information System (INIS)

    Shih, C.K.; Friedman, D.J.; Bertness, K.A.; Lindau, I.; Spicer, W.E.; Wilson, J.A.

    1986-01-01

    Auger electron spectroscopy (AES), x-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED), and angle-resolved ultraviolet photoemission spectroscopy (ARPES) were used to study the electron beam induced Hg desorption from a cleaved (110)Hg/sub 1-//sub x/Cd/sub x/Te surface and the electronic structure of the Hg depleted surface. Solid state recrystallized Hg/sub 1-//sub x/Cd/sub x/Te single crystals were used. It was found that the electron beam heating dominated the electron beam induced Hg desorption on Hg/sub 1-//sub x/Cd/sub x/Te. At the electron beam energy used, the electron beam heating extended several thousand angstroms deep. However, the Hg depletion saturated after a few monolayers were depleted of Hg atoms. At the initial stage of Hg loss (only 3%), the surface band bends upward (more p type). The ARPES spectrum showed the loss of some E vs k dispersion after 22% Hg atoms were removed from the surface region, and no dispersion was observed after 43% Hg atoms were removed. These results have important implications on the electronic structure of the surfaces and interfaces of which the stoichiometry is altered

  2. Photocatalytic properties of KBiO3 and LiBiO3 with tunnel structures

    Indian Academy of Sciences (India)

    In the present study, KBiO3 is synthesized by a standard oxidation technique while LiBiO3 is prepared by hydrothermal method. The synthesized catalysts are characterized by X-ray diffraction (XRD), Scanning ElectronMicroscopy (SEM), BET surface area analysis and Diffuse Reflectance Spectroscopy (DRS). The XRD ...

  3. Kinetics and Mechanisms of Oxygen Surface Exchange on La0.6Sr0.4FeO3-delta Thin Films

    OpenAIRE

    Mosleh, Majid; Søgaard, Martin; Hendriksen, Peter Vang

    2009-01-01

    The thermodynamic properties as well as oxygen exchange kinetics were examined on mixed ionic and electronic conducting (La0.6Sr0.4)0.99FeO3− (LSF64) thin films deposited on MgO single crystals. It is found that thin films and bulk material have the same oxygen stoichiometry for a given temperature and oxygen partial pressure [i.e., the incorporation reaction has the same reaction enthalpy (H0=−105 KJ/mol) and entropy (S0=−75.5 J/mol/K) as found for bulk material]. The thin film shows smaller...

  4. Effect of atmospheric CO2 on surface segregation and phase formation in La0.6Sr0.4Co0.2Fe0.8O3-δ thin films

    Science.gov (United States)

    Yu, Yang; Luo, Heng; Cetin, Deniz; Lin, Xi; Ludwig, Karl; Pal, Uday; Gopalan, Srikanth; Basu, Soumendra

    2014-12-01

    The effects of atmospheric CO2 on surface segregation and phase formation in La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF-6428) were investigated. (0 0 1)-oriented LSCF-6428 thin films were deposited on lattice matched (1 1 0)-oriented NdGaO3 (NGO) substrates by pulsed laser deposition (PLD). Using the synchrotron technique of total reflection X-ray fluorescence (TXRF), it was found that the kinetics of Sr surface segregation was enhanced when annealing at 800 °C in a high-CO2 partial pressure, as compared to a similar anneal in a CO2-free atmosphere, with the oxygen partial pressure being constant in both cases. Hard X-ray photoelectron spectroscopy (HAXPES) measurements showed that the contribution of the surface carbonate to surface oxide phases increased significantly for the sample annealed in the high-CO2 atmosphere. Atomic force microscopy (AFM) studies showed enhanced surface phase formation during the high-CO2 partial pressure anneal. Density functional theory (DFT) calculations provide a thermodynamic basis for the enhanced kinetics of surface segregation in the presence of atmospheric CO2.

  5. Improved DC and RF performance of InAlAs/InGaAs InP based HEMTs using ultra-thin 15 nm ALD-Al2O3 surface passivation

    Science.gov (United States)

    Asif, Muhammad; Chen, Chen; Peng, Ding; Xi, Wang; Zhi, Jin

    2018-04-01

    Owing to the great influence of surface passivation on DC and RF performance of InP-based HEMTs, the DC and RF performance of InAlAs/InGaAs InP HEMTs were studied before and after passivation, using an ultra-thin 15 nm atomic layer deposition Al2O3 layer. Increase in Cgs and Cgd was significantly limited by scaling the thickness of the Al2O3 layer. For verification, an analytical small-signal equivalent circuit model was developed. A significant increase in maximum transconductance (gm) up to 1150 mS/mm, drain current (IDS) up to 820 mA/mm and fmax up to 369.7 GHz was observed, after passivation. Good agreement was obtained between the measured and the simulated results. This shows that the RF performance of InP-based HEMTs can be improved by using an ultra-thin ALD-Al2O3 surface passivation.

  6. The synthesis of Ba2+ doped multiferroic BiFeO3 nanoparticles by using a hydrothermal approach in the presence of different surface activators and the investigation of structural and magnetic features

    Science.gov (United States)

    Mardani, Reza

    2017-05-01

    In this work, Bi1-x Ba x FeO3 nanoparticles were synthesized by a hydrothermal method in the presence of various surface activators, and different amounts of barium were inserted in a bismuth ferrite (x  =  0.1, 0.15, 0.2) structure instead of bismuth. The structural and magnetic properties, morphology, and size of the synthesized nanoparticles were investigated by XRD, FT-IR, FE-SEM, TEM, DLS and VSM. The XRD analysis results reveal that the synthetic nanoparticles have a single phase. A phase shift from a rhombohedral structure to a tetragonal structure occurs due to the enhanced barium amount in the bismuth ferrite structure. The SEM analysis exhibits a uniform shape of the Bi0.85Ba0.15FeO3 particles and the image observed by TEM clarifies the size of the particles as 11 nm. Furthermore, the effect of the diverse surfaces of activators in the synthesis of Bi0.85Ba0.15FeO3 nanoparticles was studied, revealing that when sugar was used as a surfactant, the particle size reduced and the magnetic properties increased notably.

  7. Use of fluorescence to probe the surface dynamics during disorder-to-order transition and cluster formation in dihalonaphthalene-water thin films on Al2O3(0001)

    International Nuclear Information System (INIS)

    Evans, M.A.; Hoss, D.R.; Howard, K.E.; Louie, A.D.; Bishop, A.J.; Martin, K.A.; Nishimura, A.M.

    2006-01-01

    Amorphous dihalonaphthalenes that are prepared by vacuum deposition onto a cold Al 2 O 3 surface form electronically excited dimers when optically pumped, and their emission is characteristically red-shifted, broad and featureless compared to the monomeric fluorescence. If the surface is heated, the adlayer undergoes a disorder-to-order transition at a temperature characteristic of the molecule. Since pure crystalline dihalonaphthalenes typically fluoresce and do not exhibit excimeric features, the transition was studied by taking advantage of the changes in the spectral characteristics of the adlayer. These included transmittance, and emission from fluorescence and excimer. The combination of these methods allowed a close look at the surface dynamics of molecules on the surface of Al 2 O 3 as the adlayer was heated from the deposition temperature to desorption. If a bilayer is formed by depositing water onto the surface with the organic adlayer on top, water, with its lower desorption energy, can be made to percolate into the organic layer. The optical probes indicate that the water clearly associates with the organic molecules while the excess water desorbs. By varying the coverage of either the water or the dihalonaphthalene, the stoichiometric composition of the cluster can be determined and are reported here

  8. An in situ spectroelectrochemical study on the orientation changes of an [FeiiiLN2O3] metallosurfactant deposited as LB Films on gold electrode surfaces.

    Science.gov (United States)

    Brand, Izabella; Juhaniewicz-Debinska, Joanna; Wickramasinghe, Lanka; Verani, Claudio N

    2018-03-28

    In this paper we analyze the changes in molecular orientation triggered by electrochemical reduction of an iron-containing surfactant in Langmuir-Blodgett films deposited onto gold electrodes. The metallosurfactant [Feiii(LN2O3)] (1) is an established molecular rectifier capable of unidirectional electron transfer between two electrodes. A gradual decrease in the activity is observed in sequential current vs. potential curves upon repeated cycles. Here we evaluate the redox response associated with the reduction of the Feiii/Feii couple in a single monolayer, as well as in a 5-layer LB film of 1. We use polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) to follow structural and orientation changes associated with such applied potential scans. We observe that the reduction of the Fe center becomes increasingly irreversible because an Fe-Ophenolate bond is cleaved. This transformation is accompanied by an almost vertical change in the orientation of metallosurfactant molecules in LB films.

  9. Metastable honeycomb SrTiO3/SrIrO3 heterostructures

    International Nuclear Information System (INIS)

    Anderson, T. J.; Ryu, S.; Podkaminer, J. P.; Ma, Y.; Eom, C. B.; Zhou, H.; Xie, L.; Irwin, J.; Rzchowski, M. S.; Pan, X. Q.

    2016-01-01

    Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO 3 layers sandwiched between SrTiO 3 have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO 3 film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO 3 on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO 3 films capped with SrTiO 3 grown on (111) SrTiO 3 substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO 3 monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO 3 , which provides an experimental avenue to probe the phenomena predicted for this material system.

  10. Effect of reactive surface area of minerals on mineralization and carbon dioxide trapping in a depleted gas reservoir

    NARCIS (Netherlands)

    Bolourinejad, P.; Shoeibi Omrani, P.; Herber, R.

    2014-01-01

    In this study, a long-term (up to 1000 years) geochemical modelling of subsurface CO2 storage was carried out on sandstone reservoirs of depleted gas fields in northeast Netherlands. It was found that mineral dissolution/precipitation has only a minor effect on reservoir porosity. In order to

  11. Effect of reactive surface area of minerals on mineralization and carbon dioxide trapping in a depleted gas reservoir

    NARCIS (Netherlands)

    Bolourinejad, Panteha; Omrani, Pejman Shoeibi; Herber, Rien

    In this study, a long-term (up to 1000 years) geochemical modelling of subsurface CO2 storage was carried out on sandstone reservoirs of depleted gas fields in northeast Netherlands. It was found that mineral dissolution/precipitation has only a minor effect on reservoir porosity. In order to

  12. Preparation and photocatalytic properties of BaZrO3 and SrZrO3 modified with Cu2O/Bi2O3 quantum dots

    Science.gov (United States)

    Miodyńska, Magdalena; Bajorowicz, Beata; Mazierski, Paweł; Lisowski, Wojciech; Klimczuk, Tomasz; Winiarski, Michał Jerzy; Zaleska-Medynska, Adriana; Nadolna, Joanna

    2017-12-01

    In this study, we report a novel method of BaZrO3 and SrZrO3 surface modification by two different types of quantum dots (QDs, Cu2O and Bi2O3), which improved the photocatalytic performance of the obtained materials under UV-Vis light irradiation. Pristine BaZrO3 and SrZrO3 were prepared by the hydrothermal method. The deposition of Cu2O- and Bi2O3-QDs was carried out by chemical reduction. The morphology of the nanoparticles was estimated based on microscopic analysis (SEM, TEM). The perovskite structure and phase composition of polycrystals were confirmed by X-ray powder diffraction analysis (XRD). The elemental surface composition and the chemical character of detected elements were identified by X-ray photoelectron spectroscopy (XPS). The absorption ability and luminescence properties of nanocomposites were investigated by UV-Vis diffuse-reflectance spectroscopy (DRS UV-Vis) and luminescence spectroscopy. The influence of Cu2O/Bi2O3-QDs modification on the photocatalytic activity of BaZrO3 and SrZrO3 was evaluated by the phenol photodegradation process in the liquid phase under UV-Vis and toluene degradation in the gas phase under Vis irradiation. The highest photoactivity under UV-Vis light was observed for BaZrO3/1% Cu2O/33% Bi2O3 and SrZrO3/1% Cu2O/33% Bi2O3 samples. Research also demonstrated that single-type QD deposition (Cu2O or Bi2O3) on the zirconate surface decreases the photoactivity in comparison with pristine zirconates. The mechanism of photocatalytic activity of the obtained nanocomposites was investigated by the formation of hydroxyl radicals under UV-Vis irradiation in the presence of terephthalic acid.

  13. Adsorption heats of olefins on supported MoO3/Al2O3 catalists

    International Nuclear Information System (INIS)

    Grinev, V.E.; Madden, M.; Khalit, V.A.; Aptekar', E.L.; Aldag, A.; Krylov, O.V.

    1983-01-01

    Adsorption heats of C 2 H 4 , C 3 H 6 and C 4 H 8 on supported MoO 3 /Al 2 O 3 catalysts containing 6, 10 and 15 wt. % of MoO 3 at 25, 77 and 195 deg are determimed. Adsorption heat of an olefin increases with a growing length of its carbonic chain. The number of adsorbed olefin molecules grows with an increase in the MoO 3 concentration, while initial adsorption heats decrease. The number of adsorbed olefins is proportional to mean rate of molybdenum reduction in catalysts. Adsorption heats of oxygen on the surface of the catalysts with preliminarily adsorbed olefins are determined. It is shown that adsorption of oxygen and olefins proceeeds both on the same and on different centres of the surface. Mechanisms of surface interactions are discussed

  14. Manufacturing and investigation of surface morphology and optical properties of composite thin films reinforced by TiO2, Bi2O3 and SiO2 nanoparticles

    Science.gov (United States)

    Jarka, Paweł; Tański, Tomasz; Matysiak, Wiktor; Krzemiński, Łukasz; Hajduk, Barbara; Bilewicz, Marcin

    2017-12-01

    The aim of submitted paper is to present influence of manufacturing parameters on optical properties and surface morphology of composite materials with a polymer matrix reinforced by TiO2 and SiO2 and Bi2O3 nanoparticles. The novelty proposed by the authors is the use of TiO2 and SiO2 and Bi2O3 nanoparticles simultaneously in polymeric matrix. This allows using the combined effect of nanoparticles to a result composite material. The thin films of composite material were prepared by using spin-coating method with various spinning rates from solutions of different concentration of nanoparticles. In order to prepare the spinning solution polymer, Poly(methyl methacrylate) (PMMA) was used as a matrix. The reinforcing phase was the mixture of the nanoparticles of SiO2, TiO2 and B2O3. In order to identify the surface morphology of using thin films and arrangement of the reinforcing phase Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) were used. In order to study the optical properties of the obtained thin films, the thin films of composites was subjected to an ellipsometry analysis. The measurements of absorbance of the obtained materials, from which the value of the band gap width was specified, were carried out using the UV/VIS spectroscopy. The optical properties of obtain composite thin films depend not only on the individual components used, but also on the morphology and the interfacial characteristics. Controlling the participation of three kinds of nanoparticles of different sizes and optical parameters allows to obtaining the most optimal optical properties of nanocomposites and also controlling the deposition parameters allows to obtaining the most optimal surface morphology of nanocomposites.

  15. Fragile morphotropic phase boundary and phase stability in the near-surface region of the relaxor ferroelectric (1 -x ) Pb (Z n1 /3N b2 /3) O3-x PbTi O3 : [001] field-cooled phase diagrams

    Science.gov (United States)

    Wang, Yaojin; Wang, Ding; Yuan, Guoliang; Ma, He; Xu, Feng; Li, Jiefang; Viehland, D.; Gehring, Peter M.

    2016-11-01

    We have examined the effects of field cooling on the phase diagram of the relaxor system (1 -x ) Pb (Z n1 /3N b2 /3) O3-x PbTi O3 (PZN-x PT ) for compositions near the morphotropic phase boundary (MPB). High-resolution diffraction measurements using Cu Kα x rays, which probe ≈3 μ m below the crystal surface, were made on field-cooled (FC) single-crystal specimens of PZN-4.5 %PT and PZN-6.5 %PT under electric fields of 1 and 2 kV/cm applied along [001] and combined with previous neutron diffraction data, which probe the entire crystal volume, for FC PZN-8 %PT [Ohwada et al., Phys. Rev. B 67, 094111 (2003), 10.1103/PhysRevB.67.094111]. A comparison to the zero-field-cooled (ZFC) PZN-x PT phase diagram reveals several interesting features: (1) The short-range monoclinic phase observed in the ZFC state on the low-PT side of the MPB is replaced by a monoclinic MA phase; (2) field cooling extends the tetragonal phase to higher temperatures and lower-PT concentrations; (3) the orthorhombic phase near the MPB is replaced by a monoclinic MC phase; (4) the vertical MPB in the ZFC phase diagram bends significantly towards the low-PT side in the FC state. These results demonstrate that both the phase stability and the nature of the MPB in PZN-PT within the near-surface regions are fragile in the presence of electric fields.

  16. Revealing the atomic structure and strontium distribution in nanometer-thick La0.8Sr0.2CoO3−δ grown on (001)-oriented SrTiO3

    KAUST Repository

    Feng, Zhenxing

    2014-01-01

    Surface segregation in metal oxides can greatly influence the oxygen transport and surface oxygen exchange kinetics critical to the performance of solid-state devices such as oxygen permeation membranes and solid oxide fuel/electrolytic cell electrodes. Unfortunately detecting elemental distributions at the atomic scale near the surface remains challenging, which hampers the understanding of underpinning mechanisms and control of surface segregation for the design of high-performance materials. Using the coherent Bragg rod analysis (COBRA) method, we report the first direct 3D atomic imaging of a 4 nm-thick "La0.8Sr0.2CoO 3-δ"/SrTiO3 epitaxial film. Of significance, energy differential COBRA revealed pronounced Sr segregation (La 1-xSrxCoO3-δ, x ∼ 0.4) in the four unit cells from the top surface while complete Sr depletion was detected in the five unit cells from the "La0.8Sr0.2CoO 3-δ"/SrTiO3 interface. The drastic strontium compositional changes in the film were associated with large changes in the atomic positions of apical oxygen sites in the perovskite structure. Such Sr segregation tendencies toward the surface were also found in nominal "La0.6Sr0.4CoO3-δ" thin films, which can greatly enhance the surface oxygen exchange properties of oxides. The results presented here show that COBRA and the differential COBRA methods can be used to investigate a variety of electrochemically active systems providing atomic scale structural and chemical information that can help understand the physical and chemical properties of these systems and serve as a basis for comparison with DFT calculations. © 2014 The Royal Society of Chemistry.

  17. Capacitance-Voltage Characterization of La2O3 Metal-Oxide-Semiconductor Structures on In0.53Ga0.47As Substrate with Different Surface Treatment Methods

    Science.gov (United States)

    Zade, Dariush; Kanda, Takashi; Yamashita, Koji; Kakushima, Kuniyuki; Nohira, Hiroshi; Ahmet, Parhat; Tsutsui, Kazuo; Nishiyama, Akira; Sugii, Nobuyuki; Natori, Kenji; Hattori, Takeo; Iwai, Hiroshi

    2011-10-01

    We studied InGaAs surface treatment using hexamethyldisilazane (HMDS) vapor or (NH4)2S solution after initial oxide removal by hydrofluoric acid. The effect of each treatment on interface properties of La2O3/In0.53Ga0.47As metal-oxide-semiconductor (MOS) capacitor was evaluated. We found that HMDS surface treatment of InGaAs, followed by La2O3 deposition and forming gas annealing reduces the MOS capacitor's interface state density more effectively than (NH4)2S treatment. The comparison of the capacitance-voltage data shows that the HMDS-treated sample reaches a maximum accumulation capacitance of 2.3 µF/cm2 at 1 MHz with roughly 40% less frequency dispersion near accumulation, than the sample treated with (NH4)2S solution. These results suggest that process optimization of HMDS application could lead to further improvement of InGaAs MOS interface, thereby making it a potential routine step for InGaAs surface passivation.

  18. Surface integrity in tangential turning of hybrid MMC A359/B4C/Al2O3by abrasive waterjet

    Czech Academy of Sciences Publication Activity Database

    Srivastava, A. K.; Naga, A.; Dixita, A. R.; Tiwaric, S.; Ščučka, Jiří; Zeleňák, Michal; Hloch, Sergej; Hlaváček, Petr

    2017-01-01

    Roč. 28, č. 28 (2017), s. 11-20 ISSN 1526-6125 R&D Projects: GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : metal matrix composite * abrasive waterjet turning * surface topography * surface roughness * residual stresses Subject RIV: JQ - Machines ; Tools OBOR OECD: Mechanical engineering Impact factor: 2.322, year: 2016 http://www.sciencedirect.com/science/article/pii/S1526612517301287

  19. Synthesis of high-surface-area γ-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)

    International Nuclear Information System (INIS)

    Asencios, Yvan J.O.; Sun-Kou, María R.

    2012-01-01

    Highlights: ► Aluminum hydroxide obtained from aluminum scrap led to the formation of gamma alumina. ► Acidic pH of precipitation favored the formation of small particles of high surface areas. ► Higher aging temperature favored the formation of large structures of large pore sizes. ► Higher aging temperature generated symmetrical solids of regular hexagonal prism forms. ► Aluminas of large pores adsorbed metals as following: Pb (1.75 Å) > Cd (1.54 Å) > Zn (1.38 Å). - Abstract: Several types of alumina were synthesized from sodium aluminate (NaAlO 2 ) by precipitation with sulfuric acid (H 2 SO 4 ) and subsequently calcination at 500 °C to obtain γ-Al 2 O 3 . The precursor aluminate was derived from aluminum scrap. The various γ-Al 2 O 3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption–desorption of N 2 (S BET ) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al 2 O 3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m 2 g −1 ) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined.

  20. Caracterização superficial de nanopartículas de BaTiO3 preparado pelo método dos precursores poliméricos Surface characterization of BaTiO3 nanoparticles prepared by the polymeric precursor method

    Directory of Open Access Journals (Sweden)

    S. L. M. Brito

    2010-07-01

    Full Text Available A síntese de nanopartículas e a sua caracterização têm sido a grande mola propulsora do desenvolvimento de materiais nano-estruturados. Pouca atenção tem sido dedicada aos fenômenos físico-químicos relacionados às enormes superfícies intrínsecas destes materiais. Dentre eles, o titanato de bário ocupa uma posição de destaque devido ao seu grande potencial na geração de produtos de alta tecnologia. Neste estudo o BaTiO3 foi sintetizado pelo método dos precursores poliméricos, que proporciona a geração de nanopartículas de grande uniformidade química. Contudo, o uso de cátions que formam carbonatos de alta estabilidade pode inviabilizar o uso do método. Os pós de titanato de bário preparados apresentaram elevada área de superfície específica, porém com formação de fases parasitas de carbonato de bário e carbonatos adsorvidos na superfície do titanato de bário. O estudo da química de superfície utilizando métodos como espectroscopia de infravermelho e análises eletrocinéticas permitiu a caracterização deste contaminante e demonstraram indícios de condições específicas de dissolução do carbonato de bário, que podem possibilitar a descontaminação do titanato de bário.The advance in new nanostructured materials technology is promoted by the development of new synthesis and characterization methods. The attention on the enormous specific surface area intrinsically associated to this material family and specifically on the physical-chemistry properties has been underestimated. BaTiO3 is an important material for producing ferroelectric ceramics and special attention is focused on the large potential offered by the properties of nanoparticles of this oxide. Our work proposes the understanding of the surface properties of BaTiO3 nanoparticles prepared by the polymeric precursor method. We dedicated a particular attention to the carbonates species formed during the polymeric precursor pyrolysis on the

  1. Formation of a nano-pattering NiTi surface with Ni-depleted superficial layer to promote corrosion resistance and endothelial cell-material interaction.

    Science.gov (United States)

    Zhao, Tingting; Li, Yan; Xia, Yun; Venkatraman, Subbu S; Xiang, Yan; Zhao, Xinqing

    2013-01-01

    Zirconium ion implantation was performed on NiTi alloy to suppress Ni ion release as well as to improve corrosion resistance and cell-material interaction. A thicker Ni-depleted nano-scale composite layer formed after Zr implantation and the corrosion resistance was evidently increased in aspects of increased E(br) - E(corr) (difference between corrosion potential and breakdown potential) and decreased corrosion current density. 2.5/2 NiTi sample possessed the highest E(br) - E(corr), more than 500 mV higher than that of untreated NiTi, suggesting a significant improvement on pitting corrosion resistance. Ni ion release rate of Zr-NiTi was decreased due to the depletion of Ni in the superficial surface layer and the diffusion resistance effect of the ZrO(2)/TiO(2) nano-film. Increased surface wettability induced by increased surface roughness was obtained after Zr implantation. Zr-NiTi samples were found to be favorable to endothelial cells (ECs) proliferation, especially after 5 and 7 days culture.

  2. Physical-chemical properties of the surface of B2O3-P2O5-MeOx/SiO2 catalysts and its effect on the parameters of the process of aldol condensation of propionic acid with formaldehyde

    International Nuclear Information System (INIS)

    Yivasyiv, V.V.; Pyikh, Z.G.; Zhiznevs'kij, V.M.; Nebesnij, R.V.

    2011-01-01

    Effect of catalyst B 2 O 3 -P 2 O 5 -MeO x /SiO 2 composition on its physical-chemical properties has been investigated. Relations between physical-chemical and catalytic properties of catalysts in the gas-phase reaction of propionic acid with formaldehyde to methacrylic acid have been found. Effect of the specific surface area and the specific surface acidity on the propionic acid conversion has been determined. Effect of the acidic active site's strength on the selectivity of reaction products has been determined. It has been pointed that methacrylic acid is formed on the moderate strength acidic active sites, whereas the by-product (diethyl ketone) - on the strong acidic active sites of the catalyst.

  3. Chemical characterization of surface precipitates in La0.7Sr0.3Co0.2Fe0.8O3-δ as cathode material for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yang; Nikiforov, Alexey Y.; Kaspar, Tiffany C.; Woicik, Joseph C.; Ludwig, Karl F.; Gopalan, Srikanth; Pal, Uday B.; Basu, Soumendra N.

    2016-11-01

    In this study, a strontium doped lanthanum cobalt ferrite thin film with 30% Sr on A-site, denoted as La0.7Sr0.3Co0.2Fe0.8O3-δ or LSCF-7328, was investigated before and after annealing at 800 °C under CO2 containing atmosphere for 9 hours. The formation of secondary phases on surface of post-annealed LSCF-7328 has been observed using atomic force microscope (AFM) and scanning electron microscope (SEM). The extent of Sr segregation at the film surface was observed using the synchrotron-based total reflection X-ray fluorescence (TXRF) technique. The bonding environment of the secondary phases formed on the surface was investigated by synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Transmission electron microscope (TEM) and related spectroscopy techniques were used for microstructural and quantitative elemental analyses of the secondary phases on surface. These studies revealed that the secondary phases on surface consisted of SrO covered with a capping layer of SrCO3. The formation of Co-rich phases has also been observed on the surface of post-annealed LSCF-7328.

  4. Chemical characterization of surface precipitates in La0.7Sr0.3Co0.2Fe0.8O3-δ as cathode material for solid oxide fuel cells

    Science.gov (United States)

    Yu, Yang; Nikiforov, Alexey Y.; Kaspar, Tiffany C.; Woicik, Joseph C.; Ludwig, Karl F.; Gopalan, Srikanth; Pal, Uday B.; Basu, Soumendra N.

    2016-11-01

    In this study, a strontium doped lanthanum cobalt ferrite thin film with 30% Sr on A-site, denoted as La0.7Sr0.3Co0.2Fe0.8O3-δ or LSCF-7328, is investigated before and after annealing at 800 °C under CO2 containing atmosphere for 9 h. The formation of secondary phases on surface of post-annealed LSCF-7328 is observed using atomic force microscope (AFM) and scanning electron microscope (SEM). The extent of Sr segregation at the film surface is monitored using the synchrotron-based total reflection X-ray fluorescence (TXRF) technique. The bonding environment of the secondary phases formed on the surface is investigated by synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Scanning transmission electron microscopy (STEM) and related spectroscopy techniques are used for microstructural and quantitative elemental analyses of the secondary phases on surface. These studies reveal that the secondary phases on surface consist of SrO covered with a capping layer of SrCO3. The formation of Co-rich phases is observed on the surface of post-annealed LSCF-7328.

  5. Surface-initiated polymerization of 2-hydroxyethyl methacrylate from heterotelechelic oligoperoxide-coated .gamma.-Fe2O3 nanoparticles and their engulfment by mammalian cells

    Czech Academy of Sciences Publication Activity Database

    Horák, Daniel; Shagotova, Tetiana; Mitina, N.; Trchová, Miroslava; Boiko, N.; Babič, Michal; Stoika, R.; Kovářová, Jana; Hevus, O.; Beneš, Milan J.; Klyuchivska, O.; Holler, Petr; Zaichenko, A.

    2011-01-01

    Roč. 23, č. 10 (2011), s. 2637-2649 ISSN 0897-4756 R&D Projects: GA ČR GA203/09/1242; GA ČR GAP503/10/0664; GA AV ČR(CZ) KAN401220801 Institutional research plan: CEZ:AV0Z40500505 Keywords : 2-hydroxyethyl methacrylate * oligoperoxide * surface-initiated polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 7.286, year: 2011

  6. Polyvinylpyrrolidone/Multiwall Carbon Nanotube Composite Based 36 deg. YX LiTaO3 Surface Acoustic Wave For Hydrogen Gas Sensing Applications

    International Nuclear Information System (INIS)

    Chee, Pei Song; Arsat, Rashidah; He Xiuli; Arsat, Mahyuddin; Wlodarski, Wojtek; Kalantar-zadeh, Kourosh

    2011-01-01

    Poly-vinyl-pyrrolidone (PVP)/Multiwall Carbon Nanotubes (MWNTs) based Surface Acoustic Wave (SAW) sensors are fabricated and characterized, and their performances towards hydrogen gas are investigated. The PVP/MWNTs fibers composite are prepared by electrospinning of the composite aqueous solution deposited directly onto the active area of SAW transducers. Via scanning electron microscopy (SEM), the morphology of the deposited nanostructure material is observed. From the dynamic response, frequency shifts of 530 Hz (1%H 2 ) and 11.322 kHz (0.25%H 2 ) are recorded for the sensors contain of 1.525 g and 1.025 g PVP concentrations, respectively.

  7. In Situ Studies of the Temperature-Dependent Surface Structure and Chemistry of Single-Crystalline (001)-Oriented La 0.8 Sr 0.2 CoO 3−δ Perovskite Thin Films

    KAUST Repository

    Feng, Zhenxing

    2013-05-02

    Perovskites are used to promote the kinetics of oxygen electrocatalysis in solid oxide fuel cells and oxygen permeation membranes. Little is known about the surface structure and chemistry of perovskites at high temperatures and partial oxygen pressures. Combining in situ X-ray reflectivity (XRR) and in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we report, for the first time, the evolution of the surface structure and chemistry of (001)-oriented perovskite La0.8Sr0.2CoO 3-δ (LSC113) and (La0.5Sr 0.5)2CoO4+δ (LSC214)-decorated LSC113 (LSC113/214) thin films as a function of temperature. Heating the (001)-oriented LSC113 surface leads to the formation of surface LSC214-like particles, which is further confirmed by ex situ Auger electron spectroscopy (AES). In contrast, the LSC113/214 surface, with activities much higher than that of LSC 113, is stable upon heating. Combined in situ XRR and APXPS measurements support that Sr enrichment may occur at the LSC113 and LSC214 interface, which can be responsible for its markedly enhanced activities. © 2013 American Chemical Society.

  8. Computation and empirical modeling of UV flux reaching Arabian Sea due to O3 hole

    International Nuclear Information System (INIS)

    Yousufzai, M. Ayub Khan

    2008-01-01

    Scientific organizations the world over, such as the European Space Agency, the North Atlantic Treaty Organization, the National Aeronautics and Space Administration, and the United Nations Organization, are deeply concerned about the imbalances, caused to a significant extent due to human interference in the natural make-up of the earth's ecosystem. In particular, ozone layer depletion (OLD) over the South Pole is already a serious hazard. The long-term effect of ozone layer depletion appears to be an increase in the ultraviolet radiation reaching the earth. In order to understand the effects of ozone layer depletion, investigations have been initiated by various research groups. However, to the best of our knowledge, there does not seem to be available any work treating the problem of computing and constructing an empirical model for the UV flux reaching the Arabian Sea surface due to the O3 hole. The communication presents the results of quantifying UV flux and modeling future estimation using time series analysis in a local context to understand the nature of the depletion. (author)

  9. A novel tri-layer flexible piezoelectric nanogenerator based on surface- modified graphene and PVDF-BaTiO3 nanocomposites

    Science.gov (United States)

    Yaqoob, Usman; Uddin, A. S. M. Iftekhar; Chung, Gwiy-Sang

    2017-05-01

    The fabrication and characterization of a novel tri-layer piezoelectric nanogenerator (PNG) based on poly(vinylidene fluoride) (PVDF), barium titanate (BTO), and surface-modified n- type graphene (n-Gr) have been investigated. The n-Gr, with its majority of negative charge carriers, plays a vital role in enhancing the energy-harvesting performance by aligning the dipoles in one direction. The tri-layer structure obtains by stacking two layers of PVDF-BTO nanocomposite films, one on each side of the n-Gr layer. The fabricated tri-layer PNG shows a maximum output voltage of 10 V (pk-pk) along with a current of 2.5 μA (pk-pk) at an applied force of 2 N. Furthermore, the PNG Exhibits 5.8 μW instantaneous power at 1 MΩ load resistance. Moreover, the fabricated device demonstrated good stability even after 1000 pressing-releasing cycles. This novel tri-layer PNG structure can opens a promising avenue for future piezoelectric generating technologies.

  10. Impact of La2O3 interfacial layers on InGaAs metal-oxide-semiconductor interface properties in Al2O3/La2O3/InGaAs gate stacks deposited by atomic-layer-deposition

    Science.gov (United States)

    Chang, C.-Y.; Ichikawa, O.; Osada, T.; Hata, M.; Yamada, H.; Takenaka, M.; Takagi, S.

    2015-08-01

    We examine the electrical properties of atomic layer deposition (ALD) La2O3/InGaAs and Al2O3/La2O3/InGaAs metal-oxide-semiconductor (MOS) capacitors. It is found that the thick ALD La2O3/InGaAs interface provides low interface state density (Dit) with the minimum value of ˜3 × 1011 cm-2 eV-1, which is attributable to the excellent La2O3 passivation effect for InGaAs surfaces. It is observed, on the other hand, that there are a large amount of slow traps and border traps in La2O3. In order to simultaneously satisfy low Dit and small hysteresis, the effectiveness of Al2O3/La2O3/InGaAs gate stacks with ultrathin La2O3 interfacial layers is in addition evaluated. The reduction of the La2O3 thickness to 0.4 nm in Al2O3/La2O3/InGaAs gate stacks leads to the decrease in hysteresis. On the other hand, Dit of the Al2O3/La2O3/InGaAs interfaces becomes higher than that of the La2O3/InGaAs ones, attributable to the diffusion of Al2O3 through La2O3 into InGaAs and resulting modification of the La2O3/InGaAs interface structure. As a result of the effective passivation effect of La2O3 on InGaAs, however, the Al2O3/10 cycle (0.4 nm) La2O3/InGaAs gate stacks can realize still lower Dit with maintaining small hysteresis and low leakage current than the conventional Al2O3/InGaAs MOS interfaces.

  11. Fermi Surface of Three-Dimensional La(1-x)Sr(x)MnO3 Explored by Soft-X-Ray ARPES: Rhombohedral Lattice Distortion and its Effect on Magnetoresistance.

    Science.gov (United States)

    Lev, L L; Krempaský, J; Staub, U; Rogalev, V A; Schmitt, T; Shi, M; Blaha, P; Mishchenko, A S; Veligzhanin, A A; Zubavichus, Y V; Tsetlin, M B; Volfová, H; Braun, J; Minár, J; Strocov, V N

    2015-06-12

    Electronic structure of the three-dimensional colossal magnetoresistive perovskite La(1-x)Sr(x)MnO3 has been established using soft-x-ray angle-resolved photoemission spectroscopy with its intrinsically sharp definition of three-dimensional electron momentum. The experimental results show much weaker polaronic coupling compared to the bilayer manganites and are consistent with the theoretical band structure including the empirical Hubbard parameter U. The experimental Fermi surface unveils the canonical topology of alternating three-dimensional electron spheres and hole cubes, with their shadow contours manifesting the rhombohedral lattice distortion. This picture has been confirmed by one-step photoemission calculations including displacement of the apical oxygen atoms. The rhombohedral distortion is neutral to the Jahn-Teller effect and thus polaronic coupling, but affects the double-exchange electron hopping and thus the colossal magnetoresistance effect.

  12. Intrinsic Depletion or Not

    DEFF Research Database (Denmark)

    Klösgen, Beate; Bruun, Sara; Hansen, Søren

      The presence of a depletion layer of water along extended hydrophobic interfaces, and a possibly related formation of nanobubbles, is an ongoing discussion. The phenomenon was initially reported when we, years ago, chose thick films (~300-400Å) of polystyrene as cushions between a crystalline...... carrier and biomimetic membranes deposited thereupon and exposed to bulk water. While monitoring the sequential build-up of the sandwiched composite structure by continuous neutron reflectivity experiments the formation of an unexpected additional layer was detected (1). Located at the polystyrene surface...... in between he polymer cushion and bulk water the layer was attributed to water of reduced density and was called "depletion layer".  Impurities or preparative artefacts were excluded as its origin. Later on, the formation of nanobubbles from this vapour-like water phase was initiated by tipping the surface...

  13. Switchable Induced Polarization in LaAlO3/SrTiO3 Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bark, C [University of Wisconsin, Madison; Sharma, P. [University of Nebraska; Wang, Y. [University of Nebraska; Baek, Seung Hyub [University of Wisconsin, Madison; Lee, S. [University of Wisconsin, Madison; Ryu, S. [University of Wisconsin, Madison; Folkman, C H [University of Wisconsin; Paudel, Tula R [ORNL; Kumar, Amit [ORNL; Kalinin, Sergei V [ORNL; Sokolov, A. [University of Nebraska; Tsymbal, E Y [University of Nebraska, Lincoln; Rzchowski, M [University of Wisconsin; Gruverman, Alexei [ORNL; Eom, Professor Chang-Beom [University of Wisconsin, Madison

    2012-01-01

    Demonstration of a tunable conductivity of the LaAlO3/SrTiO3 interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO3 surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the twodimensional electron gas (2DEG) density at the LaAlO3/SrTiO3 (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.

  14. Leukocytes-depleting filters preferentially remove activated leukocytes and reduce the expression of surface adhesion molecules during the simulated extracorporeal circulation of human blood.

    Science.gov (United States)

    Alexiou, Christos; Sheppard, Stuart; Tang, Augustine; Rengarajan, Arvind; Smith, David; Haw, Marcus; Gibbs, Roz

    2006-01-01

    The effect of leukocyte-depleting filters on the total and activated leukocyte counts and the expression of surface adhesion molecules CD11b, CD18, and CD62L during the in vitro extracorporeal circulation of human blood was studied. A 200 ml blood sample was taken from 10 patients undergoing CABG surgery. The blood was circulated for 60 minutes within an experimental extracorporeal circuit. A leukocyte-depleting filter was attached in five circuits (filtered group). In five other circuits, no filter was used (controls). Total leukocyte counts were determined manually. Activated leukocytes were identified using nitroblue tetrazolium staining. The expression of CD11b, CD18, and CD62L was measured with flow cytometry. At 60 minutes, total leukocyte counts were reduced by 49% from the baseline values in the filtered group and 10% in the control group (p filtered group and increased by 116% in the control group (p filtered group, the expression of CD11b, CD18, and CD612L decreased by 60%, 21%, and 79%, respectively, and in the control group it increased by 24%, 6%, and 28% (p filters preferentially remove activated leukocytes and reduce the expression of CD11b, CD18, and CD62L during the in vitro extracorporeal circulation of human blood.

  15. Sensitivity of δ15N of nitrate, surface suspended and deep sinking particulate nitrogen to seasonal nitrate depletion in the Southern Ocean

    Science.gov (United States)

    Lourey, Martin J.; Trull, Thomas W.; Sigman, Daniel M.

    2003-09-01

    We report measurements of the δ15N of nitrate, suspended particulate nitrogen (PN), and sinking PN from cruises and moored sediment traps in the Subantarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia. As expected, surface water nitrate δ15N increased as nitrate was consumed during the spring/summer bloom. In contrast, the seasonal cycles of surface water suspended and sinking PN δ15N did not fit expectations from nitrate assimilation alone. Rather than increasing, the δ15N of surface suspended PN was relatively constant in the SAZ (at ˜1‰), and decreased during the summer in the PFZ (from ˜0 to ˜-4‰), most likely due to the production of low 15N PN by summertime ammonium recycling. Deep sediment trap PN δ15N also displayed seasonal decreases (from ˜4 to ˜1‰ in the SAZ, and from ˜3.5 to ˜0.5‰ in the PFZ), which correlated with PON flux magnitude. During high-flux periods, exported PN δ15N values were close to expectations from nitrate-based export, but low-flux periods exhibited higher δ15N, consistent with either a reduction in the isotope effect of nitrate assimilation or more extensive isotopic alteration of the sinking material during low-flux periods. The mass balance between net nitrate supply and exported PN that links sinking flux δ15N to nitrate utilization requires only that the annually integrated (rather than the seasonally varying) sinking flux of PN δ15N correlates with nitrate depletion. While a correlation between annually integrated sinking PN δ15N to nitrate depletion was observed in both the SAZ and PFZ, the sensitivity of sinking PN δ15N to nitrate depletion was lower than expected. Moreover, the seasonal observations raise the possibility that loss of the summertime high-flux period represents an alternative explanation to increased nitrate utilization for the high sedimentary PN δ15N observed during glacial periods.

  16. TiO3 borosilicate glass–ceramics

    Indian Academy of Sciences (India)

    phase of the glass–ceramic sample with x ≤ 0·5 was found to have cubic structure similar to SrTiO3 ceramic. Scanning electron microscopy has been carried out to see the surface morphology of the crystallites dispersed in the glassy matrix. Keywords. (PbSr)TiO3 borosilicate glasses; infrared spectroscopy; DTA; XRD and ...

  17. Assessment of groundwater/surface-water interaction and simulation of potential streamflow depletion induced by groundwater withdrawal, Uinta River near Roosevelt, Utah

    Science.gov (United States)

    Lambert, P.M.; Marston, T.; Kimball, B.A.; Stolp, B.J.

    2011-01-01

    Roosevelt City, Utah, asserts a need for an additional supply of water to meet municipal demands and has identified a potential location for additional groundwater development at the Sprouse well field near the West Channel of the Uinta River. Groundwater is commonly hydraulically linked to surface water and, under some conditions, the pumpage of groundwater can deplete water in streams and other water bodies. In 2008, the U.S. Geological Survey, in cooperation with Roosevelt City, the Utah Department of Natural Resources, and the Ute Indian Tribe, began a study to improve understanding of the local interconnection between groundwater and surface water and to assess the potential for streamflow depletion from future groundwater withdrawals at a potential Roosevelt City development location—the Sprouse well field near the West Channel of the Uinta River.In the study, streamflow gains and losses at the river/aquifer boundary near the well field and changes in those conditions over time were assessed through (1) synoptic measurement of discharge in the stream at multiple sites using tracer-dilution methods, (2) periodic measurement of the vertical hydraulic gradient across the streambed, and (3) continuous measurement of stream and streambed water temperature using heat as a tracer of flow across the streambed. Although some contradictions among the results of the three assessment methods were observed, results of the approaches generally indicated (1) losing streamflow conditions on the West Channel of the Uinta River north of and upstream from the Sprouse well field within the study area, (2) gaining streamflow conditions south of and downstream from the well field, and (3) some seasonal changes in those conditions that correspond with seasonal changes in stream stage and local water-table altitudes.A numerical groundwater flow model was developed on the basis of previously reported observations and observations made during this study, and was used to estimate

  18. Zn2(TeO3Br2

    Directory of Open Access Journals (Sweden)

    Mats Johnsson

    2008-05-01

    Full Text Available Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetrahedra, and [TeO3E] tetrahedra (E being the 5s2 lone pair of Te4+ joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3Br2 is isostructural with the synthetic compounds Zn2(TeO3Cl2, CuZn(TeO32, Co2(TeO3Br2 and the mineral sophiite, Zn2(SeO3Cl2.

  19. Effect of Wood Flour Addition on the Pore Volume and BET Surface Area Properties of the Prepared Gamma Alumina (ɤ-Al2O3 Extrudates Used in Catalyst Carriers

    Directory of Open Access Journals (Sweden)

    Alaa D. Jawad Al-Bayati

    2015-11-01

    Full Text Available The effect of Wood Flour addition to the gamma alumina powder used in the preparation of gamma alumina (ɤ-Al2O3 catalyst carrier extrudates on the pore volume and BET surface area physical properties was investigated. Two parameters which are size of wood flour particles and its quantity were studied. The sizes of wood flour particles used are 150 µm, 212 µm and 500 µm and the weight percentage added to the gamma alumina powder during the preparation of the extrudates are (1%, 3%, 5% and 10%. The results showed that the addition of wood flour to the gamma alumina powder in order to get gamma alumina extrudates used as catalyst carrier is one of the successful methods to improve the pore volume and BET surface area of the alumina extrudates. The size of wood flour particles and its quantity have main effect on the above texture properties. The smaller the size of wood flour leaded to higher BET surface area, where maximum BET surface area of 127.3 m2/g was got with addition 10% by weight wood flour of 150µm particle size. BET surface area for the same addition percentage of 10% resulted to 114.5m2/g and 105.2m2/g when adding wood flour of 212 µm and 500 µm particle sizes respectively. The weight percentage of wood flour addition has an effect on the BET surface area, where the 3% addition gives maximum BET surface area when the size of the wood flour particles is 500 µm. Regarding the pore volume property for the gamma alumina prepared extrudates, the results showed that the pore volume of the extrudates increased to 0.83 cm3/g and 1.0 cm3/g when 10% wood flour of 150 µm and 500 µm particle sizes were added respectively. The maximum BET surface area was reached when 10% wood flour of 150 µm particle size was added, and the maximum pore volume was reached when 10% wood flour of 500 µm particle size was added, the increase percentage for the BET surface area and pore volume is more than 40% and 400% respectively.

  20. Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

    Science.gov (United States)

    Wang, Wenjie; Zhang, Honghu; Mallapragada, Surya; Travesset, Alex; Vaknin, David

    2017-12-01

    In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol-capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4 ) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that in the bulk.

  1. Scanning probe manipulation of magnetism at the LaAlO3/SrTiO3 heterointerface.

    Science.gov (United States)

    Kalisky, Beena; Bert, Julie A; Bell, Christopher; Xie, Yanwu; Sato, Hiroki K; Hosoda, Masayuki; Hikita, Yasuyuki; Hwang, Harold Y; Moler, Kathryn A

    2012-08-08

    Manipulation of magnetism is a longstanding goal of research in exotic materials. In this work, we demonstrate that the small ferromagnetic patches in LaAlO(3)/SrTiO(3) heterostructures can be dramatically changed by in situ contact of a scanning probe. Our results provide a platform for manipulation of small magnets through either a strong magneto-elastic coupling or sensitivity to surface modification. The ability to locally control magnetism is particularly interesting due to the presence of superconductivity with strong spin-orbit coupling in LaAlO(3)/SrTiO(3).

  2. High field-effect mobility at the (Sr,Ba)SnO3/BaSnO3 interface

    Science.gov (United States)

    Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

    2016-08-01

    A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,Ba)SnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,Ba)SnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  3. High field-effect mobility at the (Sr,BaSnO3/BaSnO3 interface

    Directory of Open Access Journals (Sweden)

    Kohei Fujiwara

    2016-08-01

    Full Text Available A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,BaSnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,BaSnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  4. Role of hybrid ratio in microstructural, mechanical and sliding wear properties of the Al5083/Graphitep/Al2O3p a surface hybrid nanocomposite fabricated via friction stir processing method

    International Nuclear Information System (INIS)

    Mostafapour Asl, A.; Khandani, S.T.

    2013-01-01

    Hybrid ratio of each reinforcement phase in hybrid composite can be defined as proportion of its volume to total reinforcement volume of the composite. The hybrid ratio is an important factor which controls the participation extent of each reinforcement phase in overall properties of hybrid composites. Hence, in the present work, surface hybrid nanocomposites of Al5083/Graphite p /Al 2 O 3p with different hybrid ratios were fabricated by friction stir processing method. Subsequently, effect of hybrid ratio on microstructural, mechanical and tribological properties of the nanocomposite was investigated. Optical microscopy and scanning electron microscopy were utilized to perform microstructural observation on the samples. Hardness value measurements, tensile and pin on disk dry sliding wear tests were carried out to investigate effect of hybrid ratio on mechanical and tribological properties of the nanocomposites. Microstructural investigations displayed better distribution with less agglomeration of reinforcement for lower volume fraction of reinforcement for both alumina and graphite particles. Hardness value, yield strength, ultimate tensile strength and wear rate of the nanocomposites revealed a two stage form along with hybrid ratio variation. The results are discussed based on microstructural observations of the nanocomposites and worn surface analyses.

  5. Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: Kinetics of micropollutant abatement, transformation product and bromate formation in a surface water.

    Science.gov (United States)

    Bourgin, Marc; Borowska, Ewa; Helbing, Jakob; Hollender, Juliane; Kaiser, Hans-Peter; Kienle, Cornelia; McArdell, Christa S; Simon, Eszter; von Gunten, Urs

    2017-10-01

    The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L -1 . Two pilot-scale ozonation reactors (4-5 m 3  h -1 ), a 4-chamber reactor and a tubular reactor, were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O 3 /H 2 O 2 . The effects of selected operational parameters, such as ozone dose (0.5-3 mg L -1 ) and H 2 O 2 dose (O 3 :H 2 O 2  = 1:3-3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5-8.5) and initial bromide concentration (15-200 μg L -1 ), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constants k O3 >10 4  M -1  s -1 for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg L -1 . Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H 2 O 2 addition accelerated the ozone conversion to OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr - with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX), respectively, was assessed by chemical analysis and kinetic modeling. Both selected TPs were quickly formed initially

  6. Structural and electronic properties of Ag-Pd bimetallic clusters on Al2O3 substrates: A first principles study

    Science.gov (United States)

    Nigam, Sandeep; Majumder, Chiranjib

    2012-06-01

    We report the structure and electronic properties of AgmPdn bimetallic clusters (m, n = 1-2) in gas phase and deposited on the α-Al2O3(0 0 0 1) surface using plane wave pseudopotential approach. The ground state geometry of the mixed clusters is significantly modified after deposition. For Ag2Pd2 tetramer, the gas phase compact tetrahedron structure reorients to open bent rhombus. The charge distribution analysis shows that small amount of charge is accumulated at the Pd site and depleted at the Ag site. The electronic density of states analysis reveals that after deposition, the bands near the Fermi energy become wider.

  7. Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

    Science.gov (United States)

    Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

    2018-03-21

    Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

  8. New insight into electrochemical-induced synthesis of NiAl2O4/Al2O3: Synergistic effect of surface hydroxyl groups and magnetism for enhanced adsorptivity of Pd(II)

    International Nuclear Information System (INIS)

    Salleh, N.F.M.; Jalil, A.A.; Triwahyono, S.; Efendi, J.; Mukti, R.R.; Hameed, B.H.

    2015-01-01

    Graphical abstract: - Highlights: • The introduction of Ni to γ-Al 2 O 3 by electrolysis formed NiAl 2 O 4 spinels and NiO. • Physical mixed of NiO with γ-Al 2 O 3 only produced agglomerated NiO-Ni 0 . • Ni/Al 2 O 3 -E has remarkably higher degree of magnetism than Ni/Al 2 O 3 -PM. • Ni/Al 2 O 3 -E adsorbed Pd 2+ ions more effectively (q m = 40.3 mg/g) than Ni/Al 2 O 3 -PM. • Pd 2+ ions were adsorbed to both samples via magnetic attraction and ion exchange. - Abstract: A new promising adsorbent, Ni supported on γ-Al 2 O 3 was prepared in a simple electrolysis system (Ni/Al 2 O 3 -E) in minutes and was compared with the sample prepared by a physical mixing method (Ni/Al 2 O 3 -PM). The adsorbents were characterized by XRD, TEM, FTIR, 27 Al MAS NMR, XPS, and VSM. The results showed that besides NiO nanoparticles, a NiAl 2 O 4 spinel was also formed in Ni/Al 2 O 3 -E during the electrolysis via the dealumination and isomorphous substitution of Ni 2+ ions. In contrast, only agglomerated NiO was found in the Ni/Al 2 O 3 -PM. Adsorption test on removal of Pd 2+ ions from aqueous solution showed that the Pd 2+ ions were exchanged with the hydrogen atoms of the surface–OH groups of both adsorbents. Significantly, the Ni/Al 2 O 3 -E demonstrated a higher adsorption towards Pd 2+ ions than Ni/Al 2 O 3 -PM due to its remarkably higher degree of magnetism, which came from the NiAl 2 O 4 . The use of 0.1 g L −1 Ni/Al 2 O 3 -E gave the maximum monolayer adsorption capacity (q m ) of 40.3 mg g −1 at 303 K and pH 5. The Ni/Al 2 O 3 -E showed high potential for simultaneous removal of various noble and transition metal ions and could be also used repetitively without affecting the high adsorptivity for Pd 2+ ions. This work may provide promising adsorbents for recovery of various metals as well as other materials for such related applications

  9. On-farm irrigation reservoirs for surface water storage in eastern Arkansas: Trends in construction in response to aquifer depletion

    Science.gov (United States)

    Yaeger, M. A.; Reba, M. L.; Massey, J. H.; Adviento-Borbe, A.

    2017-12-01

    On-farm surface water storage reservoirs have been constructed to address declines in the Mississippi River Valley Alluvial aquifer, the primary source of irrigation for most of the row crops grown in eastern Arkansas. These reservoirs and their associated infrastructure represent significant investments in financial and natural resources, and may cause producers to incur costs associated with foregone crop production and long-term maintenance. Thus, an analysis of reservoir construction trends in the Grand Prairie Critical Groundwater Area (GPCGA) and Cache River Critical Groundwater Area (CRCGA) was conducted to assist future water management decisions. Between 1996 and 2015, on average, 16 and 4 reservoirs were constructed per year, corresponding to cumulative new reservoir surface areas of 161 and 60 ha yr-1, for the GPCGA and the CRCGA, respectively. In terms of reservoir locations relative to aquifer status, after 1996, 84.5% of 309 total reservoirs constructed in the GPCGA and 91.0% of 78 in the CRCGA were located in areas with remaining saturated aquifer thicknesses of 50% or less. The majority of new reservoirs (74% in the GPCGA and 63% in the CRCGA) were constructed on previously productive cropland. The next most common land use, representing 11% and 15% of new reservoirs constructed in the GPCGA and CRCGA, respectively, was the combination of a field edge and a ditch, stream, or other low-lying area. Less than 10% of post-1996 reservoirs were constructed on predominately low-lying land, and the use of such lands decreased in both critical groundwater areas during the past 20 years. These disparities in reservoir construction rates, locations, and prior land uses is likely due to groundwater declines being first observed in the GPCGA as well as the existence of two large-scale river diversion projects under construction in the GPCGA that feature on-farm storage as a means to offset groundwater use.

  10. TiO3 ceramics

    Indian Academy of Sciences (India)

    Administrator

    High purity Bi2O3, Na2CO3, TiO2, MgCO3 and Nb2O5. (purity over 99⋅5%) powders were used as starting mate- rials. Our preliminary experiments found that (Bi1/2Na1/2). Ti1–x(Mg1/3Nb2/3)xO3 ceramics were not well synthesized by mixing and calcinating all these above powders as used in the conventional oxide ...

  11. Effects of surface modification with Co3O4 nanoparticles on the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ membranes

    Science.gov (United States)

    Wang, Yu; Cheng, Jigui; Huang, Min; Liu, Meng; Li, Mingming; Xu, Chenxi

    2017-09-01

    To promote the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) membranes, Co3O4 nanoparticle catalysts were loaded onto the surfaces of BSCF membranes by a dip-coating process. X-ray diffraction (XRD) results reveal that Co3O4 nanoparticles crystalize in spinel phase. Scanning electron microscope (SEM) observation indicates that the mean particle size of the Co3O4 nanoparticles is about 100 nm in diameter and 20 μm in thickness after annealing at 500 °C for 5 h. Energy dispersive spectrometer (EDS) results testify that the percentage of the elements in the modified layer are in accordance with the stoichiometric ratio of Co3O4. Oxygen permeation tests were made in a laboratory self-made device, and the results show that loading Co3O4 nanoparticle catalysts onto the surfaces of BSCF membranes can significantly increase the oxygen permeability of the BSCF membranes. The unmodified BSCF membranes have an oxygen permeation flux of 0.1080 ml cm-2 min-1 at 600 °C. This increases to 0.4302 ml cm-2 min-1, for the modified membranes, which is four times higher than that of the unmodified BSCF membranes. The oxygen permeation activation energy decreases from 91.42 to 50.71 kJ mol-1 at 600-800 °C by loading Co3O4 nanoparticle catalysts on the surface of BSCF membranes.

  12. In-Situ Catalytic Surface Modification of Micro-Structured La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF Oxygen Permeable Membrane Using Vacuum-Assisted technique

    Directory of Open Access Journals (Sweden)

    Othman Nur Hidayati

    2016-01-01

    Full Text Available This paper aims at investigating the means to carry out in-situ surface modification of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF oxygen permeable membrane by using vacuum assisted technique. The unique structure of the LSCF hollow fibre membrane used in this study, which consists of an outer dense oxygen separation layer and conical-shaped microchannels open at the inner surface has allowed the membrane to be used as oxygen separation membrane and as a structured substrate for where catalyst can be deposited. A catalyst solution of similar material, LSCF was prepared using sol-gel technique. Effects of calcination temperature and heating rate were investigated using XRD and TGA to ensure pure perovskites structure of LSCF was obtained. It was found that a lower calcination temperature can be used to obtain pure perovskite phase if slower heating rate is used. The SEM photograph shows that the distribution of catalyst onto the membrane microchannels using in-situ deposition technique was strongly related to the viscosity of LSCF catalytic sol. Interestingly, it was found that the amount of catalyst deposited using viscous solution was slightly higher than the less viscous sol. This might be due to the difficulty of catalyst sol to infiltrate the membrane and as a result, thicker catalyst layer was observed at the lumen rather than onto the conical-shaped microchannels. Therefore, the viscosity of catalyst solution and calcination process should be precisely controlled to ensure homogeneous catalyst layer deposition. Analysis of the elemental composition will be studied in the future using energy dispersive X-ray Spectroscopy (EDX to determine the elements deposited onto the membranes. Once the elemental analysis is confirmed, oxygen permeation analysis will be carried out.

  13. Review of Liquidus Surface and Phase Equilibria in the TiO2-SiO2-Al2O3-MgO-CaO Slag System at PO2 Applicable in Fluxed Titaniferous Magnetite Smelting

    Science.gov (United States)

    Goso, Xolisa; Nell, Johannes; Petersen, Jochen

    The current liquidus surface and phase equilibria established in air for fluxed titaniferous magnetite (titanomagnetite) slags conforming to a composition of 37.19% TiO2, 19.69% SiO2, 13.12% Al2O3, and 30.00% of various ratios of CaO+MgO were reviewed at applicable PO2 using FactSage simulation and phase composition of a real plant titanomagnetite slag. The testwork included the incorporation into FactSage of a private MgTi2O5-Al2TiO5 pseudobrookite solution model. The results of the investigation showed that the liquidus surface and Ti3+/ Ti4+ mass fraction ratio increased with decreasing the PO2, At low PO2, perovskite crystallizes as a primary phase at high CaO content. The spinel solution, i.e. (Mg)(Al,Ti)O4, generally crystallizes as the primary phase at high MgO contents, though it is replaced by MgTi2O5-Al2TiO5 solution at PO2 of 10-10 atm to 10-15 atm. An intermediate equilibrium phase diagram established at PO2 of 10-16 atm is proposed. This phase diagram does not show the observed primary phase crystallization competition, however, the phase composition of a real titanomagnetite slag produced by Evraz Highveld Steel and Vanadium Corporation in South Africa does show primary phase crystallization competition between (Mg)(Al,Ti)2O4 and MgTi2O5-Al2TiO5. Smelting involving such slags is likely conducted around the transition PO2, i.e. PO2 of about 10-16 atm. Complex modelling with MgTi2O5, Al2TiO5 and Ti3O5 end members and experiments are underway to verify and update the intermediate phase diagram.

  14. Analytical Modeling of Unsteady Aluminum Depletion in Thermal Barrier Coatings

    OpenAIRE

    YEŞİLATA, Bülent

    2014-01-01

    The oxidation behavior of thermal barrier coatings (TBCs) in aircraft turbines is studied. A simple, unsteady and one-dimensional, diffusion model based on aluminum depletion from a bond-coat to form an oxide layer of Al2O3 is introduced. The model is employed for a case study with currently available experimental data. The diffusion coefficient of the depleted aluminum in the alloy, the concentration profiles at different oxidation times, and the thickness of Al-depleted region are...

  15. Total column density variations of ozone (O3 O3 O3) in presence of ...

    Indian Academy of Sciences (India)

    solar zenith angles (SZAs). The slant column densities (SCDs) as well as total column densities (TCDs) of NO2, O3, H2O and O4 are derived with different SZAs in clear and cloudy sky conditions. The large enhancements and reductions in TCDs of the above gases are observed in thick cumulonimbus (Cb) clouds and thin ...

  16. Processing of Piezoelectric (Li,Na,K)NbO3 Porous Ceramics and (Li,Na,K)NbO3/KNbO3 Composites

    Science.gov (United States)

    Kakimoto, Ken-ichi; Imura, Tomoya; Fukui, Yasuchika; Kuno, Masami; Yamagiwa, Katsuya; Mitsuoka, Takeshi; Ohbayashi, Kazushige

    2007-10-01

    Porous Li0.06(Na0.5K0.5)0.94NbO3 (LNKN-6) ceramics with different pore volumes have been prepared using preceramic powder and phenol resin fiber (KynolTM) as a pore former. It was confirmed that the porous ceramics synthesized by the “two-stage firing method” suppressed the loss of alkali elements from the porous body during heat treatment. The porous LNKN-6 ceramics were then converted to LNKN-6/KNbO3 composites through soaking and heat treatment using a sol-gel precursor source composed of KNbO3 to form 3-3-type composites. The microstructure, dielectric, and piezoelectric properties of the porous LNKN-6 ceramics and LNKN-6/KNbO3 composites were characterized and compared. The LNKN-6/KNbO3 composites had a hollow structure whose pores in the region near the surface were filled and coated with KNbO3 precipitates; however, a large amount of residual air was trapped in the pores inside the composites. As a result, the LNKN-6/KNbO3 composites fabricated using 30 vol % KynolTM showed an enhanced piezoelectric voltage output coefficient (g33) of 63.0× 10-3 V\\cdotm/N, compared with monolithic LNKN-6 ceramics having a g33 of 30.2× 10-3 V\\cdotm/N.

  17. Facile and efficient synthesis of the surface tantalum hydride (≡SiO)2TaIIIH and tris-siloxy tantalum (≡SiO)3TaIII starting from novel tantalum surface species (≡SiO)TaMe4 and (≡SiO)2TaMe 3

    KAUST Repository

    Chen, Yin

    2014-03-10

    By grafting of TaMe5 (1) on the surface of silica partially dehydroxylated at 500 C (silica500), a mixture of (≡SiO)TaMe4 (2a; major, 65 ± 5%) and (≡SiO) 2TaMe3 (2b; minor, 35 ± 5%) was produced, which has been characterized by microanalysis, IR, and SS NMR (1H, 13C, 1H-13C HETCOR, proton double and triple quantum). After grafting, these surface organometallic compounds are more stable than the precursor TaMe5. Treatment of 2a,b with water and H 2 resulted in the formation of methane in amount of 3.6 ± 0.2 and 3.4 ± 0.2 mol/grafted Ta, respectively. 2a,b react with H2 (800 mbar) to form (≡SiO)2TaH. After (≡SiO) 2TaH was heated to 500 C under hydrogen or vacuum, [(≡SiO) 3Ta][≡SiH] was produced, and the structure was confirmed by IR, NMR, and EXAFS. Considering the difficulty of the previous preparation method, these syntheses represent a facile and convenient way to prepare tantalum surface species (≡SiO)2TaH and (≡SiO)3Ta via the intermediate of the new surface organometallic precursors: (≡SiO)TaMe4/(≡SiO)2TaMe3. (≡SiO)2TaH and (≡SiO)3Ta exhibit equal reactivities in alkane metathesis and ethylene polymerization in comparison to those in previous reports. © 2014 American Chemical Society.

  18. Evolution of the SrTiO3/MoO3 interface electronic structure: An in situ photoelectron spectroscopy study

    KAUST Repository

    Du, Yuanmin

    2015-05-12

    Modifying the surface energetics, particularly the work function, of advanced materials is of critical importance for a wide range of surface- and interface-based devices. In this work, using in situ photoelectron spectroscopy, we investigated the evolution of electronic structure at the SrTiO3 surface during the growth of ultrathin MoO3 layers. Thanks to the large work function difference between SrTiO3 and MoO3, the energy band alignment on the SrTiO3 surface is significantly modified. The charge transfer and dipole formation at the SrTiO3/MoO3 interface leads to a large modulation of work function and an apparent doping in SrTiO3. The measured evolution of electronic structure and upward band bending suggest that the growth of ultrathin MoO3 layers is a powerful tool to modulate the surface energetics of SrTiO3, and this surface-engineering approach could be generalized to other functional oxides.

  19. Reaction Dynamics of O((3)P) + Propyne: II. Primary Products, Branching Ratios, and Role of Intersystem Crossing from Ab Initio Coupled Triplet/Singlet Potential Energy Surfaces and Statistical Calculations.

    Science.gov (United States)

    Gimondi, Ilaria; Cavallotti, Carlo; Vanuzzo, Gianmarco; Balucani, Nadia; Casavecchia, Piergiorgio

    2016-07-14

    The mechanism of the O((3)P) + CH3CCH reaction was investigated using a combined experimental/theoretical approach. Experimentally the reaction dynamics was studied using crossed molecular beams (CMB) with mass-spectrometric detection and time-of-flight analysis at 9.2 kcal/mol collision energy. Theoretically master equation (ME) simulations were performed on a potential energy surface (PES) determined using high-level ab initio electronic structure calculations. In this paper (II) the theoretical results are described and compared with experiments, while in paper (I) are reported and discussed the results of the experimental study. The PES was investigated by determining structures and vibrational frequencies of wells and transition states at the CASPT2/aug-cc-pVTZ level using a minimal active space. Energies were then determined at the CASPT2 level increasing systematically the active space and at the CCSD(T) level extrapolating to the complete basis set limit. Two separate portions of the triplet PES were investigated, as O((3)P) can add either on the terminal or the central carbon of the unsaturated propyne bond. Minimum energy crossing points (MECPs) between the triplet and singlet PESs were searched at the CASPT2 level. The calculated spin-orbit coupling constants between the T1 and S0 electronic surfaces were ∼25 cm(-1) for both PESs. The portions of the singlet PES that can be accessed from the MECPs were investigated at the same level of theory. The system reactivity was predicted integrating stochastically the one-dimensional ME using Rice-Ramsperger-Kassel-Marcus theory to determine rate constants on the full T1/S0 PESs, accounting explicitly for intersystem crossing (ISC) using the Landau-Zener model. The computational results are compared both with the branching ratios (BRs) determined experimentally in the companion paper (I) and with those estimated in a recent kinetic study at 298 K. The ME results allow to interpret the main system reactivity: CH

  20. The performance of Y2O3 as interface layer between La2O3 and p-type silicon substrate

    Directory of Open Access Journals (Sweden)

    Shulong Wang

    2016-11-01

    Full Text Available In this study, the performance of Y2O3 as interface layer between La2O3 and p-type silicon substrate is studied with the help of atomic layer deposition (ALD and magnetron sputtering technology. The surface morphology of the bilayer films with different structures are observed after rapid thermal annealing (RTA by atomic force microscopy (AFM. The results show that Y2O3/Al2O3/Si structure has a larger number of small spikes on the surface and its surface roughness is worse than Al2O3/Y2O3/Si structure. The reason is that the density of Si substrate surface is much higher than that of ALD growth Al2O3. With the help of high-frequency capacitance-voltage(C-V measurement and conductivity method, the density of interface traps can be calculated. After a high temperature annealing, the metal silicate will generate at the substrate interface and result in silicon dangling bond and interface trap charge, which has been improved by X-ray photoelectron spectroscopy (XPS and interface trap charge density calculation. The interface trapped charge density of La2O3/Al2O3/Si stacked gate structure is lower than that of La2O3/Y2O3/Si gate structure. If Y2O3 is used to replace Al2O3 as the interfacial layer, the accumulation capacitance will increase obviously, which means lower equivalent oxide thickness (EOT. Our results show that interface layer Y2O3 grown by magnetron sputtering can effectively ensure the interface traps near the substrate at relative small level while maintain a relative higher dielectric constant than Al2O3.

  1. Preparation and catalytic activities of LaFeO3 and Fe2O3 for HMX thermal decomposition.

    Science.gov (United States)

    Wei, Zhi-Xian; Xu, Yan-Qing; Liu, Hai-Yan; Hu, Chang-Wen

    2009-06-15

    Perovskite-type LaFeO(3) and alpha-Fe(2)O(3) with high specific surface areas were directly prepared with appropriate stearic acid-nitrates ratios by a novel stearic acid solution combustion method. The obtained powders were characterized by XRD, FT-IR and XPS techniques. The catalytic activities of perovskite-type LaFeO(3) and alpha-Fe(2)O(3) for the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were investigated by TG and TG-EGA techniques. The experimental results show that the catalytic activity of perovskite-type LaFeO(3) was much higher than that of alpha-Fe(2)O(3) because of higher concentration of surface-adsorbed oxygen (O(ad)) and hydroxyl of LaFeO(3). The study points out a potential way to develop new and more active perovskite-type catalysts for the HMX thermal decomposition.

  2. Experimental and Theoretical Study of the Interactions between Fe2O3/Al2O3 and CO

    Directory of Open Access Journals (Sweden)

    Zhiyong Liang

    2017-04-01

    Full Text Available The behavior of Fe2O3/Al2O3 particles as oxygen carriers (OCs for CO chemical looping combustion (CLC under different reaction temperatures (700 °C, 800 °C, 900 °C, and 1000 °C were tested in a lab-scale fluidized bed and a thermogravimetric analysis (TGA unit. The results show that the oxygen carrier presents the highest reactivity at 800 °C, even after 30 cycles of redox reaction in a fluidized bed, while more obvious carbon deposition occurred for the case at 700 °C, and agglomeration for the case at 1000 °C. Moreover, the detailed behavior of the prepared Fe2O3/Al2O3 particle was detected in the TGA apparatus at different reaction temperatures. Furthermore, temperature-programming TGA experiments were performed to investigate the influence of different CO concentrations and CO/CO2 concentrations on the reaction between CO and OC during the chemical looping combustion processes. Based on these experimental behaviors of the prepared Fe2O3/Al2O3 during the CLC of CO, the detailed models and electronic properties of the pure and reduced Fe2O3/Al2O3 supported the slabs, CO adsorption, and oxidation, and the decomposition reactions on these surfaces were revealed using density functional theory (DFT calculations which went deep into the nature of the synergetic effect of the support of Al2O3 on the activity of Fe2O3 for the CLC of CO.

  3. Role of Tricoordinate Al Sites in CH3ReO3/Al2O3 Olefin Metathesis Catalysts.

    Science.gov (United States)

    Valla, Maxence; Wischert, Raphael; Comas-Vives, Aleix; Conley, Matthew P; Verel, René; Copéret, Christophe; Sautet, Philippe

    2016-06-01

    Re2O7 supported on γ-alumina is an alkene metathesis catalyst active at room temperature, compatible with functional groups, but the exact structures of the active sites are unknown. Using CH3ReO3/Al2O3 as a model for Re2O7/Al2O3, we show through a combination of reactivity studies, in situ solid-state NMR, and an extensive series of DFT calculations, that μ-methylene structures (Al-CH2-ReO3-Al) containing a Re═O bound to a tricoordinated Al (AlIII) and CH2 bound to a four-coordinated Al (AlIVb) are the precursors of the most active sites for olefin metathesis. The resting state of CH3ReO3/Al2O3 is a distribution of μ-methylene species formed by the activation of the C-H bond of CH3ReO3 on different surface Al-O sites. In situ reaction with ethylene results in the formation of Re metallacycle intermediates, which were studied in detail through a combination of solid-state NMR experiments, using labeled ethylene, and DFT calculations. In particular, we were able to distinguish between metallacycles in TBP (trigonal-bipyramidal) and SP (square-pyramidal) geometry, the latter being inactive and detrimental to catalytic activity. The SP sites are more likely to be formed on other Al sites (AlIVa/AlIVa). Experimentally, the activity of CH3ReO3/Al2O3 depends on the activation temperature of alumina; catalysts activated at or above 500 °C contain more active sites than those activated at 300 °C. We show that the dependence of catalytic activity on the Al2O3 activation temperature is related to the quantity of available AlIII-defect sites and adsorbed H2O.

  4. Zn2(TeO3)Br2

    Science.gov (United States)

    Zhang, Dong; Johnsson, Mats

    2008-01-01

    Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3)Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetra­hedra, and [TeO3 E] tetra­hedra (E being the 5s 2 lone pair of Te4+) joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3)Br2 is isostructural with the synthetic compounds Zn2(TeO3)Cl2, CuZn(TeO3)2, Co2(TeO3)Br2 and the mineral sophiite, Zn2(SeO3)Cl2. PMID:21202162

  5. La interstitial defect-induced insulator-metal transition in the oxide heterostructures LaAl O3 /SrTi O3

    Science.gov (United States)

    Zhou, Jun; Yang, Ming; Feng, Yuan Ping; Rusydi, Andrivo

    2017-11-01

    Perovskite oxide interfaces have attracted tremendous research interest for their fundamental physics and promising all-oxide electronic applications. Here, based on first-principles calculations, we propose a surface La interstitial promoted interface insulator-metal transition in LaAl O3 /SrTi O3 (110). Compared with surface oxygen vacancies, which play a determining role on the insulator-metal transition of LaAl O3 /SrTi O3 (001) interfaces, we find that surface La interstitials can be more experimentally realistic and accessible for manipulation and more stable in an ambient atmospheric environment. Interestingly, these surface La interstitials also induce significant spin-splitting states with a Ti dy z/dx z character at a conducting LaAl O3 /SrTi O3 (110) interface. On the other hand, for insulating LaAl O3 /SrTi O3 (110) (properties of LaAl O3 /SrTi O3 (110) for different possibilities in electronic and magnetic applications.

  6. Sol-gel-cum-hydrothermal synthesis of mesoporous Co-Fe@Al2O3 ...

    Indian Academy of Sciences (India)

    surface area, and narrow pore distribution are the key factors for an efficient adsorption of methylene blue on .... 3.1 XRD analysis. Figure 1 shows the XRD pattern of mesoporous Al2O3 and monometallic and bimetallic@Al2O3−MCM-41 samples. Mesoporous Al2O3 is .... Si−O−Si vibration bands of MCM-41 and Al2O3−.

  7. Silicon solar cells with Al2O3 antireflection coating

    Science.gov (United States)

    Dobrzański, Leszek A.; Szindler, Marek; Drygała, Aleksandra; Szindler, Magdalena M.

    2014-09-01

    The paper presents the possibility of using Al2O3 antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al2O3 thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al2O3 antireflection coating by ALD method. Results and their analysis allow to conclude that the Al2O3 antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al2O3 the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al2O3 on the bulk passivation of the silicon.

  8. Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O-3 photostationary state and peroxy radical levels

    NARCIS (Netherlands)

    Trebs, I.; Mayol-Bracero, O.L.; Pauliquevis, T.; Kuhn, U.; Sander, R.; Ganzeveld, L.N.; Meixner, F.X.; Kesselmeier, J.; Artaxo, P.; Andreae, M.O.

    2012-01-01

    We measured the mixing ratios of NO, NO2, O-3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in

  9. Microwave absorption behavior in Cr2O3 nanopowders

    International Nuclear Information System (INIS)

    Montiel, H.; Alvarez, G.; Conde-Gallardo, A.; Zamorano, R.

    2015-01-01

    Highlights: • We have investigated the microwave power absorption in Cr 2 O 3 nanopowders. • EMR spectra show the contributions of the core and the surface of the nanoparticles. • MAMMAS detected an antiferro-paramagnetic transition due to core of the nanoparticles. • LFMA signal is associated with the ferromagnetic order on the surface of the nanoparticles. - Abstract: We have investigated the microwave power absorption at X-band (8.8–9.8 GHz) in Cr 2 O 3 nanopowders, for the 294–400 K temperature range. For all temperatures, two different kinds of microwave absorptions are observed: the electron magnetic resonance (EMR) at high magnetic field and the low-field microwave absorption (LFMA) around zero field. EMR spectrum can be separated in two contributions associated with two different resonant absorption modes, where this result is interpreted as the combination of two different magnetic phases; corresponding to the core (mode A) and the surface (mode B) of the Cr 2 O 3 nanoparticles. Also, we have detected the onset of the antiferro-paramagnetic transition in resonant mode A, which is characteristic of Cr 2 O 3 samples; being confirmed the magnetic transition by means of the magnetically modulated microwave absorption spectroscopy (MAMMAS). Additionally, the temperature behaviors of the resonant mode B and the LFMA signal are associated with a ferromagnetic state on the surface of the Cr 2 O 3 nanoparticles

  10. HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

    International Nuclear Information System (INIS)

    Rice, C.E.; Jackel, J.L.

    1982-01-01

    The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

  11. Is thermospheric long-term cooling due to CO2 or O3?

    Directory of Open Access Journals (Sweden)

    P. L. Walsh

    2011-10-01

    Full Text Available While greenhouse gases trap heat emanating from the Earth and thereby heat the surface atmosphere, they act as emitters in the high atmosphere and cool the air there. In 1989 Roble and Dickinson (1989 estimated the cooling that would occur in the thermosphere (250–500 km altitude due to a doubling of greenhouse gas densities. Ever since, long-term data bases have been scoured for evidence of this thermospheric "global cooling." Here we show evidence that the thermosphere did indeed cool over the period 1966–1987, but the data suggest that the cooling accelerated at a "breakpoint year" around 1979 to a rate far larger than may be attributed to greenhouse cooling. This 1979 breakpoint year appears to coincide with a breakpoint year in ozone (O3 column density. Further, the cooling was confined largely to the daytime thermosphere while the nighttime showed only a small trend. These results suggest, first, that the greenhouse cooling of the thermosphere may well not be detectable with current data sets and, second, that the long-term cooling that is clearly seen may be due largely to O3 depletion.

  12. Directed laser processing of compacted powder mixtures Al2O3-TiO2-Y2O3

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2013-01-01

    Full Text Available The phase formation, microstructure and surface texture of laser treated ternary powder mixtures of Al2O3-TiO2-Y2O3 had been studied. Rapid high temperature heating and subsequent rapid cooling due to the directed movement of the laser beam forms concave ceramic tracks. Phase composition and microstructure of the tracks depends on the Al2O3 content and the TiO2/Y2O3 ratio of the initial mixtures. The main phases observed are Y3Al5O12, Y2Ti2O7, Al2O3 and Al2TiO5. Due to the temperature gradient in the heating zone, complex layered structures are formed. The tracks consist of three main layers: a thin surface layer, a layer of crystallization products of eutectic alloys, and a lower sintered layer. The thickness of the crystallization layer and the shrinkage of the irradiation zone depend on the amount of Y3Al5O12 and Al2O3 crystallized from the melt.

  13. Probing the Degradation Mechanism of Li2MnO3 Cathode for Li-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Xiao, Liang; Zheng, Jianming; Zhou, Yungang; He, Yang; Zu, Xiaotao; Mao, Scott X.; Xiao, Jie; Gao, Fei; Zhang, Jiguang; Wang, Chong M.

    2015-02-10

    Capacity and voltage fading of Li2MnO3 is a major challenge for the application of this category of material, which is believed to be associated with the structural and chemical evolution of the materials. This paper reports the detailed structural and chemical evolutions of Li2MnO3 cathode captured by using aberration corrected scanning/transmission electron microscope (S/TEM) after certain numbers of charge-discharge cycling of the batteries. It is found that structural degradation occurs from the very first cycle and is spatially initiated from the surface of the particle and propagates towards the inner bulk as cyclic number increase, featuring the formation of the surface phase transformation layer and gradual thickening of this layer. The structure degradation is found to follow a sequential phase transformation: monoclinic C2/m → tetragonal I41 → cubic spinel, which is consistently supported by the decreasing lattice formation energy based on DFT calculations. For the first time, high spatial resolution quantitative chemical analysis reveals that 20% oxygen in the surface phase transformation layer is removed and such newly developed surface layer is a Li-depleted layer with reduced Mn cations. This work demonstrates a direct correlation between structural degradation and cell’s electrochemical degradation, which enhances our understanding of Li-Mn-rich (LMR) cathode materials.

  14. Sintering behavior of Y2O3 doped Bi2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Alizadeh M.

    2007-01-01

    Full Text Available Influence of sintering temperature and soaking time on densification of Bi2O3 samples doped with 25%mol Y2O3 was investigated by shrinkage and relative density measurements. Samples were sintered in air at different temperatures in the range of 800 to 1000°C for 24 hr. The results showed that samples sintered at 950°C have the maximum relative density. Several samples were sintered at 950°C for duration of 0 to 36 hr in order to evaluate the effect of soaking time on densification of samples. It was found that the samples were sintered at 950°C for 36hr had higher relative density than others did for smaller time duration X-ray diffraction (XRD analyses detected δ -Bi2O3 as the sole stable phase in all samples. Scanning Electron Microscopy (SEM investigation of fractured surface of the samples showed that porosities decrease by increasing of sintering temperature and grow by further increasing of temperature.

  15. Stepwise Depletion of Coating Elements as a Result of Hot Corrosion of NiCrAlY Coatings

    Science.gov (United States)

    Rana, Nidhi; Jayaganthan, R.; Prakash, Satya

    2013-11-01

    Present investigation deals with the hot corrosion behaviour of the NiCrAlY coatings deposited by HVOF technique on Superni76 under cyclic conditions at 900 °C in the presence of Na2SO4 + 60% V2O5 salt. The weight change behaviour of the coatings was followed with time up to 200 cycles and K p value was calculated for the hot corrosion process. Surface and cross-section of the corroded samples were examined by FESEM/EDS and XRD to follow the progress of corrosion up to 200 cycles. In earlier cycles, the corrosive species oxidised top surface of the coatings. With increasing number of cycles, oxidation of the coatings occurred up to 40-μm depth. A Cr-depleted band was seen below the oxide scale. Further increase in number of cycles led to migration and oxidation of Al to form Al2O3 sublayer at coating/scale interface, thereby leading to formation of Al-depleted zone in the coating below the Al2O3 sublayer. The corrosion resistance of the NiCrAlY coatings is attributed to the formation of the continuous and dense Al2O3 sublayer at the coating/scale interface, which acts as barrier to the migration of Cr to the surface. The appearance of Al3Y after 100 and 200 cycles also contributes to the increased corrosion resistance of coatings after 100 and 200 cycles.

  16. Anomalous Interface and Surface Strontium Segregation in (La 1– y Sr y ) 2 CoO 4±δ /La 1– x Sr x CoO 3−δ Heterostructured Thin Films

    KAUST Repository

    Feng, Zhenxing

    2014-03-20

    Heterostructured oxides have shown unusual electrochemical properties including enhanced catalytic activity, ion transport, and stability. In particular, it has been shown recently that the activity of oxygen electrocatalysis on the Ruddlesden-Popper/perovskite (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ heterostructure is remarkably enhanced relative to the Ruddlesden-Popper and perovskite constituents. Here we report the first atomic-scale structure and composition of (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ grown on SrTiO3. We observe anomalous strontium segregation from the perovskite to the interface and the Ruddlesden-Popper phase using direct X-ray methods as well as with ab initio calculations. Such Sr segregation occurred during the film growth, and no significant changes were found upon subsequent annealing in O2. Our findings provide insights into the design of highly active catalysts for oxygen electrocatalysis. © 2014 American Chemical Society.

  17. Improvement of electron mobility in La:BaSnO3 thin films by insertion of an atomically flat insulating (Sr,Ba)SnO3 buffer layer

    Science.gov (United States)

    Shiogai, Junichi; Nishihara, Kazuki; Sato, Kazuhisa; Tsukazaki, Atsushi

    2016-06-01

    One perovskite oxide, ASnO3 (A = Sr, Ba), is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO3 substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO3 / (Sr,Ba)SnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,Ba)SnO3 bilayer buffer structures reduces the number of dislocations and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO3 buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO3 shows that the highest obtained value of mobility is 78 cm2V-1s-1 because of its fewer dislocations. High electron mobility films based on perovskite BaSnO3 can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.

  18. Improvement of electron mobility in La:BaSnO3 thin films by insertion of an atomically flat insulating (Sr,BaSnO3 buffer layer

    Directory of Open Access Journals (Sweden)

    Junichi Shiogai

    2016-06-01

    Full Text Available One perovskite oxide, ASnO3 (A = Sr, Ba, is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO3 substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO3 / (Sr,BaSnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,BaSnO3 bilayer buffer structures reduces the number of dislocations and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO3 buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO3 shows that the highest obtained value of mobility is 78 cm2V−1s−1 because of its fewer dislocations. High electron mobility films based on perovskite BaSnO3 can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.

  19. modified BiFeO3–BaTiO3

    Indian Academy of Sciences (India)

    based perovskite structures lead- free BiFeO3–BaTiO3 solid solutions are popularly studied due to the high Curie temperature (TC). It was reported that the BiFeO3–BaTiO3 system possessed high piezoelectric. ∗. Author for correspondence ...

  20. Synthesis and structural characterization of (Bi2O3)(Y2O3) x and ...

    Indian Academy of Sciences (India)

    Lattice parameters of fcc phase of Y2O3 doped samples were calculated from the X-ray diffraction data. The lattice constant `' gradually decreases with increasing content of dopant concentration () for the Y2O3 doped system and obeys Vegard's rule. The unit cell parameters for the (Bi2O3)1– (Gd2O3) doped ...

  1. Photocatalytic properties of KBiO3 and LiBiO3 with tunnel structures

    Indian Academy of Sciences (India)

    LiBiO3 (ICDD PDF Card No. 01–086–1187). Lattice parameters obtained are close to the reported values for these oxides. KBiO3 crystallizes in cubic KSbO3 type structure (space group Im 3) with lattice parame- ter a = 10.0198(3) Å. LiBiO3 has orthorhombic struc- ture (space group Pccn) similar to LiSbO3 and the.

  2. Dielectric collapse at the LaAlO3/SrTiO3(001) heterointerface under applied electric field.

    Science.gov (United States)

    Minohara, M; Hikita, Y; Bell, C; Inoue, H; Hosoda, M; Sato, H K; Kumigashira, H; Oshima, M; Ikenaga, E; Hwang, H Y

    2017-08-25

    The fascinating interfacial transport properties at the LaAlO 3 /SrTiO 3 heterointerface have led to intense investigations of this oxide system. Exploiting the large dielectric constant of SrTiO 3 at low temperatures, tunability in the interfacial conductivity over a wide range has been demonstrated using a back-gate device geometry. In order to understand the effect of back-gating, it is crucial to assess the interface band structure and its evolution with external bias. In this study, we report measurements of the gate-bias dependent interface band alignment, especially the confining potential profile, at the conducting LaAlO 3 /SrTiO 3 (001) heterointerface using soft and hard x-ray photoemission spectroscopy in conjunction with detailed model simulations. Depth-profiling analysis incorporating the electric field dependent dielectric constant in SrTiO 3 reveals that a significant potential drop on the SrTiO 3 side of the interface occurs within ~2 nm of the interface under negative gate-bias. These results demonstrate gate control of the collapse of the dielectric permittivity at the interface, and explain the dramatic loss of electron mobility with back-gate depletion.

  3. Coating effect of LiFePO4 and Al2O3 on Li1.2Mn0.54Ni0.13Co0.13O2 cathode surface for lithium ion batteries

    CSIR Research Space (South Africa)

    Seteni, Bonani

    2017-06-01

    Full Text Available Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4...

  4. Methanol-to-hydrocarbons conversion over MoO3/H-ZSM-5 catalysts prepared via lower temperature calcination: a route to tailor the distribution and evolution of promoter Mo species, and their corresponding catalytic properties† †Electronic supplementary information (ESI) available: more TEM images of post-run samples, CS Chem3D Model of zeolite and external surface MoO3, images and file (.c3xml). See DOI: 10.1039/c5sc01825k Click here for additional data file. Click here for additional data file.

    Science.gov (United States)

    Liu, Bonan; France, Liam; Wu, Chen; Jiang, Zheng; Kuznetsov, Vladimir L.; Al-Megren, Hamid A.; Al-Kinany, Mohammed; Aldrees, Saud A.

    2015-01-01

    A series of MoO3/H-ZSM-5 (Si/Al = 25) catalysts were prepared via calcination at a lower-than-usual temperature (400 °C) and subsequently evaluated in the methanol-to-hydrocarbon reaction at that same temperature. The catalytic properties of those catalysts were compared with the sample prepared at the more conventional, higher temperature of 500 °C. For the lower temperature preparations, molybdenum oxide was preferentially dispersed over the zeolite external surface, while only the higher loading level of MoO3 (7.5 wt% or higher) led to observable inner migration of the Mo species into the zeolite channels, with concomitant partial loss of the zeolite Brønsted acidity. On the MoO3 modified samples, the early-period gas yield, especially for valuable propylene and C4 products, was noticeably accelerated, and is gradually converted into an enhanced liquid aromatic formation. The 7.5 wt% MoO3/H-ZSM-5 sample prepared at 400 °C thereby achieved a balance between the zeolite surface dispersion of Mo species, their inner channel migration and the corresponding effect on the intrinsic Brønsted acidity of the acidic zeolite. That loading level also possessed the highest product selectivity (after 5 h reaction) to benzene, toluene and xylenes, as well as higher early-time valuable gas product yields in time-on-stream experiments. However, MoO3 loading levels of 7.5 wt% and above also resulted in earlier catalyst deactivation by enhanced coke accumulation at, or near, the zeolite channel openings. Our research illustrates that the careful adoption of moderate/lower temperature dispersion processes for zeolite catalyst modification gives considerable potential for tailoring and optimizing the system's catalytic performance. PMID:29142734

  5. Radiative forcing for changes in tropospheric O3

    International Nuclear Information System (INIS)

    Grossman, A.S.; Wuebbles, D.J.; Grant, K.E.

    1994-06-01

    We have evaluated the radiative forcing for assumed changes in tropospheric O 3 in the 500-1650 cm -1 wavenumber range. The radiative forcing calculations were performed as a function of latitude as well as for a globally and seasonally averaged model atmosphere, both in a clear sky approximation and in a model containing a representative cloud distribution. The scenarios involved radiative forcing calculations for O 3 at normal atmospheric abundance and at a tropospheric abundance depleted by 25 ppbv, at each altitude, for all northern hemisphere latitudes. Normal abundances of H 2 O, CO 2 , CH 4 , and N 2 O were included in the calculations. The IR radiative forcing was calculated using a correlated k-distribution radiative transfer model. The tropospheric radiative forcing values are compared to the IPCC formulae for ozone tropospheric forcing as well as other published values to determine the validity of the correlated k-distribution approach to the radiative forcing calculations. The results for the global average atmosphere show agreement with previous results to the order of 10 percent. We conclude that the O 3 forcing is linear in the background abundance and that the radiative forcing for ozone for the globally averaged atmosphere and the latitude averaged radiative forcing in the clear sky approximation are in agreement to within 10 percent. For the case of an atmosphere in which the tropospheric ozone has been depleted by 25 ppbv at all altitudes in the northern hemisphere, the mid latitude zone contributes ∼50 percent of the forcing, tropic zone contributes ∼37 percent of the forcing and the polar zone contributes ∼13 percent of the total forcing

  6. α-Ga2O3 grown by low temperature atomic layer deposition on sapphire

    Science.gov (United States)

    Roberts, J. W.; Jarman, J. C.; Johnstone, D. N.; Midgley, P. A.; Chalker, P. R.; Oliver, R. A.; Massabuau, F. C.-P.

    2018-04-01

    α-Ga2O3 is a metastable phase of Ga2O3 of interest for wide bandgap engineering since it is isostructural with α-In2O3 and α-Al2O3. α-Ga2O3 is generally synthesised under high pressure (several GPa) or relatively high temperature (∼500 °C). In this study, we report the growth of α-Ga2O3 by low temperature atomic layer deposition (ALD) on sapphire substrate. The film was grown at a rate of 0.48 Å/cycle, and predominantly consists of α-Ga2O3 in the form of (0001) -oriented columns originating from the interface with the substrate. Some inclusions were also present, typically at the tips of the α phase columns and most likely comprising ε-Ga2O3. The remainder of the Ga2O3 film - i.e. nearer the surface and between the α-Ga2O3 columns, was amorphous. The film was found to be highly resistive, as is expected for undoped material. This study demonstrates that α-Ga2O3 films can be grown by low temperature ALD and suggests the possibility of a new range of ultraviolet optoelectronic and power devices grown by ALD. The study also shows that scanning electron diffraction is a powerful technique to identify the different polymorphs of Ga2O3 present in multiphase samples.

  7. Ultrathin BaTiO3 templates for multiferroic nanostructures

    OpenAIRE

    Chen, Xumin; Yang, Seolun; Kim, Ji-Hyun; Kim, Hyung-Do; Kim, Jae-Sung; Rojas, Geoffrey; Skomski, Ralph; Lu, Haidong; Bhattacharya, Anand; Santos, Tiffany; Guisinger, Nathan; Bode, Matthias; Gruverman, Alexei; Enders, Axel

    2011-01-01

    Structural, electronic and dielectric properties of high-quality ultrathin BaTiO3 films are investigated. The films, which are grown by ozone-assisted molecular beam epitaxy on Nb-doped SrTiO3 (001) substrates and having thicknesses as thin 8 unit cells (3.2 nm), are unreconstructed and atomically smooth with large crystalline terraces. A strain-driven transition to 3D island formation is observed for films of of 13 unit cells thickness (5.2 nm). The high structural quality of the surfaces, t...

  8. Reinforcement of poly(amide-imide) containing N-trimellitylimido-L-phenylalanine by using nano α-Al2O3 surface-coupled with bromo-flame retardant under ultrasonic irradiation technique

    Science.gov (United States)

    Mallakpour, Shadpour; Khadem, Elham

    2014-10-01

    By the uniform dispersion of nanoparticles into a polymer matrix, a substantial improvement of physicochemical properties can be attained. In this study, a series of poly(amide-imide)/Al2O3 nanocomposites (PANC)s based on various amounts of modified α-Al2O3 nanoparticles (ANP)s were prepared using the ultrasonic irradiation method. In the process of manufacturing the nanocomposites (NC)s, severe agglomeration of ANPs into the polymer matrix can be reduced using 2,3,4,5-tetrabromo-6-[(4-hydroxyphenyl)carbamoyl]benzoic acid as novel coupling agent. The effects of modified ANPs on the morphology and properties of the polymer matrix were studied by means of Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermal gravimetric analysis (TGA). The results obtained by TGA showed that the thermal stability of the NCs was improved with the addition of the small amounts of ANPs as effective thermal degradation resistant reinforcement.

  9. Enhanced self-repairing capability of sol-gel derived SrTiO3/nano Al2O3 composite films

    International Nuclear Information System (INIS)

    Yao, Manwen; Peng, Yong; Xiao, Ruihua; Li, Qiuxia; Yao, Xi

    2016-01-01

    SrTiO 3 /nano Al 2 O 3 inorganic nanocomposites were prepared by using a conventional sol-gel spin coating process. For comparison, SrTiO 3 films doped by equivalent amount of sol-Al 2 O 3 have also been investigated. Aluminum deposited by using vacuum evaporation was used as the top electrode. The nanocomposites exhibited a significantly enhanced dielectric strength of 506.9 MV/m, which was increased by 97.4% as compared with the SrTiO 3 films doped with sol-Al 2 O 3 . The leakage current maintained of the same order of microampere until the ultimate breakdown of the nanocomposites. The excellent electrical performances are ascribed to the anodic oxidation reaction in origin, which can repair the internal and/or surface defects of the films.

  10. Phase relations in the SiC-Al2O3-Pr2O3 system

    International Nuclear Information System (INIS)

    Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

    2016-01-01

    Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

  11. Fe2O3 hollow sphere nanocomposites for supercapacitor applications

    Science.gov (United States)

    Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming

    2018-02-01

    Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.

  12. Photocatalytic Performance of a Novel MOF/BiFeO3 Composite

    Directory of Open Access Journals (Sweden)

    Yunhui Si

    2017-10-01

    Full Text Available In this study, MOF/BiFeO3 composite (MOF, metal-organic framework has been synthesized successfully through a one-pot hydrothermal method. The MOF/BiFeO3 composite samples, pure MOF samples and BiFeO3 samples were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS, and by UV–vis spectrophotometry. The results and analysis reveal that MOF/BiFeO3 composite has better photocatalytic behavior for methylene blue (MB compared to pure MOF and pure BiFeO3. The enhancement of photocatalytic performance should be due to the introduction of MOF change the surface morphology of BiFeO3, which will increase the contact area with MB. This composing strategy of MOF/BiFeO3 composite may bring new insight into the designing of highly efficient photocatalysts.

  13. Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O3 photostationary state and peroxy radical levels

    Science.gov (United States)

    Trebs, Ivonne; Mayol-Bracero, Olga L.; Pauliquevis, Theotonio; Kuhn, Uwe; Sander, Rolf; Ganzeveld, Laurens; Meixner, Franz X.; Kesselmeier, Jürgen; Artaxo, Paulo; Andreae, Meinrat O.

    2012-03-01

    We measured the mixing ratios of NO, NO2, O3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Cooperative LBA Airborne Regional Experiment-2001). The dispersion and impact of the Manaus plume was investigated by a combined analysis of ground-based (boat platform) and airborne trace gas and aerosol measurements as well as by meteorological measurements complemented by dispersion calculations (Hybrid Single-Particle Lagrangian Integrated Trajectory model). For the cases with the least anthropogenic influence (including a location in a so far unexplored region ˜150 km west of Manaus on the Rio Manacapuru), the aerosol scattering coefficient, σs, was below 11 Mm-1, NOx mixing ratios remained below 0.6 ppb, daytime O3 mixing ratios were mostly below 20 ppb and maximal isoprene mixing ratios were about 3 ppb in the afternoon. The photostationary state (PSS) was not established for these cases, as indicated by values of the Leighton ratio, Φ, well above unity. Due to the influence of river breeze systems and other thermally driven mesoscale circulations, a change of the synoptic wind direction from east-northeast to south-southeast in the afternoon often caused a substantial increase of σs and trace gas mixing ratios (about threefold for σs, fivefold for NOx, and twofold for O3), which was associated with the arrival of the Manaus pollution plume at the boat location. The ratio Φ reached unity within its uncertainty range at NOx mixing ratios of about 3 ppb, indicating "steady-state" conditions in cases when radiation variations, dry deposition, emissions, and reactions mostly involving peroxy radicals (XO2) played a minor role. The median midday/afternoon XO2 mixing ratios estimated using the PSS method range from 90 to 120 parts per trillion (ppt) for the remote cases (

  14. Catalytic oxidation of phosphorus on MoO3 as studied by infrared spectroscopy

    International Nuclear Information System (INIS)

    Paul, D.K.; Rao, L.F.; Yates, J.T. Jr.

    1992-01-01

    Transmission infrared spectroscopy and mass spectroscopy were used to study the decomposition and oxidation of phosphine on an MoO 3 /Al 2 O 3 supported catalyst at 300-800 K. At 573 K, phosphine decomposes and is oxidized to a HP=O surface species. At 673 K, further oxidation forms (HO) x P=O that desorbs from the surface around 773 K. This suggests that the MoO 3 /Al 2 O 3 catalyst may be useful for continuous organophosphorous catalytic oxidation. 30 refs., 12 figs., 1 tab

  15. Degradation of Y2O3:Eu phosphor powders

    International Nuclear Information System (INIS)

    Ntwaeaborwa, O.M.; Hillie, K.T.; Swart, H.C.

    2004-01-01

    Degradation of cathodoluminescent (CL) intensity and changes in the surface chemistry of Y 2 O 3 :Eu phosphor powders were investigated using CL spectroscopy and Auger electron spectroscopy (AES), respectively. Y 2 O 3 :Eu phosphor powders were exposed to an electron beam of energy 2 keV and a current density of 88.5 mA/cm 2 at room temperature for different oxygen pressures. The degradation of CL intensity is due to the formation of a non-luminescent ''dead layer'' on the specimen surface, resulting from non-radiative recombination of electron-hole pairs via surface states. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3 heterostructures

    Science.gov (United States)

    Groenendijk, D. J.; Manca, N.; Mattoni, G.; Kootstra, L.; Gariglio, S.; Huang, Y.; van Heumen, E.; Caviglia, A. D.

    2016-07-01

    Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO3 thin films, grown by pulsed laser deposition, can be optimized by considering the effect of laser-induced modification of the SrIrO3 target surface. We further demonstrate that bare SrIrO3 thin films are subject to degradation in air and are highly sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited in-situ is effective in preserving the film quality, allowing us to measure metallic transport behavior in films with thicknesses down to 4 unit cells. In addition, the SrTiO3 encapsulation enables the fabrication of devices such as Hall bars without altering the film properties, allowing precise (magneto)transport measurements on micro- and nanoscale devices.

  17. Effect of preparation method on the physical and catalytic property of nanocrystalline Fe2O3

    International Nuclear Information System (INIS)

    Wu, Gang; Tan, Xiaoyan; Li, Guiying; Hu, Changwei

    2010-01-01

    Nanocrystalline Fe 2 O 3 was prepared by five different methods. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is found that pure single-phase of α-Fe 2 O 3 crystal could be gained via thermal decomposition and ultrasonic-precipitation method, while both α-Fe 2 O 3 and γ-Fe 2 O 3 are obtained by the other methods. The morphologies and particle sizes of the samples obtained are approximate except that by thermal decomposition. Compared to α-Fe 2 O 3 , γ-Fe 2 O 3 possesses more surface oxygen species 'O - '. The activity test indicates that surface oxygen species 'O - ' plays a crucial role in the hydroxylation of benzene to phenol with hydrogen peroxide as oxidant.

  18. The effect of Fe2O3 crystal phases on CO2 hydrogenation.

    Science.gov (United States)

    Ning, Wensheng; Wang, Tianqi; Chen, Hongxian; Yang, Xiazhen; Jin, Yangfu

    2017-01-01

    The effect of Fe2O3 crystal phases on their performance in CO2 hydrogenation was studied. α-Fe2O3 crystal was prepared by precipitation method from Fe(NO3)3·9H2O and (NH4)2CO3, and γ-Fe2O3 was prepared by grinding Fe(NO3)3·9H2O and L(+)-Tartaric acid in agate mortar completely. The crystal phases of Fe2O3 influence the distribution of promoter Zn, K and Cu on catalysts. The dispersity of K on γ-Fe2O3 surface is higher than α-Fe2O3. On the contrary, Cu and Zn are more dispersive on α-Fe2O3 surface than γ-Fe2O3. The catalyst in γ-Fe2O3 phase is easily reduced relative to the catalyst in α-Fe2O3 phase. The former presents higher CO2 conversion and C2+ hydrocarbon selectivity than the latter in CO2 hydrogenation.

  19. Addressing Ozone Layer Depletion

    Science.gov (United States)

    Access information on EPA's efforts to address ozone layer depletion through regulations, collaborations with stakeholders, international treaties, partnerships with the private sector, and enforcement actions under Title VI of the Clean Air Act.

  20. Antimicrobial effect of Al2O3, Ag and Al2O3/Ag thin films on Escherichia coli and Pseudomonas putida

    International Nuclear Information System (INIS)

    Angelov, O; Stoyanova, D; Ivanova, I; Todorova, S

    2016-01-01

    The influence of Al 2 O 3 , Ag and Al 2 O 3 /Ag thin films on bacterial growth of Gramnegative bacteria Pseudomonas putida and Escherichia coli is studied. The nanostructured thin films are deposited on glass substrates without intentional heating through r.f. magnetron sputtering in Ar atmosphere of Al 2 O 3 and Ag targets or through sequential sputtering of Al 2 O 3 and Ag targets, respectively. The individual Ag thin films (thickness 8 nm) have a weak bacteriostatic effect on Escherichia coli expressed as an extended adaptive phase of the bacteria up to 5 hours from the beginning of the experiment, but the final effect is only 10 times lower bacterial density than in the control. The individual Al 2 O 3 film (20 nm) has no antibacterial effect against two strains E. coli - industrial and pathogenic. The Al 2 O 3 /Ag bilayer films (Al 2 O 3 20 nm/Ag 8 nm) have strong bactericidal effect on Pseudomonas putida and demonstrate an effective time of disinfection for 2 hours. The individual films Al2O3 and Ag have not pronounced antibacterial effect on Pseudomonas putida . A synergistic effect of Al2O3/Ag bilayer films in formation of oxidative species on the surface in contact with the bacterial suspension could be a reason for their antimicrobial effect on E. coli and P. putida . (paper)

  1. Antimicrobial effect of Al2O3, Ag and Al2O3/Ag thin films on Escherichia coli and Pseudomonas putida

    Science.gov (United States)

    Angelov, O.; Stoyanova, D.; Ivanova, I.; Todorova, S.

    2016-10-01

    The influence of Al2O3, Ag and Al2O3/Ag thin films on bacterial growth of Gramnegative bacteria Pseudomonas putida and Escherichia coli is studied. The nanostructured thin films are deposited on glass substrates without intentional heating through r.f. magnetron sputtering in Ar atmosphere of Al2O3 and Ag targets or through sequential sputtering of Al2O3 and Ag targets, respectively. The individual Ag thin films (thickness 8 nm) have a weak bacteriostatic effect on Escherichia coli expressed as an extended adaptive phase of the bacteria up to 5 hours from the beginning of the experiment, but the final effect is only 10 times lower bacterial density than in the control. The individual Al2O3 film (20 nm) has no antibacterial effect against two strains E. coli - industrial and pathogenic. The Al2O3/Ag bilayer films (Al2O3 20 nm/Ag 8 nm) have strong bactericidal effect on Pseudomonas putida and demonstrate an effective time of disinfection for 2 hours. The individual films Al2O3 and Ag have not pronounced antibacterial effect on Pseudomonas putida. A synergistic effect of Al2O3/Ag bilayer films in formation of oxidative species on the surface in contact with the bacterial suspension could be a reason for their antimicrobial effect on E. coli and P. putida.

  2. Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.

    Science.gov (United States)

    Valdés, H; Tardón, R F; Zaror, C A

    2009-01-01

    This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.

  3. Carrier density modulation by structural distortions at modified LaAlO3/SrTiO3 interfaces

    International Nuclear Information System (INIS)

    Schoofs, Frank; Vickers, Mary E; Egilmez, Mehmet; Fix, Thomas; Kleibeuker, Josée E; MacManus-Driscoll, Judith L; Blamire, Mark G; Carpenter, Michael A

    2013-01-01

    In order to study the fundamental conduction mechanism of LaAlO 3 /SrTiO 3 (LAO/STO) interfaces, heterostructures were modified with a single unit cell interface layer of either an isovalent titanate ATiO 3 (A = Ca, Sr, Sn, Ba) or a rare earth modified Sr 0.5 RE 0.5 TiO 3 (RE = La, Nd, Sm, Dy) between the LAO and the STO. A strong coupling between the lattice strain induced in the LAO layer by the interfacial layers and the sheet carrier density in the STO substrate is observed. The observed crystal distortion of the LAO is large and it is suggested that it couples into the sub-surface STO, causing oxygen octahedral rotation and deformation. We propose that the ‘structural reconstruction’ which occurs in the STO surface as a result of the stress in the LAO is the enabling trigger for two-dimensional conduction at the LAO/STO interface by locally changing the band structure and releasing trapped carriers. (paper)

  4. Bromine atom production and chain propagation during springtime Arctic ozone depletion events in Barrow, Alaska

    Science.gov (United States)

    Thompson, Chelsea R.; Shepson, Paul B.; Liao, Jin; Huey, L. Greg; Cantrell, Chris; Flocke, Frank; Orlando, John

    2017-03-01

    Ozone depletion events (ODEs) in the Arctic are primarily controlled by a bromine radical-catalyzed destruction mechanism that depends on the efficient production and recycling of Br atoms. Numerous laboratory and modeling studies have suggested the importance of heterogeneous recycling of Br through HOBr reaction with bromide on saline surfaces. On the other hand, the gas-phase regeneration of bromine atoms through BrO-BrO radical reactions has been assumed to be an efficient, if not dominant, pathway for Br reformation and thus ozone destruction. Indeed, it has been estimated that the rate of ozone depletion is approximately equal to twice the rate of the BrO self-reaction. Here, we use a zero-dimensional, photochemical model, largely constrained to observations of stable atmospheric species from the 2009 Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, to investigate gas-phase bromine radical propagation and recycling mechanisms of bromine atoms for a 7-day period during late March. This work is a continuation of that presented in Thompson et al. (2015) and utilizes the same model construct. Here, we use the gas-phase radical chain length as a metric for objectively quantifying the efficiency of gas-phase recycling of bromine atoms. The gas-phase bromine chain length is determined to be quite small, at < 1.5, and highly dependent on ambient O3 concentrations. Furthermore, we find that Br atom production from photolysis of Br2 and BrCl, which is predominately emitted from snow and/or aerosol surfaces, can account for between 30 and 90 % of total Br atom production. This analysis suggests that condensed-phase production of bromine is at least as important as, and at times greater than, gas-phase recycling for the occurrence of Arctic ODEs. Therefore, the rate of the BrO self-reaction is not a sufficient estimate for the rate of O3 depletion.

  5. Mnx/2Nbx/2O3 ceramics

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The paper reports investigations of relative permittivity, εr, electrical conductivity, σ, saturation polarization, Ps, infrared absorption and structural properties of compensating valency substituted BaTiO3. The compositions investigated are BaTi(1–x)Mnx/2Nbx/2O3 for x = 0⋅00; 0⋅025; 0⋅05; 0⋅1; 0⋅2; 0⋅4.

  6. Crystal growth and magnetic property of YFeO3 crystal

    Indian Academy of Sciences (India)

    tional homogeneities, crystalline qualities, inclusion defects, second phases and surface morphology have been inves- tigated on the YFeO3 crystals grown by the .... carried out systematically on magnetic property of YFeO3 crystal in the future. Acknowledgements. The authors would like to acknowledge the financial sup-.

  7. Theoretical Investigation of H2 Combustion on alphaAl2O3 Support

    National Research Council Canada - National Science Library

    Synowczynski, Jennifer; Andzelm, Jan W; Vlachos, D. G

    2008-01-01

    ... (alpha alumina oxide (alphaAl2O3)) on the dissociation of molecular hydrogen (H2), molecular oxygen (O2), hydroxyl (OH), water (H2O), and the surface diffusion of oxygen and hydrogen species along the Al2O3...

  8. Photocatalytic Degradation of Isopropanol Over PbSnO3Nanostructures Under Visible Light Irradiation

    Science.gov (United States)

    2009-01-01

    Nanostructured PbSnO3photocatalysts with particulate and tubular morphologies have been synthesized from a simple hydrothermal process. As-prepared samples were characterized by X-ray diffraction, Brunauer–Emmet–Teller surface area, transmission electron microscopy, and diffraction spectroscopy. The photoactivities of the PbSnO3nanostructures for isopropanol (IPA) degradation under visible light irradiation were investigated systematically, and the results revealed that these nanostructures show much higher photocatalytic properties than bulk PbSnO3material. The possible growth mechanism of tubular PbSnO3catalyst was also investigated briefly. PMID:20596379

  9. Influence of Impurities on the Luminescence of Er3+ Doped BaTiO3 Nanophosphors

    Directory of Open Access Journals (Sweden)

    G. D. Webler

    2014-01-01

    Full Text Available The influence of the presence of barium carbonate (BaCO3 phase on the luminescence properties of barium titanate nanocrystals (BaTiO3 powders was investigated. Structural and optical characterizations of erbium (Er3+ doped BaTiO3 synthesized by the sol-emulsion-gel were performed. Using Fourier transform infrared spectroscopy and X-ray powder diffraction, we identified the presence of impurities related to BaCO3 and quantified its fraction. It was observed that the presence of BaCO3 phase, even at low levels, depletes significantly the infrared-to-visible upconverted luminescence efficiency of the produced nanopowders.

  10. Cosmic-Ray Reaction and Greenhouse Effect of Halogenated Molecules: Culprits for Atmospheric Ozone Depletion and Global Climate Change

    Science.gov (United States)

    Lu, Q.-B.

    2013-07-01

    This study is focused on the effects of cosmic rays (solar activity) and halogen-containing molecules (mainly chlorofluorocarbons — CFCs) on atmospheric ozone depletion and global climate change. Brief reviews are first given on the cosmic-ray-driven electron-induced-reaction (CRE) theory for O3 depletion and the warming theory of halogenated molecules for climate change. Then natural and anthropogenic contributions to these phenomena are examined in detail and separated well through in-depth statistical analyses of comprehensive measured datasets of quantities, including cosmic rays (CRs), total solar irradiance, sunspot number, halogenated gases (CFCs, CCl4 and HCFCs), CO2, total O3, lower stratospheric temperatures and global surface temperatures. For O3 depletion, it is shown that an analytical equation derived from the CRE theory reproduces well 11-year cyclic variations of both polar O3 loss and stratospheric cooling, and new statistical analyses of the CRE equation with observed data of total O3 and stratospheric temperature give high linear correlation coefficients ≥ 0.92. After the removal of the CR effect, a pronounced recovery by 20 25 % of the Antarctic O3 hole is found, while no recovery of O3 loss in mid-latitudes has been observed. These results show both the correctness and dominance of the CRE mechanism and the success of the Montreal Protocol. For global climate change, in-depth analyses of the observed data clearly show that the solar effect and human-made halogenated gases played the dominant role in Earth's climate change prior to and after 1970, respectively. Remarkably, a statistical analysis gives a nearly zero correlation coefficient (R = -0.05) between corrected global surface temperature data by removing the solar effect and CO2 concentration during 1850-1970. In striking contrast, a nearly perfect linear correlation with coefficients as high as 0.96-0.97 is found between corrected or uncorrected global surface temperature and total

  11. Investigation of the electroforming and resistive switching mechanisms in Fe-doped SrTiO3 thin films

    International Nuclear Information System (INIS)

    Menke, Tobias

    2009-01-01

    To overcome the physical limits of todays memory technologies new concepts are needed. The resistive random access memory (RRAM), which bases on a nonvolatile and repeatable change of the resistance by external electrical stimuli, seems to be one promising candidate. Within the scope of this work, the model system Strontium titanate (SrTiO 3 ) has been investigated to get a deeper understanding of the underlying physical mechanism related to the resistance change. The electrical properties of SrTiO 3 (STO) can be modulated from a band insulator to metallic conduction by a self-doping with oxygen vacancies which act as shallow donors. A local accumulation or depletion of oxygen vacancies at the vicinity of the surface will lead to a local redox process which is responsible for the resistance change. To study the influence of the interfaces on the switching properties of SrTiO 3 thin films, epitaxial films of Fe-doped SrTiO 3 were grown on different bottom electrodes (SrRuO 3 , LaNiO 3 und Nb:STO) by a ''Pulsed Laser Deposition'' technique. An atomic force microscope equipped with a conductive tip (LC-AFM) allowed studying the conductivity of the deposited films on the nanometer scale. Resistive switching of lateral structures smaller than ∝5 nm could be realized which represents the potential of this material for a further downscaling of RRAM devices. The deposition of top electrodes, made of Platinum or Titanium, allowed the electrical characterization of metal-insulator-metal (MIM) structures. An extensive investigation of pristine MIM-devices by impedance spectroscopy showed the big impact of the metal-insulator interface on the overall device resistance. Furthermore, a chemical polarization was studied by dynamical current sweeps and identified as a volatile resistance variation. Usually a forming procedure is needed to ''enable'' the resistive switching properties in MIM devices. The electroforming of these devices was extensively studied and could be

  12. Effect of relative humidity on O3 and NO2 oxidation of SO2 on α-Al2O3 particles

    Science.gov (United States)

    Liu, Wenjun; He, Xiang; Pang, Shufeng; Zhang, Yunhong

    2017-10-01

    Heterogeneous reactions of SO2/O3 and SO2/NO2 with α-Al2O3 particles at different RHs were investigated using a gas-flow system combined with microscopic Fourier transform infrared (micro-FTIR) spectrometer. The results show that the trace gas O3 or NO2 leads to rapid conversion of SO2 to sulfate on the surface of α-Al2O3 particles in initial stage and then conversion rate decreases in the following stages. The rate of sulfate formation and uptake coefficient (γ) for SO2 in the two systems as a function of relative humidity (RH) are determined for the first time, which are all strongly enhanced more than seven-fold as the RH increase from 15% to 95% in initial stage for SO2/O3 and SO2/NO2. Moreover, the γ in the system of SO2/O3 on α-Al2O3 particles is more than 3-fold than that of SO2/NO2 for the similar RH condition. Our results may be broadly applicable to understand the effects of RH and trace gases (e.g., O3, NO2) for the converting SO2 into sulfate on the mineral dust, which supply basic data for atmospheric chemistry modeling studies.

  13. Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

    Science.gov (United States)

    Ze, LIU; Guogang, YU; Anping, HE; Ling, WANG

    2017-09-01

    The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor. The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis. The parameters influencing the thermal stress in the sputter process are analyzed, such as coating and substrate properties, temperature and Young’s modulus. This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness, temperature and Young’s modulus. However, this relationship is inversed with coating thickness. In addition, the rough substrate surface can increase the thermal stress in the process of coating deposition. The adhesive strength between the coating and the substrate is evaluated by the shear stress. Due to the higher compressive shear stress, the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating. Furthermore, the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.

  14. Revisiting The Depleted Self.

    Science.gov (United States)

    Abraham, Reggie

    2018-04-01

    This article revisits Donald Capps's book The Depleted Self (The depleted self: sin in a narcissistic age. Fortress Press, Minneapolis, 1993), which grew out of his 1990 Schaff Lectures at Pittsburgh Theological Seminary. In these lectures Capps proposed that the theology of guilt had dominated much of post-Reformation discourse. But with the growing prevalence of the narcissistic personality in the late twentieth century, the theology of guilt no longer adequately expressed humanity's sense of "wrongness" before God. Late twentieth-century persons sense this disjunction between God and self through shame dynamics. Narcissists are not "full" of themselves, as popular perspectives might indicate. Instead, they are empty, depleted selves. Psychologists suggest this stems from lack of emotional stimulation and the absence of mirroring in the early stages of life. The narcissist's search for attention and affirmation takes craving, paranoid, manipulative, or phallic forms and is essentially a desperate attempt to fill the internal emptiness. Capps suggests that two narratives from the Gospels are helpful here: the story of the woman with the alabaster jar and the story of Jesus's dialogue with Mary and John at Calvary. These stories provide us with clues as to how depleted selves experienced mirroring and the potential for internal peace in community with Jesus.

  15. Ozone depletion update.

    Science.gov (United States)

    Coldiron, B M

    1996-03-01

    Stratospheric ozone depletion due to chlorofluorocarbons an d increased ultraviolet radiation penetration has long been predicted. To determine if predictions of ozone depletion are correct and, if so, the significance of this depletion. Review of the English literature regarding ozone depletion and solar ultraviolet radiation. The ozone layer is showing definite thinning. Recently, significantly increased ultraviolet radiation transmission has been detected at ground level at several metering stations. It appears that man-made aerosols (air pollution) block increased UVB transmission in urban areas. Recent satellite measurements of stratospheric fluorine levels more directly implicate chlorofluorocarbons as a major source of catalytic stratospheric chlorine, although natural sources may account for up to 40% of stratospheric chlorine. Stratospheric chlorine concentrations, and resultant increased ozone destruction, will be enhanced for at least the next 70 years. The potential for increased transmission of ultraviolet radiation will exist for the next several hundred years. While little damage due to increased ultraviolet radiation has occurred so far, the potential for long-term problems is great.

  16. Raman spectroscopic study of structure and crystallisation behaviour of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses

    Science.gov (United States)

    Aleksandrov, L.; Komatsu, T.; Nagamine, K.; Oishi, K.

    2011-03-01

    In this study, we focus on the structure and crystallization behavior of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses. Glasses of both systems were prepared by a melt-quenching method. The thermal stability of the glasses was examined using differential thermal anaysis (DTA) measurements, and the crystalline phases formed by heat treatments were identified by X-ray diffraction (XRD) analysis. Raman scattering spectra at room temperature for the glasses and crystallized samples were measured with a laser microscope operated with an Ar+ (wavelength: 488 nm) laser. DTA measurements indicated that the thermal stability against crystallization of the glasses decreases drastically with increasing MoO3 content. XRD analysis confirmed that crystallization at 600°C for 3 h of glass with the nominal composition of 50MoO3-25La2O3-25B2O3 resulted in the formation of monoclinic LaMoBO6. Crystallization of 50ZnO-xMoO3-(50-x)B2O3 glasses formed triclinic α-ZnMoO4 as an initial crystalline phase. Moreover, for 30 mol% MoO3 glass, transmission electron microscopy observations showed the formation of α-ZnMoO4 nanocrystals with a diameter of ~ 5 nm. Raman bands at 860, 930 and 950 cm-1 suggested that the coordination state of Mo6+ ions in the glasses were mainly (MoO4)2- tetrahedral units. Therefore, MoO3-containing glasses have good potential for optical applications.

  17. Comparison of sludge treatment by O3 and O3/H2O2.

    Science.gov (United States)

    Yuxin, Zhao; Liang, Wang; Helong, Yu; Baojun, Jiang; Jinming, Jiang

    2014-01-01

    This work focuses on the comparison of sludge decomposition caused by ozone (O3) alone and by ozone/hydrogen peroxide (O3/H2O2). The content of carbonaceous organic materials, nitrogenous compounds and phosphoric substances in sludge supernatant were measured. The release of soluble chemical oxygen demand, total nitrogen (TN) and total phosphorus (TP) caused by O3/H2O2 treatment were more than by O3 alone. As a result, it can be concluded that the efficiency of sludge breakup in O3/H2O2 was better than that in O3 alone. However, a peak appeared in both systems for the biodegradable substances such as carbohydrate. Carbohydrate could be used as the carbon source for denitrification, and the releasing of TN and TP may become an additional burden for a subsequent biological system. So, it was of benefit for the enhancement of cryptic growth and cost reduction by raising and maintaining the content of biodegradable substance and reducing the concentrations of the nitrogenous and phosphoric substances as far as possible. Therefore, sludge treated by O3/H2O2 with lower O3 dose would be more suitable than O3 alone.

  18. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  19. Dielectric response of BaZrO3/BaTiO3 superlattice

    Directory of Open Access Journals (Sweden)

    D. Wang

    2016-06-01

    Full Text Available We use the first-principles-based molecular dynamic approach to simulate dipolar dynamics of BaZrO3/BaTiO3 superlattice, and obtain its dielectric response. The dielectric response is decomposed into its compositional, as well as the in-plane and out-of-plane parts, which are then discussed in the context of chemical ordering of Zr/Ti ions. We reveal that, while the in-plane dielectric response of BaZrO3/BaTiO3 superlattice also shows dispersion over probing frequency, it shall not be categorized as relaxor.

  20. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3

    International Nuclear Information System (INIS)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-01-01

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO 3 and SrTiO 3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO 3 , the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO 3 , our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects. (paper)

  1. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3.

    Science.gov (United States)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-10-16

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

  2. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3

    Science.gov (United States)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-10-01

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

  3. Simultaneous improvement of surface quality and productivity using grey relational analysis based Taguchi design for turning couple (AISI D3 steel/ mixed ceramic tool (Al2O3 + TiC

    Directory of Open Access Journals (Sweden)

    Oussama Zerti

    2017-07-01

    Full Text Available Current optimization strategies are based on the increase the productivity and the quality with lower cost in short time. Grey relational analysis “GRA” based on Taguchi design was proposed in this paper for simultaneous improvement of surface quality and productivity. The turning trials based on mixed Taguchi L18 factorial plan were conducted under dry cutting conditions for the machining couple: AISI D3 steel/mixed ceramic inserts (CC650. The machining parameters taken into account during this study are as follow: major cutting edge angle (χr, cutting insert nose radius (r, cutting speed (Vc, feed rate (f, and depth of cut (ap. Significant effects of machining parameters and their interactions were evaluated by the analysis of variance. Through this analysis, it have been found clearly that feed rate and cutting insert nose radius had a big significant effects on surface quality while depth of cut, feed rate followed by cutting speed had a major effect on productivity. The mathematical relationship between the machining parameters and the performance characteristics was formulated by using a linear regression model with interactions. Optimal levels of parametric combination for achieving the higher surface quality with maximum productivity were selected by grey relational analysis which is based on the high value of grey relational grade. Confirmation experiments were carried out to prove the powerful improvement of experimental results and to validate the effectiveness of the multi-optimization technique applied in this paper.

  4. Nonlinear electrostrictive lattice response of EuTiO3

    Science.gov (United States)

    Pappas, P.; Calamiotou, M.; Köhler, J.; Bussmann-Holder, A.; Liarokapis, E.

    2017-07-01

    An epitaxial EuTiO3 (ETO) film grown on the SrTiO3 substrate was studied at room temperature with synchrotron XRD and in situ application of an electric field (nominally up to 7.8 kV/cm) in near grazing incidence geometry, in order to monitor the response of the lattice to the field. 2D diffraction images show that apparently misoriented coherently diffracting domains are present close to the surface whereas the film diffracts more as a single crystal towards the interface. Diffraction intensity profiles recorded from the near surface region of the EuTiO3 film showed systematic modifications upon the application of the electric field, indicating that at a critical electric field (nominally above 3.1 kV/cm), there is a clear change in the lattice response to the field, which was much stronger when the field was almost parallel to the diffraction vector. The data suggest that the ETO film, nominally paraelectric at room temperature, transforms under the application of a critical electric field to piezoelectric in agreement with a theoretical analysis based on a double-well potential. In order to exclude effects arising from the substrate, this has been investigated separately and shown not to be affected by the field.

  5. Numerical analysis of the chemical kinetic mechanisms of ozone depletion and halogen release in the polar troposphere

    Science.gov (United States)

    Cao, L.; Sihler, H.; Platt, U.; Gutheil, E.

    2014-04-01

    The role of halogen species (e.g., Br, Cl) in the troposphere of polar regions has been investigated since the discovery of their importance for boundary layer ozone destruction in the polar spring about 25 years ago. Halogen species take part in an auto-catalytic chemical reaction cycle, which releases Br2 and BrCl from the sea salt aerosols, fresh sea ice or snowpack, leading to ozone depletion. In this study, three different chemical reaction schemes are investigated: a bromine-only reaction scheme, which then is subsequently extended to include nitrogen-containing compounds and chlorine species and corresponding chemical reactions. The importance of specific reactions and their rate constants is identified by a sensitivity analysis. The heterogeneous reaction rates are parameterized by considering the aerodynamic resistance, a reactive surface ratio, β, i.e., the ratio of reactive surface area to total ground surface area, and the boundary layer height, Lmix. It is found that for β = 1, a substantial ozone decrease occurs after five days and ozone depletion lasts for 40 h for Lmix = 200 m. For about β ≥ 20, the time required for major ozone depletion ([O3] layer, and for β = 100 it approaches two days, 28 h of which are attributable to the induction and 20 h to the depletion time. In polar regions, a small amount of NOx may exist, which stems from nitrate contained in the snow, and may have a strong impact on the ozone depletion. Therefore, the role of nitrogen-containing species on the ozone depletion rate is studied. The results show that the NOx concentrations are influenced by different chemical reactions over different time periods. During ozone depletion, the reaction cycle involving the BrONO2 hydrolysis is dominant. A critical value of 0.0004 of the uptake coefficient of the BrONO2 hydrolysis reaction at the aerosol and saline surfaces is identified, beyond which the existence of NOx species accelerates the ozone depletion event, whereas for lower

  6. Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

    Science.gov (United States)

    2016-10-14

    KEYWORDS Ferroelectric liquid crystals; solid state ferroelectrics; FLC- nanocomposites ; surface phenomena Introduction Nematic Liquid Crystals are...FLC/ BaTiO3 nanocolloids were investigated. Similar results were obtained in [10] and [11] for FLC/BaTiO3 nanocomposites studied on non- harvested...polymer concentrations were spin coated at 3500 rpm for three minutes on the ITO coated glass plates to obtain films of different thick- ness

  7. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    Science.gov (United States)

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-08

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  8. Modified structural characteristics and enhanced electrochemical properties of oxygen-deficient Li2MnO3-δ obtained from pristine Li2MnO3

    Science.gov (United States)

    Tan, Xiao; Liu, Rui; Xie, Congxin; Shen, Qiang

    2018-01-01

    Lithium-rich manganese(IV) oxide Li2MnO3 has hardly any activity as the cathode active substance of lithium-ion batteries (LIBs) but its reversible capacity can be greatly improved by introducing oxygen deficiencies. After the solid-state heat treatment of nanocrystalline Li2MnO3 by sodium borohydride (NaBH4), the resulting Li2MnO3-δ crystallites comparatively acquire distinguishable appearances in color and shape and slight differences in surface composition and lattice structure. As a LIB cathode within the potential range of 2.5-4.7 V, at 20 mA g-1 pristine Li2MnO3 gives the specific discharge capacities of 3.3, 5.0 and 7.4 mAh·g-1 in the 1st, 10th and 100th cycles, while the derivative Li2MnO3-δ delivers the relatively high values of 64.8, 103.8 and 140.2 mAh·g-1 in the 1st, 10th and 120th cycles, respectively. Aside from the similar phenomenon of gradual electrochemical activation, substituting Li2MnO3-δ for Li2MnO3 means the great enhancements of charge-transfer ability and electrochemical performances. Especially, the cationic-anionic redox mechanisms of Li2MnO3 and Li2MnO3-δ are similar to each other, suggesting a possible solution to prepare high-performance xLi2MnO3-δ·(1-x)LiMO2 solid solutions for application purposes.

  9. Discovery of monoclonal antibodies cross-reactive to novel subserotypes of K. pneumoniae O3.

    Science.gov (United States)

    Guachalla, Luis M; Stojkovic, Katarina; Hartl, Katharina; Kaszowska, Marta; Kumar, Yadhu; Wahl, Benjamin; Paprotka, Tobias; Nagy, Eszter; Lukasiewicz, Jolanta; Nagy, Gábor; Szijártó, Valéria

    2017-07-26

    Klebsiella pneumoniae is responsible for nosocomial infections causing significant morbidity and mortality. Treatment of newly emerging multi-drug resistant strains is hampered due to severely limited antibiotic choices. Passive immunization targeting LPS O-antigens has been proposed as an alternative therapeutic option, given the limited variability of Klebsiella O-antigens. Here we report that the O3 serogroup, previously considered to have uniform O-antigen built of mannan, represents three different subtypes differing in the number of mannose residues within the O-antigen repeating units. Genetic analysis of the genes encoding mannose polymerization revealed differences that underline the observed structural alterations. The O3 variants represent antigenically different types based on the different reactivity pattern of murine monoclonal antibodies raised against a K. pneumoniae O3 strain. Typing of a collection of K. pneumoniae O3 clinical isolates showed that strains expressing the novel O3b antigen, the tri-mannose form, were more prevalent than those having the penta-mannose form, traditionally called O3, while the tetra-mannose variant, termed here O3a, seems to be rare. A monoclonal antibody cross-reacting with all three O3 sub-serogroups was also selected and shown to bind to the surface of various K. pneumoniae strains expressing different O3 subtypes and capsular antigens.

  10. Poly(acrylonitrile-co-vinylacetate ) /fe2o3@pedot Core-shell Nanocapsules And Nanofibers

    OpenAIRE

    Satıcı, Mehmet Tolga

    2014-01-01

    Conducting polymers could not be directly deposited onto the surface of magnetic particles due to flocculation and the hydrophilic surfaces of magnetic particles. Therefore, P(AN-co-VAc)/Fe2O3 core-shell nanocapsules with uniform size and morphology was firstly constituted by mini-emulsion polymerization technique that comprises of coating of P(AN-co-VAc) as shell onto Fe2O3 nanoparticles using as core. Because this method facilitates fabricating homogeneously nanofibers including Fe2O3 by el...

  11. Physical and electrical properties of SrTiO3 and SrZrO3

    Directory of Open Access Journals (Sweden)

    Muhamad Norhizatol Fashren

    2017-01-01

    Full Text Available Perovskite type oxide strontium titanate (SrTiO3 and strontium zirconate (SrZrO3 ceramic powder has been synthesized using conventional solid state reaction method. The powders were mixed and ground undergone calcinations at 1400°C for 12 h and sintered at 1550°C for 5h. X-ray Diffraction exposes physical properties SrTiO3 which exhibit cubic phase (space group: pm-3m at room temperature meanwhile SrZrO3 has Orthorhombic phase (space group: pnma. The electrical properties such as dielectric constant (εr, dielectric loss (tan δ, and conductivity (σ were studied in variation temperature and frequency. High dielectric constant of SrTiO3 and SrZrO3 were observed at 10 kHz for both samples about 240 and 21 respectively at room temperature. The dielectric loss of SrTiO3 and SrZrO3 is very low loss value approximately 0.00076 and 0.67512 indicates very good dielectric.

  12. modified BiFeO3–BaTiO3

    Indian Academy of Sciences (India)

    Zr0.05Ti0.95)O3 (BF–BZT) + 0.6 wt% MnO2 (used as a donor to reduce oxygen vacancies formed during calcination and sintering) ceramics were pre- pared by the conventional solid-state reaction method. Dried oxides of high-purity Bi2O3, ...

  13. Electronic structure of buried LaNiO3 layers in (111-oriented LaNiO3/LaMnO3 superlattices probed by soft x-ray ARPES

    Directory of Open Access Journals (Sweden)

    F. Y. Bruno

    2017-01-01

    Full Text Available Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy, we report electronic structure measurements of (111-oriented [LaNiO3/LaMnO3] superlattices and LaNiO3 epitaxial films. For thin films, we observe a 3D Fermi surface with an electron pocket at the Brillouin zone center and hole pockets at the zone vertices. Superlattices with thick nickelate layers present a similar electronic structure. However, as the thickness of the LaNiO3 is reduced, the superlattices become insulating. These heterostructures do not show a marked redistribution of spectral weight in momentum space but exhibit a pseudogap of ≈50 meV.

  14. Catalytic surface promotion of highly active La0.85Sr0.15Cr0.8Ni0.2O3-δ anodes for La5.6WO11.4-δ based proton conducting fuel cells

    DEFF Research Database (Denmark)

    Solis, C.; Balaguer, M.; Bozza, Francesco

    2014-01-01

    to the widely used NiO. Under typical anode reducing conditions, Ni is segregated from the LSCN lattice on the grain surface as metallic Ni nanoparticles, which are proved to be compatible with LWO in reducing conditions. These Ni nanoparticles become the catalytic active sites for the H-2 oxidation reaction......, the R-p, values achieved for LSCN infiltrated with Ni, e.g. 0.47 Omega cm(2) at 700 degrees C, suggest the practical application of this kind of anodes in proton conducting solid oxide fuel cells (PC-SOFC). (C) 2013 Elsevier B.V. All rights reserved.......La0.85Sr0.15CrO3-delta (LSC), La0.85Sr0.15Cr0.8Ni0.2O3-delta (LSCN) and LSCN infiltrated with Ni nanoparticles were tested as anodes for symmetrical cells based on La5.6WO11.4-delta (LWO) protonic electrolyte. These chromite-based electrode materials are compatible with LWO material, in contrast...

  15. Thermoluminescence of LaAlO3

    International Nuclear Information System (INIS)

    Morales H, A.; Zarate M, J.; Rivera M, T.; Azorin N, J.

    2015-10-01

    In this paper the thermoluminescent properties of doped lanthanum aluminate (LaAlO 3 ) with dysprosium ion (Dy) were studied. The thermoluminescence characteristics in the samples were obtained using an ultraviolet radiation of 220 nm. The LaAlO 3 :Dy samples were prepared by the modified Pechini method (Spray Dryer). The structural and morphological characterization was obtained by X-ray diffraction (XRD) and scanning electron microscopy (Sem) techniques respectively. The size particle composing the agglomerate was determined by Sem, agglomerated particles composed size of 2μm were observed. The thermoluminescence response of LaAlO 3 :Dy was compared with that obtained with the undoped sample. Thermoluminescence brightness curves of LaAlO 3 :Dy showed a peak centered at 185 grades C. Sensitivity of doped sample was greater, about 100 times compared with the undoped sample. Thermoluminescence response in function of the wavelength showed a maximum at 220 nm. Also the fading in thermoluminescence response was studied. (Author)

  16. Capital expenditure and depletion

    International Nuclear Information System (INIS)

    Rech, O.; Saniere, A.

    2003-01-01

    In the future, the increase in oil demand will be covered for the most part by non conventional oils, but conventional sources will continue to represent a preponderant share of the world oil supply. Their depletion represents a complex challenge involving technological, economic and political factors. At the same time, there is reason for concern about the decrease in exploration budgets at the major oil companies. (author)

  17. Gas-sensing properties of In2O3 films modified with gold nanoparticles

    International Nuclear Information System (INIS)

    Korotcenkov, G.; Brinzari, V.; Han, S.H.; Cho, B.K.

    2016-01-01

    A study of the surface and gas–sensitive properties of In 2 O 3 films modified with gold nanoparticles and synthesized by the successive ionic layer deposition (SILD) method was conducted. In 2 O 3 films were prepared using the spray pyrolysis method. The gas-sensing characteristics were tested using CO, H 2 , and O 3 as target gases. It has been shown that the surface modification with gold nanoparticles gives the opportunity to optimize the response of In 2 O 3 -based gas sensors to both reducing (CO, H 2 ) and oxidizing (O 3 ) gases. It has been found that the sensitizing effect during ozone detection was significantly higher than the effect during CO and H 2 detection. It has been demonstrated that the sensitizing effect depended on the number of SILD cycles used for gold nanoparticle deposition and was maximal for the In 2 O 3 surface decorated with gold nanoparticles with the smallest size. The mechanism of the gold nanoparticles' influence on the gas-sensing properties of the In 2 O 3 films is also discussed. It is suggested that to explain the observed effects, we have to consider both the “electronic” and “chemical” mechanisms of sensitization. Suggestions for studies to be carried out to further improve both the understanding of the nature of the gas-sensitive effects and the parameters of In 2 O 3 :Au-based gas sensors are also formulated. - Highlights: • In 2 O 3 gas sensors modified with gold nanoparticles using SILD method are studied. • AuNPs exhibit activity during interaction with either reducing or oxidizing gases. • Maximal effect of optimization is observed during ozone detection. • Sensitizing effect depends on the number of SILD cycles. • Proposed mechanisms explain effects observed in the In 2 O 3 :Au based gas sensors.

  18. Kinetics of Transformation of Al2O3 to MgO·Al2O3 Spinel Inclusions in Mg-Containing Steel

    Science.gov (United States)

    Liu, Chunyang; Yagi, Motoki; Gao, Xu; Kim, Sun-joong; Huang, Fuxiang; Ueda, Shigeru; Kitamura, Shin-ya

    2018-02-01

    During ladle furnace refining, initial Al2O3 inclusions generally transform into MgO·Al2O3 spinel inclusions; these generated spinel inclusions consequently deteriorate the product quality. In this study, the transformation from Al2O3 to MgO·Al2O3 was investigated by immersing an Al2O3 rod into molten steel, which was in equilibrium with both MgO and MgO·Al2O3 spinel-saturated slag. A spinel layer, with a thickness of 4 μm, was generated on the Al2O3 rod surface just 10 s after its immersion at 1873 K (1600 °C). The thickness of the formed spinel layer increased with the immersion period and temperature. Moreover, the MgO content of the generated spinel layer also increased with the immersion period. In this study, the chemical reaction rate at 1873 K (1600 °C) was assumed to be sufficiently high, and only diffusion was considered as a rate-controlling step for this transformation. By evaluating the activation energy, MgO diffusion in the generated spinel layer was found to be the rate-controlling step. In addition, this estimation was confirmed by observing the Mg and Al concentration gradients in the generated spinel layer. The results of this study suggest that the MgO diffusion in the spinel inclusions plays a substantial role with regard to their formation kinetics.

  19. Characterization of Nd2AlO3N and Sm2AlO3N oxynitrides synthesized by carbothermal reduction and nitridation

    International Nuclear Information System (INIS)

    Chevire, Francois; Pallu, Arthur; Ray, Erwan; Tessier, Franck

    2011-01-01

    Research highlights: → Carbothermal reduction and nitridation leads to rare earth aluminum oxynitride starting from oxide mixture. → Absorption shifts towards visible in Nd 2 AlO 3 N (orange) and Sm 2 AlO 3 N (yellow). → Oxynitrides are stable up to 600 deg. C in air. → The so-called 'intermediate phase' phenomenon is evidenced in Sm 2 AlO 3 N. - Abstract: The Nd 2 AlO 3 N and Sm 2 AlO 3 N oxynitrides with the K 2 NiF 4 -type structure have been prepared from oxide mixture at 1250 deg. C using the carbothermal reduction and nitridation route (CRN). Optimization of the process is discussed to prevent surface oxidation of the oxynitrides during the synthesis. The absorption of Nd 2 AlO 3 N and Sm 2 AlO 3 N, orange and yellow respectively, has been characterized by diffuse reflectance as well as their thermal stability versus oxidation by thermogravimetric analyses.

  20. Synthesis of BiFeO3 thin films on single-terminated Nb : SrTiO3 (111 substrates by intermittent microwave assisted hydrothermal method

    Directory of Open Access Journals (Sweden)

    Ivan Velasco-Davalos

    2016-06-01

    Full Text Available We report on a simple and fast procedure to create arrays of atomically flat terraces on single crystal SrTiO3 (111 substrates and the deposition of ferroelectric BiFeO3 thin films on such single-terminated surfaces. A microwave-assisted hydrothermal method in deionized water and ammonia solution selectively removes either (SrO34− or Ti4+ layers to ensure the same chemical termination on all terraces. Measured step heights of 0.225 nm (d111 and uniform contrast in the phase image of the terraces confirm the single termination in pure and Nb doped SrTiO3 single crystal substrates. Multiferroic BiFeO3 thin films were then deposited by the same microwave assisted hydrothermal process on Nb : SrTiO3 (111 substrates. Bi(NO33 and Fe(NO33 along with KOH served as the precursors solution. Ferroelectric behavior of the BiFeO3 films on Nb : SrTiO3 (100 substrates was verified by piezoresponse force microscopy.

  1. Hydrothermal syntheses and characterization of two layered molybdenum selenites, Rb2(MoO3)3SeO3 and Tl2(MoO3)3SeO3

    International Nuclear Information System (INIS)

    Dussack, L.L.; Harrison, W.T.A.; Jacobson, A.J.

    1996-01-01

    The hydrothermal syntheses of Rb 2 (MoO 3 ) 3 SeO 3 , and Tl 2 (MoO 3 ) 3 SeO 3 are described. These compounds have structures built up from hexagonal-WO 3 -type sheets and are isostructural with the previously reported Cs 2 (MoO 3 ) 3 SeO 3 and (NH 4 ) 2 (MoO 3 ) 3 SeO 3 . Powder X-ray, thermogravimetric, and spectroscopic data are presented and discussed

  2. Influence of insolubility of silver on the Hirshfeld surface analyses and magnetic behavior of La0.5Ca0.1Ag0.4MnO3 compound

    Science.gov (United States)

    Felhi, H.; Smari, M.; Walha, I.; Dhahri, E.; Valente, M. A.; Bessais, L.

    2018-01-01

    In the present study, we report a detail investigation on the effect of insolubility of Ag 40% doping on the structural and magnetic properties of LCMO-Ag compound prepared by solid-state reaction. The analysis of X-ray diffraction for our samples using Rietveld refinement showed that they crystallize in the orthorhombic structure with Pnma space group. We have shown that this compound has a secondary phase (Ag metallic phase). The detailed analyses of Hirshfeld surface and fingerprint plots provide insight into the nature of intermolecular interactions in the title compound. Magnetization measurements versus temperature at different magnetic fields have shown the presence of two magnetic transitions. This result was confirmed previously in the crystallographic study. This phase exhibits magnetic properties, which has a Curie temperature (Tc) which is lower than the Curie temperature of the FM-PM transition. The critical properties of perovskite manganite LCMO-Ag around of transition with Tc = 230 K is investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis. Moreover, the critical exponents also obeyed the single scaling equation of M(H, ɛ)|ɛ|-β = f±(H|ɛ|-(β+γ)). We find that the critical exponent for LCMO-Ag is close to that theoretically predicted for mean field tricritical model.

  3. Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

    International Nuclear Information System (INIS)

    Liu Lingun; Irifune, T.

    1995-01-01

    Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

  4. Ozone-depleting Substances (ODS)

    Data.gov (United States)

    U.S. Environmental Protection Agency — This site includes all of the ozone-depleting substances (ODS) recognized by the Montreal Protocol. The data include ozone depletion potentials (ODP), global warming...

  5. Raman and Fluorescence Spectroscopy of CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7

    Directory of Open Access Journals (Sweden)

    Jianlan Cui

    2015-01-01

    Full Text Available To better understand and ascertain the mechanisms of flotation reagent interaction with rare earth (RE minerals, it is necessary to determine the physical and chemical properties of the constituent components. Seven rare earth oxides (CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7 that cover the rare earth elements (REEs from light to heavy REEs have been investigated using Raman spectroscopy. Multiple laser sources (wavelengths of 325 nm, 442 nm, 514 nm, and 632.8 nm for the Raman shift ranges from 100 cm−1 to 5000 cm−1 of these excitations were used for each individual rare earth oxide. Raman shifts and fluorescence emission have been identified. Theoretical energy levels for Er, Nd, and Yb were used for the interpretation of fluorescence emission. The experimental results showed good agreement with the theoretical calculation for Er2O3 and Nd2O3. Additional fluorescence emission was observed with Yb2O3 that did not fit the reported energy level diagram. Tb4O7 was observed undergoing laser induced changes during examination.

  6. Pretreatment of shale gas drilling flowback fluid (SGDF) by the microscale Fe0/persulfate/O3 process (mFe0/PS/O3).

    Science.gov (United States)

    Zhang, Heng; Xiong, Zhaokun; Ji, Fangzhou; Lai, Bo; Yang, Ping

    2017-06-01

    Shale gas drilling flowback fluid (SGDF) generated during shale gas extraction is of great concern due to its high total dissolved solid, radioactive elements and organic matter. To remove the toxic and refractory pollutants in SGDF and improve its biodegradability, a microsacle Fe 0 /Persulfate/O 3 process (mFe 0 /PS/O 3 ) was developed to pretreat this wastewater obtained from a shale gas well in southwestern China. First, effects of mFe 0 dosage, O 3 flow rate, PS dosage, pH values on the treatment efficiency of mFe 0 /PS/O 3 process were investigated through single-factor experiments. Afterward, the optimal conditions (i.e., pH = 6.7, mFe 0 dosage = 6.74 g/L, PS = 16.89 mmol/L, O 3 flow rate = 0.73 L/min) were obtained by using response surface methodology (RSM). Under the optimal conditions, high COD removal (75.3%) and BOD 5 /COD ratio (0.49) were obtained after 120 min treatment. Moreover, compared with control experiments (i.e., mFe 0 , O 3 , PS, mFe 0 /O 3 , mFe 0 /PS, O 3 /PS), mFe 0 /PS/O 3 system exerted better performance for pollutants removal in SGDF due to strong synergistic effect between mFe 0 , PS and O 3 . In addition, the decomposition or transformation of the organic pollutants in SGDF was analyzed by using GC-MS. Finally, the reaction mechanism of the mFe 0 /PS/O 3 process was proposed according to the analysis results of SEM-EDS and XRD. It can be concluded that high-efficient mFe 0 /PS/O 3 process was mainly resulted from the combination effect of direct oxidation by ozone and persulfate, heterogeneous and homogeneous catalytic oxidation, Fenton-like reaction and adsorption. Therefore, mFe 0 /PS/O 3 process was proven to be an effective method for pretreatment of SGDF prior to biological treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Neutron irradiation damage in Al2O3 and Y2O3

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.; Bunch, J.M.; Ranken, W.A.

    1975-01-01

    Two ceramics under consideration for use in fusion reactors, Al 2 O 3 and Y 2 O 3 , were irradiated in the EBR-II fission reactor at 650, 875, and 1025 0 K to fluences between 2 and 6 x 10 21 n/cm 2 (E greater than 0.1 MeV). Samples evaluated include sapphire, Lucalox, alumina, Y 2 O 3 , and Y 2 O 3 -10 percent ZrO 2 (Yttralox). All Al 2 O 3 specimens swelled significantly (1 to 3 percent), with most of the growth observed in sapphire along the c-axis at the higher temperatures. Al 2 O 3 samples irradiated at 875 to 1025 0 K contained a high density of small aligned ''pores''. Irradiated Y 2 O 3 -based ceramics exhibited dimensional stability and a defect content consisting primarily of unresolved damage and/or dislocation loops. The behavior of these ceramics under irradiation is discussed, and the relevance of fission neutron damage studies to fusion reactor applications is considered. (auth)

  8. Fabrication and electromagnetic performance of talc/NiTiO3 composite

    Science.gov (United States)

    Qin, Wen-Li; Xia, Tian; Ye, Ying; Zhang, Ping-Ping

    2018-02-01

    In this study, the electromagnetic (EM) performance of talc/NiTiO3 composite was evaluated. The morphology of talc displayed a lamella structure; there were many nanoparticles of NiTiO3 coated on the talc lamella. Thermal destruction occurred, which increased the surface area from 2.51 m2 g-1 to 79.09 m2 g-1 at the calcined stage at 650°C. The presence of NiTiO3 increased dielectric loss and magnetic loss of talc. The calculation of EM wave absorption of talc/NiTiO3 obtained a maximum reflection loss of -11.94 dB at the thickness of 6.85 mm; the optimum thickness for microwave absorption is 6.3-7.3 mm. This study revealed a new approach for fabricating an EM absorber and broadening applications of both talc and NiTiO3 in EM absorption.

  9. Synthesis and Characterization of Gd2O3 Hollow Microspheres Using a Template-Directed Method

    Science.gov (United States)

    Jiang, Xueliang; Yu, Lu; Yao, Chu; Zhang, Fuqing; Zhang, Jiao; Li, Chenjian

    2016-01-01

    Uniform rare-earth gadolinium oxide (Gd2O3) hollow microspheres, as formed through a urea-assisted homogenous precipitation process using carbon spheres as a template and a subsequent heat treatment, were characterized by using X-ray diffraction, Fourier transformed infared spectroscopy, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Tellet surface area measurement. The results indicate that the final products can be indexed to a cubic Gd2O3 phase with high purity and have a uniform morphology at 500 nm in diameter and 20 nm in shell thickness. The as-synthesized Gd2O3 hollow microspheres exhibited a superior photooxidation activity to that of Gd2O3 powder and an effect similar to P25, significantly broadening the potential of Gd2O3 hollow microspheres for many practical applications. PMID:28773446

  10. Synthesis and Characterization of Gd2O3 Hollow Microspheres Using a Template-Directed Method

    Directory of Open Access Journals (Sweden)

    Xueliang Jiang

    2016-04-01

    Full Text Available Uniform rare-earth gadolinium oxide (Gd2O3 hollow microspheres, as formed through a urea-assisted homogenous precipitation process using carbon spheres as a template and a subsequent heat treatment, were characterized by using X-ray diffraction, Fourier transformed infared spectroscopy, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Tellet surface area measurement. The results indicate that the final products can be indexed to a cubic Gd2O3 phase with high purity and have a uniform morphology at 500 nm in diameter and 20 nm in shell thickness. The as-synthesized Gd2O3 hollow microspheres exhibited a superior photooxidation activity to that of Gd2O3 powder and an effect similar to P25, significantly broadening the potential of Gd2O3 hollow microspheres for many practical applications.

  11. Photochemistry of the α-Al2O3-PETN Interface

    Directory of Open Access Journals (Sweden)

    Roman V. Tsyshevsky

    2016-02-01

    Full Text Available Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al2O3-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C5H8N4O12 and a wide band gap aluminum oxide (α-Al2O3 substrate. The first principles modeling is used to deconstruct and interpret the α-Al2O3-PETN absorption spectrum that has distinct peaks attributed to surface F0-centers and surface—PETN transitions. We predict the low energy α-Al2O3 F0-center—PETN transition, producing the excited triplet state, and α-Al2O3 F0-center—PETN charge transfer, generating the PETN anion radical. This implies that irradiation by commonly used lasers can easily initiate photodecomposition of both excited and charged PETN at the interface. The feasible mechanism of the photodecomposition is proposed.

  12. Residual stresses in the Al2O3 matrix of Al2O3ZrO2

    International Nuclear Information System (INIS)

    Feng, G.; Tsakalakos, T.; Mayo, W.; Wilfinger, K.; Cannon, W.R.

    1989-01-01

    Residual stresses in the Al 2 O 3 matrix of ground and unground surfaces of zirconia toughened alumina were measured with x-ray techniques. No net residual stresses were found on as-fired surfaces, but residual stresses were found on ground surfaces, increasing with severity of grinding and were proportional to the percent ZrO 2 undergoing the tetragonal monoclinic transformation during grinding. Principal stresses and directions with respect to the grinding direction were obtained. Also Warren-Averbach measurements were made on as- fired surfaces to determine the nonuniform stresses surrounding the particles. These stresses were also found to depend on the monoclinic content which in turn was controlled by the size of the particles

  13. CHF Enhancement in Flow Boiling using Al2O3 Nano-Fluid and Al2O3 Nano-Particle Deposited Tube

    International Nuclear Information System (INIS)

    Kim, Tae Il; Chun, T. H.; Chang, S. H.

    2010-01-01

    Nano-fluids are considered to have strong ability to enhance CHF. Most CHF experiments using nano-fluids were conducted in pool boiling conditions. However there are very few CHF experiments with nano-fluids in flow boiling condition. In the present study, flow boiling CHF experiments using bare round tube with Al 2 O 3 nano-fluid and Al 2 O 3 nano-particle deposited tube with DI water were conducted under atmospheric pressure. CHFs were enhanced up to ∼ 80% with Al 2 O 3 nano-fluid and CHFs with Al 2 O 3 nano-particle deposited tube were also enhanced up to ∼ 80%. Inner surface of test section tube were observed by SEM and AFM after CHF experiments

  14. Chemistry of the Fe2O3/BiFeO3 Interface in BiFeO3 Thin Film Heterostructures

    Directory of Open Access Journals (Sweden)

    Valanoor Nagarajan

    2010-12-01

    Full Text Available We investigate the interfacial chemistry of secondary Fe2O3 phases formed in a BiFeO3 (BFO layer in BFO/ La0.67Sr0.33MnO3 (LSMO/SrTiO3 (STO heterostructures. A combination of high-resolution spherical aberration corrected scanning TEM and spectroscopy results, reveals that specific chemical and crystallographic similarities between Fe2O3 and BFO, enable the BFO layer to form a facile host for Fe2O3.

  15. Pre-Treatment of Antibiotic Formulation Wastewater by O3, O3/H2O2, and O3/UV Processes

    OpenAIRE

    O, Pre-Treatment of Antibiotic Formulation

    2004-01-01

    The treatment of synthetically prepared antibiotic formulation wastewater with O3, O3/H2O2, and O3/UV processes was examined. The efficiencies of the treatment processes were compared by means of COD, absorbance removals, and biodegradability enhancement. The efficiencies of O3/pH = 7, O3/ pH = 12, and O3/H2O2 (50 mM) processes were almost identical in terms of COD and UV254 removals. The BOD5/COD ratio of formulation wastewater increased from 0.02 to 0.38 and 0.5 at the end of 1 hr...

  16. Joint effect of gate bias and light illumination on metallic LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Yang, Zhihuan; Chen, Yuansha; Zhang, Hongrui; Huang, Hailin; Wang, Shufang; Wang, Shuanhu; Shen, Baogen; Sun, Jirong

    2017-12-01

    We presented a systemic investigation on the joint effect of gate bias and light illumination on a metallic LaAlO3/SrTiO3 interface in the temperature range from 15 K to 300 K. We showed that the photo excitation significantly enhanced the gating effect for the metallic two-dimensional electron gas. However, its effect is strongly temperature dependent; it is strong at low and high temperatures, and weak in the intermediate temperature range. There are evidences that the amplified gating effect stemmed from enhanced carrier depletion while the Hall mobility remains nearly unaffected. Acceleration of the gating process, together with a training effect marked by a strong dependence on gating history of the getting effect, is induced by repeating the electric cycling, indicating atomic reconfiguration due to oxygen migration and the memory of the migration paths.

  17. Electric field modulated conduction mechanism in Al/BaTiO3/La0.67Sr0.33MnO3 heterostructures

    KAUST Repository

    Zheng, Dongxing

    2017-08-08

    Mediating a metastable state is a promising way to achieve a giant modulation of physical properties in artificial heterostructures. A metastable state La0.67Sr0.33MnO3 (LSMO) layer suffering tensile strain was grown on MgO substrates. Incorporating with the ferroelectric BaTiO3 (BTO) layer, an accumulation or depletion state controlled by electric fields can be formed at the BTO/LSMO interface, which drives a switching of the conduction mechanism between space charge limited conduction and Poole-Frenkel emission, corresponding to the low and high resistance states. Our results lighten an effective way for electric-field modulated resistance states in multiferroic magnetoelectric devices.

  18. Thermal conversion of Cu4O3 into CuO and Cu2O and the electrical properties of magnetron sputtered Cu4O3 thin films

    Science.gov (United States)

    Murali, Dhanya S.; Aryasomayajula, Subrahmanyam

    2018-03-01

    Among the three oxides of copper (CuO, Cu2O, and Cu4O3), Cu4O3 phase (paramelaconite is a natural, and very scarce mineral) is very difficult to synthesize. It contains copper in both + 1 and + 2 valence states, with an average composition Cu2 1+Cu2 2+O3. We have successfully synthesized Cu4O3 phase at room temperature (300 K) by reactive DC magnetron sputtering by controlling the oxygen flow rate (Murali and Subrahmanyam in J Phys D Appl Phys 49:375102, 2016). In the present communication, Cu4O3 thin films are converted to CuO phases by annealing in the air at 680 K and to Cu2O phase when annealed in argon at 720 K; these phase changes are confirmed by temperature-dependent Raman spectroscopy studies. Probably, this is the first report of the conversion of Cu4O3-CuO and Cu2O by thermal annealing. The temperature-dependent (300-200 K) electrical transport properties of Cu4O3 thin films show that the charge transport above 190 K follows Arrhenius-type behavior with activation energy of 0.14 eV. From photo-electron spectroscopy and electrical transport measurements of Cu4O3 thin films, a downward band bending is observed at the surface of the thin film, which shows its p-type semiconducting nature. The successful preparation of phase pure p-type semiconducting Cu4O3 could provide opportunities to further explore its potential applications.

  19. Appearance and disappearance of ferromagnetism in ultrathin LaMnO3 on SrTiO3 substrate: A viewpoint from first principles

    Science.gov (United States)

    An, Ming; Weng, Yakui; Zhang, Huimin; Zhang, Jun-Jie; Zhang, Yang; Dong, Shuai

    2017-12-01

    The intrinsic magnetic state (ferromagnetic or antiferromagnetic) of ultrathin LaMnO3 films on the most commonly used SrTiO3 substrate is a long-existing question under debate. Either strain effect or nonstoichiometry was argued to be responsible for the experimental ferromagnetism. In a recent experiment [X. R. Wang, C. J. Li, W. M. Lü, T. R. Paudel, D. P. Leusink, M. Hoek, N. Poccia, A. Vailionis, T. Venkatesan, J. M. D. Coey, E. Y. Tsymbal, Ariando, and H. Hilgenkamp, Science 349, 716 (2015), 10.1126/science.aaa5198], one more mechanism, namely, the self-doping due to polar discontinuity, was argued to be the driving force of ferromagnetism beyond the critical thickness. Here systematic first-principles calculations have been performed to check these mechanisms in ultrathin LaMnO3 films as well as superlattices. Starting from the very precise descriptions of both LaMnO3 and SrTiO3, it is found that the compressive strain is the dominant force for the appearance of ferromagnetism, while the open surface with oxygen vacancies leads to the suppression of ferromagnetism. Within LaMnO3 layers, the charge reconstructions involve many competitive factors and certainly go beyond the intuitive polar catastrophe model established for LaAlO3/SrTiO3 heterostructures. Our paper not only explains the long-term puzzle regarding the magnetism of ultrathin LaMnO3 films but also sheds light on how to overcome the notorious magnetic dead layer in ultrathin manganites.

  20. Consequences of biome depletion

    International Nuclear Information System (INIS)

    Salvucci, Emiliano

    2013-01-01

    The human microbiome is an integral part of the superorganism together with their host and they have co-evolved since the early days of the existence of the human species. The modification of the microbiome as a result changes in food and social habits of human beings throughout their life history has led to the emergence of many diseases. In contrast with the Darwinian view of nature of selfishness and competence, new holistic approaches are rising. Under these views, the reconstitution of the microbiome comes out as a fundamental therapy for emerging diseases related to biome depletion.

  1. Depleted uranium management alternatives

    Energy Technology Data Exchange (ETDEWEB)

    Hertzler, T.J.; Nishimoto, D.D.

    1994-08-01

    This report evaluates two management alternatives for Department of Energy depleted uranium: continued storage as uranium hexafluoride, and conversion to uranium metal and fabrication to shielding for spent nuclear fuel containers. The results will be used to compare the costs with other alternatives, such as disposal. Cost estimates for the continued storage alternative are based on a life-cycle of 27 years through the year 2020. Cost estimates for the recycle alternative are based on existing conversion process costs and Capital costs for fabricating the containers. Additionally, the recycle alternative accounts for costs associated with intermediate product resale and secondary waste disposal for materials generated during the conversion process.

  2. O(3)-invariant tunneling in general relativity

    International Nuclear Information System (INIS)

    Berezin, V.A.; Tkachev, I.I.; Kuzmin, V.A.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1987-12-01

    We derived a general formula for the action for any O(3)-invariant tunneling processes in false vacuum decay in general relativity. The general classification of the bubble Euclidean trajectories is elaborated and explicit expressions for bounces for some processes like the vacuum creation of a double bubble, in particular in the vicinity of a black hole; the subbarrier creation of the Einstein-Rosen bridge, creation from nothing of two Minkowski worlds connected by a shell etc., are given. (orig.)

  3. Large biogenic contribution to boundary layer O3-CO regression slope in summer

    Science.gov (United States)

    Cheng, Ye; Wang, Yuhang; Zhang, Yuzhong; Chen, Gao; Crawford, James H.; Kleb, Mary M.; Diskin, Glenn S.; Weinheimer, Andrew J.

    2017-07-01

    Strong correlation between O3 and CO was observed during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) aircraft experiment in July 2011 over the Washington-Baltimore area. The observed correlation does not vary significantly with time or altitude in the boundary layer. The observations are simulated well by a regional chemical transport model. We analyze the model results to understand the factors contributing to the observed O3-CO regression slope, which has been used in past studies to estimate the anthropogenic O3 production amount. We trace separately four different CO sources: primary anthropogenic emissions, oxidation of anthropogenic volatile organic compounds, oxidation of biogenic isoprene, and transport from the lateral and upper model boundaries. Modeling analysis suggests that the contribution from biogenic isoprene oxidation to the observed O3-CO regression slope is as large as that from primary anthropogenic CO emissions. As a result of decrease of anthropogenic primary CO emissions during the past decades, biogenic CO from oxidation of isoprene is increasingly important. Consequently, observed and simulated O3-CO regression slopes can no longer be used directly with an anthropogenic CO emission inventory to quantify anthropogenic O3 production over the United States. The consistent enhancement of O3 relative to CO observed in the boundary layer, as indicated by the O3-CO regression slope, provides a useful constraint on model photochemistry and emissions.

  4. Microemulsion mediated synthesis of BaTiO3 – Ag nanocomposites

    Directory of Open Access Journals (Sweden)

    Songhak Yoon

    2009-06-01

    Full Text Available BaTiO3 – Ag composite nanopowders were synthesized via microemulsion mediated synthesis through the hydrolytic decomposition of mixed metal alkoxide solutions as precursor for the BaTiO3 and the reduction of silver nitrate in the presence of polyvinylpyrrolidone (PVP as source for the Ag nanoparticles. The X-ray diffraction (XRD patterns indicate that BaTiO3 and Ag phases were successfully synthesized in the composite powders. Scanning electron microscopy (SEM and transmission electron microscopy (TEM show that the synthesized BaTiO3 nanoparticles were aggregates of nanosized primary particles as small as 10 nm in diameter and the average particle size of nanocrystalline Ag was about 100 nm. Calcination and sintering studies reveal that there exists a difference in the sintering behaviour of BaTiO3 and Ag in the composite nanopowders. Thermogravimetric analysis (TGA shows weight losses due to the burnout of organic residues arising from the synthesis, the release of water from the surface and separation of hydroxyl ions from the lattice of BaTiO3 nanoparticles. A dilatometric study of BaTiO3-Ag composite confi rmed a strong difference in the shrinkage behaviour compared to that of the pure BaTiO3 obtained by microemulsion mediated synthesis.

  5. LCAO calculations of SrTiO3 nanotubes

    Science.gov (United States)

    Evarestov, Robert; Bandura, Andrei

    2011-06-01

    The large-scale first-principles simulation of the structure and stability of SrTiO3 nanotubes is performed for the first time using the periodic PBE0 LCAO method. The initial structures of the nanotubes have been obtained by the rolling up of the stoichiometric SrTiO3 slabs consisting of two or four alternating (001) SrO and TiO2 atomic planes. Nanotubes (NTs) with chiralities (n,0) and (n,n) have been studied. Two different NTs were constructed for each chirality: (I) with SrO outer shell, and (II) with TiO2 outer shell. Positions of all atoms have been optimized to obtain the most stable NT structure . In the majority of considered cases the inner or outer TiO2 shells of NT undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances in the initial cubic perovskite structure. There were found two types of surface reconstruction: (1) breaking of Ti-O bonds with creating of Ti = O titanyl groups in outer surface; (2) inner surface folding due to Ti-O-Ti bending. Based on strain energy calculations the largest stability was found for (n,0) NTs with TiO2 outer shell.

  6. Structure and magnetic properties of spinel-perovskite nanocomposite thin films on SrTiO3 (111) substrates

    Science.gov (United States)

    Kim, Dong Hun; Yang, Junho; Kim, Min Seok; Kim, Tae Cheol

    2016-09-01

    Epitaxial CoFe2O4-BiFeO3 nanocomposite thin films were synthesized on perovskite structured SrTiO3 (001) and (111) substrates by combinatorial pulsed laser deposition and characterized using scanning electron microscopy, x-ray diffraction, and vibrating sample magnetometer. Triangular BiFeO3 nanopillars were formed in a CoFe2O4 matrix on (111) oriented SrTiO3 substrates, while CoFe2O4 nanopillars with rectangular or square top surfaces grew in a BiFeO3 matrix on (001) substrates. The magnetic hysteresis loops of nanocomposites on (111) oriented SrTiO3 substrates showed isotropic properties due to the strain relaxation while those of films on SrTiO3 (001) substrates exhibited a strong out-of-plane anisotropy originated from shape and strain effects.

  7. Resistance change effect in SrTiO3/Si (001) isotype heterojunction

    Science.gov (United States)

    Huang, Xiushi; Gao, Zhaomeng; Li, Pei; Wang, Longfei; Liu, Xiansheng; Zhang, Weifeng; Guo, Haizhong

    2018-02-01

    Resistance switching has been observed in double and multi-layer structures of ferroelectric films. The higher switching ratio opens up a vast path for emerging ferroelectric semiconductor devices. An n-n+ isotype heterojunction has been fabricated by depositing an oxide SrTiO3 layer on a conventional n-type Si (001) substrate (SrTiO3/Si) by pulsed laser disposition. Rectification and resistive switching behaviors in the n-n+ SrTiO3/Si heterojunction were observed by a conductive atomic force microscopy, and the n-n+ SrTiO3/Si heterojunction exhibits excellent endurance and retention characteristics. The possible mechanism was proposed based on the band structure of the n-n+ SrTiO3/Si heterojunction, and the observed electrical behaviors could be attributed to the modulation effect of the electric field reversal on the width of accumulation and the depletion region, as well as the height of potential of the n-n+ junction formed at the STO/Si interface. Moreover, oxygen vacancies are also indicated to play a crucial role in causing insulator to semiconductor transition. These results open the way to potential application in future microelectronic devices based on perovskite oxide layers on conventional semiconductors.

  8. Surface modification of cathode material 0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 by alumina for lithium-ion batteries

    Science.gov (United States)

    Li, Yonghu; Chang, Xingping; Xu, Qunjie; Lai, Chunyan; Liu, Xinnuan; Yuan, Xiaolei; Liu, Haimei; Min, Yulin

    2018-02-01

    In an attempt to overcome the irreversible capacity loss occurred during the first cycle and stabilize the surface structure, an alumina coating layer has been triumphantly prepared on the surface of 0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 cathode material with different amounts (1, 2, and 3 wt%) through a simple hydrolysis reaction, followed by an annealing process. The results reveal that the coated materials have a higher crystallinity and the particles are evenly distributed. As a cathode material for lithium-ion batteries, the 2-wt% coated sample delivers initial discharge specific capacity of 211.7 mAh g-1 at a rate of 1 C between 2.0 and 4.8 V with an initial columbic efficiency of 73.2%. Meanwhile, it exhibits the highest discharge specific capacity of 206.2 mAh g-1 with 97.4% capacity retention after 100 cycles at and much elevated rate capability compared to uncoated material. The excellent cycling stability and more superior rate property can be ascribed to alumina coating layer, which has a surface stabilization effect on these cathode materials, lessening the dissolution of metal ions. The electrochemical impedance and cyclic voltammetry studies indicate that coated by alumina improved the kinetic performance for lithium-rich layered materials, showing a prospect for practical lithium battery application.

  9. O3 Source Contribution During a Heavy O3 Pollution Episode in Shanghai China

    Science.gov (United States)

    Source culpability assessments are useful for developing effective emission control strategies. The Integrated Source Apportionment Method (ISAM) has been implemented in CMAQ to track contributions from source groups and regions to ambient levels and deposited amounts of O3. CMAQ...

  10. High-temperature phases of NaNbO3 and NaTaO3.

    Science.gov (United States)

    Darlington; Knight

    1999-02-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO(3), and sodium tantalate, NaTaO(3), have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO(3) between 753 and 793 K and of NaTaO(3) below 758 K are not as reported in the literature.

  11. [Advanced Treatment of Incineration Leachate with O3-BAC and Double O3-BAC].

    Science.gov (United States)

    Du, An-jing; Fan, Ju-hong; Liu, Rui; Qiu, Song-kai; Wen, Xiao-gang; Chen, Lü-jun

    2015-11-01

    Ozone-biological activated carbon (O3-BAC) process and double O3-BAC process were respectively used for advanced treatment of the biologically treated effluent of incineration leachate, and their pollutant removal performances were compared. The results showed that the double O3-BAC removed 75.9% ± 2.1% of chemical oxygen demand (COD), 78.8% ± 2.9% of UV254 and 96.8% ± 0.9% of color at ozone dosage of 200 mg x L(-1). The treated effluent was with COD of below 100 mg x L(-1) and color of below 40 times, meeting the emission requirements of GB 16889-2008. At the same ozone dosage, however, the O3-BAC removed 68.2% ± 1.3% of COD, 69.7% ± 0.5% of UV254 and 92.5% ± 1.1% of color. The treated effluent was with COD of around 150 mg x L(-1) and color of about 60 times, failing to meet the emission requirements. Namely, ozone of 290 mg x L(-1) was required by O3-BAC in order to achieve similar pollutant removals as those in double O3-BAC at O3 dosage of 200 mg x L(-1). In double O3-BAC at ozone dosage of 200 mg x L(-1), total phosphorus was removed by 63.5% ± 4.4%, and the phosphorus concentration in the effluent was remained 1 mg x L(-1) or less, directly meeting the emission requirement of GB 16889-2008.

  12. Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

    International Nuclear Information System (INIS)

    Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

    2012-01-01

    Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

  13. Production, characterization and application of Gd2O3 and Er2O3 nanoparticles as radiosensitizers in radiotherapy beams

    International Nuclear Information System (INIS)

    Corrêa, Eduardo de Lima

    2017-01-01

    In this study Gd 2 O 3 and Er 2 O 3 nanoparticles were produced for application as radiosensitizers in radiotherapy beams. They were synthesized at the Hyperfine Interactions Laboratory, IPEN, using thermal decomposition method and characterized by X-ray diffraction, to verify crystalline structure, transmission electron microscopy, to obtain information about shape, size and size distribution, neutron activation analysis, whereby it was possible to determine samples purity and gadolinium and erbium concentration. Magnetization and perturbed γ-γ angular correlation (PAC) measurements were performed in order to study particles magnetic behavior and quadrupole interactions, respectively. Characterization results showed a bixbyite structure, 5 nm diameter post-synthesis particles with narrow size distribution. Rare-earth mass determination in each sample was important to perform normalization in magnetic susceptibility measurements, making possible the view of a high magnetization under 30 K for post-synthesis samples, what was not observed in larger particles, together with an effective magnetic moment enhancement for nanoparticles, not seen in bulk samples, and a change in the antiferromagnetic ordering temperature for Er 2 O 3 . PAC spectroscopy results show possible surface effects. The absence of a well-defined frequency in 5 nm samples indicates the amount of 111 In( 111 Cd) at particle surface is bigger than in the core, resulting in a non-evident hyperfine interaction between the probe nuclei and the host. The X-ray diffraction and PAC spectroscopy joint was vital to understand the particles structural damage caused by 60 Co irradiation. About radiosensitizer measurements a dose enhancement factor (DEF) of up to 1,67 and 1,09 for Gd 2 O 3 nanoparticles under 60 Co and 6MV irradiation, respectively, were observed. Under same conditions DEF values of up to 1,37 and 1,06 were found for Er 2 O 3 samples. Results reached in this study provide not only important

  14. Enlargement of photocatalytic efficiency of BaSnO3 by indium doping for thiophene degradation

    Science.gov (United States)

    Sobahi, Tariq R.; Amin, M. S.; Mohamed, R. M.

    2018-02-01

    BaSnO3 nanorods were produced by a sol-gel mode. Indium, as dopant, was introduced to the surface of BaSnO3 via photo-assisted deposition technique. Phase composition, microstructure and surface area of the synthesized samples were identified via X-ray diffraction, field emission scanning electron microscopy (FESEM) and BET techniques, respectively. State of element, band gap energy and position of emission energy were measured via X-ray photoelectron spectroscopy (XPS), ultraviolet and visible spectroscopy (UV-Vis) and photoluminescence emission spectra (Pl), respectively. Furthermore, the catalytic performance of both BaSnO3 and In/BaSnO3 specimens was implemented for photocatalytic destruction of thiophene solution via visible light irradiation. XPS results displayed the patterns corresponding to the In-In at about 443.8 eV, illustrating the presence of indium metal in a nano-sized scale. A red shift was observed after indium loading within the BaSnO3 lattice which was proved via the UV-Vis analysis. 100% oxidation efficiency percent was attained using 0.3 wt% In/BaSnO3 photocatalyst after 1 h reaction time. The enhancement of the photocatalytic activity was mainly attributed to the indium doping into BaSnO3 as a result of its capability to hinder the e--h+ re-combination. The catalyst was reused up to five cycles without any change in its efficiency.

  15. Nature of Weak Magnetism in SrTiO3/LaAlO3 Multilayers

    Science.gov (United States)

    Salman, Z.; Ofer, O.; Radovic, M.; Hao, H.; Ben Shalom, M.; Chow, K. H.; Dagan, Y.; Hossain, M. D.; Levy, C. D. P.; MacFarlane, W. A.; Morris, G. M.; Patthey, L.; Pearson, M. R.; Saadaoui, H.; Schmitt, T.; Wang, D.; Kiefl, R. F.

    2012-12-01

    We report the observation of weak magnetism in superlattices of LaAlO3/SrTiO3 using β-detected nuclear magnetic resonance. The spin lattice relaxation rate of Li8 in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO3 exhibits a strong peak near ˜35K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO3/SrTiO3 interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of ˜4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (˜0.002μB) in the two samples with a larger LaAlO3 spacer thickness.

  16. Antiferromagnetism of two-dimensional electronic gas on light-irradiated SrTiO3 and at LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Gor'kov, L. P.

    2015-06-01

    To gain an insight into the origin of tunable two-dimensional (2D) electronic liquid at the interfaces of transition-metal oxides, we address properties of a conducting layer on the light-irradiated surfaces of SrTiO3; the energy spectrum of the latter is known and consists of the titanium dxz/dyz and dxy bands. Recently, Santander-Syro et al (2014 Nature Mater. 13 1085) revealed that the dxy bands actually comprise two chiral branches with the Kramers degeneracy at the zone center lifted in the absence of a magnetic moment. We suggest that interacting electrons on the irradiated SrTiO3 go over into a magnetic phase as the result of one of the instabilities of the 2D Fermi liquid with exchange interactions, and point out the concrete antiferromagnetic order parameter. Large energy scales of the order of Fermi energy ∼0.1 eV inherent in this mechanism warrant stability of the magnetic ground state against ever-present effects of disorder. Arguments are given that electrons at the irradiated SrTiO3 surface and at the LaAlO3/SrTiO3 interfaces undergo a kind of first-order transformation into one and the same phase of the 2D electronic Fermi liquid with reduced magnetic symmetry.

  17. Conductivity of A- and B-site doped LaAlO3, LaGaO3, LaScO3 and LaInO3 perovskites

    DEFF Research Database (Denmark)

    Lybye, D.; Poulsen, F.W.; Mogensen, Mogens Bjerg

    2000-01-01

    The conductivity of the materials LaAlO3, LaGaO3, LaScO3 and LaInO3 all doped with 10% strontium on the A-site and 10% magnesium at the B-site has been measured at different temperatures and oxygen partial pressures. The doped LaGaO3 is found to be an almost pure ionic conductor with a conductivi...

  18. NMR Spectroscopy of the Hydrated Layer of Composite Particles Based on Nanosized Al2O3 and Vitreous Humor

    Science.gov (United States)

    Turov, V. V.; Gerashchenko, I. I.; Markina, A. I.

    2013-11-01

    The hydrated layer of composite particles prepared using Al2O3 and cattle vitreous humor was investigated using NMR spectroscopy. It was found that water bound to Al2O3 nanoparticles was present in the form of clusters with different degrees of association and energies of interaction with the surface. Water bound to the surface of the Al2O3/vitreous humor composite became more uniform upon immobilization of vitreous humor components on the surface of the Al2O3. With this, the clusters of adsorbed water had characteristics that were close to those found in air and weakly polar CHCl3 media. Addition of polar CH3CN led to the formation of very small water clusters. PMR spectra of the surface of the Al2O3/vitreous humor composite in the presence of trifluoroacetic acid differentiated four types of hydrated structures that differed in the degree of water association.

  19. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    Administrator

    titanium oxalate (PTO) electrolyte using facile electrochemical anodization has been reported for the first time. Systematic analysis of the ... production cost, single-step process, simplicity of materi- als preparation and handling, as well ..... Liu S, Tao W, Li J, Yang Z and Liu F 2005 Powder Technol. 155 187. Martin C R 1996 ...

  20. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    friendly potassium titanium oxalate (PTO) electrolyte using facile electrochemical ... (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Tafel polarization technique and electrochemical impedance spectroscopy (EIS).

  1. Formation of a 25 mol% Fe2O3-Al2O3 solid solution prepared by ball milling

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The phase transformation process of a 25 mol% Fe2O3-Al2O3 powder mixture during high-energy ball milling has been studied by x-ray diffraction and Mossbauer spectroscopy. A metastable solid solution of 25 mol % Fe2O3 in Al2O3 with corundum structure has successfully been prepared after a milling...

  2. Inverse CeO2sbnd Fe2O3 catalyst for superior low-temperature CO conversion efficiency

    Science.gov (United States)

    Luo, Yongming; Chen, Ran; Peng, Wen; Tang, Guangbei; Gao, Xiaoya

    2017-09-01

    The paper presents a rational design of highly efficient and affordable catalysts for CO oxidation with a low operating temperature. A series of ceria-iron catalysts were inversely built via a co-precipitation method. The catalytic activity of low-temperature CO oxidation was much higher with CeO2-modified Fe2O3 (CeO2sbnd Fe2O3) than with Fe2O3-modified CeO2 (Fe2O3sbnd CeO2). In particular, the 7.5% CeO2sbnd Fe2O3 catalyst had the highest activity, reaching 96.17% CO conversion at just 25 °C. Catalyst characterization was carried out to explore the cause of the significantly different CO conversion efficiencies between the Fe2O3sbnd CeO2 and Fe2O3sbnd CeO2 catalysts. HRTEM showed a significant inhomogeneous phase in 7.5% CeO2sbnd Fe2O3 with small CeO2 nanoparticles highly dispersed on the rod-shaped Fe2O3 surface. Furthermore, the 7.5% CeO2sbnd Fe2O3 composite catalyst exhibited the highest ratios of Fe2+/Fe3+ and Ce3+/Ce4+ as well as the largest pore volume. These properties are believed to benefit the CO conversion in 7.5% CeO2sbnd Fe2O3.

  3. Renewable H2 from glycerol steam reforming: effect of La2O3 and CeO2 addition to Pt/Al2O3 catalysts.

    Science.gov (United States)

    Montini, Tiziano; Singh, Rakesh; Das, Piyali; Lorenzut, Barbara; Bertero, Nicolás; Riello, Pietro; Benedetti, Alvise; Giambastiani, Giuliano; Bianchini, Claudio; Zinoviev, Sergey; Miertus, Stanislav; Fornasiero, Paolo

    2010-05-25

    Glycerol is the main byproduct of biodiesel production and its increased production volume derives from the increasing demand for biofuels. The conversion of glycerol to hydrogen-rich mixtures presents an attractive route towards sustainable biodiesel production. Here we explored the use of Pt/Al(2)O(3)-based catalysts for the catalytic steam reforming of glycerol, evidencing the influence of La(2)O(3) and CeO(2) doping on the catalyst activity and selectivity. The addition of the latter metal oxides to a Pt/Al(2)O(3) catalyst is found to significantly improve the glycerol steam reforming, with high H(2) and CO(2) selectivities. A good catalytic stability is achieved for the Pt/La(2)O(3)/Al(2)O(3) system working at 350 degrees C, while the Pt/CeO(2)/Al(2)O(3) catalyst sharply deactivates after 20 h under similar conditions. Studies carried out on fresh and exhausted catalysts reveal that both systems maintain high surface areas and high Pt dispersions. Therefore, the observed catalyst deactivation can be attributed to coke deposition on the active sites throughout the catalytic process and only marginally to Pt nanoparticle sintering. This work suggests that an appropriate support composition is mandatory for preparing high-performance Pt-based catalysts for the sustainable conversion of glycerol into syngas.

  4. Riddle of depleted uranium

    International Nuclear Information System (INIS)

    Hussein, A.S.

    2005-01-01

    Depleted Uranium (DU) is the waste product of uranium enrichment from the manufacturing of fuel rods for nuclear reactors in nuclear power plants and nuclear power ships. DU may also results from the reprocessing of spent nuclear reactor fuel. Potentially DU has both chemical and radiological toxicity with two important targets organs being the kidney and the lungs. DU is made into a metal and, due to its availability, low price, high specific weight, density and melting point as well as its pyrophoricity; it has a wide range of civilian and military applications. Due to the use of DU over the recent years, there appeared in some press on health hazards that are alleged to be due to DU. In these paper properties, applications, potential environmental and health effects of DU are briefly reviewed

  5. Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO3) ceramics

    International Nuclear Information System (INIS)

    Billah, Masum; Ahmed, A.; Rahman, Md. Miftaur; Mahbub, Rubbayat; Gafur, M. A.; Bashar, M. Shahriar

    2016-01-01

    In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La 2 O 3 ) doped Barium Titanate (BaTiO 3 ) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO 3 with 0.3, 0.5 and 0.7 mole% La 2 O 3 under different sintering parameters. The raw materials used were La 2 O 3 nano powder of ~80 nm grain size and 99.995% purity and BaTiO 3 nano powder of 100 nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanning Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO 3 ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La 2 O 3 ) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La 2 O 3 with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La 3+ concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO 3 ceramics.

  6. Novel α-Fe2O3/CdS cornlike nanorods with enhanced photocatalytic performance.

    Science.gov (United States)

    Shi, Ye; Li, Hanying; Wang, Ling; Shen, Wei; Chen, Hongzheng

    2012-09-26

    Various semiconductors have been studied as photocatalysts for photocatalytic degradation of pollutants in aqueous solutions. As one of the promising visible-light-driven semiconductor photocatalysts, α-Fe(2)O(3) has advantages of low cost and stability. However, its application is inhibited by the poor separation of photogenerated electron-hole pair. In this work, hybrid structures were prepared to improve the performance of α-Fe(2)O(3). CdS nanoparticles were overgrown on the preformed single-crystalline α-Fe(2)O(3) nanorods by a simple and mild one-step wet-chemical method, resulting in α-Fe(2)O(3)/CdS cornlike nanocomposites. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy showed the α-Fe(2)O(3)/CdS core/shell heterostructure of the nanocomposite with high crystallinity. Furthermore, the cornlike nanocomposites exhibited superior photocatalytic performances under visible light irradiation over the pure α-Fe(2)O(3) nanorods and CdS nanoparticles. The photocatalytic activity of the composites is superior to the previously-reported pure α-Fe(2)O(3) nanomaterials, and the performance is comparable to both the commercial TiO(2) (P25) which is used under UV irradiation and the newly developed α-Fe(2)O(3)/SnO(2) photocatalyst under visible light irradiation. The enhanced performance is associated with the larger surface area of the cornlike structure, the crystalline nature of the materials and the synergy in light absorption and charge separation between α-Fe(2)O(3) and CdS. As such, our α-Fe(2)O(3)/CdS cornlike nanocomposites may be promising to be used as visible-light-driven high-performance photocatalyst.

  7. Multiferroic RMnO3 thin films

    Science.gov (United States)

    Fontcuberta, Josep

    2015-03-01

    Multiferroic materials have received an astonishing attention in the last decades due to expectations that potential coupling between distinct ferroic orders could inspire new applications and new device concepts. As a result, a new knowledge on coupling mechanisms and materials science has dramatically emerged. Multiferroic RMnO3 perovskites are central to this progress, providing a suitable platform to tailor spin-spin and spin-lattice interactions. With views towards applications, the development of thin films of multiferroic materials have also progressed enormously and nowadays thin-film manganites are available, with properties mimicking those of bulk compounds. Here we review achievements on the growth of hexagonal and orthorhombic RMnO3 epitaxial thin films and the characterization of their magnetic and ferroelectric properties, we discuss some challenging issues, and we suggest some guidelines for future research and developments. En ce qui concerne les applications, le développement de films minces de matériaux multiferroïques a aussi énormément progressé, et de nos jours des films minces de manganites avec des propriétés similaires à celles des matériaux massifs existent. Nous passons en revue ici les résultats obtenus dans le domaine de la croissance de couches minces épitaxiés de RMnO3 hexagonal et orthorhombique et de la caractérisation de leurs propriétés magnétiques et ferroélectriques. Nous discutons certains enjeux et proposons quelques idées pour des recherches et développements futurs.

  8. Nocturnal Ozone Depletion Events at the Amphitrite Point Observatory on West Vancouver Island

    Science.gov (United States)

    Garner, N.; Brownsey, D. K.; Tokarek, T. W.; Ye, C. Z.; Yordanov, N. R.; Osthoff, H. D.; Schiller, C. L.; Vingarzan, R.

    2015-12-01

    Routine monitoring stations on the West coast of North America serve to monitor baseline levels of criteria pollutants such as ozone (O3) arriving from the Pacific Ocean. In Canada, the Amphitrite Point Observatory (APO) in Ucluelet on the West coast of Vancouver Island has been added to this network to provide regional baseline measurements. Recently, McKendry and coworkers have reported frequent episodes of nocturnal O3 depletion events (ODEs) at APO (range: 5-20 ppbv) that generally correlate with alongshore winds, elevated levels of carbon dioxide (CO2), and low vertical entrainment but whose cause(s) has (have) remained unclear. In this work, results from the Ozone-depleting reactions in a coastal atmosphere (ORCA) campaign, which took place at APO from July 6 - 31, 2015, are presented. In addition to the long-term measurements that include aerosol size distribution and composition measurements, mixing ratios of speciated monoterpenes (e.g., α- and β-pinene, limonene), molecular halogens (i.e., Cl2, I2), halogen oxides (i.e., OIO), plus a full suite of nitrogen oxides (including N2O5, PAN, PPN, ΣPN, ΣAN, HNO3, HONO, and ClNO2) were quantified. Synoptic conditions at the site varied greatly between nights. During westerly flow of relatively clean marine air, O3 was generally conserved at night, indicating that deposition of O3 to the ocean surface is a minor loss pathway. When the air mass originated from other sectors, episodes of nocturnal ODEs were observed on several occasions, in which mixing ratios of biogenic VOCs were enhanced. These included air masses that originated from densely forested areas to the East, air masses polluted by marine traffic emissions from the southeast, and air masses from the NW that have traveled parallel to the coastline. In this sector, the air was likely in contact with terrestrial vegetation via land-sea breeze circulations. The results suggest that nocturnal ODEs at APO are mainly driven by local or regional processes

  9. Assessment of Ga2O3 technology

    Science.gov (United States)

    2016-09-15

    electronics application is the only driver for the technology at present. This type of electronics have a large commercial market , but there are...vol. 43, p. 7133, 2004. [119] A. J. Freeman, K. R. Poeppelmeier, T. O. Mason, R. P. H. Chang, and T. J. Marks, "Chemical and Thin-Film Strategies for...doped β-Ga2O3 single crystals," Applied Physics Letters, vol. 92, p. 201914, 2008. [138] R. A. Laudise, J. B. Mullin , B. Mutaftschiev, and K. Nassau

  10. Characterization of γ- Al2O3 nanopowders synthesized by Co-precipitation method

    International Nuclear Information System (INIS)

    Jbara, Ahmed S.; Othaman, Zulkafli; Ati, Ali A.; Saeed, M.A.

    2017-01-01

    Co-precipitation technique has been used to synthesize gamma-Al 2 O 3 (γ-Al 2 O 3 ) nanopowders under annealing temperature effect. The crystalline phase and purity for the prepared powder were characterized by different spectroscopy techniques. XRD analysis confirms the gamma phase of alumina nanopowders with particle diameter ranging from 6 to 24 nm, which confirms the quantum dots formation, which is also supported by the BET measurement. The surface area of the prepared nanopowders is in the range of 109–367 m 2 /g. Morphology analysis indicates that γ-Al 2 O 3 nanopowders are consisted of grains almost spherical in shape. Some agglomeration of nanoparticles occurs, which become more regular hexagonal shaped with the increasing annealing temperature. The small nanoparticles size and the high surface area from a simple procedure for preparing γ-Al 2 O 3 may make it more suitable for use as an adsorbent for malachite green. - Highlights: • Co-precipitation technique is used to synthesize gamma- Al 2 O 3 nanopowders. • Pure gamma- Al 2 O 3 phase was obtained having maximum nanoparticle size is 24 nm. • The quantum dots were formed inside powder. • High surface area of nanopowders at the low annealing temperature. • Increasing annealing temperature causes the hexagonal agglomeration shape.

  11. Coupling of electric charge and magnetic field via electronic phase separation in (La,Pr,Ca)MnO3/Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructures

    Science.gov (United States)

    Zheng, Ming; Wang, Wei

    2016-04-01

    The electric-field-tunable non-volatile resistivity and ferromagnetism switching in the (La0.5Pr0.5)0.67Ca0.33MnO3 films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric single-crystal substrates have been investigated. By combining the 180° ferroelectric domain switching and in situ X-ray diffraction and resistivity measurements, we identify that this voltage control of order parameters stems from the domain switching-induced accumulation/depletion of charge carriers at the interface rather than induced lattice strain effect. In particular, the polarization-induced charge effect (i.e., ferroelectric field effect) is strongly dependent on the magnetic field. This, together with the charge-modulated magnetoresistance and magnetization, reveals the strong correlation between the electric charge and the magnetic field. Further, we found that this coupling is essentially driven by the electronic phase separation, the relative strength of which could be determined by recording charge-tunability of resistivity [ (Δρ/ρ)c h arg e ] under various magnetic fields. These findings present a potential strategy for elucidating essential physics of perovskite manganites and delivering prototype electronic devices for non-volatile information storage.

  12. WOx supported on γ-Al2O3 with different morphologies as model catalysts for alkanol dehydration

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Dachuan; Wang, Huamin; Kovarik, Libor; Gao, Feng; Wan, Chuan; Hu, Jian Z.; Wang, Yong

    2018-04-21

    The distinctive morphological and surface characteristics of platelet-like γ-Al2O3 were compared to a regular, commercial γ-Al2O3. γ-Al2O3 platelets display dominant (110) surface facets and higher densities of coordinative unsaturated penta-coordinate Al3+ (Al3+penta) sites than regular γ-Al2O3, as measured by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Such Al3+penta sites are also the preferred surface anchoring sites for tungsten oxide (WOx) species consistent with NMR analysis indicating that these sites are consumed upon WOx adsorption. The higher Al3+penta density on γ-Al2O3 platelets leads to greater WOx dispersion (or smaller WOx clusters), as demonstrated by scanning transmission electron microscopy and ultraviolet–visible spectroscopy, and WOx species at intermediate WOx surface concentration are the most active for the probe reaction of 2-butanol dehydration. WOx on γ-Al2O3 platelets approaches the highest turnover rates at higher surface densities than WOx on regular γ-Al2O3, yet with similar highest rate values for both series of catalysts. This indicates that different Al2O3 supports mainly affect the dispersion of supported WOx rather than the intrinsic reactivity of individual WOx clusters with similar size.

  13. Influence of different acid etchings on the superficial characteristics of Ti sandblasted with Al2O3

    Directory of Open Access Journals (Sweden)

    Bruno Ramos Chrcanovic

    2013-01-01

    Full Text Available Some implant manufactures use Al2O3 instead TiO2 powder to sandblast the machined dental implant, because Al2O3 powder is commercially more easily available and is cheaper than TiO2 powder. However, Al2O3 powder usually leaves aluminum oxide contamination on the surface, which is potentially toxic. In this work, we subjected Ti discs previously sandblasted with Al2O3 powder to 5 different acid etchings in order to verify which treatment is able to remove incorporated particles of Al2O3 from the surface. One group of samples were only sandblasted and served as control. The samples were analyzed by electron microscopy (SEM, EDS, scanning probe microscopy, and grazing incidence XRD. The control group showed presence of Al2O3 on the surface. Three acid etchings were efficient in removing the alumina from the tested samples. Almost all the tested samples showed higher roughness parameters values than the control samples. Titanium hydride was found in almost all test groups. Moreover, the results suggest that there is no incorporation of the whole Al2O3 particle into the titanium surface after the collision, conversely a particle fragmentation occurs and what remains on the titanium surface are Al2O3 residues.

  14. Fundamental absorption of Y2O3 and YAlO3

    International Nuclear Information System (INIS)

    Abramov, V.N.; Kuznetsov, A.I.

    1978-01-01

    Reflection spectra in the range of 4-14 eV were measured for Y 2 O 3 and YAlO 3 crystals. The spectra of the following optical characteristics were calculated with the aid of the Kramers-Kroning relation: absorption, refraction, dielectric constant, and effective number of electrons. Excitons with an energy of 6.0 eV and an oscillator strength of f approximately 0.1 were found in Y 2 O 3 , and the width of the forbidden zone was determined (approximately 6.1 eV). The scheme of genealogy and arrangement of the plane zones of Y 2 O 3 , in which a substantial role is attributed to interaction of 5s and 4d states of yttrium cations, is proposed and discussed at the qualitative level. The range of the beginning of fundamental absorption (hν > or approximately 7.5 eV) was determined for YAlO 3 . The composition dependence of the width of the forbidden zone of aluminated Ysub(x)Alsub(y)Osub(z) is plotted

  15. Facile Fabrication and Properties of Gd2O3:Eu3+, Y2O3:Eu3+ Nanophosphors and Gd2O3:Eu3+/Silica, Y2O3:Eu3+/Silica Nanocomposites

    Science.gov (United States)

    Anh, Tran Kim; Chau, Pham Thi Minh; Hai, Nguyen Thi Quy; Ha, Vu Thi Thai; Van Tuyen, Ho; Bounyavong, Sengthong; Thanh, Nguyen Trong; Minh, Le Quoc

    2018-01-01

    Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been successfully fabricated by a combustion method at low temperature (350°C) in a short time (5 min) using natriethylenediaminetetraacetic acid (EDTA-Na2) as fuel. The structure, morphology and size of Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been determined by x-ray diffraction and field emission scanning electron microscopy. Photoluminescence spectra indicated that the optimum Eu3+ ion concentrations with the strongest luminescence emission intensities are 5 mol.% for Y2O3:Eu3+ and 7 mol.% for Gd2O3:Eu3+. The nanocomposites of Gd2O3:Eu3+/silica and Y2O3:Eu3+/silica were fabricated by a sol-gel process with tetraethoxysilane (TEOS) as matrix material, and the nanocomposite compositions were analyzed by energy dispersion spectra. The strongest luminescence peaks from the 5D0-7F2 transition of the Eu3+ ion in Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors are between 613 nm and 615 nm. The Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors and their silica nanocomposites were studied to elucidate the influences of the Eu3+ concentration, host materials, annealing temperature, and weight ratio of TEOS and Gd2O3:Eu3+ or Y2O3:Eu3+.

  16. The Toxicity of Depleted Uranium

    OpenAIRE

    Briner, Wayne

    2010-01-01

    Depleted uranium (DU) is an emerging environmental pollutant that is introduced into the environment primarily by military activity. While depleted uranium is less radioactive than natural uranium, it still retains all the chemical toxicity associated with the original element. In large doses the kidney is the target organ for the acute chemical toxicity of this metal, producing potentially lethal tubular necrosis. In contrast, chronic low dose exposure to depleted uranium may not produce a c...

  17. Synergistic toxic effect of nano-Al2O3 and As(V) on Ceriodaphnia dubia

    International Nuclear Information System (INIS)

    Wang Demin; Hu Ji; Forthaus, Brett E.; Wang Jianmin

    2011-01-01

    Engineered nanomaterials (ENMs) alone could negatively impact the environment and human health. However, their role in the presence of other toxic substances is not well understood. The toxicity of nano-Al 2 O 3 , inorganic As(V), and a combination of both was examined with C. dubia as the model organisms. Bare nano-Al 2 O 3 particles exhibited partial mortality at concentrations of greater than 200 mg/L. When As(V) was also present, a significant amount of As(V) was accumulated on the nano-Al 2 O 3 surface, and the calculated LC 50 of As(V) in the presence of nano-Al 2 O 3 was lower than that it was without the nano-Al 2 O 3 . The adsorption of As(V) on the nano-Al 2 O 3 surface and the uptake of nano-Al 2 O 3 by C. dubia were both verified. Therefore, the uptake of As(V)-loaded nano-Al 2 O 3 was a major reason for the enhanced toxic effect. - Highlights: → Nano-Al 2 O 3 particles alone do not have significant toxic effect on C. dubia. → However, nano-Al 2 O 3 particles significantly enhance the toxicity of As(V). → The uptake of As-loaded nano-Al 2 O 3 by C. dubia plays the major role on the toxicity. - Nano-Al 2 O 3 could accumulate background As(V) and enhance As(V) toxicity on C. dubia through the uptake of As(V)-loaded nano-Al 2 O 3 particles.

  18. Interface behaviour of Al2O3/Ti joints produced by liquid state bonding

    International Nuclear Information System (INIS)

    Lemus R, J.; Guevara L, A. O.; Zarate M, J.

    2014-08-01

    The main objective of this work was to determine various aspects during brazing of Al 2 O 3 samples to commercially titanium alloy grade 4 with biocompatibility properties, using a Au-foil as joining element. Al 2 O 3 ceramic was previously produced by sintering of powder cylindrical shape at 1550 grades C for 120 minutes. Previously to joining experiments, the surface of Al 2 O 3 samples were coating, by chemical vapor depositions (CVD) process, with a Mo layer of 2 and 4 μm thick and then stacked together with the Ti samples. Joining experiments were carried out on Al 2 O 3 -Mo/Au/Ti combinations at temperature of 1100 grades C using different holding times under vacuum atmosphere. The experimental results show a successful joining Mo-Al 2 O 3 to Ti. Analysis by scanning electron microscopy (Sem) revealed that joining of Al 2 O 3 to metal occurred by the formation of a homogeneous diffusion zone with no interfacial cracking or porosity at the interface. Results by electron probe micro analysis (EPMA) of Al 2 O 3 -Mo/Au/Ti combinations revealed that Mo traveled inside the joining elements and remained as solid solutions, however during cooling process Mo had a tendency to stay as a precipitate phase and atomic distributions of elements show a concentration line of Mo inside the joining element Au. On the other hand, well interaction of Ti with Au form different phases; like Ti 3 Au and Ti Au. (author)

  19. Porous α-Fe2O3 decorated by Au nanoparticles and their enhanced sensor performance

    Science.gov (United States)

    Liu, Xianghong; Zhang, Jun; Guo, Xianzhi; Wu, Shihua; Wang, Shurong

    2010-03-01

    Porous α-Fe2O3 was synthesized by simple calcination of a β-FeOOH precursor derived from a facile hydrothermal method. In the hydrothermal process, only FeCl3·6H2O was used as the source material and no templates or pore-directing agents were needed. The as-prepared porous α-Fe2O3 was further employed as a support for loading Au nanoparticles (AuNPs). Due to the advantages of porous nanostructures (large surface area and facile gas diffusion) and the catalytic capability of AuNPs, the derived AuNP-supported porous α-Fe2O3 was further investigated for gas sensor applications using ethanol as a probe molecule. Obtained results showed that the AuNP-supported porous α-Fe2O3 exhibited a much higher response in comparison to pure α-Fe2O3. The enhanced sensor properties are attributed to the unique porous structures of the α-Fe2O3 support and active AuNPs for promoting sensing reactions, as well as the synergic electronic interaction between Au and α-Fe2O3. It is expected that noble metals such as Ag, Pt and Pd can also be supported on other porous metal oxide semiconductors to explore superior properties of functional nanomaterials.

  20. Fabrication of hierarchical porous ZnO-Al2O3 microspheres with enhanced adsorption performance

    Science.gov (United States)

    Lei, Chunsheng; Pi, Meng; Xu, Difa; Jiang, Chuanjia; Cheng, Bei

    2017-12-01

    Hierarchical porous ZnO-Al2O3 microspheres were fabricated through a simple hydrothermal route. The as-prepared hierarchical porous ZnO-Al2O3 composites were utilized as adsorbents to remove organic dye Congo red (CR) from water. The ZnO-Al2O3 composites had morphology of microspheres with diameters in the range of 12-16 μm, which were assembled by nanosheets with thicknesses of approximately 60 nm. The adsorption kinetics of CR onto the ZnO-Al2O3 composites was properly fitted by the pseudo-second-order kinetic model. The equilibrium adsorption data were perfectly described by the Langmuir isotherm and had a maximum adsorption capacity that reached 397 mg/g, which was significantly higher than the value of the pure alumina (Al2O3) and zinc oxide (ZnO) samples. The superior CR removal efficiency of the ZnO-Al2O3 composites was attributed to its well-developed hierarchical porous structures and larger specific surface area (201 m2/g), which were conducive to the diffusion and adsorption of CR molecules. Moreover, the regeneration study reveals that the ZnO-Al2O3 composites have suitable stability and reusability. The results also indicate that the as-prepared sample can act as a highly effective adsorbent in anionic dye removal from wastewater.

  1. Octahedral rotations in strained LaAlO3/SrTiO3 (001 heterostructures

    Directory of Open Access Journals (Sweden)

    T. T. Fister

    2014-02-01

    Full Text Available Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO3/SrTiO3 (001 heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO3 transforms from the Pm3¯m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.

  2. Magnetism Control by Doping in LaAlO3/SrTiO3 Heterointerfaces.

    Science.gov (United States)

    Yan, Hong; Zhang, Zhaoting; Wang, Shuanhu; Wei, Xiangyang; Chen, Changle; Jin, Kexin

    2018-04-25

    Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO 3 /SrTiO 3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO 3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.

  3. Interaction of Pd with steps on alpha-Al2O3(0001)

    DEFF Research Database (Denmark)

    Lodziana, Zbiegniew; Nørskov, Jens Kehlet

    2002-01-01

    Based on density functional calculations, we show that steps on the alpha-Al2O3 (0 0 0 1) surface are enriched in oxygen and that they bind Pd atoms and small clusters much stronger than the terraces. We also show that Pd can diffuse quite freely on an alumina surface and use this to explain why...

  4. Electric double layer transistors with ferroelectric BaTiO3 channels

    NARCIS (Netherlands)

    Ito, M.; Matsubara, Y.; Kozuka, Y.; Takahashi, K. S.; Kagawa, F.; Ye, J. T.; Iwasa, Y.; Ueno, K.; Tokura, Y.; Kawasaki, M.

    2014-01-01

    We report the surface conduction of a BaTiO3 thin film using electric double layer transistor (EDLT) structure. A transistor operation was observed at 220 K with an on/off ratio exceeding 10(5), demonstrating that ionic liquid gating is effective to induce carriers at the surface of ferroelectric

  5. Preparation and characterization of LaNiO3 films grown by metal ...

    Indian Academy of Sciences (India)

    The LaNiO3 films prepared under optimal condition indicate highly (ℎ00) orientation and a rather smooth surface. ... Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi'an 710062, P.R. China; School of Chemistry and Chemical Engineering, Shaanxi Normal ...

  6. Enhancement of polarization property of silane-modified BaTiO3 nanoparticles and its effect in increasing dielectric property of epoxy/BaTiO3 nanocomposites

    Directory of Open Access Journals (Sweden)

    Thi Tuyet Mai Phan

    2016-03-01

    Full Text Available The surface modification of synthesized nano-BaTiO3 particles was carried out using γ-aminopropyl trimethoxy silane (γ-APS in an ethanol/water solution. The modified particles were characterized by FTIR, TGA, surface charge analysis, and by dielectric constant measurement. The silane molecules were attached to the surface of BaTiO3 particles through SiOBaTiO3 bonds. The γ-APS grafted on BaTiO3 made the dielectric constant of the particles increase at frequencies ≥0.3 kHz in a wide range of temperature (25 °C–140 °C, due to the presence of NH2 groups. The dependence of the polarization vs. electrical field was measured in order to elucidate the dielectric behavior of the silane treated BaTiO3 in comparison to untreated BaTiO3. The nanocomposite based on epoxy resin containing BaTiO3 nanoparticles untreated and treated with γ-APS was also prepared and characterized. The results indicated that the γ-APS-modified BaTiO3 surfaces significantly enhanced the dielectric property of the nanocomposite.

  7. Ferroelectric substrate effects on the magnetism, magnetotransport, and electroresistance of La0.7Ca0.3MnO3 thin films on BaTiO3

    OpenAIRE

    Alberca, A.; Munuera, C.; Tornos, J.; Mompean, F. J.; Biskup, N.; Ruiz, Amalia; Nemes, N. M.; Andrés, Alicia de; León, Carlos; Santamaría, Jacobo; García-Hernández, M.

    2012-01-01

    La 0.7Ca 0.3MnO 3 optimally doped epitaxial films were grown on ferroelectric BaTiO 3 substrates. Electronic transport (magnetoresistance and electroresistance) and magnetic properties showed important anomalies in the temperature interval between 60 and 150 K, below the metal-insulator transition. Scanning probe microscopy revealed changes in BaTiO 3 surface morphology at those temperatures. La 0.7Ca 0.3MnO 3 thickness is a critical factor: 120-thick films showed large anomalies sensitive to...

  8. Depletion zones and crystallography on pinched spheres

    Science.gov (United States)

    Chen, Jingyuan; Xing, Xiangjun; Yao, Zhenwei

    2018-03-01

    Understanding the interplay between ordered structures and substrate curvature is an interesting problem with versatile applications, including functionalization of charged supramolecular surfaces and modern microfluidic technologies. In this work, we investigate the two-dimensional packing structures of charged particles confined on a pinched sphere. By continuously pinching the sphere, we observe cleavage of elongated scars into pleats, proliferation of disclinations, and subsequently, emergence of a depletion zone at the negatively curved waist that is completely void of particles. We systematically study the geometrics and energetics of the depletion zone, and reveal its physical origin as a finite size effect, due to the interplay between Coulomb repulsion and concave geometry of the pinched sphere. These results further our understanding of crystallography on curved surfaces, and have implications in design and manipulation of charged, deformable interfaces in various applications.

  9. Synthesis and Characterization of LaNiO3, LaNi(1-xFexO3 andLaNi(1-xCoxO3 Perovskite Oxides for Catalysis Application

    Directory of Open Access Journals (Sweden)

    Lima Sania Maria de

    2002-01-01

    Full Text Available Mixed metal oxides with perovskite-type structure show a great potential to be used in catalysis, electrocatalysis and electronic ceramics. Perovskites oxides catalysts with the composition LaNiO3, LaNi(1-xFe xO3 and LaNi(1-xCo xO3 (x = 0.4 and 0.7 have been synthesized by the precipitation method to be used in the methane reforming to produce hydrogen and synthesis gas. The compounds were characterized by X-ray diffraction, thermogravimetric and differential thermal analysis, inductively coupled plasma atomic emission spectroscopy, surface area measurements, energy dispersive X-ray spectrometry coupled to scanning electron microscopy and temperature programmed reduction. The results showed that a suitable combination of the preparation method with calcination variables (time and temperature could result in oxides with the desired structure and with important properties at the application point of view in heterogeneous catalysis.

  10. Immobilizing LaFeO3 nanoparticles on carbon spheres for enhanced heterogeneous photo-Fenton like performance

    Science.gov (United States)

    Wang, Kaixuan; Niu, Helin; Chen, Jingshuai; Song, Jiming; Mao, Changjie; Zhang, Shengyi; Gao, Yuanhao

    2017-05-01

    LaFeO3 nanoparticles immobilized on the surface of monodisperse carbon spheres have been obtained through a facile and environmentally friendly ultrasonic assisted surface ions adsorption method. The LaFeO3/C nanocomposite was evaluated as photo-Fenton like catalyst for the degradation of Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). The LaFeO3/C nanocomposite possesses high specific surface area compared with pure LaFeO3 and significantly enhanced photo-Fenton like catalytic performance. The possible formation process of the LaFeO3/C nanocomposite and the mechanism for photo-Fenton like reaction were discussed. The superior property was attributed to the synergistic effects from the photo-Fenton like process and the presence of carbon spheres. In addition, the heterogeneous process led to better recyclability of this type of catalyst.

  11. LOCAL PIEZOELECTRICITY IN SrTiO3-BiTiO3 CERAMICS

    OpenAIRE

    Grigalaitis, R.; Bagdzevicius, S.; Banys, J.; Tornau, E. E.; Bormanis, K.; Sternberg, A.; Bdikin, I.; Kholkin, A.

    2014-01-01

    Local piezoelectric properties of Bi-doped SrTiO3 ceramics have been investigated by piezoresponse force microscopy. The appearance of both out-of-plane and in-plane polarization components confirmed the piezoelectric nature of the obtained signal. The absence of labyrinth-like structures in observed piezoelectric contrast is not consistent with the expected existence of a relaxor ferroelectric state in this material. The close similarity of local piezoelectric properties in Bi-doped SrTiO3 w...

  12. 2DEGs at perovskite interfaces between KTaO3 or KNbO3 and stannates.

    Science.gov (United States)

    Fan, Xiaofeng; Zheng, Weitao; Chen, Xin; Singh, David J

    2014-01-01

    We report density functional studies of electron rich interfaces between KTaO3 or KNbO3 and CaSnO3 or ZnSnO3 and in particular the nature of the interfacial electron gasses that can be formed. We find that depending on the details these may occur on either the transition metal or stannate sides of the interface and in the later case can be shifted away from the interface by ferroelectricity. We also present calculations for bulk KNbO3, KTaO3, CaSnO3, BaSnO3 and ZnSnO3, showing the different transport and optical properties that may be expected on the two sides of such interfaces. The results suggest that these interfaces may display a wide range of behaviors depending on conditions, and in particular the interplay with ferroelectricity suggests that electrical control of these properties may be possible.

  13. XAS study of V2O5/Al2O3 catalysts doped with rare earth oxides

    International Nuclear Information System (INIS)

    Centeno, M.A.; Malet, P.; Capitan, M.J.; Benitez, J.J.; Carrizosa, I.; Odriozola, J.A.

    1995-01-01

    This paper reports on XAS studies of well dispersed V 2 O 5 /Al 2 O 3 and V 2 O 5 /Sm 2 O 3 /Al 2 O 3 samples. XAS spectra at V-K and Sm-L III edges show that the rare earth oxide favours the formation of regular tetrahedral units, [VO 4 ], over the surface of the support. Positions of the preedge peak at the V-K edge, and intensities of the white line at the Sm-L III edge also suggest modifications in the electronic density around V and Sm atoms when they are simultaneously supported over Al 2 O 3 . ((orig.))

  14. Shear-induced mechanical failure of β -G a2O3 from quantum mechanics simulations

    Science.gov (United States)

    An, Qi; Li, Guodong

    2017-10-01

    Monoclinic gallium oxide (β -G a2O3 ) has important applications in power devices and deep UV optoelectronic devices because of such novel properties as a wide band gap, high breakdown electric field, and a wide range of n -type doping conductivity. However, the intrinsic failure mechanisms of β -G a2O3 remain unknown, which limits the fabrication and packaging of β -G a2O3 -based electronic devices. Here we used density-functional theory at the Perdew-Burke-Ernzerhof level to examine the shear-induced failure mechanisms of β -G a2O3 along various plausible slip systems. We found that the (001 )/〈010 〉 slip system has the lowest ideal shear strength of 3.8 GPa among five plausible slip systems, suggesting that (001 )/〈010 〉 is the most plausible activated slip system. This slip leads to an intrinsic failure mechanism arising from breaking the longest Ga-O bond between octahedral Ga and fourfold-coordinated O. Then we identified the same failure mechanism of β -G a2O3 under biaxial shear deformation that mimics indentation stress conditions. Finally, the general stacking fault energy (SFE) surface is calculated for the (001) surface from which we concluded that there is no intrinsic stacking fault structure for β -G a2O3 . The deformation modes and SFE calculations are essential to understand the intrinsic mechanical processes of this semiconductor material, which provides insightful guidance for designing high-performance semiconductor devices.

  15. Pentacene thin-film transistors and inverters with plasma-enhanced atomic-layer-deposited Al2O3 gate dielectric

    International Nuclear Information System (INIS)

    Koo, Jae Bon; Lim, Jung Wook; Kim, Seong Hyun; Yun, Sun Jin; Ku, Chan Hoe; Lim, Sang Chul; Lee, Jung Hun

    2007-01-01

    The performances of pentacene thin-film transistor with plasma-enhanced atomic-layer-deposited (PEALD) 150 nm thick Al 2 O 3 dielectric are reported. Saturation mobility of 0.38 cm 2 /V s, threshold voltage of 1 V, subthreshold swing of 0.6 V/decade, and on/off current ratio of about 10 8 have been obtained. Both depletion and enhancement mode inverter have been realized with the change of treatment method of hexamethyldisilazane on PEALD Al 2 O 3 gate dielectric. Full swing depletion mode inverter has been demonstrated at input voltages ranging from 5 V to - 5 V at supply voltage of - 5 V

  16. Formation and Photocatalytic Activity of BaTiO3 Nanocubes via Hydrothermal Process

    Directory of Open Access Journals (Sweden)

    Xinrun Xiong

    2015-01-01

    Full Text Available We reported a facile hydrothermal approach to synthesize BaTiO3 nanocubes with controlled sizes for degradation of methylene blue (MB. The nanocubes with reaction time of 48 hours exhibited the highest photocatalytic efficiency, owing to their narrower size distribution and better crystallinity compared to those of 24 hours and, at the meantime, smaller particle size than those of 72 hours. This work also demonstrated the degradation of methylene orange (MO using BaTiO3 nanocubes synthesized for 48 hours. Compared with the removal of MB, BaTiO3 had lower photocatalytic activity on MO, mainly due to the poorer absorption behavior of MO on the surface of BaTiO3 nanocubes. The degradation efficiency for each photocatalytic reaction was calculated. The possible mechanism of the photocatalytic decomposition on MB has been addressed as well.

  17. Preparation and Thermo-Physical Properties of Fe2O3-Propylene Glycol Nanofluids.

    Science.gov (United States)

    Shylaja, A; Manikandan, S; Suganthi, K S; Rajan, K S

    2015-02-01

    Iron oxide (Fe2O3) nanoparticles were prepared from ferric chloride and ferrous sulphate by precipitation reaction. Fe2O3-propylene glycol nanofluid was prepared by dispersing Fe2O3 nanoparticles in propylene glycol through stirred bead milling, shear homogenization and probe ultrasonication. The nanofluid was characterized through measurement of viscosity, particle size distribution and thermal conductivity. The interactions between Fe2O3 nanoparticles and propylene glycol on the nanoparticle surfaces lead to reduction in viscosity, the magnitude of which increases with nanoparticle concentration (0-2 vol%) at room temperature. The thermal conductivity enhancement for 2 vol% nanofluid was about 21% at room temperature, with liquid layering being the major contributor for thermal conductivity enhancement.

  18. NiTiO3 powders obtained by polymeric precursor method: Synthesis and characterization

    International Nuclear Information System (INIS)

    Lopes, K.P.; Cavalcante, L.S.; Simoes, A.Z.; Varela, J.A.; Longo, E.; Leite, E.R.

    2009-01-01

    Nickel titanate (NiTiO 3 ) powders were synthesized by the polymeric precursor method after thermal treatment at different temperatures for 2 h in air atmosphere. The decomposition of the precursors was monitored by differential scanning calorimetry and thermogravimetric analysis. The NiTiO 3 powders presented a reduction in the specific surface area and increase of the average particle size with the evolution of the temperature. The structural evolution of NiTiO 3 phase was accompanied by X-ray diffraction and Fourier transform Raman spectroscopy. By scanning electron microscopy was revealed the agglomerated nature of very fine particles of NiTiO 3 powders annealed from 600 to 1000 deg. C

  19. Seasonal total methane depletion in limestone caves.

    Science.gov (United States)

    Waring, Chris L; Hankin, Stuart I; Griffith, David W T; Kertesz, Michael A; Kobylski, Victoria; Wilson, Neil L; Coleman, Nicholas V; Kettlewell, Graham; Zlot, Robert; Bosse, Michael; Bell, Graham

    2017-08-16

    Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH 4 depletion causal mechanism is contested and dynamic links to external diurnal and seasonal temperature cycles unknown. Here, we report a continuous 3-year record of cave methane and other trace gases in Jenolan Caves, Australia which shows a seasonal cycle of extreme CH 4 depletion, from ambient ~1,775 ppb to near zero during summer and to ~800 ppb in winter. Methanotrophic bacteria, some newly-discovered, rapidly consume methane on cave surfaces and in external karst soils with lifetimes in the cave of a few hours. Extreme bacterial selection due to the absence of alternate carbon sources for growth in the cave environment has resulted in an extremely high proportion 2-12% of methanotrophs in the total bacteria present. Unexpected seasonal bias in our cave CH 4 depletion record is explained by a three-step process involving methanotrophy in aerobic karst soil above the cave, summer transport of soil-gas into the cave through epikarst, followed by further cave CH 4 depletion. Disentangling cause and effect of cave gas variations by tracing sources and sinks has identified seasonal speleothem growth bias, with implied palaeo-climate record bias.

  20. Anisotropic suppression of octahedral breathing distortion with the fully strained BaBiO3/BaCeO3 heterointerface

    Science.gov (United States)

    Lee, Han Gyeol; Kim, Rokyeon; Kim, Jinkwon; Kim, Minu; Kim, Tae Heon; Lee, Shinbuhm; Noh, Tae Won

    2018-01-01

    While the physiochemical effects of octahedral tilting and rotating distortions have been studied extensively, octahedral breathing distortion (OBD) at heterointerfaces has rarely been explored. Here, we investigated OBD in fully strained BaBiO3 (BBO) epitaxial films by making a new type of oxide heterointerface with non-breathing BaCeO3 epitaxial films. The integration of first-principles calculations with experimental observations of optical spectroscopy revealed that the oxygen displacement modes in BBO became disordered within six unit cells at the heterointerface and the surface. Controlling OBD in perovskite oxide thin films provides a means to exploit emerging material properties.

  1. Interfacial studies on the O3 modified carbon fiber-reinforced polyamide 6 composites

    International Nuclear Information System (INIS)

    Li, J.

    2008-01-01

    In this work, O 3 modification method was used for the surface treatment of polyacrylonitrile (PAN)-based carbon fiber. The surface characteristics of carbon fibers were characterized by X-ray photoelectron spectroscopy (XPS). The interfacial properties of carbon fiber-reinforced polyamide 6 (CF/PA6) composites were investigated by means of the single fiber pull-out tests. As a result, it was found that IFSS values of the composites with O 3 treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that O 3 treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PA6 matrix is effectively promoted

  2. Depletable resources and the economy

    NARCIS (Netherlands)

    Heijman, W.J.M.

    1991-01-01

    The subject of this thesis is the depletion of scarce resources. The main question to be answered is how to avoid future resource crises. After dealing with the complex relation between nature and economics, three important concepts in relation with resource depletion are discussed: steady state,

  3. The Toxicity of Depleted Uranium

    Directory of Open Access Journals (Sweden)

    Wayne Briner

    2010-01-01

    Full Text Available Depleted uranium (DU is an emerging environmental pollutant that is introduced into the environment primarily by military activity. While depleted uranium is less radioactive than natural uranium, it still retains all the chemical toxicity associated with the original element. In large doses the kidney is the target organ for the acute chemical toxicity of this metal, producing potentially lethal tubular necrosis. In contrast, chronic low dose exposure to depleted uranium may not produce a clear and defined set of symptoms. Chronic low-dose, or subacute, exposure to depleted uranium alters the appearance of milestones in developing organisms. Adult animals that were exposed to depleted uranium during development display persistent alterations in behavior, even after cessation of depleted uranium exposure. Adult animals exposed to depleted uranium demonstrate altered behaviors and a variety of alterations to brain chemistry. Despite its reduced level of radioactivity evidence continues to accumulate that depleted uranium, if ingested, may pose a radiologic hazard. The current state of knowledge concerning DU is discussed.

  4. Cooper Pair Writing at the LaAlO3/ SrTiO 3 Interface

    Science.gov (United States)

    Cen, Cheng; Bogorin, Daniela F.; Bark, Chung Wung; Folkman, Chad M.; Eom, Chang-Beom; Levy, Jeremy

    2011-03-01

    Superconducting semiconductors offer unique ways to exert electrostatic control over macroscopic quantum phases. The recently demonstrated nanoscale control over conductivity at the LaAl O3 / SrTi O3 interface raises the question of whether nanoscale control over superconducting phases can be realized. Here we report low-temperature magnetotransport experiments on structures defined with nanoscale precision at the LaAl O3 / SrTi O3 interface. A quantum phase transition is observed that is associated with the formation of Cooper pairs, but a finite resistance is observed at the lowest temperatures. Higher mobility interfaces exhibit larger Ginsburg-Landau coherence lengths, a stronger suppression of pairing by magnetic field as well as Shubnikov-de Haas oscillations. Cooper pair localization, spin-orbit coupling, and finite-size effects may factor into an explanation for some of the unusual properties observed. The work is supported by Department of Energy and State of Florida, NSF (DMR-0906443 and DMR-0704022), DOE (DE-FG02-06ER46327) and the Fine Foundation.

  5. High-temperature phases of NaNbO3 and NaTaO3

    International Nuclear Information System (INIS)

    Darlington, C.N.W.

    1999-01-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO 3 , and sodium tantalate, NaTaO 3 , have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic left angle 100 right angle directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO 3 between 753 and 793 K and of NaTaO 3 below 758 K are not as reported in the literature. (orig.)

  6. Photocatalytic activity of titanium dioxide modified by Fe2O3 nanoparticles

    International Nuclear Information System (INIS)

    Wodka, Dawid; Socha, Robert P.; Bielańska, Elżbieta; Elżbieciak-Wodka, Magdalena; Nowak, Paweł; Warszyński, Piotr

    2014-01-01

    Highlights: • 1% Fe 2 O 3 /TiO 2 composite showing high activity in the photocatalytic oxidation of organics was synthetized. • Electrochemical analysis indicated that surface modification of Degussa P25 by Fe 2 O 3 causes the appearance of surface states in such a material. • The enhanced activity of the prepared composite may be ascribed to the occurrence of the photo-Fenton process. - Abstract: Photocatalytic activity of Fe 2 O 3 /TiO 2 composites obtained by precipitation was investigated. The composite material containing 1.0 wt% of iron(III) oxide nanoparticles was obtained by depositing Fe 2 O 3 on the Evonic-Degussa P25 titania surface. SEM, XPS, DRS, CV and EIS techniques were applied to examine synthetized pale orange photocatalyst. The XPS measurements revealed that iron is present mainly in the +3 oxidation state but iron in the +2 oxidation state can be also detected. Electrochemical analysis indicated that surface modification of Degussa P25 by Fe 2 O 3 causes the appearance of surface states in such a material. Nevertheless, based on the DRS measurement it was shown that iron(III) oxide nanoparticles modified the P25 spectral properties but they did not change the band gap width. The photocatalytic activity of Fe 2 O 3 /TiO 2 composite was compared to photocatalytic activity of pristine P25 in photooxidation reaction of model compounds: oxalic acid (OxA) and formic acid (FA). Photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that nanoparticles deposited on titania surface triggers the increase in photocatalytic activity, this increase depends however on the decomposed substance

  7. Enhanced magnetic properties of chemical solution deposited BiFeO3 thin film with ZnO buffer layer

    International Nuclear Information System (INIS)

    Rajalakshmi, R.; Kambhala, Nagaiah; Angappane, S.

    2012-01-01

    Highlights: ► Enhanced magnetization of BiFeO 3 is important for strong magnetoelectric coupling. ► BiFeO 3 film with ZnO buffer layer was successfully synthesized by chemical method. ► Magnetization of BiFeO 3 has increased by more than 10 times with ZnO buffer layer. ► A mechanism for enhancement in ferromagnetism of BiFeO 3 film is proposed. - Abstract: Magnetic properties of BiFeO 3 films deposited on Si substrates with and without ZnO buffer layer have been studied in this work. We adopted the chemical solution deposition method for the deposition of BiFeO 3 as well as ZnO films. The x-ray diffraction measurements on the deposited films confirm the formation of crystalline phase of BiFeO 3 and ZnO films, while our electron microscopy measurements help to understand the morphology of few micrometers thick films. It is found that the deposited ZnO film exhibit a hexagonal particulate surface morphology, whereas BiFeO 3 film fully covers the ZnO surface. Our magnetic measurements reveal that the magnetization of BiFeO 3 has increased by more than ten times in BiFeO 3 /ZnO/Si film compared to BiFeO 3 /Si film, indicating the major role played by ZnO buffer layer in enhancing the magnetic properties of BiFeO 3 , a technologically important multiferroic material.

  8. Carrier-Controlled Ferromagnetism in SrTiO_{3}

    Directory of Open Access Journals (Sweden)

    Pouya Moetakef

    2012-06-01

    Full Text Available Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO_{3} films and GdTiO_{3}/SrTiO_{3} heterostructures, respectively. GdTiO_{3}/SrTiO_{3} interfaces exhibit a high-density 2D electron gas on the SrTiO_{3} side of the interface, while, for the SrTiO_{3} films, carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO_{3} films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO_{3}/SrTiO_{3} heterostructures scales with the thickness of the SrTiO_{3} quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO_{3}.

  9. Band alignment at epitaxial BaSnO3/SrTiO3(001) and BaSnO3/LaAlO3(001) heterojunctions

    Science.gov (United States)

    Chambers, Scott A.; Kaspar, Tiffany C.; Prakash, Abhinav; Haugstad, Greg; Jalan, Bharat

    2016-04-01

    We have spectroscopically determined the optical bandgaps and band offsets at epitaxial interfaces of BaSnO3 with SrTiO3(001) and LaAlO3(001). 28 u.c. BaSnO3 epitaxial films exhibit direct and indirect bandgaps of 3.56 ± 0.05 eV and 2.93 ± 0.05 eV, respectively. The lack of a significant Burstein-Moss shift corroborates the highly insulating, defect-free nature of the BaSnO3 films. The conduction band minimum is lower in electron energy in 5 u.c. films of BaSnO3 than in SrTiO3 and LaAlO3 by 0.4 ± 0.2 eV and 3.7 ± 0.2 eV, respectively. This result bodes well for the realization of oxide-based, high-mobility, two-dimensional electron systems that can operate at ambient temperature, since electrons generated in the SrTiO3 by modulation doping, or at the BaSnO3/LaAlO3 interface by polarization doping, can be transferred to and at least partially confined in the BaSnO3 film.

  10. Tuning the dead-layer behavior of La0.67Sr0.33MnO3/SrTiO3 via interfacial engineering

    Science.gov (United States)

    Peng, R.; Xu, H. C.; Xia, M.; Zhao, J. F.; Xie, X.; Xu, D. F.; Xie, B. P.; Feng, D. L.

    2014-02-01

    The dead-layer behavior, deterioration of the bulk properties in near-interface layers, restricts the applications of many oxide heterostructures. We present the systematic study of the dead-layer in La0.67Sr0.33MnO3/SrTiO3 grown by ozone-assisted molecular beam epitaxy. Dead-layer behavior is systematically tuned by varying the interfacial doping, while unchanged with varied doping at any other atomic layers. In situ photoemission and low energy electron diffraction measurements suggest intrinsic oxygen vacancies at the surface of ultra-thin La0.67Sr0.33MnO3, which are more concentrated in thinner films. Our results show correlation between interfacial doping, oxygen vacancies, and the dead-layer, which can be explained by a simplified electrostatic model.

  11. Dielectric and electromechanical properties of LiNbO3-modified (BiNa)TiO3-(BaCa)TiO3 lead-free piezoceramics

    Science.gov (United States)

    Zaman, Arif; Hussain, Ali; Malik, Rizwan Ahmed; Maqbool, Adnan; Nahm, Sahn; Kim, Myong-Ho

    2016-05-01

    The dielectric and electromechanical properties of LiNbO3-modified (1-x) [0.91Na0.5Bi0.5TiO3-0.09Ba0.70Ca0.30TiO3]-xLiNbO3 (abbreviated as (BiNa)TiO3-(BaCa)TiO3-LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO3-(BaCa)TiO3-LN system. A large electrostrain of ~0.418% with a normalized strain of ~690 pm V-1 at 6 kV mm-1 was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of ɛ r ~ 3300 over a broad temperature range of 147 °C-306 °C was observed along with small losses from room temperature up to 400 °C.

  12. Anisotropic-strain-relaxation-induced crosshatch morphology in epitaxial SrTiO3/NdGaO3 thin films

    Directory of Open Access Journals (Sweden)

    X. L. Tan

    2014-10-01

    Full Text Available We investigate the strain relaxation and surface morphology of epitaxial SrTiO3 (STO films grown on (001O and (110O planes of orthorhombic NdGaO3 (NGO, and (001 plane of cubic (LaAlO30.3(Sr2AlTaO60.7 (LSAT substrates. Although the average lattice mismatches are similar, strikingly regular crosshatched surface patterns can be found on STO/NGO(001O[(110O] films, contrary to the uniform surface of STO/LSAT(001. Based on the orientation and thickness dependent patterns and high-resolution x-ray diffractions, we ascribe the crosshatch morphology to the anisotropic strain relaxation with possibly the 60° misfit dislocation formation and lateral surface step flow in STO/NGO films, while an isotropic strain relaxation in STO/LSAT. Further, we show that the crosshatched STO/NGO(110O surface could be utilized as a template to modify the magnetotransport properties of epitaxial La0.6Ca0.4MnO3 films. This study highlights the crucial role of symmetry mismatch in determining the surface morphology of the perovskite oxide films, in addition to their epitaxial strain states, and offers a different route for designing and fabricating functional perovskite-oxide devices.

  13. Black Cr/a-Cr2O3 nanoparticles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2012-01-01

    Full Text Available such as the film micro- structure, surface composition and surface morphology, etc. 4. Conclusion Black Cr/a-Cr2O3 based on uniform fine ??in the range of micron? nano?? spherically shaped core-shell particles of Cr/a-Cr2O3 were Sandia National Laboratory... selective absorber, Ph.D. Thesis, Berkeley, CA: Lawrence Berkeley Laboratory, 1980. [16] P.H. Holloway, K. Shanker, R.B. Pettit, R.R. Sowell, Oxidation of Electrode- posited Black Chrome Selective Solar Absorber Films, SAND-80-1045, Sandia National...

  14. On the origin of metallic conductivity at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Christensen, Dennis; Trier, Felix

    2012-01-01

    To determine the origin of the quasi-two-dimensional electron gas formed at the interface between the two complex oxides of LaAlO3 (LAO) and SrTiO3 (STO), various amorphous films of LAO, La2O3, Al2O3, and La7/8Sr1/8MnO3 (LSMO), were deposited on TiO2-terminated (0 0 1) STO substrates by pulsed...... laser deposition at room temperature. Metallic interfaces are observed when the over-layers are amorphous LAO, La2O3, or Al2O3, while insulating interfaces are observed when the over-layer is LSMO. The interfacial conductivity of these SrTiO3-based hetero-structures shows strong dependence on both film...

  15. Depletion-mode quantum dots in intrinsic silicon

    Science.gov (United States)

    Amitonov, Sergey V.; Spruijtenburg, Paul C.; Vervoort, Max W. S.; van der Wiel, Wilfred G.; Zwanenburg, Floris A.

    2018-01-01

    We report the fabrication and electrical characterization of depletion-mode quantum dots in a two-dimensional hole gas (2DHG) in intrinsic silicon. We use fixed charge in a SiO2/Al2O3 dielectric stack to induce a 2DHG at the Si/SiO2 interface. Fabrication of the gate structures is accomplished with a single layer metallization process. Transport spectroscopy reveals regular Coulomb oscillations with charging energies of 10-15 meV and 3-5 meV for the few- and many-hole regimes, respectively. This depletion-mode design avoids complex multilayer architectures requiring precision alignment and allows us to adopt directly best practices already developed for depletion dots in other material systems. We also demonstrate a method to deactivate fixed charge in the SiO2/Al2O3 dielectric stack using deep ultraviolet light, which may become an important procedure to avoid unwanted 2DHG build-up in Si MOS quantum bits.

  16. Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

    Directory of Open Access Journals (Sweden)

    D. Howard

    2018-01-01

    Full Text Available Aerodynamic gradient measurements of the air–surface exchange of gaseous elemental mercury (GEM were undertaken over a 40 ha alpine grassland in Australia's Snowy Mountains region across a 3-week period during the late austral summer. Bi-directional GEM fluxes were observed throughout the study, with overall mean value of 0.2 ± 14.5 ng m−2 h−1 and mean nocturnal fluxes of −1.5 ± 7.8 ng m−2 h−1 compared to diurnal fluxes of 1.8 ± 18.6 ng m−2 h−1. Deposition velocities ranged from −2.2 to 2.9 cm s−1, whilst ambient GEM concentrations throughout the study were 0.59 ± 0.10 ng m−3. Cumulative GEM fluxes correlated well with 24 h running mean soil temperatures, and one precipitation event was shown to have a positive impact on diurnal emission fluxes. The underlying vegetation had largely senesced and showed little stomatal control on fluxes. Nocturnal atmospheric mercury depletion events (NAMDEs were observed concomitant with O3 depletion and dew formation under shallow, stable nocturnal boundary layers. A mass balance box model was able to reproduce ambient GEM concentration patterns during NAMDE and non-NAMDE nights without invoking chemical oxidation of GEM throughout the column, indicating a significant role of surface processes controlling deposition in these events. Surface deposition was enhanced under NAMDE nights, though uptake to dew likely represents less than one-fifth of this enhanced deposition. Instead, enhancement of the surface GEM gradient as a result of oxidation at the surface in the presence of dew is hypothesised to be responsible for a large portion of GEM depletion during these particular events. GEM emission pulses following nights with significant deposition provide evidence for the prompt recycling of 17 % of deposited mercury, with the remaining portion retained in surface sinks. The long-term impacts of any sinks are however likely to be minimal, as

  17. Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

    Science.gov (United States)

    Howard, Dean; Edwards, Grant C.

    2018-01-01

    Aerodynamic gradient measurements of the air-surface exchange of gaseous elemental mercury (GEM) were undertaken over a 40 ha alpine grassland in Australia's Snowy Mountains region across a 3-week period during the late austral summer. Bi-directional GEM fluxes were observed throughout the study, with overall mean value of 0.2 ± 14.5 ng m-2 h-1 and mean nocturnal fluxes of -1.5 ± 7.8 ng m-2 h-1 compared to diurnal fluxes of 1.8 ± 18.6 ng m-2 h-1. Deposition velocities ranged from -2.2 to 2.9 cm s-1, whilst ambient GEM concentrations throughout the study were 0.59 ± 0.10 ng m-3. Cumulative GEM fluxes correlated well with 24 h running mean soil temperatures, and one precipitation event was shown to have a positive impact on diurnal emission fluxes. The underlying vegetation had largely senesced and showed little stomatal control on fluxes. Nocturnal atmospheric mercury depletion events (NAMDEs) were observed concomitant with O3 depletion and dew formation under shallow, stable nocturnal boundary layers. A mass balance box model was able to reproduce ambient GEM concentration patterns during NAMDE and non-NAMDE nights without invoking chemical oxidation of GEM throughout the column, indicating a significant role of surface processes controlling deposition in these events. Surface deposition was enhanced under NAMDE nights, though uptake to dew likely represents less than one-fifth of this enhanced deposition. Instead, enhancement of the surface GEM gradient as a result of oxidation at the surface in the presence of dew is hypothesised to be responsible for a large portion of GEM depletion during these particular events. GEM emission pulses following nights with significant deposition provide evidence for the prompt recycling of 17 % of deposited mercury, with the remaining portion retained in surface sinks. The long-term impacts of any sinks are however likely to be minimal, as cumulative GEM flux across the study period was close to zero.

  18. Microstructure of epitaxial SrRuO 3 thin films on MgO substrates

    Science.gov (United States)

    Ai, Wan Yong; Zhu, Jun; Zhang, Ying; Li, Yan Rong; Liu, Xing Zhao; Wei, Xian Hua; Li, Jin Long; Zheng, Liang; Qin, Wen Feng; Liang, Zhu

    2006-09-01

    SrRuO 3 thin films have been grown on singular (1 0 0) MgO substrates using pulsed laser deposition (PLD) in 30 Pa oxygen ambient and at a temperature of 400-700 °C. Ex situ reflection high-energy electron diffraction (RHEED) as well as X-ray diffraction (XRD) θ/2 θ scan indicated that the films deposited above 650 °C were well crystallized though they had a rough surface as shown by atom force microscopy (AFM). XRD Φ scans revealed that these films were composed of all three different types of orientation domains, which was further confirmed by the RHEED patterns. The heteroepitaxial relationship between SrRuO 3 and MgO was found to be [1 1 0] SRO//[1 0 0] MgO and 45°-rotated cube-on-cube [0 0 1] SRO//[1 0 0] MgO. These domain structures and surface morphology are similar to that of ever-reported SrRuO 3 thin films deposited on the (0 0 1) LaAlO 3 substrates, and different from those deposited on (0 0 1) SrTiO 3 substrates that have an atomically flat surface and are composed of only the [1 1 0]-type domains. The reason for this difference was ascribed to the effect of lattice mismatch across the film/substrate interface. The room temperature resistivity of SrRuO 3 films fabricated at 700 °C was 300 μΩ cm. Therefore, epitaxial SrRuO 3 films on MgO substrate could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.

  19. Growth mechanism of NaClO 3 and NaBrO 3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

  20. Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

  1. A nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 coating fabricated by micro-arc oxidation for hip joint prosthesis

    Science.gov (United States)

    Zhang, Lan; Zhang, Wenting; Han, Yong; Tang, Wu

    2016-01-01

    A nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 coating was fabricated on Zr substrate by micro-arc oxidation (MAO). The structure, formation mechanism, anti-wear property and aging behavior of the coating were explored. The obtained results show that the coating is composed of Al2O3 and ZrO2; the amount and crystallinity of Al2O3 increase gradually from inner layer to the coating surface; monoclinic ZrO2 (m-ZrO2) and tetragonal ZrO2 (t-ZrO2) are both present in the coating, and the ratio of t-ZrO2/m-ZrO2 increases with closing to the coating surface by a "constraint" mechanism of Al2O3; the coating surface mainly consists of nanoplate-like α-Al2O3, and a small amount of nanocrystallized m- and t-ZrO2. The superimposition of α-Al2O3 growth unit on {0 0 0 1} face should be prohibited by PO43- during the MAO process, resulting in the formation of nanoplate-like α-Al2O3 on the coating surface. Compared with pure Zr, the coating shows noticeable improvement in wear-resistance. For aging behavior, although more t-ZrO2 in the coating is transformed to m-ZrO2 with increasing aging time, wear loss increases slightly. It indicates that the nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 is a potential coating for articular head replacement.

  2. Bi modification for low-temperature processing of YMnO3 thin films

    Science.gov (United States)

    Choi, Taekjib; Lee, Jaichan

    2004-06-01

    YMnO3 thin films have been modified by Bi for low-temperature processing. YMnO3 thin-film growth typically requires high temperatures possibly leading to undesirable interface reaction and device failure in further processing. We have proposed Bi modification into YMnO3 (YBM) thin films grown on Si (100) by pulsed-laser deposition for reduced temperature processing. The growth temperature of YBM films was significantly reduced by more than 150 °C from the typical growth temperature of YMnO3 films. Highly c-axis-oriented growth of hexagonal YBM films at low temperatures was effective above 5% Bi content modification. Surface analysis on YBM films suggests that very thin Bi oxide layer forms on the topmost growing surface of YBM films and enhances the surface mobility of adatoms, leading to enhanced crystallization and low-temperature processing. The Bi modification did not deteriorate the electrical properties of YMnO3 such as dielectric constant and leakage current. This Bi modification can be an effective method to reduce processing temperature for other oxide thin films in physical vapor deposition.

  3. The unusual magnetism of nanoparticle LaCoO3

    International Nuclear Information System (INIS)

    Durand, A M; Belanger, D P; Hamil, T J; Ye, F; Chi, S; Fernandez-Baca, J A; Booth, C H; Abdollahian, Y; Bhat, M

    2015-01-01

    Bulk and nanoparticle powders of LaCoO 3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, T o ≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co 3 O 4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases. (paper)

  4. Ag K- and L3-edge XAFS study on Ag species in Ag/Ga2O3 photocatalysts

    International Nuclear Information System (INIS)

    Yamamoto, M; Yamamoto, N; Yoshida, T; Nomoto, T; Yamamoto, A; Yoshida, H; Yagi, S

    2016-01-01

    Ag loaded Ga 2 O 3 (Ag/Ga 2 O 3 ) shows photocatalytic activity for reduction of CO 2 with water. Ag L 3 -edge XANES and K-edge EXAFS spectra were measured for various Ag/Ga 2 O 3 samples, which suggested that structural and chemical states of Ag species varied with the loading amount of Ag and the preparation method. The Ag species were metallic Ag particles with an AgGaO 2 -like interface structure in the sample with high loading amount of Ag while predominantly Ag metal clusters in the sample with low loading amount of Ag. The XANES feature just above the edge represented the interaction between the Ag species and the Ga 2 O 3 surface, showing that the Ag metal clusters had more electrons in the d -orbitals by interacting with the Ga 2 O 3 surface, which would contribute the high photocatalytic activity. (paper)

  5. Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

    Directory of Open Access Journals (Sweden)

    Shin H.

    2015-01-01

    Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

  6. Thermally excited multiband conduction in LaAlO3/SrTiO3 heterostructures exhibiting scattering

    NARCIS (Netherlands)

    Guduru, V.K.; McCollam, A.; Jost, A.; Wenderich, Sander; Hilgenkamp, H.; Maan, J.C.; Brinkman, Alexander; Zeitler, U.

    2013-01-01

    Magnetotransport measurements of charge carriers at the interface of a LaAlO 3 /SrTiO 3 heterostructure with 26 unit cells of LaAlO 3 show Hall resistance and magnetoresistance which at low and high temperatures is described by a single channel of electronlike charge carriers. At intermediate

  7. Model study of the influence of cross-tropopause O3 transports on tropospheric O3 levels

    NARCIS (Netherlands)

    Roelofs, G.J.; Lelieveld, J.

    1997-01-01

    Cross-tropopause transport of O3 is a significant factor in the tropospheric budget and distribution of O3. Nevertheless, the distribution in the troposphere of O3 that originates from the stratosphere is uncertain. We study this with a chemistry - general circulation model with relatively high

  8. High oxygen ion conduction in sintered oxides of the $Bi_2O_3-Er_2O_3$ system

    NARCIS (Netherlands)

    Verkerk, M.J.; Keizer, Klaas; Burggraaf, A.J.

    1980-01-01

    The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number

  9. Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

    Science.gov (United States)

    Khosa, R. Y.; Thorsteinsson, E. B.; Winters, M.; Rorsman, N.; Karhu, R.; Hassan, J.; Sveinbjörnsson, E. Ö.

    2018-02-01

    We report on the electrical properties of Al2O3 films grown on 4H-SiC by successive thermal oxidation of thin Al layers at low temperatures (200°C - 300°C). MOS capacitors made using these films contain lower density of interface traps, are more immune to electron injection and exhibit higher breakdown field (5MV/cm) than Al2O3 films grown by atomic layer deposition (ALD) or rapid thermal processing (RTP). Furthermore, the interface state density is significantly lower than in MOS capacitors with nitrided thermal silicon dioxide, grown in N2O, serving as the gate dielectric. Deposition of an additional SiO2 film on the top of the Al2O3 layer increases the breakdown voltage of the MOS capacitors while maintaining low density of interface traps. We examine the origin of negative charges frequently encountered in Al2O3 films grown on SiC and find that these charges consist of trapped electrons which can be released from the Al2O3 layer by depletion bias stress and ultraviolet light exposure. This electron trapping needs to be reduced if Al2O3 is to be used as a gate dielectric in SiC MOS technology.

  10. Metal-catalyzed growth of In2O3 nanotowers using thermal evaporation and oxidation method

    Science.gov (United States)

    Jian, Liu; Shihua, Huang; Lü, He

    2015-12-01

    Large-scale In2O3 nanotowers with different cross sections were synthesized by a thermal evaporation and oxidation technique using metal as the catalyst. The morphologies and structural characterizations of In2O3 nanotowers are dependent on growth processes, such as different metal (Au, Ag or Sn) catalysts, the relative position of the substrate and evaporation source, growth temperature, gas flow rate, and growth time. In2O3 nanotowers cannot be observed using Sn as the catalyst, which indicates that metal liquid droplets play an important role in the initial stages of the growth of In2O3 nanotowers. The formation of an In2O3 nanotower is attributed to the competitive growth model between a lateral growth controlled by vapor-solid mechanism and an axial vapor-liquid-solid growth mechanism mediated by metal liquid nanodroplets. The synthesized In2O3 nanostructures with novel tower-shaped morphology may have potential applications in optoelectronic devices and gas sensors. Project supported by the National Natural Science Foundation of China (No. 61076055), the Open Project Program of Surface Physics Laboratory (National Key Laboratory) of Fudan University (No. KF2015_02), the Zhejiang Provincial Science and Technology Key Innovation Team (No. 2011R50012), and the Zhejiang Provincial Key Laboratory (No. 2013E10022).

  11. Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO3

    Directory of Open Access Journals (Sweden)

    Mehedi Hasan

    2016-03-01

    Full Text Available Improvement in magnetic and electrical properties of multiferroic BiFeO3 in conjunction with their dependence on particle size is crucial due to its potential applications in multifunctional miniaturized devices. In this investigation, we report a study on particle size dependent structural, magnetic and electrical properties of sol-gel derived Bi0.9Ba0.1FeO3 nanoparticles of different sizes ranging from ∼ 12 to 49 nm. The substitution of Bi by Ba significantly suppresses oxygen vacancies, reduces leakage current density and Fe2+ state. An improvement in both magnetic and electrical properties is observed for 10 % Ba-doped BiFeO3 nanoparticles compared to its undoped counterpart. The saturation magnetization of Bi0.9Ba0.1FeO3 nanoparticles increase with reducing particle size in contrast with a decreasing trend of ferroelectric polarization. Moreover, a first order metamagnetic transition is noticed for ∼ 49 nm Bi0.9Ba0.1FeO3 nanoparticles which disappeared with decreasing particle size. The observed strong size dependent multiferroic properties are attributed to the complex interaction between vacancy induced crystallographic defects, multiple valence states of Fe, uncompensated surface spins, crystallographic distortion and suppression of spiral spin cycloid of BiFeO3.

  12. Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO3

    Science.gov (United States)

    Hasan, Mehedi; Hakim, M. A.; Basith, M. A.; Hossain, Md. Sarowar; Ahmmad, Bashir; Zubair, M. A.; Hussain, A.; Islam, Md. Fakhrul

    2016-03-01

    Improvement in magnetic and electrical properties of multiferroic BiFeO3 in conjunction with their dependence on particle size is crucial due to its potential applications in multifunctional miniaturized devices. In this investigation, we report a study on particle size dependent structural, magnetic and electrical properties of sol-gel derived Bi0.9Ba0.1FeO3 nanoparticles of different sizes ranging from ˜ 12 to 49 nm. The substitution of Bi by Ba significantly suppresses oxygen vacancies, reduces leakage current density and Fe2+ state. An improvement in both magnetic and electrical properties is observed for 10 % Ba-doped BiFeO3 nanoparticles compared to its undoped counterpart. The saturation magnetization of Bi0.9Ba0.1FeO3 nanoparticles increase with reducing particle size in contrast with a decreasing trend of ferroelectric polarization. Moreover, a first order metamagnetic transition is noticed for ˜ 49 nm Bi0.9Ba0.1FeO3 nanoparticles which disappeared with decreasing particle size. The observed strong size dependent multiferroic p