Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions

Tungsten-niobium oxide bronzes: a bulk and surface structural study

[EN] Materials from the WO3-Nb2O5 system, presenting bronze-type crystal structures, display outstanding functional properties for several applications as thermoelectric materials, lithium-ion battery electrodes, or catalysts. In this work, a series of W-Nb-O oxide bronzes have been synthesized by the hydrothermal method (with Nb/(W + Nb) ratios in the range of 0-1). A combination of bulk and surface characterisation techniques has been applied to get further insights into: (i) the effect of thermal treatments on as-prepared materials and (ii) the surface chemical nature of W-Nb-O oxide bronzes. Thermal treatments promote the following structural changes: (i) loss of emerging long-range order and (ii) the elimination of NH4+ and H2O species from the structural channels of the as-synthesized materials. It has been observed that W-Nb-O bronzes with Nb at% of ca. 50% are able to retain a long-range order after heat-treatments, which is attributed to the presence of a Cs-0.5[W2.5Nb2.5O14]-type structure. Increasing amounts of Nb 5T in the materials (i) promote a phase transition to pseudocrystalline phases ordered along the c-axis; (ii) stabilize surface W s. species (elucidated by XPS); and (iii) increase the proportion of surface Lewis acid sites (as determined by the FTIR of adsorbed CO). Results suggest that pseudocrystalline oxides (with a Nb at% >= 50%) are closely related to NbO2 pentagonal bipyramid-containing structures. The stabilisation of Lewis acid sites on these pseudocrystalline materials leads to a higher yield of heavy compounds, at the expense of acrolein formation, in the gas-phase dehydration of glycerol.The authors would like to acknowledge the Ministerio de Ciencia, Innovacion y Universidades in Spain for the financial support (RTI2018-099668-B-C21 and SEV-2016-0683 projects), and the Electron Microscopy Service at Universitat Politecnica de Valencia for providing facilities and technical support. D. D. also thanks Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669).Delgado-Muñoz, D.; Concepción Heydorn, P.; Trunschke, A.; López Nieto, JM. (2020). Tungsten-niobium oxide bronzes: a bulk and surface structural study. Dalton Transactions. 49(38):13282-13293. https://doi.org/10.1039/d0dt02058cS13282132934938D. J. M. Bevan and P.Hagenmuller , Non-Stoichiometric Compounds , Pergamon , 1973Quan, H., Gao, Y., & Wang, W. (2020). Tungsten oxide-based visible light-driven photocatalysts: crystal and electronic structures and strategies for photocatalytic efficiency enhancement. Inorganic Chemistry Frontiers, 7(4), 817-838. doi:10.1039/c9qi01516gWu, C.-M., Naseem, S., Chou, M.-H., Wang, J.-H., & Jian, Y.-Q. (2019). Recent Advances in Tungsten-Oxide-Based Materials and Their Applications. Frontiers in Materials, 6. doi:10.3389/fmats.2019.00049P. G. Dickens and M. F.Pye , in Intercalation Chemistry , ed. M. S. Whittingham and A. J. Jacobson , Academic Press , 1982 , pp. 539–561Tilley, R. J. D. (1995). The crystal chemistry of the higher tungsten oxides. International Journal of Refractory Metals and Hard Materials, 13(1-3), 93-109. doi:10.1016/0263-4368(95)00004-6CHEETHAM, A. K., & VON DREELE, R. B. (1973). Cation Distributions in Niobium Oxide Block Structures. Nature Physical Science, 244(139), 139-140. doi:10.1038/physci244139a0Obayashi, H., & Anderson, J. S. (1976). Intermediate phases and pseudophases in the system WO3Nb2O5: Tetragonal tungsten bronze phases. Journal of Solid State Chemistry, 17(1-2), 79-89. doi:10.1016/0022-4596(76)90205-xMAGNÉLI, A. (1950). Structure of β-Tungsten Oxide. Nature, 165(4192), 356-357. doi:10.1038/165356b0M. Greenblatt , in Physics and Chemistry of Low-Dimensional Inorganic Conductors , ed. C. Schlenker , J. Dumas , M. Greenblatt and S. van Smaalen , Springer US , Boston, MA , 1996 , vol. 2 , pp. 15–43Chen, J., Wang, H., Deng, J., Xu, C., & Wang, Y. (2018). Low-crystalline tungsten trioxide anode with superior electrochemical performance for flexible solid-state asymmetry supercapacitor. Journal of Materials Chemistry A, 6(19), 8986-8991. doi:10.1039/c8ta01323cGarcía-González, E., Soriano, M. D., Urones-Garrote, E., & López Nieto, J. M. (2014). On the origin of the spontaneous formation of nanocavities in hexagonal bronzes (W,V)O3. Dalton Trans., 43(39), 14644-14652. doi:10.1039/c4dt01465kSoriano, M. D., Concepción, P., Nieto, J. M. L., Cavani, F., Guidetti, S., & Trevisanut, C. (2011). Tungsten-Vanadium mixed oxides for the oxidehydration of glycerol into acrylic acid. Green Chemistry, 13(10), 2954. doi:10.1039/c1gc15622eMurayama, T., Kuramata, N., Takatama, S., Nakatani, K., Izumi, S., Yi, X., & Ueda, W. (2012). Synthesis of porous and acidic complex metal oxide catalyst based on group 5 and 6 elements. Catalysis Today, 185(1), 224-229. doi:10.1016/j.cattod.2011.10.029Omata, K., Izumi, S., Murayama, T., & Ueda, W. (2013). Hydrothermal synthesis of W–Nb complex metal oxides and their application to catalytic dehydration of glycerol to acrolein. Catalysis Today, 201, 7-11. doi:10.1016/j.cattod.2012.06.004Thibodeau, T. J., Canney, A. S., DeSisto, W. J., Wheeler, M. C., Amar, F. G., & Frederick, B. G. (2010). Composition of tungsten oxide bronzes active for hydrodeoxygenation. Applied Catalysis A: General, 388(1-2), 86-95. doi:10.1016/j.apcata.2010.08.025M. J. Sienko , in Nonstoichiometric Compounds, Advances in Chemistry , ed. R. Ward , American Chemical Society , 1963 , vol. 39 , ch. 21, pp. 224–236Yang, C., Chen, J.-F., Zeng, X., Cheng, D., & Cao, D. (2014). Design of the Alkali-Metal-Doped WO3 as a Near-Infrared Shielding Material for Smart Window. Industrial & Engineering Chemistry Research, 53(46), 17981-17988. doi:10.1021/ie503284xMigas, D. B., Shaposhnikov, V. L., Rodin, V. N., & Borisenko, V. E. (2010). Tungsten oxides. I. Effects of oxygen vacancies and doping on electronic and optical properties of different phases of WO3. Journal of Applied Physics, 108(9), 093713. doi:10.1063/1.3505688Ostertag, W., & Collins, C. V. (1967). Electrical resistivity of cubic rare earth, thorium and uranium tungsten bronzes. Materials Research Bulletin, 2(2), 217-221. doi:10.1016/0025-5408(67)90060-8Ostertag, W. (1966). Rare Earth Tungsten Bronzes. Inorganic Chemistry, 5(5), 758-760. doi:10.1021/ic50039a014Von Rohr, F. O., Ryser, A., Ji, H., Stolze, K., Tao, J., Frick, J. J., … Cava, R. J. (2019). The h ‐Sb x WO 3+2 x Oxygen Excess Antimony Tungsten Bronze. Chemistry – A European Journal, 25(8), 2082-2088. doi:10.1002/chem.201805251Cerretti, G., Schrade, M., Song, X., Balke, B., Lu, H., Weidner, T., … Tremel, W. (2017). Thermal stability and enhanced thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47 (0 < x < 5). Journal of Materials Chemistry A, 5(20), 9768-9774. doi:10.1039/c7ta01121kGriffith, K. J., Wiaderek, K. M., Cibin, G., Marbella, L. E., & Grey, C. P. (2018). Niobium tungsten oxides for high-rate lithium-ion energy storage. Nature, 559(7715), 556-563. doi:10.1038/s41586-018-0347-0Okumura, K., Tomiyama, T., Shirakawa, S., Ishida, S., Sanada, T., Arao, M., & Niwa, M. (2011). Hydrothermal synthesis and catalysis of Nb2O5–WOxnanofiber crystal. J. Mater. Chem., 21(1), 229-235. doi:10.1039/c0jm02882gDelgado, D., Fernández-Arroyo, A., Domine, M. E., García-González, E., & López Nieto, J. M. (2019). W–Nb–O oxides with tunable acid properties as efficient catalysts for the transformation of biomass-derived oxygenates in aqueous systems. Catalysis Science & Technology, 9(12), 3126-3136. doi:10.1039/c9cy00367cSaha, D., Jensen, K. M. Ø., Tyrsted, C., Bøjesen, E. D., Mamakhel, A. H., Dippel, A.-C., … Iversen, B. B. (2014). In Situ Total X-Ray Scattering Study of WO3Nanoparticle Formation under Hydrothermal Conditions. Angewandte Chemie International Edition, 53(14), 3667-3670. doi:10.1002/anie.201311254Juelsholt, M., Lindahl Christiansen, T., & Jensen, K. M. Ø. (2019). Mechanisms for Tungsten Oxide Nanoparticle Formation in Solvothermal Synthesis: From Polyoxometalates to Crystalline Materials. The Journal of Physical Chemistry C, 123(8), 5110-5119. doi:10.1021/acs.jpcc.8b12395Murayama, T., Kuramata, N., & Ueda, W. (2016). Hydrothermal synthesis of W–Ta–O complex metal oxides by assembling MO6 (M = W or Ta) octahedra and creation of solid acid. Journal of Catalysis, 339, 143-152. doi:10.1016/j.jcat.2016.04.007Murayama, T., Nakajima, K., Hirata, J., Omata, K., Hensen, E. J. M., & Ueda, W. (2017). Hydrothermal synthesis of a layered-type W–Ti–O mixed metal oxide and its solid acid activity. Catalysis Science & Technology, 7(1), 243-250. doi:10.1039/c6cy02198kDelgado, D., Soriano, M. D., Solsona, B., Zamora, S., Agouram, S., Concepción, P., & López Nieto, J. M. (2019). Tungsten-titanium mixed oxide bronzes: Synthesis, characterization and catalytic behavior in methanol transformation. Applied Catalysis A: General, 582, 117092. doi:10.1016/j.apcata.2019.05.026Delgado, D., Chieregato, A., Soriano, M. D., Rodríguez-Aguado, E., Ruiz-Rodríguez, L., Rodríguez-Castellón, E., & López Nieto, J. M. (2018). Influence of Phase Composition of Bulk Tungsten Vanadium Oxides on the Aerobic Transformation of Methanol and Glycerol. European Journal of Inorganic Chemistry, 2018(10), 1204-1211. doi:10.1002/ejic.201800059Delgado, D., Fernández-Arroyo, A., Salvia, N. L., Domine, M. E., & Nieto, J. M. L. (2019). Reflux-synthesized bulk and diluted W-Nb-O mixed oxide bronzes for the valorization of short-chain oxygenates aqueous mixtures. Chinese Journal of Catalysis, 40(11), 1778-1787. doi:10.1016/s1872-2067(19)63419-4La Salvia, N., Delgado, D., Ruiz-Rodríguez, L., Nadji, L., Massó, A., & Nieto, J. M. L. (2017). V- and Nb-containing tungsten bronzes catalysts for the aerobic transformation of ethanol and glycerol. Bulk and supported materials. Catalysis Today, 296, 2-9. doi:10.1016/j.cattod.2017.04.009Choi, J., Moon, K., Kang, I., Kim, S., Yoo, P. J., Oh, K. W., & Park, J. (2015). Preparation of quaternary tungsten bronze nanoparticles by a thermal decomposition of ammonium metatungstate with oleylamine. Chemical Engineering Journal, 281, 236-242. doi:10.1016/j.cej.2015.06.101Nieto, J. M. L., Botella, P., Vázquez, M. I., & Dejoz, A. (2002). The selective oxidative dehydrogenation of ethane over hydrothermally synthesised MoVTeNb catalysts. Chem. Commun., (17), 1906-1907. doi:10.1039/b204037aSadakane, M., Yamagata, K., Kodato, K., Endo, K., Toriumi, K., Ozawa, Y., … Ueda, W. (2009). Synthesis of Orthorhombic Mo-V-Sb Oxide Species by Assembly of Pentagonal Mo6O21Polyoxometalate Building Blocks. Angewandte Chemie International Edition, 48(21), 3782-3786. doi:10.1002/anie.200805792Wagner, J. B., Timpe, O., Hamid, F. A., Trunschke, A., Wild, U., Su, D. S., … Schlögl, R. (2006). Surface texturing of Mo–V–Te–Nb–O x selective oxidation catalysts. Topics in Catalysis, 38(1-3), 51-58. doi:10.1007/s11244-006-0070-1Barthel, J., Weirich, T. E., Cox, G., Hibst, H., & Thust, A. (2010). Structure of Cs0.5[Nb2.5W2.5O14] analysed by focal-series reconstruction and crystallographic image processing. Acta Materialia, 58(10), 3764-3772. doi:10.1016/j.actamat.2010.03.016Soriano, M. D., García-González, E., Concepción, P., Rodella, C. B., & López Nieto, J. M. (2017). Self-Organized Transformation from Hexagonal to Orthorhombic Bronze of Cs–Nb–W–O Mixed Oxides Prepared Hydrothermally. Crystal Growth & Design, 17(12), 6320-6331. doi:10.1021/acs.cgd.7b00999Dickens, P. G., & Whittingham, M. S. (1968). The tungsten bronzes and related compounds. Quarterly Reviews, Chemical Society, 22(1), 30. doi:10.1039/qr9682200030MAGNÉLI, A. (1952). Tungsten Bronzes containing Six-membered Rings of WO6 Octahedra. Nature, 169(4306), 791-792. doi:10.1038/169791a0Szilágyi, I. M., Madarász, J., Pokol, G., Király, P., Tárkányi, G., Saukko, S., … Varga-Josepovits, K. (2008). Stability and Controlled Composition of Hexagonal WO3. Chemistry of Materials, 20(12), 4116-4125. doi:10.1021/cm800668xPinar, A. B., Márquez-Álvarez, C., Grande-Casas, M., & Pérez-Pariente, J. (2009). Template-controlled acidity and catalytic activity of ferrierite crystals. Journal of Catalysis, 263(2), 258-265. doi:10.1016/j.jcat.2009.02.017Gu, Z., Ma, Y., Zhai, T., Gao, B., Yang, W., & Yao, J. (2006). A Simple Hydrothermal Method for the Large-Scale Synthesis of Single-Crystal Potassium Tungsten Bronze Nanowires. Chemistry - A European Journal, 12(29), 7717-7723. doi:10.1002/chem.200600077Xie, F. Y., Gong, L., Liu, X., Tao, Y. T., Zhang, W. H., Chen, S. H., … Chen, J. (2012). XPS studies on surface reduction of tungsten oxide nanowire film by Ar+ bombardment. Journal of Electron Spectroscopy and Related Phenomena, 185(3-4), 112-118. doi:10.1016/j.elspec.2012.01.004Grundner, M., & Halbritter, J. (1980). XPS and AES studies on oxide growth and oxide coatings on niobium. Journal of Applied Physics, 51(1), 397-405. doi:10.1063/1.327386Kreissl, H. T., Li, M. M. J., Peng, Y.-K., Nakagawa, K., Hooper, T. J. N., Hanna, J. V., … Tsang, S. C. E. (2017). Structural Studies of Bulk to Nanosize Niobium Oxides with Correlation to Their Acidity. Journal of the American Chemical Society, 139(36), 12670-12680. doi:10.1021/jacs.7b06856BURSILL, L. A., & HYDE, B. G. (1972). Rotation Faults in Crystals. Nature Physical Science, 240(102), 122-124. doi:10.1038/physci240122a0Bursill, L. A., & Smith, D. J. (1984). Interaction of small and extended defects in nonstoichiometric oxides. Nature, 309(5966), 319-321. doi:10.1038/309319a0Migas, D. B., Shaposhnikov, V. L., & Borisenko, V. E. (2010). Tungsten oxides. II. The metallic nature of Magnéli phases. Journal of Applied Physics, 108(9), 093714. doi:10.1063/1.3505689Dupin, J.-C., Gonbeau, D., Vinatier, P., & Levasseur, A. (2000). Systematic XPS studies of metal oxides, hydroxides and peroxides. Physical Chemistry Chemical Physics, 2(6), 1319-1324. doi:10.1039/a908800hCiftyürek, E., Šmíd, B., Li, Z., Matolín, V., & Schierbaum, K. (2019). Spectroscopic Understanding of SnO2 and WO3 Metal Oxide Surfaces with Advanced Synchrotron Based; XPS-UPS and Near Ambient Pressure (NAP) XPS Surface Sensitive Techniques for Gas Sensor Applications under Operational Conditions. Sensors, 19(21), 4737. doi:10.3390/s19214737Pawlak, D. A., Ito, M., Oku, M., Shimamura, K., & Fukuda, T. (2001). Interpretation of XPS O (1s) in Mixed Oxides Proved on Mixed Perovskite Crystals. The Journal of Physical Chemistry B, 106(2), 504-507. doi:10.1021/jp012040aA. Davydov , Molecular Spectroscopy of Oxide Catalyst Surfaces , John Wiley & Sons , Hoboken , 2003 , pp. 27–179Perra, D., Drenchev, N., Chakarova, K., Cutrufello, M. G., & Hadjiivanov, K. (2014). Remarkable acid strength of ammonium ions in zeolites: FTIR study of low-temperature CO adsorption on NH4FER. RSC Adv., 4(99), 56183-56187. doi:10.1039/c4ra12504eZecchina, A., Marchese, L., Bordiga, S., Pazè, C., & Gianotti, E. (1997). Vibrational Spectroscopy of NH4+ Ions in Zeolitic Materials:  An IR Study. The Journal of Physical Chemistry B, 101(48), 10128-10135. doi:10.1021/jp9717554Katryniok, B., Paul, S., Bellière-Baca, V., Rey, P., & Dumeignil, F. (2010). Glycerol dehydration to acrolein in the context of new uses of glycerol. Green Chemistry, 12(12), 2079. doi:10.1039/c0gc00307gFoo, G. S., Wei, D., Sholl, D. S., & Sievers, C. (2014). Role of Lewis and Brønsted Acid Sites in the Dehydration of Glycerol over Niobia. ACS Catalysis, 4(9), 3180-3192. doi:10.1021/cs5006376Sung, K.-H., & Cheng, S. (2017). Effect of Nb doping in WO3/ZrO2 catalysts on gas phase dehydration of glycerol to form acrolein. RSC Advances, 7(66), 41880-41888. doi:10.1039/c7ra08154

Pressure-Induced Amorphization of Small Pore Zeolites-the Role of Cation-H2O Topology and Anti-glass Formation

Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NAT(II)) in closer proximity to the aluminosilicate framework. We show that NAT(I) materials have a lower onset pressure of PIA than the NAT(II) materials containing Rb and Cs as EFC. The onset pressure of amorphization (P-A) of NAT(II) materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P-1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P-2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced-this opens a new way to form anti-glass structuresopen

Self-assembly of Silver Nanoparticles and Multiwall Carbon Nanotubes on Decomposed GaAs Surfaces

Atomic Force Microscopy complemented by Photoluminescence and Reflection High Energy Electron Diffraction has been used to study self-assembly of silver nanoparticles and multiwall carbon nanotubes on thermally decomposed GaAs (100) surfaces. It has been shown that the decomposition leads to the formation of arsenic plate-like structures. Multiwall carbon nanotubes spin coated on the decomposed surfaces were mostly found to occupy the depressions between the plates and formed boundaries. While direct casting of silver nanoparticles is found to induce microdroplets. Annealing at 300°C was observed to contract the microdroplets into combined structures consisting of silver spots surrounded by silver rings. Moreover, casting of colloidal suspension consists of multiwall carbon nanotubes and silver nanoparticles is observed to cause the formation of 2D compact islands. Depending on the multiwall carbon nanotubes diameter, GaAs/multiwall carbon nanotubes/silver system exhibited photoluminescence with varying strength. Such assembly provides a possible bottom up facile way of roughness controlled fabrication of plasmonic systems on GaAs surfaces

Fundamental Phenomena and Applications of Swift Heavy Ion Irradiations

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