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SOLVOTHERMAL PROCESSES: A ROUTE TO NOVEL MATERIALS, WELL DEFINED NANOPARTICLES

SOLVOTHERMAL PROCESSES: A ROUTE TO NOVEL MATERIALS, WELL DEFINED NANOPARTICLES and HYBRID NANO-SYSTEMS . Gérard DEMAZEAU Emeritus Professor, ICMCB, CNRS University BORDEAUX 1 « Sciences and Technologies » Vice-Président of ISHA (International Solvothermal Hydrothermal Association).

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SOLVOTHERMAL PROCESSES: A ROUTE TO NOVEL MATERIALS, WELL DEFINED NANOPARTICLES

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  1. SOLVOTHERMAL PROCESSES: A ROUTE TO NOVEL MATERIALS, WELL DEFINED NANOPARTICLES and HYBRID NANO-SYSTEMS. Gérard DEMAZEAUEmeritus Professor, ICMCB, CNRSUniversity BORDEAUX 1« Sciences and Technologies »Vice-Président of ISHA(International Solvothermal Hydrothermal Association)

  2. SOLVOTHERMAL PROCESSESBucarest ,october 5-7 ,2007 • Dear Colleagues • I apologize to be absent during this important Meeting organized by my friend Prof. Radu PITICESCU. • After strong efforts for organizing a specific Session devoted to « Solvothermal Reactions » during the international High Pressure Conference (AIRAPT/EHPRG) in Catania (sept.15-23, 2007) • and the participation to the XVIIIth Mendeleev Conference in Moscow (sept.22sept.28,2007) for presenting an invited lecture on « Solvothermal Processes » I was obliged –due to health problems- to stop during one week my activity!!! All my best wishes for the success of this Meeting . Nevertheless ,I shall try to do the best for supporting your scientific project

  3. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. SOLVOTHERMAL REACTIONS A “solvothermal reaction can be defined as a chemical reaction (or a transformation) between precursor(s) in a solvent (in a close system) at a temperature higher than the boiling temperature of this solvent and under high pressure” autogeneous pressureorimposed pressure.  Subcritical or supercritical domain.  Homogeneous or heterogeneous system.

  4. WHAT ARE THE MAIN FACTORS CHARACTERIZING HIGH PRESSURES • Pressure is always involved in Solvothermal Processes( autogeneous our imposed pressure) consequently it is necessary to take into account the different factors induced by such a parameter • The weak energy involved by pressure, • The negative V value leading to the denser phases,(V being the volume difference between the final state and the starting state) • The improvement of the reactivity.

  5. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • FIRST FACTOR:THE ENERGYWHAT IS THE DIFFERENCE BETWEEN PRESSURE AND TEMPERATURE FROM AN ENERGETICAL POINT OF VIEW? • 1)Comparison of the energy conveyed by HIGH PRESSURES and the energy of a CHEMICAL REACTION

  6. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • 2) Comparison between Pressure and Temperature: 1 liter of water, T=20 →T=25°C, P=1bar (constant) Energy = 20kJoules • Using a constant temperature (T=20°C) what is the pressure value able to be reached with this energy ??? P=4000bar (400MPa) • CONSEQUENTLY: Due to the small energy conveyed by pressure such a parameter can be developed in Biosciences.

  7. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • Brief history - Hydrothermal reactions (using aqueous solutions) have been developed at the end of the XIX Century →objective to prepare geomaterials. - Development of hydrothermal crystal growth SPEZIA 1898-1909 - Industrial crystal growth of -quartz and piezo-electric materials - Development of hydrothermal synthesis of new materials - 1990 Development of non-aqueous solventshydro = H2OSolvo = solventProposition of solvothermal reactions(G. Demazeau-Bordeaux) for developing non-oxides. systems

  8. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • DEVELOPMENT OF SOLVOTHERMAL REACTIONS • Main types of chemical reactions involved in Solvothermal processes: • - oxidation/reduction, - hydrolysis, • - thermolysis, - complexation, - metathesis…… • The control of such reactions associated to the formation of the target material implies : →to improve the knowledge of the chemistry in non-aqueous solvents

  9. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • Different research fields are implied in solvothermal processes: •  MATERIALS CHEMISTRY and MATERIALS SCIENCE  Synthesis of novel materials  Research of low-cost processes  Preparation of micro- or nano-crystallites  Growth of single crystal of functional materials  Low-temperature sintering processes  Thin film deposition •  DEVELOPMENT OF RESEARCH DOMAINS AT THE INTERFACE BETWEEN DIFFERENT DISCIPLINARIES.  Hybrid Materials (inorganic chemistry/Organic chemistry).  Hybrid Systems (nano-chemistry/Biosciences)

  10. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • Main parameters involved in Solvothermal Reactions: -The nature of the reagents • Chemical composition, size of the crystallites … - The chemical composition of the solvent- • Such a parameter is able to open new research areas concerning the composition of the expected materials: • Synthesis of intermetallic compounds, oxides, nitrides, phosphides, borides….. - The mild temperature conditions- • Temperature is mainly used for improving the diffusion of chemical species, • The mild temperature conditions allow- if the reaction is kinetically controlled- to prepare metastable materials. - The pressure in liquid phase is limited (10 <P<500 MPa) • Pressure is developed in order- (i) through the interactions between liquid/solid phases or between solvated chemical species (in solution) –to improve the reactivity, (ii) through the “densification effect” to orientate the structure of the expected materials.

  11. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. ROLE OF THE REAGENTS IN SOLVOTHERMAL PROCESSES SYNTHESIS OF A NEW-CLASS OF BI-DIMENSIONNAL OXIDES ISOSTRUCTURAL TO PHYLLOSILICATES: THE PHYLLOSILOXYDES. (P. REIG , G. DEMAZEAU ,R. NASLAIN) ICMCB ,LCTS, University Bordeaux 1

  12. SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES  The thermal stability of phyllosilicates is limited by OH groups. 2OH- O2-+H2O+  Anionic substitution OH-O2- in the phyllosilicates lattice.But: correlated with cationic substitutions 

  13. SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES • The anionic sustitution OH-O2- leads to an increase of the anionic charges • Consequently such an anionic substitution is correlated with cationic substitutions. One possibility: Al3+(Td)  Si4+ (Td) Mg2+(Oh)  Al3+ (Oh)

  14. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES D • sol-gel process: sol  gel aerogelConventional Solid State Solvothermal processProcess (500 1000°C) solvent = methoxy-ethanol precursor = aerogelMixture of 3D silicates T=500°C, 50P150MPa, t24h • single phase

  15. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. I.R. Spectroscopy K Mg3 (Si3Al)O10(OH)2 K(Mg2Al) Si4 O12 X. Ray Diffraction Scanning Electron Microscopy H.R.T.M. K(Mg2Al) Si4 O12 K Mg3(Si3Al)O10(OH)2

  16. SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES • X-ray diffraction analysis The X-ray spectrum of the resulting single phase is similar to that of the initial « mother phase » : mica with the phlogopite structure.  Ir spectroscopy K Mg3 (Si3Al) O10(OH)2  strong absorption band due to OH group ( 3700 – 3800 cm-1). K (Mg2Al) Si4O12  NO absorption band corresponding to OH groups. • Electronic Microscopy. SEM: platelets (l 0.2 μm) TEM: layered structure (interlayer distance corresponding to the phlogopite structure)

  17. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (A)Synthesis of metastable compounds The solvent, can induce the formation of very stable complex ions and such complex ions can act as template for stabilizing metastable compounds. Example: LI J., CHEN Z., WANG R.J., PROSERPIO D.M. Coordination Chem. Rev. (1999) 190-192 p. 707. Ethylenediamine has a strong coordination ability towards the divalent transition metals (Mn2+, Fe2+, Co2+, Ni2+, Zn2+)M2+ + 3en  M(en)32+ M(en)32+ characterized by an octahedral geometry can act as template for building new metastable materials.

  18. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (B)Orientation to a metastable structural form LU J., QI P., PENG Y., MENG Z., YANG Z., YU W., QIAN Y. Chem. Mater. (2001) 13 p. 2169. precursors: MnCl2, 4H2O and SC(NH2)24 solvents have been evaluated:H2O or ethylenediamine able to form a stable Mn complexa-MnS rocksaltnon polar C6H6g-MnS wurtzite (Metastable)tetrahydrofuran (THF) b-MnS zinc-blende (Metastable)when no stable complexes are stabilized the solvothermal reaction is kinetically controlled leading to the stabilization of two metastable forms.

  19. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (C)The oxidation-reduction properties inducing a specific composition. PANDA S.K., GORAI S., CHAUDURI S. Mater. Sci Eng. B. (2006) 129 p. 265.have underlined the role of the oxidation-reduction process induces by the solvent during the solvothermal synthesis of SnS crystallites from Sn metal. Such a solvothermal process can be described through three steps:(1) Sn0 + (few amounts of H2O) Sn2+ + 2e-(2) Sn2+ + n en.  Sn(en)n2+(3) Sn(en)n2+ + S2-SnS.

  20. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (D)Preparation of nano-crystallites with a specific morphology. Solvothermal preparation of nanocrystallites with a specific morphology has attracted a strong interest during these last years. Different compositions of nanocrystallites have been developed… but recently intermetallic nanocrystallites have been investigated. The preparation of nanoparticles of intermetallic FePt nanowires has been selected as example.

  21. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • (D) ROLE OF THE SOLVENT IN THE PREPARATION OF INTERMETALLIC FePt NANOWIRES • Interest of such FePt nanoparticlesIntensive Research due to its potential applications in high density storage and high performance permanent magnets.  WELLER D., DOERWER M.F. Annu. Rev. Mater. Sci. (2000) 30 p. 611. SUN S., MURRAY C.B., WELLER D., FOLKS L., MOJER A. Science (2000) 287 p. 1989.Conventionally FePt particles were synthesized via thermal decomposition of Fe(CO)5, reduction of Platinum acetylacetonate Pt(acac)2 and co-reduction of iron salt and Pt(acac)2.difficulty to control the morphology of FePt nanoparticles.

  22. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. • ROLE OF THE SOLVENT IN THE SOLVOTHERMAL PREPARATION OF INTERMETALLIC FePt NANOWIRES • In order to control the size and the morphology of PtFe nanoparticles • Development of a solvothermal process. • Precursors: Pt(acac)2 + Fe(CO)5 + (en) as solvent • (160 < T < 200°C , autogeneous pressure) • Pt(en)22+ inducing self organization leads to • the formation of FePt Nanowires. • MAO C.B., SOLIS D.J., REISS B.D., KOTTMANN S.T., SWEENEY R.Y., HAYHUST A., GEORGIOU G., IVERSON B., BELCHER A.M. Science (2004) 303 p. 213.

  23. Potentialities of solvothermal processes for developing hybrid systems

  24. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. Low temperature solvothermal processes allow to stabilize original hybride materials (inorganic/ organic components) as an example:  Solvothermal synthesis of Zincophosphite (C6H16N2)Zn3(HPO4)3 FU et al. Solid State Sciences6, 225 (2004)

  25. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. At the interface between BIOSCIENCES and NANO-SCIENCES • PEPTİDE ENGİNEERİNG FOR BİO-İNSPİRED MATERİALS (M.UMETSU et al. Tohoku University) J. Materials Science (in press) Peptides have affinity for non-biological materials and could mineralized inorganic materials. ZnO semi-conductor with a direct band gap ....fabricatıon of ZnO nano-structures. Peptide can bind the ZnO particles (but no ZnS) and further the ZnO-binding peptide selectively catalyses the synthesis of a highly anisotropic ZnO particles from a Zn(OH)2 solutıon at room temperature and medium pressure condıtıons

  26. SOLVOTHERMAL PROCESSES: FROM NOVEL MATERIALS TO HYBRID NANO-SYSTEMS. MAIN CHALLENGES FOR THE FUTURE ??? Why and How to reduce Temperature WHY? → FOR PRESERVING SPECIFIC COMPONENTS (in order in particular to prepare hybrid inorganic/organic or inorganic/biological systems) → FOR INDUCING METASTABLE PHASES (but it is necessary to improve the kinetical effects) → FOR SAVING ENERGY (sustainable development) HOW ? TO IMPROVE THE CHEMICAL REACTIVITY  TROUGH THE OPTIMIZATION -PRECURSORS -SOLVENT, -PRESSURE.

  27. MAIN OBJECTIVES OF SOLVOTHERMAL PROCESSES  To open a route through new « soft chemical processes» Kinetically controlled for stabilizing metastable systems, • To help the synthesis of specific structures using templates, • To control the nucleation/ crystal growth processes for the preparation of nanocrystallites well defined in size and morphology, • To facilitate ,through the improvement of the chemical reactivity and the development of mild temperature conditions, the synthesis of hybrid nano-systems.

  28. CONCLUSIONS All the objectives of SOLVOTHERMAL PROCESSES require to optimize : • The physico-chemical properties of the precursors, • The physico-chemical properties of the solvent, • The thermodynamical parameters P, T. Solvothermal processes appear to be important in the near future, not only for developing Basic Science But also for developing new industrial processes in mild P,T conditions. THANK YOU FOR YOUR ATTENTION.

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