and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

Titanium diboride (TiB2) based materials have received wide attention because of their high hardness and elastic modulus, good abrasion resistance, and superior thermal and electrical conductivity. Potential applications include high temperature structural materials, cutting tools, armour, electrodes in metal smelting and wear parts. Despite its useful properties, the application of monolithic TiB2 is limited by poor sinterability, exaggerated grain growth at high temperature and poor oxidation resistance above 1000°C. Pure TiB2 can be densified only at high temperatures (∼2000°C), with an applied pressure generally being necessary during sintering. However, these high sintering temperatures cause abnormal grain growth and microcracks, which are detrimental to the mechanical properties. Various sinter additives are commonly added to obtain dense TiB2 with optimised mechanical properties at lower sintering temperature. The present review surveys the current state of knowledge on development of bulk...

Processing and properties of monolithic TiB2 based materials

Flame aerosol synthesis of nanostructured materials and functional devices: Processing, modeling, and diagnostics

Aluminum is examined as energy storage and carrier. To provide the correct feasibility study the work includes the analysis of aluminum production process: from ore to metal. During this analysis the material and energy balances are considered. Total efficiency of aluminum-based energy storage is evaluated. Aluminum based energy generation technologies are reviewed. Technologies are categorized by aluminum oxidation method. Particularly, the work focuses on direct electrochemical (anodic) oxidation of aluminum, aluminum–water reaction in alkaline solution, mechanochemical activation of aluminum, mechanical activation of aluminum and high-temperature aluminum–water reaction. The objective is methods overview including technological principle, efficiency, urgent problems and possible application areas.

Aluminum as energy carrier: Feasibility analysis and current technologies overview

From the view point of combustion science, the fundamentals of particle formation in a flame environment are discussed. The principles of converting a gas phase precursor dopant into particles and also their growth are addressed. Various experimental methods and examples for the synthesis of particles of both single and mixed oxides are reviewed. First attempts to tune the stoichiometry of oxide particles by varying the combustion parameters of premixed flames are demonstrated. Some aspects of modelling and the problems which still need to be solved are illustrated by means of the particles’ population balance equation.

Particle synthesis in flames

Two techniques are described for synthesizing nanometer-sized TiB2 particles by gas-phase combustion reactions of sodium vapor with TiCl4 and BCl3: a low-pressure, low-temperature burner and a high-temperature flow reactor. Both methods produce TiB2 particles that are less than 15 nm in diameter. The combustion by-product, NaCl, is efficiently removed from the TiB2 by water washing or vacuum sublimation. Material collected from the low-temperature burner and annealed at 1000 °C consists of loosely agglomerated particles 20 to 100 nm in size. Washed material from the high-temperature flow reactor consists of necked agglomerates of 3 to 15 nm particles. A thermodynamic analysis of the Ti/B/Cl/Na system indicates that near 100% yields of TiB2 are possible with appropriate reactant concentrations, pressures, and temperatures.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400023128

Gas-phase combustion synthesis of titanium boride (tib2) nanocrystallites

Due to its combined properties of high electrical resistivity and high thermal conductivity aluminum nitride (AlN) is a highly desirable material for electronics applications. Methods are being sought for synthesis of unagglomerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AlCl3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants with the products being AlN, NaCl, and H2. The NaCl by-product is used to coat the AlN particles in situ. The coating allows for control of AlN agglomeration and protects the powders from hydrolysis during post-flame handling. On the basis of thermodynamic and kinetic considerations, two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AlCl3 and NH3 were premixed with HCl and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCl for the first case and NaCl and AlN for the second. After annealing at 775 C tinder dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AlN. Aluminum metal was also produced in the co-flow flame by reacting AlCl3 with Na. XRD spectra of as-produced powders show the products to be only NaCl and elemental aluminum.

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L.J. Rosen

Papers

Gas-phase combustion synthesis of titanium boride (tib2) nanocrystallites

Gas-phase combustion synthesis of aluminum nitride powder

Wet chemistry and combustion synthesis of nanoparticles of TiB2