A flame process for synthesis of unagglomerated, low-oxygen nanoparticles: Application to Ti and TiB2

Abstract

A gas-phase flame process for synthesizing unagglomerated nanoparticles of metals, intermetallics, ceramics, and composites is described. Employing this process, titanium and titanium boride have been synthesized by the vapor-phase reaction of sodium with titanium tetrachloride and a 1:2 mixture of titanium tetrachloride and boron trichloride, respectively. To minimize agglomeration and protect the particles from postflame oxidation, the NaCl by-product is allowed to condense onto the particles in situ, yielding NaCl-encapsulated particles. In this way, stable, unagglomerated Ti and TiB 2 nanoparticles have been produced and the encapsulated powders have been handled in air without oxidation. Particle size has also been varied with the encapsulation process, and titanium particles with mean sizes of 10 and 60 nm have been produced by varying operating conditions. The NaCl has been removed by water washing as well as vacuum annealing. Thermodynamic results show that the sodium/halide process is applicable for synthesis of many materials, with yields approaching 100 pct under a wide range of operating conditions. Similarly, the encapsulation process is generally applicable, making the sodium/halide flame and encapsulation process a viable one for large-scale synthesis of environmentally insensitive nanopowders.

Synthesis and characterization of nanosized titanium particles by gas-phase combustion

“…6) at the same heat-treatment. This result can be explained with reference to published data [6,9,10]. In the open tip system, the reactivity of the reaction mixture is relatively low compared to closed tip.…”

“…Consequently, the research of gas-phase combustion synthesis needs to be focused on prevention of hard agglomerates with good purity and productivity. Several researchers [6][7][8][9][10] have studied synthesis of metals or non-oxide ceramics, and developed a technique that appears to address purity, particle size, and agglomeration issues. A low-temperature burner similar to the counter flow method [8], allows for prevention of agglomeration because particles do not sinter as they would at higher flame temperature.…”

“…A low-temperature burner similar to the counter flow method [8], allows for prevention of agglomeration because particles do not sinter as they would at higher flame temperature. The process can also prohibit the hard agglomeration because of flame encapsulation technology [9][10][11][12].However, the synthesis of metal particles by coflow flame method at low temperature has not been studied extensively. Therefore, the objective of the present study is to produce nanosized Ti particles by a modified coflow method with variations in process conditions, and to evaluate the particle properties, demonstrating the formation mechanism of Ti particle with NaCl in low temperature flame.…”

Synthesis and characteristics of nanocrystalline materials in Ti, B, C and N containing system

“…Thus, it is widely used for cutting tool composites, wear resistant parts, metal melting crucibles and electrode materials [1][2][3][4][5]. Exceptional properties were shown for fine-grained TiB 2 , which is used during the manufacturing of tools used in steel machining technologies [2,5].…”

Monte Carlo Simulation of Multicomponent Aerosols Undergoing Simultaneous Coagulation and Condensation

“…Results that compared favorably with experiments were obtained with a relatively small number of bins, but the error caused by the use of bins was not discussed in this work. Huertas (1997) followed the same approach and incorporated condensation into the Monte Carlo method and employed it to study the sodium/halide flame encapsulation (SFE) process (DuFaux and Axelbaum 1995;Axelbaum et al 1997). Although valuable insight was obtained from this simulation, the results showed significant numerical dispersion due to the use of bins when condensation was considered.…”