Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Nanosized TiO 2 powders were prepared from the precipitation in the TiCl 4 precursor under various pH values. The prepared titania existed in the form of nanocrystalline anatase with some brookite, which was evidenced by X-ray diffraction analysis and Raman spectroscopy. The average crystallite sizes of the TiO 2 particles heat treated at 450 °C for 2 h are in the range of 7–9 nm. The lattice constant c of anatase increased with increasing the synthesized pH value, whereas the volume fraction of the brookite phase increased with decreasing the synthesized pH value. The beginning and ending temperatures for the anatase–rutile transformation were found to decrease with increasing the volume fraction of the brookite phase. The brookite phase in the powder is responsible for enhancing the anatase–rutile transition.

Effect of brookite phase on the anatase–rutile transition in titania nanoparticles

Photocatalytic activity of nanocrystalline TiO2 (brookite, rutile and brookite-based) powders prepared by thermohydrolysis of TiCl4 in aqueous chloride solutions

Structural characteristics and mechanical and thermodynamic properties of nanocrystalline TiO2.

Photocatalytic degradation of Rhodamine B dye under UV/solar light using ZnO nanopowder synthesized by solution combustion route

Understanding of Homogeneous Spontaneous Precipitation for Monodispersed TiO2 Ultrafine Powders with Rutile Phase around Room Temperature

Nano-crystalline Ni has been synthesized by a pulsed wire evaporation (PWE) method, and its abnormal magnetic properties in a magnetic ordered state have been characterized using high and low magnetic fields. It was found that particles with the size ranges from 20 to 80 nm has a mean crystalline size of 40 nm which might influence the magnetic hysterisis behavior. Neutron powder diffraction (NPD) and saturation magnetization results indicate the antiferromagnetic NiO phase in prepared powder exist below the detection limit of 1 wt.%. The shifted hysterisis loop and irreversibility of magnetization in a high field were observed in the magnetic-ordered state of Ni. The initial magnetization curve for Ni is started to overlap the hysterisis loop at applied field of 750 Oe. This irreversibility in a high field can be explained by the non-collinear behavior and the existence of the metastable states of the magnetization at the surface layer (or core) of the particle in the applied magnetic field due to decrease of particle size.

Magnetic properties of nano-size Ni synthesized by the pulsed wire evaporation (PWE) method

Transition metal ion of Ni 2+ doped TiO 2 nanostructured powders were synthesized by mechanical alloying to shift the adsorption threshold into the visible light region. The X-ray patterns for samples showed three phases of TiO 2 such as rutile, anatase and brookite. The 8 wt.% Ni-doped TiO 2 powders consisted of spherical primary particles with a size of about 50 nm and secondary particles about 100–300 nm. The transition metal ion of Ni 2+ doped TiO 2 powders showed excellent photo-oxidative ability in 4-chlorophenol degradation.

Photocatalytic behaviors of transition metal ion doped TiO2 powder synthesized by mechanical alloying

The present invention relates to titanium dioxide powder with a large specific surface area, a method for preparing thereof, and a use of the titanium dioxide as a photocatalyst, and more particularly, discloses a method for the preparation of titanium dioxide powder comprised of the steps of adding ice pieces or icy distilled water to pure titanium tetrachloride (TiCl4) to give an aqueous titanylchloride solution of 1.5 M or higher; diluting the aqueous titanylchloride with distilled water; obtaining precipitates from the diluted aqueous titanylchloride solution by standing for 2-20 hours at 15-70° C.; and filtering, washing and drying the above precipitates to give downy hair-shaped TiO2 powder with a specific surface area of 130-200 m2/g. The titanium dioxide powder of the present invention shows high photocatalytic activity, so that it can be used to decompose environmental organic pollutants by taking advantage of an advanced oxidation process (AOP) in which pollution-free energy, such as solar energy is utilized as a driving force. The method allows the formation of a crystalline phase of titanium dioxide at room temperature without a high temperature and high pressure process and enjoys an economical advantage of being low in production cost.

TiO2 ultrafine powder, and process for preparing thereof

Nanoparticles of γ-Fe 2 O 3 have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of γ-Fe 2 O 3 with particle sizes of 14 to 30 nm in a chamber filled with mixtures of Ar and O 2 gases. From the main peak intensities of XRD and analyses of Mossbauer spectra, the amount of γ-Fe 2 O 3 and α-Fe in the sample is composed of about 93% and 7%, respectively. Mossbauer spectra consist of two sets of six Lorentzian lines corresponding to γ-Fe 2 O 3 and α-Fe. It was found that the phase transition from both γ-Fe 2 O 3 and α-Fe to Fe 3 O 4 , which was evaluated from the results of Mossbauer spectra, strongly depended on the O 2 flow rate. As a result, γ-Fe 2 O 3 was synthesized under the O 2 flow rate of 0.05 ≤ V o2 (l/min) ≤ 0.15, whereas Fe 3 O 4 was synthesized under the O 2 flow rate of 0.15 ≤ V o2 (l/min) ≤ 0.2.

W. W. Kim

Papers

Understanding of Homogeneous Spontaneous Precipitation for Monodispersed TiO2 Ultrafine Powders with Rutile Phase around Room Temperature

Magnetic properties of nano-size Ni synthesized by the pulsed wire evaporation (PWE) method

Photocatalytic behaviors of transition metal ion doped TiO2 powder synthesized by mechanical alloying

TiO2 ultrafine powder, and process for preparing thereof

Phase control and Mössbauer spectra of nano γ‐Fe2O3 particles synthesized by the levitational gas condensation (LGC) method