Titanium dioxide supported on activated carbon, or TiO2/AC composite, exhibits bifunctionality of adsorption and photocatalysis in synergism. The authors review the TiO2/AC synthesis techniques, characteristics, and performances in removing organic pollutants in water. Practical issues pertinent to applications of the TiO2/AC composite in water treatment and reclamation are discussed. These include dispersing the particles and recovering from the product water, UV introduction and attenuation in the photoreactor, long-term photostability and mechanical stability of the composite, potential TiO2 deactivation by the organic and inorganic matrices, assessment of intermediates and byproducts, and regeneration techniques for the exhausted or fouled TiO2/AC. Coupling with a membrane separation process to recover and regenerate TiO2/AC in various continuous flow-through system configurations is proposed. There are also possible integrations of TiO2/AC treatment systems with other treatment processes that may res...

TiO2/AC Composites for Synergistic Adsorption-Photocatalysis Processes: Present Challenges and Further Developments for Water Treatment and Reclamation

Peculiarities of cluster properties are considered and processes involving them discussed. Generation methods and applications in material fabrication are described. The kinetics of cluster growth in expanding vapor is analysed. The absorption and emission properties of clusters as systems of bound atoms are examined. The properties of a cluster plasma, i.e., a cluster-containing ionized gas, are discussed in relation to cluster light sources.

Processes in plasma and gases involving clusters

The processes are considered in a cluster plasma consisting of a dense plasma of a buffer gas and a metal admixture These processes involving clusters in a gas or plasma include nucleation processes in a supersaturated vapor, formation of metallic clusters in a dense gas from metal-containing compounds, and chemical processes in the course of this conversion, processes of cluster charging in a plasma and under the action of an electron beam The basic methods are analyzed for cluster generation including formation and growth of clusters in free jet expansion of a gas, under laser action on the metallic surface, and growth of clusters in a plasma resulted from injection of metal-containing molecules into a plasma Some applications of cluster beams are discussed, which include fabrication of thin films, new materials, and creation of a hot nonuniform plasma

Generation of cluster beams

The evolution of a hot gas or a weakly ionised plasma—formed as a result of evaporation of the surfaces of a solid under the action of high energy fluxes or flow out of a nozzle—is considered. The expansion of a vapour or a plasma into the surrounding space leads to its cooling and is accompanied by a chain of processes involving both charged (electrons, ions, atoms, charged clusters) and neutral particles. The evolutionary regimes leading to the condensation of atoms, accompanied by the formation of large charged and neutral clusters, are discussed. The experimental aspects of the generation of intense cluster beams in such regimes and the applications of such beams are considered.

Processes in expanding and condensing gases

Cluster temperature is an important material parameter essential to many physical and chemical processes involving clusters and cluster beams. Because of the diverse methods by which clusters can be produced, excited, and stabilized, and also because of the widely ranging values of atomic and molecular binding energies (approximately from 10?5 to 10 eV) and numerous energy relaxation channels in clusters, cluster temperature (internal energy) ranges from 10?3 to about 108 K. This paper reviews research on cluster temperature and describes methods for its measurement and stabilization. The role of cluster temperature in and its influence on physical and chemical processes is discussed. Results on the temperature dependence of cluster properties are presented. The way in which cluster temperature relates to cluster structure and to atomic and molecular interaction potentials in clusters is addressed. Methods for strong excitation of clusters and channels for their energy relaxation are discussed. Some applications of clusters and cluster beams are considered.

https://iopscience.iop.org/article/10.1070/PU2008v051n04ABEH006421/pdf

Cluster temperature. Methods for its measurement and stabilization

Ionized cluster beam (ICB) deposition is an ion-assisted film deposition technique by which high quality films of metals, dielectric and semiconductor can be formed at a low substrate temperature. In the ICB process, film materials are vaporized from a confinement crucible under conditions which result in the formation of aggregates of atoms (clusters). Clusters are ionized by electron impact and subsequently accelerated by high potentials. Through selection of available parameters, it is possible to control the average energy of depositing species over the range from thermal to above 200 eV per atom, which make possible well controlled crystalline film deposition and epitaxy. In the ICB deposition, characteristics of the deposition are mainly caused by both the structural characteristic of the clusters and the effect of ionization and acceleration of the clusters. Unique features of ICB deposition, reactive-ICB deposition and simultaneous deposition by use of ICB and microwave ion source are described with respect to the kinetic energy and the ionic charge by comparing those of deposition methods in plasma.

T. Takagi

Papers

Ionized cluster beam (ICB) deposition and processes