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Oxide Hydrosols for Sol-Gel Technique

#A-329


Development of New Methods of Deriving Stable Oxide Hydrosols, Research of Their Properties and Application in the Sol-Gel Technique

Tech Area / Field

  • CHE-SYN/Basic and Synthetic Chemistry/Chemistry

Status
3 Approved without Funding

Registration date
02.03.1999

Leading Institute
Scientific Technological Center of Organic and Pharmaceutical Chemistry / Institute of Fine Organic Chemistry, Armenia, Yerevan

Collaborators

  • CNRS / U.M.R. 6516 Synthese, Catalyse, Chiralite, France, Marseille

Project summary

The purpose of the presented project is development of methods of deriving stable and concentrated hydrosols from Al2O3 - ZrO2 - Fe2O3 - LaO model system (where La is an element from the lantanoid group) having dense, homogeneously sized spherical particles. These hydrosols are widely used as flocculants and coagulants (purification of waste water), binding materials (production of technical ceramics, coatings), frictional agents (textile and paper industry), fillers and densificators (polymeric compositions), grinding means (production of artificial leather), as well as for synthesis of some "model" porous materials, in particular sorbents and catalyst carriers (sorbents for highly effective liquid chromatography), by sol-gel methods using hydrosols.

The hydrosols developed can also be used for deriving other materials by sol-gel methods. Such materials are, in particular those with wanted final characteristics determining mainly by the structure of initial oxide hydrosols of various metals, for example sublayers and substrates (for creation of materials with high-temperature superconductivity), functional coatings (anticorrosive, heat-shielding covers etc.), ceramic powders (production of structural ceramics), reaction mixtures (production of synthetic crystals, optical glasses, etc.) synthetic filaments and fibers (thermo-stable refractory filaments used for production of inorganic composites).

The choice of oxides in the above-mentioned model system is stipulated by their greatest demand, and that of the “model” porous materials (sorbents and catalysts’ carriers with an ordered structure) by apparent advantages of using hydrosols having homogeneous spherical particles for regulation of their porous structure and mechanical hardness. The methods of deriving hydrosols of various metal oxides developed up to now do not allow to realize their commercial production and large-scale application for the following reasons: insufficient time stability, low concentration, difficulty associated with size regulation of the particles. At present, only hydrosols of silicon dioxide free of above mentioned disadvantages are widely used. Importance of the problem represented in the project, will increase in connection with sharpening of requirements to new materials created by sol-gel technology. After elaboration (based on the model system) of general principles of deriving stable and concentrated hydrosols with spherical particles, there will be an actual possibility of commercial production of their assortment. This, in turn, should create new possibilities related to the aimed synthesis of materials with beforehand settled properties (adsorbents, catalysts, heat-shielding materials, etc.) by sol-gel technological methods.

The sol-gel process can be schematically represented as follows:

[solution]-condensation-[sol]-coagulation-[gel]maturing, syneresis, drying-[xerogel]

There are practically no publications concerning conditions of sol formation and its main parameters (shape and size of particles, their size distribution, impurities, structure, etc.), although it is known that the use of different sol types in sol-gel technology can essentially affect the whole process and result in unexpected outcomes. Based on model systems, an attempt to study influence of main sol parameters on consequent processes in the sol-gel chain and final properties of xerogel will be undertaken.

Being synthesized both with chemically homogeneous and heterogeneous dense spherical particles of different sizes, hydrosols present spherical nuclei of silicon dioxide covered by monolayer of appropriate metal hydroxide and have surface properties identical to those of oxide hydrosols having chemically homogeneous particles. The second group of hydrosols can be used use in those areas of science and engineering where the properties of surface layers of the colloidal particles (production of adsorbents and catalysts, flocculative purification of water containing weighted particles and microimpurities, heterocoagulation of microorganisms, production of cinema and photo materials, etc.) is of great importance. In both cases, synthesis will be carried out under strictly controlled conditions (allowing to optimize the synthesis parameters) thus ensuring formation of dense spherical particles. Besides, basic physical, chemical, and colloidal properties (adsorbability, aggregation stability, electrokinetics) of hydrosols to be obtained will be investigated.

All hydrosols will be synthesized, if possible, using raw resources and waste products of various Armenian industries.

Based on the synthesized metal oxide hydrosols having dense spherical particles and known structures, new adsorbents and catalyst carriers characterized by obviously expressed synergetic effects and adjustable parameters of the porous structure will be obtained by sol-gel methods and investigated. Besides, colloidal and chemical regularities of deriving above materials will be studied as well as connections between parameters of the porous structure of final products and the structure of initial colloidal solutions will be investigated.

All compositions to be obtained will be tested by appropriate scientific methods. New areas of their application will be proposed. For example, it is supposed to investigate new methods of diagnostics of biologically active fluids using cerium oxide hydrosol.

Preliminary researches, already conducted by our team of the experienced scientists and engineers having numerous papers (up to 40) on the planned works, as well as obtained earlier positive results give confidence in successful realization of the Project.

Realization of the project will allow to solve a number of problems goals meeting ISTC’s:

· Reorientation of scientists, engineers and technical personnel earlier involved in synthesis of anticholinesterase and psychotropic substances as well as production of missile fuel, towards development of materials of civil purposes;

· Support of fundamental researches and developments of peaceful branches;

· Development of science-capacious technologies;

· Creation of long-term perspectives for professional activity in civil sectors;

· Contribution to development of market relations, etc.

It is expected that fulfillment of works planned by the project, will allow:

· To develop new methods of synthesizing stable and concentrated metal oxide hydrosols having spherical, homogeneously sized particles of various chemical composition;

· To generalize obtained outcomes of the research and develop general principles of synthesizing hydrosols having spherical particles covered by oxides;

· To research main colloidal chemical properties of the developed hydrosols;

· To find new areas of their application;

· To research colloidal chemical regularities of deriving oxide adsorbents and catalysts’ carriers by sol-gel methods using synthesized hydrosols of known structure having spherical particles.

Introduction of the executed researches and recommendations in industry will enable:

· To manufacture for the first time an assortment of stable metal oxide hydrosols having spherical particles;

· To create scientific and practical backgrounds for synthesis of materials with beforehand settled properties by sol-gel methods;

· To contribute to development of market relations;

· To provide a long-term program of cooperation with the interested foreign enterprises;

· To find new consumers and civil markets, to realize production of a number of new competitive materials;

· To contribute to development of the adsorption theory and colloidal chemistry of oxide systems.

The project is open for cooperation with foreign collaborators. They could be both financial supports and co-partners in carrying out some stages of the project.

The project assumes execution of research and technological investigations at IFOC, where works on deriving fundamental bases of chemical weapon, namely anticholinesterase and psychotropic substances, were earlier conducted.

It is assumed to test the obtained materials at various enterprises. On completion of each stage, after analysis and discussions of the results, corresponding reports and recommendations will be prepared.

During the project work the known physical and chemical methods of analysis of highly dispersed systems will be used, namely IR and X-ray spectroscopy, electron microscopy, porosity measurements, etc.


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