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Hydrothermal Synthesis of Glass Complex Charges

#A-971


Development and Research of Hydrothermal Synthesis of Glass Complex Charges for Production of Special Glasses on the Base of Silica-Containing Rocks

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
20.01.2003

Leading Institute
NPF "Stone & Silicates", Armenia, Yerevan

Collaborators

  • Kochi University, Japan, Kochi\nOhio State University, USA, OH, Columbus\nUniversity of Calgary, Canada, AB, Calgary\nRheinisch-Westfalische Technische Hochschule / Institut fuer Gesteinshuttenkunde, Germany, Aachen\nCNRS / Université de Rennes 1, France, Rennes\nNational and Kapodistrian University of Athens / Department of Geology, Greece, Athens\nUniversity of Washington / Materials Science & Engineering, USA, WA, Seattle\nOklahoma State University / Department of Chemistry, USA, OK, Stillwater\nRutgers University / Department of Ceramic and Materials Engineering, USA, NJ, Piscataway\nPohang University of Science and Technology, Korea, Pohang\nVirginia Polytechnic Institute and State University / The Bradley Department of Electrical and Computer Engineering, USA, VA, Blacksburg\nInstituto Technology Nuclear, Portugal, Sacavem\nGeorgia Institute of Technology, USA, GA, Atlanta\nGeosciences Management Institute, Inc., USA, NV, Boulder City\nUniversidade de Aveiro / Ceramics and Glass Engineering Department, Portugal, Aveiro\nUniversity of Padova / Mechanical Engineering Department, Italy, Padova\nSojo University, Japan, Kumamoto\nTechnische Universität Clausthal, Germany, Clausthal\nConsiglio Nazionale delle Ricerche / Istituto dei Materiali per l'Elettronica ed il Magnetismo, Italy, Parma\nMartin-Luther Universität Halle-Wittenberg / Institut fuer Werkstoffwissenschaft, Germany, Halle\nRitsumeikan University, Japan, Shiga\nTrent University, Canada, ON, Peterborough\nArgonne National Laboratory (ANL), USA, IL, Argonne\nTU Bergakademie Freiberg / Institut fuer Keramik, Glas- und Baustofftechnik, Germany, Freiburg\nUniversity of Missouri-Rolla / Department of Ceramic Engineering, USA, MO, Rolla

Project summary

In the present Project is assumed development and research of technology of glass complex charge by a new method in scientific practice – method of hydrothermal synthesis with the purpose of obtaining special glasses obtaining on the basis of silica containing rocks.

The existing dry method of glass charge preparation has serious disadvantages and does not provide high homogeneity of charge chemical and grain structure.

Recently non-conventional methods of materials obtaining on the basis of sols and gels, the systems with high reactivity in high disperse state have more and more wider development. The advantages of sol-gel method are obtaining new materials with high degree of homogeneity and cleanliness at lower temperature of synthesis. Despite of definite advantages of sol-gel method, it has important disadvantages: high cost of initial materials, big contraction, residual porosity and hydroxyl groups, residual carbon, harmful components danger, long time of manufacturing.

Meanwhile, it is possible to develop essentially new methods of glass charge preparation with the best technical and technological characteristics at scientifically based approach. At that, is assumed not to use traditional raw materials, and to utilize the whole class of silica containing rocks as raw material the direct use of which because of high contents of colored impurities is considered impossible for special glasses obtaining.

For the first time an original hydrothermal method of active glass charge preparation was developed by us as a result of preliminary researches.

The essence of the method is transition from dry mixing of glass charge components to hashing their soluble components at 50-80 °C, that provides reactions of silicate formation and mixture homogenization during charge preparation.

By hydrothermal-alkaline processing of silica containing rocks (perlite, pumice, diatomite, rottenstone, gaize, quartz sand) solutions of alkaline silicates (Na2O·nSiO2 or K2O·nSiO2, n = 1-4), a liquid glass has been obtained by worked out method.

Further silicates are deposited on the basis of a liquid glass, after filtration the deposit is washed out, mixed up with missing components and dried at temperatures 150-200 °C. It is possible to briquette, granulate, keep for a long time and transport on any distance the synthesized glass complex charge.

Simultaneously the opportunity of liquid glass obtaining from the whole class of silica containing rocks by the method of hydrothermal-alkaline processing at lower temperatures (90-200 °C) in comparison with traditional technology is revealed. At that, by adjusting processing conditions it is possible to obtain silicate solutions with specified data which are the main raw material for silica and different silicate obtaining. By adjusting silica module and obtaining conditions of liquid glass it is possible to synthesize the whole class of amorphous hydrosilicates both as powders and as gels with general formula RxOy· nSiO2 · mH2O (where x = 1-2, y = 1-3, R – Ca, Mg, Ba, Zn, Pb, Al, Ti, Zr, La, Ce, Pr, Nd and others) with tailor-made properties.

It is possible to develop any glass charge compounds on the basis of the synthesized silicates. The difficulty of the given researches realization is in the fact that at rocks hydrothermal processing by NaOH or KOH solution iron compounds pass in silicate solutions and pollute it. The method of silicate solutions cleaning from colored impurities is offered by us, which permits to obtain high transparent technical, optical, u-viol glasses on the basis of glass complex charge.

Our researches have shown that any charge prepared by hydrothermal method by its melting behavior has certain advantages in comparison with traditional one:

– It is a mixture of ready fine-grained hydrosilicates, identical in chemical composition to the glass; it is practically X-ray-amorphous at room temperature and at heating melting of the ready chemical compounds presented in hydrothermal charge occurs in comparison with traditional one where a formation of silicates and silica various crystal forms dissolution in high alkali silicate melt take place.

– It is established that synthesized glass complex charge melts at lower temperatures (on 150-200 °C below) which conditioned by its structure. Time of charge melt also decreases (in 1.5-2 times).

– It is known, that at traditional charge melt some components’ volatilizing occurs leading to infringement of glass homogeneity, environmental contamination and loss of expensive materials. At glass complex charge synthesis there are interactions of components with liquid glass resulting in silicates formation with complex structure and glass homogeneity, which simultaneously promotes reduction and, in some cases, practical absence of charge highly volatile components loss.

It is possible to obtain alkalifree, refractory, optical, u-viol glasses, thin glass films obtaining for electronics, and also glasses obtaining without fusion by a method of pressing on the basis of complex charge obtained by hydrothermal method.

So, in particular, on example of u-viol glass for bactericidal lamps the glass from charge obtained by hydrothermal method has light transition at l=253.7 mm 63-68% while the analogical index for glasses obtained by traditional method makes 45-50%.

The developed technology of various structures glass complex charge obtaining on the basis of silica containing rocks is non-waste. The offered technology allows to obtain such products as liquid glass, various silicates, silica, zeolites, adsorbents, fillers and on the basis of waste cleaning powders, glassy facing plates, foamglass and so on.

There are all bases to assert, that hydrothermal method of above-stated silicate products obtaining in comparison with the known methods of similar materials obtaining is economically justified as the reduction of the cost price will make not less than 20-40%.

The purpose of the Project is:

– Research and establishment of obtaining mechanism of silicate solutions (Na2O · nSiO2, K2O · nSiO2) with adjustable structure on the basis of silica containing rocks.

– Research and development of clearing method of silicate solutions from colored impurities by applying physico-chemical methods. 

– Research of silicate formation and physico-chemical properties research of heterogeneous systems R(NO3)2 – Na2O · 3SiO2 – H2O (R – Ca, Mg, Ba, Zn, Pb etc.), R(NO3)3 – Na2O3 · SiO2 – H2O (R – Al, Ce, Pr, Nd etc.), R(NO3)4 – Na2O · 3SiO2 – H2O (R – Ti, Zr etc.).

– Glass complex charge synthesis of predetermined composition, its physico-chemical and technical properties research.

– Research of glass formation, melt and physico-chemical properties of glasses on the basis of hydrothermal charge.

– Development of complex technology of various glass charge obtaining for special purposes from silica containing rocks.

As a result of the Project the following problems will be solved:

– One-stage technology development of silicate solutions obtaining from silica containing rocks, surpassing with its adaptability to manufacture and profitability the known methods of obtaining from silicate block.


– Development of new method of clearing silicate solutions from colored impurities.
– Synthesis of new amorphous high-purity nano-dispersed silicates with adjustable structure and predetermined properties.
– Synthesis of amorphous high-purity silica with predetermined properties.
– Synthesis of glass complex charge by hydrothermal synthesis method.
– Development of processing methods of waste formed at hydrothermal processing of rocks for various materials obtaining.
– Reorientation of highly skilled scientists on the solving of peace problems, peace orientated researches and development support.
– Integration of scientists into the international community.

The staff of scientists of SI&P Joint-Stock Company "Stone and Silicates" long time have been en-ga-ged in development and manufacture of glasses and silicates obtained on the basis of hydrothermal processing products of silica containing rocks.

The authors of the Project invite scientists, research organizations, and also private experts from USA, the countries of European Community, Japan, Korea, and China to collaboration. We also offer to hold joint seminars and scientific researches.


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