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Ultraviolet Glass

#A-1523


A New Technology for Obtaining Complex Glass Charge for Manufacture Uviol Glass

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials
  • CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry

Status
8 Project completed

Registration date
06.04.2007

Completion date
26.04.2011

Senior Project Manager
Tyurin I A

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

Collaborators

  • Univesidad de Cadiz, Spain, Cadiz\nCNRS / Université de Rennes 1, France, Rennes\nUniversity of Thessaloniki / Department of Physics, Greece, Thessaloniki\nUniversita' Degli Studi di Modena / Dipartimento Ingegneria dei Materiali e dell'Ambiente, Italy, Modena\nInstituto Technology Nuclear, Portugal, Sacavem\nUniversidade de Aveiro / Ceramics and Glass Engineering Department, Portugal, Aveiro

Project summary

In the present Project the development and research of the technology of glass complex charge obtaining is assumed by means of a new method in the scientific practice – a method of hydrothermal synthesis with the purpose to obtain special glasses with heightened ultraviolet (UV) transmittance at 253,7 and 296 nm on the base of silica-containing rocks.

Uviol glass is used in various fields of engineering, first of all – for manufacturing the casing of the bactericidal and erythermal lamps (UVlamps), and sheet uviol glass – for glazing the hospitals, sanatoriums, houses, etc.

Today the manufacturing uviol glass for UV lamps is urgent aiming the disinfection of the premises’ air (in medical and child’s institutions, some industrial premises and administrative buildings), drinking and mineral water, food products, packing, connected with the bacteriological protection of the population and in case of possible terrorist actions.

UV-irradiation quantum possessing high energy may change the chemical structure of separate cells and living organisms’ tissues. UV-irradiation in 280-400 nm range acts healthy on the human organism, animals and birds. UV-irradiation in 200-400 nm range possesses bactericide action that may cause in appropriate conditions the death of bacteria.

The ability of the glasses to let pass UV-range of the spectrum is completely predetermined by their chemical composition. During the absorption of the UV-irradiation characterizing by relatively higher amount of energy corresponding structural transformations take place connected with the change of the energetic state of the atoms and ions presenting in the glass. At that the absorbance of the irradiation by the glass is added from its own absorbance as well as the absorbance stipulated by the presence of the elements of variable valence (d and f elements).

The best materials transmitting the UV-irradiation are melted quartz and melted boric acid. However the technology of the manufacturing the melted quartz is rather complicated and expensive. The melted boric acid is chemically unstable, it is water-soluble.

The analysis of the scientific-technical literature on the problem of the manufacturing the uviol glasses for bactericidal and erythermal lamps proved that there are large enough achievements in this field. The indicated lamps are manufactured bath on the base of the quartz and uviol glasses.

Nevertheless, together with the growth of the producing UV lamps the shortage of the raw materials for obtaining uviol glass is observed. This stipulates the necessity of the search and the usage of more available and non-deficit raw material for the manufacturing glasses, such as natural silica-containing rocks.

The existing dry method of glass charge preparation has serious disadvantages and does not pro-vide high homogeneity of the charge chemical and grain structure, as well it requests the use of the chemically pure materials. The main direction for the intensifying the glass melting processes is the radical change of the methods of glass charge preparation.

Recently non-conventional methods of materials obtained on the basis of sols and gels presenting the systems with high reactivity in highly dispersed state have more wider development. The advantages of sol-gel method are the obtaining of new materials with high degree of homogeneity and purity at lower temperature of synthesis. Despite of definite advantages of sol-gel method, it has important disadvantages: high cost of initial materials, great level of shrinkage, residual porosity and hydroxyl groups, residual carbon, protracted time of manufacturing.

Meanwhile, it is possible to develop essentially new methods of glass charge preparation with the best technical and technological characteristics in case of scientifically based approach. At that, it is not assumed to use traditional (conventional) raw materials – instead we intend to utilize the whole class of the silica-containing rocks as raw material. The direct use of which is considered impossible for obtaining the special glasses because of high content of coloring impurities is considered impossible.

For the first time an original hydrothermal method of active glass charge preparation have been 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 20-90°C which provides the occurring of the silicate formation reactions and mixture homogenization during the charge preparation.

According to the worked out method by means of hydrothermal-alkaline processing of silica containing rocks (perlite, pumice, diatomite, rottenstone, gauze, quartz sand) solutions of alkaline silicates (Na2O nSiO2 or K2O nSiO2, n = 1-4) may be obtained.

Further, on the base of liquid glass silicates of the elements which are present in the glass content are precipitated. After filtration the precipitate is washed out, mixed up with missing components and dried at temperatures 150-200°C. The synthesized glass complex charge is possible to briquette, granulate, keep for a long time and transfer to any distance.

The high light-transmittance in the UV spectral range is one of the most important demands for the uviol glasses.

The quartz raw for the manufacturing uviol glasses with the initial iron oxides content less than 0.07% undergoes preliminary enrichment which permits to decrease iron content to 0.003%. And it is laborious, energy-consuming and expensive process. The hydrothermal method for preparing the complex glass batch of the uviol glass composition permits to use silica-containing rocks with any content of the iron oxides.

During the rocks hydrothermal processing by NaOH or KOH solution the iron compounds pass in silicate solutions (up to 0.03%). In this connection it is necessary to elaborate the method of purification of silicate solutions from coloring

impurities. An original and inexpensive physico-chemical method has been worked out by us for purification of silicate solutions from iron compounds which make possible to lower its content (to less than 0.0005%).

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

  • 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; when heating and melting of the ready chemical compounds presented in the hydrothermal charge occurs contrary with traditional one where a formation of silicates and silica various crystal forms dissolution in high alkali silicate melting takes place.
  • The synthesized glass complex charge melts at lower temperatures (by 150-200°C below) which is conditioned by its structure. Time of charge melting also decreases (by 1.5-2 times).
  • During the traditional charge melting some components’ volatilizing occurs leading to infringement of glass homogeneity, environmental contamination and loss of expensive materials. In case of the glass complex charge synthesis the interactions of components with liquid glass take place resulting in the formation of silicates with complex structure as well as providing the glass homogeneity, which simultaneously promotes decrease of the loss of highly volatile components.
  • Comparative analysis of the light transmittance and iron oxides content in the uviol glass for bactericide lamps showed that the glass from the batch obtained by means of the hydrothermal method have light transmittance at = 253.7 nm 65%, and iron oxides content ≤ 0,004%, while the similar parameters for the glasses obtained from the batch prepared by means of the traditional dry way equal correspondingly to 45% and 0.01%.

What relates to the ecological aspect of the hydrothermal method of the preparation of the complex glass batch for manufacturing the uviol glass – our preliminary evaluation of the throws to the atmosphere caused by the glass melting products witnesses that when using the hydrothermal batch it equals 3-5% as water vapor, while the same parameter for the glasses obtained by mends of conventional technique is 20-22%as CO2.

There are all bases to assert, that the hydrothermal method for obtaining the above-stated silicate products is economically justified as compared with the known methods of obtaining the similar materials: preliminary calculations witness that the reduction of expenses will make not less than 50%.

We hope after the completion of the Project, there will be some organizations, companies and firms (will be found which will develop their) interested in the commercial use of the results of our studies.

The purposes of the Project are:

  • The research and establishment of the mechanism of the obtaining silicate solutions (Na2O nSiO2, K2O nSiO2) with adjustable structure on the base of silica containing rocks.
  • The research and development of the purification method of silicate solutions from coloring impurities applying physico-chemical methods.
  • The research of silicate formation processes and physico-chemical properties of heterogeneous systems R(NO3)2 – Na2O 3SiO2 – H2O (R – Ca, Mg, Ba, Zn, etc.).
  • The synthesis of glass complex charges of predetermined composition, the study of physicco-chemical and technological properties.
  • The research of glass formation, melting and physico-chemical properties of glasses on the base of hydrothermal charge.
  • The development of the technology of complex glass charge obtaining for manufacture light-technical uviol glasses from silica-containing rocks.

As a result of the Project the following problems will be solved:
  • The development of one-stage technology of the silicate solutions obtaining from the silica-containing rocks, surpassing the known methods of obtaining from silicate block by its adaptability to manufacture and profitability.
  • The evaluation of the availability of the silica-containing rocks for the manufacturing the silicate solutions.
  • The development of a newmethod for purification the silicate solutions from coloring impurities.
  • The synthesis of amorphous high-purity nano-dispersed Ca, Mg, Ba, Zn silicates with adjust-table structure and predetermined properties.
  • The synthesis of the glass complex charge by means of the method of hydrothermal synthesis.
  • The development of the methods for utilizing (alkaline aluminum silicates) the wastes formed during the hydrothermal processing of rocks for various materials obtaining.
  • Reorientation of highly skilled scientific stuff to the solving of peace problems, peace oriented researches and development support.
  • Integration of scientists into the international community.

The scientific staff of the SI&P "Stone and Silicates" Joint-Stock Company have been engaged during the long time in development and manufacture of glasses and silicates obtained on the base of hydrothermal processing products of silica containing rocks.

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


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