BASALT CONTINUOUS FIBERS STATE OF THE ART, MARKET APPLICATION PROBLEMS AND DECISION DIRECTIONS
May 2008 - Dr. Michael Ziv, “Dse-Energy”. firstname.lastname@example.org
Science, technology and know-how rush development of our age set up new problems, such as environment damage, problems of isolation, conservation and transporting hazardous waste, space familiarization, etc. These problems call for new raw materials application, as aggregated as natural ones. The basalt igneous rock suitability to get good results almost in every industrial field is already widely known. Its processing in the staple or continuous fibers, as well as in casting products gives chance to substitute many traditional complicated and expensive materials. The modern research efforts exhibits high potential of natural basalt rock to isolate radiological, nuclear and other kinds of dangerous waste for a long period. The continuous fibers production from pure basalt igneous rock stone and its further processing in finished products without any blending by additional aggregates, has a good future perspective. It makes basalt competitive in the world industry and market of fiber glass and other widely known fibers, like carbon, Kevlar etc. At the same time, the continuous fibers producing from the pure basalt igneous rock has some problems of manufacture. The main of them:
1. Bushing plates for basalt continuous fibers drawing mainly made of Platinum – Rhodium based alloy are too expensive and call for regular expensive service.
2. The big iron oxide content of basalt stone, painting a melt dark color, increase homogenization period, crystallization temperature and make viscosity curve much more abrupt in comparison with aggregated glass compositions.
These problems call for special melt furnace and equipment (look my publication “THE MAIN PRINCIPLES AND DEVICE FOR CONTINUOUS BASALT FIBERS PRODUCTION”). There are some technological methods too for finish product quality improving while melting and drawing processes.
2. A LITTLE OF THE HISTORY.
As it was told above, the new technologies development calls for new materials employ looking. The Hi-tech industry (electronic, instrument engineering, atomic, rocketry, space, etc.) needs the same and higher main technical properties (strength, termostability, etc.) raw materials, but much more lighter. Practically, the material density will be one of the main further development factors.
The composite materials, based on continuous glass fibers, began widely manufactured in the middle of XX century was really revolutionary decision in this direction. Glass marbles, prepared from special multicomponent mineral mixture, are heated in the melting furnace and the molten glass is driven by pressure head through an assembly of tiny holes in a heated platinum alloy bushing. Till nowadays almost the same technology is operated for glass fiber manufacture. Today the continuous glass fiber has a dominant position in the world composite materials industry. It is employed as based material in 60% manufactures of this field.
But farther technical development calls for fibers with increasing technical requirements of those materials, with the purpose to enlarge its application fields. The method of existing glass mixture blending with additional materials for new futures achievement makes glass fibers much more expensive. It is naturally that in many experiments for based fiber material making was tried to use basalt volcanic stone as a uni component nature raw material has a very close chemical composition to glass mixture. But numerous experimental attempts of different companies in Germany, USA, Denmark, former USSR etc. in 60-s XX century to draw continuous fiber from basalt rock did not let to industry results.
At the same time, the test results of the physical and chemical characteristics of basalt continuous fibers, drawn under experimental conditions, showed very perspective potentialities of its employment in different fields, especially such as military, security and so on. It was the main reason of the former Soviet totalitarian regime directive decision to achieve stability industrial manufacture of basalt continuous fibers based products. Many scientists and experimenters came to this new field from fiber glass industry. The shortest way to achieve results was to employ, as based technology, continuous glass fiber manufacture with platinum alloy bushing. After years of experiments directed to put into practice the known technology (of glass fiber) to different basaltic rock materials, it came true for appropriate local Ukrainian basalt stone. However the mentioned versions of apparatus are designed for industrial production of continuous basalt fiber is law efficient. The low efficiency came from the apparatuses for manufacturing borosilicate glass fiber. Many features came from glass fiber industry to basalt fiber manufacturing without essential changing and because poor mixing and not complete the high melting point complex oxides destruction/decomposing. All components of igneous rock have to be decomposed and the volatile components have to be degassing from melted basalt. Lot of attempts to draw the continuous fibers from basalt rock of different deposits differed with iron containing, employing the same technology conditions and bushing plate, were not successful. That’s why for needed fiber quality achievement, using a typical plant, presently is widely adopted a blending (aggregation) of natural basalt rock compositions by additional aggregates for maximum approximation to famous compositions (closed to glass one), permitted to keep needed study-state conditions on known equipment. Disadvantage of this way is factually application of multicomponent raw material and, as a consequence, - manufacturing complication. Besides, the fiber bushing plate is what makes the capital investment in fiber production expensive. The real Platinum-Rhodium (P-RH) alloy plate European prize achieves almost 65…70% of summary plant prize. And more amazing that even widely employed and very expensive P-Rh based bushing plates are less effective for basalt melt (!) as it was shown by later experiments.
3. BUSHING PLATE.
As it well known the bushing plate is the most important part of the plant for continuous fiber producing. Factually this is a small metal furnace containing nozzles for the fiber to be formed through. It is almost always made of platinum alloyed with rhodium for durability and due to its cost and the tendency to wear. Platinum is employed because the melt has a natural affinity for wetting it. The nozzle design is also critical. The fiber strength depends on ratio of melt η / σ (η divided), where η (“eta”) is melt viscosity and σ (“delta”) is melt surface tension. This ratio defines melt ability to fiber formation and may be regulated in different technological ways and one of them is temperature rising above fiber forming plate and high speed cooling instantly after fiber drawing out of fiber forming zone. The important part of the nozzle in continuous fibers manufacture is the thickness of its walls in the exit region. Today, the nozzles are designed to have a minimum thickness at the exit. The reason of this is that as melt flows through the nozzle it forms a drop which is suspended from the end. As it falls, it leaves a thread attached by the meniscus to the nozzle as long as the viscosity is in the correct range for fiber formation. The thinner wall at exit makes faster the drop forming and falls away, and lowers its tendency to wet the vertical part of the nozzle. The surface tension of the melt is what influences the formation of the meniscus. The utmost angle of P-Rh alloy wetting by iron included basalt melt substantially lower than its wetting by alkali free alumina-borosilicate glass melt (E-glass). This fact causes higher streak (flowing in) of fiber forming plate. Much better basalt melt wetting bushing made of doubled silicon molybdenum alloy (MoSi2) in the chromic magnesium or bacor refractory frame resistant to basalt melt, or frame made of coiling basalt as it has become possible lately.
4. SOME TECHNOLOGICAL METHODS FOR FINISH FIBERS QUALITY IMPROVING WHILE MELTING AND DRAWING PROCESS.
These methods are imported in cases of chemical composite deviation (insignificant, of course) of raw material or atmosphere or nature distinction, like in space, but not only. Typical samples of basalt rock of different deposits contain about 2-3% of ferric oxide and 11-13% of ferrous oxide, i. e. approximately the same ratio. However, when the basalt rock is melted under normal process conditions in an electric furnace and subsequently drawn through a widely prevailing platinum-rhodium nozzles, substantial portions of the ferrous oxide are oxidized to produce an increase in the ratio of ferric oxide to ferrous oxide over that ratio which is present in the initial rock, i.e. the additional oxidation of the ferrous compounds present in the melt occurs. It was found that by controlling this rate of oxidation so as to minimize the ratio of ferric oxide to ferrous oxide in the resulting fibers, the resulting fibers will demonstrate desirable increased strength characteristic. Prevention or reduction of this oxidation is achieved by application of an inert atmosphere such as nitrogen, or a reducing atmosphere, such as carbon monoxide while fiber drawing. The needed effect achieved by heating the basalt rock above its melting point and drawing the molten basalt rock through a small nozzle diameter to form fibers while maintaining the molten basalt rock and nozzles within an inert or reducing atmosphere, whereby the molten basalt rock is drawn as fibers while minimizing oxidation of its ferrous oxide content. Simultaneous sodium silicate solution put on fiber surface instantly after its drawing outside of bushing plate by special device oversaturated while diffusion in monomolecular layer formed because of this fiber surface wetting ability, and extracts hydration product in the form of colloidal mass, “treating” micro cracks on fiber’s surface. Both of these improving methods may be used separately or together according to local conditions of manufacture process.
5. DANGEROUS MATERIALS CONTAINERIZING, PROTECT AND TRANSPORTATION.
Another important problem is the crux of long term hazardous, radioactive and nuclear waste disposal lies in the fact that it remains hazardous for so long: some wastes have half-lives of tens of thousands years. It has to be taken in account substantial geologic changes, such as earthquakes or other natural phenomena. Also, over time, the material employed to encapsulate waste is susceptible to corrosion which could lead to waste release into the environment. Some leakage is inevitable and thus, places of the repository in geologic conditions likely to isolate it and prevent its escape into the greater environment over the course of its hazardous life. Responsible planners and scientists, aware of this, have developed computer models to predict the Earth’s evolution, as it makes possible now. Determining which type of rock and based vessels (capsules) would best isolate high-level nuclear and radioactive waste have been the focus of many researches over the past fifty years. The American federal government extended its research efforts to look at other rock types, such as basalt which exhibits potential to isolate waste over long periods of time. With the advance of technology, scientists have now begun to evaluate how modified natural materials or completely man-made ones could be utilized to contain high level waste within a repository or transporting. Our group patented the various methods of dangerous materials containerizing in shield, protect and transport capsules, vessels etc., made completely from basalt casting and basalt fiber based materials. These enclosed containers are of different shapes, composites, layers and thicknesses which are determined by the degree of hazardous, radioactive and nuclear waste protection. Advanced basalt technologies employed in order to give the best answer to the followings:
1. Radiation protection.
2. Long term no degradable products.
3. Elastic outer shell to protect the inner layers from physical damages and to allow safe transporting.
As natural material basalt rock has proven abilities to reduce or block radiation leaks and has a long durability with about 0 degradation assets.
6. NEW FIELDS OF BASALT ROCK PROCESSED PRODUCTS USE.
Basalt rock compositions conclude main minerals occurred in nature of many space objects and planets. Modeling of basalt processing technology and its products further using under known space or planets conditions - is the perspective way of the space familiarization. Besides, as it was found, the furnace melting and than obtaining designed shape, crushed basalt rock at the same time proceeds recrystallization. It gives to basalt casting products extreme hardness, abrasion and chemical resistance, unlimited resistance to moisture, high compressive strength and resistance to virtually all acids and alkalis and is completely corrosion free. Together with basalt continuous and staple fibers applications, basalt casting applications have to be multipurpose based material for different milieu conditions, including space conditions. The one of the options for scaling up Terrestrial experience with casting basalt as an industrial material - is to employ it in larger castings for structural construction under another planets milieu conditions. Using concrete and basalt continuous fibers based reinforcement rods as a tensile material to compress the more brittle basaltic casting will transform the combined structural element from a brittle into a ductile material, for purposes of structural design and risk evaluation in the space.
The humanity is standing nowadays at the very beginning of rush wide nature rock materials development and basalt igneous rock is one of the most perspective of them. There are very optimistic prognoses and prerequisites for further development of this direction of progress.
But nowadays concerning to basalt fibers and its based applications this progress is seriously broken by fiber glass manufactures competitions efforts. Besides, there are some additional reasons and main of them:
- Lack of professional effort for original technology designing and stabilization of nature basalt rock processing into fiber and applications. Practically the based use technology is accommodated many years ago glass fiber processing technology.
- The widely employed for bushing plates Platinum-Rhodium alloy is not only technological problematic for continuous fibers drawing from basalt natural rock, but become more expensive last years: Rhodium’s price grew by an order in comparison to Platinum.
That’s why the summary world outlet of basalt continuous fibers constitutes only about 6% of the glass fibers outlet. It calls for extremely changes.
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