Project Abstract

<p> </p><p>Glass ceramics, a new family of polycrystalline materials produced by the controlled<br>crystallization of glass has many uses cutting across all spheres of life from domestic appliances<br>through medical devices to space exploration. The production process, just like that of other<br>pyrotechnic products, takes a high toll on energy demand as a high temperature process. The best<br>example can be drawn from the US economy where the annual energy bill for the glass industry as<br>a multibillion-dollar industry is put at more than 1.3 billion USD.<br>In the present study, an attempt is made to find alternative route for ceramic glass production in<br>the Nigeria that is cost effective in terms of energy input. In the process, a novel route outside the<br>6<br>two usual routes employed in glass ceramic production was adopted in fabricating a product<br>which when subjected to some physical tests showed every attribute of glass ceramics. Although<br>the process, which involved the sintering crystallization of glass and crystalline composites, has<br>no preference to any particular glass composition or crystalline material, a low melting glass<br>composition was used in the experiment to situate the process within the many limitations of the<br>experiment. In this case an ophthalmic glass composition was selected, partially melted at<br>1200oC, fritted and remixed with a fresh batch and sintered at 1000oC. The percentage water<br>absorption, porosity bulk density and specific gravity were evaluated using by the Archimedes’<br>Principle (ASTM C373). The evaluation of these properties has a direct bearing to the ultimate<br>characteristics of the glass-ceramic product.<br>The values obtained were 0.176 % for water absorption, 0.268% for porosity, 1.528 for specific<br>gravity and 1.53gcm-3 for density. The density is indicative of a lightweight material relative to<br>the properties of the derivative materials. The XRD analysis shows the main crystalline phase in<br>the material to be cristobalite and nephline. Optical microscopy obtained confirmed the presence<br>of crystalline phases in a glassy matrix, which is conclusive of the fact that the product is indeed<br>glass ceramic.<br>With further improvement the product of the experiment is a candidate for application as an<br>electronic spacer as a lightweight material. However if substitute can be found for the Pb content,<br>which is considered a toxic substance, its future use will extend to utility objects.</p><p>&nbsp;</p> <br><p></p>

Project Overview

<p> </p><p>1.1 BACKGROUND<br>18<br>Glass ceramics, a family of polycrystalline materials prepared by the controlled crystallization of<br>glasses, constitute an essential part of modern living. From their simplest use as cookware,<br>through critical but still familiar uses in dental restoration to the even more critical use as missile<br>radomes, they are yet to find complete replacements in the face of stiff competition from synthetic<br>products such as plastics and other lightweight materials, in a world increasingly moving away<br>from reliance on naturally sourced materials. The several advantages offered by glass over other<br>materials, which has served to reinforce its competitiveness over a long period of use spanning<br>several centuries, include exceptional chemical durability, multi-faceted optical properties and<br>complete recycling capability in an era of heightened environmental consciousness.<br>Although glass ceramics, like conventional ceramics, contain a substantial refractory crystalline<br>component, the difference between the two classes of materials stems from the fact that a glass<br>ceramic starts out as a pure glass in which finely dispersed crystalline structures are made to<br>“grow” within the glass matrix by a process of controlled crystallization. The presence of the so<br>called ‘home groomed’ microstructure, in addition to enhancing the strength of the glass,<br>increases its flexibility, with the consequential minimal presence of the severe microcracks that<br>act as stress concentrators in the event of brittle failure but also simultaneously preventing the<br>deterioration of less severe flaws thus acting as crack inhibitors.<br>Due to the fact that the size and distribution of the crystalline substructure within the glass can be<br>accurately controlled, the resulting crystals confer on the end product various characteristics such<br>as lack of porosity and extremely low coefficient of thermal expansion which can all be precisely<br>controlled to suit specific applications but often the crystal chemistry is much different from that<br>of the original or residual glass.<br>19<br>That Science is at odds in finding complete substitutes to glass products generally,<br>notwithstanding the long history of use, spanning several millennia, is a factor attributable to<br>what Rao (1981) describes as the twin freedom enjoyed by materials in the glassy state vis-à-vis<br>“freedom from the restraints of periodicity and freedom from the requirements of stoichiometry”.<br>This peculiar nature of glassy materials has generated a lot of research interest in Glass Science<br>especially since the early 60s referred to, in the annals of history, as “the Golden Age of Glass<br>Science” (Doremus, 1983). Professor N. F. Molt earned the Nobel Prize “for having done so<br>much to transfer glass science from the archives to the forefront of solid state” (Rao, 1981). This<br>acknowledgement serves as a pointer to the flurry of activities in present day glass research.<br>As a non-stoichiometric substance, a single glass composition can accommodate as many as 60<br>elements at once. Michael Faraday, long ago, in recognition of the special attributes of glass,<br>preferred to call it a “solution’ rather than a compound (Doremus, 1983). This position, largely,<br>holds sway to the present day. New glass forming systems are being developed everyday. Thus<br>the same glass, which can be made stronger than steel as symbolized by fibreglasses valued as<br>structural reinforcers, can by way of alteration of composition be made to dissolve in water as<br>typified by sodium silicate composition (water glass). Again as illustrated by the Li2O-Al2O-SiO2<br>family of compositions, by way of modification of composition, glass can be made to have<br>negative or zero expansion coefficients within some ranges of temperature.<br>In spite of the usefulness of glass ceramics as a modern material, there is no form of productive<br>activity in Nigeria relating to glass ceramics or record of any research effort directed at its<br>development by the dozen or so research institutes in the country that engage in industry related<br>activities as an extension of their mandates. It is therefore reasonable to state that any research<br>20<br>directed at an important branch of glass usage such as glass ceramics, especially in a country with<br>huge potentials for industrial growth as Nigeria, cannot be in any way exhaustive, at least not at<br>this stage of her development.<br>An attempt will be made in this study to explore the possibility of production of glass ceramics<br>from local raw materials with particular reference to low energy input varieties. The energy<br>dimension is chosen as the focus of study, partly as a response to the unsteady global energy<br>situation and also because Nigeria’s precarious energy infrastructure calls for steps, in her path of<br>industrial take off, with inbuilt guarantee of sustainability.<br>1.2 DEFINITION OF GLASS<br>The versatility of glass has infused some dynamism into the term “glass” to the extent that<br>numerous definitions have been proposed for it over its many years of history. The one most<br>frequently quoted definition of glass proposed in 1945 by the American Society for Testing and<br>Materials (ASTM) refers to it as an inorganic product of fusion which has cooled to rigid<br>condition without crystallizing (Rawson, 1980). Although this “traditional” definition<br>accommodates the majority of glasses, which are usually inorganic with one known mode of<br>production materials, i.e. cooling to rigidity from the melt, it is considered too restrictive in the<br>sense that it cannot account for organic polymers and other materials with glassy structures made<br>by methods other than cooling from the melt. For instance amorphous thin glassy coatings made<br>by sputtering directly from the vapour state have every claim to being called glasses just as<br>sodium silicate glass can be made by two methods, one by cooling from the melt and the other by<br>preparing an aqueous solution of sodium silicate and evaporating to dryness.<br>These changes in the material world prompted a committee of the US National Research Council<br>21<br>to come up a broader definition in 1976 without recourse to mode of production or constituent<br>materials. The broader outlook refers to glass as “an x-ray amorphous solid, which exhibits the<br>glass transition, that being defined as that sudden change in the derivative thermodynamic<br>properties from crystal-like to liquid-like values”. Its rigidity must approach that of an ideal<br>elastic solid i.e. it should be at least 1013.7 Pa s on the viscosity scale and when examined by x-ray<br>diffraction it should have the structural attribute of liquids, which is a short range order. Critics of<br>the newer definition rest their case on the fact that only a few materials referred to as “borderline<br>cases” do not fit into the ASTM definition which they regard as the classical definition of glass.<br>1.3 THE PROBLEM OF THIS STUDY<br>According to Hoover (1964), an important consideration in the location of industries is the<br>disposition of a country’s mineral and energy resources. Nigeria on this basis has all it takes to<br>become an industrial nation. Available statistics based on studies carried out by the relevant<br>agency, the Raw Materials Research and Development Council (RMRDC), shows that the raw<br>materials for glass making exist in great abundance in the country (RMRDC, 1997). The<br>existence of commercially exploitable deposits hosted by rock of the basement complex around<br>Egbe, Udiaraku, Okene and Lokoja has been reported (RMDC, 2003). A number of other deposits<br>located in Kenyi/Madakiya in Kaduna State and Gworza in Borno State have been covered in<br>isolated studies with sketchy details regarding their glass forming ability (Malgwi, 1989; Jekada,<br>1997). These findings are in agreement with the assertion of Pincus (1967) to the effect that glass<br>raw materials are among the cheapest and most abundant of all industrial raw materials the world<br>over.<br>While the raw material need of the glass industry can be said to be met with some degree of<br>22<br>certainty, the same assertion cannot be made for the energy requirement not withstanding the fact<br>that Nigeria is the world’s sixth largest producer of fossil fuels. The country’s weak energy<br>infrastructure remains the stumbling block to the maximum utilization of the country vast oil and<br>gas resources. Apart from the fact that Nigeria is a net importer of refined petroleum products,<br>long queue of vehicles are not uncommon sights at gasoline stations due to poor storage facilities.<br>The matter is made worse by the fact that regions of petroleum resources have remained the<br>hotbed of global sociopolitical instability against the mounting energy cost of global output of<br>glass products the use of fossil fuels. Electricity power generation required for glass melting is<br>also in short supply in the country.<br>According to the US Department of Energy (2000), the total energy bill of the glass industry is<br>more than $1.3 billion. Representing an important segment of the country’s economy the industry<br>engages more than 150, 000 people in skilled jobs and generating more than 21 million tonnes of<br>consumer products each year at an estimated value of $22 billion.<br>The approach to be adopted in tackling the energy issue in glass production as the problem of this<br>study is to explore ways of producing glass ceramics with low energy input.<br>1.3 RESEARCH QUESTIONS<br>23<br>I. What would be the economic implications of such an approach?<br>II. How would it fit into the Nigerian situation of the weak energy infrastructure of the country?<br>III. How would it contribute to solving the global energy crises?<br>1.4 OBJECTIVES OF THE STUDY<br>The precise objectives are to:<br>I. Identify a source of raw material suitable for glass ceramic production in Nigeria.<br>II. Carry out chemical analysis on samples of the raw material to ascertain the chemical<br>constituents.<br>III. Identify the appropriate glass formula with the least energy input.<br>IV. Explore the most appropriate route for conversion of the raw material into glass ceramic with<br>respect to the energy demand of the product.<br>V. Test-melting the batch.<br>VI. Characterize the product of the experiment as the basis for further development.<br>1.5 JUSTIFICATION.<br>Glass ceramics fall under the category of glasses valued for high technology and specialty<br>applications, in addition to their common uses in domestic appliances. Specialty glasses differ<br>from traditional glasses in the contents of specific additives, or may be of entirely different<br>compositions. Novel processes have also been exploited in developing many of these<br>compositions.<br>According to a report by Business Communications Company, Incorporated (BCC),<br>(<a target="_blank" rel="nofollow" href="http://www.bccresearch.com">www.bccresearch.com</a>), the North American market for advanced and specialty glasses reached<br>$2.3 billion in 2002 and with a projected growth rate of 7.8% would reach $3.3 billion by 2007.<br>24<br>The global market was estimated at $8.5 billion in 2002, and at an expected growth rate of 8.3%<br>would reach $12.6 billion by 2007.<br>The largest market for advanced and specialty glasses according to the report are concentrated in<br>electronics displays, which include liquid crystal displays (LCDs) and gas and vacuum discharge<br>displays. This market in North America was worth approximately $1.3 billion in 2002 and was<br>expected to have reached almost $2 billion by the year 2007. The global market was expected to<br>grow from $4.8 billion in 2002 to $7.8 billion in 2007.<br>Over 60% of the total market according to the survey is for electronic applications. The combined<br>electronics segment market for North America was put at $1.4 billion in 2002 and was expected to<br>increase to $2.2 billion by 2007. The medical/dental market is expected to witness a relatively<br>strong growth, as demand for dental aesthetics increases and new products find their ways to the<br>market. The applications that would fuel this growth include glass-ceramic crowns and DNA<br>microanalysis. On the whole, the demand for advanced glasses is expected to maintain the growth<br>level as new applications in these various segments come on the market.<br>In the aspect of global competition, North America is in the lead in several areas, since the US<br>glass company, Corning Inc. has the largest market share in these areas. Japan follows closely<br>behind in the two market segments, for the reason that a number of Japanese companies are also<br>major producers of specialty glasses. In the same manner the German multinational, Schott Glas<br>AG, makes Europe another strong competitor, as a major player in most EU countries.<br>25<br>Glass ceramics manufacture holds great potential for employment generation in a country like<br>Nigeria as it is becoming increasingly evident that no country can afford to insulate itself from the<br>effects of the global marketplace. Glass demand, as stated by Limbs (2002), remains strong and<br>growing, exceeding worldwide gross domestic product, and will continue to grow with the focus<br>of growth shifting to Asia, especially China as her rising economic fortune is raising a new crop<br>of consumer population. For instance, the Chinese share of global demand for glass, which<br>reached 4 billion square meters in 2003, was put at 30 percent while the overall annual increase in<br>global demand for glass products between 1990 to 2003 was put at 4 percent per year, is 1.2<br>percent higher than the worldwide average GDP of 2.8 percent a year, within that same period.<br>Judging from the experience of India and China, Nigeria’s huge population translates into a<br>considerable consumer market for any local industry that specializes in glass ceramics products.<br>This market potential is further boosted by the realizable dream of a common market within the<br>West African sub region under the aegis of West African Economic Community (ECOWAS).<br>According to a report in the UNIDO Quarterly, Africa has a high potential for investment in<br>untapped human and natural resources (Punch, February 9, 2000). The report states that many<br>investors are discovering that Africa provides high returns from carefully selected investments<br>even in conflict-infested regions. The same report adds that Africa enjoys many advantages in the<br>global market place and this includes the benefits of locating projects on the continent to supply<br>the U. S., Europe and Japan. Furthermore, a joint poll by the United Nations Conference on Trade<br>and Development (UNCTAD) and the International Chamber of Commerce (IICC) released in<br>Bangkok in February 2000 placed Nigeria top among four countries on the continent that would<br>likely benefit from increased transnational activities in the next five years. (Punch, February 18,<br>2000).<br>26<br>The glass ceramics industry is certain to benefit from the attendant capital inflow to Africa by<br>virtue of the groundwork being laid by this study. It is therefore timely to embark on a study that<br>will develop the basis for glass ceramics manufacture in Nigeria and the present study is set to<br>establish that framework.<br>1.6 SIGNIFICANCE OF THE STUDY<br>The significance of this study hinges on the attempt to improve the economic situation in Nigeria<br>via the production of low energy input glass ceramics. Although energy costs in the glass industry<br>according to the US based Manufacturing Energy Consumption Survey (MECS), do not vary<br>substantially across glass sectors as a cost item, it does account for 6-12% of total production costs<br>(Dohn, 2000). The same survey revealed that in the United States, the glass industry consumed 206<br>trillion B.T.U. of energy worth about $1.4 billion on energy in 1998. About 8% of the energy<br>supply came from fossil fuels. Apart from its being physically limited, the use of fossil fuels<br>constitutes a threat to our health and environment. In addition to its contribution to global<br>warming, burning fossil fuel releases chemicals and particulates that can cause cancer, brain and<br>nerve damage, birth defects, lung injury, and respiratory problems to mention a few.<br>Those that might question the relevance of a research directed at energy reduction at this stage in<br>our national life, given that Nigeria, a major exporter (sixth largest in the world) will for a long<br>time to come have enough petroleum oil to satisfy local consumption, must take a cue from the<br>transformations that turned the United States into a modern industrial nation. In 1950, the U.S. was<br>producing half the world’s oil but fifty years on, the country no longer produce half her own oil<br>need. Moreover, the world’s burgeoning population has other uses for petroleum products that<br>extend to fertilizer such that it is feared that demands will outstrip production unless some<br>27<br>alternative is found for petroleum fuels.<br>1.7.0 LIMITATIONS OF THE STUDY<br>This form of research should ideally attract funding from government or the business community.<br>The financial constraint has undoubtedly placed a heavy limitation on the outcome of this highly<br>practical work.<br>Another limitation placed on this study is the vast size of the country and the lack of updated<br>geological information regarding the country’s mineral resources. The only mineral map<br>currently in use in the country dates as far back as the early 60s. This weak database of the<br>country’s mineral resources is most likely to affect the outcome of this and related studies.<br>Another obvious impediment in the way of a successful completion of the work is the level of<br>infrastructure needed to sustain the work. The researcher is unaware of any assembly of<br>laboratory facility needed to carry this work to a successful end. This situation calls for<br>improvisations that may have compromised the standard of the outcome.<br>1.8 SCOPE<br>Within the scope of this study, local raw materials has a restricted meaning limited to quartz,<br>quartzite or glass sand because glass ceramics as other raw materials used in the experiment as a<br>control measure are in analytical grades. More so because glass ceramics as value added products<br>require the use of analytical grades of other raw materials/chemicals as supplements to silica as<br>the main raw material.<br>The laboratory aspect of the present work was limited in scope to the sequence of procedures<br>followed in converting the raw batch to a molten glass and annealing it to the required<br>28<br>specification in physical characteristics. The work stops at any form of operation carried out on<br>the products of the experiment to transform them into testable samples but not beyond that.<br>29</p><p>&nbsp;</p> <br><p></p>