Development of Low-Temperature Glass Ceramic from Local Raw Materials.
ABSTRACT
Glass-ceramics, a new family of polycrystalline materials produced by the controlled crystallization of glass has many uses cutting across all spheres of life from domestic appliances through medical devices to space exploration. The production process, just like that of other pyrotechnic products, takes a high toll on energy demand as a high-temperature process.
In the present study, an attempt is made to find an alternative route for ceramic glass production in Nigeria that is cost-effective in terms of energy input.
In the process, a novel route outside the 6 two usual routes employed in glass-ceramic production was adopted in fabricating a product which when subjected to some physical tests showed every attribute of glass-ceramics.
Although the process, which involved the sintering crystallization of glass and crystalline composites, has no preference to any particular glass composition or crystalline material, a low melting glass composition was used in the experiment to situate the process within the many limitations of the experiment.
In this case, an ophthalmic glass composition was selected, partially melted at 1200oC, fritted and remixed with a fresh batch, and sintered at 1000oC.
TABLE OF CONTENTS
Cover page. ……. ……. …… ……. ……. `…… …… …… ….. i
Title page. ……. ……. …… ……. ……. ……. ……. …… ii
Declaration …… …… …… …… …… …… …… …… iii
Certification. ……. ……. …… ……. ……. ……. ……. ……. …… iv
Acknowledgment. ……. ……. ……. ……… …….. ……. ……. v
Abstract. ……. ……. …….. …….. …….. ………. …….. ……. vii
Content page. …… ……. ……. ……. ………. …….. …….. ix
List of Tables. …. …. …… …… …… …… …… ……. . xiii
List of Plates. …. …… …… ……. ……. ……. …… ……. …… xiv
List of Figures. ……. ……. ……. ……. ……. ……. …….. ……. xv
List of Appendices …… …… …… ……. …… ……. ……. xvi
Dedication …… …… …….. ……. …… …… ……. ……. . xvii
Definition of Special Terms …… …… ……. …… ……. …… xviii
CHAPTER ONE
1 INTRODUCTION 1
.1. Background of the study……………………………..……………. 1
.2. Definition of Glass…………………………………….…………… 3
.3. The problem of the Study…………………………………………..…… 5
.4. Research Questions …………………………………………….….. 5
.5. Objectives of the study……………………………………………… 6
.6. Justification………………………………………………….…….. 6
.7. Significance of the study…………………………………….…….. 9
.8. Limitation of the study…………………………………………….. 10
.9. Scope………………………………………………….…………… 10
CHAPTER TWO
4.5 LITERATURE REVIEW 12
2.1 Development of Glass Ceramic…………………………………………. 12
2.2 Glass Formation Versus Crystallization………………………………… 13
2.3 Devitrification………………………………………………………..…. 15
2.2.1 Solid/Solubility…………………………………………….…… 19
2.2.2 Nucleation and crystal growth……………………………….… 25
2.3 Glass-ceramics composition system…………………………………… .. 27
2.3.1 Glass-ceramic types and Nucleating agents……………………. 27
2.4 Glass and Glass-ceramic matrix composites……………………..…….. 34
2.5 Properties of Glass-ceramic materials………………………..………… 35
2.6 Applications of Glass-ceramics…………………………………….…… 37
2.6.1 Dental Applications……………………………………….…… 37
2.6.2 As Bearings…………………………………………………….. 37
2.6.3 Cookware………………………………………………………. 38
2.6.4 Heat exchangers………………………………………………… 39
2.6.5 Neutron absorbing materials…………………………………
2.6.6 As sealing and Bonding medium or thermosetting elements…… 39
2.6.7 Electrical Insulators…………………………………………..…. 40
2.7 Stages in the glass-ceramic process………………………………………………… 40
2.7.1 Raw materials selection and processing………………………… 40
2.7.2 Melting and forming……………………………………………. 43
2.7.3 Conversion into polycrystalline solid……………………….….. 44
2.8 Annealing……………………………………………………………….. 47
2.9 Established Routes for glass-ceramic production………………….….. … 50
2.10 Glass sand deposits in Nigeria…………………………………………… 51
CHAPTER THREE
3 METHODOLOGY 54
3.1 The silica source…………………………………………………. 54
3.2 Field sampling……………………………………………………. 54
3.3 Chemical Analysis………………………………………………… 54
3.4 Raw Material processing and particle characterization……………. 55
3.5 Choice of Glass composition………………………………………. 56
3.6 Batching and melting………………………………………………. 57
3.7 Product Characterization…………………………………………… 58
CHAPTER FOUR
4 RESULTS AND ANALYSIS 60
4.1. Chemical analysis…………………………………………….. 60
4.2. Choice of glass composition…………………………………. 61
4.3. Batching and melting………………………………………….. ……… 61
4.4. Produce characterization……………………………………………….. 62
4.4.1 Water absorption, porosity and specific gravity……………… 62
4.4.2 X-Ray analysis and optical microscopy……………………… 63
4.5 Cost Analysis………………………………………………………….. 68
CHAPTER FIVE
5. SUMMARY, CONCLUSION, AND RECOMMENDATIONS 69
5.1. Summary…………………………………………………….. 69
5.2. Conclusion…………………………………………………… 70
5.3. Recommendations…………………………………………..… 71
REFERENCES………………………………………………………….. 72
INTRODUCTION
Glass-ceramics, a family of polycrystalline materials prepared by the controlled crystallization of glasses, constitute an essential part of modern living. From their simplest use as cookware, through critical but still familiar uses in dental restoration to the even more critical use as missile radomes.
The several advantages offered by glass over other materials, which have served to reinforce its competitiveness over a long period of use spanning several centuries, include exceptional chemical durability, multi-faceted optical properties, and complete recycling capability in an era of heightened environmental consciousness.
Although glass ceramics, like conventional ceramics, contain a substantial refractory crystalline component, the difference between the two classes of materials stems from the fact that a glass-ceramic starts out as a pure glass in which finely dispersed crystalline structures are made to “grow” within the glass matrix by a process of controlled crystallization.
The presence of the so-called ‘home groomed’ microstructure, in addition to enhancing the strength of the glass, increases its flexibility,
with the consequential minimal presence of the severe micro-cracks that act as stress concentration in the event of brittle failure but also simultaneously preventing the deterioration of less severe flaws thus acting as crack inhibitors.
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StudentsandScholarship Team.
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