HIGH REFRACTIVE INDEX GLASS PRODUCTION USING LOCAL RAW MATERIALS

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Author

Presented To

Department of Environmental Design

ABSTRACT
Glasses of relatively high refractive index were produced using barite from Azara in Nasarawa State and sand from Kenyi in Kachia Local Government of Kaduna State. Prior to the glass production, preliminary chemical analysis of the barite and sand were carried for moisture content, loss on ignition and elemental composition by the use of Atomic Absorption Spectrophotometer (AAS) and Flame Photometer. The oxide value of each element was calculated and the following percentage compositions were obtained using l.OOOg of each sample for the determination. The average of three determinations for each element in both barite samples are shown below: Sand Sample: Moisture content = 0.02, Loss on ignition = 0.06, Na20 = 0.121, K20 = 0.947, Si02 = 98.39, CaO = 0.056, A1203 = 0.180, Fe203 = 0.029 MgO = 0.008 and R203 = 0.150. Baryte Sample A: Moisture content = 0.02, loss on ignition = 0.06, Na20 = 0.025, K20 = 0.015. Baryte Sample B: Moisture content = 0.026, loss on ignition = 0.044, CaO = 0.006, MgO = 0.024, Na20 = 0.028, K20 = 0.001, Si02 = 18.12, BaO = 65.02, Fe203 = 0.029, A1203 = 16.62. Three batches were formulated considering the oxide composition of the sand and the barite sample A due to its high BaO and low Si02 content. B203 and ZnO were introduced as additional fluxing and fining agents in the case of batch II, and only ZnO in batch III. The batches were test melted at a temperature of 1,175°C in an electric furnace of heating capacity 1,200°C. Batches II and III melted but batch I sintered. Similarly the batches were also test melted by gas firing at 1,350°C. All the batches melted giving a reddish brown paste due to contaminants. The three properties tested were refractive index, density and thermal endurance. Refractive index and density were determined by floatation method. The following results were obtained. Based on the above results, the barite is good enough for optical glass production.