Model for predicting mix formulation in the production of insulating refractory bricks using Nigerian fire-clays and coconut shell

No Abstract

The effect of kaolin and silica variation on the properties of porcelain insulators

Clay, Al2O3, feldspar and silica have been used to produce shackle-type porcelain insulators using slip casting method. The amounts of silica and kaolin were varied from 10 to 30 wt. % while keeping the amounts of other constituents constant. The samples were bisque fired at 900 °C, sintered at 1200 °C for 1 hour glazed using borax fritz. The results showed that as the amount of kaolin decreased, apparent porosity and water absorption increased from 9-19 % and 7-12 % respectively. The bulk density and linear shrinkage decreased from 1.94-1.12 g/cm3 and from 12.5 % - 7 % respectively. Breakdown voltages ranging from 23 kV to 35 kV were obtained while the highest insulation resistance value of 50GΩ was for the sample with 55 % clay, 15 % silica and 25 % feldspar and 5 % Al2O3. The results indicate that moderate variations in kaolin and silica content can be used to produce porcelain insulators for commercial applications. Keywords: Electrical porcelain, Shackle insulator, Kaolin, Feldspar, Processing

The Effects of Sintering Temperature and Agro Wastes on the Properties of Insulation Bricks

In this research, kaolin, ball clay, sawdust and rice husk were used to produce insulation bricks through the solid state synthesis method. Two temperatures, 1100oC and 1200oC were used to sinter the green samples. X-ray fluorescence, scanning electron microscopy, compressive strength tests etc. were used to analyse the properties of the produced bricks. Chemical composition analysis on the starting raw materials showed that SiO2 and Al2O3 were the major constituents while Fe2O3, Na2O, K2O and TiO2 were the minor constituents. As the amounts of kaolin used in preparing the samples decrease, the bulk density, modulus of rupture and cold crushing strength of the bricks decreases while the water absorption capacity, linear shrinkage increases. The thermal analysis showed that on heating the samples, the reactions were mainly exothermic with between 8 to 10 mW/mg of heat released. The morphology of the samples showed that the pores began to collapse when the amount of kaolin present is below 70 wt. %. Sintering the samples at 1100oC and 1200oC led to slightly different values in the results and is therefore very significant. Keywords: Insulation bricks, Kaolin, sawdust, rice husk, temperature effect

Beneficiation of Azara Barite ore using a combination of jigging, froth flotation and leaching

In this research, Jigging, Froth Flotation and leaching have been used to beneficiate barite ore from Azara, Nasarawa State Nigeria. Chemical analysis on the ore indicates that it contains 53.09% of Ba and 11.52% S with a specific gravity value of 3.207±0.03. After the jigging operation, the specific gravity values of the underflow and overflow are 3.77±0.029 and 2.77±0.058 respectively while the Ba and S increased to 78.61% and 15.87% respectively. After the froth-flotation, the specific gravity values obtained are 3.95, 4.1 and 4.05 corresponding to pH values of 5, 7 and 9 respectively. Frothed barite with pH of 7 was leached with 0.2M HCl and a mixture of 0.2M HCl and HOCl. After leaching, the specific gravity values are 4.38±0.03 and 4.27±0.02 for HCl and HCl+HOCl respectively. The X-ray diffraction patterns show that highly crystalline peaks are obtained after froth flotation while more phases are added with leaching.Keywords: Barite; Jigging; Froth Flotation; Leaching; Specific gravit

Characterization of train brake-blocks composite reinforced with aluminum-dross

Brake blocks are usually made from asbestos, metals and ceramics. It has been realised that asbestos discharges dangerous gases which can be harmful. This problem necessitated the search for human-friendly materials. Therefore, this paper studies the production and characterization of train brake blocks produced from clay reinforced with aluminum dross. This was done by producing samples of composite using clay from a deposit at Osiele and aluminum dross from Tower Rolling Mill Otta, both in Ogun state. The percentage composition of aluminum dross was varied from 0% to 25% to produce brake samples. Their wear rate, tensile strength, compressive strength, hardness, thermal conductivity and microstructure were analysed. The results from this project such as Ultimate tensile strength (UTS) of 7.4Mpa, Impact energy 6.92J, Hardness 28.8 HV, wear rate 0.0071g/sec and thermal conductivity of 0.01075 indicate that, with 5% aluminium dross it is possible to develop brake block that exhibits property recommended by Rail Industry Safety and Standard Board (RISSB). Keywords: Train, Brake blocks, Clay composite, Aluminum Dross, Mechanical properties