No abstract

A low-grade gold ore from Ilesha-Itagunmodi, south western Nigeria was panned, dried and ball-milled before sieving into fractions. The morphological, mineralogical and chemical composition was studied by optical microscopy (Reflected and Transmission), X-ray diffraction (XRD) and Energy Dispersive X-ray fluorescence (XRF), respectively. The sieved fractions were subjected to chemical analysis (AAS). The +106 μm sieve had the highest concentration of the mineral and was then selected for the upgrade through froth flotation using standard reagents. In this paper a report on a 2 k factorial experiment that provides an understanding of the impact of operational variables on the quantity of gold mineral obtained from the ore during froth flotation is presented. Analysis results showed that Ilesha-Itagunmodi gold ore is non-refractory with fine grain particles, amenable to froth flotation and contained about 20 other associated minerals, gold had a concentration of about 0.0024%. A combination of P-Xanthate and amine glycol collectors at a pH of 9.2 only produced a considerable increase in gold yield. This translated to about 87.13% increase in recovery of gold from the ore. Analysis of variance (ANOVA) was carried out and the model equation obtained was subsequently optimised to obtain a model equation that could be used in predicting the recoverable quantity of gold, indicating that F 11,1-values for Collector concentration, Frother concentration, pH and Conditioning time were 156.86, 6.96, 43.81, and 56.77 respectively. A model with an F value of 88.41 was obtained which indicated that the model was significant. The model equation obtained was subsequently optimised to be able to predict the recoverable quantity of gold. A "Pred R-Squared" value of 0.9365 (93.65%) was also obtained and is in reasonable agreement with the "Adj R-Squared" value of 0.9534 (95.34%). It was established that Ilesha placer gold ore is amenable to froth flotation using standard reagents.

The latest technological requirement demands a huge (but sometimes challenging) variety of properties which perhaps are impossible in monolithic or traditional materials. This has innovated the introduction of reinforcement in traditional materials such that the resulting composite material would be an advantage for the collaborating influence of the combined matrix and the reinforcement. Single-phase ceramics have been limited in application due to low densification and poor properties. Hence, ceramic matrix composite is the family of materials that have undertaken quick innovation in past years because of its auspicious properties for structural and functional usage. This concept has made the incorporation of sintering additives into the monolithic form of ZrO 2 of high importance because of the poor densification and fracture toughness of undoped ZrO 2 . The addition of sintering additives provides good functionality to the improvement of ceramic materials. This paper painstakingly reviews the effects of diverse sintering additives such as carbides, borides, nitrides on the microstructure, densification, and mechanical properties of ZrO 2 ceramic matrix using different sintering techniques and it lastly stated a futuristic approach to the enhancement and characterisation needed for ZrO 2 ceramic matrix composites.

No abstract

Sintering temperature is essential towards attaining desired densification and formation of phases which in turn influences the microstructure and properties of a material. In this study, the densification and microhardness behaviour of Ni-Cr-Al alloy prepared by spark plasma sintering (SPS) at different sintering temperatures were investigated. After sintering operation, the density, hardness, phase analysis, and microstructural evolution were investigated using the Archimede’s principle, hardness tester, X-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The nickel based alloy was sintered at temperatures of 600, 750, 950 and 1100 °C. The results indicated that the densification, microstructure, and hardness values were influenced by changes in the sintering temperature. The relative density increased from 73.89 % at 600 °C to 99.89 % at 1100 °C, while the hardness value was enhanced from 131.9 ± 2.8 HV to 404 ± 1.2 HV respectively.