X-ray computed tomography: Practical evaluation of beam hardening in iron ore samples

Abstract

X-ray computed tomography is a non-destructive 3D analytical technique, which in recent years has gained more widespread applications to characterise the internal structure of materials in minerals processing and metallurgical studies. Successful application of the technique relies on effective X-ray penetration. Ore samples with high average specific gravities (e.g. iron ore, massive sulfide ores) inhibit X-Ray penetration causing beam hardening artefacts that reduce data quality and limit further analysis. This contribution presents a practical way to evaluate the degree of beam hardening using a case study iron ore sample. The method quantifies the degree of beam hardening that leads to a loss of sample information, through comparing the known pore surface area of an aluminium standard sample with that of an iron ore sample. This comparison is defined as a %Error. Porosity and sample mineralogy are confidently quantified when the %Error is less than 10%. Above 10%, there is inconsistent loss of sample information (porosity and relatively low dense sample mineralogy) and the results from the volumes cannot be trusted which indicates that smaller sample sizes need to be scanned. This practical method can be routinely applied in other applications and samples with density higher than iron ore.