Papers by Keyword: Materials Characterization

Abstract: Drilling fluid rheology is very important aspect for judging its suitability for the well-drilling operation. This study looked at how fly ash affected the rheological characteristics of drilling fluids that were based on water. Six different drilling fluid samples (combination of water-bentonite-fly ash) have been prepared: 4 samples without engine oil additives and 2 samples with engine oil additive. The shear stress between fluid layers vs. shear rate curves and the viscosity of fluid vs. shear rate curves have been plotted for the controlled shear rate application by rotational rheometer MCR 102 (Make: Anton-Paar Inc.). Curve fitting have been done successfully with the Herschel-Bulkley rheology model and various parameters have been obtained. It is found that addition of fly ash as well as additive oil imparts favorable rheology to water based drilling fluids.

Abstract: In the year 2016 alone, more than 1.35 billion smartphones were manufactured globally. These smartphones contain up to 60 different chemical elements and the summarized metal weight of the 2016 production may have well exceeded 50,000 metric tons. At present, most elements contained in this very complex “mixture” represented by a smartphone have recycling rates well below 50%, and the recycling rates of rare earths, indium, tantalum or gallium are even below 1%. The major challenge of mobile phone recycling is the complex composition of the devices made of many individual components – and the lack of transparent information as to the composition of these components. This is aggravated by the fact that many elements occur in traces only and / or are located in highly complex material composites. To enable more effective recycling of mobile phones, it is thus imperative to characterize the constituent components, the presence of elements in it, as well as their behavior during comminution. In a pilot study, a Nokia mobile phone Model 5228 Type RM-625, crushed with a granulator UG300, was examined by Mineral Liberation Analysis. The analysis of three particle size fractions of the comminuted material was carried out in an automated measurement mode with a grid of energy-dispersive X-ray spectra. A total of 130 different phases were detected during this analysis. More than 100 of these phases occur at levels <1% by weight. This strongly illustrates the very complex composition of smartphones. A comparison of the modal content of the three particle size fractions showed good liberation of certain components and an enrichment of some components in specific fractions. These observations reveal the potential to successfully separate different technical components from one another with the goal to increase the resource efficiency of the recycling process.

Abstract: Niobium doped 8YSZ ceramics were prepared by sol-gel synthesis. The mixtures were calcined, compacted into cylindrical pellets, sintered and evaluated for phase stability, microstructure and electrical conductivity. Tetragonal, monoclinic and cubic phases were present, however the trend for phase seems to be erratic for the studied samples. The increasing Nb content appears to improve the morphology by increasing densification. It is noted that increasing Nb content also increases oxide conductivity. The best conductivity belongs to 1.0% mol Nb, with a value of 8.013 x 10^-6 (Ωcm)^-1. Increasing Nb content beyond 1.0% mol has detrimental effect on morphology and ionic conductivity.

Abstract: 8 mol % Yttria Stabillize Zirconia (8YSZ) generally used as solid electrolyte in solid oxide fuel cell (SOFC). In this study, niobium (0, 1, 2, 3 mol%) doped 8YSZ ceramics were prepared by the conventional solid state process. The mixtures of powders were calcined, compacted into cylinderical pellets, and sintered at 1500°C for 2 hours in air atmosphere. All samples were evaluated for phase stability, microstructure and electrical conductivity. Tetragonal phase was detected as the major phase for all studied samples. With increasing in Nb addition, tetragonal and cubic phase started to transform to monoclinic phase. The introduction of Nb₂O₅ (more than 0.5 mol %) was not only useful to enhance the densification, but also helpful to enhanced the ionic conductivity of 8YSZ samples. SEM micrographs of niobium-doped zirconia powders indicated the coalesce of fine particles with sizes varying from 10 μm to 1 μm, in response to increasing in Nb content.

Abstract: The article describes the use of ultrasonic testing methods for examining slabs made from cement based materials. For the detection of cracks, in full-scale slabs before and after the explosion, ultrasonic pulse method was used. Data obtained before the explosion confirm the high quality of the cement based material. Another set of data taken after the explosion shows the scale of cracks in the slabs. The article compares material characteristics of the unreinforced concrete, steel fibre concrete and high performance fibre reinforced concrete on the basis of materials tested by using the passage ultrasonic method after the explosion.

Abstract: For the full characterization of the hot working behaviour of a given material a large number of laboratory experiments have to be performed. The experiments themselves are time consuming and the required specimen material can be quite expensive. With the increasing versatility of the testing machines, like dilatometry with easily variable temperatures, overthinking the classical approaches for materials characterization becomes expedient.In this paper a new technique for the reduction of the experimental effort is presented at the example of a 25MoCrS4 case hardening steel. To analyse the potential for the reduction of the experimental effort the classical approach of a full experimental test matrix is chosen. Here 55 flow curves with temperatures between 700 and 1200°C and strain rates from 0.01 to 100/s are experimentally determined. Then a semi-empirical model for strain hardening and dynamic recrystallization is fitted using an automated routine for parameter determination, taking all available flow curves into account. Subsequently, the number of flow curves used to fit the model parameters is gradually reduced. The model accuracy obtained with the reduced experimental data is compared to the initial fit. The natural decrease in accuracy with the use of less data compared to the gain due to the reduction of experimental effort is analysed. In addition optimal distribution of the sampling points in the experimental matrix for a reduced number of experiments is discussed. It is shown that less than a quarter of the full matrix is sufficient to reach accuracies comparable to using the full matrix. Using the vertices and symmetrical distribution of the data within the full experimental matrix allows a drastic reduction of experimental effort while maintaining the initial accuracy. The results suggest that it might be possible to reduce the costs and effort for material characterization by 50-80%.

Abstract: The life of the components used under slurry abrasion conditions is governed by the process variables, properties of the abrasive materials in the slurry and the material properties. Slurry wear, abrasion occurs in Extruders, pumps and pipe transport slurry of minerals and ores in mineral processing industries. In the present research, the effect of operating variables such as abrasive particle size and shape, slurry concentration and normal load on the abrasive slurry wear behavior of the weld deposit martensitic steel surface produced by the Manual Metal Arc Welding Hard facing process was conceded out. The testing was conceded out using the slurry abrasion test rig. The silica sand particles were used as the abrasive medium. The qualitative nature of wear pattern and morphology of the worn out surface was examined under scanning electron microscope (SEM). These features were correlated with operating parameters.