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Effect of Calcined Colemanite Addition on the Rheological Behaviour of Porcelain Suspension

100%

Özdemir Y. , Akpınar S. , Abbak S. , Evcin A.

Acta Physica Polonica A

2017

tom 132

nr 3

825-829

A standard composition for hard porcelain production was prepared by mixing 50 wt% kaolin, 25 wt% potassium feldspar and 25 wt% quartz. Calcined colemanite powders were added to the porcelain formulation by replacing the potassium feldspar up to 5 wt% to explore its effect on the rheological behaviour of porcelain slip casting. A rheological study has been carried out in order to optimize the processing of the slip casting by using a rotational stress-controlled rheometer. The measurements were performed at constant temperature (25°C) using a parallel plate configuration. Sweep measurements were then conducted in the shear rates ranging from about 0.1-1000 s¯¹. The stability of the suspensions with ammonium polyacrylate (Darvan 821A) was determined in order to select the suitable dispersant amount. In order to achieve casting of acceptable characteristics on a plaster of Paris mould, the slurry should have the appropriate thixotropic or shear-thinning behaviours. Therefore, the same favourable thixotropic behaviour of slurries of different amount of calcined colemanite powders, the solid contents of the slurries have been optimised.

Characterization of espey colemanite and variation of its physical properties with temperature

88%

Celik A. G. , Cakal G. O.

tom Vol. 52, iss. 1

66--76

It is important to characterize boron containing minerals because of their uses in a wide range of applications. The purpose of this study is to characterize Espey colemanite by minerological, petrographical and thermal means and to investigate the variation of its physical properties with temperature (up to 600 °C). Colemanite, having a non-porous crystalline structure, was found to consist of 35.8% B2O3 and 30.5% SiO2. The thermal decomposition of colemanite occurred within the temperature range of 300–600 °C. It was found that calcination, a thermal treatment method, influenced the physical properties of colemanite. The highest surface area, 131.9 m2/g, was obtained at 500 °C. The physical properties were found to have high statistical relation.

Diffuse-layer surface potentials of colemanites mined in Turkey

88%

Senol-Arslan D. , Drelich J. W.

Physicochemical Problems of Mineral Processing

2022

tom Vol. 58, iss. 5

art. no. 151933

Colemanite crystal specimens were handpicked at Kestelek, Emet (Hisarcik, Espey), Bigadic mines in Turkey for characterization of their composition and surface potential. X-ray diffraction analysis revealed no differences in mineralogical makeup of the crystals, but elemental analysis indicated differences in the type of trace (<0.1 wt%) elements. Zeta potential measurements showed small differences in zeta potential values, with isoelectric points (iep) varying from about pH = 9.6 to pH = 10.2. However, no correlation was found between iep and the type of trace elements. Additionally, atomic force microscopy (AFM) was employed to measure the colloidal interactions between a silicon nitride (Si3N4) cantilever tip and colemanite crystal surfaces in 1 wt% colemanite-saturated aqueous solutions at three different pHs (8.4, 9.4 and 11). The Derjaguin-Landau-Verwey-Overbeek theory (DLVO) was applied to examine the AFM tip interactions with colemanite surfaces in an aqueous solution of colemanite saturated solutions. The results revealed attractive forces at pH = 8.4 and 9.4 and repulsive forces at pH = 11, confirming the location of an isoelectric point for colemanite specimens somewhere between pH = 9.5 and pH = 10.1. Theoretical analysis of the force curves using the DLVO theory allowed for assessment of both surface charge density and surface potential for colemanite specimens used in this study.