High purity synthesis of ZrB2 by a combined ball milling and carbothermal method: Structural and magnetic properties

The present work provides a new insight into the high purity synthesis of zirconium diboride (ZrB₂) powders and a method of controlling impurity during the synthesis process. The single phase ZrB₂ nano-powder was synthesized by a combined ball milling and carbothermal method using zirconium oxide (ZrO₂), boron oxide (B₂O₃) and carbon (C) as starting materials. The reaction pathway, phase purity, and morphology of the ZrB₂ produced are elucidated from X-ray diffraction (XRD) and scanning electron microscopy studies. The details of the impure phases generated during synthesis were obtained from multi-phase Rietveld refinements of XRD data. Experiments revealed that the method of synthesis carried out at 1750?°C involving ZrB₂:B₂O₃:C at a molar ratio of 1:4.5:7.5 could produce highly pure ZrB₂ nano-powders of 67?nm average crystallite size. The magnetometry studies on such pure form of ZrB₂ nano-powders indicated that both paramagnetic and diamagnetic characteristics coexisted in ZrB₂, which could be attributed to its polycrystallinity.     

Comparison of stresses obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring techniques and an evaluation of the Kaiser Effect level

The purpose of the study was to compare stress values obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring stress measurement techniques applied at an underground limestone mine in Japan, and to investigate the effect of rock anisotropy and confining pressure on the Kaiser Effect level which has been used to determine in situ stresses by the Acoustic Emission technique. Initially, Acoustic Emission tests were carried out on limestone cores extracted from horizontal boreholes in a pillar and hanging wall in the underground mine. The stress values obtained were two or three times greater than those obtained by the Compact Conical-Ended Borehole Overcoring method. In the second stage, the anisotropy of a granite block was determined by P-wave measurements. Core specimens extracted from two different directions were pre-loaded under axisymetric triaxial conditions by applying a series of differential stresses. The cores were then re-loaded under uniaxial conditions and the Kaiser Effect levels were determined. It was concluded that both the anisotropy and confining pressure have an important influence on the Kaiser Effect level.     

Some physico‐chemical characteristics of honeys produced from sunflower plant (Helianthus annuus L.)

This study was conducted to determine the physico‐chemical characteristics of honeys (n = 52 samples) produced from sunflower in Trakya region of Turkey. We have evaluated the conformity of the honeys in accordance with the criteria specified by the Turkish Honey Standard (TS 3036), Turkish Food Codex and European Union Commission. According to the results of our analysis, the average values determined were in Tekirdag (n = 10 samples), Malkara (n = 22 samples), Hayrabolu (n = 13 samples) and Muratl? (n = 7samples) respectively: 6.67%, 6.06, 8.43, 7.89 for hydroxymethyl furfural (HMF); 15.02, 23.98, 18.61, 17.61 (Goethe unit) for diastase activity; 2.01%, 2.39, 2.36, 1.69 for saccharose; 75.26, 73.78, 75.50, 76.80 for invert sugar (%); 23.38, 34.92, 31.70, 26.38 for meq kg^?1 for acidity; 0.16, 0.25, 0.31, 0.13 for ash value (%); 18.13, 18.21, 17.52, 18.21 for water content (%).