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Number of results: 6
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Abstract

The presented article describes the method for determining one of the trace elements occurring in coalbismuth. The subjects of the analysis were coal type 34, 35 and their fly ashes derived from Jastrzębska Spółka Węglowa. The main reason for the research was the extensive use of bismuth in many industry sectors. Additionally, bismuth is on the list of deficit elements, therefore the possibility of obtaining an alternative for its recycling source of it is needed, is required. The research was carried out using atomic absorption spectrometry with electrothermal atomization in a graphite cuvette. The samples were incinerated at 800°C and microwave mineralization in a high-pressure closed system was performed until the spectrometric analysis was achieved. In order to achieve mineralization, a mixture of HF and HNO3 acids was used to turn the samples into acidic solutions. The preparation of the samples was based on available literature data and own observations. In the experiment, the effects of the additive modifier was modified by changing the temperature in further steps: drying, incineration, cooling, atomization and burning were described. In addition, the palladium modifier was used in order to limit secondary reactions and enable the evaporation of matrix components. The measurement conditions which are presented in this article allow for a linear calibration curve to be established. However, this is not clear and the definitive method for determining the bismuth in coal is carried out through the use of ET-AAS.
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Abstract

In this study, an oxide reduction process and a reduction-sintering process were employed to synthesize a thermoelectric alloy from three thermoelectric composite oxide powders, and the thermoelectric properties were investigated as a function of the milling duration. Fine grain sizes were analyzed by via X-ray diffraction and scanning electron microscopy, to investigate the influence of the milling duration on the synthesized samples. It was found that microstructural changes, the Seebeck coefficient, and the electrical resistivity of the compounds were highly dependent on the sample milling duration. Additionally, the carrier concentration considerably increased in the samples milled for 6 h; this was attributed to the formation of antisite defects introduced by the accumulated thermal energy. Moreover, the highest value of ZT (=1.05) was achieved at 373K by the 6-h milled samples. The temperature at which the ZT value maximized varied according to the milling duration, which implies that the milling duration of the three thermoelectric composite oxide powders should be carefully optimized for their effective application.
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Abstract

The study presents fifteen oxygen-bearing secondary minerals of bismuth from the north-eastern part of the Variscan Karkonosze granitoid pluton in the northern zone of the Bohemian massif. The minerals were investigated by optical, electron microprobe, classic chemical, XRD, IR absorption and fluid inclusion methods. The late, very low temperature epithermal solutions most probably caused formation of sillénite, kusachiite, bismoclite, bismutite, beyerite, kettnerite, pucherite, schumacherite, namibite and eulytite. Solutions dominated by supergene (meteoric) waters were the parents for bismite, russellite, koechlinite, ximengite and walpurgite. The paper also contains information on early research on the investigated minerals.
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Abstract

In this study, the effect of electroless Pd-P plating on the bonding strength of the Bi-Te thermoelectric elements was investigated. The bonding strength was approximately doubled by electroless Pd-P plating. Brittle Sn-Te intermetallic compounds were formed on the bonding interface of the thermoelectric elements without electroless Pd-P plating, and the fracture of the bond originated from these intermetallic compounds. A Pd-Sn solder reaction layer with a thickness of approximately 20 µm was formed under the Pd-P plating layer in the case of the electroless Pd-P plating, and prevented the diffusion of Bi and Te. In addition, the fracture did not occur on the bonding interface but in the thermoelectric elements for the electroless Pd-P plating because the bonding strength of the Pd-Sn reaction layer was higher than the shear strength of the thermoelectric elements.
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Abstract

The aim of the work was to obtain thin bismuth oxide films containing, at room temperature, the Bi1,5Er0,5O3 phase. This phase corresponds to the structure of the high-temperature δ-Bi2O3 phase, in pure bismuth oxide, characterized by the highest ionic conductivity of all known solid state ionic conductors. The high-temperature δ-Bi2O3 phase with the face centered cubic structure, in pure bismuth oxide, occurs only at temperature above 730°C. Stabilization of the δ-Bi2O3 phase at room temperature was achieved by an addition of the erbium together with the employment of the Pulsed Laser Deposition (PLD) technique. The influence of an amount of Er alloying and the film thickness on surface morphology, microstructure, phase composition of thin films were investigated. The velocity of deposition of thin layers of bismuth stabilized with erbium in the PLD process using the Nd: YAG laser was about 0.5 nm/s. The investigation results of erbium doped bismuth oxide thin films deposited onto (0001) oriented Al2O3 monocrystalline substrate are presented. Thin films of uniform thickness, without cracks, and porosity were obtained. All deposited thin films (regardless of the film thickness or erbia (Er2O3) content) exhibited a columnar structure. In films stabilized with erbium, up to approx. 250 nm thickness, the columns have a diameter at the base from 25 to 75 nm. The columns densely and tightly fill the entire volume of the films. With increasing of the film thickness increases, porosity also significantly increases. In thin layers containing from 20 to 30 mole % Er2O3 the main identified phase at room temperature is Bi1.5Er0.5O3. It is similar to the defective fluorite-type structure, and belongs to the Fm-3m space group. This phase corresponds to the structure of the high-temperature δ-Bi2O3 phase in pure bismuth oxide.
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Abstract

Effects of additions of 0.00064, 0.001 and 0.0042 wt.% Bi on the graphite structure in the section thicknesses of 3, 12, 25, 38, 50, 75 and 100 mm of spheroidal graphite cast iron castings containing 2.11 wt.% Si and rare earth (RE) elements (Ce + La + Nd + Pr + Sm + Gd) in the range from 0.00297 to 0.00337 wt.% were analyzed in this paper. Addition of Bi was not necessary for obtaining high nodule count and nodularity higher than 80% in section thicknesses of 3, 12 and 25 mm. RE elements showed a beneficial effect on the nodule count and nodularity in these sections. Nodularity was below 80% in section thicknesses of 38, 50, 75 and 100 mm when Bi was not added. Detrimental effect of RE elements on graphite morphology in these sections was neutralized by adequate addition of Bi. Addition of 0.001 wt.% Bi (ratio of RE/Bi = 3.27) was enough to achieve nodularity above 80% in the section thickness of 38 mm. Nodularity was increased above 80% in section thicknesses of 50, 75 and 100 mm by addition of 0.0042 wt.% Bi (ratio of RE/Bi = 0.78). At the same time, Bi significantly increased the nodule count. Nodularity above 80% and the high nodule count in the section thicknesses of 75 and 100 mm were also achieved by using an external metallic chill in the mold. In this case, addition of Bi was not required.
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