| 1. |
- Zayed, M. E., et al.
(author)
-
Temperature dependence of the pressure induced monoclinic distortion in the spin S=1/2 Shastry-Sutherland compound SrCu2(BO3)(2)
- 2014
-
In: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 186, s. 13-17
-
Journal article (peer-reviewed)abstract
- We investigate the monoclinic distortion that occurs at 4.7 GPa at room temperature in the frustrated Shastry-Sutherland model quantum magnet SrCu2(BO3)(2) as a function of pressure and temperature by means of powder and single crystal angle dispersive synchrotron X-ray diffraction. Our results indicate that the onset of the structural distortion varies in a narrow pressure range between 4.0 and 5.0 GPa. This result will be useful in order to distinguish between magnetic transitions related to structural changes and potential intrinsic quantum phase transitions that various reports have suggested to take place in SrCu2(BO3)(2) at high pressure and low temperature.
|
|
| 2. |
- Saleemi, Mohsin, et al.
(author)
-
Fabrication of nanostructured bulk cobalt antimonide (CoSb3) based skutterudites via bottom-up synthesis
- 2013
-
In: Thermoelectric Materials Research and Device Development for Power Conversion and Refrigeration. - : Materials Research Society. - 9781605114675 ; , s. 121-126
-
Conference paper (peer-reviewed)abstract
- Skutterudites are known to be efficient thermoelectric (TE) materials in the temperature range from 600 K to 900 K. Dimensionless figure of merit (ZT) for filled skutterudite TE materials have been reported as ca. 1 at 800 K. Novel nano- engineering approaches and filling of the skutterudites crystal can further improve the transport properties and ultimately the ZT. Although classified among the promising TE materials, research on their large-scale production via bottom up synthetic routes is rather limited. In this work, large quantity of cobalt antimonide (CoSb3) based skutterudites nanopowder (NP) was fabricated through a room temperature coprecipitation precursor method. Dried precipitates were process by thermo-chemical treatment steps including calcination (in air) and reduction (in hydrogen). CoSb3 NPs were then mixed with silver (Ag) nanopanicles at different weight percentages (1%, 5% and 10% by wt) to form nanocomposites. Skutterudite NP was then consolidated by Spark Plasma Sintering (SPS) technique to produce highly dense compacts while maintaining the nanostructure. Temperature dependent TE characteristics of SPS'd CoSb3 and Ag containing nanocomposite samples were evaluated for transport properties, including thermal conductivity, electrical conductivity and Seebeck coefficient over the temperature range of 300-900 K. Physicochemical, structural and microstructural evaluation results are presented in detail.
|
|
| 3. |
- Stingaciu, M., et al.
(author)
-
Single-component fuel cells fabricated by spark plasma sintering
- 2012
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 2:32, s. 12140-12143
-
Journal article (peer-reviewed)abstract
- Porous single-component fuel cells, made up of a single layer of mixed ionic and electronic conductivity, have been fabricated using spark plasma sintering (SPS) and their performances were tested in methanol. It was possible to optimize the current/power output by changing the sintering conditions which directly influence the grain size, porosity, grain contacts and conducting paths for the fabricated cells.
|
|
| 4. |
- Battiston, S., et al.
(author)
-
Synthesis and Characterization of Al-Doped Mg2Si Thermoelectric Materials
- 2013
-
In: Journal of Electronic Materials. - New York : Springer. - 0361-5235 .- 1543-186X. ; 42:7, s. 1956-1959
-
Journal article (peer-reviewed)abstract
- Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion for the middle to high range of temperature. These materials are very attractive for TE research because of the abundance of their constituent elements in the Earth's crust. Mg2Si could replace lead-based TE materials, due to its low cost, nontoxicity, and low density. In this work, the role of aluminum doping (Mg2Si:Al = 1:x for x = 0.005, 0.01, 0.02, and 0.04 molar ratio) in dense Mg2Si materials was investigated. The synthesis process was performed by planetary milling under inert atmosphere starting from commercial Mg2Si pieces and Al powder. After ball milling, the samples were sintered by means of spark plasma sintering to density > 95%. The morphology, composition, and crystal structure of the samples were characterized by field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction analyses. Moreover, Seebeck coefficient analyses, as well as electrical and thermal conductivity measurements were performed for all samples up to 600A degrees C. The resultant estimated ZT values are comparable to those reported in the literature for these materials. In particular, the maximum ZT achieved was 0.50 for the x = 0.01 Al-doped sample at 600A degrees C.
|
|
| 5. |
- Fiameni, S., et al.
(author)
-
Introduction of Metal Oxides into Mg2Si Thermoelectric Materials by Spark Plasma Sintering
- 2013
-
In: Journal of Electronic Materials. - New York : Springer. - 0361-5235 .- 1543-186X. ; 42:7, s. 2062-2066
-
Journal article (peer-reviewed)abstract
- Oxide incorporation into thermoelectric Mg2Si-based materials was performed starting from commercial Mg2Si and commercial metal oxides by applying ball milling and spark plasma sintering (SPS) processing. The SPS conditions, such as sintering temperature, pressure, and holding time, were optimized with the aim of obtaining both full densification and oxide incorporation. Thermoelectric characterizations, such as Seebeck coefficient and electrical and thermal conductivity, were carried out and related to the pellet compositions. The morphology, composition, and crystallographic structure of the samples were characterized by field-emission scanning electron microscopy, energy-dispersive spectrometry, and x-ray diffraction analyses, respectively.
|
|
| 6. |
- Saleemi, Mohsin, et al.
(author)
-
Evaluation of the Structure and Transport Properties of Nanostructured Antimony Telluride (Sb2Te3)
- 2014
-
In: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 43:6, s. 1927-1932
-
Journal article (peer-reviewed)abstract
- Antimony telluride, (Sb2Te3), and its doped derivatives are considered to be among the best p-type thermoelectric (TE) materials for room temperature (300-400 K) applications. However, it is still desirable to develop rapid and economical routes for large-scale synthesis of Sb2Te3 nanostructures. We report herein a high yield, simple and easily scalable synthetic method for polycrystalline Sb2Te3 nanostructures. Prepared samples were compacted into dense pellets by use of spark plasma sintering. The products were characterized by x-ray diffraction and scanning electron microscopy. To investigate the anisotropic behavior of Sb2Te3 TE transport property measurements were performed along and perpendicular to the direction of compaction. Thermal conductivity, electrical conductivity, and Seebeck coefficient measurement over the temperature range 350-525 K showed that the anisotropy of the material had a large effect on TE performance.
|
|
| 7. |
- Sutka, A., et al.
(author)
-
Gas sensing properties of Zn-doped p-type nickel ferrite
- 2012
-
In: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 171, s. 354-360
-
Journal article (peer-reviewed)abstract
- The influence of zinc ion to the NiFe2O4 p-type semiconductor gas response characteristics is demonstrated. For characterization of gas sensor material, synthesized by sol-gel auto combustion method. X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistance and impedance spectroscopy (IS) measurements were employed. The response change of Zn doped nickel ferrite is related to the interruption of hole hopping between nickel ions. This was improved by change of conductivity type with temperature and gas exposure.
|
|
