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Publications (10 of 46) Show all publications
Jaffari, G. H., Rehman, A. u., Iqbal, A. M., Awan, M. S. & Saleemi, M. (2017). Extrinsic contributions to the dielectric response in sintered BaTiO3 nanostructures in paraelectric and ferroelectric regimes. Physica. B, Condensed matter, 525, 70-77
Open this publication in new window or tab >>Extrinsic contributions to the dielectric response in sintered BaTiO3 nanostructures in paraelectric and ferroelectric regimes
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2017 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 525, p. 70-77Article in journal (Refereed) Published
Abstract [en]

Post sintering studies of BaTiO3 (BTO) nanoparticles are presented in detail. Bulk nanostructures were prepared via three different compaction processes, namely, uniaxial cold pressing (UCP), Cold Isostatic Pressing (CIP) and Spark Plasma Sintering (SPS). Effect of compaction technique on microstructures have been investigated and correlated with electrical response for each sample. In addition to the transport properties, temperature and frequency dependent dielectric response of variously sintered samples and bulk counterpart was recorded. Several aspects have been identified that are essential to be taken into account in order to completely understand physical processes. Drastically distinct features were observed in paraelectric (PE) regime well above ferroelectric (FE)-PE transition temperature. These features include intra grain conduction with a reduction in the magnitude of PE to FE peak dielectric constant magnitude. Role of strain, grain boundary conduction associated with observation of Maxwell Wagner relaxation and hopping conduction in dielectric and ferroelectric response have been observed and discussed. Densification with presence of oxygen vacancies, significantly enhances conductivity associated with the hopping of the carriers, in turn deteriorated ferroelectric response.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Paraelectric, Ferroelectric, Hopping conduction, Grain boundary conduction, Strain
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-217405 (URN)10.1016/j.physb.2017.07.057 (DOI)000414178500012 ()
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-21Bibliographically approved
Saleemi, M., Tafti, M. Y., Jacquot, A., Jaegle, M., Johnson, M. & Toprak, M. S. (2016). Chemical Synthesis of Iron Antimonide (FeSb2) and Its Thermoelectric Properties. Inorganic Chemistry, 55(4), 1831-1836
Open this publication in new window or tab >>Chemical Synthesis of Iron Antimonide (FeSb2) and Its Thermoelectric Properties
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2016 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 4, p. 1831-1836Article in journal (Refereed) Published
Abstract [en]

Low temperature thermoelectric (TE) materials are in demand for more efficient cooling and power generation applications. Iron antimonide (FeSb2) draws great attention over the past few years because of its enhanced power factor values. Polycrystalline bulk FeSb2 nanopowder was prepared via a low-temperature molten salts approach followed by subsequent thermal treatment in synthetic air and hydrogen gas for calcination and reduction reactions, respectively. Structural analysis confirms the desired final phase with submicrometer grain size and high compaction density after consolidation using spark plasma sintering (SPS). TE transport properties revealed that the material is n-type below 150 K and p-type above this temperature; this suggests antimony vacancies in FeSb2. The electrical conductivity increased significantly, and the highest conductivity achieved was 6000 S/cm at 100 K. The maximum figure-of-merit, ZT, of 0.04 is achieved at 500 K, which is about 6 times higher than the earlier reported state-of-the art ZT value for the same material.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-184039 (URN)10.1021/acs.inorgchem.5b02658 (DOI)000370395000055 ()26836130 (PubMedID)2-s2.0-84958818272 (Scopus ID)
Note

QC 20160323

Available from: 2016-03-23 Created: 2016-03-22 Last updated: 2017-11-30Bibliographically approved
Afzal, M., Saleemi, M., Wang, B., Xia, C., Zhang, W., He, Y., . . . Zhu, B. (2016). Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier. Journal of Power Sources, 328, 136-142
Open this publication in new window or tab >>Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier
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2016 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, p. 136-142Article in journal (Refereed) Published
Abstract [en]

Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is synthesized via a chemical co-precipitation technique for a low temperature solid oxide fuel cell (LTSOFC) (300-600 degrees C) and electrolyte-layer free fuel cell (EFFC) in a comprehensive study. The EFFC with a homogeneous mixture of samarium doped ceria (SDC): BSCF (60%:40% by weight) which is rather similar to the cathode (SDC: BSCF in 50%:50% by weight) used for a three layer SOFC demonstrates peak power densities up to 655 mW/cm(2), while a three layer (anode/ electrolyte/cathode) SOFC has reached only 425 mW/cm(2) at 550 degrees C. Chemical phase, crystal structure and morphology of the as-prepared sample are characterized by X-ray diffraction and field emission scanning electron microscopy coupled with energy dispersive spectroscopy. The electrochemical performances of 3-layer SOFC and EFFC are studied by electrochemical impedance spectroscopy (EIS). As-prepared BSCF has exhibited a maximum conductivity above 300 S/cm at 550 degrees C. High performance of the EFFC device corresponds to a balanced combination between ionic and electronic (holes) conduction characteristic. The Schottky barrier prevents the EFFC from the electronic short circuiting problem which also enhances power output. The results provide a new way to produce highly effective cathode materials for LTSOFC and semiconductor designs for EFFC functions using a semiconducting-ionic material.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Co-precipitation, Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF), LTSOFC, Electrolyte-layer free fuel cell (EFFC), Perovskite oxide, Semi-ionic conductor
National Category
Materials Chemistry Inorganic Chemistry Ceramics
Identifiers
urn:nbn:se:kth:diva-193795 (URN)10.1016/j.jpowsour.2016.07.093 (DOI)000383293400015 ()2-s2.0-84984850892 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, TRISOFC_03042012Swedish Research Council, 621-2011-4983ÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Note

QC 20161024

Available from: 2016-10-24 Created: 2016-10-11 Last updated: 2019-03-06Bibliographically approved
Tafti, M. Y., Saleemi, M., Han, L., Nong, N. V. & Toprak, M. S. (2016). On the chemical synthesis route to bulk-scale skutterudite materials. Ceramics International, 42(4), 5312-5318
Open this publication in new window or tab >>On the chemical synthesis route to bulk-scale skutterudite materials
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2016 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, no 4, p. 5312-5318Article in journal (Refereed) Published
Abstract [en]

In this article an alternative high yield route for the synthesis of CoSb3-based unfilled skutterudites is presented. Using low-melting temperature salts of the constituents, melting and mixing them homogeneously in a hydrophobic liquid with postprocessing of the powders we achieve a more intimately mixed alloy compared to the conventional melting and metallurgical processes. The proposed method consists of a fast and low-temperature processing step followed by a thermochemical post-processing step, compared to the conventional methods of fabricating skutterudites, which require high temperatures and long processing times. Several structural characterization techniques were used to assess the mechanism of synthesis, verify the purity of the material as well as the reproducibility of the process. Detailed analysis and results are presented in support of the proposed process. Additionally, compaction of the powders with SPS technique provided a safe route to maintaining the nanopowder size and achieving low thermal conductivity (3 W/mK). The proposed method can easily be scaled up and adopted by the industry.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Thermal conductivity, Thermoelectric, Skutterudite, TGA-FTIR
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-183303 (URN)10.1016/j.ceramint.2015.12.061 (DOI)000369460500088 ()2-s2.0-84955655812 (Scopus ID)
Note

QC 20160309

Available from: 2016-03-09 Created: 2016-03-07 Last updated: 2017-11-30Bibliographically approved
Yakhshi Tafti, M., Ballikaya, S., Khachatourian, A. M., Noroozi, M., Saleemi, M., Han, L., . . . Toprak, M. S. (2016). Promising bulk nanostructured Cu2Se thermoelectrics via high throughput and rapid chemical synthesis. RSC ADVANCES, 6(112), 111457-111464
Open this publication in new window or tab >>Promising bulk nanostructured Cu2Se thermoelectrics via high throughput and rapid chemical synthesis
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2016 (English)In: RSC ADVANCES, ISSN 2046-2069, Vol. 6, no 112, p. 111457-111464Article in journal (Refereed) Published
Abstract [en]

A facile and high yield synthesis route was developed for the fabrication of bulk nanostructured copper selenide (Cu2Se) with high thermoelectric efficiency. Starting from readily available precursor materials and by means of rapid and energy-efficient microwave-assisted thermolysis, nanopowders of Cu2Se were synthesized. Powder samples and compacted pellets have been characterized in detail for their structural, microstructural and transport properties. alpha to beta phase transition of Cu2Se was confirmed using temperature dependent X-ray powder diffraction and differential scanning calorimetry analyses. Scanning electron microscopy analysis reveals the presence of secondary globular nanostructures in the order of 200 nm consisting of <50 nm primary particles. High resolution transmission electron microscopy analysis confirmed the highly crystalline nature of the primary particles with irregular truncated morphology. Through a detailed investigation of different parameters in the compaction process, such as applied load, heating rate, and cooling profiles, pellets with preserved nanostructured grains were obtained. An applied load during the controlled cooling profile was demonstrated to have a big impact on the final thermoelectric efficiency of the consolidated pellets. A very high thermoelectric figure of merit (ZT) above 2 was obtained at 900 K for SPS-compacted Cu2Se nanopowders in the absence of the applied load during the controlled cooling step. The obtained ZT exceeds the state of the art in the temperature ranges above phase transition, approaching up to 25% improvement at 900 K. The results demonstrate the prominent improvement in ZT attributed both to the low thermal conductivity, as low as 0.38 W m(-1) K-1 at 900 K, and the enhancement in the power factor of nanostructured Cu2Se. The proposed synthesis scheme as well as the consolidation could lead to reliable production of large scale thermoelectric nanopowders for niche applications.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-200061 (URN)10.1039/c6ra23005a (DOI)000389463600112 ()2-s2.0-84999274182 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , EM11-0002Swedish Research Council, VR-SRL 2013-6780
Note

QC 20170126

Available from: 2017-01-26 Created: 2017-01-20 Last updated: 2017-01-26Bibliographically approved
Saleemi, M., Nikkam, N., Muhammad, M. & Toprak, M. (2015). Aging, Thermal Cycling and Stability Studies for Nanofluids. In: Aging, Thermal Cycling and Stability Studies for Nanofluids: . Paper presented at Materials Research Society (MRS) spring meeting, April 6-10, 2015.
Open this publication in new window or tab >>Aging, Thermal Cycling and Stability Studies for Nanofluids
2015 (English)In: Aging, Thermal Cycling and Stability Studies for Nanofluids, 2015Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Stability of nanofluids is one of the critical assessments for the efficient systems that the solid content of nanofluid should be stable and well dispersed for longer time. Production of a homogenous dispersion is real technical challenge due to strong van der Waals attraction among the nanoparticles, which preferring the formation of aggregates. Stable nanofluids can be achieved via recommended physical and chemical treatments such as addition of additives and surfactants, surface-active agents to disperse hydrophobic materials, adjusting the pH value to provide electrochemical stability.Detailed investigations were carried out to identify the stability parameters, dispersion methods, application requirements, experimental investigation to determine the stability of nanofluids. Aluminum oxide (Al2O3), titanium oxide (TiO2) and cerium oxide (CeO2) were selected for these studies. Custom designed stability measurement setup was used to record the sedimentation rate. Aging test was performed in the heat transfer coefficient (HTC) setup to determine the erosion and corrosion properties. Thermal cycling was performed up to 80 oC with maximum heating cycles of 500 times. Dynamic light scattering (DLS) used to estimate the aggregate size before and after the thermal cycling and aging test. Results from the time depended DLS measurements, sedimentation rate and aging effects presents that Al2O3 nanofluids have better performance.

Keywords
nanofluid, thermal cycling, stability, nanoparticle
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:kth:diva-166183 (URN)
Conference
Materials Research Society (MRS) spring meeting, April 6-10, 2015
Note

QC 20150601

Available from: 2015-05-04 Created: 2015-05-04 Last updated: 2015-06-01Bibliographically approved
Saleemi, M., Vanapalli, S., Nikkam, N., Toprak, M. S. & Muhammed, M. (2015). Classical Behavior of Alumina (Al2O3) Nanofluids in Antifrogen N with Experimental Evidence. Journal of Nanomaterials, 2015, Article ID 256479.
Open this publication in new window or tab >>Classical Behavior of Alumina (Al2O3) Nanofluids in Antifrogen N with Experimental Evidence
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2015 (English)In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2015, article id 256479Article in journal (Refereed) Published
Abstract [en]

A nanofluid is a suspension containing nanoparticles in conventional heat transfer fluids. This paper reports on an investigation of alumina (Al2O3) nanoparticles in Antifrogen N, also called AFN, which is a popular antifreeze coolant consisting primarily of ethylene glycol and other additives to impede corrosion. The base carrier fluid is 50% by weight of water and 50% by weight of AFN. We systematically measured the nanomaterials and heat transfer data of nanofluids for four different size particles, namely, 20, 40, 150, and 250 nm alumina particles. The pH of all the nanofluids is adjusted to have a stable dispersion. The material characterizations include SEM and DLS particle measurements. We measured thermal conductivity, viscosity, and heat transfer coefficient in developing flow of the nanofluids. We observed that these nanofluids behave as any other classical fluids in thermally developing flow and classical heat transfer correlations can be used to completely describe the characteristics of these nanofluids.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2015
Keywords
Alumina, Aluminum, Coolants, Ethylene, Ethylene glycol, Heat transfer, Heat transfer coefficients, Nanoparticles, Suspensions (fluids), Thermal conductivity, Alumina particles, Classical behavior, Experimental evidence, Heat transfer correlation, Heat transfer data, Material characterizations, Particle measurement, Thermally developing flow, Nanofluidics
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-181253 (URN)10.1155/2015/256479 (DOI)2-s2.0-84945340506 (Scopus ID)
Note

QC 20160212

Available from: 2016-02-12 Created: 2016-01-29 Last updated: 2017-11-30Bibliographically approved
Jarahnejad, M., Haghighi, E. B., Saleemi, M., Nikkam, N., Khodabandeh, R., Palm, B., . . . Muhammed, M. (2015). Experimental investigation on viscosity of water-based Al2O3 and TiO2 nanofluids. Rheologica Acta, 54(5), 411-422
Open this publication in new window or tab >>Experimental investigation on viscosity of water-based Al2O3 and TiO2 nanofluids
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2015 (English)In: Rheologica Acta, ISSN 0035-4511, E-ISSN 1435-1528, Vol. 54, no 5, p. 411-422Article in journal (Refereed) Published
Abstract [en]

This article investigates the influence of temperature, concentration, and size of nanoparticles, and addition of surfactants on dynamic viscosity of water-based nanofluids containing alumina (Al2O3) and titania (TiO2) nanoparticles. Two viscometers, a capillary and a falling ball, were used for the measurements in the temperature range of 20-50 A degrees C and the particle concentration of 3-14.3 wt.%. The results indicate that the viscosity of nanofluids is reduced by increasing the temperature, similar to their base fluids. Moreover, surfactants, which are used to improve the shelf stability of nanofluids, most likely increase their viscosity. The correlations derived from the linear fluid theory such as Einstein and Batchelor, especially for solid concentration above 1.5 wt.% are not accurate to predict viscosity of nanofluids, while the modified Krieger-Dougherty equation estimates viscosity of nanofluids with acceptable accuracy in a specific range of solid particle size to aggregate size.

Keywords
Nanofluid, Viscosity, Temperature, Particle size, Concentration, Surfactant, Al2O3, TiO2
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-171683 (URN)10.1007/s00397-015-0838-y (DOI)000352848300007 ()
Note

QC 20150810

Available from: 2015-08-10 Created: 2015-08-05 Last updated: 2017-12-04Bibliographically approved
Tafti, M. Y., Saleemi, M., Toprak, M. S., Johnsson, M., Jacquot, A., Jägle, M. & Muhammed, M. (2015). Fabrication and characterization of nanostructured thermoelectric FexCo1-xSb3. Open Chemistry, 13(1), 629-635
Open this publication in new window or tab >>Fabrication and characterization of nanostructured thermoelectric FexCo1-xSb3
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2015 (English)In: Open Chemistry, E-ISSN 2391-5420, Vol. 13, no 1, p. 629-635Article in journal (Refereed) Published
Abstract [en]

A novel synthesis route for the fabrication of p-type nanostructured skutterudite, FexCo1-xSb3 in large quantity is reported. This scalable synthesis route provides nano-engineered material with less impact on the environment compared to conventional synthesis procedures. Several Fe substituted compositions have been synthesized to confirm the feasibility of the process. The process consists of a nano-sized precursor fabrication of iron and cobalt oxalate, and antimony oxides by chemical co-precipitation. Further thermochemical processes result in the formation of iron substituted skutterudites. The nanopowders are compacted by Spark Plasma Sintering (SPS) technique in order to maintain nanostructure. Detailed physicochemical as well as thermoelectric transport properties are evaluated. Results reveal strongly reduced thermal conductivity values compared to conventionally prepared counterparts, due to nanostructuring. P-type characteristic was observed from the Seebeck measurements while electrical conductivity is high and shows metallic behavior. The highest TE figure of merit of 0.25 at 800 K has been achieved, which is strongly enhanced with respect to the mother compound CoSb3. This suggests the promise of the utilized method of fabrication and processing for TE applications with improved performance.

Keywords
Skutterudite (CoSb3), thermoelectric, iron substituted skutterudite, bottom-up synthesis, SPS
National Category
Materials Chemistry
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-160646 (URN)10.1515/chem-2015-0074 (DOI)000355403100076 ()
Funder
Swedish Foundation for Strategic Research , EM11-0002EU, FP7, Seventh Framework Programme, 263167
Note

QC 20150312

Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2018-09-26Bibliographically approved
Yakhshi Tafti, M., Saleemi, M., Jacquot, A., Johnsson, M. & Toprak, M. S. (2015). Temperature Dependent Structure Stability Studies on Thermoelectric Yb0.025Fe0.3Co0.7Sb3. In: S.R. Bishop , D. Cahen , R. Chen , E. Fabbri , F.C. Fonseca and D. Ginley (Ed.), Materials Research Society Proceeding: . Paper presented at 2014 MRS Fall Meeting. Materials Research Society, 1735
Open this publication in new window or tab >>Temperature Dependent Structure Stability Studies on Thermoelectric Yb0.025Fe0.3Co0.7Sb3
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2015 (English)In: Materials Research Society Proceeding / [ed] S.R. Bishop , D. Cahen , R. Chen , E. Fabbri , F.C. Fonseca and D. Ginley, Materials Research Society , 2015, Vol. 1735Conference paper, Published paper (Refereed)
Abstract [en]

Depending on their application temperature thermoelectric (TE) materials are classified in three main categories; as low (up to 250°C), intermediate (up to 550°C) and high (above 600°C) temperature. Currently, Skutterudites (CoSb3) based materials have shown promising results in the intermediate temperature range (300-500°C). This family of material is highly suitable for automotive, marine transportation and industrial power generation applications to recover the waste heat from the exhaust and generate electricity. Conventional TE modules need p- and n-type semiconductor materials and for the skutterudite family, iron (Fe) has proven to be among the best candidates for the substitution of cobalt sites. Additionally, rare earths are introduced as rattlers in the crystal cages of the skutterudite to decrease the thermal conductivity, thus improving the figure of merit ZT of the TE material. For practical application for device fabrication, stability of these materials is of great importance. Compositional stability is being addressed as the material decomposes above certain temperature. Temperature dependent x-ray diffraction study was performed on Fe substituted, Yb-filled skutterudites, using Beam Line I711 at MAX LAB, to observe the crystal structure as a function of temperature. Diffraction patterns were collected from room temperature up to 500°C by utilizing Huber furnace. The results show success in filling process showing almost 80% reduction of the thermal conductivity from bulk. Additionally the thermal expansion coefficient value was within the average value for skutterudites which proves practical application of this powder for industrial applications.

Place, publisher, year, edition, pages
Materials Research Society, 2015
Keywords
thermoelectric, nanostructure, thermal conductivity
National Category
Materials Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-176849 (URN)10.1557/opl.2015.308 (DOI)
Conference
2014 MRS Fall Meeting
Funder
Swedish Research Council, VR-SRL 2013-6780Swedish Foundation for Strategic Research , EM11-0002
Note

QC 20151201

Available from: 2015-11-10 Created: 2015-11-10 Last updated: 2016-05-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5380-975X

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