kth.sePublications
Change search
Refine search result
1 - 9 of 9
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Toprak, Muhammet S.
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Stiewe, C
    Platzek, D
    Williams, S
    Bertini, L
    Muller, Eckhard
    Gatti, C
    Zhang, Yu
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Rowe, M
    Muhammed, Mamoun
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    The impact of nanostructuring on the thermal conductivity of thermoelectric CoSb32004In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 14, no 12, p. 1189-1196Article in journal (Refereed)
    Abstract [en]

    The high concentration of grain boundaries provided by nanostructuring is expected to lower the thermal conductivity of thermoelectric materials, which favors an increase in their thermoelectric figure-of-merit, ZT. A novel chemical alloying method has been used for the synthesis of nanoengineered-skutterudite CoSb3. The CoSb3 powders were annealed for different durations to obtain a set of samples with different particle sizes. The samples were then compacted into pellets by uniaxial pressing under various conditions and used for the thermoelectric characterization. The transport properties were investigated by measuring the Seebeck coefficient and the electrical and thermal conductivities in the temperature range 300 K to 650 K. A substantial reduction in the thermal conductivity of CoSb3 was observed with decreasing grain size in the nanometer region. For an average grain size of 140 nm, the thermal conductivity was reduced by almost an order of magnitude compared to that of a single crystalline or highly annealed polycrystalline material. The highest ZT value obtained was 0.17 at 611 K for a sample with an average grain size of 220 nm. The observed decrease in the thermal conductivity with decreasing grain size is quantified using a model that combines the macroscopic effective medium approaches with the concept of the Kapitza resistance. The compacted samples exhibit Kapitza resistances typical of semiconductors and comparable to those of Si-Ge alloys.

  • 2.
    Toprak, Muhammet
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Zhang, Yu
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jo, Yunsuk
    Kim, Do-Kyung
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nanocrystalline thermoelectric alloys: Processing, chemistry and characterization2005In: BULK AND GRADED NANOMETALS / [ed] Kurzydlowski, KJ; Pakiela, Z, 2005, Vol. 101-102, p. 197-204Conference paper (Refereed)
    Abstract [en]

    A novel chemical alloying method has been developed for the fabrication of nanocrystalline thermoelectric alloys cobalt antimonide, CoSb3, and bismuth telluride, Bi2Te3. The method combines a solution chemical method and thermal processing under controlled heating conditions. The components have been co-precipitated from a solution and the precursor consisted of a solid solution of the different intermediate compounds with different crystallinity. Calcination and hydrogen reduction of the precursor at moderate temperature, 350degreesC, resulted in the alloying of these elements to obtain the nanocrystalline thermoelectric material. Crystallization of the amorphous precursor as well as the processing route have been investigated by following the changes in the chemistry of the material from the precursor to the final alloy. Detailed microstructure investigation by electron microscopy has also been presented.

  • 3.
    Uheida, Abdusalam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Iglesias, Monica
    Fontas, Claudia
    Hidalgo, Manuela
    Salvado, Victoria
    Zhang, Yu
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sorption of palladium(II), rhodium(III), and platinum(IV) on Fe3O4 nanoparticles2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 301, no 2, p. 402-408Article in journal (Refereed)
    Abstract [en]

    The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe3O4 nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H+ and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe3O4 nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g(-1), respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be log K = 1.72, 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe3O4 nanoparticles. It was found that 0.5 mol L-1 HNO3 can elute all of the metal ions simultaneously, while 1 mol L-1 NaHSO3 was an effective eluting solution for Rh(III), and 0.5 mol L-1 NaClO4 for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).

  • 4.
    Uheida, Abdusalam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Iglesias, Mònica
    Fontàs, Claudia
    Zhang, Yu
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Adsorption Behavior of Platinum Group Metals (Pd, Pt, Rh) onNonylthiourea-Coated Fe3O4 Nanoparticles2006In: Separation science and technology (Print), ISSN 0149-6395, E-ISSN 1520-5754, Vol. 41, p. 909-923Article in journal (Refereed)
    Abstract [en]

    Magnetite nanoparticles coated with nonylthiourea (NTH) were synthesizedand analyzed for the separation and recovery of platinum group metals (PGMs) fromdiluted aqueous chloride solutions. Physical characterizations of the coated nanoparticleswere performed by Transmission Electron Microscopy (TEM), ThermogravimetricAnalysis (TGA) and FT-IR Spectrometry. Separation efficiency of the coatednanoparticles and the equilibrium adsorption isotherm of PGMs were investigated.The maximum adsorption was attained in less than 30 minutes, and the maximumloading capacity of NTH-coated Fe3O4 nanoparticles for Pt(IV) and Pd(II) was determinedto be 10.7 and 8.1 mg g21, respectively. The recovery of PGMs from the loadednanoparticles was examined using different eluting solutions, including HNO3,thiourea, and NaClO4.

  • 5.
    Uheida, Abdusalam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Salazar-Alvarez, German
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bjorkman, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Zhang, Yu
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fe3O4 and gamma-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 298, no 2, p. 501-507Article in journal (Refereed)
    Abstract [en]

    The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, Solution pH. and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 ruin. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously Studied. iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%. respectively. That has been explained by the different mechanisms by including both the surface and Structural loadings of Co2+ ions. The Surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle Surface. The conditional equilibrium constants of surface 2-adsorption of Co2+ on Fe3O4 and gamma-Fe-O-2(3) nanoparticles have been determined to be log K = -3.3 +/- 0.3 and -3.1 +/- 0.2, respectively. The Structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between CO2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1)

  • 6.
    Uheida, Abdusalam
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Zhang, Yu
    KTH, Superseded Departments (pre-2005), Chemistry.
    Muhammed, Mamoun
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Extraction of platinum(IV) with nonylthiourea dissolved in chloroform from hydrochloric acid media2003In: Solvent extraction and ion exchange, ISSN 0736-6299, E-ISSN 1532-2262, Vol. 21, no 6, p. 827-840Article in journal (Refereed)
    Abstract [en]

    The extractant nonylthiourea (NTH) in chloroform has been investigated for the extraction of Pt(IV) from chloride solutions at ionic strength of I = 4.0 M and at 22degreesC. It has been found that chloride concentration has a negative effect on the extraction equilibrium, while proton concentration has no effect. The numerical analysis of the equilibrium data has shown that the extraction of PtCl62- with NTH can be interpreted by the formation Of PtCl4(NTH) and PtCl4(NTH)(4) species with their respective equilibrium constants of log K-11 = 5.06 +/- 0.01 and log K-14 = 14.12 +/- 0.04 in 4 M HCl. FTIR spectra of the free NTH and the NTH-Pt(IV) complex were studied to obtain some information on the interaction between Pt(IV) ions and NTH molecules.

  • 7.
    Uheida, Abdusalam
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Zhang, Yu
    KTH, Superseded Departments (pre-2005), Chemistry.
    Muhammed, Mamoun
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Selective extraction of palladium(II) from chloride solutions with nonylthiourea dissolved in chloroform2002In: Solvent extraction and ion exchange, ISSN 0736-6299, E-ISSN 1532-2262, Vol. 20, no 6, p. 717-733Article in journal (Refereed)
    Abstract [en]

    The extraction of Palladium(II) [Pd(II)] from hydrochloric acid solutions with nonylthiourea (NTH) dissolved in chloroform at a constant ionic strength of LOM has been studied. The extraction of Pd(II) has been investigated as a function of the concentration of the extractant, chloride ion, and proton concentrations as well as extraction temperature. The distribution data have been treated graphically and numerically. The analysis of the experimental data has shown that Pd(II) is extracted as PdCl2 . (NTH) and PdCl2 . (NTH)(2) species with the respective extraction constants of log K-11 = 5.0 +/- 0.1 and log K-12 = 9.1 +/- 0.1. The back-extraction of Pd(II) from the organic phase using different stripping reagents has been examined. The selectivity of NTH for Pd(II) against Pt(IV), Rb(III), Cu(II), Fe(III), and Zn(II) has also been investigated.

  • 8.
    Uheida, Abdusalam
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Zhang, Yu
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Muhammed, Mamoun
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Thermodynamic modeling of extraction equilibria of platinum and palladium with nonylthiourea from hydrochloric acid media2004In: Separation science and technology (Print), ISSN 0149-6395, E-ISSN 1520-5754, Vol. 39, no 15, p. 3665-3677Article in journal (Refereed)
    Abstract [en]

    Models of extraction equilibria of Pt(IV) and Pd(II) with Nonylthiourea (NTH) from HCl media have been studied. The conditional equilibrium constants and the stoichiometry of the extracted species of Pt(IV) with NTH at different ionic strengths obtained by numerical analysis using the LETAGROP-DISTR program are reported. The dependence of the extraction constant values on the ionic strength has been analysed using the Specific Interaction Theory (SIT), from which the respective thermodynamic equilibrium constants of the extraction of Pt(IV) and Pd(II) with NTH have been determined. The thermodynamic equilibrium constants determined for Pt(IV) are log K-11o=5+/-1 and log K-14(o)=14.6+/-0.2, while for Pd(II) log K-11(o)=4.9+/-0.1 and log K-12(o)=9.17+/-0.08. The interaction coefficients, epsilon, for the pairs (H+, PtCl62-) and (H+, PdCl42-) have also been estimated to be 0.30+/-0.08 and 0.41+/-0.02, respectively.

  • 9.
    Uheida, Abdusalam
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Zhang, Yu
    KTH, Superseded Departments (pre-2005), Chemistry.
    Muhammed, Mamoun
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Transport of palladium(II) through hollow fiber supported liquid membrane facilitated by nonylthiourea2004In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 241, no 2, p. 289-295Article in journal (Refereed)
    Abstract [en]

    The facilitated transport of Pd(II) from chloride media has been investigated through a hollow-fiber supported liquid membrane using nonylthiourea (NTH) as a carrier. The influence of the chemical conditions on the permeability of Pd(II) is reported. A model is presented that describes the transport mechanism, consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion of carrier and its metal complex through the organic membrane. The diffusion resistances through organic membrane (Delta(org)) and through aqueous layer (Delta(aq)), respectively, have been calculated from the proposed model. The permeability of Pd(II) seems to be governed by the diffusion of Pd(II) species through the hollow fiber supported liquid membrane with PdCl2(NTH)(2) as a predominant carrier and PdCl2(NTH)to a lesser extent, though both have similar diffusion coefficients.

1 - 9 of 9
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf