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Tonpheng, Bounphanh
Publications (5 of 5) Show all publications
Sundqvist, B., Andersson, O., Gong, C., Liu, B., Tonpheng, B., Yu, J. & Yao, M. (2015). AC impedance of A4C60 fullerides under pressure. New Journal of Physics, 17(2), Article ID 023010.
Open this publication in new window or tab >>AC impedance of A4C60 fullerides under pressure
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2015 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, no 2, article id 023010Article in journal (Refereed) Published
Abstract [en]

Three A4C60 compounds, with A = Li, Na and K, have been studied by impedance spectroscopy between 100 K and 293 K at pressures up to 2 GPa. The results are in very good agreement with earlier DC resistance studies and with data from the literature. For all three materials the measured conductivity can be fitted by a sum of at least two Arrhenius terms. The band gaps derived from the resistance data, 0.3 eV for Na4C60 and 0.5 eV for K4C60, are in excellent agreement with data measured by other methods. For Li4C60, our results disagree with a recent suggestion that the conductivity is dominated by ionic conduction. Although a certain ionic component probably exists we suggest that electronic transport dominates in our samples at and below room temperature because the derived “activation energy” decreases under pressure, the derived “activation volume” is negative, and we observe neither a significant electrode blocking capacitance nor any significant metal transport under DC conditions.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015
Keywords
Fullerides, Li4C60, Na4C60, K4C60, high pressure, conductivity, resistivity, semiconductor, ionic conduction
National Category
Physical Sciences
Research subject
Solid State Physics
Identifiers
urn:nbn:se:umu:diva-99306 (URN)10.1088/1367-2630/17/2/023010 (DOI)000352864600010 ()
Funder
Swedish Research Council, 621-2010-3732
Available from: 2015-02-06 Created: 2015-02-06 Last updated: 2018-06-07Bibliographically approved
Yu, J., Tonpheng, B. & Andersson, O. (2010). High-pressure-induced microstructural evolution and enhancement of thermal properties of nylon-6. Macromolecules, 43(24), 10512-10520
Open this publication in new window or tab >>High-pressure-induced microstructural evolution and enhancement of thermal properties of nylon-6
2010 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 43, no 24, p. 10512-10520Article in journal (Refereed) Published
Abstract [en]

The transition behavior and thermal properties of nylon-6 at elevated pressure, p, have been established by in-situ thermal conductivity, κ, and heat capacity measurements. The glass transition temperature, Tg, of virgin nylon-6 is described well by the empirical equation Tg(p) = 319.60(1 + 1.90 p)0.24 (p in GPa and Tg in K). Moreover, isobaric heating in the 1−1.2 GPa range causes a cold-crystallization transition near 500 K. As a result, κ increased 15% whereas the heat capacity per unit volume decreased 7% slowly with time during 4 h annealing at 530 K. The transformation is associated with a significantly increased crystallinity, from 35% to 55−60%, and a pressure-induced preferred orientation and increased size for the lamellae of monoclinic α crystalline structure. This state has 8−10 K higher melting temperature and better formic acid resistance than that of virgin nylon-6. However, the results show no indication of cross-linking, as reported for similarly treated nylon-1010 and nylon-11, but instead chain scissoring.

Identifiers
urn:nbn:se:umu:diva-38807 (URN)10.1021/ma102273b (DOI)000285429400049 ()
Available from: 2011-01-03 Created: 2011-01-02 Last updated: 2018-06-08Bibliographically approved
Tonpheng, B., Yu, J., Andersson, B. M. & Andersson, O. (2010). Tensile strength and young's modulus of polyisoprene/single-wall carbon nanotube composites increased by high pressure cross-linking. Macromolecules, 43(18), 7680-7688
Open this publication in new window or tab >>Tensile strength and young's modulus of polyisoprene/single-wall carbon nanotube composites increased by high pressure cross-linking
2010 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 43, no 18, p. 7680-7688Article in journal (Refereed) Published
Abstract [en]

High-viscosity liquid cis-1,4 polyisoprene (PI), with up to 20 wt % single-wall carbon nanotubes (SWCNTs), has been cross-linked by high pressure and high temperature (HP&HT) treatment at 513 K and pressures in the range 0.5 to 1.5 GPa to yield densified network polymer composites. A composite with 5 wt % SWCNTs showed 2.2 times higher tensile strength σUTSUTS = 17 MPa), 2.3 times higher Young’s modulus E (E = 220 MPa) and longer extension at break than pure PI. The improvement is attributed to SWCNT reinforcement and improved SWCNT−PI interfacial contact as a result of the HP&HT cross-linking process, and reduced brittleness despite a higher measured cross-link density than that of pure PI. The latter may originate from an effect similar to crazing, i.e., bridging of microcracks by polymer fibrils. We surmise that the higher cross-link densities of the composites are due mainly to physical cross-links/constraints caused by the SWCNT−PI interaction, which also reflects the improved interfacial contact, and that the CNTs promote material flow by disrupting an otherwise chemically cross-linked network. We also deduce that the PI density increase at HP&HT cross-linking is augmented by the presence of CNTs.

Place, publisher, year, edition, pages
American Chemical Society, 2010
Identifiers
urn:nbn:se:umu:diva-38842 (URN)10.1021/ma101484e (DOI)000281883000035 ()
Available from: 2011-01-03 Created: 2011-01-03 Last updated: 2018-06-08Bibliographically approved
Yu, J., Tonpheng, B. & Andersson, O. (2010). Thermal conductivity and heat capacity of a nylon-6/multi-wall carbon nanotube composite under pressure. In: A. D'Amore, Domenico Acierino and Luigi Grassia (Ed.), AIP Conference Proceedings: . Paper presented at Fifth international conference on times of polymers (TOP) and composites, Ischia (Italy), 20–23 June, 2010 (pp. 145-147). American Institute of Physics, 1255(1)
Open this publication in new window or tab >>Thermal conductivity and heat capacity of a nylon-6/multi-wall carbon nanotube composite under pressure
2010 (English)In: AIP Conference Proceedings / [ed] A. D'Amore, Domenico Acierino and Luigi Grassia, American Institute of Physics , 2010, Vol. 1255, no 1, p. 145-147Conference paper, Published paper (Refereed)
Abstract [en]

The thermal conductivity, κ, of nylon-6 increased 22% whereas the heat capacity per unit volume, ρcp, decreased 10% by adding 2.1 wt% Multi-Wall Carbon Nanotubes MWCNTs. Simultaneously, the glass transition temperature, Tg, which was detected as a weak sigmoidal increase in ρcp and a decrease in dκ/dT, increased 11 K. These results show that the MWCNTs-nylon-6 interaction restricts the segmental mobility of nylon-6 and decreases cp of nylon-6.

Place, publisher, year, edition, pages
American Institute of Physics, 2010
Series
AIP Conference Proceedings, ISSN 0094-243X
Keywords
thermal conductivity, carbon nanotubes, glass transition, polymer blends, transmission electron microscopy
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-38808 (URN)10.1063/1.3455559 (DOI)000283528400048 ()9780735408043 (ISBN)
Conference
Fifth international conference on times of polymers (TOP) and composites, Ischia (Italy), 20–23 June, 2010
Note

Vol 1255 issue 1.

Available from: 2011-01-03 Created: 2011-01-02 Last updated: 2018-06-08Bibliographically approved
Tonpheng, B., Yu, J. & Andersson, O. (2009). Thermal conductivity, heat capacity, and cross-linking of polyisoprene/single-wall carbon nanotube composites under high pressure. Macromolecules, 42(23), 9295-9301
Open this publication in new window or tab >>Thermal conductivity, heat capacity, and cross-linking of polyisoprene/single-wall carbon nanotube composites under high pressure
2009 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 42, no 23, p. 9295-9301Article in journal (Refereed) Published
Abstract [en]

Polyisoprene (PI)/single-wall carbon nanotube (SWCNT) composites and pure PI have been cross-linked by high-pressure treatment to yield densified elastomeric states. Simultaneously, the SWCNT and cross-linked-induced changes of the thermal conductivity, heat capacity per unit volume, and glass transition were investigated by in situ measurements. The thermal conductivity of both the elastomeric and liquid PI improves ≈120% by the addition of 5 wt % SWCNT filler. The SWCNT filler (5 wt %) increases the glass-transition temperature of liquid PI by ≈7 K and that of the elastomeric state by as much as 12 K, which is due to a filler-induced increase in the cross-link density. Moreover, the 5 wt% filler yields a heat capacity decrease by ≈30% in both the glassy and liquid/elastomeric states, which indicates that SWCNTs cause a remarkably large reduction of both the vibrational and configurational heat capacity of PI. Finally, the consequences of high-pressure densification and the possibilities this provides to help elucidating the nature of the heat conduction in polymer/carbon nanotube composites are discussed.

Place, publisher, year, edition, pages
American Chemical Society, 2009
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-30449 (URN)10.1021/ma902122u (DOI)
Available from: 2009-12-25 Created: 2009-12-25 Last updated: 2018-06-08Bibliographically approved
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