Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 10) Show all publications
Liu, D., Pallon, L. K. H., Pourrahimi, A. M., Zhang, P., Diaz, A., Holler, M., . . . Gedde, U. W. (2017). Cavitation in strained polyethylene/aluminium oxide nanocomposites. European Polymer Journal, 87, 255-265
Open this publication in new window or tab >>Cavitation in strained polyethylene/aluminium oxide nanocomposites
Show others...
2017 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, p. 255-265Article in journal (Refereed) Published
Abstract [en]

The incorporation of metal oxide (e.g. Al2O3) nanoparticles has a pronounced positive effect on low-density polyethylene (LDPE) as an insulating material for high-voltage direct-current (HVDC) cables, the electrical conductivity being decreased by one to two orders of magnitude and charge species being trapped by the nanoparticles. The risk of debonding between the nanoparticles and the polymer matrix leading to electrical treeing via electrical discharges in the formed cavities was the motivation for this study. Scanning electron microscope (SEM), small-angle X-ray scattering (SAXS) and X-ray ptychographic tomography were used to study a series of LDPE nanocomposites which contained Al2O3 nanoparticles treated with silanes having terminal alkyl groups of different lengths (methyl, octyl and octadecyl). When specimens were subjected to a tensile strain (a typical specimen stretched beyond the onset of necking consisted of three zones according to SEM of specimens that were studied after removal of the external force: an essentially cavitation-free zone with low local plastic strain, a transitional zone in which local plastic strain showed a marked increase and the revealed concentration of permanent cavities increased with increasing plastic strain and a highly strained zone with extensive cavitation), the cavitation occurred mainly at the polymer-nanoparticle interface according to SEM and X-ray ptychographic tomography and according to SEM progressed with increasing plastic strain through an initial phase with no detectable formation of permanent cavities to a period of very fast cavitation and finally almost an order of magnitude slower cavitation. The polymer/nanoparticle interface was fractal before deformation, as revealed by the profile of the Porod region in SAXS, presumably due to the existence of bound polymers at the nanoparticle surface. A pronounced decrease in the interface fractal dimension was observed when the strain exceeded a critical value; a phenomenon attributed to the stress-induced de-bonding of nanoparticles. The strain-dependence of the interface fractal dimension value at low strain levels between composites containing differently treated nanoparticles seems to be an indicator of the strength of the nanoparticle-polymer interface.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Aluminium oxide, Cavitation, Low-density polyethylene, Nanocomposites, Aluminum, DC power transmission, Electric discharges, Fractal dimension, Fractals, HVDC power transmission, Low density polyethylenes, Metal nanoparticles, Metals, Nanoparticles, Plastic deformation, Polyethylenes, Scanning electron microscopy, Silanes, Tomography, X ray scattering, Electrical conductivity, Electrical discharges, Fractal-dimension value, High voltage direct current, Low density polyethylene(LDPE), Nanoparticle surface, Polymer nanoparticles, Tensile strain
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-201939 (URN)10.1016/j.eurpolymj.2016.12.021 (DOI)000395210900022 ()2-s2.0-85008230710 (Scopus ID)
Note

Funding text: The Swedish Foundation for Strategic Research (grant EM11-0022) is thanked for the financial support.

QC 20170307

Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2017-11-29Bibliographically approved
Liu, D., Hoang, A. T., Pourrahimi, A. M., Pallon, L. K. H., Nilsson, F., Gubanski, S. M., . . . Gedde, U. W. (2017). Influence of Nanoparticle Surface Coating on Electrical Conductivity of LDPE/Al2O3 Nanocomposites for HVDC Cable Insulations. IEEE transactions on dielectrics and electrical insulation, 24(3), 1396-1404
Open this publication in new window or tab >>Influence of Nanoparticle Surface Coating on Electrical Conductivity of LDPE/Al2O3 Nanocomposites for HVDC Cable Insulations
Show others...
2017 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 24, no 3, p. 1396-1404Article in journal (Refereed) Published
Abstract [en]

LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al2O3 nanocomposites. Al2O3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, n-octyl and n-octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m(-3,) indicating substantial porosity in the coating. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbor particle distance. The electrical conductivity of the nanocomposites was determined at both 40 and 60 degrees C. The results show that an appropriate surface coating on the nanoparticles allowed uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. The composites based on the most porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
HVDC cable insulation, LDPE/aluminum oxide nanocomposites, particle coating chemistry, particle dispersion, electrical conductivity
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-211613 (URN)10.1109/TDEI.2017.006310 (DOI)000405000300012 ()2-s2.0-85022181728 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

QC 20170810

Available from: 2017-08-10 Created: 2017-08-10 Last updated: 2017-08-11Bibliographically approved
Hoang, A. T., Pallon, L., Liu, D., Serdyuk, Y. V., Gubanski, S. M. & Gedde, U. W. (2016). Charge transport in LDPE nanocomposites part I-experimental approach. Polymers, 8(3), 1-19
Open this publication in new window or tab >>Charge transport in LDPE nanocomposites part I-experimental approach
Show others...
2016 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 8, no 3, p. 1-19Article in journal (Refereed) Published
Abstract [en]

This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene and its nanocomposites filled with uncoated MgO and Al2O3, with the aim to highlight the effect of the nanofillers on charge transport processes. Material samples at various filler contents, up to 9 wt %, were prepared in the form of thin films. The performed measurements show a significant impact of the nanofillers on reduction of material's direct current (dc) conductivity. The investigations thus focused on the nanocomposites having the lowest dc conductivity. Various mechanisms of charge generation and transport in solids, including space charge limited current, Poole-Frenkel effect and Schottky injection, were utilized for examining the experimental results. The mobilities of charge carriers were deduced from the measured surface potential decay characteristics and were found to be at least two times lower for the nanocomposites. The temperature dependencies of the mobilities were compared for different materials.

Place, publisher, year, edition, pages
MDPI AG, 2016
Keywords
Charge carrier mobility, Charge transport, dc conductivity, Low-density polyethylene, Nanocomposites, Trap depth
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-187223 (URN)10.3390/polym8030087 (DOI)000373711700034 ()2-s2.0-84963974333 (Scopus ID)
Funder
Swedish Foundation for Strategic Research
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-18 Last updated: 2017-11-30Bibliographically approved
Liu, D. (2016). Polyethylene – metal oxide particle nanocomposites for future HVDC cable insulation: From interface tailoring to designed performance. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Polyethylene – metal oxide particle nanocomposites for future HVDC cable insulation: From interface tailoring to designed performance
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Low-density polyethylene (LDPE) nanocomposites containing metal oxide nanoparticles are considered as promising candidates for insulating materials in future high-voltage direct-current (HVDC) cables. The significant improvement in dielectric properties compared with unfilled polymer is attributed to the large and active interface between the nanoparticles and the polymer. The nanoparticles may also initiate cavitation under stress and potential accelerated aging risks due to the adsorption and inactivation of the protecting antioxidants. This study is focused on the possibilities of achieving well-balanced performances of the polyethylene nanocomposites for HVDC insulation via tailoring the particle interface in the nanocomposites.

A facile and versatile surface coating method for metal oxide particles was developed based on silane chemistry. The developed method was successfully applied to 8.5 nm Fe3O4, 25 nm ZnO and 50 nm Al2O3 particles, with the aim to develop uniform coatings that universally could be applied on individual particles rather than aggregates of particles. The surface properties of the coatings were further tailored by applying silanes with terminal alkyl groups of different lengths, including methyl (C1-), octyl (C8-) and octadecyl (C18-) units. Transmission electron microscopy, infrared spectroscopy and thermal gravimetric analysis confirmed the presence of uniform coatings on the particle surface and importantly the coatings were found to be highly porous.

The capacity of metal oxide particles to adsorb relevant polar species (e.g. moisture, acetophenone, cumyl alcohol and phenolic antioxidant) was further assessed due to its potential impact on electrical conductivity and long-term stability of the nanocomposites. The oxidative stability of the nanocomposites was affected by the adsorption of phenolic antioxidants on particles and transfer of catalytic impurities (ionic species) from metal oxide particles to polymer matrix. It was found that carefully coated metal oxide particles had much less tendency to adsorb antioxidants. They could, however, adsorb moisture, acetophenone and cumyl alcohol. The coated particles did not emit any destabilizing ionic species into the polymer matrix. 

The inter-particle distance of the nanocomposites based on C8-coated nanoparticles showed only a small deviation from the ideal, theoretical value, indicating a good particle dispersion in the polymer. Scanning electron microscopy of strained nanocomposite samples suggested the cavitation mainly occurred at the polymer/nanoparticles interface. The microstructural changes at polymer/nanoparticle interface were studied by small-angle X-ray scattering coupled with tensile testing. The polymer/nanoparticle interface was fractal before deformation due to the existence of the bound polymers at the nanoparticle surface. Extensive de-bonding of particles and cavitation were observed when the nanocomposites were stretched beyond a critical strain. It was found that the composites based on carefully coated particles showed higher strain at cavitation than the composites based on uncoated particles. The composites based on C8-coated nanoparticles showed the largest decrease in electrical conductivity and the lowest temperature coefficient of the electrical conductivity among the composite samples studied.

Abstract [sv]

Nanokompositer av polyeten anses vara de mest lovande materialen för isolering av framtidens högspänningskablar (HVDC-kablar). De avsevärda förbättringarna i dielektriska egenskaper jämfört med ren polyeten kan härledas till den stora aktiv nanopartikelytan som existerar mellan partiklarna och polymermatrisen. Tillsatsen av nanopartiklar till polymeren kan dock även leda till ojämn spridning av partiklarna, där aggregat kan fungera som startpunkter för bildning av hålrum som skapas vid partikelytorna då materialen utsätts för mekaniska påfrestningar, samt accelererad åldringsbenägenhet på grund av potentiell lokal ansamling polyetens stabilisatorer vid partikelytorna. Detta arbete har fokuserats runt möjligheterna att skapa nanokompositer för HVDC-isolering med optimerad prestanda som relaterad till partikelytorna i nanokompositerna.

En metod för ytbehandling av metalloxidpartiklarna har utvecklats utifrån silankemi med fokus på användarvänlighet. Metoden tillät framgångsrik kondensering av silaner på 8.5 nm Fe3O4, 25 nm ZnO and 50 nm Al2O3 partiklar, och resulterade ytmodifiering av individuella partiklar snarare än aggregat. Ytegenskaperna hos partiklarna kunde därefter skräddarsys till att innefatta olika funktionella alkylgrupper med varierande längder från metyl (C1-), octyl (C8-) till octadecyl (C18-) enheter. Mikroskopi, infraröd spektroskopi samt termogravimetrisk analys bekräftade ytmodifieringarna resulterade i jämntjocka ytbeläggningar av individuella partiklar, medan molekylsimuleringar och densitetsvärden avslöjade att ytbeläggningarna visade hög porositet.

Metallpartiklarnas förmåga att adsorbera polära molekylstrukturer (fukt (H2O), acetofenon, kumylalkohol och fenoliska antioxidanter) utvärderades på grund av dess möjliga inverkan på elektrisk ledningsförmåga och långtidsstabilitet hos nanokompositerna. Stabiliteten gentemot oxidations visade sig var påverkad av adsorptionen av antioxidanter på partikelytorna, samt migration av katalyserande orenheter från partiklar till polymermatris. De modifierade partiklar var dock mindre benägna att adsorbera antioxidanter, men visade fortfarande adsorption av fukt, acetofenon och kumylalkohol. De ytmodifierade partiklarna bedömdes därför mindre benägna att inverka negativt på stabiliteten hos polymermatrisen.

Partikelavstånden mellan partiklarna i kompositerna baserade på C8-funktionaliserade nanopartiklar visade sig endast avvika obetydligt från det beräknade teoretiska värdet, vilket indikerade närmast en ideal dispergeringen av partiklarna. Svepelektronmikroskopi (SEM) av kompositer som utsatts för töjning visade att hålrumsbildningen främst uppstod i gränsytan mellan polymer/nanopartiklar. Förändringar av mikrostrukturen hos kompositerna studerades även med långvinkelröntgen (SAXS - small-angle X-ray) i kombination med dragprovning. Gränskiktet mellan polymer och nanopartikel hade en fraktalstruktur före deformationen på grund av närvaron av bunden polymer på nanopartikelytan. Sprickbildningen och utvecklingen av hålrum runt partiklarna kunde mest tydligt observeras när kompositerna hade sträckts mer än till en viss kritisk töjningsgräns, vilket även bekräftade att hålrumsbildningen uppstod vid högre töjningsvärden då partiklarna var ytmodifierade, i jämförelse med omodifierade partiklar. Kompositerna som framställts med C8-funktionalisering av nanopartiklarna visade den största sänkningen av ledningsförmågan och den lägsta temperatur koefficienten i elektrisk ledningsförmåga bland samtliga kompositer som utvärderats.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. p. 48
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:28
Keywords
HVDC, electrical insulation, core-shell nanoparticles, surface modification, silane chemistry, nanocomposites, polyethylene, adsorption, long-term stability, interface, particle dispersion, cavitation, conductivity, HVDC, elektrisk isolation, ytmodifiering, silankemi, nanokompositer, polyeten, adsorption, långtidsstabilitet, ytskikt, partikeldispergering, kavitation, ledningsförmåga
National Category
Textile, Rubber and Polymeric Materials
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-192355 (URN)978-91-7729-054-4 (ISBN)
External cooperation:
Public defence
2016-09-30, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

QC 20160915

Available from: 2016-09-15 Created: 2016-09-09 Last updated: 2016-09-15Bibliographically approved
Liu, D. (2015). Functional polyethylene-aluminum oxide nanocomposites for insulation materials in high-voltage direct-current (HVDC) cables. (Licentiate dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Functional polyethylene-aluminum oxide nanocomposites for insulation materials in high-voltage direct-current (HVDC) cables
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. p. IX, 33
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:27
Keywords
HVDC cables, high voltage insulation materials, Fe3O4 core-shell nanoparticles; Silane/silsesquioxane; Stöber surface modification; Al2O3 nanoparticles; Polyethylene; Aluminium oxide; Nanocomposites; Interfacial adhesion; Particle dispersion, Mechanical properties
National Category
Textile, Rubber and Polymeric Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-168235 (URN)978-91-7595-582-7 (ISBN)
Presentation
2015-06-09, D3, Lindstedtsvägen 5, Stockholm, 09:30 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

qc 20150529

Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2015-05-29Bibliographically approved
Liu, D., Pourrahimi, A. M., Olsson, R. T., Hedenqvist, M. & Gedde, U. (2015). Influence of nanoparticle surface treatment on particle dispersion and interfacial adhesion in low-density polyethylene/aluminium oxide nanocomposites. European Polymer Journal, 66, 67-77
Open this publication in new window or tab >>Influence of nanoparticle surface treatment on particle dispersion and interfacial adhesion in low-density polyethylene/aluminium oxide nanocomposites
Show others...
2015 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 66, p. 67-77Article in journal (Refereed) Published
Abstract [en]

The effect of silsesquioxane coating of aluminium oxide nanoparticles on their dispersion and on the interfacial strength between nanoparticles and polymer matrix in low-density polyethylene composites was studied. The surface chemistry of the nanoparticles was tailored from hydroxyl groups to alkyl groups with different lengths by reacting methyltrimethoxysilane (C1), octyltriethoxysilane (C8) or octadecyltrimethoxysilane (C18) with aluminium oxide nanoparticles. The core–shell structure of the coated nanoparticles was assessed by transmission electron microscopy, infrared spectroscopy and thermogravimetry. The inter-particle distance of the nanocomposite based on C8-coated nanoparticles showed only a small deviation from the ideal value, indicating a very good particle dispersion in the polymer. The interfacial adhesion between nanoparticles and matrix was determined by stretching nanocomposite specimens in a tensile testing machine to strains well beyond the yield point. A drop in the stress–strain curve indicated the onset of cavitation and necking in the nanocomposites. Samples stretched to different strain levels were studied by scanning electron microscopy and the cavitation was found to be confined to particle interfaces. The composite based on C18-coated nanoparticles showed the highest strain at cavitation/necking suggesting a high interfacial adhesion between nanoparticles and polymer.

National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-168256 (URN)10.1016/j.eurpolymj.2015.01.046 (DOI)000353854000007 ()2-s2.0-84922811618 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

QC 20150529

Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2017-12-04Bibliographically approved
Kang, J., Li, X., Xiong, B., Liu, D., Chen, J., Yang, F., . . . Xiang, M. (2015). Investigation on the Tensile Behavior and Morphology Evolution of Isotactic Polypropylene Films Polymerized with Different Ziegler-Natta Catalysts. Advances in Polymer Technology
Open this publication in new window or tab >>Investigation on the Tensile Behavior and Morphology Evolution of Isotactic Polypropylene Films Polymerized with Different Ziegler-Natta Catalysts
Show others...
2015 (English)In: Advances in Polymer Technology, ISSN 0730-6679, E-ISSN 1098-2329Article in journal (Refereed) Published
Abstract [en]

Stereodefect distribution is very important in determining the morphology and properties of isotactic polypropylene (iPP). In this study, two iPPs (PP-A and PP-B) with different uniformities of stereodefect distribution were prepared. The tensile behavior and morphology evolution of their cast films were studied. The morphology study of the cast films showed that compared with PP-B, PP-A with less uniform distribution of stereodefects has smaller spherulites and spheruilitic boundaries and higher degree of crystallinity. In uniaxial tensile measurements, PP-A exhibited higher yield strength and lower elongation at break. When strain was 500%, PP-A exhibits totally transparent appearance and highly oriented structures without cavities, whereas PP-B shows opaque appearance and mass of both nanometer- and micrometer-sized cavities. Moreover, calculation of rigid amorphous fraction (RAF) indicated that PP-B cast film has a higher amount of RAF, which might be the reason for the different morphology evolutions and tensile behaviors of the samples.

National Category
Paper, Pulp and Fiber Technology Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-174690 (URN)10.1002/adv.21573 (DOI)000394817600004 ()2-s2.0-84939838993 (Scopus ID)
Note

QC 20151113

Available from: 2015-11-13 Created: 2015-10-07 Last updated: 2017-12-01Bibliographically approved
Liu, D., Pourrahimi, A. M., Pallon, L. K. H., Andersson, R. L., Hedenqvist, M. S., Gedde, U. & Olsson, R. T. (2015). Morphology and properties of silica-based coatings with different functionalities for Fe3O4, ZnO and Al2O3 nanoparticles. RSC Advances, 5(59), 48094-48103
Open this publication in new window or tab >>Morphology and properties of silica-based coatings with different functionalities for Fe3O4, ZnO and Al2O3 nanoparticles
Show others...
2015 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 59, p. 48094-48103Article in journal (Refereed) Published
Abstract [en]

A facile single-step method for obtaining 2–3 nm thick silsesquioxane coatings on metal oxide nanoparticles using different carbon-functional silane precursors is presented. Iron oxide nanoparticles 8.5 nm in diameter were used as a model to evaluate the possibilities of forming different uniform carbon-functional coatings, ranging from hydrophobic to hydrophilic in character. Electron microscopy showed that all the coated nanoparticles could be described as core-shell nanoparticles with single Fe3O4 cores and carbon-functional silsesquioxane shells, without any core-free silicone oxide phase. Steric factors strongly influenced the deposited silicon oxide precursors with octyl-, methyl- or aminopropyl functionalities, resulting in coating densities ranging from 260 to 560 kg/m3. The methyl-functional coatings required several layers of silsesquioxane, 3–4, to build up the 2 nm structures, whereas only 1-2 layers were required for silsesquioxane with octyl groups. Pure silica coatings from tetraethoxysilanes were however considerably thicker due to the absence of steric hindrance during deposition, allowing the formation of 5–7 nm coatings of ca. 10 layers. The coating method developed for the iron oxide nanoparticles was generic and successfully transferred and up–scaled 30 and 325 times (by volume) to be applicable to 25 nm ZnO and 45 nm Al2O3 nanoparticles.

National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-168258 (URN)10.1039/C5RA04452A (DOI)000355703700096 ()2-s2.0-84930623622 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

Updated from "Submitted" to "Published". QC 20150703

Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2017-12-04Bibliographically approved
Kang, J., Xiong, B., Liu, D., Cao, Y., Chen, J., Yang, F. & Xiang, M. (2014). Understanding in the morphology and tensile behavior of isotactic polypropylene cast films with different stereo-defect distribution. Journal of polymer research, 21(6), 485
Open this publication in new window or tab >>Understanding in the morphology and tensile behavior of isotactic polypropylene cast films with different stereo-defect distribution
Show others...
2014 (English)In: Journal of polymer research, ISSN 1022-9760, E-ISSN 1572-8935, Vol. 21, no 6, p. 485-Article in journal (Refereed) Published
Abstract [en]

In this study, two iPP resins with similar molecular weight and average isotacticity but different uniformities of stereo-defect distribution were used in the production of cast films. The crystalline morphology and orientation, and tensile behavior during room temperature stretching of the cast films were investigated by scanning electronic microscopy (SEM), 2D-wide angle X-ray diffraction (2D-WAXD) and 2D-small-angle X-ray scattering (2D-SAXS). It was found that under fixed processing condition, iPP with more uniform stereo-defect distribution (PP2) favors the formation of row nucleated lamellar structure during cast film production, and therefore exhibiting hard-elastic deformation behavior during stretching; meanwhile, the sample with less uniform stereo-defect distribution (PP1) shows un-oriented spherulitical morphology in the cast film, and typical plastic deformation behavior during stretching. The crystallization and rheological analysis on the iPP raw materials revealed that, the uniformity of stereo-defect distribution determines the ability of nucleation and crystallization, and further influences the response of the crystalline morphology to the elongation effect of cast film production process, which is of great importance in the structure-property design in the production of iPP membranes.

Keywords
Isotactic polypropylene, Stereo-defect distribution, Morphology and orientation, Tensile behavior
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-147036 (URN)10.1007/s10965-014-0485-5 (DOI)000336396900001 ()2-s2.0-84901553939 (Scopus ID)
Note

QC 20140624

Available from: 2014-06-24 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
Pourrahimi, A. M., Liu, D., Pallon, L. K. H., Andersson, R. L., Martinez Abad, A., Lagaron, J.-M. -., . . . Olsson, R. T. (2014). Water-based synthesis and cleaning methods for high purity ZnO nanoparticles - comparing acetate, chloride, sulphate and nitrate zinc salt precursors. RSC Advances, 4(67), 35568-35577
Open this publication in new window or tab >>Water-based synthesis and cleaning methods for high purity ZnO nanoparticles - comparing acetate, chloride, sulphate and nitrate zinc salt precursors
Show others...
2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 67, p. 35568-35577Article in journal (Refereed) Published
Abstract [en]

A low temperature (60 degrees C) aqueous synthesis method of high purity ZnO nanoparticles intended as fillers for ultra-low electrical conductivity insulations is described. Particles were prepared under identical conditions from different zinc salts based on nitrate, chloride, sulphate or acetate to compare their abilities to form high yields of sub-50 nm particles with narrow size distribution. The acetate salt gave uniform 25 nm ZnO particles with a conical prism shape. The chloride and sulphate derived particles showed mixed morphologies of nanoprisms and submicron petals, whereas the nitrate salt yielded prisms assembled into well-defined flower shapes with spiky edges. The micron-sized flower shapes were confirmed by Xray diffraction to consist of the smaller prism units. Photoluminescence spectroscopy showed emission in the blue-violet region with little variation depending on precursor salt, suggesting that the spectra were dependent on the primary nanoprism formation and rather independent of the final particle morphology. Microscopy revealed that the salt residuals after the reaction showed different affinity to the particle surfaces depending on the type of salt used, with the acetate creating ca. 20 nm thick hydrated shells; and in falling order of affinity: chloride, sulphate and nitrate. An acetate ion shielding effect during the synthesis was therefore assumed, preventing nanoparticle fusion during growth. Varying the concentrations of the counter-ions confirmed the shielding and only the acetate anions showed an ability to stabilize solitary nanoprisms formation in reaction yields from 2 to 10 g L-1. Ultrasonic particle surface cleaning was significantly more efficient than water replacement, resulting in a stable aqueous dispersion with a high zeta potential of 38.9 mV at pH 8.

Keywords
Chlorine compounds, Ions, Metal nanoparticles, Morphology, Nanostructures, Nitrates, Photoluminescence spectroscopy, Prisms, Salts, Shielding, Sulfur compounds, Volatile fatty acids, X ray diffraction, Aqueous synthesis, Electrical conductivity, Identical conditions, Narrow size distributions, Particle morphologies, Shielding effect, Stable aqueous dispersions, ZnO nanoparticles
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-153415 (URN)10.1039/c4ra06651k (DOI)000341288100039 ()2-s2.0-84906544319 (Scopus ID)
Note

QC 20141008

Available from: 2014-10-08 Created: 2014-10-03 Last updated: 2017-12-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2201-2806

Search in DiVA

Show all publications