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- ItemColloidal Self-Assembly Concepts for Plasmonic Metasurfaces(Weinheim : Wiley-VCH, 2019) Mayer, Martin; Schnepf, Max J.; König, Tobias A.F.; Fery, AndreasMetallic nanostructures exhibit strong interactions with electromagnetic radiation, known as the localized surface plasmon resonance. In recent years, there is significant interest and growth in the area of coupled metallic nanostructures. In such assemblies, short- and long-range coupling effects can be tailored and emergent properties, e.g., metamaterial effects, can be realized. The term “plasmonic metasurfaces” is used for this novel class of assemblies deposited on planar surfaces. Herein, the focus is on plasmonic metasurfaces formed from colloidal particles. These are formed by self-assembly and can meet the demands of low-cost manufacturing of large-area, flexible, and ultrathin devices. The advances in high optical quality of the colloidal building blocks and methods for controlling their self-assembly on surfaces will lead to novel functional devices for dynamic light modulators, pulse sharpening, subwavelength imaging, sensing, and quantum devices. This progress report focuses on predicting optical properties of single colloidal building blocks and their assemblies, wet-chemical synthesis, and directed self-assembly of colloidal particles. The report concludes with a discussion of the perspectives toward expanding the colloidal plasmonic metasurfaces concept by integrating them with quantum emitters (gain materials) or mechanically responsive structures. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemEffects of (complementary) polyelectrolytes characteristics on composite calcium carbonate microparticles properties(Bucureşti : [Verlag nicht ermittelbar], 2017) Mic, Cristian Barbu; Mihai, Marcela; Varganici, Cristian Dragos; Schwarz, Simona; Scutaru, Dan; Simionescu, Bogdan C.This study follows the possibility to tune the thermal stability of some CaCO3/polymer composites by crystal growth from supersaturated solutions controlled by polymer structure or by using nonstoichiometric polyelectrolyte complexes (NPECs). As the ratio between the organic and inorganic parts in the composites controls the Ca2+/polymer network crosslinking density, the CaCO3/polymer weight ratio was kept constant at 50/1, varying the initial concentration of the polyanions solutions (0.05 or 0.06 wt.%), the NPECs molar ratio , n+/n- (0.2 or 0.4), or the inorganic precursors concentration (0.25 or 0.3 M). Poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid) (PSA) and chondroitin-4-sulfate (CSA) were used as polyanions. Some NPEC dispersions, prepared with the same polyanions and poly(allylamine hydrochloride) (PAH), were also used for calcium carbonate crystallization. The characteristics of the prepared composites were investigated by scanning electron microscopy (SEM), flow particle image analysis (FPIA), particles charge density (CD), zeta-potential (ZP). The thermal stability of the composite particles was investigated as compared to bare CaCO3 microparticles prepared at the same initial inorganic concentrations.
- ItemBenzoyl side-chains push the open-circuit voltage of PCDTBT/PCBM solar cells beyond 1 V(Amsterdam [u.a.] : Elsevier Science, 2017) Lombeck, Florian; Müllers, Stefan; Komber, Hartmut; Menke, S. Matthew; Pearson, Andrew J.; Conaghan, Patrick J.; McNeill, Christopher R.; Friend, Richard H.; Sommer, MichaelThe synthesis, characterization and solar cell performance of PCDTBT and its highly soluble analogue hexyl-PCDTBT with cross-conjugated benzoyl moieties at the carbazole comonomer are presented. Through the use of both model reactions and time-controlled microwave-assisted Suzuki polycondensation, the base-induced cleavage of the benzoyl group from the polymer backbone has been successfully suppressed. Compared to the commonly used symmetrically branched alkyl motif, the benzoyl substituent lowers the energy levels of PCDTBT as well as the band gap, and consequently increases energy of the charge transfer state in blends with PC71BM. As a result, photovoltaic diodes with high-open circuit voltage of above 1 V are realized.
- ItemScreening of Different Carbon Nanotubes in Melt-Mixed Polymer Composites with Different Polymer Matrices for Their Thermoelectrical Properties(Basel : MDPI, 2019-12-7) Krause, Beate; Barbier, Carine; Levente, Juhasz; Klaus, Maxim; Pötschke, PetraThe aim of this study is to reveal the influences of carbon nanotube (CNT) and polymer type as well as CNT content on electrical conductivity, Seebeck coefficient (S), and the resulting power factor (PF) and figure of merit (ZT). Different commercially available and laboratory made CNTs were used to prepare melt-mixed composites on a small scale. CNTs typically lead to p-type composites with positive S-values. This was found for the two types of multi-walled CNTs (MWCNT) whereby higher Seebeck coefficient in the corresponding buckypapers resulted in higher values also in the composites. Nitrogen doped MWCNTs resulted in negative S-values in the buckypapers as well as in the polymer composites. When using single-walled CNTs (SWCNTs) with a positive S-value in the buckypapers, positive (polypropylene (PP), polycarbonate (PC), poly (vinylidene fluoride) (PVDF), and poly(butylene terephthalate) (PBT)) or negative (polyamide 66 (PA66), polyamide 6 (PA6), partially aromatic polyamide (PARA), acrylonitrile butadiene styrene (ABS)) S-values were obtained depending on the matrix polymer and SWCNT type. The study shows that the direct production of n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients is possible. The highest Seebeck coefficients obtained in this study were 66.4 µV/K (PBT/7 wt % SWCNT Tuball) and −57.1 µV/K (ABS/0.5 wt % SWCNT Tuball) for p-and n-type composites, respectively. The highest power factor and ZT of 0.28 µW/m·K2 and 3.1 × 10−4, respectively, were achieved in PBT with 4 wt % SWCNT Tuball.
- ItemRheological properties of low-density polyethylene filled with hydrophobic Co(Ni)-Al layered double hydroxides(São Carlos : [Associação Brasileira de Polímeros], 2019) Jaerger, Silvia; Leuteritz, Andreas; Alves de Freitas, Rilton; Wypych, FernandoCobalt/aluminum and nickel/aluminum layered double hydroxide (LDH - M +2 :Al molar ratio of 3:1) were intercalated with dodecylsulphate (DDS), laurate (LAU), stearate (STE) and palmitate (PAL) and used as filler in low-density polyethylene (LDPE) in percentages between 0.2 and 7.0wt%. After injection molding, the samples were submitted to morphological characterization by scanning electron microscopy (SEM), analysis of thermal behavior by differential scanning calorimetry (DSC) and investigation of rheological properties. All Co/Al-LDPE samples showed the formation of a high temperature polymer crystal domain, induced by the LDH filler. The rheological properties indicated in general a reduction of shear modulus due to incompatibility between some regions of LDH and LDPE, which promoted phase separation. However, interaction with the LDH surface indicated higher affinity of the Ni/Al-LDH for the LDPE compared to Co/Al-LDH, forming permanent networks. © 2019 Associacao Brasileira de Polimeros. All Rights Reserved.
- ItemMetal Plastic Hybrids: Optimisation in model experiments [Metall-Kunststoff-Verbunde: Modellversuche zur Optimierung](Weinheim : Wiley-VCH, 2019) Bräuer, M.; Edelmann, M.; Lehmann, D.; Tuschla, M.Metal plastic hybrids will become more important as components for lightweight constructions. It is reported about optimisation of making three layer hybrids consisted of a steel plate, an adhesion layer based of uretdione powder coating material and a flexible component polyurethane in model experiments. Hybrid formation is performed in a compression moulding process. The adhesion layer and the polyurethane are modified to increase the hybrid bond strength. Peel test are conducted to quantitatively characterize the bond strength and an apparent energy release rate is calculated based on the peel force. For hybrids with widths of 2 mm polyurethane stripes it is possible to increase the apparent energy release rate for about 30 % to 16 N/mm in comparison with a hybrid with unmodified components. These hybrids have the same high bond strength level as the strongest hybrids reported in literature. Concluding the optimisation results are discussed related to their relevancy for the interpretation of the adhesion mechanisms in the interface between adhesion layer and polyurethane. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemElectrical and thermal properties of polyamide 12 composites with hybrid fillers systems of multiwalled carbon nanotubes and carbon black(Barking : Elsevier, 2011) Socher, Robert; Krause, Beate; Hermasch, Sylvia; Wursche, Roland; Pötschke, PetraHybrid filler systems of multiwalled carbon nanotubes (MWCNTs) and carbon black (CB) were incorporated into two types of polyamide 12 (PA12) using small-scale melt mixing in order to identify potential synergistic effects on the interaction of these two electrical conductive fillers. Although no synergistic effects were observed regarding the electrical percolation threshold, at loadings well above the percolation threshold higher volume conductivities were obtained for samples containing both, MWCNT and CB, as compared to single fillers. This effect was more pronounced when using a higher viscous PA12 matrix. The formation of a co-supporting network can be assumed. The combined use of CB and MWCNTs improved the macrodispersion of MWCNT agglomerates, which can be assigned as a synergistic effect. DSC measurements indicated an effect of the nanofiller on crystallisation temperatures of PA12; however this was independent of the kind or amount of the carbon nanofiller. © 2011 Elsevier Ltd.
- ItemUltralow percolation threshold in polyamide 6.6/MWCNT composites(Barking : Elsevier, 2015) Krause, Beate; Boldt, Regine; Häußler, Liane; Pötschke, PetraWhen incorporating multiwalled carbon nanotubes (MWCNTs) synthesised by the aerosol-CVD method using different solvents into polyamide 6.6 (PA66) by melt mixing an ultralow electrical percolation threshold of 0.04. wt.% was found. This very low threshold was assigned to the specific characteristic of the MWCNTs for which a very high aspect ratio, a good dispersability in aqueous surfactant dispersions, and relatively low oxygen content near the surface were measured. The investigation of the composites by transmission electron microscopy on ultrathin cuts as well as by scanning electron microscopy combined with charge contrast imaging on compression moulded plates illustrated a good MWCNT dispersion within the PA66 matrix and that the very high aspect ratio of the nanotubes remained even after melt processing. Additionally, the thermal behaviour of the PA66 composites was investigated using differential scanning calorimetry (DSC) showing that the addition of only 0.05. wt.% MWCNT leads to an increase of the onset crystallization temperature of 11. K.
- ItemInfluence of dry grinding in a ball mill on the length of multiwalled carbon nanotubes and their dispersion and percolation behaviour in melt mixed polycarbonate composites(Barking : Elsevier, 2011) Krause, Beate; Villmow, Tobias; Boldt, Regine; Mende, Mandy; Petzold, Gudrun; Pötschke, PetraBall milling of carbon nanotubes (CNTs) in the dry state is a common way to produce tailored CNT materials for composite applications, especially to adjust nanotube lengths. For NanocylTM NC7000 nanotube material before and after milling for 5 and 10h the length distributions were quantified using TEM analysis, showing decreases of the mean length to 54% and 35%, respectively. With increasing ball milling time in addition a decrease of agglomerate size and an increase of packing density took place resulting in a worse dispersability in aqueous surfactant solutions. In melt mixed CNT/polycarbonate composites produced using masterbatch dilution step, the electrical properties, the nanotube length distribution after processing, and the nano- and macrodispersion of the nanotubes were studied. The slight increase in the electrical percolation threshold in the melt mixed composites with ball milling time of CNTs can be assigned to lower nanotube lengths as well as the worse dispersability of the ball milled nanotubes. After melt compounding, the mean CNT lengths were shortened to 31%, 50%, and 66% of the initial lengths of NC7000, NC7000-5h, and NC7000-10h, respectively. © 2011 Elsevier Ltd.
- ItemCellulose-carbon nanotube composite aerogels as novel thermoelectric materials(Amsterdam [u.a.] : Elsevier, 2018) Gnanaseelan, Minoj; Chen, Yian; Luo, Jinji; Krause, Beate; Pionteck, Jürgen; Pötschke, Petra; Qu, HaisongThermoelectric materials based on cellulose/carbon nanotube (CNT) nanocomposites have been developed by a facile approach and the effects of amount (2–10 wt%) and types of CNTs (single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs)) on the morphology (films and aerogels) and the thermoelectric properties of the nanocomposites have been investigated. Composite films based on SWCNTs showed significantly higher electrical conductivity (5 S/cm at 10 wt%) and Seebeck coefficient (47.2 μV/K at 10 wt%) compared to those based on MWCNTs (0.9 S/cm and 11 μV/K, respectively). Lyophilization, leading to development of aerogels with sub-micron sized pores, decreased the electrical conductivity for both types by one order of magnitude, but did not affect the Seebeck coefficient of MWCNT based nanocomposites. For SWCNT containing aerogels, higher Seebeck coefficients than for films were measured at 3 and 4 wt% but significantly lower values at higher loadings. CNT addition increased the thermal conductivity from 0.06 to 0.12 W/(m∙K) in the films, whereas the lyophilization significantly reduced it towards values between 0.01 and 0.09 W/(m∙K) for the aerogels. The maximum Seebeck coefficient, power factor, and ZT observed in this study are 49 μV/K for aerogels with 3 wt% SWCNTs, 1.1 μW/(m∙K2) for composite films with 10 wt% SWCNTs, and 7.4 × 10−4 for films with 8 wt% SWCNTs, respectively.