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T. Beica

Bio: T. Beica is an academic researcher. The author has contributed to research in topics: Liquid crystal & Wetting. The author has an hindex of 4, co-authored 16 publications receiving 104 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a textile was functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source, depending on the number of applied laser pulses, well separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited.
Abstract: Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases.

30 citations

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TL;DR: Optical birefringence measurements for a calamitic lyotropic liquid crystal containing sodium lauryl sulphate/decanol/water were presented in this paper, where a value of the order of 10-3 was obtained, much smaller than that of thermotropic liquid crystals.
Abstract: Optical birefringence measurements for a calamitic lyotropic liquid crystal containing sodium lauryl sulphate/decanol/water are presented. A value of the order of 10-3 was obtained, much smaller than that of thermotropic liquid crystals. The order parameter temperature dependence is evaluated using an extrapolating method and taking into accounts the influence of the micelle shape. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

20 citations

Journal ArticleDOI
TL;DR: In this article, thermogravimetric measurements were applied to study the behavior of composite systems containing a nematic liquid crystal (LC), 4-n-octyl-4′-cyanobiphenyl (8CB) and aerosil particles.
Abstract: Thermal analysis measurements were applied to study the behavior of composite systems containing a nematic liquid crystal (LC), 4-n-octyl-4′-cyanobiphenyl (8CB) and aerosil particles. The silica density ρs (g of silica per 1 cm3 of LC) was varied from 0.20 to 12 g/cm3 in order to approach the monomolecular structure of the surface layer. Thus, thermogravimetric (TG) measurements were performed to get information on the LC content of the samples. Moreover, they allowed an unusual application, to characterize the interaction of 8CB molecules with aerosil surface because the corresponding curves show multistep processes the temperatures of which depend on the silica density. Differential thermal analysis (DTA) also indicates several processes. Some of them, mostly due to desorption, are endothermal. Other processes are exothermal, and these are assigned to chemical transformations. The sample with silica density of 12 g/cm3 has no endothermal desorption peak at low temperatures, and has the highest shift for the DTA peaks. It was supposed that its surface layer has a monomolecular structure. For representative samples, TG–DTA studies were supported by FTIR investigations. Thus conventional TG–DTA techniques have provided new tools to characterize the nanocomposites. Differential scanning calorimetry gives the behavior of the phase transitions. Samples with low silica density exhibit a depression of the phase transition temperatures characteristic for the bulk 8CB while those with high silica densities do not show any phase transitions.

18 citations

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TL;DR: In this paper, experimental results for the temperature dependence of the density of propyl- cyanobiphenyl (3CB), butyl - cyanobinphoenyl (4CB), and hexyl-cyanobiphexyl (6CB) are presented.
Abstract: Experimental results for the temperature dependence of the density of propyl – cyanobiphenyl (3CB), butyl – cyanobiphenyl (4CB) and hexyl – cyanobiphenyl (6CB) are presented. The results are compared with previous results for temperature dependence of other members of the alkyl cyanobiphenyl series (nCB). The deviation of the density from linear temperature dependence is discussed in terms of the recently discovered corresponding rule for nematic liquid crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

17 citations

Journal Article
TL;DR: In this article, a polystyrene (PS) layer of ca. 50nm was spin-coated onto glass plates from a toluene solution and gold layers of 10-20nm were vacuum deposited at small incidence angle.
Abstract: In the aim to improve the adherence of the nanostructured gold layers onto glass substrate, gold deposition has been first time performed onto a polystyrene (PS) layer. The PS layer of ca. 50nm was spin-coated onto glass plates from a toluene solution. Gold layers of 10-20nm were vacuum deposited at small incidence angle. We found that at variance from the plates with gold deposited directly on the glass, the plates with an intermediate PS layer do not peel under overnight treatment in ethanol solution. The layers were characterized by several methods. X-ray diffraction (XRD) measurements showed that gold peaks have the position corresponding to the face-centered cubic structure: However, the crystallites on the sample with PS layer seem to be a little bit smaller than those with gold deposited directly onto the glass. XR reflectometry measurements have given the thickness of the gold layer in good agreement with the value estimated from quartz monitor readings and with the ellipsometric data as well. Liquid crystal cells were obtained to observe the molecular alignment imposed by the nanostructured gold layer deposited onto PS film. A rather strong interaction of gold atoms with the substrate molecules can be considered on the basis of the XRD and ellipsometry measurements.

3 citations


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TL;DR: This article reviews the most relevant approaches for incorporating such nanoparticles into synthetic fibers used traditionally in the textile industry allowing to give a solution to traditional problems for textiles such as the microorganism growth onto fibers, flammability, robustness against ultraviolet radiation, and many others.
Abstract: Nanoparticles are very interesting because of their surface properties, different from bulk materials. Such properties make possible to endow ordinary products with new functionalities. Their relatively low cost with respect to other nano-additives make them a promising choice for industrial mass-production systems. Nanoparticles of different kind of materials such as silver, titania, and zinc oxide have been used in the functionalization of fibers and fabrics achieving significantly improved products with new macroscopic properties. This article reviews the most relevant approaches for incorporating such nanoparticles into synthetic fibers used traditionally in the textile industry allowing to give a solution to traditional problems for textiles such as the microorganism growth onto fibers, flammability, robustness against ultraviolet radiation, and many others. In addition, the incorporation of such nanoparticles into special ultrathin fibers is also analyzed. In this field, electrospinning is a very promising technique that allows the fabrication of ultrathin fiber mats with an extraordinary control of their structure and properties, being an ideal alternative for applications such as wound healing or even functional membranes.

209 citations

Journal ArticleDOI
TL;DR: In this article, ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction and morphology by scanning electron microscopy (SEM).

62 citations

Journal ArticleDOI
TL;DR: The liquid crystal dimer 1ʺ,7ʺ-bis (4-cyanobiphenyl-4ʹ-yl) heptane (CB7CB) has been shown to possess a nematic-nematic phase transition at 376 K as mentioned in this paper.
Abstract: The liquid crystal dimer 1ʺ,7ʺ-bis(4-cyanobiphenyl-4ʹ-yl) heptane (CB7CB) has been shown to possess a nematic–nematic phase transition at 376 K. The phase below this temperature has been identified...

61 citations

Journal ArticleDOI
TL;DR: In this review, recent progress of the technology is discussed in detail, and the common target materials, technologies and functions and characterization of coated fabrics are summarized and analyzed.
Abstract: The applications of magnetron sputtering technology on the surface coating of fabrics have attracted more and more attention from researchers. Over the past 15 years, researches on magnetron sputtering coated fabrics have been mainly focused on electromagnetic shielding, bacterial resistance, hydrophilic and hydrophobic properties and structural color etc. In this review, recent progress of the technology is discussed in detail, and the common target materials, technologies and functions and characterization of coated fabrics are summarized and analyzed. Finally, the existing problems and future prospects of this developing field are briefly proposed and discussed.

58 citations

Journal ArticleDOI
TL;DR: Transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations shows that TEM observation of alignment-controlled, photopolymersized liquid crystals can be a powerful tool to investigate complex liquid crystalline order.
Abstract: Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order.

58 citations