Materials Science Forum Vol. 955

Abstract: This thesis deals with the testing of our wet scrubber by a laboratory at the Faculty of Chemistry, Brno University of Technology. On this wet scrubber, the CO₂ capture efficiency is tested with a splash liquid consisting of 1 % NaOH. An overview of the system, which could increase the capture efficiency of CO₂ from the gas mixture or other harmful particulates in the air, could be improved after introduction. The thesis also deals with finding methods to better capture efficiency of solid particles and gases on the wet scrubber.

Abstract: Reactivity of five reactive agents with two biopolyesters, poly (3-hydroxybutyrate) (PHB) and poly (lactic acid) (PLA), was studied in situ during processing in laboratory kneader with simultaneous recording of a melt torque. Among them only Raschig, an oligomeric carbodiimide based additive, was proven to enhance melt viscosity of both. In order to find out the most efficient level of this additive for stabilizing of both polymers and PHB/PLA (70/30 w/w) blend, different concentrations were studied by means of melt torque monitoring, rheology time tests and gel permeation chromatography. Results showed the same trend for neat polymers and their blend. Addition of more than 0.5 % wt. did not have any further positive effect on molecular weight or complex viscosity of the melt. Higher amount is not consumed during the reaction and is left in the sample. Therefore, this amount was used for processing stability studies on PHB/PLA blends by subsequent extrusion cycles. Melt volume-flow rate of extruded samples was obtained and results showed lower values for all stabilized blends comparing to the first extrusion sample of non-stabilized blend. At the same, stability of the blends is secured up to the third extrusion cycle.

Abstract: This study aims to determine the para-phenylenediamine (PPD) in hair dyes by High-Performance Liquid Chromatography (HPLC). In the presented study, ten hair dye samples were collected from local markets in El-Bieda - Libya. A rapid, simple and reliable method is developed and validated for the determination of PPD in hair dyes samples using 50% methanol solution as solvent. The method was validated over a wide linear range of 5 – 25 µg/mL with correlation coefficients being consistently greater than 0.997. The LOD and LOQ were 1.21 µg/ ml and 3.67 µg/ ml, respectively. Relative standard deviation (% R.S.D.) ranged between 0.07 and 1.15 %. The minimum PPD level was observed in Beauty Touch (Blonde) sample (0.0855 % w/w), while Jourin sense Cosmetics (Black Blue) sample showed the highest PPD content (2.2526 % w/w). The HPLC measurments indicated that the results of PPD concentrations in Black colour samples were in the range of 0.3705 % - 2.2526 % w/w. Whereas its concentrations in anthor colour samples were in the range of 0.0855 % - 0.5936 % w/w. The level of PPD in Black colour samples were higher than other colour samples. The PPD content in all the samples analyzed in this study are well below the allowable limits set by the US Food and Drugs Administration.

Abstract: Alternating-current powder-based electroluminescence is currently the only technique for quick and easy preparation of large area, low cost electroluminescent panels by the means of material printing. Manufacturing of the panels is currently done exclusively by screen printing which is associated with deposition of much thicker layers than typical for other methods of material printing. Typical thickness of layers is in the order of tens of microns and more. The overall thickness of films forming the panel is however a serious shortcoming of the devices because the driving voltage for generation of light needs to be high and the thickness of layers render the panel non transparent from the side of the dielectric layer. One layer of dielectric films screen printed from the commercially available formulation is approximately 10 μm thick and cannot be effectively reduced anymore and thus another printing technique needs to be exploited. The goal of this work is to define and optimize a composition of a novel ink jet printing formulation of dielectric film and verification of parameters of the final layers for use in this type of technology. The major benefits of ink jet printed dielectric layer are the possible preparation of a panel emitting light from both sides with reduced driving voltage needed for its operation.

Abstract: This paper is focused on the determination of thermal parameters (thermal conductivity, thermal diffusivity, and specific heat capacity) of electrical insulating paper from various producers. The transient step-wise method was used to determine all thermal parameters simultaneously. Evaluation was carried out using the differential method. Thermal conductivity was determined from the steady-state temperature response on thickness (corresponding to the number of paper layers), while thermal diffusivity and specific heat capacity was obtained from the dependence of derivative maximum and the corresponding temperature on thickness. Four electro insulating papers differing by composition and thickness: materials NKN (Nomex-Kapton-Nomex), DMD (Dacron-Mylar-Dacron), TFT (TufQUIN TFT 50) and TVAR (ThermaVolt AR) were studied. As a result, the highest value of thermal conductivity (0.17 W/m/K) was determined for the DMD. Remaining three materials possessed thermal conductivity about 0.12 W/m/K. However, differences in specific heat capacity and thermal diffusivity were found to be significantly higher. The lowest specific heat capacity was found for the DMD sample (1200 J/kg/K), while the highest specific heat capacity was found for TVAR sample (4000 J/kg/K).

Abstract: This paper deals with the study of light conversion efficiency of organic photovoltaic cells with an inkjet-printed graphene oxide layer. The graphene oxide is used in this experiment as a hole-extracting, electron blocking layer in bulk heterojunction organic solar cells based on DPP(TBFu)₂:PC₆₀BM blend. It is also studied the influence of the GO reduction (chemically, by UV radiation and by annealing) on the final efficiency of photovoltaic conversion. Power conversion efficiency and the transport of charge carriers are evaluated by measuring of current-voltage characteristics and mainly by impedance spectroscopy analysis. In this regard, using of graphene oxide and its reduced form showed negative influence on the device performance caused by an inefficient charge carrier collection at the short-circuit condition.

Abstract: The paper deals with determination of two-photon absorption cross-sections of selected representatives of diketo-pyrrolo-pyrrole. The materials were optimized in order to test the influence of various substitutions on the diketo-pyrrolo-pyrrole basic molecule. The two-photon absorption cross-sections were determined using two-photon excited fluorescence technique. A considerably high two-photon absorption cross-section in order of 1000 GM was found for non-symmetrically substituted derivative with donor-acceptor structure. All of the derivatives showed strong fluorescence in solid state visible by naked eye. These results demonstrate that this class of materials can be used in e.g. two-photon fluorescence microscopy in the form of nanoparticles.

Abstract: The manufacture of optimized heavyweight concrete takes into consideration the type of aggregates, composition of blended cement, water-to-cement ratio, additives etc. The density of concrete depends mainly on the specific gravity of the used aggregates. Generally, concretes with specific gravities higher that 2600 kg m^-3 are called heavyweight concretes and aggregates with specific gravity higher than 3000 kg m^-3 are considered as heavyweight aggregates according to EN [1,2]. Concrete is a low cost material and easy to produce in varied compositions when compared to other shielding materials based on ceramics [3]. It is composed of a well-proportioned mixture of light and heavy nuclei. It is therefore efficient both in absorbing gamma rays and in slowing down fast neutrons by elastic and inelastic scattering [2]. Light materials, especially hydrogenous materials which contained in the water of hydration of the set cement (concrete) attenuate fast neutrons as a consequence of the high cross-section of hydrogen [4].

Abstract: Nowadays, in industrial production, lithium consumption is strongly increasing and it can be assumed that waste material with an increased content of this metal could also appear. One of the most important sectors where different types of waste can be utilized is the cement industry. Therefore, it is desirable to monitor the influence of lithium on formation and properties of the clinker. In the presented work, this effect was monitored in laboratory conditions up to 5 wt.% Li₂O. X-ray diffraction, DTA and optical microscopy were employed as research methods. Among other things, it has been found that Li₂O causes the decomposition of the alite, the major clinker phase, to a microcrystalline mixture of belite and free lime, depending on its content and clinker cooling rate.