Cable Aging Monitoring with Differential Scanning Calorimetry (DSC) in Nuclear Power Plants

As a requirement for plant life extension for more than 40 years, additional Cable Aging Management Program (CAMP) has to be implemented in Nuclear Power Plant Krško. Samples of cables are selected based on nuclear safety and electrical equipment criticality for inspection and testing, to check functionality and prevent unexpected failure during normal operation. Different onsite testing equipment and methods are implemented to find harsh environment due to temperature, radiation, humidity and chemical effects that could affect insulation lifetime. Infrared thermography is used for determining and evaluating temperature hot spots. The article presents a development of laboratory testing of cable insulation using Differential Scanning Calorimetry (DSC). Thirty-six samples of different nuclear qualified cables made of most frequently used materials, ethylene propylene rubber (EPR) and cross linked polyethylene (XLPE) – all with chlorosulfonated polyethylene (CSPE) jacket, were tested. Samples were 35 years old and additionally temperature aged in several steps with an intention to get acceptance criteria. Similar tests were conducted in two testing laboratories. The results showed an evident decrease in oxidation stability of the inner EPR insulation; the onset temperature of oxidation processes has been shifted from 238 °C (unaged samples) to 175 °C (most aged samples). A decrease in oxidation stability was also observed for XPLE insulation; the onset oxidation temperature decreased from 266 °C for unaged samples to 213 °C (most aged samples). For the jacket material CSPE used as the insulation protection nearly no changes were observed

Flame retardant effectiveness of nanodispersed organophosphorus-derivative in polyamide 6 textile filament yarns

The halogen-free flame retardant (FR) polyamide 6 (PA6) composite textile filament yarns fabricated via melt-compounding have never achieved effective flame retardancy. The main reason for that is related to the agglomeration of FR additives due to their poor compatibility with PA6 polymer chains. The formed FR agglomerates substantially reduce the flame retardant effectiveness, disable continuous melt-spinning process due to clogging of the filters and spinnerets, and significantly impair fibre tensile properties. Therefore, the goal of this study was to investigate how lowering of the FR additive size to the nanoscopic level affects melt-spinning process and flame retardancy of the nanocomposite PA6 filament yarns. To this aim, we established a new scalable approach for the production of new-generation PA6/FR nanocomposite filament yarns with uniformly distributed nano-dispersed halogen-free FR. So, instead of mixing FR additive with PA6 melt, we rather chose a step back, i.e. mixing of FR additive with ε-caprolactam melt and performing the in situ polymerization

Increasing the photocatalytic efficiency of ZnWO4_4 by synthesizing a Bi2_2WO6_6/ZnWO4_4 composite photocatalyst

In the present study, a Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was successfully constructed by a modified hydrothermal synthesis method with different molar concentrations of Bi$_2$WO$_6$ with respect to ZnWO$_4$. The variation in molar concentrations of Bi$_2$WO$_6$ changed the photocatalytic properties of the Bi$_2$WO$_6$/ZnWO$_4$ catalyst. The synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was characterized by various techniques to decipher its structural and spectral properties. The interaction of Bi$^{2+}$ ionic charge carriers and many-body effects cause the band gap to narrow in Bi$_2$WO$_6$/ZnWO$_4$, as shown by PL analysis. The decrease in band gap energies (E$_g$) from 4.7 eV (ZnWO$_4$) to 3.5 eV (30% Bi$_2$WO$_6$/ZnWO$_4$) is beneficial because less energy is required to excite the valence electrons. The maximum degradation of Plasmocorinth B dye was found with 30% Bi$_2$WO$_6$/ZnWO$_4$ under UV irradiation. This increased activity of 30% Bi$_2$WO$_6$/ZnWO$_4$ can be attributed to the (i) synergistic effect in the bicrystalline framework of Bi$_2$WO$_6$ and ZnWO$_4$, (ii) the high close contact between Bi$_2$WO$_6$ and ZnWO$_4$, and (iii) the small crystallite size. The photocatalytic activity of synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst shows its significant potential in water/ wastewater treatment application

Sustainable in situ synthesis of silver/titanium dioxide/organofunctional trialkoxysilane nanocomposite coatings on cotton fabric to tailor superior multifunctional protective properties

Multifunctional properties are crucial for the production of high-quality technical textiles. In this study, a cotton fabric with simultaneously superior UV-protection, self-sterilisation, photocatalytic self-cleaning and flame retardant properties was produced using a sol–gel/hydrothermal process, in which titanium(IV) isopropoxide (TTIP) as a titanium dioxide (TiO$_2$) precursor was combined for the first time with mixtures of organofunctional trialkoxysiloxanes, i.e., 3-(trihydroxysilyl)propyl methylphosphonate (TPMP) as a P-based flame retardant and dimethyloctadecyl [3-(trimethoxysilyl)propyl]ammonium chloride (SiQAC) or aminopropyltriethoxysilane (APTES) as the antimicrobial, biobarrier-forming precursors. The latter was used in two increased concentrations of APTES1 and APTES2. A sol–gel/hydrothermal approach was employed with a small amount of silver nitrate (AgNO$_3$) added during the hydrothermal treatment to produce Ag-loaded TiO$_2$. The results of scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray diffraction spectroscopy (XRD), inductively coupled plasma mass spectroscopy (ICP MS) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the successful functionalisation of TiO$_2$ by TPMP, SiQAC and APTES through the formation of Si–O–Ti bonds and the well-dispersed Ag/TiO$_2$/TPMP/SiQAC, Ag/TiO$_2$/TPMP/APTES1 and Ag/TiO$_2$/TPMP/APTES2 coatings on the surface of the cotton fabric. The type of biobarrier-forming precursor significantly influenced the formation of the Ag species after the Ag loading of TiO$_2$. The presence of SiQAC induced the formation of AgCl crystals, while APTES controlled the formation of silver nanoparticles (Ag NPs), which was more pronounced at the lower APTES1 concentration. The interactions between the coating components significantly influenced the functional protection performance, with the highest level of cooperation achieved in the Ag/TiO$_2$/TPMP/SiQAC and Ag/TiO$_2$/TPMP/APTES1 coatings, which exhibited the best overall multifunctionality, albeit with certain drawbacks. While the Ag/TiO$_2$/TPMP/APTES1 coating provided excellent UV protection for the cotton, this was only improved by the Ag/TiO$_2$/TPMP/SiQAC coating. At the same time, the Ag/TiO$_2$/TPMP/APTES1 coating impaired the development of the char barrier by TPMP, which is due to the formation of Ag NPs. Nevertheless, both coatings showed high photocatalytic self-cleaning performance, complete self-sterilisation activity and improved burning behaviour

Effect of different flame-retardant bridged DOPO derivatives on properties of in situ produced fiber-forming polyamide 6

The production of sustainable and effective flame retardant (FR) polyamide 6 (PA6) fibrous materials requires the establishment of a novel approach for the production of polyamide 6/FR nanodispersed systems. This research work explores the influence of three different flame-retardant bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivatives on the comprehensive properties of in situ produced PA6/FR systems. To this end, in situ water-catalyzed ring-opening polymerization of ε-caprolactam was conducted in the presence of three different bridged DOPO derivatives, e.g., one P−N bond phosphonamidate derivative and two P−C bond phosphinate derivatives. The selected bridged DOPO derivatives mainly act in the gas phase at the temperatures that relatively match the PA6 pyrolysis specifics. The effects of the FRs on the dispersion state, morphological, molecular, structural, melt-rheological, and thermal properties of the in situ synthesized PA6 were evaluated. The specific advantage of this approach is one-step production of PA6 with uniformly distributed nanodispersed FR, which was obtained in the case of all three applied FRs. However, the applied FRs differently interacted with monomer and polymer during the polymerization, which was reflected in the length of PA6 chains, crystalline structure, and melt-rheological properties. The applied FRs provided a comparable effect on the thermal stability of PA6 and stabilization of the PA6/FR systems above 450 °C in the oxygen-assisted pyrolysis. However, only with the specifically designed FR molecule were the comprehensive properties of the fiber-forming PA6 satisfied for the continuous conduction of the melt-spinning process

In situ tailoring of Ag-doped-TiO2_2/TPMP/cotton nanocomposite with UV-protective, self-sterilizing and flame-retardant performance for advanced technical textiles

Herein, we present a novel approach to the development of a multifunctional, UV-protective, photocatalytic, antimicrobial and flame-retardant nanocomposite fabric surface. Using a sol–gel/hydrothermal approach, a phosphorus-based flame-retardant 3-(trihydroxysilyl)propyl methylphosphonate (TPMP) in combination with Ag-doped TiO$_2$ was applied to the surface of cotton fibers for the first time, using an aqueous AgNO$_3$ solution as the dopant. The modified cotton fabrics were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and X-ray diffraction spectroscopy (XRD) to confirm the successful application of Ag-TiO$_2$ and TPMP on the cotton fabric by analyzing the surface morphology, chemical composition, chemical bonding and crystal structure. The functional properties of the modified cotton fabric were determined by measuring the UV protection factor (UPF), burning behavior and thermo-oxidative stability, as well as antibacterial activity against Escherichia coli and Staphylococcus aureus. The results show the formation of a unique nanocomposite matrix of TPMP–polysiloxane on the surface of cotton fibers with well-distributed Ag-TiO$_2$. The formation of TiO$_2$/Ag$_2$O particles on the surface of cellulose fibers was also confirmed. The synergism between all components of the nanocomposite resulted in excellent UV protection in the UVA and UVB region, with a UPF of 50+, self-sterilizing activity against both tested bacteria and enhanced thermo-oxidative stability. Therefore, the novel approach proposed herein is promising for the development of multifunctional, protective surfaces for advanced technical textiles

Searching for optimal measurement parameters by thermogravimetry for determining the degree of modification of thermally modified wood

When wood is thermally modified, several chemical reactions take place that change the chemical and physical properties of the wood. These changes correlate with the degree of modification, which is mostly a function of the temperature and duration of modification, and consequently with the mass loss during this process. There is a lack of standardised quality control to verify the degree of heat treatment of wood and thus its quality. One of the possible methods to check the degree of thermal modification of a particular type of wood is thermogravimetry (TG). It is based on the assumption that processes that did not take place during thermal modification continue when the TG experiment is carried out. In this method, calibration curves have to be established based on TG measurements of standard samples that have been thermally modified at different temperatures and whose mass loss during modification is known. The calibration curves show the mass loss during the TG measurement as a function of the mass loss during the previous thermal modification. The course of thermal decomposition during the TG measurements is influenced by many parameters, such as the mass of the sample, the heating rate, the atmosphere in which the measurement takes place, and the shape of the crucible in which the sample is placed. In this paper, the influence of these parameters on the calibration curves was investigated. We have focused on oak wood. The best parameters result in a calibration curve with the largest correlation coefficient $R^2$ and the highest slope of the line k. On this basis, we can determine the mass loss during the thermal modification of unknown samples of the same wood species under the same measurement conditions

An extensive characterization of various environmentally relevant microplastics – material properties, leaching and ecotoxicity testing

Microplastics in the environment occur in different sizes and shapes and are made of various polymers. Therefore, they also considerably differ in their properties and ecotoxicity. However, the majority of microplastics research uses pre-made spherical microplastics, which practically do not exist in the environment. Our work focused on a comprehensive study of six different types of microplastic that were prepared to simulate common microplastics found in the environment. All types of microplastics where chemically and physically characterized using Fourier-transform infrared spectroscopy, thermal analysis, field-emission scanning electron microscopy, optical microscopy and laser diffraction analysis. The specific surface area was determined using the BET method. Furthermore, effects of microplastics and microplastic leachates on a common duckweed (Lemna minor) were evaluated. All tested microplastics did not affect specific growth rate and chlorophyll a content in duckweed, while microplastics with a rough surface and sharp edges caused a significant reduction of duckweed root length. Microplastics made of Bakelite also showed an intensive leaching, which increased their ecotoxicity potential. Natural particles used as a control did not have any negative effect on duckweed. Overall, microplastic particles have significantly different ecotoxicity profiles depending on their physico-chemical properties. Therefore, the testing of environmentally relevant particles and their proper characterization, as well as the testing of microplastic leaching properties, is crucial for understanding of microplastics ecotoxicological potential

Structural and Antimicrobial Characterization of Co-Crystal [Ni(bpy)(acr)2(H2O)]·MA

A new co-crystal with the formula [Ni(bpy)(acr)2(H2O)]·MA (bpy = 2,2′-bipyridine, acr = acrylate and MA = melamine) has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis and single crystal X-ray diffraction. The complex contains discrete unities of [Ni(bpy)(acr)2(H2O)] and melamine linked in a complex network by both hydrogen bonds and π-π stacking interactions. Structural characterization revealed that Ni(II) adopts an octahedral distorted stereochemistry, and acrylate ions present both unidentate and chelate coordination modes. Thermal decomposition occurs in four steps, the ligands being stepwise released in the order of water, acrylate, bipyridine and melamine. The antimicrobial activity of the obtained complex, its precursor ([Ni(bpy)(acr)2(H2O)]) and melamine were assessed against planktonic (minimal inhibitory concentration—MIC) and biofilm-embedded (minimal biofilm eradication concentration—MBEC) Gram-positive and Gram-negative bacterial strains. The obtained results revealed that the new complex and its precursor exhibited a superior activity compared to MA, the highest susceptibility being recorded for the Staphylococcus aureus strain. The MIC and MBEC ranges were very similar, indicating the potential of this complex and its precursor to develop novel anti-biofilm agents

Preparation of air-stable expandable MoS2 and rapid expansion by low temperature heating and electron beam irradiation

We report on the intercalation of a quaternary ammonium salt into MoS2 at ambient conditions and the rapid expansion of the resulting intercalated material – an analogue to expandable graphite – both via low temperature heating and via electron beam irradiation in a scanning electron microscope. In both cases the expansion proceeds within seconds and does not alter the material's chemical properties. The range of expansion under the electron beam depends on the energy and incident angle of the electrons. The intercalated material is air-stable and remains expandable for at least a year