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  • 1
    Online Resource
    Online Resource
    Increasing Shielding Capabilities of Cement Mortars by Fly Ash Addition
    Revista de Chimie SRL ; 2019
    In:  Revista de Chimie Vol. 70, No. 8 ( 2019-9-15), p. 2742-2746
    Details
    In: Revista de Chimie, Revista de Chimie SRL, Vol. 70, No. 8 ( 2019-9-15), p. 2742-2746
    Abstract: The magnetic and dielectric behavior of Portland cement mortars with various fly ashes (waste from the thermoelectric power plant) with a Fe2O3 content of 13.8 % was studied. The dielectric losses, tgd, the real component of the dielectric permeability, e�,and the real magnet permeability, �, the parameters with which we calculated the shielding coefficients, a, of the investigated samples, have been determined for the purpose of determining the screening capacity of the investigated samples by magnetic and dielectric spectroscopy in the 50 Hz � 3 kHz (ELF) range. Following experimental data processing, it was found that by increasing the hematite microstructured hematite Fe2O3 content of mortar samples (by fly ash addition) increased shielding capacity in the ELF domain, recorded increases for shielding coefficients, a, to an addition of up to 40 % fly ash, being up to 14.5 times at 50 Hz and up to 21 times at 3 kHz.
    Type of Medium: Online Resource
    ISSN: 0034-7752 , 2668-8212
    URL: Article
    DOI: 10.37358/RC.19.8.7419
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2019
    detail.hit.zdb_id: 2488208-2
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  • 2
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    The Influence of the Ash Addition from Thermal Power Plant on the Mechanical, Thermal and Dielectric Characteristics of Mortars
    Revista de Chimie SRL ; 2018
    In:  Revista de Chimie Vol. 69, No. 8 ( 2018-9-15), p. 2040-2044
    Details
    In: Revista de Chimie, Revista de Chimie SRL, Vol. 69, No. 8 ( 2018-9-15), p. 2040-2044
    Abstract: The influence of fly ash adittion (90 % fraction [ 100 mm) on the cement mortar characteristics was studied. The XRD, XRF, SEM and FTIR determinations indicated that fly ash used has a hollow microstructure of microsphere and cenosphere whose total content in SiO2, Al2O3 and Fe2O3 is 88.63 % and that of CaO and MgO of 8.55 %. The mechanical, thermal and dielectric determinations made on mortar samples with content of fly ash in the 0-40 % range have highlighted fact that the mechanical strength of cement mortars is maximal at 20 %, the increase in fly ash content leads to a decrease in relative density and thermal conductivity as well as and to increased dielectric losses tgd.
    Type of Medium: Online Resource
    ISSN: 0034-7752 , 2668-8212
    URL: Article
    DOI: 10.37358/RC.18.8.6469
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2018
    detail.hit.zdb_id: 2488208-2
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  • 3
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    Prevention of Explosions and Fires caused by Earthquakes
    Editura Electra ; 2020
    In:  Electrotehnica, Electronica, Automatica Vol. 68, No. 3 ( 2020-09-05), p. 86-93
    Details
    In: Electrotehnica, Electronica, Automatica, Editura Electra, Vol. 68, No. 3 ( 2020-09-05), p. 86-93
    Type of Medium: Online Resource
    ISSN: 1582-5175 , 2392-828X
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.46904/eea.20.68.3
    DOI: 10.46904/eea
    DOI: 10.46904/eea.20.68.3.1108011
    Language: Unknown
    Publisher: Editura Electra
    Publication Date: 2020
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  • 4
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    Online Resource
    Electro-insulating Paper Degradation in Various Electro-insulating Fluids
    Revista de Chimie SRL ; 2018
    In:  Revista de Chimie Vol. 69, No. 1 ( 2018-2-15), p. 91-95
    Details
    In: Revista de Chimie, Revista de Chimie SRL, Vol. 69, No. 1 ( 2018-2-15), p. 91-95
    Abstract: The durability and safe operation of electrical equipment and devices with mixed insulation systems (solid/fluid - electro-insulating paper/oil) is determined by the insulation aging under simultaneous and synergic actions of electrical, thermal and chemical stress factors etc. In this context, degradations of insulating paper exposed to thermal aging in 5 different types of electro-insulating fluid have been studied experimentally. Liquid chromatography determinations have shown that the total content in furan products (resulting from cellulose degradation) in mineral oils is substantially higher than in electro-insulating fluid sorts based on of synthetic ester and/or natural ester (vegetable oil). This is due to the temperature between 90 oC and 130 oC when the activation energy of the furans formation process is up to 7.5 times lower in mineral oils than in ester-based oils. Degree determinations of cellulose polymerization (viscosimetric method) before and after exposure to heat treatment indicated that mineral oils degrade the electro-insulating paper much more strongly than ester-based oils (both synthetic and natural). Obtained results by liquid chromatography and by viscosity are in accordance with the images obtained by optical microscopy (at X 100).
    Type of Medium: Online Resource
    ISSN: 0034-7752 , 2668-8212
    URL: Article
    DOI: 10.37358/RC.18.1.6050
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2018
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  • 5
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    The Hydrophily of Some Lacquers for Electrical Use
    Revista de Chimie SRL ; 2020
    In:  Materiale Plastice Vol. 57, No. 1 ( 2020-4-17), p. 122-132
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 57, No. 1 ( 2020-4-17), p. 122-132
    Abstract: Through gravimetric determinations, volume resistivity, dielectric spectroscopy, and comparative thermal analysis (TG, DTA and DTG), the interactions between the distilled water and three different types of alkyd-epoxy-melamine, epoxy and polyurethane lacquers were studied. From the experimental determinations it was found that after 700 h of immersion in water at 20 � 2�C the alkyd-epoxy-melamine based lacquer has a maximum water uptake, respectively 1.76%, followed by the epoxy lacquer 1.4% and polyurethane 0.93%. The thermal analysis sugests that because the water retained by the investigated polymers does not change the TG diagrams in the temperature range up to 150 �C, which suggests that the weight increase of the samples during the immersion could be due to some chemical processes between the water and polymer by which the chemistry structure of the polymer changes. Through electrical measurementes one can observe that after the immersion in water (over 700 hours), dielectric loss increases and the volume resistivity (measured in DC) of the investigated lakes decreases, which is explained by the increasing of polar groups (-OH) in the polymer structure. A comparative analysis of the experimental data reveals that in electrical applications the lacquer LS (polyurethane) is superior to the lacquers L-528 (alkyd-epoxy-melamine) and LG (epoxy), because it has no mass losses (structural changes) up to 280�C it has a volume resistivity of about 21 % higher than L-G, and about 300 % higher than L-528, and has water uptake and dielectric loss substantially lower comparing to L-528 and L-G.
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Article
    DOI: 10.37358/MP.20.1.5319
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2020
    detail.hit.zdb_id: 2487166-7
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  • 6
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    Physico-chemical Characterization of Paint Films with Electromagnetic Properties
    Revista de Chimie SRL ; 2022
    In:  Materiale Plastice Vol. 59, No. 2 ( 2022-7-1), p. 9-23
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 59, No. 2 ( 2022-7-1), p. 9-23
    Abstract: Electromagnetic compatibility issues and those generated by these radiations are a major concern for electrical and electronic products, mainly in the fields of communications, information technology, transportation, security and medical services. The paper presents the way to obtain nanostructured paint/plastic/nanopowder paint systems with electromagnetic shielding properties, as well as their characterization by FTIR analysis, DSC and dielectric tests. These systems have Electro-magnetic Interference (EMI)/Electromagnetic Compatibility (EMC) and Electrostatic Discharge (ESD) applications in the manufacture of enclosures for various electronic devices and for the automotive industry. At the laboratory level, 4 non-additive experimental models (EM) coded M1-M4 and 16 additive experimental models coded M5-M20 were obtained. Revolutionary to these materials is the fact that inside they are insulating and, on the outside, they behave like a shield. The results obtained from the dielectric tests performed on the 16 additive systems showed that the samples with a maximum percentage (20 %) of metal nanopowders show the highest values of electrical conductivity. Of the two nanopowders used, that of Fe from samples M11, M12, M19 and M20 which induces the composite higher conductivities than Al nanopowders. The ATR/FTIR spectra of the two paint samples analyzed showed that they were almost identical, suggesting that the paints tested had the same basic chemical structure. DSC analysis showed that pigment paint (V2) has low thermal oxidation stability and lower decomposition temperatures than pigment-free paint (V1), therefore, V2 is less stable under usage conditions, under the influence of normal environmental factors (temperature, humidity, natural or artificial light, etc.) compared to V1.
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Issue
    URL: Article
    DOI: 10.37358/MP.59.22.2
    DOI: 10.37358/MP.22.2.5580
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2022
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  • 7
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    Online Resource
    Mineral Oil versus Vegetable Oil as Electroinsulating Fluids in Contact with Coating LacquersA thermochemical stability study
    Revista de Chimie SRL ; 2019
    In:  Materiale Plastice Vol. 56, No. 4 ( 2019-12-30), p. 951-956
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 56, No. 4 ( 2019-12-30), p. 951-956
    Abstract: The thermochemical stability of a MOL (mineral oil) electroinsulating mineral oil was studied by the gas chromatography technique, compared with a Voil (vegetable oil) electroinsulating fluid based on natural esters (oil), exposed to a longer (1000 hours) thermal treatment (110 � 5 �C) in contact with the core transformer plate (silicon steel sheet) both blank and covered by immersion with three different types of lacquers (L-G epoxide, L-528 alkyl epoxy-melamine copolymer and L-S polyurethane). Experimentally it was noted that during the thermal treatment applied and in contact with the silicon steel sheet, the investigated oils have produced mainly C2H4, CH4 and H2. The total amount of flammable gases formed in Voil (vegetable oil) is about 7.5 time lower than in MOL. It has also been found that the lacquer coating of the silicon steel sheet does not change the mechanism of gas formation processes in the investigated oils, as well as the fact that the oxygen content of the investigated oils decreases monotonously during the thermal treatment applied due to either the formation of CO2 and CO and the oxidation processes of investigated lacquers.
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Article
    DOI: 10.37358/MP.19.4.5290
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2019
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  • 8
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    Comparative Studies on the Electrical and Mechanical Behavior of Some Soldering and / or Impregnation Lacquers
    Revista de Chimie SRL ; 2019
    In:  Materiale Plastice Vol. 56, No. 1 ( 2019-3-30), p. 129-132
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 56, No. 1 ( 2019-3-30), p. 129-132
    Abstract: In order to evaluate the behavior in various electrical applications, the main mechanical and electrical characteristics of three different varieties of specifically chosen lacquers - based on alkyl-epoxy-melamine copolymer, the epoxy polymer and polyurethane were compared. From the mechanical determinations, it was found that at ambient temperature the polyurethane lacquer bending resistance was approximately equal to that of the epoxy lacquer and about 6.5 times higher that of the alkyl-epoxy-melamine copolymer. It has also been shown that at bending force of less than 150 Nm the investigated polyurethane lacquer has relatively large deformations of 0.4 mm / kN, which indicates a high capacity to take over relatively high deformations of the metal support (due to thermal expansion from various applications) without significant increasing mechanical stress. The recorded values for the alkyl-epoxy-melamine-based copolymer lacquer and the pure epoxy lacquer are 0.11 mm / kN and 0.03 mm / kN respectively. Determinations by dielectric spectroscopy have shown that at frequencies below 250 Hz the dielectric losses tgd for the epoxy and polyurethane lacquers are approximately equal and are about 2.9 times lower than for the alkyl-epoxy-melamine copolymer lacquer. It was also found that at frequencies higher than 250 Hz the investigated materials behave differently, respectively at the frequency increase up to 10 kHz, the dielectric loss tgd of the polyurethane lacquer remains constant at about 0.0045 in contrast to the epoxide lacquer at which the dielectric loss tgd increases monotone to 0.0095 at 10 kHz, respectively of the alkyl-epoxy-melamine copolymer at which the dielectric loss tgd is approximately constant 0.012 in the 250 Hz-10 kHz range.
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Article
    DOI: 10.37358/MP.19.1.5137
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2019
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  • 9
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    Assessment of Paint Layers Quality 3. Analysis by SEM-EDAX and XRF techniques of the paint layers applied on a railway bridge
    Revista de Chimie SRL ; 2018
    In:  Materiale Plastice Vol. 55, No. 4 ( 2018-12-30), p. 531-535
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 55, No. 4 ( 2018-12-30), p. 531-535
    Abstract: In order to identify the premature biodegradation causes of paint applied in 2013 on a railway bridge, top coat layers applied have been investigated by XRF and SEM-EDAX techniques after 32 years, corresponding to periods of operation under identical climatic conditions of 4.5 years and 3.5 years respectively. By analysis of the experimental results obtained, it has been found that by using suitable painting materials (titanium content of about 7.5 % - TiO2 for UV protection) an exploitation period of more than 30 years could be obtained. Low-carbon (low polymer) and titanium dyeing materials with significant content of soluble salts have a low durability and anticorrosive protection capability. They degrade relatively fast both by top coat degradation and by intense increases of biofouling.
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Article
    DOI: 10.37358/MP.18.4.5068
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2018
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  • 10
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    Online Resource
    Comparative Studies on the UV Radiations Resistance of Some Painting Materials
    Revista de Chimie SRL ; 2017
    In:  Materiale Plastice Vol. 54, No. 4 ( 2017-12-30), p. 720-725
    Details
    In: Materiale Plastice, Revista de Chimie SRL, Vol. 54, No. 4 ( 2017-12-30), p. 720-725
    Abstract: UV radiation has a long-term effect on the durability of anti-corrosive coatings applied by painting, generating conditions for accelerated localized corrosion of the protected metallic structure with adverse effects on operational safety. This paper presents a comparative study of the behavior of some painting materials ageing by exposure to UV radiation relevant by the investigation of dielectric behavior using dielectric spectroscopy in conjunction with the thermal stability investigated by coupled techniques of thermal analysis. From a practical point of view, the UV radiation behavior of two materials based on epoxy resins and polyurethane resin used as paints for protective decorative coatings was studied. The results of experimental investigations have shown that in the aging process of the studied painting materials there is a direct correlation between the evolution of the maximum temperature characteristic of the first thermooxidation process and the evolution of the dielectric performances (dielectric loss - tgd).
    Type of Medium: Online Resource
    ISSN: 0025-5289 , 2668-8220
    URL: Article
    DOI: 10.37358/MP.17.4.4931
    Language: English
    Publisher: Revista de Chimie SRL
    Publication Date: 2017
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