@CONFERENCE{MTMT:34071297, title = {Új irányok a környezetbarát fém-levegő akkumulátorok fejlesztésében}, url = {https://m2.mtmt.hu/api/publication/34071297}, author = {Kuki, Ákos and Nagy, Tibor and Nagy, Lajos and Deák, György and Kordován, Marcell Árpád and Róth, Gergő and Zsuga, Miklós and Kéki, Sándor}, booktitle = {XXVIII. Nemzetközi Vegyészkonferencia = 28th International Conference on Chemistry}, unique-id = {34071297}, year = {2022}, pages = {30-31}, orcid-numbers = {Nagy, Tibor/0000-0001-8568-914X} } @CONFERENCE{MTMT:33728889, title = {Környezetbarát akkumulátorok fejlesztése 3D nyomtatással támogatva = Development of environmentally friendly secondary battery supported by 3D printing technology}, url = {https://m2.mtmt.hu/api/publication/33728889}, author = {Kordován, Marcell Árpád and Nagy, Tibor and Nagy, Lajos and Kuki, Ákos and Erdélyi, Zoltán and Baradács, Eszter and Deák, György and Zsuga, Miklós and Kéki, Sándor}, booktitle = {XXVIII. Nemzetközi Vegyészkonferencia = 28th International Conference on Chemistry}, unique-id = {33728889}, abstract = {A megfelelő hatékonyságú akkumulátorok fejlesztése elengedhetetlen a megújuló energiaforrások szé-leskörű elterjedésének. A kutatásunkkal célunk volt egy olyan akkumulátor megalkotása, amely széles-körű alkalmazhatósággal rendelkezik. A munka során egy olyan fém-levegő (lítium, cink vagy sárgaréz) cellát hoztunk létre, amelyben a felhasznált komponensek könnyen hozzáférhetőek. A cella kialakításá-nak reprodukálhatósága céljából, a váz elemeket 3D nyomtató segítségével készítettük el polipropilén-ből. A katódként aktív szenet alkalmaztunk egy grafit kollektorral ellátva, nehézfémeket és és egyéb katalizátort ez nem tartalmazott. A cellában lévő diafragma természetes alapú pamutszövet, valamint celofán voltak. A fém-levegő rendszerek elterjedésének hiánya a nagymennyiségű dendritképződésre vezethető vissza, amely csökkentette annak energiahatékonyságát. Különböző elektrolit adalékokat (pl. karboxil telekelikus PEG) teszteltünk, amelyek alkalmazásával sikeresen visszaszorítottuk a dendritkép-ződést. The development of batteries with high efficiency is crucial for storing energy from renewable sources. Our research aimed to create a battery with a wide range of applications. During the work, we created a metal-air (lithium, zinc, brass) cell in which the used chemicals and components are easily accessible. In order to ensure a reproducible backbone, the parts were made using 3D printing. The cathode was charcoal equipped with a graphite collector. The diaphragm in the cell was also a natural-based cotton fabric as well as cellophane. The lack of spread of metal-air systems is due to the formation of a sig-nificant amount of dendrite, which reduces its energy efficiency. Different electrolyte additives were tested and with the application of them the dendrite formation was successfully suppressed.}, keywords = {DENDRITE; CELLULOSE DERIVATIVES; 3D nyomtatás; fém-levegő akkumulátor; cellulózszármazékok; metal-air secondary batter}, year = {2022}, pages = {29-30}, orcid-numbers = {Nagy, Tibor/0000-0001-8568-914X} } @article{MTMT:33348858, title = {Flexible Investment Casting Wax Patterns for 3D-Printing: Their Rheological and Mechanical Characterizations}, url = {https://m2.mtmt.hu/api/publication/33348858}, author = {Szabo, Laszlo and Deák, György and Nyul, Dávid and Kéki, Sándor}, doi = {10.3390/polym14214744}, journal-iso = {POLYMERS-BASEL}, journal = {POLYMERS}, volume = {14}, unique-id = {33348858}, abstract = {The mechanical and rheological characterizations of flexible investment casting patterns capable of 3D printing are reported. The wax pattern was composed of microcrystalline hydrocarbon wax (DMW7478), Piccotex 75 (a copolymer of alpha-methyl-styrene and vinyl toluene with a 75/25 molar ratio, respectively) and Escorene (a copolymer of ethylene and vinyl acetate with a 72/28 mass ratio, respectively). It was found that in order to obtain a wax pattern with appreciable mechanical properties, the content of the microcrystalline hydrocarbon wax in these blends should not exceed 30% (m/m). Thus, a series of patterns with 28% (m/m) wax and varying Piccotex and Escorene contents spanning from 0 to 72% (m/m) was prepared. The dependence of the dynamic viscosities of the wax patterns on the composition was described using a stretched exponential model, whereas their variations with the temperature were interpreted in terms of the Arrhenius-Guzman equation. Furthermore, the slopes of the lines fitted to the viscosity versus temperature curves at the pour point decreased linearly with the Piccotex content. Non-Newtonian changes in the shear stress with the shear rate and shear stress crystallization were observed at temperatures near the pour points. The mechanical properties were evaluated using the uniaxial tensile mode and by three-point bending experiments. It was found that the stress (sigma) versus the relative elongation (epsilon) curves can effectively be rendered by means of the standard linear solid (SLS) viscoelastic model. In addition, it was also established that the Young's modulus varied according to a sigmoid-type curve with the piccotex content, while the yield stress decreased linearly with the concentration of Piccotex. In addition, based on the spooling suitability and printability, the patterns were rated and it was found that the most appropriate wax pattern compositions for 3D printing were those which contained 30% (m/m) and 35% (m/m) Piccotex.}, keywords = {rheology; mechanical properties; 3D printing; investment casting wax; Piccotex 75; Escorene}, year = {2022}, eissn = {2073-4360} } @article{MTMT:33296641, title = {“In Situ” Formation of Zn Anode from Bimetallic Cu-Zn Alloy (Brass) for Dendrite-Free Operation of Zn-Air Rechargeable Battery}, url = {https://m2.mtmt.hu/api/publication/33296641}, author = {Nagy, Tibor and Nagy, Lajos and Erdélyi, Zoltán and Baradács, Eszter and Deák, György and Zsuga, Miklós and Kéki, Sándor}, doi = {10.3390/batteries8110212}, journal-iso = {BATTERIES}, journal = {BATTERIES}, volume = {8}, unique-id = {33296641}, abstract = {In this article, the performance of brass electrode was investigated in a Zn-air (charcoal-based cathode) rechargeable battery. The construction of the battery was carried out with biodegradable materials, namely a cotton cloth diaphragm and carboxymethyl cellulose sodium salt (CMC-Na) viscosity modifier, while the battery skeleton was printed by 3D printing technology. The brass acted as a collector and a preferable surface for the metallic Zn deposition on the brass anode surface. The electrochemical behavior of the brass anode was investigated by cyclic voltammetry (CV). Cyclic performance tests were carried out, which showed stable cell operation even in the presence or absence of additives up to more than 100 cycles. Furthermore, high energy (Eeff) and Coulomb (Ceff) efficiencies, 80% (Eeff), 95% (Ceff), 75% (Eeff), and 95% (Ceff) were obtained, respectively. The Shepherd model was applied to describe the discharging processes of the Zn-air battery containing brass as anode in the presence of additive-free electrolyte or electrolyte with CMC-Na salt additive. It was found that the Shepherd equation described only approximately the resulting discharge curves. In order to attain a more precise mathematical description, stretched exponential function was implemented into the last term of the Shepherd equation. The need for such a correction shows the complexity of the electrochemical processes occurring in these systems. In addition, the surface of the brass anode was also investigated by scanning electron microscopy (SEM) and the composition of the brass alloys was determined by X-ray fluorescence spectroscopy (XRF). Importantly, the formation of dendritic deposition was successfully suppressed and a smooth and uniform surface was obtained after the cycling tests.}, year = {2022}, eissn = {2313-0105}, orcid-numbers = {Nagy, Tibor/0000-0001-8568-914X; Erdélyi, Zoltán/0000-0003-0364-7996} } @article{MTMT:32709592, title = {Environmentally friendly high performance Zn-air rechargeable battery using cellulose derivatives: A 3D-printed prototype}, url = {https://m2.mtmt.hu/api/publication/32709592}, author = {Nagy, Tibor and Nagy, Lajos and Erdélyi, Zoltán and Baradács, Eszter and Deák, György and Zsuga, Miklós and Kéki, Sándor}, doi = {10.1016/j.est.2022.104173}, journal-iso = {J ENERGY STORAGE}, journal = {JOURNAL OF ENERGY STORAGE}, volume = {49}, unique-id = {32709592}, issn = {2352-152X}, abstract = {In this paper an environmentally friendly high performance prototype of rechargeable Zn-air battery using cellulose based biodegradable matters as additive and diaphragm is reported. During designing we were aspired to construct a heavy metal free cell containing nontoxic, commercially available biodegradable feedstock. The fix cell geometry was granted by 3D-printing. Charging/discharging cycle tests were performed using cotton lattice or cellophane diaphragms separately. The presence of carboxymethyl cellulose sodium salt (CMC-Na, Mn: 90 kDa and 250 kDa with f = 0.7 or f = 1.2 average functionality) additives in the electrolyte was also tested. Significant difference was found between the cells operated with and without additives. Two main benefits of the application of CMC-Na salts were observed: (i) by increasing the viscosity of the electrolyte the rate of evaporization of the water was decreased; (ii) owing to the higher viscosity of the lye and the good chelating agent properties of the carboxyl functional groups more stable cell operation was obtained. Using cotton lattice as diaphragm, 100% Coulomb efficiency was detected during the entire measurement (more than 1000 cycles), while the weight of zinc electrode was constant and its surface remained smooth. Additional cyclic voltammetry tests were also carried out to investigate the electrode processes and the change of the electrode surface was monitored by scanning electron microscopy.}, year = {2022}, eissn = {2352-1538}, orcid-numbers = {Nagy, Tibor/0000-0001-8568-914X} } @article{MTMT:31831970, title = {Surface characterization of plasma-modified low density polyethylene by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy combined with chemometrics}, url = {https://m2.mtmt.hu/api/publication/31831970}, author = {Kovács, Réka Lilla and Csontos, Máté and Gyöngyösi, Szilvia and Elek, János and Parditka, Bence and Deák, György and Kuki, Ákos and Kéki, Sándor and Erdélyi, Zoltán}, doi = {10.1016/j.polymertesting.2021.107080}, journal-iso = {POLYM TEST}, journal = {POLYMER TESTING}, volume = {96}, unique-id = {31831970}, issn = {0142-9418}, year = {2021}, eissn = {1873-2348}, orcid-numbers = {Kéki, Sándor/0000-0002-5274-6117} } @article{MTMT:31817752, title = {Environmentally friendly Zn-air rechargeable battery with heavy metal free charcoal based air cathode}, url = {https://m2.mtmt.hu/api/publication/31817752}, author = {Nagy, Tibor and Nagy, Lajos and Erdélyi, Zoltán and Baradács, Eszter and Deák, György and Zsuga, Miklós and Kéki, Sándor}, doi = {10.1016/j.electacta.2020.137592}, journal-iso = {ELECTROCHIM ACTA}, journal = {ELECTROCHIMICA ACTA}, volume = {368}, unique-id = {31817752}, issn = {0013-4686}, abstract = {In this article, we report the development of a novel Zn-air rechargeable battery with charcoal/graphite cathode and dicarboxyl telehelic polyethylene glycol (PEG) additives with different molecular weights (Mn: 600 Da, 1500 Da, 3300 Da). The battery is free of heavy metals and all of the used materials are easily available and non-toxic. The dicarboxyl telechelic PEGs were successfully applied to suppress the formation of dendritic and mossy deposits on the surface of the zinc electrode at both 7.5 and 2 mAcm−2 charging current density. The stability of the rechargeable battery was tested, where stable operation was achieved with all the synthesized dicarboxyl telechelic PEGs. Furthermore, the long-term cyclic performance was investigated with charging/discharging cycles up to 68 h, where stable battery potentials were obtained with near 100% Coulombic efficiency during the entire measurement. In the presence of additives, the discharging steps were also mathematically modeled. The electrode surfaces were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The additive-free systems resulted in mossy-like deposition, while in the presence of dicarboxyl telechelic PEG additives the surface of the zinc electrode remained smooth and the weight of the electrode did not change after the long-term test.}, keywords = {DEPOSIT; Rechargeable Zn-air battery; Charcoal/graphite cathode; Dicarboxyl telechelic PEGs}, year = {2021}, eissn = {1873-3859}, orcid-numbers = {Nagy, Tibor/0000-0001-8568-914X} } @CONFERENCE{MTMT:33728969, title = {Új típusú poliureánok előállítása szacharóz, 1,6-hexametilén diizocianát (HDI) és epszilon-kaprolakton felhasználásával = Preparation of New Type Polyurethanes Containing Sucrose,1,6-hexamethylene Diisocyanate (HMDI) and epsilon-Caprolacton}, url = {https://m2.mtmt.hu/api/publication/33728969}, author = {Kordován, Marcell Árpád and Nagy, Lajos and Nagy, Miklós and Vadkerti, Bence and Daróczi, Lajos and Deák, György and Zsuga, Miklós and Kéki, Sándor}, booktitle = {25th International Conference on Chemistry = XXV. Nemzetközi Vegyészkonferencia}, unique-id = {33728969}, abstract = {Az előadásban az általunk előállított poliuretánok karakterizálását és lehetséges felhasználását mutatjuk be. A szintézist két lépésben valósítottuk meg: első lépésben a prepolimert állítottuk elő, majd a képződött prepolimert szacharózzal térhálósítottuk. A polimer kémiai szerkezetét MALDI-TOF MS, 1 H-NMR és IR spektroszkópiával vizsgáltuk. A duzzadási vizsgálatokat különböző oldószerekben végeztük el. A térhálósűrűség meghatározásához a Flory-Rehner összefüggést alkalmaztuk. Tapasztalataink alapján a térhálósító szacharóz mennyiségének növelése csökkentette a térhálósűrűséget, melyet a DMA vizsgálatok is alátámasztottak. A feszültség-megnyúlás görbéket modelleztük. In this presentation, we will discuss the preparation, characterization and possible uses of polyurethanes. A series of different compositions of PUR samples were prepared. Synthesis of the polymers were done in two steps: synthesis of the pre-polymer and the network formation. MALDI-TOF MS, 1 H-NMR and IR spectroscopy were used for chemical characterization. Swelling experiments of the polymers were performed with various solvents. Flory-Rehner equation was used for the determination of crosslink density. We found that the crosslink density decreased with the increasing sucrose content. Dynamic mechanical analysis (DMA) also supported our finding. Furthermore, the stress-strain curves for the PUR samples were recorded and modeled. In addition, we also prepared PUR scaffold.}, keywords = {SCAFFOLD; poliuretán; 1,6-hexametilén-diizocianát; mechanikai vizsgálatok; duzzadás}, year = {2019}, pages = {55-56}, orcid-numbers = {Nagy, Miklós/0000-0002-3484-2244} } @CONFERENCE{MTMT:33721037, title = {Szacharóz tartalmú poliuretán scaffoldok előállítása és karakterizálása}, url = {https://m2.mtmt.hu/api/publication/33721037}, author = {Vadkerti, Bence and Nagy, Lajos and Nagy, Miklós and Daróczi, Lajos and Deák, György and Zsuga, Miklós and Kéki, Sándor}, booktitle = {Biotechnológia a Debreceni Egyetemen Tudományos szimpózium: Program és összefoglalók}, unique-id = {33721037}, year = {2019}, pages = {26-27}, orcid-numbers = {Nagy, Miklós/0000-0002-3484-2244} } @article{MTMT:30825454, title = {Designed polyurethanes for potential biomedical and pharmaceutical applications: Novel synthetic strategy for preparing sucrose containing biocompatible and biodegradable polyurethane networks}, url = {https://m2.mtmt.hu/api/publication/30825454}, author = {Nagy, Lajos and Nagy, Miklós and Vadkerti, B. and Daróczi, Lajos and Deák, György and Zsuga, Miklós and Kéki, Sándor}, doi = {10.3390/polym11050825}, journal-iso = {POLYMERS-BASEL}, journal = {POLYMERS}, volume = {11}, unique-id = {30825454}, abstract = {In this paper the preparation and detailed characterization of designed polyurethanes (SPURs) are reported for potential biological, biomedical and/or pharmaceutical applications. Importantly, in order to fulfill these goals all reactants and solvents used were selected according to the proposal of EUR-8 Pharmacopoeia. For the synthesis, a novel strategy was introduced and elaborated. Aseries ofSPURsamples was prepared frompoly(ε-caprolactone)-diol, 1,6-hexamethylene diisocyanate and sucrose as a chain extender/crosslinking agent to obtain sucrose containing polyurethanes. In addition, the mol ratios of the sucrose were varied within an order of magnitude. The prepolymers and the products of the syntheses were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and infrared spectroscopy (IR), respectively. It was found that the reactivity of the eight free hydroxyl groups of sucrose are different, and after curing the SPUR samples at 60 °C no free isocyanate groups can be observed. Furthermore, swelling experiments performed with various solvents of different polarities revealed that the highest degree of swelling took place in dimethyl-sulfoxide. However, low degrees of swelling were recognized in water and hexane. It is important to note that the gel contents were around 90% in all cases, which demonstrate that the crosslinking was almost complete. In addition, the kinetics of swelling were also evaluated and successfully modeled. The crosslink densities were calculated from the data of the swelling experiments by means of the Flory-Rehner equation. Unexpectedly, it was found that the crosslink density decreased with the increasing sucrose content also in line with the results obtained by relaxation modulus experiments and dynamic mechanical analysis (DMA). The Tg and Tm of SPUR samples, determined from DSC and DMA measurements, were around -57 °C and 27 °C, respectively. According to the mechanical tests the SPUR samples showed high elongation at break values, i.e., high flexibilities. Furthermore, the stress-strain curves were also modeled and discussed. © 2019 by the authors.}, year = {2019}, eissn = {2073-4360}, orcid-numbers = {Nagy, Miklós/0000-0002-3484-2244} }