Articoli di riviste: "Continuous powder synthesis reactor"

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Cho, Young-Sang, Chiyeop Hwang, Seong-Jun Kim e U.-Hyeon Park. "Continuous Synthesis of Monodisperse Spherical Silica Powder Using Tubular Reaction System". Korean Journal of Metals and Materials 60, n. 6 (5 giugno 2022): 409–22. http://dx.doi.org/10.3365/kjmm.2022.60.6.409.

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In the present study, monodisperse silica nanospheres were synthesized using a tubular reaction system in a continuous way. Screw-type blades were inserted inside a T-mixer for static mixing of the reactant streams which consisted of TEOS and NH4OH/H2O diluted with ethanol, for the continuous synthesis of the silica suspension. The diameter of the silica powder was monitored as a function of production time using dynamic light scattering to determine the optimum retention time and tube length, which were found to be 125 minutes and 7.5 m, respectively. The effects of reactant compositions on particle size were investigated by adjusting the amount of ammonia and water in the sol-gel reaction, which were then compared with the results from a batch reactor. Both the particle size and polydispersity index (PDI) of the silica suspension were measured to be comparable to nanospheres synthesized using a batch reactor. This implies that the tubular reaction system is more beneficial for potential industrial production applications in the size range from 115 to 310 nm, due to its continuous powder synthesis. The effect of the reaction medium was also studied, by replacing ethanol with methanol or propanol, indicating that the deviation in particle size with production time was not a serious issue in alcohols with lower molecular weight, such as methanol and ethanol.

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Kammler, Hendrik K., e Sotiris E. Pratsinis. "Carbon-coated titania nanostructured particles: Continuous, one-step flame-synthesis". Journal of Materials Research 18, n. 11 (novembre 2003): 2670–76. http://dx.doi.org/10.1557/jmr.2003.0373.

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Concurrent synthesis of titania-carbon nanoparticles (up to 52 wt.% in C) was studied in a diffusion flame aerosol reactor by combustion of titanium tetraisopropoxide and acetylene. These graphitically layered carbon-coated titania particles were characterized by high-resolution transmission electron microscopy (HRTEM), with elemental mapping of C and Ti, x-ray diffraction (XRD), and nitrogen adsorption [Brunauer-Emmett-Teller (BET)]. The specific surface area of the powder was controlled by the acetylene flow rate from 29 to 62 m2/g as the rutile content decreased from 68 to 17 wt.%. Light blue titania suboxides formed at low acetylene flow rates. The average XRD crystal size of TiO2 decreased steadily with increasing carbon content of the composite powders, while the average BET primary particle size calculated from nitrogen adsorption decreased first and then approached a constant value. The latter is attributed to the formation of individual carbon particles next to carbon-coated titania particles as observed by HRTEM and electron spectroscopic imaging.

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Courtecuisse, V. Gourincha, J. F. Bocquet, K. Chhor e C. Pommier. "Modeling of a continuous reactor for TiO2 powder synthesis in a supercritical fluid — experimental validation". Journal of Supercritical Fluids 9, n. 4 (dicembre 1996): 222–26. http://dx.doi.org/10.1016/s0896-8446(96)90052-2.

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Medesi, Anna Julia, Dorit Nötzel e Thomas Hanemann. "PVB/PEG-Based Feedstocks for Injection Molding of Alumina Microreactor Components". Materials 12, n. 8 (14 aprile 2019): 1219. http://dx.doi.org/10.3390/ma12081219.

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The ceramic injection molding (CIM) process is a cost-effective powder-based near net shape manufacturing process for large-scale production of complex-shaped ceramic functional components. This paper presents the rheological analysis of environmentally friendly CIM feedstock formulations based on the binder components polyvinyl butyral (PVB) and polyethylene gycol (PEG). The prepared PVB/PEG-based alumina molding compounds were investigated with respect to their PVB:PEG ratios as well as to their powder filling degrees in the range between 50 and 64 vol.%. Corresponding viscosities and shear stresses were determined for increasing shear rates to show the effects of increased PEG content and solid loadings on them. Two single reactor components were injection molded and subsequently joined in their green state for fabrication of an alumina microreactor. The intended purpose of the alumina microreactors is their potential application as wear-resistant and hydrothermal stable multifunctional devices (µ-mixer, µ-reactor, µ-analyzer) for continuous hydrothermal synthesis (CHTS) of metal oxide nanoparticles in supercritical water (sc-H2O) as the reaction medium.

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Zeng, Ling Ke, Yan Chun Liu, Wen Cheng Zhu, Ping An Liu, Hui Wang, Xiao Su Cheng e Qian Ying Liang. "Investigation on the Continuous Microwave Synthesis of Nano Titanium Carbide Powder". Advanced Materials Research 1064 (dicembre 2014): 66–70. http://dx.doi.org/10.4028/www.scientific.net/amr.1064.66.

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In this paper, the reaction mechanism of inorganic carbon and titanium dioxide synthesis of titanium carbide thermodynamic were explored, and a thermodynamic basis date for the microwave heating was provided. Through analyzing the experimental results for the thermal stability of titanium carbide, we could obtain the theoretical parameters for the actual synthesis process.

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Azami, Mahmoud, Sasan Jalilifiroozinezhad e Masoud Mozafari. "Calcium Fluoride/Hydroxyfluorapatite Nanocrystals as Novel Biphasic Solid Solution for Tooth Tissue Engineering and Regenerative Dentistry". Key Engineering Materials 493-494 (ottobre 2011): 626–31. http://dx.doi.org/10.4028/www.scientific.net/kem.493-494.626.

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In this research, a novel biphasic solid solution consisted of Calcium fluoride (CF) and fluorinated-hydroxyapatite (FHAp) was successfully synthesized through a modified precipitation method using buffer solution. The obtained results confirmed the formation of biphasic nanocrystalline powder composed of about 46% CF and 54% (w/w%) FHAp. This product can be considered as an osteoconductive dental filler or implant with the ability of dental carries prevention due to release of fluorine ions. Herein, the usage of buffer solution for this purpose not only can produces biphasic powder but also provides the possibility of establishment of a continuous synthesis method without manual interfere for adjusting pH of the reactor.

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Petrov, Stanislav, Serhii Bondarenko e Koichi Sato. "Consideration of the possibility of large-scale plasma-chemical production of nanosilicon for lithium-ion batteries". Technology audit and production reserves 3, n. 3(65) (27 giugno 2022): 6–14. http://dx.doi.org/10.15587/2706-5448.2022.259066.

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The object of research is the process of obtaining silicon nanomaterials for lithium-ion batteries of energy storage devices, and the subject of research is the technology of gas-phase plasma-chemical synthesis for the production of Si-nanoparticles. In the course of the study, numerical simulation methods were used, which made it possible to determine the parameters of temperature fields, velocities and concentrations. To study the processes of synthesis of nanopowders, a plasma reactor with an electric arc plasma torch of a linear scheme and using an argon-hydrogen mixture as a plasma-forming gas was developed. To analyze the influence of an external magnetic field on the control of the plasma jet parameters, a series of experiments was carried out using an electric arc plasma torch on plasma laboratory facilities with a power of 30 and 150 kW. The influence of a magnetic field on the process of formation and evaporation of a gas-powder flow in a plasma jet was studied by determining the configuration, geometric dimensions, and structure of the initial section of the jet. In this case, the dispersed material – silicon powder was fed to the plasma torch nozzle section according to the radial scheme. Experimental confirmation of the phenomenon of elongation of the high-temperature initial section of the plasma jet in a longitudinal magnetic field has been obtained. The experimental results indicate that the creation of a peripheral gas curtain significantly changes the characteristics of heat and mass transfer in the reactor. It should be expected that for optimization it is possible to exclude the deposition of nanosilicon particles on the walls of the reactor and provide conditions for continuous operation. The effect of two-phase flow, heat transfer, and mass flow of nanoparticles, including the surface of a plasma reactor with limited jet flow, in the processes of obtaining silicon nanopowders has been studied. This made it possible to correct a number of technological characteristics of the process of constructive design of the actions of plasma synthesis of nanopowders. The patterns obtained can be used for constructive and technological design in the creation and development of a pilot plant for high-performance production of nanosilicon powders.

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Li, Mi, Xiao Wu, Dongxue Han, Renyu Peng, Yong Yang, Li Wu e Wencong Zhang. "A High-Efficiency Single-Mode Traveling Wave Reactor for Continuous Flow Processing". Processes 10, n. 7 (24 giugno 2022): 1261. http://dx.doi.org/10.3390/pr10071261.

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This paper proposes a high-efficiency single-mode traveling wave reactor based on a rectangular waveguide and its design method for continuous flow processing. The reactor has a large-capacity reaction chamber (1000 mm × 742.8 mm × 120 mm) that can provide high-energy-efficiency and approximately uniform microwave heating. The microwave heating uniformity is improved by maintaining single-mode microwave transmission and eliminating higher-order modes in such a multi-mode reaction chamber. The high energy efficiency of microwave heating is achieved by adopting impedance matching techniques. The incident microwave in the reactor can remain in a traveling wave state, and the power reflection can be minimized. Several numerical simulations based on multi-physics modeling are conducted to investigate the heating uniformity, the energy efficiency and the flexibility under different operation conditions. The results show the microwave energy efficiency can be higher than 99%, and meanwhile, the coefficient of temperature variation can be lower than 0.4. Furthermore, when the reactor is operated under different flow velocities and with different heating materials, both the energy efficiency and the heating uniformity can also meet the above requirements. The proposed reactor can be used in the applications such as oil processing, wastewater tackling, chemical synthesis, beverage sterilization and other microwave-assisted continuous flow processes that require high heating uniformity, high energy efficiency and good adaptability.

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Lübke, Mechthild, Juhun Shin, Peter Marchand, Dan Brett, Paul Shearing, Zhaolin Liu e Jawwad A. Darr. "Highly pseudocapacitive Nb-doped TiO2 high power anodes for lithium-ion batteries". Journal of Materials Chemistry A 3, n. 45 (2015): 22908–14. http://dx.doi.org/10.1039/c5ta07554h.

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Yan, Xiaojie, William Trevillyan, Ioannina Castano, Yugang Sun, Ralph Muehleisen e Jie Li. "Continuous-Flow Synthesis of Thermochromic M-Phase VO2 Particles via Rapid One-Step Hydrothermal Reaction: Effect of Mixers". Journal of Nanomaterials 2019 (10 giugno 2019): 1–10. http://dx.doi.org/10.1155/2019/2570698.

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VO2 particles are promising materials for thermochromic smart windows that reduce building energy loss. Continuous-flow hydrothermal processes showcase advantages for synthesizing VO2 particles compared with traditional batch reaction systems. Mixers play a crucial role in particle fabrication in continuous-flow systems. In this study, a Center T-Mixer and a Collision Cross-Mixer are developed and implemented in a hot water fluidized suspension reaction (HWFSR) system. The influence of the resident time on the particle phase and size was evaluated, and properties of particles derived from systems equipped with differing mixers were compared. The resulting particles were characterized using techniques of X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). When compared with the Center T-Mixer, results indicate that the Collision Cross-Mixer has better control regarding the morphology and size distribution of resulting particles while improving the transition temperatures of the as-synthesized materials. HWFSR systems containing novel mixer designs are capable of producing pure M-phase VO2 particles in a single step contrary to the current reactor design that use a second postheat treatment step, and they are capable of synthesizing many other nanoparticle species, especially those requiring high temperature and pressure reaction conditions.

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Fantoni, R., E. Borsella, S. Piccirillo, R. Ceccato e S. Enzo. "Laser synthesis and crystallographic characterization of ultrafine SiC powders". Journal of Materials Research 5, n. 1 (gennaio 1990): 143–50. http://dx.doi.org/10.1557/jmr.1990.0143.

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High purity, ultrafine SiC powders have been produced from gas phase reactants (SiH4, C2H2) in a CO2 laser induced process. The flow reactor designed to operate with a medium power (10–50 W) continuous wave CO2 laser source is described. The mechanism of gas phase reactions involved has been investigated by means of on-line optical diagnostics. Powders produced have been characterized by means of conventional chemical and spectroscopic methods. The x-ray results point out a growth mechanism by coalescence; i.e., whole islands move in the flame to take part in binary collisions, analogously to that observed for particles produced by inert gas evaporation.

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Dateraksa, Kannigar, e Sujarinee Sinchai. "Influence of precursor preparation on the synthesis of boron carbide from glutinous rice flour". Journal of Metals, Materials and Minerals 31, n. 3 (28 settembre 2021): 39–46. http://dx.doi.org/10.55713/jmmm.v31i3.1165.

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Boron carbide is a promising candidate for a variety of applications, including blasting nozzles, neutron moderators, and lightweight armor. Using of inexpensive and readily available starting materials which can react with boric acid to form B-O-C bonds, e.g., glutinous rice flour, is one of alternative means to produce high purity boron carbide powder at low temperature. In this study, boric acid and glutinous rice flour, boron and carbon sources, were used for synthesizing B4C powder by the carbothermic reduction. The mole ratios of boric acid to glutinous rice flour ranging from 1:1 to 2.5:1 were formulated and mixed by continuous stirring at 80℃ for 2 h to 8 h. The influence of reaction time during the mixing process on the phase formation of the synthesized powder was investigated. It was found that appropriate reaction time for condensation of 4 h facilitated the B4C phase formation during synthesis. The precursors were synthesized under Ar flow at 1350℃ to 1450℃ for 5 h without calcination. B4C powder with the purity of 90 wt% was successfully synthesized from this study. Chemical bonding, phase analysis, and morphology of the synthesized powder were identified by Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope, respectively. The influences of starting composition and synthesis temperature on the characteristics of the synthesized powders were also discussed.

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Taddei, Marco, Nicola Casati, Daniel A. Steitz, Kim C. Dümbgen, Jeroen A. van Bokhoven e Marco Ranocchiari. "In situ high-resolution powder X-ray diffraction study of UiO-66 under synthesis conditions in a continuous-flow microwave reactor". CrystEngComm 19, n. 23 (2017): 3206–14. http://dx.doi.org/10.1039/c7ce00867h.

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Chudoba, Tadeusz, Edward Lester, Witold Łojkowski, Martin Poliakoff, Jun Li, Ewa Grzanka e Adam Presz. "Synthesis of Nano-sized Yttrium-Aluminum Garnet in a Continuous-Flow Reactor in Supercritical Fluids". Zeitschrift für Naturforschung B 63, n. 6 (1 giugno 2008): 756–64. http://dx.doi.org/10.1515/znb-2008-0625.

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The conditions for obtaining pure yttrium-aluminum garnet (YAG) in a one-step process starting from components soluble in supercritical (SCR) liquids in a flow reactor have been studied. The powders were characterized using XRD, BET, SEM and helium pycnometry. Favorable conditions for YAG production were achieved using acetates (and acetylacetonates) in aqueous-alcoholic solutions as starting materials. Aqueous and alcoholic solutions of nitrates and aqueous solutions of acetates were found not appropriate as precursors for YAG production. The powders obtained had the shape of nano-sized cubes with diameters in the range 80 - 120 nm. After annealing at 600 °C the powders have comparable density as those made via a conventional precipitation-calcination route but differ from the calcinated products form soft agglomerates.

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Vasileiadis, Savvas, e Zoe Ziaka. "Small Scale Reforming Separation Systems with Nanomembrane Reactors for Direct Fuel Cell Applications". Journal of Nano Research 12 (dicembre 2010): 105–13. http://dx.doi.org/10.4028/www.scientific.net/jnanor.12.105.

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Our recent communication focuses on small scale and nanoscale type engineering applications of alumina inorganic membrane reactors and reactor-permeator systems for the conversion of renewable and non-renewable hydrocarbons and methane rich streams into hydrogen rich gas for direct inner application and operation of fuel cell systems. This study elaborates on new nanomembrane reactors for the steam-methane/hydrocarbon reforming and water gas shift reactions, including work in the synthesis, manufacturing, modeling and operation of such microreaction systems. The projected small scale reactors, separators and overall reaction systems are of current significance in the area of multifunctional microreactor and nanoreactor design and operation in connection with the operation of fuel cells for transportation, stationary, and portable power generation applications. An added advantage of such systems is the reactive and separative operations of the fuel cell membrane-processor which are combined to convert the hydrocarbon with steam to valuable fuel gas for continuous fuel cell operation. Moreover, the nanomembrane systems under development have the unique characteristics to perform multiple operations per unit volume, such as to utilize beneficial equilibrium shift principles in reactant conversion and product yield through the removal of permselective species (i.e., hydrogen) via the inorganic membrane out of the conversion/reaction zone. In this way, improved hydrogen and product yields can be achieved which exceed the equilibrium calculated yields. Simultaneously, the reaction products, such as synthesis gas (i.e., H2, CO and CO2) at the reactor exit can be used as fuel in mostly solid oxide and molten carbonate fuel cells. The role of the alumina nanomembrane is also in the main conversion and upgrading sections of these feedstocks in order to overcome existing heat and mass transfer limitations and increase the overall efficiency of the microreactor-fuel cell system.

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Sampaio, Ana Beatriz S., Mônica Shigemi S. Mori, Lorena C. Albernaz, Laila S. Espindola, Carlos Eduardo M. Salvador e Carlos Kleber Z. Andrade. "Continuous Flow Photochemical Synthesis of 3-Methyl-4-arylmethylene Isoxazole-5(4H)-ones through Organic Photoredox Catalysis and Investigation of Their Larvicidal Activity". Catalysts 13, n. 3 (3 marzo 2023): 518. http://dx.doi.org/10.3390/catal13030518.

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Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction might be induced by light, as described in previous works. Remarkable results were obtained using a high-power lamp, reducing reaction times compared to methodologies that used heating or catalysis. Since there are many examples of successful continuous flow heterocycle synthesis, including photochemical reactions, the study evolved to run the reaction in flow conditions and scale up the synthesis of isoxazolones using a photochemical reactor set-up. Eight different compounds were obtained, and among them, three showed larvicidal activity on immature forms of Aedes aegypti in tests that investigated its growth inhibitory character. Mechanistic investigations indicate that the reactions occur through organic photoredox catalysis.

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Claes, Joris, Arne Vancleef, Marleen Segers, Bert Brabants, Mumin Enis Leblebici, Simon Kuhn, Luc Moens e Leen C. J. Thomassen. "Synthesis of amines: From a microwave batch reactor to a continuous milliflow reactor with heterogeneous feed and product". Chemical Engineering and Processing - Process Intensification 183 (gennaio 2023): 109252. http://dx.doi.org/10.1016/j.cep.2022.109252.

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Dipheko, Tshepo D., Vladimir V. Maximov, Mohamed E. Osman, Oleg L. Eliseev, Alexander G. Cherednichenko, Tatiana F. Sheshko e Victor M. Kogan. "Synthesis of Oxygenated Hydrocarbons from Ethanol over Sulfided KCoMo-Based Catalysts: Influence of Novel Fiber- and Powder-Activated Carbon Supports". Catalysts 12, n. 12 (23 novembre 2022): 1497. http://dx.doi.org/10.3390/catal12121497.

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Ethanol has become a viable feedstock for basic organic synthesis. The catalytic conversion of ethanol provides access to such chemicals as diethyl ether, ethyl acetate, and acetaldehyde. Carbonaceous materials are extensively studied as supports for heterogeneous catalysts due to their chemical and thermal stability, high surface area, and tunable texture. In this paper, ethanol conversion over K10Co3.7Mo12S-catalysts supported on novel activated carbon (AC) materials (i.e., novel powder-AC (DAS and YPK-1), fiber non-woven AC material (AHM), and fabric active sorption (TCA)) was investigated. The catalysts were prepared by the incipient wetness co-impregnation method followed by sulfidation. The catalysts were characterized by employing N2 adsorption–desorption measurements, TEM, SEM/EDX, UV–Vis spectroscopy, and XRF. Catalytic performance was assessed in a fixed-bed down-flow reactor operating at 320 °C, 2.5 MPa, and with continuous ethanol feeding in an He atmosphere. Activity is highly dependent on the support type and catalyst’s textural properties. The activity of the fiber-supported catalysts was found to be greater than the powder-supported catalysts. Ethanol conversion at T = 320 °C, P = 2.5 MPa, and GHSV = 760 L h−1 kgcat−1 increased as follows: (38.7%) KCoMoS2/YPK-1 < (49.5%) KCoMoS2/DAS < (58.2%) KCoMoS2/TCA < (67.1%) KCoMoS2/AHM. Catalysts supported by powder-AC enhanced the formation of MoS2-crystallites, whereas the high acidity of fiber-AC seemed to inhibit the formation of MoS2-crystallites. Simultaneously, a high surface area and a microporous catalytic structure enhance the formation of oxygenates from hydrocarbons. The dehydration and dehydrogenation reactions, which led to the creation of ethene and acetaldehyde, were shown to require a highly acidic catalyst, while the synthesis of ethyl acetate and higher alcohols required a less acidic catalyst.

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Yang, Guijun, e Soo-Jin Park. "Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review". Materials 12, n. 7 (11 aprile 2019): 1177. http://dx.doi.org/10.3390/ma12071177.

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With the continuous development and progress of materials science, increasingly more attention has been paid to the new technology of powder synthesis and material preparation. The hydrothermal method is a promising liquid phase preparation technology that has developed rapidly during recent years. It is widely used in many fields, such as the piezoelectric, ferroelectric, ceramic powder, and oxide film fields. The hydrothermal method has resulted in many new methods during the long-term research process, such as adding other force fields to the hydrothermal condition reaction system. These force fields mainly include direct current, electric, magnetic (autoclaves composed of non-ferroelectric materials), and microwave fields. Among them, the microwave hydrothermal method, as an extension of the hydrothermal reaction, cleverly uses the microwave temperature to compensate for the lack of temperature in the hydrothermal method, allowing better practical application. This paper reviews the development of the hydrothermal and microwave hydrothermal methods, introduces their reaction mechanisms, and focuses on the practical application of the two methods.

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Kleiber, Sascha, Moritz Pallua, Matthäus Siebenhofer e Susanne Lux. "Catalytic Hydrogenation of CO2 to Methanol over Cu/MgO Catalysts in a Semi-Continuous Reactor". Energies 14, n. 14 (17 luglio 2021): 4319. http://dx.doi.org/10.3390/en14144319.

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Methanol synthesis from carbon dioxide (CO2) may contribute to carbon capture and utilization, energy fluctuation control and the availability of CO2-neutral fuels. However, methanol synthesis is challenging due to the stringent thermodynamics. Several catalysts mainly based on the carrier material Al2O3 have been investigated. Few results on MgO as carrier material have been published. The focus of this study is the carrier material MgO. The caustic properties of MgO depend on the caustification/sintering temperature. This paper presents the first results of the activity of a Cu/MgO catalyst for the low calcining temperature of 823 K. For the chosen calcining conditions, MgO is highly active with respect to its CO2 adsorption capacity. The Cu/MgO catalyst showed good catalytic activity in CO2 hydrogenation with a high selectivity for methanol. In repeated cycles of reactant consumption and product condensation followed by reactant re-dosing, an overall relative conversion of CO2 of 76% and an overall selectivity for methanol of 59% was obtained. The maximum selectivity for methanol in a single cycle was 88%.

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Lock, Nina, Peter Hald, Mogens Christensen, Henrik Birkedal e Bo Brummerstedt Iversen. "Continuous flow supercritical water synthesis and crystallographic characterization of anisotropic boehmite nanoparticles". Journal of Applied Crystallography 43, n. 4 (24 giugno 2010): 858–66. http://dx.doi.org/10.1107/s0021889810019187.

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Crystalline boehmite nanoparticles have been prepared in a few minutes from thermal decomposition of aluminium nitrate in near- and supercritical water. Highly anisotropic nanoparticles are formed under continuous flow conditions using T-piece mixing and a large size tube diameter. The shapes and sizes of the synthesized nanocrystals were determined from peak shape analysis of powder X-ray diffraction data. The crystallite morphology is pressure dependent, and the size increases with temperature for constant reaction time and pressure. The modelled crystallite sizes and anisotropic shapes are in good agreement with transmission electron microscopy studies. At lower synthesis pressures the boehmite crystallite morphology is a mixture of platelets and bar-shaped crystals. The bar-shaped crystals align into polycrystalline fibre-like long thin needles, which again align sidewise in bundles. At higher pressures, only the polycrystalline fibres are formed. Full conversion of dried boehmite to γ-Al2O3is observed after short-term heating to 773 K with an overall conservation of the morphology.

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Asghari, Mohammadreza, Bahram Hosseinzadeh Samani, Rahim Ebrahimi, Sajad Rostami e Ebrahim Fayyazi. "Optimization of a novel liquid phase capillary discharge plasma reactor for continuous methyl ester synthesis". Energy Conversion and Management 277 (febbraio 2023): 116667. http://dx.doi.org/10.1016/j.enconman.2023.116667.

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Ötvös, Sándor B., Ádám Georgiádes, István M. Mándity, Lóránd Kiss e Ferenc Fülöp. "Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production". Beilstein Journal of Organic Chemistry 9 (29 luglio 2013): 1508–16. http://dx.doi.org/10.3762/bjoc.9.172.

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The preparation of novel multi-substituted 1,2,3-triazole-modified β-aminocyclohexanecarboxylic acid derivatives in a simple and efficient continuous-flow procedure is reported. The 1,3-dipolar cycloaddition reactions were performed with copper powder as a readily accessible Cu(I) source. Initially, high reaction rates were achieved under high-pressure/high-temperature conditions. Subsequently, the reaction temperature was lowered to room temperature by the joint use of both basic and acidic additives to improve the safety of the synthesis, as azides were to be handled as unstable reactants. Scale-up experiments were also performed, which led to the achievement of gram-scale production in a safe and straightforward way. The obtained 1,2,3-triazole-substituted β-aminocyclohexanecarboxylates can be regarded as interesting precursors for drugs with possible biological effects.

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Tulaphol, Sarttrawut, Nurak Grisdanurak, Franklin Anariba, Chantra Tongcumpou e Pummarin Khamdahsag. "Batch and Continuous Flow Treatment Studies of Trichloroethylene Contaminated in Water by Silver and Cerium Doped Zinc Oxide Adsorption and Photocatalysis". Sains Malaysiana 52, n. 2 (28 febbraio 2023): 533–45. http://dx.doi.org/10.17576/jsm-2023-5202-16.

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The development of photocatalytic treatment in continuous flow systems to be more practical is challenging. This research aimed to study batch and continuous flow treatment of trichloroethylene (TCE) contaminated in water by silver and cerium doped zinc oxide (0.005Ag-0.005Ce-ZnO) visible light driven photocatalyst. This catalyst was selected to represent the green route synthesis with simplicity and ease of upscaling. The 0.005Ag-0.005Ce-ZnO powder was synthesized using sticky rice flour as a template. Mechanical coating of the 0.005Ag-0.005Ce-ZnO powder on activated alumina (Al2O3) beads was done to improve the appropriate packing in the fixed bed columns. Characterization of 0.005Ag-0.005Ce-ZnO showed a higher response to visible light and smaller crystallite size compared to zinc oxide synthesized with the same method. Using sticky rice starch as a template increased the uniform distribution of the elements. The photocatalytic batch test over 0.005Ag-0.005Ce-ZnO powder, 0.30 g/100 mL, could remove TCE up to 80% in 180 min. The decrease of TCE via photocatalysis compared to volatilization, adsorption, and photolysis presented the predominance of photocatalysis. Langmuir-Hinshelwood kinetics described that the decrease of TCE more depended on the reaction than adsorption. In addition, the TCE degradation steadily remained at 80-90% along the run of 0.005Ag-0.005Ce-ZnO@Al2O3 photocatalysis under visible light from both warm white lamps and sunlight in the continuous flow system. Besides photocatalysis, TCE adsorption on 0.005Ag-0.005Ce-ZnO@Al2O3 packed in the columns showed significant results. Our findings presented the possibility of applying the photocatalytic continuous flow system to remove TCE in industrial wastewater.

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Li, Qingyun, Lingyu Liu, Zihua Wang e Xuezhong Wang. "Continuous Hydrothermal Flow Synthesis and Characterization of ZrO2 Nanoparticles Doped with CeO2 in Supercritical Water". Nanomaterials 12, n. 4 (17 febbraio 2022): 668. http://dx.doi.org/10.3390/nano12040668.

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A confined jet mixing reactor operated in continuous hydrothermal flow synthesis was investigated for the synthesis of CeO2-ZrO2 (CZ) nanoparticles. The obtained ultrafine powders were characterized using scanning electron microscopy–energy dispersive spectrometry (SEM-EDS), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED), a BET (Brunauer-Emmett-Teller)-specific surface area test and pore analysis, oxygen storage capacity (OSC) test, and a H2 temperature programmed reduction (H2-TPR) test. The XRD results show that all samples were composed of high-purity cubic CZ nanoparticles. High resolution transmission electron microscope (HR-TEM) analysis showed that CZ nanoparticles with uniform size and shape distributions were obtained in this investigation. The d-spacing values, determined based on the TEM-selected area electron diffraction (SAED) patterns, were in good agreements with the reference data. BET results showed that the prepared CZ samples had large specific surface areas. Pore volume and size distribution were obtained by pore analysis. Oxygen pulse adsorption technology was used to test the oxygen storage capacity of the sample. The redox capacity of the CZ material was determined by a H2 temperature-programmed reduction test.

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Kuznetsov, Maxim V., Ivan P. Parkin, A. Kvick, S. M. Busurin, I. V. Shishkovskiy e Yuri G. Morozov. "Advanced Ways and Experimental Methods in Self-Propagating High-Temperature Synthesis (SHS) of Inorganic Materials". Materials Science Forum 518 (luglio 2006): 181–88. http://dx.doi.org/10.4028/www.scientific.net/msf.518.181.

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New experimental methods for investigations of phase formation during SHS have been established. First experiments using penetrating synchrotron radiation and energy dispersive detectors for different classes of complex inorganic materials were carried out at ESRF (Grenoble, France) and Daresbury (UK). A new and very sensitive thermal imaging method (Thermal Imaging Technique (TIT)) based on continuous registration of the whole combustion process by using highly sensitive IR-camera and software developed by MIKRON Instruments Co. (USA) was used for precise registration of the combustion parameters. SHS was performed on different types of pure and doped complex inorganic materials in pellet and powder form in a range of dc magnetic fields up to 20 T and in electrical field strengths up to ±220 kV/m. The dc magnetic field was applied during the reaction, supplied either by a permanent magnet (transverse, up to 1.1 T) or by an electromagnet (longitudinal, up to 20 T). The dc electrical field was applied along the direction of the combustion wave front propagation. The combined processes of SHS and SLS (Selective Laser Sintering) of 3D articles for different powdered compositions were optimized with laser irradiation power.

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27

Pavlenko, Anatoliy M., e Hanna Koshlak. "Intensification of Gas Hydrate Formation Processes by Renewal of Interfacial Area between Phases". Energies 14, n. 18 (17 settembre 2021): 5912. http://dx.doi.org/10.3390/en14185912.

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This paper presents the analysis of the main reasons for a significant decrease in the intensity of diffusion processes during the formation of gas hydrates; solutions to this problem are proposed in a new process flow diagram for the continuous synthesis of gas hydrates. The physical processes, occurring at the corresponding stages of the process flow, have been described in detail. In the proposed device, gas hydrate is formed at the boundary of gas bubbles immersed in cooled water. The dynamic effects arising at the bubble boundary contribute to the destruction of a forming gas hydrate structure, making it possible to renew the contact surface and ensure efficient heat removal from the reaction zone. The article proposes an assessment technique for the main process parameters in the synthesis of hydrates based on the criterion of thermodynamic parameters optimization. The optimization criterion determines the relationship of intensity of heat and mass transfer processes at the phase contact interface of reacting phases, correlating with the maximum GH synthesis rate, and makes it possible to determine optimum thermodynamic parameters in the reactor zone.

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Espootin, Simin, Mohammad Sameti e Sahar Zaker. "Biodiesel from fish waste oil: synthesis via supercritical methanol and thermodynamic optimization". Clean Energy 5, n. 2 (22 aprile 2021): 187–95. http://dx.doi.org/10.1093/ce/zkab003.

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Abstract This study evaluates the potential of local fish waste oil as a feedstock for biodiesel via supercritical methanol transesterification (SCMT). Hexane was used as a cosolvent and the transesterification reaction was carried out in a continuous reactor under supercritical conditions. The response surface methodology (RSM) method was applied to analyse the effect of four independent variables, including the weight ratio of methanol to fish-waste oil (W), the reaction temperature (T), the pressure (P) and the feed flow rate (F), on the yield of the biodiesel production in supercritical methanol. According to the calculated optimal operating condition for the RSM, the values of W (22.3 weight ratio of methanol to fish waste oil), T (270°C), P (112.7 bar) and F (2.0 mL min–1) were achieved. Under the optimum conditions, the highest yield was estimated to be 94.6% (g/g). The obtained yield was found to be close to the theoretical yield (95.2%). This value suggests that the proposed strategy has a promising potential in the production of biodiesel fuel.

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Maxim, Florentina, Elena-Ecaterina Toma, Giuseppe-Stefan Stoian, Cristian Contescu, Irina Atkinson, Christian Ludwig e Speranta Tanasescu. "Continuous Supercritical Water Impregnation Method for the Preparation of Metal Oxide on Activated Carbon Composite Materials". Energies 17, n. 4 (16 febbraio 2024): 913. http://dx.doi.org/10.3390/en17040913.

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Metal oxide (MexOy) nanomaterials are used as catalysts and/or sorbents in processes taking place in supercritical water (scH2O), which is the “green” solvent needed to obtain energy-relevant products. Their properties are significantly influenced by the synthesis method used to prepare active MexOy. In addition, the use of supported MexOy nanoparticles is more practical and cost-effective in terms of their performance maintenance. Within this context, the present study reports on the preparation of carbon-supported ZnO and CuO composites using an innovative scH2O impregnation method. Metal oxides were impregnated on a carbon (C) support using a continuous-flow tubular reactor. The results show that impregnation in scH2O is a promising approach for the preparation of ZnO/C and CuO/C composite materials. This one-step synthesis method, in a continuous flow, uses neither a seed layer nor a mineralizer, and it needs substantially lower preparation times than conventional impregnation methods.

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30

Sitanggang, Azis Boing, Tsaniyah Ayu Mauliasyam, Nadine Kurniadi, Slamet Budijanto e Ho-Shing Wu. "Bioactive Peptides from Velvet Bean Tempe: Neutrase-Catalyzed Production in Membrane Reactor". Jurnal Teknologi dan Industri Pangan 34, n. 2 (25 dicembre 2023): 200–209. http://dx.doi.org/10.6066/jtip.2023.34.2.200.

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Velvet beans are potential sources of parent proteins for bioactive peptide production. In this study, a combination of fermentation and neutrase-catalyzed continuous hydrolysis in an enzymatic membrane reactor was performed to produce antioxidative and angiotensin I-converting enzyme inhibitory (ACEi) peptides. The optimum operating conditions were τ = 6 h and [E]/[S] = 7.5%. The resulting permeate, which was a<10-kDa fraction, exhibited antioxidant activity at 0.38 mg ascorbic acid equivalent antioxidant capacity (AEAC)/mL (2,2-diphenyl-1-picrylhydrazyl, DPPH inhibition) and 0.26 mg AEAC/mL (ferric reducing antioxidant power, FRAP), and ACEi activity of 81.02%. Further fractionation of the permeate increased the ACEi activity in which 2-kDa fraction showed the most potent activity (IC50 = 0.23 µg protein/mL). The IC50 value of the outcome was comparable to those reported in the literature for velvet bean-based peptides. Furthermore, this study suggests that neutrase is a good catalyst candidate for the synthesis of bioactive peptides from velvet beans.

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Sonsiam, Chaloemkrit, Amaraporn Kaewchada, Supakrit pumrod e Attasak Jaree. "Synthesis of 5-hydroxymethylfurfural (5-HMF) from fructose over cation exchange resin in a continuous flow reactor". Chemical Engineering and Processing - Process Intensification 138 (aprile 2019): 65–72. http://dx.doi.org/10.1016/j.cep.2019.03.001.

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32

QI, XIAO-YING, KAN-YI PU, CHUN FANG, QU-LI FAN, DUO-FENG TANG, GUI-AN WEN, FREDDY Y. C. BOEY, HUA ZHANG, LIAN-HUI WANG e WEI HUANG. "CADMIUM TELLURIDE NANOCRYSTALS: SYNTHESIS, GROWTH MODE AND EFFECT OF REACTION TEMPERATURE ON CRYSTAL STRUCTURES". Nano 03, n. 02 (aprile 2008): 109–15. http://dx.doi.org/10.1142/s1793292008000873.

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A series of cadmium telluride (CdTe) nanocrystals were synthesized by a modified organometallic synthesis method at various reaction temperatures ranging from 130 to 250°C. In this method, octadecylamine (ODA) was introduced as an additional coordinating component to the mixture of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP). CdO was used as a precursor. The prepared CdTe nanocrystals were studied by the absorption and emission spectra as well as the powder X-ray diffraction (XRD) patterns. The result shows that besides the traditional continuous-growth mode observed frequently at relatively high reaction temperature, a discontinuous-growth mode was confirmed at the initial growth stage of CdTe nanocrystals, arising from the change of the absorption spectra of CdTe nanocrystals with the reaction time at relatively low reaction temperature. The structures of CdTe nanocrystals, e.g., the cubic zinc blende structure at 160°C and the hexagonal wurtzite structure at 250°C, were characterized by XRD.

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33

Marinca, Traian Florin, Bogdan Viorel Neamțu, Florin Popa, Amalia Mesaroș e Ionel Chicinaș. "Spark Plasma Sintered Soft Magnetic Composite Based on Fe-Si-Al Surface Oxidized Powders". Materials 15, n. 22 (8 novembre 2022): 7875. http://dx.doi.org/10.3390/ma15227875.

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Soft magnetic composites (SMCs) need a stable matrix to apply heat treatments for enhancing their magnetic characteristics. A stable matrix can be offered by alumina, but the densification of the ferromagnetic particles covered by this oxide (by sintering) can be very difficult. This paper proposes a feasible synthesis route for obtaining alumina matrix SMCs. An Fe-Si-Al alloy with nominal composition Fe85Si9Al6 was obtained by mechanical alloying of elemental Fe, Si, and Al powders, and further, the as-milled powders were superficially oxidized by immersion in HCl solution. The oxide layer was composed of iron, silicon, and aluminum oxides, as the Fourier-transform infrared spectroscopy technique revealed. The Fe-Si-Al@oxide powder was densified by the spark plasma sintering technique—SPS. Upon sintering, a continuous matrix of oxide (mainly alumina) was formed by the reaction of the Fe-Si-Al powder coreswith their oxide layer. The main part of the composite compacts after sintering consisted of an Fe3Si-ordered phase dispersed in an oxide matrix. The DC and AC tests of magnetic composite compacts showed that upon increasing the sintering temperature, the density, magnetic induction, and magnetic permeability increased. The initial magnetic permeability was constant in the entire range of testing frequencies and the magnetic losses increased linearly. The stability of the magnetic characteristics in frequency is promising for developing further such types of magnetic composite.

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34

Zheng, Huidong, Zhongyi Yan, Shijiao Chu e Jingjing Chen. "Continuous synthesis of isobornyl acetate catalyzed by a strong acid cation exchange resin in an oscillatory flow reactor". Chemical Engineering and Processing - Process Intensification 134 (dicembre 2018): 1–8. http://dx.doi.org/10.1016/j.cep.2018.10.005.

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35

Coronado, Irene, Aitor Arandia, Matti Reinikainen, Reetta Karinen, Riikka L. Puurunen e Juha Lehtonen. "Kinetic Modelling of the Aqueous-Phase Reforming of Fischer-Tropsch Water over Ceria-Zirconia Supported Nickel-Copper Catalyst". Catalysts 9, n. 11 (8 novembre 2019): 936. http://dx.doi.org/10.3390/catal9110936.

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In the Fischer–Tropsch (FT) synthesis, a mixture of CO and H2 is converted into hydrocarbons and water with diluted organics. This water fraction with oxygenated hydrocarbons can be processed through aqueous-phase reforming (APR) to produce H2. Therefore, the APR of FT water may decrease the environmental impact of organic waters and improve the efficiency of the FT process. This work aimed at developing a kinetic model for the APR of FT water. APR experiments were conducted with real FT water in a continuous packed-bed reactor at different operating conditions of temperature (210–240 °C), pressure (3.2–4.5 MPa) and weight hourly space velocity (WHSV) (40–200 h−1) over a nickel-copper catalyst supported on ceria-zirconia. The kinetic model considered C1-C4 alcohols as reactants, H2, CO, CO2 and CH4 as the gaseous products, and acetic acid as the only liquid product. The kinetic model included seven reactions, the reaction rates of which were expressed with power law equations. The kinetic parameters were estimated with variances and confidence intervals that explain the accuracy of the model to estimate the outlet liquid composition resulting from the APR of FT water. The kinetic model developed in this work may facilitate the development of APR to be integrated in a FT synthesis process.

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36

Yakovenko, R. E., I. N. Zubkov, V. G. Bakun, O. P. Papeta e A. P. Savostyanov. "Effects of SiO2/Al2O3 Ratio in ZSM-5 Zeolite on the Activity and Selectivity of a Bifunctional Cobalt Catalyst for Synthesis of Low-Pour-Point Diesel Fuels from CO and H2". Petroleum Chemistry 62, n. 1 (gennaio 2022): 101–11. http://dx.doi.org/10.1134/s0965544122010157.

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Abstract This study investigates the production of diesel fuels by integrated Fischer–Tropsch synthesis over a bifunctional cobalt catalyst consisting of a cobalt component (Co–Al2O3/SiO2) and a zeolite-containing component (ZSM-5). The catalytic properties were tested in a continuous-flow reactor with a stationary catalyst bed at 240–250°C, 2 MPa, and gas WHSV 1000 h–1. The effects of the SiO2/Al2O3 ratio in a HZSM-5 zeolite on the catalytic performance, catalyst deactivation rate, and hydrocarbon and fractional compositions of the synthetic product were identified. The low-temperature properties of the synthesized diesel fuel satisfy the current requirements for winter fuels.

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37

Yeh, Chun-Liang, Ann Lu e Wei-Che Liang. "Fe-Si Intermetallics/Al2O3 Composites Formed between Fe-20% Si and Fe-70.5% Si by SHS Metallurgy Method". Metals 12, n. 8 (11 agosto 2022): 1337. http://dx.doi.org/10.3390/met12081337.

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Abstract (sommario):

Fe–Si intermetallics–Al2O3 composites were fabricated by thermite-assisted combustion synthesis. Combustion reactions were conducted with powder compacts composed of Fe2O3, Al, Fe, and Si. The starting stoichiometry of powder mixtures had an atomic Fe/Si proportion ranging from Fe-20% to Fe-70.5% Si to explore the variation of silicide phases formed with Si percentage. Combustion in the mode of self-propagating high-temperature synthesis (SHS) was achieved and the activation energy of the SHS reaction was deduced. It was found that the increase of Si content decreased the combustion temperature and combustion wave velocity. Three silicide compounds, Fe3Si, FeSi, and α-FeSi2, along with Al2O3 were identified by XRD in the final products. Fe3Si was formed as the single-phase silicide from the reactions with Si percentage from Fe-20% to Fe-30% Si. FeSi dominated the silicide compounds in the reactions with atomic Si content between Fe-45% and Fe-55% Si. As the Si percentage increased to Fe-66.7% Si and Fe-70.5% Si, α-FeSi2 became the major phase. The microstructure of the composite product showed that dispersed granular or nearly spherical iron silicides were embedded in Al2O3, which was dense and continuous. Most of the silicide grains were around 3–5 μm and the atomic ratio of silicide particles from the EDS analysis confirmed the presence of Fe3Si, FeSi, and FeSi2.

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38

Ramírez Cabrera, Paula Andrea, Alejandra Sophia Lozano Pérez e Carlos Alberto Guerrero Fajardo. "Design of a Semi-Continuous Microwave System for Pretreatment of Microwave-Assisted Pyrolysis Using a Theoretical Method". Inventions 10, n. 2 (4 marzo 2025): 24. https://doi.org/10.3390/inventions10020024.

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Abstract (sommario):

This article provides an overview of various microwave-assisted techniques, such as microwave-assisted extraction (MAE), microwave-assisted organic synthesis (MAOS), microwave-assisted pyrolysis (MAP), microwave-assisted hydrothermal treatment (MAHT), microwave-assisted acid hydrolysis (MAAH), microwave-assisted organosolv (MAO), microwave-assisted alkaline hydrolysis (MAA), microwave-assisted enzymatic hydrolysis (MAEH), and microwave-assisted fermentation (MAF). Microwave-assisted biomass pretreatment has emerged as a promising method to improve the efficiency of biomass conversion processes, in particular microwave-assisted pyrolysis (MAP). The focus is on microwave-assisted pyrolysis, detailing its key components, including microwave sources, applicators, feedstock characteristics, absorbers, collection systems, and reactor designs. Based on different studies reported in the literature and a mathematical model, a mechanical design of a microwave oven adapted for pyrolysis is proposed together with a computer-aided design and a finite element analysis. The semi-continuous system is designed for a 40 L capacity and a power of 800 W. The material with which the vessel was designed is suitable for the proposed process. The challenges, opportunities, and future directions of microwave-assisted technologies for the sustainable use of biomass resources are presented.

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39

Semenycheva, L. L., M. A. Uromicheva, V. O. Chasova, D. G. Fukina, A. V. Koryagin, N. B. Valetova e E. V. Suleimanov. "Synthesis of a graft copolymer of polybutyl acrylate on fish collagen substratum using the RbTe1.5W0.5O6 complex oxide photocatalyst". Proceedings of Universities. Applied Chemistry and Biotechnology 12, n. 1 (1 aprile 2022): 97–108. http://dx.doi.org/10.21285/2227-2925-2022-12-1-97-108.

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Abstract (sommario):

In order to obtain a graft copolymer of polybutyl acrylate (PBA) on the substratum of emulsified fish collagen, RbTe1.5W0.5O6 complex oxide was used as a photocatalyst under visible light irradiation (λ = 400–700 nm). The emulsion was prepared by mixing the monomer and the aqueous collagen solution in a ratio of 1:2. Next, the catalyst was introduced into the resulting mixture, followed by stirring and ultrasound treatment. Before the reaction, the emulsion was bubbled with argon for 15 min. The reaction was carried out in an argon flow with continuous stirring. The radiation source was a 30 W visible light LED lamp placed at a distance of no more than 10 cm from the reaction mixture. At the end of the reaction, the emulsified organic phase was extracted with toluene, followed by phase isolation. In order to isolate the catalyst, the aqueous part of the solution was centrifuged for 30 min. Subsequently, the powder was repeatedly washed in distilled water at a temperature of 50 °C. The washed catalyst was dried, and the surface of the oxide after emulsion polymerization was examined using a scanning electron microscope. For the PBA–collagen graft copolymer emulsion isolated from the aqueous phase, molecular weight characteristics confirming the formation of a graft copolymer were obtained. It was established that the nitrogen content of amino acid residues in the PBA–collagen graft copolymer is significantly lower than in collagen, which indicates the formation of a graft copolymer. An analysis of films and sponges of PBA–collagen graft copolymer samples by scanning electron microscopy (SEM) showed a new structural-relief organization compared to collagen. A SEM analysis of the RbTe1.5W0.5O6 powder surface after the synthesis of the PBA–collagen graft copolymer detected fragments of polymer macromolecules on its surface. This can be explained by the fact that the catalyst used not only is a source of hydroxyl radicals, but сan also participate in the formation of a polymer on the powder surface due to the abstraction of a hydrogen atom from hydroxyl groups on its surface under the action of a hydroxyl radical.

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40

Jellali, Salah, Besma Khiari, Maram Al-Balushi, Jamal Al-Sabahi, Helmi Hamdi, Zohra Bengharez, Mohammed Al-Abri, Hamed Al-Nadabi e Mejdi Jeguirim. "Use of waste marble powder for the synthesis of novel calcium-rich biochar: Characterization and application for phosphorus recovery in continuous stirring tank reactors". Journal of Environmental Management 351 (febbraio 2024): 119926. http://dx.doi.org/10.1016/j.jenvman.2023.119926.

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41

Suranani, Srinath, Yadagiri Maralla, Shekhar M. Gaikwad e Shirish H. Sonawane. "Process intensification using corning ® advanced-flow™ reactor for continuous flow synthesis of biodiesel from fresh oil and used cooking oil". Chemical Engineering and Processing - Process Intensification 126 (aprile 2018): 62–73. http://dx.doi.org/10.1016/j.cep.2018.02.013.

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42

Kim, Jae Jin, Anh Vu, Donald Cronauer, John Carter, Victor Maroni, Adam Hock e Brian J. Ingram. "Reliable Lab-Scale Evaluation for Enhanced SOFCs Electrode Performance - Influence of Electronic Transport". ECS Meeting Abstracts MA2023-01, n. 54 (28 agosto 2023): 70. http://dx.doi.org/10.1149/ma2023-015470mtgabs.

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Abstract (sommario):

Understanding and optimizing electrochemically active zone for oxygen reduction reaction (ORR) in solid oxide fuel cells (SOFCs) cathodes are indispensable to maximize device’s performance. For a mixed ionic and electronic conducting electrode, the range of this zone depends on the oxygen surface exchange and solid-state oxygen/electron transport properties of electrode materials and the oxygen gas transport through porous electrode. This implies that electrode microstructure, including surface area, porosity, and tortuosity, needs to be carefully designed and controlled to maximize electrochemically active electrode volume. This aspect is also critical to realize valid characterization of the electrode’s electrochemical activities. For instance, when a material’s electronic conductivity is low or the electrical contact points are spaced beyond a critical distance, the electrode polarization resistance measured by electrochemical impedance spectroscopy will be controlled by the sheet resistance not the oxygen exchange resistance. In this presentation, we will discuss our synthesis approach of lanthanum strontium cobalt ferrite (LSCF) and spinel powders by using co-precipitation with a continuous stirred-tank reactor, in order to precisely control powder’s chemistry and morphology (ultimately, electrode microstructure). And, we will discuss the influence of electrode microstructure and current collecting method on electronic conduction in porous electrode and, eventually, on electrochemical performance and its reliable evaluation in a lab-scale button cell configuration. This work was supported by the US Department of Energy (DOE), Office of Fossil Energy, (Office of Fossil Energy & Carbon Management), “Solid Oxide Fuel Cell Manufacturing in Support of Office of Fossil Energy” program through Argonne National Laboratory under FWP No. 27327.1.

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Poreddy, Raju, Susanne Mossin, Anker Degn Jensen e Anders Riisager. "Promoting Effect of Copper Loading and Mesoporosity on Cu-MOR in the Carbonylation of Dimethyl Ether to Methyl Acetate". Catalysts 11, n. 6 (31 maggio 2021): 696. http://dx.doi.org/10.3390/catal11060696.

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Abstract (sommario):

Cu-mordenite (Cu-MOR) catalysts with different copper loadings were prepared, characterized and examined in continuous, gas-flow synthesis of methyl acetate (MA) by dimethyl ether (DME) carbonylation. Improved activity and selectivity were observed for Cu-MOR catalysts with up to 1 wt% Cu and X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectroscopy and temperature-programmed reduction with hydrogen (H2-TPR) were used to elucidate the state of copper in the catalysts. Moreover, mesoporous MOR catalysts (RHMs) were prepared by mild stepwise recrystallization with X-ray powder diffraction (XRPD) and ammonia temperature-programmed desorption (NH3-TPD) demonstrating the retained MOR structure and the acid property of the catalysts, respectively. The RHM catalysts showed improved lifetime compared to pristine MOR giving a yield up to 78% MA with 93% selectivity after 5 h on stream (GHSV = 6711 h−1). Under identical reaction conditions, 1 wt% Cu-RHM catalysts had an even higher catalytic activity and durability resulting in a MA yield of 90% with 97% selectivity for 7–8 h of operation as well as a lower coke formation.

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Felischak, Matthias, Tanya Wolff, Leo Alvarado Perea, Andreas Seidel-Morgenstern e Christof Hamel. "Evaluation of Catalysts for the Metathesis of Ethene and 2-Butene to Propene". Catalysts 12, n. 2 (2 febbraio 2022): 188. http://dx.doi.org/10.3390/catal12020188.

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Abstract (sommario):

Different metathesis catalysts were evaluated regarding their activity for propene production from ethene and trans-butene feedstocks. Nickel, molybdenum, rhenium and tungsten, along with bimetallic nickel-rhenium systems were applied with commercial supports and self-synthesized MCM-41. For the latter support the Si/Al ratio was adjusted as an additional optimization parameter (Si/Al = 60). Attractive activities were observed using Re and NiRe based catalysts at moderate temperatures of 200–250 °C. In contrast, the tungsten-based catalysts were only active above 450 °C. Three catalysts, namely Re/AlMCM-41(60), NiRe/mix (1:1) and W/SiO2 offered propene selectivity’s exceeding 40% at attractive conversion rates. These catalysts were characterized by BET, powder XRD, NH3-TPD and TPR-TPO-TPR cycles. At specific reaction temperatures, reaction-regeneration cycles were performed, which revealed that for the Re and W catalysts the initial reactant conversions and propene selectivity can be recovered. In contrast, for the NiRe catalyst, a continuous, gradual and irreversible decrease of activity was observed. Even though the tungsten catalyst was operated at the highest temperature, no irreversible decrease in conversion and propene selectivity occurred. Therefore, this catalyst has potential as a promising candidate for the synthesis of propene.

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45

Touag, Ouardia, Gael Coquil, Mathieu Charbonneau, Denis Mankovsky e Mickaël Dollé. "One-Pot Synthesis of LiAlO₂-Coated LiNi_0.6Mn_0.2Co_0.2O₂ Cathode Material". ECS Meeting Abstracts MA2022-01, n. 2 (7 luglio 2022): 336. http://dx.doi.org/10.1149/ma2022-012336mtgabs.

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Abstract (sommario):

The chemistry of lithium-ion batteries (LIBs) is an active area of research, notably through the increasing demand for high energy and power density in LIBs, especially for application in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Among the various cathode materials, LiNixCoyMn1-x-yO2 (NMC) intercalation compounds are the best candidates for applications in high performance LIBs. However, Ni-rich NMC suffers mainly from parasitic side reactions at the interface with the electrolyte, which leads to a lower thermal and electrochemical stability. Surface modification via coating is an effective concept to counter the capacity degradation of NMC and to improve the particles’ structural stability for enhancing their cycle-life [1], [2]. Different processing techniques that usually requires several steps are presented in the literature. However, to facilitate the integration of a new product in the current battery market, it is preferable to reduce the number of steps during the synthesis process. In this work, we propose a one-pot synthesis of LiAlO2-coated LiNi0.6Mn0.2Co0.2O2 particles, by using a continuous stirred-tank reactor (CSTR). Firstly, the composition and morphology of the coated and uncoated cathode materials are characterized by SEM, TEM, EDX and XPS. Then, the structural characterization of our materials is validated by XRD analysis. Consequently, we will compare the electrochemical performance and thermal stability of coated and uncoated NMC particles. We will demonstrate that our approach provides an easy way to apply surface treatment onto Ni-rich NMC particles and simplifies the synthesis process at large scale production. KEYWORDS: Lithium-ion battery, Ni-rich NMC cathode, LiAlO2 coating, surface protection. Negi, R.S., et al., Enhancing the Electrochemical Performance of LiNi0.70Co0.15Mn0.15O2 Cathodes Using a Practical Solution-Based Al2O3 Coating. ACS Applied Materials & Interfaces, 2020. 12(28): p. 31392-31400. Kim, H.-S., et al., Enhanced electrochemical properties of LiNi1/3Co1/3Mn1/3O2 cathode material by coating with LiAlO2 nanoparticles. Journal of Power Sources, 2006. 161(1): p. 623-627.

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Lagos, Karina J., Bojan A. Marinkovic, Anja Dosen, Alexis Debut, Karla Vizuete, Victor H. Guerrero, Emilio Pardo e Patricia I. Pontón. "KOH-Based Hydrothermal Synthesis of Iron-Rich Titanate Nanosheets Assembled into 3D Hierarchical Architectures from Natural Ilmenite Mineral Sands". Minerals 13, n. 3 (15 marzo 2023): 406. http://dx.doi.org/10.3390/min13030406.

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The synthesis of titanate nanostructures from low-cost mineral precursors is a topic of continuous interest, considering not only their fundamental aspects but also the benefits of incorporating such nanomaterials in a wide variety of applications. In this work, iron-rich titanate nanosheets were synthesized from Ecuadorian ilmenite sands (ilmenite–hematite solid solution-IHSS) through an alkaline hydrothermal treatment (AHT) using potassium hydroxide (KOH). The effect of the duration of the KOH-AHT was assessed at 180 °C for 24, 48, 72, and 96 h. The morphology evolution over time and the plausible formation mechanisms of titanate nanostructures were discussed. The most significant morphological transformation was observed after 72 h. At this time interval, the titanate nanostructures were assembled into well-defined 3D hierarchical architectures such as book-block-like arrangements with open channels. Based on X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) analyses, it was determined that these nanostructures correspond to iron-rich layered titanates (Fe/Ti mass ratio of 7.1). Moreover, it was evidenced that the conversion of the precursor into layered nanostructures was not complete, since for all the tested reaction times the presence of remaining IHSS was identified. Our experiments demonstrated that the Ecuadorian ilmenite sands are relatively stable in KOH medium.

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Terechshenko, A., A. Sanbayeva, M. R. Babaa, A. Nurpeissova e Z. Bakenov. "Spray-Pyrolysis Preparation of Li4Ti5O12/Si Composites for Lithium-Ion Batteries". Eurasian Chemico-Technological Journal, n. 1 (20 febbraio 2019): 69. http://dx.doi.org/10.18321/ectj793.

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This paper introduces the novel anode material which is Li4Ti5O12/Si prepared by gas-stated method, mainly spray-pyrolysis technique. The literature review performed in this paper revealed two main components which can be potentially mixed into the efficient anode material. Silicon (Si) has the highest possible capacity of 4200 mAh g-1 among all commonly used anodes. Due to its ‘zero-strain’ (<1% volume change) properties and stable cycling, Li4Ti5O12 (LTO) is considered as a promising anode for lithium ion batteries. Combination of these two anode materials is considered as a promising approach to prepare a high performance composite anode. The precursor solution consisted of homogeneous mixture of lithium nitrate and titanium tetraisopropoxide dissolved in deionized water with equimolar concentration of 0.5 M. The aerosol formation was performed at nitrogen environment and the droplets were carried into the quartz tube reactor at the flowrate of 4 L min-1. The rector temperature was held at 800 °C. The spray-pyrolysis synthesis was performed as one-step operation, excluding the need of calcination of as-prepared powders, and continuous process by the mean of peristaltic pump. The as-prepared powders had wide size distribution from nanometers to microns. The materials obtained had well-crystallized structure with insignificant amount of impurities. The powders were analyzed by the following analytical equipment: 1) the presence of Li4Ti5O12 and Si in the obtained composite was confirmed by X-ray diffraction technique (XRD); 2) The structure and morphology of LTO and Si molecules were observed and studied with Scanning Electron Microscopy (SEM).

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Khan, Zuhaib Ali, Paul Hellier, Nicos Ladommatos e Ahmad Almaleki. "Sampling of Gas-Phase Intermediate Pyrolytic Species at Various Temperatures and Residence Times during Pyrolysis of Methane, Ethane, and Butane in a High-Temperature Flow Reactor". Sustainability 15, n. 7 (4 aprile 2023): 6183. http://dx.doi.org/10.3390/su15076183.

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Air pollution in many major cities is endangering public health and is causing deterioration of the environment. Particulate emissions (PM) contribute to air pollution as they carry toxic polyaromatic hydrocarbons (PAHs) on their surface. Abatement of PM requires continuous strict emission regulation and, in parallel, the development of fuels with reduced formation of PM. Key processes in the formation of PM are the decomposition of hydrocarbon fuels and the synthesis of potential precursors that lead to the formation of benzene rings and thereafter growth to PAHs and eventually PM. Methane, ethane and butane are important components of natural gas and liquefied petroleum gas, and are also widely used in transportation, industrial processes and power generation. This paper reports on a quantitative investigation of the intermediate gaseous species present during pyrolysis of methane, ethane and butane in a laminar flow reactor. The investigation aimed to further the understanding of the decomposition process of these fuels and the subsequent formation of aromatic rings. The pyrolysis of methane, ethane and butane were carried out in a tube reactor under laminar flow conditions and within a temperature range of 869–1213 °C. The fuels were premixed in nitrogen carrier gas at a fixed carbon atom concentration of 10,000 ppm, and were pyrolysed under oxygen-free conditions. Intermediate gaseous species were collected from within the tube reactor at different residence times using a specially designed high-temperature ceramic sampling probe with arrangements to quench and freeze the reactions at entry to the probe. Identification and quantification of intermediate species were carried out using a gas chromatography-flame ionization detector (GC-FID). During methane pyrolysis, it was observed that as the concentration of acetylene increased, the concentration of benzene also increased, suggesting that the benzene ring is formed via the cyclo trimerisation of acetylene. With all three fuels, all intermediate species disappeared at higher temperatures and residence times, suggesting that those species converted into species higher than benzene, for example naphthalene. It was observed that increasing carbon chain length lowered the temperature at which fuel breakdown occurred and also affected the relative abundance of intermediate species.

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Morowvat, Mohammad Hossein, Kimia Kazemi, Maral Ansari Jaberi, Abbas Amini e Ahmad Gholami. "Biosynthesis and Antimicrobial Evaluation of Zinc Oxide Nanoparticles Using Chlorella vulgaris Biomass against Multidrug-Resistant Pathogens". Materials 16, n. 2 (15 gennaio 2023): 842. http://dx.doi.org/10.3390/ma16020842.

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The rampant increase in antibiotic resistance has created a global barrier to the treatment of multidrug-resistant infections. Biogenic synthesis of nanomaterials is a novel approach to producing nanostructures with biological resources. Algae are known to be clean, nontoxic, cost-beneficial, and environmentally acceptable. Chlorella vulgaris is a popular microalga for its broad applications in food, supplements, pharmaceuticals, and cosmetics. In this study, we used Chlorella vulgaris biomass lyophilized powder as our green resource for the biosynthesis ZnONPs. Chlorella vulgaris culture was harvested at the end of the logarithmic phase, and the biomass was lyophilized. ZnONPs were synthesized using lyophilized biomass and 20 mM zinc acetate dihydrate at a temperature of 70 °C and continuous stirring in a water bath overnight. At the end of the reaction, UV–Vis absorption of colloidal suspension proved the synthesis of ZnONPs. The physicochemical characteristics of nanoparticles were analyzed using FTIR, DLS, TEM, and XRD. Based on FTIR spectra. The antibacterial activity of green synthesized nanostructures was evaluated against methicillin-resistant staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). The synthesized ZnONPs have oxygen-containing groups on the surface that show the synthesized nanoparticles’ stabilization. The Zeta potential was −27.4 mV, and the mean particle size was measured as 33.4 nanometers. Biogenic ZnONPs produced in this method have a notable size distribution and excellent surface energy, which can have vast applications like antimicrobial potential in pharmaceuticals as topical forms. Additionally, in order to evaluate the antimicrobial activity of ZnO nanoparticles, we used MRSA and VRE strains and the results showed the anti-MRSA activity at 400 and 625 μg mL−1, respectively. Thus, these biogenic ZnO nanoparticles revealed a substantial antibacterial effect against multidrug-resistant pathogens, associated with several serious systemic infections, and have the potential as an antimicrobial agent for further study.

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Navarro Villanueva, Merlina A., Luis A. Soto Hernández, Melquisedec Vicente Mendoza, Ángel de J. Morales Ramírez e Fernando Juárez López. "Sintering and hot corrosion of yttria silicate tablets in molten salts prepared by spark plasma sintering". Anti-Corrosion Methods and Materials 66, n. 6 (4 novembre 2019): 782–90. http://dx.doi.org/10.1108/acmm-12-2018-2043.

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Purpose This paper aims to study the microstructural hot corrosion behaviour of the sintered Y2SiO5 ceramic silicate under a Na2SO4 + V2O5 mixture at an engine representative temperature of 1150°C. Y2SiO5 is a promising candidate for thermal barrier coatings (TBC) due to its excellent chemical stability at high temperatures. As a continuous source of Y3+, it is expected that Y2SiO5 environmental barrier coating may prolong the lifetime of TBC systems by stopping the degradation caused by the loss of the Y2O3 stabilizer. Design/methodology/approach Two routes were chosen for the yttria silicate powder synthesis by sol-gel from TEOS and APTES precursors as the difference in Si source changed the ratio of Y2SiO5/Y2Si2O7 phases. Hot corrosion studies using Na2SO4 and V2O5 mixtures were conducted on both surfaces of APTES and TEOS tablets at 1150°C for 8 h in atmospheric air. The morphology and microstructure analyses of the silicate samples after hot corrosion tests were carried out using a SEM and X-ray diffraction analyse techniques. Findings Based on the degradation, the general status of the APTES tablet after hot corrosion presents a better hot corrosion resistance at a temperature of 1150°C than does that of the TEOS tablet. In the TEOS tablet, the crystal morphology of NaY9Si60O26 woodchip shapes with a size of 60 µm is developed on the surface for finally initiating some cracks. In the APTES case, the crystal morphology of rod-like shapes with a size of 100 µm is developed; hence, a dense thick layer predominately postpones the reaction of V2O5 and Na2SO4 with yttria silicate, and consequently, less damage is observed. Originality/value Coating yttria silicate preparation is very complicated; the problems of a high synthesis temperature, long production period and low yield still need to be solved. Under these perspectives, ceramics prepared via spark plasma sintering (SPS) can reach theoretical high densities and a fine grain size can be retained after the SPS process; hence, well resistance to the corrosion in molten salts is expected to obtain for the sintered yttria silicate tablets.

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