11:00
Microwave assisted chemistry and processing (1)
11:00
15 mins
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Control of Evaporation Temperature in a Microwave Vacuum Drying System
Vincent Goovaerts, Karel Groffils, Carlo Groffils
Abstract: To optimally control the temperature during drying processes, a combination of microwave energy with a vacuum has been tested. Therefore, a new set-up has been constructed in the Microwave Energy Applications Management (MEAM) test center, i.e. MEAM VP 1.2, where VP stands for vacuum pressure and 1.2 for the maximum power of the system (1.2 kW). This power can be adjusted according to the desired speed of heating/drying. The microwave system has a multi-mode cavity, like a domestic oven, and is air-cooled. The microwave part consists of a launcher, an insulator, a possibility to measure power and reflection, and a connection to the vacuum chamber. This chamber has a volume of 72 liters and its dimensions are 30 cm × 40 cm × 60 cm. The vacuum chamber is connected to a 0.48 kW vacuum pump. As a result, the actual drying or evaporation of water molecules can occur at very low temperatures. In this way, temperature shocks during ‘normal’ drying processes can be avoided, resulting in better preservation of the product. In addition, this will greatly benefit the product quality. This clearly shows the advantages of the combination of microwave energy and vacuum in drying processes.
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11:15
15 mins
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MICROWAVE-ASSISTED SYNTHESIS OF CZTS (Cu2ZnSnS4) NANOCRYSTALS USING DIFFERENT STABILIZING AGENTS
Katarzyna Matras-Postolek, Svitlana Sovinska, Adam Zaba
Abstract: Keywords: microwave, nanocrystals, CZTS
The CZTS (Cu2ZnSnS4) nanocrystals, due to their optical and electrical properties (e.g. relatively low band gap energy about 1.5 eV and high absorption coefficient about 104 cm-1), are one of the most promising materials for the absorption layers in photovoltaic devices [1]. There are lots of methods to obtain CZTS films but there is only a few methods using microwave radiation for the preparation of CZTS nanocrystals [2–4]. In this study, the CZTS nanoparticles were obtained under microwave radiation by using three different systems of stabilizing agent and solvent like 1) ethylenediamine with water, 2) oleylamine with cyclohexanone and 3) ethylene glycol used as a solvent and stabilizer, respectively. Additionally CZTS nanocrystals were also synthesized using conventional source of heating. The obtained nanomaterials were characterized with different techniques including XRD, EDX and TEM spectroscopy. This work was financially supported by National Centre for Research and Development under Lider Program, contract no. LIDER/009/185/L-5/13/NCBR/2014.
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11:30
15 mins
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DIELECTRIC CHARACTERIZATION OF THIRD GENERATION SNACKS PROCESSED BY MICROWAVE ENERGY
José D. Gutiérrez, José M. Catalá-Civera, John Bows, Pedro Plaza-González, Gabriel Llorens-Vallés
Abstract: Third generation snacks have a great potential for growth among snack foods. The production of pellets is achieved in a two stages procedure: (1) a shelf-stable glassy pellet is manufactured at low pressure; (2) an expansion procedure accomplished by baking, hot air puffing, frying or microwave energy [1]. Compared with other technologies, microwave energy can improve energy efficiency since there is an energy conversion rather than heat transfer.
The study of the parameters involved in the process is crucial to characterize the heating procedure during microwave treatment. Consequently, dielectric properties are an essential parameter as they define the interaction of dielectric materials with microwaves [2]. Most of previous works were based on measurements before and after microwave expansion and made use of multimode microwave equipment [3, 4] affected by the oven geometry and the location and size of the workload.
In this work, a dual-mode cylindrical cavity [5] allowed simultaneous microwave heating and dielectric measurements, ensuring uniform heating during microwave processing. The dielectric properties were obtained during microwave expansion and other key parameters of third generation snacks were assessed.
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11:45
15 mins
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Energy-efficient methane valorization in microwave-assisted catalytic reactors
Heidy Ramirez, Ignacio Julian, Beatriz García-Baños, José Luis Hueso, Reyes Mallada, Jesús Santamaría
Abstract: This work focuses on the one-step methane activation process via a non-oxidative coupling to hydrocarbons (essentially ethylene, benzene and naphthalene) using microwave heating.
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