NANOFOR Project: Microwave reactors for advanced synthesis of nanoparticles

The NANOFOR nanoparticula_webproject aims to obtain colorless nano-fluorophors with high optical response by excitation and up-conversion at pre-designed wavelengths. To this end, the synthesis will be developed by new microwave reactors in continuous, also including the systems of identification and recognition for the control of the process.

From the scientific point of view, it brings a new advance in the synthesis processes to obtain nanocrystals with special optical properties. Technologically it involves increasing the production capacity to levels well above the state of the art, as well as improving the optical properties obtained with the existing processes.

The consortium consists of CEINNMAT as a developer of the procedures, the ICMol-UV that brings its knowledge in design and synthesis of nanocrystals, and DIMAS-UPV group for the design of microwave reactors. The partners will address the major challenges proposed through collaboration between nanoscience, materials science, new technology developments and results marketing.

ThLogo_conjunto_MINECO_FEDER_2is project RTC-2016-5114-5 has been financially supported by Ministerio de Economía y Competitividad (MINECO) -Spanish Government- and  by European Regional Development Funds (ERDF) of European Union.

bandera-espanya  Spanish version

New paper published at IEEE MTT

DIMAS has published in April 2017 a new research paper at IEEE Transactions on Microwave Theory and Techniques. It is entitled “Enhanced Full-Wave Circuit Analysis for Modeling of a Split Cylinder Resonator” and presents another way of analysing the split resonator by circuit analysis. Circuit analysis applied to electromagnetic strutures is a technique that DIMAS has been developing last years, with several publications and applications specially in the field of dielectric characterization of material (dielectrometry).

 

2017-04-04-Imagen articulo MTT-David-v01

Split cavity and circuit analysis

In this case the improvement consists of using higher modes in the circuit characterization of all the simple networks that appear when the original structure is segmented into smallest and simplest ones. Then, not only the TM0np modes can be analysed but also all the set of TE and TM resonant modes that appear in the split cavity resonator.
The main application will be the possibility of using more resonant modes to characterize planar materials and to increase the frequency band where the permittivuity is calculated.
This paper is a part of the research work performed by David Marqués-Villarroya in his way to get the PhD in Electrical Engineering, and is the result of an extension of the original paper published in the International Microwave Symposium (IMS) held in San Francisco (USA) in May 2016.

New research paper in the “Journal of Food Engineering”

DIMAS has published a new research paper in early 2017 in the Journal of Food Engineering. The paper is entitled: “Dynamic measurement of dielectric properties of food snack pellets during microwave expansion“.

This is the result of a collaboration between PepsiCo R&D and DIMAS.

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Calorimeter facility at DIMAS laboratory

The papers presents in situ dielectric properties measurements of a starch-based foodfood pellet during microwave expansion. To do this, a dual-mode cylindrical cavity that allowed simultaneous microwave heating and dielectric measurements of a single pellet inside a quartz tube was used, ensuring uniform heating during microwave processing.
This systemm in shown in the figure. It is a DIMAS facility that included additional measurement devices to correlate the dielectric properties with the main parameters of the expansion process, such as temperature, expansion time, pellet volume
and absorbed power.

DIMAS participates in COSMIC european project

DIMAS is participating in the COSMIC (European Training Network for Continuous Sonication and Microwave Reactors) european project.
The kick-off of the project was held in Leuven (Belgium) in March 2017, where all the 12 partners (beneficiaries and partner organizations) participated and exchanged discussions about the future of the project.
All the 15 students that will be devolping their PhD in the frame of this project also participated in the kick-off meeting and also discussed with the host partners the activity to be done during their visits along the duration of the project.
DIMAS will host four of these students: two of them will arrive from KU Leuven (Belgium), one from UCL (UK) and the last one from Universidad de Zaragoza (Spain).
The student hosted by DIMAS will perform experiments with the microwave facilities available at DIMAS laboratory.

The project science and technology objectives are to develop:

1.-Resource-efficient multiphase reactions in the fields of organic synthesis (C–H, C=C and C=C bond activation) and nanoparticle synthesis (for use in catalysis and health applications);
2.-Intensified reactors that efficiently integrate milliflow technology with ultrasound and/or microwave actuation;
3.-Knowledge-based assessment and decision methodologies to evaluate and select process-intensification technologies.

2017-04-04-Imagen de COSMIC-v02

Group photo during the kick-off meeting in Leuven

New paper published in Journal Materials

logo_journal_materialsA recent work developed by Microwave Division has been published in the Journal Materials, as a part of the Special Issue “Microwave Materials Processing”.

Microwave-assisted processes have recognized advantages over more conventional heating techniques. However, the effects on the materials microstructure are still a matter of study, due to the complexity of the microwaves-matter interaction, especially at high temperatures. Recently developed advanced microwave instrumentation allows the study of high temperature microwave heating processes in a way that was not possible before.

In this paper, different materials and thermal processes induced by microwaves have been studied through the in situ characterization of their dielectric properties with temperature.

frita_special_issue

The figure shows an example of the dielectric properties of a ceramic frit sample together with the sample height up to 1200ºC. Important variations in the sample height are also observed during the process, due to different reactions and transformations. At temperatures above 450ºC the water inside the sample passes to a gas state. The gas tries to exit leading to the expansion of the sample. On the contrary, a contraction takes place above 900ºC, due to the melting of the sample.

The dielectric properties of the sample slightly increase with increasing temperature up to 700ºC. At this temperature, the dolomite decomposition starts, and a sharp change is observed in dielectric constant and loss factor.  A second increase starts about 900-1000ºC, due to the melting of the sample. The effect of the melting is more pronounced in the sample loss factor, reaching from very low values at room temperature to high values at the end of the process.

This and other examples presented in the paper illustrate how the dielectric properties correlate very well to the material transformations at increasing temperatures. This knowledge is crucial in several aspects:

  • to analyze the effects of the microwave field on the reaction pathways
  • to design and optimize microwave-assisted processes
  • to predict the behavior of materials leading to repeatable and reliable heating processes

 

Best Poster Award in GCMEA Conference

award_gcmea2016

DiMaS group has participated in the Third Global Congress on Microwave Energy Applications -GCMEA-. Our contribution entitled “Study of microwave thermal processes through in situ Raman and dielectric spectroscopy” was awarded with the Best Poster Award of the conference. We congratulate our researcher J.D. Gutiérrez for the quality of his work.

In the poster, it was explained that the use of microwave energy for materials processing is well known, however, the heating mechanisms and the particular thermal behavior of materials under high frequency electromagnetic fields is still a matter of research.  Recent works highlight the need of further investigations to understand the microwave-matter interactions behind the materials thermal processes.

The strategy presented in the poster consists of linking the information given by dielectric properties to the thermal processes that occur in the material. To this end, Raman spectroscopy is applied to obtain information about the microstructure and the chemo-physical changes in the materials. The in situ combination of both techniques (dielectric and Raman) in real time during microwave processing gives useful and innovative information about the heating mechanisms of different materials.

DIMAS at GCMEA Congress 2016

GCMEA_photo_Cartagena

The Microwave Division of ITACA will participate as an exhibitor in the Third Global Congress on Microwave Energy Applications -GCMEA- that will be held in Cartagena, Spain from the 25st to the 29th of July.

Organized every four years, the GCMEA Congress is the place to be for scientists, students and industrialists willing to have a direct access to one of the largest community of international experts of microwave technology.

In our booth, people will be able to see:

  • Innovative microwave equipment for processing and synthesis of high-tech ceramics with advanced and unique properties.
  • Advanced technology for testing and characterization of electromagnetic properties of materials from room to high temperatures (>1000ºC).
  • Equipment for real-time combination of different testing techniques (i.e. simultaneous dielectric and Raman spectroscopy) during microwave processing, allowing a fine-tuning control and a deeper understanding of microwave-matter interaction.
  • Our expertise in electromagnetic modeling and design of microwave equipment for emerging challenges and novel applications.

logo_GCMEA_2016

Jose M. Catalá will be one of the worldwide recognized personalities who will provide a Plenary Lecture on the most updated state of the art in MW Science and Technology.

Some recent results about microwave processing and characterization obtained with our technology will be presented in the conference as well:

• B. García-Baños, D. Poparova, J.D. Gutierrez-Cano, P.J. Plaza-González, “Study of microwave thermal processes through in situ Raman and dielectric spectroscopy”
• A. Borrell, A. Presenda, M.D. Salvador, F.L. Peñaranda, J.M. Catala-Civera and P. Plaza-Gonzalez, “Effect of microwave mechanisms to fabricate efficient bioceramic components”
• H. Nigar, B. Garcia-Baños, F.L. Peñaranda-Foix, J. M. Catalá-Civera, R. Mallada and J. Santamaría, “Dynamic Measurement of Dielectric Properties of different Zeolite Y sorbents at high temperature”
• F.L. Penaranda-Foix, D. Marques-Villarroya, A.J. Canos-Marin and J.D. Gutierrez-Cano, “Dielectric measurements with a kind of TM0np at different harmonics”
• B. García-Baños, E. Ognyanova Tsvetkova, G. Llorens-Vallés and J.M. Catalá-Civera, “Microwave heating of powders at high temperature: effect of grain size and bulk density”
• A.M. López-Buendía, B. García-Baños, J. Bastida, G. Llorens-Vallés, M.M. Urquiola and J.M. Catalá-Civera, “Microwave calcination of clays”

DIMAS participation in BRAVO EIP

Logo_BavoBRAVO is a European Innovation Partnership focused on advanced metal recovery, with the following objectives:

  • To boost the innovation capacity of the aluminum value chain with respect to secondary raw materials recovery
  • The creation of new value chains for the recovered raw materials from by-products of the manufacturing process
  • To test the viability of solutions and holistic processing concepts
  • To increase the impact of research , innovations and achieve technology transfer
  • To promote socially acceptable, environmentally responsible and economically viable technologies
  • Waste as a resource: generation of a more valuable waste which can be processed to recover critical raw materials

DIMAS contributes with a wide expertise in the development of low and high temperature continuous-flow processing of rotary1materials with electromagnetic energy. This can be applied in the following BRAVO key areas:

  • Al-Source: Microwave technology for aluminium extraction from bauxite.
  • Al-Ore: Microwave-assisted extraction of iron and high added value metallic concentrates.
  • Al-Build: Microwave technology for artificial aggregate manufacturing and ceramic based materials.

You can find more information at the DIMAS profile within the BRAVO site.

Best Poster Award

DiMaS group in collaboration with CSIC Institute of Ceramic and Glass, has participated in the 15th International Conference on Microwave and High Frequency Heating held in Cracow (Poland) in September, 2015.

Our joint contribution entitled “DIELECTRIC PROPERTIES OF CERAMIC FRIT UP TO 1200ºC AND CORRELATION WITH THERMAL ANALYSIS”, developed in theAward_01 frame of the european DAPhNE project (DAPHNE- Development of adaptive ProductioN systems for Eco-efficient firing processes), has been awarded with the Best Poster Award of the conference.

This award confirms the increasing interest on the in situ dielectric characterization of materials under microwave processing at high temperatures (>1000ºC), and its use for the identification of thermal processes induced by the high-frequency electromagnetic fields.

This work, as other similar shown in publications tab, is the result of years of collaboration between both research groups in the field of microwave-sintering of materials with microwave power with in-situ dielectric characterization.

New PhD at DIMAS Laboratory

DIMAS proudly announces that a staff member, Mr. Pedro J. Plaza-González presented in January 14Caratula TESIS PEDRO-v01th, 2016 his PhD, and he got the maximum qualification. All the staff at DIMAS group congratulates Dr. Pedro J. Plaza for his great research activity and contribution.

The thesis is entitled “Temperature Control in Microwave Heating Systems“, and covers most of the main issues when dealing with Microwave Heating applicators at high power and high temperature. It has been devolped completely at DIMAS laboratory facilities and next is the summary of the thesis:

Material heat processing systems using microwave energy have been used for more than 60 years. Design and implementation techniques have greatly evolved during this time, but a precise control in material temperature is still difficult to achieve due to theoretical and practical reasons.

This difficulty arises, in many cases, because a deep knowledge in several technical fields is needed in order to design the process properly, being microwave engineering only one of them. Usually it’s necessary to combine knowledge in microwaves with material technology, chemistry, and other fields, in order to have a clear idea about how the process should be.

The main aim of this work is the development of experimental equipment that allows the heat treatment of material samples using microwave energy, while providing a great control over the sample temperature and the energy absorbed. Using such an equipment, very valuable data can be obtained for the process dynamics when using microwave technology.

With this objective in mind, in a first step different suitable types of microwave applicators have been studied, as well as several optimization techniques for the temperature distribution within the sample.

Advantages and disadvantages of multimodal applicators have been analyzed, and a detailed study about the effect of mode stirrers in the field uniformity has been carried out, which is the more common technique for this aim.

A next step was the study of thermal effects in materials under high power electromagnetic fields. Heat transfer, convection and phase change phenomena have been studied in order to analyze their effect in the sample temperature.

The thermal runaway effect has a special importance in the processing of some materials, mainly when dielectric losses increase with temperature. This phenomenon has been analyzed, as well as some suitable techniques that can be used to avoid it, or at least to reduce its effects. Also, different types of temperature sensors have been reviewed to study its
usability in microwave systems, and as a result infrared temperature sensors has been chosen as the more suitable technology.

In microwave heating systems the temperature increment in the sample is determined by the microwave power absorbed by the applicator, and for this reason an accurate control over this parameter is required for a good temperature control. It should be remarked that microwave heating processes are dynamic, evolving with the changes in material temperature and properties. For this reason, different procedures for absorbed power control has been analyzed, with highlight in the work carried out regarding the development of a dynamic impedance matching system.

Moreover, other strategies for absorbed power regulation have been studied, using different control parameters as the generated power, the cavity tuning or the frequency sweep span. Two different systems have been developed. One is based on a tunable monomode cavity with a mechanic tuning system; the second is based on a non-tunable cavity and the use of a variable frequency generator. Both systems integrate temperature sensors and the equipment required to measure the power delivered to the sample. An automated process control algorithm based on PID has been implemented, allowing autonomous working during the experiments.

Both developed systems have been used in a high number of experiments with different nature of samples. Some of these results are presented in this work, showing the excellent performance of the systems and the valuable information that can be obtained for the studied materials.

As a final point, several future research lines are proposed in order to continue the work developed up to now“.