Dielectric Properties at Temperatures up to 350ºC with Dielectric Kit for Vials

The use of microwaves in fields as communications, radar, medicine, biology, agriculture and industrial processes demands accurate knowledge of the dielectric properties of materials and its variations with respect to many factors.

In particular, monitoring variations of materials dielectric properties with temperature is crucial for many applications, in which it is important to predict the materials performance over the whole working temperature range.

In order to provide a suitable technique, the Dielectric Kit for Vials has been equipped with viales_con_temperatura_v01the necessary components for the dielectric characterization of materials up to 350ºC. It allows for continuous verification of the sample complex permittivity and temperature conditions, maintaining its advantages with respect to other methods: accuracy, convenience, and easiness of use.

To illustrate this application, several tests have been performed with different materials placed in 1mL vials, and heated from room temperature to 350ºC. The figures illustrate the variation of the dielectric properties of cross-linked polystyrene (left) and silicon carbide (right) with the temperature. As figures show, this variation can be followed by simple inspection of the dielectric properties given by the Dielectric Kit during the cooling process of the samples.

Diel_properties_with_temperature_v01

DIMAS at ECerS Conference 2015

Ecers2015

The Microwave Division of ITACA will participate as an exhibitor in ECerS 2015 Conference that will be held in Toledo, Spain from the 21st to the 25th of June.

Organized every two years, the ECerS Conference 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 ceramic science and 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.

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

  • Julian Jiménez Reinosa, Beatriz García-Baños, Jose M. Catalá-Civera, Jose Francisco Fernández Lozano, “Microwave sintering processes for ceramic: microwave kinetic effect”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).
  • Rut Benavente, María D. Salvador, Ana Martínez-Amesti, Felipe Peñaranda-Foix, Adolfo Fernández, Amparo Borrell, “Effect of microcracking evolution on the thermal stability of β-eucryptite materials obtained by conventional and microwave methods”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).
  • Álvaro Presenda, María Dolores Salvador, Pedro J. Plaza-Gonzalez, Eliria Pallone, Julieta Ferreira, Amparo Borrell, “Effect of Microwave Sintering on Hydrothermal Degradation of Zirconia-Toughened-Alumina (ZTA) Composites”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).

Microwave Technology for Sintering High-Quality Materials with Unique Properties

A recent study published in the International Journal of Applied Ceramic Technology has shown the benefits of using microwave technology as a sintering technique. In this work, lithium aluminosilicate was fabricated by three different methods: conventional, spark plasma and microwave sintering, from 1200 to 1300°C.

OLYMPUS DIGITAL CAMERAMicrowave technology developed by DIMAS made possible to obtain fully dense glass-free lithium aluminosilicate bulk material (>99%) with near-zero and controlled coefficient of thermal expansion and excellent mechanical properties (7.1 GPa of hardness and 110 GPa of Young’s modulus).

Microwave sintering, compared with the other techniques, demonstrated a number of benefits. The combination of rapid heating with low energy applied by the microwave technology (eco-friendly process) and the dramatic reduction in cycle time allowed densification without glass phase formation.

The microwave sintering technique developed in this work opens the opportunity to produce breakthrough materials with low or negative coefficient of thermal expansion and excellent mechanical properties, for example, in the design of new composite materials for space applications.

Microwave Technology for Sintering Novel Composites of Alumina Using Graphene Oxide

In a recently published work, a fast approach based on microwave technology developed at DIMAS was employed for sintering novel composites of alumina at 1400ºC, using graphene oxide (GO) as susceptor.

The morphology, structure and mechanical properties of the composites sintered by microwave approach were compared to the counterparts sintered by conventional method. The results indicated the formation of an interconnecting graphene network promoted the electrical conductivity in the composite having only 2 wt.% GO. Hardness and elastic modulus decreased significantly in samples sintered by conventional method due to lower values of density while microwave technology allowed to achieve a positive effect on the densification and showed a smaller grain size when compared to the one achieved by conventional heating.

FESEM_Al2O3rGO_compositesThe figure shows FE-SEM images of Al2O3-rGO samples sintered d) by conventional method and e) by microwaves. The small grain size observed in Fig. 4e (grain size of 180 nm) is due to the differences in the heating process when using microwave technology. Further details are given in the paper.

Other advantages of microwaves have been observed over the traditional heating techniques: (i) a considerable decrease in the time scale, which in most cases implies a smaller consumption of energy; (ii) a reduction in the number of steps involved in the global process, eliminating the need for other reagents, devices, etc. and (iii) an increase in the efficiency of the global process. These advantages translate into a more economically competitive final product.

The fact that microwave sintered Al2O3–rGO materials exhibited superior mechanical properties values (as was expected from their higher densities) indicates the high potential of rGO and microwave technology to suit various engineering applications of ceramic composites.

PhD about materials sintering with microwaves

On Friday April 10th, 2015, a PhD using Microwave power to sinter materials was presented at UPV by Dr. Rut Benavente. The PhD is entitled: “DESARROLLO DE MATERIALES CERÁMICOS AVANZADOS CON ALTAS PRESTACIONES MEDIANTE TÉCNICAS NO CONVENCIONALES DE SINTERIZACIÓN: MICROONDAS” (“Development of Advanced Ceramic Materials with High Performances by Non-Conventional Techniques: Microwaves“)

Calorimeter for materials sintering

Calorimeter for materials sintering

The PhD is using a microwave applicator (shown in the figure) designed by DIMAS group. This applicator is optimized for sintering materials and is based on a tunable cylindrical cavity that allows to control the microwave power applied to the sample. This allows the engineers to control the heating speed of the sample to achieve the appropriate temperature at the correct time.

Additionally this applicator can be used for vacuum experiments or differente atmosphere inside the reaction tube, and even a Raman Spectroscopy or video recording can be included in the system to improve the performance.

The PhD shows the results for litium aluminosilicates (called LAS) and LAS composites, like LAS/Al2O3 or LAS/Graphene.

A list of publications related with this PhD is available in this site in the publications section (press here)