Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation

[EN] Microwave internal gelation (MIG) is a chemical process proposed for the production of nuclear particle fuel. The internal gelation reaction is triggered by a temperature increase of aqueous droplets falling by gravity by means of non-contact microwave heating. Due to the short residence time of a solution droplet in a microwave heating cavity, a detailed knowledge of the interaction between microwaves and chemical solution (shaped in small drops) is required. This paper describes a procedure that enables the measurement of the dielectric properties of aqueous droplets that freely fall through a microwave cavity. These measurements provide the information to determine the optimal values of the parameters (such as frequency and power) that dictate the heating of such a material under microwaves.This work is a part of the PINE (Platform for Innovative Nuclear FuEls) project which targets the development of an advanced production method for Sphere-Pac fuel and is financed by the Swiss Competence Center for Energy and Mobility. The work has been also financed by the European Commission through contract no 295664 regarding the FP7 PELGRIMM Project, as well as contract no 295825 regarding the FP7-ASGARD Project. MC-S would like to thank the ITACA research team (UPV Valencia, Spain) and the EMPA Thun (Switzerland) for their support in the measurements and Carl Beard (PSI, Switzerland) for the help provided in respect with CST simulations. The work of FLP-F was supported by the Conselleria d'Educacio of the Generalitat Valenciana for economic support (BEST/2012/010).Cabanes Sempere, M.; Catalá Civera, JM.; Penaranda-Foix, FL.; Cozzo, C.; Vaucher, S.; Pouchon, MA. (2013). Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation. Measurement Science and Technology. 24(9). https://doi.org/10.1088/0957-0233/24/9/095009S24

Influence of ECR-RF plasma modification on surface and thermal properties of polyester copolymer

In this paper we report a study on influence of radio-frequency (RF) plasma induced with electron cyclotron resonance (ECR) on multiblock copolymer containing butylene terephthalate hard segments (PBT) and butylene dilinoleate (BDLA) soft segments. The changes in thermal properties were studied by DSC. The changes in wettability of PBT-BDLA surfaces were studied by water contact angle (WCA). We found that ECR-RF plasma surface treatment for 60 s led to decrease of WCA, while prolonged exposure of plasma led to increase of WCA after N2 and N2O2 treatment up to 70°–80°. The O2 reduced the WCA to 50°–56°. IR measurements confirmed that the N2O2 plasma led to formation of polar groups. SEM investigations showed that plasma treatment led to minor surfaces changes. Collectively, plasma treatment, especially O2, induced surface hydrophilicity what could be beneficial for increased cell adhesion in future biomedical applications of these materials

Cu dispersion in microwave sintered iron compacts

Gas atomized Cu powder is added to Iron powder in varying amounts and mixed in a V-type mixer for 30 minutes at 15 rpm. As lubricant 1 wt% Acrawax C is used. The mixtures are compacted at 600 MPa to form TRS (Transverse Rupture Strength) samples with dimensions 6,35*12,8*31,8 mm. The samples are sintered using conventional and microwave furnaces for 30 minutes at 1150 °C under 90% N2 -10% H2 atmosphere. The microstructure of sintered specimens and Cu dispersion in Fe are observed by SEM and EDS, and the strength is determined by TRS tests

Microwave sintering effect on mechanical properties of iron alloys

Iron powder is mixed by 2, 3, 4 wt. % of gas atomized copper or bronze (Cu-Sn) alloy with 1 wt. % lubricant. Each mixture was compacted at 600 MPa to form Transverse Rupture Strength samples in order to sinter in microwave or electrically heating tube furnace. Half of the samples were sintered at 1150°C for 30 minutes under 90% N2 - 10% H2 atmosphere by using microwave source of maximum 1000 W in assistance of SiC sucpector. The other half were sintered using electrically heating tube furnace. The emissivity value was chosen as 0.55 and temperature corrections were done by observation of melting points of silver and copper pieces on the reference sample during sintering. The pore structure of sintered samples were observed by light microscope. Porosity level of sintered samples were measured by mercury porosimeter and Transverse Rupture Strength (TRS) values were measured using three point bending apparatus according to ASTM B528

Structure and properties of SiC and emery powder reinforced PM 316l matrix composites produced by microwave and conventional sintering

In this work, PM 316L based composite materials reinforced with SiC and emery powders in amounts of 5, 10 and 15 vol.-% were produced. The mixed powders were compacted by uniaxial pressing at 700 MPa and processed at 1160 and 1250 degrees C for 1 h by means of conventional sintering and microwave sintering. The sintering atmospheres were Ar/H-2 95/5% for conventional sintering and Ar/H-2 90/10% for microwave sintering. Mechanical properties were evaluated with transverse rupture strength (TRS) tests. Densities and porosities were determined using Archimedes method. Sintered samples were characterised by optical microscopy and SEM. All of the composite materials had lower TRS values compared with 316L base material. Among all compositions, 5 vol.-% emery powder reinforced 316L alloy composite samples exhibited the most favourable mechanical and physical properties. The 10 vol.-% SiC containing composite samples also had acceptable properties. Moreover, microwave sintering yields better mechanical and physical properties

Effect of particle size and heating rate in microwave sintering of 316L stainless steel

The work evaluates the effect of heating rate in microwave sintering, and the effect of particle size of 316L powders in microwave and conventional sintering processes. The powders of 316L stainless steel were compacted by uniaxial press at 700 MPa, and sintered at 1250 degrees C for 1 h by means of conventional sintering and microwave sintering. The sintering atmospheres were Ar/H-2 95/5% for conventional sintering and Ar/H-2 90/10% for microwave sintering. Mechanical properties were evaluated using tensile tests. The samples were characterized by optical microscopy and SEM. The porosity levels were determined using image analysis software. Microwave sintering yields fully recrystallized microstructure different from conventional sintering, however no difference in distribution and shape of pores was noticed. Heating rate in microwave sintering affects densification, tensile strength and elongation. Moreover, the use of fine powders improves physical and mechanical properties of the samples sintered by both methods. (C) 2014 Elsevier B.V. All rights reserved

Microwave Assisted Internal Gelation of Droplets - A Case Study

A microwave unit for internal gelation of metal nitride solutions at 2.45 GHz microwave radiation is presented. In the majority of cases previous investigations examined the use of frequencies in the x-band range (6 to 12 GHz). The challenge of the recent work is to apply 2.45 GHz ISM frequency instead. A microwave unit was selected and designed with the final goal of its implantation in a "glovebox", where radio-active materials are handled. Microwave radiation is supplied by a 2 kW coaxial line, which eventually can be fed through the glovebox wall, thereby permitting the microwave source to be located outside of the glovebox. Droplets of the metal nitride solution are allowed to fall by gravity through the resonator while being heated by microwave energy. Due to the very short residence times of the droplets in the resonator, the drop generating nozzle is introduced directly into the microwave field. By this means the residence time is increased due to the time of droplet formation at the nozzle tip.JRC.E.4-Nuclear fuel