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To develop a method based on urea/microwave treatment for improving the dyeability of the flax fibre.

The treatment was carried out under a variety of conditions in terms of the power of the microwave, the time of microwave treatment and the use of urea in the treatment solution. The physical chemical properties of the treated flax fibres were characterised using a variety of techniques including scanning electron microscopy (SEM), X‐ray diffractometry, spectrophotometric measurement and tensile measurement.

It was found that the treated flax fibres had significantly improved dyeability. The causes to the improvement of the dyeability of the flax fibre were found to be the increased absorption of dye on the fibre and the increased reaction probability between the dye and the fibre. The procedure for optimum modification appeared to be soaking the flax fabrics in 10 per cent urea solution; treating the fabrics with microwave at 350 W for 2.5 minutes; and treating the fabrics with microwave at 700 W for one minute.

The treatment method developed addressed a problem of great concern in textile coloration, i.e. poor dyeability of flax fibre. The method developed provided a practical and effective solution to such a problem.

The method of treatment of flax fibre, involving soaking in urea and baking in microwave, for the improvement of dyeability was novel. The method could be adapted for use in industrial scale flax dyeing with satisfactory levels of exhaustion and fixation.

The paper aims to focus on microwave (2.45 GHz) assisted SHS (MA‐SHS) preparation of NiAl intermetallic coatings on titanium substrates conducted in single mode applicator in order to promote the formation of a complex Ni‐Al‐Ti interface. This enhances the NiAl coating adhesion to the Ti substrate and presents high hardness, high toughness and the capability of stopping the fracture propagation.

Numerical modelling, coupling electromagnetic and heat transfer, allowed to demonstrate that the interface cooling rate can be controlled immediately after SHS using microwave heating, benefiting from the possibility of conveying energy to the newly formed intermetallic compounds, despite an adverse temperature gradient which would negatively affect conventional heating techniques, based exclusively on heat transfer. Experimental validation of the modelling results confirmed that by altering the synthesis conditions (load geometry, microwave power, auxiliary microwave absorbers) the thickness of the Ni‐Al‐Ti layer can be controlled.

The growth of the interface layer can be ascribed to the formation of a liquid phase (ternary eutectic) which progressively consumes NiAl and Ti from the substrate. In case of MA‐SHS, the liquid phase presence can be prolonged during cooling, thus explaining the formation of the thick interface layer.

Microwave selective heating can be used to initiate the SHS without affecting the metallic substrate, which is only heated locally by the reaction products, thus preserving its properties.

Coupling numerical simulation and experimental activity demonstrated that the different microstructures obtained by MA‐SHS are a result of the peculiar temperature profile, favoured by microwave volumetric and selective heating of the reacting powders.

This paper aims to focus on the application of low temperature co-fired ceramic (LTCC) technology in the fabrication of a microfluidic module with integrated microwave components. The design, technology and performance of such an LTCC-based module is investigated. The rapid heating of liquid samples on a microliter scale is shown to be possible with the use of microwaves.

The developed microwave-microfluidic module was fabricated using well-known LTCC technology. The finite element method was used to design the geometry of the microwave circuit. Various numerical simulations for different liquids were performed. Finally, the performance of the real LTCC-based microwave-microfluidic module was examined experimentally.

LTCC materials and technology can be used in the fabrication of microfluidic modules which use microwaves in the heating of the liquid sample. LTCC technology permits the fabrication of matching circuits with appropriate geometry, whereas microwave power can be used to heat up the liquid samples on a microliter scale.

The main limitation of the presented work is found to be in conjunction with LTCC technology. The dimensions and shape of the deposited conductors (e.g. microstrip line, matching circuit) depend on the screen-printing process. A line with resolution lower than 75 µm with well-defined edges is difficult to obtain. This can have an effect on the high-frequency properties of the LTCC modules.

The presented LTCC-based microfluidic module with integrated microwave circuits provides an opportunity for the further development of various micro-total analysis systems or lab-on-chips in which the rapid heating of liquid samples in low volumes is needed (e.g. miniature real-time polymerase chain reaction thermocycler).

Examples of the application of LTCC technology in the fabrication of microwave circuits and microfluidic systems can be found in the available literature. However, the LTCC-based module which combines microwave and microfluidic components has yet to have been reported. The preliminary work on the design, fabrication and properties of the LTCC microfluidic module with integrated microwave components is presented in this paper.

This paper aims to investigate the thermal performance involving larger heating rate, targeted heating, heating with least non-uniformity of the spatial distribution of temperature and larger penetration of heating within samples vs shapes of samples (circle, square and triangular).

Galerkin finite element method (GFEM) with adaptive meshing in a composite domain (free space and sample) is used in an in-house computer code. The finite element meshing is done in a composite domain involving triangle embedded within a semicircular hypothetical domain. The comparison of heating pattern is done for various shapes of samples involving identical cross-sectional area. Test cases reveal that triangular samples can induce larger penetration of heat and multiple heating fronts. A representative material (beef) with high dielectric loss corresponding to larger microwave power or heat absorption in contrast to low lossy samples is considered for the current study. The average power absorption within lossy samples has been computed using the spatial distribution and finite element basis sets. Four regimes have been selected based on various local maxima of the average power for detailed investigation. These regimes are selected based on thin, thick and intermediate limits of the sample size corresponding to the constant area of cross section, Ac involving circle or square or triangle.

The thin sample limit (Regime 1) corresponds to samples with spatially invariant power absorption, whereas power absorption attenuates from exposed to unexposed faces for thick samples (Regime 4). In Regimes 2 and 3, the average power absorption non-monotonically varies with sample size or area of cross section (A_c) and a few maxima of average power occur for fixed values of A_c involving various shapes. The spatial characteristics of power and temperature have been critically analyzed for all cross sections at each regime for lossy samples. Triangular samples are found to exhibit occurrence of multiple heating fronts for large samples (Regimes 3 and 4).

Length scales of samples of various shapes (circle, square and triangle) can be represented via Regimes 1-4. Regime 1 exhibits the identical heating rate for lateral and radial irradiations for any shapes of lossy samples. Regime 2 depicts that a larger heating rate with larger temperature non-uniformity can occur for square and triangular-Type 1 lossy sample during lateral irradiation. Regime 3 depicts that the penetration of heat at the core is larger for triangular samples compared to circle or square samples for lateral or radial irradiation. Regime 4 depicts that the penetration of heat is still larger for triangular samples compared to circular or square samples. Regimes 3 and 4 depict the occurrence of multiple heating fronts in triangular samples. In general, current analysis recommends the triangular samples which is also associated with larger values of temperature variation within samples.

GFEM with generalized mesh generation for all geometries has been implemented. The dielectric samples of any shape are surrounded by the circular shaped air medium. The unified mesh generation within the sample connected with circular air medium has been demonstrated. The algorithm also demonstrates the implementation of various complex boundary conditions in residuals. The numerical results compare the heating patterns for all geometries involving identical areas. The thermal characteristics are shown with a few generalized trends on enhanced heating or targeted heating. The circle or square or triangle (Type 1 or Type 2) can be selected based on specific heating objectives for length scales within various regimes.

Recent developments in microwave GaAs technology are yielding devices with higher power capabilities and increased levels of integration. The mechanical and thermal properties of GaAs and other microwave materials play a key role in the design and assembly of microwave power circuits. Thermal management is a critical element of microwave power circuit design. Thermal properties of microwave materials are discussed and compared with standard microelectronic materials. Material selection criteria are described. Assembly and packaging techniques also affect the overall performance of the GaAs power circuit. The high operating frequencies of microwave circuits make ordinary circuit elements, such as wire bonds and printed conductors, reactive. In addition, electrical performance criteria, such as high current or low impedance, create unique assembly demands. The successful development of a GaAs‐based microwave product is dependent on careful attention to the material properties and precise assembly methods. Techniques of automated assembly and processing are discussed, with ah eye towards maintaining high quality and reliability.

The study was aimed to explore the potential impact of microwave heating (450 W for 2, 4, 6 and 8 min) on antioxidant activity, anti-nutritional factors, volatile and phenolic compounds of the plum kernels.

Plum kernels are rich in proteins, lipids and bioactive compounds that are mostly underused and undervalued.

The results showed that microwave heating at 450 W for 6 min significantly (p < 0.05) increased the antioxidant activity, total phenolic and flavonoid content, while the longer treatment time (450 W for 8 min) adversely affected the phenolic compounds. Most importantly, the anti-nutritional factors like amygdalin, hydrocyanic acid, phytic acid and tannin content were reduced up to 87.1, 84.7, 20.9 and 46.2%, respectively at 450 W for 6 min treatment conditions, which was confirmed from the larger shifts observed in FT-IR spectra near 1,157 cm⁻¹. Microwave heating at 450 W for 6 min also proved beneficial in improving the bioavailability of volatile and phenolic compounds including chlorogenic acid, gallic acid, syringic acid, (+)-catechin, caffeic acid, ß-carotene, trans-ferulic acid, rutin trihydrate, 3,4-dihydroxybenzoic acid, tannic acid and quercetin by liberating them from the plant matrix.

The results thus indicate that controlled microwave heating could be an effective approach for the reduction of anti-nutritional factors besides leading to an overall improvement in antioxidant potential and volatile and phenolic compounds. This novel technological approach can proliferate the use of plum kernels in different diversified food formulations.

This paper aims to study microwave pad dyeing process for wool fabric. Influences of various dyeing process conditions including galactomannan dosage, urea dosage, sodium bisulphite dosage, pH value, microwave irradiation power, treating time and cold batching time before microwave fixation on K/S values were analysed. The colour yield, fixation and levelness were compared between microwave fixation and cold batching fixation.

Colour yield (K/S values) was calculated using a Datacolor SF650 colour measuring and matching instrument (10° standard observer, CIE D65 light source Measuring; Datacolor, USA) and was used to determine the depth of the shade of dyed wool fabrics. Levelness of dyeing was evaluated also using the Datacolor SF650 colour measuring and matching instrument by measuring average deviation (S), range (P) of the maximum and the minimum for lightness (L), chroma (C) and hue (h), and balanced colour difference (ΔE) at 20 specified uniform locations on the wool fabrics. The colour difference was calculated as per the equation ΔE=(ΔL2+Δa2+Δb2)1/2 as appearing in the Experimental section. Fixation was determined using a Datacolor SF650 colour measuring and matching instrument by measuring ratio the of K/S for wool fabrics that were rinsed, washed, neutralised and then dried, and wool fabrics that were dried after fixation without washing. The pH of the padding solution was evaluated using a PHSJ-4A PH meter (Datacolor, USA). SEM analysis was done on JEOL JSM-5600LV machine (JEOL Ltd, Japan).

This study is based on application of microwave technology in the processing of silk.

It was found in laboratory experiments that uniform dyeing and deeper colour can be achieved throughout the microwave pad dyeing process for wool by using galactomannan. The novel process could reduce the dyeing time and the energy consumption of the traditional cold pad-batch dyeing process for wool fabric.

This paper aims to focus on the most popular technique nowadays, the use of microwave irradiation in organic synthesis; in a few years, most chemists will use microwave energy to heat chemical reactions on a laboratory scale. Also, many scientists use microwave technology in the industry. They have turned to microwave synthesis as a frontline methodology for their projects. Microwave and microwave-assisted organic synthesis (MAOS) has emerged as a new “lead” in organic synthesis.

Using microwave radiation for synthesis and design of fluorescent dyes is of great interest, as it decreases the time required for synthesis and the synthesized dyes can be applied to industrial scale.

The technique offers many advantages, as it is simple, clean, fast, efficient and economical for the synthesis of a large number of organic compounds. These advantages encourage many chemists to switch from the traditional heating method to microwave-assisted chemistry.

This review highlights applications of microwave chemistry in organic synthesis for fluorescent dyes. Fluorescents are a fairly new and very heavily used class of organics. These materials have many applications, as a penetrant liquid for crack detection, synthetic resins, plastics, printing inks, non-destructive testing and sports ball dyeing.

The aim value of this review is to define the scope and limitation of microwave synthesis procedures for the synthesis of novel fluorescent dyes via a simple and economic way.

The purpose of this paper is to based upon the joining and characterization (mechanical and metallurgical) of ferritic stainless steel (SS)-430 using a microwave hybrid heating (MHH) phenomenon.

The preliminary experiments were conducted using nickel-based powder as interface material using a domestic microwave oven at a frequency of 2.45 GHz and 900 W power for 720 s. The processed joint was metallurgically characterized by means of X-ray diffraction, Energy-dispersive X-ray spectroscopy and Field emission scanning electron microscopy. Mechanical characterization was done by means of tensile and Vickers’ microhardness testing to check the hardness and strength of the joint.

The metallurgical study revealed that the microstructure and formation of numerous phases of Fe₂Si₃ accompanied by chromium and nickel carbides. The average hardness of 359 Hv at the center of the joint and 637 Hv around the boundaries of the joint was observed. The tensile strength of the joint was observed to 471 MPa with an elongation of 9.02%. The worn surface of the joint signifies the presence of plastic deformation and it was limited due to the presence of harder phases such as Ni₃Si and Ni₃C.

The concept of microwave joining of metals is a very challenging task as the temperature can not be controlled in the inert atmosphere of the microwave. It has been also observed that at certain elevated temperatures, the material starts absorbing the microwaves; which is unknown. So, a more intensive study is required to overcome these kinds of limitations.

MHH technique can be used to process different materials such as ceramics, composites and polymers. SS-430 joined by microwave heating is highly corrosion resistive and has wide applications in refrigerators cabinet panels, dishwasher linings, chimney liners, lashing wires, etc.

As of the author’s best knowledge, no work has been reported on the joining of SS-430 which has huge potential in the industries. Also, no work has been reported on the characterization of microwave joined SS-430.

This paper aims to present the implementation of a multi-layer radiation propagation model in simulations of multi-phase flow and heat transfer, for a dissociating methane hydrate reservoir subjected to microwave heating.

To model the induced heterogeneity due to dissociation of hydrates in the reservoir, a multiple homogeneous layer approach, used in food processes modelling, is suggested. The multi-layer model is incorporated in an in-house, multi-phase, multi-component hydrate dissociation simulator based on the finite volume method. The modified simulator is validated with standard experimental results in the literature and subsequently applied to a hydrate reservoir to study the effect of water content and sand dielectric nature on radiation propagation and hydrate dissociation.

The comparison of the multi-layer model with experimental results show a maximum difference in temperature estimation to be less than 2.5 K. For reservoir scale simulations, three homogeneous layers are observed to be sufficient to model the induced heterogeneity. There is a significant contribution of dielectric properties of sediments and water content of the reservoir in microwave radiation attenuation and overall hydrate dissociation. A high saturation reservoir may not always provide high gas recovery by dissociation of hydrates in the case of microwave heating.

The multi-layer approach to model microwave radiation propagation is introduced and tested for the first time in dissociating hydrate reservoirs. The multi-layer model provides better control over reservoir heterogeneity and interface conditions compared to existing homogeneous models.