Unconventionally Made-Cellular Glass Aggregate

Improving the original manufacturing process in microwave field of a cellular glass aggregate using a recipe containing colored consumed drinking bottle, calcium carbonate (CaCO3) as an expanding agent, sodium borate (borax) as a fluxing agent and sodium silicate (Na2SiO3) as a binder is shown in the work. The main adopted technological measures were the advanced mechanical processing of residual glass at a grain dimension below 100 μm and especially the use of a high electromagnetic wave susceptible ceramic tube with a wall thickness reduced from 3.5 to 2.5 mm for the protection of the pressed glass-based mixture against the aggressive effect of microwave field and, in the same time, to achieve a preponderantly direct heating with electromagnetic waves. Of the tested variants, a recipe with 1.6 % calcium carbonate, 6 % borax, 8 % sodium silicate and the rest residual glass was determined to be optimal. The cellular glass aggregate had the bulk density of 0.22 g/cm3, heat conductivity of 0.079 W/m·K and compression strength of 5.9 MPa. The specific consumption of energy was very low (0.71 kWh/kg) below the range of reported values of the industrial processes consumption (between 0.74-1.15 kWh/kg).

Fast magnetization reversal of a magnetic nanoparticle induced by cosine chirp microwave field pulse

We investigate the magnetization reversal of single-domain magnetic nanoparticle driven by the circularly polarized cosine chirp microwave pulse (CCMP). The numerical findings, based on the Landau-Lifshitz-Gilbert equation, reveal that the CCMP is by itself capable of driving fast and energy-efficient magnetization reversal. The microwave field amplitude and initial frequency required by a CCMP are much smaller than that of the linear down-chirp microwave pulse. This is achieved as the frequency change of the CCMP closely matches the frequency change of the magnetization precession which leads to an efficient stimulated microwave energy absorption (emission) by (from) the magnetic particle before (after) it crosses over the energy barrier. We further find that the enhancement of easy-plane shape anisotropy significantly reduces the required microwave amplitude and the initial frequency of CCMP. We also find that there is an optimal Gilbert damping for fast magnetization reversal. These findings may provide a pathway to realize the fast and low-cost memory device.

A review of modern numerical and analytical models of heat transfer in a dielectric layer during melting due to microwave radiation

In this work, numerical and analytical solutions of heat transfer in a dielectric layer during melting in the microwave field were considered. We considered solutions, where the source term was obtained based on the solution of Maxwell equation, as well as using the Lambert law. The conditions applicable for analytical solutions, allowing the parametric analysis, are determined. The areas of application of the technology of microwave melting of dielectrics, in particular with melting ice on water, defrosting products, etc., were also considered.

Research on the Rapid Strengthening Mechanism of Microwave Field-Controlled Gypsum-Cemented Analog Materials

Various geotechnical experiments have used gypsum-cemented analog geotechnical materials. However, this material needs a long curing time, and the target strength is not easy to control. Therefore, this research adopted microwave heating as the curing method for this kind of material. Objectively, the authors investigated the variations in the material strength versus heating power and heating time. On this basis, we clarified the influence mechanism of microwaves on the strength of analog materials by analyzing material temperature, moisture content, and microstructure, which eventually led to an experimental control method for rapid strengthening of microwave field-controlled gypsum-cemented analog materials. Consequently, we drew the following conclusions. The stable strength of the material under high-power microwave curing was much lower than that under natural curing, while the material strength under low-power microwave curing was the closest to the material under natural curing.

Microwave treatment for improved quality and safety of dehydrated pitted apricots

Dehydrated pitted apricots are widely used as a ready meal ingredient, which renders control of their quality and safety a relevant issue. Pitted apricots are rich in sugars, moisture and organic acids that serve a good medium for microorganisms. Therefore, these products require presale processing. Microwave treatment proved effective for the processing of raw and finished food products. Its impact on microorganisms depends on variant criteria, including taxonomic affiliation, total counts, dielectric cell properties and the treatment dose. The research aimed to study death kinetics in the native dried apricot surface microflora and its growth during subsequent storage. In this respect, we have studied the microwave treatment impact on dried apricot surface microflora depending on treatment dose and determined the residual microflora growth rate during subsequent storage. The doses of 120, 180 and 240 kJ at a 200 W radiation power have been shown to reduce baseline contamination of dehydrated pitted apricots by three orders of magnitude. Statistical kinetics analyses demonstrated a retarded surface microflora growth during subsequent storage. Microwave doses of 120–240 kJ (accounting for ±0.4 lg CFU/g error) exhibited a similar microflora dynamics in subsequent storage. The exposure of dried apricots to a lowest microwave field of 120 kJ ensured stability of the product microbiological dynamics.

Focusing the electromagnetic field to 10−6λ for ultra-high enhancement of field-matter interaction

Focusing electromagnetic field to enhance the interaction with matter has been promoting researches and applications of nano electronics and photonics. Usually, the evanescent-wave coupling is adopted in various nano structures and materials to confine the electromagnetic field into a subwavelength space. Here, based on the direct coupling with confined electron oscillations in a nanowire, we demonstrate a tight localization of microwave field down to 10−6λ. A hybrid nanowire-bowtie antenna is further designed to focus the free-space microwave to this deep-subwavelength space. Detected by the nitrogen vacancy center in diamond, the field intensity and microwave-spin interaction strength are enhanced by 2.0 × 108 and 1.4 × 104 times, respectively. Such a high concentration of microwave field will further promote integrated quantum information processing, sensing and microwave photonics in a nanoscale system.