Domestic Microwave Oven Research Articles

Experimental Study on the Performance Characteristics of a Microwave - Solar Heating Dryer

The use of microwave energy for drying of agricultural products is recently developed due to the advantageous of heating the product much faster and more effective than conventional methods. Moisture content of agricultural product should be evaporated immediately after harvesting in order to inhibit microbial growth and decrease enzymes activity. This work aim to investigate characteristics of microwave-solar hot air drying of agricultural products such as rice grain and potato using a commercial microwave oven and hot air from a can solar collector. A domestic microwave oven was modified in order to operate as a microwave dryer device. The state of the art of microwave-solar heating was developed for investigation on drying performance of agricultural products such as grains and potato slices. Measurements on the temperature of drying chamber and moisture content of the product were conducted under different power inputs of microwave (low, middle and high) and intensity of solar drying. It was observed that microwave-solar air dryer proposed good heating performance and quality of products. Furthermore, temperature, moisture changes and drying rate could be controlled during the drying process.

Microwave assisted synthesis of boron and nitrogen rich graphitic quantum dots to enhance fluorescence of photosynthetic pigments

Energy transfer between quantum dots and biomolecules is of interest due to high absorption capacity and high quantum efficiency of quantum dots. Amongst all types of quantum dots, graphene and graphitic quantum dots have great potential for energy transfer studies due to their high biocompatibility and low toxicity. In this study, a simple route to synthesize boron and nitrogen rich graphitic quantum dots (C-BN) and boron carbon nitride (BCN) quantum dots is demonstrated. Quantum dots were synthesized in a domestic microwave oven. Composition of quantum dots was controlled by tuning initial mole ratio of boron and nitrogen precursors. As molar ratio of boron precursor was increased, formation of C-BN quantum dots was favoured. C-BN quantum dots were mainly composed of boron and nitrogen (with around 10 % carbon) in their main composition, and sized around 2 nm with bright photoluminescence. To the best of our knowledge, this is the first study which proposes a bottom-up synthesis method to synthesize C-BN quantum dots based on domestic microwaves. Also, treating photosynthetic pigments with quantum dots resulted in 20 % enhancement of fluorescence of photosynthetic pigments at 670 nm, which demonstrates that C-BN and BCN quantum dots can be important constituents of artificial antenna systems for photosynthetic organisms.

A perspective approach towards appreciable size and cost-effective solar cell fabrication by synthesizing ZnO nanoparticles from Azadirachta indica leaves extract using domestic microwave oven

A simple domestic microwave oven-assisted solvothermal method has been used successfully to synthesize spherical nanoparticles of zinc oxide (ZnO NPs) for solar cell fabrication using Azadirachta indica (Neem) leaves extract as both capping and reducing agent. The hexagonal structure of ZnO nanoparticles was confirmed by X-ray powder diffraction analysis. The Fourier-transform infrared spectrum confirms the presence of Zn–O stretching vibrations. High-resolution transmission electron microscopy images have exhibited the spherical morphology of ZnO nanoparticles which has clearly illustrated the average particle size around 4.2 nm. The selected area electron diffraction pattern contains well uniform rings confirming standard orientation. The maximum absorption wavelength for the synthesized ZnO nanoparticles was found to be more than 352 nm. The electrical measurement demonstrated that the values of dielectric constant and dielectric loss gradually decrease with increase in frequency which is described by the basis Maxwell–Wagner model. The ac conductivity of ZnO nanoparticles was also carried out. The solar cell fabrication of ZnO nanoparticles and photovoltaic devices were displayed. It was further confirmed that smaller size of ZnO nanoparticles was synthesized which had shown better cell efficiency.

Comparison of microwave drying and oven-drying techniques for moisture determination of three paddy (Oryza sativa L.) varieties

BackgroundThe standard method for grain moisture measurement is the conventional air oven-drying technique. This method requires a longer period of time to determine the moisture content (m.c.). Although electric moisture meters are popular in rice industries, it has to be calibrated frequently with the oven-drying method. Therefore, an alternative but fast and reliable method is required, especially, for the grain marketing industries.ResultsThree different sizes of paddy (Oryza sativa L.) samples (Bg 300-intermediate bold, Bg 358-short round and At 405-long slender) were used for this study. Five different moisture levels (12–20% wet basis) were prepared by adding known amounts of water. Relationship between the microwave oven and hot air oven moisture values were evaluated using Pearson, Spearman and Kendall correlation coefficient methods. The linear regression relationship was also established between hot air oven and microwave oven moisture determination methods. According to the data, except for 870 W of absorbed MW power setting level, the other two MW power setting (265 W and 550 W) showed a significant statistical correlation (r > 0.55, P < 0.01) between the air oven and MW oven m.c. values of the three paddy samples. However, MW settings of 550 W for 7 min of absorbed power indicated a significantly higher regression coefficient of determination (r2 = 0.94, P < 0.01) with air oven m.c. values.ConclusionFrom the study, it can be concluded that the domestic microwave oven can be successfully used to determine the moisture content of different paddy varieties as an alternative method to the conventional air oven-drying method.

Ultrafast microwave-assisted synthesis of various zinc oxide nanostructures

The conventional hydrothermal process for the synthsis of zinc oxide (ZnO) nanostructures is a slow process and provides less control in terms of shape, size and nucleation time. Whereas, synthesis through microwave heating takes only a few minutes to produce high quality, ultra-pure zinc oxide nanostructures. In this study, we present a protocol to fabricate various ZnO nanostructures (vertically-aligned nanorods, vertically-aligned nanowalls, nanoflowers and nanopillars) using a domestic microwave oven. Based upon the process study, variation in diameter and length of vertically aligned ZnO nanorods with growth time is reported. Uniformly distributed ZnO nanowalls along with ZnO nanoflowers are fabricated in less than 5 minutes. In addition to this, ZnO nanopillars are fabricated for the first-time using evaporation and degradation phenomena in the microwave oven. Furthermore, the ZnO nanorods are found to exhibit a superhydrophobic behaviour, whereas the ZnO nanowalls, nanoflowers and nanopillars are observed to have a hydrophobic behaviour. The developed ZnO nanostructures may find their applications in the areas of optics, electronics, biomedical, solar cell, sensors and transistors etc.

Ion Dynamics and Dielectric Relaxation in NaPO3–MoO3Glasses Prepared By Microwave Method

Abstract The present paper emphasises on microwave synthesis of amorphous solids such as glasses and their transport property. The glasses prepared by domestic microwave oven. The Molybdo-phosphate glasses show ion conductivity. The microwave synthesis is found to be very fast, clean and energy efficient way. The glass transition temperature (Tg)of the investigated glass samples were extracted from Differential scanning calorimeter thermograms. The (Tg) of the glasses are found to between 570K-800K. The conductivity measurements have been carried out for all the samples prepared by impedance gain phase analyser and found the conductivity to be function of both temperature and structure modification. Both a.c and d.c conductivity studies are measured and studied. The conductivity seems to increase with temperature and the Na+ ion concentration. The dielectric relaxation behaviour is also studied

An investigation on aluminothermic reduction of MoO3 in domestic microwave oven

In the present study, feasibility of aluminothermic reduction of molybdenum oxide by microwave oven was studied. Furthermore, the effect of compaction pressure and the amount of used Al and CaO as flux on aluminothermic reduction of molybdenum oxide were investigated. Thermodynamic analysis of the corresponding reaction indicated that, aluminothermic reduction of MoO3 was possible at all temperatures. XRD patterns and thermodynamic investigation of reaction products indicated that aluminothermic reduction of molybdenum oxide progressed through the formation of intermediate phases such as Al2 (MoO4)3 and MoO2, where the final products were elemental Mo and Al2O3. Results revealed that by increasing the compaction pressure of the pellet, undesired phases of molybdenum dioxide (MoO2) and aluminum molybdate Al2(MoO4)3 can be detected among the final products. By increasing the amount of Al more than stoichiometric ratio, the intermediate phases, such as MoO2, were produced. The results indicated that by adding CaO to the MoO3-Al system, the unwanted molybdenum dioxide (MoO2) and aluminum molybdate (Al2 (MoO4)3) compounds were successfully reduced to Mo.. In the present work, metallic molybdenum could easily and successfully be separated from Al2O3 slag, as the side product of the reaction, in molten phase, based on the difference in their densities.

Biofriendly and competent domestic microwave assisted method for the synthesis of ZnO nanoparticles from the extract of Azadirachta indica leaves

ZnO nanoparticles are successfully prepared via eco-friendly synthesis using Azadirachta indica leaves extract with microwave assisted solvothermal method using a domestic microwave oven. The structure of green synthesized ZnO NPs and lattice parameters were confirmed using powder X-ray diffraction. Scanning electron microscopy and energy dispersive X-ray analysis exhibit the morphology and elemental analysis of the green synthesized ZnO NPs. The photoconductivity study reveals the positive photoconductive nature of ZnO nanoparticles.

Dielectric relaxation of deep eutectic solvent + water mixtures: structural implications and application to microwave heating.

We studied the dielectric response of deep eutectic solvents (DESs) composed of choline chloride (ChCl) and such hydrogen bond donors (HBDs) as glycerol (glyceline) and urea (reline) mixed with water at T = 298.15 K and frequencies varying from 0.05 to 89 GHz. The dielectric loss data were used to calculate normalized heating rates for these systems upon electromagnetic irradiation at operating frequencies of domestic (ν = 2.45 GHz) and industrial (ν = 900 MHz) microwave ovens. We show that due to slow dynamics and substantial Ohmic-loss contributions DES/water mixtures constitute promising solvents for microwave synthesis. Their dielectric spectra can be best fit by a superposition of relaxation processes assigned to the reorientation of dipolar DES components and water molecules. Static permittivities were found to smoothly decrease from the value of neat water (78.4) to 22.8 for glyceline and 41.2 for reline. The analysis of the obtained relaxation amplitudes suggests that the studied systems can be viewed as mixtures of individual choline, HBD and water dipoles without pronounced dipole-dipole correlations and negligible ChCl ion pairs. However, rotational motions of the dipoles are partly synchronized, leading to the slow-down of 22 water molecules for glyceline and 9.2 for reline at infinite dilution. At vanishing DES concentration ChCl-HBD interactions appear to be negligible. Relaxation times as a function of viscosity show a break point at the ChCl : HBD : H2O ratio equal to 1 : 2 : 4. This supports the suggestion of a structural transition from homogeneous electrolyte solution to a micro-heterogeneous mixture already discussed in the literature.

Evaluation of efficacy of microwave staining over conventional staining in replicating tissue architecture: A prospective study

ABSTRACTIntroduction:The use of microwave in the field of diagnostic pathology has gained a huge response in recent times. Use of domestic microwave ovens in the same is being widely studied. Unveiling the use of the microwave in improving the staining quality of tissue sections in the field of pathology can aid in precise diagnosis of complex conditions.Aim:The main aim of this study was to study the efficiency of microwave staining to reproduce the tissue architecture compared to that of conventional staining techniques.Materials and Methods:Thirty different tissue blocks (including 10 mucocele tissue blocks) were used to prepare 30 pairs of slides for three different stains, namely hematoxylin and eosin, Van Gieson’s, 0.1% toluidine blue and periodic acid–Schiff and 10 pairs of slides for mucicarmine stain. From each pair of slides, one slide was stained routinely, and the other was stained inside a microwave. Two pathologists evaluated the stained slides, and the results so obtained were analyzed statistically.Results:Microwave staining considerably cut down the staining time from hours to seconds. Microwave staining showed no loss of cellular and nuclear details, uniform staining characteristics, and was of excellent quality.Conclusion:The microwave stained slide showed no significant difference in terms of cell outline clarity, cytoplasmic staining, nuclear outline, nuclear staining, nuclear chromatin, and staining intensity compared to that of routine staining method, and a significant difference was observed in the total staining time consumed by all the stains that were used.

Facile and fast synthesis of a reduced graphene oxide/carbon nanotube/iron/silver hybrid and its enhanced performance in catalytic reduction of 4–nitrophenol

A facile, eco-friendly approach is proposed for fast preparation of a partially reduced graphene oxide/carbon nanotube/iron/silver hybrid (rGO/CNT/Fe/Ag) under ambient conditions. The partial reduction and exfoliation of GO, the ultrafast growth of CNT on the rGO surface, and the formation of AgNPs occurred simultaneously within 10–30 s using a domestic microwave oven. The morphology and structure of the rGO/CNT/Fe/Ag hybrid are discussed in detail, and a possible formation mechanism is proposed. The obtained rGO/CNT/Fe/Ag hybrid exhibited high catalytic activity for reduction of 4–nitrophenol (4–NP) by NaBH4 with a kinetic rate constant of 14.66 × 10−3 s−1, a normalized rate constant of 1884.31 s−1 × g−1 and a turnover frequency of 33.6 h−1 due to the synergistic effect of all consisting components in the hybrid. With a high surface area, GO serves as a good substrate for immobilization of more AgNPs, whereas rGO/CNT with a high electrical conductivity promoted the electron transfer in the reduction of 4–NP. AgNPs were the catalytic active sites for the reduction of 4–NP, whereas the presence of FeNPs and Fe3C facilitate for recovering and recycling the catalyst easily. Moreover, the rGO/CNT/Fe/Ag hybrid maintained high catalytic activity and stability after five cycles and easy reusability by an external magnet.

Selective heating and enhanced boiling in microwave heating of multicomponent (solid–liquid) foods

AbstractSelective or enhanced heating of a solid in a solid–liquid mixture in microwaves that can lead to enhanced boiling and possibly bumping was studied. A soup containing broth and particulate foods was heated in a cylindrical container in a standard domestic microwave oven. Heating patterns were obtained using a coupled three dimensional thermal‐electromagnetic model, as well as an infrared camera, and boiling was visually observed. Selective heating of the solid particulates over the broth depends on their dielectric and thermal property differential. Enhanced and early boiling on the surface resulting from selective heating also depends on factors that aid in bubble formation and growth such as the surface roughness and porosity (gas pockets) in the solid. For quick prediction of the potential for enhanced heating in product design, a characteristic number was developed that can predict situations that are more prone to enhanced heating than the surrounding liquid.Practical applicationsWhen microwave heating of a soup or a soup‐like multicomponent mixture of solid and liquid foods, for example carrot or corn pieces in a broth, the solid can end up heating faster than the surrounding liquid, leading boiling to be initiated preferentially at the solid surface, as opposed to in the bulk broth. Depending on the solid material and its surface properties, such a boiling can be further enhanced and sudden, leading to possible bumping during the heating process. A simple design parameter, based on easily available dielectric and thermal properties of the solid and liquid, was developed to quickly predict the possibility of such an enhanced heating of the solid surface (that could eventually lead to bumping). When designing microwaveable products like soups, this simple parameter can be of particular help, reducing the time and resources for experimentation by providing a quick estimate of the probability of enhanced boiling and thus bumping.

Fabrication of efficient alginate composite beads embedded with N-doped carbon dots and their application for enhanced rare earth elements adsorption from aqueous solutions

The increasing demand of rare earth elements in agriculture and industry raises the potential environmental pollution with their inevitable toxicity and biological accumulation. It is necessary to develop an efficient and low-cost technique to effectively remove rare earth elements. N-doped carbon dots (CDs) were green-synthesized using one-pot domestic microwave oven and novel alginate composite (ALG@CDs) beads were fabricated by embedding the N-doped CDs into pure alginate hydrogel beads. The synthetic materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and zeta potential measurement. The ALG@CDs beads could effectively adsorb rare earth elements from aqueous solutions. Taking the adsorption of rare earth element Gd (III) as an example, initial concentration, adsorbent dosage, pH, temperature and contact time were optimized. The adsorption isotherms and kinetics fitted to Langmuir isotherm model (R2 > 0.9991) and pseudo-second-order kinetic model (R2 = 0.9918), respectively. The adsorption capacity of ALG@CDs-3 (201.21 mg/g) for Gd (III) was much higher than that of bare ALG beads (124.38 mg/g) according to the maximum theoretical adsorption capacity of Langmuir model. Competitive adsorption results indicated that ALG@CDs beads had stronger affinity to Gd (III) than to Al (III), Co (II), Ni (II), Zn (II), and Mg (II). The adsorbent could be easily collected and reused for five adsorption-regeneration cycles. The results indicated that the fabricated ALG@CDs beads are the promising materials for adsorption or enrichment of rare earth elements from waste water.

One-step synthesis of gold and silver non-spherical nanoparticles mediated by Eosin Methylene Blue agar

Nowadays, there are several approaches reported to accomplish the green synthesis of metal nanoparticles by using bacterial and fungi supernatants or by-products generated by these microorganisms. Therefore, agars as solely reductive regents have started to be used in order to obtain metal nanoparticles. This paper shows the results of the synthesis of gold and silver nanoparticles with different morphology, mainly triangular and truncated triangular, using Eosin Methylene Blue (EMB) agar as reducing agent. To control the reaction process, the necessary activation energy for the reducer was provided by three different techniques: microwave radiation, using a domestic microwave oven, ultraviolet radiation, and heating on a conventional plate. The evolution of the reduction process and stability of the samples was performed by ultraviolet visible spectroscopy. Morphology was carefully analyzed using high-resolution transmission electron microscopy (HRTEM) and Transmission electron microscopy (TEM). A one step synthesis for gold and silver nanoparticles was optimized with an eco-friendly and economic process.

Characterization of Cobalt Based Microwave Clad Developed on SS-355

In the present work a detailed microstructural investigation of Cobalt based microwave cladding on S-355 stainless steel was carried out. The experimentations were carried out in a home based domestic microwave oven. This article clears the circumstances of clad formation during microwave hybrid heating. The solidification texture and grain structure of the developed clad scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy, and measurement of Vicker’s microhardness. Cobalt based clads developed with an approximate thickness of 1 mm without interfacial cracking. The microstructure of clad clearly illustrated excellent metallurgical bond with S-355 substrate and found dominantly fine cellular grains. Iron and cobalt were recognized inside the cells while chromium was ascertained segregated around the cell boundaries. The average microhardness of the cobalt based clad was observed in the range of 402±60 HV.

Concerns and solutions for raw milk from vending machines

The sale of raw milk from vending machines is allowed in several European Countries. Since unpasteurized milk could harbor foodborne pathogens, the boiling treatment is highly recommended before consumption. In this study, the effect of storage temperatures, generally recorded in domestic refrigerators, as well as the effect of domestic boiling and industrial microwaving on the microbiological, and nutritional quality of raw bovine milk from vending machines was evaluated. Results highlighted that some microbial groups increased during the storage at 8°C. Noticeable, Listeria spp., even if initially present in low amounts, reached levels that would be a cause of concerns. Based on these results, the effects of domestic boiling and microwaving on the survival of L. innocua intentionally added was evaluated, as well as the nutritional features of treated milk. Both treatments were able to eliminate L. innocua, but only microwaving preserved the nutritional quality of milk. Practical applications This study presents the application of microwaving as an alternative treatment to enhance the quality of raw bovine milk. Domestic storage conditions (especially refrigeration temperatures and time) produce a strong decay in the microbiological quality of the product and Listeria levels might become a real concern. In addition, boiling treatment, imposed by law prior to milk consumption, produces a further depletion of the nutritional quality, producing a strong decay in thermolabile compounds. A suitable solution for heat treatment of raw milk from vending machines could be represented by microwaving at 780 W for 1.35 min. This datum could serve for setting a specific program in domestic microwave ovens for sanitization of raw milk in home environments.

Investigation of a New Spectrophotometric Method for the Analysis of Ciprofloxacin Based on Microwave Assisted Diazotization.

A microwave-assisted diazotization reaction of ciprofloxacin was used for the analysis of ciprofloxacin in pharmaceutical samples. The ciprofloxacin was diazotized with phenol using acidified sodium nitrite in a domestic microwave oven. Faster microwave heating and microwave effects were found to be very effective for the process of diazotization. The microwave-assisted reaction was initiated in an acidic media and the colored product was stabilized in a slightly basic medium using a NaOH solution as a neutralizer. The product was found to exhibit the maximum absorbance at 440 nm. All of the experimental conditions like the concentration of reagents, microwave power and reaction time were optimized. The optimum concentrations for phenol, sodium nitrite, HCl and NaOH were found to be 140 ppm, 300 ppm, 0.006 M and 0.006 M respectively. The optimum reaction time was found to be 2 min and a medium high power of the microwave was found to be most effective. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 1.08 and 3.61 mg L-1 respectively. The developed method was successfully applied for the determination of ciprofloxacin in pharmaceutical samples. This new spectrophotometric method for the analysis of ciprofloxacin is fast, sensitive, easy and cost effective.

Evaluation of the physical properties of fluorescent carbon nanodots synthesized using Nerium oleander extracts by microwave-assisted synthesis methods

Rapid and one-step green synthesis of carbon nanodots (CDs) from Nerium oleander leaves was accomplished via domestic microwave oven and microwave-assisted hydrothermal synthesizer under various physical conditions. Effects of the synthesizer system, extract type depending on the solvents used in plant extraction, and synthesis conditions; such as reaction time, reaction temperature, surface passivation agent inclusion into the reaction medium, on the physicochemical properties and optical feature of CDs were investigated. The impacts of relevant conditions on CDs feature were determined clearly via UV–visible spectrophotometry, fluorescence spectrophotometry, dynamic light scattering analysis, and Fourier transform infrared spectroscopy. According to the results, while the most effective parameter on the fluorescence feature of CDs was determined as the presence of surface passivation agent (polyethylene glycol, PEG), the alteration in the fluorescence intensity depending on the reaction time and the reaction temperature was also observed. It was reported that the synthesis system and PEG existence in the reaction medium were more effective than the other inspected parameters on the hydrodynamic particle size, in general. Under optimum conditions, nanoparticles with a hydrodynamic size of less than 5nm were obtained. The surface zeta potential charges of all particles were found as negative. While the extract type was significantly effective on the surface zeta potential of CDs synthesized by domestic microwave oven, the reaction temperature was found to be significant for the ones synthesized via microwave-assisted hydrothermal synthesis.

Dielectric Properties of Infant Formulae, Human Milk and Whole and Low-Fat Cow Milk Relevant for Microwave Heating

Abstract The dielectric properties of three different reconstituted infant formulae, human milk, as well as, whole and low-fat pasteurized cow milk were measured at temperature interval from (5 to 70) °C and at frequency of 2450 MHz. The dependency of the dielectric properties with temperature is presented. The values of penetration depth were determined and can be used to estimate the ideal bottle-feeding or container diameter to use in a domestic microwave oven or specific microwave equipment to pasteurize human milk in Human Milk Banks (HMB).

Fabrication and Investigation of Co-based and CeO2-modified Microwave Coatings

This paper explore the viability of novel microwave hybrid heating, Co-based coatings without CeO2 (unmodified) and with CeO2 (modified) in varying wt % (1, 2 and 3 wt %) were developed. The coatings were developed using domestic microwave oven of 2.45 GHz frequency, 900 W power and an irradiation time of 15 min. The characterization of unmodified and modified clads has been done in terms of microstructure, XRD, hardness and sliding wear behavior. The influence of sliding speed (1.2 and 2.4 m/s) and distance (3000 and 6000 m) on wear behavior were investigated. It was noticed that the wear resistance of coatings containing 1wt % of CeO2 was higher than other coatings. Further, it was found that modified coating with optimum addition of cerium oxide (1wt % CeO2) refined the microstructure, promotes the formation of hard carbides CeC2, Cr23C6 and Cr7C3, enhanced microhardness to 17% as compared to unmodified.