Absorption Of Microwave Energy Research Articles

Numerical Simulation and Experimental Analysis for Microwave Sintering Process of Lithium Hydride (LiH)

Dense lithium hydride (LiH) is widely used in neutron shielding applications for thermonuclear reactors and space systems due to its unique properties. However, traditional sintering methods often lead to cracking in LiH products. This study investigates the densification sintering of LiH using microwave technology. A multiphysics model was established based on the measured dielectric properties of LiH at different temperatures, allowing for a detailed analysis of the electromagnetic and thermal field distributions during the microwave heating of cylindrical LiH samples. The results indicate that the electric field distribution within the LiH is relatively uniform, with resistive losses concentrated primarily in the LiH region of the microwave cavity. LiH rapidly absorbs microwave energy, reaching the sintering temperature of 520 °C in just 415 s. Additionally, the temperature difference between the low- and high-temperature regions during the sintering process remains below 5 °C, demonstrating excellent uniform heating characteristics. The microwave sintering process enhances interface migration within the LiH samples, resulting in dense metallurgical bonding between grains. In summary, this research provides valuable insights and theoretical support for the rapid densification of LiH materials, highlighting the potential of microwave technology in improving material properties.

Porous biochar production from microwave pyrolysis of sugarcane bagasse biomass with KOH addition

ABSTRACT Biomass-based porous carbons have diverse structures and typically exhibit good multifunctionality. Therefore, compared to direct combustion, using pyrolysis to convert agricultural waste into biochar is an environmentally friendly and effective treatment method. Preparing biomass-derived porous carbon materials (PCMs) through microwave is challenging, as biomass rarely absorbs microwave energy and necessitates the inclusion of additional microwave absorbers. In this study, a silicon carbide crucible was designed to simplify the microwave pyrolysis process, and sugarcane bagasse-based porous carbon (GZKM) was prepared using a microwave pyrolysis coupled with KOH activation method without adding additional microwave absorbers. A detailed study was conducted on the yield, surface morphology, and pore structure of biochar obtained from different temperatures (700, 750, 800, 850, and 900 °C) and different mass ratios of sugarcane bagasse to KOH (0, 4:1, 2:1, 1:1, and 1:2). The results indicated that as the pyrolysis temperature and KOH addition increased, the yield of biochar gradually decreased from a highest value of 31.41 wt% to a lowest value of 11.8 wt%. The specific surface area (SBET) of GZKM initially increased and then decreased with the increase in pyrolysis temperature and KOH mass, reaching a maximum value of 889.41 m2/g. The results of this study can provide guidance for the reuse of sugarcane bagasse and the preparation of porous biochar, and can also be applied in fields such as electrocatalysts, batteries, biomedical materials, and wastewater treatment.

Microwave-induced plasma on spherical flame dynamics of spark-ignited hydrogen-air under water dilution

Microwave-assisted spark ignition (MAI) offers a commercially feasible way to enhance conventional spark ignition performance under extreme conditions. While previous studies suggested microwave pulses had no obvious effect on self-sustained flame from the perspective of energy deposition, the hydrodynamic effect of microwave plasma remained under-explored. This study experimentally investigated the effect of the microwave-induced plasma on lean hydrogen flame dynamics (Lewis number ∼ 0.35), examining the influence of water content (rH2O) in this process under different pulse repetition frequency (PRF) and pressures. Using a linear high-speed shadow imaging system coupled with electrical diagnostics, we synchronously recorded the flame and plasma morphology evolution while monitoring spark and microwave energy. Results revealed that microwave pulses during spark ignition generated wrinkles and perturbances accelerating the cracking and cellularization of the subsequent self-sustained flame. This effect intensified with increasing PRF from 1 to 10 kHz, particularly at high rH2O. The overall microwave impact on early flame development was more pronounced at high rH2O, attributed to stronger interactions between the microwave plasma jet and flame front due to reduced distance. Interestingly, electrical diagnostics showed an inversed relationship between total absorbed microwave energy and rH2O, highlighting the crucial role of the first microwave pulse at 1 kHz PRF. This study demonstrates that early microwave pulses can influence hydrogen flame dynamics even in the self-sustained stage, offering new insights into MAI mechanisms. These findings open avenues for research into active control of self-sustained flame dynamics, potentially leading to improved ignition strategies in challenging combustion environments.

Recovery of NMC-lithium battery black mass by microwave heating processes

The exceptional microwave absorption capabilities of carbon-based materials make them highly effective for facilitating various chemical reactions, such as synthesis, reduction, exfoliation, doping, and decoration. In this study, we applied microwave irradiation to the thermochemical treatment of spent nickel manganese cobalt (NMC622) lithium-ion batteries, obtained as a mix of the cathode and the anodic graphite. This approach significantly accelerated the chemical reactions, leveraging carbon's robust ability to absorb microwave energy. As a proof-of-concept, we demonstrated that within just 5 min, the carbothermic reduction reactions in the black mass facilitated the formation of water-soluble Li2O, and enhanced the solubility of Co, Mn, and Ni in a weak acid. More than 90% of Li and 87% of Mn are recovered. This method, which bypasses the need for cathodic and anodic separation, presents a promising new approach for recovering strategic metals from spent lithium-ion batteries.

Synergistic SiC/Co3O4 composites for enhanced microwave-assisted benzene catalytic removal performance

Microwave-assisted catalysis is a promising technique for enhancing catalytic reactions through selective heating, potentially leading to improved reaction rates and energy efficiency. However, understanding the complex interactions between microwave absorption and catalytic performance in composite catalysts remains a challenge. In this study, Cobalt oxide(Co3O4)/silicon carbide(SiC) composite catalysts with varying SiC content were synthesized and characterized to investigate the relationship between their microwave absorption properties and catalytic performance. Quantitative analysis revealed that SiC and Co3O4 absorb microwave energy through relaxation polarization and magnetic loss mechanisms, respectively. Increasing SiC content enhanced the dielectric and magnetic loss capabilities of the composites, with the Co3O4/SiC composite containing 10 wt% SiC (Co3O4/SiC-10) exhibiting a dielectric loss tangent of 3.87 and a minimum reflection loss of −35dB. However, higher SiC content decreased the surface chemically adsorbed oxygen, surface oxygen mobility, and benzene adsorption capacity, weakening the catalytic activity under conventional heating. The Co3O4/SiC-10 sample achieved a significantly better balance between microwave absorption and catalytic performance, significantly outperforming the original Co3O4 sample under microwave irradiation. These founding establishes a quantitative research methodology that correlates dielectric loss tangent, reflection loss, and other crucial parameters with microwave absorption performance and further catalytic properties, providing insights for the rational design of catalysts that optimize both microwave absorption and catalytic activity.

Manipulating polarization attenuation in NbS2–NiS2 nanoflowers through homogeneous heterophase interface engineering toward microwave absorption with shifted frequency bands

Homogeneous heterogeneous (heterophase) interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization, which facilitate the transport of electrons across the substrate. Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials. Herein, we construct NbS2–NiS2 heterostructures with NiS2 nanoparticles uniformly grown in NbS2 hollow nanospheres, and such particular structure enhances the interfacial polarization. The strong electron transfer at the interface promotes electron transport throughout the material, which results in less scattering, promotes conduct ion loss and dielectric polarization relaxation, improves dielectric loss, and results in a good impedance matching of the material. Consequently, the absorbing band may be successful tuned. By regulating the amount of NiS2, the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies. With a NiS2 content of 15 ​wt% and an absorber thickness of 1.84 ​mm, the minimum reflection loss at 14.56 ​GHz is −53.1 ​dB, and the effective absorption bandwidth is 5.04 ​GHz; more importantly, the minimum reflection loss in different bands is −20 dB, and the microwave energy absorption rate reaches 99% when the thickness is about 1.5–4.5 ​mm. This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties, providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.

Temperature-dependent dielectric properties of the Korean lunar simulant and ilmenite: Lunar microwave processing potential

There is increasing interest in the potential application of microwave sintering technology in the construction of infrastructure on the Moon. This study aimed to characterize the dielectric properties of in situ lunar materials; this information is critical for an understanding of the interaction of these materials with microwave and in the application of microwave sintering technology. Dielectric properties including the real and imaginary permittivity, dielectric loss tangent, penetration depth, and electrical conductivity of Korean Lunar Simulant (KLS-1) and ilmenite (an abundant lunar mineral) were investigated at microwave frequencies as a function of temperature. X-ray dispersion (XRD) analyses confirmed that the lattice expansion of minerals with increasing temperature was consistent with an increasing trend in permittivity. The dielectric loss tangent of ilmenite was 2–36 times higher than that of KLS-1, depending on temperature, indicating that ilmenite has greater ability to absorb microwave energy, converting it to heat. Ilmenite demonstrated rapid heating to 1000°C within a few minutes on exposure to 1 kW microwave (2.45 GHz) irradiation. This study provides important information relevant to the development of microwave technology for future lunar applications.

Microwave responsive copper-ferrite (CuFe2O4) encapsulated in molybdenum-disulfide (MoS2) nanoflower catalyst for antibiotic removal via persulfate oxidation

Microwave (MW) responsive copper-ferrite/molybdenum-disulfide (CuFe2O4/MoS2) nanoflower catalyst was implemented for rapid antibiotic metronidazole (MNZ) degradation via persulfate oxidation under MW irradiation. The catalyst was synthesized via co-precipitation followed by hydrothermal methods, and characterized by XRD, FTIR, SEM, TEM, VSM, XPS, and UV-DRS. As a first step, MW induced MNZ removal was studied at different initial mass of CuFe2O4/MoS2 (2.5–20%), where 5% CuFe2O4 in the nanocomposite performed the best. Within 5 min of MW irradiation, 100% MNZ removal was observed (Kobs ∼ 1.063 min−1) under the optimal reaction conditions (i.e., CuFe2O4/MoS2 dose ∼ 0.4 g/L; PS dose ∼ 100 mg/L; temperature ∼ 90 °C; and MW power ∼ 350 W). The MNZ removal was independent of solution pH 3–11, and the removal was by SO4•−and •OH radicals alongside the limited contribution from O2•−. PS and H2O were thermally decomposed to produce SO4•−and •OH radicals, whereas intrinsic semiconductor CFO/MS with a narrow bandgap of 1.53 eV allowed electrons to jump into conduction band from valance band to create SO4•− and O2•−. However, the performance of MW system was inhibited by the presence of anions in the order of Cl−< NO3− <CO32− <H2PO4−. Robustness of the CuFe2O4/MoS2 was proved via recyclability experiments, and MNZ removal was found to be dropped ∼ 4.89% at the end of 5th cycle. It was proposed that the absorbed MW energy was dissipated through various losses to generate ‘hotspots’ (>1200 °C) for MNZ removal. Synergistically, redox couples of transitional metals contributed to MNZ degradation.

Microwave absorption, thermal and mechanical properties of amorphous nano carbon doped aluminium nitride composite ceramics

Low-cost amorphous nano-carbon (ANC) was employed as an absorbent to modify the microwave performance of AlN ceramics (AlN-4 wt% Y2O3-x wt% C, x = 0, 2.0, 3.8, 3.9, 4.0) via hot-pressing sintering, and the thermal and mechanical properties were also investigated. With the increase of ANC content from 0 to 4.0 wt%, the relative density of AlN composite decreases from 3.28 g cm−3 to 3.16 g cm−3 when sintered at 1800 °C for 2 h, and with the increase of sintering temperature from 1700 °C, the density of the 4.0 wt% ANC doped AlN composite presents trend of increase and reaches the maximum value of 3.16 g cm−3 at 1800 °C and then decreases. The XRD pattern shows that the composites are composed of AlN and Y–Al–O (YAG, YAP, YAM et al.) phases. SEM results indicate that average grain sizes for AlN and secondary phases gradually decrease with increasing carbon content, suggesting inhibited grain growth due to ANC addition. No obvious changes in phase constitution nor intensity changes were detected with the increase in carbon content and sintering temperature. As the carbon content increases from 0 to 4.0 wt%, the dielectric constant gradually increases from ∼9 to 13.89 at 10 GHz, the dielectric loss gradually increases from the vicinity of 10−3 to 0.38 at 10 GHz, and the reflective loss decreases from −27.92 dB to −49.40 dB, the thermal conductivity of the AlN-ANC composite decreases from 116.63 W m−1 K−1 to 50.13 W m−1 K−1. In addition, with 4.0 wt% ANC addition, the dielectric constant, dielectric loss, reflective loss, hardness, elastic modulus, bending strength, and fracture toughness are 13.89, 0.38, 49.40 dB, 6.4 ± 0.4 GPa, 262 GPa, 268.78 MPa, and 1.4 ± 0.1 MPa m1/2, respectively. Its ability to efficiently absorb microwave energy enhances the performance of devices including radar systems, communication equipment, and microwave heating systems, making it a promising candidate for microwave vacuum electronic applications.

Advanced Integration of Microwave Kiln Technology in Enhancing the Lost-Wax Glass Casting Process: A Study on Methodological Innovations and Practical Implications

Lost-wax glass casting, an esteemed yet technically demanding art form, traditionally relies on specialized, costly kiln equipment, presenting significant barriers to artists regarding equipment affordability, energy efficiency, and the technical mastery required for temperature control. Therefore, this study introduces an innovative approach by integrating a microwave kiln with standard household microwave ovens, thus facilitating the lost-wax glass casting process. This methodological adaptation allows artists to employ readily available home appliances for glass creation, significantly reducing the process’s cost and complexity. Our experimental investigations reveal that, by using a 500W household microwave oven for heating, the silicon carbide (SiC) in microwave kilns can efficiently absorb microwave energy, allowing the kilns to reach temperatures exceeding 700 °C, a critical threshold for casting glass softening. We further demonstrate that by adjusting the number of heating cycles, producing high-quality, three-dimensional(3D) glass artworks is feasible, even for large-scale projects. In addition, the microwave kiln can be used as an effective cooling tool to uniformly cool the formed casting glass. This study presents a possible alternative to conventional kiln technology and marks a paradigm shift in glassmaking, offering a more accessible and sustainable avenue for artists and practitioners.

Velocity match between plasma and flame in microwave-assisted spark ignition

As a prospective ignition technique, microwave-assisted spark ignition (MAI) can accelerate flame and thus satisfy the demand for effective ignition. However, its acceleration mechanism on flame velocity is still unclear, which hinders its application and optimizations. Therefore, this research focuses on understanding the flame acceleration mechanism behind MAI. In this paper, MAI is achieved through radiating a microwave pulse after spark ignition. The flame velocity and the precise absorbed energy under different combustion conditions are investigated with flame kernel's Schlieren images and microwave energy diagnostics, respectively. The results show that MAI accelerates flame primarily by the interaction between microwave plasma and flame front, rather than the free electrons within the flame. Specifically, microwave accelerating flame takes two processes: energy absorption, and velocity match. Energy absorption refers to the microwave energy absorbed by residual electrons after ignition to generate and sustain microwave plasma, while velocity match involves the outward plasma with faster velocity propelling the slower flame front. Moreover, the plasma velocity shows a positive relationship with absorbed microwave energy. The velocity match between microwave plasma and flame is important to successful flame acceleration. Besides, the efficiency of energy absorption and flame acceleration varies with plasma type (glow or incandescent). Glow plasma is characterized by effective flame acceleration but relatively low absorption efficiency, and incandescent plasma is in reverse. The maximum absorption efficiency can be elevated to 70 % with incandescent plasma occurring. Ultimately, the plasma velocity declines with its traveled distance, which might impair the flame acceleration.

Superparamagnetic iron oxide nanoparticle enhanced percutaneous microwave ablation: Ex-vivo characterization using magnetic resonance thermometry.

Percutaneous microwave ablation (pMWA) is a minimally invasive procedure that uses a microwave antenna placed at the tip of a needle to induce lethal tissue heating. It can treat cancer and other diseases with lower morbidity than conventional surgery, but one major limitation is the lack of control over the heating region around the ablation needle. Superparamagnetic iron oxide nanoparticles have the potential to enhance and control pMWA heating due to their ability to absorb microwave energy and their ease of local delivery. The purpose of this study is to experimentally quantify the capabilities of FDA-approved superparamagnetic iron oxide Feraheme nanoparticles (FHNPs) to enhance and control pMWA heating. This study aims to determine the effectiveness of locally injected FHNPs in increasing the maximum temperature during pMWA and to investigate the ability of FHNPs to create a controlled ablation zone around the pMWA needle. PMWA was performed using a clinical ablation system at 915MHz in ex-vivo porcine liver tissues. Prior to ablation, 50uL 5mg/mL FHNP injections were made on one side of the pMWA needle via a 23-gauge needle. Local temperatures at the FHNP injection site were directly compared to equidistant control sites without FHNP. First, temperatures were compared using directly inserted thermocouples. Next, temperatures were measured non-invasively using magnetic resonance thermometry (MRT), which enabled comprehensive four-dimensional (volumetric and temporal) assessment of heating effects relative to nanoparticle distribution, which was quantified using dual-echo ultrashort echo time (UTE) subtraction MR imaging. Maximum heating within FHNP-exposed tissues versus control tissues were compared at multiple pMWA energy delivery settings. The ability to generate a controlled asymmetric ablation zone using multiple FHNP injections was also tested. Finally, intra-procedural MRT-derived heat maps were correlated with gold standard gross pathology using Dice similarity analysis. Maximum temperatures at the FHNP injection site were significantly higher than control (without FHNP) sites when measured using direct thermocouples (93.1±6.0°C vs. 57.2±8.1°C, p=0.002) and using non-invasive MRT (115.6±13.4°C vs. 49.0±10.6°C, p=0.02). Temperature difference between FHNP-exposed and control sites correlated with total energy deposition: 66.6±17.6°C, 58.1±8.5°C, and 20.8±9.2°C at high (17.5±2.2kJ), medium (13.6±1.8kJ), and low (8.8±1.1kJ) energies, respectively (all pairwise p<0.05). Each FHNP injection resulted in a nanoparticle distribution within 0.9±0.2cm radially of the injection site and a local lethal heating zone confined to within 1.1±0.4cm radially of the injection epicenter. Multiple injections enabled a controllable, asymmetric ablation zone to be generated around the ablation needle, with maximal ablation radius on the FHNP injection side of 1.6±0.2cm compared to 0.7±0.2cm on the non-FHNP side (p=0.02). MRT intra-procedural predicted ablation zone correlated strongly with post procedure gold-standard gross pathology assessment (Dice similarity 0.9). Locally injected FHNPs significantly enhanced pMWA heating in liver tissues, and were able to control the ablation zone shape around a pMWA needle. MRI and MRT allowed volumetric real-time visualization of both FHNP distribution and FHNP-enhanced pMWA heating that was useful for intra-procedural monitoring. This work strongly supports further development of a FHNP-enhanced pMWA paradigm; as all individual components of this approach are approved for patient use, there is low barrier for clinical translation.

Decreasing the environmental impact of carbon fibre production via microwave carbonisation enabled by self-assembled nanostructured coatings

The use of carbon fibre (CF)-based composites is of growing global importance due to their application in high-end sectors such as aerospace, automotive, construction, sports and leisure amongst others. However, their current high production cost, high carbon footprint and reduced production capability limit their use to high-performance and luxury applications. Approximately 50% of the total cost of CF production is due to the thermal conversion of polyacrylonitrile (PAN) precursor fibre (PF) to CF as it involves the use of high energy consumption and low heating efficiency in large furnaces. Looking at this scenario, this study proposes in the present study to use microwave (MW) heating to convert PF to CF. This is scientifically and technologically challenging since PF does not absorb microwave energy. While MW plasma has been utilised to carbonise fibres, it is the high temperature from the plasma that does the carbonisation and not the MW absorption of the fibres. Therefore, for the first time, this research shows how carbonisation temperatures of >1000 °C can be reached in a matter of seconds through the use of a novel microwave (MW) susceptor nanocoating methodology developed via a layer-by-layer assembly of multiwall carbon nanotubes (MWCNTs) on the PF surface. Remarkably, these CFs can be produced in an inexpensive domestic microwave and exhibit mechanical performance equivalent to CF produced using conventional heating. Additionally, this study provides a life cycle and environmental impact analysis which shows that MW heating reduces the energy demand and environmental impact of lignin-based CF production by up to 66.8% and 69.5%, respectively.Graphical

The Law and Mechanism of the Effect of Surface Roughness on Microwave-Assisted Rock Breaking

In physical engineering, a rock surface, whether naturally or artificially formed, is rough. When irradiating rocks, microwaves produce reflections and diffractions on the surface of rough rocks, which significantly affect the absorption of microwave energy by rocks, thus influencing the result of microwave irradiation. In order to explore the influence of rough rock surfaces on the effect of microwave-assisted rock breaking, microwave irradiation tests were carried out on basalt samples with different values of roughness to test the temperature and P-wave velocity of the samples before and after microwave irradiation. Numerical test methods were used to systematically study the influence of rough rock surfaces on microwave irradiation. The results show that, under the same microwave irradiation conditions, the effect of microwave irradiation on rough surface basalt is more significant than that of flat surface basalt. The surface temperature distribution range of flat surface specimens is narrow, the surface temperature range of rough surface specimens is wider and more inhomogeneous, and the maximum surface temperatures of rough surface specimens are much higher than those of flat surface specimens. After irradiation, new macroscopic cracks were generated on the surface of the samples, and the crack propagation of the rough surface samples was more obvious. The decrease in P-wave velocity before and after the irradiation of flat surface samples is small, and that of rough surface samples is larger. The main factors affecting the effect of microwave irradiation on the rough surface are the refraction and reflection of electromagnetic waves, heat conduction, and stress concentration on the surface.

The 3D Printing of Novel Honeycomb-Hollow Pyramid Sandwich Structures for Microwave and Mechanical Energy Absorption.

Honeycomb sandwich (HS) structures are important lightweight and load-bearing materials used in the aerospace industry. In this study, novel honeycomb-hollow pyramid sandwich (HPS) structures were manufactured with the help of fused deposition modeling techniques using PLA and PLA/CNT filaments. The microwave and mechanical energy absorption properties of the HPS structures with different geometry parameters were studied. Compared with the HS structure, the HPS structure enhanced both microwave absorption and mechanical properties. The HPS structures possessed both broadband and wide-angle microwave absorption characteristics. Their reflection loss at 8-18 GHz for incident angles of up to 45° was less than -10 dB. As the thickness of the hollow pyramid increased from 1.00 mm to 5.00 mm, the compressive strength of the HPS structure increased from 4.8 MPa to 12.5 MPa, while mechanical energy absorption per volume increased from 2639 KJ/m3 to 5598 KJ/m3. The microwave absorption and compressive behaviors of the HPS structures were studied.

Kinetic study of Ni-M/CNT catalyst in methane decomposition under microwave irradiation

Methane catalytic decomposition has been studied with catalysts that can attenuate the energy of electromagnetic waves to heat and drive the reaction. Herein, we report, for the first time, a comprehensive kinetic study of Ni-M (M=Pd, Cu, or Fe)-CNT catalysts under microwave irradiation. These binary metal alloy nanoparticles have been synthesized on multiwalled carbon nanotube support with solvothermal process. These catalysts showed incredible performance for both absorbing microwave energy and catalyzing the reaction to form carbon nanotubes and hydrogen. Ni-M-CNT has a reaction order of 0.74. 10Ni-1 Pd-CNT, 10Ni-1Cu-CNT, and 10Ni-1Fe-CNT have activation energies at 87, 75, and 69 kJ/mol. The investigation was carried out in a differential reactor. The results indicated that 10Ni-1Fe-CNT had the lowest activation energy due to the increase in microwave susceptibility. This work pioneered the microwave catalytic methane decomposition field as well as paving the way for future electrification of COx-free hydrogen production.

The Evolution of Microwave-Induced Thermoacoustic Signals Generated During Pulsed Microwave Ablation in Bovine Liver

The temperature dependence of microwave-induced thermoacoustic signals generated in tissue may be exploited to monitor microwave ablation in real-time. We present an experimental study investigating the evolution of microwave-induced thermoacoustic signals that are generated within an ablation zone during microwave ablation in bovine liver tissue. An X-band interstitial coaxial ablation antenna is used to simultaneously heat liver tissue to temperatures up to 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C and excite thermoacoustic signals via the absorption of pulsed microwave energy. Thermoacoustic signals are detected using a single-element ultrasound transducer located at the surface of the tissue. Both fresh and boiled liver tissue samples are used in experiments to decouple the influence of temperature and tissue coagulation on thermoacoustic signal characteristics. We identify two thermoacoustic signal characteristics of interest: arrival time of the pulse at the ultrasound receiver and the energy in the pulse. We find that the time difference of arrival over the course of microwave ablation grows in magnitude due to temperature-dependent speed of sound and tissue shrinkage. Thermoacoustic signal energy generally increases throughout microwave ablation, implying an increasing temperature-dependent thermal expansion coefficient of liver tissue. Of the two characteristics, time difference of arrival shows the most promise as a trackable feature for monitoring microwave ablation in real time.

The microwave absorption and anti-corrosion performance of flaky FeSiCr powder coated by silane film

A silane film was prepared on the surface of flaky FeSiCr powder by sol-gel method. The phase and morphology of the samples were observed by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM), and the valence state and chemical composition of the elements were determined by X-ray Photoelectron Spectroscopy (XPS). The results showed that the observed images of homogeneous silane films confirm the successful preparation of lamellar FeSiCr@PFOTMS composites. The electromagnetic parameters measurement results showed that the complex permittivity of the samples is substantially reduced and the complex permeability changes little, then the balance of electromagnetic parameters is improved and the impedance matching is optimized. When PFOTMS is added in amounts up to 2 mL, the FeSiCr@PFOTMS composites showed the best microwave energy absorption and corrosion resistance. The minimum reflection loss value of the sample reached –32.22 dB at 2.16 GHz. The electrochemical test results showed that the open circuit corrosion potential of FeSiCr@PFOTMS composites with 2 mL PFOTMS increased from –0.217 V to 0.031 V, and the corrosion voltage increased from –0.215 V to 0.028 V. These results provide ideas for the preparation of multifunctional composites with both excellent microwave absorption properties and corrosion resistance in practical applications.

Ultra-fast solvent-free protocol remodels the large-scale synthesis of carbon dots for nucleolus-targeting and white light-emitting diodes

Carbon dots (CDs) provides unprecedented opportunities for optical applications due its unique properties, but the energy-extensive consumption, high-risk factor and time-consuming synthesis procedure greatly hinders its industrialization process. Herein, we proposed an ultra-low energy consumption solvent-free synthetic strategy for fast preparing green/red fluorescence carbon dots (G-/R-CDs) using m-/o-phenylenediamine and primary amine hydrochloride. The involvement of primary amine hydrochloride can improve the formation rate of G-CDs/R-CDs through effectively absorbing microwave energy and providing acid react environment. The developed CDs exhibit good fluorescence efficiency, optical stability and membrane permeability for dexterous bioimaging in vivo. Based on inherently high nitrogen content, the G-CDs/R-CDs possess excellent nuclear/nucleolus targeting ability, and were successfully applied for screening cancer and normal cells. Furthermore, the G-CDs/R-CDs were further applied for fabricating high-safety and high-color rendering index white light-emitting diodes, providing a perfect candidate for indoor lighting. This study opens up new horizons for advancing practical applications of CDs in related fields of biology and optics.

Effect of strong dielectric substances on the damage characteristics of rocks exposed to microwave radiation: Insight from experiments and mechanisms

It has been demonstrated that microwave pretreatment can weaken rocks, reduce tool wear, and improve mechanical rock breaking efficiency. The dielectric properties of rock minerals are a major factor affecting the ability of rocks to absorb microwaves, so it is important to conduct experimental research on rock modification to improve the microwave absorption capacity of rocks. The concept of “microwave-assisted absorbing reagents” has been proposed to increase the microwave absorption capacity of rocks. Sandstone specimens are first pretreated with strong dielectric substances before being exposed to microwave radiation to increase their microwave absorption capacity, then they are exposed to microwave fields and finally conducted to uniaxial compression tests. Enhancement in microwave absorption capacity of sandstone specimens is showed by P-wave velocity, nuclear magnetic resonance, and mechanical tests before and after microwave treatment. The results showed that barium titanate suspension and water are both effective microwave-assisted absorbing agents. The specimens treated with barium titanate suspension exhibited better microwave absorption capacity; in 5 kW microwave power irradiation, its p-wave velocity falls by 14.04%, porosity rises by 25.43%, and uniaxial compressive strength falls by 24.98%. Additionally, the failure form of sandstone specimens changes from brittle to plastic once it has fully absorbed microwave energy.