Alternating-current Field Research Articles

Possibility of the magnitude of the chiral vector having an effect on the terahertz radiation generation by hot electrons in zigzag carbon nanotubes driven by DC-AC fields

The possibility that the magnitude of a chiral or circumferential vector (Chv) influences the generation of terahertz radiations (T-rays) by hot electrons in zigzag carbon nanotubes (z-CNTs) driven by direct current (DC) and alternating current (AC) fields is taken into consideration. The study conducted a semiclassical theoretical analysis by using the Boltzmann kinetic equation to determine current density in relation to high AC field frequency (ω) and z-CNT circumference (|Chv|) when hot electrons were present. A numerical analysis was performed by varying the magnitude of the circumference of the tube at a fixed temperature and the strong hot electron injection rate at a predetermined value. When the circumference of the semiconducting zigzag carbon nanotubes (sz-CNTs) is increased, the current density's lowest and highest peaks are also enhanced (i.e., large amplitudes). This increases positive differential conductivity (PDC), necessitating enhanced domain suppression for higher potential generation of T-rays. In contrast, it was observed that reducing the tube's circumference in metallic zigzag carbon nanotubes (mz-CNTs) resulted in an increase in both the lowest and highest peaks of current density, which enhanced the PDC. These findings imply that larger circumferential sz-CNTs and smaller circumferential mz-CNTs may be more suitable candidates for a higher potential generation of T-rays with applications pertinent to modern science and technology.

Dynamic resistance of a REBCO tape carrying direct current under a mixture magnetic field of AC field with DC-biased field

Abstract When the REBCO coated conductor tape carries a direct current(DC) transport current whilst exposed to the alternating current(AC) magnetic field, a DC electrical resistance can be observed, which is called “dynamic resistance”. The High Temperature Superconducting(HTS) magnet wound by the REBCO tapes is located in the HTS electrical machine as field winding carrying DC transport current. The operational environment of the HTS electrical machine involves a complex magnetic field, encompassing both AC and DC components. The interaction between the AC magnetic field and the DC transport current induces dynamic resistance and dynamic loss in the REBCO tape which is a distinctive trait of REBCO tape. Additionally, the presence of an extra DC-biased magnetic field can decrease the critical current of the REBCO tape, thereby altering its electromagnetic properties and potentially compromising its safety. As the basis of superconducting magnets, it is particularly important to study the dynamic resistance and loss distribution of the single REBCO tape under a mixture of magnetic field backgrounds, according to the real working environments in various applications. In this paper, the electromagnetic-thermal coupling model of multilayer REBCO tape based on H-formulation is built in COMSOL Multiphysics. The electromagnetic characteristics and dynamic resistance of the tape are presented when the tape is applied AC magnetic field and carries DC transport current. The effects of perpendicular and parallel DC-biased magnetic fields on the dynamic resistance and loss distribution of the REBCO tape are investigated in the paper. And the DC transport current safety margin will be observed in different applied DC-biased magnetic fields. This study comprehensively demonstrates the variation of dynamic resistance and loss distribution under a complex background magnetic field, which is significant for exploring the electromagnetic characteristics and calculating the loss of the HTS magnets in the HTS electrical machine.

Analysis of the motion and deformation of water-in-oil emulsion droplets under the action of an electric field

Molecular dynamics simulations are used to study the aggregation dynamics of water-in-oil emulsion droplets under an electric field, and to analyze the effects of electric field strength, type, droplet position, and ionic concentration on their kinematic properties. The best droplet aggregation is observed at E=0.03V/Å for DC field condition, and E=0.045V/Å - 80ps for rectangular AC field condition. The rectangular alternating current (AC) field is able to merge the droplets farther away from the center of mass, but the two fields are not able to merge when the angle between the center of mass of the droplets and the electric field force is ≥35.54°. For different ion concentrations, t40N < t20N < t60N < t0N in the DC field and t20N < t40N < t0N < t60N in the rectangular AC field, and for the same ion concentration, the rectangular AC field takes longer time to merge.

AC electric field-induced changes in viscosity of aqueous ceramic suspensions and tuning of freeze-cast microstructure and compressive strength

A systematic parametric study was conducted on alternating current (AC) electric field-assisted freeze-casting to enable a comprehensive understanding of tuning freeze-cast microstructure and compressive strength and provide insights into the role of AC field. A novel finding was that the AC field increased the viscosity of aqueous ceramic suspensions, where the viscosity increase was dependent on the ceramic loading of suspensions, dispersant concentration, and field duration. Viscosity increased with field duration for a fixed solid loading and dispersant concentration. It was suggested that AC field-induced dielectrophoretic (DEP) forces decreased interparticle distances and increased interparticle interactions in ceramic suspensions, hence viscosity. It was revealed that the increase in viscosity of ceramic suspensions due to the AC field could be reversed. It was demonstrated that simple magnetic stirring of the suspensions previously subjected to an AC field (which increased viscosity) reduced viscosity to the level of the as-prepared suspensions. For materials fabrication, an AC electric field was applied to aqueous ceramic suspensions for the desired duration, then turned OFF, followed by freeze-casting, which remarkably influenced freeze-cast sintered microstructure. The impact of the field on microstructure increased with solid loading, dispersant concentration, and field duration, and microstructure changes were associated with viscosity of suspensions prior to freeze-casting. With increasing viscosity, freeze-cast microstructure became increasingly dendritic, i.e., bridge density increased. A positive correlation was observed between bridge density and compressive strength for all the materials. Depending on the solid loading, dispersant concentration, and field duration, about 5- to 8-fold increase in strength was achieved.

Effect of AC electric field on enhancing phytoremediation of Cd-contaminated soils in different pH soils

To increase the efficiency of phytoremediation to clean up heavy metals in soil, assisted with alternating current (AC) electric field technology is a promising choice. Our experiments utilized the hyperaccumulator Sedum alfredii Hance and the fast-growing, high-biomass willow (Salix sp.). We investigated the efficiency of AC field combined with S. alfredii—willow intercropping for removing Cd from soils with different pH values. In the AC electric field treatment with S. alfredii—willow intercropping, the available Cd content in acidic soil increased by 50.00% compared to the control, and in alkaline soil, the increase was 100.00%. Furthermore, AC electric field promoted Cd uptake by plants in both acidic and alkaline soils, with Cd accumulation in the aboveground increased by 20.52% (P < 0.05) and 11.73%, respectively. In conclusion, the integration of AC electric fields with phytoremediation demonstrates significant favorable effectiveness.

Active microparticle propulsion pervasively powered by asymmetric AC field electrophoresis

HypothesisSymmetry breaking in an electric field-driven active particle system can be induced by applying a spatially uniform, but temporally non-uniform, alternating current (AC) signal. Regardless of the type of particles exposed to sawtooth AC signals, the unevenly induced polarization of the ionic charge layer leads to a major electrohydrodynamic effect of active propulsion, termed Asymmetric Field Electrophoresis (AFEP). ExperimentsSuspensions containing latex microspheres of three sizes, as well as Janus and metal-coated particles were subjected to sawtooth AC signals of varying voltages, frequencies, and time asymmetries. Particle tracking via microscopy was used to analyze their motility as a function of the key parameters. FindingsThe particles exhibit field-colinear active propulsion, and the temporal reversal of the AC signal results in a reversal of their direction of motion. The experimental velocity data as a function of field strength, frequency, and signal asymmetry are supported by models of asymmetric ionic concentration-polarization. The direction of particle migration exhibits a size-dependent crossover in the low frequency domain. This enables new approaches for simple and efficient on-chip sorting. Combining AFEP with other AC motility mechanisms, such as induced-charge electrophoresis, allows multiaxial control of particle motion and could enable development of novel AC field-driven active microsystems.

Reversible Alignment of Nanoparticles and Intracellular Vesicles During Magnetic Hyperthermia Experiments

AbstractHeating magnetic nanoparticles (MNPs) with AC (Alternating Current) magnetic fields has received significant attention in recent years, particularly for biomedical uses. However, most studies focus on characterizing the heat release, overlooking the fact that the MNPs in the viscous cell environment constitute a dynamic magnetic colloid whose configuration may evolve over time, particularly if a driving force as the AC field is applied. Aiming to shed light on this matter, in this workthe dynamics of the colloid structure during hyperthermia experiments are studied. By combining various experimental and theoretical tools, it is concluded that the AC field may drive the formation of aligned structures, and the impact that such structures may have on the associated heating is assessed. Remarkably, the results show that those field‐driven structures are highly unstable for small particle sizes, rapidly disassembling upon field removal. Moreover, an analogous behavior in vitro is found, with the AC magnetic field also promoting a reversible alignment of vesicles containing the MNPs within the cells. The results suggest that the observed alignment, both of MNPs and intracellular vesicles, may be a common phenomenon in usual hyperthermia experiments, but unnoticed because of the intrinsic unstable nature of the aligned structures.

Comparisons of Rice Seed Growths Due to Alternating and Direct Current Electric and Magnetic Field Influences

It is commonly known that electric and magnetic fields of power transmission negatively and positively influence plants. Unfortunately, studies on these influences are minimal, particularly considering the comparison between magnetic field and electric field, on both DC (direct current) and AC (alternating current). This research aims to compare the influences of magnetic field and electric field, both on AC and DC, on rice plant growth. Firstly, prototypes, including the equipment, were constructed to generate AC and DC electric fields using parallel plates of a medium voltage transformer and Cockroft-Walton circuits. Meanwhile, the AC and DC magnetic fields were prepared using three different diameter current-injected coils. The rice seeds were exposed to electric and magnetic fields for one month, with plate distance and coil diameter variations. The results showed that the rice seeds grew differently according to the respective types and magnitudes of the fields. In the first two days, the rice seed growths exposed to electric and magnetic fields were higher than those without field exposures. However, since the thirteenth day, the rice growth rate with field exposure was lower than without. This study also shows that the influences of the DC electric and magnetic fields were more potent than the AC fields. The averages of rice seed growth decreasing rate for the AC and DC electric fields and AC and DC magnetic fields were 0.00827 cm/(kV/m), 0.01167 cm/(kV/m), -0.13267 cm/mT and 1.99005 cm/mT, respectively. As a general suggestion in sites, rice plants should be avoided from a transmission line due to high voltage direct current (DC) rather than that alternating current (AC).

Liquid Crystal Network Soft Actuator with Large Deformations Driven by High‐Frequency and Low‐Voltage Electric Field

AbstractIn this paper, electrically responsive liquid crystal network (LCN) based soft actuators are presented that can achieve large deformations under an alternating current (AC) electric field. These LCN actuators are prepared by photopolymerization of liquid crystal acrylate monomers with polar end groups, which form polar side chains in the networks. Actuation is initiated by applying a high‐frequency and low‐voltage electric field. When this AC field is applied, the LC mesogens, especially the polar side chains, can oscillate, decreasing the molecular order, and creating free volume in the LCNs, which further results in anisotropic deformation. The formed shapes range from bending to bulging, depending on the programmed molecular alignment. The actuation proceeds fast within 5 s both for activation and for the relaxation to the initial state upon switching the power on and off. This LCN soft actuator exhibits fast response, low power consumption, and high precision, making it a promising candidate for applications in soft robotics, microfluidics, and biomimetic muscles.

Dielectric Breakdown Strength of Polypropylene Blended with Ethylene Octene Elastomers

Polymer blends have become a major focus of research in exploring the potential for new dielectric material applications, particularly in the insulation of high voltage systems. In the current research area, polypropylene (PP) is being investigated as an insulation material for high voltage alternating current and direct current power cables. However, PP must be treated with rubbery materials such as elastomers to lessen its overall stiffness for power cable extrusion. While various promising results have been published on the potential use of PP/elastomer blends as dielectric materials, the dielectric effects of adding ethylene octene elastomer to PP have been less explored. This paper discusses the alternating current (AC) and direct current (DC) breakdown strength of PP that contains different amounts of ethylene octene elastomer (10, 30, and 50 wt%). The addition of ethylene octene elastomer to PP affects the breakdown performance of the blend systems under both AC and DC fields. Significantly, an increase in elastomer contents results in a notable reduction in the AC and DC breakdown strength. A discussion is presented on the mechanisms underlying the change in the breakdown strength caused by the different amounts of ethylene octene elastomer blended with PP.

Mixing performance of an expansive mixer on viscoelastic solutions under alternating current electric field

Development of effective technologies for mixing viscoelastic solutions with reagents is still a challenge, which plays an important role in the fields of disease diagnosis, water desalination, and immunoassay. The purpose of this paper is to numerically study the mixing performance of an expansive mixer on the viscoelastic solution under the impact of an alternating current (AC) electric field through the analyzation of mixing efficiency, the concentration distribution, and average outlet velocity. A poly acrylic acid (PAA) water solution with different concentrations characterized by the Oldroyd-B constitutive model is used as a mixed medium, and an open-source toolbox called rheoTool based on finite volume algorithm is applied to solve the governing equations. We quantitatively determine the mixing efficiency for different PAA concentrations, AC electric field strengths, and frequencies and compare the mixing efficiency created by AC and direct current (DC) electric fields. Our investigation indicates that the mixing efficiency of the mixer diminishes with the PAA concentrations but enhances with the AC electric field strengths for a relatively high polymer concentration, and AC electric fields with different frequencies lead to a larger mixing efficiency than DC electric fields for a low polymer concentration. Additionally, the influence of the model parameters on the average outlet velocity and concentration distribution is discussed at length. Our numerical simulation results show that the mixer has an excellent mixing performance for both Newtonian and viscoelastic solutions, with a mixing efficiency of more than 99% at a low polymer concentration and a stable outflow velocity.

Simultaneous determination of AC and DC magnetic field by a whispering gallery mode optical resonator

Alternating current (AC) and direct current (DC) magnetic fields are monitored by an optical whispering gallery mode (WGM) microcapillary resonator filled with magnetostrictive material. The DC magnetic field is demodulated with the signal-to-noise ratio of an AC-modulated magnetic field at a particular frequency and a sensitivity of 2.1 dB/mT is obtained across a detection range of 0.9 mT. An AC field sensitivity of 2.08 μT/ H z at 346 kHz is obtained with the same resonator. Introducing a biased DC field of 90Gs provides a four-fold improvement in AC field sensitivity. The AC and DC fields may be used to improve the corresponding DC and AC sensing. Therefore, this scheme may play a role monitoring magnetic fields in defence, biomedical analysis, and consumer electronics.

Electrothermally excited plasma droplet evolution on the laser-patterned surface

Droplet behavior involving electrothermal coupling fields has gradually attracted the attention of researchers, one of which includes electrosurgical scalpels that often contact biofluids. However, the evolution of bio-droplets exposed to the surface of electrosurgical scalpels is not yet well understood. Here, we experimentally studied the effect of different heating temperatures on plasma droplets on the laser-patterned surface (LPS) and the original surface (OS) under defined direct-current (DC) or alternating-current (AC) electric fields. The results show that at a lower heating temperature, the evolution of plasma droplets was dominated by electrolysis. Oxygen bubbles generated on the papillae on the LPS in the DC field inhibited the targeted adsorption of plasma proteins on this surface. In contrast, in the AC field, only a small number of bubbles was generated, which is not sufficient to inhibit protein adsorption, leading to the formation of coagulation on the papillae after heating. At higher heating temperatures, the rapid formation of coagulation resulted in the suppression of electrolysis. The plasma proteins were then transported by the Marangoni flow causing coagulation to reach a thickness of stress mutation. Stress release over the entire coagulation caused its edges to bend and then detach from the papillae. Thus, the LPS exhibited excellent anti-adhesive properties to plasma droplets under electrothermal excitations compared to the OS. This study provides valuable information for understanding the mechanisms of contact behavior between biofluids and electrosurgical scalpels and demonstrates great promise for their anti-adhesive performance.

Salt rejection and scaling on non-conductive membranes in direct- and alternating-current electric fields

This study provides a comprehensive study about the salt rejection and fouling on non-conductive membranes in the electric fields of direct current (DC) and alternating current (AC). A simple membrane cell design that facilitates the application of electric field on traditional non-conductive membrane was built. Then different salts and foulants were applied as the feeds in the electric fields with varying voltage, frequency, waveform and bias. The impact of AC and DC within 1V on ion rejection and organic fouling is insignificant due to the low current flow and membrane conductivity. However, scaling can be effectively mitigated by both DC and AC at tuned conditions. Current direction, frequency, waveform and bias are found to substantially influence the scaling tendency. The anti-scaling performance in AC field is attributed to the continuous motion of ions that disturbs nucleation and crystal growth. Compared to DC, AC may operate at lower power consumption, thus offering an energy-effective strategy for scaling reduction.

Tunable pheromone interactions among microswimmers

Indirect interactions via shared memory deposited on the field ("field memory") play an essential role in collective motions. Some motile species, such as ants and bacteria, use attractive pheromones to complete many tasks. Mimicking these kinds of collective behavior at the laboratory scale, we present a pheromone-based autonomous agent system with tunable interactions. In this system, colloidal particles leave phase-change trails reminiscent of the process of pheromone deposition by individual ants, and the trails attract other particles and themselves. To implement this, we combine two physical phenomena: the phase change of a Ge2Sb2Te5 (GST) substrate by self-propelled Janus particles (pheromone deposition) and the AC (alternating current) electroosmotic (ACEO) flow generated by this phase change (pheromone attraction). Laser irradiation causes the GST layer to crystalize locally beneath the Janus particles, owing to the lens heating effect. Under AC field application, the high conductivity of the crystalline trail causes a field concentration and generates ACEO flow, and we introduce this flow as an attractive interaction between the Janus particles and the crystalline trail. By changing the AC frequency and voltage, we can tune the attractive flow, i.e., the sensitivity of the Janus particles to the trail, and the isolated particles undergo diverse states of motion, from self-caging to directional motion. A swarm of Janus particles also shows different states of collective motion, including colony formation and line formation. This tunability enables a reconfigurable system driven by a pheromone-like memory field.

Preparation of X5R type Ni-MLCCs and capacitance response to combined out-field variations

With the continuous development of electronic devices, miniaturization and high capacitance have become important factors in the fabrication of multilayer ceramic capacitors (MLCCs) with a Ni internal electrode (Ni-MLCCs). The typical thickness of the dielectric layer of commercial MLCCs is less than 1 μm, which implies a higher capacitance compared to MLCCs with a thicker dielectric layer. In this study, 1210-type Ni-MLCCs were prepared via a tape casting method using a BaTiO3 powder chemically coated with Dy and Ho additives. The high capacitance (390 nF) Ni-MLCC sintered at 1220 °C exhibited a low dielectric loss (tan δ < 2%), high insulation resistance (>9000 MΩ), and temperature stability comparable to that of the EIA X5R standard (capacitance-temperature coefficient (TCC) = ΔC/C25 °C ≤ ±15%, between -55–85 °C). Relaxation behavior was observed between 1 Hz and 10 kHz, following the modified Curie–Weiss law and the Vogel–Fulcher relationship. The capacitive temperature stability of Ni-MLCC is closely related to the applied direct current (DC) bias field. The EIA X7R stability (TCC ≤ ±15%, between -55–125 °C) of the Ni-MLCCs at 1220 °C was gained under dc-bias field 3 and 5 V/μm. The capacitance varied as alternating current (AC) electric fields were applied. The grain shell was sensitive to both the DC bias and AC fields, but the grain core was more sensitive to the DC bias electrical field than the AC field. Furthermore, the ferroelectric response in MLCC decreases with rising temperature.

Conical breakup of droplets in dielectric liquid medium

The conical breakup behavior of droplets in immiscible dielectric liquids under non-uniform alternating current (AC) electric fields is experimentally investigated using high-speed photography. The optical-microscopic morphological characteristics of the dynamic behavioral process of charged droplets under different electric field conditions are precisely captured. Two distinct conical breakup configurations, called the trident vibration and lotus vibration modes, are proposed, and their detailed structural parameters are discussed. The extremely small stable conical meniscus (semi-angles range of 11°–18.6°) is found in the liquid–liquid system. The distribution of cone angles under various spatial conditions is determined. In addition, the multilevel asymptotic characteristics of conical fragmentation are found due to the variances in spatial and temporal scales. The diameters of the droplets produced under the cone-jet mode could be as small as a few micrometers. The differences between the droplet breakup mode of AC and DC electric fields are also discussed. Overall, several interesting features are reported for the axisymmetric multi-cone broken morphology when droplets undergo breakup.

Numerical prediction of transient electrohydrodynamic instabilities under an alternating current electric field and unipolar injection

In this paper, a direct numerical simulation (DNS) of dielectric fluid flow subjected to unipolar injection under an alternating current (AC) electric field is carried out. The effect of frequency f of pulsed direct current (PDC) and AC on the transient evolution of electroconvection and their subcritical bifurcations are investigated in details. Electroconvection under PDC or AC tends to exhibit oscillating flow due to the periodic boundary condition of charge density and potential compared to the direct current (DC) case. The results demonstrate that under the PDC field, the linear criterion Tc decreases with increasing frequency, while the nonlinear stability criterion Tf is hardly affected. Under the AC field, a critical frequency fc = 0.0316 is found, which separates electroconvection into two typical flow regimes—periodic flow regime (f < fc) and inhibited flow regime (f ≥ fc)—depending on whether free charges can reach the collector electrode before electric field inversion. AC-electrohydrodynamics (EHD) systems promote various flow patterns with relatively lower voltage regimes than DC-EHD systems. These mechanisms of electroconvection under the PDC/AC field offer unique possibilities for fluid flow control in biological EHD-driven flow and portable EHD applications.

Dual-Frequency Desalting Technology Breaks Bottlenecks, Lowers Cost of Ownership

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22365,“No More Inefficient Crude Desalting: Breaking Bottlenecks With Dual-Frequency Technology Lowering Total Cost of Ownership,” by Prabhu Elumalai, Gary Sams, and Umanath Subramani, Schlumberger, et al. The paper has not been peer reviewed. Copyright 2022 International Petroleum Technology Conference. Reproduced by permission. _ A major independent crude oil refinery in Asia is processing crude oil in two crude distillation units (CDUs) using an alternating-current (AC) desalting system. Because of inefficient desalting, only 60% desalting efficiency was achieved for each train with subsequent low dehydration efficiency. After a holistic review of the entire desalting operation, the service company recommended upgrading the CDU 1 desalter vessel to dual-frequency technology and adding a new dual-frequency desalter at the second stage of the CDU 2 vessel. The complete paper examines the successful project from early engagement through project execution leading. Refinery Desalters _ Overview of Case-Study Refinery. The refinery was operated with a design capacity of 206,000 B/D through CDUs 1 and 2. CDU 1 included two trains of two-stage legacy AC desalters (Trains 1 and 2). Train 1 operated with 40% of CDU 1’s total flow (60,000 BOPD), while Train 2 operated with 60% of CDU 1’s total flow (90,000 BOPD). The AC desalting system desalted and dehydrated crude oil before feeding the crude to preheated trains. The desalters in this refinery operated for 20 years with the AC technology. Dual-Frequency AC/Direct Current (DC) Desalter Configuration. AC crude dehydration technology is over a century old. The complete paper recaps different types of AC desalter configurations, but this synopsis concentrates on dual-frequency AC/DC desalter configurations. The vessel design for the dual-frequency technology is identical to that of the AC/DC vessel, with similar spreaders, electrodes, and collectors. What differentiates the dual-frequency technology is the power unit, which functions with two frequencies for dehydration and desalting. The base frequency typically is in the range of 800–1,600 Hz, and the modulation frequency is in the range of 0.5–4 Hz. The computer-based controller controls the output of the variable voltage/frequency power unit and produces a nearly infinite number of waveform configurations. Also, these units facilitate online changing of maximum voltage, minimum voltage, base frequency, and modulation frequency applied to the electrode. Conventional power units cannot be operated beyond 40% of their rating. The dual-frequency power unit, however, can operate successfully beyond 80% of its rating. The combination of AC/DC fields with dual-frequency performance provides the high water tolerance of the AC field, the high efficiency of the DC field, and the improved desalting offered by the dual-frequency voltage pattern. This combined electrostatic technology offers more-efficient bulk water and small-water-droplet removal from the crude oil. Highly efficient dehydration means smaller treaters, better performance, lower operating temperatures, and fewer demulsifier chemicals. Further improvements include optimized electrode configurations and enhanced fluid distribution inside the electrostatic treaters.

Simultaneous Enhancement of Magnetothermal and Photothermal Responses by Zn, Co Co-Doped Ferrite Nanoparticles.

Reducing nanoparticle (NP) dosage for hyperthermia therapy has remained a great challenge. In this work, efficiencies of alternating current (AC) magnetic field and near-infrared (NIR) heating are simultaneously enhanced by Zn and Co co-doping of magnetite NPs. The optimum magnetic anisotropy for maximized loss power under each magnetic field is achieved by tuning the doping concentration. The specific loss power of Zn0.3 Co0.08 Fe2.62 O4 @SiO2 NPs reaches 2428 W g-1 under an AC field of 27 kA m-1 at 430 kHz; 12296 W g-1 under NIR laser irradiation at 808 nm and 2.5 W cm-2 ; and an unprecedented value of 14724 W g-1 under dual mode. These values far exceed what has been achieved previously in iron oxide NPs. Ex vivo experiments on sacrificial mice show that while the NP dosage is substantially reduced to that used for magnetic resonance imaging, the surface body temperature of the mice reaches 50 °C after exposure to both AC field and laser irradiation under field parameters and laser intensity below safety limits. This nanoplatform is thus promising for multi-modal local hyperthermia therapy.