RF Induction Research Articles

INVESTIGATION OF THE EFFECT OF TITANIUM NANO PARTICLES ADDITIVES IN PHOSPHOR BRONZE COMPOSITE FOR WEAR APPLICATIONS

An investigation was carried out to assess the mechanical properties of phosphor bronze composite with addition of titanium nano particles. Phosphorous bronze composite main application is used to manufactured sleeve bearings and cam followers. The main objective of this paper is to study the effect of Titanium nano particles which improved strength and wear resistance. In this study, a series of mechanical experiments is done on casted phosphor bronze with blended titanium nano particles with varying percentage of compositions in nano titanium. The strength, hardness, Impact and wear properties are compared among them by varying titanium nano Particles. KEY WORDS: Nano Titanium, phosphor Bronze, Wear Resistance, Radio frequency (RF) induction coupled plasma technique

Plasma sprayed fluoride and zinc doped hydroxyapatite coated titanium for load-bearing implants

Titanium (Ti) alloys show excellent fatigue and corrosion resistance, high strength to weight ratio, and no toxicity; however, poor osseointegration ability of Ti may lead to implant loosening in vivo. Plasma spraying of hydroxyapatite [HA, Ca10 (PO4)6 (OH)2] coating on Ti surfaces is commercially used to enhance osseointegration and the long-term stability of these implants. The biological properties of HA can be improved with the addition of both cationic and anionic dopants, such as zinc ions (Zn2+) and fluoride (F−). However, the hygroscopic nature of fluoride restricts its utilization in the radiofrequency (RF) plasma spray process. In addition, the amount of doping needs to be optimized to ensure cytocompatibility. We have fabricated zinc and fluoride doped HA-coated Ti6Al4V (Ti64) to mitigate these challenges using compositional and parametric optimizations. The RF induction plasma spraying method is utilized to prepare the coatings. Multiple parametric optimizations with amplitude and frequency during the processing result in coating thicknesses between 80 and 145 μm. No adverse effects on the adhesion properties of the coating are noticed because of doping. The antibacterial efficacy of each composition is tested against S. aureus for 24, 48, and 72 h, and showed that the addition of zinc oxide and calcium fluoride to HA leads to nearly 70 % higher antibacterial efficacy than pure HA-coated samples. The addition of osteogenic Zn2+and F− leads to 1.5 times higher osteoblast viability for the doped samples than pure HA-coated samples after 7-days of cell culture. Zn2+ and F− doped HA-coated Ti64 with simultaneous improvements in anti-bacterial efficacy and in vitro biocompatibility can find application in load-bearing implants, particularly in revision surgeries and immune-compromised patients.

A 1.5D fluid—Monte Carlo model of a hydrogen helicon plasma

Helicon plasma sources operating with hydrogen or deuterium might be attractive for fusion applications due to their higher power efficiency compared to inductive radiofrequency plasma sources. In recent years, the resonant antenna ion device (RAID) has been investigating the physics of helicon plasmas and the possibility of employing them to produce negative ions for heating neutral beam injectors (HNBs). Herein, we present a fluid Monte Carlo (MC) model that describes plasma species transport in a typical helicon hydrogen plasma discharge. This work is motivated by an interest in better understanding the basic physics of helicon plasma devices operating in hydrogen and, in particular, the volume production of negative ions. This model is based on the synergy between two separate self-consistent approaches: a plasma fluid model that calculates ion transport and an MC model that determines the neutral and rovibrational density profiles of . By introducing the electron density and the temperature profiles measured by Langmuir probes as model constraints, the densities of ion species (, , , ) are computed in a 1.5D (dimensional) geometry. The estimate of the negative ion density profile represents a useful benchmark that is comparable with dedicated diagnostics, such as cavity ring-down spectroscopy and Langmuir probe laser photodetachment. Neutral gas particles (atoms and molecules) are calculated assuming a fixed plasma background. This gas–plasma decoupling is necessary due to the different timescales of plasma (microseconds) and gas kinetics (milliseconds).

Synthesis of Multiscale Ultrafine Copper Powder via Radio Frequency Induction Coupled Plasma Treatment

Nano-sized spherical copper powder has important applications in the fields of microelectronic devices, highly efficient catalysts and lubricant additives. In this study, nano-sized and micron-sized spherical copper powders were simultaneously prepared by radio frequency (RF) induction coupled plasma technology. The effects of processing parameters on the powder properties were studied. The results show that by inputting copper powder with D50 = 34.6 μm, nano-sized spherical powder with a particle size of 10–220 nm and micron-sized spherical powder with a particle size of 4.0–144.0 μm were obtained. The ratio of the nano-sized powder reached 86.4 wt.%. The optimal processing parameters are as follows: powder feed rate is 5.5 g/min, carrier gas flow rate is 5–6 L/min and reaction chamber pressure is 15 Psia. When the carrier gas flow rate is 6 L/min, in the plasma zone (>10,000 K), the powder with particle size <42.0 μm is completely vaporized, which forms nano-sized powder during cooling, while the powder with particle size >42.0 μm is melted and partially vaporized, forming a micron-sized powder. The research results provide a new way for engineering the production of copper nano-powder and some other nano-powders with low melting points, such as silver powder, tin powder and so on.

Modeling inductive radio frequency coupling in powerful negative hydrogen ion sources: validating a self-consistent fluid model

Radio frequency (RF) negative hydrogen ion sources utilized in fusion and for accelerators use inductively coupled plasmas, which are operated at a low driving frequency, high power densities and gas pressures in the order of 1 MHz, 10 W cm−3 and 1 Pa, respectively. In this work a numerical fluid model is developed for a self-consistent description of the RF power coupling in these discharges. After validating the RF power coupling mechanism, such a model is a valuable tool for the optimization of RF power coupling and hence can help to increase the efficiency and reliability of RF ion sources. The model validation is achieved using measurements from the ITER RF prototype ion source. Steady state numerical solutions are obtained for the first time, where all modeled trends fit well. Remaining systematic quantitative differences could be caused by 3D effects such as highly non-uniform magnetic fields that cannot be captured in the current model formulation, which is 2D cylindrically symmetric. The coupling between the RF fields and the electrons is realized in the electron momentum transport equation, where approximations consistent with the operating regime of RF ion sources are applied. Here large magnetic RF fields lead to a plasma compression by the nonlinear RF Lorentz force. Using a local approximation for the electron viscosity, it is found that increased diffusion of the RF current density mitigates the compression. Navier–Stokes equations for the neutral atoms and molecules are used to capture neutral depletion. In this way it is shown that at high powers neutral depletion has a large impact on the power coupling via the viscosity of the electrons. The application of the self-consistent model for optimization of the RF power coupling will be described in a forthcoming paper.

Induction Heating of Magnetically Susceptible Nanoparticles for Enhanced Hydrogenation of Oleic Acid.

Radio frequency (RF) induction heating was compared to conventional thermal heating for the hydrogenation of oleic acid to stearic acid. The RF reaction demonstrated decreased coke accumulation and increased product selectivity at comparable temperatures over mesoporous Fe3O4 catalysts composed of 28–32 nm diameter nanoparticles. The Fe3O4 supports were decorated with Pd and Pt active sites and served as the local heat generators when subjected to an alternating magnetic field. For hydrogenation over Pd/Fe3O4, both heating methods gave similar liquid product selectivities, but thermogravimetric analysis–differential scanning calorimetry measurements showed no coke accumulation for the RF-heated catalyst versus 6.5 wt % for the conventionally heated catalyst. A different trend emerged when hydrogenation over Pt/Fe3O4 was performed. Compared to conventional heating, the RF increased the selectivity to stearic acid by an additional 15%. Based on these results, RF heating acting upon a magnetically susceptible nanoparticle catalyst would also be expected to positively impact systems with high coking rates, for example, nonoxidative dehydrogenations.

Radio-frequency induction heating powered low-temperature catalytic CO2 conversion via bi-reforming of methane

Radio-frequency (RF) induction heating of nanoparticles has unfolded novel routes to heterogeneous catalytic chemical reactions. It offers contactless, direct, time- and energy-saving heating with high-achieved catalytic activity. Herein, the tailored chemical synthesis of mono-metallic Cu, binary Cu-Ni, Cu-Co, and ternary Cu-Ni-Co catalysts was evaluated for CO2 conversion via bi-reforming of methane (combined steam- and dry-reforming processes) under induction heating. All prepared catalysts were activated under RF heating to convert CO2 and co-reactants i.e., H2O (steam) and methane into syngas (H2 and CO) at a relatively low temperature of 400 °C. The Cu-Co sample delivered the highest catalytic performance and stability under all tested conditions. Experimental results elaborated that the concomitant presence of a magnetic element and an electrically conductive component in the catalyst system facilitates highly effective heating occurring via both hysteresis loss and Joule effects mechanisms. On account of Joule heating, the Cu-Co catalyst preserved its excellent stability for at least 50 h over the stream test at a reaction temperature higher than its Curie temperature (TC). The findings provide significant insights into the catalyst development for RF-assisted chemical reactions that are not needed to be heavily dependent on the use of strong magnetic metals or high input current to obtain desired reactant conversions.

Preparation of Spherical Wc-Co Powder by Spray Granulation Combined with Radio Frequency Induction Plasma Spheroidization

Preparation of Spherical Wc-Co Powder by Spray Granulation Combined with Radio Frequency Induction Plasma Spheroidization

Improvement of barium tungsten cathode and investigation of thermionic emission performance

<sec>The Ba-W cathode consists of the porous W matrix and the aluminate. During cathode operation, the Ba atoms are generated in the pores through the thermal reaction between the W and aluminate, and then diffuse along the pore channels to the W surface, lowering the work function. Therefore, the Ba yield and the Ba diffusion are significantly influenced by the micro pore structure of the matrix and the phase composition of the aluminate.</sec><sec>Firstly, the matrix is fabricated with the narrow particle size distribution powder by the spark plasma sintering (SPS) technique, which shows the narrow pore size distribution (FWHM = 0.43 μm). Then the spherical powder with good fluidity and high tap density is prepared using the RF induction thermal plasma. The matrix prepared with spherical powder exhibits narrower pore size distribution (FWHM = 0.4 μm), smooth pore channels and good inter-pore connectivity. The two matrixes prepared with narrow particle powder and spherical powder are named N-matrix and S-matrix, respectively.</sec><sec>The aluminates are prepared using the solid phase method and the liquid phase method, separately. The particles of solid phase aluminate precursor present all shapes and all sizes, while the particles of the liquid phase aluminate precursor are uniform in size and identical in shape. The phase of solid phase aluminate and the phase of liquid phase aluminate are analyzed by XRD, the results show that the former consists of the effective Ba<sub>3</sub>CaAl<sub>2</sub>O<sub>7</sub> phase and other impurity phases, while the latter is composed of two effective phases of Ba<sub>3</sub>CaAl<sub>2</sub>O<sub>7</sub> and Ba<sub>5</sub>CaAl<sub>4</sub>O<sub>12</sub>.</sec><sec>The N+S and S+S cathodes are obtained by using the solid phase aluminate to impregnate the N-matrix and the S-matrix, and the <i>U</i>-<i>j</i> characteristics of the two cathodes are investigated. The double logarithmic curves of <i>U</i> and <i>j</i> show that the slope of 1.37 in the space charges limited (SCL) region for the S + S cathode is higher than that of 1.25 for the N+S cathode, so the S+S cathode exhibits better emission uniformity. The current density at the deviation point (<i>j</i><sub>DEV</sub>) of the N+S cathode and that of the S+S cathode are 6.6 A·cm<sup>–2</sup> and 6.96 A·cm<sup>–2</sup>, respectively. So the improvement on the matrix obviously raises the emission uniformity of cathode, but the current density is increased less.</sec><sec>Based on the excellent matrix of the S+S cathode, the S+L cathode is obtained by improving the aluminate of the S+S cathode with liquid phase aluminate. The <i>U</i>-<i>j</i> characteristics show the slope of the S+L cathode reaches to 1.44, and the <i>j</i><sub>DEV</sub> is 21.2 A·cm<sup>–2</sup>. So the improvement on the aluminate not only increases the uniformity, but also raises the current density.</sec><sec>The present study shows that the <i>U-j</i> curve calculated from the classical thermionic emission (TE) theory accords well with that of the S + L cathode at 1000 ℃, which indicates that the Ba-W cathode follows the classical TE theory rather than other emission theories, and the Ba-O dipole layer just changes the work function of the cathode.</sec>

A Systematic Review on Recent Trends, Challenges, Privacy and Security Issues of Underwater Internet of Things.

Owing to the hasty growth of communication technologies in the Underwater Internet of Things (UIoT), many researchers and industries focus on enhancing the existing technologies of UIoT systems for developing numerous applications such as oceanography, diver networks monitoring, deep-sea exploration and early warning systems. In a constrained UIoT environment, communication media such as acoustic, infrared (IR), visible light, radiofrequency (RF) and magnet induction (MI) are generally used to transmit information via digitally linked underwater devices. However, each medium has its technical limitations: for example, the acoustic medium has challenges such as narrow-channel bandwidth, low data rate, high cost, etc., and optical medium has challenges such as high absorption, scattering, long-distance data transmission, etc. Moreover, the malicious node can steal the underwater data by employing blackhole attacks, routing attacks, Sybil attacks, etc. Furthermore, due to heavyweight, the existing privacy and security mechanism of the terrestrial internet of things (IoT) cannot be applied directly to UIoT environment. Hence, this paper aims to provide a systematic review of recent trends, applications, communication technologies, challenges, security threats and privacy issues of UIoT system. Additionally, this paper highlights the methods of preventing the technical challenges and security attacks of the UIoT environment. Finally, this systematic review contributes much to the profit of researchers to analyze and improve the performance of services in UIoT applications.

The Smart Meter Challenge: Feasibility of Autonomous Indoor IoT Devices Depending on Its Energy Harvesting Source and IoT Wireless Technology.

Most smart meters are connected and powered by the electric mains, requiring the service interruption and qualified personnel for their installation. Wireless technologies and energy harvesting techniques have been proved as alternatives for communications and power supply, respectively. In this work, we analyse the energy consumption of the most used IoT wireless technologies nowadays: Sigfox, LoRaWAN, NB-IoT, Wi-Fi, BLE. Smart meters’ energy consumption accounts for metering, standby and communication processes. Experimental measurements show that communication consumption may vary upon the specific characteristics of each wireless communication technology—payload, connection establishment, transmission time. Results show that the selection of a specific technology will depend on the application requirements (message payload, metering period) and location constraints (communication range, infrastructure availability). Besides, we compare the performance of the most suitable energy harvesting (EH) techniques for smart meters: photovoltaic (PV), radiofrequency (RF) and magnetic induction (MIEH). Thus, EH technique selection will depend on the availability of each source at the smart meter’s location. The most appropriate combination of IoT wireless technology and EH technique must be selected accordingly to the very use case requirements and constraints.

Catalytic Depolymerization of Waste Polyolefins by Induction Heating: Selective Alkane/Alkene Production.

Low- and high-density polyethylene (LDPE/HDPE) have been selectively depolymerized, without added H2, to C2–C20 + alkanes/alkenes via energy-efficient radio frequency induction heating, coupled with dual-functional heterogeneous Fe3O4 and Ni- or Pt-based catalysts. Fe3O4 was used to locally generate heat when exposed to magnetic fields. Initial results indicate that zeolite-based Ni catalysts are more selective to light olefins, while Ni supported on ceria catalysts are more selective to C7–C14 alkanes/alkenes. LDPE conversions up to 94% were obtained with minimal aromatic, coke, or methane formation which are typically observed with thermal heating. Two depolymerization mechanisms, a reverse Cossee–Arlman mechanism or a random cleavage process, were proposed to account for the different selectivities. The depolymerization process was also tested on commercial LDPE (grocery bags), polystyrene, and virgin HDPE using the Ni on Fe3O4 catalyst, with the LDPE resulting in similar product conversion (∼48%) and selectivity as for virgin LDPE.

Radio Frequency Induction Welding of Silver Nanowire Networks for Transparent Heat Films.

Transparent heat films (THFs) are attracting increasing attention for their usefulness in various applications, such as vehicle windows, outdoor displays, and biosensors. In this study, the effects of induction power and radio frequency on the welding characteristics of silver nanowires (Ag NWs) and Ag NW-based THFs were investigated. The results showed that higher induction frequency and higher power increased the welding of the Ag NWs through the nano-welding at the junctions of the Ag NWs, which produced lower sheet resistance, and improved the adhesion of the Ag NWs. Using the inductive welding condition of 800 kHz and 6 kW for 60 s, 100 ohm/sq of Ag NW thin film with 95% transmittance at 550 nm after induction heating could be decreased to 56.13 ohm/sq, without decreasing the optical transmittance. In addition, induction welding of the Ag NW-based THFs improved haziness, increased bending resistance, enabled higher operating temperature at a given voltage, and improved stability.

Spheroidization of borosilicate glass powder by RF induction coupled plasma

The International Simple Glass (ISG) spherical particles were prepared by Ar–H2 radio-frequency (RF) plasma, the effect of experimental parameters on the volatilization and size distribution of spherical particles was studied. The results show that the spherical powders can be obtained by RF plasma. The spheroidized powders (112 μm) have a smaller diameter than starting particles (124 μm). The high spheroidization (98%) was achieved under low flow rate of carry gas and low feed rate. In addition, the volatilization of B2O3 and Na2O are 23.48% and 56.36%, respectively. The higher feed rate and flow rate of carry gas, the lower volatilization of B2O3 and Na2O and well-spheroidization rate. Meanwhile, the particle surface is not completely smooth at low flow rate of carry gas. The distribution of elements was studied by Electro-probe Microanalyzer (EPMA), which shows the distribution of element is nearly homogeneous that provides a possibility for subsequent research.

Preparation of spherical Ti-6Al-4V powder by RF induction plasma spheroidization combined with spray granulation

Spray granulation was used to control morphology and particle size of raw materials for spheroidization in this work. Effects of dispersant (PAA-NH4OH) addition, pH value and solid content on stability of slurry for granulation was investigated. Influence of solid content of the slurry and atomizer speed on spray granulation were also investigated. Furthermore, difference in spheroidization effect between Ti-6Al-4V powder spheroidized from the granulated powder and irregular powder was compared. Results show that zeta potential of the slurry can be controlled at -44 mV to by addition of dispersant when pH value is 9.3. Granulated powder prepared with 50 wt% solid content and 10,000 rpm atomizer speed was best for plasma spheroidization. Ti-6Al-4V powder spheroidized from the granulated powder has better properties than that spheroidized from irregular powder. Spheroidization ratio, flow properties and apparent density of the spheroidized Ti-6Al-4V powder from granulated powder are 98%, 35.4 g/50s and 3.2 g/cm3, respectively.

RF induction heating and in-vitro study of citrate functionalized Zr-substituted Fe3O4 nanoparticles with human lung adenocarcinoma (A549) cell

We present a study on biocompatibility of citrate capped ZrxFe3-xO4 based magnetic ferrofluids with human lung adenocarcinoma (A549) cell, evaluated by Sulforhodamine B assay. It was found to be ~86% at a concentration of 1.5 mg/mL after 48 h. We approached single step and cost effective polyol methodology to get a well dispersed and homogeneous aqueous suspension of citric acid coated ZrxFe3-xO4, (0 ≤ x ≤ 0.3) MNPS. We used citric acid which anchored over the surface of freshly prepared nanoparticles to provide stability for longer duration . The X-ray and electron diffractions suggested the formation of single phasic magnetite particles of size 5–18 nm. The aggregation of MNPS was prevented by citric acid which was confirmed from Fourier-transform infrared spectroscopy spectra. The Zeta potential measurement inferred the well dispersion of nanoparticles at varying pH values (2−10). The Zr-substituted magnetite had relatively lower magnetization values than pure one. The optimum specific absorption rate (SAR) value at a field of 23 mT, 261 kHz was obtained to be 44 W/g for the sample x = 0.02 at a concentration of 10 mg/mL. In contrast, the intrinsic loss power (ILP) value was optimum (0.54 nHm2/kg) for Fe3O4 ferrofluid having a concentration of 5 mg/mL and at a field of 17 mT, 170 kHz. Nevertheless, the reported ferrofluids have displayed high heating capacity and suitable biocompatibility thus these could be used as promising materials for bioapplications including magnetic hyperthermia.

Foundations of capacitive and inductive radio-frequency discharges

This paper is the first from a set of two companion papers on radio-frequency (RF) discharges. These two papers are in turn part of a larger series on the foundations of plasma and discharge physics. In this part we cover the basics of non-magnetized capacitive and inductive RF discharges, introduce the main concepts related to them and provide reference literature for further reading. In the second part we concentrate on RF discharges in the presence of external magnetic field. These types of RF discharges find a wide range of applications in various industries. Among the most prominent examples are the microelectronics industry for etching and deposition of thin films, the medical and food industry for the application of various coatings and changing the wettability of surfaces, the space industry to power ion-gridded thrusters for satellites, the fusion and elementary particle research for the production of beams of energetic ions or atoms. The paper introduces the basic concepts of RF power deposition and describes in more detail the operating conditions of the plasma reactors. The most important physical phenomena encountered in these discharges are outlined through the use of simplified models. The paper is intended as an entry point for newcomers to the field and provides ample of references (including textbooks) for further reading on the more specific and/or subtle aspects of the operation of these types of RF discharges.

INFLUENCE OF STEP-AGING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al-Zn-Mg TERNARY ALLOYS

Al-Zn-Mg alloys were prepared using RF induction furnace. Two,out of 10 samples were left un-annealed and remaining were given step-aging in temperature range 125-180oC for 2-4 hours. Characterizations of thesamples were carried out by using optical microscopy, creep and hardness tests. The results of optical micrographs reveal an equiaxed grain structure formed in all step-aged specimens that becomes more obvious with increase of aging time and temperature. The creep deformation rate was found to be minimum in two step aged specimens, whereas, hardness of the two-step aged samples is maximum as compared to the others samples.

INFLUENCE OF STEP-AGING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al-Zn-Mg TERNARY ALLOYS

Al-Zn-Mg alloys were prepared using RF induction furnace. Two,out of 10 samples were left un-annealed and remaining were given step-aging in temperature range 125-180oC for 2-4 hours. Characterizations of thesamples were carried out by using optical microscopy, creep and hardness tests. The results of optical micrographs reveal an equiaxed grain structure formed in all step-aged specimens that becomes more obvious with increase of aging time and temperature. The creep deformation rate was found to be minimum in two step aged specimens, whereas, hardness of the two-step aged samples is maximum as compared to the others samples.

Design and Application of Intelligent House Robot

As a family-oriented hexapod bionic intelligent house robot, it takes life safety monitoring, intelligent house control, air quality detection, family security, automatic inspection and obstacle avoidance as its main functions. Combined with core technologies including Face and Radio Frequency Identification, Electromagnetic Resonance and Induction, LAM, Intelligent Navigation and Cloud Robot, the robot is established a unique triangular gait in the form of hexapod, which can maintain the function and action stability in various environments, thus become a family housekeeper with multiful functions and practical intelligence.