Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

Efficacy of electrostatically charged glyphosate on ryegrass

Using a TX-VK3 spray tip attached to an electrostatic sprayer operated at 483 kPa pressure, ryegrass was sprayed with glyphosate at 0.0033 kg ae ha⁻¹. Charge-to-mass ratio (Q/M) for the spray solution was 1.686 mC kg⁻¹ at +10.0 kV charging voltage. Treatment efficacy was assessed using NDVI (Normalized Difference Vegetation Index) spectral reflectance values. Electrostatic charging of glyphosate significantly increased volume median diameter of spray droplets (D_v0.5 = 112.8 μm) compared to uncharged glyphosate (D_v0.5 = 106.5 μm). Ryegrass health declined 80% faster by charging the glyphosate spray solution compared to the uncharged spray.     

Evidence of sustained ferroelectricity in glycine sodium nitrate single crystal

The nonlinear optical single crystals of glycine sodium nitrate were grown by the slow evaporation method. XRD confirmed monoclinic structure. Thermal stability and melting point (225 °C) were investigated. The dielectric behaviour of the crystals in the frequency range 20 Hz–2 MHz at different temperatures is reported in which a ferroelectric to paraelectric phase transition at T_c = 56 °C is observed. The activation energies of GSN were found to be 3.615 eV, 0.593 eV and 0.0733 eV in three temperature regions of conductivity plot due to a hopping conduction mechanism. The crystal has shown high piezoelectric charge coefficient (d₃₃) of 16 pC/N which is nearly double of observed value for γ-glycine single crystal. The spontaneous polarization P_s at room temperature was found to be 1.489 μC/cm² at applied maximum field of 26 kV/cm (1.194 μC/cm² at 12 kV/cm) and the pyroelectric coefficient was determined to be 400 μC/m²/°C. High value of squareness parameter (1.93) makes the GSN crystal suitable for switching applications. Detailed investigations of Ferro-/Piezoelectricity were observed for the first time in glycine sodium nitrate crystals which was found to preserve the ferroelectricity even after applying an electric field much higher than the saturation electric field (12–26 kV/cm). Application of GSN crystals as sensor, high power switch gears and storage memories has been established.     

Using an improved electrostatic precipitator for poultry dust removal

Pubic concerns related to particulate matter emissions from animal housing operations are increasing. The goal of this study was to custom develop a simple and low cost electrostatic precipitator (ESP) for poultry dust control. The performance of the improved electrostatic precipitator (iESP) to remove a test aerosol was evaluated under a series of operating voltages between ?60 kV and 60 kV. The mass and size distributions of the particles were measured by a cascade impactor. The overall dust removal efficiency ranged from 37% to 79% with the maximum efficiency obtained at ?30 kV. The iESP shows high removal efficiencies for particles less than 2.1 μm.     

A new method for detection of alpha particles in 1 mm thick polycarbonate detectors using 50 Hz – HV ECE method

Recent studies in our laboratory have proved that electrochemical etching (ECE) of polycarbonate track detectors (PCTD) under 50 Hz – high voltage (HV) field conditions has potentials for time-integrated heavy charged particle detection and dosimetry applications. The rationale in the study is the ECE process of alpha particle tracks in 1 mm thick PCTDs by a 50 Hz – HV generator at optimized ECE conditions. Tracks of 3.2 MeV alpha particles from a collimated beam of an ²⁴¹Am source degraded in air and background tracks were registered. The effects of HV and ECE duration on alpha track registration efficiency and track diameters were studied for 3 sets of 50 Hz – 4, 5 and 6 kV field conditions in a PEW solution (potassium hydroxide, ethanol and water) at 26 °C. The optimized ECE conditions obtained at this stage of development for 1 mm thick PCTDs are 50 Hz – 4 kV in PEW solution at 26 °C for 10 h. Alpha track registration efficiency at 3.2 MeV is about 30% with 37 ± 6 μm mean track diameter. The mean background track density at the above stated optimized conditions is about 571 ± 16 tracks.cm⁻² with a mean diameter of 65 ± 5 μm. All tracks are observable by the unaided eyes. The mean background track diameter is near two times larger than that of alpha particle tracks at the optimum conditions applied; they are easily distinguished against each other. This high background track density while at this stage of development seems a drawback for low dose and low fluence particle applications, it has minimal effects on high fluence ion detection applications. The simple 50 Hz – HV generator used proved to be convenient for efficient alpha track amplifications. Studies are underway for improvement of the method in particular for reducing background track density.     

A size-dependent microparticle capture and release chip using concentric membrane ring barriers

We present a size-dependent microparticle separation chip where different sized slit gaps are formed around a central inlet by membrane ring barriers, concentrically arranged, and adjusted with a single pneumatic source. Previous microparticle separation methods, using multiple filters with different pore sizes, require additional structures and processes to release microparticles after they are captured in the filter. In addition, those methods often result in particle loss due to clogging of the fixed pore filters. We suggest a microparticle separation chip capable of size-dependent capture and release without the particle loss. The present separation chip has four concentrically arranged membrane rings (b₁ ∼ b₄) with a thickness of 90 μm and widths of 182 μm, 188 μm, 194 μm, and 200 μm, respectively, which form slit gaps estimated to be 11.2 μm, 9.5 μm, 7.6 μm, and 5.8 μm, respectively, at the pneumatic pressure of 80 kPa. In the experiment, we demonstrated microparticle capture and release using two different sizes of PS (polystyrene) beads (diameter = 6.51 ± 0.43 μm and 10.32 ± 0.39 μm) immersed in 0.5% BSA (Bovine Serum Albumin) solution at a flow rate of 100 μl/min. At a pressure of 80 kPa, 10.32 μm and 6.51 μm-diameter beads were captured at ring barriers b₃ and b₄, respectively. Subsequently, at pressures of 65 kPa and 50 kPa, the 6.51 μm and 10.32 μm-diameter beads were respectively released from the outermost barrier (b₄). The capture and release efficiencies of 10.32 μm-diameter beads at the b₃ barrier were 91.7 ± 16.7% and 90.9 ± 8.1%, respectively. The purity of 10.32 μm-diameter beads at the b₃ barrier was 80.2 ± 6.2%. The capture and release efficiencies of 6.51 μm-diameter beads at the b₄ barrier were 100.0 ± 0.0% and 97.1 ± 4.0%, respectively. The purity of 6.51 μm-diameter beads at the b₄ barrier was 91.8 ± 2.9%. We have verified that different sizes of captured microparticles were released sequentially by gradually reducing the pressure. The present chip, having concentric membrane ring barriers which can form different sized slit gaps using a single pressure source, is simply capable of not only size-dependent microparticle capture, but also release in size order without particle clogging.     

Electroreflectance spectroscopy of compressively strained InGaN/GaN multi-quantum well structures

The built-in piezoelectric field induced by compressive stress in InGaN/GaN multi-quantum well (MQW) light-emitting diodes (LEDs) was investigated using the electric field dependent electroreflectance (ER) spectroscopic method. InGaN/GaN MQW structures were prepared on sapphire substrates of different thicknesses. Thinning the sapphire substrate enables control of the compressive stress by changing the curvature of the wafer bowing. The wafer bowing-induced mechanical stress alters the piezoelectric field in the InGaN/GaN MQW. The flat band voltage, estimated by measuring the applied reverse bias voltage that induces a 180° phase shift in the ER spectra, was decreased from −11.21 V to −10.51 V by thinning the sapphire substrate thickness from 200 to 60 μm. To calculate the piezoelectric field (F_pz) from the compensation voltage, the depletion width was obtained from the capacitance–voltage measurement. The F_pz estimated from the energy shift in ER peak in a bias range from 0 to −12 V was changed by 110 kV/cm.     

Synthesis and cathodoluminescent properties of Y2SiO5:Tb3+ phosphors prepared from uniform precursor

The luminescent properties of phosphors are sensitive to the size of phosphor particles. The commercial Y₂SiO₅:Tb³⁺ phosphors usually show relatively larger particle size (5–10 μm) due to the irregular morphology of rare earth oxide precursor and thus degrade the luminescent properties. In this paper, we report the Y₂SiO₅:Tb³⁺ phosphors synthesized from the uniform Tb-doped Y₂O₃ precursor by a homogeneous precipitation method. Compared with the commercial phosphors, the obtained Y₂SiO₅:Tb³⁺ phosphors manifest the uniform morphology with much smaller particles distributing from 0.8 μm to 1.9 μm. Consequently, the cathodoluminescent intensity under low excitation voltage (1–5 kV) was increased, demonstrating a strong green emission with a dominant wavelength of 545 nm. Our results indicate an effective way to develop the high-quality phosphors for field emission display.     

The effect of an external DC electric field on bipolar charged aerosol agglomeration

A direct-current (DC) electric field was exerted in a bench-scale electrostatic precipitator (ESP) to induce the agglomeration of bipolar charged aerosol particles. The test aerosol particles were generated from water with an atomizer and their average diameter was 7.71 μm. A phase doppler anemometer (PDA) was used to measure the size distribution and the number concentration of the particles. Systematic experiments were conducted to investigate the agglomeration efficiency of the system. The percentage decrease in number of sub-micron sized particles was found to be about 10.7%.     

Tuning magnetic fingerprints of FeNi nanowire arrays by varying length and diameter

Magnetic nanowires (NWs) electrodeposited into solid templates are of high interest due to their tunable properties which are required for magnetic recording media and spintronic devices. Here, highly ordered arrays of FeNi NWs with varied lengths (ranging from 2.5 to 12 μm) and diameters (between 45 and 75 nm) were fabricated into anodic aluminum oxide templates using a pulsed ac electrodeposition technique. X-ray diffraction patterns along with energy dispersive spectroscopy indicated the formation of Fe₇₀Ni₃₀ NWs with fcc and bcc alloy phases, being highly textured along the bcc [110] direction. Magnetic properties were studied by hysteresis loop measurements at room temperature and they showed reductions in coercivity and squareness values by increasing length and diameter. Further, magnetic fingerprints of the NWs were characterized using the first-order reversal curve (FORC) analysis. FORC measurements revealed that, with increasing length and diameter from 2.5 to 10 μm and 45–55 nm, respectively, besides an increase in inter-wire magnetostatic interactions, a transition from a single domain (SD) state to a pseudo SD state occurred. Moreover, a multi-domain (MD) state was found for the longest length and diameter. While the irreversible magnetization component of the SD NWs was approximately 100%, the reversible component of MD NWs increased up to 20%.     

Experimental investigation on charging characteristics and penetration efficiency of PM2.5 emitted from coal combustion enhanced by positive corona pulsed ESP

The electrostatic precipitator (ESP) has been extensively used for collecting aerosol particles emitted from coal combustion, but its collection efficiency of PM2.5 (Particulate matter whose aerodynamic diameter is less than 2.5 μm) is relatively low due to insufficient particle charging. The positive pulsed ESP is considered to enhance particle charging and improve collection efficiency. A laboratory-scale pulsed ESP with wire-plate electrode configuration was established to investigate the particle charging and penetration efficiency under controlled operating conditions of different applied impulse peak voltages, impulse frequencies, dust loadings and residence times. The results show that most particles larger than 0.2 μm are negatively charged, while most particles smaller than 0.2 μm are positively charged. For a given operating condition, the particle penetration efficiency curve has the highest penetration efficiency for particles with a diameter near 0.2 μm, and there is always a negative correlation between the particle penetration efficiency and the average number of charges per particle. Under the same operating conditions, the particle penetration efficiency decreases with increasing impulse peak voltage and impulse frequency, but increases as the dust loading increases. The results imply that residence time of 4 s is optimum for particle charging and collection. PM2.5 number reduction exceeding 90% was achieved in our pulsed ESP.     

Effect of sodium chloride and food target properties on nonelectrostatic and electrostatic coating

Salts were coated on a variety of thick food targets. The best transfer efficiency, adhesion (>70%), and percent side coverage (100%) were obtained when small (<200 μm) and cohesive (Hausner ratio > 1.20) salt was used with electrostatic coating on targets with high a_w (>0.7), low resistivity (<9 × 10⁸ Ωm), and short charge decay time (<3.8 s). Shape of salt also affected the coating performance; porous cube provided significantly better transfer efficiency and adhesion than flake salt on some targets. There was no significant effect of KCl content on coating performance.     

Fabrication and properties of PLT/PLZT/PLT structures obtained by RF magnetron sputtering

Ferroelectric Pb_0.84La_0.16Ti_0.96O₃/Pb_0.96La_0.04(Zr_0.52Ti_0.48)_0.99O₃/Pb_0.84La_0.16Ti_0.96O₃ (PLT/PLZT/PLT) structures were fabricated on platinum-coated silicon wafers by RF magnetron sputtering. A Pb_0.84La_0.16Ti_0.96O₃ layer was used as a seed layer to improve the crystallization and enhance the ferroelectric properties of the PLZT film. With the PLT seed layers, the films showed excellent ferroelectric properties in terms of large remnant polarization (2P_r) of 52.7 μC/cm², lower coercive field (2E_c) of 130 kV/cm for an applied field of 500 kV/cm. Moreover, the PLT/PLZT/PLT structures exhibited good fatigue endurance after 10¹⁰ switching cycles, which was attributed to the double-sided PLT layers. They improved the electrical fatigue by eliminating the pyrochlore phase, reduced the strong (111) orientation, and assimilated the oxygen vacancies from the PLZT layer.     

Effect of ambient air pressure on synthesis of copper and copper oxide nanoparticles by wire explosion process

Nanoparticles of copper and copper oxide were synthesized by wire explosion technique in the environment of different ambient air pressure. Copper wire with a diameter of 125 μm and 6.1 cm in length has been exploded in air at 1 bar, 500 mbar, 100 mbar and 50 mbar. Current density in the order of 10⁶ A cm⁻² has been applied to disintegrate the wire by discharging a 1.85 μF capacitor at 10 kV. It is found that the particle size distribution for nano-sized particles follows the log-normal distribution and the median diameter is found to decrease from 31.3 nm to 23.6 nm as the pressure is decreased from 1 bar to 50 mbar.     

High-frequency magnetoresonance absorption in amorphous magnetic microwires

The Fe₆₉Si₁₆B₁₀C₅, Co₇₅Si₁₀B₁₅, Co₆₈Mn₇Si₁₀B₁₅ amorphous microwires have been studied by the magnetoresonance absorption technique in the X (9.5 GHz), K (20–27 GHz) and Q (30–37 GHz) frequency bands. The specimens under study were metal threads of about 5 μm in diameter coated with dielectric Pyrex layer with thickness 5 μm. The dependences of magnetic resonance spectra on frequency and wire orientation have been measured. The analysis of the resonance signal parameters has revealed that well-known classical equations for FMR in a cylindrical-shaped sample could not be applied for these microwires. It is shown that due to the skin depth effect the model of hollow cylindrical tube has to be applied to explain the experimental results in the frequency range measured. The values of saturation magnetization, g-factor and anisotropy field have been estimated from the frequency dependence of the field for resonance.     

Improved short-circuit photocurrent densities in dye-sensitized solar cells based on ordered arrays of titania nanotubule electrodes

We report on the synthesis of highly ordered arrays of titania nanotubules and their applications in enhanced photoelectrochemical cells. Ordered arrays of titania nanotubules of ∼120 nm external diameter, ∼100 nm internal diameter, and ∼5 μm length were fabricated on transparent conductive oxide (TCO) glass substrates by sol–gel processes using in-house prepared anodic alumina templates. After thermal bonding and template removal, the resultant nanotubule structures were applied in dye-sensitized solar cells (DSCs). Overall photoconversion efficiency of nearly 4.8% was achieved with Ru-bipyridine dye, N719, and iodolyte liquid electrolyte. This remarkable performance, for electrodes only ∼5 μm thick, is attributed to an unexpectedly high short-circuit photocurrent density of 16 mA/cm² for masked cells and up to 17 mA/cm² for unmasked cells. The enhanced short-circuit photocurrent (J_sc) is attributed to the high surface area (roughness factor ca. 1207) of the nanotubules and thus improved dye adsorption to the electrodes. The improved J_sc is also attributed to the parallel and vertical orientation of the nanostructures and thus to a well-defined electron diffusion path.     

The magnetoelectric coupling in rhombohedral–tetragonal phases coexisted Bi0.84Ba0.20FeO3

Ba doped Bi_1.04−xBa_xFeO₃ ceramics with x up to 0.30 have been prepared by the tartaric acid modified sol–gel method. The X ray diffraction patterns show that the structure transforms from rhombohedral to tetragonal with increasing the Ba substitution concentration from 10% to 30% and the coexistence of distorted rhombohedral and tetragonal phases in 20% Ba substituted BiFeO₃, which was further confirmed by the Raman spectra. Bi_0.84Ba_0.20FeO₃ exhibits the highest magnetization (1.6 emu/g under magnetic field of 12 kOe) compared with the other samples of different Ba substitution concentration. Significant enhancement of the ferroelectricity has been observed in 20% and 30% Ba substituted BiFeO₃ with saturate polarization close to 6.6 μC/cm² for Bi_0.74Ba_0.30FeO₃. The magnetoelectric coupling of Bi_0.84Ba_0.20FeO₃ has been measured and the maximum decrease of magnetization under magnetic field of 9.8 kOe was about 0.06 emu/g with increasing applied electric field to 11 kV/cm, and the magnetoelectric coefficient is 1.5×10⁻¹² s/m.     

The enhanced field-emission properties of screen-printed single-wall carbon-nanotube film by electrostatic field

In this work, we improved the field-emission properties of a screen-printed single-wall carbon-nanotube (SWCNT) film by applying a strong electrostatic field during the drying process after the printing. By applying the strong field, more tips of SWCNTs could emerge from the screen-printed film and turn somewhat toward the erecting direction because of the repulsive force among the SWCNTs. The field-emission properties of the film were thus improved obviously. The improved field emitters sample has low electron emission turn-on field (E_to = 1.22 V/μm), low electron emission threshold field (E_th = 2.32 V/μm) and high brightness with good uniformity and stability. The lowest operating field of the improved sample is below 1.0 V/μm and its optimum current density exceeds 3.5 mA/cm².     

Monte-Carlo simulations of Al2O3 dosimetry in uniform MV photon beams: Influence of field and detector size

This work was to evaluate the absorbed dose to different sizes Al₂O₃ dosimeter in uniform MV photon beams using Monte Carlo simulation. The absorbed dose ratio factor f_md of Al₂O₃ dosimeters was calculated. The incident beams included 4 MV–24 MV X-rays using Mohan's spectra with different field sizes. Results show that the maximum variation of f_md due to different dosimeter sizes is 5%. As the field diameter increases from 1 cm to 3 cm, the difference of f_md can be up to 8%. The results of this work show that the effect of dosimeter size and the field size can't be neglected when using Al₂O₃ dosimeter.     

Photorefractive properties of paraelectric potassium lithium tantalate niobate crystal doped with iron

We report the successful growth of paraelectric potassium lithium tantalate niobate (KLTN) single crystal doped with iron. Detailed investigations have been made on the photorefractive properties of the as-grown crystal. The key parameters such as space-charge field, grating response time, photorefractive sensitivity and sign of the dominant charge carrier were obtained by two-wave mixing technique. 1.7 mm thick sample exhibits a high diffraction efficiency of 78% at the external field of 3.3 kV/cm and a sensitivity of 1.49 × 10⁻¹⁰E₀ cm²/J. The two-wave mixing gain coefficient increases linearly with external field, and reaches a large value of 19.4 cm⁻¹ at 4 kV/cm. Based on experimental results, iron is an effective dopant to KLTN which shows high diffraction efficiency and two-wave mixing gain coefficient.