Boron Emission Research Articles

Full-torus impurity transport simulation in boron powder injection experiments in the Large Helical Device

The toroidal distribution of boron deposition on plasma-facing components (PFCs) in boron powder injection using an impurity power dropper (IPD) was investigated by full-torus simulation and observations in a systematic plasma density-scan experiment. The images of the ablation of dropped boron powders observed with a visible CCD camera were consistently explained by the simulations of the ablation positions of the boron powders considering the size distribution. Simulations assuming full-torus boron deposition on the PFCs did not reproduce the observed intensity profile of boron emission lines for higher plasma densities. It indicated that the density of boron deposited on PFCs installed toroidally far from the IPD was low for higher plasma densities due to the change in the ablation positions of the boron powders toward the outboard side. The experimental results verified the previous full-torus simulation of the toroidal distribution of the boron deposition in both lower and higher plasma densities.

Comprehensive evaluation of boron release from Boron-containing Fluoride-free mold flux

The boron emission into air and water during the use of fluorine-free mold flux containing boron was systematically investigated to evaluate the corresponding environmental impacts. Unexpectedly, boron in mold flux was volatilized in the form of NaBO2 particulate matter as Na2O was added to mold flux. Besides, boron remained in the used mold flux residue was found to be linearly released into leachate continuously, and Na+ existed in the borosilicate network accelerated the hydrolysis of the network and the dissolution of boron by increasing no-bridging oxygen and converting BO4 groups into fragile BO3 groups. Considering the negative effect of Na2O on the stabilization of boron in mold flux, limiting the addition of Na2O in fluorine-free mold flux containing boron will further minimize the pollution originating from the use of mold flux.

Boron continuous recovery from brines by the multicolumn simulated moving bed process with boron chelating resin

The objective of this work is to develop an advanced adsorption process to continuously recover and remove boron from brines. Firstly, the adsorption and desorption performances of boron on the commercially available N-methylglucamine resin (D403 resin) are evaluated, then, the cyclic adsorption and desorption process is investigated experimentally in the fixed bed adsorber for boron recovery from brine. It is confirmed that the cyclic process involves five steps, such as boron recovery from brine, water washing 1 to remove the retained brine, boron desorption to obtain boron-rich solution, water washing 2 to recover the retained HCl solution, and resin regeneration for the reuse. Furthermore, the seven-column simulated moving bed (SMB) process with four zones is designed and investigated experimentally. Experimental results demonstrate that boron can be recovered continuously from brine in adsorption zone, and boron-rich solution is obtained continuously in desorption zone. When the inlet brine contains a low boron content (for example 296.5 mg/L), most boron in brine can be recovered by the seven-column SMB unit with 96.8 % boron adsorption efficiency, and the discharged brine contains 8.77 mg/L boron, approximately meeting the environmental protection requirement for the limitation of boron emission. Therefore, the simultaneous recovery and removal of boron from brine can be achieved by the proposed multicolumn SMB process.

Effects of process conditions on simultaneous removal and recovery of boron from boron-laden wastewater using improved bipolar membrane electrodialysis (BMED)

The anthropogenic emission of boron to the environment has posed a serious risk to human and animal health due to its non-biodegradability and the resulting accumulation in the body. Bipolar membrane electrodialysis (BMED) has been proven to be an economical and effective process to remove and recover boron from wastewater. In this work, we verified multiple process parameters to evaluate the efficiency of boron removal and recovery using intermittent and continuous BMED modes. Higher initial boron concentrations appeared to reduce the boron processing rate, but this reduction may be ameliorated by increasing current density. Similarly, higher initial pH was observed to retard the removal rate of boron with increasing mass transfer rate. When solution pH was controlled from 9.5 to 10.5 and the current density was 6.36 A/m2 under maximum allowable voltage of 12 V, boron removal and recovery efficiencies were 98.6% and 86.5%, respectively. During the pH-control process, current variation pattern indicated that current density was associated with initial boron concentrations in salt apartment. When the current variation pattern was applied to a five-cycle sequential feed-batch BMED process, it accurately reflected the timing of complete boron removal and recovery on a batch fill-and-draw process. The overall boron removal and recovery efficiencies were 98.53% and 81.2%, respectively, with an energy consumption of 31.5 Wh/g. Under these conditions, the final boron concentrations in effluent were less than 10 mg/L, as required by the Taiwan Environmental Protection Administration (EPA). Overall, BMED is a cost-effective treatment process for boron-containing wastewater. The proposed process indicator reflecting sequential BMED process progression based on process information will further elucidate the automatic process control in industrial applications.

Fluidized-bed crystallization of barium perborate for continuous boron removal from concentrated solution: Supersaturation as a master variable

The development of treatment process for boron removal is urgent to control the anthropogenic emission of boron to freshwater. Barium-based chemical oxo-precipitation (Ba-COP) is an effective method to treat boron-rich streams in ambient condition by the precipitation of barium perborate (BaPB), but it is limited to batch operation and mass production of sludge. This study aims to circumvent these drawbacks by performing Ba-COP in fluidized-bed crystallization system ([email protected]) to immobilize BaPB on the surface of the fluidized granules continuously. When [email protected] was operated at pH 10, 85% of total removal (TR) and 83% of crystallization ratio (CR) were attained from an input boron level of 600 mg-B/L, indicating that the homogeneous nucleation could be suppressed. Despite that both TR and CR varied greatly upon the dosage of H2O2 and Ba, initial concentration and reflux ratio, the influence of these parameters can be summarized by supersaturation. TR was related to the supersaturation at the effluent (SE), which was fixed at 1.15 ± 0.04; the sludge production rate increased drastically with the supersaturation at the mixing zone (SM), which in turn reflects on CR. Accordingly, an algorithm based on the supersaturation ratio was developed to predict the performance of [email protected] based on the initial concentration, hydraulic condition, dosages and ionic strength. The economic analysis reveals that [email protected] is more competitive than the Ba-COP conducted in batch stirred-tank reactor in terms of solid disposal cost due to the difference of water content between granule and sludge.

Impact of boronizations on impurity sources and performance in Wendelstein 7-X

The low-Z oxygen and carbon were the main plasma impurities in the Wendelstein 7-X (W7-X) stellarator in the last experimental campaign with the passively cooled graphite divertor. To tackle this issue boronization (Winter et al 1989 J. Nucl. Mater. 162–4 712–23) was applied, which has led to one of the main achievements of the campaign: plasma operation at high core densities of more than 1020 m−3 in hydrogen fueled plasmas due to the reduced radiation-induced density limit.In total three boronizations were applied. After the first boronization the oxygen to hydrogen flux ratio (normalized influx of oxygen) at the divertor substantially decreased by a factor of 10 and the carbon to hydrogen flux ratio (normalized influx of carbon) decreased by a factor of 4 as obtained from spectroscopy. In the same time, boron emission appeared in the spectra. Between the boronizations oxygen and carbon normalized influxes increased but never reached the pre-boronization values. With each subsequent boronization O level decreased even more, reaching the lowest values after the third boronization which were more than a factor of 100 lower than before the first boronization.Such a decrease in low-Z impurity concentration significantly extended the operation window of W7-X in terms of line-integrated electron density (from 4ċ1019 m−2 to more than 1ċ1020 m−2) and diamagnetic energy (from 330 kJ up to 510 kJ). Zeff decreased from 4.5 down to values close to 1.2 as obtained from bremsstrahlung measurements. The above mentioned values are given for the two reference discharges before and after boronization.

Hexagonal boron nitride grown using high atomic boron emission during microwave plasma chemical vapor deposition

Boron nitride (BN) is a member of Group III nitrides and continues to spark interest among the scientific community for its mechanical properties, chemical inertness, thermal conductivity, and electrical insulating properties. In this study, microwave plasma chemical vapor deposition is used to synthesize BN on silicon substrates. Feed gas mixtures of H2, NH3, and B2H6 are used for a range of systematically varied power, pressure, and flow rate conditions. Plasma optical emission from atomic boron is shown to increase nonlinearly by nearly a factor of five with decreasing chamber pressure in the range from 100 to 10 Torr. Copious amounts of atomic boron in the plasma may be beneficial under some growth conditions for producing high hardness boron-rich nitrides, such as B13N2, B50N2, or B6N, which, to date, have only been synthesized under high pressure/high temperature conditions. Despite the higher atomic boron emission in the plasma at low pressure, BN coatings grown at 15 Torr result in hexagonal BN (B/N ratio of 1), regardless of the B2H6 flow rate used in the range of 0.6–3.0 sccm.

XUV diagnostic to monitor H-like emission from B, C, N, and O for the W7-X stellarator.

The "C/O Monitor" system for the Wendelstein 7-X (W7-X) stellarator is a dedicated spectrometer with high throughput and high time resolution (order of 1 ms) for fast monitoring of content of low-Z impurities in the plasma. The observed spectral lines are fixed to Lyman-α lines of H-like atoms of carbon (3.4 nm), oxygen (1.9 nm), nitrogen (2.5 nm), and boron (4.9 nm). The quality of the wall condition will be monitored by the measurements of oxygen being released from the walls during the experiments. The strong presence of carbon is an indication for enhanced plasma-wall interaction or overload of plasma facing components. The presence of nitrogen (together with oxygen) may indicate a possible leakage in the vacuum system, whereas the intensity of the spectral emission of boron indicates the status of the boron layer evaporated onto the wall in order to reduce the influx of heavier steel ingredients or oxygen. The spectrometer will be fixed in a nearly horizontal position and is divided into two vacuum chambers, each containing two spectral channels assigned to two impurity species. Each channel will consist of a separate dispersive element and detector. The line-of-sight of both subspectrometers will cross at the main magnetic axis. This paper presents the conceptual design of the "C/O Monitor" for W7-X which has already entered the executive stage.

Comparison of the environmental impact of the conventional nickel electroplating and the new nickel electroplating

PurposeTo comply with the effluent regulation of boron, replacement of boric acid with citric acid in a nickel electroplating bath is proposed. Although the bath avoids the discharge of boron, it increases the discharge of nickel owing to the chelating effect of citric acid, which disturbs the wastewater treatment. To balance this trade-off, the environmental impacts of a traditional nickel plating process (the Watts bath) and the citrate bath must be compared by life cycle assessment.MethodsThe life cycle impact assessment method was LIME2. To estimate the trade-off between boron and nickel discharge into wastewater, the characterization and damage factors on human toxicity and ecotoxicity were calculated. The processes were then compared using data from actual processes. The functional unit was “plating per 1-kg part.” However, the plating efficiency depends on the type, shape, and surface area of the part. The data of the citrate bath were modeled. In the modeling, the amounts of nickel chloride and nickel sulfate in the citrate bath were based on the Watts bath.Results and discussionIn comparison with other chemicals, the calculated characterization and damage factors of boron and nickel were found to be reasonable. The integration results revealed that the citrate bath exerted greater environmental impact than the Watts bath. Although the Watts bath involved more environmentally damaging processes than the citrate bath, the sum of these impacts was much smaller than the impact of effluent from the citrate bath. Moreover, the environmental impact of effluent can be significantly reduced by flocculants, with almost no additional environmental impact incurred by the increased sludge.ConclusionsThe newly developed citrate plating bath exerts higher environmental impact than the traditional Watts bath because the environmental impacts of the release of nickel chelated with citric acid exceed the reduced boron emissions. Therefore, there is a trade-off between the two methods. When installing the citrate bath, the wastewater treatment must be altered to reduce the nickel emissions.

Atmospheric contribution to boron enrichment in aboveground wheat tissues

Boron is an essential trace element for all organisms and has both beneficial and harmful biological functions. A particular amount of boron is discharged into the environment every year because of industrial activities; however, the effects of environmental boron emissions on boron accumulation in cereals has not yet been estimated. The present study characterized the accumulation of boron in wheat under different ecological conditions in the Yangtze River Delta (YRD) area. This study aimed to estimate the effects of atmospheric boron that is associated with industrial activities on boron accumulation in wheat. The results showed that the concentrations of boron in aboveground wheat tissues from the highly industrialized region were significantly higher than those from the agriculture-dominated region, even though there was no significant difference in boron content in soils. Using the model based on the translocation coefficients of boron in the soil-wheat system, we estimated that the contribution of atmosphere to boron accumulation in wheat straw in the highly industrialized region exceeded that in the agriculture-dominated region by 36%. In addition, from the environmental implication of the model, it was estimated that the development of boron-utilizing industries had elevated the concentration of boron in aboveground wheat tissues by 28–53%.

Solid state emission and mechanochromic luminescence of boron 2-(2′-pyridyl)imidazole complexes

A series of boron 2-(2′-pyridyl)imidazole complexes were found to exhibit solid state emission and mechanochromic properties, meanwhile the terminal substituent play an important role in their properties. When the boron-difluoride dye bears dimethylamino moieties which can freely rotate, it emits poorly in most organic solvents and in the amorphous powder, but visible emission was observed in the crystalline state. Comparatively, the dyes comprising cyclohexylamino and diphenylamino substitutes show higher fluorescent efficiencies both in solutions and in the solid powder state, due to the larger steric hindrance. However, mechanochromism was observed only for the dyes bearing dimethylamino and diphenylamino moieties. According to XRD analysis, the transition of crystalline to amorphous state by grinding is ascribed to be the driving force for the mechanochromic character, and the flexibility of cyclohexylamino groups makes the dye inclined to be in amorphous state and non-responsive to mechanical force.

Cubic silicon carbide as a potential photovoltaic material

In this work we present a significant advancement in cubic silicon carbide (3C-SiC) growth in terms of crystal quality and domain size, and indicate its potential use in photovoltaics. To date, the use of 3C-SiC for photovoltaics has not been considered due to the band gap of 2.3eV being too large for conventional solar cells. Doping of 3C-SiC with boron introduces an energy level of 0.7eV above the valence band. Such energy level may form an intermediate band (IB) in the band gap. This IB concept has been presented in the literature to act as an energy ladder that allows absorption of sub-bandgap photons to generate extra electron–hole pairs and increase the efficiency of a solar cell. The main challenge with this concept is to find a materials system that could realize such efficient photovoltaic behavior. The 3C-SiC bandgap and boron energy level fits nicely into the concept, but has not been explored for an IB behavior.For a long time crystalline 3C-SiC has been challenging to grow due to its metastable nature. The material mainly consists of a large number of small domains if the 3C polytype is maintained. In our work a crystal growth process was realized by a new approach that is a combination of initial nucleation and step-flow growth. In the process, the domains that form initially extend laterally to make larger 3C-SiC domains, thus leading to a pronounced improvement in crystalline quality of 3C-SiC. In order to explore the feasibility of IB in 3C-SiC using boron, we have explored two routes of introducing boron impurities; ion implantation on un-doped samples and epitaxial growth on un-doped samples using pre-doped source material. The results show that 3C-SiC doped with boron is an optically active material, and thus is interesting to be further studied for IB behavior.For the ion implanted samples the crystal quality was maintained even after high implantation doses and subsequent annealing. The same was true for the samples grown with pre-doped source material, even with a high concentration of boron impurities.We present optical emission and absorption properties of as-grown and boron implanted 3C-SiC. The low-temperature photoluminescence spectra indicate the formation of optically active deep boron centers, which may be utilized for achieving an IB behavior at sufficiently high dopant concentrations. We also discuss the potential of boron doped 3C-SiC base material in a broader range of applications, such as in photovoltaics, biomarkers and hydrogen generation by splitting water.

Effect of plasma composition on nanocrystalline diamond layers deposited by a microwave linear antenna plasma‐enhanced chemical vapour deposition system

The addition of CO2 into the process gas has a significant impact on the quality and the incorporation of boron in CVD diamond layers. In this report we study the effect of CO2 addition in the gas phase on the properties of boron doped nano‐crystalline diamond (BNCD) layers grown at low substrate temperatures (450–500 °C) using a microwave linear antenna plasma‐enhanced chemical vapour deposition apparatus (MW‐LA‐PECVD). Experimental results show an increase in the layers' conductivity with a reduction in CO2 concentration, which is consistent with the variation in the atomic boron emission line intensity measured by optical emission spectroscopy (OES). At CO2 concentrations close to zero, we observed the formation of a smooth, transparent and highly resistive layer on unseeded substrates. This layer has been identified as silicon carbide (SiC) by transmission electron microscopy and X‐ray photoelectron microscopy. The presence of silicon in the plasma is confirmed by OES and it is attributed to quartz tube etching. In this specific deposition condition, diamond growth is in competition with SiC growth, which affects the diamond layer properties.SEM image of layer growth on a silicon substrate at low CO2 concentration on unseeded area (left) with a smooth, highly resistive and transparent SiC layer and seeded area (right) with a boron doped nano‐crystalline diamond layer.

Role of swift heavy ions irradiation on the emission of boron doped ZnO thin films for near white light application

Boron doped ZnO (ZnO:B) thin films on silicon substrates were synthesized with the sol–gel method using the spin coating technique. The films were irradiated by 80MeV Br+6 ions at various ion fluences. The X-ray diffraction results indicate that ZnO:B crystallized in the normal hexagonal wurtzite structure of ZnO. X-ray photoelectron spectroscopy data indicated that the O1s peak consist of three components designated as O1 (coming from ZnO), O2 (coming from defects) and O3 (coming from adsorbed species). Defect level emission (DLE) was obtained in the luminescence spectra of the pristine ZnO:B sample while the strong UV emission was observed for the ion irradiated films. The intensity of the DLE emission decreased after irradiation while the band to band emission increased after ion irradiation. A direct correlation between the amount of defects (O2 peak of XPS) and the DLE was observed. The emission of the ZnO:B is exponentially correlated with the swift heavy ion induced stress and the amount of defects. These ZnO:B thin films may be used for near white light emission applications.

Solid-state red emission of boron–fluorine complexes with extended π-conjugated structure

Two unique boron–fluorine complexes bearing extended conjugated structure were designed and synthesized facilely. These compounds absorb in visible region and emit red light in solutions with large Stokes shift. However, emission red-shift was observed with concentration increasing, showing typical J-aggregated fluorescence. Due to the J-aggregate formation, red emissions were observed in solid state for both compounds.

Application of laser-induced breakdown spectroscopy for detecting leakage of boric acid

Recently, many studies have been conducted on developing on-line leak detection techniques in the reactor vessel head of nuclear power plants. One of them, laser-induced breakdown spectroscopy (LIBS), an effective technique of leak detection, which is a kind of atomic emission spectroscopy that uses a highly energetic laser pulse as the excitation source, has been of interest due to the fast and reliable identification of chemical elements for the precipitates formed by the leakage of cooling water containing boric acid. Experimental setup and tests were performed for the boric acid precipitates formed on the steel for various conditions with a Q-switched 532nm Nd:YAG laser, optical lenses, an Echelle spectrograph and an intensified charge-coupled device detector. The LIBS system could be applied to obtain a spectral line (∼249. 2nm) corresponding to the atomic boron emission line for the precipitates of boric acid formed on low alloy steels, SA508 and SA533, as a substrate. The LIBS technique based on characterizing boric acid deposits might be used for detecting the leakage of cooling water in reactor vessel head of nuclear power plants.

Boron adsorption mechanism on polyvinyl alcohol

Recently, an increase in the use of boron compounds has led to an increase in boron emissions, and concern has grown regarding its detrimental effects on the human body. An adsorbent that adsorbs boron selectively has been developed as a countermeasure. Although certain commercially available boron selective adsorbents can be used to remove boron from aqueous solutions by utilizing the strong affinity between boron and hydroxyl groups, the adsorption capacity appears to be insufficient. So, we adopted polyvinyl alcohol (PVA), which contains many hydroxyl groups, as a model adsorbent. We investigated the boron adsorption characteristics of PVA, and then studied the relationship between the number of adsorption sites and actual adsorption amounts. We assessed the adsorption result by using adsorption site availability (ASA) as an indicator of the ratio of effectively functioning hydroxyl groups from the many hydroxyl groups in PVA. ASA was expressed as a percentage of the experimental equilibrium adsorbed amount in relation to the theoretical equilibrium adsorbed amount. We also compared the adsorption isotherms and ASA obtained with PVA, commercially available N-methylglucamine-type resin (CRB03 and CRB05) and the adsorbent we synthesized from polyallylamine (PAA) and glucose (PAA-Glu). Although PVA has many hydroxyl groups in a molecule, ASA analysis revealed that only 6% of the hydroxyl groups in PVA was used for boron adsorption. On the other hand, CRBs and PAA-Glu exhibited higher ASA values (about 15% and 35% respectively) and adsorption amounts, suggesting that the sterically congested adsorbent structure had a great influence on boron adsorption and ASA.

Use of emission spectroscopy for real-time assessment of relative wall erosion rate of BHT-200 hall thruster for various regimes of operation

Radiation emission due to Boron atoms sputtered from the Boron–Nitride ceramic walls of a BHT-200 Hall thruster was measured as a diagnostic for real time assessment of thruster wall erosion and to determine the effects of various operation conditions on thruster lifetime. Boron neutral 249.677 and 249.773 nm lines were measured using a high-resolution spectrometer. Spectral measurement results and the accompanying analysis and discussion are presented in this study. From the spectral measurements it was observed that the Boron emission intensity significantly increases for increased discharge voltage pointing to a large increase in the thruster wall erosion rate. Additionally, the measurements show that for the nominal discharge voltage and the applied magnetic field intensity, there is an optimum propellant flow rate for minimum Boron emission, thus minimum wall erosion rate. The variation in the current to the magnet coils showed that the Boron emission intensity increases for increased magnetic field and the Boron emission intensity shows similar behavior to that of the Xenon single ion emission line intensity at 248.911 nm. The findings of the study show that emission spectroscopy can be used in determining the optimum operational parameters for minimum wall erosion for SPT type Hall thrusters.

Isotopic evidence of boron in precipitation originating from coal burning in Asian continent

The boron concentration and isotopic composition (δ11B) of precipitation collected from December 2002 to March 2006 at three sites on the Japan Sea coast were measured. Those sites have been considerably affected by the long-range transport of air pollutants from the Asian continent during winter and spring when the airflows from the Asian continent are predominant. The boron concentration in the precipitation increased primarily during winter whereas the δ11B decreased during winter or spring. It is assumed that this decrease in δ11B is not associated with a Rayleigh distillation process, because the previous δD values of the precipitation collected at a site on the Japan Sea coast did not decrease in the same manner. A weak correlation (r2 = 0.13-0.24, P < 0.01) was observed between δ11B and the nonsea-salt sulfate (nss-SO42-)/B ratio at each site, suggesting that boron in the precipitation originate primarily from two sources. The first source, which is characterized by high δ11B and nss-SO42-/B = 0, is seawater. At the northern site, the enrichment factor for boron in the precipitation relative to seawater approached unity during winter. This implies that much of the boron in the precipitation is derived from unfractionated sea salts rather than gaseous boron evaporated from seawater. The second source is characterized by low δ11B and high nss-SO42-/B ratio. Most of the nss-SO42- in the precipitation originates from anthropogenic combustion activities in the Asian continent based on the previous model calculations. Coal accounts for a major portion of the total primary energy supply in China. Moreover, coal enriches boron and represents generally negative δ11B values. Hence, we propose that the emission of boron from coal burning is the most likely second source. Thus, boron isotopes may be useful as tracers of coal-burning plumes from the Asian continent.

Fully Automated Measuring Equipment for Aqueous Boron and Its Application to Online Monitoring of Industrial Process Effluents

Fully automated measuring equipment for aqueous boron (referred to as the online boron monitor) was developed on the basis of a rapid potentiometric determination method using a commercial BF4(-) ion-selective electrode (ISE). The equipment can measure boron compounds with concentration ranging from a few to several hundred mg/L, and the measurement is completed in less than 20 min without any pretreatment of the sample. In the monitor, a series of operations for the measurement, i.e., sampling and dispensing of the sample, addition of the chemicals, acquisition and processing of potentiometric data, rinsing of the measurement cell, and calibration of the BF4(-) ISE, is automated. To demonstrate the performance, we installed the monitor in full-scale coal-fired power plants and measured the effluent from a flue gas desulfurization unit. The boron concentration in the wastewater varied significantly depending on the type of coal and the load of power generation. An excellent correlation (R2 = 0.987) was obtained in the measurements between the online boron monitor and inductively coupled plasma atomic emission spectrometry, which proved that the developed monitor can serve as a useful tool for managing boron emission in industrial process effluent.