Cl2 Gas Research Articles

Doping of β‐Ga2O3 Layers by Zn Using Halide Vapor‐Phase Epitaxy Process

Development of ultrawide bandgap semiconductor β‐Ga2O3 is important considering its great potential for high‐power high‐voltage electronic applications. Halide vapor‐phase epitaxy is used to produce Zn‐doped β‐Ga2O3 layers on sapphire (0001). Zn doping concentrations is estimated to be in the range between 6 × 1018 and 2.5 × 1020 cm−3. As a precursor for Zn acceptor dopant, ZnCl2 formed by flowing of diluted Cl2 gas over a melt of metallic Zn is used. Modeling of the growth chamber and calculations of precursor concentrations inside the growth zone is carried out to optimize process parameters. The Zn doping is not affecting the optical emission properties; however, growth under oxygen‐rich conditions and formation of crystalline particles on the layer surface are factors responsible for modification of β‐Ga2O3 luminescence spectrum. It is observed that the UV band at 3.35 eV vanishes, whereas relative intensities of the blue and green bands at 2.4–2.8 eV increase.

Gas Evolution from Mixed-Acid Vanadium Redox Flow Batteries

Mixed-Acid (MA) Vanadium Redox Flow Batteries (VRFB) improve on standard VRFBs’ energy density by adding hydrochloric acid (HCl) to the standard sulfuric acid (H2SO4) electrolyte. This improves the stability of the vanadium (V) in the solution, which allows for electrolytes with higher concentrations of V ions and increased operating temperatures. The addition of HCl to the system introduces a new safety risk, the evolution of chlorine gas (Cl2) from the catholyte. In this study, we cycled an MA VRFB under a range of conditions to understand the fundamental causes of gas evolution. We constructed a single cell MA VRFB using a standard electrolyte composition of 2M H2SO4, 5M HCl and 2M V, with a gas analyzer sampling the head space of the catholyte chamber. Cl2 gas quantity was measured under systematically varied SOCs, cycling rates, electrolyte flow rates, electrode materials and electrolyte temperatures. Mechanisms of gas evolution at each condition were determined from analysis of the cycling data and the fundamental chemistry of the system. Conditions that lead to high rates of gas evolution were identified. This new understanding of gas evolution will aid development of safer MA VRFB systems that mitigate Cl2 formation during operation.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

An Economic Hypochlorous Acid Maker for Covid-19 Control

It has been shown that HOCl can inactive numerous viruses, including Corona-19 Viruses in less than one minute. HOCl inactivates viruses, bacteria, endospore and fungi whilst being safe for human tissues with a 99.999% elimination rate. HOCl is listed on the United States Environmental Protection Agency’s List for Disinfectants for Use Against SARS-CoV-2 (Covid-19). It can be used conveniently as hand sanitizer, surface cleanser, food washing solution, fogging solution for school classrooms, buses, shops, restaurants, hotels, offices, theaters, airports, trains, gyms, etc. It is a green, safe, environmentally friendly and fully biodegradable liquid which acts as a very powerful antimicrobial and sterilizing solution.Most consumers purchase pre-made HOCl products produced in a large manufacture site. The pre-made HOCl hypochlorous acid products in the market are very expansive, mostly due to high cost for packaging, transportation, distribution, storage, and in-stability of the product, which normally has a lifetime of 6 -12 months. The capacity of current on-site HOCl generation products is either too big, or too small, only economical for large quantity consumers or single household uses. Due to the Corvid-19 pandemic, there is a strong need for a safe, on-site, on-demand medium-sized HOCl generation product, which uses only non-hazardous household chemicals and has a production capacity of about 10 gallons per day. Here we report our recent development of a compact and low cost HOCl on-site generator for daily disinfection applications against Corvid-19 virus. Compared to other products on the market, which normally use >2 g/L NaCl solutions, our device uses only 0.4 g/L NaCl solution. This is highly desired for environment fogging disinfection applications. Other advantages of our device include: 1) no noticeable Cl2 gas generation during HOCl production; 2) tap water can be used directly without softening treatment; 3) produce very stable products, with 90% HOCl Stability: > 100 days. Figure 1

An on-Site, on-Demand, Medium-Sized Hypochlorous Acid Maker for Covid-19 Control

Hypochlorous acid (HOCl) is an endogenous substance and has been proven effective against many microorganisms1. It has been shown that HOCl can inactive numerous viruses, including Corona-19 Viruses in less than one minute1. HOCl already has applications in numerous industries such as farming, hospitality, food, healthcare including disinfection and wound care1. HOCl inactivates viruses, bacteria, endospore and fungi whilst being safe for human tissues with a 99.999% elimination rate2. HOCl is listed on the United States Environmental Protection Agency’s List for Disinfectants for Use Against SARS-CoV-2 (Covid-19)3. It can be used conveniently as hand sanitizer, surface cleanser, food washing solution, fogging solution for school classrooms, buses, shops, restaurants, hotels, offices, theaters, airports, trains, gyms, etc. It is a green, safe, environmentally friendly and fully biodegradable liquid which acts as a very powerful antimicrobial and sterilizing solution4-6.However, the pre-made HOCl hypochlorous acid products in the market are expansive, mostly due to high cost for packaging, transportation, distribution, storage, and in-stability of the product, which normally has a lifetime of 6 -12 months. The capacity of current on-site HOCl generation products is either too big, or too small, only economical for large quantity consumers or single household uses. Due to the Corvid-19 pandemic, there is a strong need for a safe, on-site, on-demand medium-sized HOCl generation product, which uses only non-hazardous household chemicals and has a production capacity of about 10 gallons per day. Here we report our recent development of a compact and low cost HOCl on-site generator for daily disinfection applications against Corvid-19 virus. Compared to other products on the market, which normally use >2 g/L NaCl solutions, our device uses only 0.4 g/L NaCl solution. This is highly desired for environment fogging disinfection applications. Other advantages include: 1) no noticeable Cl2 gas generation during HOCl production; 2) tap water can be used directly without softening treatment; 3) produce very stable products, with 90% HOCl Stability: > 100 days. Block, M. S., & Rowan, B. G. (2020). Hypochlorous acid - a review. Journal of Oral and Maxillofacial Surgery, 1-13. doi:10.1016/j.joms.2020.06.029Rasmussen, E. D., & Williams, J. F. (2017). Stabilized Hypochlorous Acid Disinfection for Highly Vulnerable Populations. 2017 IEEE Global Humanitarian Technology Conference, 1-8. doi:10.1109/GHTC.2017.8239259Agency, U. S. (2020, July 1). List N: Disinfectants for Use Against SARS-CoV-2 (Covid-19O). Retrieved from United States Environmental Protection Agency: https://www.epa.gov/pesticide-registration/list-n-disinfectants-use-against-sars-cov2-covid-19 Rutala, W. A., & Weber, D. J. (2014). Selection of the Ideal Disinfectant. Infection Control and Hospital Epidemiology, 35(7), 855-865Spaulding, E. H. (1957). Chemical Disinfection and Antisepsis in the Hospital. Journal of Hospital Research, 9(1), 5-31. https://www.hypochlorousacid.com Figure 1

Hybrid simulation of radio frequency biased inductively coupled Cl2 plasmas

In the etching process, a bias source is usually applied to the bottom electrode of an inductively coupled plasma (ICP) source to control the ion energy and angular distribution function (IEADF) independently. In this work, a hybrid model, i.e., a global model combined bi-directionally with a fluid sheath model, is applied to investigate the plasma properties in biased ICPs sustained in Cl2 gases. The evolutions of the plasma properties with bias voltage are presented for various ICP powers (i.e., 200, 500, and 1000 W) at a pressure of 10 mTorr and bias frequency of 13.56 MHz. The results indicate that the Cl2 (v = 0) density decreases with ICP power, whereas the densities of electrons and Cl+ ions increase strikingly and they become the dominant charged species at 1000 W. In addition, the electron density and Cl+ density increase with bias voltage, and the increasing trend becomes more obvious at higher ICP powers. However, the evolution of the Cl2+ density and Cl− density with bias voltage depends on the ICP power. For instance, they first exhibit an increasing trend and then keep constant at 200 W, while a slight downward trend is observed at 1000 W. In addition, as the bias voltage increases, both the high-energy peak and low-energy peak of IEADFs move toward higher energy, and meanwhile the peak separation becomes wider. The results obtained in this work are of significant importance for improving the etching process.

Çocuklarda Akut Klor Zehirlenmesinin Klinik Spektrumu

Objective: Chlorine gas (Cl2) is a common substance used in industry, which causes toxic inhalation as a potent pulmonary irritant. Herein, we aimed to investigate the findings of pediatric cases accidentally exposed to Cl2 gas.

Fast microwave leaching of platinum, rhodium and cerium from spent non-milled autocatalyst monolith

This work presents a new microwave leaching approach to solubilize platinum group metals (PGMs) and cerium from spent autocatalyst monoliths. In the proposed process, the catalyst does not require to be milled/pulverized prior to the leaching step in 6 M HCl for 3 min in the absence of an oxidation agent and internal mixing. Therefore, processing costs associated to catalyst comminution could be avoided. The highest extraction yields were achieved at 220°C at a liquid to solid ratio of 10 (Pt: 99±4%, Rh: 95±1%, Ce: 104±3%). At this temperature, the composition of the in situ generated headspace gas, including Cl2 gas that acts as oxidant, and the enhanced porosity of cordierite, improved PGM and Ce leaching. Furthermore, the blocks preserved their honeycomb structure after leaching, simplifying downstream solid-liquid separation, e.g. using gravity filtration. SEM/EDX analyses of residues’ cross-sections allowed for identifying the dissolution mechanism of the washcoating (150-220°C).Whereas, under the same conditions ball-milled catalyst material gave significantly lower PGM leaching (Pt:47±4%, Rh: 48.6±0.3%) and a greener leaching in 1 M HCl + 3.8 M NaCl, achieved higher selectivity towards PGMs, although overall yields decreased (Pt: 68±2%, Rh: 67±5%, Ce: 39±1%).Statement of Novelty and Significance: This work presents a novel approach to solubilize Pt, Rh and Ce from spent ceramic autocatalyst via a fast microwave leaching process (3 min) in a 6 M HCl solution at 220°C, without the need of (i) a milling pretreatment, (ii) an oxidizing/reducing agent, nor (iii) internal mixing. Therefore, the energy consumption, cost of chemicals and complexity of the process are reduced in comparison to previously described microwave assisted routes, which might benefit its upscaling. Additionally, the metal leachability was high (99±4% Pt, 95±1% Rh, 104±3% Ce), and the downstream solid-liquid separation was facilitated.

Formation of highly vertical trenches with rounded corners via inductively coupled plasma reactive ion etching for vertical GaN power devices

A trench-gate metal-oxide-semiconductor field-effect transistor (T-MOSFET) has great potential for use in gallium nitride (GaN)-based vertical power switching devices owing to its high blocking voltage and high current capability. To form an optimal trench shape that has highly vertical sidewalls and rounded corners, we developed a dry-etching technique using inductively coupled plasma reactive ion etching (ICP-RIE). A highly vertical trench was obtained by including SiCl4 reactive gas mixed with Cl2 gas in the ICP-RIE process, where Si-related byproducts suppressed the etching of the sidewall and allowed selective etching in the vertical direction. We found that the optimization of the bias power was a key to suppress the formation of subtrenches and to avoid an isotropic etching mode. The optimal etching condition leads to natural formation of rounded corners at the trench bottom. In addition, a multistep-bias etching technique was applied to reduce etching-induced damage. Cross-sectional transmission electron microscopy images revealed that lattice distortion on the sidewall surface was eliminated by multistep-bias etching. Based on the rectification properties of the Schottky barrier diodes formed on the trench sidewalls, the Schottky barrier height was comparable to the not-etched surfaces. This indicates that the gap states caused by etching-induced damage can almost be eliminated in the multistep-bias process. The proposed technique is suitable for GaN-based vertical T-MOSFETs.

Omnidirectional and Broadband Antireflection Effect with Tapered Silicon Nanostructures Fabricated with Low-Cost and Large-Area Capable Nanosphere Lithography.

In this report, we present a process for the fabrication and tapering of a silicon (Si) nanopillar (NP) array on a large Si surface area wafer (2-inch diameter) to provide enhanced light harvesting for Si solar cell application. From our N,N-dimethyl-formamide (DMF) solvent-controlled spin-coating method, silica nanosphere (SNS in 310 nm diameter) coating on the Si surface was demonstrated successfully with improved monolayer coverage (>95%) and uniformity. After combining this method with a reactive ion etching (RIE) technique, a high-density Si NP array was produced, and we revealed that controlled tapering of Si NPs could be achieved after introducing a two-step RIE process using (1) CHF3/Ar gases for SNS selective etching over Si and (2) Cl2 gas for Si vertical etching. From our experimental and computational study, we show that an effectively tapered Si NP (i.e., an Si nanotip (NT)) structure could offer a highly effective omnidirectional and broadband antireflection effect for high-efficiency Si solar cell application.

Sheet Resistance Reduction of MoS₂ Film Using Sputtering and Chlorine Plasma Treatment Followed by Sulfur Vapor Annealing

Sheet resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sheet</sub> ) reduction of a-few-layered molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) film using sputtering is investigated in this study. To enhance the carrier density, chlorine (Cl2) gas excited by inductively coupled plasma is introduced as a substitute for sulfur. To electrically activate the Cl dopants and simultaneously prevent out-diffusion of sulfur, a furnace annealing was performed in sulfur-vapor ambient. Consequently, the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sheet</sub> in the MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film with the Cl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma treatment remarkably reduced by one order lower than that without one, because of the activation of Cl dopants in the MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film.

Enhanced NO2 gas sensing performance of Ni-doped ZnO nanostructures

Pure and 1–4 at.% Ni-doped ZnO (N0Z-N4Z) nanostructures have been successfully prepared by simple and cost-effective co-precipitation method. The prepared nanostructures were studied using XRD, FESEM, HRTEM, EDX, FTIR, UV–Visible absorption and XPS techniques. The XRD study revealed that the hexagonal wurtzite structure of pure and Ni doped ZnO nanostructures, and their preferred peak growth orientation is along (101) plane without inferior phases in Ni-doped ZnO samples. The morphological investigation of Ni doped ZnO samples by FESEM and HRTEM techniques exhibited nanorods. The average diameter and length of nanorods are 25–80 nm and 140–410 nm. The results of UV–Visible absorption spectroscopy of Ni-doped ZnO nanostructures indicate red shift with varying amounts of Ni concentration. The estimated band gaps were obtained 3.11, 3.06, 3.02, 2.99 and 2.97 eV of N0Z, N1Z, N2Z, N3Z and N4Z nanostructures respectively. The NO2 gas sensing performance of fabricated N0Z-N4Z sensors were tested at different working temperatures (120–280 °C) and concentrations (5–100 ppm). Among them, the N2Z sensor showed stable, reproducible and the highest response (356%) when exposed to 100 ppm NO2 gas at 200 °C working temperature. The probable sensing mechanism of NO2 gas by Ni-doped ZnO nanostructures is investigated and discussed. Sensing response of N2Z gas sensor was also studied for 100 ppm Cl2, SO2 and H2S gases at 200 °C operating temperature and it appeared for most selective towards NO2 gas. The present study reveals that N2Z nanostructure can be attractive material as a sensor for recognition of hazardous NO2 gas at low concentrations.

Selective sensing of oxidizing gases on Co-Ni-Zn ferrite: Mechanism and response characteristics

Studies demonstrate the selective gas sensing characteristics of Co-Ni-Zn ferrite thick film towards oxidizing gases over reducing gases. The Co0.3Ni0.3Zn0.4Fe2O4 ferrite was prepared by combustion method and characterized for its phase purity, nanodimension and valence state by analytical techniques, includes X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy and X-ray photoelectron spectroscopy, respectively. The Co0.3Ni0.3Zn0.4Fe2O4 gas sensor was fabricated in the form of thick film by screen printing method, and the response of film towards selected oxidizing gases and the reducing gases were investigated. It was found that Co0.3Ni0.3Zn0.4Fe2O4 thick film is highly active towards oxidizing gases at 200 °C, whereas almost negligible response was observed for reducing gases at all temperatures ranging from RT to 300 °C. The Oxygen adsorption - desorption mechanism is proposed for sensing of NO2 and Cl2 gases, and stated to be favored by n to p type conductivity transition on the surface of sensor film at 200 °C.

Development of metallic nuclear material purification process via simultaneous chlorination and volatilization

A purification process involving simultaneous chlorination and volatilization is reported using aluminum, iron, gallium, and uranium separation from cerium metal as the demonstration system. Anhydrous Cl2 gas was reacted with the metal after it had been converted to small particles of hydride at temperatures ranging from 523 to 973 K. Each of the impurities should form chlorides with relatively high saturated vapor pressures. The objective of the process was to volatilize these chlorides after first achieving near-complete conversion of the metals to hydride and then chlorides. Complete conversion of hydrides to chlorides could not be achieved using relatively low-grade (99.5%) Cl2. High decontamination factors for all of the metal impurities required near complete conversion to chloride. It was concluded that oxygen contamination of the feed gas stream likely limits the conversion to chlorides by forming oxides instead, which then limits the volatilization of contaminants. Uranium was particularly challenging to remove in experiments suspected of having high oxygen contamination in the feed gas stream. After switching to ultra-high purity (99.999%) Cl2, complete conversion to chlorides within the measurement error was possible for the entire temperature range studied. Decontamination factors for aluminum, iron, gallium, and uranium were found to have average values of 1.9, 9.8, 14, and 5, respectively, at 973 K. While the process was most extensively studied using a once-through gas flow, recycling unreacted Cl2 gas succeeded at minimizing waste while still maintaining complete conversion and similar decontamination factors.

Machine Learning to Identify Metabolic Effects of Chlorine Gas Exposure

Background/Aim: Untargeted metabolomics enable the exploration of pathways that are affected by environmental respiratory exposures. However, traditional analyses of such data analyze each feature separately, ignoring interactions between features and reducing power. Independent component analysis (ICA) is a machine learning method that uncovers hidden patterns in data and has found widespread application in the analysis of medical imaging, video surveillance, and financial data. We propose that applying ICA to untargeted metabolomics data can alleviate the limitations of traditional feature-by-feature analyses. Methods: We applied ICA to approximately 25,000 untargeted metabolomic features measured in brachial lavage fluid (BALF) collected from 15 healthy participants who experienced separate exposures to Cl2 gas and clean air. We estimated a total of 7 components using ICA. We compared our results to traditional feature-by-feature analyses. Results: In the traditional analyses, no features remained significant after a false discovery rate (FDR) correction. Of the 7 ICA components, 3 showed statistically significant differences, assessed using paired t-tests, in expression between the two conditions (Cl vs. clean air). These three components (t-statistics: 2.4, 7.2, and 12.2) remain significant after FDR correction. Annotation of detected metabolites in these components suggests variations in oxidative stress-related metabolites, including methionine (an important anti-oxidant) and oxidized fatty acids in the Cl¬2 exposure compared with the clean air exposure. Other features in these components showed a negative mass defect, which is consistent with the presence of halogenated compounds that may form through chlorine nucleophilic substitution. These ICA components were not associated with the age or sex of the participants. Conclusions: Our results suggest Cl2 exposure influences the lung metabolome and demonstrate the value of using machine learning methods to uncover biological response to respiratory exposures. Disclaimer: The views in this abstract belong to the authors and are not necessarily those of the U.S. Environmental Protection Agency.

In Situ Study of Molecular Doping of Chlorine on MoS2 Field Effect Transistor Device in Ultrahigh Vacuum Conditions.

We report a precise measurement of the sensor behavior of the field effect transistor (FET) formed with the MoS2 channel when the channel part is exposed to Cl2 gas. The gas exposure and the electrical measurement of the MoS2 FET were executed with in situ ultrahigh-vacuum (UHV) conditions in which the surface analysis techniques were equipped. This makes it possible to detect how much sensitivity the MoS2 FET can provide and understand the surface properties. With the Cl2 gas exposure to the channel, the plot of the drain current versus the gate voltage (Id–Vg curve) shifts monotonically toward the positive direction of Vg, suggesting that the adsorbate acts as an electron acceptor. The Id–Vg shifts are numerically estimated by measuring the onset of Id (threshold voltage, Vth) and the mobility as a function of the dosing amounts of the Cl2 gas. The behaviors of both the Vth shift and the mobility with the Cl2 dosing amount can be fitted with the Langmuir adsorption kinetics, which is typically seen in the uptake curve of molecule adsorption onto well-defined surfaces. This can be accounted for by a model where an impinging molecule occupies an empty site with a certain probability, and each adsorbate receives a certain amount of negative charge from the MoS2 surface up to the monolayer coverage. The charge transfer makes the Vth shifts. In addition, the mobility is reduced by the enhancement of the Coulomb scattering for the electron flow in the MoS2 channel by the accumulated charge. From the thermal desorption spectroscopy (TDS) measurement and density functional theory (DFT) calculations, we concluded that the adsorbate that is responsible for the change of the FET property is the Cl atom that is dissociated from the Cl2 molecule. The monotonic shift of Vth with the coverage suggests that the MoS2 device sensor has a good sensitivity to detect 10–3 monolayers (ML) of adsorption corresponding to the ppb level sensor with an activation time of 1 s.

Low resistance n-contact for UVC LEDs by a two-step plasma etching process

The impact of plasma etching on the formation of low-resistance n-contacts on the AlGaN:Si current spreading layer during the chip fabrication of ultraviolet light-emitting diodes (UVLEDs) emitting at 265 nm is investigated. A two-step plasma etching process with a first rapid etching using BCl3/Cl2 gas mixture and a second slow etching step using pure Cl2 gas has been developed. The etching sequence provides smooth mesa side-walls and an n-AlGaN surface with reduced surface damage. Ohmic n-contacts with a contact resistivity of 3.5 × 10−4 Ωcm2 are obtained on Si-doped Al0.65Ga0.35N layers and the operating voltages of the UVC LEDs were reduced by 2 V for a current of 20 mA.

Development of SiC Etching by Chlorine Fluoride Gas

Amorphous SiC and 4H-SiC were etched by chlorine fluoride (ClF), chlorine trifluoride (ClF3), fluorine (F2) and chlorine (Cl2) gases, in order to evaluate the etching capability of various reactive gases. The gaseous byproducts of SiC etching were observed by the quadrupole mass spectrometry. The ClF showed slow etching rate of amorphous SiC and 4H-SiC, while ClF3 and F2 quickly etched them. By the ClF gas, the etching rate of amorphous SiC was 120 nm/min at 400 °C. The ClF gas was expected to be suitable for a shallow etching, because of its moderate etching rate even at high temperatures.

Screen-Printed Electrodes Modified with Metal Phthalocyanines: Characterization and Electrocatalysis in Chlorinated Media.

Metal phthalocyanines are well-known sensing phases with applications in different scientific fields due to their interesting properties. Detailed characterization by Raman spectroscopy was performed in order to study the shifting of the vibrational bands related to the coordination sphere of each metal phthalocyanine. In this work, a study involving the use of screen-printed electrodes (SPEs) with various metal phthalocyanines to electrochemically detect and quantify chlorine (Cl2) gas is presented. The Cl2 gas was generated in-situ via oxidation of the chloride present in form of aqueous salt solutions. The developed method offers not only the possibility to quantify chlorine, but also to discriminate among several chlorinated species due to the changes observed in the voltammetric profiles associated with the interaction between the specie assayed and the phthalocyanine metallic center. Optimization of detecting parameters was also performed to apply this procedure for the quantification of chlorine generated from commercial chlorine tablets. The development of this proof of concept shows interesting possibilities and easy-to-use applications with novel on metal phthalocyanines based SPE sensors.

Chlorination Kinetics of Synthetic Rutile with Cl2+CO Gas

The chlorination kinetics of synthetic rutile prepared by selective chlorination of ilmenite with Cl2 and CO gas mixture were studied in a fluidized bed. The effects of reaction temperature, reaction time, and the ratio of Cl2 and CO partial pressure (pCl2/pCO) on the conversion rate of TiCl4 were investigated. The conversion rate of TiCl4 was low under the high pCl2/pCO conditions. Moreover, it was considered that the partial pressure of CO gas was more effective than that of Cl2 gas when comparing the stoichiometric conversion rate and experimental results of high CO partial pressure. Considering the porous structure of particles, the rate controlling step of the chlorination of synthetic rutile was determined to be chemical reaction and the activation energy was calculated as 53.77 kJ/mol.

Numerical investigation of the effect of variation of gas mixture ratio on density distribution of etchant species (Br, Br+, Cl, Cl+, and H) in HBr/Cl2/Ar plasma discharge

A self-sustained fluid model is used to study the effect of variation of noble gas fraction (Ar) and variation of gas mixture ratio (HBr/Cl2/Ar) on density distribution of important etchant species (Br, Br+, Cl, Cl+, and H) in HBr/Cl2/Ar capacitive coupled plasma discharge that is being vastly used for dry etching of Si, GaAs, GaSb and other group III and IV semiconductor materials. A comprehensive set of 80 reactions in this plasma discharge is presented which contains electron impact reactions, neutral–neutral reactions, ion–ion reactions, and charge transfer reactions. Based on simulation results, it is found that densities of neutral species have normal distribution curve; density is higher at center of the reactor and decreases as we move towards electrode surface, while densities of charged species follow bimodal distribution in which peaks occur near electrodes. Furthermore, the addition of Ar in HBr/Cl2 causes electron density to increase which promotes ionization and dissociation. It was found that at constant supply of Cl2 gas, by increasing Ar fraction (HBr/Cl2/Ar from 80/10/10 to 10/10/80) densities of Br, Br+ and H will go down and at constant supply of Ar gas, raising Cl2 fraction in feedback gases (HBr/Cl2/Ar from 70/20/10 to 20/70/10) promoted the production of Cl and Cl+ while densities of Br, Br+, and H are dropped-off. Hence, densities and fluxes of important etchant species – for chemical vs. physical etching – can be controlled by tuning of mixture ratio.