Chlorine-containing Atmosphere Research Articles

High-Temperature Corrosion of Nickel-Based Coatings for Biomass Boilers in Chlorine-Containing Atmosphere

As there is a strong pressure in the EU to reduce CO2 emissions and overall fossil fuel consumption in the energy sector, many boilers are burning biomass instead of traditional fuels (coal, natural gas, oil, etc.). This is mainly due to the EU 2030 energy strategy, which commits Member States to reduce fossil fuel emissions by at least 40% (compared to the 1990 level) and to use at least 32% of renewable energy. The combustion of biomass containing aggressive elements such as chlorine or sulfur causes serious damage to various boiler components, with negative impacts such as reduced boiler lifetime, increased investments and maintenance costs, reduced availability, and others. These problems occur mainly in plants/boilers designed to burn coal and redesigned to burn biomass (straw, wood chips, wood pellets, etc.). In this paper, the corrosion resistance of heat coatings determined in long-term laboratory tests in an environment specifically corresponding to biomass flue gas is presented. These results can be used to design a suitable modification of existing coal boilers using conventional materials. The aim was to compare three completely different technologies currently available on local markets for the preparation of these coatings—thin wire arc spray (TWAS), high-velocity oxygen fuel (HVOF), and water-stabilized plasma. These coatings were compared with the base material of the boiler tubes—low alloyed steel 16Mo3 and high alloyed austenitic stainless steel AISI 310 as a more expensive option for retrofit. After 5000 h of exposure in an environment containing HCl and SO2, no cracks or structural defects were observed in any of the coatings, and the substrate material showed no signs of oxidation. All the tested coatings had higher corrosion resistance than the 16Mo3 material, and some of them presented a corrosion behavior close to that of the high alloy AISI 310 steel. Structurally and corrosion-wise, the thermally sprayed coating prepared by HVOF technology was the best of all tested materials.

Silicon Light-Emitting Diodes with Dislocation-Related Luminescence Fabricated with Participation of Oxygen Precipitates

Silicon light-emitting diodes with dislocation-related electroluminescence have been studied at room temperature. For the fabrication of the light-emitting diode structures, a well-known method for the formation of dislocation-related luminescence centers during anneals of silicon with a high oxygen concentration in a flow of argon was modified by introducing a preliminary O+ ion implantation and carrying out a final anneal in a chlorine-containing atmosphere. In the electroluminescence spectra, the D1 dislocation-related luminescence line dominates at currents less than <150 mA and the near-band-edge luminescence line starts to dominate with increasing current. The electroluminescence excitation efficiency for the D1 center is 3.3·10-20 cm2·s at room temperature. Keywords:: Light-emitting diodes, dislocation-related luminescence, silicon, oxygen precipitates.

Влияние дополнительной имплантации ионов кислорода на дислокационную люминесценцию кремния, содержащего кислородные преципитаты

Dislocation-related photoluminescence is studied in unimplanted and implanted with oxygen ions silicon wafers after multistage heat treatment, used for the formation of internal getter in microelectronics, and final annealing at 1000°С in a chlorine-containing atmosphere. In unimplanted sample, the dislocation-related luminescence line D1 dominates and its intensity is more than one order of magnitude in comparison with another dislocation-related luminescence line D2. With increasing temperature, an intensity of the D1 line increases and then decreases. In implanted sample, the intensities of the D1 and D2 lines increase. For both the lines, temperature quenching of their intensities is observed only. The energies of quenching and increase of the intensities of dislocation-related photoluminescence lines are determined. Possible reasons of observed effects are discussed.

Correlation between Microstructure and Chemical Composition of Zinc Oxide Gas Sensor Layers and Their Gas-Sensitive Properties in Chlorine Atmosphere.

In this article, we present results concerning the impact of structural and chemical properties of zinc oxide in various morphological forms and its gas-sensitive properties, tested in an atmosphere containing a very aggressive gas such as chlorine. The aim of this research was to understand the mechanism of chlorine detection using a resistive gas sensor with an active layer made of zinc oxide with a different structure and morphology. Two types of ZnO sensor layers obtained by two different technological methods were used in sensor construction. Their morphology, crystal structure, specific surface area, porosity, surface chemistry and structural defects were characterized, and then compared with gas-sensitive properties in a chlorine-containing atmosphere. To achieve this goal, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) methods were used. The sensing properties of obtained active layers were tested by the temperature stimulated conductance method (TSC). We have noticed that their response in a chlorine atmosphere is not determined by the size of the specific surface or porosity. The obtained results showed that the structural defects of ZnO crystals play the most important role in chlorine detection. We demonstrated that Cl2 adsorption is a concurrent process to oxygen adsorption. Both of them occur on the same active species (oxygen vacancies). Their concentration is higher on the side planes of the zinc oxide crystal than the others. Additionally, ZnO sublimation process plays an important role in the chlorine detection mechanism.

Silicon Light-Emitting Diodes with Luminescence from (113) Defects

Silicon light-emitting diodes with luminescence associated with (113) defects are fabricated by the implantation of 350-keV oxygen ions at a dose of 3.7 × 1014 cm–2 and subsequent annealing at 700°C for 1 h in a chlorine-containing atmosphere. The electroluminescence is studied in wide temperature and excitation-power ranges. The line associated with the (113) defects is dominant in all the spectra. The temperature dependence of the line intensity depends on the excitation power at low temperatures: an increase in the intensity with an activation energy of 25 meV is observed at low current densities and no rise in the intensity is observed with increasing current density. At higher temperatures, an intensity with an activation energy of 59 meV is quenched irrespective of the current density. With increasing temperature, the peak of the line of the (113) defect shifts by the same energy as the energy-gap width, whereas the half width of the line grows linearly.

Кремниевые светодиоды с люминесценцией (113) дефектов

Silicon light-emitting diodes with luminescence associated with (113) defects have been fabricated using implantation of 350 keV oxygen ions at the dose of 3.7∙1014 cm-2 and subsequent annealing at 700ᵒC for 1 h in a chlorine-containing atmosphere. Electroluminescence was studied in wide ranges of temperature and an excitation power. The line associated with (113) defects dominates in all the spectra. The temperature dependence of the line intensity depends on the excitation power in the range of low temperatures: an increase of the intensity with activation energy of 25 meV is observed at low current density and, with the increasing current density, a rise of the intensity is not observed. At higher temperatures, a decrease of the intensity with activation energy of 59 meV occurs regardless of a current density. With the increasing temperature, the peak of the line shifts by the same energy as the forbidden gap width, while the half width of the line grows linearly.

The getters in silicon

The processes of gettering of fast-diffusing metal impurities and structure defects in silicon, mainly used in the production of integrated circuits, power high-voltage devices, nuclear-doped silicon, are considered. The getters based on structural defects and gas-phase getters based on chlorine-containing compounds are analyzed. It is noted that for the formation of getters on the basis of structural defects, it is necessary to create internal sources for generation of dislocations and formation of precipitate — dislocation clusters. It is shown that dislocations are generated in the mouths of microfractures, which then form a sedentary dislocation grid on the non-working side of the plates. In the second case, defects are created in the area of the plate adjacent to the active layer of the electronic component. The process of creating an internal getter is based on the decomposition of a supersaturated solid oxygen solution in silicon, due to which a complex defect medium consisting of various precipitate-dislocation clusters is formed in the crystal. The packing defect as oxide precipitate with a cloud of Frank’s loops is formed. Two variants of creating an internal getter are considered — first is associated with the distillation of an oxygen impurity from the near-surface region of the plate, the second is associated with a fine adjustment of the distribution of vacancies along the plate thickness. The analysis of the influence of the getter as the defect structure reducing the magnitude of mechanical stress of the beginning of the generation of dislocations, which ultimately can determine the mechanical strength of the silicon wafer.This paper also considers the mechanism of gas-phase medium impurities and defects gettering with the addition of chlorine-containing compounds. It is shown that at elevated temperatures, due to the interaction of silicon atoms with chlorine in the near-surface region of the plate, it is possible to create vacancies that penetrate the sample volume with some probability. As a result, the case DСv > 0, DCi £ 0 is realized, that leads to a change in the composition of microdefects and their density. The examples of practical application of heat treatment in chlorine-containing atmosphere silicon wafer during application of the oxide film, in the case of the target the need for dissolution of the microdefects and of the withdrawal of fast diffusing impurities from the crystal volume, and to prevent the formation of generation-recombination centers in the manufacturing process of devices and in a nuclear doping silicon.

Getters in silicon

Gettering of rapidly diffusing metallic impurities and structural defects in silicon which is the main material for IC fabrication, high-power high-voltage devices and neutron doped silicon has been studied. Structural defect based getters and gas phase getters based on chlorine containing compounds have been analyzed. Formation of structural defect based getters requires producing intrinsic sources of dislocation generation and precipitate/dislocation agglomerate formation. We show that dislocations are generated at microcrack mouths and form a low-mobility dislocation network at inactive wafer sides. In the latter case the defects are generated in the wafer region adjacent to the active layer of the electronic component. The generation of intrinsic getters is based on the decomposition of the supersaturated oxygen solid solution in silicon which favors the formation of a complex defect system in silicon that consists of various precipitate/dislocation agglomerates. Stacking faults also form, i.e., oxide precipitates with Frank’s dislocation loop clouds. Two intrinsic getter formation methods have been considered: one is related to oxygen impurity drain from the wafer surface region and the other implies accurate control of vacancy distribution over wafer thickness. We have analyzed the effect of getters as defect structures on the reduction of the mechanical stress required for dislocation generation onset which may eventually determine the mechanical strength of silicon wafers. The mechanism of impurity and defect gettering by gas phase medium with chlorine-containing compound additions has been considered. We show that silicon atom interaction with chlorine in the surface wafer region at high temperatures may cause the formation of vacancies which may penetrate to the specimen bulk with some probability. This leads to the case ∆Сv > 0 and ∆Ci ≤ 0, which changes the composition and density of the microdefects. Examples have been given for practical use of heat treatment of silicon wafers in a chlorine-containing atmosphere during oxide film application with the aim to dissolve microdefects, drain rapidly diffusing impurities from crystal bulk and prevent the formation of generation/recombination centers during device fabrication and silicon neutron doping.

Dislocation-Related Photoluminescence in Silicon Implanted with Germanium Ions

The influence exerted by the conditions of the post-implantation annealing of silicon implanted with germanium ions on how luminescence centers are formed is studied. Measurements by the technique of the Rutherford backscattering of medium- and high-energy ions demonstrates that implantation with 1-MeV germanium ions at a dose of 1.5 × 1014 cm–2 does not lead to the amorphization of single-crystal silicon. It is found that subsequent high-temperature annealing of the implanted samples in a chlorine-containing atmosphere at a temperature of 1100°C for 0.5–1.5 h gives rise to so-called D1 and D2 dislocation-related luminescence lines with wavelengths of 1.54 and 1.42 μm. With increasing annealing duration, the intensity of the D1 line decreases and that of D2 remains constant, but the D1 line dominates in all the spectra. The possible factors responsible for a decrease in the intensity of the D1 line and, in particular, the diffusion of germanium atoms and the formation of a silicon–germanium solid solution are discussed.

Дислокационная фотолюминесценция в кремнии, имплантированном ионами германия

AbstractThe influence exerted by the conditions of the post-implantation annealing of silicon implanted with germanium ions on how luminescence centers are formed is studied. Measurements by the technique of the Rutherford backscattering of medium- and high-energy ions demonstrates that implantation with 1-MeV germanium ions at a dose of 1 . 5 × 10^14 cm^–2 does not lead to the amorphization of single-crystal silicon. It is found that subsequent high-temperature annealing of the implanted samples in a chlorine-containing atmosphere at a temperature of 1100°C for 0.5–1.5 h gives rise to so-called D1 and D2 dislocation-related luminescence lines with wavelengths of 1.54 and 1 . 42 μm. With increasing annealing duration, the intensity of the D1 line decreases and that of D2 remains constant, but the D1 line dominates in all the spectra. The possible factors responsible for a decrease in the intensity of the D1 line and, in particular, the diffusion of germanium atoms and the formation of a silicon–germanium solid solution are discussed.

In Situ Direct Method To Massively Prepare Hydrophilic Porous Carbide-Derived Carbons for High-Performance Supercapacitors

To build a high-performance supercapacitor, chemical surface modification and hierarchically porous construction are two widely adopted routes for electrode materials design. Unfortunately, they are suffering from perplexing steps and low yield. Herein, we reported an in situ direct method to massively prepare hierarchically porous carbide-derived carbons with nitrogen and chlorine co-doping (CDCs-N/Cl) via etching TiC0.5N0.5 in chlorine-containing atmosphere. The as-prepared CDCs-N/Cl with high ratio of heteroatoms exhibited superhydrophilicity and delivered a maximum specific capacitance of 277.7 F g–1 in 6 M KOH, which is the highest value among all the reported CDC materials. Besides, the assembled asymmetrical supercapacitor shows remarkable specific capacitance of 233.4 F g–1, and 97% initial capacitance can be retained after 20,000 cycles at 2 A g–1, revealing excellent cycling stability. This work is expected to pave a new way for rapid and scalable supercapacitive electrode materials production.

Luminescent and Structural Properties of Electron-Irradiated Silicon Light-Emitting Diodes with Dislocation-Related Luminescence

Electroluminescence (EL) from light-emitting diodes (LEDs) at wavelengths in the range 1000-1650 nm, current densities of up to 10 A/cm2, and temperature of 64 K has been studied. p-Cz-Si wafers were irradiated with low-energy electrons (a variant of the technique based on rapid thermal annealing) and annealed in a chlorine-containing atmosphere at 1100°C. To obtain p-n junctions and ohmic contacts, layers of polycrystalline silicon doped with phosphorus and boron were deposited by vapour-phase epitaxy onto the opposite sides of the wafers. The dislocation structure in the samples under study consists of gliding 60⁰-dislocations and perfect and faulted dipoles. An analysis showed that the transformation of EL spectra with current is precisely described by six Gaussian lines. The peak wavelengths are current-independent and equal to 1235, 1309, 1369, 1414, 1472, and 1515 nm. The current dependences of the intensity of the EL lines have been determined.

Influence of measurement temperature on the luminescence properties of (113) defects in oxygen-implanted silicon

Influence of the measurement temperature in the range 5–130 K on the photoluminescence spectra of (113) defects in Si implanted with 350-keV oxygen ions at doses of 3.7 × 1014 cm–2 and annealed at a temperature of 700°C for 1 h in a chlorine-containing atmosphere is studied. The temperature dependence of the line intensity is characterized by portions of intensity increase with an activation energy of 23.1 meV and intensity quenching with activation energies of 41.9 and 178.3 meV. With increasing temperature, the lines are shifted to longer wavelengths and their FWHM increases.

Dislocation-related photoluminescence in silicon implanted with fluorine ions

The implantation of 85-keV fluorine ions at a dose of 8.3 × 1014 cm–2 into single crystal Si does not lead to formation of an amorphous layer. Subsequent annealing at a temperature of 1100°C in a chlorine-containing atmosphere is accompanied by the appearance of D1 and D2 lines of dislocation-related luminescence. The intensity of both lines decreases as the annealing duration is increased from 0.25 to 3 h. As the measurement temperature is increased from 80 to 200 K, the intensities of these lines decrease and the positions of their peaks shift to longer wavelengths.

Effect of the implantation dose and annealing time on the luminescence properties of (113) defects in silicon implanted by oxygen ions

The photoluminescence properties of (113) defects formed in a silicon structure after the implantation by oxygen ions with an energy of 350 keV and doses of 1.7 × 1013–1.7 × 1015 cm–2 and the subsequent annealing at a temperature of 700°C for 0.5–2.0 h in a chlorine-containing atmosphere have been investigated. Regardless of the implantation dose and annealing time, the photoluminescence spectra are dominated by the line at a wavelength of 1.37 μm, which is attributed to a (113) defect. The dependences of the line intensity on the implantation dose and annealing time are characterized by curves with maxima. As the measurement temperature increases in the range from 64 to 120 K, the line intensity decreases monotonically.

Fabrication of Light-Emitting Diodes with Dislocation-Related Luminescence by Annealing of Electron-Irradiated Silicon

Structural defects induced by electron irradiation of n-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined and the optimal annealing conditions were found. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

The electrically active centers in oxygen-implanted silicon

Electrically active centers have been firstly studied by the capacitance transient spectroscopy technique in p-Cz-Si implanted with oxygen ions and annealed in a chlorine-containing atmosphere. The temperature dependences of the thermal emission rates of holes from the levels to the valence band were measured and the influence of the annealing conditions on the level concentrations were studied. The deep and shallow levels revealed in the samples with dislocation related luminescence are characterized by similar level parameters to those observed in samples containing extended defects and performed by different techniques (deformation, formation of oxygen precipitates and direct bonding of wafers). Some distinctions in the parameters are associated with the changes of the extended defect strain fields due to specific conditions of their preparing.

Trigonal and triclinic Fe3+ paramagnetic centers in ferroelectric Pb5Ge3O11

In the EPR spectra of iron-doped lead germanate single crystals, triclinic Fe3+ paramagnetic centers have been found in addition to trigonal centers. Their contribution increases upon annealing in a chlorine-containing atmosphere. The parameters of the spin Hamiltonian of three triclinic centers assigned to Fe3+-Cl− dimeric complexes have been determined. The localization of iron and chlorine ions in Pb5Ge3O11 has been discussed.

Perchloropyracylene and its Fusion with C60 by Chlorine-Assisted Radio-Frequency Furnace Synthesis

Elusive perchloropyracylene has been obtained during conventional fullerene synthesis in a chlorine-containing atmosphere by using the radio-frequency furnace technique. In contrast to its hydrocarbon analogue, the title compound was found to be unexpectedly stable. Although the high stability of perchloropyracylene impedes its direct addition to C(60) fullerene, the corresponding adduct was found in the synthesis products extracted from the raw soot. Both new species were separated and unambiguously characterized by single-crystal X-ray analysis. According to experimental observations and quantum chemical calculations, the addition of perchloropyracylene to the C(60) fullerene can only be realized by involving highly reactive species such as C(14) clusters displaying the pyracylene connectivity. Such a viable mechanism includes capturing of free or partially chlorinated C(14) clusters with pyracylene-type connectivity by the fullerene molecule and subsequent stabilization through chlorine addition. The data obtained provide experimental evidence for the presence of pyracylene-like C(14) clusters in the gas phase, which have evolved during the graphite vaporization process. According to the pentagon road mechanism, such clusters are regarded as crucial intermediates in fullerene formation.

Photoluminescence in silicon implanted with silicon ions at amorphizing doses

Luminescent and structural properties of n-FZ-Si and n-Cz-Si implanted with Si ions at amorphizing doses and annealed at 1100°C in a chlorine-containing atmosphere have been studied. An analysis of proton Rutherford backscattering spectra of implanted samples demonstrated that an amorphous layer is formed, and its position and thickness depend on the implantation dose. An X-ray diffraction analysis revealed that defects of the interstitial type are formed in the samples upon annealing. Photoluminescence spectra measured at 78 K and low excitation levels are dominated by the dislocation-related line D1, which is also observed at 300 K. The peak position of this line, its full width at half-maximum, and intensity depend on the conduction type of Si and implantation dose. As the luminescence excitation power is raised, a continuous band appears in the spectrum. A model is suggested that explains the fundamental aspects of the behavior of the photoluminescence spectra in relation to the experimental conditions.