Bromine Absorption Research Articles

Simulation study of single solar cell structures based on the compositionally variable perovskite material CsSn(I1−xBrx)3 for tandem configured solar cells

This work involves simulating the performance of a single solar cell configured TiO2/CsSn(I1−xBrx)3/Cu2O, based on the lead-free, metallic CsSn(I1−xBrx)3 perovskite absorber, whose bandgap energy is tunable as a function of its bromine content. The simulation model used takes into account the variation of the physical parameters of the absorber as a function of its composition, represented by the ratio x, and also makes it possible to obtain the photovoltaic performance of the device studied as a function of x. The state of the front interface between the ETL electron-transport layer and the perovskite absorber was evaluated as a function of (x), by calculating the conduction bandgap offset and the misfit strain. Different electron transport layers were considered. The simulation results showed that the absorber composition influences all photovoltaic parameters, and that the choice of electron transport layer is important to achieve a compromise between device performance and the correct state of the front interface. The results indicate that CdZnS and CdS ETL materials correspond to bromine absorption ratios of x = 0 and x = 0.35 for which the conduction band offset values are − 0.03 eV and 0 eV respectively and the misfit strain 0.09 and 0.057, while ZnSe and ZnS correspond to ratios of x = 0.75 and x = 1 for which the conduction band offsets are 0 eV and 0.38 eV respectively and the strain 0.056 and 0.08. Based on these results, we determined the following optimal structures: CdZnS/CsSnI3/Cu2O and CdS/CsSn(I0.65Br0.35)3/Cu2O, which achieved yields of 18.1% and 18.5% respectively, as suitable for lower subcells with narrow bandgap energies, while the structures: ZnSe/CsSn(I0.25Br0.75)3/Cu2O and ZnS/CsSnBr3/Cu2O, which achieved efficiencies of 17.5% and 18% respectively, as top sub-cells with wide bandgap energies, in a tandem solar cell device. The aim is to develop highly efficient, non-toxic and stable single and tandem perovskite cells.

Mechanism of CF3Br Photolysis at the Wavelength of 253.7 nm

The kinetics of the photolysis of CF3Br (Halon 1301) at various durations of irradiation of CF3Br−oxygen mixtures at a wavelength of 253.7 nm is studied. The spectra and absorbances of the reactants are obtained within the range of 200−900 nm using an M-40 spectrophotometer. Kinetic data are determined from a change in the absorption spectra at a wavelength of 416 nm, which corresponds to the maximum absorption of molecular bromine. A kinetic mechanism of CF3Br photolysis is proposed, and the quantum yield and the absorption cross section of CF3Br at this wavelength are determined.

Population Diagnostics of a Hot NaBr Plasma by DetailedSimulation of Absorption Spectra

The experimental absorption spectra of a hot NaBr plasma aretheoretically studied by using a detailed level accounting model.The sodium and bromine absorption spectra have been wellreproduced respectively in the approach of local thermodynamicequilibrium, in which the populations between and within ionsare obtained by solving the Saha–Boltzmann equation. Thetemperature of bromine however is found to be much lower than the one ofsodium. Such discrepancy indicates that thermodynamic equilibriumis not reached between the sodium and bromine atoms during themeasurement.

Xenon derivatization of halide-soaked protein crystals.

Crystals of porcine pancreatic elastase can be derived by soaking in high-molarity bromide solutions. These crystals, either in a glycerol-based cryoprotectant solution or in paraffin oil, can be subsequently pressurized under a xenon atmosphere to incorporate xenon. When paraffin oil is used, a larger number of bromide ions are observed on the protein surface. Intensity data collected to lower energy than the bromine absorption edge can be used to determine the xenon position and the resultant phase information can be used to determine the bromine substructure from data collected to higher energy than the bromine absorption edge. The method would appear to have general applicability where large substructures need to be determined.

Observation of a nanoscale chessboard superstructure in the Br–Cu(100) adsorbate system.

The absorption of bromine on Cu(100) has been studied by scanning tunnelling microscopy. At bromine coverages below that required to saturate the well-known c(2×2) reconstruction, a novel mesocopic superstructure is formed by gently annealing a room-temperature-exposed surface. This involves islands of a new c(2×2)-Br reconstruction of typical dimension 20 Å×20 Å interspersed with regions of bare Cu(100) to produce a striking nanoscale chessboard pattern characterised by monoatomic step heights at the edges of the squares.

Composite Substrate for Bipolar Electrodes

Substrate compositions having a polymeric matrix, a reinforcing compo nent, and a conductive filler were developed for bipolar electrodes to be used in zinc- bromine battery systems. Among the various possible composite combinations, those based on carbon black as a conductive filler were given special attention. They combine the inherent properties of polymers—such as toughness, flexibility, low density, etc—with a high conductivity (σ = 0.2 to 1 ohm-1-cm-1). One of the problems recognized with the use of bipolar electrodes containing high surface area carbon blacks in zinc-bromide bat teries is the warpage of the electrodes. Under service conditions, warpage causes an uneven flow distribution of the electrolyte on the electrode surface and results in loss of cell capacity at low cycle life. The warpage was found to occur because of physical expan sion of electrodes resulting from bromine absorption by the high surface area carbon black. Composite substrate compositions with excellent dimensional stability that have eliminated electrode warpage as the primary battery failure mechanism were prepared by using two novel thermoplastic-composite fabrication techniques.

Reaction of mesophase pitch and semicoke with halogens and halides

The reaction of both mesophase pitch and semicoke with halogens and halides has been studied. Absorption of chlorine and bromine, and subsequent desorption indicate the existence of both loosely- and strongly-held halogens in the pyrolysed pitch. The absorbed halogen concentration decreases when the pyrolysis temperature of the pitch increases. The total concentration of absorbed bromine in mesophase pitch is three times higher than that in stage 2 bromine graphite, however, no X-ray evidence for intercalation has been found. The mechanism of fixation of the strongly-held halogen atoms is discussed in view of the content of C-H groups. Mesophase pitch absorbs non-oxidizing halides (e.g. AsCl 3, SbCl 3) without any indication of interlayer intercalate ordering. Oxidizing halides (e.g. SbCl 5, PCl 5) react with mesophase pitches and semi-cokes, forming halogenated pitches with a halogen content ranging from ≈ 30–50 wt%.

A simple F-center laser spectrometer for continuous single frequency scans

We report a simple and novel scheme for continuous, single frequency scanning of a commercial F-center laser without any computer interfacing. The scheme utilizes galvo tuning of the cavity length with intracavity CaF 2 Brewster plates with servo loop control of the intracavity etalon. This permits continuous tuning of the F-center frequency over 0.8 cm −1 under complete manual control, as well as arbitrarily long, concatenated scans, and trivial interfacing to a data acquisition system. This scanning spectrometer operation is demonstrated on direct absorption of atomic bromine.

Searching the evidence for the intercalation of bromine in high-rank coal

Similar to graphite, meta-anthracite absorbs bromine at room temperature to a concentration close to that of stage-2 graphite-bromine. Subsequent desorption at room temperature was incomplete, indicating that 88% of the bromine was loosely held and 12% was relatively strongly held in the meta-anthracite. The rate of bromine absorption and the amount and rate of bromine desorption were greater for meta-anthracite than for graphite. X-Ray diffraction, electron diffraction and differential scanning calorimetry showed the absence of intralayer or interlayer intercalate ordering in brominated meta-anthracite after desorption, hence yielding no evidence for intercalation. We conclude that the meta-anthracite was not intercalated. The ignition temperature of meta-anthracite was lowered by ≈ 80 °C by the bromination.

Bromine absorption from air by plant leaves

Trace elements present in the leaves of “Populus” grown in the city of Athens are determined by XRF, and compared with leaves of trees grown far from the city. The results of this work show a manyfold increase in the bromine content of the leaves in trees grown in the city. The increased presence of this element is attributed entirely to the increase of the bromine content in the air of the city, due to car exhaust, from which the leaves uptake this element. The implication to public health of this finding is discussed.

13. Absorption of bromine by pyrocarbons containing silicon

13. Absorption of bromine by pyrocarbons containing silicon

Selective absorption of bromine on columns of silver nitrate-loaded porous glass powder and its application in the neutron activation analysis of high-purity selenium

A very simple method for the determination of bromine in selenium has been developed. The manual handling of the irradiated selenium sample is reduced to a minimum. After the placing of the sample into the dissolution flask, no further manipulation is necessary except for the transference of the82Br counting sample from the dissolution apparatus to the scintillation counter.82Br is very selectively absorbed on columns prepared from surface-rich porous glass powder coated with silver nitrate. More than 95% of the bromine is absorbed on the columns and the decontamination factor for75Se is better than 10−7. Commercially available selenium brands with bromine contents down to 0.025 ppm have been analyzed.

Electrical Conductivity of Graphite Bromine Lamellar Compounds

Abstract Polycrystalline graphite was allowed to react with bromine vapor, and the change of its electrical conductivity during the course of bromination and debromination was studied. The graphite was found to behave in two different ways depending on the process of bromination. When the vapor pressure of bromine was changed stepwise, following the equilibrium line of bromine absorption of graphite, the electrical conductivity showed a reversible change. On the other hand, when a graphite sample was brominated with the saturated vapor, an increase of the electrical conductivity steeper than that of the former case was observed. These results were discussed in relation to the structural analysis of the brominated graphite. A metastable phase of graphite bromide, the electrical conductivity of which remained unchanged in spite of a considerable increase of absorbed bromine, was found. The electrical conductivity of the residue compounds was also investigated, and a steep decrease was observed at high concentrations of bromine.

Hydrogen exchange of saturated hydrocarbons in homogeneous media Communication 3. Ionic-chain mechanism of the reaction of isotopic exchange of the hydrogen of methylcyclohexane in solutions of trifluoroacetic and sulfuric acids

1. An ionic-chain mechanism of the isotopic exchange of the hydrogen of methylcyclohexane in acid media was demonstrated by comparing the rate of isotopic exchange of hydrogen and the rate of absorption of bromine by methylcyclohexane in a solution of trifluoroacetic and sulfuric acids. 2. Participation of the olefin in the reaction of isotopic exchange of the hydrogen of methylcyclohexane in acid media was demonstrated.

BROMINE TREATMENT OF NYLON 6

Iodine treatment of nylon 6 (polycaproamide) accompanied with α-γ transition is well known, and in this report the changes in the fine structure and properties of nylon 6, treated with bromine-potassium bromide aqueous solution, are studied by means of absorption isotherm, X-rav diffraction, infrared absorption, and relative viscosity. In a diluted bromine solution, bromine penetrates the amorphous part of nylon 6, and as the bromine concentration increases, it enters the crystalline part and finally causes the change into γ-form.Bromine absorption isotherm of nylon 6 differs from the one with iodine and is somewhat similar to the phenol absorption isotherm. It is found that in the various heat treated nylon 6 different degree of the recrystallization of the para-crystalline part into the γ-form occurs and that nylon 6 absorbed with bromine becomes insoluble in usual solvents of nylon 6.It is noted that bromine treated nylon 6 is depolymerized by water even at room temperature, and more rapidly at higher temperature. Thus depolymerized nylon 6 has a lower melting point than normal nylon 6, and it can be ground into powder.

The dimensional changes produced in graphite by absorption of bromine

It is well known that, in general, polycrystalline graphites have substantially lower volume coefficients of thermal expansion than the crystallites of which they are composed. It has previously been suggested that this is because microporosity, orientated parallel to the layer planes, absorbs part of the c-axis expansion of the crystallites. If this is true then the volume expansion of polycrystalline graphite when it absorbs bromine should also be lower than that of the crystallites and there should be a correlation between linear thermal expansion and initial linear growth per unit bromine concentration. The dimensional changes of a wide variety of polycrystalline graphites, when they absorb bromine, have been investigated and the correlation between initial growth per unit concentration of bromine and thermal expansion coefficient has been demonstrated. It has also been observed that when the strain of the crystallites in the c-axis direction becomes large the orientated microporosity fills up. When this happens the volume growth of the polycrystalline graphites per unit concentration of bromine approaches that of the crystallites. At even higher crystallite strains in the c-axis direction, anisotropic polycrystalline materials tend to expand faster than the crystallites and this is considered to be caused by the generation of additional porosity. This effect is less marked in the isotropic polycrystalline graphites. The relation between growth due to bromination and dimensional changes produced by fast neutron irradiation is discussed. Data on the effect of graphitization temperature on the subsequent dimensional changes produced by bromination are also described.

57. The dimensional changes produced in graphite by absorption of bromine

57. The dimensional changes produced in graphite by absorption of bromine

Dimensional changes in graphite: The relationship between those produced by absorption of bromine and those produced by irradiation

A study of the macroscopic growth which occurs when graphite absorbs bromine was made to determine whether the bromination-induced dimensional changes could be related to those which occur in graphite under fast neutron irradiation. For a number of extruded graphites the initial growth per unit concentration of absorbed bromine is related to the linear thermal expansion coefficient of the original graphite sample, and this enables the crystallite changes on bromination in the c and a axial directions to be derived. Bromination causes large increases in the dimensions of the graphite crystallites in the c direction and is therefore able to close up the oriented microporosity which, in the initial stages of growth, partially absorbs the crystal strain in this direction. Irradiation growth also involves an increase in the dimensions of the crystallites in the c direction, and the amount of accommodation of strain in this direction by microporosity is important in determining the macroscopic growth behaviour. It is believed that the amount of accommodation for a given graphite is determined uniquely by the crystal strain in the c direction. The variation in the amount of accommodation of crystal strain as the oriented microporosity is closed up by absorption of bromine was determined and expressed in a manner which provides a basis for comparing different graphites and enables a comparison to be made with similar data from the irradiation work. There is good agreement between the bromination and irradiation data up to a crystal strain in the c direction of about 8 %; above this level, the discrepancies are believed to result from an assumption made in interpreting the irradiation results, i.e. that the thermal expansion coefficients of the crystallites in the c and a directions are unchanged by irradiation. At high levels of crystal strain there is evidence of porosity generation in the anisotropic graphites, but the effect was not marked in the isotropic material examined. The work presents a basis for predicting, from bromination experiments, the irradiation-induced dimensional behaviour of new graphites, providing these have a well developed crystal structure. Tests can be performed cheaply on a large number of specimens and thus provide statistical nformation.

The Activation Energy of Bromine Absorption by Carbonaceous Materials

Abstract In the present paper, the temperature dependence of the rate of bromine absorption by the carbonaceous materials has been studied. The apparent energies of activation of the reaction have been found to be 5∼7 kcal./mol. and had a dependence upon the degree of graphitization of carbonaceous materials. The value of the activation energy became smaller with an increase in the degree of graphitization. The results indicate that the mobilities of reactant molecules of the interlamellar compounds increase with the growth of the net plane of graphite crystals. The saturation concentration of bromine in carbonaceous materials, under a saturated vapor pressure of bromine, was found to decrease with an increase in the temperature at temperatures above 30°C.

Mechanism of the formation of halogen monoxides during flash photolysis of halogen + oxygen mixtures

The mechanism of the formation of BrO and CIO in the flash photolysis of halogen + oxygen mixtures was investigated. It was found that the predominant mechanism for the production of BrO (about 90 % in our experiments) involves the absorption of light by the oxygen molecules. The O* 2 or the oxygen atoms produced create ozone, which in turn produces BrO when photolyzed. It is possible that some of O* 2 or O produces BrO directly and not via an ozone intermediate. About 10 % of the BrO is produced when two quanta of radiant energy are absorbed by the Br 2 molecule. The highly energetic molecule formed in this way is capable of breaking the O—O bond and forming BrO. The reaction between the excited Br atoms and O 2 , suggested by Durie & Bamsey (1958), does not occur. It seems likely that IO is formed by a mechanism similar to that of BrO. On the other hand, CIO is produced predominantly in a reaction of Cl( 2 P ) atoms with O 2 , as suggested by Porter & Wright (1953). Chlorine and bromine absorption spectra were measured down to 1880 and 1930 Å, respectively.